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 In an architecture environment that supports process recording and
5012 replay, a special @dfn{process record and replay} target can record a
5013 log of the process execution, and replay it later with both forward
5014 and reverse execution commands.
5017 When this target is in use, if the execution log includes the record
5018 for the next instruction, @value{GDBN} will debug in @dfn{replay
5019 mode}. In the replay mode, the inferior does not really execute code
5020 instructions. Instead, all the events that normally happen during
5021 code execution are taken from the execution log. While code is not
5022 really executed in replay mode, the values of registers (including the
5023 program counter register) and the memory of the inferior are still
5024 changed as they normally would.
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 For architecture environments that support process record and replay,
5033 @value{GDBN} provides the following commands:
5036 @kindex target record
5040 This command starts the process record and replay target. The process
5041 record and replay target can only debug a process that is already
5042 running. Therefore, you need first to start the process with the
5043 @kbd{run} or @kbd{start} commands, and then start the recording with
5044 the @kbd{target record} command.
5046 Both @code{record} and @code{rec} are aliases of @code{target record}.
5048 @cindex displaced stepping, and process record and replay
5049 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5050 will be automatically disabled when process record and replay target
5051 is started. That's because the process record and replay target
5052 doesn't support displaced stepping.
5054 @cindex non-stop mode, and process record and replay
5055 @cindex asynchronous execution, and process record and replay
5056 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5057 the asynchronous execution mode (@pxref{Background Execution}), the
5058 process record and replay target cannot be started because it doesn't
5059 support these two modes.
5064 Stop the process record and replay target. When process record and
5065 replay target stops, the entire execution log will be deleted and the
5066 inferior will either be terminated, or will remain in its final state.
5068 When you stop the process record and replay target in record mode (at
5069 the end of the execution log), the inferior will be stopped at the
5070 next instruction that would have been recorded. In other words, if
5071 you record for a while and then stop recording, the inferior process
5072 will be left in the same state as if the recording never happened.
5074 On the other hand, if the process record and replay target is stopped
5075 while in replay mode (that is, not at the end of the execution log,
5076 but at some earlier point), the inferior process will become ``live''
5077 at that earlier state, and it will then be possible to continue the
5078 usual ``live'' debugging of the process from that state.
5080 When the inferior process exits, or @value{GDBN} detaches from it,
5081 process record and replay target will automatically stop itself.
5083 @kindex set record insn-number-max
5084 @item set record insn-number-max @var{limit}
5085 Set the limit of instructions to be recorded. Default value is 200000.
5087 If @var{limit} is a positive number, then @value{GDBN} will start
5088 deleting instructions from the log once the number of the record
5089 instructions becomes greater than @var{limit}. For every new recorded
5090 instruction, @value{GDBN} will delete the earliest recorded
5091 instruction to keep the number of recorded instructions at the limit.
5092 (Since deleting recorded instructions loses information, @value{GDBN}
5093 lets you control what happens when the limit is reached, by means of
5094 the @code{stop-at-limit} option, described below.)
5096 If @var{limit} is zero, @value{GDBN} will never delete recorded
5097 instructions from the execution log. The number of recorded
5098 instructions is unlimited in this case.
5100 @kindex show record insn-number-max
5101 @item show record insn-number-max
5102 Show the limit of instructions to be recorded.
5104 @kindex set record stop-at-limit
5105 @item set record stop-at-limit
5106 Control the behavior when the number of recorded instructions reaches
5107 the limit. If ON (the default), @value{GDBN} will stop when the limit
5108 is reached for the first time and ask you whether you want to stop the
5109 inferior or continue running it and recording the execution log. If
5110 you decide to continue recording, each new recorded instruction will
5111 cause the oldest one to be deleted.
5113 If this option is OFF, @value{GDBN} will automatically delete the
5114 oldest record to make room for each new one, without asking.
5116 @kindex show record stop-at-limit
5117 @item show record stop-at-limit
5118 Show the current setting of @code{stop-at-limit}.
5120 @kindex info record insn-number
5121 @item info record insn-number
5122 Show the current number of recorded instructions.
5124 @kindex record delete
5127 When record target runs in replay mode (``in the past''), delete the
5128 subsequent execution log and begin to record a new execution log starting
5129 from the current address. This means you will abandon the previously
5130 recorded ``future'' and begin recording a new ``future''.
5135 @chapter Examining the Stack
5137 When your program has stopped, the first thing you need to know is where it
5138 stopped and how it got there.
5141 Each time your program performs a function call, information about the call
5143 That information includes the location of the call in your program,
5144 the arguments of the call,
5145 and the local variables of the function being called.
5146 The information is saved in a block of data called a @dfn{stack frame}.
5147 The stack frames are allocated in a region of memory called the @dfn{call
5150 When your program stops, the @value{GDBN} commands for examining the
5151 stack allow you to see all of this information.
5153 @cindex selected frame
5154 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5155 @value{GDBN} commands refer implicitly to the selected frame. In
5156 particular, whenever you ask @value{GDBN} for the value of a variable in
5157 your program, the value is found in the selected frame. There are
5158 special @value{GDBN} commands to select whichever frame you are
5159 interested in. @xref{Selection, ,Selecting a Frame}.
5161 When your program stops, @value{GDBN} automatically selects the
5162 currently executing frame and describes it briefly, similar to the
5163 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5166 * Frames:: Stack frames
5167 * Backtrace:: Backtraces
5168 * Selection:: Selecting a frame
5169 * Frame Info:: Information on a frame
5174 @section Stack Frames
5176 @cindex frame, definition
5178 The call stack is divided up into contiguous pieces called @dfn{stack
5179 frames}, or @dfn{frames} for short; each frame is the data associated
5180 with one call to one function. The frame contains the arguments given
5181 to the function, the function's local variables, and the address at
5182 which the function is executing.
5184 @cindex initial frame
5185 @cindex outermost frame
5186 @cindex innermost frame
5187 When your program is started, the stack has only one frame, that of the
5188 function @code{main}. This is called the @dfn{initial} frame or the
5189 @dfn{outermost} frame. Each time a function is called, a new frame is
5190 made. Each time a function returns, the frame for that function invocation
5191 is eliminated. If a function is recursive, there can be many frames for
5192 the same function. The frame for the function in which execution is
5193 actually occurring is called the @dfn{innermost} frame. This is the most
5194 recently created of all the stack frames that still exist.
5196 @cindex frame pointer
5197 Inside your program, stack frames are identified by their addresses. A
5198 stack frame consists of many bytes, each of which has its own address; each
5199 kind of computer has a convention for choosing one byte whose
5200 address serves as the address of the frame. Usually this address is kept
5201 in a register called the @dfn{frame pointer register}
5202 (@pxref{Registers, $fp}) while execution is going on in that frame.
5204 @cindex frame number
5205 @value{GDBN} assigns numbers to all existing stack frames, starting with
5206 zero for the innermost frame, one for the frame that called it,
5207 and so on upward. These numbers do not really exist in your program;
5208 they are assigned by @value{GDBN} to give you a way of designating stack
5209 frames in @value{GDBN} commands.
5211 @c The -fomit-frame-pointer below perennially causes hbox overflow
5212 @c underflow problems.
5213 @cindex frameless execution
5214 Some compilers provide a way to compile functions so that they operate
5215 without stack frames. (For example, the @value{NGCC} option
5217 @samp{-fomit-frame-pointer}
5219 generates functions without a frame.)
5220 This is occasionally done with heavily used library functions to save
5221 the frame setup time. @value{GDBN} has limited facilities for dealing
5222 with these function invocations. If the innermost function invocation
5223 has no stack frame, @value{GDBN} nevertheless regards it as though
5224 it had a separate frame, which is numbered zero as usual, allowing
5225 correct tracing of the function call chain. However, @value{GDBN} has
5226 no provision for frameless functions elsewhere in the stack.
5229 @kindex frame@r{, command}
5230 @cindex current stack frame
5231 @item frame @var{args}
5232 The @code{frame} command allows you to move from one stack frame to another,
5233 and to print the stack frame you select. @var{args} may be either the
5234 address of the frame or the stack frame number. Without an argument,
5235 @code{frame} prints the current stack frame.
5237 @kindex select-frame
5238 @cindex selecting frame silently
5240 The @code{select-frame} command allows you to move from one stack frame
5241 to another without printing the frame. This is the silent version of
5249 @cindex call stack traces
5250 A backtrace is a summary of how your program got where it is. It shows one
5251 line per frame, for many frames, starting with the currently executing
5252 frame (frame zero), followed by its caller (frame one), and on up the
5257 @kindex bt @r{(@code{backtrace})}
5260 Print a backtrace of the entire stack: one line per frame for all
5261 frames in the stack.
5263 You can stop the backtrace at any time by typing the system interrupt
5264 character, normally @kbd{Ctrl-c}.
5266 @item backtrace @var{n}
5268 Similar, but print only the innermost @var{n} frames.
5270 @item backtrace -@var{n}
5272 Similar, but print only the outermost @var{n} frames.
5274 @item backtrace full
5276 @itemx bt full @var{n}
5277 @itemx bt full -@var{n}
5278 Print the values of the local variables also. @var{n} specifies the
5279 number of frames to print, as described above.
5284 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5285 are additional aliases for @code{backtrace}.
5287 @cindex multiple threads, backtrace
5288 In a multi-threaded program, @value{GDBN} by default shows the
5289 backtrace only for the current thread. To display the backtrace for
5290 several or all of the threads, use the command @code{thread apply}
5291 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5292 apply all backtrace}, @value{GDBN} will display the backtrace for all
5293 the threads; this is handy when you debug a core dump of a
5294 multi-threaded program.
5296 Each line in the backtrace shows the frame number and the function name.
5297 The program counter value is also shown---unless you use @code{set
5298 print address off}. The backtrace also shows the source file name and
5299 line number, as well as the arguments to the function. The program
5300 counter value is omitted if it is at the beginning of the code for that
5303 Here is an example of a backtrace. It was made with the command
5304 @samp{bt 3}, so it shows the innermost three frames.
5308 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5310 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5311 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5313 (More stack frames follow...)
5318 The display for frame zero does not begin with a program counter
5319 value, indicating that your program has stopped at the beginning of the
5320 code for line @code{993} of @code{builtin.c}.
5323 The value of parameter @code{data} in frame 1 has been replaced by
5324 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5325 only if it is a scalar (integer, pointer, enumeration, etc). See command
5326 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5327 on how to configure the way function parameter values are printed.
5329 @cindex value optimized out, in backtrace
5330 @cindex function call arguments, optimized out
5331 If your program was compiled with optimizations, some compilers will
5332 optimize away arguments passed to functions if those arguments are
5333 never used after the call. Such optimizations generate code that
5334 passes arguments through registers, but doesn't store those arguments
5335 in the stack frame. @value{GDBN} has no way of displaying such
5336 arguments in stack frames other than the innermost one. Here's what
5337 such a backtrace might look like:
5341 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5343 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5344 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5346 (More stack frames follow...)
5351 The values of arguments that were not saved in their stack frames are
5352 shown as @samp{<value optimized out>}.
5354 If you need to display the values of such optimized-out arguments,
5355 either deduce that from other variables whose values depend on the one
5356 you are interested in, or recompile without optimizations.
5358 @cindex backtrace beyond @code{main} function
5359 @cindex program entry point
5360 @cindex startup code, and backtrace
5361 Most programs have a standard user entry point---a place where system
5362 libraries and startup code transition into user code. For C this is
5363 @code{main}@footnote{
5364 Note that embedded programs (the so-called ``free-standing''
5365 environment) are not required to have a @code{main} function as the
5366 entry point. They could even have multiple entry points.}.
5367 When @value{GDBN} finds the entry function in a backtrace
5368 it will terminate the backtrace, to avoid tracing into highly
5369 system-specific (and generally uninteresting) code.
5371 If you need to examine the startup code, or limit the number of levels
5372 in a backtrace, you can change this behavior:
5375 @item set backtrace past-main
5376 @itemx set backtrace past-main on
5377 @kindex set backtrace
5378 Backtraces will continue past the user entry point.
5380 @item set backtrace past-main off
5381 Backtraces will stop when they encounter the user entry point. This is the
5384 @item show backtrace past-main
5385 @kindex show backtrace
5386 Display the current user entry point backtrace policy.
5388 @item set backtrace past-entry
5389 @itemx set backtrace past-entry on
5390 Backtraces will continue past the internal entry point of an application.
5391 This entry point is encoded by the linker when the application is built,
5392 and is likely before the user entry point @code{main} (or equivalent) is called.
5394 @item set backtrace past-entry off
5395 Backtraces will stop when they encounter the internal entry point of an
5396 application. This is the default.
5398 @item show backtrace past-entry
5399 Display the current internal entry point backtrace policy.
5401 @item set backtrace limit @var{n}
5402 @itemx set backtrace limit 0
5403 @cindex backtrace limit
5404 Limit the backtrace to @var{n} levels. A value of zero means
5407 @item show backtrace limit
5408 Display the current limit on backtrace levels.
5412 @section Selecting a Frame
5414 Most commands for examining the stack and other data in your program work on
5415 whichever stack frame is selected at the moment. Here are the commands for
5416 selecting a stack frame; all of them finish by printing a brief description
5417 of the stack frame just selected.
5420 @kindex frame@r{, selecting}
5421 @kindex f @r{(@code{frame})}
5424 Select frame number @var{n}. Recall that frame zero is the innermost
5425 (currently executing) frame, frame one is the frame that called the
5426 innermost one, and so on. The highest-numbered frame is the one for
5429 @item frame @var{addr}
5431 Select the frame at address @var{addr}. This is useful mainly if the
5432 chaining of stack frames has been damaged by a bug, making it
5433 impossible for @value{GDBN} to assign numbers properly to all frames. In
5434 addition, this can be useful when your program has multiple stacks and
5435 switches between them.
5437 On the SPARC architecture, @code{frame} needs two addresses to
5438 select an arbitrary frame: a frame pointer and a stack pointer.
5440 On the MIPS and Alpha architecture, it needs two addresses: a stack
5441 pointer and a program counter.
5443 On the 29k architecture, it needs three addresses: a register stack
5444 pointer, a program counter, and a memory stack pointer.
5448 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5449 advances toward the outermost frame, to higher frame numbers, to frames
5450 that have existed longer. @var{n} defaults to one.
5453 @kindex do @r{(@code{down})}
5455 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5456 advances toward the innermost frame, to lower frame numbers, to frames
5457 that were created more recently. @var{n} defaults to one. You may
5458 abbreviate @code{down} as @code{do}.
5461 All of these commands end by printing two lines of output describing the
5462 frame. The first line shows the frame number, the function name, the
5463 arguments, and the source file and line number of execution in that
5464 frame. The second line shows the text of that source line.
5472 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5474 10 read_input_file (argv[i]);
5478 After such a printout, the @code{list} command with no arguments
5479 prints ten lines centered on the point of execution in the frame.
5480 You can also edit the program at the point of execution with your favorite
5481 editing program by typing @code{edit}.
5482 @xref{List, ,Printing Source Lines},
5486 @kindex down-silently
5488 @item up-silently @var{n}
5489 @itemx down-silently @var{n}
5490 These two commands are variants of @code{up} and @code{down},
5491 respectively; they differ in that they do their work silently, without
5492 causing display of the new frame. They are intended primarily for use
5493 in @value{GDBN} command scripts, where the output might be unnecessary and
5498 @section Information About a Frame
5500 There are several other commands to print information about the selected
5506 When used without any argument, this command does not change which
5507 frame is selected, but prints a brief description of the currently
5508 selected stack frame. It can be abbreviated @code{f}. With an
5509 argument, this command is used to select a stack frame.
5510 @xref{Selection, ,Selecting a Frame}.
5513 @kindex info f @r{(@code{info frame})}
5516 This command prints a verbose description of the selected stack frame,
5521 the address of the frame
5523 the address of the next frame down (called by this frame)
5525 the address of the next frame up (caller of this frame)
5527 the language in which the source code corresponding to this frame is written
5529 the address of the frame's arguments
5531 the address of the frame's local variables
5533 the program counter saved in it (the address of execution in the caller frame)
5535 which registers were saved in the frame
5538 @noindent The verbose description is useful when
5539 something has gone wrong that has made the stack format fail to fit
5540 the usual conventions.
5542 @item info frame @var{addr}
5543 @itemx info f @var{addr}
5544 Print a verbose description of the frame at address @var{addr}, without
5545 selecting that frame. The selected frame remains unchanged by this
5546 command. This requires the same kind of address (more than one for some
5547 architectures) that you specify in the @code{frame} command.
5548 @xref{Selection, ,Selecting a Frame}.
5552 Print the arguments of the selected frame, each on a separate line.
5556 Print the local variables of the selected frame, each on a separate
5557 line. These are all variables (declared either static or automatic)
5558 accessible at the point of execution of the selected frame.
5561 @cindex catch exceptions, list active handlers
5562 @cindex exception handlers, how to list
5564 Print a list of all the exception handlers that are active in the
5565 current stack frame at the current point of execution. To see other
5566 exception handlers, visit the associated frame (using the @code{up},
5567 @code{down}, or @code{frame} commands); then type @code{info catch}.
5568 @xref{Set Catchpoints, , Setting Catchpoints}.
5574 @chapter Examining Source Files
5576 @value{GDBN} can print parts of your program's source, since the debugging
5577 information recorded in the program tells @value{GDBN} what source files were
5578 used to build it. When your program stops, @value{GDBN} spontaneously prints
5579 the line where it stopped. Likewise, when you select a stack frame
5580 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5581 execution in that frame has stopped. You can print other portions of
5582 source files by explicit command.
5584 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5585 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5586 @value{GDBN} under @sc{gnu} Emacs}.
5589 * List:: Printing source lines
5590 * Specify Location:: How to specify code locations
5591 * Edit:: Editing source files
5592 * Search:: Searching source files
5593 * Source Path:: Specifying source directories
5594 * Machine Code:: Source and machine code
5598 @section Printing Source Lines
5601 @kindex l @r{(@code{list})}
5602 To print lines from a source file, use the @code{list} command
5603 (abbreviated @code{l}). By default, ten lines are printed.
5604 There are several ways to specify what part of the file you want to
5605 print; see @ref{Specify Location}, for the full list.
5607 Here are the forms of the @code{list} command most commonly used:
5610 @item list @var{linenum}
5611 Print lines centered around line number @var{linenum} in the
5612 current source file.
5614 @item list @var{function}
5615 Print lines centered around the beginning of function
5619 Print more lines. If the last lines printed were printed with a
5620 @code{list} command, this prints lines following the last lines
5621 printed; however, if the last line printed was a solitary line printed
5622 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5623 Stack}), this prints lines centered around that line.
5626 Print lines just before the lines last printed.
5629 @cindex @code{list}, how many lines to display
5630 By default, @value{GDBN} prints ten source lines with any of these forms of
5631 the @code{list} command. You can change this using @code{set listsize}:
5634 @kindex set listsize
5635 @item set listsize @var{count}
5636 Make the @code{list} command display @var{count} source lines (unless
5637 the @code{list} argument explicitly specifies some other number).
5639 @kindex show listsize
5641 Display the number of lines that @code{list} prints.
5644 Repeating a @code{list} command with @key{RET} discards the argument,
5645 so it is equivalent to typing just @code{list}. This is more useful
5646 than listing the same lines again. An exception is made for an
5647 argument of @samp{-}; that argument is preserved in repetition so that
5648 each repetition moves up in the source file.
5650 In general, the @code{list} command expects you to supply zero, one or two
5651 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5652 of writing them (@pxref{Specify Location}), but the effect is always
5653 to specify some source line.
5655 Here is a complete description of the possible arguments for @code{list}:
5658 @item list @var{linespec}
5659 Print lines centered around the line specified by @var{linespec}.
5661 @item list @var{first},@var{last}
5662 Print lines from @var{first} to @var{last}. Both arguments are
5663 linespecs. When a @code{list} command has two linespecs, and the
5664 source file of the second linespec is omitted, this refers to
5665 the same source file as the first linespec.
5667 @item list ,@var{last}
5668 Print lines ending with @var{last}.
5670 @item list @var{first},
5671 Print lines starting with @var{first}.
5674 Print lines just after the lines last printed.
5677 Print lines just before the lines last printed.
5680 As described in the preceding table.
5683 @node Specify Location
5684 @section Specifying a Location
5685 @cindex specifying location
5688 Several @value{GDBN} commands accept arguments that specify a location
5689 of your program's code. Since @value{GDBN} is a source-level
5690 debugger, a location usually specifies some line in the source code;
5691 for that reason, locations are also known as @dfn{linespecs}.
5693 Here are all the different ways of specifying a code location that
5694 @value{GDBN} understands:
5698 Specifies the line number @var{linenum} of the current source file.
5701 @itemx +@var{offset}
5702 Specifies the line @var{offset} lines before or after the @dfn{current
5703 line}. For the @code{list} command, the current line is the last one
5704 printed; for the breakpoint commands, this is the line at which
5705 execution stopped in the currently selected @dfn{stack frame}
5706 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5707 used as the second of the two linespecs in a @code{list} command,
5708 this specifies the line @var{offset} lines up or down from the first
5711 @item @var{filename}:@var{linenum}
5712 Specifies the line @var{linenum} in the source file @var{filename}.
5714 @item @var{function}
5715 Specifies the line that begins the body of the function @var{function}.
5716 For example, in C, this is the line with the open brace.
5718 @item @var{filename}:@var{function}
5719 Specifies the line that begins the body of the function @var{function}
5720 in the file @var{filename}. You only need the file name with a
5721 function name to avoid ambiguity when there are identically named
5722 functions in different source files.
5724 @item *@var{address}
5725 Specifies the program address @var{address}. For line-oriented
5726 commands, such as @code{list} and @code{edit}, this specifies a source
5727 line that contains @var{address}. For @code{break} and other
5728 breakpoint oriented commands, this can be used to set breakpoints in
5729 parts of your program which do not have debugging information or
5732 Here @var{address} may be any expression valid in the current working
5733 language (@pxref{Languages, working language}) that specifies a code
5734 address. In addition, as a convenience, @value{GDBN} extends the
5735 semantics of expressions used in locations to cover the situations
5736 that frequently happen during debugging. Here are the various forms
5740 @item @var{expression}
5741 Any expression valid in the current working language.
5743 @item @var{funcaddr}
5744 An address of a function or procedure derived from its name. In C,
5745 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5746 simply the function's name @var{function} (and actually a special case
5747 of a valid expression). In Pascal and Modula-2, this is
5748 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5749 (although the Pascal form also works).
5751 This form specifies the address of the function's first instruction,
5752 before the stack frame and arguments have been set up.
5754 @item '@var{filename}'::@var{funcaddr}
5755 Like @var{funcaddr} above, but also specifies the name of the source
5756 file explicitly. This is useful if the name of the function does not
5757 specify the function unambiguously, e.g., if there are several
5758 functions with identical names in different source files.
5765 @section Editing Source Files
5766 @cindex editing source files
5769 @kindex e @r{(@code{edit})}
5770 To edit the lines in a source file, use the @code{edit} command.
5771 The editing program of your choice
5772 is invoked with the current line set to
5773 the active line in the program.
5774 Alternatively, there are several ways to specify what part of the file you
5775 want to print if you want to see other parts of the program:
5778 @item edit @var{location}
5779 Edit the source file specified by @code{location}. Editing starts at
5780 that @var{location}, e.g., at the specified source line of the
5781 specified file. @xref{Specify Location}, for all the possible forms
5782 of the @var{location} argument; here are the forms of the @code{edit}
5783 command most commonly used:
5786 @item edit @var{number}
5787 Edit the current source file with @var{number} as the active line number.
5789 @item edit @var{function}
5790 Edit the file containing @var{function} at the beginning of its definition.
5795 @subsection Choosing your Editor
5796 You can customize @value{GDBN} to use any editor you want
5798 The only restriction is that your editor (say @code{ex}), recognizes the
5799 following command-line syntax:
5801 ex +@var{number} file
5803 The optional numeric value +@var{number} specifies the number of the line in
5804 the file where to start editing.}.
5805 By default, it is @file{@value{EDITOR}}, but you can change this
5806 by setting the environment variable @code{EDITOR} before using
5807 @value{GDBN}. For example, to configure @value{GDBN} to use the
5808 @code{vi} editor, you could use these commands with the @code{sh} shell:
5814 or in the @code{csh} shell,
5816 setenv EDITOR /usr/bin/vi
5821 @section Searching Source Files
5822 @cindex searching source files
5824 There are two commands for searching through the current source file for a
5829 @kindex forward-search
5830 @item forward-search @var{regexp}
5831 @itemx search @var{regexp}
5832 The command @samp{forward-search @var{regexp}} checks each line,
5833 starting with the one following the last line listed, for a match for
5834 @var{regexp}. It lists the line that is found. You can use the
5835 synonym @samp{search @var{regexp}} or abbreviate the command name as
5838 @kindex reverse-search
5839 @item reverse-search @var{regexp}
5840 The command @samp{reverse-search @var{regexp}} checks each line, starting
5841 with the one before the last line listed and going backward, for a match
5842 for @var{regexp}. It lists the line that is found. You can abbreviate
5843 this command as @code{rev}.
5847 @section Specifying Source Directories
5850 @cindex directories for source files
5851 Executable programs sometimes do not record the directories of the source
5852 files from which they were compiled, just the names. Even when they do,
5853 the directories could be moved between the compilation and your debugging
5854 session. @value{GDBN} has a list of directories to search for source files;
5855 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5856 it tries all the directories in the list, in the order they are present
5857 in the list, until it finds a file with the desired name.
5859 For example, suppose an executable references the file
5860 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5861 @file{/mnt/cross}. The file is first looked up literally; if this
5862 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5863 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5864 message is printed. @value{GDBN} does not look up the parts of the
5865 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5866 Likewise, the subdirectories of the source path are not searched: if
5867 the source path is @file{/mnt/cross}, and the binary refers to
5868 @file{foo.c}, @value{GDBN} would not find it under
5869 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5871 Plain file names, relative file names with leading directories, file
5872 names containing dots, etc.@: are all treated as described above; for
5873 instance, if the source path is @file{/mnt/cross}, and the source file
5874 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5875 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5876 that---@file{/mnt/cross/foo.c}.
5878 Note that the executable search path is @emph{not} used to locate the
5881 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5882 any information it has cached about where source files are found and where
5883 each line is in the file.
5887 When you start @value{GDBN}, its source path includes only @samp{cdir}
5888 and @samp{cwd}, in that order.
5889 To add other directories, use the @code{directory} command.
5891 The search path is used to find both program source files and @value{GDBN}
5892 script files (read using the @samp{-command} option and @samp{source} command).
5894 In addition to the source path, @value{GDBN} provides a set of commands
5895 that manage a list of source path substitution rules. A @dfn{substitution
5896 rule} specifies how to rewrite source directories stored in the program's
5897 debug information in case the sources were moved to a different
5898 directory between compilation and debugging. A rule is made of
5899 two strings, the first specifying what needs to be rewritten in
5900 the path, and the second specifying how it should be rewritten.
5901 In @ref{set substitute-path}, we name these two parts @var{from} and
5902 @var{to} respectively. @value{GDBN} does a simple string replacement
5903 of @var{from} with @var{to} at the start of the directory part of the
5904 source file name, and uses that result instead of the original file
5905 name to look up the sources.
5907 Using the previous example, suppose the @file{foo-1.0} tree has been
5908 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5909 @value{GDBN} to replace @file{/usr/src} in all source path names with
5910 @file{/mnt/cross}. The first lookup will then be
5911 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5912 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5913 substitution rule, use the @code{set substitute-path} command
5914 (@pxref{set substitute-path}).
5916 To avoid unexpected substitution results, a rule is applied only if the
5917 @var{from} part of the directory name ends at a directory separator.
5918 For instance, a rule substituting @file{/usr/source} into
5919 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5920 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5921 is applied only at the beginning of the directory name, this rule will
5922 not be applied to @file{/root/usr/source/baz.c} either.
5924 In many cases, you can achieve the same result using the @code{directory}
5925 command. However, @code{set substitute-path} can be more efficient in
5926 the case where the sources are organized in a complex tree with multiple
5927 subdirectories. With the @code{directory} command, you need to add each
5928 subdirectory of your project. If you moved the entire tree while
5929 preserving its internal organization, then @code{set substitute-path}
5930 allows you to direct the debugger to all the sources with one single
5933 @code{set substitute-path} is also more than just a shortcut command.
5934 The source path is only used if the file at the original location no
5935 longer exists. On the other hand, @code{set substitute-path} modifies
5936 the debugger behavior to look at the rewritten location instead. So, if
5937 for any reason a source file that is not relevant to your executable is
5938 located at the original location, a substitution rule is the only
5939 method available to point @value{GDBN} at the new location.
5941 @cindex @samp{--with-relocated-sources}
5942 @cindex default source path substitution
5943 You can configure a default source path substitution rule by
5944 configuring @value{GDBN} with the
5945 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
5946 should be the name of a directory under @value{GDBN}'s configured
5947 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
5948 directory names in debug information under @var{dir} will be adjusted
5949 automatically if the installed @value{GDBN} is moved to a new
5950 location. This is useful if @value{GDBN}, libraries or executables
5951 with debug information and corresponding source code are being moved
5955 @item directory @var{dirname} @dots{}
5956 @item dir @var{dirname} @dots{}
5957 Add directory @var{dirname} to the front of the source path. Several
5958 directory names may be given to this command, separated by @samp{:}
5959 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5960 part of absolute file names) or
5961 whitespace. You may specify a directory that is already in the source
5962 path; this moves it forward, so @value{GDBN} searches it sooner.
5966 @vindex $cdir@r{, convenience variable}
5967 @vindex $cwd@r{, convenience variable}
5968 @cindex compilation directory
5969 @cindex current directory
5970 @cindex working directory
5971 @cindex directory, current
5972 @cindex directory, compilation
5973 You can use the string @samp{$cdir} to refer to the compilation
5974 directory (if one is recorded), and @samp{$cwd} to refer to the current
5975 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5976 tracks the current working directory as it changes during your @value{GDBN}
5977 session, while the latter is immediately expanded to the current
5978 directory at the time you add an entry to the source path.
5981 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5983 @c RET-repeat for @code{directory} is explicitly disabled, but since
5984 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5986 @item show directories
5987 @kindex show directories
5988 Print the source path: show which directories it contains.
5990 @anchor{set substitute-path}
5991 @item set substitute-path @var{from} @var{to}
5992 @kindex set substitute-path
5993 Define a source path substitution rule, and add it at the end of the
5994 current list of existing substitution rules. If a rule with the same
5995 @var{from} was already defined, then the old rule is also deleted.
5997 For example, if the file @file{/foo/bar/baz.c} was moved to
5998 @file{/mnt/cross/baz.c}, then the command
6001 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6005 will tell @value{GDBN} to replace @samp{/usr/src} with
6006 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6007 @file{baz.c} even though it was moved.
6009 In the case when more than one substitution rule have been defined,
6010 the rules are evaluated one by one in the order where they have been
6011 defined. The first one matching, if any, is selected to perform
6014 For instance, if we had entered the following commands:
6017 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6018 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6022 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6023 @file{/mnt/include/defs.h} by using the first rule. However, it would
6024 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6025 @file{/mnt/src/lib/foo.c}.
6028 @item unset substitute-path [path]
6029 @kindex unset substitute-path
6030 If a path is specified, search the current list of substitution rules
6031 for a rule that would rewrite that path. Delete that rule if found.
6032 A warning is emitted by the debugger if no rule could be found.
6034 If no path is specified, then all substitution rules are deleted.
6036 @item show substitute-path [path]
6037 @kindex show substitute-path
6038 If a path is specified, then print the source path substitution rule
6039 which would rewrite that path, if any.
6041 If no path is specified, then print all existing source path substitution
6046 If your source path is cluttered with directories that are no longer of
6047 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6048 versions of source. You can correct the situation as follows:
6052 Use @code{directory} with no argument to reset the source path to its default value.
6055 Use @code{directory} with suitable arguments to reinstall the
6056 directories you want in the source path. You can add all the
6057 directories in one command.
6061 @section Source and Machine Code
6062 @cindex source line and its code address
6064 You can use the command @code{info line} to map source lines to program
6065 addresses (and vice versa), and the command @code{disassemble} to display
6066 a range of addresses as machine instructions. You can use the command
6067 @code{set disassemble-next-line} to set whether to disassemble next
6068 source line when execution stops. When run under @sc{gnu} Emacs
6069 mode, the @code{info line} command causes the arrow to point to the
6070 line specified. Also, @code{info line} prints addresses in symbolic form as
6075 @item info line @var{linespec}
6076 Print the starting and ending addresses of the compiled code for
6077 source line @var{linespec}. You can specify source lines in any of
6078 the ways documented in @ref{Specify Location}.
6081 For example, we can use @code{info line} to discover the location of
6082 the object code for the first line of function
6083 @code{m4_changequote}:
6085 @c FIXME: I think this example should also show the addresses in
6086 @c symbolic form, as they usually would be displayed.
6088 (@value{GDBP}) info line m4_changequote
6089 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6093 @cindex code address and its source line
6094 We can also inquire (using @code{*@var{addr}} as the form for
6095 @var{linespec}) what source line covers a particular address:
6097 (@value{GDBP}) info line *0x63ff
6098 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6101 @cindex @code{$_} and @code{info line}
6102 @cindex @code{x} command, default address
6103 @kindex x@r{(examine), and} info line
6104 After @code{info line}, the default address for the @code{x} command
6105 is changed to the starting address of the line, so that @samp{x/i} is
6106 sufficient to begin examining the machine code (@pxref{Memory,
6107 ,Examining Memory}). Also, this address is saved as the value of the
6108 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6113 @cindex assembly instructions
6114 @cindex instructions, assembly
6115 @cindex machine instructions
6116 @cindex listing machine instructions
6118 @itemx disassemble /m
6119 This specialized command dumps a range of memory as machine
6120 instructions. It can also print mixed source+disassembly by specifying
6121 the @code{/m} modifier.
6122 The default memory range is the function surrounding the
6123 program counter of the selected frame. A single argument to this
6124 command is a program counter value; @value{GDBN} dumps the function
6125 surrounding this value. Two arguments specify a range of addresses
6126 (first inclusive, second exclusive) to dump.
6129 The following example shows the disassembly of a range of addresses of
6130 HP PA-RISC 2.0 code:
6133 (@value{GDBP}) disas 0x32c4 0x32e4
6134 Dump of assembler code from 0x32c4 to 0x32e4:
6135 0x32c4 <main+204>: addil 0,dp
6136 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6137 0x32cc <main+212>: ldil 0x3000,r31
6138 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6139 0x32d4 <main+220>: ldo 0(r31),rp
6140 0x32d8 <main+224>: addil -0x800,dp
6141 0x32dc <main+228>: ldo 0x588(r1),r26
6142 0x32e0 <main+232>: ldil 0x3000,r31
6143 End of assembler dump.
6146 Here is an example showing mixed source+assembly for Intel x86:
6149 (@value{GDBP}) disas /m main
6150 Dump of assembler code for function main:
6152 0x08048330 <main+0>: push %ebp
6153 0x08048331 <main+1>: mov %esp,%ebp
6154 0x08048333 <main+3>: sub $0x8,%esp
6155 0x08048336 <main+6>: and $0xfffffff0,%esp
6156 0x08048339 <main+9>: sub $0x10,%esp
6158 6 printf ("Hello.\n");
6159 0x0804833c <main+12>: movl $0x8048440,(%esp)
6160 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6164 0x08048348 <main+24>: mov $0x0,%eax
6165 0x0804834d <main+29>: leave
6166 0x0804834e <main+30>: ret
6168 End of assembler dump.
6171 Some architectures have more than one commonly-used set of instruction
6172 mnemonics or other syntax.
6174 For programs that were dynamically linked and use shared libraries,
6175 instructions that call functions or branch to locations in the shared
6176 libraries might show a seemingly bogus location---it's actually a
6177 location of the relocation table. On some architectures, @value{GDBN}
6178 might be able to resolve these to actual function names.
6181 @kindex set disassembly-flavor
6182 @cindex Intel disassembly flavor
6183 @cindex AT&T disassembly flavor
6184 @item set disassembly-flavor @var{instruction-set}
6185 Select the instruction set to use when disassembling the
6186 program via the @code{disassemble} or @code{x/i} commands.
6188 Currently this command is only defined for the Intel x86 family. You
6189 can set @var{instruction-set} to either @code{intel} or @code{att}.
6190 The default is @code{att}, the AT&T flavor used by default by Unix
6191 assemblers for x86-based targets.
6193 @kindex show disassembly-flavor
6194 @item show disassembly-flavor
6195 Show the current setting of the disassembly flavor.
6199 @kindex set disassemble-next-line
6200 @kindex show disassemble-next-line
6201 @item set disassemble-next-line
6202 @itemx show disassemble-next-line
6203 Control whether or not @value{GDBN} will disassemble the next source
6204 line or instruction when execution stops. If ON, @value{GDBN} will
6205 display disassembly of the next source line when execution of the
6206 program being debugged stops. This is @emph{in addition} to
6207 displaying the source line itself, which @value{GDBN} always does if
6208 possible. If the next source line cannot be displayed for some reason
6209 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6210 info in the debug info), @value{GDBN} will display disassembly of the
6211 next @emph{instruction} instead of showing the next source line. If
6212 AUTO, @value{GDBN} will display disassembly of next instruction only
6213 if the source line cannot be displayed. This setting causes
6214 @value{GDBN} to display some feedback when you step through a function
6215 with no line info or whose source file is unavailable. The default is
6216 OFF, which means never display the disassembly of the next line or
6222 @chapter Examining Data
6224 @cindex printing data
6225 @cindex examining data
6228 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6229 @c document because it is nonstandard... Under Epoch it displays in a
6230 @c different window or something like that.
6231 The usual way to examine data in your program is with the @code{print}
6232 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6233 evaluates and prints the value of an expression of the language your
6234 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6235 Different Languages}).
6238 @item print @var{expr}
6239 @itemx print /@var{f} @var{expr}
6240 @var{expr} is an expression (in the source language). By default the
6241 value of @var{expr} is printed in a format appropriate to its data type;
6242 you can choose a different format by specifying @samp{/@var{f}}, where
6243 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6247 @itemx print /@var{f}
6248 @cindex reprint the last value
6249 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6250 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6251 conveniently inspect the same value in an alternative format.
6254 A more low-level way of examining data is with the @code{x} command.
6255 It examines data in memory at a specified address and prints it in a
6256 specified format. @xref{Memory, ,Examining Memory}.
6258 If you are interested in information about types, or about how the
6259 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6260 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6264 * Expressions:: Expressions
6265 * Ambiguous Expressions:: Ambiguous Expressions
6266 * Variables:: Program variables
6267 * Arrays:: Artificial arrays
6268 * Output Formats:: Output formats
6269 * Memory:: Examining memory
6270 * Auto Display:: Automatic display
6271 * Print Settings:: Print settings
6272 * Value History:: Value history
6273 * Convenience Vars:: Convenience variables
6274 * Registers:: Registers
6275 * Floating Point Hardware:: Floating point hardware
6276 * Vector Unit:: Vector Unit
6277 * OS Information:: Auxiliary data provided by operating system
6278 * Memory Region Attributes:: Memory region attributes
6279 * Dump/Restore Files:: Copy between memory and a file
6280 * Core File Generation:: Cause a program dump its core
6281 * Character Sets:: Debugging programs that use a different
6282 character set than GDB does
6283 * Caching Remote Data:: Data caching for remote targets
6284 * Searching Memory:: Searching memory for a sequence of bytes
6288 @section Expressions
6291 @code{print} and many other @value{GDBN} commands accept an expression and
6292 compute its value. Any kind of constant, variable or operator defined
6293 by the programming language you are using is valid in an expression in
6294 @value{GDBN}. This includes conditional expressions, function calls,
6295 casts, and string constants. It also includes preprocessor macros, if
6296 you compiled your program to include this information; see
6299 @cindex arrays in expressions
6300 @value{GDBN} supports array constants in expressions input by
6301 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6302 you can use the command @code{print @{1, 2, 3@}} to create an array
6303 of three integers. If you pass an array to a function or assign it
6304 to a program variable, @value{GDBN} copies the array to memory that
6305 is @code{malloc}ed in the target program.
6307 Because C is so widespread, most of the expressions shown in examples in
6308 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6309 Languages}, for information on how to use expressions in other
6312 In this section, we discuss operators that you can use in @value{GDBN}
6313 expressions regardless of your programming language.
6315 @cindex casts, in expressions
6316 Casts are supported in all languages, not just in C, because it is so
6317 useful to cast a number into a pointer in order to examine a structure
6318 at that address in memory.
6319 @c FIXME: casts supported---Mod2 true?
6321 @value{GDBN} supports these operators, in addition to those common
6322 to programming languages:
6326 @samp{@@} is a binary operator for treating parts of memory as arrays.
6327 @xref{Arrays, ,Artificial Arrays}, for more information.
6330 @samp{::} allows you to specify a variable in terms of the file or
6331 function where it is defined. @xref{Variables, ,Program Variables}.
6333 @cindex @{@var{type}@}
6334 @cindex type casting memory
6335 @cindex memory, viewing as typed object
6336 @cindex casts, to view memory
6337 @item @{@var{type}@} @var{addr}
6338 Refers to an object of type @var{type} stored at address @var{addr} in
6339 memory. @var{addr} may be any expression whose value is an integer or
6340 pointer (but parentheses are required around binary operators, just as in
6341 a cast). This construct is allowed regardless of what kind of data is
6342 normally supposed to reside at @var{addr}.
6345 @node Ambiguous Expressions
6346 @section Ambiguous Expressions
6347 @cindex ambiguous expressions
6349 Expressions can sometimes contain some ambiguous elements. For instance,
6350 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6351 a single function name to be defined several times, for application in
6352 different contexts. This is called @dfn{overloading}. Another example
6353 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6354 templates and is typically instantiated several times, resulting in
6355 the same function name being defined in different contexts.
6357 In some cases and depending on the language, it is possible to adjust
6358 the expression to remove the ambiguity. For instance in C@t{++}, you
6359 can specify the signature of the function you want to break on, as in
6360 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6361 qualified name of your function often makes the expression unambiguous
6364 When an ambiguity that needs to be resolved is detected, the debugger
6365 has the capability to display a menu of numbered choices for each
6366 possibility, and then waits for the selection with the prompt @samp{>}.
6367 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6368 aborts the current command. If the command in which the expression was
6369 used allows more than one choice to be selected, the next option in the
6370 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6373 For example, the following session excerpt shows an attempt to set a
6374 breakpoint at the overloaded symbol @code{String::after}.
6375 We choose three particular definitions of that function name:
6377 @c FIXME! This is likely to change to show arg type lists, at least
6380 (@value{GDBP}) b String::after
6383 [2] file:String.cc; line number:867
6384 [3] file:String.cc; line number:860
6385 [4] file:String.cc; line number:875
6386 [5] file:String.cc; line number:853
6387 [6] file:String.cc; line number:846
6388 [7] file:String.cc; line number:735
6390 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6391 Breakpoint 2 at 0xb344: file String.cc, line 875.
6392 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6393 Multiple breakpoints were set.
6394 Use the "delete" command to delete unwanted
6401 @kindex set multiple-symbols
6402 @item set multiple-symbols @var{mode}
6403 @cindex multiple-symbols menu
6405 This option allows you to adjust the debugger behavior when an expression
6408 By default, @var{mode} is set to @code{all}. If the command with which
6409 the expression is used allows more than one choice, then @value{GDBN}
6410 automatically selects all possible choices. For instance, inserting
6411 a breakpoint on a function using an ambiguous name results in a breakpoint
6412 inserted on each possible match. However, if a unique choice must be made,
6413 then @value{GDBN} uses the menu to help you disambiguate the expression.
6414 For instance, printing the address of an overloaded function will result
6415 in the use of the menu.
6417 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6418 when an ambiguity is detected.
6420 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6421 an error due to the ambiguity and the command is aborted.
6423 @kindex show multiple-symbols
6424 @item show multiple-symbols
6425 Show the current value of the @code{multiple-symbols} setting.
6429 @section Program Variables
6431 The most common kind of expression to use is the name of a variable
6434 Variables in expressions are understood in the selected stack frame
6435 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6439 global (or file-static)
6446 visible according to the scope rules of the
6447 programming language from the point of execution in that frame
6450 @noindent This means that in the function
6465 you can examine and use the variable @code{a} whenever your program is
6466 executing within the function @code{foo}, but you can only use or
6467 examine the variable @code{b} while your program is executing inside
6468 the block where @code{b} is declared.
6470 @cindex variable name conflict
6471 There is an exception: you can refer to a variable or function whose
6472 scope is a single source file even if the current execution point is not
6473 in this file. But it is possible to have more than one such variable or
6474 function with the same name (in different source files). If that
6475 happens, referring to that name has unpredictable effects. If you wish,
6476 you can specify a static variable in a particular function or file,
6477 using the colon-colon (@code{::}) notation:
6479 @cindex colon-colon, context for variables/functions
6481 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6482 @cindex @code{::}, context for variables/functions
6485 @var{file}::@var{variable}
6486 @var{function}::@var{variable}
6490 Here @var{file} or @var{function} is the name of the context for the
6491 static @var{variable}. In the case of file names, you can use quotes to
6492 make sure @value{GDBN} parses the file name as a single word---for example,
6493 to print a global value of @code{x} defined in @file{f2.c}:
6496 (@value{GDBP}) p 'f2.c'::x
6499 @cindex C@t{++} scope resolution
6500 This use of @samp{::} is very rarely in conflict with the very similar
6501 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6502 scope resolution operator in @value{GDBN} expressions.
6503 @c FIXME: Um, so what happens in one of those rare cases where it's in
6506 @cindex wrong values
6507 @cindex variable values, wrong
6508 @cindex function entry/exit, wrong values of variables
6509 @cindex optimized code, wrong values of variables
6511 @emph{Warning:} Occasionally, a local variable may appear to have the
6512 wrong value at certain points in a function---just after entry to a new
6513 scope, and just before exit.
6515 You may see this problem when you are stepping by machine instructions.
6516 This is because, on most machines, it takes more than one instruction to
6517 set up a stack frame (including local variable definitions); if you are
6518 stepping by machine instructions, variables may appear to have the wrong
6519 values until the stack frame is completely built. On exit, it usually
6520 also takes more than one machine instruction to destroy a stack frame;
6521 after you begin stepping through that group of instructions, local
6522 variable definitions may be gone.
6524 This may also happen when the compiler does significant optimizations.
6525 To be sure of always seeing accurate values, turn off all optimization
6528 @cindex ``No symbol "foo" in current context''
6529 Another possible effect of compiler optimizations is to optimize
6530 unused variables out of existence, or assign variables to registers (as
6531 opposed to memory addresses). Depending on the support for such cases
6532 offered by the debug info format used by the compiler, @value{GDBN}
6533 might not be able to display values for such local variables. If that
6534 happens, @value{GDBN} will print a message like this:
6537 No symbol "foo" in current context.
6540 To solve such problems, either recompile without optimizations, or use a
6541 different debug info format, if the compiler supports several such
6542 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6543 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6544 produces debug info in a format that is superior to formats such as
6545 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6546 an effective form for debug info. @xref{Debugging Options,,Options
6547 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6548 Compiler Collection (GCC)}.
6549 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6550 that are best suited to C@t{++} programs.
6552 If you ask to print an object whose contents are unknown to
6553 @value{GDBN}, e.g., because its data type is not completely specified
6554 by the debug information, @value{GDBN} will say @samp{<incomplete
6555 type>}. @xref{Symbols, incomplete type}, for more about this.
6557 Strings are identified as arrays of @code{char} values without specified
6558 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6559 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6560 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6561 defines literal string type @code{"char"} as @code{char} without a sign.
6566 signed char var1[] = "A";
6569 You get during debugging
6574 $2 = @{65 'A', 0 '\0'@}
6578 @section Artificial Arrays
6580 @cindex artificial array
6582 @kindex @@@r{, referencing memory as an array}
6583 It is often useful to print out several successive objects of the
6584 same type in memory; a section of an array, or an array of
6585 dynamically determined size for which only a pointer exists in the
6588 You can do this by referring to a contiguous span of memory as an
6589 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6590 operand of @samp{@@} should be the first element of the desired array
6591 and be an individual object. The right operand should be the desired length
6592 of the array. The result is an array value whose elements are all of
6593 the type of the left argument. The first element is actually the left
6594 argument; the second element comes from bytes of memory immediately
6595 following those that hold the first element, and so on. Here is an
6596 example. If a program says
6599 int *array = (int *) malloc (len * sizeof (int));
6603 you can print the contents of @code{array} with
6609 The left operand of @samp{@@} must reside in memory. Array values made
6610 with @samp{@@} in this way behave just like other arrays in terms of
6611 subscripting, and are coerced to pointers when used in expressions.
6612 Artificial arrays most often appear in expressions via the value history
6613 (@pxref{Value History, ,Value History}), after printing one out.
6615 Another way to create an artificial array is to use a cast.
6616 This re-interprets a value as if it were an array.
6617 The value need not be in memory:
6619 (@value{GDBP}) p/x (short[2])0x12345678
6620 $1 = @{0x1234, 0x5678@}
6623 As a convenience, if you leave the array length out (as in
6624 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6625 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6627 (@value{GDBP}) p/x (short[])0x12345678
6628 $2 = @{0x1234, 0x5678@}
6631 Sometimes the artificial array mechanism is not quite enough; in
6632 moderately complex data structures, the elements of interest may not
6633 actually be adjacent---for example, if you are interested in the values
6634 of pointers in an array. One useful work-around in this situation is
6635 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6636 Variables}) as a counter in an expression that prints the first
6637 interesting value, and then repeat that expression via @key{RET}. For
6638 instance, suppose you have an array @code{dtab} of pointers to
6639 structures, and you are interested in the values of a field @code{fv}
6640 in each structure. Here is an example of what you might type:
6650 @node Output Formats
6651 @section Output Formats
6653 @cindex formatted output
6654 @cindex output formats
6655 By default, @value{GDBN} prints a value according to its data type. Sometimes
6656 this is not what you want. For example, you might want to print a number
6657 in hex, or a pointer in decimal. Or you might want to view data in memory
6658 at a certain address as a character string or as an instruction. To do
6659 these things, specify an @dfn{output format} when you print a value.
6661 The simplest use of output formats is to say how to print a value
6662 already computed. This is done by starting the arguments of the
6663 @code{print} command with a slash and a format letter. The format
6664 letters supported are:
6668 Regard the bits of the value as an integer, and print the integer in
6672 Print as integer in signed decimal.
6675 Print as integer in unsigned decimal.
6678 Print as integer in octal.
6681 Print as integer in binary. The letter @samp{t} stands for ``two''.
6682 @footnote{@samp{b} cannot be used because these format letters are also
6683 used with the @code{x} command, where @samp{b} stands for ``byte'';
6684 see @ref{Memory,,Examining Memory}.}
6687 @cindex unknown address, locating
6688 @cindex locate address
6689 Print as an address, both absolute in hexadecimal and as an offset from
6690 the nearest preceding symbol. You can use this format used to discover
6691 where (in what function) an unknown address is located:
6694 (@value{GDBP}) p/a 0x54320
6695 $3 = 0x54320 <_initialize_vx+396>
6699 The command @code{info symbol 0x54320} yields similar results.
6700 @xref{Symbols, info symbol}.
6703 Regard as an integer and print it as a character constant. This
6704 prints both the numerical value and its character representation. The
6705 character representation is replaced with the octal escape @samp{\nnn}
6706 for characters outside the 7-bit @sc{ascii} range.
6708 Without this format, @value{GDBN} displays @code{char},
6709 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6710 constants. Single-byte members of vectors are displayed as integer
6714 Regard the bits of the value as a floating point number and print
6715 using typical floating point syntax.
6718 @cindex printing strings
6719 @cindex printing byte arrays
6720 Regard as a string, if possible. With this format, pointers to single-byte
6721 data are displayed as null-terminated strings and arrays of single-byte data
6722 are displayed as fixed-length strings. Other values are displayed in their
6725 Without this format, @value{GDBN} displays pointers to and arrays of
6726 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6727 strings. Single-byte members of a vector are displayed as an integer
6731 For example, to print the program counter in hex (@pxref{Registers}), type
6738 Note that no space is required before the slash; this is because command
6739 names in @value{GDBN} cannot contain a slash.
6741 To reprint the last value in the value history with a different format,
6742 you can use the @code{print} command with just a format and no
6743 expression. For example, @samp{p/x} reprints the last value in hex.
6746 @section Examining Memory
6748 You can use the command @code{x} (for ``examine'') to examine memory in
6749 any of several formats, independently of your program's data types.
6751 @cindex examining memory
6753 @kindex x @r{(examine memory)}
6754 @item x/@var{nfu} @var{addr}
6757 Use the @code{x} command to examine memory.
6760 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6761 much memory to display and how to format it; @var{addr} is an
6762 expression giving the address where you want to start displaying memory.
6763 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6764 Several commands set convenient defaults for @var{addr}.
6767 @item @var{n}, the repeat count
6768 The repeat count is a decimal integer; the default is 1. It specifies
6769 how much memory (counting by units @var{u}) to display.
6770 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6773 @item @var{f}, the display format
6774 The display format is one of the formats used by @code{print}
6775 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6776 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6777 The default is @samp{x} (hexadecimal) initially. The default changes
6778 each time you use either @code{x} or @code{print}.
6780 @item @var{u}, the unit size
6781 The unit size is any of
6787 Halfwords (two bytes).
6789 Words (four bytes). This is the initial default.
6791 Giant words (eight bytes).
6794 Each time you specify a unit size with @code{x}, that size becomes the
6795 default unit the next time you use @code{x}. (For the @samp{s} and
6796 @samp{i} formats, the unit size is ignored and is normally not written.)
6798 @item @var{addr}, starting display address
6799 @var{addr} is the address where you want @value{GDBN} to begin displaying
6800 memory. The expression need not have a pointer value (though it may);
6801 it is always interpreted as an integer address of a byte of memory.
6802 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6803 @var{addr} is usually just after the last address examined---but several
6804 other commands also set the default address: @code{info breakpoints} (to
6805 the address of the last breakpoint listed), @code{info line} (to the
6806 starting address of a line), and @code{print} (if you use it to display
6807 a value from memory).
6810 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6811 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6812 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6813 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6814 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6816 Since the letters indicating unit sizes are all distinct from the
6817 letters specifying output formats, you do not have to remember whether
6818 unit size or format comes first; either order works. The output
6819 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6820 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6822 Even though the unit size @var{u} is ignored for the formats @samp{s}
6823 and @samp{i}, you might still want to use a count @var{n}; for example,
6824 @samp{3i} specifies that you want to see three machine instructions,
6825 including any operands. For convenience, especially when used with
6826 the @code{display} command, the @samp{i} format also prints branch delay
6827 slot instructions, if any, beyond the count specified, which immediately
6828 follow the last instruction that is within the count. The command
6829 @code{disassemble} gives an alternative way of inspecting machine
6830 instructions; see @ref{Machine Code,,Source and Machine Code}.
6832 All the defaults for the arguments to @code{x} are designed to make it
6833 easy to continue scanning memory with minimal specifications each time
6834 you use @code{x}. For example, after you have inspected three machine
6835 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6836 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6837 the repeat count @var{n} is used again; the other arguments default as
6838 for successive uses of @code{x}.
6840 @cindex @code{$_}, @code{$__}, and value history
6841 The addresses and contents printed by the @code{x} command are not saved
6842 in the value history because there is often too much of them and they
6843 would get in the way. Instead, @value{GDBN} makes these values available for
6844 subsequent use in expressions as values of the convenience variables
6845 @code{$_} and @code{$__}. After an @code{x} command, the last address
6846 examined is available for use in expressions in the convenience variable
6847 @code{$_}. The contents of that address, as examined, are available in
6848 the convenience variable @code{$__}.
6850 If the @code{x} command has a repeat count, the address and contents saved
6851 are from the last memory unit printed; this is not the same as the last
6852 address printed if several units were printed on the last line of output.
6854 @cindex remote memory comparison
6855 @cindex verify remote memory image
6856 When you are debugging a program running on a remote target machine
6857 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6858 remote machine's memory against the executable file you downloaded to
6859 the target. The @code{compare-sections} command is provided for such
6863 @kindex compare-sections
6864 @item compare-sections @r{[}@var{section-name}@r{]}
6865 Compare the data of a loadable section @var{section-name} in the
6866 executable file of the program being debugged with the same section in
6867 the remote machine's memory, and report any mismatches. With no
6868 arguments, compares all loadable sections. This command's
6869 availability depends on the target's support for the @code{"qCRC"}
6874 @section Automatic Display
6875 @cindex automatic display
6876 @cindex display of expressions
6878 If you find that you want to print the value of an expression frequently
6879 (to see how it changes), you might want to add it to the @dfn{automatic
6880 display list} so that @value{GDBN} prints its value each time your program stops.
6881 Each expression added to the list is given a number to identify it;
6882 to remove an expression from the list, you specify that number.
6883 The automatic display looks like this:
6887 3: bar[5] = (struct hack *) 0x3804
6891 This display shows item numbers, expressions and their current values. As with
6892 displays you request manually using @code{x} or @code{print}, you can
6893 specify the output format you prefer; in fact, @code{display} decides
6894 whether to use @code{print} or @code{x} depending your format
6895 specification---it uses @code{x} if you specify either the @samp{i}
6896 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6900 @item display @var{expr}
6901 Add the expression @var{expr} to the list of expressions to display
6902 each time your program stops. @xref{Expressions, ,Expressions}.
6904 @code{display} does not repeat if you press @key{RET} again after using it.
6906 @item display/@var{fmt} @var{expr}
6907 For @var{fmt} specifying only a display format and not a size or
6908 count, add the expression @var{expr} to the auto-display list but
6909 arrange to display it each time in the specified format @var{fmt}.
6910 @xref{Output Formats,,Output Formats}.
6912 @item display/@var{fmt} @var{addr}
6913 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6914 number of units, add the expression @var{addr} as a memory address to
6915 be examined each time your program stops. Examining means in effect
6916 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6919 For example, @samp{display/i $pc} can be helpful, to see the machine
6920 instruction about to be executed each time execution stops (@samp{$pc}
6921 is a common name for the program counter; @pxref{Registers, ,Registers}).
6924 @kindex delete display
6926 @item undisplay @var{dnums}@dots{}
6927 @itemx delete display @var{dnums}@dots{}
6928 Remove item numbers @var{dnums} from the list of expressions to display.
6930 @code{undisplay} does not repeat if you press @key{RET} after using it.
6931 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6933 @kindex disable display
6934 @item disable display @var{dnums}@dots{}
6935 Disable the display of item numbers @var{dnums}. A disabled display
6936 item is not printed automatically, but is not forgotten. It may be
6937 enabled again later.
6939 @kindex enable display
6940 @item enable display @var{dnums}@dots{}
6941 Enable display of item numbers @var{dnums}. It becomes effective once
6942 again in auto display of its expression, until you specify otherwise.
6945 Display the current values of the expressions on the list, just as is
6946 done when your program stops.
6948 @kindex info display
6950 Print the list of expressions previously set up to display
6951 automatically, each one with its item number, but without showing the
6952 values. This includes disabled expressions, which are marked as such.
6953 It also includes expressions which would not be displayed right now
6954 because they refer to automatic variables not currently available.
6957 @cindex display disabled out of scope
6958 If a display expression refers to local variables, then it does not make
6959 sense outside the lexical context for which it was set up. Such an
6960 expression is disabled when execution enters a context where one of its
6961 variables is not defined. For example, if you give the command
6962 @code{display last_char} while inside a function with an argument
6963 @code{last_char}, @value{GDBN} displays this argument while your program
6964 continues to stop inside that function. When it stops elsewhere---where
6965 there is no variable @code{last_char}---the display is disabled
6966 automatically. The next time your program stops where @code{last_char}
6967 is meaningful, you can enable the display expression once again.
6969 @node Print Settings
6970 @section Print Settings
6972 @cindex format options
6973 @cindex print settings
6974 @value{GDBN} provides the following ways to control how arrays, structures,
6975 and symbols are printed.
6978 These settings are useful for debugging programs in any language:
6982 @item set print address
6983 @itemx set print address on
6984 @cindex print/don't print memory addresses
6985 @value{GDBN} prints memory addresses showing the location of stack
6986 traces, structure values, pointer values, breakpoints, and so forth,
6987 even when it also displays the contents of those addresses. The default
6988 is @code{on}. For example, this is what a stack frame display looks like with
6989 @code{set print address on}:
6994 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6996 530 if (lquote != def_lquote)
7000 @item set print address off
7001 Do not print addresses when displaying their contents. For example,
7002 this is the same stack frame displayed with @code{set print address off}:
7006 (@value{GDBP}) set print addr off
7008 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7009 530 if (lquote != def_lquote)
7013 You can use @samp{set print address off} to eliminate all machine
7014 dependent displays from the @value{GDBN} interface. For example, with
7015 @code{print address off}, you should get the same text for backtraces on
7016 all machines---whether or not they involve pointer arguments.
7019 @item show print address
7020 Show whether or not addresses are to be printed.
7023 When @value{GDBN} prints a symbolic address, it normally prints the
7024 closest earlier symbol plus an offset. If that symbol does not uniquely
7025 identify the address (for example, it is a name whose scope is a single
7026 source file), you may need to clarify. One way to do this is with
7027 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7028 you can set @value{GDBN} to print the source file and line number when
7029 it prints a symbolic address:
7032 @item set print symbol-filename on
7033 @cindex source file and line of a symbol
7034 @cindex symbol, source file and line
7035 Tell @value{GDBN} to print the source file name and line number of a
7036 symbol in the symbolic form of an address.
7038 @item set print symbol-filename off
7039 Do not print source file name and line number of a symbol. This is the
7042 @item show print symbol-filename
7043 Show whether or not @value{GDBN} will print the source file name and
7044 line number of a symbol in the symbolic form of an address.
7047 Another situation where it is helpful to show symbol filenames and line
7048 numbers is when disassembling code; @value{GDBN} shows you the line
7049 number and source file that corresponds to each instruction.
7051 Also, you may wish to see the symbolic form only if the address being
7052 printed is reasonably close to the closest earlier symbol:
7055 @item set print max-symbolic-offset @var{max-offset}
7056 @cindex maximum value for offset of closest symbol
7057 Tell @value{GDBN} to only display the symbolic form of an address if the
7058 offset between the closest earlier symbol and the address is less than
7059 @var{max-offset}. The default is 0, which tells @value{GDBN}
7060 to always print the symbolic form of an address if any symbol precedes it.
7062 @item show print max-symbolic-offset
7063 Ask how large the maximum offset is that @value{GDBN} prints in a
7067 @cindex wild pointer, interpreting
7068 @cindex pointer, finding referent
7069 If you have a pointer and you are not sure where it points, try
7070 @samp{set print symbol-filename on}. Then you can determine the name
7071 and source file location of the variable where it points, using
7072 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7073 For example, here @value{GDBN} shows that a variable @code{ptt} points
7074 at another variable @code{t}, defined in @file{hi2.c}:
7077 (@value{GDBP}) set print symbol-filename on
7078 (@value{GDBP}) p/a ptt
7079 $4 = 0xe008 <t in hi2.c>
7083 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7084 does not show the symbol name and filename of the referent, even with
7085 the appropriate @code{set print} options turned on.
7088 Other settings control how different kinds of objects are printed:
7091 @item set print array
7092 @itemx set print array on
7093 @cindex pretty print arrays
7094 Pretty print arrays. This format is more convenient to read,
7095 but uses more space. The default is off.
7097 @item set print array off
7098 Return to compressed format for arrays.
7100 @item show print array
7101 Show whether compressed or pretty format is selected for displaying
7104 @cindex print array indexes
7105 @item set print array-indexes
7106 @itemx set print array-indexes on
7107 Print the index of each element when displaying arrays. May be more
7108 convenient to locate a given element in the array or quickly find the
7109 index of a given element in that printed array. The default is off.
7111 @item set print array-indexes off
7112 Stop printing element indexes when displaying arrays.
7114 @item show print array-indexes
7115 Show whether the index of each element is printed when displaying
7118 @item set print elements @var{number-of-elements}
7119 @cindex number of array elements to print
7120 @cindex limit on number of printed array elements
7121 Set a limit on how many elements of an array @value{GDBN} will print.
7122 If @value{GDBN} is printing a large array, it stops printing after it has
7123 printed the number of elements set by the @code{set print elements} command.
7124 This limit also applies to the display of strings.
7125 When @value{GDBN} starts, this limit is set to 200.
7126 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7128 @item show print elements
7129 Display the number of elements of a large array that @value{GDBN} will print.
7130 If the number is 0, then the printing is unlimited.
7132 @item set print frame-arguments @var{value}
7133 @kindex set print frame-arguments
7134 @cindex printing frame argument values
7135 @cindex print all frame argument values
7136 @cindex print frame argument values for scalars only
7137 @cindex do not print frame argument values
7138 This command allows to control how the values of arguments are printed
7139 when the debugger prints a frame (@pxref{Frames}). The possible
7144 The values of all arguments are printed.
7147 Print the value of an argument only if it is a scalar. The value of more
7148 complex arguments such as arrays, structures, unions, etc, is replaced
7149 by @code{@dots{}}. This is the default. Here is an example where
7150 only scalar arguments are shown:
7153 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7158 None of the argument values are printed. Instead, the value of each argument
7159 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7162 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7167 By default, only scalar arguments are printed. This command can be used
7168 to configure the debugger to print the value of all arguments, regardless
7169 of their type. However, it is often advantageous to not print the value
7170 of more complex parameters. For instance, it reduces the amount of
7171 information printed in each frame, making the backtrace more readable.
7172 Also, it improves performance when displaying Ada frames, because
7173 the computation of large arguments can sometimes be CPU-intensive,
7174 especially in large applications. Setting @code{print frame-arguments}
7175 to @code{scalars} (the default) or @code{none} avoids this computation,
7176 thus speeding up the display of each Ada frame.
