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
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
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
48 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
49 Free Software Foundation, Inc.
51 Permission is granted to copy, distribute and/or modify this document
52 under the terms of the GNU Free Documentation License, Version 1.1 or
53 any later version published by the Free Software Foundation; with the
54 Invariant Sections being ``Free Software'' and ``Free Software Needs
55 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
56 and with the Back-Cover Texts as in (a) below.
58 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
59 this GNU Manual. Buying copies from GNU Press supports the FSF in
60 developing GNU and promoting software freedom.''
64 This file documents the @sc{gnu} debugger @value{GDBN}.
66 This is the @value{EDITION} Edition, of @cite{Debugging with
67 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
68 @ifset VERSION_PACKAGE
69 @value{VERSION_PACKAGE}
71 Version @value{GDBVN}.
77 @title Debugging with @value{GDBN}
78 @subtitle The @sc{gnu} Source-Level Debugger
80 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
81 @ifset VERSION_PACKAGE
83 @subtitle @value{VERSION_PACKAGE}
85 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
89 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
90 \hfill {\it Debugging with @value{GDBN}}\par
91 \hfill \TeX{}info \texinfoversion\par
95 @vskip 0pt plus 1filll
96 Published by the Free Software Foundation @*
97 51 Franklin Street, Fifth Floor,
98 Boston, MA 02110-1301, USA@*
103 This edition of the GDB manual is dedicated to the memory of Fred
104 Fish. Fred was a long-standing contributor to GDB and to Free
105 software in general. We will miss him.
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2009 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Process Record and Replay:: Recording inferior's execution and replaying it
138 * Stack:: Examining the stack
139 * Source:: Examining source files
140 * Data:: Examining data
141 * Macros:: Preprocessor Macros
142 * Tracepoints:: Debugging remote targets non-intrusively
143 * Overlays:: Debugging programs that use overlays
145 * Languages:: Using @value{GDBN} with different languages
147 * Symbols:: Examining the symbol table
148 * Altering:: Altering execution
149 * GDB Files:: @value{GDBN} files
150 * Targets:: Specifying a debugging target
151 * Remote Debugging:: Debugging remote programs
152 * Configurations:: Configuration-specific information
153 * Controlling GDB:: Controlling @value{GDBN}
154 * Extending GDB:: Extending @value{GDBN}
155 * Interpreters:: Command Interpreters
156 * TUI:: @value{GDBN} Text User Interface
157 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
158 * GDB/MI:: @value{GDBN}'s Machine Interface.
159 * Annotations:: @value{GDBN}'s annotation interface.
161 * GDB Bugs:: Reporting bugs in @value{GDBN}
163 * Command Line Editing:: Command Line Editing
164 * Using History Interactively:: Using History Interactively
165 * Formatting Documentation:: How to format and print @value{GDBN} documentation
166 * Installing GDB:: Installing GDB
167 * Maintenance Commands:: Maintenance Commands
168 * Remote Protocol:: GDB Remote Serial Protocol
169 * Agent Expressions:: The GDB Agent Expression Mechanism
170 * Target Descriptions:: How targets can describe themselves to
172 * Operating System Information:: Getting additional information from
174 * Copying:: GNU General Public License says
175 how you can copy and share GDB
176 * GNU Free Documentation License:: The license for this documentation
185 @unnumbered Summary of @value{GDBN}
187 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
188 going on ``inside'' another program while it executes---or what another
189 program was doing at the moment it crashed.
191 @value{GDBN} can do four main kinds of things (plus other things in support of
192 these) to help you catch bugs in the act:
196 Start your program, specifying anything that might affect its behavior.
199 Make your program stop on specified conditions.
202 Examine what has happened, when your program has stopped.
205 Change things in your program, so you can experiment with correcting the
206 effects of one bug and go on to learn about another.
209 You can use @value{GDBN} to debug programs written in C and C@t{++}.
210 For more information, see @ref{Supported Languages,,Supported Languages}.
211 For more information, see @ref{C,,C and C++}.
214 Support for Modula-2 is partial. For information on Modula-2, see
215 @ref{Modula-2,,Modula-2}.
218 Debugging Pascal programs which use sets, subranges, file variables, or
219 nested functions does not currently work. @value{GDBN} does not support
220 entering expressions, printing values, or similar features using Pascal
224 @value{GDBN} can be used to debug programs written in Fortran, although
225 it may be necessary to refer to some variables with a trailing
228 @value{GDBN} can be used to debug programs written in Objective-C,
229 using either the Apple/NeXT or the GNU Objective-C runtime.
232 * Free Software:: Freely redistributable software
233 * Contributors:: Contributors to GDB
237 @unnumberedsec Free Software
239 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
240 General Public License
241 (GPL). The GPL gives you the freedom to copy or adapt a licensed
242 program---but every person getting a copy also gets with it the
243 freedom to modify that copy (which means that they must get access to
244 the source code), and the freedom to distribute further copies.
245 Typical software companies use copyrights to limit your freedoms; the
246 Free Software Foundation uses the GPL to preserve these freedoms.
248 Fundamentally, the General Public License is a license which says that
249 you have these freedoms and that you cannot take these freedoms away
252 @unnumberedsec Free Software Needs Free Documentation
254 The biggest deficiency in the free software community today is not in
255 the software---it is the lack of good free documentation that we can
256 include with the free software. Many of our most important
257 programs do not come with free reference manuals and free introductory
258 texts. Documentation is an essential part of any software package;
259 when an important free software package does not come with a free
260 manual and a free tutorial, that is a major gap. We have many such
263 Consider Perl, for instance. The tutorial manuals that people
264 normally use are non-free. How did this come about? Because the
265 authors of those manuals published them with restrictive terms---no
266 copying, no modification, source files not available---which exclude
267 them from the free software world.
269 That wasn't the first time this sort of thing happened, and it was far
270 from the last. Many times we have heard a GNU user eagerly describe a
271 manual that he is writing, his intended contribution to the community,
272 only to learn that he had ruined everything by signing a publication
273 contract to make it non-free.
275 Free documentation, like free software, is a matter of freedom, not
276 price. The problem with the non-free manual is not that publishers
277 charge a price for printed copies---that in itself is fine. (The Free
278 Software Foundation sells printed copies of manuals, too.) The
279 problem is the restrictions on the use of the manual. Free manuals
280 are available in source code form, and give you permission to copy and
281 modify. Non-free manuals do not allow this.
283 The criteria of freedom for a free manual are roughly the same as for
284 free software. Redistribution (including the normal kinds of
285 commercial redistribution) must be permitted, so that the manual can
286 accompany every copy of the program, both on-line and on paper.
288 Permission for modification of the technical content is crucial too.
289 When people modify the software, adding or changing features, if they
290 are conscientious they will change the manual too---so they can
291 provide accurate and clear documentation for the modified program. A
292 manual that leaves you no choice but to write a new manual to document
293 a changed version of the program is not really available to our
296 Some kinds of limits on the way modification is handled are
297 acceptable. For example, requirements to preserve the original
298 author's copyright notice, the distribution terms, or the list of
299 authors, are ok. It is also no problem to require modified versions
300 to include notice that they were modified. Even entire sections that
301 may not be deleted or changed are acceptable, as long as they deal
302 with nontechnical topics (like this one). These kinds of restrictions
303 are acceptable because they don't obstruct the community's normal use
306 However, it must be possible to modify all the @emph{technical}
307 content of the manual, and then distribute the result in all the usual
308 media, through all the usual channels. Otherwise, the restrictions
309 obstruct the use of the manual, it is not free, and we need another
310 manual to replace it.
312 Please spread the word about this issue. Our community continues to
313 lose manuals to proprietary publishing. If we spread the word that
314 free software needs free reference manuals and free tutorials, perhaps
315 the next person who wants to contribute by writing documentation will
316 realize, before it is too late, that only free manuals contribute to
317 the free software community.
319 If you are writing documentation, please insist on publishing it under
320 the GNU Free Documentation License or another free documentation
321 license. Remember that this decision requires your approval---you
322 don't have to let the publisher decide. Some commercial publishers
323 will use a free license if you insist, but they will not propose the
324 option; it is up to you to raise the issue and say firmly that this is
325 what you want. If the publisher you are dealing with refuses, please
326 try other publishers. If you're not sure whether a proposed license
327 is free, write to @email{licensing@@gnu.org}.
329 You can encourage commercial publishers to sell more free, copylefted
330 manuals and tutorials by buying them, and particularly by buying
331 copies from the publishers that paid for their writing or for major
332 improvements. Meanwhile, try to avoid buying non-free documentation
333 at all. Check the distribution terms of a manual before you buy it,
334 and insist that whoever seeks your business must respect your freedom.
335 Check the history of the book, and try to reward the publishers that
336 have paid or pay the authors to work on it.
338 The Free Software Foundation maintains a list of free documentation
339 published by other publishers, at
340 @url{http://www.fsf.org/doc/other-free-books.html}.
343 @unnumberedsec Contributors to @value{GDBN}
345 Richard Stallman was the original author of @value{GDBN}, and of many
346 other @sc{gnu} programs. Many others have contributed to its
347 development. This section attempts to credit major contributors. One
348 of the virtues of free software is that everyone is free to contribute
349 to it; with regret, we cannot actually acknowledge everyone here. The
350 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
351 blow-by-blow account.
353 Changes much prior to version 2.0 are lost in the mists of time.
356 @emph{Plea:} Additions to this section are particularly welcome. If you
357 or your friends (or enemies, to be evenhanded) have been unfairly
358 omitted from this list, we would like to add your names!
361 So that they may not regard their many labors as thankless, we
362 particularly thank those who shepherded @value{GDBN} through major
364 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
365 Jim Blandy (release 4.18);
366 Jason Molenda (release 4.17);
367 Stan Shebs (release 4.14);
368 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
369 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
370 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
371 Jim Kingdon (releases 3.5, 3.4, and 3.3);
372 and Randy Smith (releases 3.2, 3.1, and 3.0).
374 Richard Stallman, assisted at various times by Peter TerMaat, Chris
375 Hanson, and Richard Mlynarik, handled releases through 2.8.
377 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
378 in @value{GDBN}, with significant additional contributions from Per
379 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
380 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
381 much general update work leading to release 3.0).
383 @value{GDBN} uses the BFD subroutine library to examine multiple
384 object-file formats; BFD was a joint project of David V.
385 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
387 David Johnson wrote the original COFF support; Pace Willison did
388 the original support for encapsulated COFF.
390 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
392 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
393 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
395 Jean-Daniel Fekete contributed Sun 386i support.
396 Chris Hanson improved the HP9000 support.
397 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
398 David Johnson contributed Encore Umax support.
399 Jyrki Kuoppala contributed Altos 3068 support.
400 Jeff Law contributed HP PA and SOM support.
401 Keith Packard contributed NS32K support.
402 Doug Rabson contributed Acorn Risc Machine support.
403 Bob Rusk contributed Harris Nighthawk CX-UX support.
404 Chris Smith contributed Convex support (and Fortran debugging).
405 Jonathan Stone contributed Pyramid support.
406 Michael Tiemann contributed SPARC support.
407 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
408 Pace Willison contributed Intel 386 support.
409 Jay Vosburgh contributed Symmetry support.
410 Marko Mlinar contributed OpenRISC 1000 support.
412 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
414 Rich Schaefer and Peter Schauer helped with support of SunOS shared
417 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
418 about several machine instruction sets.
420 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
421 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
422 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
423 and RDI targets, respectively.
425 Brian Fox is the author of the readline libraries providing
426 command-line editing and command history.
428 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
429 Modula-2 support, and contributed the Languages chapter of this manual.
431 Fred Fish wrote most of the support for Unix System Vr4.
432 He also enhanced the command-completion support to cover C@t{++} overloaded
435 Hitachi America (now Renesas America), Ltd. sponsored the support for
436 H8/300, H8/500, and Super-H processors.
438 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
440 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
443 Toshiba sponsored the support for the TX39 Mips processor.
445 Matsushita sponsored the support for the MN10200 and MN10300 processors.
447 Fujitsu sponsored the support for SPARClite and FR30 processors.
449 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
452 Michael Snyder added support for tracepoints.
454 Stu Grossman wrote gdbserver.
456 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
457 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
459 The following people at the Hewlett-Packard Company contributed
460 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
461 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
462 compiler, and the Text User Interface (nee Terminal User Interface):
463 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
464 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
465 provided HP-specific information in this manual.
467 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
468 Robert Hoehne made significant contributions to the DJGPP port.
470 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
471 development since 1991. Cygnus engineers who have worked on @value{GDBN}
472 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
473 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
474 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
475 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
476 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
477 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
478 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
479 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
480 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
481 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
482 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
483 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
484 Zuhn have made contributions both large and small.
486 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
487 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
489 Jim Blandy added support for preprocessor macros, while working for Red
492 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
493 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
494 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
495 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
496 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
497 with the migration of old architectures to this new framework.
499 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
500 unwinder framework, this consisting of a fresh new design featuring
501 frame IDs, independent frame sniffers, and the sentinel frame. Mark
502 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
503 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
504 trad unwinders. The architecture-specific changes, each involving a
505 complete rewrite of the architecture's frame code, were carried out by
506 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
507 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
508 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
509 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
512 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
513 Tensilica, Inc.@: contributed support for Xtensa processors. Others
514 who have worked on the Xtensa port of @value{GDBN} in the past include
515 Steve Tjiang, John Newlin, and Scott Foehner.
518 @chapter A Sample @value{GDBN} Session
520 You can use this manual at your leisure to read all about @value{GDBN}.
521 However, a handful of commands are enough to get started using the
522 debugger. This chapter illustrates those commands.
525 In this sample session, we emphasize user input like this: @b{input},
526 to make it easier to pick out from the surrounding output.
529 @c FIXME: this example may not be appropriate for some configs, where
530 @c FIXME...primary interest is in remote use.
532 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
533 processor) exhibits the following bug: sometimes, when we change its
534 quote strings from the default, the commands used to capture one macro
535 definition within another stop working. In the following short @code{m4}
536 session, we define a macro @code{foo} which expands to @code{0000}; we
537 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
538 same thing. However, when we change the open quote string to
539 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
540 procedure fails to define a new synonym @code{baz}:
549 @b{define(bar,defn(`foo'))}
553 @b{changequote(<QUOTE>,<UNQUOTE>)}
555 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
558 m4: End of input: 0: fatal error: EOF in string
562 Let us use @value{GDBN} to try to see what is going on.
565 $ @b{@value{GDBP} m4}
566 @c FIXME: this falsifies the exact text played out, to permit smallbook
567 @c FIXME... format to come out better.
568 @value{GDBN} is free software and you are welcome to distribute copies
569 of it under certain conditions; type "show copying" to see
571 There is absolutely no warranty for @value{GDBN}; type "show warranty"
574 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
579 @value{GDBN} reads only enough symbol data to know where to find the
580 rest when needed; as a result, the first prompt comes up very quickly.
581 We now tell @value{GDBN} to use a narrower display width than usual, so
582 that examples fit in this manual.
585 (@value{GDBP}) @b{set width 70}
589 We need to see how the @code{m4} built-in @code{changequote} works.
590 Having looked at the source, we know the relevant subroutine is
591 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
592 @code{break} command.
595 (@value{GDBP}) @b{break m4_changequote}
596 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
600 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
601 control; as long as control does not reach the @code{m4_changequote}
602 subroutine, the program runs as usual:
605 (@value{GDBP}) @b{run}
606 Starting program: /work/Editorial/gdb/gnu/m4/m4
614 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
615 suspends execution of @code{m4}, displaying information about the
616 context where it stops.
619 @b{changequote(<QUOTE>,<UNQUOTE>)}
621 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
623 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
627 Now we use the command @code{n} (@code{next}) to advance execution to
628 the next line of the current function.
632 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
637 @code{set_quotes} looks like a promising subroutine. We can go into it
638 by using the command @code{s} (@code{step}) instead of @code{next}.
639 @code{step} goes to the next line to be executed in @emph{any}
640 subroutine, so it steps into @code{set_quotes}.
644 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
646 530 if (lquote != def_lquote)
650 The display that shows the subroutine where @code{m4} is now
651 suspended (and its arguments) is called a stack frame display. It
652 shows a summary of the stack. We can use the @code{backtrace}
653 command (which can also be spelled @code{bt}), to see where we are
654 in the stack as a whole: the @code{backtrace} command displays a
655 stack frame for each active subroutine.
658 (@value{GDBP}) @b{bt}
659 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
661 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
663 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
664 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
666 #4 0x79dc in expand_input () at macro.c:40
667 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
671 We step through a few more lines to see what happens. The first two
672 times, we can use @samp{s}; the next two times we use @code{n} to avoid
673 falling into the @code{xstrdup} subroutine.
677 0x3b5c 532 if (rquote != def_rquote)
679 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
680 def_lquote : xstrdup(lq);
682 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
685 538 len_lquote = strlen(rquote);
689 The last line displayed looks a little odd; we can examine the variables
690 @code{lquote} and @code{rquote} to see if they are in fact the new left
691 and right quotes we specified. We use the command @code{p}
692 (@code{print}) to see their values.
695 (@value{GDBP}) @b{p lquote}
696 $1 = 0x35d40 "<QUOTE>"
697 (@value{GDBP}) @b{p rquote}
698 $2 = 0x35d50 "<UNQUOTE>"
702 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
703 To look at some context, we can display ten lines of source
704 surrounding the current line with the @code{l} (@code{list}) command.
710 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
712 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
715 538 len_lquote = strlen(rquote);
716 539 len_rquote = strlen(lquote);
723 Let us step past the two lines that set @code{len_lquote} and
724 @code{len_rquote}, and then examine the values of those variables.
728 539 len_rquote = strlen(lquote);
731 (@value{GDBP}) @b{p len_lquote}
733 (@value{GDBP}) @b{p len_rquote}
738 That certainly looks wrong, assuming @code{len_lquote} and
739 @code{len_rquote} are meant to be the lengths of @code{lquote} and
740 @code{rquote} respectively. We can set them to better values using
741 the @code{p} command, since it can print the value of
742 any expression---and that expression can include subroutine calls and
746 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
748 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
753 Is that enough to fix the problem of using the new quotes with the
754 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
755 executing with the @code{c} (@code{continue}) command, and then try the
756 example that caused trouble initially:
762 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
769 Success! The new quotes now work just as well as the default ones. The
770 problem seems to have been just the two typos defining the wrong
771 lengths. We allow @code{m4} exit by giving it an EOF as input:
775 Program exited normally.
779 The message @samp{Program exited normally.} is from @value{GDBN}; it
780 indicates @code{m4} has finished executing. We can end our @value{GDBN}
781 session with the @value{GDBN} @code{quit} command.
784 (@value{GDBP}) @b{quit}
788 @chapter Getting In and Out of @value{GDBN}
790 This chapter discusses how to start @value{GDBN}, and how to get out of it.
794 type @samp{@value{GDBP}} to start @value{GDBN}.
796 type @kbd{quit} or @kbd{Ctrl-d} to exit.
800 * Invoking GDB:: How to start @value{GDBN}
801 * Quitting GDB:: How to quit @value{GDBN}
802 * Shell Commands:: How to use shell commands inside @value{GDBN}
803 * Logging Output:: How to log @value{GDBN}'s output to a file
807 @section Invoking @value{GDBN}
809 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
810 @value{GDBN} reads commands from the terminal until you tell it to exit.
812 You can also run @code{@value{GDBP}} with a variety of arguments and options,
813 to specify more of your debugging environment at the outset.
815 The command-line options described here are designed
816 to cover a variety of situations; in some environments, some of these
817 options may effectively be unavailable.
819 The most usual way to start @value{GDBN} is with one argument,
820 specifying an executable program:
823 @value{GDBP} @var{program}
827 You can also start with both an executable program and a core file
831 @value{GDBP} @var{program} @var{core}
834 You can, instead, specify a process ID as a second argument, if you want
835 to debug a running process:
838 @value{GDBP} @var{program} 1234
842 would attach @value{GDBN} to process @code{1234} (unless you also have a file
843 named @file{1234}; @value{GDBN} does check for a core file first).
845 Taking advantage of the second command-line argument requires a fairly
846 complete operating system; when you use @value{GDBN} as a remote
847 debugger attached to a bare board, there may not be any notion of
848 ``process'', and there is often no way to get a core dump. @value{GDBN}
849 will warn you if it is unable to attach or to read core dumps.
851 You can optionally have @code{@value{GDBP}} pass any arguments after the
852 executable file to the inferior using @code{--args}. This option stops
855 @value{GDBP} --args gcc -O2 -c foo.c
857 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
858 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
860 You can run @code{@value{GDBP}} without printing the front material, which describes
861 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
868 You can further control how @value{GDBN} starts up by using command-line
869 options. @value{GDBN} itself can remind you of the options available.
879 to display all available options and briefly describe their use
880 (@samp{@value{GDBP} -h} is a shorter equivalent).
882 All options and command line arguments you give are processed
883 in sequential order. The order makes a difference when the
884 @samp{-x} option is used.
888 * File Options:: Choosing files
889 * Mode Options:: Choosing modes
890 * Startup:: What @value{GDBN} does during startup
894 @subsection Choosing Files
896 When @value{GDBN} starts, it reads any arguments other than options as
897 specifying an executable file and core file (or process ID). This is
898 the same as if the arguments were specified by the @samp{-se} and
899 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
900 first argument that does not have an associated option flag as
901 equivalent to the @samp{-se} option followed by that argument; and the
902 second argument that does not have an associated option flag, if any, as
903 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
904 If the second argument begins with a decimal digit, @value{GDBN} will
905 first attempt to attach to it as a process, and if that fails, attempt
906 to open it as a corefile. If you have a corefile whose name begins with
907 a digit, you can prevent @value{GDBN} from treating it as a pid by
908 prefixing it with @file{./}, e.g.@: @file{./12345}.
910 If @value{GDBN} has not been configured to included core file support,
911 such as for most embedded targets, then it will complain about a second
912 argument and ignore it.
914 Many options have both long and short forms; both are shown in the
915 following list. @value{GDBN} also recognizes the long forms if you truncate
916 them, so long as enough of the option is present to be unambiguous.
917 (If you prefer, you can flag option arguments with @samp{--} rather
918 than @samp{-}, though we illustrate the more usual convention.)
920 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
921 @c way, both those who look for -foo and --foo in the index, will find
925 @item -symbols @var{file}
927 @cindex @code{--symbols}
929 Read symbol table from file @var{file}.
931 @item -exec @var{file}
933 @cindex @code{--exec}
935 Use file @var{file} as the executable file to execute when appropriate,
936 and for examining pure data in conjunction with a core dump.
940 Read symbol table from file @var{file} and use it as the executable
943 @item -core @var{file}
945 @cindex @code{--core}
947 Use file @var{file} as a core dump to examine.
949 @item -pid @var{number}
950 @itemx -p @var{number}
953 Connect to process ID @var{number}, as with the @code{attach} command.
955 @item -command @var{file}
957 @cindex @code{--command}
959 Execute @value{GDBN} commands from file @var{file}. @xref{Command
960 Files,, Command files}.
962 @item -eval-command @var{command}
963 @itemx -ex @var{command}
964 @cindex @code{--eval-command}
966 Execute a single @value{GDBN} command.
968 This option may be used multiple times to call multiple commands. It may
969 also be interleaved with @samp{-command} as required.
972 @value{GDBP} -ex 'target sim' -ex 'load' \
973 -x setbreakpoints -ex 'run' a.out
976 @item -directory @var{directory}
977 @itemx -d @var{directory}
978 @cindex @code{--directory}
980 Add @var{directory} to the path to search for source and script files.
984 @cindex @code{--readnow}
986 Read each symbol file's entire symbol table immediately, rather than
987 the default, which is to read it incrementally as it is needed.
988 This makes startup slower, but makes future operations faster.
993 @subsection Choosing Modes
995 You can run @value{GDBN} in various alternative modes---for example, in
996 batch mode or quiet mode.
1003 Do not execute commands found in any initialization files. Normally,
1004 @value{GDBN} executes the commands in these files after all the command
1005 options and arguments have been processed. @xref{Command Files,,Command
1011 @cindex @code{--quiet}
1012 @cindex @code{--silent}
1014 ``Quiet''. Do not print the introductory and copyright messages. These
1015 messages are also suppressed in batch mode.
1018 @cindex @code{--batch}
1019 Run in batch mode. Exit with status @code{0} after processing all the
1020 command files specified with @samp{-x} (and all commands from
1021 initialization files, if not inhibited with @samp{-n}). Exit with
1022 nonzero status if an error occurs in executing the @value{GDBN} commands
1023 in the command files.
1025 Batch mode may be useful for running @value{GDBN} as a filter, for
1026 example to download and run a program on another computer; in order to
1027 make this more useful, the message
1030 Program exited normally.
1034 (which is ordinarily issued whenever a program running under
1035 @value{GDBN} control terminates) is not issued when running in batch
1039 @cindex @code{--batch-silent}
1040 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1041 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1042 unaffected). This is much quieter than @samp{-silent} and would be useless
1043 for an interactive session.
1045 This is particularly useful when using targets that give @samp{Loading section}
1046 messages, for example.
1048 Note that targets that give their output via @value{GDBN}, as opposed to
1049 writing directly to @code{stdout}, will also be made silent.
1051 @item -return-child-result
1052 @cindex @code{--return-child-result}
1053 The return code from @value{GDBN} will be the return code from the child
1054 process (the process being debugged), with the following exceptions:
1058 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1059 internal error. In this case the exit code is the same as it would have been
1060 without @samp{-return-child-result}.
1062 The user quits with an explicit value. E.g., @samp{quit 1}.
1064 The child process never runs, or is not allowed to terminate, in which case
1065 the exit code will be -1.
1068 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1069 when @value{GDBN} is being used as a remote program loader or simulator
1074 @cindex @code{--nowindows}
1076 ``No windows''. If @value{GDBN} comes with a graphical user interface
1077 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1078 interface. If no GUI is available, this option has no effect.
1082 @cindex @code{--windows}
1084 If @value{GDBN} includes a GUI, then this option requires it to be
1087 @item -cd @var{directory}
1089 Run @value{GDBN} using @var{directory} as its working directory,
1090 instead of the current directory.
1094 @cindex @code{--fullname}
1096 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1097 subprocess. It tells @value{GDBN} to output the full file name and line
1098 number in a standard, recognizable fashion each time a stack frame is
1099 displayed (which includes each time your program stops). This
1100 recognizable format looks like two @samp{\032} characters, followed by
1101 the file name, line number and character position separated by colons,
1102 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1103 @samp{\032} characters as a signal to display the source code for the
1107 @cindex @code{--epoch}
1108 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1109 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1110 routines so as to allow Epoch to display values of expressions in a
1113 @item -annotate @var{level}
1114 @cindex @code{--annotate}
1115 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1116 effect is identical to using @samp{set annotate @var{level}}
1117 (@pxref{Annotations}). The annotation @var{level} controls how much
1118 information @value{GDBN} prints together with its prompt, values of
1119 expressions, source lines, and other types of output. Level 0 is the
1120 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1121 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1122 that control @value{GDBN}, and level 2 has been deprecated.
1124 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1128 @cindex @code{--args}
1129 Change interpretation of command line so that arguments following the
1130 executable file are passed as command line arguments to the inferior.
1131 This option stops option processing.
1133 @item -baud @var{bps}
1135 @cindex @code{--baud}
1137 Set the line speed (baud rate or bits per second) of any serial
1138 interface used by @value{GDBN} for remote debugging.
1140 @item -l @var{timeout}
1142 Set the timeout (in seconds) of any communication used by @value{GDBN}
1143 for remote debugging.
1145 @item -tty @var{device}
1146 @itemx -t @var{device}
1147 @cindex @code{--tty}
1149 Run using @var{device} for your program's standard input and output.
1150 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1152 @c resolve the situation of these eventually
1154 @cindex @code{--tui}
1155 Activate the @dfn{Text User Interface} when starting. The Text User
1156 Interface manages several text windows on the terminal, showing
1157 source, assembly, registers and @value{GDBN} command outputs
1158 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1159 Text User Interface can be enabled by invoking the program
1160 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1161 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1164 @c @cindex @code{--xdb}
1165 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1166 @c For information, see the file @file{xdb_trans.html}, which is usually
1167 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1170 @item -interpreter @var{interp}
1171 @cindex @code{--interpreter}
1172 Use the interpreter @var{interp} for interface with the controlling
1173 program or device. This option is meant to be set by programs which
1174 communicate with @value{GDBN} using it as a back end.
1175 @xref{Interpreters, , Command Interpreters}.
1177 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1178 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1179 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1180 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1181 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1182 @sc{gdb/mi} interfaces are no longer supported.
1185 @cindex @code{--write}
1186 Open the executable and core files for both reading and writing. This
1187 is equivalent to the @samp{set write on} command inside @value{GDBN}
1191 @cindex @code{--statistics}
1192 This option causes @value{GDBN} to print statistics about time and
1193 memory usage after it completes each command and returns to the prompt.
1196 @cindex @code{--version}
1197 This option causes @value{GDBN} to print its version number and
1198 no-warranty blurb, and exit.
1203 @subsection What @value{GDBN} Does During Startup
1204 @cindex @value{GDBN} startup
1206 Here's the description of what @value{GDBN} does during session startup:
1210 Sets up the command interpreter as specified by the command line
1211 (@pxref{Mode Options, interpreter}).
1215 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1216 used when building @value{GDBN}; @pxref{System-wide configuration,
1217 ,System-wide configuration and settings}) and executes all the commands in
1221 Reads the init file (if any) in your home directory@footnote{On
1222 DOS/Windows systems, the home directory is the one pointed to by the
1223 @code{HOME} environment variable.} and executes all the commands in
1227 Processes command line options and operands.
1230 Reads and executes the commands from init file (if any) in the current
1231 working directory. This is only done if the current directory is
1232 different from your home directory. Thus, you can have more than one
1233 init file, one generic in your home directory, and another, specific
1234 to the program you are debugging, in the directory where you invoke
1238 Reads command files specified by the @samp{-x} option. @xref{Command
1239 Files}, for more details about @value{GDBN} command files.
1242 Reads the command history recorded in the @dfn{history file}.
1243 @xref{Command History}, for more details about the command history and the
1244 files where @value{GDBN} records it.
1247 Init files use the same syntax as @dfn{command files} (@pxref{Command
1248 Files}) and are processed by @value{GDBN} in the same way. The init
1249 file in your home directory can set options (such as @samp{set
1250 complaints}) that affect subsequent processing of command line options
1251 and operands. Init files are not executed if you use the @samp{-nx}
1252 option (@pxref{Mode Options, ,Choosing Modes}).
1254 To display the list of init files loaded by gdb at startup, you
1255 can use @kbd{gdb --help}.
1257 @cindex init file name
1258 @cindex @file{.gdbinit}
1259 @cindex @file{gdb.ini}
1260 The @value{GDBN} init files are normally called @file{.gdbinit}.
1261 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1262 the limitations of file names imposed by DOS filesystems. The Windows
1263 ports of @value{GDBN} use the standard name, but if they find a
1264 @file{gdb.ini} file, they warn you about that and suggest to rename
1265 the file to the standard name.
1269 @section Quitting @value{GDBN}
1270 @cindex exiting @value{GDBN}
1271 @cindex leaving @value{GDBN}
1274 @kindex quit @r{[}@var{expression}@r{]}
1275 @kindex q @r{(@code{quit})}
1276 @item quit @r{[}@var{expression}@r{]}
1278 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1279 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1280 do not supply @var{expression}, @value{GDBN} will terminate normally;
1281 otherwise it will terminate using the result of @var{expression} as the
1286 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1287 terminates the action of any @value{GDBN} command that is in progress and
1288 returns to @value{GDBN} command level. It is safe to type the interrupt
1289 character at any time because @value{GDBN} does not allow it to take effect
1290 until a time when it is safe.
1292 If you have been using @value{GDBN} to control an attached process or
1293 device, you can release it with the @code{detach} command
1294 (@pxref{Attach, ,Debugging an Already-running Process}).
1296 @node Shell Commands
1297 @section Shell Commands
1299 If you need to execute occasional shell commands during your
1300 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1301 just use the @code{shell} command.
1305 @cindex shell escape
1306 @item shell @var{command string}
1307 Invoke a standard shell to execute @var{command string}.
1308 If it exists, the environment variable @code{SHELL} determines which
1309 shell to run. Otherwise @value{GDBN} uses the default shell
1310 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1313 The utility @code{make} is often needed in development environments.
1314 You do not have to use the @code{shell} command for this purpose in
1319 @cindex calling make
1320 @item make @var{make-args}
1321 Execute the @code{make} program with the specified
1322 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1325 @node Logging Output
1326 @section Logging Output
1327 @cindex logging @value{GDBN} output
1328 @cindex save @value{GDBN} output to a file
1330 You may want to save the output of @value{GDBN} commands to a file.
1331 There are several commands to control @value{GDBN}'s logging.
1335 @item set logging on
1337 @item set logging off
1339 @cindex logging file name
1340 @item set logging file @var{file}
1341 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1342 @item set logging overwrite [on|off]
1343 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1344 you want @code{set logging on} to overwrite the logfile instead.
1345 @item set logging redirect [on|off]
1346 By default, @value{GDBN} output will go to both the terminal and the logfile.
1347 Set @code{redirect} if you want output to go only to the log file.
1348 @kindex show logging
1350 Show the current values of the logging settings.
1354 @chapter @value{GDBN} Commands
1356 You can abbreviate a @value{GDBN} command to the first few letters of the command
1357 name, if that abbreviation is unambiguous; and you can repeat certain
1358 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1359 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1360 show you the alternatives available, if there is more than one possibility).
1363 * Command Syntax:: How to give commands to @value{GDBN}
1364 * Completion:: Command completion
1365 * Help:: How to ask @value{GDBN} for help
1368 @node Command Syntax
1369 @section Command Syntax
1371 A @value{GDBN} command is a single line of input. There is no limit on
1372 how long it can be. It starts with a command name, which is followed by
1373 arguments whose meaning depends on the command name. For example, the
1374 command @code{step} accepts an argument which is the number of times to
1375 step, as in @samp{step 5}. You can also use the @code{step} command
1376 with no arguments. Some commands do not allow any arguments.
1378 @cindex abbreviation
1379 @value{GDBN} command names may always be truncated if that abbreviation is
1380 unambiguous. Other possible command abbreviations are listed in the
1381 documentation for individual commands. In some cases, even ambiguous
1382 abbreviations are allowed; for example, @code{s} is specially defined as
1383 equivalent to @code{step} even though there are other commands whose
1384 names start with @code{s}. You can test abbreviations by using them as
1385 arguments to the @code{help} command.
1387 @cindex repeating commands
1388 @kindex RET @r{(repeat last command)}
1389 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1390 repeat the previous command. Certain commands (for example, @code{run})
1391 will not repeat this way; these are commands whose unintentional
1392 repetition might cause trouble and which you are unlikely to want to
1393 repeat. User-defined commands can disable this feature; see
1394 @ref{Define, dont-repeat}.
1396 The @code{list} and @code{x} commands, when you repeat them with
1397 @key{RET}, construct new arguments rather than repeating
1398 exactly as typed. This permits easy scanning of source or memory.
1400 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1401 output, in a way similar to the common utility @code{more}
1402 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1403 @key{RET} too many in this situation, @value{GDBN} disables command
1404 repetition after any command that generates this sort of display.
1406 @kindex # @r{(a comment)}
1408 Any text from a @kbd{#} to the end of the line is a comment; it does
1409 nothing. This is useful mainly in command files (@pxref{Command
1410 Files,,Command Files}).
1412 @cindex repeating command sequences
1413 @kindex Ctrl-o @r{(operate-and-get-next)}
1414 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1415 commands. This command accepts the current line, like @key{RET}, and
1416 then fetches the next line relative to the current line from the history
1420 @section Command Completion
1423 @cindex word completion
1424 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1425 only one possibility; it can also show you what the valid possibilities
1426 are for the next word in a command, at any time. This works for @value{GDBN}
1427 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1429 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1430 of a word. If there is only one possibility, @value{GDBN} fills in the
1431 word, and waits for you to finish the command (or press @key{RET} to
1432 enter it). For example, if you type
1434 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1435 @c complete accuracy in these examples; space introduced for clarity.
1436 @c If texinfo enhancements make it unnecessary, it would be nice to
1437 @c replace " @key" by "@key" in the following...
1439 (@value{GDBP}) info bre @key{TAB}
1443 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1444 the only @code{info} subcommand beginning with @samp{bre}:
1447 (@value{GDBP}) info breakpoints
1451 You can either press @key{RET} at this point, to run the @code{info
1452 breakpoints} command, or backspace and enter something else, if
1453 @samp{breakpoints} does not look like the command you expected. (If you
1454 were sure you wanted @code{info breakpoints} in the first place, you
1455 might as well just type @key{RET} immediately after @samp{info bre},
1456 to exploit command abbreviations rather than command completion).
1458 If there is more than one possibility for the next word when you press
1459 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1460 characters and try again, or just press @key{TAB} a second time;
1461 @value{GDBN} displays all the possible completions for that word. For
1462 example, you might want to set a breakpoint on a subroutine whose name
1463 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1464 just sounds the bell. Typing @key{TAB} again displays all the
1465 function names in your program that begin with those characters, for
1469 (@value{GDBP}) b make_ @key{TAB}
1470 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1471 make_a_section_from_file make_environ
1472 make_abs_section make_function_type
1473 make_blockvector make_pointer_type
1474 make_cleanup make_reference_type
1475 make_command make_symbol_completion_list
1476 (@value{GDBP}) b make_
1480 After displaying the available possibilities, @value{GDBN} copies your
1481 partial input (@samp{b make_} in the example) so you can finish the
1484 If you just want to see the list of alternatives in the first place, you
1485 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1486 means @kbd{@key{META} ?}. You can type this either by holding down a
1487 key designated as the @key{META} shift on your keyboard (if there is
1488 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1490 @cindex quotes in commands
1491 @cindex completion of quoted strings
1492 Sometimes the string you need, while logically a ``word'', may contain
1493 parentheses or other characters that @value{GDBN} normally excludes from
1494 its notion of a word. To permit word completion to work in this
1495 situation, you may enclose words in @code{'} (single quote marks) in
1496 @value{GDBN} commands.
1498 The most likely situation where you might need this is in typing the
1499 name of a C@t{++} function. This is because C@t{++} allows function
1500 overloading (multiple definitions of the same function, distinguished
1501 by argument type). For example, when you want to set a breakpoint you
1502 may need to distinguish whether you mean the version of @code{name}
1503 that takes an @code{int} parameter, @code{name(int)}, or the version
1504 that takes a @code{float} parameter, @code{name(float)}. To use the
1505 word-completion facilities in this situation, type a single quote
1506 @code{'} at the beginning of the function name. This alerts
1507 @value{GDBN} that it may need to consider more information than usual
1508 when you press @key{TAB} or @kbd{M-?} to request word completion:
1511 (@value{GDBP}) b 'bubble( @kbd{M-?}
1512 bubble(double,double) bubble(int,int)
1513 (@value{GDBP}) b 'bubble(
1516 In some cases, @value{GDBN} can tell that completing a name requires using
1517 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1518 completing as much as it can) if you do not type the quote in the first
1522 (@value{GDBP}) b bub @key{TAB}
1523 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1524 (@value{GDBP}) b 'bubble(
1528 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1529 you have not yet started typing the argument list when you ask for
1530 completion on an overloaded symbol.
1532 For more information about overloaded functions, see @ref{C Plus Plus
1533 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1534 overload-resolution off} to disable overload resolution;
1535 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1537 @cindex completion of structure field names
1538 @cindex structure field name completion
1539 @cindex completion of union field names
1540 @cindex union field name completion
1541 When completing in an expression which looks up a field in a
1542 structure, @value{GDBN} also tries@footnote{The completer can be
1543 confused by certain kinds of invalid expressions. Also, it only
1544 examines the static type of the expression, not the dynamic type.} to
1545 limit completions to the field names available in the type of the
1549 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1550 magic to_delete to_fputs to_put to_rewind
1551 to_data to_flush to_isatty to_read to_write
1555 This is because the @code{gdb_stdout} is a variable of the type
1556 @code{struct ui_file} that is defined in @value{GDBN} sources as
1563 ui_file_flush_ftype *to_flush;
1564 ui_file_write_ftype *to_write;
1565 ui_file_fputs_ftype *to_fputs;
1566 ui_file_read_ftype *to_read;
1567 ui_file_delete_ftype *to_delete;
1568 ui_file_isatty_ftype *to_isatty;
1569 ui_file_rewind_ftype *to_rewind;
1570 ui_file_put_ftype *to_put;
1577 @section Getting Help
1578 @cindex online documentation
1581 You can always ask @value{GDBN} itself for information on its commands,
1582 using the command @code{help}.
1585 @kindex h @r{(@code{help})}
1588 You can use @code{help} (abbreviated @code{h}) with no arguments to
1589 display a short list of named classes of commands:
1593 List of classes of commands:
1595 aliases -- Aliases of other commands
1596 breakpoints -- Making program stop at certain points
1597 data -- Examining data
1598 files -- Specifying and examining files
1599 internals -- Maintenance commands
1600 obscure -- Obscure features
1601 running -- Running the program
1602 stack -- Examining the stack
1603 status -- Status inquiries
1604 support -- Support facilities
1605 tracepoints -- Tracing of program execution without
1606 stopping the program
1607 user-defined -- User-defined commands
1609 Type "help" followed by a class name for a list of
1610 commands in that class.
1611 Type "help" followed by command name for full
1613 Command name abbreviations are allowed if unambiguous.
1616 @c the above line break eliminates huge line overfull...
1618 @item help @var{class}
1619 Using one of the general help classes as an argument, you can get a
1620 list of the individual commands in that class. For example, here is the
1621 help display for the class @code{status}:
1624 (@value{GDBP}) help status
1629 @c Line break in "show" line falsifies real output, but needed
1630 @c to fit in smallbook page size.
1631 info -- Generic command for showing things
1632 about the program being debugged
1633 show -- Generic command for showing things
1636 Type "help" followed by command name for full
1638 Command name abbreviations are allowed if unambiguous.
1642 @item help @var{command}
1643 With a command name as @code{help} argument, @value{GDBN} displays a
1644 short paragraph on how to use that command.
1647 @item apropos @var{args}
1648 The @code{apropos} command searches through all of the @value{GDBN}
1649 commands, and their documentation, for the regular expression specified in
1650 @var{args}. It prints out all matches found. For example:
1661 set symbol-reloading -- Set dynamic symbol table reloading
1662 multiple times in one run
1663 show symbol-reloading -- Show dynamic symbol table reloading
1664 multiple times in one run
1669 @item complete @var{args}
1670 The @code{complete @var{args}} command lists all the possible completions
1671 for the beginning of a command. Use @var{args} to specify the beginning of the
1672 command you want completed. For example:
1678 @noindent results in:
1689 @noindent This is intended for use by @sc{gnu} Emacs.
1692 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1693 and @code{show} to inquire about the state of your program, or the state
1694 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1695 manual introduces each of them in the appropriate context. The listings
1696 under @code{info} and under @code{show} in the Index point to
1697 all the sub-commands. @xref{Index}.
1702 @kindex i @r{(@code{info})}
1704 This command (abbreviated @code{i}) is for describing the state of your
1705 program. For example, you can show the arguments passed to a function
1706 with @code{info args}, list the registers currently in use with @code{info
1707 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1708 You can get a complete list of the @code{info} sub-commands with
1709 @w{@code{help info}}.
1713 You can assign the result of an expression to an environment variable with
1714 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1715 @code{set prompt $}.
1719 In contrast to @code{info}, @code{show} is for describing the state of
1720 @value{GDBN} itself.
1721 You can change most of the things you can @code{show}, by using the
1722 related command @code{set}; for example, you can control what number
1723 system is used for displays with @code{set radix}, or simply inquire
1724 which is currently in use with @code{show radix}.
1727 To display all the settable parameters and their current
1728 values, you can use @code{show} with no arguments; you may also use
1729 @code{info set}. Both commands produce the same display.
1730 @c FIXME: "info set" violates the rule that "info" is for state of
1731 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1732 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1736 Here are three miscellaneous @code{show} subcommands, all of which are
1737 exceptional in lacking corresponding @code{set} commands:
1740 @kindex show version
1741 @cindex @value{GDBN} version number
1743 Show what version of @value{GDBN} is running. You should include this
1744 information in @value{GDBN} bug-reports. If multiple versions of
1745 @value{GDBN} are in use at your site, you may need to determine which
1746 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1747 commands are introduced, and old ones may wither away. Also, many
1748 system vendors ship variant versions of @value{GDBN}, and there are
1749 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1750 The version number is the same as the one announced when you start
1753 @kindex show copying
1754 @kindex info copying
1755 @cindex display @value{GDBN} copyright
1758 Display information about permission for copying @value{GDBN}.
1760 @kindex show warranty
1761 @kindex info warranty
1763 @itemx info warranty
1764 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1765 if your version of @value{GDBN} comes with one.
1770 @chapter Running Programs Under @value{GDBN}
1772 When you run a program under @value{GDBN}, you must first generate
1773 debugging information when you compile it.
1775 You may start @value{GDBN} with its arguments, if any, in an environment
1776 of your choice. If you are doing native debugging, you may redirect
1777 your program's input and output, debug an already running process, or
1778 kill a child process.
1781 * Compilation:: Compiling for debugging
1782 * Starting:: Starting your program
1783 * Arguments:: Your program's arguments
1784 * Environment:: Your program's environment
1786 * Working Directory:: Your program's working directory
1787 * Input/Output:: Your program's input and output
1788 * Attach:: Debugging an already-running process
1789 * Kill Process:: Killing the child process
1791 * Inferiors:: Debugging multiple inferiors
1792 * Threads:: Debugging programs with multiple threads
1793 * Processes:: Debugging programs with multiple processes
1794 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1798 @section Compiling for Debugging
1800 In order to debug a program effectively, you need to generate
1801 debugging information when you compile it. This debugging information
1802 is stored in the object file; it describes the data type of each
1803 variable or function and the correspondence between source line numbers
1804 and addresses in the executable code.
1806 To request debugging information, specify the @samp{-g} option when you run
1809 Programs that are to be shipped to your customers are compiled with
1810 optimizations, using the @samp{-O} compiler option. However, many
1811 compilers are unable to handle the @samp{-g} and @samp{-O} options
1812 together. Using those compilers, you cannot generate optimized
1813 executables containing debugging information.
1815 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1816 without @samp{-O}, making it possible to debug optimized code. We
1817 recommend that you @emph{always} use @samp{-g} whenever you compile a
1818 program. You may think your program is correct, but there is no sense
1819 in pushing your luck.
1821 @cindex optimized code, debugging
1822 @cindex debugging optimized code
1823 When you debug a program compiled with @samp{-g -O}, remember that the
1824 optimizer is rearranging your code; the debugger shows you what is
1825 really there. Do not be too surprised when the execution path does not
1826 exactly match your source file! An extreme example: if you define a
1827 variable, but never use it, @value{GDBN} never sees that
1828 variable---because the compiler optimizes it out of existence.
1830 Some things do not work as well with @samp{-g -O} as with just
1831 @samp{-g}, particularly on machines with instruction scheduling. If in
1832 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1833 please report it to us as a bug (including a test case!).
1834 @xref{Variables}, for more information about debugging optimized code.
1836 Older versions of the @sc{gnu} C compiler permitted a variant option
1837 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1838 format; if your @sc{gnu} C compiler has this option, do not use it.
1840 @value{GDBN} knows about preprocessor macros and can show you their
1841 expansion (@pxref{Macros}). Most compilers do not include information
1842 about preprocessor macros in the debugging information if you specify
1843 the @option{-g} flag alone, because this information is rather large.
1844 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1845 provides macro information if you specify the options
1846 @option{-gdwarf-2} and @option{-g3}; the former option requests
1847 debugging information in the Dwarf 2 format, and the latter requests
1848 ``extra information''. In the future, we hope to find more compact
1849 ways to represent macro information, so that it can be included with
1854 @section Starting your Program
1860 @kindex r @r{(@code{run})}
1863 Use the @code{run} command to start your program under @value{GDBN}.
1864 You must first specify the program name (except on VxWorks) with an
1865 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1866 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1867 (@pxref{Files, ,Commands to Specify Files}).
1871 If you are running your program in an execution environment that
1872 supports processes, @code{run} creates an inferior process and makes
1873 that process run your program. In some environments without processes,
1874 @code{run} jumps to the start of your program. Other targets,
1875 like @samp{remote}, are always running. If you get an error
1876 message like this one:
1879 The "remote" target does not support "run".
1880 Try "help target" or "continue".
1884 then use @code{continue} to run your program. You may need @code{load}
1885 first (@pxref{load}).
1887 The execution of a program is affected by certain information it
1888 receives from its superior. @value{GDBN} provides ways to specify this
1889 information, which you must do @emph{before} starting your program. (You
1890 can change it after starting your program, but such changes only affect
1891 your program the next time you start it.) This information may be
1892 divided into four categories:
1895 @item The @emph{arguments.}
1896 Specify the arguments to give your program as the arguments of the
1897 @code{run} command. If a shell is available on your target, the shell
1898 is used to pass the arguments, so that you may use normal conventions
1899 (such as wildcard expansion or variable substitution) in describing
1901 In Unix systems, you can control which shell is used with the
1902 @code{SHELL} environment variable.
1903 @xref{Arguments, ,Your Program's Arguments}.
1905 @item The @emph{environment.}
1906 Your program normally inherits its environment from @value{GDBN}, but you can
1907 use the @value{GDBN} commands @code{set environment} and @code{unset
1908 environment} to change parts of the environment that affect
1909 your program. @xref{Environment, ,Your Program's Environment}.
1911 @item The @emph{working directory.}
1912 Your program inherits its working directory from @value{GDBN}. You can set
1913 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1914 @xref{Working Directory, ,Your Program's Working Directory}.
1916 @item The @emph{standard input and output.}
1917 Your program normally uses the same device for standard input and
1918 standard output as @value{GDBN} is using. You can redirect input and output
1919 in the @code{run} command line, or you can use the @code{tty} command to
1920 set a different device for your program.
1921 @xref{Input/Output, ,Your Program's Input and Output}.
1924 @emph{Warning:} While input and output redirection work, you cannot use
1925 pipes to pass the output of the program you are debugging to another
1926 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1930 When you issue the @code{run} command, your program begins to execute
1931 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1932 of how to arrange for your program to stop. Once your program has
1933 stopped, you may call functions in your program, using the @code{print}
1934 or @code{call} commands. @xref{Data, ,Examining Data}.
1936 If the modification time of your symbol file has changed since the last
1937 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1938 table, and reads it again. When it does this, @value{GDBN} tries to retain
1939 your current breakpoints.
1944 @cindex run to main procedure
1945 The name of the main procedure can vary from language to language.
1946 With C or C@t{++}, the main procedure name is always @code{main}, but
1947 other languages such as Ada do not require a specific name for their
1948 main procedure. The debugger provides a convenient way to start the
1949 execution of the program and to stop at the beginning of the main
1950 procedure, depending on the language used.
1952 The @samp{start} command does the equivalent of setting a temporary
1953 breakpoint at the beginning of the main procedure and then invoking
1954 the @samp{run} command.
1956 @cindex elaboration phase
1957 Some programs contain an @dfn{elaboration} phase where some startup code is
1958 executed before the main procedure is called. This depends on the
1959 languages used to write your program. In C@t{++}, for instance,
1960 constructors for static and global objects are executed before
1961 @code{main} is called. It is therefore possible that the debugger stops
1962 before reaching the main procedure. However, the temporary breakpoint
1963 will remain to halt execution.
1965 Specify the arguments to give to your program as arguments to the
1966 @samp{start} command. These arguments will be given verbatim to the
1967 underlying @samp{run} command. Note that the same arguments will be
1968 reused if no argument is provided during subsequent calls to
1969 @samp{start} or @samp{run}.
1971 It is sometimes necessary to debug the program during elaboration. In
1972 these cases, using the @code{start} command would stop the execution of
1973 your program too late, as the program would have already completed the
1974 elaboration phase. Under these circumstances, insert breakpoints in your
1975 elaboration code before running your program.
1977 @kindex set exec-wrapper
1978 @item set exec-wrapper @var{wrapper}
1979 @itemx show exec-wrapper
1980 @itemx unset exec-wrapper
1981 When @samp{exec-wrapper} is set, the specified wrapper is used to
1982 launch programs for debugging. @value{GDBN} starts your program
1983 with a shell command of the form @kbd{exec @var{wrapper}
1984 @var{program}}. Quoting is added to @var{program} and its
1985 arguments, but not to @var{wrapper}, so you should add quotes if
1986 appropriate for your shell. The wrapper runs until it executes
1987 your program, and then @value{GDBN} takes control.
1989 You can use any program that eventually calls @code{execve} with
1990 its arguments as a wrapper. Several standard Unix utilities do
1991 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1992 with @code{exec "$@@"} will also work.
1994 For example, you can use @code{env} to pass an environment variable to
1995 the debugged program, without setting the variable in your shell's
1999 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2003 This command is available when debugging locally on most targets, excluding
2004 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2006 @kindex set disable-randomization
2007 @item set disable-randomization
2008 @itemx set disable-randomization on
2009 This option (enabled by default in @value{GDBN}) will turn off the native
2010 randomization of the virtual address space of the started program. This option
2011 is useful for multiple debugging sessions to make the execution better
2012 reproducible and memory addresses reusable across debugging sessions.
2014 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2018 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2021 @item set disable-randomization off
2022 Leave the behavior of the started executable unchanged. Some bugs rear their
2023 ugly heads only when the program is loaded at certain addresses. If your bug
2024 disappears when you run the program under @value{GDBN}, that might be because
2025 @value{GDBN} by default disables the address randomization on platforms, such
2026 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2027 disable-randomization off} to try to reproduce such elusive bugs.
2029 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2030 It protects the programs against some kinds of security attacks. In these
2031 cases the attacker needs to know the exact location of a concrete executable
2032 code. Randomizing its location makes it impossible to inject jumps misusing
2033 a code at its expected addresses.
2035 Prelinking shared libraries provides a startup performance advantage but it
2036 makes addresses in these libraries predictable for privileged processes by
2037 having just unprivileged access at the target system. Reading the shared
2038 library binary gives enough information for assembling the malicious code
2039 misusing it. Still even a prelinked shared library can get loaded at a new
2040 random address just requiring the regular relocation process during the
2041 startup. Shared libraries not already prelinked are always loaded at
2042 a randomly chosen address.
2044 Position independent executables (PIE) contain position independent code
2045 similar to the shared libraries and therefore such executables get loaded at
2046 a randomly chosen address upon startup. PIE executables always load even
2047 already prelinked shared libraries at a random address. You can build such
2048 executable using @command{gcc -fPIE -pie}.
2050 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2051 (as long as the randomization is enabled).
2053 @item show disable-randomization
2054 Show the current setting of the explicit disable of the native randomization of
2055 the virtual address space of the started program.
2060 @section Your Program's Arguments
2062 @cindex arguments (to your program)
2063 The arguments to your program can be specified by the arguments of the
2065 They are passed to a shell, which expands wildcard characters and
2066 performs redirection of I/O, and thence to your program. Your
2067 @code{SHELL} environment variable (if it exists) specifies what shell
2068 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2069 the default shell (@file{/bin/sh} on Unix).
2071 On non-Unix systems, the program is usually invoked directly by
2072 @value{GDBN}, which emulates I/O redirection via the appropriate system
2073 calls, and the wildcard characters are expanded by the startup code of
2074 the program, not by the shell.
2076 @code{run} with no arguments uses the same arguments used by the previous
2077 @code{run}, or those set by the @code{set args} command.
2082 Specify the arguments to be used the next time your program is run. If
2083 @code{set args} has no arguments, @code{run} executes your program
2084 with no arguments. Once you have run your program with arguments,
2085 using @code{set args} before the next @code{run} is the only way to run
2086 it again without arguments.
2090 Show the arguments to give your program when it is started.
2094 @section Your Program's Environment
2096 @cindex environment (of your program)
2097 The @dfn{environment} consists of a set of environment variables and
2098 their values. Environment variables conventionally record such things as
2099 your user name, your home directory, your terminal type, and your search
2100 path for programs to run. Usually you set up environment variables with
2101 the shell and they are inherited by all the other programs you run. When
2102 debugging, it can be useful to try running your program with a modified
2103 environment without having to start @value{GDBN} over again.
2107 @item path @var{directory}
2108 Add @var{directory} to the front of the @code{PATH} environment variable
2109 (the search path for executables) that will be passed to your program.
2110 The value of @code{PATH} used by @value{GDBN} does not change.
2111 You may specify several directory names, separated by whitespace or by a
2112 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2113 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2114 is moved to the front, so it is searched sooner.
2116 You can use the string @samp{$cwd} to refer to whatever is the current
2117 working directory at the time @value{GDBN} searches the path. If you
2118 use @samp{.} instead, it refers to the directory where you executed the
2119 @code{path} command. @value{GDBN} replaces @samp{.} in the
2120 @var{directory} argument (with the current path) before adding
2121 @var{directory} to the search path.
2122 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2123 @c document that, since repeating it would be a no-op.
2127 Display the list of search paths for executables (the @code{PATH}
2128 environment variable).
2130 @kindex show environment
2131 @item show environment @r{[}@var{varname}@r{]}
2132 Print the value of environment variable @var{varname} to be given to
2133 your program when it starts. If you do not supply @var{varname},
2134 print the names and values of all environment variables to be given to
2135 your program. You can abbreviate @code{environment} as @code{env}.
2137 @kindex set environment
2138 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2139 Set environment variable @var{varname} to @var{value}. The value
2140 changes for your program only, not for @value{GDBN} itself. @var{value} may
2141 be any string; the values of environment variables are just strings, and
2142 any interpretation is supplied by your program itself. The @var{value}
2143 parameter is optional; if it is eliminated, the variable is set to a
2145 @c "any string" here does not include leading, trailing
2146 @c blanks. Gnu asks: does anyone care?
2148 For example, this command:
2155 tells the debugged program, when subsequently run, that its user is named
2156 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2157 are not actually required.)
2159 @kindex unset environment
2160 @item unset environment @var{varname}
2161 Remove variable @var{varname} from the environment to be passed to your
2162 program. This is different from @samp{set env @var{varname} =};
2163 @code{unset environment} removes the variable from the environment,
2164 rather than assigning it an empty value.
2167 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2169 by your @code{SHELL} environment variable if it exists (or
2170 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2171 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2172 @file{.bashrc} for BASH---any variables you set in that file affect
2173 your program. You may wish to move setting of environment variables to
2174 files that are only run when you sign on, such as @file{.login} or
2177 @node Working Directory
2178 @section Your Program's Working Directory
2180 @cindex working directory (of your program)
2181 Each time you start your program with @code{run}, it inherits its
2182 working directory from the current working directory of @value{GDBN}.
2183 The @value{GDBN} working directory is initially whatever it inherited
2184 from its parent process (typically the shell), but you can specify a new
2185 working directory in @value{GDBN} with the @code{cd} command.
2187 The @value{GDBN} working directory also serves as a default for the commands
2188 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2193 @cindex change working directory
2194 @item cd @var{directory}
2195 Set the @value{GDBN} working directory to @var{directory}.
2199 Print the @value{GDBN} working directory.
2202 It is generally impossible to find the current working directory of
2203 the process being debugged (since a program can change its directory
2204 during its run). If you work on a system where @value{GDBN} is
2205 configured with the @file{/proc} support, you can use the @code{info
2206 proc} command (@pxref{SVR4 Process Information}) to find out the
2207 current working directory of the debuggee.
2210 @section Your Program's Input and Output
2215 By default, the program you run under @value{GDBN} does input and output to
2216 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2217 to its own terminal modes to interact with you, but it records the terminal
2218 modes your program was using and switches back to them when you continue
2219 running your program.
2222 @kindex info terminal
2224 Displays information recorded by @value{GDBN} about the terminal modes your
2228 You can redirect your program's input and/or output using shell
2229 redirection with the @code{run} command. For example,
2236 starts your program, diverting its output to the file @file{outfile}.
2239 @cindex controlling terminal
2240 Another way to specify where your program should do input and output is
2241 with the @code{tty} command. This command accepts a file name as
2242 argument, and causes this file to be the default for future @code{run}
2243 commands. It also resets the controlling terminal for the child
2244 process, for future @code{run} commands. For example,
2251 directs that processes started with subsequent @code{run} commands
2252 default to do input and output on the terminal @file{/dev/ttyb} and have
2253 that as their controlling terminal.
2255 An explicit redirection in @code{run} overrides the @code{tty} command's
2256 effect on the input/output device, but not its effect on the controlling
2259 When you use the @code{tty} command or redirect input in the @code{run}
2260 command, only the input @emph{for your program} is affected. The input
2261 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2262 for @code{set inferior-tty}.
2264 @cindex inferior tty
2265 @cindex set inferior controlling terminal
2266 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2267 display the name of the terminal that will be used for future runs of your
2271 @item set inferior-tty /dev/ttyb
2272 @kindex set inferior-tty
2273 Set the tty for the program being debugged to /dev/ttyb.
2275 @item show inferior-tty
2276 @kindex show inferior-tty
2277 Show the current tty for the program being debugged.
2281 @section Debugging an Already-running Process
2286 @item attach @var{process-id}
2287 This command attaches to a running process---one that was started
2288 outside @value{GDBN}. (@code{info files} shows your active
2289 targets.) The command takes as argument a process ID. The usual way to
2290 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2291 or with the @samp{jobs -l} shell command.
2293 @code{attach} does not repeat if you press @key{RET} a second time after
2294 executing the command.
2297 To use @code{attach}, your program must be running in an environment
2298 which supports processes; for example, @code{attach} does not work for
2299 programs on bare-board targets that lack an operating system. You must
2300 also have permission to send the process a signal.
2302 When you use @code{attach}, the debugger finds the program running in
2303 the process first by looking in the current working directory, then (if
2304 the program is not found) by using the source file search path
2305 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2306 the @code{file} command to load the program. @xref{Files, ,Commands to
2309 The first thing @value{GDBN} does after arranging to debug the specified
2310 process is to stop it. You can examine and modify an attached process
2311 with all the @value{GDBN} commands that are ordinarily available when
2312 you start processes with @code{run}. You can insert breakpoints; you
2313 can step and continue; you can modify storage. If you would rather the
2314 process continue running, you may use the @code{continue} command after
2315 attaching @value{GDBN} to the process.
2320 When you have finished debugging the attached process, you can use the
2321 @code{detach} command to release it from @value{GDBN} control. Detaching
2322 the process continues its execution. After the @code{detach} command,
2323 that process and @value{GDBN} become completely independent once more, and you
2324 are ready to @code{attach} another process or start one with @code{run}.
2325 @code{detach} does not repeat if you press @key{RET} again after
2326 executing the command.
2329 If you exit @value{GDBN} while you have an attached process, you detach
2330 that process. If you use the @code{run} command, you kill that process.
2331 By default, @value{GDBN} asks for confirmation if you try to do either of these
2332 things; you can control whether or not you need to confirm by using the
2333 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2337 @section Killing the Child Process
2342 Kill the child process in which your program is running under @value{GDBN}.
2345 This command is useful if you wish to debug a core dump instead of a
2346 running process. @value{GDBN} ignores any core dump file while your program
2349 On some operating systems, a program cannot be executed outside @value{GDBN}
2350 while you have breakpoints set on it inside @value{GDBN}. You can use the
2351 @code{kill} command in this situation to permit running your program
2352 outside the debugger.
2354 The @code{kill} command is also useful if you wish to recompile and
2355 relink your program, since on many systems it is impossible to modify an
2356 executable file while it is running in a process. In this case, when you
2357 next type @code{run}, @value{GDBN} notices that the file has changed, and
2358 reads the symbol table again (while trying to preserve your current
2359 breakpoint settings).
2362 @section Debugging Multiple Inferiors
2364 Some @value{GDBN} targets are able to run multiple processes created
2365 from a single executable. This can happen, for instance, with an
2366 embedded system reporting back several processes via the remote
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 (in future) be retained after a process exits. Each run of an
2375 executable creates a new inferior, as does each attachment to an
2376 existing process. Inferiors have unique identifiers that are
2377 different from process ids, and may optionally be named as well.
2378 Usually each inferior will also have its own distinct address space,
2379 although some embedded targets may have several inferiors running in
2380 different parts of a single space.
2382 Each inferior may in turn have multiple threads running in it.
2384 To find out what inferiors exist at any moment, use @code{info inferiors}:
2387 @kindex info inferiors
2388 @item info inferiors
2389 Print a list of all inferiors currently being managed by @value{GDBN}.
2391 @kindex set print inferior-events
2392 @cindex print messages on inferior start and exit
2393 @item set print inferior-events
2394 @itemx set print inferior-events on
2395 @itemx set print inferior-events off
2396 The @code{set print inferior-events} command allows you to enable or
2397 disable printing of messages when @value{GDBN} notices that new
2398 inferiors have started or that inferiors have exited or have been
2399 detached. By default, these messages will not be printed.
2401 @kindex show print inferior-events
2402 @item show print inferior-events
2403 Show whether messages will be printed when @value{GDBN} detects that
2404 inferiors have started, exited or have been detached.
2408 @section Debugging Programs with Multiple Threads
2410 @cindex threads of execution
2411 @cindex multiple threads
2412 @cindex switching threads
2413 In some operating systems, such as HP-UX and Solaris, a single program
2414 may have more than one @dfn{thread} of execution. The precise semantics
2415 of threads differ from one operating system to another, but in general
2416 the threads of a single program are akin to multiple processes---except
2417 that they share one address space (that is, they can all examine and
2418 modify the same variables). On the other hand, each thread has its own
2419 registers and execution stack, and perhaps private memory.
2421 @value{GDBN} provides these facilities for debugging multi-thread
2425 @item automatic notification of new threads
2426 @item @samp{thread @var{threadno}}, a command to switch among threads
2427 @item @samp{info threads}, a command to inquire about existing threads
2428 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2429 a command to apply a command to a list of threads
2430 @item thread-specific breakpoints
2431 @item @samp{set print thread-events}, which controls printing of
2432 messages on thread start and exit.
2436 @emph{Warning:} These facilities are not yet available on every
2437 @value{GDBN} configuration where the operating system supports threads.
2438 If your @value{GDBN} does not support threads, these commands have no
2439 effect. For example, a system without thread support shows no output
2440 from @samp{info threads}, and always rejects the @code{thread} command,
2444 (@value{GDBP}) info threads
2445 (@value{GDBP}) thread 1
2446 Thread ID 1 not known. Use the "info threads" command to
2447 see the IDs of currently known threads.
2449 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2450 @c doesn't support threads"?
2453 @cindex focus of debugging
2454 @cindex current thread
2455 The @value{GDBN} thread debugging facility allows you to observe all
2456 threads while your program runs---but whenever @value{GDBN} takes
2457 control, one thread in particular is always the focus of debugging.
2458 This thread is called the @dfn{current thread}. Debugging commands show
2459 program information from the perspective of the current thread.
2461 @cindex @code{New} @var{systag} message
2462 @cindex thread identifier (system)
2463 @c FIXME-implementors!! It would be more helpful if the [New...] message
2464 @c included GDB's numeric thread handle, so you could just go to that
2465 @c thread without first checking `info threads'.
2466 Whenever @value{GDBN} detects a new thread in your program, it displays
2467 the target system's identification for the thread with a message in the
2468 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2469 whose form varies depending on the particular system. For example, on
2470 @sc{gnu}/Linux, you might see
2473 [New Thread 46912507313328 (LWP 25582)]
2477 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2478 the @var{systag} is simply something like @samp{process 368}, with no
2481 @c FIXME!! (1) Does the [New...] message appear even for the very first
2482 @c thread of a program, or does it only appear for the
2483 @c second---i.e.@: when it becomes obvious we have a multithread
2485 @c (2) *Is* there necessarily a first thread always? Or do some
2486 @c multithread systems permit starting a program with multiple
2487 @c threads ab initio?
2489 @cindex thread number
2490 @cindex thread identifier (GDB)
2491 For debugging purposes, @value{GDBN} associates its own thread
2492 number---always a single integer---with each thread in your program.
2495 @kindex info threads
2497 Display a summary of all threads currently in your
2498 program. @value{GDBN} displays for each thread (in this order):
2502 the thread number assigned by @value{GDBN}
2505 the target system's thread identifier (@var{systag})
2508 the current stack frame summary for that thread
2512 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2513 indicates the current thread.
2517 @c end table here to get a little more width for example
2520 (@value{GDBP}) info threads
2521 3 process 35 thread 27 0x34e5 in sigpause ()
2522 2 process 35 thread 23 0x34e5 in sigpause ()
2523 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2529 @cindex debugging multithreaded programs (on HP-UX)
2530 @cindex thread identifier (GDB), on HP-UX
2531 For debugging purposes, @value{GDBN} associates its own thread
2532 number---a small integer assigned in thread-creation order---with each
2533 thread in your program.
2535 @cindex @code{New} @var{systag} message, on HP-UX
2536 @cindex thread identifier (system), on HP-UX
2537 @c FIXME-implementors!! It would be more helpful if the [New...] message
2538 @c included GDB's numeric thread handle, so you could just go to that
2539 @c thread without first checking `info threads'.
2540 Whenever @value{GDBN} detects a new thread in your program, it displays
2541 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2542 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2543 whose form varies depending on the particular system. For example, on
2547 [New thread 2 (system thread 26594)]
2551 when @value{GDBN} notices a new thread.
2554 @kindex info threads (HP-UX)
2556 Display a summary of all threads currently in your
2557 program. @value{GDBN} displays for each thread (in this order):
2560 @item the thread number assigned by @value{GDBN}
2562 @item the target system's thread identifier (@var{systag})
2564 @item the current stack frame summary for that thread
2568 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2569 indicates the current thread.
2573 @c end table here to get a little more width for example
2576 (@value{GDBP}) info threads
2577 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2579 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2580 from /usr/lib/libc.2
2581 1 system thread 27905 0x7b003498 in _brk () \@*
2582 from /usr/lib/libc.2
2585 On Solaris, you can display more information about user threads with a
2586 Solaris-specific command:
2589 @item maint info sol-threads
2590 @kindex maint info sol-threads
2591 @cindex thread info (Solaris)
2592 Display info on Solaris user threads.
2596 @kindex thread @var{threadno}
2597 @item thread @var{threadno}
2598 Make thread number @var{threadno} the current thread. The command
2599 argument @var{threadno} is the internal @value{GDBN} thread number, as
2600 shown in the first field of the @samp{info threads} display.
2601 @value{GDBN} responds by displaying the system identifier of the thread
2602 you selected, and its current stack frame summary:
2605 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2606 (@value{GDBP}) thread 2
2607 [Switching to process 35 thread 23]
2608 0x34e5 in sigpause ()
2612 As with the @samp{[New @dots{}]} message, the form of the text after
2613 @samp{Switching to} depends on your system's conventions for identifying
2616 @kindex thread apply
2617 @cindex apply command to several threads
2618 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2619 The @code{thread apply} command allows you to apply the named
2620 @var{command} to one or more threads. Specify the numbers of the
2621 threads that you want affected with the command argument
2622 @var{threadno}. It can be a single thread number, one of the numbers
2623 shown in the first field of the @samp{info threads} display; or it
2624 could be a range of thread numbers, as in @code{2-4}. To apply a
2625 command to all threads, type @kbd{thread apply all @var{command}}.
2627 @kindex set print thread-events
2628 @cindex print messages on thread start and exit
2629 @item set print thread-events
2630 @itemx set print thread-events on
2631 @itemx set print thread-events off
2632 The @code{set print thread-events} command allows you to enable or
2633 disable printing of messages when @value{GDBN} notices that new threads have
2634 started or that threads have exited. By default, these messages will
2635 be printed if detection of these events is supported by the target.
2636 Note that these messages cannot be disabled on all targets.
2638 @kindex show print thread-events
2639 @item show print thread-events
2640 Show whether messages will be printed when @value{GDBN} detects that threads
2641 have started and exited.
2644 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2645 more information about how @value{GDBN} behaves when you stop and start
2646 programs with multiple threads.
2648 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2649 watchpoints in programs with multiple threads.
2652 @section Debugging Programs with Multiple Processes
2654 @cindex fork, debugging programs which call
2655 @cindex multiple processes
2656 @cindex processes, multiple
2657 On most systems, @value{GDBN} has no special support for debugging
2658 programs which create additional processes using the @code{fork}
2659 function. When a program forks, @value{GDBN} will continue to debug the
2660 parent process and the child process will run unimpeded. If you have
2661 set a breakpoint in any code which the child then executes, the child
2662 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2663 will cause it to terminate.
2665 However, if you want to debug the child process there is a workaround
2666 which isn't too painful. Put a call to @code{sleep} in the code which
2667 the child process executes after the fork. It may be useful to sleep
2668 only if a certain environment variable is set, or a certain file exists,
2669 so that the delay need not occur when you don't want to run @value{GDBN}
2670 on the child. While the child is sleeping, use the @code{ps} program to
2671 get its process ID. Then tell @value{GDBN} (a new invocation of
2672 @value{GDBN} if you are also debugging the parent process) to attach to
2673 the child process (@pxref{Attach}). From that point on you can debug
2674 the child process just like any other process which you attached to.
2676 On some systems, @value{GDBN} provides support for debugging programs that
2677 create additional processes using the @code{fork} or @code{vfork} functions.
2678 Currently, the only platforms with this feature are HP-UX (11.x and later
2679 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2681 By default, when a program forks, @value{GDBN} will continue to debug
2682 the parent process and the child process will run unimpeded.
2684 If you want to follow the child process instead of the parent process,
2685 use the command @w{@code{set follow-fork-mode}}.
2688 @kindex set follow-fork-mode
2689 @item set follow-fork-mode @var{mode}
2690 Set the debugger response to a program call of @code{fork} or
2691 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2692 process. The @var{mode} argument can be:
2696 The original process is debugged after a fork. The child process runs
2697 unimpeded. This is the default.
2700 The new process is debugged after a fork. The parent process runs
2705 @kindex show follow-fork-mode
2706 @item show follow-fork-mode
2707 Display the current debugger response to a @code{fork} or @code{vfork} call.
2710 @cindex debugging multiple processes
2711 On Linux, if you want to debug both the parent and child processes, use the
2712 command @w{@code{set detach-on-fork}}.
2715 @kindex set detach-on-fork
2716 @item set detach-on-fork @var{mode}
2717 Tells gdb whether to detach one of the processes after a fork, or
2718 retain debugger control over them both.
2722 The child process (or parent process, depending on the value of
2723 @code{follow-fork-mode}) will be detached and allowed to run
2724 independently. This is the default.
2727 Both processes will be held under the control of @value{GDBN}.
2728 One process (child or parent, depending on the value of
2729 @code{follow-fork-mode}) is debugged as usual, while the other
2734 @kindex show detach-on-fork
2735 @item show detach-on-fork
2736 Show whether detach-on-fork mode is on/off.
2739 If you choose to set @samp{detach-on-fork} mode off, then
2740 @value{GDBN} will retain control of all forked processes (including
2741 nested forks). You can list the forked processes under the control of
2742 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2743 from one fork to another by using the @w{@code{fork}} command.
2748 Print a list of all forked processes under the control of @value{GDBN}.
2749 The listing will include a fork id, a process id, and the current
2750 position (program counter) of the process.
2752 @kindex fork @var{fork-id}
2753 @item fork @var{fork-id}
2754 Make fork number @var{fork-id} the current process. The argument
2755 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2756 as shown in the first field of the @samp{info forks} display.
2758 @kindex process @var{process-id}
2759 @item process @var{process-id}
2760 Make process number @var{process-id} the current process. The
2761 argument @var{process-id} must be one that is listed in the output of
2766 To quit debugging one of the forked processes, you can either detach
2767 from it by using the @w{@code{detach fork}} command (allowing it to
2768 run independently), or delete (and kill) it using the
2769 @w{@code{delete fork}} command.
2772 @kindex detach fork @var{fork-id}
2773 @item detach fork @var{fork-id}
2774 Detach from the process identified by @value{GDBN} fork number
2775 @var{fork-id}, and remove it from the fork list. The process will be
2776 allowed to run independently.
2778 @kindex delete fork @var{fork-id}
2779 @item delete fork @var{fork-id}
2780 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2781 and remove it from the fork list.
2785 If you ask to debug a child process and a @code{vfork} is followed by an
2786 @code{exec}, @value{GDBN} executes the new target up to the first
2787 breakpoint in the new target. If you have a breakpoint set on
2788 @code{main} in your original program, the breakpoint will also be set on
2789 the child process's @code{main}.
2791 When a child process is spawned by @code{vfork}, you cannot debug the
2792 child or parent until an @code{exec} call completes.
2794 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2795 call executes, the new target restarts. To restart the parent process,
2796 use the @code{file} command with the parent executable name as its
2799 You can use the @code{catch} command to make @value{GDBN} stop whenever
2800 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2801 Catchpoints, ,Setting Catchpoints}.
2803 @node Checkpoint/Restart
2804 @section Setting a @emph{Bookmark} to Return to Later
2809 @cindex snapshot of a process
2810 @cindex rewind program state
2812 On certain operating systems@footnote{Currently, only
2813 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2814 program's state, called a @dfn{checkpoint}, and come back to it
2817 Returning to a checkpoint effectively undoes everything that has
2818 happened in the program since the @code{checkpoint} was saved. This
2819 includes changes in memory, registers, and even (within some limits)
2820 system state. Effectively, it is like going back in time to the
2821 moment when the checkpoint was saved.
2823 Thus, if you're stepping thru a program and you think you're
2824 getting close to the point where things go wrong, you can save
2825 a checkpoint. Then, if you accidentally go too far and miss
2826 the critical statement, instead of having to restart your program
2827 from the beginning, you can just go back to the checkpoint and
2828 start again from there.
2830 This can be especially useful if it takes a lot of time or
2831 steps to reach the point where you think the bug occurs.
2833 To use the @code{checkpoint}/@code{restart} method of debugging:
2838 Save a snapshot of the debugged program's current execution state.
2839 The @code{checkpoint} command takes no arguments, but each checkpoint
2840 is assigned a small integer id, similar to a breakpoint id.
2842 @kindex info checkpoints
2843 @item info checkpoints
2844 List the checkpoints that have been saved in the current debugging
2845 session. For each checkpoint, the following information will be
2852 @item Source line, or label
2855 @kindex restart @var{checkpoint-id}
2856 @item restart @var{checkpoint-id}
2857 Restore the program state that was saved as checkpoint number
2858 @var{checkpoint-id}. All program variables, registers, stack frames
2859 etc.@: will be returned to the values that they had when the checkpoint
2860 was saved. In essence, gdb will ``wind back the clock'' to the point
2861 in time when the checkpoint was saved.
2863 Note that breakpoints, @value{GDBN} variables, command history etc.
2864 are not affected by restoring a checkpoint. In general, a checkpoint
2865 only restores things that reside in the program being debugged, not in
2868 @kindex delete checkpoint @var{checkpoint-id}
2869 @item delete checkpoint @var{checkpoint-id}
2870 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2874 Returning to a previously saved checkpoint will restore the user state
2875 of the program being debugged, plus a significant subset of the system
2876 (OS) state, including file pointers. It won't ``un-write'' data from
2877 a file, but it will rewind the file pointer to the previous location,
2878 so that the previously written data can be overwritten. For files
2879 opened in read mode, the pointer will also be restored so that the
2880 previously read data can be read again.
2882 Of course, characters that have been sent to a printer (or other
2883 external device) cannot be ``snatched back'', and characters received
2884 from eg.@: a serial device can be removed from internal program buffers,
2885 but they cannot be ``pushed back'' into the serial pipeline, ready to
2886 be received again. Similarly, the actual contents of files that have
2887 been changed cannot be restored (at this time).
2889 However, within those constraints, you actually can ``rewind'' your
2890 program to a previously saved point in time, and begin debugging it
2891 again --- and you can change the course of events so as to debug a
2892 different execution path this time.
2894 @cindex checkpoints and process id
2895 Finally, there is one bit of internal program state that will be
2896 different when you return to a checkpoint --- the program's process
2897 id. Each checkpoint will have a unique process id (or @var{pid}),
2898 and each will be different from the program's original @var{pid}.
2899 If your program has saved a local copy of its process id, this could
2900 potentially pose a problem.
2902 @subsection A Non-obvious Benefit of Using Checkpoints
2904 On some systems such as @sc{gnu}/Linux, address space randomization
2905 is performed on new processes for security reasons. This makes it
2906 difficult or impossible to set a breakpoint, or watchpoint, on an
2907 absolute address if you have to restart the program, since the
2908 absolute location of a symbol will change from one execution to the
2911 A checkpoint, however, is an @emph{identical} copy of a process.
2912 Therefore if you create a checkpoint at (eg.@:) the start of main,
2913 and simply return to that checkpoint instead of restarting the
2914 process, you can avoid the effects of address randomization and
2915 your symbols will all stay in the same place.
2918 @chapter Stopping and Continuing
2920 The principal purposes of using a debugger are so that you can stop your
2921 program before it terminates; or so that, if your program runs into
2922 trouble, you can investigate and find out why.
2924 Inside @value{GDBN}, your program may stop for any of several reasons,
2925 such as a signal, a breakpoint, or reaching a new line after a
2926 @value{GDBN} command such as @code{step}. You may then examine and
2927 change variables, set new breakpoints or remove old ones, and then
2928 continue execution. Usually, the messages shown by @value{GDBN} provide
2929 ample explanation of the status of your program---but you can also
2930 explicitly request this information at any time.
2933 @kindex info program
2935 Display information about the status of your program: whether it is
2936 running or not, what process it is, and why it stopped.
2940 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2941 * Continuing and Stepping:: Resuming execution
2943 * Thread Stops:: Stopping and starting multi-thread programs
2947 @section Breakpoints, Watchpoints, and Catchpoints
2950 A @dfn{breakpoint} makes your program stop whenever a certain point in
2951 the program is reached. For each breakpoint, you can add conditions to
2952 control in finer detail whether your program stops. You can set
2953 breakpoints with the @code{break} command and its variants (@pxref{Set
2954 Breaks, ,Setting Breakpoints}), to specify the place where your program
2955 should stop by line number, function name or exact address in the
2958 On some systems, you can set breakpoints in shared libraries before
2959 the executable is run. There is a minor limitation on HP-UX systems:
2960 you must wait until the executable is run in order to set breakpoints
2961 in shared library routines that are not called directly by the program
2962 (for example, routines that are arguments in a @code{pthread_create}
2966 @cindex data breakpoints
2967 @cindex memory tracing
2968 @cindex breakpoint on memory address
2969 @cindex breakpoint on variable modification
2970 A @dfn{watchpoint} is a special breakpoint that stops your program
2971 when the value of an expression changes. The expression may be a value
2972 of a variable, or it could involve values of one or more variables
2973 combined by operators, such as @samp{a + b}. This is sometimes called
2974 @dfn{data breakpoints}. You must use a different command to set
2975 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2976 from that, you can manage a watchpoint like any other breakpoint: you
2977 enable, disable, and delete both breakpoints and watchpoints using the
2980 You can arrange to have values from your program displayed automatically
2981 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2985 @cindex breakpoint on events
2986 A @dfn{catchpoint} is another special breakpoint that stops your program
2987 when a certain kind of event occurs, such as the throwing of a C@t{++}
2988 exception or the loading of a library. As with watchpoints, you use a
2989 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2990 Catchpoints}), but aside from that, you can manage a catchpoint like any
2991 other breakpoint. (To stop when your program receives a signal, use the
2992 @code{handle} command; see @ref{Signals, ,Signals}.)
2994 @cindex breakpoint numbers
2995 @cindex numbers for breakpoints
2996 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2997 catchpoint when you create it; these numbers are successive integers
2998 starting with one. In many of the commands for controlling various
2999 features of breakpoints you use the breakpoint number to say which
3000 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3001 @dfn{disabled}; if disabled, it has no effect on your program until you
3004 @cindex breakpoint ranges
3005 @cindex ranges of breakpoints
3006 Some @value{GDBN} commands accept a range of breakpoints on which to
3007 operate. A breakpoint range is either a single breakpoint number, like
3008 @samp{5}, or two such numbers, in increasing order, separated by a
3009 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3010 all breakpoints in that range are operated on.
3013 * Set Breaks:: Setting breakpoints
3014 * Set Watchpoints:: Setting watchpoints
3015 * Set Catchpoints:: Setting catchpoints
3016 * Delete Breaks:: Deleting breakpoints
3017 * Disabling:: Disabling breakpoints
3018 * Conditions:: Break conditions
3019 * Break Commands:: Breakpoint command lists
3020 * Error in Breakpoints:: ``Cannot insert breakpoints''
3021 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3025 @subsection Setting Breakpoints
3027 @c FIXME LMB what does GDB do if no code on line of breakpt?
3028 @c consider in particular declaration with/without initialization.
3030 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3033 @kindex b @r{(@code{break})}
3034 @vindex $bpnum@r{, convenience variable}
3035 @cindex latest breakpoint
3036 Breakpoints are set with the @code{break} command (abbreviated
3037 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3038 number of the breakpoint you've set most recently; see @ref{Convenience
3039 Vars,, Convenience Variables}, for a discussion of what you can do with
3040 convenience variables.
3043 @item break @var{location}
3044 Set a breakpoint at the given @var{location}, which can specify a
3045 function name, a line number, or an address of an instruction.
3046 (@xref{Specify Location}, for a list of all the possible ways to
3047 specify a @var{location}.) The breakpoint will stop your program just
3048 before it executes any of the code in the specified @var{location}.
3050 When using source languages that permit overloading of symbols, such as
3051 C@t{++}, a function name may refer to more than one possible place to break.
3052 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3055 It is also possible to insert a breakpoint that will stop the program
3056 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3057 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3060 When called without any arguments, @code{break} sets a breakpoint at
3061 the next instruction to be executed in the selected stack frame
3062 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3063 innermost, this makes your program stop as soon as control
3064 returns to that frame. This is similar to the effect of a
3065 @code{finish} command in the frame inside the selected frame---except
3066 that @code{finish} does not leave an active breakpoint. If you use
3067 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3068 the next time it reaches the current location; this may be useful
3071 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3072 least one instruction has been executed. If it did not do this, you
3073 would be unable to proceed past a breakpoint without first disabling the
3074 breakpoint. This rule applies whether or not the breakpoint already
3075 existed when your program stopped.
3077 @item break @dots{} if @var{cond}
3078 Set a breakpoint with condition @var{cond}; evaluate the expression
3079 @var{cond} each time the breakpoint is reached, and stop only if the
3080 value is nonzero---that is, if @var{cond} evaluates as true.
3081 @samp{@dots{}} stands for one of the possible arguments described
3082 above (or no argument) specifying where to break. @xref{Conditions,
3083 ,Break Conditions}, for more information on breakpoint conditions.
3086 @item tbreak @var{args}
3087 Set a breakpoint enabled only for one stop. @var{args} are the
3088 same as for the @code{break} command, and the breakpoint is set in the same
3089 way, but the breakpoint is automatically deleted after the first time your
3090 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3093 @cindex hardware breakpoints
3094 @item hbreak @var{args}
3095 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3096 @code{break} command and the breakpoint is set in the same way, but the
3097 breakpoint requires hardware support and some target hardware may not
3098 have this support. The main purpose of this is EPROM/ROM code
3099 debugging, so you can set a breakpoint at an instruction without
3100 changing the instruction. This can be used with the new trap-generation
3101 provided by SPARClite DSU and most x86-based targets. These targets
3102 will generate traps when a program accesses some data or instruction
3103 address that is assigned to the debug registers. However the hardware
3104 breakpoint registers can take a limited number of breakpoints. For
3105 example, on the DSU, only two data breakpoints can be set at a time, and
3106 @value{GDBN} will reject this command if more than two are used. Delete
3107 or disable unused hardware breakpoints before setting new ones
3108 (@pxref{Disabling, ,Disabling Breakpoints}).
3109 @xref{Conditions, ,Break Conditions}.
3110 For remote targets, you can restrict the number of hardware
3111 breakpoints @value{GDBN} will use, see @ref{set remote
3112 hardware-breakpoint-limit}.
3115 @item thbreak @var{args}
3116 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3117 are the same as for the @code{hbreak} command and the breakpoint is set in
3118 the same way. However, like the @code{tbreak} command,
3119 the breakpoint is automatically deleted after the
3120 first time your program stops there. Also, like the @code{hbreak}
3121 command, the breakpoint requires hardware support and some target hardware
3122 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3123 See also @ref{Conditions, ,Break Conditions}.
3126 @cindex regular expression
3127 @cindex breakpoints in functions matching a regexp
3128 @cindex set breakpoints in many functions
3129 @item rbreak @var{regex}
3130 Set breakpoints on all functions matching the regular expression
3131 @var{regex}. This command sets an unconditional breakpoint on all
3132 matches, printing a list of all breakpoints it set. Once these
3133 breakpoints are set, they are treated just like the breakpoints set with
3134 the @code{break} command. You can delete them, disable them, or make
3135 them conditional the same way as any other breakpoint.
3137 The syntax of the regular expression is the standard one used with tools
3138 like @file{grep}. Note that this is different from the syntax used by
3139 shells, so for instance @code{foo*} matches all functions that include
3140 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3141 @code{.*} leading and trailing the regular expression you supply, so to
3142 match only functions that begin with @code{foo}, use @code{^foo}.
3144 @cindex non-member C@t{++} functions, set breakpoint in
3145 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3146 breakpoints on overloaded functions that are not members of any special
3149 @cindex set breakpoints on all functions
3150 The @code{rbreak} command can be used to set breakpoints in
3151 @strong{all} the functions in a program, like this:
3154 (@value{GDBP}) rbreak .
3157 @kindex info breakpoints
3158 @cindex @code{$_} and @code{info breakpoints}
3159 @item info breakpoints @r{[}@var{n}@r{]}
3160 @itemx info break @r{[}@var{n}@r{]}
3161 @itemx info watchpoints @r{[}@var{n}@r{]}
3162 Print a table of all breakpoints, watchpoints, and catchpoints set and
3163 not deleted. Optional argument @var{n} means print information only
3164 about the specified breakpoint (or watchpoint or catchpoint). For
3165 each breakpoint, following columns are printed:
3168 @item Breakpoint Numbers
3170 Breakpoint, watchpoint, or catchpoint.
3172 Whether the breakpoint is marked to be disabled or deleted when hit.
3173 @item Enabled or Disabled
3174 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3175 that are not enabled.
3177 Where the breakpoint is in your program, as a memory address. For a
3178 pending breakpoint whose address is not yet known, this field will
3179 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3180 library that has the symbol or line referred by breakpoint is loaded.
3181 See below for details. A breakpoint with several locations will
3182 have @samp{<MULTIPLE>} in this field---see below for details.
3184 Where the breakpoint is in the source for your program, as a file and
3185 line number. For a pending breakpoint, the original string passed to
3186 the breakpoint command will be listed as it cannot be resolved until
3187 the appropriate shared library is loaded in the future.
3191 If a breakpoint is conditional, @code{info break} shows the condition on
3192 the line following the affected breakpoint; breakpoint commands, if any,
3193 are listed after that. A pending breakpoint is allowed to have a condition
3194 specified for it. The condition is not parsed for validity until a shared
3195 library is loaded that allows the pending breakpoint to resolve to a
3199 @code{info break} with a breakpoint
3200 number @var{n} as argument lists only that breakpoint. The
3201 convenience variable @code{$_} and the default examining-address for
3202 the @code{x} command are set to the address of the last breakpoint
3203 listed (@pxref{Memory, ,Examining Memory}).
3206 @code{info break} displays a count of the number of times the breakpoint
3207 has been hit. This is especially useful in conjunction with the
3208 @code{ignore} command. You can ignore a large number of breakpoint
3209 hits, look at the breakpoint info to see how many times the breakpoint
3210 was hit, and then run again, ignoring one less than that number. This
3211 will get you quickly to the last hit of that breakpoint.
3214 @value{GDBN} allows you to set any number of breakpoints at the same place in
3215 your program. There is nothing silly or meaningless about this. When
3216 the breakpoints are conditional, this is even useful
3217 (@pxref{Conditions, ,Break Conditions}).
3219 @cindex multiple locations, breakpoints
3220 @cindex breakpoints, multiple locations
3221 It is possible that a breakpoint corresponds to several locations
3222 in your program. Examples of this situation are:
3226 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3227 instances of the function body, used in different cases.
3230 For a C@t{++} template function, a given line in the function can
3231 correspond to any number of instantiations.
3234 For an inlined function, a given source line can correspond to
3235 several places where that function is inlined.
3238 In all those cases, @value{GDBN} will insert a breakpoint at all
3239 the relevant locations@footnote{
3240 As of this writing, multiple-location breakpoints work only if there's
3241 line number information for all the locations. This means that they
3242 will generally not work in system libraries, unless you have debug
3243 info with line numbers for them.}.
3245 A breakpoint with multiple locations is displayed in the breakpoint
3246 table using several rows---one header row, followed by one row for
3247 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3248 address column. The rows for individual locations contain the actual
3249 addresses for locations, and show the functions to which those
3250 locations belong. The number column for a location is of the form
3251 @var{breakpoint-number}.@var{location-number}.
3256 Num Type Disp Enb Address What
3257 1 breakpoint keep y <MULTIPLE>
3259 breakpoint already hit 1 time
3260 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3261 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3264 Each location can be individually enabled or disabled by passing
3265 @var{breakpoint-number}.@var{location-number} as argument to the
3266 @code{enable} and @code{disable} commands. Note that you cannot
3267 delete the individual locations from the list, you can only delete the
3268 entire list of locations that belong to their parent breakpoint (with
3269 the @kbd{delete @var{num}} command, where @var{num} is the number of
3270 the parent breakpoint, 1 in the above example). Disabling or enabling
3271 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3272 that belong to that breakpoint.
3274 @cindex pending breakpoints
3275 It's quite common to have a breakpoint inside a shared library.
3276 Shared libraries can be loaded and unloaded explicitly,
3277 and possibly repeatedly, as the program is executed. To support
3278 this use case, @value{GDBN} updates breakpoint locations whenever
3279 any shared library is loaded or unloaded. Typically, you would
3280 set a breakpoint in a shared library at the beginning of your
3281 debugging session, when the library is not loaded, and when the
3282 symbols from the library are not available. When you try to set
3283 breakpoint, @value{GDBN} will ask you if you want to set
3284 a so called @dfn{pending breakpoint}---breakpoint whose address
3285 is not yet resolved.
3287 After the program is run, whenever a new shared library is loaded,
3288 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3289 shared library contains the symbol or line referred to by some
3290 pending breakpoint, that breakpoint is resolved and becomes an
3291 ordinary breakpoint. When a library is unloaded, all breakpoints
3292 that refer to its symbols or source lines become pending again.
3294 This logic works for breakpoints with multiple locations, too. For
3295 example, if you have a breakpoint in a C@t{++} template function, and
3296 a newly loaded shared library has an instantiation of that template,
3297 a new location is added to the list of locations for the breakpoint.
3299 Except for having unresolved address, pending breakpoints do not
3300 differ from regular breakpoints. You can set conditions or commands,
3301 enable and disable them and perform other breakpoint operations.
3303 @value{GDBN} provides some additional commands for controlling what
3304 happens when the @samp{break} command cannot resolve breakpoint
3305 address specification to an address:
3307 @kindex set breakpoint pending
3308 @kindex show breakpoint pending
3310 @item set breakpoint pending auto
3311 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3312 location, it queries you whether a pending breakpoint should be created.
3314 @item set breakpoint pending on
3315 This indicates that an unrecognized breakpoint location should automatically
3316 result in a pending breakpoint being created.
3318 @item set breakpoint pending off
3319 This indicates that pending breakpoints are not to be created. Any
3320 unrecognized breakpoint location results in an error. This setting does
3321 not affect any pending breakpoints previously created.
3323 @item show breakpoint pending
3324 Show the current behavior setting for creating pending breakpoints.
3327 The settings above only affect the @code{break} command and its
3328 variants. Once breakpoint is set, it will be automatically updated
3329 as shared libraries are loaded and unloaded.
3331 @cindex automatic hardware breakpoints
3332 For some targets, @value{GDBN} can automatically decide if hardware or
3333 software breakpoints should be used, depending on whether the
3334 breakpoint address is read-only or read-write. This applies to
3335 breakpoints set with the @code{break} command as well as to internal
3336 breakpoints set by commands like @code{next} and @code{finish}. For
3337 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3340 You can control this automatic behaviour with the following commands::
3342 @kindex set breakpoint auto-hw
3343 @kindex show breakpoint auto-hw
3345 @item set breakpoint auto-hw on
3346 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3347 will try to use the target memory map to decide if software or hardware
3348 breakpoint must be used.
3350 @item set breakpoint auto-hw off
3351 This indicates @value{GDBN} should not automatically select breakpoint
3352 type. If the target provides a memory map, @value{GDBN} will warn when
3353 trying to set software breakpoint at a read-only address.
3356 @value{GDBN} normally implements breakpoints by replacing the program code
3357 at the breakpoint address with a special instruction, which, when
3358 executed, given control to the debugger. By default, the program
3359 code is so modified only when the program is resumed. As soon as
3360 the program stops, @value{GDBN} restores the original instructions. This
3361 behaviour guards against leaving breakpoints inserted in the
3362 target should gdb abrubptly disconnect. However, with slow remote
3363 targets, inserting and removing breakpoint can reduce the performance.
3364 This behavior can be controlled with the following commands::
3366 @kindex set breakpoint always-inserted
3367 @kindex show breakpoint always-inserted
3369 @item set breakpoint always-inserted off
3370 All breakpoints, including newly added by the user, are inserted in
3371 the target only when the target is resumed. All breakpoints are
3372 removed from the target when it stops.
3374 @item set breakpoint always-inserted on
3375 Causes all breakpoints to be inserted in the target at all times. If
3376 the user adds a new breakpoint, or changes an existing breakpoint, the
3377 breakpoints in the target are updated immediately. A breakpoint is
3378 removed from the target only when breakpoint itself is removed.
3380 @cindex non-stop mode, and @code{breakpoint always-inserted}
3381 @item set breakpoint always-inserted auto
3382 This is the default mode. If @value{GDBN} is controlling the inferior
3383 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3384 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3385 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3386 @code{breakpoint always-inserted} mode is off.
3389 @cindex negative breakpoint numbers
3390 @cindex internal @value{GDBN} breakpoints
3391 @value{GDBN} itself sometimes sets breakpoints in your program for
3392 special purposes, such as proper handling of @code{longjmp} (in C
3393 programs). These internal breakpoints are assigned negative numbers,
3394 starting with @code{-1}; @samp{info breakpoints} does not display them.
3395 You can see these breakpoints with the @value{GDBN} maintenance command
3396 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3399 @node Set Watchpoints
3400 @subsection Setting Watchpoints
3402 @cindex setting watchpoints
3403 You can use a watchpoint to stop execution whenever the value of an
3404 expression changes, without having to predict a particular place where
3405 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3406 The expression may be as simple as the value of a single variable, or
3407 as complex as many variables combined by operators. Examples include:
3411 A reference to the value of a single variable.
3414 An address cast to an appropriate data type. For example,
3415 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3416 address (assuming an @code{int} occupies 4 bytes).
3419 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3420 expression can use any operators valid in the program's native
3421 language (@pxref{Languages}).
3424 You can set a watchpoint on an expression even if the expression can
3425 not be evaluated yet. For instance, you can set a watchpoint on
3426 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3427 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3428 the expression produces a valid value. If the expression becomes
3429 valid in some other way than changing a variable (e.g.@: if the memory
3430 pointed to by @samp{*global_ptr} becomes readable as the result of a
3431 @code{malloc} call), @value{GDBN} may not stop until the next time
3432 the expression changes.
3434 @cindex software watchpoints
3435 @cindex hardware watchpoints
3436 Depending on your system, watchpoints may be implemented in software or
3437 hardware. @value{GDBN} does software watchpointing by single-stepping your
3438 program and testing the variable's value each time, which is hundreds of
3439 times slower than normal execution. (But this may still be worth it, to
3440 catch errors where you have no clue what part of your program is the
3443 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3444 x86-based targets, @value{GDBN} includes support for hardware
3445 watchpoints, which do not slow down the running of your program.
3449 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3450 Set a watchpoint for an expression. @value{GDBN} will break when the
3451 expression @var{expr} is written into by the program and its value
3452 changes. The simplest (and the most popular) use of this command is
3453 to watch the value of a single variable:
3456 (@value{GDBP}) watch foo
3459 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3460 clause, @value{GDBN} breaks only when the thread identified by
3461 @var{threadnum} changes the value of @var{expr}. If any other threads
3462 change the value of @var{expr}, @value{GDBN} will not break. Note
3463 that watchpoints restricted to a single thread in this way only work
3464 with Hardware Watchpoints.
3467 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3468 Set a watchpoint that will break when the value of @var{expr} is read
3472 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3473 Set a watchpoint that will break when @var{expr} is either read from
3474 or written into by the program.
3476 @kindex info watchpoints @r{[}@var{n}@r{]}
3477 @item info watchpoints
3478 This command prints a list of watchpoints, breakpoints, and catchpoints;
3479 it is the same as @code{info break} (@pxref{Set Breaks}).
3482 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3483 watchpoints execute very quickly, and the debugger reports a change in
3484 value at the exact instruction where the change occurs. If @value{GDBN}
3485 cannot set a hardware watchpoint, it sets a software watchpoint, which
3486 executes more slowly and reports the change in value at the next
3487 @emph{statement}, not the instruction, after the change occurs.
3489 @cindex use only software watchpoints
3490 You can force @value{GDBN} to use only software watchpoints with the
3491 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3492 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3493 the underlying system supports them. (Note that hardware-assisted
3494 watchpoints that were set @emph{before} setting
3495 @code{can-use-hw-watchpoints} to zero will still use the hardware
3496 mechanism of watching expression values.)
3499 @item set can-use-hw-watchpoints
3500 @kindex set can-use-hw-watchpoints
3501 Set whether or not to use hardware watchpoints.
3503 @item show can-use-hw-watchpoints
3504 @kindex show can-use-hw-watchpoints
3505 Show the current mode of using hardware watchpoints.
3508 For remote targets, you can restrict the number of hardware
3509 watchpoints @value{GDBN} will use, see @ref{set remote
3510 hardware-breakpoint-limit}.
3512 When you issue the @code{watch} command, @value{GDBN} reports
3515 Hardware watchpoint @var{num}: @var{expr}
3519 if it was able to set a hardware watchpoint.
3521 Currently, the @code{awatch} and @code{rwatch} commands can only set
3522 hardware watchpoints, because accesses to data that don't change the
3523 value of the watched expression cannot be detected without examining
3524 every instruction as it is being executed, and @value{GDBN} does not do
3525 that currently. If @value{GDBN} finds that it is unable to set a
3526 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3527 will print a message like this:
3530 Expression cannot be implemented with read/access watchpoint.
3533 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3534 data type of the watched expression is wider than what a hardware
3535 watchpoint on the target machine can handle. For example, some systems
3536 can only watch regions that are up to 4 bytes wide; on such systems you
3537 cannot set hardware watchpoints for an expression that yields a
3538 double-precision floating-point number (which is typically 8 bytes
3539 wide). As a work-around, it might be possible to break the large region
3540 into a series of smaller ones and watch them with separate watchpoints.
3542 If you set too many hardware watchpoints, @value{GDBN} might be unable
3543 to insert all of them when you resume the execution of your program.
3544 Since the precise number of active watchpoints is unknown until such
3545 time as the program is about to be resumed, @value{GDBN} might not be
3546 able to warn you about this when you set the watchpoints, and the
3547 warning will be printed only when the program is resumed:
3550 Hardware watchpoint @var{num}: Could not insert watchpoint
3554 If this happens, delete or disable some of the watchpoints.
3556 Watching complex expressions that reference many variables can also
3557 exhaust the resources available for hardware-assisted watchpoints.
3558 That's because @value{GDBN} needs to watch every variable in the
3559 expression with separately allocated resources.
3561 If you call a function interactively using @code{print} or @code{call},
3562 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3563 kind of breakpoint or the call completes.
3565 @value{GDBN} automatically deletes watchpoints that watch local
3566 (automatic) variables, or expressions that involve such variables, when
3567 they go out of scope, that is, when the execution leaves the block in
3568 which these variables were defined. In particular, when the program
3569 being debugged terminates, @emph{all} local variables go out of scope,
3570 and so only watchpoints that watch global variables remain set. If you
3571 rerun the program, you will need to set all such watchpoints again. One
3572 way of doing that would be to set a code breakpoint at the entry to the
3573 @code{main} function and when it breaks, set all the watchpoints.
3575 @cindex watchpoints and threads
3576 @cindex threads and watchpoints
3577 In multi-threaded programs, watchpoints will detect changes to the
3578 watched expression from every thread.
