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;
1035 @pxref{Screen Size} and acts as if @kbd{set confirm off} were in
1036 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}, and remove it from the inferior list.
2486 @kindex kill inferior @var{infno}
2487 @item kill inferior @var{infno}
2488 Kill the inferior identified by @value{GDBN} inferior number
2489 @var{infno}, and remove it from the inferior list.
2492 After the successful completion of a command such as @code{detach},
2493 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2494 a normal process exit, the inferior is still valid and listed with
2495 @code{info inferiors}, ready to be restarted.
2498 To be notified when inferiors are started or exit under @value{GDBN}'s
2499 control use @w{@code{set print inferior-events}}:
2502 @kindex set print inferior-events
2503 @cindex print messages on inferior start and exit
2504 @item set print inferior-events
2505 @itemx set print inferior-events on
2506 @itemx set print inferior-events off
2507 The @code{set print inferior-events} command allows you to enable or
2508 disable printing of messages when @value{GDBN} notices that new
2509 inferiors have started or that inferiors have exited or have been
2510 detached. By default, these messages will not be printed.
2512 @kindex show print inferior-events
2513 @item show print inferior-events
2514 Show whether messages will be printed when @value{GDBN} detects that
2515 inferiors have started, exited or have been detached.
2518 Many commands will work the same with multiple programs as with a
2519 single program: e.g., @code{print myglobal} will simply display the
2520 value of @code{myglobal} in the current inferior.
2523 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2524 get more info about the relationship of inferiors, programs, address
2525 spaces in a debug session. You can do that with the @w{@code{maint
2526 info program-spaces}} command.
2529 @kindex maint info program-spaces
2530 @item maint info program-spaces
2531 Print a list of all program spaces currently being managed by
2534 @value{GDBN} displays for each program space (in this order):
2538 the program space number assigned by @value{GDBN}
2541 the name of the executable loaded into the program space, with e.g.,
2542 the @code{file} command.
2547 An asterisk @samp{*} preceding the @value{GDBN} program space number
2548 indicates the current program space.
2550 In addition, below each program space line, @value{GDBN} prints extra
2551 information that isn't suitable to display in tabular form. For
2552 example, the list of inferiors bound to the program space.
2555 (@value{GDBP}) maint info program-spaces
2558 Bound inferiors: ID 1 (process 21561)
2562 Here we can see that no inferior is running the program @code{hello},
2563 while @code{process 21561} is running the program @code{goodbye}. On
2564 some targets, it is possible that multiple inferiors are bound to the
2565 same program space. The most common example is that of debugging both
2566 the parent and child processes of a @code{vfork} call. For example,
2569 (@value{GDBP}) maint info program-spaces
2572 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2575 Here, both inferior 2 and inferior 1 are running in the same program
2576 space as a result of inferior 1 having executed a @code{vfork} call.
2580 @section Debugging Programs with Multiple Threads
2582 @cindex threads of execution
2583 @cindex multiple threads
2584 @cindex switching threads
2585 In some operating systems, such as HP-UX and Solaris, a single program
2586 may have more than one @dfn{thread} of execution. The precise semantics
2587 of threads differ from one operating system to another, but in general
2588 the threads of a single program are akin to multiple processes---except
2589 that they share one address space (that is, they can all examine and
2590 modify the same variables). On the other hand, each thread has its own
2591 registers and execution stack, and perhaps private memory.
2593 @value{GDBN} provides these facilities for debugging multi-thread
2597 @item automatic notification of new threads
2598 @item @samp{thread @var{threadno}}, a command to switch among threads
2599 @item @samp{info threads}, a command to inquire about existing threads
2600 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2601 a command to apply a command to a list of threads
2602 @item thread-specific breakpoints
2603 @item @samp{set print thread-events}, which controls printing of
2604 messages on thread start and exit.
2605 @item @samp{set libthread-db-search-path @var{path}}, which lets
2606 the user specify which @code{libthread_db} to use if the default choice
2607 isn't compatible with the program.
2611 @emph{Warning:} These facilities are not yet available on every
2612 @value{GDBN} configuration where the operating system supports threads.
2613 If your @value{GDBN} does not support threads, these commands have no
2614 effect. For example, a system without thread support shows no output
2615 from @samp{info threads}, and always rejects the @code{thread} command,
2619 (@value{GDBP}) info threads
2620 (@value{GDBP}) thread 1
2621 Thread ID 1 not known. Use the "info threads" command to
2622 see the IDs of currently known threads.
2624 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2625 @c doesn't support threads"?
2628 @cindex focus of debugging
2629 @cindex current thread
2630 The @value{GDBN} thread debugging facility allows you to observe all
2631 threads while your program runs---but whenever @value{GDBN} takes
2632 control, one thread in particular is always the focus of debugging.
2633 This thread is called the @dfn{current thread}. Debugging commands show
2634 program information from the perspective of the current thread.
2636 @cindex @code{New} @var{systag} message
2637 @cindex thread identifier (system)
2638 @c FIXME-implementors!! It would be more helpful if the [New...] message
2639 @c included GDB's numeric thread handle, so you could just go to that
2640 @c thread without first checking `info threads'.
2641 Whenever @value{GDBN} detects a new thread in your program, it displays
2642 the target system's identification for the thread with a message in the
2643 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2644 whose form varies depending on the particular system. For example, on
2645 @sc{gnu}/Linux, you might see
2648 [New Thread 46912507313328 (LWP 25582)]
2652 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2653 the @var{systag} is simply something like @samp{process 368}, with no
2656 @c FIXME!! (1) Does the [New...] message appear even for the very first
2657 @c thread of a program, or does it only appear for the
2658 @c second---i.e.@: when it becomes obvious we have a multithread
2660 @c (2) *Is* there necessarily a first thread always? Or do some
2661 @c multithread systems permit starting a program with multiple
2662 @c threads ab initio?
2664 @cindex thread number
2665 @cindex thread identifier (GDB)
2666 For debugging purposes, @value{GDBN} associates its own thread
2667 number---always a single integer---with each thread in your program.
2670 @kindex info threads
2672 Display a summary of all threads currently in your
2673 program. @value{GDBN} displays for each thread (in this order):
2677 the thread number assigned by @value{GDBN}
2680 the target system's thread identifier (@var{systag})
2683 the current stack frame summary for that thread
2687 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2688 indicates the current thread.
2692 @c end table here to get a little more width for example
2695 (@value{GDBP}) info threads
2696 3 process 35 thread 27 0x34e5 in sigpause ()
2697 2 process 35 thread 23 0x34e5 in sigpause ()
2698 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2704 @cindex debugging multithreaded programs (on HP-UX)
2705 @cindex thread identifier (GDB), on HP-UX
2706 For debugging purposes, @value{GDBN} associates its own thread
2707 number---a small integer assigned in thread-creation order---with each
2708 thread in your program.
2710 @cindex @code{New} @var{systag} message, on HP-UX
2711 @cindex thread identifier (system), on HP-UX
2712 @c FIXME-implementors!! It would be more helpful if the [New...] message
2713 @c included GDB's numeric thread handle, so you could just go to that
2714 @c thread without first checking `info threads'.
2715 Whenever @value{GDBN} detects a new thread in your program, it displays
2716 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2717 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2718 whose form varies depending on the particular system. For example, on
2722 [New thread 2 (system thread 26594)]
2726 when @value{GDBN} notices a new thread.
2729 @kindex info threads (HP-UX)
2731 Display a summary of all threads currently in your
2732 program. @value{GDBN} displays for each thread (in this order):
2735 @item the thread number assigned by @value{GDBN}
2737 @item the target system's thread identifier (@var{systag})
2739 @item the current stack frame summary for that thread
2743 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2744 indicates the current thread.
2748 @c end table here to get a little more width for example
2751 (@value{GDBP}) info threads
2752 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2754 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2755 from /usr/lib/libc.2
2756 1 system thread 27905 0x7b003498 in _brk () \@*
2757 from /usr/lib/libc.2
2760 On Solaris, you can display more information about user threads with a
2761 Solaris-specific command:
2764 @item maint info sol-threads
2765 @kindex maint info sol-threads
2766 @cindex thread info (Solaris)
2767 Display info on Solaris user threads.
2771 @kindex thread @var{threadno}
2772 @item thread @var{threadno}
2773 Make thread number @var{threadno} the current thread. The command
2774 argument @var{threadno} is the internal @value{GDBN} thread number, as
2775 shown in the first field of the @samp{info threads} display.
2776 @value{GDBN} responds by displaying the system identifier of the thread
2777 you selected, and its current stack frame summary:
2780 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2781 (@value{GDBP}) thread 2
2782 [Switching to process 35 thread 23]
2783 0x34e5 in sigpause ()
2787 As with the @samp{[New @dots{}]} message, the form of the text after
2788 @samp{Switching to} depends on your system's conventions for identifying
2791 @vindex $_thread@r{, convenience variable}
2792 The debugger convenience variable @samp{$_thread} contains the number
2793 of the current thread. You may find this useful in writing breakpoint
2794 conditional expressions, command scripts, and so forth. See
2795 @xref{Convenience Vars,, Convenience Variables}, for general
2796 information on convenience variables.
2798 @kindex thread apply
2799 @cindex apply command to several threads
2800 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2801 The @code{thread apply} command allows you to apply the named
2802 @var{command} to one or more threads. Specify the numbers of the
2803 threads that you want affected with the command argument
2804 @var{threadno}. It can be a single thread number, one of the numbers
2805 shown in the first field of the @samp{info threads} display; or it
2806 could be a range of thread numbers, as in @code{2-4}. To apply a
2807 command to all threads, type @kbd{thread apply all @var{command}}.
2809 @kindex set print thread-events
2810 @cindex print messages on thread start and exit
2811 @item set print thread-events
2812 @itemx set print thread-events on
2813 @itemx set print thread-events off
2814 The @code{set print thread-events} command allows you to enable or
2815 disable printing of messages when @value{GDBN} notices that new threads have
2816 started or that threads have exited. By default, these messages will
2817 be printed if detection of these events is supported by the target.
2818 Note that these messages cannot be disabled on all targets.
2820 @kindex show print thread-events
2821 @item show print thread-events
2822 Show whether messages will be printed when @value{GDBN} detects that threads
2823 have started and exited.
2826 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2827 more information about how @value{GDBN} behaves when you stop and start
2828 programs with multiple threads.
2830 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2831 watchpoints in programs with multiple threads.
2834 @kindex set libthread-db-search-path
2835 @cindex search path for @code{libthread_db}
2836 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2837 If this variable is set, @var{path} is a colon-separated list of
2838 directories @value{GDBN} will use to search for @code{libthread_db}.
2839 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2842 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2843 @code{libthread_db} library to obtain information about threads in the
2844 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2845 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2846 with default system shared library directories, and finally the directory
2847 from which @code{libpthread} was loaded in the inferior process.
2849 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2850 @value{GDBN} attempts to initialize it with the current inferior process.
2851 If this initialization fails (which could happen because of a version
2852 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2853 will unload @code{libthread_db}, and continue with the next directory.
2854 If none of @code{libthread_db} libraries initialize successfully,
2855 @value{GDBN} will issue a warning and thread debugging will be disabled.
2857 Setting @code{libthread-db-search-path} is currently implemented
2858 only on some platforms.
2860 @kindex show libthread-db-search-path
2861 @item show libthread-db-search-path
2862 Display current libthread_db search path.
2866 @section Debugging Forks
2868 @cindex fork, debugging programs which call
2869 @cindex multiple processes
2870 @cindex processes, multiple
2871 On most systems, @value{GDBN} has no special support for debugging
2872 programs which create additional processes using the @code{fork}
2873 function. When a program forks, @value{GDBN} will continue to debug the
2874 parent process and the child process will run unimpeded. If you have
2875 set a breakpoint in any code which the child then executes, the child
2876 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2877 will cause it to terminate.
2879 However, if you want to debug the child process there is a workaround
2880 which isn't too painful. Put a call to @code{sleep} in the code which
2881 the child process executes after the fork. It may be useful to sleep
2882 only if a certain environment variable is set, or a certain file exists,
2883 so that the delay need not occur when you don't want to run @value{GDBN}
2884 on the child. While the child is sleeping, use the @code{ps} program to
2885 get its process ID. Then tell @value{GDBN} (a new invocation of
2886 @value{GDBN} if you are also debugging the parent process) to attach to
2887 the child process (@pxref{Attach}). From that point on you can debug
2888 the child process just like any other process which you attached to.
2890 On some systems, @value{GDBN} provides support for debugging programs that
2891 create additional processes using the @code{fork} or @code{vfork} functions.
2892 Currently, the only platforms with this feature are HP-UX (11.x and later
2893 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2895 By default, when a program forks, @value{GDBN} will continue to debug
2896 the parent process and the child process will run unimpeded.
2898 If you want to follow the child process instead of the parent process,
2899 use the command @w{@code{set follow-fork-mode}}.
2902 @kindex set follow-fork-mode
2903 @item set follow-fork-mode @var{mode}
2904 Set the debugger response to a program call of @code{fork} or
2905 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2906 process. The @var{mode} argument can be:
2910 The original process is debugged after a fork. The child process runs
2911 unimpeded. This is the default.
2914 The new process is debugged after a fork. The parent process runs
2919 @kindex show follow-fork-mode
2920 @item show follow-fork-mode
2921 Display the current debugger response to a @code{fork} or @code{vfork} call.
2924 @cindex debugging multiple processes
2925 On Linux, if you want to debug both the parent and child processes, use the
2926 command @w{@code{set detach-on-fork}}.
2929 @kindex set detach-on-fork
2930 @item set detach-on-fork @var{mode}
2931 Tells gdb whether to detach one of the processes after a fork, or
2932 retain debugger control over them both.
2936 The child process (or parent process, depending on the value of
2937 @code{follow-fork-mode}) will be detached and allowed to run
2938 independently. This is the default.
2941 Both processes will be held under the control of @value{GDBN}.
2942 One process (child or parent, depending on the value of
2943 @code{follow-fork-mode}) is debugged as usual, while the other
2948 @kindex show detach-on-fork
2949 @item show detach-on-fork
2950 Show whether detach-on-fork mode is on/off.
2953 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2954 will retain control of all forked processes (including nested forks).
2955 You can list the forked processes under the control of @value{GDBN} by
2956 using the @w{@code{info inferiors}} command, and switch from one fork
2957 to another by using the @code{inferior} command (@pxref{Inferiors and
2958 Programs, ,Debugging Multiple Inferiors and Programs}).
2960 To quit debugging one of the forked processes, you can either detach
2961 from it by using the @w{@code{detach inferior}} command (allowing it
2962 to run independently), or kill it using the @w{@code{kill inferior}}
2963 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2966 If you ask to debug a child process and a @code{vfork} is followed by an
2967 @code{exec}, @value{GDBN} executes the new target up to the first
2968 breakpoint in the new target. If you have a breakpoint set on
2969 @code{main} in your original program, the breakpoint will also be set on
2970 the child process's @code{main}.
2972 On some systems, when a child process is spawned by @code{vfork}, you
2973 cannot debug the child or parent until an @code{exec} call completes.
2975 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2976 call executes, the new target restarts. To restart the parent
2977 process, use the @code{file} command with the parent executable name
2978 as its argument. By default, after an @code{exec} call executes,
2979 @value{GDBN} discards the symbols of the previous executable image.
2980 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2984 @kindex set follow-exec-mode
2985 @item set follow-exec-mode @var{mode}
2987 Set debugger response to a program call of @code{exec}. An
2988 @code{exec} call replaces the program image of a process.
2990 @code{follow-exec-mode} can be:
2994 @value{GDBN} creates a new inferior and rebinds the process to this
2995 new inferior. The program the process was running before the
2996 @code{exec} call can be restarted afterwards by restarting the
3002 (@value{GDBP}) info inferiors
3004 Id Description Executable
3007 process 12020 is executing new program: prog2
3008 Program exited normally.
3009 (@value{GDBP}) info inferiors
3010 Id Description Executable
3016 @value{GDBN} keeps the process bound to the same inferior. The new
3017 executable image replaces the previous executable loaded in the
3018 inferior. Restarting the inferior after the @code{exec} call, with
3019 e.g., the @code{run} command, restarts the executable the process was
3020 running after the @code{exec} call. This is the default mode.
3025 (@value{GDBP}) info inferiors
3026 Id Description Executable
3029 process 12020 is executing new program: prog2
3030 Program exited normally.
3031 (@value{GDBP}) info inferiors
3032 Id Description Executable
3039 You can use the @code{catch} command to make @value{GDBN} stop whenever
3040 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3041 Catchpoints, ,Setting Catchpoints}.
3043 @node Checkpoint/Restart
3044 @section Setting a @emph{Bookmark} to Return to Later
3049 @cindex snapshot of a process
3050 @cindex rewind program state
3052 On certain operating systems@footnote{Currently, only
3053 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3054 program's state, called a @dfn{checkpoint}, and come back to it
3057 Returning to a checkpoint effectively undoes everything that has
3058 happened in the program since the @code{checkpoint} was saved. This
3059 includes changes in memory, registers, and even (within some limits)
3060 system state. Effectively, it is like going back in time to the
3061 moment when the checkpoint was saved.
3063 Thus, if you're stepping thru a program and you think you're
3064 getting close to the point where things go wrong, you can save
3065 a checkpoint. Then, if you accidentally go too far and miss
3066 the critical statement, instead of having to restart your program
3067 from the beginning, you can just go back to the checkpoint and
3068 start again from there.
3070 This can be especially useful if it takes a lot of time or
3071 steps to reach the point where you think the bug occurs.
3073 To use the @code{checkpoint}/@code{restart} method of debugging:
3078 Save a snapshot of the debugged program's current execution state.
3079 The @code{checkpoint} command takes no arguments, but each checkpoint
3080 is assigned a small integer id, similar to a breakpoint id.
3082 @kindex info checkpoints
3083 @item info checkpoints
3084 List the checkpoints that have been saved in the current debugging
3085 session. For each checkpoint, the following information will be
3092 @item Source line, or label
3095 @kindex restart @var{checkpoint-id}
3096 @item restart @var{checkpoint-id}
3097 Restore the program state that was saved as checkpoint number
3098 @var{checkpoint-id}. All program variables, registers, stack frames
3099 etc.@: will be returned to the values that they had when the checkpoint
3100 was saved. In essence, gdb will ``wind back the clock'' to the point
3101 in time when the checkpoint was saved.
3103 Note that breakpoints, @value{GDBN} variables, command history etc.
3104 are not affected by restoring a checkpoint. In general, a checkpoint
3105 only restores things that reside in the program being debugged, not in
3108 @kindex delete checkpoint @var{checkpoint-id}
3109 @item delete checkpoint @var{checkpoint-id}
3110 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3114 Returning to a previously saved checkpoint will restore the user state
3115 of the program being debugged, plus a significant subset of the system
3116 (OS) state, including file pointers. It won't ``un-write'' data from
3117 a file, but it will rewind the file pointer to the previous location,
3118 so that the previously written data can be overwritten. For files
3119 opened in read mode, the pointer will also be restored so that the
3120 previously read data can be read again.
3122 Of course, characters that have been sent to a printer (or other
3123 external device) cannot be ``snatched back'', and characters received
3124 from eg.@: a serial device can be removed from internal program buffers,
3125 but they cannot be ``pushed back'' into the serial pipeline, ready to
3126 be received again. Similarly, the actual contents of files that have
3127 been changed cannot be restored (at this time).
3129 However, within those constraints, you actually can ``rewind'' your
3130 program to a previously saved point in time, and begin debugging it
3131 again --- and you can change the course of events so as to debug a
3132 different execution path this time.
3134 @cindex checkpoints and process id
3135 Finally, there is one bit of internal program state that will be
3136 different when you return to a checkpoint --- the program's process
3137 id. Each checkpoint will have a unique process id (or @var{pid}),
3138 and each will be different from the program's original @var{pid}.
3139 If your program has saved a local copy of its process id, this could
3140 potentially pose a problem.
3142 @subsection A Non-obvious Benefit of Using Checkpoints
3144 On some systems such as @sc{gnu}/Linux, address space randomization
3145 is performed on new processes for security reasons. This makes it
3146 difficult or impossible to set a breakpoint, or watchpoint, on an
3147 absolute address if you have to restart the program, since the
3148 absolute location of a symbol will change from one execution to the
3151 A checkpoint, however, is an @emph{identical} copy of a process.
3152 Therefore if you create a checkpoint at (eg.@:) the start of main,
3153 and simply return to that checkpoint instead of restarting the
3154 process, you can avoid the effects of address randomization and
3155 your symbols will all stay in the same place.
3158 @chapter Stopping and Continuing
3160 The principal purposes of using a debugger are so that you can stop your
3161 program before it terminates; or so that, if your program runs into
3162 trouble, you can investigate and find out why.
3164 Inside @value{GDBN}, your program may stop for any of several reasons,
3165 such as a signal, a breakpoint, or reaching a new line after a
3166 @value{GDBN} command such as @code{step}. You may then examine and
3167 change variables, set new breakpoints or remove old ones, and then
3168 continue execution. Usually, the messages shown by @value{GDBN} provide
3169 ample explanation of the status of your program---but you can also
3170 explicitly request this information at any time.
3173 @kindex info program
3175 Display information about the status of your program: whether it is
3176 running or not, what process it is, and why it stopped.
3180 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3181 * Continuing and Stepping:: Resuming execution
3183 * Thread Stops:: Stopping and starting multi-thread programs
3187 @section Breakpoints, Watchpoints, and Catchpoints
3190 A @dfn{breakpoint} makes your program stop whenever a certain point in
3191 the program is reached. For each breakpoint, you can add conditions to
3192 control in finer detail whether your program stops. You can set
3193 breakpoints with the @code{break} command and its variants (@pxref{Set
3194 Breaks, ,Setting Breakpoints}), to specify the place where your program
3195 should stop by line number, function name or exact address in the
3198 On some systems, you can set breakpoints in shared libraries before
3199 the executable is run. There is a minor limitation on HP-UX systems:
3200 you must wait until the executable is run in order to set breakpoints
3201 in shared library routines that are not called directly by the program
3202 (for example, routines that are arguments in a @code{pthread_create}
3206 @cindex data breakpoints
3207 @cindex memory tracing
3208 @cindex breakpoint on memory address
3209 @cindex breakpoint on variable modification
3210 A @dfn{watchpoint} is a special breakpoint that stops your program
3211 when the value of an expression changes. The expression may be a value
3212 of a variable, or it could involve values of one or more variables
3213 combined by operators, such as @samp{a + b}. This is sometimes called
3214 @dfn{data breakpoints}. You must use a different command to set
3215 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3216 from that, you can manage a watchpoint like any other breakpoint: you
3217 enable, disable, and delete both breakpoints and watchpoints using the
3220 You can arrange to have values from your program displayed automatically
3221 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3225 @cindex breakpoint on events
3226 A @dfn{catchpoint} is another special breakpoint that stops your program
3227 when a certain kind of event occurs, such as the throwing of a C@t{++}
3228 exception or the loading of a library. As with watchpoints, you use a
3229 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3230 Catchpoints}), but aside from that, you can manage a catchpoint like any
3231 other breakpoint. (To stop when your program receives a signal, use the
3232 @code{handle} command; see @ref{Signals, ,Signals}.)
3234 @cindex breakpoint numbers
3235 @cindex numbers for breakpoints
3236 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3237 catchpoint when you create it; these numbers are successive integers
3238 starting with one. In many of the commands for controlling various
3239 features of breakpoints you use the breakpoint number to say which
3240 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3241 @dfn{disabled}; if disabled, it has no effect on your program until you
3244 @cindex breakpoint ranges
3245 @cindex ranges of breakpoints
3246 Some @value{GDBN} commands accept a range of breakpoints on which to
3247 operate. A breakpoint range is either a single breakpoint number, like
3248 @samp{5}, or two such numbers, in increasing order, separated by a
3249 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3250 all breakpoints in that range are operated on.
3253 * Set Breaks:: Setting breakpoints
3254 * Set Watchpoints:: Setting watchpoints
3255 * Set Catchpoints:: Setting catchpoints
3256 * Delete Breaks:: Deleting breakpoints
3257 * Disabling:: Disabling breakpoints
3258 * Conditions:: Break conditions
3259 * Break Commands:: Breakpoint command lists
3260 * Save Breakpoints:: How to save breakpoints in a file
3261 * Error in Breakpoints:: ``Cannot insert breakpoints''
3262 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3266 @subsection Setting Breakpoints
3268 @c FIXME LMB what does GDB do if no code on line of breakpt?
3269 @c consider in particular declaration with/without initialization.
3271 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3274 @kindex b @r{(@code{break})}
3275 @vindex $bpnum@r{, convenience variable}
3276 @cindex latest breakpoint
3277 Breakpoints are set with the @code{break} command (abbreviated
3278 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3279 number of the breakpoint you've set most recently; see @ref{Convenience
3280 Vars,, Convenience Variables}, for a discussion of what you can do with
3281 convenience variables.
3284 @item break @var{location}
3285 Set a breakpoint at the given @var{location}, which can specify a
3286 function name, a line number, or an address of an instruction.
3287 (@xref{Specify Location}, for a list of all the possible ways to
3288 specify a @var{location}.) The breakpoint will stop your program just
3289 before it executes any of the code in the specified @var{location}.
3291 When using source languages that permit overloading of symbols, such as
3292 C@t{++}, a function name may refer to more than one possible place to break.
3293 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3296 It is also possible to insert a breakpoint that will stop the program
3297 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3298 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3301 When called without any arguments, @code{break} sets a breakpoint at
3302 the next instruction to be executed in the selected stack frame
3303 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3304 innermost, this makes your program stop as soon as control
3305 returns to that frame. This is similar to the effect of a
3306 @code{finish} command in the frame inside the selected frame---except
3307 that @code{finish} does not leave an active breakpoint. If you use
3308 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3309 the next time it reaches the current location; this may be useful
3312 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3313 least one instruction has been executed. If it did not do this, you
3314 would be unable to proceed past a breakpoint without first disabling the
3315 breakpoint. This rule applies whether or not the breakpoint already
3316 existed when your program stopped.
3318 @item break @dots{} if @var{cond}
3319 Set a breakpoint with condition @var{cond}; evaluate the expression
3320 @var{cond} each time the breakpoint is reached, and stop only if the
3321 value is nonzero---that is, if @var{cond} evaluates as true.
3322 @samp{@dots{}} stands for one of the possible arguments described
3323 above (or no argument) specifying where to break. @xref{Conditions,
3324 ,Break Conditions}, for more information on breakpoint conditions.
3327 @item tbreak @var{args}
3328 Set a breakpoint enabled only for one stop. @var{args} are the
3329 same as for the @code{break} command, and the breakpoint is set in the same
3330 way, but the breakpoint is automatically deleted after the first time your
3331 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3334 @cindex hardware breakpoints
3335 @item hbreak @var{args}
3336 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3337 @code{break} command and the breakpoint is set in the same way, but the
3338 breakpoint requires hardware support and some target hardware may not
3339 have this support. The main purpose of this is EPROM/ROM code
3340 debugging, so you can set a breakpoint at an instruction without
3341 changing the instruction. This can be used with the new trap-generation
3342 provided by SPARClite DSU and most x86-based targets. These targets
3343 will generate traps when a program accesses some data or instruction
3344 address that is assigned to the debug registers. However the hardware
3345 breakpoint registers can take a limited number of breakpoints. For
3346 example, on the DSU, only two data breakpoints can be set at a time, and
3347 @value{GDBN} will reject this command if more than two are used. Delete
3348 or disable unused hardware breakpoints before setting new ones
3349 (@pxref{Disabling, ,Disabling Breakpoints}).
3350 @xref{Conditions, ,Break Conditions}.
3351 For remote targets, you can restrict the number of hardware
3352 breakpoints @value{GDBN} will use, see @ref{set remote
3353 hardware-breakpoint-limit}.
3356 @item thbreak @var{args}
3357 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3358 are the same as for the @code{hbreak} command and the breakpoint is set in
3359 the same way. However, like the @code{tbreak} command,
3360 the breakpoint is automatically deleted after the
3361 first time your program stops there. Also, like the @code{hbreak}
3362 command, the breakpoint requires hardware support and some target hardware
3363 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3364 See also @ref{Conditions, ,Break Conditions}.
3367 @cindex regular expression
3368 @cindex breakpoints at functions matching a regexp
3369 @cindex set breakpoints in many functions
3370 @item rbreak @var{regex}
3371 Set breakpoints on all functions matching the regular expression
3372 @var{regex}. This command sets an unconditional breakpoint on all
3373 matches, printing a list of all breakpoints it set. Once these
3374 breakpoints are set, they are treated just like the breakpoints set with
3375 the @code{break} command. You can delete them, disable them, or make
3376 them conditional the same way as any other breakpoint.
3378 The syntax of the regular expression is the standard one used with tools
3379 like @file{grep}. Note that this is different from the syntax used by
3380 shells, so for instance @code{foo*} matches all functions that include
3381 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3382 @code{.*} leading and trailing the regular expression you supply, so to
3383 match only functions that begin with @code{foo}, use @code{^foo}.
3385 @cindex non-member C@t{++} functions, set breakpoint in
3386 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3387 breakpoints on overloaded functions that are not members of any special
3390 @cindex set breakpoints on all functions
3391 The @code{rbreak} command can be used to set breakpoints in
3392 @strong{all} the functions in a program, like this:
3395 (@value{GDBP}) rbreak .
3398 @item rbreak @var{file}:@var{regex}
3399 If @code{rbreak} is called with a filename qualification, it limits
3400 the search for functions matching the given regular expression to the
3401 specified @var{file}. This can be used, for example, to set breakpoints on
3402 every function in a given file:
3405 (@value{GDBP}) rbreak file.c:.
3408 The colon separating the filename qualifier from the regex may
3409 optionally be surrounded by spaces.
3411 @kindex info breakpoints
3412 @cindex @code{$_} and @code{info breakpoints}
3413 @item info breakpoints @r{[}@var{n}@r{]}
3414 @itemx info break @r{[}@var{n}@r{]}
3415 Print a table of all breakpoints, watchpoints, and catchpoints set and
3416 not deleted. Optional argument @var{n} means print information only
3417 about the specified breakpoint (or watchpoint or catchpoint). For
3418 each breakpoint, following columns are printed:
3421 @item Breakpoint Numbers
3423 Breakpoint, watchpoint, or catchpoint.
3425 Whether the breakpoint is marked to be disabled or deleted when hit.
3426 @item Enabled or Disabled
3427 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3428 that are not enabled.
3430 Where the breakpoint is in your program, as a memory address. For a
3431 pending breakpoint whose address is not yet known, this field will
3432 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3433 library that has the symbol or line referred by breakpoint is loaded.
3434 See below for details. A breakpoint with several locations will
3435 have @samp{<MULTIPLE>} in this field---see below for details.
3437 Where the breakpoint is in the source for your program, as a file and
3438 line number. For a pending breakpoint, the original string passed to
3439 the breakpoint command will be listed as it cannot be resolved until
3440 the appropriate shared library is loaded in the future.
3444 If a breakpoint is conditional, @code{info break} shows the condition on
3445 the line following the affected breakpoint; breakpoint commands, if any,
3446 are listed after that. A pending breakpoint is allowed to have a condition
3447 specified for it. The condition is not parsed for validity until a shared
3448 library is loaded that allows the pending breakpoint to resolve to a
3452 @code{info break} with a breakpoint
3453 number @var{n} as argument lists only that breakpoint. The
3454 convenience variable @code{$_} and the default examining-address for
3455 the @code{x} command are set to the address of the last breakpoint
3456 listed (@pxref{Memory, ,Examining Memory}).
3459 @code{info break} displays a count of the number of times the breakpoint
3460 has been hit. This is especially useful in conjunction with the
3461 @code{ignore} command. You can ignore a large number of breakpoint
3462 hits, look at the breakpoint info to see how many times the breakpoint
3463 was hit, and then run again, ignoring one less than that number. This
3464 will get you quickly to the last hit of that breakpoint.
3467 @value{GDBN} allows you to set any number of breakpoints at the same place in
3468 your program. There is nothing silly or meaningless about this. When
3469 the breakpoints are conditional, this is even useful
3470 (@pxref{Conditions, ,Break Conditions}).
3472 @cindex multiple locations, breakpoints
3473 @cindex breakpoints, multiple locations
3474 It is possible that a breakpoint corresponds to several locations
3475 in your program. Examples of this situation are:
3479 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3480 instances of the function body, used in different cases.
3483 For a C@t{++} template function, a given line in the function can
3484 correspond to any number of instantiations.
3487 For an inlined function, a given source line can correspond to
3488 several places where that function is inlined.
3491 In all those cases, @value{GDBN} will insert a breakpoint at all
3492 the relevant locations@footnote{
3493 As of this writing, multiple-location breakpoints work only if there's
3494 line number information for all the locations. This means that they
3495 will generally not work in system libraries, unless you have debug
3496 info with line numbers for them.}.
3498 A breakpoint with multiple locations is displayed in the breakpoint
3499 table using several rows---one header row, followed by one row for
3500 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3501 address column. The rows for individual locations contain the actual
3502 addresses for locations, and show the functions to which those
3503 locations belong. The number column for a location is of the form
3504 @var{breakpoint-number}.@var{location-number}.
3509 Num Type Disp Enb Address What
3510 1 breakpoint keep y <MULTIPLE>
3512 breakpoint already hit 1 time
3513 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3514 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3517 Each location can be individually enabled or disabled by passing
3518 @var{breakpoint-number}.@var{location-number} as argument to the
3519 @code{enable} and @code{disable} commands. Note that you cannot
3520 delete the individual locations from the list, you can only delete the
3521 entire list of locations that belong to their parent breakpoint (with
3522 the @kbd{delete @var{num}} command, where @var{num} is the number of
3523 the parent breakpoint, 1 in the above example). Disabling or enabling
3524 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3525 that belong to that breakpoint.
3527 @cindex pending breakpoints
3528 It's quite common to have a breakpoint inside a shared library.
3529 Shared libraries can be loaded and unloaded explicitly,
3530 and possibly repeatedly, as the program is executed. To support
3531 this use case, @value{GDBN} updates breakpoint locations whenever
3532 any shared library is loaded or unloaded. Typically, you would
3533 set a breakpoint in a shared library at the beginning of your
3534 debugging session, when the library is not loaded, and when the
3535 symbols from the library are not available. When you try to set
3536 breakpoint, @value{GDBN} will ask you if you want to set
3537 a so called @dfn{pending breakpoint}---breakpoint whose address
3538 is not yet resolved.
3540 After the program is run, whenever a new shared library is loaded,
3541 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3542 shared library contains the symbol or line referred to by some
3543 pending breakpoint, that breakpoint is resolved and becomes an
3544 ordinary breakpoint. When a library is unloaded, all breakpoints
3545 that refer to its symbols or source lines become pending again.
3547 This logic works for breakpoints with multiple locations, too. For
3548 example, if you have a breakpoint in a C@t{++} template function, and
3549 a newly loaded shared library has an instantiation of that template,
3550 a new location is added to the list of locations for the breakpoint.
3552 Except for having unresolved address, pending breakpoints do not
3553 differ from regular breakpoints. You can set conditions or commands,
3554 enable and disable them and perform other breakpoint operations.
3556 @value{GDBN} provides some additional commands for controlling what
3557 happens when the @samp{break} command cannot resolve breakpoint
3558 address specification to an address:
3560 @kindex set breakpoint pending
3561 @kindex show breakpoint pending
3563 @item set breakpoint pending auto
3564 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3565 location, it queries you whether a pending breakpoint should be created.
3567 @item set breakpoint pending on
3568 This indicates that an unrecognized breakpoint location should automatically
3569 result in a pending breakpoint being created.
3571 @item set breakpoint pending off
3572 This indicates that pending breakpoints are not to be created. Any
3573 unrecognized breakpoint location results in an error. This setting does
3574 not affect any pending breakpoints previously created.
3576 @item show breakpoint pending
3577 Show the current behavior setting for creating pending breakpoints.
3580 The settings above only affect the @code{break} command and its
3581 variants. Once breakpoint is set, it will be automatically updated
3582 as shared libraries are loaded and unloaded.
3584 @cindex automatic hardware breakpoints
3585 For some targets, @value{GDBN} can automatically decide if hardware or
3586 software breakpoints should be used, depending on whether the
3587 breakpoint address is read-only or read-write. This applies to
3588 breakpoints set with the @code{break} command as well as to internal
3589 breakpoints set by commands like @code{next} and @code{finish}. For
3590 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3593 You can control this automatic behaviour with the following commands::
3595 @kindex set breakpoint auto-hw
3596 @kindex show breakpoint auto-hw
3598 @item set breakpoint auto-hw on
3599 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3600 will try to use the target memory map to decide if software or hardware
3601 breakpoint must be used.
3603 @item set breakpoint auto-hw off
3604 This indicates @value{GDBN} should not automatically select breakpoint
3605 type. If the target provides a memory map, @value{GDBN} will warn when
3606 trying to set software breakpoint at a read-only address.
3609 @value{GDBN} normally implements breakpoints by replacing the program code
3610 at the breakpoint address with a special instruction, which, when
3611 executed, given control to the debugger. By default, the program
3612 code is so modified only when the program is resumed. As soon as
3613 the program stops, @value{GDBN} restores the original instructions. This
3614 behaviour guards against leaving breakpoints inserted in the
3615 target should gdb abrubptly disconnect. However, with slow remote
3616 targets, inserting and removing breakpoint can reduce the performance.
3617 This behavior can be controlled with the following commands::
3619 @kindex set breakpoint always-inserted
3620 @kindex show breakpoint always-inserted
3622 @item set breakpoint always-inserted off
3623 All breakpoints, including newly added by the user, are inserted in
3624 the target only when the target is resumed. All breakpoints are
3625 removed from the target when it stops.
3627 @item set breakpoint always-inserted on
3628 Causes all breakpoints to be inserted in the target at all times. If
3629 the user adds a new breakpoint, or changes an existing breakpoint, the
3630 breakpoints in the target are updated immediately. A breakpoint is
3631 removed from the target only when breakpoint itself is removed.
3633 @cindex non-stop mode, and @code{breakpoint always-inserted}
3634 @item set breakpoint always-inserted auto
3635 This is the default mode. If @value{GDBN} is controlling the inferior
3636 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3637 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3638 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3639 @code{breakpoint always-inserted} mode is off.
3642 @cindex negative breakpoint numbers
3643 @cindex internal @value{GDBN} breakpoints
3644 @value{GDBN} itself sometimes sets breakpoints in your program for
3645 special purposes, such as proper handling of @code{longjmp} (in C
3646 programs). These internal breakpoints are assigned negative numbers,
3647 starting with @code{-1}; @samp{info breakpoints} does not display them.
3648 You can see these breakpoints with the @value{GDBN} maintenance command
3649 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3652 @node Set Watchpoints
3653 @subsection Setting Watchpoints
3655 @cindex setting watchpoints
3656 You can use a watchpoint to stop execution whenever the value of an
3657 expression changes, without having to predict a particular place where
3658 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3659 The expression may be as simple as the value of a single variable, or
3660 as complex as many variables combined by operators. Examples include:
3664 A reference to the value of a single variable.
3667 An address cast to an appropriate data type. For example,
3668 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3669 address (assuming an @code{int} occupies 4 bytes).
3672 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3673 expression can use any operators valid in the program's native
3674 language (@pxref{Languages}).
3677 You can set a watchpoint on an expression even if the expression can
3678 not be evaluated yet. For instance, you can set a watchpoint on
3679 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3680 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3681 the expression produces a valid value. If the expression becomes
3682 valid in some other way than changing a variable (e.g.@: if the memory
3683 pointed to by @samp{*global_ptr} becomes readable as the result of a
3684 @code{malloc} call), @value{GDBN} may not stop until the next time
3685 the expression changes.
3687 @cindex software watchpoints
3688 @cindex hardware watchpoints
3689 Depending on your system, watchpoints may be implemented in software or
3690 hardware. @value{GDBN} does software watchpointing by single-stepping your
3691 program and testing the variable's value each time, which is hundreds of
3692 times slower than normal execution. (But this may still be worth it, to
3693 catch errors where you have no clue what part of your program is the
3696 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3697 x86-based targets, @value{GDBN} includes support for hardware
3698 watchpoints, which do not slow down the running of your program.
3702 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3703 Set a watchpoint for an expression. @value{GDBN} will break when the
3704 expression @var{expr} is written into by the program and its value
3705 changes. The simplest (and the most popular) use of this command is
3706 to watch the value of a single variable:
3709 (@value{GDBP}) watch foo
3712 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3713 clause, @value{GDBN} breaks only when the thread identified by
3714 @var{threadnum} changes the value of @var{expr}. If any other threads
3715 change the value of @var{expr}, @value{GDBN} will not break. Note
3716 that watchpoints restricted to a single thread in this way only work
3717 with Hardware Watchpoints.
3720 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3721 Set a watchpoint that will break when the value of @var{expr} is read
3725 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3726 Set a watchpoint that will break when @var{expr} is either read from
3727 or written into by the program.
3729 @kindex info watchpoints @r{[}@var{n}@r{]}
3730 @item info watchpoints
3731 This command prints a list of watchpoints, using the same format as
3732 @code{info break} (@pxref{Set Breaks}).
3735 If you watch for a change in a numerically entered address you need to
3736 dereference it, as the address itself is just a constant number which will
3737 never change. @value{GDBN} refuses to create a watchpoint that watches
3738 a never-changing value:
3741 (@value{GDBP}) watch 0x600850
3742 Cannot watch constant value 0x600850.
3743 (@value{GDBP}) watch *(int *) 0x600850
3744 Watchpoint 1: *(int *) 6293584
3747 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3748 watchpoints execute very quickly, and the debugger reports a change in
3749 value at the exact instruction where the change occurs. If @value{GDBN}
3750 cannot set a hardware watchpoint, it sets a software watchpoint, which
3751 executes more slowly and reports the change in value at the next
3752 @emph{statement}, not the instruction, after the change occurs.
3754 @cindex use only software watchpoints
3755 You can force @value{GDBN} to use only software watchpoints with the
3756 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3757 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3758 the underlying system supports them. (Note that hardware-assisted
3759 watchpoints that were set @emph{before} setting
3760 @code{can-use-hw-watchpoints} to zero will still use the hardware
3761 mechanism of watching expression values.)
3764 @item set can-use-hw-watchpoints
3765 @kindex set can-use-hw-watchpoints
3766 Set whether or not to use hardware watchpoints.
3768 @item show can-use-hw-watchpoints
3769 @kindex show can-use-hw-watchpoints
3770 Show the current mode of using hardware watchpoints.
3773 For remote targets, you can restrict the number of hardware
3774 watchpoints @value{GDBN} will use, see @ref{set remote
3775 hardware-breakpoint-limit}.
3777 When you issue the @code{watch} command, @value{GDBN} reports
3780 Hardware watchpoint @var{num}: @var{expr}
3784 if it was able to set a hardware watchpoint.
3786 Currently, the @code{awatch} and @code{rwatch} commands can only set
3787 hardware watchpoints, because accesses to data that don't change the
3788 value of the watched expression cannot be detected without examining
3789 every instruction as it is being executed, and @value{GDBN} does not do
3790 that currently. If @value{GDBN} finds that it is unable to set a
3791 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3792 will print a message like this:
3795 Expression cannot be implemented with read/access watchpoint.
3798 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3799 data type of the watched expression is wider than what a hardware
3800 watchpoint on the target machine can handle. For example, some systems
3801 can only watch regions that are up to 4 bytes wide; on such systems you
3802 cannot set hardware watchpoints for an expression that yields a
3803 double-precision floating-point number (which is typically 8 bytes
3804 wide). As a work-around, it might be possible to break the large region
3805 into a series of smaller ones and watch them with separate watchpoints.
3807 If you set too many hardware watchpoints, @value{GDBN} might be unable
3808 to insert all of them when you resume the execution of your program.
3809 Since the precise number of active watchpoints is unknown until such
3810 time as the program is about to be resumed, @value{GDBN} might not be
3811 able to warn you about this when you set the watchpoints, and the
3812 warning will be printed only when the program is resumed:
3815 Hardware watchpoint @var{num}: Could not insert watchpoint
3819 If this happens, delete or disable some of the watchpoints.
3821 Watching complex expressions that reference many variables can also
3822 exhaust the resources available for hardware-assisted watchpoints.
3823 That's because @value{GDBN} needs to watch every variable in the
3824 expression with separately allocated resources.
3826 If you call a function interactively using @code{print} or @code{call},
3827 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3828 kind of breakpoint or the call completes.
3830 @value{GDBN} automatically deletes watchpoints that watch local
3831 (automatic) variables, or expressions that involve such variables, when
3832 they go out of scope, that is, when the execution leaves the block in
3833 which these variables were defined. In particular, when the program
3834 being debugged terminates, @emph{all} local variables go out of scope,
3835 and so only watchpoints that watch global variables remain set. If you
3836 rerun the program, you will need to set all such watchpoints again. One
3837 way of doing that would be to set a code breakpoint at the entry to the
3838 @code{main} function and when it breaks, set all the watchpoints.
3840 @cindex watchpoints and threads
3841 @cindex threads and watchpoints
3842 In multi-threaded programs, watchpoints will detect changes to the
3843 watched expression from every thread.
3846 @emph{Warning:} In multi-threaded programs, software watchpoints
3847 have only limited usefulness. If @value{GDBN} creates a software
3848 watchpoint, it can only watch the value of an expression @emph{in a
3849 single thread}. If you are confident that the expression can only
3850 change due to the current thread's activity (and if you are also
3851 confident that no other thread can become current), then you can use
3852 software watchpoints as usual. However, @value{GDBN} may not notice
3853 when a non-current thread's activity changes the expression. (Hardware
3854 watchpoints, in contrast, watch an expression in all threads.)
3857 @xref{set remote hardware-watchpoint-limit}.
3859 @node Set Catchpoints
3860 @subsection Setting Catchpoints
3861 @cindex catchpoints, setting
3862 @cindex exception handlers
3863 @cindex event handling
3865 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3866 kinds of program events, such as C@t{++} exceptions or the loading of a
3867 shared library. Use the @code{catch} command to set a catchpoint.
3871 @item catch @var{event}
3872 Stop when @var{event} occurs. @var{event} can be any of the following:
3875 @cindex stop on C@t{++} exceptions
3876 The throwing of a C@t{++} exception.
3879 The catching of a C@t{++} exception.
3882 @cindex Ada exception catching
3883 @cindex catch Ada exceptions
3884 An Ada exception being raised. If an exception name is specified
3885 at the end of the command (eg @code{catch exception Program_Error}),
3886 the debugger will stop only when this specific exception is raised.
3887 Otherwise, the debugger stops execution when any Ada exception is raised.
3889 When inserting an exception catchpoint on a user-defined exception whose
3890 name is identical to one of the exceptions defined by the language, the
3891 fully qualified name must be used as the exception name. Otherwise,
3892 @value{GDBN} will assume that it should stop on the pre-defined exception
3893 rather than the user-defined one. For instance, assuming an exception
3894 called @code{Constraint_Error} is defined in package @code{Pck}, then
3895 the command to use to catch such exceptions is @kbd{catch exception
3896 Pck.Constraint_Error}.
3898 @item exception unhandled
3899 An exception that was raised but is not handled by the program.
3902 A failed Ada assertion.
3905 @cindex break on fork/exec
3906 A call to @code{exec}. This is currently only available for HP-UX
3910 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3911 @cindex break on a system call.
3912 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3913 syscall is a mechanism for application programs to request a service
3914 from the operating system (OS) or one of the OS system services.
3915 @value{GDBN} can catch some or all of the syscalls issued by the
3916 debuggee, and show the related information for each syscall. If no
3917 argument is specified, calls to and returns from all system calls
3920 @var{name} can be any system call name that is valid for the
3921 underlying OS. Just what syscalls are valid depends on the OS. On
3922 GNU and Unix systems, you can find the full list of valid syscall
3923 names on @file{/usr/include/asm/unistd.h}.
3925 @c For MS-Windows, the syscall names and the corresponding numbers
3926 @c can be found, e.g., on this URL:
3927 @c http://www.metasploit.com/users/opcode/syscalls.html
3928 @c but we don't support Windows syscalls yet.
3930 Normally, @value{GDBN} knows in advance which syscalls are valid for
3931 each OS, so you can use the @value{GDBN} command-line completion
3932 facilities (@pxref{Completion,, command completion}) to list the
3935 You may also specify the system call numerically. A syscall's
3936 number is the value passed to the OS's syscall dispatcher to
3937 identify the requested service. When you specify the syscall by its
3938 name, @value{GDBN} uses its database of syscalls to convert the name
3939 into the corresponding numeric code, but using the number directly
3940 may be useful if @value{GDBN}'s database does not have the complete
3941 list of syscalls on your system (e.g., because @value{GDBN} lags
3942 behind the OS upgrades).
3944 The example below illustrates how this command works if you don't provide
3948 (@value{GDBP}) catch syscall
3949 Catchpoint 1 (syscall)
3951 Starting program: /tmp/catch-syscall
3953 Catchpoint 1 (call to syscall 'close'), \
3954 0xffffe424 in __kernel_vsyscall ()
3958 Catchpoint 1 (returned from syscall 'close'), \
3959 0xffffe424 in __kernel_vsyscall ()
3963 Here is an example of catching a system call by name:
3966 (@value{GDBP}) catch syscall chroot
3967 Catchpoint 1 (syscall 'chroot' [61])
3969 Starting program: /tmp/catch-syscall
3971 Catchpoint 1 (call to syscall 'chroot'), \
3972 0xffffe424 in __kernel_vsyscall ()
3976 Catchpoint 1 (returned from syscall 'chroot'), \
3977 0xffffe424 in __kernel_vsyscall ()
3981 An example of specifying a system call numerically. In the case
3982 below, the syscall number has a corresponding entry in the XML
3983 file, so @value{GDBN} finds its name and prints it:
3986 (@value{GDBP}) catch syscall 252
3987 Catchpoint 1 (syscall(s) 'exit_group')
3989 Starting program: /tmp/catch-syscall
3991 Catchpoint 1 (call to syscall 'exit_group'), \
3992 0xffffe424 in __kernel_vsyscall ()
3996 Program exited normally.
4000 However, there can be situations when there is no corresponding name
4001 in XML file for that syscall number. In this case, @value{GDBN} prints
4002 a warning message saying that it was not able to find the syscall name,
4003 but the catchpoint will be set anyway. See the example below:
4006 (@value{GDBP}) catch syscall 764
4007 warning: The number '764' does not represent a known syscall.
4008 Catchpoint 2 (syscall 764)
4012 If you configure @value{GDBN} using the @samp{--without-expat} option,
4013 it will not be able to display syscall names. Also, if your
4014 architecture does not have an XML file describing its system calls,
4015 you will not be able to see the syscall names. It is important to
4016 notice that these two features are used for accessing the syscall
4017 name database. In either case, you will see a warning like this:
4020 (@value{GDBP}) catch syscall
4021 warning: Could not open "syscalls/i386-linux.xml"
4022 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4023 GDB will not be able to display syscall names.
4024 Catchpoint 1 (syscall)
4028 Of course, the file name will change depending on your architecture and system.
4030 Still using the example above, you can also try to catch a syscall by its
4031 number. In this case, you would see something like:
4034 (@value{GDBP}) catch syscall 252
4035 Catchpoint 1 (syscall(s) 252)
4038 Again, in this case @value{GDBN} would not be able to display syscall's names.
4041 A call to @code{fork}. This is currently only available for HP-UX
4045 A call to @code{vfork}. This is currently only available for HP-UX
4050 @item tcatch @var{event}
4051 Set a catchpoint that is enabled only for one stop. The catchpoint is
4052 automatically deleted after the first time the event is caught.
4056 Use the @code{info break} command to list the current catchpoints.
4058 There are currently some limitations to C@t{++} exception handling
4059 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4063 If you call a function interactively, @value{GDBN} normally returns
4064 control to you when the function has finished executing. If the call
4065 raises an exception, however, the call may bypass the mechanism that
4066 returns control to you and cause your program either to abort or to
4067 simply continue running until it hits a breakpoint, catches a signal
4068 that @value{GDBN} is listening for, or exits. This is the case even if
4069 you set a catchpoint for the exception; catchpoints on exceptions are
4070 disabled within interactive calls.
4073 You cannot raise an exception interactively.
4076 You cannot install an exception handler interactively.
4079 @cindex raise exceptions
4080 Sometimes @code{catch} is not the best way to debug exception handling:
4081 if you need to know exactly where an exception is raised, it is better to
4082 stop @emph{before} the exception handler is called, since that way you
4083 can see the stack before any unwinding takes place. If you set a
4084 breakpoint in an exception handler instead, it may not be easy to find
4085 out where the exception was raised.
4087 To stop just before an exception handler is called, you need some
4088 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4089 raised by calling a library function named @code{__raise_exception}
4090 which has the following ANSI C interface:
4093 /* @var{addr} is where the exception identifier is stored.
4094 @var{id} is the exception identifier. */
4095 void __raise_exception (void **addr, void *id);
4099 To make the debugger catch all exceptions before any stack
4100 unwinding takes place, set a breakpoint on @code{__raise_exception}
4101 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4103 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4104 that depends on the value of @var{id}, you can stop your program when
4105 a specific exception is raised. You can use multiple conditional
4106 breakpoints to stop your program when any of a number of exceptions are
4111 @subsection Deleting Breakpoints
4113 @cindex clearing breakpoints, watchpoints, catchpoints
4114 @cindex deleting breakpoints, watchpoints, catchpoints
4115 It is often necessary to eliminate a breakpoint, watchpoint, or
4116 catchpoint once it has done its job and you no longer want your program
4117 to stop there. This is called @dfn{deleting} the breakpoint. A
4118 breakpoint that has been deleted no longer exists; it is forgotten.
4120 With the @code{clear} command you can delete breakpoints according to
4121 where they are in your program. With the @code{delete} command you can
4122 delete individual breakpoints, watchpoints, or catchpoints by specifying
4123 their breakpoint numbers.
4125 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4126 automatically ignores breakpoints on the first instruction to be executed
4127 when you continue execution without changing the execution address.
4132 Delete any breakpoints at the next instruction to be executed in the
4133 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4134 the innermost frame is selected, this is a good way to delete a
4135 breakpoint where your program just stopped.
4137 @item clear @var{location}
4138 Delete any breakpoints set at the specified @var{location}.
4139 @xref{Specify Location}, for the various forms of @var{location}; the
4140 most useful ones are listed below:
4143 @item clear @var{function}
4144 @itemx clear @var{filename}:@var{function}
4145 Delete any breakpoints set at entry to the named @var{function}.
4147 @item clear @var{linenum}
4148 @itemx clear @var{filename}:@var{linenum}
4149 Delete any breakpoints set at or within the code of the specified
4150 @var{linenum} of the specified @var{filename}.
4153 @cindex delete breakpoints
4155 @kindex d @r{(@code{delete})}
4156 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4157 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4158 ranges specified as arguments. If no argument is specified, delete all
4159 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4160 confirm off}). You can abbreviate this command as @code{d}.
4164 @subsection Disabling Breakpoints
4166 @cindex enable/disable a breakpoint
4167 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4168 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4169 it had been deleted, but remembers the information on the breakpoint so
4170 that you can @dfn{enable} it again later.
4172 You disable and enable breakpoints, watchpoints, and catchpoints with
4173 the @code{enable} and @code{disable} commands, optionally specifying
4174 one or more breakpoint numbers as arguments. Use @code{info break} to
4175 print a list of all breakpoints, watchpoints, and catchpoints if you
4176 do not know which numbers to use.
4178 Disabling and enabling a breakpoint that has multiple locations
4179 affects all of its locations.
4181 A breakpoint, watchpoint, or catchpoint can have any of four different
4182 states of enablement:
4186 Enabled. The breakpoint stops your program. A breakpoint set
4187 with the @code{break} command starts out in this state.
4189 Disabled. The breakpoint has no effect on your program.
4191 Enabled once. The breakpoint stops your program, but then becomes
4194 Enabled for deletion. The breakpoint stops your program, but
4195 immediately after it does so it is deleted permanently. A breakpoint
4196 set with the @code{tbreak} command starts out in this state.
4199 You can use the following commands to enable or disable breakpoints,
4200 watchpoints, and catchpoints:
4204 @kindex dis @r{(@code{disable})}
4205 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4206 Disable the specified breakpoints---or all breakpoints, if none are
4207 listed. A disabled breakpoint has no effect but is not forgotten. All
4208 options such as ignore-counts, conditions and commands are remembered in
4209 case the breakpoint is enabled again later. You may abbreviate
4210 @code{disable} as @code{dis}.
4213 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4214 Enable the specified breakpoints (or all defined breakpoints). They
4215 become effective once again in stopping your program.
4217 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4218 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4219 of these breakpoints immediately after stopping your program.
4221 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4222 Enable the specified breakpoints to work once, then die. @value{GDBN}
4223 deletes any of these breakpoints as soon as your program stops there.
4224 Breakpoints set by the @code{tbreak} command start out in this state.
4227 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4228 @c confusing: tbreak is also initially enabled.
4229 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4230 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4231 subsequently, they become disabled or enabled only when you use one of
4232 the commands above. (The command @code{until} can set and delete a
4233 breakpoint of its own, but it does not change the state of your other
4234 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4238 @subsection Break Conditions
4239 @cindex conditional breakpoints
4240 @cindex breakpoint conditions
4242 @c FIXME what is scope of break condition expr? Context where wanted?
4243 @c in particular for a watchpoint?
4244 The simplest sort of breakpoint breaks every time your program reaches a
4245 specified place. You can also specify a @dfn{condition} for a
4246 breakpoint. A condition is just a Boolean expression in your
4247 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4248 a condition evaluates the expression each time your program reaches it,
4249 and your program stops only if the condition is @emph{true}.
4251 This is the converse of using assertions for program validation; in that
4252 situation, you want to stop when the assertion is violated---that is,
4253 when the condition is false. In C, if you want to test an assertion expressed
4254 by the condition @var{assert}, you should set the condition
4255 @samp{! @var{assert}} on the appropriate breakpoint.
4257 Conditions are also accepted for watchpoints; you may not need them,
4258 since a watchpoint is inspecting the value of an expression anyhow---but
4259 it might be simpler, say, to just set a watchpoint on a variable name,
4260 and specify a condition that tests whether the new value is an interesting
4263 Break conditions can have side effects, and may even call functions in
4264 your program. This can be useful, for example, to activate functions
4265 that log program progress, or to use your own print functions to
4266 format special data structures. The effects are completely predictable
4267 unless there is another enabled breakpoint at the same address. (In
4268 that case, @value{GDBN} might see the other breakpoint first and stop your
4269 program without checking the condition of this one.) Note that
4270 breakpoint commands are usually more convenient and flexible than break
4272 purpose of performing side effects when a breakpoint is reached
4273 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4275 Break conditions can be specified when a breakpoint is set, by using
4276 @samp{if} in the arguments to the @code{break} command. @xref{Set
4277 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4278 with the @code{condition} command.
4280 You can also use the @code{if} keyword with the @code{watch} command.
4281 The @code{catch} command does not recognize the @code{if} keyword;
4282 @code{condition} is the only way to impose a further condition on a
4287 @item condition @var{bnum} @var{expression}
4288 Specify @var{expression} as the break condition for breakpoint,
4289 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4290 breakpoint @var{bnum} stops your program only if the value of
4291 @var{expression} is true (nonzero, in C). When you use
4292 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4293 syntactic correctness, and to determine whether symbols in it have
4294 referents in the context of your breakpoint. If @var{expression} uses
4295 symbols not referenced in the context of the breakpoint, @value{GDBN}
4296 prints an error message:
4299 No symbol "foo" in current context.
4304 not actually evaluate @var{expression} at the time the @code{condition}
4305 command (or a command that sets a breakpoint with a condition, like
4306 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4308 @item condition @var{bnum}
4309 Remove the condition from breakpoint number @var{bnum}. It becomes
4310 an ordinary unconditional breakpoint.
4313 @cindex ignore count (of breakpoint)
4314 A special case of a breakpoint condition is to stop only when the
4315 breakpoint has been reached a certain number of times. This is so
4316 useful that there is a special way to do it, using the @dfn{ignore
4317 count} of the breakpoint. Every breakpoint has an ignore count, which
4318 is an integer. Most of the time, the ignore count is zero, and
4319 therefore has no effect. But if your program reaches a breakpoint whose
4320 ignore count is positive, then instead of stopping, it just decrements
4321 the ignore count by one and continues. As a result, if the ignore count
4322 value is @var{n}, the breakpoint does not stop the next @var{n} times
4323 your program reaches it.
4327 @item ignore @var{bnum} @var{count}
4328 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4329 The next @var{count} times the breakpoint is reached, your program's
4330 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4333 To make the breakpoint stop the next time it is reached, specify
4336 When you use @code{continue} to resume execution of your program from a
4337 breakpoint, you can specify an ignore count directly as an argument to
4338 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4339 Stepping,,Continuing and Stepping}.
4341 If a breakpoint has a positive ignore count and a condition, the
4342 condition is not checked. Once the ignore count reaches zero,
4343 @value{GDBN} resumes checking the condition.
4345 You could achieve the effect of the ignore count with a condition such
4346 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4347 is decremented each time. @xref{Convenience Vars, ,Convenience
4351 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4354 @node Break Commands
4355 @subsection Breakpoint Command Lists
4357 @cindex breakpoint commands
4358 You can give any breakpoint (or watchpoint or catchpoint) a series of
4359 commands to execute when your program stops due to that breakpoint. For
4360 example, you might want to print the values of certain expressions, or
4361 enable other breakpoints.
4365 @kindex end@r{ (breakpoint commands)}
4366 @item commands @r{[}@var{range}@dots{}@r{]}
4367 @itemx @dots{} @var{command-list} @dots{}
4369 Specify a list of commands for the given breakpoints. The commands
4370 themselves appear on the following lines. Type a line containing just
4371 @code{end} to terminate the commands.
4373 To remove all commands from a breakpoint, type @code{commands} and
4374 follow it immediately with @code{end}; that is, give no commands.
4376 With no argument, @code{commands} refers to the last breakpoint,
4377 watchpoint, or catchpoint set (not to the breakpoint most recently
4378 encountered). If the most recent breakpoints were set with a single
4379 command, then the @code{commands} will apply to all the breakpoints
4380 set by that command. This applies to breakpoints set by
4381 @code{rbreak}, and also applies when a single @code{break} command
4382 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4386 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4387 disabled within a @var{command-list}.
4389 You can use breakpoint commands to start your program up again. Simply
4390 use the @code{continue} command, or @code{step}, or any other command
4391 that resumes execution.
4393 Any other commands in the command list, after a command that resumes
4394 execution, are ignored. This is because any time you resume execution
4395 (even with a simple @code{next} or @code{step}), you may encounter
4396 another breakpoint---which could have its own command list, leading to
4397 ambiguities about which list to execute.
4400 If the first command you specify in a command list is @code{silent}, the
4401 usual message about stopping at a breakpoint is not printed. This may
4402 be desirable for breakpoints that are to print a specific message and
4403 then continue. If none of the remaining commands print anything, you
4404 see no sign that the breakpoint was reached. @code{silent} is
4405 meaningful only at the beginning of a breakpoint command list.
4407 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4408 print precisely controlled output, and are often useful in silent
4409 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4411 For example, here is how you could use breakpoint commands to print the
4412 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4418 printf "x is %d\n",x
4423 One application for breakpoint commands is to compensate for one bug so
4424 you can test for another. Put a breakpoint just after the erroneous line
4425 of code, give it a condition to detect the case in which something
4426 erroneous has been done, and give it commands to assign correct values
4427 to any variables that need them. End with the @code{continue} command
4428 so that your program does not stop, and start with the @code{silent}
4429 command so that no output is produced. Here is an example:
4440 @node Save Breakpoints
4441 @subsection How to save breakpoints to a file
4443 To save breakpoint definitions to a file use the @w{@code{save
4444 breakpoints}} command.
4447 @kindex save breakpoints
4448 @cindex save breakpoints to a file for future sessions
4449 @item save breakpoints [@var{filename}]
4450 This command saves all current breakpoint definitions together with
4451 their commands and ignore counts, into a file @file{@var{filename}}
4452 suitable for use in a later debugging session. This includes all
4453 types of breakpoints (breakpoints, watchpoints, catchpoints,
4454 tracepoints). To read the saved breakpoint definitions, use the
4455 @code{source} command (@pxref{Command Files}). Note that watchpoints
4456 with expressions involving local variables may fail to be recreated
4457 because it may not be possible to access the context where the
4458 watchpoint is valid anymore. Because the saved breakpoint definitions
4459 are simply a sequence of @value{GDBN} commands that recreate the
4460 breakpoints, you can edit the file in your favorite editing program,
4461 and remove the breakpoint definitions you're not interested in, or
4462 that can no longer be recreated.
4465 @c @ifclear BARETARGET
4466 @node Error in Breakpoints
4467 @subsection ``Cannot insert breakpoints''
4469 If you request too many active hardware-assisted breakpoints and
4470 watchpoints, you will see this error message:
4472 @c FIXME: the precise wording of this message may change; the relevant
4473 @c source change is not committed yet (Sep 3, 1999).
4475 Stopped; cannot insert breakpoints.
4476 You may have requested too many hardware breakpoints and watchpoints.
4480 This message is printed when you attempt to resume the program, since
4481 only then @value{GDBN} knows exactly how many hardware breakpoints and
4482 watchpoints it needs to insert.
4484 When this message is printed, you need to disable or remove some of the
4485 hardware-assisted breakpoints and watchpoints, and then continue.
4487 @node Breakpoint-related Warnings
4488 @subsection ``Breakpoint address adjusted...''
4489 @cindex breakpoint address adjusted
4491 Some processor architectures place constraints on the addresses at
4492 which breakpoints may be placed. For architectures thus constrained,
4493 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4494 with the constraints dictated by the architecture.
4496 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4497 a VLIW architecture in which a number of RISC-like instructions may be
4498 bundled together for parallel execution. The FR-V architecture
4499 constrains the location of a breakpoint instruction within such a
4500 bundle to the instruction with the lowest address. @value{GDBN}
4501 honors this constraint by adjusting a breakpoint's address to the
4502 first in the bundle.
4504 It is not uncommon for optimized code to have bundles which contain
4505 instructions from different source statements, thus it may happen that
4506 a breakpoint's address will be adjusted from one source statement to
4507 another. Since this adjustment may significantly alter @value{GDBN}'s
4508 breakpoint related behavior from what the user expects, a warning is
4509 printed when the breakpoint is first set and also when the breakpoint
4512 A warning like the one below is printed when setting a breakpoint
4513 that's been subject to address adjustment:
4516 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4519 Such warnings are printed both for user settable and @value{GDBN}'s
4520 internal breakpoints. If you see one of these warnings, you should
4521 verify that a breakpoint set at the adjusted address will have the
4522 desired affect. If not, the breakpoint in question may be removed and
4523 other breakpoints may be set which will have the desired behavior.
4524 E.g., it may be sufficient to place the breakpoint at a later
4525 instruction. A conditional breakpoint may also be useful in some
4526 cases to prevent the breakpoint from triggering too often.
4528 @value{GDBN} will also issue a warning when stopping at one of these
4529 adjusted breakpoints:
4532 warning: Breakpoint 1 address previously adjusted from 0x00010414
4536 When this warning is encountered, it may be too late to take remedial
4537 action except in cases where the breakpoint is hit earlier or more
4538 frequently than expected.
4540 @node Continuing and Stepping
4541 @section Continuing and Stepping
4545 @cindex resuming execution
4546 @dfn{Continuing} means resuming program execution until your program
4547 completes normally. In contrast, @dfn{stepping} means executing just
4548 one more ``step'' of your program, where ``step'' may mean either one
4549 line of source code, or one machine instruction (depending on what
4550 particular command you use). Either when continuing or when stepping,
4551 your program may stop even sooner, due to a breakpoint or a signal. (If
4552 it stops due to a signal, you may want to use @code{handle}, or use
4553 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4557 @kindex c @r{(@code{continue})}
4558 @kindex fg @r{(resume foreground execution)}
4559 @item continue @r{[}@var{ignore-count}@r{]}
4560 @itemx c @r{[}@var{ignore-count}@r{]}
4561 @itemx fg @r{[}@var{ignore-count}@r{]}
4562 Resume program execution, at the address where your program last stopped;
4563 any breakpoints set at that address are bypassed. The optional argument
4564 @var{ignore-count} allows you to specify a further number of times to
4565 ignore a breakpoint at this location; its effect is like that of
4566 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4568 The argument @var{ignore-count} is meaningful only when your program
4569 stopped due to a breakpoint. At other times, the argument to
4570 @code{continue} is ignored.
4572 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4573 debugged program is deemed to be the foreground program) are provided
4574 purely for convenience, and have exactly the same behavior as
4578 To resume execution at a different place, you can use @code{return}
4579 (@pxref{Returning, ,Returning from a Function}) to go back to the
4580 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4581 Different Address}) to go to an arbitrary location in your program.
4583 A typical technique for using stepping is to set a breakpoint
4584 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4585 beginning of the function or the section of your program where a problem
4586 is believed to lie, run your program until it stops at that breakpoint,
4587 and then step through the suspect area, examining the variables that are
4588 interesting, until you see the problem happen.
4592 @kindex s @r{(@code{step})}
4594 Continue running your program until control reaches a different source
4595 line, then stop it and return control to @value{GDBN}. This command is
4596 abbreviated @code{s}.
4599 @c "without debugging information" is imprecise; actually "without line
4600 @c numbers in the debugging information". (gcc -g1 has debugging info but
4601 @c not line numbers). But it seems complex to try to make that
4602 @c distinction here.
4603 @emph{Warning:} If you use the @code{step} command while control is
4604 within a function that was compiled without debugging information,
4605 execution proceeds until control reaches a function that does have
4606 debugging information. Likewise, it will not step into a function which
4607 is compiled without debugging information. To step through functions
4608 without debugging information, use the @code{stepi} command, described
4612 The @code{step} command only stops at the first instruction of a source
4613 line. This prevents the multiple stops that could otherwise occur in
4614 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4615 to stop if a function that has debugging information is called within
4616 the line. In other words, @code{step} @emph{steps inside} any functions
4617 called within the line.
4619 Also, the @code{step} command only enters a function if there is line
4620 number information for the function. Otherwise it acts like the
4621 @code{next} command. This avoids problems when using @code{cc -gl}
4622 on MIPS machines. Previously, @code{step} entered subroutines if there
4623 was any debugging information about the routine.
4625 @item step @var{count}
4626 Continue running as in @code{step}, but do so @var{count} times. If a
4627 breakpoint is reached, or a signal not related to stepping occurs before
4628 @var{count} steps, stepping stops right away.
4631 @kindex n @r{(@code{next})}
4632 @item next @r{[}@var{count}@r{]}
4633 Continue to the next source line in the current (innermost) stack frame.
4634 This is similar to @code{step}, but function calls that appear within
4635 the line of code are executed without stopping. Execution stops when
4636 control reaches a different line of code at the original stack level
4637 that was executing when you gave the @code{next} command. This command
4638 is abbreviated @code{n}.
4640 An argument @var{count} is a repeat count, as for @code{step}.
4643 @c FIX ME!! Do we delete this, or is there a way it fits in with
4644 @c the following paragraph? --- Vctoria
4646 @c @code{next} within a function that lacks debugging information acts like
4647 @c @code{step}, but any function calls appearing within the code of the
4648 @c function are executed without stopping.
4650 The @code{next} command only stops at the first instruction of a
4651 source line. This prevents multiple stops that could otherwise occur in
4652 @code{switch} statements, @code{for} loops, etc.
4654 @kindex set step-mode
4656 @cindex functions without line info, and stepping
4657 @cindex stepping into functions with no line info
4658 @itemx set step-mode on
4659 The @code{set step-mode on} command causes the @code{step} command to
4660 stop at the first instruction of a function which contains no debug line
4661 information rather than stepping over it.
4663 This is useful in cases where you may be interested in inspecting the
4664 machine instructions of a function which has no symbolic info and do not
4665 want @value{GDBN} to automatically skip over this function.
4667 @item set step-mode off
4668 Causes the @code{step} command to step over any functions which contains no
4669 debug information. This is the default.
4671 @item show step-mode
4672 Show whether @value{GDBN} will stop in or step over functions without
4673 source line debug information.
4676 @kindex fin @r{(@code{finish})}
4678 Continue running until just after function in the selected stack frame
4679 returns. Print the returned value (if any). This command can be
4680 abbreviated as @code{fin}.
4682 Contrast this with the @code{return} command (@pxref{Returning,
4683 ,Returning from a Function}).
4686 @kindex u @r{(@code{until})}
4687 @cindex run until specified location
4690 Continue running until a source line past the current line, in the
4691 current stack frame, is reached. This command is used to avoid single
4692 stepping through a loop more than once. It is like the @code{next}
4693 command, except that when @code{until} encounters a jump, it
4694 automatically continues execution until the program counter is greater
4695 than the address of the jump.
4697 This means that when you reach the end of a loop after single stepping
4698 though it, @code{until} makes your program continue execution until it
4699 exits the loop. In contrast, a @code{next} command at the end of a loop
4700 simply steps back to the beginning of the loop, which forces you to step
4701 through the next iteration.
4703 @code{until} always stops your program if it attempts to exit the current
4706 @code{until} may produce somewhat counterintuitive results if the order
4707 of machine code does not match the order of the source lines. For
4708 example, in the following excerpt from a debugging session, the @code{f}
4709 (@code{frame}) command shows that execution is stopped at line
4710 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4714 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4716 (@value{GDBP}) until
4717 195 for ( ; argc > 0; NEXTARG) @{
4720 This happened because, for execution efficiency, the compiler had
4721 generated code for the loop closure test at the end, rather than the
4722 start, of the loop---even though the test in a C @code{for}-loop is
4723 written before the body of the loop. The @code{until} command appeared
4724 to step back to the beginning of the loop when it advanced to this
4725 expression; however, it has not really gone to an earlier
4726 statement---not in terms of the actual machine code.
4728 @code{until} with no argument works by means of single
4729 instruction stepping, and hence is slower than @code{until} with an
4732 @item until @var{location}
4733 @itemx u @var{location}
4734 Continue running your program until either the specified location is
4735 reached, or the current stack frame returns. @var{location} is any of
4736 the forms described in @ref{Specify Location}.
4737 This form of the command uses temporary breakpoints, and
4738 hence is quicker than @code{until} without an argument. The specified
4739 location is actually reached only if it is in the current frame. This
4740 implies that @code{until} can be used to skip over recursive function
4741 invocations. For instance in the code below, if the current location is
4742 line @code{96}, issuing @code{until 99} will execute the program up to
4743 line @code{99} in the same invocation of factorial, i.e., after the inner
4744 invocations have returned.
4747 94 int factorial (int value)
4749 96 if (value > 1) @{
4750 97 value *= factorial (value - 1);
4757 @kindex advance @var{location}
4758 @itemx advance @var{location}
4759 Continue running the program up to the given @var{location}. An argument is
4760 required, which should be of one of the forms described in
4761 @ref{Specify Location}.
4762 Execution will also stop upon exit from the current stack
4763 frame. This command is similar to @code{until}, but @code{advance} will
4764 not skip over recursive function calls, and the target location doesn't
4765 have to be in the same frame as the current one.
4769 @kindex si @r{(@code{stepi})}
4771 @itemx stepi @var{arg}
4773 Execute one machine instruction, then stop and return to the debugger.
4775 It is often useful to do @samp{display/i $pc} when stepping by machine
4776 instructions. This makes @value{GDBN} automatically display the next
4777 instruction to be executed, each time your program stops. @xref{Auto
4778 Display,, Automatic Display}.
4780 An argument is a repeat count, as in @code{step}.
4784 @kindex ni @r{(@code{nexti})}
4786 @itemx nexti @var{arg}
4788 Execute one machine instruction, but if it is a function call,
4789 proceed until the function returns.
4791 An argument is a repeat count, as in @code{next}.
4798 A signal is an asynchronous event that can happen in a program. The
4799 operating system defines the possible kinds of signals, and gives each
4800 kind a name and a number. For example, in Unix @code{SIGINT} is the
4801 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4802 @code{SIGSEGV} is the signal a program gets from referencing a place in
4803 memory far away from all the areas in use; @code{SIGALRM} occurs when
4804 the alarm clock timer goes off (which happens only if your program has
4805 requested an alarm).
4807 @cindex fatal signals
4808 Some signals, including @code{SIGALRM}, are a normal part of the
4809 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4810 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4811 program has not specified in advance some other way to handle the signal.
4812 @code{SIGINT} does not indicate an error in your program, but it is normally
4813 fatal so it can carry out the purpose of the interrupt: to kill the program.
4815 @value{GDBN} has the ability to detect any occurrence of a signal in your
4816 program. You can tell @value{GDBN} in advance what to do for each kind of
4819 @cindex handling signals
4820 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4821 @code{SIGALRM} be silently passed to your program
4822 (so as not to interfere with their role in the program's functioning)
4823 but to stop your program immediately whenever an error signal happens.
4824 You can change these settings with the @code{handle} command.
4827 @kindex info signals
4831 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4832 handle each one. You can use this to see the signal numbers of all
4833 the defined types of signals.
4835 @item info signals @var{sig}
4836 Similar, but print information only about the specified signal number.
4838 @code{info handle} is an alias for @code{info signals}.
4841 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4842 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4843 can be the number of a signal or its name (with or without the
4844 @samp{SIG} at the beginning); a list of signal numbers of the form
4845 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4846 known signals. Optional arguments @var{keywords}, described below,
4847 say what change to make.
4851 The keywords allowed by the @code{handle} command can be abbreviated.
4852 Their full names are:
4856 @value{GDBN} should not stop your program when this signal happens. It may
4857 still print a message telling you that the signal has come in.
4860 @value{GDBN} should stop your program when this signal happens. This implies
4861 the @code{print} keyword as well.
4864 @value{GDBN} should print a message when this signal happens.
4867 @value{GDBN} should not mention the occurrence of the signal at all. This
4868 implies the @code{nostop} keyword as well.
4872 @value{GDBN} should allow your program to see this signal; your program
4873 can handle the signal, or else it may terminate if the signal is fatal
4874 and not handled. @code{pass} and @code{noignore} are synonyms.
4878 @value{GDBN} should not allow your program to see this signal.
4879 @code{nopass} and @code{ignore} are synonyms.
4883 When a signal stops your program, the signal is not visible to the
4885 continue. Your program sees the signal then, if @code{pass} is in
4886 effect for the signal in question @emph{at that time}. In other words,
4887 after @value{GDBN} reports a signal, you can use the @code{handle}
4888 command with @code{pass} or @code{nopass} to control whether your
4889 program sees that signal when you continue.
4891 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4892 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4893 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4896 You can also use the @code{signal} command to prevent your program from
4897 seeing a signal, or cause it to see a signal it normally would not see,
4898 or to give it any signal at any time. For example, if your program stopped
4899 due to some sort of memory reference error, you might store correct
4900 values into the erroneous variables and continue, hoping to see more
4901 execution; but your program would probably terminate immediately as
4902 a result of the fatal signal once it saw the signal. To prevent this,
4903 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4906 @cindex extra signal information
4907 @anchor{extra signal information}
4909 On some targets, @value{GDBN} can inspect extra signal information
4910 associated with the intercepted signal, before it is actually
4911 delivered to the program being debugged. This information is exported
4912 by the convenience variable @code{$_siginfo}, and consists of data
4913 that is passed by the kernel to the signal handler at the time of the
4914 receipt of a signal. The data type of the information itself is
4915 target dependent. You can see the data type using the @code{ptype
4916 $_siginfo} command. On Unix systems, it typically corresponds to the
4917 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4920 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4921 referenced address that raised a segmentation fault.
4925 (@value{GDBP}) continue
4926 Program received signal SIGSEGV, Segmentation fault.
4927 0x0000000000400766 in main ()
4929 (@value{GDBP}) ptype $_siginfo
4936 struct @{...@} _kill;
4937 struct @{...@} _timer;
4939 struct @{...@} _sigchld;
4940 struct @{...@} _sigfault;
4941 struct @{...@} _sigpoll;
4944 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4948 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4949 $1 = (void *) 0x7ffff7ff7000
4953 Depending on target support, @code{$_siginfo} may also be writable.
4956 @section Stopping and Starting Multi-thread Programs
4958 @cindex stopped threads
4959 @cindex threads, stopped
4961 @cindex continuing threads
4962 @cindex threads, continuing
4964 @value{GDBN} supports debugging programs with multiple threads
4965 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4966 are two modes of controlling execution of your program within the
4967 debugger. In the default mode, referred to as @dfn{all-stop mode},
4968 when any thread in your program stops (for example, at a breakpoint
4969 or while being stepped), all other threads in the program are also stopped by
4970 @value{GDBN}. On some targets, @value{GDBN} also supports
4971 @dfn{non-stop mode}, in which other threads can continue to run freely while
4972 you examine the stopped thread in the debugger.
4975 * All-Stop Mode:: All threads stop when GDB takes control
4976 * Non-Stop Mode:: Other threads continue to execute
4977 * Background Execution:: Running your program asynchronously
4978 * Thread-Specific Breakpoints:: Controlling breakpoints
4979 * Interrupted System Calls:: GDB may interfere with system calls
4980 * Observer Mode:: GDB does not alter program behavior
4984 @subsection All-Stop Mode
4986 @cindex all-stop mode
4988 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4989 @emph{all} threads of execution stop, not just the current thread. This
4990 allows you to examine the overall state of the program, including
4991 switching between threads, without worrying that things may change
4994 Conversely, whenever you restart the program, @emph{all} threads start
4995 executing. @emph{This is true even when single-stepping} with commands
4996 like @code{step} or @code{next}.
4998 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4999 Since thread scheduling is up to your debugging target's operating
5000 system (not controlled by @value{GDBN}), other threads may
5001 execute more than one statement while the current thread completes a
5002 single step. Moreover, in general other threads stop in the middle of a
5003 statement, rather than at a clean statement boundary, when the program
5006 You might even find your program stopped in another thread after
5007 continuing or even single-stepping. This happens whenever some other
5008 thread runs into a breakpoint, a signal, or an exception before the
5009 first thread completes whatever you requested.
5011 @cindex automatic thread selection
5012 @cindex switching threads automatically
5013 @cindex threads, automatic switching
5014 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5015 signal, it automatically selects the thread where that breakpoint or
5016 signal happened. @value{GDBN} alerts you to the context switch with a
5017 message such as @samp{[Switching to Thread @var{n}]} to identify the
5020 On some OSes, you can modify @value{GDBN}'s default behavior by
5021 locking the OS scheduler to allow only a single thread to run.
5024 @item set scheduler-locking @var{mode}
5025 @cindex scheduler locking mode
5026 @cindex lock scheduler
5027 Set the scheduler locking mode. If it is @code{off}, then there is no
5028 locking and any thread may run at any time. If @code{on}, then only the
5029 current thread may run when the inferior is resumed. The @code{step}
5030 mode optimizes for single-stepping; it prevents other threads
5031 from preempting the current thread while you are stepping, so that
5032 the focus of debugging does not change unexpectedly.
5033 Other threads only rarely (or never) get a chance to run
5034 when you step. They are more likely to run when you @samp{next} over a
5035 function call, and they are completely free to run when you use commands
5036 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5037 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5038 the current thread away from the thread that you are debugging.
5040 @item show scheduler-locking
5041 Display the current scheduler locking mode.
5044 @cindex resume threads of multiple processes simultaneously
5045 By default, when you issue one of the execution commands such as
5046 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5047 threads of the current inferior to run. For example, if @value{GDBN}
5048 is attached to two inferiors, each with two threads, the
5049 @code{continue} command resumes only the two threads of the current
5050 inferior. This is useful, for example, when you debug a program that
5051 forks and you want to hold the parent stopped (so that, for instance,
5052 it doesn't run to exit), while you debug the child. In other
5053 situations, you may not be interested in inspecting the current state
5054 of any of the processes @value{GDBN} is attached to, and you may want
5055 to resume them all until some breakpoint is hit. In the latter case,
5056 you can instruct @value{GDBN} to allow all threads of all the
5057 inferiors to run with the @w{@code{set schedule-multiple}} command.
5060 @kindex set schedule-multiple
5061 @item set schedule-multiple
5062 Set the mode for allowing threads of multiple processes to be resumed
5063 when an execution command is issued. When @code{on}, all threads of
5064 all processes are allowed to run. When @code{off}, only the threads
5065 of the current process are resumed. The default is @code{off}. The
5066 @code{scheduler-locking} mode takes precedence when set to @code{on},
5067 or while you are stepping and set to @code{step}.
5069 @item show schedule-multiple
5070 Display the current mode for resuming the execution of threads of
5075 @subsection Non-Stop Mode
5077 @cindex non-stop mode
5079 @c This section is really only a place-holder, and needs to be expanded
5080 @c with more details.
5082 For some multi-threaded targets, @value{GDBN} supports an optional
5083 mode of operation in which you can examine stopped program threads in
5084 the debugger while other threads continue to execute freely. This
5085 minimizes intrusion when debugging live systems, such as programs
5086 where some threads have real-time constraints or must continue to
5087 respond to external events. This is referred to as @dfn{non-stop} mode.
5089 In non-stop mode, when a thread stops to report a debugging event,
5090 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5091 threads as well, in contrast to the all-stop mode behavior. Additionally,
5092 execution commands such as @code{continue} and @code{step} apply by default
5093 only to the current thread in non-stop mode, rather than all threads as
5094 in all-stop mode. This allows you to control threads explicitly in
5095 ways that are not possible in all-stop mode --- for example, stepping
5096 one thread while allowing others to run freely, stepping
5097 one thread while holding all others stopped, or stepping several threads
5098 independently and simultaneously.
5100 To enter non-stop mode, use this sequence of commands before you run
5101 or attach to your program:
5104 # Enable the async interface.
5107 # If using the CLI, pagination breaks non-stop.
5110 # Finally, turn it on!
5114 You can use these commands to manipulate the non-stop mode setting:
5117 @kindex set non-stop
5118 @item set non-stop on
5119 Enable selection of non-stop mode.
5120 @item set non-stop off
5121 Disable selection of non-stop mode.
5122 @kindex show non-stop
5124 Show the current non-stop enablement setting.
5127 Note these commands only reflect whether non-stop mode is enabled,
5128 not whether the currently-executing program is being run in non-stop mode.
5129 In particular, the @code{set non-stop} preference is only consulted when
5130 @value{GDBN} starts or connects to the target program, and it is generally
5131 not possible to switch modes once debugging has started. Furthermore,
5132 since not all targets support non-stop mode, even when you have enabled
5133 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5136 In non-stop mode, all execution commands apply only to the current thread
5137 by default. That is, @code{continue} only continues one thread.
5138 To continue all threads, issue @code{continue -a} or @code{c -a}.
5140 You can use @value{GDBN}'s background execution commands
5141 (@pxref{Background Execution}) to run some threads in the background
5142 while you continue to examine or step others from @value{GDBN}.
5143 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5144 always executed asynchronously in non-stop mode.
5146 Suspending execution is done with the @code{interrupt} command when
5147 running in the background, or @kbd{Ctrl-c} during foreground execution.
5148 In all-stop mode, this stops the whole process;
5149 but in non-stop mode the interrupt applies only to the current thread.
5150 To stop the whole program, use @code{interrupt -a}.
5152 Other execution commands do not currently support the @code{-a} option.
5154 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5155 that thread current, as it does in all-stop mode. This is because the
5156 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5157 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5158 changed to a different thread just as you entered a command to operate on the
5159 previously current thread.
5161 @node Background Execution
5162 @subsection Background Execution
5164 @cindex foreground execution
5165 @cindex background execution
5166 @cindex asynchronous execution
5167 @cindex execution, foreground, background and asynchronous
5169 @value{GDBN}'s execution commands have two variants: the normal
5170 foreground (synchronous) behavior, and a background
5171 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5172 the program to report that some thread has stopped before prompting for
5173 another command. In background execution, @value{GDBN} immediately gives
5174 a command prompt so that you can issue other commands while your program runs.
5176 You need to explicitly enable asynchronous mode before you can use
5177 background execution commands. You can use these commands to
5178 manipulate the asynchronous mode setting:
5181 @kindex set target-async
5182 @item set target-async on
5183 Enable asynchronous mode.
5184 @item set target-async off
5185 Disable asynchronous mode.
5186 @kindex show target-async
5187 @item show target-async
5188 Show the current target-async setting.
5191 If the target doesn't support async mode, @value{GDBN} issues an error
5192 message if you attempt to use the background execution commands.
5194 To specify background execution, add a @code{&} to the command. For example,
5195 the background form of the @code{continue} command is @code{continue&}, or
5196 just @code{c&}. The execution commands that accept background execution
5202 @xref{Starting, , Starting your Program}.
5206 @xref{Attach, , Debugging an Already-running Process}.
5210 @xref{Continuing and Stepping, step}.
5214 @xref{Continuing and Stepping, stepi}.
5218 @xref{Continuing and Stepping, next}.
5222 @xref{Continuing and Stepping, nexti}.
5226 @xref{Continuing and Stepping, continue}.
5230 @xref{Continuing and Stepping, finish}.
5234 @xref{Continuing and Stepping, until}.
5238 Background execution is especially useful in conjunction with non-stop
5239 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5240 However, you can also use these commands in the normal all-stop mode with
5241 the restriction that you cannot issue another execution command until the
5242 previous one finishes. Examples of commands that are valid in all-stop
5243 mode while the program is running include @code{help} and @code{info break}.
5245 You can interrupt your program while it is running in the background by
5246 using the @code{interrupt} command.
5253 Suspend execution of the running program. In all-stop mode,
5254 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5255 only the current thread. To stop the whole program in non-stop mode,
5256 use @code{interrupt -a}.
5259 @node Thread-Specific Breakpoints
5260 @subsection Thread-Specific Breakpoints
5262 When your program has multiple threads (@pxref{Threads,, Debugging
5263 Programs with Multiple Threads}), you can choose whether to set
5264 breakpoints on all threads, or on a particular thread.
5267 @cindex breakpoints and threads
5268 @cindex thread breakpoints
5269 @kindex break @dots{} thread @var{threadno}
5270 @item break @var{linespec} thread @var{threadno}
5271 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5272 @var{linespec} specifies source lines; there are several ways of
5273 writing them (@pxref{Specify Location}), but the effect is always to
5274 specify some source line.
5276 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5277 to specify that you only want @value{GDBN} to stop the program when a
5278 particular thread reaches this breakpoint. @var{threadno} is one of the
5279 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5280 column of the @samp{info threads} display.
5282 If you do not specify @samp{thread @var{threadno}} when you set a
5283 breakpoint, the breakpoint applies to @emph{all} threads of your
5286 You can use the @code{thread} qualifier on conditional breakpoints as
5287 well; in this case, place @samp{thread @var{threadno}} before or
5288 after the breakpoint condition, like this:
5291 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5296 @node Interrupted System Calls
5297 @subsection Interrupted System Calls
5299 @cindex thread breakpoints and system calls
5300 @cindex system calls and thread breakpoints
5301 @cindex premature return from system calls
5302 There is an unfortunate side effect when using @value{GDBN} to debug
5303 multi-threaded programs. If one thread stops for a
5304 breakpoint, or for some other reason, and another thread is blocked in a
5305 system call, then the system call may return prematurely. This is a
5306 consequence of the interaction between multiple threads and the signals
5307 that @value{GDBN} uses to implement breakpoints and other events that
5310 To handle this problem, your program should check the return value of
5311 each system call and react appropriately. This is good programming
5314 For example, do not write code like this:
5320 The call to @code{sleep} will return early if a different thread stops
5321 at a breakpoint or for some other reason.
5323 Instead, write this:
5328 unslept = sleep (unslept);
5331 A system call is allowed to return early, so the system is still
5332 conforming to its specification. But @value{GDBN} does cause your
5333 multi-threaded program to behave differently than it would without
5336 Also, @value{GDBN} uses internal breakpoints in the thread library to
5337 monitor certain events such as thread creation and thread destruction.
5338 When such an event happens, a system call in another thread may return
5339 prematurely, even though your program does not appear to stop.
5342 @subsection Observer Mode
5344 If you want to build on non-stop mode and observe program behavior
5345 without any chance of disruption by @value{GDBN}, you can set
5346 variables to disable all of the debugger's attempts to modify state,
5347 whether by writing memory, inserting breakpoints, etc. These operate
5348 at a low level, intercepting operations from all commands.
5350 When all of these are set to @code{off}, then @value{GDBN} is said to
5351 be @dfn{observer mode}. As a convenience, the variable
5352 @code{observer} can be set to disable these, plus enable non-stop
5355 Note that @value{GDBN} will not prevent you from making nonsensical
5356 combinations of these settings. For instance, if you have enabled
5357 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5358 then breakpoints that work by writing trap instructions into the code
5359 stream will still not be able to be placed.
5364 @item set observer on
5365 @itemx set observer off
5366 When set to @code{on}, this disables all the permission variables
5367 below (except for @code{insert-fast-tracepoints}), plus enables
5368 non-stop debugging. Setting this to @code{off} switches back to
5369 normal debugging, though remaining in non-stop mode.
5372 Show whether observer mode is on or off.
5374 @kindex may-write-registers
5375 @item set may-write-registers on
5376 @itemx set may-write-registers off
5377 This controls whether @value{GDBN} will attempt to alter the values of
5378 registers, such as with assignment expressions in @code{print}, or the
5379 @code{jump} command. It defaults to @code{on}.
5381 @item show may-write-registers
5382 Show the current permission to write registers.
5384 @kindex may-write-memory
5385 @item set may-write-memory on
5386 @itemx set may-write-memory off
5387 This controls whether @value{GDBN} will attempt to alter the contents
5388 of memory, such as with assignment expressions in @code{print}. It
5389 defaults to @code{on}.
5391 @item show may-write-memory
5392 Show the current permission to write memory.
5394 @kindex may-insert-breakpoints
5395 @item set may-insert-breakpoints on
5396 @itemx set may-insert-breakpoints off
5397 This controls whether @value{GDBN} will attempt to insert breakpoints.
5398 This affects all breakpoints, including internal breakpoints defined
5399 by @value{GDBN}. It defaults to @code{on}.
5401 @item show may-insert-breakpoints
5402 Show the current permission to insert breakpoints.
5404 @kindex may-insert-tracepoints
5405 @item set may-insert-tracepoints on
5406 @itemx set may-insert-tracepoints off
5407 This controls whether @value{GDBN} will attempt to insert (regular)
5408 tracepoints at the beginning of a tracing experiment. It affects only
5409 non-fast tracepoints, fast tracepoints being under the control of
5410 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5412 @item show may-insert-tracepoints
5413 Show the current permission to insert tracepoints.
5415 @kindex may-insert-fast-tracepoints
5416 @item set may-insert-fast-tracepoints on
5417 @itemx set may-insert-fast-tracepoints off
5418 This controls whether @value{GDBN} will attempt to insert fast
5419 tracepoints at the beginning of a tracing experiment. It affects only
5420 fast tracepoints, regular (non-fast) tracepoints being under the
5421 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5423 @item show may-insert-fast-tracepoints
5424 Show the current permission to insert fast tracepoints.
5426 @kindex may-interrupt
5427 @item set may-interrupt on
5428 @itemx set may-interrupt off
5429 This controls whether @value{GDBN} will attempt to interrupt or stop
5430 program execution. When this variable is @code{off}, the
5431 @code{interrupt} command will have no effect, nor will
5432 @kbd{Ctrl-c}. It defaults to @code{on}.
5434 @item show may-interrupt
5435 Show the current permission to interrupt or stop the program.
5439 @node Reverse Execution
5440 @chapter Running programs backward
5441 @cindex reverse execution
5442 @cindex running programs backward
5444 When you are debugging a program, it is not unusual to realize that
5445 you have gone too far, and some event of interest has already happened.
5446 If the target environment supports it, @value{GDBN} can allow you to
5447 ``rewind'' the program by running it backward.
5449 A target environment that supports reverse execution should be able
5450 to ``undo'' the changes in machine state that have taken place as the
5451 program was executing normally. Variables, registers etc.@: should
5452 revert to their previous values. Obviously this requires a great
5453 deal of sophistication on the part of the target environment; not
5454 all target environments can support reverse execution.
5456 When a program is executed in reverse, the instructions that
5457 have most recently been executed are ``un-executed'', in reverse
5458 order. The program counter runs backward, following the previous
5459 thread of execution in reverse. As each instruction is ``un-executed'',
5460 the values of memory and/or registers that were changed by that
5461 instruction are reverted to their previous states. After executing
5462 a piece of source code in reverse, all side effects of that code
5463 should be ``undone'', and all variables should be returned to their
5464 prior values@footnote{
5465 Note that some side effects are easier to undo than others. For instance,
5466 memory and registers are relatively easy, but device I/O is hard. Some
5467 targets may be able undo things like device I/O, and some may not.
5469 The contract between @value{GDBN} and the reverse executing target
5470 requires only that the target do something reasonable when
5471 @value{GDBN} tells it to execute backwards, and then report the
5472 results back to @value{GDBN}. Whatever the target reports back to
5473 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5474 assumes that the memory and registers that the target reports are in a
5475 consistant state, but @value{GDBN} accepts whatever it is given.
5478 If you are debugging in a target environment that supports
5479 reverse execution, @value{GDBN} provides the following commands.
5482 @kindex reverse-continue
5483 @kindex rc @r{(@code{reverse-continue})}
5484 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5485 @itemx rc @r{[}@var{ignore-count}@r{]}
5486 Beginning at the point where your program last stopped, start executing
5487 in reverse. Reverse execution will stop for breakpoints and synchronous
5488 exceptions (signals), just like normal execution. Behavior of
5489 asynchronous signals depends on the target environment.
5491 @kindex reverse-step
5492 @kindex rs @r{(@code{step})}
5493 @item reverse-step @r{[}@var{count}@r{]}
5494 Run the program backward until control reaches the start of a
5495 different source line; then stop it, and return control to @value{GDBN}.
5497 Like the @code{step} command, @code{reverse-step} will only stop
5498 at the beginning of a source line. It ``un-executes'' the previously
5499 executed source line. If the previous source line included calls to
5500 debuggable functions, @code{reverse-step} will step (backward) into
5501 the called function, stopping at the beginning of the @emph{last}
5502 statement in the called function (typically a return statement).
5504 Also, as with the @code{step} command, if non-debuggable functions are
5505 called, @code{reverse-step} will run thru them backward without stopping.
5507 @kindex reverse-stepi
5508 @kindex rsi @r{(@code{reverse-stepi})}
5509 @item reverse-stepi @r{[}@var{count}@r{]}
5510 Reverse-execute one machine instruction. Note that the instruction
5511 to be reverse-executed is @emph{not} the one pointed to by the program
5512 counter, but the instruction executed prior to that one. For instance,
5513 if the last instruction was a jump, @code{reverse-stepi} will take you
5514 back from the destination of the jump to the jump instruction itself.
5516 @kindex reverse-next
5517 @kindex rn @r{(@code{reverse-next})}
5518 @item reverse-next @r{[}@var{count}@r{]}
5519 Run backward to the beginning of the previous line executed in
5520 the current (innermost) stack frame. If the line contains function
5521 calls, they will be ``un-executed'' without stopping. Starting from
5522 the first line of a function, @code{reverse-next} will take you back
5523 to the caller of that function, @emph{before} the function was called,
5524 just as the normal @code{next} command would take you from the last
5525 line of a function back to its return to its caller
5526 @footnote{Unless the code is too heavily optimized.}.
5528 @kindex reverse-nexti
5529 @kindex rni @r{(@code{reverse-nexti})}
5530 @item reverse-nexti @r{[}@var{count}@r{]}
5531 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5532 in reverse, except that called functions are ``un-executed'' atomically.
5533 That is, if the previously executed instruction was a return from
5534 another function, @code{reverse-nexti} will continue to execute
5535 in reverse until the call to that function (from the current stack
5538 @kindex reverse-finish
5539 @item reverse-finish
5540 Just as the @code{finish} command takes you to the point where the
5541 current function returns, @code{reverse-finish} takes you to the point
5542 where it was called. Instead of ending up at the end of the current
5543 function invocation, you end up at the beginning.
5545 @kindex set exec-direction
5546 @item set exec-direction
5547 Set the direction of target execution.
5548 @itemx set exec-direction reverse
5549 @cindex execute forward or backward in time
5550 @value{GDBN} will perform all execution commands in reverse, until the
5551 exec-direction mode is changed to ``forward''. Affected commands include
5552 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5553 command cannot be used in reverse mode.
5554 @item set exec-direction forward
5555 @value{GDBN} will perform all execution commands in the normal fashion.
5556 This is the default.
5560 @node Process Record and Replay
5561 @chapter Recording Inferior's Execution and Replaying It
5562 @cindex process record and replay
5563 @cindex recording inferior's execution and replaying it
5565 On some platforms, @value{GDBN} provides a special @dfn{process record
5566 and replay} target that can record a log of the process execution, and
5567 replay it later with both forward and reverse execution commands.
5570 When this target is in use, if the execution log includes the record
5571 for the next instruction, @value{GDBN} will debug in @dfn{replay
5572 mode}. In the replay mode, the inferior does not really execute code
5573 instructions. Instead, all the events that normally happen during
5574 code execution are taken from the execution log. While code is not
5575 really executed in replay mode, the values of registers (including the
5576 program counter register) and the memory of the inferior are still
5577 changed as they normally would. Their contents are taken from the
5581 If the record for the next instruction is not in the execution log,
5582 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5583 inferior executes normally, and @value{GDBN} records the execution log
5586 The process record and replay target supports reverse execution
5587 (@pxref{Reverse Execution}), even if the platform on which the
5588 inferior runs does not. However, the reverse execution is limited in
5589 this case by the range of the instructions recorded in the execution
5590 log. In other words, reverse execution on platforms that don't
5591 support it directly can only be done in the replay mode.
5593 When debugging in the reverse direction, @value{GDBN} will work in
5594 replay mode as long as the execution log includes the record for the
5595 previous instruction; otherwise, it will work in record mode, if the
5596 platform supports reverse execution, or stop if not.
5598 For architecture environments that support process record and replay,
5599 @value{GDBN} provides the following commands:
5602 @kindex target record
5606 This command starts the process record and replay target. The process
5607 record and replay target can only debug a process that is already
5608 running. Therefore, you need first to start the process with the
5609 @kbd{run} or @kbd{start} commands, and then start the recording with
5610 the @kbd{target record} command.
5612 Both @code{record} and @code{rec} are aliases of @code{target record}.
5614 @cindex displaced stepping, and process record and replay
5615 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5616 will be automatically disabled when process record and replay target
5617 is started. That's because the process record and replay target
5618 doesn't support displaced stepping.
5620 @cindex non-stop mode, and process record and replay
5621 @cindex asynchronous execution, and process record and replay
5622 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5623 the asynchronous execution mode (@pxref{Background Execution}), the
5624 process record and replay target cannot be started because it doesn't
5625 support these two modes.
5630 Stop the process record and replay target. When process record and
5631 replay target stops, the entire execution log will be deleted and the
5632 inferior will either be terminated, or will remain in its final state.
5634 When you stop the process record and replay target in record mode (at
5635 the end of the execution log), the inferior will be stopped at the
5636 next instruction that would have been recorded. In other words, if
5637 you record for a while and then stop recording, the inferior process
5638 will be left in the same state as if the recording never happened.
5640 On the other hand, if the process record and replay target is stopped
5641 while in replay mode (that is, not at the end of the execution log,
5642 but at some earlier point), the inferior process will become ``live''
5643 at that earlier state, and it will then be possible to continue the
5644 usual ``live'' debugging of the process from that state.
5646 When the inferior process exits, or @value{GDBN} detaches from it,
5647 process record and replay target will automatically stop itself.
5650 @item record save @var{filename}
5651 Save the execution log to a file @file{@var{filename}}.
5652 Default filename is @file{gdb_record.@var{process_id}}, where
5653 @var{process_id} is the process ID of the inferior.
5655 @kindex record restore
5656 @item record restore @var{filename}
5657 Restore the execution log from a file @file{@var{filename}}.
5658 File must have been created with @code{record save}.
5660 @kindex set record insn-number-max
5661 @item set record insn-number-max @var{limit}
5662 Set the limit of instructions to be recorded. Default value is 200000.
5664 If @var{limit} is a positive number, then @value{GDBN} will start
5665 deleting instructions from the log once the number of the record
5666 instructions becomes greater than @var{limit}. For every new recorded
5667 instruction, @value{GDBN} will delete the earliest recorded
5668 instruction to keep the number of recorded instructions at the limit.
5669 (Since deleting recorded instructions loses information, @value{GDBN}
5670 lets you control what happens when the limit is reached, by means of
5671 the @code{stop-at-limit} option, described below.)
5673 If @var{limit} is zero, @value{GDBN} will never delete recorded
5674 instructions from the execution log. The number of recorded
5675 instructions is unlimited in this case.
5677 @kindex show record insn-number-max
5678 @item show record insn-number-max
5679 Show the limit of instructions to be recorded.
5681 @kindex set record stop-at-limit
5682 @item set record stop-at-limit
5683 Control the behavior when the number of recorded instructions reaches
5684 the limit. If ON (the default), @value{GDBN} will stop when the limit
5685 is reached for the first time and ask you whether you want to stop the
5686 inferior or continue running it and recording the execution log. If
5687 you decide to continue recording, each new recorded instruction will
5688 cause the oldest one to be deleted.
5690 If this option is OFF, @value{GDBN} will automatically delete the
5691 oldest record to make room for each new one, without asking.
5693 @kindex show record stop-at-limit
5694 @item show record stop-at-limit
5695 Show the current setting of @code{stop-at-limit}.
5697 @kindex set record memory-query
5698 @item set record memory-query
5699 Control the behavior when @value{GDBN} is unable to record memory
5700 changes caused by an instruction. If ON, @value{GDBN} will query
5701 whether to stop the inferior in that case.
5703 If this option is OFF (the default), @value{GDBN} will automatically
5704 ignore the effect of such instructions on memory. Later, when
5705 @value{GDBN} replays this execution log, it will mark the log of this
5706 instruction as not accessible, and it will not affect the replay
5709 @kindex show record memory-query
5710 @item show record memory-query
5711 Show the current setting of @code{memory-query}.
5715 Show various statistics about the state of process record and its
5716 in-memory execution log buffer, including:
5720 Whether in record mode or replay mode.
5722 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5724 Highest recorded instruction number.
5726 Current instruction about to be replayed (if in replay mode).
5728 Number of instructions contained in the execution log.
5730 Maximum number of instructions that may be contained in the execution log.
5733 @kindex record delete
5736 When record target runs in replay mode (``in the past''), delete the
5737 subsequent execution log and begin to record a new execution log starting
5738 from the current address. This means you will abandon the previously
5739 recorded ``future'' and begin recording a new ``future''.
5744 @chapter Examining the Stack
5746 When your program has stopped, the first thing you need to know is where it
5747 stopped and how it got there.
5750 Each time your program performs a function call, information about the call
5752 That information includes the location of the call in your program,
5753 the arguments of the call,
5754 and the local variables of the function being called.
5755 The information is saved in a block of data called a @dfn{stack frame}.
5756 The stack frames are allocated in a region of memory called the @dfn{call
5759 When your program stops, the @value{GDBN} commands for examining the
5760 stack allow you to see all of this information.
5762 @cindex selected frame
5763 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5764 @value{GDBN} commands refer implicitly to the selected frame. In
5765 particular, whenever you ask @value{GDBN} for the value of a variable in
5766 your program, the value is found in the selected frame. There are
5767 special @value{GDBN} commands to select whichever frame you are
5768 interested in. @xref{Selection, ,Selecting a Frame}.
5770 When your program stops, @value{GDBN} automatically selects the
5771 currently executing frame and describes it briefly, similar to the
5772 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5775 * Frames:: Stack frames
5776 * Backtrace:: Backtraces
5777 * Selection:: Selecting a frame
5778 * Frame Info:: Information on a frame
5783 @section Stack Frames
5785 @cindex frame, definition
5787 The call stack is divided up into contiguous pieces called @dfn{stack
5788 frames}, or @dfn{frames} for short; each frame is the data associated
5789 with one call to one function. The frame contains the arguments given
5790 to the function, the function's local variables, and the address at
5791 which the function is executing.
5793 @cindex initial frame
5794 @cindex outermost frame
5795 @cindex innermost frame
5796 When your program is started, the stack has only one frame, that of the
5797 function @code{main}. This is called the @dfn{initial} frame or the
5798 @dfn{outermost} frame. Each time a function is called, a new frame is
5799 made. Each time a function returns, the frame for that function invocation
5800 is eliminated. If a function is recursive, there can be many frames for
5801 the same function. The frame for the function in which execution is
5802 actually occurring is called the @dfn{innermost} frame. This is the most
5803 recently created of all the stack frames that still exist.
5805 @cindex frame pointer
5806 Inside your program, stack frames are identified by their addresses. A
5807 stack frame consists of many bytes, each of which has its own address; each
5808 kind of computer has a convention for choosing one byte whose
5809 address serves as the address of the frame. Usually this address is kept
5810 in a register called the @dfn{frame pointer register}
5811 (@pxref{Registers, $fp}) while execution is going on in that frame.
5813 @cindex frame number
5814 @value{GDBN} assigns numbers to all existing stack frames, starting with
5815 zero for the innermost frame, one for the frame that called it,
5816 and so on upward. These numbers do not really exist in your program;
5817 they are assigned by @value{GDBN} to give you a way of designating stack
5818 frames in @value{GDBN} commands.
5820 @c The -fomit-frame-pointer below perennially causes hbox overflow
5821 @c underflow problems.
5822 @cindex frameless execution
5823 Some compilers provide a way to compile functions so that they operate
5824 without stack frames. (For example, the @value{NGCC} option
5826 @samp{-fomit-frame-pointer}
5828 generates functions without a frame.)
5829 This is occasionally done with heavily used library functions to save
5830 the frame setup time. @value{GDBN} has limited facilities for dealing
5831 with these function invocations. If the innermost function invocation
5832 has no stack frame, @value{GDBN} nevertheless regards it as though
5833 it had a separate frame, which is numbered zero as usual, allowing
5834 correct tracing of the function call chain. However, @value{GDBN} has
5835 no provision for frameless functions elsewhere in the stack.
5838 @kindex frame@r{, command}
5839 @cindex current stack frame
5840 @item frame @var{args}
5841 The @code{frame} command allows you to move from one stack frame to another,
5842 and to print the stack frame you select. @var{args} may be either the
5843 address of the frame or the stack frame number. Without an argument,
5844 @code{frame} prints the current stack frame.
5846 @kindex select-frame
5847 @cindex selecting frame silently
5849 The @code{select-frame} command allows you to move from one stack frame
5850 to another without printing the frame. This is the silent version of
5858 @cindex call stack traces
5859 A backtrace is a summary of how your program got where it is. It shows one
5860 line per frame, for many frames, starting with the currently executing
5861 frame (frame zero), followed by its caller (frame one), and on up the
5866 @kindex bt @r{(@code{backtrace})}
5869 Print a backtrace of the entire stack: one line per frame for all
5870 frames in the stack.
5872 You can stop the backtrace at any time by typing the system interrupt
5873 character, normally @kbd{Ctrl-c}.
5875 @item backtrace @var{n}
5877 Similar, but print only the innermost @var{n} frames.
5879 @item backtrace -@var{n}
5881 Similar, but print only the outermost @var{n} frames.
5883 @item backtrace full
5885 @itemx bt full @var{n}
5886 @itemx bt full -@var{n}
5887 Print the values of the local variables also. @var{n} specifies the
5888 number of frames to print, as described above.
5893 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5894 are additional aliases for @code{backtrace}.
5896 @cindex multiple threads, backtrace
5897 In a multi-threaded program, @value{GDBN} by default shows the
5898 backtrace only for the current thread. To display the backtrace for
5899 several or all of the threads, use the command @code{thread apply}
5900 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5901 apply all backtrace}, @value{GDBN} will display the backtrace for all
5902 the threads; this is handy when you debug a core dump of a
5903 multi-threaded program.
5905 Each line in the backtrace shows the frame number and the function name.
5906 The program counter value is also shown---unless you use @code{set
5907 print address off}. The backtrace also shows the source file name and
5908 line number, as well as the arguments to the function. The program
5909 counter value is omitted if it is at the beginning of the code for that
5912 Here is an example of a backtrace. It was made with the command
5913 @samp{bt 3}, so it shows the innermost three frames.
5917 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5919 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5920 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5922 (More stack frames follow...)
5927 The display for frame zero does not begin with a program counter
5928 value, indicating that your program has stopped at the beginning of the
5929 code for line @code{993} of @code{builtin.c}.
5932 The value of parameter @code{data} in frame 1 has been replaced by
5933 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5934 only if it is a scalar (integer, pointer, enumeration, etc). See command
5935 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5936 on how to configure the way function parameter values are printed.
5938 @cindex value optimized out, in backtrace
5939 @cindex function call arguments, optimized out
5940 If your program was compiled with optimizations, some compilers will
5941 optimize away arguments passed to functions if those arguments are
5942 never used after the call. Such optimizations generate code that
5943 passes arguments through registers, but doesn't store those arguments
5944 in the stack frame. @value{GDBN} has no way of displaying such
5945 arguments in stack frames other than the innermost one. Here's what
5946 such a backtrace might look like:
5950 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5952 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5953 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5955 (More stack frames follow...)
5960 The values of arguments that were not saved in their stack frames are
5961 shown as @samp{<value optimized out>}.
5963 If you need to display the values of such optimized-out arguments,
5964 either deduce that from other variables whose values depend on the one
5965 you are interested in, or recompile without optimizations.
5967 @cindex backtrace beyond @code{main} function
5968 @cindex program entry point
5969 @cindex startup code, and backtrace
5970 Most programs have a standard user entry point---a place where system
5971 libraries and startup code transition into user code. For C this is
5972 @code{main}@footnote{
5973 Note that embedded programs (the so-called ``free-standing''
5974 environment) are not required to have a @code{main} function as the
5975 entry point. They could even have multiple entry points.}.
5976 When @value{GDBN} finds the entry function in a backtrace
5977 it will terminate the backtrace, to avoid tracing into highly
5978 system-specific (and generally uninteresting) code.
5980 If you need to examine the startup code, or limit the number of levels
5981 in a backtrace, you can change this behavior:
5984 @item set backtrace past-main
5985 @itemx set backtrace past-main on
5986 @kindex set backtrace
5987 Backtraces will continue past the user entry point.
5989 @item set backtrace past-main off
5990 Backtraces will stop when they encounter the user entry point. This is the
5993 @item show backtrace past-main
5994 @kindex show backtrace
5995 Display the current user entry point backtrace policy.
5997 @item set backtrace past-entry
5998 @itemx set backtrace past-entry on
5999 Backtraces will continue past the internal entry point of an application.
6000 This entry point is encoded by the linker when the application is built,
6001 and is likely before the user entry point @code{main} (or equivalent) is called.
6003 @item set backtrace past-entry off
6004 Backtraces will stop when they encounter the internal entry point of an
6005 application. This is the default.
6007 @item show backtrace past-entry
6008 Display the current internal entry point backtrace policy.
6010 @item set backtrace limit @var{n}
6011 @itemx set backtrace limit 0
6012 @cindex backtrace limit
6013 Limit the backtrace to @var{n} levels. A value of zero means
6016 @item show backtrace limit
6017 Display the current limit on backtrace levels.
6021 @section Selecting a Frame
6023 Most commands for examining the stack and other data in your program work on
6024 whichever stack frame is selected at the moment. Here are the commands for
6025 selecting a stack frame; all of them finish by printing a brief description
6026 of the stack frame just selected.
6029 @kindex frame@r{, selecting}
6030 @kindex f @r{(@code{frame})}
6033 Select frame number @var{n}. Recall that frame zero is the innermost
6034 (currently executing) frame, frame one is the frame that called the
6035 innermost one, and so on. The highest-numbered frame is the one for
6038 @item frame @var{addr}
6040 Select the frame at address @var{addr}. This is useful mainly if the
6041 chaining of stack frames has been damaged by a bug, making it
6042 impossible for @value{GDBN} to assign numbers properly to all frames. In
6043 addition, this can be useful when your program has multiple stacks and
6044 switches between them.
6046 On the SPARC architecture, @code{frame} needs two addresses to
6047 select an arbitrary frame: a frame pointer and a stack pointer.
6049 On the MIPS and Alpha architecture, it needs two addresses: a stack
6050 pointer and a program counter.
6052 On the 29k architecture, it needs three addresses: a register stack
6053 pointer, a program counter, and a memory stack pointer.
6057 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6058 advances toward the outermost frame, to higher frame numbers, to frames
6059 that have existed longer. @var{n} defaults to one.