7178 @item show print frame-arguments
7179 Show how the value of arguments should be displayed when printing a frame.
7181 @item set print repeats
7182 @cindex repeated array elements
7183 Set the threshold for suppressing display of repeated array
7184 elements. When the number of consecutive identical elements of an
7185 array exceeds the threshold, @value{GDBN} prints the string
7186 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7187 identical repetitions, instead of displaying the identical elements
7188 themselves. Setting the threshold to zero will cause all elements to
7189 be individually printed. The default threshold is 10.
7191 @item show print repeats
7192 Display the current threshold for printing repeated identical
7195 @item set print null-stop
7196 @cindex @sc{null} elements in arrays
7197 Cause @value{GDBN} to stop printing the characters of an array when the first
7198 @sc{null} is encountered. This is useful when large arrays actually
7199 contain only short strings.
7202 @item show print null-stop
7203 Show whether @value{GDBN} stops printing an array on the first
7204 @sc{null} character.
7206 @item set print pretty on
7207 @cindex print structures in indented form
7208 @cindex indentation in structure display
7209 Cause @value{GDBN} to print structures in an indented format with one member
7210 per line, like this:
7225 @item set print pretty off
7226 Cause @value{GDBN} to print structures in a compact format, like this:
7230 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7231 meat = 0x54 "Pork"@}
7236 This is the default format.
7238 @item show print pretty
7239 Show which format @value{GDBN} is using to print structures.
7241 @item set print sevenbit-strings on
7242 @cindex eight-bit characters in strings
7243 @cindex octal escapes in strings
7244 Print using only seven-bit characters; if this option is set,
7245 @value{GDBN} displays any eight-bit characters (in strings or
7246 character values) using the notation @code{\}@var{nnn}. This setting is
7247 best if you are working in English (@sc{ascii}) and you use the
7248 high-order bit of characters as a marker or ``meta'' bit.
7250 @item set print sevenbit-strings off
7251 Print full eight-bit characters. This allows the use of more
7252 international character sets, and is the default.
7254 @item show print sevenbit-strings
7255 Show whether or not @value{GDBN} is printing only seven-bit characters.
7257 @item set print union on
7258 @cindex unions in structures, printing
7259 Tell @value{GDBN} to print unions which are contained in structures
7260 and other unions. This is the default setting.
7262 @item set print union off
7263 Tell @value{GDBN} not to print unions which are contained in
7264 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7267 @item show print union
7268 Ask @value{GDBN} whether or not it will print unions which are contained in
7269 structures and other unions.
7271 For example, given the declarations
7274 typedef enum @{Tree, Bug@} Species;
7275 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7276 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7287 struct thing foo = @{Tree, @{Acorn@}@};
7291 with @code{set print union on} in effect @samp{p foo} would print
7294 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7298 and with @code{set print union off} in effect it would print
7301 $1 = @{it = Tree, form = @{...@}@}
7305 @code{set print union} affects programs written in C-like languages
7311 These settings are of interest when debugging C@t{++} programs:
7314 @cindex demangling C@t{++} names
7315 @item set print demangle
7316 @itemx set print demangle on
7317 Print C@t{++} names in their source form rather than in the encoded
7318 (``mangled'') form passed to the assembler and linker for type-safe
7319 linkage. The default is on.
7321 @item show print demangle
7322 Show whether C@t{++} names are printed in mangled or demangled form.
7324 @item set print asm-demangle
7325 @itemx set print asm-demangle on
7326 Print C@t{++} names in their source form rather than their mangled form, even
7327 in assembler code printouts such as instruction disassemblies.
7330 @item show print asm-demangle
7331 Show whether C@t{++} names in assembly listings are printed in mangled
7334 @cindex C@t{++} symbol decoding style
7335 @cindex symbol decoding style, C@t{++}
7336 @kindex set demangle-style
7337 @item set demangle-style @var{style}
7338 Choose among several encoding schemes used by different compilers to
7339 represent C@t{++} names. The choices for @var{style} are currently:
7343 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7346 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7347 This is the default.
7350 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7353 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7356 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7357 @strong{Warning:} this setting alone is not sufficient to allow
7358 debugging @code{cfront}-generated executables. @value{GDBN} would
7359 require further enhancement to permit that.
7362 If you omit @var{style}, you will see a list of possible formats.
7364 @item show demangle-style
7365 Display the encoding style currently in use for decoding C@t{++} symbols.
7367 @item set print object
7368 @itemx set print object on
7369 @cindex derived type of an object, printing
7370 @cindex display derived types
7371 When displaying a pointer to an object, identify the @emph{actual}
7372 (derived) type of the object rather than the @emph{declared} type, using
7373 the virtual function table.
7375 @item set print object off
7376 Display only the declared type of objects, without reference to the
7377 virtual function table. This is the default setting.
7379 @item show print object
7380 Show whether actual, or declared, object types are displayed.
7382 @item set print static-members
7383 @itemx set print static-members on
7384 @cindex static members of C@t{++} objects
7385 Print static members when displaying a C@t{++} object. The default is on.
7387 @item set print static-members off
7388 Do not print static members when displaying a C@t{++} object.
7390 @item show print static-members
7391 Show whether C@t{++} static members are printed or not.
7393 @item set print pascal_static-members
7394 @itemx set print pascal_static-members on
7395 @cindex static members of Pascal objects
7396 @cindex Pascal objects, static members display
7397 Print static members when displaying a Pascal object. The default is on.
7399 @item set print pascal_static-members off
7400 Do not print static members when displaying a Pascal object.
7402 @item show print pascal_static-members
7403 Show whether Pascal static members are printed or not.
7405 @c These don't work with HP ANSI C++ yet.
7406 @item set print vtbl
7407 @itemx set print vtbl on
7408 @cindex pretty print C@t{++} virtual function tables
7409 @cindex virtual functions (C@t{++}) display
7410 @cindex VTBL display
7411 Pretty print C@t{++} virtual function tables. The default is off.
7412 (The @code{vtbl} commands do not work on programs compiled with the HP
7413 ANSI C@t{++} compiler (@code{aCC}).)
7415 @item set print vtbl off
7416 Do not pretty print C@t{++} virtual function tables.
7418 @item show print vtbl
7419 Show whether C@t{++} virtual function tables are pretty printed, or not.
7423 @section Value History
7425 @cindex value history
7426 @cindex history of values printed by @value{GDBN}
7427 Values printed by the @code{print} command are saved in the @value{GDBN}
7428 @dfn{value history}. This allows you to refer to them in other expressions.
7429 Values are kept until the symbol table is re-read or discarded
7430 (for example with the @code{file} or @code{symbol-file} commands).
7431 When the symbol table changes, the value history is discarded,
7432 since the values may contain pointers back to the types defined in the
7437 @cindex history number
7438 The values printed are given @dfn{history numbers} by which you can
7439 refer to them. These are successive integers starting with one.
7440 @code{print} shows you the history number assigned to a value by
7441 printing @samp{$@var{num} = } before the value; here @var{num} is the
7444 To refer to any previous value, use @samp{$} followed by the value's
7445 history number. The way @code{print} labels its output is designed to
7446 remind you of this. Just @code{$} refers to the most recent value in
7447 the history, and @code{$$} refers to the value before that.
7448 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7449 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7450 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7452 For example, suppose you have just printed a pointer to a structure and
7453 want to see the contents of the structure. It suffices to type
7459 If you have a chain of structures where the component @code{next} points
7460 to the next one, you can print the contents of the next one with this:
7467 You can print successive links in the chain by repeating this
7468 command---which you can do by just typing @key{RET}.
7470 Note that the history records values, not expressions. If the value of
7471 @code{x} is 4 and you type these commands:
7479 then the value recorded in the value history by the @code{print} command
7480 remains 4 even though the value of @code{x} has changed.
7485 Print the last ten values in the value history, with their item numbers.
7486 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7487 values} does not change the history.
7489 @item show values @var{n}
7490 Print ten history values centered on history item number @var{n}.
7493 Print ten history values just after the values last printed. If no more
7494 values are available, @code{show values +} produces no display.
7497 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7498 same effect as @samp{show values +}.
7500 @node Convenience Vars
7501 @section Convenience Variables
7503 @cindex convenience variables
7504 @cindex user-defined variables
7505 @value{GDBN} provides @dfn{convenience variables} that you can use within
7506 @value{GDBN} to hold on to a value and refer to it later. These variables
7507 exist entirely within @value{GDBN}; they are not part of your program, and
7508 setting a convenience variable has no direct effect on further execution
7509 of your program. That is why you can use them freely.
7511 Convenience variables are prefixed with @samp{$}. Any name preceded by
7512 @samp{$} can be used for a convenience variable, unless it is one of
7513 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7514 (Value history references, in contrast, are @emph{numbers} preceded
7515 by @samp{$}. @xref{Value History, ,Value History}.)
7517 You can save a value in a convenience variable with an assignment
7518 expression, just as you would set a variable in your program.
7522 set $foo = *object_ptr
7526 would save in @code{$foo} the value contained in the object pointed to by
7529 Using a convenience variable for the first time creates it, but its
7530 value is @code{void} until you assign a new value. You can alter the
7531 value with another assignment at any time.
7533 Convenience variables have no fixed types. You can assign a convenience
7534 variable any type of value, including structures and arrays, even if
7535 that variable already has a value of a different type. The convenience
7536 variable, when used as an expression, has the type of its current value.
7539 @kindex show convenience
7540 @cindex show all user variables
7541 @item show convenience
7542 Print a list of convenience variables used so far, and their values.
7543 Abbreviated @code{show conv}.
7545 @kindex init-if-undefined
7546 @cindex convenience variables, initializing
7547 @item init-if-undefined $@var{variable} = @var{expression}
7548 Set a convenience variable if it has not already been set. This is useful
7549 for user-defined commands that keep some state. It is similar, in concept,
7550 to using local static variables with initializers in C (except that
7551 convenience variables are global). It can also be used to allow users to
7552 override default values used in a command script.
7554 If the variable is already defined then the expression is not evaluated so
7555 any side-effects do not occur.
7558 One of the ways to use a convenience variable is as a counter to be
7559 incremented or a pointer to be advanced. For example, to print
7560 a field from successive elements of an array of structures:
7564 print bar[$i++]->contents
7568 Repeat that command by typing @key{RET}.
7570 Some convenience variables are created automatically by @value{GDBN} and given
7571 values likely to be useful.
7574 @vindex $_@r{, convenience variable}
7576 The variable @code{$_} is automatically set by the @code{x} command to
7577 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7578 commands which provide a default address for @code{x} to examine also
7579 set @code{$_} to that address; these commands include @code{info line}
7580 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7581 except when set by the @code{x} command, in which case it is a pointer
7582 to the type of @code{$__}.
7584 @vindex $__@r{, convenience variable}
7586 The variable @code{$__} is automatically set by the @code{x} command
7587 to the value found in the last address examined. Its type is chosen
7588 to match the format in which the data was printed.
7591 @vindex $_exitcode@r{, convenience variable}
7592 The variable @code{$_exitcode} is automatically set to the exit code when
7593 the program being debugged terminates.
7596 @vindex $_siginfo@r{, convenience variable}
7597 The variable @code{$_siginfo} is bound to extra signal information
7598 inspection (@pxref{extra signal information}).
7601 On HP-UX systems, if you refer to a function or variable name that
7602 begins with a dollar sign, @value{GDBN} searches for a user or system
7603 name first, before it searches for a convenience variable.
7605 @cindex convenience functions
7606 @value{GDBN} also supplies some @dfn{convenience functions}. These
7607 have a syntax similar to convenience variables. A convenience
7608 function can be used in an expression just like an ordinary function;
7609 however, a convenience function is implemented internally to
7614 @kindex help function
7615 @cindex show all convenience functions
7616 Print a list of all convenience functions.
7623 You can refer to machine register contents, in expressions, as variables
7624 with names starting with @samp{$}. The names of registers are different
7625 for each machine; use @code{info registers} to see the names used on
7629 @kindex info registers
7630 @item info registers
7631 Print the names and values of all registers except floating-point
7632 and vector registers (in the selected stack frame).
7634 @kindex info all-registers
7635 @cindex floating point registers
7636 @item info all-registers
7637 Print the names and values of all registers, including floating-point
7638 and vector registers (in the selected stack frame).
7640 @item info registers @var{regname} @dots{}
7641 Print the @dfn{relativized} value of each specified register @var{regname}.
7642 As discussed in detail below, register values are normally relative to
7643 the selected stack frame. @var{regname} may be any register name valid on
7644 the machine you are using, with or without the initial @samp{$}.
7647 @cindex stack pointer register
7648 @cindex program counter register
7649 @cindex process status register
7650 @cindex frame pointer register
7651 @cindex standard registers
7652 @value{GDBN} has four ``standard'' register names that are available (in
7653 expressions) on most machines---whenever they do not conflict with an
7654 architecture's canonical mnemonics for registers. The register names
7655 @code{$pc} and @code{$sp} are used for the program counter register and
7656 the stack pointer. @code{$fp} is used for a register that contains a
7657 pointer to the current stack frame, and @code{$ps} is used for a
7658 register that contains the processor status. For example,
7659 you could print the program counter in hex with
7666 or print the instruction to be executed next with
7673 or add four to the stack pointer@footnote{This is a way of removing
7674 one word from the stack, on machines where stacks grow downward in
7675 memory (most machines, nowadays). This assumes that the innermost
7676 stack frame is selected; setting @code{$sp} is not allowed when other
7677 stack frames are selected. To pop entire frames off the stack,
7678 regardless of machine architecture, use @code{return};
7679 see @ref{Returning, ,Returning from a Function}.} with
7685 Whenever possible, these four standard register names are available on
7686 your machine even though the machine has different canonical mnemonics,
7687 so long as there is no conflict. The @code{info registers} command
7688 shows the canonical names. For example, on the SPARC, @code{info
7689 registers} displays the processor status register as @code{$psr} but you
7690 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7691 is an alias for the @sc{eflags} register.
7693 @value{GDBN} always considers the contents of an ordinary register as an
7694 integer when the register is examined in this way. Some machines have
7695 special registers which can hold nothing but floating point; these
7696 registers are considered to have floating point values. There is no way
7697 to refer to the contents of an ordinary register as floating point value
7698 (although you can @emph{print} it as a floating point value with
7699 @samp{print/f $@var{regname}}).
7701 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7702 means that the data format in which the register contents are saved by
7703 the operating system is not the same one that your program normally
7704 sees. For example, the registers of the 68881 floating point
7705 coprocessor are always saved in ``extended'' (raw) format, but all C
7706 programs expect to work with ``double'' (virtual) format. In such
7707 cases, @value{GDBN} normally works with the virtual format only (the format
7708 that makes sense for your program), but the @code{info registers} command
7709 prints the data in both formats.
7711 @cindex SSE registers (x86)
7712 @cindex MMX registers (x86)
7713 Some machines have special registers whose contents can be interpreted
7714 in several different ways. For example, modern x86-based machines
7715 have SSE and MMX registers that can hold several values packed
7716 together in several different formats. @value{GDBN} refers to such
7717 registers in @code{struct} notation:
7720 (@value{GDBP}) print $xmm1
7722 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7723 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7724 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7725 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7726 v4_int32 = @{0, 20657912, 11, 13@},
7727 v2_int64 = @{88725056443645952, 55834574859@},
7728 uint128 = 0x0000000d0000000b013b36f800000000
7733 To set values of such registers, you need to tell @value{GDBN} which
7734 view of the register you wish to change, as if you were assigning
7735 value to a @code{struct} member:
7738 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7741 Normally, register values are relative to the selected stack frame
7742 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7743 value that the register would contain if all stack frames farther in
7744 were exited and their saved registers restored. In order to see the
7745 true contents of hardware registers, you must select the innermost
7746 frame (with @samp{frame 0}).
7748 However, @value{GDBN} must deduce where registers are saved, from the machine
7749 code generated by your compiler. If some registers are not saved, or if
7750 @value{GDBN} is unable to locate the saved registers, the selected stack
7751 frame makes no difference.
7753 @node Floating Point Hardware
7754 @section Floating Point Hardware
7755 @cindex floating point
7757 Depending on the configuration, @value{GDBN} may be able to give
7758 you more information about the status of the floating point hardware.
7763 Display hardware-dependent information about the floating
7764 point unit. The exact contents and layout vary depending on the
7765 floating point chip. Currently, @samp{info float} is supported on
7766 the ARM and x86 machines.
7770 @section Vector Unit
7773 Depending on the configuration, @value{GDBN} may be able to give you
7774 more information about the status of the vector unit.
7779 Display information about the vector unit. The exact contents and
7780 layout vary depending on the hardware.
7783 @node OS Information
7784 @section Operating System Auxiliary Information
7785 @cindex OS information
7787 @value{GDBN} provides interfaces to useful OS facilities that can help
7788 you debug your program.
7790 @cindex @code{ptrace} system call
7791 @cindex @code{struct user} contents
7792 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7793 machines), it interfaces with the inferior via the @code{ptrace}
7794 system call. The operating system creates a special sata structure,
7795 called @code{struct user}, for this interface. You can use the
7796 command @code{info udot} to display the contents of this data
7802 Display the contents of the @code{struct user} maintained by the OS
7803 kernel for the program being debugged. @value{GDBN} displays the
7804 contents of @code{struct user} as a list of hex numbers, similar to
7805 the @code{examine} command.
7808 @cindex auxiliary vector
7809 @cindex vector, auxiliary
7810 Some operating systems supply an @dfn{auxiliary vector} to programs at
7811 startup. This is akin to the arguments and environment that you
7812 specify for a program, but contains a system-dependent variety of
7813 binary values that tell system libraries important details about the
7814 hardware, operating system, and process. Each value's purpose is
7815 identified by an integer tag; the meanings are well-known but system-specific.
7816 Depending on the configuration and operating system facilities,
7817 @value{GDBN} may be able to show you this information. For remote
7818 targets, this functionality may further depend on the remote stub's
7819 support of the @samp{qXfer:auxv:read} packet, see
7820 @ref{qXfer auxiliary vector read}.
7825 Display the auxiliary vector of the inferior, which can be either a
7826 live process or a core dump file. @value{GDBN} prints each tag value
7827 numerically, and also shows names and text descriptions for recognized
7828 tags. Some values in the vector are numbers, some bit masks, and some
7829 pointers to strings or other data. @value{GDBN} displays each value in the
7830 most appropriate form for a recognized tag, and in hexadecimal for
7831 an unrecognized tag.
7834 On some targets, @value{GDBN} can access operating-system-specific information
7835 and display it to user, without interpretation. For remote targets,
7836 this functionality depends on the remote stub's support of the
7837 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7840 @kindex info os processes
7841 @item info os processes
7842 Display the list of processes on the target. For each process,
7843 @value{GDBN} prints the process identifier, the name of the user, and
7844 the command corresponding to the process.
7847 @node Memory Region Attributes
7848 @section Memory Region Attributes
7849 @cindex memory region attributes
7851 @dfn{Memory region attributes} allow you to describe special handling
7852 required by regions of your target's memory. @value{GDBN} uses
7853 attributes to determine whether to allow certain types of memory
7854 accesses; whether to use specific width accesses; and whether to cache
7855 target memory. By default the description of memory regions is
7856 fetched from the target (if the current target supports this), but the
7857 user can override the fetched regions.
7859 Defined memory regions can be individually enabled and disabled. When a
7860 memory region is disabled, @value{GDBN} uses the default attributes when
7861 accessing memory in that region. Similarly, if no memory regions have
7862 been defined, @value{GDBN} uses the default attributes when accessing
7865 When a memory region is defined, it is given a number to identify it;
7866 to enable, disable, or remove a memory region, you specify that number.
7870 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7871 Define a memory region bounded by @var{lower} and @var{upper} with
7872 attributes @var{attributes}@dots{}, and add it to the list of regions
7873 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7874 case: it is treated as the target's maximum memory address.
7875 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7878 Discard any user changes to the memory regions and use target-supplied
7879 regions, if available, or no regions if the target does not support.
7882 @item delete mem @var{nums}@dots{}
7883 Remove memory regions @var{nums}@dots{} from the list of regions
7884 monitored by @value{GDBN}.
7887 @item disable mem @var{nums}@dots{}
7888 Disable monitoring of memory regions @var{nums}@dots{}.
7889 A disabled memory region is not forgotten.
7890 It may be enabled again later.
7893 @item enable mem @var{nums}@dots{}
7894 Enable monitoring of memory regions @var{nums}@dots{}.
7898 Print a table of all defined memory regions, with the following columns
7902 @item Memory Region Number
7903 @item Enabled or Disabled.
7904 Enabled memory regions are marked with @samp{y}.
7905 Disabled memory regions are marked with @samp{n}.
7908 The address defining the inclusive lower bound of the memory region.
7911 The address defining the exclusive upper bound of the memory region.
7914 The list of attributes set for this memory region.
7919 @subsection Attributes
7921 @subsubsection Memory Access Mode
7922 The access mode attributes set whether @value{GDBN} may make read or
7923 write accesses to a memory region.
7925 While these attributes prevent @value{GDBN} from performing invalid
7926 memory accesses, they do nothing to prevent the target system, I/O DMA,
7927 etc.@: from accessing memory.
7931 Memory is read only.
7933 Memory is write only.
7935 Memory is read/write. This is the default.
7938 @subsubsection Memory Access Size
7939 The access size attribute tells @value{GDBN} to use specific sized
7940 accesses in the memory region. Often memory mapped device registers
7941 require specific sized accesses. If no access size attribute is
7942 specified, @value{GDBN} may use accesses of any size.
7946 Use 8 bit memory accesses.
7948 Use 16 bit memory accesses.
7950 Use 32 bit memory accesses.
7952 Use 64 bit memory accesses.
7955 @c @subsubsection Hardware/Software Breakpoints
7956 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7957 @c will use hardware or software breakpoints for the internal breakpoints
7958 @c used by the step, next, finish, until, etc. commands.
7962 @c Always use hardware breakpoints
7963 @c @item swbreak (default)
7966 @subsubsection Data Cache
7967 The data cache attributes set whether @value{GDBN} will cache target
7968 memory. While this generally improves performance by reducing debug
7969 protocol overhead, it can lead to incorrect results because @value{GDBN}
7970 does not know about volatile variables or memory mapped device
7975 Enable @value{GDBN} to cache target memory.
7977 Disable @value{GDBN} from caching target memory. This is the default.
7980 @subsection Memory Access Checking
7981 @value{GDBN} can be instructed to refuse accesses to memory that is
7982 not explicitly described. This can be useful if accessing such
7983 regions has undesired effects for a specific target, or to provide
7984 better error checking. The following commands control this behaviour.
7987 @kindex set mem inaccessible-by-default
7988 @item set mem inaccessible-by-default [on|off]
7989 If @code{on} is specified, make @value{GDBN} treat memory not
7990 explicitly described by the memory ranges as non-existent and refuse accesses
7991 to such memory. The checks are only performed if there's at least one
7992 memory range defined. If @code{off} is specified, make @value{GDBN}
7993 treat the memory not explicitly described by the memory ranges as RAM.
7994 The default value is @code{on}.
7995 @kindex show mem inaccessible-by-default
7996 @item show mem inaccessible-by-default
7997 Show the current handling of accesses to unknown memory.
8001 @c @subsubsection Memory Write Verification
8002 @c The memory write verification attributes set whether @value{GDBN}
8003 @c will re-reads data after each write to verify the write was successful.
8007 @c @item noverify (default)
8010 @node Dump/Restore Files
8011 @section Copy Between Memory and a File
8012 @cindex dump/restore files
8013 @cindex append data to a file
8014 @cindex dump data to a file
8015 @cindex restore data from a file
8017 You can use the commands @code{dump}, @code{append}, and
8018 @code{restore} to copy data between target memory and a file. The
8019 @code{dump} and @code{append} commands write data to a file, and the
8020 @code{restore} command reads data from a file back into the inferior's
8021 memory. Files may be in binary, Motorola S-record, Intel hex, or
8022 Tektronix Hex format; however, @value{GDBN} can only append to binary
8028 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8029 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8030 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8031 or the value of @var{expr}, to @var{filename} in the given format.
8033 The @var{format} parameter may be any one of:
8040 Motorola S-record format.
8042 Tektronix Hex format.
8045 @value{GDBN} uses the same definitions of these formats as the
8046 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8047 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8051 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8052 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8053 Append the contents of memory from @var{start_addr} to @var{end_addr},
8054 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8055 (@value{GDBN} can only append data to files in raw binary form.)
8058 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8059 Restore the contents of file @var{filename} into memory. The
8060 @code{restore} command can automatically recognize any known @sc{bfd}
8061 file format, except for raw binary. To restore a raw binary file you
8062 must specify the optional keyword @code{binary} after the filename.
8064 If @var{bias} is non-zero, its value will be added to the addresses
8065 contained in the file. Binary files always start at address zero, so
8066 they will be restored at address @var{bias}. Other bfd files have
8067 a built-in location; they will be restored at offset @var{bias}
8070 If @var{start} and/or @var{end} are non-zero, then only data between
8071 file offset @var{start} and file offset @var{end} will be restored.
8072 These offsets are relative to the addresses in the file, before
8073 the @var{bias} argument is applied.
8077 @node Core File Generation
8078 @section How to Produce a Core File from Your Program
8079 @cindex dump core from inferior
8081 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8082 image of a running process and its process status (register values
8083 etc.). Its primary use is post-mortem debugging of a program that
8084 crashed while it ran outside a debugger. A program that crashes
8085 automatically produces a core file, unless this feature is disabled by
8086 the user. @xref{Files}, for information on invoking @value{GDBN} in
8087 the post-mortem debugging mode.
8089 Occasionally, you may wish to produce a core file of the program you
8090 are debugging in order to preserve a snapshot of its state.
8091 @value{GDBN} has a special command for that.
8095 @kindex generate-core-file
8096 @item generate-core-file [@var{file}]
8097 @itemx gcore [@var{file}]
8098 Produce a core dump of the inferior process. The optional argument
8099 @var{file} specifies the file name where to put the core dump. If not
8100 specified, the file name defaults to @file{core.@var{pid}}, where
8101 @var{pid} is the inferior process ID.
8103 Note that this command is implemented only for some systems (as of
8104 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8107 @node Character Sets
8108 @section Character Sets
8109 @cindex character sets
8111 @cindex translating between character sets
8112 @cindex host character set
8113 @cindex target character set
8115 If the program you are debugging uses a different character set to
8116 represent characters and strings than the one @value{GDBN} uses itself,
8117 @value{GDBN} can automatically translate between the character sets for
8118 you. The character set @value{GDBN} uses we call the @dfn{host
8119 character set}; the one the inferior program uses we call the
8120 @dfn{target character set}.
8122 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8123 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8124 remote protocol (@pxref{Remote Debugging}) to debug a program
8125 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8126 then the host character set is Latin-1, and the target character set is
8127 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8128 target-charset EBCDIC-US}, then @value{GDBN} translates between
8129 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8130 character and string literals in expressions.
8132 @value{GDBN} has no way to automatically recognize which character set
8133 the inferior program uses; you must tell it, using the @code{set
8134 target-charset} command, described below.
8136 Here are the commands for controlling @value{GDBN}'s character set
8140 @item set target-charset @var{charset}
8141 @kindex set target-charset
8142 Set the current target character set to @var{charset}. To display the
8143 list of supported target character sets, type
8144 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8146 @item set host-charset @var{charset}
8147 @kindex set host-charset
8148 Set the current host character set to @var{charset}.
8150 By default, @value{GDBN} uses a host character set appropriate to the
8151 system it is running on; you can override that default using the
8152 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8153 automatically determine the appropriate host character set. In this
8154 case, @value{GDBN} uses @samp{UTF-8}.
8156 @value{GDBN} can only use certain character sets as its host character
8157 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8158 @value{GDBN} will list the host character sets it supports.
8160 @item set charset @var{charset}
8162 Set the current host and target character sets to @var{charset}. As
8163 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8164 @value{GDBN} will list the names of the character sets that can be used
8165 for both host and target.
8168 @kindex show charset
8169 Show the names of the current host and target character sets.
8171 @item show host-charset
8172 @kindex show host-charset
8173 Show the name of the current host character set.
8175 @item show target-charset
8176 @kindex show target-charset
8177 Show the name of the current target character set.
8179 @item set target-wide-charset @var{charset}
8180 @kindex set target-wide-charset
8181 Set the current target's wide character set to @var{charset}. This is
8182 the character set used by the target's @code{wchar_t} type. To
8183 display the list of supported wide character sets, type
8184 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8186 @item show target-wide-charset
8187 @kindex show target-wide-charset
8188 Show the name of the current target's wide character set.
8191 Here is an example of @value{GDBN}'s character set support in action.
8192 Assume that the following source code has been placed in the file
8193 @file{charset-test.c}:
8199 = @{72, 101, 108, 108, 111, 44, 32, 119,
8200 111, 114, 108, 100, 33, 10, 0@};
8201 char ibm1047_hello[]
8202 = @{200, 133, 147, 147, 150, 107, 64, 166,
8203 150, 153, 147, 132, 90, 37, 0@};
8207 printf ("Hello, world!\n");
8211 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8212 containing the string @samp{Hello, world!} followed by a newline,
8213 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8215 We compile the program, and invoke the debugger on it:
8218 $ gcc -g charset-test.c -o charset-test
8219 $ gdb -nw charset-test
8220 GNU gdb 2001-12-19-cvs
8221 Copyright 2001 Free Software Foundation, Inc.
8226 We can use the @code{show charset} command to see what character sets
8227 @value{GDBN} is currently using to interpret and display characters and
8231 (@value{GDBP}) show charset
8232 The current host and target character set is `ISO-8859-1'.
8236 For the sake of printing this manual, let's use @sc{ascii} as our
8237 initial character set:
8239 (@value{GDBP}) set charset ASCII
8240 (@value{GDBP}) show charset
8241 The current host and target character set is `ASCII'.
8245 Let's assume that @sc{ascii} is indeed the correct character set for our
8246 host system --- in other words, let's assume that if @value{GDBN} prints
8247 characters using the @sc{ascii} character set, our terminal will display
8248 them properly. Since our current target character set is also
8249 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8252 (@value{GDBP}) print ascii_hello
8253 $1 = 0x401698 "Hello, world!\n"
8254 (@value{GDBP}) print ascii_hello[0]
8259 @value{GDBN} uses the target character set for character and string
8260 literals you use in expressions:
8263 (@value{GDBP}) print '+'
8268 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8271 @value{GDBN} relies on the user to tell it which character set the
8272 target program uses. If we print @code{ibm1047_hello} while our target
8273 character set is still @sc{ascii}, we get jibberish:
8276 (@value{GDBP}) print ibm1047_hello
8277 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8278 (@value{GDBP}) print ibm1047_hello[0]
8283 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8284 @value{GDBN} tells us the character sets it supports:
8287 (@value{GDBP}) set target-charset
8288 ASCII EBCDIC-US IBM1047 ISO-8859-1
8289 (@value{GDBP}) set target-charset
8292 We can select @sc{ibm1047} as our target character set, and examine the
8293 program's strings again. Now the @sc{ascii} string is wrong, but
8294 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8295 target character set, @sc{ibm1047}, to the host character set,
8296 @sc{ascii}, and they display correctly:
8299 (@value{GDBP}) set target-charset IBM1047
8300 (@value{GDBP}) show charset
8301 The current host character set is `ASCII'.
8302 The current target character set is `IBM1047'.
8303 (@value{GDBP}) print ascii_hello
8304 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8305 (@value{GDBP}) print ascii_hello[0]
8307 (@value{GDBP}) print ibm1047_hello
8308 $8 = 0x4016a8 "Hello, world!\n"
8309 (@value{GDBP}) print ibm1047_hello[0]
8314 As above, @value{GDBN} uses the target character set for character and
8315 string literals you use in expressions:
8318 (@value{GDBP}) print '+'
8323 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8326 @node Caching Remote Data
8327 @section Caching Data of Remote Targets
8328 @cindex caching data of remote targets
8330 @value{GDBN} can cache data exchanged between the debugger and a
8331 remote target (@pxref{Remote Debugging}). Such caching generally improves
8332 performance, because it reduces the overhead of the remote protocol by
8333 bundling memory reads and writes into large chunks. Unfortunately,
8334 @value{GDBN} does not currently know anything about volatile
8335 registers, and thus data caching will produce incorrect results when
8336 volatile registers are in use.
8339 @kindex set remotecache
8340 @item set remotecache on
8341 @itemx set remotecache off
8342 Set caching state for remote targets. When @code{ON}, use data
8343 caching. By default, this option is @code{OFF}.
8345 @kindex show remotecache
8346 @item show remotecache
8347 Show the current state of data caching for remote targets.
8351 Print the information about the data cache performance. The
8352 information displayed includes: the dcache width and depth; and for
8353 each cache line, how many times it was referenced, and its data and
8354 state (invalid, dirty, valid). This command is useful for debugging
8355 the data cache operation.
8358 @node Searching Memory
8359 @section Search Memory
8360 @cindex searching memory
8362 Memory can be searched for a particular sequence of bytes with the
8363 @code{find} command.
8367 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8368 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8369 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8370 etc. The search begins at address @var{start_addr} and continues for either
8371 @var{len} bytes or through to @var{end_addr} inclusive.
8374 @var{s} and @var{n} are optional parameters.
8375 They may be specified in either order, apart or together.
8378 @item @var{s}, search query size
8379 The size of each search query value.
8385 halfwords (two bytes)
8389 giant words (eight bytes)
8392 All values are interpreted in the current language.
8393 This means, for example, that if the current source language is C/C@t{++}
8394 then searching for the string ``hello'' includes the trailing '\0'.
8396 If the value size is not specified, it is taken from the
8397 value's type in the current language.
8398 This is useful when one wants to specify the search
8399 pattern as a mixture of types.
8400 Note that this means, for example, that in the case of C-like languages
8401 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8402 which is typically four bytes.
8404 @item @var{n}, maximum number of finds
8405 The maximum number of matches to print. The default is to print all finds.
8408 You can use strings as search values. Quote them with double-quotes
8410 The string value is copied into the search pattern byte by byte,
8411 regardless of the endianness of the target and the size specification.
8413 The address of each match found is printed as well as a count of the
8414 number of matches found.
8416 The address of the last value found is stored in convenience variable
8418 A count of the number of matches is stored in @samp{$numfound}.
8420 For example, if stopped at the @code{printf} in this function:
8426 static char hello[] = "hello-hello";
8427 static struct @{ char c; short s; int i; @}
8428 __attribute__ ((packed)) mixed
8429 = @{ 'c', 0x1234, 0x87654321 @};
8430 printf ("%s\n", hello);
8435 you get during debugging:
8438 (gdb) find &hello[0], +sizeof(hello), "hello"
8439 0x804956d <hello.1620+6>
8441 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8442 0x8049567 <hello.1620>
8443 0x804956d <hello.1620+6>
8445 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8446 0x8049567 <hello.1620>
8448 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8449 0x8049560 <mixed.1625>
8451 (gdb) print $numfound
8454 $2 = (void *) 0x8049560
8458 @chapter C Preprocessor Macros
8460 Some languages, such as C and C@t{++}, provide a way to define and invoke
8461 ``preprocessor macros'' which expand into strings of tokens.
8462 @value{GDBN} can evaluate expressions containing macro invocations, show
8463 the result of macro expansion, and show a macro's definition, including
8464 where it was defined.
8466 You may need to compile your program specially to provide @value{GDBN}
8467 with information about preprocessor macros. Most compilers do not
8468 include macros in their debugging information, even when you compile
8469 with the @option{-g} flag. @xref{Compilation}.
8471 A program may define a macro at one point, remove that definition later,
8472 and then provide a different definition after that. Thus, at different
8473 points in the program, a macro may have different definitions, or have
8474 no definition at all. If there is a current stack frame, @value{GDBN}
8475 uses the macros in scope at that frame's source code line. Otherwise,
8476 @value{GDBN} uses the macros in scope at the current listing location;
8479 Whenever @value{GDBN} evaluates an expression, it always expands any
8480 macro invocations present in the expression. @value{GDBN} also provides
8481 the following commands for working with macros explicitly.
8485 @kindex macro expand
8486 @cindex macro expansion, showing the results of preprocessor
8487 @cindex preprocessor macro expansion, showing the results of
8488 @cindex expanding preprocessor macros
8489 @item macro expand @var{expression}
8490 @itemx macro exp @var{expression}
8491 Show the results of expanding all preprocessor macro invocations in
8492 @var{expression}. Since @value{GDBN} simply expands macros, but does
8493 not parse the result, @var{expression} need not be a valid expression;
8494 it can be any string of tokens.
8497 @item macro expand-once @var{expression}
8498 @itemx macro exp1 @var{expression}
8499 @cindex expand macro once
8500 @i{(This command is not yet implemented.)} Show the results of
8501 expanding those preprocessor macro invocations that appear explicitly in
8502 @var{expression}. Macro invocations appearing in that expansion are
8503 left unchanged. This command allows you to see the effect of a
8504 particular macro more clearly, without being confused by further
8505 expansions. Since @value{GDBN} simply expands macros, but does not
8506 parse the result, @var{expression} need not be a valid expression; it
8507 can be any string of tokens.
8510 @cindex macro definition, showing
8511 @cindex definition, showing a macro's
8512 @item info macro @var{macro}
8513 Show the definition of the macro named @var{macro}, and describe the
8514 source location or compiler command-line where that definition was established.
8516 @kindex macro define
8517 @cindex user-defined macros
8518 @cindex defining macros interactively
8519 @cindex macros, user-defined
8520 @item macro define @var{macro} @var{replacement-list}
8521 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8522 Introduce a definition for a preprocessor macro named @var{macro},
8523 invocations of which are replaced by the tokens given in
8524 @var{replacement-list}. The first form of this command defines an
8525 ``object-like'' macro, which takes no arguments; the second form
8526 defines a ``function-like'' macro, which takes the arguments given in
8529 A definition introduced by this command is in scope in every
8530 expression evaluated in @value{GDBN}, until it is removed with the
8531 @code{macro undef} command, described below. The definition overrides
8532 all definitions for @var{macro} present in the program being debugged,
8533 as well as any previous user-supplied definition.
8536 @item macro undef @var{macro}
8537 Remove any user-supplied definition for the macro named @var{macro}.
8538 This command only affects definitions provided with the @code{macro
8539 define} command, described above; it cannot remove definitions present
8540 in the program being debugged.
8544 List all the macros defined using the @code{macro define} command.
8547 @cindex macros, example of debugging with
8548 Here is a transcript showing the above commands in action. First, we
8549 show our source files:
8557 #define ADD(x) (M + x)
8562 printf ("Hello, world!\n");
8564 printf ("We're so creative.\n");
8566 printf ("Goodbye, world!\n");
8573 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8574 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8575 compiler includes information about preprocessor macros in the debugging
8579 $ gcc -gdwarf-2 -g3 sample.c -o sample
8583 Now, we start @value{GDBN} on our sample program:
8587 GNU gdb 2002-05-06-cvs
8588 Copyright 2002 Free Software Foundation, Inc.
8589 GDB is free software, @dots{}
8593 We can expand macros and examine their definitions, even when the
8594 program is not running. @value{GDBN} uses the current listing position
8595 to decide which macro definitions are in scope:
8598 (@value{GDBP}) list main
8601 5 #define ADD(x) (M + x)
8606 10 printf ("Hello, world!\n");
8608 12 printf ("We're so creative.\n");
8609 (@value{GDBP}) info macro ADD
8610 Defined at /home/jimb/gdb/macros/play/sample.c:5
8611 #define ADD(x) (M + x)
8612 (@value{GDBP}) info macro Q
8613 Defined at /home/jimb/gdb/macros/play/sample.h:1
8614 included at /home/jimb/gdb/macros/play/sample.c:2
8616 (@value{GDBP}) macro expand ADD(1)
8617 expands to: (42 + 1)
8618 (@value{GDBP}) macro expand-once ADD(1)
8619 expands to: once (M + 1)
8623 In the example above, note that @code{macro expand-once} expands only
8624 the macro invocation explicit in the original text --- the invocation of
8625 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8626 which was introduced by @code{ADD}.
8628 Once the program is running, @value{GDBN} uses the macro definitions in
8629 force at the source line of the current stack frame:
8632 (@value{GDBP}) break main
8633 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8635 Starting program: /home/jimb/gdb/macros/play/sample
8637 Breakpoint 1, main () at sample.c:10
8638 10 printf ("Hello, world!\n");
8642 At line 10, the definition of the macro @code{N} at line 9 is in force:
8645 (@value{GDBP}) info macro N
8646 Defined at /home/jimb/gdb/macros/play/sample.c:9
8648 (@value{GDBP}) macro expand N Q M
8650 (@value{GDBP}) print N Q M
8655 As we step over directives that remove @code{N}'s definition, and then
8656 give it a new definition, @value{GDBN} finds the definition (or lack
8657 thereof) in force at each point:
8662 12 printf ("We're so creative.\n");
8663 (@value{GDBP}) info macro N
8664 The symbol `N' has no definition as a C/C++ preprocessor macro
8665 at /home/jimb/gdb/macros/play/sample.c:12
8668 14 printf ("Goodbye, world!\n");
8669 (@value{GDBP}) info macro N
8670 Defined at /home/jimb/gdb/macros/play/sample.c:13
8672 (@value{GDBP}) macro expand N Q M
8673 expands to: 1729 < 42
8674 (@value{GDBP}) print N Q M
8679 In addition to source files, macros can be defined on the compilation command
8680 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
8681 such a way, @value{GDBN} displays the location of their definition as line zero
8682 of the source file submitted to the compiler.
8685 (@value{GDBP}) info macro __STDC__
8686 Defined at /home/jimb/gdb/macros/play/sample.c:0
8693 @chapter Tracepoints
8694 @c This chapter is based on the documentation written by Michael
8695 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8698 In some applications, it is not feasible for the debugger to interrupt
8699 the program's execution long enough for the developer to learn
8700 anything helpful about its behavior. If the program's correctness
8701 depends on its real-time behavior, delays introduced by a debugger
8702 might cause the program to change its behavior drastically, or perhaps
8703 fail, even when the code itself is correct. It is useful to be able
8704 to observe the program's behavior without interrupting it.
8706 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8707 specify locations in the program, called @dfn{tracepoints}, and
8708 arbitrary expressions to evaluate when those tracepoints are reached.
8709 Later, using the @code{tfind} command, you can examine the values
8710 those expressions had when the program hit the tracepoints. The
8711 expressions may also denote objects in memory---structures or arrays,
8712 for example---whose values @value{GDBN} should record; while visiting
8713 a particular tracepoint, you may inspect those objects as if they were
8714 in memory at that moment. However, because @value{GDBN} records these
8715 values without interacting with you, it can do so quickly and
8716 unobtrusively, hopefully not disturbing the program's behavior.
8718 The tracepoint facility is currently available only for remote
8719 targets. @xref{Targets}. In addition, your remote target must know
8720 how to collect trace data. This functionality is implemented in the
8721 remote stub; however, none of the stubs distributed with @value{GDBN}
8722 support tracepoints as of this writing. The format of the remote
8723 packets used to implement tracepoints are described in @ref{Tracepoint
8726 This chapter describes the tracepoint commands and features.
8730 * Analyze Collected Data::
8731 * Tracepoint Variables::
8734 @node Set Tracepoints
8735 @section Commands to Set Tracepoints
8737 Before running such a @dfn{trace experiment}, an arbitrary number of
8738 tracepoints can be set. A tracepoint is actually a special type of
8739 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
8740 standard breakpoint commands. For instance, as with breakpoints,
8741 tracepoint numbers are successive integers starting from one, and many
8742 of the commands associated with tracepoints take the tracepoint number
8743 as their argument, to identify which tracepoint to work on.
8745 For each tracepoint, you can specify, in advance, some arbitrary set
8746 of data that you want the target to collect in the trace buffer when
8747 it hits that tracepoint. The collected data can include registers,
8748 local variables, or global data. Later, you can use @value{GDBN}
8749 commands to examine the values these data had at the time the
8752 Tracepoints do not support every breakpoint feature. Conditional
8753 expressions and ignore counts on tracepoints have no effect, and
8754 tracepoints cannot run @value{GDBN} commands when they are
8755 hit. Tracepoints may not be thread-specific either.
8757 This section describes commands to set tracepoints and associated
8758 conditions and actions.
8761 * Create and Delete Tracepoints::
8762 * Enable and Disable Tracepoints::
8763 * Tracepoint Passcounts::
8764 * Tracepoint Actions::
8765 * Listing Tracepoints::
8766 * Starting and Stopping Trace Experiments::
8769 @node Create and Delete Tracepoints
8770 @subsection Create and Delete Tracepoints
8773 @cindex set tracepoint
8775 @item trace @var{location}
8776 The @code{trace} command is very similar to the @code{break} command.
8777 Its argument @var{location} can be a source line, a function name, or
8778 an address in the target program. @xref{Specify Location}. The
8779 @code{trace} command defines a tracepoint, which is a point in the
8780 target program where the debugger will briefly stop, collect some
8781 data, and then allow the program to continue. Setting a tracepoint or
8782 changing its actions doesn't take effect until the next @code{tstart}
8783 command, and once a trace experiment is running, further changes will
8784 not have any effect until the next trace experiment starts.
8786 Here are some examples of using the @code{trace} command:
8789 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8791 (@value{GDBP}) @b{trace +2} // 2 lines forward
8793 (@value{GDBP}) @b{trace my_function} // first source line of function
8795 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8797 (@value{GDBP}) @b{trace *0x2117c4} // an address
8801 You can abbreviate @code{trace} as @code{tr}.
8804 @cindex last tracepoint number
8805 @cindex recent tracepoint number
8806 @cindex tracepoint number
8807 The convenience variable @code{$tpnum} records the tracepoint number
8808 of the most recently set tracepoint.
8810 @kindex delete tracepoint
8811 @cindex tracepoint deletion
8812 @item delete tracepoint @r{[}@var{num}@r{]}
8813 Permanently delete one or more tracepoints. With no argument, the
8814 default is to delete all tracepoints. Note that the regular
8815 @code{delete} command can remove tracepoints also.
8820 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8822 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8826 You can abbreviate this command as @code{del tr}.
8829 @node Enable and Disable Tracepoints
8830 @subsection Enable and Disable Tracepoints
8832 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
8835 @kindex disable tracepoint
8836 @item disable tracepoint @r{[}@var{num}@r{]}
8837 Disable tracepoint @var{num}, or all tracepoints if no argument
8838 @var{num} is given. A disabled tracepoint will have no effect during
8839 the next trace experiment, but it is not forgotten. You can re-enable
8840 a disabled tracepoint using the @code{enable tracepoint} command.
8842 @kindex enable tracepoint
8843 @item enable tracepoint @r{[}@var{num}@r{]}
8844 Enable tracepoint @var{num}, or all tracepoints. The enabled
8845 tracepoints will become effective the next time a trace experiment is
8849 @node Tracepoint Passcounts
8850 @subsection Tracepoint Passcounts
8854 @cindex tracepoint pass count
8855 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8856 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8857 automatically stop a trace experiment. If a tracepoint's passcount is
8858 @var{n}, then the trace experiment will be automatically stopped on
8859 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8860 @var{num} is not specified, the @code{passcount} command sets the
8861 passcount of the most recently defined tracepoint. If no passcount is
8862 given, the trace experiment will run until stopped explicitly by the
8868 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8869 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8871 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8872 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8873 (@value{GDBP}) @b{trace foo}
8874 (@value{GDBP}) @b{pass 3}
8875 (@value{GDBP}) @b{trace bar}
8876 (@value{GDBP}) @b{pass 2}
8877 (@value{GDBP}) @b{trace baz}
8878 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8879 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8880 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8881 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8885 @node Tracepoint Actions
8886 @subsection Tracepoint Action Lists
8890 @cindex tracepoint actions
8891 @item actions @r{[}@var{num}@r{]}
8892 This command will prompt for a list of actions to be taken when the
8893 tracepoint is hit. If the tracepoint number @var{num} is not
8894 specified, this command sets the actions for the one that was most
8895 recently defined (so that you can define a tracepoint and then say
8896 @code{actions} without bothering about its number). You specify the
8897 actions themselves on the following lines, one action at a time, and
8898 terminate the actions list with a line containing just @code{end}. So
8899 far, the only defined actions are @code{collect} and
8900 @code{while-stepping}.
8902 @cindex remove actions from a tracepoint
8903 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8904 and follow it immediately with @samp{end}.
8907 (@value{GDBP}) @b{collect @var{data}} // collect some data
8909 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8911 (@value{GDBP}) @b{end} // signals the end of actions.
8914 In the following example, the action list begins with @code{collect}
8915 commands indicating the things to be collected when the tracepoint is
8916 hit. Then, in order to single-step and collect additional data
8917 following the tracepoint, a @code{while-stepping} command is used,
8918 followed by the list of things to be collected while stepping. The
8919 @code{while-stepping} command is terminated by its own separate
8920 @code{end} command. Lastly, the action list is terminated by an
8924 (@value{GDBP}) @b{trace foo}
8925 (@value{GDBP}) @b{actions}
8926 Enter actions for tracepoint 1, one per line:
8935 @kindex collect @r{(tracepoints)}
8936 @item collect @var{expr1}, @var{expr2}, @dots{}
8937 Collect values of the given expressions when the tracepoint is hit.
8938 This command accepts a comma-separated list of any valid expressions.
8939 In addition to global, static, or local variables, the following
8940 special arguments are supported:
8944 collect all registers
8947 collect all function arguments
8950 collect all local variables.
8953 You can give several consecutive @code{collect} commands, each one
8954 with a single argument, or one @code{collect} command with several
8955 arguments separated by commas: the effect is the same.
8957 The command @code{info scope} (@pxref{Symbols, info scope}) is
8958 particularly useful for figuring out what data to collect.
8960 @kindex while-stepping @r{(tracepoints)}
8961 @item while-stepping @var{n}
8962 Perform @var{n} single-step traces after the tracepoint, collecting
8963 new data at each step. The @code{while-stepping} command is
8964 followed by the list of what to collect while stepping (followed by
8965 its own @code{end} command):
8969 > collect $regs, myglobal
8975 You may abbreviate @code{while-stepping} as @code{ws} or
8979 @node Listing Tracepoints
8980 @subsection Listing Tracepoints
8983 @kindex info tracepoints
8985 @cindex information about tracepoints
8986 @item info tracepoints @r{[}@var{num}@r{]}
8987 Display information about the tracepoint @var{num}. If you don't
8988 specify a tracepoint number, displays information about all the
8989 tracepoints defined so far. The format is similar to that used for
8990 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
8991 command, simply restricting itself to tracepoints.
8993 A tracepoint's listing may include additional information specific to
8998 its passcount as given by the @code{passcount @var{n}} command
9000 its step count as given by the @code{while-stepping @var{n}} command
9002 its action list as given by the @code{actions} command. The actions
9003 are prefixed with an @samp{A} so as to distinguish them from commands.
9007 (@value{GDBP}) @b{info trace}
9008 Num Type Disp Enb Address What
9009 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9013 A collect globfoo, $regs
9021 This command can be abbreviated @code{info tp}.
9024 @node Starting and Stopping Trace Experiments
9025 @subsection Starting and Stopping Trace Experiments
9029 @cindex start a new trace experiment
9030 @cindex collected data discarded
9032 This command takes no arguments. It starts the trace experiment, and
9033 begins collecting data. This has the side effect of discarding all
9034 the data collected in the trace buffer during the previous trace
9038 @cindex stop a running trace experiment
9040 This command takes no arguments. It ends the trace experiment, and
9041 stops collecting data.
9043 @strong{Note}: a trace experiment and data collection may stop
9044 automatically if any tracepoint's passcount is reached
9045 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9048 @cindex status of trace data collection
9049 @cindex trace experiment, status of
9051 This command displays the status of the current trace data
9055 Here is an example of the commands we described so far:
9058 (@value{GDBP}) @b{trace gdb_c_test}
9059 (@value{GDBP}) @b{actions}
9060 Enter actions for tracepoint #1, one per line.
9061 > collect $regs,$locals,$args
9066 (@value{GDBP}) @b{tstart}
9067 [time passes @dots{}]
9068 (@value{GDBP}) @b{tstop}
9072 @node Analyze Collected Data
9073 @section Using the Collected Data
9075 After the tracepoint experiment ends, you use @value{GDBN} commands
9076 for examining the trace data. The basic idea is that each tracepoint
9077 collects a trace @dfn{snapshot} every time it is hit and another
9078 snapshot every time it single-steps. All these snapshots are
9079 consecutively numbered from zero and go into a buffer, and you can
9080 examine them later. The way you examine them is to @dfn{focus} on a
9081 specific trace snapshot. When the remote stub is focused on a trace
9082 snapshot, it will respond to all @value{GDBN} requests for memory and
9083 registers by reading from the buffer which belongs to that snapshot,
9084 rather than from @emph{real} memory or registers of the program being
9085 debugged. This means that @strong{all} @value{GDBN} commands
9086 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9087 behave as if we were currently debugging the program state as it was
9088 when the tracepoint occurred. Any requests for data that are not in
9089 the buffer will fail.
9092 * tfind:: How to select a trace snapshot
9093 * tdump:: How to display all data for a snapshot
9094 * save-tracepoints:: How to save tracepoints for a future run
9098 @subsection @code{tfind @var{n}}
9101 @cindex select trace snapshot
9102 @cindex find trace snapshot
9103 The basic command for selecting a trace snapshot from the buffer is
9104 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9105 counting from zero. If no argument @var{n} is given, the next
9106 snapshot is selected.
9108 Here are the various forms of using the @code{tfind} command.
9112 Find the first snapshot in the buffer. This is a synonym for
9113 @code{tfind 0} (since 0 is the number of the first snapshot).
9116 Stop debugging trace snapshots, resume @emph{live} debugging.
9119 Same as @samp{tfind none}.
9122 No argument means find the next trace snapshot.
9125 Find the previous trace snapshot before the current one. This permits
9126 retracing earlier steps.
9128 @item tfind tracepoint @var{num}
9129 Find the next snapshot associated with tracepoint @var{num}. Search
9130 proceeds forward from the last examined trace snapshot. If no
9131 argument @var{num} is given, it means find the next snapshot collected
9132 for the same tracepoint as the current snapshot.
9134 @item tfind pc @var{addr}
9135 Find the next snapshot associated with the value @var{addr} of the
9136 program counter. Search proceeds forward from the last examined trace
9137 snapshot. If no argument @var{addr} is given, it means find the next
9138 snapshot with the same value of PC as the current snapshot.
9140 @item tfind outside @var{addr1}, @var{addr2}
9141 Find the next snapshot whose PC is outside the given range of
9144 @item tfind range @var{addr1}, @var{addr2}
9145 Find the next snapshot whose PC is between @var{addr1} and
9146 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
9148 @item tfind line @r{[}@var{file}:@r{]}@var{n}
9149 Find the next snapshot associated with the source line @var{n}. If
9150 the optional argument @var{file} is given, refer to line @var{n} in
9151 that source file. Search proceeds forward from the last examined
9152 trace snapshot. If no argument @var{n} is given, it means find the
9153 next line other than the one currently being examined; thus saying
9154 @code{tfind line} repeatedly can appear to have the same effect as
9155 stepping from line to line in a @emph{live} debugging session.
9158 The default arguments for the @code{tfind} commands are specifically
9159 designed to make it easy to scan through the trace buffer. For
9160 instance, @code{tfind} with no argument selects the next trace
9161 snapshot, and @code{tfind -} with no argument selects the previous
9162 trace snapshot. So, by giving one @code{tfind} command, and then
9163 simply hitting @key{RET} repeatedly you can examine all the trace
9164 snapshots in order. Or, by saying @code{tfind -} and then hitting
9165 @key{RET} repeatedly you can examine the snapshots in reverse order.
9166 The @code{tfind line} command with no argument selects the snapshot
9167 for the next source line executed. The @code{tfind pc} command with
9168 no argument selects the next snapshot with the same program counter
9169 (PC) as the current frame. The @code{tfind tracepoint} command with
9170 no argument selects the next trace snapshot collected by the same
9171 tracepoint as the current one.
9173 In addition to letting you scan through the trace buffer manually,
9174 these commands make it easy to construct @value{GDBN} scripts that
9175 scan through the trace buffer and print out whatever collected data
9176 you are interested in. Thus, if we want to examine the PC, FP, and SP
9177 registers from each trace frame in the buffer, we can say this:
9180 (@value{GDBP}) @b{tfind start}
9181 (@value{GDBP}) @b{while ($trace_frame != -1)}
9182 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9183 $trace_frame, $pc, $sp, $fp
9187 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9188 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9189 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9190 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9191 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9192 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9193 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9194 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9195 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9196 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9197 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9200 Or, if we want to examine the variable @code{X} at each source line in
9204 (@value{GDBP}) @b{tfind start}
9205 (@value{GDBP}) @b{while ($trace_frame != -1)}
9206 > printf "Frame %d, X == %d\n", $trace_frame, X
9216 @subsection @code{tdump}
9218 @cindex dump all data collected at tracepoint
9219 @cindex tracepoint data, display
9221 This command takes no arguments. It prints all the data collected at
9222 the current trace snapshot.
9225 (@value{GDBP}) @b{trace 444}
9226 (@value{GDBP}) @b{actions}
9227 Enter actions for tracepoint #2, one per line:
9228 > collect $regs, $locals, $args, gdb_long_test
9231 (@value{GDBP}) @b{tstart}
9233 (@value{GDBP}) @b{tfind line 444}
9234 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9236 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9238 (@value{GDBP}) @b{tdump}
9239 Data collected at tracepoint 2, trace frame 1:
9240 d0 0xc4aa0085 -995491707
9244 d4 0x71aea3d 119204413
9249 a1 0x3000668 50333288
9252 a4 0x3000698 50333336
9254 fp 0x30bf3c 0x30bf3c
9255 sp 0x30bf34 0x30bf34
9257 pc 0x20b2c8 0x20b2c8
9261 p = 0x20e5b4 "gdb-test"
9268 gdb_long_test = 17 '\021'
9273 @node save-tracepoints
9274 @subsection @code{save-tracepoints @var{filename}}
9275 @kindex save-tracepoints
9276 @cindex save tracepoints for future sessions
9278 This command saves all current tracepoint definitions together with
9279 their actions and passcounts, into a file @file{@var{filename}}
9280 suitable for use in a later debugging session. To read the saved
9281 tracepoint definitions, use the @code{source} command (@pxref{Command
9284 @node Tracepoint Variables
9285 @section Convenience Variables for Tracepoints
9286 @cindex tracepoint variables
9287 @cindex convenience variables for tracepoints
9290 @vindex $trace_frame
9291 @item (int) $trace_frame
9292 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9293 snapshot is selected.
9296 @item (int) $tracepoint
9297 The tracepoint for the current trace snapshot.
9300 @item (int) $trace_line
9301 The line number for the current trace snapshot.
9304 @item (char []) $trace_file
9305 The source file for the current trace snapshot.
9308 @item (char []) $trace_func
9309 The name of the function containing @code{$tracepoint}.
9312 Note: @code{$trace_file} is not suitable for use in @code{printf},
9313 use @code{output} instead.
9315 Here's a simple example of using these convenience variables for
9316 stepping through all the trace snapshots and printing some of their
9320 (@value{GDBP}) @b{tfind start}
9322 (@value{GDBP}) @b{while $trace_frame != -1}
9323 > output $trace_file
9324 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9330 @chapter Debugging Programs That Use Overlays
9333 If your program is too large to fit completely in your target system's
9334 memory, you can sometimes use @dfn{overlays} to work around this
9335 problem. @value{GDBN} provides some support for debugging programs that
9339 * How Overlays Work:: A general explanation of overlays.
9340 * Overlay Commands:: Managing overlays in @value{GDBN}.
9341 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9342 mapped by asking the inferior.
9343 * Overlay Sample Program:: A sample program using overlays.
9346 @node How Overlays Work
9347 @section How Overlays Work
9348 @cindex mapped overlays
9349 @cindex unmapped overlays
9350 @cindex load address, overlay's
9351 @cindex mapped address
9352 @cindex overlay area
9354 Suppose you have a computer whose instruction address space is only 64
9355 kilobytes long, but which has much more memory which can be accessed by
9356 other means: special instructions, segment registers, or memory
9357 management hardware, for example. Suppose further that you want to
9358 adapt a program which is larger than 64 kilobytes to run on this system.
9360 One solution is to identify modules of your program which are relatively
9361 independent, and need not call each other directly; call these modules
9362 @dfn{overlays}. Separate the overlays from the main program, and place
9363 their machine code in the larger memory. Place your main program in
9364 instruction memory, but leave at least enough space there to hold the
9365 largest overlay as well.
9367 Now, to call a function located in an overlay, you must first copy that
9368 overlay's machine code from the large memory into the space set aside
9369 for it in the instruction memory, and then jump to its entry point
9372 @c NB: In the below the mapped area's size is greater or equal to the
9373 @c size of all overlays. This is intentional to remind the developer
9374 @c that overlays don't necessarily need to be the same size.
9378 Data Instruction Larger
9379 Address Space Address Space Address Space
9380 +-----------+ +-----------+ +-----------+
9382 +-----------+ +-----------+ +-----------+<-- overlay 1
9383 | program | | main | .----| overlay 1 | load address
9384 | variables | | program | | +-----------+
9385 | and heap | | | | | |
9386 +-----------+ | | | +-----------+<-- overlay 2
9387 | | +-----------+ | | | load address
9388 +-----------+ | | | .-| overlay 2 |
9390 mapped --->+-----------+ | | +-----------+
9392 | overlay | <-' | | |
9393 | area | <---' +-----------+<-- overlay 3
9394 | | <---. | | load address
9395 +-----------+ `--| overlay 3 |
9402 @anchor{A code overlay}A code overlay
9406 The diagram (@pxref{A code overlay}) shows a system with separate data
9407 and instruction address spaces. To map an overlay, the program copies
9408 its code from the larger address space to the instruction address space.
9409 Since the overlays shown here all use the same mapped address, only one
9410 may be mapped at a time. For a system with a single address space for
9411 data and instructions, the diagram would be similar, except that the
9412 program variables and heap would share an address space with the main
9413 program and the overlay area.
9415 An overlay loaded into instruction memory and ready for use is called a
9416 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9417 instruction memory. An overlay not present (or only partially present)
9418 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9419 is its address in the larger memory. The mapped address is also called
9420 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9421 called the @dfn{load memory address}, or @dfn{LMA}.
9423 Unfortunately, overlays are not a completely transparent way to adapt a
9424 program to limited instruction memory. They introduce a new set of
9425 global constraints you must keep in mind as you design your program:
9430 Before calling or returning to a function in an overlay, your program
9431 must make sure that overlay is actually mapped. Otherwise, the call or
9432 return will transfer control to the right address, but in the wrong
9433 overlay, and your program will probably crash.
9436 If the process of mapping an overlay is expensive on your system, you
9437 will need to choose your overlays carefully to minimize their effect on
9438 your program's performance.
9441 The executable file you load onto your system must contain each
9442 overlay's instructions, appearing at the overlay's load address, not its
9443 mapped address. However, each overlay's instructions must be relocated
9444 and its symbols defined as if the overlay were at its mapped address.
9445 You can use GNU linker scripts to specify different load and relocation
9446 addresses for pieces of your program; see @ref{Overlay Description,,,
9447 ld.info, Using ld: the GNU linker}.
9450 The procedure for loading executable files onto your system must be able
9451 to load their contents into the larger address space as well as the
9452 instruction and data spaces.
9456 The overlay system described above is rather simple, and could be
9457 improved in many ways:
9462 If your system has suitable bank switch registers or memory management
9463 hardware, you could use those facilities to make an overlay's load area
9464 contents simply appear at their mapped address in instruction space.
9465 This would probably be faster than copying the overlay to its mapped
9466 area in the usual way.
9469 If your overlays are small enough, you could set aside more than one
9470 overlay area, and have more than one overlay mapped at a time.
9473 You can use overlays to manage data, as well as instructions. In
9474 general, data overlays are even less transparent to your design than
9475 code overlays: whereas code overlays only require care when you call or
9476 return to functions, data overlays require care every time you access
9477 the data. Also, if you change the contents of a data overlay, you
9478 must copy its contents back out to its load address before you can copy a
9479 different data overlay into the same mapped area.
9484 @node Overlay Commands
9485 @section Overlay Commands
9487 To use @value{GDBN}'s overlay support, each overlay in your program must
9488 correspond to a separate section of the executable file. The section's
9489 virtual memory address and load memory address must be the overlay's
9490 mapped and load addresses. Identifying overlays with sections allows
9491 @value{GDBN} to determine the appropriate address of a function or
9492 variable, depending on whether the overlay is mapped or not.
9494 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9495 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9500 Disable @value{GDBN}'s overlay support. When overlay support is
9501 disabled, @value{GDBN} assumes that all functions and variables are
9502 always present at their mapped addresses. By default, @value{GDBN}'s
9503 overlay support is disabled.
9505 @item overlay manual
9506 @cindex manual overlay debugging
9507 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9508 relies on you to tell it which overlays are mapped, and which are not,
9509 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9510 commands described below.
9512 @item overlay map-overlay @var{overlay}
9513 @itemx overlay map @var{overlay}
9514 @cindex map an overlay
9515 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9516 be the name of the object file section containing the overlay. When an
9517 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9518 functions and variables at their mapped addresses. @value{GDBN} assumes
9519 that any other overlays whose mapped ranges overlap that of
9520 @var{overlay} are now unmapped.
9522 @item overlay unmap-overlay @var{overlay}
9523 @itemx overlay unmap @var{overlay}
9524 @cindex unmap an overlay
9525 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9526 must be the name of the object file section containing the overlay.
9527 When an overlay is unmapped, @value{GDBN} assumes it can find the
9528 overlay's functions and variables at their load addresses.
9531 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9532 consults a data structure the overlay manager maintains in the inferior
9533 to see which overlays are mapped. For details, see @ref{Automatic
9536 @item overlay load-target
9538 @cindex reloading the overlay table
9539 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9540 re-reads the table @value{GDBN} automatically each time the inferior
9541 stops, so this command should only be necessary if you have changed the
9542 overlay mapping yourself using @value{GDBN}. This command is only
9543 useful when using automatic overlay debugging.
9545 @item overlay list-overlays
9547 @cindex listing mapped overlays
9548 Display a list of the overlays currently mapped, along with their mapped
9549 addresses, load addresses, and sizes.