3581 @emph{Warning:} In multi-threaded programs, software watchpoints
3582 have only limited usefulness. If @value{GDBN} creates a software
3583 watchpoint, it can only watch the value of an expression @emph{in a
3584 single thread}. If you are confident that the expression can only
3585 change due to the current thread's activity (and if you are also
3586 confident that no other thread can become current), then you can use
3587 software watchpoints as usual. However, @value{GDBN} may not notice
3588 when a non-current thread's activity changes the expression. (Hardware
3589 watchpoints, in contrast, watch an expression in all threads.)
3592 @xref{set remote hardware-watchpoint-limit}.
3594 @node Set Catchpoints
3595 @subsection Setting Catchpoints
3596 @cindex catchpoints, setting
3597 @cindex exception handlers
3598 @cindex event handling
3600 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3601 kinds of program events, such as C@t{++} exceptions or the loading of a
3602 shared library. Use the @code{catch} command to set a catchpoint.
3606 @item catch @var{event}
3607 Stop when @var{event} occurs. @var{event} can be any of the following:
3610 @cindex stop on C@t{++} exceptions
3611 The throwing of a C@t{++} exception.
3614 The catching of a C@t{++} exception.
3617 @cindex Ada exception catching
3618 @cindex catch Ada exceptions
3619 An Ada exception being raised. If an exception name is specified
3620 at the end of the command (eg @code{catch exception Program_Error}),
3621 the debugger will stop only when this specific exception is raised.
3622 Otherwise, the debugger stops execution when any Ada exception is raised.
3624 When inserting an exception catchpoint on a user-defined exception whose
3625 name is identical to one of the exceptions defined by the language, the
3626 fully qualified name must be used as the exception name. Otherwise,
3627 @value{GDBN} will assume that it should stop on the pre-defined exception
3628 rather than the user-defined one. For instance, assuming an exception
3629 called @code{Constraint_Error} is defined in package @code{Pck}, then
3630 the command to use to catch such exceptions is @kbd{catch exception
3631 Pck.Constraint_Error}.
3633 @item exception unhandled
3634 An exception that was raised but is not handled by the program.
3637 A failed Ada assertion.
3640 @cindex break on fork/exec
3641 A call to @code{exec}. This is currently only available for HP-UX
3645 A call to @code{fork}. This is currently only available for HP-UX
3649 A call to @code{vfork}. This is currently only available for HP-UX
3654 @item tcatch @var{event}
3655 Set a catchpoint that is enabled only for one stop. The catchpoint is
3656 automatically deleted after the first time the event is caught.
3660 Use the @code{info break} command to list the current catchpoints.
3662 There are currently some limitations to C@t{++} exception handling
3663 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3667 If you call a function interactively, @value{GDBN} normally returns
3668 control to you when the function has finished executing. If the call
3669 raises an exception, however, the call may bypass the mechanism that
3670 returns control to you and cause your program either to abort or to
3671 simply continue running until it hits a breakpoint, catches a signal
3672 that @value{GDBN} is listening for, or exits. This is the case even if
3673 you set a catchpoint for the exception; catchpoints on exceptions are
3674 disabled within interactive calls.
3677 You cannot raise an exception interactively.
3680 You cannot install an exception handler interactively.
3683 @cindex raise exceptions
3684 Sometimes @code{catch} is not the best way to debug exception handling:
3685 if you need to know exactly where an exception is raised, it is better to
3686 stop @emph{before} the exception handler is called, since that way you
3687 can see the stack before any unwinding takes place. If you set a
3688 breakpoint in an exception handler instead, it may not be easy to find
3689 out where the exception was raised.
3691 To stop just before an exception handler is called, you need some
3692 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3693 raised by calling a library function named @code{__raise_exception}
3694 which has the following ANSI C interface:
3697 /* @var{addr} is where the exception identifier is stored.
3698 @var{id} is the exception identifier. */
3699 void __raise_exception (void **addr, void *id);
3703 To make the debugger catch all exceptions before any stack
3704 unwinding takes place, set a breakpoint on @code{__raise_exception}
3705 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3707 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3708 that depends on the value of @var{id}, you can stop your program when
3709 a specific exception is raised. You can use multiple conditional
3710 breakpoints to stop your program when any of a number of exceptions are
3715 @subsection Deleting Breakpoints
3717 @cindex clearing breakpoints, watchpoints, catchpoints
3718 @cindex deleting breakpoints, watchpoints, catchpoints
3719 It is often necessary to eliminate a breakpoint, watchpoint, or
3720 catchpoint once it has done its job and you no longer want your program
3721 to stop there. This is called @dfn{deleting} the breakpoint. A
3722 breakpoint that has been deleted no longer exists; it is forgotten.
3724 With the @code{clear} command you can delete breakpoints according to
3725 where they are in your program. With the @code{delete} command you can
3726 delete individual breakpoints, watchpoints, or catchpoints by specifying
3727 their breakpoint numbers.
3729 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3730 automatically ignores breakpoints on the first instruction to be executed
3731 when you continue execution without changing the execution address.
3736 Delete any breakpoints at the next instruction to be executed in the
3737 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3738 the innermost frame is selected, this is a good way to delete a
3739 breakpoint where your program just stopped.
3741 @item clear @var{location}
3742 Delete any breakpoints set at the specified @var{location}.
3743 @xref{Specify Location}, for the various forms of @var{location}; the
3744 most useful ones are listed below:
3747 @item clear @var{function}
3748 @itemx clear @var{filename}:@var{function}
3749 Delete any breakpoints set at entry to the named @var{function}.
3751 @item clear @var{linenum}
3752 @itemx clear @var{filename}:@var{linenum}
3753 Delete any breakpoints set at or within the code of the specified
3754 @var{linenum} of the specified @var{filename}.
3757 @cindex delete breakpoints
3759 @kindex d @r{(@code{delete})}
3760 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3761 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3762 ranges specified as arguments. If no argument is specified, delete all
3763 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3764 confirm off}). You can abbreviate this command as @code{d}.
3768 @subsection Disabling Breakpoints
3770 @cindex enable/disable a breakpoint
3771 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3772 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3773 it had been deleted, but remembers the information on the breakpoint so
3774 that you can @dfn{enable} it again later.
3776 You disable and enable breakpoints, watchpoints, and catchpoints with
3777 the @code{enable} and @code{disable} commands, optionally specifying one
3778 or more breakpoint numbers as arguments. Use @code{info break} or
3779 @code{info watch} to print a list of breakpoints, watchpoints, and
3780 catchpoints if you do not know which numbers to use.
3782 Disabling and enabling a breakpoint that has multiple locations
3783 affects all of its locations.
3785 A breakpoint, watchpoint, or catchpoint can have any of four different
3786 states of enablement:
3790 Enabled. The breakpoint stops your program. A breakpoint set
3791 with the @code{break} command starts out in this state.
3793 Disabled. The breakpoint has no effect on your program.
3795 Enabled once. The breakpoint stops your program, but then becomes
3798 Enabled for deletion. The breakpoint stops your program, but
3799 immediately after it does so it is deleted permanently. A breakpoint
3800 set with the @code{tbreak} command starts out in this state.
3803 You can use the following commands to enable or disable breakpoints,
3804 watchpoints, and catchpoints:
3808 @kindex dis @r{(@code{disable})}
3809 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3810 Disable the specified breakpoints---or all breakpoints, if none are
3811 listed. A disabled breakpoint has no effect but is not forgotten. All
3812 options such as ignore-counts, conditions and commands are remembered in
3813 case the breakpoint is enabled again later. You may abbreviate
3814 @code{disable} as @code{dis}.
3817 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3818 Enable the specified breakpoints (or all defined breakpoints). They
3819 become effective once again in stopping your program.
3821 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3822 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3823 of these breakpoints immediately after stopping your program.
3825 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3826 Enable the specified breakpoints to work once, then die. @value{GDBN}
3827 deletes any of these breakpoints as soon as your program stops there.
3828 Breakpoints set by the @code{tbreak} command start out in this state.
3831 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3832 @c confusing: tbreak is also initially enabled.
3833 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3834 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3835 subsequently, they become disabled or enabled only when you use one of
3836 the commands above. (The command @code{until} can set and delete a
3837 breakpoint of its own, but it does not change the state of your other
3838 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3842 @subsection Break Conditions
3843 @cindex conditional breakpoints
3844 @cindex breakpoint conditions
3846 @c FIXME what is scope of break condition expr? Context where wanted?
3847 @c in particular for a watchpoint?
3848 The simplest sort of breakpoint breaks every time your program reaches a
3849 specified place. You can also specify a @dfn{condition} for a
3850 breakpoint. A condition is just a Boolean expression in your
3851 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3852 a condition evaluates the expression each time your program reaches it,
3853 and your program stops only if the condition is @emph{true}.
3855 This is the converse of using assertions for program validation; in that
3856 situation, you want to stop when the assertion is violated---that is,
3857 when the condition is false. In C, if you want to test an assertion expressed
3858 by the condition @var{assert}, you should set the condition
3859 @samp{! @var{assert}} on the appropriate breakpoint.
3861 Conditions are also accepted for watchpoints; you may not need them,
3862 since a watchpoint is inspecting the value of an expression anyhow---but
3863 it might be simpler, say, to just set a watchpoint on a variable name,
3864 and specify a condition that tests whether the new value is an interesting
3867 Break conditions can have side effects, and may even call functions in
3868 your program. This can be useful, for example, to activate functions
3869 that log program progress, or to use your own print functions to
3870 format special data structures. The effects are completely predictable
3871 unless there is another enabled breakpoint at the same address. (In
3872 that case, @value{GDBN} might see the other breakpoint first and stop your
3873 program without checking the condition of this one.) Note that
3874 breakpoint commands are usually more convenient and flexible than break
3876 purpose of performing side effects when a breakpoint is reached
3877 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3879 Break conditions can be specified when a breakpoint is set, by using
3880 @samp{if} in the arguments to the @code{break} command. @xref{Set
3881 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3882 with the @code{condition} command.
3884 You can also use the @code{if} keyword with the @code{watch} command.
3885 The @code{catch} command does not recognize the @code{if} keyword;
3886 @code{condition} is the only way to impose a further condition on a
3891 @item condition @var{bnum} @var{expression}
3892 Specify @var{expression} as the break condition for breakpoint,
3893 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3894 breakpoint @var{bnum} stops your program only if the value of
3895 @var{expression} is true (nonzero, in C). When you use
3896 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3897 syntactic correctness, and to determine whether symbols in it have
3898 referents in the context of your breakpoint. If @var{expression} uses
3899 symbols not referenced in the context of the breakpoint, @value{GDBN}
3900 prints an error message:
3903 No symbol "foo" in current context.
3908 not actually evaluate @var{expression} at the time the @code{condition}
3909 command (or a command that sets a breakpoint with a condition, like
3910 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3912 @item condition @var{bnum}
3913 Remove the condition from breakpoint number @var{bnum}. It becomes
3914 an ordinary unconditional breakpoint.
3917 @cindex ignore count (of breakpoint)
3918 A special case of a breakpoint condition is to stop only when the
3919 breakpoint has been reached a certain number of times. This is so
3920 useful that there is a special way to do it, using the @dfn{ignore
3921 count} of the breakpoint. Every breakpoint has an ignore count, which
3922 is an integer. Most of the time, the ignore count is zero, and
3923 therefore has no effect. But if your program reaches a breakpoint whose
3924 ignore count is positive, then instead of stopping, it just decrements
3925 the ignore count by one and continues. As a result, if the ignore count
3926 value is @var{n}, the breakpoint does not stop the next @var{n} times
3927 your program reaches it.
3931 @item ignore @var{bnum} @var{count}
3932 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3933 The next @var{count} times the breakpoint is reached, your program's
3934 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3937 To make the breakpoint stop the next time it is reached, specify
3940 When you use @code{continue} to resume execution of your program from a
3941 breakpoint, you can specify an ignore count directly as an argument to
3942 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3943 Stepping,,Continuing and Stepping}.
3945 If a breakpoint has a positive ignore count and a condition, the
3946 condition is not checked. Once the ignore count reaches zero,
3947 @value{GDBN} resumes checking the condition.
3949 You could achieve the effect of the ignore count with a condition such
3950 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3951 is decremented each time. @xref{Convenience Vars, ,Convenience
3955 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3958 @node Break Commands
3959 @subsection Breakpoint Command Lists
3961 @cindex breakpoint commands
3962 You can give any breakpoint (or watchpoint or catchpoint) a series of
3963 commands to execute when your program stops due to that breakpoint. For
3964 example, you might want to print the values of certain expressions, or
3965 enable other breakpoints.
3969 @kindex end@r{ (breakpoint commands)}
3970 @item commands @r{[}@var{bnum}@r{]}
3971 @itemx @dots{} @var{command-list} @dots{}
3973 Specify a list of commands for breakpoint number @var{bnum}. The commands
3974 themselves appear on the following lines. Type a line containing just
3975 @code{end} to terminate the commands.
3977 To remove all commands from a breakpoint, type @code{commands} and
3978 follow it immediately with @code{end}; that is, give no commands.
3980 With no @var{bnum} argument, @code{commands} refers to the last
3981 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3982 recently encountered).
3985 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3986 disabled within a @var{command-list}.
3988 You can use breakpoint commands to start your program up again. Simply
3989 use the @code{continue} command, or @code{step}, or any other command
3990 that resumes execution.
3992 Any other commands in the command list, after a command that resumes
3993 execution, are ignored. This is because any time you resume execution
3994 (even with a simple @code{next} or @code{step}), you may encounter
3995 another breakpoint---which could have its own command list, leading to
3996 ambiguities about which list to execute.
3999 If the first command you specify in a command list is @code{silent}, the
4000 usual message about stopping at a breakpoint is not printed. This may
4001 be desirable for breakpoints that are to print a specific message and
4002 then continue. If none of the remaining commands print anything, you
4003 see no sign that the breakpoint was reached. @code{silent} is
4004 meaningful only at the beginning of a breakpoint command list.
4006 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4007 print precisely controlled output, and are often useful in silent
4008 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4010 For example, here is how you could use breakpoint commands to print the
4011 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4017 printf "x is %d\n",x
4022 One application for breakpoint commands is to compensate for one bug so
4023 you can test for another. Put a breakpoint just after the erroneous line
4024 of code, give it a condition to detect the case in which something
4025 erroneous has been done, and give it commands to assign correct values
4026 to any variables that need them. End with the @code{continue} command
4027 so that your program does not stop, and start with the @code{silent}
4028 command so that no output is produced. Here is an example:
4039 @c @ifclear BARETARGET
4040 @node Error in Breakpoints
4041 @subsection ``Cannot insert breakpoints''
4043 If you request too many active hardware-assisted breakpoints and
4044 watchpoints, you will see this error message:
4046 @c FIXME: the precise wording of this message may change; the relevant
4047 @c source change is not committed yet (Sep 3, 1999).
4049 Stopped; cannot insert breakpoints.
4050 You may have requested too many hardware breakpoints and watchpoints.
4054 This message is printed when you attempt to resume the program, since
4055 only then @value{GDBN} knows exactly how many hardware breakpoints and
4056 watchpoints it needs to insert.
4058 When this message is printed, you need to disable or remove some of the
4059 hardware-assisted breakpoints and watchpoints, and then continue.
4061 @node Breakpoint-related Warnings
4062 @subsection ``Breakpoint address adjusted...''
4063 @cindex breakpoint address adjusted
4065 Some processor architectures place constraints on the addresses at
4066 which breakpoints may be placed. For architectures thus constrained,
4067 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4068 with the constraints dictated by the architecture.
4070 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4071 a VLIW architecture in which a number of RISC-like instructions may be
4072 bundled together for parallel execution. The FR-V architecture
4073 constrains the location of a breakpoint instruction within such a
4074 bundle to the instruction with the lowest address. @value{GDBN}
4075 honors this constraint by adjusting a breakpoint's address to the
4076 first in the bundle.
4078 It is not uncommon for optimized code to have bundles which contain
4079 instructions from different source statements, thus it may happen that
4080 a breakpoint's address will be adjusted from one source statement to
4081 another. Since this adjustment may significantly alter @value{GDBN}'s
4082 breakpoint related behavior from what the user expects, a warning is
4083 printed when the breakpoint is first set and also when the breakpoint
4086 A warning like the one below is printed when setting a breakpoint
4087 that's been subject to address adjustment:
4090 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4093 Such warnings are printed both for user settable and @value{GDBN}'s
4094 internal breakpoints. If you see one of these warnings, you should
4095 verify that a breakpoint set at the adjusted address will have the
4096 desired affect. If not, the breakpoint in question may be removed and
4097 other breakpoints may be set which will have the desired behavior.
4098 E.g., it may be sufficient to place the breakpoint at a later
4099 instruction. A conditional breakpoint may also be useful in some
4100 cases to prevent the breakpoint from triggering too often.
4102 @value{GDBN} will also issue a warning when stopping at one of these
4103 adjusted breakpoints:
4106 warning: Breakpoint 1 address previously adjusted from 0x00010414
4110 When this warning is encountered, it may be too late to take remedial
4111 action except in cases where the breakpoint is hit earlier or more
4112 frequently than expected.
4114 @node Continuing and Stepping
4115 @section Continuing and Stepping
4119 @cindex resuming execution
4120 @dfn{Continuing} means resuming program execution until your program
4121 completes normally. In contrast, @dfn{stepping} means executing just
4122 one more ``step'' of your program, where ``step'' may mean either one
4123 line of source code, or one machine instruction (depending on what
4124 particular command you use). Either when continuing or when stepping,
4125 your program may stop even sooner, due to a breakpoint or a signal. (If
4126 it stops due to a signal, you may want to use @code{handle}, or use
4127 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4131 @kindex c @r{(@code{continue})}
4132 @kindex fg @r{(resume foreground execution)}
4133 @item continue @r{[}@var{ignore-count}@r{]}
4134 @itemx c @r{[}@var{ignore-count}@r{]}
4135 @itemx fg @r{[}@var{ignore-count}@r{]}
4136 Resume program execution, at the address where your program last stopped;
4137 any breakpoints set at that address are bypassed. The optional argument
4138 @var{ignore-count} allows you to specify a further number of times to
4139 ignore a breakpoint at this location; its effect is like that of
4140 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4142 The argument @var{ignore-count} is meaningful only when your program
4143 stopped due to a breakpoint. At other times, the argument to
4144 @code{continue} is ignored.
4146 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4147 debugged program is deemed to be the foreground program) are provided
4148 purely for convenience, and have exactly the same behavior as
4152 To resume execution at a different place, you can use @code{return}
4153 (@pxref{Returning, ,Returning from a Function}) to go back to the
4154 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4155 Different Address}) to go to an arbitrary location in your program.
4157 A typical technique for using stepping is to set a breakpoint
4158 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4159 beginning of the function or the section of your program where a problem
4160 is believed to lie, run your program until it stops at that breakpoint,
4161 and then step through the suspect area, examining the variables that are
4162 interesting, until you see the problem happen.
4166 @kindex s @r{(@code{step})}
4168 Continue running your program until control reaches a different source
4169 line, then stop it and return control to @value{GDBN}. This command is
4170 abbreviated @code{s}.
4173 @c "without debugging information" is imprecise; actually "without line
4174 @c numbers in the debugging information". (gcc -g1 has debugging info but
4175 @c not line numbers). But it seems complex to try to make that
4176 @c distinction here.
4177 @emph{Warning:} If you use the @code{step} command while control is
4178 within a function that was compiled without debugging information,
4179 execution proceeds until control reaches a function that does have
4180 debugging information. Likewise, it will not step into a function which
4181 is compiled without debugging information. To step through functions
4182 without debugging information, use the @code{stepi} command, described
4186 The @code{step} command only stops at the first instruction of a source
4187 line. This prevents the multiple stops that could otherwise occur in
4188 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4189 to stop if a function that has debugging information is called within
4190 the line. In other words, @code{step} @emph{steps inside} any functions
4191 called within the line.
4193 Also, the @code{step} command only enters a function if there is line
4194 number information for the function. Otherwise it acts like the
4195 @code{next} command. This avoids problems when using @code{cc -gl}
4196 on MIPS machines. Previously, @code{step} entered subroutines if there
4197 was any debugging information about the routine.
4199 @item step @var{count}
4200 Continue running as in @code{step}, but do so @var{count} times. If a
4201 breakpoint is reached, or a signal not related to stepping occurs before
4202 @var{count} steps, stepping stops right away.
4205 @kindex n @r{(@code{next})}
4206 @item next @r{[}@var{count}@r{]}
4207 Continue to the next source line in the current (innermost) stack frame.
4208 This is similar to @code{step}, but function calls that appear within
4209 the line of code are executed without stopping. Execution stops when
4210 control reaches a different line of code at the original stack level
4211 that was executing when you gave the @code{next} command. This command
4212 is abbreviated @code{n}.
4214 An argument @var{count} is a repeat count, as for @code{step}.
4217 @c FIX ME!! Do we delete this, or is there a way it fits in with
4218 @c the following paragraph? --- Vctoria
4220 @c @code{next} within a function that lacks debugging information acts like
4221 @c @code{step}, but any function calls appearing within the code of the
4222 @c function are executed without stopping.
4224 The @code{next} command only stops at the first instruction of a
4225 source line. This prevents multiple stops that could otherwise occur in
4226 @code{switch} statements, @code{for} loops, etc.
4228 @kindex set step-mode
4230 @cindex functions without line info, and stepping
4231 @cindex stepping into functions with no line info
4232 @itemx set step-mode on
4233 The @code{set step-mode on} command causes the @code{step} command to
4234 stop at the first instruction of a function which contains no debug line
4235 information rather than stepping over it.
4237 This is useful in cases where you may be interested in inspecting the
4238 machine instructions of a function which has no symbolic info and do not
4239 want @value{GDBN} to automatically skip over this function.
4241 @item set step-mode off
4242 Causes the @code{step} command to step over any functions which contains no
4243 debug information. This is the default.
4245 @item show step-mode
4246 Show whether @value{GDBN} will stop in or step over functions without
4247 source line debug information.
4250 @kindex fin @r{(@code{finish})}
4252 Continue running until just after function in the selected stack frame
4253 returns. Print the returned value (if any). This command can be
4254 abbreviated as @code{fin}.
4256 Contrast this with the @code{return} command (@pxref{Returning,
4257 ,Returning from a Function}).
4260 @kindex u @r{(@code{until})}
4261 @cindex run until specified location
4264 Continue running until a source line past the current line, in the
4265 current stack frame, is reached. This command is used to avoid single
4266 stepping through a loop more than once. It is like the @code{next}
4267 command, except that when @code{until} encounters a jump, it
4268 automatically continues execution until the program counter is greater
4269 than the address of the jump.
4271 This means that when you reach the end of a loop after single stepping
4272 though it, @code{until} makes your program continue execution until it
4273 exits the loop. In contrast, a @code{next} command at the end of a loop
4274 simply steps back to the beginning of the loop, which forces you to step
4275 through the next iteration.
4277 @code{until} always stops your program if it attempts to exit the current
4280 @code{until} may produce somewhat counterintuitive results if the order
4281 of machine code does not match the order of the source lines. For
4282 example, in the following excerpt from a debugging session, the @code{f}
4283 (@code{frame}) command shows that execution is stopped at line
4284 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4288 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4290 (@value{GDBP}) until
4291 195 for ( ; argc > 0; NEXTARG) @{
4294 This happened because, for execution efficiency, the compiler had
4295 generated code for the loop closure test at the end, rather than the
4296 start, of the loop---even though the test in a C @code{for}-loop is
4297 written before the body of the loop. The @code{until} command appeared
4298 to step back to the beginning of the loop when it advanced to this
4299 expression; however, it has not really gone to an earlier
4300 statement---not in terms of the actual machine code.
4302 @code{until} with no argument works by means of single
4303 instruction stepping, and hence is slower than @code{until} with an
4306 @item until @var{location}
4307 @itemx u @var{location}
4308 Continue running your program until either the specified location is
4309 reached, or the current stack frame returns. @var{location} is any of
4310 the forms described in @ref{Specify Location}.
4311 This form of the command uses temporary breakpoints, and
4312 hence is quicker than @code{until} without an argument. The specified
4313 location is actually reached only if it is in the current frame. This
4314 implies that @code{until} can be used to skip over recursive function
4315 invocations. For instance in the code below, if the current location is
4316 line @code{96}, issuing @code{until 99} will execute the program up to
4317 line @code{99} in the same invocation of factorial, i.e., after the inner
4318 invocations have returned.
4321 94 int factorial (int value)
4323 96 if (value > 1) @{
4324 97 value *= factorial (value - 1);
4331 @kindex advance @var{location}
4332 @itemx advance @var{location}
4333 Continue running the program up to the given @var{location}. An argument is
4334 required, which should be of one of the forms described in
4335 @ref{Specify Location}.
4336 Execution will also stop upon exit from the current stack
4337 frame. This command is similar to @code{until}, but @code{advance} will
4338 not skip over recursive function calls, and the target location doesn't
4339 have to be in the same frame as the current one.
4343 @kindex si @r{(@code{stepi})}
4345 @itemx stepi @var{arg}
4347 Execute one machine instruction, then stop and return to the debugger.
4349 It is often useful to do @samp{display/i $pc} when stepping by machine
4350 instructions. This makes @value{GDBN} automatically display the next
4351 instruction to be executed, each time your program stops. @xref{Auto
4352 Display,, Automatic Display}.
4354 An argument is a repeat count, as in @code{step}.
4358 @kindex ni @r{(@code{nexti})}
4360 @itemx nexti @var{arg}
4362 Execute one machine instruction, but if it is a function call,
4363 proceed until the function returns.
4365 An argument is a repeat count, as in @code{next}.
4372 A signal is an asynchronous event that can happen in a program. The
4373 operating system defines the possible kinds of signals, and gives each
4374 kind a name and a number. For example, in Unix @code{SIGINT} is the
4375 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4376 @code{SIGSEGV} is the signal a program gets from referencing a place in
4377 memory far away from all the areas in use; @code{SIGALRM} occurs when
4378 the alarm clock timer goes off (which happens only if your program has
4379 requested an alarm).
4381 @cindex fatal signals
4382 Some signals, including @code{SIGALRM}, are a normal part of the
4383 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4384 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4385 program has not specified in advance some other way to handle the signal.
4386 @code{SIGINT} does not indicate an error in your program, but it is normally
4387 fatal so it can carry out the purpose of the interrupt: to kill the program.
4389 @value{GDBN} has the ability to detect any occurrence of a signal in your
4390 program. You can tell @value{GDBN} in advance what to do for each kind of
4393 @cindex handling signals
4394 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4395 @code{SIGALRM} be silently passed to your program
4396 (so as not to interfere with their role in the program's functioning)
4397 but to stop your program immediately whenever an error signal happens.
4398 You can change these settings with the @code{handle} command.
4401 @kindex info signals
4405 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4406 handle each one. You can use this to see the signal numbers of all
4407 the defined types of signals.
4409 @item info signals @var{sig}
4410 Similar, but print information only about the specified signal number.
4412 @code{info handle} is an alias for @code{info signals}.
4415 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4416 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4417 can be the number of a signal or its name (with or without the
4418 @samp{SIG} at the beginning); a list of signal numbers of the form
4419 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4420 known signals. Optional arguments @var{keywords}, described below,
4421 say what change to make.
4425 The keywords allowed by the @code{handle} command can be abbreviated.
4426 Their full names are:
4430 @value{GDBN} should not stop your program when this signal happens. It may
4431 still print a message telling you that the signal has come in.
4434 @value{GDBN} should stop your program when this signal happens. This implies
4435 the @code{print} keyword as well.
4438 @value{GDBN} should print a message when this signal happens.
4441 @value{GDBN} should not mention the occurrence of the signal at all. This
4442 implies the @code{nostop} keyword as well.
4446 @value{GDBN} should allow your program to see this signal; your program
4447 can handle the signal, or else it may terminate if the signal is fatal
4448 and not handled. @code{pass} and @code{noignore} are synonyms.
4452 @value{GDBN} should not allow your program to see this signal.
4453 @code{nopass} and @code{ignore} are synonyms.
4457 When a signal stops your program, the signal is not visible to the
4459 continue. Your program sees the signal then, if @code{pass} is in
4460 effect for the signal in question @emph{at that time}. In other words,
4461 after @value{GDBN} reports a signal, you can use the @code{handle}
4462 command with @code{pass} or @code{nopass} to control whether your
4463 program sees that signal when you continue.
4465 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4466 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4467 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4470 You can also use the @code{signal} command to prevent your program from
4471 seeing a signal, or cause it to see a signal it normally would not see,
4472 or to give it any signal at any time. For example, if your program stopped
4473 due to some sort of memory reference error, you might store correct
4474 values into the erroneous variables and continue, hoping to see more
4475 execution; but your program would probably terminate immediately as
4476 a result of the fatal signal once it saw the signal. To prevent this,
4477 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4480 @cindex extra signal information
4481 @anchor{extra signal information}
4483 On some targets, @value{GDBN} can inspect extra signal information
4484 associated with the intercepted signal, before it is actually
4485 delivered to the program being debugged. This information is exported
4486 by the convenience variable @code{$_siginfo}, and consists of data
4487 that is passed by the kernel to the signal handler at the time of the
4488 receipt of a signal. The data type of the information itself is
4489 target dependent. You can see the data type using the @code{ptype
4490 $_siginfo} command. On Unix systems, it typically corresponds to the
4491 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4494 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4495 referenced address that raised a segmentation fault.
4499 (@value{GDBP}) continue
4500 Program received signal SIGSEGV, Segmentation fault.
4501 0x0000000000400766 in main ()
4503 (@value{GDBP}) ptype $_siginfo
4510 struct @{...@} _kill;
4511 struct @{...@} _timer;
4513 struct @{...@} _sigchld;
4514 struct @{...@} _sigfault;
4515 struct @{...@} _sigpoll;
4518 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4522 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4523 $1 = (void *) 0x7ffff7ff7000
4527 Depending on target support, @code{$_siginfo} may also be writable.
4530 @section Stopping and Starting Multi-thread Programs
4532 @cindex stopped threads
4533 @cindex threads, stopped
4535 @cindex continuing threads
4536 @cindex threads, continuing
4538 @value{GDBN} supports debugging programs with multiple threads
4539 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4540 are two modes of controlling execution of your program within the
4541 debugger. In the default mode, referred to as @dfn{all-stop mode},
4542 when any thread in your program stops (for example, at a breakpoint
4543 or while being stepped), all other threads in the program are also stopped by
4544 @value{GDBN}. On some targets, @value{GDBN} also supports
4545 @dfn{non-stop mode}, in which other threads can continue to run freely while
4546 you examine the stopped thread in the debugger.
4549 * All-Stop Mode:: All threads stop when GDB takes control
4550 * Non-Stop Mode:: Other threads continue to execute
4551 * Background Execution:: Running your program asynchronously
4552 * Thread-Specific Breakpoints:: Controlling breakpoints
4553 * Interrupted System Calls:: GDB may interfere with system calls
4557 @subsection All-Stop Mode
4559 @cindex all-stop mode
4561 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4562 @emph{all} threads of execution stop, not just the current thread. This
4563 allows you to examine the overall state of the program, including
4564 switching between threads, without worrying that things may change
4567 Conversely, whenever you restart the program, @emph{all} threads start
4568 executing. @emph{This is true even when single-stepping} with commands
4569 like @code{step} or @code{next}.
4571 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4572 Since thread scheduling is up to your debugging target's operating
4573 system (not controlled by @value{GDBN}), other threads may
4574 execute more than one statement while the current thread completes a
4575 single step. Moreover, in general other threads stop in the middle of a
4576 statement, rather than at a clean statement boundary, when the program
4579 You might even find your program stopped in another thread after
4580 continuing or even single-stepping. This happens whenever some other
4581 thread runs into a breakpoint, a signal, or an exception before the
4582 first thread completes whatever you requested.
4584 @cindex automatic thread selection
4585 @cindex switching threads automatically
4586 @cindex threads, automatic switching
4587 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4588 signal, it automatically selects the thread where that breakpoint or
4589 signal happened. @value{GDBN} alerts you to the context switch with a
4590 message such as @samp{[Switching to Thread @var{n}]} to identify the
4593 On some OSes, you can modify @value{GDBN}'s default behavior by
4594 locking the OS scheduler to allow only a single thread to run.
4597 @item set scheduler-locking @var{mode}
4598 @cindex scheduler locking mode
4599 @cindex lock scheduler
4600 Set the scheduler locking mode. If it is @code{off}, then there is no
4601 locking and any thread may run at any time. If @code{on}, then only the
4602 current thread may run when the inferior is resumed. The @code{step}
4603 mode optimizes for single-stepping; it prevents other threads
4604 from preempting the current thread while you are stepping, so that
4605 the focus of debugging does not change unexpectedly.
4606 Other threads only rarely (or never) get a chance to run
4607 when you step. They are more likely to run when you @samp{next} over a
4608 function call, and they are completely free to run when you use commands
4609 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4610 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4611 the current thread away from the thread that you are debugging.
4613 @item show scheduler-locking
4614 Display the current scheduler locking mode.
4618 @subsection Non-Stop Mode
4620 @cindex non-stop mode
4622 @c This section is really only a place-holder, and needs to be expanded
4623 @c with more details.
4625 For some multi-threaded targets, @value{GDBN} supports an optional
4626 mode of operation in which you can examine stopped program threads in
4627 the debugger while other threads continue to execute freely. This
4628 minimizes intrusion when debugging live systems, such as programs
4629 where some threads have real-time constraints or must continue to
4630 respond to external events. This is referred to as @dfn{non-stop} mode.
4632 In non-stop mode, when a thread stops to report a debugging event,
4633 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4634 threads as well, in contrast to the all-stop mode behavior. Additionally,
4635 execution commands such as @code{continue} and @code{step} apply by default
4636 only to the current thread in non-stop mode, rather than all threads as
4637 in all-stop mode. This allows you to control threads explicitly in
4638 ways that are not possible in all-stop mode --- for example, stepping
4639 one thread while allowing others to run freely, stepping
4640 one thread while holding all others stopped, or stepping several threads
4641 independently and simultaneously.
4643 To enter non-stop mode, use this sequence of commands before you run
4644 or attach to your program:
4647 # Enable the async interface.
4650 # If using the CLI, pagination breaks non-stop.
4653 # Finally, turn it on!
4657 You can use these commands to manipulate the non-stop mode setting:
4660 @kindex set non-stop
4661 @item set non-stop on
4662 Enable selection of non-stop mode.
4663 @item set non-stop off
4664 Disable selection of non-stop mode.
4665 @kindex show non-stop
4667 Show the current non-stop enablement setting.
4670 Note these commands only reflect whether non-stop mode is enabled,
4671 not whether the currently-executing program is being run in non-stop mode.
4672 In particular, the @code{set non-stop} preference is only consulted when
4673 @value{GDBN} starts or connects to the target program, and it is generally
4674 not possible to switch modes once debugging has started. Furthermore,
4675 since not all targets support non-stop mode, even when you have enabled
4676 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4679 In non-stop mode, all execution commands apply only to the current thread
4680 by default. That is, @code{continue} only continues one thread.
4681 To continue all threads, issue @code{continue -a} or @code{c -a}.
4683 You can use @value{GDBN}'s background execution commands
4684 (@pxref{Background Execution}) to run some threads in the background
4685 while you continue to examine or step others from @value{GDBN}.
4686 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4687 always executed asynchronously in non-stop mode.
4689 Suspending execution is done with the @code{interrupt} command when
4690 running in the background, or @kbd{Ctrl-c} during foreground execution.
4691 In all-stop mode, this stops the whole process;
4692 but in non-stop mode the interrupt applies only to the current thread.
4693 To stop the whole program, use @code{interrupt -a}.
4695 Other execution commands do not currently support the @code{-a} option.
4697 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4698 that thread current, as it does in all-stop mode. This is because the
4699 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4700 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4701 changed to a different thread just as you entered a command to operate on the
4702 previously current thread.
4704 @node Background Execution
4705 @subsection Background Execution
4707 @cindex foreground execution
4708 @cindex background execution
4709 @cindex asynchronous execution
4710 @cindex execution, foreground, background and asynchronous
4712 @value{GDBN}'s execution commands have two variants: the normal
4713 foreground (synchronous) behavior, and a background
4714 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4715 the program to report that some thread has stopped before prompting for
4716 another command. In background execution, @value{GDBN} immediately gives
4717 a command prompt so that you can issue other commands while your program runs.
4719 You need to explicitly enable asynchronous mode before you can use
4720 background execution commands. You can use these commands to
4721 manipulate the asynchronous mode setting:
4724 @kindex set target-async
4725 @item set target-async on
4726 Enable asynchronous mode.
4727 @item set target-async off
4728 Disable asynchronous mode.
4729 @kindex show target-async
4730 @item show target-async
4731 Show the current target-async setting.
4734 If the target doesn't support async mode, @value{GDBN} issues an error
4735 message if you attempt to use the background execution commands.
4737 To specify background execution, add a @code{&} to the command. For example,
4738 the background form of the @code{continue} command is @code{continue&}, or
4739 just @code{c&}. The execution commands that accept background execution
4745 @xref{Starting, , Starting your Program}.
4749 @xref{Attach, , Debugging an Already-running Process}.
4753 @xref{Continuing and Stepping, step}.
4757 @xref{Continuing and Stepping, stepi}.
4761 @xref{Continuing and Stepping, next}.
4765 @xref{Continuing and Stepping, nexti}.
4769 @xref{Continuing and Stepping, continue}.
4773 @xref{Continuing and Stepping, finish}.
4777 @xref{Continuing and Stepping, until}.
4781 Background execution is especially useful in conjunction with non-stop
4782 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4783 However, you can also use these commands in the normal all-stop mode with
4784 the restriction that you cannot issue another execution command until the
4785 previous one finishes. Examples of commands that are valid in all-stop
4786 mode while the program is running include @code{help} and @code{info break}.
4788 You can interrupt your program while it is running in the background by
4789 using the @code{interrupt} command.
4796 Suspend execution of the running program. In all-stop mode,
4797 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4798 only the current thread. To stop the whole program in non-stop mode,
4799 use @code{interrupt -a}.
4802 @node Thread-Specific Breakpoints
4803 @subsection Thread-Specific Breakpoints
4805 When your program has multiple threads (@pxref{Threads,, Debugging
4806 Programs with Multiple Threads}), you can choose whether to set
4807 breakpoints on all threads, or on a particular thread.
4810 @cindex breakpoints and threads
4811 @cindex thread breakpoints
4812 @kindex break @dots{} thread @var{threadno}
4813 @item break @var{linespec} thread @var{threadno}
4814 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4815 @var{linespec} specifies source lines; there are several ways of
4816 writing them (@pxref{Specify Location}), but the effect is always to
4817 specify some source line.
4819 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4820 to specify that you only want @value{GDBN} to stop the program when a
4821 particular thread reaches this breakpoint. @var{threadno} is one of the
4822 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4823 column of the @samp{info threads} display.
4825 If you do not specify @samp{thread @var{threadno}} when you set a
4826 breakpoint, the breakpoint applies to @emph{all} threads of your
4829 You can use the @code{thread} qualifier on conditional breakpoints as
4830 well; in this case, place @samp{thread @var{threadno}} before the
4831 breakpoint condition, like this:
4834 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4839 @node Interrupted System Calls
4840 @subsection Interrupted System Calls
4842 @cindex thread breakpoints and system calls
4843 @cindex system calls and thread breakpoints
4844 @cindex premature return from system calls
4845 There is an unfortunate side effect when using @value{GDBN} to debug
4846 multi-threaded programs. If one thread stops for a
4847 breakpoint, or for some other reason, and another thread is blocked in a
4848 system call, then the system call may return prematurely. This is a
4849 consequence of the interaction between multiple threads and the signals
4850 that @value{GDBN} uses to implement breakpoints and other events that
4853 To handle this problem, your program should check the return value of
4854 each system call and react appropriately. This is good programming
4857 For example, do not write code like this:
4863 The call to @code{sleep} will return early if a different thread stops
4864 at a breakpoint or for some other reason.
4866 Instead, write this:
4871 unslept = sleep (unslept);
4874 A system call is allowed to return early, so the system is still
4875 conforming to its specification. But @value{GDBN} does cause your
4876 multi-threaded program to behave differently than it would without
4879 Also, @value{GDBN} uses internal breakpoints in the thread library to
4880 monitor certain events such as thread creation and thread destruction.
4881 When such an event happens, a system call in another thread may return
4882 prematurely, even though your program does not appear to stop.
4885 @node Reverse Execution
4886 @chapter Running programs backward
4887 @cindex reverse execution
4888 @cindex running programs backward
4890 When you are debugging a program, it is not unusual to realize that
4891 you have gone too far, and some event of interest has already happened.
4892 If the target environment supports it, @value{GDBN} can allow you to
4893 ``rewind'' the program by running it backward.
4895 A target environment that supports reverse execution should be able
4896 to ``undo'' the changes in machine state that have taken place as the
4897 program was executing normally. Variables, registers etc.@: should
4898 revert to their previous values. Obviously this requires a great
4899 deal of sophistication on the part of the target environment; not
4900 all target environments can support reverse execution.
4902 When a program is executed in reverse, the instructions that
4903 have most recently been executed are ``un-executed'', in reverse
4904 order. The program counter runs backward, following the previous
4905 thread of execution in reverse. As each instruction is ``un-executed'',
4906 the values of memory and/or registers that were changed by that
4907 instruction are reverted to their previous states. After executing
4908 a piece of source code in reverse, all side effects of that code
4909 should be ``undone'', and all variables should be returned to their
4910 prior values@footnote{
4911 Note that some side effects are easier to undo than others. For instance,
4912 memory and registers are relatively easy, but device I/O is hard. Some
4913 targets may be able undo things like device I/O, and some may not.
4915 The contract between @value{GDBN} and the reverse executing target
4916 requires only that the target do something reasonable when
4917 @value{GDBN} tells it to execute backwards, and then report the
4918 results back to @value{GDBN}. Whatever the target reports back to
4919 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4920 assumes that the memory and registers that the target reports are in a
4921 consistant state, but @value{GDBN} accepts whatever it is given.
4924 If you are debugging in a target environment that supports
4925 reverse execution, @value{GDBN} provides the following commands.
4928 @kindex reverse-continue
4929 @kindex rc @r{(@code{reverse-continue})}
4930 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4931 @itemx rc @r{[}@var{ignore-count}@r{]}
4932 Beginning at the point where your program last stopped, start executing
4933 in reverse. Reverse execution will stop for breakpoints and synchronous
4934 exceptions (signals), just like normal execution. Behavior of
4935 asynchronous signals depends on the target environment.
4937 @kindex reverse-step
4938 @kindex rs @r{(@code{step})}
4939 @item reverse-step @r{[}@var{count}@r{]}
4940 Run the program backward until control reaches the start of a
4941 different source line; then stop it, and return control to @value{GDBN}.
4943 Like the @code{step} command, @code{reverse-step} will only stop
4944 at the beginning of a source line. It ``un-executes'' the previously
4945 executed source line. If the previous source line included calls to
4946 debuggable functions, @code{reverse-step} will step (backward) into
4947 the called function, stopping at the beginning of the @emph{last}
4948 statement in the called function (typically a return statement).
4950 Also, as with the @code{step} command, if non-debuggable functions are
4951 called, @code{reverse-step} will run thru them backward without stopping.
4953 @kindex reverse-stepi
4954 @kindex rsi @r{(@code{reverse-stepi})}
4955 @item reverse-stepi @r{[}@var{count}@r{]}
4956 Reverse-execute one machine instruction. Note that the instruction
4957 to be reverse-executed is @emph{not} the one pointed to by the program
4958 counter, but the instruction executed prior to that one. For instance,
4959 if the last instruction was a jump, @code{reverse-stepi} will take you
4960 back from the destination of the jump to the jump instruction itself.
4962 @kindex reverse-next
4963 @kindex rn @r{(@code{reverse-next})}
4964 @item reverse-next @r{[}@var{count}@r{]}
4965 Run backward to the beginning of the previous line executed in
4966 the current (innermost) stack frame. If the line contains function
4967 calls, they will be ``un-executed'' without stopping. Starting from
4968 the first line of a function, @code{reverse-next} will take you back
4969 to the caller of that function, @emph{before} the function was called,
4970 just as the normal @code{next} command would take you from the last
4971 line of a function back to its return to its caller
4972 @footnote{Unles the code is too heavily optimized.}.
4974 @kindex reverse-nexti
4975 @kindex rni @r{(@code{reverse-nexti})}
4976 @item reverse-nexti @r{[}@var{count}@r{]}
4977 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
4978 in reverse, except that called functions are ``un-executed'' atomically.
4979 That is, if the previously executed instruction was a return from
4980 another instruction, @code{reverse-nexti} will continue to execute
4981 in reverse until the call to that function (from the current stack
4984 @kindex reverse-finish
4985 @item reverse-finish
4986 Just as the @code{finish} command takes you to the point where the
4987 current function returns, @code{reverse-finish} takes you to the point
4988 where it was called. Instead of ending up at the end of the current
4989 function invocation, you end up at the beginning.
4991 @kindex set exec-direction
4992 @item set exec-direction
4993 Set the direction of target execution.
4994 @itemx set exec-direction reverse
4995 @cindex execute forward or backward in time
4996 @value{GDBN} will perform all execution commands in reverse, until the
4997 exec-direction mode is changed to ``forward''. Affected commands include
4998 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
4999 command cannot be used in reverse mode.
5000 @item set exec-direction forward
5001 @value{GDBN} will perform all execution commands in the normal fashion.
5002 This is the default.
5006 @node Process Record and Replay
5007 @chapter Recording Inferior's Execution and Replaying It
5008 @cindex process record and replay
5009 @cindex recording inferior's execution and replaying it
5011 On some platforms, @value{GDBN} provides a special @dfn{process record
5012 and replay} target that can record a log of the process execution, and
5013 replay it later with both forward and reverse execution commands.
5016 When this target is in use, if the execution log includes the record
5017 for the next instruction, @value{GDBN} will debug in @dfn{replay
5018 mode}. In the replay mode, the inferior does not really execute code
5019 instructions. Instead, all the events that normally happen during
5020 code execution are taken from the execution log. While code is not
5021 really executed in replay mode, the values of registers (including the
5022 program counter register) and the memory of the inferior are still
5023 changed as they normally would. Their contents are taken from the
5027 If the record for the next instruction is not in the execution log,
5028 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5029 inferior executes normally, and @value{GDBN} records the execution log
5032 The process record and replay target supports reverse execution
5033 (@pxref{Reverse Execution}), even if the platform on which the
5034 inferior runs does not. However, the reverse execution is limited in
5035 this case by the range of the instructions recorded in the execution
5036 log. In other words, reverse execution on platforms that don't
5037 support it directly can only be done in the replay mode.
5039 When debugging in the reverse direction, @value{GDBN} will work in
5040 replay mode as long as the execution log includes the record for the
5041 previous instruction; otherwise, it will work in record mode, if the
5042 platform supports reverse execution, or stop if not.
5044 For architecture environments that support process record and replay,
5045 @value{GDBN} provides the following commands:
5048 @kindex target record
5052 This command starts the process record and replay target. The process
5053 record and replay target can only debug a process that is already
5054 running. Therefore, you need first to start the process with the
5055 @kbd{run} or @kbd{start} commands, and then start the recording with
5056 the @kbd{target record} command.
5058 Both @code{record} and @code{rec} are aliases of @code{target record}.
5060 @cindex displaced stepping, and process record and replay
5061 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5062 will be automatically disabled when process record and replay target
5063 is started. That's because the process record and replay target
5064 doesn't support displaced stepping.
5066 @cindex non-stop mode, and process record and replay
5067 @cindex asynchronous execution, and process record and replay
5068 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5069 the asynchronous execution mode (@pxref{Background Execution}), the
5070 process record and replay target cannot be started because it doesn't
5071 support these two modes.
5076 Stop the process record and replay target. When process record and
5077 replay target stops, the entire execution log will be deleted and the
5078 inferior will either be terminated, or will remain in its final state.
5080 When you stop the process record and replay target in record mode (at
5081 the end of the execution log), the inferior will be stopped at the
5082 next instruction that would have been recorded. In other words, if
5083 you record for a while and then stop recording, the inferior process
5084 will be left in the same state as if the recording never happened.
5086 On the other hand, if the process record and replay target is stopped
5087 while in replay mode (that is, not at the end of the execution log,
5088 but at some earlier point), the inferior process will become ``live''
5089 at that earlier state, and it will then be possible to continue the
5090 usual ``live'' debugging of the process from that state.
5092 When the inferior process exits, or @value{GDBN} detaches from it,
5093 process record and replay target will automatically stop itself.
5095 @kindex set record insn-number-max
5096 @item set record insn-number-max @var{limit}
5097 Set the limit of instructions to be recorded. Default value is 200000.
5099 If @var{limit} is a positive number, then @value{GDBN} will start
5100 deleting instructions from the log once the number of the record
5101 instructions becomes greater than @var{limit}. For every new recorded
5102 instruction, @value{GDBN} will delete the earliest recorded
5103 instruction to keep the number of recorded instructions at the limit.
5104 (Since deleting recorded instructions loses information, @value{GDBN}
5105 lets you control what happens when the limit is reached, by means of
5106 the @code{stop-at-limit} option, described below.)
5108 If @var{limit} is zero, @value{GDBN} will never delete recorded
5109 instructions from the execution log. The number of recorded
5110 instructions is unlimited in this case.
5112 @kindex show record insn-number-max
5113 @item show record insn-number-max
5114 Show the limit of instructions to be recorded.
5116 @kindex set record stop-at-limit
5117 @item set record stop-at-limit
5118 Control the behavior when the number of recorded instructions reaches
5119 the limit. If ON (the default), @value{GDBN} will stop when the limit
5120 is reached for the first time and ask you whether you want to stop the
5121 inferior or continue running it and recording the execution log. If
5122 you decide to continue recording, each new recorded instruction will
5123 cause the oldest one to be deleted.
5125 If this option is OFF, @value{GDBN} will automatically delete the
5126 oldest record to make room for each new one, without asking.
5128 @kindex show record stop-at-limit
5129 @item show record stop-at-limit
5130 Show the current setting of @code{stop-at-limit}.
5132 @kindex info record insn-number
5133 @item info record insn-number
5134 Show the current number of recorded instructions.
5136 @kindex record delete
5139 When record target runs in replay mode (``in the past''), delete the
5140 subsequent execution log and begin to record a new execution log starting
5141 from the current address. This means you will abandon the previously
5142 recorded ``future'' and begin recording a new ``future''.
5147 @chapter Examining the Stack
5149 When your program has stopped, the first thing you need to know is where it
5150 stopped and how it got there.
5153 Each time your program performs a function call, information about the call
5155 That information includes the location of the call in your program,
5156 the arguments of the call,
5157 and the local variables of the function being called.
5158 The information is saved in a block of data called a @dfn{stack frame}.
5159 The stack frames are allocated in a region of memory called the @dfn{call
5162 When your program stops, the @value{GDBN} commands for examining the
5163 stack allow you to see all of this information.
5165 @cindex selected frame
5166 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5167 @value{GDBN} commands refer implicitly to the selected frame. In
5168 particular, whenever you ask @value{GDBN} for the value of a variable in
5169 your program, the value is found in the selected frame. There are
5170 special @value{GDBN} commands to select whichever frame you are
5171 interested in. @xref{Selection, ,Selecting a Frame}.
5173 When your program stops, @value{GDBN} automatically selects the
5174 currently executing frame and describes it briefly, similar to the
5175 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5178 * Frames:: Stack frames
5179 * Backtrace:: Backtraces
5180 * Selection:: Selecting a frame
5181 * Frame Info:: Information on a frame
5186 @section Stack Frames
5188 @cindex frame, definition
5190 The call stack is divided up into contiguous pieces called @dfn{stack
5191 frames}, or @dfn{frames} for short; each frame is the data associated
5192 with one call to one function. The frame contains the arguments given
5193 to the function, the function's local variables, and the address at
5194 which the function is executing.
5196 @cindex initial frame
5197 @cindex outermost frame
5198 @cindex innermost frame
5199 When your program is started, the stack has only one frame, that of the
5200 function @code{main}. This is called the @dfn{initial} frame or the
5201 @dfn{outermost} frame. Each time a function is called, a new frame is
5202 made. Each time a function returns, the frame for that function invocation
5203 is eliminated. If a function is recursive, there can be many frames for
5204 the same function. The frame for the function in which execution is
5205 actually occurring is called the @dfn{innermost} frame. This is the most
5206 recently created of all the stack frames that still exist.
5208 @cindex frame pointer
5209 Inside your program, stack frames are identified by their addresses. A
5210 stack frame consists of many bytes, each of which has its own address; each
5211 kind of computer has a convention for choosing one byte whose
5212 address serves as the address of the frame. Usually this address is kept
5213 in a register called the @dfn{frame pointer register}
5214 (@pxref{Registers, $fp}) while execution is going on in that frame.
5216 @cindex frame number
5217 @value{GDBN} assigns numbers to all existing stack frames, starting with
5218 zero for the innermost frame, one for the frame that called it,
5219 and so on upward. These numbers do not really exist in your program;
5220 they are assigned by @value{GDBN} to give you a way of designating stack
5221 frames in @value{GDBN} commands.
5223 @c The -fomit-frame-pointer below perennially causes hbox overflow
5224 @c underflow problems.
5225 @cindex frameless execution
5226 Some compilers provide a way to compile functions so that they operate
5227 without stack frames. (For example, the @value{NGCC} option
5229 @samp{-fomit-frame-pointer}
5231 generates functions without a frame.)
5232 This is occasionally done with heavily used library functions to save
5233 the frame setup time. @value{GDBN} has limited facilities for dealing
5234 with these function invocations. If the innermost function invocation
5235 has no stack frame, @value{GDBN} nevertheless regards it as though
5236 it had a separate frame, which is numbered zero as usual, allowing
5237 correct tracing of the function call chain. However, @value{GDBN} has
5238 no provision for frameless functions elsewhere in the stack.
5241 @kindex frame@r{, command}
5242 @cindex current stack frame
5243 @item frame @var{args}
5244 The @code{frame} command allows you to move from one stack frame to another,
5245 and to print the stack frame you select. @var{args} may be either the
5246 address of the frame or the stack frame number. Without an argument,
5247 @code{frame} prints the current stack frame.
5249 @kindex select-frame
5250 @cindex selecting frame silently
5252 The @code{select-frame} command allows you to move from one stack frame
5253 to another without printing the frame. This is the silent version of
5261 @cindex call stack traces
5262 A backtrace is a summary of how your program got where it is. It shows one
5263 line per frame, for many frames, starting with the currently executing
5264 frame (frame zero), followed by its caller (frame one), and on up the
5269 @kindex bt @r{(@code{backtrace})}
5272 Print a backtrace of the entire stack: one line per frame for all
5273 frames in the stack.
5275 You can stop the backtrace at any time by typing the system interrupt
5276 character, normally @kbd{Ctrl-c}.
5278 @item backtrace @var{n}
5280 Similar, but print only the innermost @var{n} frames.
5282 @item backtrace -@var{n}
5284 Similar, but print only the outermost @var{n} frames.
5286 @item backtrace full
5288 @itemx bt full @var{n}
5289 @itemx bt full -@var{n}
5290 Print the values of the local variables also. @var{n} specifies the
5291 number of frames to print, as described above.
5296 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5297 are additional aliases for @code{backtrace}.
5299 @cindex multiple threads, backtrace
5300 In a multi-threaded program, @value{GDBN} by default shows the
5301 backtrace only for the current thread. To display the backtrace for
5302 several or all of the threads, use the command @code{thread apply}
5303 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5304 apply all backtrace}, @value{GDBN} will display the backtrace for all
5305 the threads; this is handy when you debug a core dump of a
5306 multi-threaded program.
5308 Each line in the backtrace shows the frame number and the function name.
5309 The program counter value is also shown---unless you use @code{set
5310 print address off}. The backtrace also shows the source file name and
5311 line number, as well as the arguments to the function. The program
5312 counter value is omitted if it is at the beginning of the code for that
5315 Here is an example of a backtrace. It was made with the command
5316 @samp{bt 3}, so it shows the innermost three frames.
5320 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5322 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5323 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5325 (More stack frames follow...)
5330 The display for frame zero does not begin with a program counter
5331 value, indicating that your program has stopped at the beginning of the
5332 code for line @code{993} of @code{builtin.c}.
5335 The value of parameter @code{data} in frame 1 has been replaced by
5336 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5337 only if it is a scalar (integer, pointer, enumeration, etc). See command
5338 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5339 on how to configure the way function parameter values are printed.
5341 @cindex value optimized out, in backtrace
5342 @cindex function call arguments, optimized out
5343 If your program was compiled with optimizations, some compilers will
5344 optimize away arguments passed to functions if those arguments are
5345 never used after the call. Such optimizations generate code that
5346 passes arguments through registers, but doesn't store those arguments
5347 in the stack frame. @value{GDBN} has no way of displaying such
5348 arguments in stack frames other than the innermost one. Here's what
5349 such a backtrace might look like:
5353 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5355 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5356 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5358 (More stack frames follow...)
5363 The values of arguments that were not saved in their stack frames are
5364 shown as @samp{<value optimized out>}.
5366 If you need to display the values of such optimized-out arguments,
5367 either deduce that from other variables whose values depend on the one
5368 you are interested in, or recompile without optimizations.
5370 @cindex backtrace beyond @code{main} function
5371 @cindex program entry point
5372 @cindex startup code, and backtrace
5373 Most programs have a standard user entry point---a place where system
5374 libraries and startup code transition into user code. For C this is
5375 @code{main}@footnote{
5376 Note that embedded programs (the so-called ``free-standing''
5377 environment) are not required to have a @code{main} function as the
5378 entry point. They could even have multiple entry points.}.
5379 When @value{GDBN} finds the entry function in a backtrace
5380 it will terminate the backtrace, to avoid tracing into highly
5381 system-specific (and generally uninteresting) code.
5383 If you need to examine the startup code, or limit the number of levels
5384 in a backtrace, you can change this behavior:
5387 @item set backtrace past-main
5388 @itemx set backtrace past-main on
5389 @kindex set backtrace
5390 Backtraces will continue past the user entry point.
5392 @item set backtrace past-main off
5393 Backtraces will stop when they encounter the user entry point. This is the
5396 @item show backtrace past-main
5397 @kindex show backtrace
5398 Display the current user entry point backtrace policy.
5400 @item set backtrace past-entry
5401 @itemx set backtrace past-entry on
5402 Backtraces will continue past the internal entry point of an application.
5403 This entry point is encoded by the linker when the application is built,
5404 and is likely before the user entry point @code{main} (or equivalent) is called.
5406 @item set backtrace past-entry off
5407 Backtraces will stop when they encounter the internal entry point of an
5408 application. This is the default.
5410 @item show backtrace past-entry
5411 Display the current internal entry point backtrace policy.
5413 @item set backtrace limit @var{n}
5414 @itemx set backtrace limit 0
5415 @cindex backtrace limit
5416 Limit the backtrace to @var{n} levels. A value of zero means
5419 @item show backtrace limit
5420 Display the current limit on backtrace levels.
5424 @section Selecting a Frame
5426 Most commands for examining the stack and other data in your program work on
5427 whichever stack frame is selected at the moment. Here are the commands for
5428 selecting a stack frame; all of them finish by printing a brief description
5429 of the stack frame just selected.
5432 @kindex frame@r{, selecting}
5433 @kindex f @r{(@code{frame})}
5436 Select frame number @var{n}. Recall that frame zero is the innermost
5437 (currently executing) frame, frame one is the frame that called the
5438 innermost one, and so on. The highest-numbered frame is the one for
5441 @item frame @var{addr}
5443 Select the frame at address @var{addr}. This is useful mainly if the
5444 chaining of stack frames has been damaged by a bug, making it
5445 impossible for @value{GDBN} to assign numbers properly to all frames. In
5446 addition, this can be useful when your program has multiple stacks and
5447 switches between them.
5449 On the SPARC architecture, @code{frame} needs two addresses to
5450 select an arbitrary frame: a frame pointer and a stack pointer.
5452 On the MIPS and Alpha architecture, it needs two addresses: a stack
5453 pointer and a program counter.
5455 On the 29k architecture, it needs three addresses: a register stack
5456 pointer, a program counter, and a memory stack pointer.
5460 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5461 advances toward the outermost frame, to higher frame numbers, to frames
5462 that have existed longer. @var{n} defaults to one.
5465 @kindex do @r{(@code{down})}
5467 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5468 advances toward the innermost frame, to lower frame numbers, to frames
5469 that were created more recently. @var{n} defaults to one. You may
5470 abbreviate @code{down} as @code{do}.
5473 All of these commands end by printing two lines of output describing the
5474 frame. The first line shows the frame number, the function name, the
5475 arguments, and the source file and line number of execution in that
5476 frame. The second line shows the text of that source line.
5484 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5486 10 read_input_file (argv[i]);
5490 After such a printout, the @code{list} command with no arguments
5491 prints ten lines centered on the point of execution in the frame.
5492 You can also edit the program at the point of execution with your favorite
5493 editing program by typing @code{edit}.
5494 @xref{List, ,Printing Source Lines},
5498 @kindex down-silently
5500 @item up-silently @var{n}
5501 @itemx down-silently @var{n}
5502 These two commands are variants of @code{up} and @code{down},
5503 respectively; they differ in that they do their work silently, without
5504 causing display of the new frame. They are intended primarily for use
5505 in @value{GDBN} command scripts, where the output might be unnecessary and
5510 @section Information About a Frame
5512 There are several other commands to print information about the selected
5518 When used without any argument, this command does not change which
5519 frame is selected, but prints a brief description of the currently
5520 selected stack frame. It can be abbreviated @code{f}. With an
5521 argument, this command is used to select a stack frame.
5522 @xref{Selection, ,Selecting a Frame}.
5525 @kindex info f @r{(@code{info frame})}
5528 This command prints a verbose description of the selected stack frame,
5533 the address of the frame
5535 the address of the next frame down (called by this frame)
5537 the address of the next frame up (caller of this frame)
5539 the language in which the source code corresponding to this frame is written
5541 the address of the frame's arguments
5543 the address of the frame's local variables
5545 the program counter saved in it (the address of execution in the caller frame)
5547 which registers were saved in the frame
5550 @noindent The verbose description is useful when
5551 something has gone wrong that has made the stack format fail to fit
5552 the usual conventions.
5554 @item info frame @var{addr}
5555 @itemx info f @var{addr}
5556 Print a verbose description of the frame at address @var{addr}, without
5557 selecting that frame. The selected frame remains unchanged by this
5558 command. This requires the same kind of address (more than one for some
5559 architectures) that you specify in the @code{frame} command.
5560 @xref{Selection, ,Selecting a Frame}.
5564 Print the arguments of the selected frame, each on a separate line.
5568 Print the local variables of the selected frame, each on a separate
5569 line. These are all variables (declared either static or automatic)
5570 accessible at the point of execution of the selected frame.
5573 @cindex catch exceptions, list active handlers
5574 @cindex exception handlers, how to list
5576 Print a list of all the exception handlers that are active in the
5577 current stack frame at the current point of execution. To see other
5578 exception handlers, visit the associated frame (using the @code{up},
5579 @code{down}, or @code{frame} commands); then type @code{info catch}.
5580 @xref{Set Catchpoints, , Setting Catchpoints}.
5586 @chapter Examining Source Files
5588 @value{GDBN} can print parts of your program's source, since the debugging
5589 information recorded in the program tells @value{GDBN} what source files were
5590 used to build it. When your program stops, @value{GDBN} spontaneously prints
5591 the line where it stopped. Likewise, when you select a stack frame
5592 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5593 execution in that frame has stopped. You can print other portions of
5594 source files by explicit command.
5596 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5597 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5598 @value{GDBN} under @sc{gnu} Emacs}.
5601 * List:: Printing source lines
5602 * Specify Location:: How to specify code locations
5603 * Edit:: Editing source files
5604 * Search:: Searching source files
5605 * Source Path:: Specifying source directories
5606 * Machine Code:: Source and machine code
5610 @section Printing Source Lines
5613 @kindex l @r{(@code{list})}
5614 To print lines from a source file, use the @code{list} command
5615 (abbreviated @code{l}). By default, ten lines are printed.
5616 There are several ways to specify what part of the file you want to
5617 print; see @ref{Specify Location}, for the full list.
5619 Here are the forms of the @code{list} command most commonly used:
5622 @item list @var{linenum}
5623 Print lines centered around line number @var{linenum} in the
5624 current source file.
5626 @item list @var{function}
5627 Print lines centered around the beginning of function
5631 Print more lines. If the last lines printed were printed with a
5632 @code{list} command, this prints lines following the last lines
5633 printed; however, if the last line printed was a solitary line printed
5634 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5635 Stack}), this prints lines centered around that line.
5638 Print lines just before the lines last printed.
5641 @cindex @code{list}, how many lines to display
5642 By default, @value{GDBN} prints ten source lines with any of these forms of
5643 the @code{list} command. You can change this using @code{set listsize}:
5646 @kindex set listsize
5647 @item set listsize @var{count}
5648 Make the @code{list} command display @var{count} source lines (unless
5649 the @code{list} argument explicitly specifies some other number).
5651 @kindex show listsize
5653 Display the number of lines that @code{list} prints.
5656 Repeating a @code{list} command with @key{RET} discards the argument,
5657 so it is equivalent to typing just @code{list}. This is more useful
5658 than listing the same lines again. An exception is made for an
5659 argument of @samp{-}; that argument is preserved in repetition so that
5660 each repetition moves up in the source file.
5662 In general, the @code{list} command expects you to supply zero, one or two
5663 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5664 of writing them (@pxref{Specify Location}), but the effect is always
5665 to specify some source line.
5667 Here is a complete description of the possible arguments for @code{list}:
5670 @item list @var{linespec}
5671 Print lines centered around the line specified by @var{linespec}.
5673 @item list @var{first},@var{last}
5674 Print lines from @var{first} to @var{last}. Both arguments are
5675 linespecs. When a @code{list} command has two linespecs, and the
5676 source file of the second linespec is omitted, this refers to
5677 the same source file as the first linespec.
5679 @item list ,@var{last}
5680 Print lines ending with @var{last}.
5682 @item list @var{first},
5683 Print lines starting with @var{first}.
5686 Print lines just after the lines last printed.
5689 Print lines just before the lines last printed.
5692 As described in the preceding table.
5695 @node Specify Location
5696 @section Specifying a Location
5697 @cindex specifying location
5700 Several @value{GDBN} commands accept arguments that specify a location
5701 of your program's code. Since @value{GDBN} is a source-level
5702 debugger, a location usually specifies some line in the source code;
5703 for that reason, locations are also known as @dfn{linespecs}.
5705 Here are all the different ways of specifying a code location that
5706 @value{GDBN} understands:
5710 Specifies the line number @var{linenum} of the current source file.
5713 @itemx +@var{offset}
5714 Specifies the line @var{offset} lines before or after the @dfn{current
5715 line}. For the @code{list} command, the current line is the last one
5716 printed; for the breakpoint commands, this is the line at which
5717 execution stopped in the currently selected @dfn{stack frame}
5718 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5719 used as the second of the two linespecs in a @code{list} command,
5720 this specifies the line @var{offset} lines up or down from the first
5723 @item @var{filename}:@var{linenum}
5724 Specifies the line @var{linenum} in the source file @var{filename}.
5726 @item @var{function}
5727 Specifies the line that begins the body of the function @var{function}.
5728 For example, in C, this is the line with the open brace.
5730 @item @var{filename}:@var{function}
5731 Specifies the line that begins the body of the function @var{function}
5732 in the file @var{filename}. You only need the file name with a
5733 function name to avoid ambiguity when there are identically named
5734 functions in different source files.
5736 @item *@var{address}
5737 Specifies the program address @var{address}. For line-oriented
5738 commands, such as @code{list} and @code{edit}, this specifies a source
5739 line that contains @var{address}. For @code{break} and other
5740 breakpoint oriented commands, this can be used to set breakpoints in
5741 parts of your program which do not have debugging information or
5744 Here @var{address} may be any expression valid in the current working
5745 language (@pxref{Languages, working language}) that specifies a code
5746 address. In addition, as a convenience, @value{GDBN} extends the
5747 semantics of expressions used in locations to cover the situations
5748 that frequently happen during debugging. Here are the various forms
5752 @item @var{expression}
5753 Any expression valid in the current working language.
5755 @item @var{funcaddr}
5756 An address of a function or procedure derived from its name. In C,
5757 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5758 simply the function's name @var{function} (and actually a special case
5759 of a valid expression). In Pascal and Modula-2, this is
5760 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5761 (although the Pascal form also works).
5763 This form specifies the address of the function's first instruction,
5764 before the stack frame and arguments have been set up.
5766 @item '@var{filename}'::@var{funcaddr}
5767 Like @var{funcaddr} above, but also specifies the name of the source
5768 file explicitly. This is useful if the name of the function does not
5769 specify the function unambiguously, e.g., if there are several
5770 functions with identical names in different source files.
5777 @section Editing Source Files
5778 @cindex editing source files
5781 @kindex e @r{(@code{edit})}
5782 To edit the lines in a source file, use the @code{edit} command.
5783 The editing program of your choice
5784 is invoked with the current line set to
5785 the active line in the program.
5786 Alternatively, there are several ways to specify what part of the file you
5787 want to print if you want to see other parts of the program:
5790 @item edit @var{location}
5791 Edit the source file specified by @code{location}. Editing starts at
5792 that @var{location}, e.g., at the specified source line of the
5793 specified file. @xref{Specify Location}, for all the possible forms
5794 of the @var{location} argument; here are the forms of the @code{edit}
5795 command most commonly used:
5798 @item edit @var{number}
5799 Edit the current source file with @var{number} as the active line number.
5801 @item edit @var{function}
5802 Edit the file containing @var{function} at the beginning of its definition.
5807 @subsection Choosing your Editor
5808 You can customize @value{GDBN} to use any editor you want
5810 The only restriction is that your editor (say @code{ex}), recognizes the
5811 following command-line syntax:
5813 ex +@var{number} file
5815 The optional numeric value +@var{number} specifies the number of the line in
5816 the file where to start editing.}.
5817 By default, it is @file{@value{EDITOR}}, but you can change this
5818 by setting the environment variable @code{EDITOR} before using
5819 @value{GDBN}. For example, to configure @value{GDBN} to use the
5820 @code{vi} editor, you could use these commands with the @code{sh} shell:
5826 or in the @code{csh} shell,
5828 setenv EDITOR /usr/bin/vi
5833 @section Searching Source Files
5834 @cindex searching source files
5836 There are two commands for searching through the current source file for a
5841 @kindex forward-search
5842 @item forward-search @var{regexp}
5843 @itemx search @var{regexp}
5844 The command @samp{forward-search @var{regexp}} checks each line,
5845 starting with the one following the last line listed, for a match for
5846 @var{regexp}. It lists the line that is found. You can use the
5847 synonym @samp{search @var{regexp}} or abbreviate the command name as
5850 @kindex reverse-search
5851 @item reverse-search @var{regexp}
5852 The command @samp{reverse-search @var{regexp}} checks each line, starting
5853 with the one before the last line listed and going backward, for a match
5854 for @var{regexp}. It lists the line that is found. You can abbreviate
5855 this command as @code{rev}.
5859 @section Specifying Source Directories
5862 @cindex directories for source files
5863 Executable programs sometimes do not record the directories of the source
5864 files from which they were compiled, just the names. Even when they do,
5865 the directories could be moved between the compilation and your debugging
5866 session. @value{GDBN} has a list of directories to search for source files;
5867 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5868 it tries all the directories in the list, in the order they are present
5869 in the list, until it finds a file with the desired name.
5871 For example, suppose an executable references the file
5872 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5873 @file{/mnt/cross}. The file is first looked up literally; if this
5874 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5875 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5876 message is printed. @value{GDBN} does not look up the parts of the
5877 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5878 Likewise, the subdirectories of the source path are not searched: if
5879 the source path is @file{/mnt/cross}, and the binary refers to
5880 @file{foo.c}, @value{GDBN} would not find it under
5881 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5883 Plain file names, relative file names with leading directories, file
5884 names containing dots, etc.@: are all treated as described above; for
5885 instance, if the source path is @file{/mnt/cross}, and the source file
5886 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5887 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5888 that---@file{/mnt/cross/foo.c}.
5890 Note that the executable search path is @emph{not} used to locate the
5893 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5894 any information it has cached about where source files are found and where
5895 each line is in the file.
5899 When you start @value{GDBN}, its source path includes only @samp{cdir}
5900 and @samp{cwd}, in that order.
5901 To add other directories, use the @code{directory} command.
5903 The search path is used to find both program source files and @value{GDBN}
5904 script files (read using the @samp{-command} option and @samp{source} command).
5906 In addition to the source path, @value{GDBN} provides a set of commands
5907 that manage a list of source path substitution rules. A @dfn{substitution
5908 rule} specifies how to rewrite source directories stored in the program's
5909 debug information in case the sources were moved to a different
5910 directory between compilation and debugging. A rule is made of
5911 two strings, the first specifying what needs to be rewritten in
5912 the path, and the second specifying how it should be rewritten.
5913 In @ref{set substitute-path}, we name these two parts @var{from} and
5914 @var{to} respectively. @value{GDBN} does a simple string replacement
5915 of @var{from} with @var{to} at the start of the directory part of the
5916 source file name, and uses that result instead of the original file
5917 name to look up the sources.
5919 Using the previous example, suppose the @file{foo-1.0} tree has been
5920 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5921 @value{GDBN} to replace @file{/usr/src} in all source path names with
5922 @file{/mnt/cross}. The first lookup will then be
5923 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5924 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5925 substitution rule, use the @code{set substitute-path} command
5926 (@pxref{set substitute-path}).
5928 To avoid unexpected substitution results, a rule is applied only if the
5929 @var{from} part of the directory name ends at a directory separator.
5930 For instance, a rule substituting @file{/usr/source} into
5931 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5932 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5933 is applied only at the beginning of the directory name, this rule will
5934 not be applied to @file{/root/usr/source/baz.c} either.
5936 In many cases, you can achieve the same result using the @code{directory}
5937 command. However, @code{set substitute-path} can be more efficient in
5938 the case where the sources are organized in a complex tree with multiple
5939 subdirectories. With the @code{directory} command, you need to add each
5940 subdirectory of your project. If you moved the entire tree while
5941 preserving its internal organization, then @code{set substitute-path}
5942 allows you to direct the debugger to all the sources with one single
5945 @code{set substitute-path} is also more than just a shortcut command.
5946 The source path is only used if the file at the original location no
5947 longer exists. On the other hand, @code{set substitute-path} modifies
5948 the debugger behavior to look at the rewritten location instead. So, if
5949 for any reason a source file that is not relevant to your executable is
5950 located at the original location, a substitution rule is the only
5951 method available to point @value{GDBN} at the new location.
5953 @cindex @samp{--with-relocated-sources}
5954 @cindex default source path substitution
5955 You can configure a default source path substitution rule by
5956 configuring @value{GDBN} with the
5957 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
5958 should be the name of a directory under @value{GDBN}'s configured
5959 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
5960 directory names in debug information under @var{dir} will be adjusted
5961 automatically if the installed @value{GDBN} is moved to a new
5962 location. This is useful if @value{GDBN}, libraries or executables
5963 with debug information and corresponding source code are being moved
5967 @item directory @var{dirname} @dots{}
5968 @item dir @var{dirname} @dots{}
5969 Add directory @var{dirname} to the front of the source path. Several
5970 directory names may be given to this command, separated by @samp{:}
5971 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5972 part of absolute file names) or
5973 whitespace. You may specify a directory that is already in the source
5974 path; this moves it forward, so @value{GDBN} searches it sooner.
5978 @vindex $cdir@r{, convenience variable}
5979 @vindex $cwd@r{, convenience variable}
5980 @cindex compilation directory
5981 @cindex current directory
5982 @cindex working directory
5983 @cindex directory, current
5984 @cindex directory, compilation
5985 You can use the string @samp{$cdir} to refer to the compilation
5986 directory (if one is recorded), and @samp{$cwd} to refer to the current
5987 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5988 tracks the current working directory as it changes during your @value{GDBN}
5989 session, while the latter is immediately expanded to the current
5990 directory at the time you add an entry to the source path.
5993 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5995 @c RET-repeat for @code{directory} is explicitly disabled, but since
5996 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5998 @item show directories
5999 @kindex show directories
6000 Print the source path: show which directories it contains.
6002 @anchor{set substitute-path}
6003 @item set substitute-path @var{from} @var{to}
6004 @kindex set substitute-path
6005 Define a source path substitution rule, and add it at the end of the
6006 current list of existing substitution rules. If a rule with the same
6007 @var{from} was already defined, then the old rule is also deleted.
6009 For example, if the file @file{/foo/bar/baz.c} was moved to
6010 @file{/mnt/cross/baz.c}, then the command
6013 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6017 will tell @value{GDBN} to replace @samp{/usr/src} with
6018 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6019 @file{baz.c} even though it was moved.
6021 In the case when more than one substitution rule have been defined,
6022 the rules are evaluated one by one in the order where they have been
6023 defined. The first one matching, if any, is selected to perform
6026 For instance, if we had entered the following commands:
6029 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6030 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6034 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6035 @file{/mnt/include/defs.h} by using the first rule. However, it would
6036 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6037 @file{/mnt/src/lib/foo.c}.
6040 @item unset substitute-path [path]
6041 @kindex unset substitute-path
6042 If a path is specified, search the current list of substitution rules
6043 for a rule that would rewrite that path. Delete that rule if found.
6044 A warning is emitted by the debugger if no rule could be found.
6046 If no path is specified, then all substitution rules are deleted.
6048 @item show substitute-path [path]
6049 @kindex show substitute-path
6050 If a path is specified, then print the source path substitution rule
6051 which would rewrite that path, if any.
6053 If no path is specified, then print all existing source path substitution
6058 If your source path is cluttered with directories that are no longer of
6059 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6060 versions of source. You can correct the situation as follows:
6064 Use @code{directory} with no argument to reset the source path to its default value.
6067 Use @code{directory} with suitable arguments to reinstall the
6068 directories you want in the source path. You can add all the
6069 directories in one command.
6073 @section Source and Machine Code
6074 @cindex source line and its code address
6076 You can use the command @code{info line} to map source lines to program
6077 addresses (and vice versa), and the command @code{disassemble} to display
6078 a range of addresses as machine instructions. You can use the command
6079 @code{set disassemble-next-line} to set whether to disassemble next
6080 source line when execution stops. When run under @sc{gnu} Emacs
6081 mode, the @code{info line} command causes the arrow to point to the
6082 line specified. Also, @code{info line} prints addresses in symbolic form as
6087 @item info line @var{linespec}
6088 Print the starting and ending addresses of the compiled code for
6089 source line @var{linespec}. You can specify source lines in any of
6090 the ways documented in @ref{Specify Location}.
6093 For example, we can use @code{info line} to discover the location of
6094 the object code for the first line of function
6095 @code{m4_changequote}:
6097 @c FIXME: I think this example should also show the addresses in
6098 @c symbolic form, as they usually would be displayed.
6100 (@value{GDBP}) info line m4_changequote
6101 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6105 @cindex code address and its source line
6106 We can also inquire (using @code{*@var{addr}} as the form for
6107 @var{linespec}) what source line covers a particular address:
6109 (@value{GDBP}) info line *0x63ff
6110 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6113 @cindex @code{$_} and @code{info line}
6114 @cindex @code{x} command, default address
6115 @kindex x@r{(examine), and} info line
6116 After @code{info line}, the default address for the @code{x} command
6117 is changed to the starting address of the line, so that @samp{x/i} is
6118 sufficient to begin examining the machine code (@pxref{Memory,
6119 ,Examining Memory}). Also, this address is saved as the value of the
6120 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6125 @cindex assembly instructions
6126 @cindex instructions, assembly
6127 @cindex machine instructions
6128 @cindex listing machine instructions
6130 @itemx disassemble /m
6131 This specialized command dumps a range of memory as machine
6132 instructions. It can also print mixed source+disassembly by specifying
6133 the @code{/m} modifier.
6134 The default memory range is the function surrounding the
6135 program counter of the selected frame. A single argument to this
6136 command is a program counter value; @value{GDBN} dumps the function
6137 surrounding this value. Two arguments specify a range of addresses
6138 (first inclusive, second exclusive) to dump.
6141 The following example shows the disassembly of a range of addresses of
6142 HP PA-RISC 2.0 code:
6145 (@value{GDBP}) disas 0x32c4 0x32e4
6146 Dump of assembler code from 0x32c4 to 0x32e4:
6147 0x32c4 <main+204>: addil 0,dp
6148 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6149 0x32cc <main+212>: ldil 0x3000,r31
6150 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6151 0x32d4 <main+220>: ldo 0(r31),rp
6152 0x32d8 <main+224>: addil -0x800,dp
6153 0x32dc <main+228>: ldo 0x588(r1),r26
6154 0x32e0 <main+232>: ldil 0x3000,r31
6155 End of assembler dump.
6158 Here is an example showing mixed source+assembly for Intel x86:
6161 (@value{GDBP}) disas /m main
6162 Dump of assembler code for function main:
6164 0x08048330 <main+0>: push %ebp
6165 0x08048331 <main+1>: mov %esp,%ebp
6166 0x08048333 <main+3>: sub $0x8,%esp
6167 0x08048336 <main+6>: and $0xfffffff0,%esp
6168 0x08048339 <main+9>: sub $0x10,%esp
6170 6 printf ("Hello.\n");
6171 0x0804833c <main+12>: movl $0x8048440,(%esp)
6172 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6176 0x08048348 <main+24>: mov $0x0,%eax
6177 0x0804834d <main+29>: leave
6178 0x0804834e <main+30>: ret
6180 End of assembler dump.
6183 Some architectures have more than one commonly-used set of instruction
6184 mnemonics or other syntax.
6186 For programs that were dynamically linked and use shared libraries,
6187 instructions that call functions or branch to locations in the shared
6188 libraries might show a seemingly bogus location---it's actually a
6189 location of the relocation table. On some architectures, @value{GDBN}
6190 might be able to resolve these to actual function names.
6193 @kindex set disassembly-flavor
6194 @cindex Intel disassembly flavor
6195 @cindex AT&T disassembly flavor
6196 @item set disassembly-flavor @var{instruction-set}
6197 Select the instruction set to use when disassembling the
6198 program via the @code{disassemble} or @code{x/i} commands.
6200 Currently this command is only defined for the Intel x86 family. You
6201 can set @var{instruction-set} to either @code{intel} or @code{att}.
6202 The default is @code{att}, the AT&T flavor used by default by Unix
6203 assemblers for x86-based targets.
6205 @kindex show disassembly-flavor
6206 @item show disassembly-flavor
6207 Show the current setting of the disassembly flavor.
6211 @kindex set disassemble-next-line
6212 @kindex show disassemble-next-line
6213 @item set disassemble-next-line
6214 @itemx show disassemble-next-line
6215 Control whether or not @value{GDBN} will disassemble the next source
6216 line or instruction when execution stops. If ON, @value{GDBN} will
6217 display disassembly of the next source line when execution of the
6218 program being debugged stops. This is @emph{in addition} to
6219 displaying the source line itself, which @value{GDBN} always does if
6220 possible. If the next source line cannot be displayed for some reason
6221 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6222 info in the debug info), @value{GDBN} will display disassembly of the
6223 next @emph{instruction} instead of showing the next source line. If
6224 AUTO, @value{GDBN} will display disassembly of next instruction only
6225 if the source line cannot be displayed. This setting causes
6226 @value{GDBN} to display some feedback when you step through a function
6227 with no line info or whose source file is unavailable. The default is
6228 OFF, which means never display the disassembly of the next line or
6234 @chapter Examining Data
6236 @cindex printing data
6237 @cindex examining data
6240 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6241 @c document because it is nonstandard... Under Epoch it displays in a
6242 @c different window or something like that.
6243 The usual way to examine data in your program is with the @code{print}
6244 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6245 evaluates and prints the value of an expression of the language your
6246 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6247 Different Languages}).
6250 @item print @var{expr}
6251 @itemx print /@var{f} @var{expr}
6252 @var{expr} is an expression (in the source language). By default the
6253 value of @var{expr} is printed in a format appropriate to its data type;
6254 you can choose a different format by specifying @samp{/@var{f}}, where
6255 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6259 @itemx print /@var{f}
6260 @cindex reprint the last value
6261 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6262 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6263 conveniently inspect the same value in an alternative format.
6266 A more low-level way of examining data is with the @code{x} command.
6267 It examines data in memory at a specified address and prints it in a
6268 specified format. @xref{Memory, ,Examining Memory}.
6270 If you are interested in information about types, or about how the
6271 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6272 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6276 * Expressions:: Expressions
6277 * Ambiguous Expressions:: Ambiguous Expressions
6278 * Variables:: Program variables
6279 * Arrays:: Artificial arrays
6280 * Output Formats:: Output formats
6281 * Memory:: Examining memory
6282 * Auto Display:: Automatic display
6283 * Print Settings:: Print settings
6284 * Value History:: Value history
6285 * Convenience Vars:: Convenience variables
6286 * Registers:: Registers
6287 * Floating Point Hardware:: Floating point hardware
6288 * Vector Unit:: Vector Unit
6289 * OS Information:: Auxiliary data provided by operating system
6290 * Memory Region Attributes:: Memory region attributes
6291 * Dump/Restore Files:: Copy between memory and a file
6292 * Core File Generation:: Cause a program dump its core
6293 * Character Sets:: Debugging programs that use a different
6294 character set than GDB does
6295 * Caching Remote Data:: Data caching for remote targets
6296 * Searching Memory:: Searching memory for a sequence of bytes
6300 @section Expressions
6303 @code{print} and many other @value{GDBN} commands accept an expression and
6304 compute its value. Any kind of constant, variable or operator defined
6305 by the programming language you are using is valid in an expression in
6306 @value{GDBN}. This includes conditional expressions, function calls,
6307 casts, and string constants. It also includes preprocessor macros, if
6308 you compiled your program to include this information; see
6311 @cindex arrays in expressions
6312 @value{GDBN} supports array constants in expressions input by
6313 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6314 you can use the command @code{print @{1, 2, 3@}} to create an array
6315 of three integers. If you pass an array to a function or assign it
6316 to a program variable, @value{GDBN} copies the array to memory that
6317 is @code{malloc}ed in the target program.
6319 Because C is so widespread, most of the expressions shown in examples in
6320 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6321 Languages}, for information on how to use expressions in other
6324 In this section, we discuss operators that you can use in @value{GDBN}
6325 expressions regardless of your programming language.
6327 @cindex casts, in expressions
6328 Casts are supported in all languages, not just in C, because it is so
6329 useful to cast a number into a pointer in order to examine a structure
6330 at that address in memory.
6331 @c FIXME: casts supported---Mod2 true?
6333 @value{GDBN} supports these operators, in addition to those common
6334 to programming languages:
6338 @samp{@@} is a binary operator for treating parts of memory as arrays.
6339 @xref{Arrays, ,Artificial Arrays}, for more information.
6342 @samp{::} allows you to specify a variable in terms of the file or
6343 function where it is defined. @xref{Variables, ,Program Variables}.
6345 @cindex @{@var{type}@}
6346 @cindex type casting memory
6347 @cindex memory, viewing as typed object
6348 @cindex casts, to view memory
6349 @item @{@var{type}@} @var{addr}
6350 Refers to an object of type @var{type} stored at address @var{addr} in
6351 memory. @var{addr} may be any expression whose value is an integer or
6352 pointer (but parentheses are required around binary operators, just as in
6353 a cast). This construct is allowed regardless of what kind of data is
6354 normally supposed to reside at @var{addr}.
6357 @node Ambiguous Expressions
6358 @section Ambiguous Expressions
6359 @cindex ambiguous expressions
6361 Expressions can sometimes contain some ambiguous elements. For instance,
6362 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6363 a single function name to be defined several times, for application in
6364 different contexts. This is called @dfn{overloading}. Another example
6365 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6366 templates and is typically instantiated several times, resulting in
6367 the same function name being defined in different contexts.
6369 In some cases and depending on the language, it is possible to adjust
6370 the expression to remove the ambiguity. For instance in C@t{++}, you
6371 can specify the signature of the function you want to break on, as in
6372 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6373 qualified name of your function often makes the expression unambiguous
6376 When an ambiguity that needs to be resolved is detected, the debugger
6377 has the capability to display a menu of numbered choices for each
6378 possibility, and then waits for the selection with the prompt @samp{>}.
6379 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6380 aborts the current command. If the command in which the expression was
6381 used allows more than one choice to be selected, the next option in the
6382 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6385 For example, the following session excerpt shows an attempt to set a
6386 breakpoint at the overloaded symbol @code{String::after}.
6387 We choose three particular definitions of that function name:
6389 @c FIXME! This is likely to change to show arg type lists, at least
6392 (@value{GDBP}) b String::after
6395 [2] file:String.cc; line number:867
6396 [3] file:String.cc; line number:860
6397 [4] file:String.cc; line number:875
6398 [5] file:String.cc; line number:853
6399 [6] file:String.cc; line number:846
6400 [7] file:String.cc; line number:735
6402 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6403 Breakpoint 2 at 0xb344: file String.cc, line 875.
6404 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6405 Multiple breakpoints were set.
6406 Use the "delete" command to delete unwanted
6413 @kindex set multiple-symbols
6414 @item set multiple-symbols @var{mode}
6415 @cindex multiple-symbols menu
6417 This option allows you to adjust the debugger behavior when an expression
6420 By default, @var{mode} is set to @code{all}. If the command with which
6421 the expression is used allows more than one choice, then @value{GDBN}
6422 automatically selects all possible choices. For instance, inserting
6423 a breakpoint on a function using an ambiguous name results in a breakpoint
6424 inserted on each possible match. However, if a unique choice must be made,
6425 then @value{GDBN} uses the menu to help you disambiguate the expression.
6426 For instance, printing the address of an overloaded function will result
6427 in the use of the menu.
6429 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6430 when an ambiguity is detected.
6432 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6433 an error due to the ambiguity and the command is aborted.
6435 @kindex show multiple-symbols
6436 @item show multiple-symbols
6437 Show the current value of the @code{multiple-symbols} setting.
6441 @section Program Variables
6443 The most common kind of expression to use is the name of a variable
6446 Variables in expressions are understood in the selected stack frame
6447 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6451 global (or file-static)
6458 visible according to the scope rules of the
6459 programming language from the point of execution in that frame
6462 @noindent This means that in the function
6477 you can examine and use the variable @code{a} whenever your program is
6478 executing within the function @code{foo}, but you can only use or
6479 examine the variable @code{b} while your program is executing inside
6480 the block where @code{b} is declared.
6482 @cindex variable name conflict
6483 There is an exception: you can refer to a variable or function whose
6484 scope is a single source file even if the current execution point is not
6485 in this file. But it is possible to have more than one such variable or
6486 function with the same name (in different source files). If that
6487 happens, referring to that name has unpredictable effects. If you wish,
6488 you can specify a static variable in a particular function or file,
6489 using the colon-colon (@code{::}) notation:
6491 @cindex colon-colon, context for variables/functions
6493 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6494 @cindex @code{::}, context for variables/functions
6497 @var{file}::@var{variable}
6498 @var{function}::@var{variable}
6502 Here @var{file} or @var{function} is the name of the context for the
6503 static @var{variable}. In the case of file names, you can use quotes to
6504 make sure @value{GDBN} parses the file name as a single word---for example,
6505 to print a global value of @code{x} defined in @file{f2.c}:
6508 (@value{GDBP}) p 'f2.c'::x
6511 @cindex C@t{++} scope resolution
6512 This use of @samp{::} is very rarely in conflict with the very similar
6513 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6514 scope resolution operator in @value{GDBN} expressions.
6515 @c FIXME: Um, so what happens in one of those rare cases where it's in
6518 @cindex wrong values
6519 @cindex variable values, wrong
6520 @cindex function entry/exit, wrong values of variables
6521 @cindex optimized code, wrong values of variables
6523 @emph{Warning:} Occasionally, a local variable may appear to have the
6524 wrong value at certain points in a function---just after entry to a new
6525 scope, and just before exit.
6527 You may see this problem when you are stepping by machine instructions.
6528 This is because, on most machines, it takes more than one instruction to
6529 set up a stack frame (including local variable definitions); if you are
6530 stepping by machine instructions, variables may appear to have the wrong
6531 values until the stack frame is completely built. On exit, it usually
6532 also takes more than one machine instruction to destroy a stack frame;
6533 after you begin stepping through that group of instructions, local
6534 variable definitions may be gone.
6536 This may also happen when the compiler does significant optimizations.
6537 To be sure of always seeing accurate values, turn off all optimization
6540 @cindex ``No symbol "foo" in current context''
6541 Another possible effect of compiler optimizations is to optimize
6542 unused variables out of existence, or assign variables to registers (as
6543 opposed to memory addresses). Depending on the support for such cases
6544 offered by the debug info format used by the compiler, @value{GDBN}
6545 might not be able to display values for such local variables. If that
6546 happens, @value{GDBN} will print a message like this:
6549 No symbol "foo" in current context.
6552 To solve such problems, either recompile without optimizations, or use a
6553 different debug info format, if the compiler supports several such
6554 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6555 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6556 produces debug info in a format that is superior to formats such as
6557 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6558 an effective form for debug info. @xref{Debugging Options,,Options
6559 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6560 Compiler Collection (GCC)}.
6561 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6562 that are best suited to C@t{++} programs.
6564 If you ask to print an object whose contents are unknown to
6565 @value{GDBN}, e.g., because its data type is not completely specified
6566 by the debug information, @value{GDBN} will say @samp{<incomplete
6567 type>}. @xref{Symbols, incomplete type}, for more about this.
6569 Strings are identified as arrays of @code{char} values without specified
6570 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6571 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6572 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6573 defines literal string type @code{"char"} as @code{char} without a sign.
6578 signed char var1[] = "A";
6581 You get during debugging
6586 $2 = @{65 'A', 0 '\0'@}
6590 @section Artificial Arrays
6592 @cindex artificial array
6594 @kindex @@@r{, referencing memory as an array}
6595 It is often useful to print out several successive objects of the
6596 same type in memory; a section of an array, or an array of
6597 dynamically determined size for which only a pointer exists in the
6600 You can do this by referring to a contiguous span of memory as an
6601 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6602 operand of @samp{@@} should be the first element of the desired array
6603 and be an individual object. The right operand should be the desired length
6604 of the array. The result is an array value whose elements are all of
6605 the type of the left argument. The first element is actually the left
6606 argument; the second element comes from bytes of memory immediately
6607 following those that hold the first element, and so on. Here is an
6608 example. If a program says
6611 int *array = (int *) malloc (len * sizeof (int));
6615 you can print the contents of @code{array} with
6621 The left operand of @samp{@@} must reside in memory. Array values made
6622 with @samp{@@} in this way behave just like other arrays in terms of
6623 subscripting, and are coerced to pointers when used in expressions.
6624 Artificial arrays most often appear in expressions via the value history
6625 (@pxref{Value History, ,Value History}), after printing one out.
6627 Another way to create an artificial array is to use a cast.
6628 This re-interprets a value as if it were an array.
6629 The value need not be in memory:
6631 (@value{GDBP}) p/x (short[2])0x12345678
6632 $1 = @{0x1234, 0x5678@}
6635 As a convenience, if you leave the array length out (as in
6636 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6637 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6639 (@value{GDBP}) p/x (short[])0x12345678
6640 $2 = @{0x1234, 0x5678@}
6643 Sometimes the artificial array mechanism is not quite enough; in
6644 moderately complex data structures, the elements of interest may not
6645 actually be adjacent---for example, if you are interested in the values
6646 of pointers in an array. One useful work-around in this situation is
6647 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6648 Variables}) as a counter in an expression that prints the first
6649 interesting value, and then repeat that expression via @key{RET}. For
6650 instance, suppose you have an array @code{dtab} of pointers to
6651 structures, and you are interested in the values of a field @code{fv}
6652 in each structure. Here is an example of what you might type:
6662 @node Output Formats
6663 @section Output Formats
6665 @cindex formatted output
6666 @cindex output formats
6667 By default, @value{GDBN} prints a value according to its data type. Sometimes
6668 this is not what you want. For example, you might want to print a number
6669 in hex, or a pointer in decimal. Or you might want to view data in memory
6670 at a certain address as a character string or as an instruction. To do
6671 these things, specify an @dfn{output format} when you print a value.
6673 The simplest use of output formats is to say how to print a value
6674 already computed. This is done by starting the arguments of the
6675 @code{print} command with a slash and a format letter. The format
6676 letters supported are:
6680 Regard the bits of the value as an integer, and print the integer in
6684 Print as integer in signed decimal.
6687 Print as integer in unsigned decimal.
6690 Print as integer in octal.
6693 Print as integer in binary. The letter @samp{t} stands for ``two''.
6694 @footnote{@samp{b} cannot be used because these format letters are also
6695 used with the @code{x} command, where @samp{b} stands for ``byte'';
6696 see @ref{Memory,,Examining Memory}.}
6699 @cindex unknown address, locating
6700 @cindex locate address
6701 Print as an address, both absolute in hexadecimal and as an offset from
6702 the nearest preceding symbol. You can use this format used to discover
6703 where (in what function) an unknown address is located:
6706 (@value{GDBP}) p/a 0x54320
6707 $3 = 0x54320 <_initialize_vx+396>
6711 The command @code{info symbol 0x54320} yields similar results.
6712 @xref{Symbols, info symbol}.
6715 Regard as an integer and print it as a character constant. This
6716 prints both the numerical value and its character representation. The
6717 character representation is replaced with the octal escape @samp{\nnn}
6718 for characters outside the 7-bit @sc{ascii} range.
6720 Without this format, @value{GDBN} displays @code{char},
6721 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6722 constants. Single-byte members of vectors are displayed as integer
6726 Regard the bits of the value as a floating point number and print
6727 using typical floating point syntax.
6730 @cindex printing strings
6731 @cindex printing byte arrays
6732 Regard as a string, if possible. With this format, pointers to single-byte
6733 data are displayed as null-terminated strings and arrays of single-byte data
6734 are displayed as fixed-length strings. Other values are displayed in their
6737 Without this format, @value{GDBN} displays pointers to and arrays of
6738 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6739 strings. Single-byte members of a vector are displayed as an integer
6743 For example, to print the program counter in hex (@pxref{Registers}), type
6750 Note that no space is required before the slash; this is because command
6751 names in @value{GDBN} cannot contain a slash.
6753 To reprint the last value in the value history with a different format,
6754 you can use the @code{print} command with just a format and no
6755 expression. For example, @samp{p/x} reprints the last value in hex.
6758 @section Examining Memory
6760 You can use the command @code{x} (for ``examine'') to examine memory in
6761 any of several formats, independently of your program's data types.
6763 @cindex examining memory
6765 @kindex x @r{(examine memory)}
6766 @item x/@var{nfu} @var{addr}
6769 Use the @code{x} command to examine memory.
6772 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6773 much memory to display and how to format it; @var{addr} is an
6774 expression giving the address where you want to start displaying memory.
6775 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6776 Several commands set convenient defaults for @var{addr}.
6779 @item @var{n}, the repeat count
6780 The repeat count is a decimal integer; the default is 1. It specifies
6781 how much memory (counting by units @var{u}) to display.
6782 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6785 @item @var{f}, the display format
6786 The display format is one of the formats used by @code{print}
6787 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6788 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6789 The default is @samp{x} (hexadecimal) initially. The default changes
6790 each time you use either @code{x} or @code{print}.
6792 @item @var{u}, the unit size
6793 The unit size is any of
6799 Halfwords (two bytes).
6801 Words (four bytes). This is the initial default.
6803 Giant words (eight bytes).
6806 Each time you specify a unit size with @code{x}, that size becomes the
6807 default unit the next time you use @code{x}. (For the @samp{s} and
6808 @samp{i} formats, the unit size is ignored and is normally not written.)
6810 @item @var{addr}, starting display address
6811 @var{addr} is the address where you want @value{GDBN} to begin displaying
6812 memory. The expression need not have a pointer value (though it may);
6813 it is always interpreted as an integer address of a byte of memory.
6814 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6815 @var{addr} is usually just after the last address examined---but several
6816 other commands also set the default address: @code{info breakpoints} (to
6817 the address of the last breakpoint listed), @code{info line} (to the
6818 starting address of a line), and @code{print} (if you use it to display
6819 a value from memory).
6822 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6823 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6824 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6825 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6826 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6828 Since the letters indicating unit sizes are all distinct from the
6829 letters specifying output formats, you do not have to remember whether
6830 unit size or format comes first; either order works. The output
6831 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6832 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6834 Even though the unit size @var{u} is ignored for the formats @samp{s}
6835 and @samp{i}, you might still want to use a count @var{n}; for example,
6836 @samp{3i} specifies that you want to see three machine instructions,
6837 including any operands. For convenience, especially when used with
6838 the @code{display} command, the @samp{i} format also prints branch delay
6839 slot instructions, if any, beyond the count specified, which immediately
6840 follow the last instruction that is within the count. The command
6841 @code{disassemble} gives an alternative way of inspecting machine
6842 instructions; see @ref{Machine Code,,Source and Machine Code}.
6844 All the defaults for the arguments to @code{x} are designed to make it
6845 easy to continue scanning memory with minimal specifications each time
6846 you use @code{x}. For example, after you have inspected three machine
6847 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6848 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6849 the repeat count @var{n} is used again; the other arguments default as
6850 for successive uses of @code{x}.
6852 @cindex @code{$_}, @code{$__}, and value history
6853 The addresses and contents printed by the @code{x} command are not saved
6854 in the value history because there is often too much of them and they
6855 would get in the way. Instead, @value{GDBN} makes these values available for
6856 subsequent use in expressions as values of the convenience variables
6857 @code{$_} and @code{$__}. After an @code{x} command, the last address
6858 examined is available for use in expressions in the convenience variable
6859 @code{$_}. The contents of that address, as examined, are available in
6860 the convenience variable @code{$__}.
6862 If the @code{x} command has a repeat count, the address and contents saved
6863 are from the last memory unit printed; this is not the same as the last
6864 address printed if several units were printed on the last line of output.
6866 @cindex remote memory comparison
6867 @cindex verify remote memory image
6868 When you are debugging a program running on a remote target machine
6869 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6870 remote machine's memory against the executable file you downloaded to
6871 the target. The @code{compare-sections} command is provided for such
6875 @kindex compare-sections
6876 @item compare-sections @r{[}@var{section-name}@r{]}
6877 Compare the data of a loadable section @var{section-name} in the
6878 executable file of the program being debugged with the same section in
6879 the remote machine's memory, and report any mismatches. With no
6880 arguments, compares all loadable sections. This command's
6881 availability depends on the target's support for the @code{"qCRC"}
6886 @section Automatic Display
6887 @cindex automatic display
6888 @cindex display of expressions
6890 If you find that you want to print the value of an expression frequently
6891 (to see how it changes), you might want to add it to the @dfn{automatic
6892 display list} so that @value{GDBN} prints its value each time your program stops.
6893 Each expression added to the list is given a number to identify it;
6894 to remove an expression from the list, you specify that number.
6895 The automatic display looks like this:
6899 3: bar[5] = (struct hack *) 0x3804
6903 This display shows item numbers, expressions and their current values. As with
6904 displays you request manually using @code{x} or @code{print}, you can
6905 specify the output format you prefer; in fact, @code{display} decides
6906 whether to use @code{print} or @code{x} depending your format
6907 specification---it uses @code{x} if you specify either the @samp{i}
6908 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6912 @item display @var{expr}
6913 Add the expression @var{expr} to the list of expressions to display
6914 each time your program stops. @xref{Expressions, ,Expressions}.
6916 @code{display} does not repeat if you press @key{RET} again after using it.
6918 @item display/@var{fmt} @var{expr}
6919 For @var{fmt} specifying only a display format and not a size or
6920 count, add the expression @var{expr} to the auto-display list but
6921 arrange to display it each time in the specified format @var{fmt}.
6922 @xref{Output Formats,,Output Formats}.
6924 @item display/@var{fmt} @var{addr}
6925 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6926 number of units, add the expression @var{addr} as a memory address to
6927 be examined each time your program stops. Examining means in effect
6928 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6931 For example, @samp{display/i $pc} can be helpful, to see the machine
6932 instruction about to be executed each time execution stops (@samp{$pc}
6933 is a common name for the program counter; @pxref{Registers, ,Registers}).
6936 @kindex delete display
6938 @item undisplay @var{dnums}@dots{}
6939 @itemx delete display @var{dnums}@dots{}
6940 Remove item numbers @var{dnums} from the list of expressions to display.
6942 @code{undisplay} does not repeat if you press @key{RET} after using it.