6062 @kindex do @r{(@code{down})}
6064 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6065 advances toward the innermost frame, to lower frame numbers, to frames
6066 that were created more recently. @var{n} defaults to one. You may
6067 abbreviate @code{down} as @code{do}.
6070 All of these commands end by printing two lines of output describing the
6071 frame. The first line shows the frame number, the function name, the
6072 arguments, and the source file and line number of execution in that
6073 frame. The second line shows the text of that source line.
6081 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6083 10 read_input_file (argv[i]);
6087 After such a printout, the @code{list} command with no arguments
6088 prints ten lines centered on the point of execution in the frame.
6089 You can also edit the program at the point of execution with your favorite
6090 editing program by typing @code{edit}.
6091 @xref{List, ,Printing Source Lines},
6095 @kindex down-silently
6097 @item up-silently @var{n}
6098 @itemx down-silently @var{n}
6099 These two commands are variants of @code{up} and @code{down},
6100 respectively; they differ in that they do their work silently, without
6101 causing display of the new frame. They are intended primarily for use
6102 in @value{GDBN} command scripts, where the output might be unnecessary and
6107 @section Information About a Frame
6109 There are several other commands to print information about the selected
6115 When used without any argument, this command does not change which
6116 frame is selected, but prints a brief description of the currently
6117 selected stack frame. It can be abbreviated @code{f}. With an
6118 argument, this command is used to select a stack frame.
6119 @xref{Selection, ,Selecting a Frame}.
6122 @kindex info f @r{(@code{info frame})}
6125 This command prints a verbose description of the selected stack frame,
6130 the address of the frame
6132 the address of the next frame down (called by this frame)
6134 the address of the next frame up (caller of this frame)
6136 the language in which the source code corresponding to this frame is written
6138 the address of the frame's arguments
6140 the address of the frame's local variables
6142 the program counter saved in it (the address of execution in the caller frame)
6144 which registers were saved in the frame
6147 @noindent The verbose description is useful when
6148 something has gone wrong that has made the stack format fail to fit
6149 the usual conventions.
6151 @item info frame @var{addr}
6152 @itemx info f @var{addr}
6153 Print a verbose description of the frame at address @var{addr}, without
6154 selecting that frame. The selected frame remains unchanged by this
6155 command. This requires the same kind of address (more than one for some
6156 architectures) that you specify in the @code{frame} command.
6157 @xref{Selection, ,Selecting a Frame}.
6161 Print the arguments of the selected frame, each on a separate line.
6165 Print the local variables of the selected frame, each on a separate
6166 line. These are all variables (declared either static or automatic)
6167 accessible at the point of execution of the selected frame.
6170 @cindex catch exceptions, list active handlers
6171 @cindex exception handlers, how to list
6173 Print a list of all the exception handlers that are active in the
6174 current stack frame at the current point of execution. To see other
6175 exception handlers, visit the associated frame (using the @code{up},
6176 @code{down}, or @code{frame} commands); then type @code{info catch}.
6177 @xref{Set Catchpoints, , Setting Catchpoints}.
6183 @chapter Examining Source Files
6185 @value{GDBN} can print parts of your program's source, since the debugging
6186 information recorded in the program tells @value{GDBN} what source files were
6187 used to build it. When your program stops, @value{GDBN} spontaneously prints
6188 the line where it stopped. Likewise, when you select a stack frame
6189 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6190 execution in that frame has stopped. You can print other portions of
6191 source files by explicit command.
6193 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6194 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6195 @value{GDBN} under @sc{gnu} Emacs}.
6198 * List:: Printing source lines
6199 * Specify Location:: How to specify code locations
6200 * Edit:: Editing source files
6201 * Search:: Searching source files
6202 * Source Path:: Specifying source directories
6203 * Machine Code:: Source and machine code
6207 @section Printing Source Lines
6210 @kindex l @r{(@code{list})}
6211 To print lines from a source file, use the @code{list} command
6212 (abbreviated @code{l}). By default, ten lines are printed.
6213 There are several ways to specify what part of the file you want to
6214 print; see @ref{Specify Location}, for the full list.
6216 Here are the forms of the @code{list} command most commonly used:
6219 @item list @var{linenum}
6220 Print lines centered around line number @var{linenum} in the
6221 current source file.
6223 @item list @var{function}
6224 Print lines centered around the beginning of function
6228 Print more lines. If the last lines printed were printed with a
6229 @code{list} command, this prints lines following the last lines
6230 printed; however, if the last line printed was a solitary line printed
6231 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6232 Stack}), this prints lines centered around that line.
6235 Print lines just before the lines last printed.
6238 @cindex @code{list}, how many lines to display
6239 By default, @value{GDBN} prints ten source lines with any of these forms of
6240 the @code{list} command. You can change this using @code{set listsize}:
6243 @kindex set listsize
6244 @item set listsize @var{count}
6245 Make the @code{list} command display @var{count} source lines (unless
6246 the @code{list} argument explicitly specifies some other number).
6248 @kindex show listsize
6250 Display the number of lines that @code{list} prints.
6253 Repeating a @code{list} command with @key{RET} discards the argument,
6254 so it is equivalent to typing just @code{list}. This is more useful
6255 than listing the same lines again. An exception is made for an
6256 argument of @samp{-}; that argument is preserved in repetition so that
6257 each repetition moves up in the source file.
6259 In general, the @code{list} command expects you to supply zero, one or two
6260 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6261 of writing them (@pxref{Specify Location}), but the effect is always
6262 to specify some source line.
6264 Here is a complete description of the possible arguments for @code{list}:
6267 @item list @var{linespec}
6268 Print lines centered around the line specified by @var{linespec}.
6270 @item list @var{first},@var{last}
6271 Print lines from @var{first} to @var{last}. Both arguments are
6272 linespecs. When a @code{list} command has two linespecs, and the
6273 source file of the second linespec is omitted, this refers to
6274 the same source file as the first linespec.
6276 @item list ,@var{last}
6277 Print lines ending with @var{last}.
6279 @item list @var{first},
6280 Print lines starting with @var{first}.
6283 Print lines just after the lines last printed.
6286 Print lines just before the lines last printed.
6289 As described in the preceding table.
6292 @node Specify Location
6293 @section Specifying a Location
6294 @cindex specifying location
6297 Several @value{GDBN} commands accept arguments that specify a location
6298 of your program's code. Since @value{GDBN} is a source-level
6299 debugger, a location usually specifies some line in the source code;
6300 for that reason, locations are also known as @dfn{linespecs}.
6302 Here are all the different ways of specifying a code location that
6303 @value{GDBN} understands:
6307 Specifies the line number @var{linenum} of the current source file.
6310 @itemx +@var{offset}
6311 Specifies the line @var{offset} lines before or after the @dfn{current
6312 line}. For the @code{list} command, the current line is the last one
6313 printed; for the breakpoint commands, this is the line at which
6314 execution stopped in the currently selected @dfn{stack frame}
6315 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6316 used as the second of the two linespecs in a @code{list} command,
6317 this specifies the line @var{offset} lines up or down from the first
6320 @item @var{filename}:@var{linenum}
6321 Specifies the line @var{linenum} in the source file @var{filename}.
6323 @item @var{function}
6324 Specifies the line that begins the body of the function @var{function}.
6325 For example, in C, this is the line with the open brace.
6327 @item @var{filename}:@var{function}
6328 Specifies the line that begins the body of the function @var{function}
6329 in the file @var{filename}. You only need the file name with a
6330 function name to avoid ambiguity when there are identically named
6331 functions in different source files.
6334 Specifies the line at which the label named @var{label} appears.
6335 @value{GDBN} searches for the label in the function corresponding to
6336 the currently selected stack frame. If there is no current selected
6337 stack frame (for instance, if the inferior is not running), then
6338 @value{GDBN} will not search for a label.
6340 @item *@var{address}
6341 Specifies the program address @var{address}. For line-oriented
6342 commands, such as @code{list} and @code{edit}, this specifies a source
6343 line that contains @var{address}. For @code{break} and other
6344 breakpoint oriented commands, this can be used to set breakpoints in
6345 parts of your program which do not have debugging information or
6348 Here @var{address} may be any expression valid in the current working
6349 language (@pxref{Languages, working language}) that specifies a code
6350 address. In addition, as a convenience, @value{GDBN} extends the
6351 semantics of expressions used in locations to cover the situations
6352 that frequently happen during debugging. Here are the various forms
6356 @item @var{expression}
6357 Any expression valid in the current working language.
6359 @item @var{funcaddr}
6360 An address of a function or procedure derived from its name. In C,
6361 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6362 simply the function's name @var{function} (and actually a special case
6363 of a valid expression). In Pascal and Modula-2, this is
6364 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6365 (although the Pascal form also works).
6367 This form specifies the address of the function's first instruction,
6368 before the stack frame and arguments have been set up.
6370 @item '@var{filename}'::@var{funcaddr}
6371 Like @var{funcaddr} above, but also specifies the name of the source
6372 file explicitly. This is useful if the name of the function does not
6373 specify the function unambiguously, e.g., if there are several
6374 functions with identical names in different source files.
6381 @section Editing Source Files
6382 @cindex editing source files
6385 @kindex e @r{(@code{edit})}
6386 To edit the lines in a source file, use the @code{edit} command.
6387 The editing program of your choice
6388 is invoked with the current line set to
6389 the active line in the program.
6390 Alternatively, there are several ways to specify what part of the file you
6391 want to print if you want to see other parts of the program:
6394 @item edit @var{location}
6395 Edit the source file specified by @code{location}. Editing starts at
6396 that @var{location}, e.g., at the specified source line of the
6397 specified file. @xref{Specify Location}, for all the possible forms
6398 of the @var{location} argument; here are the forms of the @code{edit}
6399 command most commonly used:
6402 @item edit @var{number}
6403 Edit the current source file with @var{number} as the active line number.
6405 @item edit @var{function}
6406 Edit the file containing @var{function} at the beginning of its definition.
6411 @subsection Choosing your Editor
6412 You can customize @value{GDBN} to use any editor you want
6414 The only restriction is that your editor (say @code{ex}), recognizes the
6415 following command-line syntax:
6417 ex +@var{number} file
6419 The optional numeric value +@var{number} specifies the number of the line in
6420 the file where to start editing.}.
6421 By default, it is @file{@value{EDITOR}}, but you can change this
6422 by setting the environment variable @code{EDITOR} before using
6423 @value{GDBN}. For example, to configure @value{GDBN} to use the
6424 @code{vi} editor, you could use these commands with the @code{sh} shell:
6430 or in the @code{csh} shell,
6432 setenv EDITOR /usr/bin/vi
6437 @section Searching Source Files
6438 @cindex searching source files
6440 There are two commands for searching through the current source file for a
6445 @kindex forward-search
6446 @item forward-search @var{regexp}
6447 @itemx search @var{regexp}
6448 The command @samp{forward-search @var{regexp}} checks each line,
6449 starting with the one following the last line listed, for a match for
6450 @var{regexp}. It lists the line that is found. You can use the
6451 synonym @samp{search @var{regexp}} or abbreviate the command name as
6454 @kindex reverse-search
6455 @item reverse-search @var{regexp}
6456 The command @samp{reverse-search @var{regexp}} checks each line, starting
6457 with the one before the last line listed and going backward, for a match
6458 for @var{regexp}. It lists the line that is found. You can abbreviate
6459 this command as @code{rev}.
6463 @section Specifying Source Directories
6466 @cindex directories for source files
6467 Executable programs sometimes do not record the directories of the source
6468 files from which they were compiled, just the names. Even when they do,
6469 the directories could be moved between the compilation and your debugging
6470 session. @value{GDBN} has a list of directories to search for source files;
6471 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6472 it tries all the directories in the list, in the order they are present
6473 in the list, until it finds a file with the desired name.
6475 For example, suppose an executable references the file
6476 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6477 @file{/mnt/cross}. The file is first looked up literally; if this
6478 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6479 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6480 message is printed. @value{GDBN} does not look up the parts of the
6481 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6482 Likewise, the subdirectories of the source path are not searched: if
6483 the source path is @file{/mnt/cross}, and the binary refers to
6484 @file{foo.c}, @value{GDBN} would not find it under
6485 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6487 Plain file names, relative file names with leading directories, file
6488 names containing dots, etc.@: are all treated as described above; for
6489 instance, if the source path is @file{/mnt/cross}, and the source file
6490 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6491 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6492 that---@file{/mnt/cross/foo.c}.
6494 Note that the executable search path is @emph{not} used to locate the
6497 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6498 any information it has cached about where source files are found and where
6499 each line is in the file.
6503 When you start @value{GDBN}, its source path includes only @samp{cdir}
6504 and @samp{cwd}, in that order.
6505 To add other directories, use the @code{directory} command.
6507 The search path is used to find both program source files and @value{GDBN}
6508 script files (read using the @samp{-command} option and @samp{source} command).
6510 In addition to the source path, @value{GDBN} provides a set of commands
6511 that manage a list of source path substitution rules. A @dfn{substitution
6512 rule} specifies how to rewrite source directories stored in the program's
6513 debug information in case the sources were moved to a different
6514 directory between compilation and debugging. A rule is made of
6515 two strings, the first specifying what needs to be rewritten in
6516 the path, and the second specifying how it should be rewritten.
6517 In @ref{set substitute-path}, we name these two parts @var{from} and
6518 @var{to} respectively. @value{GDBN} does a simple string replacement
6519 of @var{from} with @var{to} at the start of the directory part of the
6520 source file name, and uses that result instead of the original file
6521 name to look up the sources.
6523 Using the previous example, suppose the @file{foo-1.0} tree has been
6524 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6525 @value{GDBN} to replace @file{/usr/src} in all source path names with
6526 @file{/mnt/cross}. The first lookup will then be
6527 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6528 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6529 substitution rule, use the @code{set substitute-path} command
6530 (@pxref{set substitute-path}).
6532 To avoid unexpected substitution results, a rule is applied only if the
6533 @var{from} part of the directory name ends at a directory separator.
6534 For instance, a rule substituting @file{/usr/source} into
6535 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6536 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6537 is applied only at the beginning of the directory name, this rule will
6538 not be applied to @file{/root/usr/source/baz.c} either.
6540 In many cases, you can achieve the same result using the @code{directory}
6541 command. However, @code{set substitute-path} can be more efficient in
6542 the case where the sources are organized in a complex tree with multiple
6543 subdirectories. With the @code{directory} command, you need to add each
6544 subdirectory of your project. If you moved the entire tree while
6545 preserving its internal organization, then @code{set substitute-path}
6546 allows you to direct the debugger to all the sources with one single
6549 @code{set substitute-path} is also more than just a shortcut command.
6550 The source path is only used if the file at the original location no
6551 longer exists. On the other hand, @code{set substitute-path} modifies
6552 the debugger behavior to look at the rewritten location instead. So, if
6553 for any reason a source file that is not relevant to your executable is
6554 located at the original location, a substitution rule is the only
6555 method available to point @value{GDBN} at the new location.
6557 @cindex @samp{--with-relocated-sources}
6558 @cindex default source path substitution
6559 You can configure a default source path substitution rule by
6560 configuring @value{GDBN} with the
6561 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6562 should be the name of a directory under @value{GDBN}'s configured
6563 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6564 directory names in debug information under @var{dir} will be adjusted
6565 automatically if the installed @value{GDBN} is moved to a new
6566 location. This is useful if @value{GDBN}, libraries or executables
6567 with debug information and corresponding source code are being moved
6571 @item directory @var{dirname} @dots{}
6572 @item dir @var{dirname} @dots{}
6573 Add directory @var{dirname} to the front of the source path. Several
6574 directory names may be given to this command, separated by @samp{:}
6575 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6576 part of absolute file names) or
6577 whitespace. You may specify a directory that is already in the source
6578 path; this moves it forward, so @value{GDBN} searches it sooner.
6582 @vindex $cdir@r{, convenience variable}
6583 @vindex $cwd@r{, convenience variable}
6584 @cindex compilation directory
6585 @cindex current directory
6586 @cindex working directory
6587 @cindex directory, current
6588 @cindex directory, compilation
6589 You can use the string @samp{$cdir} to refer to the compilation
6590 directory (if one is recorded), and @samp{$cwd} to refer to the current
6591 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6592 tracks the current working directory as it changes during your @value{GDBN}
6593 session, while the latter is immediately expanded to the current
6594 directory at the time you add an entry to the source path.
6597 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6599 @c RET-repeat for @code{directory} is explicitly disabled, but since
6600 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6602 @item show directories
6603 @kindex show directories
6604 Print the source path: show which directories it contains.
6606 @anchor{set substitute-path}
6607 @item set substitute-path @var{from} @var{to}
6608 @kindex set substitute-path
6609 Define a source path substitution rule, and add it at the end of the
6610 current list of existing substitution rules. If a rule with the same
6611 @var{from} was already defined, then the old rule is also deleted.
6613 For example, if the file @file{/foo/bar/baz.c} was moved to
6614 @file{/mnt/cross/baz.c}, then the command
6617 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6621 will tell @value{GDBN} to replace @samp{/usr/src} with
6622 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6623 @file{baz.c} even though it was moved.
6625 In the case when more than one substitution rule have been defined,
6626 the rules are evaluated one by one in the order where they have been
6627 defined. The first one matching, if any, is selected to perform
6630 For instance, if we had entered the following commands:
6633 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6634 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6638 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6639 @file{/mnt/include/defs.h} by using the first rule. However, it would
6640 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6641 @file{/mnt/src/lib/foo.c}.
6644 @item unset substitute-path [path]
6645 @kindex unset substitute-path
6646 If a path is specified, search the current list of substitution rules
6647 for a rule that would rewrite that path. Delete that rule if found.
6648 A warning is emitted by the debugger if no rule could be found.
6650 If no path is specified, then all substitution rules are deleted.
6652 @item show substitute-path [path]
6653 @kindex show substitute-path
6654 If a path is specified, then print the source path substitution rule
6655 which would rewrite that path, if any.
6657 If no path is specified, then print all existing source path substitution
6662 If your source path is cluttered with directories that are no longer of
6663 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6664 versions of source. You can correct the situation as follows:
6668 Use @code{directory} with no argument to reset the source path to its default value.
6671 Use @code{directory} with suitable arguments to reinstall the
6672 directories you want in the source path. You can add all the
6673 directories in one command.
6677 @section Source and Machine Code
6678 @cindex source line and its code address
6680 You can use the command @code{info line} to map source lines to program
6681 addresses (and vice versa), and the command @code{disassemble} to display
6682 a range of addresses as machine instructions. You can use the command
6683 @code{set disassemble-next-line} to set whether to disassemble next
6684 source line when execution stops. When run under @sc{gnu} Emacs
6685 mode, the @code{info line} command causes the arrow to point to the
6686 line specified. Also, @code{info line} prints addresses in symbolic form as
6691 @item info line @var{linespec}
6692 Print the starting and ending addresses of the compiled code for
6693 source line @var{linespec}. You can specify source lines in any of
6694 the ways documented in @ref{Specify Location}.
6697 For example, we can use @code{info line} to discover the location of
6698 the object code for the first line of function
6699 @code{m4_changequote}:
6701 @c FIXME: I think this example should also show the addresses in
6702 @c symbolic form, as they usually would be displayed.
6704 (@value{GDBP}) info line m4_changequote
6705 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6709 @cindex code address and its source line
6710 We can also inquire (using @code{*@var{addr}} as the form for
6711 @var{linespec}) what source line covers a particular address:
6713 (@value{GDBP}) info line *0x63ff
6714 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6717 @cindex @code{$_} and @code{info line}
6718 @cindex @code{x} command, default address
6719 @kindex x@r{(examine), and} info line
6720 After @code{info line}, the default address for the @code{x} command
6721 is changed to the starting address of the line, so that @samp{x/i} is
6722 sufficient to begin examining the machine code (@pxref{Memory,
6723 ,Examining Memory}). Also, this address is saved as the value of the
6724 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6729 @cindex assembly instructions
6730 @cindex instructions, assembly
6731 @cindex machine instructions
6732 @cindex listing machine instructions
6734 @itemx disassemble /m
6735 @itemx disassemble /r
6736 This specialized command dumps a range of memory as machine
6737 instructions. It can also print mixed source+disassembly by specifying
6738 the @code{/m} modifier and print the raw instructions in hex as well as
6739 in symbolic form by specifying the @code{/r}.
6740 The default memory range is the function surrounding the
6741 program counter of the selected frame. A single argument to this
6742 command is a program counter value; @value{GDBN} dumps the function
6743 surrounding this value. When two arguments are given, they should
6744 be separated by a comma, possibly surrounded by whitespace. The
6745 arguments specify a range of addresses to dump, in one of two forms:
6748 @item @var{start},@var{end}
6749 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6750 @item @var{start},+@var{length}
6751 the addresses from @var{start} (inclusive) to
6752 @code{@var{start}+@var{length}} (exclusive).
6756 When 2 arguments are specified, the name of the function is also
6757 printed (since there could be several functions in the given range).
6759 The argument(s) can be any expression yielding a numeric value, such as
6760 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6762 If the range of memory being disassembled contains current program counter,
6763 the instruction at that location is shown with a @code{=>} marker.
6766 The following example shows the disassembly of a range of addresses of
6767 HP PA-RISC 2.0 code:
6770 (@value{GDBP}) disas 0x32c4, 0x32e4
6771 Dump of assembler code from 0x32c4 to 0x32e4:
6772 0x32c4 <main+204>: addil 0,dp
6773 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6774 0x32cc <main+212>: ldil 0x3000,r31
6775 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6776 0x32d4 <main+220>: ldo 0(r31),rp
6777 0x32d8 <main+224>: addil -0x800,dp
6778 0x32dc <main+228>: ldo 0x588(r1),r26
6779 0x32e0 <main+232>: ldil 0x3000,r31
6780 End of assembler dump.
6783 Here is an example showing mixed source+assembly for Intel x86, when the
6784 program is stopped just after function prologue:
6787 (@value{GDBP}) disas /m main
6788 Dump of assembler code for function main:
6790 0x08048330 <+0>: push %ebp
6791 0x08048331 <+1>: mov %esp,%ebp
6792 0x08048333 <+3>: sub $0x8,%esp
6793 0x08048336 <+6>: and $0xfffffff0,%esp
6794 0x08048339 <+9>: sub $0x10,%esp
6796 6 printf ("Hello.\n");
6797 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6798 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6802 0x08048348 <+24>: mov $0x0,%eax
6803 0x0804834d <+29>: leave
6804 0x0804834e <+30>: ret
6806 End of assembler dump.
6809 Here is another example showing raw instructions in hex for AMD x86-64,
6812 (gdb) disas /r 0x400281,+10
6813 Dump of assembler code from 0x400281 to 0x40028b:
6814 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6815 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6816 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6817 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6818 End of assembler dump.
6821 Some architectures have more than one commonly-used set of instruction
6822 mnemonics or other syntax.
6824 For programs that were dynamically linked and use shared libraries,
6825 instructions that call functions or branch to locations in the shared
6826 libraries might show a seemingly bogus location---it's actually a
6827 location of the relocation table. On some architectures, @value{GDBN}
6828 might be able to resolve these to actual function names.
6831 @kindex set disassembly-flavor
6832 @cindex Intel disassembly flavor
6833 @cindex AT&T disassembly flavor
6834 @item set disassembly-flavor @var{instruction-set}
6835 Select the instruction set to use when disassembling the
6836 program via the @code{disassemble} or @code{x/i} commands.
6838 Currently this command is only defined for the Intel x86 family. You
6839 can set @var{instruction-set} to either @code{intel} or @code{att}.
6840 The default is @code{att}, the AT&T flavor used by default by Unix
6841 assemblers for x86-based targets.
6843 @kindex show disassembly-flavor
6844 @item show disassembly-flavor
6845 Show the current setting of the disassembly flavor.
6849 @kindex set disassemble-next-line
6850 @kindex show disassemble-next-line
6851 @item set disassemble-next-line
6852 @itemx show disassemble-next-line
6853 Control whether or not @value{GDBN} will disassemble the next source
6854 line or instruction when execution stops. If ON, @value{GDBN} will
6855 display disassembly of the next source line when execution of the
6856 program being debugged stops. This is @emph{in addition} to
6857 displaying the source line itself, which @value{GDBN} always does if
6858 possible. If the next source line cannot be displayed for some reason
6859 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6860 info in the debug info), @value{GDBN} will display disassembly of the
6861 next @emph{instruction} instead of showing the next source line. If
6862 AUTO, @value{GDBN} will display disassembly of next instruction only
6863 if the source line cannot be displayed. This setting causes
6864 @value{GDBN} to display some feedback when you step through a function
6865 with no line info or whose source file is unavailable. The default is
6866 OFF, which means never display the disassembly of the next line or
6872 @chapter Examining Data
6874 @cindex printing data
6875 @cindex examining data
6878 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6879 @c document because it is nonstandard... Under Epoch it displays in a
6880 @c different window or something like that.
6881 The usual way to examine data in your program is with the @code{print}
6882 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6883 evaluates and prints the value of an expression of the language your
6884 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6885 Different Languages}). It may also print the expression using a
6886 Python-based pretty-printer (@pxref{Pretty Printing}).
6889 @item print @var{expr}
6890 @itemx print /@var{f} @var{expr}
6891 @var{expr} is an expression (in the source language). By default the
6892 value of @var{expr} is printed in a format appropriate to its data type;
6893 you can choose a different format by specifying @samp{/@var{f}}, where
6894 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6898 @itemx print /@var{f}
6899 @cindex reprint the last value
6900 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6901 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6902 conveniently inspect the same value in an alternative format.
6905 A more low-level way of examining data is with the @code{x} command.
6906 It examines data in memory at a specified address and prints it in a
6907 specified format. @xref{Memory, ,Examining Memory}.
6909 If you are interested in information about types, or about how the
6910 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6911 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6915 * Expressions:: Expressions
6916 * Ambiguous Expressions:: Ambiguous Expressions
6917 * Variables:: Program variables
6918 * Arrays:: Artificial arrays
6919 * Output Formats:: Output formats
6920 * Memory:: Examining memory
6921 * Auto Display:: Automatic display
6922 * Print Settings:: Print settings
6923 * Pretty Printing:: Python pretty printing
6924 * Value History:: Value history
6925 * Convenience Vars:: Convenience variables
6926 * Registers:: Registers
6927 * Floating Point Hardware:: Floating point hardware
6928 * Vector Unit:: Vector Unit
6929 * OS Information:: Auxiliary data provided by operating system
6930 * Memory Region Attributes:: Memory region attributes
6931 * Dump/Restore Files:: Copy between memory and a file
6932 * Core File Generation:: Cause a program dump its core
6933 * Character Sets:: Debugging programs that use a different
6934 character set than GDB does
6935 * Caching Remote Data:: Data caching for remote targets
6936 * Searching Memory:: Searching memory for a sequence of bytes
6940 @section Expressions
6943 @code{print} and many other @value{GDBN} commands accept an expression and
6944 compute its value. Any kind of constant, variable or operator defined
6945 by the programming language you are using is valid in an expression in
6946 @value{GDBN}. This includes conditional expressions, function calls,
6947 casts, and string constants. It also includes preprocessor macros, if
6948 you compiled your program to include this information; see
6951 @cindex arrays in expressions
6952 @value{GDBN} supports array constants in expressions input by
6953 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6954 you can use the command @code{print @{1, 2, 3@}} to create an array
6955 of three integers. If you pass an array to a function or assign it
6956 to a program variable, @value{GDBN} copies the array to memory that
6957 is @code{malloc}ed in the target program.
6959 Because C is so widespread, most of the expressions shown in examples in
6960 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6961 Languages}, for information on how to use expressions in other
6964 In this section, we discuss operators that you can use in @value{GDBN}
6965 expressions regardless of your programming language.
6967 @cindex casts, in expressions
6968 Casts are supported in all languages, not just in C, because it is so
6969 useful to cast a number into a pointer in order to examine a structure
6970 at that address in memory.
6971 @c FIXME: casts supported---Mod2 true?
6973 @value{GDBN} supports these operators, in addition to those common
6974 to programming languages:
6978 @samp{@@} is a binary operator for treating parts of memory as arrays.
6979 @xref{Arrays, ,Artificial Arrays}, for more information.
6982 @samp{::} allows you to specify a variable in terms of the file or
6983 function where it is defined. @xref{Variables, ,Program Variables}.
6985 @cindex @{@var{type}@}
6986 @cindex type casting memory
6987 @cindex memory, viewing as typed object
6988 @cindex casts, to view memory
6989 @item @{@var{type}@} @var{addr}
6990 Refers to an object of type @var{type} stored at address @var{addr} in
6991 memory. @var{addr} may be any expression whose value is an integer or
6992 pointer (but parentheses are required around binary operators, just as in
6993 a cast). This construct is allowed regardless of what kind of data is
6994 normally supposed to reside at @var{addr}.
6997 @node Ambiguous Expressions
6998 @section Ambiguous Expressions
6999 @cindex ambiguous expressions
7001 Expressions can sometimes contain some ambiguous elements. For instance,
7002 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7003 a single function name to be defined several times, for application in
7004 different contexts. This is called @dfn{overloading}. Another example
7005 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7006 templates and is typically instantiated several times, resulting in
7007 the same function name being defined in different contexts.
7009 In some cases and depending on the language, it is possible to adjust
7010 the expression to remove the ambiguity. For instance in C@t{++}, you
7011 can specify the signature of the function you want to break on, as in
7012 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7013 qualified name of your function often makes the expression unambiguous
7016 When an ambiguity that needs to be resolved is detected, the debugger
7017 has the capability to display a menu of numbered choices for each
7018 possibility, and then waits for the selection with the prompt @samp{>}.
7019 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7020 aborts the current command. If the command in which the expression was
7021 used allows more than one choice to be selected, the next option in the
7022 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7025 For example, the following session excerpt shows an attempt to set a
7026 breakpoint at the overloaded symbol @code{String::after}.
7027 We choose three particular definitions of that function name:
7029 @c FIXME! This is likely to change to show arg type lists, at least
7032 (@value{GDBP}) b String::after
7035 [2] file:String.cc; line number:867
7036 [3] file:String.cc; line number:860
7037 [4] file:String.cc; line number:875
7038 [5] file:String.cc; line number:853
7039 [6] file:String.cc; line number:846
7040 [7] file:String.cc; line number:735
7042 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7043 Breakpoint 2 at 0xb344: file String.cc, line 875.
7044 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7045 Multiple breakpoints were set.
7046 Use the "delete" command to delete unwanted
7053 @kindex set multiple-symbols
7054 @item set multiple-symbols @var{mode}
7055 @cindex multiple-symbols menu
7057 This option allows you to adjust the debugger behavior when an expression
7060 By default, @var{mode} is set to @code{all}. If the command with which
7061 the expression is used allows more than one choice, then @value{GDBN}
7062 automatically selects all possible choices. For instance, inserting
7063 a breakpoint on a function using an ambiguous name results in a breakpoint
7064 inserted on each possible match. However, if a unique choice must be made,
7065 then @value{GDBN} uses the menu to help you disambiguate the expression.
7066 For instance, printing the address of an overloaded function will result
7067 in the use of the menu.
7069 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7070 when an ambiguity is detected.
7072 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7073 an error due to the ambiguity and the command is aborted.
7075 @kindex show multiple-symbols
7076 @item show multiple-symbols
7077 Show the current value of the @code{multiple-symbols} setting.
7081 @section Program Variables
7083 The most common kind of expression to use is the name of a variable
7086 Variables in expressions are understood in the selected stack frame
7087 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7091 global (or file-static)
7098 visible according to the scope rules of the
7099 programming language from the point of execution in that frame
7102 @noindent This means that in the function
7117 you can examine and use the variable @code{a} whenever your program is
7118 executing within the function @code{foo}, but you can only use or
7119 examine the variable @code{b} while your program is executing inside
7120 the block where @code{b} is declared.
7122 @cindex variable name conflict
7123 There is an exception: you can refer to a variable or function whose
7124 scope is a single source file even if the current execution point is not
7125 in this file. But it is possible to have more than one such variable or
7126 function with the same name (in different source files). If that
7127 happens, referring to that name has unpredictable effects. If you wish,
7128 you can specify a static variable in a particular function or file,
7129 using the colon-colon (@code{::}) notation:
7131 @cindex colon-colon, context for variables/functions
7133 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7134 @cindex @code{::}, context for variables/functions
7137 @var{file}::@var{variable}
7138 @var{function}::@var{variable}
7142 Here @var{file} or @var{function} is the name of the context for the
7143 static @var{variable}. In the case of file names, you can use quotes to
7144 make sure @value{GDBN} parses the file name as a single word---for example,
7145 to print a global value of @code{x} defined in @file{f2.c}:
7148 (@value{GDBP}) p 'f2.c'::x
7151 @cindex C@t{++} scope resolution
7152 This use of @samp{::} is very rarely in conflict with the very similar
7153 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7154 scope resolution operator in @value{GDBN} expressions.
7155 @c FIXME: Um, so what happens in one of those rare cases where it's in
7158 @cindex wrong values
7159 @cindex variable values, wrong
7160 @cindex function entry/exit, wrong values of variables
7161 @cindex optimized code, wrong values of variables
7163 @emph{Warning:} Occasionally, a local variable may appear to have the
7164 wrong value at certain points in a function---just after entry to a new
7165 scope, and just before exit.
7167 You may see this problem when you are stepping by machine instructions.
7168 This is because, on most machines, it takes more than one instruction to
7169 set up a stack frame (including local variable definitions); if you are
7170 stepping by machine instructions, variables may appear to have the wrong
7171 values until the stack frame is completely built. On exit, it usually
7172 also takes more than one machine instruction to destroy a stack frame;
7173 after you begin stepping through that group of instructions, local
7174 variable definitions may be gone.
7176 This may also happen when the compiler does significant optimizations.
7177 To be sure of always seeing accurate values, turn off all optimization
7180 @cindex ``No symbol "foo" in current context''
7181 Another possible effect of compiler optimizations is to optimize
7182 unused variables out of existence, or assign variables to registers (as
7183 opposed to memory addresses). Depending on the support for such cases
7184 offered by the debug info format used by the compiler, @value{GDBN}
7185 might not be able to display values for such local variables. If that
7186 happens, @value{GDBN} will print a message like this:
7189 No symbol "foo" in current context.
7192 To solve such problems, either recompile without optimizations, or use a
7193 different debug info format, if the compiler supports several such
7194 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7195 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7196 produces debug info in a format that is superior to formats such as
7197 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7198 an effective form for debug info. @xref{Debugging Options,,Options
7199 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7200 Compiler Collection (GCC)}.
7201 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7202 that are best suited to C@t{++} programs.
7204 If you ask to print an object whose contents are unknown to
7205 @value{GDBN}, e.g., because its data type is not completely specified
7206 by the debug information, @value{GDBN} will say @samp{<incomplete
7207 type>}. @xref{Symbols, incomplete type}, for more about this.
7209 Strings are identified as arrays of @code{char} values without specified
7210 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7211 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7212 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7213 defines literal string type @code{"char"} as @code{char} without a sign.
7218 signed char var1[] = "A";
7221 You get during debugging
7226 $2 = @{65 'A', 0 '\0'@}
7230 @section Artificial Arrays
7232 @cindex artificial array
7234 @kindex @@@r{, referencing memory as an array}
7235 It is often useful to print out several successive objects of the
7236 same type in memory; a section of an array, or an array of
7237 dynamically determined size for which only a pointer exists in the
7240 You can do this by referring to a contiguous span of memory as an
7241 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7242 operand of @samp{@@} should be the first element of the desired array
7243 and be an individual object. The right operand should be the desired length
7244 of the array. The result is an array value whose elements are all of
7245 the type of the left argument. The first element is actually the left
7246 argument; the second element comes from bytes of memory immediately
7247 following those that hold the first element, and so on. Here is an
7248 example. If a program says
7251 int *array = (int *) malloc (len * sizeof (int));
7255 you can print the contents of @code{array} with
7261 The left operand of @samp{@@} must reside in memory. Array values made
7262 with @samp{@@} in this way behave just like other arrays in terms of
7263 subscripting, and are coerced to pointers when used in expressions.
7264 Artificial arrays most often appear in expressions via the value history
7265 (@pxref{Value History, ,Value History}), after printing one out.
7267 Another way to create an artificial array is to use a cast.
7268 This re-interprets a value as if it were an array.
7269 The value need not be in memory:
7271 (@value{GDBP}) p/x (short[2])0x12345678
7272 $1 = @{0x1234, 0x5678@}
7275 As a convenience, if you leave the array length out (as in
7276 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7277 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7279 (@value{GDBP}) p/x (short[])0x12345678
7280 $2 = @{0x1234, 0x5678@}
7283 Sometimes the artificial array mechanism is not quite enough; in
7284 moderately complex data structures, the elements of interest may not
7285 actually be adjacent---for example, if you are interested in the values
7286 of pointers in an array. One useful work-around in this situation is
7287 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7288 Variables}) as a counter in an expression that prints the first
7289 interesting value, and then repeat that expression via @key{RET}. For
7290 instance, suppose you have an array @code{dtab} of pointers to
7291 structures, and you are interested in the values of a field @code{fv}
7292 in each structure. Here is an example of what you might type:
7302 @node Output Formats
7303 @section Output Formats
7305 @cindex formatted output
7306 @cindex output formats
7307 By default, @value{GDBN} prints a value according to its data type. Sometimes
7308 this is not what you want. For example, you might want to print a number
7309 in hex, or a pointer in decimal. Or you might want to view data in memory
7310 at a certain address as a character string or as an instruction. To do
7311 these things, specify an @dfn{output format} when you print a value.
7313 The simplest use of output formats is to say how to print a value
7314 already computed. This is done by starting the arguments of the
7315 @code{print} command with a slash and a format letter. The format
7316 letters supported are:
7320 Regard the bits of the value as an integer, and print the integer in
7324 Print as integer in signed decimal.
7327 Print as integer in unsigned decimal.
7330 Print as integer in octal.
7333 Print as integer in binary. The letter @samp{t} stands for ``two''.
7334 @footnote{@samp{b} cannot be used because these format letters are also
7335 used with the @code{x} command, where @samp{b} stands for ``byte'';
7336 see @ref{Memory,,Examining Memory}.}
7339 @cindex unknown address, locating
7340 @cindex locate address
7341 Print as an address, both absolute in hexadecimal and as an offset from
7342 the nearest preceding symbol. You can use this format used to discover
7343 where (in what function) an unknown address is located:
7346 (@value{GDBP}) p/a 0x54320
7347 $3 = 0x54320 <_initialize_vx+396>
7351 The command @code{info symbol 0x54320} yields similar results.
7352 @xref{Symbols, info symbol}.
7355 Regard as an integer and print it as a character constant. This
7356 prints both the numerical value and its character representation. The
7357 character representation is replaced with the octal escape @samp{\nnn}
7358 for characters outside the 7-bit @sc{ascii} range.
7360 Without this format, @value{GDBN} displays @code{char},
7361 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7362 constants. Single-byte members of vectors are displayed as integer
7366 Regard the bits of the value as a floating point number and print
7367 using typical floating point syntax.
7370 @cindex printing strings
7371 @cindex printing byte arrays
7372 Regard as a string, if possible. With this format, pointers to single-byte
7373 data are displayed as null-terminated strings and arrays of single-byte data
7374 are displayed as fixed-length strings. Other values are displayed in their
7377 Without this format, @value{GDBN} displays pointers to and arrays of
7378 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7379 strings. Single-byte members of a vector are displayed as an integer
7383 @cindex raw printing
7384 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7385 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7386 Printing}). This typically results in a higher-level display of the
7387 value's contents. The @samp{r} format bypasses any Python
7388 pretty-printer which might exist.
7391 For example, to print the program counter in hex (@pxref{Registers}), type
7398 Note that no space is required before the slash; this is because command
7399 names in @value{GDBN} cannot contain a slash.
7401 To reprint the last value in the value history with a different format,
7402 you can use the @code{print} command with just a format and no
7403 expression. For example, @samp{p/x} reprints the last value in hex.
7406 @section Examining Memory
7408 You can use the command @code{x} (for ``examine'') to examine memory in
7409 any of several formats, independently of your program's data types.
7411 @cindex examining memory
7413 @kindex x @r{(examine memory)}
7414 @item x/@var{nfu} @var{addr}
7417 Use the @code{x} command to examine memory.
7420 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7421 much memory to display and how to format it; @var{addr} is an
7422 expression giving the address where you want to start displaying memory.
7423 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7424 Several commands set convenient defaults for @var{addr}.
7427 @item @var{n}, the repeat count
7428 The repeat count is a decimal integer; the default is 1. It specifies
7429 how much memory (counting by units @var{u}) to display.
7430 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7433 @item @var{f}, the display format
7434 The display format is one of the formats used by @code{print}
7435 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7436 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7437 The default is @samp{x} (hexadecimal) initially. The default changes
7438 each time you use either @code{x} or @code{print}.
7440 @item @var{u}, the unit size
7441 The unit size is any of
7447 Halfwords (two bytes).
7449 Words (four bytes). This is the initial default.
7451 Giant words (eight bytes).
7454 Each time you specify a unit size with @code{x}, that size becomes the
7455 default unit the next time you use @code{x}. For the @samp{i} format,
7456 the unit size is ignored and is normally not written. For the @samp{s} format,
7457 the unit size defaults to @samp{b}, unless it is explicitly given.
7458 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7459 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7460 Note that the results depend on the programming language of the
7461 current compilation unit. If the language is C, the @samp{s}
7462 modifier will use the UTF-16 encoding while @samp{w} will use
7463 UTF-32. The encoding is set by the programming language and cannot
7466 @item @var{addr}, starting display address
7467 @var{addr} is the address where you want @value{GDBN} to begin displaying
7468 memory. The expression need not have a pointer value (though it may);
7469 it is always interpreted as an integer address of a byte of memory.
7470 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7471 @var{addr} is usually just after the last address examined---but several
7472 other commands also set the default address: @code{info breakpoints} (to
7473 the address of the last breakpoint listed), @code{info line} (to the
7474 starting address of a line), and @code{print} (if you use it to display
7475 a value from memory).
7478 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7479 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7480 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7481 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7482 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7484 Since the letters indicating unit sizes are all distinct from the
7485 letters specifying output formats, you do not have to remember whether
7486 unit size or format comes first; either order works. The output
7487 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7488 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7490 Even though the unit size @var{u} is ignored for the formats @samp{s}
7491 and @samp{i}, you might still want to use a count @var{n}; for example,
7492 @samp{3i} specifies that you want to see three machine instructions,
7493 including any operands. For convenience, especially when used with
7494 the @code{display} command, the @samp{i} format also prints branch delay
7495 slot instructions, if any, beyond the count specified, which immediately
7496 follow the last instruction that is within the count. The command
7497 @code{disassemble} gives an alternative way of inspecting machine
7498 instructions; see @ref{Machine Code,,Source and Machine Code}.
7500 All the defaults for the arguments to @code{x} are designed to make it
7501 easy to continue scanning memory with minimal specifications each time
7502 you use @code{x}. For example, after you have inspected three machine
7503 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7504 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7505 the repeat count @var{n} is used again; the other arguments default as
7506 for successive uses of @code{x}.
7508 When examining machine instructions, the instruction at current program
7509 counter is shown with a @code{=>} marker. For example:
7512 (@value{GDBP}) x/5i $pc-6
7513 0x804837f <main+11>: mov %esp,%ebp
7514 0x8048381 <main+13>: push %ecx
7515 0x8048382 <main+14>: sub $0x4,%esp
7516 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7517 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7520 @cindex @code{$_}, @code{$__}, and value history
7521 The addresses and contents printed by the @code{x} command are not saved
7522 in the value history because there is often too much of them and they
7523 would get in the way. Instead, @value{GDBN} makes these values available for
7524 subsequent use in expressions as values of the convenience variables
7525 @code{$_} and @code{$__}. After an @code{x} command, the last address
7526 examined is available for use in expressions in the convenience variable
7527 @code{$_}. The contents of that address, as examined, are available in
7528 the convenience variable @code{$__}.
7530 If the @code{x} command has a repeat count, the address and contents saved
7531 are from the last memory unit printed; this is not the same as the last
7532 address printed if several units were printed on the last line of output.
7534 @cindex remote memory comparison
7535 @cindex verify remote memory image
7536 When you are debugging a program running on a remote target machine
7537 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7538 remote machine's memory against the executable file you downloaded to
7539 the target. The @code{compare-sections} command is provided for such
7543 @kindex compare-sections
7544 @item compare-sections @r{[}@var{section-name}@r{]}
7545 Compare the data of a loadable section @var{section-name} in the
7546 executable file of the program being debugged with the same section in
7547 the remote machine's memory, and report any mismatches. With no
7548 arguments, compares all loadable sections. This command's
7549 availability depends on the target's support for the @code{"qCRC"}
7554 @section Automatic Display
7555 @cindex automatic display
7556 @cindex display of expressions
7558 If you find that you want to print the value of an expression frequently
7559 (to see how it changes), you might want to add it to the @dfn{automatic
7560 display list} so that @value{GDBN} prints its value each time your program stops.
7561 Each expression added to the list is given a number to identify it;
7562 to remove an expression from the list, you specify that number.
7563 The automatic display looks like this:
7567 3: bar[5] = (struct hack *) 0x3804
7571 This display shows item numbers, expressions and their current values. As with
7572 displays you request manually using @code{x} or @code{print}, you can
7573 specify the output format you prefer; in fact, @code{display} decides
7574 whether to use @code{print} or @code{x} depending your format
7575 specification---it uses @code{x} if you specify either the @samp{i}
7576 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7580 @item display @var{expr}
7581 Add the expression @var{expr} to the list of expressions to display
7582 each time your program stops. @xref{Expressions, ,Expressions}.
7584 @code{display} does not repeat if you press @key{RET} again after using it.
7586 @item display/@var{fmt} @var{expr}
7587 For @var{fmt} specifying only a display format and not a size or
7588 count, add the expression @var{expr} to the auto-display list but
7589 arrange to display it each time in the specified format @var{fmt}.
7590 @xref{Output Formats,,Output Formats}.
7592 @item display/@var{fmt} @var{addr}
7593 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7594 number of units, add the expression @var{addr} as a memory address to
7595 be examined each time your program stops. Examining means in effect
7596 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7599 For example, @samp{display/i $pc} can be helpful, to see the machine
7600 instruction about to be executed each time execution stops (@samp{$pc}
7601 is a common name for the program counter; @pxref{Registers, ,Registers}).
7604 @kindex delete display
7606 @item undisplay @var{dnums}@dots{}
7607 @itemx delete display @var{dnums}@dots{}
7608 Remove item numbers @var{dnums} from the list of expressions to display.
7610 @code{undisplay} does not repeat if you press @key{RET} after using it.
7611 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7613 @kindex disable display
7614 @item disable display @var{dnums}@dots{}
7615 Disable the display of item numbers @var{dnums}. A disabled display
7616 item is not printed automatically, but is not forgotten. It may be
7617 enabled again later.
7619 @kindex enable display
7620 @item enable display @var{dnums}@dots{}
7621 Enable display of item numbers @var{dnums}. It becomes effective once
7622 again in auto display of its expression, until you specify otherwise.
7625 Display the current values of the expressions on the list, just as is
7626 done when your program stops.
7628 @kindex info display
7630 Print the list of expressions previously set up to display
7631 automatically, each one with its item number, but without showing the
7632 values. This includes disabled expressions, which are marked as such.
7633 It also includes expressions which would not be displayed right now
7634 because they refer to automatic variables not currently available.
7637 @cindex display disabled out of scope
7638 If a display expression refers to local variables, then it does not make
7639 sense outside the lexical context for which it was set up. Such an
7640 expression is disabled when execution enters a context where one of its
7641 variables is not defined. For example, if you give the command
7642 @code{display last_char} while inside a function with an argument
7643 @code{last_char}, @value{GDBN} displays this argument while your program
7644 continues to stop inside that function. When it stops elsewhere---where
7645 there is no variable @code{last_char}---the display is disabled
7646 automatically. The next time your program stops where @code{last_char}
7647 is meaningful, you can enable the display expression once again.
7649 @node Print Settings
7650 @section Print Settings
7652 @cindex format options
7653 @cindex print settings
7654 @value{GDBN} provides the following ways to control how arrays, structures,
7655 and symbols are printed.
7658 These settings are useful for debugging programs in any language:
7662 @item set print address
7663 @itemx set print address on
7664 @cindex print/don't print memory addresses
7665 @value{GDBN} prints memory addresses showing the location of stack
7666 traces, structure values, pointer values, breakpoints, and so forth,
7667 even when it also displays the contents of those addresses. The default
7668 is @code{on}. For example, this is what a stack frame display looks like with
7669 @code{set print address on}:
7674 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7676 530 if (lquote != def_lquote)
7680 @item set print address off
7681 Do not print addresses when displaying their contents. For example,
7682 this is the same stack frame displayed with @code{set print address off}:
7686 (@value{GDBP}) set print addr off
7688 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7689 530 if (lquote != def_lquote)
7693 You can use @samp{set print address off} to eliminate all machine
7694 dependent displays from the @value{GDBN} interface. For example, with
7695 @code{print address off}, you should get the same text for backtraces on
7696 all machines---whether or not they involve pointer arguments.
7699 @item show print address
7700 Show whether or not addresses are to be printed.
7703 When @value{GDBN} prints a symbolic address, it normally prints the
7704 closest earlier symbol plus an offset. If that symbol does not uniquely
7705 identify the address (for example, it is a name whose scope is a single
7706 source file), you may need to clarify. One way to do this is with
7707 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7708 you can set @value{GDBN} to print the source file and line number when
7709 it prints a symbolic address:
7712 @item set print symbol-filename on
7713 @cindex source file and line of a symbol
7714 @cindex symbol, source file and line
7715 Tell @value{GDBN} to print the source file name and line number of a
7716 symbol in the symbolic form of an address.
7718 @item set print symbol-filename off
7719 Do not print source file name and line number of a symbol. This is the
7722 @item show print symbol-filename
7723 Show whether or not @value{GDBN} will print the source file name and
7724 line number of a symbol in the symbolic form of an address.
7727 Another situation where it is helpful to show symbol filenames and line
7728 numbers is when disassembling code; @value{GDBN} shows you the line
7729 number and source file that corresponds to each instruction.
7731 Also, you may wish to see the symbolic form only if the address being
7732 printed is reasonably close to the closest earlier symbol:
7735 @item set print max-symbolic-offset @var{max-offset}
7736 @cindex maximum value for offset of closest symbol
7737 Tell @value{GDBN} to only display the symbolic form of an address if the
7738 offset between the closest earlier symbol and the address is less than
7739 @var{max-offset}. The default is 0, which tells @value{GDBN}
7740 to always print the symbolic form of an address if any symbol precedes it.
7742 @item show print max-symbolic-offset
7743 Ask how large the maximum offset is that @value{GDBN} prints in a
7747 @cindex wild pointer, interpreting
7748 @cindex pointer, finding referent
7749 If you have a pointer and you are not sure where it points, try
7750 @samp{set print symbol-filename on}. Then you can determine the name
7751 and source file location of the variable where it points, using
7752 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7753 For example, here @value{GDBN} shows that a variable @code{ptt} points
7754 at another variable @code{t}, defined in @file{hi2.c}:
7757 (@value{GDBP}) set print symbol-filename on
7758 (@value{GDBP}) p/a ptt
7759 $4 = 0xe008 <t in hi2.c>
7763 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7764 does not show the symbol name and filename of the referent, even with
7765 the appropriate @code{set print} options turned on.
7768 Other settings control how different kinds of objects are printed:
7771 @item set print array
7772 @itemx set print array on
7773 @cindex pretty print arrays
7774 Pretty print arrays. This format is more convenient to read,
7775 but uses more space. The default is off.
7777 @item set print array off
7778 Return to compressed format for arrays.
7780 @item show print array
7781 Show whether compressed or pretty format is selected for displaying
7784 @cindex print array indexes
7785 @item set print array-indexes
7786 @itemx set print array-indexes on
7787 Print the index of each element when displaying arrays. May be more
7788 convenient to locate a given element in the array or quickly find the
7789 index of a given element in that printed array. The default is off.
7791 @item set print array-indexes off
7792 Stop printing element indexes when displaying arrays.
7794 @item show print array-indexes
7795 Show whether the index of each element is printed when displaying
7798 @item set print elements @var{number-of-elements}
7799 @cindex number of array elements to print
7800 @cindex limit on number of printed array elements
7801 Set a limit on how many elements of an array @value{GDBN} will print.
7802 If @value{GDBN} is printing a large array, it stops printing after it has
7803 printed the number of elements set by the @code{set print elements} command.
7804 This limit also applies to the display of strings.
7805 When @value{GDBN} starts, this limit is set to 200.
7806 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7808 @item show print elements
7809 Display the number of elements of a large array that @value{GDBN} will print.
7810 If the number is 0, then the printing is unlimited.
7812 @item set print frame-arguments @var{value}
7813 @kindex set print frame-arguments
7814 @cindex printing frame argument values
7815 @cindex print all frame argument values
7816 @cindex print frame argument values for scalars only
7817 @cindex do not print frame argument values
7818 This command allows to control how the values of arguments are printed
7819 when the debugger prints a frame (@pxref{Frames}). The possible
7824 The values of all arguments are printed.
7827 Print the value of an argument only if it is a scalar. The value of more
7828 complex arguments such as arrays, structures, unions, etc, is replaced
7829 by @code{@dots{}}. This is the default. Here is an example where
7830 only scalar arguments are shown:
7833 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7838 None of the argument values are printed. Instead, the value of each argument
7839 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7842 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7847 By default, only scalar arguments are printed. This command can be used
7848 to configure the debugger to print the value of all arguments, regardless
7849 of their type. However, it is often advantageous to not print the value
7850 of more complex parameters. For instance, it reduces the amount of
7851 information printed in each frame, making the backtrace more readable.
7852 Also, it improves performance when displaying Ada frames, because
7853 the computation of large arguments can sometimes be CPU-intensive,
7854 especially in large applications. Setting @code{print frame-arguments}
7855 to @code{scalars} (the default) or @code{none} avoids this computation,
7856 thus speeding up the display of each Ada frame.
7858 @item show print frame-arguments
7859 Show how the value of arguments should be displayed when printing a frame.
7861 @item set print repeats
7862 @cindex repeated array elements
7863 Set the threshold for suppressing display of repeated array
7864 elements. When the number of consecutive identical elements of an
7865 array exceeds the threshold, @value{GDBN} prints the string
7866 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7867 identical repetitions, instead of displaying the identical elements
7868 themselves. Setting the threshold to zero will cause all elements to
7869 be individually printed. The default threshold is 10.
7871 @item show print repeats
7872 Display the current threshold for printing repeated identical
7875 @item set print null-stop
7876 @cindex @sc{null} elements in arrays
7877 Cause @value{GDBN} to stop printing the characters of an array when the first
7878 @sc{null} is encountered. This is useful when large arrays actually
7879 contain only short strings.
7882 @item show print null-stop
7883 Show whether @value{GDBN} stops printing an array on the first
7884 @sc{null} character.
7886 @item set print pretty on
7887 @cindex print structures in indented form
7888 @cindex indentation in structure display
7889 Cause @value{GDBN} to print structures in an indented format with one member
7890 per line, like this:
7905 @item set print pretty off
7906 Cause @value{GDBN} to print structures in a compact format, like this:
7910 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7911 meat = 0x54 "Pork"@}
7916 This is the default format.
7918 @item show print pretty
7919 Show which format @value{GDBN} is using to print structures.
7921 @item set print sevenbit-strings on
7922 @cindex eight-bit characters in strings
7923 @cindex octal escapes in strings
7924 Print using only seven-bit characters; if this option is set,
7925 @value{GDBN} displays any eight-bit characters (in strings or
7926 character values) using the notation @code{\}@var{nnn}. This setting is
7927 best if you are working in English (@sc{ascii}) and you use the
7928 high-order bit of characters as a marker or ``meta'' bit.
7930 @item set print sevenbit-strings off
7931 Print full eight-bit characters. This allows the use of more
7932 international character sets, and is the default.
7934 @item show print sevenbit-strings
7935 Show whether or not @value{GDBN} is printing only seven-bit characters.
7937 @item set print union on
7938 @cindex unions in structures, printing
7939 Tell @value{GDBN} to print unions which are contained in structures
7940 and other unions. This is the default setting.
7942 @item set print union off
7943 Tell @value{GDBN} not to print unions which are contained in
7944 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7947 @item show print union
7948 Ask @value{GDBN} whether or not it will print unions which are contained in
7949 structures and other unions.
7951 For example, given the declarations
7954 typedef enum @{Tree, Bug@} Species;
7955 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7956 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7967 struct thing foo = @{Tree, @{Acorn@}@};
7971 with @code{set print union on} in effect @samp{p foo} would print
7974 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7978 and with @code{set print union off} in effect it would print
7981 $1 = @{it = Tree, form = @{...@}@}
7985 @code{set print union} affects programs written in C-like languages
7991 These settings are of interest when debugging C@t{++} programs:
7994 @cindex demangling C@t{++} names
7995 @item set print demangle
7996 @itemx set print demangle on
7997 Print C@t{++} names in their source form rather than in the encoded
7998 (``mangled'') form passed to the assembler and linker for type-safe
7999 linkage. The default is on.
8001 @item show print demangle
8002 Show whether C@t{++} names are printed in mangled or demangled form.
8004 @item set print asm-demangle
8005 @itemx set print asm-demangle on
8006 Print C@t{++} names in their source form rather than their mangled form, even
8007 in assembler code printouts such as instruction disassemblies.
8010 @item show print asm-demangle
8011 Show whether C@t{++} names in assembly listings are printed in mangled
8014 @cindex C@t{++} symbol decoding style
8015 @cindex symbol decoding style, C@t{++}
8016 @kindex set demangle-style
8017 @item set demangle-style @var{style}
8018 Choose among several encoding schemes used by different compilers to
8019 represent C@t{++} names. The choices for @var{style} are currently:
8023 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8026 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8027 This is the default.
8030 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8033 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8036 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8037 @strong{Warning:} this setting alone is not sufficient to allow
8038 debugging @code{cfront}-generated executables. @value{GDBN} would
8039 require further enhancement to permit that.
8042 If you omit @var{style}, you will see a list of possible formats.
8044 @item show demangle-style
8045 Display the encoding style currently in use for decoding C@t{++} symbols.
8047 @item set print object
8048 @itemx set print object on
8049 @cindex derived type of an object, printing
8050 @cindex display derived types
8051 When displaying a pointer to an object, identify the @emph{actual}
8052 (derived) type of the object rather than the @emph{declared} type, using
8053 the virtual function table.
8055 @item set print object off
8056 Display only the declared type of objects, without reference to the
8057 virtual function table. This is the default setting.
8059 @item show print object
8060 Show whether actual, or declared, object types are displayed.
8062 @item set print static-members
8063 @itemx set print static-members on
8064 @cindex static members of C@t{++} objects
8065 Print static members when displaying a C@t{++} object. The default is on.
8067 @item set print static-members off
8068 Do not print static members when displaying a C@t{++} object.
8070 @item show print static-members
8071 Show whether C@t{++} static members are printed or not.
8073 @item set print pascal_static-members
8074 @itemx set print pascal_static-members on
8075 @cindex static members of Pascal objects
8076 @cindex Pascal objects, static members display
8077 Print static members when displaying a Pascal object. The default is on.
8079 @item set print pascal_static-members off
8080 Do not print static members when displaying a Pascal object.
8082 @item show print pascal_static-members
8083 Show whether Pascal static members are printed or not.
8085 @c These don't work with HP ANSI C++ yet.
8086 @item set print vtbl
8087 @itemx set print vtbl on
8088 @cindex pretty print C@t{++} virtual function tables
8089 @cindex virtual functions (C@t{++}) display
8090 @cindex VTBL display
8091 Pretty print C@t{++} virtual function tables. The default is off.
8092 (The @code{vtbl} commands do not work on programs compiled with the HP
8093 ANSI C@t{++} compiler (@code{aCC}).)
8095 @item set print vtbl off
8096 Do not pretty print C@t{++} virtual function tables.
8098 @item show print vtbl
8099 Show whether C@t{++} virtual function tables are pretty printed, or not.
8102 @node Pretty Printing
8103 @section Pretty Printing
8105 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8106 Python code. It greatly simplifies the display of complex objects. This
8107 mechanism works for both MI and the CLI.
8109 For example, here is how a C@t{++} @code{std::string} looks without a
8113 (@value{GDBP}) print s
8115 static npos = 4294967295,
8117 <std::allocator<char>> = @{
8118 <__gnu_cxx::new_allocator<char>> = @{
8119 <No data fields>@}, <No data fields>
8121 members of std::basic_string<char, std::char_traits<char>,
8122 std::allocator<char> >::_Alloc_hider:
8123 _M_p = 0x804a014 "abcd"
8128 With a pretty-printer for @code{std::string} only the contents are printed:
8131 (@value{GDBP}) print s
8135 For implementing pretty printers for new types you should read the Python API
8136 details (@pxref{Pretty Printing API}).
8139 @section Value History
8141 @cindex value history
8142 @cindex history of values printed by @value{GDBN}
8143 Values printed by the @code{print} command are saved in the @value{GDBN}
8144 @dfn{value history}. This allows you to refer to them in other expressions.
8145 Values are kept until the symbol table is re-read or discarded
8146 (for example with the @code{file} or @code{symbol-file} commands).
8147 When the symbol table changes, the value history is discarded,
8148 since the values may contain pointers back to the types defined in the
8153 @cindex history number
8154 The values printed are given @dfn{history numbers} by which you can
8155 refer to them. These are successive integers starting with one.
8156 @code{print} shows you the history number assigned to a value by
8157 printing @samp{$@var{num} = } before the value; here @var{num} is the
8160 To refer to any previous value, use @samp{$} followed by the value's
8161 history number. The way @code{print} labels its output is designed to
8162 remind you of this. Just @code{$} refers to the most recent value in
8163 the history, and @code{$$} refers to the value before that.
8164 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8165 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8166 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8168 For example, suppose you have just printed a pointer to a structure and
8169 want to see the contents of the structure. It suffices to type
8175 If you have a chain of structures where the component @code{next} points
8176 to the next one, you can print the contents of the next one with this:
8183 You can print successive links in the chain by repeating this
8184 command---which you can do by just typing @key{RET}.
8186 Note that the history records values, not expressions. If the value of
8187 @code{x} is 4 and you type these commands:
8195 then the value recorded in the value history by the @code{print} command
8196 remains 4 even though the value of @code{x} has changed.
8201 Print the last ten values in the value history, with their item numbers.
8202 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8203 values} does not change the history.
8205 @item show values @var{n}
8206 Print ten history values centered on history item number @var{n}.
8209 Print ten history values just after the values last printed. If no more
8210 values are available, @code{show values +} produces no display.
8213 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8214 same effect as @samp{show values +}.
8216 @node Convenience Vars
8217 @section Convenience Variables
8219 @cindex convenience variables
8220 @cindex user-defined variables
8221 @value{GDBN} provides @dfn{convenience variables} that you can use within
8222 @value{GDBN} to hold on to a value and refer to it later. These variables
8223 exist entirely within @value{GDBN}; they are not part of your program, and
8224 setting a convenience variable has no direct effect on further execution
8225 of your program. That is why you can use them freely.
8227 Convenience variables are prefixed with @samp{$}. Any name preceded by
8228 @samp{$} can be used for a convenience variable, unless it is one of
8229 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8230 (Value history references, in contrast, are @emph{numbers} preceded
8231 by @samp{$}. @xref{Value History, ,Value History}.)
8233 You can save a value in a convenience variable with an assignment
8234 expression, just as you would set a variable in your program.
8238 set $foo = *object_ptr
8242 would save in @code{$foo} the value contained in the object pointed to by
8245 Using a convenience variable for the first time creates it, but its
8246 value is @code{void} until you assign a new value. You can alter the
8247 value with another assignment at any time.
8249 Convenience variables have no fixed types. You can assign a convenience
8250 variable any type of value, including structures and arrays, even if
8251 that variable already has a value of a different type. The convenience
8252 variable, when used as an expression, has the type of its current value.
8255 @kindex show convenience
8256 @cindex show all user variables
8257 @item show convenience
8258 Print a list of convenience variables used so far, and their values.
8259 Abbreviated @code{show conv}.
8261 @kindex init-if-undefined
8262 @cindex convenience variables, initializing
8263 @item init-if-undefined $@var{variable} = @var{expression}
8264 Set a convenience variable if it has not already been set. This is useful
8265 for user-defined commands that keep some state. It is similar, in concept,
8266 to using local static variables with initializers in C (except that
8267 convenience variables are global). It can also be used to allow users to
8268 override default values used in a command script.
8270 If the variable is already defined then the expression is not evaluated so
8271 any side-effects do not occur.
8274 One of the ways to use a convenience variable is as a counter to be
8275 incremented or a pointer to be advanced. For example, to print
8276 a field from successive elements of an array of structures:
8280 print bar[$i++]->contents
8284 Repeat that command by typing @key{RET}.
8286 Some convenience variables are created automatically by @value{GDBN} and given
8287 values likely to be useful.
8290 @vindex $_@r{, convenience variable}
8292 The variable @code{$_} is automatically set by the @code{x} command to
8293 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8294 commands which provide a default address for @code{x} to examine also
8295 set @code{$_} to that address; these commands include @code{info line}
8296 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8297 except when set by the @code{x} command, in which case it is a pointer
8298 to the type of @code{$__}.
8300 @vindex $__@r{, convenience variable}
8302 The variable @code{$__} is automatically set by the @code{x} command
8303 to the value found in the last address examined. Its type is chosen
8304 to match the format in which the data was printed.
8307 @vindex $_exitcode@r{, convenience variable}
8308 The variable @code{$_exitcode} is automatically set to the exit code when
8309 the program being debugged terminates.
8312 @vindex $_sdata@r{, inspect, convenience variable}
8313 The variable @code{$_sdata} contains extra collected static tracepoint
8314 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8315 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8316 if extra static tracepoint data has not been collected.
8319 @vindex $_siginfo@r{, convenience variable}
8320 The variable @code{$_siginfo} contains extra signal information
8321 (@pxref{extra signal information}). Note that @code{$_siginfo}
8322 could be empty, if the application has not yet received any signals.
8323 For example, it will be empty before you execute the @code{run} command.
8326 @vindex $_tlb@r{, convenience variable}
8327 The variable @code{$_tlb} is automatically set when debugging
8328 applications running on MS-Windows in native mode or connected to
8329 gdbserver that supports the @code{qGetTIBAddr} request.
8330 @xref{General Query Packets}.
8331 This variable contains the address of the thread information block.
8335 On HP-UX systems, if you refer to a function or variable name that
8336 begins with a dollar sign, @value{GDBN} searches for a user or system
8337 name first, before it searches for a convenience variable.
8339 @cindex convenience functions
8340 @value{GDBN} also supplies some @dfn{convenience functions}. These
8341 have a syntax similar to convenience variables. A convenience
8342 function can be used in an expression just like an ordinary function;
8343 however, a convenience function is implemented internally to
8348 @kindex help function
8349 @cindex show all convenience functions
8350 Print a list of all convenience functions.
8357 You can refer to machine register contents, in expressions, as variables
8358 with names starting with @samp{$}. The names of registers are different
8359 for each machine; use @code{info registers} to see the names used on
8363 @kindex info registers
8364 @item info registers
8365 Print the names and values of all registers except floating-point
8366 and vector registers (in the selected stack frame).
8368 @kindex info all-registers
8369 @cindex floating point registers
8370 @item info all-registers
8371 Print the names and values of all registers, including floating-point
8372 and vector registers (in the selected stack frame).
8374 @item info registers @var{regname} @dots{}
8375 Print the @dfn{relativized} value of each specified register @var{regname}.
8376 As discussed in detail below, register values are normally relative to
8377 the selected stack frame. @var{regname} may be any register name valid on
8378 the machine you are using, with or without the initial @samp{$}.
8381 @cindex stack pointer register
8382 @cindex program counter register
8383 @cindex process status register
8384 @cindex frame pointer register
8385 @cindex standard registers
8386 @value{GDBN} has four ``standard'' register names that are available (in
8387 expressions) on most machines---whenever they do not conflict with an
8388 architecture's canonical mnemonics for registers. The register names
8389 @code{$pc} and @code{$sp} are used for the program counter register and
8390 the stack pointer. @code{$fp} is used for a register that contains a
8391 pointer to the current stack frame, and @code{$ps} is used for a
8392 register that contains the processor status. For example,
8393 you could print the program counter in hex with
8400 or print the instruction to be executed next with
8407 or add four to the stack pointer@footnote{This is a way of removing
8408 one word from the stack, on machines where stacks grow downward in
8409 memory (most machines, nowadays). This assumes that the innermost
8410 stack frame is selected; setting @code{$sp} is not allowed when other
8411 stack frames are selected. To pop entire frames off the stack,
8412 regardless of machine architecture, use @code{return};
8413 see @ref{Returning, ,Returning from a Function}.} with
8419 Whenever possible, these four standard register names are available on
8420 your machine even though the machine has different canonical mnemonics,
8421 so long as there is no conflict. The @code{info registers} command
8422 shows the canonical names. For example, on the SPARC, @code{info
8423 registers} displays the processor status register as @code{$psr} but you
8424 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8425 is an alias for the @sc{eflags} register.
8427 @value{GDBN} always considers the contents of an ordinary register as an
8428 integer when the register is examined in this way. Some machines have
8429 special registers which can hold nothing but floating point; these
8430 registers are considered to have floating point values. There is no way
8431 to refer to the contents of an ordinary register as floating point value
8432 (although you can @emph{print} it as a floating point value with
8433 @samp{print/f $@var{regname}}).
8435 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8436 means that the data format in which the register contents are saved by
8437 the operating system is not the same one that your program normally
8438 sees. For example, the registers of the 68881 floating point
8439 coprocessor are always saved in ``extended'' (raw) format, but all C
8440 programs expect to work with ``double'' (virtual) format. In such
8441 cases, @value{GDBN} normally works with the virtual format only (the format
8442 that makes sense for your program), but the @code{info registers} command
8443 prints the data in both formats.
8445 @cindex SSE registers (x86)
8446 @cindex MMX registers (x86)
8447 Some machines have special registers whose contents can be interpreted
8448 in several different ways. For example, modern x86-based machines
8449 have SSE and MMX registers that can hold several values packed
8450 together in several different formats. @value{GDBN} refers to such
8451 registers in @code{struct} notation:
8454 (@value{GDBP}) print $xmm1
8456 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8457 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8458 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8459 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8460 v4_int32 = @{0, 20657912, 11, 13@},
8461 v2_int64 = @{88725056443645952, 55834574859@},
8462 uint128 = 0x0000000d0000000b013b36f800000000
8467 To set values of such registers, you need to tell @value{GDBN} which
8468 view of the register you wish to change, as if you were assigning
8469 value to a @code{struct} member:
8472 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8475 Normally, register values are relative to the selected stack frame
8476 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8477 value that the register would contain if all stack frames farther in
8478 were exited and their saved registers restored. In order to see the
8479 true contents of hardware registers, you must select the innermost
8480 frame (with @samp{frame 0}).
8482 However, @value{GDBN} must deduce where registers are saved, from the machine
8483 code generated by your compiler. If some registers are not saved, or if
8484 @value{GDBN} is unable to locate the saved registers, the selected stack
8485 frame makes no difference.
8487 @node Floating Point Hardware
8488 @section Floating Point Hardware
8489 @cindex floating point
8491 Depending on the configuration, @value{GDBN} may be able to give
8492 you more information about the status of the floating point hardware.
8497 Display hardware-dependent information about the floating
8498 point unit. The exact contents and layout vary depending on the
8499 floating point chip. Currently, @samp{info float} is supported on
8500 the ARM and x86 machines.
8504 @section Vector Unit
8507 Depending on the configuration, @value{GDBN} may be able to give you
8508 more information about the status of the vector unit.
8513 Display information about the vector unit. The exact contents and
8514 layout vary depending on the hardware.
8517 @node OS Information
8518 @section Operating System Auxiliary Information
8519 @cindex OS information
8521 @value{GDBN} provides interfaces to useful OS facilities that can help
8522 you debug your program.
8524 @cindex @code{ptrace} system call
8525 @cindex @code{struct user} contents
8526 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8527 machines), it interfaces with the inferior via the @code{ptrace}
8528 system call. The operating system creates a special sata structure,
8529 called @code{struct user}, for this interface. You can use the
8530 command @code{info udot} to display the contents of this data
8536 Display the contents of the @code{struct user} maintained by the OS
8537 kernel for the program being debugged. @value{GDBN} displays the
8538 contents of @code{struct user} as a list of hex numbers, similar to
8539 the @code{examine} command.
8542 @cindex auxiliary vector
8543 @cindex vector, auxiliary
8544 Some operating systems supply an @dfn{auxiliary vector} to programs at
8545 startup. This is akin to the arguments and environment that you
8546 specify for a program, but contains a system-dependent variety of
8547 binary values that tell system libraries important details about the
8548 hardware, operating system, and process. Each value's purpose is
8549 identified by an integer tag; the meanings are well-known but system-specific.
8550 Depending on the configuration and operating system facilities,
8551 @value{GDBN} may be able to show you this information. For remote
8552 targets, this functionality may further depend on the remote stub's
8553 support of the @samp{qXfer:auxv:read} packet, see
8554 @ref{qXfer auxiliary vector read}.
8559 Display the auxiliary vector of the inferior, which can be either a
8560 live process or a core dump file. @value{GDBN} prints each tag value
8561 numerically, and also shows names and text descriptions for recognized
8562 tags. Some values in the vector are numbers, some bit masks, and some
8563 pointers to strings or other data. @value{GDBN} displays each value in the
8564 most appropriate form for a recognized tag, and in hexadecimal for
8565 an unrecognized tag.
8568 On some targets, @value{GDBN} can access operating-system-specific information
8569 and display it to user, without interpretation. For remote targets,
8570 this functionality depends on the remote stub's support of the
8571 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8576 List the types of OS information available for the target. If the
8577 target does not return a list of possible types, this command will
8580 @kindex info os processes
8581 @item info os processes
8582 Display the list of processes on the target. For each process,
8583 @value{GDBN} prints the process identifier, the name of the user, and
8584 the command corresponding to the process.
8587 @node Memory Region Attributes
8588 @section Memory Region Attributes
8589 @cindex memory region attributes
8591 @dfn{Memory region attributes} allow you to describe special handling
8592 required by regions of your target's memory. @value{GDBN} uses
8593 attributes to determine whether to allow certain types of memory
8594 accesses; whether to use specific width accesses; and whether to cache
8595 target memory. By default the description of memory regions is
8596 fetched from the target (if the current target supports this), but the
8597 user can override the fetched regions.
8599 Defined memory regions can be individually enabled and disabled. When a
8600 memory region is disabled, @value{GDBN} uses the default attributes when
8601 accessing memory in that region. Similarly, if no memory regions have
8602 been defined, @value{GDBN} uses the default attributes when accessing
8605 When a memory region is defined, it is given a number to identify it;
8606 to enable, disable, or remove a memory region, you specify that number.
8610 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8611 Define a memory region bounded by @var{lower} and @var{upper} with
8612 attributes @var{attributes}@dots{}, and add it to the list of regions
8613 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8614 case: it is treated as the target's maximum memory address.
8615 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8618 Discard any user changes to the memory regions and use target-supplied
8619 regions, if available, or no regions if the target does not support.
8622 @item delete mem @var{nums}@dots{}
8623 Remove memory regions @var{nums}@dots{} from the list of regions
8624 monitored by @value{GDBN}.
8627 @item disable mem @var{nums}@dots{}
8628 Disable monitoring of memory regions @var{nums}@dots{}.
8629 A disabled memory region is not forgotten.
8630 It may be enabled again later.
8633 @item enable mem @var{nums}@dots{}
8634 Enable monitoring of memory regions @var{nums}@dots{}.
8638 Print a table of all defined memory regions, with the following columns
8642 @item Memory Region Number
8643 @item Enabled or Disabled.
8644 Enabled memory regions are marked with @samp{y}.
8645 Disabled memory regions are marked with @samp{n}.
8648 The address defining the inclusive lower bound of the memory region.
8651 The address defining the exclusive upper bound of the memory region.
8654 The list of attributes set for this memory region.
8659 @subsection Attributes
8661 @subsubsection Memory Access Mode
8662 The access mode attributes set whether @value{GDBN} may make read or
8663 write accesses to a memory region.
8665 While these attributes prevent @value{GDBN} from performing invalid
8666 memory accesses, they do nothing to prevent the target system, I/O DMA,
8667 etc.@: from accessing memory.
8671 Memory is read only.
8673 Memory is write only.
8675 Memory is read/write. This is the default.
8678 @subsubsection Memory Access Size
8679 The access size attribute tells @value{GDBN} to use specific sized
8680 accesses in the memory region. Often memory mapped device registers
8681 require specific sized accesses. If no access size attribute is
8682 specified, @value{GDBN} may use accesses of any size.
8686 Use 8 bit memory accesses.
8688 Use 16 bit memory accesses.
8690 Use 32 bit memory accesses.
8692 Use 64 bit memory accesses.
8695 @c @subsubsection Hardware/Software Breakpoints
8696 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8697 @c will use hardware or software breakpoints for the internal breakpoints
8698 @c used by the step, next, finish, until, etc. commands.
8702 @c Always use hardware breakpoints
8703 @c @item swbreak (default)
8706 @subsubsection Data Cache
8707 The data cache attributes set whether @value{GDBN} will cache target
8708 memory. While this generally improves performance by reducing debug
8709 protocol overhead, it can lead to incorrect results because @value{GDBN}
8710 does not know about volatile variables or memory mapped device
8715 Enable @value{GDBN} to cache target memory.
8717 Disable @value{GDBN} from caching target memory. This is the default.
8720 @subsection Memory Access Checking
8721 @value{GDBN} can be instructed to refuse accesses to memory that is
8722 not explicitly described. This can be useful if accessing such
8723 regions has undesired effects for a specific target, or to provide
8724 better error checking. The following commands control this behaviour.
8727 @kindex set mem inaccessible-by-default
8728 @item set mem inaccessible-by-default [on|off]
8729 If @code{on} is specified, make @value{GDBN} treat memory not
8730 explicitly described by the memory ranges as non-existent and refuse accesses
8731 to such memory. The checks are only performed if there's at least one
8732 memory range defined. If @code{off} is specified, make @value{GDBN}
8733 treat the memory not explicitly described by the memory ranges as RAM.
8734 The default value is @code{on}.
8735 @kindex show mem inaccessible-by-default
8736 @item show mem inaccessible-by-default
8737 Show the current handling of accesses to unknown memory.
8741 @c @subsubsection Memory Write Verification
8742 @c The memory write verification attributes set whether @value{GDBN}
8743 @c will re-reads data after each write to verify the write was successful.
8747 @c @item noverify (default)
8750 @node Dump/Restore Files
8751 @section Copy Between Memory and a File
8752 @cindex dump/restore files
8753 @cindex append data to a file
8754 @cindex dump data to a file
8755 @cindex restore data from a file
8757 You can use the commands @code{dump}, @code{append}, and
8758 @code{restore} to copy data between target memory and a file. The
8759 @code{dump} and @code{append} commands write data to a file, and the
8760 @code{restore} command reads data from a file back into the inferior's
8761 memory. Files may be in binary, Motorola S-record, Intel hex, or
8762 Tektronix Hex format; however, @value{GDBN} can only append to binary
8768 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8769 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8770 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8771 or the value of @var{expr}, to @var{filename} in the given format.
8773 The @var{format} parameter may be any one of:
8780 Motorola S-record format.
8782 Tektronix Hex format.
8785 @value{GDBN} uses the same definitions of these formats as the
8786 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8787 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8791 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8792 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8793 Append the contents of memory from @var{start_addr} to @var{end_addr},
8794 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8795 (@value{GDBN} can only append data to files in raw binary form.)
8798 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8799 Restore the contents of file @var{filename} into memory. The
8800 @code{restore} command can automatically recognize any known @sc{bfd}
8801 file format, except for raw binary. To restore a raw binary file you
8802 must specify the optional keyword @code{binary} after the filename.
8804 If @var{bias} is non-zero, its value will be added to the addresses
8805 contained in the file. Binary files always start at address zero, so
8806 they will be restored at address @var{bias}. Other bfd files have
8807 a built-in location; they will be restored at offset @var{bias}
8810 If @var{start} and/or @var{end} are non-zero, then only data between
8811 file offset @var{start} and file offset @var{end} will be restored.
8812 These offsets are relative to the addresses in the file, before
8813 the @var{bias} argument is applied.
8817 @node Core File Generation
8818 @section How to Produce a Core File from Your Program
8819 @cindex dump core from inferior
8821 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8822 image of a running process and its process status (register values
8823 etc.). Its primary use is post-mortem debugging of a program that
8824 crashed while it ran outside a debugger. A program that crashes
8825 automatically produces a core file, unless this feature is disabled by
8826 the user. @xref{Files}, for information on invoking @value{GDBN} in
8827 the post-mortem debugging mode.
8829 Occasionally, you may wish to produce a core file of the program you
8830 are debugging in order to preserve a snapshot of its state.
8831 @value{GDBN} has a special command for that.
8835 @kindex generate-core-file
8836 @item generate-core-file [@var{file}]
8837 @itemx gcore [@var{file}]
8838 Produce a core dump of the inferior process. The optional argument
8839 @var{file} specifies the file name where to put the core dump. If not
8840 specified, the file name defaults to @file{core.@var{pid}}, where
8841 @var{pid} is the inferior process ID.
8843 Note that this command is implemented only for some systems (as of
8844 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8847 @node Character Sets
8848 @section Character Sets
8849 @cindex character sets
8851 @cindex translating between character sets
8852 @cindex host character set
8853 @cindex target character set
8855 If the program you are debugging uses a different character set to
8856 represent characters and strings than the one @value{GDBN} uses itself,
8857 @value{GDBN} can automatically translate between the character sets for
8858 you. The character set @value{GDBN} uses we call the @dfn{host
8859 character set}; the one the inferior program uses we call the
8860 @dfn{target character set}.
8862 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8863 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8864 remote protocol (@pxref{Remote Debugging}) to debug a program
8865 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8866 then the host character set is Latin-1, and the target character set is
8867 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8868 target-charset EBCDIC-US}, then @value{GDBN} translates between
8869 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8870 character and string literals in expressions.
8872 @value{GDBN} has no way to automatically recognize which character set
8873 the inferior program uses; you must tell it, using the @code{set
8874 target-charset} command, described below.
8876 Here are the commands for controlling @value{GDBN}'s character set
8880 @item set target-charset @var{charset}
8881 @kindex set target-charset
8882 Set the current target character set to @var{charset}. To display the
8883 list of supported target character sets, type
8884 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8886 @item set host-charset @var{charset}
8887 @kindex set host-charset
8888 Set the current host character set to @var{charset}.
8890 By default, @value{GDBN} uses a host character set appropriate to the
8891 system it is running on; you can override that default using the
8892 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8893 automatically determine the appropriate host character set. In this
8894 case, @value{GDBN} uses @samp{UTF-8}.
8896 @value{GDBN} can only use certain character sets as its host character
8897 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8898 @value{GDBN} will list the host character sets it supports.
8900 @item set charset @var{charset}
8902 Set the current host and target character sets to @var{charset}. As
8903 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8904 @value{GDBN} will list the names of the character sets that can be used
8905 for both host and target.
8908 @kindex show charset
8909 Show the names of the current host and target character sets.
8911 @item show host-charset
8912 @kindex show host-charset
8913 Show the name of the current host character set.
8915 @item show target-charset
8916 @kindex show target-charset
8917 Show the name of the current target character set.
8919 @item set target-wide-charset @var{charset}
8920 @kindex set target-wide-charset
8921 Set the current target's wide character set to @var{charset}. This is
8922 the character set used by the target's @code{wchar_t} type. To
8923 display the list of supported wide character sets, type
8924 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8926 @item show target-wide-charset
8927 @kindex show target-wide-charset
8928 Show the name of the current target's wide character set.
8931 Here is an example of @value{GDBN}'s character set support in action.
8932 Assume that the following source code has been placed in the file
8933 @file{charset-test.c}:
8939 = @{72, 101, 108, 108, 111, 44, 32, 119,
8940 111, 114, 108, 100, 33, 10, 0@};
8941 char ibm1047_hello[]
8942 = @{200, 133, 147, 147, 150, 107, 64, 166,
8943 150, 153, 147, 132, 90, 37, 0@};
8947 printf ("Hello, world!\n");
8951 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8952 containing the string @samp{Hello, world!} followed by a newline,
8953 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8955 We compile the program, and invoke the debugger on it:
8958 $ gcc -g charset-test.c -o charset-test
8959 $ gdb -nw charset-test
8960 GNU gdb 2001-12-19-cvs
8961 Copyright 2001 Free Software Foundation, Inc.
8966 We can use the @code{show charset} command to see what character sets
8967 @value{GDBN} is currently using to interpret and display characters and
8971 (@value{GDBP}) show charset
8972 The current host and target character set is `ISO-8859-1'.
8976 For the sake of printing this manual, let's use @sc{ascii} as our
8977 initial character set:
8979 (@value{GDBP}) set charset ASCII
8980 (@value{GDBP}) show charset
8981 The current host and target character set is `ASCII'.
8985 Let's assume that @sc{ascii} is indeed the correct character set for our
8986 host system --- in other words, let's assume that if @value{GDBN} prints
8987 characters using the @sc{ascii} character set, our terminal will display
8988 them properly. Since our current target character set is also
8989 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8992 (@value{GDBP}) print ascii_hello
8993 $1 = 0x401698 "Hello, world!\n"
8994 (@value{GDBP}) print ascii_hello[0]
8999 @value{GDBN} uses the target character set for character and string
9000 literals you use in expressions:
9003 (@value{GDBP}) print '+'
9008 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9011 @value{GDBN} relies on the user to tell it which character set the
9012 target program uses. If we print @code{ibm1047_hello} while our target
9013 character set is still @sc{ascii}, we get jibberish:
9016 (@value{GDBP}) print ibm1047_hello
9017 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9018 (@value{GDBP}) print ibm1047_hello[0]
9023 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9024 @value{GDBN} tells us the character sets it supports:
9027 (@value{GDBP}) set target-charset
9028 ASCII EBCDIC-US IBM1047 ISO-8859-1
9029 (@value{GDBP}) set target-charset
9032 We can select @sc{ibm1047} as our target character set, and examine the
9033 program's strings again. Now the @sc{ascii} string is wrong, but
9034 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9035 target character set, @sc{ibm1047}, to the host character set,
9036 @sc{ascii}, and they display correctly:
9039 (@value{GDBP}) set target-charset IBM1047
9040 (@value{GDBP}) show charset
9041 The current host character set is `ASCII'.
9042 The current target character set is `IBM1047'.
9043 (@value{GDBP}) print ascii_hello
9044 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9045 (@value{GDBP}) print ascii_hello[0]
9047 (@value{GDBP}) print ibm1047_hello
9048 $8 = 0x4016a8 "Hello, world!\n"
9049 (@value{GDBP}) print ibm1047_hello[0]
9054 As above, @value{GDBN} uses the target character set for character and
9055 string literals you use in expressions:
9058 (@value{GDBP}) print '+'
9063 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9066 @node Caching Remote Data
9067 @section Caching Data of Remote Targets
9068 @cindex caching data of remote targets
9070 @value{GDBN} caches data exchanged between the debugger and a
9071 remote target (@pxref{Remote Debugging}). Such caching generally improves
9072 performance, because it reduces the overhead of the remote protocol by
9073 bundling memory reads and writes into large chunks. Unfortunately, simply
9074 caching everything would lead to incorrect results, since @value{GDBN}
9075 does not necessarily know anything about volatile values, memory-mapped I/O
9076 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9077 memory can be changed @emph{while} a gdb command is executing.
9078 Therefore, by default, @value{GDBN} only caches data
9079 known to be on the stack@footnote{In non-stop mode, it is moderately
9080 rare for a running thread to modify the stack of a stopped thread
9081 in a way that would interfere with a backtrace, and caching of
9082 stack reads provides a significant speed up of remote backtraces.}.
9083 Other regions of memory can be explicitly marked as
9084 cacheable; see @pxref{Memory Region Attributes}.
9087 @kindex set remotecache
9088 @item set remotecache on
9089 @itemx set remotecache off
9090 This option no longer does anything; it exists for compatibility
9093 @kindex show remotecache
9094 @item show remotecache
9095 Show the current state of the obsolete remotecache flag.
9097 @kindex set stack-cache
9098 @item set stack-cache on
9099 @itemx set stack-cache off
9100 Enable or disable caching of stack accesses. When @code{ON}, use
9101 caching. By default, this option is @code{ON}.
9103 @kindex show stack-cache
9104 @item show stack-cache
9105 Show the current state of data caching for memory accesses.
9108 @item info dcache @r{[}line@r{]}
9109 Print the information about the data cache performance. The
9110 information displayed includes the dcache width and depth, and for
9111 each cache line, its number, address, and how many times it was
9112 referenced. This command is useful for debugging the data cache
9115 If a line number is specified, the contents of that line will be
9119 @node Searching Memory
9120 @section Search Memory
9121 @cindex searching memory
9123 Memory can be searched for a particular sequence of bytes with the
9124 @code{find} command.
9128 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9129 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9130 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9131 etc. The search begins at address @var{start_addr} and continues for either
9132 @var{len} bytes or through to @var{end_addr} inclusive.
9135 @var{s} and @var{n} are optional parameters.
9136 They may be specified in either order, apart or together.
9139 @item @var{s}, search query size
9140 The size of each search query value.
9146 halfwords (two bytes)
9150 giant words (eight bytes)
9153 All values are interpreted in the current language.
9154 This means, for example, that if the current source language is C/C@t{++}
9155 then searching for the string ``hello'' includes the trailing '\0'.
9157 If the value size is not specified, it is taken from the
9158 value's type in the current language.
9159 This is useful when one wants to specify the search
9160 pattern as a mixture of types.
9161 Note that this means, for example, that in the case of C-like languages
9162 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9163 which is typically four bytes.
9165 @item @var{n}, maximum number of finds
9166 The maximum number of matches to print. The default is to print all finds.
9169 You can use strings as search values. Quote them with double-quotes
9171 The string value is copied into the search pattern byte by byte,
9172 regardless of the endianness of the target and the size specification.
9174 The address of each match found is printed as well as a count of the
9175 number of matches found.
9177 The address of the last value found is stored in convenience variable
9179 A count of the number of matches is stored in @samp{$numfound}.
9181 For example, if stopped at the @code{printf} in this function:
9187 static char hello[] = "hello-hello";
9188 static struct @{ char c; short s; int i; @}
9189 __attribute__ ((packed)) mixed
9190 = @{ 'c', 0x1234, 0x87654321 @};
9191 printf ("%s\n", hello);
9196 you get during debugging:
9199 (gdb) find &hello[0], +sizeof(hello), "hello"
9200 0x804956d <hello.1620+6>
9202 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9203 0x8049567 <hello.1620>
9204 0x804956d <hello.1620+6>
9206 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9207 0x8049567 <hello.1620>
9209 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9210 0x8049560 <mixed.1625>
9212 (gdb) print $numfound
9215 $2 = (void *) 0x8049560
9218 @node Optimized Code
9219 @chapter Debugging Optimized Code
9220 @cindex optimized code, debugging
9221 @cindex debugging optimized code
9223 Almost all compilers support optimization. With optimization
9224 disabled, the compiler generates assembly code that corresponds
9225 directly to your source code, in a simplistic way. As the compiler
9226 applies more powerful optimizations, the generated assembly code
9227 diverges from your original source code. With help from debugging
9228 information generated by the compiler, @value{GDBN} can map from
9229 the running program back to constructs from your original source.
9231 @value{GDBN} is more accurate with optimization disabled. If you
9232 can recompile without optimization, it is easier to follow the
9233 progress of your program during debugging. But, there are many cases
9234 where you may need to debug an optimized version.
9236 When you debug a program compiled with @samp{-g -O}, remember that the
9237 optimizer has rearranged your code; the debugger shows you what is
9238 really there. Do not be too surprised when the execution path does not
9239 exactly match your source file! An extreme example: if you define a
9240 variable, but never use it, @value{GDBN} never sees that
9241 variable---because the compiler optimizes it out of existence.
9243 Some things do not work as well with @samp{-g -O} as with just
9244 @samp{-g}, particularly on machines with instruction scheduling. If in
9245 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9246 please report it to us as a bug (including a test case!).
9247 @xref{Variables}, for more information about debugging optimized code.
9250 * Inline Functions:: How @value{GDBN} presents inlining
9253 @node Inline Functions
9254 @section Inline Functions
9255 @cindex inline functions, debugging
9257 @dfn{Inlining} is an optimization that inserts a copy of the function
9258 body directly at each call site, instead of jumping to a shared
9259 routine. @value{GDBN} displays inlined functions just like
9260 non-inlined functions. They appear in backtraces. You can view their
9261 arguments and local variables, step into them with @code{step}, skip
9262 them with @code{next}, and escape from them with @code{finish}.
9263 You can check whether a function was inlined by using the
9264 @code{info frame} command.
9266 For @value{GDBN} to support inlined functions, the compiler must
9267 record information about inlining in the debug information ---
9268 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9269 other compilers do also. @value{GDBN} only supports inlined functions
9270 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9271 do not emit two required attributes (@samp{DW_AT_call_file} and
9272 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9273 function calls with earlier versions of @value{NGCC}. It instead
9274 displays the arguments and local variables of inlined functions as
9275 local variables in the caller.
9277 The body of an inlined function is directly included at its call site;
9278 unlike a non-inlined function, there are no instructions devoted to
9279 the call. @value{GDBN} still pretends that the call site and the
9280 start of the inlined function are different instructions. Stepping to
9281 the call site shows the call site, and then stepping again shows
9282 the first line of the inlined function, even though no additional
9283 instructions are executed.
9285 This makes source-level debugging much clearer; you can see both the
9286 context of the call and then the effect of the call. Only stepping by
9287 a single instruction using @code{stepi} or @code{nexti} does not do
9288 this; single instruction steps always show the inlined body.
9290 There are some ways that @value{GDBN} does not pretend that inlined
9291 function calls are the same as normal calls:
9295 You cannot set breakpoints on inlined functions. @value{GDBN}
9296 either reports that there is no symbol with that name, or else sets the
9297 breakpoint only on non-inlined copies of the function. This limitation
9298 will be removed in a future version of @value{GDBN}; until then,
9299 set a breakpoint by line number on the first line of the inlined
9303 Setting breakpoints at the call site of an inlined function may not
9304 work, because the call site does not contain any code. @value{GDBN}
9305 may incorrectly move the breakpoint to the next line of the enclosing
9306 function, after the call. This limitation will be removed in a future
9307 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9308 or inside the inlined function instead.
9311 @value{GDBN} cannot locate the return value of inlined calls after
9312 using the @code{finish} command. This is a limitation of compiler-generated
9313 debugging information; after @code{finish}, you can step to the next line
9314 and print a variable where your program stored the return value.
9320 @chapter C Preprocessor Macros
9322 Some languages, such as C and C@t{++}, provide a way to define and invoke
9323 ``preprocessor macros'' which expand into strings of tokens.
9324 @value{GDBN} can evaluate expressions containing macro invocations, show
9325 the result of macro expansion, and show a macro's definition, including
9326 where it was defined.
9328 You may need to compile your program specially to provide @value{GDBN}
9329 with information about preprocessor macros. Most compilers do not
9330 include macros in their debugging information, even when you compile
9331 with the @option{-g} flag. @xref{Compilation}.
9333 A program may define a macro at one point, remove that definition later,
9334 and then provide a different definition after that. Thus, at different
9335 points in the program, a macro may have different definitions, or have
9336 no definition at all. If there is a current stack frame, @value{GDBN}
9337 uses the macros in scope at that frame's source code line. Otherwise,
9338 @value{GDBN} uses the macros in scope at the current listing location;
9341 Whenever @value{GDBN} evaluates an expression, it always expands any
9342 macro invocations present in the expression. @value{GDBN} also provides
9343 the following commands for working with macros explicitly.
9347 @kindex macro expand
9348 @cindex macro expansion, showing the results of preprocessor
9349 @cindex preprocessor macro expansion, showing the results of
9350 @cindex expanding preprocessor macros
9351 @item macro expand @var{expression}
9352 @itemx macro exp @var{expression}
9353 Show the results of expanding all preprocessor macro invocations in
9354 @var{expression}. Since @value{GDBN} simply expands macros, but does
9355 not parse the result, @var{expression} need not be a valid expression;
9356 it can be any string of tokens.
9359 @item macro expand-once @var{expression}
9360 @itemx macro exp1 @var{expression}
9361 @cindex expand macro once
9362 @i{(This command is not yet implemented.)} Show the results of
9363 expanding those preprocessor macro invocations that appear explicitly in
9364 @var{expression}. Macro invocations appearing in that expansion are
9365 left unchanged. This command allows you to see the effect of a
9366 particular macro more clearly, without being confused by further
9367 expansions. Since @value{GDBN} simply expands macros, but does not
9368 parse the result, @var{expression} need not be a valid expression; it
9369 can be any string of tokens.
9372 @cindex macro definition, showing
9373 @cindex definition, showing a macro's
9374 @item info macro @var{macro}
9375 Show the definition of the macro named @var{macro}, and describe the
9376 source location or compiler command-line where that definition was established.
9378 @kindex macro define
9379 @cindex user-defined macros
9380 @cindex defining macros interactively
9381 @cindex macros, user-defined
9382 @item macro define @var{macro} @var{replacement-list}
9383 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9384 Introduce a definition for a preprocessor macro named @var{macro},
9385 invocations of which are replaced by the tokens given in
9386 @var{replacement-list}. The first form of this command defines an
9387 ``object-like'' macro, which takes no arguments; the second form
9388 defines a ``function-like'' macro, which takes the arguments given in
9391 A definition introduced by this command is in scope in every
9392 expression evaluated in @value{GDBN}, until it is removed with the
9393 @code{macro undef} command, described below. The definition overrides
9394 all definitions for @var{macro} present in the program being debugged,
9395 as well as any previous user-supplied definition.
9398 @item macro undef @var{macro}
9399 Remove any user-supplied definition for the macro named @var{macro}.
9400 This command only affects definitions provided with the @code{macro
9401 define} command, described above; it cannot remove definitions present
9402 in the program being debugged.
9406 List all the macros defined using the @code{macro define} command.
9409 @cindex macros, example of debugging with
9410 Here is a transcript showing the above commands in action. First, we
9411 show our source files:
9419 #define ADD(x) (M + x)
9424 printf ("Hello, world!\n");
9426 printf ("We're so creative.\n");
9428 printf ("Goodbye, world!\n");
9435 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9436 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9437 compiler includes information about preprocessor macros in the debugging
9441 $ gcc -gdwarf-2 -g3 sample.c -o sample
9445 Now, we start @value{GDBN} on our sample program:
9449 GNU gdb 2002-05-06-cvs
9450 Copyright 2002 Free Software Foundation, Inc.
9451 GDB is free software, @dots{}
9455 We can expand macros and examine their definitions, even when the
9456 program is not running. @value{GDBN} uses the current listing position
9457 to decide which macro definitions are in scope:
9460 (@value{GDBP}) list main
9463 5 #define ADD(x) (M + x)
9468 10 printf ("Hello, world!\n");
9470 12 printf ("We're so creative.\n");
9471 (@value{GDBP}) info macro ADD
9472 Defined at /home/jimb/gdb/macros/play/sample.c:5
9473 #define ADD(x) (M + x)
9474 (@value{GDBP}) info macro Q
9475 Defined at /home/jimb/gdb/macros/play/sample.h:1
9476 included at /home/jimb/gdb/macros/play/sample.c:2
9478 (@value{GDBP}) macro expand ADD(1)
9479 expands to: (42 + 1)
9480 (@value{GDBP}) macro expand-once ADD(1)
9481 expands to: once (M + 1)
9485 In the example above, note that @code{macro expand-once} expands only
9486 the macro invocation explicit in the original text --- the invocation of
9487 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9488 which was introduced by @code{ADD}.
9490 Once the program is running, @value{GDBN} uses the macro definitions in
9491 force at the source line of the current stack frame:
9494 (@value{GDBP}) break main
9495 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9497 Starting program: /home/jimb/gdb/macros/play/sample
9499 Breakpoint 1, main () at sample.c:10
9500 10 printf ("Hello, world!\n");
9504 At line 10, the definition of the macro @code{N} at line 9 is in force:
9507 (@value{GDBP}) info macro N
9508 Defined at /home/jimb/gdb/macros/play/sample.c:9
9510 (@value{GDBP}) macro expand N Q M
9512 (@value{GDBP}) print N Q M
9517 As we step over directives that remove @code{N}'s definition, and then
9518 give it a new definition, @value{GDBN} finds the definition (or lack
9519 thereof) in force at each point:
9524 12 printf ("We're so creative.\n");
9525 (@value{GDBP}) info macro N
9526 The symbol `N' has no definition as a C/C++ preprocessor macro
9527 at /home/jimb/gdb/macros/play/sample.c:12
9530 14 printf ("Goodbye, world!\n");
9531 (@value{GDBP}) info macro N
9532 Defined at /home/jimb/gdb/macros/play/sample.c:13
9534 (@value{GDBP}) macro expand N Q M
9535 expands to: 1729 < 42
9536 (@value{GDBP}) print N Q M
9541 In addition to source files, macros can be defined on the compilation command
9542 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9543 such a way, @value{GDBN} displays the location of their definition as line zero
9544 of the source file submitted to the compiler.
9547 (@value{GDBP}) info macro __STDC__
9548 Defined at /home/jimb/gdb/macros/play/sample.c:0
9555 @chapter Tracepoints
9556 @c This chapter is based on the documentation written by Michael
9557 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9560 In some applications, it is not feasible for the debugger to interrupt
9561 the program's execution long enough for the developer to learn
9562 anything helpful about its behavior. If the program's correctness
9563 depends on its real-time behavior, delays introduced by a debugger
9564 might cause the program to change its behavior drastically, or perhaps
9565 fail, even when the code itself is correct. It is useful to be able
9566 to observe the program's behavior without interrupting it.
9568 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9569 specify locations in the program, called @dfn{tracepoints}, and
9570 arbitrary expressions to evaluate when those tracepoints are reached.
9571 Later, using the @code{tfind} command, you can examine the values
9572 those expressions had when the program hit the tracepoints. The
9573 expressions may also denote objects in memory---structures or arrays,
9574 for example---whose values @value{GDBN} should record; while visiting
9575 a particular tracepoint, you may inspect those objects as if they were
9576 in memory at that moment. However, because @value{GDBN} records these
9577 values without interacting with you, it can do so quickly and
9578 unobtrusively, hopefully not disturbing the program's behavior.
9580 The tracepoint facility is currently available only for remote
9581 targets. @xref{Targets}. In addition, your remote target must know
9582 how to collect trace data. This functionality is implemented in the
9583 remote stub; however, none of the stubs distributed with @value{GDBN}
9584 support tracepoints as of this writing. The format of the remote
9585 packets used to implement tracepoints are described in @ref{Tracepoint
9588 It is also possible to get trace data from a file, in a manner reminiscent
9589 of corefiles; you specify the filename, and use @code{tfind} to search
9590 through the file. @xref{Trace Files}, for more details.
9592 This chapter describes the tracepoint commands and features.
9596 * Analyze Collected Data::
9597 * Tracepoint Variables::
9601 @node Set Tracepoints
9602 @section Commands to Set Tracepoints
9604 Before running such a @dfn{trace experiment}, an arbitrary number of
9605 tracepoints can be set. A tracepoint is actually a special type of
9606 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9607 standard breakpoint commands. For instance, as with breakpoints,
9608 tracepoint numbers are successive integers starting from one, and many
9609 of the commands associated with tracepoints take the tracepoint number
9610 as their argument, to identify which tracepoint to work on.
9612 For each tracepoint, you can specify, in advance, some arbitrary set
9613 of data that you want the target to collect in the trace buffer when
9614 it hits that tracepoint. The collected data can include registers,
9615 local variables, or global data. Later, you can use @value{GDBN}
9616 commands to examine the values these data had at the time the
9619 Tracepoints do not support every breakpoint feature. Ignore counts on
9620 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9621 commands when they are hit. Tracepoints may not be thread-specific
9624 @cindex fast tracepoints
9625 Some targets may support @dfn{fast tracepoints}, which are inserted in
9626 a different way (such as with a jump instead of a trap), that is
9627 faster but possibly restricted in where they may be installed.
9629 @cindex static tracepoints
9630 @cindex markers, static tracepoints
9631 @cindex probing markers, static tracepoints
9632 Regular and fast tracepoints are dynamic tracing facilities, meaning
9633 that they can be used to insert tracepoints at (almost) any location
9634 in the target. Some targets may also support controlling @dfn{static
9635 tracepoints} from @value{GDBN}. With static tracing, a set of
9636 instrumentation points, also known as @dfn{markers}, are embedded in
9637 the target program, and can be activated or deactivated by name or
9638 address. These are usually placed at locations which facilitate
9639 investigating what the target is actually doing. @value{GDBN}'s
9640 support for static tracing includes being able to list instrumentation
9641 points, and attach them with @value{GDBN} defined high level
9642 tracepoints that expose the whole range of convenience of
9643 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9644 registers values and values of global or local (to the instrumentation
9645 point) variables; tracepoint conditions and trace state variables.
9646 The act of installing a @value{GDBN} static tracepoint on an
9647 instrumentation point, or marker, is referred to as @dfn{probing} a
9648 static tracepoint marker.
9650 @code{gdbserver} supports tracepoints on some target systems.
9651 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9653 This section describes commands to set tracepoints and associated
9654 conditions and actions.
9657 * Create and Delete Tracepoints::
9658 * Enable and Disable Tracepoints::
9659 * Tracepoint Passcounts::
9660 * Tracepoint Conditions::
9661 * Trace State Variables::
9662 * Tracepoint Actions::
9663 * Listing Tracepoints::
9664 * Listing Static Tracepoint Markers::
9665 * Starting and Stopping Trace Experiments::
9666 * Tracepoint Restrictions::
9669 @node Create and Delete Tracepoints
9670 @subsection Create and Delete Tracepoints
9673 @cindex set tracepoint
9675 @item trace @var{location}
9676 The @code{trace} command is very similar to the @code{break} command.
9677 Its argument @var{location} can be a source line, a function name, or
9678 an address in the target program. @xref{Specify Location}. The
9679 @code{trace} command defines a tracepoint, which is a point in the
9680 target program where the debugger will briefly stop, collect some
9681 data, and then allow the program to continue. Setting a tracepoint or
9682 changing its actions doesn't take effect until the next @code{tstart}
9683 command, and once a trace experiment is running, further changes will
9684 not have any effect until the next trace experiment starts.
9686 Here are some examples of using the @code{trace} command:
9689 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9691 (@value{GDBP}) @b{trace +2} // 2 lines forward
9693 (@value{GDBP}) @b{trace my_function} // first source line of function
9695 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9697 (@value{GDBP}) @b{trace *0x2117c4} // an address
9701 You can abbreviate @code{trace} as @code{tr}.
9703 @item trace @var{location} if @var{cond}
9704 Set a tracepoint with condition @var{cond}; evaluate the expression
9705 @var{cond} each time the tracepoint is reached, and collect data only
9706 if the value is nonzero---that is, if @var{cond} evaluates as true.
9707 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9708 information on tracepoint conditions.
9710 @item ftrace @var{location} [ if @var{cond} ]
9711 @cindex set fast tracepoint
9712 @cindex fast tracepoints, setting
9714 The @code{ftrace} command sets a fast tracepoint. For targets that
9715 support them, fast tracepoints will use a more efficient but possibly
9716 less general technique to trigger data collection, such as a jump
9717 instruction instead of a trap, or some sort of hardware support. It
9718 may not be possible to create a fast tracepoint at the desired
9719 location, in which case the command will exit with an explanatory
9722 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9725 @item strace @var{location} [ if @var{cond} ]
9726 @cindex set static tracepoint
9727 @cindex static tracepoints, setting
9728 @cindex probe static tracepoint marker
9730 The @code{strace} command sets a static tracepoint. For targets that
9731 support it, setting a static tracepoint probes a static
9732 instrumentation point, or marker, found at @var{location}. It may not
9733 be possible to set a static tracepoint at the desired location, in
9734 which case the command will exit with an explanatory message.
9736 @value{GDBN} handles arguments to @code{strace} exactly as for
9737 @code{trace}, with the addition that the user can also specify
9738 @code{-m @var{marker}} as @var{location}. This probes the marker
9739 identified by the @var{marker} string identifier. This identifier
9740 depends on the static tracepoint backend library your program is
9741 using. You can find all the marker identifiers in the @samp{ID} field
9742 of the @code{info static-tracepoint-markers} command output.
9743 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9744 Markers}. For example, in the following small program using the UST
9750 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9755 the marker id is composed of joining the first two arguments to the
9756 @code{trace_mark} call with a slash, which translates to:
9759 (@value{GDBP}) info static-tracepoint-markers
9760 Cnt Enb ID Address What
9761 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9767 so you may probe the marker above with:
9770 (@value{GDBP}) strace -m ust/bar33
9773 Static tracepoints accept an extra collect action --- @code{collect
9774 $_sdata}. This collects arbitrary user data passed in the probe point
9775 call to the tracing library. In the UST example above, you'll see
9776 that the third argument to @code{trace_mark} is a printf-like format
9777 string. The user data is then the result of running that formating
9778 string against the following arguments. Note that @code{info
9779 static-tracepoint-markers} command output lists that format string in
9780 the @samp{Data:} field.
9782 You can inspect this data when analyzing the trace buffer, by printing
9783 the $_sdata variable like any other variable available to
9784 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9787 @cindex last tracepoint number
9788 @cindex recent tracepoint number
9789 @cindex tracepoint number
9790 The convenience variable @code{$tpnum} records the tracepoint number
9791 of the most recently set tracepoint.
9793 @kindex delete tracepoint
9794 @cindex tracepoint deletion
9795 @item delete tracepoint @r{[}@var{num}@r{]}
9796 Permanently delete one or more tracepoints. With no argument, the
9797 default is to delete all tracepoints. Note that the regular
9798 @code{delete} command can remove tracepoints also.
9803 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9805 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9809 You can abbreviate this command as @code{del tr}.
9812 @node Enable and Disable Tracepoints
9813 @subsection Enable and Disable Tracepoints
9815 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9818 @kindex disable tracepoint
9819 @item disable tracepoint @r{[}@var{num}@r{]}
9820 Disable tracepoint @var{num}, or all tracepoints if no argument
9821 @var{num} is given. A disabled tracepoint will have no effect during
9822 the next trace experiment, but it is not forgotten. You can re-enable
9823 a disabled tracepoint using the @code{enable tracepoint} command.
9825 @kindex enable tracepoint
9826 @item enable tracepoint @r{[}@var{num}@r{]}
9827 Enable tracepoint @var{num}, or all tracepoints. The enabled
9828 tracepoints will become effective the next time a trace experiment is
9832 @node Tracepoint Passcounts
9833 @subsection Tracepoint Passcounts
9837 @cindex tracepoint pass count
9838 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9839 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9840 automatically stop a trace experiment. If a tracepoint's passcount is
9841 @var{n}, then the trace experiment will be automatically stopped on
9842 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9843 @var{num} is not specified, the @code{passcount} command sets the
9844 passcount of the most recently defined tracepoint. If no passcount is
9845 given, the trace experiment will run until stopped explicitly by the
9851 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9852 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9854 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9855 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9856 (@value{GDBP}) @b{trace foo}
9857 (@value{GDBP}) @b{pass 3}
9858 (@value{GDBP}) @b{trace bar}
9859 (@value{GDBP}) @b{pass 2}
9860 (@value{GDBP}) @b{trace baz}
9861 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9862 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9863 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9864 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9868 @node Tracepoint Conditions
9869 @subsection Tracepoint Conditions
9870 @cindex conditional tracepoints
9871 @cindex tracepoint conditions
9873 The simplest sort of tracepoint collects data every time your program
9874 reaches a specified place. You can also specify a @dfn{condition} for
9875 a tracepoint. A condition is just a Boolean expression in your
9876 programming language (@pxref{Expressions, ,Expressions}). A
9877 tracepoint with a condition evaluates the expression each time your
9878 program reaches it, and data collection happens only if the condition
9881 Tracepoint conditions can be specified when a tracepoint is set, by
9882 using @samp{if} in the arguments to the @code{trace} command.
9883 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9884 also be set or changed at any time with the @code{condition} command,
9885 just as with breakpoints.
9887 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9888 the conditional expression itself. Instead, @value{GDBN} encodes the
9889 expression into an agent expression (@pxref{Agent Expressions}
9890 suitable for execution on the target, independently of @value{GDBN}.
9891 Global variables become raw memory locations, locals become stack
9892 accesses, and so forth.
9894 For instance, suppose you have a function that is usually called
9895 frequently, but should not be called after an error has occurred. You
9896 could use the following tracepoint command to collect data about calls
9897 of that function that happen while the error code is propagating
9898 through the program; an unconditional tracepoint could end up
9899 collecting thousands of useless trace frames that you would have to
9903 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9906 @node Trace State Variables
9907 @subsection Trace State Variables
9908 @cindex trace state variables
9910 A @dfn{trace state variable} is a special type of variable that is
9911 created and managed by target-side code. The syntax is the same as
9912 that for GDB's convenience variables (a string prefixed with ``$''),
9913 but they are stored on the target. They must be created explicitly,
9914 using a @code{tvariable} command. They are always 64-bit signed
9917 Trace state variables are remembered by @value{GDBN}, and downloaded
9918 to the target along with tracepoint information when the trace
9919 experiment starts. There are no intrinsic limits on the number of
9920 trace state variables, beyond memory limitations of the target.
9922 @cindex convenience variables, and trace state variables
9923 Although trace state variables are managed by the target, you can use
9924 them in print commands and expressions as if they were convenience
9925 variables; @value{GDBN} will get the current value from the target
9926 while the trace experiment is running. Trace state variables share
9927 the same namespace as other ``$'' variables, which means that you
9928 cannot have trace state variables with names like @code{$23} or
9929 @code{$pc}, nor can you have a trace state variable and a convenience
9930 variable with the same name.
9934 @item tvariable $@var{name} [ = @var{expression} ]
9936 The @code{tvariable} command creates a new trace state variable named
9937 @code{$@var{name}}, and optionally gives it an initial value of
9938 @var{expression}. @var{expression} is evaluated when this command is
9939 entered; the result will be converted to an integer if possible,
9940 otherwise @value{GDBN} will report an error. A subsequent
9941 @code{tvariable} command specifying the same name does not create a
9942 variable, but instead assigns the supplied initial value to the
9943 existing variable of that name, overwriting any previous initial
9944 value. The default initial value is 0.
9946 @item info tvariables
9947 @kindex info tvariables
9948 List all the trace state variables along with their initial values.
9949 Their current values may also be displayed, if the trace experiment is
9952 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9953 @kindex delete tvariable
9954 Delete the given trace state variables, or all of them if no arguments
9959 @node Tracepoint Actions
9960 @subsection Tracepoint Action Lists
9964 @cindex tracepoint actions
9965 @item actions @r{[}@var{num}@r{]}
9966 This command will prompt for a list of actions to be taken when the
9967 tracepoint is hit. If the tracepoint number @var{num} is not
9968 specified, this command sets the actions for the one that was most
9969 recently defined (so that you can define a tracepoint and then say
9970 @code{actions} without bothering about its number). You specify the
9971 actions themselves on the following lines, one action at a time, and
9972 terminate the actions list with a line containing just @code{end}. So
9973 far, the only defined actions are @code{collect}, @code{teval}, and
9974 @code{while-stepping}.
9976 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9977 Commands, ,Breakpoint Command Lists}), except that only the defined
9978 actions are allowed; any other @value{GDBN} command is rejected.
9980 @cindex remove actions from a tracepoint
9981 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9982 and follow it immediately with @samp{end}.
9985 (@value{GDBP}) @b{collect @var{data}} // collect some data
9987 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9989 (@value{GDBP}) @b{end} // signals the end of actions.
9992 In the following example, the action list begins with @code{collect}
9993 commands indicating the things to be collected when the tracepoint is
9994 hit. Then, in order to single-step and collect additional data
9995 following the tracepoint, a @code{while-stepping} command is used,
9996 followed by the list of things to be collected after each step in a
9997 sequence of single steps. The @code{while-stepping} command is
9998 terminated by its own separate @code{end} command. Lastly, the action
9999 list is terminated by an @code{end} command.