9553 Normally, when @value{GDBN} prints a code address, it includes the name
9554 of the function the address falls in:
9557 (@value{GDBP}) print main
9558 $3 = @{int ()@} 0x11a0 <main>
9561 When overlay debugging is enabled, @value{GDBN} recognizes code in
9562 unmapped overlays, and prints the names of unmapped functions with
9563 asterisks around them. For example, if @code{foo} is a function in an
9564 unmapped overlay, @value{GDBN} prints it this way:
9567 (@value{GDBP}) overlay list
9568 No sections are mapped.
9569 (@value{GDBP}) print foo
9570 $5 = @{int (int)@} 0x100000 <*foo*>
9573 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9577 (@value{GDBP}) overlay list
9578 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9579 mapped at 0x1016 - 0x104a
9580 (@value{GDBP}) print foo
9581 $6 = @{int (int)@} 0x1016 <foo>
9584 When overlay debugging is enabled, @value{GDBN} can find the correct
9585 address for functions and variables in an overlay, whether or not the
9586 overlay is mapped. This allows most @value{GDBN} commands, like
9587 @code{break} and @code{disassemble}, to work normally, even on unmapped
9588 code. However, @value{GDBN}'s breakpoint support has some limitations:
9592 @cindex breakpoints in overlays
9593 @cindex overlays, setting breakpoints in
9594 You can set breakpoints in functions in unmapped overlays, as long as
9595 @value{GDBN} can write to the overlay at its load address.
9597 @value{GDBN} can not set hardware or simulator-based breakpoints in
9598 unmapped overlays. However, if you set a breakpoint at the end of your
9599 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9600 you are using manual overlay management), @value{GDBN} will re-set its
9601 breakpoints properly.
9605 @node Automatic Overlay Debugging
9606 @section Automatic Overlay Debugging
9607 @cindex automatic overlay debugging
9609 @value{GDBN} can automatically track which overlays are mapped and which
9610 are not, given some simple co-operation from the overlay manager in the
9611 inferior. If you enable automatic overlay debugging with the
9612 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9613 looks in the inferior's memory for certain variables describing the
9614 current state of the overlays.
9616 Here are the variables your overlay manager must define to support
9617 @value{GDBN}'s automatic overlay debugging:
9621 @item @code{_ovly_table}:
9622 This variable must be an array of the following structures:
9627 /* The overlay's mapped address. */
9630 /* The size of the overlay, in bytes. */
9633 /* The overlay's load address. */
9636 /* Non-zero if the overlay is currently mapped;
9638 unsigned long mapped;
9642 @item @code{_novlys}:
9643 This variable must be a four-byte signed integer, holding the total
9644 number of elements in @code{_ovly_table}.
9648 To decide whether a particular overlay is mapped or not, @value{GDBN}
9649 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9650 @code{lma} members equal the VMA and LMA of the overlay's section in the
9651 executable file. When @value{GDBN} finds a matching entry, it consults
9652 the entry's @code{mapped} member to determine whether the overlay is
9655 In addition, your overlay manager may define a function called
9656 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9657 will silently set a breakpoint there. If the overlay manager then
9658 calls this function whenever it has changed the overlay table, this
9659 will enable @value{GDBN} to accurately keep track of which overlays
9660 are in program memory, and update any breakpoints that may be set
9661 in overlays. This will allow breakpoints to work even if the
9662 overlays are kept in ROM or other non-writable memory while they
9663 are not being executed.
9665 @node Overlay Sample Program
9666 @section Overlay Sample Program
9667 @cindex overlay example program
9669 When linking a program which uses overlays, you must place the overlays
9670 at their load addresses, while relocating them to run at their mapped
9671 addresses. To do this, you must write a linker script (@pxref{Overlay
9672 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9673 since linker scripts are specific to a particular host system, target
9674 architecture, and target memory layout, this manual cannot provide
9675 portable sample code demonstrating @value{GDBN}'s overlay support.
9677 However, the @value{GDBN} source distribution does contain an overlaid
9678 program, with linker scripts for a few systems, as part of its test
9679 suite. The program consists of the following files from
9680 @file{gdb/testsuite/gdb.base}:
9684 The main program file.
9686 A simple overlay manager, used by @file{overlays.c}.
9691 Overlay modules, loaded and used by @file{overlays.c}.
9694 Linker scripts for linking the test program on the @code{d10v-elf}
9695 and @code{m32r-elf} targets.
9698 You can build the test program using the @code{d10v-elf} GCC
9699 cross-compiler like this:
9702 $ d10v-elf-gcc -g -c overlays.c
9703 $ d10v-elf-gcc -g -c ovlymgr.c
9704 $ d10v-elf-gcc -g -c foo.c
9705 $ d10v-elf-gcc -g -c bar.c
9706 $ d10v-elf-gcc -g -c baz.c
9707 $ d10v-elf-gcc -g -c grbx.c
9708 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9709 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9712 The build process is identical for any other architecture, except that
9713 you must substitute the appropriate compiler and linker script for the
9714 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9718 @chapter Using @value{GDBN} with Different Languages
9721 Although programming languages generally have common aspects, they are
9722 rarely expressed in the same manner. For instance, in ANSI C,
9723 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9724 Modula-2, it is accomplished by @code{p^}. Values can also be
9725 represented (and displayed) differently. Hex numbers in C appear as
9726 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9728 @cindex working language
9729 Language-specific information is built into @value{GDBN} for some languages,
9730 allowing you to express operations like the above in your program's
9731 native language, and allowing @value{GDBN} to output values in a manner
9732 consistent with the syntax of your program's native language. The
9733 language you use to build expressions is called the @dfn{working
9737 * Setting:: Switching between source languages
9738 * Show:: Displaying the language
9739 * Checks:: Type and range checks
9740 * Supported Languages:: Supported languages
9741 * Unsupported Languages:: Unsupported languages
9745 @section Switching Between Source Languages
9747 There are two ways to control the working language---either have @value{GDBN}
9748 set it automatically, or select it manually yourself. You can use the
9749 @code{set language} command for either purpose. On startup, @value{GDBN}
9750 defaults to setting the language automatically. The working language is
9751 used to determine how expressions you type are interpreted, how values
9754 In addition to the working language, every source file that
9755 @value{GDBN} knows about has its own working language. For some object
9756 file formats, the compiler might indicate which language a particular
9757 source file is in. However, most of the time @value{GDBN} infers the
9758 language from the name of the file. The language of a source file
9759 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9760 show each frame appropriately for its own language. There is no way to
9761 set the language of a source file from within @value{GDBN}, but you can
9762 set the language associated with a filename extension. @xref{Show, ,
9763 Displaying the Language}.
9765 This is most commonly a problem when you use a program, such
9766 as @code{cfront} or @code{f2c}, that generates C but is written in
9767 another language. In that case, make the
9768 program use @code{#line} directives in its C output; that way
9769 @value{GDBN} will know the correct language of the source code of the original
9770 program, and will display that source code, not the generated C code.
9773 * Filenames:: Filename extensions and languages.
9774 * Manually:: Setting the working language manually
9775 * Automatically:: Having @value{GDBN} infer the source language
9779 @subsection List of Filename Extensions and Languages
9781 If a source file name ends in one of the following extensions, then
9782 @value{GDBN} infers that its language is the one indicated.
9803 Objective-C source file
9810 Modula-2 source file
9814 Assembler source file. This actually behaves almost like C, but
9815 @value{GDBN} does not skip over function prologues when stepping.
9818 In addition, you may set the language associated with a filename
9819 extension. @xref{Show, , Displaying the Language}.
9822 @subsection Setting the Working Language
9824 If you allow @value{GDBN} to set the language automatically,
9825 expressions are interpreted the same way in your debugging session and
9828 @kindex set language
9829 If you wish, you may set the language manually. To do this, issue the
9830 command @samp{set language @var{lang}}, where @var{lang} is the name of
9832 @code{c} or @code{modula-2}.
9833 For a list of the supported languages, type @samp{set language}.
9835 Setting the language manually prevents @value{GDBN} from updating the working
9836 language automatically. This can lead to confusion if you try
9837 to debug a program when the working language is not the same as the
9838 source language, when an expression is acceptable to both
9839 languages---but means different things. For instance, if the current
9840 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9848 might not have the effect you intended. In C, this means to add
9849 @code{b} and @code{c} and place the result in @code{a}. The result
9850 printed would be the value of @code{a}. In Modula-2, this means to compare
9851 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9854 @subsection Having @value{GDBN} Infer the Source Language
9856 To have @value{GDBN} set the working language automatically, use
9857 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9858 then infers the working language. That is, when your program stops in a
9859 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9860 working language to the language recorded for the function in that
9861 frame. If the language for a frame is unknown (that is, if the function
9862 or block corresponding to the frame was defined in a source file that
9863 does not have a recognized extension), the current working language is
9864 not changed, and @value{GDBN} issues a warning.
9866 This may not seem necessary for most programs, which are written
9867 entirely in one source language. However, program modules and libraries
9868 written in one source language can be used by a main program written in
9869 a different source language. Using @samp{set language auto} in this
9870 case frees you from having to set the working language manually.
9873 @section Displaying the Language
9875 The following commands help you find out which language is the
9876 working language, and also what language source files were written in.
9880 @kindex show language
9881 Display the current working language. This is the
9882 language you can use with commands such as @code{print} to
9883 build and compute expressions that may involve variables in your program.
9886 @kindex info frame@r{, show the source language}
9887 Display the source language for this frame. This language becomes the
9888 working language if you use an identifier from this frame.
9889 @xref{Frame Info, ,Information about a Frame}, to identify the other
9890 information listed here.
9893 @kindex info source@r{, show the source language}
9894 Display the source language of this source file.
9895 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9896 information listed here.
9899 In unusual circumstances, you may have source files with extensions
9900 not in the standard list. You can then set the extension associated
9901 with a language explicitly:
9904 @item set extension-language @var{ext} @var{language}
9905 @kindex set extension-language
9906 Tell @value{GDBN} that source files with extension @var{ext} are to be
9907 assumed as written in the source language @var{language}.
9909 @item info extensions
9910 @kindex info extensions
9911 List all the filename extensions and the associated languages.
9915 @section Type and Range Checking
9918 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9919 checking are included, but they do not yet have any effect. This
9920 section documents the intended facilities.
9922 @c FIXME remove warning when type/range code added
9924 Some languages are designed to guard you against making seemingly common
9925 errors through a series of compile- and run-time checks. These include
9926 checking the type of arguments to functions and operators, and making
9927 sure mathematical overflows are caught at run time. Checks such as
9928 these help to ensure a program's correctness once it has been compiled
9929 by eliminating type mismatches, and providing active checks for range
9930 errors when your program is running.
9932 @value{GDBN} can check for conditions like the above if you wish.
9933 Although @value{GDBN} does not check the statements in your program,
9934 it can check expressions entered directly into @value{GDBN} for
9935 evaluation via the @code{print} command, for example. As with the
9936 working language, @value{GDBN} can also decide whether or not to check
9937 automatically based on your program's source language.
9938 @xref{Supported Languages, ,Supported Languages}, for the default
9939 settings of supported languages.
9942 * Type Checking:: An overview of type checking
9943 * Range Checking:: An overview of range checking
9946 @cindex type checking
9947 @cindex checks, type
9949 @subsection An Overview of Type Checking
9951 Some languages, such as Modula-2, are strongly typed, meaning that the
9952 arguments to operators and functions have to be of the correct type,
9953 otherwise an error occurs. These checks prevent type mismatch
9954 errors from ever causing any run-time problems. For example,
9962 The second example fails because the @code{CARDINAL} 1 is not
9963 type-compatible with the @code{REAL} 2.3.
9965 For the expressions you use in @value{GDBN} commands, you can tell the
9966 @value{GDBN} type checker to skip checking;
9967 to treat any mismatches as errors and abandon the expression;
9968 or to only issue warnings when type mismatches occur,
9969 but evaluate the expression anyway. When you choose the last of
9970 these, @value{GDBN} evaluates expressions like the second example above, but
9971 also issues a warning.
9973 Even if you turn type checking off, there may be other reasons
9974 related to type that prevent @value{GDBN} from evaluating an expression.
9975 For instance, @value{GDBN} does not know how to add an @code{int} and
9976 a @code{struct foo}. These particular type errors have nothing to do
9977 with the language in use, and usually arise from expressions, such as
9978 the one described above, which make little sense to evaluate anyway.
9980 Each language defines to what degree it is strict about type. For
9981 instance, both Modula-2 and C require the arguments to arithmetical
9982 operators to be numbers. In C, enumerated types and pointers can be
9983 represented as numbers, so that they are valid arguments to mathematical
9984 operators. @xref{Supported Languages, ,Supported Languages}, for further
9985 details on specific languages.
9987 @value{GDBN} provides some additional commands for controlling the type checker:
9989 @kindex set check type
9990 @kindex show check type
9992 @item set check type auto
9993 Set type checking on or off based on the current working language.
9994 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9997 @item set check type on
9998 @itemx set check type off
9999 Set type checking on or off, overriding the default setting for the
10000 current working language. Issue a warning if the setting does not
10001 match the language default. If any type mismatches occur in
10002 evaluating an expression while type checking is on, @value{GDBN} prints a
10003 message and aborts evaluation of the expression.
10005 @item set check type warn
10006 Cause the type checker to issue warnings, but to always attempt to
10007 evaluate the expression. Evaluating the expression may still
10008 be impossible for other reasons. For example, @value{GDBN} cannot add
10009 numbers and structures.
10012 Show the current setting of the type checker, and whether or not @value{GDBN}
10013 is setting it automatically.
10016 @cindex range checking
10017 @cindex checks, range
10018 @node Range Checking
10019 @subsection An Overview of Range Checking
10021 In some languages (such as Modula-2), it is an error to exceed the
10022 bounds of a type; this is enforced with run-time checks. Such range
10023 checking is meant to ensure program correctness by making sure
10024 computations do not overflow, or indices on an array element access do
10025 not exceed the bounds of the array.
10027 For expressions you use in @value{GDBN} commands, you can tell
10028 @value{GDBN} to treat range errors in one of three ways: ignore them,
10029 always treat them as errors and abandon the expression, or issue
10030 warnings but evaluate the expression anyway.
10032 A range error can result from numerical overflow, from exceeding an
10033 array index bound, or when you type a constant that is not a member
10034 of any type. Some languages, however, do not treat overflows as an
10035 error. In many implementations of C, mathematical overflow causes the
10036 result to ``wrap around'' to lower values---for example, if @var{m} is
10037 the largest integer value, and @var{s} is the smallest, then
10040 @var{m} + 1 @result{} @var{s}
10043 This, too, is specific to individual languages, and in some cases
10044 specific to individual compilers or machines. @xref{Supported Languages, ,
10045 Supported Languages}, for further details on specific languages.
10047 @value{GDBN} provides some additional commands for controlling the range checker:
10049 @kindex set check range
10050 @kindex show check range
10052 @item set check range auto
10053 Set range checking on or off based on the current working language.
10054 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10057 @item set check range on
10058 @itemx set check range off
10059 Set range checking on or off, overriding the default setting for the
10060 current working language. A warning is issued if the setting does not
10061 match the language default. If a range error occurs and range checking is on,
10062 then a message is printed and evaluation of the expression is aborted.
10064 @item set check range warn
10065 Output messages when the @value{GDBN} range checker detects a range error,
10066 but attempt to evaluate the expression anyway. Evaluating the
10067 expression may still be impossible for other reasons, such as accessing
10068 memory that the process does not own (a typical example from many Unix
10072 Show the current setting of the range checker, and whether or not it is
10073 being set automatically by @value{GDBN}.
10076 @node Supported Languages
10077 @section Supported Languages
10079 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
10080 assembly, Modula-2, and Ada.
10081 @c This is false ...
10082 Some @value{GDBN} features may be used in expressions regardless of the
10083 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
10084 and the @samp{@{type@}addr} construct (@pxref{Expressions,
10085 ,Expressions}) can be used with the constructs of any supported
10088 The following sections detail to what degree each source language is
10089 supported by @value{GDBN}. These sections are not meant to be language
10090 tutorials or references, but serve only as a reference guide to what the
10091 @value{GDBN} expression parser accepts, and what input and output
10092 formats should look like for different languages. There are many good
10093 books written on each of these languages; please look to these for a
10094 language reference or tutorial.
10097 * C:: C and C@t{++}
10098 * Objective-C:: Objective-C
10099 * Fortran:: Fortran
10101 * Modula-2:: Modula-2
10106 @subsection C and C@t{++}
10108 @cindex C and C@t{++}
10109 @cindex expressions in C or C@t{++}
10111 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
10112 to both languages. Whenever this is the case, we discuss those languages
10116 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
10117 @cindex @sc{gnu} C@t{++}
10118 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
10119 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
10120 effectively, you must compile your C@t{++} programs with a supported
10121 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
10122 compiler (@code{aCC}).
10124 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
10125 format; if it doesn't work on your system, try the stabs+ debugging
10126 format. You can select those formats explicitly with the @code{g++}
10127 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
10128 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
10129 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
10132 * C Operators:: C and C@t{++} operators
10133 * C Constants:: C and C@t{++} constants
10134 * C Plus Plus Expressions:: C@t{++} expressions
10135 * C Defaults:: Default settings for C and C@t{++}
10136 * C Checks:: C and C@t{++} type and range checks
10137 * Debugging C:: @value{GDBN} and C
10138 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
10139 * Decimal Floating Point:: Numbers in Decimal Floating Point format
10143 @subsubsection C and C@t{++} Operators
10145 @cindex C and C@t{++} operators
10147 Operators must be defined on values of specific types. For instance,
10148 @code{+} is defined on numbers, but not on structures. Operators are
10149 often defined on groups of types.
10151 For the purposes of C and C@t{++}, the following definitions hold:
10156 @emph{Integral types} include @code{int} with any of its storage-class
10157 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
10160 @emph{Floating-point types} include @code{float}, @code{double}, and
10161 @code{long double} (if supported by the target platform).
10164 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10167 @emph{Scalar types} include all of the above.
10172 The following operators are supported. They are listed here
10173 in order of increasing precedence:
10177 The comma or sequencing operator. Expressions in a comma-separated list
10178 are evaluated from left to right, with the result of the entire
10179 expression being the last expression evaluated.
10182 Assignment. The value of an assignment expression is the value
10183 assigned. Defined on scalar types.
10186 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10187 and translated to @w{@code{@var{a} = @var{a op b}}}.
10188 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10189 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10190 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10193 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10194 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10198 Logical @sc{or}. Defined on integral types.
10201 Logical @sc{and}. Defined on integral types.
10204 Bitwise @sc{or}. Defined on integral types.
10207 Bitwise exclusive-@sc{or}. Defined on integral types.
10210 Bitwise @sc{and}. Defined on integral types.
10213 Equality and inequality. Defined on scalar types. The value of these
10214 expressions is 0 for false and non-zero for true.
10216 @item <@r{, }>@r{, }<=@r{, }>=
10217 Less than, greater than, less than or equal, greater than or equal.
10218 Defined on scalar types. The value of these expressions is 0 for false
10219 and non-zero for true.
10222 left shift, and right shift. Defined on integral types.
10225 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10228 Addition and subtraction. Defined on integral types, floating-point types and
10231 @item *@r{, }/@r{, }%
10232 Multiplication, division, and modulus. Multiplication and division are
10233 defined on integral and floating-point types. Modulus is defined on
10237 Increment and decrement. When appearing before a variable, the
10238 operation is performed before the variable is used in an expression;
10239 when appearing after it, the variable's value is used before the
10240 operation takes place.
10243 Pointer dereferencing. Defined on pointer types. Same precedence as
10247 Address operator. Defined on variables. Same precedence as @code{++}.
10249 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10250 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10251 to examine the address
10252 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10256 Negative. Defined on integral and floating-point types. Same
10257 precedence as @code{++}.
10260 Logical negation. Defined on integral types. Same precedence as
10264 Bitwise complement operator. Defined on integral types. Same precedence as
10269 Structure member, and pointer-to-structure member. For convenience,
10270 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10271 pointer based on the stored type information.
10272 Defined on @code{struct} and @code{union} data.
10275 Dereferences of pointers to members.
10278 Array indexing. @code{@var{a}[@var{i}]} is defined as
10279 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10282 Function parameter list. Same precedence as @code{->}.
10285 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10286 and @code{class} types.
10289 Doubled colons also represent the @value{GDBN} scope operator
10290 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10294 If an operator is redefined in the user code, @value{GDBN} usually
10295 attempts to invoke the redefined version instead of using the operator's
10296 predefined meaning.
10299 @subsubsection C and C@t{++} Constants
10301 @cindex C and C@t{++} constants
10303 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10308 Integer constants are a sequence of digits. Octal constants are
10309 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10310 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10311 @samp{l}, specifying that the constant should be treated as a
10315 Floating point constants are a sequence of digits, followed by a decimal
10316 point, followed by a sequence of digits, and optionally followed by an
10317 exponent. An exponent is of the form:
10318 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10319 sequence of digits. The @samp{+} is optional for positive exponents.
10320 A floating-point constant may also end with a letter @samp{f} or
10321 @samp{F}, specifying that the constant should be treated as being of
10322 the @code{float} (as opposed to the default @code{double}) type; or with
10323 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10327 Enumerated constants consist of enumerated identifiers, or their
10328 integral equivalents.
10331 Character constants are a single character surrounded by single quotes
10332 (@code{'}), or a number---the ordinal value of the corresponding character
10333 (usually its @sc{ascii} value). Within quotes, the single character may
10334 be represented by a letter or by @dfn{escape sequences}, which are of
10335 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10336 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10337 @samp{@var{x}} is a predefined special character---for example,
10338 @samp{\n} for newline.
10341 String constants are a sequence of character constants surrounded by
10342 double quotes (@code{"}). Any valid character constant (as described
10343 above) may appear. Double quotes within the string must be preceded by
10344 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10348 Pointer constants are an integral value. You can also write pointers
10349 to constants using the C operator @samp{&}.
10352 Array constants are comma-separated lists surrounded by braces @samp{@{}
10353 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10354 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10355 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10358 @node C Plus Plus Expressions
10359 @subsubsection C@t{++} Expressions
10361 @cindex expressions in C@t{++}
10362 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10364 @cindex debugging C@t{++} programs
10365 @cindex C@t{++} compilers
10366 @cindex debug formats and C@t{++}
10367 @cindex @value{NGCC} and C@t{++}
10369 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10370 proper compiler and the proper debug format. Currently, @value{GDBN}
10371 works best when debugging C@t{++} code that is compiled with
10372 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10373 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10374 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10375 stabs+ as their default debug format, so you usually don't need to
10376 specify a debug format explicitly. Other compilers and/or debug formats
10377 are likely to work badly or not at all when using @value{GDBN} to debug
10383 @cindex member functions
10385 Member function calls are allowed; you can use expressions like
10388 count = aml->GetOriginal(x, y)
10391 @vindex this@r{, inside C@t{++} member functions}
10392 @cindex namespace in C@t{++}
10394 While a member function is active (in the selected stack frame), your
10395 expressions have the same namespace available as the member function;
10396 that is, @value{GDBN} allows implicit references to the class instance
10397 pointer @code{this} following the same rules as C@t{++}.
10399 @cindex call overloaded functions
10400 @cindex overloaded functions, calling
10401 @cindex type conversions in C@t{++}
10403 You can call overloaded functions; @value{GDBN} resolves the function
10404 call to the right definition, with some restrictions. @value{GDBN} does not
10405 perform overload resolution involving user-defined type conversions,
10406 calls to constructors, or instantiations of templates that do not exist
10407 in the program. It also cannot handle ellipsis argument lists or
10410 It does perform integral conversions and promotions, floating-point
10411 promotions, arithmetic conversions, pointer conversions, conversions of
10412 class objects to base classes, and standard conversions such as those of
10413 functions or arrays to pointers; it requires an exact match on the
10414 number of function arguments.
10416 Overload resolution is always performed, unless you have specified
10417 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10418 ,@value{GDBN} Features for C@t{++}}.
10420 You must specify @code{set overload-resolution off} in order to use an
10421 explicit function signature to call an overloaded function, as in
10423 p 'foo(char,int)'('x', 13)
10426 The @value{GDBN} command-completion facility can simplify this;
10427 see @ref{Completion, ,Command Completion}.
10429 @cindex reference declarations
10431 @value{GDBN} understands variables declared as C@t{++} references; you can use
10432 them in expressions just as you do in C@t{++} source---they are automatically
10435 In the parameter list shown when @value{GDBN} displays a frame, the values of
10436 reference variables are not displayed (unlike other variables); this
10437 avoids clutter, since references are often used for large structures.
10438 The @emph{address} of a reference variable is always shown, unless
10439 you have specified @samp{set print address off}.
10442 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10443 expressions can use it just as expressions in your program do. Since
10444 one scope may be defined in another, you can use @code{::} repeatedly if
10445 necessary, for example in an expression like
10446 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10447 resolving name scope by reference to source files, in both C and C@t{++}
10448 debugging (@pxref{Variables, ,Program Variables}).
10451 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10452 calling virtual functions correctly, printing out virtual bases of
10453 objects, calling functions in a base subobject, casting objects, and
10454 invoking user-defined operators.
10457 @subsubsection C and C@t{++} Defaults
10459 @cindex C and C@t{++} defaults
10461 If you allow @value{GDBN} to set type and range checking automatically, they
10462 both default to @code{off} whenever the working language changes to
10463 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10464 selects the working language.
10466 If you allow @value{GDBN} to set the language automatically, it
10467 recognizes source files whose names end with @file{.c}, @file{.C}, or
10468 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10469 these files, it sets the working language to C or C@t{++}.
10470 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10471 for further details.
10473 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10474 @c unimplemented. If (b) changes, it might make sense to let this node
10475 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10478 @subsubsection C and C@t{++} Type and Range Checks
10480 @cindex C and C@t{++} checks
10482 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10483 is not used. However, if you turn type checking on, @value{GDBN}
10484 considers two variables type equivalent if:
10488 The two variables are structured and have the same structure, union, or
10492 The two variables have the same type name, or types that have been
10493 declared equivalent through @code{typedef}.
10496 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10499 The two @code{struct}, @code{union}, or @code{enum} variables are
10500 declared in the same declaration. (Note: this may not be true for all C
10505 Range checking, if turned on, is done on mathematical operations. Array
10506 indices are not checked, since they are often used to index a pointer
10507 that is not itself an array.
10510 @subsubsection @value{GDBN} and C
10512 The @code{set print union} and @code{show print union} commands apply to
10513 the @code{union} type. When set to @samp{on}, any @code{union} that is
10514 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10515 appears as @samp{@{...@}}.
10517 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10518 with pointers and a memory allocation function. @xref{Expressions,
10521 @node Debugging C Plus Plus
10522 @subsubsection @value{GDBN} Features for C@t{++}
10524 @cindex commands for C@t{++}
10526 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10527 designed specifically for use with C@t{++}. Here is a summary:
10530 @cindex break in overloaded functions
10531 @item @r{breakpoint menus}
10532 When you want a breakpoint in a function whose name is overloaded,
10533 @value{GDBN} has the capability to display a menu of possible breakpoint
10534 locations to help you specify which function definition you want.
10535 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10537 @cindex overloading in C@t{++}
10538 @item rbreak @var{regex}
10539 Setting breakpoints using regular expressions is helpful for setting
10540 breakpoints on overloaded functions that are not members of any special
10542 @xref{Set Breaks, ,Setting Breakpoints}.
10544 @cindex C@t{++} exception handling
10547 Debug C@t{++} exception handling using these commands. @xref{Set
10548 Catchpoints, , Setting Catchpoints}.
10550 @cindex inheritance
10551 @item ptype @var{typename}
10552 Print inheritance relationships as well as other information for type
10554 @xref{Symbols, ,Examining the Symbol Table}.
10556 @cindex C@t{++} symbol display
10557 @item set print demangle
10558 @itemx show print demangle
10559 @itemx set print asm-demangle
10560 @itemx show print asm-demangle
10561 Control whether C@t{++} symbols display in their source form, both when
10562 displaying code as C@t{++} source and when displaying disassemblies.
10563 @xref{Print Settings, ,Print Settings}.
10565 @item set print object
10566 @itemx show print object
10567 Choose whether to print derived (actual) or declared types of objects.
10568 @xref{Print Settings, ,Print Settings}.
10570 @item set print vtbl
10571 @itemx show print vtbl
10572 Control the format for printing virtual function tables.
10573 @xref{Print Settings, ,Print Settings}.
10574 (The @code{vtbl} commands do not work on programs compiled with the HP
10575 ANSI C@t{++} compiler (@code{aCC}).)
10577 @kindex set overload-resolution
10578 @cindex overloaded functions, overload resolution
10579 @item set overload-resolution on
10580 Enable overload resolution for C@t{++} expression evaluation. The default
10581 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10582 and searches for a function whose signature matches the argument types,
10583 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10584 Expressions, ,C@t{++} Expressions}, for details).
10585 If it cannot find a match, it emits a message.
10587 @item set overload-resolution off
10588 Disable overload resolution for C@t{++} expression evaluation. For
10589 overloaded functions that are not class member functions, @value{GDBN}
10590 chooses the first function of the specified name that it finds in the
10591 symbol table, whether or not its arguments are of the correct type. For
10592 overloaded functions that are class member functions, @value{GDBN}
10593 searches for a function whose signature @emph{exactly} matches the
10596 @kindex show overload-resolution
10597 @item show overload-resolution
10598 Show the current setting of overload resolution.
10600 @item @r{Overloaded symbol names}
10601 You can specify a particular definition of an overloaded symbol, using
10602 the same notation that is used to declare such symbols in C@t{++}: type
10603 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10604 also use the @value{GDBN} command-line word completion facilities to list the
10605 available choices, or to finish the type list for you.
10606 @xref{Completion,, Command Completion}, for details on how to do this.
10609 @node Decimal Floating Point
10610 @subsubsection Decimal Floating Point format
10611 @cindex decimal floating point format
10613 @value{GDBN} can examine, set and perform computations with numbers in
10614 decimal floating point format, which in the C language correspond to the
10615 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10616 specified by the extension to support decimal floating-point arithmetic.
10618 There are two encodings in use, depending on the architecture: BID (Binary
10619 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10620 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10623 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10624 to manipulate decimal floating point numbers, it is not possible to convert
10625 (using a cast, for example) integers wider than 32-bit to decimal float.
10627 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10628 point computations, error checking in decimal float operations ignores
10629 underflow, overflow and divide by zero exceptions.
10631 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10632 to inspect @code{_Decimal128} values stored in floating point registers. See
10633 @ref{PowerPC,,PowerPC} for more details.
10636 @subsection Objective-C
10638 @cindex Objective-C
10639 This section provides information about some commands and command
10640 options that are useful for debugging Objective-C code. See also
10641 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10642 few more commands specific to Objective-C support.
10645 * Method Names in Commands::
10646 * The Print Command with Objective-C::
10649 @node Method Names in Commands
10650 @subsubsection Method Names in Commands
10652 The following commands have been extended to accept Objective-C method
10653 names as line specifications:
10655 @kindex clear@r{, and Objective-C}
10656 @kindex break@r{, and Objective-C}
10657 @kindex info line@r{, and Objective-C}
10658 @kindex jump@r{, and Objective-C}
10659 @kindex list@r{, and Objective-C}
10663 @item @code{info line}
10668 A fully qualified Objective-C method name is specified as
10671 -[@var{Class} @var{methodName}]
10674 where the minus sign is used to indicate an instance method and a
10675 plus sign (not shown) is used to indicate a class method. The class
10676 name @var{Class} and method name @var{methodName} are enclosed in
10677 brackets, similar to the way messages are specified in Objective-C
10678 source code. For example, to set a breakpoint at the @code{create}
10679 instance method of class @code{Fruit} in the program currently being
10683 break -[Fruit create]
10686 To list ten program lines around the @code{initialize} class method,
10690 list +[NSText initialize]
10693 In the current version of @value{GDBN}, the plus or minus sign is
10694 required. In future versions of @value{GDBN}, the plus or minus
10695 sign will be optional, but you can use it to narrow the search. It
10696 is also possible to specify just a method name:
10702 You must specify the complete method name, including any colons. If
10703 your program's source files contain more than one @code{create} method,
10704 you'll be presented with a numbered list of classes that implement that
10705 method. Indicate your choice by number, or type @samp{0} to exit if
10708 As another example, to clear a breakpoint established at the
10709 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10712 clear -[NSWindow makeKeyAndOrderFront:]
10715 @node The Print Command with Objective-C
10716 @subsubsection The Print Command With Objective-C
10717 @cindex Objective-C, print objects
10718 @kindex print-object
10719 @kindex po @r{(@code{print-object})}
10721 The print command has also been extended to accept methods. For example:
10724 print -[@var{object} hash]
10727 @cindex print an Objective-C object description
10728 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10730 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10731 and print the result. Also, an additional command has been added,
10732 @code{print-object} or @code{po} for short, which is meant to print
10733 the description of an object. However, this command may only work
10734 with certain Objective-C libraries that have a particular hook
10735 function, @code{_NSPrintForDebugger}, defined.
10738 @subsection Fortran
10739 @cindex Fortran-specific support in @value{GDBN}
10741 @value{GDBN} can be used to debug programs written in Fortran, but it
10742 currently supports only the features of Fortran 77 language.
10744 @cindex trailing underscore, in Fortran symbols
10745 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10746 among them) append an underscore to the names of variables and
10747 functions. When you debug programs compiled by those compilers, you
10748 will need to refer to variables and functions with a trailing
10752 * Fortran Operators:: Fortran operators and expressions
10753 * Fortran Defaults:: Default settings for Fortran
10754 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10757 @node Fortran Operators
10758 @subsubsection Fortran Operators and Expressions
10760 @cindex Fortran operators and expressions
10762 Operators must be defined on values of specific types. For instance,
10763 @code{+} is defined on numbers, but not on characters or other non-
10764 arithmetic types. Operators are often defined on groups of types.
10768 The exponentiation operator. It raises the first operand to the power
10772 The range operator. Normally used in the form of array(low:high) to
10773 represent a section of array.
10776 The access component operator. Normally used to access elements in derived
10777 types. Also suitable for unions. As unions aren't part of regular Fortran,
10778 this can only happen when accessing a register that uses a gdbarch-defined
10782 @node Fortran Defaults
10783 @subsubsection Fortran Defaults
10785 @cindex Fortran Defaults
10787 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10788 default uses case-insensitive matches for Fortran symbols. You can
10789 change that with the @samp{set case-insensitive} command, see
10790 @ref{Symbols}, for the details.
10792 @node Special Fortran Commands
10793 @subsubsection Special Fortran Commands
10795 @cindex Special Fortran commands
10797 @value{GDBN} has some commands to support Fortran-specific features,
10798 such as displaying common blocks.
10801 @cindex @code{COMMON} blocks, Fortran
10802 @kindex info common
10803 @item info common @r{[}@var{common-name}@r{]}
10804 This command prints the values contained in the Fortran @code{COMMON}
10805 block whose name is @var{common-name}. With no argument, the names of
10806 all @code{COMMON} blocks visible at the current program location are
10813 @cindex Pascal support in @value{GDBN}, limitations
10814 Debugging Pascal programs which use sets, subranges, file variables, or
10815 nested functions does not currently work. @value{GDBN} does not support
10816 entering expressions, printing values, or similar features using Pascal
10819 The Pascal-specific command @code{set print pascal_static-members}
10820 controls whether static members of Pascal objects are displayed.
10821 @xref{Print Settings, pascal_static-members}.
10824 @subsection Modula-2
10826 @cindex Modula-2, @value{GDBN} support
10828 The extensions made to @value{GDBN} to support Modula-2 only support
10829 output from the @sc{gnu} Modula-2 compiler (which is currently being
10830 developed). Other Modula-2 compilers are not currently supported, and
10831 attempting to debug executables produced by them is most likely
10832 to give an error as @value{GDBN} reads in the executable's symbol
10835 @cindex expressions in Modula-2
10837 * M2 Operators:: Built-in operators
10838 * Built-In Func/Proc:: Built-in functions and procedures
10839 * M2 Constants:: Modula-2 constants
10840 * M2 Types:: Modula-2 types
10841 * M2 Defaults:: Default settings for Modula-2
10842 * Deviations:: Deviations from standard Modula-2
10843 * M2 Checks:: Modula-2 type and range checks
10844 * M2 Scope:: The scope operators @code{::} and @code{.}
10845 * GDB/M2:: @value{GDBN} and Modula-2
10849 @subsubsection Operators
10850 @cindex Modula-2 operators
10852 Operators must be defined on values of specific types. For instance,
10853 @code{+} is defined on numbers, but not on structures. Operators are
10854 often defined on groups of types. For the purposes of Modula-2, the
10855 following definitions hold:
10860 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10864 @emph{Character types} consist of @code{CHAR} and its subranges.
10867 @emph{Floating-point types} consist of @code{REAL}.
10870 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10874 @emph{Scalar types} consist of all of the above.
10877 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10880 @emph{Boolean types} consist of @code{BOOLEAN}.
10884 The following operators are supported, and appear in order of
10885 increasing precedence:
10889 Function argument or array index separator.
10892 Assignment. The value of @var{var} @code{:=} @var{value} is
10896 Less than, greater than on integral, floating-point, or enumerated
10900 Less than or equal to, greater than or equal to
10901 on integral, floating-point and enumerated types, or set inclusion on
10902 set types. Same precedence as @code{<}.
10904 @item =@r{, }<>@r{, }#
10905 Equality and two ways of expressing inequality, valid on scalar types.
10906 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10907 available for inequality, since @code{#} conflicts with the script
10911 Set membership. Defined on set types and the types of their members.
10912 Same precedence as @code{<}.
10915 Boolean disjunction. Defined on boolean types.
10918 Boolean conjunction. Defined on boolean types.
10921 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10924 Addition and subtraction on integral and floating-point types, or union
10925 and difference on set types.
10928 Multiplication on integral and floating-point types, or set intersection
10932 Division on floating-point types, or symmetric set difference on set
10933 types. Same precedence as @code{*}.
10936 Integer division and remainder. Defined on integral types. Same
10937 precedence as @code{*}.
10940 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10943 Pointer dereferencing. Defined on pointer types.
10946 Boolean negation. Defined on boolean types. Same precedence as
10950 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10951 precedence as @code{^}.
10954 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10957 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10961 @value{GDBN} and Modula-2 scope operators.
10965 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10966 treats the use of the operator @code{IN}, or the use of operators
10967 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10968 @code{<=}, and @code{>=} on sets as an error.
10972 @node Built-In Func/Proc
10973 @subsubsection Built-in Functions and Procedures
10974 @cindex Modula-2 built-ins
10976 Modula-2 also makes available several built-in procedures and functions.
10977 In describing these, the following metavariables are used:
10982 represents an @code{ARRAY} variable.
10985 represents a @code{CHAR} constant or variable.
10988 represents a variable or constant of integral type.
10991 represents an identifier that belongs to a set. Generally used in the
10992 same function with the metavariable @var{s}. The type of @var{s} should
10993 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10996 represents a variable or constant of integral or floating-point type.
10999 represents a variable or constant of floating-point type.
11005 represents a variable.
11008 represents a variable or constant of one of many types. See the
11009 explanation of the function for details.
11012 All Modula-2 built-in procedures also return a result, described below.
11016 Returns the absolute value of @var{n}.
11019 If @var{c} is a lower case letter, it returns its upper case
11020 equivalent, otherwise it returns its argument.
11023 Returns the character whose ordinal value is @var{i}.
11026 Decrements the value in the variable @var{v} by one. Returns the new value.
11028 @item DEC(@var{v},@var{i})
11029 Decrements the value in the variable @var{v} by @var{i}. Returns the
11032 @item EXCL(@var{m},@var{s})
11033 Removes the element @var{m} from the set @var{s}. Returns the new
11036 @item FLOAT(@var{i})
11037 Returns the floating point equivalent of the integer @var{i}.
11039 @item HIGH(@var{a})
11040 Returns the index of the last member of @var{a}.
11043 Increments the value in the variable @var{v} by one. Returns the new value.
11045 @item INC(@var{v},@var{i})
11046 Increments the value in the variable @var{v} by @var{i}. Returns the
11049 @item INCL(@var{m},@var{s})
11050 Adds the element @var{m} to the set @var{s} if it is not already
11051 there. Returns the new set.
11054 Returns the maximum value of the type @var{t}.
11057 Returns the minimum value of the type @var{t}.
11060 Returns boolean TRUE if @var{i} is an odd number.
11063 Returns the ordinal value of its argument. For example, the ordinal
11064 value of a character is its @sc{ascii} value (on machines supporting the
11065 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11066 integral, character and enumerated types.
11068 @item SIZE(@var{x})
11069 Returns the size of its argument. @var{x} can be a variable or a type.
11071 @item TRUNC(@var{r})
11072 Returns the integral part of @var{r}.
11074 @item TSIZE(@var{x})
11075 Returns the size of its argument. @var{x} can be a variable or a type.
11077 @item VAL(@var{t},@var{i})
11078 Returns the member of the type @var{t} whose ordinal value is @var{i}.
11082 @emph{Warning:} Sets and their operations are not yet supported, so
11083 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
11087 @cindex Modula-2 constants
11089 @subsubsection Constants
11091 @value{GDBN} allows you to express the constants of Modula-2 in the following
11097 Integer constants are simply a sequence of digits. When used in an
11098 expression, a constant is interpreted to be type-compatible with the
11099 rest of the expression. Hexadecimal integers are specified by a
11100 trailing @samp{H}, and octal integers by a trailing @samp{B}.
11103 Floating point constants appear as a sequence of digits, followed by a
11104 decimal point and another sequence of digits. An optional exponent can
11105 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
11106 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
11107 digits of the floating point constant must be valid decimal (base 10)
11111 Character constants consist of a single character enclosed by a pair of
11112 like quotes, either single (@code{'}) or double (@code{"}). They may
11113 also be expressed by their ordinal value (their @sc{ascii} value, usually)
11114 followed by a @samp{C}.
11117 String constants consist of a sequence of characters enclosed by a
11118 pair of like quotes, either single (@code{'}) or double (@code{"}).
11119 Escape sequences in the style of C are also allowed. @xref{C
11120 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
11124 Enumerated constants consist of an enumerated identifier.
11127 Boolean constants consist of the identifiers @code{TRUE} and
11131 Pointer constants consist of integral values only.
11134 Set constants are not yet supported.
11138 @subsubsection Modula-2 Types
11139 @cindex Modula-2 types
11141 Currently @value{GDBN} can print the following data types in Modula-2
11142 syntax: array types, record types, set types, pointer types, procedure
11143 types, enumerated types, subrange types and base types. You can also
11144 print the contents of variables declared using these type.
11145 This section gives a number of simple source code examples together with
11146 sample @value{GDBN} sessions.
11148 The first example contains the following section of code:
11157 and you can request @value{GDBN} to interrogate the type and value of
11158 @code{r} and @code{s}.
11161 (@value{GDBP}) print s
11163 (@value{GDBP}) ptype s
11165 (@value{GDBP}) print r
11167 (@value{GDBP}) ptype r
11172 Likewise if your source code declares @code{s} as:
11176 s: SET ['A'..'Z'] ;
11180 then you may query the type of @code{s} by:
11183 (@value{GDBP}) ptype s
11184 type = SET ['A'..'Z']
11188 Note that at present you cannot interactively manipulate set
11189 expressions using the debugger.
11191 The following example shows how you might declare an array in Modula-2
11192 and how you can interact with @value{GDBN} to print its type and contents:
11196 s: ARRAY [-10..10] OF CHAR ;
11200 (@value{GDBP}) ptype s
11201 ARRAY [-10..10] OF CHAR
11204 Note that the array handling is not yet complete and although the type
11205 is printed correctly, expression handling still assumes that all
11206 arrays have a lower bound of zero and not @code{-10} as in the example
11209 Here are some more type related Modula-2 examples:
11213 colour = (blue, red, yellow, green) ;
11214 t = [blue..yellow] ;
11222 The @value{GDBN} interaction shows how you can query the data type
11223 and value of a variable.
11226 (@value{GDBP}) print s
11228 (@value{GDBP}) ptype t
11229 type = [blue..yellow]
11233 In this example a Modula-2 array is declared and its contents
11234 displayed. Observe that the contents are written in the same way as
11235 their @code{C} counterparts.
11239 s: ARRAY [1..5] OF CARDINAL ;
11245 (@value{GDBP}) print s
11246 $1 = @{1, 0, 0, 0, 0@}
11247 (@value{GDBP}) ptype s
11248 type = ARRAY [1..5] OF CARDINAL
11251 The Modula-2 language interface to @value{GDBN} also understands
11252 pointer types as shown in this example:
11256 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11263 and you can request that @value{GDBN} describes the type of @code{s}.
11266 (@value{GDBP}) ptype s
11267 type = POINTER TO ARRAY [1..5] OF CARDINAL
11270 @value{GDBN} handles compound types as we can see in this example.
11271 Here we combine array types, record types, pointer types and subrange
11282 myarray = ARRAY myrange OF CARDINAL ;
11283 myrange = [-2..2] ;
11285 s: POINTER TO ARRAY myrange OF foo ;
11289 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11293 (@value{GDBP}) ptype s
11294 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11297 f3 : ARRAY [-2..2] OF CARDINAL;
11302 @subsubsection Modula-2 Defaults
11303 @cindex Modula-2 defaults
11305 If type and range checking are set automatically by @value{GDBN}, they
11306 both default to @code{on} whenever the working language changes to
11307 Modula-2. This happens regardless of whether you or @value{GDBN}
11308 selected the working language.
11310 If you allow @value{GDBN} to set the language automatically, then entering
11311 code compiled from a file whose name ends with @file{.mod} sets the
11312 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11313 Infer the Source Language}, for further details.
11316 @subsubsection Deviations from Standard Modula-2
11317 @cindex Modula-2, deviations from
11319 A few changes have been made to make Modula-2 programs easier to debug.
11320 This is done primarily via loosening its type strictness:
11324 Unlike in standard Modula-2, pointer constants can be formed by
11325 integers. This allows you to modify pointer variables during
11326 debugging. (In standard Modula-2, the actual address contained in a
11327 pointer variable is hidden from you; it can only be modified
11328 through direct assignment to another pointer variable or expression that
11329 returned a pointer.)
11332 C escape sequences can be used in strings and characters to represent
11333 non-printable characters. @value{GDBN} prints out strings with these
11334 escape sequences embedded. Single non-printable characters are
11335 printed using the @samp{CHR(@var{nnn})} format.
11338 The assignment operator (@code{:=}) returns the value of its right-hand
11342 All built-in procedures both modify @emph{and} return their argument.
11346 @subsubsection Modula-2 Type and Range Checks
11347 @cindex Modula-2 checks
11350 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11353 @c FIXME remove warning when type/range checks added
11355 @value{GDBN} considers two Modula-2 variables type equivalent if:
11359 They are of types that have been declared equivalent via a @code{TYPE
11360 @var{t1} = @var{t2}} statement
11363 They have been declared on the same line. (Note: This is true of the
11364 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11367 As long as type checking is enabled, any attempt to combine variables
11368 whose types are not equivalent is an error.
11370 Range checking is done on all mathematical operations, assignment, array
11371 index bounds, and all built-in functions and procedures.
11374 @subsubsection The Scope Operators @code{::} and @code{.}
11376 @cindex @code{.}, Modula-2 scope operator
11377 @cindex colon, doubled as scope operator
11379 @vindex colon-colon@r{, in Modula-2}
11380 @c Info cannot handle :: but TeX can.
11383 @vindex ::@r{, in Modula-2}
11386 There are a few subtle differences between the Modula-2 scope operator
11387 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11392 @var{module} . @var{id}
11393 @var{scope} :: @var{id}
11397 where @var{scope} is the name of a module or a procedure,
11398 @var{module} the name of a module, and @var{id} is any declared
11399 identifier within your program, except another module.
11401 Using the @code{::} operator makes @value{GDBN} search the scope
11402 specified by @var{scope} for the identifier @var{id}. If it is not
11403 found in the specified scope, then @value{GDBN} searches all scopes
11404 enclosing the one specified by @var{scope}.
11406 Using the @code{.} operator makes @value{GDBN} search the current scope for
11407 the identifier specified by @var{id} that was imported from the
11408 definition module specified by @var{module}. With this operator, it is
11409 an error if the identifier @var{id} was not imported from definition
11410 module @var{module}, or if @var{id} is not an identifier in
11414 @subsubsection @value{GDBN} and Modula-2
11416 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11417 Five subcommands of @code{set print} and @code{show print} apply
11418 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11419 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11420 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11421 analogue in Modula-2.
11423 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11424 with any language, is not useful with Modula-2. Its
11425 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11426 created in Modula-2 as they can in C or C@t{++}. However, because an
11427 address can be specified by an integral constant, the construct
11428 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11430 @cindex @code{#} in Modula-2
11431 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11432 interpreted as the beginning of a comment. Use @code{<>} instead.
11438 The extensions made to @value{GDBN} for Ada only support
11439 output from the @sc{gnu} Ada (GNAT) compiler.
11440 Other Ada compilers are not currently supported, and
11441 attempting to debug executables produced by them is most likely
11445 @cindex expressions in Ada
11447 * Ada Mode Intro:: General remarks on the Ada syntax
11448 and semantics supported by Ada mode
11450 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11451 * Additions to Ada:: Extensions of the Ada expression syntax.
11452 * Stopping Before Main Program:: Debugging the program during elaboration.
11453 * Ada Tasks:: Listing and setting breakpoints in tasks.
11454 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11455 * Ada Glitches:: Known peculiarities of Ada mode.
11458 @node Ada Mode Intro
11459 @subsubsection Introduction
11460 @cindex Ada mode, general
11462 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11463 syntax, with some extensions.
11464 The philosophy behind the design of this subset is
11468 That @value{GDBN} should provide basic literals and access to operations for
11469 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11470 leaving more sophisticated computations to subprograms written into the
11471 program (which therefore may be called from @value{GDBN}).
11474 That type safety and strict adherence to Ada language restrictions
11475 are not particularly important to the @value{GDBN} user.
11478 That brevity is important to the @value{GDBN} user.
11481 Thus, for brevity, the debugger acts as if all names declared in
11482 user-written packages are directly visible, even if they are not visible
11483 according to Ada rules, thus making it unnecessary to fully qualify most
11484 names with their packages, regardless of context. Where this causes
11485 ambiguity, @value{GDBN} asks the user's intent.
11487 The debugger will start in Ada mode if it detects an Ada main program.
11488 As for other languages, it will enter Ada mode when stopped in a program that
11489 was translated from an Ada source file.
11491 While in Ada mode, you may use `@t{--}' for comments. This is useful
11492 mostly for documenting command files. The standard @value{GDBN} comment
11493 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11494 middle (to allow based literals).
11496 The debugger supports limited overloading. Given a subprogram call in which
11497 the function symbol has multiple definitions, it will use the number of
11498 actual parameters and some information about their types to attempt to narrow
11499 the set of definitions. It also makes very limited use of context, preferring
11500 procedures to functions in the context of the @code{call} command, and
11501 functions to procedures elsewhere.
11503 @node Omissions from Ada
11504 @subsubsection Omissions from Ada
11505 @cindex Ada, omissions from
11507 Here are the notable omissions from the subset:
11511 Only a subset of the attributes are supported:
11515 @t{'First}, @t{'Last}, and @t{'Length}
11516 on array objects (not on types and subtypes).
11519 @t{'Min} and @t{'Max}.
11522 @t{'Pos} and @t{'Val}.
11528 @t{'Range} on array objects (not subtypes), but only as the right
11529 operand of the membership (@code{in}) operator.
11532 @t{'Access}, @t{'Unchecked_Access}, and
11533 @t{'Unrestricted_Access} (a GNAT extension).
11541 @code{Characters.Latin_1} are not available and
11542 concatenation is not implemented. Thus, escape characters in strings are
11543 not currently available.
11546 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11547 equality of representations. They will generally work correctly
11548 for strings and arrays whose elements have integer or enumeration types.
11549 They may not work correctly for arrays whose element
11550 types have user-defined equality, for arrays of real values
11551 (in particular, IEEE-conformant floating point, because of negative
11552 zeroes and NaNs), and for arrays whose elements contain unused bits with
11553 indeterminate values.
11556 The other component-by-component array operations (@code{and}, @code{or},
11557 @code{xor}, @code{not}, and relational tests other than equality)
11558 are not implemented.
11561 @cindex array aggregates (Ada)
11562 @cindex record aggregates (Ada)
11563 @cindex aggregates (Ada)
11564 There is limited support for array and record aggregates. They are
11565 permitted only on the right sides of assignments, as in these examples:
11568 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11569 (@value{GDBP}) set An_Array := (1, others => 0)
11570 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11571 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11572 (@value{GDBP}) set A_Record := (1, "Peter", True);
11573 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11577 discriminant's value by assigning an aggregate has an
11578 undefined effect if that discriminant is used within the record.
11579 However, you can first modify discriminants by directly assigning to
11580 them (which normally would not be allowed in Ada), and then performing an
11581 aggregate assignment. For example, given a variable @code{A_Rec}
11582 declared to have a type such as:
11585 type Rec (Len : Small_Integer := 0) is record
11587 Vals : IntArray (1 .. Len);
11591 you can assign a value with a different size of @code{Vals} with two
11595 (@value{GDBP}) set A_Rec.Len := 4
11596 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11599 As this example also illustrates, @value{GDBN} is very loose about the usual
11600 rules concerning aggregates. You may leave out some of the
11601 components of an array or record aggregate (such as the @code{Len}
11602 component in the assignment to @code{A_Rec} above); they will retain their
11603 original values upon assignment. You may freely use dynamic values as
11604 indices in component associations. You may even use overlapping or
11605 redundant component associations, although which component values are
11606 assigned in such cases is not defined.
11609 Calls to dispatching subprograms are not implemented.
11612 The overloading algorithm is much more limited (i.e., less selective)
11613 than that of real Ada. It makes only limited use of the context in
11614 which a subexpression appears to resolve its meaning, and it is much
11615 looser in its rules for allowing type matches. As a result, some
11616 function calls will be ambiguous, and the user will be asked to choose
11617 the proper resolution.
11620 The @code{new} operator is not implemented.
11623 Entry calls are not implemented.
11626 Aside from printing, arithmetic operations on the native VAX floating-point
11627 formats are not supported.
11630 It is not possible to slice a packed array.
11633 The names @code{True} and @code{False}, when not part of a qualified name,
11634 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11636 Should your program
11637 redefine these names in a package or procedure (at best a dubious practice),
11638 you will have to use fully qualified names to access their new definitions.
11641 @node Additions to Ada
11642 @subsubsection Additions to Ada
11643 @cindex Ada, deviations from
11645 As it does for other languages, @value{GDBN} makes certain generic
11646 extensions to Ada (@pxref{Expressions}):
11650 If the expression @var{E} is a variable residing in memory (typically
11651 a local variable or array element) and @var{N} is a positive integer,
11652 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11653 @var{N}-1 adjacent variables following it in memory as an array. In
11654 Ada, this operator is generally not necessary, since its prime use is
11655 in displaying parts of an array, and slicing will usually do this in
11656 Ada. However, there are occasional uses when debugging programs in
11657 which certain debugging information has been optimized away.
11660 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11661 appears in function or file @var{B}.'' When @var{B} is a file name,
11662 you must typically surround it in single quotes.
11665 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11666 @var{type} that appears at address @var{addr}.''
11669 A name starting with @samp{$} is a convenience variable
11670 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11673 In addition, @value{GDBN} provides a few other shortcuts and outright
11674 additions specific to Ada:
11678 The assignment statement is allowed as an expression, returning
11679 its right-hand operand as its value. Thus, you may enter
11682 (@value{GDBP}) set x := y + 3
11683 (@value{GDBP}) print A(tmp := y + 1)
11687 The semicolon is allowed as an ``operator,'' returning as its value
11688 the value of its right-hand operand.
11689 This allows, for example,
11690 complex conditional breaks:
11693 (@value{GDBP}) break f
11694 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11698 Rather than use catenation and symbolic character names to introduce special
11699 characters into strings, one may instead use a special bracket notation,
11700 which is also used to print strings. A sequence of characters of the form
11701 @samp{["@var{XX}"]} within a string or character literal denotes the
11702 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11703 sequence of characters @samp{["""]} also denotes a single quotation mark
11704 in strings. For example,
11706 "One line.["0a"]Next line.["0a"]"
11709 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11713 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11714 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11718 (@value{GDBP}) print 'max(x, y)
11722 When printing arrays, @value{GDBN} uses positional notation when the
11723 array has a lower bound of 1, and uses a modified named notation otherwise.
11724 For example, a one-dimensional array of three integers with a lower bound
11725 of 3 might print as
11732 That is, in contrast to valid Ada, only the first component has a @code{=>}
11736 You may abbreviate attributes in expressions with any unique,
11737 multi-character subsequence of
11738 their names (an exact match gets preference).
11739 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11740 in place of @t{a'length}.
11743 @cindex quoting Ada internal identifiers
11744 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11745 to lower case. The GNAT compiler uses upper-case characters for
11746 some of its internal identifiers, which are normally of no interest to users.
11747 For the rare occasions when you actually have to look at them,
11748 enclose them in angle brackets to avoid the lower-case mapping.
11751 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11755 Printing an object of class-wide type or dereferencing an
11756 access-to-class-wide value will display all the components of the object's
11757 specific type (as indicated by its run-time tag). Likewise, component
11758 selection on such a value will operate on the specific type of the
11763 @node Stopping Before Main Program
11764 @subsubsection Stopping at the Very Beginning
11766 @cindex breakpointing Ada elaboration code
11767 It is sometimes necessary to debug the program during elaboration, and
11768 before reaching the main procedure.
11769 As defined in the Ada Reference
11770 Manual, the elaboration code is invoked from a procedure called
11771 @code{adainit}. To run your program up to the beginning of
11772 elaboration, simply use the following two commands:
11773 @code{tbreak adainit} and @code{run}.
11776 @subsubsection Extensions for Ada Tasks
11777 @cindex Ada, tasking
11779 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11780 @value{GDBN} provides the following task-related commands:
11785 This command shows a list of current Ada tasks, as in the following example:
11792 (@value{GDBP}) info tasks
11793 ID TID P-ID Pri State Name
11794 1 8088000 0 15 Child Activation Wait main_task
11795 2 80a4000 1 15 Accept Statement b
11796 3 809a800 1 15 Child Activation Wait a
11797 * 4 80ae800 3 15 Runnable c
11802 In this listing, the asterisk before the last task indicates it to be the
11803 task currently being inspected.
11807 Represents @value{GDBN}'s internal task number.
11813 The parent's task ID (@value{GDBN}'s internal task number).
11816 The base priority of the task.
11819 Current state of the task.
11823 The task has been created but has not been activated. It cannot be
11827 The task is not blocked for any reason known to Ada. (It may be waiting
11828 for a mutex, though.) It is conceptually "executing" in normal mode.
11831 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11832 that were waiting on terminate alternatives have been awakened and have
11833 terminated themselves.
11835 @item Child Activation Wait
11836 The task is waiting for created tasks to complete activation.
11838 @item Accept Statement
11839 The task is waiting on an accept or selective wait statement.
11841 @item Waiting on entry call
11842 The task is waiting on an entry call.
11844 @item Async Select Wait
11845 The task is waiting to start the abortable part of an asynchronous
11849 The task is waiting on a select statement with only a delay
11852 @item Child Termination Wait
11853 The task is sleeping having completed a master within itself, and is
11854 waiting for the tasks dependent on that master to become terminated or
11855 waiting on a terminate Phase.
11857 @item Wait Child in Term Alt
11858 The task is sleeping waiting for tasks on terminate alternatives to
11859 finish terminating.
11861 @item Accepting RV with @var{taskno}
11862 The task is accepting a rendez-vous with the task @var{taskno}.
11866 Name of the task in the program.
11870 @kindex info task @var{taskno}
11871 @item info task @var{taskno}
11872 This command shows detailled informations on the specified task, as in
11873 the following example:
11878 (@value{GDBP}) info tasks
11879 ID TID P-ID Pri State Name
11880 1 8077880 0 15 Child Activation Wait main_task
11881 * 2 807c468 1 15 Runnable task_1
11882 (@value{GDBP}) info task 2
11883 Ada Task: 0x807c468
11886 Parent: 1 (main_task)
11892 @kindex task@r{ (Ada)}
11893 @cindex current Ada task ID
11894 This command prints the ID of the current task.
11900 (@value{GDBP}) info tasks
11901 ID TID P-ID Pri State Name
11902 1 8077870 0 15 Child Activation Wait main_task
11903 * 2 807c458 1 15 Runnable t
11904 (@value{GDBP}) task
11905 [Current task is 2]
11908 @item task @var{taskno}
11909 @cindex Ada task switching
11910 This command is like the @code{thread @var{threadno}}
11911 command (@pxref{Threads}). It switches the context of debugging
11912 from the current task to the given task.
11918 (@value{GDBP}) info tasks
11919 ID TID P-ID Pri State Name
11920 1 8077870 0 15 Child Activation Wait main_task
11921 * 2 807c458 1 15 Runnable t
11922 (@value{GDBP}) task 1
11923 [Switching to task 1]
11924 #0 0x8067726 in pthread_cond_wait ()
11926 #0 0x8067726 in pthread_cond_wait ()
11927 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11928 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11929 #3 0x806153e in system.tasking.stages.activate_tasks ()
11930 #4 0x804aacc in un () at un.adb:5
11933 @item break @var{linespec} task @var{taskno}
11934 @itemx break @var{linespec} task @var{taskno} if @dots{}
11935 @cindex breakpoints and tasks, in Ada
11936 @cindex task breakpoints, in Ada
11937 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
11938 These commands are like the @code{break @dots{} thread @dots{}}
11939 command (@pxref{Thread Stops}).
11940 @var{linespec} specifies source lines, as described
11941 in @ref{Specify Location}.
11943 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
11944 to specify that you only want @value{GDBN} to stop the program when a
11945 particular Ada task reaches this breakpoint. @var{taskno} is one of the
11946 numeric task identifiers assigned by @value{GDBN}, shown in the first
11947 column of the @samp{info tasks} display.
11949 If you do not specify @samp{task @var{taskno}} when you set a
11950 breakpoint, the breakpoint applies to @emph{all} tasks of your
11953 You can use the @code{task} qualifier on conditional breakpoints as
11954 well; in this case, place @samp{task @var{taskno}} before the
11955 breakpoint condition (before the @code{if}).
11963 (@value{GDBP}) info tasks
11964 ID TID P-ID Pri State Name
11965 1 140022020 0 15 Child Activation Wait main_task
11966 2 140045060 1 15 Accept/Select Wait t2
11967 3 140044840 1 15 Runnable t1
11968 * 4 140056040 1 15 Runnable t3
11969 (@value{GDBP}) b 15 task 2
11970 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
11971 (@value{GDBP}) cont
11976 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
11978 (@value{GDBP}) info tasks
11979 ID TID P-ID Pri State Name
11980 1 140022020 0 15 Child Activation Wait main_task
11981 * 2 140045060 1 15 Runnable t2
11982 3 140044840 1 15 Runnable t1
11983 4 140056040 1 15 Delay Sleep t3
11987 @node Ada Tasks and Core Files
11988 @subsubsection Tasking Support when Debugging Core Files
11989 @cindex Ada tasking and core file debugging
11991 When inspecting a core file, as opposed to debugging a live program,
11992 tasking support may be limited or even unavailable, depending on
11993 the platform being used.
11994 For instance, on x86-linux, the list of tasks is available, but task
11995 switching is not supported. On Tru64, however, task switching will work
11998 On certain platforms, including Tru64, the debugger needs to perform some
11999 memory writes in order to provide Ada tasking support. When inspecting
12000 a core file, this means that the core file must be opened with read-write
12001 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12002 Under these circumstances, you should make a backup copy of the core
12003 file before inspecting it with @value{GDBN}.
12006 @subsubsection Known Peculiarities of Ada Mode
12007 @cindex Ada, problems
12009 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12010 we know of several problems with and limitations of Ada mode in
12012 some of which will be fixed with planned future releases of the debugger
12013 and the GNU Ada compiler.
12017 Currently, the debugger
12018 has insufficient information to determine whether certain pointers represent
12019 pointers to objects or the objects themselves.
12020 Thus, the user may have to tack an extra @code{.all} after an expression
12021 to get it printed properly.
12024 Static constants that the compiler chooses not to materialize as objects in
12025 storage are invisible to the debugger.
12028 Named parameter associations in function argument lists are ignored (the
12029 argument lists are treated as positional).
12032 Many useful library packages are currently invisible to the debugger.
12035 Fixed-point arithmetic, conversions, input, and output is carried out using
12036 floating-point arithmetic, and may give results that only approximate those on
12040 The GNAT compiler never generates the prefix @code{Standard} for any of
12041 the standard symbols defined by the Ada language. @value{GDBN} knows about
12042 this: it will strip the prefix from names when you use it, and will never
12043 look for a name you have so qualified among local symbols, nor match against
12044 symbols in other packages or subprograms. If you have
12045 defined entities anywhere in your program other than parameters and
12046 local variables whose simple names match names in @code{Standard},
12047 GNAT's lack of qualification here can cause confusion. When this happens,
12048 you can usually resolve the confusion
12049 by qualifying the problematic names with package
12050 @code{Standard} explicitly.
12053 @node Unsupported Languages
12054 @section Unsupported Languages
12056 @cindex unsupported languages
12057 @cindex minimal language
12058 In addition to the other fully-supported programming languages,
12059 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
12060 It does not represent a real programming language, but provides a set
12061 of capabilities close to what the C or assembly languages provide.
12062 This should allow most simple operations to be performed while debugging
12063 an application that uses a language currently not supported by @value{GDBN}.
12065 If the language is set to @code{auto}, @value{GDBN} will automatically
12066 select this language if the current frame corresponds to an unsupported
12070 @chapter Examining the Symbol Table
12072 The commands described in this chapter allow you to inquire about the
12073 symbols (names of variables, functions and types) defined in your
12074 program. This information is inherent in the text of your program and
12075 does not change as your program executes. @value{GDBN} finds it in your
12076 program's symbol table, in the file indicated when you started @value{GDBN}
12077 (@pxref{File Options, ,Choosing Files}), or by one of the
12078 file-management commands (@pxref{Files, ,Commands to Specify Files}).