6943 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6945 @kindex disable display
6946 @item disable display @var{dnums}@dots{}
6947 Disable the display of item numbers @var{dnums}. A disabled display
6948 item is not printed automatically, but is not forgotten. It may be
6949 enabled again later.
6951 @kindex enable display
6952 @item enable display @var{dnums}@dots{}
6953 Enable display of item numbers @var{dnums}. It becomes effective once
6954 again in auto display of its expression, until you specify otherwise.
6957 Display the current values of the expressions on the list, just as is
6958 done when your program stops.
6960 @kindex info display
6962 Print the list of expressions previously set up to display
6963 automatically, each one with its item number, but without showing the
6964 values. This includes disabled expressions, which are marked as such.
6965 It also includes expressions which would not be displayed right now
6966 because they refer to automatic variables not currently available.
6969 @cindex display disabled out of scope
6970 If a display expression refers to local variables, then it does not make
6971 sense outside the lexical context for which it was set up. Such an
6972 expression is disabled when execution enters a context where one of its
6973 variables is not defined. For example, if you give the command
6974 @code{display last_char} while inside a function with an argument
6975 @code{last_char}, @value{GDBN} displays this argument while your program
6976 continues to stop inside that function. When it stops elsewhere---where
6977 there is no variable @code{last_char}---the display is disabled
6978 automatically. The next time your program stops where @code{last_char}
6979 is meaningful, you can enable the display expression once again.
6981 @node Print Settings
6982 @section Print Settings
6984 @cindex format options
6985 @cindex print settings
6986 @value{GDBN} provides the following ways to control how arrays, structures,
6987 and symbols are printed.
6990 These settings are useful for debugging programs in any language:
6994 @item set print address
6995 @itemx set print address on
6996 @cindex print/don't print memory addresses
6997 @value{GDBN} prints memory addresses showing the location of stack
6998 traces, structure values, pointer values, breakpoints, and so forth,
6999 even when it also displays the contents of those addresses. The default
7000 is @code{on}. For example, this is what a stack frame display looks like with
7001 @code{set print address on}:
7006 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7008 530 if (lquote != def_lquote)
7012 @item set print address off
7013 Do not print addresses when displaying their contents. For example,
7014 this is the same stack frame displayed with @code{set print address off}:
7018 (@value{GDBP}) set print addr off
7020 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7021 530 if (lquote != def_lquote)
7025 You can use @samp{set print address off} to eliminate all machine
7026 dependent displays from the @value{GDBN} interface. For example, with
7027 @code{print address off}, you should get the same text for backtraces on
7028 all machines---whether or not they involve pointer arguments.
7031 @item show print address
7032 Show whether or not addresses are to be printed.
7035 When @value{GDBN} prints a symbolic address, it normally prints the
7036 closest earlier symbol plus an offset. If that symbol does not uniquely
7037 identify the address (for example, it is a name whose scope is a single
7038 source file), you may need to clarify. One way to do this is with
7039 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7040 you can set @value{GDBN} to print the source file and line number when
7041 it prints a symbolic address:
7044 @item set print symbol-filename on
7045 @cindex source file and line of a symbol
7046 @cindex symbol, source file and line
7047 Tell @value{GDBN} to print the source file name and line number of a
7048 symbol in the symbolic form of an address.
7050 @item set print symbol-filename off
7051 Do not print source file name and line number of a symbol. This is the
7054 @item show print symbol-filename
7055 Show whether or not @value{GDBN} will print the source file name and
7056 line number of a symbol in the symbolic form of an address.
7059 Another situation where it is helpful to show symbol filenames and line
7060 numbers is when disassembling code; @value{GDBN} shows you the line
7061 number and source file that corresponds to each instruction.
7063 Also, you may wish to see the symbolic form only if the address being
7064 printed is reasonably close to the closest earlier symbol:
7067 @item set print max-symbolic-offset @var{max-offset}
7068 @cindex maximum value for offset of closest symbol
7069 Tell @value{GDBN} to only display the symbolic form of an address if the
7070 offset between the closest earlier symbol and the address is less than
7071 @var{max-offset}. The default is 0, which tells @value{GDBN}
7072 to always print the symbolic form of an address if any symbol precedes it.
7074 @item show print max-symbolic-offset
7075 Ask how large the maximum offset is that @value{GDBN} prints in a
7079 @cindex wild pointer, interpreting
7080 @cindex pointer, finding referent
7081 If you have a pointer and you are not sure where it points, try
7082 @samp{set print symbol-filename on}. Then you can determine the name
7083 and source file location of the variable where it points, using
7084 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7085 For example, here @value{GDBN} shows that a variable @code{ptt} points
7086 at another variable @code{t}, defined in @file{hi2.c}:
7089 (@value{GDBP}) set print symbol-filename on
7090 (@value{GDBP}) p/a ptt
7091 $4 = 0xe008 <t in hi2.c>
7095 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7096 does not show the symbol name and filename of the referent, even with
7097 the appropriate @code{set print} options turned on.
7100 Other settings control how different kinds of objects are printed:
7103 @item set print array
7104 @itemx set print array on
7105 @cindex pretty print arrays
7106 Pretty print arrays. This format is more convenient to read,
7107 but uses more space. The default is off.
7109 @item set print array off
7110 Return to compressed format for arrays.
7112 @item show print array
7113 Show whether compressed or pretty format is selected for displaying
7116 @cindex print array indexes
7117 @item set print array-indexes
7118 @itemx set print array-indexes on
7119 Print the index of each element when displaying arrays. May be more
7120 convenient to locate a given element in the array or quickly find the
7121 index of a given element in that printed array. The default is off.
7123 @item set print array-indexes off
7124 Stop printing element indexes when displaying arrays.
7126 @item show print array-indexes
7127 Show whether the index of each element is printed when displaying
7130 @item set print elements @var{number-of-elements}
7131 @cindex number of array elements to print
7132 @cindex limit on number of printed array elements
7133 Set a limit on how many elements of an array @value{GDBN} will print.
7134 If @value{GDBN} is printing a large array, it stops printing after it has
7135 printed the number of elements set by the @code{set print elements} command.
7136 This limit also applies to the display of strings.
7137 When @value{GDBN} starts, this limit is set to 200.
7138 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7140 @item show print elements
7141 Display the number of elements of a large array that @value{GDBN} will print.
7142 If the number is 0, then the printing is unlimited.
7144 @item set print frame-arguments @var{value}
7145 @kindex set print frame-arguments
7146 @cindex printing frame argument values
7147 @cindex print all frame argument values
7148 @cindex print frame argument values for scalars only
7149 @cindex do not print frame argument values
7150 This command allows to control how the values of arguments are printed
7151 when the debugger prints a frame (@pxref{Frames}). The possible
7156 The values of all arguments are printed.
7159 Print the value of an argument only if it is a scalar. The value of more
7160 complex arguments such as arrays, structures, unions, etc, is replaced
7161 by @code{@dots{}}. This is the default. Here is an example where
7162 only scalar arguments are shown:
7165 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7170 None of the argument values are printed. Instead, the value of each argument
7171 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7174 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7179 By default, only scalar arguments are printed. This command can be used
7180 to configure the debugger to print the value of all arguments, regardless
7181 of their type. However, it is often advantageous to not print the value
7182 of more complex parameters. For instance, it reduces the amount of
7183 information printed in each frame, making the backtrace more readable.
7184 Also, it improves performance when displaying Ada frames, because
7185 the computation of large arguments can sometimes be CPU-intensive,
7186 especially in large applications. Setting @code{print frame-arguments}
7187 to @code{scalars} (the default) or @code{none} avoids this computation,
7188 thus speeding up the display of each Ada frame.
7190 @item show print frame-arguments
7191 Show how the value of arguments should be displayed when printing a frame.
7193 @item set print repeats
7194 @cindex repeated array elements
7195 Set the threshold for suppressing display of repeated array
7196 elements. When the number of consecutive identical elements of an
7197 array exceeds the threshold, @value{GDBN} prints the string
7198 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7199 identical repetitions, instead of displaying the identical elements
7200 themselves. Setting the threshold to zero will cause all elements to
7201 be individually printed. The default threshold is 10.
7203 @item show print repeats
7204 Display the current threshold for printing repeated identical
7207 @item set print null-stop
7208 @cindex @sc{null} elements in arrays
7209 Cause @value{GDBN} to stop printing the characters of an array when the first
7210 @sc{null} is encountered. This is useful when large arrays actually
7211 contain only short strings.
7214 @item show print null-stop
7215 Show whether @value{GDBN} stops printing an array on the first
7216 @sc{null} character.
7218 @item set print pretty on
7219 @cindex print structures in indented form
7220 @cindex indentation in structure display
7221 Cause @value{GDBN} to print structures in an indented format with one member
7222 per line, like this:
7237 @item set print pretty off
7238 Cause @value{GDBN} to print structures in a compact format, like this:
7242 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7243 meat = 0x54 "Pork"@}
7248 This is the default format.
7250 @item show print pretty
7251 Show which format @value{GDBN} is using to print structures.
7253 @item set print sevenbit-strings on
7254 @cindex eight-bit characters in strings
7255 @cindex octal escapes in strings
7256 Print using only seven-bit characters; if this option is set,
7257 @value{GDBN} displays any eight-bit characters (in strings or
7258 character values) using the notation @code{\}@var{nnn}. This setting is
7259 best if you are working in English (@sc{ascii}) and you use the
7260 high-order bit of characters as a marker or ``meta'' bit.
7262 @item set print sevenbit-strings off
7263 Print full eight-bit characters. This allows the use of more
7264 international character sets, and is the default.
7266 @item show print sevenbit-strings
7267 Show whether or not @value{GDBN} is printing only seven-bit characters.
7269 @item set print union on
7270 @cindex unions in structures, printing
7271 Tell @value{GDBN} to print unions which are contained in structures
7272 and other unions. This is the default setting.
7274 @item set print union off
7275 Tell @value{GDBN} not to print unions which are contained in
7276 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7279 @item show print union
7280 Ask @value{GDBN} whether or not it will print unions which are contained in
7281 structures and other unions.
7283 For example, given the declarations
7286 typedef enum @{Tree, Bug@} Species;
7287 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7288 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7299 struct thing foo = @{Tree, @{Acorn@}@};
7303 with @code{set print union on} in effect @samp{p foo} would print
7306 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7310 and with @code{set print union off} in effect it would print
7313 $1 = @{it = Tree, form = @{...@}@}
7317 @code{set print union} affects programs written in C-like languages
7323 These settings are of interest when debugging C@t{++} programs:
7326 @cindex demangling C@t{++} names
7327 @item set print demangle
7328 @itemx set print demangle on
7329 Print C@t{++} names in their source form rather than in the encoded
7330 (``mangled'') form passed to the assembler and linker for type-safe
7331 linkage. The default is on.
7333 @item show print demangle
7334 Show whether C@t{++} names are printed in mangled or demangled form.
7336 @item set print asm-demangle
7337 @itemx set print asm-demangle on
7338 Print C@t{++} names in their source form rather than their mangled form, even
7339 in assembler code printouts such as instruction disassemblies.
7342 @item show print asm-demangle
7343 Show whether C@t{++} names in assembly listings are printed in mangled
7346 @cindex C@t{++} symbol decoding style
7347 @cindex symbol decoding style, C@t{++}
7348 @kindex set demangle-style
7349 @item set demangle-style @var{style}
7350 Choose among several encoding schemes used by different compilers to
7351 represent C@t{++} names. The choices for @var{style} are currently:
7355 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7358 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7359 This is the default.
7362 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7365 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7368 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7369 @strong{Warning:} this setting alone is not sufficient to allow
7370 debugging @code{cfront}-generated executables. @value{GDBN} would
7371 require further enhancement to permit that.
7374 If you omit @var{style}, you will see a list of possible formats.
7376 @item show demangle-style
7377 Display the encoding style currently in use for decoding C@t{++} symbols.
7379 @item set print object
7380 @itemx set print object on
7381 @cindex derived type of an object, printing
7382 @cindex display derived types
7383 When displaying a pointer to an object, identify the @emph{actual}
7384 (derived) type of the object rather than the @emph{declared} type, using
7385 the virtual function table.
7387 @item set print object off
7388 Display only the declared type of objects, without reference to the
7389 virtual function table. This is the default setting.
7391 @item show print object
7392 Show whether actual, or declared, object types are displayed.
7394 @item set print static-members
7395 @itemx set print static-members on
7396 @cindex static members of C@t{++} objects
7397 Print static members when displaying a C@t{++} object. The default is on.
7399 @item set print static-members off
7400 Do not print static members when displaying a C@t{++} object.
7402 @item show print static-members
7403 Show whether C@t{++} static members are printed or not.
7405 @item set print pascal_static-members
7406 @itemx set print pascal_static-members on
7407 @cindex static members of Pascal objects
7408 @cindex Pascal objects, static members display
7409 Print static members when displaying a Pascal object. The default is on.
7411 @item set print pascal_static-members off
7412 Do not print static members when displaying a Pascal object.
7414 @item show print pascal_static-members
7415 Show whether Pascal static members are printed or not.
7417 @c These don't work with HP ANSI C++ yet.
7418 @item set print vtbl
7419 @itemx set print vtbl on
7420 @cindex pretty print C@t{++} virtual function tables
7421 @cindex virtual functions (C@t{++}) display
7422 @cindex VTBL display
7423 Pretty print C@t{++} virtual function tables. The default is off.
7424 (The @code{vtbl} commands do not work on programs compiled with the HP
7425 ANSI C@t{++} compiler (@code{aCC}).)
7427 @item set print vtbl off
7428 Do not pretty print C@t{++} virtual function tables.
7430 @item show print vtbl
7431 Show whether C@t{++} virtual function tables are pretty printed, or not.
7435 @section Value History
7437 @cindex value history
7438 @cindex history of values printed by @value{GDBN}
7439 Values printed by the @code{print} command are saved in the @value{GDBN}
7440 @dfn{value history}. This allows you to refer to them in other expressions.
7441 Values are kept until the symbol table is re-read or discarded
7442 (for example with the @code{file} or @code{symbol-file} commands).
7443 When the symbol table changes, the value history is discarded,
7444 since the values may contain pointers back to the types defined in the
7449 @cindex history number
7450 The values printed are given @dfn{history numbers} by which you can
7451 refer to them. These are successive integers starting with one.
7452 @code{print} shows you the history number assigned to a value by
7453 printing @samp{$@var{num} = } before the value; here @var{num} is the
7456 To refer to any previous value, use @samp{$} followed by the value's
7457 history number. The way @code{print} labels its output is designed to
7458 remind you of this. Just @code{$} refers to the most recent value in
7459 the history, and @code{$$} refers to the value before that.
7460 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7461 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7462 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7464 For example, suppose you have just printed a pointer to a structure and
7465 want to see the contents of the structure. It suffices to type
7471 If you have a chain of structures where the component @code{next} points
7472 to the next one, you can print the contents of the next one with this:
7479 You can print successive links in the chain by repeating this
7480 command---which you can do by just typing @key{RET}.
7482 Note that the history records values, not expressions. If the value of
7483 @code{x} is 4 and you type these commands:
7491 then the value recorded in the value history by the @code{print} command
7492 remains 4 even though the value of @code{x} has changed.
7497 Print the last ten values in the value history, with their item numbers.
7498 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7499 values} does not change the history.
7501 @item show values @var{n}
7502 Print ten history values centered on history item number @var{n}.
7505 Print ten history values just after the values last printed. If no more
7506 values are available, @code{show values +} produces no display.
7509 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7510 same effect as @samp{show values +}.
7512 @node Convenience Vars
7513 @section Convenience Variables
7515 @cindex convenience variables
7516 @cindex user-defined variables
7517 @value{GDBN} provides @dfn{convenience variables} that you can use within
7518 @value{GDBN} to hold on to a value and refer to it later. These variables
7519 exist entirely within @value{GDBN}; they are not part of your program, and
7520 setting a convenience variable has no direct effect on further execution
7521 of your program. That is why you can use them freely.
7523 Convenience variables are prefixed with @samp{$}. Any name preceded by
7524 @samp{$} can be used for a convenience variable, unless it is one of
7525 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7526 (Value history references, in contrast, are @emph{numbers} preceded
7527 by @samp{$}. @xref{Value History, ,Value History}.)
7529 You can save a value in a convenience variable with an assignment
7530 expression, just as you would set a variable in your program.
7534 set $foo = *object_ptr
7538 would save in @code{$foo} the value contained in the object pointed to by
7541 Using a convenience variable for the first time creates it, but its
7542 value is @code{void} until you assign a new value. You can alter the
7543 value with another assignment at any time.
7545 Convenience variables have no fixed types. You can assign a convenience
7546 variable any type of value, including structures and arrays, even if
7547 that variable already has a value of a different type. The convenience
7548 variable, when used as an expression, has the type of its current value.
7551 @kindex show convenience
7552 @cindex show all user variables
7553 @item show convenience
7554 Print a list of convenience variables used so far, and their values.
7555 Abbreviated @code{show conv}.
7557 @kindex init-if-undefined
7558 @cindex convenience variables, initializing
7559 @item init-if-undefined $@var{variable} = @var{expression}
7560 Set a convenience variable if it has not already been set. This is useful
7561 for user-defined commands that keep some state. It is similar, in concept,
7562 to using local static variables with initializers in C (except that
7563 convenience variables are global). It can also be used to allow users to
7564 override default values used in a command script.
7566 If the variable is already defined then the expression is not evaluated so
7567 any side-effects do not occur.
7570 One of the ways to use a convenience variable is as a counter to be
7571 incremented or a pointer to be advanced. For example, to print
7572 a field from successive elements of an array of structures:
7576 print bar[$i++]->contents
7580 Repeat that command by typing @key{RET}.
7582 Some convenience variables are created automatically by @value{GDBN} and given
7583 values likely to be useful.
7586 @vindex $_@r{, convenience variable}
7588 The variable @code{$_} is automatically set by the @code{x} command to
7589 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7590 commands which provide a default address for @code{x} to examine also
7591 set @code{$_} to that address; these commands include @code{info line}
7592 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7593 except when set by the @code{x} command, in which case it is a pointer
7594 to the type of @code{$__}.
7596 @vindex $__@r{, convenience variable}
7598 The variable @code{$__} is automatically set by the @code{x} command
7599 to the value found in the last address examined. Its type is chosen
7600 to match the format in which the data was printed.
7603 @vindex $_exitcode@r{, convenience variable}
7604 The variable @code{$_exitcode} is automatically set to the exit code when
7605 the program being debugged terminates.
7608 @vindex $_siginfo@r{, convenience variable}
7609 The variable @code{$_siginfo} is bound to extra signal information
7610 inspection (@pxref{extra signal information}).
7613 On HP-UX systems, if you refer to a function or variable name that
7614 begins with a dollar sign, @value{GDBN} searches for a user or system
7615 name first, before it searches for a convenience variable.
7617 @cindex convenience functions
7618 @value{GDBN} also supplies some @dfn{convenience functions}. These
7619 have a syntax similar to convenience variables. A convenience
7620 function can be used in an expression just like an ordinary function;
7621 however, a convenience function is implemented internally to
7626 @kindex help function
7627 @cindex show all convenience functions
7628 Print a list of all convenience functions.
7635 You can refer to machine register contents, in expressions, as variables
7636 with names starting with @samp{$}. The names of registers are different
7637 for each machine; use @code{info registers} to see the names used on
7641 @kindex info registers
7642 @item info registers
7643 Print the names and values of all registers except floating-point
7644 and vector registers (in the selected stack frame).
7646 @kindex info all-registers
7647 @cindex floating point registers
7648 @item info all-registers
7649 Print the names and values of all registers, including floating-point
7650 and vector registers (in the selected stack frame).
7652 @item info registers @var{regname} @dots{}
7653 Print the @dfn{relativized} value of each specified register @var{regname}.
7654 As discussed in detail below, register values are normally relative to
7655 the selected stack frame. @var{regname} may be any register name valid on
7656 the machine you are using, with or without the initial @samp{$}.
7659 @cindex stack pointer register
7660 @cindex program counter register
7661 @cindex process status register
7662 @cindex frame pointer register
7663 @cindex standard registers
7664 @value{GDBN} has four ``standard'' register names that are available (in
7665 expressions) on most machines---whenever they do not conflict with an
7666 architecture's canonical mnemonics for registers. The register names
7667 @code{$pc} and @code{$sp} are used for the program counter register and
7668 the stack pointer. @code{$fp} is used for a register that contains a
7669 pointer to the current stack frame, and @code{$ps} is used for a
7670 register that contains the processor status. For example,
7671 you could print the program counter in hex with
7678 or print the instruction to be executed next with
7685 or add four to the stack pointer@footnote{This is a way of removing
7686 one word from the stack, on machines where stacks grow downward in
7687 memory (most machines, nowadays). This assumes that the innermost
7688 stack frame is selected; setting @code{$sp} is not allowed when other
7689 stack frames are selected. To pop entire frames off the stack,
7690 regardless of machine architecture, use @code{return};
7691 see @ref{Returning, ,Returning from a Function}.} with
7697 Whenever possible, these four standard register names are available on
7698 your machine even though the machine has different canonical mnemonics,
7699 so long as there is no conflict. The @code{info registers} command
7700 shows the canonical names. For example, on the SPARC, @code{info
7701 registers} displays the processor status register as @code{$psr} but you
7702 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7703 is an alias for the @sc{eflags} register.
7705 @value{GDBN} always considers the contents of an ordinary register as an
7706 integer when the register is examined in this way. Some machines have
7707 special registers which can hold nothing but floating point; these
7708 registers are considered to have floating point values. There is no way
7709 to refer to the contents of an ordinary register as floating point value
7710 (although you can @emph{print} it as a floating point value with
7711 @samp{print/f $@var{regname}}).
7713 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7714 means that the data format in which the register contents are saved by
7715 the operating system is not the same one that your program normally
7716 sees. For example, the registers of the 68881 floating point
7717 coprocessor are always saved in ``extended'' (raw) format, but all C
7718 programs expect to work with ``double'' (virtual) format. In such
7719 cases, @value{GDBN} normally works with the virtual format only (the format
7720 that makes sense for your program), but the @code{info registers} command
7721 prints the data in both formats.
7723 @cindex SSE registers (x86)
7724 @cindex MMX registers (x86)
7725 Some machines have special registers whose contents can be interpreted
7726 in several different ways. For example, modern x86-based machines
7727 have SSE and MMX registers that can hold several values packed
7728 together in several different formats. @value{GDBN} refers to such
7729 registers in @code{struct} notation:
7732 (@value{GDBP}) print $xmm1
7734 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7735 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7736 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7737 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7738 v4_int32 = @{0, 20657912, 11, 13@},
7739 v2_int64 = @{88725056443645952, 55834574859@},
7740 uint128 = 0x0000000d0000000b013b36f800000000
7745 To set values of such registers, you need to tell @value{GDBN} which
7746 view of the register you wish to change, as if you were assigning
7747 value to a @code{struct} member:
7750 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7753 Normally, register values are relative to the selected stack frame
7754 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7755 value that the register would contain if all stack frames farther in
7756 were exited and their saved registers restored. In order to see the
7757 true contents of hardware registers, you must select the innermost
7758 frame (with @samp{frame 0}).
7760 However, @value{GDBN} must deduce where registers are saved, from the machine
7761 code generated by your compiler. If some registers are not saved, or if
7762 @value{GDBN} is unable to locate the saved registers, the selected stack
7763 frame makes no difference.
7765 @node Floating Point Hardware
7766 @section Floating Point Hardware
7767 @cindex floating point
7769 Depending on the configuration, @value{GDBN} may be able to give
7770 you more information about the status of the floating point hardware.
7775 Display hardware-dependent information about the floating
7776 point unit. The exact contents and layout vary depending on the
7777 floating point chip. Currently, @samp{info float} is supported on
7778 the ARM and x86 machines.
7782 @section Vector Unit
7785 Depending on the configuration, @value{GDBN} may be able to give you
7786 more information about the status of the vector unit.
7791 Display information about the vector unit. The exact contents and
7792 layout vary depending on the hardware.
7795 @node OS Information
7796 @section Operating System Auxiliary Information
7797 @cindex OS information
7799 @value{GDBN} provides interfaces to useful OS facilities that can help
7800 you debug your program.
7802 @cindex @code{ptrace} system call
7803 @cindex @code{struct user} contents
7804 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7805 machines), it interfaces with the inferior via the @code{ptrace}
7806 system call. The operating system creates a special sata structure,
7807 called @code{struct user}, for this interface. You can use the
7808 command @code{info udot} to display the contents of this data
7814 Display the contents of the @code{struct user} maintained by the OS
7815 kernel for the program being debugged. @value{GDBN} displays the
7816 contents of @code{struct user} as a list of hex numbers, similar to
7817 the @code{examine} command.
7820 @cindex auxiliary vector
7821 @cindex vector, auxiliary
7822 Some operating systems supply an @dfn{auxiliary vector} to programs at
7823 startup. This is akin to the arguments and environment that you
7824 specify for a program, but contains a system-dependent variety of
7825 binary values that tell system libraries important details about the
7826 hardware, operating system, and process. Each value's purpose is
7827 identified by an integer tag; the meanings are well-known but system-specific.
7828 Depending on the configuration and operating system facilities,
7829 @value{GDBN} may be able to show you this information. For remote
7830 targets, this functionality may further depend on the remote stub's
7831 support of the @samp{qXfer:auxv:read} packet, see
7832 @ref{qXfer auxiliary vector read}.
7837 Display the auxiliary vector of the inferior, which can be either a
7838 live process or a core dump file. @value{GDBN} prints each tag value
7839 numerically, and also shows names and text descriptions for recognized
7840 tags. Some values in the vector are numbers, some bit masks, and some
7841 pointers to strings or other data. @value{GDBN} displays each value in the
7842 most appropriate form for a recognized tag, and in hexadecimal for
7843 an unrecognized tag.
7846 On some targets, @value{GDBN} can access operating-system-specific information
7847 and display it to user, without interpretation. For remote targets,
7848 this functionality depends on the remote stub's support of the
7849 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7852 @kindex info os processes
7853 @item info os processes
7854 Display the list of processes on the target. For each process,
7855 @value{GDBN} prints the process identifier, the name of the user, and
7856 the command corresponding to the process.
7859 @node Memory Region Attributes
7860 @section Memory Region Attributes
7861 @cindex memory region attributes
7863 @dfn{Memory region attributes} allow you to describe special handling
7864 required by regions of your target's memory. @value{GDBN} uses
7865 attributes to determine whether to allow certain types of memory
7866 accesses; whether to use specific width accesses; and whether to cache
7867 target memory. By default the description of memory regions is
7868 fetched from the target (if the current target supports this), but the
7869 user can override the fetched regions.
7871 Defined memory regions can be individually enabled and disabled. When a
7872 memory region is disabled, @value{GDBN} uses the default attributes when
7873 accessing memory in that region. Similarly, if no memory regions have
7874 been defined, @value{GDBN} uses the default attributes when accessing
7877 When a memory region is defined, it is given a number to identify it;
7878 to enable, disable, or remove a memory region, you specify that number.
7882 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7883 Define a memory region bounded by @var{lower} and @var{upper} with
7884 attributes @var{attributes}@dots{}, and add it to the list of regions
7885 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7886 case: it is treated as the target's maximum memory address.
7887 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7890 Discard any user changes to the memory regions and use target-supplied
7891 regions, if available, or no regions if the target does not support.
7894 @item delete mem @var{nums}@dots{}
7895 Remove memory regions @var{nums}@dots{} from the list of regions
7896 monitored by @value{GDBN}.
7899 @item disable mem @var{nums}@dots{}
7900 Disable monitoring of memory regions @var{nums}@dots{}.
7901 A disabled memory region is not forgotten.
7902 It may be enabled again later.
7905 @item enable mem @var{nums}@dots{}
7906 Enable monitoring of memory regions @var{nums}@dots{}.
7910 Print a table of all defined memory regions, with the following columns
7914 @item Memory Region Number
7915 @item Enabled or Disabled.
7916 Enabled memory regions are marked with @samp{y}.
7917 Disabled memory regions are marked with @samp{n}.
7920 The address defining the inclusive lower bound of the memory region.
7923 The address defining the exclusive upper bound of the memory region.
7926 The list of attributes set for this memory region.
7931 @subsection Attributes
7933 @subsubsection Memory Access Mode
7934 The access mode attributes set whether @value{GDBN} may make read or
7935 write accesses to a memory region.
7937 While these attributes prevent @value{GDBN} from performing invalid
7938 memory accesses, they do nothing to prevent the target system, I/O DMA,
7939 etc.@: from accessing memory.
7943 Memory is read only.
7945 Memory is write only.
7947 Memory is read/write. This is the default.
7950 @subsubsection Memory Access Size
7951 The access size attribute tells @value{GDBN} to use specific sized
7952 accesses in the memory region. Often memory mapped device registers
7953 require specific sized accesses. If no access size attribute is
7954 specified, @value{GDBN} may use accesses of any size.
7958 Use 8 bit memory accesses.
7960 Use 16 bit memory accesses.
7962 Use 32 bit memory accesses.
7964 Use 64 bit memory accesses.
7967 @c @subsubsection Hardware/Software Breakpoints
7968 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7969 @c will use hardware or software breakpoints for the internal breakpoints
7970 @c used by the step, next, finish, until, etc. commands.
7974 @c Always use hardware breakpoints
7975 @c @item swbreak (default)
7978 @subsubsection Data Cache
7979 The data cache attributes set whether @value{GDBN} will cache target
7980 memory. While this generally improves performance by reducing debug
7981 protocol overhead, it can lead to incorrect results because @value{GDBN}
7982 does not know about volatile variables or memory mapped device
7987 Enable @value{GDBN} to cache target memory.
7989 Disable @value{GDBN} from caching target memory. This is the default.
7992 @subsection Memory Access Checking
7993 @value{GDBN} can be instructed to refuse accesses to memory that is
7994 not explicitly described. This can be useful if accessing such
7995 regions has undesired effects for a specific target, or to provide
7996 better error checking. The following commands control this behaviour.
7999 @kindex set mem inaccessible-by-default
8000 @item set mem inaccessible-by-default [on|off]
8001 If @code{on} is specified, make @value{GDBN} treat memory not
8002 explicitly described by the memory ranges as non-existent and refuse accesses
8003 to such memory. The checks are only performed if there's at least one
8004 memory range defined. If @code{off} is specified, make @value{GDBN}
8005 treat the memory not explicitly described by the memory ranges as RAM.
8006 The default value is @code{on}.
8007 @kindex show mem inaccessible-by-default
8008 @item show mem inaccessible-by-default
8009 Show the current handling of accesses to unknown memory.
8013 @c @subsubsection Memory Write Verification
8014 @c The memory write verification attributes set whether @value{GDBN}
8015 @c will re-reads data after each write to verify the write was successful.
8019 @c @item noverify (default)
8022 @node Dump/Restore Files
8023 @section Copy Between Memory and a File
8024 @cindex dump/restore files
8025 @cindex append data to a file
8026 @cindex dump data to a file
8027 @cindex restore data from a file
8029 You can use the commands @code{dump}, @code{append}, and
8030 @code{restore} to copy data between target memory and a file. The
8031 @code{dump} and @code{append} commands write data to a file, and the
8032 @code{restore} command reads data from a file back into the inferior's
8033 memory. Files may be in binary, Motorola S-record, Intel hex, or
8034 Tektronix Hex format; however, @value{GDBN} can only append to binary
8040 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8041 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8042 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8043 or the value of @var{expr}, to @var{filename} in the given format.
8045 The @var{format} parameter may be any one of:
8052 Motorola S-record format.
8054 Tektronix Hex format.
8057 @value{GDBN} uses the same definitions of these formats as the
8058 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8059 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8063 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8064 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8065 Append the contents of memory from @var{start_addr} to @var{end_addr},
8066 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8067 (@value{GDBN} can only append data to files in raw binary form.)
8070 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8071 Restore the contents of file @var{filename} into memory. The
8072 @code{restore} command can automatically recognize any known @sc{bfd}
8073 file format, except for raw binary. To restore a raw binary file you
8074 must specify the optional keyword @code{binary} after the filename.
8076 If @var{bias} is non-zero, its value will be added to the addresses
8077 contained in the file. Binary files always start at address zero, so
8078 they will be restored at address @var{bias}. Other bfd files have
8079 a built-in location; they will be restored at offset @var{bias}
8082 If @var{start} and/or @var{end} are non-zero, then only data between
8083 file offset @var{start} and file offset @var{end} will be restored.
8084 These offsets are relative to the addresses in the file, before
8085 the @var{bias} argument is applied.
8089 @node Core File Generation
8090 @section How to Produce a Core File from Your Program
8091 @cindex dump core from inferior
8093 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8094 image of a running process and its process status (register values
8095 etc.). Its primary use is post-mortem debugging of a program that
8096 crashed while it ran outside a debugger. A program that crashes
8097 automatically produces a core file, unless this feature is disabled by
8098 the user. @xref{Files}, for information on invoking @value{GDBN} in
8099 the post-mortem debugging mode.
8101 Occasionally, you may wish to produce a core file of the program you
8102 are debugging in order to preserve a snapshot of its state.
8103 @value{GDBN} has a special command for that.
8107 @kindex generate-core-file
8108 @item generate-core-file [@var{file}]
8109 @itemx gcore [@var{file}]
8110 Produce a core dump of the inferior process. The optional argument
8111 @var{file} specifies the file name where to put the core dump. If not
8112 specified, the file name defaults to @file{core.@var{pid}}, where
8113 @var{pid} is the inferior process ID.
8115 Note that this command is implemented only for some systems (as of
8116 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8119 @node Character Sets
8120 @section Character Sets
8121 @cindex character sets
8123 @cindex translating between character sets
8124 @cindex host character set
8125 @cindex target character set
8127 If the program you are debugging uses a different character set to
8128 represent characters and strings than the one @value{GDBN} uses itself,
8129 @value{GDBN} can automatically translate between the character sets for
8130 you. The character set @value{GDBN} uses we call the @dfn{host
8131 character set}; the one the inferior program uses we call the
8132 @dfn{target character set}.
8134 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8135 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8136 remote protocol (@pxref{Remote Debugging}) to debug a program
8137 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8138 then the host character set is Latin-1, and the target character set is
8139 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8140 target-charset EBCDIC-US}, then @value{GDBN} translates between
8141 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8142 character and string literals in expressions.
8144 @value{GDBN} has no way to automatically recognize which character set
8145 the inferior program uses; you must tell it, using the @code{set
8146 target-charset} command, described below.
8148 Here are the commands for controlling @value{GDBN}'s character set
8152 @item set target-charset @var{charset}
8153 @kindex set target-charset
8154 Set the current target character set to @var{charset}. To display the
8155 list of supported target character sets, type
8156 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8158 @item set host-charset @var{charset}
8159 @kindex set host-charset
8160 Set the current host character set to @var{charset}.
8162 By default, @value{GDBN} uses a host character set appropriate to the
8163 system it is running on; you can override that default using the
8164 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8165 automatically determine the appropriate host character set. In this
8166 case, @value{GDBN} uses @samp{UTF-8}.
8168 @value{GDBN} can only use certain character sets as its host character
8169 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8170 @value{GDBN} will list the host character sets it supports.
8172 @item set charset @var{charset}
8174 Set the current host and target character sets to @var{charset}. As
8175 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8176 @value{GDBN} will list the names of the character sets that can be used
8177 for both host and target.
8180 @kindex show charset
8181 Show the names of the current host and target character sets.
8183 @item show host-charset
8184 @kindex show host-charset
8185 Show the name of the current host character set.
8187 @item show target-charset
8188 @kindex show target-charset
8189 Show the name of the current target character set.
8191 @item set target-wide-charset @var{charset}
8192 @kindex set target-wide-charset
8193 Set the current target's wide character set to @var{charset}. This is
8194 the character set used by the target's @code{wchar_t} type. To
8195 display the list of supported wide character sets, type
8196 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8198 @item show target-wide-charset
8199 @kindex show target-wide-charset
8200 Show the name of the current target's wide character set.
8203 Here is an example of @value{GDBN}'s character set support in action.
8204 Assume that the following source code has been placed in the file
8205 @file{charset-test.c}:
8211 = @{72, 101, 108, 108, 111, 44, 32, 119,
8212 111, 114, 108, 100, 33, 10, 0@};
8213 char ibm1047_hello[]
8214 = @{200, 133, 147, 147, 150, 107, 64, 166,
8215 150, 153, 147, 132, 90, 37, 0@};
8219 printf ("Hello, world!\n");
8223 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8224 containing the string @samp{Hello, world!} followed by a newline,
8225 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8227 We compile the program, and invoke the debugger on it:
8230 $ gcc -g charset-test.c -o charset-test
8231 $ gdb -nw charset-test
8232 GNU gdb 2001-12-19-cvs
8233 Copyright 2001 Free Software Foundation, Inc.
8238 We can use the @code{show charset} command to see what character sets
8239 @value{GDBN} is currently using to interpret and display characters and
8243 (@value{GDBP}) show charset
8244 The current host and target character set is `ISO-8859-1'.
8248 For the sake of printing this manual, let's use @sc{ascii} as our
8249 initial character set:
8251 (@value{GDBP}) set charset ASCII
8252 (@value{GDBP}) show charset
8253 The current host and target character set is `ASCII'.
8257 Let's assume that @sc{ascii} is indeed the correct character set for our
8258 host system --- in other words, let's assume that if @value{GDBN} prints
8259 characters using the @sc{ascii} character set, our terminal will display
8260 them properly. Since our current target character set is also
8261 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8264 (@value{GDBP}) print ascii_hello
8265 $1 = 0x401698 "Hello, world!\n"
8266 (@value{GDBP}) print ascii_hello[0]
8271 @value{GDBN} uses the target character set for character and string
8272 literals you use in expressions:
8275 (@value{GDBP}) print '+'
8280 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8283 @value{GDBN} relies on the user to tell it which character set the
8284 target program uses. If we print @code{ibm1047_hello} while our target
8285 character set is still @sc{ascii}, we get jibberish:
8288 (@value{GDBP}) print ibm1047_hello
8289 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8290 (@value{GDBP}) print ibm1047_hello[0]
8295 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8296 @value{GDBN} tells us the character sets it supports:
8299 (@value{GDBP}) set target-charset
8300 ASCII EBCDIC-US IBM1047 ISO-8859-1
8301 (@value{GDBP}) set target-charset
8304 We can select @sc{ibm1047} as our target character set, and examine the
8305 program's strings again. Now the @sc{ascii} string is wrong, but
8306 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8307 target character set, @sc{ibm1047}, to the host character set,
8308 @sc{ascii}, and they display correctly:
8311 (@value{GDBP}) set target-charset IBM1047
8312 (@value{GDBP}) show charset
8313 The current host character set is `ASCII'.
8314 The current target character set is `IBM1047'.
8315 (@value{GDBP}) print ascii_hello
8316 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8317 (@value{GDBP}) print ascii_hello[0]
8319 (@value{GDBP}) print ibm1047_hello
8320 $8 = 0x4016a8 "Hello, world!\n"
8321 (@value{GDBP}) print ibm1047_hello[0]
8326 As above, @value{GDBN} uses the target character set for character and
8327 string literals you use in expressions:
8330 (@value{GDBP}) print '+'
8335 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8338 @node Caching Remote Data
8339 @section Caching Data of Remote Targets
8340 @cindex caching data of remote targets
8342 @value{GDBN} can cache data exchanged between the debugger and a
8343 remote target (@pxref{Remote Debugging}). Such caching generally improves
8344 performance, because it reduces the overhead of the remote protocol by
8345 bundling memory reads and writes into large chunks. Unfortunately,
8346 @value{GDBN} does not currently know anything about volatile
8347 registers, and thus data caching will produce incorrect results when
8348 volatile registers are in use.
8351 @kindex set remotecache
8352 @item set remotecache on
8353 @itemx set remotecache off
8354 Set caching state for remote targets. When @code{ON}, use data
8355 caching. By default, this option is @code{OFF}.
8357 @kindex show remotecache
8358 @item show remotecache
8359 Show the current state of data caching for remote targets.
8363 Print the information about the data cache performance. The
8364 information displayed includes: the dcache width and depth; and for
8365 each cache line, how many times it was referenced, and its data and
8366 state (invalid, dirty, valid). This command is useful for debugging
8367 the data cache operation.
8370 @node Searching Memory
8371 @section Search Memory
8372 @cindex searching memory
8374 Memory can be searched for a particular sequence of bytes with the
8375 @code{find} command.
8379 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8380 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8381 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8382 etc. The search begins at address @var{start_addr} and continues for either
8383 @var{len} bytes or through to @var{end_addr} inclusive.
8386 @var{s} and @var{n} are optional parameters.
8387 They may be specified in either order, apart or together.
8390 @item @var{s}, search query size
8391 The size of each search query value.
8397 halfwords (two bytes)
8401 giant words (eight bytes)
8404 All values are interpreted in the current language.
8405 This means, for example, that if the current source language is C/C@t{++}
8406 then searching for the string ``hello'' includes the trailing '\0'.
8408 If the value size is not specified, it is taken from the
8409 value's type in the current language.
8410 This is useful when one wants to specify the search
8411 pattern as a mixture of types.
8412 Note that this means, for example, that in the case of C-like languages
8413 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8414 which is typically four bytes.
8416 @item @var{n}, maximum number of finds
8417 The maximum number of matches to print. The default is to print all finds.
8420 You can use strings as search values. Quote them with double-quotes
8422 The string value is copied into the search pattern byte by byte,
8423 regardless of the endianness of the target and the size specification.
8425 The address of each match found is printed as well as a count of the
8426 number of matches found.
8428 The address of the last value found is stored in convenience variable
8430 A count of the number of matches is stored in @samp{$numfound}.
8432 For example, if stopped at the @code{printf} in this function:
8438 static char hello[] = "hello-hello";
8439 static struct @{ char c; short s; int i; @}
8440 __attribute__ ((packed)) mixed
8441 = @{ 'c', 0x1234, 0x87654321 @};
8442 printf ("%s\n", hello);
8447 you get during debugging:
8450 (gdb) find &hello[0], +sizeof(hello), "hello"
8451 0x804956d <hello.1620+6>
8453 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8454 0x8049567 <hello.1620>
8455 0x804956d <hello.1620+6>
8457 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8458 0x8049567 <hello.1620>
8460 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8461 0x8049560 <mixed.1625>
8463 (gdb) print $numfound
8466 $2 = (void *) 0x8049560
8470 @chapter C Preprocessor Macros
8472 Some languages, such as C and C@t{++}, provide a way to define and invoke
8473 ``preprocessor macros'' which expand into strings of tokens.
8474 @value{GDBN} can evaluate expressions containing macro invocations, show
8475 the result of macro expansion, and show a macro's definition, including
8476 where it was defined.
8478 You may need to compile your program specially to provide @value{GDBN}
8479 with information about preprocessor macros. Most compilers do not
8480 include macros in their debugging information, even when you compile
8481 with the @option{-g} flag. @xref{Compilation}.
8483 A program may define a macro at one point, remove that definition later,
8484 and then provide a different definition after that. Thus, at different
8485 points in the program, a macro may have different definitions, or have
8486 no definition at all. If there is a current stack frame, @value{GDBN}
8487 uses the macros in scope at that frame's source code line. Otherwise,
8488 @value{GDBN} uses the macros in scope at the current listing location;
8491 Whenever @value{GDBN} evaluates an expression, it always expands any
8492 macro invocations present in the expression. @value{GDBN} also provides
8493 the following commands for working with macros explicitly.
8497 @kindex macro expand
8498 @cindex macro expansion, showing the results of preprocessor
8499 @cindex preprocessor macro expansion, showing the results of
8500 @cindex expanding preprocessor macros
8501 @item macro expand @var{expression}
8502 @itemx macro exp @var{expression}
8503 Show the results of expanding all preprocessor macro invocations in
8504 @var{expression}. Since @value{GDBN} simply expands macros, but does
8505 not parse the result, @var{expression} need not be a valid expression;
8506 it can be any string of tokens.
8509 @item macro expand-once @var{expression}
8510 @itemx macro exp1 @var{expression}
8511 @cindex expand macro once
8512 @i{(This command is not yet implemented.)} Show the results of
8513 expanding those preprocessor macro invocations that appear explicitly in
8514 @var{expression}. Macro invocations appearing in that expansion are
8515 left unchanged. This command allows you to see the effect of a
8516 particular macro more clearly, without being confused by further
8517 expansions. Since @value{GDBN} simply expands macros, but does not
8518 parse the result, @var{expression} need not be a valid expression; it
8519 can be any string of tokens.
8522 @cindex macro definition, showing
8523 @cindex definition, showing a macro's
8524 @item info macro @var{macro}
8525 Show the definition of the macro named @var{macro}, and describe the
8526 source location or compiler command-line where that definition was established.
8528 @kindex macro define
8529 @cindex user-defined macros
8530 @cindex defining macros interactively
8531 @cindex macros, user-defined
8532 @item macro define @var{macro} @var{replacement-list}
8533 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8534 Introduce a definition for a preprocessor macro named @var{macro},
8535 invocations of which are replaced by the tokens given in
8536 @var{replacement-list}. The first form of this command defines an
8537 ``object-like'' macro, which takes no arguments; the second form
8538 defines a ``function-like'' macro, which takes the arguments given in
8541 A definition introduced by this command is in scope in every
8542 expression evaluated in @value{GDBN}, until it is removed with the
8543 @code{macro undef} command, described below. The definition overrides
8544 all definitions for @var{macro} present in the program being debugged,
8545 as well as any previous user-supplied definition.
8548 @item macro undef @var{macro}
8549 Remove any user-supplied definition for the macro named @var{macro}.
8550 This command only affects definitions provided with the @code{macro
8551 define} command, described above; it cannot remove definitions present
8552 in the program being debugged.
8556 List all the macros defined using the @code{macro define} command.
8559 @cindex macros, example of debugging with
8560 Here is a transcript showing the above commands in action. First, we
8561 show our source files:
8569 #define ADD(x) (M + x)
8574 printf ("Hello, world!\n");
8576 printf ("We're so creative.\n");
8578 printf ("Goodbye, world!\n");
8585 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8586 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8587 compiler includes information about preprocessor macros in the debugging
8591 $ gcc -gdwarf-2 -g3 sample.c -o sample
8595 Now, we start @value{GDBN} on our sample program:
8599 GNU gdb 2002-05-06-cvs
8600 Copyright 2002 Free Software Foundation, Inc.
8601 GDB is free software, @dots{}
8605 We can expand macros and examine their definitions, even when the
8606 program is not running. @value{GDBN} uses the current listing position
8607 to decide which macro definitions are in scope:
8610 (@value{GDBP}) list main
8613 5 #define ADD(x) (M + x)
8618 10 printf ("Hello, world!\n");
8620 12 printf ("We're so creative.\n");
8621 (@value{GDBP}) info macro ADD
8622 Defined at /home/jimb/gdb/macros/play/sample.c:5
8623 #define ADD(x) (M + x)
8624 (@value{GDBP}) info macro Q
8625 Defined at /home/jimb/gdb/macros/play/sample.h:1
8626 included at /home/jimb/gdb/macros/play/sample.c:2
8628 (@value{GDBP}) macro expand ADD(1)
8629 expands to: (42 + 1)
8630 (@value{GDBP}) macro expand-once ADD(1)
8631 expands to: once (M + 1)
8635 In the example above, note that @code{macro expand-once} expands only
8636 the macro invocation explicit in the original text --- the invocation of
8637 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8638 which was introduced by @code{ADD}.
8640 Once the program is running, @value{GDBN} uses the macro definitions in
8641 force at the source line of the current stack frame:
8644 (@value{GDBP}) break main
8645 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8647 Starting program: /home/jimb/gdb/macros/play/sample
8649 Breakpoint 1, main () at sample.c:10
8650 10 printf ("Hello, world!\n");
8654 At line 10, the definition of the macro @code{N} at line 9 is in force:
8657 (@value{GDBP}) info macro N
8658 Defined at /home/jimb/gdb/macros/play/sample.c:9
8660 (@value{GDBP}) macro expand N Q M
8662 (@value{GDBP}) print N Q M
8667 As we step over directives that remove @code{N}'s definition, and then
8668 give it a new definition, @value{GDBN} finds the definition (or lack
8669 thereof) in force at each point:
8674 12 printf ("We're so creative.\n");
8675 (@value{GDBP}) info macro N
8676 The symbol `N' has no definition as a C/C++ preprocessor macro
8677 at /home/jimb/gdb/macros/play/sample.c:12
8680 14 printf ("Goodbye, world!\n");
8681 (@value{GDBP}) info macro N
8682 Defined at /home/jimb/gdb/macros/play/sample.c:13
8684 (@value{GDBP}) macro expand N Q M
8685 expands to: 1729 < 42
8686 (@value{GDBP}) print N Q M
8691 In addition to source files, macros can be defined on the compilation command
8692 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
8693 such a way, @value{GDBN} displays the location of their definition as line zero
8694 of the source file submitted to the compiler.
8697 (@value{GDBP}) info macro __STDC__
8698 Defined at /home/jimb/gdb/macros/play/sample.c:0
8705 @chapter Tracepoints
8706 @c This chapter is based on the documentation written by Michael
8707 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8710 In some applications, it is not feasible for the debugger to interrupt
8711 the program's execution long enough for the developer to learn
8712 anything helpful about its behavior. If the program's correctness
8713 depends on its real-time behavior, delays introduced by a debugger
8714 might cause the program to change its behavior drastically, or perhaps
8715 fail, even when the code itself is correct. It is useful to be able
8716 to observe the program's behavior without interrupting it.
8718 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8719 specify locations in the program, called @dfn{tracepoints}, and
8720 arbitrary expressions to evaluate when those tracepoints are reached.
8721 Later, using the @code{tfind} command, you can examine the values
8722 those expressions had when the program hit the tracepoints. The
8723 expressions may also denote objects in memory---structures or arrays,
8724 for example---whose values @value{GDBN} should record; while visiting
8725 a particular tracepoint, you may inspect those objects as if they were
8726 in memory at that moment. However, because @value{GDBN} records these
8727 values without interacting with you, it can do so quickly and
8728 unobtrusively, hopefully not disturbing the program's behavior.
8730 The tracepoint facility is currently available only for remote
8731 targets. @xref{Targets}. In addition, your remote target must know
8732 how to collect trace data. This functionality is implemented in the
8733 remote stub; however, none of the stubs distributed with @value{GDBN}
8734 support tracepoints as of this writing. The format of the remote
8735 packets used to implement tracepoints are described in @ref{Tracepoint
8738 This chapter describes the tracepoint commands and features.
8742 * Analyze Collected Data::
8743 * Tracepoint Variables::
8746 @node Set Tracepoints
8747 @section Commands to Set Tracepoints
8749 Before running such a @dfn{trace experiment}, an arbitrary number of
8750 tracepoints can be set. A tracepoint is actually a special type of
8751 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
8752 standard breakpoint commands. For instance, as with breakpoints,
8753 tracepoint numbers are successive integers starting from one, and many
8754 of the commands associated with tracepoints take the tracepoint number
8755 as their argument, to identify which tracepoint to work on.
8757 For each tracepoint, you can specify, in advance, some arbitrary set
8758 of data that you want the target to collect in the trace buffer when
8759 it hits that tracepoint. The collected data can include registers,
8760 local variables, or global data. Later, you can use @value{GDBN}
8761 commands to examine the values these data had at the time the
8764 Tracepoints do not support every breakpoint feature. Conditional
8765 expressions and ignore counts on tracepoints have no effect, and
8766 tracepoints cannot run @value{GDBN} commands when they are
8767 hit. Tracepoints may not be thread-specific either.
8769 This section describes commands to set tracepoints and associated
8770 conditions and actions.
8773 * Create and Delete Tracepoints::
8774 * Enable and Disable Tracepoints::
8775 * Tracepoint Passcounts::
8776 * Tracepoint Actions::
8777 * Listing Tracepoints::
8778 * Starting and Stopping Trace Experiments::
8781 @node Create and Delete Tracepoints
8782 @subsection Create and Delete Tracepoints
8785 @cindex set tracepoint
8787 @item trace @var{location}
8788 The @code{trace} command is very similar to the @code{break} command.
8789 Its argument @var{location} can be a source line, a function name, or
8790 an address in the target program. @xref{Specify Location}. The
8791 @code{trace} command defines a tracepoint, which is a point in the
8792 target program where the debugger will briefly stop, collect some
8793 data, and then allow the program to continue. Setting a tracepoint or
8794 changing its actions doesn't take effect until the next @code{tstart}
8795 command, and once a trace experiment is running, further changes will
8796 not have any effect until the next trace experiment starts.
8798 Here are some examples of using the @code{trace} command:
8801 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8803 (@value{GDBP}) @b{trace +2} // 2 lines forward
8805 (@value{GDBP}) @b{trace my_function} // first source line of function
8807 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8809 (@value{GDBP}) @b{trace *0x2117c4} // an address
8813 You can abbreviate @code{trace} as @code{tr}.
8816 @cindex last tracepoint number
8817 @cindex recent tracepoint number
8818 @cindex tracepoint number
8819 The convenience variable @code{$tpnum} records the tracepoint number
8820 of the most recently set tracepoint.
8822 @kindex delete tracepoint
8823 @cindex tracepoint deletion
8824 @item delete tracepoint @r{[}@var{num}@r{]}
8825 Permanently delete one or more tracepoints. With no argument, the
8826 default is to delete all tracepoints. Note that the regular
8827 @code{delete} command can remove tracepoints also.
8832 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8834 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8838 You can abbreviate this command as @code{del tr}.
8841 @node Enable and Disable Tracepoints
8842 @subsection Enable and Disable Tracepoints
8844 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
8847 @kindex disable tracepoint
8848 @item disable tracepoint @r{[}@var{num}@r{]}
8849 Disable tracepoint @var{num}, or all tracepoints if no argument
8850 @var{num} is given. A disabled tracepoint will have no effect during
8851 the next trace experiment, but it is not forgotten. You can re-enable
8852 a disabled tracepoint using the @code{enable tracepoint} command.
8854 @kindex enable tracepoint
8855 @item enable tracepoint @r{[}@var{num}@r{]}
8856 Enable tracepoint @var{num}, or all tracepoints. The enabled
8857 tracepoints will become effective the next time a trace experiment is
8861 @node Tracepoint Passcounts
8862 @subsection Tracepoint Passcounts
8866 @cindex tracepoint pass count
8867 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8868 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8869 automatically stop a trace experiment. If a tracepoint's passcount is
8870 @var{n}, then the trace experiment will be automatically stopped on
8871 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8872 @var{num} is not specified, the @code{passcount} command sets the
8873 passcount of the most recently defined tracepoint. If no passcount is
8874 given, the trace experiment will run until stopped explicitly by the
8880 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8881 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8883 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8884 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8885 (@value{GDBP}) @b{trace foo}
8886 (@value{GDBP}) @b{pass 3}
8887 (@value{GDBP}) @b{trace bar}
8888 (@value{GDBP}) @b{pass 2}
8889 (@value{GDBP}) @b{trace baz}
8890 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8891 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8892 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8893 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8897 @node Tracepoint Actions
8898 @subsection Tracepoint Action Lists
8902 @cindex tracepoint actions
8903 @item actions @r{[}@var{num}@r{]}
8904 This command will prompt for a list of actions to be taken when the
8905 tracepoint is hit. If the tracepoint number @var{num} is not
8906 specified, this command sets the actions for the one that was most
8907 recently defined (so that you can define a tracepoint and then say
8908 @code{actions} without bothering about its number). You specify the
8909 actions themselves on the following lines, one action at a time, and
8910 terminate the actions list with a line containing just @code{end}. So
8911 far, the only defined actions are @code{collect} and
8912 @code{while-stepping}.
8914 @cindex remove actions from a tracepoint
8915 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8916 and follow it immediately with @samp{end}.
8919 (@value{GDBP}) @b{collect @var{data}} // collect some data
8921 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8923 (@value{GDBP}) @b{end} // signals the end of actions.
8926 In the following example, the action list begins with @code{collect}
8927 commands indicating the things to be collected when the tracepoint is
8928 hit. Then, in order to single-step and collect additional data
8929 following the tracepoint, a @code{while-stepping} command is used,
8930 followed by the list of things to be collected while stepping. The
8931 @code{while-stepping} command is terminated by its own separate
8932 @code{end} command. Lastly, the action list is terminated by an
8936 (@value{GDBP}) @b{trace foo}
8937 (@value{GDBP}) @b{actions}
8938 Enter actions for tracepoint 1, one per line:
8947 @kindex collect @r{(tracepoints)}
8948 @item collect @var{expr1}, @var{expr2}, @dots{}
8949 Collect values of the given expressions when the tracepoint is hit.
8950 This command accepts a comma-separated list of any valid expressions.
8951 In addition to global, static, or local variables, the following
8952 special arguments are supported:
8956 collect all registers
8959 collect all function arguments
8962 collect all local variables.
8965 You can give several consecutive @code{collect} commands, each one
8966 with a single argument, or one @code{collect} command with several
8967 arguments separated by commas: the effect is the same.
8969 The command @code{info scope} (@pxref{Symbols, info scope}) is
8970 particularly useful for figuring out what data to collect.
8972 @kindex while-stepping @r{(tracepoints)}
8973 @item while-stepping @var{n}
8974 Perform @var{n} single-step traces after the tracepoint, collecting
8975 new data at each step. The @code{while-stepping} command is
8976 followed by the list of what to collect while stepping (followed by
8977 its own @code{end} command):
8981 > collect $regs, myglobal
8987 You may abbreviate @code{while-stepping} as @code{ws} or
8991 @node Listing Tracepoints
8992 @subsection Listing Tracepoints
8995 @kindex info tracepoints
8997 @cindex information about tracepoints
8998 @item info tracepoints @r{[}@var{num}@r{]}
8999 Display information about the tracepoint @var{num}. If you don't
9000 specify a tracepoint number, displays information about all the
9001 tracepoints defined so far. The format is similar to that used for
9002 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9003 command, simply restricting itself to tracepoints.
9005 A tracepoint's listing may include additional information specific to
9010 its passcount as given by the @code{passcount @var{n}} command
9012 its step count as given by the @code{while-stepping @var{n}} command
9014 its action list as given by the @code{actions} command. The actions
9015 are prefixed with an @samp{A} so as to distinguish them from commands.
9019 (@value{GDBP}) @b{info trace}
9020 Num Type Disp Enb Address What
9021 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9025 A collect globfoo, $regs
9033 This command can be abbreviated @code{info tp}.
9036 @node Starting and Stopping Trace Experiments
9037 @subsection Starting and Stopping Trace Experiments
9041 @cindex start a new trace experiment
9042 @cindex collected data discarded
9044 This command takes no arguments. It starts the trace experiment, and
9045 begins collecting data. This has the side effect of discarding all
9046 the data collected in the trace buffer during the previous trace
9050 @cindex stop a running trace experiment
9052 This command takes no arguments. It ends the trace experiment, and
9053 stops collecting data.
9055 @strong{Note}: a trace experiment and data collection may stop
9056 automatically if any tracepoint's passcount is reached
9057 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9060 @cindex status of trace data collection
9061 @cindex trace experiment, status of
9063 This command displays the status of the current trace data
9067 Here is an example of the commands we described so far:
9070 (@value{GDBP}) @b{trace gdb_c_test}
9071 (@value{GDBP}) @b{actions}
9072 Enter actions for tracepoint #1, one per line.
9073 > collect $regs,$locals,$args
9078 (@value{GDBP}) @b{tstart}
9079 [time passes @dots{}]
9080 (@value{GDBP}) @b{tstop}
9084 @node Analyze Collected Data
9085 @section Using the Collected Data
9087 After the tracepoint experiment ends, you use @value{GDBN} commands
9088 for examining the trace data. The basic idea is that each tracepoint
9089 collects a trace @dfn{snapshot} every time it is hit and another
9090 snapshot every time it single-steps. All these snapshots are
9091 consecutively numbered from zero and go into a buffer, and you can
9092 examine them later. The way you examine them is to @dfn{focus} on a
9093 specific trace snapshot. When the remote stub is focused on a trace
9094 snapshot, it will respond to all @value{GDBN} requests for memory and
9095 registers by reading from the buffer which belongs to that snapshot,
9096 rather than from @emph{real} memory or registers of the program being
9097 debugged. This means that @strong{all} @value{GDBN} commands
9098 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9099 behave as if we were currently debugging the program state as it was
9100 when the tracepoint occurred. Any requests for data that are not in
9101 the buffer will fail.
9104 * tfind:: How to select a trace snapshot
9105 * tdump:: How to display all data for a snapshot
9106 * save-tracepoints:: How to save tracepoints for a future run
9110 @subsection @code{tfind @var{n}}
9113 @cindex select trace snapshot
9114 @cindex find trace snapshot
9115 The basic command for selecting a trace snapshot from the buffer is
9116 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9117 counting from zero. If no argument @var{n} is given, the next
9118 snapshot is selected.
9120 Here are the various forms of using the @code{tfind} command.
9124 Find the first snapshot in the buffer. This is a synonym for
9125 @code{tfind 0} (since 0 is the number of the first snapshot).
9128 Stop debugging trace snapshots, resume @emph{live} debugging.
9131 Same as @samp{tfind none}.
9134 No argument means find the next trace snapshot.
9137 Find the previous trace snapshot before the current one. This permits
9138 retracing earlier steps.
9140 @item tfind tracepoint @var{num}
9141 Find the next snapshot associated with tracepoint @var{num}. Search
9142 proceeds forward from the last examined trace snapshot. If no
9143 argument @var{num} is given, it means find the next snapshot collected
9144 for the same tracepoint as the current snapshot.
9146 @item tfind pc @var{addr}
9147 Find the next snapshot associated with the value @var{addr} of the
9148 program counter. Search proceeds forward from the last examined trace
9149 snapshot. If no argument @var{addr} is given, it means find the next
9150 snapshot with the same value of PC as the current snapshot.
9152 @item tfind outside @var{addr1}, @var{addr2}
9153 Find the next snapshot whose PC is outside the given range of
9156 @item tfind range @var{addr1}, @var{addr2}
9157 Find the next snapshot whose PC is between @var{addr1} and
9158 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
9160 @item tfind line @r{[}@var{file}:@r{]}@var{n}
9161 Find the next snapshot associated with the source line @var{n}. If
9162 the optional argument @var{file} is given, refer to line @var{n} in
9163 that source file. Search proceeds forward from the last examined
9164 trace snapshot. If no argument @var{n} is given, it means find the
9165 next line other than the one currently being examined; thus saying
9166 @code{tfind line} repeatedly can appear to have the same effect as
9167 stepping from line to line in a @emph{live} debugging session.
9170 The default arguments for the @code{tfind} commands are specifically
9171 designed to make it easy to scan through the trace buffer. For
9172 instance, @code{tfind} with no argument selects the next trace
9173 snapshot, and @code{tfind -} with no argument selects the previous
9174 trace snapshot. So, by giving one @code{tfind} command, and then
9175 simply hitting @key{RET} repeatedly you can examine all the trace
9176 snapshots in order. Or, by saying @code{tfind -} and then hitting
9177 @key{RET} repeatedly you can examine the snapshots in reverse order.
9178 The @code{tfind line} command with no argument selects the snapshot
9179 for the next source line executed. The @code{tfind pc} command with
9180 no argument selects the next snapshot with the same program counter
9181 (PC) as the current frame. The @code{tfind tracepoint} command with
9182 no argument selects the next trace snapshot collected by the same
9183 tracepoint as the current one.
9185 In addition to letting you scan through the trace buffer manually,
9186 these commands make it easy to construct @value{GDBN} scripts that
9187 scan through the trace buffer and print out whatever collected data
9188 you are interested in. Thus, if we want to examine the PC, FP, and SP
9189 registers from each trace frame in the buffer, we can say this:
9192 (@value{GDBP}) @b{tfind start}
9193 (@value{GDBP}) @b{while ($trace_frame != -1)}
9194 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9195 $trace_frame, $pc, $sp, $fp
9199 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9200 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9201 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9202 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9203 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9204 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9205 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9206 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9207 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9208 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9209 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9212 Or, if we want to examine the variable @code{X} at each source line in
9216 (@value{GDBP}) @b{tfind start}
9217 (@value{GDBP}) @b{while ($trace_frame != -1)}
9218 > printf "Frame %d, X == %d\n", $trace_frame, X
9228 @subsection @code{tdump}
9230 @cindex dump all data collected at tracepoint
9231 @cindex tracepoint data, display
9233 This command takes no arguments. It prints all the data collected at
9234 the current trace snapshot.
9237 (@value{GDBP}) @b{trace 444}
9238 (@value{GDBP}) @b{actions}
9239 Enter actions for tracepoint #2, one per line:
9240 > collect $regs, $locals, $args, gdb_long_test
9243 (@value{GDBP}) @b{tstart}
9245 (@value{GDBP}) @b{tfind line 444}
9246 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9248 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9250 (@value{GDBP}) @b{tdump}
9251 Data collected at tracepoint 2, trace frame 1:
9252 d0 0xc4aa0085 -995491707
9256 d4 0x71aea3d 119204413
9261 a1 0x3000668 50333288
9264 a4 0x3000698 50333336
9266 fp 0x30bf3c 0x30bf3c
9267 sp 0x30bf34 0x30bf34
9269 pc 0x20b2c8 0x20b2c8
9273 p = 0x20e5b4 "gdb-test"
9280 gdb_long_test = 17 '\021'
9285 @node save-tracepoints
9286 @subsection @code{save-tracepoints @var{filename}}
9287 @kindex save-tracepoints
9288 @cindex save tracepoints for future sessions
9290 This command saves all current tracepoint definitions together with
9291 their actions and passcounts, into a file @file{@var{filename}}
9292 suitable for use in a later debugging session. To read the saved
9293 tracepoint definitions, use the @code{source} command (@pxref{Command
9296 @node Tracepoint Variables
9297 @section Convenience Variables for Tracepoints
9298 @cindex tracepoint variables
9299 @cindex convenience variables for tracepoints
9302 @vindex $trace_frame
9303 @item (int) $trace_frame
9304 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9305 snapshot is selected.
9308 @item (int) $tracepoint
9309 The tracepoint for the current trace snapshot.
9312 @item (int) $trace_line
9313 The line number for the current trace snapshot.
9316 @item (char []) $trace_file
9317 The source file for the current trace snapshot.
9320 @item (char []) $trace_func
9321 The name of the function containing @code{$tracepoint}.
9324 Note: @code{$trace_file} is not suitable for use in @code{printf},
9325 use @code{output} instead.
9327 Here's a simple example of using these convenience variables for
9328 stepping through all the trace snapshots and printing some of their
9332 (@value{GDBP}) @b{tfind start}
9334 (@value{GDBP}) @b{while $trace_frame != -1}
9335 > output $trace_file
9336 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9342 @chapter Debugging Programs That Use Overlays
9345 If your program is too large to fit completely in your target system's
9346 memory, you can sometimes use @dfn{overlays} to work around this
9347 problem. @value{GDBN} provides some support for debugging programs that
9351 * How Overlays Work:: A general explanation of overlays.
9352 * Overlay Commands:: Managing overlays in @value{GDBN}.
9353 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9354 mapped by asking the inferior.
9355 * Overlay Sample Program:: A sample program using overlays.
9358 @node How Overlays Work
9359 @section How Overlays Work
9360 @cindex mapped overlays
9361 @cindex unmapped overlays
9362 @cindex load address, overlay's
9363 @cindex mapped address
9364 @cindex overlay area
9366 Suppose you have a computer whose instruction address space is only 64
9367 kilobytes long, but which has much more memory which can be accessed by
9368 other means: special instructions, segment registers, or memory
9369 management hardware, for example. Suppose further that you want to
9370 adapt a program which is larger than 64 kilobytes to run on this system.
9372 One solution is to identify modules of your program which are relatively
9373 independent, and need not call each other directly; call these modules
9374 @dfn{overlays}. Separate the overlays from the main program, and place
9375 their machine code in the larger memory. Place your main program in
9376 instruction memory, but leave at least enough space there to hold the
9377 largest overlay as well.
9379 Now, to call a function located in an overlay, you must first copy that
9380 overlay's machine code from the large memory into the space set aside
9381 for it in the instruction memory, and then jump to its entry point
9384 @c NB: In the below the mapped area's size is greater or equal to the
9385 @c size of all overlays. This is intentional to remind the developer
9386 @c that overlays don't necessarily need to be the same size.
9390 Data Instruction Larger
9391 Address Space Address Space Address Space
9392 +-----------+ +-----------+ +-----------+
9394 +-----------+ +-----------+ +-----------+<-- overlay 1
9395 | program | | main | .----| overlay 1 | load address
9396 | variables | | program | | +-----------+
9397 | and heap | | | | | |
9398 +-----------+ | | | +-----------+<-- overlay 2
9399 | | +-----------+ | | | load address
9400 +-----------+ | | | .-| overlay 2 |
9402 mapped --->+-----------+ | | +-----------+
9404 | overlay | <-' | | |
9405 | area | <---' +-----------+<-- overlay 3
9406 | | <---. | | load address
9407 +-----------+ `--| overlay 3 |
9414 @anchor{A code overlay}A code overlay
9418 The diagram (@pxref{A code overlay}) shows a system with separate data
9419 and instruction address spaces. To map an overlay, the program copies
9420 its code from the larger address space to the instruction address space.
9421 Since the overlays shown here all use the same mapped address, only one
9422 may be mapped at a time. For a system with a single address space for
9423 data and instructions, the diagram would be similar, except that the
9424 program variables and heap would share an address space with the main
9425 program and the overlay area.
9427 An overlay loaded into instruction memory and ready for use is called a
9428 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9429 instruction memory. An overlay not present (or only partially present)
9430 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9431 is its address in the larger memory. The mapped address is also called
9432 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9433 called the @dfn{load memory address}, or @dfn{LMA}.
9435 Unfortunately, overlays are not a completely transparent way to adapt a
9436 program to limited instruction memory. They introduce a new set of
9437 global constraints you must keep in mind as you design your program:
9442 Before calling or returning to a function in an overlay, your program
9443 must make sure that overlay is actually mapped. Otherwise, the call or
9444 return will transfer control to the right address, but in the wrong
9445 overlay, and your program will probably crash.
9448 If the process of mapping an overlay is expensive on your system, you
9449 will need to choose your overlays carefully to minimize their effect on
9450 your program's performance.
9453 The executable file you load onto your system must contain each
9454 overlay's instructions, appearing at the overlay's load address, not its
9455 mapped address. However, each overlay's instructions must be relocated
9456 and its symbols defined as if the overlay were at its mapped address.
9457 You can use GNU linker scripts to specify different load and relocation
9458 addresses for pieces of your program; see @ref{Overlay Description,,,
9459 ld.info, Using ld: the GNU linker}.
9462 The procedure for loading executable files onto your system must be able
9463 to load their contents into the larger address space as well as the
9464 instruction and data spaces.
9468 The overlay system described above is rather simple, and could be
9469 improved in many ways:
9474 If your system has suitable bank switch registers or memory management
9475 hardware, you could use those facilities to make an overlay's load area
9476 contents simply appear at their mapped address in instruction space.
9477 This would probably be faster than copying the overlay to its mapped
9478 area in the usual way.
9481 If your overlays are small enough, you could set aside more than one
9482 overlay area, and have more than one overlay mapped at a time.
9485 You can use overlays to manage data, as well as instructions. In
9486 general, data overlays are even less transparent to your design than
9487 code overlays: whereas code overlays only require care when you call or
9488 return to functions, data overlays require care every time you access
9489 the data. Also, if you change the contents of a data overlay, you
9490 must copy its contents back out to its load address before you can copy a
9491 different data overlay into the same mapped area.
9496 @node Overlay Commands
9497 @section Overlay Commands
9499 To use @value{GDBN}'s overlay support, each overlay in your program must
9500 correspond to a separate section of the executable file. The section's
9501 virtual memory address and load memory address must be the overlay's
9502 mapped and load addresses. Identifying overlays with sections allows
9503 @value{GDBN} to determine the appropriate address of a function or
9504 variable, depending on whether the overlay is mapped or not.
9506 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9507 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9512 Disable @value{GDBN}'s overlay support. When overlay support is
9513 disabled, @value{GDBN} assumes that all functions and variables are
9514 always present at their mapped addresses. By default, @value{GDBN}'s
9515 overlay support is disabled.
9517 @item overlay manual
9518 @cindex manual overlay debugging
9519 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9520 relies on you to tell it which overlays are mapped, and which are not,
9521 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9522 commands described below.
9524 @item overlay map-overlay @var{overlay}
9525 @itemx overlay map @var{overlay}
9526 @cindex map an overlay
9527 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9528 be the name of the object file section containing the overlay. When an
9529 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9530 functions and variables at their mapped addresses. @value{GDBN} assumes
9531 that any other overlays whose mapped ranges overlap that of
9532 @var{overlay} are now unmapped.
9534 @item overlay unmap-overlay @var{overlay}
9535 @itemx overlay unmap @var{overlay}
9536 @cindex unmap an overlay
9537 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9538 must be the name of the object file section containing the overlay.
9539 When an overlay is unmapped, @value{GDBN} assumes it can find the
9540 overlay's functions and variables at their load addresses.
9543 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9544 consults a data structure the overlay manager maintains in the inferior
9545 to see which overlays are mapped. For details, see @ref{Automatic
9548 @item overlay load-target
9550 @cindex reloading the overlay table
9551 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9552 re-reads the table @value{GDBN} automatically each time the inferior
9553 stops, so this command should only be necessary if you have changed the
9554 overlay mapping yourself using @value{GDBN}. This command is only
9555 useful when using automatic overlay debugging.
9557 @item overlay list-overlays
9559 @cindex listing mapped overlays
9560 Display a list of the overlays currently mapped, along with their mapped
9561 addresses, load addresses, and sizes.
9565 Normally, when @value{GDBN} prints a code address, it includes the name
9566 of the function the address falls in:
9569 (@value{GDBP}) print main
9570 $3 = @{int ()@} 0x11a0 <main>
9573 When overlay debugging is enabled, @value{GDBN} recognizes code in
9574 unmapped overlays, and prints the names of unmapped functions with
9575 asterisks around them. For example, if @code{foo} is a function in an
9576 unmapped overlay, @value{GDBN} prints it this way:
9579 (@value{GDBP}) overlay list
9580 No sections are mapped.
9581 (@value{GDBP}) print foo
9582 $5 = @{int (int)@} 0x100000 <*foo*>
9585 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9589 (@value{GDBP}) overlay list
9590 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9591 mapped at 0x1016 - 0x104a
9592 (@value{GDBP}) print foo
9593 $6 = @{int (int)@} 0x1016 <foo>
9596 When overlay debugging is enabled, @value{GDBN} can find the correct
9597 address for functions and variables in an overlay, whether or not the
9598 overlay is mapped. This allows most @value{GDBN} commands, like
9599 @code{break} and @code{disassemble}, to work normally, even on unmapped
9600 code. However, @value{GDBN}'s breakpoint support has some limitations:
9604 @cindex breakpoints in overlays
9605 @cindex overlays, setting breakpoints in
9606 You can set breakpoints in functions in unmapped overlays, as long as
9607 @value{GDBN} can write to the overlay at its load address.
9609 @value{GDBN} can not set hardware or simulator-based breakpoints in
9610 unmapped overlays. However, if you set a breakpoint at the end of your
9611 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9612 you are using manual overlay management), @value{GDBN} will re-set its
9613 breakpoints properly.
9617 @node Automatic Overlay Debugging
9618 @section Automatic Overlay Debugging
9619 @cindex automatic overlay debugging
9621 @value{GDBN} can automatically track which overlays are mapped and which
9622 are not, given some simple co-operation from the overlay manager in the
9623 inferior. If you enable automatic overlay debugging with the
9624 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9625 looks in the inferior's memory for certain variables describing the
9626 current state of the overlays.
9628 Here are the variables your overlay manager must define to support
9629 @value{GDBN}'s automatic overlay debugging:
9633 @item @code{_ovly_table}:
9634 This variable must be an array of the following structures:
9639 /* The overlay's mapped address. */
9642 /* The size of the overlay, in bytes. */
9645 /* The overlay's load address. */
9648 /* Non-zero if the overlay is currently mapped;
9650 unsigned long mapped;
9654 @item @code{_novlys}:
9655 This variable must be a four-byte signed integer, holding the total
9656 number of elements in @code{_ovly_table}.
9660 To decide whether a particular overlay is mapped or not, @value{GDBN}
9661 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9662 @code{lma} members equal the VMA and LMA of the overlay's section in the
9663 executable file. When @value{GDBN} finds a matching entry, it consults
9664 the entry's @code{mapped} member to determine whether the overlay is
9667 In addition, your overlay manager may define a function called
9668 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9669 will silently set a breakpoint there. If the overlay manager then
9670 calls this function whenever it has changed the overlay table, this
9671 will enable @value{GDBN} to accurately keep track of which overlays
9672 are in program memory, and update any breakpoints that may be set
9673 in overlays. This will allow breakpoints to work even if the
9674 overlays are kept in ROM or other non-writable memory while they
9675 are not being executed.
9677 @node Overlay Sample Program
9678 @section Overlay Sample Program
9679 @cindex overlay example program
9681 When linking a program which uses overlays, you must place the overlays
9682 at their load addresses, while relocating them to run at their mapped
9683 addresses. To do this, you must write a linker script (@pxref{Overlay
9684 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9685 since linker scripts are specific to a particular host system, target
9686 architecture, and target memory layout, this manual cannot provide
9687 portable sample code demonstrating @value{GDBN}'s overlay support.
9689 However, the @value{GDBN} source distribution does contain an overlaid
9690 program, with linker scripts for a few systems, as part of its test
9691 suite. The program consists of the following files from
9692 @file{gdb/testsuite/gdb.base}:
9696 The main program file.
9698 A simple overlay manager, used by @file{overlays.c}.
9703 Overlay modules, loaded and used by @file{overlays.c}.
9706 Linker scripts for linking the test program on the @code{d10v-elf}
9707 and @code{m32r-elf} targets.
9710 You can build the test program using the @code{d10v-elf} GCC
9711 cross-compiler like this:
9714 $ d10v-elf-gcc -g -c overlays.c
9715 $ d10v-elf-gcc -g -c ovlymgr.c
9716 $ d10v-elf-gcc -g -c foo.c
9717 $ d10v-elf-gcc -g -c bar.c
9718 $ d10v-elf-gcc -g -c baz.c
9719 $ d10v-elf-gcc -g -c grbx.c
9720 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9721 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9724 The build process is identical for any other architecture, except that
9725 you must substitute the appropriate compiler and linker script for the
9726 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9730 @chapter Using @value{GDBN} with Different Languages
9733 Although programming languages generally have common aspects, they are
9734 rarely expressed in the same manner. For instance, in ANSI C,
9735 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9736 Modula-2, it is accomplished by @code{p^}. Values can also be
9737 represented (and displayed) differently. Hex numbers in C appear as
9738 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9740 @cindex working language
9741 Language-specific information is built into @value{GDBN} for some languages,
9742 allowing you to express operations like the above in your program's
9743 native language, and allowing @value{GDBN} to output values in a manner
9744 consistent with the syntax of your program's native language. The
9745 language you use to build expressions is called the @dfn{working
9749 * Setting:: Switching between source languages
9750 * Show:: Displaying the language
9751 * Checks:: Type and range checks
9752 * Supported Languages:: Supported languages
9753 * Unsupported Languages:: Unsupported languages
9757 @section Switching Between Source Languages
9759 There are two ways to control the working language---either have @value{GDBN}
9760 set it automatically, or select it manually yourself. You can use the
9761 @code{set language} command for either purpose. On startup, @value{GDBN}
9762 defaults to setting the language automatically. The working language is
9763 used to determine how expressions you type are interpreted, how values
9766 In addition to the working language, every source file that
9767 @value{GDBN} knows about has its own working language. For some object
9768 file formats, the compiler might indicate which language a particular
9769 source file is in. However, most of the time @value{GDBN} infers the
9770 language from the name of the file. The language of a source file
9771 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9772 show each frame appropriately for its own language. There is no way to
9773 set the language of a source file from within @value{GDBN}, but you can
9774 set the language associated with a filename extension. @xref{Show, ,
9775 Displaying the Language}.
9777 This is most commonly a problem when you use a program, such
9778 as @code{cfront} or @code{f2c}, that generates C but is written in
9779 another language. In that case, make the
9780 program use @code{#line} directives in its C output; that way
9781 @value{GDBN} will know the correct language of the source code of the original
9782 program, and will display that source code, not the generated C code.
9785 * Filenames:: Filename extensions and languages.
9786 * Manually:: Setting the working language manually
9787 * Automatically:: Having @value{GDBN} infer the source language
9791 @subsection List of Filename Extensions and Languages
9793 If a source file name ends in one of the following extensions, then
9794 @value{GDBN} infers that its language is the one indicated.
9815 Objective-C source file
9822 Modula-2 source file
9826 Assembler source file. This actually behaves almost like C, but
9827 @value{GDBN} does not skip over function prologues when stepping.
9830 In addition, you may set the language associated with a filename
9831 extension. @xref{Show, , Displaying the Language}.
9834 @subsection Setting the Working Language
9836 If you allow @value{GDBN} to set the language automatically,
9837 expressions are interpreted the same way in your debugging session and
9840 @kindex set language
9841 If you wish, you may set the language manually. To do this, issue the
9842 command @samp{set language @var{lang}}, where @var{lang} is the name of
9844 @code{c} or @code{modula-2}.
9845 For a list of the supported languages, type @samp{set language}.
9847 Setting the language manually prevents @value{GDBN} from updating the working
9848 language automatically. This can lead to confusion if you try
9849 to debug a program when the working language is not the same as the
9850 source language, when an expression is acceptable to both
9851 languages---but means different things. For instance, if the current
9852 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9860 might not have the effect you intended. In C, this means to add
9861 @code{b} and @code{c} and place the result in @code{a}. The result
9862 printed would be the value of @code{a}. In Modula-2, this means to compare
9863 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9866 @subsection Having @value{GDBN} Infer the Source Language
9868 To have @value{GDBN} set the working language automatically, use
9869 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9870 then infers the working language. That is, when your program stops in a
9871 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9872 working language to the language recorded for the function in that
9873 frame. If the language for a frame is unknown (that is, if the function
9874 or block corresponding to the frame was defined in a source file that
9875 does not have a recognized extension), the current working language is
9876 not changed, and @value{GDBN} issues a warning.
9878 This may not seem necessary for most programs, which are written
9879 entirely in one source language. However, program modules and libraries
9880 written in one source language can be used by a main program written in
9881 a different source language. Using @samp{set language auto} in this
9882 case frees you from having to set the working language manually.
9885 @section Displaying the Language
9887 The following commands help you find out which language is the
9888 working language, and also what language source files were written in.
9892 @kindex show language
9893 Display the current working language. This is the
9894 language you can use with commands such as @code{print} to
9895 build and compute expressions that may involve variables in your program.
9898 @kindex info frame@r{, show the source language}
9899 Display the source language for this frame. This language becomes the
9900 working language if you use an identifier from this frame.
9901 @xref{Frame Info, ,Information about a Frame}, to identify the other
9902 information listed here.
9905 @kindex info source@r{, show the source language}
9906 Display the source language of this source file.
9907 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9908 information listed here.
9911 In unusual circumstances, you may have source files with extensions
9912 not in the standard list. You can then set the extension associated
9913 with a language explicitly:
9916 @item set extension-language @var{ext} @var{language}
9917 @kindex set extension-language
9918 Tell @value{GDBN} that source files with extension @var{ext} are to be
9919 assumed as written in the source language @var{language}.
9921 @item info extensions
9922 @kindex info extensions
9923 List all the filename extensions and the associated languages.
9927 @section Type and Range Checking
9930 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9931 checking are included, but they do not yet have any effect. This
9932 section documents the intended facilities.
9934 @c FIXME remove warning when type/range code added
9936 Some languages are designed to guard you against making seemingly common
9937 errors through a series of compile- and run-time checks. These include
9938 checking the type of arguments to functions and operators, and making
9939 sure mathematical overflows are caught at run time. Checks such as
9940 these help to ensure a program's correctness once it has been compiled
9941 by eliminating type mismatches, and providing active checks for range
9942 errors when your program is running.
9944 @value{GDBN} can check for conditions like the above if you wish.
9945 Although @value{GDBN} does not check the statements in your program,
9946 it can check expressions entered directly into @value{GDBN} for
9947 evaluation via the @code{print} command, for example. As with the
9948 working language, @value{GDBN} can also decide whether or not to check
9949 automatically based on your program's source language.
9950 @xref{Supported Languages, ,Supported Languages}, for the default
9951 settings of supported languages.
9954 * Type Checking:: An overview of type checking
9955 * Range Checking:: An overview of range checking
9958 @cindex type checking
9959 @cindex checks, type
9961 @subsection An Overview of Type Checking
9963 Some languages, such as Modula-2, are strongly typed, meaning that the
9964 arguments to operators and functions have to be of the correct type,
9965 otherwise an error occurs. These checks prevent type mismatch
9966 errors from ever causing any run-time problems. For example,
9974 The second example fails because the @code{CARDINAL} 1 is not
9975 type-compatible with the @code{REAL} 2.3.
9977 For the expressions you use in @value{GDBN} commands, you can tell the
9978 @value{GDBN} type checker to skip checking;
9979 to treat any mismatches as errors and abandon the expression;
9980 or to only issue warnings when type mismatches occur,
9981 but evaluate the expression anyway. When you choose the last of
9982 these, @value{GDBN} evaluates expressions like the second example above, but
9983 also issues a warning.
9985 Even if you turn type checking off, there may be other reasons
9986 related to type that prevent @value{GDBN} from evaluating an expression.
9987 For instance, @value{GDBN} does not know how to add an @code{int} and
9988 a @code{struct foo}. These particular type errors have nothing to do
9989 with the language in use, and usually arise from expressions, such as
9990 the one described above, which make little sense to evaluate anyway.
9992 Each language defines to what degree it is strict about type. For
9993 instance, both Modula-2 and C require the arguments to arithmetical
9994 operators to be numbers. In C, enumerated types and pointers can be
9995 represented as numbers, so that they are valid arguments to mathematical
9996 operators. @xref{Supported Languages, ,Supported Languages}, for further
9997 details on specific languages.
9999 @value{GDBN} provides some additional commands for controlling the type checker:
10001 @kindex set check type
10002 @kindex show check type
10004 @item set check type auto
10005 Set type checking on or off based on the current working language.
10006 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10009 @item set check type on
10010 @itemx set check type off
10011 Set type checking on or off, overriding the default setting for the
10012 current working language. Issue a warning if the setting does not
10013 match the language default. If any type mismatches occur in
10014 evaluating an expression while type checking is on, @value{GDBN} prints a
10015 message and aborts evaluation of the expression.
10017 @item set check type warn
10018 Cause the type checker to issue warnings, but to always attempt to
10019 evaluate the expression. Evaluating the expression may still
10020 be impossible for other reasons. For example, @value{GDBN} cannot add
10021 numbers and structures.
10024 Show the current setting of the type checker, and whether or not @value{GDBN}
10025 is setting it automatically.
10028 @cindex range checking
10029 @cindex checks, range
10030 @node Range Checking
10031 @subsection An Overview of Range Checking
10033 In some languages (such as Modula-2), it is an error to exceed the
10034 bounds of a type; this is enforced with run-time checks. Such range
10035 checking is meant to ensure program correctness by making sure
10036 computations do not overflow, or indices on an array element access do
10037 not exceed the bounds of the array.
10039 For expressions you use in @value{GDBN} commands, you can tell
10040 @value{GDBN} to treat range errors in one of three ways: ignore them,
10041 always treat them as errors and abandon the expression, or issue
10042 warnings but evaluate the expression anyway.
10044 A range error can result from numerical overflow, from exceeding an
10045 array index bound, or when you type a constant that is not a member
10046 of any type. Some languages, however, do not treat overflows as an
10047 error. In many implementations of C, mathematical overflow causes the
10048 result to ``wrap around'' to lower values---for example, if @var{m} is
10049 the largest integer value, and @var{s} is the smallest, then
10052 @var{m} + 1 @result{} @var{s}
10055 This, too, is specific to individual languages, and in some cases
10056 specific to individual compilers or machines. @xref{Supported Languages, ,
10057 Supported Languages}, for further details on specific languages.
10059 @value{GDBN} provides some additional commands for controlling the range checker:
10061 @kindex set check range
10062 @kindex show check range
10064 @item set check range auto
10065 Set range checking on or off based on the current working language.
10066 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10069 @item set check range on
10070 @itemx set check range off
10071 Set range checking on or off, overriding the default setting for the
10072 current working language. A warning is issued if the setting does not
10073 match the language default. If a range error occurs and range checking is on,
10074 then a message is printed and evaluation of the expression is aborted.
10076 @item set check range warn
10077 Output messages when the @value{GDBN} range checker detects a range error,
10078 but attempt to evaluate the expression anyway. Evaluating the
10079 expression may still be impossible for other reasons, such as accessing
10080 memory that the process does not own (a typical example from many Unix
10084 Show the current setting of the range checker, and whether or not it is
10085 being set automatically by @value{GDBN}.
10088 @node Supported Languages
10089 @section Supported Languages
10091 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
10092 assembly, Modula-2, and Ada.
10093 @c This is false ...
10094 Some @value{GDBN} features may be used in expressions regardless of the
10095 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
10096 and the @samp{@{type@}addr} construct (@pxref{Expressions,
10097 ,Expressions}) can be used with the constructs of any supported
10100 The following sections detail to what degree each source language is
10101 supported by @value{GDBN}. These sections are not meant to be language
10102 tutorials or references, but serve only as a reference guide to what the
10103 @value{GDBN} expression parser accepts, and what input and output
10104 formats should look like for different languages. There are many good
10105 books written on each of these languages; please look to these for a
10106 language reference or tutorial.
10109 * C:: C and C@t{++}
10110 * Objective-C:: Objective-C
10111 * Fortran:: Fortran
10113 * Modula-2:: Modula-2
10118 @subsection C and C@t{++}
10120 @cindex C and C@t{++}
10121 @cindex expressions in C or C@t{++}
10123 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
10124 to both languages. Whenever this is the case, we discuss those languages
10128 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
10129 @cindex @sc{gnu} C@t{++}
10130 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
10131 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
10132 effectively, you must compile your C@t{++} programs with a supported
10133 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
10134 compiler (@code{aCC}).
10136 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
10137 format; if it doesn't work on your system, try the stabs+ debugging
10138 format. You can select those formats explicitly with the @code{g++}
10139 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
10140 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
10141 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
10144 * C Operators:: C and C@t{++} operators
10145 * C Constants:: C and C@t{++} constants
10146 * C Plus Plus Expressions:: C@t{++} expressions
10147 * C Defaults:: Default settings for C and C@t{++}
10148 * C Checks:: C and C@t{++} type and range checks
10149 * Debugging C:: @value{GDBN} and C
10150 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
10151 * Decimal Floating Point:: Numbers in Decimal Floating Point format
10155 @subsubsection C and C@t{++} Operators
10157 @cindex C and C@t{++} operators
10159 Operators must be defined on values of specific types. For instance,
10160 @code{+} is defined on numbers, but not on structures. Operators are
10161 often defined on groups of types.
10163 For the purposes of C and C@t{++}, the following definitions hold:
10168 @emph{Integral types} include @code{int} with any of its storage-class
10169 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
10172 @emph{Floating-point types} include @code{float}, @code{double}, and
10173 @code{long double} (if supported by the target platform).
10176 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10179 @emph{Scalar types} include all of the above.
10184 The following operators are supported. They are listed here
10185 in order of increasing precedence:
10189 The comma or sequencing operator. Expressions in a comma-separated list
10190 are evaluated from left to right, with the result of the entire
10191 expression being the last expression evaluated.
10194 Assignment. The value of an assignment expression is the value
10195 assigned. Defined on scalar types.
10198 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10199 and translated to @w{@code{@var{a} = @var{a op b}}}.
10200 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10201 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10202 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10205 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10206 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10210 Logical @sc{or}. Defined on integral types.
10213 Logical @sc{and}. Defined on integral types.
10216 Bitwise @sc{or}. Defined on integral types.
10219 Bitwise exclusive-@sc{or}. Defined on integral types.
10222 Bitwise @sc{and}. Defined on integral types.
10225 Equality and inequality. Defined on scalar types. The value of these
10226 expressions is 0 for false and non-zero for true.
10228 @item <@r{, }>@r{, }<=@r{, }>=
10229 Less than, greater than, less than or equal, greater than or equal.
10230 Defined on scalar types. The value of these expressions is 0 for false
10231 and non-zero for true.
10234 left shift, and right shift. Defined on integral types.
10237 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10240 Addition and subtraction. Defined on integral types, floating-point types and
10243 @item *@r{, }/@r{, }%
10244 Multiplication, division, and modulus. Multiplication and division are
10245 defined on integral and floating-point types. Modulus is defined on
10249 Increment and decrement. When appearing before a variable, the
10250 operation is performed before the variable is used in an expression;
10251 when appearing after it, the variable's value is used before the
10252 operation takes place.
10255 Pointer dereferencing. Defined on pointer types. Same precedence as
10259 Address operator. Defined on variables. Same precedence as @code{++}.
10261 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10262 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10263 to examine the address
10264 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10268 Negative. Defined on integral and floating-point types. Same
10269 precedence as @code{++}.
10272 Logical negation. Defined on integral types. Same precedence as
10276 Bitwise complement operator. Defined on integral types. Same precedence as
10281 Structure member, and pointer-to-structure member. For convenience,
10282 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10283 pointer based on the stored type information.
10284 Defined on @code{struct} and @code{union} data.
10287 Dereferences of pointers to members.
10290 Array indexing. @code{@var{a}[@var{i}]} is defined as
10291 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10294 Function parameter list. Same precedence as @code{->}.
10297 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10298 and @code{class} types.
10301 Doubled colons also represent the @value{GDBN} scope operator
10302 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10306 If an operator is redefined in the user code, @value{GDBN} usually
10307 attempts to invoke the redefined version instead of using the operator's
10308 predefined meaning.
10311 @subsubsection C and C@t{++} Constants
10313 @cindex C and C@t{++} constants
10315 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10320 Integer constants are a sequence of digits. Octal constants are
10321 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10322 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10323 @samp{l}, specifying that the constant should be treated as a
10327 Floating point constants are a sequence of digits, followed by a decimal
10328 point, followed by a sequence of digits, and optionally followed by an
10329 exponent. An exponent is of the form:
10330 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10331 sequence of digits. The @samp{+} is optional for positive exponents.
10332 A floating-point constant may also end with a letter @samp{f} or
10333 @samp{F}, specifying that the constant should be treated as being of
10334 the @code{float} (as opposed to the default @code{double}) type; or with
10335 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10339 Enumerated constants consist of enumerated identifiers, or their
10340 integral equivalents.
10343 Character constants are a single character surrounded by single quotes
10344 (@code{'}), or a number---the ordinal value of the corresponding character
10345 (usually its @sc{ascii} value). Within quotes, the single character may
10346 be represented by a letter or by @dfn{escape sequences}, which are of
10347 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10348 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10349 @samp{@var{x}} is a predefined special character---for example,
10350 @samp{\n} for newline.
10353 String constants are a sequence of character constants surrounded by
10354 double quotes (@code{"}). Any valid character constant (as described
10355 above) may appear. Double quotes within the string must be preceded by
10356 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10360 Pointer constants are an integral value. You can also write pointers
10361 to constants using the C operator @samp{&}.
10364 Array constants are comma-separated lists surrounded by braces @samp{@{}
10365 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10366 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10367 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10370 @node C Plus Plus Expressions
10371 @subsubsection C@t{++} Expressions
10373 @cindex expressions in C@t{++}
10374 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10376 @cindex debugging C@t{++} programs
10377 @cindex C@t{++} compilers
10378 @cindex debug formats and C@t{++}
10379 @cindex @value{NGCC} and C@t{++}
10381 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10382 proper compiler and the proper debug format. Currently, @value{GDBN}
10383 works best when debugging C@t{++} code that is compiled with
10384 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10385 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10386 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10387 stabs+ as their default debug format, so you usually don't need to
10388 specify a debug format explicitly. Other compilers and/or debug formats
10389 are likely to work badly or not at all when using @value{GDBN} to debug
10395 @cindex member functions
10397 Member function calls are allowed; you can use expressions like
10400 count = aml->GetOriginal(x, y)
10403 @vindex this@r{, inside C@t{++} member functions}
10404 @cindex namespace in C@t{++}
10406 While a member function is active (in the selected stack frame), your
10407 expressions have the same namespace available as the member function;
10408 that is, @value{GDBN} allows implicit references to the class instance
10409 pointer @code{this} following the same rules as C@t{++}.
10411 @cindex call overloaded functions
10412 @cindex overloaded functions, calling
10413 @cindex type conversions in C@t{++}
10415 You can call overloaded functions; @value{GDBN} resolves the function
10416 call to the right definition, with some restrictions. @value{GDBN} does not
10417 perform overload resolution involving user-defined type conversions,
10418 calls to constructors, or instantiations of templates that do not exist
10419 in the program. It also cannot handle ellipsis argument lists or
10422 It does perform integral conversions and promotions, floating-point
10423 promotions, arithmetic conversions, pointer conversions, conversions of
10424 class objects to base classes, and standard conversions such as those of
10425 functions or arrays to pointers; it requires an exact match on the
10426 number of function arguments.
10428 Overload resolution is always performed, unless you have specified
10429 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10430 ,@value{GDBN} Features for C@t{++}}.
10432 You must specify @code{set overload-resolution off} in order to use an
10433 explicit function signature to call an overloaded function, as in
10435 p 'foo(char,int)'('x', 13)
10438 The @value{GDBN} command-completion facility can simplify this;
10439 see @ref{Completion, ,Command Completion}.
10441 @cindex reference declarations
10443 @value{GDBN} understands variables declared as C@t{++} references; you can use
10444 them in expressions just as you do in C@t{++} source---they are automatically
10447 In the parameter list shown when @value{GDBN} displays a frame, the values of
10448 reference variables are not displayed (unlike other variables); this
10449 avoids clutter, since references are often used for large structures.
10450 The @emph{address} of a reference variable is always shown, unless
10451 you have specified @samp{set print address off}.
10454 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10455 expressions can use it just as expressions in your program do. Since
10456 one scope may be defined in another, you can use @code{::} repeatedly if
10457 necessary, for example in an expression like
10458 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10459 resolving name scope by reference to source files, in both C and C@t{++}
10460 debugging (@pxref{Variables, ,Program Variables}).
10463 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10464 calling virtual functions correctly, printing out virtual bases of
10465 objects, calling functions in a base subobject, casting objects, and
10466 invoking user-defined operators.
10469 @subsubsection C and C@t{++} Defaults
10471 @cindex C and C@t{++} defaults
10473 If you allow @value{GDBN} to set type and range checking automatically, they
10474 both default to @code{off} whenever the working language changes to
10475 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10476 selects the working language.
10478 If you allow @value{GDBN} to set the language automatically, it
10479 recognizes source files whose names end with @file{.c}, @file{.C}, or
10480 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10481 these files, it sets the working language to C or C@t{++}.
10482 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10483 for further details.
10485 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10486 @c unimplemented. If (b) changes, it might make sense to let this node
10487 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10490 @subsubsection C and C@t{++} Type and Range Checks
10492 @cindex C and C@t{++} checks
10494 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10495 is not used. However, if you turn type checking on, @value{GDBN}
10496 considers two variables type equivalent if:
10500 The two variables are structured and have the same structure, union, or
10504 The two variables have the same type name, or types that have been
10505 declared equivalent through @code{typedef}.
10508 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10511 The two @code{struct}, @code{union}, or @code{enum} variables are
10512 declared in the same declaration. (Note: this may not be true for all C
10517 Range checking, if turned on, is done on mathematical operations. Array
10518 indices are not checked, since they are often used to index a pointer
10519 that is not itself an array.
10522 @subsubsection @value{GDBN} and C
10524 The @code{set print union} and @code{show print union} commands apply to
10525 the @code{union} type. When set to @samp{on}, any @code{union} that is
10526 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10527 appears as @samp{@{...@}}.
10529 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10530 with pointers and a memory allocation function. @xref{Expressions,
10533 @node Debugging C Plus Plus
10534 @subsubsection @value{GDBN} Features for C@t{++}
10536 @cindex commands for C@t{++}
10538 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10539 designed specifically for use with C@t{++}. Here is a summary:
10542 @cindex break in overloaded functions
10543 @item @r{breakpoint menus}
10544 When you want a breakpoint in a function whose name is overloaded,
10545 @value{GDBN} has the capability to display a menu of possible breakpoint
10546 locations to help you specify which function definition you want.
10547 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10549 @cindex overloading in C@t{++}
10550 @item rbreak @var{regex}
10551 Setting breakpoints using regular expressions is helpful for setting
10552 breakpoints on overloaded functions that are not members of any special
10554 @xref{Set Breaks, ,Setting Breakpoints}.
10556 @cindex C@t{++} exception handling
10559 Debug C@t{++} exception handling using these commands. @xref{Set
10560 Catchpoints, , Setting Catchpoints}.
10562 @cindex inheritance
10563 @item ptype @var{typename}
10564 Print inheritance relationships as well as other information for type
10566 @xref{Symbols, ,Examining the Symbol Table}.
10568 @cindex C@t{++} symbol display
10569 @item set print demangle
10570 @itemx show print demangle
10571 @itemx set print asm-demangle
10572 @itemx show print asm-demangle
10573 Control whether C@t{++} symbols display in their source form, both when
10574 displaying code as C@t{++} source and when displaying disassemblies.
10575 @xref{Print Settings, ,Print Settings}.
10577 @item set print object
10578 @itemx show print object
10579 Choose whether to print derived (actual) or declared types of objects.
10580 @xref{Print Settings, ,Print Settings}.
10582 @item set print vtbl
10583 @itemx show print vtbl
10584 Control the format for printing virtual function tables.
10585 @xref{Print Settings, ,Print Settings}.
10586 (The @code{vtbl} commands do not work on programs compiled with the HP
10587 ANSI C@t{++} compiler (@code{aCC}).)
10589 @kindex set overload-resolution
10590 @cindex overloaded functions, overload resolution
10591 @item set overload-resolution on
10592 Enable overload resolution for C@t{++} expression evaluation. The default
10593 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10594 and searches for a function whose signature matches the argument types,
10595 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10596 Expressions, ,C@t{++} Expressions}, for details).
10597 If it cannot find a match, it emits a message.
10599 @item set overload-resolution off
10600 Disable overload resolution for C@t{++} expression evaluation. For
10601 overloaded functions that are not class member functions, @value{GDBN}
10602 chooses the first function of the specified name that it finds in the
10603 symbol table, whether or not its arguments are of the correct type. For
10604 overloaded functions that are class member functions, @value{GDBN}
10605 searches for a function whose signature @emph{exactly} matches the
10608 @kindex show overload-resolution
10609 @item show overload-resolution
10610 Show the current setting of overload resolution.
10612 @item @r{Overloaded symbol names}
10613 You can specify a particular definition of an overloaded symbol, using
10614 the same notation that is used to declare such symbols in C@t{++}: type
10615 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10616 also use the @value{GDBN} command-line word completion facilities to list the
10617 available choices, or to finish the type list for you.
10618 @xref{Completion,, Command Completion}, for details on how to do this.
10621 @node Decimal Floating Point
10622 @subsubsection Decimal Floating Point format
10623 @cindex decimal floating point format
10625 @value{GDBN} can examine, set and perform computations with numbers in
10626 decimal floating point format, which in the C language correspond to the
10627 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10628 specified by the extension to support decimal floating-point arithmetic.
10630 There are two encodings in use, depending on the architecture: BID (Binary
10631 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10632 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10635 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10636 to manipulate decimal floating point numbers, it is not possible to convert
10637 (using a cast, for example) integers wider than 32-bit to decimal float.
10639 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10640 point computations, error checking in decimal float operations ignores
10641 underflow, overflow and divide by zero exceptions.
10643 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10644 to inspect @code{_Decimal128} values stored in floating point registers. See
10645 @ref{PowerPC,,PowerPC} for more details.
10648 @subsection Objective-C
10650 @cindex Objective-C
10651 This section provides information about some commands and command
10652 options that are useful for debugging Objective-C code. See also
10653 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10654 few more commands specific to Objective-C support.