10002 (@value{GDBP}) @b{trace foo}
10003 (@value{GDBP}) @b{actions}
10004 Enter actions for tracepoint 1, one per line:
10007 > while-stepping 12
10008 > collect $pc, arr[i]
10013 @kindex collect @r{(tracepoints)}
10014 @item collect @var{expr1}, @var{expr2}, @dots{}
10015 Collect values of the given expressions when the tracepoint is hit.
10016 This command accepts a comma-separated list of any valid expressions.
10017 In addition to global, static, or local variables, the following
10018 special arguments are supported:
10022 Collect all registers.
10025 Collect all function arguments.
10028 Collect all local variables.
10031 @vindex $_sdata@r{, collect}
10032 Collect static tracepoint marker specific data. Only available for
10033 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10034 Lists}. On the UST static tracepoints library backend, an
10035 instrumentation point resembles a @code{printf} function call. The
10036 tracing library is able to collect user specified data formatted to a
10037 character string using the format provided by the programmer that
10038 instrumented the program. Other backends have similar mechanisms.
10039 Here's an example of a UST marker call:
10042 const char master_name[] = "$your_name";
10043 trace_mark(channel1, marker1, "hello %s", master_name)
10046 In this case, collecting @code{$_sdata} collects the string
10047 @samp{hello $yourname}. When analyzing the trace buffer, you can
10048 inspect @samp{$_sdata} like any other variable available to
10052 You can give several consecutive @code{collect} commands, each one
10053 with a single argument, or one @code{collect} command with several
10054 arguments separated by commas; the effect is the same.
10056 The command @code{info scope} (@pxref{Symbols, info scope}) is
10057 particularly useful for figuring out what data to collect.
10059 @kindex teval @r{(tracepoints)}
10060 @item teval @var{expr1}, @var{expr2}, @dots{}
10061 Evaluate the given expressions when the tracepoint is hit. This
10062 command accepts a comma-separated list of expressions. The results
10063 are discarded, so this is mainly useful for assigning values to trace
10064 state variables (@pxref{Trace State Variables}) without adding those
10065 values to the trace buffer, as would be the case if the @code{collect}
10068 @kindex while-stepping @r{(tracepoints)}
10069 @item while-stepping @var{n}
10070 Perform @var{n} single-step instruction traces after the tracepoint,
10071 collecting new data after each step. The @code{while-stepping}
10072 command is followed by the list of what to collect while stepping
10073 (followed by its own @code{end} command):
10076 > while-stepping 12
10077 > collect $regs, myglobal
10083 Note that @code{$pc} is not automatically collected by
10084 @code{while-stepping}; you need to explicitly collect that register if
10085 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10088 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10089 @kindex set default-collect
10090 @cindex default collection action
10091 This variable is a list of expressions to collect at each tracepoint
10092 hit. It is effectively an additional @code{collect} action prepended
10093 to every tracepoint action list. The expressions are parsed
10094 individually for each tracepoint, so for instance a variable named
10095 @code{xyz} may be interpreted as a global for one tracepoint, and a
10096 local for another, as appropriate to the tracepoint's location.
10098 @item show default-collect
10099 @kindex show default-collect
10100 Show the list of expressions that are collected by default at each
10105 @node Listing Tracepoints
10106 @subsection Listing Tracepoints
10109 @kindex info tracepoints
10111 @cindex information about tracepoints
10112 @item info tracepoints @r{[}@var{num}@r{]}
10113 Display information about the tracepoint @var{num}. If you don't
10114 specify a tracepoint number, displays information about all the
10115 tracepoints defined so far. The format is similar to that used for
10116 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10117 command, simply restricting itself to tracepoints.
10119 A tracepoint's listing may include additional information specific to
10124 its passcount as given by the @code{passcount @var{n}} command
10128 (@value{GDBP}) @b{info trace}
10129 Num Type Disp Enb Address What
10130 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10132 collect globfoo, $regs
10141 This command can be abbreviated @code{info tp}.
10144 @node Listing Static Tracepoint Markers
10145 @subsection Listing Static Tracepoint Markers
10148 @kindex info static-tracepoint-markers
10149 @cindex information about static tracepoint markers
10150 @item info static-tracepoint-markers
10151 Display information about all static tracepoint markers defined in the
10154 For each marker, the following columns are printed:
10158 An incrementing counter, output to help readability. This is not a
10161 The marker ID, as reported by the target.
10162 @item Enabled or Disabled
10163 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10164 that are not enabled.
10166 Where the marker is in your program, as a memory address.
10168 Where the marker is in the source for your program, as a file and line
10169 number. If the debug information included in the program does not
10170 allow @value{GDBN} to locate the source of the marker, this column
10171 will be left blank.
10175 In addition, the following information may be printed for each marker:
10179 User data passed to the tracing library by the marker call. In the
10180 UST backend, this is the format string passed as argument to the
10182 @item Static tracepoints probing the marker
10183 The list of static tracepoints attached to the marker.
10187 (@value{GDBP}) info static-tracepoint-markers
10188 Cnt ID Enb Address What
10189 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10190 Data: number1 %d number2 %d
10191 Probed by static tracepoints: #2
10192 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10198 @node Starting and Stopping Trace Experiments
10199 @subsection Starting and Stopping Trace Experiments
10203 @cindex start a new trace experiment
10204 @cindex collected data discarded
10206 This command takes no arguments. It starts the trace experiment, and
10207 begins collecting data. This has the side effect of discarding all
10208 the data collected in the trace buffer during the previous trace
10212 @cindex stop a running trace experiment
10214 This command takes no arguments. It ends the trace experiment, and
10215 stops collecting data.
10217 @strong{Note}: a trace experiment and data collection may stop
10218 automatically if any tracepoint's passcount is reached
10219 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10222 @cindex status of trace data collection
10223 @cindex trace experiment, status of
10225 This command displays the status of the current trace data
10229 Here is an example of the commands we described so far:
10232 (@value{GDBP}) @b{trace gdb_c_test}
10233 (@value{GDBP}) @b{actions}
10234 Enter actions for tracepoint #1, one per line.
10235 > collect $regs,$locals,$args
10236 > while-stepping 11
10240 (@value{GDBP}) @b{tstart}
10241 [time passes @dots{}]
10242 (@value{GDBP}) @b{tstop}
10245 @cindex disconnected tracing
10246 You can choose to continue running the trace experiment even if
10247 @value{GDBN} disconnects from the target, voluntarily or
10248 involuntarily. For commands such as @code{detach}, the debugger will
10249 ask what you want to do with the trace. But for unexpected
10250 terminations (@value{GDBN} crash, network outage), it would be
10251 unfortunate to lose hard-won trace data, so the variable
10252 @code{disconnected-tracing} lets you decide whether the trace should
10253 continue running without @value{GDBN}.
10256 @item set disconnected-tracing on
10257 @itemx set disconnected-tracing off
10258 @kindex set disconnected-tracing
10259 Choose whether a tracing run should continue to run if @value{GDBN}
10260 has disconnected from the target. Note that @code{detach} or
10261 @code{quit} will ask you directly what to do about a running trace no
10262 matter what this variable's setting, so the variable is mainly useful
10263 for handling unexpected situations, such as loss of the network.
10265 @item show disconnected-tracing
10266 @kindex show disconnected-tracing
10267 Show the current choice for disconnected tracing.
10271 When you reconnect to the target, the trace experiment may or may not
10272 still be running; it might have filled the trace buffer in the
10273 meantime, or stopped for one of the other reasons. If it is running,
10274 it will continue after reconnection.
10276 Upon reconnection, the target will upload information about the
10277 tracepoints in effect. @value{GDBN} will then compare that
10278 information to the set of tracepoints currently defined, and attempt
10279 to match them up, allowing for the possibility that the numbers may
10280 have changed due to creation and deletion in the meantime. If one of
10281 the target's tracepoints does not match any in @value{GDBN}, the
10282 debugger will create a new tracepoint, so that you have a number with
10283 which to specify that tracepoint. This matching-up process is
10284 necessarily heuristic, and it may result in useless tracepoints being
10285 created; you may simply delete them if they are of no use.
10287 @cindex circular trace buffer
10288 If your target agent supports a @dfn{circular trace buffer}, then you
10289 can run a trace experiment indefinitely without filling the trace
10290 buffer; when space runs out, the agent deletes already-collected trace
10291 frames, oldest first, until there is enough room to continue
10292 collecting. This is especially useful if your tracepoints are being
10293 hit too often, and your trace gets terminated prematurely because the
10294 buffer is full. To ask for a circular trace buffer, simply set
10295 @samp{circular_trace_buffer} to on. You can set this at any time,
10296 including during tracing; if the agent can do it, it will change
10297 buffer handling on the fly, otherwise it will not take effect until
10301 @item set circular-trace-buffer on
10302 @itemx set circular-trace-buffer off
10303 @kindex set circular-trace-buffer
10304 Choose whether a tracing run should use a linear or circular buffer
10305 for trace data. A linear buffer will not lose any trace data, but may
10306 fill up prematurely, while a circular buffer will discard old trace
10307 data, but it will have always room for the latest tracepoint hits.
10309 @item show circular-trace-buffer
10310 @kindex show circular-trace-buffer
10311 Show the current choice for the trace buffer. Note that this may not
10312 match the agent's current buffer handling, nor is it guaranteed to
10313 match the setting that might have been in effect during a past run,
10314 for instance if you are looking at frames from a trace file.
10318 @node Tracepoint Restrictions
10319 @subsection Tracepoint Restrictions
10321 @cindex tracepoint restrictions
10322 There are a number of restrictions on the use of tracepoints. As
10323 described above, tracepoint data gathering occurs on the target
10324 without interaction from @value{GDBN}. Thus the full capabilities of
10325 the debugger are not available during data gathering, and then at data
10326 examination time, you will be limited by only having what was
10327 collected. The following items describe some common problems, but it
10328 is not exhaustive, and you may run into additional difficulties not
10334 Tracepoint expressions are intended to gather objects (lvalues). Thus
10335 the full flexibility of GDB's expression evaluator is not available.
10336 You cannot call functions, cast objects to aggregate types, access
10337 convenience variables or modify values (except by assignment to trace
10338 state variables). Some language features may implicitly call
10339 functions (for instance Objective-C fields with accessors), and therefore
10340 cannot be collected either.
10343 Collection of local variables, either individually or in bulk with
10344 @code{$locals} or @code{$args}, during @code{while-stepping} may
10345 behave erratically. The stepping action may enter a new scope (for
10346 instance by stepping into a function), or the location of the variable
10347 may change (for instance it is loaded into a register). The
10348 tracepoint data recorded uses the location information for the
10349 variables that is correct for the tracepoint location. When the
10350 tracepoint is created, it is not possible, in general, to determine
10351 where the steps of a @code{while-stepping} sequence will advance the
10352 program---particularly if a conditional branch is stepped.
10355 Collection of an incompletely-initialized or partially-destroyed object
10356 may result in something that @value{GDBN} cannot display, or displays
10357 in a misleading way.
10360 When @value{GDBN} displays a pointer to character it automatically
10361 dereferences the pointer to also display characters of the string
10362 being pointed to. However, collecting the pointer during tracing does
10363 not automatically collect the string. You need to explicitly
10364 dereference the pointer and provide size information if you want to
10365 collect not only the pointer, but the memory pointed to. For example,
10366 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10370 It is not possible to collect a complete stack backtrace at a
10371 tracepoint. Instead, you may collect the registers and a few hundred
10372 bytes from the stack pointer with something like @code{*$esp@@300}
10373 (adjust to use the name of the actual stack pointer register on your
10374 target architecture, and the amount of stack you wish to capture).
10375 Then the @code{backtrace} command will show a partial backtrace when
10376 using a trace frame. The number of stack frames that can be examined
10377 depends on the sizes of the frames in the collected stack. Note that
10378 if you ask for a block so large that it goes past the bottom of the
10379 stack, the target agent may report an error trying to read from an
10383 If you do not collect registers at a tracepoint, @value{GDBN} can
10384 infer that the value of @code{$pc} must be the same as the address of
10385 the tracepoint and use that when you are looking at a trace frame
10386 for that tracepoint. However, this cannot work if the tracepoint has
10387 multiple locations (for instance if it was set in a function that was
10388 inlined), or if it has a @code{while-stepping} loop. In those cases
10389 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10394 @node Analyze Collected Data
10395 @section Using the Collected Data
10397 After the tracepoint experiment ends, you use @value{GDBN} commands
10398 for examining the trace data. The basic idea is that each tracepoint
10399 collects a trace @dfn{snapshot} every time it is hit and another
10400 snapshot every time it single-steps. All these snapshots are
10401 consecutively numbered from zero and go into a buffer, and you can
10402 examine them later. The way you examine them is to @dfn{focus} on a
10403 specific trace snapshot. When the remote stub is focused on a trace
10404 snapshot, it will respond to all @value{GDBN} requests for memory and
10405 registers by reading from the buffer which belongs to that snapshot,
10406 rather than from @emph{real} memory or registers of the program being
10407 debugged. This means that @strong{all} @value{GDBN} commands
10408 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10409 behave as if we were currently debugging the program state as it was
10410 when the tracepoint occurred. Any requests for data that are not in
10411 the buffer will fail.
10414 * tfind:: How to select a trace snapshot
10415 * tdump:: How to display all data for a snapshot
10416 * save tracepoints:: How to save tracepoints for a future run
10420 @subsection @code{tfind @var{n}}
10423 @cindex select trace snapshot
10424 @cindex find trace snapshot
10425 The basic command for selecting a trace snapshot from the buffer is
10426 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10427 counting from zero. If no argument @var{n} is given, the next
10428 snapshot is selected.
10430 Here are the various forms of using the @code{tfind} command.
10434 Find the first snapshot in the buffer. This is a synonym for
10435 @code{tfind 0} (since 0 is the number of the first snapshot).
10438 Stop debugging trace snapshots, resume @emph{live} debugging.
10441 Same as @samp{tfind none}.
10444 No argument means find the next trace snapshot.
10447 Find the previous trace snapshot before the current one. This permits
10448 retracing earlier steps.
10450 @item tfind tracepoint @var{num}
10451 Find the next snapshot associated with tracepoint @var{num}. Search
10452 proceeds forward from the last examined trace snapshot. If no
10453 argument @var{num} is given, it means find the next snapshot collected
10454 for the same tracepoint as the current snapshot.
10456 @item tfind pc @var{addr}
10457 Find the next snapshot associated with the value @var{addr} of the
10458 program counter. Search proceeds forward from the last examined trace
10459 snapshot. If no argument @var{addr} is given, it means find the next
10460 snapshot with the same value of PC as the current snapshot.
10462 @item tfind outside @var{addr1}, @var{addr2}
10463 Find the next snapshot whose PC is outside the given range of
10464 addresses (exclusive).
10466 @item tfind range @var{addr1}, @var{addr2}
10467 Find the next snapshot whose PC is between @var{addr1} and
10468 @var{addr2} (inclusive).
10470 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10471 Find the next snapshot associated with the source line @var{n}. If
10472 the optional argument @var{file} is given, refer to line @var{n} in
10473 that source file. Search proceeds forward from the last examined
10474 trace snapshot. If no argument @var{n} is given, it means find the
10475 next line other than the one currently being examined; thus saying
10476 @code{tfind line} repeatedly can appear to have the same effect as
10477 stepping from line to line in a @emph{live} debugging session.
10480 The default arguments for the @code{tfind} commands are specifically
10481 designed to make it easy to scan through the trace buffer. For
10482 instance, @code{tfind} with no argument selects the next trace
10483 snapshot, and @code{tfind -} with no argument selects the previous
10484 trace snapshot. So, by giving one @code{tfind} command, and then
10485 simply hitting @key{RET} repeatedly you can examine all the trace
10486 snapshots in order. Or, by saying @code{tfind -} and then hitting
10487 @key{RET} repeatedly you can examine the snapshots in reverse order.
10488 The @code{tfind line} command with no argument selects the snapshot
10489 for the next source line executed. The @code{tfind pc} command with
10490 no argument selects the next snapshot with the same program counter
10491 (PC) as the current frame. The @code{tfind tracepoint} command with
10492 no argument selects the next trace snapshot collected by the same
10493 tracepoint as the current one.
10495 In addition to letting you scan through the trace buffer manually,
10496 these commands make it easy to construct @value{GDBN} scripts that
10497 scan through the trace buffer and print out whatever collected data
10498 you are interested in. Thus, if we want to examine the PC, FP, and SP
10499 registers from each trace frame in the buffer, we can say this:
10502 (@value{GDBP}) @b{tfind start}
10503 (@value{GDBP}) @b{while ($trace_frame != -1)}
10504 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10505 $trace_frame, $pc, $sp, $fp
10509 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10510 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10511 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10512 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10513 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10514 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10515 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10516 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10517 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10518 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10519 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10522 Or, if we want to examine the variable @code{X} at each source line in
10526 (@value{GDBP}) @b{tfind start}
10527 (@value{GDBP}) @b{while ($trace_frame != -1)}
10528 > printf "Frame %d, X == %d\n", $trace_frame, X
10538 @subsection @code{tdump}
10540 @cindex dump all data collected at tracepoint
10541 @cindex tracepoint data, display
10543 This command takes no arguments. It prints all the data collected at
10544 the current trace snapshot.
10547 (@value{GDBP}) @b{trace 444}
10548 (@value{GDBP}) @b{actions}
10549 Enter actions for tracepoint #2, one per line:
10550 > collect $regs, $locals, $args, gdb_long_test
10553 (@value{GDBP}) @b{tstart}
10555 (@value{GDBP}) @b{tfind line 444}
10556 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10558 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10560 (@value{GDBP}) @b{tdump}
10561 Data collected at tracepoint 2, trace frame 1:
10562 d0 0xc4aa0085 -995491707
10566 d4 0x71aea3d 119204413
10569 d7 0x380035 3670069
10570 a0 0x19e24a 1696330
10571 a1 0x3000668 50333288
10573 a3 0x322000 3284992
10574 a4 0x3000698 50333336
10575 a5 0x1ad3cc 1758156
10576 fp 0x30bf3c 0x30bf3c
10577 sp 0x30bf34 0x30bf34
10579 pc 0x20b2c8 0x20b2c8
10583 p = 0x20e5b4 "gdb-test"
10590 gdb_long_test = 17 '\021'
10595 @code{tdump} works by scanning the tracepoint's current collection
10596 actions and printing the value of each expression listed. So
10597 @code{tdump} can fail, if after a run, you change the tracepoint's
10598 actions to mention variables that were not collected during the run.
10600 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10601 uses the collected value of @code{$pc} to distinguish between trace
10602 frames that were collected at the tracepoint hit, and frames that were
10603 collected while stepping. This allows it to correctly choose whether
10604 to display the basic list of collections, or the collections from the
10605 body of the while-stepping loop. However, if @code{$pc} was not collected,
10606 then @code{tdump} will always attempt to dump using the basic collection
10607 list, and may fail if a while-stepping frame does not include all the
10608 same data that is collected at the tracepoint hit.
10609 @c This is getting pretty arcane, example would be good.
10611 @node save tracepoints
10612 @subsection @code{save tracepoints @var{filename}}
10613 @kindex save tracepoints
10614 @kindex save-tracepoints
10615 @cindex save tracepoints for future sessions
10617 This command saves all current tracepoint definitions together with
10618 their actions and passcounts, into a file @file{@var{filename}}
10619 suitable for use in a later debugging session. To read the saved
10620 tracepoint definitions, use the @code{source} command (@pxref{Command
10621 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10622 alias for @w{@code{save tracepoints}}
10624 @node Tracepoint Variables
10625 @section Convenience Variables for Tracepoints
10626 @cindex tracepoint variables
10627 @cindex convenience variables for tracepoints
10630 @vindex $trace_frame
10631 @item (int) $trace_frame
10632 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10633 snapshot is selected.
10635 @vindex $tracepoint
10636 @item (int) $tracepoint
10637 The tracepoint for the current trace snapshot.
10639 @vindex $trace_line
10640 @item (int) $trace_line
10641 The line number for the current trace snapshot.
10643 @vindex $trace_file
10644 @item (char []) $trace_file
10645 The source file for the current trace snapshot.
10647 @vindex $trace_func
10648 @item (char []) $trace_func
10649 The name of the function containing @code{$tracepoint}.
10652 Note: @code{$trace_file} is not suitable for use in @code{printf},
10653 use @code{output} instead.
10655 Here's a simple example of using these convenience variables for
10656 stepping through all the trace snapshots and printing some of their
10657 data. Note that these are not the same as trace state variables,
10658 which are managed by the target.
10661 (@value{GDBP}) @b{tfind start}
10663 (@value{GDBP}) @b{while $trace_frame != -1}
10664 > output $trace_file
10665 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10671 @section Using Trace Files
10672 @cindex trace files
10674 In some situations, the target running a trace experiment may no
10675 longer be available; perhaps it crashed, or the hardware was needed
10676 for a different activity. To handle these cases, you can arrange to
10677 dump the trace data into a file, and later use that file as a source
10678 of trace data, via the @code{target tfile} command.
10683 @item tsave [ -r ] @var{filename}
10684 Save the trace data to @var{filename}. By default, this command
10685 assumes that @var{filename} refers to the host filesystem, so if
10686 necessary @value{GDBN} will copy raw trace data up from the target and
10687 then save it. If the target supports it, you can also supply the
10688 optional argument @code{-r} (``remote'') to direct the target to save
10689 the data directly into @var{filename} in its own filesystem, which may be
10690 more efficient if the trace buffer is very large. (Note, however, that
10691 @code{target tfile} can only read from files accessible to the host.)
10693 @kindex target tfile
10695 @item target tfile @var{filename}
10696 Use the file named @var{filename} as a source of trace data. Commands
10697 that examine data work as they do with a live target, but it is not
10698 possible to run any new trace experiments. @code{tstatus} will report
10699 the state of the trace run at the moment the data was saved, as well
10700 as the current trace frame you are examining. @var{filename} must be
10701 on a filesystem accessible to the host.
10706 @chapter Debugging Programs That Use Overlays
10709 If your program is too large to fit completely in your target system's
10710 memory, you can sometimes use @dfn{overlays} to work around this
10711 problem. @value{GDBN} provides some support for debugging programs that
10715 * How Overlays Work:: A general explanation of overlays.
10716 * Overlay Commands:: Managing overlays in @value{GDBN}.
10717 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10718 mapped by asking the inferior.
10719 * Overlay Sample Program:: A sample program using overlays.
10722 @node How Overlays Work
10723 @section How Overlays Work
10724 @cindex mapped overlays
10725 @cindex unmapped overlays
10726 @cindex load address, overlay's
10727 @cindex mapped address
10728 @cindex overlay area
10730 Suppose you have a computer whose instruction address space is only 64
10731 kilobytes long, but which has much more memory which can be accessed by
10732 other means: special instructions, segment registers, or memory
10733 management hardware, for example. Suppose further that you want to
10734 adapt a program which is larger than 64 kilobytes to run on this system.
10736 One solution is to identify modules of your program which are relatively
10737 independent, and need not call each other directly; call these modules
10738 @dfn{overlays}. Separate the overlays from the main program, and place
10739 their machine code in the larger memory. Place your main program in
10740 instruction memory, but leave at least enough space there to hold the
10741 largest overlay as well.
10743 Now, to call a function located in an overlay, you must first copy that
10744 overlay's machine code from the large memory into the space set aside
10745 for it in the instruction memory, and then jump to its entry point
10748 @c NB: In the below the mapped area's size is greater or equal to the
10749 @c size of all overlays. This is intentional to remind the developer
10750 @c that overlays don't necessarily need to be the same size.
10754 Data Instruction Larger
10755 Address Space Address Space Address Space
10756 +-----------+ +-----------+ +-----------+
10758 +-----------+ +-----------+ +-----------+<-- overlay 1
10759 | program | | main | .----| overlay 1 | load address
10760 | variables | | program | | +-----------+
10761 | and heap | | | | | |
10762 +-----------+ | | | +-----------+<-- overlay 2
10763 | | +-----------+ | | | load address
10764 +-----------+ | | | .-| overlay 2 |
10766 mapped --->+-----------+ | | +-----------+
10767 address | | | | | |
10768 | overlay | <-' | | |
10769 | area | <---' +-----------+<-- overlay 3
10770 | | <---. | | load address
10771 +-----------+ `--| overlay 3 |
10778 @anchor{A code overlay}A code overlay
10782 The diagram (@pxref{A code overlay}) shows a system with separate data
10783 and instruction address spaces. To map an overlay, the program copies
10784 its code from the larger address space to the instruction address space.
10785 Since the overlays shown here all use the same mapped address, only one
10786 may be mapped at a time. For a system with a single address space for
10787 data and instructions, the diagram would be similar, except that the
10788 program variables and heap would share an address space with the main
10789 program and the overlay area.
10791 An overlay loaded into instruction memory and ready for use is called a
10792 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10793 instruction memory. An overlay not present (or only partially present)
10794 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10795 is its address in the larger memory. The mapped address is also called
10796 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10797 called the @dfn{load memory address}, or @dfn{LMA}.
10799 Unfortunately, overlays are not a completely transparent way to adapt a
10800 program to limited instruction memory. They introduce a new set of
10801 global constraints you must keep in mind as you design your program:
10806 Before calling or returning to a function in an overlay, your program
10807 must make sure that overlay is actually mapped. Otherwise, the call or
10808 return will transfer control to the right address, but in the wrong
10809 overlay, and your program will probably crash.
10812 If the process of mapping an overlay is expensive on your system, you
10813 will need to choose your overlays carefully to minimize their effect on
10814 your program's performance.
10817 The executable file you load onto your system must contain each
10818 overlay's instructions, appearing at the overlay's load address, not its
10819 mapped address. However, each overlay's instructions must be relocated
10820 and its symbols defined as if the overlay were at its mapped address.
10821 You can use GNU linker scripts to specify different load and relocation
10822 addresses for pieces of your program; see @ref{Overlay Description,,,
10823 ld.info, Using ld: the GNU linker}.
10826 The procedure for loading executable files onto your system must be able
10827 to load their contents into the larger address space as well as the
10828 instruction and data spaces.
10832 The overlay system described above is rather simple, and could be
10833 improved in many ways:
10838 If your system has suitable bank switch registers or memory management
10839 hardware, you could use those facilities to make an overlay's load area
10840 contents simply appear at their mapped address in instruction space.
10841 This would probably be faster than copying the overlay to its mapped
10842 area in the usual way.
10845 If your overlays are small enough, you could set aside more than one
10846 overlay area, and have more than one overlay mapped at a time.
10849 You can use overlays to manage data, as well as instructions. In
10850 general, data overlays are even less transparent to your design than
10851 code overlays: whereas code overlays only require care when you call or
10852 return to functions, data overlays require care every time you access
10853 the data. Also, if you change the contents of a data overlay, you
10854 must copy its contents back out to its load address before you can copy a
10855 different data overlay into the same mapped area.
10860 @node Overlay Commands
10861 @section Overlay Commands
10863 To use @value{GDBN}'s overlay support, each overlay in your program must
10864 correspond to a separate section of the executable file. The section's
10865 virtual memory address and load memory address must be the overlay's
10866 mapped and load addresses. Identifying overlays with sections allows
10867 @value{GDBN} to determine the appropriate address of a function or
10868 variable, depending on whether the overlay is mapped or not.
10870 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10871 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10876 Disable @value{GDBN}'s overlay support. When overlay support is
10877 disabled, @value{GDBN} assumes that all functions and variables are
10878 always present at their mapped addresses. By default, @value{GDBN}'s
10879 overlay support is disabled.
10881 @item overlay manual
10882 @cindex manual overlay debugging
10883 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10884 relies on you to tell it which overlays are mapped, and which are not,
10885 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10886 commands described below.
10888 @item overlay map-overlay @var{overlay}
10889 @itemx overlay map @var{overlay}
10890 @cindex map an overlay
10891 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10892 be the name of the object file section containing the overlay. When an
10893 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10894 functions and variables at their mapped addresses. @value{GDBN} assumes
10895 that any other overlays whose mapped ranges overlap that of
10896 @var{overlay} are now unmapped.
10898 @item overlay unmap-overlay @var{overlay}
10899 @itemx overlay unmap @var{overlay}
10900 @cindex unmap an overlay
10901 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10902 must be the name of the object file section containing the overlay.
10903 When an overlay is unmapped, @value{GDBN} assumes it can find the
10904 overlay's functions and variables at their load addresses.
10907 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10908 consults a data structure the overlay manager maintains in the inferior
10909 to see which overlays are mapped. For details, see @ref{Automatic
10910 Overlay Debugging}.
10912 @item overlay load-target
10913 @itemx overlay load
10914 @cindex reloading the overlay table
10915 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10916 re-reads the table @value{GDBN} automatically each time the inferior
10917 stops, so this command should only be necessary if you have changed the
10918 overlay mapping yourself using @value{GDBN}. This command is only
10919 useful when using automatic overlay debugging.
10921 @item overlay list-overlays
10922 @itemx overlay list
10923 @cindex listing mapped overlays
10924 Display a list of the overlays currently mapped, along with their mapped
10925 addresses, load addresses, and sizes.
10929 Normally, when @value{GDBN} prints a code address, it includes the name
10930 of the function the address falls in:
10933 (@value{GDBP}) print main
10934 $3 = @{int ()@} 0x11a0 <main>
10937 When overlay debugging is enabled, @value{GDBN} recognizes code in
10938 unmapped overlays, and prints the names of unmapped functions with
10939 asterisks around them. For example, if @code{foo} is a function in an
10940 unmapped overlay, @value{GDBN} prints it this way:
10943 (@value{GDBP}) overlay list
10944 No sections are mapped.
10945 (@value{GDBP}) print foo
10946 $5 = @{int (int)@} 0x100000 <*foo*>
10949 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10953 (@value{GDBP}) overlay list
10954 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10955 mapped at 0x1016 - 0x104a
10956 (@value{GDBP}) print foo
10957 $6 = @{int (int)@} 0x1016 <foo>
10960 When overlay debugging is enabled, @value{GDBN} can find the correct
10961 address for functions and variables in an overlay, whether or not the
10962 overlay is mapped. This allows most @value{GDBN} commands, like
10963 @code{break} and @code{disassemble}, to work normally, even on unmapped
10964 code. However, @value{GDBN}'s breakpoint support has some limitations:
10968 @cindex breakpoints in overlays
10969 @cindex overlays, setting breakpoints in
10970 You can set breakpoints in functions in unmapped overlays, as long as
10971 @value{GDBN} can write to the overlay at its load address.
10973 @value{GDBN} can not set hardware or simulator-based breakpoints in
10974 unmapped overlays. However, if you set a breakpoint at the end of your
10975 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10976 you are using manual overlay management), @value{GDBN} will re-set its
10977 breakpoints properly.
10981 @node Automatic Overlay Debugging
10982 @section Automatic Overlay Debugging
10983 @cindex automatic overlay debugging
10985 @value{GDBN} can automatically track which overlays are mapped and which
10986 are not, given some simple co-operation from the overlay manager in the
10987 inferior. If you enable automatic overlay debugging with the
10988 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10989 looks in the inferior's memory for certain variables describing the
10990 current state of the overlays.
10992 Here are the variables your overlay manager must define to support
10993 @value{GDBN}'s automatic overlay debugging:
10997 @item @code{_ovly_table}:
10998 This variable must be an array of the following structures:
11003 /* The overlay's mapped address. */
11006 /* The size of the overlay, in bytes. */
11007 unsigned long size;
11009 /* The overlay's load address. */
11012 /* Non-zero if the overlay is currently mapped;
11014 unsigned long mapped;
11018 @item @code{_novlys}:
11019 This variable must be a four-byte signed integer, holding the total
11020 number of elements in @code{_ovly_table}.
11024 To decide whether a particular overlay is mapped or not, @value{GDBN}
11025 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11026 @code{lma} members equal the VMA and LMA of the overlay's section in the
11027 executable file. When @value{GDBN} finds a matching entry, it consults
11028 the entry's @code{mapped} member to determine whether the overlay is
11031 In addition, your overlay manager may define a function called
11032 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11033 will silently set a breakpoint there. If the overlay manager then
11034 calls this function whenever it has changed the overlay table, this
11035 will enable @value{GDBN} to accurately keep track of which overlays
11036 are in program memory, and update any breakpoints that may be set
11037 in overlays. This will allow breakpoints to work even if the
11038 overlays are kept in ROM or other non-writable memory while they
11039 are not being executed.
11041 @node Overlay Sample Program
11042 @section Overlay Sample Program
11043 @cindex overlay example program
11045 When linking a program which uses overlays, you must place the overlays
11046 at their load addresses, while relocating them to run at their mapped
11047 addresses. To do this, you must write a linker script (@pxref{Overlay
11048 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11049 since linker scripts are specific to a particular host system, target
11050 architecture, and target memory layout, this manual cannot provide
11051 portable sample code demonstrating @value{GDBN}'s overlay support.
11053 However, the @value{GDBN} source distribution does contain an overlaid
11054 program, with linker scripts for a few systems, as part of its test
11055 suite. The program consists of the following files from
11056 @file{gdb/testsuite/gdb.base}:
11060 The main program file.
11062 A simple overlay manager, used by @file{overlays.c}.
11067 Overlay modules, loaded and used by @file{overlays.c}.
11070 Linker scripts for linking the test program on the @code{d10v-elf}
11071 and @code{m32r-elf} targets.
11074 You can build the test program using the @code{d10v-elf} GCC
11075 cross-compiler like this:
11078 $ d10v-elf-gcc -g -c overlays.c
11079 $ d10v-elf-gcc -g -c ovlymgr.c
11080 $ d10v-elf-gcc -g -c foo.c
11081 $ d10v-elf-gcc -g -c bar.c
11082 $ d10v-elf-gcc -g -c baz.c
11083 $ d10v-elf-gcc -g -c grbx.c
11084 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11085 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11088 The build process is identical for any other architecture, except that
11089 you must substitute the appropriate compiler and linker script for the
11090 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11094 @chapter Using @value{GDBN} with Different Languages
11097 Although programming languages generally have common aspects, they are
11098 rarely expressed in the same manner. For instance, in ANSI C,
11099 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11100 Modula-2, it is accomplished by @code{p^}. Values can also be
11101 represented (and displayed) differently. Hex numbers in C appear as
11102 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11104 @cindex working language
11105 Language-specific information is built into @value{GDBN} for some languages,
11106 allowing you to express operations like the above in your program's
11107 native language, and allowing @value{GDBN} to output values in a manner
11108 consistent with the syntax of your program's native language. The
11109 language you use to build expressions is called the @dfn{working
11113 * Setting:: Switching between source languages
11114 * Show:: Displaying the language
11115 * Checks:: Type and range checks
11116 * Supported Languages:: Supported languages
11117 * Unsupported Languages:: Unsupported languages
11121 @section Switching Between Source Languages
11123 There are two ways to control the working language---either have @value{GDBN}
11124 set it automatically, or select it manually yourself. You can use the
11125 @code{set language} command for either purpose. On startup, @value{GDBN}
11126 defaults to setting the language automatically. The working language is
11127 used to determine how expressions you type are interpreted, how values
11130 In addition to the working language, every source file that
11131 @value{GDBN} knows about has its own working language. For some object
11132 file formats, the compiler might indicate which language a particular
11133 source file is in. However, most of the time @value{GDBN} infers the
11134 language from the name of the file. The language of a source file
11135 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11136 show each frame appropriately for its own language. There is no way to
11137 set the language of a source file from within @value{GDBN}, but you can
11138 set the language associated with a filename extension. @xref{Show, ,
11139 Displaying the Language}.
11141 This is most commonly a problem when you use a program, such
11142 as @code{cfront} or @code{f2c}, that generates C but is written in
11143 another language. In that case, make the
11144 program use @code{#line} directives in its C output; that way
11145 @value{GDBN} will know the correct language of the source code of the original
11146 program, and will display that source code, not the generated C code.
11149 * Filenames:: Filename extensions and languages.
11150 * Manually:: Setting the working language manually
11151 * Automatically:: Having @value{GDBN} infer the source language
11155 @subsection List of Filename Extensions and Languages
11157 If a source file name ends in one of the following extensions, then
11158 @value{GDBN} infers that its language is the one indicated.
11176 C@t{++} source file
11182 Objective-C source file
11186 Fortran source file
11189 Modula-2 source file
11193 Assembler source file. This actually behaves almost like C, but
11194 @value{GDBN} does not skip over function prologues when stepping.
11197 In addition, you may set the language associated with a filename
11198 extension. @xref{Show, , Displaying the Language}.
11201 @subsection Setting the Working Language
11203 If you allow @value{GDBN} to set the language automatically,
11204 expressions are interpreted the same way in your debugging session and
11207 @kindex set language
11208 If you wish, you may set the language manually. To do this, issue the
11209 command @samp{set language @var{lang}}, where @var{lang} is the name of
11210 a language, such as
11211 @code{c} or @code{modula-2}.
11212 For a list of the supported languages, type @samp{set language}.
11214 Setting the language manually prevents @value{GDBN} from updating the working
11215 language automatically. This can lead to confusion if you try
11216 to debug a program when the working language is not the same as the
11217 source language, when an expression is acceptable to both
11218 languages---but means different things. For instance, if the current
11219 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11227 might not have the effect you intended. In C, this means to add
11228 @code{b} and @code{c} and place the result in @code{a}. The result
11229 printed would be the value of @code{a}. In Modula-2, this means to compare
11230 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11232 @node Automatically
11233 @subsection Having @value{GDBN} Infer the Source Language
11235 To have @value{GDBN} set the working language automatically, use
11236 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11237 then infers the working language. That is, when your program stops in a
11238 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11239 working language to the language recorded for the function in that
11240 frame. If the language for a frame is unknown (that is, if the function
11241 or block corresponding to the frame was defined in a source file that
11242 does not have a recognized extension), the current working language is
11243 not changed, and @value{GDBN} issues a warning.
11245 This may not seem necessary for most programs, which are written
11246 entirely in one source language. However, program modules and libraries
11247 written in one source language can be used by a main program written in
11248 a different source language. Using @samp{set language auto} in this
11249 case frees you from having to set the working language manually.
11252 @section Displaying the Language
11254 The following commands help you find out which language is the
11255 working language, and also what language source files were written in.
11258 @item show language
11259 @kindex show language
11260 Display the current working language. This is the
11261 language you can use with commands such as @code{print} to
11262 build and compute expressions that may involve variables in your program.
11265 @kindex info frame@r{, show the source language}
11266 Display the source language for this frame. This language becomes the
11267 working language if you use an identifier from this frame.
11268 @xref{Frame Info, ,Information about a Frame}, to identify the other
11269 information listed here.
11272 @kindex info source@r{, show the source language}
11273 Display the source language of this source file.
11274 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11275 information listed here.
11278 In unusual circumstances, you may have source files with extensions
11279 not in the standard list. You can then set the extension associated
11280 with a language explicitly:
11283 @item set extension-language @var{ext} @var{language}
11284 @kindex set extension-language
11285 Tell @value{GDBN} that source files with extension @var{ext} are to be
11286 assumed as written in the source language @var{language}.
11288 @item info extensions
11289 @kindex info extensions
11290 List all the filename extensions and the associated languages.
11294 @section Type and Range Checking
11297 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11298 checking are included, but they do not yet have any effect. This
11299 section documents the intended facilities.
11301 @c FIXME remove warning when type/range code added
11303 Some languages are designed to guard you against making seemingly common
11304 errors through a series of compile- and run-time checks. These include
11305 checking the type of arguments to functions and operators, and making
11306 sure mathematical overflows are caught at run time. Checks such as
11307 these help to ensure a program's correctness once it has been compiled
11308 by eliminating type mismatches, and providing active checks for range
11309 errors when your program is running.
11311 @value{GDBN} can check for conditions like the above if you wish.
11312 Although @value{GDBN} does not check the statements in your program,
11313 it can check expressions entered directly into @value{GDBN} for
11314 evaluation via the @code{print} command, for example. As with the
11315 working language, @value{GDBN} can also decide whether or not to check
11316 automatically based on your program's source language.
11317 @xref{Supported Languages, ,Supported Languages}, for the default
11318 settings of supported languages.
11321 * Type Checking:: An overview of type checking
11322 * Range Checking:: An overview of range checking
11325 @cindex type checking
11326 @cindex checks, type
11327 @node Type Checking
11328 @subsection An Overview of Type Checking
11330 Some languages, such as Modula-2, are strongly typed, meaning that the
11331 arguments to operators and functions have to be of the correct type,
11332 otherwise an error occurs. These checks prevent type mismatch
11333 errors from ever causing any run-time problems. For example,
11341 The second example fails because the @code{CARDINAL} 1 is not
11342 type-compatible with the @code{REAL} 2.3.
11344 For the expressions you use in @value{GDBN} commands, you can tell the
11345 @value{GDBN} type checker to skip checking;
11346 to treat any mismatches as errors and abandon the expression;
11347 or to only issue warnings when type mismatches occur,
11348 but evaluate the expression anyway. When you choose the last of
11349 these, @value{GDBN} evaluates expressions like the second example above, but
11350 also issues a warning.
11352 Even if you turn type checking off, there may be other reasons
11353 related to type that prevent @value{GDBN} from evaluating an expression.
11354 For instance, @value{GDBN} does not know how to add an @code{int} and
11355 a @code{struct foo}. These particular type errors have nothing to do
11356 with the language in use, and usually arise from expressions, such as
11357 the one described above, which make little sense to evaluate anyway.
11359 Each language defines to what degree it is strict about type. For
11360 instance, both Modula-2 and C require the arguments to arithmetical
11361 operators to be numbers. In C, enumerated types and pointers can be
11362 represented as numbers, so that they are valid arguments to mathematical
11363 operators. @xref{Supported Languages, ,Supported Languages}, for further
11364 details on specific languages.
11366 @value{GDBN} provides some additional commands for controlling the type checker:
11368 @kindex set check type
11369 @kindex show check type
11371 @item set check type auto
11372 Set type checking on or off based on the current working language.
11373 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11376 @item set check type on
11377 @itemx set check type off
11378 Set type checking on or off, overriding the default setting for the
11379 current working language. Issue a warning if the setting does not
11380 match the language default. If any type mismatches occur in
11381 evaluating an expression while type checking is on, @value{GDBN} prints a
11382 message and aborts evaluation of the expression.
11384 @item set check type warn
11385 Cause the type checker to issue warnings, but to always attempt to
11386 evaluate the expression. Evaluating the expression may still
11387 be impossible for other reasons. For example, @value{GDBN} cannot add
11388 numbers and structures.
11391 Show the current setting of the type checker, and whether or not @value{GDBN}
11392 is setting it automatically.
11395 @cindex range checking
11396 @cindex checks, range
11397 @node Range Checking
11398 @subsection An Overview of Range Checking
11400 In some languages (such as Modula-2), it is an error to exceed the
11401 bounds of a type; this is enforced with run-time checks. Such range
11402 checking is meant to ensure program correctness by making sure
11403 computations do not overflow, or indices on an array element access do
11404 not exceed the bounds of the array.
11406 For expressions you use in @value{GDBN} commands, you can tell
11407 @value{GDBN} to treat range errors in one of three ways: ignore them,
11408 always treat them as errors and abandon the expression, or issue
11409 warnings but evaluate the expression anyway.
11411 A range error can result from numerical overflow, from exceeding an
11412 array index bound, or when you type a constant that is not a member
11413 of any type. Some languages, however, do not treat overflows as an
11414 error. In many implementations of C, mathematical overflow causes the
11415 result to ``wrap around'' to lower values---for example, if @var{m} is
11416 the largest integer value, and @var{s} is the smallest, then
11419 @var{m} + 1 @result{} @var{s}
11422 This, too, is specific to individual languages, and in some cases
11423 specific to individual compilers or machines. @xref{Supported Languages, ,
11424 Supported Languages}, for further details on specific languages.
11426 @value{GDBN} provides some additional commands for controlling the range checker:
11428 @kindex set check range
11429 @kindex show check range
11431 @item set check range auto
11432 Set range checking on or off based on the current working language.
11433 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11436 @item set check range on
11437 @itemx set check range off
11438 Set range checking on or off, overriding the default setting for the
11439 current working language. A warning is issued if the setting does not
11440 match the language default. If a range error occurs and range checking is on,
11441 then a message is printed and evaluation of the expression is aborted.
11443 @item set check range warn
11444 Output messages when the @value{GDBN} range checker detects a range error,
11445 but attempt to evaluate the expression anyway. Evaluating the
11446 expression may still be impossible for other reasons, such as accessing
11447 memory that the process does not own (a typical example from many Unix
11451 Show the current setting of the range checker, and whether or not it is
11452 being set automatically by @value{GDBN}.
11455 @node Supported Languages
11456 @section Supported Languages
11458 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11459 assembly, Modula-2, and Ada.
11460 @c This is false ...
11461 Some @value{GDBN} features may be used in expressions regardless of the
11462 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11463 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11464 ,Expressions}) can be used with the constructs of any supported
11467 The following sections detail to what degree each source language is
11468 supported by @value{GDBN}. These sections are not meant to be language
11469 tutorials or references, but serve only as a reference guide to what the
11470 @value{GDBN} expression parser accepts, and what input and output
11471 formats should look like for different languages. There are many good
11472 books written on each of these languages; please look to these for a
11473 language reference or tutorial.
11476 * C:: C and C@t{++}
11478 * Objective-C:: Objective-C
11479 * Fortran:: Fortran
11481 * Modula-2:: Modula-2
11486 @subsection C and C@t{++}
11488 @cindex C and C@t{++}
11489 @cindex expressions in C or C@t{++}
11491 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11492 to both languages. Whenever this is the case, we discuss those languages
11496 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11497 @cindex @sc{gnu} C@t{++}
11498 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11499 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11500 effectively, you must compile your C@t{++} programs with a supported
11501 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11502 compiler (@code{aCC}).
11504 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11505 format; if it doesn't work on your system, try the stabs+ debugging
11506 format. You can select those formats explicitly with the @code{g++}
11507 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11508 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11509 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11512 * C Operators:: C and C@t{++} operators
11513 * C Constants:: C and C@t{++} constants
11514 * C Plus Plus Expressions:: C@t{++} expressions
11515 * C Defaults:: Default settings for C and C@t{++}
11516 * C Checks:: C and C@t{++} type and range checks
11517 * Debugging C:: @value{GDBN} and C
11518 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11519 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11523 @subsubsection C and C@t{++} Operators
11525 @cindex C and C@t{++} operators
11527 Operators must be defined on values of specific types. For instance,
11528 @code{+} is defined on numbers, but not on structures. Operators are
11529 often defined on groups of types.
11531 For the purposes of C and C@t{++}, the following definitions hold:
11536 @emph{Integral types} include @code{int} with any of its storage-class
11537 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11540 @emph{Floating-point types} include @code{float}, @code{double}, and
11541 @code{long double} (if supported by the target platform).
11544 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11547 @emph{Scalar types} include all of the above.
11552 The following operators are supported. They are listed here
11553 in order of increasing precedence:
11557 The comma or sequencing operator. Expressions in a comma-separated list
11558 are evaluated from left to right, with the result of the entire
11559 expression being the last expression evaluated.
11562 Assignment. The value of an assignment expression is the value
11563 assigned. Defined on scalar types.
11566 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11567 and translated to @w{@code{@var{a} = @var{a op b}}}.
11568 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11569 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11570 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11573 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11574 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11578 Logical @sc{or}. Defined on integral types.
11581 Logical @sc{and}. Defined on integral types.
11584 Bitwise @sc{or}. Defined on integral types.
11587 Bitwise exclusive-@sc{or}. Defined on integral types.
11590 Bitwise @sc{and}. Defined on integral types.
11593 Equality and inequality. Defined on scalar types. The value of these
11594 expressions is 0 for false and non-zero for true.
11596 @item <@r{, }>@r{, }<=@r{, }>=
11597 Less than, greater than, less than or equal, greater than or equal.
11598 Defined on scalar types. The value of these expressions is 0 for false
11599 and non-zero for true.
11602 left shift, and right shift. Defined on integral types.
11605 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11608 Addition and subtraction. Defined on integral types, floating-point types and
11611 @item *@r{, }/@r{, }%
11612 Multiplication, division, and modulus. Multiplication and division are
11613 defined on integral and floating-point types. Modulus is defined on
11617 Increment and decrement. When appearing before a variable, the
11618 operation is performed before the variable is used in an expression;
11619 when appearing after it, the variable's value is used before the
11620 operation takes place.
11623 Pointer dereferencing. Defined on pointer types. Same precedence as
11627 Address operator. Defined on variables. Same precedence as @code{++}.
11629 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11630 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11631 to examine the address
11632 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11636 Negative. Defined on integral and floating-point types. Same
11637 precedence as @code{++}.
11640 Logical negation. Defined on integral types. Same precedence as
11644 Bitwise complement operator. Defined on integral types. Same precedence as
11649 Structure member, and pointer-to-structure member. For convenience,
11650 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11651 pointer based on the stored type information.
11652 Defined on @code{struct} and @code{union} data.
11655 Dereferences of pointers to members.
11658 Array indexing. @code{@var{a}[@var{i}]} is defined as
11659 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11662 Function parameter list. Same precedence as @code{->}.
11665 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11666 and @code{class} types.
11669 Doubled colons also represent the @value{GDBN} scope operator
11670 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11674 If an operator is redefined in the user code, @value{GDBN} usually
11675 attempts to invoke the redefined version instead of using the operator's
11676 predefined meaning.
11679 @subsubsection C and C@t{++} Constants
11681 @cindex C and C@t{++} constants
11683 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11688 Integer constants are a sequence of digits. Octal constants are
11689 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11690 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11691 @samp{l}, specifying that the constant should be treated as a
11695 Floating point constants are a sequence of digits, followed by a decimal
11696 point, followed by a sequence of digits, and optionally followed by an
11697 exponent. An exponent is of the form:
11698 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11699 sequence of digits. The @samp{+} is optional for positive exponents.
11700 A floating-point constant may also end with a letter @samp{f} or
11701 @samp{F}, specifying that the constant should be treated as being of
11702 the @code{float} (as opposed to the default @code{double}) type; or with
11703 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11707 Enumerated constants consist of enumerated identifiers, or their
11708 integral equivalents.
11711 Character constants are a single character surrounded by single quotes
11712 (@code{'}), or a number---the ordinal value of the corresponding character
11713 (usually its @sc{ascii} value). Within quotes, the single character may
11714 be represented by a letter or by @dfn{escape sequences}, which are of
11715 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11716 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11717 @samp{@var{x}} is a predefined special character---for example,
11718 @samp{\n} for newline.
11721 String constants are a sequence of character constants surrounded by
11722 double quotes (@code{"}). Any valid character constant (as described
11723 above) may appear. Double quotes within the string must be preceded by
11724 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11728 Pointer constants are an integral value. You can also write pointers
11729 to constants using the C operator @samp{&}.
11732 Array constants are comma-separated lists surrounded by braces @samp{@{}
11733 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11734 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11735 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11738 @node C Plus Plus Expressions
11739 @subsubsection C@t{++} Expressions
11741 @cindex expressions in C@t{++}
11742 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11744 @cindex debugging C@t{++} programs
11745 @cindex C@t{++} compilers
11746 @cindex debug formats and C@t{++}
11747 @cindex @value{NGCC} and C@t{++}
11749 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11750 proper compiler and the proper debug format. Currently, @value{GDBN}
11751 works best when debugging C@t{++} code that is compiled with
11752 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11753 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11754 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11755 stabs+ as their default debug format, so you usually don't need to
11756 specify a debug format explicitly. Other compilers and/or debug formats
11757 are likely to work badly or not at all when using @value{GDBN} to debug
11763 @cindex member functions
11765 Member function calls are allowed; you can use expressions like
11768 count = aml->GetOriginal(x, y)
11771 @vindex this@r{, inside C@t{++} member functions}
11772 @cindex namespace in C@t{++}
11774 While a member function is active (in the selected stack frame), your
11775 expressions have the same namespace available as the member function;
11776 that is, @value{GDBN} allows implicit references to the class instance
11777 pointer @code{this} following the same rules as C@t{++}.
11779 @cindex call overloaded functions
11780 @cindex overloaded functions, calling
11781 @cindex type conversions in C@t{++}
11783 You can call overloaded functions; @value{GDBN} resolves the function
11784 call to the right definition, with some restrictions. @value{GDBN} does not
11785 perform overload resolution involving user-defined type conversions,
11786 calls to constructors, or instantiations of templates that do not exist
11787 in the program. It also cannot handle ellipsis argument lists or
11790 It does perform integral conversions and promotions, floating-point
11791 promotions, arithmetic conversions, pointer conversions, conversions of
11792 class objects to base classes, and standard conversions such as those of
11793 functions or arrays to pointers; it requires an exact match on the
11794 number of function arguments.
11796 Overload resolution is always performed, unless you have specified
11797 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11798 ,@value{GDBN} Features for C@t{++}}.
11800 You must specify @code{set overload-resolution off} in order to use an
11801 explicit function signature to call an overloaded function, as in
11803 p 'foo(char,int)'('x', 13)
11806 The @value{GDBN} command-completion facility can simplify this;
11807 see @ref{Completion, ,Command Completion}.
11809 @cindex reference declarations
11811 @value{GDBN} understands variables declared as C@t{++} references; you can use
11812 them in expressions just as you do in C@t{++} source---they are automatically
11815 In the parameter list shown when @value{GDBN} displays a frame, the values of
11816 reference variables are not displayed (unlike other variables); this
11817 avoids clutter, since references are often used for large structures.
11818 The @emph{address} of a reference variable is always shown, unless
11819 you have specified @samp{set print address off}.
11822 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11823 expressions can use it just as expressions in your program do. Since
11824 one scope may be defined in another, you can use @code{::} repeatedly if
11825 necessary, for example in an expression like
11826 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11827 resolving name scope by reference to source files, in both C and C@t{++}
11828 debugging (@pxref{Variables, ,Program Variables}).
11831 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11832 calling virtual functions correctly, printing out virtual bases of
11833 objects, calling functions in a base subobject, casting objects, and
11834 invoking user-defined operators.
11837 @subsubsection C and C@t{++} Defaults
11839 @cindex C and C@t{++} defaults
11841 If you allow @value{GDBN} to set type and range checking automatically, they
11842 both default to @code{off} whenever the working language changes to
11843 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11844 selects the working language.
11846 If you allow @value{GDBN} to set the language automatically, it
11847 recognizes source files whose names end with @file{.c}, @file{.C}, or
11848 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11849 these files, it sets the working language to C or C@t{++}.
11850 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11851 for further details.
11853 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11854 @c unimplemented. If (b) changes, it might make sense to let this node
11855 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11858 @subsubsection C and C@t{++} Type and Range Checks
11860 @cindex C and C@t{++} checks
11862 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11863 is not used. However, if you turn type checking on, @value{GDBN}
11864 considers two variables type equivalent if:
11868 The two variables are structured and have the same structure, union, or
11872 The two variables have the same type name, or types that have been
11873 declared equivalent through @code{typedef}.
11876 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11879 The two @code{struct}, @code{union}, or @code{enum} variables are
11880 declared in the same declaration. (Note: this may not be true for all C
11885 Range checking, if turned on, is done on mathematical operations. Array
11886 indices are not checked, since they are often used to index a pointer
11887 that is not itself an array.
11890 @subsubsection @value{GDBN} and C
11892 The @code{set print union} and @code{show print union} commands apply to
11893 the @code{union} type. When set to @samp{on}, any @code{union} that is
11894 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11895 appears as @samp{@{...@}}.
11897 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11898 with pointers and a memory allocation function. @xref{Expressions,
11901 @node Debugging C Plus Plus
11902 @subsubsection @value{GDBN} Features for C@t{++}
11904 @cindex commands for C@t{++}
11906 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11907 designed specifically for use with C@t{++}. Here is a summary:
11910 @cindex break in overloaded functions
11911 @item @r{breakpoint menus}
11912 When you want a breakpoint in a function whose name is overloaded,
11913 @value{GDBN} has the capability to display a menu of possible breakpoint
11914 locations to help you specify which function definition you want.
11915 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11917 @cindex overloading in C@t{++}
11918 @item rbreak @var{regex}
11919 Setting breakpoints using regular expressions is helpful for setting
11920 breakpoints on overloaded functions that are not members of any special
11922 @xref{Set Breaks, ,Setting Breakpoints}.
11924 @cindex C@t{++} exception handling
11927 Debug C@t{++} exception handling using these commands. @xref{Set
11928 Catchpoints, , Setting Catchpoints}.
11930 @cindex inheritance
11931 @item ptype @var{typename}
11932 Print inheritance relationships as well as other information for type
11934 @xref{Symbols, ,Examining the Symbol Table}.
11936 @cindex C@t{++} symbol display
11937 @item set print demangle
11938 @itemx show print demangle
11939 @itemx set print asm-demangle
11940 @itemx show print asm-demangle
11941 Control whether C@t{++} symbols display in their source form, both when
11942 displaying code as C@t{++} source and when displaying disassemblies.
11943 @xref{Print Settings, ,Print Settings}.
11945 @item set print object
11946 @itemx show print object
11947 Choose whether to print derived (actual) or declared types of objects.
11948 @xref{Print Settings, ,Print Settings}.
11950 @item set print vtbl
11951 @itemx show print vtbl
11952 Control the format for printing virtual function tables.
11953 @xref{Print Settings, ,Print Settings}.
11954 (The @code{vtbl} commands do not work on programs compiled with the HP
11955 ANSI C@t{++} compiler (@code{aCC}).)
11957 @kindex set overload-resolution
11958 @cindex overloaded functions, overload resolution
11959 @item set overload-resolution on
11960 Enable overload resolution for C@t{++} expression evaluation. The default
11961 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11962 and searches for a function whose signature matches the argument types,
11963 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11964 Expressions, ,C@t{++} Expressions}, for details).
11965 If it cannot find a match, it emits a message.
11967 @item set overload-resolution off
11968 Disable overload resolution for C@t{++} expression evaluation. For
11969 overloaded functions that are not class member functions, @value{GDBN}
11970 chooses the first function of the specified name that it finds in the
11971 symbol table, whether or not its arguments are of the correct type. For
11972 overloaded functions that are class member functions, @value{GDBN}
11973 searches for a function whose signature @emph{exactly} matches the
11976 @kindex show overload-resolution
11977 @item show overload-resolution
11978 Show the current setting of overload resolution.
11980 @item @r{Overloaded symbol names}
11981 You can specify a particular definition of an overloaded symbol, using
11982 the same notation that is used to declare such symbols in C@t{++}: type
11983 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11984 also use the @value{GDBN} command-line word completion facilities to list the
11985 available choices, or to finish the type list for you.
11986 @xref{Completion,, Command Completion}, for details on how to do this.
11989 @node Decimal Floating Point
11990 @subsubsection Decimal Floating Point format
11991 @cindex decimal floating point format
11993 @value{GDBN} can examine, set and perform computations with numbers in
11994 decimal floating point format, which in the C language correspond to the
11995 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11996 specified by the extension to support decimal floating-point arithmetic.
11998 There are two encodings in use, depending on the architecture: BID (Binary
11999 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12000 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12003 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12004 to manipulate decimal floating point numbers, it is not possible to convert
12005 (using a cast, for example) integers wider than 32-bit to decimal float.
12007 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12008 point computations, error checking in decimal float operations ignores
12009 underflow, overflow and divide by zero exceptions.
12011 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12012 to inspect @code{_Decimal128} values stored in floating point registers.
12013 See @ref{PowerPC,,PowerPC} for more details.
12019 @value{GDBN} can be used to debug programs written in D and compiled with
12020 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12021 specific feature --- dynamic arrays.
12024 @subsection Objective-C
12026 @cindex Objective-C
12027 This section provides information about some commands and command
12028 options that are useful for debugging Objective-C code. See also
12029 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12030 few more commands specific to Objective-C support.
12033 * Method Names in Commands::
12034 * The Print Command with Objective-C::
12037 @node Method Names in Commands
12038 @subsubsection Method Names in Commands
12040 The following commands have been extended to accept Objective-C method
12041 names as line specifications:
12043 @kindex clear@r{, and Objective-C}
12044 @kindex break@r{, and Objective-C}
12045 @kindex info line@r{, and Objective-C}
12046 @kindex jump@r{, and Objective-C}
12047 @kindex list@r{, and Objective-C}
12051 @item @code{info line}
12056 A fully qualified Objective-C method name is specified as
12059 -[@var{Class} @var{methodName}]
12062 where the minus sign is used to indicate an instance method and a
12063 plus sign (not shown) is used to indicate a class method. The class
12064 name @var{Class} and method name @var{methodName} are enclosed in
12065 brackets, similar to the way messages are specified in Objective-C
12066 source code. For example, to set a breakpoint at the @code{create}
12067 instance method of class @code{Fruit} in the program currently being
12071 break -[Fruit create]
12074 To list ten program lines around the @code{initialize} class method,
12078 list +[NSText initialize]
12081 In the current version of @value{GDBN}, the plus or minus sign is
12082 required. In future versions of @value{GDBN}, the plus or minus
12083 sign will be optional, but you can use it to narrow the search. It
12084 is also possible to specify just a method name:
12090 You must specify the complete method name, including any colons. If
12091 your program's source files contain more than one @code{create} method,
12092 you'll be presented with a numbered list of classes that implement that
12093 method. Indicate your choice by number, or type @samp{0} to exit if
12096 As another example, to clear a breakpoint established at the
12097 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12100 clear -[NSWindow makeKeyAndOrderFront:]
12103 @node The Print Command with Objective-C
12104 @subsubsection The Print Command With Objective-C
12105 @cindex Objective-C, print objects
12106 @kindex print-object
12107 @kindex po @r{(@code{print-object})}
12109 The print command has also been extended to accept methods. For example:
12112 print -[@var{object} hash]
12115 @cindex print an Objective-C object description
12116 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12118 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12119 and print the result. Also, an additional command has been added,
12120 @code{print-object} or @code{po} for short, which is meant to print
12121 the description of an object. However, this command may only work
12122 with certain Objective-C libraries that have a particular hook
12123 function, @code{_NSPrintForDebugger}, defined.
12126 @subsection Fortran
12127 @cindex Fortran-specific support in @value{GDBN}
12129 @value{GDBN} can be used to debug programs written in Fortran, but it
12130 currently supports only the features of Fortran 77 language.
12132 @cindex trailing underscore, in Fortran symbols
12133 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12134 among them) append an underscore to the names of variables and
12135 functions. When you debug programs compiled by those compilers, you
12136 will need to refer to variables and functions with a trailing
12140 * Fortran Operators:: Fortran operators and expressions
12141 * Fortran Defaults:: Default settings for Fortran
12142 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12145 @node Fortran Operators
12146 @subsubsection Fortran Operators and Expressions
12148 @cindex Fortran operators and expressions
12150 Operators must be defined on values of specific types. For instance,
12151 @code{+} is defined on numbers, but not on characters or other non-
12152 arithmetic types. Operators are often defined on groups of types.
12156 The exponentiation operator. It raises the first operand to the power
12160 The range operator. Normally used in the form of array(low:high) to
12161 represent a section of array.
12164 The access component operator. Normally used to access elements in derived
12165 types. Also suitable for unions. As unions aren't part of regular Fortran,
12166 this can only happen when accessing a register that uses a gdbarch-defined
12170 @node Fortran Defaults
12171 @subsubsection Fortran Defaults
12173 @cindex Fortran Defaults
12175 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12176 default uses case-insensitive matches for Fortran symbols. You can
12177 change that with the @samp{set case-insensitive} command, see
12178 @ref{Symbols}, for the details.
12180 @node Special Fortran Commands
12181 @subsubsection Special Fortran Commands
12183 @cindex Special Fortran commands
12185 @value{GDBN} has some commands to support Fortran-specific features,
12186 such as displaying common blocks.
12189 @cindex @code{COMMON} blocks, Fortran
12190 @kindex info common
12191 @item info common @r{[}@var{common-name}@r{]}
12192 This command prints the values contained in the Fortran @code{COMMON}
12193 block whose name is @var{common-name}. With no argument, the names of
12194 all @code{COMMON} blocks visible at the current program location are
12201 @cindex Pascal support in @value{GDBN}, limitations
12202 Debugging Pascal programs which use sets, subranges, file variables, or
12203 nested functions does not currently work. @value{GDBN} does not support
12204 entering expressions, printing values, or similar features using Pascal
12207 The Pascal-specific command @code{set print pascal_static-members}
12208 controls whether static members of Pascal objects are displayed.
12209 @xref{Print Settings, pascal_static-members}.
12212 @subsection Modula-2
12214 @cindex Modula-2, @value{GDBN} support
12216 The extensions made to @value{GDBN} to support Modula-2 only support
12217 output from the @sc{gnu} Modula-2 compiler (which is currently being
12218 developed). Other Modula-2 compilers are not currently supported, and
12219 attempting to debug executables produced by them is most likely
12220 to give an error as @value{GDBN} reads in the executable's symbol
12223 @cindex expressions in Modula-2
12225 * M2 Operators:: Built-in operators
12226 * Built-In Func/Proc:: Built-in functions and procedures
12227 * M2 Constants:: Modula-2 constants
12228 * M2 Types:: Modula-2 types
12229 * M2 Defaults:: Default settings for Modula-2
12230 * Deviations:: Deviations from standard Modula-2
12231 * M2 Checks:: Modula-2 type and range checks
12232 * M2 Scope:: The scope operators @code{::} and @code{.}
12233 * GDB/M2:: @value{GDBN} and Modula-2
12237 @subsubsection Operators
12238 @cindex Modula-2 operators
12240 Operators must be defined on values of specific types. For instance,
12241 @code{+} is defined on numbers, but not on structures. Operators are
12242 often defined on groups of types. For the purposes of Modula-2, the
12243 following definitions hold:
12248 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12252 @emph{Character types} consist of @code{CHAR} and its subranges.
12255 @emph{Floating-point types} consist of @code{REAL}.
12258 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12262 @emph{Scalar types} consist of all of the above.
12265 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12268 @emph{Boolean types} consist of @code{BOOLEAN}.
12272 The following operators are supported, and appear in order of
12273 increasing precedence:
12277 Function argument or array index separator.
12280 Assignment. The value of @var{var} @code{:=} @var{value} is
12284 Less than, greater than on integral, floating-point, or enumerated
12288 Less than or equal to, greater than or equal to
12289 on integral, floating-point and enumerated types, or set inclusion on
12290 set types. Same precedence as @code{<}.
12292 @item =@r{, }<>@r{, }#
12293 Equality and two ways of expressing inequality, valid on scalar types.
12294 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12295 available for inequality, since @code{#} conflicts with the script
12299 Set membership. Defined on set types and the types of their members.
12300 Same precedence as @code{<}.
12303 Boolean disjunction. Defined on boolean types.
12306 Boolean conjunction. Defined on boolean types.
12309 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12312 Addition and subtraction on integral and floating-point types, or union
12313 and difference on set types.
12316 Multiplication on integral and floating-point types, or set intersection
12320 Division on floating-point types, or symmetric set difference on set
12321 types. Same precedence as @code{*}.
12324 Integer division and remainder. Defined on integral types. Same
12325 precedence as @code{*}.
12328 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12331 Pointer dereferencing. Defined on pointer types.
12334 Boolean negation. Defined on boolean types. Same precedence as
12338 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12339 precedence as @code{^}.
12342 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12345 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12349 @value{GDBN} and Modula-2 scope operators.
12353 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12354 treats the use of the operator @code{IN}, or the use of operators
12355 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12356 @code{<=}, and @code{>=} on sets as an error.
12360 @node Built-In Func/Proc
12361 @subsubsection Built-in Functions and Procedures
12362 @cindex Modula-2 built-ins
12364 Modula-2 also makes available several built-in procedures and functions.
12365 In describing these, the following metavariables are used:
12370 represents an @code{ARRAY} variable.
12373 represents a @code{CHAR} constant or variable.
12376 represents a variable or constant of integral type.
12379 represents an identifier that belongs to a set. Generally used in the
12380 same function with the metavariable @var{s}. The type of @var{s} should
12381 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12384 represents a variable or constant of integral or floating-point type.
12387 represents a variable or constant of floating-point type.
12393 represents a variable.
12396 represents a variable or constant of one of many types. See the
12397 explanation of the function for details.
12400 All Modula-2 built-in procedures also return a result, described below.
12404 Returns the absolute value of @var{n}.
12407 If @var{c} is a lower case letter, it returns its upper case
12408 equivalent, otherwise it returns its argument.
12411 Returns the character whose ordinal value is @var{i}.
12414 Decrements the value in the variable @var{v} by one. Returns the new value.
12416 @item DEC(@var{v},@var{i})
12417 Decrements the value in the variable @var{v} by @var{i}. Returns the
12420 @item EXCL(@var{m},@var{s})
12421 Removes the element @var{m} from the set @var{s}. Returns the new
12424 @item FLOAT(@var{i})
12425 Returns the floating point equivalent of the integer @var{i}.
12427 @item HIGH(@var{a})
12428 Returns the index of the last member of @var{a}.
12431 Increments the value in the variable @var{v} by one. Returns the new value.
12433 @item INC(@var{v},@var{i})
12434 Increments the value in the variable @var{v} by @var{i}. Returns the
12437 @item INCL(@var{m},@var{s})
12438 Adds the element @var{m} to the set @var{s} if it is not already
12439 there. Returns the new set.
12442 Returns the maximum value of the type @var{t}.
12445 Returns the minimum value of the type @var{t}.
12448 Returns boolean TRUE if @var{i} is an odd number.
12451 Returns the ordinal value of its argument. For example, the ordinal
12452 value of a character is its @sc{ascii} value (on machines supporting the
12453 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12454 integral, character and enumerated types.
12456 @item SIZE(@var{x})
12457 Returns the size of its argument. @var{x} can be a variable or a type.
12459 @item TRUNC(@var{r})
12460 Returns the integral part of @var{r}.
12462 @item TSIZE(@var{x})
12463 Returns the size of its argument. @var{x} can be a variable or a type.
12465 @item VAL(@var{t},@var{i})
12466 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12470 @emph{Warning:} Sets and their operations are not yet supported, so
12471 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12475 @cindex Modula-2 constants
12477 @subsubsection Constants
12479 @value{GDBN} allows you to express the constants of Modula-2 in the following
12485 Integer constants are simply a sequence of digits. When used in an
12486 expression, a constant is interpreted to be type-compatible with the
12487 rest of the expression. Hexadecimal integers are specified by a
12488 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12491 Floating point constants appear as a sequence of digits, followed by a
12492 decimal point and another sequence of digits. An optional exponent can
12493 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12494 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12495 digits of the floating point constant must be valid decimal (base 10)
12499 Character constants consist of a single character enclosed by a pair of
12500 like quotes, either single (@code{'}) or double (@code{"}). They may
12501 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12502 followed by a @samp{C}.
12505 String constants consist of a sequence of characters enclosed by a
12506 pair of like quotes, either single (@code{'}) or double (@code{"}).
12507 Escape sequences in the style of C are also allowed. @xref{C
12508 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12512 Enumerated constants consist of an enumerated identifier.
12515 Boolean constants consist of the identifiers @code{TRUE} and
12519 Pointer constants consist of integral values only.
12522 Set constants are not yet supported.
12526 @subsubsection Modula-2 Types
12527 @cindex Modula-2 types
12529 Currently @value{GDBN} can print the following data types in Modula-2
12530 syntax: array types, record types, set types, pointer types, procedure
12531 types, enumerated types, subrange types and base types. You can also
12532 print the contents of variables declared using these type.
12533 This section gives a number of simple source code examples together with
12534 sample @value{GDBN} sessions.
12536 The first example contains the following section of code:
12545 and you can request @value{GDBN} to interrogate the type and value of
12546 @code{r} and @code{s}.
12549 (@value{GDBP}) print s
12551 (@value{GDBP}) ptype s
12553 (@value{GDBP}) print r
12555 (@value{GDBP}) ptype r
12560 Likewise if your source code declares @code{s} as:
12564 s: SET ['A'..'Z'] ;
12568 then you may query the type of @code{s} by:
12571 (@value{GDBP}) ptype s
12572 type = SET ['A'..'Z']
12576 Note that at present you cannot interactively manipulate set
12577 expressions using the debugger.
12579 The following example shows how you might declare an array in Modula-2
12580 and how you can interact with @value{GDBN} to print its type and contents:
12584 s: ARRAY [-10..10] OF CHAR ;
12588 (@value{GDBP}) ptype s
12589 ARRAY [-10..10] OF CHAR
12592 Note that the array handling is not yet complete and although the type
12593 is printed correctly, expression handling still assumes that all
12594 arrays have a lower bound of zero and not @code{-10} as in the example
12597 Here are some more type related Modula-2 examples:
12601 colour = (blue, red, yellow, green) ;
12602 t = [blue..yellow] ;
12610 The @value{GDBN} interaction shows how you can query the data type
12611 and value of a variable.
12614 (@value{GDBP}) print s
12616 (@value{GDBP}) ptype t
12617 type = [blue..yellow]
12621 In this example a Modula-2 array is declared and its contents
12622 displayed. Observe that the contents are written in the same way as
12623 their @code{C} counterparts.
12627 s: ARRAY [1..5] OF CARDINAL ;
12633 (@value{GDBP}) print s
12634 $1 = @{1, 0, 0, 0, 0@}
12635 (@value{GDBP}) ptype s
12636 type = ARRAY [1..5] OF CARDINAL
12639 The Modula-2 language interface to @value{GDBN} also understands
12640 pointer types as shown in this example:
12644 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12651 and you can request that @value{GDBN} describes the type of @code{s}.
12654 (@value{GDBP}) ptype s
12655 type = POINTER TO ARRAY [1..5] OF CARDINAL
12658 @value{GDBN} handles compound types as we can see in this example.
12659 Here we combine array types, record types, pointer types and subrange
12670 myarray = ARRAY myrange OF CARDINAL ;
12671 myrange = [-2..2] ;
12673 s: POINTER TO ARRAY myrange OF foo ;
12677 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12681 (@value{GDBP}) ptype s
12682 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12685 f3 : ARRAY [-2..2] OF CARDINAL;
12690 @subsubsection Modula-2 Defaults
12691 @cindex Modula-2 defaults
12693 If type and range checking are set automatically by @value{GDBN}, they
12694 both default to @code{on} whenever the working language changes to
12695 Modula-2. This happens regardless of whether you or @value{GDBN}
12696 selected the working language.
12698 If you allow @value{GDBN} to set the language automatically, then entering
12699 code compiled from a file whose name ends with @file{.mod} sets the
12700 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12701 Infer the Source Language}, for further details.
12704 @subsubsection Deviations from Standard Modula-2
12705 @cindex Modula-2, deviations from
12707 A few changes have been made to make Modula-2 programs easier to debug.
12708 This is done primarily via loosening its type strictness:
12712 Unlike in standard Modula-2, pointer constants can be formed by
12713 integers. This allows you to modify pointer variables during
12714 debugging. (In standard Modula-2, the actual address contained in a
12715 pointer variable is hidden from you; it can only be modified
12716 through direct assignment to another pointer variable or expression that
12717 returned a pointer.)
12720 C escape sequences can be used in strings and characters to represent
12721 non-printable characters. @value{GDBN} prints out strings with these
12722 escape sequences embedded. Single non-printable characters are
12723 printed using the @samp{CHR(@var{nnn})} format.
12726 The assignment operator (@code{:=}) returns the value of its right-hand
12730 All built-in procedures both modify @emph{and} return their argument.
12734 @subsubsection Modula-2 Type and Range Checks
12735 @cindex Modula-2 checks
12738 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12741 @c FIXME remove warning when type/range checks added
12743 @value{GDBN} considers two Modula-2 variables type equivalent if:
12747 They are of types that have been declared equivalent via a @code{TYPE
12748 @var{t1} = @var{t2}} statement
12751 They have been declared on the same line. (Note: This is true of the
12752 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12755 As long as type checking is enabled, any attempt to combine variables
12756 whose types are not equivalent is an error.
12758 Range checking is done on all mathematical operations, assignment, array
12759 index bounds, and all built-in functions and procedures.
12762 @subsubsection The Scope Operators @code{::} and @code{.}
12764 @cindex @code{.}, Modula-2 scope operator
12765 @cindex colon, doubled as scope operator
12767 @vindex colon-colon@r{, in Modula-2}
12768 @c Info cannot handle :: but TeX can.
12771 @vindex ::@r{, in Modula-2}
12774 There are a few subtle differences between the Modula-2 scope operator
12775 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12780 @var{module} . @var{id}
12781 @var{scope} :: @var{id}
12785 where @var{scope} is the name of a module or a procedure,
12786 @var{module} the name of a module, and @var{id} is any declared
12787 identifier within your program, except another module.
12789 Using the @code{::} operator makes @value{GDBN} search the scope
12790 specified by @var{scope} for the identifier @var{id}. If it is not
12791 found in the specified scope, then @value{GDBN} searches all scopes
12792 enclosing the one specified by @var{scope}.
12794 Using the @code{.} operator makes @value{GDBN} search the current scope for
12795 the identifier specified by @var{id} that was imported from the
12796 definition module specified by @var{module}. With this operator, it is
12797 an error if the identifier @var{id} was not imported from definition
12798 module @var{module}, or if @var{id} is not an identifier in
12802 @subsubsection @value{GDBN} and Modula-2
12804 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12805 Five subcommands of @code{set print} and @code{show print} apply
12806 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12807 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12808 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12809 analogue in Modula-2.
12811 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12812 with any language, is not useful with Modula-2. Its
12813 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12814 created in Modula-2 as they can in C or C@t{++}. However, because an
12815 address can be specified by an integral constant, the construct
12816 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12818 @cindex @code{#} in Modula-2
12819 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12820 interpreted as the beginning of a comment. Use @code{<>} instead.
12826 The extensions made to @value{GDBN} for Ada only support
12827 output from the @sc{gnu} Ada (GNAT) compiler.
12828 Other Ada compilers are not currently supported, and
12829 attempting to debug executables produced by them is most likely
12833 @cindex expressions in Ada
12835 * Ada Mode Intro:: General remarks on the Ada syntax
12836 and semantics supported by Ada mode
12838 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12839 * Additions to Ada:: Extensions of the Ada expression syntax.
12840 * Stopping Before Main Program:: Debugging the program during elaboration.
12841 * Ada Tasks:: Listing and setting breakpoints in tasks.
12842 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12843 * Ada Glitches:: Known peculiarities of Ada mode.
12846 @node Ada Mode Intro
12847 @subsubsection Introduction
12848 @cindex Ada mode, general
12850 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12851 syntax, with some extensions.
12852 The philosophy behind the design of this subset is
12856 That @value{GDBN} should provide basic literals and access to operations for
12857 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12858 leaving more sophisticated computations to subprograms written into the
12859 program (which therefore may be called from @value{GDBN}).
12862 That type safety and strict adherence to Ada language restrictions
12863 are not particularly important to the @value{GDBN} user.
12866 That brevity is important to the @value{GDBN} user.
12869 Thus, for brevity, the debugger acts as if all names declared in
12870 user-written packages are directly visible, even if they are not visible
12871 according to Ada rules, thus making it unnecessary to fully qualify most
12872 names with their packages, regardless of context. Where this causes
12873 ambiguity, @value{GDBN} asks the user's intent.
12875 The debugger will start in Ada mode if it detects an Ada main program.
12876 As for other languages, it will enter Ada mode when stopped in a program that
12877 was translated from an Ada source file.
12879 While in Ada mode, you may use `@t{--}' for comments. This is useful
12880 mostly for documenting command files. The standard @value{GDBN} comment
12881 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12882 middle (to allow based literals).
12884 The debugger supports limited overloading. Given a subprogram call in which
12885 the function symbol has multiple definitions, it will use the number of
12886 actual parameters and some information about their types to attempt to narrow
12887 the set of definitions. It also makes very limited use of context, preferring
12888 procedures to functions in the context of the @code{call} command, and
12889 functions to procedures elsewhere.
12891 @node Omissions from Ada
12892 @subsubsection Omissions from Ada
12893 @cindex Ada, omissions from
12895 Here are the notable omissions from the subset:
12899 Only a subset of the attributes are supported:
12903 @t{'First}, @t{'Last}, and @t{'Length}
12904 on array objects (not on types and subtypes).
12907 @t{'Min} and @t{'Max}.
12910 @t{'Pos} and @t{'Val}.
12916 @t{'Range} on array objects (not subtypes), but only as the right
12917 operand of the membership (@code{in}) operator.
12920 @t{'Access}, @t{'Unchecked_Access}, and
12921 @t{'Unrestricted_Access} (a GNAT extension).
12929 @code{Characters.Latin_1} are not available and
12930 concatenation is not implemented. Thus, escape characters in strings are
12931 not currently available.
12934 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12935 equality of representations. They will generally work correctly
12936 for strings and arrays whose elements have integer or enumeration types.
12937 They may not work correctly for arrays whose element
12938 types have user-defined equality, for arrays of real values
12939 (in particular, IEEE-conformant floating point, because of negative
12940 zeroes and NaNs), and for arrays whose elements contain unused bits with
12941 indeterminate values.
12944 The other component-by-component array operations (@code{and}, @code{or},
12945 @code{xor}, @code{not}, and relational tests other than equality)
12946 are not implemented.
12949 @cindex array aggregates (Ada)
12950 @cindex record aggregates (Ada)
12951 @cindex aggregates (Ada)
12952 There is limited support for array and record aggregates. They are
12953 permitted only on the right sides of assignments, as in these examples:
12956 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12957 (@value{GDBP}) set An_Array := (1, others => 0)
12958 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12959 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12960 (@value{GDBP}) set A_Record := (1, "Peter", True);
12961 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12965 discriminant's value by assigning an aggregate has an
12966 undefined effect if that discriminant is used within the record.
12967 However, you can first modify discriminants by directly assigning to
12968 them (which normally would not be allowed in Ada), and then performing an
12969 aggregate assignment. For example, given a variable @code{A_Rec}
12970 declared to have a type such as:
12973 type Rec (Len : Small_Integer := 0) is record
12975 Vals : IntArray (1 .. Len);
12979 you can assign a value with a different size of @code{Vals} with two
12983 (@value{GDBP}) set A_Rec.Len := 4
12984 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12987 As this example also illustrates, @value{GDBN} is very loose about the usual
12988 rules concerning aggregates. You may leave out some of the
12989 components of an array or record aggregate (such as the @code{Len}
12990 component in the assignment to @code{A_Rec} above); they will retain their
12991 original values upon assignment. You may freely use dynamic values as
12992 indices in component associations. You may even use overlapping or
12993 redundant component associations, although which component values are
12994 assigned in such cases is not defined.
12997 Calls to dispatching subprograms are not implemented.
13000 The overloading algorithm is much more limited (i.e., less selective)
13001 than that of real Ada. It makes only limited use of the context in
13002 which a subexpression appears to resolve its meaning, and it is much
13003 looser in its rules for allowing type matches. As a result, some
13004 function calls will be ambiguous, and the user will be asked to choose
13005 the proper resolution.
13008 The @code{new} operator is not implemented.
13011 Entry calls are not implemented.
13014 Aside from printing, arithmetic operations on the native VAX floating-point
13015 formats are not supported.
13018 It is not possible to slice a packed array.
13021 The names @code{True} and @code{False}, when not part of a qualified name,
13022 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13024 Should your program
13025 redefine these names in a package or procedure (at best a dubious practice),
13026 you will have to use fully qualified names to access their new definitions.
13029 @node Additions to Ada
13030 @subsubsection Additions to Ada
13031 @cindex Ada, deviations from
13033 As it does for other languages, @value{GDBN} makes certain generic
13034 extensions to Ada (@pxref{Expressions}):
13038 If the expression @var{E} is a variable residing in memory (typically
13039 a local variable or array element) and @var{N} is a positive integer,
13040 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13041 @var{N}-1 adjacent variables following it in memory as an array. In
13042 Ada, this operator is generally not necessary, since its prime use is
13043 in displaying parts of an array, and slicing will usually do this in
13044 Ada. However, there are occasional uses when debugging programs in
13045 which certain debugging information has been optimized away.
13048 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13049 appears in function or file @var{B}.'' When @var{B} is a file name,
13050 you must typically surround it in single quotes.
13053 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13054 @var{type} that appears at address @var{addr}.''
13057 A name starting with @samp{$} is a convenience variable
13058 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13061 In addition, @value{GDBN} provides a few other shortcuts and outright
13062 additions specific to Ada:
13066 The assignment statement is allowed as an expression, returning
13067 its right-hand operand as its value. Thus, you may enter
13070 (@value{GDBP}) set x := y + 3
13071 (@value{GDBP}) print A(tmp := y + 1)
13075 The semicolon is allowed as an ``operator,'' returning as its value
13076 the value of its right-hand operand.
13077 This allows, for example,
13078 complex conditional breaks:
13081 (@value{GDBP}) break f
13082 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13086 Rather than use catenation and symbolic character names to introduce special
13087 characters into strings, one may instead use a special bracket notation,
13088 which is also used to print strings. A sequence of characters of the form
13089 @samp{["@var{XX}"]} within a string or character literal denotes the
13090 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13091 sequence of characters @samp{["""]} also denotes a single quotation mark
13092 in strings. For example,
13094 "One line.["0a"]Next line.["0a"]"
13097 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13101 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13102 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13106 (@value{GDBP}) print 'max(x, y)
13110 When printing arrays, @value{GDBN} uses positional notation when the
13111 array has a lower bound of 1, and uses a modified named notation otherwise.
13112 For example, a one-dimensional array of three integers with a lower bound
13113 of 3 might print as
13120 That is, in contrast to valid Ada, only the first component has a @code{=>}
13124 You may abbreviate attributes in expressions with any unique,
13125 multi-character subsequence of
13126 their names (an exact match gets preference).
13127 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13128 in place of @t{a'length}.
13131 @cindex quoting Ada internal identifiers
13132 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13133 to lower case. The GNAT compiler uses upper-case characters for
13134 some of its internal identifiers, which are normally of no interest to users.
13135 For the rare occasions when you actually have to look at them,
13136 enclose them in angle brackets to avoid the lower-case mapping.
13139 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13143 Printing an object of class-wide type or dereferencing an
13144 access-to-class-wide value will display all the components of the object's
13145 specific type (as indicated by its run-time tag). Likewise, component
13146 selection on such a value will operate on the specific type of the
13151 @node Stopping Before Main Program
13152 @subsubsection Stopping at the Very Beginning
13154 @cindex breakpointing Ada elaboration code
13155 It is sometimes necessary to debug the program during elaboration, and
13156 before reaching the main procedure.
13157 As defined in the Ada Reference
13158 Manual, the elaboration code is invoked from a procedure called
13159 @code{adainit}. To run your program up to the beginning of
13160 elaboration, simply use the following two commands:
13161 @code{tbreak adainit} and @code{run}.
13164 @subsubsection Extensions for Ada Tasks
13165 @cindex Ada, tasking
13167 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13168 @value{GDBN} provides the following task-related commands:
13173 This command shows a list of current Ada tasks, as in the following example:
13180 (@value{GDBP}) info tasks
13181 ID TID P-ID Pri State Name
13182 1 8088000 0 15 Child Activation Wait main_task
13183 2 80a4000 1 15 Accept Statement b
13184 3 809a800 1 15 Child Activation Wait a
13185 * 4 80ae800 3 15 Runnable c
13190 In this listing, the asterisk before the last task indicates it to be the
13191 task currently being inspected.
13195 Represents @value{GDBN}'s internal task number.
13201 The parent's task ID (@value{GDBN}'s internal task number).
13204 The base priority of the task.
13207 Current state of the task.
13211 The task has been created but has not been activated. It cannot be
13215 The task is not blocked for any reason known to Ada. (It may be waiting
13216 for a mutex, though.) It is conceptually "executing" in normal mode.
13219 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13220 that were waiting on terminate alternatives have been awakened and have
13221 terminated themselves.
13223 @item Child Activation Wait
13224 The task is waiting for created tasks to complete activation.
13226 @item Accept Statement
13227 The task is waiting on an accept or selective wait statement.
13229 @item Waiting on entry call
13230 The task is waiting on an entry call.
13232 @item Async Select Wait
13233 The task is waiting to start the abortable part of an asynchronous
13237 The task is waiting on a select statement with only a delay
13240 @item Child Termination Wait
13241 The task is sleeping having completed a master within itself, and is
13242 waiting for the tasks dependent on that master to become terminated or
13243 waiting on a terminate Phase.
13245 @item Wait Child in Term Alt
13246 The task is sleeping waiting for tasks on terminate alternatives to
13247 finish terminating.
13249 @item Accepting RV with @var{taskno}
13250 The task is accepting a rendez-vous with the task @var{taskno}.
13254 Name of the task in the program.
13258 @kindex info task @var{taskno}
13259 @item info task @var{taskno}
13260 This command shows detailled informations on the specified task, as in
13261 the following example:
13266 (@value{GDBP}) info tasks
13267 ID TID P-ID Pri State Name
13268 1 8077880 0 15 Child Activation Wait main_task
13269 * 2 807c468 1 15 Runnable task_1
13270 (@value{GDBP}) info task 2
13271 Ada Task: 0x807c468
13274 Parent: 1 (main_task)
13280 @kindex task@r{ (Ada)}
13281 @cindex current Ada task ID
13282 This command prints the ID of the current task.
13288 (@value{GDBP}) info tasks
13289 ID TID P-ID Pri State Name
13290 1 8077870 0 15 Child Activation Wait main_task
13291 * 2 807c458 1 15 Runnable t
13292 (@value{GDBP}) task
13293 [Current task is 2]
13296 @item task @var{taskno}
13297 @cindex Ada task switching
13298 This command is like the @code{thread @var{threadno}}
13299 command (@pxref{Threads}). It switches the context of debugging
13300 from the current task to the given task.
13306 (@value{GDBP}) info tasks
13307 ID TID P-ID Pri State Name
13308 1 8077870 0 15 Child Activation Wait main_task
13309 * 2 807c458 1 15 Runnable t
13310 (@value{GDBP}) task 1
13311 [Switching to task 1]
13312 #0 0x8067726 in pthread_cond_wait ()
13314 #0 0x8067726 in pthread_cond_wait ()
13315 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13316 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13317 #3 0x806153e in system.tasking.stages.activate_tasks ()
13318 #4 0x804aacc in un () at un.adb:5
13321 @item break @var{linespec} task @var{taskno}
13322 @itemx break @var{linespec} task @var{taskno} if @dots{}
13323 @cindex breakpoints and tasks, in Ada
13324 @cindex task breakpoints, in Ada
13325 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13326 These commands are like the @code{break @dots{} thread @dots{}}
13327 command (@pxref{Thread Stops}).
13328 @var{linespec} specifies source lines, as described
13329 in @ref{Specify Location}.
13331 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13332 to specify that you only want @value{GDBN} to stop the program when a
13333 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13334 numeric task identifiers assigned by @value{GDBN}, shown in the first
13335 column of the @samp{info tasks} display.
13337 If you do not specify @samp{task @var{taskno}} when you set a
13338 breakpoint, the breakpoint applies to @emph{all} tasks of your
13341 You can use the @code{task} qualifier on conditional breakpoints as
13342 well; in this case, place @samp{task @var{taskno}} before the
13343 breakpoint condition (before the @code{if}).
13351 (@value{GDBP}) info tasks
13352 ID TID P-ID Pri State Name
13353 1 140022020 0 15 Child Activation Wait main_task
13354 2 140045060 1 15 Accept/Select Wait t2
13355 3 140044840 1 15 Runnable t1
13356 * 4 140056040 1 15 Runnable t3
13357 (@value{GDBP}) b 15 task 2
13358 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13359 (@value{GDBP}) cont
13364 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13366 (@value{GDBP}) info tasks
13367 ID TID P-ID Pri State Name
13368 1 140022020 0 15 Child Activation Wait main_task
13369 * 2 140045060 1 15 Runnable t2
13370 3 140044840 1 15 Runnable t1
13371 4 140056040 1 15 Delay Sleep t3
13375 @node Ada Tasks and Core Files
13376 @subsubsection Tasking Support when Debugging Core Files
13377 @cindex Ada tasking and core file debugging
13379 When inspecting a core file, as opposed to debugging a live program,
13380 tasking support may be limited or even unavailable, depending on
13381 the platform being used.
13382 For instance, on x86-linux, the list of tasks is available, but task
13383 switching is not supported. On Tru64, however, task switching will work
13386 On certain platforms, including Tru64, the debugger needs to perform some
13387 memory writes in order to provide Ada tasking support. When inspecting
13388 a core file, this means that the core file must be opened with read-write
13389 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13390 Under these circumstances, you should make a backup copy of the core
13391 file before inspecting it with @value{GDBN}.
13394 @subsubsection Known Peculiarities of Ada Mode
13395 @cindex Ada, problems
13397 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13398 we know of several problems with and limitations of Ada mode in
13400 some of which will be fixed with planned future releases of the debugger
13401 and the GNU Ada compiler.
13405 Currently, the debugger
13406 has insufficient information to determine whether certain pointers represent
13407 pointers to objects or the objects themselves.
13408 Thus, the user may have to tack an extra @code{.all} after an expression
13409 to get it printed properly.
13412 Static constants that the compiler chooses not to materialize as objects in
13413 storage are invisible to the debugger.
13416 Named parameter associations in function argument lists are ignored (the
13417 argument lists are treated as positional).
13420 Many useful library packages are currently invisible to the debugger.
13423 Fixed-point arithmetic, conversions, input, and output is carried out using
13424 floating-point arithmetic, and may give results that only approximate those on
13428 The GNAT compiler never generates the prefix @code{Standard} for any of
13429 the standard symbols defined by the Ada language. @value{GDBN} knows about
13430 this: it will strip the prefix from names when you use it, and will never
13431 look for a name you have so qualified among local symbols, nor match against
13432 symbols in other packages or subprograms. If you have
13433 defined entities anywhere in your program other than parameters and
13434 local variables whose simple names match names in @code{Standard},
13435 GNAT's lack of qualification here can cause confusion. When this happens,
13436 you can usually resolve the confusion
13437 by qualifying the problematic names with package
13438 @code{Standard} explicitly.
13441 Older versions of the compiler sometimes generate erroneous debugging
13442 information, resulting in the debugger incorrectly printing the value
13443 of affected entities. In some cases, the debugger is able to work
13444 around an issue automatically. In other cases, the debugger is able
13445 to work around the issue, but the work-around has to be specifically
13448 @kindex set ada trust-PAD-over-XVS
13449 @kindex show ada trust-PAD-over-XVS
13452 @item set ada trust-PAD-over-XVS on
13453 Configure GDB to strictly follow the GNAT encoding when computing the
13454 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13455 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13456 a complete description of the encoding used by the GNAT compiler).
13457 This is the default.
13459 @item set ada trust-PAD-over-XVS off
13460 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13461 sometimes prints the wrong value for certain entities, changing @code{ada
13462 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13463 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13464 @code{off}, but this incurs a slight performance penalty, so it is
13465 recommended to leave this setting to @code{on} unless necessary.
13469 @node Unsupported Languages
13470 @section Unsupported Languages
13472 @cindex unsupported languages
13473 @cindex minimal language
13474 In addition to the other fully-supported programming languages,
13475 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13476 It does not represent a real programming language, but provides a set
13477 of capabilities close to what the C or assembly languages provide.
13478 This should allow most simple operations to be performed while debugging
13479 an application that uses a language currently not supported by @value{GDBN}.
13481 If the language is set to @code{auto}, @value{GDBN} will automatically
13482 select this language if the current frame corresponds to an unsupported
13486 @chapter Examining the Symbol Table
13488 The commands described in this chapter allow you to inquire about the
13489 symbols (names of variables, functions and types) defined in your
13490 program. This information is inherent in the text of your program and
13491 does not change as your program executes. @value{GDBN} finds it in your
13492 program's symbol table, in the file indicated when you started @value{GDBN}
13493 (@pxref{File Options, ,Choosing Files}), or by one of the
13494 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13496 @cindex symbol names
13497 @cindex names of symbols
13498 @cindex quoting names
13499 Occasionally, you may need to refer to symbols that contain unusual
13500 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13501 most frequent case is in referring to static variables in other
13502 source files (@pxref{Variables,,Program Variables}). File names
13503 are recorded in object files as debugging symbols, but @value{GDBN} would
13504 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13505 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13506 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13513 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13516 @cindex case-insensitive symbol names
13517 @cindex case sensitivity in symbol names
13518 @kindex set case-sensitive
13519 @item set case-sensitive on
13520 @itemx set case-sensitive off
13521 @itemx set case-sensitive auto
13522 Normally, when @value{GDBN} looks up symbols, it matches their names
13523 with case sensitivity determined by the current source language.
13524 Occasionally, you may wish to control that. The command @code{set
13525 case-sensitive} lets you do that by specifying @code{on} for
13526 case-sensitive matches or @code{off} for case-insensitive ones. If
13527 you specify @code{auto}, case sensitivity is reset to the default
13528 suitable for the source language. The default is case-sensitive
13529 matches for all languages except for Fortran, for which the default is
13530 case-insensitive matches.
13532 @kindex show case-sensitive
13533 @item show case-sensitive
13534 This command shows the current setting of case sensitivity for symbols
13537 @kindex info address
13538 @cindex address of a symbol
13539 @item info address @var{symbol}
13540 Describe where the data for @var{symbol} is stored. For a register
13541 variable, this says which register it is kept in. For a non-register
13542 local variable, this prints the stack-frame offset at which the variable
13545 Note the contrast with @samp{print &@var{symbol}}, which does not work
13546 at all for a register variable, and for a stack local variable prints
13547 the exact address of the current instantiation of the variable.
13549 @kindex info symbol
13550 @cindex symbol from address
13551 @cindex closest symbol and offset for an address
13552 @item info symbol @var{addr}
13553 Print the name of a symbol which is stored at the address @var{addr}.
13554 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13555 nearest symbol and an offset from it:
13558 (@value{GDBP}) info symbol 0x54320
13559 _initialize_vx + 396 in section .text
13563 This is the opposite of the @code{info address} command. You can use
13564 it to find out the name of a variable or a function given its address.
13566 For dynamically linked executables, the name of executable or shared
13567 library containing the symbol is also printed:
13570 (@value{GDBP}) info symbol 0x400225
13571 _start + 5 in section .text of /tmp/a.out
13572 (@value{GDBP}) info symbol 0x2aaaac2811cf
13573 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13577 @item whatis [@var{arg}]
13578 Print the data type of @var{arg}, which can be either an expression or
13579 a data type. With no argument, print the data type of @code{$}, the
13580 last value in the value history. If @var{arg} is an expression, it is
13581 not actually evaluated, and any side-effecting operations (such as
13582 assignments or function calls) inside it do not take place. If
13583 @var{arg} is a type name, it may be the name of a type or typedef, or
13584 for C code it may have the form @samp{class @var{class-name}},
13585 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13586 @samp{enum @var{enum-tag}}.
13587 @xref{Expressions, ,Expressions}.
13590 @item ptype [@var{arg}]
13591 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13592 detailed description of the type, instead of just the name of the type.
13593 @xref{Expressions, ,Expressions}.
13595 For example, for this variable declaration:
13598 struct complex @{double real; double imag;@} v;
13602 the two commands give this output:
13606 (@value{GDBP}) whatis v
13607 type = struct complex
13608 (@value{GDBP}) ptype v
13609 type = struct complex @{
13617 As with @code{whatis}, using @code{ptype} without an argument refers to
13618 the type of @code{$}, the last value in the value history.
13620 @cindex incomplete type
13621 Sometimes, programs use opaque data types or incomplete specifications
13622 of complex data structure. If the debug information included in the
13623 program does not allow @value{GDBN} to display a full declaration of
13624 the data type, it will say @samp{<incomplete type>}. For example,
13625 given these declarations:
13629 struct foo *fooptr;
13633 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13636 (@value{GDBP}) ptype foo
13637 $1 = <incomplete type>
13641 ``Incomplete type'' is C terminology for data types that are not
13642 completely specified.
13645 @item info types @var{regexp}
13647 Print a brief description of all types whose names match the regular
13648 expression @var{regexp} (or all types in your program, if you supply
13649 no argument). Each complete typename is matched as though it were a
13650 complete line; thus, @samp{i type value} gives information on all
13651 types in your program whose names include the string @code{value}, but
13652 @samp{i type ^value$} gives information only on types whose complete
13653 name is @code{value}.
13655 This command differs from @code{ptype} in two ways: first, like
13656 @code{whatis}, it does not print a detailed description; second, it
13657 lists all source files where a type is defined.
13660 @cindex local variables
13661 @item info scope @var{location}
13662 List all the variables local to a particular scope. This command
13663 accepts a @var{location} argument---a function name, a source line, or
13664 an address preceded by a @samp{*}, and prints all the variables local
13665 to the scope defined by that location. (@xref{Specify Location}, for
13666 details about supported forms of @var{location}.) For example:
13669 (@value{GDBP}) @b{info scope command_line_handler}
13670 Scope for command_line_handler:
13671 Symbol rl is an argument at stack/frame offset 8, length 4.
13672 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13673 Symbol linelength is in static storage at address 0x150a1c, length 4.
13674 Symbol p is a local variable in register $esi, length 4.
13675 Symbol p1 is a local variable in register $ebx, length 4.
13676 Symbol nline is a local variable in register $edx, length 4.
13677 Symbol repeat is a local variable at frame offset -8, length 4.
13681 This command is especially useful for determining what data to collect
13682 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13685 @kindex info source
13687 Show information about the current source file---that is, the source file for
13688 the function containing the current point of execution:
13691 the name of the source file, and the directory containing it,
13693 the directory it was compiled in,
13695 its length, in lines,
13697 which programming language it is written in,
13699 whether the executable includes debugging information for that file, and
13700 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13702 whether the debugging information includes information about
13703 preprocessor macros.
13707 @kindex info sources
13709 Print the names of all source files in your program for which there is
13710 debugging information, organized into two lists: files whose symbols
13711 have already been read, and files whose symbols will be read when needed.
13713 @kindex info functions
13714 @item info functions
13715 Print the names and data types of all defined functions.
13717 @item info functions @var{regexp}
13718 Print the names and data types of all defined functions
13719 whose names contain a match for regular expression @var{regexp}.
13720 Thus, @samp{info fun step} finds all functions whose names
13721 include @code{step}; @samp{info fun ^step} finds those whose names
13722 start with @code{step}. If a function name contains characters
13723 that conflict with the regular expression language (e.g.@:
13724 @samp{operator*()}), they may be quoted with a backslash.
13726 @kindex info variables
13727 @item info variables
13728 Print the names and data types of all variables that are defined
13729 outside of functions (i.e.@: excluding local variables).
13731 @item info variables @var{regexp}
13732 Print the names and data types of all variables (except for local
13733 variables) whose names contain a match for regular expression
13736 @kindex info classes
13737 @cindex Objective-C, classes and selectors
13739 @itemx info classes @var{regexp}
13740 Display all Objective-C classes in your program, or
13741 (with the @var{regexp} argument) all those matching a particular regular
13744 @kindex info selectors
13745 @item info selectors
13746 @itemx info selectors @var{regexp}
13747 Display all Objective-C selectors in your program, or
13748 (with the @var{regexp} argument) all those matching a particular regular
13752 This was never implemented.
13753 @kindex info methods
13755 @itemx info methods @var{regexp}
13756 The @code{info methods} command permits the user to examine all defined
13757 methods within C@t{++} program, or (with the @var{regexp} argument) a
13758 specific set of methods found in the various C@t{++} classes. Many
13759 C@t{++} classes provide a large number of methods. Thus, the output
13760 from the @code{ptype} command can be overwhelming and hard to use. The
13761 @code{info-methods} command filters the methods, printing only those
13762 which match the regular-expression @var{regexp}.
13765 @cindex reloading symbols
13766 Some systems allow individual object files that make up your program to
13767 be replaced without stopping and restarting your program. For example,
13768 in VxWorks you can simply recompile a defective object file and keep on
13769 running. If you are running on one of these systems, you can allow
13770 @value{GDBN} to reload the symbols for automatically relinked modules:
13773 @kindex set symbol-reloading
13774 @item set symbol-reloading on
13775 Replace symbol definitions for the corresponding source file when an
13776 object file with a particular name is seen again.
13778 @item set symbol-reloading off
13779 Do not replace symbol definitions when encountering object files of the
13780 same name more than once. This is the default state; if you are not
13781 running on a system that permits automatic relinking of modules, you
13782 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13783 may discard symbols when linking large programs, that may contain
13784 several modules (from different directories or libraries) with the same
13787 @kindex show symbol-reloading
13788 @item show symbol-reloading
13789 Show the current @code{on} or @code{off} setting.
13792 @cindex opaque data types
13793 @kindex set opaque-type-resolution
13794 @item set opaque-type-resolution on
13795 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13796 declared as a pointer to a @code{struct}, @code{class}, or
13797 @code{union}---for example, @code{struct MyType *}---that is used in one
13798 source file although the full declaration of @code{struct MyType} is in
13799 another source file. The default is on.
13801 A change in the setting of this subcommand will not take effect until
13802 the next time symbols for a file are loaded.
13804 @item set opaque-type-resolution off
13805 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13806 is printed as follows:
13808 @{<no data fields>@}
13811 @kindex show opaque-type-resolution
13812 @item show opaque-type-resolution
13813 Show whether opaque types are resolved or not.
13815 @kindex maint print symbols
13816 @cindex symbol dump
13817 @kindex maint print psymbols
13818 @cindex partial symbol dump
13819 @item maint print symbols @var{filename}
13820 @itemx maint print psymbols @var{filename}
13821 @itemx maint print msymbols @var{filename}
13822 Write a dump of debugging symbol data into the file @var{filename}.
13823 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13824 symbols with debugging data are included. If you use @samp{maint print
13825 symbols}, @value{GDBN} includes all the symbols for which it has already
13826 collected full details: that is, @var{filename} reflects symbols for
13827 only those files whose symbols @value{GDBN} has read. You can use the
13828 command @code{info sources} to find out which files these are. If you
13829 use @samp{maint print psymbols} instead, the dump shows information about
13830 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13831 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13832 @samp{maint print msymbols} dumps just the minimal symbol information
13833 required for each object file from which @value{GDBN} has read some symbols.
13834 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13835 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13837 @kindex maint info symtabs
13838 @kindex maint info psymtabs
13839 @cindex listing @value{GDBN}'s internal symbol tables
13840 @cindex symbol tables, listing @value{GDBN}'s internal
13841 @cindex full symbol tables, listing @value{GDBN}'s internal
13842 @cindex partial symbol tables, listing @value{GDBN}'s internal
13843 @item maint info symtabs @r{[} @var{regexp} @r{]}
13844 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13846 List the @code{struct symtab} or @code{struct partial_symtab}
13847 structures whose names match @var{regexp}. If @var{regexp} is not
13848 given, list them all. The output includes expressions which you can
13849 copy into a @value{GDBN} debugging this one to examine a particular
13850 structure in more detail. For example:
13853 (@value{GDBP}) maint info psymtabs dwarf2read
13854 @{ objfile /home/gnu/build/gdb/gdb
13855 ((struct objfile *) 0x82e69d0)
13856 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13857 ((struct partial_symtab *) 0x8474b10)
13860 text addresses 0x814d3c8 -- 0x8158074
13861 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13862 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13863 dependencies (none)
13866 (@value{GDBP}) maint info symtabs
13870 We see that there is one partial symbol table whose filename contains
13871 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13872 and we see that @value{GDBN} has not read in any symtabs yet at all.
13873 If we set a breakpoint on a function, that will cause @value{GDBN} to
13874 read the symtab for the compilation unit containing that function:
13877 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13878 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13880 (@value{GDBP}) maint info symtabs
13881 @{ objfile /home/gnu/build/gdb/gdb
13882 ((struct objfile *) 0x82e69d0)
13883 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13884 ((struct symtab *) 0x86c1f38)
13887 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13888 linetable ((struct linetable *) 0x8370fa0)
13889 debugformat DWARF 2
13898 @chapter Altering Execution
13900 Once you think you have found an error in your program, you might want to
13901 find out for certain whether correcting the apparent error would lead to
13902 correct results in the rest of the run. You can find the answer by
13903 experiment, using the @value{GDBN} features for altering execution of the
13906 For example, you can store new values into variables or memory
13907 locations, give your program a signal, restart it at a different
13908 address, or even return prematurely from a function.
13911 * Assignment:: Assignment to variables
13912 * Jumping:: Continuing at a different address
13913 * Signaling:: Giving your program a signal
13914 * Returning:: Returning from a function
13915 * Calling:: Calling your program's functions
13916 * Patching:: Patching your program
13920 @section Assignment to Variables
13923 @cindex setting variables
13924 To alter the value of a variable, evaluate an assignment expression.
13925 @xref{Expressions, ,Expressions}. For example,
13932 stores the value 4 into the variable @code{x}, and then prints the
13933 value of the assignment expression (which is 4).
13934 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13935 information on operators in supported languages.
13937 @kindex set variable
13938 @cindex variables, setting
13939 If you are not interested in seeing the value of the assignment, use the
13940 @code{set} command instead of the @code{print} command. @code{set} is
13941 really the same as @code{print} except that the expression's value is
13942 not printed and is not put in the value history (@pxref{Value History,
13943 ,Value History}). The expression is evaluated only for its effects.
13945 If the beginning of the argument string of the @code{set} command
13946 appears identical to a @code{set} subcommand, use the @code{set
13947 variable} command instead of just @code{set}. This command is identical
13948 to @code{set} except for its lack of subcommands. For example, if your
13949 program has a variable @code{width}, you get an error if you try to set
13950 a new value with just @samp{set width=13}, because @value{GDBN} has the
13951 command @code{set width}:
13954 (@value{GDBP}) whatis width
13956 (@value{GDBP}) p width
13958 (@value{GDBP}) set width=47
13959 Invalid syntax in expression.
13963 The invalid expression, of course, is @samp{=47}. In
13964 order to actually set the program's variable @code{width}, use
13967 (@value{GDBP}) set var width=47
13970 Because the @code{set} command has many subcommands that can conflict
13971 with the names of program variables, it is a good idea to use the
13972 @code{set variable} command instead of just @code{set}. For example, if
13973 your program has a variable @code{g}, you run into problems if you try
13974 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13975 the command @code{set gnutarget}, abbreviated @code{set g}:
13979 (@value{GDBP}) whatis g
13983 (@value{GDBP}) set g=4
13987 The program being debugged has been started already.
13988 Start it from the beginning? (y or n) y
13989 Starting program: /home/smith/cc_progs/a.out
13990 "/home/smith/cc_progs/a.out": can't open to read symbols:
13991 Invalid bfd target.
13992 (@value{GDBP}) show g
13993 The current BFD target is "=4".
13998 The program variable @code{g} did not change, and you silently set the
13999 @code{gnutarget} to an invalid value. In order to set the variable
14003 (@value{GDBP}) set var g=4
14006 @value{GDBN} allows more implicit conversions in assignments than C; you can
14007 freely store an integer value into a pointer variable or vice versa,
14008 and you can convert any structure to any other structure that is the
14009 same length or shorter.
14010 @comment FIXME: how do structs align/pad in these conversions?
14011 @comment /doc@cygnus.com 18dec1990
14013 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14014 construct to generate a value of specified type at a specified address
14015 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14016 to memory location @code{0x83040} as an integer (which implies a certain size
14017 and representation in memory), and
14020 set @{int@}0x83040 = 4
14024 stores the value 4 into that memory location.
14027 @section Continuing at a Different Address
14029 Ordinarily, when you continue your program, you do so at the place where
14030 it stopped, with the @code{continue} command. You can instead continue at
14031 an address of your own choosing, with the following commands:
14035 @item jump @var{linespec}
14036 @itemx jump @var{location}
14037 Resume execution at line @var{linespec} or at address given by
14038 @var{location}. Execution stops again immediately if there is a
14039 breakpoint there. @xref{Specify Location}, for a description of the
14040 different forms of @var{linespec} and @var{location}. It is common
14041 practice to use the @code{tbreak} command in conjunction with
14042 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14044 The @code{jump} command does not change the current stack frame, or
14045 the stack pointer, or the contents of any memory location or any
14046 register other than the program counter. If line @var{linespec} is in
14047 a different function from the one currently executing, the results may
14048 be bizarre if the two functions expect different patterns of arguments or
14049 of local variables. For this reason, the @code{jump} command requests
14050 confirmation if the specified line is not in the function currently
14051 executing. However, even bizarre results are predictable if you are
14052 well acquainted with the machine-language code of your program.
14055 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14056 On many systems, you can get much the same effect as the @code{jump}
14057 command by storing a new value into the register @code{$pc}. The
14058 difference is that this does not start your program running; it only
14059 changes the address of where it @emph{will} run when you continue. For
14067 makes the next @code{continue} command or stepping command execute at
14068 address @code{0x485}, rather than at the address where your program stopped.
14069 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14071 The most common occasion to use the @code{jump} command is to back
14072 up---perhaps with more breakpoints set---over a portion of a program
14073 that has already executed, in order to examine its execution in more
14078 @section Giving your Program a Signal
14079 @cindex deliver a signal to a program
14083 @item signal @var{signal}
14084 Resume execution where your program stopped, but immediately give it the
14085 signal @var{signal}. @var{signal} can be the name or the number of a
14086 signal. For example, on many systems @code{signal 2} and @code{signal
14087 SIGINT} are both ways of sending an interrupt signal.
14089 Alternatively, if @var{signal} is zero, continue execution without
14090 giving a signal. This is useful when your program stopped on account of
14091 a signal and would ordinary see the signal when resumed with the
14092 @code{continue} command; @samp{signal 0} causes it to resume without a
14095 @code{signal} does not repeat when you press @key{RET} a second time
14096 after executing the command.
14100 Invoking the @code{signal} command is not the same as invoking the
14101 @code{kill} utility from the shell. Sending a signal with @code{kill}
14102 causes @value{GDBN} to decide what to do with the signal depending on
14103 the signal handling tables (@pxref{Signals}). The @code{signal} command
14104 passes the signal directly to your program.
14108 @section Returning from a Function
14111 @cindex returning from a function
14114 @itemx return @var{expression}
14115 You can cancel execution of a function call with the @code{return}
14116 command. If you give an
14117 @var{expression} argument, its value is used as the function's return
14121 When you use @code{return}, @value{GDBN} discards the selected stack frame
14122 (and all frames within it). You can think of this as making the
14123 discarded frame return prematurely. If you wish to specify a value to
14124 be returned, give that value as the argument to @code{return}.
14126 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14127 Frame}), and any other frames inside of it, leaving its caller as the
14128 innermost remaining frame. That frame becomes selected. The
14129 specified value is stored in the registers used for returning values
14132 The @code{return} command does not resume execution; it leaves the
14133 program stopped in the state that would exist if the function had just
14134 returned. In contrast, the @code{finish} command (@pxref{Continuing
14135 and Stepping, ,Continuing and Stepping}) resumes execution until the
14136 selected stack frame returns naturally.
14138 @value{GDBN} needs to know how the @var{expression} argument should be set for
14139 the inferior. The concrete registers assignment depends on the OS ABI and the
14140 type being returned by the selected stack frame. For example it is common for
14141 OS ABI to return floating point values in FPU registers while integer values in
14142 CPU registers. Still some ABIs return even floating point values in CPU
14143 registers. Larger integer widths (such as @code{long long int}) also have
14144 specific placement rules. @value{GDBN} already knows the OS ABI from its
14145 current target so it needs to find out also the type being returned to make the
14146 assignment into the right register(s).
14148 Normally, the selected stack frame has debug info. @value{GDBN} will always
14149 use the debug info instead of the implicit type of @var{expression} when the
14150 debug info is available. For example, if you type @kbd{return -1}, and the
14151 function in the current stack frame is declared to return a @code{long long
14152 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14153 into a @code{long long int}:
14156 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14158 (@value{GDBP}) return -1
14159 Make func return now? (y or n) y
14160 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14161 43 printf ("result=%lld\n", func ());
14165 However, if the selected stack frame does not have a debug info, e.g., if the
14166 function was compiled without debug info, @value{GDBN} has to find out the type
14167 to return from user. Specifying a different type by mistake may set the value
14168 in different inferior registers than the caller code expects. For example,
14169 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14170 of a @code{long long int} result for a debug info less function (on 32-bit
14171 architectures). Therefore the user is required to specify the return type by
14172 an appropriate cast explicitly:
14175 Breakpoint 2, 0x0040050b in func ()
14176 (@value{GDBP}) return -1
14177 Return value type not available for selected stack frame.
14178 Please use an explicit cast of the value to return.
14179 (@value{GDBP}) return (long long int) -1
14180 Make selected stack frame return now? (y or n) y
14181 #0 0x00400526 in main ()
14186 @section Calling Program Functions
14189 @cindex calling functions
14190 @cindex inferior functions, calling
14191 @item print @var{expr}
14192 Evaluate the expression @var{expr} and display the resulting value.
14193 @var{expr} may include calls to functions in the program being
14197 @item call @var{expr}
14198 Evaluate the expression @var{expr} without displaying @code{void}
14201 You can use this variant of the @code{print} command if you want to
14202 execute a function from your program that does not return anything
14203 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14204 with @code{void} returned values that @value{GDBN} will otherwise
14205 print. If the result is not void, it is printed and saved in the
14209 It is possible for the function you call via the @code{print} or
14210 @code{call} command to generate a signal (e.g., if there's a bug in
14211 the function, or if you passed it incorrect arguments). What happens
14212 in that case is controlled by the @code{set unwindonsignal} command.