12080 @cindex symbol names
12081 @cindex names of symbols
12082 @cindex quoting names
12083 Occasionally, you may need to refer to symbols that contain unusual
12084 characters, which @value{GDBN} ordinarily treats as word delimiters. The
12085 most frequent case is in referring to static variables in other
12086 source files (@pxref{Variables,,Program Variables}). File names
12087 are recorded in object files as debugging symbols, but @value{GDBN} would
12088 ordinarily parse a typical file name, like @file{foo.c}, as the three words
12089 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
12090 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
12097 looks up the value of @code{x} in the scope of the file @file{foo.c}.
12100 @cindex case-insensitive symbol names
12101 @cindex case sensitivity in symbol names
12102 @kindex set case-sensitive
12103 @item set case-sensitive on
12104 @itemx set case-sensitive off
12105 @itemx set case-sensitive auto
12106 Normally, when @value{GDBN} looks up symbols, it matches their names
12107 with case sensitivity determined by the current source language.
12108 Occasionally, you may wish to control that. The command @code{set
12109 case-sensitive} lets you do that by specifying @code{on} for
12110 case-sensitive matches or @code{off} for case-insensitive ones. If
12111 you specify @code{auto}, case sensitivity is reset to the default
12112 suitable for the source language. The default is case-sensitive
12113 matches for all languages except for Fortran, for which the default is
12114 case-insensitive matches.
12116 @kindex show case-sensitive
12117 @item show case-sensitive
12118 This command shows the current setting of case sensitivity for symbols
12121 @kindex info address
12122 @cindex address of a symbol
12123 @item info address @var{symbol}
12124 Describe where the data for @var{symbol} is stored. For a register
12125 variable, this says which register it is kept in. For a non-register
12126 local variable, this prints the stack-frame offset at which the variable
12129 Note the contrast with @samp{print &@var{symbol}}, which does not work
12130 at all for a register variable, and for a stack local variable prints
12131 the exact address of the current instantiation of the variable.
12133 @kindex info symbol
12134 @cindex symbol from address
12135 @cindex closest symbol and offset for an address
12136 @item info symbol @var{addr}
12137 Print the name of a symbol which is stored at the address @var{addr}.
12138 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
12139 nearest symbol and an offset from it:
12142 (@value{GDBP}) info symbol 0x54320
12143 _initialize_vx + 396 in section .text
12147 This is the opposite of the @code{info address} command. You can use
12148 it to find out the name of a variable or a function given its address.
12150 For dynamically linked executables, the name of executable or shared
12151 library containing the symbol is also printed:
12154 (@value{GDBP}) info symbol 0x400225
12155 _start + 5 in section .text of /tmp/a.out
12156 (@value{GDBP}) info symbol 0x2aaaac2811cf
12157 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
12161 @item whatis [@var{arg}]
12162 Print the data type of @var{arg}, which can be either an expression or
12163 a data type. With no argument, print the data type of @code{$}, the
12164 last value in the value history. If @var{arg} is an expression, it is
12165 not actually evaluated, and any side-effecting operations (such as
12166 assignments or function calls) inside it do not take place. If
12167 @var{arg} is a type name, it may be the name of a type or typedef, or
12168 for C code it may have the form @samp{class @var{class-name}},
12169 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12170 @samp{enum @var{enum-tag}}.
12171 @xref{Expressions, ,Expressions}.
12174 @item ptype [@var{arg}]
12175 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12176 detailed description of the type, instead of just the name of the type.
12177 @xref{Expressions, ,Expressions}.
12179 For example, for this variable declaration:
12182 struct complex @{double real; double imag;@} v;
12186 the two commands give this output:
12190 (@value{GDBP}) whatis v
12191 type = struct complex
12192 (@value{GDBP}) ptype v
12193 type = struct complex @{
12201 As with @code{whatis}, using @code{ptype} without an argument refers to
12202 the type of @code{$}, the last value in the value history.
12204 @cindex incomplete type
12205 Sometimes, programs use opaque data types or incomplete specifications
12206 of complex data structure. If the debug information included in the
12207 program does not allow @value{GDBN} to display a full declaration of
12208 the data type, it will say @samp{<incomplete type>}. For example,
12209 given these declarations:
12213 struct foo *fooptr;
12217 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12220 (@value{GDBP}) ptype foo
12221 $1 = <incomplete type>
12225 ``Incomplete type'' is C terminology for data types that are not
12226 completely specified.
12229 @item info types @var{regexp}
12231 Print a brief description of all types whose names match the regular
12232 expression @var{regexp} (or all types in your program, if you supply
12233 no argument). Each complete typename is matched as though it were a
12234 complete line; thus, @samp{i type value} gives information on all
12235 types in your program whose names include the string @code{value}, but
12236 @samp{i type ^value$} gives information only on types whose complete
12237 name is @code{value}.
12239 This command differs from @code{ptype} in two ways: first, like
12240 @code{whatis}, it does not print a detailed description; second, it
12241 lists all source files where a type is defined.
12244 @cindex local variables
12245 @item info scope @var{location}
12246 List all the variables local to a particular scope. This command
12247 accepts a @var{location} argument---a function name, a source line, or
12248 an address preceded by a @samp{*}, and prints all the variables local
12249 to the scope defined by that location. (@xref{Specify Location}, for
12250 details about supported forms of @var{location}.) For example:
12253 (@value{GDBP}) @b{info scope command_line_handler}
12254 Scope for command_line_handler:
12255 Symbol rl is an argument at stack/frame offset 8, length 4.
12256 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12257 Symbol linelength is in static storage at address 0x150a1c, length 4.
12258 Symbol p is a local variable in register $esi, length 4.
12259 Symbol p1 is a local variable in register $ebx, length 4.
12260 Symbol nline is a local variable in register $edx, length 4.
12261 Symbol repeat is a local variable at frame offset -8, length 4.
12265 This command is especially useful for determining what data to collect
12266 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12269 @kindex info source
12271 Show information about the current source file---that is, the source file for
12272 the function containing the current point of execution:
12275 the name of the source file, and the directory containing it,
12277 the directory it was compiled in,
12279 its length, in lines,
12281 which programming language it is written in,
12283 whether the executable includes debugging information for that file, and
12284 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12286 whether the debugging information includes information about
12287 preprocessor macros.
12291 @kindex info sources
12293 Print the names of all source files in your program for which there is
12294 debugging information, organized into two lists: files whose symbols
12295 have already been read, and files whose symbols will be read when needed.
12297 @kindex info functions
12298 @item info functions
12299 Print the names and data types of all defined functions.
12301 @item info functions @var{regexp}
12302 Print the names and data types of all defined functions
12303 whose names contain a match for regular expression @var{regexp}.
12304 Thus, @samp{info fun step} finds all functions whose names
12305 include @code{step}; @samp{info fun ^step} finds those whose names
12306 start with @code{step}. If a function name contains characters
12307 that conflict with the regular expression language (e.g.@:
12308 @samp{operator*()}), they may be quoted with a backslash.
12310 @kindex info variables
12311 @item info variables
12312 Print the names and data types of all variables that are declared
12313 outside of functions (i.e.@: excluding local variables).
12315 @item info variables @var{regexp}
12316 Print the names and data types of all variables (except for local
12317 variables) whose names contain a match for regular expression
12320 @kindex info classes
12321 @cindex Objective-C, classes and selectors
12323 @itemx info classes @var{regexp}
12324 Display all Objective-C classes in your program, or
12325 (with the @var{regexp} argument) all those matching a particular regular
12328 @kindex info selectors
12329 @item info selectors
12330 @itemx info selectors @var{regexp}
12331 Display all Objective-C selectors in your program, or
12332 (with the @var{regexp} argument) all those matching a particular regular
12336 This was never implemented.
12337 @kindex info methods
12339 @itemx info methods @var{regexp}
12340 The @code{info methods} command permits the user to examine all defined
12341 methods within C@t{++} program, or (with the @var{regexp} argument) a
12342 specific set of methods found in the various C@t{++} classes. Many
12343 C@t{++} classes provide a large number of methods. Thus, the output
12344 from the @code{ptype} command can be overwhelming and hard to use. The
12345 @code{info-methods} command filters the methods, printing only those
12346 which match the regular-expression @var{regexp}.
12349 @cindex reloading symbols
12350 Some systems allow individual object files that make up your program to
12351 be replaced without stopping and restarting your program. For example,
12352 in VxWorks you can simply recompile a defective object file and keep on
12353 running. If you are running on one of these systems, you can allow
12354 @value{GDBN} to reload the symbols for automatically relinked modules:
12357 @kindex set symbol-reloading
12358 @item set symbol-reloading on
12359 Replace symbol definitions for the corresponding source file when an
12360 object file with a particular name is seen again.
12362 @item set symbol-reloading off
12363 Do not replace symbol definitions when encountering object files of the
12364 same name more than once. This is the default state; if you are not
12365 running on a system that permits automatic relinking of modules, you
12366 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12367 may discard symbols when linking large programs, that may contain
12368 several modules (from different directories or libraries) with the same
12371 @kindex show symbol-reloading
12372 @item show symbol-reloading
12373 Show the current @code{on} or @code{off} setting.
12376 @cindex opaque data types
12377 @kindex set opaque-type-resolution
12378 @item set opaque-type-resolution on
12379 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12380 declared as a pointer to a @code{struct}, @code{class}, or
12381 @code{union}---for example, @code{struct MyType *}---that is used in one
12382 source file although the full declaration of @code{struct MyType} is in
12383 another source file. The default is on.
12385 A change in the setting of this subcommand will not take effect until
12386 the next time symbols for a file are loaded.
12388 @item set opaque-type-resolution off
12389 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12390 is printed as follows:
12392 @{<no data fields>@}
12395 @kindex show opaque-type-resolution
12396 @item show opaque-type-resolution
12397 Show whether opaque types are resolved or not.
12399 @kindex set print symbol-loading
12400 @cindex print messages when symbols are loaded
12401 @item set print symbol-loading
12402 @itemx set print symbol-loading on
12403 @itemx set print symbol-loading off
12404 The @code{set print symbol-loading} command allows you to enable or
12405 disable printing of messages when @value{GDBN} loads symbols.
12406 By default, these messages will be printed, and normally this is what
12407 you want. Disabling these messages is useful when debugging applications
12408 with lots of shared libraries where the quantity of output can be more
12409 annoying than useful.
12411 @kindex show print symbol-loading
12412 @item show print symbol-loading
12413 Show whether messages will be printed when @value{GDBN} loads symbols.
12415 @kindex maint print symbols
12416 @cindex symbol dump
12417 @kindex maint print psymbols
12418 @cindex partial symbol dump
12419 @item maint print symbols @var{filename}
12420 @itemx maint print psymbols @var{filename}
12421 @itemx maint print msymbols @var{filename}
12422 Write a dump of debugging symbol data into the file @var{filename}.
12423 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12424 symbols with debugging data are included. If you use @samp{maint print
12425 symbols}, @value{GDBN} includes all the symbols for which it has already
12426 collected full details: that is, @var{filename} reflects symbols for
12427 only those files whose symbols @value{GDBN} has read. You can use the
12428 command @code{info sources} to find out which files these are. If you
12429 use @samp{maint print psymbols} instead, the dump shows information about
12430 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12431 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12432 @samp{maint print msymbols} dumps just the minimal symbol information
12433 required for each object file from which @value{GDBN} has read some symbols.
12434 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12435 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12437 @kindex maint info symtabs
12438 @kindex maint info psymtabs
12439 @cindex listing @value{GDBN}'s internal symbol tables
12440 @cindex symbol tables, listing @value{GDBN}'s internal
12441 @cindex full symbol tables, listing @value{GDBN}'s internal
12442 @cindex partial symbol tables, listing @value{GDBN}'s internal
12443 @item maint info symtabs @r{[} @var{regexp} @r{]}
12444 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12446 List the @code{struct symtab} or @code{struct partial_symtab}
12447 structures whose names match @var{regexp}. If @var{regexp} is not
12448 given, list them all. The output includes expressions which you can
12449 copy into a @value{GDBN} debugging this one to examine a particular
12450 structure in more detail. For example:
12453 (@value{GDBP}) maint info psymtabs dwarf2read
12454 @{ objfile /home/gnu/build/gdb/gdb
12455 ((struct objfile *) 0x82e69d0)
12456 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12457 ((struct partial_symtab *) 0x8474b10)
12460 text addresses 0x814d3c8 -- 0x8158074
12461 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12462 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12463 dependencies (none)
12466 (@value{GDBP}) maint info symtabs
12470 We see that there is one partial symbol table whose filename contains
12471 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12472 and we see that @value{GDBN} has not read in any symtabs yet at all.
12473 If we set a breakpoint on a function, that will cause @value{GDBN} to
12474 read the symtab for the compilation unit containing that function:
12477 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12478 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12480 (@value{GDBP}) maint info symtabs
12481 @{ objfile /home/gnu/build/gdb/gdb
12482 ((struct objfile *) 0x82e69d0)
12483 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12484 ((struct symtab *) 0x86c1f38)
12487 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12488 linetable ((struct linetable *) 0x8370fa0)
12489 debugformat DWARF 2
12498 @chapter Altering Execution
12500 Once you think you have found an error in your program, you might want to
12501 find out for certain whether correcting the apparent error would lead to
12502 correct results in the rest of the run. You can find the answer by
12503 experiment, using the @value{GDBN} features for altering execution of the
12506 For example, you can store new values into variables or memory
12507 locations, give your program a signal, restart it at a different
12508 address, or even return prematurely from a function.
12511 * Assignment:: Assignment to variables
12512 * Jumping:: Continuing at a different address
12513 * Signaling:: Giving your program a signal
12514 * Returning:: Returning from a function
12515 * Calling:: Calling your program's functions
12516 * Patching:: Patching your program
12520 @section Assignment to Variables
12523 @cindex setting variables
12524 To alter the value of a variable, evaluate an assignment expression.
12525 @xref{Expressions, ,Expressions}. For example,
12532 stores the value 4 into the variable @code{x}, and then prints the
12533 value of the assignment expression (which is 4).
12534 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12535 information on operators in supported languages.
12537 @kindex set variable
12538 @cindex variables, setting
12539 If you are not interested in seeing the value of the assignment, use the
12540 @code{set} command instead of the @code{print} command. @code{set} is
12541 really the same as @code{print} except that the expression's value is
12542 not printed and is not put in the value history (@pxref{Value History,
12543 ,Value History}). The expression is evaluated only for its effects.
12545 If the beginning of the argument string of the @code{set} command
12546 appears identical to a @code{set} subcommand, use the @code{set
12547 variable} command instead of just @code{set}. This command is identical
12548 to @code{set} except for its lack of subcommands. For example, if your
12549 program has a variable @code{width}, you get an error if you try to set
12550 a new value with just @samp{set width=13}, because @value{GDBN} has the
12551 command @code{set width}:
12554 (@value{GDBP}) whatis width
12556 (@value{GDBP}) p width
12558 (@value{GDBP}) set width=47
12559 Invalid syntax in expression.
12563 The invalid expression, of course, is @samp{=47}. In
12564 order to actually set the program's variable @code{width}, use
12567 (@value{GDBP}) set var width=47
12570 Because the @code{set} command has many subcommands that can conflict
12571 with the names of program variables, it is a good idea to use the
12572 @code{set variable} command instead of just @code{set}. For example, if
12573 your program has a variable @code{g}, you run into problems if you try
12574 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12575 the command @code{set gnutarget}, abbreviated @code{set g}:
12579 (@value{GDBP}) whatis g
12583 (@value{GDBP}) set g=4
12587 The program being debugged has been started already.
12588 Start it from the beginning? (y or n) y
12589 Starting program: /home/smith/cc_progs/a.out
12590 "/home/smith/cc_progs/a.out": can't open to read symbols:
12591 Invalid bfd target.
12592 (@value{GDBP}) show g
12593 The current BFD target is "=4".
12598 The program variable @code{g} did not change, and you silently set the
12599 @code{gnutarget} to an invalid value. In order to set the variable
12603 (@value{GDBP}) set var g=4
12606 @value{GDBN} allows more implicit conversions in assignments than C; you can
12607 freely store an integer value into a pointer variable or vice versa,
12608 and you can convert any structure to any other structure that is the
12609 same length or shorter.
12610 @comment FIXME: how do structs align/pad in these conversions?
12611 @comment /doc@cygnus.com 18dec1990
12613 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12614 construct to generate a value of specified type at a specified address
12615 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12616 to memory location @code{0x83040} as an integer (which implies a certain size
12617 and representation in memory), and
12620 set @{int@}0x83040 = 4
12624 stores the value 4 into that memory location.
12627 @section Continuing at a Different Address
12629 Ordinarily, when you continue your program, you do so at the place where
12630 it stopped, with the @code{continue} command. You can instead continue at
12631 an address of your own choosing, with the following commands:
12635 @item jump @var{linespec}
12636 @itemx jump @var{location}
12637 Resume execution at line @var{linespec} or at address given by
12638 @var{location}. Execution stops again immediately if there is a
12639 breakpoint there. @xref{Specify Location}, for a description of the
12640 different forms of @var{linespec} and @var{location}. It is common
12641 practice to use the @code{tbreak} command in conjunction with
12642 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12644 The @code{jump} command does not change the current stack frame, or
12645 the stack pointer, or the contents of any memory location or any
12646 register other than the program counter. If line @var{linespec} is in
12647 a different function from the one currently executing, the results may
12648 be bizarre if the two functions expect different patterns of arguments or
12649 of local variables. For this reason, the @code{jump} command requests
12650 confirmation if the specified line is not in the function currently
12651 executing. However, even bizarre results are predictable if you are
12652 well acquainted with the machine-language code of your program.
12655 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12656 On many systems, you can get much the same effect as the @code{jump}
12657 command by storing a new value into the register @code{$pc}. The
12658 difference is that this does not start your program running; it only
12659 changes the address of where it @emph{will} run when you continue. For
12667 makes the next @code{continue} command or stepping command execute at
12668 address @code{0x485}, rather than at the address where your program stopped.
12669 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12671 The most common occasion to use the @code{jump} command is to back
12672 up---perhaps with more breakpoints set---over a portion of a program
12673 that has already executed, in order to examine its execution in more
12678 @section Giving your Program a Signal
12679 @cindex deliver a signal to a program
12683 @item signal @var{signal}
12684 Resume execution where your program stopped, but immediately give it the
12685 signal @var{signal}. @var{signal} can be the name or the number of a
12686 signal. For example, on many systems @code{signal 2} and @code{signal
12687 SIGINT} are both ways of sending an interrupt signal.
12689 Alternatively, if @var{signal} is zero, continue execution without
12690 giving a signal. This is useful when your program stopped on account of
12691 a signal and would ordinary see the signal when resumed with the
12692 @code{continue} command; @samp{signal 0} causes it to resume without a
12695 @code{signal} does not repeat when you press @key{RET} a second time
12696 after executing the command.
12700 Invoking the @code{signal} command is not the same as invoking the
12701 @code{kill} utility from the shell. Sending a signal with @code{kill}
12702 causes @value{GDBN} to decide what to do with the signal depending on
12703 the signal handling tables (@pxref{Signals}). The @code{signal} command
12704 passes the signal directly to your program.
12708 @section Returning from a Function
12711 @cindex returning from a function
12714 @itemx return @var{expression}
12715 You can cancel execution of a function call with the @code{return}
12716 command. If you give an
12717 @var{expression} argument, its value is used as the function's return
12721 When you use @code{return}, @value{GDBN} discards the selected stack frame
12722 (and all frames within it). You can think of this as making the
12723 discarded frame return prematurely. If you wish to specify a value to
12724 be returned, give that value as the argument to @code{return}.
12726 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12727 Frame}), and any other frames inside of it, leaving its caller as the
12728 innermost remaining frame. That frame becomes selected. The
12729 specified value is stored in the registers used for returning values
12732 The @code{return} command does not resume execution; it leaves the
12733 program stopped in the state that would exist if the function had just
12734 returned. In contrast, the @code{finish} command (@pxref{Continuing
12735 and Stepping, ,Continuing and Stepping}) resumes execution until the
12736 selected stack frame returns naturally.
12738 @value{GDBN} needs to know how the @var{expression} argument should be set for
12739 the inferior. The concrete registers assignment depends on the OS ABI and the
12740 type being returned by the selected stack frame. For example it is common for
12741 OS ABI to return floating point values in FPU registers while integer values in
12742 CPU registers. Still some ABIs return even floating point values in CPU
12743 registers. Larger integer widths (such as @code{long long int}) also have
12744 specific placement rules. @value{GDBN} already knows the OS ABI from its
12745 current target so it needs to find out also the type being returned to make the
12746 assignment into the right register(s).
12748 Normally, the selected stack frame has debug info. @value{GDBN} will always
12749 use the debug info instead of the implicit type of @var{expression} when the
12750 debug info is available. For example, if you type @kbd{return -1}, and the
12751 function in the current stack frame is declared to return a @code{long long
12752 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
12753 into a @code{long long int}:
12756 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
12758 (@value{GDBP}) return -1
12759 Make func return now? (y or n) y
12760 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
12761 43 printf ("result=%lld\n", func ());
12765 However, if the selected stack frame does not have a debug info, e.g., if the
12766 function was compiled without debug info, @value{GDBN} has to find out the type
12767 to return from user. Specifying a different type by mistake may set the value
12768 in different inferior registers than the caller code expects. For example,
12769 typing @kbd{return -1} with its implicit type @code{int} would set only a part
12770 of a @code{long long int} result for a debug info less function (on 32-bit
12771 architectures). Therefore the user is required to specify the return type by
12772 an appropriate cast explicitly:
12775 Breakpoint 2, 0x0040050b in func ()
12776 (@value{GDBP}) return -1
12777 Return value type not available for selected stack frame.
12778 Please use an explicit cast of the value to return.
12779 (@value{GDBP}) return (long long int) -1
12780 Make selected stack frame return now? (y or n) y
12781 #0 0x00400526 in main ()
12786 @section Calling Program Functions
12789 @cindex calling functions
12790 @cindex inferior functions, calling
12791 @item print @var{expr}
12792 Evaluate the expression @var{expr} and display the resulting value.
12793 @var{expr} may include calls to functions in the program being
12797 @item call @var{expr}
12798 Evaluate the expression @var{expr} without displaying @code{void}
12801 You can use this variant of the @code{print} command if you want to
12802 execute a function from your program that does not return anything
12803 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12804 with @code{void} returned values that @value{GDBN} will otherwise
12805 print. If the result is not void, it is printed and saved in the
12809 It is possible for the function you call via the @code{print} or
12810 @code{call} command to generate a signal (e.g., if there's a bug in
12811 the function, or if you passed it incorrect arguments). What happens
12812 in that case is controlled by the @code{set unwindonsignal} command.
12815 @item set unwindonsignal
12816 @kindex set unwindonsignal
12817 @cindex unwind stack in called functions
12818 @cindex call dummy stack unwinding
12819 Set unwinding of the stack if a signal is received while in a function
12820 that @value{GDBN} called in the program being debugged. If set to on,
12821 @value{GDBN} unwinds the stack it created for the call and restores
12822 the context to what it was before the call. If set to off (the
12823 default), @value{GDBN} stops in the frame where the signal was
12826 @item show unwindonsignal
12827 @kindex show unwindonsignal
12828 Show the current setting of stack unwinding in the functions called by
12832 @cindex weak alias functions
12833 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12834 for another function. In such case, @value{GDBN} might not pick up
12835 the type information, including the types of the function arguments,
12836 which causes @value{GDBN} to call the inferior function incorrectly.
12837 As a result, the called function will function erroneously and may
12838 even crash. A solution to that is to use the name of the aliased
12842 @section Patching Programs
12844 @cindex patching binaries
12845 @cindex writing into executables
12846 @cindex writing into corefiles
12848 By default, @value{GDBN} opens the file containing your program's
12849 executable code (or the corefile) read-only. This prevents accidental
12850 alterations to machine code; but it also prevents you from intentionally
12851 patching your program's binary.
12853 If you'd like to be able to patch the binary, you can specify that
12854 explicitly with the @code{set write} command. For example, you might
12855 want to turn on internal debugging flags, or even to make emergency
12861 @itemx set write off
12862 If you specify @samp{set write on}, @value{GDBN} opens executable and
12863 core files for both reading and writing; if you specify @kbd{set write
12864 off} (the default), @value{GDBN} opens them read-only.
12866 If you have already loaded a file, you must load it again (using the
12867 @code{exec-file} or @code{core-file} command) after changing @code{set
12868 write}, for your new setting to take effect.
12872 Display whether executable files and core files are opened for writing
12873 as well as reading.
12877 @chapter @value{GDBN} Files
12879 @value{GDBN} needs to know the file name of the program to be debugged,
12880 both in order to read its symbol table and in order to start your
12881 program. To debug a core dump of a previous run, you must also tell
12882 @value{GDBN} the name of the core dump file.
12885 * Files:: Commands to specify files
12886 * Separate Debug Files:: Debugging information in separate files
12887 * Symbol Errors:: Errors reading symbol files
12888 * Data Files:: GDB data files
12892 @section Commands to Specify Files
12894 @cindex symbol table
12895 @cindex core dump file
12897 You may want to specify executable and core dump file names. The usual
12898 way to do this is at start-up time, using the arguments to
12899 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12900 Out of @value{GDBN}}).
12902 Occasionally it is necessary to change to a different file during a
12903 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12904 specify a file you want to use. Or you are debugging a remote target
12905 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12906 Program}). In these situations the @value{GDBN} commands to specify
12907 new files are useful.
12910 @cindex executable file
12912 @item file @var{filename}
12913 Use @var{filename} as the program to be debugged. It is read for its
12914 symbols and for the contents of pure memory. It is also the program
12915 executed when you use the @code{run} command. If you do not specify a
12916 directory and the file is not found in the @value{GDBN} working directory,
12917 @value{GDBN} uses the environment variable @code{PATH} as a list of
12918 directories to search, just as the shell does when looking for a program
12919 to run. You can change the value of this variable, for both @value{GDBN}
12920 and your program, using the @code{path} command.
12922 @cindex unlinked object files
12923 @cindex patching object files
12924 You can load unlinked object @file{.o} files into @value{GDBN} using
12925 the @code{file} command. You will not be able to ``run'' an object
12926 file, but you can disassemble functions and inspect variables. Also,
12927 if the underlying BFD functionality supports it, you could use
12928 @kbd{gdb -write} to patch object files using this technique. Note
12929 that @value{GDBN} can neither interpret nor modify relocations in this
12930 case, so branches and some initialized variables will appear to go to
12931 the wrong place. But this feature is still handy from time to time.
12934 @code{file} with no argument makes @value{GDBN} discard any information it
12935 has on both executable file and the symbol table.
12938 @item exec-file @r{[} @var{filename} @r{]}
12939 Specify that the program to be run (but not the symbol table) is found
12940 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12941 if necessary to locate your program. Omitting @var{filename} means to
12942 discard information on the executable file.
12944 @kindex symbol-file
12945 @item symbol-file @r{[} @var{filename} @r{]}
12946 Read symbol table information from file @var{filename}. @code{PATH} is
12947 searched when necessary. Use the @code{file} command to get both symbol
12948 table and program to run from the same file.
12950 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12951 program's symbol table.
12953 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12954 some breakpoints and auto-display expressions. This is because they may
12955 contain pointers to the internal data recording symbols and data types,
12956 which are part of the old symbol table data being discarded inside
12959 @code{symbol-file} does not repeat if you press @key{RET} again after
12962 When @value{GDBN} is configured for a particular environment, it
12963 understands debugging information in whatever format is the standard
12964 generated for that environment; you may use either a @sc{gnu} compiler, or
12965 other compilers that adhere to the local conventions.
12966 Best results are usually obtained from @sc{gnu} compilers; for example,
12967 using @code{@value{NGCC}} you can generate debugging information for
12970 For most kinds of object files, with the exception of old SVR3 systems
12971 using COFF, the @code{symbol-file} command does not normally read the
12972 symbol table in full right away. Instead, it scans the symbol table
12973 quickly to find which source files and which symbols are present. The
12974 details are read later, one source file at a time, as they are needed.
12976 The purpose of this two-stage reading strategy is to make @value{GDBN}
12977 start up faster. For the most part, it is invisible except for
12978 occasional pauses while the symbol table details for a particular source
12979 file are being read. (The @code{set verbose} command can turn these
12980 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12981 Warnings and Messages}.)
12983 We have not implemented the two-stage strategy for COFF yet. When the
12984 symbol table is stored in COFF format, @code{symbol-file} reads the
12985 symbol table data in full right away. Note that ``stabs-in-COFF''
12986 still does the two-stage strategy, since the debug info is actually
12990 @cindex reading symbols immediately
12991 @cindex symbols, reading immediately
12992 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12993 @itemx file @var{filename} @r{[} -readnow @r{]}
12994 You can override the @value{GDBN} two-stage strategy for reading symbol
12995 tables by using the @samp{-readnow} option with any of the commands that
12996 load symbol table information, if you want to be sure @value{GDBN} has the
12997 entire symbol table available.
12999 @c FIXME: for now no mention of directories, since this seems to be in
13000 @c flux. 13mar1992 status is that in theory GDB would look either in
13001 @c current dir or in same dir as myprog; but issues like competing
13002 @c GDB's, or clutter in system dirs, mean that in practice right now
13003 @c only current dir is used. FFish says maybe a special GDB hierarchy
13004 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13008 @item core-file @r{[}@var{filename}@r{]}
13010 Specify the whereabouts of a core dump file to be used as the ``contents
13011 of memory''. Traditionally, core files contain only some parts of the
13012 address space of the process that generated them; @value{GDBN} can access the
13013 executable file itself for other parts.
13015 @code{core-file} with no argument specifies that no core file is
13018 Note that the core file is ignored when your program is actually running
13019 under @value{GDBN}. So, if you have been running your program and you
13020 wish to debug a core file instead, you must kill the subprocess in which
13021 the program is running. To do this, use the @code{kill} command
13022 (@pxref{Kill Process, ,Killing the Child Process}).
13024 @kindex add-symbol-file
13025 @cindex dynamic linking
13026 @item add-symbol-file @var{filename} @var{address}
13027 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13028 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
13029 The @code{add-symbol-file} command reads additional symbol table
13030 information from the file @var{filename}. You would use this command
13031 when @var{filename} has been dynamically loaded (by some other means)
13032 into the program that is running. @var{address} should be the memory
13033 address at which the file has been loaded; @value{GDBN} cannot figure
13034 this out for itself. You can additionally specify an arbitrary number
13035 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
13036 section name and base address for that section. You can specify any
13037 @var{address} as an expression.
13039 The symbol table of the file @var{filename} is added to the symbol table
13040 originally read with the @code{symbol-file} command. You can use the
13041 @code{add-symbol-file} command any number of times; the new symbol data
13042 thus read keeps adding to the old. To discard all old symbol data
13043 instead, use the @code{symbol-file} command without any arguments.
13045 @cindex relocatable object files, reading symbols from
13046 @cindex object files, relocatable, reading symbols from
13047 @cindex reading symbols from relocatable object files
13048 @cindex symbols, reading from relocatable object files
13049 @cindex @file{.o} files, reading symbols from
13050 Although @var{filename} is typically a shared library file, an
13051 executable file, or some other object file which has been fully
13052 relocated for loading into a process, you can also load symbolic
13053 information from relocatable @file{.o} files, as long as:
13057 the file's symbolic information refers only to linker symbols defined in
13058 that file, not to symbols defined by other object files,
13060 every section the file's symbolic information refers to has actually
13061 been loaded into the inferior, as it appears in the file, and
13063 you can determine the address at which every section was loaded, and
13064 provide these to the @code{add-symbol-file} command.
13068 Some embedded operating systems, like Sun Chorus and VxWorks, can load
13069 relocatable files into an already running program; such systems
13070 typically make the requirements above easy to meet. However, it's
13071 important to recognize that many native systems use complex link
13072 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
13073 assembly, for example) that make the requirements difficult to meet. In
13074 general, one cannot assume that using @code{add-symbol-file} to read a
13075 relocatable object file's symbolic information will have the same effect
13076 as linking the relocatable object file into the program in the normal
13079 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
13081 @kindex add-symbol-file-from-memory
13082 @cindex @code{syscall DSO}
13083 @cindex load symbols from memory
13084 @item add-symbol-file-from-memory @var{address}
13085 Load symbols from the given @var{address} in a dynamically loaded
13086 object file whose image is mapped directly into the inferior's memory.
13087 For example, the Linux kernel maps a @code{syscall DSO} into each
13088 process's address space; this DSO provides kernel-specific code for
13089 some system calls. The argument can be any expression whose
13090 evaluation yields the address of the file's shared object file header.
13091 For this command to work, you must have used @code{symbol-file} or
13092 @code{exec-file} commands in advance.
13094 @kindex add-shared-symbol-files
13096 @item add-shared-symbol-files @var{library-file}
13097 @itemx assf @var{library-file}
13098 The @code{add-shared-symbol-files} command can currently be used only
13099 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
13100 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
13101 @value{GDBN} automatically looks for shared libraries, however if
13102 @value{GDBN} does not find yours, you can invoke
13103 @code{add-shared-symbol-files}. It takes one argument: the shared
13104 library's file name. @code{assf} is a shorthand alias for
13105 @code{add-shared-symbol-files}.
13108 @item section @var{section} @var{addr}
13109 The @code{section} command changes the base address of the named
13110 @var{section} of the exec file to @var{addr}. This can be used if the
13111 exec file does not contain section addresses, (such as in the
13112 @code{a.out} format), or when the addresses specified in the file
13113 itself are wrong. Each section must be changed separately. The
13114 @code{info files} command, described below, lists all the sections and
13118 @kindex info target
13121 @code{info files} and @code{info target} are synonymous; both print the
13122 current target (@pxref{Targets, ,Specifying a Debugging Target}),
13123 including the names of the executable and core dump files currently in
13124 use by @value{GDBN}, and the files from which symbols were loaded. The
13125 command @code{help target} lists all possible targets rather than
13128 @kindex maint info sections
13129 @item maint info sections
13130 Another command that can give you extra information about program sections
13131 is @code{maint info sections}. In addition to the section information
13132 displayed by @code{info files}, this command displays the flags and file
13133 offset of each section in the executable and core dump files. In addition,
13134 @code{maint info sections} provides the following command options (which
13135 may be arbitrarily combined):
13139 Display sections for all loaded object files, including shared libraries.
13140 @item @var{sections}
13141 Display info only for named @var{sections}.
13142 @item @var{section-flags}
13143 Display info only for sections for which @var{section-flags} are true.
13144 The section flags that @value{GDBN} currently knows about are:
13147 Section will have space allocated in the process when loaded.
13148 Set for all sections except those containing debug information.
13150 Section will be loaded from the file into the child process memory.
13151 Set for pre-initialized code and data, clear for @code{.bss} sections.
13153 Section needs to be relocated before loading.
13155 Section cannot be modified by the child process.
13157 Section contains executable code only.
13159 Section contains data only (no executable code).
13161 Section will reside in ROM.
13163 Section contains data for constructor/destructor lists.
13165 Section is not empty.
13167 An instruction to the linker to not output the section.
13168 @item COFF_SHARED_LIBRARY
13169 A notification to the linker that the section contains
13170 COFF shared library information.
13172 Section contains common symbols.
13175 @kindex set trust-readonly-sections
13176 @cindex read-only sections
13177 @item set trust-readonly-sections on
13178 Tell @value{GDBN} that readonly sections in your object file
13179 really are read-only (i.e.@: that their contents will not change).
13180 In that case, @value{GDBN} can fetch values from these sections
13181 out of the object file, rather than from the target program.
13182 For some targets (notably embedded ones), this can be a significant
13183 enhancement to debugging performance.
13185 The default is off.
13187 @item set trust-readonly-sections off
13188 Tell @value{GDBN} not to trust readonly sections. This means that
13189 the contents of the section might change while the program is running,
13190 and must therefore be fetched from the target when needed.
13192 @item show trust-readonly-sections
13193 Show the current setting of trusting readonly sections.
13196 All file-specifying commands allow both absolute and relative file names
13197 as arguments. @value{GDBN} always converts the file name to an absolute file
13198 name and remembers it that way.
13200 @cindex shared libraries
13201 @anchor{Shared Libraries}
13202 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13203 and IBM RS/6000 AIX shared libraries.
13205 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13206 shared libraries. @xref{Expat}.
13208 @value{GDBN} automatically loads symbol definitions from shared libraries
13209 when you use the @code{run} command, or when you examine a core file.
13210 (Before you issue the @code{run} command, @value{GDBN} does not understand
13211 references to a function in a shared library, however---unless you are
13212 debugging a core file).
13214 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13215 automatically loads the symbols at the time of the @code{shl_load} call.
13217 @c FIXME: some @value{GDBN} release may permit some refs to undef
13218 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13219 @c FIXME...lib; check this from time to time when updating manual
13221 There are times, however, when you may wish to not automatically load
13222 symbol definitions from shared libraries, such as when they are
13223 particularly large or there are many of them.
13225 To control the automatic loading of shared library symbols, use the
13229 @kindex set auto-solib-add
13230 @item set auto-solib-add @var{mode}
13231 If @var{mode} is @code{on}, symbols from all shared object libraries
13232 will be loaded automatically when the inferior begins execution, you
13233 attach to an independently started inferior, or when the dynamic linker
13234 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13235 is @code{off}, symbols must be loaded manually, using the
13236 @code{sharedlibrary} command. The default value is @code{on}.
13238 @cindex memory used for symbol tables
13239 If your program uses lots of shared libraries with debug info that
13240 takes large amounts of memory, you can decrease the @value{GDBN}
13241 memory footprint by preventing it from automatically loading the
13242 symbols from shared libraries. To that end, type @kbd{set
13243 auto-solib-add off} before running the inferior, then load each
13244 library whose debug symbols you do need with @kbd{sharedlibrary
13245 @var{regexp}}, where @var{regexp} is a regular expression that matches
13246 the libraries whose symbols you want to be loaded.
13248 @kindex show auto-solib-add
13249 @item show auto-solib-add
13250 Display the current autoloading mode.
13253 @cindex load shared library
13254 To explicitly load shared library symbols, use the @code{sharedlibrary}
13258 @kindex info sharedlibrary
13261 @itemx info sharedlibrary
13262 Print the names of the shared libraries which are currently loaded.
13264 @kindex sharedlibrary
13266 @item sharedlibrary @var{regex}
13267 @itemx share @var{regex}
13268 Load shared object library symbols for files matching a
13269 Unix regular expression.
13270 As with files loaded automatically, it only loads shared libraries
13271 required by your program for a core file or after typing @code{run}. If
13272 @var{regex} is omitted all shared libraries required by your program are
13275 @item nosharedlibrary
13276 @kindex nosharedlibrary
13277 @cindex unload symbols from shared libraries
13278 Unload all shared object library symbols. This discards all symbols
13279 that have been loaded from all shared libraries. Symbols from shared
13280 libraries that were loaded by explicit user requests are not
13284 Sometimes you may wish that @value{GDBN} stops and gives you control
13285 when any of shared library events happen. Use the @code{set
13286 stop-on-solib-events} command for this:
13289 @item set stop-on-solib-events
13290 @kindex set stop-on-solib-events
13291 This command controls whether @value{GDBN} should give you control
13292 when the dynamic linker notifies it about some shared library event.
13293 The most common event of interest is loading or unloading of a new
13296 @item show stop-on-solib-events
13297 @kindex show stop-on-solib-events
13298 Show whether @value{GDBN} stops and gives you control when shared
13299 library events happen.
13302 Shared libraries are also supported in many cross or remote debugging
13303 configurations. @value{GDBN} needs to have access to the target's libraries;
13304 this can be accomplished either by providing copies of the libraries
13305 on the host system, or by asking @value{GDBN} to automatically retrieve the
13306 libraries from the target. If copies of the target libraries are
13307 provided, they need to be the same as the target libraries, although the
13308 copies on the target can be stripped as long as the copies on the host are
13311 @cindex where to look for shared libraries
13312 For remote debugging, you need to tell @value{GDBN} where the target
13313 libraries are, so that it can load the correct copies---otherwise, it
13314 may try to load the host's libraries. @value{GDBN} has two variables
13315 to specify the search directories for target libraries.
13318 @cindex prefix for shared library file names
13319 @cindex system root, alternate
13320 @kindex set solib-absolute-prefix
13321 @kindex set sysroot
13322 @item set sysroot @var{path}
13323 Use @var{path} as the system root for the program being debugged. Any
13324 absolute shared library paths will be prefixed with @var{path}; many
13325 runtime loaders store the absolute paths to the shared library in the
13326 target program's memory. If you use @code{set sysroot} to find shared
13327 libraries, they need to be laid out in the same way that they are on
13328 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13331 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13332 retrieve the target libraries from the remote system. This is only
13333 supported when using a remote target that supports the @code{remote get}
13334 command (@pxref{File Transfer,,Sending files to a remote system}).
13335 The part of @var{path} following the initial @file{remote:}
13336 (if present) is used as system root prefix on the remote file system.
13337 @footnote{If you want to specify a local system root using a directory
13338 that happens to be named @file{remote:}, you need to use some equivalent
13339 variant of the name like @file{./remote:}.}
13341 The @code{set solib-absolute-prefix} command is an alias for @code{set
13344 @cindex default system root
13345 @cindex @samp{--with-sysroot}
13346 You can set the default system root by using the configure-time
13347 @samp{--with-sysroot} option. If the system root is inside
13348 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13349 @samp{--exec-prefix}), then the default system root will be updated
13350 automatically if the installed @value{GDBN} is moved to a new
13353 @kindex show sysroot
13355 Display the current shared library prefix.
13357 @kindex set solib-search-path
13358 @item set solib-search-path @var{path}
13359 If this variable is set, @var{path} is a colon-separated list of
13360 directories to search for shared libraries. @samp{solib-search-path}
13361 is used after @samp{sysroot} fails to locate the library, or if the
13362 path to the library is relative instead of absolute. If you want to
13363 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13364 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13365 finding your host's libraries. @samp{sysroot} is preferred; setting
13366 it to a nonexistent directory may interfere with automatic loading
13367 of shared library symbols.
13369 @kindex show solib-search-path
13370 @item show solib-search-path
13371 Display the current shared library search path.
13375 @node Separate Debug Files
13376 @section Debugging Information in Separate Files
13377 @cindex separate debugging information files
13378 @cindex debugging information in separate files
13379 @cindex @file{.debug} subdirectories
13380 @cindex debugging information directory, global
13381 @cindex global debugging information directory
13382 @cindex build ID, and separate debugging files
13383 @cindex @file{.build-id} directory
13385 @value{GDBN} allows you to put a program's debugging information in a
13386 file separate from the executable itself, in a way that allows
13387 @value{GDBN} to find and load the debugging information automatically.
13388 Since debugging information can be very large---sometimes larger
13389 than the executable code itself---some systems distribute debugging
13390 information for their executables in separate files, which users can
13391 install only when they need to debug a problem.
13393 @value{GDBN} supports two ways of specifying the separate debug info
13398 The executable contains a @dfn{debug link} that specifies the name of
13399 the separate debug info file. The separate debug file's name is
13400 usually @file{@var{executable}.debug}, where @var{executable} is the
13401 name of the corresponding executable file without leading directories
13402 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13403 debug link specifies a CRC32 checksum for the debug file, which
13404 @value{GDBN} uses to validate that the executable and the debug file
13405 came from the same build.
13408 The executable contains a @dfn{build ID}, a unique bit string that is
13409 also present in the corresponding debug info file. (This is supported
13410 only on some operating systems, notably those which use the ELF format
13411 for binary files and the @sc{gnu} Binutils.) For more details about
13412 this feature, see the description of the @option{--build-id}
13413 command-line option in @ref{Options, , Command Line Options, ld.info,
13414 The GNU Linker}. The debug info file's name is not specified
13415 explicitly by the build ID, but can be computed from the build ID, see
13419 Depending on the way the debug info file is specified, @value{GDBN}
13420 uses two different methods of looking for the debug file:
13424 For the ``debug link'' method, @value{GDBN} looks up the named file in
13425 the directory of the executable file, then in a subdirectory of that
13426 directory named @file{.debug}, and finally under the global debug
13427 directory, in a subdirectory whose name is identical to the leading
13428 directories of the executable's absolute file name.
13431 For the ``build ID'' method, @value{GDBN} looks in the
13432 @file{.build-id} subdirectory of the global debug directory for a file
13433 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13434 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13435 are the rest of the bit string. (Real build ID strings are 32 or more
13436 hex characters, not 10.)
13439 So, for example, suppose you ask @value{GDBN} to debug
13440 @file{/usr/bin/ls}, which has a debug link that specifies the
13441 file @file{ls.debug}, and a build ID whose value in hex is
13442 @code{abcdef1234}. If the global debug directory is
13443 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13444 debug information files, in the indicated order:
13448 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13450 @file{/usr/bin/ls.debug}
13452 @file{/usr/bin/.debug/ls.debug}
13454 @file{/usr/lib/debug/usr/bin/ls.debug}.
13457 You can set the global debugging info directory's name, and view the
13458 name @value{GDBN} is currently using.
13462 @kindex set debug-file-directory
13463 @item set debug-file-directory @var{directory}
13464 Set the directory which @value{GDBN} searches for separate debugging
13465 information files to @var{directory}.
13467 @kindex show debug-file-directory
13468 @item show debug-file-directory
13469 Show the directory @value{GDBN} searches for separate debugging
13474 @cindex @code{.gnu_debuglink} sections
13475 @cindex debug link sections
13476 A debug link is a special section of the executable file named
13477 @code{.gnu_debuglink}. The section must contain:
13481 A filename, with any leading directory components removed, followed by
13484 zero to three bytes of padding, as needed to reach the next four-byte
13485 boundary within the section, and
13487 a four-byte CRC checksum, stored in the same endianness used for the
13488 executable file itself. The checksum is computed on the debugging
13489 information file's full contents by the function given below, passing
13490 zero as the @var{crc} argument.
13493 Any executable file format can carry a debug link, as long as it can
13494 contain a section named @code{.gnu_debuglink} with the contents
13497 @cindex @code{.note.gnu.build-id} sections
13498 @cindex build ID sections
13499 The build ID is a special section in the executable file (and in other
13500 ELF binary files that @value{GDBN} may consider). This section is
13501 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13502 It contains unique identification for the built files---the ID remains
13503 the same across multiple builds of the same build tree. The default
13504 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13505 content for the build ID string. The same section with an identical
13506 value is present in the original built binary with symbols, in its
13507 stripped variant, and in the separate debugging information file.
13509 The debugging information file itself should be an ordinary
13510 executable, containing a full set of linker symbols, sections, and
13511 debugging information. The sections of the debugging information file
13512 should have the same names, addresses, and sizes as the original file,
13513 but they need not contain any data---much like a @code{.bss} section
13514 in an ordinary executable.
13516 The @sc{gnu} binary utilities (Binutils) package includes the
13517 @samp{objcopy} utility that can produce
13518 the separated executable / debugging information file pairs using the
13519 following commands:
13522 @kbd{objcopy --only-keep-debug foo foo.debug}
13527 These commands remove the debugging
13528 information from the executable file @file{foo} and place it in the file
13529 @file{foo.debug}. You can use the first, second or both methods to link the
13534 The debug link method needs the following additional command to also leave
13535 behind a debug link in @file{foo}:
13538 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13541 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13542 a version of the @code{strip} command such that the command @kbd{strip foo -f
13543 foo.debug} has the same functionality as the two @code{objcopy} commands and
13544 the @code{ln -s} command above, together.
13547 Build ID gets embedded into the main executable using @code{ld --build-id} or
13548 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13549 compatibility fixes for debug files separation are present in @sc{gnu} binary
13550 utilities (Binutils) package since version 2.18.
13555 Since there are many different ways to compute CRC's for the debug
13556 link (different polynomials, reversals, byte ordering, etc.), the
13557 simplest way to describe the CRC used in @code{.gnu_debuglink}
13558 sections is to give the complete code for a function that computes it:
13560 @kindex gnu_debuglink_crc32
13563 gnu_debuglink_crc32 (unsigned long crc,
13564 unsigned char *buf, size_t len)
13566 static const unsigned long crc32_table[256] =
13568 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13569 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13570 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13571 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13572 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13573 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13574 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13575 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13576 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13577 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13578 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13579 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13580 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13581 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13582 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13583 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13584 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13585 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13586 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13587 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13588 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13589 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13590 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13591 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13592 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13593 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13594 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13595 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13596 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13597 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13598 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13599 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13600 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13601 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13602 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13603 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13604 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13605 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13606 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13607 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13608 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13609 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13610 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13611 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13612 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13613 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13614 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13615 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13616 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13617 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13618 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13621 unsigned char *end;
13623 crc = ~crc & 0xffffffff;
13624 for (end = buf + len; buf < end; ++buf)
13625 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13626 return ~crc & 0xffffffff;
13631 This computation does not apply to the ``build ID'' method.
13634 @node Symbol Errors
13635 @section Errors Reading Symbol Files
13637 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13638 such as symbol types it does not recognize, or known bugs in compiler
13639 output. By default, @value{GDBN} does not notify you of such problems, since
13640 they are relatively common and primarily of interest to people
13641 debugging compilers. If you are interested in seeing information
13642 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13643 only one message about each such type of problem, no matter how many
13644 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13645 to see how many times the problems occur, with the @code{set
13646 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13649 The messages currently printed, and their meanings, include:
13652 @item inner block not inside outer block in @var{symbol}
13654 The symbol information shows where symbol scopes begin and end
13655 (such as at the start of a function or a block of statements). This
13656 error indicates that an inner scope block is not fully contained
13657 in its outer scope blocks.
13659 @value{GDBN} circumvents the problem by treating the inner block as if it had
13660 the same scope as the outer block. In the error message, @var{symbol}
13661 may be shown as ``@code{(don't know)}'' if the outer block is not a
13664 @item block at @var{address} out of order
13666 The symbol information for symbol scope blocks should occur in
13667 order of increasing addresses. This error indicates that it does not
13670 @value{GDBN} does not circumvent this problem, and has trouble
13671 locating symbols in the source file whose symbols it is reading. (You
13672 can often determine what source file is affected by specifying
13673 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13676 @item bad block start address patched
13678 The symbol information for a symbol scope block has a start address
13679 smaller than the address of the preceding source line. This is known
13680 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13682 @value{GDBN} circumvents the problem by treating the symbol scope block as
13683 starting on the previous source line.
13685 @item bad string table offset in symbol @var{n}
13688 Symbol number @var{n} contains a pointer into the string table which is
13689 larger than the size of the string table.
13691 @value{GDBN} circumvents the problem by considering the symbol to have the
13692 name @code{foo}, which may cause other problems if many symbols end up
13695 @item unknown symbol type @code{0x@var{nn}}
13697 The symbol information contains new data types that @value{GDBN} does
13698 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13699 uncomprehended information, in hexadecimal.
13701 @value{GDBN} circumvents the error by ignoring this symbol information.
13702 This usually allows you to debug your program, though certain symbols
13703 are not accessible. If you encounter such a problem and feel like
13704 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13705 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13706 and examine @code{*bufp} to see the symbol.
13708 @item stub type has NULL name
13710 @value{GDBN} could not find the full definition for a struct or class.
13712 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13713 The symbol information for a C@t{++} member function is missing some
13714 information that recent versions of the compiler should have output for
13717 @item info mismatch between compiler and debugger
13719 @value{GDBN} could not parse a type specification output by the compiler.
13724 @section GDB Data Files
13726 @cindex prefix for data files
13727 @value{GDBN} will sometimes read an auxiliary data file. These files
13728 are kept in a directory known as the @dfn{data directory}.
13730 You can set the data directory's name, and view the name @value{GDBN}
13731 is currently using.
13734 @kindex set data-directory
13735 @item set data-directory @var{directory}
13736 Set the directory which @value{GDBN} searches for auxiliary data files
13737 to @var{directory}.
13739 @kindex show data-directory
13740 @item show data-directory
13741 Show the directory @value{GDBN} searches for auxiliary data files.
13744 @cindex default data directory
13745 @cindex @samp{--with-gdb-datadir}
13746 You can set the default data directory by using the configure-time
13747 @samp{--with-gdb-datadir} option. If the data directory is inside
13748 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13749 @samp{--exec-prefix}), then the default data directory will be updated
13750 automatically if the installed @value{GDBN} is moved to a new
13754 @chapter Specifying a Debugging Target
13756 @cindex debugging target
13757 A @dfn{target} is the execution environment occupied by your program.
13759 Often, @value{GDBN} runs in the same host environment as your program;
13760 in that case, the debugging target is specified as a side effect when
13761 you use the @code{file} or @code{core} commands. When you need more
13762 flexibility---for example, running @value{GDBN} on a physically separate
13763 host, or controlling a standalone system over a serial port or a
13764 realtime system over a TCP/IP connection---you can use the @code{target}
13765 command to specify one of the target types configured for @value{GDBN}
13766 (@pxref{Target Commands, ,Commands for Managing Targets}).
13768 @cindex target architecture
13769 It is possible to build @value{GDBN} for several different @dfn{target
13770 architectures}. When @value{GDBN} is built like that, you can choose
13771 one of the available architectures with the @kbd{set architecture}
13775 @kindex set architecture
13776 @kindex show architecture
13777 @item set architecture @var{arch}
13778 This command sets the current target architecture to @var{arch}. The
13779 value of @var{arch} can be @code{"auto"}, in addition to one of the
13780 supported architectures.
13782 @item show architecture
13783 Show the current target architecture.
13785 @item set processor
13787 @kindex set processor
13788 @kindex show processor
13789 These are alias commands for, respectively, @code{set architecture}
13790 and @code{show architecture}.
13794 * Active Targets:: Active targets
13795 * Target Commands:: Commands for managing targets
13796 * Byte Order:: Choosing target byte order
13799 @node Active Targets
13800 @section Active Targets
13802 @cindex stacking targets
13803 @cindex active targets
13804 @cindex multiple targets
13806 There are three classes of targets: processes, core files, and
13807 executable files. @value{GDBN} can work concurrently on up to three
13808 active targets, one in each class. This allows you to (for example)
13809 start a process and inspect its activity without abandoning your work on
13812 For example, if you execute @samp{gdb a.out}, then the executable file
13813 @code{a.out} is the only active target. If you designate a core file as
13814 well---presumably from a prior run that crashed and coredumped---then
13815 @value{GDBN} has two active targets and uses them in tandem, looking
13816 first in the corefile target, then in the executable file, to satisfy
13817 requests for memory addresses. (Typically, these two classes of target
13818 are complementary, since core files contain only a program's
13819 read-write memory---variables and so on---plus machine status, while
13820 executable files contain only the program text and initialized data.)
13822 When you type @code{run}, your executable file becomes an active process
13823 target as well. When a process target is active, all @value{GDBN}
13824 commands requesting memory addresses refer to that target; addresses in
13825 an active core file or executable file target are obscured while the
13826 process target is active.
13828 Use the @code{core-file} and @code{exec-file} commands to select a new
13829 core file or executable target (@pxref{Files, ,Commands to Specify
13830 Files}). To specify as a target a process that is already running, use
13831 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13834 @node Target Commands
13835 @section Commands for Managing Targets
13838 @item target @var{type} @var{parameters}
13839 Connects the @value{GDBN} host environment to a target machine or
13840 process. A target is typically a protocol for talking to debugging
13841 facilities. You use the argument @var{type} to specify the type or
13842 protocol of the target machine.
13844 Further @var{parameters} are interpreted by the target protocol, but
13845 typically include things like device names or host names to connect
13846 with, process numbers, and baud rates.
13848 The @code{target} command does not repeat if you press @key{RET} again
13849 after executing the command.
13851 @kindex help target
13853 Displays the names of all targets available. To display targets
13854 currently selected, use either @code{info target} or @code{info files}
13855 (@pxref{Files, ,Commands to Specify Files}).
13857 @item help target @var{name}
13858 Describe a particular target, including any parameters necessary to
13861 @kindex set gnutarget
13862 @item set gnutarget @var{args}
13863 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13864 knows whether it is reading an @dfn{executable},
13865 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13866 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13867 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13870 @emph{Warning:} To specify a file format with @code{set gnutarget},
13871 you must know the actual BFD name.
13875 @xref{Files, , Commands to Specify Files}.
13877 @kindex show gnutarget
13878 @item show gnutarget
13879 Use the @code{show gnutarget} command to display what file format
13880 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13881 @value{GDBN} will determine the file format for each file automatically,
13882 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13885 @cindex common targets
13886 Here are some common targets (available, or not, depending on the GDB
13891 @item target exec @var{program}
13892 @cindex executable file target
13893 An executable file. @samp{target exec @var{program}} is the same as
13894 @samp{exec-file @var{program}}.
13896 @item target core @var{filename}
13897 @cindex core dump file target
13898 A core dump file. @samp{target core @var{filename}} is the same as
13899 @samp{core-file @var{filename}}.
13901 @item target remote @var{medium}
13902 @cindex remote target
13903 A remote system connected to @value{GDBN} via a serial line or network
13904 connection. This command tells @value{GDBN} to use its own remote
13905 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13907 For example, if you have a board connected to @file{/dev/ttya} on the
13908 machine running @value{GDBN}, you could say:
13911 target remote /dev/ttya
13914 @code{target remote} supports the @code{load} command. This is only
13915 useful if you have some other way of getting the stub to the target
13916 system, and you can put it somewhere in memory where it won't get
13917 clobbered by the download.
13920 @cindex built-in simulator target
13921 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13929 works; however, you cannot assume that a specific memory map, device
13930 drivers, or even basic I/O is available, although some simulators do
13931 provide these. For info about any processor-specific simulator details,
13932 see the appropriate section in @ref{Embedded Processors, ,Embedded
13937 Some configurations may include these targets as well:
13941 @item target nrom @var{dev}
13942 @cindex NetROM ROM emulator target
13943 NetROM ROM emulator. This target only supports downloading.
13947 Different targets are available on different configurations of @value{GDBN};
13948 your configuration may have more or fewer targets.
13950 Many remote targets require you to download the executable's code once
13951 you've successfully established a connection. You may wish to control
13952 various aspects of this process.
13957 @kindex set hash@r{, for remote monitors}
13958 @cindex hash mark while downloading
13959 This command controls whether a hash mark @samp{#} is displayed while
13960 downloading a file to the remote monitor. If on, a hash mark is
13961 displayed after each S-record is successfully downloaded to the
13965 @kindex show hash@r{, for remote monitors}
13966 Show the current status of displaying the hash mark.
13968 @item set debug monitor
13969 @kindex set debug monitor
13970 @cindex display remote monitor communications
13971 Enable or disable display of communications messages between
13972 @value{GDBN} and the remote monitor.
13974 @item show debug monitor
13975 @kindex show debug monitor
13976 Show the current status of displaying communications between
13977 @value{GDBN} and the remote monitor.
13982 @kindex load @var{filename}
13983 @item load @var{filename}
13985 Depending on what remote debugging facilities are configured into
13986 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13987 is meant to make @var{filename} (an executable) available for debugging
13988 on the remote system---by downloading, or dynamic linking, for example.
13989 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13990 the @code{add-symbol-file} command.
13992 If your @value{GDBN} does not have a @code{load} command, attempting to
13993 execute it gets the error message ``@code{You can't do that when your
13994 target is @dots{}}''
13996 The file is loaded at whatever address is specified in the executable.
13997 For some object file formats, you can specify the load address when you
13998 link the program; for other formats, like a.out, the object file format
13999 specifies a fixed address.
14000 @c FIXME! This would be a good place for an xref to the GNU linker doc.
14002 Depending on the remote side capabilities, @value{GDBN} may be able to
14003 load programs into flash memory.
14005 @code{load} does not repeat if you press @key{RET} again after using it.
14009 @section Choosing Target Byte Order
14011 @cindex choosing target byte order
14012 @cindex target byte order
14014 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
14015 offer the ability to run either big-endian or little-endian byte
14016 orders. Usually the executable or symbol will include a bit to
14017 designate the endian-ness, and you will not need to worry about
14018 which to use. However, you may still find it useful to adjust
14019 @value{GDBN}'s idea of processor endian-ness manually.
14023 @item set endian big
14024 Instruct @value{GDBN} to assume the target is big-endian.
14026 @item set endian little
14027 Instruct @value{GDBN} to assume the target is little-endian.
14029 @item set endian auto
14030 Instruct @value{GDBN} to use the byte order associated with the
14034 Display @value{GDBN}'s current idea of the target byte order.
14038 Note that these commands merely adjust interpretation of symbolic
14039 data on the host, and that they have absolutely no effect on the
14043 @node Remote Debugging
14044 @chapter Debugging Remote Programs
14045 @cindex remote debugging
14047 If you are trying to debug a program running on a machine that cannot run
14048 @value{GDBN} in the usual way, it is often useful to use remote debugging.
14049 For example, you might use remote debugging on an operating system kernel,
14050 or on a small system which does not have a general purpose operating system
14051 powerful enough to run a full-featured debugger.
14053 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
14054 to make this work with particular debugging targets. In addition,
14055 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
14056 but not specific to any particular target system) which you can use if you
14057 write the remote stubs---the code that runs on the remote system to
14058 communicate with @value{GDBN}.
14060 Other remote targets may be available in your
14061 configuration of @value{GDBN}; use @code{help target} to list them.
14064 * Connecting:: Connecting to a remote target
14065 * File Transfer:: Sending files to a remote system
14066 * Server:: Using the gdbserver program
14067 * Remote Configuration:: Remote configuration
14068 * Remote Stub:: Implementing a remote stub
14072 @section Connecting to a Remote Target
14074 On the @value{GDBN} host machine, you will need an unstripped copy of
14075 your program, since @value{GDBN} needs symbol and debugging information.
14076 Start up @value{GDBN} as usual, using the name of the local copy of your
14077 program as the first argument.
14079 @cindex @code{target remote}
14080 @value{GDBN} can communicate with the target over a serial line, or
14081 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
14082 each case, @value{GDBN} uses the same protocol for debugging your
14083 program; only the medium carrying the debugging packets varies. The
14084 @code{target remote} command establishes a connection to the target.
14085 Its arguments indicate which medium to use:
14089 @item target remote @var{serial-device}
14090 @cindex serial line, @code{target remote}
14091 Use @var{serial-device} to communicate with the target. For example,
14092 to use a serial line connected to the device named @file{/dev/ttyb}:
14095 target remote /dev/ttyb
14098 If you're using a serial line, you may want to give @value{GDBN} the
14099 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
14100 (@pxref{Remote Configuration, set remotebaud}) before the
14101 @code{target} command.
14103 @item target remote @code{@var{host}:@var{port}}
14104 @itemx target remote @code{tcp:@var{host}:@var{port}}
14105 @cindex @acronym{TCP} port, @code{target remote}
14106 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
14107 The @var{host} may be either a host name or a numeric @acronym{IP}
14108 address; @var{port} must be a decimal number. The @var{host} could be
14109 the target machine itself, if it is directly connected to the net, or
14110 it might be a terminal server which in turn has a serial line to the
14113 For example, to connect to port 2828 on a terminal server named
14117 target remote manyfarms:2828
14120 If your remote target is actually running on the same machine as your
14121 debugger session (e.g.@: a simulator for your target running on the
14122 same host), you can omit the hostname. For example, to connect to
14123 port 1234 on your local machine:
14126 target remote :1234
14130 Note that the colon is still required here.
14132 @item target remote @code{udp:@var{host}:@var{port}}
14133 @cindex @acronym{UDP} port, @code{target remote}
14134 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
14135 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
14138 target remote udp:manyfarms:2828
14141 When using a @acronym{UDP} connection for remote debugging, you should
14142 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
14143 can silently drop packets on busy or unreliable networks, which will
14144 cause havoc with your debugging session.
14146 @item target remote | @var{command}
14147 @cindex pipe, @code{target remote} to
14148 Run @var{command} in the background and communicate with it using a
14149 pipe. The @var{command} is a shell command, to be parsed and expanded
14150 by the system's command shell, @code{/bin/sh}; it should expect remote
14151 protocol packets on its standard input, and send replies on its
14152 standard output. You could use this to run a stand-alone simulator
14153 that speaks the remote debugging protocol, to make net connections
14154 using programs like @code{ssh}, or for other similar tricks.
14156 If @var{command} closes its standard output (perhaps by exiting),
14157 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
14158 program has already exited, this will have no effect.)
14162 Once the connection has been established, you can use all the usual
14163 commands to examine and change data. The remote program is already
14164 running; you can use @kbd{step} and @kbd{continue}, and you do not
14165 need to use @kbd{run}.
14167 @cindex interrupting remote programs
14168 @cindex remote programs, interrupting
14169 Whenever @value{GDBN} is waiting for the remote program, if you type the
14170 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
14171 program. This may or may not succeed, depending in part on the hardware
14172 and the serial drivers the remote system uses. If you type the
14173 interrupt character once again, @value{GDBN} displays this prompt:
14176 Interrupted while waiting for the program.
14177 Give up (and stop debugging it)? (y or n)
14180 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
14181 (If you decide you want to try again later, you can use @samp{target
14182 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
14183 goes back to waiting.
14186 @kindex detach (remote)
14188 When you have finished debugging the remote program, you can use the
14189 @code{detach} command to release it from @value{GDBN} control.
14190 Detaching from the target normally resumes its execution, but the results
14191 will depend on your particular remote stub. After the @code{detach}
14192 command, @value{GDBN} is free to connect to another target.
14196 The @code{disconnect} command behaves like @code{detach}, except that
14197 the target is generally not resumed. It will wait for @value{GDBN}
14198 (this instance or another one) to connect and continue debugging. After
14199 the @code{disconnect} command, @value{GDBN} is again free to connect to
14202 @cindex send command to remote monitor
14203 @cindex extend @value{GDBN} for remote targets
14204 @cindex add new commands for external monitor
14206 @item monitor @var{cmd}
14207 This command allows you to send arbitrary commands directly to the
14208 remote monitor. Since @value{GDBN} doesn't care about the commands it
14209 sends like this, this command is the way to extend @value{GDBN}---you
14210 can add new commands that only the external monitor will understand
14214 @node File Transfer
14215 @section Sending files to a remote system
14216 @cindex remote target, file transfer
14217 @cindex file transfer
14218 @cindex sending files to remote systems
14220 Some remote targets offer the ability to transfer files over the same
14221 connection used to communicate with @value{GDBN}. This is convenient
14222 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14223 running @code{gdbserver} over a network interface. For other targets,
14224 e.g.@: embedded devices with only a single serial port, this may be
14225 the only way to upload or download files.