10657 * Method Names in Commands::
10658 * The Print Command with Objective-C::
10661 @node Method Names in Commands
10662 @subsubsection Method Names in Commands
10664 The following commands have been extended to accept Objective-C method
10665 names as line specifications:
10667 @kindex clear@r{, and Objective-C}
10668 @kindex break@r{, and Objective-C}
10669 @kindex info line@r{, and Objective-C}
10670 @kindex jump@r{, and Objective-C}
10671 @kindex list@r{, and Objective-C}
10675 @item @code{info line}
10680 A fully qualified Objective-C method name is specified as
10683 -[@var{Class} @var{methodName}]
10686 where the minus sign is used to indicate an instance method and a
10687 plus sign (not shown) is used to indicate a class method. The class
10688 name @var{Class} and method name @var{methodName} are enclosed in
10689 brackets, similar to the way messages are specified in Objective-C
10690 source code. For example, to set a breakpoint at the @code{create}
10691 instance method of class @code{Fruit} in the program currently being
10695 break -[Fruit create]
10698 To list ten program lines around the @code{initialize} class method,
10702 list +[NSText initialize]
10705 In the current version of @value{GDBN}, the plus or minus sign is
10706 required. In future versions of @value{GDBN}, the plus or minus
10707 sign will be optional, but you can use it to narrow the search. It
10708 is also possible to specify just a method name:
10714 You must specify the complete method name, including any colons. If
10715 your program's source files contain more than one @code{create} method,
10716 you'll be presented with a numbered list of classes that implement that
10717 method. Indicate your choice by number, or type @samp{0} to exit if
10720 As another example, to clear a breakpoint established at the
10721 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10724 clear -[NSWindow makeKeyAndOrderFront:]
10727 @node The Print Command with Objective-C
10728 @subsubsection The Print Command With Objective-C
10729 @cindex Objective-C, print objects
10730 @kindex print-object
10731 @kindex po @r{(@code{print-object})}
10733 The print command has also been extended to accept methods. For example:
10736 print -[@var{object} hash]
10739 @cindex print an Objective-C object description
10740 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10742 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10743 and print the result. Also, an additional command has been added,
10744 @code{print-object} or @code{po} for short, which is meant to print
10745 the description of an object. However, this command may only work
10746 with certain Objective-C libraries that have a particular hook
10747 function, @code{_NSPrintForDebugger}, defined.
10750 @subsection Fortran
10751 @cindex Fortran-specific support in @value{GDBN}
10753 @value{GDBN} can be used to debug programs written in Fortran, but it
10754 currently supports only the features of Fortran 77 language.
10756 @cindex trailing underscore, in Fortran symbols
10757 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10758 among them) append an underscore to the names of variables and
10759 functions. When you debug programs compiled by those compilers, you
10760 will need to refer to variables and functions with a trailing
10764 * Fortran Operators:: Fortran operators and expressions
10765 * Fortran Defaults:: Default settings for Fortran
10766 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10769 @node Fortran Operators
10770 @subsubsection Fortran Operators and Expressions
10772 @cindex Fortran operators and expressions
10774 Operators must be defined on values of specific types. For instance,
10775 @code{+} is defined on numbers, but not on characters or other non-
10776 arithmetic types. Operators are often defined on groups of types.
10780 The exponentiation operator. It raises the first operand to the power
10784 The range operator. Normally used in the form of array(low:high) to
10785 represent a section of array.
10788 The access component operator. Normally used to access elements in derived
10789 types. Also suitable for unions. As unions aren't part of regular Fortran,
10790 this can only happen when accessing a register that uses a gdbarch-defined
10794 @node Fortran Defaults
10795 @subsubsection Fortran Defaults
10797 @cindex Fortran Defaults
10799 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10800 default uses case-insensitive matches for Fortran symbols. You can
10801 change that with the @samp{set case-insensitive} command, see
10802 @ref{Symbols}, for the details.
10804 @node Special Fortran Commands
10805 @subsubsection Special Fortran Commands
10807 @cindex Special Fortran commands
10809 @value{GDBN} has some commands to support Fortran-specific features,
10810 such as displaying common blocks.
10813 @cindex @code{COMMON} blocks, Fortran
10814 @kindex info common
10815 @item info common @r{[}@var{common-name}@r{]}
10816 This command prints the values contained in the Fortran @code{COMMON}
10817 block whose name is @var{common-name}. With no argument, the names of
10818 all @code{COMMON} blocks visible at the current program location are
10825 @cindex Pascal support in @value{GDBN}, limitations
10826 Debugging Pascal programs which use sets, subranges, file variables, or
10827 nested functions does not currently work. @value{GDBN} does not support
10828 entering expressions, printing values, or similar features using Pascal
10831 The Pascal-specific command @code{set print pascal_static-members}
10832 controls whether static members of Pascal objects are displayed.
10833 @xref{Print Settings, pascal_static-members}.
10836 @subsection Modula-2
10838 @cindex Modula-2, @value{GDBN} support
10840 The extensions made to @value{GDBN} to support Modula-2 only support
10841 output from the @sc{gnu} Modula-2 compiler (which is currently being
10842 developed). Other Modula-2 compilers are not currently supported, and
10843 attempting to debug executables produced by them is most likely
10844 to give an error as @value{GDBN} reads in the executable's symbol
10847 @cindex expressions in Modula-2
10849 * M2 Operators:: Built-in operators
10850 * Built-In Func/Proc:: Built-in functions and procedures
10851 * M2 Constants:: Modula-2 constants
10852 * M2 Types:: Modula-2 types
10853 * M2 Defaults:: Default settings for Modula-2
10854 * Deviations:: Deviations from standard Modula-2
10855 * M2 Checks:: Modula-2 type and range checks
10856 * M2 Scope:: The scope operators @code{::} and @code{.}
10857 * GDB/M2:: @value{GDBN} and Modula-2
10861 @subsubsection Operators
10862 @cindex Modula-2 operators
10864 Operators must be defined on values of specific types. For instance,
10865 @code{+} is defined on numbers, but not on structures. Operators are
10866 often defined on groups of types. For the purposes of Modula-2, the
10867 following definitions hold:
10872 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10876 @emph{Character types} consist of @code{CHAR} and its subranges.
10879 @emph{Floating-point types} consist of @code{REAL}.
10882 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10886 @emph{Scalar types} consist of all of the above.
10889 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10892 @emph{Boolean types} consist of @code{BOOLEAN}.
10896 The following operators are supported, and appear in order of
10897 increasing precedence:
10901 Function argument or array index separator.
10904 Assignment. The value of @var{var} @code{:=} @var{value} is
10908 Less than, greater than on integral, floating-point, or enumerated
10912 Less than or equal to, greater than or equal to
10913 on integral, floating-point and enumerated types, or set inclusion on
10914 set types. Same precedence as @code{<}.
10916 @item =@r{, }<>@r{, }#
10917 Equality and two ways of expressing inequality, valid on scalar types.
10918 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10919 available for inequality, since @code{#} conflicts with the script
10923 Set membership. Defined on set types and the types of their members.
10924 Same precedence as @code{<}.
10927 Boolean disjunction. Defined on boolean types.
10930 Boolean conjunction. Defined on boolean types.
10933 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10936 Addition and subtraction on integral and floating-point types, or union
10937 and difference on set types.
10940 Multiplication on integral and floating-point types, or set intersection
10944 Division on floating-point types, or symmetric set difference on set
10945 types. Same precedence as @code{*}.
10948 Integer division and remainder. Defined on integral types. Same
10949 precedence as @code{*}.
10952 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10955 Pointer dereferencing. Defined on pointer types.
10958 Boolean negation. Defined on boolean types. Same precedence as
10962 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10963 precedence as @code{^}.
10966 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10969 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10973 @value{GDBN} and Modula-2 scope operators.
10977 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10978 treats the use of the operator @code{IN}, or the use of operators
10979 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10980 @code{<=}, and @code{>=} on sets as an error.
10984 @node Built-In Func/Proc
10985 @subsubsection Built-in Functions and Procedures
10986 @cindex Modula-2 built-ins
10988 Modula-2 also makes available several built-in procedures and functions.
10989 In describing these, the following metavariables are used:
10994 represents an @code{ARRAY} variable.
10997 represents a @code{CHAR} constant or variable.
11000 represents a variable or constant of integral type.
11003 represents an identifier that belongs to a set. Generally used in the
11004 same function with the metavariable @var{s}. The type of @var{s} should
11005 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11008 represents a variable or constant of integral or floating-point type.
11011 represents a variable or constant of floating-point type.
11017 represents a variable.
11020 represents a variable or constant of one of many types. See the
11021 explanation of the function for details.
11024 All Modula-2 built-in procedures also return a result, described below.
11028 Returns the absolute value of @var{n}.
11031 If @var{c} is a lower case letter, it returns its upper case
11032 equivalent, otherwise it returns its argument.
11035 Returns the character whose ordinal value is @var{i}.
11038 Decrements the value in the variable @var{v} by one. Returns the new value.
11040 @item DEC(@var{v},@var{i})
11041 Decrements the value in the variable @var{v} by @var{i}. Returns the
11044 @item EXCL(@var{m},@var{s})
11045 Removes the element @var{m} from the set @var{s}. Returns the new
11048 @item FLOAT(@var{i})
11049 Returns the floating point equivalent of the integer @var{i}.
11051 @item HIGH(@var{a})
11052 Returns the index of the last member of @var{a}.
11055 Increments the value in the variable @var{v} by one. Returns the new value.
11057 @item INC(@var{v},@var{i})
11058 Increments the value in the variable @var{v} by @var{i}. Returns the
11061 @item INCL(@var{m},@var{s})
11062 Adds the element @var{m} to the set @var{s} if it is not already
11063 there. Returns the new set.
11066 Returns the maximum value of the type @var{t}.
11069 Returns the minimum value of the type @var{t}.
11072 Returns boolean TRUE if @var{i} is an odd number.
11075 Returns the ordinal value of its argument. For example, the ordinal
11076 value of a character is its @sc{ascii} value (on machines supporting the
11077 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11078 integral, character and enumerated types.
11080 @item SIZE(@var{x})
11081 Returns the size of its argument. @var{x} can be a variable or a type.
11083 @item TRUNC(@var{r})
11084 Returns the integral part of @var{r}.
11086 @item TSIZE(@var{x})
11087 Returns the size of its argument. @var{x} can be a variable or a type.
11089 @item VAL(@var{t},@var{i})
11090 Returns the member of the type @var{t} whose ordinal value is @var{i}.
11094 @emph{Warning:} Sets and their operations are not yet supported, so
11095 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
11099 @cindex Modula-2 constants
11101 @subsubsection Constants
11103 @value{GDBN} allows you to express the constants of Modula-2 in the following
11109 Integer constants are simply a sequence of digits. When used in an
11110 expression, a constant is interpreted to be type-compatible with the
11111 rest of the expression. Hexadecimal integers are specified by a
11112 trailing @samp{H}, and octal integers by a trailing @samp{B}.
11115 Floating point constants appear as a sequence of digits, followed by a
11116 decimal point and another sequence of digits. An optional exponent can
11117 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
11118 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
11119 digits of the floating point constant must be valid decimal (base 10)
11123 Character constants consist of a single character enclosed by a pair of
11124 like quotes, either single (@code{'}) or double (@code{"}). They may
11125 also be expressed by their ordinal value (their @sc{ascii} value, usually)
11126 followed by a @samp{C}.
11129 String constants consist of a sequence of characters enclosed by a
11130 pair of like quotes, either single (@code{'}) or double (@code{"}).
11131 Escape sequences in the style of C are also allowed. @xref{C
11132 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
11136 Enumerated constants consist of an enumerated identifier.
11139 Boolean constants consist of the identifiers @code{TRUE} and
11143 Pointer constants consist of integral values only.
11146 Set constants are not yet supported.
11150 @subsubsection Modula-2 Types
11151 @cindex Modula-2 types
11153 Currently @value{GDBN} can print the following data types in Modula-2
11154 syntax: array types, record types, set types, pointer types, procedure
11155 types, enumerated types, subrange types and base types. You can also
11156 print the contents of variables declared using these type.
11157 This section gives a number of simple source code examples together with
11158 sample @value{GDBN} sessions.
11160 The first example contains the following section of code:
11169 and you can request @value{GDBN} to interrogate the type and value of
11170 @code{r} and @code{s}.
11173 (@value{GDBP}) print s
11175 (@value{GDBP}) ptype s
11177 (@value{GDBP}) print r
11179 (@value{GDBP}) ptype r
11184 Likewise if your source code declares @code{s} as:
11188 s: SET ['A'..'Z'] ;
11192 then you may query the type of @code{s} by:
11195 (@value{GDBP}) ptype s
11196 type = SET ['A'..'Z']
11200 Note that at present you cannot interactively manipulate set
11201 expressions using the debugger.
11203 The following example shows how you might declare an array in Modula-2
11204 and how you can interact with @value{GDBN} to print its type and contents:
11208 s: ARRAY [-10..10] OF CHAR ;
11212 (@value{GDBP}) ptype s
11213 ARRAY [-10..10] OF CHAR
11216 Note that the array handling is not yet complete and although the type
11217 is printed correctly, expression handling still assumes that all
11218 arrays have a lower bound of zero and not @code{-10} as in the example
11221 Here are some more type related Modula-2 examples:
11225 colour = (blue, red, yellow, green) ;
11226 t = [blue..yellow] ;
11234 The @value{GDBN} interaction shows how you can query the data type
11235 and value of a variable.
11238 (@value{GDBP}) print s
11240 (@value{GDBP}) ptype t
11241 type = [blue..yellow]
11245 In this example a Modula-2 array is declared and its contents
11246 displayed. Observe that the contents are written in the same way as
11247 their @code{C} counterparts.
11251 s: ARRAY [1..5] OF CARDINAL ;
11257 (@value{GDBP}) print s
11258 $1 = @{1, 0, 0, 0, 0@}
11259 (@value{GDBP}) ptype s
11260 type = ARRAY [1..5] OF CARDINAL
11263 The Modula-2 language interface to @value{GDBN} also understands
11264 pointer types as shown in this example:
11268 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11275 and you can request that @value{GDBN} describes the type of @code{s}.
11278 (@value{GDBP}) ptype s
11279 type = POINTER TO ARRAY [1..5] OF CARDINAL
11282 @value{GDBN} handles compound types as we can see in this example.
11283 Here we combine array types, record types, pointer types and subrange
11294 myarray = ARRAY myrange OF CARDINAL ;
11295 myrange = [-2..2] ;
11297 s: POINTER TO ARRAY myrange OF foo ;
11301 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11305 (@value{GDBP}) ptype s
11306 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11309 f3 : ARRAY [-2..2] OF CARDINAL;
11314 @subsubsection Modula-2 Defaults
11315 @cindex Modula-2 defaults
11317 If type and range checking are set automatically by @value{GDBN}, they
11318 both default to @code{on} whenever the working language changes to
11319 Modula-2. This happens regardless of whether you or @value{GDBN}
11320 selected the working language.
11322 If you allow @value{GDBN} to set the language automatically, then entering
11323 code compiled from a file whose name ends with @file{.mod} sets the
11324 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11325 Infer the Source Language}, for further details.
11328 @subsubsection Deviations from Standard Modula-2
11329 @cindex Modula-2, deviations from
11331 A few changes have been made to make Modula-2 programs easier to debug.
11332 This is done primarily via loosening its type strictness:
11336 Unlike in standard Modula-2, pointer constants can be formed by
11337 integers. This allows you to modify pointer variables during
11338 debugging. (In standard Modula-2, the actual address contained in a
11339 pointer variable is hidden from you; it can only be modified
11340 through direct assignment to another pointer variable or expression that
11341 returned a pointer.)
11344 C escape sequences can be used in strings and characters to represent
11345 non-printable characters. @value{GDBN} prints out strings with these
11346 escape sequences embedded. Single non-printable characters are
11347 printed using the @samp{CHR(@var{nnn})} format.
11350 The assignment operator (@code{:=}) returns the value of its right-hand
11354 All built-in procedures both modify @emph{and} return their argument.
11358 @subsubsection Modula-2 Type and Range Checks
11359 @cindex Modula-2 checks
11362 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11365 @c FIXME remove warning when type/range checks added
11367 @value{GDBN} considers two Modula-2 variables type equivalent if:
11371 They are of types that have been declared equivalent via a @code{TYPE
11372 @var{t1} = @var{t2}} statement
11375 They have been declared on the same line. (Note: This is true of the
11376 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11379 As long as type checking is enabled, any attempt to combine variables
11380 whose types are not equivalent is an error.
11382 Range checking is done on all mathematical operations, assignment, array
11383 index bounds, and all built-in functions and procedures.
11386 @subsubsection The Scope Operators @code{::} and @code{.}
11388 @cindex @code{.}, Modula-2 scope operator
11389 @cindex colon, doubled as scope operator
11391 @vindex colon-colon@r{, in Modula-2}
11392 @c Info cannot handle :: but TeX can.
11395 @vindex ::@r{, in Modula-2}
11398 There are a few subtle differences between the Modula-2 scope operator
11399 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11404 @var{module} . @var{id}
11405 @var{scope} :: @var{id}
11409 where @var{scope} is the name of a module or a procedure,
11410 @var{module} the name of a module, and @var{id} is any declared
11411 identifier within your program, except another module.
11413 Using the @code{::} operator makes @value{GDBN} search the scope
11414 specified by @var{scope} for the identifier @var{id}. If it is not
11415 found in the specified scope, then @value{GDBN} searches all scopes
11416 enclosing the one specified by @var{scope}.
11418 Using the @code{.} operator makes @value{GDBN} search the current scope for
11419 the identifier specified by @var{id} that was imported from the
11420 definition module specified by @var{module}. With this operator, it is
11421 an error if the identifier @var{id} was not imported from definition
11422 module @var{module}, or if @var{id} is not an identifier in
11426 @subsubsection @value{GDBN} and Modula-2
11428 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11429 Five subcommands of @code{set print} and @code{show print} apply
11430 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11431 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11432 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11433 analogue in Modula-2.
11435 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11436 with any language, is not useful with Modula-2. Its
11437 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11438 created in Modula-2 as they can in C or C@t{++}. However, because an
11439 address can be specified by an integral constant, the construct
11440 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11442 @cindex @code{#} in Modula-2
11443 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11444 interpreted as the beginning of a comment. Use @code{<>} instead.
11450 The extensions made to @value{GDBN} for Ada only support
11451 output from the @sc{gnu} Ada (GNAT) compiler.
11452 Other Ada compilers are not currently supported, and
11453 attempting to debug executables produced by them is most likely
11457 @cindex expressions in Ada
11459 * Ada Mode Intro:: General remarks on the Ada syntax
11460 and semantics supported by Ada mode
11462 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11463 * Additions to Ada:: Extensions of the Ada expression syntax.
11464 * Stopping Before Main Program:: Debugging the program during elaboration.
11465 * Ada Tasks:: Listing and setting breakpoints in tasks.
11466 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11467 * Ada Glitches:: Known peculiarities of Ada mode.
11470 @node Ada Mode Intro
11471 @subsubsection Introduction
11472 @cindex Ada mode, general
11474 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11475 syntax, with some extensions.
11476 The philosophy behind the design of this subset is
11480 That @value{GDBN} should provide basic literals and access to operations for
11481 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11482 leaving more sophisticated computations to subprograms written into the
11483 program (which therefore may be called from @value{GDBN}).
11486 That type safety and strict adherence to Ada language restrictions
11487 are not particularly important to the @value{GDBN} user.
11490 That brevity is important to the @value{GDBN} user.
11493 Thus, for brevity, the debugger acts as if all names declared in
11494 user-written packages are directly visible, even if they are not visible
11495 according to Ada rules, thus making it unnecessary to fully qualify most
11496 names with their packages, regardless of context. Where this causes
11497 ambiguity, @value{GDBN} asks the user's intent.
11499 The debugger will start in Ada mode if it detects an Ada main program.
11500 As for other languages, it will enter Ada mode when stopped in a program that
11501 was translated from an Ada source file.
11503 While in Ada mode, you may use `@t{--}' for comments. This is useful
11504 mostly for documenting command files. The standard @value{GDBN} comment
11505 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11506 middle (to allow based literals).
11508 The debugger supports limited overloading. Given a subprogram call in which
11509 the function symbol has multiple definitions, it will use the number of
11510 actual parameters and some information about their types to attempt to narrow
11511 the set of definitions. It also makes very limited use of context, preferring
11512 procedures to functions in the context of the @code{call} command, and
11513 functions to procedures elsewhere.
11515 @node Omissions from Ada
11516 @subsubsection Omissions from Ada
11517 @cindex Ada, omissions from
11519 Here are the notable omissions from the subset:
11523 Only a subset of the attributes are supported:
11527 @t{'First}, @t{'Last}, and @t{'Length}
11528 on array objects (not on types and subtypes).
11531 @t{'Min} and @t{'Max}.
11534 @t{'Pos} and @t{'Val}.
11540 @t{'Range} on array objects (not subtypes), but only as the right
11541 operand of the membership (@code{in}) operator.
11544 @t{'Access}, @t{'Unchecked_Access}, and
11545 @t{'Unrestricted_Access} (a GNAT extension).
11553 @code{Characters.Latin_1} are not available and
11554 concatenation is not implemented. Thus, escape characters in strings are
11555 not currently available.
11558 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11559 equality of representations. They will generally work correctly
11560 for strings and arrays whose elements have integer or enumeration types.
11561 They may not work correctly for arrays whose element
11562 types have user-defined equality, for arrays of real values
11563 (in particular, IEEE-conformant floating point, because of negative
11564 zeroes and NaNs), and for arrays whose elements contain unused bits with
11565 indeterminate values.
11568 The other component-by-component array operations (@code{and}, @code{or},
11569 @code{xor}, @code{not}, and relational tests other than equality)
11570 are not implemented.
11573 @cindex array aggregates (Ada)
11574 @cindex record aggregates (Ada)
11575 @cindex aggregates (Ada)
11576 There is limited support for array and record aggregates. They are
11577 permitted only on the right sides of assignments, as in these examples:
11580 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11581 (@value{GDBP}) set An_Array := (1, others => 0)
11582 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11583 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11584 (@value{GDBP}) set A_Record := (1, "Peter", True);
11585 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11589 discriminant's value by assigning an aggregate has an
11590 undefined effect if that discriminant is used within the record.
11591 However, you can first modify discriminants by directly assigning to
11592 them (which normally would not be allowed in Ada), and then performing an
11593 aggregate assignment. For example, given a variable @code{A_Rec}
11594 declared to have a type such as:
11597 type Rec (Len : Small_Integer := 0) is record
11599 Vals : IntArray (1 .. Len);
11603 you can assign a value with a different size of @code{Vals} with two
11607 (@value{GDBP}) set A_Rec.Len := 4
11608 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11611 As this example also illustrates, @value{GDBN} is very loose about the usual
11612 rules concerning aggregates. You may leave out some of the
11613 components of an array or record aggregate (such as the @code{Len}
11614 component in the assignment to @code{A_Rec} above); they will retain their
11615 original values upon assignment. You may freely use dynamic values as
11616 indices in component associations. You may even use overlapping or
11617 redundant component associations, although which component values are
11618 assigned in such cases is not defined.
11621 Calls to dispatching subprograms are not implemented.
11624 The overloading algorithm is much more limited (i.e., less selective)
11625 than that of real Ada. It makes only limited use of the context in
11626 which a subexpression appears to resolve its meaning, and it is much
11627 looser in its rules for allowing type matches. As a result, some
11628 function calls will be ambiguous, and the user will be asked to choose
11629 the proper resolution.
11632 The @code{new} operator is not implemented.
11635 Entry calls are not implemented.
11638 Aside from printing, arithmetic operations on the native VAX floating-point
11639 formats are not supported.
11642 It is not possible to slice a packed array.
11645 The names @code{True} and @code{False}, when not part of a qualified name,
11646 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11648 Should your program
11649 redefine these names in a package or procedure (at best a dubious practice),
11650 you will have to use fully qualified names to access their new definitions.
11653 @node Additions to Ada
11654 @subsubsection Additions to Ada
11655 @cindex Ada, deviations from
11657 As it does for other languages, @value{GDBN} makes certain generic
11658 extensions to Ada (@pxref{Expressions}):
11662 If the expression @var{E} is a variable residing in memory (typically
11663 a local variable or array element) and @var{N} is a positive integer,
11664 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11665 @var{N}-1 adjacent variables following it in memory as an array. In
11666 Ada, this operator is generally not necessary, since its prime use is
11667 in displaying parts of an array, and slicing will usually do this in
11668 Ada. However, there are occasional uses when debugging programs in
11669 which certain debugging information has been optimized away.
11672 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11673 appears in function or file @var{B}.'' When @var{B} is a file name,
11674 you must typically surround it in single quotes.
11677 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11678 @var{type} that appears at address @var{addr}.''
11681 A name starting with @samp{$} is a convenience variable
11682 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11685 In addition, @value{GDBN} provides a few other shortcuts and outright
11686 additions specific to Ada:
11690 The assignment statement is allowed as an expression, returning
11691 its right-hand operand as its value. Thus, you may enter
11694 (@value{GDBP}) set x := y + 3
11695 (@value{GDBP}) print A(tmp := y + 1)
11699 The semicolon is allowed as an ``operator,'' returning as its value
11700 the value of its right-hand operand.
11701 This allows, for example,
11702 complex conditional breaks:
11705 (@value{GDBP}) break f
11706 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11710 Rather than use catenation and symbolic character names to introduce special
11711 characters into strings, one may instead use a special bracket notation,
11712 which is also used to print strings. A sequence of characters of the form
11713 @samp{["@var{XX}"]} within a string or character literal denotes the
11714 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11715 sequence of characters @samp{["""]} also denotes a single quotation mark
11716 in strings. For example,
11718 "One line.["0a"]Next line.["0a"]"
11721 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11725 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11726 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11730 (@value{GDBP}) print 'max(x, y)
11734 When printing arrays, @value{GDBN} uses positional notation when the
11735 array has a lower bound of 1, and uses a modified named notation otherwise.
11736 For example, a one-dimensional array of three integers with a lower bound
11737 of 3 might print as
11744 That is, in contrast to valid Ada, only the first component has a @code{=>}
11748 You may abbreviate attributes in expressions with any unique,
11749 multi-character subsequence of
11750 their names (an exact match gets preference).
11751 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11752 in place of @t{a'length}.
11755 @cindex quoting Ada internal identifiers
11756 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11757 to lower case. The GNAT compiler uses upper-case characters for
11758 some of its internal identifiers, which are normally of no interest to users.
11759 For the rare occasions when you actually have to look at them,
11760 enclose them in angle brackets to avoid the lower-case mapping.
11763 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11767 Printing an object of class-wide type or dereferencing an
11768 access-to-class-wide value will display all the components of the object's
11769 specific type (as indicated by its run-time tag). Likewise, component
11770 selection on such a value will operate on the specific type of the
11775 @node Stopping Before Main Program
11776 @subsubsection Stopping at the Very Beginning
11778 @cindex breakpointing Ada elaboration code
11779 It is sometimes necessary to debug the program during elaboration, and
11780 before reaching the main procedure.
11781 As defined in the Ada Reference
11782 Manual, the elaboration code is invoked from a procedure called
11783 @code{adainit}. To run your program up to the beginning of
11784 elaboration, simply use the following two commands:
11785 @code{tbreak adainit} and @code{run}.
11788 @subsubsection Extensions for Ada Tasks
11789 @cindex Ada, tasking
11791 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11792 @value{GDBN} provides the following task-related commands:
11797 This command shows a list of current Ada tasks, as in the following example:
11804 (@value{GDBP}) info tasks
11805 ID TID P-ID Pri State Name
11806 1 8088000 0 15 Child Activation Wait main_task
11807 2 80a4000 1 15 Accept Statement b
11808 3 809a800 1 15 Child Activation Wait a
11809 * 4 80ae800 3 15 Runnable c
11814 In this listing, the asterisk before the last task indicates it to be the
11815 task currently being inspected.
11819 Represents @value{GDBN}'s internal task number.
11825 The parent's task ID (@value{GDBN}'s internal task number).
11828 The base priority of the task.
11831 Current state of the task.
11835 The task has been created but has not been activated. It cannot be
11839 The task is not blocked for any reason known to Ada. (It may be waiting
11840 for a mutex, though.) It is conceptually "executing" in normal mode.
11843 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11844 that were waiting on terminate alternatives have been awakened and have
11845 terminated themselves.
11847 @item Child Activation Wait
11848 The task is waiting for created tasks to complete activation.
11850 @item Accept Statement
11851 The task is waiting on an accept or selective wait statement.
11853 @item Waiting on entry call
11854 The task is waiting on an entry call.
11856 @item Async Select Wait
11857 The task is waiting to start the abortable part of an asynchronous
11861 The task is waiting on a select statement with only a delay
11864 @item Child Termination Wait
11865 The task is sleeping having completed a master within itself, and is
11866 waiting for the tasks dependent on that master to become terminated or
11867 waiting on a terminate Phase.
11869 @item Wait Child in Term Alt
11870 The task is sleeping waiting for tasks on terminate alternatives to
11871 finish terminating.
11873 @item Accepting RV with @var{taskno}
11874 The task is accepting a rendez-vous with the task @var{taskno}.
11878 Name of the task in the program.
11882 @kindex info task @var{taskno}
11883 @item info task @var{taskno}
11884 This command shows detailled informations on the specified task, as in
11885 the following example:
11890 (@value{GDBP}) info tasks
11891 ID TID P-ID Pri State Name
11892 1 8077880 0 15 Child Activation Wait main_task
11893 * 2 807c468 1 15 Runnable task_1
11894 (@value{GDBP}) info task 2
11895 Ada Task: 0x807c468
11898 Parent: 1 (main_task)
11904 @kindex task@r{ (Ada)}
11905 @cindex current Ada task ID
11906 This command prints the ID of the current task.
11912 (@value{GDBP}) info tasks
11913 ID TID P-ID Pri State Name
11914 1 8077870 0 15 Child Activation Wait main_task
11915 * 2 807c458 1 15 Runnable t
11916 (@value{GDBP}) task
11917 [Current task is 2]
11920 @item task @var{taskno}
11921 @cindex Ada task switching
11922 This command is like the @code{thread @var{threadno}}
11923 command (@pxref{Threads}). It switches the context of debugging
11924 from the current task to the given task.
11930 (@value{GDBP}) info tasks
11931 ID TID P-ID Pri State Name
11932 1 8077870 0 15 Child Activation Wait main_task
11933 * 2 807c458 1 15 Runnable t
11934 (@value{GDBP}) task 1
11935 [Switching to task 1]
11936 #0 0x8067726 in pthread_cond_wait ()
11938 #0 0x8067726 in pthread_cond_wait ()
11939 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11940 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11941 #3 0x806153e in system.tasking.stages.activate_tasks ()
11942 #4 0x804aacc in un () at un.adb:5
11945 @item break @var{linespec} task @var{taskno}
11946 @itemx break @var{linespec} task @var{taskno} if @dots{}
11947 @cindex breakpoints and tasks, in Ada
11948 @cindex task breakpoints, in Ada
11949 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
11950 These commands are like the @code{break @dots{} thread @dots{}}
11951 command (@pxref{Thread Stops}).
11952 @var{linespec} specifies source lines, as described
11953 in @ref{Specify Location}.
11955 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
11956 to specify that you only want @value{GDBN} to stop the program when a
11957 particular Ada task reaches this breakpoint. @var{taskno} is one of the
11958 numeric task identifiers assigned by @value{GDBN}, shown in the first
11959 column of the @samp{info tasks} display.
11961 If you do not specify @samp{task @var{taskno}} when you set a
11962 breakpoint, the breakpoint applies to @emph{all} tasks of your
11965 You can use the @code{task} qualifier on conditional breakpoints as
11966 well; in this case, place @samp{task @var{taskno}} before the
11967 breakpoint condition (before the @code{if}).
11975 (@value{GDBP}) info tasks
11976 ID TID P-ID Pri State Name
11977 1 140022020 0 15 Child Activation Wait main_task
11978 2 140045060 1 15 Accept/Select Wait t2
11979 3 140044840 1 15 Runnable t1
11980 * 4 140056040 1 15 Runnable t3
11981 (@value{GDBP}) b 15 task 2
11982 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
11983 (@value{GDBP}) cont
11988 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
11990 (@value{GDBP}) info tasks
11991 ID TID P-ID Pri State Name
11992 1 140022020 0 15 Child Activation Wait main_task
11993 * 2 140045060 1 15 Runnable t2
11994 3 140044840 1 15 Runnable t1
11995 4 140056040 1 15 Delay Sleep t3
11999 @node Ada Tasks and Core Files
12000 @subsubsection Tasking Support when Debugging Core Files
12001 @cindex Ada tasking and core file debugging
12003 When inspecting a core file, as opposed to debugging a live program,
12004 tasking support may be limited or even unavailable, depending on
12005 the platform being used.
12006 For instance, on x86-linux, the list of tasks is available, but task
12007 switching is not supported. On Tru64, however, task switching will work
12010 On certain platforms, including Tru64, the debugger needs to perform some
12011 memory writes in order to provide Ada tasking support. When inspecting
12012 a core file, this means that the core file must be opened with read-write
12013 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12014 Under these circumstances, you should make a backup copy of the core
12015 file before inspecting it with @value{GDBN}.
12018 @subsubsection Known Peculiarities of Ada Mode
12019 @cindex Ada, problems
12021 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12022 we know of several problems with and limitations of Ada mode in
12024 some of which will be fixed with planned future releases of the debugger
12025 and the GNU Ada compiler.
12029 Currently, the debugger
12030 has insufficient information to determine whether certain pointers represent
12031 pointers to objects or the objects themselves.
12032 Thus, the user may have to tack an extra @code{.all} after an expression
12033 to get it printed properly.
12036 Static constants that the compiler chooses not to materialize as objects in
12037 storage are invisible to the debugger.
12040 Named parameter associations in function argument lists are ignored (the
12041 argument lists are treated as positional).
12044 Many useful library packages are currently invisible to the debugger.
12047 Fixed-point arithmetic, conversions, input, and output is carried out using
12048 floating-point arithmetic, and may give results that only approximate those on
12052 The GNAT compiler never generates the prefix @code{Standard} for any of
12053 the standard symbols defined by the Ada language. @value{GDBN} knows about
12054 this: it will strip the prefix from names when you use it, and will never
12055 look for a name you have so qualified among local symbols, nor match against
12056 symbols in other packages or subprograms. If you have
12057 defined entities anywhere in your program other than parameters and
12058 local variables whose simple names match names in @code{Standard},
12059 GNAT's lack of qualification here can cause confusion. When this happens,
12060 you can usually resolve the confusion
12061 by qualifying the problematic names with package
12062 @code{Standard} explicitly.
12065 @node Unsupported Languages
12066 @section Unsupported Languages
12068 @cindex unsupported languages
12069 @cindex minimal language
12070 In addition to the other fully-supported programming languages,
12071 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
12072 It does not represent a real programming language, but provides a set
12073 of capabilities close to what the C or assembly languages provide.
12074 This should allow most simple operations to be performed while debugging
12075 an application that uses a language currently not supported by @value{GDBN}.
12077 If the language is set to @code{auto}, @value{GDBN} will automatically
12078 select this language if the current frame corresponds to an unsupported
12082 @chapter Examining the Symbol Table
12084 The commands described in this chapter allow you to inquire about the
12085 symbols (names of variables, functions and types) defined in your
12086 program. This information is inherent in the text of your program and
12087 does not change as your program executes. @value{GDBN} finds it in your
12088 program's symbol table, in the file indicated when you started @value{GDBN}
12089 (@pxref{File Options, ,Choosing Files}), or by one of the
12090 file-management commands (@pxref{Files, ,Commands to Specify Files}).
12092 @cindex symbol names
12093 @cindex names of symbols
12094 @cindex quoting names
12095 Occasionally, you may need to refer to symbols that contain unusual
12096 characters, which @value{GDBN} ordinarily treats as word delimiters. The
12097 most frequent case is in referring to static variables in other
12098 source files (@pxref{Variables,,Program Variables}). File names
12099 are recorded in object files as debugging symbols, but @value{GDBN} would
12100 ordinarily parse a typical file name, like @file{foo.c}, as the three words
12101 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
12102 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
12109 looks up the value of @code{x} in the scope of the file @file{foo.c}.
12112 @cindex case-insensitive symbol names
12113 @cindex case sensitivity in symbol names
12114 @kindex set case-sensitive
12115 @item set case-sensitive on
12116 @itemx set case-sensitive off
12117 @itemx set case-sensitive auto
12118 Normally, when @value{GDBN} looks up symbols, it matches their names
12119 with case sensitivity determined by the current source language.
12120 Occasionally, you may wish to control that. The command @code{set
12121 case-sensitive} lets you do that by specifying @code{on} for
12122 case-sensitive matches or @code{off} for case-insensitive ones. If
12123 you specify @code{auto}, case sensitivity is reset to the default
12124 suitable for the source language. The default is case-sensitive
12125 matches for all languages except for Fortran, for which the default is
12126 case-insensitive matches.
12128 @kindex show case-sensitive
12129 @item show case-sensitive
12130 This command shows the current setting of case sensitivity for symbols
12133 @kindex info address
12134 @cindex address of a symbol
12135 @item info address @var{symbol}
12136 Describe where the data for @var{symbol} is stored. For a register
12137 variable, this says which register it is kept in. For a non-register
12138 local variable, this prints the stack-frame offset at which the variable
12141 Note the contrast with @samp{print &@var{symbol}}, which does not work
12142 at all for a register variable, and for a stack local variable prints
12143 the exact address of the current instantiation of the variable.
12145 @kindex info symbol
12146 @cindex symbol from address
12147 @cindex closest symbol and offset for an address
12148 @item info symbol @var{addr}
12149 Print the name of a symbol which is stored at the address @var{addr}.
12150 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
12151 nearest symbol and an offset from it:
12154 (@value{GDBP}) info symbol 0x54320
12155 _initialize_vx + 396 in section .text
12159 This is the opposite of the @code{info address} command. You can use
12160 it to find out the name of a variable or a function given its address.
12162 For dynamically linked executables, the name of executable or shared
12163 library containing the symbol is also printed:
12166 (@value{GDBP}) info symbol 0x400225
12167 _start + 5 in section .text of /tmp/a.out
12168 (@value{GDBP}) info symbol 0x2aaaac2811cf
12169 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
12173 @item whatis [@var{arg}]
12174 Print the data type of @var{arg}, which can be either an expression or
12175 a data type. With no argument, print the data type of @code{$}, the
12176 last value in the value history. If @var{arg} is an expression, it is
12177 not actually evaluated, and any side-effecting operations (such as
12178 assignments or function calls) inside it do not take place. If
12179 @var{arg} is a type name, it may be the name of a type or typedef, or
12180 for C code it may have the form @samp{class @var{class-name}},
12181 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12182 @samp{enum @var{enum-tag}}.
12183 @xref{Expressions, ,Expressions}.
12186 @item ptype [@var{arg}]
12187 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12188 detailed description of the type, instead of just the name of the type.
12189 @xref{Expressions, ,Expressions}.
12191 For example, for this variable declaration:
12194 struct complex @{double real; double imag;@} v;
12198 the two commands give this output:
12202 (@value{GDBP}) whatis v
12203 type = struct complex
12204 (@value{GDBP}) ptype v
12205 type = struct complex @{
12213 As with @code{whatis}, using @code{ptype} without an argument refers to
12214 the type of @code{$}, the last value in the value history.
12216 @cindex incomplete type
12217 Sometimes, programs use opaque data types or incomplete specifications
12218 of complex data structure. If the debug information included in the
12219 program does not allow @value{GDBN} to display a full declaration of
12220 the data type, it will say @samp{<incomplete type>}. For example,
12221 given these declarations:
12225 struct foo *fooptr;
12229 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12232 (@value{GDBP}) ptype foo
12233 $1 = <incomplete type>
12237 ``Incomplete type'' is C terminology for data types that are not
12238 completely specified.
12241 @item info types @var{regexp}
12243 Print a brief description of all types whose names match the regular
12244 expression @var{regexp} (or all types in your program, if you supply
12245 no argument). Each complete typename is matched as though it were a
12246 complete line; thus, @samp{i type value} gives information on all
12247 types in your program whose names include the string @code{value}, but
12248 @samp{i type ^value$} gives information only on types whose complete
12249 name is @code{value}.
12251 This command differs from @code{ptype} in two ways: first, like
12252 @code{whatis}, it does not print a detailed description; second, it
12253 lists all source files where a type is defined.
12256 @cindex local variables
12257 @item info scope @var{location}
12258 List all the variables local to a particular scope. This command
12259 accepts a @var{location} argument---a function name, a source line, or
12260 an address preceded by a @samp{*}, and prints all the variables local
12261 to the scope defined by that location. (@xref{Specify Location}, for
12262 details about supported forms of @var{location}.) For example:
12265 (@value{GDBP}) @b{info scope command_line_handler}
12266 Scope for command_line_handler:
12267 Symbol rl is an argument at stack/frame offset 8, length 4.
12268 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12269 Symbol linelength is in static storage at address 0x150a1c, length 4.
12270 Symbol p is a local variable in register $esi, length 4.
12271 Symbol p1 is a local variable in register $ebx, length 4.
12272 Symbol nline is a local variable in register $edx, length 4.
12273 Symbol repeat is a local variable at frame offset -8, length 4.
12277 This command is especially useful for determining what data to collect
12278 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12281 @kindex info source
12283 Show information about the current source file---that is, the source file for
12284 the function containing the current point of execution:
12287 the name of the source file, and the directory containing it,
12289 the directory it was compiled in,
12291 its length, in lines,
12293 which programming language it is written in,
12295 whether the executable includes debugging information for that file, and
12296 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12298 whether the debugging information includes information about
12299 preprocessor macros.
12303 @kindex info sources
12305 Print the names of all source files in your program for which there is
12306 debugging information, organized into two lists: files whose symbols
12307 have already been read, and files whose symbols will be read when needed.
12309 @kindex info functions
12310 @item info functions
12311 Print the names and data types of all defined functions.
12313 @item info functions @var{regexp}
12314 Print the names and data types of all defined functions
12315 whose names contain a match for regular expression @var{regexp}.
12316 Thus, @samp{info fun step} finds all functions whose names
12317 include @code{step}; @samp{info fun ^step} finds those whose names
12318 start with @code{step}. If a function name contains characters
12319 that conflict with the regular expression language (e.g.@:
12320 @samp{operator*()}), they may be quoted with a backslash.
12322 @kindex info variables
12323 @item info variables
12324 Print the names and data types of all variables that are declared
12325 outside of functions (i.e.@: excluding local variables).
12327 @item info variables @var{regexp}
12328 Print the names and data types of all variables (except for local
12329 variables) whose names contain a match for regular expression
12332 @kindex info classes
12333 @cindex Objective-C, classes and selectors
12335 @itemx info classes @var{regexp}
12336 Display all Objective-C classes in your program, or
12337 (with the @var{regexp} argument) all those matching a particular regular
12340 @kindex info selectors
12341 @item info selectors
12342 @itemx info selectors @var{regexp}
12343 Display all Objective-C selectors in your program, or
12344 (with the @var{regexp} argument) all those matching a particular regular
12348 This was never implemented.
12349 @kindex info methods
12351 @itemx info methods @var{regexp}
12352 The @code{info methods} command permits the user to examine all defined
12353 methods within C@t{++} program, or (with the @var{regexp} argument) a
12354 specific set of methods found in the various C@t{++} classes. Many
12355 C@t{++} classes provide a large number of methods. Thus, the output
12356 from the @code{ptype} command can be overwhelming and hard to use. The
12357 @code{info-methods} command filters the methods, printing only those
12358 which match the regular-expression @var{regexp}.
12361 @cindex reloading symbols
12362 Some systems allow individual object files that make up your program to
12363 be replaced without stopping and restarting your program. For example,
12364 in VxWorks you can simply recompile a defective object file and keep on
12365 running. If you are running on one of these systems, you can allow
12366 @value{GDBN} to reload the symbols for automatically relinked modules:
12369 @kindex set symbol-reloading
12370 @item set symbol-reloading on
12371 Replace symbol definitions for the corresponding source file when an
12372 object file with a particular name is seen again.
12374 @item set symbol-reloading off
12375 Do not replace symbol definitions when encountering object files of the
12376 same name more than once. This is the default state; if you are not
12377 running on a system that permits automatic relinking of modules, you
12378 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12379 may discard symbols when linking large programs, that may contain
12380 several modules (from different directories or libraries) with the same
12383 @kindex show symbol-reloading
12384 @item show symbol-reloading
12385 Show the current @code{on} or @code{off} setting.
12388 @cindex opaque data types
12389 @kindex set opaque-type-resolution
12390 @item set opaque-type-resolution on
12391 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12392 declared as a pointer to a @code{struct}, @code{class}, or
12393 @code{union}---for example, @code{struct MyType *}---that is used in one
12394 source file although the full declaration of @code{struct MyType} is in
12395 another source file. The default is on.
12397 A change in the setting of this subcommand will not take effect until
12398 the next time symbols for a file are loaded.
12400 @item set opaque-type-resolution off
12401 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12402 is printed as follows:
12404 @{<no data fields>@}
12407 @kindex show opaque-type-resolution
12408 @item show opaque-type-resolution
12409 Show whether opaque types are resolved or not.
12411 @kindex set print symbol-loading
12412 @cindex print messages when symbols are loaded
12413 @item set print symbol-loading
12414 @itemx set print symbol-loading on
12415 @itemx set print symbol-loading off
12416 The @code{set print symbol-loading} command allows you to enable or
12417 disable printing of messages when @value{GDBN} loads symbols.
12418 By default, these messages will be printed, and normally this is what
12419 you want. Disabling these messages is useful when debugging applications
12420 with lots of shared libraries where the quantity of output can be more
12421 annoying than useful.
12423 @kindex show print symbol-loading
12424 @item show print symbol-loading
12425 Show whether messages will be printed when @value{GDBN} loads symbols.
12427 @kindex maint print symbols
12428 @cindex symbol dump
12429 @kindex maint print psymbols
12430 @cindex partial symbol dump
12431 @item maint print symbols @var{filename}
12432 @itemx maint print psymbols @var{filename}
12433 @itemx maint print msymbols @var{filename}
12434 Write a dump of debugging symbol data into the file @var{filename}.
12435 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12436 symbols with debugging data are included. If you use @samp{maint print
12437 symbols}, @value{GDBN} includes all the symbols for which it has already
12438 collected full details: that is, @var{filename} reflects symbols for
12439 only those files whose symbols @value{GDBN} has read. You can use the
12440 command @code{info sources} to find out which files these are. If you
12441 use @samp{maint print psymbols} instead, the dump shows information about
12442 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12443 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12444 @samp{maint print msymbols} dumps just the minimal symbol information
12445 required for each object file from which @value{GDBN} has read some symbols.
12446 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12447 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12449 @kindex maint info symtabs
12450 @kindex maint info psymtabs
12451 @cindex listing @value{GDBN}'s internal symbol tables
12452 @cindex symbol tables, listing @value{GDBN}'s internal
12453 @cindex full symbol tables, listing @value{GDBN}'s internal
12454 @cindex partial symbol tables, listing @value{GDBN}'s internal
12455 @item maint info symtabs @r{[} @var{regexp} @r{]}
12456 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12458 List the @code{struct symtab} or @code{struct partial_symtab}
12459 structures whose names match @var{regexp}. If @var{regexp} is not
12460 given, list them all. The output includes expressions which you can
12461 copy into a @value{GDBN} debugging this one to examine a particular
12462 structure in more detail. For example:
12465 (@value{GDBP}) maint info psymtabs dwarf2read
12466 @{ objfile /home/gnu/build/gdb/gdb
12467 ((struct objfile *) 0x82e69d0)
12468 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12469 ((struct partial_symtab *) 0x8474b10)
12472 text addresses 0x814d3c8 -- 0x8158074
12473 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12474 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12475 dependencies (none)
12478 (@value{GDBP}) maint info symtabs
12482 We see that there is one partial symbol table whose filename contains
12483 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12484 and we see that @value{GDBN} has not read in any symtabs yet at all.
12485 If we set a breakpoint on a function, that will cause @value{GDBN} to
12486 read the symtab for the compilation unit containing that function:
12489 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12490 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12492 (@value{GDBP}) maint info symtabs
12493 @{ objfile /home/gnu/build/gdb/gdb
12494 ((struct objfile *) 0x82e69d0)
12495 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12496 ((struct symtab *) 0x86c1f38)
12499 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12500 linetable ((struct linetable *) 0x8370fa0)
12501 debugformat DWARF 2
12510 @chapter Altering Execution
12512 Once you think you have found an error in your program, you might want to
12513 find out for certain whether correcting the apparent error would lead to
12514 correct results in the rest of the run. You can find the answer by
12515 experiment, using the @value{GDBN} features for altering execution of the
12518 For example, you can store new values into variables or memory
12519 locations, give your program a signal, restart it at a different
12520 address, or even return prematurely from a function.
12523 * Assignment:: Assignment to variables
12524 * Jumping:: Continuing at a different address
12525 * Signaling:: Giving your program a signal
12526 * Returning:: Returning from a function
12527 * Calling:: Calling your program's functions
12528 * Patching:: Patching your program
12532 @section Assignment to Variables
12535 @cindex setting variables
12536 To alter the value of a variable, evaluate an assignment expression.
12537 @xref{Expressions, ,Expressions}. For example,
12544 stores the value 4 into the variable @code{x}, and then prints the
12545 value of the assignment expression (which is 4).
12546 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12547 information on operators in supported languages.
12549 @kindex set variable
12550 @cindex variables, setting
12551 If you are not interested in seeing the value of the assignment, use the
12552 @code{set} command instead of the @code{print} command. @code{set} is
12553 really the same as @code{print} except that the expression's value is
12554 not printed and is not put in the value history (@pxref{Value History,
12555 ,Value History}). The expression is evaluated only for its effects.
12557 If the beginning of the argument string of the @code{set} command
12558 appears identical to a @code{set} subcommand, use the @code{set
12559 variable} command instead of just @code{set}. This command is identical
12560 to @code{set} except for its lack of subcommands. For example, if your
12561 program has a variable @code{width}, you get an error if you try to set
12562 a new value with just @samp{set width=13}, because @value{GDBN} has the
12563 command @code{set width}:
12566 (@value{GDBP}) whatis width
12568 (@value{GDBP}) p width
12570 (@value{GDBP}) set width=47
12571 Invalid syntax in expression.
12575 The invalid expression, of course, is @samp{=47}. In
12576 order to actually set the program's variable @code{width}, use
12579 (@value{GDBP}) set var width=47
12582 Because the @code{set} command has many subcommands that can conflict
12583 with the names of program variables, it is a good idea to use the
12584 @code{set variable} command instead of just @code{set}. For example, if
12585 your program has a variable @code{g}, you run into problems if you try
12586 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12587 the command @code{set gnutarget}, abbreviated @code{set g}:
12591 (@value{GDBP}) whatis g
12595 (@value{GDBP}) set g=4
12599 The program being debugged has been started already.
12600 Start it from the beginning? (y or n) y
12601 Starting program: /home/smith/cc_progs/a.out
12602 "/home/smith/cc_progs/a.out": can't open to read symbols:
12603 Invalid bfd target.
12604 (@value{GDBP}) show g
12605 The current BFD target is "=4".
12610 The program variable @code{g} did not change, and you silently set the
12611 @code{gnutarget} to an invalid value. In order to set the variable
12615 (@value{GDBP}) set var g=4
12618 @value{GDBN} allows more implicit conversions in assignments than C; you can
12619 freely store an integer value into a pointer variable or vice versa,
12620 and you can convert any structure to any other structure that is the
12621 same length or shorter.
12622 @comment FIXME: how do structs align/pad in these conversions?
12623 @comment /doc@cygnus.com 18dec1990
12625 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12626 construct to generate a value of specified type at a specified address
12627 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12628 to memory location @code{0x83040} as an integer (which implies a certain size
12629 and representation in memory), and
12632 set @{int@}0x83040 = 4
12636 stores the value 4 into that memory location.
12639 @section Continuing at a Different Address
12641 Ordinarily, when you continue your program, you do so at the place where
12642 it stopped, with the @code{continue} command. You can instead continue at
12643 an address of your own choosing, with the following commands:
12647 @item jump @var{linespec}
12648 @itemx jump @var{location}
12649 Resume execution at line @var{linespec} or at address given by
12650 @var{location}. Execution stops again immediately if there is a
12651 breakpoint there. @xref{Specify Location}, for a description of the
12652 different forms of @var{linespec} and @var{location}. It is common
12653 practice to use the @code{tbreak} command in conjunction with
12654 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12656 The @code{jump} command does not change the current stack frame, or
12657 the stack pointer, or the contents of any memory location or any
12658 register other than the program counter. If line @var{linespec} is in
12659 a different function from the one currently executing, the results may
12660 be bizarre if the two functions expect different patterns of arguments or
12661 of local variables. For this reason, the @code{jump} command requests
12662 confirmation if the specified line is not in the function currently
12663 executing. However, even bizarre results are predictable if you are
12664 well acquainted with the machine-language code of your program.
12667 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12668 On many systems, you can get much the same effect as the @code{jump}
12669 command by storing a new value into the register @code{$pc}. The
12670 difference is that this does not start your program running; it only
12671 changes the address of where it @emph{will} run when you continue. For
12679 makes the next @code{continue} command or stepping command execute at
12680 address @code{0x485}, rather than at the address where your program stopped.
12681 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12683 The most common occasion to use the @code{jump} command is to back
12684 up---perhaps with more breakpoints set---over a portion of a program
12685 that has already executed, in order to examine its execution in more
12690 @section Giving your Program a Signal
12691 @cindex deliver a signal to a program
12695 @item signal @var{signal}
12696 Resume execution where your program stopped, but immediately give it the
12697 signal @var{signal}. @var{signal} can be the name or the number of a
12698 signal. For example, on many systems @code{signal 2} and @code{signal
12699 SIGINT} are both ways of sending an interrupt signal.
12701 Alternatively, if @var{signal} is zero, continue execution without
12702 giving a signal. This is useful when your program stopped on account of
12703 a signal and would ordinary see the signal when resumed with the
12704 @code{continue} command; @samp{signal 0} causes it to resume without a
12707 @code{signal} does not repeat when you press @key{RET} a second time
12708 after executing the command.
12712 Invoking the @code{signal} command is not the same as invoking the
12713 @code{kill} utility from the shell. Sending a signal with @code{kill}
12714 causes @value{GDBN} to decide what to do with the signal depending on
12715 the signal handling tables (@pxref{Signals}). The @code{signal} command
12716 passes the signal directly to your program.
12720 @section Returning from a Function
12723 @cindex returning from a function
12726 @itemx return @var{expression}
12727 You can cancel execution of a function call with the @code{return}
12728 command. If you give an
12729 @var{expression} argument, its value is used as the function's return
12733 When you use @code{return}, @value{GDBN} discards the selected stack frame
12734 (and all frames within it). You can think of this as making the
12735 discarded frame return prematurely. If you wish to specify a value to
12736 be returned, give that value as the argument to @code{return}.
12738 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12739 Frame}), and any other frames inside of it, leaving its caller as the
12740 innermost remaining frame. That frame becomes selected. The
12741 specified value is stored in the registers used for returning values
12744 The @code{return} command does not resume execution; it leaves the
12745 program stopped in the state that would exist if the function had just
12746 returned. In contrast, the @code{finish} command (@pxref{Continuing
12747 and Stepping, ,Continuing and Stepping}) resumes execution until the
12748 selected stack frame returns naturally.
12750 @value{GDBN} needs to know how the @var{expression} argument should be set for
12751 the inferior. The concrete registers assignment depends on the OS ABI and the
12752 type being returned by the selected stack frame. For example it is common for
12753 OS ABI to return floating point values in FPU registers while integer values in
12754 CPU registers. Still some ABIs return even floating point values in CPU
12755 registers. Larger integer widths (such as @code{long long int}) also have
12756 specific placement rules. @value{GDBN} already knows the OS ABI from its
12757 current target so it needs to find out also the type being returned to make the
12758 assignment into the right register(s).
12760 Normally, the selected stack frame has debug info. @value{GDBN} will always
12761 use the debug info instead of the implicit type of @var{expression} when the
12762 debug info is available. For example, if you type @kbd{return -1}, and the
12763 function in the current stack frame is declared to return a @code{long long
12764 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
12765 into a @code{long long int}:
12768 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
12770 (@value{GDBP}) return -1
12771 Make func return now? (y or n) y
12772 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
12773 43 printf ("result=%lld\n", func ());
12777 However, if the selected stack frame does not have a debug info, e.g., if the
12778 function was compiled without debug info, @value{GDBN} has to find out the type
12779 to return from user. Specifying a different type by mistake may set the value
12780 in different inferior registers than the caller code expects. For example,
12781 typing @kbd{return -1} with its implicit type @code{int} would set only a part
12782 of a @code{long long int} result for a debug info less function (on 32-bit
12783 architectures). Therefore the user is required to specify the return type by
12784 an appropriate cast explicitly:
12787 Breakpoint 2, 0x0040050b in func ()
12788 (@value{GDBP}) return -1
12789 Return value type not available for selected stack frame.
12790 Please use an explicit cast of the value to return.
12791 (@value{GDBP}) return (long long int) -1
12792 Make selected stack frame return now? (y or n) y
12793 #0 0x00400526 in main ()
12798 @section Calling Program Functions
12801 @cindex calling functions
12802 @cindex inferior functions, calling
12803 @item print @var{expr}
12804 Evaluate the expression @var{expr} and display the resulting value.
12805 @var{expr} may include calls to functions in the program being
12809 @item call @var{expr}
12810 Evaluate the expression @var{expr} without displaying @code{void}
12813 You can use this variant of the @code{print} command if you want to
12814 execute a function from your program that does not return anything
12815 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12816 with @code{void} returned values that @value{GDBN} will otherwise
12817 print. If the result is not void, it is printed and saved in the
12821 It is possible for the function you call via the @code{print} or
12822 @code{call} command to generate a signal (e.g., if there's a bug in
12823 the function, or if you passed it incorrect arguments). What happens
12824 in that case is controlled by the @code{set unwindonsignal} command.
12827 @item set unwindonsignal
12828 @kindex set unwindonsignal
12829 @cindex unwind stack in called functions
12830 @cindex call dummy stack unwinding
12831 Set unwinding of the stack if a signal is received while in a function
12832 that @value{GDBN} called in the program being debugged. If set to on,
12833 @value{GDBN} unwinds the stack it created for the call and restores
12834 the context to what it was before the call. If set to off (the
12835 default), @value{GDBN} stops in the frame where the signal was
12838 @item show unwindonsignal
12839 @kindex show unwindonsignal
12840 Show the current setting of stack unwinding in the functions called by
12844 @cindex weak alias functions
12845 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12846 for another function. In such case, @value{GDBN} might not pick up
12847 the type information, including the types of the function arguments,
12848 which causes @value{GDBN} to call the inferior function incorrectly.
12849 As a result, the called function will function erroneously and may
12850 even crash. A solution to that is to use the name of the aliased
12854 @section Patching Programs
12856 @cindex patching binaries
12857 @cindex writing into executables
12858 @cindex writing into corefiles
12860 By default, @value{GDBN} opens the file containing your program's
12861 executable code (or the corefile) read-only. This prevents accidental
12862 alterations to machine code; but it also prevents you from intentionally
12863 patching your program's binary.
12865 If you'd like to be able to patch the binary, you can specify that
12866 explicitly with the @code{set write} command. For example, you might
12867 want to turn on internal debugging flags, or even to make emergency
12873 @itemx set write off
12874 If you specify @samp{set write on}, @value{GDBN} opens executable and
12875 core files for both reading and writing; if you specify @kbd{set write
12876 off} (the default), @value{GDBN} opens them read-only.
12878 If you have already loaded a file, you must load it again (using the
12879 @code{exec-file} or @code{core-file} command) after changing @code{set
12880 write}, for your new setting to take effect.
12884 Display whether executable files and core files are opened for writing
12885 as well as reading.
12889 @chapter @value{GDBN} Files
12891 @value{GDBN} needs to know the file name of the program to be debugged,
12892 both in order to read its symbol table and in order to start your
12893 program. To debug a core dump of a previous run, you must also tell
12894 @value{GDBN} the name of the core dump file.
12897 * Files:: Commands to specify files
12898 * Separate Debug Files:: Debugging information in separate files
12899 * Symbol Errors:: Errors reading symbol files
12900 * Data Files:: GDB data files
12904 @section Commands to Specify Files
12906 @cindex symbol table
12907 @cindex core dump file
12909 You may want to specify executable and core dump file names. The usual
12910 way to do this is at start-up time, using the arguments to
12911 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12912 Out of @value{GDBN}}).
12914 Occasionally it is necessary to change to a different file during a
12915 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12916 specify a file you want to use. Or you are debugging a remote target
12917 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12918 Program}). In these situations the @value{GDBN} commands to specify
12919 new files are useful.
12922 @cindex executable file
12924 @item file @var{filename}
12925 Use @var{filename} as the program to be debugged. It is read for its
12926 symbols and for the contents of pure memory. It is also the program
12927 executed when you use the @code{run} command. If you do not specify a
12928 directory and the file is not found in the @value{GDBN} working directory,
12929 @value{GDBN} uses the environment variable @code{PATH} as a list of
12930 directories to search, just as the shell does when looking for a program
12931 to run. You can change the value of this variable, for both @value{GDBN}
12932 and your program, using the @code{path} command.
12934 @cindex unlinked object files
12935 @cindex patching object files
12936 You can load unlinked object @file{.o} files into @value{GDBN} using
12937 the @code{file} command. You will not be able to ``run'' an object
12938 file, but you can disassemble functions and inspect variables. Also,
12939 if the underlying BFD functionality supports it, you could use
12940 @kbd{gdb -write} to patch object files using this technique. Note
12941 that @value{GDBN} can neither interpret nor modify relocations in this
12942 case, so branches and some initialized variables will appear to go to
12943 the wrong place. But this feature is still handy from time to time.
12946 @code{file} with no argument makes @value{GDBN} discard any information it
12947 has on both executable file and the symbol table.
12950 @item exec-file @r{[} @var{filename} @r{]}
12951 Specify that the program to be run (but not the symbol table) is found
12952 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12953 if necessary to locate your program. Omitting @var{filename} means to
12954 discard information on the executable file.
12956 @kindex symbol-file
12957 @item symbol-file @r{[} @var{filename} @r{]}
12958 Read symbol table information from file @var{filename}. @code{PATH} is
12959 searched when necessary. Use the @code{file} command to get both symbol
12960 table and program to run from the same file.
12962 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12963 program's symbol table.
12965 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12966 some breakpoints and auto-display expressions. This is because they may
12967 contain pointers to the internal data recording symbols and data types,
12968 which are part of the old symbol table data being discarded inside
12971 @code{symbol-file} does not repeat if you press @key{RET} again after
12974 When @value{GDBN} is configured for a particular environment, it
12975 understands debugging information in whatever format is the standard
12976 generated for that environment; you may use either a @sc{gnu} compiler, or
12977 other compilers that adhere to the local conventions.
12978 Best results are usually obtained from @sc{gnu} compilers; for example,
12979 using @code{@value{NGCC}} you can generate debugging information for
12982 For most kinds of object files, with the exception of old SVR3 systems
12983 using COFF, the @code{symbol-file} command does not normally read the
12984 symbol table in full right away. Instead, it scans the symbol table
12985 quickly to find which source files and which symbols are present. The
12986 details are read later, one source file at a time, as they are needed.
12988 The purpose of this two-stage reading strategy is to make @value{GDBN}
12989 start up faster. For the most part, it is invisible except for
12990 occasional pauses while the symbol table details for a particular source
12991 file are being read. (The @code{set verbose} command can turn these
12992 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12993 Warnings and Messages}.)
12995 We have not implemented the two-stage strategy for COFF yet. When the
12996 symbol table is stored in COFF format, @code{symbol-file} reads the
12997 symbol table data in full right away. Note that ``stabs-in-COFF''
12998 still does the two-stage strategy, since the debug info is actually
13002 @cindex reading symbols immediately
13003 @cindex symbols, reading immediately
13004 @item symbol-file @var{filename} @r{[} -readnow @r{]}
13005 @itemx file @var{filename} @r{[} -readnow @r{]}
13006 You can override the @value{GDBN} two-stage strategy for reading symbol
13007 tables by using the @samp{-readnow} option with any of the commands that
13008 load symbol table information, if you want to be sure @value{GDBN} has the
13009 entire symbol table available.
13011 @c FIXME: for now no mention of directories, since this seems to be in
13012 @c flux. 13mar1992 status is that in theory GDB would look either in
13013 @c current dir or in same dir as myprog; but issues like competing
13014 @c GDB's, or clutter in system dirs, mean that in practice right now
13015 @c only current dir is used. FFish says maybe a special GDB hierarchy
13016 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13020 @item core-file @r{[}@var{filename}@r{]}
13022 Specify the whereabouts of a core dump file to be used as the ``contents
13023 of memory''. Traditionally, core files contain only some parts of the
13024 address space of the process that generated them; @value{GDBN} can access the
13025 executable file itself for other parts.
13027 @code{core-file} with no argument specifies that no core file is
13030 Note that the core file is ignored when your program is actually running
13031 under @value{GDBN}. So, if you have been running your program and you
13032 wish to debug a core file instead, you must kill the subprocess in which
13033 the program is running. To do this, use the @code{kill} command
13034 (@pxref{Kill Process, ,Killing the Child Process}).
13036 @kindex add-symbol-file
13037 @cindex dynamic linking
13038 @item add-symbol-file @var{filename} @var{address}
13039 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13040 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
13041 The @code{add-symbol-file} command reads additional symbol table
13042 information from the file @var{filename}. You would use this command
13043 when @var{filename} has been dynamically loaded (by some other means)
13044 into the program that is running. @var{address} should be the memory
13045 address at which the file has been loaded; @value{GDBN} cannot figure
13046 this out for itself. You can additionally specify an arbitrary number
13047 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
13048 section name and base address for that section. You can specify any
13049 @var{address} as an expression.
13051 The symbol table of the file @var{filename} is added to the symbol table
13052 originally read with the @code{symbol-file} command. You can use the
13053 @code{add-symbol-file} command any number of times; the new symbol data
13054 thus read keeps adding to the old. To discard all old symbol data
13055 instead, use the @code{symbol-file} command without any arguments.
13057 @cindex relocatable object files, reading symbols from
13058 @cindex object files, relocatable, reading symbols from
13059 @cindex reading symbols from relocatable object files
13060 @cindex symbols, reading from relocatable object files
13061 @cindex @file{.o} files, reading symbols from
13062 Although @var{filename} is typically a shared library file, an
13063 executable file, or some other object file which has been fully
13064 relocated for loading into a process, you can also load symbolic
13065 information from relocatable @file{.o} files, as long as:
13069 the file's symbolic information refers only to linker symbols defined in
13070 that file, not to symbols defined by other object files,
13072 every section the file's symbolic information refers to has actually
13073 been loaded into the inferior, as it appears in the file, and
13075 you can determine the address at which every section was loaded, and
13076 provide these to the @code{add-symbol-file} command.
13080 Some embedded operating systems, like Sun Chorus and VxWorks, can load
13081 relocatable files into an already running program; such systems
13082 typically make the requirements above easy to meet. However, it's
13083 important to recognize that many native systems use complex link
13084 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
13085 assembly, for example) that make the requirements difficult to meet. In
13086 general, one cannot assume that using @code{add-symbol-file} to read a
13087 relocatable object file's symbolic information will have the same effect
13088 as linking the relocatable object file into the program in the normal
13091 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
13093 @kindex add-symbol-file-from-memory
13094 @cindex @code{syscall DSO}
13095 @cindex load symbols from memory
13096 @item add-symbol-file-from-memory @var{address}
13097 Load symbols from the given @var{address} in a dynamically loaded
13098 object file whose image is mapped directly into the inferior's memory.
13099 For example, the Linux kernel maps a @code{syscall DSO} into each
13100 process's address space; this DSO provides kernel-specific code for
13101 some system calls. The argument can be any expression whose
13102 evaluation yields the address of the file's shared object file header.
13103 For this command to work, you must have used @code{symbol-file} or
13104 @code{exec-file} commands in advance.
13106 @kindex add-shared-symbol-files
13108 @item add-shared-symbol-files @var{library-file}
13109 @itemx assf @var{library-file}
13110 The @code{add-shared-symbol-files} command can currently be used only
13111 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
13112 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
13113 @value{GDBN} automatically looks for shared libraries, however if
13114 @value{GDBN} does not find yours, you can invoke
13115 @code{add-shared-symbol-files}. It takes one argument: the shared
13116 library's file name. @code{assf} is a shorthand alias for
13117 @code{add-shared-symbol-files}.
13120 @item section @var{section} @var{addr}
13121 The @code{section} command changes the base address of the named
13122 @var{section} of the exec file to @var{addr}. This can be used if the
13123 exec file does not contain section addresses, (such as in the
13124 @code{a.out} format), or when the addresses specified in the file
13125 itself are wrong. Each section must be changed separately. The
13126 @code{info files} command, described below, lists all the sections and
13130 @kindex info target
13133 @code{info files} and @code{info target} are synonymous; both print the
13134 current target (@pxref{Targets, ,Specifying a Debugging Target}),
13135 including the names of the executable and core dump files currently in
13136 use by @value{GDBN}, and the files from which symbols were loaded. The
13137 command @code{help target} lists all possible targets rather than
13140 @kindex maint info sections
13141 @item maint info sections
13142 Another command that can give you extra information about program sections
13143 is @code{maint info sections}. In addition to the section information
13144 displayed by @code{info files}, this command displays the flags and file
13145 offset of each section in the executable and core dump files. In addition,
13146 @code{maint info sections} provides the following command options (which
13147 may be arbitrarily combined):
13151 Display sections for all loaded object files, including shared libraries.
13152 @item @var{sections}
13153 Display info only for named @var{sections}.
13154 @item @var{section-flags}
13155 Display info only for sections for which @var{section-flags} are true.
13156 The section flags that @value{GDBN} currently knows about are:
13159 Section will have space allocated in the process when loaded.
13160 Set for all sections except those containing debug information.
13162 Section will be loaded from the file into the child process memory.
13163 Set for pre-initialized code and data, clear for @code{.bss} sections.
13165 Section needs to be relocated before loading.
13167 Section cannot be modified by the child process.
13169 Section contains executable code only.
13171 Section contains data only (no executable code).
13173 Section will reside in ROM.
13175 Section contains data for constructor/destructor lists.
13177 Section is not empty.
13179 An instruction to the linker to not output the section.
13180 @item COFF_SHARED_LIBRARY
13181 A notification to the linker that the section contains
13182 COFF shared library information.
13184 Section contains common symbols.
13187 @kindex set trust-readonly-sections
13188 @cindex read-only sections
13189 @item set trust-readonly-sections on
13190 Tell @value{GDBN} that readonly sections in your object file
13191 really are read-only (i.e.@: that their contents will not change).
13192 In that case, @value{GDBN} can fetch values from these sections
13193 out of the object file, rather than from the target program.
13194 For some targets (notably embedded ones), this can be a significant
13195 enhancement to debugging performance.
13197 The default is off.
13199 @item set trust-readonly-sections off
13200 Tell @value{GDBN} not to trust readonly sections. This means that
13201 the contents of the section might change while the program is running,
13202 and must therefore be fetched from the target when needed.
13204 @item show trust-readonly-sections
13205 Show the current setting of trusting readonly sections.
13208 All file-specifying commands allow both absolute and relative file names
13209 as arguments. @value{GDBN} always converts the file name to an absolute file
13210 name and remembers it that way.
13212 @cindex shared libraries
13213 @anchor{Shared Libraries}
13214 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13215 and IBM RS/6000 AIX shared libraries.
13217 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13218 shared libraries. @xref{Expat}.
13220 @value{GDBN} automatically loads symbol definitions from shared libraries
13221 when you use the @code{run} command, or when you examine a core file.
13222 (Before you issue the @code{run} command, @value{GDBN} does not understand
13223 references to a function in a shared library, however---unless you are
13224 debugging a core file).
13226 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13227 automatically loads the symbols at the time of the @code{shl_load} call.
13229 @c FIXME: some @value{GDBN} release may permit some refs to undef
13230 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13231 @c FIXME...lib; check this from time to time when updating manual
13233 There are times, however, when you may wish to not automatically load
13234 symbol definitions from shared libraries, such as when they are
13235 particularly large or there are many of them.
13237 To control the automatic loading of shared library symbols, use the
13241 @kindex set auto-solib-add
13242 @item set auto-solib-add @var{mode}
13243 If @var{mode} is @code{on}, symbols from all shared object libraries
13244 will be loaded automatically when the inferior begins execution, you
13245 attach to an independently started inferior, or when the dynamic linker
13246 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13247 is @code{off}, symbols must be loaded manually, using the
13248 @code{sharedlibrary} command. The default value is @code{on}.
13250 @cindex memory used for symbol tables
13251 If your program uses lots of shared libraries with debug info that
13252 takes large amounts of memory, you can decrease the @value{GDBN}
13253 memory footprint by preventing it from automatically loading the
13254 symbols from shared libraries. To that end, type @kbd{set
13255 auto-solib-add off} before running the inferior, then load each
13256 library whose debug symbols you do need with @kbd{sharedlibrary
13257 @var{regexp}}, where @var{regexp} is a regular expression that matches
13258 the libraries whose symbols you want to be loaded.
13260 @kindex show auto-solib-add
13261 @item show auto-solib-add
13262 Display the current autoloading mode.
13265 @cindex load shared library
13266 To explicitly load shared library symbols, use the @code{sharedlibrary}
13270 @kindex info sharedlibrary
13273 @itemx info sharedlibrary
13274 Print the names of the shared libraries which are currently loaded.
13276 @kindex sharedlibrary
13278 @item sharedlibrary @var{regex}
13279 @itemx share @var{regex}
13280 Load shared object library symbols for files matching a
13281 Unix regular expression.
13282 As with files loaded automatically, it only loads shared libraries
13283 required by your program for a core file or after typing @code{run}. If
13284 @var{regex} is omitted all shared libraries required by your program are
13287 @item nosharedlibrary
13288 @kindex nosharedlibrary
13289 @cindex unload symbols from shared libraries
13290 Unload all shared object library symbols. This discards all symbols
13291 that have been loaded from all shared libraries. Symbols from shared
13292 libraries that were loaded by explicit user requests are not
13296 Sometimes you may wish that @value{GDBN} stops and gives you control
13297 when any of shared library events happen. Use the @code{set
13298 stop-on-solib-events} command for this:
13301 @item set stop-on-solib-events
13302 @kindex set stop-on-solib-events
13303 This command controls whether @value{GDBN} should give you control
13304 when the dynamic linker notifies it about some shared library event.
13305 The most common event of interest is loading or unloading of a new
13308 @item show stop-on-solib-events
13309 @kindex show stop-on-solib-events
13310 Show whether @value{GDBN} stops and gives you control when shared
13311 library events happen.
13314 Shared libraries are also supported in many cross or remote debugging
13315 configurations. @value{GDBN} needs to have access to the target's libraries;
13316 this can be accomplished either by providing copies of the libraries
13317 on the host system, or by asking @value{GDBN} to automatically retrieve the
13318 libraries from the target. If copies of the target libraries are
13319 provided, they need to be the same as the target libraries, although the
13320 copies on the target can be stripped as long as the copies on the host are
13323 @cindex where to look for shared libraries
13324 For remote debugging, you need to tell @value{GDBN} where the target
13325 libraries are, so that it can load the correct copies---otherwise, it
13326 may try to load the host's libraries. @value{GDBN} has two variables
13327 to specify the search directories for target libraries.
13330 @cindex prefix for shared library file names
13331 @cindex system root, alternate
13332 @kindex set solib-absolute-prefix
13333 @kindex set sysroot
13334 @item set sysroot @var{path}
13335 Use @var{path} as the system root for the program being debugged. Any
13336 absolute shared library paths will be prefixed with @var{path}; many
13337 runtime loaders store the absolute paths to the shared library in the
13338 target program's memory. If you use @code{set sysroot} to find shared
13339 libraries, they need to be laid out in the same way that they are on
13340 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13343 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13344 retrieve the target libraries from the remote system. This is only
13345 supported when using a remote target that supports the @code{remote get}
13346 command (@pxref{File Transfer,,Sending files to a remote system}).
13347 The part of @var{path} following the initial @file{remote:}
13348 (if present) is used as system root prefix on the remote file system.
13349 @footnote{If you want to specify a local system root using a directory
13350 that happens to be named @file{remote:}, you need to use some equivalent
13351 variant of the name like @file{./remote:}.}
13353 The @code{set solib-absolute-prefix} command is an alias for @code{set
13356 @cindex default system root
13357 @cindex @samp{--with-sysroot}
13358 You can set the default system root by using the configure-time
13359 @samp{--with-sysroot} option. If the system root is inside
13360 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13361 @samp{--exec-prefix}), then the default system root will be updated
13362 automatically if the installed @value{GDBN} is moved to a new
13365 @kindex show sysroot
13367 Display the current shared library prefix.
13369 @kindex set solib-search-path
13370 @item set solib-search-path @var{path}
13371 If this variable is set, @var{path} is a colon-separated list of
13372 directories to search for shared libraries. @samp{solib-search-path}
13373 is used after @samp{sysroot} fails to locate the library, or if the
13374 path to the library is relative instead of absolute. If you want to
13375 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13376 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13377 finding your host's libraries. @samp{sysroot} is preferred; setting
13378 it to a nonexistent directory may interfere with automatic loading
13379 of shared library symbols.
13381 @kindex show solib-search-path
13382 @item show solib-search-path
13383 Display the current shared library search path.
13387 @node Separate Debug Files
13388 @section Debugging Information in Separate Files
13389 @cindex separate debugging information files
13390 @cindex debugging information in separate files
13391 @cindex @file{.debug} subdirectories
13392 @cindex debugging information directory, global
13393 @cindex global debugging information directory
13394 @cindex build ID, and separate debugging files
13395 @cindex @file{.build-id} directory
13397 @value{GDBN} allows you to put a program's debugging information in a
13398 file separate from the executable itself, in a way that allows
13399 @value{GDBN} to find and load the debugging information automatically.
13400 Since debugging information can be very large---sometimes larger
13401 than the executable code itself---some systems distribute debugging
13402 information for their executables in separate files, which users can
13403 install only when they need to debug a problem.
13405 @value{GDBN} supports two ways of specifying the separate debug info
13410 The executable contains a @dfn{debug link} that specifies the name of
13411 the separate debug info file. The separate debug file's name is
13412 usually @file{@var{executable}.debug}, where @var{executable} is the
13413 name of the corresponding executable file without leading directories
13414 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13415 debug link specifies a CRC32 checksum for the debug file, which
13416 @value{GDBN} uses to validate that the executable and the debug file
13417 came from the same build.
13420 The executable contains a @dfn{build ID}, a unique bit string that is
13421 also present in the corresponding debug info file. (This is supported
13422 only on some operating systems, notably those which use the ELF format
13423 for binary files and the @sc{gnu} Binutils.) For more details about
13424 this feature, see the description of the @option{--build-id}
13425 command-line option in @ref{Options, , Command Line Options, ld.info,
13426 The GNU Linker}. The debug info file's name is not specified
13427 explicitly by the build ID, but can be computed from the build ID, see
13431 Depending on the way the debug info file is specified, @value{GDBN}
13432 uses two different methods of looking for the debug file:
13436 For the ``debug link'' method, @value{GDBN} looks up the named file in
13437 the directory of the executable file, then in a subdirectory of that
13438 directory named @file{.debug}, and finally under the global debug
13439 directory, in a subdirectory whose name is identical to the leading
13440 directories of the executable's absolute file name.
13443 For the ``build ID'' method, @value{GDBN} looks in the
13444 @file{.build-id} subdirectory of the global debug directory for a file
13445 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13446 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13447 are the rest of the bit string. (Real build ID strings are 32 or more
13448 hex characters, not 10.)
13451 So, for example, suppose you ask @value{GDBN} to debug
13452 @file{/usr/bin/ls}, which has a debug link that specifies the
13453 file @file{ls.debug}, and a build ID whose value in hex is
13454 @code{abcdef1234}. If the global debug directory is
13455 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13456 debug information files, in the indicated order:
13460 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13462 @file{/usr/bin/ls.debug}
13464 @file{/usr/bin/.debug/ls.debug}
13466 @file{/usr/lib/debug/usr/bin/ls.debug}.
13469 You can set the global debugging info directory's name, and view the
13470 name @value{GDBN} is currently using.
13474 @kindex set debug-file-directory
13475 @item set debug-file-directory @var{directory}
13476 Set the directory which @value{GDBN} searches for separate debugging
13477 information files to @var{directory}.
13479 @kindex show debug-file-directory
13480 @item show debug-file-directory
13481 Show the directory @value{GDBN} searches for separate debugging
13486 @cindex @code{.gnu_debuglink} sections
13487 @cindex debug link sections
13488 A debug link is a special section of the executable file named
13489 @code{.gnu_debuglink}. The section must contain:
13493 A filename, with any leading directory components removed, followed by
13496 zero to three bytes of padding, as needed to reach the next four-byte
13497 boundary within the section, and
13499 a four-byte CRC checksum, stored in the same endianness used for the
13500 executable file itself. The checksum is computed on the debugging
13501 information file's full contents by the function given below, passing
13502 zero as the @var{crc} argument.
13505 Any executable file format can carry a debug link, as long as it can
13506 contain a section named @code{.gnu_debuglink} with the contents
13509 @cindex @code{.note.gnu.build-id} sections
13510 @cindex build ID sections
13511 The build ID is a special section in the executable file (and in other
13512 ELF binary files that @value{GDBN} may consider). This section is
13513 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13514 It contains unique identification for the built files---the ID remains
13515 the same across multiple builds of the same build tree. The default
13516 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13517 content for the build ID string. The same section with an identical
13518 value is present in the original built binary with symbols, in its
13519 stripped variant, and in the separate debugging information file.
13521 The debugging information file itself should be an ordinary
13522 executable, containing a full set of linker symbols, sections, and
13523 debugging information. The sections of the debugging information file
13524 should have the same names, addresses, and sizes as the original file,
13525 but they need not contain any data---much like a @code{.bss} section
13526 in an ordinary executable.
13528 The @sc{gnu} binary utilities (Binutils) package includes the
13529 @samp{objcopy} utility that can produce
13530 the separated executable / debugging information file pairs using the
13531 following commands:
13534 @kbd{objcopy --only-keep-debug foo foo.debug}
13539 These commands remove the debugging
13540 information from the executable file @file{foo} and place it in the file
13541 @file{foo.debug}. You can use the first, second or both methods to link the
13546 The debug link method needs the following additional command to also leave
13547 behind a debug link in @file{foo}:
13550 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13553 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13554 a version of the @code{strip} command such that the command @kbd{strip foo -f
13555 foo.debug} has the same functionality as the two @code{objcopy} commands and
13556 the @code{ln -s} command above, together.
13559 Build ID gets embedded into the main executable using @code{ld --build-id} or
13560 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13561 compatibility fixes for debug files separation are present in @sc{gnu} binary
13562 utilities (Binutils) package since version 2.18.
13567 Since there are many different ways to compute CRC's for the debug
13568 link (different polynomials, reversals, byte ordering, etc.), the
13569 simplest way to describe the CRC used in @code{.gnu_debuglink}
13570 sections is to give the complete code for a function that computes it:
13572 @kindex gnu_debuglink_crc32
13575 gnu_debuglink_crc32 (unsigned long crc,
13576 unsigned char *buf, size_t len)
13578 static const unsigned long crc32_table[256] =
13580 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13581 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13582 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13583 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13584 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13585 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13586 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13587 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13588 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13589 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13590 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13591 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13592 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13593 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13594 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13595 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13596 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13597 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13598 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13599 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13600 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13601 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13602 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13603 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13604 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13605 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13606 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13607 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13608 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13609 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13610 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13611 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13612 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13613 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13614 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13615 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13616 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13617 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13618 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13619 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13620 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13621 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13622 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13623 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13624 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13625 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13626 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13627 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13628 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13629 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13630 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13633 unsigned char *end;
13635 crc = ~crc & 0xffffffff;
13636 for (end = buf + len; buf < end; ++buf)
13637 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13638 return ~crc & 0xffffffff;
13643 This computation does not apply to the ``build ID'' method.
13646 @node Symbol Errors
13647 @section Errors Reading Symbol Files
13649 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13650 such as symbol types it does not recognize, or known bugs in compiler
13651 output. By default, @value{GDBN} does not notify you of such problems, since
13652 they are relatively common and primarily of interest to people
13653 debugging compilers. If you are interested in seeing information
13654 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13655 only one message about each such type of problem, no matter how many
13656 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13657 to see how many times the problems occur, with the @code{set
13658 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13661 The messages currently printed, and their meanings, include:
13664 @item inner block not inside outer block in @var{symbol}
13666 The symbol information shows where symbol scopes begin and end
13667 (such as at the start of a function or a block of statements). This
13668 error indicates that an inner scope block is not fully contained
13669 in its outer scope blocks.
13671 @value{GDBN} circumvents the problem by treating the inner block as if it had
13672 the same scope as the outer block. In the error message, @var{symbol}
13673 may be shown as ``@code{(don't know)}'' if the outer block is not a
13676 @item block at @var{address} out of order
13678 The symbol information for symbol scope blocks should occur in
13679 order of increasing addresses. This error indicates that it does not
13682 @value{GDBN} does not circumvent this problem, and has trouble
13683 locating symbols in the source file whose symbols it is reading. (You
13684 can often determine what source file is affected by specifying
13685 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13688 @item bad block start address patched
13690 The symbol information for a symbol scope block has a start address
13691 smaller than the address of the preceding source line. This is known
13692 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13694 @value{GDBN} circumvents the problem by treating the symbol scope block as
13695 starting on the previous source line.
13697 @item bad string table offset in symbol @var{n}
13700 Symbol number @var{n} contains a pointer into the string table which is
13701 larger than the size of the string table.
13703 @value{GDBN} circumvents the problem by considering the symbol to have the
13704 name @code{foo}, which may cause other problems if many symbols end up
13707 @item unknown symbol type @code{0x@var{nn}}
13709 The symbol information contains new data types that @value{GDBN} does
13710 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13711 uncomprehended information, in hexadecimal.
13713 @value{GDBN} circumvents the error by ignoring this symbol information.
13714 This usually allows you to debug your program, though certain symbols
13715 are not accessible. If you encounter such a problem and feel like
13716 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13717 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13718 and examine @code{*bufp} to see the symbol.
13720 @item stub type has NULL name
13722 @value{GDBN} could not find the full definition for a struct or class.
13724 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13725 The symbol information for a C@t{++} member function is missing some
13726 information that recent versions of the compiler should have output for
13729 @item info mismatch between compiler and debugger
13731 @value{GDBN} could not parse a type specification output by the compiler.
13736 @section GDB Data Files
13738 @cindex prefix for data files
13739 @value{GDBN} will sometimes read an auxiliary data file. These files
13740 are kept in a directory known as the @dfn{data directory}.
13742 You can set the data directory's name, and view the name @value{GDBN}
13743 is currently using.
13746 @kindex set data-directory
13747 @item set data-directory @var{directory}
13748 Set the directory which @value{GDBN} searches for auxiliary data files
13749 to @var{directory}.
13751 @kindex show data-directory
13752 @item show data-directory
13753 Show the directory @value{GDBN} searches for auxiliary data files.
13756 @cindex default data directory
13757 @cindex @samp{--with-gdb-datadir}
13758 You can set the default data directory by using the configure-time
13759 @samp{--with-gdb-datadir} option. If the data directory is inside
13760 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13761 @samp{--exec-prefix}), then the default data directory will be updated
13762 automatically if the installed @value{GDBN} is moved to a new
13766 @chapter Specifying a Debugging Target
13768 @cindex debugging target
13769 A @dfn{target} is the execution environment occupied by your program.
13771 Often, @value{GDBN} runs in the same host environment as your program;
13772 in that case, the debugging target is specified as a side effect when
13773 you use the @code{file} or @code{core} commands. When you need more
13774 flexibility---for example, running @value{GDBN} on a physically separate
13775 host, or controlling a standalone system over a serial port or a
13776 realtime system over a TCP/IP connection---you can use the @code{target}
13777 command to specify one of the target types configured for @value{GDBN}
13778 (@pxref{Target Commands, ,Commands for Managing Targets}).
13780 @cindex target architecture
13781 It is possible to build @value{GDBN} for several different @dfn{target
13782 architectures}. When @value{GDBN} is built like that, you can choose
13783 one of the available architectures with the @kbd{set architecture}
13787 @kindex set architecture
13788 @kindex show architecture
13789 @item set architecture @var{arch}
13790 This command sets the current target architecture to @var{arch}. The
13791 value of @var{arch} can be @code{"auto"}, in addition to one of the
13792 supported architectures.
13794 @item show architecture
13795 Show the current target architecture.
13797 @item set processor
13799 @kindex set processor
13800 @kindex show processor
13801 These are alias commands for, respectively, @code{set architecture}
13802 and @code{show architecture}.
13806 * Active Targets:: Active targets
13807 * Target Commands:: Commands for managing targets
13808 * Byte Order:: Choosing target byte order
13811 @node Active Targets
13812 @section Active Targets
13814 @cindex stacking targets
13815 @cindex active targets
13816 @cindex multiple targets
13818 There are three classes of targets: processes, core files, and
13819 executable files. @value{GDBN} can work concurrently on up to three
13820 active targets, one in each class. This allows you to (for example)
13821 start a process and inspect its activity without abandoning your work on
13824 For example, if you execute @samp{gdb a.out}, then the executable file
13825 @code{a.out} is the only active target. If you designate a core file as
13826 well---presumably from a prior run that crashed and coredumped---then
13827 @value{GDBN} has two active targets and uses them in tandem, looking
13828 first in the corefile target, then in the executable file, to satisfy
13829 requests for memory addresses. (Typically, these two classes of target
13830 are complementary, since core files contain only a program's
13831 read-write memory---variables and so on---plus machine status, while
13832 executable files contain only the program text and initialized data.)
13834 When you type @code{run}, your executable file becomes an active process
13835 target as well. When a process target is active, all @value{GDBN}
13836 commands requesting memory addresses refer to that target; addresses in
13837 an active core file or executable file target are obscured while the
13838 process target is active.
13840 Use the @code{core-file} and @code{exec-file} commands to select a new
13841 core file or executable target (@pxref{Files, ,Commands to Specify
13842 Files}). To specify as a target a process that is already running, use
13843 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13846 @node Target Commands
13847 @section Commands for Managing Targets
13850 @item target @var{type} @var{parameters}
13851 Connects the @value{GDBN} host environment to a target machine or
13852 process. A target is typically a protocol for talking to debugging
13853 facilities. You use the argument @var{type} to specify the type or
13854 protocol of the target machine.
13856 Further @var{parameters} are interpreted by the target protocol, but
13857 typically include things like device names or host names to connect
13858 with, process numbers, and baud rates.
13860 The @code{target} command does not repeat if you press @key{RET} again
13861 after executing the command.
13863 @kindex help target
13865 Displays the names of all targets available. To display targets
13866 currently selected, use either @code{info target} or @code{info files}
13867 (@pxref{Files, ,Commands to Specify Files}).
13869 @item help target @var{name}
13870 Describe a particular target, including any parameters necessary to
13873 @kindex set gnutarget
13874 @item set gnutarget @var{args}
13875 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13876 knows whether it is reading an @dfn{executable},
13877 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13878 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13879 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13882 @emph{Warning:} To specify a file format with @code{set gnutarget},
13883 you must know the actual BFD name.
13887 @xref{Files, , Commands to Specify Files}.
13889 @kindex show gnutarget
13890 @item show gnutarget
13891 Use the @code{show gnutarget} command to display what file format
13892 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13893 @value{GDBN} will determine the file format for each file automatically,
13894 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13897 @cindex common targets
13898 Here are some common targets (available, or not, depending on the GDB
13903 @item target exec @var{program}
13904 @cindex executable file target
13905 An executable file. @samp{target exec @var{program}} is the same as
13906 @samp{exec-file @var{program}}.
13908 @item target core @var{filename}
13909 @cindex core dump file target
13910 A core dump file. @samp{target core @var{filename}} is the same as
13911 @samp{core-file @var{filename}}.
13913 @item target remote @var{medium}
13914 @cindex remote target
13915 A remote system connected to @value{GDBN} via a serial line or network
13916 connection. This command tells @value{GDBN} to use its own remote
13917 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13919 For example, if you have a board connected to @file{/dev/ttya} on the
13920 machine running @value{GDBN}, you could say:
13923 target remote /dev/ttya
13926 @code{target remote} supports the @code{load} command. This is only
13927 useful if you have some other way of getting the stub to the target
13928 system, and you can put it somewhere in memory where it won't get
13929 clobbered by the download.
13932 @cindex built-in simulator target
13933 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13941 works; however, you cannot assume that a specific memory map, device
13942 drivers, or even basic I/O is available, although some simulators do
13943 provide these. For info about any processor-specific simulator details,
13944 see the appropriate section in @ref{Embedded Processors, ,Embedded
13949 Some configurations may include these targets as well:
13953 @item target nrom @var{dev}
13954 @cindex NetROM ROM emulator target
13955 NetROM ROM emulator. This target only supports downloading.
13959 Different targets are available on different configurations of @value{GDBN};
13960 your configuration may have more or fewer targets.
13962 Many remote targets require you to download the executable's code once
13963 you've successfully established a connection. You may wish to control
13964 various aspects of this process.
13969 @kindex set hash@r{, for remote monitors}
13970 @cindex hash mark while downloading
13971 This command controls whether a hash mark @samp{#} is displayed while
13972 downloading a file to the remote monitor. If on, a hash mark is
13973 displayed after each S-record is successfully downloaded to the
13977 @kindex show hash@r{, for remote monitors}
13978 Show the current status of displaying the hash mark.
13980 @item set debug monitor
13981 @kindex set debug monitor
13982 @cindex display remote monitor communications
13983 Enable or disable display of communications messages between
13984 @value{GDBN} and the remote monitor.
13986 @item show debug monitor
13987 @kindex show debug monitor
13988 Show the current status of displaying communications between
13989 @value{GDBN} and the remote monitor.
13994 @kindex load @var{filename}
13995 @item load @var{filename}
13997 Depending on what remote debugging facilities are configured into
13998 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13999 is meant to make @var{filename} (an executable) available for debugging
14000 on the remote system---by downloading, or dynamic linking, for example.
14001 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
14002 the @code{add-symbol-file} command.
14004 If your @value{GDBN} does not have a @code{load} command, attempting to
14005 execute it gets the error message ``@code{You can't do that when your
14006 target is @dots{}}''
14008 The file is loaded at whatever address is specified in the executable.
14009 For some object file formats, you can specify the load address when you
14010 link the program; for other formats, like a.out, the object file format
14011 specifies a fixed address.
14012 @c FIXME! This would be a good place for an xref to the GNU linker doc.
14014 Depending on the remote side capabilities, @value{GDBN} may be able to
14015 load programs into flash memory.
14017 @code{load} does not repeat if you press @key{RET} again after using it.
14021 @section Choosing Target Byte Order
14023 @cindex choosing target byte order
14024 @cindex target byte order
14026 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
14027 offer the ability to run either big-endian or little-endian byte
14028 orders. Usually the executable or symbol will include a bit to
14029 designate the endian-ness, and you will not need to worry about
14030 which to use. However, you may still find it useful to adjust
14031 @value{GDBN}'s idea of processor endian-ness manually.
14035 @item set endian big
14036 Instruct @value{GDBN} to assume the target is big-endian.
14038 @item set endian little
14039 Instruct @value{GDBN} to assume the target is little-endian.
14041 @item set endian auto
14042 Instruct @value{GDBN} to use the byte order associated with the
14046 Display @value{GDBN}'s current idea of the target byte order.
14050 Note that these commands merely adjust interpretation of symbolic
14051 data on the host, and that they have absolutely no effect on the
14055 @node Remote Debugging
14056 @chapter Debugging Remote Programs
14057 @cindex remote debugging
14059 If you are trying to debug a program running on a machine that cannot run
14060 @value{GDBN} in the usual way, it is often useful to use remote debugging.
14061 For example, you might use remote debugging on an operating system kernel,
14062 or on a small system which does not have a general purpose operating system
14063 powerful enough to run a full-featured debugger.
14065 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
14066 to make this work with particular debugging targets. In addition,
14067 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
14068 but not specific to any particular target system) which you can use if you
14069 write the remote stubs---the code that runs on the remote system to
14070 communicate with @value{GDBN}.
14072 Other remote targets may be available in your
14073 configuration of @value{GDBN}; use @code{help target} to list them.
14076 * Connecting:: Connecting to a remote target
14077 * File Transfer:: Sending files to a remote system
14078 * Server:: Using the gdbserver program
14079 * Remote Configuration:: Remote configuration
14080 * Remote Stub:: Implementing a remote stub
14084 @section Connecting to a Remote Target
14086 On the @value{GDBN} host machine, you will need an unstripped copy of
14087 your program, since @value{GDBN} needs symbol and debugging information.
14088 Start up @value{GDBN} as usual, using the name of the local copy of your
14089 program as the first argument.
14091 @cindex @code{target remote}
14092 @value{GDBN} can communicate with the target over a serial line, or
14093 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
14094 each case, @value{GDBN} uses the same protocol for debugging your
14095 program; only the medium carrying the debugging packets varies. The
14096 @code{target remote} command establishes a connection to the target.
14097 Its arguments indicate which medium to use:
14101 @item target remote @var{serial-device}
14102 @cindex serial line, @code{target remote}
14103 Use @var{serial-device} to communicate with the target. For example,
14104 to use a serial line connected to the device named @file{/dev/ttyb}:
14107 target remote /dev/ttyb
14110 If you're using a serial line, you may want to give @value{GDBN} the
14111 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
14112 (@pxref{Remote Configuration, set remotebaud}) before the
14113 @code{target} command.
14115 @item target remote @code{@var{host}:@var{port}}
14116 @itemx target remote @code{tcp:@var{host}:@var{port}}
14117 @cindex @acronym{TCP} port, @code{target remote}
14118 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
14119 The @var{host} may be either a host name or a numeric @acronym{IP}
14120 address; @var{port} must be a decimal number. The @var{host} could be
14121 the target machine itself, if it is directly connected to the net, or
14122 it might be a terminal server which in turn has a serial line to the
14125 For example, to connect to port 2828 on a terminal server named
14129 target remote manyfarms:2828
14132 If your remote target is actually running on the same machine as your
14133 debugger session (e.g.@: a simulator for your target running on the
14134 same host), you can omit the hostname. For example, to connect to
14135 port 1234 on your local machine:
14138 target remote :1234
14142 Note that the colon is still required here.
14144 @item target remote @code{udp:@var{host}:@var{port}}
14145 @cindex @acronym{UDP} port, @code{target remote}
14146 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
14147 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
14150 target remote udp:manyfarms:2828
14153 When using a @acronym{UDP} connection for remote debugging, you should
14154 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
14155 can silently drop packets on busy or unreliable networks, which will
14156 cause havoc with your debugging session.
14158 @item target remote | @var{command}
14159 @cindex pipe, @code{target remote} to
14160 Run @var{command} in the background and communicate with it using a
14161 pipe. The @var{command} is a shell command, to be parsed and expanded
14162 by the system's command shell, @code{/bin/sh}; it should expect remote
14163 protocol packets on its standard input, and send replies on its
14164 standard output. You could use this to run a stand-alone simulator
14165 that speaks the remote debugging protocol, to make net connections
14166 using programs like @code{ssh}, or for other similar tricks.
14168 If @var{command} closes its standard output (perhaps by exiting),
14169 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
14170 program has already exited, this will have no effect.)
14174 Once the connection has been established, you can use all the usual
14175 commands to examine and change data. The remote program is already
14176 running; you can use @kbd{step} and @kbd{continue}, and you do not
14177 need to use @kbd{run}.
14179 @cindex interrupting remote programs
14180 @cindex remote programs, interrupting
14181 Whenever @value{GDBN} is waiting for the remote program, if you type the
14182 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
14183 program. This may or may not succeed, depending in part on the hardware
14184 and the serial drivers the remote system uses. If you type the
14185 interrupt character once again, @value{GDBN} displays this prompt:
14188 Interrupted while waiting for the program.
14189 Give up (and stop debugging it)? (y or n)
14192 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
14193 (If you decide you want to try again later, you can use @samp{target
14194 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
14195 goes back to waiting.
14198 @kindex detach (remote)
14200 When you have finished debugging the remote program, you can use the
14201 @code{detach} command to release it from @value{GDBN} control.
14202 Detaching from the target normally resumes its execution, but the results
14203 will depend on your particular remote stub. After the @code{detach}
14204 command, @value{GDBN} is free to connect to another target.
14208 The @code{disconnect} command behaves like @code{detach}, except that
14209 the target is generally not resumed. It will wait for @value{GDBN}
14210 (this instance or another one) to connect and continue debugging. After
14211 the @code{disconnect} command, @value{GDBN} is again free to connect to
14214 @cindex send command to remote monitor
14215 @cindex extend @value{GDBN} for remote targets
14216 @cindex add new commands for external monitor
14218 @item monitor @var{cmd}
14219 This command allows you to send arbitrary commands directly to the
14220 remote monitor. Since @value{GDBN} doesn't care about the commands it
14221 sends like this, this command is the way to extend @value{GDBN}---you
14222 can add new commands that only the external monitor will understand
14226 @node File Transfer
14227 @section Sending files to a remote system
14228 @cindex remote target, file transfer
14229 @cindex file transfer
14230 @cindex sending files to remote systems
14232 Some remote targets offer the ability to transfer files over the same
14233 connection used to communicate with @value{GDBN}. This is convenient
14234 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14235 running @code{gdbserver} over a network interface. For other targets,
14236 e.g.@: embedded devices with only a single serial port, this may be
14237 the only way to upload or download files.
14239 Not all remote targets support these commands.
14243 @item remote put @var{hostfile} @var{targetfile}
14244 Copy file @var{hostfile} from the host system (the machine running
14245 @value{GDBN}) to @var{targetfile} on the target system.
14248 @item remote get @var{targetfile} @var{hostfile}
14249 Copy file @var{targetfile} from the target system to @var{hostfile}
14250 on the host system.
14252 @kindex remote delete
14253 @item remote delete @var{targetfile}
14254 Delete @var{targetfile} from the target system.
14259 @section Using the @code{gdbserver} Program
14262 @cindex remote connection without stubs
14263 @code{gdbserver} is a control program for Unix-like systems, which
14264 allows you to connect your program with a remote @value{GDBN} via
14265 @code{target remote}---but without linking in the usual debugging stub.
14267 @code{gdbserver} is not a complete replacement for the debugging stubs,
14268 because it requires essentially the same operating-system facilities
14269 that @value{GDBN} itself does. In fact, a system that can run
14270 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14271 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14272 because it is a much smaller program than @value{GDBN} itself. It is
14273 also easier to port than all of @value{GDBN}, so you may be able to get
14274 started more quickly on a new system by using @code{gdbserver}.
14275 Finally, if you develop code for real-time systems, you may find that
14276 the tradeoffs involved in real-time operation make it more convenient to
14277 do as much development work as possible on another system, for example
14278 by cross-compiling. You can use @code{gdbserver} to make a similar
14279 choice for debugging.
14281 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14282 or a TCP connection, using the standard @value{GDBN} remote serial
14286 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14287 Do not run @code{gdbserver} connected to any public network; a
14288 @value{GDBN} connection to @code{gdbserver} provides access to the
14289 target system with the same privileges as the user running
14293 @subsection Running @code{gdbserver}
14294 @cindex arguments, to @code{gdbserver}
14296 Run @code{gdbserver} on the target system. You need a copy of the
14297 program you want to debug, including any libraries it requires.
14298 @code{gdbserver} does not need your program's symbol table, so you can
14299 strip the program if necessary to save space. @value{GDBN} on the host
14300 system does all the symbol handling.
14302 To use the server, you must tell it how to communicate with @value{GDBN};
14303 the name of your program; and the arguments for your program. The usual
14307 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14310 @var{comm} is either a device name (to use a serial line) or a TCP
14311 hostname and portnumber. For example, to debug Emacs with the argument
14312 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14316 target> gdbserver /dev/com1 emacs foo.txt
14319 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14322 To use a TCP connection instead of a serial line:
14325 target> gdbserver host:2345 emacs foo.txt
14328 The only difference from the previous example is the first argument,
14329 specifying that you are communicating with the host @value{GDBN} via
14330 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14331 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14332 (Currently, the @samp{host} part is ignored.) You can choose any number
14333 you want for the port number as long as it does not conflict with any
14334 TCP ports already in use on the target system (for example, @code{23} is
14335 reserved for @code{telnet}).@footnote{If you choose a port number that
14336 conflicts with another service, @code{gdbserver} prints an error message
14337 and exits.} You must use the same port number with the host @value{GDBN}
14338 @code{target remote} command.
14340 @subsubsection Attaching to a Running Program
14342 On some targets, @code{gdbserver} can also attach to running programs.
14343 This is accomplished via the @code{--attach} argument. The syntax is:
14346 target> gdbserver --attach @var{comm} @var{pid}
14349 @var{pid} is the process ID of a currently running process. It isn't necessary
14350 to point @code{gdbserver} at a binary for the running process.