14214 Similarly, with a C@t{++} program it is possible for the function you
14215 call via the @code{print} or @code{call} command to generate an
14216 exception that is not handled due to the constraints of the dummy
14217 frame. In this case, any exception that is raised in the frame, but has
14218 an out-of-frame exception handler will not be found. GDB builds a
14219 dummy-frame for the inferior function call, and the unwinder cannot
14220 seek for exception handlers outside of this dummy-frame. What happens
14221 in that case is controlled by the
14222 @code{set unwind-on-terminating-exception} command.
14225 @item set unwindonsignal
14226 @kindex set unwindonsignal
14227 @cindex unwind stack in called functions
14228 @cindex call dummy stack unwinding
14229 Set unwinding of the stack if a signal is received while in a function
14230 that @value{GDBN} called in the program being debugged. If set to on,
14231 @value{GDBN} unwinds the stack it created for the call and restores
14232 the context to what it was before the call. If set to off (the
14233 default), @value{GDBN} stops in the frame where the signal was
14236 @item show unwindonsignal
14237 @kindex show unwindonsignal
14238 Show the current setting of stack unwinding in the functions called by
14241 @item set unwind-on-terminating-exception
14242 @kindex set unwind-on-terminating-exception
14243 @cindex unwind stack in called functions with unhandled exceptions
14244 @cindex call dummy stack unwinding on unhandled exception.
14245 Set unwinding of the stack if a C@t{++} exception is raised, but left
14246 unhandled while in a function that @value{GDBN} called in the program being
14247 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14248 it created for the call and restores the context to what it was before
14249 the call. If set to off, @value{GDBN} the exception is delivered to
14250 the default C@t{++} exception handler and the inferior terminated.
14252 @item show unwind-on-terminating-exception
14253 @kindex show unwind-on-terminating-exception
14254 Show the current setting of stack unwinding in the functions called by
14259 @cindex weak alias functions
14260 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14261 for another function. In such case, @value{GDBN} might not pick up
14262 the type information, including the types of the function arguments,
14263 which causes @value{GDBN} to call the inferior function incorrectly.
14264 As a result, the called function will function erroneously and may
14265 even crash. A solution to that is to use the name of the aliased
14269 @section Patching Programs
14271 @cindex patching binaries
14272 @cindex writing into executables
14273 @cindex writing into corefiles
14275 By default, @value{GDBN} opens the file containing your program's
14276 executable code (or the corefile) read-only. This prevents accidental
14277 alterations to machine code; but it also prevents you from intentionally
14278 patching your program's binary.
14280 If you'd like to be able to patch the binary, you can specify that
14281 explicitly with the @code{set write} command. For example, you might
14282 want to turn on internal debugging flags, or even to make emergency
14288 @itemx set write off
14289 If you specify @samp{set write on}, @value{GDBN} opens executable and
14290 core files for both reading and writing; if you specify @kbd{set write
14291 off} (the default), @value{GDBN} opens them read-only.
14293 If you have already loaded a file, you must load it again (using the
14294 @code{exec-file} or @code{core-file} command) after changing @code{set
14295 write}, for your new setting to take effect.
14299 Display whether executable files and core files are opened for writing
14300 as well as reading.
14304 @chapter @value{GDBN} Files
14306 @value{GDBN} needs to know the file name of the program to be debugged,
14307 both in order to read its symbol table and in order to start your
14308 program. To debug a core dump of a previous run, you must also tell
14309 @value{GDBN} the name of the core dump file.
14312 * Files:: Commands to specify files
14313 * Separate Debug Files:: Debugging information in separate files
14314 * Index Files:: Index files speed up GDB
14315 * Symbol Errors:: Errors reading symbol files
14316 * Data Files:: GDB data files
14320 @section Commands to Specify Files
14322 @cindex symbol table
14323 @cindex core dump file
14325 You may want to specify executable and core dump file names. The usual
14326 way to do this is at start-up time, using the arguments to
14327 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14328 Out of @value{GDBN}}).
14330 Occasionally it is necessary to change to a different file during a
14331 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14332 specify a file you want to use. Or you are debugging a remote target
14333 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14334 Program}). In these situations the @value{GDBN} commands to specify
14335 new files are useful.
14338 @cindex executable file
14340 @item file @var{filename}
14341 Use @var{filename} as the program to be debugged. It is read for its
14342 symbols and for the contents of pure memory. It is also the program
14343 executed when you use the @code{run} command. If you do not specify a
14344 directory and the file is not found in the @value{GDBN} working directory,
14345 @value{GDBN} uses the environment variable @code{PATH} as a list of
14346 directories to search, just as the shell does when looking for a program
14347 to run. You can change the value of this variable, for both @value{GDBN}
14348 and your program, using the @code{path} command.
14350 @cindex unlinked object files
14351 @cindex patching object files
14352 You can load unlinked object @file{.o} files into @value{GDBN} using
14353 the @code{file} command. You will not be able to ``run'' an object
14354 file, but you can disassemble functions and inspect variables. Also,
14355 if the underlying BFD functionality supports it, you could use
14356 @kbd{gdb -write} to patch object files using this technique. Note
14357 that @value{GDBN} can neither interpret nor modify relocations in this
14358 case, so branches and some initialized variables will appear to go to
14359 the wrong place. But this feature is still handy from time to time.
14362 @code{file} with no argument makes @value{GDBN} discard any information it
14363 has on both executable file and the symbol table.
14366 @item exec-file @r{[} @var{filename} @r{]}
14367 Specify that the program to be run (but not the symbol table) is found
14368 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14369 if necessary to locate your program. Omitting @var{filename} means to
14370 discard information on the executable file.
14372 @kindex symbol-file
14373 @item symbol-file @r{[} @var{filename} @r{]}
14374 Read symbol table information from file @var{filename}. @code{PATH} is
14375 searched when necessary. Use the @code{file} command to get both symbol
14376 table and program to run from the same file.
14378 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14379 program's symbol table.
14381 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14382 some breakpoints and auto-display expressions. This is because they may
14383 contain pointers to the internal data recording symbols and data types,
14384 which are part of the old symbol table data being discarded inside
14387 @code{symbol-file} does not repeat if you press @key{RET} again after
14390 When @value{GDBN} is configured for a particular environment, it
14391 understands debugging information in whatever format is the standard
14392 generated for that environment; you may use either a @sc{gnu} compiler, or
14393 other compilers that adhere to the local conventions.
14394 Best results are usually obtained from @sc{gnu} compilers; for example,
14395 using @code{@value{NGCC}} you can generate debugging information for
14398 For most kinds of object files, with the exception of old SVR3 systems
14399 using COFF, the @code{symbol-file} command does not normally read the
14400 symbol table in full right away. Instead, it scans the symbol table
14401 quickly to find which source files and which symbols are present. The
14402 details are read later, one source file at a time, as they are needed.
14404 The purpose of this two-stage reading strategy is to make @value{GDBN}
14405 start up faster. For the most part, it is invisible except for
14406 occasional pauses while the symbol table details for a particular source
14407 file are being read. (The @code{set verbose} command can turn these
14408 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14409 Warnings and Messages}.)
14411 We have not implemented the two-stage strategy for COFF yet. When the
14412 symbol table is stored in COFF format, @code{symbol-file} reads the
14413 symbol table data in full right away. Note that ``stabs-in-COFF''
14414 still does the two-stage strategy, since the debug info is actually
14418 @cindex reading symbols immediately
14419 @cindex symbols, reading immediately
14420 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14421 @itemx file @r{[} -readnow @r{]} @var{filename}
14422 You can override the @value{GDBN} two-stage strategy for reading symbol
14423 tables by using the @samp{-readnow} option with any of the commands that
14424 load symbol table information, if you want to be sure @value{GDBN} has the
14425 entire symbol table available.
14427 @c FIXME: for now no mention of directories, since this seems to be in
14428 @c flux. 13mar1992 status is that in theory GDB would look either in
14429 @c current dir or in same dir as myprog; but issues like competing
14430 @c GDB's, or clutter in system dirs, mean that in practice right now
14431 @c only current dir is used. FFish says maybe a special GDB hierarchy
14432 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14436 @item core-file @r{[}@var{filename}@r{]}
14438 Specify the whereabouts of a core dump file to be used as the ``contents
14439 of memory''. Traditionally, core files contain only some parts of the
14440 address space of the process that generated them; @value{GDBN} can access the
14441 executable file itself for other parts.
14443 @code{core-file} with no argument specifies that no core file is
14446 Note that the core file is ignored when your program is actually running
14447 under @value{GDBN}. So, if you have been running your program and you
14448 wish to debug a core file instead, you must kill the subprocess in which
14449 the program is running. To do this, use the @code{kill} command
14450 (@pxref{Kill Process, ,Killing the Child Process}).
14452 @kindex add-symbol-file
14453 @cindex dynamic linking
14454 @item add-symbol-file @var{filename} @var{address}
14455 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14456 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14457 The @code{add-symbol-file} command reads additional symbol table
14458 information from the file @var{filename}. You would use this command
14459 when @var{filename} has been dynamically loaded (by some other means)
14460 into the program that is running. @var{address} should be the memory
14461 address at which the file has been loaded; @value{GDBN} cannot figure
14462 this out for itself. You can additionally specify an arbitrary number
14463 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14464 section name and base address for that section. You can specify any
14465 @var{address} as an expression.
14467 The symbol table of the file @var{filename} is added to the symbol table
14468 originally read with the @code{symbol-file} command. You can use the
14469 @code{add-symbol-file} command any number of times; the new symbol data
14470 thus read keeps adding to the old. To discard all old symbol data
14471 instead, use the @code{symbol-file} command without any arguments.
14473 @cindex relocatable object files, reading symbols from
14474 @cindex object files, relocatable, reading symbols from
14475 @cindex reading symbols from relocatable object files
14476 @cindex symbols, reading from relocatable object files
14477 @cindex @file{.o} files, reading symbols from
14478 Although @var{filename} is typically a shared library file, an
14479 executable file, or some other object file which has been fully
14480 relocated for loading into a process, you can also load symbolic
14481 information from relocatable @file{.o} files, as long as:
14485 the file's symbolic information refers only to linker symbols defined in
14486 that file, not to symbols defined by other object files,
14488 every section the file's symbolic information refers to has actually
14489 been loaded into the inferior, as it appears in the file, and
14491 you can determine the address at which every section was loaded, and
14492 provide these to the @code{add-symbol-file} command.
14496 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14497 relocatable files into an already running program; such systems
14498 typically make the requirements above easy to meet. However, it's
14499 important to recognize that many native systems use complex link
14500 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14501 assembly, for example) that make the requirements difficult to meet. In
14502 general, one cannot assume that using @code{add-symbol-file} to read a
14503 relocatable object file's symbolic information will have the same effect
14504 as linking the relocatable object file into the program in the normal
14507 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14509 @kindex add-symbol-file-from-memory
14510 @cindex @code{syscall DSO}
14511 @cindex load symbols from memory
14512 @item add-symbol-file-from-memory @var{address}
14513 Load symbols from the given @var{address} in a dynamically loaded
14514 object file whose image is mapped directly into the inferior's memory.
14515 For example, the Linux kernel maps a @code{syscall DSO} into each
14516 process's address space; this DSO provides kernel-specific code for
14517 some system calls. The argument can be any expression whose
14518 evaluation yields the address of the file's shared object file header.
14519 For this command to work, you must have used @code{symbol-file} or
14520 @code{exec-file} commands in advance.
14522 @kindex add-shared-symbol-files
14524 @item add-shared-symbol-files @var{library-file}
14525 @itemx assf @var{library-file}
14526 The @code{add-shared-symbol-files} command can currently be used only
14527 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14528 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14529 @value{GDBN} automatically looks for shared libraries, however if
14530 @value{GDBN} does not find yours, you can invoke
14531 @code{add-shared-symbol-files}. It takes one argument: the shared
14532 library's file name. @code{assf} is a shorthand alias for
14533 @code{add-shared-symbol-files}.
14536 @item section @var{section} @var{addr}
14537 The @code{section} command changes the base address of the named
14538 @var{section} of the exec file to @var{addr}. This can be used if the
14539 exec file does not contain section addresses, (such as in the
14540 @code{a.out} format), or when the addresses specified in the file
14541 itself are wrong. Each section must be changed separately. The
14542 @code{info files} command, described below, lists all the sections and
14546 @kindex info target
14549 @code{info files} and @code{info target} are synonymous; both print the
14550 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14551 including the names of the executable and core dump files currently in
14552 use by @value{GDBN}, and the files from which symbols were loaded. The
14553 command @code{help target} lists all possible targets rather than
14556 @kindex maint info sections
14557 @item maint info sections
14558 Another command that can give you extra information about program sections
14559 is @code{maint info sections}. In addition to the section information
14560 displayed by @code{info files}, this command displays the flags and file
14561 offset of each section in the executable and core dump files. In addition,
14562 @code{maint info sections} provides the following command options (which
14563 may be arbitrarily combined):
14567 Display sections for all loaded object files, including shared libraries.
14568 @item @var{sections}
14569 Display info only for named @var{sections}.
14570 @item @var{section-flags}
14571 Display info only for sections for which @var{section-flags} are true.
14572 The section flags that @value{GDBN} currently knows about are:
14575 Section will have space allocated in the process when loaded.
14576 Set for all sections except those containing debug information.
14578 Section will be loaded from the file into the child process memory.
14579 Set for pre-initialized code and data, clear for @code{.bss} sections.
14581 Section needs to be relocated before loading.
14583 Section cannot be modified by the child process.
14585 Section contains executable code only.
14587 Section contains data only (no executable code).
14589 Section will reside in ROM.
14591 Section contains data for constructor/destructor lists.
14593 Section is not empty.
14595 An instruction to the linker to not output the section.
14596 @item COFF_SHARED_LIBRARY
14597 A notification to the linker that the section contains
14598 COFF shared library information.
14600 Section contains common symbols.
14603 @kindex set trust-readonly-sections
14604 @cindex read-only sections
14605 @item set trust-readonly-sections on
14606 Tell @value{GDBN} that readonly sections in your object file
14607 really are read-only (i.e.@: that their contents will not change).
14608 In that case, @value{GDBN} can fetch values from these sections
14609 out of the object file, rather than from the target program.
14610 For some targets (notably embedded ones), this can be a significant
14611 enhancement to debugging performance.
14613 The default is off.
14615 @item set trust-readonly-sections off
14616 Tell @value{GDBN} not to trust readonly sections. This means that
14617 the contents of the section might change while the program is running,
14618 and must therefore be fetched from the target when needed.
14620 @item show trust-readonly-sections
14621 Show the current setting of trusting readonly sections.
14624 All file-specifying commands allow both absolute and relative file names
14625 as arguments. @value{GDBN} always converts the file name to an absolute file
14626 name and remembers it that way.
14628 @cindex shared libraries
14629 @anchor{Shared Libraries}
14630 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14631 and IBM RS/6000 AIX shared libraries.
14633 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14634 shared libraries. @xref{Expat}.
14636 @value{GDBN} automatically loads symbol definitions from shared libraries
14637 when you use the @code{run} command, or when you examine a core file.
14638 (Before you issue the @code{run} command, @value{GDBN} does not understand
14639 references to a function in a shared library, however---unless you are
14640 debugging a core file).
14642 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14643 automatically loads the symbols at the time of the @code{shl_load} call.
14645 @c FIXME: some @value{GDBN} release may permit some refs to undef
14646 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14647 @c FIXME...lib; check this from time to time when updating manual
14649 There are times, however, when you may wish to not automatically load
14650 symbol definitions from shared libraries, such as when they are
14651 particularly large or there are many of them.
14653 To control the automatic loading of shared library symbols, use the
14657 @kindex set auto-solib-add
14658 @item set auto-solib-add @var{mode}
14659 If @var{mode} is @code{on}, symbols from all shared object libraries
14660 will be loaded automatically when the inferior begins execution, you
14661 attach to an independently started inferior, or when the dynamic linker
14662 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14663 is @code{off}, symbols must be loaded manually, using the
14664 @code{sharedlibrary} command. The default value is @code{on}.
14666 @cindex memory used for symbol tables
14667 If your program uses lots of shared libraries with debug info that
14668 takes large amounts of memory, you can decrease the @value{GDBN}
14669 memory footprint by preventing it from automatically loading the
14670 symbols from shared libraries. To that end, type @kbd{set
14671 auto-solib-add off} before running the inferior, then load each
14672 library whose debug symbols you do need with @kbd{sharedlibrary
14673 @var{regexp}}, where @var{regexp} is a regular expression that matches
14674 the libraries whose symbols you want to be loaded.
14676 @kindex show auto-solib-add
14677 @item show auto-solib-add
14678 Display the current autoloading mode.
14681 @cindex load shared library
14682 To explicitly load shared library symbols, use the @code{sharedlibrary}
14686 @kindex info sharedlibrary
14688 @item info share @var{regex}
14689 @itemx info sharedlibrary @var{regex}
14690 Print the names of the shared libraries which are currently loaded
14691 that match @var{regex}. If @var{regex} is omitted then print
14692 all shared libraries that are loaded.
14694 @kindex sharedlibrary
14696 @item sharedlibrary @var{regex}
14697 @itemx share @var{regex}
14698 Load shared object library symbols for files matching a
14699 Unix regular expression.
14700 As with files loaded automatically, it only loads shared libraries
14701 required by your program for a core file or after typing @code{run}. If
14702 @var{regex} is omitted all shared libraries required by your program are
14705 @item nosharedlibrary
14706 @kindex nosharedlibrary
14707 @cindex unload symbols from shared libraries
14708 Unload all shared object library symbols. This discards all symbols
14709 that have been loaded from all shared libraries. Symbols from shared
14710 libraries that were loaded by explicit user requests are not
14714 Sometimes you may wish that @value{GDBN} stops and gives you control
14715 when any of shared library events happen. Use the @code{set
14716 stop-on-solib-events} command for this:
14719 @item set stop-on-solib-events
14720 @kindex set stop-on-solib-events
14721 This command controls whether @value{GDBN} should give you control
14722 when the dynamic linker notifies it about some shared library event.
14723 The most common event of interest is loading or unloading of a new
14726 @item show stop-on-solib-events
14727 @kindex show stop-on-solib-events
14728 Show whether @value{GDBN} stops and gives you control when shared
14729 library events happen.
14732 Shared libraries are also supported in many cross or remote debugging
14733 configurations. @value{GDBN} needs to have access to the target's libraries;
14734 this can be accomplished either by providing copies of the libraries
14735 on the host system, or by asking @value{GDBN} to automatically retrieve the
14736 libraries from the target. If copies of the target libraries are
14737 provided, they need to be the same as the target libraries, although the
14738 copies on the target can be stripped as long as the copies on the host are
14741 @cindex where to look for shared libraries
14742 For remote debugging, you need to tell @value{GDBN} where the target
14743 libraries are, so that it can load the correct copies---otherwise, it
14744 may try to load the host's libraries. @value{GDBN} has two variables
14745 to specify the search directories for target libraries.
14748 @cindex prefix for shared library file names
14749 @cindex system root, alternate
14750 @kindex set solib-absolute-prefix
14751 @kindex set sysroot
14752 @item set sysroot @var{path}
14753 Use @var{path} as the system root for the program being debugged. Any
14754 absolute shared library paths will be prefixed with @var{path}; many
14755 runtime loaders store the absolute paths to the shared library in the
14756 target program's memory. If you use @code{set sysroot} to find shared
14757 libraries, they need to be laid out in the same way that they are on
14758 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14761 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14762 retrieve the target libraries from the remote system. This is only
14763 supported when using a remote target that supports the @code{remote get}
14764 command (@pxref{File Transfer,,Sending files to a remote system}).
14765 The part of @var{path} following the initial @file{remote:}
14766 (if present) is used as system root prefix on the remote file system.
14767 @footnote{If you want to specify a local system root using a directory
14768 that happens to be named @file{remote:}, you need to use some equivalent
14769 variant of the name like @file{./remote:}.}
14771 For targets with an MS-DOS based filesystem, such as MS-Windows and
14772 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14773 absolute file name with @var{path}. But first, on Unix hosts,
14774 @value{GDBN} converts all backslash directory separators into forward
14775 slashes, because the backslash is not a directory separator on Unix:
14778 c:\foo\bar.dll @result{} c:/foo/bar.dll
14781 Then, @value{GDBN} attempts prefixing the target file name with
14782 @var{path}, and looks for the resulting file name in the host file
14786 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14789 If that does not find the shared library, @value{GDBN} tries removing
14790 the @samp{:} character from the drive spec, both for convenience, and,
14791 for the case of the host file system not supporting file names with
14795 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14798 This makes it possible to have a system root that mirrors a target
14799 with more than one drive. E.g., you may want to setup your local
14800 copies of the target system shared libraries like so (note @samp{c} vs
14804 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14805 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14806 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14810 and point the system root at @file{/path/to/sysroot}, so that
14811 @value{GDBN} can find the correct copies of both
14812 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14814 If that still does not find the shared library, @value{GDBN} tries
14815 removing the whole drive spec from the target file name:
14818 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14821 This last lookup makes it possible to not care about the drive name,
14822 if you don't want or need to.
14824 The @code{set solib-absolute-prefix} command is an alias for @code{set
14827 @cindex default system root
14828 @cindex @samp{--with-sysroot}
14829 You can set the default system root by using the configure-time
14830 @samp{--with-sysroot} option. If the system root is inside
14831 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14832 @samp{--exec-prefix}), then the default system root will be updated
14833 automatically if the installed @value{GDBN} is moved to a new
14836 @kindex show sysroot
14838 Display the current shared library prefix.
14840 @kindex set solib-search-path
14841 @item set solib-search-path @var{path}
14842 If this variable is set, @var{path} is a colon-separated list of
14843 directories to search for shared libraries. @samp{solib-search-path}
14844 is used after @samp{sysroot} fails to locate the library, or if the
14845 path to the library is relative instead of absolute. If you want to
14846 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14847 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14848 finding your host's libraries. @samp{sysroot} is preferred; setting
14849 it to a nonexistent directory may interfere with automatic loading
14850 of shared library symbols.
14852 @kindex show solib-search-path
14853 @item show solib-search-path
14854 Display the current shared library search path.
14856 @cindex DOS file-name semantics of file names.
14857 @kindex set target-file-system-kind (unix|dos-based|auto)
14858 @kindex show target-file-system-kind
14859 @item set target-file-system-kind @var{kind}
14860 Set assumed file system kind for target reported file names.
14862 Shared library file names as reported by the target system may not
14863 make sense as is on the system @value{GDBN} is running on. For
14864 example, when remote debugging a target that has MS-DOS based file
14865 system semantics, from a Unix host, the target may be reporting to
14866 @value{GDBN} a list of loaded shared libraries with file names such as
14867 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14868 drive letters, so the @samp{c:\} prefix is not normally understood as
14869 indicating an absolute file name, and neither is the backslash
14870 normally considered a directory separator character. In that case,
14871 the native file system would interpret this whole absolute file name
14872 as a relative file name with no directory components. This would make
14873 it impossible to point @value{GDBN} at a copy of the remote target's
14874 shared libraries on the host using @code{set sysroot}, and impractical
14875 with @code{set solib-search-path}. Setting
14876 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14877 to interpret such file names similarly to how the target would, and to
14878 map them to file names valid on @value{GDBN}'s native file system
14879 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14880 to one of the supported file system kinds. In that case, @value{GDBN}
14881 tries to determine the appropriate file system variant based on the
14882 current target's operating system (@pxref{ABI, ,Configuring the
14883 Current ABI}). The supported file system settings are:
14887 Instruct @value{GDBN} to assume the target file system is of Unix
14888 kind. Only file names starting the forward slash (@samp{/}) character
14889 are considered absolute, and the directory separator character is also
14893 Instruct @value{GDBN} to assume the target file system is DOS based.
14894 File names starting with either a forward slash, or a drive letter
14895 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14896 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14897 considered directory separators.
14900 Instruct @value{GDBN} to use the file system kind associated with the
14901 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14902 This is the default.
14907 @node Separate Debug Files
14908 @section Debugging Information in Separate Files
14909 @cindex separate debugging information files
14910 @cindex debugging information in separate files
14911 @cindex @file{.debug} subdirectories
14912 @cindex debugging information directory, global
14913 @cindex global debugging information directory
14914 @cindex build ID, and separate debugging files
14915 @cindex @file{.build-id} directory
14917 @value{GDBN} allows you to put a program's debugging information in a
14918 file separate from the executable itself, in a way that allows
14919 @value{GDBN} to find and load the debugging information automatically.
14920 Since debugging information can be very large---sometimes larger
14921 than the executable code itself---some systems distribute debugging
14922 information for their executables in separate files, which users can
14923 install only when they need to debug a problem.
14925 @value{GDBN} supports two ways of specifying the separate debug info
14930 The executable contains a @dfn{debug link} that specifies the name of
14931 the separate debug info file. The separate debug file's name is
14932 usually @file{@var{executable}.debug}, where @var{executable} is the
14933 name of the corresponding executable file without leading directories
14934 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14935 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14936 checksum for the debug file, which @value{GDBN} uses to validate that
14937 the executable and the debug file came from the same build.
14940 The executable contains a @dfn{build ID}, a unique bit string that is
14941 also present in the corresponding debug info file. (This is supported
14942 only on some operating systems, notably those which use the ELF format
14943 for binary files and the @sc{gnu} Binutils.) For more details about
14944 this feature, see the description of the @option{--build-id}
14945 command-line option in @ref{Options, , Command Line Options, ld.info,
14946 The GNU Linker}. The debug info file's name is not specified
14947 explicitly by the build ID, but can be computed from the build ID, see
14951 Depending on the way the debug info file is specified, @value{GDBN}
14952 uses two different methods of looking for the debug file:
14956 For the ``debug link'' method, @value{GDBN} looks up the named file in
14957 the directory of the executable file, then in a subdirectory of that
14958 directory named @file{.debug}, and finally under the global debug
14959 directory, in a subdirectory whose name is identical to the leading
14960 directories of the executable's absolute file name.
14963 For the ``build ID'' method, @value{GDBN} looks in the
14964 @file{.build-id} subdirectory of the global debug directory for a file
14965 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14966 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14967 are the rest of the bit string. (Real build ID strings are 32 or more
14968 hex characters, not 10.)
14971 So, for example, suppose you ask @value{GDBN} to debug
14972 @file{/usr/bin/ls}, which has a debug link that specifies the
14973 file @file{ls.debug}, and a build ID whose value in hex is
14974 @code{abcdef1234}. If the global debug directory is
14975 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14976 debug information files, in the indicated order:
14980 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14982 @file{/usr/bin/ls.debug}
14984 @file{/usr/bin/.debug/ls.debug}
14986 @file{/usr/lib/debug/usr/bin/ls.debug}.
14989 You can set the global debugging info directory's name, and view the
14990 name @value{GDBN} is currently using.
14994 @kindex set debug-file-directory
14995 @item set debug-file-directory @var{directories}
14996 Set the directories which @value{GDBN} searches for separate debugging
14997 information files to @var{directory}. Multiple directory components can be set
14998 concatenating them by a directory separator.
15000 @kindex show debug-file-directory
15001 @item show debug-file-directory
15002 Show the directories @value{GDBN} searches for separate debugging
15007 @cindex @code{.gnu_debuglink} sections
15008 @cindex debug link sections
15009 A debug link is a special section of the executable file named
15010 @code{.gnu_debuglink}. The section must contain:
15014 A filename, with any leading directory components removed, followed by
15017 zero to three bytes of padding, as needed to reach the next four-byte
15018 boundary within the section, and
15020 a four-byte CRC checksum, stored in the same endianness used for the
15021 executable file itself. The checksum is computed on the debugging
15022 information file's full contents by the function given below, passing
15023 zero as the @var{crc} argument.
15026 Any executable file format can carry a debug link, as long as it can
15027 contain a section named @code{.gnu_debuglink} with the contents
15030 @cindex @code{.note.gnu.build-id} sections
15031 @cindex build ID sections
15032 The build ID is a special section in the executable file (and in other
15033 ELF binary files that @value{GDBN} may consider). This section is
15034 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15035 It contains unique identification for the built files---the ID remains
15036 the same across multiple builds of the same build tree. The default
15037 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15038 content for the build ID string. The same section with an identical
15039 value is present in the original built binary with symbols, in its
15040 stripped variant, and in the separate debugging information file.
15042 The debugging information file itself should be an ordinary
15043 executable, containing a full set of linker symbols, sections, and
15044 debugging information. The sections of the debugging information file
15045 should have the same names, addresses, and sizes as the original file,
15046 but they need not contain any data---much like a @code{.bss} section
15047 in an ordinary executable.
15049 The @sc{gnu} binary utilities (Binutils) package includes the
15050 @samp{objcopy} utility that can produce
15051 the separated executable / debugging information file pairs using the
15052 following commands:
15055 @kbd{objcopy --only-keep-debug foo foo.debug}
15060 These commands remove the debugging
15061 information from the executable file @file{foo} and place it in the file
15062 @file{foo.debug}. You can use the first, second or both methods to link the
15067 The debug link method needs the following additional command to also leave
15068 behind a debug link in @file{foo}:
15071 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15074 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15075 a version of the @code{strip} command such that the command @kbd{strip foo -f
15076 foo.debug} has the same functionality as the two @code{objcopy} commands and
15077 the @code{ln -s} command above, together.
15080 Build ID gets embedded into the main executable using @code{ld --build-id} or
15081 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15082 compatibility fixes for debug files separation are present in @sc{gnu} binary
15083 utilities (Binutils) package since version 2.18.
15088 @cindex CRC algorithm definition
15089 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15090 IEEE 802.3 using the polynomial:
15092 @c TexInfo requires naked braces for multi-digit exponents for Tex
15093 @c output, but this causes HTML output to barf. HTML has to be set using
15094 @c raw commands. So we end up having to specify this equation in 2
15099 <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>
15100 + <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
15106 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15107 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15111 The function is computed byte at a time, taking the least
15112 significant bit of each byte first. The initial pattern
15113 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15114 the final result is inverted to ensure trailing zeros also affect the
15117 @emph{Note:} This is the same CRC polynomial as used in handling the
15118 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15119 , @value{GDBN} Remote Serial Protocol}). However in the
15120 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15121 significant bit first, and the result is not inverted, so trailing
15122 zeros have no effect on the CRC value.
15124 To complete the description, we show below the code of the function
15125 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15126 initially supplied @code{crc} argument means that an initial call to
15127 this function passing in zero will start computing the CRC using
15130 @kindex gnu_debuglink_crc32
15133 gnu_debuglink_crc32 (unsigned long crc,
15134 unsigned char *buf, size_t len)
15136 static const unsigned long crc32_table[256] =
15138 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15139 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15140 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15141 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15142 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15143 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15144 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15145 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15146 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15147 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15148 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15149 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15150 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15151 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15152 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15153 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15154 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15155 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15156 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15157 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15158 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15159 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15160 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15161 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15162 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15163 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15164 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15165 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15166 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15167 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15168 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15169 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15170 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15171 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15172 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15173 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15174 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15175 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15176 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15177 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15178 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15179 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15180 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15181 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15182 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15183 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15184 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15185 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15186 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15187 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15188 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15191 unsigned char *end;
15193 crc = ~crc & 0xffffffff;
15194 for (end = buf + len; buf < end; ++buf)
15195 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15196 return ~crc & 0xffffffff;
15201 This computation does not apply to the ``build ID'' method.
15205 @section Index Files Speed Up @value{GDBN}
15206 @cindex index files
15207 @cindex @samp{.gdb_index} section
15209 When @value{GDBN} finds a symbol file, it scans the symbols in the
15210 file in order to construct an internal symbol table. This lets most
15211 @value{GDBN} operations work quickly---at the cost of a delay early
15212 on. For large programs, this delay can be quite lengthy, so
15213 @value{GDBN} provides a way to build an index, which speeds up
15216 The index is stored as a section in the symbol file. @value{GDBN} can
15217 write the index to a file, then you can put it into the symbol file
15218 using @command{objcopy}.
15220 To create an index file, use the @code{save gdb-index} command:
15223 @item save gdb-index @var{directory}
15224 @kindex save gdb-index
15225 Create an index file for each symbol file currently known by
15226 @value{GDBN}. Each file is named after its corresponding symbol file,
15227 with @samp{.gdb-index} appended, and is written into the given
15231 Once you have created an index file you can merge it into your symbol
15232 file, here named @file{symfile}, using @command{objcopy}:
15235 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15236 --set-section-flags .gdb_index=readonly symfile symfile
15239 There are currently some limitation on indices. They only work when
15240 for DWARF debugging information, not stabs. And, they do not
15241 currently work for programs using Ada.
15244 @node Symbol Errors
15245 @section Errors Reading Symbol Files
15247 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15248 such as symbol types it does not recognize, or known bugs in compiler
15249 output. By default, @value{GDBN} does not notify you of such problems, since
15250 they are relatively common and primarily of interest to people
15251 debugging compilers. If you are interested in seeing information
15252 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15253 only one message about each such type of problem, no matter how many
15254 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15255 to see how many times the problems occur, with the @code{set
15256 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15259 The messages currently printed, and their meanings, include:
15262 @item inner block not inside outer block in @var{symbol}
15264 The symbol information shows where symbol scopes begin and end
15265 (such as at the start of a function or a block of statements). This
15266 error indicates that an inner scope block is not fully contained
15267 in its outer scope blocks.
15269 @value{GDBN} circumvents the problem by treating the inner block as if it had
15270 the same scope as the outer block. In the error message, @var{symbol}
15271 may be shown as ``@code{(don't know)}'' if the outer block is not a
15274 @item block at @var{address} out of order
15276 The symbol information for symbol scope blocks should occur in
15277 order of increasing addresses. This error indicates that it does not
15280 @value{GDBN} does not circumvent this problem, and has trouble
15281 locating symbols in the source file whose symbols it is reading. (You
15282 can often determine what source file is affected by specifying
15283 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15286 @item bad block start address patched
15288 The symbol information for a symbol scope block has a start address
15289 smaller than the address of the preceding source line. This is known
15290 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15292 @value{GDBN} circumvents the problem by treating the symbol scope block as
15293 starting on the previous source line.
15295 @item bad string table offset in symbol @var{n}
15298 Symbol number @var{n} contains a pointer into the string table which is
15299 larger than the size of the string table.
15301 @value{GDBN} circumvents the problem by considering the symbol to have the
15302 name @code{foo}, which may cause other problems if many symbols end up
15305 @item unknown symbol type @code{0x@var{nn}}
15307 The symbol information contains new data types that @value{GDBN} does
15308 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15309 uncomprehended information, in hexadecimal.
15311 @value{GDBN} circumvents the error by ignoring this symbol information.
15312 This usually allows you to debug your program, though certain symbols
15313 are not accessible. If you encounter such a problem and feel like
15314 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15315 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15316 and examine @code{*bufp} to see the symbol.
15318 @item stub type has NULL name
15320 @value{GDBN} could not find the full definition for a struct or class.
15322 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15323 The symbol information for a C@t{++} member function is missing some
15324 information that recent versions of the compiler should have output for
15327 @item info mismatch between compiler and debugger
15329 @value{GDBN} could not parse a type specification output by the compiler.
15334 @section GDB Data Files
15336 @cindex prefix for data files
15337 @value{GDBN} will sometimes read an auxiliary data file. These files
15338 are kept in a directory known as the @dfn{data directory}.
15340 You can set the data directory's name, and view the name @value{GDBN}
15341 is currently using.
15344 @kindex set data-directory
15345 @item set data-directory @var{directory}
15346 Set the directory which @value{GDBN} searches for auxiliary data files
15347 to @var{directory}.
15349 @kindex show data-directory
15350 @item show data-directory
15351 Show the directory @value{GDBN} searches for auxiliary data files.
15354 @cindex default data directory
15355 @cindex @samp{--with-gdb-datadir}
15356 You can set the default data directory by using the configure-time
15357 @samp{--with-gdb-datadir} option. If the data directory is inside
15358 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15359 @samp{--exec-prefix}), then the default data directory will be updated
15360 automatically if the installed @value{GDBN} is moved to a new
15364 @chapter Specifying a Debugging Target
15366 @cindex debugging target
15367 A @dfn{target} is the execution environment occupied by your program.
15369 Often, @value{GDBN} runs in the same host environment as your program;
15370 in that case, the debugging target is specified as a side effect when
15371 you use the @code{file} or @code{core} commands. When you need more
15372 flexibility---for example, running @value{GDBN} on a physically separate
15373 host, or controlling a standalone system over a serial port or a
15374 realtime system over a TCP/IP connection---you can use the @code{target}
15375 command to specify one of the target types configured for @value{GDBN}
15376 (@pxref{Target Commands, ,Commands for Managing Targets}).
15378 @cindex target architecture
15379 It is possible to build @value{GDBN} for several different @dfn{target
15380 architectures}. When @value{GDBN} is built like that, you can choose
15381 one of the available architectures with the @kbd{set architecture}
15385 @kindex set architecture
15386 @kindex show architecture
15387 @item set architecture @var{arch}
15388 This command sets the current target architecture to @var{arch}. The
15389 value of @var{arch} can be @code{"auto"}, in addition to one of the
15390 supported architectures.
15392 @item show architecture
15393 Show the current target architecture.
15395 @item set processor
15397 @kindex set processor
15398 @kindex show processor
15399 These are alias commands for, respectively, @code{set architecture}
15400 and @code{show architecture}.
15404 * Active Targets:: Active targets
15405 * Target Commands:: Commands for managing targets
15406 * Byte Order:: Choosing target byte order
15409 @node Active Targets
15410 @section Active Targets
15412 @cindex stacking targets
15413 @cindex active targets
15414 @cindex multiple targets
15416 There are multiple classes of targets such as: processes, executable files or
15417 recording sessions. Core files belong to the process class, making core file
15418 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15419 on multiple active targets, one in each class. This allows you to (for
15420 example) start a process and inspect its activity, while still having access to
15421 the executable file after the process finishes. Or if you start process
15422 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15423 presented a virtual layer of the recording target, while the process target
15424 remains stopped at the chronologically last point of the process execution.
15426 Use the @code{core-file} and @code{exec-file} commands to select a new core
15427 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15428 specify as a target a process that is already running, use the @code{attach}
15429 command (@pxref{Attach, ,Debugging an Already-running Process}).
15431 @node Target Commands
15432 @section Commands for Managing Targets
15435 @item target @var{type} @var{parameters}
15436 Connects the @value{GDBN} host environment to a target machine or
15437 process. A target is typically a protocol for talking to debugging
15438 facilities. You use the argument @var{type} to specify the type or
15439 protocol of the target machine.
15441 Further @var{parameters} are interpreted by the target protocol, but
15442 typically include things like device names or host names to connect
15443 with, process numbers, and baud rates.
15445 The @code{target} command does not repeat if you press @key{RET} again
15446 after executing the command.
15448 @kindex help target
15450 Displays the names of all targets available. To display targets
15451 currently selected, use either @code{info target} or @code{info files}
15452 (@pxref{Files, ,Commands to Specify Files}).
15454 @item help target @var{name}
15455 Describe a particular target, including any parameters necessary to
15458 @kindex set gnutarget
15459 @item set gnutarget @var{args}
15460 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15461 knows whether it is reading an @dfn{executable},
15462 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15463 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15464 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15467 @emph{Warning:} To specify a file format with @code{set gnutarget},
15468 you must know the actual BFD name.
15472 @xref{Files, , Commands to Specify Files}.
15474 @kindex show gnutarget
15475 @item show gnutarget
15476 Use the @code{show gnutarget} command to display what file format
15477 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15478 @value{GDBN} will determine the file format for each file automatically,
15479 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15482 @cindex common targets
15483 Here are some common targets (available, or not, depending on the GDB
15488 @item target exec @var{program}
15489 @cindex executable file target
15490 An executable file. @samp{target exec @var{program}} is the same as
15491 @samp{exec-file @var{program}}.
15493 @item target core @var{filename}
15494 @cindex core dump file target
15495 A core dump file. @samp{target core @var{filename}} is the same as
15496 @samp{core-file @var{filename}}.
15498 @item target remote @var{medium}
15499 @cindex remote target
15500 A remote system connected to @value{GDBN} via a serial line or network
15501 connection. This command tells @value{GDBN} to use its own remote
15502 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15504 For example, if you have a board connected to @file{/dev/ttya} on the
15505 machine running @value{GDBN}, you could say:
15508 target remote /dev/ttya
15511 @code{target remote} supports the @code{load} command. This is only
15512 useful if you have some other way of getting the stub to the target
15513 system, and you can put it somewhere in memory where it won't get
15514 clobbered by the download.
15516 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15517 @cindex built-in simulator target
15518 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15526 works; however, you cannot assume that a specific memory map, device
15527 drivers, or even basic I/O is available, although some simulators do
15528 provide these. For info about any processor-specific simulator details,
15529 see the appropriate section in @ref{Embedded Processors, ,Embedded
15534 Some configurations may include these targets as well:
15538 @item target nrom @var{dev}
15539 @cindex NetROM ROM emulator target
15540 NetROM ROM emulator. This target only supports downloading.
15544 Different targets are available on different configurations of @value{GDBN};
15545 your configuration may have more or fewer targets.
15547 Many remote targets require you to download the executable's code once
15548 you've successfully established a connection. You may wish to control
15549 various aspects of this process.
15554 @kindex set hash@r{, for remote monitors}
15555 @cindex hash mark while downloading
15556 This command controls whether a hash mark @samp{#} is displayed while
15557 downloading a file to the remote monitor. If on, a hash mark is
15558 displayed after each S-record is successfully downloaded to the
15562 @kindex show hash@r{, for remote monitors}
15563 Show the current status of displaying the hash mark.
15565 @item set debug monitor
15566 @kindex set debug monitor
15567 @cindex display remote monitor communications
15568 Enable or disable display of communications messages between
15569 @value{GDBN} and the remote monitor.
15571 @item show debug monitor
15572 @kindex show debug monitor
15573 Show the current status of displaying communications between
15574 @value{GDBN} and the remote monitor.
15579 @kindex load @var{filename}
15580 @item load @var{filename}
15582 Depending on what remote debugging facilities are configured into
15583 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15584 is meant to make @var{filename} (an executable) available for debugging
15585 on the remote system---by downloading, or dynamic linking, for example.
15586 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15587 the @code{add-symbol-file} command.
15589 If your @value{GDBN} does not have a @code{load} command, attempting to
15590 execute it gets the error message ``@code{You can't do that when your
15591 target is @dots{}}''
15593 The file is loaded at whatever address is specified in the executable.
15594 For some object file formats, you can specify the load address when you
15595 link the program; for other formats, like a.out, the object file format
15596 specifies a fixed address.
15597 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15599 Depending on the remote side capabilities, @value{GDBN} may be able to
15600 load programs into flash memory.
15602 @code{load} does not repeat if you press @key{RET} again after using it.
15606 @section Choosing Target Byte Order
15608 @cindex choosing target byte order
15609 @cindex target byte order
15611 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15612 offer the ability to run either big-endian or little-endian byte
15613 orders. Usually the executable or symbol will include a bit to
15614 designate the endian-ness, and you will not need to worry about
15615 which to use. However, you may still find it useful to adjust
15616 @value{GDBN}'s idea of processor endian-ness manually.
15620 @item set endian big
15621 Instruct @value{GDBN} to assume the target is big-endian.
15623 @item set endian little
15624 Instruct @value{GDBN} to assume the target is little-endian.
15626 @item set endian auto
15627 Instruct @value{GDBN} to use the byte order associated with the
15631 Display @value{GDBN}'s current idea of the target byte order.
15635 Note that these commands merely adjust interpretation of symbolic
15636 data on the host, and that they have absolutely no effect on the
15640 @node Remote Debugging
15641 @chapter Debugging Remote Programs
15642 @cindex remote debugging
15644 If you are trying to debug a program running on a machine that cannot run
15645 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15646 For example, you might use remote debugging on an operating system kernel,
15647 or on a small system which does not have a general purpose operating system
15648 powerful enough to run a full-featured debugger.
15650 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15651 to make this work with particular debugging targets. In addition,
15652 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15653 but not specific to any particular target system) which you can use if you
15654 write the remote stubs---the code that runs on the remote system to
15655 communicate with @value{GDBN}.
15657 Other remote targets may be available in your
15658 configuration of @value{GDBN}; use @code{help target} to list them.
15661 * Connecting:: Connecting to a remote target
15662 * File Transfer:: Sending files to a remote system
15663 * Server:: Using the gdbserver program
15664 * Remote Configuration:: Remote configuration
15665 * Remote Stub:: Implementing a remote stub
15669 @section Connecting to a Remote Target
15671 On the @value{GDBN} host machine, you will need an unstripped copy of
15672 your program, since @value{GDBN} needs symbol and debugging information.
15673 Start up @value{GDBN} as usual, using the name of the local copy of your
15674 program as the first argument.
15676 @cindex @code{target remote}
15677 @value{GDBN} can communicate with the target over a serial line, or
15678 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15679 each case, @value{GDBN} uses the same protocol for debugging your
15680 program; only the medium carrying the debugging packets varies. The
15681 @code{target remote} command establishes a connection to the target.
15682 Its arguments indicate which medium to use:
15686 @item target remote @var{serial-device}
15687 @cindex serial line, @code{target remote}
15688 Use @var{serial-device} to communicate with the target. For example,
15689 to use a serial line connected to the device named @file{/dev/ttyb}:
15692 target remote /dev/ttyb
15695 If you're using a serial line, you may want to give @value{GDBN} the
15696 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15697 (@pxref{Remote Configuration, set remotebaud}) before the
15698 @code{target} command.
15700 @item target remote @code{@var{host}:@var{port}}
15701 @itemx target remote @code{tcp:@var{host}:@var{port}}
15702 @cindex @acronym{TCP} port, @code{target remote}
15703 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15704 The @var{host} may be either a host name or a numeric @acronym{IP}
15705 address; @var{port} must be a decimal number. The @var{host} could be
15706 the target machine itself, if it is directly connected to the net, or
15707 it might be a terminal server which in turn has a serial line to the
15710 For example, to connect to port 2828 on a terminal server named
15714 target remote manyfarms:2828
15717 If your remote target is actually running on the same machine as your
15718 debugger session (e.g.@: a simulator for your target running on the
15719 same host), you can omit the hostname. For example, to connect to
15720 port 1234 on your local machine:
15723 target remote :1234
15727 Note that the colon is still required here.
15729 @item target remote @code{udp:@var{host}:@var{port}}
15730 @cindex @acronym{UDP} port, @code{target remote}
15731 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15732 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15735 target remote udp:manyfarms:2828
15738 When using a @acronym{UDP} connection for remote debugging, you should
15739 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15740 can silently drop packets on busy or unreliable networks, which will
15741 cause havoc with your debugging session.
15743 @item target remote | @var{command}
15744 @cindex pipe, @code{target remote} to
15745 Run @var{command} in the background and communicate with it using a
15746 pipe. The @var{command} is a shell command, to be parsed and expanded
15747 by the system's command shell, @code{/bin/sh}; it should expect remote
15748 protocol packets on its standard input, and send replies on its
15749 standard output. You could use this to run a stand-alone simulator
15750 that speaks the remote debugging protocol, to make net connections
15751 using programs like @code{ssh}, or for other similar tricks.
15753 If @var{command} closes its standard output (perhaps by exiting),
15754 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15755 program has already exited, this will have no effect.)
15759 Once the connection has been established, you can use all the usual
15760 commands to examine and change data. The remote program is already
15761 running; you can use @kbd{step} and @kbd{continue}, and you do not
15762 need to use @kbd{run}.
15764 @cindex interrupting remote programs
15765 @cindex remote programs, interrupting
15766 Whenever @value{GDBN} is waiting for the remote program, if you type the
15767 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15768 program. This may or may not succeed, depending in part on the hardware
15769 and the serial drivers the remote system uses. If you type the
15770 interrupt character once again, @value{GDBN} displays this prompt:
15773 Interrupted while waiting for the program.
15774 Give up (and stop debugging it)? (y or n)
15777 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15778 (If you decide you want to try again later, you can use @samp{target
15779 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15780 goes back to waiting.
15783 @kindex detach (remote)
15785 When you have finished debugging the remote program, you can use the
15786 @code{detach} command to release it from @value{GDBN} control.
15787 Detaching from the target normally resumes its execution, but the results
15788 will depend on your particular remote stub. After the @code{detach}
15789 command, @value{GDBN} is free to connect to another target.
15793 The @code{disconnect} command behaves like @code{detach}, except that
15794 the target is generally not resumed. It will wait for @value{GDBN}
15795 (this instance or another one) to connect and continue debugging. After
15796 the @code{disconnect} command, @value{GDBN} is again free to connect to
15799 @cindex send command to remote monitor
15800 @cindex extend @value{GDBN} for remote targets
15801 @cindex add new commands for external monitor
15803 @item monitor @var{cmd}
15804 This command allows you to send arbitrary commands directly to the
15805 remote monitor. Since @value{GDBN} doesn't care about the commands it
15806 sends like this, this command is the way to extend @value{GDBN}---you
15807 can add new commands that only the external monitor will understand
15811 @node File Transfer
15812 @section Sending files to a remote system
15813 @cindex remote target, file transfer
15814 @cindex file transfer
15815 @cindex sending files to remote systems
15817 Some remote targets offer the ability to transfer files over the same
15818 connection used to communicate with @value{GDBN}. This is convenient
15819 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15820 running @code{gdbserver} over a network interface. For other targets,
15821 e.g.@: embedded devices with only a single serial port, this may be
15822 the only way to upload or download files.
15824 Not all remote targets support these commands.
15828 @item remote put @var{hostfile} @var{targetfile}
15829 Copy file @var{hostfile} from the host system (the machine running
15830 @value{GDBN}) to @var{targetfile} on the target system.
15833 @item remote get @var{targetfile} @var{hostfile}
15834 Copy file @var{targetfile} from the target system to @var{hostfile}
15835 on the host system.
15837 @kindex remote delete
15838 @item remote delete @var{targetfile}
15839 Delete @var{targetfile} from the target system.
15844 @section Using the @code{gdbserver} Program
15847 @cindex remote connection without stubs
15848 @code{gdbserver} is a control program for Unix-like systems, which
15849 allows you to connect your program with a remote @value{GDBN} via
15850 @code{target remote}---but without linking in the usual debugging stub.
15852 @code{gdbserver} is not a complete replacement for the debugging stubs,
15853 because it requires essentially the same operating-system facilities
15854 that @value{GDBN} itself does. In fact, a system that can run
15855 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15856 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15857 because it is a much smaller program than @value{GDBN} itself. It is
15858 also easier to port than all of @value{GDBN}, so you may be able to get
15859 started more quickly on a new system by using @code{gdbserver}.
15860 Finally, if you develop code for real-time systems, you may find that
15861 the tradeoffs involved in real-time operation make it more convenient to
15862 do as much development work as possible on another system, for example
15863 by cross-compiling. You can use @code{gdbserver} to make a similar
15864 choice for debugging.
15866 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15867 or a TCP connection, using the standard @value{GDBN} remote serial
15871 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15872 Do not run @code{gdbserver} connected to any public network; a
15873 @value{GDBN} connection to @code{gdbserver} provides access to the
15874 target system with the same privileges as the user running
15878 @subsection Running @code{gdbserver}
15879 @cindex arguments, to @code{gdbserver}
15881 Run @code{gdbserver} on the target system. You need a copy of the
15882 program you want to debug, including any libraries it requires.
15883 @code{gdbserver} does not need your program's symbol table, so you can
15884 strip the program if necessary to save space. @value{GDBN} on the host
15885 system does all the symbol handling.
15887 To use the server, you must tell it how to communicate with @value{GDBN};
15888 the name of your program; and the arguments for your program. The usual
15892 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15895 @var{comm} is either a device name (to use a serial line) or a TCP
15896 hostname and portnumber. For example, to debug Emacs with the argument
15897 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15901 target> gdbserver /dev/com1 emacs foo.txt
15904 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15907 To use a TCP connection instead of a serial line:
15910 target> gdbserver host:2345 emacs foo.txt
15913 The only difference from the previous example is the first argument,
15914 specifying that you are communicating with the host @value{GDBN} via
15915 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15916 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15917 (Currently, the @samp{host} part is ignored.) You can choose any number
15918 you want for the port number as long as it does not conflict with any
15919 TCP ports already in use on the target system (for example, @code{23} is
15920 reserved for @code{telnet}).@footnote{If you choose a port number that
15921 conflicts with another service, @code{gdbserver} prints an error message
15922 and exits.} You must use the same port number with the host @value{GDBN}
15923 @code{target remote} command.
15925 @subsubsection Attaching to a Running Program
15927 On some targets, @code{gdbserver} can also attach to running programs.
15928 This is accomplished via the @code{--attach} argument. The syntax is:
15931 target> gdbserver --attach @var{comm} @var{pid}
15934 @var{pid} is the process ID of a currently running process. It isn't necessary
15935 to point @code{gdbserver} at a binary for the running process.
15938 @cindex attach to a program by name
15939 You can debug processes by name instead of process ID if your target has the
15940 @code{pidof} utility:
15943 target> gdbserver --attach @var{comm} `pidof @var{program}`
15946 In case more than one copy of @var{program} is running, or @var{program}
15947 has multiple threads, most versions of @code{pidof} support the
15948 @code{-s} option to only return the first process ID.
15950 @subsubsection Multi-Process Mode for @code{gdbserver}
15951 @cindex gdbserver, multiple processes
15952 @cindex multiple processes with gdbserver
15954 When you connect to @code{gdbserver} using @code{target remote},
15955 @code{gdbserver} debugs the specified program only once. When the
15956 program exits, or you detach from it, @value{GDBN} closes the connection
15957 and @code{gdbserver} exits.
15959 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15960 enters multi-process mode. When the debugged program exits, or you
15961 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15962 though no program is running. The @code{run} and @code{attach}
15963 commands instruct @code{gdbserver} to run or attach to a new program.
15964 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15965 remote exec-file}) to select the program to run. Command line
15966 arguments are supported, except for wildcard expansion and I/O
15967 redirection (@pxref{Arguments}).
15969 To start @code{gdbserver} without supplying an initial command to run
15970 or process ID to attach, use the @option{--multi} command line option.
15971 Then you can connect using @kbd{target extended-remote} and start
15972 the program you want to debug.
15974 @code{gdbserver} does not automatically exit in multi-process mode.
15975 You can terminate it by using @code{monitor exit}
15976 (@pxref{Monitor Commands for gdbserver}).
15978 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15980 The @option{--debug} option tells @code{gdbserver} to display extra
15981 status information about the debugging process. The
15982 @option{--remote-debug} option tells @code{gdbserver} to display
15983 remote protocol debug output. These options are intended for
15984 @code{gdbserver} development and for bug reports to the developers.
15986 The @option{--wrapper} option specifies a wrapper to launch programs
15987 for debugging. The option should be followed by the name of the
15988 wrapper, then any command-line arguments to pass to the wrapper, then
15989 @kbd{--} indicating the end of the wrapper arguments.
15991 @code{gdbserver} runs the specified wrapper program with a combined
15992 command line including the wrapper arguments, then the name of the
15993 program to debug, then any arguments to the program. The wrapper
15994 runs until it executes your program, and then @value{GDBN} gains control.
15996 You can use any program that eventually calls @code{execve} with
15997 its arguments as a wrapper. Several standard Unix utilities do
15998 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15999 with @code{exec "$@@"} will also work.
16001 For example, you can use @code{env} to pass an environment variable to
16002 the debugged program, without setting the variable in @code{gdbserver}'s
16006 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16009 @subsection Connecting to @code{gdbserver}
16011 Run @value{GDBN} on the host system.
16013 First make sure you have the necessary symbol files. Load symbols for
16014 your application using the @code{file} command before you connect. Use
16015 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16016 was compiled with the correct sysroot using @code{--with-sysroot}).
16018 The symbol file and target libraries must exactly match the executable
16019 and libraries on the target, with one exception: the files on the host
16020 system should not be stripped, even if the files on the target system
16021 are. Mismatched or missing files will lead to confusing results
16022 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16023 files may also prevent @code{gdbserver} from debugging multi-threaded
16026 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16027 For TCP connections, you must start up @code{gdbserver} prior to using
16028 the @code{target remote} command. Otherwise you may get an error whose
16029 text depends on the host system, but which usually looks something like
16030 @samp{Connection refused}. Don't use the @code{load}
16031 command in @value{GDBN} when using @code{gdbserver}, since the program is
16032 already on the target.
16034 @subsection Monitor Commands for @code{gdbserver}
16035 @cindex monitor commands, for @code{gdbserver}
16036 @anchor{Monitor Commands for gdbserver}
16038 During a @value{GDBN} session using @code{gdbserver}, you can use the
16039 @code{monitor} command to send special requests to @code{gdbserver}.
16040 Here are the available commands.
16044 List the available monitor commands.
16046 @item monitor set debug 0
16047 @itemx monitor set debug 1
16048 Disable or enable general debugging messages.
16050 @item monitor set remote-debug 0
16051 @itemx monitor set remote-debug 1
16052 Disable or enable specific debugging messages associated with the remote
16053 protocol (@pxref{Remote Protocol}).
16055 @item monitor set libthread-db-search-path [PATH]
16056 @cindex gdbserver, search path for @code{libthread_db}
16057 When this command is issued, @var{path} is a colon-separated list of
16058 directories to search for @code{libthread_db} (@pxref{Threads,,set
16059 libthread-db-search-path}). If you omit @var{path},
16060 @samp{libthread-db-search-path} will be reset to an empty list.
16063 Tell gdbserver to exit immediately. This command should be followed by
16064 @code{disconnect} to close the debugging session. @code{gdbserver} will
16065 detach from any attached processes and kill any processes it created.
16066 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16067 of a multi-process mode debug session.
16071 @subsection Tracepoints support in @code{gdbserver}
16072 @cindex tracepoints support in @code{gdbserver}
16074 On some targets, @code{gdbserver} supports tracepoints, fast
16075 tracepoints and static tracepoints.
16077 For fast or static tracepoints to work, a special library called the
16078 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16079 This library is built and distributed as an integral part of
16080 @code{gdbserver}. In addition, support for static tracepoints
16081 requires building the in-process agent library with static tracepoints
16082 support. At present, the UST (LTTng Userspace Tracer,
16083 @url{http://lttng.org/ust}) tracing engine is supported. This support
16084 is automatically available if UST development headers are found in the
16085 standard include path when @code{gdbserver} is built, or if
16086 @code{gdbserver} was explicitly configured using @option{--with-ust}
16087 to point at such headers. You can explicitly disable the support
16088 using @option{--with-ust=no}.
16090 There are several ways to load the in-process agent in your program:
16093 @item Specifying it as dependency at link time
16095 You can link your program dynamically with the in-process agent
16096 library. On most systems, this is accomplished by adding
16097 @code{-linproctrace} to the link command.
16099 @item Using the system's preloading mechanisms
16101 You can force loading the in-process agent at startup time by using
16102 your system's support for preloading shared libraries. Many Unixes
16103 support the concept of preloading user defined libraries. In most
16104 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16105 in the environment. See also the description of @code{gdbserver}'s
16106 @option{--wrapper} command line option.
16108 @item Using @value{GDBN} to force loading the agent at run time
16110 On some systems, you can force the inferior to load a shared library,
16111 by calling a dynamic loader function in the inferior that takes care
16112 of dynamically looking up and loading a shared library. On most Unix
16113 systems, the function is @code{dlopen}. You'll use the @code{call}
16114 command for that. For example:
16117 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16120 Note that on most Unix systems, for the @code{dlopen} function to be
16121 available, the program needs to be linked with @code{-ldl}.
16124 On systems that have a userspace dynamic loader, like most Unix
16125 systems, when you connect to @code{gdbserver} using @code{target
16126 remote}, you'll find that the program is stopped at the dynamic
16127 loader's entry point, and no shared library has been loaded in the
16128 program's address space yet, including the in-process agent. In that
16129 case, before being able to use any of the fast or static tracepoints
16130 features, you need to let the loader run and load the shared
16131 libraries. The simplest way to do that is to run the program to the
16132 main procedure. E.g., if debugging a C or C@t{++} program, start
16133 @code{gdbserver} like so:
16136 $ gdbserver :9999 myprogram
16139 Start GDB and connect to @code{gdbserver} like so, and run to main:
16143 (@value{GDBP}) target remote myhost:9999
16144 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16145 (@value{GDBP}) b main
16146 (@value{GDBP}) continue
16149 The in-process tracing agent library should now be loaded into the
16150 process; you can confirm it with the @code{info sharedlibrary}
16151 command, which will list @file{libinproctrace.so} as loaded in the
16152 process. You are now ready to install fast tracepoints, list static
16153 tracepoint markers, probe static tracepoints markers, and start
16156 @node Remote Configuration
16157 @section Remote Configuration
16160 @kindex show remote
16161 This section documents the configuration options available when
16162 debugging remote programs. For the options related to the File I/O
16163 extensions of the remote protocol, see @ref{system,
16164 system-call-allowed}.
16167 @item set remoteaddresssize @var{bits}
16168 @cindex address size for remote targets
16169 @cindex bits in remote address
16170 Set the maximum size of address in a memory packet to the specified
16171 number of bits. @value{GDBN} will mask off the address bits above
16172 that number, when it passes addresses to the remote target. The
16173 default value is the number of bits in the target's address.
16175 @item show remoteaddresssize
16176 Show the current value of remote address size in bits.
16178 @item set remotebaud @var{n}
16179 @cindex baud rate for remote targets
16180 Set the baud rate for the remote serial I/O to @var{n} baud. The
16181 value is used to set the speed of the serial port used for debugging
16184 @item show remotebaud
16185 Show the current speed of the remote connection.
16187 @item set remotebreak
16188 @cindex interrupt remote programs
16189 @cindex BREAK signal instead of Ctrl-C
16190 @anchor{set remotebreak}
16191 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16192 when you type @kbd{Ctrl-c} to interrupt the program running
16193 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16194 character instead. The default is off, since most remote systems
16195 expect to see @samp{Ctrl-C} as the interrupt signal.
16197 @item show remotebreak
16198 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16199 interrupt the remote program.
16201 @item set remoteflow on
16202 @itemx set remoteflow off
16203 @kindex set remoteflow
16204 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16205 on the serial port used to communicate to the remote target.
16207 @item show remoteflow
16208 @kindex show remoteflow
16209 Show the current setting of hardware flow control.
16211 @item set remotelogbase @var{base}
16212 Set the base (a.k.a.@: radix) of logging serial protocol
16213 communications to @var{base}. Supported values of @var{base} are:
16214 @code{ascii}, @code{octal}, and @code{hex}. The default is
16217 @item show remotelogbase
16218 Show the current setting of the radix for logging remote serial
16221 @item set remotelogfile @var{file}
16222 @cindex record serial communications on file
16223 Record remote serial communications on the named @var{file}. The
16224 default is not to record at all.
16226 @item show remotelogfile.
16227 Show the current setting of the file name on which to record the
16228 serial communications.
16230 @item set remotetimeout @var{num}
16231 @cindex timeout for serial communications
16232 @cindex remote timeout
16233 Set the timeout limit to wait for the remote target to respond to
16234 @var{num} seconds. The default is 2 seconds.
16236 @item show remotetimeout
16237 Show the current number of seconds to wait for the remote target
16240 @cindex limit hardware breakpoints and watchpoints
16241 @cindex remote target, limit break- and watchpoints
16242 @anchor{set remote hardware-watchpoint-limit}
16243 @anchor{set remote hardware-breakpoint-limit}
16244 @item set remote hardware-watchpoint-limit @var{limit}
16245 @itemx set remote hardware-breakpoint-limit @var{limit}
16246 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16247 watchpoints. A limit of -1, the default, is treated as unlimited.
16249 @item set remote exec-file @var{filename}
16250 @itemx show remote exec-file
16251 @anchor{set remote exec-file}
16252 @cindex executable file, for remote target
16253 Select the file used for @code{run} with @code{target
16254 extended-remote}. This should be set to a filename valid on the
16255 target system. If it is not set, the target will use a default
16256 filename (e.g.@: the last program run).
16258 @item set remote interrupt-sequence
16259 @cindex interrupt remote programs
16260 @cindex select Ctrl-C, BREAK or BREAK-g
16261 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16262 @samp{BREAK-g} as the
16263 sequence to the remote target in order to interrupt the execution.
16264 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16265 is high level of serial line for some certain time.
16266 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16267 It is @code{BREAK} signal followed by character @code{g}.
16269 @item show interrupt-sequence
16270 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16271 is sent by @value{GDBN} to interrupt the remote program.
16272 @code{BREAK-g} is BREAK signal followed by @code{g} and
16273 also known as Magic SysRq g.
16275 @item set remote interrupt-on-connect
16276 @cindex send interrupt-sequence on start
16277 Specify whether interrupt-sequence is sent to remote target when
16278 @value{GDBN} connects to it. This is mostly needed when you debug
16279 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16280 which is known as Magic SysRq g in order to connect @value{GDBN}.
16282 @item show interrupt-on-connect
16283 Show whether interrupt-sequence is sent
16284 to remote target when @value{GDBN} connects to it.
16288 @item set tcp auto-retry on
16289 @cindex auto-retry, for remote TCP target
16290 Enable auto-retry for remote TCP connections. This is useful if the remote
16291 debugging agent is launched in parallel with @value{GDBN}; there is a race
16292 condition because the agent may not become ready to accept the connection
16293 before @value{GDBN} attempts to connect. When auto-retry is
16294 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16295 to establish the connection using the timeout specified by
16296 @code{set tcp connect-timeout}.
16298 @item set tcp auto-retry off
16299 Do not auto-retry failed TCP connections.
16301 @item show tcp auto-retry
16302 Show the current auto-retry setting.
16304 @item set tcp connect-timeout @var{seconds}
16305 @cindex connection timeout, for remote TCP target
16306 @cindex timeout, for remote target connection
16307 Set the timeout for establishing a TCP connection to the remote target to
16308 @var{seconds}. The timeout affects both polling to retry failed connections
16309 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16310 that are merely slow to complete, and represents an approximate cumulative
16313 @item show tcp connect-timeout
16314 Show the current connection timeout setting.
16317 @cindex remote packets, enabling and disabling
16318 The @value{GDBN} remote protocol autodetects the packets supported by
16319 your debugging stub. If you need to override the autodetection, you
16320 can use these commands to enable or disable individual packets. Each
16321 packet can be set to @samp{on} (the remote target supports this
16322 packet), @samp{off} (the remote target does not support this packet),
16323 or @samp{auto} (detect remote target support for this packet). They
16324 all default to @samp{auto}. For more information about each packet,
16325 see @ref{Remote Protocol}.
16327 During normal use, you should not have to use any of these commands.
16328 If you do, that may be a bug in your remote debugging stub, or a bug
16329 in @value{GDBN}. You may want to report the problem to the
16330 @value{GDBN} developers.
16332 For each packet @var{name}, the command to enable or disable the
16333 packet is @code{set remote @var{name}-packet}. The available settings
16336 @multitable @columnfractions 0.28 0.32 0.25
16339 @tab Related Features
16341 @item @code{fetch-register}
16343 @tab @code{info registers}
16345 @item @code{set-register}
16349 @item @code{binary-download}
16351 @tab @code{load}, @code{set}
16353 @item @code{read-aux-vector}
16354 @tab @code{qXfer:auxv:read}
16355 @tab @code{info auxv}
16357 @item @code{symbol-lookup}
16358 @tab @code{qSymbol}
16359 @tab Detecting multiple threads
16361 @item @code{attach}
16362 @tab @code{vAttach}
16365 @item @code{verbose-resume}
16367 @tab Stepping or resuming multiple threads
16373 @item @code{software-breakpoint}
16377 @item @code{hardware-breakpoint}
16381 @item @code{write-watchpoint}
16385 @item @code{read-watchpoint}
16389 @item @code{access-watchpoint}
16393 @item @code{target-features}
16394 @tab @code{qXfer:features:read}
16395 @tab @code{set architecture}
16397 @item @code{library-info}
16398 @tab @code{qXfer:libraries:read}
16399 @tab @code{info sharedlibrary}
16401 @item @code{memory-map}
16402 @tab @code{qXfer:memory-map:read}
16403 @tab @code{info mem}
16405 @item @code{read-sdata-object}
16406 @tab @code{qXfer:sdata:read}
16407 @tab @code{print $_sdata}
16409 @item @code{read-spu-object}
16410 @tab @code{qXfer:spu:read}
16411 @tab @code{info spu}
16413 @item @code{write-spu-object}
16414 @tab @code{qXfer:spu:write}
16415 @tab @code{info spu}
16417 @item @code{read-siginfo-object}
16418 @tab @code{qXfer:siginfo:read}
16419 @tab @code{print $_siginfo}
16421 @item @code{write-siginfo-object}
16422 @tab @code{qXfer:siginfo:write}
16423 @tab @code{set $_siginfo}
16425 @item @code{threads}
16426 @tab @code{qXfer:threads:read}
16427 @tab @code{info threads}
16429 @item @code{get-thread-local-@*storage-address}
16430 @tab @code{qGetTLSAddr}
16431 @tab Displaying @code{__thread} variables
16433 @item @code{get-thread-information-block-address}
16434 @tab @code{qGetTIBAddr}
16435 @tab Display MS-Windows Thread Information Block.
16437 @item @code{search-memory}
16438 @tab @code{qSearch:memory}
16441 @item @code{supported-packets}
16442 @tab @code{qSupported}
16443 @tab Remote communications parameters
16445 @item @code{pass-signals}
16446 @tab @code{QPassSignals}
16447 @tab @code{handle @var{signal}}
16449 @item @code{hostio-close-packet}
16450 @tab @code{vFile:close}
16451 @tab @code{remote get}, @code{remote put}
16453 @item @code{hostio-open-packet}
16454 @tab @code{vFile:open}
16455 @tab @code{remote get}, @code{remote put}
16457 @item @code{hostio-pread-packet}
16458 @tab @code{vFile:pread}
16459 @tab @code{remote get}, @code{remote put}
16461 @item @code{hostio-pwrite-packet}
16462 @tab @code{vFile:pwrite}
16463 @tab @code{remote get}, @code{remote put}
16465 @item @code{hostio-unlink-packet}
16466 @tab @code{vFile:unlink}
16467 @tab @code{remote delete}
16469 @item @code{noack-packet}
16470 @tab @code{QStartNoAckMode}
16471 @tab Packet acknowledgment
16473 @item @code{osdata}
16474 @tab @code{qXfer:osdata:read}
16475 @tab @code{info os}
16477 @item @code{query-attached}
16478 @tab @code{qAttached}
16479 @tab Querying remote process attach state.
16483 @section Implementing a Remote Stub
16485 @cindex debugging stub, example
16486 @cindex remote stub, example
16487 @cindex stub example, remote debugging
16488 The stub files provided with @value{GDBN} implement the target side of the
16489 communication protocol, and the @value{GDBN} side is implemented in the
16490 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16491 these subroutines to communicate, and ignore the details. (If you're
16492 implementing your own stub file, you can still ignore the details: start
16493 with one of the existing stub files. @file{sparc-stub.c} is the best
16494 organized, and therefore the easiest to read.)
16496 @cindex remote serial debugging, overview
16497 To debug a program running on another machine (the debugging
16498 @dfn{target} machine), you must first arrange for all the usual
16499 prerequisites for the program to run by itself. For example, for a C
16504 A startup routine to set up the C runtime environment; these usually
16505 have a name like @file{crt0}. The startup routine may be supplied by
16506 your hardware supplier, or you may have to write your own.
16509 A C subroutine library to support your program's
16510 subroutine calls, notably managing input and output.
16513 A way of getting your program to the other machine---for example, a
16514 download program. These are often supplied by the hardware
16515 manufacturer, but you may have to write your own from hardware
16519 The next step is to arrange for your program to use a serial port to
16520 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16521 machine). In general terms, the scheme looks like this:
16525 @value{GDBN} already understands how to use this protocol; when everything
16526 else is set up, you can simply use the @samp{target remote} command
16527 (@pxref{Targets,,Specifying a Debugging Target}).
16529 @item On the target,
16530 you must link with your program a few special-purpose subroutines that
16531 implement the @value{GDBN} remote serial protocol. The file containing these
16532 subroutines is called a @dfn{debugging stub}.
16534 On certain remote targets, you can use an auxiliary program
16535 @code{gdbserver} instead of linking a stub into your program.
16536 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16539 The debugging stub is specific to the architecture of the remote
16540 machine; for example, use @file{sparc-stub.c} to debug programs on
16543 @cindex remote serial stub list
16544 These working remote stubs are distributed with @value{GDBN}:
16549 @cindex @file{i386-stub.c}
16552 For Intel 386 and compatible architectures.
16555 @cindex @file{m68k-stub.c}
16556 @cindex Motorola 680x0
16558 For Motorola 680x0 architectures.
16561 @cindex @file{sh-stub.c}
16564 For Renesas SH architectures.
16567 @cindex @file{sparc-stub.c}
16569 For @sc{sparc} architectures.
16571 @item sparcl-stub.c
16572 @cindex @file{sparcl-stub.c}
16575 For Fujitsu @sc{sparclite} architectures.
16579 The @file{README} file in the @value{GDBN} distribution may list other
16580 recently added stubs.
16583 * Stub Contents:: What the stub can do for you
16584 * Bootstrapping:: What you must do for the stub
16585 * Debug Session:: Putting it all together
16588 @node Stub Contents
16589 @subsection What the Stub Can Do for You
16591 @cindex remote serial stub
16592 The debugging stub for your architecture supplies these three
16596 @item set_debug_traps
16597 @findex set_debug_traps
16598 @cindex remote serial stub, initialization
16599 This routine arranges for @code{handle_exception} to run when your
16600 program stops. You must call this subroutine explicitly near the
16601 beginning of your program.
16603 @item handle_exception
16604 @findex handle_exception
16605 @cindex remote serial stub, main routine
16606 This is the central workhorse, but your program never calls it
16607 explicitly---the setup code arranges for @code{handle_exception} to
16608 run when a trap is triggered.
16610 @code{handle_exception} takes control when your program stops during
16611 execution (for example, on a breakpoint), and mediates communications
16612 with @value{GDBN} on the host machine. This is where the communications
16613 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16614 representative on the target machine. It begins by sending summary
16615 information on the state of your program, then continues to execute,
16616 retrieving and transmitting any information @value{GDBN} needs, until you
16617 execute a @value{GDBN} command that makes your program resume; at that point,
16618 @code{handle_exception} returns control to your own code on the target
16622 @cindex @code{breakpoint} subroutine, remote
16623 Use this auxiliary subroutine to make your program contain a
16624 breakpoint. Depending on the particular situation, this may be the only
16625 way for @value{GDBN} to get control. For instance, if your target
16626 machine has some sort of interrupt button, you won't need to call this;
16627 pressing the interrupt button transfers control to
16628 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16629 simply receiving characters on the serial port may also trigger a trap;
16630 again, in that situation, you don't need to call @code{breakpoint} from
16631 your own program---simply running @samp{target remote} from the host
16632 @value{GDBN} session gets control.
16634 Call @code{breakpoint} if none of these is true, or if you simply want
16635 to make certain your program stops at a predetermined point for the
16636 start of your debugging session.
16639 @node Bootstrapping
16640 @subsection What You Must Do for the Stub
16642 @cindex remote stub, support routines
16643 The debugging stubs that come with @value{GDBN} are set up for a particular
16644 chip architecture, but they have no information about the rest of your
16645 debugging target machine.
16647 First of all you need to tell the stub how to communicate with the
16651 @item int getDebugChar()
16652 @findex getDebugChar
16653 Write this subroutine to read a single character from the serial port.
16654 It may be identical to @code{getchar} for your target system; a
16655 different name is used to allow you to distinguish the two if you wish.
16657 @item void putDebugChar(int)
16658 @findex putDebugChar
16659 Write this subroutine to write a single character to the serial port.
16660 It may be identical to @code{putchar} for your target system; a
16661 different name is used to allow you to distinguish the two if you wish.
16664 @cindex control C, and remote debugging
16665 @cindex interrupting remote targets
16666 If you want @value{GDBN} to be able to stop your program while it is
16667 running, you need to use an interrupt-driven serial driver, and arrange
16668 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16669 character). That is the character which @value{GDBN} uses to tell the
16670 remote system to stop.
16672 Getting the debugging target to return the proper status to @value{GDBN}
16673 probably requires changes to the standard stub; one quick and dirty way
16674 is to just execute a breakpoint instruction (the ``dirty'' part is that
16675 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16677 Other routines you need to supply are:
16680 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16681 @findex exceptionHandler
16682 Write this function to install @var{exception_address} in the exception
16683 handling tables. You need to do this because the stub does not have any
16684 way of knowing what the exception handling tables on your target system
16685 are like (for example, the processor's table might be in @sc{rom},
16686 containing entries which point to a table in @sc{ram}).
16687 @var{exception_number} is the exception number which should be changed;
16688 its meaning is architecture-dependent (for example, different numbers
16689 might represent divide by zero, misaligned access, etc). When this
16690 exception occurs, control should be transferred directly to
16691 @var{exception_address}, and the processor state (stack, registers,
16692 and so on) should be just as it is when a processor exception occurs. So if
16693 you want to use a jump instruction to reach @var{exception_address}, it
16694 should be a simple jump, not a jump to subroutine.
16696 For the 386, @var{exception_address} should be installed as an interrupt
16697 gate so that interrupts are masked while the handler runs. The gate
16698 should be at privilege level 0 (the most privileged level). The
16699 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16700 help from @code{exceptionHandler}.
16702 @item void flush_i_cache()
16703 @findex flush_i_cache
16704 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16705 instruction cache, if any, on your target machine. If there is no
16706 instruction cache, this subroutine may be a no-op.
16708 On target machines that have instruction caches, @value{GDBN} requires this
16709 function to make certain that the state of your program is stable.
16713 You must also make sure this library routine is available:
16716 @item void *memset(void *, int, int)
16718 This is the standard library function @code{memset} that sets an area of
16719 memory to a known value. If you have one of the free versions of
16720 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16721 either obtain it from your hardware manufacturer, or write your own.
16724 If you do not use the GNU C compiler, you may need other standard
16725 library subroutines as well; this varies from one stub to another,
16726 but in general the stubs are likely to use any of the common library
16727 subroutines which @code{@value{NGCC}} generates as inline code.
16730 @node Debug Session
16731 @subsection Putting it All Together
16733 @cindex remote serial debugging summary
16734 In summary, when your program is ready to debug, you must follow these
16739 Make sure you have defined the supporting low-level routines
16740 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16742 @code{getDebugChar}, @code{putDebugChar},
16743 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16747 Insert these lines near the top of your program:
16755 For the 680x0 stub only, you need to provide a variable called
16756 @code{exceptionHook}. Normally you just use:
16759 void (*exceptionHook)() = 0;
16763 but if before calling @code{set_debug_traps}, you set it to point to a
16764 function in your program, that function is called when
16765 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16766 error). The function indicated by @code{exceptionHook} is called with
16767 one parameter: an @code{int} which is the exception number.
16770 Compile and link together: your program, the @value{GDBN} debugging stub for
16771 your target architecture, and the supporting subroutines.
16774 Make sure you have a serial connection between your target machine and
16775 the @value{GDBN} host, and identify the serial port on the host.
16778 @c The "remote" target now provides a `load' command, so we should
16779 @c document that. FIXME.
16780 Download your program to your target machine (or get it there by
16781 whatever means the manufacturer provides), and start it.
16784 Start @value{GDBN} on the host, and connect to the target
16785 (@pxref{Connecting,,Connecting to a Remote Target}).
16789 @node Configurations
16790 @chapter Configuration-Specific Information
16792 While nearly all @value{GDBN} commands are available for all native and
16793 cross versions of the debugger, there are some exceptions. This chapter
16794 describes things that are only available in certain configurations.
16796 There are three major categories of configurations: native
16797 configurations, where the host and target are the same, embedded
16798 operating system configurations, which are usually the same for several
16799 different processor architectures, and bare embedded processors, which
16800 are quite different from each other.
16805 * Embedded Processors::
16812 This section describes details specific to particular native
16817 * BSD libkvm Interface:: Debugging BSD kernel memory images
16818 * SVR4 Process Information:: SVR4 process information
16819 * DJGPP Native:: Features specific to the DJGPP port
16820 * Cygwin Native:: Features specific to the Cygwin port
16821 * Hurd Native:: Features specific to @sc{gnu} Hurd
16822 * Neutrino:: Features specific to QNX Neutrino
16823 * Darwin:: Features specific to Darwin
16829 On HP-UX systems, if you refer to a function or variable name that
16830 begins with a dollar sign, @value{GDBN} searches for a user or system
16831 name first, before it searches for a convenience variable.
16834 @node BSD libkvm Interface
16835 @subsection BSD libkvm Interface
16838 @cindex kernel memory image
16839 @cindex kernel crash dump
16841 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16842 interface that provides a uniform interface for accessing kernel virtual
16843 memory images, including live systems and crash dumps. @value{GDBN}
16844 uses this interface to allow you to debug live kernels and kernel crash
16845 dumps on many native BSD configurations. This is implemented as a
16846 special @code{kvm} debugging target. For debugging a live system, load
16847 the currently running kernel into @value{GDBN} and connect to the
16851 (@value{GDBP}) @b{target kvm}
16854 For debugging crash dumps, provide the file name of the crash dump as an
16858 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16861 Once connected to the @code{kvm} target, the following commands are
16867 Set current context from the @dfn{Process Control Block} (PCB) address.
16870 Set current context from proc address. This command isn't available on
16871 modern FreeBSD systems.
16874 @node SVR4 Process Information
16875 @subsection SVR4 Process Information
16877 @cindex examine process image
16878 @cindex process info via @file{/proc}
16880 Many versions of SVR4 and compatible systems provide a facility called
16881 @samp{/proc} that can be used to examine the image of a running
16882 process using file-system subroutines. If @value{GDBN} is configured
16883 for an operating system with this facility, the command @code{info
16884 proc} is available to report information about the process running
16885 your program, or about any process running on your system. @code{info
16886 proc} works only on SVR4 systems that include the @code{procfs} code.
16887 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16888 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16894 @itemx info proc @var{process-id}
16895 Summarize available information about any running process. If a
16896 process ID is specified by @var{process-id}, display information about
16897 that process; otherwise display information about the program being
16898 debugged. The summary includes the debugged process ID, the command
16899 line used to invoke it, its current working directory, and its
16900 executable file's absolute file name.
16902 On some systems, @var{process-id} can be of the form
16903 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16904 within a process. If the optional @var{pid} part is missing, it means
16905 a thread from the process being debugged (the leading @samp{/} still
16906 needs to be present, or else @value{GDBN} will interpret the number as
16907 a process ID rather than a thread ID).
16909 @item info proc mappings
16910 @cindex memory address space mappings
16911 Report the memory address space ranges accessible in the program, with
16912 information on whether the process has read, write, or execute access
16913 rights to each range. On @sc{gnu}/Linux systems, each memory range
16914 includes the object file which is mapped to that range, instead of the
16915 memory access rights to that range.
16917 @item info proc stat
16918 @itemx info proc status
16919 @cindex process detailed status information
16920 These subcommands are specific to @sc{gnu}/Linux systems. They show
16921 the process-related information, including the user ID and group ID;
16922 how many threads are there in the process; its virtual memory usage;
16923 the signals that are pending, blocked, and ignored; its TTY; its
16924 consumption of system and user time; its stack size; its @samp{nice}
16925 value; etc. For more information, see the @samp{proc} man page
16926 (type @kbd{man 5 proc} from your shell prompt).
16928 @item info proc all
16929 Show all the information about the process described under all of the
16930 above @code{info proc} subcommands.
16933 @comment These sub-options of 'info proc' were not included when
16934 @comment procfs.c was re-written. Keep their descriptions around
16935 @comment against the day when someone finds the time to put them back in.
16936 @kindex info proc times
16937 @item info proc times
16938 Starting time, user CPU time, and system CPU time for your program and
16941 @kindex info proc id
16943 Report on the process IDs related to your program: its own process ID,
16944 the ID of its parent, the process group ID, and the session ID.
16947 @item set procfs-trace
16948 @kindex set procfs-trace
16949 @cindex @code{procfs} API calls
16950 This command enables and disables tracing of @code{procfs} API calls.
16952 @item show procfs-trace
16953 @kindex show procfs-trace
16954 Show the current state of @code{procfs} API call tracing.
16956 @item set procfs-file @var{file}
16957 @kindex set procfs-file
16958 Tell @value{GDBN} to write @code{procfs} API trace to the named
16959 @var{file}. @value{GDBN} appends the trace info to the previous
16960 contents of the file. The default is to display the trace on the
16963 @item show procfs-file
16964 @kindex show procfs-file
16965 Show the file to which @code{procfs} API trace is written.
16967 @item proc-trace-entry
16968 @itemx proc-trace-exit
16969 @itemx proc-untrace-entry
16970 @itemx proc-untrace-exit
16971 @kindex proc-trace-entry
16972 @kindex proc-trace-exit
16973 @kindex proc-untrace-entry
16974 @kindex proc-untrace-exit
16975 These commands enable and disable tracing of entries into and exits
16976 from the @code{syscall} interface.
16979 @kindex info pidlist
16980 @cindex process list, QNX Neutrino
16981 For QNX Neutrino only, this command displays the list of all the
16982 processes and all the threads within each process.
16985 @kindex info meminfo
16986 @cindex mapinfo list, QNX Neutrino
16987 For QNX Neutrino only, this command displays the list of all mapinfos.
16991 @subsection Features for Debugging @sc{djgpp} Programs
16992 @cindex @sc{djgpp} debugging
16993 @cindex native @sc{djgpp} debugging
16994 @cindex MS-DOS-specific commands
16997 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16998 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16999 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17000 top of real-mode DOS systems and their emulations.
17002 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17003 defines a few commands specific to the @sc{djgpp} port. This
17004 subsection describes those commands.
17009 This is a prefix of @sc{djgpp}-specific commands which print
17010 information about the target system and important OS structures.
17013 @cindex MS-DOS system info
17014 @cindex free memory information (MS-DOS)
17015 @item info dos sysinfo
17016 This command displays assorted information about the underlying
17017 platform: the CPU type and features, the OS version and flavor, the
17018 DPMI version, and the available conventional and DPMI memory.
17023 @cindex segment descriptor tables
17024 @cindex descriptor tables display
17026 @itemx info dos ldt
17027 @itemx info dos idt
17028 These 3 commands display entries from, respectively, Global, Local,
17029 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17030 tables are data structures which store a descriptor for each segment
17031 that is currently in use. The segment's selector is an index into a
17032 descriptor table; the table entry for that index holds the
17033 descriptor's base address and limit, and its attributes and access
17036 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17037 segment (used for both data and the stack), and a DOS segment (which
17038 allows access to DOS/BIOS data structures and absolute addresses in
17039 conventional memory). However, the DPMI host will usually define
17040 additional segments in order to support the DPMI environment.
17042 @cindex garbled pointers
17043 These commands allow to display entries from the descriptor tables.
17044 Without an argument, all entries from the specified table are
17045 displayed. An argument, which should be an integer expression, means
17046 display a single entry whose index is given by the argument. For
17047 example, here's a convenient way to display information about the
17048 debugged program's data segment:
17051 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17052 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17056 This comes in handy when you want to see whether a pointer is outside
17057 the data segment's limit (i.e.@: @dfn{garbled}).
17059 @cindex page tables display (MS-DOS)
17061 @itemx info dos pte
17062 These two commands display entries from, respectively, the Page
17063 Directory and the Page Tables. Page Directories and Page Tables are
17064 data structures which control how virtual memory addresses are mapped
17065 into physical addresses. A Page Table includes an entry for every
17066 page of memory that is mapped into the program's address space; there
17067 may be several Page Tables, each one holding up to 4096 entries. A
17068 Page Directory has up to 4096 entries, one each for every Page Table
17069 that is currently in use.
17071 Without an argument, @kbd{info dos pde} displays the entire Page
17072 Directory, and @kbd{info dos pte} displays all the entries in all of
17073 the Page Tables. An argument, an integer expression, given to the
17074 @kbd{info dos pde} command means display only that entry from the Page
17075 Directory table. An argument given to the @kbd{info dos pte} command
17076 means display entries from a single Page Table, the one pointed to by
17077 the specified entry in the Page Directory.
17079 @cindex direct memory access (DMA) on MS-DOS
17080 These commands are useful when your program uses @dfn{DMA} (Direct
17081 Memory Access), which needs physical addresses to program the DMA
17084 These commands are supported only with some DPMI servers.
17086 @cindex physical address from linear address
17087 @item info dos address-pte @var{addr}
17088 This command displays the Page Table entry for a specified linear
17089 address. The argument @var{addr} is a linear address which should
17090 already have the appropriate segment's base address added to it,
17091 because this command accepts addresses which may belong to @emph{any}
17092 segment. For example, here's how to display the Page Table entry for
17093 the page where a variable @code{i} is stored:
17096 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17097 @exdent @code{Page Table entry for address 0x11a00d30:}
17098 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17102 This says that @code{i} is stored at offset @code{0xd30} from the page
17103 whose physical base address is @code{0x02698000}, and shows all the
17104 attributes of that page.
17106 Note that you must cast the addresses of variables to a @code{char *},
17107 since otherwise the value of @code{__djgpp_base_address}, the base
17108 address of all variables and functions in a @sc{djgpp} program, will
17109 be added using the rules of C pointer arithmetics: if @code{i} is
17110 declared an @code{int}, @value{GDBN} will add 4 times the value of
17111 @code{__djgpp_base_address} to the address of @code{i}.
17113 Here's another example, it displays the Page Table entry for the
17117 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17118 @exdent @code{Page Table entry for address 0x29110:}
17119 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17123 (The @code{+ 3} offset is because the transfer buffer's address is the
17124 3rd member of the @code{_go32_info_block} structure.) The output
17125 clearly shows that this DPMI server maps the addresses in conventional
17126 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17127 linear (@code{0x29110}) addresses are identical.
17129 This command is supported only with some DPMI servers.
17132 @cindex DOS serial data link, remote debugging
17133 In addition to native debugging, the DJGPP port supports remote
17134 debugging via a serial data link. The following commands are specific
17135 to remote serial debugging in the DJGPP port of @value{GDBN}.
17138 @kindex set com1base
17139 @kindex set com1irq
17140 @kindex set com2base
17141 @kindex set com2irq
17142 @kindex set com3base
17143 @kindex set com3irq
17144 @kindex set com4base
17145 @kindex set com4irq
17146 @item set com1base @var{addr}
17147 This command sets the base I/O port address of the @file{COM1} serial
17150 @item set com1irq @var{irq}
17151 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17152 for the @file{COM1} serial port.
17154 There are similar commands @samp{set com2base}, @samp{set com3irq},
17155 etc.@: for setting the port address and the @code{IRQ} lines for the
17158 @kindex show com1base
17159 @kindex show com1irq
17160 @kindex show com2base
17161 @kindex show com2irq
17162 @kindex show com3base
17163 @kindex show com3irq
17164 @kindex show com4base
17165 @kindex show com4irq
17166 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17167 display the current settings of the base address and the @code{IRQ}
17168 lines used by the COM ports.
17171 @kindex info serial
17172 @cindex DOS serial port status
17173 This command prints the status of the 4 DOS serial ports. For each
17174 port, it prints whether it's active or not, its I/O base address and
17175 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17176 counts of various errors encountered so far.
17180 @node Cygwin Native
17181 @subsection Features for Debugging MS Windows PE Executables
17182 @cindex MS Windows debugging
17183 @cindex native Cygwin debugging
17184 @cindex Cygwin-specific commands
17186 @value{GDBN} supports native debugging of MS Windows programs, including
17187 DLLs with and without symbolic debugging information.
17189 @cindex Ctrl-BREAK, MS-Windows
17190 @cindex interrupt debuggee on MS-Windows
17191 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17192 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17193 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17194 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17195 sequence, which can be used to interrupt the debuggee even if it
17198 There are various additional Cygwin-specific commands, described in
17199 this section. Working with DLLs that have no debugging symbols is
17200 described in @ref{Non-debug DLL Symbols}.
17205 This is a prefix of MS Windows-specific commands which print
17206 information about the target system and important OS structures.
17208 @item info w32 selector
17209 This command displays information returned by
17210 the Win32 API @code{GetThreadSelectorEntry} function.
17211 It takes an optional argument that is evaluated to
17212 a long value to give the information about this given selector.
17213 Without argument, this command displays information
17214 about the six segment registers.
17216 @item info w32 thread-information-block
17217 This command displays thread specific information stored in the
17218 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17219 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17223 This is a Cygwin-specific alias of @code{info shared}.
17225 @kindex dll-symbols
17227 This command loads symbols from a dll similarly to
17228 add-sym command but without the need to specify a base address.
17230 @kindex set cygwin-exceptions
17231 @cindex debugging the Cygwin DLL
17232 @cindex Cygwin DLL, debugging
17233 @item set cygwin-exceptions @var{mode}
17234 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17235 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17236 @value{GDBN} will delay recognition of exceptions, and may ignore some
17237 exceptions which seem to be caused by internal Cygwin DLL
17238 ``bookkeeping''. This option is meant primarily for debugging the
17239 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17240 @value{GDBN} users with false @code{SIGSEGV} signals.
17242 @kindex show cygwin-exceptions
17243 @item show cygwin-exceptions
17244 Displays whether @value{GDBN} will break on exceptions that happen
17245 inside the Cygwin DLL itself.
17247 @kindex set new-console
17248 @item set new-console @var{mode}
17249 If @var{mode} is @code{on} the debuggee will
17250 be started in a new console on next start.
17251 If @var{mode} is @code{off}, the debuggee will
17252 be started in the same console as the debugger.
17254 @kindex show new-console
17255 @item show new-console
17256 Displays whether a new console is used
17257 when the debuggee is started.
17259 @kindex set new-group
17260 @item set new-group @var{mode}
17261 This boolean value controls whether the debuggee should
17262 start a new group or stay in the same group as the debugger.
17263 This affects the way the Windows OS handles
17266 @kindex show new-group
17267 @item show new-group
17268 Displays current value of new-group boolean.
17270 @kindex set debugevents
17271 @item set debugevents
17272 This boolean value adds debug output concerning kernel events related
17273 to the debuggee seen by the debugger. This includes events that
17274 signal thread and process creation and exit, DLL loading and
17275 unloading, console interrupts, and debugging messages produced by the
17276 Windows @code{OutputDebugString} API call.
17278 @kindex set debugexec
17279 @item set debugexec
17280 This boolean value adds debug output concerning execute events
17281 (such as resume thread) seen by the debugger.
17283 @kindex set debugexceptions
17284 @item set debugexceptions
17285 This boolean value adds debug output concerning exceptions in the
17286 debuggee seen by the debugger.
17288 @kindex set debugmemory
17289 @item set debugmemory
17290 This boolean value adds debug output concerning debuggee memory reads
17291 and writes by the debugger.
17295 This boolean values specifies whether the debuggee is called
17296 via a shell or directly (default value is on).
17300 Displays if the debuggee will be started with a shell.
17305 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17308 @node Non-debug DLL Symbols
17309 @subsubsection Support for DLLs without Debugging Symbols
17310 @cindex DLLs with no debugging symbols
17311 @cindex Minimal symbols and DLLs
17313 Very often on windows, some of the DLLs that your program relies on do
17314 not include symbolic debugging information (for example,
17315 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17316 symbols in a DLL, it relies on the minimal amount of symbolic
17317 information contained in the DLL's export table. This section
17318 describes working with such symbols, known internally to @value{GDBN} as
17319 ``minimal symbols''.
17321 Note that before the debugged program has started execution, no DLLs
17322 will have been loaded. The easiest way around this problem is simply to
17323 start the program --- either by setting a breakpoint or letting the
17324 program run once to completion. It is also possible to force
17325 @value{GDBN} to load a particular DLL before starting the executable ---
17326 see the shared library information in @ref{Files}, or the
17327 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17328 explicitly loading symbols from a DLL with no debugging information will
17329 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17330 which may adversely affect symbol lookup performance.
17332 @subsubsection DLL Name Prefixes
17334 In keeping with the naming conventions used by the Microsoft debugging
17335 tools, DLL export symbols are made available with a prefix based on the
17336 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17337 also entered into the symbol table, so @code{CreateFileA} is often
17338 sufficient. In some cases there will be name clashes within a program
17339 (particularly if the executable itself includes full debugging symbols)
17340 necessitating the use of the fully qualified name when referring to the
17341 contents of the DLL. Use single-quotes around the name to avoid the
17342 exclamation mark (``!'') being interpreted as a language operator.
17344 Note that the internal name of the DLL may be all upper-case, even
17345 though the file name of the DLL is lower-case, or vice-versa. Since
17346 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17347 some confusion. If in doubt, try the @code{info functions} and
17348 @code{info variables} commands or even @code{maint print msymbols}
17349 (@pxref{Symbols}). Here's an example:
17352 (@value{GDBP}) info function CreateFileA
17353 All functions matching regular expression "CreateFileA":
17355 Non-debugging symbols:
17356 0x77e885f4 CreateFileA
17357 0x77e885f4 KERNEL32!CreateFileA
17361 (@value{GDBP}) info function !
17362 All functions matching regular expression "!":
17364 Non-debugging symbols:
17365 0x6100114c cygwin1!__assert
17366 0x61004034 cygwin1!_dll_crt0@@0
17367 0x61004240 cygwin1!dll_crt0(per_process *)
17371 @subsubsection Working with Minimal Symbols
17373 Symbols extracted from a DLL's export table do not contain very much
17374 type information. All that @value{GDBN} can do is guess whether a symbol
17375 refers to a function or variable depending on the linker section that
17376 contains the symbol. Also note that the actual contents of the memory
17377 contained in a DLL are not available unless the program is running. This
17378 means that you cannot examine the contents of a variable or disassemble
17379 a function within a DLL without a running program.
17381 Variables are generally treated as pointers and dereferenced
17382 automatically. For this reason, it is often necessary to prefix a
17383 variable name with the address-of operator (``&'') and provide explicit
17384 type information in the command. Here's an example of the type of
17388 (@value{GDBP}) print 'cygwin1!__argv'
17393 (@value{GDBP}) x 'cygwin1!__argv'
17394 0x10021610: "\230y\""
17397 And two possible solutions:
17400 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17401 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17405 (@value{GDBP}) x/2x &'cygwin1!__argv'
17406 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17407 (@value{GDBP}) x/x 0x10021608
17408 0x10021608: 0x0022fd98
17409 (@value{GDBP}) x/s 0x0022fd98
17410 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17413 Setting a break point within a DLL is possible even before the program
17414 starts execution. However, under these circumstances, @value{GDBN} can't
17415 examine the initial instructions of the function in order to skip the
17416 function's frame set-up code. You can work around this by using ``*&''
17417 to set the breakpoint at a raw memory address:
17420 (@value{GDBP}) break *&'python22!PyOS_Readline'
17421 Breakpoint 1 at 0x1e04eff0
17424 The author of these extensions is not entirely convinced that setting a
17425 break point within a shared DLL like @file{kernel32.dll} is completely
17429 @subsection Commands Specific to @sc{gnu} Hurd Systems
17430 @cindex @sc{gnu} Hurd debugging
17432 This subsection describes @value{GDBN} commands specific to the
17433 @sc{gnu} Hurd native debugging.
17438 @kindex set signals@r{, Hurd command}
17439 @kindex set sigs@r{, Hurd command}
17440 This command toggles the state of inferior signal interception by
17441 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17442 affected by this command. @code{sigs} is a shorthand alias for
17447 @kindex show signals@r{, Hurd command}
17448 @kindex show sigs@r{, Hurd command}
17449 Show the current state of intercepting inferior's signals.
17451 @item set signal-thread
17452 @itemx set sigthread
17453 @kindex set signal-thread
17454 @kindex set sigthread
17455 This command tells @value{GDBN} which thread is the @code{libc} signal
17456 thread. That thread is run when a signal is delivered to a running
17457 process. @code{set sigthread} is the shorthand alias of @code{set
17460 @item show signal-thread
17461 @itemx show sigthread
17462 @kindex show signal-thread
17463 @kindex show sigthread
17464 These two commands show which thread will run when the inferior is
17465 delivered a signal.
17468 @kindex set stopped@r{, Hurd command}
17469 This commands tells @value{GDBN} that the inferior process is stopped,
17470 as with the @code{SIGSTOP} signal. The stopped process can be
17471 continued by delivering a signal to it.
17474 @kindex show stopped@r{, Hurd command}
17475 This command shows whether @value{GDBN} thinks the debuggee is
17478 @item set exceptions
17479 @kindex set exceptions@r{, Hurd command}
17480 Use this command to turn off trapping of exceptions in the inferior.
17481 When exception trapping is off, neither breakpoints nor
17482 single-stepping will work. To restore the default, set exception
17485 @item show exceptions
17486 @kindex show exceptions@r{, Hurd command}
17487 Show the current state of trapping exceptions in the inferior.
17489 @item set task pause
17490 @kindex set task@r{, Hurd commands}
17491 @cindex task attributes (@sc{gnu} Hurd)
17492 @cindex pause current task (@sc{gnu} Hurd)
17493 This command toggles task suspension when @value{GDBN} has control.
17494 Setting it to on takes effect immediately, and the task is suspended
17495 whenever @value{GDBN} gets control. Setting it to off will take
17496 effect the next time the inferior is continued. If this option is set
17497 to off, you can use @code{set thread default pause on} or @code{set
17498 thread pause on} (see below) to pause individual threads.
17500 @item show task pause
17501 @kindex show task@r{, Hurd commands}
17502 Show the current state of task suspension.
17504 @item set task detach-suspend-count
17505 @cindex task suspend count
17506 @cindex detach from task, @sc{gnu} Hurd
17507 This command sets the suspend count the task will be left with when
17508 @value{GDBN} detaches from it.
17510 @item show task detach-suspend-count
17511 Show the suspend count the task will be left with when detaching.
17513 @item set task exception-port
17514 @itemx set task excp
17515 @cindex task exception port, @sc{gnu} Hurd
17516 This command sets the task exception port to which @value{GDBN} will
17517 forward exceptions. The argument should be the value of the @dfn{send
17518 rights} of the task. @code{set task excp} is a shorthand alias.
17520 @item set noninvasive
17521 @cindex noninvasive task options
17522 This command switches @value{GDBN} to a mode that is the least
17523 invasive as far as interfering with the inferior is concerned. This
17524 is the same as using @code{set task pause}, @code{set exceptions}, and
17525 @code{set signals} to values opposite to the defaults.
17527 @item info send-rights
17528 @itemx info receive-rights
17529 @itemx info port-rights
17530 @itemx info port-sets
17531 @itemx info dead-names
17534 @cindex send rights, @sc{gnu} Hurd
17535 @cindex receive rights, @sc{gnu} Hurd
17536 @cindex port rights, @sc{gnu} Hurd
17537 @cindex port sets, @sc{gnu} Hurd
17538 @cindex dead names, @sc{gnu} Hurd
17539 These commands display information about, respectively, send rights,
17540 receive rights, port rights, port sets, and dead names of a task.
17541 There are also shorthand aliases: @code{info ports} for @code{info
17542 port-rights} and @code{info psets} for @code{info port-sets}.
17544 @item set thread pause
17545 @kindex set thread@r{, Hurd command}
17546 @cindex thread properties, @sc{gnu} Hurd
17547 @cindex pause current thread (@sc{gnu} Hurd)
17548 This command toggles current thread suspension when @value{GDBN} has
17549 control. Setting it to on takes effect immediately, and the current
17550 thread is suspended whenever @value{GDBN} gets control. Setting it to
17551 off will take effect the next time the inferior is continued.
17552 Normally, this command has no effect, since when @value{GDBN} has
17553 control, the whole task is suspended. However, if you used @code{set
17554 task pause off} (see above), this command comes in handy to suspend
17555 only the current thread.
17557 @item show thread pause
17558 @kindex show thread@r{, Hurd command}
17559 This command shows the state of current thread suspension.
17561 @item set thread run
17562 This command sets whether the current thread is allowed to run.
17564 @item show thread run
17565 Show whether the current thread is allowed to run.
17567 @item set thread detach-suspend-count
17568 @cindex thread suspend count, @sc{gnu} Hurd
17569 @cindex detach from thread, @sc{gnu} Hurd
17570 This command sets the suspend count @value{GDBN} will leave on a
17571 thread when detaching. This number is relative to the suspend count
17572 found by @value{GDBN} when it notices the thread; use @code{set thread
17573 takeover-suspend-count} to force it to an absolute value.
17575 @item show thread detach-suspend-count
17576 Show the suspend count @value{GDBN} will leave on the thread when
17579 @item set thread exception-port
17580 @itemx set thread excp
17581 Set the thread exception port to which to forward exceptions. This
17582 overrides the port set by @code{set task exception-port} (see above).
17583 @code{set thread excp} is the shorthand alias.
17585 @item set thread takeover-suspend-count
17586 Normally, @value{GDBN}'s thread suspend counts are relative to the
17587 value @value{GDBN} finds when it notices each thread. This command
17588 changes the suspend counts to be absolute instead.
17590 @item set thread default
17591 @itemx show thread default
17592 @cindex thread default settings, @sc{gnu} Hurd
17593 Each of the above @code{set thread} commands has a @code{set thread
17594 default} counterpart (e.g., @code{set thread default pause}, @code{set
17595 thread default exception-port}, etc.). The @code{thread default}
17596 variety of commands sets the default thread properties for all
17597 threads; you can then change the properties of individual threads with
17598 the non-default commands.
17603 @subsection QNX Neutrino
17604 @cindex QNX Neutrino
17606 @value{GDBN} provides the following commands specific to the QNX
17610 @item set debug nto-debug
17611 @kindex set debug nto-debug
17612 When set to on, enables debugging messages specific to the QNX
17615 @item show debug nto-debug
17616 @kindex show debug nto-debug
17617 Show the current state of QNX Neutrino messages.
17624 @value{GDBN} provides the following commands specific to the Darwin target:
17627 @item set debug darwin @var{num}
17628 @kindex set debug darwin
17629 When set to a non zero value, enables debugging messages specific to
17630 the Darwin support. Higher values produce more verbose output.
17632 @item show debug darwin
17633 @kindex show debug darwin
17634 Show the current state of Darwin messages.
17636 @item set debug mach-o @var{num}
17637 @kindex set debug mach-o
17638 When set to a non zero value, enables debugging messages while
17639 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17640 file format used on Darwin for object and executable files.) Higher
17641 values produce more verbose output. This is a command to diagnose
17642 problems internal to @value{GDBN} and should not be needed in normal
17645 @item show debug mach-o
17646 @kindex show debug mach-o
17647 Show the current state of Mach-O file messages.
17649 @item set mach-exceptions on
17650 @itemx set mach-exceptions off
17651 @kindex set mach-exceptions
17652 On Darwin, faults are first reported as a Mach exception and are then
17653 mapped to a Posix signal. Use this command to turn on trapping of
17654 Mach exceptions in the inferior. This might be sometimes useful to
17655 better understand the cause of a fault. The default is off.
17657 @item show mach-exceptions
17658 @kindex show mach-exceptions
17659 Show the current state of exceptions trapping.
17664 @section Embedded Operating Systems
17666 This section describes configurations involving the debugging of
17667 embedded operating systems that are available for several different
17671 * VxWorks:: Using @value{GDBN} with VxWorks
17674 @value{GDBN} includes the ability to debug programs running on
17675 various real-time operating systems.
17678 @subsection Using @value{GDBN} with VxWorks
17684 @kindex target vxworks
17685 @item target vxworks @var{machinename}
17686 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17687 is the target system's machine name or IP address.
17691 On VxWorks, @code{load} links @var{filename} dynamically on the
17692 current target system as well as adding its symbols in @value{GDBN}.
17694 @value{GDBN} enables developers to spawn and debug tasks running on networked
17695 VxWorks targets from a Unix host. Already-running tasks spawned from
17696 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17697 both the Unix host and on the VxWorks target. The program
17698 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17699 installed with the name @code{vxgdb}, to distinguish it from a
17700 @value{GDBN} for debugging programs on the host itself.)
17703 @item VxWorks-timeout @var{args}
17704 @kindex vxworks-timeout
17705 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17706 This option is set by the user, and @var{args} represents the number of
17707 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17708 your VxWorks target is a slow software simulator or is on the far side
17709 of a thin network line.
17712 The following information on connecting to VxWorks was current when
17713 this manual was produced; newer releases of VxWorks may use revised
17716 @findex INCLUDE_RDB
17717 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17718 to include the remote debugging interface routines in the VxWorks
17719 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17720 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17721 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17722 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17723 information on configuring and remaking VxWorks, see the manufacturer's
17725 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17727 Once you have included @file{rdb.a} in your VxWorks system image and set
17728 your Unix execution search path to find @value{GDBN}, you are ready to
17729 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17730 @code{vxgdb}, depending on your installation).
17732 @value{GDBN} comes up showing the prompt:
17739 * VxWorks Connection:: Connecting to VxWorks
17740 * VxWorks Download:: VxWorks download
17741 * VxWorks Attach:: Running tasks
17744 @node VxWorks Connection
17745 @subsubsection Connecting to VxWorks
17747 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17748 network. To connect to a target whose host name is ``@code{tt}'', type:
17751 (vxgdb) target vxworks tt
17755 @value{GDBN} displays messages like these:
17758 Attaching remote machine across net...
17763 @value{GDBN} then attempts to read the symbol tables of any object modules
17764 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17765 these files by searching the directories listed in the command search
17766 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17767 to find an object file, it displays a message such as:
17770 prog.o: No such file or directory.
17773 When this happens, add the appropriate directory to the search path with
17774 the @value{GDBN} command @code{path}, and execute the @code{target}
17777 @node VxWorks Download
17778 @subsubsection VxWorks Download
17780 @cindex download to VxWorks
17781 If you have connected to the VxWorks target and you want to debug an
17782 object that has not yet been loaded, you can use the @value{GDBN}
17783 @code{load} command to download a file from Unix to VxWorks
17784 incrementally. The object file given as an argument to the @code{load}
17785 command is actually opened twice: first by the VxWorks target in order
17786 to download the code, then by @value{GDBN} in order to read the symbol
17787 table. This can lead to problems if the current working directories on
17788 the two systems differ. If both systems have NFS mounted the same
17789 filesystems, you can avoid these problems by using absolute paths.
17790 Otherwise, it is simplest to set the working directory on both systems
17791 to the directory in which the object file resides, and then to reference
17792 the file by its name, without any path. For instance, a program
17793 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17794 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17795 program, type this on VxWorks:
17798 -> cd "@var{vxpath}/vw/demo/rdb"
17802 Then, in @value{GDBN}, type:
17805 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17806 (vxgdb) load prog.o
17809 @value{GDBN} displays a response similar to this:
17812 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17815 You can also use the @code{load} command to reload an object module
17816 after editing and recompiling the corresponding source file. Note that
17817 this makes @value{GDBN} delete all currently-defined breakpoints,
17818 auto-displays, and convenience variables, and to clear the value
17819 history. (This is necessary in order to preserve the integrity of
17820 debugger's data structures that reference the target system's symbol
17823 @node VxWorks Attach
17824 @subsubsection Running Tasks
17826 @cindex running VxWorks tasks
17827 You can also attach to an existing task using the @code{attach} command as
17831 (vxgdb) attach @var{task}
17835 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17836 or suspended when you attach to it. Running tasks are suspended at
17837 the time of attachment.
17839 @node Embedded Processors
17840 @section Embedded Processors
17842 This section goes into details specific to particular embedded
17845 @cindex send command to simulator
17846 Whenever a specific embedded processor has a simulator, @value{GDBN}
17847 allows to send an arbitrary command to the simulator.
17850 @item sim @var{command}
17851 @kindex sim@r{, a command}
17852 Send an arbitrary @var{command} string to the simulator. Consult the
17853 documentation for the specific simulator in use for information about
17854 acceptable commands.
17860 * M32R/D:: Renesas M32R/D
17861 * M68K:: Motorola M68K
17862 * MicroBlaze:: Xilinx MicroBlaze
17863 * MIPS Embedded:: MIPS Embedded
17864 * OpenRISC 1000:: OpenRisc 1000
17865 * PA:: HP PA Embedded
17866 * PowerPC Embedded:: PowerPC Embedded
17867 * Sparclet:: Tsqware Sparclet
17868 * Sparclite:: Fujitsu Sparclite
17869 * Z8000:: Zilog Z8000
17872 * Super-H:: Renesas Super-H
17881 @item target rdi @var{dev}
17882 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17883 use this target to communicate with both boards running the Angel
17884 monitor, or with the EmbeddedICE JTAG debug device.
17887 @item target rdp @var{dev}
17892 @value{GDBN} provides the following ARM-specific commands:
17895 @item set arm disassembler
17897 This commands selects from a list of disassembly styles. The
17898 @code{"std"} style is the standard style.
17900 @item show arm disassembler
17902 Show the current disassembly style.
17904 @item set arm apcs32
17905 @cindex ARM 32-bit mode
17906 This command toggles ARM operation mode between 32-bit and 26-bit.
17908 @item show arm apcs32
17909 Display the current usage of the ARM 32-bit mode.
17911 @item set arm fpu @var{fputype}
17912 This command sets the ARM floating-point unit (FPU) type. The
17913 argument @var{fputype} can be one of these:
17917 Determine the FPU type by querying the OS ABI.
17919 Software FPU, with mixed-endian doubles on little-endian ARM
17922 GCC-compiled FPA co-processor.
17924 Software FPU with pure-endian doubles.
17930 Show the current type of the FPU.
17933 This command forces @value{GDBN} to use the specified ABI.
17936 Show the currently used ABI.
17938 @item set arm fallback-mode (arm|thumb|auto)
17939 @value{GDBN} uses the symbol table, when available, to determine
17940 whether instructions are ARM or Thumb. This command controls
17941 @value{GDBN}'s default behavior when the symbol table is not
17942 available. The default is @samp{auto}, which causes @value{GDBN} to
17943 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17946 @item show arm fallback-mode
17947 Show the current fallback instruction mode.
17949 @item set arm force-mode (arm|thumb|auto)
17950 This command overrides use of the symbol table to determine whether
17951 instructions are ARM or Thumb. The default is @samp{auto}, which
17952 causes @value{GDBN} to use the symbol table and then the setting
17953 of @samp{set arm fallback-mode}.
17955 @item show arm force-mode
17956 Show the current forced instruction mode.
17958 @item set debug arm
17959 Toggle whether to display ARM-specific debugging messages from the ARM
17960 target support subsystem.
17962 @item show debug arm
17963 Show whether ARM-specific debugging messages are enabled.
17966 The following commands are available when an ARM target is debugged
17967 using the RDI interface:
17970 @item rdilogfile @r{[}@var{file}@r{]}
17972 @cindex ADP (Angel Debugger Protocol) logging
17973 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17974 With an argument, sets the log file to the specified @var{file}. With
17975 no argument, show the current log file name. The default log file is
17978 @item rdilogenable @r{[}@var{arg}@r{]}
17979 @kindex rdilogenable
17980 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17981 enables logging, with an argument 0 or @code{"no"} disables it. With
17982 no arguments displays the current setting. When logging is enabled,
17983 ADP packets exchanged between @value{GDBN} and the RDI target device
17984 are logged to a file.
17986 @item set rdiromatzero
17987 @kindex set rdiromatzero
17988 @cindex ROM at zero address, RDI
17989 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17990 vector catching is disabled, so that zero address can be used. If off
17991 (the default), vector catching is enabled. For this command to take
17992 effect, it needs to be invoked prior to the @code{target rdi} command.
17994 @item show rdiromatzero
17995 @kindex show rdiromatzero
17996 Show the current setting of ROM at zero address.
17998 @item set rdiheartbeat
17999 @kindex set rdiheartbeat
18000 @cindex RDI heartbeat
18001 Enable or disable RDI heartbeat packets. It is not recommended to
18002 turn on this option, since it confuses ARM and EPI JTAG interface, as
18003 well as the Angel monitor.
18005 @item show rdiheartbeat
18006 @kindex show rdiheartbeat
18007 Show the setting of RDI heartbeat packets.
18011 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18012 The @value{GDBN} ARM simulator accepts the following optional arguments.
18015 @item --swi-support=@var{type}
18016 Tell the simulator which SWI interfaces to support.
18017 @var{type} may be a comma separated list of the following values.