14227 Not all remote targets support these commands.
14231 @item remote put @var{hostfile} @var{targetfile}
14232 Copy file @var{hostfile} from the host system (the machine running
14233 @value{GDBN}) to @var{targetfile} on the target system.
14236 @item remote get @var{targetfile} @var{hostfile}
14237 Copy file @var{targetfile} from the target system to @var{hostfile}
14238 on the host system.
14240 @kindex remote delete
14241 @item remote delete @var{targetfile}
14242 Delete @var{targetfile} from the target system.
14247 @section Using the @code{gdbserver} Program
14250 @cindex remote connection without stubs
14251 @code{gdbserver} is a control program for Unix-like systems, which
14252 allows you to connect your program with a remote @value{GDBN} via
14253 @code{target remote}---but without linking in the usual debugging stub.
14255 @code{gdbserver} is not a complete replacement for the debugging stubs,
14256 because it requires essentially the same operating-system facilities
14257 that @value{GDBN} itself does. In fact, a system that can run
14258 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14259 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14260 because it is a much smaller program than @value{GDBN} itself. It is
14261 also easier to port than all of @value{GDBN}, so you may be able to get
14262 started more quickly on a new system by using @code{gdbserver}.
14263 Finally, if you develop code for real-time systems, you may find that
14264 the tradeoffs involved in real-time operation make it more convenient to
14265 do as much development work as possible on another system, for example
14266 by cross-compiling. You can use @code{gdbserver} to make a similar
14267 choice for debugging.
14269 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14270 or a TCP connection, using the standard @value{GDBN} remote serial
14274 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14275 Do not run @code{gdbserver} connected to any public network; a
14276 @value{GDBN} connection to @code{gdbserver} provides access to the
14277 target system with the same privileges as the user running
14281 @subsection Running @code{gdbserver}
14282 @cindex arguments, to @code{gdbserver}
14284 Run @code{gdbserver} on the target system. You need a copy of the
14285 program you want to debug, including any libraries it requires.
14286 @code{gdbserver} does not need your program's symbol table, so you can
14287 strip the program if necessary to save space. @value{GDBN} on the host
14288 system does all the symbol handling.
14290 To use the server, you must tell it how to communicate with @value{GDBN};
14291 the name of your program; and the arguments for your program. The usual
14295 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14298 @var{comm} is either a device name (to use a serial line) or a TCP
14299 hostname and portnumber. For example, to debug Emacs with the argument
14300 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14304 target> gdbserver /dev/com1 emacs foo.txt
14307 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14310 To use a TCP connection instead of a serial line:
14313 target> gdbserver host:2345 emacs foo.txt
14316 The only difference from the previous example is the first argument,
14317 specifying that you are communicating with the host @value{GDBN} via
14318 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14319 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14320 (Currently, the @samp{host} part is ignored.) You can choose any number
14321 you want for the port number as long as it does not conflict with any
14322 TCP ports already in use on the target system (for example, @code{23} is
14323 reserved for @code{telnet}).@footnote{If you choose a port number that
14324 conflicts with another service, @code{gdbserver} prints an error message
14325 and exits.} You must use the same port number with the host @value{GDBN}
14326 @code{target remote} command.
14328 @subsubsection Attaching to a Running Program
14330 On some targets, @code{gdbserver} can also attach to running programs.
14331 This is accomplished via the @code{--attach} argument. The syntax is:
14334 target> gdbserver --attach @var{comm} @var{pid}
14337 @var{pid} is the process ID of a currently running process. It isn't necessary
14338 to point @code{gdbserver} at a binary for the running process.
14341 @cindex attach to a program by name
14342 You can debug processes by name instead of process ID if your target has the
14343 @code{pidof} utility:
14346 target> gdbserver --attach @var{comm} `pidof @var{program}`
14349 In case more than one copy of @var{program} is running, or @var{program}
14350 has multiple threads, most versions of @code{pidof} support the
14351 @code{-s} option to only return the first process ID.
14353 @subsubsection Multi-Process Mode for @code{gdbserver}
14354 @cindex gdbserver, multiple processes
14355 @cindex multiple processes with gdbserver
14357 When you connect to @code{gdbserver} using @code{target remote},
14358 @code{gdbserver} debugs the specified program only once. When the
14359 program exits, or you detach from it, @value{GDBN} closes the connection
14360 and @code{gdbserver} exits.
14362 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14363 enters multi-process mode. When the debugged program exits, or you
14364 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14365 though no program is running. The @code{run} and @code{attach}
14366 commands instruct @code{gdbserver} to run or attach to a new program.
14367 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14368 remote exec-file}) to select the program to run. Command line
14369 arguments are supported, except for wildcard expansion and I/O
14370 redirection (@pxref{Arguments}).
14372 To start @code{gdbserver} without supplying an initial command to run
14373 or process ID to attach, use the @option{--multi} command line option.
14374 Then you can connect using @kbd{target extended-remote} and start
14375 the program you want to debug.
14377 @code{gdbserver} does not automatically exit in multi-process mode.
14378 You can terminate it by using @code{monitor exit}
14379 (@pxref{Monitor Commands for gdbserver}).
14381 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14383 The @option{--debug} option tells @code{gdbserver} to display extra
14384 status information about the debugging process. The
14385 @option{--remote-debug} option tells @code{gdbserver} to display
14386 remote protocol debug output. These options are intended for
14387 @code{gdbserver} development and for bug reports to the developers.
14389 The @option{--wrapper} option specifies a wrapper to launch programs
14390 for debugging. The option should be followed by the name of the
14391 wrapper, then any command-line arguments to pass to the wrapper, then
14392 @kbd{--} indicating the end of the wrapper arguments.
14394 @code{gdbserver} runs the specified wrapper program with a combined
14395 command line including the wrapper arguments, then the name of the
14396 program to debug, then any arguments to the program. The wrapper
14397 runs until it executes your program, and then @value{GDBN} gains control.
14399 You can use any program that eventually calls @code{execve} with
14400 its arguments as a wrapper. Several standard Unix utilities do
14401 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14402 with @code{exec "$@@"} will also work.
14404 For example, you can use @code{env} to pass an environment variable to
14405 the debugged program, without setting the variable in @code{gdbserver}'s
14409 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14412 @subsection Connecting to @code{gdbserver}
14414 Run @value{GDBN} on the host system.
14416 First make sure you have the necessary symbol files. Load symbols for
14417 your application using the @code{file} command before you connect. Use
14418 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14419 was compiled with the correct sysroot using @code{--with-sysroot}).
14421 The symbol file and target libraries must exactly match the executable
14422 and libraries on the target, with one exception: the files on the host
14423 system should not be stripped, even if the files on the target system
14424 are. Mismatched or missing files will lead to confusing results
14425 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14426 files may also prevent @code{gdbserver} from debugging multi-threaded
14429 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14430 For TCP connections, you must start up @code{gdbserver} prior to using
14431 the @code{target remote} command. Otherwise you may get an error whose
14432 text depends on the host system, but which usually looks something like
14433 @samp{Connection refused}. Don't use the @code{load}
14434 command in @value{GDBN} when using @code{gdbserver}, since the program is
14435 already on the target.
14437 @subsection Monitor Commands for @code{gdbserver}
14438 @cindex monitor commands, for @code{gdbserver}
14439 @anchor{Monitor Commands for gdbserver}
14441 During a @value{GDBN} session using @code{gdbserver}, you can use the
14442 @code{monitor} command to send special requests to @code{gdbserver}.
14443 Here are the available commands.
14447 List the available monitor commands.
14449 @item monitor set debug 0
14450 @itemx monitor set debug 1
14451 Disable or enable general debugging messages.
14453 @item monitor set remote-debug 0
14454 @itemx monitor set remote-debug 1
14455 Disable or enable specific debugging messages associated with the remote
14456 protocol (@pxref{Remote Protocol}).
14459 Tell gdbserver to exit immediately. This command should be followed by
14460 @code{disconnect} to close the debugging session. @code{gdbserver} will
14461 detach from any attached processes and kill any processes it created.
14462 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14463 of a multi-process mode debug session.
14467 @node Remote Configuration
14468 @section Remote Configuration
14471 @kindex show remote
14472 This section documents the configuration options available when
14473 debugging remote programs. For the options related to the File I/O
14474 extensions of the remote protocol, see @ref{system,
14475 system-call-allowed}.
14478 @item set remoteaddresssize @var{bits}
14479 @cindex address size for remote targets
14480 @cindex bits in remote address
14481 Set the maximum size of address in a memory packet to the specified
14482 number of bits. @value{GDBN} will mask off the address bits above
14483 that number, when it passes addresses to the remote target. The
14484 default value is the number of bits in the target's address.
14486 @item show remoteaddresssize
14487 Show the current value of remote address size in bits.
14489 @item set remotebaud @var{n}
14490 @cindex baud rate for remote targets
14491 Set the baud rate for the remote serial I/O to @var{n} baud. The
14492 value is used to set the speed of the serial port used for debugging
14495 @item show remotebaud
14496 Show the current speed of the remote connection.
14498 @item set remotebreak
14499 @cindex interrupt remote programs
14500 @cindex BREAK signal instead of Ctrl-C
14501 @anchor{set remotebreak}
14502 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14503 when you type @kbd{Ctrl-c} to interrupt the program running
14504 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14505 character instead. The default is off, since most remote systems
14506 expect to see @samp{Ctrl-C} as the interrupt signal.
14508 @item show remotebreak
14509 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14510 interrupt the remote program.
14512 @item set remoteflow on
14513 @itemx set remoteflow off
14514 @kindex set remoteflow
14515 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14516 on the serial port used to communicate to the remote target.
14518 @item show remoteflow
14519 @kindex show remoteflow
14520 Show the current setting of hardware flow control.
14522 @item set remotelogbase @var{base}
14523 Set the base (a.k.a.@: radix) of logging serial protocol
14524 communications to @var{base}. Supported values of @var{base} are:
14525 @code{ascii}, @code{octal}, and @code{hex}. The default is
14528 @item show remotelogbase
14529 Show the current setting of the radix for logging remote serial
14532 @item set remotelogfile @var{file}
14533 @cindex record serial communications on file
14534 Record remote serial communications on the named @var{file}. The
14535 default is not to record at all.
14537 @item show remotelogfile.
14538 Show the current setting of the file name on which to record the
14539 serial communications.
14541 @item set remotetimeout @var{num}
14542 @cindex timeout for serial communications
14543 @cindex remote timeout
14544 Set the timeout limit to wait for the remote target to respond to
14545 @var{num} seconds. The default is 2 seconds.
14547 @item show remotetimeout
14548 Show the current number of seconds to wait for the remote target
14551 @cindex limit hardware breakpoints and watchpoints
14552 @cindex remote target, limit break- and watchpoints
14553 @anchor{set remote hardware-watchpoint-limit}
14554 @anchor{set remote hardware-breakpoint-limit}
14555 @item set remote hardware-watchpoint-limit @var{limit}
14556 @itemx set remote hardware-breakpoint-limit @var{limit}
14557 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14558 watchpoints. A limit of -1, the default, is treated as unlimited.
14560 @item set remote exec-file @var{filename}
14561 @itemx show remote exec-file
14562 @anchor{set remote exec-file}
14563 @cindex executable file, for remote target
14564 Select the file used for @code{run} with @code{target
14565 extended-remote}. This should be set to a filename valid on the
14566 target system. If it is not set, the target will use a default
14567 filename (e.g.@: the last program run).
14571 @item set tcp auto-retry on
14572 @cindex auto-retry, for remote TCP target
14573 Enable auto-retry for remote TCP connections. This is useful if the remote
14574 debugging agent is launched in parallel with @value{GDBN}; there is a race
14575 condition because the agent may not become ready to accept the connection
14576 before @value{GDBN} attempts to connect. When auto-retry is
14577 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14578 to establish the connection using the timeout specified by
14579 @code{set tcp connect-timeout}.
14581 @item set tcp auto-retry off
14582 Do not auto-retry failed TCP connections.
14584 @item show tcp auto-retry
14585 Show the current auto-retry setting.
14587 @item set tcp connect-timeout @var{seconds}
14588 @cindex connection timeout, for remote TCP target
14589 @cindex timeout, for remote target connection
14590 Set the timeout for establishing a TCP connection to the remote target to
14591 @var{seconds}. The timeout affects both polling to retry failed connections
14592 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14593 that are merely slow to complete, and represents an approximate cumulative
14596 @item show tcp connect-timeout
14597 Show the current connection timeout setting.
14600 @cindex remote packets, enabling and disabling
14601 The @value{GDBN} remote protocol autodetects the packets supported by
14602 your debugging stub. If you need to override the autodetection, you
14603 can use these commands to enable or disable individual packets. Each
14604 packet can be set to @samp{on} (the remote target supports this
14605 packet), @samp{off} (the remote target does not support this packet),
14606 or @samp{auto} (detect remote target support for this packet). They
14607 all default to @samp{auto}. For more information about each packet,
14608 see @ref{Remote Protocol}.
14610 During normal use, you should not have to use any of these commands.
14611 If you do, that may be a bug in your remote debugging stub, or a bug
14612 in @value{GDBN}. You may want to report the problem to the
14613 @value{GDBN} developers.
14615 For each packet @var{name}, the command to enable or disable the
14616 packet is @code{set remote @var{name}-packet}. The available settings
14619 @multitable @columnfractions 0.28 0.32 0.25
14622 @tab Related Features
14624 @item @code{fetch-register}
14626 @tab @code{info registers}
14628 @item @code{set-register}
14632 @item @code{binary-download}
14634 @tab @code{load}, @code{set}
14636 @item @code{read-aux-vector}
14637 @tab @code{qXfer:auxv:read}
14638 @tab @code{info auxv}
14640 @item @code{symbol-lookup}
14641 @tab @code{qSymbol}
14642 @tab Detecting multiple threads
14644 @item @code{attach}
14645 @tab @code{vAttach}
14648 @item @code{verbose-resume}
14650 @tab Stepping or resuming multiple threads
14656 @item @code{software-breakpoint}
14660 @item @code{hardware-breakpoint}
14664 @item @code{write-watchpoint}
14668 @item @code{read-watchpoint}
14672 @item @code{access-watchpoint}
14676 @item @code{target-features}
14677 @tab @code{qXfer:features:read}
14678 @tab @code{set architecture}
14680 @item @code{library-info}
14681 @tab @code{qXfer:libraries:read}
14682 @tab @code{info sharedlibrary}
14684 @item @code{memory-map}
14685 @tab @code{qXfer:memory-map:read}
14686 @tab @code{info mem}
14688 @item @code{read-spu-object}
14689 @tab @code{qXfer:spu:read}
14690 @tab @code{info spu}
14692 @item @code{write-spu-object}
14693 @tab @code{qXfer:spu:write}
14694 @tab @code{info spu}
14696 @item @code{read-siginfo-object}
14697 @tab @code{qXfer:siginfo:read}
14698 @tab @code{print $_siginfo}
14700 @item @code{write-siginfo-object}
14701 @tab @code{qXfer:siginfo:write}
14702 @tab @code{set $_siginfo}
14704 @item @code{get-thread-local-@*storage-address}
14705 @tab @code{qGetTLSAddr}
14706 @tab Displaying @code{__thread} variables
14708 @item @code{search-memory}
14709 @tab @code{qSearch:memory}
14712 @item @code{supported-packets}
14713 @tab @code{qSupported}
14714 @tab Remote communications parameters
14716 @item @code{pass-signals}
14717 @tab @code{QPassSignals}
14718 @tab @code{handle @var{signal}}
14720 @item @code{hostio-close-packet}
14721 @tab @code{vFile:close}
14722 @tab @code{remote get}, @code{remote put}
14724 @item @code{hostio-open-packet}
14725 @tab @code{vFile:open}
14726 @tab @code{remote get}, @code{remote put}
14728 @item @code{hostio-pread-packet}
14729 @tab @code{vFile:pread}
14730 @tab @code{remote get}, @code{remote put}
14732 @item @code{hostio-pwrite-packet}
14733 @tab @code{vFile:pwrite}
14734 @tab @code{remote get}, @code{remote put}
14736 @item @code{hostio-unlink-packet}
14737 @tab @code{vFile:unlink}
14738 @tab @code{remote delete}
14740 @item @code{noack-packet}
14741 @tab @code{QStartNoAckMode}
14742 @tab Packet acknowledgment
14744 @item @code{osdata}
14745 @tab @code{qXfer:osdata:read}
14746 @tab @code{info os}
14748 @item @code{query-attached}
14749 @tab @code{qAttached}
14750 @tab Querying remote process attach state.
14754 @section Implementing a Remote Stub
14756 @cindex debugging stub, example
14757 @cindex remote stub, example
14758 @cindex stub example, remote debugging
14759 The stub files provided with @value{GDBN} implement the target side of the
14760 communication protocol, and the @value{GDBN} side is implemented in the
14761 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14762 these subroutines to communicate, and ignore the details. (If you're
14763 implementing your own stub file, you can still ignore the details: start
14764 with one of the existing stub files. @file{sparc-stub.c} is the best
14765 organized, and therefore the easiest to read.)
14767 @cindex remote serial debugging, overview
14768 To debug a program running on another machine (the debugging
14769 @dfn{target} machine), you must first arrange for all the usual
14770 prerequisites for the program to run by itself. For example, for a C
14775 A startup routine to set up the C runtime environment; these usually
14776 have a name like @file{crt0}. The startup routine may be supplied by
14777 your hardware supplier, or you may have to write your own.
14780 A C subroutine library to support your program's
14781 subroutine calls, notably managing input and output.
14784 A way of getting your program to the other machine---for example, a
14785 download program. These are often supplied by the hardware
14786 manufacturer, but you may have to write your own from hardware
14790 The next step is to arrange for your program to use a serial port to
14791 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14792 machine). In general terms, the scheme looks like this:
14796 @value{GDBN} already understands how to use this protocol; when everything
14797 else is set up, you can simply use the @samp{target remote} command
14798 (@pxref{Targets,,Specifying a Debugging Target}).
14800 @item On the target,
14801 you must link with your program a few special-purpose subroutines that
14802 implement the @value{GDBN} remote serial protocol. The file containing these
14803 subroutines is called a @dfn{debugging stub}.
14805 On certain remote targets, you can use an auxiliary program
14806 @code{gdbserver} instead of linking a stub into your program.
14807 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14810 The debugging stub is specific to the architecture of the remote
14811 machine; for example, use @file{sparc-stub.c} to debug programs on
14814 @cindex remote serial stub list
14815 These working remote stubs are distributed with @value{GDBN}:
14820 @cindex @file{i386-stub.c}
14823 For Intel 386 and compatible architectures.
14826 @cindex @file{m68k-stub.c}
14827 @cindex Motorola 680x0
14829 For Motorola 680x0 architectures.
14832 @cindex @file{sh-stub.c}
14835 For Renesas SH architectures.
14838 @cindex @file{sparc-stub.c}
14840 For @sc{sparc} architectures.
14842 @item sparcl-stub.c
14843 @cindex @file{sparcl-stub.c}
14846 For Fujitsu @sc{sparclite} architectures.
14850 The @file{README} file in the @value{GDBN} distribution may list other
14851 recently added stubs.
14854 * Stub Contents:: What the stub can do for you
14855 * Bootstrapping:: What you must do for the stub
14856 * Debug Session:: Putting it all together
14859 @node Stub Contents
14860 @subsection What the Stub Can Do for You
14862 @cindex remote serial stub
14863 The debugging stub for your architecture supplies these three
14867 @item set_debug_traps
14868 @findex set_debug_traps
14869 @cindex remote serial stub, initialization
14870 This routine arranges for @code{handle_exception} to run when your
14871 program stops. You must call this subroutine explicitly near the
14872 beginning of your program.
14874 @item handle_exception
14875 @findex handle_exception
14876 @cindex remote serial stub, main routine
14877 This is the central workhorse, but your program never calls it
14878 explicitly---the setup code arranges for @code{handle_exception} to
14879 run when a trap is triggered.
14881 @code{handle_exception} takes control when your program stops during
14882 execution (for example, on a breakpoint), and mediates communications
14883 with @value{GDBN} on the host machine. This is where the communications
14884 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14885 representative on the target machine. It begins by sending summary
14886 information on the state of your program, then continues to execute,
14887 retrieving and transmitting any information @value{GDBN} needs, until you
14888 execute a @value{GDBN} command that makes your program resume; at that point,
14889 @code{handle_exception} returns control to your own code on the target
14893 @cindex @code{breakpoint} subroutine, remote
14894 Use this auxiliary subroutine to make your program contain a
14895 breakpoint. Depending on the particular situation, this may be the only
14896 way for @value{GDBN} to get control. For instance, if your target
14897 machine has some sort of interrupt button, you won't need to call this;
14898 pressing the interrupt button transfers control to
14899 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14900 simply receiving characters on the serial port may also trigger a trap;
14901 again, in that situation, you don't need to call @code{breakpoint} from
14902 your own program---simply running @samp{target remote} from the host
14903 @value{GDBN} session gets control.
14905 Call @code{breakpoint} if none of these is true, or if you simply want
14906 to make certain your program stops at a predetermined point for the
14907 start of your debugging session.
14910 @node Bootstrapping
14911 @subsection What You Must Do for the Stub
14913 @cindex remote stub, support routines
14914 The debugging stubs that come with @value{GDBN} are set up for a particular
14915 chip architecture, but they have no information about the rest of your
14916 debugging target machine.
14918 First of all you need to tell the stub how to communicate with the
14922 @item int getDebugChar()
14923 @findex getDebugChar
14924 Write this subroutine to read a single character from the serial port.
14925 It may be identical to @code{getchar} for your target system; a
14926 different name is used to allow you to distinguish the two if you wish.
14928 @item void putDebugChar(int)
14929 @findex putDebugChar
14930 Write this subroutine to write a single character to the serial port.
14931 It may be identical to @code{putchar} for your target system; a
14932 different name is used to allow you to distinguish the two if you wish.
14935 @cindex control C, and remote debugging
14936 @cindex interrupting remote targets
14937 If you want @value{GDBN} to be able to stop your program while it is
14938 running, you need to use an interrupt-driven serial driver, and arrange
14939 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14940 character). That is the character which @value{GDBN} uses to tell the
14941 remote system to stop.
14943 Getting the debugging target to return the proper status to @value{GDBN}
14944 probably requires changes to the standard stub; one quick and dirty way
14945 is to just execute a breakpoint instruction (the ``dirty'' part is that
14946 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14948 Other routines you need to supply are:
14951 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14952 @findex exceptionHandler
14953 Write this function to install @var{exception_address} in the exception
14954 handling tables. You need to do this because the stub does not have any
14955 way of knowing what the exception handling tables on your target system
14956 are like (for example, the processor's table might be in @sc{rom},
14957 containing entries which point to a table in @sc{ram}).
14958 @var{exception_number} is the exception number which should be changed;
14959 its meaning is architecture-dependent (for example, different numbers
14960 might represent divide by zero, misaligned access, etc). When this
14961 exception occurs, control should be transferred directly to
14962 @var{exception_address}, and the processor state (stack, registers,
14963 and so on) should be just as it is when a processor exception occurs. So if
14964 you want to use a jump instruction to reach @var{exception_address}, it
14965 should be a simple jump, not a jump to subroutine.
14967 For the 386, @var{exception_address} should be installed as an interrupt
14968 gate so that interrupts are masked while the handler runs. The gate
14969 should be at privilege level 0 (the most privileged level). The
14970 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14971 help from @code{exceptionHandler}.
14973 @item void flush_i_cache()
14974 @findex flush_i_cache
14975 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14976 instruction cache, if any, on your target machine. If there is no
14977 instruction cache, this subroutine may be a no-op.
14979 On target machines that have instruction caches, @value{GDBN} requires this
14980 function to make certain that the state of your program is stable.
14984 You must also make sure this library routine is available:
14987 @item void *memset(void *, int, int)
14989 This is the standard library function @code{memset} that sets an area of
14990 memory to a known value. If you have one of the free versions of
14991 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14992 either obtain it from your hardware manufacturer, or write your own.
14995 If you do not use the GNU C compiler, you may need other standard
14996 library subroutines as well; this varies from one stub to another,
14997 but in general the stubs are likely to use any of the common library
14998 subroutines which @code{@value{NGCC}} generates as inline code.
15001 @node Debug Session
15002 @subsection Putting it All Together
15004 @cindex remote serial debugging summary
15005 In summary, when your program is ready to debug, you must follow these
15010 Make sure you have defined the supporting low-level routines
15011 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
15013 @code{getDebugChar}, @code{putDebugChar},
15014 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
15018 Insert these lines near the top of your program:
15026 For the 680x0 stub only, you need to provide a variable called
15027 @code{exceptionHook}. Normally you just use:
15030 void (*exceptionHook)() = 0;
15034 but if before calling @code{set_debug_traps}, you set it to point to a
15035 function in your program, that function is called when
15036 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
15037 error). The function indicated by @code{exceptionHook} is called with
15038 one parameter: an @code{int} which is the exception number.
15041 Compile and link together: your program, the @value{GDBN} debugging stub for
15042 your target architecture, and the supporting subroutines.
15045 Make sure you have a serial connection between your target machine and
15046 the @value{GDBN} host, and identify the serial port on the host.
15049 @c The "remote" target now provides a `load' command, so we should
15050 @c document that. FIXME.
15051 Download your program to your target machine (or get it there by
15052 whatever means the manufacturer provides), and start it.
15055 Start @value{GDBN} on the host, and connect to the target
15056 (@pxref{Connecting,,Connecting to a Remote Target}).
15060 @node Configurations
15061 @chapter Configuration-Specific Information
15063 While nearly all @value{GDBN} commands are available for all native and
15064 cross versions of the debugger, there are some exceptions. This chapter
15065 describes things that are only available in certain configurations.
15067 There are three major categories of configurations: native
15068 configurations, where the host and target are the same, embedded
15069 operating system configurations, which are usually the same for several
15070 different processor architectures, and bare embedded processors, which
15071 are quite different from each other.
15076 * Embedded Processors::
15083 This section describes details specific to particular native
15088 * BSD libkvm Interface:: Debugging BSD kernel memory images
15089 * SVR4 Process Information:: SVR4 process information
15090 * DJGPP Native:: Features specific to the DJGPP port
15091 * Cygwin Native:: Features specific to the Cygwin port
15092 * Hurd Native:: Features specific to @sc{gnu} Hurd
15093 * Neutrino:: Features specific to QNX Neutrino
15094 * Darwin:: Features specific to Darwin
15100 On HP-UX systems, if you refer to a function or variable name that
15101 begins with a dollar sign, @value{GDBN} searches for a user or system
15102 name first, before it searches for a convenience variable.
15105 @node BSD libkvm Interface
15106 @subsection BSD libkvm Interface
15109 @cindex kernel memory image
15110 @cindex kernel crash dump
15112 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
15113 interface that provides a uniform interface for accessing kernel virtual
15114 memory images, including live systems and crash dumps. @value{GDBN}
15115 uses this interface to allow you to debug live kernels and kernel crash
15116 dumps on many native BSD configurations. This is implemented as a
15117 special @code{kvm} debugging target. For debugging a live system, load
15118 the currently running kernel into @value{GDBN} and connect to the
15122 (@value{GDBP}) @b{target kvm}
15125 For debugging crash dumps, provide the file name of the crash dump as an
15129 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
15132 Once connected to the @code{kvm} target, the following commands are
15138 Set current context from the @dfn{Process Control Block} (PCB) address.
15141 Set current context from proc address. This command isn't available on
15142 modern FreeBSD systems.
15145 @node SVR4 Process Information
15146 @subsection SVR4 Process Information
15148 @cindex examine process image
15149 @cindex process info via @file{/proc}
15151 Many versions of SVR4 and compatible systems provide a facility called
15152 @samp{/proc} that can be used to examine the image of a running
15153 process using file-system subroutines. If @value{GDBN} is configured
15154 for an operating system with this facility, the command @code{info
15155 proc} is available to report information about the process running
15156 your program, or about any process running on your system. @code{info
15157 proc} works only on SVR4 systems that include the @code{procfs} code.
15158 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
15159 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
15165 @itemx info proc @var{process-id}
15166 Summarize available information about any running process. If a
15167 process ID is specified by @var{process-id}, display information about
15168 that process; otherwise display information about the program being
15169 debugged. The summary includes the debugged process ID, the command
15170 line used to invoke it, its current working directory, and its
15171 executable file's absolute file name.
15173 On some systems, @var{process-id} can be of the form
15174 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
15175 within a process. If the optional @var{pid} part is missing, it means
15176 a thread from the process being debugged (the leading @samp{/} still
15177 needs to be present, or else @value{GDBN} will interpret the number as
15178 a process ID rather than a thread ID).
15180 @item info proc mappings
15181 @cindex memory address space mappings
15182 Report the memory address space ranges accessible in the program, with
15183 information on whether the process has read, write, or execute access
15184 rights to each range. On @sc{gnu}/Linux systems, each memory range
15185 includes the object file which is mapped to that range, instead of the
15186 memory access rights to that range.
15188 @item info proc stat
15189 @itemx info proc status
15190 @cindex process detailed status information
15191 These subcommands are specific to @sc{gnu}/Linux systems. They show
15192 the process-related information, including the user ID and group ID;
15193 how many threads are there in the process; its virtual memory usage;
15194 the signals that are pending, blocked, and ignored; its TTY; its
15195 consumption of system and user time; its stack size; its @samp{nice}
15196 value; etc. For more information, see the @samp{proc} man page
15197 (type @kbd{man 5 proc} from your shell prompt).
15199 @item info proc all
15200 Show all the information about the process described under all of the
15201 above @code{info proc} subcommands.
15204 @comment These sub-options of 'info proc' were not included when
15205 @comment procfs.c was re-written. Keep their descriptions around
15206 @comment against the day when someone finds the time to put them back in.
15207 @kindex info proc times
15208 @item info proc times
15209 Starting time, user CPU time, and system CPU time for your program and
15212 @kindex info proc id
15214 Report on the process IDs related to your program: its own process ID,
15215 the ID of its parent, the process group ID, and the session ID.
15218 @item set procfs-trace
15219 @kindex set procfs-trace
15220 @cindex @code{procfs} API calls
15221 This command enables and disables tracing of @code{procfs} API calls.
15223 @item show procfs-trace
15224 @kindex show procfs-trace
15225 Show the current state of @code{procfs} API call tracing.
15227 @item set procfs-file @var{file}
15228 @kindex set procfs-file
15229 Tell @value{GDBN} to write @code{procfs} API trace to the named
15230 @var{file}. @value{GDBN} appends the trace info to the previous
15231 contents of the file. The default is to display the trace on the
15234 @item show procfs-file
15235 @kindex show procfs-file
15236 Show the file to which @code{procfs} API trace is written.
15238 @item proc-trace-entry
15239 @itemx proc-trace-exit
15240 @itemx proc-untrace-entry
15241 @itemx proc-untrace-exit
15242 @kindex proc-trace-entry
15243 @kindex proc-trace-exit
15244 @kindex proc-untrace-entry
15245 @kindex proc-untrace-exit
15246 These commands enable and disable tracing of entries into and exits
15247 from the @code{syscall} interface.
15250 @kindex info pidlist
15251 @cindex process list, QNX Neutrino
15252 For QNX Neutrino only, this command displays the list of all the
15253 processes and all the threads within each process.
15256 @kindex info meminfo
15257 @cindex mapinfo list, QNX Neutrino
15258 For QNX Neutrino only, this command displays the list of all mapinfos.
15262 @subsection Features for Debugging @sc{djgpp} Programs
15263 @cindex @sc{djgpp} debugging
15264 @cindex native @sc{djgpp} debugging
15265 @cindex MS-DOS-specific commands
15268 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15269 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15270 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15271 top of real-mode DOS systems and their emulations.
15273 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15274 defines a few commands specific to the @sc{djgpp} port. This
15275 subsection describes those commands.
15280 This is a prefix of @sc{djgpp}-specific commands which print
15281 information about the target system and important OS structures.
15284 @cindex MS-DOS system info
15285 @cindex free memory information (MS-DOS)
15286 @item info dos sysinfo
15287 This command displays assorted information about the underlying
15288 platform: the CPU type and features, the OS version and flavor, the
15289 DPMI version, and the available conventional and DPMI memory.
15294 @cindex segment descriptor tables
15295 @cindex descriptor tables display
15297 @itemx info dos ldt
15298 @itemx info dos idt
15299 These 3 commands display entries from, respectively, Global, Local,
15300 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15301 tables are data structures which store a descriptor for each segment
15302 that is currently in use. The segment's selector is an index into a
15303 descriptor table; the table entry for that index holds the
15304 descriptor's base address and limit, and its attributes and access
15307 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15308 segment (used for both data and the stack), and a DOS segment (which
15309 allows access to DOS/BIOS data structures and absolute addresses in
15310 conventional memory). However, the DPMI host will usually define
15311 additional segments in order to support the DPMI environment.
15313 @cindex garbled pointers
15314 These commands allow to display entries from the descriptor tables.
15315 Without an argument, all entries from the specified table are
15316 displayed. An argument, which should be an integer expression, means
15317 display a single entry whose index is given by the argument. For
15318 example, here's a convenient way to display information about the
15319 debugged program's data segment:
15322 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15323 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15327 This comes in handy when you want to see whether a pointer is outside
15328 the data segment's limit (i.e.@: @dfn{garbled}).
15330 @cindex page tables display (MS-DOS)
15332 @itemx info dos pte
15333 These two commands display entries from, respectively, the Page
15334 Directory and the Page Tables. Page Directories and Page Tables are
15335 data structures which control how virtual memory addresses are mapped
15336 into physical addresses. A Page Table includes an entry for every
15337 page of memory that is mapped into the program's address space; there
15338 may be several Page Tables, each one holding up to 4096 entries. A
15339 Page Directory has up to 4096 entries, one each for every Page Table
15340 that is currently in use.
15342 Without an argument, @kbd{info dos pde} displays the entire Page
15343 Directory, and @kbd{info dos pte} displays all the entries in all of
15344 the Page Tables. An argument, an integer expression, given to the
15345 @kbd{info dos pde} command means display only that entry from the Page
15346 Directory table. An argument given to the @kbd{info dos pte} command
15347 means display entries from a single Page Table, the one pointed to by
15348 the specified entry in the Page Directory.
15350 @cindex direct memory access (DMA) on MS-DOS
15351 These commands are useful when your program uses @dfn{DMA} (Direct
15352 Memory Access), which needs physical addresses to program the DMA
15355 These commands are supported only with some DPMI servers.
15357 @cindex physical address from linear address
15358 @item info dos address-pte @var{addr}
15359 This command displays the Page Table entry for a specified linear
15360 address. The argument @var{addr} is a linear address which should
15361 already have the appropriate segment's base address added to it,
15362 because this command accepts addresses which may belong to @emph{any}
15363 segment. For example, here's how to display the Page Table entry for
15364 the page where a variable @code{i} is stored:
15367 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15368 @exdent @code{Page Table entry for address 0x11a00d30:}
15369 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15373 This says that @code{i} is stored at offset @code{0xd30} from the page
15374 whose physical base address is @code{0x02698000}, and shows all the
15375 attributes of that page.
15377 Note that you must cast the addresses of variables to a @code{char *},
15378 since otherwise the value of @code{__djgpp_base_address}, the base
15379 address of all variables and functions in a @sc{djgpp} program, will
15380 be added using the rules of C pointer arithmetics: if @code{i} is
15381 declared an @code{int}, @value{GDBN} will add 4 times the value of
15382 @code{__djgpp_base_address} to the address of @code{i}.
15384 Here's another example, it displays the Page Table entry for the
15388 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15389 @exdent @code{Page Table entry for address 0x29110:}
15390 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15394 (The @code{+ 3} offset is because the transfer buffer's address is the
15395 3rd member of the @code{_go32_info_block} structure.) The output
15396 clearly shows that this DPMI server maps the addresses in conventional
15397 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15398 linear (@code{0x29110}) addresses are identical.
15400 This command is supported only with some DPMI servers.
15403 @cindex DOS serial data link, remote debugging
15404 In addition to native debugging, the DJGPP port supports remote
15405 debugging via a serial data link. The following commands are specific
15406 to remote serial debugging in the DJGPP port of @value{GDBN}.
15409 @kindex set com1base
15410 @kindex set com1irq
15411 @kindex set com2base
15412 @kindex set com2irq
15413 @kindex set com3base
15414 @kindex set com3irq
15415 @kindex set com4base
15416 @kindex set com4irq
15417 @item set com1base @var{addr}
15418 This command sets the base I/O port address of the @file{COM1} serial
15421 @item set com1irq @var{irq}
15422 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15423 for the @file{COM1} serial port.
15425 There are similar commands @samp{set com2base}, @samp{set com3irq},
15426 etc.@: for setting the port address and the @code{IRQ} lines for the
15429 @kindex show com1base
15430 @kindex show com1irq
15431 @kindex show com2base
15432 @kindex show com2irq
15433 @kindex show com3base
15434 @kindex show com3irq
15435 @kindex show com4base
15436 @kindex show com4irq
15437 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15438 display the current settings of the base address and the @code{IRQ}
15439 lines used by the COM ports.
15442 @kindex info serial
15443 @cindex DOS serial port status
15444 This command prints the status of the 4 DOS serial ports. For each
15445 port, it prints whether it's active or not, its I/O base address and
15446 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15447 counts of various errors encountered so far.
15451 @node Cygwin Native
15452 @subsection Features for Debugging MS Windows PE Executables
15453 @cindex MS Windows debugging
15454 @cindex native Cygwin debugging
15455 @cindex Cygwin-specific commands
15457 @value{GDBN} supports native debugging of MS Windows programs, including
15458 DLLs with and without symbolic debugging information. There are various
15459 additional Cygwin-specific commands, described in this section.
15460 Working with DLLs that have no debugging symbols is described in
15461 @ref{Non-debug DLL Symbols}.
15466 This is a prefix of MS Windows-specific commands which print
15467 information about the target system and important OS structures.
15469 @item info w32 selector
15470 This command displays information returned by
15471 the Win32 API @code{GetThreadSelectorEntry} function.
15472 It takes an optional argument that is evaluated to
15473 a long value to give the information about this given selector.
15474 Without argument, this command displays information
15475 about the six segment registers.
15479 This is a Cygwin-specific alias of @code{info shared}.
15481 @kindex dll-symbols
15483 This command loads symbols from a dll similarly to
15484 add-sym command but without the need to specify a base address.
15486 @kindex set cygwin-exceptions
15487 @cindex debugging the Cygwin DLL
15488 @cindex Cygwin DLL, debugging
15489 @item set cygwin-exceptions @var{mode}
15490 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15491 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15492 @value{GDBN} will delay recognition of exceptions, and may ignore some
15493 exceptions which seem to be caused by internal Cygwin DLL
15494 ``bookkeeping''. This option is meant primarily for debugging the
15495 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15496 @value{GDBN} users with false @code{SIGSEGV} signals.
15498 @kindex show cygwin-exceptions
15499 @item show cygwin-exceptions
15500 Displays whether @value{GDBN} will break on exceptions that happen
15501 inside the Cygwin DLL itself.
15503 @kindex set new-console
15504 @item set new-console @var{mode}
15505 If @var{mode} is @code{on} the debuggee will
15506 be started in a new console on next start.
15507 If @var{mode} is @code{off}i, the debuggee will
15508 be started in the same console as the debugger.
15510 @kindex show new-console
15511 @item show new-console
15512 Displays whether a new console is used
15513 when the debuggee is started.
15515 @kindex set new-group
15516 @item set new-group @var{mode}
15517 This boolean value controls whether the debuggee should
15518 start a new group or stay in the same group as the debugger.
15519 This affects the way the Windows OS handles
15522 @kindex show new-group
15523 @item show new-group
15524 Displays current value of new-group boolean.
15526 @kindex set debugevents
15527 @item set debugevents
15528 This boolean value adds debug output concerning kernel events related
15529 to the debuggee seen by the debugger. This includes events that
15530 signal thread and process creation and exit, DLL loading and
15531 unloading, console interrupts, and debugging messages produced by the
15532 Windows @code{OutputDebugString} API call.
15534 @kindex set debugexec
15535 @item set debugexec
15536 This boolean value adds debug output concerning execute events
15537 (such as resume thread) seen by the debugger.
15539 @kindex set debugexceptions
15540 @item set debugexceptions
15541 This boolean value adds debug output concerning exceptions in the
15542 debuggee seen by the debugger.
15544 @kindex set debugmemory
15545 @item set debugmemory
15546 This boolean value adds debug output concerning debuggee memory reads
15547 and writes by the debugger.
15551 This boolean values specifies whether the debuggee is called
15552 via a shell or directly (default value is on).
15556 Displays if the debuggee will be started with a shell.
15561 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15564 @node Non-debug DLL Symbols
15565 @subsubsection Support for DLLs without Debugging Symbols
15566 @cindex DLLs with no debugging symbols
15567 @cindex Minimal symbols and DLLs
15569 Very often on windows, some of the DLLs that your program relies on do
15570 not include symbolic debugging information (for example,
15571 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15572 symbols in a DLL, it relies on the minimal amount of symbolic
15573 information contained in the DLL's export table. This section
15574 describes working with such symbols, known internally to @value{GDBN} as
15575 ``minimal symbols''.
15577 Note that before the debugged program has started execution, no DLLs
15578 will have been loaded. The easiest way around this problem is simply to
15579 start the program --- either by setting a breakpoint or letting the
15580 program run once to completion. It is also possible to force
15581 @value{GDBN} to load a particular DLL before starting the executable ---
15582 see the shared library information in @ref{Files}, or the
15583 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15584 explicitly loading symbols from a DLL with no debugging information will
15585 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15586 which may adversely affect symbol lookup performance.
15588 @subsubsection DLL Name Prefixes
15590 In keeping with the naming conventions used by the Microsoft debugging
15591 tools, DLL export symbols are made available with a prefix based on the
15592 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15593 also entered into the symbol table, so @code{CreateFileA} is often
15594 sufficient. In some cases there will be name clashes within a program
15595 (particularly if the executable itself includes full debugging symbols)
15596 necessitating the use of the fully qualified name when referring to the
15597 contents of the DLL. Use single-quotes around the name to avoid the
15598 exclamation mark (``!'') being interpreted as a language operator.
15600 Note that the internal name of the DLL may be all upper-case, even
15601 though the file name of the DLL is lower-case, or vice-versa. Since
15602 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15603 some confusion. If in doubt, try the @code{info functions} and
15604 @code{info variables} commands or even @code{maint print msymbols}
15605 (@pxref{Symbols}). Here's an example:
15608 (@value{GDBP}) info function CreateFileA
15609 All functions matching regular expression "CreateFileA":
15611 Non-debugging symbols:
15612 0x77e885f4 CreateFileA
15613 0x77e885f4 KERNEL32!CreateFileA
15617 (@value{GDBP}) info function !
15618 All functions matching regular expression "!":
15620 Non-debugging symbols:
15621 0x6100114c cygwin1!__assert
15622 0x61004034 cygwin1!_dll_crt0@@0
15623 0x61004240 cygwin1!dll_crt0(per_process *)
15627 @subsubsection Working with Minimal Symbols
15629 Symbols extracted from a DLL's export table do not contain very much
15630 type information. All that @value{GDBN} can do is guess whether a symbol
15631 refers to a function or variable depending on the linker section that
15632 contains the symbol. Also note that the actual contents of the memory
15633 contained in a DLL are not available unless the program is running. This
15634 means that you cannot examine the contents of a variable or disassemble
15635 a function within a DLL without a running program.
15637 Variables are generally treated as pointers and dereferenced
15638 automatically. For this reason, it is often necessary to prefix a
15639 variable name with the address-of operator (``&'') and provide explicit
15640 type information in the command. Here's an example of the type of
15644 (@value{GDBP}) print 'cygwin1!__argv'
15649 (@value{GDBP}) x 'cygwin1!__argv'
15650 0x10021610: "\230y\""
15653 And two possible solutions:
15656 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15657 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15661 (@value{GDBP}) x/2x &'cygwin1!__argv'
15662 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15663 (@value{GDBP}) x/x 0x10021608
15664 0x10021608: 0x0022fd98
15665 (@value{GDBP}) x/s 0x0022fd98
15666 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15669 Setting a break point within a DLL is possible even before the program
15670 starts execution. However, under these circumstances, @value{GDBN} can't
15671 examine the initial instructions of the function in order to skip the
15672 function's frame set-up code. You can work around this by using ``*&''
15673 to set the breakpoint at a raw memory address:
15676 (@value{GDBP}) break *&'python22!PyOS_Readline'
15677 Breakpoint 1 at 0x1e04eff0
15680 The author of these extensions is not entirely convinced that setting a
15681 break point within a shared DLL like @file{kernel32.dll} is completely
15685 @subsection Commands Specific to @sc{gnu} Hurd Systems
15686 @cindex @sc{gnu} Hurd debugging
15688 This subsection describes @value{GDBN} commands specific to the
15689 @sc{gnu} Hurd native debugging.
15694 @kindex set signals@r{, Hurd command}
15695 @kindex set sigs@r{, Hurd command}
15696 This command toggles the state of inferior signal interception by
15697 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15698 affected by this command. @code{sigs} is a shorthand alias for
15703 @kindex show signals@r{, Hurd command}
15704 @kindex show sigs@r{, Hurd command}
15705 Show the current state of intercepting inferior's signals.
15707 @item set signal-thread
15708 @itemx set sigthread
15709 @kindex set signal-thread
15710 @kindex set sigthread
15711 This command tells @value{GDBN} which thread is the @code{libc} signal
15712 thread. That thread is run when a signal is delivered to a running
15713 process. @code{set sigthread} is the shorthand alias of @code{set
15716 @item show signal-thread
15717 @itemx show sigthread
15718 @kindex show signal-thread
15719 @kindex show sigthread
15720 These two commands show which thread will run when the inferior is
15721 delivered a signal.
15724 @kindex set stopped@r{, Hurd command}
15725 This commands tells @value{GDBN} that the inferior process is stopped,
15726 as with the @code{SIGSTOP} signal. The stopped process can be
15727 continued by delivering a signal to it.
15730 @kindex show stopped@r{, Hurd command}
15731 This command shows whether @value{GDBN} thinks the debuggee is
15734 @item set exceptions
15735 @kindex set exceptions@r{, Hurd command}
15736 Use this command to turn off trapping of exceptions in the inferior.
15737 When exception trapping is off, neither breakpoints nor
15738 single-stepping will work. To restore the default, set exception
15741 @item show exceptions
15742 @kindex show exceptions@r{, Hurd command}
15743 Show the current state of trapping exceptions in the inferior.
15745 @item set task pause
15746 @kindex set task@r{, Hurd commands}
15747 @cindex task attributes (@sc{gnu} Hurd)
15748 @cindex pause current task (@sc{gnu} Hurd)
15749 This command toggles task suspension when @value{GDBN} has control.
15750 Setting it to on takes effect immediately, and the task is suspended
15751 whenever @value{GDBN} gets control. Setting it to off will take
15752 effect the next time the inferior is continued. If this option is set
15753 to off, you can use @code{set thread default pause on} or @code{set
15754 thread pause on} (see below) to pause individual threads.
15756 @item show task pause
15757 @kindex show task@r{, Hurd commands}
15758 Show the current state of task suspension.
15760 @item set task detach-suspend-count
15761 @cindex task suspend count
15762 @cindex detach from task, @sc{gnu} Hurd
15763 This command sets the suspend count the task will be left with when
15764 @value{GDBN} detaches from it.
15766 @item show task detach-suspend-count
15767 Show the suspend count the task will be left with when detaching.
15769 @item set task exception-port
15770 @itemx set task excp
15771 @cindex task exception port, @sc{gnu} Hurd
15772 This command sets the task exception port to which @value{GDBN} will
15773 forward exceptions. The argument should be the value of the @dfn{send
15774 rights} of the task. @code{set task excp} is a shorthand alias.
15776 @item set noninvasive
15777 @cindex noninvasive task options
15778 This command switches @value{GDBN} to a mode that is the least
15779 invasive as far as interfering with the inferior is concerned. This
15780 is the same as using @code{set task pause}, @code{set exceptions}, and
15781 @code{set signals} to values opposite to the defaults.
15783 @item info send-rights
15784 @itemx info receive-rights
15785 @itemx info port-rights
15786 @itemx info port-sets
15787 @itemx info dead-names
15790 @cindex send rights, @sc{gnu} Hurd
15791 @cindex receive rights, @sc{gnu} Hurd
15792 @cindex port rights, @sc{gnu} Hurd
15793 @cindex port sets, @sc{gnu} Hurd
15794 @cindex dead names, @sc{gnu} Hurd
15795 These commands display information about, respectively, send rights,
15796 receive rights, port rights, port sets, and dead names of a task.
15797 There are also shorthand aliases: @code{info ports} for @code{info
15798 port-rights} and @code{info psets} for @code{info port-sets}.
15800 @item set thread pause
15801 @kindex set thread@r{, Hurd command}
15802 @cindex thread properties, @sc{gnu} Hurd
15803 @cindex pause current thread (@sc{gnu} Hurd)
15804 This command toggles current thread suspension when @value{GDBN} has
15805 control. Setting it to on takes effect immediately, and the current
15806 thread is suspended whenever @value{GDBN} gets control. Setting it to
15807 off will take effect the next time the inferior is continued.
15808 Normally, this command has no effect, since when @value{GDBN} has
15809 control, the whole task is suspended. However, if you used @code{set
15810 task pause off} (see above), this command comes in handy to suspend
15811 only the current thread.
15813 @item show thread pause
15814 @kindex show thread@r{, Hurd command}
15815 This command shows the state of current thread suspension.
15817 @item set thread run
15818 This command sets whether the current thread is allowed to run.
15820 @item show thread run
15821 Show whether the current thread is allowed to run.
15823 @item set thread detach-suspend-count
15824 @cindex thread suspend count, @sc{gnu} Hurd
15825 @cindex detach from thread, @sc{gnu} Hurd
15826 This command sets the suspend count @value{GDBN} will leave on a
15827 thread when detaching. This number is relative to the suspend count
15828 found by @value{GDBN} when it notices the thread; use @code{set thread
15829 takeover-suspend-count} to force it to an absolute value.
15831 @item show thread detach-suspend-count
15832 Show the suspend count @value{GDBN} will leave on the thread when
15835 @item set thread exception-port
15836 @itemx set thread excp
15837 Set the thread exception port to which to forward exceptions. This
15838 overrides the port set by @code{set task exception-port} (see above).
15839 @code{set thread excp} is the shorthand alias.
15841 @item set thread takeover-suspend-count
15842 Normally, @value{GDBN}'s thread suspend counts are relative to the
15843 value @value{GDBN} finds when it notices each thread. This command
15844 changes the suspend counts to be absolute instead.
15846 @item set thread default
15847 @itemx show thread default
15848 @cindex thread default settings, @sc{gnu} Hurd
15849 Each of the above @code{set thread} commands has a @code{set thread
15850 default} counterpart (e.g., @code{set thread default pause}, @code{set
15851 thread default exception-port}, etc.). The @code{thread default}
15852 variety of commands sets the default thread properties for all
15853 threads; you can then change the properties of individual threads with
15854 the non-default commands.
15859 @subsection QNX Neutrino
15860 @cindex QNX Neutrino
15862 @value{GDBN} provides the following commands specific to the QNX
15866 @item set debug nto-debug
15867 @kindex set debug nto-debug
15868 When set to on, enables debugging messages specific to the QNX
15871 @item show debug nto-debug
15872 @kindex show debug nto-debug
15873 Show the current state of QNX Neutrino messages.
15880 @value{GDBN} provides the following commands specific to the Darwin target:
15883 @item set debug darwin @var{num}
15884 @kindex set debug darwin
15885 When set to a non zero value, enables debugging messages specific to
15886 the Darwin support. Higher values produce more verbose output.
15888 @item show debug darwin
15889 @kindex show debug darwin
15890 Show the current state of Darwin messages.
15892 @item set debug mach-o @var{num}
15893 @kindex set debug mach-o
15894 When set to a non zero value, enables debugging messages while
15895 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15896 file format used on Darwin for object and executable files.) Higher
15897 values produce more verbose output. This is a command to diagnose
15898 problems internal to @value{GDBN} and should not be needed in normal
15901 @item show debug mach-o
15902 @kindex show debug mach-o
15903 Show the current state of Mach-O file messages.
15905 @item set mach-exceptions on
15906 @itemx set mach-exceptions off
15907 @kindex set mach-exceptions
15908 On Darwin, faults are first reported as a Mach exception and are then
15909 mapped to a Posix signal. Use this command to turn on trapping of
15910 Mach exceptions in the inferior. This might be sometimes useful to
15911 better understand the cause of a fault. The default is off.
15913 @item show mach-exceptions
15914 @kindex show mach-exceptions
15915 Show the current state of exceptions trapping.
15920 @section Embedded Operating Systems
15922 This section describes configurations involving the debugging of
15923 embedded operating systems that are available for several different
15927 * VxWorks:: Using @value{GDBN} with VxWorks
15930 @value{GDBN} includes the ability to debug programs running on
15931 various real-time operating systems.
15934 @subsection Using @value{GDBN} with VxWorks
15940 @kindex target vxworks
15941 @item target vxworks @var{machinename}
15942 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15943 is the target system's machine name or IP address.
15947 On VxWorks, @code{load} links @var{filename} dynamically on the
15948 current target system as well as adding its symbols in @value{GDBN}.
15950 @value{GDBN} enables developers to spawn and debug tasks running on networked
15951 VxWorks targets from a Unix host. Already-running tasks spawned from
15952 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15953 both the Unix host and on the VxWorks target. The program
15954 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15955 installed with the name @code{vxgdb}, to distinguish it from a
15956 @value{GDBN} for debugging programs on the host itself.)
15959 @item VxWorks-timeout @var{args}
15960 @kindex vxworks-timeout
15961 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15962 This option is set by the user, and @var{args} represents the number of
15963 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15964 your VxWorks target is a slow software simulator or is on the far side
15965 of a thin network line.
15968 The following information on connecting to VxWorks was current when
15969 this manual was produced; newer releases of VxWorks may use revised
15972 @findex INCLUDE_RDB
15973 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15974 to include the remote debugging interface routines in the VxWorks
15975 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15976 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15977 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15978 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15979 information on configuring and remaking VxWorks, see the manufacturer's
15981 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15983 Once you have included @file{rdb.a} in your VxWorks system image and set
15984 your Unix execution search path to find @value{GDBN}, you are ready to
15985 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15986 @code{vxgdb}, depending on your installation).
15988 @value{GDBN} comes up showing the prompt:
15995 * VxWorks Connection:: Connecting to VxWorks
15996 * VxWorks Download:: VxWorks download
15997 * VxWorks Attach:: Running tasks
16000 @node VxWorks Connection
16001 @subsubsection Connecting to VxWorks
16003 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
16004 network. To connect to a target whose host name is ``@code{tt}'', type:
16007 (vxgdb) target vxworks tt
16011 @value{GDBN} displays messages like these:
16014 Attaching remote machine across net...
16019 @value{GDBN} then attempts to read the symbol tables of any object modules
16020 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
16021 these files by searching the directories listed in the command search
16022 path (@pxref{Environment, ,Your Program's Environment}); if it fails
16023 to find an object file, it displays a message such as:
16026 prog.o: No such file or directory.
16029 When this happens, add the appropriate directory to the search path with
16030 the @value{GDBN} command @code{path}, and execute the @code{target}
16033 @node VxWorks Download
16034 @subsubsection VxWorks Download
16036 @cindex download to VxWorks
16037 If you have connected to the VxWorks target and you want to debug an
16038 object that has not yet been loaded, you can use the @value{GDBN}
16039 @code{load} command to download a file from Unix to VxWorks
16040 incrementally. The object file given as an argument to the @code{load}
16041 command is actually opened twice: first by the VxWorks target in order
16042 to download the code, then by @value{GDBN} in order to read the symbol
16043 table. This can lead to problems if the current working directories on
16044 the two systems differ. If both systems have NFS mounted the same
16045 filesystems, you can avoid these problems by using absolute paths.
16046 Otherwise, it is simplest to set the working directory on both systems
16047 to the directory in which the object file resides, and then to reference
16048 the file by its name, without any path. For instance, a program
16049 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
16050 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
16051 program, type this on VxWorks:
16054 -> cd "@var{vxpath}/vw/demo/rdb"
16058 Then, in @value{GDBN}, type:
16061 (vxgdb) cd @var{hostpath}/vw/demo/rdb
16062 (vxgdb) load prog.o
16065 @value{GDBN} displays a response similar to this:
16068 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
16071 You can also use the @code{load} command to reload an object module
16072 after editing and recompiling the corresponding source file. Note that
16073 this makes @value{GDBN} delete all currently-defined breakpoints,
16074 auto-displays, and convenience variables, and to clear the value
16075 history. (This is necessary in order to preserve the integrity of
16076 debugger's data structures that reference the target system's symbol
16079 @node VxWorks Attach
16080 @subsubsection Running Tasks
16082 @cindex running VxWorks tasks
16083 You can also attach to an existing task using the @code{attach} command as
16087 (vxgdb) attach @var{task}
16091 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
16092 or suspended when you attach to it. Running tasks are suspended at
16093 the time of attachment.
16095 @node Embedded Processors
16096 @section Embedded Processors
16098 This section goes into details specific to particular embedded
16101 @cindex send command to simulator
16102 Whenever a specific embedded processor has a simulator, @value{GDBN}
16103 allows to send an arbitrary command to the simulator.
16106 @item sim @var{command}
16107 @kindex sim@r{, a command}
16108 Send an arbitrary @var{command} string to the simulator. Consult the
16109 documentation for the specific simulator in use for information about
16110 acceptable commands.
16116 * M32R/D:: Renesas M32R/D
16117 * M68K:: Motorola M68K
16118 * MIPS Embedded:: MIPS Embedded
16119 * OpenRISC 1000:: OpenRisc 1000
16120 * PA:: HP PA Embedded
16121 * PowerPC Embedded:: PowerPC Embedded
16122 * Sparclet:: Tsqware Sparclet
16123 * Sparclite:: Fujitsu Sparclite
16124 * Z8000:: Zilog Z8000
16127 * Super-H:: Renesas Super-H
16136 @item target rdi @var{dev}
16137 ARM Angel monitor, via RDI library interface to ADP protocol. You may
16138 use this target to communicate with both boards running the Angel
16139 monitor, or with the EmbeddedICE JTAG debug device.
16142 @item target rdp @var{dev}
16147 @value{GDBN} provides the following ARM-specific commands:
16150 @item set arm disassembler
16152 This commands selects from a list of disassembly styles. The
16153 @code{"std"} style is the standard style.
16155 @item show arm disassembler
16157 Show the current disassembly style.
16159 @item set arm apcs32
16160 @cindex ARM 32-bit mode
16161 This command toggles ARM operation mode between 32-bit and 26-bit.
16163 @item show arm apcs32
16164 Display the current usage of the ARM 32-bit mode.
16166 @item set arm fpu @var{fputype}
16167 This command sets the ARM floating-point unit (FPU) type. The
16168 argument @var{fputype} can be one of these:
16172 Determine the FPU type by querying the OS ABI.
16174 Software FPU, with mixed-endian doubles on little-endian ARM
16177 GCC-compiled FPA co-processor.
16179 Software FPU with pure-endian doubles.
16185 Show the current type of the FPU.
16188 This command forces @value{GDBN} to use the specified ABI.
16191 Show the currently used ABI.
16193 @item set arm fallback-mode (arm|thumb|auto)
16194 @value{GDBN} uses the symbol table, when available, to determine
16195 whether instructions are ARM or Thumb. This command controls
16196 @value{GDBN}'s default behavior when the symbol table is not
16197 available. The default is @samp{auto}, which causes @value{GDBN} to
16198 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16201 @item show arm fallback-mode
16202 Show the current fallback instruction mode.
16204 @item set arm force-mode (arm|thumb|auto)
16205 This command overrides use of the symbol table to determine whether
16206 instructions are ARM or Thumb. The default is @samp{auto}, which
16207 causes @value{GDBN} to use the symbol table and then the setting
16208 of @samp{set arm fallback-mode}.
16210 @item show arm force-mode
16211 Show the current forced instruction mode.
16213 @item set debug arm
16214 Toggle whether to display ARM-specific debugging messages from the ARM
16215 target support subsystem.
16217 @item show debug arm
16218 Show whether ARM-specific debugging messages are enabled.
16221 The following commands are available when an ARM target is debugged
16222 using the RDI interface:
16225 @item rdilogfile @r{[}@var{file}@r{]}
16227 @cindex ADP (Angel Debugger Protocol) logging
16228 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16229 With an argument, sets the log file to the specified @var{file}. With
16230 no argument, show the current log file name. The default log file is
16233 @item rdilogenable @r{[}@var{arg}@r{]}
16234 @kindex rdilogenable
16235 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16236 enables logging, with an argument 0 or @code{"no"} disables it. With
16237 no arguments displays the current setting. When logging is enabled,
16238 ADP packets exchanged between @value{GDBN} and the RDI target device
16239 are logged to a file.
16241 @item set rdiromatzero
16242 @kindex set rdiromatzero
16243 @cindex ROM at zero address, RDI
16244 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16245 vector catching is disabled, so that zero address can be used. If off
16246 (the default), vector catching is enabled. For this command to take
16247 effect, it needs to be invoked prior to the @code{target rdi} command.
16249 @item show rdiromatzero
16250 @kindex show rdiromatzero
16251 Show the current setting of ROM at zero address.
16253 @item set rdiheartbeat
16254 @kindex set rdiheartbeat
16255 @cindex RDI heartbeat
16256 Enable or disable RDI heartbeat packets. It is not recommended to
16257 turn on this option, since it confuses ARM and EPI JTAG interface, as
16258 well as the Angel monitor.
16260 @item show rdiheartbeat
16261 @kindex show rdiheartbeat
16262 Show the setting of RDI heartbeat packets.
16267 @subsection Renesas M32R/D and M32R/SDI
16270 @kindex target m32r
16271 @item target m32r @var{dev}
16272 Renesas M32R/D ROM monitor.
16274 @kindex target m32rsdi
16275 @item target m32rsdi @var{dev}
16276 Renesas M32R SDI server, connected via parallel port to the board.
16279 The following @value{GDBN} commands are specific to the M32R monitor:
16282 @item set download-path @var{path}
16283 @kindex set download-path
16284 @cindex find downloadable @sc{srec} files (M32R)
16285 Set the default path for finding downloadable @sc{srec} files.
16287 @item show download-path
16288 @kindex show download-path
16289 Show the default path for downloadable @sc{srec} files.
16291 @item set board-address @var{addr}
16292 @kindex set board-address
16293 @cindex M32-EVA target board address
16294 Set the IP address for the M32R-EVA target board.
16296 @item show board-address
16297 @kindex show board-address
16298 Show the current IP address of the target board.
16300 @item set server-address @var{addr}
16301 @kindex set server-address
16302 @cindex download server address (M32R)
16303 Set the IP address for the download server, which is the @value{GDBN}'s
16306 @item show server-address
16307 @kindex show server-address
16308 Display the IP address of the download server.
16310 @item upload @r{[}@var{file}@r{]}
16311 @kindex upload@r{, M32R}
16312 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16313 upload capability. If no @var{file} argument is given, the current
16314 executable file is uploaded.
16316 @item tload @r{[}@var{file}@r{]}
16317 @kindex tload@r{, M32R}
16318 Test the @code{upload} command.
16321 The following commands are available for M32R/SDI:
16326 @cindex reset SDI connection, M32R
16327 This command resets the SDI connection.
16331 This command shows the SDI connection status.
16334 @kindex debug_chaos
16335 @cindex M32R/Chaos debugging
16336 Instructs the remote that M32R/Chaos debugging is to be used.
16338 @item use_debug_dma
16339 @kindex use_debug_dma
16340 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16343 @kindex use_mon_code
16344 Instructs the remote to use the MON_CODE method of accessing memory.
16347 @kindex use_ib_break
16348 Instructs the remote to set breakpoints by IB break.
16350 @item use_dbt_break
16351 @kindex use_dbt_break
16352 Instructs the remote to set breakpoints by DBT.
16358 The Motorola m68k configuration includes ColdFire support, and a
16359 target command for the following ROM monitor.
16363 @kindex target dbug
16364 @item target dbug @var{dev}
16365 dBUG ROM monitor for Motorola ColdFire.
16369 @node MIPS Embedded
16370 @subsection MIPS Embedded
16372 @cindex MIPS boards
16373 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16374 MIPS board attached to a serial line. This is available when
16375 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16378 Use these @value{GDBN} commands to specify the connection to your target board:
16381 @item target mips @var{port}
16382 @kindex target mips @var{port}
16383 To run a program on the board, start up @code{@value{GDBP}} with the
16384 name of your program as the argument. To connect to the board, use the
16385 command @samp{target mips @var{port}}, where @var{port} is the name of
16386 the serial port connected to the board. If the program has not already
16387 been downloaded to the board, you may use the @code{load} command to
16388 download it. You can then use all the usual @value{GDBN} commands.
16390 For example, this sequence connects to the target board through a serial
16391 port, and loads and runs a program called @var{prog} through the
16395 host$ @value{GDBP} @var{prog}
16396 @value{GDBN} is free software and @dots{}
16397 (@value{GDBP}) target mips /dev/ttyb
16398 (@value{GDBP}) load @var{prog}
16402 @item target mips @var{hostname}:@var{portnumber}
16403 On some @value{GDBN} host configurations, you can specify a TCP
16404 connection (for instance, to a serial line managed by a terminal
16405 concentrator) instead of a serial port, using the syntax
16406 @samp{@var{hostname}:@var{portnumber}}.