14353 @cindex attach to a program by name
14354 You can debug processes by name instead of process ID if your target has the
14355 @code{pidof} utility:
14358 target> gdbserver --attach @var{comm} `pidof @var{program}`
14361 In case more than one copy of @var{program} is running, or @var{program}
14362 has multiple threads, most versions of @code{pidof} support the
14363 @code{-s} option to only return the first process ID.
14365 @subsubsection Multi-Process Mode for @code{gdbserver}
14366 @cindex gdbserver, multiple processes
14367 @cindex multiple processes with gdbserver
14369 When you connect to @code{gdbserver} using @code{target remote},
14370 @code{gdbserver} debugs the specified program only once. When the
14371 program exits, or you detach from it, @value{GDBN} closes the connection
14372 and @code{gdbserver} exits.
14374 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14375 enters multi-process mode. When the debugged program exits, or you
14376 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14377 though no program is running. The @code{run} and @code{attach}
14378 commands instruct @code{gdbserver} to run or attach to a new program.
14379 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14380 remote exec-file}) to select the program to run. Command line
14381 arguments are supported, except for wildcard expansion and I/O
14382 redirection (@pxref{Arguments}).
14384 To start @code{gdbserver} without supplying an initial command to run
14385 or process ID to attach, use the @option{--multi} command line option.
14386 Then you can connect using @kbd{target extended-remote} and start
14387 the program you want to debug.
14389 @code{gdbserver} does not automatically exit in multi-process mode.
14390 You can terminate it by using @code{monitor exit}
14391 (@pxref{Monitor Commands for gdbserver}).
14393 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14395 The @option{--debug} option tells @code{gdbserver} to display extra
14396 status information about the debugging process. The
14397 @option{--remote-debug} option tells @code{gdbserver} to display
14398 remote protocol debug output. These options are intended for
14399 @code{gdbserver} development and for bug reports to the developers.
14401 The @option{--wrapper} option specifies a wrapper to launch programs
14402 for debugging. The option should be followed by the name of the
14403 wrapper, then any command-line arguments to pass to the wrapper, then
14404 @kbd{--} indicating the end of the wrapper arguments.
14406 @code{gdbserver} runs the specified wrapper program with a combined
14407 command line including the wrapper arguments, then the name of the
14408 program to debug, then any arguments to the program. The wrapper
14409 runs until it executes your program, and then @value{GDBN} gains control.
14411 You can use any program that eventually calls @code{execve} with
14412 its arguments as a wrapper. Several standard Unix utilities do
14413 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14414 with @code{exec "$@@"} will also work.
14416 For example, you can use @code{env} to pass an environment variable to
14417 the debugged program, without setting the variable in @code{gdbserver}'s
14421 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14424 @subsection Connecting to @code{gdbserver}
14426 Run @value{GDBN} on the host system.
14428 First make sure you have the necessary symbol files. Load symbols for
14429 your application using the @code{file} command before you connect. Use
14430 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14431 was compiled with the correct sysroot using @code{--with-sysroot}).
14433 The symbol file and target libraries must exactly match the executable
14434 and libraries on the target, with one exception: the files on the host
14435 system should not be stripped, even if the files on the target system
14436 are. Mismatched or missing files will lead to confusing results
14437 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14438 files may also prevent @code{gdbserver} from debugging multi-threaded
14441 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14442 For TCP connections, you must start up @code{gdbserver} prior to using
14443 the @code{target remote} command. Otherwise you may get an error whose
14444 text depends on the host system, but which usually looks something like
14445 @samp{Connection refused}. Don't use the @code{load}
14446 command in @value{GDBN} when using @code{gdbserver}, since the program is
14447 already on the target.
14449 @subsection Monitor Commands for @code{gdbserver}
14450 @cindex monitor commands, for @code{gdbserver}
14451 @anchor{Monitor Commands for gdbserver}
14453 During a @value{GDBN} session using @code{gdbserver}, you can use the
14454 @code{monitor} command to send special requests to @code{gdbserver}.
14455 Here are the available commands.
14459 List the available monitor commands.
14461 @item monitor set debug 0
14462 @itemx monitor set debug 1
14463 Disable or enable general debugging messages.
14465 @item monitor set remote-debug 0
14466 @itemx monitor set remote-debug 1
14467 Disable or enable specific debugging messages associated with the remote
14468 protocol (@pxref{Remote Protocol}).
14471 Tell gdbserver to exit immediately. This command should be followed by
14472 @code{disconnect} to close the debugging session. @code{gdbserver} will
14473 detach from any attached processes and kill any processes it created.
14474 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14475 of a multi-process mode debug session.
14479 @node Remote Configuration
14480 @section Remote Configuration
14483 @kindex show remote
14484 This section documents the configuration options available when
14485 debugging remote programs. For the options related to the File I/O
14486 extensions of the remote protocol, see @ref{system,
14487 system-call-allowed}.
14490 @item set remoteaddresssize @var{bits}
14491 @cindex address size for remote targets
14492 @cindex bits in remote address
14493 Set the maximum size of address in a memory packet to the specified
14494 number of bits. @value{GDBN} will mask off the address bits above
14495 that number, when it passes addresses to the remote target. The
14496 default value is the number of bits in the target's address.
14498 @item show remoteaddresssize
14499 Show the current value of remote address size in bits.
14501 @item set remotebaud @var{n}
14502 @cindex baud rate for remote targets
14503 Set the baud rate for the remote serial I/O to @var{n} baud. The
14504 value is used to set the speed of the serial port used for debugging
14507 @item show remotebaud
14508 Show the current speed of the remote connection.
14510 @item set remotebreak
14511 @cindex interrupt remote programs
14512 @cindex BREAK signal instead of Ctrl-C
14513 @anchor{set remotebreak}
14514 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14515 when you type @kbd{Ctrl-c} to interrupt the program running
14516 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14517 character instead. The default is off, since most remote systems
14518 expect to see @samp{Ctrl-C} as the interrupt signal.
14520 @item show remotebreak
14521 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14522 interrupt the remote program.
14524 @item set remoteflow on
14525 @itemx set remoteflow off
14526 @kindex set remoteflow
14527 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14528 on the serial port used to communicate to the remote target.
14530 @item show remoteflow
14531 @kindex show remoteflow
14532 Show the current setting of hardware flow control.
14534 @item set remotelogbase @var{base}
14535 Set the base (a.k.a.@: radix) of logging serial protocol
14536 communications to @var{base}. Supported values of @var{base} are:
14537 @code{ascii}, @code{octal}, and @code{hex}. The default is
14540 @item show remotelogbase
14541 Show the current setting of the radix for logging remote serial
14544 @item set remotelogfile @var{file}
14545 @cindex record serial communications on file
14546 Record remote serial communications on the named @var{file}. The
14547 default is not to record at all.
14549 @item show remotelogfile.
14550 Show the current setting of the file name on which to record the
14551 serial communications.
14553 @item set remotetimeout @var{num}
14554 @cindex timeout for serial communications
14555 @cindex remote timeout
14556 Set the timeout limit to wait for the remote target to respond to
14557 @var{num} seconds. The default is 2 seconds.
14559 @item show remotetimeout
14560 Show the current number of seconds to wait for the remote target
14563 @cindex limit hardware breakpoints and watchpoints
14564 @cindex remote target, limit break- and watchpoints
14565 @anchor{set remote hardware-watchpoint-limit}
14566 @anchor{set remote hardware-breakpoint-limit}
14567 @item set remote hardware-watchpoint-limit @var{limit}
14568 @itemx set remote hardware-breakpoint-limit @var{limit}
14569 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14570 watchpoints. A limit of -1, the default, is treated as unlimited.
14572 @item set remote exec-file @var{filename}
14573 @itemx show remote exec-file
14574 @anchor{set remote exec-file}
14575 @cindex executable file, for remote target
14576 Select the file used for @code{run} with @code{target
14577 extended-remote}. This should be set to a filename valid on the
14578 target system. If it is not set, the target will use a default
14579 filename (e.g.@: the last program run).
14583 @item set tcp auto-retry on
14584 @cindex auto-retry, for remote TCP target
14585 Enable auto-retry for remote TCP connections. This is useful if the remote
14586 debugging agent is launched in parallel with @value{GDBN}; there is a race
14587 condition because the agent may not become ready to accept the connection
14588 before @value{GDBN} attempts to connect. When auto-retry is
14589 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14590 to establish the connection using the timeout specified by
14591 @code{set tcp connect-timeout}.
14593 @item set tcp auto-retry off
14594 Do not auto-retry failed TCP connections.
14596 @item show tcp auto-retry
14597 Show the current auto-retry setting.
14599 @item set tcp connect-timeout @var{seconds}
14600 @cindex connection timeout, for remote TCP target
14601 @cindex timeout, for remote target connection
14602 Set the timeout for establishing a TCP connection to the remote target to
14603 @var{seconds}. The timeout affects both polling to retry failed connections
14604 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14605 that are merely slow to complete, and represents an approximate cumulative
14608 @item show tcp connect-timeout
14609 Show the current connection timeout setting.
14612 @cindex remote packets, enabling and disabling
14613 The @value{GDBN} remote protocol autodetects the packets supported by
14614 your debugging stub. If you need to override the autodetection, you
14615 can use these commands to enable or disable individual packets. Each
14616 packet can be set to @samp{on} (the remote target supports this
14617 packet), @samp{off} (the remote target does not support this packet),
14618 or @samp{auto} (detect remote target support for this packet). They
14619 all default to @samp{auto}. For more information about each packet,
14620 see @ref{Remote Protocol}.
14622 During normal use, you should not have to use any of these commands.
14623 If you do, that may be a bug in your remote debugging stub, or a bug
14624 in @value{GDBN}. You may want to report the problem to the
14625 @value{GDBN} developers.
14627 For each packet @var{name}, the command to enable or disable the
14628 packet is @code{set remote @var{name}-packet}. The available settings
14631 @multitable @columnfractions 0.28 0.32 0.25
14634 @tab Related Features
14636 @item @code{fetch-register}
14638 @tab @code{info registers}
14640 @item @code{set-register}
14644 @item @code{binary-download}
14646 @tab @code{load}, @code{set}
14648 @item @code{read-aux-vector}
14649 @tab @code{qXfer:auxv:read}
14650 @tab @code{info auxv}
14652 @item @code{symbol-lookup}
14653 @tab @code{qSymbol}
14654 @tab Detecting multiple threads
14656 @item @code{attach}
14657 @tab @code{vAttach}
14660 @item @code{verbose-resume}
14662 @tab Stepping or resuming multiple threads
14668 @item @code{software-breakpoint}
14672 @item @code{hardware-breakpoint}
14676 @item @code{write-watchpoint}
14680 @item @code{read-watchpoint}
14684 @item @code{access-watchpoint}
14688 @item @code{target-features}
14689 @tab @code{qXfer:features:read}
14690 @tab @code{set architecture}
14692 @item @code{library-info}
14693 @tab @code{qXfer:libraries:read}
14694 @tab @code{info sharedlibrary}
14696 @item @code{memory-map}
14697 @tab @code{qXfer:memory-map:read}
14698 @tab @code{info mem}
14700 @item @code{read-spu-object}
14701 @tab @code{qXfer:spu:read}
14702 @tab @code{info spu}
14704 @item @code{write-spu-object}
14705 @tab @code{qXfer:spu:write}
14706 @tab @code{info spu}
14708 @item @code{read-siginfo-object}
14709 @tab @code{qXfer:siginfo:read}
14710 @tab @code{print $_siginfo}
14712 @item @code{write-siginfo-object}
14713 @tab @code{qXfer:siginfo:write}
14714 @tab @code{set $_siginfo}
14716 @item @code{get-thread-local-@*storage-address}
14717 @tab @code{qGetTLSAddr}
14718 @tab Displaying @code{__thread} variables
14720 @item @code{search-memory}
14721 @tab @code{qSearch:memory}
14724 @item @code{supported-packets}
14725 @tab @code{qSupported}
14726 @tab Remote communications parameters
14728 @item @code{pass-signals}
14729 @tab @code{QPassSignals}
14730 @tab @code{handle @var{signal}}
14732 @item @code{hostio-close-packet}
14733 @tab @code{vFile:close}
14734 @tab @code{remote get}, @code{remote put}
14736 @item @code{hostio-open-packet}
14737 @tab @code{vFile:open}
14738 @tab @code{remote get}, @code{remote put}
14740 @item @code{hostio-pread-packet}
14741 @tab @code{vFile:pread}
14742 @tab @code{remote get}, @code{remote put}
14744 @item @code{hostio-pwrite-packet}
14745 @tab @code{vFile:pwrite}
14746 @tab @code{remote get}, @code{remote put}
14748 @item @code{hostio-unlink-packet}
14749 @tab @code{vFile:unlink}
14750 @tab @code{remote delete}
14752 @item @code{noack-packet}
14753 @tab @code{QStartNoAckMode}
14754 @tab Packet acknowledgment
14756 @item @code{osdata}
14757 @tab @code{qXfer:osdata:read}
14758 @tab @code{info os}
14760 @item @code{query-attached}
14761 @tab @code{qAttached}
14762 @tab Querying remote process attach state.
14766 @section Implementing a Remote Stub
14768 @cindex debugging stub, example
14769 @cindex remote stub, example
14770 @cindex stub example, remote debugging
14771 The stub files provided with @value{GDBN} implement the target side of the
14772 communication protocol, and the @value{GDBN} side is implemented in the
14773 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14774 these subroutines to communicate, and ignore the details. (If you're
14775 implementing your own stub file, you can still ignore the details: start
14776 with one of the existing stub files. @file{sparc-stub.c} is the best
14777 organized, and therefore the easiest to read.)
14779 @cindex remote serial debugging, overview
14780 To debug a program running on another machine (the debugging
14781 @dfn{target} machine), you must first arrange for all the usual
14782 prerequisites for the program to run by itself. For example, for a C
14787 A startup routine to set up the C runtime environment; these usually
14788 have a name like @file{crt0}. The startup routine may be supplied by
14789 your hardware supplier, or you may have to write your own.
14792 A C subroutine library to support your program's
14793 subroutine calls, notably managing input and output.
14796 A way of getting your program to the other machine---for example, a
14797 download program. These are often supplied by the hardware
14798 manufacturer, but you may have to write your own from hardware
14802 The next step is to arrange for your program to use a serial port to
14803 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14804 machine). In general terms, the scheme looks like this:
14808 @value{GDBN} already understands how to use this protocol; when everything
14809 else is set up, you can simply use the @samp{target remote} command
14810 (@pxref{Targets,,Specifying a Debugging Target}).
14812 @item On the target,
14813 you must link with your program a few special-purpose subroutines that
14814 implement the @value{GDBN} remote serial protocol. The file containing these
14815 subroutines is called a @dfn{debugging stub}.
14817 On certain remote targets, you can use an auxiliary program
14818 @code{gdbserver} instead of linking a stub into your program.
14819 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14822 The debugging stub is specific to the architecture of the remote
14823 machine; for example, use @file{sparc-stub.c} to debug programs on
14826 @cindex remote serial stub list
14827 These working remote stubs are distributed with @value{GDBN}:
14832 @cindex @file{i386-stub.c}
14835 For Intel 386 and compatible architectures.
14838 @cindex @file{m68k-stub.c}
14839 @cindex Motorola 680x0
14841 For Motorola 680x0 architectures.
14844 @cindex @file{sh-stub.c}
14847 For Renesas SH architectures.
14850 @cindex @file{sparc-stub.c}
14852 For @sc{sparc} architectures.
14854 @item sparcl-stub.c
14855 @cindex @file{sparcl-stub.c}
14858 For Fujitsu @sc{sparclite} architectures.
14862 The @file{README} file in the @value{GDBN} distribution may list other
14863 recently added stubs.
14866 * Stub Contents:: What the stub can do for you
14867 * Bootstrapping:: What you must do for the stub
14868 * Debug Session:: Putting it all together
14871 @node Stub Contents
14872 @subsection What the Stub Can Do for You
14874 @cindex remote serial stub
14875 The debugging stub for your architecture supplies these three
14879 @item set_debug_traps
14880 @findex set_debug_traps
14881 @cindex remote serial stub, initialization
14882 This routine arranges for @code{handle_exception} to run when your
14883 program stops. You must call this subroutine explicitly near the
14884 beginning of your program.
14886 @item handle_exception
14887 @findex handle_exception
14888 @cindex remote serial stub, main routine
14889 This is the central workhorse, but your program never calls it
14890 explicitly---the setup code arranges for @code{handle_exception} to
14891 run when a trap is triggered.
14893 @code{handle_exception} takes control when your program stops during
14894 execution (for example, on a breakpoint), and mediates communications
14895 with @value{GDBN} on the host machine. This is where the communications
14896 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14897 representative on the target machine. It begins by sending summary
14898 information on the state of your program, then continues to execute,
14899 retrieving and transmitting any information @value{GDBN} needs, until you
14900 execute a @value{GDBN} command that makes your program resume; at that point,
14901 @code{handle_exception} returns control to your own code on the target
14905 @cindex @code{breakpoint} subroutine, remote
14906 Use this auxiliary subroutine to make your program contain a
14907 breakpoint. Depending on the particular situation, this may be the only
14908 way for @value{GDBN} to get control. For instance, if your target
14909 machine has some sort of interrupt button, you won't need to call this;
14910 pressing the interrupt button transfers control to
14911 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14912 simply receiving characters on the serial port may also trigger a trap;
14913 again, in that situation, you don't need to call @code{breakpoint} from
14914 your own program---simply running @samp{target remote} from the host
14915 @value{GDBN} session gets control.
14917 Call @code{breakpoint} if none of these is true, or if you simply want
14918 to make certain your program stops at a predetermined point for the
14919 start of your debugging session.
14922 @node Bootstrapping
14923 @subsection What You Must Do for the Stub
14925 @cindex remote stub, support routines
14926 The debugging stubs that come with @value{GDBN} are set up for a particular
14927 chip architecture, but they have no information about the rest of your
14928 debugging target machine.
14930 First of all you need to tell the stub how to communicate with the
14934 @item int getDebugChar()
14935 @findex getDebugChar
14936 Write this subroutine to read a single character from the serial port.
14937 It may be identical to @code{getchar} for your target system; a
14938 different name is used to allow you to distinguish the two if you wish.
14940 @item void putDebugChar(int)
14941 @findex putDebugChar
14942 Write this subroutine to write a single character to the serial port.
14943 It may be identical to @code{putchar} for your target system; a
14944 different name is used to allow you to distinguish the two if you wish.
14947 @cindex control C, and remote debugging
14948 @cindex interrupting remote targets
14949 If you want @value{GDBN} to be able to stop your program while it is
14950 running, you need to use an interrupt-driven serial driver, and arrange
14951 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14952 character). That is the character which @value{GDBN} uses to tell the
14953 remote system to stop.
14955 Getting the debugging target to return the proper status to @value{GDBN}
14956 probably requires changes to the standard stub; one quick and dirty way
14957 is to just execute a breakpoint instruction (the ``dirty'' part is that
14958 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14960 Other routines you need to supply are:
14963 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14964 @findex exceptionHandler
14965 Write this function to install @var{exception_address} in the exception
14966 handling tables. You need to do this because the stub does not have any
14967 way of knowing what the exception handling tables on your target system
14968 are like (for example, the processor's table might be in @sc{rom},
14969 containing entries which point to a table in @sc{ram}).
14970 @var{exception_number} is the exception number which should be changed;
14971 its meaning is architecture-dependent (for example, different numbers
14972 might represent divide by zero, misaligned access, etc). When this
14973 exception occurs, control should be transferred directly to
14974 @var{exception_address}, and the processor state (stack, registers,
14975 and so on) should be just as it is when a processor exception occurs. So if
14976 you want to use a jump instruction to reach @var{exception_address}, it
14977 should be a simple jump, not a jump to subroutine.
14979 For the 386, @var{exception_address} should be installed as an interrupt
14980 gate so that interrupts are masked while the handler runs. The gate
14981 should be at privilege level 0 (the most privileged level). The
14982 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14983 help from @code{exceptionHandler}.
14985 @item void flush_i_cache()
14986 @findex flush_i_cache
14987 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14988 instruction cache, if any, on your target machine. If there is no
14989 instruction cache, this subroutine may be a no-op.
14991 On target machines that have instruction caches, @value{GDBN} requires this
14992 function to make certain that the state of your program is stable.
14996 You must also make sure this library routine is available:
14999 @item void *memset(void *, int, int)
15001 This is the standard library function @code{memset} that sets an area of
15002 memory to a known value. If you have one of the free versions of
15003 @code{libc.a}, @code{memset} can be found there; otherwise, you must
15004 either obtain it from your hardware manufacturer, or write your own.
15007 If you do not use the GNU C compiler, you may need other standard
15008 library subroutines as well; this varies from one stub to another,
15009 but in general the stubs are likely to use any of the common library
15010 subroutines which @code{@value{NGCC}} generates as inline code.
15013 @node Debug Session
15014 @subsection Putting it All Together
15016 @cindex remote serial debugging summary
15017 In summary, when your program is ready to debug, you must follow these
15022 Make sure you have defined the supporting low-level routines
15023 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
15025 @code{getDebugChar}, @code{putDebugChar},
15026 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
15030 Insert these lines near the top of your program:
15038 For the 680x0 stub only, you need to provide a variable called
15039 @code{exceptionHook}. Normally you just use:
15042 void (*exceptionHook)() = 0;
15046 but if before calling @code{set_debug_traps}, you set it to point to a
15047 function in your program, that function is called when
15048 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
15049 error). The function indicated by @code{exceptionHook} is called with
15050 one parameter: an @code{int} which is the exception number.
15053 Compile and link together: your program, the @value{GDBN} debugging stub for
15054 your target architecture, and the supporting subroutines.
15057 Make sure you have a serial connection between your target machine and
15058 the @value{GDBN} host, and identify the serial port on the host.
15061 @c The "remote" target now provides a `load' command, so we should
15062 @c document that. FIXME.
15063 Download your program to your target machine (or get it there by
15064 whatever means the manufacturer provides), and start it.
15067 Start @value{GDBN} on the host, and connect to the target
15068 (@pxref{Connecting,,Connecting to a Remote Target}).
15072 @node Configurations
15073 @chapter Configuration-Specific Information
15075 While nearly all @value{GDBN} commands are available for all native and
15076 cross versions of the debugger, there are some exceptions. This chapter
15077 describes things that are only available in certain configurations.
15079 There are three major categories of configurations: native
15080 configurations, where the host and target are the same, embedded
15081 operating system configurations, which are usually the same for several
15082 different processor architectures, and bare embedded processors, which
15083 are quite different from each other.
15088 * Embedded Processors::
15095 This section describes details specific to particular native
15100 * BSD libkvm Interface:: Debugging BSD kernel memory images
15101 * SVR4 Process Information:: SVR4 process information
15102 * DJGPP Native:: Features specific to the DJGPP port
15103 * Cygwin Native:: Features specific to the Cygwin port
15104 * Hurd Native:: Features specific to @sc{gnu} Hurd
15105 * Neutrino:: Features specific to QNX Neutrino
15106 * Darwin:: Features specific to Darwin
15112 On HP-UX systems, if you refer to a function or variable name that
15113 begins with a dollar sign, @value{GDBN} searches for a user or system
15114 name first, before it searches for a convenience variable.
15117 @node BSD libkvm Interface
15118 @subsection BSD libkvm Interface
15121 @cindex kernel memory image
15122 @cindex kernel crash dump
15124 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
15125 interface that provides a uniform interface for accessing kernel virtual
15126 memory images, including live systems and crash dumps. @value{GDBN}
15127 uses this interface to allow you to debug live kernels and kernel crash
15128 dumps on many native BSD configurations. This is implemented as a
15129 special @code{kvm} debugging target. For debugging a live system, load
15130 the currently running kernel into @value{GDBN} and connect to the
15134 (@value{GDBP}) @b{target kvm}
15137 For debugging crash dumps, provide the file name of the crash dump as an
15141 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
15144 Once connected to the @code{kvm} target, the following commands are
15150 Set current context from the @dfn{Process Control Block} (PCB) address.
15153 Set current context from proc address. This command isn't available on
15154 modern FreeBSD systems.
15157 @node SVR4 Process Information
15158 @subsection SVR4 Process Information
15160 @cindex examine process image
15161 @cindex process info via @file{/proc}
15163 Many versions of SVR4 and compatible systems provide a facility called
15164 @samp{/proc} that can be used to examine the image of a running
15165 process using file-system subroutines. If @value{GDBN} is configured
15166 for an operating system with this facility, the command @code{info
15167 proc} is available to report information about the process running
15168 your program, or about any process running on your system. @code{info
15169 proc} works only on SVR4 systems that include the @code{procfs} code.
15170 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
15171 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
15177 @itemx info proc @var{process-id}
15178 Summarize available information about any running process. If a
15179 process ID is specified by @var{process-id}, display information about
15180 that process; otherwise display information about the program being
15181 debugged. The summary includes the debugged process ID, the command
15182 line used to invoke it, its current working directory, and its
15183 executable file's absolute file name.
15185 On some systems, @var{process-id} can be of the form
15186 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
15187 within a process. If the optional @var{pid} part is missing, it means
15188 a thread from the process being debugged (the leading @samp{/} still
15189 needs to be present, or else @value{GDBN} will interpret the number as
15190 a process ID rather than a thread ID).
15192 @item info proc mappings
15193 @cindex memory address space mappings
15194 Report the memory address space ranges accessible in the program, with
15195 information on whether the process has read, write, or execute access
15196 rights to each range. On @sc{gnu}/Linux systems, each memory range
15197 includes the object file which is mapped to that range, instead of the
15198 memory access rights to that range.
15200 @item info proc stat
15201 @itemx info proc status
15202 @cindex process detailed status information
15203 These subcommands are specific to @sc{gnu}/Linux systems. They show
15204 the process-related information, including the user ID and group ID;
15205 how many threads are there in the process; its virtual memory usage;
15206 the signals that are pending, blocked, and ignored; its TTY; its
15207 consumption of system and user time; its stack size; its @samp{nice}
15208 value; etc. For more information, see the @samp{proc} man page
15209 (type @kbd{man 5 proc} from your shell prompt).
15211 @item info proc all
15212 Show all the information about the process described under all of the
15213 above @code{info proc} subcommands.
15216 @comment These sub-options of 'info proc' were not included when
15217 @comment procfs.c was re-written. Keep their descriptions around
15218 @comment against the day when someone finds the time to put them back in.
15219 @kindex info proc times
15220 @item info proc times
15221 Starting time, user CPU time, and system CPU time for your program and
15224 @kindex info proc id
15226 Report on the process IDs related to your program: its own process ID,
15227 the ID of its parent, the process group ID, and the session ID.
15230 @item set procfs-trace
15231 @kindex set procfs-trace
15232 @cindex @code{procfs} API calls
15233 This command enables and disables tracing of @code{procfs} API calls.
15235 @item show procfs-trace
15236 @kindex show procfs-trace
15237 Show the current state of @code{procfs} API call tracing.
15239 @item set procfs-file @var{file}
15240 @kindex set procfs-file
15241 Tell @value{GDBN} to write @code{procfs} API trace to the named
15242 @var{file}. @value{GDBN} appends the trace info to the previous
15243 contents of the file. The default is to display the trace on the
15246 @item show procfs-file
15247 @kindex show procfs-file
15248 Show the file to which @code{procfs} API trace is written.
15250 @item proc-trace-entry
15251 @itemx proc-trace-exit
15252 @itemx proc-untrace-entry
15253 @itemx proc-untrace-exit
15254 @kindex proc-trace-entry
15255 @kindex proc-trace-exit
15256 @kindex proc-untrace-entry
15257 @kindex proc-untrace-exit
15258 These commands enable and disable tracing of entries into and exits
15259 from the @code{syscall} interface.
15262 @kindex info pidlist
15263 @cindex process list, QNX Neutrino
15264 For QNX Neutrino only, this command displays the list of all the
15265 processes and all the threads within each process.
15268 @kindex info meminfo
15269 @cindex mapinfo list, QNX Neutrino
15270 For QNX Neutrino only, this command displays the list of all mapinfos.
15274 @subsection Features for Debugging @sc{djgpp} Programs
15275 @cindex @sc{djgpp} debugging
15276 @cindex native @sc{djgpp} debugging
15277 @cindex MS-DOS-specific commands
15280 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15281 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15282 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15283 top of real-mode DOS systems and their emulations.
15285 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15286 defines a few commands specific to the @sc{djgpp} port. This
15287 subsection describes those commands.
15292 This is a prefix of @sc{djgpp}-specific commands which print
15293 information about the target system and important OS structures.
15296 @cindex MS-DOS system info
15297 @cindex free memory information (MS-DOS)
15298 @item info dos sysinfo
15299 This command displays assorted information about the underlying
15300 platform: the CPU type and features, the OS version and flavor, the
15301 DPMI version, and the available conventional and DPMI memory.
15306 @cindex segment descriptor tables
15307 @cindex descriptor tables display
15309 @itemx info dos ldt
15310 @itemx info dos idt
15311 These 3 commands display entries from, respectively, Global, Local,
15312 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15313 tables are data structures which store a descriptor for each segment
15314 that is currently in use. The segment's selector is an index into a
15315 descriptor table; the table entry for that index holds the
15316 descriptor's base address and limit, and its attributes and access
15319 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15320 segment (used for both data and the stack), and a DOS segment (which
15321 allows access to DOS/BIOS data structures and absolute addresses in
15322 conventional memory). However, the DPMI host will usually define
15323 additional segments in order to support the DPMI environment.
15325 @cindex garbled pointers
15326 These commands allow to display entries from the descriptor tables.
15327 Without an argument, all entries from the specified table are
15328 displayed. An argument, which should be an integer expression, means
15329 display a single entry whose index is given by the argument. For
15330 example, here's a convenient way to display information about the
15331 debugged program's data segment:
15334 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15335 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15339 This comes in handy when you want to see whether a pointer is outside
15340 the data segment's limit (i.e.@: @dfn{garbled}).
15342 @cindex page tables display (MS-DOS)
15344 @itemx info dos pte
15345 These two commands display entries from, respectively, the Page
15346 Directory and the Page Tables. Page Directories and Page Tables are
15347 data structures which control how virtual memory addresses are mapped
15348 into physical addresses. A Page Table includes an entry for every
15349 page of memory that is mapped into the program's address space; there
15350 may be several Page Tables, each one holding up to 4096 entries. A
15351 Page Directory has up to 4096 entries, one each for every Page Table
15352 that is currently in use.
15354 Without an argument, @kbd{info dos pde} displays the entire Page
15355 Directory, and @kbd{info dos pte} displays all the entries in all of
15356 the Page Tables. An argument, an integer expression, given to the
15357 @kbd{info dos pde} command means display only that entry from the Page
15358 Directory table. An argument given to the @kbd{info dos pte} command
15359 means display entries from a single Page Table, the one pointed to by
15360 the specified entry in the Page Directory.
15362 @cindex direct memory access (DMA) on MS-DOS
15363 These commands are useful when your program uses @dfn{DMA} (Direct
15364 Memory Access), which needs physical addresses to program the DMA
15367 These commands are supported only with some DPMI servers.
15369 @cindex physical address from linear address
15370 @item info dos address-pte @var{addr}
15371 This command displays the Page Table entry for a specified linear
15372 address. The argument @var{addr} is a linear address which should
15373 already have the appropriate segment's base address added to it,
15374 because this command accepts addresses which may belong to @emph{any}
15375 segment. For example, here's how to display the Page Table entry for
15376 the page where a variable @code{i} is stored:
15379 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15380 @exdent @code{Page Table entry for address 0x11a00d30:}
15381 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15385 This says that @code{i} is stored at offset @code{0xd30} from the page
15386 whose physical base address is @code{0x02698000}, and shows all the
15387 attributes of that page.
15389 Note that you must cast the addresses of variables to a @code{char *},
15390 since otherwise the value of @code{__djgpp_base_address}, the base
15391 address of all variables and functions in a @sc{djgpp} program, will
15392 be added using the rules of C pointer arithmetics: if @code{i} is
15393 declared an @code{int}, @value{GDBN} will add 4 times the value of
15394 @code{__djgpp_base_address} to the address of @code{i}.
15396 Here's another example, it displays the Page Table entry for the
15400 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15401 @exdent @code{Page Table entry for address 0x29110:}
15402 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15406 (The @code{+ 3} offset is because the transfer buffer's address is the
15407 3rd member of the @code{_go32_info_block} structure.) The output
15408 clearly shows that this DPMI server maps the addresses in conventional
15409 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15410 linear (@code{0x29110}) addresses are identical.
15412 This command is supported only with some DPMI servers.
15415 @cindex DOS serial data link, remote debugging
15416 In addition to native debugging, the DJGPP port supports remote
15417 debugging via a serial data link. The following commands are specific
15418 to remote serial debugging in the DJGPP port of @value{GDBN}.
15421 @kindex set com1base
15422 @kindex set com1irq
15423 @kindex set com2base
15424 @kindex set com2irq
15425 @kindex set com3base
15426 @kindex set com3irq
15427 @kindex set com4base
15428 @kindex set com4irq
15429 @item set com1base @var{addr}
15430 This command sets the base I/O port address of the @file{COM1} serial
15433 @item set com1irq @var{irq}
15434 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15435 for the @file{COM1} serial port.
15437 There are similar commands @samp{set com2base}, @samp{set com3irq},
15438 etc.@: for setting the port address and the @code{IRQ} lines for the
15441 @kindex show com1base
15442 @kindex show com1irq
15443 @kindex show com2base
15444 @kindex show com2irq
15445 @kindex show com3base
15446 @kindex show com3irq
15447 @kindex show com4base
15448 @kindex show com4irq
15449 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15450 display the current settings of the base address and the @code{IRQ}
15451 lines used by the COM ports.
15454 @kindex info serial
15455 @cindex DOS serial port status
15456 This command prints the status of the 4 DOS serial ports. For each
15457 port, it prints whether it's active or not, its I/O base address and
15458 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15459 counts of various errors encountered so far.
15463 @node Cygwin Native
15464 @subsection Features for Debugging MS Windows PE Executables
15465 @cindex MS Windows debugging
15466 @cindex native Cygwin debugging
15467 @cindex Cygwin-specific commands
15469 @value{GDBN} supports native debugging of MS Windows programs, including
15470 DLLs with and without symbolic debugging information. There are various
15471 additional Cygwin-specific commands, described in this section.
15472 Working with DLLs that have no debugging symbols is described in
15473 @ref{Non-debug DLL Symbols}.
15478 This is a prefix of MS Windows-specific commands which print
15479 information about the target system and important OS structures.
15481 @item info w32 selector
15482 This command displays information returned by
15483 the Win32 API @code{GetThreadSelectorEntry} function.
15484 It takes an optional argument that is evaluated to
15485 a long value to give the information about this given selector.
15486 Without argument, this command displays information
15487 about the six segment registers.
15491 This is a Cygwin-specific alias of @code{info shared}.
15493 @kindex dll-symbols
15495 This command loads symbols from a dll similarly to
15496 add-sym command but without the need to specify a base address.
15498 @kindex set cygwin-exceptions
15499 @cindex debugging the Cygwin DLL
15500 @cindex Cygwin DLL, debugging
15501 @item set cygwin-exceptions @var{mode}
15502 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15503 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15504 @value{GDBN} will delay recognition of exceptions, and may ignore some
15505 exceptions which seem to be caused by internal Cygwin DLL
15506 ``bookkeeping''. This option is meant primarily for debugging the
15507 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15508 @value{GDBN} users with false @code{SIGSEGV} signals.
15510 @kindex show cygwin-exceptions
15511 @item show cygwin-exceptions
15512 Displays whether @value{GDBN} will break on exceptions that happen
15513 inside the Cygwin DLL itself.
15515 @kindex set new-console
15516 @item set new-console @var{mode}
15517 If @var{mode} is @code{on} the debuggee will
15518 be started in a new console on next start.
15519 If @var{mode} is @code{off}i, the debuggee will
15520 be started in the same console as the debugger.
15522 @kindex show new-console
15523 @item show new-console
15524 Displays whether a new console is used
15525 when the debuggee is started.
15527 @kindex set new-group
15528 @item set new-group @var{mode}
15529 This boolean value controls whether the debuggee should
15530 start a new group or stay in the same group as the debugger.
15531 This affects the way the Windows OS handles
15534 @kindex show new-group
15535 @item show new-group
15536 Displays current value of new-group boolean.
15538 @kindex set debugevents
15539 @item set debugevents
15540 This boolean value adds debug output concerning kernel events related
15541 to the debuggee seen by the debugger. This includes events that
15542 signal thread and process creation and exit, DLL loading and
15543 unloading, console interrupts, and debugging messages produced by the
15544 Windows @code{OutputDebugString} API call.
15546 @kindex set debugexec
15547 @item set debugexec
15548 This boolean value adds debug output concerning execute events
15549 (such as resume thread) seen by the debugger.
15551 @kindex set debugexceptions
15552 @item set debugexceptions
15553 This boolean value adds debug output concerning exceptions in the
15554 debuggee seen by the debugger.
15556 @kindex set debugmemory
15557 @item set debugmemory
15558 This boolean value adds debug output concerning debuggee memory reads
15559 and writes by the debugger.
15563 This boolean values specifies whether the debuggee is called
15564 via a shell or directly (default value is on).
15568 Displays if the debuggee will be started with a shell.
15573 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15576 @node Non-debug DLL Symbols
15577 @subsubsection Support for DLLs without Debugging Symbols
15578 @cindex DLLs with no debugging symbols
15579 @cindex Minimal symbols and DLLs
15581 Very often on windows, some of the DLLs that your program relies on do
15582 not include symbolic debugging information (for example,
15583 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15584 symbols in a DLL, it relies on the minimal amount of symbolic
15585 information contained in the DLL's export table. This section
15586 describes working with such symbols, known internally to @value{GDBN} as
15587 ``minimal symbols''.
15589 Note that before the debugged program has started execution, no DLLs
15590 will have been loaded. The easiest way around this problem is simply to
15591 start the program --- either by setting a breakpoint or letting the
15592 program run once to completion. It is also possible to force
15593 @value{GDBN} to load a particular DLL before starting the executable ---
15594 see the shared library information in @ref{Files}, or the
15595 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15596 explicitly loading symbols from a DLL with no debugging information will
15597 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15598 which may adversely affect symbol lookup performance.
15600 @subsubsection DLL Name Prefixes
15602 In keeping with the naming conventions used by the Microsoft debugging
15603 tools, DLL export symbols are made available with a prefix based on the
15604 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15605 also entered into the symbol table, so @code{CreateFileA} is often
15606 sufficient. In some cases there will be name clashes within a program
15607 (particularly if the executable itself includes full debugging symbols)
15608 necessitating the use of the fully qualified name when referring to the
15609 contents of the DLL. Use single-quotes around the name to avoid the
15610 exclamation mark (``!'') being interpreted as a language operator.
15612 Note that the internal name of the DLL may be all upper-case, even
15613 though the file name of the DLL is lower-case, or vice-versa. Since
15614 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15615 some confusion. If in doubt, try the @code{info functions} and
15616 @code{info variables} commands or even @code{maint print msymbols}
15617 (@pxref{Symbols}). Here's an example:
15620 (@value{GDBP}) info function CreateFileA
15621 All functions matching regular expression "CreateFileA":
15623 Non-debugging symbols:
15624 0x77e885f4 CreateFileA
15625 0x77e885f4 KERNEL32!CreateFileA
15629 (@value{GDBP}) info function !
15630 All functions matching regular expression "!":
15632 Non-debugging symbols:
15633 0x6100114c cygwin1!__assert
15634 0x61004034 cygwin1!_dll_crt0@@0
15635 0x61004240 cygwin1!dll_crt0(per_process *)
15639 @subsubsection Working with Minimal Symbols
15641 Symbols extracted from a DLL's export table do not contain very much
15642 type information. All that @value{GDBN} can do is guess whether a symbol
15643 refers to a function or variable depending on the linker section that
15644 contains the symbol. Also note that the actual contents of the memory
15645 contained in a DLL are not available unless the program is running. This
15646 means that you cannot examine the contents of a variable or disassemble
15647 a function within a DLL without a running program.
15649 Variables are generally treated as pointers and dereferenced
15650 automatically. For this reason, it is often necessary to prefix a
15651 variable name with the address-of operator (``&'') and provide explicit
15652 type information in the command. Here's an example of the type of
15656 (@value{GDBP}) print 'cygwin1!__argv'
15661 (@value{GDBP}) x 'cygwin1!__argv'
15662 0x10021610: "\230y\""
15665 And two possible solutions:
15668 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15669 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15673 (@value{GDBP}) x/2x &'cygwin1!__argv'
15674 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15675 (@value{GDBP}) x/x 0x10021608
15676 0x10021608: 0x0022fd98
15677 (@value{GDBP}) x/s 0x0022fd98
15678 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15681 Setting a break point within a DLL is possible even before the program
15682 starts execution. However, under these circumstances, @value{GDBN} can't
15683 examine the initial instructions of the function in order to skip the
15684 function's frame set-up code. You can work around this by using ``*&''
15685 to set the breakpoint at a raw memory address:
15688 (@value{GDBP}) break *&'python22!PyOS_Readline'
15689 Breakpoint 1 at 0x1e04eff0
15692 The author of these extensions is not entirely convinced that setting a
15693 break point within a shared DLL like @file{kernel32.dll} is completely
15697 @subsection Commands Specific to @sc{gnu} Hurd Systems
15698 @cindex @sc{gnu} Hurd debugging
15700 This subsection describes @value{GDBN} commands specific to the
15701 @sc{gnu} Hurd native debugging.
15706 @kindex set signals@r{, Hurd command}
15707 @kindex set sigs@r{, Hurd command}
15708 This command toggles the state of inferior signal interception by
15709 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15710 affected by this command. @code{sigs} is a shorthand alias for
15715 @kindex show signals@r{, Hurd command}
15716 @kindex show sigs@r{, Hurd command}
15717 Show the current state of intercepting inferior's signals.
15719 @item set signal-thread
15720 @itemx set sigthread
15721 @kindex set signal-thread
15722 @kindex set sigthread
15723 This command tells @value{GDBN} which thread is the @code{libc} signal
15724 thread. That thread is run when a signal is delivered to a running
15725 process. @code{set sigthread} is the shorthand alias of @code{set
15728 @item show signal-thread
15729 @itemx show sigthread
15730 @kindex show signal-thread
15731 @kindex show sigthread
15732 These two commands show which thread will run when the inferior is
15733 delivered a signal.
15736 @kindex set stopped@r{, Hurd command}
15737 This commands tells @value{GDBN} that the inferior process is stopped,
15738 as with the @code{SIGSTOP} signal. The stopped process can be
15739 continued by delivering a signal to it.
15742 @kindex show stopped@r{, Hurd command}
15743 This command shows whether @value{GDBN} thinks the debuggee is
15746 @item set exceptions
15747 @kindex set exceptions@r{, Hurd command}
15748 Use this command to turn off trapping of exceptions in the inferior.
15749 When exception trapping is off, neither breakpoints nor
15750 single-stepping will work. To restore the default, set exception
15753 @item show exceptions
15754 @kindex show exceptions@r{, Hurd command}
15755 Show the current state of trapping exceptions in the inferior.
15757 @item set task pause
15758 @kindex set task@r{, Hurd commands}
15759 @cindex task attributes (@sc{gnu} Hurd)
15760 @cindex pause current task (@sc{gnu} Hurd)
15761 This command toggles task suspension when @value{GDBN} has control.
15762 Setting it to on takes effect immediately, and the task is suspended
15763 whenever @value{GDBN} gets control. Setting it to off will take
15764 effect the next time the inferior is continued. If this option is set
15765 to off, you can use @code{set thread default pause on} or @code{set
15766 thread pause on} (see below) to pause individual threads.
15768 @item show task pause
15769 @kindex show task@r{, Hurd commands}
15770 Show the current state of task suspension.
15772 @item set task detach-suspend-count
15773 @cindex task suspend count
15774 @cindex detach from task, @sc{gnu} Hurd
15775 This command sets the suspend count the task will be left with when
15776 @value{GDBN} detaches from it.
15778 @item show task detach-suspend-count
15779 Show the suspend count the task will be left with when detaching.
15781 @item set task exception-port
15782 @itemx set task excp
15783 @cindex task exception port, @sc{gnu} Hurd
15784 This command sets the task exception port to which @value{GDBN} will
15785 forward exceptions. The argument should be the value of the @dfn{send
15786 rights} of the task. @code{set task excp} is a shorthand alias.
15788 @item set noninvasive
15789 @cindex noninvasive task options
15790 This command switches @value{GDBN} to a mode that is the least
15791 invasive as far as interfering with the inferior is concerned. This
15792 is the same as using @code{set task pause}, @code{set exceptions}, and
15793 @code{set signals} to values opposite to the defaults.
15795 @item info send-rights
15796 @itemx info receive-rights
15797 @itemx info port-rights
15798 @itemx info port-sets
15799 @itemx info dead-names
15802 @cindex send rights, @sc{gnu} Hurd
15803 @cindex receive rights, @sc{gnu} Hurd
15804 @cindex port rights, @sc{gnu} Hurd
15805 @cindex port sets, @sc{gnu} Hurd
15806 @cindex dead names, @sc{gnu} Hurd
15807 These commands display information about, respectively, send rights,
15808 receive rights, port rights, port sets, and dead names of a task.
15809 There are also shorthand aliases: @code{info ports} for @code{info
15810 port-rights} and @code{info psets} for @code{info port-sets}.
15812 @item set thread pause
15813 @kindex set thread@r{, Hurd command}
15814 @cindex thread properties, @sc{gnu} Hurd
15815 @cindex pause current thread (@sc{gnu} Hurd)
15816 This command toggles current thread suspension when @value{GDBN} has
15817 control. Setting it to on takes effect immediately, and the current
15818 thread is suspended whenever @value{GDBN} gets control. Setting it to
15819 off will take effect the next time the inferior is continued.
15820 Normally, this command has no effect, since when @value{GDBN} has
15821 control, the whole task is suspended. However, if you used @code{set
15822 task pause off} (see above), this command comes in handy to suspend
15823 only the current thread.
15825 @item show thread pause
15826 @kindex show thread@r{, Hurd command}
15827 This command shows the state of current thread suspension.
15829 @item set thread run
15830 This command sets whether the current thread is allowed to run.
15832 @item show thread run
15833 Show whether the current thread is allowed to run.
15835 @item set thread detach-suspend-count
15836 @cindex thread suspend count, @sc{gnu} Hurd
15837 @cindex detach from thread, @sc{gnu} Hurd
15838 This command sets the suspend count @value{GDBN} will leave on a
15839 thread when detaching. This number is relative to the suspend count
15840 found by @value{GDBN} when it notices the thread; use @code{set thread
15841 takeover-suspend-count} to force it to an absolute value.
15843 @item show thread detach-suspend-count
15844 Show the suspend count @value{GDBN} will leave on the thread when
15847 @item set thread exception-port
15848 @itemx set thread excp
15849 Set the thread exception port to which to forward exceptions. This
15850 overrides the port set by @code{set task exception-port} (see above).
15851 @code{set thread excp} is the shorthand alias.
15853 @item set thread takeover-suspend-count
15854 Normally, @value{GDBN}'s thread suspend counts are relative to the
15855 value @value{GDBN} finds when it notices each thread. This command
15856 changes the suspend counts to be absolute instead.
15858 @item set thread default
15859 @itemx show thread default
15860 @cindex thread default settings, @sc{gnu} Hurd
15861 Each of the above @code{set thread} commands has a @code{set thread
15862 default} counterpart (e.g., @code{set thread default pause}, @code{set
15863 thread default exception-port}, etc.). The @code{thread default}
15864 variety of commands sets the default thread properties for all
15865 threads; you can then change the properties of individual threads with
15866 the non-default commands.
15871 @subsection QNX Neutrino
15872 @cindex QNX Neutrino
15874 @value{GDBN} provides the following commands specific to the QNX
15878 @item set debug nto-debug
15879 @kindex set debug nto-debug
15880 When set to on, enables debugging messages specific to the QNX
15883 @item show debug nto-debug
15884 @kindex show debug nto-debug
15885 Show the current state of QNX Neutrino messages.
15892 @value{GDBN} provides the following commands specific to the Darwin target:
15895 @item set debug darwin @var{num}
15896 @kindex set debug darwin
15897 When set to a non zero value, enables debugging messages specific to
15898 the Darwin support. Higher values produce more verbose output.
15900 @item show debug darwin
15901 @kindex show debug darwin
15902 Show the current state of Darwin messages.
15904 @item set debug mach-o @var{num}
15905 @kindex set debug mach-o
15906 When set to a non zero value, enables debugging messages while
15907 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15908 file format used on Darwin for object and executable files.) Higher
15909 values produce more verbose output. This is a command to diagnose
15910 problems internal to @value{GDBN} and should not be needed in normal
15913 @item show debug mach-o
15914 @kindex show debug mach-o
15915 Show the current state of Mach-O file messages.
15917 @item set mach-exceptions on
15918 @itemx set mach-exceptions off
15919 @kindex set mach-exceptions
15920 On Darwin, faults are first reported as a Mach exception and are then
15921 mapped to a Posix signal. Use this command to turn on trapping of
15922 Mach exceptions in the inferior. This might be sometimes useful to
15923 better understand the cause of a fault. The default is off.
15925 @item show mach-exceptions
15926 @kindex show mach-exceptions
15927 Show the current state of exceptions trapping.
15932 @section Embedded Operating Systems
15934 This section describes configurations involving the debugging of
15935 embedded operating systems that are available for several different
15939 * VxWorks:: Using @value{GDBN} with VxWorks
15942 @value{GDBN} includes the ability to debug programs running on
15943 various real-time operating systems.
15946 @subsection Using @value{GDBN} with VxWorks
15952 @kindex target vxworks
15953 @item target vxworks @var{machinename}
15954 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15955 is the target system's machine name or IP address.
15959 On VxWorks, @code{load} links @var{filename} dynamically on the
15960 current target system as well as adding its symbols in @value{GDBN}.
15962 @value{GDBN} enables developers to spawn and debug tasks running on networked
15963 VxWorks targets from a Unix host. Already-running tasks spawned from
15964 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15965 both the Unix host and on the VxWorks target. The program
15966 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15967 installed with the name @code{vxgdb}, to distinguish it from a
15968 @value{GDBN} for debugging programs on the host itself.)
15971 @item VxWorks-timeout @var{args}
15972 @kindex vxworks-timeout
15973 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15974 This option is set by the user, and @var{args} represents the number of
15975 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15976 your VxWorks target is a slow software simulator or is on the far side
15977 of a thin network line.
15980 The following information on connecting to VxWorks was current when
15981 this manual was produced; newer releases of VxWorks may use revised
15984 @findex INCLUDE_RDB
15985 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15986 to include the remote debugging interface routines in the VxWorks
15987 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15988 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15989 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15990 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15991 information on configuring and remaking VxWorks, see the manufacturer's
15993 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15995 Once you have included @file{rdb.a} in your VxWorks system image and set
15996 your Unix execution search path to find @value{GDBN}, you are ready to
15997 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15998 @code{vxgdb}, depending on your installation).
16000 @value{GDBN} comes up showing the prompt:
16007 * VxWorks Connection:: Connecting to VxWorks
16008 * VxWorks Download:: VxWorks download
16009 * VxWorks Attach:: Running tasks
16012 @node VxWorks Connection
16013 @subsubsection Connecting to VxWorks
16015 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
16016 network. To connect to a target whose host name is ``@code{tt}'', type:
16019 (vxgdb) target vxworks tt
16023 @value{GDBN} displays messages like these:
16026 Attaching remote machine across net...
16031 @value{GDBN} then attempts to read the symbol tables of any object modules
16032 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
16033 these files by searching the directories listed in the command search
16034 path (@pxref{Environment, ,Your Program's Environment}); if it fails
16035 to find an object file, it displays a message such as:
16038 prog.o: No such file or directory.
16041 When this happens, add the appropriate directory to the search path with
16042 the @value{GDBN} command @code{path}, and execute the @code{target}
16045 @node VxWorks Download
16046 @subsubsection VxWorks Download
16048 @cindex download to VxWorks
16049 If you have connected to the VxWorks target and you want to debug an
16050 object that has not yet been loaded, you can use the @value{GDBN}
16051 @code{load} command to download a file from Unix to VxWorks
16052 incrementally. The object file given as an argument to the @code{load}
16053 command is actually opened twice: first by the VxWorks target in order
16054 to download the code, then by @value{GDBN} in order to read the symbol
16055 table. This can lead to problems if the current working directories on
16056 the two systems differ. If both systems have NFS mounted the same
16057 filesystems, you can avoid these problems by using absolute paths.
16058 Otherwise, it is simplest to set the working directory on both systems
16059 to the directory in which the object file resides, and then to reference
16060 the file by its name, without any path. For instance, a program
16061 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
16062 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
16063 program, type this on VxWorks:
16066 -> cd "@var{vxpath}/vw/demo/rdb"
16070 Then, in @value{GDBN}, type:
16073 (vxgdb) cd @var{hostpath}/vw/demo/rdb
16074 (vxgdb) load prog.o
16077 @value{GDBN} displays a response similar to this:
16080 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
16083 You can also use the @code{load} command to reload an object module
16084 after editing and recompiling the corresponding source file. Note that
16085 this makes @value{GDBN} delete all currently-defined breakpoints,
16086 auto-displays, and convenience variables, and to clear the value
16087 history. (This is necessary in order to preserve the integrity of
16088 debugger's data structures that reference the target system's symbol
16091 @node VxWorks Attach
16092 @subsubsection Running Tasks
16094 @cindex running VxWorks tasks
16095 You can also attach to an existing task using the @code{attach} command as
16099 (vxgdb) attach @var{task}
16103 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
16104 or suspended when you attach to it. Running tasks are suspended at
16105 the time of attachment.
16107 @node Embedded Processors
16108 @section Embedded Processors
16110 This section goes into details specific to particular embedded
16113 @cindex send command to simulator
16114 Whenever a specific embedded processor has a simulator, @value{GDBN}
16115 allows to send an arbitrary command to the simulator.
16118 @item sim @var{command}
16119 @kindex sim@r{, a command}
16120 Send an arbitrary @var{command} string to the simulator. Consult the
16121 documentation for the specific simulator in use for information about
16122 acceptable commands.
16128 * M32R/D:: Renesas M32R/D
16129 * M68K:: Motorola M68K
16130 * MIPS Embedded:: MIPS Embedded
16131 * OpenRISC 1000:: OpenRisc 1000
16132 * PA:: HP PA Embedded
16133 * PowerPC Embedded:: PowerPC Embedded
16134 * Sparclet:: Tsqware Sparclet
16135 * Sparclite:: Fujitsu Sparclite
16136 * Z8000:: Zilog Z8000
16139 * Super-H:: Renesas Super-H
16148 @item target rdi @var{dev}
16149 ARM Angel monitor, via RDI library interface to ADP protocol. You may
16150 use this target to communicate with both boards running the Angel
16151 monitor, or with the EmbeddedICE JTAG debug device.
16154 @item target rdp @var{dev}
16159 @value{GDBN} provides the following ARM-specific commands:
16162 @item set arm disassembler
16164 This commands selects from a list of disassembly styles. The
16165 @code{"std"} style is the standard style.
16167 @item show arm disassembler
16169 Show the current disassembly style.
16171 @item set arm apcs32
16172 @cindex ARM 32-bit mode
16173 This command toggles ARM operation mode between 32-bit and 26-bit.
16175 @item show arm apcs32
16176 Display the current usage of the ARM 32-bit mode.
16178 @item set arm fpu @var{fputype}
16179 This command sets the ARM floating-point unit (FPU) type. The
16180 argument @var{fputype} can be one of these:
16184 Determine the FPU type by querying the OS ABI.
16186 Software FPU, with mixed-endian doubles on little-endian ARM
16189 GCC-compiled FPA co-processor.
16191 Software FPU with pure-endian doubles.
16197 Show the current type of the FPU.
16200 This command forces @value{GDBN} to use the specified ABI.
16203 Show the currently used ABI.
16205 @item set arm fallback-mode (arm|thumb|auto)
16206 @value{GDBN} uses the symbol table, when available, to determine
16207 whether instructions are ARM or Thumb. This command controls
16208 @value{GDBN}'s default behavior when the symbol table is not
16209 available. The default is @samp{auto}, which causes @value{GDBN} to
16210 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16213 @item show arm fallback-mode
16214 Show the current fallback instruction mode.
16216 @item set arm force-mode (arm|thumb|auto)
16217 This command overrides use of the symbol table to determine whether
16218 instructions are ARM or Thumb. The default is @samp{auto}, which
16219 causes @value{GDBN} to use the symbol table and then the setting
16220 of @samp{set arm fallback-mode}.
16222 @item show arm force-mode
16223 Show the current forced instruction mode.
16225 @item set debug arm
16226 Toggle whether to display ARM-specific debugging messages from the ARM
16227 target support subsystem.
16229 @item show debug arm
16230 Show whether ARM-specific debugging messages are enabled.
16233 The following commands are available when an ARM target is debugged
16234 using the RDI interface:
16237 @item rdilogfile @r{[}@var{file}@r{]}
16239 @cindex ADP (Angel Debugger Protocol) logging
16240 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16241 With an argument, sets the log file to the specified @var{file}. With
16242 no argument, show the current log file name. The default log file is
16245 @item rdilogenable @r{[}@var{arg}@r{]}
16246 @kindex rdilogenable
16247 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16248 enables logging, with an argument 0 or @code{"no"} disables it. With
16249 no arguments displays the current setting. When logging is enabled,
16250 ADP packets exchanged between @value{GDBN} and the RDI target device
16251 are logged to a file.
16253 @item set rdiromatzero
16254 @kindex set rdiromatzero
16255 @cindex ROM at zero address, RDI
16256 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16257 vector catching is disabled, so that zero address can be used. If off
16258 (the default), vector catching is enabled. For this command to take
16259 effect, it needs to be invoked prior to the @code{target rdi} command.
16261 @item show rdiromatzero
16262 @kindex show rdiromatzero
16263 Show the current setting of ROM at zero address.
16265 @item set rdiheartbeat
16266 @kindex set rdiheartbeat
16267 @cindex RDI heartbeat
16268 Enable or disable RDI heartbeat packets. It is not recommended to
16269 turn on this option, since it confuses ARM and EPI JTAG interface, as
16270 well as the Angel monitor.
16272 @item show rdiheartbeat
16273 @kindex show rdiheartbeat
16274 Show the setting of RDI heartbeat packets.
16279 @subsection Renesas M32R/D and M32R/SDI
16282 @kindex target m32r
16283 @item target m32r @var{dev}
16284 Renesas M32R/D ROM monitor.
16286 @kindex target m32rsdi
16287 @item target m32rsdi @var{dev}
16288 Renesas M32R SDI server, connected via parallel port to the board.
16291 The following @value{GDBN} commands are specific to the M32R monitor:
16294 @item set download-path @var{path}
16295 @kindex set download-path
16296 @cindex find downloadable @sc{srec} files (M32R)
16297 Set the default path for finding downloadable @sc{srec} files.
16299 @item show download-path
16300 @kindex show download-path
16301 Show the default path for downloadable @sc{srec} files.
16303 @item set board-address @var{addr}
16304 @kindex set board-address
16305 @cindex M32-EVA target board address
16306 Set the IP address for the M32R-EVA target board.
16308 @item show board-address
16309 @kindex show board-address
16310 Show the current IP address of the target board.
16312 @item set server-address @var{addr}
16313 @kindex set server-address
16314 @cindex download server address (M32R)
16315 Set the IP address for the download server, which is the @value{GDBN}'s
16318 @item show server-address
16319 @kindex show server-address
16320 Display the IP address of the download server.
16322 @item upload @r{[}@var{file}@r{]}
16323 @kindex upload@r{, M32R}
16324 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16325 upload capability. If no @var{file} argument is given, the current
16326 executable file is uploaded.
16328 @item tload @r{[}@var{file}@r{]}
16329 @kindex tload@r{, M32R}
16330 Test the @code{upload} command.
16333 The following commands are available for M32R/SDI:
16338 @cindex reset SDI connection, M32R
16339 This command resets the SDI connection.
16343 This command shows the SDI connection status.
16346 @kindex debug_chaos
16347 @cindex M32R/Chaos debugging
16348 Instructs the remote that M32R/Chaos debugging is to be used.
16350 @item use_debug_dma
16351 @kindex use_debug_dma
16352 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16355 @kindex use_mon_code
16356 Instructs the remote to use the MON_CODE method of accessing memory.
16359 @kindex use_ib_break
16360 Instructs the remote to set breakpoints by IB break.
16362 @item use_dbt_break
16363 @kindex use_dbt_break
16364 Instructs the remote to set breakpoints by DBT.
16370 The Motorola m68k configuration includes ColdFire support, and a
16371 target command for the following ROM monitor.
16375 @kindex target dbug
16376 @item target dbug @var{dev}
16377 dBUG ROM monitor for Motorola ColdFire.
16381 @node MIPS Embedded
16382 @subsection MIPS Embedded
16384 @cindex MIPS boards
16385 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16386 MIPS board attached to a serial line. This is available when
16387 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16390 Use these @value{GDBN} commands to specify the connection to your target board:
16393 @item target mips @var{port}
16394 @kindex target mips @var{port}
16395 To run a program on the board, start up @code{@value{GDBP}} with the
16396 name of your program as the argument. To connect to the board, use the
16397 command @samp{target mips @var{port}}, where @var{port} is the name of
16398 the serial port connected to the board. If the program has not already
16399 been downloaded to the board, you may use the @code{load} command to
16400 download it. You can then use all the usual @value{GDBN} commands.
16402 For example, this sequence connects to the target board through a serial
16403 port, and loads and runs a program called @var{prog} through the
16407 host$ @value{GDBP} @var{prog}
16408 @value{GDBN} is free software and @dots{}
16409 (@value{GDBP}) target mips /dev/ttyb
16410 (@value{GDBP}) load @var{prog}
16414 @item target mips @var{hostname}:@var{portnumber}
16415 On some @value{GDBN} host configurations, you can specify a TCP
16416 connection (for instance, to a serial line managed by a terminal
16417 concentrator) instead of a serial port, using the syntax
16418 @samp{@var{hostname}:@var{portnumber}}.
16420 @item target pmon @var{port}
16421 @kindex target pmon @var{port}
16424 @item target ddb @var{port}
16425 @kindex target ddb @var{port}
16426 NEC's DDB variant of PMON for Vr4300.
16428 @item target lsi @var{port}
16429 @kindex target lsi @var{port}
16430 LSI variant of PMON.
16432 @kindex target r3900
16433 @item target r3900 @var{dev}
16434 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16436 @kindex target array
16437 @item target array @var{dev}
16438 Array Tech LSI33K RAID controller board.
16444 @value{GDBN} also supports these special commands for MIPS targets:
16447 @item set mipsfpu double
16448 @itemx set mipsfpu single
16449 @itemx set mipsfpu none
16450 @itemx set mipsfpu auto
16451 @itemx show mipsfpu
16452 @kindex set mipsfpu
16453 @kindex show mipsfpu
16454 @cindex MIPS remote floating point
16455 @cindex floating point, MIPS remote
16456 If your target board does not support the MIPS floating point
16457 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16458 need this, you may wish to put the command in your @value{GDBN} init
16459 file). This tells @value{GDBN} how to find the return value of
16460 functions which return floating point values. It also allows
16461 @value{GDBN} to avoid saving the floating point registers when calling
16462 functions on the board. If you are using a floating point coprocessor
16463 with only single precision floating point support, as on the @sc{r4650}
16464 processor, use the command @samp{set mipsfpu single}. The default
16465 double precision floating point coprocessor may be selected using
16466 @samp{set mipsfpu double}.
16468 In previous versions the only choices were double precision or no
16469 floating point, so @samp{set mipsfpu on} will select double precision
16470 and @samp{set mipsfpu off} will select no floating point.
16472 As usual, you can inquire about the @code{mipsfpu} variable with
16473 @samp{show mipsfpu}.
16475 @item set timeout @var{seconds}
16476 @itemx set retransmit-timeout @var{seconds}
16477 @itemx show timeout
16478 @itemx show retransmit-timeout
16479 @cindex @code{timeout}, MIPS protocol
16480 @cindex @code{retransmit-timeout}, MIPS protocol
16481 @kindex set timeout
16482 @kindex show timeout
16483 @kindex set retransmit-timeout
16484 @kindex show retransmit-timeout
16485 You can control the timeout used while waiting for a packet, in the MIPS
16486 remote protocol, with the @code{set timeout @var{seconds}} command. The
16487 default is 5 seconds. Similarly, you can control the timeout used while
16488 waiting for an acknowledgment of a packet with the @code{set
16489 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16490 You can inspect both values with @code{show timeout} and @code{show
16491 retransmit-timeout}. (These commands are @emph{only} available when
16492 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16494 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16495 is waiting for your program to stop. In that case, @value{GDBN} waits
16496 forever because it has no way of knowing how long the program is going
16497 to run before stopping.
16499 @item set syn-garbage-limit @var{num}
16500 @kindex set syn-garbage-limit@r{, MIPS remote}
16501 @cindex synchronize with remote MIPS target
16502 Limit the maximum number of characters @value{GDBN} should ignore when
16503 it tries to synchronize with the remote target. The default is 10
16504 characters. Setting the limit to -1 means there's no limit.
16506 @item show syn-garbage-limit
16507 @kindex show syn-garbage-limit@r{, MIPS remote}
16508 Show the current limit on the number of characters to ignore when
16509 trying to synchronize with the remote system.
16511 @item set monitor-prompt @var{prompt}
16512 @kindex set monitor-prompt@r{, MIPS remote}
16513 @cindex remote monitor prompt
16514 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16515 remote monitor. The default depends on the target:
16525 @item show monitor-prompt
16526 @kindex show monitor-prompt@r{, MIPS remote}
16527 Show the current strings @value{GDBN} expects as the prompt from the
16530 @item set monitor-warnings
16531 @kindex set monitor-warnings@r{, MIPS remote}
16532 Enable or disable monitor warnings about hardware breakpoints. This
16533 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16534 display warning messages whose codes are returned by the @code{lsi}
16535 PMON monitor for breakpoint commands.
16537 @item show monitor-warnings
16538 @kindex show monitor-warnings@r{, MIPS remote}
16539 Show the current setting of printing monitor warnings.
16541 @item pmon @var{command}
16542 @kindex pmon@r{, MIPS remote}
16543 @cindex send PMON command
16544 This command allows sending an arbitrary @var{command} string to the
16545 monitor. The monitor must be in debug mode for this to work.
16548 @node OpenRISC 1000
16549 @subsection OpenRISC 1000
16550 @cindex OpenRISC 1000
16552 @cindex or1k boards
16553 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16554 about platform and commands.
16558 @kindex target jtag
16559 @item target jtag jtag://@var{host}:@var{port}
16561 Connects to remote JTAG server.
16562 JTAG remote server can be either an or1ksim or JTAG server,
16563 connected via parallel port to the board.
16565 Example: @code{target jtag jtag://localhost:9999}
16568 @item or1ksim @var{command}
16569 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16570 Simulator, proprietary commands can be executed.
16572 @kindex info or1k spr
16573 @item info or1k spr
16574 Displays spr groups.
16576 @item info or1k spr @var{group}
16577 @itemx info or1k spr @var{groupno}
16578 Displays register names in selected group.
16580 @item info or1k spr @var{group} @var{register}
16581 @itemx info or1k spr @var{register}
16582 @itemx info or1k spr @var{groupno} @var{registerno}
16583 @itemx info or1k spr @var{registerno}
16584 Shows information about specified spr register.
16587 @item spr @var{group} @var{register} @var{value}
16588 @itemx spr @var{register @var{value}}
16589 @itemx spr @var{groupno} @var{registerno @var{value}}
16590 @itemx spr @var{registerno @var{value}}
16591 Writes @var{value} to specified spr register.
16594 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16595 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16596 program execution and is thus much faster. Hardware breakpoints/watchpoint
16597 triggers can be set using:
16600 Load effective address/data
16602 Store effective address/data
16604 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16609 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16610 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16612 @code{htrace} commands:
16613 @cindex OpenRISC 1000 htrace
16616 @item hwatch @var{conditional}
16617 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16618 or Data. For example:
16620 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16622 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16626 Display information about current HW trace configuration.
16628 @item htrace trigger @var{conditional}
16629 Set starting criteria for HW trace.
16631 @item htrace qualifier @var{conditional}
16632 Set acquisition qualifier for HW trace.
16634 @item htrace stop @var{conditional}
16635 Set HW trace stopping criteria.
16637 @item htrace record [@var{data}]*
16638 Selects the data to be recorded, when qualifier is met and HW trace was
16641 @item htrace enable
16642 @itemx htrace disable
16643 Enables/disables the HW trace.
16645 @item htrace rewind [@var{filename}]
16646 Clears currently recorded trace data.
16648 If filename is specified, new trace file is made and any newly collected data
16649 will be written there.
16651 @item htrace print [@var{start} [@var{len}]]
16652 Prints trace buffer, using current record configuration.
16654 @item htrace mode continuous
16655 Set continuous trace mode.
16657 @item htrace mode suspend
16658 Set suspend trace mode.
16662 @node PowerPC Embedded
16663 @subsection PowerPC Embedded
16665 @value{GDBN} provides the following PowerPC-specific commands:
16668 @kindex set powerpc
16669 @item set powerpc soft-float
16670 @itemx show powerpc soft-float
16671 Force @value{GDBN} to use (or not use) a software floating point calling
16672 convention. By default, @value{GDBN} selects the calling convention based
16673 on the selected architecture and the provided executable file.
16675 @item set powerpc vector-abi
16676 @itemx show powerpc vector-abi
16677 Force @value{GDBN} to use the specified calling convention for vector
16678 arguments and return values. The valid options are @samp{auto};
16679 @samp{generic}, to avoid vector registers even if they are present;
16680 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16681 registers. By default, @value{GDBN} selects the calling convention
16682 based on the selected architecture and the provided executable file.
16684 @kindex target dink32
16685 @item target dink32 @var{dev}
16686 DINK32 ROM monitor.
16688 @kindex target ppcbug
16689 @item target ppcbug @var{dev}
16690 @kindex target ppcbug1
16691 @item target ppcbug1 @var{dev}
16692 PPCBUG ROM monitor for PowerPC.
16695 @item target sds @var{dev}
16696 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16699 @cindex SDS protocol
16700 The following commands specific to the SDS protocol are supported
16704 @item set sdstimeout @var{nsec}
16705 @kindex set sdstimeout
16706 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16707 default is 2 seconds.
16709 @item show sdstimeout
16710 @kindex show sdstimeout
16711 Show the current value of the SDS timeout.
16713 @item sds @var{command}
16714 @kindex sds@r{, a command}
16715 Send the specified @var{command} string to the SDS monitor.
16720 @subsection HP PA Embedded
16724 @kindex target op50n
16725 @item target op50n @var{dev}
16726 OP50N monitor, running on an OKI HPPA board.
16728 @kindex target w89k
16729 @item target w89k @var{dev}
16730 W89K monitor, running on a Winbond HPPA board.
16735 @subsection Tsqware Sparclet
16739 @value{GDBN} enables developers to debug tasks running on
16740 Sparclet targets from a Unix host.
16741 @value{GDBN} uses code that runs on
16742 both the Unix host and on the Sparclet target. The program
16743 @code{@value{GDBP}} is installed and executed on the Unix host.
16746 @item remotetimeout @var{args}
16747 @kindex remotetimeout
16748 @value{GDBN} supports the option @code{remotetimeout}.
16749 This option is set by the user, and @var{args} represents the number of
16750 seconds @value{GDBN} waits for responses.
16753 @cindex compiling, on Sparclet
16754 When compiling for debugging, include the options @samp{-g} to get debug
16755 information and @samp{-Ttext} to relocate the program to where you wish to
16756 load it on the target. You may also want to add the options @samp{-n} or
16757 @samp{-N} in order to reduce the size of the sections. Example:
16760 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16763 You can use @code{objdump} to verify that the addresses are what you intended:
16766 sparclet-aout-objdump --headers --syms prog
16769 @cindex running, on Sparclet
16771 your Unix execution search path to find @value{GDBN}, you are ready to
16772 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16773 (or @code{sparclet-aout-gdb}, depending on your installation).
16775 @value{GDBN} comes up showing the prompt:
16782 * Sparclet File:: Setting the file to debug
16783 * Sparclet Connection:: Connecting to Sparclet
16784 * Sparclet Download:: Sparclet download
16785 * Sparclet Execution:: Running and debugging
16788 @node Sparclet File
16789 @subsubsection Setting File to Debug
16791 The @value{GDBN} command @code{file} lets you choose with program to debug.
16794 (gdbslet) file prog
16798 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16799 @value{GDBN} locates
16800 the file by searching the directories listed in the command search
16802 If the file was compiled with debug information (option @samp{-g}), source
16803 files will be searched as well.
16804 @value{GDBN} locates
16805 the source files by searching the directories listed in the directory search
16806 path (@pxref{Environment, ,Your Program's Environment}).
16808 to find a file, it displays a message such as:
16811 prog: No such file or directory.
16814 When this happens, add the appropriate directories to the search paths with
16815 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16816 @code{target} command again.
16818 @node Sparclet Connection
16819 @subsubsection Connecting to Sparclet
16821 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16822 To connect to a target on serial port ``@code{ttya}'', type:
16825 (gdbslet) target sparclet /dev/ttya
16826 Remote target sparclet connected to /dev/ttya
16827 main () at ../prog.c:3
16831 @value{GDBN} displays messages like these:
16837 @node Sparclet Download
16838 @subsubsection Sparclet Download
16840 @cindex download to Sparclet
16841 Once connected to the Sparclet target,
16842 you can use the @value{GDBN}
16843 @code{load} command to download the file from the host to the target.
16844 The file name and load offset should be given as arguments to the @code{load}
16846 Since the file format is aout, the program must be loaded to the starting
16847 address. You can use @code{objdump} to find out what this value is. The load
16848 offset is an offset which is added to the VMA (virtual memory address)
16849 of each of the file's sections.
16850 For instance, if the program
16851 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16852 and bss at 0x12010170, in @value{GDBN}, type:
16855 (gdbslet) load prog 0x12010000
16856 Loading section .text, size 0xdb0 vma 0x12010000
16859 If the code is loaded at a different address then what the program was linked
16860 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16861 to tell @value{GDBN} where to map the symbol table.
16863 @node Sparclet Execution
16864 @subsubsection Running and Debugging
16866 @cindex running and debugging Sparclet programs
16867 You can now begin debugging the task using @value{GDBN}'s execution control
16868 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16869 manual for the list of commands.
16873 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16875 Starting program: prog
16876 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16877 3 char *symarg = 0;
16879 4 char *execarg = "hello!";
16884 @subsection Fujitsu Sparclite
16888 @kindex target sparclite
16889 @item target sparclite @var{dev}
16890 Fujitsu sparclite boards, used only for the purpose of loading.
16891 You must use an additional command to debug the program.
16892 For example: target remote @var{dev} using @value{GDBN} standard
16898 @subsection Zilog Z8000
16901 @cindex simulator, Z8000
16902 @cindex Zilog Z8000 simulator
16904 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16907 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16908 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16909 segmented variant). The simulator recognizes which architecture is
16910 appropriate by inspecting the object code.
16913 @item target sim @var{args}
16915 @kindex target sim@r{, with Z8000}
16916 Debug programs on a simulated CPU. If the simulator supports setup
16917 options, specify them via @var{args}.
16921 After specifying this target, you can debug programs for the simulated
16922 CPU in the same style as programs for your host computer; use the
16923 @code{file} command to load a new program image, the @code{run} command
16924 to run your program, and so on.
16926 As well as making available all the usual machine registers
16927 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16928 additional items of information as specially named registers:
16933 Counts clock-ticks in the simulator.
16936 Counts instructions run in the simulator.
16939 Execution time in 60ths of a second.
16943 You can refer to these values in @value{GDBN} expressions with the usual
16944 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16945 conditional breakpoint that suspends only after at least 5000
16946 simulated clock ticks.
16949 @subsection Atmel AVR
16952 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16953 following AVR-specific commands:
16956 @item info io_registers
16957 @kindex info io_registers@r{, AVR}
16958 @cindex I/O registers (Atmel AVR)
16959 This command displays information about the AVR I/O registers. For
16960 each register, @value{GDBN} prints its number and value.
16967 When configured for debugging CRIS, @value{GDBN} provides the
16968 following CRIS-specific commands:
16971 @item set cris-version @var{ver}
16972 @cindex CRIS version
16973 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16974 The CRIS version affects register names and sizes. This command is useful in
16975 case autodetection of the CRIS version fails.
16977 @item show cris-version
16978 Show the current CRIS version.
16980 @item set cris-dwarf2-cfi
16981 @cindex DWARF-2 CFI and CRIS
16982 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16983 Change to @samp{off} when using @code{gcc-cris} whose version is below
16986 @item show cris-dwarf2-cfi
16987 Show the current state of using DWARF-2 CFI.
16989 @item set cris-mode @var{mode}
16991 Set the current CRIS mode to @var{mode}. It should only be changed when
16992 debugging in guru mode, in which case it should be set to
16993 @samp{guru} (the default is @samp{normal}).
16995 @item show cris-mode
16996 Show the current CRIS mode.
17000 @subsection Renesas Super-H
17003 For the Renesas Super-H processor, @value{GDBN} provides these
17008 @kindex regs@r{, Super-H}
17009 Show the values of all Super-H registers.
17011 @item set sh calling-convention @var{convention}
17012 @kindex set sh calling-convention
17013 Set the calling-convention used when calling functions from @value{GDBN}.
17014 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
17015 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
17016 convention. If the DWARF-2 information of the called function specifies
17017 that the function follows the Renesas calling convention, the function
17018 is called using the Renesas calling convention. If the calling convention
17019 is set to @samp{renesas}, the Renesas calling convention is always used,
17020 regardless of the DWARF-2 information. This can be used to override the
17021 default of @samp{gcc} if debug information is missing, or the compiler
17022 does not emit the DWARF-2 calling convention entry for a function.
17024 @item show sh calling-convention
17025 @kindex show sh calling-convention
17026 Show the current calling convention setting.
17031 @node Architectures
17032 @section Architectures
17034 This section describes characteristics of architectures that affect
17035 all uses of @value{GDBN} with the architecture, both native and cross.
17042 * HPPA:: HP PA architecture
17043 * SPU:: Cell Broadband Engine SPU architecture
17048 @subsection x86 Architecture-specific Issues
17051 @item set struct-convention @var{mode}
17052 @kindex set struct-convention
17053 @cindex struct return convention
17054 @cindex struct/union returned in registers
17055 Set the convention used by the inferior to return @code{struct}s and
17056 @code{union}s from functions to @var{mode}. Possible values of
17057 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
17058 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
17059 are returned on the stack, while @code{"reg"} means that a
17060 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
17061 be returned in a register.
17063 @item show struct-convention
17064 @kindex show struct-convention
17065 Show the current setting of the convention to return @code{struct}s
17074 @kindex set rstack_high_address
17075 @cindex AMD 29K register stack
17076 @cindex register stack, AMD29K
17077 @item set rstack_high_address @var{address}
17078 On AMD 29000 family processors, registers are saved in a separate
17079 @dfn{register stack}. There is no way for @value{GDBN} to determine the
17080 extent of this stack. Normally, @value{GDBN} just assumes that the
17081 stack is ``large enough''. This may result in @value{GDBN} referencing
17082 memory locations that do not exist. If necessary, you can get around
17083 this problem by specifying the ending address of the register stack with
17084 the @code{set rstack_high_address} command. The argument should be an
17085 address, which you probably want to precede with @samp{0x} to specify in
17088 @kindex show rstack_high_address
17089 @item show rstack_high_address
17090 Display the current limit of the register stack, on AMD 29000 family
17098 See the following section.
17103 @cindex stack on Alpha
17104 @cindex stack on MIPS
17105 @cindex Alpha stack
17107 Alpha- and MIPS-based computers use an unusual stack frame, which
17108 sometimes requires @value{GDBN} to search backward in the object code to
17109 find the beginning of a function.
17111 @cindex response time, MIPS debugging
17112 To improve response time (especially for embedded applications, where
17113 @value{GDBN} may be restricted to a slow serial line for this search)
17114 you may want to limit the size of this search, using one of these
17118 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
17119 @item set heuristic-fence-post @var{limit}
17120 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
17121 search for the beginning of a function. A value of @var{0} (the
17122 default) means there is no limit. However, except for @var{0}, the
17123 larger the limit the more bytes @code{heuristic-fence-post} must search
17124 and therefore the longer it takes to run. You should only need to use
17125 this command when debugging a stripped executable.
17127 @item show heuristic-fence-post
17128 Display the current limit.
17132 These commands are available @emph{only} when @value{GDBN} is configured
17133 for debugging programs on Alpha or MIPS processors.
17135 Several MIPS-specific commands are available when debugging MIPS
17139 @item set mips abi @var{arg}
17140 @kindex set mips abi
17141 @cindex set ABI for MIPS
17142 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
17143 values of @var{arg} are:
17147 The default ABI associated with the current binary (this is the
17158 @item show mips abi
17159 @kindex show mips abi
17160 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
17163 @itemx show mipsfpu
17164 @xref{MIPS Embedded, set mipsfpu}.
17166 @item set mips mask-address @var{arg}
17167 @kindex set mips mask-address
17168 @cindex MIPS addresses, masking
17169 This command determines whether the most-significant 32 bits of 64-bit
17170 MIPS addresses are masked off. The argument @var{arg} can be
17171 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
17172 setting, which lets @value{GDBN} determine the correct value.
17174 @item show mips mask-address
17175 @kindex show mips mask-address
17176 Show whether the upper 32 bits of MIPS addresses are masked off or
17179 @item set remote-mips64-transfers-32bit-regs
17180 @kindex set remote-mips64-transfers-32bit-regs
17181 This command controls compatibility with 64-bit MIPS targets that
17182 transfer data in 32-bit quantities. If you have an old MIPS 64 target
17183 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
17184 and 64 bits for other registers, set this option to @samp{on}.
17186 @item show remote-mips64-transfers-32bit-regs
17187 @kindex show remote-mips64-transfers-32bit-regs
17188 Show the current setting of compatibility with older MIPS 64 targets.
17190 @item set debug mips
17191 @kindex set debug mips
17192 This command turns on and off debugging messages for the MIPS-specific
17193 target code in @value{GDBN}.
17195 @item show debug mips
17196 @kindex show debug mips
17197 Show the current setting of MIPS debugging messages.
17203 @cindex HPPA support
17205 When @value{GDBN} is debugging the HP PA architecture, it provides the
17206 following special commands:
17209 @item set debug hppa
17210 @kindex set debug hppa
17211 This command determines whether HPPA architecture-specific debugging
17212 messages are to be displayed.
17214 @item show debug hppa
17215 Show whether HPPA debugging messages are displayed.
17217 @item maint print unwind @var{address}
17218 @kindex maint print unwind@r{, HPPA}
17219 This command displays the contents of the unwind table entry at the
17220 given @var{address}.
17226 @subsection Cell Broadband Engine SPU architecture
17227 @cindex Cell Broadband Engine
17230 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17231 it provides the following special commands:
17234 @item info spu event
17236 Display SPU event facility status. Shows current event mask
17237 and pending event status.
17239 @item info spu signal
17240 Display SPU signal notification facility status. Shows pending
17241 signal-control word and signal notification mode of both signal
17242 notification channels.
17244 @item info spu mailbox
17245 Display SPU mailbox facility status. Shows all pending entries,
17246 in order of processing, in each of the SPU Write Outbound,
17247 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17250 Display MFC DMA status. Shows all pending commands in the MFC
17251 DMA queue. For each entry, opcode, tag, class IDs, effective
17252 and local store addresses and transfer size are shown.
17254 @item info spu proxydma
17255 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17256 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17257 and local store addresses and transfer size are shown.
17262 @subsection PowerPC
17263 @cindex PowerPC architecture
17265 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17266 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17267 numbers stored in the floating point registers. These values must be stored
17268 in two consecutive registers, always starting at an even register like
17269 @code{f0} or @code{f2}.
17271 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
17272 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
17273 @code{f2} and @code{f3} for @code{$dl1} and so on.
17275 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
17276 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
17279 @node Controlling GDB
17280 @chapter Controlling @value{GDBN}
17282 You can alter the way @value{GDBN} interacts with you by using the
17283 @code{set} command. For commands controlling how @value{GDBN} displays
17284 data, see @ref{Print Settings, ,Print Settings}. Other settings are
17289 * Editing:: Command editing
17290 * Command History:: Command history
17291 * Screen Size:: Screen size
17292 * Numbers:: Numbers
17293 * ABI:: Configuring the current ABI
17294 * Messages/Warnings:: Optional warnings and messages
17295 * Debugging Output:: Optional messages about internal happenings
17303 @value{GDBN} indicates its readiness to read a command by printing a string
17304 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17305 can change the prompt string with the @code{set prompt} command. For
17306 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17307 the prompt in one of the @value{GDBN} sessions so that you can always tell
17308 which one you are talking to.
17310 @emph{Note:} @code{set prompt} does not add a space for you after the
17311 prompt you set. This allows you to set a prompt which ends in a space
17312 or a prompt that does not.
17316 @item set prompt @var{newprompt}
17317 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17319 @kindex show prompt
17321 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17325 @section Command Editing
17327 @cindex command line editing
17329 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17330 @sc{gnu} library provides consistent behavior for programs which provide a
17331 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17332 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17333 substitution, and a storage and recall of command history across
17334 debugging sessions.
17336 You may control the behavior of command line editing in @value{GDBN} with the
17337 command @code{set}.
17340 @kindex set editing
17343 @itemx set editing on
17344 Enable command line editing (enabled by default).
17346 @item set editing off
17347 Disable command line editing.
17349 @kindex show editing
17351 Show whether command line editing is enabled.
17354 @xref{Command Line Editing}, for more details about the Readline
17355 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17356 encouraged to read that chapter.
17358 @node Command History
17359 @section Command History
17360 @cindex command history
17362 @value{GDBN} can keep track of the commands you type during your
17363 debugging sessions, so that you can be certain of precisely what
17364 happened. Use these commands to manage the @value{GDBN} command
17367 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17368 package, to provide the history facility. @xref{Using History
17369 Interactively}, for the detailed description of the History library.
17371 To issue a command to @value{GDBN} without affecting certain aspects of
17372 the state which is seen by users, prefix it with @samp{server }
17373 (@pxref{Server Prefix}). This
17374 means that this command will not affect the command history, nor will it
17375 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17376 pressed on a line by itself.
17378 @cindex @code{server}, command prefix
17379 The server prefix does not affect the recording of values into the value
17380 history; to print a value without recording it into the value history,
17381 use the @code{output} command instead of the @code{print} command.
17383 Here is the description of @value{GDBN} commands related to command
17387 @cindex history substitution
17388 @cindex history file
17389 @kindex set history filename
17390 @cindex @env{GDBHISTFILE}, environment variable
17391 @item set history filename @var{fname}
17392 Set the name of the @value{GDBN} command history file to @var{fname}.
17393 This is the file where @value{GDBN} reads an initial command history
17394 list, and where it writes the command history from this session when it
17395 exits. You can access this list through history expansion or through
17396 the history command editing characters listed below. This file defaults
17397 to the value of the environment variable @code{GDBHISTFILE}, or to
17398 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17401 @cindex save command history
17402 @kindex set history save
17403 @item set history save
17404 @itemx set history save on
17405 Record command history in a file, whose name may be specified with the
17406 @code{set history filename} command. By default, this option is disabled.
17408 @item set history save off
17409 Stop recording command history in a file.
17411 @cindex history size
17412 @kindex set history size
17413 @cindex @env{HISTSIZE}, environment variable
17414 @item set history size @var{size}
17415 Set the number of commands which @value{GDBN} keeps in its history list.
17416 This defaults to the value of the environment variable
17417 @code{HISTSIZE}, or to 256 if this variable is not set.
17420 History expansion assigns special meaning to the character @kbd{!}.
17421 @xref{Event Designators}, for more details.
17423 @cindex history expansion, turn on/off
17424 Since @kbd{!} is also the logical not operator in C, history expansion
17425 is off by default. If you decide to enable history expansion with the
17426 @code{set history expansion on} command, you may sometimes need to
17427 follow @kbd{!} (when it is used as logical not, in an expression) with
17428 a space or a tab to prevent it from being expanded. The readline
17429 history facilities do not attempt substitution on the strings
17430 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17432 The commands to control history expansion are:
17435 @item set history expansion on
17436 @itemx set history expansion
17437 @kindex set history expansion
17438 Enable history expansion. History expansion is off by default.
17440 @item set history expansion off
17441 Disable history expansion.
17444 @kindex show history
17446 @itemx show history filename
17447 @itemx show history save
17448 @itemx show history size
17449 @itemx show history expansion
17450 These commands display the state of the @value{GDBN} history parameters.
17451 @code{show history} by itself displays all four states.
17456 @kindex show commands
17457 @cindex show last commands
17458 @cindex display command history
17459 @item show commands
17460 Display the last ten commands in the command history.
17462 @item show commands @var{n}
17463 Print ten commands centered on command number @var{n}.
17465 @item show commands +
17466 Print ten commands just after the commands last printed.
17470 @section Screen Size
17471 @cindex size of screen
17472 @cindex pauses in output
17474 Certain commands to @value{GDBN} may produce large amounts of
17475 information output to the screen. To help you read all of it,
17476 @value{GDBN} pauses and asks you for input at the end of each page of
17477 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17478 to discard the remaining output. Also, the screen width setting
17479 determines when to wrap lines of output. Depending on what is being
17480 printed, @value{GDBN} tries to break the line at a readable place,
17481 rather than simply letting it overflow onto the following line.
17483 Normally @value{GDBN} knows the size of the screen from the terminal
17484 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17485 together with the value of the @code{TERM} environment variable and the
17486 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17487 you can override it with the @code{set height} and @code{set
17494 @kindex show height
17495 @item set height @var{lpp}
17497 @itemx set width @var{cpl}
17499 These @code{set} commands specify a screen height of @var{lpp} lines and
17500 a screen width of @var{cpl} characters. The associated @code{show}
17501 commands display the current settings.
17503 If you specify a height of zero lines, @value{GDBN} does not pause during
17504 output no matter how long the output is. This is useful if output is to a
17505 file or to an editor buffer.
17507 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17508 from wrapping its output.
17510 @item set pagination on
17511 @itemx set pagination off
17512 @kindex set pagination
17513 Turn the output pagination on or off; the default is on. Turning
17514 pagination off is the alternative to @code{set height 0}.
17516 @item show pagination
17517 @kindex show pagination
17518 Show the current pagination mode.
17523 @cindex number representation
17524 @cindex entering numbers
17526 You can always enter numbers in octal, decimal, or hexadecimal in
17527 @value{GDBN} by the usual conventions: octal numbers begin with
17528 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17529 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17530 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17531 10; likewise, the default display for numbers---when no particular
17532 format is specified---is base 10. You can change the default base for
17533 both input and output with the commands described below.
17536 @kindex set input-radix
17537 @item set input-radix @var{base}
17538 Set the default base for numeric input. Supported choices
17539 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17540 specified either unambiguously or using the current input radix; for
17544 set input-radix 012
17545 set input-radix 10.
17546 set input-radix 0xa
17550 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17551 leaves the input radix unchanged, no matter what it was, since
17552 @samp{10}, being without any leading or trailing signs of its base, is
17553 interpreted in the current radix. Thus, if the current radix is 16,
17554 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17557 @kindex set output-radix
17558 @item set output-radix @var{base}
17559 Set the default base for numeric display. Supported choices
17560 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17561 specified either unambiguously or using the current input radix.
17563 @kindex show input-radix
17564 @item show input-radix
17565 Display the current default base for numeric input.
17567 @kindex show output-radix
17568 @item show output-radix
17569 Display the current default base for numeric display.
17571 @item set radix @r{[}@var{base}@r{]}
17575 These commands set and show the default base for both input and output
17576 of numbers. @code{set radix} sets the radix of input and output to
17577 the same base; without an argument, it resets the radix back to its
17578 default value of 10.
17583 @section Configuring the Current ABI
17585 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17586 application automatically. However, sometimes you need to override its
17587 conclusions. Use these commands to manage @value{GDBN}'s view of the
17594 One @value{GDBN} configuration can debug binaries for multiple operating
17595 system targets, either via remote debugging or native emulation.
17596 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17597 but you can override its conclusion using the @code{set osabi} command.
17598 One example where this is useful is in debugging of binaries which use
17599 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17600 not have the same identifying marks that the standard C library for your
17605 Show the OS ABI currently in use.
17608 With no argument, show the list of registered available OS ABI's.
17610 @item set osabi @var{abi}
17611 Set the current OS ABI to @var{abi}.
17614 @cindex float promotion
17616 Generally, the way that an argument of type @code{float} is passed to a
17617 function depends on whether the function is prototyped. For a prototyped
17618 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17619 according to the architecture's convention for @code{float}. For unprototyped
17620 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17621 @code{double} and then passed.
17623 Unfortunately, some forms of debug information do not reliably indicate whether
17624 a function is prototyped. If @value{GDBN} calls a function that is not marked
17625 as prototyped, it consults @kbd{set coerce-float-to-double}.
17628 @kindex set coerce-float-to-double
17629 @item set coerce-float-to-double
17630 @itemx set coerce-float-to-double on
17631 Arguments of type @code{float} will be promoted to @code{double} when passed
17632 to an unprototyped function. This is the default setting.
17634 @item set coerce-float-to-double off
17635 Arguments of type @code{float} will be passed directly to unprototyped
17638 @kindex show coerce-float-to-double
17639 @item show coerce-float-to-double
17640 Show the current setting of promoting @code{float} to @code{double}.
17644 @kindex show cp-abi
17645 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17646 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17647 used to build your application. @value{GDBN} only fully supports
17648 programs with a single C@t{++} ABI; if your program contains code using
17649 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17650 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17651 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17652 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17653 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17654 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17659 Show the C@t{++} ABI currently in use.
17662 With no argument, show the list of supported C@t{++} ABI's.
17664 @item set cp-abi @var{abi}
17665 @itemx set cp-abi auto
17666 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17669 @node Messages/Warnings
17670 @section Optional Warnings and Messages
17672 @cindex verbose operation
17673 @cindex optional warnings
17674 By default, @value{GDBN} is silent about its inner workings. If you are
17675 running on a slow machine, you may want to use the @code{set verbose}
17676 command. This makes @value{GDBN} tell you when it does a lengthy
17677 internal operation, so you will not think it has crashed.
17679 Currently, the messages controlled by @code{set verbose} are those
17680 which announce that the symbol table for a source file is being read;
17681 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17684 @kindex set verbose
17685 @item set verbose on
17686 Enables @value{GDBN} output of certain informational messages.
17688 @item set verbose off
17689 Disables @value{GDBN} output of certain informational messages.
17691 @kindex show verbose
17693 Displays whether @code{set verbose} is on or off.
17696 By default, if @value{GDBN} encounters bugs in the symbol table of an
17697 object file, it is silent; but if you are debugging a compiler, you may
17698 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17703 @kindex set complaints
17704 @item set complaints @var{limit}
17705 Permits @value{GDBN} to output @var{limit} complaints about each type of
17706 unusual symbols before becoming silent about the problem. Set
17707 @var{limit} to zero to suppress all complaints; set it to a large number
17708 to prevent complaints from being suppressed.
17710 @kindex show complaints
17711 @item show complaints
17712 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17716 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17717 lot of stupid questions to confirm certain commands. For example, if
17718 you try to run a program which is already running:
17722 The program being debugged has been started already.
17723 Start it from the beginning? (y or n)
17726 If you are willing to unflinchingly face the consequences of your own
17727 commands, you can disable this ``feature'':
17731 @kindex set confirm
17733 @cindex confirmation
17734 @cindex stupid questions
17735 @item set confirm off
17736 Disables confirmation requests.
17738 @item set confirm on
17739 Enables confirmation requests (the default).
17741 @kindex show confirm
17743 Displays state of confirmation requests.
17747 @cindex command tracing
17748 If you need to debug user-defined commands or sourced files you may find it
17749 useful to enable @dfn{command tracing}. In this mode each command will be
17750 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17751 quantity denoting the call depth of each command.
17754 @kindex set trace-commands
17755 @cindex command scripts, debugging
17756 @item set trace-commands on
17757 Enable command tracing.
17758 @item set trace-commands off
17759 Disable command tracing.
17760 @item show trace-commands
17761 Display the current state of command tracing.
17764 @node Debugging Output
17765 @section Optional Messages about Internal Happenings
17766 @cindex optional debugging messages
17768 @value{GDBN} has commands that enable optional debugging messages from
17769 various @value{GDBN} subsystems; normally these commands are of
17770 interest to @value{GDBN} maintainers, or when reporting a bug. This
17771 section documents those commands.
17774 @kindex set exec-done-display
17775 @item set exec-done-display
17776 Turns on or off the notification of asynchronous commands'
17777 completion. When on, @value{GDBN} will print a message when an
17778 asynchronous command finishes its execution. The default is off.
17779 @kindex show exec-done-display
17780 @item show exec-done-display
17781 Displays the current setting of asynchronous command completion
17784 @cindex gdbarch debugging info
17785 @cindex architecture debugging info
17786 @item set debug arch
17787 Turns on or off display of gdbarch debugging info. The default is off
17789 @item show debug arch
17790 Displays the current state of displaying gdbarch debugging info.
17791 @item set debug aix-thread
17792 @cindex AIX threads
17793 Display debugging messages about inner workings of the AIX thread
17795 @item show debug aix-thread
17796 Show the current state of AIX thread debugging info display.
17797 @item set debug dwarf2-die
17798 @cindex DWARF2 DIEs
17799 Dump DWARF2 DIEs after they are read in.
17800 The value is the number of nesting levels to print.
17801 A value of zero turns off the display.
17802 @item show debug dwarf2-die
17803 Show the current state of DWARF2 DIE debugging.
17804 @item set debug displaced
17805 @cindex displaced stepping debugging info
17806 Turns on or off display of @value{GDBN} debugging info for the
17807 displaced stepping support. The default is off.
17808 @item show debug displaced
17809 Displays the current state of displaying @value{GDBN} debugging info
17810 related to displaced stepping.
17811 @item set debug event
17812 @cindex event debugging info
17813 Turns on or off display of @value{GDBN} event debugging info. The
17815 @item show debug event
17816 Displays the current state of displaying @value{GDBN} event debugging
17818 @item set debug expression
17819 @cindex expression debugging info
17820 Turns on or off display of debugging info about @value{GDBN}
17821 expression parsing. The default is off.
17822 @item show debug expression
17823 Displays the current state of displaying debugging info about
17824 @value{GDBN} expression parsing.
17825 @item set debug frame
17826 @cindex frame debugging info
17827 Turns on or off display of @value{GDBN} frame debugging info. The
17829 @item show debug frame
17830 Displays the current state of displaying @value{GDBN} frame debugging
17832 @item set debug gnu-nat
17833 @cindex @sc{gnu}/Hurd debug messages
17834 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
17835 @item show debug gnu-nat
17836 Show the current state of @sc{gnu}/Hurd debugging messages.
17837 @item set debug infrun
17838 @cindex inferior debugging info
17839 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17840 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17841 for implementing operations such as single-stepping the inferior.
17842 @item show debug infrun
17843 Displays the current state of @value{GDBN} inferior debugging.
17844 @item set debug lin-lwp
17845 @cindex @sc{gnu}/Linux LWP debug messages
17846 @cindex Linux lightweight processes
17847 Turns on or off debugging messages from the Linux LWP debug support.
17848 @item show debug lin-lwp
17849 Show the current state of Linux LWP debugging messages.
17850 @item set debug lin-lwp-async
17851 @cindex @sc{gnu}/Linux LWP async debug messages
17852 @cindex Linux lightweight processes
17853 Turns on or off debugging messages from the Linux LWP async debug support.
17854 @item show debug lin-lwp-async
17855 Show the current state of Linux LWP async debugging messages.
17856 @item set debug observer
17857 @cindex observer debugging info
17858 Turns on or off display of @value{GDBN} observer debugging. This
17859 includes info such as the notification of observable events.
17860 @item show debug observer
17861 Displays the current state of observer debugging.
17862 @item set debug overload
17863 @cindex C@t{++} overload debugging info
17864 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17865 info. This includes info such as ranking of functions, etc. The default
17867 @item show debug overload
17868 Displays the current state of displaying @value{GDBN} C@t{++} overload
17870 @cindex packets, reporting on stdout
17871 @cindex serial connections, debugging
17872 @cindex debug remote protocol
17873 @cindex remote protocol debugging
17874 @cindex display remote packets
17875 @item set debug remote
17876 Turns on or off display of reports on all packets sent back and forth across
17877 the serial line to the remote machine. The info is printed on the
17878 @value{GDBN} standard output stream. The default is off.
17879 @item show debug remote
17880 Displays the state of display of remote packets.
17881 @item set debug serial
17882 Turns on or off display of @value{GDBN} serial debugging info. The
17884 @item show debug serial
17885 Displays the current state of displaying @value{GDBN} serial debugging
17887 @item set debug solib-frv
17888 @cindex FR-V shared-library debugging
17889 Turns on or off debugging messages for FR-V shared-library code.
17890 @item show debug solib-frv
17891 Display the current state of FR-V shared-library code debugging
17893 @item set debug target
17894 @cindex target debugging info
17895 Turns on or off display of @value{GDBN} target debugging info. This info
17896 includes what is going on at the target level of GDB, as it happens. The
17897 default is 0. Set it to 1 to track events, and to 2 to also track the
17898 value of large memory transfers. Changes to this flag do not take effect
17899 until the next time you connect to a target or use the @code{run} command.
17900 @item show debug target
17901 Displays the current state of displaying @value{GDBN} target debugging
17903 @item set debug timestamp
17904 @cindex timestampping debugging info
17905 Turns on or off display of timestamps with @value{GDBN} debugging info.
17906 When enabled, seconds and microseconds are displayed before each debugging
17908 @item show debug timestamp
17909 Displays the current state of displaying timestamps with @value{GDBN}
17911 @item set debugvarobj
17912 @cindex variable object debugging info
17913 Turns on or off display of @value{GDBN} variable object debugging
17914 info. The default is off.
17915 @item show debugvarobj
17916 Displays the current state of displaying @value{GDBN} variable object
17918 @item set debug xml
17919 @cindex XML parser debugging
17920 Turns on or off debugging messages for built-in XML parsers.
17921 @item show debug xml
17922 Displays the current state of XML debugging messages.
17925 @node Extending GDB
17926 @chapter Extending @value{GDBN}
17927 @cindex extending GDB
17929 @value{GDBN} provides two mechanisms for extension. The first is based
17930 on composition of @value{GDBN} commands, and the second is based on the
17931 Python scripting language.
17934 * Sequences:: Canned Sequences of Commands
17935 * Python:: Scripting @value{GDBN} using Python
17939 @section Canned Sequences of Commands
17941 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17942 Command Lists}), @value{GDBN} provides two ways to store sequences of
17943 commands for execution as a unit: user-defined commands and command
17947 * Define:: How to define your own commands
17948 * Hooks:: Hooks for user-defined commands
17949 * Command Files:: How to write scripts of commands to be stored in a file
17950 * Output:: Commands for controlled output
17954 @subsection User-defined Commands
17956 @cindex user-defined command
17957 @cindex arguments, to user-defined commands
17958 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17959 which you assign a new name as a command. This is done with the
17960 @code{define} command. User commands may accept up to 10 arguments
17961 separated by whitespace. Arguments are accessed within the user command
17962 via @code{$arg0@dots{}$arg9}. A trivial example:
17966 print $arg0 + $arg1 + $arg2
17971 To execute the command use:
17978 This defines the command @code{adder}, which prints the sum of
17979 its three arguments. Note the arguments are text substitutions, so they may
17980 reference variables, use complex expressions, or even perform inferior
17983 @cindex argument count in user-defined commands
17984 @cindex how many arguments (user-defined commands)
17985 In addition, @code{$argc} may be used to find out how many arguments have
17986 been passed. This expands to a number in the range 0@dots{}10.
17991 print $arg0 + $arg1
17994 print $arg0 + $arg1 + $arg2
18002 @item define @var{commandname}
18003 Define a command named @var{commandname}. If there is already a command
18004 by that name, you are asked to confirm that you want to redefine it.
18005 @var{commandname} may be a bare command name consisting of letters,
18006 numbers, dashes, and underscores. It may also start with any predefined
18007 prefix command. For example, @samp{define target my-target} creates
18008 a user-defined @samp{target my-target} command.
18010 The definition of the command is made up of other @value{GDBN} command lines,
18011 which are given following the @code{define} command. The end of these
18012 commands is marked by a line containing @code{end}.