18018 The default value is @code{all}.
18031 @subsection Renesas M32R/D and M32R/SDI
18034 @kindex target m32r
18035 @item target m32r @var{dev}
18036 Renesas M32R/D ROM monitor.
18038 @kindex target m32rsdi
18039 @item target m32rsdi @var{dev}
18040 Renesas M32R SDI server, connected via parallel port to the board.
18043 The following @value{GDBN} commands are specific to the M32R monitor:
18046 @item set download-path @var{path}
18047 @kindex set download-path
18048 @cindex find downloadable @sc{srec} files (M32R)
18049 Set the default path for finding downloadable @sc{srec} files.
18051 @item show download-path
18052 @kindex show download-path
18053 Show the default path for downloadable @sc{srec} files.
18055 @item set board-address @var{addr}
18056 @kindex set board-address
18057 @cindex M32-EVA target board address
18058 Set the IP address for the M32R-EVA target board.
18060 @item show board-address
18061 @kindex show board-address
18062 Show the current IP address of the target board.
18064 @item set server-address @var{addr}
18065 @kindex set server-address
18066 @cindex download server address (M32R)
18067 Set the IP address for the download server, which is the @value{GDBN}'s
18070 @item show server-address
18071 @kindex show server-address
18072 Display the IP address of the download server.
18074 @item upload @r{[}@var{file}@r{]}
18075 @kindex upload@r{, M32R}
18076 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18077 upload capability. If no @var{file} argument is given, the current
18078 executable file is uploaded.
18080 @item tload @r{[}@var{file}@r{]}
18081 @kindex tload@r{, M32R}
18082 Test the @code{upload} command.
18085 The following commands are available for M32R/SDI:
18090 @cindex reset SDI connection, M32R
18091 This command resets the SDI connection.
18095 This command shows the SDI connection status.
18098 @kindex debug_chaos
18099 @cindex M32R/Chaos debugging
18100 Instructs the remote that M32R/Chaos debugging is to be used.
18102 @item use_debug_dma
18103 @kindex use_debug_dma
18104 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18107 @kindex use_mon_code
18108 Instructs the remote to use the MON_CODE method of accessing memory.
18111 @kindex use_ib_break
18112 Instructs the remote to set breakpoints by IB break.
18114 @item use_dbt_break
18115 @kindex use_dbt_break
18116 Instructs the remote to set breakpoints by DBT.
18122 The Motorola m68k configuration includes ColdFire support, and a
18123 target command for the following ROM monitor.
18127 @kindex target dbug
18128 @item target dbug @var{dev}
18129 dBUG ROM monitor for Motorola ColdFire.
18134 @subsection MicroBlaze
18135 @cindex Xilinx MicroBlaze
18136 @cindex XMD, Xilinx Microprocessor Debugger
18138 The MicroBlaze is a soft-core processor supported on various Xilinx
18139 FPGAs, such as Spartan or Virtex series. Boards with these processors
18140 usually have JTAG ports which connect to a host system running the Xilinx
18141 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18142 This host system is used to download the configuration bitstream to
18143 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18144 communicates with the target board using the JTAG interface and
18145 presents a @code{gdbserver} interface to the board. By default
18146 @code{xmd} uses port @code{1234}. (While it is possible to change
18147 this default port, it requires the use of undocumented @code{xmd}
18148 commands. Contact Xilinx support if you need to do this.)
18150 Use these GDB commands to connect to the MicroBlaze target processor.
18153 @item target remote :1234
18154 Use this command to connect to the target if you are running @value{GDBN}
18155 on the same system as @code{xmd}.
18157 @item target remote @var{xmd-host}:1234
18158 Use this command to connect to the target if it is connected to @code{xmd}
18159 running on a different system named @var{xmd-host}.
18162 Use this command to download a program to the MicroBlaze target.
18164 @item set debug microblaze @var{n}
18165 Enable MicroBlaze-specific debugging messages if non-zero.
18167 @item show debug microblaze @var{n}
18168 Show MicroBlaze-specific debugging level.
18171 @node MIPS Embedded
18172 @subsection MIPS Embedded
18174 @cindex MIPS boards
18175 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18176 MIPS board attached to a serial line. This is available when
18177 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18180 Use these @value{GDBN} commands to specify the connection to your target board:
18183 @item target mips @var{port}
18184 @kindex target mips @var{port}
18185 To run a program on the board, start up @code{@value{GDBP}} with the
18186 name of your program as the argument. To connect to the board, use the
18187 command @samp{target mips @var{port}}, where @var{port} is the name of
18188 the serial port connected to the board. If the program has not already
18189 been downloaded to the board, you may use the @code{load} command to
18190 download it. You can then use all the usual @value{GDBN} commands.
18192 For example, this sequence connects to the target board through a serial
18193 port, and loads and runs a program called @var{prog} through the
18197 host$ @value{GDBP} @var{prog}
18198 @value{GDBN} is free software and @dots{}
18199 (@value{GDBP}) target mips /dev/ttyb
18200 (@value{GDBP}) load @var{prog}
18204 @item target mips @var{hostname}:@var{portnumber}
18205 On some @value{GDBN} host configurations, you can specify a TCP
18206 connection (for instance, to a serial line managed by a terminal
18207 concentrator) instead of a serial port, using the syntax
18208 @samp{@var{hostname}:@var{portnumber}}.
18210 @item target pmon @var{port}
18211 @kindex target pmon @var{port}
18214 @item target ddb @var{port}
18215 @kindex target ddb @var{port}
18216 NEC's DDB variant of PMON for Vr4300.
18218 @item target lsi @var{port}
18219 @kindex target lsi @var{port}
18220 LSI variant of PMON.
18222 @kindex target r3900
18223 @item target r3900 @var{dev}
18224 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18226 @kindex target array
18227 @item target array @var{dev}
18228 Array Tech LSI33K RAID controller board.
18234 @value{GDBN} also supports these special commands for MIPS targets:
18237 @item set mipsfpu double
18238 @itemx set mipsfpu single
18239 @itemx set mipsfpu none
18240 @itemx set mipsfpu auto
18241 @itemx show mipsfpu
18242 @kindex set mipsfpu
18243 @kindex show mipsfpu
18244 @cindex MIPS remote floating point
18245 @cindex floating point, MIPS remote
18246 If your target board does not support the MIPS floating point
18247 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18248 need this, you may wish to put the command in your @value{GDBN} init
18249 file). This tells @value{GDBN} how to find the return value of
18250 functions which return floating point values. It also allows
18251 @value{GDBN} to avoid saving the floating point registers when calling
18252 functions on the board. If you are using a floating point coprocessor
18253 with only single precision floating point support, as on the @sc{r4650}
18254 processor, use the command @samp{set mipsfpu single}. The default
18255 double precision floating point coprocessor may be selected using
18256 @samp{set mipsfpu double}.
18258 In previous versions the only choices were double precision or no
18259 floating point, so @samp{set mipsfpu on} will select double precision
18260 and @samp{set mipsfpu off} will select no floating point.
18262 As usual, you can inquire about the @code{mipsfpu} variable with
18263 @samp{show mipsfpu}.
18265 @item set timeout @var{seconds}
18266 @itemx set retransmit-timeout @var{seconds}
18267 @itemx show timeout
18268 @itemx show retransmit-timeout
18269 @cindex @code{timeout}, MIPS protocol
18270 @cindex @code{retransmit-timeout}, MIPS protocol
18271 @kindex set timeout
18272 @kindex show timeout
18273 @kindex set retransmit-timeout
18274 @kindex show retransmit-timeout
18275 You can control the timeout used while waiting for a packet, in the MIPS
18276 remote protocol, with the @code{set timeout @var{seconds}} command. The
18277 default is 5 seconds. Similarly, you can control the timeout used while
18278 waiting for an acknowledgment of a packet with the @code{set
18279 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18280 You can inspect both values with @code{show timeout} and @code{show
18281 retransmit-timeout}. (These commands are @emph{only} available when
18282 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18284 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18285 is waiting for your program to stop. In that case, @value{GDBN} waits
18286 forever because it has no way of knowing how long the program is going
18287 to run before stopping.
18289 @item set syn-garbage-limit @var{num}
18290 @kindex set syn-garbage-limit@r{, MIPS remote}
18291 @cindex synchronize with remote MIPS target
18292 Limit the maximum number of characters @value{GDBN} should ignore when
18293 it tries to synchronize with the remote target. The default is 10
18294 characters. Setting the limit to -1 means there's no limit.
18296 @item show syn-garbage-limit
18297 @kindex show syn-garbage-limit@r{, MIPS remote}
18298 Show the current limit on the number of characters to ignore when
18299 trying to synchronize with the remote system.
18301 @item set monitor-prompt @var{prompt}
18302 @kindex set monitor-prompt@r{, MIPS remote}
18303 @cindex remote monitor prompt
18304 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18305 remote monitor. The default depends on the target:
18315 @item show monitor-prompt
18316 @kindex show monitor-prompt@r{, MIPS remote}
18317 Show the current strings @value{GDBN} expects as the prompt from the
18320 @item set monitor-warnings
18321 @kindex set monitor-warnings@r{, MIPS remote}
18322 Enable or disable monitor warnings about hardware breakpoints. This
18323 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18324 display warning messages whose codes are returned by the @code{lsi}
18325 PMON monitor for breakpoint commands.
18327 @item show monitor-warnings
18328 @kindex show monitor-warnings@r{, MIPS remote}
18329 Show the current setting of printing monitor warnings.
18331 @item pmon @var{command}
18332 @kindex pmon@r{, MIPS remote}
18333 @cindex send PMON command
18334 This command allows sending an arbitrary @var{command} string to the
18335 monitor. The monitor must be in debug mode for this to work.
18338 @node OpenRISC 1000
18339 @subsection OpenRISC 1000
18340 @cindex OpenRISC 1000
18342 @cindex or1k boards
18343 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18344 about platform and commands.
18348 @kindex target jtag
18349 @item target jtag jtag://@var{host}:@var{port}
18351 Connects to remote JTAG server.
18352 JTAG remote server can be either an or1ksim or JTAG server,
18353 connected via parallel port to the board.
18355 Example: @code{target jtag jtag://localhost:9999}
18358 @item or1ksim @var{command}
18359 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18360 Simulator, proprietary commands can be executed.
18362 @kindex info or1k spr
18363 @item info or1k spr
18364 Displays spr groups.
18366 @item info or1k spr @var{group}
18367 @itemx info or1k spr @var{groupno}
18368 Displays register names in selected group.
18370 @item info or1k spr @var{group} @var{register}
18371 @itemx info or1k spr @var{register}
18372 @itemx info or1k spr @var{groupno} @var{registerno}
18373 @itemx info or1k spr @var{registerno}
18374 Shows information about specified spr register.
18377 @item spr @var{group} @var{register} @var{value}
18378 @itemx spr @var{register @var{value}}
18379 @itemx spr @var{groupno} @var{registerno @var{value}}
18380 @itemx spr @var{registerno @var{value}}
18381 Writes @var{value} to specified spr register.
18384 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18385 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18386 program execution and is thus much faster. Hardware breakpoints/watchpoint
18387 triggers can be set using:
18390 Load effective address/data
18392 Store effective address/data
18394 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18399 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18400 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18402 @code{htrace} commands:
18403 @cindex OpenRISC 1000 htrace
18406 @item hwatch @var{conditional}
18407 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18408 or Data. For example:
18410 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18412 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18416 Display information about current HW trace configuration.
18418 @item htrace trigger @var{conditional}
18419 Set starting criteria for HW trace.
18421 @item htrace qualifier @var{conditional}
18422 Set acquisition qualifier for HW trace.
18424 @item htrace stop @var{conditional}
18425 Set HW trace stopping criteria.
18427 @item htrace record [@var{data}]*
18428 Selects the data to be recorded, when qualifier is met and HW trace was
18431 @item htrace enable
18432 @itemx htrace disable
18433 Enables/disables the HW trace.
18435 @item htrace rewind [@var{filename}]
18436 Clears currently recorded trace data.
18438 If filename is specified, new trace file is made and any newly collected data
18439 will be written there.
18441 @item htrace print [@var{start} [@var{len}]]
18442 Prints trace buffer, using current record configuration.
18444 @item htrace mode continuous
18445 Set continuous trace mode.
18447 @item htrace mode suspend
18448 Set suspend trace mode.
18452 @node PowerPC Embedded
18453 @subsection PowerPC Embedded
18455 @value{GDBN} provides the following PowerPC-specific commands:
18458 @kindex set powerpc
18459 @item set powerpc soft-float
18460 @itemx show powerpc soft-float
18461 Force @value{GDBN} to use (or not use) a software floating point calling
18462 convention. By default, @value{GDBN} selects the calling convention based
18463 on the selected architecture and the provided executable file.
18465 @item set powerpc vector-abi
18466 @itemx show powerpc vector-abi
18467 Force @value{GDBN} to use the specified calling convention for vector
18468 arguments and return values. The valid options are @samp{auto};
18469 @samp{generic}, to avoid vector registers even if they are present;
18470 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18471 registers. By default, @value{GDBN} selects the calling convention
18472 based on the selected architecture and the provided executable file.
18474 @kindex target dink32
18475 @item target dink32 @var{dev}
18476 DINK32 ROM monitor.
18478 @kindex target ppcbug
18479 @item target ppcbug @var{dev}
18480 @kindex target ppcbug1
18481 @item target ppcbug1 @var{dev}
18482 PPCBUG ROM monitor for PowerPC.
18485 @item target sds @var{dev}
18486 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18489 @cindex SDS protocol
18490 The following commands specific to the SDS protocol are supported
18494 @item set sdstimeout @var{nsec}
18495 @kindex set sdstimeout
18496 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18497 default is 2 seconds.
18499 @item show sdstimeout
18500 @kindex show sdstimeout
18501 Show the current value of the SDS timeout.
18503 @item sds @var{command}
18504 @kindex sds@r{, a command}
18505 Send the specified @var{command} string to the SDS monitor.
18510 @subsection HP PA Embedded
18514 @kindex target op50n
18515 @item target op50n @var{dev}
18516 OP50N monitor, running on an OKI HPPA board.
18518 @kindex target w89k
18519 @item target w89k @var{dev}
18520 W89K monitor, running on a Winbond HPPA board.
18525 @subsection Tsqware Sparclet
18529 @value{GDBN} enables developers to debug tasks running on
18530 Sparclet targets from a Unix host.
18531 @value{GDBN} uses code that runs on
18532 both the Unix host and on the Sparclet target. The program
18533 @code{@value{GDBP}} is installed and executed on the Unix host.
18536 @item remotetimeout @var{args}
18537 @kindex remotetimeout
18538 @value{GDBN} supports the option @code{remotetimeout}.
18539 This option is set by the user, and @var{args} represents the number of
18540 seconds @value{GDBN} waits for responses.
18543 @cindex compiling, on Sparclet
18544 When compiling for debugging, include the options @samp{-g} to get debug
18545 information and @samp{-Ttext} to relocate the program to where you wish to
18546 load it on the target. You may also want to add the options @samp{-n} or
18547 @samp{-N} in order to reduce the size of the sections. Example:
18550 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18553 You can use @code{objdump} to verify that the addresses are what you intended:
18556 sparclet-aout-objdump --headers --syms prog
18559 @cindex running, on Sparclet
18561 your Unix execution search path to find @value{GDBN}, you are ready to
18562 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18563 (or @code{sparclet-aout-gdb}, depending on your installation).
18565 @value{GDBN} comes up showing the prompt:
18572 * Sparclet File:: Setting the file to debug
18573 * Sparclet Connection:: Connecting to Sparclet
18574 * Sparclet Download:: Sparclet download
18575 * Sparclet Execution:: Running and debugging
18578 @node Sparclet File
18579 @subsubsection Setting File to Debug
18581 The @value{GDBN} command @code{file} lets you choose with program to debug.
18584 (gdbslet) file prog
18588 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18589 @value{GDBN} locates
18590 the file by searching the directories listed in the command search
18592 If the file was compiled with debug information (option @samp{-g}), source
18593 files will be searched as well.
18594 @value{GDBN} locates
18595 the source files by searching the directories listed in the directory search
18596 path (@pxref{Environment, ,Your Program's Environment}).
18598 to find a file, it displays a message such as:
18601 prog: No such file or directory.
18604 When this happens, add the appropriate directories to the search paths with
18605 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18606 @code{target} command again.
18608 @node Sparclet Connection
18609 @subsubsection Connecting to Sparclet
18611 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18612 To connect to a target on serial port ``@code{ttya}'', type:
18615 (gdbslet) target sparclet /dev/ttya
18616 Remote target sparclet connected to /dev/ttya
18617 main () at ../prog.c:3
18621 @value{GDBN} displays messages like these:
18627 @node Sparclet Download
18628 @subsubsection Sparclet Download
18630 @cindex download to Sparclet
18631 Once connected to the Sparclet target,
18632 you can use the @value{GDBN}
18633 @code{load} command to download the file from the host to the target.
18634 The file name and load offset should be given as arguments to the @code{load}
18636 Since the file format is aout, the program must be loaded to the starting
18637 address. You can use @code{objdump} to find out what this value is. The load
18638 offset is an offset which is added to the VMA (virtual memory address)
18639 of each of the file's sections.
18640 For instance, if the program
18641 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18642 and bss at 0x12010170, in @value{GDBN}, type:
18645 (gdbslet) load prog 0x12010000
18646 Loading section .text, size 0xdb0 vma 0x12010000
18649 If the code is loaded at a different address then what the program was linked
18650 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18651 to tell @value{GDBN} where to map the symbol table.
18653 @node Sparclet Execution
18654 @subsubsection Running and Debugging
18656 @cindex running and debugging Sparclet programs
18657 You can now begin debugging the task using @value{GDBN}'s execution control
18658 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18659 manual for the list of commands.
18663 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18665 Starting program: prog
18666 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18667 3 char *symarg = 0;
18669 4 char *execarg = "hello!";
18674 @subsection Fujitsu Sparclite
18678 @kindex target sparclite
18679 @item target sparclite @var{dev}
18680 Fujitsu sparclite boards, used only for the purpose of loading.
18681 You must use an additional command to debug the program.
18682 For example: target remote @var{dev} using @value{GDBN} standard
18688 @subsection Zilog Z8000
18691 @cindex simulator, Z8000
18692 @cindex Zilog Z8000 simulator
18694 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18697 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18698 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18699 segmented variant). The simulator recognizes which architecture is
18700 appropriate by inspecting the object code.
18703 @item target sim @var{args}
18705 @kindex target sim@r{, with Z8000}
18706 Debug programs on a simulated CPU. If the simulator supports setup
18707 options, specify them via @var{args}.
18711 After specifying this target, you can debug programs for the simulated
18712 CPU in the same style as programs for your host computer; use the
18713 @code{file} command to load a new program image, the @code{run} command
18714 to run your program, and so on.
18716 As well as making available all the usual machine registers
18717 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18718 additional items of information as specially named registers:
18723 Counts clock-ticks in the simulator.
18726 Counts instructions run in the simulator.
18729 Execution time in 60ths of a second.
18733 You can refer to these values in @value{GDBN} expressions with the usual
18734 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18735 conditional breakpoint that suspends only after at least 5000
18736 simulated clock ticks.
18739 @subsection Atmel AVR
18742 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18743 following AVR-specific commands:
18746 @item info io_registers
18747 @kindex info io_registers@r{, AVR}
18748 @cindex I/O registers (Atmel AVR)
18749 This command displays information about the AVR I/O registers. For
18750 each register, @value{GDBN} prints its number and value.
18757 When configured for debugging CRIS, @value{GDBN} provides the
18758 following CRIS-specific commands:
18761 @item set cris-version @var{ver}
18762 @cindex CRIS version
18763 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18764 The CRIS version affects register names and sizes. This command is useful in
18765 case autodetection of the CRIS version fails.
18767 @item show cris-version
18768 Show the current CRIS version.
18770 @item set cris-dwarf2-cfi
18771 @cindex DWARF-2 CFI and CRIS
18772 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18773 Change to @samp{off} when using @code{gcc-cris} whose version is below
18776 @item show cris-dwarf2-cfi
18777 Show the current state of using DWARF-2 CFI.
18779 @item set cris-mode @var{mode}
18781 Set the current CRIS mode to @var{mode}. It should only be changed when
18782 debugging in guru mode, in which case it should be set to
18783 @samp{guru} (the default is @samp{normal}).
18785 @item show cris-mode
18786 Show the current CRIS mode.
18790 @subsection Renesas Super-H
18793 For the Renesas Super-H processor, @value{GDBN} provides these
18798 @kindex regs@r{, Super-H}
18799 Show the values of all Super-H registers.
18801 @item set sh calling-convention @var{convention}
18802 @kindex set sh calling-convention
18803 Set the calling-convention used when calling functions from @value{GDBN}.
18804 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18805 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18806 convention. If the DWARF-2 information of the called function specifies
18807 that the function follows the Renesas calling convention, the function
18808 is called using the Renesas calling convention. If the calling convention
18809 is set to @samp{renesas}, the Renesas calling convention is always used,
18810 regardless of the DWARF-2 information. This can be used to override the
18811 default of @samp{gcc} if debug information is missing, or the compiler
18812 does not emit the DWARF-2 calling convention entry for a function.
18814 @item show sh calling-convention
18815 @kindex show sh calling-convention
18816 Show the current calling convention setting.
18821 @node Architectures
18822 @section Architectures
18824 This section describes characteristics of architectures that affect
18825 all uses of @value{GDBN} with the architecture, both native and cross.
18832 * HPPA:: HP PA architecture
18833 * SPU:: Cell Broadband Engine SPU architecture
18838 @subsection x86 Architecture-specific Issues
18841 @item set struct-convention @var{mode}
18842 @kindex set struct-convention
18843 @cindex struct return convention
18844 @cindex struct/union returned in registers
18845 Set the convention used by the inferior to return @code{struct}s and
18846 @code{union}s from functions to @var{mode}. Possible values of
18847 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18848 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18849 are returned on the stack, while @code{"reg"} means that a
18850 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18851 be returned in a register.
18853 @item show struct-convention
18854 @kindex show struct-convention
18855 Show the current setting of the convention to return @code{struct}s
18864 @kindex set rstack_high_address
18865 @cindex AMD 29K register stack
18866 @cindex register stack, AMD29K
18867 @item set rstack_high_address @var{address}
18868 On AMD 29000 family processors, registers are saved in a separate
18869 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18870 extent of this stack. Normally, @value{GDBN} just assumes that the
18871 stack is ``large enough''. This may result in @value{GDBN} referencing
18872 memory locations that do not exist. If necessary, you can get around
18873 this problem by specifying the ending address of the register stack with
18874 the @code{set rstack_high_address} command. The argument should be an
18875 address, which you probably want to precede with @samp{0x} to specify in
18878 @kindex show rstack_high_address
18879 @item show rstack_high_address
18880 Display the current limit of the register stack, on AMD 29000 family
18888 See the following section.
18893 @cindex stack on Alpha
18894 @cindex stack on MIPS
18895 @cindex Alpha stack
18897 Alpha- and MIPS-based computers use an unusual stack frame, which
18898 sometimes requires @value{GDBN} to search backward in the object code to
18899 find the beginning of a function.
18901 @cindex response time, MIPS debugging
18902 To improve response time (especially for embedded applications, where
18903 @value{GDBN} may be restricted to a slow serial line for this search)
18904 you may want to limit the size of this search, using one of these
18908 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18909 @item set heuristic-fence-post @var{limit}
18910 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18911 search for the beginning of a function. A value of @var{0} (the
18912 default) means there is no limit. However, except for @var{0}, the
18913 larger the limit the more bytes @code{heuristic-fence-post} must search
18914 and therefore the longer it takes to run. You should only need to use
18915 this command when debugging a stripped executable.
18917 @item show heuristic-fence-post
18918 Display the current limit.
18922 These commands are available @emph{only} when @value{GDBN} is configured
18923 for debugging programs on Alpha or MIPS processors.
18925 Several MIPS-specific commands are available when debugging MIPS
18929 @item set mips abi @var{arg}
18930 @kindex set mips abi
18931 @cindex set ABI for MIPS
18932 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18933 values of @var{arg} are:
18937 The default ABI associated with the current binary (this is the
18948 @item show mips abi
18949 @kindex show mips abi
18950 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18953 @itemx show mipsfpu
18954 @xref{MIPS Embedded, set mipsfpu}.
18956 @item set mips mask-address @var{arg}
18957 @kindex set mips mask-address
18958 @cindex MIPS addresses, masking
18959 This command determines whether the most-significant 32 bits of 64-bit
18960 MIPS addresses are masked off. The argument @var{arg} can be
18961 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18962 setting, which lets @value{GDBN} determine the correct value.
18964 @item show mips mask-address
18965 @kindex show mips mask-address
18966 Show whether the upper 32 bits of MIPS addresses are masked off or
18969 @item set remote-mips64-transfers-32bit-regs
18970 @kindex set remote-mips64-transfers-32bit-regs
18971 This command controls compatibility with 64-bit MIPS targets that
18972 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18973 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18974 and 64 bits for other registers, set this option to @samp{on}.
18976 @item show remote-mips64-transfers-32bit-regs
18977 @kindex show remote-mips64-transfers-32bit-regs
18978 Show the current setting of compatibility with older MIPS 64 targets.
18980 @item set debug mips
18981 @kindex set debug mips
18982 This command turns on and off debugging messages for the MIPS-specific
18983 target code in @value{GDBN}.
18985 @item show debug mips
18986 @kindex show debug mips
18987 Show the current setting of MIPS debugging messages.
18993 @cindex HPPA support
18995 When @value{GDBN} is debugging the HP PA architecture, it provides the
18996 following special commands:
18999 @item set debug hppa
19000 @kindex set debug hppa
19001 This command determines whether HPPA architecture-specific debugging
19002 messages are to be displayed.
19004 @item show debug hppa
19005 Show whether HPPA debugging messages are displayed.
19007 @item maint print unwind @var{address}
19008 @kindex maint print unwind@r{, HPPA}
19009 This command displays the contents of the unwind table entry at the
19010 given @var{address}.
19016 @subsection Cell Broadband Engine SPU architecture
19017 @cindex Cell Broadband Engine
19020 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19021 it provides the following special commands:
19024 @item info spu event
19026 Display SPU event facility status. Shows current event mask
19027 and pending event status.
19029 @item info spu signal
19030 Display SPU signal notification facility status. Shows pending
19031 signal-control word and signal notification mode of both signal
19032 notification channels.
19034 @item info spu mailbox
19035 Display SPU mailbox facility status. Shows all pending entries,
19036 in order of processing, in each of the SPU Write Outbound,
19037 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19040 Display MFC DMA status. Shows all pending commands in the MFC
19041 DMA queue. For each entry, opcode, tag, class IDs, effective
19042 and local store addresses and transfer size are shown.
19044 @item info spu proxydma
19045 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19046 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19047 and local store addresses and transfer size are shown.
19051 When @value{GDBN} is debugging a combined PowerPC/SPU application
19052 on the Cell Broadband Engine, it provides in addition the following
19056 @item set spu stop-on-load @var{arg}
19058 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19059 will give control to the user when a new SPE thread enters its @code{main}
19060 function. The default is @code{off}.
19062 @item show spu stop-on-load
19064 Show whether to stop for new SPE threads.
19066 @item set spu auto-flush-cache @var{arg}
19067 Set whether to automatically flush the software-managed cache. When set to
19068 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19069 cache to be flushed whenever SPE execution stops. This provides a consistent
19070 view of PowerPC memory that is accessed via the cache. If an application
19071 does not use the software-managed cache, this option has no effect.
19073 @item show spu auto-flush-cache
19074 Show whether to automatically flush the software-managed cache.
19079 @subsection PowerPC
19080 @cindex PowerPC architecture
19082 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19083 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19084 numbers stored in the floating point registers. These values must be stored
19085 in two consecutive registers, always starting at an even register like
19086 @code{f0} or @code{f2}.
19088 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19089 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19090 @code{f2} and @code{f3} for @code{$dl1} and so on.
19092 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19093 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19096 @node Controlling GDB
19097 @chapter Controlling @value{GDBN}
19099 You can alter the way @value{GDBN} interacts with you by using the
19100 @code{set} command. For commands controlling how @value{GDBN} displays
19101 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19106 * Editing:: Command editing
19107 * Command History:: Command history
19108 * Screen Size:: Screen size
19109 * Numbers:: Numbers
19110 * ABI:: Configuring the current ABI
19111 * Messages/Warnings:: Optional warnings and messages
19112 * Debugging Output:: Optional messages about internal happenings
19113 * Other Misc Settings:: Other Miscellaneous Settings
19121 @value{GDBN} indicates its readiness to read a command by printing a string
19122 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19123 can change the prompt string with the @code{set prompt} command. For
19124 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19125 the prompt in one of the @value{GDBN} sessions so that you can always tell
19126 which one you are talking to.
19128 @emph{Note:} @code{set prompt} does not add a space for you after the
19129 prompt you set. This allows you to set a prompt which ends in a space
19130 or a prompt that does not.
19134 @item set prompt @var{newprompt}
19135 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19137 @kindex show prompt
19139 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19143 @section Command Editing
19145 @cindex command line editing
19147 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19148 @sc{gnu} library provides consistent behavior for programs which provide a
19149 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19150 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19151 substitution, and a storage and recall of command history across
19152 debugging sessions.
19154 You may control the behavior of command line editing in @value{GDBN} with the
19155 command @code{set}.
19158 @kindex set editing
19161 @itemx set editing on
19162 Enable command line editing (enabled by default).
19164 @item set editing off
19165 Disable command line editing.
19167 @kindex show editing
19169 Show whether command line editing is enabled.
19172 @xref{Command Line Editing}, for more details about the Readline
19173 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19174 encouraged to read that chapter.
19176 @node Command History
19177 @section Command History
19178 @cindex command history
19180 @value{GDBN} can keep track of the commands you type during your
19181 debugging sessions, so that you can be certain of precisely what
19182 happened. Use these commands to manage the @value{GDBN} command
19185 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19186 package, to provide the history facility. @xref{Using History
19187 Interactively}, for the detailed description of the History library.
19189 To issue a command to @value{GDBN} without affecting certain aspects of
19190 the state which is seen by users, prefix it with @samp{server }
19191 (@pxref{Server Prefix}). This
19192 means that this command will not affect the command history, nor will it
19193 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19194 pressed on a line by itself.
19196 @cindex @code{server}, command prefix
19197 The server prefix does not affect the recording of values into the value
19198 history; to print a value without recording it into the value history,
19199 use the @code{output} command instead of the @code{print} command.
19201 Here is the description of @value{GDBN} commands related to command
19205 @cindex history substitution
19206 @cindex history file
19207 @kindex set history filename
19208 @cindex @env{GDBHISTFILE}, environment variable
19209 @item set history filename @var{fname}
19210 Set the name of the @value{GDBN} command history file to @var{fname}.
19211 This is the file where @value{GDBN} reads an initial command history
19212 list, and where it writes the command history from this session when it
19213 exits. You can access this list through history expansion or through
19214 the history command editing characters listed below. This file defaults
19215 to the value of the environment variable @code{GDBHISTFILE}, or to
19216 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19219 @cindex save command history
19220 @kindex set history save
19221 @item set history save
19222 @itemx set history save on
19223 Record command history in a file, whose name may be specified with the
19224 @code{set history filename} command. By default, this option is disabled.
19226 @item set history save off
19227 Stop recording command history in a file.
19229 @cindex history size
19230 @kindex set history size
19231 @cindex @env{HISTSIZE}, environment variable
19232 @item set history size @var{size}
19233 Set the number of commands which @value{GDBN} keeps in its history list.
19234 This defaults to the value of the environment variable
19235 @code{HISTSIZE}, or to 256 if this variable is not set.
19238 History expansion assigns special meaning to the character @kbd{!}.
19239 @xref{Event Designators}, for more details.
19241 @cindex history expansion, turn on/off
19242 Since @kbd{!} is also the logical not operator in C, history expansion
19243 is off by default. If you decide to enable history expansion with the
19244 @code{set history expansion on} command, you may sometimes need to
19245 follow @kbd{!} (when it is used as logical not, in an expression) with
19246 a space or a tab to prevent it from being expanded. The readline
19247 history facilities do not attempt substitution on the strings
19248 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19250 The commands to control history expansion are:
19253 @item set history expansion on
19254 @itemx set history expansion
19255 @kindex set history expansion
19256 Enable history expansion. History expansion is off by default.
19258 @item set history expansion off
19259 Disable history expansion.
19262 @kindex show history
19264 @itemx show history filename
19265 @itemx show history save
19266 @itemx show history size
19267 @itemx show history expansion
19268 These commands display the state of the @value{GDBN} history parameters.
19269 @code{show history} by itself displays all four states.
19274 @kindex show commands
19275 @cindex show last commands
19276 @cindex display command history
19277 @item show commands
19278 Display the last ten commands in the command history.
19280 @item show commands @var{n}
19281 Print ten commands centered on command number @var{n}.
19283 @item show commands +
19284 Print ten commands just after the commands last printed.
19288 @section Screen Size
19289 @cindex size of screen
19290 @cindex pauses in output
19292 Certain commands to @value{GDBN} may produce large amounts of
19293 information output to the screen. To help you read all of it,
19294 @value{GDBN} pauses and asks you for input at the end of each page of
19295 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19296 to discard the remaining output. Also, the screen width setting
19297 determines when to wrap lines of output. Depending on what is being
19298 printed, @value{GDBN} tries to break the line at a readable place,
19299 rather than simply letting it overflow onto the following line.
19301 Normally @value{GDBN} knows the size of the screen from the terminal
19302 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19303 together with the value of the @code{TERM} environment variable and the
19304 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19305 you can override it with the @code{set height} and @code{set
19312 @kindex show height
19313 @item set height @var{lpp}
19315 @itemx set width @var{cpl}
19317 These @code{set} commands specify a screen height of @var{lpp} lines and
19318 a screen width of @var{cpl} characters. The associated @code{show}
19319 commands display the current settings.
19321 If you specify a height of zero lines, @value{GDBN} does not pause during
19322 output no matter how long the output is. This is useful if output is to a
19323 file or to an editor buffer.
19325 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19326 from wrapping its output.
19328 @item set pagination on
19329 @itemx set pagination off
19330 @kindex set pagination
19331 Turn the output pagination on or off; the default is on. Turning
19332 pagination off is the alternative to @code{set height 0}. Note that
19333 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19334 Options, -batch}) also automatically disables pagination.
19336 @item show pagination
19337 @kindex show pagination
19338 Show the current pagination mode.
19343 @cindex number representation
19344 @cindex entering numbers
19346 You can always enter numbers in octal, decimal, or hexadecimal in
19347 @value{GDBN} by the usual conventions: octal numbers begin with
19348 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19349 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19350 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19351 10; likewise, the default display for numbers---when no particular
19352 format is specified---is base 10. You can change the default base for
19353 both input and output with the commands described below.
19356 @kindex set input-radix
19357 @item set input-radix @var{base}
19358 Set the default base for numeric input. Supported choices
19359 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19360 specified either unambiguously or using the current input radix; for
19364 set input-radix 012
19365 set input-radix 10.
19366 set input-radix 0xa
19370 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19371 leaves the input radix unchanged, no matter what it was, since
19372 @samp{10}, being without any leading or trailing signs of its base, is
19373 interpreted in the current radix. Thus, if the current radix is 16,
19374 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19377 @kindex set output-radix
19378 @item set output-radix @var{base}
19379 Set the default base for numeric display. 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.
19383 @kindex show input-radix
19384 @item show input-radix
19385 Display the current default base for numeric input.
19387 @kindex show output-radix
19388 @item show output-radix
19389 Display the current default base for numeric display.
19391 @item set radix @r{[}@var{base}@r{]}
19395 These commands set and show the default base for both input and output
19396 of numbers. @code{set radix} sets the radix of input and output to
19397 the same base; without an argument, it resets the radix back to its
19398 default value of 10.
19403 @section Configuring the Current ABI
19405 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19406 application automatically. However, sometimes you need to override its
19407 conclusions. Use these commands to manage @value{GDBN}'s view of the
19414 One @value{GDBN} configuration can debug binaries for multiple operating
19415 system targets, either via remote debugging or native emulation.
19416 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19417 but you can override its conclusion using the @code{set osabi} command.
19418 One example where this is useful is in debugging of binaries which use
19419 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19420 not have the same identifying marks that the standard C library for your
19425 Show the OS ABI currently in use.
19428 With no argument, show the list of registered available OS ABI's.
19430 @item set osabi @var{abi}
19431 Set the current OS ABI to @var{abi}.
19434 @cindex float promotion
19436 Generally, the way that an argument of type @code{float} is passed to a
19437 function depends on whether the function is prototyped. For a prototyped
19438 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19439 according to the architecture's convention for @code{float}. For unprototyped
19440 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19441 @code{double} and then passed.
19443 Unfortunately, some forms of debug information do not reliably indicate whether
19444 a function is prototyped. If @value{GDBN} calls a function that is not marked
19445 as prototyped, it consults @kbd{set coerce-float-to-double}.
19448 @kindex set coerce-float-to-double
19449 @item set coerce-float-to-double
19450 @itemx set coerce-float-to-double on
19451 Arguments of type @code{float} will be promoted to @code{double} when passed
19452 to an unprototyped function. This is the default setting.
19454 @item set coerce-float-to-double off
19455 Arguments of type @code{float} will be passed directly to unprototyped
19458 @kindex show coerce-float-to-double
19459 @item show coerce-float-to-double
19460 Show the current setting of promoting @code{float} to @code{double}.
19464 @kindex show cp-abi
19465 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19466 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19467 used to build your application. @value{GDBN} only fully supports
19468 programs with a single C@t{++} ABI; if your program contains code using
19469 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19470 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19471 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19472 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19473 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19474 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19479 Show the C@t{++} ABI currently in use.
19482 With no argument, show the list of supported C@t{++} ABI's.
19484 @item set cp-abi @var{abi}
19485 @itemx set cp-abi auto
19486 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19489 @node Messages/Warnings
19490 @section Optional Warnings and Messages
19492 @cindex verbose operation
19493 @cindex optional warnings
19494 By default, @value{GDBN} is silent about its inner workings. If you are
19495 running on a slow machine, you may want to use the @code{set verbose}
19496 command. This makes @value{GDBN} tell you when it does a lengthy
19497 internal operation, so you will not think it has crashed.
19499 Currently, the messages controlled by @code{set verbose} are those
19500 which announce that the symbol table for a source file is being read;
19501 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19504 @kindex set verbose
19505 @item set verbose on
19506 Enables @value{GDBN} output of certain informational messages.
19508 @item set verbose off
19509 Disables @value{GDBN} output of certain informational messages.
19511 @kindex show verbose
19513 Displays whether @code{set verbose} is on or off.
19516 By default, if @value{GDBN} encounters bugs in the symbol table of an
19517 object file, it is silent; but if you are debugging a compiler, you may
19518 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19523 @kindex set complaints
19524 @item set complaints @var{limit}
19525 Permits @value{GDBN} to output @var{limit} complaints about each type of
19526 unusual symbols before becoming silent about the problem. Set
19527 @var{limit} to zero to suppress all complaints; set it to a large number
19528 to prevent complaints from being suppressed.
19530 @kindex show complaints
19531 @item show complaints
19532 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19536 @anchor{confirmation requests}
19537 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19538 lot of stupid questions to confirm certain commands. For example, if
19539 you try to run a program which is already running:
19543 The program being debugged has been started already.
19544 Start it from the beginning? (y or n)
19547 If you are willing to unflinchingly face the consequences of your own
19548 commands, you can disable this ``feature'':
19552 @kindex set confirm
19554 @cindex confirmation
19555 @cindex stupid questions
19556 @item set confirm off
19557 Disables confirmation requests. Note that running @value{GDBN} with
19558 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19559 automatically disables confirmation requests.
19561 @item set confirm on
19562 Enables confirmation requests (the default).
19564 @kindex show confirm
19566 Displays state of confirmation requests.
19570 @cindex command tracing
19571 If you need to debug user-defined commands or sourced files you may find it
19572 useful to enable @dfn{command tracing}. In this mode each command will be
19573 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19574 quantity denoting the call depth of each command.
19577 @kindex set trace-commands
19578 @cindex command scripts, debugging
19579 @item set trace-commands on
19580 Enable command tracing.
19581 @item set trace-commands off
19582 Disable command tracing.
19583 @item show trace-commands
19584 Display the current state of command tracing.
19587 @node Debugging Output
19588 @section Optional Messages about Internal Happenings
19589 @cindex optional debugging messages
19591 @value{GDBN} has commands that enable optional debugging messages from
19592 various @value{GDBN} subsystems; normally these commands are of
19593 interest to @value{GDBN} maintainers, or when reporting a bug. This
19594 section documents those commands.
19597 @kindex set exec-done-display
19598 @item set exec-done-display
19599 Turns on or off the notification of asynchronous commands'
19600 completion. When on, @value{GDBN} will print a message when an
19601 asynchronous command finishes its execution. The default is off.
19602 @kindex show exec-done-display
19603 @item show exec-done-display
19604 Displays the current setting of asynchronous command completion
19607 @cindex gdbarch debugging info
19608 @cindex architecture debugging info
19609 @item set debug arch
19610 Turns on or off display of gdbarch debugging info. The default is off
19612 @item show debug arch
19613 Displays the current state of displaying gdbarch debugging info.
19614 @item set debug aix-thread
19615 @cindex AIX threads
19616 Display debugging messages about inner workings of the AIX thread
19618 @item show debug aix-thread
19619 Show the current state of AIX thread debugging info display.
19620 @item set debug dwarf2-die
19621 @cindex DWARF2 DIEs
19622 Dump DWARF2 DIEs after they are read in.
19623 The value is the number of nesting levels to print.
19624 A value of zero turns off the display.
19625 @item show debug dwarf2-die
19626 Show the current state of DWARF2 DIE debugging.
19627 @item set debug displaced
19628 @cindex displaced stepping debugging info
19629 Turns on or off display of @value{GDBN} debugging info for the
19630 displaced stepping support. The default is off.
19631 @item show debug displaced
19632 Displays the current state of displaying @value{GDBN} debugging info
19633 related to displaced stepping.
19634 @item set debug event
19635 @cindex event debugging info
19636 Turns on or off display of @value{GDBN} event debugging info. The
19638 @item show debug event
19639 Displays the current state of displaying @value{GDBN} event debugging
19641 @item set debug expression
19642 @cindex expression debugging info
19643 Turns on or off display of debugging info about @value{GDBN}
19644 expression parsing. The default is off.
19645 @item show debug expression
19646 Displays the current state of displaying debugging info about
19647 @value{GDBN} expression parsing.
19648 @item set debug frame
19649 @cindex frame debugging info
19650 Turns on or off display of @value{GDBN} frame debugging info. The
19652 @item show debug frame
19653 Displays the current state of displaying @value{GDBN} frame debugging
19655 @item set debug gnu-nat
19656 @cindex @sc{gnu}/Hurd debug messages
19657 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19658 @item show debug gnu-nat
19659 Show the current state of @sc{gnu}/Hurd debugging messages.
19660 @item set debug infrun
19661 @cindex inferior debugging info
19662 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19663 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19664 for implementing operations such as single-stepping the inferior.
19665 @item show debug infrun
19666 Displays the current state of @value{GDBN} inferior debugging.
19667 @item set debug lin-lwp
19668 @cindex @sc{gnu}/Linux LWP debug messages
19669 @cindex Linux lightweight processes
19670 Turns on or off debugging messages from the Linux LWP debug support.
19671 @item show debug lin-lwp
19672 Show the current state of Linux LWP debugging messages.
19673 @item set debug lin-lwp-async
19674 @cindex @sc{gnu}/Linux LWP async debug messages
19675 @cindex Linux lightweight processes
19676 Turns on or off debugging messages from the Linux LWP async debug support.
19677 @item show debug lin-lwp-async
19678 Show the current state of Linux LWP async debugging messages.
19679 @item set debug observer
19680 @cindex observer debugging info
19681 Turns on or off display of @value{GDBN} observer debugging. This
19682 includes info such as the notification of observable events.
19683 @item show debug observer
19684 Displays the current state of observer debugging.
19685 @item set debug overload
19686 @cindex C@t{++} overload debugging info
19687 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19688 info. This includes info such as ranking of functions, etc. The default
19690 @item show debug overload
19691 Displays the current state of displaying @value{GDBN} C@t{++} overload
19693 @cindex expression parser, debugging info
19694 @cindex debug expression parser
19695 @item set debug parser
19696 Turns on or off the display of expression parser debugging output.
19697 Internally, this sets the @code{yydebug} variable in the expression
19698 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19699 details. The default is off.
19700 @item show debug parser
19701 Show the current state of expression parser debugging.
19702 @cindex packets, reporting on stdout
19703 @cindex serial connections, debugging
19704 @cindex debug remote protocol
19705 @cindex remote protocol debugging
19706 @cindex display remote packets
19707 @item set debug remote
19708 Turns on or off display of reports on all packets sent back and forth across
19709 the serial line to the remote machine. The info is printed on the
19710 @value{GDBN} standard output stream. The default is off.
19711 @item show debug remote
19712 Displays the state of display of remote packets.
19713 @item set debug serial
19714 Turns on or off display of @value{GDBN} serial debugging info. The
19716 @item show debug serial
19717 Displays the current state of displaying @value{GDBN} serial debugging
19719 @item set debug solib-frv
19720 @cindex FR-V shared-library debugging
19721 Turns on or off debugging messages for FR-V shared-library code.
19722 @item show debug solib-frv
19723 Display the current state of FR-V shared-library code debugging
19725 @item set debug target
19726 @cindex target debugging info
19727 Turns on or off display of @value{GDBN} target debugging info. This info
19728 includes what is going on at the target level of GDB, as it happens. The
19729 default is 0. Set it to 1 to track events, and to 2 to also track the
19730 value of large memory transfers. Changes to this flag do not take effect
19731 until the next time you connect to a target or use the @code{run} command.
19732 @item show debug target
19733 Displays the current state of displaying @value{GDBN} target debugging
19735 @item set debug timestamp
19736 @cindex timestampping debugging info
19737 Turns on or off display of timestamps with @value{GDBN} debugging info.
19738 When enabled, seconds and microseconds are displayed before each debugging
19740 @item show debug timestamp
19741 Displays the current state of displaying timestamps with @value{GDBN}
19743 @item set debugvarobj
19744 @cindex variable object debugging info
19745 Turns on or off display of @value{GDBN} variable object debugging
19746 info. The default is off.
19747 @item show debugvarobj
19748 Displays the current state of displaying @value{GDBN} variable object
19750 @item set debug xml
19751 @cindex XML parser debugging
19752 Turns on or off debugging messages for built-in XML parsers.
19753 @item show debug xml
19754 Displays the current state of XML debugging messages.
19757 @node Other Misc Settings
19758 @section Other Miscellaneous Settings
19759 @cindex miscellaneous settings
19762 @kindex set interactive-mode
19763 @item set interactive-mode
19764 If @code{on}, forces @value{GDBN} to operate interactively.
19765 If @code{off}, forces @value{GDBN} to operate non-interactively,
19766 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19767 based on whether the debugger was started in a terminal or not.
19769 In the vast majority of cases, the debugger should be able to guess
19770 correctly which mode should be used. But this setting can be useful
19771 in certain specific cases, such as running a MinGW @value{GDBN}
19772 inside a cygwin window.
19774 @kindex show interactive-mode
19775 @item show interactive-mode
19776 Displays whether the debugger is operating in interactive mode or not.
19779 @node Extending GDB
19780 @chapter Extending @value{GDBN}
19781 @cindex extending GDB
19783 @value{GDBN} provides two mechanisms for extension. The first is based
19784 on composition of @value{GDBN} commands, and the second is based on the
19785 Python scripting language.
19787 To facilitate the use of these extensions, @value{GDBN} is capable
19788 of evaluating the contents of a file. When doing so, @value{GDBN}
19789 can recognize which scripting language is being used by looking at
19790 the filename extension. Files with an unrecognized filename extension
19791 are always treated as a @value{GDBN} Command Files.
19792 @xref{Command Files,, Command files}.
19794 You can control how @value{GDBN} evaluates these files with the following
19798 @kindex set script-extension
19799 @kindex show script-extension
19800 @item set script-extension off
19801 All scripts are always evaluated as @value{GDBN} Command Files.
19803 @item set script-extension soft
19804 The debugger determines the scripting language based on filename
19805 extension. If this scripting language is supported, @value{GDBN}
19806 evaluates the script using that language. Otherwise, it evaluates
19807 the file as a @value{GDBN} Command File.
19809 @item set script-extension strict
19810 The debugger determines the scripting language based on filename
19811 extension, and evaluates the script using that language. If the
19812 language is not supported, then the evaluation fails.
19814 @item show script-extension
19815 Display the current value of the @code{script-extension} option.
19820 * Sequences:: Canned Sequences of Commands
19821 * Python:: Scripting @value{GDBN} using Python
19825 @section Canned Sequences of Commands
19827 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19828 Command Lists}), @value{GDBN} provides two ways to store sequences of
19829 commands for execution as a unit: user-defined commands and command
19833 * Define:: How to define your own commands
19834 * Hooks:: Hooks for user-defined commands
19835 * Command Files:: How to write scripts of commands to be stored in a file
19836 * Output:: Commands for controlled output
19840 @subsection User-defined Commands
19842 @cindex user-defined command
19843 @cindex arguments, to user-defined commands
19844 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19845 which you assign a new name as a command. This is done with the
19846 @code{define} command. User commands may accept up to 10 arguments
19847 separated by whitespace. Arguments are accessed within the user command
19848 via @code{$arg0@dots{}$arg9}. A trivial example:
19852 print $arg0 + $arg1 + $arg2
19857 To execute the command use:
19864 This defines the command @code{adder}, which prints the sum of
19865 its three arguments. Note the arguments are text substitutions, so they may
19866 reference variables, use complex expressions, or even perform inferior
19869 @cindex argument count in user-defined commands
19870 @cindex how many arguments (user-defined commands)
19871 In addition, @code{$argc} may be used to find out how many arguments have
19872 been passed. This expands to a number in the range 0@dots{}10.
19877 print $arg0 + $arg1
19880 print $arg0 + $arg1 + $arg2
19888 @item define @var{commandname}
19889 Define a command named @var{commandname}. If there is already a command
19890 by that name, you are asked to confirm that you want to redefine it.
19891 @var{commandname} may be a bare command name consisting of letters,
19892 numbers, dashes, and underscores. It may also start with any predefined
19893 prefix command. For example, @samp{define target my-target} creates
19894 a user-defined @samp{target my-target} command.
19896 The definition of the command is made up of other @value{GDBN} command lines,
19897 which are given following the @code{define} command. The end of these
19898 commands is marked by a line containing @code{end}.
19901 @kindex end@r{ (user-defined commands)}
19902 @item document @var{commandname}
19903 Document the user-defined command @var{commandname}, so that it can be
19904 accessed by @code{help}. The command @var{commandname} must already be
19905 defined. This command reads lines of documentation just as @code{define}
19906 reads the lines of the command definition, ending with @code{end}.
19907 After the @code{document} command is finished, @code{help} on command
19908 @var{commandname} displays the documentation you have written.
19910 You may use the @code{document} command again to change the
19911 documentation of a command. Redefining the command with @code{define}
19912 does not change the documentation.
19914 @kindex dont-repeat
19915 @cindex don't repeat command
19917 Used inside a user-defined command, this tells @value{GDBN} that this
19918 command should not be repeated when the user hits @key{RET}
19919 (@pxref{Command Syntax, repeat last command}).
19921 @kindex help user-defined
19922 @item help user-defined
19923 List all user-defined commands, with the first line of the documentation
19928 @itemx show user @var{commandname}
19929 Display the @value{GDBN} commands used to define @var{commandname} (but
19930 not its documentation). If no @var{commandname} is given, display the
19931 definitions for all user-defined commands.
19933 @cindex infinite recursion in user-defined commands
19934 @kindex show max-user-call-depth
19935 @kindex set max-user-call-depth
19936 @item show max-user-call-depth
19937 @itemx set max-user-call-depth
19938 The value of @code{max-user-call-depth} controls how many recursion
19939 levels are allowed in user-defined commands before @value{GDBN} suspects an
19940 infinite recursion and aborts the command.
19943 In addition to the above commands, user-defined commands frequently
19944 use control flow commands, described in @ref{Command Files}.
19946 When user-defined commands are executed, the
19947 commands of the definition are not printed. An error in any command
19948 stops execution of the user-defined command.
19950 If used interactively, commands that would ask for confirmation proceed
19951 without asking when used inside a user-defined command. Many @value{GDBN}
19952 commands that normally print messages to say what they are doing omit the
19953 messages when used in a user-defined command.
19956 @subsection User-defined Command Hooks
19957 @cindex command hooks
19958 @cindex hooks, for commands
19959 @cindex hooks, pre-command
19962 You may define @dfn{hooks}, which are a special kind of user-defined
19963 command. Whenever you run the command @samp{foo}, if the user-defined
19964 command @samp{hook-foo} exists, it is executed (with no arguments)
19965 before that command.
19967 @cindex hooks, post-command
19969 A hook may also be defined which is run after the command you executed.
19970 Whenever you run the command @samp{foo}, if the user-defined command
19971 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19972 that command. Post-execution hooks may exist simultaneously with
19973 pre-execution hooks, for the same command.
19975 It is valid for a hook to call the command which it hooks. If this
19976 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19978 @c It would be nice if hookpost could be passed a parameter indicating
19979 @c if the command it hooks executed properly or not. FIXME!
19981 @kindex stop@r{, a pseudo-command}
19982 In addition, a pseudo-command, @samp{stop} exists. Defining
19983 (@samp{hook-stop}) makes the associated commands execute every time
19984 execution stops in your program: before breakpoint commands are run,
19985 displays are printed, or the stack frame is printed.
19987 For example, to ignore @code{SIGALRM} signals while
19988 single-stepping, but treat them normally during normal execution,
19993 handle SIGALRM nopass
19997 handle SIGALRM pass
20000 define hook-continue
20001 handle SIGALRM pass
20005 As a further example, to hook at the beginning and end of the @code{echo}
20006 command, and to add extra text to the beginning and end of the message,
20014 define hookpost-echo
20018 (@value{GDBP}) echo Hello World
20019 <<<---Hello World--->>>
20024 You can define a hook for any single-word command in @value{GDBN}, but
20025 not for command aliases; you should define a hook for the basic command
20026 name, e.g.@: @code{backtrace} rather than @code{bt}.
20027 @c FIXME! So how does Joe User discover whether a command is an alias
20029 You can hook a multi-word command by adding @code{hook-} or
20030 @code{hookpost-} to the last word of the command, e.g.@:
20031 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20033 If an error occurs during the execution of your hook, execution of
20034 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20035 (before the command that you actually typed had a chance to run).
20037 If you try to define a hook which does not match any known command, you
20038 get a warning from the @code{define} command.
20040 @node Command Files
20041 @subsection Command Files
20043 @cindex command files
20044 @cindex scripting commands
20045 A command file for @value{GDBN} is a text file made of lines that are
20046 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20047 also be included. An empty line in a command file does nothing; it
20048 does not mean to repeat the last command, as it would from the
20051 You can request the execution of a command file with the @code{source}
20052 command. Note that the @code{source} command is also used to evaluate
20053 scripts that are not Command Files. The exact behavior can be configured
20054 using the @code{script-extension} setting.
20055 @xref{Extending GDB,, Extending GDB}.
20059 @cindex execute commands from a file
20060 @item source [-s] [-v] @var{filename}
20061 Execute the command file @var{filename}.
20064 The lines in a command file are generally executed sequentially,
20065 unless the order of execution is changed by one of the
20066 @emph{flow-control commands} described below. The commands are not
20067 printed as they are executed. An error in any command terminates
20068 execution of the command file and control is returned to the console.
20070 @value{GDBN} first searches for @var{filename} in the current directory.
20071 If the file is not found there, and @var{filename} does not specify a
20072 directory, then @value{GDBN} also looks for the file on the source search path
20073 (specified with the @samp{directory} command);
20074 except that @file{$cdir} is not searched because the compilation directory
20075 is not relevant to scripts.
20077 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20078 on the search path even if @var{filename} specifies a directory.
20079 The search is done by appending @var{filename} to each element of the
20080 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20081 and the search path contains @file{/home/user} then @value{GDBN} will
20082 look for the script @file{/home/user/mylib/myscript}.
20083 The search is also done if @var{filename} is an absolute path.
20084 For example, if @var{filename} is @file{/tmp/myscript} and
20085 the search path contains @file{/home/user} then @value{GDBN} will
20086 look for the script @file{/home/user/tmp/myscript}.
20087 For DOS-like systems, if @var{filename} contains a drive specification,
20088 it is stripped before concatenation. For example, if @var{filename} is
20089 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20090 will look for the script @file{c:/tmp/myscript}.
20092 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20093 each command as it is executed. The option must be given before
20094 @var{filename}, and is interpreted as part of the filename anywhere else.
20096 Commands that would ask for confirmation if used interactively proceed
20097 without asking when used in a command file. Many @value{GDBN} commands that
20098 normally print messages to say what they are doing omit the messages
20099 when called from command files.
20101 @value{GDBN} also accepts command input from standard input. In this
20102 mode, normal output goes to standard output and error output goes to
20103 standard error. Errors in a command file supplied on standard input do
20104 not terminate execution of the command file---execution continues with
20108 gdb < cmds > log 2>&1
20111 (The syntax above will vary depending on the shell used.) This example
20112 will execute commands from the file @file{cmds}. All output and errors
20113 would be directed to @file{log}.
20115 Since commands stored on command files tend to be more general than
20116 commands typed interactively, they frequently need to deal with
20117 complicated situations, such as different or unexpected values of
20118 variables and symbols, changes in how the program being debugged is
20119 built, etc. @value{GDBN} provides a set of flow-control commands to
20120 deal with these complexities. Using these commands, you can write
20121 complex scripts that loop over data structures, execute commands
20122 conditionally, etc.
20129 This command allows to include in your script conditionally executed
20130 commands. The @code{if} command takes a single argument, which is an
20131 expression to evaluate. It is followed by a series of commands that
20132 are executed only if the expression is true (its value is nonzero).
20133 There can then optionally be an @code{else} line, followed by a series
20134 of commands that are only executed if the expression was false. The
20135 end of the list is marked by a line containing @code{end}.
20139 This command allows to write loops. Its syntax is similar to
20140 @code{if}: the command takes a single argument, which is an expression
20141 to evaluate, and must be followed by the commands to execute, one per
20142 line, terminated by an @code{end}. These commands are called the
20143 @dfn{body} of the loop. The commands in the body of @code{while} are
20144 executed repeatedly as long as the expression evaluates to true.
20148 This command exits the @code{while} loop in whose body it is included.
20149 Execution of the script continues after that @code{while}s @code{end}
20152 @kindex loop_continue
20153 @item loop_continue
20154 This command skips the execution of the rest of the body of commands
20155 in the @code{while} loop in whose body it is included. Execution
20156 branches to the beginning of the @code{while} loop, where it evaluates
20157 the controlling expression.
20159 @kindex end@r{ (if/else/while commands)}
20161 Terminate the block of commands that are the body of @code{if},
20162 @code{else}, or @code{while} flow-control commands.
20167 @subsection Commands for Controlled Output
20169 During the execution of a command file or a user-defined command, normal
20170 @value{GDBN} output is suppressed; the only output that appears is what is
20171 explicitly printed by the commands in the definition. This section
20172 describes three commands useful for generating exactly the output you
20177 @item echo @var{text}
20178 @c I do not consider backslash-space a standard C escape sequence
20179 @c because it is not in ANSI.
20180 Print @var{text}. Nonprinting characters can be included in
20181 @var{text} using C escape sequences, such as @samp{\n} to print a
20182 newline. @strong{No newline is printed unless you specify one.}
20183 In addition to the standard C escape sequences, a backslash followed
20184 by a space stands for a space. This is useful for displaying a
20185 string with spaces at the beginning or the end, since leading and
20186 trailing spaces are otherwise trimmed from all arguments.
20187 To print @samp{@w{ }and foo =@w{ }}, use the command
20188 @samp{echo \@w{ }and foo = \@w{ }}.
20190 A backslash at the end of @var{text} can be used, as in C, to continue
20191 the command onto subsequent lines. For example,
20194 echo This is some text\n\
20195 which is continued\n\
20196 onto several lines.\n
20199 produces the same output as
20202 echo This is some text\n
20203 echo which is continued\n
20204 echo onto several lines.\n
20208 @item output @var{expression}
20209 Print the value of @var{expression} and nothing but that value: no
20210 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20211 value history either. @xref{Expressions, ,Expressions}, for more information
20214 @item output/@var{fmt} @var{expression}
20215 Print the value of @var{expression} in format @var{fmt}. You can use
20216 the same formats as for @code{print}. @xref{Output Formats,,Output
20217 Formats}, for more information.
20220 @item printf @var{template}, @var{expressions}@dots{}
20221 Print the values of one or more @var{expressions} under the control of
20222 the string @var{template}. To print several values, make
20223 @var{expressions} be a comma-separated list of individual expressions,
20224 which may be either numbers or pointers. Their values are printed as
20225 specified by @var{template}, exactly as a C program would do by
20226 executing the code below:
20229 printf (@var{template}, @var{expressions}@dots{});
20232 As in @code{C} @code{printf}, ordinary characters in @var{template}
20233 are printed verbatim, while @dfn{conversion specification} introduced
20234 by the @samp{%} character cause subsequent @var{expressions} to be
20235 evaluated, their values converted and formatted according to type and
20236 style information encoded in the conversion specifications, and then
20239 For example, you can print two values in hex like this:
20242 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20245 @code{printf} supports all the standard @code{C} conversion
20246 specifications, including the flags and modifiers between the @samp{%}
20247 character and the conversion letter, with the following exceptions:
20251 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20254 The modifier @samp{*} is not supported for specifying precision or
20258 The @samp{'} flag (for separation of digits into groups according to
20259 @code{LC_NUMERIC'}) is not supported.
20262 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20266 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20269 The conversion letters @samp{a} and @samp{A} are not supported.
20273 Note that the @samp{ll} type modifier is supported only if the
20274 underlying @code{C} implementation used to build @value{GDBN} supports
20275 the @code{long long int} type, and the @samp{L} type modifier is
20276 supported only if @code{long double} type is available.
20278 As in @code{C}, @code{printf} supports simple backslash-escape
20279 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20280 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20281 single character. Octal and hexadecimal escape sequences are not
20284 Additionally, @code{printf} supports conversion specifications for DFP
20285 (@dfn{Decimal Floating Point}) types using the following length modifiers
20286 together with a floating point specifier.
20291 @samp{H} for printing @code{Decimal32} types.
20294 @samp{D} for printing @code{Decimal64} types.
20297 @samp{DD} for printing @code{Decimal128} types.
20300 If the underlying @code{C} implementation used to build @value{GDBN} has
20301 support for the three length modifiers for DFP types, other modifiers
20302 such as width and precision will also be available for @value{GDBN} to use.
20304 In case there is no such @code{C} support, no additional modifiers will be
20305 available and the value will be printed in the standard way.
20307 Here's an example of printing DFP types using the above conversion letters:
20309 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20313 @item eval @var{template}, @var{expressions}@dots{}
20314 Convert the values of one or more @var{expressions} under the control of
20315 the string @var{template} to a command line, and call it.
20320 @section Scripting @value{GDBN} using Python
20321 @cindex python scripting
20322 @cindex scripting with python
20324 You can script @value{GDBN} using the @uref{http://www.python.org/,
20325 Python programming language}. This feature is available only if
20326 @value{GDBN} was configured using @option{--with-python}.
20328 @cindex python directory
20329 Python scripts used by @value{GDBN} should be installed in
20330 @file{@var{data-directory}/python}, where @var{data-directory} is
20331 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). This directory, known as the @dfn{python directory},
20332 is automatically added to the Python Search Path in order to allow
20333 the Python interpreter to locate all scripts installed at this location.
20336 * Python Commands:: Accessing Python from @value{GDBN}.
20337 * Python API:: Accessing @value{GDBN} from Python.
20338 * Auto-loading:: Automatically loading Python code.
20341 @node Python Commands
20342 @subsection Python Commands
20343 @cindex python commands
20344 @cindex commands to access python
20346 @value{GDBN} provides one command for accessing the Python interpreter,
20347 and one related setting:
20351 @item python @r{[}@var{code}@r{]}
20352 The @code{python} command can be used to evaluate Python code.
20354 If given an argument, the @code{python} command will evaluate the
20355 argument as a Python command. For example:
20358 (@value{GDBP}) python print 23
20362 If you do not provide an argument to @code{python}, it will act as a
20363 multi-line command, like @code{define}. In this case, the Python
20364 script is made up of subsequent command lines, given after the
20365 @code{python} command. This command list is terminated using a line
20366 containing @code{end}. For example:
20369 (@value{GDBP}) python
20371 End with a line saying just "end".
20377 @kindex maint set python print-stack
20378 @item maint set python print-stack
20379 By default, @value{GDBN} will print a stack trace when an error occurs
20380 in a Python script. This can be controlled using @code{maint set
20381 python print-stack}: if @code{on}, the default, then Python stack
20382 printing is enabled; if @code{off}, then Python stack printing is
20386 It is also possible to execute a Python script from the @value{GDBN}
20390 @item source @file{script-name}
20391 The script name must end with @samp{.py} and @value{GDBN} must be configured
20392 to recognize the script language based on filename extension using
20393 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20395 @item python execfile ("script-name")
20396 This method is based on the @code{execfile} Python built-in function,
20397 and thus is always available.
20401 @subsection Python API
20403 @cindex programming in python
20405 @cindex python stdout
20406 @cindex python pagination
20407 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20408 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20409 A Python program which outputs to one of these streams may have its
20410 output interrupted by the user (@pxref{Screen Size}). In this
20411 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20414 * Basic Python:: Basic Python Functions.
20415 * Exception Handling::
20416 * Values From Inferior::
20417 * Types In Python:: Python representation of types.
20418 * Pretty Printing API:: Pretty-printing values.
20419 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20420 * Disabling Pretty-Printers:: Disabling broken printers.
20421 * Inferiors In Python:: Python representation of inferiors (processes)
20422 * Threads In Python:: Accessing inferior threads from Python.
20423 * Commands In Python:: Implementing new commands in Python.
20424 * Parameters In Python:: Adding new @value{GDBN} parameters.
20425 * Functions In Python:: Writing new convenience functions.
20426 * Progspaces In Python:: Program spaces.
20427 * Objfiles In Python:: Object files.
20428 * Frames In Python:: Accessing inferior stack frames from Python.
20429 * Blocks In Python:: Accessing frame blocks from Python.
20430 * Symbols In Python:: Python representation of symbols.
20431 * Symbol Tables In Python:: Python representation of symbol tables.
20432 * Lazy Strings In Python:: Python representation of lazy strings.
20433 * Breakpoints In Python:: Manipulating breakpoints using Python.
20437 @subsubsection Basic Python
20439 @cindex python functions
20440 @cindex python module
20442 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20443 methods and classes added by @value{GDBN} are placed in this module.
20444 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20445 use in all scripts evaluated by the @code{python} command.
20447 @findex gdb.PYTHONDIR
20449 A string containing the python directory (@pxref{Python}).
20452 @findex gdb.execute
20453 @defun execute command [from_tty] [to_string]
20454 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20455 If a GDB exception happens while @var{command} runs, it is
20456 translated as described in @ref{Exception Handling,,Exception Handling}.
20458 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20459 command as having originated from the user invoking it interactively.
20460 It must be a boolean value. If omitted, it defaults to @code{False}.
20462 By default, any output produced by @var{command} is sent to
20463 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20464 @code{True}, then output will be collected by @code{gdb.execute} and
20465 returned as a string. The default is @code{False}, in which case the
20466 return value is @code{None}.
20469 @findex gdb.breakpoints
20471 Return a sequence holding all of @value{GDBN}'s breakpoints.
20472 @xref{Breakpoints In Python}, for more information.
20475 @findex gdb.parameter
20476 @defun parameter parameter
20477 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20478 string naming the parameter to look up; @var{parameter} may contain
20479 spaces if the parameter has a multi-part name. For example,
20480 @samp{print object} is a valid parameter name.
20482 If the named parameter does not exist, this function throws a
20483 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20484 a Python value of the appropriate type, and returned.
20487 @findex gdb.history
20488 @defun history number
20489 Return a value from @value{GDBN}'s value history (@pxref{Value
20490 History}). @var{number} indicates which history element to return.
20491 If @var{number} is negative, then @value{GDBN} will take its absolute value
20492 and count backward from the last element (i.e., the most recent element) to
20493 find the value to return. If @var{number} is zero, then @value{GDBN} will
20494 return the most recent element. If the element specified by @var{number}
20495 doesn't exist in the value history, a @code{RuntimeError} exception will be
20498 If no exception is raised, the return value is always an instance of
20499 @code{gdb.Value} (@pxref{Values From Inferior}).
20502 @findex gdb.parse_and_eval
20503 @defun parse_and_eval expression
20504 Parse @var{expression} as an expression in the current language,
20505 evaluate it, and return the result as a @code{gdb.Value}.
20506 @var{expression} must be a string.
20508 This function can be useful when implementing a new command
20509 (@pxref{Commands In Python}), as it provides a way to parse the
20510 command's argument as an expression. It is also useful simply to
20511 compute values, for example, it is the only way to get the value of a
20512 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20516 @defun write string
20517 Print a string to @value{GDBN}'s paginated standard output stream.
20518 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20519 call this function.
20524 Flush @value{GDBN}'s paginated standard output stream. Flushing
20525 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20529 @findex gdb.target_charset
20530 @defun target_charset
20531 Return the name of the current target character set (@pxref{Character
20532 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20533 that @samp{auto} is never returned.
20536 @findex gdb.target_wide_charset
20537 @defun target_wide_charset
20538 Return the name of the current target wide character set
20539 (@pxref{Character Sets}). This differs from
20540 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20544 @node Exception Handling
20545 @subsubsection Exception Handling
20546 @cindex python exceptions
20547 @cindex exceptions, python
20549 When executing the @code{python} command, Python exceptions
20550 uncaught within the Python code are translated to calls to
20551 @value{GDBN} error-reporting mechanism. If the command that called
20552 @code{python} does not handle the error, @value{GDBN} will
20553 terminate it and print an error message containing the Python
20554 exception name, the associated value, and the Python call stack
20555 backtrace at the point where the exception was raised. Example:
20558 (@value{GDBP}) python print foo
20559 Traceback (most recent call last):
20560 File "<string>", line 1, in <module>
20561 NameError: name 'foo' is not defined
20564 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20565 code are converted to Python @code{RuntimeError} exceptions. User
20566 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20567 prompt) is translated to a Python @code{KeyboardInterrupt}
20568 exception. If you catch these exceptions in your Python code, your
20569 exception handler will see @code{RuntimeError} or
20570 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20571 message as its value, and the Python call stack backtrace at the
20572 Python statement closest to where the @value{GDBN} error occured as the
20575 @findex gdb.GdbError
20576 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20577 it is useful to be able to throw an exception that doesn't cause a
20578 traceback to be printed. For example, the user may have invoked the
20579 command incorrectly. Use the @code{gdb.GdbError} exception
20580 to handle this case. Example:
20584 >class HelloWorld (gdb.Command):
20585 > """Greet the whole world."""
20586 > def __init__ (self):
20587 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20588 > def invoke (self, args, from_tty):
20589 > argv = gdb.string_to_argv (args)
20590 > if len (argv) != 0:
20591 > raise gdb.GdbError ("hello-world takes no arguments")
20592 > print "Hello, World!"
20595 (gdb) hello-world 42
20596 hello-world takes no arguments
20599 @node Values From Inferior
20600 @subsubsection Values From Inferior
20601 @cindex values from inferior, with Python
20602 @cindex python, working with values from inferior
20604 @cindex @code{gdb.Value}
20605 @value{GDBN} provides values it obtains from the inferior program in
20606 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20607 for its internal bookkeeping of the inferior's values, and for
20608 fetching values when necessary.
20610 Inferior values that are simple scalars can be used directly in
20611 Python expressions that are valid for the value's data type. Here's
20612 an example for an integer or floating-point value @code{some_val}:
20619 As result of this, @code{bar} will also be a @code{gdb.Value} object
20620 whose values are of the same type as those of @code{some_val}.
20622 Inferior values that are structures or instances of some class can
20623 be accessed using the Python @dfn{dictionary syntax}. For example, if
20624 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20625 can access its @code{foo} element with:
20628 bar = some_val['foo']
20631 Again, @code{bar} will also be a @code{gdb.Value} object.
20633 A @code{gdb.Value} that represents a function can be executed via
20634 inferior function call. Any arguments provided to the call must match
20635 the function's prototype, and must be provided in the order specified
20638 For example, @code{some_val} is a @code{gdb.Value} instance
20639 representing a function that takes two integers as arguments. To
20640 execute this function, call it like so:
20643 result = some_val (10,20)
20646 Any values returned from a function call will be stored as a
20649 The following attributes are provided:
20652 @defivar Value address
20653 If this object is addressable, this read-only attribute holds a
20654 @code{gdb.Value} object representing the address. Otherwise,
20655 this attribute holds @code{None}.
20658 @cindex optimized out value in Python
20659 @defivar Value is_optimized_out
20660 This read-only boolean attribute is true if the compiler optimized out
20661 this value, thus it is not available for fetching from the inferior.
20664 @defivar Value type
20665 The type of this @code{gdb.Value}. The value of this attribute is a
20666 @code{gdb.Type} object.
20670 The following methods are provided:
20673 @defmethod Value cast type
20674 Return a new instance of @code{gdb.Value} that is the result of
20675 casting this instance to the type described by @var{type}, which must
20676 be a @code{gdb.Type} object. If the cast cannot be performed for some
20677 reason, this method throws an exception.
20680 @defmethod Value dereference
20681 For pointer data types, this method returns a new @code{gdb.Value} object
20682 whose contents is the object pointed to by the pointer. For example, if
20683 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20690 then you can use the corresponding @code{gdb.Value} to access what
20691 @code{foo} points to like this:
20694 bar = foo.dereference ()
20697 The result @code{bar} will be a @code{gdb.Value} object holding the
20698 value pointed to by @code{foo}.
20701 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20702 If this @code{gdb.Value} represents a string, then this method
20703 converts the contents to a Python string. Otherwise, this method will
20704 throw an exception.
20706 Strings are recognized in a language-specific way; whether a given
20707 @code{gdb.Value} represents a string is determined by the current
20710 For C-like languages, a value is a string if it is a pointer to or an
20711 array of characters or ints. The string is assumed to be terminated
20712 by a zero of the appropriate width. However if the optional length
20713 argument is given, the string will be converted to that given length,
20714 ignoring any embedded zeros that the string may contain.
20716 If the optional @var{encoding} argument is given, it must be a string
20717 naming the encoding of the string in the @code{gdb.Value}, such as
20718 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20719 the same encodings as the corresponding argument to Python's
20720 @code{string.decode} method, and the Python codec machinery will be used
20721 to convert the string. If @var{encoding} is not given, or if
20722 @var{encoding} is the empty string, then either the @code{target-charset}
20723 (@pxref{Character Sets}) will be used, or a language-specific encoding
20724 will be used, if the current language is able to supply one.
20726 The optional @var{errors} argument is the same as the corresponding
20727 argument to Python's @code{string.decode} method.
20729 If the optional @var{length} argument is given, the string will be
20730 fetched and converted to the given length.
20733 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20734 If this @code{gdb.Value} represents a string, then this method
20735 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20736 In Python}). Otherwise, this method will throw an exception.
20738 If the optional @var{encoding} argument is given, it must be a string
20739 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20740 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20741 @var{encoding} argument is an encoding that @value{GDBN} does
20742 recognize, @value{GDBN} will raise an error.
20744 When a lazy string is printed, the @value{GDBN} encoding machinery is
20745 used to convert the string during printing. If the optional
20746 @var{encoding} argument is not provided, or is an empty string,
20747 @value{GDBN} will automatically select the encoding most suitable for
20748 the string type. For further information on encoding in @value{GDBN}
20749 please see @ref{Character Sets}.
20751 If the optional @var{length} argument is given, the string will be
20752 fetched and encoded to the length of characters specified. If
20753 the @var{length} argument is not provided, the string will be fetched
20754 and encoded until a null of appropriate width is found.
20758 @node Types In Python
20759 @subsubsection Types In Python
20760 @cindex types in Python
20761 @cindex Python, working with types
20764 @value{GDBN} represents types from the inferior using the class
20767 The following type-related functions are available in the @code{gdb}
20770 @findex gdb.lookup_type
20771 @defun lookup_type name [block]
20772 This function looks up a type by name. @var{name} is the name of the
20773 type to look up. It must be a string.
20775 If @var{block} is given, then @var{name} is looked up in that scope.
20776 Otherwise, it is searched for globally.
20778 Ordinarily, this function will return an instance of @code{gdb.Type}.
20779 If the named type cannot be found, it will throw an exception.
20782 An instance of @code{Type} has the following attributes:
20786 The type code for this type. The type code will be one of the
20787 @code{TYPE_CODE_} constants defined below.
20790 @defivar Type sizeof
20791 The size of this type, in target @code{char} units. Usually, a
20792 target's @code{char} type will be an 8-bit byte. However, on some
20793 unusual platforms, this type may have a different size.
20797 The tag name for this type. The tag name is the name after
20798 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20799 languages have this concept. If this type has no tag name, then
20800 @code{None} is returned.
20804 The following methods are provided:
20807 @defmethod Type fields
20808 For structure and union types, this method returns the fields. Range
20809 types have two fields, the minimum and maximum values. Enum types
20810 have one field per enum constant. Function and method types have one
20811 field per parameter. The base types of C@t{++} classes are also
20812 represented as fields. If the type has no fields, or does not fit
20813 into one of these categories, an empty sequence will be returned.
20815 Each field is an object, with some pre-defined attributes:
20818 This attribute is not available for @code{static} fields (as in
20819 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20820 position of the field.
20823 The name of the field, or @code{None} for anonymous fields.
20826 This is @code{True} if the field is artificial, usually meaning that
20827 it was provided by the compiler and not the user. This attribute is
20828 always provided, and is @code{False} if the field is not artificial.
20830 @item is_base_class
20831 This is @code{True} if the field represents a base class of a C@t{++}
20832 structure. This attribute is always provided, and is @code{False}
20833 if the field is not a base class of the type that is the argument of
20834 @code{fields}, or if that type was not a C@t{++} class.
20837 If the field is packed, or is a bitfield, then this will have a
20838 non-zero value, which is the size of the field in bits. Otherwise,
20839 this will be zero; in this case the field's size is given by its type.
20842 The type of the field. This is usually an instance of @code{Type},
20843 but it can be @code{None} in some situations.
20847 @defmethod Type const
20848 Return a new @code{gdb.Type} object which represents a
20849 @code{const}-qualified variant of this type.
20852 @defmethod Type volatile
20853 Return a new @code{gdb.Type} object which represents a
20854 @code{volatile}-qualified variant of this type.
20857 @defmethod Type unqualified
20858 Return a new @code{gdb.Type} object which represents an unqualified
20859 variant of this type. That is, the result is neither @code{const} nor
20863 @defmethod Type range
20864 Return a Python @code{Tuple} object that contains two elements: the
20865 low bound of the argument type and the high bound of that type. If
20866 the type does not have a range, @value{GDBN} will raise a
20867 @code{RuntimeError} exception.
20870 @defmethod Type reference
20871 Return a new @code{gdb.Type} object which represents a reference to this
20875 @defmethod Type pointer
20876 Return a new @code{gdb.Type} object which represents a pointer to this
20880 @defmethod Type strip_typedefs
20881 Return a new @code{gdb.Type} that represents the real type,
20882 after removing all layers of typedefs.
20885 @defmethod Type target
20886 Return a new @code{gdb.Type} object which represents the target type
20889 For a pointer type, the target type is the type of the pointed-to
20890 object. For an array type (meaning C-like arrays), the target type is
20891 the type of the elements of the array. For a function or method type,
20892 the target type is the type of the return value. For a complex type,
20893 the target type is the type of the elements. For a typedef, the
20894 target type is the aliased type.
20896 If the type does not have a target, this method will throw an
20900 @defmethod Type template_argument n [block]
20901 If this @code{gdb.Type} is an instantiation of a template, this will
20902 return a new @code{gdb.Type} which represents the type of the
20903 @var{n}th template argument.
20905 If this @code{gdb.Type} is not a template type, this will throw an
20906 exception. Ordinarily, only C@t{++} code will have template types.
20908 If @var{block} is given, then @var{name} is looked up in that scope.
20909 Otherwise, it is searched for globally.
20914 Each type has a code, which indicates what category this type falls
20915 into. The available type categories are represented by constants
20916 defined in the @code{gdb} module:
20919 @findex TYPE_CODE_PTR
20920 @findex gdb.TYPE_CODE_PTR
20921 @item TYPE_CODE_PTR
20922 The type is a pointer.
20924 @findex TYPE_CODE_ARRAY
20925 @findex gdb.TYPE_CODE_ARRAY
20926 @item TYPE_CODE_ARRAY
20927 The type is an array.
20929 @findex TYPE_CODE_STRUCT
20930 @findex gdb.TYPE_CODE_STRUCT
20931 @item TYPE_CODE_STRUCT
20932 The type is a structure.
20934 @findex TYPE_CODE_UNION
20935 @findex gdb.TYPE_CODE_UNION
20936 @item TYPE_CODE_UNION
20937 The type is a union.
20939 @findex TYPE_CODE_ENUM
20940 @findex gdb.TYPE_CODE_ENUM
20941 @item TYPE_CODE_ENUM
20942 The type is an enum.
20944 @findex TYPE_CODE_FLAGS
20945 @findex gdb.TYPE_CODE_FLAGS
20946 @item TYPE_CODE_FLAGS
20947 A bit flags type, used for things such as status registers.
20949 @findex TYPE_CODE_FUNC
20950 @findex gdb.TYPE_CODE_FUNC
20951 @item TYPE_CODE_FUNC
20952 The type is a function.
20954 @findex TYPE_CODE_INT
20955 @findex gdb.TYPE_CODE_INT
20956 @item TYPE_CODE_INT
20957 The type is an integer type.
20959 @findex TYPE_CODE_FLT
20960 @findex gdb.TYPE_CODE_FLT
20961 @item TYPE_CODE_FLT
20962 A floating point type.
20964 @findex TYPE_CODE_VOID
20965 @findex gdb.TYPE_CODE_VOID
20966 @item TYPE_CODE_VOID
20967 The special type @code{void}.
20969 @findex TYPE_CODE_SET
20970 @findex gdb.TYPE_CODE_SET
20971 @item TYPE_CODE_SET
20974 @findex TYPE_CODE_RANGE
20975 @findex gdb.TYPE_CODE_RANGE
20976 @item TYPE_CODE_RANGE
20977 A range type, that is, an integer type with bounds.
20979 @findex TYPE_CODE_STRING
20980 @findex gdb.TYPE_CODE_STRING
20981 @item TYPE_CODE_STRING
20982 A string type. Note that this is only used for certain languages with
20983 language-defined string types; C strings are not represented this way.
20985 @findex TYPE_CODE_BITSTRING
20986 @findex gdb.TYPE_CODE_BITSTRING
20987 @item TYPE_CODE_BITSTRING
20990 @findex TYPE_CODE_ERROR
20991 @findex gdb.TYPE_CODE_ERROR
20992 @item TYPE_CODE_ERROR
20993 An unknown or erroneous type.
20995 @findex TYPE_CODE_METHOD
20996 @findex gdb.TYPE_CODE_METHOD
20997 @item TYPE_CODE_METHOD
20998 A method type, as found in C@t{++} or Java.
21000 @findex TYPE_CODE_METHODPTR
21001 @findex gdb.TYPE_CODE_METHODPTR
21002 @item TYPE_CODE_METHODPTR
21003 A pointer-to-member-function.
21005 @findex TYPE_CODE_MEMBERPTR
21006 @findex gdb.TYPE_CODE_MEMBERPTR
21007 @item TYPE_CODE_MEMBERPTR
21008 A pointer-to-member.
21010 @findex TYPE_CODE_REF
21011 @findex gdb.TYPE_CODE_REF
21012 @item TYPE_CODE_REF
21015 @findex TYPE_CODE_CHAR
21016 @findex gdb.TYPE_CODE_CHAR
21017 @item TYPE_CODE_CHAR
21020 @findex TYPE_CODE_BOOL
21021 @findex gdb.TYPE_CODE_BOOL
21022 @item TYPE_CODE_BOOL
21025 @findex TYPE_CODE_COMPLEX
21026 @findex gdb.TYPE_CODE_COMPLEX
21027 @item TYPE_CODE_COMPLEX
21028 A complex float type.
21030 @findex TYPE_CODE_TYPEDEF
21031 @findex gdb.TYPE_CODE_TYPEDEF
21032 @item TYPE_CODE_TYPEDEF
21033 A typedef to some other type.
21035 @findex TYPE_CODE_NAMESPACE
21036 @findex gdb.TYPE_CODE_NAMESPACE
21037 @item TYPE_CODE_NAMESPACE
21038 A C@t{++} namespace.
21040 @findex TYPE_CODE_DECFLOAT
21041 @findex gdb.TYPE_CODE_DECFLOAT
21042 @item TYPE_CODE_DECFLOAT
21043 A decimal floating point type.
21045 @findex TYPE_CODE_INTERNAL_FUNCTION
21046 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21047 @item TYPE_CODE_INTERNAL_FUNCTION
21048 A function internal to @value{GDBN}. This is the type used to represent
21049 convenience functions.
21052 @node Pretty Printing API
21053 @subsubsection Pretty Printing API
21055 An example output is provided (@pxref{Pretty Printing}).
21057 A pretty-printer is just an object that holds a value and implements a
21058 specific interface, defined here.
21060 @defop Operation {pretty printer} children (self)
21061 @value{GDBN} will call this method on a pretty-printer to compute the
21062 children of the pretty-printer's value.
21064 This method must return an object conforming to the Python iterator
21065 protocol. Each item returned by the iterator must be a tuple holding
21066 two elements. The first element is the ``name'' of the child; the
21067 second element is the child's value. The value can be any Python
21068 object which is convertible to a @value{GDBN} value.
21070 This method is optional. If it does not exist, @value{GDBN} will act
21071 as though the value has no children.
21074 @defop Operation {pretty printer} display_hint (self)
21075 The CLI may call this method and use its result to change the
21076 formatting of a value. The result will also be supplied to an MI
21077 consumer as a @samp{displayhint} attribute of the variable being
21080 This method is optional. If it does exist, this method must return a
21083 Some display hints are predefined by @value{GDBN}:
21087 Indicate that the object being printed is ``array-like''. The CLI
21088 uses this to respect parameters such as @code{set print elements} and
21089 @code{set print array}.
21092 Indicate that the object being printed is ``map-like'', and that the
21093 children of this value can be assumed to alternate between keys and
21097 Indicate that the object being printed is ``string-like''. If the
21098 printer's @code{to_string} method returns a Python string of some
21099 kind, then @value{GDBN} will call its internal language-specific
21100 string-printing function to format the string. For the CLI this means
21101 adding quotation marks, possibly escaping some characters, respecting
21102 @code{set print elements}, and the like.
21106 @defop Operation {pretty printer} to_string (self)
21107 @value{GDBN} will call this method to display the string
21108 representation of the value passed to the object's constructor.
21110 When printing from the CLI, if the @code{to_string} method exists,
21111 then @value{GDBN} will prepend its result to the values returned by
21112 @code{children}. Exactly how this formatting is done is dependent on
21113 the display hint, and may change as more hints are added. Also,
21114 depending on the print settings (@pxref{Print Settings}), the CLI may
21115 print just the result of @code{to_string} in a stack trace, omitting
21116 the result of @code{children}.
21118 If this method returns a string, it is printed verbatim.
21120 Otherwise, if this method returns an instance of @code{gdb.Value},
21121 then @value{GDBN} prints this value. This may result in a call to
21122 another pretty-printer.
21124 If instead the method returns a Python value which is convertible to a
21125 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21126 the resulting value. Again, this may result in a call to another
21127 pretty-printer. Python scalars (integers, floats, and booleans) and
21128 strings are convertible to @code{gdb.Value}; other types are not.
21130 Finally, if this method returns @code{None} then no further operations
21131 are peformed in this method and nothing is printed.
21133 If the result is not one of these types, an exception is raised.
21136 @node Selecting Pretty-Printers
21137 @subsubsection Selecting Pretty-Printers
21139 The Python list @code{gdb.pretty_printers} contains an array of
21140 functions or callable objects that have been registered via addition
21141 as a pretty-printer.
21142 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21143 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21146 A function on one of these lists is passed a single @code{gdb.Value}
21147 argument and should return a pretty-printer object conforming to the
21148 interface definition above (@pxref{Pretty Printing API}). If a function
21149 cannot create a pretty-printer for the value, it should return
21152 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21153 @code{gdb.Objfile} in the current program space and iteratively calls
21154 each enabled function (@pxref{Disabling Pretty-Printers})
21155 in the list for that @code{gdb.Objfile} until it receives
21156 a pretty-printer object.
21157 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21158 searches the pretty-printer list of the current program space,
21159 calling each enabled function until an object is returned.
21160 After these lists have been exhausted, it tries the global
21161 @code{gdb.pretty_printers} list, again calling each enabled function until an
21162 object is returned.
21164 The order in which the objfiles are searched is not specified. For a
21165 given list, functions are always invoked from the head of the list,
21166 and iterated over sequentially until the end of the list, or a printer
21167 object is returned.
21169 Here is an example showing how a @code{std::string} printer might be
21173 class StdStringPrinter:
21174 "Print a std::string"
21176 def __init__ (self, val):
21179 def to_string (self):
21180 return self.val['_M_dataplus']['_M_p']
21182 def display_hint (self):
21186 And here is an example showing how a lookup function for the printer
21187 example above might be written.
21190 def str_lookup_function (val):
21192 lookup_tag = val.type.tag
21193 regex = re.compile ("^std::basic_string<char,.*>$")
21194 if lookup_tag == None:
21196 if regex.match (lookup_tag):
21197 return StdStringPrinter (val)
21202 The example lookup function extracts the value's type, and attempts to
21203 match it to a type that it can pretty-print. If it is a type the
21204 printer can pretty-print, it will return a printer object. If not, it
21205 returns @code{None}.
21207 We recommend that you put your core pretty-printers into a Python
21208 package. If your pretty-printers are for use with a library, we
21209 further recommend embedding a version number into the package name.
21210 This practice will enable @value{GDBN} to load multiple versions of
21211 your pretty-printers at the same time, because they will have
21214 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21215 can be evaluated multiple times without changing its meaning. An
21216 ideal auto-load file will consist solely of @code{import}s of your
21217 printer modules, followed by a call to a register pretty-printers with
21218 the current objfile.
21220 Taken as a whole, this approach will scale nicely to multiple
21221 inferiors, each potentially using a different library version.
21222 Embedding a version number in the Python package name will ensure that
21223 @value{GDBN} is able to load both sets of printers simultaneously.
21224 Then, because the search for pretty-printers is done by objfile, and
21225 because your auto-loaded code took care to register your library's
21226 printers with a specific objfile, @value{GDBN} will find the correct
21227 printers for the specific version of the library used by each
21230 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21231 this code might appear in @code{gdb.libstdcxx.v6}:
21234 def register_printers (objfile):
21235 objfile.pretty_printers.add (str_lookup_function)
21239 And then the corresponding contents of the auto-load file would be:
21242 import gdb.libstdcxx.v6
21243 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
21246 @node Disabling Pretty-Printers
21247 @subsubsection Disabling Pretty-Printers
21248 @cindex disabling pretty-printers
21250 For various reasons a pretty-printer may not work.
21251 For example, the underlying data structure may have changed and
21252 the pretty-printer is out of date.
21254 The consequences of a broken pretty-printer are severe enough that
21255 @value{GDBN} provides support for enabling and disabling individual
21256 printers. For example, if @code{print frame-arguments} is on,
21257 a backtrace can become highly illegible if any argument is printed
21258 with a broken printer.
21260 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21261 attribute to the registered function or callable object. If this attribute
21262 is present and its value is @code{False}, the printer is disabled, otherwise
21263 the printer is enabled.
21265 @node Inferiors In Python
21266 @subsubsection Inferiors In Python
21267 @cindex inferiors in python
21269 @findex gdb.Inferior
21270 Programs which are being run under @value{GDBN} are called inferiors
21271 (@pxref{Inferiors and Programs}). Python scripts can access
21272 information about and manipulate inferiors controlled by @value{GDBN}
21273 via objects of the @code{gdb.Inferior} class.
21275 The following inferior-related functions are available in the @code{gdb}
21279 Return a tuple containing all inferior objects.
21282 A @code{gdb.Inferior} object has the following attributes:
21285 @defivar Inferior num
21286 ID of inferior, as assigned by GDB.
21289 @defivar Inferior pid
21290 Process ID of the inferior, as assigned by the underlying operating
21294 @defivar Inferior was_attached
21295 Boolean signaling whether the inferior was created using `attach', or
21296 started by @value{GDBN} itself.
21300 A @code{gdb.Inferior} object has the following methods:
21303 @defmethod Inferior threads
21304 This method returns a tuple holding all the threads which are valid
21305 when it is called. If there are no valid threads, the method will
21306 return an empty tuple.
21309 @findex gdb.read_memory
21310 @defmethod Inferior read_memory address length
21311 Read @var{length} bytes of memory from the inferior, starting at
21312 @var{address}. Returns a buffer object, which behaves much like an array
21313 or a string. It can be modified and given to the @code{gdb.write_memory}
21317 @findex gdb.write_memory
21318 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21319 Write the contents of @var{buffer} to the inferior, starting at
21320 @var{address}. The @var{buffer} parameter must be a Python object
21321 which supports the buffer protocol, i.e., a string, an array or the
21322 object returned from @code{gdb.read_memory}. If given, @var{length}
21323 determines the number of bytes from @var{buffer} to be written.
21326 @findex gdb.search_memory
21327 @defmethod Inferior search_memory address length pattern
21328 Search a region of the inferior memory starting at @var{address} with
21329 the given @var{length} using the search pattern supplied in
21330 @var{pattern}. The @var{pattern} parameter must be a Python object
21331 which supports the buffer protocol, i.e., a string, an array or the
21332 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21333 containing the address where the pattern was found, or @code{None} if
21334 the pattern could not be found.
21338 @node Threads In Python
21339 @subsubsection Threads In Python
21340 @cindex threads in python
21342 @findex gdb.InferiorThread
21343 Python scripts can access information about, and manipulate inferior threads
21344 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21346 The following thread-related functions are available in the @code{gdb}
21349 @findex gdb.selected_thread
21350 @defun selected_thread
21351 This function returns the thread object for the selected thread. If there
21352 is no selected thread, this will return @code{None}.
21355 A @code{gdb.InferiorThread} object has the following attributes:
21358 @defivar InferiorThread num
21359 ID of the thread, as assigned by GDB.
21362 @defivar InferiorThread ptid
21363 ID of the thread, as assigned by the operating system. This attribute is a
21364 tuple containing three integers. The first is the Process ID (PID); the second
21365 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21366 Either the LWPID or TID may be 0, which indicates that the operating system
21367 does not use that identifier.
21371 A @code{gdb.InferiorThread} object has the following methods:
21374 @defmethod InferiorThread switch
21375 This changes @value{GDBN}'s currently selected thread to the one represented
21379 @defmethod InferiorThread is_stopped
21380 Return a Boolean indicating whether the thread is stopped.
21383 @defmethod InferiorThread is_running
21384 Return a Boolean indicating whether the thread is running.
21387 @defmethod InferiorThread is_exited
21388 Return a Boolean indicating whether the thread is exited.
21392 @node Commands In Python
21393 @subsubsection Commands In Python
21395 @cindex commands in python
21396 @cindex python commands
21397 You can implement new @value{GDBN} CLI commands in Python. A CLI
21398 command is implemented using an instance of the @code{gdb.Command}
21399 class, most commonly using a subclass.
21401 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21402 The object initializer for @code{Command} registers the new command
21403 with @value{GDBN}. This initializer is normally invoked from the
21404 subclass' own @code{__init__} method.
21406 @var{name} is the name of the command. If @var{name} consists of
21407 multiple words, then the initial words are looked for as prefix
21408 commands. In this case, if one of the prefix commands does not exist,
21409 an exception is raised.
21411 There is no support for multi-line commands.
21413 @var{command_class} should be one of the @samp{COMMAND_} constants
21414 defined below. This argument tells @value{GDBN} how to categorize the
21415 new command in the help system.
21417 @var{completer_class} is an optional argument. If given, it should be
21418 one of the @samp{COMPLETE_} constants defined below. This argument
21419 tells @value{GDBN} how to perform completion for this command. If not
21420 given, @value{GDBN} will attempt to complete using the object's
21421 @code{complete} method (see below); if no such method is found, an
21422 error will occur when completion is attempted.
21424 @var{prefix} is an optional argument. If @code{True}, then the new
21425 command is a prefix command; sub-commands of this command may be
21428 The help text for the new command is taken from the Python
21429 documentation string for the command's class, if there is one. If no
21430 documentation string is provided, the default value ``This command is
21431 not documented.'' is used.
21434 @cindex don't repeat Python command
21435 @defmethod Command dont_repeat
21436 By default, a @value{GDBN} command is repeated when the user enters a
21437 blank line at the command prompt. A command can suppress this
21438 behavior by invoking the @code{dont_repeat} method. This is similar
21439 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21442 @defmethod Command invoke argument from_tty
21443 This method is called by @value{GDBN} when this command is invoked.
21445 @var{argument} is a string. It is the argument to the command, after
21446 leading and trailing whitespace has been stripped.
21448 @var{from_tty} is a boolean argument. When true, this means that the
21449 command was entered by the user at the terminal; when false it means
21450 that the command came from elsewhere.
21452 If this method throws an exception, it is turned into a @value{GDBN}
21453 @code{error} call. Otherwise, the return value is ignored.
21455 @findex gdb.string_to_argv
21456 To break @var{argument} up into an argv-like string use
21457 @code{gdb.string_to_argv}. This function behaves identically to
21458 @value{GDBN}'s internal argument lexer @code{buildargv}.
21459 It is recommended to use this for consistency.
21460 Arguments are separated by spaces and may be quoted.
21464 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21465 ['1', '2 "3', '4 "5', "6 '7"]
21470 @cindex completion of Python commands
21471 @defmethod Command complete text word
21472 This method is called by @value{GDBN} when the user attempts
21473 completion on this command. All forms of completion are handled by
21474 this method, that is, the @key{TAB} and @key{M-?} key bindings
21475 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21478 The arguments @var{text} and @var{word} are both strings. @var{text}
21479 holds the complete command line up to the cursor's location.
21480 @var{word} holds the last word of the command line; this is computed
21481 using a word-breaking heuristic.
21483 The @code{complete} method can return several values:
21486 If the return value is a sequence, the contents of the sequence are
21487 used as the completions. It is up to @code{complete} to ensure that the
21488 contents actually do complete the word. A zero-length sequence is
21489 allowed, it means that there were no completions available. Only
21490 string elements of the sequence are used; other elements in the
21491 sequence are ignored.
21494 If the return value is one of the @samp{COMPLETE_} constants defined
21495 below, then the corresponding @value{GDBN}-internal completion
21496 function is invoked, and its result is used.
21499 All other results are treated as though there were no available
21504 When a new command is registered, it must be declared as a member of
21505 some general class of commands. This is used to classify top-level
21506 commands in the on-line help system; note that prefix commands are not
21507 listed under their own category but rather that of their top-level
21508 command. The available classifications are represented by constants
21509 defined in the @code{gdb} module:
21512 @findex COMMAND_NONE
21513 @findex gdb.COMMAND_NONE
21515 The command does not belong to any particular class. A command in
21516 this category will not be displayed in any of the help categories.
21518 @findex COMMAND_RUNNING
21519 @findex gdb.COMMAND_RUNNING
21520 @item COMMAND_RUNNING
21521 The command is related to running the inferior. For example,
21522 @code{start}, @code{step}, and @code{continue} are in this category.
21523 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21524 commands in this category.
21526 @findex COMMAND_DATA
21527 @findex gdb.COMMAND_DATA
21529 The command is related to data or variables. For example,
21530 @code{call}, @code{find}, and @code{print} are in this category. Type
21531 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21534 @findex COMMAND_STACK
21535 @findex gdb.COMMAND_STACK
21536 @item COMMAND_STACK
21537 The command has to do with manipulation of the stack. For example,
21538 @code{backtrace}, @code{frame}, and @code{return} are in this
21539 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21540 list of commands in this category.
21542 @findex COMMAND_FILES
21543 @findex gdb.COMMAND_FILES
21544 @item COMMAND_FILES
21545 This class is used for file-related commands. For example,
21546 @code{file}, @code{list} and @code{section} are in this category.
21547 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21548 commands in this category.
21550 @findex COMMAND_SUPPORT
21551 @findex gdb.COMMAND_SUPPORT
21552 @item COMMAND_SUPPORT
21553 This should be used for ``support facilities'', generally meaning
21554 things that are useful to the user when interacting with @value{GDBN},
21555 but not related to the state of the inferior. For example,
21556 @code{help}, @code{make}, and @code{shell} are in this category. Type
21557 @kbd{help support} at the @value{GDBN} prompt to see a list of
21558 commands in this category.
21560 @findex COMMAND_STATUS
21561 @findex gdb.COMMAND_STATUS
21562 @item COMMAND_STATUS
21563 The command is an @samp{info}-related command, that is, related to the
21564 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21565 and @code{show} are in this category. Type @kbd{help status} at the
21566 @value{GDBN} prompt to see a list of commands in this category.
21568 @findex COMMAND_BREAKPOINTS
21569 @findex gdb.COMMAND_BREAKPOINTS
21570 @item COMMAND_BREAKPOINTS
21571 The command has to do with breakpoints. For example, @code{break},
21572 @code{clear}, and @code{delete} are in this category. Type @kbd{help
21573 breakpoints} at the @value{GDBN} prompt to see a list of commands in
21576 @findex COMMAND_TRACEPOINTS
21577 @findex gdb.COMMAND_TRACEPOINTS
21578 @item COMMAND_TRACEPOINTS
21579 The command has to do with tracepoints. For example, @code{trace},
21580 @code{actions}, and @code{tfind} are in this category. Type
21581 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
21582 commands in this category.
21584 @findex COMMAND_OBSCURE
21585 @findex gdb.COMMAND_OBSCURE
21586 @item COMMAND_OBSCURE
21587 The command is only used in unusual circumstances, or is not of
21588 general interest to users. For example, @code{checkpoint},
21589 @code{fork}, and @code{stop} are in this category. Type @kbd{help
21590 obscure} at the @value{GDBN} prompt to see a list of commands in this
21593 @findex COMMAND_MAINTENANCE
21594 @findex gdb.COMMAND_MAINTENANCE
21595 @item COMMAND_MAINTENANCE
21596 The command is only useful to @value{GDBN} maintainers. The
21597 @code{maintenance} and @code{flushregs} commands are in this category.
21598 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
21599 commands in this category.
21602 A new command can use a predefined completion function, either by
21603 specifying it via an argument at initialization, or by returning it
21604 from the @code{complete} method. These predefined completion
21605 constants are all defined in the @code{gdb} module:
21608 @findex COMPLETE_NONE
21609 @findex gdb.COMPLETE_NONE
21610 @item COMPLETE_NONE
21611 This constant means that no completion should be done.
21613 @findex COMPLETE_FILENAME
21614 @findex gdb.COMPLETE_FILENAME
21615 @item COMPLETE_FILENAME
21616 This constant means that filename completion should be performed.
21618 @findex COMPLETE_LOCATION
21619 @findex gdb.COMPLETE_LOCATION
21620 @item COMPLETE_LOCATION
21621 This constant means that location completion should be done.
21622 @xref{Specify Location}.
21624 @findex COMPLETE_COMMAND
21625 @findex gdb.COMPLETE_COMMAND
21626 @item COMPLETE_COMMAND
21627 This constant means that completion should examine @value{GDBN}
21630 @findex COMPLETE_SYMBOL
21631 @findex gdb.COMPLETE_SYMBOL
21632 @item COMPLETE_SYMBOL
21633 This constant means that completion should be done using symbol names
21637 The following code snippet shows how a trivial CLI command can be
21638 implemented in Python:
21641 class HelloWorld (gdb.Command):
21642 """Greet the whole world."""
21644 def __init__ (self):
21645 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21647 def invoke (self, arg, from_tty):
21648 print "Hello, World!"
21653 The last line instantiates the class, and is necessary to trigger the
21654 registration of the command with @value{GDBN}. Depending on how the
21655 Python code is read into @value{GDBN}, you may need to import the
21656 @code{gdb} module explicitly.
21658 @node Parameters In Python
21659 @subsubsection Parameters In Python
21661 @cindex parameters in python
21662 @cindex python parameters
21663 @tindex gdb.Parameter
21665 You can implement new @value{GDBN} parameters using Python. A new
21666 parameter is implemented as an instance of the @code{gdb.Parameter}
21669 Parameters are exposed to the user via the @code{set} and
21670 @code{show} commands. @xref{Help}.
21672 There are many parameters that already exist and can be set in
21673 @value{GDBN}. Two examples are: @code{set follow fork} and
21674 @code{set charset}. Setting these parameters influences certain
21675 behavior in @value{GDBN}. Similarly, you can define parameters that
21676 can be used to influence behavior in custom Python scripts and commands.
21678 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21679 The object initializer for @code{Parameter} registers the new
21680 parameter with @value{GDBN}. This initializer is normally invoked
21681 from the subclass' own @code{__init__} method.
21683 @var{name} is the name of the new parameter. If @var{name} consists
21684 of multiple words, then the initial words are looked for as prefix
21685 parameters. An example of this can be illustrated with the
21686 @code{set print} set of parameters. If @var{name} is
21687 @code{print foo}, then @code{print} will be searched as the prefix
21688 parameter. In this case the parameter can subsequently be accessed in
21689 @value{GDBN} as @code{set print foo}.
21691 If @var{name} consists of multiple words, and no prefix parameter group
21692 can be found, an exception is raised.
21694 @var{command-class} should be one of the @samp{COMMAND_} constants
21695 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21696 categorize the new parameter in the help system.
21698 @var{parameter-class} should be one of the @samp{PARAM_} constants
21699 defined below. This argument tells @value{GDBN} the type of the new
21700 parameter; this information is used for input validation and
21703 If @var{parameter-class} is @code{PARAM_ENUM}, then
21704 @var{enum-sequence} must be a sequence of strings. These strings
21705 represent the possible values for the parameter.
21707 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21708 of a fourth argument will cause an exception to be thrown.
21710 The help text for the new parameter is taken from the Python
21711 documentation string for the parameter's class, if there is one. If
21712 there is no documentation string, a default value is used.
21715 @defivar Parameter set_doc
21716 If this attribute exists, and is a string, then its value is used as
21717 the help text for this parameter's @code{set} command. The value is
21718 examined when @code{Parameter.__init__} is invoked; subsequent changes
21722 @defivar Parameter show_doc
21723 If this attribute exists, and is a string, then its value is used as
21724 the help text for this parameter's @code{show} command. The value is
21725 examined when @code{Parameter.__init__} is invoked; subsequent changes
21729 @defivar Parameter value
21730 The @code{value} attribute holds the underlying value of the
21731 parameter. It can be read and assigned to just as any other
21732 attribute. @value{GDBN} does validation when assignments are made.
21736 When a new parameter is defined, its type must be specified. The
21737 available types are represented by constants defined in the @code{gdb}
21741 @findex PARAM_BOOLEAN
21742 @findex gdb.PARAM_BOOLEAN
21743 @item PARAM_BOOLEAN
21744 The value is a plain boolean. The Python boolean values, @code{True}
21745 and @code{False} are the only valid values.
21747 @findex PARAM_AUTO_BOOLEAN
21748 @findex gdb.PARAM_AUTO_BOOLEAN
21749 @item PARAM_AUTO_BOOLEAN
21750 The value has three possible states: true, false, and @samp{auto}. In
21751 Python, true and false are represented using boolean constants, and
21752 @samp{auto} is represented using @code{None}.
21754 @findex PARAM_UINTEGER
21755 @findex gdb.PARAM_UINTEGER
21756 @item PARAM_UINTEGER
21757 The value is an unsigned integer. The value of 0 should be
21758 interpreted to mean ``unlimited''.
21760 @findex PARAM_INTEGER
21761 @findex gdb.PARAM_INTEGER
21762 @item PARAM_INTEGER
21763 The value is a signed integer. The value of 0 should be interpreted
21764 to mean ``unlimited''.
21766 @findex PARAM_STRING
21767 @findex gdb.PARAM_STRING
21769 The value is a string. When the user modifies the string, any escape
21770 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21771 translated into corresponding characters and encoded into the current
21774 @findex PARAM_STRING_NOESCAPE
21775 @findex gdb.PARAM_STRING_NOESCAPE
21776 @item PARAM_STRING_NOESCAPE
21777 The value is a string. When the user modifies the string, escapes are
21778 passed through untranslated.
21780 @findex PARAM_OPTIONAL_FILENAME
21781 @findex gdb.PARAM_OPTIONAL_FILENAME
21782 @item PARAM_OPTIONAL_FILENAME
21783 The value is a either a filename (a string), or @code{None}.
21785 @findex PARAM_FILENAME
21786 @findex gdb.PARAM_FILENAME
21787 @item PARAM_FILENAME
21788 The value is a filename. This is just like
21789 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
21791 @findex PARAM_ZINTEGER
21792 @findex gdb.PARAM_ZINTEGER
21793 @item PARAM_ZINTEGER
21794 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
21795 is interpreted as itself.
21798 @findex gdb.PARAM_ENUM
21800 The value is a string, which must be one of a collection string
21801 constants provided when the parameter is created.
21804 @node Functions In Python
21805 @subsubsection Writing new convenience functions
21807 @cindex writing convenience functions
21808 @cindex convenience functions in python
21809 @cindex python convenience functions
21810 @tindex gdb.Function
21812 You can implement new convenience functions (@pxref{Convenience Vars})
21813 in Python. A convenience function is an instance of a subclass of the
21814 class @code{gdb.Function}.
21816 @defmethod Function __init__ name
21817 The initializer for @code{Function} registers the new function with
21818 @value{GDBN}. The argument @var{name} is the name of the function,
21819 a string. The function will be visible to the user as a convenience
21820 variable of type @code{internal function}, whose name is the same as
21821 the given @var{name}.
21823 The documentation for the new function is taken from the documentation
21824 string for the new class.
21827 @defmethod Function invoke @var{*args}
21828 When a convenience function is evaluated, its arguments are converted
21829 to instances of @code{gdb.Value}, and then the function's
21830 @code{invoke} method is called. Note that @value{GDBN} does not
21831 predetermine the arity of convenience functions. Instead, all
21832 available arguments are passed to @code{invoke}, following the
21833 standard Python calling convention. In particular, a convenience
21834 function can have default values for parameters without ill effect.
21836 The return value of this method is used as its value in the enclosing
21837 expression. If an ordinary Python value is returned, it is converted
21838 to a @code{gdb.Value} following the usual rules.
21841 The following code snippet shows how a trivial convenience function can
21842 be implemented in Python:
21845 class Greet (gdb.Function):
21846 """Return string to greet someone.
21847 Takes a name as argument."""
21849 def __init__ (self):
21850 super (Greet, self).__init__ ("greet")
21852 def invoke (self, name):
21853 return "Hello, %s!" % name.string ()
21858 The last line instantiates the class, and is necessary to trigger the
21859 registration of the function with @value{GDBN}. Depending on how the
21860 Python code is read into @value{GDBN}, you may need to import the
21861 @code{gdb} module explicitly.
21863 @node Progspaces In Python
21864 @subsubsection Program Spaces In Python
21866 @cindex progspaces in python
21867 @tindex gdb.Progspace
21869 A program space, or @dfn{progspace}, represents a symbolic view
21870 of an address space.
21871 It consists of all of the objfiles of the program.
21872 @xref{Objfiles In Python}.
21873 @xref{Inferiors and Programs, program spaces}, for more details
21874 about program spaces.
21876 The following progspace-related functions are available in the
21879 @findex gdb.current_progspace
21880 @defun current_progspace
21881 This function returns the program space of the currently selected inferior.
21882 @xref{Inferiors and Programs}.
21885 @findex gdb.progspaces
21887 Return a sequence of all the progspaces currently known to @value{GDBN}.
21890 Each progspace is represented by an instance of the @code{gdb.Progspace}
21893 @defivar Progspace filename
21894 The file name of the progspace as a string.
21897 @defivar Progspace pretty_printers
21898 The @code{pretty_printers} attribute is a list of functions. It is
21899 used to look up pretty-printers. A @code{Value} is passed to each
21900 function in order; if the function returns @code{None}, then the
21901 search continues. Otherwise, the return value should be an object
21902 which is used to format the value. @xref{Pretty Printing API}, for more
21906 @node Objfiles In Python
21907 @subsubsection Objfiles In Python
21909 @cindex objfiles in python
21910 @tindex gdb.Objfile
21912 @value{GDBN} loads symbols for an inferior from various
21913 symbol-containing files (@pxref{Files}). These include the primary
21914 executable file, any shared libraries used by the inferior, and any
21915 separate debug info files (@pxref{Separate Debug Files}).
21916 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
21918 The following objfile-related functions are available in the
21921 @findex gdb.current_objfile
21922 @defun current_objfile
21923 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
21924 sets the ``current objfile'' to the corresponding objfile. This
21925 function returns the current objfile. If there is no current objfile,
21926 this function returns @code{None}.
21929 @findex gdb.objfiles
21931 Return a sequence of all the objfiles current known to @value{GDBN}.
21932 @xref{Objfiles In Python}.
21935 Each objfile is represented by an instance of the @code{gdb.Objfile}
21938 @defivar Objfile filename
21939 The file name of the objfile as a string.
21942 @defivar Objfile pretty_printers
21943 The @code{pretty_printers} attribute is a list of functions. It is
21944 used to look up pretty-printers. A @code{Value} is passed to each
21945 function in order; if the function returns @code{None}, then the
21946 search continues. Otherwise, the return value should be an object
21947 which is used to format the value. @xref{Pretty Printing API}, for more
21951 @node Frames In Python
21952 @subsubsection Accessing inferior stack frames from Python.
21954 @cindex frames in python
21955 When the debugged program stops, @value{GDBN} is able to analyze its call
21956 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21957 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21958 while its corresponding frame exists in the inferior's stack. If you try
21959 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21962 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21966 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21970 The following frame-related functions are available in the @code{gdb} module:
21972 @findex gdb.selected_frame
21973 @defun selected_frame
21974 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
21977 @defun frame_stop_reason_string reason
21978 Return a string explaining the reason why @value{GDBN} stopped unwinding
21979 frames, as expressed by the given @var{reason} code (an integer, see the
21980 @code{unwind_stop_reason} method further down in this section).
21983 A @code{gdb.Frame} object has the following methods:
21986 @defmethod Frame is_valid
21987 Returns true if the @code{gdb.Frame} object is valid, false if not.
21988 A frame object can become invalid if the frame it refers to doesn't
21989 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
21990 an exception if it is invalid at the time the method is called.
21993 @defmethod Frame name
21994 Returns the function name of the frame, or @code{None} if it can't be
21998 @defmethod Frame type
21999 Returns the type of the frame. The value can be one of
22000 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
22001 or @code{gdb.SENTINEL_FRAME}.
22004 @defmethod Frame unwind_stop_reason
22005 Return an integer representing the reason why it's not possible to find
22006 more frames toward the outermost frame. Use
22007 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22008 function to a string.
22011 @defmethod Frame pc
22012 Returns the frame's resume address.
22015 @defmethod Frame block
22016 Return the frame's code block. @xref{Blocks In Python}.
22019 @defmethod Frame function
22020 Return the symbol for the function corresponding to this frame.
22021 @xref{Symbols In Python}.
22024 @defmethod Frame older
22025 Return the frame that called this frame.
22028 @defmethod Frame newer
22029 Return the frame called by this frame.
22032 @defmethod Frame find_sal
22033 Return the frame's symtab and line object.
22034 @xref{Symbol Tables In Python}.
22037 @defmethod Frame read_var variable @r{[}block@r{]}
22038 Return the value of @var{variable} in this frame. If the optional
22039 argument @var{block} is provided, search for the variable from that
22040 block; otherwise start at the frame's current block (which is
22041 determined by the frame's current program counter). @var{variable}
22042 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22043 @code{gdb.Block} object.
22046 @defmethod Frame select
22047 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22052 @node Blocks In Python
22053 @subsubsection Accessing frame blocks from Python.
22055 @cindex blocks in python
22058 Within each frame, @value{GDBN} maintains information on each block
22059 stored in that frame. These blocks are organized hierarchically, and
22060 are represented individually in Python as a @code{gdb.Block}.
22061 Please see @ref{Frames In Python}, for a more in-depth discussion on
22062 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22063 detailed technical information on @value{GDBN}'s book-keeping of the
22066 The following block-related functions are available in the @code{gdb}
22069 @findex gdb.block_for_pc
22070 @defun block_for_pc pc
22071 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22072 block cannot be found for the @var{pc} value specified, the function
22073 will return @code{None}.