16408 @item target pmon @var{port}
16409 @kindex target pmon @var{port}
16412 @item target ddb @var{port}
16413 @kindex target ddb @var{port}
16414 NEC's DDB variant of PMON for Vr4300.
16416 @item target lsi @var{port}
16417 @kindex target lsi @var{port}
16418 LSI variant of PMON.
16420 @kindex target r3900
16421 @item target r3900 @var{dev}
16422 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16424 @kindex target array
16425 @item target array @var{dev}
16426 Array Tech LSI33K RAID controller board.
16432 @value{GDBN} also supports these special commands for MIPS targets:
16435 @item set mipsfpu double
16436 @itemx set mipsfpu single
16437 @itemx set mipsfpu none
16438 @itemx set mipsfpu auto
16439 @itemx show mipsfpu
16440 @kindex set mipsfpu
16441 @kindex show mipsfpu
16442 @cindex MIPS remote floating point
16443 @cindex floating point, MIPS remote
16444 If your target board does not support the MIPS floating point
16445 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16446 need this, you may wish to put the command in your @value{GDBN} init
16447 file). This tells @value{GDBN} how to find the return value of
16448 functions which return floating point values. It also allows
16449 @value{GDBN} to avoid saving the floating point registers when calling
16450 functions on the board. If you are using a floating point coprocessor
16451 with only single precision floating point support, as on the @sc{r4650}
16452 processor, use the command @samp{set mipsfpu single}. The default
16453 double precision floating point coprocessor may be selected using
16454 @samp{set mipsfpu double}.
16456 In previous versions the only choices were double precision or no
16457 floating point, so @samp{set mipsfpu on} will select double precision
16458 and @samp{set mipsfpu off} will select no floating point.
16460 As usual, you can inquire about the @code{mipsfpu} variable with
16461 @samp{show mipsfpu}.
16463 @item set timeout @var{seconds}
16464 @itemx set retransmit-timeout @var{seconds}
16465 @itemx show timeout
16466 @itemx show retransmit-timeout
16467 @cindex @code{timeout}, MIPS protocol
16468 @cindex @code{retransmit-timeout}, MIPS protocol
16469 @kindex set timeout
16470 @kindex show timeout
16471 @kindex set retransmit-timeout
16472 @kindex show retransmit-timeout
16473 You can control the timeout used while waiting for a packet, in the MIPS
16474 remote protocol, with the @code{set timeout @var{seconds}} command. The
16475 default is 5 seconds. Similarly, you can control the timeout used while
16476 waiting for an acknowledgment of a packet with the @code{set
16477 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16478 You can inspect both values with @code{show timeout} and @code{show
16479 retransmit-timeout}. (These commands are @emph{only} available when
16480 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16482 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16483 is waiting for your program to stop. In that case, @value{GDBN} waits
16484 forever because it has no way of knowing how long the program is going
16485 to run before stopping.
16487 @item set syn-garbage-limit @var{num}
16488 @kindex set syn-garbage-limit@r{, MIPS remote}
16489 @cindex synchronize with remote MIPS target
16490 Limit the maximum number of characters @value{GDBN} should ignore when
16491 it tries to synchronize with the remote target. The default is 10
16492 characters. Setting the limit to -1 means there's no limit.
16494 @item show syn-garbage-limit
16495 @kindex show syn-garbage-limit@r{, MIPS remote}
16496 Show the current limit on the number of characters to ignore when
16497 trying to synchronize with the remote system.
16499 @item set monitor-prompt @var{prompt}
16500 @kindex set monitor-prompt@r{, MIPS remote}
16501 @cindex remote monitor prompt
16502 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16503 remote monitor. The default depends on the target:
16513 @item show monitor-prompt
16514 @kindex show monitor-prompt@r{, MIPS remote}
16515 Show the current strings @value{GDBN} expects as the prompt from the
16518 @item set monitor-warnings
16519 @kindex set monitor-warnings@r{, MIPS remote}
16520 Enable or disable monitor warnings about hardware breakpoints. This
16521 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16522 display warning messages whose codes are returned by the @code{lsi}
16523 PMON monitor for breakpoint commands.
16525 @item show monitor-warnings
16526 @kindex show monitor-warnings@r{, MIPS remote}
16527 Show the current setting of printing monitor warnings.
16529 @item pmon @var{command}
16530 @kindex pmon@r{, MIPS remote}
16531 @cindex send PMON command
16532 This command allows sending an arbitrary @var{command} string to the
16533 monitor. The monitor must be in debug mode for this to work.
16536 @node OpenRISC 1000
16537 @subsection OpenRISC 1000
16538 @cindex OpenRISC 1000
16540 @cindex or1k boards
16541 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16542 about platform and commands.
16546 @kindex target jtag
16547 @item target jtag jtag://@var{host}:@var{port}
16549 Connects to remote JTAG server.
16550 JTAG remote server can be either an or1ksim or JTAG server,
16551 connected via parallel port to the board.
16553 Example: @code{target jtag jtag://localhost:9999}
16556 @item or1ksim @var{command}
16557 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16558 Simulator, proprietary commands can be executed.
16560 @kindex info or1k spr
16561 @item info or1k spr
16562 Displays spr groups.
16564 @item info or1k spr @var{group}
16565 @itemx info or1k spr @var{groupno}
16566 Displays register names in selected group.
16568 @item info or1k spr @var{group} @var{register}
16569 @itemx info or1k spr @var{register}
16570 @itemx info or1k spr @var{groupno} @var{registerno}
16571 @itemx info or1k spr @var{registerno}
16572 Shows information about specified spr register.
16575 @item spr @var{group} @var{register} @var{value}
16576 @itemx spr @var{register @var{value}}
16577 @itemx spr @var{groupno} @var{registerno @var{value}}
16578 @itemx spr @var{registerno @var{value}}
16579 Writes @var{value} to specified spr register.
16582 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16583 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16584 program execution and is thus much faster. Hardware breakpoints/watchpoint
16585 triggers can be set using:
16588 Load effective address/data
16590 Store effective address/data
16592 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16597 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16598 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16600 @code{htrace} commands:
16601 @cindex OpenRISC 1000 htrace
16604 @item hwatch @var{conditional}
16605 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16606 or Data. For example:
16608 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16610 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16614 Display information about current HW trace configuration.
16616 @item htrace trigger @var{conditional}
16617 Set starting criteria for HW trace.
16619 @item htrace qualifier @var{conditional}
16620 Set acquisition qualifier for HW trace.
16622 @item htrace stop @var{conditional}
16623 Set HW trace stopping criteria.
16625 @item htrace record [@var{data}]*
16626 Selects the data to be recorded, when qualifier is met and HW trace was
16629 @item htrace enable
16630 @itemx htrace disable
16631 Enables/disables the HW trace.
16633 @item htrace rewind [@var{filename}]
16634 Clears currently recorded trace data.
16636 If filename is specified, new trace file is made and any newly collected data
16637 will be written there.
16639 @item htrace print [@var{start} [@var{len}]]
16640 Prints trace buffer, using current record configuration.
16642 @item htrace mode continuous
16643 Set continuous trace mode.
16645 @item htrace mode suspend
16646 Set suspend trace mode.
16650 @node PowerPC Embedded
16651 @subsection PowerPC Embedded
16653 @value{GDBN} provides the following PowerPC-specific commands:
16656 @kindex set powerpc
16657 @item set powerpc soft-float
16658 @itemx show powerpc soft-float
16659 Force @value{GDBN} to use (or not use) a software floating point calling
16660 convention. By default, @value{GDBN} selects the calling convention based
16661 on the selected architecture and the provided executable file.
16663 @item set powerpc vector-abi
16664 @itemx show powerpc vector-abi
16665 Force @value{GDBN} to use the specified calling convention for vector
16666 arguments and return values. The valid options are @samp{auto};
16667 @samp{generic}, to avoid vector registers even if they are present;
16668 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16669 registers. By default, @value{GDBN} selects the calling convention
16670 based on the selected architecture and the provided executable file.
16672 @kindex target dink32
16673 @item target dink32 @var{dev}
16674 DINK32 ROM monitor.
16676 @kindex target ppcbug
16677 @item target ppcbug @var{dev}
16678 @kindex target ppcbug1
16679 @item target ppcbug1 @var{dev}
16680 PPCBUG ROM monitor for PowerPC.
16683 @item target sds @var{dev}
16684 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16687 @cindex SDS protocol
16688 The following commands specific to the SDS protocol are supported
16692 @item set sdstimeout @var{nsec}
16693 @kindex set sdstimeout
16694 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16695 default is 2 seconds.
16697 @item show sdstimeout
16698 @kindex show sdstimeout
16699 Show the current value of the SDS timeout.
16701 @item sds @var{command}
16702 @kindex sds@r{, a command}
16703 Send the specified @var{command} string to the SDS monitor.
16708 @subsection HP PA Embedded
16712 @kindex target op50n
16713 @item target op50n @var{dev}
16714 OP50N monitor, running on an OKI HPPA board.
16716 @kindex target w89k
16717 @item target w89k @var{dev}
16718 W89K monitor, running on a Winbond HPPA board.
16723 @subsection Tsqware Sparclet
16727 @value{GDBN} enables developers to debug tasks running on
16728 Sparclet targets from a Unix host.
16729 @value{GDBN} uses code that runs on
16730 both the Unix host and on the Sparclet target. The program
16731 @code{@value{GDBP}} is installed and executed on the Unix host.
16734 @item remotetimeout @var{args}
16735 @kindex remotetimeout
16736 @value{GDBN} supports the option @code{remotetimeout}.
16737 This option is set by the user, and @var{args} represents the number of
16738 seconds @value{GDBN} waits for responses.
16741 @cindex compiling, on Sparclet
16742 When compiling for debugging, include the options @samp{-g} to get debug
16743 information and @samp{-Ttext} to relocate the program to where you wish to
16744 load it on the target. You may also want to add the options @samp{-n} or
16745 @samp{-N} in order to reduce the size of the sections. Example:
16748 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16751 You can use @code{objdump} to verify that the addresses are what you intended:
16754 sparclet-aout-objdump --headers --syms prog
16757 @cindex running, on Sparclet
16759 your Unix execution search path to find @value{GDBN}, you are ready to
16760 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16761 (or @code{sparclet-aout-gdb}, depending on your installation).
16763 @value{GDBN} comes up showing the prompt:
16770 * Sparclet File:: Setting the file to debug
16771 * Sparclet Connection:: Connecting to Sparclet
16772 * Sparclet Download:: Sparclet download
16773 * Sparclet Execution:: Running and debugging
16776 @node Sparclet File
16777 @subsubsection Setting File to Debug
16779 The @value{GDBN} command @code{file} lets you choose with program to debug.
16782 (gdbslet) file prog
16786 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16787 @value{GDBN} locates
16788 the file by searching the directories listed in the command search
16790 If the file was compiled with debug information (option @samp{-g}), source
16791 files will be searched as well.
16792 @value{GDBN} locates
16793 the source files by searching the directories listed in the directory search
16794 path (@pxref{Environment, ,Your Program's Environment}).
16796 to find a file, it displays a message such as:
16799 prog: No such file or directory.
16802 When this happens, add the appropriate directories to the search paths with
16803 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16804 @code{target} command again.
16806 @node Sparclet Connection
16807 @subsubsection Connecting to Sparclet
16809 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16810 To connect to a target on serial port ``@code{ttya}'', type:
16813 (gdbslet) target sparclet /dev/ttya
16814 Remote target sparclet connected to /dev/ttya
16815 main () at ../prog.c:3
16819 @value{GDBN} displays messages like these:
16825 @node Sparclet Download
16826 @subsubsection Sparclet Download
16828 @cindex download to Sparclet
16829 Once connected to the Sparclet target,
16830 you can use the @value{GDBN}
16831 @code{load} command to download the file from the host to the target.
16832 The file name and load offset should be given as arguments to the @code{load}
16834 Since the file format is aout, the program must be loaded to the starting
16835 address. You can use @code{objdump} to find out what this value is. The load
16836 offset is an offset which is added to the VMA (virtual memory address)
16837 of each of the file's sections.
16838 For instance, if the program
16839 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16840 and bss at 0x12010170, in @value{GDBN}, type:
16843 (gdbslet) load prog 0x12010000
16844 Loading section .text, size 0xdb0 vma 0x12010000
16847 If the code is loaded at a different address then what the program was linked
16848 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16849 to tell @value{GDBN} where to map the symbol table.
16851 @node Sparclet Execution
16852 @subsubsection Running and Debugging
16854 @cindex running and debugging Sparclet programs
16855 You can now begin debugging the task using @value{GDBN}'s execution control
16856 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16857 manual for the list of commands.
16861 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16863 Starting program: prog
16864 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16865 3 char *symarg = 0;
16867 4 char *execarg = "hello!";
16872 @subsection Fujitsu Sparclite
16876 @kindex target sparclite
16877 @item target sparclite @var{dev}
16878 Fujitsu sparclite boards, used only for the purpose of loading.
16879 You must use an additional command to debug the program.
16880 For example: target remote @var{dev} using @value{GDBN} standard
16886 @subsection Zilog Z8000
16889 @cindex simulator, Z8000
16890 @cindex Zilog Z8000 simulator
16892 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16895 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16896 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16897 segmented variant). The simulator recognizes which architecture is
16898 appropriate by inspecting the object code.
16901 @item target sim @var{args}
16903 @kindex target sim@r{, with Z8000}
16904 Debug programs on a simulated CPU. If the simulator supports setup
16905 options, specify them via @var{args}.
16909 After specifying this target, you can debug programs for the simulated
16910 CPU in the same style as programs for your host computer; use the
16911 @code{file} command to load a new program image, the @code{run} command
16912 to run your program, and so on.
16914 As well as making available all the usual machine registers
16915 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16916 additional items of information as specially named registers:
16921 Counts clock-ticks in the simulator.
16924 Counts instructions run in the simulator.
16927 Execution time in 60ths of a second.
16931 You can refer to these values in @value{GDBN} expressions with the usual
16932 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16933 conditional breakpoint that suspends only after at least 5000
16934 simulated clock ticks.
16937 @subsection Atmel AVR
16940 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16941 following AVR-specific commands:
16944 @item info io_registers
16945 @kindex info io_registers@r{, AVR}
16946 @cindex I/O registers (Atmel AVR)
16947 This command displays information about the AVR I/O registers. For
16948 each register, @value{GDBN} prints its number and value.
16955 When configured for debugging CRIS, @value{GDBN} provides the
16956 following CRIS-specific commands:
16959 @item set cris-version @var{ver}
16960 @cindex CRIS version
16961 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16962 The CRIS version affects register names and sizes. This command is useful in
16963 case autodetection of the CRIS version fails.
16965 @item show cris-version
16966 Show the current CRIS version.
16968 @item set cris-dwarf2-cfi
16969 @cindex DWARF-2 CFI and CRIS
16970 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16971 Change to @samp{off} when using @code{gcc-cris} whose version is below
16974 @item show cris-dwarf2-cfi
16975 Show the current state of using DWARF-2 CFI.
16977 @item set cris-mode @var{mode}
16979 Set the current CRIS mode to @var{mode}. It should only be changed when
16980 debugging in guru mode, in which case it should be set to
16981 @samp{guru} (the default is @samp{normal}).
16983 @item show cris-mode
16984 Show the current CRIS mode.
16988 @subsection Renesas Super-H
16991 For the Renesas Super-H processor, @value{GDBN} provides these
16996 @kindex regs@r{, Super-H}
16997 Show the values of all Super-H registers.
16999 @item set sh calling-convention @var{convention}
17000 @kindex set sh calling-convention
17001 Set the calling-convention used when calling functions from @value{GDBN}.
17002 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
17003 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
17004 convention. If the DWARF-2 information of the called function specifies
17005 that the function follows the Renesas calling convention, the function
17006 is called using the Renesas calling convention. If the calling convention
17007 is set to @samp{renesas}, the Renesas calling convention is always used,
17008 regardless of the DWARF-2 information. This can be used to override the
17009 default of @samp{gcc} if debug information is missing, or the compiler
17010 does not emit the DWARF-2 calling convention entry for a function.
17012 @item show sh calling-convention
17013 @kindex show sh calling-convention
17014 Show the current calling convention setting.
17019 @node Architectures
17020 @section Architectures
17022 This section describes characteristics of architectures that affect
17023 all uses of @value{GDBN} with the architecture, both native and cross.
17030 * HPPA:: HP PA architecture
17031 * SPU:: Cell Broadband Engine SPU architecture
17036 @subsection x86 Architecture-specific Issues
17039 @item set struct-convention @var{mode}
17040 @kindex set struct-convention
17041 @cindex struct return convention
17042 @cindex struct/union returned in registers
17043 Set the convention used by the inferior to return @code{struct}s and
17044 @code{union}s from functions to @var{mode}. Possible values of
17045 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
17046 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
17047 are returned on the stack, while @code{"reg"} means that a
17048 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
17049 be returned in a register.
17051 @item show struct-convention
17052 @kindex show struct-convention
17053 Show the current setting of the convention to return @code{struct}s
17062 @kindex set rstack_high_address
17063 @cindex AMD 29K register stack
17064 @cindex register stack, AMD29K
17065 @item set rstack_high_address @var{address}
17066 On AMD 29000 family processors, registers are saved in a separate
17067 @dfn{register stack}. There is no way for @value{GDBN} to determine the
17068 extent of this stack. Normally, @value{GDBN} just assumes that the
17069 stack is ``large enough''. This may result in @value{GDBN} referencing
17070 memory locations that do not exist. If necessary, you can get around
17071 this problem by specifying the ending address of the register stack with
17072 the @code{set rstack_high_address} command. The argument should be an
17073 address, which you probably want to precede with @samp{0x} to specify in
17076 @kindex show rstack_high_address
17077 @item show rstack_high_address
17078 Display the current limit of the register stack, on AMD 29000 family
17086 See the following section.
17091 @cindex stack on Alpha
17092 @cindex stack on MIPS
17093 @cindex Alpha stack
17095 Alpha- and MIPS-based computers use an unusual stack frame, which
17096 sometimes requires @value{GDBN} to search backward in the object code to
17097 find the beginning of a function.
17099 @cindex response time, MIPS debugging
17100 To improve response time (especially for embedded applications, where
17101 @value{GDBN} may be restricted to a slow serial line for this search)
17102 you may want to limit the size of this search, using one of these
17106 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
17107 @item set heuristic-fence-post @var{limit}
17108 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
17109 search for the beginning of a function. A value of @var{0} (the
17110 default) means there is no limit. However, except for @var{0}, the
17111 larger the limit the more bytes @code{heuristic-fence-post} must search
17112 and therefore the longer it takes to run. You should only need to use
17113 this command when debugging a stripped executable.
17115 @item show heuristic-fence-post
17116 Display the current limit.
17120 These commands are available @emph{only} when @value{GDBN} is configured
17121 for debugging programs on Alpha or MIPS processors.
17123 Several MIPS-specific commands are available when debugging MIPS
17127 @item set mips abi @var{arg}
17128 @kindex set mips abi
17129 @cindex set ABI for MIPS
17130 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
17131 values of @var{arg} are:
17135 The default ABI associated with the current binary (this is the
17146 @item show mips abi
17147 @kindex show mips abi
17148 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
17151 @itemx show mipsfpu
17152 @xref{MIPS Embedded, set mipsfpu}.
17154 @item set mips mask-address @var{arg}
17155 @kindex set mips mask-address
17156 @cindex MIPS addresses, masking
17157 This command determines whether the most-significant 32 bits of 64-bit
17158 MIPS addresses are masked off. The argument @var{arg} can be
17159 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
17160 setting, which lets @value{GDBN} determine the correct value.
17162 @item show mips mask-address
17163 @kindex show mips mask-address
17164 Show whether the upper 32 bits of MIPS addresses are masked off or
17167 @item set remote-mips64-transfers-32bit-regs
17168 @kindex set remote-mips64-transfers-32bit-regs
17169 This command controls compatibility with 64-bit MIPS targets that
17170 transfer data in 32-bit quantities. If you have an old MIPS 64 target
17171 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
17172 and 64 bits for other registers, set this option to @samp{on}.
17174 @item show remote-mips64-transfers-32bit-regs
17175 @kindex show remote-mips64-transfers-32bit-regs
17176 Show the current setting of compatibility with older MIPS 64 targets.
17178 @item set debug mips
17179 @kindex set debug mips
17180 This command turns on and off debugging messages for the MIPS-specific
17181 target code in @value{GDBN}.
17183 @item show debug mips
17184 @kindex show debug mips
17185 Show the current setting of MIPS debugging messages.
17191 @cindex HPPA support
17193 When @value{GDBN} is debugging the HP PA architecture, it provides the
17194 following special commands:
17197 @item set debug hppa
17198 @kindex set debug hppa
17199 This command determines whether HPPA architecture-specific debugging
17200 messages are to be displayed.
17202 @item show debug hppa
17203 Show whether HPPA debugging messages are displayed.
17205 @item maint print unwind @var{address}
17206 @kindex maint print unwind@r{, HPPA}
17207 This command displays the contents of the unwind table entry at the
17208 given @var{address}.
17214 @subsection Cell Broadband Engine SPU architecture
17215 @cindex Cell Broadband Engine
17218 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17219 it provides the following special commands:
17222 @item info spu event
17224 Display SPU event facility status. Shows current event mask
17225 and pending event status.
17227 @item info spu signal
17228 Display SPU signal notification facility status. Shows pending
17229 signal-control word and signal notification mode of both signal
17230 notification channels.
17232 @item info spu mailbox
17233 Display SPU mailbox facility status. Shows all pending entries,
17234 in order of processing, in each of the SPU Write Outbound,
17235 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17238 Display MFC DMA status. Shows all pending commands in the MFC
17239 DMA queue. For each entry, opcode, tag, class IDs, effective
17240 and local store addresses and transfer size are shown.
17242 @item info spu proxydma
17243 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17244 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17245 and local store addresses and transfer size are shown.
17250 @subsection PowerPC
17251 @cindex PowerPC architecture
17253 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17254 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17255 numbers stored in the floating point registers. These values must be stored
17256 in two consecutive registers, always starting at an even register like
17257 @code{f0} or @code{f2}.
17259 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
17260 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
17261 @code{f2} and @code{f3} for @code{$dl1} and so on.
17263 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
17264 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
17267 @node Controlling GDB
17268 @chapter Controlling @value{GDBN}
17270 You can alter the way @value{GDBN} interacts with you by using the
17271 @code{set} command. For commands controlling how @value{GDBN} displays
17272 data, see @ref{Print Settings, ,Print Settings}. Other settings are
17277 * Editing:: Command editing
17278 * Command History:: Command history
17279 * Screen Size:: Screen size
17280 * Numbers:: Numbers
17281 * ABI:: Configuring the current ABI
17282 * Messages/Warnings:: Optional warnings and messages
17283 * Debugging Output:: Optional messages about internal happenings
17291 @value{GDBN} indicates its readiness to read a command by printing a string
17292 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17293 can change the prompt string with the @code{set prompt} command. For
17294 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17295 the prompt in one of the @value{GDBN} sessions so that you can always tell
17296 which one you are talking to.
17298 @emph{Note:} @code{set prompt} does not add a space for you after the
17299 prompt you set. This allows you to set a prompt which ends in a space
17300 or a prompt that does not.
17304 @item set prompt @var{newprompt}
17305 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17307 @kindex show prompt
17309 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17313 @section Command Editing
17315 @cindex command line editing
17317 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17318 @sc{gnu} library provides consistent behavior for programs which provide a
17319 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17320 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17321 substitution, and a storage and recall of command history across
17322 debugging sessions.
17324 You may control the behavior of command line editing in @value{GDBN} with the
17325 command @code{set}.
17328 @kindex set editing
17331 @itemx set editing on
17332 Enable command line editing (enabled by default).
17334 @item set editing off
17335 Disable command line editing.
17337 @kindex show editing
17339 Show whether command line editing is enabled.
17342 @xref{Command Line Editing}, for more details about the Readline
17343 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17344 encouraged to read that chapter.
17346 @node Command History
17347 @section Command History
17348 @cindex command history
17350 @value{GDBN} can keep track of the commands you type during your
17351 debugging sessions, so that you can be certain of precisely what
17352 happened. Use these commands to manage the @value{GDBN} command
17355 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17356 package, to provide the history facility. @xref{Using History
17357 Interactively}, for the detailed description of the History library.
17359 To issue a command to @value{GDBN} without affecting certain aspects of
17360 the state which is seen by users, prefix it with @samp{server }
17361 (@pxref{Server Prefix}). This
17362 means that this command will not affect the command history, nor will it
17363 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17364 pressed on a line by itself.
17366 @cindex @code{server}, command prefix
17367 The server prefix does not affect the recording of values into the value
17368 history; to print a value without recording it into the value history,
17369 use the @code{output} command instead of the @code{print} command.
17371 Here is the description of @value{GDBN} commands related to command
17375 @cindex history substitution
17376 @cindex history file
17377 @kindex set history filename
17378 @cindex @env{GDBHISTFILE}, environment variable
17379 @item set history filename @var{fname}
17380 Set the name of the @value{GDBN} command history file to @var{fname}.
17381 This is the file where @value{GDBN} reads an initial command history
17382 list, and where it writes the command history from this session when it
17383 exits. You can access this list through history expansion or through
17384 the history command editing characters listed below. This file defaults
17385 to the value of the environment variable @code{GDBHISTFILE}, or to
17386 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17389 @cindex save command history
17390 @kindex set history save
17391 @item set history save
17392 @itemx set history save on
17393 Record command history in a file, whose name may be specified with the
17394 @code{set history filename} command. By default, this option is disabled.
17396 @item set history save off
17397 Stop recording command history in a file.
17399 @cindex history size
17400 @kindex set history size
17401 @cindex @env{HISTSIZE}, environment variable
17402 @item set history size @var{size}
17403 Set the number of commands which @value{GDBN} keeps in its history list.
17404 This defaults to the value of the environment variable
17405 @code{HISTSIZE}, or to 256 if this variable is not set.
17408 History expansion assigns special meaning to the character @kbd{!}.
17409 @xref{Event Designators}, for more details.
17411 @cindex history expansion, turn on/off
17412 Since @kbd{!} is also the logical not operator in C, history expansion
17413 is off by default. If you decide to enable history expansion with the
17414 @code{set history expansion on} command, you may sometimes need to
17415 follow @kbd{!} (when it is used as logical not, in an expression) with
17416 a space or a tab to prevent it from being expanded. The readline
17417 history facilities do not attempt substitution on the strings
17418 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17420 The commands to control history expansion are:
17423 @item set history expansion on
17424 @itemx set history expansion
17425 @kindex set history expansion
17426 Enable history expansion. History expansion is off by default.
17428 @item set history expansion off
17429 Disable history expansion.
17432 @kindex show history
17434 @itemx show history filename
17435 @itemx show history save
17436 @itemx show history size
17437 @itemx show history expansion
17438 These commands display the state of the @value{GDBN} history parameters.
17439 @code{show history} by itself displays all four states.
17444 @kindex show commands
17445 @cindex show last commands
17446 @cindex display command history
17447 @item show commands
17448 Display the last ten commands in the command history.
17450 @item show commands @var{n}
17451 Print ten commands centered on command number @var{n}.
17453 @item show commands +
17454 Print ten commands just after the commands last printed.
17458 @section Screen Size
17459 @cindex size of screen
17460 @cindex pauses in output
17462 Certain commands to @value{GDBN} may produce large amounts of
17463 information output to the screen. To help you read all of it,
17464 @value{GDBN} pauses and asks you for input at the end of each page of
17465 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17466 to discard the remaining output. Also, the screen width setting
17467 determines when to wrap lines of output. Depending on what is being
17468 printed, @value{GDBN} tries to break the line at a readable place,
17469 rather than simply letting it overflow onto the following line.
17471 Normally @value{GDBN} knows the size of the screen from the terminal
17472 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17473 together with the value of the @code{TERM} environment variable and the
17474 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17475 you can override it with the @code{set height} and @code{set
17482 @kindex show height
17483 @item set height @var{lpp}
17485 @itemx set width @var{cpl}
17487 These @code{set} commands specify a screen height of @var{lpp} lines and
17488 a screen width of @var{cpl} characters. The associated @code{show}
17489 commands display the current settings.
17491 If you specify a height of zero lines, @value{GDBN} does not pause during
17492 output no matter how long the output is. This is useful if output is to a
17493 file or to an editor buffer.
17495 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17496 from wrapping its output.
17498 @item set pagination on
17499 @itemx set pagination off
17500 @kindex set pagination
17501 Turn the output pagination on or off; the default is on. Turning
17502 pagination off is the alternative to @code{set height 0}.
17504 @item show pagination
17505 @kindex show pagination
17506 Show the current pagination mode.
17511 @cindex number representation
17512 @cindex entering numbers
17514 You can always enter numbers in octal, decimal, or hexadecimal in
17515 @value{GDBN} by the usual conventions: octal numbers begin with
17516 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17517 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17518 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17519 10; likewise, the default display for numbers---when no particular
17520 format is specified---is base 10. You can change the default base for
17521 both input and output with the commands described below.
17524 @kindex set input-radix
17525 @item set input-radix @var{base}
17526 Set the default base for numeric input. Supported choices
17527 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17528 specified either unambiguously or using the current input radix; for
17532 set input-radix 012
17533 set input-radix 10.
17534 set input-radix 0xa
17538 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17539 leaves the input radix unchanged, no matter what it was, since
17540 @samp{10}, being without any leading or trailing signs of its base, is
17541 interpreted in the current radix. Thus, if the current radix is 16,
17542 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17545 @kindex set output-radix
17546 @item set output-radix @var{base}
17547 Set the default base for numeric display. Supported choices
17548 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17549 specified either unambiguously or using the current input radix.
17551 @kindex show input-radix
17552 @item show input-radix
17553 Display the current default base for numeric input.
17555 @kindex show output-radix
17556 @item show output-radix
17557 Display the current default base for numeric display.
17559 @item set radix @r{[}@var{base}@r{]}
17563 These commands set and show the default base for both input and output
17564 of numbers. @code{set radix} sets the radix of input and output to
17565 the same base; without an argument, it resets the radix back to its
17566 default value of 10.
17571 @section Configuring the Current ABI
17573 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17574 application automatically. However, sometimes you need to override its
17575 conclusions. Use these commands to manage @value{GDBN}'s view of the
17582 One @value{GDBN} configuration can debug binaries for multiple operating
17583 system targets, either via remote debugging or native emulation.
17584 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17585 but you can override its conclusion using the @code{set osabi} command.
17586 One example where this is useful is in debugging of binaries which use
17587 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17588 not have the same identifying marks that the standard C library for your
17593 Show the OS ABI currently in use.
17596 With no argument, show the list of registered available OS ABI's.
17598 @item set osabi @var{abi}
17599 Set the current OS ABI to @var{abi}.
17602 @cindex float promotion
17604 Generally, the way that an argument of type @code{float} is passed to a
17605 function depends on whether the function is prototyped. For a prototyped
17606 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17607 according to the architecture's convention for @code{float}. For unprototyped
17608 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17609 @code{double} and then passed.
17611 Unfortunately, some forms of debug information do not reliably indicate whether
17612 a function is prototyped. If @value{GDBN} calls a function that is not marked
17613 as prototyped, it consults @kbd{set coerce-float-to-double}.
17616 @kindex set coerce-float-to-double
17617 @item set coerce-float-to-double
17618 @itemx set coerce-float-to-double on
17619 Arguments of type @code{float} will be promoted to @code{double} when passed
17620 to an unprototyped function. This is the default setting.
17622 @item set coerce-float-to-double off
17623 Arguments of type @code{float} will be passed directly to unprototyped
17626 @kindex show coerce-float-to-double
17627 @item show coerce-float-to-double
17628 Show the current setting of promoting @code{float} to @code{double}.
17632 @kindex show cp-abi
17633 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17634 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17635 used to build your application. @value{GDBN} only fully supports
17636 programs with a single C@t{++} ABI; if your program contains code using
17637 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17638 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17639 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17640 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17641 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17642 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17647 Show the C@t{++} ABI currently in use.
17650 With no argument, show the list of supported C@t{++} ABI's.
17652 @item set cp-abi @var{abi}
17653 @itemx set cp-abi auto
17654 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17657 @node Messages/Warnings
17658 @section Optional Warnings and Messages
17660 @cindex verbose operation
17661 @cindex optional warnings
17662 By default, @value{GDBN} is silent about its inner workings. If you are
17663 running on a slow machine, you may want to use the @code{set verbose}
17664 command. This makes @value{GDBN} tell you when it does a lengthy
17665 internal operation, so you will not think it has crashed.
17667 Currently, the messages controlled by @code{set verbose} are those
17668 which announce that the symbol table for a source file is being read;
17669 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17672 @kindex set verbose
17673 @item set verbose on
17674 Enables @value{GDBN} output of certain informational messages.
17676 @item set verbose off
17677 Disables @value{GDBN} output of certain informational messages.
17679 @kindex show verbose
17681 Displays whether @code{set verbose} is on or off.
17684 By default, if @value{GDBN} encounters bugs in the symbol table of an
17685 object file, it is silent; but if you are debugging a compiler, you may
17686 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17691 @kindex set complaints
17692 @item set complaints @var{limit}
17693 Permits @value{GDBN} to output @var{limit} complaints about each type of
17694 unusual symbols before becoming silent about the problem. Set
17695 @var{limit} to zero to suppress all complaints; set it to a large number
17696 to prevent complaints from being suppressed.
17698 @kindex show complaints
17699 @item show complaints
17700 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17704 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17705 lot of stupid questions to confirm certain commands. For example, if
17706 you try to run a program which is already running:
17710 The program being debugged has been started already.
17711 Start it from the beginning? (y or n)
17714 If you are willing to unflinchingly face the consequences of your own
17715 commands, you can disable this ``feature'':
17719 @kindex set confirm
17721 @cindex confirmation
17722 @cindex stupid questions
17723 @item set confirm off
17724 Disables confirmation requests.
17726 @item set confirm on
17727 Enables confirmation requests (the default).
17729 @kindex show confirm
17731 Displays state of confirmation requests.
17735 @cindex command tracing
17736 If you need to debug user-defined commands or sourced files you may find it
17737 useful to enable @dfn{command tracing}. In this mode each command will be
17738 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17739 quantity denoting the call depth of each command.
17742 @kindex set trace-commands
17743 @cindex command scripts, debugging
17744 @item set trace-commands on
17745 Enable command tracing.
17746 @item set trace-commands off
17747 Disable command tracing.
17748 @item show trace-commands
17749 Display the current state of command tracing.
17752 @node Debugging Output
17753 @section Optional Messages about Internal Happenings
17754 @cindex optional debugging messages
17756 @value{GDBN} has commands that enable optional debugging messages from
17757 various @value{GDBN} subsystems; normally these commands are of
17758 interest to @value{GDBN} maintainers, or when reporting a bug. This
17759 section documents those commands.
17762 @kindex set exec-done-display
17763 @item set exec-done-display
17764 Turns on or off the notification of asynchronous commands'
17765 completion. When on, @value{GDBN} will print a message when an
17766 asynchronous command finishes its execution. The default is off.
17767 @kindex show exec-done-display
17768 @item show exec-done-display
17769 Displays the current setting of asynchronous command completion
17772 @cindex gdbarch debugging info
17773 @cindex architecture debugging info
17774 @item set debug arch
17775 Turns on or off display of gdbarch debugging info. The default is off
17777 @item show debug arch
17778 Displays the current state of displaying gdbarch debugging info.
17779 @item set debug aix-thread
17780 @cindex AIX threads
17781 Display debugging messages about inner workings of the AIX thread
17783 @item show debug aix-thread
17784 Show the current state of AIX thread debugging info display.
17785 @item set debug dwarf2-die
17786 @cindex DWARF2 DIEs
17787 Dump DWARF2 DIEs after they are read in.
17788 The value is the number of nesting levels to print.
17789 A value of zero turns off the display.
17790 @item show debug dwarf2-die
17791 Show the current state of DWARF2 DIE debugging.
17792 @item set debug displaced
17793 @cindex displaced stepping debugging info
17794 Turns on or off display of @value{GDBN} debugging info for the
17795 displaced stepping support. The default is off.
17796 @item show debug displaced
17797 Displays the current state of displaying @value{GDBN} debugging info
17798 related to displaced stepping.
17799 @item set debug event
17800 @cindex event debugging info
17801 Turns on or off display of @value{GDBN} event debugging info. The
17803 @item show debug event
17804 Displays the current state of displaying @value{GDBN} event debugging
17806 @item set debug expression
17807 @cindex expression debugging info
17808 Turns on or off display of debugging info about @value{GDBN}
17809 expression parsing. The default is off.
17810 @item show debug expression
17811 Displays the current state of displaying debugging info about
17812 @value{GDBN} expression parsing.
17813 @item set debug frame
17814 @cindex frame debugging info
17815 Turns on or off display of @value{GDBN} frame debugging info. The
17817 @item show debug frame
17818 Displays the current state of displaying @value{GDBN} frame debugging
17820 @item set debug infrun
17821 @cindex inferior debugging info
17822 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17823 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17824 for implementing operations such as single-stepping the inferior.
17825 @item show debug infrun
17826 Displays the current state of @value{GDBN} inferior debugging.
17827 @item set debug lin-lwp
17828 @cindex @sc{gnu}/Linux LWP debug messages
17829 @cindex Linux lightweight processes
17830 Turns on or off debugging messages from the Linux LWP debug support.
17831 @item show debug lin-lwp
17832 Show the current state of Linux LWP debugging messages.
17833 @item set debug lin-lwp-async
17834 @cindex @sc{gnu}/Linux LWP async debug messages
17835 @cindex Linux lightweight processes
17836 Turns on or off debugging messages from the Linux LWP async debug support.
17837 @item show debug lin-lwp-async
17838 Show the current state of Linux LWP async debugging messages.
17839 @item set debug observer
17840 @cindex observer debugging info
17841 Turns on or off display of @value{GDBN} observer debugging. This
17842 includes info such as the notification of observable events.
17843 @item show debug observer
17844 Displays the current state of observer debugging.
17845 @item set debug overload
17846 @cindex C@t{++} overload debugging info
17847 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17848 info. This includes info such as ranking of functions, etc. The default
17850 @item show debug overload
17851 Displays the current state of displaying @value{GDBN} C@t{++} overload
17853 @cindex packets, reporting on stdout
17854 @cindex serial connections, debugging
17855 @cindex debug remote protocol
17856 @cindex remote protocol debugging
17857 @cindex display remote packets
17858 @item set debug remote
17859 Turns on or off display of reports on all packets sent back and forth across
17860 the serial line to the remote machine. The info is printed on the
17861 @value{GDBN} standard output stream. The default is off.
17862 @item show debug remote
17863 Displays the state of display of remote packets.
17864 @item set debug serial
17865 Turns on or off display of @value{GDBN} serial debugging info. The
17867 @item show debug serial
17868 Displays the current state of displaying @value{GDBN} serial debugging
17870 @item set debug solib-frv
17871 @cindex FR-V shared-library debugging
17872 Turns on or off debugging messages for FR-V shared-library code.
17873 @item show debug solib-frv
17874 Display the current state of FR-V shared-library code debugging
17876 @item set debug target
17877 @cindex target debugging info
17878 Turns on or off display of @value{GDBN} target debugging info. This info
17879 includes what is going on at the target level of GDB, as it happens. The
17880 default is 0. Set it to 1 to track events, and to 2 to also track the
17881 value of large memory transfers. Changes to this flag do not take effect
17882 until the next time you connect to a target or use the @code{run} command.
17883 @item show debug target
17884 Displays the current state of displaying @value{GDBN} target debugging
17886 @item set debug timestamp
17887 @cindex timestampping debugging info
17888 Turns on or off display of timestamps with @value{GDBN} debugging info.
17889 When enabled, seconds and microseconds are displayed before each debugging
17891 @item show debug timestamp
17892 Displays the current state of displaying timestamps with @value{GDBN}
17894 @item set debugvarobj
17895 @cindex variable object debugging info
17896 Turns on or off display of @value{GDBN} variable object debugging
17897 info. The default is off.
17898 @item show debugvarobj
17899 Displays the current state of displaying @value{GDBN} variable object
17901 @item set debug xml
17902 @cindex XML parser debugging
17903 Turns on or off debugging messages for built-in XML parsers.
17904 @item show debug xml
17905 Displays the current state of XML debugging messages.
17908 @node Extending GDB
17909 @chapter Extending @value{GDBN}
17910 @cindex extending GDB
17912 @value{GDBN} provides two mechanisms for extension. The first is based
17913 on composition of @value{GDBN} commands, and the second is based on the
17914 Python scripting language.
17917 * Sequences:: Canned Sequences of Commands
17918 * Python:: Scripting @value{GDBN} using Python
17922 @section Canned Sequences of Commands
17924 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17925 Command Lists}), @value{GDBN} provides two ways to store sequences of
17926 commands for execution as a unit: user-defined commands and command
17930 * Define:: How to define your own commands
17931 * Hooks:: Hooks for user-defined commands
17932 * Command Files:: How to write scripts of commands to be stored in a file
17933 * Output:: Commands for controlled output
17937 @subsection User-defined Commands
17939 @cindex user-defined command
17940 @cindex arguments, to user-defined commands
17941 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17942 which you assign a new name as a command. This is done with the
17943 @code{define} command. User commands may accept up to 10 arguments
17944 separated by whitespace. Arguments are accessed within the user command
17945 via @code{$arg0@dots{}$arg9}. A trivial example:
17949 print $arg0 + $arg1 + $arg2
17954 To execute the command use:
17961 This defines the command @code{adder}, which prints the sum of
17962 its three arguments. Note the arguments are text substitutions, so they may
17963 reference variables, use complex expressions, or even perform inferior
17966 @cindex argument count in user-defined commands
17967 @cindex how many arguments (user-defined commands)
17968 In addition, @code{$argc} may be used to find out how many arguments have
17969 been passed. This expands to a number in the range 0@dots{}10.
17974 print $arg0 + $arg1
17977 print $arg0 + $arg1 + $arg2
17985 @item define @var{commandname}
17986 Define a command named @var{commandname}. If there is already a command
17987 by that name, you are asked to confirm that you want to redefine it.
17988 @var{commandname} may be a bare command name consisting of letters,
17989 numbers, dashes, and underscores. It may also start with any predefined
17990 prefix command. For example, @samp{define target my-target} creates
17991 a user-defined @samp{target my-target} command.
17993 The definition of the command is made up of other @value{GDBN} command lines,
17994 which are given following the @code{define} command. The end of these
17995 commands is marked by a line containing @code{end}.
17998 @kindex end@r{ (user-defined commands)}
17999 @item document @var{commandname}
18000 Document the user-defined command @var{commandname}, so that it can be
18001 accessed by @code{help}. The command @var{commandname} must already be
18002 defined. This command reads lines of documentation just as @code{define}
18003 reads the lines of the command definition, ending with @code{end}.
18004 After the @code{document} command is finished, @code{help} on command
18005 @var{commandname} displays the documentation you have written.
18007 You may use the @code{document} command again to change the
18008 documentation of a command. Redefining the command with @code{define}
18009 does not change the documentation.
18011 @kindex dont-repeat
18012 @cindex don't repeat command
18014 Used inside a user-defined command, this tells @value{GDBN} that this
18015 command should not be repeated when the user hits @key{RET}
18016 (@pxref{Command Syntax, repeat last command}).
18018 @kindex help user-defined
18019 @item help user-defined
18020 List all user-defined commands, with the first line of the documentation
18025 @itemx show user @var{commandname}
18026 Display the @value{GDBN} commands used to define @var{commandname} (but
18027 not its documentation). If no @var{commandname} is given, display the
18028 definitions for all user-defined commands.
18030 @cindex infinite recursion in user-defined commands
18031 @kindex show max-user-call-depth
18032 @kindex set max-user-call-depth
18033 @item show max-user-call-depth
18034 @itemx set max-user-call-depth
18035 The value of @code{max-user-call-depth} controls how many recursion
18036 levels are allowed in user-defined commands before @value{GDBN} suspects an
18037 infinite recursion and aborts the command.
18040 In addition to the above commands, user-defined commands frequently
18041 use control flow commands, described in @ref{Command Files}.
18043 When user-defined commands are executed, the
18044 commands of the definition are not printed. An error in any command
18045 stops execution of the user-defined command.
18047 If used interactively, commands that would ask for confirmation proceed
18048 without asking when used inside a user-defined command. Many @value{GDBN}
18049 commands that normally print messages to say what they are doing omit the
18050 messages when used in a user-defined command.
18053 @subsection User-defined Command Hooks
18054 @cindex command hooks
18055 @cindex hooks, for commands
18056 @cindex hooks, pre-command
18059 You may define @dfn{hooks}, which are a special kind of user-defined
18060 command. Whenever you run the command @samp{foo}, if the user-defined
18061 command @samp{hook-foo} exists, it is executed (with no arguments)
18062 before that command.
18064 @cindex hooks, post-command
18066 A hook may also be defined which is run after the command you executed.
18067 Whenever you run the command @samp{foo}, if the user-defined command
18068 @samp{hookpost-foo} exists, it is executed (with no arguments) after
18069 that command. Post-execution hooks may exist simultaneously with
18070 pre-execution hooks, for the same command.
18072 It is valid for a hook to call the command which it hooks. If this
18073 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
18075 @c It would be nice if hookpost could be passed a parameter indicating
18076 @c if the command it hooks executed properly or not. FIXME!
18078 @kindex stop@r{, a pseudo-command}
18079 In addition, a pseudo-command, @samp{stop} exists. Defining
18080 (@samp{hook-stop}) makes the associated commands execute every time
18081 execution stops in your program: before breakpoint commands are run,
18082 displays are printed, or the stack frame is printed.
18084 For example, to ignore @code{SIGALRM} signals while
18085 single-stepping, but treat them normally during normal execution,
18090 handle SIGALRM nopass
18094 handle SIGALRM pass
18097 define hook-continue
18098 handle SIGALRM pass
18102 As a further example, to hook at the beginning and end of the @code{echo}
18103 command, and to add extra text to the beginning and end of the message,
18111 define hookpost-echo
18115 (@value{GDBP}) echo Hello World
18116 <<<---Hello World--->>>
18121 You can define a hook for any single-word command in @value{GDBN}, but
18122 not for command aliases; you should define a hook for the basic command
18123 name, e.g.@: @code{backtrace} rather than @code{bt}.
18124 @c FIXME! So how does Joe User discover whether a command is an alias
18126 You can hook a multi-word command by adding @code{hook-} or
18127 @code{hookpost-} to the last word of the command, e.g.@:
18128 @samp{define target hook-remote} to add a hook to @samp{target remote}.
18130 If an error occurs during the execution of your hook, execution of
18131 @value{GDBN} commands stops and @value{GDBN} issues a prompt
18132 (before the command that you actually typed had a chance to run).
18134 If you try to define a hook which does not match any known command, you
18135 get a warning from the @code{define} command.
18137 @node Command Files
18138 @subsection Command Files
18140 @cindex command files
18141 @cindex scripting commands
18142 A command file for @value{GDBN} is a text file made of lines that are
18143 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
18144 also be included. An empty line in a command file does nothing; it
18145 does not mean to repeat the last command, as it would from the
18148 You can request the execution of a command file with the @code{source}
18153 @cindex execute commands from a file
18154 @item source [@code{-v}] @var{filename}
18155 Execute the command file @var{filename}.
18158 The lines in a command file are generally executed sequentially,
18159 unless the order of execution is changed by one of the
18160 @emph{flow-control commands} described below. The commands are not
18161 printed as they are executed. An error in any command terminates
18162 execution of the command file and control is returned to the console.
18164 @value{GDBN} searches for @var{filename} in the current directory and then
18165 on the search path (specified with the @samp{directory} command).
18167 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
18168 each command as it is executed. The option must be given before
18169 @var{filename}, and is interpreted as part of the filename anywhere else.
18171 Commands that would ask for confirmation if used interactively proceed
18172 without asking when used in a command file. Many @value{GDBN} commands that
18173 normally print messages to say what they are doing omit the messages
18174 when called from command files.
18176 @value{GDBN} also accepts command input from standard input. In this
18177 mode, normal output goes to standard output and error output goes to
18178 standard error. Errors in a command file supplied on standard input do
18179 not terminate execution of the command file---execution continues with
18183 gdb < cmds > log 2>&1
18186 (The syntax above will vary depending on the shell used.) This example
18187 will execute commands from the file @file{cmds}. All output and errors
18188 would be directed to @file{log}.
18190 Since commands stored on command files tend to be more general than
18191 commands typed interactively, they frequently need to deal with
18192 complicated situations, such as different or unexpected values of
18193 variables and symbols, changes in how the program being debugged is
18194 built, etc. @value{GDBN} provides a set of flow-control commands to
18195 deal with these complexities. Using these commands, you can write
18196 complex scripts that loop over data structures, execute commands
18197 conditionally, etc.
18204 This command allows to include in your script conditionally executed
18205 commands. The @code{if} command takes a single argument, which is an
18206 expression to evaluate. It is followed by a series of commands that
18207 are executed only if the expression is true (its value is nonzero).
18208 There can then optionally be an @code{else} line, followed by a series
18209 of commands that are only executed if the expression was false. The
18210 end of the list is marked by a line containing @code{end}.
18214 This command allows to write loops. Its syntax is similar to
18215 @code{if}: the command takes a single argument, which is an expression
18216 to evaluate, and must be followed by the commands to execute, one per
18217 line, terminated by an @code{end}. These commands are called the
18218 @dfn{body} of the loop. The commands in the body of @code{while} are
18219 executed repeatedly as long as the expression evaluates to true.
18223 This command exits the @code{while} loop in whose body it is included.
18224 Execution of the script continues after that @code{while}s @code{end}
18227 @kindex loop_continue
18228 @item loop_continue
18229 This command skips the execution of the rest of the body of commands
18230 in the @code{while} loop in whose body it is included. Execution
18231 branches to the beginning of the @code{while} loop, where it evaluates
18232 the controlling expression.
18234 @kindex end@r{ (if/else/while commands)}
18236 Terminate the block of commands that are the body of @code{if},
18237 @code{else}, or @code{while} flow-control commands.
18242 @subsection Commands for Controlled Output
18244 During the execution of a command file or a user-defined command, normal
18245 @value{GDBN} output is suppressed; the only output that appears is what is
18246 explicitly printed by the commands in the definition. This section
18247 describes three commands useful for generating exactly the output you
18252 @item echo @var{text}
18253 @c I do not consider backslash-space a standard C escape sequence
18254 @c because it is not in ANSI.
18255 Print @var{text}. Nonprinting characters can be included in
18256 @var{text} using C escape sequences, such as @samp{\n} to print a
18257 newline. @strong{No newline is printed unless you specify one.}
18258 In addition to the standard C escape sequences, a backslash followed
18259 by a space stands for a space. This is useful for displaying a
18260 string with spaces at the beginning or the end, since leading and
18261 trailing spaces are otherwise trimmed from all arguments.
18262 To print @samp{@w{ }and foo =@w{ }}, use the command
18263 @samp{echo \@w{ }and foo = \@w{ }}.
18265 A backslash at the end of @var{text} can be used, as in C, to continue
18266 the command onto subsequent lines. For example,
18269 echo This is some text\n\
18270 which is continued\n\
18271 onto several lines.\n
18274 produces the same output as
18277 echo This is some text\n
18278 echo which is continued\n
18279 echo onto several lines.\n
18283 @item output @var{expression}
18284 Print the value of @var{expression} and nothing but that value: no
18285 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18286 value history either. @xref{Expressions, ,Expressions}, for more information
18289 @item output/@var{fmt} @var{expression}
18290 Print the value of @var{expression} in format @var{fmt}. You can use
18291 the same formats as for @code{print}. @xref{Output Formats,,Output
18292 Formats}, for more information.
18295 @item printf @var{template}, @var{expressions}@dots{}
18296 Print the values of one or more @var{expressions} under the control of
18297 the string @var{template}. To print several values, make
18298 @var{expressions} be a comma-separated list of individual expressions,
18299 which may be either numbers or pointers. Their values are printed as
18300 specified by @var{template}, exactly as a C program would do by
18301 executing the code below:
18304 printf (@var{template}, @var{expressions}@dots{});
18307 As in @code{C} @code{printf}, ordinary characters in @var{template}
18308 are printed verbatim, while @dfn{conversion specification} introduced
18309 by the @samp{%} character cause subsequent @var{expressions} to be
18310 evaluated, their values converted and formatted according to type and
18311 style information encoded in the conversion specifications, and then
18314 For example, you can print two values in hex like this:
18317 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18320 @code{printf} supports all the standard @code{C} conversion
18321 specifications, including the flags and modifiers between the @samp{%}
18322 character and the conversion letter, with the following exceptions:
18326 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18329 The modifier @samp{*} is not supported for specifying precision or
18333 The @samp{'} flag (for separation of digits into groups according to
18334 @code{LC_NUMERIC'}) is not supported.
18337 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18341 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18344 The conversion letters @samp{a} and @samp{A} are not supported.
18348 Note that the @samp{ll} type modifier is supported only if the
18349 underlying @code{C} implementation used to build @value{GDBN} supports
18350 the @code{long long int} type, and the @samp{L} type modifier is
18351 supported only if @code{long double} type is available.
18353 As in @code{C}, @code{printf} supports simple backslash-escape
18354 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18355 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18356 single character. Octal and hexadecimal escape sequences are not
18359 Additionally, @code{printf} supports conversion specifications for DFP
18360 (@dfn{Decimal Floating Point}) types using the following length modifiers
18361 together with a floating point specifier.
18366 @samp{H} for printing @code{Decimal32} types.
18369 @samp{D} for printing @code{Decimal64} types.
18372 @samp{DD} for printing @code{Decimal128} types.
18375 If the underlying @code{C} implementation used to build @value{GDBN} has
18376 support for the three length modifiers for DFP types, other modifiers
18377 such as width and precision will also be available for @value{GDBN} to use.
18379 In case there is no such @code{C} support, no additional modifiers will be
18380 available and the value will be printed in the standard way.
18382 Here's an example of printing DFP types using the above conversion letters:
18384 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18390 @section Scripting @value{GDBN} using Python
18391 @cindex python scripting
18392 @cindex scripting with python
18394 You can script @value{GDBN} using the @uref{http://www.python.org/,
18395 Python programming language}. This feature is available only if
18396 @value{GDBN} was configured using @option{--with-python}.
18399 * Python Commands:: Accessing Python from @value{GDBN}.
18400 * Python API:: Accessing @value{GDBN} from Python.
18403 @node Python Commands
18404 @subsection Python Commands
18405 @cindex python commands
18406 @cindex commands to access python
18408 @value{GDBN} provides one command for accessing the Python interpreter,
18409 and one related setting:
18413 @item python @r{[}@var{code}@r{]}
18414 The @code{python} command can be used to evaluate Python code.
18416 If given an argument, the @code{python} command will evaluate the
18417 argument as a Python command. For example:
18420 (@value{GDBP}) python print 23
18424 If you do not provide an argument to @code{python}, it will act as a
18425 multi-line command, like @code{define}. In this case, the Python
18426 script is made up of subsequent command lines, given after the
18427 @code{python} command. This command list is terminated using a line
18428 containing @code{end}. For example:
18431 (@value{GDBP}) python
18433 End with a line saying just "end".
18439 @kindex maint set python print-stack
18440 @item maint set python print-stack
18441 By default, @value{GDBN} will print a stack trace when an error occurs
18442 in a Python script. This can be controlled using @code{maint set
18443 python print-stack}: if @code{on}, the default, then Python stack
18444 printing is enabled; if @code{off}, then Python stack printing is
18449 @subsection Python API
18451 @cindex programming in python
18453 @cindex python stdout
18454 @cindex python pagination
18455 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18456 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18457 A Python program which outputs to one of these streams may have its
18458 output interrupted by the user (@pxref{Screen Size}). In this
18459 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18462 * Basic Python:: Basic Python Functions.
18463 * Exception Handling::
18464 * Values From Inferior::
18465 * Commands In Python:: Implementing new commands in Python.
18466 * Functions In Python:: Writing new convenience functions.
18467 * Frames In Python:: Acessing inferior stack frames from Python.
18471 @subsubsection Basic Python
18473 @cindex python functions
18474 @cindex python module
18476 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18477 methods and classes added by @value{GDBN} are placed in this module.
18478 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18479 use in all scripts evaluated by the @code{python} command.
18481 @findex gdb.execute
18482 @defun execute command [from_tty]
18483 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18484 If a GDB exception happens while @var{command} runs, it is
18485 translated as described in @ref{Exception Handling,,Exception Handling}.
18486 If no exceptions occur, this function returns @code{None}.
18488 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18489 command as having originated from the user invoking it interactively.
18490 It must be a boolean value. If omitted, it defaults to @code{False}.
18493 @findex gdb.get_parameter
18494 @defun get_parameter parameter
18495 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18496 string naming the parameter to look up; @var{parameter} may contain
18497 spaces if the parameter has a multi-part name. For example,
18498 @samp{print object} is a valid parameter name.
18500 If the named parameter does not exist, this function throws a
18501 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18502 a Python value of the appropriate type, and returned.
18505 @findex gdb.history
18506 @defun history number
18507 Return a value from @value{GDBN}'s value history (@pxref{Value
18508 History}). @var{number} indicates which history element to return.
18509 If @var{number} is negative, then @value{GDBN} will take its absolute value
18510 and count backward from the last element (i.e., the most recent element) to
18511 find the value to return. If @var{number} is zero, then @value{GDBN} will
18512 return the most recent element. If the element specified by @var{number}
18513 doesn't exist in the value history, a @code{RuntimeError} exception will be
18516 If no exception is raised, the return value is always an instance of
18517 @code{gdb.Value} (@pxref{Values From Inferior}).
18521 @defun write string
18522 Print a string to @value{GDBN}'s paginated standard output stream.
18523 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18524 call this function.
18529 Flush @value{GDBN}'s paginated standard output stream. Flushing
18530 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18534 @node Exception Handling
18535 @subsubsection Exception Handling
18536 @cindex python exceptions
18537 @cindex exceptions, python
18539 When executing the @code{python} command, Python exceptions
18540 uncaught within the Python code are translated to calls to
18541 @value{GDBN} error-reporting mechanism. If the command that called
18542 @code{python} does not handle the error, @value{GDBN} will
18543 terminate it and print an error message containing the Python
18544 exception name, the associated value, and the Python call stack
18545 backtrace at the point where the exception was raised. Example:
18548 (@value{GDBP}) python print foo
18549 Traceback (most recent call last):
18550 File "<string>", line 1, in <module>
18551 NameError: name 'foo' is not defined
18554 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18555 code are converted to Python @code{RuntimeError} exceptions. User
18556 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18557 prompt) is translated to a Python @code{KeyboardInterrupt}
18558 exception. If you catch these exceptions in your Python code, your
18559 exception handler will see @code{RuntimeError} or
18560 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18561 message as its value, and the Python call stack backtrace at the
18562 Python statement closest to where the @value{GDBN} error occured as the
18565 @node Values From Inferior
18566 @subsubsection Values From Inferior
18567 @cindex values from inferior, with Python
18568 @cindex python, working with values from inferior
18570 @cindex @code{gdb.Value}
18571 @value{GDBN} provides values it obtains from the inferior program in
18572 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18573 for its internal bookkeeping of the inferior's values, and for
18574 fetching values when necessary.
18576 Inferior values that are simple scalars can be used directly in
18577 Python expressions that are valid for the value's data type. Here's
18578 an example for an integer or floating-point value @code{some_val}:
18585 As result of this, @code{bar} will also be a @code{gdb.Value} object
18586 whose values are of the same type as those of @code{some_val}.
18588 Inferior values that are structures or instances of some class can
18589 be accessed using the Python @dfn{dictionary syntax}. For example, if
18590 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18591 can access its @code{foo} element with:
18594 bar = some_val['foo']
18597 Again, @code{bar} will also be a @code{gdb.Value} object.
18599 The following attributes are provided:
18602 @defmethod Value address
18603 If this object is addressable, this read-only attribute holds a
18604 @code{gdb.Value} object representing the address. Otherwise,
18605 this attribute holds @code{None}.
18608 @cindex optimized out value in Python
18609 @defmethod Value is_optimized_out
18610 This read-only boolean attribute is true if the compiler optimized out
18611 this value, thus it is not available for fetching from the inferior.
18615 The following methods are provided:
18618 @defmethod Value dereference
18619 For pointer data types, this method returns a new @code{gdb.Value} object
18620 whose contents is the object pointed to by the pointer. For example, if
18621 @code{foo} is a C pointer to an @code{int}, declared in your C program as
18628 then you can use the corresponding @code{gdb.Value} to access what
18629 @code{foo} points to like this:
18632 bar = foo.dereference ()
18635 The result @code{bar} will be a @code{gdb.Value} object holding the
18636 value pointed to by @code{foo}.
18639 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]}
18640 If this @code{gdb.Value} represents a string, then this method
18641 converts the contents to a Python string. Otherwise, this method will
18642 throw an exception.
18644 Strings are recognized in a language-specific way; whether a given
18645 @code{gdb.Value} represents a string is determined by the current
18648 For C-like languages, a value is a string if it is a pointer to or an
18649 array of characters or ints. The string is assumed to be terminated
18650 by a zero of the appropriate width.
18652 If the optional @var{encoding} argument is given, it must be a string
18653 naming the encoding of the string in the @code{gdb.Value}, such as
18654 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18655 the same encodings as the corresponding argument to Python's
18656 @code{string.decode} method, and the Python codec machinery will be used
18657 to convert the string. If @var{encoding} is not given, or if
18658 @var{encoding} is the empty string, then either the @code{target-charset}
18659 (@pxref{Character Sets}) will be used, or a language-specific encoding
18660 will be used, if the current language is able to supply one.
18662 The optional @var{errors} argument is the same as the corresponding
18663 argument to Python's @code{string.decode} method.
18667 @node Commands In Python
18668 @subsubsection Commands In Python
18670 @cindex commands in python
18671 @cindex python commands
18672 You can implement new @value{GDBN} CLI commands in Python. A CLI
18673 command is implemented using an instance of the @code{gdb.Command}
18674 class, most commonly using a subclass.
18676 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
18677 The object initializer for @code{Command} registers the new command
18678 with @value{GDBN}. This initializer is normally invoked from the
18679 subclass' own @code{__init__} method.
18681 @var{name} is the name of the command. If @var{name} consists of
18682 multiple words, then the initial words are looked for as prefix
18683 commands. In this case, if one of the prefix commands does not exist,
18684 an exception is raised.
18686 There is no support for multi-line commands.
18688 @var{command_class} should be one of the @samp{COMMAND_} constants
18689 defined below. This argument tells @value{GDBN} how to categorize the
18690 new command in the help system.
18692 @var{completer_class} is an optional argument. If given, it should be
18693 one of the @samp{COMPLETE_} constants defined below. This argument
18694 tells @value{GDBN} how to perform completion for this command. If not
18695 given, @value{GDBN} will attempt to complete using the object's
18696 @code{complete} method (see below); if no such method is found, an
18697 error will occur when completion is attempted.
18699 @var{prefix} is an optional argument. If @code{True}, then the new
18700 command is a prefix command; sub-commands of this command may be
18703 The help text for the new command is taken from the Python
18704 documentation string for the command's class, if there is one. If no
18705 documentation string is provided, the default value ``This command is
18706 not documented.'' is used.
18709 @cindex don't repeat Python command
18710 @defmethod Command dont_repeat
18711 By default, a @value{GDBN} command is repeated when the user enters a
18712 blank line at the command prompt. A command can suppress this
18713 behavior by invoking the @code{dont_repeat} method. This is similar
18714 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
18717 @defmethod Command invoke argument from_tty
18718 This method is called by @value{GDBN} when this command is invoked.
18720 @var{argument} is a string. It is the argument to the command, after
18721 leading and trailing whitespace has been stripped.
18723 @var{from_tty} is a boolean argument. When true, this means that the
18724 command was entered by the user at the terminal; when false it means
18725 that the command came from elsewhere.
18727 If this method throws an exception, it is turned into a @value{GDBN}
18728 @code{error} call. Otherwise, the return value is ignored.
18731 @cindex completion of Python commands
18732 @defmethod Command complete text word
18733 This method is called by @value{GDBN} when the user attempts
18734 completion on this command. All forms of completion are handled by
18735 this method, that is, the @key{TAB} and @key{M-?} key bindings
18736 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
18739 The arguments @var{text} and @var{word} are both strings. @var{text}
18740 holds the complete command line up to the cursor's location.
18741 @var{word} holds the last word of the command line; this is computed
18742 using a word-breaking heuristic.
18744 The @code{complete} method can return several values:
18747 If the return value is a sequence, the contents of the sequence are
18748 used as the completions. It is up to @code{complete} to ensure that the
18749 contents actually do complete the word. A zero-length sequence is
18750 allowed, it means that there were no completions available. Only
18751 string elements of the sequence are used; other elements in the
18752 sequence are ignored.
18755 If the return value is one of the @samp{COMPLETE_} constants defined
18756 below, then the corresponding @value{GDBN}-internal completion
18757 function is invoked, and its result is used.
18760 All other results are treated as though there were no available
18765 When a new command is registered, it must be declared as a member of
18766 some general class of commands. This is used to classify top-level
18767 commands in the on-line help system; note that prefix commands are not
18768 listed under their own category but rather that of their top-level
18769 command. The available classifications are represented by constants
18770 defined in the @code{gdb} module:
18773 @findex COMMAND_NONE
18774 @findex gdb.COMMAND_NONE
18776 The command does not belong to any particular class. A command in
18777 this category will not be displayed in any of the help categories.
18779 @findex COMMAND_RUNNING
18780 @findex gdb.COMMAND_RUNNING
18781 @item COMMAND_RUNNING
18782 The command is related to running the inferior. For example,
18783 @code{start}, @code{step}, and @code{continue} are in this category.
18784 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
18785 commands in this category.
18787 @findex COMMAND_DATA
18788 @findex gdb.COMMAND_DATA
18790 The command is related to data or variables. For example,
18791 @code{call}, @code{find}, and @code{print} are in this category. Type
18792 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
18795 @findex COMMAND_STACK
18796 @findex gdb.COMMAND_STACK
18797 @item COMMAND_STACK
18798 The command has to do with manipulation of the stack. For example,
18799 @code{backtrace}, @code{frame}, and @code{return} are in this
18800 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
18801 list of commands in this category.