18015 @kindex end@r{ (user-defined commands)}
18016 @item document @var{commandname}
18017 Document the user-defined command @var{commandname}, so that it can be
18018 accessed by @code{help}. The command @var{commandname} must already be
18019 defined. This command reads lines of documentation just as @code{define}
18020 reads the lines of the command definition, ending with @code{end}.
18021 After the @code{document} command is finished, @code{help} on command
18022 @var{commandname} displays the documentation you have written.
18024 You may use the @code{document} command again to change the
18025 documentation of a command. Redefining the command with @code{define}
18026 does not change the documentation.
18028 @kindex dont-repeat
18029 @cindex don't repeat command
18031 Used inside a user-defined command, this tells @value{GDBN} that this
18032 command should not be repeated when the user hits @key{RET}
18033 (@pxref{Command Syntax, repeat last command}).
18035 @kindex help user-defined
18036 @item help user-defined
18037 List all user-defined commands, with the first line of the documentation
18042 @itemx show user @var{commandname}
18043 Display the @value{GDBN} commands used to define @var{commandname} (but
18044 not its documentation). If no @var{commandname} is given, display the
18045 definitions for all user-defined commands.
18047 @cindex infinite recursion in user-defined commands
18048 @kindex show max-user-call-depth
18049 @kindex set max-user-call-depth
18050 @item show max-user-call-depth
18051 @itemx set max-user-call-depth
18052 The value of @code{max-user-call-depth} controls how many recursion
18053 levels are allowed in user-defined commands before @value{GDBN} suspects an
18054 infinite recursion and aborts the command.
18057 In addition to the above commands, user-defined commands frequently
18058 use control flow commands, described in @ref{Command Files}.
18060 When user-defined commands are executed, the
18061 commands of the definition are not printed. An error in any command
18062 stops execution of the user-defined command.
18064 If used interactively, commands that would ask for confirmation proceed
18065 without asking when used inside a user-defined command. Many @value{GDBN}
18066 commands that normally print messages to say what they are doing omit the
18067 messages when used in a user-defined command.
18070 @subsection User-defined Command Hooks
18071 @cindex command hooks
18072 @cindex hooks, for commands
18073 @cindex hooks, pre-command
18076 You may define @dfn{hooks}, which are a special kind of user-defined
18077 command. Whenever you run the command @samp{foo}, if the user-defined
18078 command @samp{hook-foo} exists, it is executed (with no arguments)
18079 before that command.
18081 @cindex hooks, post-command
18083 A hook may also be defined which is run after the command you executed.
18084 Whenever you run the command @samp{foo}, if the user-defined command
18085 @samp{hookpost-foo} exists, it is executed (with no arguments) after
18086 that command. Post-execution hooks may exist simultaneously with
18087 pre-execution hooks, for the same command.
18089 It is valid for a hook to call the command which it hooks. If this
18090 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
18092 @c It would be nice if hookpost could be passed a parameter indicating
18093 @c if the command it hooks executed properly or not. FIXME!
18095 @kindex stop@r{, a pseudo-command}
18096 In addition, a pseudo-command, @samp{stop} exists. Defining
18097 (@samp{hook-stop}) makes the associated commands execute every time
18098 execution stops in your program: before breakpoint commands are run,
18099 displays are printed, or the stack frame is printed.
18101 For example, to ignore @code{SIGALRM} signals while
18102 single-stepping, but treat them normally during normal execution,
18107 handle SIGALRM nopass
18111 handle SIGALRM pass
18114 define hook-continue
18115 handle SIGALRM pass
18119 As a further example, to hook at the beginning and end of the @code{echo}
18120 command, and to add extra text to the beginning and end of the message,
18128 define hookpost-echo
18132 (@value{GDBP}) echo Hello World
18133 <<<---Hello World--->>>
18138 You can define a hook for any single-word command in @value{GDBN}, but
18139 not for command aliases; you should define a hook for the basic command
18140 name, e.g.@: @code{backtrace} rather than @code{bt}.
18141 @c FIXME! So how does Joe User discover whether a command is an alias
18143 You can hook a multi-word command by adding @code{hook-} or
18144 @code{hookpost-} to the last word of the command, e.g.@:
18145 @samp{define target hook-remote} to add a hook to @samp{target remote}.
18147 If an error occurs during the execution of your hook, execution of
18148 @value{GDBN} commands stops and @value{GDBN} issues a prompt
18149 (before the command that you actually typed had a chance to run).
18151 If you try to define a hook which does not match any known command, you
18152 get a warning from the @code{define} command.
18154 @node Command Files
18155 @subsection Command Files
18157 @cindex command files
18158 @cindex scripting commands
18159 A command file for @value{GDBN} is a text file made of lines that are
18160 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
18161 also be included. An empty line in a command file does nothing; it
18162 does not mean to repeat the last command, as it would from the
18165 You can request the execution of a command file with the @code{source}
18170 @cindex execute commands from a file
18171 @item source [@code{-v}] @var{filename}
18172 Execute the command file @var{filename}.
18175 The lines in a command file are generally executed sequentially,
18176 unless the order of execution is changed by one of the
18177 @emph{flow-control commands} described below. The commands are not
18178 printed as they are executed. An error in any command terminates
18179 execution of the command file and control is returned to the console.
18181 @value{GDBN} searches for @var{filename} in the current directory and then
18182 on the search path (specified with the @samp{directory} command).
18184 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
18185 each command as it is executed. The option must be given before
18186 @var{filename}, and is interpreted as part of the filename anywhere else.
18188 Commands that would ask for confirmation if used interactively proceed
18189 without asking when used in a command file. Many @value{GDBN} commands that
18190 normally print messages to say what they are doing omit the messages
18191 when called from command files.
18193 @value{GDBN} also accepts command input from standard input. In this
18194 mode, normal output goes to standard output and error output goes to
18195 standard error. Errors in a command file supplied on standard input do
18196 not terminate execution of the command file---execution continues with
18200 gdb < cmds > log 2>&1
18203 (The syntax above will vary depending on the shell used.) This example
18204 will execute commands from the file @file{cmds}. All output and errors
18205 would be directed to @file{log}.
18207 Since commands stored on command files tend to be more general than
18208 commands typed interactively, they frequently need to deal with
18209 complicated situations, such as different or unexpected values of
18210 variables and symbols, changes in how the program being debugged is
18211 built, etc. @value{GDBN} provides a set of flow-control commands to
18212 deal with these complexities. Using these commands, you can write
18213 complex scripts that loop over data structures, execute commands
18214 conditionally, etc.
18221 This command allows to include in your script conditionally executed
18222 commands. The @code{if} command takes a single argument, which is an
18223 expression to evaluate. It is followed by a series of commands that
18224 are executed only if the expression is true (its value is nonzero).
18225 There can then optionally be an @code{else} line, followed by a series
18226 of commands that are only executed if the expression was false. The
18227 end of the list is marked by a line containing @code{end}.
18231 This command allows to write loops. Its syntax is similar to
18232 @code{if}: the command takes a single argument, which is an expression
18233 to evaluate, and must be followed by the commands to execute, one per
18234 line, terminated by an @code{end}. These commands are called the
18235 @dfn{body} of the loop. The commands in the body of @code{while} are
18236 executed repeatedly as long as the expression evaluates to true.
18240 This command exits the @code{while} loop in whose body it is included.
18241 Execution of the script continues after that @code{while}s @code{end}
18244 @kindex loop_continue
18245 @item loop_continue
18246 This command skips the execution of the rest of the body of commands
18247 in the @code{while} loop in whose body it is included. Execution
18248 branches to the beginning of the @code{while} loop, where it evaluates
18249 the controlling expression.
18251 @kindex end@r{ (if/else/while commands)}
18253 Terminate the block of commands that are the body of @code{if},
18254 @code{else}, or @code{while} flow-control commands.
18259 @subsection Commands for Controlled Output
18261 During the execution of a command file or a user-defined command, normal
18262 @value{GDBN} output is suppressed; the only output that appears is what is
18263 explicitly printed by the commands in the definition. This section
18264 describes three commands useful for generating exactly the output you
18269 @item echo @var{text}
18270 @c I do not consider backslash-space a standard C escape sequence
18271 @c because it is not in ANSI.
18272 Print @var{text}. Nonprinting characters can be included in
18273 @var{text} using C escape sequences, such as @samp{\n} to print a
18274 newline. @strong{No newline is printed unless you specify one.}
18275 In addition to the standard C escape sequences, a backslash followed
18276 by a space stands for a space. This is useful for displaying a
18277 string with spaces at the beginning or the end, since leading and
18278 trailing spaces are otherwise trimmed from all arguments.
18279 To print @samp{@w{ }and foo =@w{ }}, use the command
18280 @samp{echo \@w{ }and foo = \@w{ }}.
18282 A backslash at the end of @var{text} can be used, as in C, to continue
18283 the command onto subsequent lines. For example,
18286 echo This is some text\n\
18287 which is continued\n\
18288 onto several lines.\n
18291 produces the same output as
18294 echo This is some text\n
18295 echo which is continued\n
18296 echo onto several lines.\n
18300 @item output @var{expression}
18301 Print the value of @var{expression} and nothing but that value: no
18302 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18303 value history either. @xref{Expressions, ,Expressions}, for more information
18306 @item output/@var{fmt} @var{expression}
18307 Print the value of @var{expression} in format @var{fmt}. You can use
18308 the same formats as for @code{print}. @xref{Output Formats,,Output
18309 Formats}, for more information.
18312 @item printf @var{template}, @var{expressions}@dots{}
18313 Print the values of one or more @var{expressions} under the control of
18314 the string @var{template}. To print several values, make
18315 @var{expressions} be a comma-separated list of individual expressions,
18316 which may be either numbers or pointers. Their values are printed as
18317 specified by @var{template}, exactly as a C program would do by
18318 executing the code below:
18321 printf (@var{template}, @var{expressions}@dots{});
18324 As in @code{C} @code{printf}, ordinary characters in @var{template}
18325 are printed verbatim, while @dfn{conversion specification} introduced
18326 by the @samp{%} character cause subsequent @var{expressions} to be
18327 evaluated, their values converted and formatted according to type and
18328 style information encoded in the conversion specifications, and then
18331 For example, you can print two values in hex like this:
18334 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18337 @code{printf} supports all the standard @code{C} conversion
18338 specifications, including the flags and modifiers between the @samp{%}
18339 character and the conversion letter, with the following exceptions:
18343 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18346 The modifier @samp{*} is not supported for specifying precision or
18350 The @samp{'} flag (for separation of digits into groups according to
18351 @code{LC_NUMERIC'}) is not supported.
18354 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18358 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18361 The conversion letters @samp{a} and @samp{A} are not supported.
18365 Note that the @samp{ll} type modifier is supported only if the
18366 underlying @code{C} implementation used to build @value{GDBN} supports
18367 the @code{long long int} type, and the @samp{L} type modifier is
18368 supported only if @code{long double} type is available.
18370 As in @code{C}, @code{printf} supports simple backslash-escape
18371 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18372 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18373 single character. Octal and hexadecimal escape sequences are not
18376 Additionally, @code{printf} supports conversion specifications for DFP
18377 (@dfn{Decimal Floating Point}) types using the following length modifiers
18378 together with a floating point specifier.
18383 @samp{H} for printing @code{Decimal32} types.
18386 @samp{D} for printing @code{Decimal64} types.
18389 @samp{DD} for printing @code{Decimal128} types.
18392 If the underlying @code{C} implementation used to build @value{GDBN} has
18393 support for the three length modifiers for DFP types, other modifiers
18394 such as width and precision will also be available for @value{GDBN} to use.
18396 In case there is no such @code{C} support, no additional modifiers will be
18397 available and the value will be printed in the standard way.
18399 Here's an example of printing DFP types using the above conversion letters:
18401 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18407 @section Scripting @value{GDBN} using Python
18408 @cindex python scripting
18409 @cindex scripting with python
18411 You can script @value{GDBN} using the @uref{http://www.python.org/,
18412 Python programming language}. This feature is available only if
18413 @value{GDBN} was configured using @option{--with-python}.
18416 * Python Commands:: Accessing Python from @value{GDBN}.
18417 * Python API:: Accessing @value{GDBN} from Python.
18420 @node Python Commands
18421 @subsection Python Commands
18422 @cindex python commands
18423 @cindex commands to access python
18425 @value{GDBN} provides one command for accessing the Python interpreter,
18426 and one related setting:
18430 @item python @r{[}@var{code}@r{]}
18431 The @code{python} command can be used to evaluate Python code.
18433 If given an argument, the @code{python} command will evaluate the
18434 argument as a Python command. For example:
18437 (@value{GDBP}) python print 23
18441 If you do not provide an argument to @code{python}, it will act as a
18442 multi-line command, like @code{define}. In this case, the Python
18443 script is made up of subsequent command lines, given after the
18444 @code{python} command. This command list is terminated using a line
18445 containing @code{end}. For example:
18448 (@value{GDBP}) python
18450 End with a line saying just "end".
18456 @kindex maint set python print-stack
18457 @item maint set python print-stack
18458 By default, @value{GDBN} will print a stack trace when an error occurs
18459 in a Python script. This can be controlled using @code{maint set
18460 python print-stack}: if @code{on}, the default, then Python stack
18461 printing is enabled; if @code{off}, then Python stack printing is
18466 @subsection Python API
18468 @cindex programming in python
18470 @cindex python stdout
18471 @cindex python pagination
18472 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18473 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18474 A Python program which outputs to one of these streams may have its
18475 output interrupted by the user (@pxref{Screen Size}). In this
18476 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18479 * Basic Python:: Basic Python Functions.
18480 * Exception Handling::
18481 * Values From Inferior::
18482 * Commands In Python:: Implementing new commands in Python.
18483 * Functions In Python:: Writing new convenience functions.
18484 * Frames In Python:: Acessing inferior stack frames from Python.
18488 @subsubsection Basic Python
18490 @cindex python functions
18491 @cindex python module
18493 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18494 methods and classes added by @value{GDBN} are placed in this module.
18495 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18496 use in all scripts evaluated by the @code{python} command.
18498 @findex gdb.execute
18499 @defun execute command [from_tty]
18500 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18501 If a GDB exception happens while @var{command} runs, it is
18502 translated as described in @ref{Exception Handling,,Exception Handling}.
18503 If no exceptions occur, this function returns @code{None}.
18505 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18506 command as having originated from the user invoking it interactively.
18507 It must be a boolean value. If omitted, it defaults to @code{False}.
18510 @findex gdb.get_parameter
18511 @defun get_parameter parameter
18512 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18513 string naming the parameter to look up; @var{parameter} may contain
18514 spaces if the parameter has a multi-part name. For example,
18515 @samp{print object} is a valid parameter name.
18517 If the named parameter does not exist, this function throws a
18518 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18519 a Python value of the appropriate type, and returned.
18522 @findex gdb.history
18523 @defun history number
18524 Return a value from @value{GDBN}'s value history (@pxref{Value
18525 History}). @var{number} indicates which history element to return.
18526 If @var{number} is negative, then @value{GDBN} will take its absolute value
18527 and count backward from the last element (i.e., the most recent element) to
18528 find the value to return. If @var{number} is zero, then @value{GDBN} will
18529 return the most recent element. If the element specified by @var{number}
18530 doesn't exist in the value history, a @code{RuntimeError} exception will be
18533 If no exception is raised, the return value is always an instance of
18534 @code{gdb.Value} (@pxref{Values From Inferior}).
18538 @defun write string
18539 Print a string to @value{GDBN}'s paginated standard output stream.
18540 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18541 call this function.
18546 Flush @value{GDBN}'s paginated standard output stream. Flushing
18547 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18551 @node Exception Handling
18552 @subsubsection Exception Handling
18553 @cindex python exceptions
18554 @cindex exceptions, python
18556 When executing the @code{python} command, Python exceptions
18557 uncaught within the Python code are translated to calls to
18558 @value{GDBN} error-reporting mechanism. If the command that called
18559 @code{python} does not handle the error, @value{GDBN} will
18560 terminate it and print an error message containing the Python
18561 exception name, the associated value, and the Python call stack
18562 backtrace at the point where the exception was raised. Example:
18565 (@value{GDBP}) python print foo
18566 Traceback (most recent call last):
18567 File "<string>", line 1, in <module>
18568 NameError: name 'foo' is not defined
18571 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18572 code are converted to Python @code{RuntimeError} exceptions. User
18573 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18574 prompt) is translated to a Python @code{KeyboardInterrupt}
18575 exception. If you catch these exceptions in your Python code, your
18576 exception handler will see @code{RuntimeError} or
18577 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18578 message as its value, and the Python call stack backtrace at the
18579 Python statement closest to where the @value{GDBN} error occured as the
18582 @node Values From Inferior
18583 @subsubsection Values From Inferior
18584 @cindex values from inferior, with Python
18585 @cindex python, working with values from inferior
18587 @cindex @code{gdb.Value}
18588 @value{GDBN} provides values it obtains from the inferior program in
18589 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18590 for its internal bookkeeping of the inferior's values, and for
18591 fetching values when necessary.
18593 Inferior values that are simple scalars can be used directly in
18594 Python expressions that are valid for the value's data type. Here's
18595 an example for an integer or floating-point value @code{some_val}:
18602 As result of this, @code{bar} will also be a @code{gdb.Value} object
18603 whose values are of the same type as those of @code{some_val}.
18605 Inferior values that are structures or instances of some class can
18606 be accessed using the Python @dfn{dictionary syntax}. For example, if
18607 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18608 can access its @code{foo} element with:
18611 bar = some_val['foo']
18614 Again, @code{bar} will also be a @code{gdb.Value} object.
18616 The following attributes are provided:
18619 @defmethod Value address
18620 If this object is addressable, this read-only attribute holds a
18621 @code{gdb.Value} object representing the address. Otherwise,
18622 this attribute holds @code{None}.
18625 @cindex optimized out value in Python
18626 @defmethod Value is_optimized_out
18627 This read-only boolean attribute is true if the compiler optimized out
18628 this value, thus it is not available for fetching from the inferior.
18632 The following methods are provided:
18635 @defmethod Value dereference
18636 For pointer data types, this method returns a new @code{gdb.Value} object
18637 whose contents is the object pointed to by the pointer. For example, if
18638 @code{foo} is a C pointer to an @code{int}, declared in your C program as
18645 then you can use the corresponding @code{gdb.Value} to access what
18646 @code{foo} points to like this:
18649 bar = foo.dereference ()
18652 The result @code{bar} will be a @code{gdb.Value} object holding the
18653 value pointed to by @code{foo}.
18656 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]}
18657 If this @code{gdb.Value} represents a string, then this method
18658 converts the contents to a Python string. Otherwise, this method will
18659 throw an exception.
18661 Strings are recognized in a language-specific way; whether a given
18662 @code{gdb.Value} represents a string is determined by the current
18665 For C-like languages, a value is a string if it is a pointer to or an
18666 array of characters or ints. The string is assumed to be terminated
18667 by a zero of the appropriate width.
18669 If the optional @var{encoding} argument is given, it must be a string
18670 naming the encoding of the string in the @code{gdb.Value}, such as
18671 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18672 the same encodings as the corresponding argument to Python's
18673 @code{string.decode} method, and the Python codec machinery will be used
18674 to convert the string. If @var{encoding} is not given, or if
18675 @var{encoding} is the empty string, then either the @code{target-charset}
18676 (@pxref{Character Sets}) will be used, or a language-specific encoding
18677 will be used, if the current language is able to supply one.
18679 The optional @var{errors} argument is the same as the corresponding
18680 argument to Python's @code{string.decode} method.
18684 @node Commands In Python
18685 @subsubsection Commands In Python
18687 @cindex commands in python
18688 @cindex python commands
18689 You can implement new @value{GDBN} CLI commands in Python. A CLI
18690 command is implemented using an instance of the @code{gdb.Command}
18691 class, most commonly using a subclass.
18693 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
18694 The object initializer for @code{Command} registers the new command
18695 with @value{GDBN}. This initializer is normally invoked from the
18696 subclass' own @code{__init__} method.
18698 @var{name} is the name of the command. If @var{name} consists of
18699 multiple words, then the initial words are looked for as prefix
18700 commands. In this case, if one of the prefix commands does not exist,
18701 an exception is raised.
18703 There is no support for multi-line commands.
18705 @var{command_class} should be one of the @samp{COMMAND_} constants
18706 defined below. This argument tells @value{GDBN} how to categorize the
18707 new command in the help system.
18709 @var{completer_class} is an optional argument. If given, it should be
18710 one of the @samp{COMPLETE_} constants defined below. This argument
18711 tells @value{GDBN} how to perform completion for this command. If not
18712 given, @value{GDBN} will attempt to complete using the object's
18713 @code{complete} method (see below); if no such method is found, an
18714 error will occur when completion is attempted.
18716 @var{prefix} is an optional argument. If @code{True}, then the new
18717 command is a prefix command; sub-commands of this command may be
18720 The help text for the new command is taken from the Python
18721 documentation string for the command's class, if there is one. If no
18722 documentation string is provided, the default value ``This command is
18723 not documented.'' is used.
18726 @cindex don't repeat Python command
18727 @defmethod Command dont_repeat
18728 By default, a @value{GDBN} command is repeated when the user enters a
18729 blank line at the command prompt. A command can suppress this
18730 behavior by invoking the @code{dont_repeat} method. This is similar
18731 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
18734 @defmethod Command invoke argument from_tty
18735 This method is called by @value{GDBN} when this command is invoked.
18737 @var{argument} is a string. It is the argument to the command, after
18738 leading and trailing whitespace has been stripped.
18740 @var{from_tty} is a boolean argument. When true, this means that the
18741 command was entered by the user at the terminal; when false it means
18742 that the command came from elsewhere.
18744 If this method throws an exception, it is turned into a @value{GDBN}
18745 @code{error} call. Otherwise, the return value is ignored.
18748 @cindex completion of Python commands
18749 @defmethod Command complete text word
18750 This method is called by @value{GDBN} when the user attempts
18751 completion on this command. All forms of completion are handled by
18752 this method, that is, the @key{TAB} and @key{M-?} key bindings
18753 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
18756 The arguments @var{text} and @var{word} are both strings. @var{text}
18757 holds the complete command line up to the cursor's location.
18758 @var{word} holds the last word of the command line; this is computed
18759 using a word-breaking heuristic.
18761 The @code{complete} method can return several values:
18764 If the return value is a sequence, the contents of the sequence are
18765 used as the completions. It is up to @code{complete} to ensure that the
18766 contents actually do complete the word. A zero-length sequence is
18767 allowed, it means that there were no completions available. Only
18768 string elements of the sequence are used; other elements in the
18769 sequence are ignored.
18772 If the return value is one of the @samp{COMPLETE_} constants defined
18773 below, then the corresponding @value{GDBN}-internal completion
18774 function is invoked, and its result is used.
18777 All other results are treated as though there were no available
18782 When a new command is registered, it must be declared as a member of
18783 some general class of commands. This is used to classify top-level
18784 commands in the on-line help system; note that prefix commands are not
18785 listed under their own category but rather that of their top-level
18786 command. The available classifications are represented by constants
18787 defined in the @code{gdb} module:
18790 @findex COMMAND_NONE
18791 @findex gdb.COMMAND_NONE
18793 The command does not belong to any particular class. A command in
18794 this category will not be displayed in any of the help categories.
18796 @findex COMMAND_RUNNING
18797 @findex gdb.COMMAND_RUNNING
18798 @item COMMAND_RUNNING
18799 The command is related to running the inferior. For example,
18800 @code{start}, @code{step}, and @code{continue} are in this category.
18801 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
18802 commands in this category.
18804 @findex COMMAND_DATA
18805 @findex gdb.COMMAND_DATA
18807 The command is related to data or variables. For example,
18808 @code{call}, @code{find}, and @code{print} are in this category. Type
18809 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
18812 @findex COMMAND_STACK
18813 @findex gdb.COMMAND_STACK
18814 @item COMMAND_STACK
18815 The command has to do with manipulation of the stack. For example,
18816 @code{backtrace}, @code{frame}, and @code{return} are in this
18817 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
18818 list of commands in this category.
18820 @findex COMMAND_FILES
18821 @findex gdb.COMMAND_FILES
18822 @item COMMAND_FILES
18823 This class is used for file-related commands. For example,
18824 @code{file}, @code{list} and @code{section} are in this category.
18825 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
18826 commands in this category.
18828 @findex COMMAND_SUPPORT
18829 @findex gdb.COMMAND_SUPPORT
18830 @item COMMAND_SUPPORT
18831 This should be used for ``support facilities'', generally meaning
18832 things that are useful to the user when interacting with @value{GDBN},
18833 but not related to the state of the inferior. For example,
18834 @code{help}, @code{make}, and @code{shell} are in this category. Type
18835 @kbd{help support} at the @value{GDBN} prompt to see a list of
18836 commands in this category.
18838 @findex COMMAND_STATUS
18839 @findex gdb.COMMAND_STATUS
18840 @item COMMAND_STATUS
18841 The command is an @samp{info}-related command, that is, related to the
18842 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
18843 and @code{show} are in this category. Type @kbd{help status} at the
18844 @value{GDBN} prompt to see a list of commands in this category.
18846 @findex COMMAND_BREAKPOINTS
18847 @findex gdb.COMMAND_BREAKPOINTS
18848 @item COMMAND_BREAKPOINTS
18849 The command has to do with breakpoints. For example, @code{break},
18850 @code{clear}, and @code{delete} are in this category. Type @kbd{help
18851 breakpoints} at the @value{GDBN} prompt to see a list of commands in
18854 @findex COMMAND_TRACEPOINTS
18855 @findex gdb.COMMAND_TRACEPOINTS
18856 @item COMMAND_TRACEPOINTS
18857 The command has to do with tracepoints. For example, @code{trace},
18858 @code{actions}, and @code{tfind} are in this category. Type
18859 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
18860 commands in this category.
18862 @findex COMMAND_OBSCURE
18863 @findex gdb.COMMAND_OBSCURE
18864 @item COMMAND_OBSCURE
18865 The command is only used in unusual circumstances, or is not of
18866 general interest to users. For example, @code{checkpoint},
18867 @code{fork}, and @code{stop} are in this category. Type @kbd{help
18868 obscure} at the @value{GDBN} prompt to see a list of commands in this
18871 @findex COMMAND_MAINTENANCE
18872 @findex gdb.COMMAND_MAINTENANCE
18873 @item COMMAND_MAINTENANCE
18874 The command is only useful to @value{GDBN} maintainers. The
18875 @code{maintenance} and @code{flushregs} commands are in this category.
18876 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
18877 commands in this category.
18880 A new command can use a predefined completion function, either by
18881 specifying it via an argument at initialization, or by returning it
18882 from the @code{complete} method. These predefined completion
18883 constants are all defined in the @code{gdb} module:
18886 @findex COMPLETE_NONE
18887 @findex gdb.COMPLETE_NONE
18888 @item COMPLETE_NONE
18889 This constant means that no completion should be done.
18891 @findex COMPLETE_FILENAME
18892 @findex gdb.COMPLETE_FILENAME
18893 @item COMPLETE_FILENAME
18894 This constant means that filename completion should be performed.
18896 @findex COMPLETE_LOCATION
18897 @findex gdb.COMPLETE_LOCATION
18898 @item COMPLETE_LOCATION
18899 This constant means that location completion should be done.
18900 @xref{Specify Location}.
18902 @findex COMPLETE_COMMAND
18903 @findex gdb.COMPLETE_COMMAND
18904 @item COMPLETE_COMMAND
18905 This constant means that completion should examine @value{GDBN}
18908 @findex COMPLETE_SYMBOL
18909 @findex gdb.COMPLETE_SYMBOL
18910 @item COMPLETE_SYMBOL
18911 This constant means that completion should be done using symbol names
18915 The following code snippet shows how a trivial CLI command can be
18916 implemented in Python:
18919 class HelloWorld (gdb.Command):
18920 """Greet the whole world."""
18922 def __init__ (self):
18923 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
18925 def invoke (self, arg, from_tty):
18926 print "Hello, World!"
18931 The last line instantiates the class, and is necessary to trigger the
18932 registration of the command with @value{GDBN}. Depending on how the
18933 Python code is read into @value{GDBN}, you may need to import the
18934 @code{gdb} module explicitly.
18936 @node Functions In Python
18937 @subsubsection Writing new convenience functions
18939 @cindex writing convenience functions
18940 @cindex convenience functions in python
18941 @cindex python convenience functions
18942 @tindex gdb.Function
18944 You can implement new convenience functions (@pxref{Convenience Vars})
18945 in Python. A convenience function is an instance of a subclass of the
18946 class @code{gdb.Function}.
18948 @defmethod Function __init__ name
18949 The initializer for @code{Function} registers the new function with
18950 @value{GDBN}. The argument @var{name} is the name of the function,
18951 a string. The function will be visible to the user as a convenience
18952 variable of type @code{internal function}, whose name is the same as
18953 the given @var{name}.
18955 The documentation for the new function is taken from the documentation
18956 string for the new class.
18959 @defmethod Function invoke @var{*args}
18960 When a convenience function is evaluated, its arguments are converted
18961 to instances of @code{gdb.Value}, and then the function's
18962 @code{invoke} method is called. Note that @value{GDBN} does not
18963 predetermine the arity of convenience functions. Instead, all
18964 available arguments are passed to @code{invoke}, following the
18965 standard Python calling convention. In particular, a convenience
18966 function can have default values for parameters without ill effect.
18968 The return value of this method is used as its value in the enclosing
18969 expression. If an ordinary Python value is returned, it is converted
18970 to a @code{gdb.Value} following the usual rules.
18973 The following code snippet shows how a trivial convenience function can
18974 be implemented in Python:
18977 class Greet (gdb.Function):
18978 """Return string to greet someone.
18979 Takes a name as argument."""
18981 def __init__ (self):
18982 super (Greet, self).__init__ ("greet")
18984 def invoke (self, name):
18985 return "Hello, %s!" % name.string ()
18990 The last line instantiates the class, and is necessary to trigger the
18991 registration of the function with @value{GDBN}. Depending on how the
18992 Python code is read into @value{GDBN}, you may need to import the
18993 @code{gdb} module explicitly.
18995 @node Frames In Python
18996 @subsubsection Acessing inferior stack frames from Python.
18998 @cindex frames in python
18999 When the debugged program stops, @value{GDBN} is able to analyze its call
19000 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
19001 represents a frame in the stack. A @code{gdb.Frame} object is only valid
19002 while its corresponding frame exists in the inferior's stack. If you try
19003 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
19006 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
19010 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
19014 The following frame-related functions are available in the @code{gdb} module:
19016 @findex gdb.selected_frame
19017 @defun selected_frame
19018 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
19021 @defun frame_stop_reason_string reason
19022 Return a string explaining the reason why @value{GDBN} stopped unwinding
19023 frames, as expressed by the given @var{reason} code (an integer, see the
19024 @code{unwind_stop_reason} method further down in this section).
19027 A @code{gdb.Frame} object has the following methods:
19030 @defmethod Frame is_valid
19031 Returns true if the @code{gdb.Frame} object is valid, false if not.
19032 A frame object can become invalid if the frame it refers to doesn't
19033 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
19034 an exception if it is invalid at the time the method is called.
19037 @defmethod Frame name
19038 Returns the function name of the frame, or @code{None} if it can't be
19042 @defmethod Frame type
19043 Returns the type of the frame. The value can be one of
19044 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
19045 or @code{gdb.SENTINEL_FRAME}.
19048 @defmethod Frame unwind_stop_reason
19049 Return an integer representing the reason why it's not possible to find
19050 more frames toward the outermost frame. Use
19051 @code{gdb.frame_stop_reason_string} to convert the value returned by this
19052 function to a string.
19055 @defmethod Frame pc
19056 Returns the frame's resume address.
19059 @defmethod Frame older
19060 Return the frame that called this frame.
19063 @defmethod Frame newer
19064 Return the frame called by this frame.
19067 @defmethod Frame read_var variable
19068 Return the value of the given variable in this frame. @var{variable} must
19074 @chapter Command Interpreters
19075 @cindex command interpreters
19077 @value{GDBN} supports multiple command interpreters, and some command
19078 infrastructure to allow users or user interface writers to switch
19079 between interpreters or run commands in other interpreters.
19081 @value{GDBN} currently supports two command interpreters, the console
19082 interpreter (sometimes called the command-line interpreter or @sc{cli})
19083 and the machine interface interpreter (or @sc{gdb/mi}). This manual
19084 describes both of these interfaces in great detail.
19086 By default, @value{GDBN} will start with the console interpreter.
19087 However, the user may choose to start @value{GDBN} with another
19088 interpreter by specifying the @option{-i} or @option{--interpreter}
19089 startup options. Defined interpreters include:
19093 @cindex console interpreter
19094 The traditional console or command-line interpreter. This is the most often
19095 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
19096 @value{GDBN} will use this interpreter.
19099 @cindex mi interpreter
19100 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
19101 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
19102 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
19106 @cindex mi2 interpreter
19107 The current @sc{gdb/mi} interface.
19110 @cindex mi1 interpreter
19111 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
19115 @cindex invoke another interpreter
19116 The interpreter being used by @value{GDBN} may not be dynamically
19117 switched at runtime. Although possible, this could lead to a very
19118 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
19119 enters the command "interpreter-set console" in a console view,
19120 @value{GDBN} would switch to using the console interpreter, rendering
19121 the IDE inoperable!
19123 @kindex interpreter-exec
19124 Although you may only choose a single interpreter at startup, you may execute
19125 commands in any interpreter from the current interpreter using the appropriate
19126 command. If you are running the console interpreter, simply use the
19127 @code{interpreter-exec} command:
19130 interpreter-exec mi "-data-list-register-names"
19133 @sc{gdb/mi} has a similar command, although it is only available in versions of
19134 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
19137 @chapter @value{GDBN} Text User Interface
19139 @cindex Text User Interface
19142 * TUI Overview:: TUI overview
19143 * TUI Keys:: TUI key bindings
19144 * TUI Single Key Mode:: TUI single key mode
19145 * TUI Commands:: TUI-specific commands
19146 * TUI Configuration:: TUI configuration variables
19149 The @value{GDBN} Text User Interface (TUI) is a terminal
19150 interface which uses the @code{curses} library to show the source
19151 file, the assembly output, the program registers and @value{GDBN}
19152 commands in separate text windows. The TUI mode is supported only
19153 on platforms where a suitable version of the @code{curses} library
19156 @pindex @value{GDBTUI}
19157 The TUI mode is enabled by default when you invoke @value{GDBN} as
19158 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
19159 You can also switch in and out of TUI mode while @value{GDBN} runs by
19160 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
19161 @xref{TUI Keys, ,TUI Key Bindings}.
19164 @section TUI Overview
19166 In TUI mode, @value{GDBN} can display several text windows:
19170 This window is the @value{GDBN} command window with the @value{GDBN}
19171 prompt and the @value{GDBN} output. The @value{GDBN} input is still
19172 managed using readline.
19175 The source window shows the source file of the program. The current
19176 line and active breakpoints are displayed in this window.
19179 The assembly window shows the disassembly output of the program.
19182 This window shows the processor registers. Registers are highlighted
19183 when their values change.
19186 The source and assembly windows show the current program position
19187 by highlighting the current line and marking it with a @samp{>} marker.
19188 Breakpoints are indicated with two markers. The first marker
19189 indicates the breakpoint type:
19193 Breakpoint which was hit at least once.
19196 Breakpoint which was never hit.
19199 Hardware breakpoint which was hit at least once.
19202 Hardware breakpoint which was never hit.
19205 The second marker indicates whether the breakpoint is enabled or not:
19209 Breakpoint is enabled.
19212 Breakpoint is disabled.
19215 The source, assembly and register windows are updated when the current
19216 thread changes, when the frame changes, or when the program counter
19219 These windows are not all visible at the same time. The command
19220 window is always visible. The others can be arranged in several
19231 source and assembly,
19234 source and registers, or
19237 assembly and registers.
19240 A status line above the command window shows the following information:
19244 Indicates the current @value{GDBN} target.
19245 (@pxref{Targets, ,Specifying a Debugging Target}).
19248 Gives the current process or thread number.
19249 When no process is being debugged, this field is set to @code{No process}.
19252 Gives the current function name for the selected frame.
19253 The name is demangled if demangling is turned on (@pxref{Print Settings}).
19254 When there is no symbol corresponding to the current program counter,
19255 the string @code{??} is displayed.
19258 Indicates the current line number for the selected frame.
19259 When the current line number is not known, the string @code{??} is displayed.
19262 Indicates the current program counter address.
19266 @section TUI Key Bindings
19267 @cindex TUI key bindings
19269 The TUI installs several key bindings in the readline keymaps
19270 (@pxref{Command Line Editing}). The following key bindings
19271 are installed for both TUI mode and the @value{GDBN} standard mode.
19280 Enter or leave the TUI mode. When leaving the TUI mode,
19281 the curses window management stops and @value{GDBN} operates using
19282 its standard mode, writing on the terminal directly. When reentering
19283 the TUI mode, control is given back to the curses windows.
19284 The screen is then refreshed.
19288 Use a TUI layout with only one window. The layout will
19289 either be @samp{source} or @samp{assembly}. When the TUI mode
19290 is not active, it will switch to the TUI mode.
19292 Think of this key binding as the Emacs @kbd{C-x 1} binding.
19296 Use a TUI layout with at least two windows. When the current
19297 layout already has two windows, the next layout with two windows is used.
19298 When a new layout is chosen, one window will always be common to the
19299 previous layout and the new one.
19301 Think of it as the Emacs @kbd{C-x 2} binding.
19305 Change the active window. The TUI associates several key bindings
19306 (like scrolling and arrow keys) with the active window. This command
19307 gives the focus to the next TUI window.
19309 Think of it as the Emacs @kbd{C-x o} binding.
19313 Switch in and out of the TUI SingleKey mode that binds single
19314 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
19317 The following key bindings only work in the TUI mode:
19322 Scroll the active window one page up.
19326 Scroll the active window one page down.
19330 Scroll the active window one line up.
19334 Scroll the active window one line down.
19338 Scroll the active window one column left.
19342 Scroll the active window one column right.
19346 Refresh the screen.
19349 Because the arrow keys scroll the active window in the TUI mode, they
19350 are not available for their normal use by readline unless the command
19351 window has the focus. When another window is active, you must use
19352 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
19353 and @kbd{C-f} to control the command window.
19355 @node TUI Single Key Mode
19356 @section TUI Single Key Mode
19357 @cindex TUI single key mode
19359 The TUI also provides a @dfn{SingleKey} mode, which binds several
19360 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
19361 switch into this mode, where the following key bindings are used:
19364 @kindex c @r{(SingleKey TUI key)}
19368 @kindex d @r{(SingleKey TUI key)}
19372 @kindex f @r{(SingleKey TUI key)}
19376 @kindex n @r{(SingleKey TUI key)}
19380 @kindex q @r{(SingleKey TUI key)}
19382 exit the SingleKey mode.
19384 @kindex r @r{(SingleKey TUI key)}
19388 @kindex s @r{(SingleKey TUI key)}
19392 @kindex u @r{(SingleKey TUI key)}
19396 @kindex v @r{(SingleKey TUI key)}
19400 @kindex w @r{(SingleKey TUI key)}
19405 Other keys temporarily switch to the @value{GDBN} command prompt.
19406 The key that was pressed is inserted in the editing buffer so that
19407 it is possible to type most @value{GDBN} commands without interaction
19408 with the TUI SingleKey mode. Once the command is entered the TUI
19409 SingleKey mode is restored. The only way to permanently leave
19410 this mode is by typing @kbd{q} or @kbd{C-x s}.
19414 @section TUI-specific Commands
19415 @cindex TUI commands
19417 The TUI has specific commands to control the text windows.
19418 These commands are always available, even when @value{GDBN} is not in
19419 the TUI mode. When @value{GDBN} is in the standard mode, most
19420 of these commands will automatically switch to the TUI mode.
19425 List and give the size of all displayed windows.
19429 Display the next layout.
19432 Display the previous layout.
19435 Display the source window only.
19438 Display the assembly window only.
19441 Display the source and assembly window.
19444 Display the register window together with the source or assembly window.
19448 Make the next window active for scrolling.
19451 Make the previous window active for scrolling.
19454 Make the source window active for scrolling.
19457 Make the assembly window active for scrolling.
19460 Make the register window active for scrolling.
19463 Make the command window active for scrolling.
19467 Refresh the screen. This is similar to typing @kbd{C-L}.
19469 @item tui reg float
19471 Show the floating point registers in the register window.
19473 @item tui reg general
19474 Show the general registers in the register window.
19477 Show the next register group. The list of register groups as well as
19478 their order is target specific. The predefined register groups are the
19479 following: @code{general}, @code{float}, @code{system}, @code{vector},
19480 @code{all}, @code{save}, @code{restore}.
19482 @item tui reg system
19483 Show the system registers in the register window.
19487 Update the source window and the current execution point.
19489 @item winheight @var{name} +@var{count}
19490 @itemx winheight @var{name} -@var{count}
19492 Change the height of the window @var{name} by @var{count}
19493 lines. Positive counts increase the height, while negative counts
19496 @item tabset @var{nchars}
19498 Set the width of tab stops to be @var{nchars} characters.
19501 @node TUI Configuration
19502 @section TUI Configuration Variables
19503 @cindex TUI configuration variables
19505 Several configuration variables control the appearance of TUI windows.
19508 @item set tui border-kind @var{kind}
19509 @kindex set tui border-kind
19510 Select the border appearance for the source, assembly and register windows.
19511 The possible values are the following:
19514 Use a space character to draw the border.
19517 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
19520 Use the Alternate Character Set to draw the border. The border is
19521 drawn using character line graphics if the terminal supports them.
19524 @item set tui border-mode @var{mode}
19525 @kindex set tui border-mode
19526 @itemx set tui active-border-mode @var{mode}
19527 @kindex set tui active-border-mode
19528 Select the display attributes for the borders of the inactive windows
19529 or the active window. The @var{mode} can be one of the following:
19532 Use normal attributes to display the border.
19538 Use reverse video mode.
19541 Use half bright mode.
19543 @item half-standout
19544 Use half bright and standout mode.
19547 Use extra bright or bold mode.
19549 @item bold-standout
19550 Use extra bright or bold and standout mode.
19555 @chapter Using @value{GDBN} under @sc{gnu} Emacs
19558 @cindex @sc{gnu} Emacs
19559 A special interface allows you to use @sc{gnu} Emacs to view (and
19560 edit) the source files for the program you are debugging with
19563 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
19564 executable file you want to debug as an argument. This command starts
19565 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
19566 created Emacs buffer.
19567 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
19569 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
19574 All ``terminal'' input and output goes through an Emacs buffer, called
19577 This applies both to @value{GDBN} commands and their output, and to the input
19578 and output done by the program you are debugging.
19580 This is useful because it means that you can copy the text of previous
19581 commands and input them again; you can even use parts of the output
19584 All the facilities of Emacs' Shell mode are available for interacting
19585 with your program. In particular, you can send signals the usual
19586 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
19590 @value{GDBN} displays source code through Emacs.
19592 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
19593 source file for that frame and puts an arrow (@samp{=>}) at the
19594 left margin of the current line. Emacs uses a separate buffer for
19595 source display, and splits the screen to show both your @value{GDBN} session
19598 Explicit @value{GDBN} @code{list} or search commands still produce output as
19599 usual, but you probably have no reason to use them from Emacs.
19602 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
19603 a graphical mode, enabled by default, which provides further buffers
19604 that can control the execution and describe the state of your program.
19605 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
19607 If you specify an absolute file name when prompted for the @kbd{M-x
19608 gdb} argument, then Emacs sets your current working directory to where
19609 your program resides. If you only specify the file name, then Emacs
19610 sets your current working directory to to the directory associated
19611 with the previous buffer. In this case, @value{GDBN} may find your
19612 program by searching your environment's @code{PATH} variable, but on
19613 some operating systems it might not find the source. So, although the
19614 @value{GDBN} input and output session proceeds normally, the auxiliary
19615 buffer does not display the current source and line of execution.
19617 The initial working directory of @value{GDBN} is printed on the top
19618 line of the GUD buffer and this serves as a default for the commands
19619 that specify files for @value{GDBN} to operate on. @xref{Files,
19620 ,Commands to Specify Files}.
19622 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
19623 need to call @value{GDBN} by a different name (for example, if you
19624 keep several configurations around, with different names) you can
19625 customize the Emacs variable @code{gud-gdb-command-name} to run the
19628 In the GUD buffer, you can use these special Emacs commands in
19629 addition to the standard Shell mode commands:
19633 Describe the features of Emacs' GUD Mode.
19636 Execute to another source line, like the @value{GDBN} @code{step} command; also
19637 update the display window to show the current file and location.
19640 Execute to next source line in this function, skipping all function
19641 calls, like the @value{GDBN} @code{next} command. Then update the display window
19642 to show the current file and location.
19645 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
19646 display window accordingly.
19649 Execute until exit from the selected stack frame, like the @value{GDBN}
19650 @code{finish} command.
19653 Continue execution of your program, like the @value{GDBN} @code{continue}
19657 Go up the number of frames indicated by the numeric argument
19658 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
19659 like the @value{GDBN} @code{up} command.
19662 Go down the number of frames indicated by the numeric argument, like the
19663 @value{GDBN} @code{down} command.
19666 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
19667 tells @value{GDBN} to set a breakpoint on the source line point is on.
19669 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
19670 separate frame which shows a backtrace when the GUD buffer is current.
19671 Move point to any frame in the stack and type @key{RET} to make it
19672 become the current frame and display the associated source in the
19673 source buffer. Alternatively, click @kbd{Mouse-2} to make the
19674 selected frame become the current one. In graphical mode, the
19675 speedbar displays watch expressions.
19677 If you accidentally delete the source-display buffer, an easy way to get
19678 it back is to type the command @code{f} in the @value{GDBN} buffer, to
19679 request a frame display; when you run under Emacs, this recreates
19680 the source buffer if necessary to show you the context of the current
19683 The source files displayed in Emacs are in ordinary Emacs buffers
19684 which are visiting the source files in the usual way. You can edit
19685 the files with these buffers if you wish; but keep in mind that @value{GDBN}
19686 communicates with Emacs in terms of line numbers. If you add or
19687 delete lines from the text, the line numbers that @value{GDBN} knows cease
19688 to correspond properly with the code.
19690 A more detailed description of Emacs' interaction with @value{GDBN} is
19691 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
19694 @c The following dropped because Epoch is nonstandard. Reactivate
19695 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
19697 @kindex Emacs Epoch environment
19701 Version 18 of @sc{gnu} Emacs has a built-in window system
19702 called the @code{epoch}
19703 environment. Users of this environment can use a new command,
19704 @code{inspect} which performs identically to @code{print} except that
19705 each value is printed in its own window.
19710 @chapter The @sc{gdb/mi} Interface
19712 @unnumberedsec Function and Purpose
19714 @cindex @sc{gdb/mi}, its purpose
19715 @sc{gdb/mi} is a line based machine oriented text interface to
19716 @value{GDBN} and is activated by specifying using the
19717 @option{--interpreter} command line option (@pxref{Mode Options}). It
19718 is specifically intended to support the development of systems which
19719 use the debugger as just one small component of a larger system.
19721 This chapter is a specification of the @sc{gdb/mi} interface. It is written
19722 in the form of a reference manual.
19724 Note that @sc{gdb/mi} is still under construction, so some of the
19725 features described below are incomplete and subject to change
19726 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
19728 @unnumberedsec Notation and Terminology
19730 @cindex notational conventions, for @sc{gdb/mi}
19731 This chapter uses the following notation:
19735 @code{|} separates two alternatives.
19738 @code{[ @var{something} ]} indicates that @var{something} is optional:
19739 it may or may not be given.
19742 @code{( @var{group} )*} means that @var{group} inside the parentheses
19743 may repeat zero or more times.
19746 @code{( @var{group} )+} means that @var{group} inside the parentheses
19747 may repeat one or more times.
19750 @code{"@var{string}"} means a literal @var{string}.
19754 @heading Dependencies
19758 * GDB/MI General Design::
19759 * GDB/MI Command Syntax::
19760 * GDB/MI Compatibility with CLI::
19761 * GDB/MI Development and Front Ends::
19762 * GDB/MI Output Records::
19763 * GDB/MI Simple Examples::
19764 * GDB/MI Command Description Format::
19765 * GDB/MI Breakpoint Commands::
19766 * GDB/MI Program Context::
19767 * GDB/MI Thread Commands::
19768 * GDB/MI Program Execution::
19769 * GDB/MI Stack Manipulation::
19770 * GDB/MI Variable Objects::
19771 * GDB/MI Data Manipulation::
19772 * GDB/MI Tracepoint Commands::
19773 * GDB/MI Symbol Query::
19774 * GDB/MI File Commands::
19776 * GDB/MI Kod Commands::
19777 * GDB/MI Memory Overlay Commands::
19778 * GDB/MI Signal Handling Commands::
19780 * GDB/MI Target Manipulation::
19781 * GDB/MI File Transfer Commands::
19782 * GDB/MI Miscellaneous Commands::
19785 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19786 @node GDB/MI General Design
19787 @section @sc{gdb/mi} General Design
19788 @cindex GDB/MI General Design
19790 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
19791 parts---commands sent to @value{GDBN}, responses to those commands
19792 and notifications. Each command results in exactly one response,
19793 indicating either successful completion of the command, or an error.
19794 For the commands that do not resume the target, the response contains the
19795 requested information. For the commands that resume the target, the
19796 response only indicates whether the target was successfully resumed.
19797 Notifications is the mechanism for reporting changes in the state of the
19798 target, or in @value{GDBN} state, that cannot conveniently be associated with
19799 a command and reported as part of that command response.
19801 The important examples of notifications are:
19805 Exec notifications. These are used to report changes in
19806 target state---when a target is resumed, or stopped. It would not
19807 be feasible to include this information in response of resuming
19808 commands, because one resume commands can result in multiple events in
19809 different threads. Also, quite some time may pass before any event
19810 happens in the target, while a frontend needs to know whether the resuming
19811 command itself was successfully executed.
19814 Console output, and status notifications. Console output
19815 notifications are used to report output of CLI commands, as well as
19816 diagnostics for other commands. Status notifications are used to
19817 report the progress of a long-running operation. Naturally, including
19818 this information in command response would mean no output is produced
19819 until the command is finished, which is undesirable.
19822 General notifications. Commands may have various side effects on
19823 the @value{GDBN} or target state beyond their official purpose. For example,
19824 a command may change the selected thread. Although such changes can
19825 be included in command response, using notification allows for more
19826 orthogonal frontend design.
19830 There's no guarantee that whenever an MI command reports an error,
19831 @value{GDBN} or the target are in any specific state, and especially,
19832 the state is not reverted to the state before the MI command was
19833 processed. Therefore, whenever an MI command results in an error,
19834 we recommend that the frontend refreshes all the information shown in
19835 the user interface.
19837 @subsection Context management
19839 In most cases when @value{GDBN} accesses the target, this access is
19840 done in context of a specific thread and frame (@pxref{Frames}).
19841 Often, even when accessing global data, the target requires that a thread
19842 be specified. The CLI interface maintains the selected thread and frame,
19843 and supplies them to target on each command. This is convenient,
19844 because a command line user would not want to specify that information
19845 explicitly on each command, and because user interacts with
19846 @value{GDBN} via a single terminal, so no confusion is possible as
19847 to what thread and frame are the current ones.
19849 In the case of MI, the concept of selected thread and frame is less
19850 useful. First, a frontend can easily remember this information
19851 itself. Second, a graphical frontend can have more than one window,
19852 each one used for debugging a different thread, and the frontend might
19853 want to access additional threads for internal purposes. This
19854 increases the risk that by relying on implicitly selected thread, the
19855 frontend may be operating on a wrong one. Therefore, each MI command
19856 should explicitly specify which thread and frame to operate on. To
19857 make it possible, each MI command accepts the @samp{--thread} and
19858 @samp{--frame} options, the value to each is @value{GDBN} identifier
19859 for thread and frame to operate on.
19861 Usually, each top-level window in a frontend allows the user to select
19862 a thread and a frame, and remembers the user selection for further
19863 operations. However, in some cases @value{GDBN} may suggest that the
19864 current thread be changed. For example, when stopping on a breakpoint
19865 it is reasonable to switch to the thread where breakpoint is hit. For
19866 another example, if the user issues the CLI @samp{thread} command via
19867 the frontend, it is desirable to change the frontend's selected thread to the
19868 one specified by user. @value{GDBN} communicates the suggestion to
19869 change current thread using the @samp{=thread-selected} notification.
19870 No such notification is available for the selected frame at the moment.
19872 Note that historically, MI shares the selected thread with CLI, so
19873 frontends used the @code{-thread-select} to execute commands in the
19874 right context. However, getting this to work right is cumbersome. The
19875 simplest way is for frontend to emit @code{-thread-select} command
19876 before every command. This doubles the number of commands that need
19877 to be sent. The alternative approach is to suppress @code{-thread-select}
19878 if the selected thread in @value{GDBN} is supposed to be identical to the
19879 thread the frontend wants to operate on. However, getting this
19880 optimization right can be tricky. In particular, if the frontend
19881 sends several commands to @value{GDBN}, and one of the commands changes the
19882 selected thread, then the behaviour of subsequent commands will
19883 change. So, a frontend should either wait for response from such
19884 problematic commands, or explicitly add @code{-thread-select} for
19885 all subsequent commands. No frontend is known to do this exactly
19886 right, so it is suggested to just always pass the @samp{--thread} and
19887 @samp{--frame} options.
19889 @subsection Asynchronous command execution and non-stop mode
19891 On some targets, @value{GDBN} is capable of processing MI commands
19892 even while the target is running. This is called @dfn{asynchronous
19893 command execution} (@pxref{Background Execution}). The frontend may
19894 specify a preferrence for asynchronous execution using the
19895 @code{-gdb-set target-async 1} command, which should be emitted before
19896 either running the executable or attaching to the target. After the
19897 frontend has started the executable or attached to the target, it can
19898 find if asynchronous execution is enabled using the
19899 @code{-list-target-features} command.
19901 Even if @value{GDBN} can accept a command while target is running,
19902 many commands that access the target do not work when the target is
19903 running. Therefore, asynchronous command execution is most useful
19904 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19905 it is possible to examine the state of one thread, while other threads
19908 When a given thread is running, MI commands that try to access the
19909 target in the context of that thread may not work, or may work only on
19910 some targets. In particular, commands that try to operate on thread's
19911 stack will not work, on any target. Commands that read memory, or
19912 modify breakpoints, may work or not work, depending on the target. Note
19913 that even commands that operate on global state, such as @code{print},
19914 @code{set}, and breakpoint commands, still access the target in the
19915 context of a specific thread, so frontend should try to find a
19916 stopped thread and perform the operation on that thread (using the
19917 @samp{--thread} option).
19919 Which commands will work in the context of a running thread is
19920 highly target dependent. However, the two commands
19921 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19922 to find the state of a thread, will always work.
19924 @subsection Thread groups
19925 @value{GDBN} may be used to debug several processes at the same time.
19926 On some platfroms, @value{GDBN} may support debugging of several
19927 hardware systems, each one having several cores with several different
19928 processes running on each core. This section describes the MI
19929 mechanism to support such debugging scenarios.
19931 The key observation is that regardless of the structure of the
19932 target, MI can have a global list of threads, because most commands that
19933 accept the @samp{--thread} option do not need to know what process that
19934 thread belongs to. Therefore, it is not necessary to introduce
19935 neither additional @samp{--process} option, nor an notion of the
19936 current process in the MI interface. The only strictly new feature
19937 that is required is the ability to find how the threads are grouped
19940 To allow the user to discover such grouping, and to support arbitrary
19941 hierarchy of machines/cores/processes, MI introduces the concept of a
19942 @dfn{thread group}. Thread group is a collection of threads and other
19943 thread groups. A thread group always has a string identifier, a type,
19944 and may have additional attributes specific to the type. A new
19945 command, @code{-list-thread-groups}, returns the list of top-level
19946 thread groups, which correspond to processes that @value{GDBN} is
19947 debugging at the moment. By passing an identifier of a thread group
19948 to the @code{-list-thread-groups} command, it is possible to obtain
19949 the members of specific thread group.
19951 To allow the user to easily discover processes, and other objects, he
19952 wishes to debug, a concept of @dfn{available thread group} is
19953 introduced. Available thread group is an thread group that
19954 @value{GDBN} is not debugging, but that can be attached to, using the
19955 @code{-target-attach} command. The list of available top-level thread
19956 groups can be obtained using @samp{-list-thread-groups --available}.
19957 In general, the content of a thread group may be only retrieved only
19958 after attaching to that thread group.
19960 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19961 @node GDB/MI Command Syntax
19962 @section @sc{gdb/mi} Command Syntax
19965 * GDB/MI Input Syntax::
19966 * GDB/MI Output Syntax::
19969 @node GDB/MI Input Syntax
19970 @subsection @sc{gdb/mi} Input Syntax
19972 @cindex input syntax for @sc{gdb/mi}
19973 @cindex @sc{gdb/mi}, input syntax
19975 @item @var{command} @expansion{}
19976 @code{@var{cli-command} | @var{mi-command}}
19978 @item @var{cli-command} @expansion{}
19979 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19980 @var{cli-command} is any existing @value{GDBN} CLI command.
19982 @item @var{mi-command} @expansion{}
19983 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19984 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19986 @item @var{token} @expansion{}
19987 "any sequence of digits"
19989 @item @var{option} @expansion{}
19990 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19992 @item @var{parameter} @expansion{}
19993 @code{@var{non-blank-sequence} | @var{c-string}}
19995 @item @var{operation} @expansion{}
19996 @emph{any of the operations described in this chapter}
19998 @item @var{non-blank-sequence} @expansion{}
19999 @emph{anything, provided it doesn't contain special characters such as
20000 "-", @var{nl}, """ and of course " "}
20002 @item @var{c-string} @expansion{}
20003 @code{""" @var{seven-bit-iso-c-string-content} """}
20005 @item @var{nl} @expansion{}
20014 The CLI commands are still handled by the @sc{mi} interpreter; their
20015 output is described below.
20018 The @code{@var{token}}, when present, is passed back when the command
20022 Some @sc{mi} commands accept optional arguments as part of the parameter
20023 list. Each option is identified by a leading @samp{-} (dash) and may be
20024 followed by an optional argument parameter. Options occur first in the
20025 parameter list and can be delimited from normal parameters using
20026 @samp{--} (this is useful when some parameters begin with a dash).
20033 We want easy access to the existing CLI syntax (for debugging).
20036 We want it to be easy to spot a @sc{mi} operation.
20039 @node GDB/MI Output Syntax
20040 @subsection @sc{gdb/mi} Output Syntax
20042 @cindex output syntax of @sc{gdb/mi}
20043 @cindex @sc{gdb/mi}, output syntax
20044 The output from @sc{gdb/mi} consists of zero or more out-of-band records
20045 followed, optionally, by a single result record. This result record
20046 is for the most recent command. The sequence of output records is
20047 terminated by @samp{(gdb)}.
20049 If an input command was prefixed with a @code{@var{token}} then the
20050 corresponding output for that command will also be prefixed by that same
20054 @item @var{output} @expansion{}
20055 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
20057 @item @var{result-record} @expansion{}
20058 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
20060 @item @var{out-of-band-record} @expansion{}
20061 @code{@var{async-record} | @var{stream-record}}
20063 @item @var{async-record} @expansion{}
20064 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
20066 @item @var{exec-async-output} @expansion{}
20067 @code{[ @var{token} ] "*" @var{async-output}}
20069 @item @var{status-async-output} @expansion{}
20070 @code{[ @var{token} ] "+" @var{async-output}}
20072 @item @var{notify-async-output} @expansion{}
20073 @code{[ @var{token} ] "=" @var{async-output}}
20075 @item @var{async-output} @expansion{}
20076 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
20078 @item @var{result-class} @expansion{}
20079 @code{"done" | "running" | "connected" | "error" | "exit"}
20081 @item @var{async-class} @expansion{}
20082 @code{"stopped" | @var{others}} (where @var{others} will be added
20083 depending on the needs---this is still in development).
20085 @item @var{result} @expansion{}
20086 @code{ @var{variable} "=" @var{value}}
20088 @item @var{variable} @expansion{}
20089 @code{ @var{string} }
20091 @item @var{value} @expansion{}
20092 @code{ @var{const} | @var{tuple} | @var{list} }
20094 @item @var{const} @expansion{}
20095 @code{@var{c-string}}
20097 @item @var{tuple} @expansion{}
20098 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
20100 @item @var{list} @expansion{}
20101 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
20102 @var{result} ( "," @var{result} )* "]" }
20104 @item @var{stream-record} @expansion{}
20105 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
20107 @item @var{console-stream-output} @expansion{}
20108 @code{"~" @var{c-string}}
20110 @item @var{target-stream-output} @expansion{}
20111 @code{"@@" @var{c-string}}
20113 @item @var{log-stream-output} @expansion{}
20114 @code{"&" @var{c-string}}
20116 @item @var{nl} @expansion{}
20119 @item @var{token} @expansion{}
20120 @emph{any sequence of digits}.
20128 All output sequences end in a single line containing a period.
20131 The @code{@var{token}} is from the corresponding request. Note that
20132 for all async output, while the token is allowed by the grammar and
20133 may be output by future versions of @value{GDBN} for select async
20134 output messages, it is generally omitted. Frontends should treat
20135 all async output as reporting general changes in the state of the
20136 target and there should be no need to associate async output to any
20140 @cindex status output in @sc{gdb/mi}
20141 @var{status-async-output} contains on-going status information about the
20142 progress of a slow operation. It can be discarded. All status output is
20143 prefixed by @samp{+}.
20146 @cindex async output in @sc{gdb/mi}
20147 @var{exec-async-output} contains asynchronous state change on the target
20148 (stopped, started, disappeared). All async output is prefixed by
20152 @cindex notify output in @sc{gdb/mi}
20153 @var{notify-async-output} contains supplementary information that the
20154 client should handle (e.g., a new breakpoint information). All notify
20155 output is prefixed by @samp{=}.
20158 @cindex console output in @sc{gdb/mi}
20159 @var{console-stream-output} is output that should be displayed as is in the
20160 console. It is the textual response to a CLI command. All the console
20161 output is prefixed by @samp{~}.
20164 @cindex target output in @sc{gdb/mi}
20165 @var{target-stream-output} is the output produced by the target program.
20166 All the target output is prefixed by @samp{@@}.
20169 @cindex log output in @sc{gdb/mi}
20170 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
20171 instance messages that should be displayed as part of an error log. All
20172 the log output is prefixed by @samp{&}.
20175 @cindex list output in @sc{gdb/mi}
20176 New @sc{gdb/mi} commands should only output @var{lists} containing
20182 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
20183 details about the various output records.
20185 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20186 @node GDB/MI Compatibility with CLI
20187 @section @sc{gdb/mi} Compatibility with CLI
20189 @cindex compatibility, @sc{gdb/mi} and CLI
20190 @cindex @sc{gdb/mi}, compatibility with CLI
20192 For the developers convenience CLI commands can be entered directly,
20193 but there may be some unexpected behaviour. For example, commands
20194 that query the user will behave as if the user replied yes, breakpoint
20195 command lists are not executed and some CLI commands, such as
20196 @code{if}, @code{when} and @code{define}, prompt for further input with
20197 @samp{>}, which is not valid MI output.
20199 This feature may be removed at some stage in the future and it is
20200 recommended that front ends use the @code{-interpreter-exec} command
20201 (@pxref{-interpreter-exec}).
20203 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20204 @node GDB/MI Development and Front Ends
20205 @section @sc{gdb/mi} Development and Front Ends
20206 @cindex @sc{gdb/mi} development
20208 The application which takes the MI output and presents the state of the
20209 program being debugged to the user is called a @dfn{front end}.
20211 Although @sc{gdb/mi} is still incomplete, it is currently being used
20212 by a variety of front ends to @value{GDBN}. This makes it difficult
20213 to introduce new functionality without breaking existing usage. This
20214 section tries to minimize the problems by describing how the protocol
20217 Some changes in MI need not break a carefully designed front end, and
20218 for these the MI version will remain unchanged. The following is a
20219 list of changes that may occur within one level, so front ends should
20220 parse MI output in a way that can handle them:
20224 New MI commands may be added.
20227 New fields may be added to the output of any MI command.
20230 The range of values for fields with specified values, e.g.,
20231 @code{in_scope} (@pxref{-var-update}) may be extended.
20233 @c The format of field's content e.g type prefix, may change so parse it
20234 @c at your own risk. Yes, in general?
20236 @c The order of fields may change? Shouldn't really matter but it might
20237 @c resolve inconsistencies.
20240 If the changes are likely to break front ends, the MI version level
20241 will be increased by one. This will allow the front end to parse the
20242 output according to the MI version. Apart from mi0, new versions of
20243 @value{GDBN} will not support old versions of MI and it will be the
20244 responsibility of the front end to work with the new one.
20246 @c Starting with mi3, add a new command -mi-version that prints the MI
20249 The best way to avoid unexpected changes in MI that might break your front
20250 end is to make your project known to @value{GDBN} developers and
20251 follow development on @email{gdb@@sourceware.org} and
20252 @email{gdb-patches@@sourceware.org}.
20253 @cindex mailing lists
20255 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20256 @node GDB/MI Output Records
20257 @section @sc{gdb/mi} Output Records
20260 * GDB/MI Result Records::
20261 * GDB/MI Stream Records::
20262 * GDB/MI Async Records::
20263 * GDB/MI Frame Information::
20266 @node GDB/MI Result Records
20267 @subsection @sc{gdb/mi} Result Records
20269 @cindex result records in @sc{gdb/mi}
20270 @cindex @sc{gdb/mi}, result records
20271 In addition to a number of out-of-band notifications, the response to a
20272 @sc{gdb/mi} command includes one of the following result indications:
20276 @item "^done" [ "," @var{results} ]
20277 The synchronous operation was successful, @code{@var{results}} are the return
20282 @c Is this one correct? Should it be an out-of-band notification?
20283 The asynchronous operation was successfully started. The target is
20288 @value{GDBN} has connected to a remote target.
20290 @item "^error" "," @var{c-string}
20292 The operation failed. The @code{@var{c-string}} contains the corresponding
20297 @value{GDBN} has terminated.
20301 @node GDB/MI Stream Records
20302 @subsection @sc{gdb/mi} Stream Records
20304 @cindex @sc{gdb/mi}, stream records
20305 @cindex stream records in @sc{gdb/mi}
20306 @value{GDBN} internally maintains a number of output streams: the console, the
20307 target, and the log. The output intended for each of these streams is
20308 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
20310 Each stream record begins with a unique @dfn{prefix character} which
20311 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
20312 Syntax}). In addition to the prefix, each stream record contains a
20313 @code{@var{string-output}}. This is either raw text (with an implicit new
20314 line) or a quoted C string (which does not contain an implicit newline).
20317 @item "~" @var{string-output}
20318 The console output stream contains text that should be displayed in the
20319 CLI console window. It contains the textual responses to CLI commands.
20321 @item "@@" @var{string-output}
20322 The target output stream contains any textual output from the running
20323 target. This is only present when GDB's event loop is truly
20324 asynchronous, which is currently only the case for remote targets.
20326 @item "&" @var{string-output}
20327 The log stream contains debugging messages being produced by @value{GDBN}'s
20331 @node GDB/MI Async Records
20332 @subsection @sc{gdb/mi} Async Records
20334 @cindex async records in @sc{gdb/mi}
20335 @cindex @sc{gdb/mi}, async records
20336 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
20337 additional changes that have occurred. Those changes can either be a
20338 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
20339 target activity (e.g., target stopped).
20341 The following is the list of possible async records:
20345 @item *running,thread-id="@var{thread}"
20346 The target is now running. The @var{thread} field tells which
20347 specific thread is now running, and can be @samp{all} if all threads
20348 are running. The frontend should assume that no interaction with a
20349 running thread is possible after this notification is produced.
20350 The frontend should not assume that this notification is output
20351 only once for any command. @value{GDBN} may emit this notification
20352 several times, either for different threads, because it cannot resume
20353 all threads together, or even for a single thread, if the thread must
20354 be stepped though some code before letting it run freely.
20356 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
20357 The target has stopped. The @var{reason} field can have one of the
20361 @item breakpoint-hit
20362 A breakpoint was reached.
20363 @item watchpoint-trigger
20364 A watchpoint was triggered.
20365 @item read-watchpoint-trigger
20366 A read watchpoint was triggered.
20367 @item access-watchpoint-trigger
20368 An access watchpoint was triggered.
20369 @item function-finished
20370 An -exec-finish or similar CLI command was accomplished.
20371 @item location-reached
20372 An -exec-until or similar CLI command was accomplished.
20373 @item watchpoint-scope
20374 A watchpoint has gone out of scope.
20375 @item end-stepping-range
20376 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
20377 similar CLI command was accomplished.
20378 @item exited-signalled
20379 The inferior exited because of a signal.
20381 The inferior exited.
20382 @item exited-normally
20383 The inferior exited normally.
20384 @item signal-received
20385 A signal was received by the inferior.
20388 The @var{id} field identifies the thread that directly caused the stop
20389 -- for example by hitting a breakpoint. Depending on whether all-stop
20390 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
20391 stop all threads, or only the thread that directly triggered the stop.
20392 If all threads are stopped, the @var{stopped} field will have the
20393 value of @code{"all"}. Otherwise, the value of the @var{stopped}
20394 field will be a list of thread identifiers. Presently, this list will
20395 always include a single thread, but frontend should be prepared to see
20396 several threads in the list.
20398 @item =thread-group-created,id="@var{id}"
20399 @itemx =thread-group-exited,id="@var{id}"
20400 A thread thread group either was attached to, or has exited/detached
20401 from. The @var{id} field contains the @value{GDBN} identifier of the
20404 @item =thread-created,id="@var{id}",group-id="@var{gid}"
20405 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
20406 A thread either was created, or has exited. The @var{id} field
20407 contains the @value{GDBN} identifier of the thread. The @var{gid}
20408 field identifies the thread group this thread belongs to.
20410 @item =thread-selected,id="@var{id}"
20411 Informs that the selected thread was changed as result of the last
20412 command. This notification is not emitted as result of @code{-thread-select}
20413 command but is emitted whenever an MI command that is not documented
20414 to change the selected thread actually changes it. In particular,
20415 invoking, directly or indirectly (via user-defined command), the CLI
20416 @code{thread} command, will generate this notification.
20418 We suggest that in response to this notification, front ends
20419 highlight the selected thread and cause subsequent commands to apply to
20422 @item =library-loaded,...
20423 Reports that a new library file was loaded by the program. This
20424 notification has 4 fields---@var{id}, @var{target-name},
20425 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
20426 opaque identifier of the library. For remote debugging case,
20427 @var{target-name} and @var{host-name} fields give the name of the
20428 library file on the target, and on the host respectively. For native
20429 debugging, both those fields have the same value. The
20430 @var{symbols-loaded} field reports if the debug symbols for this
20431 library are loaded.
20433 @item =library-unloaded,...
20434 Reports that a library was unloaded by the program. This notification
20435 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
20436 the same meaning as for the @code{=library-loaded} notification
20440 @node GDB/MI Frame Information
20441 @subsection @sc{gdb/mi} Frame Information
20443 Response from many MI commands includes an information about stack
20444 frame. This information is a tuple that may have the following
20449 The level of the stack frame. The innermost frame has the level of
20450 zero. This field is always present.
20453 The name of the function corresponding to the frame. This field may
20454 be absent if @value{GDBN} is unable to determine the function name.
20457 The code address for the frame. This field is always present.
20460 The name of the source files that correspond to the frame's code
20461 address. This field may be absent.
20464 The source line corresponding to the frames' code address. This field
20468 The name of the binary file (either executable or shared library) the
20469 corresponds to the frame's code address. This field may be absent.
20474 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20475 @node GDB/MI Simple Examples
20476 @section Simple Examples of @sc{gdb/mi} Interaction
20477 @cindex @sc{gdb/mi}, simple examples
20479 This subsection presents several simple examples of interaction using
20480 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
20481 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
20482 the output received from @sc{gdb/mi}.
20484 Note the line breaks shown in the examples are here only for
20485 readability, they don't appear in the real output.
20487 @subheading Setting a Breakpoint
20489 Setting a breakpoint generates synchronous output which contains detailed
20490 information of the breakpoint.
20493 -> -break-insert main
20494 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20495 enabled="y",addr="0x08048564",func="main",file="myprog.c",
20496 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
20500 @subheading Program Execution
20502 Program execution generates asynchronous records and MI gives the
20503 reason that execution stopped.
20509 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
20510 frame=@{addr="0x08048564",func="main",
20511 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
20512 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
20517 <- *stopped,reason="exited-normally"
20521 @subheading Quitting @value{GDBN}
20523 Quitting @value{GDBN} just prints the result class @samp{^exit}.
20531 @subheading A Bad Command
20533 Here's what happens if you pass a non-existent command:
20537 <- ^error,msg="Undefined MI command: rubbish"
20542 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20543 @node GDB/MI Command Description Format
20544 @section @sc{gdb/mi} Command Description Format
20546 The remaining sections describe blocks of commands. Each block of
20547 commands is laid out in a fashion similar to this section.
20549 @subheading Motivation
20551 The motivation for this collection of commands.
20553 @subheading Introduction
20555 A brief introduction to this collection of commands as a whole.
20557 @subheading Commands
20559 For each command in the block, the following is described:
20561 @subsubheading Synopsis
20564 -command @var{args}@dots{}
20567 @subsubheading Result
20569 @subsubheading @value{GDBN} Command
20571 The corresponding @value{GDBN} CLI command(s), if any.
20573 @subsubheading Example
20575 Example(s) formatted for readability. Some of the described commands have
20576 not been implemented yet and these are labeled N.A.@: (not available).
20579 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20580 @node GDB/MI Breakpoint Commands
20581 @section @sc{gdb/mi} Breakpoint Commands
20583 @cindex breakpoint commands for @sc{gdb/mi}
20584 @cindex @sc{gdb/mi}, breakpoint commands
20585 This section documents @sc{gdb/mi} commands for manipulating
20588 @subheading The @code{-break-after} Command
20589 @findex -break-after
20591 @subsubheading Synopsis
20594 -break-after @var{number} @var{count}
20597 The breakpoint number @var{number} is not in effect until it has been
20598 hit @var{count} times. To see how this is reflected in the output of
20599 the @samp{-break-list} command, see the description of the
20600 @samp{-break-list} command below.
20602 @subsubheading @value{GDBN} Command
20604 The corresponding @value{GDBN} command is @samp{ignore}.
20606 @subsubheading Example
20611 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20612 enabled="y",addr="0x000100d0",func="main",file="hello.c",
20613 fullname="/home/foo/hello.c",line="5",times="0"@}
20620 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20621 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20622 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20623 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20624 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20625 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20626 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20627 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20628 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20629 line="5",times="0",ignore="3"@}]@}
20634 @subheading The @code{-break-catch} Command
20635 @findex -break-catch
20637 @subheading The @code{-break-commands} Command
20638 @findex -break-commands
20642 @subheading The @code{-break-condition} Command
20643 @findex -break-condition
20645 @subsubheading Synopsis
20648 -break-condition @var{number} @var{expr}
20651 Breakpoint @var{number} will stop the program only if the condition in
20652 @var{expr} is true. The condition becomes part of the
20653 @samp{-break-list} output (see the description of the @samp{-break-list}
20656 @subsubheading @value{GDBN} Command
20658 The corresponding @value{GDBN} command is @samp{condition}.
20660 @subsubheading Example
20664 -break-condition 1 1
20668 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20669 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20670 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20671 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20672 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20673 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20674 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20675 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20676 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20677 line="5",cond="1",times="0",ignore="3"@}]@}
20681 @subheading The @code{-break-delete} Command
20682 @findex -break-delete
20684 @subsubheading Synopsis
20687 -break-delete ( @var{breakpoint} )+
20690 Delete the breakpoint(s) whose number(s) are specified in the argument
20691 list. This is obviously reflected in the breakpoint list.
20693 @subsubheading @value{GDBN} Command
20695 The corresponding @value{GDBN} command is @samp{delete}.
20697 @subsubheading Example
20705 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20706 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20707 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20708 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20709 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20710 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20711 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20716 @subheading The @code{-break-disable} Command
20717 @findex -break-disable
20719 @subsubheading Synopsis
20722 -break-disable ( @var{breakpoint} )+
20725 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
20726 break list is now set to @samp{n} for the named @var{breakpoint}(s).
20728 @subsubheading @value{GDBN} Command
20730 The corresponding @value{GDBN} command is @samp{disable}.
20732 @subsubheading Example
20740 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20741 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20742 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20743 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20744 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20745 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20746 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20747 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
20748 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20749 line="5",times="0"@}]@}
20753 @subheading The @code{-break-enable} Command
20754 @findex -break-enable
20756 @subsubheading Synopsis
20759 -break-enable ( @var{breakpoint} )+
20762 Enable (previously disabled) @var{breakpoint}(s).
20764 @subsubheading @value{GDBN} Command
20766 The corresponding @value{GDBN} command is @samp{enable}.
20768 @subsubheading Example
20776 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20777 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20778 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20779 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20780 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20781 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20782 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20783 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20784 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20785 line="5",times="0"@}]@}
20789 @subheading The @code{-break-info} Command
20790 @findex -break-info
20792 @subsubheading Synopsis
20795 -break-info @var{breakpoint}
20799 Get information about a single breakpoint.
20801 @subsubheading @value{GDBN} Command
20803 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
20805 @subsubheading Example
20808 @subheading The @code{-break-insert} Command
20809 @findex -break-insert
20811 @subsubheading Synopsis
20814 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
20815 [ -c @var{condition} ] [ -i @var{ignore-count} ]
20816 [ -p @var{thread} ] [ @var{location} ]
20820 If specified, @var{location}, can be one of:
20827 @item filename:linenum
20828 @item filename:function
20832 The possible optional parameters of this command are:
20836 Insert a temporary breakpoint.
20838 Insert a hardware breakpoint.
20839 @item -c @var{condition}
20840 Make the breakpoint conditional on @var{condition}.
20841 @item -i @var{ignore-count}
20842 Initialize the @var{ignore-count}.
20844 If @var{location} cannot be parsed (for example if it
20845 refers to unknown files or functions), create a pending
20846 breakpoint. Without this flag, @value{GDBN} will report
20847 an error, and won't create a breakpoint, if @var{location}
20850 Create a disabled breakpoint.
20853 @subsubheading Result
20855 The result is in the form:
20858 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
20859 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
20860 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
20861 times="@var{times}"@}
20865 where @var{number} is the @value{GDBN} number for this breakpoint,
20866 @var{funcname} is the name of the function where the breakpoint was
20867 inserted, @var{filename} is the name of the source file which contains
20868 this function, @var{lineno} is the source line number within that file
20869 and @var{times} the number of times that the breakpoint has been hit
20870 (always 0 for -break-insert but may be greater for -break-info or -break-list
20871 which use the same output).
20873 Note: this format is open to change.
20874 @c An out-of-band breakpoint instead of part of the result?
20876 @subsubheading @value{GDBN} Command
20878 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
20879 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
20881 @subsubheading Example
20886 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
20887 fullname="/home/foo/recursive2.c,line="4",times="0"@}
20889 -break-insert -t foo
20890 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
20891 fullname="/home/foo/recursive2.c,line="11",times="0"@}
20894 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20895 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20896 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20897 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20898 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20899 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20900 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20901 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20902 addr="0x0001072c", func="main",file="recursive2.c",
20903 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20904 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20905 addr="0x00010774",func="foo",file="recursive2.c",
20906 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20908 -break-insert -r foo.*
20909 ~int foo(int, int);
20910 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20911 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20915 @subheading The @code{-break-list} Command
20916 @findex -break-list
20918 @subsubheading Synopsis
20924 Displays the list of inserted breakpoints, showing the following fields:
20928 number of the breakpoint
20930 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20932 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20935 is the breakpoint enabled or no: @samp{y} or @samp{n}
20937 memory location at which the breakpoint is set
20939 logical location of the breakpoint, expressed by function name, file
20942 number of times the breakpoint has been hit
20945 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20946 @code{body} field is an empty list.
20948 @subsubheading @value{GDBN} Command
20950 The corresponding @value{GDBN} command is @samp{info break}.
20952 @subsubheading Example
20957 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20958 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20959 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20960 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20961 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20962 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20963 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20964 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20965 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20966 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20967 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20968 line="13",times="0"@}]@}
20972 Here's an example of the result when there are no breakpoints:
20977 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20978 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20979 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20980 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20981 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20982 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20983 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20988 @subheading The @code{-break-watch} Command
20989 @findex -break-watch
20991 @subsubheading Synopsis
20994 -break-watch [ -a | -r ]
20997 Create a watchpoint. With the @samp{-a} option it will create an
20998 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20999 read from or on a write to the memory location. With the @samp{-r}
21000 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
21001 trigger only when the memory location is accessed for reading. Without
21002 either of the options, the watchpoint created is a regular watchpoint,
21003 i.e., it will trigger when the memory location is accessed for writing.
21004 @xref{Set Watchpoints, , Setting Watchpoints}.
21006 Note that @samp{-break-list} will report a single list of watchpoints and
21007 breakpoints inserted.
21009 @subsubheading @value{GDBN} Command
21011 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
21014 @subsubheading Example
21016 Setting a watchpoint on a variable in the @code{main} function:
21021 ^done,wpt=@{number="2",exp="x"@}
21026 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
21027 value=@{old="-268439212",new="55"@},
21028 frame=@{func="main",args=[],file="recursive2.c",
21029 fullname="/home/foo/bar/recursive2.c",line="5"@}
21033 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
21034 the program execution twice: first for the variable changing value, then
21035 for the watchpoint going out of scope.
21040 ^done,wpt=@{number="5",exp="C"@}
21045 *stopped,reason="watchpoint-trigger",
21046 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
21047 frame=@{func="callee4",args=[],
21048 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21049 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
21054 *stopped,reason="watchpoint-scope",wpnum="5",
21055 frame=@{func="callee3",args=[@{name="strarg",
21056 value="0x11940 \"A string argument.\""@}],
21057 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21058 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21062 Listing breakpoints and watchpoints, at different points in the program
21063 execution. Note that once the watchpoint goes out of scope, it is
21069 ^done,wpt=@{number="2",exp="C"@}
21072 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
21073 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21074 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21075 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21076 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21077 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21078 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21079 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21080 addr="0x00010734",func="callee4",
21081 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21082 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
21083 bkpt=@{number="2",type="watchpoint",disp="keep",
21084 enabled="y",addr="",what="C",times="0"@}]@}
21089 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
21090 value=@{old="-276895068",new="3"@},
21091 frame=@{func="callee4",args=[],
21092 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21093 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
21096 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
21097 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21098 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21099 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21100 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21101 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21102 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21103 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21104 addr="0x00010734",func="callee4",
21105 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21106 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
21107 bkpt=@{number="2",type="watchpoint",disp="keep",
21108 enabled="y",addr="",what="C",times="-5"@}]@}
21112 ^done,reason="watchpoint-scope",wpnum="2",
21113 frame=@{func="callee3",args=[@{name="strarg",
21114 value="0x11940 \"A string argument.\""@}],
21115 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21116 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21119 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21120 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21121 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21122 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21123 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21124 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21125 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21126 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21127 addr="0x00010734",func="callee4",
21128 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21129 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
21134 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21135 @node GDB/MI Program Context
21136 @section @sc{gdb/mi} Program Context
21138 @subheading The @code{-exec-arguments} Command
21139 @findex -exec-arguments
21142 @subsubheading Synopsis
21145 -exec-arguments @var{args}
21148 Set the inferior program arguments, to be used in the next
21151 @subsubheading @value{GDBN} Command
21153 The corresponding @value{GDBN} command is @samp{set args}.
21155 @subsubheading Example
21159 -exec-arguments -v word
21165 @subheading The @code{-exec-show-arguments} Command
21166 @findex -exec-show-arguments
21168 @subsubheading Synopsis
21171 -exec-show-arguments
21174 Print the arguments of the program.
21176 @subsubheading @value{GDBN} Command
21178 The corresponding @value{GDBN} command is @samp{show args}.
21180 @subsubheading Example
21184 @subheading The @code{-environment-cd} Command
21185 @findex -environment-cd
21187 @subsubheading Synopsis
21190 -environment-cd @var{pathdir}
21193 Set @value{GDBN}'s working directory.
21195 @subsubheading @value{GDBN} Command
21197 The corresponding @value{GDBN} command is @samp{cd}.
21199 @subsubheading Example
21203 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
21209 @subheading The @code{-environment-directory} Command
21210 @findex -environment-directory
21212 @subsubheading Synopsis
21215 -environment-directory [ -r ] [ @var{pathdir} ]+
21218 Add directories @var{pathdir} to beginning of search path for source files.
21219 If the @samp{-r} option is used, the search path is reset to the default
21220 search path. If directories @var{pathdir} are supplied in addition to the
21221 @samp{-r} option, the search path is first reset and then addition
21223 Multiple directories may be specified, separated by blanks. Specifying
21224 multiple directories in a single command
21225 results in the directories added to the beginning of the
21226 search path in the same order they were presented in the command.
21227 If blanks are needed as
21228 part of a directory name, double-quotes should be used around
21229 the name. In the command output, the path will show up separated
21230 by the system directory-separator character. The directory-separator
21231 character must not be used
21232 in any directory name.
21233 If no directories are specified, the current search path is displayed.
21235 @subsubheading @value{GDBN} Command
21237 The corresponding @value{GDBN} command is @samp{dir}.
21239 @subsubheading Example
21243 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
21244 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21246 -environment-directory ""
21247 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21249 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
21250 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
21252 -environment-directory -r
21253 ^done,source-path="$cdir:$cwd"
21258 @subheading The @code{-environment-path} Command
21259 @findex -environment-path
21261 @subsubheading Synopsis
21264 -environment-path [ -r ] [ @var{pathdir} ]+
21267 Add directories @var{pathdir} to beginning of search path for object files.
21268 If the @samp{-r} option is used, the search path is reset to the original
21269 search path that existed at gdb start-up. If directories @var{pathdir} are
21270 supplied in addition to the
21271 @samp{-r} option, the search path is first reset and then addition
21273 Multiple directories may be specified, separated by blanks. Specifying
21274 multiple directories in a single command
21275 results in the directories added to the beginning of the
21276 search path in the same order they were presented in the command.
21277 If blanks are needed as
21278 part of a directory name, double-quotes should be used around
21279 the name. In the command output, the path will show up separated
21280 by the system directory-separator character. The directory-separator
21281 character must not be used
21282 in any directory name.
21283 If no directories are specified, the current path is displayed.
21286 @subsubheading @value{GDBN} Command
21288 The corresponding @value{GDBN} command is @samp{path}.
21290 @subsubheading Example
21295 ^done,path="/usr/bin"
21297 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
21298 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
21300 -environment-path -r /usr/local/bin
21301 ^done,path="/usr/local/bin:/usr/bin"
21306 @subheading The @code{-environment-pwd} Command
21307 @findex -environment-pwd
21309 @subsubheading Synopsis
21315 Show the current working directory.
21317 @subsubheading @value{GDBN} Command
21319 The corresponding @value{GDBN} command is @samp{pwd}.
21321 @subsubheading Example
21326 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
21330 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21331 @node GDB/MI Thread Commands
21332 @section @sc{gdb/mi} Thread Commands
21335 @subheading The @code{-thread-info} Command
21336 @findex -thread-info
21338 @subsubheading Synopsis
21341 -thread-info [ @var{thread-id} ]
21344 Reports information about either a specific thread, if
21345 the @var{thread-id} parameter is present, or about all
21346 threads. When printing information about all threads,
21347 also reports the current thread.
21349 @subsubheading @value{GDBN} Command
21351 The @samp{info thread} command prints the same information
21354 @subsubheading Example
21359 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
21360 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
21361 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
21362 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
21363 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
21364 current-thread-id="1"
21368 The @samp{state} field may have the following values:
21372 The thread is stopped. Frame information is available for stopped
21376 The thread is running. There's no frame information for running
21381 @subheading The @code{-thread-list-ids} Command
21382 @findex -thread-list-ids
21384 @subsubheading Synopsis
21390 Produces a list of the currently known @value{GDBN} thread ids. At the
21391 end of the list it also prints the total number of such threads.
21393 This command is retained for historical reasons, the
21394 @code{-thread-info} command should be used instead.
21396 @subsubheading @value{GDBN} Command
21398 Part of @samp{info threads} supplies the same information.
21400 @subsubheading Example
21405 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21406 current-thread-id="1",number-of-threads="3"
21411 @subheading The @code{-thread-select} Command
21412 @findex -thread-select
21414 @subsubheading Synopsis
21417 -thread-select @var{threadnum}
21420 Make @var{threadnum} the current thread. It prints the number of the new
21421 current thread, and the topmost frame for that thread.
21423 This command is deprecated in favor of explicitly using the
21424 @samp{--thread} option to each command.
21426 @subsubheading @value{GDBN} Command
21428 The corresponding @value{GDBN} command is @samp{thread}.
21430 @subsubheading Example
21437 *stopped,reason="end-stepping-range",thread-id="2",line="187",
21438 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
21442 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21443 number-of-threads="3"
21446 ^done,new-thread-id="3",
21447 frame=@{level="0",func="vprintf",
21448 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
21449 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
21453 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21454 @node GDB/MI Program Execution
21455 @section @sc{gdb/mi} Program Execution
21457 These are the asynchronous commands which generate the out-of-band
21458 record @samp{*stopped}. Currently @value{GDBN} only really executes
21459 asynchronously with remote targets and this interaction is mimicked in
21462 @subheading The @code{-exec-continue} Command
21463 @findex -exec-continue
21465 @subsubheading Synopsis
21468 -exec-continue [--all|--thread-group N]
21471 Resumes the execution of the inferior program until a breakpoint is
21472 encountered, or until the inferior exits. In all-stop mode
21473 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
21474 depending on the value of the @samp{scheduler-locking} variable. In
21475 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
21476 specified, only the thread specified with the @samp{--thread} option
21477 (or current thread, if no @samp{--thread} is provided) is resumed. If
21478 @samp{--all} is specified, all threads will be resumed. The
21479 @samp{--all} option is ignored in all-stop mode. If the
21480 @samp{--thread-group} options is specified, then all threads in that
21481 thread group are resumed.
21483 @subsubheading @value{GDBN} Command
21485 The corresponding @value{GDBN} corresponding is @samp{continue}.
21487 @subsubheading Example
21494 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
21495 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
21501 @subheading The @code{-exec-finish} Command
21502 @findex -exec-finish
21504 @subsubheading Synopsis
21510 Resumes the execution of the inferior program until the current
21511 function is exited. Displays the results returned by the function.
21513 @subsubheading @value{GDBN} Command
21515 The corresponding @value{GDBN} command is @samp{finish}.
21517 @subsubheading Example
21519 Function returning @code{void}.
21526 *stopped,reason="function-finished",frame=@{func="main",args=[],
21527 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
21531 Function returning other than @code{void}. The name of the internal
21532 @value{GDBN} variable storing the result is printed, together with the
21539 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
21540 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
21541 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21542 gdb-result-var="$1",return-value="0"
21547 @subheading The @code{-exec-interrupt} Command
21548 @findex -exec-interrupt
21550 @subsubheading Synopsis
21553 -exec-interrupt [--all|--thread-group N]
21556 Interrupts the background execution of the target. Note how the token
21557 associated with the stop message is the one for the execution command
21558 that has been interrupted. The token for the interrupt itself only
21559 appears in the @samp{^done} output. If the user is trying to
21560 interrupt a non-running program, an error message will be printed.
21562 Note that when asynchronous execution is enabled, this command is
21563 asynchronous just like other execution commands. That is, first the
21564 @samp{^done} response will be printed, and the target stop will be
21565 reported after that using the @samp{*stopped} notification.
21567 In non-stop mode, only the context thread is interrupted by default.
21568 All threads will be interrupted if the @samp{--all} option is
21569 specified. If the @samp{--thread-group} option is specified, all
21570 threads in that group will be interrupted.
21572 @subsubheading @value{GDBN} Command
21574 The corresponding @value{GDBN} command is @samp{interrupt}.
21576 @subsubheading Example
21587 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
21588 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
21589 fullname="/home/foo/bar/try.c",line="13"@}
21594 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
21598 @subheading The @code{-exec-jump} Command
21601 @subsubheading Synopsis
21604 -exec-jump @var{location}
21607 Resumes execution of the inferior program at the location specified by
21608 parameter. @xref{Specify Location}, for a description of the
21609 different forms of @var{location}.
21611 @subsubheading @value{GDBN} Command
21613 The corresponding @value{GDBN} command is @samp{jump}.
21615 @subsubheading Example
21618 -exec-jump foo.c:10
21619 *running,thread-id="all"
21624 @subheading The @code{-exec-next} Command
21627 @subsubheading Synopsis
21633 Resumes execution of the inferior program, stopping when the beginning
21634 of the next source line is reached.
21636 @subsubheading @value{GDBN} Command
21638 The corresponding @value{GDBN} command is @samp{next}.
21640 @subsubheading Example
21646 *stopped,reason="end-stepping-range",line="8",file="hello.c"
21651 @subheading The @code{-exec-next-instruction} Command
21652 @findex -exec-next-instruction
21654 @subsubheading Synopsis
21657 -exec-next-instruction
21660 Executes one machine instruction. If the instruction is a function
21661 call, continues until the function returns. If the program stops at an
21662 instruction in the middle of a source line, the address will be
21665 @subsubheading @value{GDBN} Command
21667 The corresponding @value{GDBN} command is @samp{nexti}.
21669 @subsubheading Example
21673 -exec-next-instruction
21677 *stopped,reason="end-stepping-range",
21678 addr="0x000100d4",line="5",file="hello.c"
21683 @subheading The @code{-exec-return} Command
21684 @findex -exec-return
21686 @subsubheading Synopsis
21692 Makes current function return immediately. Doesn't execute the inferior.
21693 Displays the new current frame.
21695 @subsubheading @value{GDBN} Command
21697 The corresponding @value{GDBN} command is @samp{return}.
21699 @subsubheading Example
21703 200-break-insert callee4
21704 200^done,bkpt=@{number="1",addr="0x00010734",
21705 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21710 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21711 frame=@{func="callee4",args=[],
21712 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21713 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21719 111^done,frame=@{level="0",func="callee3",
21720 args=[@{name="strarg",
21721 value="0x11940 \"A string argument.\""@}],
21722 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21723 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21728 @subheading The @code{-exec-run} Command
21731 @subsubheading Synopsis
21737 Starts execution of the inferior from the beginning. The inferior
21738 executes until either a breakpoint is encountered or the program
21739 exits. In the latter case the output will include an exit code, if
21740 the program has exited exceptionally.
21742 @subsubheading @value{GDBN} Command
21744 The corresponding @value{GDBN} command is @samp{run}.
21746 @subsubheading Examples
21751 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
21756 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21757 frame=@{func="main",args=[],file="recursive2.c",
21758 fullname="/home/foo/bar/recursive2.c",line="4"@}
21763 Program exited normally:
21771 *stopped,reason="exited-normally"
21776 Program exited exceptionally:
21784 *stopped,reason="exited",exit-code="01"
21788 Another way the program can terminate is if it receives a signal such as
21789 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
21793 *stopped,reason="exited-signalled",signal-name="SIGINT",
21794 signal-meaning="Interrupt"
21798 @c @subheading -exec-signal
21801 @subheading The @code{-exec-step} Command
21804 @subsubheading Synopsis
21810 Resumes execution of the inferior program, stopping when the beginning
21811 of the next source line is reached, if the next source line is not a
21812 function call. If it is, stop at the first instruction of the called
21815 @subsubheading @value{GDBN} Command
21817 The corresponding @value{GDBN} command is @samp{step}.
21819 @subsubheading Example
21821 Stepping into a function:
21827 *stopped,reason="end-stepping-range",
21828 frame=@{func="foo",args=[@{name="a",value="10"@},
21829 @{name="b",value="0"@}],file="recursive2.c",
21830 fullname="/home/foo/bar/recursive2.c",line="11"@}
21840 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
21845 @subheading The @code{-exec-step-instruction} Command
21846 @findex -exec-step-instruction
21848 @subsubheading Synopsis
21851 -exec-step-instruction
21854 Resumes the inferior which executes one machine instruction. The
21855 output, once @value{GDBN} has stopped, will vary depending on whether
21856 we have stopped in the middle of a source line or not. In the former
21857 case, the address at which the program stopped will be printed as
21860 @subsubheading @value{GDBN} Command
21862 The corresponding @value{GDBN} command is @samp{stepi}.
21864 @subsubheading Example
21868 -exec-step-instruction
21872 *stopped,reason="end-stepping-range",
21873 frame=@{func="foo",args=[],file="try.c",
21874 fullname="/home/foo/bar/try.c",line="10"@}
21876 -exec-step-instruction
21880 *stopped,reason="end-stepping-range",
21881 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
21882 fullname="/home/foo/bar/try.c",line="10"@}
21887 @subheading The @code{-exec-until} Command
21888 @findex -exec-until
21890 @subsubheading Synopsis
21893 -exec-until [ @var{location} ]
21896 Executes the inferior until the @var{location} specified in the
21897 argument is reached. If there is no argument, the inferior executes
21898 until a source line greater than the current one is reached. The
21899 reason for stopping in this case will be @samp{location-reached}.
21901 @subsubheading @value{GDBN} Command
21903 The corresponding @value{GDBN} command is @samp{until}.
21905 @subsubheading Example
21909 -exec-until recursive2.c:6
21913 *stopped,reason="location-reached",frame=@{func="main",args=[],
21914 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21919 @subheading -file-clear
21920 Is this going away????
21923 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21924 @node GDB/MI Stack Manipulation
21925 @section @sc{gdb/mi} Stack Manipulation Commands
21928 @subheading The @code{-stack-info-frame} Command
21929 @findex -stack-info-frame
21931 @subsubheading Synopsis
21937 Get info on the selected frame.
21939 @subsubheading @value{GDBN} Command
21941 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21942 (without arguments).
21944 @subsubheading Example
21949 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21950 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21951 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21955 @subheading The @code{-stack-info-depth} Command
21956 @findex -stack-info-depth
21958 @subsubheading Synopsis
21961 -stack-info-depth [ @var{max-depth} ]
21964 Return the depth of the stack. If the integer argument @var{max-depth}
21965 is specified, do not count beyond @var{max-depth} frames.
21967 @subsubheading @value{GDBN} Command
21969 There's no equivalent @value{GDBN} command.
21971 @subsubheading Example
21973 For a stack with frame levels 0 through 11:
21980 -stack-info-depth 4
21983 -stack-info-depth 12
21986 -stack-info-depth 11
21989 -stack-info-depth 13
21994 @subheading The @code{-stack-list-arguments} Command
21995 @findex -stack-list-arguments
21997 @subsubheading Synopsis
22000 -stack-list-arguments @var{show-values}
22001 [ @var{low-frame} @var{high-frame} ]
22004 Display a list of the arguments for the frames between @var{low-frame}
22005 and @var{high-frame} (inclusive). If @var{low-frame} and
22006 @var{high-frame} are not provided, list the arguments for the whole
22007 call stack. If the two arguments are equal, show the single frame
22008 at the corresponding level. It is an error if @var{low-frame} is
22009 larger than the actual number of frames. On the other hand,
22010 @var{high-frame} may be larger than the actual number of frames, in
22011 which case only existing frames will be returned.
22013 The @var{show-values} argument must have a value of 0 or 1. A value of
22014 0 means that only the names of the arguments are listed, a value of 1
22015 means that both names and values of the arguments are printed.
22017 @subsubheading @value{GDBN} Command
22019 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
22020 @samp{gdb_get_args} command which partially overlaps with the
22021 functionality of @samp{-stack-list-arguments}.
22023 @subsubheading Example
22030 frame=@{level="0",addr="0x00010734",func="callee4",
22031 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22032 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
22033 frame=@{level="1",addr="0x0001076c",func="callee3",
22034 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22035 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
22036 frame=@{level="2",addr="0x0001078c",func="callee2",
22037 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22038 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
22039 frame=@{level="3",addr="0x000107b4",func="callee1",
22040 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22041 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
22042 frame=@{level="4",addr="0x000107e0",func="main",
22043 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22044 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
22046 -stack-list-arguments 0
22049 frame=@{level="0",args=[]@},
22050 frame=@{level="1",args=[name="strarg"]@},
22051 frame=@{level="2",args=[name="intarg",name="strarg"]@},
22052 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
22053 frame=@{level="4",args=[]@}]
22055 -stack-list-arguments 1
22058 frame=@{level="0",args=[]@},
22060 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
22061 frame=@{level="2",args=[
22062 @{name="intarg",value="2"@},
22063 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
22064 @{frame=@{level="3",args=[
22065 @{name="intarg",value="2"@},
22066 @{name="strarg",value="0x11940 \"A string argument.\""@},
22067 @{name="fltarg",value="3.5"@}]@},
22068 frame=@{level="4",args=[]@}]
22070 -stack-list-arguments 0 2 2
22071 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
22073 -stack-list-arguments 1 2 2
22074 ^done,stack-args=[frame=@{level="2",
22075 args=[@{name="intarg",value="2"@},
22076 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
22080 @c @subheading -stack-list-exception-handlers
22083 @subheading The @code{-stack-list-frames} Command
22084 @findex -stack-list-frames
22086 @subsubheading Synopsis
22089 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
22092 List the frames currently on the stack. For each frame it displays the
22097 The frame number, 0 being the topmost frame, i.e., the innermost function.
22099 The @code{$pc} value for that frame.
22103 File name of the source file where the function lives.
22105 Line number corresponding to the @code{$pc}.
22108 If invoked without arguments, this command prints a backtrace for the
22109 whole stack. If given two integer arguments, it shows the frames whose
22110 levels are between the two arguments (inclusive). If the two arguments
22111 are equal, it shows the single frame at the corresponding level. It is
22112 an error if @var{low-frame} is larger than the actual number of
22113 frames. On the other hand, @var{high-frame} may be larger than the
22114 actual number of frames, in which case only existing frames will be returned.
22116 @subsubheading @value{GDBN} Command
22118 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
22120 @subsubheading Example
22122 Full stack backtrace:
22128 [frame=@{level="0",addr="0x0001076c",func="foo",
22129 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
22130 frame=@{level="1",addr="0x000107a4",func="foo",
22131 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22132 frame=@{level="2",addr="0x000107a4",func="foo",
22133 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22134 frame=@{level="3",addr="0x000107a4",func="foo",
22135 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22136 frame=@{level="4",addr="0x000107a4",func="foo",
22137 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22138 frame=@{level="5",addr="0x000107a4",func="foo",
22139 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22140 frame=@{level="6",addr="0x000107a4",func="foo",
22141 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22142 frame=@{level="7",addr="0x000107a4",func="foo",
22143 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22144 frame=@{level="8",addr="0x000107a4",func="foo",
22145 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22146 frame=@{level="9",addr="0x000107a4",func="foo",
22147 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22148 frame=@{level="10",addr="0x000107a4",func="foo",
22149 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22150 frame=@{level="11",addr="0x00010738",func="main",
22151 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
22155 Show frames between @var{low_frame} and @var{high_frame}:
22159 -stack-list-frames 3 5
22161 [frame=@{level="3",addr="0x000107a4",func="foo",
22162 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22163 frame=@{level="4",addr="0x000107a4",func="foo",
22164 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22165 frame=@{level="5",addr="0x000107a4",func="foo",
22166 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
22170 Show a single frame:
22174 -stack-list-frames 3 3
22176 [frame=@{level="3",addr="0x000107a4",func="foo",
22177 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
22182 @subheading The @code{-stack-list-locals} Command
22183 @findex -stack-list-locals
22185 @subsubheading Synopsis
22188 -stack-list-locals @var{print-values}
22191 Display the local variable names for the selected frame. If
22192 @var{print-values} is 0 or @code{--no-values}, print only the names of
22193 the variables; if it is 1 or @code{--all-values}, print also their
22194 values; and if it is 2 or @code{--simple-values}, print the name,
22195 type and value for simple data types and the name and type for arrays,
22196 structures and unions. In this last case, a frontend can immediately
22197 display the value of simple data types and create variable objects for
22198 other data types when the user wishes to explore their values in
22201 @subsubheading @value{GDBN} Command
22203 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
22205 @subsubheading Example
22209 -stack-list-locals 0
22210 ^done,locals=[name="A",name="B",name="C"]
22212 -stack-list-locals --all-values
22213 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
22214 @{name="C",value="@{1, 2, 3@}"@}]
22215 -stack-list-locals --simple-values
22216 ^done,locals=[@{name="A",type="int",value="1"@},
22217 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
22222 @subheading The @code{-stack-select-frame} Command
22223 @findex -stack-select-frame
22225 @subsubheading Synopsis
22228 -stack-select-frame @var{framenum}
22231 Change the selected frame. Select a different frame @var{framenum} on
22234 This command in deprecated in favor of passing the @samp{--frame}
22235 option to every command.