22076 A @code{gdb.Block} object has the following attributes:
22079 @defivar Block start
22080 The start address of the block. This attribute is not writable.
22084 The end address of the block. This attribute is not writable.
22087 @defivar Block function
22088 The name of the block represented as a @code{gdb.Symbol}. If the
22089 block is not named, then this attribute holds @code{None}. This
22090 attribute is not writable.
22093 @defivar Block superblock
22094 The block containing this block. If this parent block does not exist,
22095 this attribute holds @code{None}. This attribute is not writable.
22099 @node Symbols In Python
22100 @subsubsection Python representation of Symbols.
22102 @cindex symbols in python
22105 @value{GDBN} represents every variable, function and type as an
22106 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22107 Similarly, Python represents these symbols in @value{GDBN} with the
22108 @code{gdb.Symbol} object.
22110 The following symbol-related functions are available in the @code{gdb}
22113 @findex gdb.lookup_symbol
22114 @defun lookup_symbol name [block] [domain]
22115 This function searches for a symbol by name. The search scope can be
22116 restricted to the parameters defined in the optional domain and block
22119 @var{name} is the name of the symbol. It must be a string. The
22120 optional @var{block} argument restricts the search to symbols visible
22121 in that @var{block}. The @var{block} argument must be a
22122 @code{gdb.Block} object. The optional @var{domain} argument restricts
22123 the search to the domain type. The @var{domain} argument must be a
22124 domain constant defined in the @code{gdb} module and described later
22128 A @code{gdb.Symbol} object has the following attributes:
22131 @defivar Symbol symtab
22132 The symbol table in which the symbol appears. This attribute is
22133 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22134 Python}. This attribute is not writable.
22137 @defivar Symbol name
22138 The name of the symbol as a string. This attribute is not writable.
22141 @defivar Symbol linkage_name
22142 The name of the symbol, as used by the linker (i.e., may be mangled).
22143 This attribute is not writable.
22146 @defivar Symbol print_name
22147 The name of the symbol in a form suitable for output. This is either
22148 @code{name} or @code{linkage_name}, depending on whether the user
22149 asked @value{GDBN} to display demangled or mangled names.
22152 @defivar Symbol addr_class
22153 The address class of the symbol. This classifies how to find the value
22154 of a symbol. Each address class is a constant defined in the
22155 @code{gdb} module and described later in this chapter.
22158 @defivar Symbol is_argument
22159 @code{True} if the symbol is an argument of a function.
22162 @defivar Symbol is_constant
22163 @code{True} if the symbol is a constant.
22166 @defivar Symbol is_function
22167 @code{True} if the symbol is a function or a method.
22170 @defivar Symbol is_variable
22171 @code{True} if the symbol is a variable.
22175 The available domain categories in @code{gdb.Symbol} are represented
22176 as constants in the @code{gdb} module:
22179 @findex SYMBOL_UNDEF_DOMAIN
22180 @findex gdb.SYMBOL_UNDEF_DOMAIN
22181 @item SYMBOL_UNDEF_DOMAIN
22182 This is used when a domain has not been discovered or none of the
22183 following domains apply. This usually indicates an error either
22184 in the symbol information or in @value{GDBN}'s handling of symbols.
22185 @findex SYMBOL_VAR_DOMAIN
22186 @findex gdb.SYMBOL_VAR_DOMAIN
22187 @item SYMBOL_VAR_DOMAIN
22188 This domain contains variables, function names, typedef names and enum
22190 @findex SYMBOL_STRUCT_DOMAIN
22191 @findex gdb.SYMBOL_STRUCT_DOMAIN
22192 @item SYMBOL_STRUCT_DOMAIN
22193 This domain holds struct, union and enum type names.
22194 @findex SYMBOL_LABEL_DOMAIN
22195 @findex gdb.SYMBOL_LABEL_DOMAIN
22196 @item SYMBOL_LABEL_DOMAIN
22197 This domain contains names of labels (for gotos).
22198 @findex SYMBOL_VARIABLES_DOMAIN
22199 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22200 @item SYMBOL_VARIABLES_DOMAIN
22201 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22202 contains everything minus functions and types.
22203 @findex SYMBOL_FUNCTIONS_DOMAIN
22204 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22205 @item SYMBOL_FUNCTION_DOMAIN
22206 This domain contains all functions.
22207 @findex SYMBOL_TYPES_DOMAIN
22208 @findex gdb.SYMBOL_TYPES_DOMAIN
22209 @item SYMBOL_TYPES_DOMAIN
22210 This domain contains all types.
22213 The available address class categories in @code{gdb.Symbol} are represented
22214 as constants in the @code{gdb} module:
22217 @findex SYMBOL_LOC_UNDEF
22218 @findex gdb.SYMBOL_LOC_UNDEF
22219 @item SYMBOL_LOC_UNDEF
22220 If this is returned by address class, it indicates an error either in
22221 the symbol information or in @value{GDBN}'s handling of symbols.
22222 @findex SYMBOL_LOC_CONST
22223 @findex gdb.SYMBOL_LOC_CONST
22224 @item SYMBOL_LOC_CONST
22225 Value is constant int.
22226 @findex SYMBOL_LOC_STATIC
22227 @findex gdb.SYMBOL_LOC_STATIC
22228 @item SYMBOL_LOC_STATIC
22229 Value is at a fixed address.
22230 @findex SYMBOL_LOC_REGISTER
22231 @findex gdb.SYMBOL_LOC_REGISTER
22232 @item SYMBOL_LOC_REGISTER
22233 Value is in a register.
22234 @findex SYMBOL_LOC_ARG
22235 @findex gdb.SYMBOL_LOC_ARG
22236 @item SYMBOL_LOC_ARG
22237 Value is an argument. This value is at the offset stored within the
22238 symbol inside the frame's argument list.
22239 @findex SYMBOL_LOC_REF_ARG
22240 @findex gdb.SYMBOL_LOC_REF_ARG
22241 @item SYMBOL_LOC_REF_ARG
22242 Value address is stored in the frame's argument list. Just like
22243 @code{LOC_ARG} except that the value's address is stored at the
22244 offset, not the value itself.
22245 @findex SYMBOL_LOC_REGPARM_ADDR
22246 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22247 @item SYMBOL_LOC_REGPARM_ADDR
22248 Value is a specified register. Just like @code{LOC_REGISTER} except
22249 the register holds the address of the argument instead of the argument
22251 @findex SYMBOL_LOC_LOCAL
22252 @findex gdb.SYMBOL_LOC_LOCAL
22253 @item SYMBOL_LOC_LOCAL
22254 Value is a local variable.
22255 @findex SYMBOL_LOC_TYPEDEF
22256 @findex gdb.SYMBOL_LOC_TYPEDEF
22257 @item SYMBOL_LOC_TYPEDEF
22258 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22260 @findex SYMBOL_LOC_BLOCK
22261 @findex gdb.SYMBOL_LOC_BLOCK
22262 @item SYMBOL_LOC_BLOCK
22264 @findex SYMBOL_LOC_CONST_BYTES
22265 @findex gdb.SYMBOL_LOC_CONST_BYTES
22266 @item SYMBOL_LOC_CONST_BYTES
22267 Value is a byte-sequence.
22268 @findex SYMBOL_LOC_UNRESOLVED
22269 @findex gdb.SYMBOL_LOC_UNRESOLVED
22270 @item SYMBOL_LOC_UNRESOLVED
22271 Value is at a fixed address, but the address of the variable has to be
22272 determined from the minimal symbol table whenever the variable is
22274 @findex SYMBOL_LOC_OPTIMIZED_OUT
22275 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22276 @item SYMBOL_LOC_OPTIMIZED_OUT
22277 The value does not actually exist in the program.
22278 @findex SYMBOL_LOC_COMPUTED
22279 @findex gdb.SYMBOL_LOC_COMPUTED
22280 @item SYMBOL_LOC_COMPUTED
22281 The value's address is a computed location.
22284 @node Symbol Tables In Python
22285 @subsubsection Symbol table representation in Python.
22287 @cindex symbol tables in python
22289 @tindex gdb.Symtab_and_line
22291 Access to symbol table data maintained by @value{GDBN} on the inferior
22292 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22293 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22294 from the @code{find_sal} method in @code{gdb.Frame} object.
22295 @xref{Frames In Python}.
22297 For more information on @value{GDBN}'s symbol table management, see
22298 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22300 A @code{gdb.Symtab_and_line} object has the following attributes:
22303 @defivar Symtab_and_line symtab
22304 The symbol table object (@code{gdb.Symtab}) for this frame.
22305 This attribute is not writable.
22308 @defivar Symtab_and_line pc
22309 Indicates the current program counter address. This attribute is not
22313 @defivar Symtab_and_line line
22314 Indicates the current line number for this object. This
22315 attribute is not writable.
22319 A @code{gdb.Symtab} object has the following attributes:
22322 @defivar Symtab filename
22323 The symbol table's source filename. This attribute is not writable.
22326 @defivar Symtab objfile
22327 The symbol table's backing object file. @xref{Objfiles In Python}.
22328 This attribute is not writable.
22332 The following methods are provided:
22335 @defmethod Symtab fullname
22336 Return the symbol table's source absolute file name.
22340 @node Breakpoints In Python
22341 @subsubsection Manipulating breakpoints using Python
22343 @cindex breakpoints in python
22344 @tindex gdb.Breakpoint
22346 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22349 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
22350 Create a new breakpoint. @var{spec} is a string naming the
22351 location of the breakpoint, or an expression that defines a
22352 watchpoint. The contents can be any location recognized by the
22353 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22354 command. The optional @var{type} denotes the breakpoint to create
22355 from the types defined later in this chapter. This argument can be
22356 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22357 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
22358 argument defines the class of watchpoint to create, if @var{type} is
22359 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
22360 provided, it is assumed to be a @var{WP_WRITE} class.
22363 The available watchpoint types represented by constants are defined in the
22368 @findex gdb.WP_READ
22370 Read only watchpoint.
22373 @findex gdb.WP_WRITE
22375 Write only watchpoint.
22378 @findex gdb.WP_ACCESS
22380 Read/Write watchpoint.
22383 @defmethod Breakpoint is_valid
22384 Return @code{True} if this @code{Breakpoint} object is valid,
22385 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22386 if the user deletes the breakpoint. In this case, the object still
22387 exists, but the underlying breakpoint does not. In the cases of
22388 watchpoint scope, the watchpoint remains valid even if execution of the
22389 inferior leaves the scope of that watchpoint.
22392 @defivar Breakpoint enabled
22393 This attribute is @code{True} if the breakpoint is enabled, and
22394 @code{False} otherwise. This attribute is writable.
22397 @defivar Breakpoint silent
22398 This attribute is @code{True} if the breakpoint is silent, and
22399 @code{False} otherwise. This attribute is writable.
22401 Note that a breakpoint can also be silent if it has commands and the
22402 first command is @code{silent}. This is not reported by the
22403 @code{silent} attribute.
22406 @defivar Breakpoint thread
22407 If the breakpoint is thread-specific, this attribute holds the thread
22408 id. If the breakpoint is not thread-specific, this attribute is
22409 @code{None}. This attribute is writable.
22412 @defivar Breakpoint task
22413 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22414 id. If the breakpoint is not task-specific (or the underlying
22415 language is not Ada), this attribute is @code{None}. This attribute
22419 @defivar Breakpoint ignore_count
22420 This attribute holds the ignore count for the breakpoint, an integer.
22421 This attribute is writable.
22424 @defivar Breakpoint number
22425 This attribute holds the breakpoint's number --- the identifier used by
22426 the user to manipulate the breakpoint. This attribute is not writable.
22429 @defivar Breakpoint type
22430 This attribute holds the breakpoint's type --- the identifier used to
22431 determine the actual breakpoint type or use-case. This attribute is not
22435 The available types are represented by constants defined in the @code{gdb}
22439 @findex BP_BREAKPOINT
22440 @findex gdb.BP_BREAKPOINT
22441 @item BP_BREAKPOINT
22442 Normal code breakpoint.
22444 @findex BP_WATCHPOINT
22445 @findex gdb.BP_WATCHPOINT
22446 @item BP_WATCHPOINT
22447 Watchpoint breakpoint.
22449 @findex BP_HARDWARE_WATCHPOINT
22450 @findex gdb.BP_HARDWARE_WATCHPOINT
22451 @item BP_HARDWARE_WATCHPOINT
22452 Hardware assisted watchpoint.
22454 @findex BP_READ_WATCHPOINT
22455 @findex gdb.BP_READ_WATCHPOINT
22456 @item BP_READ_WATCHPOINT
22457 Hardware assisted read watchpoint.
22459 @findex BP_ACCESS_WATCHPOINT
22460 @findex gdb.BP_ACCESS_WATCHPOINT
22461 @item BP_ACCESS_WATCHPOINT
22462 Hardware assisted access watchpoint.
22465 @defivar Breakpoint hit_count
22466 This attribute holds the hit count for the breakpoint, an integer.
22467 This attribute is writable, but currently it can only be set to zero.
22470 @defivar Breakpoint location
22471 This attribute holds the location of the breakpoint, as specified by
22472 the user. It is a string. If the breakpoint does not have a location
22473 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22474 attribute is not writable.
22477 @defivar Breakpoint expression
22478 This attribute holds a breakpoint expression, as specified by
22479 the user. It is a string. If the breakpoint does not have an
22480 expression (the breakpoint is not a watchpoint) the attribute's value
22481 is @code{None}. This attribute is not writable.
22484 @defivar Breakpoint condition
22485 This attribute holds the condition of the breakpoint, as specified by
22486 the user. It is a string. If there is no condition, this attribute's
22487 value is @code{None}. This attribute is writable.
22490 @defivar Breakpoint commands
22491 This attribute holds the commands attached to the breakpoint. If
22492 there are commands, this attribute's value is a string holding all the
22493 commands, separated by newlines. If there are no commands, this
22494 attribute is @code{None}. This attribute is not writable.
22497 @node Lazy Strings In Python
22498 @subsubsection Python representation of lazy strings.
22500 @cindex lazy strings in python
22501 @tindex gdb.LazyString
22503 A @dfn{lazy string} is a string whose contents is not retrieved or
22504 encoded until it is needed.
22506 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22507 @code{address} that points to a region of memory, an @code{encoding}
22508 that will be used to encode that region of memory, and a @code{length}
22509 to delimit the region of memory that represents the string. The
22510 difference between a @code{gdb.LazyString} and a string wrapped within
22511 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22512 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22513 retrieved and encoded during printing, while a @code{gdb.Value}
22514 wrapping a string is immediately retrieved and encoded on creation.
22516 A @code{gdb.LazyString} object has the following functions:
22518 @defmethod LazyString value
22519 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22520 will point to the string in memory, but will lose all the delayed
22521 retrieval, encoding and handling that @value{GDBN} applies to a
22522 @code{gdb.LazyString}.
22525 @defivar LazyString address
22526 This attribute holds the address of the string. This attribute is not
22530 @defivar LazyString length
22531 This attribute holds the length of the string in characters. If the
22532 length is -1, then the string will be fetched and encoded up to the
22533 first null of appropriate width. This attribute is not writable.
22536 @defivar LazyString encoding
22537 This attribute holds the encoding that will be applied to the string
22538 when the string is printed by @value{GDBN}. If the encoding is not
22539 set, or contains an empty string, then @value{GDBN} will select the
22540 most appropriate encoding when the string is printed. This attribute
22544 @defivar LazyString type
22545 This attribute holds the type that is represented by the lazy string's
22546 type. For a lazy string this will always be a pointer type. To
22547 resolve this to the lazy string's character type, use the type's
22548 @code{target} method. @xref{Types In Python}. This attribute is not
22553 @subsection Auto-loading
22554 @cindex auto-loading, Python
22556 When a new object file is read (for example, due to the @code{file}
22557 command, or because the inferior has loaded a shared library),
22558 @value{GDBN} will look for Python support scripts in several ways:
22559 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22562 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22563 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22564 * Which flavor to choose?::
22567 The auto-loading feature is useful for supplying application-specific
22568 debugging commands and scripts.
22570 Auto-loading can be enabled or disabled.
22573 @kindex maint set python auto-load
22574 @item maint set python auto-load [yes|no]
22575 Enable or disable the Python auto-loading feature.
22577 @kindex maint show python auto-load
22578 @item maint show python auto-load
22579 Show whether Python auto-loading is enabled or disabled.
22582 When reading an auto-loaded file, @value{GDBN} sets the
22583 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
22584 function (@pxref{Objfiles In Python}). This can be useful for
22585 registering objfile-specific pretty-printers.
22587 @node objfile-gdb.py file
22588 @subsubsection The @file{@var{objfile}-gdb.py} file
22589 @cindex @file{@var{objfile}-gdb.py}
22591 When a new object file is read, @value{GDBN} looks for
22592 a file named @file{@var{objfile}-gdb.py},
22593 where @var{objfile} is the object file's real name, formed by ensuring
22594 that the file name is absolute, following all symlinks, and resolving
22595 @code{.} and @code{..} components. If this file exists and is
22596 readable, @value{GDBN} will evaluate it as a Python script.
22598 If this file does not exist, and if the parameter
22599 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
22600 then @value{GDBN} will look for @var{real-name} in all of the
22601 directories mentioned in the value of @code{debug-file-directory}.
22603 Finally, if this file does not exist, then @value{GDBN} will look for
22604 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
22605 @var{data-directory} is @value{GDBN}'s data directory (available via
22606 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
22607 is the object file's real name, as described above.
22609 @value{GDBN} does not track which files it has already auto-loaded this way.
22610 @value{GDBN} will load the associated script every time the corresponding
22611 @var{objfile} is opened.
22612 So your @file{-gdb.py} file should be careful to avoid errors if it
22613 is evaluated more than once.
22615 @node .debug_gdb_scripts section
22616 @subsubsection The @code{.debug_gdb_scripts} section
22617 @cindex @code{.debug_gdb_scripts} section
22619 For systems using file formats like ELF and COFF,
22620 when @value{GDBN} loads a new object file
22621 it will look for a special section named @samp{.debug_gdb_scripts}.
22622 If this section exists, its contents is a list of names of scripts to load.
22624 @value{GDBN} will look for each specified script file first in the
22625 current directory and then along the source search path
22626 (@pxref{Source Path, ,Specifying Source Directories}),
22627 except that @file{$cdir} is not searched, since the compilation
22628 directory is not relevant to scripts.
22630 Entries can be placed in section @code{.debug_gdb_scripts} with,
22631 for example, this GCC macro:
22634 /* Note: The "MS" section flags are to remote duplicates. */
22635 #define DEFINE_GDB_SCRIPT(script_name) \
22637 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
22639 .asciz \"" script_name "\"\n\
22645 Then one can reference the macro in a header or source file like this:
22648 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
22651 The script name may include directories if desired.
22653 If the macro is put in a header, any application or library
22654 using this header will get a reference to the specified script.
22656 @node Which flavor to choose?
22657 @subsubsection Which flavor to choose?
22659 Given the multiple ways of auto-loading Python scripts, it might not always
22660 be clear which one to choose. This section provides some guidance.
22662 Benefits of the @file{-gdb.py} way:
22666 Can be used with file formats that don't support multiple sections.
22669 Ease of finding scripts for public libraries.
22671 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22672 in the source search path.
22673 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22674 isn't a source directory in which to find the script.
22677 Doesn't require source code additions.
22680 Benefits of the @code{.debug_gdb_scripts} way:
22684 Works with static linking.
22686 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22687 trigger their loading. When an application is statically linked the only
22688 objfile available is the executable, and it is cumbersome to attach all the
22689 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22692 Works with classes that are entirely inlined.
22694 Some classes can be entirely inlined, and thus there may not be an associated
22695 shared library to attach a @file{-gdb.py} script to.
22698 Scripts needn't be copied out of the source tree.
22700 In some circumstances, apps can be built out of large collections of internal
22701 libraries, and the build infrastructure necessary to install the
22702 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22703 cumbersome. It may be easier to specify the scripts in the
22704 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22705 top of the source tree to the source search path.
22709 @chapter Command Interpreters
22710 @cindex command interpreters
22712 @value{GDBN} supports multiple command interpreters, and some command
22713 infrastructure to allow users or user interface writers to switch
22714 between interpreters or run commands in other interpreters.
22716 @value{GDBN} currently supports two command interpreters, the console
22717 interpreter (sometimes called the command-line interpreter or @sc{cli})
22718 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22719 describes both of these interfaces in great detail.
22721 By default, @value{GDBN} will start with the console interpreter.
22722 However, the user may choose to start @value{GDBN} with another
22723 interpreter by specifying the @option{-i} or @option{--interpreter}
22724 startup options. Defined interpreters include:
22728 @cindex console interpreter
22729 The traditional console or command-line interpreter. This is the most often
22730 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22731 @value{GDBN} will use this interpreter.
22734 @cindex mi interpreter
22735 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22736 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22737 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22741 @cindex mi2 interpreter
22742 The current @sc{gdb/mi} interface.
22745 @cindex mi1 interpreter
22746 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
22750 @cindex invoke another interpreter
22751 The interpreter being used by @value{GDBN} may not be dynamically
22752 switched at runtime. Although possible, this could lead to a very
22753 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
22754 enters the command "interpreter-set console" in a console view,
22755 @value{GDBN} would switch to using the console interpreter, rendering
22756 the IDE inoperable!
22758 @kindex interpreter-exec
22759 Although you may only choose a single interpreter at startup, you may execute
22760 commands in any interpreter from the current interpreter using the appropriate
22761 command. If you are running the console interpreter, simply use the
22762 @code{interpreter-exec} command:
22765 interpreter-exec mi "-data-list-register-names"
22768 @sc{gdb/mi} has a similar command, although it is only available in versions of
22769 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
22772 @chapter @value{GDBN} Text User Interface
22774 @cindex Text User Interface
22777 * TUI Overview:: TUI overview
22778 * TUI Keys:: TUI key bindings
22779 * TUI Single Key Mode:: TUI single key mode
22780 * TUI Commands:: TUI-specific commands
22781 * TUI Configuration:: TUI configuration variables
22784 The @value{GDBN} Text User Interface (TUI) is a terminal
22785 interface which uses the @code{curses} library to show the source
22786 file, the assembly output, the program registers and @value{GDBN}
22787 commands in separate text windows. The TUI mode is supported only
22788 on platforms where a suitable version of the @code{curses} library
22791 @pindex @value{GDBTUI}
22792 The TUI mode is enabled by default when you invoke @value{GDBN} as
22793 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
22794 You can also switch in and out of TUI mode while @value{GDBN} runs by
22795 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
22796 @xref{TUI Keys, ,TUI Key Bindings}.
22799 @section TUI Overview
22801 In TUI mode, @value{GDBN} can display several text windows:
22805 This window is the @value{GDBN} command window with the @value{GDBN}
22806 prompt and the @value{GDBN} output. The @value{GDBN} input is still
22807 managed using readline.
22810 The source window shows the source file of the program. The current
22811 line and active breakpoints are displayed in this window.
22814 The assembly window shows the disassembly output of the program.
22817 This window shows the processor registers. Registers are highlighted
22818 when their values change.
22821 The source and assembly windows show the current program position
22822 by highlighting the current line and marking it with a @samp{>} marker.
22823 Breakpoints are indicated with two markers. The first marker
22824 indicates the breakpoint type:
22828 Breakpoint which was hit at least once.
22831 Breakpoint which was never hit.
22834 Hardware breakpoint which was hit at least once.
22837 Hardware breakpoint which was never hit.
22840 The second marker indicates whether the breakpoint is enabled or not:
22844 Breakpoint is enabled.
22847 Breakpoint is disabled.
22850 The source, assembly and register windows are updated when the current
22851 thread changes, when the frame changes, or when the program counter
22854 These windows are not all visible at the same time. The command
22855 window is always visible. The others can be arranged in several
22866 source and assembly,
22869 source and registers, or
22872 assembly and registers.
22875 A status line above the command window shows the following information:
22879 Indicates the current @value{GDBN} target.
22880 (@pxref{Targets, ,Specifying a Debugging Target}).
22883 Gives the current process or thread number.
22884 When no process is being debugged, this field is set to @code{No process}.
22887 Gives the current function name for the selected frame.
22888 The name is demangled if demangling is turned on (@pxref{Print Settings}).
22889 When there is no symbol corresponding to the current program counter,
22890 the string @code{??} is displayed.
22893 Indicates the current line number for the selected frame.
22894 When the current line number is not known, the string @code{??} is displayed.
22897 Indicates the current program counter address.
22901 @section TUI Key Bindings
22902 @cindex TUI key bindings
22904 The TUI installs several key bindings in the readline keymaps
22905 (@pxref{Command Line Editing}). The following key bindings
22906 are installed for both TUI mode and the @value{GDBN} standard mode.
22915 Enter or leave the TUI mode. When leaving the TUI mode,
22916 the curses window management stops and @value{GDBN} operates using
22917 its standard mode, writing on the terminal directly. When reentering
22918 the TUI mode, control is given back to the curses windows.
22919 The screen is then refreshed.
22923 Use a TUI layout with only one window. The layout will
22924 either be @samp{source} or @samp{assembly}. When the TUI mode
22925 is not active, it will switch to the TUI mode.
22927 Think of this key binding as the Emacs @kbd{C-x 1} binding.
22931 Use a TUI layout with at least two windows. When the current
22932 layout already has two windows, the next layout with two windows is used.
22933 When a new layout is chosen, one window will always be common to the
22934 previous layout and the new one.
22936 Think of it as the Emacs @kbd{C-x 2} binding.
22940 Change the active window. The TUI associates several key bindings
22941 (like scrolling and arrow keys) with the active window. This command
22942 gives the focus to the next TUI window.
22944 Think of it as the Emacs @kbd{C-x o} binding.
22948 Switch in and out of the TUI SingleKey mode that binds single
22949 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
22952 The following key bindings only work in the TUI mode:
22957 Scroll the active window one page up.
22961 Scroll the active window one page down.
22965 Scroll the active window one line up.
22969 Scroll the active window one line down.
22973 Scroll the active window one column left.
22977 Scroll the active window one column right.
22981 Refresh the screen.
22984 Because the arrow keys scroll the active window in the TUI mode, they
22985 are not available for their normal use by readline unless the command
22986 window has the focus. When another window is active, you must use
22987 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
22988 and @kbd{C-f} to control the command window.
22990 @node TUI Single Key Mode
22991 @section TUI Single Key Mode
22992 @cindex TUI single key mode
22994 The TUI also provides a @dfn{SingleKey} mode, which binds several
22995 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
22996 switch into this mode, where the following key bindings are used:
22999 @kindex c @r{(SingleKey TUI key)}
23003 @kindex d @r{(SingleKey TUI key)}
23007 @kindex f @r{(SingleKey TUI key)}
23011 @kindex n @r{(SingleKey TUI key)}
23015 @kindex q @r{(SingleKey TUI key)}
23017 exit the SingleKey mode.
23019 @kindex r @r{(SingleKey TUI key)}
23023 @kindex s @r{(SingleKey TUI key)}
23027 @kindex u @r{(SingleKey TUI key)}
23031 @kindex v @r{(SingleKey TUI key)}
23035 @kindex w @r{(SingleKey TUI key)}
23040 Other keys temporarily switch to the @value{GDBN} command prompt.
23041 The key that was pressed is inserted in the editing buffer so that
23042 it is possible to type most @value{GDBN} commands without interaction
23043 with the TUI SingleKey mode. Once the command is entered the TUI
23044 SingleKey mode is restored. The only way to permanently leave
23045 this mode is by typing @kbd{q} or @kbd{C-x s}.
23049 @section TUI-specific Commands
23050 @cindex TUI commands
23052 The TUI has specific commands to control the text windows.
23053 These commands are always available, even when @value{GDBN} is not in
23054 the TUI mode. When @value{GDBN} is in the standard mode, most
23055 of these commands will automatically switch to the TUI mode.
23057 Note that if @value{GDBN}'s @code{stdout} is not connected to a
23058 terminal, or @value{GDBN} has been started with the machine interface
23059 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
23060 these commands will fail with an error, because it would not be
23061 possible or desirable to enable curses window management.
23066 List and give the size of all displayed windows.
23070 Display the next layout.
23073 Display the previous layout.
23076 Display the source window only.
23079 Display the assembly window only.
23082 Display the source and assembly window.
23085 Display the register window together with the source or assembly window.
23089 Make the next window active for scrolling.
23092 Make the previous window active for scrolling.
23095 Make the source window active for scrolling.
23098 Make the assembly window active for scrolling.
23101 Make the register window active for scrolling.
23104 Make the command window active for scrolling.
23108 Refresh the screen. This is similar to typing @kbd{C-L}.
23110 @item tui reg float
23112 Show the floating point registers in the register window.
23114 @item tui reg general
23115 Show the general registers in the register window.
23118 Show the next register group. The list of register groups as well as
23119 their order is target specific. The predefined register groups are the
23120 following: @code{general}, @code{float}, @code{system}, @code{vector},
23121 @code{all}, @code{save}, @code{restore}.
23123 @item tui reg system
23124 Show the system registers in the register window.
23128 Update the source window and the current execution point.
23130 @item winheight @var{name} +@var{count}
23131 @itemx winheight @var{name} -@var{count}
23133 Change the height of the window @var{name} by @var{count}
23134 lines. Positive counts increase the height, while negative counts
23137 @item tabset @var{nchars}
23139 Set the width of tab stops to be @var{nchars} characters.
23142 @node TUI Configuration
23143 @section TUI Configuration Variables
23144 @cindex TUI configuration variables
23146 Several configuration variables control the appearance of TUI windows.
23149 @item set tui border-kind @var{kind}
23150 @kindex set tui border-kind
23151 Select the border appearance for the source, assembly and register windows.
23152 The possible values are the following:
23155 Use a space character to draw the border.
23158 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23161 Use the Alternate Character Set to draw the border. The border is
23162 drawn using character line graphics if the terminal supports them.
23165 @item set tui border-mode @var{mode}
23166 @kindex set tui border-mode
23167 @itemx set tui active-border-mode @var{mode}
23168 @kindex set tui active-border-mode
23169 Select the display attributes for the borders of the inactive windows
23170 or the active window. The @var{mode} can be one of the following:
23173 Use normal attributes to display the border.
23179 Use reverse video mode.
23182 Use half bright mode.
23184 @item half-standout
23185 Use half bright and standout mode.
23188 Use extra bright or bold mode.
23190 @item bold-standout
23191 Use extra bright or bold and standout mode.
23196 @chapter Using @value{GDBN} under @sc{gnu} Emacs
23199 @cindex @sc{gnu} Emacs
23200 A special interface allows you to use @sc{gnu} Emacs to view (and
23201 edit) the source files for the program you are debugging with
23204 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
23205 executable file you want to debug as an argument. This command starts
23206 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
23207 created Emacs buffer.
23208 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
23210 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
23215 All ``terminal'' input and output goes through an Emacs buffer, called
23218 This applies both to @value{GDBN} commands and their output, and to the input
23219 and output done by the program you are debugging.
23221 This is useful because it means that you can copy the text of previous
23222 commands and input them again; you can even use parts of the output
23225 All the facilities of Emacs' Shell mode are available for interacting
23226 with your program. In particular, you can send signals the usual
23227 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
23231 @value{GDBN} displays source code through Emacs.
23233 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
23234 source file for that frame and puts an arrow (@samp{=>}) at the
23235 left margin of the current line. Emacs uses a separate buffer for
23236 source display, and splits the screen to show both your @value{GDBN} session
23239 Explicit @value{GDBN} @code{list} or search commands still produce output as
23240 usual, but you probably have no reason to use them from Emacs.
23243 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
23244 a graphical mode, enabled by default, which provides further buffers
23245 that can control the execution and describe the state of your program.
23246 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
23248 If you specify an absolute file name when prompted for the @kbd{M-x
23249 gdb} argument, then Emacs sets your current working directory to where
23250 your program resides. If you only specify the file name, then Emacs
23251 sets your current working directory to to the directory associated
23252 with the previous buffer. In this case, @value{GDBN} may find your
23253 program by searching your environment's @code{PATH} variable, but on
23254 some operating systems it might not find the source. So, although the
23255 @value{GDBN} input and output session proceeds normally, the auxiliary
23256 buffer does not display the current source and line of execution.
23258 The initial working directory of @value{GDBN} is printed on the top
23259 line of the GUD buffer and this serves as a default for the commands
23260 that specify files for @value{GDBN} to operate on. @xref{Files,
23261 ,Commands to Specify Files}.
23263 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23264 need to call @value{GDBN} by a different name (for example, if you
23265 keep several configurations around, with different names) you can
23266 customize the Emacs variable @code{gud-gdb-command-name} to run the
23269 In the GUD buffer, you can use these special Emacs commands in
23270 addition to the standard Shell mode commands:
23274 Describe the features of Emacs' GUD Mode.
23277 Execute to another source line, like the @value{GDBN} @code{step} command; also
23278 update the display window to show the current file and location.
23281 Execute to next source line in this function, skipping all function
23282 calls, like the @value{GDBN} @code{next} command. Then update the display window
23283 to show the current file and location.
23286 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23287 display window accordingly.
23290 Execute until exit from the selected stack frame, like the @value{GDBN}
23291 @code{finish} command.
23294 Continue execution of your program, like the @value{GDBN} @code{continue}
23298 Go up the number of frames indicated by the numeric argument
23299 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23300 like the @value{GDBN} @code{up} command.
23303 Go down the number of frames indicated by the numeric argument, like the
23304 @value{GDBN} @code{down} command.
23307 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23308 tells @value{GDBN} to set a breakpoint on the source line point is on.
23310 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23311 separate frame which shows a backtrace when the GUD buffer is current.
23312 Move point to any frame in the stack and type @key{RET} to make it
23313 become the current frame and display the associated source in the
23314 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23315 selected frame become the current one. In graphical mode, the
23316 speedbar displays watch expressions.
23318 If you accidentally delete the source-display buffer, an easy way to get
23319 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23320 request a frame display; when you run under Emacs, this recreates
23321 the source buffer if necessary to show you the context of the current
23324 The source files displayed in Emacs are in ordinary Emacs buffers
23325 which are visiting the source files in the usual way. You can edit
23326 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23327 communicates with Emacs in terms of line numbers. If you add or
23328 delete lines from the text, the line numbers that @value{GDBN} knows cease
23329 to correspond properly with the code.
23331 A more detailed description of Emacs' interaction with @value{GDBN} is
23332 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23335 @c The following dropped because Epoch is nonstandard. Reactivate
23336 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23338 @kindex Emacs Epoch environment
23342 Version 18 of @sc{gnu} Emacs has a built-in window system
23343 called the @code{epoch}
23344 environment. Users of this environment can use a new command,
23345 @code{inspect} which performs identically to @code{print} except that
23346 each value is printed in its own window.
23351 @chapter The @sc{gdb/mi} Interface
23353 @unnumberedsec Function and Purpose
23355 @cindex @sc{gdb/mi}, its purpose
23356 @sc{gdb/mi} is a line based machine oriented text interface to
23357 @value{GDBN} and is activated by specifying using the
23358 @option{--interpreter} command line option (@pxref{Mode Options}). It
23359 is specifically intended to support the development of systems which
23360 use the debugger as just one small component of a larger system.
23362 This chapter is a specification of the @sc{gdb/mi} interface. It is written
23363 in the form of a reference manual.
23365 Note that @sc{gdb/mi} is still under construction, so some of the
23366 features described below are incomplete and subject to change
23367 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
23369 @unnumberedsec Notation and Terminology
23371 @cindex notational conventions, for @sc{gdb/mi}
23372 This chapter uses the following notation:
23376 @code{|} separates two alternatives.
23379 @code{[ @var{something} ]} indicates that @var{something} is optional:
23380 it may or may not be given.
23383 @code{( @var{group} )*} means that @var{group} inside the parentheses
23384 may repeat zero or more times.
23387 @code{( @var{group} )+} means that @var{group} inside the parentheses
23388 may repeat one or more times.
23391 @code{"@var{string}"} means a literal @var{string}.
23395 @heading Dependencies
23399 * GDB/MI General Design::
23400 * GDB/MI Command Syntax::
23401 * GDB/MI Compatibility with CLI::
23402 * GDB/MI Development and Front Ends::
23403 * GDB/MI Output Records::
23404 * GDB/MI Simple Examples::
23405 * GDB/MI Command Description Format::
23406 * GDB/MI Breakpoint Commands::
23407 * GDB/MI Program Context::
23408 * GDB/MI Thread Commands::
23409 * GDB/MI Program Execution::
23410 * GDB/MI Stack Manipulation::
23411 * GDB/MI Variable Objects::
23412 * GDB/MI Data Manipulation::
23413 * GDB/MI Tracepoint Commands::
23414 * GDB/MI Symbol Query::
23415 * GDB/MI File Commands::
23417 * GDB/MI Kod Commands::
23418 * GDB/MI Memory Overlay Commands::
23419 * GDB/MI Signal Handling Commands::
23421 * GDB/MI Target Manipulation::
23422 * GDB/MI File Transfer Commands::
23423 * GDB/MI Miscellaneous Commands::
23426 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23427 @node GDB/MI General Design
23428 @section @sc{gdb/mi} General Design
23429 @cindex GDB/MI General Design
23431 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
23432 parts---commands sent to @value{GDBN}, responses to those commands
23433 and notifications. Each command results in exactly one response,
23434 indicating either successful completion of the command, or an error.
23435 For the commands that do not resume the target, the response contains the
23436 requested information. For the commands that resume the target, the
23437 response only indicates whether the target was successfully resumed.
23438 Notifications is the mechanism for reporting changes in the state of the
23439 target, or in @value{GDBN} state, that cannot conveniently be associated with
23440 a command and reported as part of that command response.
23442 The important examples of notifications are:
23446 Exec notifications. These are used to report changes in
23447 target state---when a target is resumed, or stopped. It would not
23448 be feasible to include this information in response of resuming
23449 commands, because one resume commands can result in multiple events in
23450 different threads. Also, quite some time may pass before any event
23451 happens in the target, while a frontend needs to know whether the resuming
23452 command itself was successfully executed.
23455 Console output, and status notifications. Console output
23456 notifications are used to report output of CLI commands, as well as
23457 diagnostics for other commands. Status notifications are used to
23458 report the progress of a long-running operation. Naturally, including
23459 this information in command response would mean no output is produced
23460 until the command is finished, which is undesirable.
23463 General notifications. Commands may have various side effects on
23464 the @value{GDBN} or target state beyond their official purpose. For example,
23465 a command may change the selected thread. Although such changes can
23466 be included in command response, using notification allows for more
23467 orthogonal frontend design.
23471 There's no guarantee that whenever an MI command reports an error,
23472 @value{GDBN} or the target are in any specific state, and especially,
23473 the state is not reverted to the state before the MI command was
23474 processed. Therefore, whenever an MI command results in an error,
23475 we recommend that the frontend refreshes all the information shown in
23476 the user interface.
23480 * Context management::
23481 * Asynchronous and non-stop modes::
23485 @node Context management
23486 @subsection Context management
23488 In most cases when @value{GDBN} accesses the target, this access is
23489 done in context of a specific thread and frame (@pxref{Frames}).
23490 Often, even when accessing global data, the target requires that a thread
23491 be specified. The CLI interface maintains the selected thread and frame,
23492 and supplies them to target on each command. This is convenient,
23493 because a command line user would not want to specify that information
23494 explicitly on each command, and because user interacts with
23495 @value{GDBN} via a single terminal, so no confusion is possible as
23496 to what thread and frame are the current ones.
23498 In the case of MI, the concept of selected thread and frame is less
23499 useful. First, a frontend can easily remember this information
23500 itself. Second, a graphical frontend can have more than one window,
23501 each one used for debugging a different thread, and the frontend might
23502 want to access additional threads for internal purposes. This
23503 increases the risk that by relying on implicitly selected thread, the
23504 frontend may be operating on a wrong one. Therefore, each MI command
23505 should explicitly specify which thread and frame to operate on. To
23506 make it possible, each MI command accepts the @samp{--thread} and
23507 @samp{--frame} options, the value to each is @value{GDBN} identifier
23508 for thread and frame to operate on.
23510 Usually, each top-level window in a frontend allows the user to select
23511 a thread and a frame, and remembers the user selection for further
23512 operations. However, in some cases @value{GDBN} may suggest that the
23513 current thread be changed. For example, when stopping on a breakpoint
23514 it is reasonable to switch to the thread where breakpoint is hit. For
23515 another example, if the user issues the CLI @samp{thread} command via
23516 the frontend, it is desirable to change the frontend's selected thread to the
23517 one specified by user. @value{GDBN} communicates the suggestion to
23518 change current thread using the @samp{=thread-selected} notification.
23519 No such notification is available for the selected frame at the moment.
23521 Note that historically, MI shares the selected thread with CLI, so
23522 frontends used the @code{-thread-select} to execute commands in the
23523 right context. However, getting this to work right is cumbersome. The
23524 simplest way is for frontend to emit @code{-thread-select} command
23525 before every command. This doubles the number of commands that need
23526 to be sent. The alternative approach is to suppress @code{-thread-select}
23527 if the selected thread in @value{GDBN} is supposed to be identical to the
23528 thread the frontend wants to operate on. However, getting this
23529 optimization right can be tricky. In particular, if the frontend
23530 sends several commands to @value{GDBN}, and one of the commands changes the
23531 selected thread, then the behaviour of subsequent commands will
23532 change. So, a frontend should either wait for response from such
23533 problematic commands, or explicitly add @code{-thread-select} for
23534 all subsequent commands. No frontend is known to do this exactly
23535 right, so it is suggested to just always pass the @samp{--thread} and
23536 @samp{--frame} options.
23538 @node Asynchronous and non-stop modes
23539 @subsection Asynchronous command execution and non-stop mode
23541 On some targets, @value{GDBN} is capable of processing MI commands
23542 even while the target is running. This is called @dfn{asynchronous
23543 command execution} (@pxref{Background Execution}). The frontend may
23544 specify a preferrence for asynchronous execution using the
23545 @code{-gdb-set target-async 1} command, which should be emitted before
23546 either running the executable or attaching to the target. After the
23547 frontend has started the executable or attached to the target, it can
23548 find if asynchronous execution is enabled using the
23549 @code{-list-target-features} command.
23551 Even if @value{GDBN} can accept a command while target is running,
23552 many commands that access the target do not work when the target is
23553 running. Therefore, asynchronous command execution is most useful
23554 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
23555 it is possible to examine the state of one thread, while other threads
23558 When a given thread is running, MI commands that try to access the
23559 target in the context of that thread may not work, or may work only on
23560 some targets. In particular, commands that try to operate on thread's
23561 stack will not work, on any target. Commands that read memory, or
23562 modify breakpoints, may work or not work, depending on the target. Note
23563 that even commands that operate on global state, such as @code{print},
23564 @code{set}, and breakpoint commands, still access the target in the
23565 context of a specific thread, so frontend should try to find a
23566 stopped thread and perform the operation on that thread (using the
23567 @samp{--thread} option).
23569 Which commands will work in the context of a running thread is
23570 highly target dependent. However, the two commands
23571 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
23572 to find the state of a thread, will always work.
23574 @node Thread groups
23575 @subsection Thread groups
23576 @value{GDBN} may be used to debug several processes at the same time.
23577 On some platfroms, @value{GDBN} may support debugging of several
23578 hardware systems, each one having several cores with several different
23579 processes running on each core. This section describes the MI
23580 mechanism to support such debugging scenarios.
23582 The key observation is that regardless of the structure of the
23583 target, MI can have a global list of threads, because most commands that
23584 accept the @samp{--thread} option do not need to know what process that
23585 thread belongs to. Therefore, it is not necessary to introduce
23586 neither additional @samp{--process} option, nor an notion of the
23587 current process in the MI interface. The only strictly new feature
23588 that is required is the ability to find how the threads are grouped
23591 To allow the user to discover such grouping, and to support arbitrary
23592 hierarchy of machines/cores/processes, MI introduces the concept of a
23593 @dfn{thread group}. Thread group is a collection of threads and other
23594 thread groups. A thread group always has a string identifier, a type,
23595 and may have additional attributes specific to the type. A new
23596 command, @code{-list-thread-groups}, returns the list of top-level
23597 thread groups, which correspond to processes that @value{GDBN} is
23598 debugging at the moment. By passing an identifier of a thread group
23599 to the @code{-list-thread-groups} command, it is possible to obtain
23600 the members of specific thread group.
23602 To allow the user to easily discover processes, and other objects, he
23603 wishes to debug, a concept of @dfn{available thread group} is
23604 introduced. Available thread group is an thread group that
23605 @value{GDBN} is not debugging, but that can be attached to, using the
23606 @code{-target-attach} command. The list of available top-level thread
23607 groups can be obtained using @samp{-list-thread-groups --available}.
23608 In general, the content of a thread group may be only retrieved only
23609 after attaching to that thread group.
23611 Thread groups are related to inferiors (@pxref{Inferiors and
23612 Programs}). Each inferior corresponds to a thread group of a special
23613 type @samp{process}, and some additional operations are permitted on
23614 such thread groups.
23616 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23617 @node GDB/MI Command Syntax
23618 @section @sc{gdb/mi} Command Syntax
23621 * GDB/MI Input Syntax::
23622 * GDB/MI Output Syntax::
23625 @node GDB/MI Input Syntax
23626 @subsection @sc{gdb/mi} Input Syntax
23628 @cindex input syntax for @sc{gdb/mi}
23629 @cindex @sc{gdb/mi}, input syntax
23631 @item @var{command} @expansion{}
23632 @code{@var{cli-command} | @var{mi-command}}
23634 @item @var{cli-command} @expansion{}
23635 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
23636 @var{cli-command} is any existing @value{GDBN} CLI command.
23638 @item @var{mi-command} @expansion{}
23639 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
23640 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
23642 @item @var{token} @expansion{}
23643 "any sequence of digits"
23645 @item @var{option} @expansion{}
23646 @code{"-" @var{parameter} [ " " @var{parameter} ]}
23648 @item @var{parameter} @expansion{}
23649 @code{@var{non-blank-sequence} | @var{c-string}}
23651 @item @var{operation} @expansion{}
23652 @emph{any of the operations described in this chapter}
23654 @item @var{non-blank-sequence} @expansion{}
23655 @emph{anything, provided it doesn't contain special characters such as
23656 "-", @var{nl}, """ and of course " "}
23658 @item @var{c-string} @expansion{}
23659 @code{""" @var{seven-bit-iso-c-string-content} """}
23661 @item @var{nl} @expansion{}
23670 The CLI commands are still handled by the @sc{mi} interpreter; their
23671 output is described below.
23674 The @code{@var{token}}, when present, is passed back when the command
23678 Some @sc{mi} commands accept optional arguments as part of the parameter
23679 list. Each option is identified by a leading @samp{-} (dash) and may be
23680 followed by an optional argument parameter. Options occur first in the
23681 parameter list and can be delimited from normal parameters using
23682 @samp{--} (this is useful when some parameters begin with a dash).
23689 We want easy access to the existing CLI syntax (for debugging).
23692 We want it to be easy to spot a @sc{mi} operation.
23695 @node GDB/MI Output Syntax
23696 @subsection @sc{gdb/mi} Output Syntax
23698 @cindex output syntax of @sc{gdb/mi}
23699 @cindex @sc{gdb/mi}, output syntax
23700 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23701 followed, optionally, by a single result record. This result record
23702 is for the most recent command. The sequence of output records is
23703 terminated by @samp{(gdb)}.
23705 If an input command was prefixed with a @code{@var{token}} then the
23706 corresponding output for that command will also be prefixed by that same
23710 @item @var{output} @expansion{}
23711 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23713 @item @var{result-record} @expansion{}
23714 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23716 @item @var{out-of-band-record} @expansion{}
23717 @code{@var{async-record} | @var{stream-record}}
23719 @item @var{async-record} @expansion{}
23720 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23722 @item @var{exec-async-output} @expansion{}
23723 @code{[ @var{token} ] "*" @var{async-output}}
23725 @item @var{status-async-output} @expansion{}
23726 @code{[ @var{token} ] "+" @var{async-output}}
23728 @item @var{notify-async-output} @expansion{}
23729 @code{[ @var{token} ] "=" @var{async-output}}
23731 @item @var{async-output} @expansion{}
23732 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23734 @item @var{result-class} @expansion{}
23735 @code{"done" | "running" | "connected" | "error" | "exit"}
23737 @item @var{async-class} @expansion{}
23738 @code{"stopped" | @var{others}} (where @var{others} will be added
23739 depending on the needs---this is still in development).
23741 @item @var{result} @expansion{}
23742 @code{ @var{variable} "=" @var{value}}
23744 @item @var{variable} @expansion{}
23745 @code{ @var{string} }
23747 @item @var{value} @expansion{}
23748 @code{ @var{const} | @var{tuple} | @var{list} }
23750 @item @var{const} @expansion{}
23751 @code{@var{c-string}}
23753 @item @var{tuple} @expansion{}
23754 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
23756 @item @var{list} @expansion{}
23757 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
23758 @var{result} ( "," @var{result} )* "]" }
23760 @item @var{stream-record} @expansion{}
23761 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
23763 @item @var{console-stream-output} @expansion{}
23764 @code{"~" @var{c-string}}
23766 @item @var{target-stream-output} @expansion{}
23767 @code{"@@" @var{c-string}}
23769 @item @var{log-stream-output} @expansion{}
23770 @code{"&" @var{c-string}}
23772 @item @var{nl} @expansion{}
23775 @item @var{token} @expansion{}
23776 @emph{any sequence of digits}.
23784 All output sequences end in a single line containing a period.
23787 The @code{@var{token}} is from the corresponding request. Note that
23788 for all async output, while the token is allowed by the grammar and
23789 may be output by future versions of @value{GDBN} for select async
23790 output messages, it is generally omitted. Frontends should treat
23791 all async output as reporting general changes in the state of the
23792 target and there should be no need to associate async output to any
23796 @cindex status output in @sc{gdb/mi}
23797 @var{status-async-output} contains on-going status information about the
23798 progress of a slow operation. It can be discarded. All status output is
23799 prefixed by @samp{+}.
23802 @cindex async output in @sc{gdb/mi}
23803 @var{exec-async-output} contains asynchronous state change on the target
23804 (stopped, started, disappeared). All async output is prefixed by
23808 @cindex notify output in @sc{gdb/mi}
23809 @var{notify-async-output} contains supplementary information that the
23810 client should handle (e.g., a new breakpoint information). All notify
23811 output is prefixed by @samp{=}.
23814 @cindex console output in @sc{gdb/mi}
23815 @var{console-stream-output} is output that should be displayed as is in the
23816 console. It is the textual response to a CLI command. All the console
23817 output is prefixed by @samp{~}.
23820 @cindex target output in @sc{gdb/mi}
23821 @var{target-stream-output} is the output produced by the target program.
23822 All the target output is prefixed by @samp{@@}.
23825 @cindex log output in @sc{gdb/mi}
23826 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
23827 instance messages that should be displayed as part of an error log. All
23828 the log output is prefixed by @samp{&}.
23831 @cindex list output in @sc{gdb/mi}
23832 New @sc{gdb/mi} commands should only output @var{lists} containing
23838 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
23839 details about the various output records.
23841 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23842 @node GDB/MI Compatibility with CLI
23843 @section @sc{gdb/mi} Compatibility with CLI
23845 @cindex compatibility, @sc{gdb/mi} and CLI
23846 @cindex @sc{gdb/mi}, compatibility with CLI
23848 For the developers convenience CLI commands can be entered directly,
23849 but there may be some unexpected behaviour. For example, commands
23850 that query the user will behave as if the user replied yes, breakpoint
23851 command lists are not executed and some CLI commands, such as
23852 @code{if}, @code{when} and @code{define}, prompt for further input with
23853 @samp{>}, which is not valid MI output.
23855 This feature may be removed at some stage in the future and it is
23856 recommended that front ends use the @code{-interpreter-exec} command
23857 (@pxref{-interpreter-exec}).
23859 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23860 @node GDB/MI Development and Front Ends
23861 @section @sc{gdb/mi} Development and Front Ends
23862 @cindex @sc{gdb/mi} development
23864 The application which takes the MI output and presents the state of the
23865 program being debugged to the user is called a @dfn{front end}.
23867 Although @sc{gdb/mi} is still incomplete, it is currently being used
23868 by a variety of front ends to @value{GDBN}. This makes it difficult
23869 to introduce new functionality without breaking existing usage. This
23870 section tries to minimize the problems by describing how the protocol
23873 Some changes in MI need not break a carefully designed front end, and
23874 for these the MI version will remain unchanged. The following is a
23875 list of changes that may occur within one level, so front ends should
23876 parse MI output in a way that can handle them:
23880 New MI commands may be added.
23883 New fields may be added to the output of any MI command.
23886 The range of values for fields with specified values, e.g.,
23887 @code{in_scope} (@pxref{-var-update}) may be extended.
23889 @c The format of field's content e.g type prefix, may change so parse it
23890 @c at your own risk. Yes, in general?
23892 @c The order of fields may change? Shouldn't really matter but it might
23893 @c resolve inconsistencies.
23896 If the changes are likely to break front ends, the MI version level
23897 will be increased by one. This will allow the front end to parse the
23898 output according to the MI version. Apart from mi0, new versions of
23899 @value{GDBN} will not support old versions of MI and it will be the
23900 responsibility of the front end to work with the new one.
23902 @c Starting with mi3, add a new command -mi-version that prints the MI
23905 The best way to avoid unexpected changes in MI that might break your front
23906 end is to make your project known to @value{GDBN} developers and
23907 follow development on @email{gdb@@sourceware.org} and
23908 @email{gdb-patches@@sourceware.org}.
23909 @cindex mailing lists
23911 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23912 @node GDB/MI Output Records
23913 @section @sc{gdb/mi} Output Records
23916 * GDB/MI Result Records::
23917 * GDB/MI Stream Records::
23918 * GDB/MI Async Records::
23919 * GDB/MI Frame Information::
23920 * GDB/MI Thread Information::
23923 @node GDB/MI Result Records
23924 @subsection @sc{gdb/mi} Result Records
23926 @cindex result records in @sc{gdb/mi}
23927 @cindex @sc{gdb/mi}, result records
23928 In addition to a number of out-of-band notifications, the response to a
23929 @sc{gdb/mi} command includes one of the following result indications:
23933 @item "^done" [ "," @var{results} ]
23934 The synchronous operation was successful, @code{@var{results}} are the return
23939 This result record is equivalent to @samp{^done}. Historically, it
23940 was output instead of @samp{^done} if the command has resumed the
23941 target. This behaviour is maintained for backward compatibility, but
23942 all frontends should treat @samp{^done} and @samp{^running}
23943 identically and rely on the @samp{*running} output record to determine
23944 which threads are resumed.
23948 @value{GDBN} has connected to a remote target.
23950 @item "^error" "," @var{c-string}
23952 The operation failed. The @code{@var{c-string}} contains the corresponding
23957 @value{GDBN} has terminated.
23961 @node GDB/MI Stream Records
23962 @subsection @sc{gdb/mi} Stream Records
23964 @cindex @sc{gdb/mi}, stream records
23965 @cindex stream records in @sc{gdb/mi}
23966 @value{GDBN} internally maintains a number of output streams: the console, the
23967 target, and the log. The output intended for each of these streams is
23968 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
23970 Each stream record begins with a unique @dfn{prefix character} which
23971 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
23972 Syntax}). In addition to the prefix, each stream record contains a
23973 @code{@var{string-output}}. This is either raw text (with an implicit new
23974 line) or a quoted C string (which does not contain an implicit newline).
23977 @item "~" @var{string-output}
23978 The console output stream contains text that should be displayed in the
23979 CLI console window. It contains the textual responses to CLI commands.
23981 @item "@@" @var{string-output}
23982 The target output stream contains any textual output from the running
23983 target. This is only present when GDB's event loop is truly
23984 asynchronous, which is currently only the case for remote targets.
23986 @item "&" @var{string-output}
23987 The log stream contains debugging messages being produced by @value{GDBN}'s
23991 @node GDB/MI Async Records
23992 @subsection @sc{gdb/mi} Async Records
23994 @cindex async records in @sc{gdb/mi}
23995 @cindex @sc{gdb/mi}, async records
23996 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
23997 additional changes that have occurred. Those changes can either be a
23998 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
23999 target activity (e.g., target stopped).
24001 The following is the list of possible async records:
24005 @item *running,thread-id="@var{thread}"
24006 The target is now running. The @var{thread} field tells which
24007 specific thread is now running, and can be @samp{all} if all threads
24008 are running. The frontend should assume that no interaction with a
24009 running thread is possible after this notification is produced.
24010 The frontend should not assume that this notification is output
24011 only once for any command. @value{GDBN} may emit this notification
24012 several times, either for different threads, because it cannot resume
24013 all threads together, or even for a single thread, if the thread must
24014 be stepped though some code before letting it run freely.
24016 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
24017 The target has stopped. The @var{reason} field can have one of the
24021 @item breakpoint-hit
24022 A breakpoint was reached.
24023 @item watchpoint-trigger
24024 A watchpoint was triggered.
24025 @item read-watchpoint-trigger
24026 A read watchpoint was triggered.
24027 @item access-watchpoint-trigger
24028 An access watchpoint was triggered.
24029 @item function-finished
24030 An -exec-finish or similar CLI command was accomplished.
24031 @item location-reached
24032 An -exec-until or similar CLI command was accomplished.
24033 @item watchpoint-scope
24034 A watchpoint has gone out of scope.
24035 @item end-stepping-range
24036 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
24037 similar CLI command was accomplished.
24038 @item exited-signalled
24039 The inferior exited because of a signal.
24041 The inferior exited.
24042 @item exited-normally
24043 The inferior exited normally.
24044 @item signal-received
24045 A signal was received by the inferior.
24048 The @var{id} field identifies the thread that directly caused the stop
24049 -- for example by hitting a breakpoint. Depending on whether all-stop
24050 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
24051 stop all threads, or only the thread that directly triggered the stop.
24052 If all threads are stopped, the @var{stopped} field will have the
24053 value of @code{"all"}. Otherwise, the value of the @var{stopped}
24054 field will be a list of thread identifiers. Presently, this list will
24055 always include a single thread, but frontend should be prepared to see
24056 several threads in the list. The @var{core} field reports the
24057 processor core on which the stop event has happened. This field may be absent
24058 if such information is not available.
24060 @item =thread-group-added,id="@var{id}"
24061 @itemx =thread-group-removed,id="@var{id}"
24062 A thread group was either added or removed. The @var{id} field
24063 contains the @value{GDBN} identifier of the thread group. When a thread
24064 group is added, it generally might not be associated with a running
24065 process. When a thread group is removed, its id becomes invalid and
24066 cannot be used in any way.
24068 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
24069 A thread group became associated with a running program,
24070 either because the program was just started or the thread group
24071 was attached to a program. The @var{id} field contains the
24072 @value{GDBN} identifier of the thread group. The @var{pid} field
24073 contains process identifier, specific to the operating system.
24075 @itemx =thread-group-exited,id="@var{id}"
24076 A thread group is no longer associated with a running program,
24077 either because the program has exited, or because it was detached
24078 from. The @var{id} field contains the @value{GDBN} identifier of the
24081 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24082 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24083 A thread either was created, or has exited. The @var{id} field
24084 contains the @value{GDBN} identifier of the thread. The @var{gid}
24085 field identifies the thread group this thread belongs to.
24087 @item =thread-selected,id="@var{id}"
24088 Informs that the selected thread was changed as result of the last
24089 command. This notification is not emitted as result of @code{-thread-select}
24090 command but is emitted whenever an MI command that is not documented
24091 to change the selected thread actually changes it. In particular,
24092 invoking, directly or indirectly (via user-defined command), the CLI
24093 @code{thread} command, will generate this notification.
24095 We suggest that in response to this notification, front ends
24096 highlight the selected thread and cause subsequent commands to apply to
24099 @item =library-loaded,...
24100 Reports that a new library file was loaded by the program. This
24101 notification has 4 fields---@var{id}, @var{target-name},
24102 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24103 opaque identifier of the library. For remote debugging case,
24104 @var{target-name} and @var{host-name} fields give the name of the
24105 library file on the target, and on the host respectively. For native
24106 debugging, both those fields have the same value. The
24107 @var{symbols-loaded} field reports if the debug symbols for this
24108 library are loaded. The @var{thread-group} field, if present,
24109 specifies the id of the thread group in whose context the library was loaded.
24110 If the field is absent, it means the library was loaded in the context
24111 of all present thread groups.
24113 @item =library-unloaded,...
24114 Reports that a library was unloaded by the program. This notification
24115 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24116 the same meaning as for the @code{=library-loaded} notification.
24117 The @var{thread-group} field, if present, specifies the id of the
24118 thread group in whose context the library was unloaded. If the field is
24119 absent, it means the library was unloaded in the context of all present
24124 @node GDB/MI Frame Information
24125 @subsection @sc{gdb/mi} Frame Information
24127 Response from many MI commands includes an information about stack
24128 frame. This information is a tuple that may have the following
24133 The level of the stack frame. The innermost frame has the level of
24134 zero. This field is always present.
24137 The name of the function corresponding to the frame. This field may
24138 be absent if @value{GDBN} is unable to determine the function name.
24141 The code address for the frame. This field is always present.
24144 The name of the source files that correspond to the frame's code
24145 address. This field may be absent.
24148 The source line corresponding to the frames' code address. This field
24152 The name of the binary file (either executable or shared library) the
24153 corresponds to the frame's code address. This field may be absent.
24157 @node GDB/MI Thread Information
24158 @subsection @sc{gdb/mi} Thread Information
24160 Whenever @value{GDBN} has to report an information about a thread, it
24161 uses a tuple with the following fields:
24165 The numeric id assigned to the thread by @value{GDBN}. This field is
24169 Target-specific string identifying the thread. This field is always present.
24172 Additional information about the thread provided by the target.
24173 It is supposed to be human-readable and not interpreted by the
24174 frontend. This field is optional.
24177 Either @samp{stopped} or @samp{running}, depending on whether the
24178 thread is presently running. This field is always present.
24181 The value of this field is an integer number of the processor core the
24182 thread was last seen on. This field is optional.
24186 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24187 @node GDB/MI Simple Examples
24188 @section Simple Examples of @sc{gdb/mi} Interaction
24189 @cindex @sc{gdb/mi}, simple examples
24191 This subsection presents several simple examples of interaction using
24192 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
24193 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
24194 the output received from @sc{gdb/mi}.
24196 Note the line breaks shown in the examples are here only for
24197 readability, they don't appear in the real output.
24199 @subheading Setting a Breakpoint
24201 Setting a breakpoint generates synchronous output which contains detailed
24202 information of the breakpoint.
24205 -> -break-insert main
24206 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24207 enabled="y",addr="0x08048564",func="main",file="myprog.c",
24208 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
24212 @subheading Program Execution
24214 Program execution generates asynchronous records and MI gives the
24215 reason that execution stopped.
24221 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24222 frame=@{addr="0x08048564",func="main",
24223 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
24224 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
24229 <- *stopped,reason="exited-normally"
24233 @subheading Quitting @value{GDBN}
24235 Quitting @value{GDBN} just prints the result class @samp{^exit}.
24243 Please note that @samp{^exit} is printed immediately, but it might
24244 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
24245 performs necessary cleanups, including killing programs being debugged
24246 or disconnecting from debug hardware, so the frontend should wait till
24247 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
24248 fails to exit in reasonable time.
24250 @subheading A Bad Command
24252 Here's what happens if you pass a non-existent command:
24256 <- ^error,msg="Undefined MI command: rubbish"
24261 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24262 @node GDB/MI Command Description Format
24263 @section @sc{gdb/mi} Command Description Format
24265 The remaining sections describe blocks of commands. Each block of
24266 commands is laid out in a fashion similar to this section.
24268 @subheading Motivation
24270 The motivation for this collection of commands.
24272 @subheading Introduction
24274 A brief introduction to this collection of commands as a whole.
24276 @subheading Commands
24278 For each command in the block, the following is described:
24280 @subsubheading Synopsis
24283 -command @var{args}@dots{}
24286 @subsubheading Result
24288 @subsubheading @value{GDBN} Command
24290 The corresponding @value{GDBN} CLI command(s), if any.
24292 @subsubheading Example
24294 Example(s) formatted for readability. Some of the described commands have
24295 not been implemented yet and these are labeled N.A.@: (not available).
24298 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24299 @node GDB/MI Breakpoint Commands
24300 @section @sc{gdb/mi} Breakpoint Commands
24302 @cindex breakpoint commands for @sc{gdb/mi}
24303 @cindex @sc{gdb/mi}, breakpoint commands
24304 This section documents @sc{gdb/mi} commands for manipulating
24307 @subheading The @code{-break-after} Command
24308 @findex -break-after
24310 @subsubheading Synopsis
24313 -break-after @var{number} @var{count}
24316 The breakpoint number @var{number} is not in effect until it has been
24317 hit @var{count} times. To see how this is reflected in the output of
24318 the @samp{-break-list} command, see the description of the
24319 @samp{-break-list} command below.
24321 @subsubheading @value{GDBN} Command
24323 The corresponding @value{GDBN} command is @samp{ignore}.
24325 @subsubheading Example
24330 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24331 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24332 fullname="/home/foo/hello.c",line="5",times="0"@}
24339 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24340 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24341 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24342 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24343 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24344 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24345 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24346 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24347 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24348 line="5",times="0",ignore="3"@}]@}
24353 @subheading The @code{-break-catch} Command
24354 @findex -break-catch
24357 @subheading The @code{-break-commands} Command
24358 @findex -break-commands
24360 @subsubheading Synopsis
24363 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
24366 Specifies the CLI commands that should be executed when breakpoint
24367 @var{number} is hit. The parameters @var{command1} to @var{commandN}
24368 are the commands. If no command is specified, any previously-set
24369 commands are cleared. @xref{Break Commands}. Typical use of this
24370 functionality is tracing a program, that is, printing of values of
24371 some variables whenever breakpoint is hit and then continuing.
24373 @subsubheading @value{GDBN} Command
24375 The corresponding @value{GDBN} command is @samp{commands}.
24377 @subsubheading Example
24382 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24383 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24384 fullname="/home/foo/hello.c",line="5",times="0"@}
24386 -break-commands 1 "print v" "continue"
24391 @subheading The @code{-break-condition} Command
24392 @findex -break-condition
24394 @subsubheading Synopsis
24397 -break-condition @var{number} @var{expr}
24400 Breakpoint @var{number} will stop the program only if the condition in
24401 @var{expr} is true. The condition becomes part of the
24402 @samp{-break-list} output (see the description of the @samp{-break-list}
24405 @subsubheading @value{GDBN} Command
24407 The corresponding @value{GDBN} command is @samp{condition}.
24409 @subsubheading Example
24413 -break-condition 1 1
24417 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24418 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24419 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24420 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24421 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24422 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24423 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24424 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24425 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24426 line="5",cond="1",times="0",ignore="3"@}]@}
24430 @subheading The @code{-break-delete} Command
24431 @findex -break-delete
24433 @subsubheading Synopsis
24436 -break-delete ( @var{breakpoint} )+
24439 Delete the breakpoint(s) whose number(s) are specified in the argument
24440 list. This is obviously reflected in the breakpoint list.
24442 @subsubheading @value{GDBN} Command
24444 The corresponding @value{GDBN} command is @samp{delete}.
24446 @subsubheading Example
24454 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24455 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24456 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24457 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24458 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24459 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24460 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24465 @subheading The @code{-break-disable} Command
24466 @findex -break-disable
24468 @subsubheading Synopsis
24471 -break-disable ( @var{breakpoint} )+
24474 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24475 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24477 @subsubheading @value{GDBN} Command
24479 The corresponding @value{GDBN} command is @samp{disable}.
24481 @subsubheading Example
24489 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24490 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24491 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24492 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24493 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24494 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24495 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24496 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
24497 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24498 line="5",times="0"@}]@}
24502 @subheading The @code{-break-enable} Command
24503 @findex -break-enable
24505 @subsubheading Synopsis
24508 -break-enable ( @var{breakpoint} )+
24511 Enable (previously disabled) @var{breakpoint}(s).
24513 @subsubheading @value{GDBN} Command
24515 The corresponding @value{GDBN} command is @samp{enable}.
24517 @subsubheading Example
24525 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24526 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24527 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24528 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24529 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24530 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24531 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24532 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24533 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24534 line="5",times="0"@}]@}
24538 @subheading The @code{-break-info} Command
24539 @findex -break-info
24541 @subsubheading Synopsis
24544 -break-info @var{breakpoint}
24548 Get information about a single breakpoint.
24550 @subsubheading @value{GDBN} Command
24552 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
24554 @subsubheading Example
24557 @subheading The @code{-break-insert} Command
24558 @findex -break-insert
24560 @subsubheading Synopsis
24563 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
24564 [ -c @var{condition} ] [ -i @var{ignore-count} ]
24565 [ -p @var{thread} ] [ @var{location} ]
24569 If specified, @var{location}, can be one of:
24576 @item filename:linenum
24577 @item filename:function
24581 The possible optional parameters of this command are:
24585 Insert a temporary breakpoint.
24587 Insert a hardware breakpoint.
24588 @item -c @var{condition}
24589 Make the breakpoint conditional on @var{condition}.
24590 @item -i @var{ignore-count}
24591 Initialize the @var{ignore-count}.
24593 If @var{location} cannot be parsed (for example if it
24594 refers to unknown files or functions), create a pending
24595 breakpoint. Without this flag, @value{GDBN} will report
24596 an error, and won't create a breakpoint, if @var{location}
24599 Create a disabled breakpoint.
24601 Create a tracepoint. @xref{Tracepoints}. When this parameter
24602 is used together with @samp{-h}, a fast tracepoint is created.
24605 @subsubheading Result
24607 The result is in the form:
24610 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
24611 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
24612 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
24613 times="@var{times}"@}
24617 where @var{number} is the @value{GDBN} number for this breakpoint,
24618 @var{funcname} is the name of the function where the breakpoint was
24619 inserted, @var{filename} is the name of the source file which contains
24620 this function, @var{lineno} is the source line number within that file
24621 and @var{times} the number of times that the breakpoint has been hit
24622 (always 0 for -break-insert but may be greater for -break-info or -break-list
24623 which use the same output).
24625 Note: this format is open to change.
24626 @c An out-of-band breakpoint instead of part of the result?
24628 @subsubheading @value{GDBN} Command
24630 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
24631 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
24633 @subsubheading Example
24638 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
24639 fullname="/home/foo/recursive2.c,line="4",times="0"@}
24641 -break-insert -t foo
24642 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
24643 fullname="/home/foo/recursive2.c,line="11",times="0"@}
24646 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24647 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24648 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24649 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24650 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24651 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24652 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24653 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24654 addr="0x0001072c", func="main",file="recursive2.c",
24655 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24656 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24657 addr="0x00010774",func="foo",file="recursive2.c",
24658 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24660 -break-insert -r foo.*
24661 ~int foo(int, int);
24662 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24663 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24667 @subheading The @code{-break-list} Command
24668 @findex -break-list
24670 @subsubheading Synopsis
24676 Displays the list of inserted breakpoints, showing the following fields:
24680 number of the breakpoint
24682 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24684 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24687 is the breakpoint enabled or no: @samp{y} or @samp{n}
24689 memory location at which the breakpoint is set
24691 logical location of the breakpoint, expressed by function name, file
24694 number of times the breakpoint has been hit
24697 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24698 @code{body} field is an empty list.
24700 @subsubheading @value{GDBN} Command
24702 The corresponding @value{GDBN} command is @samp{info break}.
24704 @subsubheading Example
24709 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24710 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24711 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24712 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24713 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24714 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24715 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24716 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24717 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24718 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24719 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24720 line="13",times="0"@}]@}
24724 Here's an example of the result when there are no breakpoints:
24729 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24730 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24731 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24732 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24733 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24734 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24735 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24740 @subheading The @code{-break-passcount} Command
24741 @findex -break-passcount
24743 @subsubheading Synopsis
24746 -break-passcount @var{tracepoint-number} @var{passcount}
24749 Set the passcount for tracepoint @var{tracepoint-number} to
24750 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
24751 is not a tracepoint, error is emitted. This corresponds to CLI
24752 command @samp{passcount}.
24754 @subheading The @code{-break-watch} Command
24755 @findex -break-watch
24757 @subsubheading Synopsis
24760 -break-watch [ -a | -r ]
24763 Create a watchpoint. With the @samp{-a} option it will create an
24764 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
24765 read from or on a write to the memory location. With the @samp{-r}
24766 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
24767 trigger only when the memory location is accessed for reading. Without
24768 either of the options, the watchpoint created is a regular watchpoint,
24769 i.e., it will trigger when the memory location is accessed for writing.
24770 @xref{Set Watchpoints, , Setting Watchpoints}.
24772 Note that @samp{-break-list} will report a single list of watchpoints and
24773 breakpoints inserted.
24775 @subsubheading @value{GDBN} Command
24777 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
24780 @subsubheading Example
24782 Setting a watchpoint on a variable in the @code{main} function:
24787 ^done,wpt=@{number="2",exp="x"@}
24792 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
24793 value=@{old="-268439212",new="55"@},
24794 frame=@{func="main",args=[],file="recursive2.c",
24795 fullname="/home/foo/bar/recursive2.c",line="5"@}
24799 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
24800 the program execution twice: first for the variable changing value, then
24801 for the watchpoint going out of scope.
24806 ^done,wpt=@{number="5",exp="C"@}
24811 *stopped,reason="watchpoint-trigger",
24812 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
24813 frame=@{func="callee4",args=[],
24814 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24815 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24820 *stopped,reason="watchpoint-scope",wpnum="5",
24821 frame=@{func="callee3",args=[@{name="strarg",
24822 value="0x11940 \"A string argument.\""@}],
24823 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24824 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24828 Listing breakpoints and watchpoints, at different points in the program
24829 execution. Note that once the watchpoint goes out of scope, it is
24835 ^done,wpt=@{number="2",exp="C"@}
24838 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24839 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24840 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24841 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24842 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24843 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24844 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24845 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24846 addr="0x00010734",func="callee4",
24847 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24848 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
24849 bkpt=@{number="2",type="watchpoint",disp="keep",
24850 enabled="y",addr="",what="C",times="0"@}]@}
24855 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24856 value=@{old="-276895068",new="3"@},
24857 frame=@{func="callee4",args=[],
24858 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24859 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24862 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24863 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24864 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24865 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24866 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24867 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24868 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24869 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24870 addr="0x00010734",func="callee4",
24871 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24872 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24873 bkpt=@{number="2",type="watchpoint",disp="keep",
24874 enabled="y",addr="",what="C",times="-5"@}]@}
24878 ^done,reason="watchpoint-scope",wpnum="2",
24879 frame=@{func="callee3",args=[@{name="strarg",
24880 value="0x11940 \"A string argument.\""@}],
24881 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24882 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24885 ^done,BreakpointTable=@{nr_rows="1",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",
24900 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24901 @node GDB/MI Program Context
24902 @section @sc{gdb/mi} Program Context
24904 @subheading The @code{-exec-arguments} Command
24905 @findex -exec-arguments
24908 @subsubheading Synopsis
24911 -exec-arguments @var{args}
24914 Set the inferior program arguments, to be used in the next
24917 @subsubheading @value{GDBN} Command
24919 The corresponding @value{GDBN} command is @samp{set args}.
24921 @subsubheading Example
24925 -exec-arguments -v word
24932 @subheading The @code{-exec-show-arguments} Command
24933 @findex -exec-show-arguments
24935 @subsubheading Synopsis
24938 -exec-show-arguments
24941 Print the arguments of the program.
24943 @subsubheading @value{GDBN} Command
24945 The corresponding @value{GDBN} command is @samp{show args}.
24947 @subsubheading Example
24952 @subheading The @code{-environment-cd} Command
24953 @findex -environment-cd
24955 @subsubheading Synopsis
24958 -environment-cd @var{pathdir}
24961 Set @value{GDBN}'s working directory.
24963 @subsubheading @value{GDBN} Command
24965 The corresponding @value{GDBN} command is @samp{cd}.
24967 @subsubheading Example
24971 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24977 @subheading The @code{-environment-directory} Command
24978 @findex -environment-directory
24980 @subsubheading Synopsis
24983 -environment-directory [ -r ] [ @var{pathdir} ]+
24986 Add directories @var{pathdir} to beginning of search path for source files.
24987 If the @samp{-r} option is used, the search path is reset to the default
24988 search path. If directories @var{pathdir} are supplied in addition to the
24989 @samp{-r} option, the search path is first reset and then addition
24991 Multiple directories may be specified, separated by blanks. Specifying
24992 multiple directories in a single command
24993 results in the directories added to the beginning of the
24994 search path in the same order they were presented in the command.
24995 If blanks are needed as
24996 part of a directory name, double-quotes should be used around
24997 the name. In the command output, the path will show up separated
24998 by the system directory-separator character. The directory-separator
24999 character must not be used
25000 in any directory name.
25001 If no directories are specified, the current search path is displayed.
25003 @subsubheading @value{GDBN} Command
25005 The corresponding @value{GDBN} command is @samp{dir}.
25007 @subsubheading Example
25011 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25012 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25014 -environment-directory ""
25015 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25017 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
25018 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
25020 -environment-directory -r
25021 ^done,source-path="$cdir:$cwd"
25026 @subheading The @code{-environment-path} Command
25027 @findex -environment-path
25029 @subsubheading Synopsis
25032 -environment-path [ -r ] [ @var{pathdir} ]+
25035 Add directories @var{pathdir} to beginning of search path for object files.
25036 If the @samp{-r} option is used, the search path is reset to the original
25037 search path that existed at gdb start-up. If directories @var{pathdir} are
25038 supplied in addition to the
25039 @samp{-r} option, the search path is first reset and then addition
25041 Multiple directories may be specified, separated by blanks. Specifying
25042 multiple directories in a single command
25043 results in the directories added to the beginning of the
25044 search path in the same order they were presented in the command.
25045 If blanks are needed as
25046 part of a directory name, double-quotes should be used around
25047 the name. In the command output, the path will show up separated
25048 by the system directory-separator character. The directory-separator
25049 character must not be used
25050 in any directory name.
25051 If no directories are specified, the current path is displayed.
25054 @subsubheading @value{GDBN} Command
25056 The corresponding @value{GDBN} command is @samp{path}.
25058 @subsubheading Example
25063 ^done,path="/usr/bin"
25065 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
25066 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
25068 -environment-path -r /usr/local/bin
25069 ^done,path="/usr/local/bin:/usr/bin"
25074 @subheading The @code{-environment-pwd} Command
25075 @findex -environment-pwd
25077 @subsubheading Synopsis
25083 Show the current working directory.
25085 @subsubheading @value{GDBN} Command
25087 The corresponding @value{GDBN} command is @samp{pwd}.
25089 @subsubheading Example
25094 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25098 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25099 @node GDB/MI Thread Commands
25100 @section @sc{gdb/mi} Thread Commands
25103 @subheading The @code{-thread-info} Command
25104 @findex -thread-info
25106 @subsubheading Synopsis
25109 -thread-info [ @var{thread-id} ]
25112 Reports information about either a specific thread, if
25113 the @var{thread-id} parameter is present, or about all
25114 threads. When printing information about all threads,
25115 also reports the current thread.
25117 @subsubheading @value{GDBN} Command
25119 The @samp{info thread} command prints the same information
25122 @subsubheading Example
25127 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25128 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25129 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25130 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25131 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
25132 current-thread-id="1"
25136 The @samp{state} field may have the following values:
25140 The thread is stopped. Frame information is available for stopped
25144 The thread is running. There's no frame information for running
25149 @subheading The @code{-thread-list-ids} Command
25150 @findex -thread-list-ids
25152 @subsubheading Synopsis
25158 Produces a list of the currently known @value{GDBN} thread ids. At the
25159 end of the list it also prints the total number of such threads.
25161 This command is retained for historical reasons, the
25162 @code{-thread-info} command should be used instead.
25164 @subsubheading @value{GDBN} Command
25166 Part of @samp{info threads} supplies the same information.
25168 @subsubheading Example
25173 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25174 current-thread-id="1",number-of-threads="3"
25179 @subheading The @code{-thread-select} Command
25180 @findex -thread-select
25182 @subsubheading Synopsis
25185 -thread-select @var{threadnum}
25188 Make @var{threadnum} the current thread. It prints the number of the new
25189 current thread, and the topmost frame for that thread.
25191 This command is deprecated in favor of explicitly using the
25192 @samp{--thread} option to each command.
25194 @subsubheading @value{GDBN} Command
25196 The corresponding @value{GDBN} command is @samp{thread}.
25198 @subsubheading Example
25205 *stopped,reason="end-stepping-range",thread-id="2",line="187",
25206 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
25210 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25211 number-of-threads="3"
25214 ^done,new-thread-id="3",
25215 frame=@{level="0",func="vprintf",
25216 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
25217 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
25221 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25222 @node GDB/MI Program Execution
25223 @section @sc{gdb/mi} Program Execution
25225 These are the asynchronous commands which generate the out-of-band
25226 record @samp{*stopped}. Currently @value{GDBN} only really executes
25227 asynchronously with remote targets and this interaction is mimicked in
25230 @subheading The @code{-exec-continue} Command
25231 @findex -exec-continue
25233 @subsubheading Synopsis
25236 -exec-continue [--reverse] [--all|--thread-group N]
25239 Resumes the execution of the inferior program, which will continue
25240 to execute until it reaches a debugger stop event. If the
25241 @samp{--reverse} option is specified, execution resumes in reverse until
25242 it reaches a stop event. Stop events may include
25245 breakpoints or watchpoints
25247 signals or exceptions
25249 the end of the process (or its beginning under @samp{--reverse})
25251 the end or beginning of a replay log if one is being used.
25253 In all-stop mode (@pxref{All-Stop
25254 Mode}), may resume only one thread, or all threads, depending on the
25255 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25256 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25257 ignored in all-stop mode. If the @samp{--thread-group} options is
25258 specified, then all threads in that thread group are resumed.
25260 @subsubheading @value{GDBN} Command
25262 The corresponding @value{GDBN} corresponding is @samp{continue}.
25264 @subsubheading Example
25271 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25272 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25278 @subheading The @code{-exec-finish} Command
25279 @findex -exec-finish
25281 @subsubheading Synopsis
25284 -exec-finish [--reverse]
25287 Resumes the execution of the inferior program until the current
25288 function is exited. Displays the results returned by the function.
25289 If the @samp{--reverse} option is specified, resumes the reverse
25290 execution of the inferior program until the point where current
25291 function was called.
25293 @subsubheading @value{GDBN} Command
25295 The corresponding @value{GDBN} command is @samp{finish}.
25297 @subsubheading Example
25299 Function returning @code{void}.
25306 *stopped,reason="function-finished",frame=@{func="main",args=[],
25307 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25311 Function returning other than @code{void}. The name of the internal
25312 @value{GDBN} variable storing the result is printed, together with the
25319 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25320 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25321 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25322 gdb-result-var="$1",return-value="0"
25327 @subheading The @code{-exec-interrupt} Command
25328 @findex -exec-interrupt
25330 @subsubheading Synopsis
25333 -exec-interrupt [--all|--thread-group N]
25336 Interrupts the background execution of the target. Note how the token
25337 associated with the stop message is the one for the execution command
25338 that has been interrupted. The token for the interrupt itself only
25339 appears in the @samp{^done} output. If the user is trying to
25340 interrupt a non-running program, an error message will be printed.
25342 Note that when asynchronous execution is enabled, this command is
25343 asynchronous just like other execution commands. That is, first the
25344 @samp{^done} response will be printed, and the target stop will be
25345 reported after that using the @samp{*stopped} notification.
25347 In non-stop mode, only the context thread is interrupted by default.
25348 All threads (in all inferiors) will be interrupted if the
25349 @samp{--all} option is specified. If the @samp{--thread-group}
25350 option is specified, all threads in that group will be interrupted.
25352 @subsubheading @value{GDBN} Command
25354 The corresponding @value{GDBN} command is @samp{interrupt}.
25356 @subsubheading Example
25367 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
25368 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
25369 fullname="/home/foo/bar/try.c",line="13"@}
25374 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
25378 @subheading The @code{-exec-jump} Command
25381 @subsubheading Synopsis
25384 -exec-jump @var{location}
25387 Resumes execution of the inferior program at the location specified by
25388 parameter. @xref{Specify Location}, for a description of the
25389 different forms of @var{location}.
25391 @subsubheading @value{GDBN} Command
25393 The corresponding @value{GDBN} command is @samp{jump}.
25395 @subsubheading Example
25398 -exec-jump foo.c:10
25399 *running,thread-id="all"
25404 @subheading The @code{-exec-next} Command
25407 @subsubheading Synopsis
25410 -exec-next [--reverse]
25413 Resumes execution of the inferior program, stopping when the beginning
25414 of the next source line is reached.
25416 If the @samp{--reverse} option is specified, resumes reverse execution
25417 of the inferior program, stopping at the beginning of the previous
25418 source line. If you issue this command on the first line of a
25419 function, it will take you back to the caller of that function, to the
25420 source line where the function was called.
25423 @subsubheading @value{GDBN} Command
25425 The corresponding @value{GDBN} command is @samp{next}.
25427 @subsubheading Example
25433 *stopped,reason="end-stepping-range",line="8",file="hello.c"
25438 @subheading The @code{-exec-next-instruction} Command
25439 @findex -exec-next-instruction
25441 @subsubheading Synopsis
25444 -exec-next-instruction [--reverse]
25447 Executes one machine instruction. If the instruction is a function
25448 call, continues until the function returns. If the program stops at an
25449 instruction in the middle of a source line, the address will be
25452 If the @samp{--reverse} option is specified, resumes reverse execution
25453 of the inferior program, stopping at the previous instruction. If the
25454 previously executed instruction was a return from another function,
25455 it will continue to execute in reverse until the call to that function
25456 (from the current stack frame) is reached.
25458 @subsubheading @value{GDBN} Command
25460 The corresponding @value{GDBN} command is @samp{nexti}.
25462 @subsubheading Example
25466 -exec-next-instruction
25470 *stopped,reason="end-stepping-range",
25471 addr="0x000100d4",line="5",file="hello.c"
25476 @subheading The @code{-exec-return} Command
25477 @findex -exec-return
25479 @subsubheading Synopsis
25485 Makes current function return immediately. Doesn't execute the inferior.
25486 Displays the new current frame.
25488 @subsubheading @value{GDBN} Command
25490 The corresponding @value{GDBN} command is @samp{return}.
25492 @subsubheading Example
25496 200-break-insert callee4
25497 200^done,bkpt=@{number="1",addr="0x00010734",
25498 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25503 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25504 frame=@{func="callee4",args=[],
25505 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25506 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25512 111^done,frame=@{level="0",func="callee3",
25513 args=[@{name="strarg",
25514 value="0x11940 \"A string argument.\""@}],
25515 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25516 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25521 @subheading The @code{-exec-run} Command
25524 @subsubheading Synopsis
25527 -exec-run [--all | --thread-group N]
25530 Starts execution of the inferior from the beginning. The inferior
25531 executes until either a breakpoint is encountered or the program
25532 exits. In the latter case the output will include an exit code, if
25533 the program has exited exceptionally.
25535 When no option is specified, the current inferior is started. If the
25536 @samp{--thread-group} option is specified, it should refer to a thread
25537 group of type @samp{process}, and that thread group will be started.
25538 If the @samp{--all} option is specified, then all inferiors will be started.
25540 @subsubheading @value{GDBN} Command
25542 The corresponding @value{GDBN} command is @samp{run}.
25544 @subsubheading Examples
25549 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
25554 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25555 frame=@{func="main",args=[],file="recursive2.c",
25556 fullname="/home/foo/bar/recursive2.c",line="4"@}
25561 Program exited normally:
25569 *stopped,reason="exited-normally"
25574 Program exited exceptionally:
25582 *stopped,reason="exited",exit-code="01"
25586 Another way the program can terminate is if it receives a signal such as
25587 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
25591 *stopped,reason="exited-signalled",signal-name="SIGINT",
25592 signal-meaning="Interrupt"
25596 @c @subheading -exec-signal
25599 @subheading The @code{-exec-step} Command
25602 @subsubheading Synopsis
25605 -exec-step [--reverse]
25608 Resumes execution of the inferior program, stopping when the beginning
25609 of the next source line is reached, if the next source line is not a
25610 function call. If it is, stop at the first instruction of the called
25611 function. If the @samp{--reverse} option is specified, resumes reverse
25612 execution of the inferior program, stopping at the beginning of the
25613 previously executed source line.
25615 @subsubheading @value{GDBN} Command
25617 The corresponding @value{GDBN} command is @samp{step}.
25619 @subsubheading Example
25621 Stepping into a function:
25627 *stopped,reason="end-stepping-range",
25628 frame=@{func="foo",args=[@{name="a",value="10"@},
25629 @{name="b",value="0"@}],file="recursive2.c",
25630 fullname="/home/foo/bar/recursive2.c",line="11"@}
25640 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
25645 @subheading The @code{-exec-step-instruction} Command
25646 @findex -exec-step-instruction
25648 @subsubheading Synopsis
25651 -exec-step-instruction [--reverse]
25654 Resumes the inferior which executes one machine instruction. If the
25655 @samp{--reverse} option is specified, resumes reverse execution of the
25656 inferior program, stopping at the previously executed instruction.
25657 The output, once @value{GDBN} has stopped, will vary depending on
25658 whether we have stopped in the middle of a source line or not. In the
25659 former case, the address at which the program stopped will be printed
25662 @subsubheading @value{GDBN} Command
25664 The corresponding @value{GDBN} command is @samp{stepi}.
25666 @subsubheading Example
25670 -exec-step-instruction
25674 *stopped,reason="end-stepping-range",
25675 frame=@{func="foo",args=[],file="try.c",
25676 fullname="/home/foo/bar/try.c",line="10"@}
25678 -exec-step-instruction
25682 *stopped,reason="end-stepping-range",
25683 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25684 fullname="/home/foo/bar/try.c",line="10"@}
25689 @subheading The @code{-exec-until} Command
25690 @findex -exec-until
25692 @subsubheading Synopsis
25695 -exec-until [ @var{location} ]
25698 Executes the inferior until the @var{location} specified in the
25699 argument is reached. If there is no argument, the inferior executes
25700 until a source line greater than the current one is reached. The
25701 reason for stopping in this case will be @samp{location-reached}.
25703 @subsubheading @value{GDBN} Command
25705 The corresponding @value{GDBN} command is @samp{until}.
25707 @subsubheading Example
25711 -exec-until recursive2.c:6
25715 *stopped,reason="location-reached",frame=@{func="main",args=[],
25716 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25721 @subheading -file-clear
25722 Is this going away????
25725 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25726 @node GDB/MI Stack Manipulation
25727 @section @sc{gdb/mi} Stack Manipulation Commands
25730 @subheading The @code{-stack-info-frame} Command
25731 @findex -stack-info-frame
25733 @subsubheading Synopsis
25739 Get info on the selected frame.
25741 @subsubheading @value{GDBN} Command
25743 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
25744 (without arguments).
25746 @subsubheading Example
25751 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
25752 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25753 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
25757 @subheading The @code{-stack-info-depth} Command
25758 @findex -stack-info-depth
25760 @subsubheading Synopsis
25763 -stack-info-depth [ @var{max-depth} ]
25766 Return the depth of the stack. If the integer argument @var{max-depth}
25767 is specified, do not count beyond @var{max-depth} frames.
25769 @subsubheading @value{GDBN} Command
25771 There's no equivalent @value{GDBN} command.
25773 @subsubheading Example
25775 For a stack with frame levels 0 through 11:
25782 -stack-info-depth 4
25785 -stack-info-depth 12
25788 -stack-info-depth 11
25791 -stack-info-depth 13
25796 @subheading The @code{-stack-list-arguments} Command
25797 @findex -stack-list-arguments
25799 @subsubheading Synopsis
25802 -stack-list-arguments @var{print-values}
25803 [ @var{low-frame} @var{high-frame} ]
25806 Display a list of the arguments for the frames between @var{low-frame}
25807 and @var{high-frame} (inclusive). If @var{low-frame} and
25808 @var{high-frame} are not provided, list the arguments for the whole
25809 call stack. If the two arguments are equal, show the single frame
25810 at the corresponding level. It is an error if @var{low-frame} is
25811 larger than the actual number of frames. On the other hand,
25812 @var{high-frame} may be larger than the actual number of frames, in
25813 which case only existing frames will be returned.
25815 If @var{print-values} is 0 or @code{--no-values}, print only the names of
25816 the variables; if it is 1 or @code{--all-values}, print also their
25817 values; and if it is 2 or @code{--simple-values}, print the name,
25818 type and value for simple data types, and the name and type for arrays,
25819 structures and unions.
25821 Use of this command to obtain arguments in a single frame is
25822 deprecated in favor of the @samp{-stack-list-variables} command.
25824 @subsubheading @value{GDBN} Command
25826 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
25827 @samp{gdb_get_args} command which partially overlaps with the
25828 functionality of @samp{-stack-list-arguments}.
25830 @subsubheading Example
25837 frame=@{level="0",addr="0x00010734",func="callee4",
25838 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25839 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
25840 frame=@{level="1",addr="0x0001076c",func="callee3",
25841 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25842 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
25843 frame=@{level="2",addr="0x0001078c",func="callee2",
25844 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25845 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
25846 frame=@{level="3",addr="0x000107b4",func="callee1",
25847 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25848 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
25849 frame=@{level="4",addr="0x000107e0",func="main",
25850 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25851 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
25853 -stack-list-arguments 0
25856 frame=@{level="0",args=[]@},
25857 frame=@{level="1",args=[name="strarg"]@},
25858 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25859 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25860 frame=@{level="4",args=[]@}]
25862 -stack-list-arguments 1
25865 frame=@{level="0",args=[]@},
25867 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25868 frame=@{level="2",args=[
25869 @{name="intarg",value="2"@},
25870 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25871 @{frame=@{level="3",args=[
25872 @{name="intarg",value="2"@},
25873 @{name="strarg",value="0x11940 \"A string argument.\""@},
25874 @{name="fltarg",value="3.5"@}]@},
25875 frame=@{level="4",args=[]@}]
25877 -stack-list-arguments 0 2 2
25878 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
25880 -stack-list-arguments 1 2 2
25881 ^done,stack-args=[frame=@{level="2",
25882 args=[@{name="intarg",value="2"@},
25883 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
25887 @c @subheading -stack-list-exception-handlers
25890 @subheading The @code{-stack-list-frames} Command
25891 @findex -stack-list-frames
25893 @subsubheading Synopsis
25896 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
25899 List the frames currently on the stack. For each frame it displays the
25904 The frame number, 0 being the topmost frame, i.e., the innermost function.
25906 The @code{$pc} value for that frame.
25910 File name of the source file where the function lives.
25912 Line number corresponding to the @code{$pc}.
25915 If invoked without arguments, this command prints a backtrace for the
25916 whole stack. If given two integer arguments, it shows the frames whose
25917 levels are between the two arguments (inclusive). If the two arguments
25918 are equal, it shows the single frame at the corresponding level. It is
25919 an error if @var{low-frame} is larger than the actual number of
25920 frames. On the other hand, @var{high-frame} may be larger than the
25921 actual number of frames, in which case only existing frames will be returned.
25923 @subsubheading @value{GDBN} Command
25925 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
25927 @subsubheading Example
25929 Full stack backtrace:
25935 [frame=@{level="0",addr="0x0001076c",func="foo",
25936 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
25937 frame=@{level="1",addr="0x000107a4",func="foo",
25938 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25939 frame=@{level="2",addr="0x000107a4",func="foo",
25940 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25941 frame=@{level="3",addr="0x000107a4",func="foo",
25942 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25943 frame=@{level="4",addr="0x000107a4",func="foo",
25944 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25945 frame=@{level="5",addr="0x000107a4",func="foo",
25946 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25947 frame=@{level="6",addr="0x000107a4",func="foo",
25948 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25949 frame=@{level="7",addr="0x000107a4",func="foo",
25950 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25951 frame=@{level="8",addr="0x000107a4",func="foo",
25952 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25953 frame=@{level="9",addr="0x000107a4",func="foo",
25954 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25955 frame=@{level="10",addr="0x000107a4",func="foo",
25956 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25957 frame=@{level="11",addr="0x00010738",func="main",
25958 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
25962 Show frames between @var{low_frame} and @var{high_frame}:
25966 -stack-list-frames 3 5
25968 [frame=@{level="3",addr="0x000107a4",func="foo",
25969 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25970 frame=@{level="4",addr="0x000107a4",func="foo",
25971 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25972 frame=@{level="5",addr="0x000107a4",func="foo",
25973 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25977 Show a single frame:
25981 -stack-list-frames 3 3
25983 [frame=@{level="3",addr="0x000107a4",func="foo",
25984 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25989 @subheading The @code{-stack-list-locals} Command
25990 @findex -stack-list-locals
25992 @subsubheading Synopsis
25995 -stack-list-locals @var{print-values}
25998 Display the local variable names for the selected frame. If
25999 @var{print-values} is 0 or @code{--no-values}, print only the names of
26000 the variables; if it is 1 or @code{--all-values}, print also their
26001 values; and if it is 2 or @code{--simple-values}, print the name,
26002 type and value for simple data types, and the name and type for arrays,
26003 structures and unions. In this last case, a frontend can immediately
26004 display the value of simple data types and create variable objects for
26005 other data types when the user wishes to explore their values in
26008 This command is deprecated in favor of the
26009 @samp{-stack-list-variables} command.
26011 @subsubheading @value{GDBN} Command
26013 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
26015 @subsubheading Example
26019 -stack-list-locals 0
26020 ^done,locals=[name="A",name="B",name="C"]
26022 -stack-list-locals --all-values
26023 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
26024 @{name="C",value="@{1, 2, 3@}"@}]
26025 -stack-list-locals --simple-values
26026 ^done,locals=[@{name="A",type="int",value="1"@},
26027 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
26031 @subheading The @code{-stack-list-variables} Command
26032 @findex -stack-list-variables
26034 @subsubheading Synopsis
26037 -stack-list-variables @var{print-values}
26040 Display the names of local variables and function arguments for the selected frame. If
26041 @var{print-values} is 0 or @code{--no-values}, print only the names of
26042 the variables; if it is 1 or @code{--all-values}, print also their
26043 values; and if it is 2 or @code{--simple-values}, print the name,
26044 type and value for simple data types, and the name and type for arrays,
26045 structures and unions.
26047 @subsubheading Example
26051 -stack-list-variables --thread 1 --frame 0 --all-values
26052 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
26057 @subheading The @code{-stack-select-frame} Command
26058 @findex -stack-select-frame
26060 @subsubheading Synopsis
26063 -stack-select-frame @var{framenum}
26066 Change the selected frame. Select a different frame @var{framenum} on
26069 This command in deprecated in favor of passing the @samp{--frame}
26070 option to every command.
26072 @subsubheading @value{GDBN} Command
26074 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
26075 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26077 @subsubheading Example
26081 -stack-select-frame 2
26086 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26087 @node GDB/MI Variable Objects
26088 @section @sc{gdb/mi} Variable Objects
26092 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26094 For the implementation of a variable debugger window (locals, watched
26095 expressions, etc.), we are proposing the adaptation of the existing code
26096 used by @code{Insight}.
26098 The two main reasons for that are:
26102 It has been proven in practice (it is already on its second generation).
26105 It will shorten development time (needless to say how important it is
26109 The original interface was designed to be used by Tcl code, so it was
26110 slightly changed so it could be used through @sc{gdb/mi}. This section
26111 describes the @sc{gdb/mi} operations that will be available and gives some
26112 hints about their use.
26114 @emph{Note}: In addition to the set of operations described here, we
26115 expect the @sc{gui} implementation of a variable window to require, at
26116 least, the following operations:
26119 @item @code{-gdb-show} @code{output-radix}
26120 @item @code{-stack-list-arguments}
26121 @item @code{-stack-list-locals}
26122 @item @code{-stack-select-frame}
26127 @subheading Introduction to Variable Objects
26129 @cindex variable objects in @sc{gdb/mi}
26131 Variable objects are "object-oriented" MI interface for examining and
26132 changing values of expressions. Unlike some other MI interfaces that
26133 work with expressions, variable objects are specifically designed for
26134 simple and efficient presentation in the frontend. A variable object
26135 is identified by string name. When a variable object is created, the
26136 frontend specifies the expression for that variable object. The
26137 expression can be a simple variable, or it can be an arbitrary complex
26138 expression, and can even involve CPU registers. After creating a
26139 variable object, the frontend can invoke other variable object
26140 operations---for example to obtain or change the value of a variable
26141 object, or to change display format.
26143 Variable objects have hierarchical tree structure. Any variable object
26144 that corresponds to a composite type, such as structure in C, has
26145 a number of child variable objects, for example corresponding to each
26146 element of a structure. A child variable object can itself have
26147 children, recursively. Recursion ends when we reach
26148 leaf variable objects, which always have built-in types. Child variable
26149 objects are created only by explicit request, so if a frontend
26150 is not interested in the children of a particular variable object, no
26151 child will be created.
26153 For a leaf variable object it is possible to obtain its value as a
26154 string, or set the value from a string. String value can be also
26155 obtained for a non-leaf variable object, but it's generally a string
26156 that only indicates the type of the object, and does not list its
26157 contents. Assignment to a non-leaf variable object is not allowed.
26159 A frontend does not need to read the values of all variable objects each time
26160 the program stops. Instead, MI provides an update command that lists all
26161 variable objects whose values has changed since the last update
26162 operation. This considerably reduces the amount of data that must
26163 be transferred to the frontend. As noted above, children variable
26164 objects are created on demand, and only leaf variable objects have a
26165 real value. As result, gdb will read target memory only for leaf
26166 variables that frontend has created.
26168 The automatic update is not always desirable. For example, a frontend
26169 might want to keep a value of some expression for future reference,
26170 and never update it. For another example, fetching memory is
26171 relatively slow for embedded targets, so a frontend might want
26172 to disable automatic update for the variables that are either not
26173 visible on the screen, or ``closed''. This is possible using so
26174 called ``frozen variable objects''. Such variable objects are never
26175 implicitly updated.
26177 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
26178 fixed variable object, the expression is parsed when the variable
26179 object is created, including associating identifiers to specific
26180 variables. The meaning of expression never changes. For a floating
26181 variable object the values of variables whose names appear in the
26182 expressions are re-evaluated every time in the context of the current
26183 frame. Consider this example:
26188 struct work_state state;
26195 If a fixed variable object for the @code{state} variable is created in
26196 this function, and we enter the recursive call, the the variable
26197 object will report the value of @code{state} in the top-level
26198 @code{do_work} invocation. On the other hand, a floating variable
26199 object will report the value of @code{state} in the current frame.
26201 If an expression specified when creating a fixed variable object
26202 refers to a local variable, the variable object becomes bound to the
26203 thread and frame in which the variable object is created. When such
26204 variable object is updated, @value{GDBN} makes sure that the
26205 thread/frame combination the variable object is bound to still exists,
26206 and re-evaluates the variable object in context of that thread/frame.
26208 The following is the complete set of @sc{gdb/mi} operations defined to
26209 access this functionality:
26211 @multitable @columnfractions .4 .6
26212 @item @strong{Operation}
26213 @tab @strong{Description}
26215 @item @code{-enable-pretty-printing}
26216 @tab enable Python-based pretty-printing
26217 @item @code{-var-create}
26218 @tab create a variable object
26219 @item @code{-var-delete}
26220 @tab delete the variable object and/or its children
26221 @item @code{-var-set-format}
26222 @tab set the display format of this variable
26223 @item @code{-var-show-format}
26224 @tab show the display format of this variable
26225 @item @code{-var-info-num-children}
26226 @tab tells how many children this object has
26227 @item @code{-var-list-children}
26228 @tab return a list of the object's children
26229 @item @code{-var-info-type}
26230 @tab show the type of this variable object
26231 @item @code{-var-info-expression}
26232 @tab print parent-relative expression that this variable object represents
26233 @item @code{-var-info-path-expression}
26234 @tab print full expression that this variable object represents
26235 @item @code{-var-show-attributes}
26236 @tab is this variable editable? does it exist here?
26237 @item @code{-var-evaluate-expression}
26238 @tab get the value of this variable
26239 @item @code{-var-assign}
26240 @tab set the value of this variable
26241 @item @code{-var-update}
26242 @tab update the variable and its children
26243 @item @code{-var-set-frozen}
26244 @tab set frozeness attribute
26245 @item @code{-var-set-update-range}
26246 @tab set range of children to display on update
26249 In the next subsection we describe each operation in detail and suggest
26250 how it can be used.
26252 @subheading Description And Use of Operations on Variable Objects
26254 @subheading The @code{-enable-pretty-printing} Command
26255 @findex -enable-pretty-printing
26258 -enable-pretty-printing
26261 @value{GDBN} allows Python-based visualizers to affect the output of the
26262 MI variable object commands. However, because there was no way to
26263 implement this in a fully backward-compatible way, a front end must
26264 request that this functionality be enabled.
26266 Once enabled, this feature cannot be disabled.
26268 Note that if Python support has not been compiled into @value{GDBN},
26269 this command will still succeed (and do nothing).
26271 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26272 may work differently in future versions of @value{GDBN}.
26274 @subheading The @code{-var-create} Command
26275 @findex -var-create
26277 @subsubheading Synopsis
26280 -var-create @{@var{name} | "-"@}
26281 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26284 This operation creates a variable object, which allows the monitoring of
26285 a variable, the result of an expression, a memory cell or a CPU
26288 The @var{name} parameter is the string by which the object can be
26289 referenced. It must be unique. If @samp{-} is specified, the varobj
26290 system will generate a string ``varNNNNNN'' automatically. It will be
26291 unique provided that one does not specify @var{name} of that format.
26292 The command fails if a duplicate name is found.
26294 The frame under which the expression should be evaluated can be
26295 specified by @var{frame-addr}. A @samp{*} indicates that the current
26296 frame should be used. A @samp{@@} indicates that a floating variable
26297 object must be created.
26299 @var{expression} is any expression valid on the current language set (must not
26300 begin with a @samp{*}), or one of the following:
26304 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26307 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26310 @samp{$@var{regname}} --- a CPU register name
26313 @cindex dynamic varobj
26314 A varobj's contents may be provided by a Python-based pretty-printer. In this
26315 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26316 have slightly different semantics in some cases. If the
26317 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26318 will never create a dynamic varobj. This ensures backward
26319 compatibility for existing clients.
26321 @subsubheading Result
26323 This operation returns attributes of the newly-created varobj. These
26328 The name of the varobj.
26331 The number of children of the varobj. This number is not necessarily
26332 reliable for a dynamic varobj. Instead, you must examine the
26333 @samp{has_more} attribute.
26336 The varobj's scalar value. For a varobj whose type is some sort of
26337 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26338 will not be interesting.
26341 The varobj's type. This is a string representation of the type, as
26342 would be printed by the @value{GDBN} CLI.
26345 If a variable object is bound to a specific thread, then this is the
26346 thread's identifier.
26349 For a dynamic varobj, this indicates whether there appear to be any
26350 children available. For a non-dynamic varobj, this will be 0.
26353 This attribute will be present and have the value @samp{1} if the
26354 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26355 then this attribute will not be present.
26358 A dynamic varobj can supply a display hint to the front end. The
26359 value comes directly from the Python pretty-printer object's
26360 @code{display_hint} method. @xref{Pretty Printing API}.
26363 Typical output will look like this:
26366 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
26367 has_more="@var{has_more}"
26371 @subheading The @code{-var-delete} Command
26372 @findex -var-delete
26374 @subsubheading Synopsis
26377 -var-delete [ -c ] @var{name}
26380 Deletes a previously created variable object and all of its children.
26381 With the @samp{-c} option, just deletes the children.
26383 Returns an error if the object @var{name} is not found.
26386 @subheading The @code{-var-set-format} Command
26387 @findex -var-set-format
26389 @subsubheading Synopsis
26392 -var-set-format @var{name} @var{format-spec}
26395 Sets the output format for the value of the object @var{name} to be
26398 @anchor{-var-set-format}
26399 The syntax for the @var{format-spec} is as follows:
26402 @var{format-spec} @expansion{}
26403 @{binary | decimal | hexadecimal | octal | natural@}
26406 The natural format is the default format choosen automatically
26407 based on the variable type (like decimal for an @code{int}, hex
26408 for pointers, etc.).
26410 For a variable with children, the format is set only on the
26411 variable itself, and the children are not affected.
26413 @subheading The @code{-var-show-format} Command
26414 @findex -var-show-format
26416 @subsubheading Synopsis
26419 -var-show-format @var{name}
26422 Returns the format used to display the value of the object @var{name}.
26425 @var{format} @expansion{}
26430 @subheading The @code{-var-info-num-children} Command
26431 @findex -var-info-num-children
26433 @subsubheading Synopsis
26436 -var-info-num-children @var{name}
26439 Returns the number of children of a variable object @var{name}:
26445 Note that this number is not completely reliable for a dynamic varobj.
26446 It will return the current number of children, but more children may
26450 @subheading The @code{-var-list-children} Command
26451 @findex -var-list-children
26453 @subsubheading Synopsis
26456 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26458 @anchor{-var-list-children}
26460 Return a list of the children of the specified variable object and
26461 create variable objects for them, if they do not already exist. With
26462 a single argument or if @var{print-values} has a value of 0 or
26463 @code{--no-values}, print only the names of the variables; if
26464 @var{print-values} is 1 or @code{--all-values}, also print their
26465 values; and if it is 2 or @code{--simple-values} print the name and
26466 value for simple data types and just the name for arrays, structures
26469 @var{from} and @var{to}, if specified, indicate the range of children
26470 to report. If @var{from} or @var{to} is less than zero, the range is
26471 reset and all children will be reported. Otherwise, children starting
26472 at @var{from} (zero-based) and up to and excluding @var{to} will be
26475 If a child range is requested, it will only affect the current call to
26476 @code{-var-list-children}, but not future calls to @code{-var-update}.
26477 For this, you must instead use @code{-var-set-update-range}. The
26478 intent of this approach is to enable a front end to implement any
26479 update approach it likes; for example, scrolling a view may cause the
26480 front end to request more children with @code{-var-list-children}, and
26481 then the front end could call @code{-var-set-update-range} with a
26482 different range to ensure that future updates are restricted to just
26485 For each child the following results are returned:
26490 Name of the variable object created for this child.
26493 The expression to be shown to the user by the front end to designate this child.
26494 For example this may be the name of a structure member.
26496 For a dynamic varobj, this value cannot be used to form an
26497 expression. There is no way to do this at all with a dynamic varobj.
26499 For C/C@t{++} structures there are several pseudo children returned to
26500 designate access qualifiers. For these pseudo children @var{exp} is
26501 @samp{public}, @samp{private}, or @samp{protected}. In this case the
26502 type and value are not present.
26504 A dynamic varobj will not report the access qualifying
26505 pseudo-children, regardless of the language. This information is not
26506 available at all with a dynamic varobj.
26509 Number of children this child has. For a dynamic varobj, this will be
26513 The type of the child.
26516 If values were requested, this is the value.
26519 If this variable object is associated with a thread, this is the thread id.
26520 Otherwise this result is not present.
26523 If the variable object is frozen, this variable will be present with a value of 1.
26526 The result may have its own attributes:
26530 A dynamic varobj can supply a display hint to the front end. The
26531 value comes directly from the Python pretty-printer object's
26532 @code{display_hint} method. @xref{Pretty Printing API}.
26535 This is an integer attribute which is nonzero if there are children
26536 remaining after the end of the selected range.
26539 @subsubheading Example
26543 -var-list-children n
26544 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26545 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
26547 -var-list-children --all-values n
26548 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26549 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
26553 @subheading The @code{-var-info-type} Command
26554 @findex -var-info-type
26556 @subsubheading Synopsis
26559 -var-info-type @var{name}
26562 Returns the type of the specified variable @var{name}. The type is
26563 returned as a string in the same format as it is output by the
26567 type=@var{typename}
26571 @subheading The @code{-var-info-expression} Command
26572 @findex -var-info-expression
26574 @subsubheading Synopsis
26577 -var-info-expression @var{name}
26580 Returns a string that is suitable for presenting this
26581 variable object in user interface. The string is generally
26582 not valid expression in the current language, and cannot be evaluated.
26584 For example, if @code{a} is an array, and variable object
26585 @code{A} was created for @code{a}, then we'll get this output:
26588 (gdb) -var-info-expression A.1
26589 ^done,lang="C",exp="1"
26593 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
26595 Note that the output of the @code{-var-list-children} command also
26596 includes those expressions, so the @code{-var-info-expression} command
26599 @subheading The @code{-var-info-path-expression} Command
26600 @findex -var-info-path-expression
26602 @subsubheading Synopsis
26605 -var-info-path-expression @var{name}
26608 Returns an expression that can be evaluated in the current
26609 context and will yield the same value that a variable object has.
26610 Compare this with the @code{-var-info-expression} command, which
26611 result can be used only for UI presentation. Typical use of
26612 the @code{-var-info-path-expression} command is creating a
26613 watchpoint from a variable object.
26615 This command is currently not valid for children of a dynamic varobj,
26616 and will give an error when invoked on one.
26618 For example, suppose @code{C} is a C@t{++} class, derived from class
26619 @code{Base}, and that the @code{Base} class has a member called
26620 @code{m_size}. Assume a variable @code{c} is has the type of
26621 @code{C} and a variable object @code{C} was created for variable
26622 @code{c}. Then, we'll get this output:
26624 (gdb) -var-info-path-expression C.Base.public.m_size
26625 ^done,path_expr=((Base)c).m_size)
26628 @subheading The @code{-var-show-attributes} Command
26629 @findex -var-show-attributes
26631 @subsubheading Synopsis
26634 -var-show-attributes @var{name}
26637 List attributes of the specified variable object @var{name}:
26640 status=@var{attr} [ ( ,@var{attr} )* ]
26644 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
26646 @subheading The @code{-var-evaluate-expression} Command
26647 @findex -var-evaluate-expression
26649 @subsubheading Synopsis
26652 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26655 Evaluates the expression that is represented by the specified variable
26656 object and returns its value as a string. The format of the string
26657 can be specified with the @samp{-f} option. The possible values of
26658 this option are the same as for @code{-var-set-format}
26659 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26660 the current display format will be used. The current display format
26661 can be changed using the @code{-var-set-format} command.
26667 Note that one must invoke @code{-var-list-children} for a variable
26668 before the value of a child variable can be evaluated.
26670 @subheading The @code{-var-assign} Command
26671 @findex -var-assign
26673 @subsubheading Synopsis
26676 -var-assign @var{name} @var{expression}
26679 Assigns the value of @var{expression} to the variable object specified
26680 by @var{name}. The object must be @samp{editable}. If the variable's
26681 value is altered by the assign, the variable will show up in any
26682 subsequent @code{-var-update} list.
26684 @subsubheading Example
26692 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26696 @subheading The @code{-var-update} Command
26697 @findex -var-update
26699 @subsubheading Synopsis
26702 -var-update [@var{print-values}] @{@var{name} | "*"@}
26705 Reevaluate the expressions corresponding to the variable object
26706 @var{name} and all its direct and indirect children, and return the
26707 list of variable objects whose values have changed; @var{name} must
26708 be a root variable object. Here, ``changed'' means that the result of
26709 @code{-var-evaluate-expression} before and after the
26710 @code{-var-update} is different. If @samp{*} is used as the variable
26711 object names, all existing variable objects are updated, except
26712 for frozen ones (@pxref{-var-set-frozen}). The option
26713 @var{print-values} determines whether both names and values, or just
26714 names are printed. The possible values of this option are the same
26715 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26716 recommended to use the @samp{--all-values} option, to reduce the
26717 number of MI commands needed on each program stop.
26719 With the @samp{*} parameter, if a variable object is bound to a
26720 currently running thread, it will not be updated, without any
26723 If @code{-var-set-update-range} was previously used on a varobj, then
26724 only the selected range of children will be reported.
26726 @code{-var-update} reports all the changed varobjs in a tuple named
26729 Each item in the change list is itself a tuple holding:
26733 The name of the varobj.
26736 If values were requested for this update, then this field will be
26737 present and will hold the value of the varobj.
26740 @anchor{-var-update}
26741 This field is a string which may take one of three values:
26745 The variable object's current value is valid.
26748 The variable object does not currently hold a valid value but it may
26749 hold one in the future if its associated expression comes back into
26753 The variable object no longer holds a valid value.
26754 This can occur when the executable file being debugged has changed,
26755 either through recompilation or by using the @value{GDBN} @code{file}
26756 command. The front end should normally choose to delete these variable
26760 In the future new values may be added to this list so the front should
26761 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
26764 This is only present if the varobj is still valid. If the type
26765 changed, then this will be the string @samp{true}; otherwise it will
26769 If the varobj's type changed, then this field will be present and will
26772 @item new_num_children
26773 For a dynamic varobj, if the number of children changed, or if the
26774 type changed, this will be the new number of children.