18803 @findex COMMAND_FILES
18804 @findex gdb.COMMAND_FILES
18805 @item COMMAND_FILES
18806 This class is used for file-related commands. For example,
18807 @code{file}, @code{list} and @code{section} are in this category.
18808 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
18809 commands in this category.
18811 @findex COMMAND_SUPPORT
18812 @findex gdb.COMMAND_SUPPORT
18813 @item COMMAND_SUPPORT
18814 This should be used for ``support facilities'', generally meaning
18815 things that are useful to the user when interacting with @value{GDBN},
18816 but not related to the state of the inferior. For example,
18817 @code{help}, @code{make}, and @code{shell} are in this category. Type
18818 @kbd{help support} at the @value{GDBN} prompt to see a list of
18819 commands in this category.
18821 @findex COMMAND_STATUS
18822 @findex gdb.COMMAND_STATUS
18823 @item COMMAND_STATUS
18824 The command is an @samp{info}-related command, that is, related to the
18825 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
18826 and @code{show} are in this category. Type @kbd{help status} at the
18827 @value{GDBN} prompt to see a list of commands in this category.
18829 @findex COMMAND_BREAKPOINTS
18830 @findex gdb.COMMAND_BREAKPOINTS
18831 @item COMMAND_BREAKPOINTS
18832 The command has to do with breakpoints. For example, @code{break},
18833 @code{clear}, and @code{delete} are in this category. Type @kbd{help
18834 breakpoints} at the @value{GDBN} prompt to see a list of commands in
18837 @findex COMMAND_TRACEPOINTS
18838 @findex gdb.COMMAND_TRACEPOINTS
18839 @item COMMAND_TRACEPOINTS
18840 The command has to do with tracepoints. For example, @code{trace},
18841 @code{actions}, and @code{tfind} are in this category. Type
18842 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
18843 commands in this category.
18845 @findex COMMAND_OBSCURE
18846 @findex gdb.COMMAND_OBSCURE
18847 @item COMMAND_OBSCURE
18848 The command is only used in unusual circumstances, or is not of
18849 general interest to users. For example, @code{checkpoint},
18850 @code{fork}, and @code{stop} are in this category. Type @kbd{help
18851 obscure} at the @value{GDBN} prompt to see a list of commands in this
18854 @findex COMMAND_MAINTENANCE
18855 @findex gdb.COMMAND_MAINTENANCE
18856 @item COMMAND_MAINTENANCE
18857 The command is only useful to @value{GDBN} maintainers. The
18858 @code{maintenance} and @code{flushregs} commands are in this category.
18859 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
18860 commands in this category.
18863 A new command can use a predefined completion function, either by
18864 specifying it via an argument at initialization, or by returning it
18865 from the @code{complete} method. These predefined completion
18866 constants are all defined in the @code{gdb} module:
18869 @findex COMPLETE_NONE
18870 @findex gdb.COMPLETE_NONE
18871 @item COMPLETE_NONE
18872 This constant means that no completion should be done.
18874 @findex COMPLETE_FILENAME
18875 @findex gdb.COMPLETE_FILENAME
18876 @item COMPLETE_FILENAME
18877 This constant means that filename completion should be performed.
18879 @findex COMPLETE_LOCATION
18880 @findex gdb.COMPLETE_LOCATION
18881 @item COMPLETE_LOCATION
18882 This constant means that location completion should be done.
18883 @xref{Specify Location}.
18885 @findex COMPLETE_COMMAND
18886 @findex gdb.COMPLETE_COMMAND
18887 @item COMPLETE_COMMAND
18888 This constant means that completion should examine @value{GDBN}
18891 @findex COMPLETE_SYMBOL
18892 @findex gdb.COMPLETE_SYMBOL
18893 @item COMPLETE_SYMBOL
18894 This constant means that completion should be done using symbol names
18898 The following code snippet shows how a trivial CLI command can be
18899 implemented in Python:
18902 class HelloWorld (gdb.Command):
18903 """Greet the whole world."""
18905 def __init__ (self):
18906 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
18908 def invoke (self, arg, from_tty):
18909 print "Hello, World!"
18914 The last line instantiates the class, and is necessary to trigger the
18915 registration of the command with @value{GDBN}. Depending on how the
18916 Python code is read into @value{GDBN}, you may need to import the
18917 @code{gdb} module explicitly.
18919 @node Functions In Python
18920 @subsubsection Writing new convenience functions
18922 @cindex writing convenience functions
18923 @cindex convenience functions in python
18924 @cindex python convenience functions
18925 @tindex gdb.Function
18927 You can implement new convenience functions (@pxref{Convenience Vars})
18928 in Python. A convenience function is an instance of a subclass of the
18929 class @code{gdb.Function}.
18931 @defmethod Function __init__ name
18932 The initializer for @code{Function} registers the new function with
18933 @value{GDBN}. The argument @var{name} is the name of the function,
18934 a string. The function will be visible to the user as a convenience
18935 variable of type @code{internal function}, whose name is the same as
18936 the given @var{name}.
18938 The documentation for the new function is taken from the documentation
18939 string for the new class.
18942 @defmethod Function invoke @var{*args}
18943 When a convenience function is evaluated, its arguments are converted
18944 to instances of @code{gdb.Value}, and then the function's
18945 @code{invoke} method is called. Note that @value{GDBN} does not
18946 predetermine the arity of convenience functions. Instead, all
18947 available arguments are passed to @code{invoke}, following the
18948 standard Python calling convention. In particular, a convenience
18949 function can have default values for parameters without ill effect.
18951 The return value of this method is used as its value in the enclosing
18952 expression. If an ordinary Python value is returned, it is converted
18953 to a @code{gdb.Value} following the usual rules.
18956 The following code snippet shows how a trivial convenience function can
18957 be implemented in Python:
18960 class Greet (gdb.Function):
18961 """Return string to greet someone.
18962 Takes a name as argument."""
18964 def __init__ (self):
18965 super (Greet, self).__init__ ("greet")
18967 def invoke (self, name):
18968 return "Hello, %s!" % name.string ()
18973 The last line instantiates the class, and is necessary to trigger the
18974 registration of the function with @value{GDBN}. Depending on how the
18975 Python code is read into @value{GDBN}, you may need to import the
18976 @code{gdb} module explicitly.
18978 @node Frames In Python
18979 @subsubsection Acessing inferior stack frames from Python.
18981 @cindex frames in python
18982 When the debugged program stops, @value{GDBN} is able to analyze its call
18983 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
18984 represents a frame in the stack. A @code{gdb.Frame} object is only valid
18985 while its corresponding frame exists in the inferior's stack. If you try
18986 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
18989 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
18993 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
18997 The following frame-related functions are available in the @code{gdb} module:
18999 @findex gdb.selected_frame
19000 @defun selected_frame
19001 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
19004 @defun frame_stop_reason_string reason
19005 Return a string explaining the reason why @value{GDBN} stopped unwinding
19006 frames, as expressed by the given @var{reason} code (an integer, see the
19007 @code{unwind_stop_reason} method further down in this section).
19010 A @code{gdb.Frame} object has the following methods:
19013 @defmethod Frame is_valid
19014 Returns true if the @code{gdb.Frame} object is valid, false if not.
19015 A frame object can become invalid if the frame it refers to doesn't
19016 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
19017 an exception if it is invalid at the time the method is called.
19020 @defmethod Frame name
19021 Returns the function name of the frame, or @code{None} if it can't be
19025 @defmethod Frame type
19026 Returns the type of the frame. The value can be one of
19027 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
19028 or @code{gdb.SENTINEL_FRAME}.
19031 @defmethod Frame unwind_stop_reason
19032 Return an integer representing the reason why it's not possible to find
19033 more frames toward the outermost frame. Use
19034 @code{gdb.frame_stop_reason_string} to convert the value returned by this
19035 function to a string.
19038 @defmethod Frame pc
19039 Returns the frame's resume address.
19042 @defmethod Frame older
19043 Return the frame that called this frame.
19046 @defmethod Frame newer
19047 Return the frame called by this frame.
19050 @defmethod Frame read_var variable
19051 Return the value of the given variable in this frame. @var{variable} must
19057 @chapter Command Interpreters
19058 @cindex command interpreters
19060 @value{GDBN} supports multiple command interpreters, and some command
19061 infrastructure to allow users or user interface writers to switch
19062 between interpreters or run commands in other interpreters.
19064 @value{GDBN} currently supports two command interpreters, the console
19065 interpreter (sometimes called the command-line interpreter or @sc{cli})
19066 and the machine interface interpreter (or @sc{gdb/mi}). This manual
19067 describes both of these interfaces in great detail.
19069 By default, @value{GDBN} will start with the console interpreter.
19070 However, the user may choose to start @value{GDBN} with another
19071 interpreter by specifying the @option{-i} or @option{--interpreter}
19072 startup options. Defined interpreters include:
19076 @cindex console interpreter
19077 The traditional console or command-line interpreter. This is the most often
19078 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
19079 @value{GDBN} will use this interpreter.
19082 @cindex mi interpreter
19083 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
19084 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
19085 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
19089 @cindex mi2 interpreter
19090 The current @sc{gdb/mi} interface.
19093 @cindex mi1 interpreter
19094 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
19098 @cindex invoke another interpreter
19099 The interpreter being used by @value{GDBN} may not be dynamically
19100 switched at runtime. Although possible, this could lead to a very
19101 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
19102 enters the command "interpreter-set console" in a console view,
19103 @value{GDBN} would switch to using the console interpreter, rendering
19104 the IDE inoperable!
19106 @kindex interpreter-exec
19107 Although you may only choose a single interpreter at startup, you may execute
19108 commands in any interpreter from the current interpreter using the appropriate
19109 command. If you are running the console interpreter, simply use the
19110 @code{interpreter-exec} command:
19113 interpreter-exec mi "-data-list-register-names"
19116 @sc{gdb/mi} has a similar command, although it is only available in versions of
19117 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
19120 @chapter @value{GDBN} Text User Interface
19122 @cindex Text User Interface
19125 * TUI Overview:: TUI overview
19126 * TUI Keys:: TUI key bindings
19127 * TUI Single Key Mode:: TUI single key mode
19128 * TUI Commands:: TUI-specific commands
19129 * TUI Configuration:: TUI configuration variables
19132 The @value{GDBN} Text User Interface (TUI) is a terminal
19133 interface which uses the @code{curses} library to show the source
19134 file, the assembly output, the program registers and @value{GDBN}
19135 commands in separate text windows. The TUI mode is supported only
19136 on platforms where a suitable version of the @code{curses} library
19139 @pindex @value{GDBTUI}
19140 The TUI mode is enabled by default when you invoke @value{GDBN} as
19141 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
19142 You can also switch in and out of TUI mode while @value{GDBN} runs by
19143 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
19144 @xref{TUI Keys, ,TUI Key Bindings}.
19147 @section TUI Overview
19149 In TUI mode, @value{GDBN} can display several text windows:
19153 This window is the @value{GDBN} command window with the @value{GDBN}
19154 prompt and the @value{GDBN} output. The @value{GDBN} input is still
19155 managed using readline.
19158 The source window shows the source file of the program. The current
19159 line and active breakpoints are displayed in this window.
19162 The assembly window shows the disassembly output of the program.
19165 This window shows the processor registers. Registers are highlighted
19166 when their values change.
19169 The source and assembly windows show the current program position
19170 by highlighting the current line and marking it with a @samp{>} marker.
19171 Breakpoints are indicated with two markers. The first marker
19172 indicates the breakpoint type:
19176 Breakpoint which was hit at least once.
19179 Breakpoint which was never hit.
19182 Hardware breakpoint which was hit at least once.
19185 Hardware breakpoint which was never hit.
19188 The second marker indicates whether the breakpoint is enabled or not:
19192 Breakpoint is enabled.
19195 Breakpoint is disabled.
19198 The source, assembly and register windows are updated when the current
19199 thread changes, when the frame changes, or when the program counter
19202 These windows are not all visible at the same time. The command
19203 window is always visible. The others can be arranged in several
19214 source and assembly,
19217 source and registers, or
19220 assembly and registers.
19223 A status line above the command window shows the following information:
19227 Indicates the current @value{GDBN} target.
19228 (@pxref{Targets, ,Specifying a Debugging Target}).
19231 Gives the current process or thread number.
19232 When no process is being debugged, this field is set to @code{No process}.
19235 Gives the current function name for the selected frame.
19236 The name is demangled if demangling is turned on (@pxref{Print Settings}).
19237 When there is no symbol corresponding to the current program counter,
19238 the string @code{??} is displayed.
19241 Indicates the current line number for the selected frame.
19242 When the current line number is not known, the string @code{??} is displayed.
19245 Indicates the current program counter address.
19249 @section TUI Key Bindings
19250 @cindex TUI key bindings
19252 The TUI installs several key bindings in the readline keymaps
19253 (@pxref{Command Line Editing}). The following key bindings
19254 are installed for both TUI mode and the @value{GDBN} standard mode.
19263 Enter or leave the TUI mode. When leaving the TUI mode,
19264 the curses window management stops and @value{GDBN} operates using
19265 its standard mode, writing on the terminal directly. When reentering
19266 the TUI mode, control is given back to the curses windows.
19267 The screen is then refreshed.
19271 Use a TUI layout with only one window. The layout will
19272 either be @samp{source} or @samp{assembly}. When the TUI mode
19273 is not active, it will switch to the TUI mode.
19275 Think of this key binding as the Emacs @kbd{C-x 1} binding.
19279 Use a TUI layout with at least two windows. When the current
19280 layout already has two windows, the next layout with two windows is used.
19281 When a new layout is chosen, one window will always be common to the
19282 previous layout and the new one.
19284 Think of it as the Emacs @kbd{C-x 2} binding.
19288 Change the active window. The TUI associates several key bindings
19289 (like scrolling and arrow keys) with the active window. This command
19290 gives the focus to the next TUI window.
19292 Think of it as the Emacs @kbd{C-x o} binding.
19296 Switch in and out of the TUI SingleKey mode that binds single
19297 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
19300 The following key bindings only work in the TUI mode:
19305 Scroll the active window one page up.
19309 Scroll the active window one page down.
19313 Scroll the active window one line up.
19317 Scroll the active window one line down.
19321 Scroll the active window one column left.
19325 Scroll the active window one column right.
19329 Refresh the screen.
19332 Because the arrow keys scroll the active window in the TUI mode, they
19333 are not available for their normal use by readline unless the command
19334 window has the focus. When another window is active, you must use
19335 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
19336 and @kbd{C-f} to control the command window.
19338 @node TUI Single Key Mode
19339 @section TUI Single Key Mode
19340 @cindex TUI single key mode
19342 The TUI also provides a @dfn{SingleKey} mode, which binds several
19343 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
19344 switch into this mode, where the following key bindings are used:
19347 @kindex c @r{(SingleKey TUI key)}
19351 @kindex d @r{(SingleKey TUI key)}
19355 @kindex f @r{(SingleKey TUI key)}
19359 @kindex n @r{(SingleKey TUI key)}
19363 @kindex q @r{(SingleKey TUI key)}
19365 exit the SingleKey mode.
19367 @kindex r @r{(SingleKey TUI key)}
19371 @kindex s @r{(SingleKey TUI key)}
19375 @kindex u @r{(SingleKey TUI key)}
19379 @kindex v @r{(SingleKey TUI key)}
19383 @kindex w @r{(SingleKey TUI key)}
19388 Other keys temporarily switch to the @value{GDBN} command prompt.
19389 The key that was pressed is inserted in the editing buffer so that
19390 it is possible to type most @value{GDBN} commands without interaction
19391 with the TUI SingleKey mode. Once the command is entered the TUI
19392 SingleKey mode is restored. The only way to permanently leave
19393 this mode is by typing @kbd{q} or @kbd{C-x s}.
19397 @section TUI-specific Commands
19398 @cindex TUI commands
19400 The TUI has specific commands to control the text windows.
19401 These commands are always available, even when @value{GDBN} is not in
19402 the TUI mode. When @value{GDBN} is in the standard mode, most
19403 of these commands will automatically switch to the TUI mode.
19408 List and give the size of all displayed windows.
19412 Display the next layout.
19415 Display the previous layout.
19418 Display the source window only.
19421 Display the assembly window only.
19424 Display the source and assembly window.
19427 Display the register window together with the source or assembly window.
19431 Make the next window active for scrolling.
19434 Make the previous window active for scrolling.
19437 Make the source window active for scrolling.
19440 Make the assembly window active for scrolling.
19443 Make the register window active for scrolling.
19446 Make the command window active for scrolling.
19450 Refresh the screen. This is similar to typing @kbd{C-L}.
19452 @item tui reg float
19454 Show the floating point registers in the register window.
19456 @item tui reg general
19457 Show the general registers in the register window.
19460 Show the next register group. The list of register groups as well as
19461 their order is target specific. The predefined register groups are the
19462 following: @code{general}, @code{float}, @code{system}, @code{vector},
19463 @code{all}, @code{save}, @code{restore}.
19465 @item tui reg system
19466 Show the system registers in the register window.
19470 Update the source window and the current execution point.
19472 @item winheight @var{name} +@var{count}
19473 @itemx winheight @var{name} -@var{count}
19475 Change the height of the window @var{name} by @var{count}
19476 lines. Positive counts increase the height, while negative counts
19479 @item tabset @var{nchars}
19481 Set the width of tab stops to be @var{nchars} characters.
19484 @node TUI Configuration
19485 @section TUI Configuration Variables
19486 @cindex TUI configuration variables
19488 Several configuration variables control the appearance of TUI windows.
19491 @item set tui border-kind @var{kind}
19492 @kindex set tui border-kind
19493 Select the border appearance for the source, assembly and register windows.
19494 The possible values are the following:
19497 Use a space character to draw the border.
19500 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
19503 Use the Alternate Character Set to draw the border. The border is
19504 drawn using character line graphics if the terminal supports them.
19507 @item set tui border-mode @var{mode}
19508 @kindex set tui border-mode
19509 @itemx set tui active-border-mode @var{mode}
19510 @kindex set tui active-border-mode
19511 Select the display attributes for the borders of the inactive windows
19512 or the active window. The @var{mode} can be one of the following:
19515 Use normal attributes to display the border.
19521 Use reverse video mode.
19524 Use half bright mode.
19526 @item half-standout
19527 Use half bright and standout mode.
19530 Use extra bright or bold mode.
19532 @item bold-standout
19533 Use extra bright or bold and standout mode.
19538 @chapter Using @value{GDBN} under @sc{gnu} Emacs
19541 @cindex @sc{gnu} Emacs
19542 A special interface allows you to use @sc{gnu} Emacs to view (and
19543 edit) the source files for the program you are debugging with
19546 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
19547 executable file you want to debug as an argument. This command starts
19548 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
19549 created Emacs buffer.
19550 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
19552 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
19557 All ``terminal'' input and output goes through an Emacs buffer, called
19560 This applies both to @value{GDBN} commands and their output, and to the input
19561 and output done by the program you are debugging.
19563 This is useful because it means that you can copy the text of previous
19564 commands and input them again; you can even use parts of the output
19567 All the facilities of Emacs' Shell mode are available for interacting
19568 with your program. In particular, you can send signals the usual
19569 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
19573 @value{GDBN} displays source code through Emacs.
19575 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
19576 source file for that frame and puts an arrow (@samp{=>}) at the
19577 left margin of the current line. Emacs uses a separate buffer for
19578 source display, and splits the screen to show both your @value{GDBN} session
19581 Explicit @value{GDBN} @code{list} or search commands still produce output as
19582 usual, but you probably have no reason to use them from Emacs.
19585 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
19586 a graphical mode, enabled by default, which provides further buffers
19587 that can control the execution and describe the state of your program.
19588 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
19590 If you specify an absolute file name when prompted for the @kbd{M-x
19591 gdb} argument, then Emacs sets your current working directory to where
19592 your program resides. If you only specify the file name, then Emacs
19593 sets your current working directory to to the directory associated
19594 with the previous buffer. In this case, @value{GDBN} may find your
19595 program by searching your environment's @code{PATH} variable, but on
19596 some operating systems it might not find the source. So, although the
19597 @value{GDBN} input and output session proceeds normally, the auxiliary
19598 buffer does not display the current source and line of execution.
19600 The initial working directory of @value{GDBN} is printed on the top
19601 line of the GUD buffer and this serves as a default for the commands
19602 that specify files for @value{GDBN} to operate on. @xref{Files,
19603 ,Commands to Specify Files}.
19605 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
19606 need to call @value{GDBN} by a different name (for example, if you
19607 keep several configurations around, with different names) you can
19608 customize the Emacs variable @code{gud-gdb-command-name} to run the
19611 In the GUD buffer, you can use these special Emacs commands in
19612 addition to the standard Shell mode commands:
19616 Describe the features of Emacs' GUD Mode.
19619 Execute to another source line, like the @value{GDBN} @code{step} command; also
19620 update the display window to show the current file and location.
19623 Execute to next source line in this function, skipping all function
19624 calls, like the @value{GDBN} @code{next} command. Then update the display window
19625 to show the current file and location.
19628 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
19629 display window accordingly.
19632 Execute until exit from the selected stack frame, like the @value{GDBN}
19633 @code{finish} command.
19636 Continue execution of your program, like the @value{GDBN} @code{continue}
19640 Go up the number of frames indicated by the numeric argument
19641 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
19642 like the @value{GDBN} @code{up} command.
19645 Go down the number of frames indicated by the numeric argument, like the
19646 @value{GDBN} @code{down} command.
19649 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
19650 tells @value{GDBN} to set a breakpoint on the source line point is on.
19652 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
19653 separate frame which shows a backtrace when the GUD buffer is current.
19654 Move point to any frame in the stack and type @key{RET} to make it
19655 become the current frame and display the associated source in the
19656 source buffer. Alternatively, click @kbd{Mouse-2} to make the
19657 selected frame become the current one. In graphical mode, the
19658 speedbar displays watch expressions.
19660 If you accidentally delete the source-display buffer, an easy way to get
19661 it back is to type the command @code{f} in the @value{GDBN} buffer, to
19662 request a frame display; when you run under Emacs, this recreates
19663 the source buffer if necessary to show you the context of the current
19666 The source files displayed in Emacs are in ordinary Emacs buffers
19667 which are visiting the source files in the usual way. You can edit
19668 the files with these buffers if you wish; but keep in mind that @value{GDBN}
19669 communicates with Emacs in terms of line numbers. If you add or
19670 delete lines from the text, the line numbers that @value{GDBN} knows cease
19671 to correspond properly with the code.
19673 A more detailed description of Emacs' interaction with @value{GDBN} is
19674 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
19677 @c The following dropped because Epoch is nonstandard. Reactivate
19678 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
19680 @kindex Emacs Epoch environment
19684 Version 18 of @sc{gnu} Emacs has a built-in window system
19685 called the @code{epoch}
19686 environment. Users of this environment can use a new command,
19687 @code{inspect} which performs identically to @code{print} except that
19688 each value is printed in its own window.
19693 @chapter The @sc{gdb/mi} Interface
19695 @unnumberedsec Function and Purpose
19697 @cindex @sc{gdb/mi}, its purpose
19698 @sc{gdb/mi} is a line based machine oriented text interface to
19699 @value{GDBN} and is activated by specifying using the
19700 @option{--interpreter} command line option (@pxref{Mode Options}). It
19701 is specifically intended to support the development of systems which
19702 use the debugger as just one small component of a larger system.
19704 This chapter is a specification of the @sc{gdb/mi} interface. It is written
19705 in the form of a reference manual.
19707 Note that @sc{gdb/mi} is still under construction, so some of the
19708 features described below are incomplete and subject to change
19709 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
19711 @unnumberedsec Notation and Terminology
19713 @cindex notational conventions, for @sc{gdb/mi}
19714 This chapter uses the following notation:
19718 @code{|} separates two alternatives.
19721 @code{[ @var{something} ]} indicates that @var{something} is optional:
19722 it may or may not be given.
19725 @code{( @var{group} )*} means that @var{group} inside the parentheses
19726 may repeat zero or more times.
19729 @code{( @var{group} )+} means that @var{group} inside the parentheses
19730 may repeat one or more times.
19733 @code{"@var{string}"} means a literal @var{string}.
19737 @heading Dependencies
19741 * GDB/MI General Design::
19742 * GDB/MI Command Syntax::
19743 * GDB/MI Compatibility with CLI::
19744 * GDB/MI Development and Front Ends::
19745 * GDB/MI Output Records::
19746 * GDB/MI Simple Examples::
19747 * GDB/MI Command Description Format::
19748 * GDB/MI Breakpoint Commands::
19749 * GDB/MI Program Context::
19750 * GDB/MI Thread Commands::
19751 * GDB/MI Program Execution::
19752 * GDB/MI Stack Manipulation::
19753 * GDB/MI Variable Objects::
19754 * GDB/MI Data Manipulation::
19755 * GDB/MI Tracepoint Commands::
19756 * GDB/MI Symbol Query::
19757 * GDB/MI File Commands::
19759 * GDB/MI Kod Commands::
19760 * GDB/MI Memory Overlay Commands::
19761 * GDB/MI Signal Handling Commands::
19763 * GDB/MI Target Manipulation::
19764 * GDB/MI File Transfer Commands::
19765 * GDB/MI Miscellaneous Commands::
19768 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19769 @node GDB/MI General Design
19770 @section @sc{gdb/mi} General Design
19771 @cindex GDB/MI General Design
19773 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
19774 parts---commands sent to @value{GDBN}, responses to those commands
19775 and notifications. Each command results in exactly one response,
19776 indicating either successful completion of the command, or an error.
19777 For the commands that do not resume the target, the response contains the
19778 requested information. For the commands that resume the target, the
19779 response only indicates whether the target was successfully resumed.
19780 Notifications is the mechanism for reporting changes in the state of the
19781 target, or in @value{GDBN} state, that cannot conveniently be associated with
19782 a command and reported as part of that command response.
19784 The important examples of notifications are:
19788 Exec notifications. These are used to report changes in
19789 target state---when a target is resumed, or stopped. It would not
19790 be feasible to include this information in response of resuming
19791 commands, because one resume commands can result in multiple events in
19792 different threads. Also, quite some time may pass before any event
19793 happens in the target, while a frontend needs to know whether the resuming
19794 command itself was successfully executed.
19797 Console output, and status notifications. Console output
19798 notifications are used to report output of CLI commands, as well as
19799 diagnostics for other commands. Status notifications are used to
19800 report the progress of a long-running operation. Naturally, including
19801 this information in command response would mean no output is produced
19802 until the command is finished, which is undesirable.
19805 General notifications. Commands may have various side effects on
19806 the @value{GDBN} or target state beyond their official purpose. For example,
19807 a command may change the selected thread. Although such changes can
19808 be included in command response, using notification allows for more
19809 orthogonal frontend design.
19813 There's no guarantee that whenever an MI command reports an error,
19814 @value{GDBN} or the target are in any specific state, and especially,
19815 the state is not reverted to the state before the MI command was
19816 processed. Therefore, whenever an MI command results in an error,
19817 we recommend that the frontend refreshes all the information shown in
19818 the user interface.
19820 @subsection Context management
19822 In most cases when @value{GDBN} accesses the target, this access is
19823 done in context of a specific thread and frame (@pxref{Frames}).
19824 Often, even when accessing global data, the target requires that a thread
19825 be specified. The CLI interface maintains the selected thread and frame,
19826 and supplies them to target on each command. This is convenient,
19827 because a command line user would not want to specify that information
19828 explicitly on each command, and because user interacts with
19829 @value{GDBN} via a single terminal, so no confusion is possible as
19830 to what thread and frame are the current ones.
19832 In the case of MI, the concept of selected thread and frame is less
19833 useful. First, a frontend can easily remember this information
19834 itself. Second, a graphical frontend can have more than one window,
19835 each one used for debugging a different thread, and the frontend might
19836 want to access additional threads for internal purposes. This
19837 increases the risk that by relying on implicitly selected thread, the
19838 frontend may be operating on a wrong one. Therefore, each MI command
19839 should explicitly specify which thread and frame to operate on. To
19840 make it possible, each MI command accepts the @samp{--thread} and
19841 @samp{--frame} options, the value to each is @value{GDBN} identifier
19842 for thread and frame to operate on.
19844 Usually, each top-level window in a frontend allows the user to select
19845 a thread and a frame, and remembers the user selection for further
19846 operations. However, in some cases @value{GDBN} may suggest that the
19847 current thread be changed. For example, when stopping on a breakpoint
19848 it is reasonable to switch to the thread where breakpoint is hit. For
19849 another example, if the user issues the CLI @samp{thread} command via
19850 the frontend, it is desirable to change the frontend's selected thread to the
19851 one specified by user. @value{GDBN} communicates the suggestion to
19852 change current thread using the @samp{=thread-selected} notification.
19853 No such notification is available for the selected frame at the moment.
19855 Note that historically, MI shares the selected thread with CLI, so
19856 frontends used the @code{-thread-select} to execute commands in the
19857 right context. However, getting this to work right is cumbersome. The
19858 simplest way is for frontend to emit @code{-thread-select} command
19859 before every command. This doubles the number of commands that need
19860 to be sent. The alternative approach is to suppress @code{-thread-select}
19861 if the selected thread in @value{GDBN} is supposed to be identical to the
19862 thread the frontend wants to operate on. However, getting this
19863 optimization right can be tricky. In particular, if the frontend
19864 sends several commands to @value{GDBN}, and one of the commands changes the
19865 selected thread, then the behaviour of subsequent commands will
19866 change. So, a frontend should either wait for response from such
19867 problematic commands, or explicitly add @code{-thread-select} for
19868 all subsequent commands. No frontend is known to do this exactly
19869 right, so it is suggested to just always pass the @samp{--thread} and
19870 @samp{--frame} options.
19872 @subsection Asynchronous command execution and non-stop mode
19874 On some targets, @value{GDBN} is capable of processing MI commands
19875 even while the target is running. This is called @dfn{asynchronous
19876 command execution} (@pxref{Background Execution}). The frontend may
19877 specify a preferrence for asynchronous execution using the
19878 @code{-gdb-set target-async 1} command, which should be emitted before
19879 either running the executable or attaching to the target. After the
19880 frontend has started the executable or attached to the target, it can
19881 find if asynchronous execution is enabled using the
19882 @code{-list-target-features} command.
19884 Even if @value{GDBN} can accept a command while target is running,
19885 many commands that access the target do not work when the target is
19886 running. Therefore, asynchronous command execution is most useful
19887 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19888 it is possible to examine the state of one thread, while other threads
19891 When a given thread is running, MI commands that try to access the
19892 target in the context of that thread may not work, or may work only on
19893 some targets. In particular, commands that try to operate on thread's
19894 stack will not work, on any target. Commands that read memory, or
19895 modify breakpoints, may work or not work, depending on the target. Note
19896 that even commands that operate on global state, such as @code{print},
19897 @code{set}, and breakpoint commands, still access the target in the
19898 context of a specific thread, so frontend should try to find a
19899 stopped thread and perform the operation on that thread (using the
19900 @samp{--thread} option).
19902 Which commands will work in the context of a running thread is
19903 highly target dependent. However, the two commands
19904 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19905 to find the state of a thread, will always work.
19907 @subsection Thread groups
19908 @value{GDBN} may be used to debug several processes at the same time.
19909 On some platfroms, @value{GDBN} may support debugging of several
19910 hardware systems, each one having several cores with several different
19911 processes running on each core. This section describes the MI
19912 mechanism to support such debugging scenarios.
19914 The key observation is that regardless of the structure of the
19915 target, MI can have a global list of threads, because most commands that
19916 accept the @samp{--thread} option do not need to know what process that
19917 thread belongs to. Therefore, it is not necessary to introduce
19918 neither additional @samp{--process} option, nor an notion of the
19919 current process in the MI interface. The only strictly new feature
19920 that is required is the ability to find how the threads are grouped
19923 To allow the user to discover such grouping, and to support arbitrary
19924 hierarchy of machines/cores/processes, MI introduces the concept of a
19925 @dfn{thread group}. Thread group is a collection of threads and other
19926 thread groups. A thread group always has a string identifier, a type,
19927 and may have additional attributes specific to the type. A new
19928 command, @code{-list-thread-groups}, returns the list of top-level
19929 thread groups, which correspond to processes that @value{GDBN} is
19930 debugging at the moment. By passing an identifier of a thread group
19931 to the @code{-list-thread-groups} command, it is possible to obtain
19932 the members of specific thread group.
19934 To allow the user to easily discover processes, and other objects, he
19935 wishes to debug, a concept of @dfn{available thread group} is
19936 introduced. Available thread group is an thread group that
19937 @value{GDBN} is not debugging, but that can be attached to, using the
19938 @code{-target-attach} command. The list of available top-level thread
19939 groups can be obtained using @samp{-list-thread-groups --available}.
19940 In general, the content of a thread group may be only retrieved only
19941 after attaching to that thread group.
19943 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19944 @node GDB/MI Command Syntax
19945 @section @sc{gdb/mi} Command Syntax
19948 * GDB/MI Input Syntax::
19949 * GDB/MI Output Syntax::
19952 @node GDB/MI Input Syntax
19953 @subsection @sc{gdb/mi} Input Syntax
19955 @cindex input syntax for @sc{gdb/mi}
19956 @cindex @sc{gdb/mi}, input syntax
19958 @item @var{command} @expansion{}
19959 @code{@var{cli-command} | @var{mi-command}}
19961 @item @var{cli-command} @expansion{}
19962 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19963 @var{cli-command} is any existing @value{GDBN} CLI command.
19965 @item @var{mi-command} @expansion{}
19966 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19967 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19969 @item @var{token} @expansion{}
19970 "any sequence of digits"
19972 @item @var{option} @expansion{}
19973 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19975 @item @var{parameter} @expansion{}
19976 @code{@var{non-blank-sequence} | @var{c-string}}
19978 @item @var{operation} @expansion{}
19979 @emph{any of the operations described in this chapter}
19981 @item @var{non-blank-sequence} @expansion{}
19982 @emph{anything, provided it doesn't contain special characters such as
19983 "-", @var{nl}, """ and of course " "}
19985 @item @var{c-string} @expansion{}
19986 @code{""" @var{seven-bit-iso-c-string-content} """}
19988 @item @var{nl} @expansion{}
19997 The CLI commands are still handled by the @sc{mi} interpreter; their
19998 output is described below.
20001 The @code{@var{token}}, when present, is passed back when the command
20005 Some @sc{mi} commands accept optional arguments as part of the parameter
20006 list. Each option is identified by a leading @samp{-} (dash) and may be
20007 followed by an optional argument parameter. Options occur first in the
20008 parameter list and can be delimited from normal parameters using
20009 @samp{--} (this is useful when some parameters begin with a dash).
20016 We want easy access to the existing CLI syntax (for debugging).
20019 We want it to be easy to spot a @sc{mi} operation.
20022 @node GDB/MI Output Syntax
20023 @subsection @sc{gdb/mi} Output Syntax
20025 @cindex output syntax of @sc{gdb/mi}
20026 @cindex @sc{gdb/mi}, output syntax
20027 The output from @sc{gdb/mi} consists of zero or more out-of-band records
20028 followed, optionally, by a single result record. This result record
20029 is for the most recent command. The sequence of output records is
20030 terminated by @samp{(gdb)}.
20032 If an input command was prefixed with a @code{@var{token}} then the
20033 corresponding output for that command will also be prefixed by that same
20037 @item @var{output} @expansion{}
20038 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
20040 @item @var{result-record} @expansion{}
20041 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
20043 @item @var{out-of-band-record} @expansion{}
20044 @code{@var{async-record} | @var{stream-record}}
20046 @item @var{async-record} @expansion{}
20047 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
20049 @item @var{exec-async-output} @expansion{}
20050 @code{[ @var{token} ] "*" @var{async-output}}
20052 @item @var{status-async-output} @expansion{}
20053 @code{[ @var{token} ] "+" @var{async-output}}
20055 @item @var{notify-async-output} @expansion{}
20056 @code{[ @var{token} ] "=" @var{async-output}}
20058 @item @var{async-output} @expansion{}
20059 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
20061 @item @var{result-class} @expansion{}
20062 @code{"done" | "running" | "connected" | "error" | "exit"}
20064 @item @var{async-class} @expansion{}
20065 @code{"stopped" | @var{others}} (where @var{others} will be added
20066 depending on the needs---this is still in development).
20068 @item @var{result} @expansion{}
20069 @code{ @var{variable} "=" @var{value}}
20071 @item @var{variable} @expansion{}
20072 @code{ @var{string} }
20074 @item @var{value} @expansion{}
20075 @code{ @var{const} | @var{tuple} | @var{list} }
20077 @item @var{const} @expansion{}
20078 @code{@var{c-string}}
20080 @item @var{tuple} @expansion{}
20081 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
20083 @item @var{list} @expansion{}
20084 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
20085 @var{result} ( "," @var{result} )* "]" }
20087 @item @var{stream-record} @expansion{}
20088 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
20090 @item @var{console-stream-output} @expansion{}
20091 @code{"~" @var{c-string}}
20093 @item @var{target-stream-output} @expansion{}
20094 @code{"@@" @var{c-string}}
20096 @item @var{log-stream-output} @expansion{}
20097 @code{"&" @var{c-string}}
20099 @item @var{nl} @expansion{}
20102 @item @var{token} @expansion{}
20103 @emph{any sequence of digits}.
20111 All output sequences end in a single line containing a period.
20114 The @code{@var{token}} is from the corresponding request. Note that
20115 for all async output, while the token is allowed by the grammar and
20116 may be output by future versions of @value{GDBN} for select async
20117 output messages, it is generally omitted. Frontends should treat
20118 all async output as reporting general changes in the state of the
20119 target and there should be no need to associate async output to any
20123 @cindex status output in @sc{gdb/mi}
20124 @var{status-async-output} contains on-going status information about the
20125 progress of a slow operation. It can be discarded. All status output is
20126 prefixed by @samp{+}.
20129 @cindex async output in @sc{gdb/mi}
20130 @var{exec-async-output} contains asynchronous state change on the target
20131 (stopped, started, disappeared). All async output is prefixed by
20135 @cindex notify output in @sc{gdb/mi}
20136 @var{notify-async-output} contains supplementary information that the
20137 client should handle (e.g., a new breakpoint information). All notify
20138 output is prefixed by @samp{=}.
20141 @cindex console output in @sc{gdb/mi}
20142 @var{console-stream-output} is output that should be displayed as is in the
20143 console. It is the textual response to a CLI command. All the console
20144 output is prefixed by @samp{~}.
20147 @cindex target output in @sc{gdb/mi}
20148 @var{target-stream-output} is the output produced by the target program.
20149 All the target output is prefixed by @samp{@@}.
20152 @cindex log output in @sc{gdb/mi}
20153 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
20154 instance messages that should be displayed as part of an error log. All
20155 the log output is prefixed by @samp{&}.
20158 @cindex list output in @sc{gdb/mi}
20159 New @sc{gdb/mi} commands should only output @var{lists} containing
20165 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
20166 details about the various output records.
20168 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20169 @node GDB/MI Compatibility with CLI
20170 @section @sc{gdb/mi} Compatibility with CLI
20172 @cindex compatibility, @sc{gdb/mi} and CLI
20173 @cindex @sc{gdb/mi}, compatibility with CLI
20175 For the developers convenience CLI commands can be entered directly,
20176 but there may be some unexpected behaviour. For example, commands
20177 that query the user will behave as if the user replied yes, breakpoint
20178 command lists are not executed and some CLI commands, such as
20179 @code{if}, @code{when} and @code{define}, prompt for further input with
20180 @samp{>}, which is not valid MI output.
20182 This feature may be removed at some stage in the future and it is
20183 recommended that front ends use the @code{-interpreter-exec} command
20184 (@pxref{-interpreter-exec}).
20186 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20187 @node GDB/MI Development and Front Ends
20188 @section @sc{gdb/mi} Development and Front Ends
20189 @cindex @sc{gdb/mi} development
20191 The application which takes the MI output and presents the state of the
20192 program being debugged to the user is called a @dfn{front end}.
20194 Although @sc{gdb/mi} is still incomplete, it is currently being used
20195 by a variety of front ends to @value{GDBN}. This makes it difficult
20196 to introduce new functionality without breaking existing usage. This
20197 section tries to minimize the problems by describing how the protocol
20200 Some changes in MI need not break a carefully designed front end, and
20201 for these the MI version will remain unchanged. The following is a
20202 list of changes that may occur within one level, so front ends should
20203 parse MI output in a way that can handle them:
20207 New MI commands may be added.
20210 New fields may be added to the output of any MI command.
20213 The range of values for fields with specified values, e.g.,
20214 @code{in_scope} (@pxref{-var-update}) may be extended.
20216 @c The format of field's content e.g type prefix, may change so parse it
20217 @c at your own risk. Yes, in general?
20219 @c The order of fields may change? Shouldn't really matter but it might
20220 @c resolve inconsistencies.
20223 If the changes are likely to break front ends, the MI version level
20224 will be increased by one. This will allow the front end to parse the
20225 output according to the MI version. Apart from mi0, new versions of
20226 @value{GDBN} will not support old versions of MI and it will be the
20227 responsibility of the front end to work with the new one.
20229 @c Starting with mi3, add a new command -mi-version that prints the MI
20232 The best way to avoid unexpected changes in MI that might break your front
20233 end is to make your project known to @value{GDBN} developers and
20234 follow development on @email{gdb@@sourceware.org} and
20235 @email{gdb-patches@@sourceware.org}.
20236 @cindex mailing lists
20238 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20239 @node GDB/MI Output Records
20240 @section @sc{gdb/mi} Output Records
20243 * GDB/MI Result Records::
20244 * GDB/MI Stream Records::
20245 * GDB/MI Async Records::
20246 * GDB/MI Frame Information::
20249 @node GDB/MI Result Records
20250 @subsection @sc{gdb/mi} Result Records
20252 @cindex result records in @sc{gdb/mi}
20253 @cindex @sc{gdb/mi}, result records
20254 In addition to a number of out-of-band notifications, the response to a
20255 @sc{gdb/mi} command includes one of the following result indications:
20259 @item "^done" [ "," @var{results} ]
20260 The synchronous operation was successful, @code{@var{results}} are the return
20265 @c Is this one correct? Should it be an out-of-band notification?
20266 The asynchronous operation was successfully started. The target is
20271 @value{GDBN} has connected to a remote target.
20273 @item "^error" "," @var{c-string}
20275 The operation failed. The @code{@var{c-string}} contains the corresponding
20280 @value{GDBN} has terminated.
20284 @node GDB/MI Stream Records
20285 @subsection @sc{gdb/mi} Stream Records
20287 @cindex @sc{gdb/mi}, stream records
20288 @cindex stream records in @sc{gdb/mi}
20289 @value{GDBN} internally maintains a number of output streams: the console, the
20290 target, and the log. The output intended for each of these streams is
20291 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
20293 Each stream record begins with a unique @dfn{prefix character} which
20294 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
20295 Syntax}). In addition to the prefix, each stream record contains a
20296 @code{@var{string-output}}. This is either raw text (with an implicit new
20297 line) or a quoted C string (which does not contain an implicit newline).
20300 @item "~" @var{string-output}
20301 The console output stream contains text that should be displayed in the
20302 CLI console window. It contains the textual responses to CLI commands.
20304 @item "@@" @var{string-output}
20305 The target output stream contains any textual output from the running
20306 target. This is only present when GDB's event loop is truly
20307 asynchronous, which is currently only the case for remote targets.
20309 @item "&" @var{string-output}
20310 The log stream contains debugging messages being produced by @value{GDBN}'s
20314 @node GDB/MI Async Records
20315 @subsection @sc{gdb/mi} Async Records
20317 @cindex async records in @sc{gdb/mi}
20318 @cindex @sc{gdb/mi}, async records
20319 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
20320 additional changes that have occurred. Those changes can either be a
20321 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
20322 target activity (e.g., target stopped).
20324 The following is the list of possible async records:
20328 @item *running,thread-id="@var{thread}"
20329 The target is now running. The @var{thread} field tells which
20330 specific thread is now running, and can be @samp{all} if all threads
20331 are running. The frontend should assume that no interaction with a
20332 running thread is possible after this notification is produced.
20333 The frontend should not assume that this notification is output
20334 only once for any command. @value{GDBN} may emit this notification
20335 several times, either for different threads, because it cannot resume
20336 all threads together, or even for a single thread, if the thread must
20337 be stepped though some code before letting it run freely.
20339 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
20340 The target has stopped. The @var{reason} field can have one of the
20344 @item breakpoint-hit
20345 A breakpoint was reached.
20346 @item watchpoint-trigger
20347 A watchpoint was triggered.
20348 @item read-watchpoint-trigger
20349 A read watchpoint was triggered.
20350 @item access-watchpoint-trigger
20351 An access watchpoint was triggered.
20352 @item function-finished
20353 An -exec-finish or similar CLI command was accomplished.
20354 @item location-reached
20355 An -exec-until or similar CLI command was accomplished.
20356 @item watchpoint-scope
20357 A watchpoint has gone out of scope.
20358 @item end-stepping-range
20359 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
20360 similar CLI command was accomplished.
20361 @item exited-signalled
20362 The inferior exited because of a signal.
20364 The inferior exited.
20365 @item exited-normally
20366 The inferior exited normally.
20367 @item signal-received
20368 A signal was received by the inferior.
20371 The @var{id} field identifies the thread that directly caused the stop
20372 -- for example by hitting a breakpoint. Depending on whether all-stop
20373 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
20374 stop all threads, or only the thread that directly triggered the stop.
20375 If all threads are stopped, the @var{stopped} field will have the
20376 value of @code{"all"}. Otherwise, the value of the @var{stopped}
20377 field will be a list of thread identifiers. Presently, this list will
20378 always include a single thread, but frontend should be prepared to see
20379 several threads in the list.
20381 @item =thread-group-created,id="@var{id}"
20382 @itemx =thread-group-exited,id="@var{id}"
20383 A thread thread group either was attached to, or has exited/detached
20384 from. The @var{id} field contains the @value{GDBN} identifier of the
20387 @item =thread-created,id="@var{id}",group-id="@var{gid}"
20388 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
20389 A thread either was created, or has exited. The @var{id} field
20390 contains the @value{GDBN} identifier of the thread. The @var{gid}
20391 field identifies the thread group this thread belongs to.
20393 @item =thread-selected,id="@var{id}"
20394 Informs that the selected thread was changed as result of the last
20395 command. This notification is not emitted as result of @code{-thread-select}
20396 command but is emitted whenever an MI command that is not documented
20397 to change the selected thread actually changes it. In particular,
20398 invoking, directly or indirectly (via user-defined command), the CLI
20399 @code{thread} command, will generate this notification.
20401 We suggest that in response to this notification, front ends
20402 highlight the selected thread and cause subsequent commands to apply to
20405 @item =library-loaded,...
20406 Reports that a new library file was loaded by the program. This
20407 notification has 4 fields---@var{id}, @var{target-name},
20408 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
20409 opaque identifier of the library. For remote debugging case,
20410 @var{target-name} and @var{host-name} fields give the name of the
20411 library file on the target, and on the host respectively. For native
20412 debugging, both those fields have the same value. The
20413 @var{symbols-loaded} field reports if the debug symbols for this
20414 library are loaded.
20416 @item =library-unloaded,...
20417 Reports that a library was unloaded by the program. This notification
20418 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
20419 the same meaning as for the @code{=library-loaded} notification
20423 @node GDB/MI Frame Information
20424 @subsection @sc{gdb/mi} Frame Information
20426 Response from many MI commands includes an information about stack
20427 frame. This information is a tuple that may have the following
20432 The level of the stack frame. The innermost frame has the level of
20433 zero. This field is always present.
20436 The name of the function corresponding to the frame. This field may
20437 be absent if @value{GDBN} is unable to determine the function name.
20440 The code address for the frame. This field is always present.
20443 The name of the source files that correspond to the frame's code
20444 address. This field may be absent.
20447 The source line corresponding to the frames' code address. This field
20451 The name of the binary file (either executable or shared library) the
20452 corresponds to the frame's code address. This field may be absent.
20457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20458 @node GDB/MI Simple Examples
20459 @section Simple Examples of @sc{gdb/mi} Interaction
20460 @cindex @sc{gdb/mi}, simple examples
20462 This subsection presents several simple examples of interaction using
20463 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
20464 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
20465 the output received from @sc{gdb/mi}.
20467 Note the line breaks shown in the examples are here only for
20468 readability, they don't appear in the real output.
20470 @subheading Setting a Breakpoint
20472 Setting a breakpoint generates synchronous output which contains detailed
20473 information of the breakpoint.
20476 -> -break-insert main
20477 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20478 enabled="y",addr="0x08048564",func="main",file="myprog.c",
20479 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
20483 @subheading Program Execution
20485 Program execution generates asynchronous records and MI gives the
20486 reason that execution stopped.
20492 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
20493 frame=@{addr="0x08048564",func="main",
20494 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
20495 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
20500 <- *stopped,reason="exited-normally"
20504 @subheading Quitting @value{GDBN}
20506 Quitting @value{GDBN} just prints the result class @samp{^exit}.
20514 @subheading A Bad Command
20516 Here's what happens if you pass a non-existent command:
20520 <- ^error,msg="Undefined MI command: rubbish"
20525 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20526 @node GDB/MI Command Description Format
20527 @section @sc{gdb/mi} Command Description Format
20529 The remaining sections describe blocks of commands. Each block of
20530 commands is laid out in a fashion similar to this section.
20532 @subheading Motivation
20534 The motivation for this collection of commands.
20536 @subheading Introduction
20538 A brief introduction to this collection of commands as a whole.
20540 @subheading Commands
20542 For each command in the block, the following is described:
20544 @subsubheading Synopsis
20547 -command @var{args}@dots{}
20550 @subsubheading Result
20552 @subsubheading @value{GDBN} Command
20554 The corresponding @value{GDBN} CLI command(s), if any.
20556 @subsubheading Example
20558 Example(s) formatted for readability. Some of the described commands have
20559 not been implemented yet and these are labeled N.A.@: (not available).
20562 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20563 @node GDB/MI Breakpoint Commands
20564 @section @sc{gdb/mi} Breakpoint Commands
20566 @cindex breakpoint commands for @sc{gdb/mi}
20567 @cindex @sc{gdb/mi}, breakpoint commands
20568 This section documents @sc{gdb/mi} commands for manipulating
20571 @subheading The @code{-break-after} Command
20572 @findex -break-after
20574 @subsubheading Synopsis
20577 -break-after @var{number} @var{count}
20580 The breakpoint number @var{number} is not in effect until it has been
20581 hit @var{count} times. To see how this is reflected in the output of
20582 the @samp{-break-list} command, see the description of the
20583 @samp{-break-list} command below.
20585 @subsubheading @value{GDBN} Command
20587 The corresponding @value{GDBN} command is @samp{ignore}.
20589 @subsubheading Example
20594 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20595 enabled="y",addr="0x000100d0",func="main",file="hello.c",
20596 fullname="/home/foo/hello.c",line="5",times="0"@}
20603 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20604 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20605 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20606 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20607 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20608 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20609 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20610 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20611 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20612 line="5",times="0",ignore="3"@}]@}
20617 @subheading The @code{-break-catch} Command
20618 @findex -break-catch
20620 @subheading The @code{-break-commands} Command
20621 @findex -break-commands
20625 @subheading The @code{-break-condition} Command
20626 @findex -break-condition
20628 @subsubheading Synopsis
20631 -break-condition @var{number} @var{expr}
20634 Breakpoint @var{number} will stop the program only if the condition in
20635 @var{expr} is true. The condition becomes part of the
20636 @samp{-break-list} output (see the description of the @samp{-break-list}
20639 @subsubheading @value{GDBN} Command
20641 The corresponding @value{GDBN} command is @samp{condition}.
20643 @subsubheading Example
20647 -break-condition 1 1
20651 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20652 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20653 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20654 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20655 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20656 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20657 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20658 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20659 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20660 line="5",cond="1",times="0",ignore="3"@}]@}
20664 @subheading The @code{-break-delete} Command
20665 @findex -break-delete
20667 @subsubheading Synopsis
20670 -break-delete ( @var{breakpoint} )+
20673 Delete the breakpoint(s) whose number(s) are specified in the argument
20674 list. This is obviously reflected in the breakpoint list.
20676 @subsubheading @value{GDBN} Command
20678 The corresponding @value{GDBN} command is @samp{delete}.
20680 @subsubheading Example
20688 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20689 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20690 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20691 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20692 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20693 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20694 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20699 @subheading The @code{-break-disable} Command
20700 @findex -break-disable
20702 @subsubheading Synopsis
20705 -break-disable ( @var{breakpoint} )+
20708 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
20709 break list is now set to @samp{n} for the named @var{breakpoint}(s).
20711 @subsubheading @value{GDBN} Command
20713 The corresponding @value{GDBN} command is @samp{disable}.
20715 @subsubheading Example
20723 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20724 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20725 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20726 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20727 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20728 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20729 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20730 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
20731 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20732 line="5",times="0"@}]@}
20736 @subheading The @code{-break-enable} Command
20737 @findex -break-enable
20739 @subsubheading Synopsis
20742 -break-enable ( @var{breakpoint} )+
20745 Enable (previously disabled) @var{breakpoint}(s).
20747 @subsubheading @value{GDBN} Command
20749 The corresponding @value{GDBN} command is @samp{enable}.
20751 @subsubheading Example
20759 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20760 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20761 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20762 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20763 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20764 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20765 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20766 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20767 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20768 line="5",times="0"@}]@}
20772 @subheading The @code{-break-info} Command
20773 @findex -break-info
20775 @subsubheading Synopsis
20778 -break-info @var{breakpoint}
20782 Get information about a single breakpoint.
20784 @subsubheading @value{GDBN} Command
20786 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
20788 @subsubheading Example
20791 @subheading The @code{-break-insert} Command
20792 @findex -break-insert
20794 @subsubheading Synopsis
20797 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
20798 [ -c @var{condition} ] [ -i @var{ignore-count} ]
20799 [ -p @var{thread} ] [ @var{location} ]
20803 If specified, @var{location}, can be one of:
20810 @item filename:linenum
20811 @item filename:function
20815 The possible optional parameters of this command are:
20819 Insert a temporary breakpoint.
20821 Insert a hardware breakpoint.
20822 @item -c @var{condition}
20823 Make the breakpoint conditional on @var{condition}.
20824 @item -i @var{ignore-count}
20825 Initialize the @var{ignore-count}.
20827 If @var{location} cannot be parsed (for example if it
20828 refers to unknown files or functions), create a pending
20829 breakpoint. Without this flag, @value{GDBN} will report
20830 an error, and won't create a breakpoint, if @var{location}
20833 Create a disabled breakpoint.
20836 @subsubheading Result
20838 The result is in the form:
20841 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
20842 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
20843 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
20844 times="@var{times}"@}
20848 where @var{number} is the @value{GDBN} number for this breakpoint,
20849 @var{funcname} is the name of the function where the breakpoint was
20850 inserted, @var{filename} is the name of the source file which contains
20851 this function, @var{lineno} is the source line number within that file
20852 and @var{times} the number of times that the breakpoint has been hit
20853 (always 0 for -break-insert but may be greater for -break-info or -break-list
20854 which use the same output).
20856 Note: this format is open to change.
20857 @c An out-of-band breakpoint instead of part of the result?
20859 @subsubheading @value{GDBN} Command
20861 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
20862 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
20864 @subsubheading Example
20869 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
20870 fullname="/home/foo/recursive2.c,line="4",times="0"@}
20872 -break-insert -t foo
20873 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
20874 fullname="/home/foo/recursive2.c,line="11",times="0"@}
20877 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20878 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20879 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20880 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20881 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20882 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20883 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20884 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20885 addr="0x0001072c", func="main",file="recursive2.c",
20886 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20887 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20888 addr="0x00010774",func="foo",file="recursive2.c",
20889 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20891 -break-insert -r foo.*
20892 ~int foo(int, int);
20893 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20894 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20898 @subheading The @code{-break-list} Command
20899 @findex -break-list
20901 @subsubheading Synopsis
20907 Displays the list of inserted breakpoints, showing the following fields:
20911 number of the breakpoint
20913 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20915 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20918 is the breakpoint enabled or no: @samp{y} or @samp{n}
20920 memory location at which the breakpoint is set
20922 logical location of the breakpoint, expressed by function name, file
20925 number of times the breakpoint has been hit
20928 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20929 @code{body} field is an empty list.
20931 @subsubheading @value{GDBN} Command
20933 The corresponding @value{GDBN} command is @samp{info break}.
20935 @subsubheading Example
20940 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20941 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20942 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20943 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20944 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20945 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20946 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20947 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20948 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20949 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20950 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20951 line="13",times="0"@}]@}
20955 Here's an example of the result when there are no breakpoints:
20960 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20961 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20962 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20963 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20964 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20965 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20966 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20971 @subheading The @code{-break-watch} Command
20972 @findex -break-watch
20974 @subsubheading Synopsis
20977 -break-watch [ -a | -r ]
20980 Create a watchpoint. With the @samp{-a} option it will create an
20981 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20982 read from or on a write to the memory location. With the @samp{-r}
20983 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
20984 trigger only when the memory location is accessed for reading. Without
20985 either of the options, the watchpoint created is a regular watchpoint,
20986 i.e., it will trigger when the memory location is accessed for writing.
20987 @xref{Set Watchpoints, , Setting Watchpoints}.
20989 Note that @samp{-break-list} will report a single list of watchpoints and
20990 breakpoints inserted.
20992 @subsubheading @value{GDBN} Command
20994 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
20997 @subsubheading Example
20999 Setting a watchpoint on a variable in the @code{main} function:
21004 ^done,wpt=@{number="2",exp="x"@}
21009 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
21010 value=@{old="-268439212",new="55"@},
21011 frame=@{func="main",args=[],file="recursive2.c",
21012 fullname="/home/foo/bar/recursive2.c",line="5"@}
21016 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
21017 the program execution twice: first for the variable changing value, then
21018 for the watchpoint going out of scope.
21023 ^done,wpt=@{number="5",exp="C"@}
21028 *stopped,reason="watchpoint-trigger",
21029 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
21030 frame=@{func="callee4",args=[],
21031 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21032 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
21037 *stopped,reason="watchpoint-scope",wpnum="5",
21038 frame=@{func="callee3",args=[@{name="strarg",
21039 value="0x11940 \"A string argument.\""@}],
21040 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21041 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21045 Listing breakpoints and watchpoints, at different points in the program
21046 execution. Note that once the watchpoint goes out of scope, it is
21052 ^done,wpt=@{number="2",exp="C"@}
21055 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
21056 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21057 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21058 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21059 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21060 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21061 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21062 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21063 addr="0x00010734",func="callee4",
21064 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21065 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
21066 bkpt=@{number="2",type="watchpoint",disp="keep",
21067 enabled="y",addr="",what="C",times="0"@}]@}
21072 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
21073 value=@{old="-276895068",new="3"@},
21074 frame=@{func="callee4",args=[],
21075 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21076 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
21079 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
21080 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21081 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21082 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21083 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21084 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21085 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21086 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21087 addr="0x00010734",func="callee4",
21088 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21089 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
21090 bkpt=@{number="2",type="watchpoint",disp="keep",
21091 enabled="y",addr="",what="C",times="-5"@}]@}
21095 ^done,reason="watchpoint-scope",wpnum="2",
21096 frame=@{func="callee3",args=[@{name="strarg",
21097 value="0x11940 \"A string argument.\""@}],
21098 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21099 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21102 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21103 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21104 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21105 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21106 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21107 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21108 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21109 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21110 addr="0x00010734",func="callee4",
21111 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21112 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
21117 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21118 @node GDB/MI Program Context
21119 @section @sc{gdb/mi} Program Context
21121 @subheading The @code{-exec-arguments} Command
21122 @findex -exec-arguments
21125 @subsubheading Synopsis
21128 -exec-arguments @var{args}
21131 Set the inferior program arguments, to be used in the next
21134 @subsubheading @value{GDBN} Command
21136 The corresponding @value{GDBN} command is @samp{set args}.
21138 @subsubheading Example
21142 -exec-arguments -v word
21148 @subheading The @code{-exec-show-arguments} Command
21149 @findex -exec-show-arguments
21151 @subsubheading Synopsis
21154 -exec-show-arguments
21157 Print the arguments of the program.
21159 @subsubheading @value{GDBN} Command
21161 The corresponding @value{GDBN} command is @samp{show args}.
21163 @subsubheading Example
21167 @subheading The @code{-environment-cd} Command
21168 @findex -environment-cd
21170 @subsubheading Synopsis
21173 -environment-cd @var{pathdir}
21176 Set @value{GDBN}'s working directory.
21178 @subsubheading @value{GDBN} Command
21180 The corresponding @value{GDBN} command is @samp{cd}.
21182 @subsubheading Example
21186 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
21192 @subheading The @code{-environment-directory} Command
21193 @findex -environment-directory
21195 @subsubheading Synopsis
21198 -environment-directory [ -r ] [ @var{pathdir} ]+
21201 Add directories @var{pathdir} to beginning of search path for source files.
21202 If the @samp{-r} option is used, the search path is reset to the default
21203 search path. If directories @var{pathdir} are supplied in addition to the
21204 @samp{-r} option, the search path is first reset and then addition
21206 Multiple directories may be specified, separated by blanks. Specifying
21207 multiple directories in a single command
21208 results in the directories added to the beginning of the
21209 search path in the same order they were presented in the command.
21210 If blanks are needed as
21211 part of a directory name, double-quotes should be used around
21212 the name. In the command output, the path will show up separated
21213 by the system directory-separator character. The directory-separator
21214 character must not be used
21215 in any directory name.
21216 If no directories are specified, the current search path is displayed.
21218 @subsubheading @value{GDBN} Command
21220 The corresponding @value{GDBN} command is @samp{dir}.
21222 @subsubheading Example
21226 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
21227 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21229 -environment-directory ""
21230 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21232 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
21233 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
21235 -environment-directory -r
21236 ^done,source-path="$cdir:$cwd"
21241 @subheading The @code{-environment-path} Command
21242 @findex -environment-path
21244 @subsubheading Synopsis
21247 -environment-path [ -r ] [ @var{pathdir} ]+
21250 Add directories @var{pathdir} to beginning of search path for object files.
21251 If the @samp{-r} option is used, the search path is reset to the original
21252 search path that existed at gdb start-up. If directories @var{pathdir} are
21253 supplied in addition to the
21254 @samp{-r} option, the search path is first reset and then addition
21256 Multiple directories may be specified, separated by blanks. Specifying
21257 multiple directories in a single command
21258 results in the directories added to the beginning of the
21259 search path in the same order they were presented in the command.
21260 If blanks are needed as
21261 part of a directory name, double-quotes should be used around
21262 the name. In the command output, the path will show up separated
21263 by the system directory-separator character. The directory-separator
21264 character must not be used
21265 in any directory name.
21266 If no directories are specified, the current path is displayed.
21269 @subsubheading @value{GDBN} Command
21271 The corresponding @value{GDBN} command is @samp{path}.
21273 @subsubheading Example
21278 ^done,path="/usr/bin"
21280 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
21281 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
21283 -environment-path -r /usr/local/bin
21284 ^done,path="/usr/local/bin:/usr/bin"
21289 @subheading The @code{-environment-pwd} Command
21290 @findex -environment-pwd
21292 @subsubheading Synopsis
21298 Show the current working directory.
21300 @subsubheading @value{GDBN} Command
21302 The corresponding @value{GDBN} command is @samp{pwd}.
21304 @subsubheading Example
21309 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
21313 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21314 @node GDB/MI Thread Commands
21315 @section @sc{gdb/mi} Thread Commands
21318 @subheading The @code{-thread-info} Command
21319 @findex -thread-info
21321 @subsubheading Synopsis
21324 -thread-info [ @var{thread-id} ]
21327 Reports information about either a specific thread, if
21328 the @var{thread-id} parameter is present, or about all
21329 threads. When printing information about all threads,
21330 also reports the current thread.
21332 @subsubheading @value{GDBN} Command
21334 The @samp{info thread} command prints the same information
21337 @subsubheading Example
21342 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
21343 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
21344 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
21345 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
21346 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
21347 current-thread-id="1"
21351 The @samp{state} field may have the following values:
21355 The thread is stopped. Frame information is available for stopped
21359 The thread is running. There's no frame information for running
21364 @subheading The @code{-thread-list-ids} Command
21365 @findex -thread-list-ids
21367 @subsubheading Synopsis
21373 Produces a list of the currently known @value{GDBN} thread ids. At the
21374 end of the list it also prints the total number of such threads.
21376 This command is retained for historical reasons, the
21377 @code{-thread-info} command should be used instead.
21379 @subsubheading @value{GDBN} Command
21381 Part of @samp{info threads} supplies the same information.
21383 @subsubheading Example
21388 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21389 current-thread-id="1",number-of-threads="3"
21394 @subheading The @code{-thread-select} Command
21395 @findex -thread-select
21397 @subsubheading Synopsis
21400 -thread-select @var{threadnum}
21403 Make @var{threadnum} the current thread. It prints the number of the new
21404 current thread, and the topmost frame for that thread.
21406 This command is deprecated in favor of explicitly using the
21407 @samp{--thread} option to each command.
21409 @subsubheading @value{GDBN} Command
21411 The corresponding @value{GDBN} command is @samp{thread}.
21413 @subsubheading Example
21420 *stopped,reason="end-stepping-range",thread-id="2",line="187",
21421 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
21425 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21426 number-of-threads="3"
21429 ^done,new-thread-id="3",
21430 frame=@{level="0",func="vprintf",
21431 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
21432 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
21436 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21437 @node GDB/MI Program Execution
21438 @section @sc{gdb/mi} Program Execution
21440 These are the asynchronous commands which generate the out-of-band
21441 record @samp{*stopped}. Currently @value{GDBN} only really executes
21442 asynchronously with remote targets and this interaction is mimicked in
21445 @subheading The @code{-exec-continue} Command
21446 @findex -exec-continue
21448 @subsubheading Synopsis
21451 -exec-continue [--all|--thread-group N]
21454 Resumes the execution of the inferior program until a breakpoint is
21455 encountered, or until the inferior exits. In all-stop mode
21456 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
21457 depending on the value of the @samp{scheduler-locking} variable. In
21458 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
21459 specified, only the thread specified with the @samp{--thread} option
21460 (or current thread, if no @samp{--thread} is provided) is resumed. If
21461 @samp{--all} is specified, all threads will be resumed. The
21462 @samp{--all} option is ignored in all-stop mode. If the
21463 @samp{--thread-group} options is specified, then all threads in that
21464 thread group are resumed.