22237 @subsubheading @value{GDBN} Command
22239 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
22240 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
22242 @subsubheading Example
22246 -stack-select-frame 2
22251 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22252 @node GDB/MI Variable Objects
22253 @section @sc{gdb/mi} Variable Objects
22257 @subheading Motivation for Variable Objects in @sc{gdb/mi}
22259 For the implementation of a variable debugger window (locals, watched
22260 expressions, etc.), we are proposing the adaptation of the existing code
22261 used by @code{Insight}.
22263 The two main reasons for that are:
22267 It has been proven in practice (it is already on its second generation).
22270 It will shorten development time (needless to say how important it is
22274 The original interface was designed to be used by Tcl code, so it was
22275 slightly changed so it could be used through @sc{gdb/mi}. This section
22276 describes the @sc{gdb/mi} operations that will be available and gives some
22277 hints about their use.
22279 @emph{Note}: In addition to the set of operations described here, we
22280 expect the @sc{gui} implementation of a variable window to require, at
22281 least, the following operations:
22284 @item @code{-gdb-show} @code{output-radix}
22285 @item @code{-stack-list-arguments}
22286 @item @code{-stack-list-locals}
22287 @item @code{-stack-select-frame}
22292 @subheading Introduction to Variable Objects
22294 @cindex variable objects in @sc{gdb/mi}
22296 Variable objects are "object-oriented" MI interface for examining and
22297 changing values of expressions. Unlike some other MI interfaces that
22298 work with expressions, variable objects are specifically designed for
22299 simple and efficient presentation in the frontend. A variable object
22300 is identified by string name. When a variable object is created, the
22301 frontend specifies the expression for that variable object. The
22302 expression can be a simple variable, or it can be an arbitrary complex
22303 expression, and can even involve CPU registers. After creating a
22304 variable object, the frontend can invoke other variable object
22305 operations---for example to obtain or change the value of a variable
22306 object, or to change display format.
22308 Variable objects have hierarchical tree structure. Any variable object
22309 that corresponds to a composite type, such as structure in C, has
22310 a number of child variable objects, for example corresponding to each
22311 element of a structure. A child variable object can itself have
22312 children, recursively. Recursion ends when we reach
22313 leaf variable objects, which always have built-in types. Child variable
22314 objects are created only by explicit request, so if a frontend
22315 is not interested in the children of a particular variable object, no
22316 child will be created.
22318 For a leaf variable object it is possible to obtain its value as a
22319 string, or set the value from a string. String value can be also
22320 obtained for a non-leaf variable object, but it's generally a string
22321 that only indicates the type of the object, and does not list its
22322 contents. Assignment to a non-leaf variable object is not allowed.
22324 A frontend does not need to read the values of all variable objects each time
22325 the program stops. Instead, MI provides an update command that lists all
22326 variable objects whose values has changed since the last update
22327 operation. This considerably reduces the amount of data that must
22328 be transferred to the frontend. As noted above, children variable
22329 objects are created on demand, and only leaf variable objects have a
22330 real value. As result, gdb will read target memory only for leaf
22331 variables that frontend has created.
22333 The automatic update is not always desirable. For example, a frontend
22334 might want to keep a value of some expression for future reference,
22335 and never update it. For another example, fetching memory is
22336 relatively slow for embedded targets, so a frontend might want
22337 to disable automatic update for the variables that are either not
22338 visible on the screen, or ``closed''. This is possible using so
22339 called ``frozen variable objects''. Such variable objects are never
22340 implicitly updated.
22342 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
22343 fixed variable object, the expression is parsed when the variable
22344 object is created, including associating identifiers to specific
22345 variables. The meaning of expression never changes. For a floating
22346 variable object the values of variables whose names appear in the
22347 expressions are re-evaluated every time in the context of the current
22348 frame. Consider this example:
22353 struct work_state state;
22360 If a fixed variable object for the @code{state} variable is created in
22361 this function, and we enter the recursive call, the the variable
22362 object will report the value of @code{state} in the top-level
22363 @code{do_work} invocation. On the other hand, a floating variable
22364 object will report the value of @code{state} in the current frame.
22366 If an expression specified when creating a fixed variable object
22367 refers to a local variable, the variable object becomes bound to the
22368 thread and frame in which the variable object is created. When such
22369 variable object is updated, @value{GDBN} makes sure that the
22370 thread/frame combination the variable object is bound to still exists,
22371 and re-evaluates the variable object in context of that thread/frame.
22373 The following is the complete set of @sc{gdb/mi} operations defined to
22374 access this functionality:
22376 @multitable @columnfractions .4 .6
22377 @item @strong{Operation}
22378 @tab @strong{Description}
22380 @item @code{-var-create}
22381 @tab create a variable object
22382 @item @code{-var-delete}
22383 @tab delete the variable object and/or its children
22384 @item @code{-var-set-format}
22385 @tab set the display format of this variable
22386 @item @code{-var-show-format}
22387 @tab show the display format of this variable
22388 @item @code{-var-info-num-children}
22389 @tab tells how many children this object has
22390 @item @code{-var-list-children}
22391 @tab return a list of the object's children
22392 @item @code{-var-info-type}
22393 @tab show the type of this variable object
22394 @item @code{-var-info-expression}
22395 @tab print parent-relative expression that this variable object represents
22396 @item @code{-var-info-path-expression}
22397 @tab print full expression that this variable object represents
22398 @item @code{-var-show-attributes}
22399 @tab is this variable editable? does it exist here?
22400 @item @code{-var-evaluate-expression}
22401 @tab get the value of this variable
22402 @item @code{-var-assign}
22403 @tab set the value of this variable
22404 @item @code{-var-update}
22405 @tab update the variable and its children
22406 @item @code{-var-set-frozen}
22407 @tab set frozeness attribute
22410 In the next subsection we describe each operation in detail and suggest
22411 how it can be used.
22413 @subheading Description And Use of Operations on Variable Objects
22415 @subheading The @code{-var-create} Command
22416 @findex -var-create
22418 @subsubheading Synopsis
22421 -var-create @{@var{name} | "-"@}
22422 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
22425 This operation creates a variable object, which allows the monitoring of
22426 a variable, the result of an expression, a memory cell or a CPU
22429 The @var{name} parameter is the string by which the object can be
22430 referenced. It must be unique. If @samp{-} is specified, the varobj
22431 system will generate a string ``varNNNNNN'' automatically. It will be
22432 unique provided that one does not specify @var{name} of that format.
22433 The command fails if a duplicate name is found.
22435 The frame under which the expression should be evaluated can be
22436 specified by @var{frame-addr}. A @samp{*} indicates that the current
22437 frame should be used. A @samp{@@} indicates that a floating variable
22438 object must be created.
22440 @var{expression} is any expression valid on the current language set (must not
22441 begin with a @samp{*}), or one of the following:
22445 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
22448 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
22451 @samp{$@var{regname}} --- a CPU register name
22454 @subsubheading Result
22456 This operation returns the name, number of children and the type of the
22457 object created. Type is returned as a string as the ones generated by
22458 the @value{GDBN} CLI. If a fixed variable object is bound to a
22459 specific thread, the thread is is also printed:
22462 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
22466 @subheading The @code{-var-delete} Command
22467 @findex -var-delete
22469 @subsubheading Synopsis
22472 -var-delete [ -c ] @var{name}
22475 Deletes a previously created variable object and all of its children.
22476 With the @samp{-c} option, just deletes the children.
22478 Returns an error if the object @var{name} is not found.
22481 @subheading The @code{-var-set-format} Command
22482 @findex -var-set-format
22484 @subsubheading Synopsis
22487 -var-set-format @var{name} @var{format-spec}
22490 Sets the output format for the value of the object @var{name} to be
22493 @anchor{-var-set-format}
22494 The syntax for the @var{format-spec} is as follows:
22497 @var{format-spec} @expansion{}
22498 @{binary | decimal | hexadecimal | octal | natural@}
22501 The natural format is the default format choosen automatically
22502 based on the variable type (like decimal for an @code{int}, hex
22503 for pointers, etc.).
22505 For a variable with children, the format is set only on the
22506 variable itself, and the children are not affected.
22508 @subheading The @code{-var-show-format} Command
22509 @findex -var-show-format
22511 @subsubheading Synopsis
22514 -var-show-format @var{name}
22517 Returns the format used to display the value of the object @var{name}.
22520 @var{format} @expansion{}
22525 @subheading The @code{-var-info-num-children} Command
22526 @findex -var-info-num-children
22528 @subsubheading Synopsis
22531 -var-info-num-children @var{name}
22534 Returns the number of children of a variable object @var{name}:
22541 @subheading The @code{-var-list-children} Command
22542 @findex -var-list-children
22544 @subsubheading Synopsis
22547 -var-list-children [@var{print-values}] @var{name}
22549 @anchor{-var-list-children}
22551 Return a list of the children of the specified variable object and
22552 create variable objects for them, if they do not already exist. With
22553 a single argument or if @var{print-values} has a value for of 0 or
22554 @code{--no-values}, print only the names of the variables; if
22555 @var{print-values} is 1 or @code{--all-values}, also print their
22556 values; and if it is 2 or @code{--simple-values} print the name and
22557 value for simple data types and just the name for arrays, structures
22560 @subsubheading Example
22564 -var-list-children n
22565 ^done,numchild=@var{n},children=[@{name=@var{name},
22566 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
22568 -var-list-children --all-values n
22569 ^done,numchild=@var{n},children=[@{name=@var{name},
22570 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
22574 @subheading The @code{-var-info-type} Command
22575 @findex -var-info-type
22577 @subsubheading Synopsis
22580 -var-info-type @var{name}
22583 Returns the type of the specified variable @var{name}. The type is
22584 returned as a string in the same format as it is output by the
22588 type=@var{typename}
22592 @subheading The @code{-var-info-expression} Command
22593 @findex -var-info-expression
22595 @subsubheading Synopsis
22598 -var-info-expression @var{name}
22601 Returns a string that is suitable for presenting this
22602 variable object in user interface. The string is generally
22603 not valid expression in the current language, and cannot be evaluated.
22605 For example, if @code{a} is an array, and variable object
22606 @code{A} was created for @code{a}, then we'll get this output:
22609 (gdb) -var-info-expression A.1
22610 ^done,lang="C",exp="1"
22614 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
22616 Note that the output of the @code{-var-list-children} command also
22617 includes those expressions, so the @code{-var-info-expression} command
22620 @subheading The @code{-var-info-path-expression} Command
22621 @findex -var-info-path-expression
22623 @subsubheading Synopsis
22626 -var-info-path-expression @var{name}
22629 Returns an expression that can be evaluated in the current
22630 context and will yield the same value that a variable object has.
22631 Compare this with the @code{-var-info-expression} command, which
22632 result can be used only for UI presentation. Typical use of
22633 the @code{-var-info-path-expression} command is creating a
22634 watchpoint from a variable object.
22636 For example, suppose @code{C} is a C@t{++} class, derived from class
22637 @code{Base}, and that the @code{Base} class has a member called
22638 @code{m_size}. Assume a variable @code{c} is has the type of
22639 @code{C} and a variable object @code{C} was created for variable
22640 @code{c}. Then, we'll get this output:
22642 (gdb) -var-info-path-expression C.Base.public.m_size
22643 ^done,path_expr=((Base)c).m_size)
22646 @subheading The @code{-var-show-attributes} Command
22647 @findex -var-show-attributes
22649 @subsubheading Synopsis
22652 -var-show-attributes @var{name}
22655 List attributes of the specified variable object @var{name}:
22658 status=@var{attr} [ ( ,@var{attr} )* ]
22662 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
22664 @subheading The @code{-var-evaluate-expression} Command
22665 @findex -var-evaluate-expression
22667 @subsubheading Synopsis
22670 -var-evaluate-expression [-f @var{format-spec}] @var{name}
22673 Evaluates the expression that is represented by the specified variable
22674 object and returns its value as a string. The format of the string
22675 can be specified with the @samp{-f} option. The possible values of
22676 this option are the same as for @code{-var-set-format}
22677 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
22678 the current display format will be used. The current display format
22679 can be changed using the @code{-var-set-format} command.
22685 Note that one must invoke @code{-var-list-children} for a variable
22686 before the value of a child variable can be evaluated.
22688 @subheading The @code{-var-assign} Command
22689 @findex -var-assign
22691 @subsubheading Synopsis
22694 -var-assign @var{name} @var{expression}
22697 Assigns the value of @var{expression} to the variable object specified
22698 by @var{name}. The object must be @samp{editable}. If the variable's
22699 value is altered by the assign, the variable will show up in any
22700 subsequent @code{-var-update} list.
22702 @subsubheading Example
22710 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
22714 @subheading The @code{-var-update} Command
22715 @findex -var-update
22717 @subsubheading Synopsis
22720 -var-update [@var{print-values}] @{@var{name} | "*"@}
22723 Reevaluate the expressions corresponding to the variable object
22724 @var{name} and all its direct and indirect children, and return the
22725 list of variable objects whose values have changed; @var{name} must
22726 be a root variable object. Here, ``changed'' means that the result of
22727 @code{-var-evaluate-expression} before and after the
22728 @code{-var-update} is different. If @samp{*} is used as the variable
22729 object names, all existing variable objects are updated, except
22730 for frozen ones (@pxref{-var-set-frozen}). The option
22731 @var{print-values} determines whether both names and values, or just
22732 names are printed. The possible values of this option are the same
22733 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
22734 recommended to use the @samp{--all-values} option, to reduce the
22735 number of MI commands needed on each program stop.
22737 With the @samp{*} parameter, if a variable object is bound to a
22738 currently running thread, it will not be updated, without any
22741 @subsubheading Example
22748 -var-update --all-values var1
22749 ^done,changelist=[@{name="var1",value="3",in_scope="true",
22750 type_changed="false"@}]
22754 @anchor{-var-update}
22755 The field in_scope may take three values:
22759 The variable object's current value is valid.
22762 The variable object does not currently hold a valid value but it may
22763 hold one in the future if its associated expression comes back into
22767 The variable object no longer holds a valid value.
22768 This can occur when the executable file being debugged has changed,
22769 either through recompilation or by using the @value{GDBN} @code{file}
22770 command. The front end should normally choose to delete these variable
22774 In the future new values may be added to this list so the front should
22775 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
22777 @subheading The @code{-var-set-frozen} Command
22778 @findex -var-set-frozen
22779 @anchor{-var-set-frozen}
22781 @subsubheading Synopsis
22784 -var-set-frozen @var{name} @var{flag}
22787 Set the frozenness flag on the variable object @var{name}. The
22788 @var{flag} parameter should be either @samp{1} to make the variable
22789 frozen or @samp{0} to make it unfrozen. If a variable object is
22790 frozen, then neither itself, nor any of its children, are
22791 implicitly updated by @code{-var-update} of
22792 a parent variable or by @code{-var-update *}. Only
22793 @code{-var-update} of the variable itself will update its value and
22794 values of its children. After a variable object is unfrozen, it is
22795 implicitly updated by all subsequent @code{-var-update} operations.
22796 Unfreezing a variable does not update it, only subsequent
22797 @code{-var-update} does.
22799 @subsubheading Example
22803 -var-set-frozen V 1
22809 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22810 @node GDB/MI Data Manipulation
22811 @section @sc{gdb/mi} Data Manipulation
22813 @cindex data manipulation, in @sc{gdb/mi}
22814 @cindex @sc{gdb/mi}, data manipulation
22815 This section describes the @sc{gdb/mi} commands that manipulate data:
22816 examine memory and registers, evaluate expressions, etc.
22818 @c REMOVED FROM THE INTERFACE.
22819 @c @subheading -data-assign
22820 @c Change the value of a program variable. Plenty of side effects.
22821 @c @subsubheading GDB Command
22823 @c @subsubheading Example
22826 @subheading The @code{-data-disassemble} Command
22827 @findex -data-disassemble
22829 @subsubheading Synopsis
22833 [ -s @var{start-addr} -e @var{end-addr} ]
22834 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
22842 @item @var{start-addr}
22843 is the beginning address (or @code{$pc})
22844 @item @var{end-addr}
22846 @item @var{filename}
22847 is the name of the file to disassemble
22848 @item @var{linenum}
22849 is the line number to disassemble around
22851 is the number of disassembly lines to be produced. If it is -1,
22852 the whole function will be disassembled, in case no @var{end-addr} is
22853 specified. If @var{end-addr} is specified as a non-zero value, and
22854 @var{lines} is lower than the number of disassembly lines between
22855 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
22856 displayed; if @var{lines} is higher than the number of lines between
22857 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
22860 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
22864 @subsubheading Result
22866 The output for each instruction is composed of four fields:
22875 Note that whatever included in the instruction field, is not manipulated
22876 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
22878 @subsubheading @value{GDBN} Command
22880 There's no direct mapping from this command to the CLI.
22882 @subsubheading Example
22884 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
22888 -data-disassemble -s $pc -e "$pc + 20" -- 0
22891 @{address="0x000107c0",func-name="main",offset="4",
22892 inst="mov 2, %o0"@},
22893 @{address="0x000107c4",func-name="main",offset="8",
22894 inst="sethi %hi(0x11800), %o2"@},
22895 @{address="0x000107c8",func-name="main",offset="12",
22896 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
22897 @{address="0x000107cc",func-name="main",offset="16",
22898 inst="sethi %hi(0x11800), %o2"@},
22899 @{address="0x000107d0",func-name="main",offset="20",
22900 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
22904 Disassemble the whole @code{main} function. Line 32 is part of
22908 -data-disassemble -f basics.c -l 32 -- 0
22910 @{address="0x000107bc",func-name="main",offset="0",
22911 inst="save %sp, -112, %sp"@},
22912 @{address="0x000107c0",func-name="main",offset="4",
22913 inst="mov 2, %o0"@},
22914 @{address="0x000107c4",func-name="main",offset="8",
22915 inst="sethi %hi(0x11800), %o2"@},
22917 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22918 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22922 Disassemble 3 instructions from the start of @code{main}:
22926 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22928 @{address="0x000107bc",func-name="main",offset="0",
22929 inst="save %sp, -112, %sp"@},
22930 @{address="0x000107c0",func-name="main",offset="4",
22931 inst="mov 2, %o0"@},
22932 @{address="0x000107c4",func-name="main",offset="8",
22933 inst="sethi %hi(0x11800), %o2"@}]
22937 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22941 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22943 src_and_asm_line=@{line="31",
22944 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22945 testsuite/gdb.mi/basics.c",line_asm_insn=[
22946 @{address="0x000107bc",func-name="main",offset="0",
22947 inst="save %sp, -112, %sp"@}]@},
22948 src_and_asm_line=@{line="32",
22949 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22950 testsuite/gdb.mi/basics.c",line_asm_insn=[
22951 @{address="0x000107c0",func-name="main",offset="4",
22952 inst="mov 2, %o0"@},
22953 @{address="0x000107c4",func-name="main",offset="8",
22954 inst="sethi %hi(0x11800), %o2"@}]@}]
22959 @subheading The @code{-data-evaluate-expression} Command
22960 @findex -data-evaluate-expression
22962 @subsubheading Synopsis
22965 -data-evaluate-expression @var{expr}
22968 Evaluate @var{expr} as an expression. The expression could contain an
22969 inferior function call. The function call will execute synchronously.
22970 If the expression contains spaces, it must be enclosed in double quotes.
22972 @subsubheading @value{GDBN} Command
22974 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22975 @samp{call}. In @code{gdbtk} only, there's a corresponding
22976 @samp{gdb_eval} command.
22978 @subsubheading Example
22980 In the following example, the numbers that precede the commands are the
22981 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22982 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22986 211-data-evaluate-expression A
22989 311-data-evaluate-expression &A
22990 311^done,value="0xefffeb7c"
22992 411-data-evaluate-expression A+3
22995 511-data-evaluate-expression "A + 3"
23001 @subheading The @code{-data-list-changed-registers} Command
23002 @findex -data-list-changed-registers
23004 @subsubheading Synopsis
23007 -data-list-changed-registers
23010 Display a list of the registers that have changed.
23012 @subsubheading @value{GDBN} Command
23014 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
23015 has the corresponding command @samp{gdb_changed_register_list}.
23017 @subsubheading Example
23019 On a PPC MBX board:
23027 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
23028 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
23031 -data-list-changed-registers
23032 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
23033 "10","11","13","14","15","16","17","18","19","20","21","22","23",
23034 "24","25","26","27","28","30","31","64","65","66","67","69"]
23039 @subheading The @code{-data-list-register-names} Command
23040 @findex -data-list-register-names
23042 @subsubheading Synopsis
23045 -data-list-register-names [ ( @var{regno} )+ ]
23048 Show a list of register names for the current target. If no arguments
23049 are given, it shows a list of the names of all the registers. If
23050 integer numbers are given as arguments, it will print a list of the
23051 names of the registers corresponding to the arguments. To ensure
23052 consistency between a register name and its number, the output list may
23053 include empty register names.
23055 @subsubheading @value{GDBN} Command
23057 @value{GDBN} does not have a command which corresponds to
23058 @samp{-data-list-register-names}. In @code{gdbtk} there is a
23059 corresponding command @samp{gdb_regnames}.
23061 @subsubheading Example
23063 For the PPC MBX board:
23066 -data-list-register-names
23067 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
23068 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
23069 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
23070 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
23071 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
23072 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
23073 "", "pc","ps","cr","lr","ctr","xer"]
23075 -data-list-register-names 1 2 3
23076 ^done,register-names=["r1","r2","r3"]
23080 @subheading The @code{-data-list-register-values} Command
23081 @findex -data-list-register-values
23083 @subsubheading Synopsis
23086 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
23089 Display the registers' contents. @var{fmt} is the format according to
23090 which the registers' contents are to be returned, followed by an optional
23091 list of numbers specifying the registers to display. A missing list of
23092 numbers indicates that the contents of all the registers must be returned.
23094 Allowed formats for @var{fmt} are:
23111 @subsubheading @value{GDBN} Command
23113 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
23114 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
23116 @subsubheading Example
23118 For a PPC MBX board (note: line breaks are for readability only, they
23119 don't appear in the actual output):
23123 -data-list-register-values r 64 65
23124 ^done,register-values=[@{number="64",value="0xfe00a300"@},
23125 @{number="65",value="0x00029002"@}]
23127 -data-list-register-values x
23128 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
23129 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
23130 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
23131 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
23132 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
23133 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
23134 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
23135 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
23136 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
23137 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
23138 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
23139 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
23140 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
23141 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
23142 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
23143 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
23144 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
23145 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
23146 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
23147 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
23148 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
23149 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
23150 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
23151 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
23152 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
23153 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
23154 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
23155 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
23156 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
23157 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
23158 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
23159 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
23160 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
23161 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
23162 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
23163 @{number="69",value="0x20002b03"@}]
23168 @subheading The @code{-data-read-memory} Command
23169 @findex -data-read-memory
23171 @subsubheading Synopsis
23174 -data-read-memory [ -o @var{byte-offset} ]
23175 @var{address} @var{word-format} @var{word-size}
23176 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
23183 @item @var{address}
23184 An expression specifying the address of the first memory word to be
23185 read. Complex expressions containing embedded white space should be
23186 quoted using the C convention.
23188 @item @var{word-format}
23189 The format to be used to print the memory words. The notation is the
23190 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
23193 @item @var{word-size}
23194 The size of each memory word in bytes.
23196 @item @var{nr-rows}
23197 The number of rows in the output table.
23199 @item @var{nr-cols}
23200 The number of columns in the output table.
23203 If present, indicates that each row should include an @sc{ascii} dump. The
23204 value of @var{aschar} is used as a padding character when a byte is not a
23205 member of the printable @sc{ascii} character set (printable @sc{ascii}
23206 characters are those whose code is between 32 and 126, inclusively).
23208 @item @var{byte-offset}
23209 An offset to add to the @var{address} before fetching memory.
23212 This command displays memory contents as a table of @var{nr-rows} by
23213 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
23214 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
23215 (returned as @samp{total-bytes}). Should less than the requested number
23216 of bytes be returned by the target, the missing words are identified
23217 using @samp{N/A}. The number of bytes read from the target is returned
23218 in @samp{nr-bytes} and the starting address used to read memory in
23221 The address of the next/previous row or page is available in
23222 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
23225 @subsubheading @value{GDBN} Command
23227 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
23228 @samp{gdb_get_mem} memory read command.
23230 @subsubheading Example
23232 Read six bytes of memory starting at @code{bytes+6} but then offset by
23233 @code{-6} bytes. Format as three rows of two columns. One byte per
23234 word. Display each word in hex.
23238 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
23239 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
23240 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
23241 prev-page="0x0000138a",memory=[
23242 @{addr="0x00001390",data=["0x00","0x01"]@},
23243 @{addr="0x00001392",data=["0x02","0x03"]@},
23244 @{addr="0x00001394",data=["0x04","0x05"]@}]
23248 Read two bytes of memory starting at address @code{shorts + 64} and
23249 display as a single word formatted in decimal.
23253 5-data-read-memory shorts+64 d 2 1 1
23254 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
23255 next-row="0x00001512",prev-row="0x0000150e",
23256 next-page="0x00001512",prev-page="0x0000150e",memory=[
23257 @{addr="0x00001510",data=["128"]@}]
23261 Read thirty two bytes of memory starting at @code{bytes+16} and format
23262 as eight rows of four columns. Include a string encoding with @samp{x}
23263 used as the non-printable character.
23267 4-data-read-memory bytes+16 x 1 8 4 x
23268 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
23269 next-row="0x000013c0",prev-row="0x0000139c",
23270 next-page="0x000013c0",prev-page="0x00001380",memory=[
23271 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
23272 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
23273 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
23274 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
23275 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
23276 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
23277 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
23278 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
23282 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23283 @node GDB/MI Tracepoint Commands
23284 @section @sc{gdb/mi} Tracepoint Commands
23286 The tracepoint commands are not yet implemented.
23288 @c @subheading -trace-actions
23290 @c @subheading -trace-delete
23292 @c @subheading -trace-disable
23294 @c @subheading -trace-dump
23296 @c @subheading -trace-enable
23298 @c @subheading -trace-exists
23300 @c @subheading -trace-find
23302 @c @subheading -trace-frame-number
23304 @c @subheading -trace-info
23306 @c @subheading -trace-insert
23308 @c @subheading -trace-list
23310 @c @subheading -trace-pass-count
23312 @c @subheading -trace-save
23314 @c @subheading -trace-start
23316 @c @subheading -trace-stop
23319 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23320 @node GDB/MI Symbol Query
23321 @section @sc{gdb/mi} Symbol Query Commands
23324 @subheading The @code{-symbol-info-address} Command
23325 @findex -symbol-info-address
23327 @subsubheading Synopsis
23330 -symbol-info-address @var{symbol}
23333 Describe where @var{symbol} is stored.
23335 @subsubheading @value{GDBN} Command
23337 The corresponding @value{GDBN} command is @samp{info address}.
23339 @subsubheading Example
23343 @subheading The @code{-symbol-info-file} Command
23344 @findex -symbol-info-file
23346 @subsubheading Synopsis
23352 Show the file for the symbol.
23354 @subsubheading @value{GDBN} Command
23356 There's no equivalent @value{GDBN} command. @code{gdbtk} has
23357 @samp{gdb_find_file}.
23359 @subsubheading Example
23363 @subheading The @code{-symbol-info-function} Command
23364 @findex -symbol-info-function
23366 @subsubheading Synopsis
23369 -symbol-info-function
23372 Show which function the symbol lives in.
23374 @subsubheading @value{GDBN} Command
23376 @samp{gdb_get_function} in @code{gdbtk}.
23378 @subsubheading Example
23382 @subheading The @code{-symbol-info-line} Command
23383 @findex -symbol-info-line
23385 @subsubheading Synopsis
23391 Show the core addresses of the code for a source line.
23393 @subsubheading @value{GDBN} Command
23395 The corresponding @value{GDBN} command is @samp{info line}.
23396 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
23398 @subsubheading Example
23402 @subheading The @code{-symbol-info-symbol} Command
23403 @findex -symbol-info-symbol
23405 @subsubheading Synopsis
23408 -symbol-info-symbol @var{addr}
23411 Describe what symbol is at location @var{addr}.
23413 @subsubheading @value{GDBN} Command
23415 The corresponding @value{GDBN} command is @samp{info symbol}.
23417 @subsubheading Example
23421 @subheading The @code{-symbol-list-functions} Command
23422 @findex -symbol-list-functions
23424 @subsubheading Synopsis
23427 -symbol-list-functions
23430 List the functions in the executable.
23432 @subsubheading @value{GDBN} Command
23434 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
23435 @samp{gdb_search} in @code{gdbtk}.
23437 @subsubheading Example
23441 @subheading The @code{-symbol-list-lines} Command
23442 @findex -symbol-list-lines
23444 @subsubheading Synopsis
23447 -symbol-list-lines @var{filename}
23450 Print the list of lines that contain code and their associated program
23451 addresses for the given source filename. The entries are sorted in
23452 ascending PC order.
23454 @subsubheading @value{GDBN} Command
23456 There is no corresponding @value{GDBN} command.
23458 @subsubheading Example
23461 -symbol-list-lines basics.c
23462 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
23467 @subheading The @code{-symbol-list-types} Command
23468 @findex -symbol-list-types
23470 @subsubheading Synopsis
23476 List all the type names.
23478 @subsubheading @value{GDBN} Command
23480 The corresponding commands are @samp{info types} in @value{GDBN},
23481 @samp{gdb_search} in @code{gdbtk}.
23483 @subsubheading Example
23487 @subheading The @code{-symbol-list-variables} Command
23488 @findex -symbol-list-variables
23490 @subsubheading Synopsis
23493 -symbol-list-variables
23496 List all the global and static variable names.
23498 @subsubheading @value{GDBN} Command
23500 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
23502 @subsubheading Example
23506 @subheading The @code{-symbol-locate} Command
23507 @findex -symbol-locate
23509 @subsubheading Synopsis
23515 @subsubheading @value{GDBN} Command
23517 @samp{gdb_loc} in @code{gdbtk}.
23519 @subsubheading Example
23523 @subheading The @code{-symbol-type} Command
23524 @findex -symbol-type
23526 @subsubheading Synopsis
23529 -symbol-type @var{variable}
23532 Show type of @var{variable}.
23534 @subsubheading @value{GDBN} Command
23536 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
23537 @samp{gdb_obj_variable}.
23539 @subsubheading Example
23543 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23544 @node GDB/MI File Commands
23545 @section @sc{gdb/mi} File Commands
23547 This section describes the GDB/MI commands to specify executable file names
23548 and to read in and obtain symbol table information.
23550 @subheading The @code{-file-exec-and-symbols} Command
23551 @findex -file-exec-and-symbols
23553 @subsubheading Synopsis
23556 -file-exec-and-symbols @var{file}
23559 Specify the executable file to be debugged. This file is the one from
23560 which the symbol table is also read. If no file is specified, the
23561 command clears the executable and symbol information. If breakpoints
23562 are set when using this command with no arguments, @value{GDBN} will produce
23563 error messages. Otherwise, no output is produced, except a completion
23566 @subsubheading @value{GDBN} Command
23568 The corresponding @value{GDBN} command is @samp{file}.
23570 @subsubheading Example
23574 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23580 @subheading The @code{-file-exec-file} Command
23581 @findex -file-exec-file
23583 @subsubheading Synopsis
23586 -file-exec-file @var{file}
23589 Specify the executable file to be debugged. Unlike
23590 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
23591 from this file. If used without argument, @value{GDBN} clears the information
23592 about the executable file. No output is produced, except a completion
23595 @subsubheading @value{GDBN} Command
23597 The corresponding @value{GDBN} command is @samp{exec-file}.
23599 @subsubheading Example
23603 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23609 @subheading The @code{-file-list-exec-sections} Command
23610 @findex -file-list-exec-sections
23612 @subsubheading Synopsis
23615 -file-list-exec-sections
23618 List the sections of the current executable file.
23620 @subsubheading @value{GDBN} Command
23622 The @value{GDBN} command @samp{info file} shows, among the rest, the same
23623 information as this command. @code{gdbtk} has a corresponding command
23624 @samp{gdb_load_info}.
23626 @subsubheading Example
23630 @subheading The @code{-file-list-exec-source-file} Command
23631 @findex -file-list-exec-source-file
23633 @subsubheading Synopsis
23636 -file-list-exec-source-file
23639 List the line number, the current source file, and the absolute path
23640 to the current source file for the current executable. The macro
23641 information field has a value of @samp{1} or @samp{0} depending on
23642 whether or not the file includes preprocessor macro information.
23644 @subsubheading @value{GDBN} Command
23646 The @value{GDBN} equivalent is @samp{info source}
23648 @subsubheading Example
23652 123-file-list-exec-source-file
23653 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
23658 @subheading The @code{-file-list-exec-source-files} Command
23659 @findex -file-list-exec-source-files
23661 @subsubheading Synopsis
23664 -file-list-exec-source-files
23667 List the source files for the current executable.
23669 It will always output the filename, but only when @value{GDBN} can find
23670 the absolute file name of a source file, will it output the fullname.
23672 @subsubheading @value{GDBN} Command
23674 The @value{GDBN} equivalent is @samp{info sources}.
23675 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
23677 @subsubheading Example
23680 -file-list-exec-source-files
23682 @{file=foo.c,fullname=/home/foo.c@},
23683 @{file=/home/bar.c,fullname=/home/bar.c@},
23684 @{file=gdb_could_not_find_fullpath.c@}]
23688 @subheading The @code{-file-list-shared-libraries} Command
23689 @findex -file-list-shared-libraries
23691 @subsubheading Synopsis
23694 -file-list-shared-libraries
23697 List the shared libraries in the program.
23699 @subsubheading @value{GDBN} Command
23701 The corresponding @value{GDBN} command is @samp{info shared}.
23703 @subsubheading Example
23707 @subheading The @code{-file-list-symbol-files} Command
23708 @findex -file-list-symbol-files
23710 @subsubheading Synopsis
23713 -file-list-symbol-files
23718 @subsubheading @value{GDBN} Command
23720 The corresponding @value{GDBN} command is @samp{info file} (part of it).
23722 @subsubheading Example
23726 @subheading The @code{-file-symbol-file} Command
23727 @findex -file-symbol-file
23729 @subsubheading Synopsis
23732 -file-symbol-file @var{file}
23735 Read symbol table info from the specified @var{file} argument. When
23736 used without arguments, clears @value{GDBN}'s symbol table info. No output is
23737 produced, except for a completion notification.
23739 @subsubheading @value{GDBN} Command
23741 The corresponding @value{GDBN} command is @samp{symbol-file}.
23743 @subsubheading Example
23747 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23753 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23754 @node GDB/MI Memory Overlay Commands
23755 @section @sc{gdb/mi} Memory Overlay Commands
23757 The memory overlay commands are not implemented.
23759 @c @subheading -overlay-auto
23761 @c @subheading -overlay-list-mapping-state
23763 @c @subheading -overlay-list-overlays
23765 @c @subheading -overlay-map
23767 @c @subheading -overlay-off
23769 @c @subheading -overlay-on
23771 @c @subheading -overlay-unmap
23773 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23774 @node GDB/MI Signal Handling Commands
23775 @section @sc{gdb/mi} Signal Handling Commands
23777 Signal handling commands are not implemented.
23779 @c @subheading -signal-handle
23781 @c @subheading -signal-list-handle-actions
23783 @c @subheading -signal-list-signal-types
23787 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23788 @node GDB/MI Target Manipulation
23789 @section @sc{gdb/mi} Target Manipulation Commands
23792 @subheading The @code{-target-attach} Command
23793 @findex -target-attach
23795 @subsubheading Synopsis
23798 -target-attach @var{pid} | @var{gid} | @var{file}
23801 Attach to a process @var{pid} or a file @var{file} outside of
23802 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
23803 group, the id previously returned by
23804 @samp{-list-thread-groups --available} must be used.
23806 @subsubheading @value{GDBN} Command
23808 The corresponding @value{GDBN} command is @samp{attach}.
23810 @subsubheading Example
23814 =thread-created,id="1"
23815 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
23820 @subheading The @code{-target-compare-sections} Command
23821 @findex -target-compare-sections
23823 @subsubheading Synopsis
23826 -target-compare-sections [ @var{section} ]
23829 Compare data of section @var{section} on target to the exec file.
23830 Without the argument, all sections are compared.
23832 @subsubheading @value{GDBN} Command
23834 The @value{GDBN} equivalent is @samp{compare-sections}.
23836 @subsubheading Example
23840 @subheading The @code{-target-detach} Command
23841 @findex -target-detach
23843 @subsubheading Synopsis
23846 -target-detach [ @var{pid} | @var{gid} ]
23849 Detach from the remote target which normally resumes its execution.
23850 If either @var{pid} or @var{gid} is specified, detaches from either
23851 the specified process, or specified thread group. There's no output.
23853 @subsubheading @value{GDBN} Command
23855 The corresponding @value{GDBN} command is @samp{detach}.
23857 @subsubheading Example
23867 @subheading The @code{-target-disconnect} Command
23868 @findex -target-disconnect
23870 @subsubheading Synopsis
23876 Disconnect from the remote target. There's no output and the target is
23877 generally not resumed.
23879 @subsubheading @value{GDBN} Command
23881 The corresponding @value{GDBN} command is @samp{disconnect}.
23883 @subsubheading Example
23893 @subheading The @code{-target-download} Command
23894 @findex -target-download
23896 @subsubheading Synopsis
23902 Loads the executable onto the remote target.
23903 It prints out an update message every half second, which includes the fields:
23907 The name of the section.
23909 The size of what has been sent so far for that section.
23911 The size of the section.
23913 The total size of what was sent so far (the current and the previous sections).
23915 The size of the overall executable to download.
23919 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23920 @sc{gdb/mi} Output Syntax}).
23922 In addition, it prints the name and size of the sections, as they are
23923 downloaded. These messages include the following fields:
23927 The name of the section.
23929 The size of the section.
23931 The size of the overall executable to download.
23935 At the end, a summary is printed.
23937 @subsubheading @value{GDBN} Command
23939 The corresponding @value{GDBN} command is @samp{load}.
23941 @subsubheading Example
23943 Note: each status message appears on a single line. Here the messages
23944 have been broken down so that they can fit onto a page.
23949 +download,@{section=".text",section-size="6668",total-size="9880"@}
23950 +download,@{section=".text",section-sent="512",section-size="6668",
23951 total-sent="512",total-size="9880"@}
23952 +download,@{section=".text",section-sent="1024",section-size="6668",
23953 total-sent="1024",total-size="9880"@}
23954 +download,@{section=".text",section-sent="1536",section-size="6668",
23955 total-sent="1536",total-size="9880"@}
23956 +download,@{section=".text",section-sent="2048",section-size="6668",
23957 total-sent="2048",total-size="9880"@}
23958 +download,@{section=".text",section-sent="2560",section-size="6668",
23959 total-sent="2560",total-size="9880"@}
23960 +download,@{section=".text",section-sent="3072",section-size="6668",
23961 total-sent="3072",total-size="9880"@}
23962 +download,@{section=".text",section-sent="3584",section-size="6668",
23963 total-sent="3584",total-size="9880"@}
23964 +download,@{section=".text",section-sent="4096",section-size="6668",
23965 total-sent="4096",total-size="9880"@}
23966 +download,@{section=".text",section-sent="4608",section-size="6668",
23967 total-sent="4608",total-size="9880"@}
23968 +download,@{section=".text",section-sent="5120",section-size="6668",
23969 total-sent="5120",total-size="9880"@}
23970 +download,@{section=".text",section-sent="5632",section-size="6668",
23971 total-sent="5632",total-size="9880"@}
23972 +download,@{section=".text",section-sent="6144",section-size="6668",
23973 total-sent="6144",total-size="9880"@}
23974 +download,@{section=".text",section-sent="6656",section-size="6668",
23975 total-sent="6656",total-size="9880"@}
23976 +download,@{section=".init",section-size="28",total-size="9880"@}
23977 +download,@{section=".fini",section-size="28",total-size="9880"@}
23978 +download,@{section=".data",section-size="3156",total-size="9880"@}
23979 +download,@{section=".data",section-sent="512",section-size="3156",
23980 total-sent="7236",total-size="9880"@}
23981 +download,@{section=".data",section-sent="1024",section-size="3156",
23982 total-sent="7748",total-size="9880"@}
23983 +download,@{section=".data",section-sent="1536",section-size="3156",
23984 total-sent="8260",total-size="9880"@}
23985 +download,@{section=".data",section-sent="2048",section-size="3156",
23986 total-sent="8772",total-size="9880"@}
23987 +download,@{section=".data",section-sent="2560",section-size="3156",
23988 total-sent="9284",total-size="9880"@}
23989 +download,@{section=".data",section-sent="3072",section-size="3156",
23990 total-sent="9796",total-size="9880"@}
23991 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23997 @subheading The @code{-target-exec-status} Command
23998 @findex -target-exec-status
24000 @subsubheading Synopsis
24003 -target-exec-status
24006 Provide information on the state of the target (whether it is running or
24007 not, for instance).
24009 @subsubheading @value{GDBN} Command
24011 There's no equivalent @value{GDBN} command.
24013 @subsubheading Example
24017 @subheading The @code{-target-list-available-targets} Command
24018 @findex -target-list-available-targets
24020 @subsubheading Synopsis
24023 -target-list-available-targets
24026 List the possible targets to connect to.
24028 @subsubheading @value{GDBN} Command
24030 The corresponding @value{GDBN} command is @samp{help target}.
24032 @subsubheading Example
24036 @subheading The @code{-target-list-current-targets} Command
24037 @findex -target-list-current-targets
24039 @subsubheading Synopsis
24042 -target-list-current-targets
24045 Describe the current target.
24047 @subsubheading @value{GDBN} Command
24049 The corresponding information is printed by @samp{info file} (among
24052 @subsubheading Example
24056 @subheading The @code{-target-list-parameters} Command
24057 @findex -target-list-parameters
24059 @subsubheading Synopsis
24062 -target-list-parameters
24067 @subsubheading @value{GDBN} Command
24071 @subsubheading Example
24075 @subheading The @code{-target-select} Command
24076 @findex -target-select
24078 @subsubheading Synopsis
24081 -target-select @var{type} @var{parameters @dots{}}
24084 Connect @value{GDBN} to the remote target. This command takes two args:
24088 The type of target, for instance @samp{remote}, etc.
24089 @item @var{parameters}
24090 Device names, host names and the like. @xref{Target Commands, ,
24091 Commands for Managing Targets}, for more details.
24094 The output is a connection notification, followed by the address at
24095 which the target program is, in the following form:
24098 ^connected,addr="@var{address}",func="@var{function name}",
24099 args=[@var{arg list}]
24102 @subsubheading @value{GDBN} Command
24104 The corresponding @value{GDBN} command is @samp{target}.
24106 @subsubheading Example
24110 -target-select remote /dev/ttya
24111 ^connected,addr="0xfe00a300",func="??",args=[]
24115 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24116 @node GDB/MI File Transfer Commands
24117 @section @sc{gdb/mi} File Transfer Commands
24120 @subheading The @code{-target-file-put} Command
24121 @findex -target-file-put
24123 @subsubheading Synopsis
24126 -target-file-put @var{hostfile} @var{targetfile}
24129 Copy file @var{hostfile} from the host system (the machine running
24130 @value{GDBN}) to @var{targetfile} on the target system.
24132 @subsubheading @value{GDBN} Command
24134 The corresponding @value{GDBN} command is @samp{remote put}.
24136 @subsubheading Example
24140 -target-file-put localfile remotefile
24146 @subheading The @code{-target-file-get} Command
24147 @findex -target-file-get
24149 @subsubheading Synopsis
24152 -target-file-get @var{targetfile} @var{hostfile}
24155 Copy file @var{targetfile} from the target system to @var{hostfile}
24156 on the host system.
24158 @subsubheading @value{GDBN} Command
24160 The corresponding @value{GDBN} command is @samp{remote get}.
24162 @subsubheading Example
24166 -target-file-get remotefile localfile
24172 @subheading The @code{-target-file-delete} Command
24173 @findex -target-file-delete
24175 @subsubheading Synopsis
24178 -target-file-delete @var{targetfile}
24181 Delete @var{targetfile} from the target system.
24183 @subsubheading @value{GDBN} Command
24185 The corresponding @value{GDBN} command is @samp{remote delete}.
24187 @subsubheading Example
24191 -target-file-delete remotefile
24197 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24198 @node GDB/MI Miscellaneous Commands
24199 @section Miscellaneous @sc{gdb/mi} Commands
24201 @c @subheading -gdb-complete
24203 @subheading The @code{-gdb-exit} Command
24206 @subsubheading Synopsis
24212 Exit @value{GDBN} immediately.
24214 @subsubheading @value{GDBN} Command
24216 Approximately corresponds to @samp{quit}.
24218 @subsubheading Example
24227 @subheading The @code{-exec-abort} Command
24228 @findex -exec-abort
24230 @subsubheading Synopsis
24236 Kill the inferior running program.
24238 @subsubheading @value{GDBN} Command
24240 The corresponding @value{GDBN} command is @samp{kill}.
24242 @subsubheading Example
24246 @subheading The @code{-gdb-set} Command
24249 @subsubheading Synopsis
24255 Set an internal @value{GDBN} variable.
24256 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
24258 @subsubheading @value{GDBN} Command
24260 The corresponding @value{GDBN} command is @samp{set}.
24262 @subsubheading Example
24272 @subheading The @code{-gdb-show} Command
24275 @subsubheading Synopsis
24281 Show the current value of a @value{GDBN} variable.
24283 @subsubheading @value{GDBN} Command
24285 The corresponding @value{GDBN} command is @samp{show}.
24287 @subsubheading Example
24296 @c @subheading -gdb-source
24299 @subheading The @code{-gdb-version} Command
24300 @findex -gdb-version
24302 @subsubheading Synopsis
24308 Show version information for @value{GDBN}. Used mostly in testing.
24310 @subsubheading @value{GDBN} Command
24312 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
24313 default shows this information when you start an interactive session.
24315 @subsubheading Example
24317 @c This example modifies the actual output from GDB to avoid overfull
24323 ~Copyright 2000 Free Software Foundation, Inc.
24324 ~GDB is free software, covered by the GNU General Public License, and
24325 ~you are welcome to change it and/or distribute copies of it under
24326 ~ certain conditions.
24327 ~Type "show copying" to see the conditions.
24328 ~There is absolutely no warranty for GDB. Type "show warranty" for
24330 ~This GDB was configured as
24331 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
24336 @subheading The @code{-list-features} Command
24337 @findex -list-features
24339 Returns a list of particular features of the MI protocol that
24340 this version of gdb implements. A feature can be a command,
24341 or a new field in an output of some command, or even an
24342 important bugfix. While a frontend can sometimes detect presence
24343 of a feature at runtime, it is easier to perform detection at debugger
24346 The command returns a list of strings, with each string naming an
24347 available feature. Each returned string is just a name, it does not
24348 have any internal structure. The list of possible feature names
24354 (gdb) -list-features
24355 ^done,result=["feature1","feature2"]
24358 The current list of features is:
24361 @item frozen-varobjs
24362 Indicates presence of the @code{-var-set-frozen} command, as well
24363 as possible presense of the @code{frozen} field in the output
24364 of @code{-varobj-create}.
24365 @item pending-breakpoints
24366 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
24368 Indicates presence of the @code{-thread-info} command.
24372 @subheading The @code{-list-target-features} Command
24373 @findex -list-target-features
24375 Returns a list of particular features that are supported by the
24376 target. Those features affect the permitted MI commands, but
24377 unlike the features reported by the @code{-list-features} command, the
24378 features depend on which target GDB is using at the moment. Whenever
24379 a target can change, due to commands such as @code{-target-select},
24380 @code{-target-attach} or @code{-exec-run}, the list of target features
24381 may change, and the frontend should obtain it again.
24385 (gdb) -list-features
24386 ^done,result=["async"]
24389 The current list of features is:
24393 Indicates that the target is capable of asynchronous command
24394 execution, which means that @value{GDBN} will accept further commands
24395 while the target is running.
24399 @subheading The @code{-list-thread-groups} Command
24400 @findex -list-thread-groups
24402 @subheading Synopsis
24405 -list-thread-groups [ --available ] [ @var{group} ]
24408 When used without the @var{group} parameter, lists top-level thread
24409 groups that are being debugged. When used with the @var{group}
24410 parameter, the children of the specified group are listed. The
24411 children can be either threads, or other groups. At present,
24412 @value{GDBN} will not report both threads and groups as children at
24413 the same time, but it may change in future.
24415 With the @samp{--available} option, instead of reporting groups that
24416 are been debugged, GDB will report all thread groups available on the
24417 target. Using the @samp{--available} option together with @var{group}
24420 @subheading Example
24424 -list-thread-groups
24425 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
24426 -list-thread-groups 17
24427 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24428 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24429 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24430 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24431 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
24434 @subheading The @code{-interpreter-exec} Command
24435 @findex -interpreter-exec
24437 @subheading Synopsis
24440 -interpreter-exec @var{interpreter} @var{command}
24442 @anchor{-interpreter-exec}
24444 Execute the specified @var{command} in the given @var{interpreter}.
24446 @subheading @value{GDBN} Command
24448 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
24450 @subheading Example
24454 -interpreter-exec console "break main"
24455 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
24456 &"During symbol reading, bad structure-type format.\n"
24457 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
24462 @subheading The @code{-inferior-tty-set} Command
24463 @findex -inferior-tty-set
24465 @subheading Synopsis
24468 -inferior-tty-set /dev/pts/1
24471 Set terminal for future runs of the program being debugged.
24473 @subheading @value{GDBN} Command
24475 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
24477 @subheading Example
24481 -inferior-tty-set /dev/pts/1
24486 @subheading The @code{-inferior-tty-show} Command
24487 @findex -inferior-tty-show
24489 @subheading Synopsis
24495 Show terminal for future runs of program being debugged.
24497 @subheading @value{GDBN} Command
24499 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
24501 @subheading Example
24505 -inferior-tty-set /dev/pts/1
24509 ^done,inferior_tty_terminal="/dev/pts/1"
24513 @subheading The @code{-enable-timings} Command
24514 @findex -enable-timings
24516 @subheading Synopsis
24519 -enable-timings [yes | no]
24522 Toggle the printing of the wallclock, user and system times for an MI
24523 command as a field in its output. This command is to help frontend
24524 developers optimize the performance of their code. No argument is
24525 equivalent to @samp{yes}.
24527 @subheading @value{GDBN} Command
24531 @subheading Example
24539 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24540 addr="0x080484ed",func="main",file="myprog.c",
24541 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
24542 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
24550 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24551 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
24552 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
24553 fullname="/home/nickrob/myprog.c",line="73"@}
24558 @chapter @value{GDBN} Annotations
24560 This chapter describes annotations in @value{GDBN}. Annotations were
24561 designed to interface @value{GDBN} to graphical user interfaces or other
24562 similar programs which want to interact with @value{GDBN} at a
24563 relatively high level.
24565 The annotation mechanism has largely been superseded by @sc{gdb/mi}
24569 This is Edition @value{EDITION}, @value{DATE}.
24573 * Annotations Overview:: What annotations are; the general syntax.
24574 * Server Prefix:: Issuing a command without affecting user state.
24575 * Prompting:: Annotations marking @value{GDBN}'s need for input.
24576 * Errors:: Annotations for error messages.
24577 * Invalidation:: Some annotations describe things now invalid.
24578 * Annotations for Running::
24579 Whether the program is running, how it stopped, etc.
24580 * Source Annotations:: Annotations describing source code.
24583 @node Annotations Overview
24584 @section What is an Annotation?
24585 @cindex annotations
24587 Annotations start with a newline character, two @samp{control-z}
24588 characters, and the name of the annotation. If there is no additional
24589 information associated with this annotation, the name of the annotation
24590 is followed immediately by a newline. If there is additional
24591 information, the name of the annotation is followed by a space, the
24592 additional information, and a newline. The additional information
24593 cannot contain newline characters.
24595 Any output not beginning with a newline and two @samp{control-z}
24596 characters denotes literal output from @value{GDBN}. Currently there is
24597 no need for @value{GDBN} to output a newline followed by two
24598 @samp{control-z} characters, but if there was such a need, the
24599 annotations could be extended with an @samp{escape} annotation which
24600 means those three characters as output.
24602 The annotation @var{level}, which is specified using the
24603 @option{--annotate} command line option (@pxref{Mode Options}), controls
24604 how much information @value{GDBN} prints together with its prompt,
24605 values of expressions, source lines, and other types of output. Level 0
24606 is for no annotations, level 1 is for use when @value{GDBN} is run as a
24607 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
24608 for programs that control @value{GDBN}, and level 2 annotations have
24609 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
24610 Interface, annotate, GDB's Obsolete Annotations}).
24613 @kindex set annotate
24614 @item set annotate @var{level}
24615 The @value{GDBN} command @code{set annotate} sets the level of
24616 annotations to the specified @var{level}.
24618 @item show annotate
24619 @kindex show annotate
24620 Show the current annotation level.
24623 This chapter describes level 3 annotations.
24625 A simple example of starting up @value{GDBN} with annotations is:
24628 $ @kbd{gdb --annotate=3}
24630 Copyright 2003 Free Software Foundation, Inc.
24631 GDB is free software, covered by the GNU General Public License,
24632 and you are welcome to change it and/or distribute copies of it
24633 under certain conditions.
24634 Type "show copying" to see the conditions.
24635 There is absolutely no warranty for GDB. Type "show warranty"
24637 This GDB was configured as "i386-pc-linux-gnu"
24648 Here @samp{quit} is input to @value{GDBN}; the rest is output from
24649 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
24650 denotes a @samp{control-z} character) are annotations; the rest is
24651 output from @value{GDBN}.
24653 @node Server Prefix
24654 @section The Server Prefix
24655 @cindex server prefix
24657 If you prefix a command with @samp{server } then it will not affect
24658 the command history, nor will it affect @value{GDBN}'s notion of which
24659 command to repeat if @key{RET} is pressed on a line by itself. This
24660 means that commands can be run behind a user's back by a front-end in
24661 a transparent manner.
24663 The server prefix does not affect the recording of values into the value
24664 history; to print a value without recording it into the value history,
24665 use the @code{output} command instead of the @code{print} command.
24668 @section Annotation for @value{GDBN} Input
24670 @cindex annotations for prompts
24671 When @value{GDBN} prompts for input, it annotates this fact so it is possible
24672 to know when to send output, when the output from a given command is
24675 Different kinds of input each have a different @dfn{input type}. Each
24676 input type has three annotations: a @code{pre-} annotation, which
24677 denotes the beginning of any prompt which is being output, a plain
24678 annotation, which denotes the end of the prompt, and then a @code{post-}
24679 annotation which denotes the end of any echo which may (or may not) be
24680 associated with the input. For example, the @code{prompt} input type
24681 features the following annotations:
24689 The input types are
24692 @findex pre-prompt annotation
24693 @findex prompt annotation
24694 @findex post-prompt annotation
24696 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
24698 @findex pre-commands annotation
24699 @findex commands annotation
24700 @findex post-commands annotation
24702 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
24703 command. The annotations are repeated for each command which is input.
24705 @findex pre-overload-choice annotation
24706 @findex overload-choice annotation
24707 @findex post-overload-choice annotation
24708 @item overload-choice
24709 When @value{GDBN} wants the user to select between various overloaded functions.
24711 @findex pre-query annotation
24712 @findex query annotation
24713 @findex post-query annotation
24715 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
24717 @findex pre-prompt-for-continue annotation
24718 @findex prompt-for-continue annotation
24719 @findex post-prompt-for-continue annotation
24720 @item prompt-for-continue
24721 When @value{GDBN} is asking the user to press return to continue. Note: Don't
24722 expect this to work well; instead use @code{set height 0} to disable
24723 prompting. This is because the counting of lines is buggy in the
24724 presence of annotations.
24729 @cindex annotations for errors, warnings and interrupts
24731 @findex quit annotation
24736 This annotation occurs right before @value{GDBN} responds to an interrupt.
24738 @findex error annotation
24743 This annotation occurs right before @value{GDBN} responds to an error.
24745 Quit and error annotations indicate that any annotations which @value{GDBN} was
24746 in the middle of may end abruptly. For example, if a
24747 @code{value-history-begin} annotation is followed by a @code{error}, one
24748 cannot expect to receive the matching @code{value-history-end}. One
24749 cannot expect not to receive it either, however; an error annotation
24750 does not necessarily mean that @value{GDBN} is immediately returning all the way
24753 @findex error-begin annotation
24754 A quit or error annotation may be preceded by
24760 Any output between that and the quit or error annotation is the error
24763 Warning messages are not yet annotated.
24764 @c If we want to change that, need to fix warning(), type_error(),
24765 @c range_error(), and possibly other places.
24768 @section Invalidation Notices
24770 @cindex annotations for invalidation messages
24771 The following annotations say that certain pieces of state may have
24775 @findex frames-invalid annotation
24776 @item ^Z^Zframes-invalid
24778 The frames (for example, output from the @code{backtrace} command) may
24781 @findex breakpoints-invalid annotation
24782 @item ^Z^Zbreakpoints-invalid
24784 The breakpoints may have changed. For example, the user just added or
24785 deleted a breakpoint.
24788 @node Annotations for Running
24789 @section Running the Program
24790 @cindex annotations for running programs
24792 @findex starting annotation
24793 @findex stopping annotation
24794 When the program starts executing due to a @value{GDBN} command such as
24795 @code{step} or @code{continue},
24801 is output. When the program stops,
24807 is output. Before the @code{stopped} annotation, a variety of
24808 annotations describe how the program stopped.
24811 @findex exited annotation
24812 @item ^Z^Zexited @var{exit-status}
24813 The program exited, and @var{exit-status} is the exit status (zero for
24814 successful exit, otherwise nonzero).
24816 @findex signalled annotation
24817 @findex signal-name annotation
24818 @findex signal-name-end annotation
24819 @findex signal-string annotation
24820 @findex signal-string-end annotation
24821 @item ^Z^Zsignalled
24822 The program exited with a signal. After the @code{^Z^Zsignalled}, the
24823 annotation continues:
24829 ^Z^Zsignal-name-end
24833 ^Z^Zsignal-string-end
24838 where @var{name} is the name of the signal, such as @code{SIGILL} or
24839 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
24840 as @code{Illegal Instruction} or @code{Segmentation fault}.
24841 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
24842 user's benefit and have no particular format.
24844 @findex signal annotation
24846 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
24847 just saying that the program received the signal, not that it was
24848 terminated with it.
24850 @findex breakpoint annotation
24851 @item ^Z^Zbreakpoint @var{number}
24852 The program hit breakpoint number @var{number}.
24854 @findex watchpoint annotation
24855 @item ^Z^Zwatchpoint @var{number}
24856 The program hit watchpoint number @var{number}.
24859 @node Source Annotations
24860 @section Displaying Source
24861 @cindex annotations for source display
24863 @findex source annotation
24864 The following annotation is used instead of displaying source code:
24867 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
24870 where @var{filename} is an absolute file name indicating which source
24871 file, @var{line} is the line number within that file (where 1 is the
24872 first line in the file), @var{character} is the character position
24873 within the file (where 0 is the first character in the file) (for most
24874 debug formats this will necessarily point to the beginning of a line),
24875 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
24876 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
24877 @var{addr} is the address in the target program associated with the
24878 source which is being displayed. @var{addr} is in the form @samp{0x}
24879 followed by one or more lowercase hex digits (note that this does not
24880 depend on the language).
24883 @chapter Reporting Bugs in @value{GDBN}
24884 @cindex bugs in @value{GDBN}
24885 @cindex reporting bugs in @value{GDBN}
24887 Your bug reports play an essential role in making @value{GDBN} reliable.
24889 Reporting a bug may help you by bringing a solution to your problem, or it
24890 may not. But in any case the principal function of a bug report is to help
24891 the entire community by making the next version of @value{GDBN} work better. Bug
24892 reports are your contribution to the maintenance of @value{GDBN}.
24894 In order for a bug report to serve its purpose, you must include the
24895 information that enables us to fix the bug.
24898 * Bug Criteria:: Have you found a bug?
24899 * Bug Reporting:: How to report bugs
24903 @section Have You Found a Bug?
24904 @cindex bug criteria
24906 If you are not sure whether you have found a bug, here are some guidelines:
24909 @cindex fatal signal
24910 @cindex debugger crash
24911 @cindex crash of debugger
24913 If the debugger gets a fatal signal, for any input whatever, that is a
24914 @value{GDBN} bug. Reliable debuggers never crash.
24916 @cindex error on valid input
24918 If @value{GDBN} produces an error message for valid input, that is a
24919 bug. (Note that if you're cross debugging, the problem may also be
24920 somewhere in the connection to the target.)
24922 @cindex invalid input
24924 If @value{GDBN} does not produce an error message for invalid input,
24925 that is a bug. However, you should note that your idea of
24926 ``invalid input'' might be our idea of ``an extension'' or ``support
24927 for traditional practice''.
24930 If you are an experienced user of debugging tools, your suggestions
24931 for improvement of @value{GDBN} are welcome in any case.
24934 @node Bug Reporting
24935 @section How to Report Bugs
24936 @cindex bug reports
24937 @cindex @value{GDBN} bugs, reporting
24939 A number of companies and individuals offer support for @sc{gnu} products.
24940 If you obtained @value{GDBN} from a support organization, we recommend you
24941 contact that organization first.
24943 You can find contact information for many support companies and
24944 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24946 @c should add a web page ref...
24949 @ifset BUGURL_DEFAULT
24950 In any event, we also recommend that you submit bug reports for
24951 @value{GDBN}. The preferred method is to submit them directly using
24952 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24953 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24956 @strong{Do not send bug reports to @samp{info-gdb}, or to
24957 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24958 not want to receive bug reports. Those that do have arranged to receive
24961 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24962 serves as a repeater. The mailing list and the newsgroup carry exactly
24963 the same messages. Often people think of posting bug reports to the
24964 newsgroup instead of mailing them. This appears to work, but it has one
24965 problem which can be crucial: a newsgroup posting often lacks a mail
24966 path back to the sender. Thus, if we need to ask for more information,
24967 we may be unable to reach you. For this reason, it is better to send
24968 bug reports to the mailing list.
24970 @ifclear BUGURL_DEFAULT
24971 In any event, we also recommend that you submit bug reports for
24972 @value{GDBN} to @value{BUGURL}.
24976 The fundamental principle of reporting bugs usefully is this:
24977 @strong{report all the facts}. If you are not sure whether to state a
24978 fact or leave it out, state it!
24980 Often people omit facts because they think they know what causes the
24981 problem and assume that some details do not matter. Thus, you might
24982 assume that the name of the variable you use in an example does not matter.
24983 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24984 stray memory reference which happens to fetch from the location where that
24985 name is stored in memory; perhaps, if the name were different, the contents
24986 of that location would fool the debugger into doing the right thing despite
24987 the bug. Play it safe and give a specific, complete example. That is the
24988 easiest thing for you to do, and the most helpful.
24990 Keep in mind that the purpose of a bug report is to enable us to fix the
24991 bug. It may be that the bug has been reported previously, but neither
24992 you nor we can know that unless your bug report is complete and
24995 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24996 bell?'' Those bug reports are useless, and we urge everyone to
24997 @emph{refuse to respond to them} except to chide the sender to report
25000 To enable us to fix the bug, you should include all these things:
25004 The version of @value{GDBN}. @value{GDBN} announces it if you start
25005 with no arguments; you can also print it at any time using @code{show
25008 Without this, we will not know whether there is any point in looking for
25009 the bug in the current version of @value{GDBN}.
25012 The type of machine you are using, and the operating system name and
25016 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
25017 ``@value{GCC}--2.8.1''.
25020 What compiler (and its version) was used to compile the program you are
25021 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
25022 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
25023 to get this information; for other compilers, see the documentation for
25027 The command arguments you gave the compiler to compile your example and
25028 observe the bug. For example, did you use @samp{-O}? To guarantee
25029 you will not omit something important, list them all. A copy of the
25030 Makefile (or the output from make) is sufficient.
25032 If we were to try to guess the arguments, we would probably guess wrong
25033 and then we might not encounter the bug.
25036 A complete input script, and all necessary source files, that will
25040 A description of what behavior you observe that you believe is
25041 incorrect. For example, ``It gets a fatal signal.''
25043 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
25044 will certainly notice it. But if the bug is incorrect output, we might
25045 not notice unless it is glaringly wrong. You might as well not give us
25046 a chance to make a mistake.
25048 Even if the problem you experience is a fatal signal, you should still
25049 say so explicitly. Suppose something strange is going on, such as, your
25050 copy of @value{GDBN} is out of synch, or you have encountered a bug in
25051 the C library on your system. (This has happened!) Your copy might
25052 crash and ours would not. If you told us to expect a crash, then when
25053 ours fails to crash, we would know that the bug was not happening for
25054 us. If you had not told us to expect a crash, then we would not be able
25055 to draw any conclusion from our observations.
25058 @cindex recording a session script
25059 To collect all this information, you can use a session recording program
25060 such as @command{script}, which is available on many Unix systems.
25061 Just run your @value{GDBN} session inside @command{script} and then
25062 include the @file{typescript} file with your bug report.
25064 Another way to record a @value{GDBN} session is to run @value{GDBN}
25065 inside Emacs and then save the entire buffer to a file.
25068 If you wish to suggest changes to the @value{GDBN} source, send us context
25069 diffs. If you even discuss something in the @value{GDBN} source, refer to
25070 it by context, not by line number.
25072 The line numbers in our development sources will not match those in your
25073 sources. Your line numbers would convey no useful information to us.
25077 Here are some things that are not necessary:
25081 A description of the envelope of the bug.
25083 Often people who encounter a bug spend a lot of time investigating
25084 which changes to the input file will make the bug go away and which
25085 changes will not affect it.
25087 This is often time consuming and not very useful, because the way we
25088 will find the bug is by running a single example under the debugger
25089 with breakpoints, not by pure deduction from a series of examples.
25090 We recommend that you save your time for something else.
25092 Of course, if you can find a simpler example to report @emph{instead}
25093 of the original one, that is a convenience for us. Errors in the
25094 output will be easier to spot, running under the debugger will take
25095 less time, and so on.
25097 However, simplification is not vital; if you do not want to do this,
25098 report the bug anyway and send us the entire test case you used.
25101 A patch for the bug.
25103 A patch for the bug does help us if it is a good one. But do not omit
25104 the necessary information, such as the test case, on the assumption that
25105 a patch is all we need. We might see problems with your patch and decide
25106 to fix the problem another way, or we might not understand it at all.
25108 Sometimes with a program as complicated as @value{GDBN} it is very hard to
25109 construct an example that will make the program follow a certain path
25110 through the code. If you do not send us the example, we will not be able
25111 to construct one, so we will not be able to verify that the bug is fixed.
25113 And if we cannot understand what bug you are trying to fix, or why your
25114 patch should be an improvement, we will not install it. A test case will
25115 help us to understand.
25118 A guess about what the bug is or what it depends on.
25120 Such guesses are usually wrong. Even we cannot guess right about such
25121 things without first using the debugger to find the facts.
25124 @c The readline documentation is distributed with the readline code
25125 @c and consists of the two following files:
25127 @c inc-hist.texinfo
25128 @c Use -I with makeinfo to point to the appropriate directory,
25129 @c environment var TEXINPUTS with TeX.
25130 @include rluser.texi
25131 @include inc-hist.texinfo
25134 @node Formatting Documentation
25135 @appendix Formatting Documentation
25137 @cindex @value{GDBN} reference card
25138 @cindex reference card
25139 The @value{GDBN} 4 release includes an already-formatted reference card, ready
25140 for printing with PostScript or Ghostscript, in the @file{gdb}
25141 subdirectory of the main source directory@footnote{In
25142 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
25143 release.}. If you can use PostScript or Ghostscript with your printer,
25144 you can print the reference card immediately with @file{refcard.ps}.
25146 The release also includes the source for the reference card. You
25147 can format it, using @TeX{}, by typing:
25153 The @value{GDBN} reference card is designed to print in @dfn{landscape}
25154 mode on US ``letter'' size paper;
25155 that is, on a sheet 11 inches wide by 8.5 inches
25156 high. You will need to specify this form of printing as an option to
25157 your @sc{dvi} output program.
25159 @cindex documentation
25161 All the documentation for @value{GDBN} comes as part of the machine-readable
25162 distribution. The documentation is written in Texinfo format, which is
25163 a documentation system that uses a single source file to produce both
25164 on-line information and a printed manual. You can use one of the Info
25165 formatting commands to create the on-line version of the documentation
25166 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
25168 @value{GDBN} includes an already formatted copy of the on-line Info
25169 version of this manual in the @file{gdb} subdirectory. The main Info
25170 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
25171 subordinate files matching @samp{gdb.info*} in the same directory. If
25172 necessary, you can print out these files, or read them with any editor;
25173 but they are easier to read using the @code{info} subsystem in @sc{gnu}
25174 Emacs or the standalone @code{info} program, available as part of the
25175 @sc{gnu} Texinfo distribution.
25177 If you want to format these Info files yourself, you need one of the
25178 Info formatting programs, such as @code{texinfo-format-buffer} or
25181 If you have @code{makeinfo} installed, and are in the top level
25182 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
25183 version @value{GDBVN}), you can make the Info file by typing:
25190 If you want to typeset and print copies of this manual, you need @TeX{},
25191 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
25192 Texinfo definitions file.
25194 @TeX{} is a typesetting program; it does not print files directly, but
25195 produces output files called @sc{dvi} files. To print a typeset
25196 document, you need a program to print @sc{dvi} files. If your system
25197 has @TeX{} installed, chances are it has such a program. The precise
25198 command to use depends on your system; @kbd{lpr -d} is common; another
25199 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
25200 require a file name without any extension or a @samp{.dvi} extension.
25202 @TeX{} also requires a macro definitions file called
25203 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
25204 written in Texinfo format. On its own, @TeX{} cannot either read or
25205 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
25206 and is located in the @file{gdb-@var{version-number}/texinfo}
25209 If you have @TeX{} and a @sc{dvi} printer program installed, you can
25210 typeset and print this manual. First switch to the @file{gdb}
25211 subdirectory of the main source directory (for example, to
25212 @file{gdb-@value{GDBVN}/gdb}) and type:
25218 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
25220 @node Installing GDB
25221 @appendix Installing @value{GDBN}
25222 @cindex installation
25225 * Requirements:: Requirements for building @value{GDBN}
25226 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
25227 * Separate Objdir:: Compiling @value{GDBN} in another directory
25228 * Config Names:: Specifying names for hosts and targets
25229 * Configure Options:: Summary of options for configure
25230 * System-wide configuration:: Having a system-wide init file
25234 @section Requirements for Building @value{GDBN}
25235 @cindex building @value{GDBN}, requirements for
25237 Building @value{GDBN} requires various tools and packages to be available.
25238 Other packages will be used only if they are found.
25240 @heading Tools/Packages Necessary for Building @value{GDBN}
25242 @item ISO C90 compiler
25243 @value{GDBN} is written in ISO C90. It should be buildable with any
25244 working C90 compiler, e.g.@: GCC.
25248 @heading Tools/Packages Optional for Building @value{GDBN}
25252 @value{GDBN} can use the Expat XML parsing library. This library may be
25253 included with your operating system distribution; if it is not, you
25254 can get the latest version from @url{http://expat.sourceforge.net}.
25255 The @file{configure} script will search for this library in several
25256 standard locations; if it is installed in an unusual path, you can
25257 use the @option{--with-libexpat-prefix} option to specify its location.
25263 Remote protocol memory maps (@pxref{Memory Map Format})
25265 Target descriptions (@pxref{Target Descriptions})
25267 Remote shared library lists (@pxref{Library List Format})
25269 MS-Windows shared libraries (@pxref{Shared Libraries})
25273 @cindex compressed debug sections
25274 @value{GDBN} will use the @samp{zlib} library, if available, to read
25275 compressed debug sections. Some linkers, such as GNU gold, are capable
25276 of producing binaries with compressed debug sections. If @value{GDBN}
25277 is compiled with @samp{zlib}, it will be able to read the debug
25278 information in such binaries.
25280 The @samp{zlib} library is likely included with your operating system
25281 distribution; if it is not, you can get the latest version from
25282 @url{http://zlib.net}.
25285 @value{GDBN}'s features related to character sets (@pxref{Character
25286 Sets}) require a functioning @code{iconv} implementation. If you are
25287 on a GNU system, then this is provided by the GNU C Library. Some
25288 other systems also provide a working @code{iconv}.
25290 On systems with @code{iconv}, you can install GNU Libiconv. If you
25291 have previously installed Libiconv, you can use the
25292 @option{--with-libiconv-prefix} option to configure.
25294 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
25295 arrange to build Libiconv if a directory named @file{libiconv} appears
25296 in the top-most source directory. If Libiconv is built this way, and
25297 if the operating system does not provide a suitable @code{iconv}
25298 implementation, then the just-built library will automatically be used
25299 by @value{GDBN}. One easy way to set this up is to download GNU
25300 Libiconv, unpack it, and then rename the directory holding the
25301 Libiconv source code to @samp{libiconv}.
25304 @node Running Configure
25305 @section Invoking the @value{GDBN} @file{configure} Script
25306 @cindex configuring @value{GDBN}
25307 @value{GDBN} comes with a @file{configure} script that automates the process
25308 of preparing @value{GDBN} for installation; you can then use @code{make} to
25309 build the @code{gdb} program.
25311 @c irrelevant in info file; it's as current as the code it lives with.
25312 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
25313 look at the @file{README} file in the sources; we may have improved the
25314 installation procedures since publishing this manual.}
25317 The @value{GDBN} distribution includes all the source code you need for
25318 @value{GDBN} in a single directory, whose name is usually composed by
25319 appending the version number to @samp{gdb}.
25321 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
25322 @file{gdb-@value{GDBVN}} directory. That directory contains:
25325 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
25326 script for configuring @value{GDBN} and all its supporting libraries
25328 @item gdb-@value{GDBVN}/gdb
25329 the source specific to @value{GDBN} itself
25331 @item gdb-@value{GDBVN}/bfd
25332 source for the Binary File Descriptor library
25334 @item gdb-@value{GDBVN}/include
25335 @sc{gnu} include files
25337 @item gdb-@value{GDBVN}/libiberty
25338 source for the @samp{-liberty} free software library
25340 @item gdb-@value{GDBVN}/opcodes
25341 source for the library of opcode tables and disassemblers
25343 @item gdb-@value{GDBVN}/readline
25344 source for the @sc{gnu} command-line interface
25346 @item gdb-@value{GDBVN}/glob
25347 source for the @sc{gnu} filename pattern-matching subroutine
25349 @item gdb-@value{GDBVN}/mmalloc
25350 source for the @sc{gnu} memory-mapped malloc package
25353 The simplest way to configure and build @value{GDBN} is to run @file{configure}
25354 from the @file{gdb-@var{version-number}} source directory, which in
25355 this example is the @file{gdb-@value{GDBVN}} directory.
25357 First switch to the @file{gdb-@var{version-number}} source directory
25358 if you are not already in it; then run @file{configure}. Pass the
25359 identifier for the platform on which @value{GDBN} will run as an
25365 cd gdb-@value{GDBVN}
25366 ./configure @var{host}
25371 where @var{host} is an identifier such as @samp{sun4} or
25372 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
25373 (You can often leave off @var{host}; @file{configure} tries to guess the
25374 correct value by examining your system.)
25376 Running @samp{configure @var{host}} and then running @code{make} builds the
25377 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
25378 libraries, then @code{gdb} itself. The configured source files, and the
25379 binaries, are left in the corresponding source directories.
25382 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
25383 system does not recognize this automatically when you run a different
25384 shell, you may need to run @code{sh} on it explicitly:
25387 sh configure @var{host}
25390 If you run @file{configure} from a directory that contains source
25391 directories for multiple libraries or programs, such as the
25392 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
25394 creates configuration files for every directory level underneath (unless
25395 you tell it not to, with the @samp{--norecursion} option).
25397 You should run the @file{configure} script from the top directory in the
25398 source tree, the @file{gdb-@var{version-number}} directory. If you run
25399 @file{configure} from one of the subdirectories, you will configure only
25400 that subdirectory. That is usually not what you want. In particular,
25401 if you run the first @file{configure} from the @file{gdb} subdirectory
25402 of the @file{gdb-@var{version-number}} directory, you will omit the
25403 configuration of @file{bfd}, @file{readline}, and other sibling
25404 directories of the @file{gdb} subdirectory. This leads to build errors
25405 about missing include files such as @file{bfd/bfd.h}.
25407 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
25408 However, you should make sure that the shell on your path (named by
25409 the @samp{SHELL} environment variable) is publicly readable. Remember
25410 that @value{GDBN} uses the shell to start your program---some systems refuse to
25411 let @value{GDBN} debug child processes whose programs are not readable.
25413 @node Separate Objdir
25414 @section Compiling @value{GDBN} in Another Directory
25416 If you want to run @value{GDBN} versions for several host or target machines,
25417 you need a different @code{gdb} compiled for each combination of
25418 host and target. @file{configure} is designed to make this easy by
25419 allowing you to generate each configuration in a separate subdirectory,
25420 rather than in the source directory. If your @code{make} program
25421 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
25422 @code{make} in each of these directories builds the @code{gdb}
25423 program specified there.
25425 To build @code{gdb} in a separate directory, run @file{configure}
25426 with the @samp{--srcdir} option to specify where to find the source.
25427 (You also need to specify a path to find @file{configure}
25428 itself from your working directory. If the path to @file{configure}
25429 would be the same as the argument to @samp{--srcdir}, you can leave out
25430 the @samp{--srcdir} option; it is assumed.)
25432 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
25433 separate directory for a Sun 4 like this:
25437 cd gdb-@value{GDBVN}
25440 ../gdb-@value{GDBVN}/configure sun4
25445 When @file{configure} builds a configuration using a remote source
25446 directory, it creates a tree for the binaries with the same structure
25447 (and using the same names) as the tree under the source directory. In
25448 the example, you'd find the Sun 4 library @file{libiberty.a} in the
25449 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
25450 @file{gdb-sun4/gdb}.
25452 Make sure that your path to the @file{configure} script has just one
25453 instance of @file{gdb} in it. If your path to @file{configure} looks
25454 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
25455 one subdirectory of @value{GDBN}, not the whole package. This leads to
25456 build errors about missing include files such as @file{bfd/bfd.h}.
25458 One popular reason to build several @value{GDBN} configurations in separate
25459 directories is to configure @value{GDBN} for cross-compiling (where
25460 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
25461 programs that run on another machine---the @dfn{target}).
25462 You specify a cross-debugging target by
25463 giving the @samp{--target=@var{target}} option to @file{configure}.
25465 When you run @code{make} to build a program or library, you must run
25466 it in a configured directory---whatever directory you were in when you
25467 called @file{configure} (or one of its subdirectories).
25469 The @code{Makefile} that @file{configure} generates in each source
25470 directory also runs recursively. If you type @code{make} in a source
25471 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
25472 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
25473 will build all the required libraries, and then build GDB.
25475 When you have multiple hosts or targets configured in separate
25476 directories, you can run @code{make} on them in parallel (for example,
25477 if they are NFS-mounted on each of the hosts); they will not interfere
25481 @section Specifying Names for Hosts and Targets
25483 The specifications used for hosts and targets in the @file{configure}
25484 script are based on a three-part naming scheme, but some short predefined
25485 aliases are also supported. The full naming scheme encodes three pieces
25486 of information in the following pattern:
25489 @var{architecture}-@var{vendor}-@var{os}
25492 For example, you can use the alias @code{sun4} as a @var{host} argument,
25493 or as the value for @var{target} in a @code{--target=@var{target}}
25494 option. The equivalent full name is @samp{sparc-sun-sunos4}.
25496 The @file{configure} script accompanying @value{GDBN} does not provide
25497 any query facility to list all supported host and target names or
25498 aliases. @file{configure} calls the Bourne shell script
25499 @code{config.sub} to map abbreviations to full names; you can read the
25500 script, if you wish, or you can use it to test your guesses on
25501 abbreviations---for example:
25504 % sh config.sub i386-linux
25506 % sh config.sub alpha-linux
25507 alpha-unknown-linux-gnu
25508 % sh config.sub hp9k700
25510 % sh config.sub sun4
25511 sparc-sun-sunos4.1.1
25512 % sh config.sub sun3
25513 m68k-sun-sunos4.1.1
25514 % sh config.sub i986v
25515 Invalid configuration `i986v': machine `i986v' not recognized
25519 @code{config.sub} is also distributed in the @value{GDBN} source
25520 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
25522 @node Configure Options
25523 @section @file{configure} Options
25525 Here is a summary of the @file{configure} options and arguments that
25526 are most often useful for building @value{GDBN}. @file{configure} also has
25527 several other options not listed here. @inforef{What Configure
25528 Does,,configure.info}, for a full explanation of @file{configure}.
25531 configure @r{[}--help@r{]}
25532 @r{[}--prefix=@var{dir}@r{]}
25533 @r{[}--exec-prefix=@var{dir}@r{]}
25534 @r{[}--srcdir=@var{dirname}@r{]}
25535 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
25536 @r{[}--target=@var{target}@r{]}
25541 You may introduce options with a single @samp{-} rather than
25542 @samp{--} if you prefer; but you may abbreviate option names if you use
25547 Display a quick summary of how to invoke @file{configure}.
25549 @item --prefix=@var{dir}
25550 Configure the source to install programs and files under directory
25553 @item --exec-prefix=@var{dir}
25554 Configure the source to install programs under directory
25557 @c avoid splitting the warning from the explanation:
25559 @item --srcdir=@var{dirname}
25560 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
25561 @code{make} that implements the @code{VPATH} feature.}@*
25562 Use this option to make configurations in directories separate from the
25563 @value{GDBN} source directories. Among other things, you can use this to
25564 build (or maintain) several configurations simultaneously, in separate
25565 directories. @file{configure} writes configuration-specific files in
25566 the current directory, but arranges for them to use the source in the
25567 directory @var{dirname}. @file{configure} creates directories under
25568 the working directory in parallel to the source directories below
25571 @item --norecursion
25572 Configure only the directory level where @file{configure} is executed; do not
25573 propagate configuration to subdirectories.
25575 @item --target=@var{target}
25576 Configure @value{GDBN} for cross-debugging programs running on the specified
25577 @var{target}. Without this option, @value{GDBN} is configured to debug
25578 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
25580 There is no convenient way to generate a list of all available targets.
25582 @item @var{host} @dots{}
25583 Configure @value{GDBN} to run on the specified @var{host}.
25585 There is no convenient way to generate a list of all available hosts.
25588 There are many other options available as well, but they are generally
25589 needed for special purposes only.
25591 @node System-wide configuration
25592 @section System-wide configuration and settings
25593 @cindex system-wide init file
25595 @value{GDBN} can be configured to have a system-wide init file;
25596 this file will be read and executed at startup (@pxref{Startup, , What
25597 @value{GDBN} does during startup}).
25599 Here is the corresponding configure option:
25602 @item --with-system-gdbinit=@var{file}
25603 Specify that the default location of the system-wide init file is
25607 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
25608 it may be subject to relocation. Two possible cases:
25612 If the default location of this init file contains @file{$prefix},
25613 it will be subject to relocation. Suppose that the configure options
25614 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
25615 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
25616 init file is looked for as @file{$install/etc/gdbinit} instead of
25617 @file{$prefix/etc/gdbinit}.
25620 By contrast, if the default location does not contain the prefix,
25621 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
25622 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
25623 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
25624 wherever @value{GDBN} is installed.
25627 @node Maintenance Commands
25628 @appendix Maintenance Commands
25629 @cindex maintenance commands
25630 @cindex internal commands
25632 In addition to commands intended for @value{GDBN} users, @value{GDBN}
25633 includes a number of commands intended for @value{GDBN} developers,
25634 that are not documented elsewhere in this manual. These commands are
25635 provided here for reference. (For commands that turn on debugging
25636 messages, see @ref{Debugging Output}.)
25639 @kindex maint agent
25640 @item maint agent @var{expression}
25641 Translate the given @var{expression} into remote agent bytecodes.
25642 This command is useful for debugging the Agent Expression mechanism
25643 (@pxref{Agent Expressions}).
25645 @kindex maint info breakpoints
25646 @item @anchor{maint info breakpoints}maint info breakpoints
25647 Using the same format as @samp{info breakpoints}, display both the
25648 breakpoints you've set explicitly, and those @value{GDBN} is using for
25649 internal purposes. Internal breakpoints are shown with negative
25650 breakpoint numbers. The type column identifies what kind of breakpoint
25655 Normal, explicitly set breakpoint.
25658 Normal, explicitly set watchpoint.
25661 Internal breakpoint, used to handle correctly stepping through
25662 @code{longjmp} calls.
25664 @item longjmp resume
25665 Internal breakpoint at the target of a @code{longjmp}.
25668 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
25671 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
25674 Shared library events.
25678 @kindex set displaced-stepping
25679 @kindex show displaced-stepping
25680 @cindex displaced stepping support
25681 @cindex out-of-line single-stepping
25682 @item set displaced-stepping
25683 @itemx show displaced-stepping
25684 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
25685 if the target supports it. Displaced stepping is a way to single-step
25686 over breakpoints without removing them from the inferior, by executing
25687 an out-of-line copy of the instruction that was originally at the
25688 breakpoint location. It is also known as out-of-line single-stepping.
25691 @item set displaced-stepping on
25692 If the target architecture supports it, @value{GDBN} will use
25693 displaced stepping to step over breakpoints.
25695 @item set displaced-stepping off
25696 @value{GDBN} will not use displaced stepping to step over breakpoints,
25697 even if such is supported by the target architecture.
25699 @cindex non-stop mode, and @samp{set displaced-stepping}
25700 @item set displaced-stepping auto
25701 This is the default mode. @value{GDBN} will use displaced stepping
25702 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
25703 architecture supports displaced stepping.
25706 @kindex maint check-symtabs
25707 @item maint check-symtabs
25708 Check the consistency of psymtabs and symtabs.
25710 @kindex maint cplus first_component
25711 @item maint cplus first_component @var{name}
25712 Print the first C@t{++} class/namespace component of @var{name}.
25714 @kindex maint cplus namespace
25715 @item maint cplus namespace
25716 Print the list of possible C@t{++} namespaces.
25718 @kindex maint demangle
25719 @item maint demangle @var{name}
25720 Demangle a C@t{++} or Objective-C mangled @var{name}.
25722 @kindex maint deprecate
25723 @kindex maint undeprecate
25724 @cindex deprecated commands
25725 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
25726 @itemx maint undeprecate @var{command}
25727 Deprecate or undeprecate the named @var{command}. Deprecated commands
25728 cause @value{GDBN} to issue a warning when you use them. The optional
25729 argument @var{replacement} says which newer command should be used in
25730 favor of the deprecated one; if it is given, @value{GDBN} will mention
25731 the replacement as part of the warning.
25733 @kindex maint dump-me
25734 @item maint dump-me
25735 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
25736 Cause a fatal signal in the debugger and force it to dump its core.
25737 This is supported only on systems which support aborting a program
25738 with the @code{SIGQUIT} signal.
25740 @kindex maint internal-error
25741 @kindex maint internal-warning
25742 @item maint internal-error @r{[}@var{message-text}@r{]}
25743 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
25744 Cause @value{GDBN} to call the internal function @code{internal_error}
25745 or @code{internal_warning} and hence behave as though an internal error
25746 or internal warning has been detected. In addition to reporting the
25747 internal problem, these functions give the user the opportunity to
25748 either quit @value{GDBN} or create a core file of the current
25749 @value{GDBN} session.
25751 These commands take an optional parameter @var{message-text} that is
25752 used as the text of the error or warning message.
25754 Here's an example of using @code{internal-error}:
25757 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
25758 @dots{}/maint.c:121: internal-error: testing, 1, 2
25759 A problem internal to GDB has been detected. Further
25760 debugging may prove unreliable.
25761 Quit this debugging session? (y or n) @kbd{n}
25762 Create a core file? (y or n) @kbd{n}
25766 @cindex @value{GDBN} internal error
25767 @cindex internal errors, control of @value{GDBN} behavior
25769 @kindex maint set internal-error
25770 @kindex maint show internal-error
25771 @kindex maint set internal-warning
25772 @kindex maint show internal-warning
25773 @item maint set internal-error @var{action} [ask|yes|no]
25774 @itemx maint show internal-error @var{action}
25775 @itemx maint set internal-warning @var{action} [ask|yes|no]
25776 @itemx maint show internal-warning @var{action}
25777 When @value{GDBN} reports an internal problem (error or warning) it
25778 gives the user the opportunity to both quit @value{GDBN} and create a
25779 core file of the current @value{GDBN} session. These commands let you
25780 override the default behaviour for each particular @var{action},
25781 described in the table below.
25785 You can specify that @value{GDBN} should always (yes) or never (no)
25786 quit. The default is to ask the user what to do.
25789 You can specify that @value{GDBN} should always (yes) or never (no)
25790 create a core file. The default is to ask the user what to do.
25793 @kindex maint packet
25794 @item maint packet @var{text}
25795 If @value{GDBN} is talking to an inferior via the serial protocol,
25796 then this command sends the string @var{text} to the inferior, and
25797 displays the response packet. @value{GDBN} supplies the initial
25798 @samp{$} character, the terminating @samp{#} character, and the
25801 @kindex maint print architecture
25802 @item maint print architecture @r{[}@var{file}@r{]}
25803 Print the entire architecture configuration. The optional argument
25804 @var{file} names the file where the output goes.
25806 @kindex maint print c-tdesc
25807 @item maint print c-tdesc
25808 Print the current target description (@pxref{Target Descriptions}) as
25809 a C source file. The created source file can be used in @value{GDBN}
25810 when an XML parser is not available to parse the description.
25812 @kindex maint print dummy-frames
25813 @item maint print dummy-frames
25814 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
25817 (@value{GDBP}) @kbd{b add}
25819 (@value{GDBP}) @kbd{print add(2,3)}
25820 Breakpoint 2, add (a=2, b=3) at @dots{}
25822 The program being debugged stopped while in a function called from GDB.
25824 (@value{GDBP}) @kbd{maint print dummy-frames}
25825 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
25826 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
25827 call_lo=0x01014000 call_hi=0x01014001
25831 Takes an optional file parameter.
25833 @kindex maint print registers
25834 @kindex maint print raw-registers
25835 @kindex maint print cooked-registers
25836 @kindex maint print register-groups
25837 @item maint print registers @r{[}@var{file}@r{]}
25838 @itemx maint print raw-registers @r{[}@var{file}@r{]}
25839 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
25840 @itemx maint print register-groups @r{[}@var{file}@r{]}
25841 Print @value{GDBN}'s internal register data structures.
25843 The command @code{maint print raw-registers} includes the contents of
25844 the raw register cache; the command @code{maint print cooked-registers}
25845 includes the (cooked) value of all registers; and the command
25846 @code{maint print register-groups} includes the groups that each
25847 register is a member of. @xref{Registers,, Registers, gdbint,
25848 @value{GDBN} Internals}.
25850 These commands take an optional parameter, a file name to which to
25851 write the information.
25853 @kindex maint print reggroups
25854 @item maint print reggroups @r{[}@var{file}@r{]}
25855 Print @value{GDBN}'s internal register group data structures. The
25856 optional argument @var{file} tells to what file to write the
25859 The register groups info looks like this:
25862 (@value{GDBP}) @kbd{maint print reggroups}
25875 This command forces @value{GDBN} to flush its internal register cache.
25877 @kindex maint print objfiles
25878 @cindex info for known object files
25879 @item maint print objfiles
25880 Print a dump of all known object files. For each object file, this
25881 command prints its name, address in memory, and all of its psymtabs
25884 @kindex maint print statistics
25885 @cindex bcache statistics
25886 @item maint print statistics
25887 This command prints, for each object file in the program, various data
25888 about that object file followed by the byte cache (@dfn{bcache})
25889 statistics for the object file. The objfile data includes the number
25890 of minimal, partial, full, and stabs symbols, the number of types
25891 defined by the objfile, the number of as yet unexpanded psym tables,
25892 the number of line tables and string tables, and the amount of memory
25893 used by the various tables. The bcache statistics include the counts,
25894 sizes, and counts of duplicates of all and unique objects, max,
25895 average, and median entry size, total memory used and its overhead and
25896 savings, and various measures of the hash table size and chain
25899 @kindex maint print target-stack
25900 @cindex target stack description
25901 @item maint print target-stack
25902 A @dfn{target} is an interface between the debugger and a particular
25903 kind of file or process. Targets can be stacked in @dfn{strata},
25904 so that more than one target can potentially respond to a request.
25905 In particular, memory accesses will walk down the stack of targets
25906 until they find a target that is interested in handling that particular
25909 This command prints a short description of each layer that was pushed on
25910 the @dfn{target stack}, starting from the top layer down to the bottom one.
25912 @kindex maint print type
25913 @cindex type chain of a data type
25914 @item maint print type @var{expr}
25915 Print the type chain for a type specified by @var{expr}. The argument
25916 can be either a type name or a symbol. If it is a symbol, the type of
25917 that symbol is described. The type chain produced by this command is
25918 a recursive definition of the data type as stored in @value{GDBN}'s
25919 data structures, including its flags and contained types.
25921 @kindex maint set dwarf2 max-cache-age
25922 @kindex maint show dwarf2 max-cache-age
25923 @item maint set dwarf2 max-cache-age
25924 @itemx maint show dwarf2 max-cache-age
25925 Control the DWARF 2 compilation unit cache.
25927 @cindex DWARF 2 compilation units cache
25928 In object files with inter-compilation-unit references, such as those
25929 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
25930 reader needs to frequently refer to previously read compilation units.
25931 This setting controls how long a compilation unit will remain in the
25932 cache if it is not referenced. A higher limit means that cached
25933 compilation units will be stored in memory longer, and more total
25934 memory will be used. Setting it to zero disables caching, which will
25935 slow down @value{GDBN} startup, but reduce memory consumption.
25937 @kindex maint set profile
25938 @kindex maint show profile
25939 @cindex profiling GDB
25940 @item maint set profile
25941 @itemx maint show profile
25942 Control profiling of @value{GDBN}.
25944 Profiling will be disabled until you use the @samp{maint set profile}
25945 command to enable it. When you enable profiling, the system will begin
25946 collecting timing and execution count data; when you disable profiling or
25947 exit @value{GDBN}, the results will be written to a log file. Remember that
25948 if you use profiling, @value{GDBN} will overwrite the profiling log file
25949 (often called @file{gmon.out}). If you have a record of important profiling
25950 data in a @file{gmon.out} file, be sure to move it to a safe location.
25952 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
25953 compiled with the @samp{-pg} compiler option.
25955 @kindex maint set show-debug-regs
25956 @kindex maint show show-debug-regs
25957 @cindex hardware debug registers
25958 @item maint set show-debug-regs
25959 @itemx maint show show-debug-regs
25960 Control whether to show variables that mirror the hardware debug
25961 registers. Use @code{ON} to enable, @code{OFF} to disable. If
25962 enabled, the debug registers values are shown when @value{GDBN} inserts or
25963 removes a hardware breakpoint or watchpoint, and when the inferior
25964 triggers a hardware-assisted breakpoint or watchpoint.
25966 @kindex maint space
25967 @cindex memory used by commands
25969 Control whether to display memory usage for each command. If set to a
25970 nonzero value, @value{GDBN} will display how much memory each command
25971 took, following the command's own output. This can also be requested
25972 by invoking @value{GDBN} with the @option{--statistics} command-line
25973 switch (@pxref{Mode Options}).
25976 @cindex time of command execution
25978 Control whether to display the execution time for each command. If
25979 set to a nonzero value, @value{GDBN} will display how much time it
25980 took to execute each command, following the command's own output.
25981 The time is not printed for the commands that run the target, since
25982 there's no mechanism currently to compute how much time was spend
25983 by @value{GDBN} and how much time was spend by the program been debugged.
25984 it's not possibly currently
25985 This can also be requested by invoking @value{GDBN} with the
25986 @option{--statistics} command-line switch (@pxref{Mode Options}).
25988 @kindex maint translate-address
25989 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25990 Find the symbol stored at the location specified by the address
25991 @var{addr} and an optional section name @var{section}. If found,
25992 @value{GDBN} prints the name of the closest symbol and an offset from
25993 the symbol's location to the specified address. This is similar to
25994 the @code{info address} command (@pxref{Symbols}), except that this
25995 command also allows to find symbols in other sections.
25997 If section was not specified, the section in which the symbol was found
25998 is also printed. For dynamically linked executables, the name of
25999 executable or shared library containing the symbol is printed as well.
26003 The following command is useful for non-interactive invocations of
26004 @value{GDBN}, such as in the test suite.
26007 @item set watchdog @var{nsec}
26008 @kindex set watchdog
26009 @cindex watchdog timer
26010 @cindex timeout for commands
26011 Set the maximum number of seconds @value{GDBN} will wait for the
26012 target operation to finish. If this time expires, @value{GDBN}
26013 reports and error and the command is aborted.
26015 @item show watchdog
26016 Show the current setting of the target wait timeout.
26019 @node Remote Protocol
26020 @appendix @value{GDBN} Remote Serial Protocol
26025 * Stop Reply Packets::
26026 * General Query Packets::
26027 * Register Packet Format::
26028 * Tracepoint Packets::
26029 * Host I/O Packets::
26031 * Notification Packets::
26032 * Remote Non-Stop::
26033 * Packet Acknowledgment::
26035 * File-I/O Remote Protocol Extension::
26036 * Library List Format::
26037 * Memory Map Format::
26043 There may be occasions when you need to know something about the
26044 protocol---for example, if there is only one serial port to your target
26045 machine, you might want your program to do something special if it
26046 recognizes a packet meant for @value{GDBN}.
26048 In the examples below, @samp{->} and @samp{<-} are used to indicate
26049 transmitted and received data, respectively.
26051 @cindex protocol, @value{GDBN} remote serial
26052 @cindex serial protocol, @value{GDBN} remote
26053 @cindex remote serial protocol
26054 All @value{GDBN} commands and responses (other than acknowledgments
26055 and notifications, see @ref{Notification Packets}) are sent as a
26056 @var{packet}. A @var{packet} is introduced with the character
26057 @samp{$}, the actual @var{packet-data}, and the terminating character
26058 @samp{#} followed by a two-digit @var{checksum}:
26061 @code{$}@var{packet-data}@code{#}@var{checksum}
26065 @cindex checksum, for @value{GDBN} remote
26067 The two-digit @var{checksum} is computed as the modulo 256 sum of all
26068 characters between the leading @samp{$} and the trailing @samp{#} (an
26069 eight bit unsigned checksum).
26071 Implementors should note that prior to @value{GDBN} 5.0 the protocol
26072 specification also included an optional two-digit @var{sequence-id}:
26075 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
26078 @cindex sequence-id, for @value{GDBN} remote
26080 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
26081 has never output @var{sequence-id}s. Stubs that handle packets added
26082 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
26084 When either the host or the target machine receives a packet, the first
26085 response expected is an acknowledgment: either @samp{+} (to indicate
26086 the package was received correctly) or @samp{-} (to request
26090 -> @code{$}@var{packet-data}@code{#}@var{checksum}
26095 The @samp{+}/@samp{-} acknowledgments can be disabled
26096 once a connection is established.
26097 @xref{Packet Acknowledgment}, for details.
26099 The host (@value{GDBN}) sends @var{command}s, and the target (the
26100 debugging stub incorporated in your program) sends a @var{response}. In
26101 the case of step and continue @var{command}s, the response is only sent
26102 when the operation has completed, and the target has again stopped all
26103 threads in all attached processes. This is the default all-stop mode
26104 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
26105 execution mode; see @ref{Remote Non-Stop}, for details.
26107 @var{packet-data} consists of a sequence of characters with the
26108 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
26111 @cindex remote protocol, field separator
26112 Fields within the packet should be separated using @samp{,} @samp{;} or
26113 @samp{:}. Except where otherwise noted all numbers are represented in
26114 @sc{hex} with leading zeros suppressed.
26116 Implementors should note that prior to @value{GDBN} 5.0, the character
26117 @samp{:} could not appear as the third character in a packet (as it
26118 would potentially conflict with the @var{sequence-id}).
26120 @cindex remote protocol, binary data
26121 @anchor{Binary Data}
26122 Binary data in most packets is encoded either as two hexadecimal
26123 digits per byte of binary data. This allowed the traditional remote
26124 protocol to work over connections which were only seven-bit clean.
26125 Some packets designed more recently assume an eight-bit clean
26126 connection, and use a more efficient encoding to send and receive
26129 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
26130 as an escape character. Any escaped byte is transmitted as the escape
26131 character followed by the original character XORed with @code{0x20}.
26132 For example, the byte @code{0x7d} would be transmitted as the two
26133 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
26134 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
26135 @samp{@}}) must always be escaped. Responses sent by the stub
26136 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
26137 is not interpreted as the start of a run-length encoded sequence
26140 Response @var{data} can be run-length encoded to save space.
26141 Run-length encoding replaces runs of identical characters with one
26142 instance of the repeated character, followed by a @samp{*} and a
26143 repeat count. The repeat count is itself sent encoded, to avoid
26144 binary characters in @var{data}: a value of @var{n} is sent as
26145 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
26146 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
26147 code 32) for a repeat count of 3. (This is because run-length
26148 encoding starts to win for counts 3 or more.) Thus, for example,
26149 @samp{0* } is a run-length encoding of ``0000'': the space character
26150 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
26153 The printable characters @samp{#} and @samp{$} or with a numeric value
26154 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
26155 seven repeats (@samp{$}) can be expanded using a repeat count of only
26156 five (@samp{"}). For example, @samp{00000000} can be encoded as
26159 The error response returned for some packets includes a two character
26160 error number. That number is not well defined.
26162 @cindex empty response, for unsupported packets
26163 For any @var{command} not supported by the stub, an empty response
26164 (@samp{$#00}) should be returned. That way it is possible to extend the
26165 protocol. A newer @value{GDBN} can tell if a packet is supported based
26168 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
26169 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
26175 The following table provides a complete list of all currently defined
26176 @var{command}s and their corresponding response @var{data}.
26177 @xref{File-I/O Remote Protocol Extension}, for details about the File
26178 I/O extension of the remote protocol.
26180 Each packet's description has a template showing the packet's overall
26181 syntax, followed by an explanation of the packet's meaning. We
26182 include spaces in some of the templates for clarity; these are not
26183 part of the packet's syntax. No @value{GDBN} packet uses spaces to
26184 separate its components. For example, a template like @samp{foo
26185 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
26186 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
26187 @var{baz}. @value{GDBN} does not transmit a space character between the
26188 @samp{foo} and the @var{bar}, or between the @var{bar} and the
26191 @cindex @var{thread-id}, in remote protocol
26192 @anchor{thread-id syntax}
26193 Several packets and replies include a @var{thread-id} field to identify
26194 a thread. Normally these are positive numbers with a target-specific
26195 interpretation, formatted as big-endian hex strings. A @var{thread-id}
26196 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
26199 In addition, the remote protocol supports a multiprocess feature in
26200 which the @var{thread-id} syntax is extended to optionally include both
26201 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
26202 The @var{pid} (process) and @var{tid} (thread) components each have the
26203 format described above: a positive number with target-specific
26204 interpretation formatted as a big-endian hex string, literal @samp{-1}
26205 to indicate all processes or threads (respectively), or @samp{0} to
26206 indicate an arbitrary process or thread. Specifying just a process, as
26207 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
26208 error to specify all processes but a specific thread, such as
26209 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
26210 for those packets and replies explicitly documented to include a process
26211 ID, rather than a @var{thread-id}.
26213 The multiprocess @var{thread-id} syntax extensions are only used if both
26214 @value{GDBN} and the stub report support for the @samp{multiprocess}
26215 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
26218 Note that all packet forms beginning with an upper- or lower-case
26219 letter, other than those described here, are reserved for future use.
26221 Here are the packet descriptions.
26226 @cindex @samp{!} packet
26227 @anchor{extended mode}
26228 Enable extended mode. In extended mode, the remote server is made
26229 persistent. The @samp{R} packet is used to restart the program being
26235 The remote target both supports and has enabled extended mode.
26239 @cindex @samp{?} packet
26240 Indicate the reason the target halted. The reply is the same as for
26241 step and continue. This packet has a special interpretation when the
26242 target is in non-stop mode; see @ref{Remote Non-Stop}.
26245 @xref{Stop Reply Packets}, for the reply specifications.
26247 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
26248 @cindex @samp{A} packet
26249 Initialized @code{argv[]} array passed into program. @var{arglen}
26250 specifies the number of bytes in the hex encoded byte stream
26251 @var{arg}. See @code{gdbserver} for more details.