26776 The @samp{numchild} field in other varobj responses is generally not
26777 valid for a dynamic varobj -- it will show the number of children that
26778 @value{GDBN} knows about, but because dynamic varobjs lazily
26779 instantiate their children, this will not reflect the number of
26780 children which may be available.
26782 The @samp{new_num_children} attribute only reports changes to the
26783 number of children known by @value{GDBN}. This is the only way to
26784 detect whether an update has removed children (which necessarily can
26785 only happen at the end of the update range).
26788 The display hint, if any.
26791 This is an integer value, which will be 1 if there are more children
26792 available outside the varobj's update range.
26795 This attribute will be present and have the value @samp{1} if the
26796 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26797 then this attribute will not be present.
26800 If new children were added to a dynamic varobj within the selected
26801 update range (as set by @code{-var-set-update-range}), then they will
26802 be listed in this attribute.
26805 @subsubheading Example
26812 -var-update --all-values var1
26813 ^done,changelist=[@{name="var1",value="3",in_scope="true",
26814 type_changed="false"@}]
26818 @subheading The @code{-var-set-frozen} Command
26819 @findex -var-set-frozen
26820 @anchor{-var-set-frozen}
26822 @subsubheading Synopsis
26825 -var-set-frozen @var{name} @var{flag}
26828 Set the frozenness flag on the variable object @var{name}. The
26829 @var{flag} parameter should be either @samp{1} to make the variable
26830 frozen or @samp{0} to make it unfrozen. If a variable object is
26831 frozen, then neither itself, nor any of its children, are
26832 implicitly updated by @code{-var-update} of
26833 a parent variable or by @code{-var-update *}. Only
26834 @code{-var-update} of the variable itself will update its value and
26835 values of its children. After a variable object is unfrozen, it is
26836 implicitly updated by all subsequent @code{-var-update} operations.
26837 Unfreezing a variable does not update it, only subsequent
26838 @code{-var-update} does.
26840 @subsubheading Example
26844 -var-set-frozen V 1
26849 @subheading The @code{-var-set-update-range} command
26850 @findex -var-set-update-range
26851 @anchor{-var-set-update-range}
26853 @subsubheading Synopsis
26856 -var-set-update-range @var{name} @var{from} @var{to}
26859 Set the range of children to be returned by future invocations of
26860 @code{-var-update}.
26862 @var{from} and @var{to} indicate the range of children to report. If
26863 @var{from} or @var{to} is less than zero, the range is reset and all
26864 children will be reported. Otherwise, children starting at @var{from}
26865 (zero-based) and up to and excluding @var{to} will be reported.
26867 @subsubheading Example
26871 -var-set-update-range V 1 2
26875 @subheading The @code{-var-set-visualizer} command
26876 @findex -var-set-visualizer
26877 @anchor{-var-set-visualizer}
26879 @subsubheading Synopsis
26882 -var-set-visualizer @var{name} @var{visualizer}
26885 Set a visualizer for the variable object @var{name}.
26887 @var{visualizer} is the visualizer to use. The special value
26888 @samp{None} means to disable any visualizer in use.
26890 If not @samp{None}, @var{visualizer} must be a Python expression.
26891 This expression must evaluate to a callable object which accepts a
26892 single argument. @value{GDBN} will call this object with the value of
26893 the varobj @var{name} as an argument (this is done so that the same
26894 Python pretty-printing code can be used for both the CLI and MI).
26895 When called, this object must return an object which conforms to the
26896 pretty-printing interface (@pxref{Pretty Printing API}).
26898 The pre-defined function @code{gdb.default_visualizer} may be used to
26899 select a visualizer by following the built-in process
26900 (@pxref{Selecting Pretty-Printers}). This is done automatically when
26901 a varobj is created, and so ordinarily is not needed.
26903 This feature is only available if Python support is enabled. The MI
26904 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
26905 can be used to check this.
26907 @subsubheading Example
26909 Resetting the visualizer:
26913 -var-set-visualizer V None
26917 Reselecting the default (type-based) visualizer:
26921 -var-set-visualizer V gdb.default_visualizer
26925 Suppose @code{SomeClass} is a visualizer class. A lambda expression
26926 can be used to instantiate this class for a varobj:
26930 -var-set-visualizer V "lambda val: SomeClass()"
26934 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26935 @node GDB/MI Data Manipulation
26936 @section @sc{gdb/mi} Data Manipulation
26938 @cindex data manipulation, in @sc{gdb/mi}
26939 @cindex @sc{gdb/mi}, data manipulation
26940 This section describes the @sc{gdb/mi} commands that manipulate data:
26941 examine memory and registers, evaluate expressions, etc.
26943 @c REMOVED FROM THE INTERFACE.
26944 @c @subheading -data-assign
26945 @c Change the value of a program variable. Plenty of side effects.
26946 @c @subsubheading GDB Command
26948 @c @subsubheading Example
26951 @subheading The @code{-data-disassemble} Command
26952 @findex -data-disassemble
26954 @subsubheading Synopsis
26958 [ -s @var{start-addr} -e @var{end-addr} ]
26959 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
26967 @item @var{start-addr}
26968 is the beginning address (or @code{$pc})
26969 @item @var{end-addr}
26971 @item @var{filename}
26972 is the name of the file to disassemble
26973 @item @var{linenum}
26974 is the line number to disassemble around
26976 is the number of disassembly lines to be produced. If it is -1,
26977 the whole function will be disassembled, in case no @var{end-addr} is
26978 specified. If @var{end-addr} is specified as a non-zero value, and
26979 @var{lines} is lower than the number of disassembly lines between
26980 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
26981 displayed; if @var{lines} is higher than the number of lines between
26982 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
26985 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
26989 @subsubheading Result
26991 The output for each instruction is composed of four fields:
27000 Note that whatever included in the instruction field, is not manipulated
27001 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
27003 @subsubheading @value{GDBN} Command
27005 There's no direct mapping from this command to the CLI.
27007 @subsubheading Example
27009 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
27013 -data-disassemble -s $pc -e "$pc + 20" -- 0
27016 @{address="0x000107c0",func-name="main",offset="4",
27017 inst="mov 2, %o0"@},
27018 @{address="0x000107c4",func-name="main",offset="8",
27019 inst="sethi %hi(0x11800), %o2"@},
27020 @{address="0x000107c8",func-name="main",offset="12",
27021 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
27022 @{address="0x000107cc",func-name="main",offset="16",
27023 inst="sethi %hi(0x11800), %o2"@},
27024 @{address="0x000107d0",func-name="main",offset="20",
27025 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
27029 Disassemble the whole @code{main} function. Line 32 is part of
27033 -data-disassemble -f basics.c -l 32 -- 0
27035 @{address="0x000107bc",func-name="main",offset="0",
27036 inst="save %sp, -112, %sp"@},
27037 @{address="0x000107c0",func-name="main",offset="4",
27038 inst="mov 2, %o0"@},
27039 @{address="0x000107c4",func-name="main",offset="8",
27040 inst="sethi %hi(0x11800), %o2"@},
27042 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
27043 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
27047 Disassemble 3 instructions from the start of @code{main}:
27051 -data-disassemble -f basics.c -l 32 -n 3 -- 0
27053 @{address="0x000107bc",func-name="main",offset="0",
27054 inst="save %sp, -112, %sp"@},
27055 @{address="0x000107c0",func-name="main",offset="4",
27056 inst="mov 2, %o0"@},
27057 @{address="0x000107c4",func-name="main",offset="8",
27058 inst="sethi %hi(0x11800), %o2"@}]
27062 Disassemble 3 instructions from the start of @code{main} in mixed mode:
27066 -data-disassemble -f basics.c -l 32 -n 3 -- 1
27068 src_and_asm_line=@{line="31",
27069 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27070 testsuite/gdb.mi/basics.c",line_asm_insn=[
27071 @{address="0x000107bc",func-name="main",offset="0",
27072 inst="save %sp, -112, %sp"@}]@},
27073 src_and_asm_line=@{line="32",
27074 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27075 testsuite/gdb.mi/basics.c",line_asm_insn=[
27076 @{address="0x000107c0",func-name="main",offset="4",
27077 inst="mov 2, %o0"@},
27078 @{address="0x000107c4",func-name="main",offset="8",
27079 inst="sethi %hi(0x11800), %o2"@}]@}]
27084 @subheading The @code{-data-evaluate-expression} Command
27085 @findex -data-evaluate-expression
27087 @subsubheading Synopsis
27090 -data-evaluate-expression @var{expr}
27093 Evaluate @var{expr} as an expression. The expression could contain an
27094 inferior function call. The function call will execute synchronously.
27095 If the expression contains spaces, it must be enclosed in double quotes.
27097 @subsubheading @value{GDBN} Command
27099 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27100 @samp{call}. In @code{gdbtk} only, there's a corresponding
27101 @samp{gdb_eval} command.
27103 @subsubheading Example
27105 In the following example, the numbers that precede the commands are the
27106 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27107 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27111 211-data-evaluate-expression A
27114 311-data-evaluate-expression &A
27115 311^done,value="0xefffeb7c"
27117 411-data-evaluate-expression A+3
27120 511-data-evaluate-expression "A + 3"
27126 @subheading The @code{-data-list-changed-registers} Command
27127 @findex -data-list-changed-registers
27129 @subsubheading Synopsis
27132 -data-list-changed-registers
27135 Display a list of the registers that have changed.
27137 @subsubheading @value{GDBN} Command
27139 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27140 has the corresponding command @samp{gdb_changed_register_list}.
27142 @subsubheading Example
27144 On a PPC MBX board:
27152 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
27153 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
27156 -data-list-changed-registers
27157 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
27158 "10","11","13","14","15","16","17","18","19","20","21","22","23",
27159 "24","25","26","27","28","30","31","64","65","66","67","69"]
27164 @subheading The @code{-data-list-register-names} Command
27165 @findex -data-list-register-names
27167 @subsubheading Synopsis
27170 -data-list-register-names [ ( @var{regno} )+ ]
27173 Show a list of register names for the current target. If no arguments
27174 are given, it shows a list of the names of all the registers. If
27175 integer numbers are given as arguments, it will print a list of the
27176 names of the registers corresponding to the arguments. To ensure
27177 consistency between a register name and its number, the output list may
27178 include empty register names.
27180 @subsubheading @value{GDBN} Command
27182 @value{GDBN} does not have a command which corresponds to
27183 @samp{-data-list-register-names}. In @code{gdbtk} there is a
27184 corresponding command @samp{gdb_regnames}.
27186 @subsubheading Example
27188 For the PPC MBX board:
27191 -data-list-register-names
27192 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
27193 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
27194 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
27195 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
27196 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
27197 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
27198 "", "pc","ps","cr","lr","ctr","xer"]
27200 -data-list-register-names 1 2 3
27201 ^done,register-names=["r1","r2","r3"]
27205 @subheading The @code{-data-list-register-values} Command
27206 @findex -data-list-register-values
27208 @subsubheading Synopsis
27211 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
27214 Display the registers' contents. @var{fmt} is the format according to
27215 which the registers' contents are to be returned, followed by an optional
27216 list of numbers specifying the registers to display. A missing list of
27217 numbers indicates that the contents of all the registers must be returned.
27219 Allowed formats for @var{fmt} are:
27236 @subsubheading @value{GDBN} Command
27238 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
27239 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
27241 @subsubheading Example
27243 For a PPC MBX board (note: line breaks are for readability only, they
27244 don't appear in the actual output):
27248 -data-list-register-values r 64 65
27249 ^done,register-values=[@{number="64",value="0xfe00a300"@},
27250 @{number="65",value="0x00029002"@}]
27252 -data-list-register-values x
27253 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27254 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27255 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27256 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27257 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27258 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27259 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27260 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27261 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27262 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27263 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27264 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27265 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27266 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27267 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27268 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27269 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27270 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27271 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27272 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27273 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27274 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27275 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27276 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27277 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27278 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27279 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27280 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27281 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27282 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27283 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27284 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27285 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27286 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27287 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27288 @{number="69",value="0x20002b03"@}]
27293 @subheading The @code{-data-read-memory} Command
27294 @findex -data-read-memory
27296 @subsubheading Synopsis
27299 -data-read-memory [ -o @var{byte-offset} ]
27300 @var{address} @var{word-format} @var{word-size}
27301 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27308 @item @var{address}
27309 An expression specifying the address of the first memory word to be
27310 read. Complex expressions containing embedded white space should be
27311 quoted using the C convention.
27313 @item @var{word-format}
27314 The format to be used to print the memory words. The notation is the
27315 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27318 @item @var{word-size}
27319 The size of each memory word in bytes.
27321 @item @var{nr-rows}
27322 The number of rows in the output table.
27324 @item @var{nr-cols}
27325 The number of columns in the output table.
27328 If present, indicates that each row should include an @sc{ascii} dump. The
27329 value of @var{aschar} is used as a padding character when a byte is not a
27330 member of the printable @sc{ascii} character set (printable @sc{ascii}
27331 characters are those whose code is between 32 and 126, inclusively).
27333 @item @var{byte-offset}
27334 An offset to add to the @var{address} before fetching memory.
27337 This command displays memory contents as a table of @var{nr-rows} by
27338 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27339 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27340 (returned as @samp{total-bytes}). Should less than the requested number
27341 of bytes be returned by the target, the missing words are identified
27342 using @samp{N/A}. The number of bytes read from the target is returned
27343 in @samp{nr-bytes} and the starting address used to read memory in
27346 The address of the next/previous row or page is available in
27347 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
27350 @subsubheading @value{GDBN} Command
27352 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
27353 @samp{gdb_get_mem} memory read command.
27355 @subsubheading Example
27357 Read six bytes of memory starting at @code{bytes+6} but then offset by
27358 @code{-6} bytes. Format as three rows of two columns. One byte per
27359 word. Display each word in hex.
27363 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
27364 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
27365 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
27366 prev-page="0x0000138a",memory=[
27367 @{addr="0x00001390",data=["0x00","0x01"]@},
27368 @{addr="0x00001392",data=["0x02","0x03"]@},
27369 @{addr="0x00001394",data=["0x04","0x05"]@}]
27373 Read two bytes of memory starting at address @code{shorts + 64} and
27374 display as a single word formatted in decimal.
27378 5-data-read-memory shorts+64 d 2 1 1
27379 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
27380 next-row="0x00001512",prev-row="0x0000150e",
27381 next-page="0x00001512",prev-page="0x0000150e",memory=[
27382 @{addr="0x00001510",data=["128"]@}]
27386 Read thirty two bytes of memory starting at @code{bytes+16} and format
27387 as eight rows of four columns. Include a string encoding with @samp{x}
27388 used as the non-printable character.
27392 4-data-read-memory bytes+16 x 1 8 4 x
27393 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
27394 next-row="0x000013c0",prev-row="0x0000139c",
27395 next-page="0x000013c0",prev-page="0x00001380",memory=[
27396 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
27397 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
27398 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
27399 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
27400 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
27401 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
27402 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
27403 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
27407 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27408 @node GDB/MI Tracepoint Commands
27409 @section @sc{gdb/mi} Tracepoint Commands
27411 The commands defined in this section implement MI support for
27412 tracepoints. For detailed introduction, see @ref{Tracepoints}.
27414 @subheading The @code{-trace-find} Command
27415 @findex -trace-find
27417 @subsubheading Synopsis
27420 -trace-find @var{mode} [@var{parameters}@dots{}]
27423 Find a trace frame using criteria defined by @var{mode} and
27424 @var{parameters}. The following table lists permissible
27425 modes and their parameters. For details of operation, see @ref{tfind}.
27430 No parameters are required. Stops examining trace frames.
27433 An integer is required as parameter. Selects tracepoint frame with
27436 @item tracepoint-number
27437 An integer is required as parameter. Finds next
27438 trace frame that corresponds to tracepoint with the specified number.
27441 An address is required as parameter. Finds
27442 next trace frame that corresponds to any tracepoint at the specified
27445 @item pc-inside-range
27446 Two addresses are required as parameters. Finds next trace
27447 frame that corresponds to a tracepoint at an address inside the
27448 specified range. Both bounds are considered to be inside the range.
27450 @item pc-outside-range
27451 Two addresses are required as parameters. Finds
27452 next trace frame that corresponds to a tracepoint at an address outside
27453 the specified range. Both bounds are considered to be inside the range.
27456 Line specification is required as parameter. @xref{Specify Location}.
27457 Finds next trace frame that corresponds to a tracepoint at
27458 the specified location.
27462 If @samp{none} was passed as @var{mode}, the response does not
27463 have fields. Otherwise, the response may have the following fields:
27467 This field has either @samp{0} or @samp{1} as the value, depending
27468 on whether a matching tracepoint was found.
27471 The index of the found traceframe. This field is present iff
27472 the @samp{found} field has value of @samp{1}.
27475 The index of the found tracepoint. This field is present iff
27476 the @samp{found} field has value of @samp{1}.
27479 The information about the frame corresponding to the found trace
27480 frame. This field is present only if a trace frame was found.
27481 @xref{GDB/MI Frame Information}, for description of this field.
27485 @subsubheading @value{GDBN} Command
27487 The corresponding @value{GDBN} command is @samp{tfind}.
27489 @subheading -trace-define-variable
27490 @findex -trace-define-variable
27492 @subsubheading Synopsis
27495 -trace-define-variable @var{name} [ @var{value} ]
27498 Create trace variable @var{name} if it does not exist. If
27499 @var{value} is specified, sets the initial value of the specified
27500 trace variable to that value. Note that the @var{name} should start
27501 with the @samp{$} character.
27503 @subsubheading @value{GDBN} Command
27505 The corresponding @value{GDBN} command is @samp{tvariable}.
27507 @subheading -trace-list-variables
27508 @findex -trace-list-variables
27510 @subsubheading Synopsis
27513 -trace-list-variables
27516 Return a table of all defined trace variables. Each element of the
27517 table has the following fields:
27521 The name of the trace variable. This field is always present.
27524 The initial value. This is a 64-bit signed integer. This
27525 field is always present.
27528 The value the trace variable has at the moment. This is a 64-bit
27529 signed integer. This field is absent iff current value is
27530 not defined, for example if the trace was never run, or is
27535 @subsubheading @value{GDBN} Command
27537 The corresponding @value{GDBN} command is @samp{tvariables}.
27539 @subsubheading Example
27543 -trace-list-variables
27544 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
27545 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
27546 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
27547 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
27548 body=[variable=@{name="$trace_timestamp",initial="0"@}
27549 variable=@{name="$foo",initial="10",current="15"@}]@}
27553 @subheading -trace-save
27554 @findex -trace-save
27556 @subsubheading Synopsis
27559 -trace-save [-r ] @var{filename}
27562 Saves the collected trace data to @var{filename}. Without the
27563 @samp{-r} option, the data is downloaded from the target and saved
27564 in a local file. With the @samp{-r} option the target is asked
27565 to perform the save.
27567 @subsubheading @value{GDBN} Command
27569 The corresponding @value{GDBN} command is @samp{tsave}.
27572 @subheading -trace-start
27573 @findex -trace-start
27575 @subsubheading Synopsis
27581 Starts a tracing experiments. The result of this command does not
27584 @subsubheading @value{GDBN} Command
27586 The corresponding @value{GDBN} command is @samp{tstart}.
27588 @subheading -trace-status
27589 @findex -trace-status
27591 @subsubheading Synopsis
27597 Obtains the status of a tracing experiment. The result may include
27598 the following fields:
27603 May have a value of either @samp{0}, when no tracing operations are
27604 supported, @samp{1}, when all tracing operations are supported, or
27605 @samp{file} when examining trace file. In the latter case, examining
27606 of trace frame is possible but new tracing experiement cannot be
27607 started. This field is always present.
27610 May have a value of either @samp{0} or @samp{1} depending on whether
27611 tracing experiement is in progress on target. This field is present
27612 if @samp{supported} field is not @samp{0}.
27615 Report the reason why the tracing was stopped last time. This field
27616 may be absent iff tracing was never stopped on target yet. The
27617 value of @samp{request} means the tracing was stopped as result of
27618 the @code{-trace-stop} command. The value of @samp{overflow} means
27619 the tracing buffer is full. The value of @samp{disconnection} means
27620 tracing was automatically stopped when @value{GDBN} has disconnected.
27621 The value of @samp{passcount} means tracing was stopped when a
27622 tracepoint was passed a maximal number of times for that tracepoint.
27623 This field is present if @samp{supported} field is not @samp{0}.
27625 @item stopping-tracepoint
27626 The number of tracepoint whose passcount as exceeded. This field is
27627 present iff the @samp{stop-reason} field has the value of
27631 @itemx frames-created
27632 The @samp{frames} field is a count of the total number of trace frames
27633 in the trace buffer, while @samp{frames-created} is the total created
27634 during the run, including ones that were discarded, such as when a
27635 circular trace buffer filled up. Both fields are optional.
27639 These fields tell the current size of the tracing buffer and the
27640 remaining space. These fields are optional.
27643 The value of the circular trace buffer flag. @code{1} means that the
27644 trace buffer is circular and old trace frames will be discarded if
27645 necessary to make room, @code{0} means that the trace buffer is linear
27649 The value of the disconnected tracing flag. @code{1} means that
27650 tracing will continue after @value{GDBN} disconnects, @code{0} means
27651 that the trace run will stop.
27655 @subsubheading @value{GDBN} Command
27657 The corresponding @value{GDBN} command is @samp{tstatus}.
27659 @subheading -trace-stop
27660 @findex -trace-stop
27662 @subsubheading Synopsis
27668 Stops a tracing experiment. The result of this command has the same
27669 fields as @code{-trace-status}, except that the @samp{supported} and
27670 @samp{running} fields are not output.
27672 @subsubheading @value{GDBN} Command
27674 The corresponding @value{GDBN} command is @samp{tstop}.
27677 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27678 @node GDB/MI Symbol Query
27679 @section @sc{gdb/mi} Symbol Query Commands
27683 @subheading The @code{-symbol-info-address} Command
27684 @findex -symbol-info-address
27686 @subsubheading Synopsis
27689 -symbol-info-address @var{symbol}
27692 Describe where @var{symbol} is stored.
27694 @subsubheading @value{GDBN} Command
27696 The corresponding @value{GDBN} command is @samp{info address}.
27698 @subsubheading Example
27702 @subheading The @code{-symbol-info-file} Command
27703 @findex -symbol-info-file
27705 @subsubheading Synopsis
27711 Show the file for the symbol.
27713 @subsubheading @value{GDBN} Command
27715 There's no equivalent @value{GDBN} command. @code{gdbtk} has
27716 @samp{gdb_find_file}.
27718 @subsubheading Example
27722 @subheading The @code{-symbol-info-function} Command
27723 @findex -symbol-info-function
27725 @subsubheading Synopsis
27728 -symbol-info-function
27731 Show which function the symbol lives in.
27733 @subsubheading @value{GDBN} Command
27735 @samp{gdb_get_function} in @code{gdbtk}.
27737 @subsubheading Example
27741 @subheading The @code{-symbol-info-line} Command
27742 @findex -symbol-info-line
27744 @subsubheading Synopsis
27750 Show the core addresses of the code for a source line.
27752 @subsubheading @value{GDBN} Command
27754 The corresponding @value{GDBN} command is @samp{info line}.
27755 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
27757 @subsubheading Example
27761 @subheading The @code{-symbol-info-symbol} Command
27762 @findex -symbol-info-symbol
27764 @subsubheading Synopsis
27767 -symbol-info-symbol @var{addr}
27770 Describe what symbol is at location @var{addr}.
27772 @subsubheading @value{GDBN} Command
27774 The corresponding @value{GDBN} command is @samp{info symbol}.
27776 @subsubheading Example
27780 @subheading The @code{-symbol-list-functions} Command
27781 @findex -symbol-list-functions
27783 @subsubheading Synopsis
27786 -symbol-list-functions
27789 List the functions in the executable.
27791 @subsubheading @value{GDBN} Command
27793 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
27794 @samp{gdb_search} in @code{gdbtk}.
27796 @subsubheading Example
27801 @subheading The @code{-symbol-list-lines} Command
27802 @findex -symbol-list-lines
27804 @subsubheading Synopsis
27807 -symbol-list-lines @var{filename}
27810 Print the list of lines that contain code and their associated program
27811 addresses for the given source filename. The entries are sorted in
27812 ascending PC order.
27814 @subsubheading @value{GDBN} Command
27816 There is no corresponding @value{GDBN} command.
27818 @subsubheading Example
27821 -symbol-list-lines basics.c
27822 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
27828 @subheading The @code{-symbol-list-types} Command
27829 @findex -symbol-list-types
27831 @subsubheading Synopsis
27837 List all the type names.
27839 @subsubheading @value{GDBN} Command
27841 The corresponding commands are @samp{info types} in @value{GDBN},
27842 @samp{gdb_search} in @code{gdbtk}.
27844 @subsubheading Example
27848 @subheading The @code{-symbol-list-variables} Command
27849 @findex -symbol-list-variables
27851 @subsubheading Synopsis
27854 -symbol-list-variables
27857 List all the global and static variable names.
27859 @subsubheading @value{GDBN} Command
27861 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
27863 @subsubheading Example
27867 @subheading The @code{-symbol-locate} Command
27868 @findex -symbol-locate
27870 @subsubheading Synopsis
27876 @subsubheading @value{GDBN} Command
27878 @samp{gdb_loc} in @code{gdbtk}.
27880 @subsubheading Example
27884 @subheading The @code{-symbol-type} Command
27885 @findex -symbol-type
27887 @subsubheading Synopsis
27890 -symbol-type @var{variable}
27893 Show type of @var{variable}.
27895 @subsubheading @value{GDBN} Command
27897 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
27898 @samp{gdb_obj_variable}.
27900 @subsubheading Example
27905 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27906 @node GDB/MI File Commands
27907 @section @sc{gdb/mi} File Commands
27909 This section describes the GDB/MI commands to specify executable file names
27910 and to read in and obtain symbol table information.
27912 @subheading The @code{-file-exec-and-symbols} Command
27913 @findex -file-exec-and-symbols
27915 @subsubheading Synopsis
27918 -file-exec-and-symbols @var{file}
27921 Specify the executable file to be debugged. This file is the one from
27922 which the symbol table is also read. If no file is specified, the
27923 command clears the executable and symbol information. If breakpoints
27924 are set when using this command with no arguments, @value{GDBN} will produce
27925 error messages. Otherwise, no output is produced, except a completion
27928 @subsubheading @value{GDBN} Command
27930 The corresponding @value{GDBN} command is @samp{file}.
27932 @subsubheading Example
27936 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27942 @subheading The @code{-file-exec-file} Command
27943 @findex -file-exec-file
27945 @subsubheading Synopsis
27948 -file-exec-file @var{file}
27951 Specify the executable file to be debugged. Unlike
27952 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
27953 from this file. If used without argument, @value{GDBN} clears the information
27954 about the executable file. No output is produced, except a completion
27957 @subsubheading @value{GDBN} Command
27959 The corresponding @value{GDBN} command is @samp{exec-file}.
27961 @subsubheading Example
27965 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27972 @subheading The @code{-file-list-exec-sections} Command
27973 @findex -file-list-exec-sections
27975 @subsubheading Synopsis
27978 -file-list-exec-sections
27981 List the sections of the current executable file.
27983 @subsubheading @value{GDBN} Command
27985 The @value{GDBN} command @samp{info file} shows, among the rest, the same
27986 information as this command. @code{gdbtk} has a corresponding command
27987 @samp{gdb_load_info}.
27989 @subsubheading Example
27994 @subheading The @code{-file-list-exec-source-file} Command
27995 @findex -file-list-exec-source-file
27997 @subsubheading Synopsis
28000 -file-list-exec-source-file
28003 List the line number, the current source file, and the absolute path
28004 to the current source file for the current executable. The macro
28005 information field has a value of @samp{1} or @samp{0} depending on
28006 whether or not the file includes preprocessor macro information.
28008 @subsubheading @value{GDBN} Command
28010 The @value{GDBN} equivalent is @samp{info source}
28012 @subsubheading Example
28016 123-file-list-exec-source-file
28017 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
28022 @subheading The @code{-file-list-exec-source-files} Command
28023 @findex -file-list-exec-source-files
28025 @subsubheading Synopsis
28028 -file-list-exec-source-files
28031 List the source files for the current executable.
28033 It will always output the filename, but only when @value{GDBN} can find
28034 the absolute file name of a source file, will it output the fullname.
28036 @subsubheading @value{GDBN} Command
28038 The @value{GDBN} equivalent is @samp{info sources}.
28039 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
28041 @subsubheading Example
28044 -file-list-exec-source-files
28046 @{file=foo.c,fullname=/home/foo.c@},
28047 @{file=/home/bar.c,fullname=/home/bar.c@},
28048 @{file=gdb_could_not_find_fullpath.c@}]
28053 @subheading The @code{-file-list-shared-libraries} Command
28054 @findex -file-list-shared-libraries
28056 @subsubheading Synopsis
28059 -file-list-shared-libraries
28062 List the shared libraries in the program.
28064 @subsubheading @value{GDBN} Command
28066 The corresponding @value{GDBN} command is @samp{info shared}.
28068 @subsubheading Example
28072 @subheading The @code{-file-list-symbol-files} Command
28073 @findex -file-list-symbol-files
28075 @subsubheading Synopsis
28078 -file-list-symbol-files
28083 @subsubheading @value{GDBN} Command
28085 The corresponding @value{GDBN} command is @samp{info file} (part of it).
28087 @subsubheading Example
28092 @subheading The @code{-file-symbol-file} Command
28093 @findex -file-symbol-file
28095 @subsubheading Synopsis
28098 -file-symbol-file @var{file}
28101 Read symbol table info from the specified @var{file} argument. When
28102 used without arguments, clears @value{GDBN}'s symbol table info. No output is
28103 produced, except for a completion notification.
28105 @subsubheading @value{GDBN} Command
28107 The corresponding @value{GDBN} command is @samp{symbol-file}.
28109 @subsubheading Example
28113 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28119 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28120 @node GDB/MI Memory Overlay Commands
28121 @section @sc{gdb/mi} Memory Overlay Commands
28123 The memory overlay commands are not implemented.
28125 @c @subheading -overlay-auto
28127 @c @subheading -overlay-list-mapping-state
28129 @c @subheading -overlay-list-overlays
28131 @c @subheading -overlay-map
28133 @c @subheading -overlay-off
28135 @c @subheading -overlay-on
28137 @c @subheading -overlay-unmap
28139 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28140 @node GDB/MI Signal Handling Commands
28141 @section @sc{gdb/mi} Signal Handling Commands
28143 Signal handling commands are not implemented.
28145 @c @subheading -signal-handle
28147 @c @subheading -signal-list-handle-actions
28149 @c @subheading -signal-list-signal-types
28153 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28154 @node GDB/MI Target Manipulation
28155 @section @sc{gdb/mi} Target Manipulation Commands
28158 @subheading The @code{-target-attach} Command
28159 @findex -target-attach
28161 @subsubheading Synopsis
28164 -target-attach @var{pid} | @var{gid} | @var{file}
28167 Attach to a process @var{pid} or a file @var{file} outside of
28168 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
28169 group, the id previously returned by
28170 @samp{-list-thread-groups --available} must be used.
28172 @subsubheading @value{GDBN} Command
28174 The corresponding @value{GDBN} command is @samp{attach}.
28176 @subsubheading Example
28180 =thread-created,id="1"
28181 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
28187 @subheading The @code{-target-compare-sections} Command
28188 @findex -target-compare-sections
28190 @subsubheading Synopsis
28193 -target-compare-sections [ @var{section} ]
28196 Compare data of section @var{section} on target to the exec file.
28197 Without the argument, all sections are compared.
28199 @subsubheading @value{GDBN} Command
28201 The @value{GDBN} equivalent is @samp{compare-sections}.
28203 @subsubheading Example
28208 @subheading The @code{-target-detach} Command
28209 @findex -target-detach
28211 @subsubheading Synopsis
28214 -target-detach [ @var{pid} | @var{gid} ]
28217 Detach from the remote target which normally resumes its execution.
28218 If either @var{pid} or @var{gid} is specified, detaches from either
28219 the specified process, or specified thread group. There's no output.
28221 @subsubheading @value{GDBN} Command
28223 The corresponding @value{GDBN} command is @samp{detach}.
28225 @subsubheading Example
28235 @subheading The @code{-target-disconnect} Command
28236 @findex -target-disconnect
28238 @subsubheading Synopsis
28244 Disconnect from the remote target. There's no output and the target is
28245 generally not resumed.
28247 @subsubheading @value{GDBN} Command
28249 The corresponding @value{GDBN} command is @samp{disconnect}.
28251 @subsubheading Example
28261 @subheading The @code{-target-download} Command
28262 @findex -target-download
28264 @subsubheading Synopsis
28270 Loads the executable onto the remote target.
28271 It prints out an update message every half second, which includes the fields:
28275 The name of the section.
28277 The size of what has been sent so far for that section.
28279 The size of the section.
28281 The total size of what was sent so far (the current and the previous sections).
28283 The size of the overall executable to download.
28287 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
28288 @sc{gdb/mi} Output Syntax}).
28290 In addition, it prints the name and size of the sections, as they are
28291 downloaded. These messages include the following fields:
28295 The name of the section.
28297 The size of the section.
28299 The size of the overall executable to download.
28303 At the end, a summary is printed.
28305 @subsubheading @value{GDBN} Command
28307 The corresponding @value{GDBN} command is @samp{load}.
28309 @subsubheading Example
28311 Note: each status message appears on a single line. Here the messages
28312 have been broken down so that they can fit onto a page.
28317 +download,@{section=".text",section-size="6668",total-size="9880"@}
28318 +download,@{section=".text",section-sent="512",section-size="6668",
28319 total-sent="512",total-size="9880"@}
28320 +download,@{section=".text",section-sent="1024",section-size="6668",
28321 total-sent="1024",total-size="9880"@}
28322 +download,@{section=".text",section-sent="1536",section-size="6668",
28323 total-sent="1536",total-size="9880"@}
28324 +download,@{section=".text",section-sent="2048",section-size="6668",
28325 total-sent="2048",total-size="9880"@}
28326 +download,@{section=".text",section-sent="2560",section-size="6668",
28327 total-sent="2560",total-size="9880"@}
28328 +download,@{section=".text",section-sent="3072",section-size="6668",
28329 total-sent="3072",total-size="9880"@}
28330 +download,@{section=".text",section-sent="3584",section-size="6668",
28331 total-sent="3584",total-size="9880"@}
28332 +download,@{section=".text",section-sent="4096",section-size="6668",
28333 total-sent="4096",total-size="9880"@}
28334 +download,@{section=".text",section-sent="4608",section-size="6668",
28335 total-sent="4608",total-size="9880"@}
28336 +download,@{section=".text",section-sent="5120",section-size="6668",
28337 total-sent="5120",total-size="9880"@}
28338 +download,@{section=".text",section-sent="5632",section-size="6668",
28339 total-sent="5632",total-size="9880"@}
28340 +download,@{section=".text",section-sent="6144",section-size="6668",
28341 total-sent="6144",total-size="9880"@}
28342 +download,@{section=".text",section-sent="6656",section-size="6668",
28343 total-sent="6656",total-size="9880"@}
28344 +download,@{section=".init",section-size="28",total-size="9880"@}
28345 +download,@{section=".fini",section-size="28",total-size="9880"@}
28346 +download,@{section=".data",section-size="3156",total-size="9880"@}
28347 +download,@{section=".data",section-sent="512",section-size="3156",
28348 total-sent="7236",total-size="9880"@}
28349 +download,@{section=".data",section-sent="1024",section-size="3156",
28350 total-sent="7748",total-size="9880"@}
28351 +download,@{section=".data",section-sent="1536",section-size="3156",
28352 total-sent="8260",total-size="9880"@}
28353 +download,@{section=".data",section-sent="2048",section-size="3156",
28354 total-sent="8772",total-size="9880"@}
28355 +download,@{section=".data",section-sent="2560",section-size="3156",
28356 total-sent="9284",total-size="9880"@}
28357 +download,@{section=".data",section-sent="3072",section-size="3156",
28358 total-sent="9796",total-size="9880"@}
28359 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
28366 @subheading The @code{-target-exec-status} Command
28367 @findex -target-exec-status
28369 @subsubheading Synopsis
28372 -target-exec-status
28375 Provide information on the state of the target (whether it is running or
28376 not, for instance).
28378 @subsubheading @value{GDBN} Command
28380 There's no equivalent @value{GDBN} command.
28382 @subsubheading Example
28386 @subheading The @code{-target-list-available-targets} Command
28387 @findex -target-list-available-targets
28389 @subsubheading Synopsis
28392 -target-list-available-targets
28395 List the possible targets to connect to.
28397 @subsubheading @value{GDBN} Command
28399 The corresponding @value{GDBN} command is @samp{help target}.
28401 @subsubheading Example
28405 @subheading The @code{-target-list-current-targets} Command
28406 @findex -target-list-current-targets
28408 @subsubheading Synopsis
28411 -target-list-current-targets
28414 Describe the current target.
28416 @subsubheading @value{GDBN} Command
28418 The corresponding information is printed by @samp{info file} (among
28421 @subsubheading Example
28425 @subheading The @code{-target-list-parameters} Command
28426 @findex -target-list-parameters
28428 @subsubheading Synopsis
28431 -target-list-parameters
28437 @subsubheading @value{GDBN} Command
28441 @subsubheading Example
28445 @subheading The @code{-target-select} Command
28446 @findex -target-select
28448 @subsubheading Synopsis
28451 -target-select @var{type} @var{parameters @dots{}}
28454 Connect @value{GDBN} to the remote target. This command takes two args:
28458 The type of target, for instance @samp{remote}, etc.
28459 @item @var{parameters}
28460 Device names, host names and the like. @xref{Target Commands, ,
28461 Commands for Managing Targets}, for more details.
28464 The output is a connection notification, followed by the address at
28465 which the target program is, in the following form:
28468 ^connected,addr="@var{address}",func="@var{function name}",
28469 args=[@var{arg list}]
28472 @subsubheading @value{GDBN} Command
28474 The corresponding @value{GDBN} command is @samp{target}.
28476 @subsubheading Example
28480 -target-select remote /dev/ttya
28481 ^connected,addr="0xfe00a300",func="??",args=[]
28485 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28486 @node GDB/MI File Transfer Commands
28487 @section @sc{gdb/mi} File Transfer Commands
28490 @subheading The @code{-target-file-put} Command
28491 @findex -target-file-put
28493 @subsubheading Synopsis
28496 -target-file-put @var{hostfile} @var{targetfile}
28499 Copy file @var{hostfile} from the host system (the machine running
28500 @value{GDBN}) to @var{targetfile} on the target system.
28502 @subsubheading @value{GDBN} Command
28504 The corresponding @value{GDBN} command is @samp{remote put}.
28506 @subsubheading Example
28510 -target-file-put localfile remotefile
28516 @subheading The @code{-target-file-get} Command
28517 @findex -target-file-get
28519 @subsubheading Synopsis
28522 -target-file-get @var{targetfile} @var{hostfile}
28525 Copy file @var{targetfile} from the target system to @var{hostfile}
28526 on the host system.
28528 @subsubheading @value{GDBN} Command
28530 The corresponding @value{GDBN} command is @samp{remote get}.
28532 @subsubheading Example
28536 -target-file-get remotefile localfile
28542 @subheading The @code{-target-file-delete} Command
28543 @findex -target-file-delete
28545 @subsubheading Synopsis
28548 -target-file-delete @var{targetfile}
28551 Delete @var{targetfile} from the target system.
28553 @subsubheading @value{GDBN} Command
28555 The corresponding @value{GDBN} command is @samp{remote delete}.
28557 @subsubheading Example
28561 -target-file-delete remotefile
28567 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28568 @node GDB/MI Miscellaneous Commands
28569 @section Miscellaneous @sc{gdb/mi} Commands
28571 @c @subheading -gdb-complete
28573 @subheading The @code{-gdb-exit} Command
28576 @subsubheading Synopsis
28582 Exit @value{GDBN} immediately.
28584 @subsubheading @value{GDBN} Command
28586 Approximately corresponds to @samp{quit}.
28588 @subsubheading Example
28598 @subheading The @code{-exec-abort} Command
28599 @findex -exec-abort
28601 @subsubheading Synopsis
28607 Kill the inferior running program.
28609 @subsubheading @value{GDBN} Command
28611 The corresponding @value{GDBN} command is @samp{kill}.
28613 @subsubheading Example
28618 @subheading The @code{-gdb-set} Command
28621 @subsubheading Synopsis
28627 Set an internal @value{GDBN} variable.
28628 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
28630 @subsubheading @value{GDBN} Command
28632 The corresponding @value{GDBN} command is @samp{set}.
28634 @subsubheading Example
28644 @subheading The @code{-gdb-show} Command
28647 @subsubheading Synopsis
28653 Show the current value of a @value{GDBN} variable.
28655 @subsubheading @value{GDBN} Command
28657 The corresponding @value{GDBN} command is @samp{show}.
28659 @subsubheading Example
28668 @c @subheading -gdb-source
28671 @subheading The @code{-gdb-version} Command
28672 @findex -gdb-version
28674 @subsubheading Synopsis
28680 Show version information for @value{GDBN}. Used mostly in testing.
28682 @subsubheading @value{GDBN} Command
28684 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
28685 default shows this information when you start an interactive session.
28687 @subsubheading Example
28689 @c This example modifies the actual output from GDB to avoid overfull
28695 ~Copyright 2000 Free Software Foundation, Inc.
28696 ~GDB is free software, covered by the GNU General Public License, and
28697 ~you are welcome to change it and/or distribute copies of it under
28698 ~ certain conditions.
28699 ~Type "show copying" to see the conditions.
28700 ~There is absolutely no warranty for GDB. Type "show warranty" for
28702 ~This GDB was configured as
28703 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
28708 @subheading The @code{-list-features} Command
28709 @findex -list-features
28711 Returns a list of particular features of the MI protocol that
28712 this version of gdb implements. A feature can be a command,
28713 or a new field in an output of some command, or even an
28714 important bugfix. While a frontend can sometimes detect presence
28715 of a feature at runtime, it is easier to perform detection at debugger
28718 The command returns a list of strings, with each string naming an
28719 available feature. Each returned string is just a name, it does not
28720 have any internal structure. The list of possible feature names
28726 (gdb) -list-features
28727 ^done,result=["feature1","feature2"]
28730 The current list of features is:
28733 @item frozen-varobjs
28734 Indicates presence of the @code{-var-set-frozen} command, as well
28735 as possible presense of the @code{frozen} field in the output
28736 of @code{-varobj-create}.
28737 @item pending-breakpoints
28738 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
28740 Indicates presence of Python scripting support, Python-based
28741 pretty-printing commands, and possible presence of the
28742 @samp{display_hint} field in the output of @code{-var-list-children}
28744 Indicates presence of the @code{-thread-info} command.
28748 @subheading The @code{-list-target-features} Command
28749 @findex -list-target-features
28751 Returns a list of particular features that are supported by the
28752 target. Those features affect the permitted MI commands, but
28753 unlike the features reported by the @code{-list-features} command, the
28754 features depend on which target GDB is using at the moment. Whenever
28755 a target can change, due to commands such as @code{-target-select},
28756 @code{-target-attach} or @code{-exec-run}, the list of target features
28757 may change, and the frontend should obtain it again.
28761 (gdb) -list-features
28762 ^done,result=["async"]
28765 The current list of features is:
28769 Indicates that the target is capable of asynchronous command
28770 execution, which means that @value{GDBN} will accept further commands
28771 while the target is running.
28775 @subheading The @code{-list-thread-groups} Command
28776 @findex -list-thread-groups
28778 @subheading Synopsis
28781 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
28784 Lists thread groups (@pxref{Thread groups}). When a single thread
28785 group is passed as the argument, lists the children of that group.
28786 When several thread group are passed, lists information about those
28787 thread groups. Without any parameters, lists information about all
28788 top-level thread groups.
28790 Normally, thread groups that are being debugged are reported.
28791 With the @samp{--available} option, @value{GDBN} reports thread groups
28792 available on the target.
28794 The output of this command may have either a @samp{threads} result or
28795 a @samp{groups} result. The @samp{thread} result has a list of tuples
28796 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
28797 Information}). The @samp{groups} result has a list of tuples as value,
28798 each tuple describing a thread group. If top-level groups are
28799 requested (that is, no parameter is passed), or when several groups
28800 are passed, the output always has a @samp{groups} result. The format
28801 of the @samp{group} result is described below.
28803 To reduce the number of roundtrips it's possible to list thread groups
28804 together with their children, by passing the @samp{--recurse} option
28805 and the recursion depth. Presently, only recursion depth of 1 is
28806 permitted. If this option is present, then every reported thread group
28807 will also include its children, either as @samp{group} or
28808 @samp{threads} field.
28810 In general, any combination of option and parameters is permitted, with
28811 the following caveats:
28815 When a single thread group is passed, the output will typically
28816 be the @samp{threads} result. Because threads may not contain
28817 anything, the @samp{recurse} option will be ignored.
28820 When the @samp{--available} option is passed, limited information may
28821 be available. In particular, the list of threads of a process might
28822 be inaccessible. Further, specifying specific thread groups might
28823 not give any performance advantage over listing all thread groups.
28824 The frontend should assume that @samp{-list-thread-groups --available}
28825 is always an expensive operation and cache the results.
28829 The @samp{groups} result is a list of tuples, where each tuple may
28830 have the following fields:
28834 Identifier of the thread group. This field is always present.
28835 The identifier is an opaque string; frontends should not try to
28836 convert it to an integer, even though it might look like one.
28839 The type of the thread group. At present, only @samp{process} is a
28843 The target-specific process identifier. This field is only present
28844 for thread groups of type @samp{process} and only if the process exists.
28847 The number of children this thread group has. This field may be
28848 absent for an available thread group.
28851 This field has a list of tuples as value, each tuple describing a
28852 thread. It may be present if the @samp{--recurse} option is
28853 specified, and it's actually possible to obtain the threads.
28856 This field is a list of integers, each identifying a core that one
28857 thread of the group is running on. This field may be absent if
28858 such information is not available.
28861 The name of the executable file that corresponds to this thread group.
28862 The field is only present for thread groups of type @samp{process},
28863 and only if there is a corresponding executable file.
28867 @subheading Example
28871 -list-thread-groups
28872 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
28873 -list-thread-groups 17
28874 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28875 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
28876 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28877 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
28878 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
28879 -list-thread-groups --available
28880 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
28881 -list-thread-groups --available --recurse 1
28882 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28883 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28884 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
28885 -list-thread-groups --available --recurse 1 17 18
28886 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28887 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28888 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
28892 @subheading The @code{-add-inferior} Command
28893 @findex -add-inferior
28895 @subheading Synopsis
28901 Creates a new inferior (@pxref{Inferiors and Programs}). The created
28902 inferior is not associated with any executable. Such association may
28903 be established with the @samp{-file-exec-and-symbols} command
28904 (@pxref{GDB/MI File Commands}). The command response has a single
28905 field, @samp{thread-group}, whose value is the identifier of the
28906 thread group corresponding to the new inferior.
28908 @subheading Example
28913 ^done,thread-group="i3"
28916 @subheading The @code{-interpreter-exec} Command
28917 @findex -interpreter-exec
28919 @subheading Synopsis
28922 -interpreter-exec @var{interpreter} @var{command}
28924 @anchor{-interpreter-exec}
28926 Execute the specified @var{command} in the given @var{interpreter}.
28928 @subheading @value{GDBN} Command
28930 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
28932 @subheading Example
28936 -interpreter-exec console "break main"
28937 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
28938 &"During symbol reading, bad structure-type format.\n"
28939 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
28944 @subheading The @code{-inferior-tty-set} Command
28945 @findex -inferior-tty-set
28947 @subheading Synopsis
28950 -inferior-tty-set /dev/pts/1
28953 Set terminal for future runs of the program being debugged.
28955 @subheading @value{GDBN} Command
28957 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
28959 @subheading Example
28963 -inferior-tty-set /dev/pts/1
28968 @subheading The @code{-inferior-tty-show} Command
28969 @findex -inferior-tty-show
28971 @subheading Synopsis
28977 Show terminal for future runs of program being debugged.
28979 @subheading @value{GDBN} Command
28981 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
28983 @subheading Example
28987 -inferior-tty-set /dev/pts/1
28991 ^done,inferior_tty_terminal="/dev/pts/1"
28995 @subheading The @code{-enable-timings} Command
28996 @findex -enable-timings
28998 @subheading Synopsis
29001 -enable-timings [yes | no]
29004 Toggle the printing of the wallclock, user and system times for an MI
29005 command as a field in its output. This command is to help frontend
29006 developers optimize the performance of their code. No argument is
29007 equivalent to @samp{yes}.
29009 @subheading @value{GDBN} Command
29013 @subheading Example
29021 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29022 addr="0x080484ed",func="main",file="myprog.c",
29023 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
29024 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
29032 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29033 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
29034 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
29035 fullname="/home/nickrob/myprog.c",line="73"@}
29040 @chapter @value{GDBN} Annotations
29042 This chapter describes annotations in @value{GDBN}. Annotations were
29043 designed to interface @value{GDBN} to graphical user interfaces or other
29044 similar programs which want to interact with @value{GDBN} at a
29045 relatively high level.
29047 The annotation mechanism has largely been superseded by @sc{gdb/mi}
29051 This is Edition @value{EDITION}, @value{DATE}.
29055 * Annotations Overview:: What annotations are; the general syntax.
29056 * Server Prefix:: Issuing a command without affecting user state.
29057 * Prompting:: Annotations marking @value{GDBN}'s need for input.
29058 * Errors:: Annotations for error messages.
29059 * Invalidation:: Some annotations describe things now invalid.
29060 * Annotations for Running::
29061 Whether the program is running, how it stopped, etc.
29062 * Source Annotations:: Annotations describing source code.
29065 @node Annotations Overview
29066 @section What is an Annotation?
29067 @cindex annotations
29069 Annotations start with a newline character, two @samp{control-z}
29070 characters, and the name of the annotation. If there is no additional
29071 information associated with this annotation, the name of the annotation
29072 is followed immediately by a newline. If there is additional
29073 information, the name of the annotation is followed by a space, the
29074 additional information, and a newline. The additional information
29075 cannot contain newline characters.
29077 Any output not beginning with a newline and two @samp{control-z}
29078 characters denotes literal output from @value{GDBN}. Currently there is
29079 no need for @value{GDBN} to output a newline followed by two
29080 @samp{control-z} characters, but if there was such a need, the
29081 annotations could be extended with an @samp{escape} annotation which
29082 means those three characters as output.
29084 The annotation @var{level}, which is specified using the
29085 @option{--annotate} command line option (@pxref{Mode Options}), controls
29086 how much information @value{GDBN} prints together with its prompt,
29087 values of expressions, source lines, and other types of output. Level 0
29088 is for no annotations, level 1 is for use when @value{GDBN} is run as a
29089 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
29090 for programs that control @value{GDBN}, and level 2 annotations have
29091 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
29092 Interface, annotate, GDB's Obsolete Annotations}).
29095 @kindex set annotate
29096 @item set annotate @var{level}
29097 The @value{GDBN} command @code{set annotate} sets the level of
29098 annotations to the specified @var{level}.
29100 @item show annotate
29101 @kindex show annotate
29102 Show the current annotation level.
29105 This chapter describes level 3 annotations.
29107 A simple example of starting up @value{GDBN} with annotations is:
29110 $ @kbd{gdb --annotate=3}
29112 Copyright 2003 Free Software Foundation, Inc.
29113 GDB is free software, covered by the GNU General Public License,
29114 and you are welcome to change it and/or distribute copies of it
29115 under certain conditions.
29116 Type "show copying" to see the conditions.
29117 There is absolutely no warranty for GDB. Type "show warranty"
29119 This GDB was configured as "i386-pc-linux-gnu"
29130 Here @samp{quit} is input to @value{GDBN}; the rest is output from
29131 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
29132 denotes a @samp{control-z} character) are annotations; the rest is
29133 output from @value{GDBN}.
29135 @node Server Prefix
29136 @section The Server Prefix
29137 @cindex server prefix
29139 If you prefix a command with @samp{server } then it will not affect
29140 the command history, nor will it affect @value{GDBN}'s notion of which
29141 command to repeat if @key{RET} is pressed on a line by itself. This
29142 means that commands can be run behind a user's back by a front-end in
29143 a transparent manner.
29145 The @code{server } prefix does not affect the recording of values into
29146 the value history; to print a value without recording it into the
29147 value history, use the @code{output} command instead of the
29148 @code{print} command.
29150 Using this prefix also disables confirmation requests
29151 (@pxref{confirmation requests}).
29154 @section Annotation for @value{GDBN} Input
29156 @cindex annotations for prompts
29157 When @value{GDBN} prompts for input, it annotates this fact so it is possible
29158 to know when to send output, when the output from a given command is
29161 Different kinds of input each have a different @dfn{input type}. Each
29162 input type has three annotations: a @code{pre-} annotation, which
29163 denotes the beginning of any prompt which is being output, a plain
29164 annotation, which denotes the end of the prompt, and then a @code{post-}
29165 annotation which denotes the end of any echo which may (or may not) be
29166 associated with the input. For example, the @code{prompt} input type
29167 features the following annotations:
29175 The input types are
29178 @findex pre-prompt annotation
29179 @findex prompt annotation
29180 @findex post-prompt annotation
29182 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
29184 @findex pre-commands annotation
29185 @findex commands annotation
29186 @findex post-commands annotation
29188 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
29189 command. The annotations are repeated for each command which is input.
29191 @findex pre-overload-choice annotation
29192 @findex overload-choice annotation
29193 @findex post-overload-choice annotation
29194 @item overload-choice
29195 When @value{GDBN} wants the user to select between various overloaded functions.
29197 @findex pre-query annotation
29198 @findex query annotation
29199 @findex post-query annotation
29201 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
29203 @findex pre-prompt-for-continue annotation
29204 @findex prompt-for-continue annotation
29205 @findex post-prompt-for-continue annotation
29206 @item prompt-for-continue
29207 When @value{GDBN} is asking the user to press return to continue. Note: Don't
29208 expect this to work well; instead use @code{set height 0} to disable
29209 prompting. This is because the counting of lines is buggy in the
29210 presence of annotations.
29215 @cindex annotations for errors, warnings and interrupts
29217 @findex quit annotation
29222 This annotation occurs right before @value{GDBN} responds to an interrupt.
29224 @findex error annotation
29229 This annotation occurs right before @value{GDBN} responds to an error.
29231 Quit and error annotations indicate that any annotations which @value{GDBN} was
29232 in the middle of may end abruptly. For example, if a
29233 @code{value-history-begin} annotation is followed by a @code{error}, one
29234 cannot expect to receive the matching @code{value-history-end}. One
29235 cannot expect not to receive it either, however; an error annotation
29236 does not necessarily mean that @value{GDBN} is immediately returning all the way
29239 @findex error-begin annotation
29240 A quit or error annotation may be preceded by
29246 Any output between that and the quit or error annotation is the error
29249 Warning messages are not yet annotated.
29250 @c If we want to change that, need to fix warning(), type_error(),
29251 @c range_error(), and possibly other places.
29254 @section Invalidation Notices
29256 @cindex annotations for invalidation messages
29257 The following annotations say that certain pieces of state may have
29261 @findex frames-invalid annotation
29262 @item ^Z^Zframes-invalid
29264 The frames (for example, output from the @code{backtrace} command) may
29267 @findex breakpoints-invalid annotation
29268 @item ^Z^Zbreakpoints-invalid
29270 The breakpoints may have changed. For example, the user just added or
29271 deleted a breakpoint.
29274 @node Annotations for Running
29275 @section Running the Program
29276 @cindex annotations for running programs
29278 @findex starting annotation
29279 @findex stopping annotation
29280 When the program starts executing due to a @value{GDBN} command such as
29281 @code{step} or @code{continue},
29287 is output. When the program stops,
29293 is output. Before the @code{stopped} annotation, a variety of
29294 annotations describe how the program stopped.
29297 @findex exited annotation
29298 @item ^Z^Zexited @var{exit-status}
29299 The program exited, and @var{exit-status} is the exit status (zero for
29300 successful exit, otherwise nonzero).
29302 @findex signalled annotation
29303 @findex signal-name annotation
29304 @findex signal-name-end annotation
29305 @findex signal-string annotation
29306 @findex signal-string-end annotation
29307 @item ^Z^Zsignalled
29308 The program exited with a signal. After the @code{^Z^Zsignalled}, the
29309 annotation continues:
29315 ^Z^Zsignal-name-end
29319 ^Z^Zsignal-string-end
29324 where @var{name} is the name of the signal, such as @code{SIGILL} or
29325 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
29326 as @code{Illegal Instruction} or @code{Segmentation fault}.
29327 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
29328 user's benefit and have no particular format.
29330 @findex signal annotation
29332 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
29333 just saying that the program received the signal, not that it was
29334 terminated with it.
29336 @findex breakpoint annotation
29337 @item ^Z^Zbreakpoint @var{number}
29338 The program hit breakpoint number @var{number}.
29340 @findex watchpoint annotation
29341 @item ^Z^Zwatchpoint @var{number}
29342 The program hit watchpoint number @var{number}.
29345 @node Source Annotations
29346 @section Displaying Source
29347 @cindex annotations for source display
29349 @findex source annotation
29350 The following annotation is used instead of displaying source code:
29353 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
29356 where @var{filename} is an absolute file name indicating which source
29357 file, @var{line} is the line number within that file (where 1 is the
29358 first line in the file), @var{character} is the character position
29359 within the file (where 0 is the first character in the file) (for most
29360 debug formats this will necessarily point to the beginning of a line),
29361 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
29362 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
29363 @var{addr} is the address in the target program associated with the
29364 source which is being displayed. @var{addr} is in the form @samp{0x}
29365 followed by one or more lowercase hex digits (note that this does not
29366 depend on the language).
29368 @node JIT Interface
29369 @chapter JIT Compilation Interface
29370 @cindex just-in-time compilation
29371 @cindex JIT compilation interface
29373 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
29374 interface. A JIT compiler is a program or library that generates native
29375 executable code at runtime and executes it, usually in order to achieve good
29376 performance while maintaining platform independence.
29378 Programs that use JIT compilation are normally difficult to debug because
29379 portions of their code are generated at runtime, instead of being loaded from
29380 object files, which is where @value{GDBN} normally finds the program's symbols
29381 and debug information. In order to debug programs that use JIT compilation,
29382 @value{GDBN} has an interface that allows the program to register in-memory
29383 symbol files with @value{GDBN} at runtime.
29385 If you are using @value{GDBN} to debug a program that uses this interface, then
29386 it should work transparently so long as you have not stripped the binary. If
29387 you are developing a JIT compiler, then the interface is documented in the rest
29388 of this chapter. At this time, the only known client of this interface is the
29391 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
29392 JIT compiler communicates with @value{GDBN} by writing data into a global
29393 variable and calling a fuction at a well-known symbol. When @value{GDBN}
29394 attaches, it reads a linked list of symbol files from the global variable to
29395 find existing code, and puts a breakpoint in the function so that it can find
29396 out about additional code.
29399 * Declarations:: Relevant C struct declarations
29400 * Registering Code:: Steps to register code
29401 * Unregistering Code:: Steps to unregister code
29405 @section JIT Declarations
29407 These are the relevant struct declarations that a C program should include to
29408 implement the interface:
29418 struct jit_code_entry
29420 struct jit_code_entry *next_entry;
29421 struct jit_code_entry *prev_entry;
29422 const char *symfile_addr;
29423 uint64_t symfile_size;
29426 struct jit_descriptor
29429 /* This type should be jit_actions_t, but we use uint32_t
29430 to be explicit about the bitwidth. */
29431 uint32_t action_flag;
29432 struct jit_code_entry *relevant_entry;
29433 struct jit_code_entry *first_entry;
29436 /* GDB puts a breakpoint in this function. */
29437 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
29439 /* Make sure to specify the version statically, because the
29440 debugger may check the version before we can set it. */
29441 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
29444 If the JIT is multi-threaded, then it is important that the JIT synchronize any
29445 modifications to this global data properly, which can easily be done by putting
29446 a global mutex around modifications to these structures.
29448 @node Registering Code
29449 @section Registering Code
29451 To register code with @value{GDBN}, the JIT should follow this protocol:
29455 Generate an object file in memory with symbols and other desired debug
29456 information. The file must include the virtual addresses of the sections.
29459 Create a code entry for the file, which gives the start and size of the symbol
29463 Add it to the linked list in the JIT descriptor.
29466 Point the relevant_entry field of the descriptor at the entry.
29469 Set @code{action_flag} to @code{JIT_REGISTER} and call
29470 @code{__jit_debug_register_code}.
29473 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
29474 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
29475 new code. However, the linked list must still be maintained in order to allow
29476 @value{GDBN} to attach to a running process and still find the symbol files.
29478 @node Unregistering Code
29479 @section Unregistering Code
29481 If code is freed, then the JIT should use the following protocol:
29485 Remove the code entry corresponding to the code from the linked list.
29488 Point the @code{relevant_entry} field of the descriptor at the code entry.
29491 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
29492 @code{__jit_debug_register_code}.
29495 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
29496 and the JIT will leak the memory used for the associated symbol files.
29499 @chapter Reporting Bugs in @value{GDBN}
29500 @cindex bugs in @value{GDBN}
29501 @cindex reporting bugs in @value{GDBN}
29503 Your bug reports play an essential role in making @value{GDBN} reliable.
29505 Reporting a bug may help you by bringing a solution to your problem, or it
29506 may not. But in any case the principal function of a bug report is to help
29507 the entire community by making the next version of @value{GDBN} work better. Bug
29508 reports are your contribution to the maintenance of @value{GDBN}.
29510 In order for a bug report to serve its purpose, you must include the
29511 information that enables us to fix the bug.
29514 * Bug Criteria:: Have you found a bug?
29515 * Bug Reporting:: How to report bugs
29519 @section Have You Found a Bug?
29520 @cindex bug criteria
29522 If you are not sure whether you have found a bug, here are some guidelines:
29525 @cindex fatal signal
29526 @cindex debugger crash
29527 @cindex crash of debugger
29529 If the debugger gets a fatal signal, for any input whatever, that is a
29530 @value{GDBN} bug. Reliable debuggers never crash.
29532 @cindex error on valid input
29534 If @value{GDBN} produces an error message for valid input, that is a
29535 bug. (Note that if you're cross debugging, the problem may also be
29536 somewhere in the connection to the target.)
29538 @cindex invalid input
29540 If @value{GDBN} does not produce an error message for invalid input,
29541 that is a bug. However, you should note that your idea of
29542 ``invalid input'' might be our idea of ``an extension'' or ``support
29543 for traditional practice''.
29546 If you are an experienced user of debugging tools, your suggestions
29547 for improvement of @value{GDBN} are welcome in any case.
29550 @node Bug Reporting
29551 @section How to Report Bugs
29552 @cindex bug reports
29553 @cindex @value{GDBN} bugs, reporting
29555 A number of companies and individuals offer support for @sc{gnu} products.
29556 If you obtained @value{GDBN} from a support organization, we recommend you
29557 contact that organization first.
29559 You can find contact information for many support companies and
29560 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
29562 @c should add a web page ref...
29565 @ifset BUGURL_DEFAULT
29566 In any event, we also recommend that you submit bug reports for
29567 @value{GDBN}. The preferred method is to submit them directly using
29568 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
29569 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
29572 @strong{Do not send bug reports to @samp{info-gdb}, or to
29573 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
29574 not want to receive bug reports. Those that do have arranged to receive
29577 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
29578 serves as a repeater. The mailing list and the newsgroup carry exactly
29579 the same messages. Often people think of posting bug reports to the
29580 newsgroup instead of mailing them. This appears to work, but it has one
29581 problem which can be crucial: a newsgroup posting often lacks a mail
29582 path back to the sender. Thus, if we need to ask for more information,
29583 we may be unable to reach you. For this reason, it is better to send
29584 bug reports to the mailing list.
29586 @ifclear BUGURL_DEFAULT
29587 In any event, we also recommend that you submit bug reports for
29588 @value{GDBN} to @value{BUGURL}.
29592 The fundamental principle of reporting bugs usefully is this:
29593 @strong{report all the facts}. If you are not sure whether to state a
29594 fact or leave it out, state it!
29596 Often people omit facts because they think they know what causes the
29597 problem and assume that some details do not matter. Thus, you might
29598 assume that the name of the variable you use in an example does not matter.
29599 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
29600 stray memory reference which happens to fetch from the location where that
29601 name is stored in memory; perhaps, if the name were different, the contents
29602 of that location would fool the debugger into doing the right thing despite
29603 the bug. Play it safe and give a specific, complete example. That is the
29604 easiest thing for you to do, and the most helpful.
29606 Keep in mind that the purpose of a bug report is to enable us to fix the
29607 bug. It may be that the bug has been reported previously, but neither
29608 you nor we can know that unless your bug report is complete and
29611 Sometimes people give a few sketchy facts and ask, ``Does this ring a
29612 bell?'' Those bug reports are useless, and we urge everyone to
29613 @emph{refuse to respond to them} except to chide the sender to report
29616 To enable us to fix the bug, you should include all these things:
29620 The version of @value{GDBN}. @value{GDBN} announces it if you start
29621 with no arguments; you can also print it at any time using @code{show
29624 Without this, we will not know whether there is any point in looking for
29625 the bug in the current version of @value{GDBN}.
29628 The type of machine you are using, and the operating system name and
29632 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
29633 ``@value{GCC}--2.8.1''.
29636 What compiler (and its version) was used to compile the program you are
29637 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
29638 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
29639 to get this information; for other compilers, see the documentation for
29643 The command arguments you gave the compiler to compile your example and
29644 observe the bug. For example, did you use @samp{-O}? To guarantee
29645 you will not omit something important, list them all. A copy of the
29646 Makefile (or the output from make) is sufficient.
29648 If we were to try to guess the arguments, we would probably guess wrong
29649 and then we might not encounter the bug.
29652 A complete input script, and all necessary source files, that will
29656 A description of what behavior you observe that you believe is
29657 incorrect. For example, ``It gets a fatal signal.''
29659 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
29660 will certainly notice it. But if the bug is incorrect output, we might
29661 not notice unless it is glaringly wrong. You might as well not give us
29662 a chance to make a mistake.
29664 Even if the problem you experience is a fatal signal, you should still
29665 say so explicitly. Suppose something strange is going on, such as, your
29666 copy of @value{GDBN} is out of synch, or you have encountered a bug in
29667 the C library on your system. (This has happened!) Your copy might
29668 crash and ours would not. If you told us to expect a crash, then when
29669 ours fails to crash, we would know that the bug was not happening for
29670 us. If you had not told us to expect a crash, then we would not be able
29671 to draw any conclusion from our observations.
29674 @cindex recording a session script
29675 To collect all this information, you can use a session recording program
29676 such as @command{script}, which is available on many Unix systems.
29677 Just run your @value{GDBN} session inside @command{script} and then
29678 include the @file{typescript} file with your bug report.
29680 Another way to record a @value{GDBN} session is to run @value{GDBN}
29681 inside Emacs and then save the entire buffer to a file.
29684 If you wish to suggest changes to the @value{GDBN} source, send us context
29685 diffs. If you even discuss something in the @value{GDBN} source, refer to
29686 it by context, not by line number.
29688 The line numbers in our development sources will not match those in your
29689 sources. Your line numbers would convey no useful information to us.
29693 Here are some things that are not necessary:
29697 A description of the envelope of the bug.
29699 Often people who encounter a bug spend a lot of time investigating
29700 which changes to the input file will make the bug go away and which
29701 changes will not affect it.
29703 This is often time consuming and not very useful, because the way we
29704 will find the bug is by running a single example under the debugger
29705 with breakpoints, not by pure deduction from a series of examples.
29706 We recommend that you save your time for something else.
29708 Of course, if you can find a simpler example to report @emph{instead}
29709 of the original one, that is a convenience for us. Errors in the
29710 output will be easier to spot, running under the debugger will take
29711 less time, and so on.
29713 However, simplification is not vital; if you do not want to do this,
29714 report the bug anyway and send us the entire test case you used.
29717 A patch for the bug.
29719 A patch for the bug does help us if it is a good one. But do not omit
29720 the necessary information, such as the test case, on the assumption that
29721 a patch is all we need. We might see problems with your patch and decide
29722 to fix the problem another way, or we might not understand it at all.
29724 Sometimes with a program as complicated as @value{GDBN} it is very hard to
29725 construct an example that will make the program follow a certain path
29726 through the code. If you do not send us the example, we will not be able
29727 to construct one, so we will not be able to verify that the bug is fixed.
29729 And if we cannot understand what bug you are trying to fix, or why your
29730 patch should be an improvement, we will not install it. A test case will
29731 help us to understand.
29734 A guess about what the bug is or what it depends on.
29736 Such guesses are usually wrong. Even we cannot guess right about such
29737 things without first using the debugger to find the facts.
29740 @c The readline documentation is distributed with the readline code
29741 @c and consists of the two following files:
29743 @c inc-hist.texinfo
29744 @c Use -I with makeinfo to point to the appropriate directory,
29745 @c environment var TEXINPUTS with TeX.
29746 @include rluser.texi
29747 @include inc-hist.texinfo
29750 @node Formatting Documentation
29751 @appendix Formatting Documentation
29753 @cindex @value{GDBN} reference card
29754 @cindex reference card
29755 The @value{GDBN} 4 release includes an already-formatted reference card, ready
29756 for printing with PostScript or Ghostscript, in the @file{gdb}
29757 subdirectory of the main source directory@footnote{In
29758 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
29759 release.}. If you can use PostScript or Ghostscript with your printer,
29760 you can print the reference card immediately with @file{refcard.ps}.
29762 The release also includes the source for the reference card. You
29763 can format it, using @TeX{}, by typing:
29769 The @value{GDBN} reference card is designed to print in @dfn{landscape}
29770 mode on US ``letter'' size paper;
29771 that is, on a sheet 11 inches wide by 8.5 inches
29772 high. You will need to specify this form of printing as an option to
29773 your @sc{dvi} output program.
29775 @cindex documentation
29777 All the documentation for @value{GDBN} comes as part of the machine-readable
29778 distribution. The documentation is written in Texinfo format, which is
29779 a documentation system that uses a single source file to produce both
29780 on-line information and a printed manual. You can use one of the Info
29781 formatting commands to create the on-line version of the documentation
29782 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
29784 @value{GDBN} includes an already formatted copy of the on-line Info
29785 version of this manual in the @file{gdb} subdirectory. The main Info
29786 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
29787 subordinate files matching @samp{gdb.info*} in the same directory. If
29788 necessary, you can print out these files, or read them with any editor;
29789 but they are easier to read using the @code{info} subsystem in @sc{gnu}
29790 Emacs or the standalone @code{info} program, available as part of the
29791 @sc{gnu} Texinfo distribution.
29793 If you want to format these Info files yourself, you need one of the
29794 Info formatting programs, such as @code{texinfo-format-buffer} or
29797 If you have @code{makeinfo} installed, and are in the top level
29798 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
29799 version @value{GDBVN}), you can make the Info file by typing:
29806 If you want to typeset and print copies of this manual, you need @TeX{},
29807 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
29808 Texinfo definitions file.
29810 @TeX{} is a typesetting program; it does not print files directly, but
29811 produces output files called @sc{dvi} files. To print a typeset
29812 document, you need a program to print @sc{dvi} files. If your system
29813 has @TeX{} installed, chances are it has such a program. The precise
29814 command to use depends on your system; @kbd{lpr -d} is common; another
29815 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
29816 require a file name without any extension or a @samp{.dvi} extension.
29818 @TeX{} also requires a macro definitions file called
29819 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
29820 written in Texinfo format. On its own, @TeX{} cannot either read or
29821 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
29822 and is located in the @file{gdb-@var{version-number}/texinfo}
29825 If you have @TeX{} and a @sc{dvi} printer program installed, you can
29826 typeset and print this manual. First switch to the @file{gdb}
29827 subdirectory of the main source directory (for example, to
29828 @file{gdb-@value{GDBVN}/gdb}) and type:
29834 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
29836 @node Installing GDB
29837 @appendix Installing @value{GDBN}
29838 @cindex installation
29841 * Requirements:: Requirements for building @value{GDBN}
29842 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
29843 * Separate Objdir:: Compiling @value{GDBN} in another directory
29844 * Config Names:: Specifying names for hosts and targets
29845 * Configure Options:: Summary of options for configure
29846 * System-wide configuration:: Having a system-wide init file
29850 @section Requirements for Building @value{GDBN}
29851 @cindex building @value{GDBN}, requirements for
29853 Building @value{GDBN} requires various tools and packages to be available.
29854 Other packages will be used only if they are found.
29856 @heading Tools/Packages Necessary for Building @value{GDBN}
29858 @item ISO C90 compiler
29859 @value{GDBN} is written in ISO C90. It should be buildable with any
29860 working C90 compiler, e.g.@: GCC.
29864 @heading Tools/Packages Optional for Building @value{GDBN}
29868 @value{GDBN} can use the Expat XML parsing library. This library may be
29869 included with your operating system distribution; if it is not, you
29870 can get the latest version from @url{http://expat.sourceforge.net}.
29871 The @file{configure} script will search for this library in several
29872 standard locations; if it is installed in an unusual path, you can
29873 use the @option{--with-libexpat-prefix} option to specify its location.
29879 Remote protocol memory maps (@pxref{Memory Map Format})
29881 Target descriptions (@pxref{Target Descriptions})
29883 Remote shared library lists (@pxref{Library List Format})
29885 MS-Windows shared libraries (@pxref{Shared Libraries})
29889 @cindex compressed debug sections
29890 @value{GDBN} will use the @samp{zlib} library, if available, to read
29891 compressed debug sections. Some linkers, such as GNU gold, are capable
29892 of producing binaries with compressed debug sections. If @value{GDBN}
29893 is compiled with @samp{zlib}, it will be able to read the debug
29894 information in such binaries.
29896 The @samp{zlib} library is likely included with your operating system
29897 distribution; if it is not, you can get the latest version from
29898 @url{http://zlib.net}.
29901 @value{GDBN}'s features related to character sets (@pxref{Character
29902 Sets}) require a functioning @code{iconv} implementation. If you are
29903 on a GNU system, then this is provided by the GNU C Library. Some
29904 other systems also provide a working @code{iconv}.
29906 On systems with @code{iconv}, you can install GNU Libiconv. If you
29907 have previously installed Libiconv, you can use the
29908 @option{--with-libiconv-prefix} option to configure.
29910 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
29911 arrange to build Libiconv if a directory named @file{libiconv} appears
29912 in the top-most source directory. If Libiconv is built this way, and
29913 if the operating system does not provide a suitable @code{iconv}
29914 implementation, then the just-built library will automatically be used
29915 by @value{GDBN}. One easy way to set this up is to download GNU
29916 Libiconv, unpack it, and then rename the directory holding the
29917 Libiconv source code to @samp{libiconv}.
29920 @node Running Configure
29921 @section Invoking the @value{GDBN} @file{configure} Script
29922 @cindex configuring @value{GDBN}
29923 @value{GDBN} comes with a @file{configure} script that automates the process
29924 of preparing @value{GDBN} for installation; you can then use @code{make} to
29925 build the @code{gdb} program.
29927 @c irrelevant in info file; it's as current as the code it lives with.
29928 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
29929 look at the @file{README} file in the sources; we may have improved the
29930 installation procedures since publishing this manual.}
29933 The @value{GDBN} distribution includes all the source code you need for
29934 @value{GDBN} in a single directory, whose name is usually composed by
29935 appending the version number to @samp{gdb}.
29937 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
29938 @file{gdb-@value{GDBVN}} directory. That directory contains:
29941 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
29942 script for configuring @value{GDBN} and all its supporting libraries
29944 @item gdb-@value{GDBVN}/gdb
29945 the source specific to @value{GDBN} itself
29947 @item gdb-@value{GDBVN}/bfd
29948 source for the Binary File Descriptor library
29950 @item gdb-@value{GDBVN}/include
29951 @sc{gnu} include files
29953 @item gdb-@value{GDBVN}/libiberty
29954 source for the @samp{-liberty} free software library
29956 @item gdb-@value{GDBVN}/opcodes
29957 source for the library of opcode tables and disassemblers
29959 @item gdb-@value{GDBVN}/readline
29960 source for the @sc{gnu} command-line interface
29962 @item gdb-@value{GDBVN}/glob
29963 source for the @sc{gnu} filename pattern-matching subroutine
29965 @item gdb-@value{GDBVN}/mmalloc
29966 source for the @sc{gnu} memory-mapped malloc package
29969 The simplest way to configure and build @value{GDBN} is to run @file{configure}
29970 from the @file{gdb-@var{version-number}} source directory, which in
29971 this example is the @file{gdb-@value{GDBVN}} directory.
29973 First switch to the @file{gdb-@var{version-number}} source directory
29974 if you are not already in it; then run @file{configure}. Pass the
29975 identifier for the platform on which @value{GDBN} will run as an
29981 cd gdb-@value{GDBVN}
29982 ./configure @var{host}
29987 where @var{host} is an identifier such as @samp{sun4} or
29988 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
29989 (You can often leave off @var{host}; @file{configure} tries to guess the
29990 correct value by examining your system.)
29992 Running @samp{configure @var{host}} and then running @code{make} builds the
29993 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
29994 libraries, then @code{gdb} itself. The configured source files, and the
29995 binaries, are left in the corresponding source directories.
29998 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
29999 system does not recognize this automatically when you run a different
30000 shell, you may need to run @code{sh} on it explicitly:
30003 sh configure @var{host}
30006 If you run @file{configure} from a directory that contains source
30007 directories for multiple libraries or programs, such as the
30008 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
30010 creates configuration files for every directory level underneath (unless
30011 you tell it not to, with the @samp{--norecursion} option).
30013 You should run the @file{configure} script from the top directory in the
30014 source tree, the @file{gdb-@var{version-number}} directory. If you run
30015 @file{configure} from one of the subdirectories, you will configure only
30016 that subdirectory. That is usually not what you want. In particular,
30017 if you run the first @file{configure} from the @file{gdb} subdirectory
30018 of the @file{gdb-@var{version-number}} directory, you will omit the
30019 configuration of @file{bfd}, @file{readline}, and other sibling
30020 directories of the @file{gdb} subdirectory. This leads to build errors
30021 about missing include files such as @file{bfd/bfd.h}.
30023 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
30024 However, you should make sure that the shell on your path (named by
30025 the @samp{SHELL} environment variable) is publicly readable. Remember
30026 that @value{GDBN} uses the shell to start your program---some systems refuse to
30027 let @value{GDBN} debug child processes whose programs are not readable.
30029 @node Separate Objdir
30030 @section Compiling @value{GDBN} in Another Directory
30032 If you want to run @value{GDBN} versions for several host or target machines,
30033 you need a different @code{gdb} compiled for each combination of
30034 host and target. @file{configure} is designed to make this easy by
30035 allowing you to generate each configuration in a separate subdirectory,
30036 rather than in the source directory. If your @code{make} program
30037 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
30038 @code{make} in each of these directories builds the @code{gdb}
30039 program specified there.
30041 To build @code{gdb} in a separate directory, run @file{configure}
30042 with the @samp{--srcdir} option to specify where to find the source.
30043 (You also need to specify a path to find @file{configure}
30044 itself from your working directory. If the path to @file{configure}
30045 would be the same as the argument to @samp{--srcdir}, you can leave out
30046 the @samp{--srcdir} option; it is assumed.)
30048 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
30049 separate directory for a Sun 4 like this:
30053 cd gdb-@value{GDBVN}
30056 ../gdb-@value{GDBVN}/configure sun4
30061 When @file{configure} builds a configuration using a remote source
30062 directory, it creates a tree for the binaries with the same structure
30063 (and using the same names) as the tree under the source directory. In
30064 the example, you'd find the Sun 4 library @file{libiberty.a} in the
30065 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
30066 @file{gdb-sun4/gdb}.
30068 Make sure that your path to the @file{configure} script has just one
30069 instance of @file{gdb} in it. If your path to @file{configure} looks
30070 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
30071 one subdirectory of @value{GDBN}, not the whole package. This leads to
30072 build errors about missing include files such as @file{bfd/bfd.h}.
30074 One popular reason to build several @value{GDBN} configurations in separate
30075 directories is to configure @value{GDBN} for cross-compiling (where
30076 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
30077 programs that run on another machine---the @dfn{target}).
30078 You specify a cross-debugging target by
30079 giving the @samp{--target=@var{target}} option to @file{configure}.
30081 When you run @code{make} to build a program or library, you must run
30082 it in a configured directory---whatever directory you were in when you
30083 called @file{configure} (or one of its subdirectories).
30085 The @code{Makefile} that @file{configure} generates in each source
30086 directory also runs recursively. If you type @code{make} in a source
30087 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
30088 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
30089 will build all the required libraries, and then build GDB.
30091 When you have multiple hosts or targets configured in separate
30092 directories, you can run @code{make} on them in parallel (for example,
30093 if they are NFS-mounted on each of the hosts); they will not interfere
30097 @section Specifying Names for Hosts and Targets
30099 The specifications used for hosts and targets in the @file{configure}
30100 script are based on a three-part naming scheme, but some short predefined
30101 aliases are also supported. The full naming scheme encodes three pieces
30102 of information in the following pattern:
30105 @var{architecture}-@var{vendor}-@var{os}
30108 For example, you can use the alias @code{sun4} as a @var{host} argument,
30109 or as the value for @var{target} in a @code{--target=@var{target}}
30110 option. The equivalent full name is @samp{sparc-sun-sunos4}.
30112 The @file{configure} script accompanying @value{GDBN} does not provide
30113 any query facility to list all supported host and target names or
30114 aliases. @file{configure} calls the Bourne shell script
30115 @code{config.sub} to map abbreviations to full names; you can read the
30116 script, if you wish, or you can use it to test your guesses on
30117 abbreviations---for example:
30120 % sh config.sub i386-linux
30122 % sh config.sub alpha-linux
30123 alpha-unknown-linux-gnu
30124 % sh config.sub hp9k700
30126 % sh config.sub sun4
30127 sparc-sun-sunos4.1.1
30128 % sh config.sub sun3
30129 m68k-sun-sunos4.1.1
30130 % sh config.sub i986v
30131 Invalid configuration `i986v': machine `i986v' not recognized
30135 @code{config.sub} is also distributed in the @value{GDBN} source
30136 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
30138 @node Configure Options
30139 @section @file{configure} Options
30141 Here is a summary of the @file{configure} options and arguments that
30142 are most often useful for building @value{GDBN}. @file{configure} also has
30143 several other options not listed here. @inforef{What Configure
30144 Does,,configure.info}, for a full explanation of @file{configure}.
30147 configure @r{[}--help@r{]}
30148 @r{[}--prefix=@var{dir}@r{]}
30149 @r{[}--exec-prefix=@var{dir}@r{]}
30150 @r{[}--srcdir=@var{dirname}@r{]}
30151 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
30152 @r{[}--target=@var{target}@r{]}
30157 You may introduce options with a single @samp{-} rather than
30158 @samp{--} if you prefer; but you may abbreviate option names if you use
30163 Display a quick summary of how to invoke @file{configure}.
30165 @item --prefix=@var{dir}
30166 Configure the source to install programs and files under directory
30169 @item --exec-prefix=@var{dir}
30170 Configure the source to install programs under directory
30173 @c avoid splitting the warning from the explanation:
30175 @item --srcdir=@var{dirname}
30176 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
30177 @code{make} that implements the @code{VPATH} feature.}@*
30178 Use this option to make configurations in directories separate from the
30179 @value{GDBN} source directories. Among other things, you can use this to
30180 build (or maintain) several configurations simultaneously, in separate
30181 directories. @file{configure} writes configuration-specific files in
30182 the current directory, but arranges for them to use the source in the
30183 directory @var{dirname}. @file{configure} creates directories under
30184 the working directory in parallel to the source directories below
30187 @item --norecursion
30188 Configure only the directory level where @file{configure} is executed; do not
30189 propagate configuration to subdirectories.
30191 @item --target=@var{target}
30192 Configure @value{GDBN} for cross-debugging programs running on the specified
30193 @var{target}. Without this option, @value{GDBN} is configured to debug
30194 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
30196 There is no convenient way to generate a list of all available targets.
30198 @item @var{host} @dots{}
30199 Configure @value{GDBN} to run on the specified @var{host}.
30201 There is no convenient way to generate a list of all available hosts.
30204 There are many other options available as well, but they are generally
30205 needed for special purposes only.
30207 @node System-wide configuration
30208 @section System-wide configuration and settings
30209 @cindex system-wide init file
30211 @value{GDBN} can be configured to have a system-wide init file;
30212 this file will be read and executed at startup (@pxref{Startup, , What
30213 @value{GDBN} does during startup}).
30215 Here is the corresponding configure option:
30218 @item --with-system-gdbinit=@var{file}
30219 Specify that the default location of the system-wide init file is
30223 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
30224 it may be subject to relocation. Two possible cases:
30228 If the default location of this init file contains @file{$prefix},
30229 it will be subject to relocation. Suppose that the configure options
30230 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
30231 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
30232 init file is looked for as @file{$install/etc/gdbinit} instead of
30233 @file{$prefix/etc/gdbinit}.
30236 By contrast, if the default location does not contain the prefix,
30237 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
30238 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
30239 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
30240 wherever @value{GDBN} is installed.
30243 @node Maintenance Commands
30244 @appendix Maintenance Commands
30245 @cindex maintenance commands
30246 @cindex internal commands
30248 In addition to commands intended for @value{GDBN} users, @value{GDBN}
30249 includes a number of commands intended for @value{GDBN} developers,
30250 that are not documented elsewhere in this manual. These commands are
30251 provided here for reference. (For commands that turn on debugging
30252 messages, see @ref{Debugging Output}.)
30255 @kindex maint agent
30256 @kindex maint agent-eval
30257 @item maint agent @var{expression}
30258 @itemx maint agent-eval @var{expression}
30259 Translate the given @var{expression} into remote agent bytecodes.
30260 This command is useful for debugging the Agent Expression mechanism
30261 (@pxref{Agent Expressions}). The @samp{agent} version produces an
30262 expression useful for data collection, such as by tracepoints, while
30263 @samp{maint agent-eval} produces an expression that evaluates directly
30264 to a result. For instance, a collection expression for @code{globa +
30265 globb} will include bytecodes to record four bytes of memory at each
30266 of the addresses of @code{globa} and @code{globb}, while discarding
30267 the result of the addition, while an evaluation expression will do the
30268 addition and return the sum.
30270 @kindex maint info breakpoints
30271 @item @anchor{maint info breakpoints}maint info breakpoints
30272 Using the same format as @samp{info breakpoints}, display both the
30273 breakpoints you've set explicitly, and those @value{GDBN} is using for
30274 internal purposes. Internal breakpoints are shown with negative
30275 breakpoint numbers. The type column identifies what kind of breakpoint
30280 Normal, explicitly set breakpoint.
30283 Normal, explicitly set watchpoint.
30286 Internal breakpoint, used to handle correctly stepping through
30287 @code{longjmp} calls.
30289 @item longjmp resume
30290 Internal breakpoint at the target of a @code{longjmp}.
30293 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
30296 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
30299 Shared library events.
30303 @kindex set displaced-stepping
30304 @kindex show displaced-stepping
30305 @cindex displaced stepping support
30306 @cindex out-of-line single-stepping
30307 @item set displaced-stepping
30308 @itemx show displaced-stepping
30309 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
30310 if the target supports it. Displaced stepping is a way to single-step
30311 over breakpoints without removing them from the inferior, by executing
30312 an out-of-line copy of the instruction that was originally at the
30313 breakpoint location. It is also known as out-of-line single-stepping.
30316 @item set displaced-stepping on
30317 If the target architecture supports it, @value{GDBN} will use
30318 displaced stepping to step over breakpoints.
30320 @item set displaced-stepping off
30321 @value{GDBN} will not use displaced stepping to step over breakpoints,
30322 even if such is supported by the target architecture.
30324 @cindex non-stop mode, and @samp{set displaced-stepping}
30325 @item set displaced-stepping auto
30326 This is the default mode. @value{GDBN} will use displaced stepping
30327 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
30328 architecture supports displaced stepping.
30331 @kindex maint check-symtabs
30332 @item maint check-symtabs
30333 Check the consistency of psymtabs and symtabs.
30335 @kindex maint cplus first_component
30336 @item maint cplus first_component @var{name}
30337 Print the first C@t{++} class/namespace component of @var{name}.
30339 @kindex maint cplus namespace
30340 @item maint cplus namespace
30341 Print the list of possible C@t{++} namespaces.
30343 @kindex maint demangle
30344 @item maint demangle @var{name}
30345 Demangle a C@t{++} or Objective-C mangled @var{name}.
30347 @kindex maint deprecate
30348 @kindex maint undeprecate
30349 @cindex deprecated commands
30350 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
30351 @itemx maint undeprecate @var{command}
30352 Deprecate or undeprecate the named @var{command}. Deprecated commands
30353 cause @value{GDBN} to issue a warning when you use them. The optional
30354 argument @var{replacement} says which newer command should be used in
30355 favor of the deprecated one; if it is given, @value{GDBN} will mention
30356 the replacement as part of the warning.
30358 @kindex maint dump-me
30359 @item maint dump-me
30360 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
30361 Cause a fatal signal in the debugger and force it to dump its core.
30362 This is supported only on systems which support aborting a program
30363 with the @code{SIGQUIT} signal.
30365 @kindex maint internal-error
30366 @kindex maint internal-warning
30367 @item maint internal-error @r{[}@var{message-text}@r{]}
30368 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
30369 Cause @value{GDBN} to call the internal function @code{internal_error}
30370 or @code{internal_warning} and hence behave as though an internal error
30371 or internal warning has been detected. In addition to reporting the
30372 internal problem, these functions give the user the opportunity to
30373 either quit @value{GDBN} or create a core file of the current
30374 @value{GDBN} session.
30376 These commands take an optional parameter @var{message-text} that is
30377 used as the text of the error or warning message.
30379 Here's an example of using @code{internal-error}:
30382 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
30383 @dots{}/maint.c:121: internal-error: testing, 1, 2
30384 A problem internal to GDB has been detected. Further
30385 debugging may prove unreliable.
30386 Quit this debugging session? (y or n) @kbd{n}
30387 Create a core file? (y or n) @kbd{n}
30391 @cindex @value{GDBN} internal error
30392 @cindex internal errors, control of @value{GDBN} behavior
30394 @kindex maint set internal-error
30395 @kindex maint show internal-error
30396 @kindex maint set internal-warning
30397 @kindex maint show internal-warning
30398 @item maint set internal-error @var{action} [ask|yes|no]
30399 @itemx maint show internal-error @var{action}
30400 @itemx maint set internal-warning @var{action} [ask|yes|no]
30401 @itemx maint show internal-warning @var{action}
30402 When @value{GDBN} reports an internal problem (error or warning) it
30403 gives the user the opportunity to both quit @value{GDBN} and create a
30404 core file of the current @value{GDBN} session. These commands let you
30405 override the default behaviour for each particular @var{action},
30406 described in the table below.
30410 You can specify that @value{GDBN} should always (yes) or never (no)
30411 quit. The default is to ask the user what to do.
30414 You can specify that @value{GDBN} should always (yes) or never (no)
30415 create a core file. The default is to ask the user what to do.
30418 @kindex maint packet
30419 @item maint packet @var{text}
30420 If @value{GDBN} is talking to an inferior via the serial protocol,
30421 then this command sends the string @var{text} to the inferior, and
30422 displays the response packet. @value{GDBN} supplies the initial
30423 @samp{$} character, the terminating @samp{#} character, and the
30426 @kindex maint print architecture
30427 @item maint print architecture @r{[}@var{file}@r{]}
30428 Print the entire architecture configuration. The optional argument
30429 @var{file} names the file where the output goes.
30431 @kindex maint print c-tdesc
30432 @item maint print c-tdesc
30433 Print the current target description (@pxref{Target Descriptions}) as
30434 a C source file. The created source file can be used in @value{GDBN}
30435 when an XML parser is not available to parse the description.
30437 @kindex maint print dummy-frames
30438 @item maint print dummy-frames
30439 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
30442 (@value{GDBP}) @kbd{b add}
30444 (@value{GDBP}) @kbd{print add(2,3)}
30445 Breakpoint 2, add (a=2, b=3) at @dots{}
30447 The program being debugged stopped while in a function called from GDB.
30449 (@value{GDBP}) @kbd{maint print dummy-frames}
30450 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
30451 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
30452 call_lo=0x01014000 call_hi=0x01014001
30456 Takes an optional file parameter.
30458 @kindex maint print registers
30459 @kindex maint print raw-registers
30460 @kindex maint print cooked-registers
30461 @kindex maint print register-groups
30462 @item maint print registers @r{[}@var{file}@r{]}
30463 @itemx maint print raw-registers @r{[}@var{file}@r{]}
30464 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
30465 @itemx maint print register-groups @r{[}@var{file}@r{]}
30466 Print @value{GDBN}'s internal register data structures.
30468 The command @code{maint print raw-registers} includes the contents of
30469 the raw register cache; the command @code{maint print cooked-registers}
30470 includes the (cooked) value of all registers, including registers which
30471 aren't available on the target nor visible to user; and the
30472 command @code{maint print register-groups} includes the groups that each
30473 register is a member of. @xref{Registers,, Registers, gdbint,
30474 @value{GDBN} Internals}.
30476 These commands take an optional parameter, a file name to which to
30477 write the information.
30479 @kindex maint print reggroups
30480 @item maint print reggroups @r{[}@var{file}@r{]}
30481 Print @value{GDBN}'s internal register group data structures. The
30482 optional argument @var{file} tells to what file to write the
30485 The register groups info looks like this:
30488 (@value{GDBP}) @kbd{maint print reggroups}
30501 This command forces @value{GDBN} to flush its internal register cache.
30503 @kindex maint print objfiles
30504 @cindex info for known object files
30505 @item maint print objfiles
30506 Print a dump of all known object files. For each object file, this
30507 command prints its name, address in memory, and all of its psymtabs
30510 @kindex maint print section-scripts
30511 @cindex info for known .debug_gdb_scripts-loaded scripts
30512 @item maint print section-scripts [@var{regexp}]
30513 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
30514 If @var{regexp} is specified, only print scripts loaded by object files
30515 matching @var{regexp}.
30516 For each script, this command prints its name as specified in the objfile,
30517 and the full path if known.
30518 @xref{.debug_gdb_scripts section}.
30520 @kindex maint print statistics
30521 @cindex bcache statistics
30522 @item maint print statistics
30523 This command prints, for each object file in the program, various data
30524 about that object file followed by the byte cache (@dfn{bcache})
30525 statistics for the object file. The objfile data includes the number
30526 of minimal, partial, full, and stabs symbols, the number of types
30527 defined by the objfile, the number of as yet unexpanded psym tables,
30528 the number of line tables and string tables, and the amount of memory
30529 used by the various tables. The bcache statistics include the counts,
30530 sizes, and counts of duplicates of all and unique objects, max,
30531 average, and median entry size, total memory used and its overhead and
30532 savings, and various measures of the hash table size and chain
30535 @kindex maint print target-stack
30536 @cindex target stack description
30537 @item maint print target-stack
30538 A @dfn{target} is an interface between the debugger and a particular
30539 kind of file or process. Targets can be stacked in @dfn{strata},
30540 so that more than one target can potentially respond to a request.
30541 In particular, memory accesses will walk down the stack of targets
30542 until they find a target that is interested in handling that particular
30545 This command prints a short description of each layer that was pushed on
30546 the @dfn{target stack}, starting from the top layer down to the bottom one.
30548 @kindex maint print type
30549 @cindex type chain of a data type
30550 @item maint print type @var{expr}
30551 Print the type chain for a type specified by @var{expr}. The argument
30552 can be either a type name or a symbol. If it is a symbol, the type of
30553 that symbol is described. The type chain produced by this command is
30554 a recursive definition of the data type as stored in @value{GDBN}'s
30555 data structures, including its flags and contained types.
30557 @kindex maint set dwarf2 always-disassemble
30558 @kindex maint show dwarf2 always-disassemble
30559 @item maint set dwarf2 always-disassemble
30560 @item maint show dwarf2 always-disassemble
30561 Control the behavior of @code{info address} when using DWARF debugging
30564 The default is @code{off}, which means that @value{GDBN} should try to
30565 describe a variable's location in an easily readable format. When
30566 @code{on}, @value{GDBN} will instead display the DWARF location
30567 expression in an assembly-like format. Note that some locations are
30568 too complex for @value{GDBN} to describe simply; in this case you will
30569 always see the disassembly form.
30571 Here is an example of the resulting disassembly:
30574 (gdb) info addr argc
30575 Symbol "argc" is a complex DWARF expression:
30579 For more information on these expressions, see
30580 @uref{http://www.dwarfstd.org/, the DWARF standard}.
30582 @kindex maint set dwarf2 max-cache-age
30583 @kindex maint show dwarf2 max-cache-age
30584 @item maint set dwarf2 max-cache-age
30585 @itemx maint show dwarf2 max-cache-age
30586 Control the DWARF 2 compilation unit cache.
30588 @cindex DWARF 2 compilation units cache
30589 In object files with inter-compilation-unit references, such as those
30590 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
30591 reader needs to frequently refer to previously read compilation units.
30592 This setting controls how long a compilation unit will remain in the
30593 cache if it is not referenced. A higher limit means that cached
30594 compilation units will be stored in memory longer, and more total
30595 memory will be used. Setting it to zero disables caching, which will
30596 slow down @value{GDBN} startup, but reduce memory consumption.
30598 @kindex maint set profile
30599 @kindex maint show profile
30600 @cindex profiling GDB
30601 @item maint set profile
30602 @itemx maint show profile
30603 Control profiling of @value{GDBN}.
30605 Profiling will be disabled until you use the @samp{maint set profile}
30606 command to enable it. When you enable profiling, the system will begin
30607 collecting timing and execution count data; when you disable profiling or
30608 exit @value{GDBN}, the results will be written to a log file. Remember that
30609 if you use profiling, @value{GDBN} will overwrite the profiling log file
30610 (often called @file{gmon.out}). If you have a record of important profiling
30611 data in a @file{gmon.out} file, be sure to move it to a safe location.
30613 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
30614 compiled with the @samp{-pg} compiler option.
30616 @kindex maint set show-debug-regs
30617 @kindex maint show show-debug-regs
30618 @cindex hardware debug registers
30619 @item maint set show-debug-regs
30620 @itemx maint show show-debug-regs
30621 Control whether to show variables that mirror the hardware debug
30622 registers. Use @code{ON} to enable, @code{OFF} to disable. If
30623 enabled, the debug registers values are shown when @value{GDBN} inserts or
30624 removes a hardware breakpoint or watchpoint, and when the inferior
30625 triggers a hardware-assisted breakpoint or watchpoint.
30627 @kindex maint set show-all-tib
30628 @kindex maint show show-all-tib
30629 @item maint set show-all-tib
30630 @itemx maint show show-all-tib
30631 Control whether to show all non zero areas within a 1k block starting
30632 at thread local base, when using the @samp{info w32 thread-information-block}
30635 @kindex maint space
30636 @cindex memory used by commands
30638 Control whether to display memory usage for each command. If set to a
30639 nonzero value, @value{GDBN} will display how much memory each command
30640 took, following the command's own output. This can also be requested
30641 by invoking @value{GDBN} with the @option{--statistics} command-line
30642 switch (@pxref{Mode Options}).
30645 @cindex time of command execution
30647 Control whether to display the execution time for each command. If
30648 set to a nonzero value, @value{GDBN} will display how much time it
30649 took to execute each command, following the command's own output.
30650 The time is not printed for the commands that run the target, since
30651 there's no mechanism currently to compute how much time was spend
30652 by @value{GDBN} and how much time was spend by the program been debugged.
30653 it's not possibly currently
30654 This can also be requested by invoking @value{GDBN} with the
30655 @option{--statistics} command-line switch (@pxref{Mode Options}).
30657 @kindex maint translate-address
30658 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
30659 Find the symbol stored at the location specified by the address
30660 @var{addr} and an optional section name @var{section}. If found,
30661 @value{GDBN} prints the name of the closest symbol and an offset from
30662 the symbol's location to the specified address. This is similar to
30663 the @code{info address} command (@pxref{Symbols}), except that this
30664 command also allows to find symbols in other sections.
30666 If section was not specified, the section in which the symbol was found
30667 is also printed. For dynamically linked executables, the name of
30668 executable or shared library containing the symbol is printed as well.
30672 The following command is useful for non-interactive invocations of
30673 @value{GDBN}, such as in the test suite.
30676 @item set watchdog @var{nsec}
30677 @kindex set watchdog
30678 @cindex watchdog timer
30679 @cindex timeout for commands
30680 Set the maximum number of seconds @value{GDBN} will wait for the
30681 target operation to finish. If this time expires, @value{GDBN}
30682 reports and error and the command is aborted.
30684 @item show watchdog
30685 Show the current setting of the target wait timeout.
30688 @node Remote Protocol
30689 @appendix @value{GDBN} Remote Serial Protocol
30694 * Stop Reply Packets::
30695 * General Query Packets::
30696 * Architecture-Specific Protocol Details::
30697 * Tracepoint Packets::
30698 * Host I/O Packets::
30700 * Notification Packets::
30701 * Remote Non-Stop::
30702 * Packet Acknowledgment::
30704 * File-I/O Remote Protocol Extension::
30705 * Library List Format::
30706 * Memory Map Format::
30707 * Thread List Format::
30713 There may be occasions when you need to know something about the
30714 protocol---for example, if there is only one serial port to your target
30715 machine, you might want your program to do something special if it
30716 recognizes a packet meant for @value{GDBN}.
30718 In the examples below, @samp{->} and @samp{<-} are used to indicate
30719 transmitted and received data, respectively.
30721 @cindex protocol, @value{GDBN} remote serial
30722 @cindex serial protocol, @value{GDBN} remote
30723 @cindex remote serial protocol
30724 All @value{GDBN} commands and responses (other than acknowledgments
30725 and notifications, see @ref{Notification Packets}) are sent as a
30726 @var{packet}. A @var{packet} is introduced with the character
30727 @samp{$}, the actual @var{packet-data}, and the terminating character
30728 @samp{#} followed by a two-digit @var{checksum}:
30731 @code{$}@var{packet-data}@code{#}@var{checksum}
30735 @cindex checksum, for @value{GDBN} remote
30737 The two-digit @var{checksum} is computed as the modulo 256 sum of all
30738 characters between the leading @samp{$} and the trailing @samp{#} (an
30739 eight bit unsigned checksum).
30741 Implementors should note that prior to @value{GDBN} 5.0 the protocol
30742 specification also included an optional two-digit @var{sequence-id}:
30745 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
30748 @cindex sequence-id, for @value{GDBN} remote
30750 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
30751 has never output @var{sequence-id}s. Stubs that handle packets added
30752 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
30754 When either the host or the target machine receives a packet, the first
30755 response expected is an acknowledgment: either @samp{+} (to indicate
30756 the package was received correctly) or @samp{-} (to request
30760 -> @code{$}@var{packet-data}@code{#}@var{checksum}
30765 The @samp{+}/@samp{-} acknowledgments can be disabled
30766 once a connection is established.
30767 @xref{Packet Acknowledgment}, for details.
30769 The host (@value{GDBN}) sends @var{command}s, and the target (the
30770 debugging stub incorporated in your program) sends a @var{response}. In
30771 the case of step and continue @var{command}s, the response is only sent
30772 when the operation has completed, and the target has again stopped all
30773 threads in all attached processes. This is the default all-stop mode
30774 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
30775 execution mode; see @ref{Remote Non-Stop}, for details.
30777 @var{packet-data} consists of a sequence of characters with the
30778 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
30781 @cindex remote protocol, field separator
30782 Fields within the packet should be separated using @samp{,} @samp{;} or
30783 @samp{:}. Except where otherwise noted all numbers are represented in
30784 @sc{hex} with leading zeros suppressed.
30786 Implementors should note that prior to @value{GDBN} 5.0, the character
30787 @samp{:} could not appear as the third character in a packet (as it
30788 would potentially conflict with the @var{sequence-id}).
30790 @cindex remote protocol, binary data
30791 @anchor{Binary Data}
30792 Binary data in most packets is encoded either as two hexadecimal
30793 digits per byte of binary data. This allowed the traditional remote
30794 protocol to work over connections which were only seven-bit clean.
30795 Some packets designed more recently assume an eight-bit clean
30796 connection, and use a more efficient encoding to send and receive
30799 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
30800 as an escape character. Any escaped byte is transmitted as the escape
30801 character followed by the original character XORed with @code{0x20}.
30802 For example, the byte @code{0x7d} would be transmitted as the two
30803 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
30804 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
30805 @samp{@}}) must always be escaped. Responses sent by the stub
30806 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
30807 is not interpreted as the start of a run-length encoded sequence
30810 Response @var{data} can be run-length encoded to save space.
30811 Run-length encoding replaces runs of identical characters with one
30812 instance of the repeated character, followed by a @samp{*} and a
30813 repeat count. The repeat count is itself sent encoded, to avoid
30814 binary characters in @var{data}: a value of @var{n} is sent as
30815 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
30816 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
30817 code 32) for a repeat count of 3. (This is because run-length
30818 encoding starts to win for counts 3 or more.) Thus, for example,
30819 @samp{0* } is a run-length encoding of ``0000'': the space character
30820 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
30823 The printable characters @samp{#} and @samp{$} or with a numeric value
30824 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
30825 seven repeats (@samp{$}) can be expanded using a repeat count of only
30826 five (@samp{"}). For example, @samp{00000000} can be encoded as
30829 The error response returned for some packets includes a two character
30830 error number. That number is not well defined.
30832 @cindex empty response, for unsupported packets
30833 For any @var{command} not supported by the stub, an empty response
30834 (@samp{$#00}) should be returned. That way it is possible to extend the
30835 protocol. A newer @value{GDBN} can tell if a packet is supported based
30838 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
30839 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
30845 The following table provides a complete list of all currently defined
30846 @var{command}s and their corresponding response @var{data}.
30847 @xref{File-I/O Remote Protocol Extension}, for details about the File
30848 I/O extension of the remote protocol.
30850 Each packet's description has a template showing the packet's overall
30851 syntax, followed by an explanation of the packet's meaning. We
30852 include spaces in some of the templates for clarity; these are not
30853 part of the packet's syntax. No @value{GDBN} packet uses spaces to
30854 separate its components. For example, a template like @samp{foo
30855 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
30856 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
30857 @var{baz}. @value{GDBN} does not transmit a space character between the
30858 @samp{foo} and the @var{bar}, or between the @var{bar} and the
30861 @cindex @var{thread-id}, in remote protocol
30862 @anchor{thread-id syntax}
30863 Several packets and replies include a @var{thread-id} field to identify
30864 a thread. Normally these are positive numbers with a target-specific
30865 interpretation, formatted as big-endian hex strings. A @var{thread-id}
30866 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
30869 In addition, the remote protocol supports a multiprocess feature in
30870 which the @var{thread-id} syntax is extended to optionally include both
30871 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
30872 The @var{pid} (process) and @var{tid} (thread) components each have the
30873 format described above: a positive number with target-specific
30874 interpretation formatted as a big-endian hex string, literal @samp{-1}
30875 to indicate all processes or threads (respectively), or @samp{0} to
30876 indicate an arbitrary process or thread. Specifying just a process, as
30877 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
30878 error to specify all processes but a specific thread, such as
30879 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
30880 for those packets and replies explicitly documented to include a process
30881 ID, rather than a @var{thread-id}.
30883 The multiprocess @var{thread-id} syntax extensions are only used if both
30884 @value{GDBN} and the stub report support for the @samp{multiprocess}
30885 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
30888 Note that all packet forms beginning with an upper- or lower-case
30889 letter, other than those described here, are reserved for future use.
30891 Here are the packet descriptions.
30896 @cindex @samp{!} packet
30897 @anchor{extended mode}
30898 Enable extended mode. In extended mode, the remote server is made
30899 persistent. The @samp{R} packet is used to restart the program being
30905 The remote target both supports and has enabled extended mode.
30909 @cindex @samp{?} packet
30910 Indicate the reason the target halted. The reply is the same as for
30911 step and continue. This packet has a special interpretation when the
30912 target is in non-stop mode; see @ref{Remote Non-Stop}.
30915 @xref{Stop Reply Packets}, for the reply specifications.
30917 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
30918 @cindex @samp{A} packet
30919 Initialized @code{argv[]} array passed into program. @var{arglen}
30920 specifies the number of bytes in the hex encoded byte stream
30921 @var{arg}. See @code{gdbserver} for more details.
30926 The arguments were set.
30932 @cindex @samp{b} packet
30933 (Don't use this packet; its behavior is not well-defined.)
30934 Change the serial line speed to @var{baud}.
30936 JTC: @emph{When does the transport layer state change? When it's
30937 received, or after the ACK is transmitted. In either case, there are
30938 problems if the command or the acknowledgment packet is dropped.}
30940 Stan: @emph{If people really wanted to add something like this, and get
30941 it working for the first time, they ought to modify ser-unix.c to send
30942 some kind of out-of-band message to a specially-setup stub and have the
30943 switch happen "in between" packets, so that from remote protocol's point
30944 of view, nothing actually happened.}
30946 @item B @var{addr},@var{mode}
30947 @cindex @samp{B} packet
30948 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
30949 breakpoint at @var{addr}.
30951 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
30952 (@pxref{insert breakpoint or watchpoint packet}).
30954 @cindex @samp{bc} packet
30957 Backward continue. Execute the target system in reverse. No parameter.
30958 @xref{Reverse Execution}, for more information.
30961 @xref{Stop Reply Packets}, for the reply specifications.
30963 @cindex @samp{bs} packet
30966 Backward single step. Execute one instruction in reverse. No parameter.
30967 @xref{Reverse Execution}, for more information.
30970 @xref{Stop Reply Packets}, for the reply specifications.
30972 @item c @r{[}@var{addr}@r{]}
30973 @cindex @samp{c} packet
30974 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
30975 resume at current address.
30978 @xref{Stop Reply Packets}, for the reply specifications.
30980 @item C @var{sig}@r{[};@var{addr}@r{]}
30981 @cindex @samp{C} packet
30982 Continue with signal @var{sig} (hex signal number). If
30983 @samp{;@var{addr}} is omitted, resume at same address.
30986 @xref{Stop Reply Packets}, for the reply specifications.
30989 @cindex @samp{d} packet
30992 Don't use this packet; instead, define a general set packet
30993 (@pxref{General Query Packets}).
30997 @cindex @samp{D} packet
30998 The first form of the packet is used to detach @value{GDBN} from the
30999 remote system. It is sent to the remote target
31000 before @value{GDBN} disconnects via the @code{detach} command.
31002 The second form, including a process ID, is used when multiprocess
31003 protocol extensions are enabled (@pxref{multiprocess extensions}), to
31004 detach only a specific process. The @var{pid} is specified as a
31005 big-endian hex string.
31015 @item F @var{RC},@var{EE},@var{CF};@var{XX}
31016 @cindex @samp{F} packet
31017 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
31018 This is part of the File-I/O protocol extension. @xref{File-I/O
31019 Remote Protocol Extension}, for the specification.
31022 @anchor{read registers packet}
31023 @cindex @samp{g} packet
31024 Read general registers.
31028 @item @var{XX@dots{}}
31029 Each byte of register data is described by two hex digits. The bytes
31030 with the register are transmitted in target byte order. The size of
31031 each register and their position within the @samp{g} packet are
31032 determined by the @value{GDBN} internal gdbarch functions
31033 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
31034 specification of several standard @samp{g} packets is specified below.
31039 @item G @var{XX@dots{}}
31040 @cindex @samp{G} packet
31041 Write general registers. @xref{read registers packet}, for a
31042 description of the @var{XX@dots{}} data.
31052 @item H @var{c} @var{thread-id}
31053 @cindex @samp{H} packet
31054 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
31055 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
31056 should be @samp{c} for step and continue operations, @samp{g} for other
31057 operations. The thread designator @var{thread-id} has the format and
31058 interpretation described in @ref{thread-id syntax}.
31069 @c 'H': How restrictive (or permissive) is the thread model. If a
31070 @c thread is selected and stopped, are other threads allowed
31071 @c to continue to execute? As I mentioned above, I think the
31072 @c semantics of each command when a thread is selected must be
31073 @c described. For example:
31075 @c 'g': If the stub supports threads and a specific thread is
31076 @c selected, returns the register block from that thread;
31077 @c otherwise returns current registers.
31079 @c 'G' If the stub supports threads and a specific thread is
31080 @c selected, sets the registers of the register block of
31081 @c that thread; otherwise sets current registers.
31083 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
31084 @anchor{cycle step packet}
31085 @cindex @samp{i} packet
31086 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
31087 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
31088 step starting at that address.
31091 @cindex @samp{I} packet
31092 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
31096 @cindex @samp{k} packet
31099 FIXME: @emph{There is no description of how to operate when a specific
31100 thread context has been selected (i.e.@: does 'k' kill only that
31103 @item m @var{addr},@var{length}
31104 @cindex @samp{m} packet
31105 Read @var{length} bytes of memory starting at address @var{addr}.
31106 Note that @var{addr} may not be aligned to any particular boundary.
31108 The stub need not use any particular size or alignment when gathering
31109 data from memory for the response; even if @var{addr} is word-aligned
31110 and @var{length} is a multiple of the word size, the stub is free to
31111 use byte accesses, or not. For this reason, this packet may not be
31112 suitable for accessing memory-mapped I/O devices.
31113 @cindex alignment of remote memory accesses
31114 @cindex size of remote memory accesses
31115 @cindex memory, alignment and size of remote accesses
31119 @item @var{XX@dots{}}
31120 Memory contents; each byte is transmitted as a two-digit hexadecimal
31121 number. The reply may contain fewer bytes than requested if the
31122 server was able to read only part of the region of memory.
31127 @item M @var{addr},@var{length}:@var{XX@dots{}}
31128 @cindex @samp{M} packet
31129 Write @var{length} bytes of memory starting at address @var{addr}.
31130 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
31131 hexadecimal number.
31138 for an error (this includes the case where only part of the data was
31143 @cindex @samp{p} packet
31144 Read the value of register @var{n}; @var{n} is in hex.
31145 @xref{read registers packet}, for a description of how the returned
31146 register value is encoded.
31150 @item @var{XX@dots{}}
31151 the register's value
31155 Indicating an unrecognized @var{query}.
31158 @item P @var{n@dots{}}=@var{r@dots{}}
31159 @anchor{write register packet}
31160 @cindex @samp{P} packet
31161 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
31162 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
31163 digits for each byte in the register (target byte order).
31173 @item q @var{name} @var{params}@dots{}
31174 @itemx Q @var{name} @var{params}@dots{}
31175 @cindex @samp{q} packet
31176 @cindex @samp{Q} packet
31177 General query (@samp{q}) and set (@samp{Q}). These packets are
31178 described fully in @ref{General Query Packets}.
31181 @cindex @samp{r} packet
31182 Reset the entire system.
31184 Don't use this packet; use the @samp{R} packet instead.
31187 @cindex @samp{R} packet
31188 Restart the program being debugged. @var{XX}, while needed, is ignored.
31189 This packet is only available in extended mode (@pxref{extended mode}).
31191 The @samp{R} packet has no reply.
31193 @item s @r{[}@var{addr}@r{]}
31194 @cindex @samp{s} packet
31195 Single step. @var{addr} is the address at which to resume. If
31196 @var{addr} is omitted, resume at same address.
31199 @xref{Stop Reply Packets}, for the reply specifications.
31201 @item S @var{sig}@r{[};@var{addr}@r{]}
31202 @anchor{step with signal packet}
31203 @cindex @samp{S} packet
31204 Step with signal. This is analogous to the @samp{C} packet, but
31205 requests a single-step, rather than a normal resumption of execution.
31208 @xref{Stop Reply Packets}, for the reply specifications.
31210 @item t @var{addr}:@var{PP},@var{MM}
31211 @cindex @samp{t} packet
31212 Search backwards starting at address @var{addr} for a match with pattern
31213 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
31214 @var{addr} must be at least 3 digits.
31216 @item T @var{thread-id}
31217 @cindex @samp{T} packet
31218 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
31223 thread is still alive
31229 Packets starting with @samp{v} are identified by a multi-letter name,
31230 up to the first @samp{;} or @samp{?} (or the end of the packet).
31232 @item vAttach;@var{pid}
31233 @cindex @samp{vAttach} packet
31234 Attach to a new process with the specified process ID @var{pid}.
31235 The process ID is a
31236 hexadecimal integer identifying the process. In all-stop mode, all
31237 threads in the attached process are stopped; in non-stop mode, it may be
31238 attached without being stopped if that is supported by the target.
31240 @c In non-stop mode, on a successful vAttach, the stub should set the
31241 @c current thread to a thread of the newly-attached process. After
31242 @c attaching, GDB queries for the attached process's thread ID with qC.
31243 @c Also note that, from a user perspective, whether or not the
31244 @c target is stopped on attach in non-stop mode depends on whether you
31245 @c use the foreground or background version of the attach command, not
31246 @c on what vAttach does; GDB does the right thing with respect to either
31247 @c stopping or restarting threads.
31249 This packet is only available in extended mode (@pxref{extended mode}).
31255 @item @r{Any stop packet}
31256 for success in all-stop mode (@pxref{Stop Reply Packets})
31258 for success in non-stop mode (@pxref{Remote Non-Stop})
31261 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
31262 @cindex @samp{vCont} packet
31263 Resume the inferior, specifying different actions for each thread.
31264 If an action is specified with no @var{thread-id}, then it is applied to any
31265 threads that don't have a specific action specified; if no default action is
31266 specified then other threads should remain stopped in all-stop mode and
31267 in their current state in non-stop mode.
31268 Specifying multiple
31269 default actions is an error; specifying no actions is also an error.
31270 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
31272 Currently supported actions are:
31278 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
31282 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
31287 The optional argument @var{addr} normally associated with the
31288 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
31289 not supported in @samp{vCont}.
31291 The @samp{t} action is only relevant in non-stop mode
31292 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
31293 A stop reply should be generated for any affected thread not already stopped.
31294 When a thread is stopped by means of a @samp{t} action,
31295 the corresponding stop reply should indicate that the thread has stopped with
31296 signal @samp{0}, regardless of whether the target uses some other signal
31297 as an implementation detail.
31300 @xref{Stop Reply Packets}, for the reply specifications.
31303 @cindex @samp{vCont?} packet
31304 Request a list of actions supported by the @samp{vCont} packet.
31308 @item vCont@r{[};@var{action}@dots{}@r{]}
31309 The @samp{vCont} packet is supported. Each @var{action} is a supported
31310 command in the @samp{vCont} packet.
31312 The @samp{vCont} packet is not supported.
31315 @item vFile:@var{operation}:@var{parameter}@dots{}
31316 @cindex @samp{vFile} packet
31317 Perform a file operation on the target system. For details,
31318 see @ref{Host I/O Packets}.
31320 @item vFlashErase:@var{addr},@var{length}
31321 @cindex @samp{vFlashErase} packet
31322 Direct the stub to erase @var{length} bytes of flash starting at
31323 @var{addr}. The region may enclose any number of flash blocks, but
31324 its start and end must fall on block boundaries, as indicated by the
31325 flash block size appearing in the memory map (@pxref{Memory Map
31326 Format}). @value{GDBN} groups flash memory programming operations
31327 together, and sends a @samp{vFlashDone} request after each group; the
31328 stub is allowed to delay erase operation until the @samp{vFlashDone}
31329 packet is received.
31331 The stub must support @samp{vCont} if it reports support for
31332 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
31333 this case @samp{vCont} actions can be specified to apply to all threads
31334 in a process by using the @samp{p@var{pid}.-1} form of the
31345 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
31346 @cindex @samp{vFlashWrite} packet
31347 Direct the stub to write data to flash address @var{addr}. The data
31348 is passed in binary form using the same encoding as for the @samp{X}
31349 packet (@pxref{Binary Data}). The memory ranges specified by
31350 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
31351 not overlap, and must appear in order of increasing addresses
31352 (although @samp{vFlashErase} packets for higher addresses may already
31353 have been received; the ordering is guaranteed only between
31354 @samp{vFlashWrite} packets). If a packet writes to an address that was
31355 neither erased by a preceding @samp{vFlashErase} packet nor by some other
31356 target-specific method, the results are unpredictable.
31364 for vFlashWrite addressing non-flash memory
31370 @cindex @samp{vFlashDone} packet
31371 Indicate to the stub that flash programming operation is finished.
31372 The stub is permitted to delay or batch the effects of a group of
31373 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
31374 @samp{vFlashDone} packet is received. The contents of the affected
31375 regions of flash memory are unpredictable until the @samp{vFlashDone}
31376 request is completed.
31378 @item vKill;@var{pid}
31379 @cindex @samp{vKill} packet
31380 Kill the process with the specified process ID. @var{pid} is a
31381 hexadecimal integer identifying the process. This packet is used in
31382 preference to @samp{k} when multiprocess protocol extensions are
31383 supported; see @ref{multiprocess extensions}.
31393 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
31394 @cindex @samp{vRun} packet
31395 Run the program @var{filename}, passing it each @var{argument} on its
31396 command line. The file and arguments are hex-encoded strings. If
31397 @var{filename} is an empty string, the stub may use a default program
31398 (e.g.@: the last program run). The program is created in the stopped
31401 @c FIXME: What about non-stop mode?
31403 This packet is only available in extended mode (@pxref{extended mode}).
31409 @item @r{Any stop packet}
31410 for success (@pxref{Stop Reply Packets})
31414 @anchor{vStopped packet}
31415 @cindex @samp{vStopped} packet
31417 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
31418 reply and prompt for the stub to report another one.
31422 @item @r{Any stop packet}
31423 if there is another unreported stop event (@pxref{Stop Reply Packets})
31425 if there are no unreported stop events
31428 @item X @var{addr},@var{length}:@var{XX@dots{}}
31430 @cindex @samp{X} packet
31431 Write data to memory, where the data is transmitted in binary.
31432 @var{addr} is address, @var{length} is number of bytes,
31433 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
31443 @item z @var{type},@var{addr},@var{kind}
31444 @itemx Z @var{type},@var{addr},@var{kind}
31445 @anchor{insert breakpoint or watchpoint packet}
31446 @cindex @samp{z} packet
31447 @cindex @samp{Z} packets
31448 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
31449 watchpoint starting at address @var{address} of kind @var{kind}.
31451 Each breakpoint and watchpoint packet @var{type} is documented
31454 @emph{Implementation notes: A remote target shall return an empty string
31455 for an unrecognized breakpoint or watchpoint packet @var{type}. A
31456 remote target shall support either both or neither of a given
31457 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
31458 avoid potential problems with duplicate packets, the operations should
31459 be implemented in an idempotent way.}
31461 @item z0,@var{addr},@var{kind}
31462 @itemx Z0,@var{addr},@var{kind}
31463 @cindex @samp{z0} packet
31464 @cindex @samp{Z0} packet
31465 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
31466 @var{addr} of type @var{kind}.
31468 A memory breakpoint is implemented by replacing the instruction at
31469 @var{addr} with a software breakpoint or trap instruction. The
31470 @var{kind} is target-specific and typically indicates the size of
31471 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
31472 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
31473 architectures have additional meanings for @var{kind};
31474 see @ref{Architecture-Specific Protocol Details}.
31476 @emph{Implementation note: It is possible for a target to copy or move
31477 code that contains memory breakpoints (e.g., when implementing
31478 overlays). The behavior of this packet, in the presence of such a
31479 target, is not defined.}
31491 @item z1,@var{addr},@var{kind}
31492 @itemx Z1,@var{addr},@var{kind}
31493 @cindex @samp{z1} packet
31494 @cindex @samp{Z1} packet
31495 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
31496 address @var{addr}.
31498 A hardware breakpoint is implemented using a mechanism that is not
31499 dependant on being able to modify the target's memory. @var{kind}
31500 has the same meaning as in @samp{Z0} packets.
31502 @emph{Implementation note: A hardware breakpoint is not affected by code
31515 @item z2,@var{addr},@var{kind}
31516 @itemx Z2,@var{addr},@var{kind}
31517 @cindex @samp{z2} packet
31518 @cindex @samp{Z2} packet
31519 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
31520 @var{kind} is interpreted as the number of bytes to watch.
31532 @item z3,@var{addr},@var{kind}
31533 @itemx Z3,@var{addr},@var{kind}
31534 @cindex @samp{z3} packet
31535 @cindex @samp{Z3} packet
31536 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
31537 @var{kind} is interpreted as the number of bytes to watch.
31549 @item z4,@var{addr},@var{kind}
31550 @itemx Z4,@var{addr},@var{kind}
31551 @cindex @samp{z4} packet
31552 @cindex @samp{Z4} packet
31553 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
31554 @var{kind} is interpreted as the number of bytes to watch.
31568 @node Stop Reply Packets
31569 @section Stop Reply Packets
31570 @cindex stop reply packets
31572 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
31573 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
31574 receive any of the below as a reply. Except for @samp{?}
31575 and @samp{vStopped}, that reply is only returned
31576 when the target halts. In the below the exact meaning of @dfn{signal
31577 number} is defined by the header @file{include/gdb/signals.h} in the
31578 @value{GDBN} source code.
31580 As in the description of request packets, we include spaces in the
31581 reply templates for clarity; these are not part of the reply packet's
31582 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
31588 The program received signal number @var{AA} (a two-digit hexadecimal
31589 number). This is equivalent to a @samp{T} response with no
31590 @var{n}:@var{r} pairs.
31592 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
31593 @cindex @samp{T} packet reply
31594 The program received signal number @var{AA} (a two-digit hexadecimal
31595 number). This is equivalent to an @samp{S} response, except that the
31596 @samp{@var{n}:@var{r}} pairs can carry values of important registers
31597 and other information directly in the stop reply packet, reducing
31598 round-trip latency. Single-step and breakpoint traps are reported
31599 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
31603 If @var{n} is a hexadecimal number, it is a register number, and the
31604 corresponding @var{r} gives that register's value. @var{r} is a
31605 series of bytes in target byte order, with each byte given by a
31606 two-digit hex number.
31609 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
31610 the stopped thread, as specified in @ref{thread-id syntax}.
31613 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
31614 the core on which the stop event was detected.
31617 If @var{n} is a recognized @dfn{stop reason}, it describes a more
31618 specific event that stopped the target. The currently defined stop
31619 reasons are listed below. @var{aa} should be @samp{05}, the trap
31620 signal. At most one stop reason should be present.
31623 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
31624 and go on to the next; this allows us to extend the protocol in the
31628 The currently defined stop reasons are:
31634 The packet indicates a watchpoint hit, and @var{r} is the data address, in
31637 @cindex shared library events, remote reply
31639 The packet indicates that the loaded libraries have changed.
31640 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
31641 list of loaded libraries. @var{r} is ignored.
31643 @cindex replay log events, remote reply
31645 The packet indicates that the target cannot continue replaying
31646 logged execution events, because it has reached the end (or the
31647 beginning when executing backward) of the log. The value of @var{r}
31648 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
31649 for more information.
31653 @itemx W @var{AA} ; process:@var{pid}
31654 The process exited, and @var{AA} is the exit status. This is only
31655 applicable to certain targets.
31657 The second form of the response, including the process ID of the exited
31658 process, can be used only when @value{GDBN} has reported support for
31659 multiprocess protocol extensions; see @ref{multiprocess extensions}.
31660 The @var{pid} is formatted as a big-endian hex string.
31663 @itemx X @var{AA} ; process:@var{pid}
31664 The process terminated with signal @var{AA}.
31666 The second form of the response, including the process ID of the
31667 terminated process, can be used only when @value{GDBN} has reported
31668 support for multiprocess protocol extensions; see @ref{multiprocess
31669 extensions}. The @var{pid} is formatted as a big-endian hex string.
31671 @item O @var{XX}@dots{}
31672 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
31673 written as the program's console output. This can happen at any time
31674 while the program is running and the debugger should continue to wait
31675 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
31677 @item F @var{call-id},@var{parameter}@dots{}
31678 @var{call-id} is the identifier which says which host system call should
31679 be called. This is just the name of the function. Translation into the
31680 correct system call is only applicable as it's defined in @value{GDBN}.
31681 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
31684 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
31685 this very system call.
31687 The target replies with this packet when it expects @value{GDBN} to
31688 call a host system call on behalf of the target. @value{GDBN} replies
31689 with an appropriate @samp{F} packet and keeps up waiting for the next
31690 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
31691 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
31692 Protocol Extension}, for more details.
31696 @node General Query Packets
31697 @section General Query Packets
31698 @cindex remote query requests
31700 Packets starting with @samp{q} are @dfn{general query packets};
31701 packets starting with @samp{Q} are @dfn{general set packets}. General
31702 query and set packets are a semi-unified form for retrieving and
31703 sending information to and from the stub.
31705 The initial letter of a query or set packet is followed by a name
31706 indicating what sort of thing the packet applies to. For example,
31707 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
31708 definitions with the stub. These packet names follow some
31713 The name must not contain commas, colons or semicolons.
31715 Most @value{GDBN} query and set packets have a leading upper case
31718 The names of custom vendor packets should use a company prefix, in
31719 lower case, followed by a period. For example, packets designed at
31720 the Acme Corporation might begin with @samp{qacme.foo} (for querying
31721 foos) or @samp{Qacme.bar} (for setting bars).
31724 The name of a query or set packet should be separated from any
31725 parameters by a @samp{:}; the parameters themselves should be
31726 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
31727 full packet name, and check for a separator or the end of the packet,
31728 in case two packet names share a common prefix. New packets should not begin
31729 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
31730 packets predate these conventions, and have arguments without any terminator
31731 for the packet name; we suspect they are in widespread use in places that
31732 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
31733 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
31736 Like the descriptions of the other packets, each description here
31737 has a template showing the packet's overall syntax, followed by an
31738 explanation of the packet's meaning. We include spaces in some of the
31739 templates for clarity; these are not part of the packet's syntax. No
31740 @value{GDBN} packet uses spaces to separate its components.
31742 Here are the currently defined query and set packets:
31746 @item QAllow:@var{op}:@var{val}@dots{}
31747 @cindex @samp{QAllow} packet
31748 Specify which operations @value{GDBN} expects to request of the
31749 target, as a semicolon-separated list of operation name and value
31750 pairs. Possible values for @var{op} include @samp{WriteReg},
31751 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
31752 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
31753 indicating that @value{GDBN} will not request the operation, or 1,
31754 indicating that it may. (The target can then use this to set up its
31755 own internals optimally, for instance if the debugger never expects to
31756 insert breakpoints, it may not need to install its own trap handler.)
31759 @cindex current thread, remote request
31760 @cindex @samp{qC} packet
31761 Return the current thread ID.
31765 @item QC @var{thread-id}
31766 Where @var{thread-id} is a thread ID as documented in
31767 @ref{thread-id syntax}.
31768 @item @r{(anything else)}
31769 Any other reply implies the old thread ID.
31772 @item qCRC:@var{addr},@var{length}
31773 @cindex CRC of memory block, remote request
31774 @cindex @samp{qCRC} packet
31775 Compute the CRC checksum of a block of memory using CRC-32 defined in
31776 IEEE 802.3. The CRC is computed byte at a time, taking the most
31777 significant bit of each byte first. The initial pattern code
31778 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
31780 @emph{Note:} This is the same CRC used in validating separate debug
31781 files (@pxref{Separate Debug Files, , Debugging Information in Separate
31782 Files}). However the algorithm is slightly different. When validating
31783 separate debug files, the CRC is computed taking the @emph{least}
31784 significant bit of each byte first, and the final result is inverted to
31785 detect trailing zeros.
31790 An error (such as memory fault)
31791 @item C @var{crc32}
31792 The specified memory region's checksum is @var{crc32}.
31796 @itemx qsThreadInfo
31797 @cindex list active threads, remote request
31798 @cindex @samp{qfThreadInfo} packet
31799 @cindex @samp{qsThreadInfo} packet
31800 Obtain a list of all active thread IDs from the target (OS). Since there
31801 may be too many active threads to fit into one reply packet, this query
31802 works iteratively: it may require more than one query/reply sequence to
31803 obtain the entire list of threads. The first query of the sequence will
31804 be the @samp{qfThreadInfo} query; subsequent queries in the
31805 sequence will be the @samp{qsThreadInfo} query.
31807 NOTE: This packet replaces the @samp{qL} query (see below).
31811 @item m @var{thread-id}
31813 @item m @var{thread-id},@var{thread-id}@dots{}
31814 a comma-separated list of thread IDs
31816 (lower case letter @samp{L}) denotes end of list.
31819 In response to each query, the target will reply with a list of one or
31820 more thread IDs, separated by commas.
31821 @value{GDBN} will respond to each reply with a request for more thread
31822 ids (using the @samp{qs} form of the query), until the target responds
31823 with @samp{l} (lower-case ell, for @dfn{last}).
31824 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
31827 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
31828 @cindex get thread-local storage address, remote request
31829 @cindex @samp{qGetTLSAddr} packet
31830 Fetch the address associated with thread local storage specified
31831 by @var{thread-id}, @var{offset}, and @var{lm}.
31833 @var{thread-id} is the thread ID associated with the
31834 thread for which to fetch the TLS address. @xref{thread-id syntax}.
31836 @var{offset} is the (big endian, hex encoded) offset associated with the
31837 thread local variable. (This offset is obtained from the debug
31838 information associated with the variable.)
31840 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
31841 the load module associated with the thread local storage. For example,
31842 a @sc{gnu}/Linux system will pass the link map address of the shared
31843 object associated with the thread local storage under consideration.
31844 Other operating environments may choose to represent the load module
31845 differently, so the precise meaning of this parameter will vary.
31849 @item @var{XX}@dots{}
31850 Hex encoded (big endian) bytes representing the address of the thread
31851 local storage requested.
31854 An error occurred. @var{nn} are hex digits.
31857 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
31860 @item qGetTIBAddr:@var{thread-id}
31861 @cindex get thread information block address
31862 @cindex @samp{qGetTIBAddr} packet
31863 Fetch address of the Windows OS specific Thread Information Block.
31865 @var{thread-id} is the thread ID associated with the thread.
31869 @item @var{XX}@dots{}
31870 Hex encoded (big endian) bytes representing the linear address of the
31871 thread information block.
31874 An error occured. This means that either the thread was not found, or the
31875 address could not be retrieved.
31878 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
31881 @item qL @var{startflag} @var{threadcount} @var{nextthread}
31882 Obtain thread information from RTOS. Where: @var{startflag} (one hex
31883 digit) is one to indicate the first query and zero to indicate a
31884 subsequent query; @var{threadcount} (two hex digits) is the maximum
31885 number of threads the response packet can contain; and @var{nextthread}
31886 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
31887 returned in the response as @var{argthread}.
31889 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
31893 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
31894 Where: @var{count} (two hex digits) is the number of threads being
31895 returned; @var{done} (one hex digit) is zero to indicate more threads
31896 and one indicates no further threads; @var{argthreadid} (eight hex
31897 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
31898 is a sequence of thread IDs from the target. @var{threadid} (eight hex
31899 digits). See @code{remote.c:parse_threadlist_response()}.
31903 @cindex section offsets, remote request
31904 @cindex @samp{qOffsets} packet
31905 Get section offsets that the target used when relocating the downloaded
31910 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
31911 Relocate the @code{Text} section by @var{xxx} from its original address.
31912 Relocate the @code{Data} section by @var{yyy} from its original address.
31913 If the object file format provides segment information (e.g.@: @sc{elf}
31914 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
31915 segments by the supplied offsets.
31917 @emph{Note: while a @code{Bss} offset may be included in the response,
31918 @value{GDBN} ignores this and instead applies the @code{Data} offset
31919 to the @code{Bss} section.}
31921 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
31922 Relocate the first segment of the object file, which conventionally
31923 contains program code, to a starting address of @var{xxx}. If
31924 @samp{DataSeg} is specified, relocate the second segment, which
31925 conventionally contains modifiable data, to a starting address of
31926 @var{yyy}. @value{GDBN} will report an error if the object file
31927 does not contain segment information, or does not contain at least
31928 as many segments as mentioned in the reply. Extra segments are
31929 kept at fixed offsets relative to the last relocated segment.
31932 @item qP @var{mode} @var{thread-id}
31933 @cindex thread information, remote request
31934 @cindex @samp{qP} packet
31935 Returns information on @var{thread-id}. Where: @var{mode} is a hex
31936 encoded 32 bit mode; @var{thread-id} is a thread ID
31937 (@pxref{thread-id syntax}).
31939 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
31942 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
31946 @cindex non-stop mode, remote request
31947 @cindex @samp{QNonStop} packet
31949 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
31950 @xref{Remote Non-Stop}, for more information.
31955 The request succeeded.
31958 An error occurred. @var{nn} are hex digits.
31961 An empty reply indicates that @samp{QNonStop} is not supported by
31965 This packet is not probed by default; the remote stub must request it,
31966 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31967 Use of this packet is controlled by the @code{set non-stop} command;
31968 @pxref{Non-Stop Mode}.
31970 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
31971 @cindex pass signals to inferior, remote request
31972 @cindex @samp{QPassSignals} packet
31973 @anchor{QPassSignals}
31974 Each listed @var{signal} should be passed directly to the inferior process.
31975 Signals are numbered identically to continue packets and stop replies
31976 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
31977 strictly greater than the previous item. These signals do not need to stop
31978 the inferior, or be reported to @value{GDBN}. All other signals should be
31979 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
31980 combine; any earlier @samp{QPassSignals} list is completely replaced by the
31981 new list. This packet improves performance when using @samp{handle
31982 @var{signal} nostop noprint pass}.
31987 The request succeeded.
31990 An error occurred. @var{nn} are hex digits.
31993 An empty reply indicates that @samp{QPassSignals} is not supported by
31997 Use of this packet is controlled by the @code{set remote pass-signals}
31998 command (@pxref{Remote Configuration, set remote pass-signals}).
31999 This packet is not probed by default; the remote stub must request it,
32000 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32002 @item qRcmd,@var{command}
32003 @cindex execute remote command, remote request
32004 @cindex @samp{qRcmd} packet
32005 @var{command} (hex encoded) is passed to the local interpreter for
32006 execution. Invalid commands should be reported using the output
32007 string. Before the final result packet, the target may also respond
32008 with a number of intermediate @samp{O@var{output}} console output
32009 packets. @emph{Implementors should note that providing access to a
32010 stubs's interpreter may have security implications}.
32015 A command response with no output.
32017 A command response with the hex encoded output string @var{OUTPUT}.
32019 Indicate a badly formed request.
32021 An empty reply indicates that @samp{qRcmd} is not recognized.
32024 (Note that the @code{qRcmd} packet's name is separated from the
32025 command by a @samp{,}, not a @samp{:}, contrary to the naming
32026 conventions above. Please don't use this packet as a model for new
32029 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
32030 @cindex searching memory, in remote debugging
32031 @cindex @samp{qSearch:memory} packet
32032 @anchor{qSearch memory}
32033 Search @var{length} bytes at @var{address} for @var{search-pattern}.
32034 @var{address} and @var{length} are encoded in hex.
32035 @var{search-pattern} is a sequence of bytes, hex encoded.
32040 The pattern was not found.
32042 The pattern was found at @var{address}.
32044 A badly formed request or an error was encountered while searching memory.
32046 An empty reply indicates that @samp{qSearch:memory} is not recognized.
32049 @item QStartNoAckMode
32050 @cindex @samp{QStartNoAckMode} packet
32051 @anchor{QStartNoAckMode}
32052 Request that the remote stub disable the normal @samp{+}/@samp{-}
32053 protocol acknowledgments (@pxref{Packet Acknowledgment}).
32058 The stub has switched to no-acknowledgment mode.
32059 @value{GDBN} acknowledges this reponse,
32060 but neither the stub nor @value{GDBN} shall send or expect further
32061 @samp{+}/@samp{-} acknowledgments in the current connection.
32063 An empty reply indicates that the stub does not support no-acknowledgment mode.
32066 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
32067 @cindex supported packets, remote query
32068 @cindex features of the remote protocol
32069 @cindex @samp{qSupported} packet
32070 @anchor{qSupported}
32071 Tell the remote stub about features supported by @value{GDBN}, and
32072 query the stub for features it supports. This packet allows
32073 @value{GDBN} and the remote stub to take advantage of each others'
32074 features. @samp{qSupported} also consolidates multiple feature probes
32075 at startup, to improve @value{GDBN} performance---a single larger
32076 packet performs better than multiple smaller probe packets on
32077 high-latency links. Some features may enable behavior which must not
32078 be on by default, e.g.@: because it would confuse older clients or
32079 stubs. Other features may describe packets which could be
32080 automatically probed for, but are not. These features must be
32081 reported before @value{GDBN} will use them. This ``default
32082 unsupported'' behavior is not appropriate for all packets, but it
32083 helps to keep the initial connection time under control with new
32084 versions of @value{GDBN} which support increasing numbers of packets.
32088 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
32089 The stub supports or does not support each returned @var{stubfeature},
32090 depending on the form of each @var{stubfeature} (see below for the
32093 An empty reply indicates that @samp{qSupported} is not recognized,
32094 or that no features needed to be reported to @value{GDBN}.
32097 The allowed forms for each feature (either a @var{gdbfeature} in the
32098 @samp{qSupported} packet, or a @var{stubfeature} in the response)
32102 @item @var{name}=@var{value}
32103 The remote protocol feature @var{name} is supported, and associated
32104 with the specified @var{value}. The format of @var{value} depends
32105 on the feature, but it must not include a semicolon.
32107 The remote protocol feature @var{name} is supported, and does not
32108 need an associated value.
32110 The remote protocol feature @var{name} is not supported.
32112 The remote protocol feature @var{name} may be supported, and
32113 @value{GDBN} should auto-detect support in some other way when it is
32114 needed. This form will not be used for @var{gdbfeature} notifications,
32115 but may be used for @var{stubfeature} responses.
32118 Whenever the stub receives a @samp{qSupported} request, the
32119 supplied set of @value{GDBN} features should override any previous
32120 request. This allows @value{GDBN} to put the stub in a known
32121 state, even if the stub had previously been communicating with
32122 a different version of @value{GDBN}.
32124 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
32129 This feature indicates whether @value{GDBN} supports multiprocess
32130 extensions to the remote protocol. @value{GDBN} does not use such
32131 extensions unless the stub also reports that it supports them by
32132 including @samp{multiprocess+} in its @samp{qSupported} reply.
32133 @xref{multiprocess extensions}, for details.
32136 This feature indicates that @value{GDBN} supports the XML target
32137 description. If the stub sees @samp{xmlRegisters=} with target
32138 specific strings separated by a comma, it will report register
32142 This feature indicates whether @value{GDBN} supports the
32143 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
32144 instruction reply packet}).
32147 Stubs should ignore any unknown values for
32148 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
32149 packet supports receiving packets of unlimited length (earlier
32150 versions of @value{GDBN} may reject overly long responses). Additional values
32151 for @var{gdbfeature} may be defined in the future to let the stub take
32152 advantage of new features in @value{GDBN}, e.g.@: incompatible
32153 improvements in the remote protocol---the @samp{multiprocess} feature is
32154 an example of such a feature. The stub's reply should be independent
32155 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
32156 describes all the features it supports, and then the stub replies with
32157 all the features it supports.
32159 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
32160 responses, as long as each response uses one of the standard forms.
32162 Some features are flags. A stub which supports a flag feature
32163 should respond with a @samp{+} form response. Other features
32164 require values, and the stub should respond with an @samp{=}
32167 Each feature has a default value, which @value{GDBN} will use if
32168 @samp{qSupported} is not available or if the feature is not mentioned
32169 in the @samp{qSupported} response. The default values are fixed; a
32170 stub is free to omit any feature responses that match the defaults.
32172 Not all features can be probed, but for those which can, the probing
32173 mechanism is useful: in some cases, a stub's internal
32174 architecture may not allow the protocol layer to know some information
32175 about the underlying target in advance. This is especially common in
32176 stubs which may be configured for multiple targets.
32178 These are the currently defined stub features and their properties:
32180 @multitable @columnfractions 0.35 0.2 0.12 0.2
32181 @c NOTE: The first row should be @headitem, but we do not yet require
32182 @c a new enough version of Texinfo (4.7) to use @headitem.
32184 @tab Value Required
32188 @item @samp{PacketSize}
32193 @item @samp{qXfer:auxv:read}
32198 @item @samp{qXfer:features:read}
32203 @item @samp{qXfer:libraries:read}
32208 @item @samp{qXfer:memory-map:read}
32213 @item @samp{qXfer:sdata:read}
32218 @item @samp{qXfer:spu:read}
32223 @item @samp{qXfer:spu:write}
32228 @item @samp{qXfer:siginfo:read}
32233 @item @samp{qXfer:siginfo:write}
32238 @item @samp{qXfer:threads:read}
32244 @item @samp{QNonStop}
32249 @item @samp{QPassSignals}
32254 @item @samp{QStartNoAckMode}
32259 @item @samp{multiprocess}
32264 @item @samp{ConditionalTracepoints}
32269 @item @samp{ReverseContinue}
32274 @item @samp{ReverseStep}
32279 @item @samp{TracepointSource}
32284 @item @samp{QAllow}
32291 These are the currently defined stub features, in more detail:
32294 @cindex packet size, remote protocol
32295 @item PacketSize=@var{bytes}
32296 The remote stub can accept packets up to at least @var{bytes} in
32297 length. @value{GDBN} will send packets up to this size for bulk
32298 transfers, and will never send larger packets. This is a limit on the
32299 data characters in the packet, including the frame and checksum.
32300 There is no trailing NUL byte in a remote protocol packet; if the stub
32301 stores packets in a NUL-terminated format, it should allow an extra
32302 byte in its buffer for the NUL. If this stub feature is not supported,
32303 @value{GDBN} guesses based on the size of the @samp{g} packet response.
32305 @item qXfer:auxv:read
32306 The remote stub understands the @samp{qXfer:auxv:read} packet
32307 (@pxref{qXfer auxiliary vector read}).
32309 @item qXfer:features:read
32310 The remote stub understands the @samp{qXfer:features:read} packet
32311 (@pxref{qXfer target description read}).
32313 @item qXfer:libraries:read
32314 The remote stub understands the @samp{qXfer:libraries:read} packet
32315 (@pxref{qXfer library list read}).
32317 @item qXfer:memory-map:read
32318 The remote stub understands the @samp{qXfer:memory-map:read} packet
32319 (@pxref{qXfer memory map read}).
32321 @item qXfer:sdata:read
32322 The remote stub understands the @samp{qXfer:sdata:read} packet
32323 (@pxref{qXfer sdata read}).
32325 @item qXfer:spu:read
32326 The remote stub understands the @samp{qXfer:spu:read} packet
32327 (@pxref{qXfer spu read}).
32329 @item qXfer:spu:write
32330 The remote stub understands the @samp{qXfer:spu:write} packet
32331 (@pxref{qXfer spu write}).
32333 @item qXfer:siginfo:read
32334 The remote stub understands the @samp{qXfer:siginfo:read} packet
32335 (@pxref{qXfer siginfo read}).
32337 @item qXfer:siginfo:write
32338 The remote stub understands the @samp{qXfer:siginfo:write} packet
32339 (@pxref{qXfer siginfo write}).
32341 @item qXfer:threads:read
32342 The remote stub understands the @samp{qXfer:threads:read} packet
32343 (@pxref{qXfer threads read}).
32346 The remote stub understands the @samp{QNonStop} packet
32347 (@pxref{QNonStop}).
32350 The remote stub understands the @samp{QPassSignals} packet
32351 (@pxref{QPassSignals}).
32353 @item QStartNoAckMode
32354 The remote stub understands the @samp{QStartNoAckMode} packet and
32355 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
32358 @anchor{multiprocess extensions}
32359 @cindex multiprocess extensions, in remote protocol
32360 The remote stub understands the multiprocess extensions to the remote
32361 protocol syntax. The multiprocess extensions affect the syntax of
32362 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
32363 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
32364 replies. Note that reporting this feature indicates support for the
32365 syntactic extensions only, not that the stub necessarily supports
32366 debugging of more than one process at a time. The stub must not use
32367 multiprocess extensions in packet replies unless @value{GDBN} has also
32368 indicated it supports them in its @samp{qSupported} request.
32370 @item qXfer:osdata:read
32371 The remote stub understands the @samp{qXfer:osdata:read} packet
32372 ((@pxref{qXfer osdata read}).
32374 @item ConditionalTracepoints
32375 The remote stub accepts and implements conditional expressions defined
32376 for tracepoints (@pxref{Tracepoint Conditions}).
32378 @item ReverseContinue
32379 The remote stub accepts and implements the reverse continue packet
32383 The remote stub accepts and implements the reverse step packet
32386 @item TracepointSource
32387 The remote stub understands the @samp{QTDPsrc} packet that supplies
32388 the source form of tracepoint definitions.
32391 The remote stub understands the @samp{QAllow} packet.
32393 @item StaticTracepoint
32394 @cindex static tracepoints, in remote protocol
32395 The remote stub supports static tracepoints.
32400 @cindex symbol lookup, remote request
32401 @cindex @samp{qSymbol} packet
32402 Notify the target that @value{GDBN} is prepared to serve symbol lookup
32403 requests. Accept requests from the target for the values of symbols.
32408 The target does not need to look up any (more) symbols.
32409 @item qSymbol:@var{sym_name}
32410 The target requests the value of symbol @var{sym_name} (hex encoded).
32411 @value{GDBN} may provide the value by using the
32412 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
32416 @item qSymbol:@var{sym_value}:@var{sym_name}
32417 Set the value of @var{sym_name} to @var{sym_value}.
32419 @var{sym_name} (hex encoded) is the name of a symbol whose value the
32420 target has previously requested.
32422 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
32423 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
32429 The target does not need to look up any (more) symbols.
32430 @item qSymbol:@var{sym_name}
32431 The target requests the value of a new symbol @var{sym_name} (hex
32432 encoded). @value{GDBN} will continue to supply the values of symbols
32433 (if available), until the target ceases to request them.
32438 @item QTDisconnected
32445 @xref{Tracepoint Packets}.
32447 @item qThreadExtraInfo,@var{thread-id}
32448 @cindex thread attributes info, remote request
32449 @cindex @samp{qThreadExtraInfo} packet
32450 Obtain a printable string description of a thread's attributes from
32451 the target OS. @var{thread-id} is a thread ID;
32452 see @ref{thread-id syntax}. This
32453 string may contain anything that the target OS thinks is interesting
32454 for @value{GDBN} to tell the user about the thread. The string is
32455 displayed in @value{GDBN}'s @code{info threads} display. Some
32456 examples of possible thread extra info strings are @samp{Runnable}, or
32457 @samp{Blocked on Mutex}.
32461 @item @var{XX}@dots{}
32462 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
32463 comprising the printable string containing the extra information about
32464 the thread's attributes.
32467 (Note that the @code{qThreadExtraInfo} packet's name is separated from
32468 the command by a @samp{,}, not a @samp{:}, contrary to the naming
32469 conventions above. Please don't use this packet as a model for new
32484 @xref{Tracepoint Packets}.
32486 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
32487 @cindex read special object, remote request
32488 @cindex @samp{qXfer} packet
32489 @anchor{qXfer read}
32490 Read uninterpreted bytes from the target's special data area
32491 identified by the keyword @var{object}. Request @var{length} bytes
32492 starting at @var{offset} bytes into the data. The content and
32493 encoding of @var{annex} is specific to @var{object}; it can supply
32494 additional details about what data to access.
32496 Here are the specific requests of this form defined so far. All
32497 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
32498 formats, listed below.
32501 @item qXfer:auxv:read::@var{offset},@var{length}
32502 @anchor{qXfer auxiliary vector read}
32503 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
32504 auxiliary vector}. Note @var{annex} must be empty.
32506 This packet is not probed by default; the remote stub must request it,
32507 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32509 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
32510 @anchor{qXfer target description read}
32511 Access the @dfn{target description}. @xref{Target Descriptions}. The
32512 annex specifies which XML document to access. The main description is
32513 always loaded from the @samp{target.xml} annex.
32515 This packet is not probed by default; the remote stub must request it,
32516 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32518 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
32519 @anchor{qXfer library list read}
32520 Access the target's list of loaded libraries. @xref{Library List Format}.
32521 The annex part of the generic @samp{qXfer} packet must be empty
32522 (@pxref{qXfer read}).
32524 Targets which maintain a list of libraries in the program's memory do
32525 not need to implement this packet; it is designed for platforms where
32526 the operating system manages the list of loaded libraries.
32528 This packet is not probed by default; the remote stub must request it,
32529 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32531 @item qXfer:memory-map:read::@var{offset},@var{length}
32532 @anchor{qXfer memory map read}
32533 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
32534 annex part of the generic @samp{qXfer} packet must be empty
32535 (@pxref{qXfer read}).
32537 This packet is not probed by default; the remote stub must request it,
32538 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32540 @item qXfer:sdata:read::@var{offset},@var{length}
32541 @anchor{qXfer sdata read}
32543 Read contents of the extra collected static tracepoint marker
32544 information. The annex part of the generic @samp{qXfer} packet must
32545 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
32548 This packet is not probed by default; the remote stub must request it,
32549 by supplying an appropriate @samp{qSupported} response
32550 (@pxref{qSupported}).
32552 @item qXfer:siginfo:read::@var{offset},@var{length}
32553 @anchor{qXfer siginfo read}
32554 Read contents of the extra signal information on the target
32555 system. The annex part of the generic @samp{qXfer} packet must be
32556 empty (@pxref{qXfer read}).
32558 This packet is not probed by default; the remote stub must request it,
32559 by supplying an appropriate @samp{qSupported} response
32560 (@pxref{qSupported}).
32562 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
32563 @anchor{qXfer spu read}
32564 Read contents of an @code{spufs} file on the target system. The
32565 annex specifies which file to read; it must be of the form
32566 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32567 in the target process, and @var{name} identifes the @code{spufs} file
32568 in that context to be accessed.
32570 This packet is not probed by default; the remote stub must request it,
32571 by supplying an appropriate @samp{qSupported} response
32572 (@pxref{qSupported}).
32574 @item qXfer:threads:read::@var{offset},@var{length}
32575 @anchor{qXfer threads read}
32576 Access the list of threads on target. @xref{Thread List Format}. The
32577 annex part of the generic @samp{qXfer} packet must be empty
32578 (@pxref{qXfer read}).
32580 This packet is not probed by default; the remote stub must request it,
32581 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32583 @item qXfer:osdata:read::@var{offset},@var{length}
32584 @anchor{qXfer osdata read}
32585 Access the target's @dfn{operating system information}.
32586 @xref{Operating System Information}.
32593 Data @var{data} (@pxref{Binary Data}) has been read from the
32594 target. There may be more data at a higher address (although
32595 it is permitted to return @samp{m} even for the last valid
32596 block of data, as long as at least one byte of data was read).
32597 @var{data} may have fewer bytes than the @var{length} in the
32601 Data @var{data} (@pxref{Binary Data}) has been read from the target.
32602 There is no more data to be read. @var{data} may have fewer bytes
32603 than the @var{length} in the request.
32606 The @var{offset} in the request is at the end of the data.
32607 There is no more data to be read.
32610 The request was malformed, or @var{annex} was invalid.
32613 The offset was invalid, or there was an error encountered reading the data.
32614 @var{nn} is a hex-encoded @code{errno} value.
32617 An empty reply indicates the @var{object} string was not recognized by
32618 the stub, or that the object does not support reading.
32621 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
32622 @cindex write data into object, remote request
32623 @anchor{qXfer write}
32624 Write uninterpreted bytes into the target's special data area
32625 identified by the keyword @var{object}, starting at @var{offset} bytes
32626 into the data. @var{data}@dots{} is the binary-encoded data
32627 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
32628 is specific to @var{object}; it can supply additional details about what data
32631 Here are the specific requests of this form defined so far. All
32632 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
32633 formats, listed below.
32636 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
32637 @anchor{qXfer siginfo write}
32638 Write @var{data} to the extra signal information on the target system.
32639 The annex part of the generic @samp{qXfer} packet must be
32640 empty (@pxref{qXfer write}).
32642 This packet is not probed by default; the remote stub must request it,
32643 by supplying an appropriate @samp{qSupported} response
32644 (@pxref{qSupported}).
32646 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
32647 @anchor{qXfer spu write}
32648 Write @var{data} to an @code{spufs} file on the target system. The
32649 annex specifies which file to write; it must be of the form
32650 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32651 in the target process, and @var{name} identifes the @code{spufs} file
32652 in that context to be accessed.
32654 This packet is not probed by default; the remote stub must request it,
32655 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32661 @var{nn} (hex encoded) is the number of bytes written.
32662 This may be fewer bytes than supplied in the request.
32665 The request was malformed, or @var{annex} was invalid.
32668 The offset was invalid, or there was an error encountered writing the data.
32669 @var{nn} is a hex-encoded @code{errno} value.
32672 An empty reply indicates the @var{object} string was not
32673 recognized by the stub, or that the object does not support writing.
32676 @item qXfer:@var{object}:@var{operation}:@dots{}
32677 Requests of this form may be added in the future. When a stub does
32678 not recognize the @var{object} keyword, or its support for
32679 @var{object} does not recognize the @var{operation} keyword, the stub
32680 must respond with an empty packet.
32682 @item qAttached:@var{pid}
32683 @cindex query attached, remote request
32684 @cindex @samp{qAttached} packet
32685 Return an indication of whether the remote server attached to an
32686 existing process or created a new process. When the multiprocess
32687 protocol extensions are supported (@pxref{multiprocess extensions}),
32688 @var{pid} is an integer in hexadecimal format identifying the target
32689 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
32690 the query packet will be simplified as @samp{qAttached}.
32692 This query is used, for example, to know whether the remote process
32693 should be detached or killed when a @value{GDBN} session is ended with
32694 the @code{quit} command.
32699 The remote server attached to an existing process.
32701 The remote server created a new process.
32703 A badly formed request or an error was encountered.
32708 @node Architecture-Specific Protocol Details
32709 @section Architecture-Specific Protocol Details
32711 This section describes how the remote protocol is applied to specific
32712 target architectures. Also see @ref{Standard Target Features}, for
32713 details of XML target descriptions for each architecture.
32717 @subsubsection Breakpoint Kinds
32719 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
32724 16-bit Thumb mode breakpoint.
32727 32-bit Thumb mode (Thumb-2) breakpoint.
32730 32-bit ARM mode breakpoint.
32736 @subsubsection Register Packet Format
32738 The following @code{g}/@code{G} packets have previously been defined.
32739 In the below, some thirty-two bit registers are transferred as
32740 sixty-four bits. Those registers should be zero/sign extended (which?)
32741 to fill the space allocated. Register bytes are transferred in target
32742 byte order. The two nibbles within a register byte are transferred
32743 most-significant - least-significant.
32749 All registers are transferred as thirty-two bit quantities in the order:
32750 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
32751 registers; fsr; fir; fp.
32755 All registers are transferred as sixty-four bit quantities (including
32756 thirty-two bit registers such as @code{sr}). The ordering is the same
32761 @node Tracepoint Packets
32762 @section Tracepoint Packets
32763 @cindex tracepoint packets
32764 @cindex packets, tracepoint
32766 Here we describe the packets @value{GDBN} uses to implement
32767 tracepoints (@pxref{Tracepoints}).
32771 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
32772 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
32773 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
32774 the tracepoint is disabled. @var{step} is the tracepoint's step
32775 count, and @var{pass} is its pass count. If an @samp{F} is present,
32776 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
32777 the number of bytes that the target should copy elsewhere to make room
32778 for the tracepoint. If an @samp{X} is present, it introduces a
32779 tracepoint condition, which consists of a hexadecimal length, followed
32780 by a comma and hex-encoded bytes, in a manner similar to action
32781 encodings as described below. If the trailing @samp{-} is present,
32782 further @samp{QTDP} packets will follow to specify this tracepoint's
32788 The packet was understood and carried out.
32790 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32792 The packet was not recognized.
32795 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
32796 Define actions to be taken when a tracepoint is hit. @var{n} and
32797 @var{addr} must be the same as in the initial @samp{QTDP} packet for
32798 this tracepoint. This packet may only be sent immediately after
32799 another @samp{QTDP} packet that ended with a @samp{-}. If the
32800 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
32801 specifying more actions for this tracepoint.
32803 In the series of action packets for a given tracepoint, at most one
32804 can have an @samp{S} before its first @var{action}. If such a packet
32805 is sent, it and the following packets define ``while-stepping''
32806 actions. Any prior packets define ordinary actions --- that is, those
32807 taken when the tracepoint is first hit. If no action packet has an
32808 @samp{S}, then all the packets in the series specify ordinary
32809 tracepoint actions.
32811 The @samp{@var{action}@dots{}} portion of the packet is a series of
32812 actions, concatenated without separators. Each action has one of the
32818 Collect the registers whose bits are set in @var{mask}. @var{mask} is
32819 a hexadecimal number whose @var{i}'th bit is set if register number
32820 @var{i} should be collected. (The least significant bit is numbered
32821 zero.) Note that @var{mask} may be any number of digits long; it may
32822 not fit in a 32-bit word.
32824 @item M @var{basereg},@var{offset},@var{len}
32825 Collect @var{len} bytes of memory starting at the address in register
32826 number @var{basereg}, plus @var{offset}. If @var{basereg} is
32827 @samp{-1}, then the range has a fixed address: @var{offset} is the
32828 address of the lowest byte to collect. The @var{basereg},
32829 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
32830 values (the @samp{-1} value for @var{basereg} is a special case).
32832 @item X @var{len},@var{expr}
32833 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
32834 it directs. @var{expr} is an agent expression, as described in
32835 @ref{Agent Expressions}. Each byte of the expression is encoded as a
32836 two-digit hex number in the packet; @var{len} is the number of bytes
32837 in the expression (and thus one-half the number of hex digits in the
32842 Any number of actions may be packed together in a single @samp{QTDP}
32843 packet, as long as the packet does not exceed the maximum packet
32844 length (400 bytes, for many stubs). There may be only one @samp{R}
32845 action per tracepoint, and it must precede any @samp{M} or @samp{X}
32846 actions. Any registers referred to by @samp{M} and @samp{X} actions
32847 must be collected by a preceding @samp{R} action. (The
32848 ``while-stepping'' actions are treated as if they were attached to a
32849 separate tracepoint, as far as these restrictions are concerned.)
32854 The packet was understood and carried out.
32856 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32858 The packet was not recognized.
32861 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
32862 @cindex @samp{QTDPsrc} packet
32863 Specify a source string of tracepoint @var{n} at address @var{addr}.
32864 This is useful to get accurate reproduction of the tracepoints
32865 originally downloaded at the beginning of the trace run. @var{type}
32866 is the name of the tracepoint part, such as @samp{cond} for the
32867 tracepoint's conditional expression (see below for a list of types), while
32868 @var{bytes} is the string, encoded in hexadecimal.
32870 @var{start} is the offset of the @var{bytes} within the overall source
32871 string, while @var{slen} is the total length of the source string.
32872 This is intended for handling source strings that are longer than will
32873 fit in a single packet.
32874 @c Add detailed example when this info is moved into a dedicated
32875 @c tracepoint descriptions section.
32877 The available string types are @samp{at} for the location,
32878 @samp{cond} for the conditional, and @samp{cmd} for an action command.
32879 @value{GDBN} sends a separate packet for each command in the action
32880 list, in the same order in which the commands are stored in the list.
32882 The target does not need to do anything with source strings except
32883 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
32886 Although this packet is optional, and @value{GDBN} will only send it
32887 if the target replies with @samp{TracepointSource} @xref{General
32888 Query Packets}, it makes both disconnected tracing and trace files
32889 much easier to use. Otherwise the user must be careful that the
32890 tracepoints in effect while looking at trace frames are identical to
32891 the ones in effect during the trace run; even a small discrepancy
32892 could cause @samp{tdump} not to work, or a particular trace frame not
32895 @item QTDV:@var{n}:@var{value}
32896 @cindex define trace state variable, remote request
32897 @cindex @samp{QTDV} packet
32898 Create a new trace state variable, number @var{n}, with an initial
32899 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
32900 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
32901 the option of not using this packet for initial values of zero; the
32902 target should simply create the trace state variables as they are
32903 mentioned in expressions.
32905 @item QTFrame:@var{n}
32906 Select the @var{n}'th tracepoint frame from the buffer, and use the
32907 register and memory contents recorded there to answer subsequent
32908 request packets from @value{GDBN}.
32910 A successful reply from the stub indicates that the stub has found the
32911 requested frame. The response is a series of parts, concatenated
32912 without separators, describing the frame we selected. Each part has
32913 one of the following forms:
32917 The selected frame is number @var{n} in the trace frame buffer;
32918 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
32919 was no frame matching the criteria in the request packet.
32922 The selected trace frame records a hit of tracepoint number @var{t};
32923 @var{t} is a hexadecimal number.
32927 @item QTFrame:pc:@var{addr}
32928 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32929 currently selected frame whose PC is @var{addr};
32930 @var{addr} is a hexadecimal number.
32932 @item QTFrame:tdp:@var{t}
32933 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32934 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
32935 is a hexadecimal number.
32937 @item QTFrame:range:@var{start}:@var{end}
32938 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32939 currently selected frame whose PC is between @var{start} (inclusive)
32940 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
32943 @item QTFrame:outside:@var{start}:@var{end}
32944 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
32945 frame @emph{outside} the given range of addresses (exclusive).
32948 Begin the tracepoint experiment. Begin collecting data from
32949 tracepoint hits in the trace frame buffer. This packet supports the
32950 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
32951 instruction reply packet}).
32954 End the tracepoint experiment. Stop collecting trace frames.
32957 Clear the table of tracepoints, and empty the trace frame buffer.
32959 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
32960 Establish the given ranges of memory as ``transparent''. The stub
32961 will answer requests for these ranges from memory's current contents,
32962 if they were not collected as part of the tracepoint hit.
32964 @value{GDBN} uses this to mark read-only regions of memory, like those
32965 containing program code. Since these areas never change, they should
32966 still have the same contents they did when the tracepoint was hit, so
32967 there's no reason for the stub to refuse to provide their contents.
32969 @item QTDisconnected:@var{value}
32970 Set the choice to what to do with the tracing run when @value{GDBN}
32971 disconnects from the target. A @var{value} of 1 directs the target to
32972 continue the tracing run, while 0 tells the target to stop tracing if
32973 @value{GDBN} is no longer in the picture.
32976 Ask the stub if there is a trace experiment running right now.
32978 The reply has the form:
32982 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
32983 @var{running} is a single digit @code{1} if the trace is presently
32984 running, or @code{0} if not. It is followed by semicolon-separated
32985 optional fields that an agent may use to report additional status.
32989 If the trace is not running, the agent may report any of several
32990 explanations as one of the optional fields:
32995 No trace has been run yet.
32998 The trace was stopped by a user-originated stop command.
33001 The trace stopped because the trace buffer filled up.
33003 @item tdisconnected:0
33004 The trace stopped because @value{GDBN} disconnected from the target.
33006 @item tpasscount:@var{tpnum}
33007 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
33009 @item terror:@var{text}:@var{tpnum}
33010 The trace stopped because tracepoint @var{tpnum} had an error. The
33011 string @var{text} is available to describe the nature of the error
33012 (for instance, a divide by zero in the condition expression).
33013 @var{text} is hex encoded.
33016 The trace stopped for some other reason.
33020 Additional optional fields supply statistical and other information.
33021 Although not required, they are extremely useful for users monitoring
33022 the progress of a trace run. If a trace has stopped, and these
33023 numbers are reported, they must reflect the state of the just-stopped
33028 @item tframes:@var{n}
33029 The number of trace frames in the buffer.
33031 @item tcreated:@var{n}
33032 The total number of trace frames created during the run. This may
33033 be larger than the trace frame count, if the buffer is circular.
33035 @item tsize:@var{n}
33036 The total size of the trace buffer, in bytes.
33038 @item tfree:@var{n}
33039 The number of bytes still unused in the buffer.
33041 @item circular:@var{n}
33042 The value of the circular trace buffer flag. @code{1} means that the
33043 trace buffer is circular and old trace frames will be discarded if
33044 necessary to make room, @code{0} means that the trace buffer is linear
33047 @item disconn:@var{n}
33048 The value of the disconnected tracing flag. @code{1} means that
33049 tracing will continue after @value{GDBN} disconnects, @code{0} means
33050 that the trace run will stop.
33054 @item qTV:@var{var}
33055 @cindex trace state variable value, remote request
33056 @cindex @samp{qTV} packet
33057 Ask the stub for the value of the trace state variable number @var{var}.
33062 The value of the variable is @var{value}. This will be the current
33063 value of the variable if the user is examining a running target, or a
33064 saved value if the variable was collected in the trace frame that the
33065 user is looking at. Note that multiple requests may result in
33066 different reply values, such as when requesting values while the
33067 program is running.
33070 The value of the variable is unknown. This would occur, for example,
33071 if the user is examining a trace frame in which the requested variable
33077 These packets request data about tracepoints that are being used by
33078 the target. @value{GDBN} sends @code{qTfP} to get the first piece
33079 of data, and multiple @code{qTsP} to get additional pieces. Replies
33080 to these packets generally take the form of the @code{QTDP} packets
33081 that define tracepoints. (FIXME add detailed syntax)
33085 These packets request data about trace state variables that are on the
33086 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
33087 and multiple @code{qTsV} to get additional variables. Replies to
33088 these packets follow the syntax of the @code{QTDV} packets that define
33089 trace state variables.
33093 These packets request data about static tracepoint markers that exist
33094 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
33095 first piece of data, and multiple @code{qTsSTM} to get additional
33096 pieces. Replies to these packets take the following form:
33100 @item m @var{address}:@var{id}:@var{extra}
33102 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
33103 a comma-separated list of markers
33105 (lower case letter @samp{L}) denotes end of list.
33107 An error occurred. @var{nn} are hex digits.
33109 An empty reply indicates that the request is not supported by the
33113 @var{address} is encoded in hex.
33114 @var{id} and @var{extra} are strings encoded in hex.
33116 In response to each query, the target will reply with a list of one or
33117 more markers, separated by commas. @value{GDBN} will respond to each
33118 reply with a request for more markers (using the @samp{qs} form of the
33119 query), until the target responds with @samp{l} (lower-case ell, for
33122 @item qTSTMat:@var{address}
33123 This packets requests data about static tracepoint markers in the
33124 target program at @var{address}. Replies to this packet follow the
33125 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
33126 tracepoint markers.
33128 @item QTSave:@var{filename}
33129 This packet directs the target to save trace data to the file name
33130 @var{filename} in the target's filesystem. @var{filename} is encoded
33131 as a hex string; the interpretation of the file name (relative vs
33132 absolute, wild cards, etc) is up to the target.
33134 @item qTBuffer:@var{offset},@var{len}
33135 Return up to @var{len} bytes of the current contents of trace buffer,
33136 starting at @var{offset}. The trace buffer is treated as if it were
33137 a contiguous collection of traceframes, as per the trace file format.
33138 The reply consists as many hex-encoded bytes as the target can deliver
33139 in a packet; it is not an error to return fewer than were asked for.
33140 A reply consisting of just @code{l} indicates that no bytes are
33143 @item QTBuffer:circular:@var{value}
33144 This packet directs the target to use a circular trace buffer if
33145 @var{value} is 1, or a linear buffer if the value is 0.
33149 @subsection Relocate instruction reply packet
33150 When installing fast tracepoints in memory, the target may need to
33151 relocate the instruction currently at the tracepoint address to a
33152 different address in memory. For most instructions, a simple copy is
33153 enough, but, for example, call instructions that implicitly push the
33154 return address on the stack, and relative branches or other
33155 PC-relative instructions require offset adjustment, so that the effect
33156 of executing the instruction at a different address is the same as if
33157 it had executed in the original location.
33159 In response to several of the tracepoint packets, the target may also
33160 respond with a number of intermediate @samp{qRelocInsn} request
33161 packets before the final result packet, to have @value{GDBN} handle
33162 this relocation operation. If a packet supports this mechanism, its
33163 documentation will explicitly say so. See for example the above
33164 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
33165 format of the request is:
33168 @item qRelocInsn:@var{from};@var{to}
33170 This requests @value{GDBN} to copy instruction at address @var{from}
33171 to address @var{to}, possibly adjusted so that executing the
33172 instruction at @var{to} has the same effect as executing it at
33173 @var{from}. @value{GDBN} writes the adjusted instruction to target
33174 memory starting at @var{to}.
33179 @item qRelocInsn:@var{adjusted_size}
33180 Informs the stub the relocation is complete. @var{adjusted_size} is
33181 the length in bytes of resulting relocated instruction sequence.
33183 A badly formed request was detected, or an error was encountered while
33184 relocating the instruction.
33187 @node Host I/O Packets
33188 @section Host I/O Packets
33189 @cindex Host I/O, remote protocol
33190 @cindex file transfer, remote protocol
33192 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
33193 operations on the far side of a remote link. For example, Host I/O is
33194 used to upload and download files to a remote target with its own
33195 filesystem. Host I/O uses the same constant values and data structure
33196 layout as the target-initiated File-I/O protocol. However, the
33197 Host I/O packets are structured differently. The target-initiated
33198 protocol relies on target memory to store parameters and buffers.
33199 Host I/O requests are initiated by @value{GDBN}, and the
33200 target's memory is not involved. @xref{File-I/O Remote Protocol
33201 Extension}, for more details on the target-initiated protocol.
33203 The Host I/O request packets all encode a single operation along with
33204 its arguments. They have this format:
33208 @item vFile:@var{operation}: @var{parameter}@dots{}
33209 @var{operation} is the name of the particular request; the target
33210 should compare the entire packet name up to the second colon when checking
33211 for a supported operation. The format of @var{parameter} depends on
33212 the operation. Numbers are always passed in hexadecimal. Negative
33213 numbers have an explicit minus sign (i.e.@: two's complement is not
33214 used). Strings (e.g.@: filenames) are encoded as a series of
33215 hexadecimal bytes. The last argument to a system call may be a
33216 buffer of escaped binary data (@pxref{Binary Data}).
33220 The valid responses to Host I/O packets are:
33224 @item F @var{result} [, @var{errno}] [; @var{attachment}]
33225 @var{result} is the integer value returned by this operation, usually
33226 non-negative for success and -1 for errors. If an error has occured,
33227 @var{errno} will be included in the result. @var{errno} will have a
33228 value defined by the File-I/O protocol (@pxref{Errno Values}). For
33229 operations which return data, @var{attachment} supplies the data as a
33230 binary buffer. Binary buffers in response packets are escaped in the
33231 normal way (@pxref{Binary Data}). See the individual packet
33232 documentation for the interpretation of @var{result} and
33236 An empty response indicates that this operation is not recognized.
33240 These are the supported Host I/O operations:
33243 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
33244 Open a file at @var{pathname} and return a file descriptor for it, or
33245 return -1 if an error occurs. @var{pathname} is a string,
33246 @var{flags} is an integer indicating a mask of open flags
33247 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
33248 of mode bits to use if the file is created (@pxref{mode_t Values}).
33249 @xref{open}, for details of the open flags and mode values.
33251 @item vFile:close: @var{fd}
33252 Close the open file corresponding to @var{fd} and return 0, or
33253 -1 if an error occurs.
33255 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
33256 Read data from the open file corresponding to @var{fd}. Up to
33257 @var{count} bytes will be read from the file, starting at @var{offset}
33258 relative to the start of the file. The target may read fewer bytes;
33259 common reasons include packet size limits and an end-of-file
33260 condition. The number of bytes read is returned. Zero should only be
33261 returned for a successful read at the end of the file, or if
33262 @var{count} was zero.
33264 The data read should be returned as a binary attachment on success.
33265 If zero bytes were read, the response should include an empty binary
33266 attachment (i.e.@: a trailing semicolon). The return value is the
33267 number of target bytes read; the binary attachment may be longer if
33268 some characters were escaped.
33270 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
33271 Write @var{data} (a binary buffer) to the open file corresponding
33272 to @var{fd}. Start the write at @var{offset} from the start of the
33273 file. Unlike many @code{write} system calls, there is no
33274 separate @var{count} argument; the length of @var{data} in the
33275 packet is used. @samp{vFile:write} returns the number of bytes written,
33276 which may be shorter than the length of @var{data}, or -1 if an
33279 @item vFile:unlink: @var{pathname}
33280 Delete the file at @var{pathname} on the target. Return 0,
33281 or -1 if an error occurs. @var{pathname} is a string.
33286 @section Interrupts
33287 @cindex interrupts (remote protocol)
33289 When a program on the remote target is running, @value{GDBN} may
33290 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
33291 a @code{BREAK} followed by @code{g},
33292 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
33294 The precise meaning of @code{BREAK} is defined by the transport
33295 mechanism and may, in fact, be undefined. @value{GDBN} does not
33296 currently define a @code{BREAK} mechanism for any of the network
33297 interfaces except for TCP, in which case @value{GDBN} sends the
33298 @code{telnet} BREAK sequence.
33300 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
33301 transport mechanisms. It is represented by sending the single byte
33302 @code{0x03} without any of the usual packet overhead described in
33303 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
33304 transmitted as part of a packet, it is considered to be packet data
33305 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
33306 (@pxref{X packet}), used for binary downloads, may include an unescaped
33307 @code{0x03} as part of its packet.
33309 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
33310 When Linux kernel receives this sequence from serial port,
33311 it stops execution and connects to gdb.
33313 Stubs are not required to recognize these interrupt mechanisms and the
33314 precise meaning associated with receipt of the interrupt is
33315 implementation defined. If the target supports debugging of multiple
33316 threads and/or processes, it should attempt to interrupt all
33317 currently-executing threads and processes.
33318 If the stub is successful at interrupting the
33319 running program, it should send one of the stop
33320 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
33321 of successfully stopping the program in all-stop mode, and a stop reply
33322 for each stopped thread in non-stop mode.
33323 Interrupts received while the
33324 program is stopped are discarded.
33326 @node Notification Packets
33327 @section Notification Packets
33328 @cindex notification packets
33329 @cindex packets, notification
33331 The @value{GDBN} remote serial protocol includes @dfn{notifications},
33332 packets that require no acknowledgment. Both the GDB and the stub
33333 may send notifications (although the only notifications defined at
33334 present are sent by the stub). Notifications carry information
33335 without incurring the round-trip latency of an acknowledgment, and so
33336 are useful for low-impact communications where occasional packet loss
33339 A notification packet has the form @samp{% @var{data} #
33340 @var{checksum}}, where @var{data} is the content of the notification,
33341 and @var{checksum} is a checksum of @var{data}, computed and formatted
33342 as for ordinary @value{GDBN} packets. A notification's @var{data}
33343 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
33344 receiving a notification, the recipient sends no @samp{+} or @samp{-}
33345 to acknowledge the notification's receipt or to report its corruption.
33347 Every notification's @var{data} begins with a name, which contains no
33348 colon characters, followed by a colon character.
33350 Recipients should silently ignore corrupted notifications and
33351 notifications they do not understand. Recipients should restart
33352 timeout periods on receipt of a well-formed notification, whether or
33353 not they understand it.
33355 Senders should only send the notifications described here when this
33356 protocol description specifies that they are permitted. In the
33357 future, we may extend the protocol to permit existing notifications in
33358 new contexts; this rule helps older senders avoid confusing newer
33361 (Older versions of @value{GDBN} ignore bytes received until they see
33362 the @samp{$} byte that begins an ordinary packet, so new stubs may
33363 transmit notifications without fear of confusing older clients. There
33364 are no notifications defined for @value{GDBN} to send at the moment, but we
33365 assume that most older stubs would ignore them, as well.)
33367 The following notification packets from the stub to @value{GDBN} are
33371 @item Stop: @var{reply}
33372 Report an asynchronous stop event in non-stop mode.
33373 The @var{reply} has the form of a stop reply, as
33374 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
33375 for information on how these notifications are acknowledged by
33379 @node Remote Non-Stop
33380 @section Remote Protocol Support for Non-Stop Mode
33382 @value{GDBN}'s remote protocol supports non-stop debugging of
33383 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
33384 supports non-stop mode, it should report that to @value{GDBN} by including
33385 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
33387 @value{GDBN} typically sends a @samp{QNonStop} packet only when
33388 establishing a new connection with the stub. Entering non-stop mode
33389 does not alter the state of any currently-running threads, but targets
33390 must stop all threads in any already-attached processes when entering
33391 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
33392 probe the target state after a mode change.
33394 In non-stop mode, when an attached process encounters an event that
33395 would otherwise be reported with a stop reply, it uses the
33396 asynchronous notification mechanism (@pxref{Notification Packets}) to
33397 inform @value{GDBN}. In contrast to all-stop mode, where all threads
33398 in all processes are stopped when a stop reply is sent, in non-stop
33399 mode only the thread reporting the stop event is stopped. That is,
33400 when reporting a @samp{S} or @samp{T} response to indicate completion
33401 of a step operation, hitting a breakpoint, or a fault, only the
33402 affected thread is stopped; any other still-running threads continue
33403 to run. When reporting a @samp{W} or @samp{X} response, all running
33404 threads belonging to other attached processes continue to run.
33406 Only one stop reply notification at a time may be pending; if
33407 additional stop events occur before @value{GDBN} has acknowledged the
33408 previous notification, they must be queued by the stub for later
33409 synchronous transmission in response to @samp{vStopped} packets from
33410 @value{GDBN}. Because the notification mechanism is unreliable,
33411 the stub is permitted to resend a stop reply notification
33412 if it believes @value{GDBN} may not have received it. @value{GDBN}
33413 ignores additional stop reply notifications received before it has
33414 finished processing a previous notification and the stub has completed
33415 sending any queued stop events.
33417 Otherwise, @value{GDBN} must be prepared to receive a stop reply
33418 notification at any time. Specifically, they may appear when
33419 @value{GDBN} is not otherwise reading input from the stub, or when
33420 @value{GDBN} is expecting to read a normal synchronous response or a
33421 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
33422 Notification packets are distinct from any other communication from
33423 the stub so there is no ambiguity.
33425 After receiving a stop reply notification, @value{GDBN} shall
33426 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
33427 as a regular, synchronous request to the stub. Such acknowledgment
33428 is not required to happen immediately, as @value{GDBN} is permitted to
33429 send other, unrelated packets to the stub first, which the stub should
33432 Upon receiving a @samp{vStopped} packet, if the stub has other queued
33433 stop events to report to @value{GDBN}, it shall respond by sending a
33434 normal stop reply response. @value{GDBN} shall then send another
33435 @samp{vStopped} packet to solicit further responses; again, it is
33436 permitted to send other, unrelated packets as well which the stub
33437 should process normally.
33439 If the stub receives a @samp{vStopped} packet and there are no
33440 additional stop events to report, the stub shall return an @samp{OK}
33441 response. At this point, if further stop events occur, the stub shall
33442 send a new stop reply notification, @value{GDBN} shall accept the
33443 notification, and the process shall be repeated.
33445 In non-stop mode, the target shall respond to the @samp{?} packet as
33446 follows. First, any incomplete stop reply notification/@samp{vStopped}
33447 sequence in progress is abandoned. The target must begin a new
33448 sequence reporting stop events for all stopped threads, whether or not
33449 it has previously reported those events to @value{GDBN}. The first
33450 stop reply is sent as a synchronous reply to the @samp{?} packet, and
33451 subsequent stop replies are sent as responses to @samp{vStopped} packets
33452 using the mechanism described above. The target must not send
33453 asynchronous stop reply notifications until the sequence is complete.
33454 If all threads are running when the target receives the @samp{?} packet,
33455 or if the target is not attached to any process, it shall respond
33458 @node Packet Acknowledgment
33459 @section Packet Acknowledgment
33461 @cindex acknowledgment, for @value{GDBN} remote
33462 @cindex packet acknowledgment, for @value{GDBN} remote
33463 By default, when either the host or the target machine receives a packet,
33464 the first response expected is an acknowledgment: either @samp{+} (to indicate
33465 the package was received correctly) or @samp{-} (to request retransmission).
33466 This mechanism allows the @value{GDBN} remote protocol to operate over
33467 unreliable transport mechanisms, such as a serial line.
33469 In cases where the transport mechanism is itself reliable (such as a pipe or
33470 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
33471 It may be desirable to disable them in that case to reduce communication
33472 overhead, or for other reasons. This can be accomplished by means of the
33473 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
33475 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
33476 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
33477 and response format still includes the normal checksum, as described in
33478 @ref{Overview}, but the checksum may be ignored by the receiver.
33480 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
33481 no-acknowledgment mode, it should report that to @value{GDBN}
33482 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
33483 @pxref{qSupported}.
33484 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
33485 disabled via the @code{set remote noack-packet off} command
33486 (@pxref{Remote Configuration}),
33487 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
33488 Only then may the stub actually turn off packet acknowledgments.
33489 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
33490 response, which can be safely ignored by the stub.
33492 Note that @code{set remote noack-packet} command only affects negotiation
33493 between @value{GDBN} and the stub when subsequent connections are made;
33494 it does not affect the protocol acknowledgment state for any current
33496 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
33497 new connection is established,
33498 there is also no protocol request to re-enable the acknowledgments
33499 for the current connection, once disabled.
33504 Example sequence of a target being re-started. Notice how the restart
33505 does not get any direct output:
33510 @emph{target restarts}
33513 <- @code{T001:1234123412341234}
33517 Example sequence of a target being stepped by a single instruction:
33520 -> @code{G1445@dots{}}
33525 <- @code{T001:1234123412341234}
33529 <- @code{1455@dots{}}
33533 @node File-I/O Remote Protocol Extension
33534 @section File-I/O Remote Protocol Extension
33535 @cindex File-I/O remote protocol extension
33538 * File-I/O Overview::
33539 * Protocol Basics::
33540 * The F Request Packet::
33541 * The F Reply Packet::
33542 * The Ctrl-C Message::
33544 * List of Supported Calls::
33545 * Protocol-specific Representation of Datatypes::
33547 * File-I/O Examples::
33550 @node File-I/O Overview
33551 @subsection File-I/O Overview
33552 @cindex file-i/o overview
33554 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
33555 target to use the host's file system and console I/O to perform various
33556 system calls. System calls on the target system are translated into a
33557 remote protocol packet to the host system, which then performs the needed
33558 actions and returns a response packet to the target system.
33559 This simulates file system operations even on targets that lack file systems.
33561 The protocol is defined to be independent of both the host and target systems.
33562 It uses its own internal representation of datatypes and values. Both
33563 @value{GDBN} and the target's @value{GDBN} stub are responsible for
33564 translating the system-dependent value representations into the internal
33565 protocol representations when data is transmitted.
33567 The communication is synchronous. A system call is possible only when
33568 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
33569 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
33570 the target is stopped to allow deterministic access to the target's
33571 memory. Therefore File-I/O is not interruptible by target signals. On
33572 the other hand, it is possible to interrupt File-I/O by a user interrupt
33573 (@samp{Ctrl-C}) within @value{GDBN}.
33575 The target's request to perform a host system call does not finish
33576 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
33577 after finishing the system call, the target returns to continuing the
33578 previous activity (continue, step). No additional continue or step
33579 request from @value{GDBN} is required.
33582 (@value{GDBP}) continue
33583 <- target requests 'system call X'
33584 target is stopped, @value{GDBN} executes system call
33585 -> @value{GDBN} returns result
33586 ... target continues, @value{GDBN} returns to wait for the target
33587 <- target hits breakpoint and sends a Txx packet
33590 The protocol only supports I/O on the console and to regular files on
33591 the host file system. Character or block special devices, pipes,
33592 named pipes, sockets or any other communication method on the host
33593 system are not supported by this protocol.
33595 File I/O is not supported in non-stop mode.
33597 @node Protocol Basics
33598 @subsection Protocol Basics
33599 @cindex protocol basics, file-i/o
33601 The File-I/O protocol uses the @code{F} packet as the request as well
33602 as reply packet. Since a File-I/O system call can only occur when
33603 @value{GDBN} is waiting for a response from the continuing or stepping target,
33604 the File-I/O request is a reply that @value{GDBN} has to expect as a result
33605 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
33606 This @code{F} packet contains all information needed to allow @value{GDBN}
33607 to call the appropriate host system call:
33611 A unique identifier for the requested system call.
33614 All parameters to the system call. Pointers are given as addresses
33615 in the target memory address space. Pointers to strings are given as
33616 pointer/length pair. Numerical values are given as they are.
33617 Numerical control flags are given in a protocol-specific representation.
33621 At this point, @value{GDBN} has to perform the following actions.
33625 If the parameters include pointer values to data needed as input to a
33626 system call, @value{GDBN} requests this data from the target with a
33627 standard @code{m} packet request. This additional communication has to be
33628 expected by the target implementation and is handled as any other @code{m}
33632 @value{GDBN} translates all value from protocol representation to host
33633 representation as needed. Datatypes are coerced into the host types.
33636 @value{GDBN} calls the system call.
33639 It then coerces datatypes back to protocol representation.
33642 If the system call is expected to return data in buffer space specified
33643 by pointer parameters to the call, the data is transmitted to the
33644 target using a @code{M} or @code{X} packet. This packet has to be expected
33645 by the target implementation and is handled as any other @code{M} or @code{X}
33650 Eventually @value{GDBN} replies with another @code{F} packet which contains all
33651 necessary information for the target to continue. This at least contains
33658 @code{errno}, if has been changed by the system call.
33665 After having done the needed type and value coercion, the target continues
33666 the latest continue or step action.
33668 @node The F Request Packet
33669 @subsection The @code{F} Request Packet
33670 @cindex file-i/o request packet
33671 @cindex @code{F} request packet
33673 The @code{F} request packet has the following format:
33676 @item F@var{call-id},@var{parameter@dots{}}
33678 @var{call-id} is the identifier to indicate the host system call to be called.
33679 This is just the name of the function.
33681 @var{parameter@dots{}} are the parameters to the system call.
33682 Parameters are hexadecimal integer values, either the actual values in case
33683 of scalar datatypes, pointers to target buffer space in case of compound
33684 datatypes and unspecified memory areas, or pointer/length pairs in case
33685 of string parameters. These are appended to the @var{call-id} as a
33686 comma-delimited list. All values are transmitted in ASCII
33687 string representation, pointer/length pairs separated by a slash.
33693 @node The F Reply Packet
33694 @subsection The @code{F} Reply Packet
33695 @cindex file-i/o reply packet
33696 @cindex @code{F} reply packet
33698 The @code{F} reply packet has the following format:
33702 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
33704 @var{retcode} is the return code of the system call as hexadecimal value.
33706 @var{errno} is the @code{errno} set by the call, in protocol-specific
33708 This parameter can be omitted if the call was successful.
33710 @var{Ctrl-C flag} is only sent if the user requested a break. In this
33711 case, @var{errno} must be sent as well, even if the call was successful.
33712 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
33719 or, if the call was interrupted before the host call has been performed:
33726 assuming 4 is the protocol-specific representation of @code{EINTR}.
33731 @node The Ctrl-C Message
33732 @subsection The @samp{Ctrl-C} Message
33733 @cindex ctrl-c message, in file-i/o protocol
33735 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
33736 reply packet (@pxref{The F Reply Packet}),
33737 the target should behave as if it had
33738 gotten a break message. The meaning for the target is ``system call
33739 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
33740 (as with a break message) and return to @value{GDBN} with a @code{T02}
33743 It's important for the target to know in which
33744 state the system call was interrupted. There are two possible cases:
33748 The system call hasn't been performed on the host yet.
33751 The system call on the host has been finished.
33755 These two states can be distinguished by the target by the value of the
33756 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
33757 call hasn't been performed. This is equivalent to the @code{EINTR} handling
33758 on POSIX systems. In any other case, the target may presume that the
33759 system call has been finished --- successfully or not --- and should behave
33760 as if the break message arrived right after the system call.
33762 @value{GDBN} must behave reliably. If the system call has not been called
33763 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
33764 @code{errno} in the packet. If the system call on the host has been finished
33765 before the user requests a break, the full action must be finished by
33766 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
33767 The @code{F} packet may only be sent when either nothing has happened
33768 or the full action has been completed.
33771 @subsection Console I/O
33772 @cindex console i/o as part of file-i/o
33774 By default and if not explicitly closed by the target system, the file
33775 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
33776 on the @value{GDBN} console is handled as any other file output operation
33777 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
33778 by @value{GDBN} so that after the target read request from file descriptor
33779 0 all following typing is buffered until either one of the following
33784 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
33786 system call is treated as finished.
33789 The user presses @key{RET}. This is treated as end of input with a trailing
33793 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
33794 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
33798 If the user has typed more characters than fit in the buffer given to
33799 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
33800 either another @code{read(0, @dots{})} is requested by the target, or debugging
33801 is stopped at the user's request.
33804 @node List of Supported Calls
33805 @subsection List of Supported Calls
33806 @cindex list of supported file-i/o calls
33823 @unnumberedsubsubsec open
33824 @cindex open, file-i/o system call
33829 int open(const char *pathname, int flags);
33830 int open(const char *pathname, int flags, mode_t mode);
33834 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
33837 @var{flags} is the bitwise @code{OR} of the following values:
33841 If the file does not exist it will be created. The host
33842 rules apply as far as file ownership and time stamps
33846 When used with @code{O_CREAT}, if the file already exists it is
33847 an error and open() fails.
33850 If the file already exists and the open mode allows
33851 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
33852 truncated to zero length.
33855 The file is opened in append mode.
33858 The file is opened for reading only.
33861 The file is opened for writing only.
33864 The file is opened for reading and writing.
33868 Other bits are silently ignored.
33872 @var{mode} is the bitwise @code{OR} of the following values:
33876 User has read permission.
33879 User has write permission.
33882 Group has read permission.
33885 Group has write permission.
33888 Others have read permission.
33891 Others have write permission.
33895 Other bits are silently ignored.
33898 @item Return value:
33899 @code{open} returns the new file descriptor or -1 if an error
33906 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
33909 @var{pathname} refers to a directory.
33912 The requested access is not allowed.
33915 @var{pathname} was too long.
33918 A directory component in @var{pathname} does not exist.
33921 @var{pathname} refers to a device, pipe, named pipe or socket.
33924 @var{pathname} refers to a file on a read-only filesystem and
33925 write access was requested.
33928 @var{pathname} is an invalid pointer value.
33931 No space on device to create the file.
33934 The process already has the maximum number of files open.
33937 The limit on the total number of files open on the system
33941 The call was interrupted by the user.
33947 @unnumberedsubsubsec close
33948 @cindex close, file-i/o system call
33957 @samp{Fclose,@var{fd}}
33959 @item Return value:
33960 @code{close} returns zero on success, or -1 if an error occurred.
33966 @var{fd} isn't a valid open file descriptor.
33969 The call was interrupted by the user.
33975 @unnumberedsubsubsec read
33976 @cindex read, file-i/o system call
33981 int read(int fd, void *buf, unsigned int count);
33985 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
33987 @item Return value:
33988 On success, the number of bytes read is returned.
33989 Zero indicates end of file. If count is zero, read
33990 returns zero as well. On error, -1 is returned.
33996 @var{fd} is not a valid file descriptor or is not open for
34000 @var{bufptr} is an invalid pointer value.
34003 The call was interrupted by the user.
34009 @unnumberedsubsubsec write
34010 @cindex write, file-i/o system call
34015 int write(int fd, const void *buf, unsigned int count);
34019 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
34021 @item Return value:
34022 On success, the number of bytes written are returned.
34023 Zero indicates nothing was written. On error, -1
34030 @var{fd} is not a valid file descriptor or is not open for
34034 @var{bufptr} is an invalid pointer value.
34037 An attempt was made to write a file that exceeds the
34038 host-specific maximum file size allowed.
34041 No space on device to write the data.
34044 The call was interrupted by the user.
34050 @unnumberedsubsubsec lseek
34051 @cindex lseek, file-i/o system call
34056 long lseek (int fd, long offset, int flag);
34060 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
34062 @var{flag} is one of:
34066 The offset is set to @var{offset} bytes.
34069 The offset is set to its current location plus @var{offset}
34073 The offset is set to the size of the file plus @var{offset}
34077 @item Return value:
34078 On success, the resulting unsigned offset in bytes from
34079 the beginning of the file is returned. Otherwise, a
34080 value of -1 is returned.
34086 @var{fd} is not a valid open file descriptor.
34089 @var{fd} is associated with the @value{GDBN} console.
34092 @var{flag} is not a proper value.
34095 The call was interrupted by the user.
34101 @unnumberedsubsubsec rename
34102 @cindex rename, file-i/o system call
34107 int rename(const char *oldpath, const char *newpath);
34111 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
34113 @item Return value:
34114 On success, zero is returned. On error, -1 is returned.
34120 @var{newpath} is an existing directory, but @var{oldpath} is not a
34124 @var{newpath} is a non-empty directory.
34127 @var{oldpath} or @var{newpath} is a directory that is in use by some
34131 An attempt was made to make a directory a subdirectory
34135 A component used as a directory in @var{oldpath} or new
34136 path is not a directory. Or @var{oldpath} is a directory
34137 and @var{newpath} exists but is not a directory.
34140 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
34143 No access to the file or the path of the file.
34147 @var{oldpath} or @var{newpath} was too long.
34150 A directory component in @var{oldpath} or @var{newpath} does not exist.
34153 The file is on a read-only filesystem.
34156 The device containing the file has no room for the new
34160 The call was interrupted by the user.
34166 @unnumberedsubsubsec unlink
34167 @cindex unlink, file-i/o system call
34172 int unlink(const char *pathname);
34176 @samp{Funlink,@var{pathnameptr}/@var{len}}
34178 @item Return value:
34179 On success, zero is returned. On error, -1 is returned.
34185 No access to the file or the path of the file.
34188 The system does not allow unlinking of directories.
34191 The file @var{pathname} cannot be unlinked because it's
34192 being used by another process.
34195 @var{pathnameptr} is an invalid pointer value.
34198 @var{pathname} was too long.
34201 A directory component in @var{pathname} does not exist.
34204 A component of the path is not a directory.
34207 The file is on a read-only filesystem.
34210 The call was interrupted by the user.
34216 @unnumberedsubsubsec stat/fstat
34217 @cindex fstat, file-i/o system call
34218 @cindex stat, file-i/o system call
34223 int stat(const char *pathname, struct stat *buf);
34224 int fstat(int fd, struct stat *buf);
34228 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
34229 @samp{Ffstat,@var{fd},@var{bufptr}}
34231 @item Return value:
34232 On success, zero is returned. On error, -1 is returned.
34238 @var{fd} is not a valid open file.
34241 A directory component in @var{pathname} does not exist or the
34242 path is an empty string.
34245 A component of the path is not a directory.
34248 @var{pathnameptr} is an invalid pointer value.
34251 No access to the file or the path of the file.
34254 @var{pathname} was too long.
34257 The call was interrupted by the user.
34263 @unnumberedsubsubsec gettimeofday
34264 @cindex gettimeofday, file-i/o system call
34269 int gettimeofday(struct timeval *tv, void *tz);
34273 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
34275 @item Return value:
34276 On success, 0 is returned, -1 otherwise.
34282 @var{tz} is a non-NULL pointer.
34285 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
34291 @unnumberedsubsubsec isatty
34292 @cindex isatty, file-i/o system call
34297 int isatty(int fd);
34301 @samp{Fisatty,@var{fd}}
34303 @item Return value:
34304 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
34310 The call was interrupted by the user.
34315 Note that the @code{isatty} call is treated as a special case: it returns
34316 1 to the target if the file descriptor is attached
34317 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
34318 would require implementing @code{ioctl} and would be more complex than
34323 @unnumberedsubsubsec system
34324 @cindex system, file-i/o system call
34329 int system(const char *command);
34333 @samp{Fsystem,@var{commandptr}/@var{len}}
34335 @item Return value:
34336 If @var{len} is zero, the return value indicates whether a shell is
34337 available. A zero return value indicates a shell is not available.
34338 For non-zero @var{len}, the value returned is -1 on error and the
34339 return status of the command otherwise. Only the exit status of the
34340 command is returned, which is extracted from the host's @code{system}
34341 return value by calling @code{WEXITSTATUS(retval)}. In case
34342 @file{/bin/sh} could not be executed, 127 is returned.
34348 The call was interrupted by the user.
34353 @value{GDBN} takes over the full task of calling the necessary host calls
34354 to perform the @code{system} call. The return value of @code{system} on
34355 the host is simplified before it's returned
34356 to the target. Any termination signal information from the child process
34357 is discarded, and the return value consists
34358 entirely of the exit status of the called command.
34360 Due to security concerns, the @code{system} call is by default refused
34361 by @value{GDBN}. The user has to allow this call explicitly with the
34362 @code{set remote system-call-allowed 1} command.
34365 @item set remote system-call-allowed
34366 @kindex set remote system-call-allowed
34367 Control whether to allow the @code{system} calls in the File I/O
34368 protocol for the remote target. The default is zero (disabled).
34370 @item show remote system-call-allowed
34371 @kindex show remote system-call-allowed
34372 Show whether the @code{system} calls are allowed in the File I/O
34376 @node Protocol-specific Representation of Datatypes
34377 @subsection Protocol-specific Representation of Datatypes
34378 @cindex protocol-specific representation of datatypes, in file-i/o protocol
34381 * Integral Datatypes::
34383 * Memory Transfer::
34388 @node Integral Datatypes
34389 @unnumberedsubsubsec Integral Datatypes
34390 @cindex integral datatypes, in file-i/o protocol
34392 The integral datatypes used in the system calls are @code{int},
34393 @code{unsigned int}, @code{long}, @code{unsigned long},
34394 @code{mode_t}, and @code{time_t}.
34396 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
34397 implemented as 32 bit values in this protocol.
34399 @code{long} and @code{unsigned long} are implemented as 64 bit types.
34401 @xref{Limits}, for corresponding MIN and MAX values (similar to those
34402 in @file{limits.h}) to allow range checking on host and target.
34404 @code{time_t} datatypes are defined as seconds since the Epoch.
34406 All integral datatypes transferred as part of a memory read or write of a
34407 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
34410 @node Pointer Values
34411 @unnumberedsubsubsec Pointer Values
34412 @cindex pointer values, in file-i/o protocol
34414 Pointers to target data are transmitted as they are. An exception
34415 is made for pointers to buffers for which the length isn't
34416 transmitted as part of the function call, namely strings. Strings
34417 are transmitted as a pointer/length pair, both as hex values, e.g.@:
34424 which is a pointer to data of length 18 bytes at position 0x1aaf.
34425 The length is defined as the full string length in bytes, including
34426 the trailing null byte. For example, the string @code{"hello world"}
34427 at address 0x123456 is transmitted as
34433 @node Memory Transfer
34434 @unnumberedsubsubsec Memory Transfer
34435 @cindex memory transfer, in file-i/o protocol
34437 Structured data which is transferred using a memory read or write (for
34438 example, a @code{struct stat}) is expected to be in a protocol-specific format
34439 with all scalar multibyte datatypes being big endian. Translation to
34440 this representation needs to be done both by the target before the @code{F}
34441 packet is sent, and by @value{GDBN} before
34442 it transfers memory to the target. Transferred pointers to structured
34443 data should point to the already-coerced data at any time.
34447 @unnumberedsubsubsec struct stat
34448 @cindex struct stat, in file-i/o protocol
34450 The buffer of type @code{struct stat} used by the target and @value{GDBN}
34451 is defined as follows:
34455 unsigned int st_dev; /* device */
34456 unsigned int st_ino; /* inode */
34457 mode_t st_mode; /* protection */
34458 unsigned int st_nlink; /* number of hard links */
34459 unsigned int st_uid; /* user ID of owner */
34460 unsigned int st_gid; /* group ID of owner */
34461 unsigned int st_rdev; /* device type (if inode device) */
34462 unsigned long st_size; /* total size, in bytes */
34463 unsigned long st_blksize; /* blocksize for filesystem I/O */
34464 unsigned long st_blocks; /* number of blocks allocated */
34465 time_t st_atime; /* time of last access */
34466 time_t st_mtime; /* time of last modification */
34467 time_t st_ctime; /* time of last change */
34471 The integral datatypes conform to the definitions given in the
34472 appropriate section (see @ref{Integral Datatypes}, for details) so this
34473 structure is of size 64 bytes.
34475 The values of several fields have a restricted meaning and/or
34481 A value of 0 represents a file, 1 the console.
34484 No valid meaning for the target. Transmitted unchanged.
34487 Valid mode bits are described in @ref{Constants}. Any other
34488 bits have currently no meaning for the target.
34493 No valid meaning for the target. Transmitted unchanged.
34498 These values have a host and file system dependent
34499 accuracy. Especially on Windows hosts, the file system may not
34500 support exact timing values.
34503 The target gets a @code{struct stat} of the above representation and is
34504 responsible for coercing it to the target representation before
34507 Note that due to size differences between the host, target, and protocol
34508 representations of @code{struct stat} members, these members could eventually
34509 get truncated on the target.
34511 @node struct timeval
34512 @unnumberedsubsubsec struct timeval
34513 @cindex struct timeval, in file-i/o protocol
34515 The buffer of type @code{struct timeval} used by the File-I/O protocol
34516 is defined as follows:
34520 time_t tv_sec; /* second */
34521 long tv_usec; /* microsecond */
34525 The integral datatypes conform to the definitions given in the
34526 appropriate section (see @ref{Integral Datatypes}, for details) so this
34527 structure is of size 8 bytes.
34530 @subsection Constants
34531 @cindex constants, in file-i/o protocol
34533 The following values are used for the constants inside of the
34534 protocol. @value{GDBN} and target are responsible for translating these
34535 values before and after the call as needed.
34546 @unnumberedsubsubsec Open Flags
34547 @cindex open flags, in file-i/o protocol
34549 All values are given in hexadecimal representation.
34561 @node mode_t Values
34562 @unnumberedsubsubsec mode_t Values
34563 @cindex mode_t values, in file-i/o protocol
34565 All values are given in octal representation.
34582 @unnumberedsubsubsec Errno Values
34583 @cindex errno values, in file-i/o protocol
34585 All values are given in decimal representation.
34610 @code{EUNKNOWN} is used as a fallback error value if a host system returns
34611 any error value not in the list of supported error numbers.
34614 @unnumberedsubsubsec Lseek Flags
34615 @cindex lseek flags, in file-i/o protocol
34624 @unnumberedsubsubsec Limits
34625 @cindex limits, in file-i/o protocol
34627 All values are given in decimal representation.
34630 INT_MIN -2147483648
34632 UINT_MAX 4294967295
34633 LONG_MIN -9223372036854775808
34634 LONG_MAX 9223372036854775807
34635 ULONG_MAX 18446744073709551615
34638 @node File-I/O Examples
34639 @subsection File-I/O Examples
34640 @cindex file-i/o examples
34642 Example sequence of a write call, file descriptor 3, buffer is at target
34643 address 0x1234, 6 bytes should be written:
34646 <- @code{Fwrite,3,1234,6}
34647 @emph{request memory read from target}
34650 @emph{return "6 bytes written"}
34654 Example sequence of a read call, file descriptor 3, buffer is at target
34655 address 0x1234, 6 bytes should be read:
34658 <- @code{Fread,3,1234,6}
34659 @emph{request memory write to target}
34660 -> @code{X1234,6:XXXXXX}
34661 @emph{return "6 bytes read"}
34665 Example sequence of a read call, call fails on the host due to invalid
34666 file descriptor (@code{EBADF}):
34669 <- @code{Fread,3,1234,6}
34673 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
34677 <- @code{Fread,3,1234,6}
34682 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
34686 <- @code{Fread,3,1234,6}
34687 -> @code{X1234,6:XXXXXX}
34691 @node Library List Format
34692 @section Library List Format
34693 @cindex library list format, remote protocol
34695 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
34696 same process as your application to manage libraries. In this case,
34697 @value{GDBN} can use the loader's symbol table and normal memory
34698 operations to maintain a list of shared libraries. On other
34699 platforms, the operating system manages loaded libraries.
34700 @value{GDBN} can not retrieve the list of currently loaded libraries
34701 through memory operations, so it uses the @samp{qXfer:libraries:read}
34702 packet (@pxref{qXfer library list read}) instead. The remote stub
34703 queries the target's operating system and reports which libraries
34706 The @samp{qXfer:libraries:read} packet returns an XML document which
34707 lists loaded libraries and their offsets. Each library has an
34708 associated name and one or more segment or section base addresses,
34709 which report where the library was loaded in memory.
34711 For the common case of libraries that are fully linked binaries, the
34712 library should have a list of segments. If the target supports
34713 dynamic linking of a relocatable object file, its library XML element
34714 should instead include a list of allocated sections. The segment or
34715 section bases are start addresses, not relocation offsets; they do not
34716 depend on the library's link-time base addresses.
34718 @value{GDBN} must be linked with the Expat library to support XML
34719 library lists. @xref{Expat}.
34721 A simple memory map, with one loaded library relocated by a single
34722 offset, looks like this:
34726 <library name="/lib/libc.so.6">
34727 <segment address="0x10000000"/>
34732 Another simple memory map, with one loaded library with three
34733 allocated sections (.text, .data, .bss), looks like this:
34737 <library name="sharedlib.o">
34738 <section address="0x10000000"/>
34739 <section address="0x20000000"/>
34740 <section address="0x30000000"/>
34745 The format of a library list is described by this DTD:
34748 <!-- library-list: Root element with versioning -->
34749 <!ELEMENT library-list (library)*>
34750 <!ATTLIST library-list version CDATA #FIXED "1.0">
34751 <!ELEMENT library (segment*, section*)>
34752 <!ATTLIST library name CDATA #REQUIRED>
34753 <!ELEMENT segment EMPTY>
34754 <!ATTLIST segment address CDATA #REQUIRED>
34755 <!ELEMENT section EMPTY>
34756 <!ATTLIST section address CDATA #REQUIRED>
34759 In addition, segments and section descriptors cannot be mixed within a
34760 single library element, and you must supply at least one segment or
34761 section for each library.
34763 @node Memory Map Format
34764 @section Memory Map Format
34765 @cindex memory map format
34767 To be able to write into flash memory, @value{GDBN} needs to obtain a
34768 memory map from the target. This section describes the format of the
34771 The memory map is obtained using the @samp{qXfer:memory-map:read}
34772 (@pxref{qXfer memory map read}) packet and is an XML document that
34773 lists memory regions.
34775 @value{GDBN} must be linked with the Expat library to support XML
34776 memory maps. @xref{Expat}.
34778 The top-level structure of the document is shown below:
34781 <?xml version="1.0"?>
34782 <!DOCTYPE memory-map
34783 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
34784 "http://sourceware.org/gdb/gdb-memory-map.dtd">
34790 Each region can be either:
34795 A region of RAM starting at @var{addr} and extending for @var{length}
34799 <memory type="ram" start="@var{addr}" length="@var{length}"/>
34804 A region of read-only memory:
34807 <memory type="rom" start="@var{addr}" length="@var{length}"/>
34812 A region of flash memory, with erasure blocks @var{blocksize}
34816 <memory type="flash" start="@var{addr}" length="@var{length}">
34817 <property name="blocksize">@var{blocksize}</property>
34823 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
34824 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
34825 packets to write to addresses in such ranges.
34827 The formal DTD for memory map format is given below:
34830 <!-- ................................................... -->
34831 <!-- Memory Map XML DTD ................................ -->
34832 <!-- File: memory-map.dtd .............................. -->
34833 <!-- .................................... .............. -->
34834 <!-- memory-map.dtd -->
34835 <!-- memory-map: Root element with versioning -->
34836 <!ELEMENT memory-map (memory | property)>
34837 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
34838 <!ELEMENT memory (property)>
34839 <!-- memory: Specifies a memory region,
34840 and its type, or device. -->
34841 <!ATTLIST memory type CDATA #REQUIRED
34842 start CDATA #REQUIRED
34843 length CDATA #REQUIRED
34844 device CDATA #IMPLIED>
34845 <!-- property: Generic attribute tag -->
34846 <!ELEMENT property (#PCDATA | property)*>
34847 <!ATTLIST property name CDATA #REQUIRED>
34850 @node Thread List Format
34851 @section Thread List Format
34852 @cindex thread list format
34854 To efficiently update the list of threads and their attributes,
34855 @value{GDBN} issues the @samp{qXfer:threads:read} packet
34856 (@pxref{qXfer threads read}) and obtains the XML document with
34857 the following structure:
34860 <?xml version="1.0"?>
34862 <thread id="id" core="0">
34863 ... description ...
34868 Each @samp{thread} element must have the @samp{id} attribute that
34869 identifies the thread (@pxref{thread-id syntax}). The
34870 @samp{core} attribute, if present, specifies which processor core
34871 the thread was last executing on. The content of the of @samp{thread}
34872 element is interpreted as human-readable auxilliary information.
34874 @include agentexpr.texi
34876 @node Trace File Format
34877 @appendix Trace File Format
34878 @cindex trace file format
34880 The trace file comes in three parts: a header, a textual description
34881 section, and a trace frame section with binary data.
34883 The header has the form @code{\x7fTRACE0\n}. The first byte is
34884 @code{0x7f} so as to indicate that the file contains binary data,
34885 while the @code{0} is a version number that may have different values
34888 The description section consists of multiple lines of @sc{ascii} text
34889 separated by newline characters (@code{0xa}). The lines may include a
34890 variety of optional descriptive or context-setting information, such
34891 as tracepoint definitions or register set size. @value{GDBN} will
34892 ignore any line that it does not recognize. An empty line marks the end
34895 @c FIXME add some specific types of data
34897 The trace frame section consists of a number of consecutive frames.
34898 Each frame begins with a two-byte tracepoint number, followed by a
34899 four-byte size giving the amount of data in the frame. The data in
34900 the frame consists of a number of blocks, each introduced by a
34901 character indicating its type (at least register, memory, and trace
34902 state variable). The data in this section is raw binary, not a
34903 hexadecimal or other encoding; its endianness matches the target's
34906 @c FIXME bi-arch may require endianness/arch info in description section
34909 @item R @var{bytes}
34910 Register block. The number and ordering of bytes matches that of a
34911 @code{g} packet in the remote protocol. Note that these are the
34912 actual bytes, in target order and @value{GDBN} register order, not a
34913 hexadecimal encoding.
34915 @item M @var{address} @var{length} @var{bytes}...
34916 Memory block. This is a contiguous block of memory, at the 8-byte
34917 address @var{address}, with a 2-byte length @var{length}, followed by
34918 @var{length} bytes.
34920 @item V @var{number} @var{value}
34921 Trace state variable block. This records the 8-byte signed value
34922 @var{value} of trace state variable numbered @var{number}.
34926 Future enhancements of the trace file format may include additional types
34929 @node Target Descriptions
34930 @appendix Target Descriptions
34931 @cindex target descriptions
34933 @strong{Warning:} target descriptions are still under active development,
34934 and the contents and format may change between @value{GDBN} releases.
34935 The format is expected to stabilize in the future.
34937 One of the challenges of using @value{GDBN} to debug embedded systems
34938 is that there are so many minor variants of each processor
34939 architecture in use. It is common practice for vendors to start with
34940 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
34941 and then make changes to adapt it to a particular market niche. Some
34942 architectures have hundreds of variants, available from dozens of
34943 vendors. This leads to a number of problems:
34947 With so many different customized processors, it is difficult for
34948 the @value{GDBN} maintainers to keep up with the changes.
34950 Since individual variants may have short lifetimes or limited
34951 audiences, it may not be worthwhile to carry information about every
34952 variant in the @value{GDBN} source tree.
34954 When @value{GDBN} does support the architecture of the embedded system
34955 at hand, the task of finding the correct architecture name to give the
34956 @command{set architecture} command can be error-prone.
34959 To address these problems, the @value{GDBN} remote protocol allows a
34960 target system to not only identify itself to @value{GDBN}, but to
34961 actually describe its own features. This lets @value{GDBN} support
34962 processor variants it has never seen before --- to the extent that the
34963 descriptions are accurate, and that @value{GDBN} understands them.
34965 @value{GDBN} must be linked with the Expat library to support XML
34966 target descriptions. @xref{Expat}.
34969 * Retrieving Descriptions:: How descriptions are fetched from a target.
34970 * Target Description Format:: The contents of a target description.
34971 * Predefined Target Types:: Standard types available for target
34973 * Standard Target Features:: Features @value{GDBN} knows about.
34976 @node Retrieving Descriptions
34977 @section Retrieving Descriptions
34979 Target descriptions can be read from the target automatically, or
34980 specified by the user manually. The default behavior is to read the
34981 description from the target. @value{GDBN} retrieves it via the remote
34982 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
34983 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
34984 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
34985 XML document, of the form described in @ref{Target Description
34988 Alternatively, you can specify a file to read for the target description.
34989 If a file is set, the target will not be queried. The commands to
34990 specify a file are:
34993 @cindex set tdesc filename
34994 @item set tdesc filename @var{path}
34995 Read the target description from @var{path}.
34997 @cindex unset tdesc filename
34998 @item unset tdesc filename
34999 Do not read the XML target description from a file. @value{GDBN}
35000 will use the description supplied by the current target.
35002 @cindex show tdesc filename
35003 @item show tdesc filename
35004 Show the filename to read for a target description, if any.
35008 @node Target Description Format
35009 @section Target Description Format
35010 @cindex target descriptions, XML format
35012 A target description annex is an @uref{http://www.w3.org/XML/, XML}
35013 document which complies with the Document Type Definition provided in
35014 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
35015 means you can use generally available tools like @command{xmllint} to
35016 check that your feature descriptions are well-formed and valid.
35017 However, to help people unfamiliar with XML write descriptions for
35018 their targets, we also describe the grammar here.
35020 Target descriptions can identify the architecture of the remote target
35021 and (for some architectures) provide information about custom register
35022 sets. They can also identify the OS ABI of the remote target.
35023 @value{GDBN} can use this information to autoconfigure for your
35024 target, or to warn you if you connect to an unsupported target.
35026 Here is a simple target description:
35029 <target version="1.0">
35030 <architecture>i386:x86-64</architecture>
35035 This minimal description only says that the target uses
35036 the x86-64 architecture.
35038 A target description has the following overall form, with [ ] marking
35039 optional elements and @dots{} marking repeatable elements. The elements
35040 are explained further below.
35043 <?xml version="1.0"?>
35044 <!DOCTYPE target SYSTEM "gdb-target.dtd">
35045 <target version="1.0">
35046 @r{[}@var{architecture}@r{]}
35047 @r{[}@var{osabi}@r{]}
35048 @r{[}@var{compatible}@r{]}
35049 @r{[}@var{feature}@dots{}@r{]}
35054 The description is generally insensitive to whitespace and line
35055 breaks, under the usual common-sense rules. The XML version
35056 declaration and document type declaration can generally be omitted
35057 (@value{GDBN} does not require them), but specifying them may be
35058 useful for XML validation tools. The @samp{version} attribute for
35059 @samp{<target>} may also be omitted, but we recommend
35060 including it; if future versions of @value{GDBN} use an incompatible
35061 revision of @file{gdb-target.dtd}, they will detect and report
35062 the version mismatch.
35064 @subsection Inclusion
35065 @cindex target descriptions, inclusion
35068 @cindex <xi:include>
35071 It can sometimes be valuable to split a target description up into
35072 several different annexes, either for organizational purposes, or to
35073 share files between different possible target descriptions. You can
35074 divide a description into multiple files by replacing any element of
35075 the target description with an inclusion directive of the form:
35078 <xi:include href="@var{document}"/>
35082 When @value{GDBN} encounters an element of this form, it will retrieve
35083 the named XML @var{document}, and replace the inclusion directive with
35084 the contents of that document. If the current description was read
35085 using @samp{qXfer}, then so will be the included document;
35086 @var{document} will be interpreted as the name of an annex. If the
35087 current description was read from a file, @value{GDBN} will look for
35088 @var{document} as a file in the same directory where it found the
35089 original description.
35091 @subsection Architecture
35092 @cindex <architecture>
35094 An @samp{<architecture>} element has this form:
35097 <architecture>@var{arch}</architecture>
35100 @var{arch} is one of the architectures from the set accepted by
35101 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35104 @cindex @code{<osabi>}
35106 This optional field was introduced in @value{GDBN} version 7.0.
35107 Previous versions of @value{GDBN} ignore it.
35109 An @samp{<osabi>} element has this form:
35112 <osabi>@var{abi-name}</osabi>
35115 @var{abi-name} is an OS ABI name from the same selection accepted by
35116 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
35118 @subsection Compatible Architecture
35119 @cindex @code{<compatible>}
35121 This optional field was introduced in @value{GDBN} version 7.0.
35122 Previous versions of @value{GDBN} ignore it.
35124 A @samp{<compatible>} element has this form:
35127 <compatible>@var{arch}</compatible>
35130 @var{arch} is one of the architectures from the set accepted by
35131 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35133 A @samp{<compatible>} element is used to specify that the target
35134 is able to run binaries in some other than the main target architecture
35135 given by the @samp{<architecture>} element. For example, on the
35136 Cell Broadband Engine, the main architecture is @code{powerpc:common}
35137 or @code{powerpc:common64}, but the system is able to run binaries
35138 in the @code{spu} architecture as well. The way to describe this
35139 capability with @samp{<compatible>} is as follows:
35142 <architecture>powerpc:common</architecture>
35143 <compatible>spu</compatible>
35146 @subsection Features
35149 Each @samp{<feature>} describes some logical portion of the target
35150 system. Features are currently used to describe available CPU
35151 registers and the types of their contents. A @samp{<feature>} element
35155 <feature name="@var{name}">
35156 @r{[}@var{type}@dots{}@r{]}
35162 Each feature's name should be unique within the description. The name
35163 of a feature does not matter unless @value{GDBN} has some special
35164 knowledge of the contents of that feature; if it does, the feature
35165 should have its standard name. @xref{Standard Target Features}.
35169 Any register's value is a collection of bits which @value{GDBN} must
35170 interpret. The default interpretation is a two's complement integer,
35171 but other types can be requested by name in the register description.
35172 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
35173 Target Types}), and the description can define additional composite types.
35175 Each type element must have an @samp{id} attribute, which gives
35176 a unique (within the containing @samp{<feature>}) name to the type.
35177 Types must be defined before they are used.
35180 Some targets offer vector registers, which can be treated as arrays
35181 of scalar elements. These types are written as @samp{<vector>} elements,
35182 specifying the array element type, @var{type}, and the number of elements,
35186 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
35190 If a register's value is usefully viewed in multiple ways, define it
35191 with a union type containing the useful representations. The
35192 @samp{<union>} element contains one or more @samp{<field>} elements,
35193 each of which has a @var{name} and a @var{type}:
35196 <union id="@var{id}">
35197 <field name="@var{name}" type="@var{type}"/>
35203 If a register's value is composed from several separate values, define
35204 it with a structure type. There are two forms of the @samp{<struct>}
35205 element; a @samp{<struct>} element must either contain only bitfields
35206 or contain no bitfields. If the structure contains only bitfields,
35207 its total size in bytes must be specified, each bitfield must have an
35208 explicit start and end, and bitfields are automatically assigned an
35209 integer type. The field's @var{start} should be less than or
35210 equal to its @var{end}, and zero represents the least significant bit.
35213 <struct id="@var{id}" size="@var{size}">
35214 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35219 If the structure contains no bitfields, then each field has an
35220 explicit type, and no implicit padding is added.
35223 <struct id="@var{id}">
35224 <field name="@var{name}" type="@var{type}"/>
35230 If a register's value is a series of single-bit flags, define it with
35231 a flags type. The @samp{<flags>} element has an explicit @var{size}
35232 and contains one or more @samp{<field>} elements. Each field has a
35233 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
35237 <flags id="@var{id}" size="@var{size}">
35238 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35243 @subsection Registers
35246 Each register is represented as an element with this form:
35249 <reg name="@var{name}"
35250 bitsize="@var{size}"
35251 @r{[}regnum="@var{num}"@r{]}
35252 @r{[}save-restore="@var{save-restore}"@r{]}
35253 @r{[}type="@var{type}"@r{]}
35254 @r{[}group="@var{group}"@r{]}/>
35258 The components are as follows:
35263 The register's name; it must be unique within the target description.
35266 The register's size, in bits.
35269 The register's number. If omitted, a register's number is one greater
35270 than that of the previous register (either in the current feature or in
35271 a preceeding feature); the first register in the target description
35272 defaults to zero. This register number is used to read or write
35273 the register; e.g.@: it is used in the remote @code{p} and @code{P}
35274 packets, and registers appear in the @code{g} and @code{G} packets
35275 in order of increasing register number.
35278 Whether the register should be preserved across inferior function
35279 calls; this must be either @code{yes} or @code{no}. The default is
35280 @code{yes}, which is appropriate for most registers except for
35281 some system control registers; this is not related to the target's
35285 The type of the register. @var{type} may be a predefined type, a type
35286 defined in the current feature, or one of the special types @code{int}
35287 and @code{float}. @code{int} is an integer type of the correct size
35288 for @var{bitsize}, and @code{float} is a floating point type (in the
35289 architecture's normal floating point format) of the correct size for
35290 @var{bitsize}. The default is @code{int}.
35293 The register group to which this register belongs. @var{group} must
35294 be either @code{general}, @code{float}, or @code{vector}. If no
35295 @var{group} is specified, @value{GDBN} will not display the register
35296 in @code{info registers}.
35300 @node Predefined Target Types
35301 @section Predefined Target Types
35302 @cindex target descriptions, predefined types
35304 Type definitions in the self-description can build up composite types
35305 from basic building blocks, but can not define fundamental types. Instead,
35306 standard identifiers are provided by @value{GDBN} for the fundamental
35307 types. The currently supported types are:
35316 Signed integer types holding the specified number of bits.
35323 Unsigned integer types holding the specified number of bits.
35327 Pointers to unspecified code and data. The program counter and
35328 any dedicated return address register may be marked as code
35329 pointers; printing a code pointer converts it into a symbolic
35330 address. The stack pointer and any dedicated address registers
35331 may be marked as data pointers.
35334 Single precision IEEE floating point.
35337 Double precision IEEE floating point.
35340 The 12-byte extended precision format used by ARM FPA registers.
35343 The 10-byte extended precision format used by x87 registers.
35346 32bit @sc{eflags} register used by x86.
35349 32bit @sc{mxcsr} register used by x86.
35353 @node Standard Target Features
35354 @section Standard Target Features
35355 @cindex target descriptions, standard features
35357 A target description must contain either no registers or all the
35358 target's registers. If the description contains no registers, then
35359 @value{GDBN} will assume a default register layout, selected based on
35360 the architecture. If the description contains any registers, the
35361 default layout will not be used; the standard registers must be
35362 described in the target description, in such a way that @value{GDBN}
35363 can recognize them.
35365 This is accomplished by giving specific names to feature elements
35366 which contain standard registers. @value{GDBN} will look for features
35367 with those names and verify that they contain the expected registers;
35368 if any known feature is missing required registers, or if any required
35369 feature is missing, @value{GDBN} will reject the target
35370 description. You can add additional registers to any of the
35371 standard features --- @value{GDBN} will display them just as if
35372 they were added to an unrecognized feature.
35374 This section lists the known features and their expected contents.
35375 Sample XML documents for these features are included in the
35376 @value{GDBN} source tree, in the directory @file{gdb/features}.
35378 Names recognized by @value{GDBN} should include the name of the
35379 company or organization which selected the name, and the overall
35380 architecture to which the feature applies; so e.g.@: the feature
35381 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
35383 The names of registers are not case sensitive for the purpose
35384 of recognizing standard features, but @value{GDBN} will only display
35385 registers using the capitalization used in the description.
35392 * PowerPC Features::
35397 @subsection ARM Features
35398 @cindex target descriptions, ARM features
35400 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
35401 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
35402 @samp{lr}, @samp{pc}, and @samp{cpsr}.
35404 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
35405 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
35407 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
35408 it should contain at least registers @samp{wR0} through @samp{wR15} and
35409 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
35410 @samp{wCSSF}, and @samp{wCASF} registers are optional.
35412 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
35413 should contain at least registers @samp{d0} through @samp{d15}. If
35414 they are present, @samp{d16} through @samp{d31} should also be included.
35415 @value{GDBN} will synthesize the single-precision registers from
35416 halves of the double-precision registers.
35418 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
35419 need to contain registers; it instructs @value{GDBN} to display the
35420 VFP double-precision registers as vectors and to synthesize the
35421 quad-precision registers from pairs of double-precision registers.
35422 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
35423 be present and include 32 double-precision registers.
35425 @node i386 Features
35426 @subsection i386 Features
35427 @cindex target descriptions, i386 features
35429 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
35430 targets. It should describe the following registers:
35434 @samp{eax} through @samp{edi} plus @samp{eip} for i386
35436 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
35438 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
35439 @samp{fs}, @samp{gs}
35441 @samp{st0} through @samp{st7}
35443 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
35444 @samp{foseg}, @samp{fooff} and @samp{fop}
35447 The register sets may be different, depending on the target.
35449 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
35450 describe registers:
35454 @samp{xmm0} through @samp{xmm7} for i386
35456 @samp{xmm0} through @samp{xmm15} for amd64
35461 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
35462 @samp{org.gnu.gdb.i386.sse} feature. It should
35463 describe the upper 128 bits of @sc{ymm} registers:
35467 @samp{ymm0h} through @samp{ymm7h} for i386
35469 @samp{ymm0h} through @samp{ymm15h} for amd64
35473 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
35474 describe a single register, @samp{orig_eax}.
35476 @node MIPS Features
35477 @subsection MIPS Features
35478 @cindex target descriptions, MIPS features
35480 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
35481 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
35482 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
35485 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
35486 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
35487 registers. They may be 32-bit or 64-bit depending on the target.
35489 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
35490 it may be optional in a future version of @value{GDBN}. It should
35491 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
35492 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
35494 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
35495 contain a single register, @samp{restart}, which is used by the
35496 Linux kernel to control restartable syscalls.
35498 @node M68K Features
35499 @subsection M68K Features
35500 @cindex target descriptions, M68K features
35503 @item @samp{org.gnu.gdb.m68k.core}
35504 @itemx @samp{org.gnu.gdb.coldfire.core}
35505 @itemx @samp{org.gnu.gdb.fido.core}
35506 One of those features must be always present.
35507 The feature that is present determines which flavor of m68k is
35508 used. The feature that is present should contain registers
35509 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
35510 @samp{sp}, @samp{ps} and @samp{pc}.
35512 @item @samp{org.gnu.gdb.coldfire.fp}
35513 This feature is optional. If present, it should contain registers
35514 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
35518 @node PowerPC Features
35519 @subsection PowerPC Features
35520 @cindex target descriptions, PowerPC features
35522 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
35523 targets. It should contain registers @samp{r0} through @samp{r31},
35524 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
35525 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
35527 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
35528 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
35530 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
35531 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
35534 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
35535 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
35536 will combine these registers with the floating point registers
35537 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
35538 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
35539 through @samp{vs63}, the set of vector registers for POWER7.
35541 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
35542 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
35543 @samp{spefscr}. SPE targets should provide 32-bit registers in
35544 @samp{org.gnu.gdb.power.core} and provide the upper halves in
35545 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
35546 these to present registers @samp{ev0} through @samp{ev31} to the
35549 @node Operating System Information
35550 @appendix Operating System Information
35551 @cindex operating system information
35557 Users of @value{GDBN} often wish to obtain information about the state of
35558 the operating system running on the target---for example the list of
35559 processes, or the list of open files. This section describes the
35560 mechanism that makes it possible. This mechanism is similar to the
35561 target features mechanism (@pxref{Target Descriptions}), but focuses
35562 on a different aspect of target.
35564 Operating system information is retrived from the target via the
35565 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
35566 read}). The object name in the request should be @samp{osdata}, and
35567 the @var{annex} identifies the data to be fetched.
35570 @appendixsection Process list
35571 @cindex operating system information, process list
35573 When requesting the process list, the @var{annex} field in the
35574 @samp{qXfer} request should be @samp{processes}. The returned data is
35575 an XML document. The formal syntax of this document is defined in
35576 @file{gdb/features/osdata.dtd}.
35578 An example document is:
35581 <?xml version="1.0"?>
35582 <!DOCTYPE target SYSTEM "osdata.dtd">
35583 <osdata type="processes">
35585 <column name="pid">1</column>
35586 <column name="user">root</column>
35587 <column name="command">/sbin/init</column>
35588 <column name="cores">1,2,3</column>
35593 Each item should include a column whose name is @samp{pid}. The value
35594 of that column should identify the process on the target. The
35595 @samp{user} and @samp{command} columns are optional, and will be
35596 displayed by @value{GDBN}. The @samp{cores} column, if present,
35597 should contain a comma-separated list of cores that this process
35598 is running on. Target may provide additional columns,
35599 which @value{GDBN} currently ignores.
35603 @node GNU Free Documentation License
35604 @appendix GNU Free Documentation License
35613 % I think something like @colophon should be in texinfo. In the
35615 \long\def\colophon{\hbox to0pt{}\vfill
35616 \centerline{The body of this manual is set in}
35617 \centerline{\fontname\tenrm,}
35618 \centerline{with headings in {\bf\fontname\tenbf}}
35619 \centerline{and examples in {\tt\fontname\tentt}.}
35620 \centerline{{\it\fontname\tenit\/},}
35621 \centerline{{\bf\fontname\tenbf}, and}
35622 \centerline{{\sl\fontname\tensl\/}}
35623 \centerline{are used for emphasis.}\vfill}
35625 % Blame: doc@cygnus.com, 1991.