26256 The arguments were set.
26262 @cindex @samp{b} packet
26263 (Don't use this packet; its behavior is not well-defined.)
26264 Change the serial line speed to @var{baud}.
26266 JTC: @emph{When does the transport layer state change? When it's
26267 received, or after the ACK is transmitted. In either case, there are
26268 problems if the command or the acknowledgment packet is dropped.}
26270 Stan: @emph{If people really wanted to add something like this, and get
26271 it working for the first time, they ought to modify ser-unix.c to send
26272 some kind of out-of-band message to a specially-setup stub and have the
26273 switch happen "in between" packets, so that from remote protocol's point
26274 of view, nothing actually happened.}
26276 @item B @var{addr},@var{mode}
26277 @cindex @samp{B} packet
26278 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
26279 breakpoint at @var{addr}.
26281 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
26282 (@pxref{insert breakpoint or watchpoint packet}).
26285 @cindex @samp{bc} packet
26286 Backward continue. Execute the target system in reverse. No parameter.
26287 @xref{Reverse Execution}, for more information.
26290 @xref{Stop Reply Packets}, for the reply specifications.
26293 @cindex @samp{bs} packet
26294 Backward single step. Execute one instruction in reverse. No parameter.
26295 @xref{Reverse Execution}, for more information.
26298 @xref{Stop Reply Packets}, for the reply specifications.
26300 @item c @r{[}@var{addr}@r{]}
26301 @cindex @samp{c} packet
26302 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
26303 resume at current address.
26306 @xref{Stop Reply Packets}, for the reply specifications.
26308 @item C @var{sig}@r{[};@var{addr}@r{]}
26309 @cindex @samp{C} packet
26310 Continue with signal @var{sig} (hex signal number). If
26311 @samp{;@var{addr}} is omitted, resume at same address.
26314 @xref{Stop Reply Packets}, for the reply specifications.
26317 @cindex @samp{d} packet
26320 Don't use this packet; instead, define a general set packet
26321 (@pxref{General Query Packets}).
26325 @cindex @samp{D} packet
26326 The first form of the packet is used to detach @value{GDBN} from the
26327 remote system. It is sent to the remote target
26328 before @value{GDBN} disconnects via the @code{detach} command.
26330 The second form, including a process ID, is used when multiprocess
26331 protocol extensions are enabled (@pxref{multiprocess extensions}), to
26332 detach only a specific process. The @var{pid} is specified as a
26333 big-endian hex string.
26343 @item F @var{RC},@var{EE},@var{CF};@var{XX}
26344 @cindex @samp{F} packet
26345 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
26346 This is part of the File-I/O protocol extension. @xref{File-I/O
26347 Remote Protocol Extension}, for the specification.
26350 @anchor{read registers packet}
26351 @cindex @samp{g} packet
26352 Read general registers.
26356 @item @var{XX@dots{}}
26357 Each byte of register data is described by two hex digits. The bytes
26358 with the register are transmitted in target byte order. The size of
26359 each register and their position within the @samp{g} packet are
26360 determined by the @value{GDBN} internal gdbarch functions
26361 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
26362 specification of several standard @samp{g} packets is specified below.
26367 @item G @var{XX@dots{}}
26368 @cindex @samp{G} packet
26369 Write general registers. @xref{read registers packet}, for a
26370 description of the @var{XX@dots{}} data.
26380 @item H @var{c} @var{thread-id}
26381 @cindex @samp{H} packet
26382 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
26383 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
26384 should be @samp{c} for step and continue operations, @samp{g} for other
26385 operations. The thread designator @var{thread-id} has the format and
26386 interpretation described in @ref{thread-id syntax}.
26397 @c 'H': How restrictive (or permissive) is the thread model. If a
26398 @c thread is selected and stopped, are other threads allowed
26399 @c to continue to execute? As I mentioned above, I think the
26400 @c semantics of each command when a thread is selected must be
26401 @c described. For example:
26403 @c 'g': If the stub supports threads and a specific thread is
26404 @c selected, returns the register block from that thread;
26405 @c otherwise returns current registers.
26407 @c 'G' If the stub supports threads and a specific thread is
26408 @c selected, sets the registers of the register block of
26409 @c that thread; otherwise sets current registers.
26411 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
26412 @anchor{cycle step packet}
26413 @cindex @samp{i} packet
26414 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
26415 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
26416 step starting at that address.
26419 @cindex @samp{I} packet
26420 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
26424 @cindex @samp{k} packet
26427 FIXME: @emph{There is no description of how to operate when a specific
26428 thread context has been selected (i.e.@: does 'k' kill only that
26431 @item m @var{addr},@var{length}
26432 @cindex @samp{m} packet
26433 Read @var{length} bytes of memory starting at address @var{addr}.
26434 Note that @var{addr} may not be aligned to any particular boundary.
26436 The stub need not use any particular size or alignment when gathering
26437 data from memory for the response; even if @var{addr} is word-aligned
26438 and @var{length} is a multiple of the word size, the stub is free to
26439 use byte accesses, or not. For this reason, this packet may not be
26440 suitable for accessing memory-mapped I/O devices.
26441 @cindex alignment of remote memory accesses
26442 @cindex size of remote memory accesses
26443 @cindex memory, alignment and size of remote accesses
26447 @item @var{XX@dots{}}
26448 Memory contents; each byte is transmitted as a two-digit hexadecimal
26449 number. The reply may contain fewer bytes than requested if the
26450 server was able to read only part of the region of memory.
26455 @item M @var{addr},@var{length}:@var{XX@dots{}}
26456 @cindex @samp{M} packet
26457 Write @var{length} bytes of memory starting at address @var{addr}.
26458 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
26459 hexadecimal number.
26466 for an error (this includes the case where only part of the data was
26471 @cindex @samp{p} packet
26472 Read the value of register @var{n}; @var{n} is in hex.
26473 @xref{read registers packet}, for a description of how the returned
26474 register value is encoded.
26478 @item @var{XX@dots{}}
26479 the register's value
26483 Indicating an unrecognized @var{query}.
26486 @item P @var{n@dots{}}=@var{r@dots{}}
26487 @anchor{write register packet}
26488 @cindex @samp{P} packet
26489 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
26490 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
26491 digits for each byte in the register (target byte order).
26501 @item q @var{name} @var{params}@dots{}
26502 @itemx Q @var{name} @var{params}@dots{}
26503 @cindex @samp{q} packet
26504 @cindex @samp{Q} packet
26505 General query (@samp{q}) and set (@samp{Q}). These packets are
26506 described fully in @ref{General Query Packets}.
26509 @cindex @samp{r} packet
26510 Reset the entire system.
26512 Don't use this packet; use the @samp{R} packet instead.
26515 @cindex @samp{R} packet
26516 Restart the program being debugged. @var{XX}, while needed, is ignored.
26517 This packet is only available in extended mode (@pxref{extended mode}).
26519 The @samp{R} packet has no reply.
26521 @item s @r{[}@var{addr}@r{]}
26522 @cindex @samp{s} packet
26523 Single step. @var{addr} is the address at which to resume. If
26524 @var{addr} is omitted, resume at same address.
26527 @xref{Stop Reply Packets}, for the reply specifications.
26529 @item S @var{sig}@r{[};@var{addr}@r{]}
26530 @anchor{step with signal packet}
26531 @cindex @samp{S} packet
26532 Step with signal. This is analogous to the @samp{C} packet, but
26533 requests a single-step, rather than a normal resumption of execution.
26536 @xref{Stop Reply Packets}, for the reply specifications.
26538 @item t @var{addr}:@var{PP},@var{MM}
26539 @cindex @samp{t} packet
26540 Search backwards starting at address @var{addr} for a match with pattern
26541 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
26542 @var{addr} must be at least 3 digits.
26544 @item T @var{thread-id}
26545 @cindex @samp{T} packet
26546 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
26551 thread is still alive
26557 Packets starting with @samp{v} are identified by a multi-letter name,
26558 up to the first @samp{;} or @samp{?} (or the end of the packet).
26560 @item vAttach;@var{pid}
26561 @cindex @samp{vAttach} packet
26562 Attach to a new process with the specified process ID @var{pid}.
26563 The process ID is a
26564 hexadecimal integer identifying the process. In all-stop mode, all
26565 threads in the attached process are stopped; in non-stop mode, it may be
26566 attached without being stopped if that is supported by the target.
26568 @c In non-stop mode, on a successful vAttach, the stub should set the
26569 @c current thread to a thread of the newly-attached process. After
26570 @c attaching, GDB queries for the attached process's thread ID with qC.
26571 @c Also note that, from a user perspective, whether or not the
26572 @c target is stopped on attach in non-stop mode depends on whether you
26573 @c use the foreground or background version of the attach command, not
26574 @c on what vAttach does; GDB does the right thing with respect to either
26575 @c stopping or restarting threads.
26577 This packet is only available in extended mode (@pxref{extended mode}).
26583 @item @r{Any stop packet}
26584 for success in all-stop mode (@pxref{Stop Reply Packets})
26586 for success in non-stop mode (@pxref{Remote Non-Stop})
26589 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
26590 @cindex @samp{vCont} packet
26591 Resume the inferior, specifying different actions for each thread.
26592 If an action is specified with no @var{thread-id}, then it is applied to any
26593 threads that don't have a specific action specified; if no default action is
26594 specified then other threads should remain stopped in all-stop mode and
26595 in their current state in non-stop mode.
26596 Specifying multiple
26597 default actions is an error; specifying no actions is also an error.
26598 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
26600 Currently supported actions are:
26606 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
26610 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
26614 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
26617 The optional argument @var{addr} normally associated with the
26618 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
26619 not supported in @samp{vCont}.
26621 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
26622 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
26623 A stop reply should be generated for any affected thread not already stopped.
26624 When a thread is stopped by means of a @samp{t} action,
26625 the corresponding stop reply should indicate that the thread has stopped with
26626 signal @samp{0}, regardless of whether the target uses some other signal
26627 as an implementation detail.
26630 @xref{Stop Reply Packets}, for the reply specifications.
26633 @cindex @samp{vCont?} packet
26634 Request a list of actions supported by the @samp{vCont} packet.
26638 @item vCont@r{[};@var{action}@dots{}@r{]}
26639 The @samp{vCont} packet is supported. Each @var{action} is a supported
26640 command in the @samp{vCont} packet.
26642 The @samp{vCont} packet is not supported.
26645 @item vFile:@var{operation}:@var{parameter}@dots{}
26646 @cindex @samp{vFile} packet
26647 Perform a file operation on the target system. For details,
26648 see @ref{Host I/O Packets}.
26650 @item vFlashErase:@var{addr},@var{length}
26651 @cindex @samp{vFlashErase} packet
26652 Direct the stub to erase @var{length} bytes of flash starting at
26653 @var{addr}. The region may enclose any number of flash blocks, but
26654 its start and end must fall on block boundaries, as indicated by the
26655 flash block size appearing in the memory map (@pxref{Memory Map
26656 Format}). @value{GDBN} groups flash memory programming operations
26657 together, and sends a @samp{vFlashDone} request after each group; the
26658 stub is allowed to delay erase operation until the @samp{vFlashDone}
26659 packet is received.
26661 The stub must support @samp{vCont} if it reports support for
26662 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
26663 this case @samp{vCont} actions can be specified to apply to all threads
26664 in a process by using the @samp{p@var{pid}.-1} form of the
26675 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
26676 @cindex @samp{vFlashWrite} packet
26677 Direct the stub to write data to flash address @var{addr}. The data
26678 is passed in binary form using the same encoding as for the @samp{X}
26679 packet (@pxref{Binary Data}). The memory ranges specified by
26680 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
26681 not overlap, and must appear in order of increasing addresses
26682 (although @samp{vFlashErase} packets for higher addresses may already
26683 have been received; the ordering is guaranteed only between
26684 @samp{vFlashWrite} packets). If a packet writes to an address that was
26685 neither erased by a preceding @samp{vFlashErase} packet nor by some other
26686 target-specific method, the results are unpredictable.
26694 for vFlashWrite addressing non-flash memory
26700 @cindex @samp{vFlashDone} packet
26701 Indicate to the stub that flash programming operation is finished.
26702 The stub is permitted to delay or batch the effects of a group of
26703 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
26704 @samp{vFlashDone} packet is received. The contents of the affected
26705 regions of flash memory are unpredictable until the @samp{vFlashDone}
26706 request is completed.
26708 @item vKill;@var{pid}
26709 @cindex @samp{vKill} packet
26710 Kill the process with the specified process ID. @var{pid} is a
26711 hexadecimal integer identifying the process. This packet is used in
26712 preference to @samp{k} when multiprocess protocol extensions are
26713 supported; see @ref{multiprocess extensions}.
26723 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
26724 @cindex @samp{vRun} packet
26725 Run the program @var{filename}, passing it each @var{argument} on its
26726 command line. The file and arguments are hex-encoded strings. If
26727 @var{filename} is an empty string, the stub may use a default program
26728 (e.g.@: the last program run). The program is created in the stopped
26731 @c FIXME: What about non-stop mode?
26733 This packet is only available in extended mode (@pxref{extended mode}).
26739 @item @r{Any stop packet}
26740 for success (@pxref{Stop Reply Packets})
26744 @anchor{vStopped packet}
26745 @cindex @samp{vStopped} packet
26747 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
26748 reply and prompt for the stub to report another one.
26752 @item @r{Any stop packet}
26753 if there is another unreported stop event (@pxref{Stop Reply Packets})
26755 if there are no unreported stop events
26758 @item X @var{addr},@var{length}:@var{XX@dots{}}
26760 @cindex @samp{X} packet
26761 Write data to memory, where the data is transmitted in binary.
26762 @var{addr} is address, @var{length} is number of bytes,
26763 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
26773 @item z @var{type},@var{addr},@var{length}
26774 @itemx Z @var{type},@var{addr},@var{length}
26775 @anchor{insert breakpoint or watchpoint packet}
26776 @cindex @samp{z} packet
26777 @cindex @samp{Z} packets
26778 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
26779 watchpoint starting at address @var{address} and covering the next
26780 @var{length} bytes.
26782 Each breakpoint and watchpoint packet @var{type} is documented
26785 @emph{Implementation notes: A remote target shall return an empty string
26786 for an unrecognized breakpoint or watchpoint packet @var{type}. A
26787 remote target shall support either both or neither of a given
26788 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
26789 avoid potential problems with duplicate packets, the operations should
26790 be implemented in an idempotent way.}
26792 @item z0,@var{addr},@var{length}
26793 @itemx Z0,@var{addr},@var{length}
26794 @cindex @samp{z0} packet
26795 @cindex @samp{Z0} packet
26796 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
26797 @var{addr} of size @var{length}.
26799 A memory breakpoint is implemented by replacing the instruction at
26800 @var{addr} with a software breakpoint or trap instruction. The
26801 @var{length} is used by targets that indicates the size of the
26802 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
26803 @sc{mips} can insert either a 2 or 4 byte breakpoint).
26805 @emph{Implementation note: It is possible for a target to copy or move
26806 code that contains memory breakpoints (e.g., when implementing
26807 overlays). The behavior of this packet, in the presence of such a
26808 target, is not defined.}
26820 @item z1,@var{addr},@var{length}
26821 @itemx Z1,@var{addr},@var{length}
26822 @cindex @samp{z1} packet
26823 @cindex @samp{Z1} packet
26824 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
26825 address @var{addr} of size @var{length}.
26827 A hardware breakpoint is implemented using a mechanism that is not
26828 dependant on being able to modify the target's memory.
26830 @emph{Implementation note: A hardware breakpoint is not affected by code
26843 @item z2,@var{addr},@var{length}
26844 @itemx Z2,@var{addr},@var{length}
26845 @cindex @samp{z2} packet
26846 @cindex @samp{Z2} packet
26847 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
26859 @item z3,@var{addr},@var{length}
26860 @itemx Z3,@var{addr},@var{length}
26861 @cindex @samp{z3} packet
26862 @cindex @samp{Z3} packet
26863 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
26875 @item z4,@var{addr},@var{length}
26876 @itemx Z4,@var{addr},@var{length}
26877 @cindex @samp{z4} packet
26878 @cindex @samp{Z4} packet
26879 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
26893 @node Stop Reply Packets
26894 @section Stop Reply Packets
26895 @cindex stop reply packets
26897 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
26898 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
26899 receive any of the below as a reply. Except for @samp{?}
26900 and @samp{vStopped}, that reply is only returned
26901 when the target halts. In the below the exact meaning of @dfn{signal
26902 number} is defined by the header @file{include/gdb/signals.h} in the
26903 @value{GDBN} source code.
26905 As in the description of request packets, we include spaces in the
26906 reply templates for clarity; these are not part of the reply packet's
26907 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
26913 The program received signal number @var{AA} (a two-digit hexadecimal
26914 number). This is equivalent to a @samp{T} response with no
26915 @var{n}:@var{r} pairs.
26917 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
26918 @cindex @samp{T} packet reply
26919 The program received signal number @var{AA} (a two-digit hexadecimal
26920 number). This is equivalent to an @samp{S} response, except that the
26921 @samp{@var{n}:@var{r}} pairs can carry values of important registers
26922 and other information directly in the stop reply packet, reducing
26923 round-trip latency. Single-step and breakpoint traps are reported
26924 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
26928 If @var{n} is a hexadecimal number, it is a register number, and the
26929 corresponding @var{r} gives that register's value. @var{r} is a
26930 series of bytes in target byte order, with each byte given by a
26931 two-digit hex number.
26934 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
26935 the stopped thread, as specified in @ref{thread-id syntax}.
26938 If @var{n} is a recognized @dfn{stop reason}, it describes a more
26939 specific event that stopped the target. The currently defined stop
26940 reasons are listed below. @var{aa} should be @samp{05}, the trap
26941 signal. At most one stop reason should be present.
26944 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
26945 and go on to the next; this allows us to extend the protocol in the
26949 The currently defined stop reasons are:
26955 The packet indicates a watchpoint hit, and @var{r} is the data address, in
26958 @cindex shared library events, remote reply
26960 The packet indicates that the loaded libraries have changed.
26961 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
26962 list of loaded libraries. @var{r} is ignored.
26964 @cindex replay log events, remote reply
26966 The packet indicates that the target cannot continue replaying
26967 logged execution events, because it has reached the end (or the
26968 beginning when executing backward) of the log. The value of @var{r}
26969 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
26970 for more information.
26976 @itemx W @var{AA} ; process:@var{pid}
26977 The process exited, and @var{AA} is the exit status. This is only
26978 applicable to certain targets.
26980 The second form of the response, including the process ID of the exited
26981 process, can be used only when @value{GDBN} has reported support for
26982 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26983 The @var{pid} is formatted as a big-endian hex string.
26986 @itemx X @var{AA} ; process:@var{pid}
26987 The process terminated with signal @var{AA}.
26989 The second form of the response, including the process ID of the
26990 terminated process, can be used only when @value{GDBN} has reported
26991 support for multiprocess protocol extensions; see @ref{multiprocess
26992 extensions}. The @var{pid} is formatted as a big-endian hex string.
26994 @item O @var{XX}@dots{}
26995 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26996 written as the program's console output. This can happen at any time
26997 while the program is running and the debugger should continue to wait
26998 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
27000 @item F @var{call-id},@var{parameter}@dots{}
27001 @var{call-id} is the identifier which says which host system call should
27002 be called. This is just the name of the function. Translation into the
27003 correct system call is only applicable as it's defined in @value{GDBN}.
27004 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
27007 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
27008 this very system call.
27010 The target replies with this packet when it expects @value{GDBN} to
27011 call a host system call on behalf of the target. @value{GDBN} replies
27012 with an appropriate @samp{F} packet and keeps up waiting for the next
27013 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
27014 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
27015 Protocol Extension}, for more details.
27019 @node General Query Packets
27020 @section General Query Packets
27021 @cindex remote query requests
27023 Packets starting with @samp{q} are @dfn{general query packets};
27024 packets starting with @samp{Q} are @dfn{general set packets}. General
27025 query and set packets are a semi-unified form for retrieving and
27026 sending information to and from the stub.
27028 The initial letter of a query or set packet is followed by a name
27029 indicating what sort of thing the packet applies to. For example,
27030 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
27031 definitions with the stub. These packet names follow some
27036 The name must not contain commas, colons or semicolons.
27038 Most @value{GDBN} query and set packets have a leading upper case
27041 The names of custom vendor packets should use a company prefix, in
27042 lower case, followed by a period. For example, packets designed at
27043 the Acme Corporation might begin with @samp{qacme.foo} (for querying
27044 foos) or @samp{Qacme.bar} (for setting bars).
27047 The name of a query or set packet should be separated from any
27048 parameters by a @samp{:}; the parameters themselves should be
27049 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
27050 full packet name, and check for a separator or the end of the packet,
27051 in case two packet names share a common prefix. New packets should not begin
27052 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
27053 packets predate these conventions, and have arguments without any terminator
27054 for the packet name; we suspect they are in widespread use in places that
27055 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
27056 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
27059 Like the descriptions of the other packets, each description here
27060 has a template showing the packet's overall syntax, followed by an
27061 explanation of the packet's meaning. We include spaces in some of the
27062 templates for clarity; these are not part of the packet's syntax. No
27063 @value{GDBN} packet uses spaces to separate its components.
27065 Here are the currently defined query and set packets:
27070 @cindex current thread, remote request
27071 @cindex @samp{qC} packet
27072 Return the current thread ID.
27076 @item QC @var{thread-id}
27077 Where @var{thread-id} is a thread ID as documented in
27078 @ref{thread-id syntax}.
27079 @item @r{(anything else)}
27080 Any other reply implies the old thread ID.
27083 @item qCRC:@var{addr},@var{length}
27084 @cindex CRC of memory block, remote request
27085 @cindex @samp{qCRC} packet
27086 Compute the CRC checksum of a block of memory.
27090 An error (such as memory fault)
27091 @item C @var{crc32}
27092 The specified memory region's checksum is @var{crc32}.
27096 @itemx qsThreadInfo
27097 @cindex list active threads, remote request
27098 @cindex @samp{qfThreadInfo} packet
27099 @cindex @samp{qsThreadInfo} packet
27100 Obtain a list of all active thread IDs from the target (OS). Since there
27101 may be too many active threads to fit into one reply packet, this query
27102 works iteratively: it may require more than one query/reply sequence to
27103 obtain the entire list of threads. The first query of the sequence will
27104 be the @samp{qfThreadInfo} query; subsequent queries in the
27105 sequence will be the @samp{qsThreadInfo} query.
27107 NOTE: This packet replaces the @samp{qL} query (see below).
27111 @item m @var{thread-id}
27113 @item m @var{thread-id},@var{thread-id}@dots{}
27114 a comma-separated list of thread IDs
27116 (lower case letter @samp{L}) denotes end of list.
27119 In response to each query, the target will reply with a list of one or
27120 more thread IDs, separated by commas.
27121 @value{GDBN} will respond to each reply with a request for more thread
27122 ids (using the @samp{qs} form of the query), until the target responds
27123 with @samp{l} (lower-case el, for @dfn{last}).
27124 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
27127 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
27128 @cindex get thread-local storage address, remote request
27129 @cindex @samp{qGetTLSAddr} packet
27130 Fetch the address associated with thread local storage specified
27131 by @var{thread-id}, @var{offset}, and @var{lm}.
27133 @var{thread-id} is the thread ID associated with the
27134 thread for which to fetch the TLS address. @xref{thread-id syntax}.
27136 @var{offset} is the (big endian, hex encoded) offset associated with the
27137 thread local variable. (This offset is obtained from the debug
27138 information associated with the variable.)
27140 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
27141 the load module associated with the thread local storage. For example,
27142 a @sc{gnu}/Linux system will pass the link map address of the shared
27143 object associated with the thread local storage under consideration.
27144 Other operating environments may choose to represent the load module
27145 differently, so the precise meaning of this parameter will vary.
27149 @item @var{XX}@dots{}
27150 Hex encoded (big endian) bytes representing the address of the thread
27151 local storage requested.
27154 An error occurred. @var{nn} are hex digits.
27157 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
27160 @item qL @var{startflag} @var{threadcount} @var{nextthread}
27161 Obtain thread information from RTOS. Where: @var{startflag} (one hex
27162 digit) is one to indicate the first query and zero to indicate a
27163 subsequent query; @var{threadcount} (two hex digits) is the maximum
27164 number of threads the response packet can contain; and @var{nextthread}
27165 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
27166 returned in the response as @var{argthread}.
27168 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
27172 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
27173 Where: @var{count} (two hex digits) is the number of threads being
27174 returned; @var{done} (one hex digit) is zero to indicate more threads
27175 and one indicates no further threads; @var{argthreadid} (eight hex
27176 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
27177 is a sequence of thread IDs from the target. @var{threadid} (eight hex
27178 digits). See @code{remote.c:parse_threadlist_response()}.
27182 @cindex section offsets, remote request
27183 @cindex @samp{qOffsets} packet
27184 Get section offsets that the target used when relocating the downloaded
27189 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
27190 Relocate the @code{Text} section by @var{xxx} from its original address.
27191 Relocate the @code{Data} section by @var{yyy} from its original address.
27192 If the object file format provides segment information (e.g.@: @sc{elf}
27193 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
27194 segments by the supplied offsets.
27196 @emph{Note: while a @code{Bss} offset may be included in the response,
27197 @value{GDBN} ignores this and instead applies the @code{Data} offset
27198 to the @code{Bss} section.}
27200 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
27201 Relocate the first segment of the object file, which conventionally
27202 contains program code, to a starting address of @var{xxx}. If
27203 @samp{DataSeg} is specified, relocate the second segment, which
27204 conventionally contains modifiable data, to a starting address of
27205 @var{yyy}. @value{GDBN} will report an error if the object file
27206 does not contain segment information, or does not contain at least
27207 as many segments as mentioned in the reply. Extra segments are
27208 kept at fixed offsets relative to the last relocated segment.
27211 @item qP @var{mode} @var{thread-id}
27212 @cindex thread information, remote request
27213 @cindex @samp{qP} packet
27214 Returns information on @var{thread-id}. Where: @var{mode} is a hex
27215 encoded 32 bit mode; @var{thread-id} is a thread ID
27216 (@pxref{thread-id syntax}).
27218 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
27221 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
27225 @cindex non-stop mode, remote request
27226 @cindex @samp{QNonStop} packet
27228 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
27229 @xref{Remote Non-Stop}, for more information.
27234 The request succeeded.
27237 An error occurred. @var{nn} are hex digits.
27240 An empty reply indicates that @samp{QNonStop} is not supported by
27244 This packet is not probed by default; the remote stub must request it,
27245 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27246 Use of this packet is controlled by the @code{set non-stop} command;
27247 @pxref{Non-Stop Mode}.
27249 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
27250 @cindex pass signals to inferior, remote request
27251 @cindex @samp{QPassSignals} packet
27252 @anchor{QPassSignals}
27253 Each listed @var{signal} should be passed directly to the inferior process.
27254 Signals are numbered identically to continue packets and stop replies
27255 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
27256 strictly greater than the previous item. These signals do not need to stop
27257 the inferior, or be reported to @value{GDBN}. All other signals should be
27258 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
27259 combine; any earlier @samp{QPassSignals} list is completely replaced by the
27260 new list. This packet improves performance when using @samp{handle
27261 @var{signal} nostop noprint pass}.
27266 The request succeeded.
27269 An error occurred. @var{nn} are hex digits.
27272 An empty reply indicates that @samp{QPassSignals} is not supported by
27276 Use of this packet is controlled by the @code{set remote pass-signals}
27277 command (@pxref{Remote Configuration, set remote pass-signals}).
27278 This packet is not probed by default; the remote stub must request it,
27279 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27281 @item qRcmd,@var{command}
27282 @cindex execute remote command, remote request
27283 @cindex @samp{qRcmd} packet
27284 @var{command} (hex encoded) is passed to the local interpreter for
27285 execution. Invalid commands should be reported using the output
27286 string. Before the final result packet, the target may also respond
27287 with a number of intermediate @samp{O@var{output}} console output
27288 packets. @emph{Implementors should note that providing access to a
27289 stubs's interpreter may have security implications}.
27294 A command response with no output.
27296 A command response with the hex encoded output string @var{OUTPUT}.
27298 Indicate a badly formed request.
27300 An empty reply indicates that @samp{qRcmd} is not recognized.
27303 (Note that the @code{qRcmd} packet's name is separated from the
27304 command by a @samp{,}, not a @samp{:}, contrary to the naming
27305 conventions above. Please don't use this packet as a model for new
27308 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
27309 @cindex searching memory, in remote debugging
27310 @cindex @samp{qSearch:memory} packet
27311 @anchor{qSearch memory}
27312 Search @var{length} bytes at @var{address} for @var{search-pattern}.
27313 @var{address} and @var{length} are encoded in hex.
27314 @var{search-pattern} is a sequence of bytes, hex encoded.
27319 The pattern was not found.
27321 The pattern was found at @var{address}.
27323 A badly formed request or an error was encountered while searching memory.
27325 An empty reply indicates that @samp{qSearch:memory} is not recognized.
27328 @item QStartNoAckMode
27329 @cindex @samp{QStartNoAckMode} packet
27330 @anchor{QStartNoAckMode}
27331 Request that the remote stub disable the normal @samp{+}/@samp{-}
27332 protocol acknowledgments (@pxref{Packet Acknowledgment}).
27337 The stub has switched to no-acknowledgment mode.
27338 @value{GDBN} acknowledges this reponse,
27339 but neither the stub nor @value{GDBN} shall send or expect further
27340 @samp{+}/@samp{-} acknowledgments in the current connection.
27342 An empty reply indicates that the stub does not support no-acknowledgment mode.
27345 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
27346 @cindex supported packets, remote query
27347 @cindex features of the remote protocol
27348 @cindex @samp{qSupported} packet
27349 @anchor{qSupported}
27350 Tell the remote stub about features supported by @value{GDBN}, and
27351 query the stub for features it supports. This packet allows
27352 @value{GDBN} and the remote stub to take advantage of each others'
27353 features. @samp{qSupported} also consolidates multiple feature probes
27354 at startup, to improve @value{GDBN} performance---a single larger
27355 packet performs better than multiple smaller probe packets on
27356 high-latency links. Some features may enable behavior which must not
27357 be on by default, e.g.@: because it would confuse older clients or
27358 stubs. Other features may describe packets which could be
27359 automatically probed for, but are not. These features must be
27360 reported before @value{GDBN} will use them. This ``default
27361 unsupported'' behavior is not appropriate for all packets, but it
27362 helps to keep the initial connection time under control with new
27363 versions of @value{GDBN} which support increasing numbers of packets.
27367 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
27368 The stub supports or does not support each returned @var{stubfeature},
27369 depending on the form of each @var{stubfeature} (see below for the
27372 An empty reply indicates that @samp{qSupported} is not recognized,
27373 or that no features needed to be reported to @value{GDBN}.
27376 The allowed forms for each feature (either a @var{gdbfeature} in the
27377 @samp{qSupported} packet, or a @var{stubfeature} in the response)
27381 @item @var{name}=@var{value}
27382 The remote protocol feature @var{name} is supported, and associated
27383 with the specified @var{value}. The format of @var{value} depends
27384 on the feature, but it must not include a semicolon.
27386 The remote protocol feature @var{name} is supported, and does not
27387 need an associated value.
27389 The remote protocol feature @var{name} is not supported.
27391 The remote protocol feature @var{name} may be supported, and
27392 @value{GDBN} should auto-detect support in some other way when it is
27393 needed. This form will not be used for @var{gdbfeature} notifications,
27394 but may be used for @var{stubfeature} responses.
27397 Whenever the stub receives a @samp{qSupported} request, the
27398 supplied set of @value{GDBN} features should override any previous
27399 request. This allows @value{GDBN} to put the stub in a known
27400 state, even if the stub had previously been communicating with
27401 a different version of @value{GDBN}.
27403 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
27408 This feature indicates whether @value{GDBN} supports multiprocess
27409 extensions to the remote protocol. @value{GDBN} does not use such
27410 extensions unless the stub also reports that it supports them by
27411 including @samp{multiprocess+} in its @samp{qSupported} reply.
27412 @xref{multiprocess extensions}, for details.
27415 Stubs should ignore any unknown values for
27416 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
27417 packet supports receiving packets of unlimited length (earlier
27418 versions of @value{GDBN} may reject overly long responses). Additional values
27419 for @var{gdbfeature} may be defined in the future to let the stub take
27420 advantage of new features in @value{GDBN}, e.g.@: incompatible
27421 improvements in the remote protocol---the @samp{multiprocess} feature is
27422 an example of such a feature. The stub's reply should be independent
27423 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
27424 describes all the features it supports, and then the stub replies with
27425 all the features it supports.
27427 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
27428 responses, as long as each response uses one of the standard forms.
27430 Some features are flags. A stub which supports a flag feature
27431 should respond with a @samp{+} form response. Other features
27432 require values, and the stub should respond with an @samp{=}
27435 Each feature has a default value, which @value{GDBN} will use if
27436 @samp{qSupported} is not available or if the feature is not mentioned
27437 in the @samp{qSupported} response. The default values are fixed; a
27438 stub is free to omit any feature responses that match the defaults.
27440 Not all features can be probed, but for those which can, the probing
27441 mechanism is useful: in some cases, a stub's internal
27442 architecture may not allow the protocol layer to know some information
27443 about the underlying target in advance. This is especially common in
27444 stubs which may be configured for multiple targets.
27446 These are the currently defined stub features and their properties:
27448 @multitable @columnfractions 0.35 0.2 0.12 0.2
27449 @c NOTE: The first row should be @headitem, but we do not yet require
27450 @c a new enough version of Texinfo (4.7) to use @headitem.
27452 @tab Value Required
27456 @item @samp{PacketSize}
27461 @item @samp{qXfer:auxv:read}
27466 @item @samp{qXfer:features:read}
27471 @item @samp{qXfer:libraries:read}
27476 @item @samp{qXfer:memory-map:read}
27481 @item @samp{qXfer:spu:read}
27486 @item @samp{qXfer:spu:write}
27491 @item @samp{qXfer:siginfo:read}
27496 @item @samp{qXfer:siginfo:write}
27501 @item @samp{QNonStop}
27506 @item @samp{QPassSignals}
27511 @item @samp{QStartNoAckMode}
27516 @item @samp{multiprocess}
27523 These are the currently defined stub features, in more detail:
27526 @cindex packet size, remote protocol
27527 @item PacketSize=@var{bytes}
27528 The remote stub can accept packets up to at least @var{bytes} in
27529 length. @value{GDBN} will send packets up to this size for bulk
27530 transfers, and will never send larger packets. This is a limit on the
27531 data characters in the packet, including the frame and checksum.
27532 There is no trailing NUL byte in a remote protocol packet; if the stub
27533 stores packets in a NUL-terminated format, it should allow an extra
27534 byte in its buffer for the NUL. If this stub feature is not supported,
27535 @value{GDBN} guesses based on the size of the @samp{g} packet response.
27537 @item qXfer:auxv:read
27538 The remote stub understands the @samp{qXfer:auxv:read} packet
27539 (@pxref{qXfer auxiliary vector read}).
27541 @item qXfer:features:read
27542 The remote stub understands the @samp{qXfer:features:read} packet
27543 (@pxref{qXfer target description read}).
27545 @item qXfer:libraries:read
27546 The remote stub understands the @samp{qXfer:libraries:read} packet
27547 (@pxref{qXfer library list read}).
27549 @item qXfer:memory-map:read
27550 The remote stub understands the @samp{qXfer:memory-map:read} packet
27551 (@pxref{qXfer memory map read}).
27553 @item qXfer:spu:read
27554 The remote stub understands the @samp{qXfer:spu:read} packet
27555 (@pxref{qXfer spu read}).
27557 @item qXfer:spu:write
27558 The remote stub understands the @samp{qXfer:spu:write} packet
27559 (@pxref{qXfer spu write}).
27561 @item qXfer:siginfo:read
27562 The remote stub understands the @samp{qXfer:siginfo:read} packet
27563 (@pxref{qXfer siginfo read}).
27565 @item qXfer:siginfo:write
27566 The remote stub understands the @samp{qXfer:siginfo:write} packet
27567 (@pxref{qXfer siginfo write}).
27570 The remote stub understands the @samp{QNonStop} packet
27571 (@pxref{QNonStop}).
27574 The remote stub understands the @samp{QPassSignals} packet
27575 (@pxref{QPassSignals}).
27577 @item QStartNoAckMode
27578 The remote stub understands the @samp{QStartNoAckMode} packet and
27579 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
27582 @anchor{multiprocess extensions}
27583 @cindex multiprocess extensions, in remote protocol
27584 The remote stub understands the multiprocess extensions to the remote
27585 protocol syntax. The multiprocess extensions affect the syntax of
27586 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
27587 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
27588 replies. Note that reporting this feature indicates support for the
27589 syntactic extensions only, not that the stub necessarily supports
27590 debugging of more than one process at a time. The stub must not use
27591 multiprocess extensions in packet replies unless @value{GDBN} has also
27592 indicated it supports them in its @samp{qSupported} request.
27594 @item qXfer:osdata:read
27595 The remote stub understands the @samp{qXfer:osdata:read} packet
27596 ((@pxref{qXfer osdata read}).
27601 @cindex symbol lookup, remote request
27602 @cindex @samp{qSymbol} packet
27603 Notify the target that @value{GDBN} is prepared to serve symbol lookup
27604 requests. Accept requests from the target for the values of symbols.
27609 The target does not need to look up any (more) symbols.
27610 @item qSymbol:@var{sym_name}
27611 The target requests the value of symbol @var{sym_name} (hex encoded).
27612 @value{GDBN} may provide the value by using the
27613 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
27617 @item qSymbol:@var{sym_value}:@var{sym_name}
27618 Set the value of @var{sym_name} to @var{sym_value}.
27620 @var{sym_name} (hex encoded) is the name of a symbol whose value the
27621 target has previously requested.
27623 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
27624 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
27630 The target does not need to look up any (more) symbols.
27631 @item qSymbol:@var{sym_name}
27632 The target requests the value of a new symbol @var{sym_name} (hex
27633 encoded). @value{GDBN} will continue to supply the values of symbols
27634 (if available), until the target ceases to request them.
27639 @xref{Tracepoint Packets}.
27641 @item qThreadExtraInfo,@var{thread-id}
27642 @cindex thread attributes info, remote request
27643 @cindex @samp{qThreadExtraInfo} packet
27644 Obtain a printable string description of a thread's attributes from
27645 the target OS. @var{thread-id} is a thread ID;
27646 see @ref{thread-id syntax}. This
27647 string may contain anything that the target OS thinks is interesting
27648 for @value{GDBN} to tell the user about the thread. The string is
27649 displayed in @value{GDBN}'s @code{info threads} display. Some
27650 examples of possible thread extra info strings are @samp{Runnable}, or
27651 @samp{Blocked on Mutex}.
27655 @item @var{XX}@dots{}
27656 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
27657 comprising the printable string containing the extra information about
27658 the thread's attributes.
27661 (Note that the @code{qThreadExtraInfo} packet's name is separated from
27662 the command by a @samp{,}, not a @samp{:}, contrary to the naming
27663 conventions above. Please don't use this packet as a model for new
27671 @xref{Tracepoint Packets}.
27673 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
27674 @cindex read special object, remote request
27675 @cindex @samp{qXfer} packet
27676 @anchor{qXfer read}
27677 Read uninterpreted bytes from the target's special data area
27678 identified by the keyword @var{object}. Request @var{length} bytes
27679 starting at @var{offset} bytes into the data. The content and
27680 encoding of @var{annex} is specific to @var{object}; it can supply
27681 additional details about what data to access.
27683 Here are the specific requests of this form defined so far. All
27684 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
27685 formats, listed below.
27688 @item qXfer:auxv:read::@var{offset},@var{length}
27689 @anchor{qXfer auxiliary vector read}
27690 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
27691 auxiliary vector}. Note @var{annex} must be empty.
27693 This packet is not probed by default; the remote stub must request it,
27694 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27696 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
27697 @anchor{qXfer target description read}
27698 Access the @dfn{target description}. @xref{Target Descriptions}. The
27699 annex specifies which XML document to access. The main description is
27700 always loaded from the @samp{target.xml} annex.
27702 This packet is not probed by default; the remote stub must request it,
27703 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27705 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
27706 @anchor{qXfer library list read}
27707 Access the target's list of loaded libraries. @xref{Library List Format}.
27708 The annex part of the generic @samp{qXfer} packet must be empty
27709 (@pxref{qXfer read}).
27711 Targets which maintain a list of libraries in the program's memory do
27712 not need to implement this packet; it is designed for platforms where
27713 the operating system manages the list of loaded libraries.
27715 This packet is not probed by default; the remote stub must request it,
27716 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27718 @item qXfer:memory-map:read::@var{offset},@var{length}
27719 @anchor{qXfer memory map read}
27720 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
27721 annex part of the generic @samp{qXfer} packet must be empty
27722 (@pxref{qXfer read}).
27724 This packet is not probed by default; the remote stub must request it,
27725 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27727 @item qXfer:siginfo:read::@var{offset},@var{length}
27728 @anchor{qXfer siginfo read}
27729 Read contents of the extra signal information on the target
27730 system. The annex part of the generic @samp{qXfer} packet must be
27731 empty (@pxref{qXfer read}).
27733 This packet is not probed by default; the remote stub must request it,
27734 by supplying an appropriate @samp{qSupported} response
27735 (@pxref{qSupported}).
27737 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
27738 @anchor{qXfer spu read}
27739 Read contents of an @code{spufs} file on the target system. The
27740 annex specifies which file to read; it must be of the form
27741 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27742 in the target process, and @var{name} identifes the @code{spufs} file
27743 in that context to be accessed.
27745 This packet is not probed by default; the remote stub must request it,
27746 by supplying an appropriate @samp{qSupported} response
27747 (@pxref{qSupported}).
27749 @item qXfer:osdata:read::@var{offset},@var{length}
27750 @anchor{qXfer osdata read}
27751 Access the target's @dfn{operating system information}.
27752 @xref{Operating System Information}.
27759 Data @var{data} (@pxref{Binary Data}) has been read from the
27760 target. There may be more data at a higher address (although
27761 it is permitted to return @samp{m} even for the last valid
27762 block of data, as long as at least one byte of data was read).
27763 @var{data} may have fewer bytes than the @var{length} in the
27767 Data @var{data} (@pxref{Binary Data}) has been read from the target.
27768 There is no more data to be read. @var{data} may have fewer bytes
27769 than the @var{length} in the request.
27772 The @var{offset} in the request is at the end of the data.
27773 There is no more data to be read.
27776 The request was malformed, or @var{annex} was invalid.
27779 The offset was invalid, or there was an error encountered reading the data.
27780 @var{nn} is a hex-encoded @code{errno} value.
27783 An empty reply indicates the @var{object} string was not recognized by
27784 the stub, or that the object does not support reading.
27787 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
27788 @cindex write data into object, remote request
27789 @anchor{qXfer write}
27790 Write uninterpreted bytes into the target's special data area
27791 identified by the keyword @var{object}, starting at @var{offset} bytes
27792 into the data. @var{data}@dots{} is the binary-encoded data
27793 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
27794 is specific to @var{object}; it can supply additional details about what data
27797 Here are the specific requests of this form defined so far. All
27798 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
27799 formats, listed below.
27802 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
27803 @anchor{qXfer siginfo write}
27804 Write @var{data} to the extra signal information on the target system.
27805 The annex part of the generic @samp{qXfer} packet must be
27806 empty (@pxref{qXfer write}).
27808 This packet is not probed by default; the remote stub must request it,
27809 by supplying an appropriate @samp{qSupported} response
27810 (@pxref{qSupported}).
27812 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
27813 @anchor{qXfer spu write}
27814 Write @var{data} to an @code{spufs} file on the target system. The
27815 annex specifies which file to write; it must be of the form
27816 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27817 in the target process, and @var{name} identifes the @code{spufs} file
27818 in that context to be accessed.
27820 This packet is not probed by default; the remote stub must request it,
27821 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27827 @var{nn} (hex encoded) is the number of bytes written.
27828 This may be fewer bytes than supplied in the request.
27831 The request was malformed, or @var{annex} was invalid.
27834 The offset was invalid, or there was an error encountered writing the data.
27835 @var{nn} is a hex-encoded @code{errno} value.
27838 An empty reply indicates the @var{object} string was not
27839 recognized by the stub, or that the object does not support writing.
27842 @item qXfer:@var{object}:@var{operation}:@dots{}
27843 Requests of this form may be added in the future. When a stub does
27844 not recognize the @var{object} keyword, or its support for
27845 @var{object} does not recognize the @var{operation} keyword, the stub
27846 must respond with an empty packet.
27848 @item qAttached:@var{pid}
27849 @cindex query attached, remote request
27850 @cindex @samp{qAttached} packet
27851 Return an indication of whether the remote server attached to an
27852 existing process or created a new process. When the multiprocess
27853 protocol extensions are supported (@pxref{multiprocess extensions}),
27854 @var{pid} is an integer in hexadecimal format identifying the target
27855 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
27856 the query packet will be simplified as @samp{qAttached}.
27858 This query is used, for example, to know whether the remote process
27859 should be detached or killed when a @value{GDBN} session is ended with
27860 the @code{quit} command.
27865 The remote server attached to an existing process.
27867 The remote server created a new process.
27869 A badly formed request or an error was encountered.
27874 @node Register Packet Format
27875 @section Register Packet Format
27877 The following @code{g}/@code{G} packets have previously been defined.
27878 In the below, some thirty-two bit registers are transferred as
27879 sixty-four bits. Those registers should be zero/sign extended (which?)
27880 to fill the space allocated. Register bytes are transferred in target
27881 byte order. The two nibbles within a register byte are transferred
27882 most-significant - least-significant.
27888 All registers are transferred as thirty-two bit quantities in the order:
27889 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
27890 registers; fsr; fir; fp.
27894 All registers are transferred as sixty-four bit quantities (including
27895 thirty-two bit registers such as @code{sr}). The ordering is the same
27900 @node Tracepoint Packets
27901 @section Tracepoint Packets
27902 @cindex tracepoint packets
27903 @cindex packets, tracepoint
27905 Here we describe the packets @value{GDBN} uses to implement
27906 tracepoints (@pxref{Tracepoints}).
27910 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
27911 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
27912 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
27913 the tracepoint is disabled. @var{step} is the tracepoint's step
27914 count, and @var{pass} is its pass count. If the trailing @samp{-} is
27915 present, further @samp{QTDP} packets will follow to specify this
27916 tracepoint's actions.
27921 The packet was understood and carried out.
27923 The packet was not recognized.
27926 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
27927 Define actions to be taken when a tracepoint is hit. @var{n} and
27928 @var{addr} must be the same as in the initial @samp{QTDP} packet for
27929 this tracepoint. This packet may only be sent immediately after
27930 another @samp{QTDP} packet that ended with a @samp{-}. If the
27931 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
27932 specifying more actions for this tracepoint.
27934 In the series of action packets for a given tracepoint, at most one
27935 can have an @samp{S} before its first @var{action}. If such a packet
27936 is sent, it and the following packets define ``while-stepping''
27937 actions. Any prior packets define ordinary actions --- that is, those
27938 taken when the tracepoint is first hit. If no action packet has an
27939 @samp{S}, then all the packets in the series specify ordinary
27940 tracepoint actions.
27942 The @samp{@var{action}@dots{}} portion of the packet is a series of
27943 actions, concatenated without separators. Each action has one of the
27949 Collect the registers whose bits are set in @var{mask}. @var{mask} is
27950 a hexadecimal number whose @var{i}'th bit is set if register number
27951 @var{i} should be collected. (The least significant bit is numbered
27952 zero.) Note that @var{mask} may be any number of digits long; it may
27953 not fit in a 32-bit word.
27955 @item M @var{basereg},@var{offset},@var{len}
27956 Collect @var{len} bytes of memory starting at the address in register
27957 number @var{basereg}, plus @var{offset}. If @var{basereg} is
27958 @samp{-1}, then the range has a fixed address: @var{offset} is the
27959 address of the lowest byte to collect. The @var{basereg},
27960 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
27961 values (the @samp{-1} value for @var{basereg} is a special case).
27963 @item X @var{len},@var{expr}
27964 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
27965 it directs. @var{expr} is an agent expression, as described in
27966 @ref{Agent Expressions}. Each byte of the expression is encoded as a
27967 two-digit hex number in the packet; @var{len} is the number of bytes
27968 in the expression (and thus one-half the number of hex digits in the
27973 Any number of actions may be packed together in a single @samp{QTDP}
27974 packet, as long as the packet does not exceed the maximum packet
27975 length (400 bytes, for many stubs). There may be only one @samp{R}
27976 action per tracepoint, and it must precede any @samp{M} or @samp{X}
27977 actions. Any registers referred to by @samp{M} and @samp{X} actions
27978 must be collected by a preceding @samp{R} action. (The
27979 ``while-stepping'' actions are treated as if they were attached to a
27980 separate tracepoint, as far as these restrictions are concerned.)
27985 The packet was understood and carried out.
27987 The packet was not recognized.
27990 @item QTFrame:@var{n}
27991 Select the @var{n}'th tracepoint frame from the buffer, and use the
27992 register and memory contents recorded there to answer subsequent
27993 request packets from @value{GDBN}.
27995 A successful reply from the stub indicates that the stub has found the
27996 requested frame. The response is a series of parts, concatenated
27997 without separators, describing the frame we selected. Each part has
27998 one of the following forms:
28002 The selected frame is number @var{n} in the trace frame buffer;
28003 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
28004 was no frame matching the criteria in the request packet.
28007 The selected trace frame records a hit of tracepoint number @var{t};
28008 @var{t} is a hexadecimal number.
28012 @item QTFrame:pc:@var{addr}
28013 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
28014 currently selected frame whose PC is @var{addr};
28015 @var{addr} is a hexadecimal number.
28017 @item QTFrame:tdp:@var{t}
28018 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
28019 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
28020 is a hexadecimal number.
28022 @item QTFrame:range:@var{start}:@var{end}
28023 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
28024 currently selected frame whose PC is between @var{start} (inclusive)
28025 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
28028 @item QTFrame:outside:@var{start}:@var{end}
28029 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
28030 frame @emph{outside} the given range of addresses.
28033 Begin the tracepoint experiment. Begin collecting data from tracepoint
28034 hits in the trace frame buffer.
28037 End the tracepoint experiment. Stop collecting trace frames.
28040 Clear the table of tracepoints, and empty the trace frame buffer.
28042 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
28043 Establish the given ranges of memory as ``transparent''. The stub
28044 will answer requests for these ranges from memory's current contents,
28045 if they were not collected as part of the tracepoint hit.
28047 @value{GDBN} uses this to mark read-only regions of memory, like those
28048 containing program code. Since these areas never change, they should
28049 still have the same contents they did when the tracepoint was hit, so
28050 there's no reason for the stub to refuse to provide their contents.
28053 Ask the stub if there is a trace experiment running right now.
28058 There is no trace experiment running.
28060 There is a trace experiment running.
28066 @node Host I/O Packets
28067 @section Host I/O Packets
28068 @cindex Host I/O, remote protocol
28069 @cindex file transfer, remote protocol
28071 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
28072 operations on the far side of a remote link. For example, Host I/O is
28073 used to upload and download files to a remote target with its own
28074 filesystem. Host I/O uses the same constant values and data structure
28075 layout as the target-initiated File-I/O protocol. However, the
28076 Host I/O packets are structured differently. The target-initiated
28077 protocol relies on target memory to store parameters and buffers.
28078 Host I/O requests are initiated by @value{GDBN}, and the
28079 target's memory is not involved. @xref{File-I/O Remote Protocol
28080 Extension}, for more details on the target-initiated protocol.
28082 The Host I/O request packets all encode a single operation along with
28083 its arguments. They have this format:
28087 @item vFile:@var{operation}: @var{parameter}@dots{}
28088 @var{operation} is the name of the particular request; the target
28089 should compare the entire packet name up to the second colon when checking
28090 for a supported operation. The format of @var{parameter} depends on
28091 the operation. Numbers are always passed in hexadecimal. Negative
28092 numbers have an explicit minus sign (i.e.@: two's complement is not
28093 used). Strings (e.g.@: filenames) are encoded as a series of
28094 hexadecimal bytes. The last argument to a system call may be a
28095 buffer of escaped binary data (@pxref{Binary Data}).
28099 The valid responses to Host I/O packets are:
28103 @item F @var{result} [, @var{errno}] [; @var{attachment}]
28104 @var{result} is the integer value returned by this operation, usually
28105 non-negative for success and -1 for errors. If an error has occured,
28106 @var{errno} will be included in the result. @var{errno} will have a
28107 value defined by the File-I/O protocol (@pxref{Errno Values}). For
28108 operations which return data, @var{attachment} supplies the data as a
28109 binary buffer. Binary buffers in response packets are escaped in the
28110 normal way (@pxref{Binary Data}). See the individual packet
28111 documentation for the interpretation of @var{result} and
28115 An empty response indicates that this operation is not recognized.
28119 These are the supported Host I/O operations:
28122 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
28123 Open a file at @var{pathname} and return a file descriptor for it, or
28124 return -1 if an error occurs. @var{pathname} is a string,
28125 @var{flags} is an integer indicating a mask of open flags
28126 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
28127 of mode bits to use if the file is created (@pxref{mode_t Values}).
28128 @xref{open}, for details of the open flags and mode values.
28130 @item vFile:close: @var{fd}
28131 Close the open file corresponding to @var{fd} and return 0, or
28132 -1 if an error occurs.
28134 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
28135 Read data from the open file corresponding to @var{fd}. Up to
28136 @var{count} bytes will be read from the file, starting at @var{offset}
28137 relative to the start of the file. The target may read fewer bytes;
28138 common reasons include packet size limits and an end-of-file
28139 condition. The number of bytes read is returned. Zero should only be
28140 returned for a successful read at the end of the file, or if
28141 @var{count} was zero.
28143 The data read should be returned as a binary attachment on success.
28144 If zero bytes were read, the response should include an empty binary
28145 attachment (i.e.@: a trailing semicolon). The return value is the
28146 number of target bytes read; the binary attachment may be longer if
28147 some characters were escaped.
28149 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
28150 Write @var{data} (a binary buffer) to the open file corresponding
28151 to @var{fd}. Start the write at @var{offset} from the start of the
28152 file. Unlike many @code{write} system calls, there is no
28153 separate @var{count} argument; the length of @var{data} in the
28154 packet is used. @samp{vFile:write} returns the number of bytes written,
28155 which may be shorter than the length of @var{data}, or -1 if an
28158 @item vFile:unlink: @var{pathname}
28159 Delete the file at @var{pathname} on the target. Return 0,
28160 or -1 if an error occurs. @var{pathname} is a string.
28165 @section Interrupts
28166 @cindex interrupts (remote protocol)
28168 When a program on the remote target is running, @value{GDBN} may
28169 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
28170 control of which is specified via @value{GDBN}'s @samp{remotebreak}
28171 setting (@pxref{set remotebreak}).
28173 The precise meaning of @code{BREAK} is defined by the transport
28174 mechanism and may, in fact, be undefined. @value{GDBN} does not
28175 currently define a @code{BREAK} mechanism for any of the network
28176 interfaces except for TCP, in which case @value{GDBN} sends the
28177 @code{telnet} BREAK sequence.
28179 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
28180 transport mechanisms. It is represented by sending the single byte
28181 @code{0x03} without any of the usual packet overhead described in
28182 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
28183 transmitted as part of a packet, it is considered to be packet data
28184 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
28185 (@pxref{X packet}), used for binary downloads, may include an unescaped
28186 @code{0x03} as part of its packet.
28188 Stubs are not required to recognize these interrupt mechanisms and the
28189 precise meaning associated with receipt of the interrupt is
28190 implementation defined. If the target supports debugging of multiple
28191 threads and/or processes, it should attempt to interrupt all
28192 currently-executing threads and processes.
28193 If the stub is successful at interrupting the
28194 running program, it should send one of the stop
28195 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
28196 of successfully stopping the program in all-stop mode, and a stop reply
28197 for each stopped thread in non-stop mode.
28198 Interrupts received while the
28199 program is stopped are discarded.
28201 @node Notification Packets
28202 @section Notification Packets
28203 @cindex notification packets
28204 @cindex packets, notification
28206 The @value{GDBN} remote serial protocol includes @dfn{notifications},
28207 packets that require no acknowledgment. Both the GDB and the stub
28208 may send notifications (although the only notifications defined at
28209 present are sent by the stub). Notifications carry information
28210 without incurring the round-trip latency of an acknowledgment, and so
28211 are useful for low-impact communications where occasional packet loss
28214 A notification packet has the form @samp{% @var{data} #
28215 @var{checksum}}, where @var{data} is the content of the notification,
28216 and @var{checksum} is a checksum of @var{data}, computed and formatted
28217 as for ordinary @value{GDBN} packets. A notification's @var{data}
28218 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
28219 receiving a notification, the recipient sends no @samp{+} or @samp{-}
28220 to acknowledge the notification's receipt or to report its corruption.
28222 Every notification's @var{data} begins with a name, which contains no
28223 colon characters, followed by a colon character.
28225 Recipients should silently ignore corrupted notifications and
28226 notifications they do not understand. Recipients should restart
28227 timeout periods on receipt of a well-formed notification, whether or
28228 not they understand it.
28230 Senders should only send the notifications described here when this
28231 protocol description specifies that they are permitted. In the
28232 future, we may extend the protocol to permit existing notifications in
28233 new contexts; this rule helps older senders avoid confusing newer
28236 (Older versions of @value{GDBN} ignore bytes received until they see
28237 the @samp{$} byte that begins an ordinary packet, so new stubs may
28238 transmit notifications without fear of confusing older clients. There
28239 are no notifications defined for @value{GDBN} to send at the moment, but we
28240 assume that most older stubs would ignore them, as well.)
28242 The following notification packets from the stub to @value{GDBN} are
28246 @item Stop: @var{reply}
28247 Report an asynchronous stop event in non-stop mode.
28248 The @var{reply} has the form of a stop reply, as
28249 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
28250 for information on how these notifications are acknowledged by
28254 @node Remote Non-Stop
28255 @section Remote Protocol Support for Non-Stop Mode
28257 @value{GDBN}'s remote protocol supports non-stop debugging of
28258 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
28259 supports non-stop mode, it should report that to @value{GDBN} by including
28260 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
28262 @value{GDBN} typically sends a @samp{QNonStop} packet only when
28263 establishing a new connection with the stub. Entering non-stop mode
28264 does not alter the state of any currently-running threads, but targets
28265 must stop all threads in any already-attached processes when entering
28266 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
28267 probe the target state after a mode change.
28269 In non-stop mode, when an attached process encounters an event that
28270 would otherwise be reported with a stop reply, it uses the
28271 asynchronous notification mechanism (@pxref{Notification Packets}) to
28272 inform @value{GDBN}. In contrast to all-stop mode, where all threads
28273 in all processes are stopped when a stop reply is sent, in non-stop
28274 mode only the thread reporting the stop event is stopped. That is,
28275 when reporting a @samp{S} or @samp{T} response to indicate completion
28276 of a step operation, hitting a breakpoint, or a fault, only the
28277 affected thread is stopped; any other still-running threads continue
28278 to run. When reporting a @samp{W} or @samp{X} response, all running
28279 threads belonging to other attached processes continue to run.
28281 Only one stop reply notification at a time may be pending; if
28282 additional stop events occur before @value{GDBN} has acknowledged the
28283 previous notification, they must be queued by the stub for later
28284 synchronous transmission in response to @samp{vStopped} packets from
28285 @value{GDBN}. Because the notification mechanism is unreliable,
28286 the stub is permitted to resend a stop reply notification
28287 if it believes @value{GDBN} may not have received it. @value{GDBN}
28288 ignores additional stop reply notifications received before it has
28289 finished processing a previous notification and the stub has completed
28290 sending any queued stop events.
28292 Otherwise, @value{GDBN} must be prepared to receive a stop reply
28293 notification at any time. Specifically, they may appear when
28294 @value{GDBN} is not otherwise reading input from the stub, or when
28295 @value{GDBN} is expecting to read a normal synchronous response or a
28296 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
28297 Notification packets are distinct from any other communication from
28298 the stub so there is no ambiguity.
28300 After receiving a stop reply notification, @value{GDBN} shall
28301 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
28302 as a regular, synchronous request to the stub. Such acknowledgment
28303 is not required to happen immediately, as @value{GDBN} is permitted to
28304 send other, unrelated packets to the stub first, which the stub should
28307 Upon receiving a @samp{vStopped} packet, if the stub has other queued
28308 stop events to report to @value{GDBN}, it shall respond by sending a
28309 normal stop reply response. @value{GDBN} shall then send another
28310 @samp{vStopped} packet to solicit further responses; again, it is
28311 permitted to send other, unrelated packets as well which the stub
28312 should process normally.
28314 If the stub receives a @samp{vStopped} packet and there are no
28315 additional stop events to report, the stub shall return an @samp{OK}
28316 response. At this point, if further stop events occur, the stub shall
28317 send a new stop reply notification, @value{GDBN} shall accept the
28318 notification, and the process shall be repeated.
28320 In non-stop mode, the target shall respond to the @samp{?} packet as
28321 follows. First, any incomplete stop reply notification/@samp{vStopped}
28322 sequence in progress is abandoned. The target must begin a new
28323 sequence reporting stop events for all stopped threads, whether or not
28324 it has previously reported those events to @value{GDBN}. The first
28325 stop reply is sent as a synchronous reply to the @samp{?} packet, and
28326 subsequent stop replies are sent as responses to @samp{vStopped} packets
28327 using the mechanism described above. The target must not send
28328 asynchronous stop reply notifications until the sequence is complete.
28329 If all threads are running when the target receives the @samp{?} packet,
28330 or if the target is not attached to any process, it shall respond
28333 @node Packet Acknowledgment
28334 @section Packet Acknowledgment
28336 @cindex acknowledgment, for @value{GDBN} remote
28337 @cindex packet acknowledgment, for @value{GDBN} remote
28338 By default, when either the host or the target machine receives a packet,
28339 the first response expected is an acknowledgment: either @samp{+} (to indicate
28340 the package was received correctly) or @samp{-} (to request retransmission).
28341 This mechanism allows the @value{GDBN} remote protocol to operate over
28342 unreliable transport mechanisms, such as a serial line.
28344 In cases where the transport mechanism is itself reliable (such as a pipe or
28345 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
28346 It may be desirable to disable them in that case to reduce communication
28347 overhead, or for other reasons. This can be accomplished by means of the
28348 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
28350 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
28351 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
28352 and response format still includes the normal checksum, as described in
28353 @ref{Overview}, but the checksum may be ignored by the receiver.
28355 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
28356 no-acknowledgment mode, it should report that to @value{GDBN}
28357 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
28358 @pxref{qSupported}.
28359 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
28360 disabled via the @code{set remote noack-packet off} command
28361 (@pxref{Remote Configuration}),
28362 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
28363 Only then may the stub actually turn off packet acknowledgments.
28364 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
28365 response, which can be safely ignored by the stub.
28367 Note that @code{set remote noack-packet} command only affects negotiation
28368 between @value{GDBN} and the stub when subsequent connections are made;
28369 it does not affect the protocol acknowledgment state for any current
28371 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
28372 new connection is established,
28373 there is also no protocol request to re-enable the acknowledgments
28374 for the current connection, once disabled.
28379 Example sequence of a target being re-started. Notice how the restart
28380 does not get any direct output:
28385 @emph{target restarts}
28388 <- @code{T001:1234123412341234}
28392 Example sequence of a target being stepped by a single instruction:
28395 -> @code{G1445@dots{}}
28400 <- @code{T001:1234123412341234}
28404 <- @code{1455@dots{}}
28408 @node File-I/O Remote Protocol Extension
28409 @section File-I/O Remote Protocol Extension
28410 @cindex File-I/O remote protocol extension
28413 * File-I/O Overview::
28414 * Protocol Basics::
28415 * The F Request Packet::
28416 * The F Reply Packet::
28417 * The Ctrl-C Message::
28419 * List of Supported Calls::
28420 * Protocol-specific Representation of Datatypes::
28422 * File-I/O Examples::
28425 @node File-I/O Overview
28426 @subsection File-I/O Overview
28427 @cindex file-i/o overview
28429 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
28430 target to use the host's file system and console I/O to perform various
28431 system calls. System calls on the target system are translated into a
28432 remote protocol packet to the host system, which then performs the needed
28433 actions and returns a response packet to the target system.
28434 This simulates file system operations even on targets that lack file systems.
28436 The protocol is defined to be independent of both the host and target systems.
28437 It uses its own internal representation of datatypes and values. Both
28438 @value{GDBN} and the target's @value{GDBN} stub are responsible for
28439 translating the system-dependent value representations into the internal
28440 protocol representations when data is transmitted.
28442 The communication is synchronous. A system call is possible only when
28443 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
28444 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
28445 the target is stopped to allow deterministic access to the target's
28446 memory. Therefore File-I/O is not interruptible by target signals. On
28447 the other hand, it is possible to interrupt File-I/O by a user interrupt
28448 (@samp{Ctrl-C}) within @value{GDBN}.
28450 The target's request to perform a host system call does not finish
28451 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
28452 after finishing the system call, the target returns to continuing the
28453 previous activity (continue, step). No additional continue or step
28454 request from @value{GDBN} is required.
28457 (@value{GDBP}) continue
28458 <- target requests 'system call X'
28459 target is stopped, @value{GDBN} executes system call
28460 -> @value{GDBN} returns result
28461 ... target continues, @value{GDBN} returns to wait for the target
28462 <- target hits breakpoint and sends a Txx packet
28465 The protocol only supports I/O on the console and to regular files on
28466 the host file system. Character or block special devices, pipes,
28467 named pipes, sockets or any other communication method on the host
28468 system are not supported by this protocol.
28470 File I/O is not supported in non-stop mode.
28472 @node Protocol Basics
28473 @subsection Protocol Basics
28474 @cindex protocol basics, file-i/o
28476 The File-I/O protocol uses the @code{F} packet as the request as well
28477 as reply packet. Since a File-I/O system call can only occur when
28478 @value{GDBN} is waiting for a response from the continuing or stepping target,
28479 the File-I/O request is a reply that @value{GDBN} has to expect as a result
28480 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
28481 This @code{F} packet contains all information needed to allow @value{GDBN}
28482 to call the appropriate host system call:
28486 A unique identifier for the requested system call.
28489 All parameters to the system call. Pointers are given as addresses
28490 in the target memory address space. Pointers to strings are given as
28491 pointer/length pair. Numerical values are given as they are.
28492 Numerical control flags are given in a protocol-specific representation.
28496 At this point, @value{GDBN} has to perform the following actions.
28500 If the parameters include pointer values to data needed as input to a
28501 system call, @value{GDBN} requests this data from the target with a
28502 standard @code{m} packet request. This additional communication has to be
28503 expected by the target implementation and is handled as any other @code{m}
28507 @value{GDBN} translates all value from protocol representation to host
28508 representation as needed. Datatypes are coerced into the host types.
28511 @value{GDBN} calls the system call.
28514 It then coerces datatypes back to protocol representation.
28517 If the system call is expected to return data in buffer space specified
28518 by pointer parameters to the call, the data is transmitted to the
28519 target using a @code{M} or @code{X} packet. This packet has to be expected
28520 by the target implementation and is handled as any other @code{M} or @code{X}
28525 Eventually @value{GDBN} replies with another @code{F} packet which contains all
28526 necessary information for the target to continue. This at least contains
28533 @code{errno}, if has been changed by the system call.
28540 After having done the needed type and value coercion, the target continues
28541 the latest continue or step action.
28543 @node The F Request Packet
28544 @subsection The @code{F} Request Packet
28545 @cindex file-i/o request packet
28546 @cindex @code{F} request packet
28548 The @code{F} request packet has the following format:
28551 @item F@var{call-id},@var{parameter@dots{}}
28553 @var{call-id} is the identifier to indicate the host system call to be called.
28554 This is just the name of the function.
28556 @var{parameter@dots{}} are the parameters to the system call.
28557 Parameters are hexadecimal integer values, either the actual values in case
28558 of scalar datatypes, pointers to target buffer space in case of compound
28559 datatypes and unspecified memory areas, or pointer/length pairs in case
28560 of string parameters. These are appended to the @var{call-id} as a
28561 comma-delimited list. All values are transmitted in ASCII
28562 string representation, pointer/length pairs separated by a slash.
28568 @node The F Reply Packet
28569 @subsection The @code{F} Reply Packet
28570 @cindex file-i/o reply packet
28571 @cindex @code{F} reply packet
28573 The @code{F} reply packet has the following format:
28577 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
28579 @var{retcode} is the return code of the system call as hexadecimal value.
28581 @var{errno} is the @code{errno} set by the call, in protocol-specific
28583 This parameter can be omitted if the call was successful.
28585 @var{Ctrl-C flag} is only sent if the user requested a break. In this
28586 case, @var{errno} must be sent as well, even if the call was successful.
28587 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
28594 or, if the call was interrupted before the host call has been performed:
28601 assuming 4 is the protocol-specific representation of @code{EINTR}.
28606 @node The Ctrl-C Message
28607 @subsection The @samp{Ctrl-C} Message
28608 @cindex ctrl-c message, in file-i/o protocol
28610 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
28611 reply packet (@pxref{The F Reply Packet}),
28612 the target should behave as if it had
28613 gotten a break message. The meaning for the target is ``system call
28614 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
28615 (as with a break message) and return to @value{GDBN} with a @code{T02}
28618 It's important for the target to know in which
28619 state the system call was interrupted. There are two possible cases:
28623 The system call hasn't been performed on the host yet.
28626 The system call on the host has been finished.
28630 These two states can be distinguished by the target by the value of the
28631 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
28632 call hasn't been performed. This is equivalent to the @code{EINTR} handling
28633 on POSIX systems. In any other case, the target may presume that the
28634 system call has been finished --- successfully or not --- and should behave
28635 as if the break message arrived right after the system call.
28637 @value{GDBN} must behave reliably. If the system call has not been called
28638 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
28639 @code{errno} in the packet. If the system call on the host has been finished
28640 before the user requests a break, the full action must be finished by
28641 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
28642 The @code{F} packet may only be sent when either nothing has happened
28643 or the full action has been completed.
28646 @subsection Console I/O
28647 @cindex console i/o as part of file-i/o
28649 By default and if not explicitly closed by the target system, the file
28650 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
28651 on the @value{GDBN} console is handled as any other file output operation
28652 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
28653 by @value{GDBN} so that after the target read request from file descriptor
28654 0 all following typing is buffered until either one of the following
28659 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
28661 system call is treated as finished.
28664 The user presses @key{RET}. This is treated as end of input with a trailing
28668 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
28669 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
28673 If the user has typed more characters than fit in the buffer given to
28674 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
28675 either another @code{read(0, @dots{})} is requested by the target, or debugging
28676 is stopped at the user's request.
28679 @node List of Supported Calls
28680 @subsection List of Supported Calls
28681 @cindex list of supported file-i/o calls
28698 @unnumberedsubsubsec open
28699 @cindex open, file-i/o system call
28704 int open(const char *pathname, int flags);
28705 int open(const char *pathname, int flags, mode_t mode);
28709 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
28712 @var{flags} is the bitwise @code{OR} of the following values:
28716 If the file does not exist it will be created. The host
28717 rules apply as far as file ownership and time stamps
28721 When used with @code{O_CREAT}, if the file already exists it is
28722 an error and open() fails.
28725 If the file already exists and the open mode allows
28726 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
28727 truncated to zero length.
28730 The file is opened in append mode.
28733 The file is opened for reading only.
28736 The file is opened for writing only.
28739 The file is opened for reading and writing.
28743 Other bits are silently ignored.
28747 @var{mode} is the bitwise @code{OR} of the following values:
28751 User has read permission.
28754 User has write permission.
28757 Group has read permission.
28760 Group has write permission.
28763 Others have read permission.
28766 Others have write permission.
28770 Other bits are silently ignored.
28773 @item Return value:
28774 @code{open} returns the new file descriptor or -1 if an error
28781 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
28784 @var{pathname} refers to a directory.
28787 The requested access is not allowed.
28790 @var{pathname} was too long.
28793 A directory component in @var{pathname} does not exist.
28796 @var{pathname} refers to a device, pipe, named pipe or socket.
28799 @var{pathname} refers to a file on a read-only filesystem and
28800 write access was requested.
28803 @var{pathname} is an invalid pointer value.
28806 No space on device to create the file.
28809 The process already has the maximum number of files open.
28812 The limit on the total number of files open on the system
28816 The call was interrupted by the user.
28822 @unnumberedsubsubsec close
28823 @cindex close, file-i/o system call
28832 @samp{Fclose,@var{fd}}
28834 @item Return value:
28835 @code{close} returns zero on success, or -1 if an error occurred.
28841 @var{fd} isn't a valid open file descriptor.
28844 The call was interrupted by the user.
28850 @unnumberedsubsubsec read
28851 @cindex read, file-i/o system call
28856 int read(int fd, void *buf, unsigned int count);
28860 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
28862 @item Return value:
28863 On success, the number of bytes read is returned.
28864 Zero indicates end of file. If count is zero, read
28865 returns zero as well. On error, -1 is returned.
28871 @var{fd} is not a valid file descriptor or is not open for
28875 @var{bufptr} is an invalid pointer value.
28878 The call was interrupted by the user.
28884 @unnumberedsubsubsec write
28885 @cindex write, file-i/o system call
28890 int write(int fd, const void *buf, unsigned int count);
28894 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
28896 @item Return value:
28897 On success, the number of bytes written are returned.
28898 Zero indicates nothing was written. On error, -1
28905 @var{fd} is not a valid file descriptor or is not open for
28909 @var{bufptr} is an invalid pointer value.
28912 An attempt was made to write a file that exceeds the
28913 host-specific maximum file size allowed.
28916 No space on device to write the data.
28919 The call was interrupted by the user.
28925 @unnumberedsubsubsec lseek
28926 @cindex lseek, file-i/o system call
28931 long lseek (int fd, long offset, int flag);
28935 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
28937 @var{flag} is one of:
28941 The offset is set to @var{offset} bytes.
28944 The offset is set to its current location plus @var{offset}
28948 The offset is set to the size of the file plus @var{offset}
28952 @item Return value:
28953 On success, the resulting unsigned offset in bytes from
28954 the beginning of the file is returned. Otherwise, a
28955 value of -1 is returned.
28961 @var{fd} is not a valid open file descriptor.
28964 @var{fd} is associated with the @value{GDBN} console.
28967 @var{flag} is not a proper value.
28970 The call was interrupted by the user.
28976 @unnumberedsubsubsec rename
28977 @cindex rename, file-i/o system call
28982 int rename(const char *oldpath, const char *newpath);
28986 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
28988 @item Return value:
28989 On success, zero is returned. On error, -1 is returned.
28995 @var{newpath} is an existing directory, but @var{oldpath} is not a
28999 @var{newpath} is a non-empty directory.
29002 @var{oldpath} or @var{newpath} is a directory that is in use by some
29006 An attempt was made to make a directory a subdirectory
29010 A component used as a directory in @var{oldpath} or new
29011 path is not a directory. Or @var{oldpath} is a directory
29012 and @var{newpath} exists but is not a directory.
29015 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
29018 No access to the file or the path of the file.
29022 @var{oldpath} or @var{newpath} was too long.
29025 A directory component in @var{oldpath} or @var{newpath} does not exist.
29028 The file is on a read-only filesystem.
29031 The device containing the file has no room for the new
29035 The call was interrupted by the user.
29041 @unnumberedsubsubsec unlink
29042 @cindex unlink, file-i/o system call
29047 int unlink(const char *pathname);
29051 @samp{Funlink,@var{pathnameptr}/@var{len}}
29053 @item Return value:
29054 On success, zero is returned. On error, -1 is returned.
29060 No access to the file or the path of the file.
29063 The system does not allow unlinking of directories.
29066 The file @var{pathname} cannot be unlinked because it's
29067 being used by another process.
29070 @var{pathnameptr} is an invalid pointer value.
29073 @var{pathname} was too long.
29076 A directory component in @var{pathname} does not exist.
29079 A component of the path is not a directory.
29082 The file is on a read-only filesystem.
29085 The call was interrupted by the user.
29091 @unnumberedsubsubsec stat/fstat
29092 @cindex fstat, file-i/o system call
29093 @cindex stat, file-i/o system call
29098 int stat(const char *pathname, struct stat *buf);
29099 int fstat(int fd, struct stat *buf);
29103 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
29104 @samp{Ffstat,@var{fd},@var{bufptr}}
29106 @item Return value:
29107 On success, zero is returned. On error, -1 is returned.
29113 @var{fd} is not a valid open file.
29116 A directory component in @var{pathname} does not exist or the
29117 path is an empty string.
29120 A component of the path is not a directory.
29123 @var{pathnameptr} is an invalid pointer value.
29126 No access to the file or the path of the file.
29129 @var{pathname} was too long.
29132 The call was interrupted by the user.
29138 @unnumberedsubsubsec gettimeofday
29139 @cindex gettimeofday, file-i/o system call
29144 int gettimeofday(struct timeval *tv, void *tz);
29148 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
29150 @item Return value:
29151 On success, 0 is returned, -1 otherwise.
29157 @var{tz} is a non-NULL pointer.
29160 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
29166 @unnumberedsubsubsec isatty
29167 @cindex isatty, file-i/o system call
29172 int isatty(int fd);
29176 @samp{Fisatty,@var{fd}}
29178 @item Return value:
29179 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
29185 The call was interrupted by the user.
29190 Note that the @code{isatty} call is treated as a special case: it returns
29191 1 to the target if the file descriptor is attached
29192 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
29193 would require implementing @code{ioctl} and would be more complex than
29198 @unnumberedsubsubsec system
29199 @cindex system, file-i/o system call
29204 int system(const char *command);
29208 @samp{Fsystem,@var{commandptr}/@var{len}}
29210 @item Return value:
29211 If @var{len} is zero, the return value indicates whether a shell is
29212 available. A zero return value indicates a shell is not available.
29213 For non-zero @var{len}, the value returned is -1 on error and the
29214 return status of the command otherwise. Only the exit status of the
29215 command is returned, which is extracted from the host's @code{system}
29216 return value by calling @code{WEXITSTATUS(retval)}. In case
29217 @file{/bin/sh} could not be executed, 127 is returned.
29223 The call was interrupted by the user.
29228 @value{GDBN} takes over the full task of calling the necessary host calls
29229 to perform the @code{system} call. The return value of @code{system} on
29230 the host is simplified before it's returned
29231 to the target. Any termination signal information from the child process
29232 is discarded, and the return value consists
29233 entirely of the exit status of the called command.
29235 Due to security concerns, the @code{system} call is by default refused
29236 by @value{GDBN}. The user has to allow this call explicitly with the
29237 @code{set remote system-call-allowed 1} command.
29240 @item set remote system-call-allowed
29241 @kindex set remote system-call-allowed
29242 Control whether to allow the @code{system} calls in the File I/O
29243 protocol for the remote target. The default is zero (disabled).
29245 @item show remote system-call-allowed
29246 @kindex show remote system-call-allowed
29247 Show whether the @code{system} calls are allowed in the File I/O
29251 @node Protocol-specific Representation of Datatypes
29252 @subsection Protocol-specific Representation of Datatypes
29253 @cindex protocol-specific representation of datatypes, in file-i/o protocol
29256 * Integral Datatypes::
29258 * Memory Transfer::
29263 @node Integral Datatypes
29264 @unnumberedsubsubsec Integral Datatypes
29265 @cindex integral datatypes, in file-i/o protocol
29267 The integral datatypes used in the system calls are @code{int},
29268 @code{unsigned int}, @code{long}, @code{unsigned long},
29269 @code{mode_t}, and @code{time_t}.
29271 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
29272 implemented as 32 bit values in this protocol.
29274 @code{long} and @code{unsigned long} are implemented as 64 bit types.
29276 @xref{Limits}, for corresponding MIN and MAX values (similar to those
29277 in @file{limits.h}) to allow range checking on host and target.
29279 @code{time_t} datatypes are defined as seconds since the Epoch.
29281 All integral datatypes transferred as part of a memory read or write of a
29282 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
29285 @node Pointer Values
29286 @unnumberedsubsubsec Pointer Values
29287 @cindex pointer values, in file-i/o protocol
29289 Pointers to target data are transmitted as they are. An exception
29290 is made for pointers to buffers for which the length isn't
29291 transmitted as part of the function call, namely strings. Strings
29292 are transmitted as a pointer/length pair, both as hex values, e.g.@:
29299 which is a pointer to data of length 18 bytes at position 0x1aaf.
29300 The length is defined as the full string length in bytes, including
29301 the trailing null byte. For example, the string @code{"hello world"}
29302 at address 0x123456 is transmitted as
29308 @node Memory Transfer
29309 @unnumberedsubsubsec Memory Transfer
29310 @cindex memory transfer, in file-i/o protocol
29312 Structured data which is transferred using a memory read or write (for
29313 example, a @code{struct stat}) is expected to be in a protocol-specific format
29314 with all scalar multibyte datatypes being big endian. Translation to
29315 this representation needs to be done both by the target before the @code{F}
29316 packet is sent, and by @value{GDBN} before
29317 it transfers memory to the target. Transferred pointers to structured
29318 data should point to the already-coerced data at any time.
29322 @unnumberedsubsubsec struct stat
29323 @cindex struct stat, in file-i/o protocol
29325 The buffer of type @code{struct stat} used by the target and @value{GDBN}
29326 is defined as follows:
29330 unsigned int st_dev; /* device */
29331 unsigned int st_ino; /* inode */
29332 mode_t st_mode; /* protection */
29333 unsigned int st_nlink; /* number of hard links */
29334 unsigned int st_uid; /* user ID of owner */
29335 unsigned int st_gid; /* group ID of owner */
29336 unsigned int st_rdev; /* device type (if inode device) */
29337 unsigned long st_size; /* total size, in bytes */
29338 unsigned long st_blksize; /* blocksize for filesystem I/O */
29339 unsigned long st_blocks; /* number of blocks allocated */
29340 time_t st_atime; /* time of last access */
29341 time_t st_mtime; /* time of last modification */
29342 time_t st_ctime; /* time of last change */
29346 The integral datatypes conform to the definitions given in the
29347 appropriate section (see @ref{Integral Datatypes}, for details) so this
29348 structure is of size 64 bytes.
29350 The values of several fields have a restricted meaning and/or
29356 A value of 0 represents a file, 1 the console.
29359 No valid meaning for the target. Transmitted unchanged.
29362 Valid mode bits are described in @ref{Constants}. Any other
29363 bits have currently no meaning for the target.
29368 No valid meaning for the target. Transmitted unchanged.
29373 These values have a host and file system dependent
29374 accuracy. Especially on Windows hosts, the file system may not
29375 support exact timing values.
29378 The target gets a @code{struct stat} of the above representation and is
29379 responsible for coercing it to the target representation before
29382 Note that due to size differences between the host, target, and protocol
29383 representations of @code{struct stat} members, these members could eventually
29384 get truncated on the target.
29386 @node struct timeval
29387 @unnumberedsubsubsec struct timeval
29388 @cindex struct timeval, in file-i/o protocol
29390 The buffer of type @code{struct timeval} used by the File-I/O protocol
29391 is defined as follows:
29395 time_t tv_sec; /* second */
29396 long tv_usec; /* microsecond */
29400 The integral datatypes conform to the definitions given in the
29401 appropriate section (see @ref{Integral Datatypes}, for details) so this
29402 structure is of size 8 bytes.
29405 @subsection Constants
29406 @cindex constants, in file-i/o protocol
29408 The following values are used for the constants inside of the
29409 protocol. @value{GDBN} and target are responsible for translating these
29410 values before and after the call as needed.
29421 @unnumberedsubsubsec Open Flags
29422 @cindex open flags, in file-i/o protocol
29424 All values are given in hexadecimal representation.
29436 @node mode_t Values
29437 @unnumberedsubsubsec mode_t Values
29438 @cindex mode_t values, in file-i/o protocol
29440 All values are given in octal representation.
29457 @unnumberedsubsubsec Errno Values
29458 @cindex errno values, in file-i/o protocol
29460 All values are given in decimal representation.
29485 @code{EUNKNOWN} is used as a fallback error value if a host system returns
29486 any error value not in the list of supported error numbers.
29489 @unnumberedsubsubsec Lseek Flags
29490 @cindex lseek flags, in file-i/o protocol
29499 @unnumberedsubsubsec Limits
29500 @cindex limits, in file-i/o protocol
29502 All values are given in decimal representation.
29505 INT_MIN -2147483648
29507 UINT_MAX 4294967295
29508 LONG_MIN -9223372036854775808
29509 LONG_MAX 9223372036854775807
29510 ULONG_MAX 18446744073709551615
29513 @node File-I/O Examples
29514 @subsection File-I/O Examples
29515 @cindex file-i/o examples
29517 Example sequence of a write call, file descriptor 3, buffer is at target
29518 address 0x1234, 6 bytes should be written:
29521 <- @code{Fwrite,3,1234,6}
29522 @emph{request memory read from target}
29525 @emph{return "6 bytes written"}
29529 Example sequence of a read call, file descriptor 3, buffer is at target
29530 address 0x1234, 6 bytes should be read:
29533 <- @code{Fread,3,1234,6}
29534 @emph{request memory write to target}
29535 -> @code{X1234,6:XXXXXX}
29536 @emph{return "6 bytes read"}
29540 Example sequence of a read call, call fails on the host due to invalid
29541 file descriptor (@code{EBADF}):
29544 <- @code{Fread,3,1234,6}
29548 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
29552 <- @code{Fread,3,1234,6}
29557 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
29561 <- @code{Fread,3,1234,6}
29562 -> @code{X1234,6:XXXXXX}
29566 @node Library List Format
29567 @section Library List Format
29568 @cindex library list format, remote protocol
29570 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
29571 same process as your application to manage libraries. In this case,
29572 @value{GDBN} can use the loader's symbol table and normal memory
29573 operations to maintain a list of shared libraries. On other
29574 platforms, the operating system manages loaded libraries.
29575 @value{GDBN} can not retrieve the list of currently loaded libraries
29576 through memory operations, so it uses the @samp{qXfer:libraries:read}
29577 packet (@pxref{qXfer library list read}) instead. The remote stub
29578 queries the target's operating system and reports which libraries
29581 The @samp{qXfer:libraries:read} packet returns an XML document which
29582 lists loaded libraries and their offsets. Each library has an
29583 associated name and one or more segment or section base addresses,
29584 which report where the library was loaded in memory.
29586 For the common case of libraries that are fully linked binaries, the
29587 library should have a list of segments. If the target supports
29588 dynamic linking of a relocatable object file, its library XML element
29589 should instead include a list of allocated sections. The segment or
29590 section bases are start addresses, not relocation offsets; they do not
29591 depend on the library's link-time base addresses.
29593 @value{GDBN} must be linked with the Expat library to support XML
29594 library lists. @xref{Expat}.
29596 A simple memory map, with one loaded library relocated by a single
29597 offset, looks like this:
29601 <library name="/lib/libc.so.6">
29602 <segment address="0x10000000"/>
29607 Another simple memory map, with one loaded library with three
29608 allocated sections (.text, .data, .bss), looks like this:
29612 <library name="sharedlib.o">
29613 <section address="0x10000000"/>
29614 <section address="0x20000000"/>
29615 <section address="0x30000000"/>
29620 The format of a library list is described by this DTD:
29623 <!-- library-list: Root element with versioning -->
29624 <!ELEMENT library-list (library)*>
29625 <!ATTLIST library-list version CDATA #FIXED "1.0">
29626 <!ELEMENT library (segment*, section*)>
29627 <!ATTLIST library name CDATA #REQUIRED>
29628 <!ELEMENT segment EMPTY>
29629 <!ATTLIST segment address CDATA #REQUIRED>
29630 <!ELEMENT section EMPTY>
29631 <!ATTLIST section address CDATA #REQUIRED>
29634 In addition, segments and section descriptors cannot be mixed within a
29635 single library element, and you must supply at least one segment or
29636 section for each library.
29638 @node Memory Map Format
29639 @section Memory Map Format
29640 @cindex memory map format
29642 To be able to write into flash memory, @value{GDBN} needs to obtain a
29643 memory map from the target. This section describes the format of the
29646 The memory map is obtained using the @samp{qXfer:memory-map:read}
29647 (@pxref{qXfer memory map read}) packet and is an XML document that
29648 lists memory regions.
29650 @value{GDBN} must be linked with the Expat library to support XML
29651 memory maps. @xref{Expat}.
29653 The top-level structure of the document is shown below:
29656 <?xml version="1.0"?>
29657 <!DOCTYPE memory-map
29658 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
29659 "http://sourceware.org/gdb/gdb-memory-map.dtd">
29665 Each region can be either:
29670 A region of RAM starting at @var{addr} and extending for @var{length}
29674 <memory type="ram" start="@var{addr}" length="@var{length}"/>
29679 A region of read-only memory:
29682 <memory type="rom" start="@var{addr}" length="@var{length}"/>
29687 A region of flash memory, with erasure blocks @var{blocksize}
29691 <memory type="flash" start="@var{addr}" length="@var{length}">
29692 <property name="blocksize">@var{blocksize}</property>
29698 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
29699 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
29700 packets to write to addresses in such ranges.
29702 The formal DTD for memory map format is given below:
29705 <!-- ................................................... -->
29706 <!-- Memory Map XML DTD ................................ -->
29707 <!-- File: memory-map.dtd .............................. -->
29708 <!-- .................................... .............. -->
29709 <!-- memory-map.dtd -->
29710 <!-- memory-map: Root element with versioning -->
29711 <!ELEMENT memory-map (memory | property)>
29712 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
29713 <!ELEMENT memory (property)>
29714 <!-- memory: Specifies a memory region,
29715 and its type, or device. -->
29716 <!ATTLIST memory type CDATA #REQUIRED
29717 start CDATA #REQUIRED
29718 length CDATA #REQUIRED
29719 device CDATA #IMPLIED>
29720 <!-- property: Generic attribute tag -->
29721 <!ELEMENT property (#PCDATA | property)*>
29722 <!ATTLIST property name CDATA #REQUIRED>
29725 @include agentexpr.texi
29727 @node Target Descriptions
29728 @appendix Target Descriptions
29729 @cindex target descriptions
29731 @strong{Warning:} target descriptions are still under active development,
29732 and the contents and format may change between @value{GDBN} releases.
29733 The format is expected to stabilize in the future.
29735 One of the challenges of using @value{GDBN} to debug embedded systems
29736 is that there are so many minor variants of each processor
29737 architecture in use. It is common practice for vendors to start with
29738 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
29739 and then make changes to adapt it to a particular market niche. Some
29740 architectures have hundreds of variants, available from dozens of
29741 vendors. This leads to a number of problems:
29745 With so many different customized processors, it is difficult for
29746 the @value{GDBN} maintainers to keep up with the changes.
29748 Since individual variants may have short lifetimes or limited
29749 audiences, it may not be worthwhile to carry information about every
29750 variant in the @value{GDBN} source tree.
29752 When @value{GDBN} does support the architecture of the embedded system
29753 at hand, the task of finding the correct architecture name to give the
29754 @command{set architecture} command can be error-prone.
29757 To address these problems, the @value{GDBN} remote protocol allows a
29758 target system to not only identify itself to @value{GDBN}, but to
29759 actually describe its own features. This lets @value{GDBN} support
29760 processor variants it has never seen before --- to the extent that the
29761 descriptions are accurate, and that @value{GDBN} understands them.
29763 @value{GDBN} must be linked with the Expat library to support XML
29764 target descriptions. @xref{Expat}.
29767 * Retrieving Descriptions:: How descriptions are fetched from a target.
29768 * Target Description Format:: The contents of a target description.
29769 * Predefined Target Types:: Standard types available for target
29771 * Standard Target Features:: Features @value{GDBN} knows about.
29774 @node Retrieving Descriptions
29775 @section Retrieving Descriptions
29777 Target descriptions can be read from the target automatically, or
29778 specified by the user manually. The default behavior is to read the
29779 description from the target. @value{GDBN} retrieves it via the remote
29780 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
29781 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
29782 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
29783 XML document, of the form described in @ref{Target Description
29786 Alternatively, you can specify a file to read for the target description.
29787 If a file is set, the target will not be queried. The commands to
29788 specify a file are:
29791 @cindex set tdesc filename
29792 @item set tdesc filename @var{path}
29793 Read the target description from @var{path}.
29795 @cindex unset tdesc filename
29796 @item unset tdesc filename
29797 Do not read the XML target description from a file. @value{GDBN}
29798 will use the description supplied by the current target.
29800 @cindex show tdesc filename
29801 @item show tdesc filename
29802 Show the filename to read for a target description, if any.
29806 @node Target Description Format
29807 @section Target Description Format
29808 @cindex target descriptions, XML format
29810 A target description annex is an @uref{http://www.w3.org/XML/, XML}
29811 document which complies with the Document Type Definition provided in
29812 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
29813 means you can use generally available tools like @command{xmllint} to
29814 check that your feature descriptions are well-formed and valid.
29815 However, to help people unfamiliar with XML write descriptions for
29816 their targets, we also describe the grammar here.
29818 Target descriptions can identify the architecture of the remote target
29819 and (for some architectures) provide information about custom register
29820 sets. @value{GDBN} can use this information to autoconfigure for your
29821 target, or to warn you if you connect to an unsupported target.
29823 Here is a simple target description:
29826 <target version="1.0">
29827 <architecture>i386:x86-64</architecture>
29832 This minimal description only says that the target uses
29833 the x86-64 architecture.
29835 A target description has the following overall form, with [ ] marking
29836 optional elements and @dots{} marking repeatable elements. The elements
29837 are explained further below.
29840 <?xml version="1.0"?>
29841 <!DOCTYPE target SYSTEM "gdb-target.dtd">
29842 <target version="1.0">
29843 @r{[}@var{architecture}@r{]}
29844 @r{[}@var{feature}@dots{}@r{]}
29849 The description is generally insensitive to whitespace and line
29850 breaks, under the usual common-sense rules. The XML version
29851 declaration and document type declaration can generally be omitted
29852 (@value{GDBN} does not require them), but specifying them may be
29853 useful for XML validation tools. The @samp{version} attribute for
29854 @samp{<target>} may also be omitted, but we recommend
29855 including it; if future versions of @value{GDBN} use an incompatible
29856 revision of @file{gdb-target.dtd}, they will detect and report
29857 the version mismatch.
29859 @subsection Inclusion
29860 @cindex target descriptions, inclusion
29863 @cindex <xi:include>
29866 It can sometimes be valuable to split a target description up into
29867 several different annexes, either for organizational purposes, or to
29868 share files between different possible target descriptions. You can
29869 divide a description into multiple files by replacing any element of
29870 the target description with an inclusion directive of the form:
29873 <xi:include href="@var{document}"/>
29877 When @value{GDBN} encounters an element of this form, it will retrieve
29878 the named XML @var{document}, and replace the inclusion directive with
29879 the contents of that document. If the current description was read
29880 using @samp{qXfer}, then so will be the included document;
29881 @var{document} will be interpreted as the name of an annex. If the
29882 current description was read from a file, @value{GDBN} will look for
29883 @var{document} as a file in the same directory where it found the
29884 original description.
29886 @subsection Architecture
29887 @cindex <architecture>
29889 An @samp{<architecture>} element has this form:
29892 <architecture>@var{arch}</architecture>
29895 @var{arch} is an architecture name from the same selection
29896 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
29897 Debugging Target}).
29899 @subsection Features
29902 Each @samp{<feature>} describes some logical portion of the target
29903 system. Features are currently used to describe available CPU
29904 registers and the types of their contents. A @samp{<feature>} element
29908 <feature name="@var{name}">
29909 @r{[}@var{type}@dots{}@r{]}
29915 Each feature's name should be unique within the description. The name
29916 of a feature does not matter unless @value{GDBN} has some special
29917 knowledge of the contents of that feature; if it does, the feature
29918 should have its standard name. @xref{Standard Target Features}.
29922 Any register's value is a collection of bits which @value{GDBN} must
29923 interpret. The default interpretation is a two's complement integer,
29924 but other types can be requested by name in the register description.
29925 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
29926 Target Types}), and the description can define additional composite types.
29928 Each type element must have an @samp{id} attribute, which gives
29929 a unique (within the containing @samp{<feature>}) name to the type.
29930 Types must be defined before they are used.
29933 Some targets offer vector registers, which can be treated as arrays
29934 of scalar elements. These types are written as @samp{<vector>} elements,
29935 specifying the array element type, @var{type}, and the number of elements,
29939 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
29943 If a register's value is usefully viewed in multiple ways, define it
29944 with a union type containing the useful representations. The
29945 @samp{<union>} element contains one or more @samp{<field>} elements,
29946 each of which has a @var{name} and a @var{type}:
29949 <union id="@var{id}">
29950 <field name="@var{name}" type="@var{type}"/>
29955 @subsection Registers
29958 Each register is represented as an element with this form:
29961 <reg name="@var{name}"
29962 bitsize="@var{size}"
29963 @r{[}regnum="@var{num}"@r{]}
29964 @r{[}save-restore="@var{save-restore}"@r{]}
29965 @r{[}type="@var{type}"@r{]}
29966 @r{[}group="@var{group}"@r{]}/>
29970 The components are as follows:
29975 The register's name; it must be unique within the target description.
29978 The register's size, in bits.
29981 The register's number. If omitted, a register's number is one greater
29982 than that of the previous register (either in the current feature or in
29983 a preceeding feature); the first register in the target description
29984 defaults to zero. This register number is used to read or write
29985 the register; e.g.@: it is used in the remote @code{p} and @code{P}
29986 packets, and registers appear in the @code{g} and @code{G} packets
29987 in order of increasing register number.
29990 Whether the register should be preserved across inferior function
29991 calls; this must be either @code{yes} or @code{no}. The default is
29992 @code{yes}, which is appropriate for most registers except for
29993 some system control registers; this is not related to the target's
29997 The type of the register. @var{type} may be a predefined type, a type
29998 defined in the current feature, or one of the special types @code{int}
29999 and @code{float}. @code{int} is an integer type of the correct size
30000 for @var{bitsize}, and @code{float} is a floating point type (in the
30001 architecture's normal floating point format) of the correct size for
30002 @var{bitsize}. The default is @code{int}.
30005 The register group to which this register belongs. @var{group} must
30006 be either @code{general}, @code{float}, or @code{vector}. If no
30007 @var{group} is specified, @value{GDBN} will not display the register
30008 in @code{info registers}.
30012 @node Predefined Target Types
30013 @section Predefined Target Types
30014 @cindex target descriptions, predefined types
30016 Type definitions in the self-description can build up composite types
30017 from basic building blocks, but can not define fundamental types. Instead,
30018 standard identifiers are provided by @value{GDBN} for the fundamental
30019 types. The currently supported types are:
30028 Signed integer types holding the specified number of bits.
30035 Unsigned integer types holding the specified number of bits.
30039 Pointers to unspecified code and data. The program counter and
30040 any dedicated return address register may be marked as code
30041 pointers; printing a code pointer converts it into a symbolic
30042 address. The stack pointer and any dedicated address registers
30043 may be marked as data pointers.
30046 Single precision IEEE floating point.
30049 Double precision IEEE floating point.
30052 The 12-byte extended precision format used by ARM FPA registers.
30056 @node Standard Target Features
30057 @section Standard Target Features
30058 @cindex target descriptions, standard features
30060 A target description must contain either no registers or all the
30061 target's registers. If the description contains no registers, then
30062 @value{GDBN} will assume a default register layout, selected based on
30063 the architecture. If the description contains any registers, the
30064 default layout will not be used; the standard registers must be
30065 described in the target description, in such a way that @value{GDBN}
30066 can recognize them.
30068 This is accomplished by giving specific names to feature elements
30069 which contain standard registers. @value{GDBN} will look for features
30070 with those names and verify that they contain the expected registers;
30071 if any known feature is missing required registers, or if any required
30072 feature is missing, @value{GDBN} will reject the target
30073 description. You can add additional registers to any of the
30074 standard features --- @value{GDBN} will display them just as if
30075 they were added to an unrecognized feature.
30077 This section lists the known features and their expected contents.
30078 Sample XML documents for these features are included in the
30079 @value{GDBN} source tree, in the directory @file{gdb/features}.
30081 Names recognized by @value{GDBN} should include the name of the
30082 company or organization which selected the name, and the overall
30083 architecture to which the feature applies; so e.g.@: the feature
30084 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
30086 The names of registers are not case sensitive for the purpose
30087 of recognizing standard features, but @value{GDBN} will only display
30088 registers using the capitalization used in the description.
30094 * PowerPC Features::
30099 @subsection ARM Features
30100 @cindex target descriptions, ARM features
30102 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
30103 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
30104 @samp{lr}, @samp{pc}, and @samp{cpsr}.
30106 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
30107 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
30109 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
30110 it should contain at least registers @samp{wR0} through @samp{wR15} and
30111 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
30112 @samp{wCSSF}, and @samp{wCASF} registers are optional.
30114 @node MIPS Features
30115 @subsection MIPS Features
30116 @cindex target descriptions, MIPS features
30118 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
30119 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
30120 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
30123 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
30124 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
30125 registers. They may be 32-bit or 64-bit depending on the target.
30127 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
30128 it may be optional in a future version of @value{GDBN}. It should
30129 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
30130 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
30132 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
30133 contain a single register, @samp{restart}, which is used by the
30134 Linux kernel to control restartable syscalls.
30136 @node M68K Features
30137 @subsection M68K Features
30138 @cindex target descriptions, M68K features
30141 @item @samp{org.gnu.gdb.m68k.core}
30142 @itemx @samp{org.gnu.gdb.coldfire.core}
30143 @itemx @samp{org.gnu.gdb.fido.core}
30144 One of those features must be always present.
30145 The feature that is present determines which flavor of m68k is
30146 used. The feature that is present should contain registers
30147 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
30148 @samp{sp}, @samp{ps} and @samp{pc}.
30150 @item @samp{org.gnu.gdb.coldfire.fp}
30151 This feature is optional. If present, it should contain registers
30152 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
30156 @node PowerPC Features
30157 @subsection PowerPC Features
30158 @cindex target descriptions, PowerPC features
30160 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
30161 targets. It should contain registers @samp{r0} through @samp{r31},
30162 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
30163 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
30165 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
30166 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
30168 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
30169 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
30172 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
30173 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
30174 will combine these registers with the floating point registers
30175 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
30176 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
30177 through @samp{vs63}, the set of vector registers for POWER7.
30179 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
30180 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
30181 @samp{spefscr}. SPE targets should provide 32-bit registers in
30182 @samp{org.gnu.gdb.power.core} and provide the upper halves in
30183 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
30184 these to present registers @samp{ev0} through @samp{ev31} to the
30187 @node Operating System Information
30188 @appendix Operating System Information
30189 @cindex operating system information
30195 Users of @value{GDBN} often wish to obtain information about the state of
30196 the operating system running on the target---for example the list of
30197 processes, or the list of open files. This section describes the
30198 mechanism that makes it possible. This mechanism is similar to the
30199 target features mechanism (@pxref{Target Descriptions}), but focuses
30200 on a different aspect of target.
30202 Operating system information is retrived from the target via the
30203 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
30204 read}). The object name in the request should be @samp{osdata}, and
30205 the @var{annex} identifies the data to be fetched.
30208 @appendixsection Process list
30209 @cindex operating system information, process list
30211 When requesting the process list, the @var{annex} field in the
30212 @samp{qXfer} request should be @samp{processes}. The returned data is
30213 an XML document. The formal syntax of this document is defined in
30214 @file{gdb/features/osdata.dtd}.
30216 An example document is:
30219 <?xml version="1.0"?>
30220 <!DOCTYPE target SYSTEM "osdata.dtd">
30221 <osdata type="processes">
30223 <column name="pid">1</column>
30224 <column name="user">root</column>
30225 <column name="command">/sbin/init</column>
30230 Each item should include a column whose name is @samp{pid}. The value
30231 of that column should identify the process on the target. The
30232 @samp{user} and @samp{command} columns are optional, and will be
30233 displayed by @value{GDBN}. Target may provide additional columns,
30234 which @value{GDBN} currently ignores.
30248 % I think something like @colophon should be in texinfo. In the
30250 \long\def\colophon{\hbox to0pt{}\vfill
30251 \centerline{The body of this manual is set in}
30252 \centerline{\fontname\tenrm,}
30253 \centerline{with headings in {\bf\fontname\tenbf}}
30254 \centerline{and examples in {\tt\fontname\tentt}.}
30255 \centerline{{\it\fontname\tenit\/},}
30256 \centerline{{\bf\fontname\tenbf}, and}
30257 \centerline{{\sl\fontname\tensl\/}}
30258 \centerline{are used for emphasis.}\vfill}
30260 % Blame: doc@cygnus.com, 1991.