21466 @subsubheading @value{GDBN} Command
21468 The corresponding @value{GDBN} corresponding is @samp{continue}.
21470 @subsubheading Example
21477 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
21478 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
21484 @subheading The @code{-exec-finish} Command
21485 @findex -exec-finish
21487 @subsubheading Synopsis
21493 Resumes the execution of the inferior program until the current
21494 function is exited. Displays the results returned by the function.
21496 @subsubheading @value{GDBN} Command
21498 The corresponding @value{GDBN} command is @samp{finish}.
21500 @subsubheading Example
21502 Function returning @code{void}.
21509 *stopped,reason="function-finished",frame=@{func="main",args=[],
21510 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
21514 Function returning other than @code{void}. The name of the internal
21515 @value{GDBN} variable storing the result is printed, together with the
21522 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
21523 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
21524 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21525 gdb-result-var="$1",return-value="0"
21530 @subheading The @code{-exec-interrupt} Command
21531 @findex -exec-interrupt
21533 @subsubheading Synopsis
21536 -exec-interrupt [--all|--thread-group N]
21539 Interrupts the background execution of the target. Note how the token
21540 associated with the stop message is the one for the execution command
21541 that has been interrupted. The token for the interrupt itself only
21542 appears in the @samp{^done} output. If the user is trying to
21543 interrupt a non-running program, an error message will be printed.
21545 Note that when asynchronous execution is enabled, this command is
21546 asynchronous just like other execution commands. That is, first the
21547 @samp{^done} response will be printed, and the target stop will be
21548 reported after that using the @samp{*stopped} notification.
21550 In non-stop mode, only the context thread is interrupted by default.
21551 All threads will be interrupted if the @samp{--all} option is
21552 specified. If the @samp{--thread-group} option is specified, all
21553 threads in that group will be interrupted.
21555 @subsubheading @value{GDBN} Command
21557 The corresponding @value{GDBN} command is @samp{interrupt}.
21559 @subsubheading Example
21570 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
21571 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
21572 fullname="/home/foo/bar/try.c",line="13"@}
21577 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
21581 @subheading The @code{-exec-jump} Command
21584 @subsubheading Synopsis
21587 -exec-jump @var{location}
21590 Resumes execution of the inferior program at the location specified by
21591 parameter. @xref{Specify Location}, for a description of the
21592 different forms of @var{location}.
21594 @subsubheading @value{GDBN} Command
21596 The corresponding @value{GDBN} command is @samp{jump}.
21598 @subsubheading Example
21601 -exec-jump foo.c:10
21602 *running,thread-id="all"
21607 @subheading The @code{-exec-next} Command
21610 @subsubheading Synopsis
21616 Resumes execution of the inferior program, stopping when the beginning
21617 of the next source line is reached.
21619 @subsubheading @value{GDBN} Command
21621 The corresponding @value{GDBN} command is @samp{next}.
21623 @subsubheading Example
21629 *stopped,reason="end-stepping-range",line="8",file="hello.c"
21634 @subheading The @code{-exec-next-instruction} Command
21635 @findex -exec-next-instruction
21637 @subsubheading Synopsis
21640 -exec-next-instruction
21643 Executes one machine instruction. If the instruction is a function
21644 call, continues until the function returns. If the program stops at an
21645 instruction in the middle of a source line, the address will be
21648 @subsubheading @value{GDBN} Command
21650 The corresponding @value{GDBN} command is @samp{nexti}.
21652 @subsubheading Example
21656 -exec-next-instruction
21660 *stopped,reason="end-stepping-range",
21661 addr="0x000100d4",line="5",file="hello.c"
21666 @subheading The @code{-exec-return} Command
21667 @findex -exec-return
21669 @subsubheading Synopsis
21675 Makes current function return immediately. Doesn't execute the inferior.
21676 Displays the new current frame.
21678 @subsubheading @value{GDBN} Command
21680 The corresponding @value{GDBN} command is @samp{return}.
21682 @subsubheading Example
21686 200-break-insert callee4
21687 200^done,bkpt=@{number="1",addr="0x00010734",
21688 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21693 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21694 frame=@{func="callee4",args=[],
21695 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21696 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21702 111^done,frame=@{level="0",func="callee3",
21703 args=[@{name="strarg",
21704 value="0x11940 \"A string argument.\""@}],
21705 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21706 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21711 @subheading The @code{-exec-run} Command
21714 @subsubheading Synopsis
21720 Starts execution of the inferior from the beginning. The inferior
21721 executes until either a breakpoint is encountered or the program
21722 exits. In the latter case the output will include an exit code, if
21723 the program has exited exceptionally.
21725 @subsubheading @value{GDBN} Command
21727 The corresponding @value{GDBN} command is @samp{run}.
21729 @subsubheading Examples
21734 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
21739 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21740 frame=@{func="main",args=[],file="recursive2.c",
21741 fullname="/home/foo/bar/recursive2.c",line="4"@}
21746 Program exited normally:
21754 *stopped,reason="exited-normally"
21759 Program exited exceptionally:
21767 *stopped,reason="exited",exit-code="01"
21771 Another way the program can terminate is if it receives a signal such as
21772 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
21776 *stopped,reason="exited-signalled",signal-name="SIGINT",
21777 signal-meaning="Interrupt"
21781 @c @subheading -exec-signal
21784 @subheading The @code{-exec-step} Command
21787 @subsubheading Synopsis
21793 Resumes execution of the inferior program, stopping when the beginning
21794 of the next source line is reached, if the next source line is not a
21795 function call. If it is, stop at the first instruction of the called
21798 @subsubheading @value{GDBN} Command
21800 The corresponding @value{GDBN} command is @samp{step}.
21802 @subsubheading Example
21804 Stepping into a function:
21810 *stopped,reason="end-stepping-range",
21811 frame=@{func="foo",args=[@{name="a",value="10"@},
21812 @{name="b",value="0"@}],file="recursive2.c",
21813 fullname="/home/foo/bar/recursive2.c",line="11"@}
21823 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
21828 @subheading The @code{-exec-step-instruction} Command
21829 @findex -exec-step-instruction
21831 @subsubheading Synopsis
21834 -exec-step-instruction
21837 Resumes the inferior which executes one machine instruction. The
21838 output, once @value{GDBN} has stopped, will vary depending on whether
21839 we have stopped in the middle of a source line or not. In the former
21840 case, the address at which the program stopped will be printed as
21843 @subsubheading @value{GDBN} Command
21845 The corresponding @value{GDBN} command is @samp{stepi}.
21847 @subsubheading Example
21851 -exec-step-instruction
21855 *stopped,reason="end-stepping-range",
21856 frame=@{func="foo",args=[],file="try.c",
21857 fullname="/home/foo/bar/try.c",line="10"@}
21859 -exec-step-instruction
21863 *stopped,reason="end-stepping-range",
21864 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
21865 fullname="/home/foo/bar/try.c",line="10"@}
21870 @subheading The @code{-exec-until} Command
21871 @findex -exec-until
21873 @subsubheading Synopsis
21876 -exec-until [ @var{location} ]
21879 Executes the inferior until the @var{location} specified in the
21880 argument is reached. If there is no argument, the inferior executes
21881 until a source line greater than the current one is reached. The
21882 reason for stopping in this case will be @samp{location-reached}.
21884 @subsubheading @value{GDBN} Command
21886 The corresponding @value{GDBN} command is @samp{until}.
21888 @subsubheading Example
21892 -exec-until recursive2.c:6
21896 *stopped,reason="location-reached",frame=@{func="main",args=[],
21897 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21902 @subheading -file-clear
21903 Is this going away????
21906 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21907 @node GDB/MI Stack Manipulation
21908 @section @sc{gdb/mi} Stack Manipulation Commands
21911 @subheading The @code{-stack-info-frame} Command
21912 @findex -stack-info-frame
21914 @subsubheading Synopsis
21920 Get info on the selected frame.
21922 @subsubheading @value{GDBN} Command
21924 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21925 (without arguments).
21927 @subsubheading Example
21932 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21933 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21934 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21938 @subheading The @code{-stack-info-depth} Command
21939 @findex -stack-info-depth
21941 @subsubheading Synopsis
21944 -stack-info-depth [ @var{max-depth} ]
21947 Return the depth of the stack. If the integer argument @var{max-depth}
21948 is specified, do not count beyond @var{max-depth} frames.
21950 @subsubheading @value{GDBN} Command
21952 There's no equivalent @value{GDBN} command.
21954 @subsubheading Example
21956 For a stack with frame levels 0 through 11:
21963 -stack-info-depth 4
21966 -stack-info-depth 12
21969 -stack-info-depth 11
21972 -stack-info-depth 13
21977 @subheading The @code{-stack-list-arguments} Command
21978 @findex -stack-list-arguments
21980 @subsubheading Synopsis
21983 -stack-list-arguments @var{show-values}
21984 [ @var{low-frame} @var{high-frame} ]
21987 Display a list of the arguments for the frames between @var{low-frame}
21988 and @var{high-frame} (inclusive). If @var{low-frame} and
21989 @var{high-frame} are not provided, list the arguments for the whole
21990 call stack. If the two arguments are equal, show the single frame
21991 at the corresponding level. It is an error if @var{low-frame} is
21992 larger than the actual number of frames. On the other hand,
21993 @var{high-frame} may be larger than the actual number of frames, in
21994 which case only existing frames will be returned.
21996 The @var{show-values} argument must have a value of 0 or 1. A value of
21997 0 means that only the names of the arguments are listed, a value of 1
21998 means that both names and values of the arguments are printed.
22000 @subsubheading @value{GDBN} Command
22002 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
22003 @samp{gdb_get_args} command which partially overlaps with the
22004 functionality of @samp{-stack-list-arguments}.
22006 @subsubheading Example
22013 frame=@{level="0",addr="0x00010734",func="callee4",
22014 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22015 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
22016 frame=@{level="1",addr="0x0001076c",func="callee3",
22017 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22018 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
22019 frame=@{level="2",addr="0x0001078c",func="callee2",
22020 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22021 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
22022 frame=@{level="3",addr="0x000107b4",func="callee1",
22023 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22024 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
22025 frame=@{level="4",addr="0x000107e0",func="main",
22026 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22027 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
22029 -stack-list-arguments 0
22032 frame=@{level="0",args=[]@},
22033 frame=@{level="1",args=[name="strarg"]@},
22034 frame=@{level="2",args=[name="intarg",name="strarg"]@},
22035 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
22036 frame=@{level="4",args=[]@}]
22038 -stack-list-arguments 1
22041 frame=@{level="0",args=[]@},
22043 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
22044 frame=@{level="2",args=[
22045 @{name="intarg",value="2"@},
22046 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
22047 @{frame=@{level="3",args=[
22048 @{name="intarg",value="2"@},
22049 @{name="strarg",value="0x11940 \"A string argument.\""@},
22050 @{name="fltarg",value="3.5"@}]@},
22051 frame=@{level="4",args=[]@}]
22053 -stack-list-arguments 0 2 2
22054 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
22056 -stack-list-arguments 1 2 2
22057 ^done,stack-args=[frame=@{level="2",
22058 args=[@{name="intarg",value="2"@},
22059 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
22063 @c @subheading -stack-list-exception-handlers
22066 @subheading The @code{-stack-list-frames} Command
22067 @findex -stack-list-frames
22069 @subsubheading Synopsis
22072 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
22075 List the frames currently on the stack. For each frame it displays the
22080 The frame number, 0 being the topmost frame, i.e., the innermost function.
22082 The @code{$pc} value for that frame.
22086 File name of the source file where the function lives.
22088 Line number corresponding to the @code{$pc}.
22091 If invoked without arguments, this command prints a backtrace for the
22092 whole stack. If given two integer arguments, it shows the frames whose
22093 levels are between the two arguments (inclusive). If the two arguments
22094 are equal, it shows the single frame at the corresponding level. It is
22095 an error if @var{low-frame} is larger than the actual number of
22096 frames. On the other hand, @var{high-frame} may be larger than the
22097 actual number of frames, in which case only existing frames will be returned.
22099 @subsubheading @value{GDBN} Command
22101 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
22103 @subsubheading Example
22105 Full stack backtrace:
22111 [frame=@{level="0",addr="0x0001076c",func="foo",
22112 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
22113 frame=@{level="1",addr="0x000107a4",func="foo",
22114 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22115 frame=@{level="2",addr="0x000107a4",func="foo",
22116 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22117 frame=@{level="3",addr="0x000107a4",func="foo",
22118 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22119 frame=@{level="4",addr="0x000107a4",func="foo",
22120 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22121 frame=@{level="5",addr="0x000107a4",func="foo",
22122 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22123 frame=@{level="6",addr="0x000107a4",func="foo",
22124 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22125 frame=@{level="7",addr="0x000107a4",func="foo",
22126 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22127 frame=@{level="8",addr="0x000107a4",func="foo",
22128 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22129 frame=@{level="9",addr="0x000107a4",func="foo",
22130 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22131 frame=@{level="10",addr="0x000107a4",func="foo",
22132 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22133 frame=@{level="11",addr="0x00010738",func="main",
22134 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
22138 Show frames between @var{low_frame} and @var{high_frame}:
22142 -stack-list-frames 3 5
22144 [frame=@{level="3",addr="0x000107a4",func="foo",
22145 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22146 frame=@{level="4",addr="0x000107a4",func="foo",
22147 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22148 frame=@{level="5",addr="0x000107a4",func="foo",
22149 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
22153 Show a single frame:
22157 -stack-list-frames 3 3
22159 [frame=@{level="3",addr="0x000107a4",func="foo",
22160 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
22165 @subheading The @code{-stack-list-locals} Command
22166 @findex -stack-list-locals
22168 @subsubheading Synopsis
22171 -stack-list-locals @var{print-values}
22174 Display the local variable names for the selected frame. If
22175 @var{print-values} is 0 or @code{--no-values}, print only the names of
22176 the variables; if it is 1 or @code{--all-values}, print also their
22177 values; and if it is 2 or @code{--simple-values}, print the name,
22178 type and value for simple data types and the name and type for arrays,
22179 structures and unions. In this last case, a frontend can immediately
22180 display the value of simple data types and create variable objects for
22181 other data types when the user wishes to explore their values in
22184 @subsubheading @value{GDBN} Command
22186 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
22188 @subsubheading Example
22192 -stack-list-locals 0
22193 ^done,locals=[name="A",name="B",name="C"]
22195 -stack-list-locals --all-values
22196 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
22197 @{name="C",value="@{1, 2, 3@}"@}]
22198 -stack-list-locals --simple-values
22199 ^done,locals=[@{name="A",type="int",value="1"@},
22200 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
22205 @subheading The @code{-stack-select-frame} Command
22206 @findex -stack-select-frame
22208 @subsubheading Synopsis
22211 -stack-select-frame @var{framenum}
22214 Change the selected frame. Select a different frame @var{framenum} on
22217 This command in deprecated in favor of passing the @samp{--frame}
22218 option to every command.
22220 @subsubheading @value{GDBN} Command
22222 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
22223 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
22225 @subsubheading Example
22229 -stack-select-frame 2
22234 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22235 @node GDB/MI Variable Objects
22236 @section @sc{gdb/mi} Variable Objects
22240 @subheading Motivation for Variable Objects in @sc{gdb/mi}
22242 For the implementation of a variable debugger window (locals, watched
22243 expressions, etc.), we are proposing the adaptation of the existing code
22244 used by @code{Insight}.
22246 The two main reasons for that are:
22250 It has been proven in practice (it is already on its second generation).
22253 It will shorten development time (needless to say how important it is
22257 The original interface was designed to be used by Tcl code, so it was
22258 slightly changed so it could be used through @sc{gdb/mi}. This section
22259 describes the @sc{gdb/mi} operations that will be available and gives some
22260 hints about their use.
22262 @emph{Note}: In addition to the set of operations described here, we
22263 expect the @sc{gui} implementation of a variable window to require, at
22264 least, the following operations:
22267 @item @code{-gdb-show} @code{output-radix}
22268 @item @code{-stack-list-arguments}
22269 @item @code{-stack-list-locals}
22270 @item @code{-stack-select-frame}
22275 @subheading Introduction to Variable Objects
22277 @cindex variable objects in @sc{gdb/mi}
22279 Variable objects are "object-oriented" MI interface for examining and
22280 changing values of expressions. Unlike some other MI interfaces that
22281 work with expressions, variable objects are specifically designed for
22282 simple and efficient presentation in the frontend. A variable object
22283 is identified by string name. When a variable object is created, the
22284 frontend specifies the expression for that variable object. The
22285 expression can be a simple variable, or it can be an arbitrary complex
22286 expression, and can even involve CPU registers. After creating a
22287 variable object, the frontend can invoke other variable object
22288 operations---for example to obtain or change the value of a variable
22289 object, or to change display format.
22291 Variable objects have hierarchical tree structure. Any variable object
22292 that corresponds to a composite type, such as structure in C, has
22293 a number of child variable objects, for example corresponding to each
22294 element of a structure. A child variable object can itself have
22295 children, recursively. Recursion ends when we reach
22296 leaf variable objects, which always have built-in types. Child variable
22297 objects are created only by explicit request, so if a frontend
22298 is not interested in the children of a particular variable object, no
22299 child will be created.
22301 For a leaf variable object it is possible to obtain its value as a
22302 string, or set the value from a string. String value can be also
22303 obtained for a non-leaf variable object, but it's generally a string
22304 that only indicates the type of the object, and does not list its
22305 contents. Assignment to a non-leaf variable object is not allowed.
22307 A frontend does not need to read the values of all variable objects each time
22308 the program stops. Instead, MI provides an update command that lists all
22309 variable objects whose values has changed since the last update
22310 operation. This considerably reduces the amount of data that must
22311 be transferred to the frontend. As noted above, children variable
22312 objects are created on demand, and only leaf variable objects have a
22313 real value. As result, gdb will read target memory only for leaf
22314 variables that frontend has created.
22316 The automatic update is not always desirable. For example, a frontend
22317 might want to keep a value of some expression for future reference,
22318 and never update it. For another example, fetching memory is
22319 relatively slow for embedded targets, so a frontend might want
22320 to disable automatic update for the variables that are either not
22321 visible on the screen, or ``closed''. This is possible using so
22322 called ``frozen variable objects''. Such variable objects are never
22323 implicitly updated.
22325 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
22326 fixed variable object, the expression is parsed when the variable
22327 object is created, including associating identifiers to specific
22328 variables. The meaning of expression never changes. For a floating
22329 variable object the values of variables whose names appear in the
22330 expressions are re-evaluated every time in the context of the current
22331 frame. Consider this example:
22336 struct work_state state;
22343 If a fixed variable object for the @code{state} variable is created in
22344 this function, and we enter the recursive call, the the variable
22345 object will report the value of @code{state} in the top-level
22346 @code{do_work} invocation. On the other hand, a floating variable
22347 object will report the value of @code{state} in the current frame.
22349 If an expression specified when creating a fixed variable object
22350 refers to a local variable, the variable object becomes bound to the
22351 thread and frame in which the variable object is created. When such
22352 variable object is updated, @value{GDBN} makes sure that the
22353 thread/frame combination the variable object is bound to still exists,
22354 and re-evaluates the variable object in context of that thread/frame.
22356 The following is the complete set of @sc{gdb/mi} operations defined to
22357 access this functionality:
22359 @multitable @columnfractions .4 .6
22360 @item @strong{Operation}
22361 @tab @strong{Description}
22363 @item @code{-var-create}
22364 @tab create a variable object
22365 @item @code{-var-delete}
22366 @tab delete the variable object and/or its children
22367 @item @code{-var-set-format}
22368 @tab set the display format of this variable
22369 @item @code{-var-show-format}
22370 @tab show the display format of this variable
22371 @item @code{-var-info-num-children}
22372 @tab tells how many children this object has
22373 @item @code{-var-list-children}
22374 @tab return a list of the object's children
22375 @item @code{-var-info-type}
22376 @tab show the type of this variable object
22377 @item @code{-var-info-expression}
22378 @tab print parent-relative expression that this variable object represents
22379 @item @code{-var-info-path-expression}
22380 @tab print full expression that this variable object represents
22381 @item @code{-var-show-attributes}
22382 @tab is this variable editable? does it exist here?
22383 @item @code{-var-evaluate-expression}
22384 @tab get the value of this variable
22385 @item @code{-var-assign}
22386 @tab set the value of this variable
22387 @item @code{-var-update}
22388 @tab update the variable and its children
22389 @item @code{-var-set-frozen}
22390 @tab set frozeness attribute
22393 In the next subsection we describe each operation in detail and suggest
22394 how it can be used.
22396 @subheading Description And Use of Operations on Variable Objects
22398 @subheading The @code{-var-create} Command
22399 @findex -var-create
22401 @subsubheading Synopsis
22404 -var-create @{@var{name} | "-"@}
22405 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
22408 This operation creates a variable object, which allows the monitoring of
22409 a variable, the result of an expression, a memory cell or a CPU
22412 The @var{name} parameter is the string by which the object can be
22413 referenced. It must be unique. If @samp{-} is specified, the varobj
22414 system will generate a string ``varNNNNNN'' automatically. It will be
22415 unique provided that one does not specify @var{name} of that format.
22416 The command fails if a duplicate name is found.
22418 The frame under which the expression should be evaluated can be
22419 specified by @var{frame-addr}. A @samp{*} indicates that the current
22420 frame should be used. A @samp{@@} indicates that a floating variable
22421 object must be created.
22423 @var{expression} is any expression valid on the current language set (must not
22424 begin with a @samp{*}), or one of the following:
22428 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
22431 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
22434 @samp{$@var{regname}} --- a CPU register name
22437 @subsubheading Result
22439 This operation returns the name, number of children and the type of the
22440 object created. Type is returned as a string as the ones generated by
22441 the @value{GDBN} CLI. If a fixed variable object is bound to a
22442 specific thread, the thread is is also printed:
22445 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
22449 @subheading The @code{-var-delete} Command
22450 @findex -var-delete
22452 @subsubheading Synopsis
22455 -var-delete [ -c ] @var{name}
22458 Deletes a previously created variable object and all of its children.
22459 With the @samp{-c} option, just deletes the children.
22461 Returns an error if the object @var{name} is not found.
22464 @subheading The @code{-var-set-format} Command
22465 @findex -var-set-format
22467 @subsubheading Synopsis
22470 -var-set-format @var{name} @var{format-spec}
22473 Sets the output format for the value of the object @var{name} to be
22476 @anchor{-var-set-format}
22477 The syntax for the @var{format-spec} is as follows:
22480 @var{format-spec} @expansion{}
22481 @{binary | decimal | hexadecimal | octal | natural@}
22484 The natural format is the default format choosen automatically
22485 based on the variable type (like decimal for an @code{int}, hex
22486 for pointers, etc.).
22488 For a variable with children, the format is set only on the
22489 variable itself, and the children are not affected.
22491 @subheading The @code{-var-show-format} Command
22492 @findex -var-show-format
22494 @subsubheading Synopsis
22497 -var-show-format @var{name}
22500 Returns the format used to display the value of the object @var{name}.
22503 @var{format} @expansion{}
22508 @subheading The @code{-var-info-num-children} Command
22509 @findex -var-info-num-children
22511 @subsubheading Synopsis
22514 -var-info-num-children @var{name}
22517 Returns the number of children of a variable object @var{name}:
22524 @subheading The @code{-var-list-children} Command
22525 @findex -var-list-children
22527 @subsubheading Synopsis
22530 -var-list-children [@var{print-values}] @var{name}
22532 @anchor{-var-list-children}
22534 Return a list of the children of the specified variable object and
22535 create variable objects for them, if they do not already exist. With
22536 a single argument or if @var{print-values} has a value for of 0 or
22537 @code{--no-values}, print only the names of the variables; if
22538 @var{print-values} is 1 or @code{--all-values}, also print their
22539 values; and if it is 2 or @code{--simple-values} print the name and
22540 value for simple data types and just the name for arrays, structures
22543 @subsubheading Example
22547 -var-list-children n
22548 ^done,numchild=@var{n},children=[@{name=@var{name},
22549 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
22551 -var-list-children --all-values n
22552 ^done,numchild=@var{n},children=[@{name=@var{name},
22553 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
22557 @subheading The @code{-var-info-type} Command
22558 @findex -var-info-type
22560 @subsubheading Synopsis
22563 -var-info-type @var{name}
22566 Returns the type of the specified variable @var{name}. The type is
22567 returned as a string in the same format as it is output by the
22571 type=@var{typename}
22575 @subheading The @code{-var-info-expression} Command
22576 @findex -var-info-expression
22578 @subsubheading Synopsis
22581 -var-info-expression @var{name}
22584 Returns a string that is suitable for presenting this
22585 variable object in user interface. The string is generally
22586 not valid expression in the current language, and cannot be evaluated.
22588 For example, if @code{a} is an array, and variable object
22589 @code{A} was created for @code{a}, then we'll get this output:
22592 (gdb) -var-info-expression A.1
22593 ^done,lang="C",exp="1"
22597 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
22599 Note that the output of the @code{-var-list-children} command also
22600 includes those expressions, so the @code{-var-info-expression} command
22603 @subheading The @code{-var-info-path-expression} Command
22604 @findex -var-info-path-expression
22606 @subsubheading Synopsis
22609 -var-info-path-expression @var{name}
22612 Returns an expression that can be evaluated in the current
22613 context and will yield the same value that a variable object has.
22614 Compare this with the @code{-var-info-expression} command, which
22615 result can be used only for UI presentation. Typical use of
22616 the @code{-var-info-path-expression} command is creating a
22617 watchpoint from a variable object.
22619 For example, suppose @code{C} is a C@t{++} class, derived from class
22620 @code{Base}, and that the @code{Base} class has a member called
22621 @code{m_size}. Assume a variable @code{c} is has the type of
22622 @code{C} and a variable object @code{C} was created for variable
22623 @code{c}. Then, we'll get this output:
22625 (gdb) -var-info-path-expression C.Base.public.m_size
22626 ^done,path_expr=((Base)c).m_size)
22629 @subheading The @code{-var-show-attributes} Command
22630 @findex -var-show-attributes
22632 @subsubheading Synopsis
22635 -var-show-attributes @var{name}
22638 List attributes of the specified variable object @var{name}:
22641 status=@var{attr} [ ( ,@var{attr} )* ]
22645 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
22647 @subheading The @code{-var-evaluate-expression} Command
22648 @findex -var-evaluate-expression
22650 @subsubheading Synopsis
22653 -var-evaluate-expression [-f @var{format-spec}] @var{name}
22656 Evaluates the expression that is represented by the specified variable
22657 object and returns its value as a string. The format of the string
22658 can be specified with the @samp{-f} option. The possible values of
22659 this option are the same as for @code{-var-set-format}
22660 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
22661 the current display format will be used. The current display format
22662 can be changed using the @code{-var-set-format} command.
22668 Note that one must invoke @code{-var-list-children} for a variable
22669 before the value of a child variable can be evaluated.
22671 @subheading The @code{-var-assign} Command
22672 @findex -var-assign
22674 @subsubheading Synopsis
22677 -var-assign @var{name} @var{expression}
22680 Assigns the value of @var{expression} to the variable object specified
22681 by @var{name}. The object must be @samp{editable}. If the variable's
22682 value is altered by the assign, the variable will show up in any
22683 subsequent @code{-var-update} list.
22685 @subsubheading Example
22693 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
22697 @subheading The @code{-var-update} Command
22698 @findex -var-update
22700 @subsubheading Synopsis
22703 -var-update [@var{print-values}] @{@var{name} | "*"@}
22706 Reevaluate the expressions corresponding to the variable object
22707 @var{name} and all its direct and indirect children, and return the
22708 list of variable objects whose values have changed; @var{name} must
22709 be a root variable object. Here, ``changed'' means that the result of
22710 @code{-var-evaluate-expression} before and after the
22711 @code{-var-update} is different. If @samp{*} is used as the variable
22712 object names, all existing variable objects are updated, except
22713 for frozen ones (@pxref{-var-set-frozen}). The option
22714 @var{print-values} determines whether both names and values, or just
22715 names are printed. The possible values of this option are the same
22716 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
22717 recommended to use the @samp{--all-values} option, to reduce the
22718 number of MI commands needed on each program stop.
22720 With the @samp{*} parameter, if a variable object is bound to a
22721 currently running thread, it will not be updated, without any
22724 @subsubheading Example
22731 -var-update --all-values var1
22732 ^done,changelist=[@{name="var1",value="3",in_scope="true",
22733 type_changed="false"@}]
22737 @anchor{-var-update}
22738 The field in_scope may take three values:
22742 The variable object's current value is valid.
22745 The variable object does not currently hold a valid value but it may
22746 hold one in the future if its associated expression comes back into
22750 The variable object no longer holds a valid value.
22751 This can occur when the executable file being debugged has changed,
22752 either through recompilation or by using the @value{GDBN} @code{file}
22753 command. The front end should normally choose to delete these variable
22757 In the future new values may be added to this list so the front should
22758 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
22760 @subheading The @code{-var-set-frozen} Command
22761 @findex -var-set-frozen
22762 @anchor{-var-set-frozen}
22764 @subsubheading Synopsis
22767 -var-set-frozen @var{name} @var{flag}
22770 Set the frozenness flag on the variable object @var{name}. The
22771 @var{flag} parameter should be either @samp{1} to make the variable
22772 frozen or @samp{0} to make it unfrozen. If a variable object is
22773 frozen, then neither itself, nor any of its children, are
22774 implicitly updated by @code{-var-update} of
22775 a parent variable or by @code{-var-update *}. Only
22776 @code{-var-update} of the variable itself will update its value and
22777 values of its children. After a variable object is unfrozen, it is
22778 implicitly updated by all subsequent @code{-var-update} operations.
22779 Unfreezing a variable does not update it, only subsequent
22780 @code{-var-update} does.
22782 @subsubheading Example
22786 -var-set-frozen V 1
22792 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22793 @node GDB/MI Data Manipulation
22794 @section @sc{gdb/mi} Data Manipulation
22796 @cindex data manipulation, in @sc{gdb/mi}
22797 @cindex @sc{gdb/mi}, data manipulation
22798 This section describes the @sc{gdb/mi} commands that manipulate data:
22799 examine memory and registers, evaluate expressions, etc.
22801 @c REMOVED FROM THE INTERFACE.
22802 @c @subheading -data-assign
22803 @c Change the value of a program variable. Plenty of side effects.
22804 @c @subsubheading GDB Command
22806 @c @subsubheading Example
22809 @subheading The @code{-data-disassemble} Command
22810 @findex -data-disassemble
22812 @subsubheading Synopsis
22816 [ -s @var{start-addr} -e @var{end-addr} ]
22817 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
22825 @item @var{start-addr}
22826 is the beginning address (or @code{$pc})
22827 @item @var{end-addr}
22829 @item @var{filename}
22830 is the name of the file to disassemble
22831 @item @var{linenum}
22832 is the line number to disassemble around
22834 is the number of disassembly lines to be produced. If it is -1,
22835 the whole function will be disassembled, in case no @var{end-addr} is
22836 specified. If @var{end-addr} is specified as a non-zero value, and
22837 @var{lines} is lower than the number of disassembly lines between
22838 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
22839 displayed; if @var{lines} is higher than the number of lines between
22840 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
22843 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
22847 @subsubheading Result
22849 The output for each instruction is composed of four fields:
22858 Note that whatever included in the instruction field, is not manipulated
22859 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
22861 @subsubheading @value{GDBN} Command
22863 There's no direct mapping from this command to the CLI.
22865 @subsubheading Example
22867 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
22871 -data-disassemble -s $pc -e "$pc + 20" -- 0
22874 @{address="0x000107c0",func-name="main",offset="4",
22875 inst="mov 2, %o0"@},
22876 @{address="0x000107c4",func-name="main",offset="8",
22877 inst="sethi %hi(0x11800), %o2"@},
22878 @{address="0x000107c8",func-name="main",offset="12",
22879 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
22880 @{address="0x000107cc",func-name="main",offset="16",
22881 inst="sethi %hi(0x11800), %o2"@},
22882 @{address="0x000107d0",func-name="main",offset="20",
22883 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
22887 Disassemble the whole @code{main} function. Line 32 is part of
22891 -data-disassemble -f basics.c -l 32 -- 0
22893 @{address="0x000107bc",func-name="main",offset="0",
22894 inst="save %sp, -112, %sp"@},
22895 @{address="0x000107c0",func-name="main",offset="4",
22896 inst="mov 2, %o0"@},
22897 @{address="0x000107c4",func-name="main",offset="8",
22898 inst="sethi %hi(0x11800), %o2"@},
22900 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22901 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22905 Disassemble 3 instructions from the start of @code{main}:
22909 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22911 @{address="0x000107bc",func-name="main",offset="0",
22912 inst="save %sp, -112, %sp"@},
22913 @{address="0x000107c0",func-name="main",offset="4",
22914 inst="mov 2, %o0"@},
22915 @{address="0x000107c4",func-name="main",offset="8",
22916 inst="sethi %hi(0x11800), %o2"@}]
22920 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22924 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22926 src_and_asm_line=@{line="31",
22927 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22928 testsuite/gdb.mi/basics.c",line_asm_insn=[
22929 @{address="0x000107bc",func-name="main",offset="0",
22930 inst="save %sp, -112, %sp"@}]@},
22931 src_and_asm_line=@{line="32",
22932 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22933 testsuite/gdb.mi/basics.c",line_asm_insn=[
22934 @{address="0x000107c0",func-name="main",offset="4",
22935 inst="mov 2, %o0"@},
22936 @{address="0x000107c4",func-name="main",offset="8",
22937 inst="sethi %hi(0x11800), %o2"@}]@}]
22942 @subheading The @code{-data-evaluate-expression} Command
22943 @findex -data-evaluate-expression
22945 @subsubheading Synopsis
22948 -data-evaluate-expression @var{expr}
22951 Evaluate @var{expr} as an expression. The expression could contain an
22952 inferior function call. The function call will execute synchronously.
22953 If the expression contains spaces, it must be enclosed in double quotes.
22955 @subsubheading @value{GDBN} Command
22957 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22958 @samp{call}. In @code{gdbtk} only, there's a corresponding
22959 @samp{gdb_eval} command.
22961 @subsubheading Example
22963 In the following example, the numbers that precede the commands are the
22964 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22965 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22969 211-data-evaluate-expression A
22972 311-data-evaluate-expression &A
22973 311^done,value="0xefffeb7c"
22975 411-data-evaluate-expression A+3
22978 511-data-evaluate-expression "A + 3"
22984 @subheading The @code{-data-list-changed-registers} Command
22985 @findex -data-list-changed-registers
22987 @subsubheading Synopsis
22990 -data-list-changed-registers
22993 Display a list of the registers that have changed.
22995 @subsubheading @value{GDBN} Command
22997 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
22998 has the corresponding command @samp{gdb_changed_register_list}.
23000 @subsubheading Example
23002 On a PPC MBX board:
23010 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
23011 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
23014 -data-list-changed-registers
23015 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
23016 "10","11","13","14","15","16","17","18","19","20","21","22","23",
23017 "24","25","26","27","28","30","31","64","65","66","67","69"]
23022 @subheading The @code{-data-list-register-names} Command
23023 @findex -data-list-register-names
23025 @subsubheading Synopsis
23028 -data-list-register-names [ ( @var{regno} )+ ]
23031 Show a list of register names for the current target. If no arguments
23032 are given, it shows a list of the names of all the registers. If
23033 integer numbers are given as arguments, it will print a list of the
23034 names of the registers corresponding to the arguments. To ensure
23035 consistency between a register name and its number, the output list may
23036 include empty register names.
23038 @subsubheading @value{GDBN} Command
23040 @value{GDBN} does not have a command which corresponds to
23041 @samp{-data-list-register-names}. In @code{gdbtk} there is a
23042 corresponding command @samp{gdb_regnames}.
23044 @subsubheading Example
23046 For the PPC MBX board:
23049 -data-list-register-names
23050 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
23051 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
23052 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
23053 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
23054 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
23055 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
23056 "", "pc","ps","cr","lr","ctr","xer"]
23058 -data-list-register-names 1 2 3
23059 ^done,register-names=["r1","r2","r3"]
23063 @subheading The @code{-data-list-register-values} Command
23064 @findex -data-list-register-values
23066 @subsubheading Synopsis
23069 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
23072 Display the registers' contents. @var{fmt} is the format according to
23073 which the registers' contents are to be returned, followed by an optional
23074 list of numbers specifying the registers to display. A missing list of
23075 numbers indicates that the contents of all the registers must be returned.
23077 Allowed formats for @var{fmt} are:
23094 @subsubheading @value{GDBN} Command
23096 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
23097 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
23099 @subsubheading Example
23101 For a PPC MBX board (note: line breaks are for readability only, they
23102 don't appear in the actual output):
23106 -data-list-register-values r 64 65
23107 ^done,register-values=[@{number="64",value="0xfe00a300"@},
23108 @{number="65",value="0x00029002"@}]
23110 -data-list-register-values x
23111 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
23112 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
23113 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
23114 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
23115 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
23116 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
23117 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
23118 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
23119 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
23120 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
23121 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
23122 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
23123 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
23124 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
23125 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
23126 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
23127 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
23128 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
23129 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
23130 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
23131 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
23132 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
23133 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
23134 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
23135 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
23136 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
23137 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
23138 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
23139 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
23140 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
23141 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
23142 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
23143 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
23144 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
23145 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
23146 @{number="69",value="0x20002b03"@}]
23151 @subheading The @code{-data-read-memory} Command
23152 @findex -data-read-memory
23154 @subsubheading Synopsis
23157 -data-read-memory [ -o @var{byte-offset} ]
23158 @var{address} @var{word-format} @var{word-size}
23159 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
23166 @item @var{address}
23167 An expression specifying the address of the first memory word to be
23168 read. Complex expressions containing embedded white space should be
23169 quoted using the C convention.
23171 @item @var{word-format}
23172 The format to be used to print the memory words. The notation is the
23173 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
23176 @item @var{word-size}
23177 The size of each memory word in bytes.
23179 @item @var{nr-rows}
23180 The number of rows in the output table.
23182 @item @var{nr-cols}
23183 The number of columns in the output table.
23186 If present, indicates that each row should include an @sc{ascii} dump. The
23187 value of @var{aschar} is used as a padding character when a byte is not a
23188 member of the printable @sc{ascii} character set (printable @sc{ascii}
23189 characters are those whose code is between 32 and 126, inclusively).
23191 @item @var{byte-offset}
23192 An offset to add to the @var{address} before fetching memory.
23195 This command displays memory contents as a table of @var{nr-rows} by
23196 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
23197 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
23198 (returned as @samp{total-bytes}). Should less than the requested number
23199 of bytes be returned by the target, the missing words are identified
23200 using @samp{N/A}. The number of bytes read from the target is returned
23201 in @samp{nr-bytes} and the starting address used to read memory in
23204 The address of the next/previous row or page is available in
23205 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
23208 @subsubheading @value{GDBN} Command
23210 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
23211 @samp{gdb_get_mem} memory read command.
23213 @subsubheading Example
23215 Read six bytes of memory starting at @code{bytes+6} but then offset by
23216 @code{-6} bytes. Format as three rows of two columns. One byte per
23217 word. Display each word in hex.
23221 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
23222 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
23223 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
23224 prev-page="0x0000138a",memory=[
23225 @{addr="0x00001390",data=["0x00","0x01"]@},
23226 @{addr="0x00001392",data=["0x02","0x03"]@},
23227 @{addr="0x00001394",data=["0x04","0x05"]@}]
23231 Read two bytes of memory starting at address @code{shorts + 64} and
23232 display as a single word formatted in decimal.
23236 5-data-read-memory shorts+64 d 2 1 1
23237 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
23238 next-row="0x00001512",prev-row="0x0000150e",
23239 next-page="0x00001512",prev-page="0x0000150e",memory=[
23240 @{addr="0x00001510",data=["128"]@}]
23244 Read thirty two bytes of memory starting at @code{bytes+16} and format
23245 as eight rows of four columns. Include a string encoding with @samp{x}
23246 used as the non-printable character.
23250 4-data-read-memory bytes+16 x 1 8 4 x
23251 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
23252 next-row="0x000013c0",prev-row="0x0000139c",
23253 next-page="0x000013c0",prev-page="0x00001380",memory=[
23254 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
23255 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
23256 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
23257 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
23258 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
23259 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
23260 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
23261 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
23265 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23266 @node GDB/MI Tracepoint Commands
23267 @section @sc{gdb/mi} Tracepoint Commands
23269 The tracepoint commands are not yet implemented.
23271 @c @subheading -trace-actions
23273 @c @subheading -trace-delete
23275 @c @subheading -trace-disable
23277 @c @subheading -trace-dump
23279 @c @subheading -trace-enable
23281 @c @subheading -trace-exists
23283 @c @subheading -trace-find
23285 @c @subheading -trace-frame-number
23287 @c @subheading -trace-info
23289 @c @subheading -trace-insert
23291 @c @subheading -trace-list
23293 @c @subheading -trace-pass-count
23295 @c @subheading -trace-save
23297 @c @subheading -trace-start
23299 @c @subheading -trace-stop
23302 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23303 @node GDB/MI Symbol Query
23304 @section @sc{gdb/mi} Symbol Query Commands
23307 @subheading The @code{-symbol-info-address} Command
23308 @findex -symbol-info-address
23310 @subsubheading Synopsis
23313 -symbol-info-address @var{symbol}
23316 Describe where @var{symbol} is stored.
23318 @subsubheading @value{GDBN} Command
23320 The corresponding @value{GDBN} command is @samp{info address}.
23322 @subsubheading Example
23326 @subheading The @code{-symbol-info-file} Command
23327 @findex -symbol-info-file
23329 @subsubheading Synopsis
23335 Show the file for the symbol.
23337 @subsubheading @value{GDBN} Command
23339 There's no equivalent @value{GDBN} command. @code{gdbtk} has
23340 @samp{gdb_find_file}.
23342 @subsubheading Example
23346 @subheading The @code{-symbol-info-function} Command
23347 @findex -symbol-info-function
23349 @subsubheading Synopsis
23352 -symbol-info-function
23355 Show which function the symbol lives in.
23357 @subsubheading @value{GDBN} Command
23359 @samp{gdb_get_function} in @code{gdbtk}.
23361 @subsubheading Example
23365 @subheading The @code{-symbol-info-line} Command
23366 @findex -symbol-info-line
23368 @subsubheading Synopsis
23374 Show the core addresses of the code for a source line.
23376 @subsubheading @value{GDBN} Command
23378 The corresponding @value{GDBN} command is @samp{info line}.
23379 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
23381 @subsubheading Example
23385 @subheading The @code{-symbol-info-symbol} Command
23386 @findex -symbol-info-symbol
23388 @subsubheading Synopsis
23391 -symbol-info-symbol @var{addr}
23394 Describe what symbol is at location @var{addr}.
23396 @subsubheading @value{GDBN} Command
23398 The corresponding @value{GDBN} command is @samp{info symbol}.
23400 @subsubheading Example
23404 @subheading The @code{-symbol-list-functions} Command
23405 @findex -symbol-list-functions
23407 @subsubheading Synopsis
23410 -symbol-list-functions
23413 List the functions in the executable.
23415 @subsubheading @value{GDBN} Command
23417 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
23418 @samp{gdb_search} in @code{gdbtk}.
23420 @subsubheading Example
23424 @subheading The @code{-symbol-list-lines} Command
23425 @findex -symbol-list-lines
23427 @subsubheading Synopsis
23430 -symbol-list-lines @var{filename}
23433 Print the list of lines that contain code and their associated program
23434 addresses for the given source filename. The entries are sorted in
23435 ascending PC order.
23437 @subsubheading @value{GDBN} Command
23439 There is no corresponding @value{GDBN} command.
23441 @subsubheading Example
23444 -symbol-list-lines basics.c
23445 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
23450 @subheading The @code{-symbol-list-types} Command
23451 @findex -symbol-list-types
23453 @subsubheading Synopsis
23459 List all the type names.
23461 @subsubheading @value{GDBN} Command
23463 The corresponding commands are @samp{info types} in @value{GDBN},
23464 @samp{gdb_search} in @code{gdbtk}.
23466 @subsubheading Example
23470 @subheading The @code{-symbol-list-variables} Command
23471 @findex -symbol-list-variables
23473 @subsubheading Synopsis
23476 -symbol-list-variables
23479 List all the global and static variable names.
23481 @subsubheading @value{GDBN} Command
23483 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
23485 @subsubheading Example
23489 @subheading The @code{-symbol-locate} Command
23490 @findex -symbol-locate
23492 @subsubheading Synopsis
23498 @subsubheading @value{GDBN} Command
23500 @samp{gdb_loc} in @code{gdbtk}.
23502 @subsubheading Example
23506 @subheading The @code{-symbol-type} Command
23507 @findex -symbol-type
23509 @subsubheading Synopsis
23512 -symbol-type @var{variable}
23515 Show type of @var{variable}.
23517 @subsubheading @value{GDBN} Command
23519 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
23520 @samp{gdb_obj_variable}.
23522 @subsubheading Example
23526 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23527 @node GDB/MI File Commands
23528 @section @sc{gdb/mi} File Commands
23530 This section describes the GDB/MI commands to specify executable file names
23531 and to read in and obtain symbol table information.
23533 @subheading The @code{-file-exec-and-symbols} Command
23534 @findex -file-exec-and-symbols
23536 @subsubheading Synopsis
23539 -file-exec-and-symbols @var{file}
23542 Specify the executable file to be debugged. This file is the one from
23543 which the symbol table is also read. If no file is specified, the
23544 command clears the executable and symbol information. If breakpoints
23545 are set when using this command with no arguments, @value{GDBN} will produce
23546 error messages. Otherwise, no output is produced, except a completion
23549 @subsubheading @value{GDBN} Command
23551 The corresponding @value{GDBN} command is @samp{file}.
23553 @subsubheading Example
23557 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23563 @subheading The @code{-file-exec-file} Command
23564 @findex -file-exec-file
23566 @subsubheading Synopsis
23569 -file-exec-file @var{file}
23572 Specify the executable file to be debugged. Unlike
23573 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
23574 from this file. If used without argument, @value{GDBN} clears the information
23575 about the executable file. No output is produced, except a completion
23578 @subsubheading @value{GDBN} Command
23580 The corresponding @value{GDBN} command is @samp{exec-file}.
23582 @subsubheading Example
23586 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23592 @subheading The @code{-file-list-exec-sections} Command
23593 @findex -file-list-exec-sections
23595 @subsubheading Synopsis
23598 -file-list-exec-sections
23601 List the sections of the current executable file.
23603 @subsubheading @value{GDBN} Command
23605 The @value{GDBN} command @samp{info file} shows, among the rest, the same
23606 information as this command. @code{gdbtk} has a corresponding command
23607 @samp{gdb_load_info}.
23609 @subsubheading Example
23613 @subheading The @code{-file-list-exec-source-file} Command
23614 @findex -file-list-exec-source-file
23616 @subsubheading Synopsis
23619 -file-list-exec-source-file
23622 List the line number, the current source file, and the absolute path
23623 to the current source file for the current executable. The macro
23624 information field has a value of @samp{1} or @samp{0} depending on
23625 whether or not the file includes preprocessor macro information.
23627 @subsubheading @value{GDBN} Command
23629 The @value{GDBN} equivalent is @samp{info source}
23631 @subsubheading Example
23635 123-file-list-exec-source-file
23636 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
23641 @subheading The @code{-file-list-exec-source-files} Command
23642 @findex -file-list-exec-source-files
23644 @subsubheading Synopsis
23647 -file-list-exec-source-files
23650 List the source files for the current executable.
23652 It will always output the filename, but only when @value{GDBN} can find
23653 the absolute file name of a source file, will it output the fullname.
23655 @subsubheading @value{GDBN} Command
23657 The @value{GDBN} equivalent is @samp{info sources}.
23658 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
23660 @subsubheading Example
23663 -file-list-exec-source-files
23665 @{file=foo.c,fullname=/home/foo.c@},
23666 @{file=/home/bar.c,fullname=/home/bar.c@},
23667 @{file=gdb_could_not_find_fullpath.c@}]
23671 @subheading The @code{-file-list-shared-libraries} Command
23672 @findex -file-list-shared-libraries
23674 @subsubheading Synopsis
23677 -file-list-shared-libraries
23680 List the shared libraries in the program.
23682 @subsubheading @value{GDBN} Command
23684 The corresponding @value{GDBN} command is @samp{info shared}.
23686 @subsubheading Example
23690 @subheading The @code{-file-list-symbol-files} Command
23691 @findex -file-list-symbol-files
23693 @subsubheading Synopsis
23696 -file-list-symbol-files
23701 @subsubheading @value{GDBN} Command
23703 The corresponding @value{GDBN} command is @samp{info file} (part of it).
23705 @subsubheading Example
23709 @subheading The @code{-file-symbol-file} Command
23710 @findex -file-symbol-file
23712 @subsubheading Synopsis
23715 -file-symbol-file @var{file}
23718 Read symbol table info from the specified @var{file} argument. When
23719 used without arguments, clears @value{GDBN}'s symbol table info. No output is
23720 produced, except for a completion notification.
23722 @subsubheading @value{GDBN} Command
23724 The corresponding @value{GDBN} command is @samp{symbol-file}.
23726 @subsubheading Example
23730 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23736 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23737 @node GDB/MI Memory Overlay Commands
23738 @section @sc{gdb/mi} Memory Overlay Commands
23740 The memory overlay commands are not implemented.
23742 @c @subheading -overlay-auto
23744 @c @subheading -overlay-list-mapping-state
23746 @c @subheading -overlay-list-overlays
23748 @c @subheading -overlay-map
23750 @c @subheading -overlay-off
23752 @c @subheading -overlay-on
23754 @c @subheading -overlay-unmap
23756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23757 @node GDB/MI Signal Handling Commands
23758 @section @sc{gdb/mi} Signal Handling Commands
23760 Signal handling commands are not implemented.
23762 @c @subheading -signal-handle
23764 @c @subheading -signal-list-handle-actions
23766 @c @subheading -signal-list-signal-types
23770 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23771 @node GDB/MI Target Manipulation
23772 @section @sc{gdb/mi} Target Manipulation Commands
23775 @subheading The @code{-target-attach} Command
23776 @findex -target-attach
23778 @subsubheading Synopsis
23781 -target-attach @var{pid} | @var{gid} | @var{file}
23784 Attach to a process @var{pid} or a file @var{file} outside of
23785 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
23786 group, the id previously returned by
23787 @samp{-list-thread-groups --available} must be used.
23789 @subsubheading @value{GDBN} Command
23791 The corresponding @value{GDBN} command is @samp{attach}.
23793 @subsubheading Example
23797 =thread-created,id="1"
23798 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
23803 @subheading The @code{-target-compare-sections} Command
23804 @findex -target-compare-sections
23806 @subsubheading Synopsis
23809 -target-compare-sections [ @var{section} ]
23812 Compare data of section @var{section} on target to the exec file.
23813 Without the argument, all sections are compared.
23815 @subsubheading @value{GDBN} Command
23817 The @value{GDBN} equivalent is @samp{compare-sections}.
23819 @subsubheading Example
23823 @subheading The @code{-target-detach} Command
23824 @findex -target-detach
23826 @subsubheading Synopsis
23829 -target-detach [ @var{pid} | @var{gid} ]
23832 Detach from the remote target which normally resumes its execution.
23833 If either @var{pid} or @var{gid} is specified, detaches from either
23834 the specified process, or specified thread group. There's no output.
23836 @subsubheading @value{GDBN} Command
23838 The corresponding @value{GDBN} command is @samp{detach}.
23840 @subsubheading Example
23850 @subheading The @code{-target-disconnect} Command
23851 @findex -target-disconnect
23853 @subsubheading Synopsis
23859 Disconnect from the remote target. There's no output and the target is
23860 generally not resumed.
23862 @subsubheading @value{GDBN} Command
23864 The corresponding @value{GDBN} command is @samp{disconnect}.
23866 @subsubheading Example
23876 @subheading The @code{-target-download} Command
23877 @findex -target-download
23879 @subsubheading Synopsis
23885 Loads the executable onto the remote target.
23886 It prints out an update message every half second, which includes the fields:
23890 The name of the section.
23892 The size of what has been sent so far for that section.
23894 The size of the section.
23896 The total size of what was sent so far (the current and the previous sections).
23898 The size of the overall executable to download.
23902 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23903 @sc{gdb/mi} Output Syntax}).
23905 In addition, it prints the name and size of the sections, as they are
23906 downloaded. These messages include the following fields:
23910 The name of the section.
23912 The size of the section.
23914 The size of the overall executable to download.
23918 At the end, a summary is printed.
23920 @subsubheading @value{GDBN} Command
23922 The corresponding @value{GDBN} command is @samp{load}.
23924 @subsubheading Example
23926 Note: each status message appears on a single line. Here the messages
23927 have been broken down so that they can fit onto a page.
23932 +download,@{section=".text",section-size="6668",total-size="9880"@}
23933 +download,@{section=".text",section-sent="512",section-size="6668",
23934 total-sent="512",total-size="9880"@}
23935 +download,@{section=".text",section-sent="1024",section-size="6668",
23936 total-sent="1024",total-size="9880"@}
23937 +download,@{section=".text",section-sent="1536",section-size="6668",
23938 total-sent="1536",total-size="9880"@}
23939 +download,@{section=".text",section-sent="2048",section-size="6668",
23940 total-sent="2048",total-size="9880"@}
23941 +download,@{section=".text",section-sent="2560",section-size="6668",
23942 total-sent="2560",total-size="9880"@}
23943 +download,@{section=".text",section-sent="3072",section-size="6668",
23944 total-sent="3072",total-size="9880"@}
23945 +download,@{section=".text",section-sent="3584",section-size="6668",
23946 total-sent="3584",total-size="9880"@}
23947 +download,@{section=".text",section-sent="4096",section-size="6668",
23948 total-sent="4096",total-size="9880"@}
23949 +download,@{section=".text",section-sent="4608",section-size="6668",
23950 total-sent="4608",total-size="9880"@}
23951 +download,@{section=".text",section-sent="5120",section-size="6668",
23952 total-sent="5120",total-size="9880"@}
23953 +download,@{section=".text",section-sent="5632",section-size="6668",
23954 total-sent="5632",total-size="9880"@}
23955 +download,@{section=".text",section-sent="6144",section-size="6668",
23956 total-sent="6144",total-size="9880"@}
23957 +download,@{section=".text",section-sent="6656",section-size="6668",
23958 total-sent="6656",total-size="9880"@}
23959 +download,@{section=".init",section-size="28",total-size="9880"@}
23960 +download,@{section=".fini",section-size="28",total-size="9880"@}
23961 +download,@{section=".data",section-size="3156",total-size="9880"@}
23962 +download,@{section=".data",section-sent="512",section-size="3156",
23963 total-sent="7236",total-size="9880"@}
23964 +download,@{section=".data",section-sent="1024",section-size="3156",
23965 total-sent="7748",total-size="9880"@}
23966 +download,@{section=".data",section-sent="1536",section-size="3156",
23967 total-sent="8260",total-size="9880"@}
23968 +download,@{section=".data",section-sent="2048",section-size="3156",
23969 total-sent="8772",total-size="9880"@}
23970 +download,@{section=".data",section-sent="2560",section-size="3156",
23971 total-sent="9284",total-size="9880"@}
23972 +download,@{section=".data",section-sent="3072",section-size="3156",
23973 total-sent="9796",total-size="9880"@}
23974 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23980 @subheading The @code{-target-exec-status} Command
23981 @findex -target-exec-status
23983 @subsubheading Synopsis
23986 -target-exec-status
23989 Provide information on the state of the target (whether it is running or
23990 not, for instance).
23992 @subsubheading @value{GDBN} Command
23994 There's no equivalent @value{GDBN} command.
23996 @subsubheading Example
24000 @subheading The @code{-target-list-available-targets} Command
24001 @findex -target-list-available-targets
24003 @subsubheading Synopsis
24006 -target-list-available-targets
24009 List the possible targets to connect to.
24011 @subsubheading @value{GDBN} Command
24013 The corresponding @value{GDBN} command is @samp{help target}.
24015 @subsubheading Example
24019 @subheading The @code{-target-list-current-targets} Command
24020 @findex -target-list-current-targets
24022 @subsubheading Synopsis
24025 -target-list-current-targets
24028 Describe the current target.
24030 @subsubheading @value{GDBN} Command
24032 The corresponding information is printed by @samp{info file} (among
24035 @subsubheading Example
24039 @subheading The @code{-target-list-parameters} Command
24040 @findex -target-list-parameters
24042 @subsubheading Synopsis
24045 -target-list-parameters
24050 @subsubheading @value{GDBN} Command
24054 @subsubheading Example
24058 @subheading The @code{-target-select} Command
24059 @findex -target-select
24061 @subsubheading Synopsis
24064 -target-select @var{type} @var{parameters @dots{}}
24067 Connect @value{GDBN} to the remote target. This command takes two args:
24071 The type of target, for instance @samp{remote}, etc.
24072 @item @var{parameters}
24073 Device names, host names and the like. @xref{Target Commands, ,
24074 Commands for Managing Targets}, for more details.
24077 The output is a connection notification, followed by the address at
24078 which the target program is, in the following form:
24081 ^connected,addr="@var{address}",func="@var{function name}",
24082 args=[@var{arg list}]
24085 @subsubheading @value{GDBN} Command
24087 The corresponding @value{GDBN} command is @samp{target}.
24089 @subsubheading Example
24093 -target-select remote /dev/ttya
24094 ^connected,addr="0xfe00a300",func="??",args=[]
24098 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24099 @node GDB/MI File Transfer Commands
24100 @section @sc{gdb/mi} File Transfer Commands
24103 @subheading The @code{-target-file-put} Command
24104 @findex -target-file-put
24106 @subsubheading Synopsis
24109 -target-file-put @var{hostfile} @var{targetfile}
24112 Copy file @var{hostfile} from the host system (the machine running
24113 @value{GDBN}) to @var{targetfile} on the target system.
24115 @subsubheading @value{GDBN} Command
24117 The corresponding @value{GDBN} command is @samp{remote put}.
24119 @subsubheading Example
24123 -target-file-put localfile remotefile
24129 @subheading The @code{-target-file-get} Command
24130 @findex -target-file-get
24132 @subsubheading Synopsis
24135 -target-file-get @var{targetfile} @var{hostfile}
24138 Copy file @var{targetfile} from the target system to @var{hostfile}
24139 on the host system.
24141 @subsubheading @value{GDBN} Command
24143 The corresponding @value{GDBN} command is @samp{remote get}.
24145 @subsubheading Example
24149 -target-file-get remotefile localfile
24155 @subheading The @code{-target-file-delete} Command
24156 @findex -target-file-delete
24158 @subsubheading Synopsis
24161 -target-file-delete @var{targetfile}
24164 Delete @var{targetfile} from the target system.
24166 @subsubheading @value{GDBN} Command
24168 The corresponding @value{GDBN} command is @samp{remote delete}.
24170 @subsubheading Example
24174 -target-file-delete remotefile
24180 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24181 @node GDB/MI Miscellaneous Commands
24182 @section Miscellaneous @sc{gdb/mi} Commands
24184 @c @subheading -gdb-complete
24186 @subheading The @code{-gdb-exit} Command
24189 @subsubheading Synopsis
24195 Exit @value{GDBN} immediately.
24197 @subsubheading @value{GDBN} Command
24199 Approximately corresponds to @samp{quit}.
24201 @subsubheading Example
24210 @subheading The @code{-exec-abort} Command
24211 @findex -exec-abort
24213 @subsubheading Synopsis
24219 Kill the inferior running program.
24221 @subsubheading @value{GDBN} Command
24223 The corresponding @value{GDBN} command is @samp{kill}.
24225 @subsubheading Example
24229 @subheading The @code{-gdb-set} Command
24232 @subsubheading Synopsis
24238 Set an internal @value{GDBN} variable.
24239 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
24241 @subsubheading @value{GDBN} Command
24243 The corresponding @value{GDBN} command is @samp{set}.
24245 @subsubheading Example
24255 @subheading The @code{-gdb-show} Command
24258 @subsubheading Synopsis
24264 Show the current value of a @value{GDBN} variable.
24266 @subsubheading @value{GDBN} Command
24268 The corresponding @value{GDBN} command is @samp{show}.
24270 @subsubheading Example
24279 @c @subheading -gdb-source
24282 @subheading The @code{-gdb-version} Command
24283 @findex -gdb-version
24285 @subsubheading Synopsis
24291 Show version information for @value{GDBN}. Used mostly in testing.
24293 @subsubheading @value{GDBN} Command
24295 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
24296 default shows this information when you start an interactive session.
24298 @subsubheading Example
24300 @c This example modifies the actual output from GDB to avoid overfull
24306 ~Copyright 2000 Free Software Foundation, Inc.
24307 ~GDB is free software, covered by the GNU General Public License, and
24308 ~you are welcome to change it and/or distribute copies of it under
24309 ~ certain conditions.
24310 ~Type "show copying" to see the conditions.
24311 ~There is absolutely no warranty for GDB. Type "show warranty" for
24313 ~This GDB was configured as
24314 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
24319 @subheading The @code{-list-features} Command
24320 @findex -list-features
24322 Returns a list of particular features of the MI protocol that
24323 this version of gdb implements. A feature can be a command,
24324 or a new field in an output of some command, or even an
24325 important bugfix. While a frontend can sometimes detect presence
24326 of a feature at runtime, it is easier to perform detection at debugger
24329 The command returns a list of strings, with each string naming an
24330 available feature. Each returned string is just a name, it does not
24331 have any internal structure. The list of possible feature names
24337 (gdb) -list-features
24338 ^done,result=["feature1","feature2"]
24341 The current list of features is:
24344 @item frozen-varobjs
24345 Indicates presence of the @code{-var-set-frozen} command, as well
24346 as possible presense of the @code{frozen} field in the output
24347 of @code{-varobj-create}.
24348 @item pending-breakpoints
24349 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
24351 Indicates presence of the @code{-thread-info} command.
24355 @subheading The @code{-list-target-features} Command
24356 @findex -list-target-features
24358 Returns a list of particular features that are supported by the
24359 target. Those features affect the permitted MI commands, but
24360 unlike the features reported by the @code{-list-features} command, the
24361 features depend on which target GDB is using at the moment. Whenever
24362 a target can change, due to commands such as @code{-target-select},
24363 @code{-target-attach} or @code{-exec-run}, the list of target features
24364 may change, and the frontend should obtain it again.
24368 (gdb) -list-features
24369 ^done,result=["async"]
24372 The current list of features is:
24376 Indicates that the target is capable of asynchronous command
24377 execution, which means that @value{GDBN} will accept further commands
24378 while the target is running.
24382 @subheading The @code{-list-thread-groups} Command
24383 @findex -list-thread-groups
24385 @subheading Synopsis
24388 -list-thread-groups [ --available ] [ @var{group} ]
24391 When used without the @var{group} parameter, lists top-level thread
24392 groups that are being debugged. When used with the @var{group}
24393 parameter, the children of the specified group are listed. The
24394 children can be either threads, or other groups. At present,
24395 @value{GDBN} will not report both threads and groups as children at
24396 the same time, but it may change in future.
24398 With the @samp{--available} option, instead of reporting groups that
24399 are been debugged, GDB will report all thread groups available on the
24400 target. Using the @samp{--available} option together with @var{group}
24403 @subheading Example
24407 -list-thread-groups
24408 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
24409 -list-thread-groups 17
24410 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24411 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24412 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24413 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24414 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
24417 @subheading The @code{-interpreter-exec} Command
24418 @findex -interpreter-exec
24420 @subheading Synopsis
24423 -interpreter-exec @var{interpreter} @var{command}
24425 @anchor{-interpreter-exec}
24427 Execute the specified @var{command} in the given @var{interpreter}.
24429 @subheading @value{GDBN} Command
24431 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
24433 @subheading Example
24437 -interpreter-exec console "break main"
24438 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
24439 &"During symbol reading, bad structure-type format.\n"
24440 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
24445 @subheading The @code{-inferior-tty-set} Command
24446 @findex -inferior-tty-set
24448 @subheading Synopsis
24451 -inferior-tty-set /dev/pts/1
24454 Set terminal for future runs of the program being debugged.
24456 @subheading @value{GDBN} Command
24458 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
24460 @subheading Example
24464 -inferior-tty-set /dev/pts/1
24469 @subheading The @code{-inferior-tty-show} Command
24470 @findex -inferior-tty-show
24472 @subheading Synopsis
24478 Show terminal for future runs of program being debugged.
24480 @subheading @value{GDBN} Command
24482 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
24484 @subheading Example
24488 -inferior-tty-set /dev/pts/1
24492 ^done,inferior_tty_terminal="/dev/pts/1"
24496 @subheading The @code{-enable-timings} Command
24497 @findex -enable-timings
24499 @subheading Synopsis
24502 -enable-timings [yes | no]
24505 Toggle the printing of the wallclock, user and system times for an MI
24506 command as a field in its output. This command is to help frontend
24507 developers optimize the performance of their code. No argument is
24508 equivalent to @samp{yes}.
24510 @subheading @value{GDBN} Command
24514 @subheading Example
24522 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24523 addr="0x080484ed",func="main",file="myprog.c",
24524 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
24525 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
24533 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24534 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
24535 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
24536 fullname="/home/nickrob/myprog.c",line="73"@}
24541 @chapter @value{GDBN} Annotations
24543 This chapter describes annotations in @value{GDBN}. Annotations were
24544 designed to interface @value{GDBN} to graphical user interfaces or other
24545 similar programs which want to interact with @value{GDBN} at a
24546 relatively high level.
24548 The annotation mechanism has largely been superseded by @sc{gdb/mi}
24552 This is Edition @value{EDITION}, @value{DATE}.
24556 * Annotations Overview:: What annotations are; the general syntax.
24557 * Server Prefix:: Issuing a command without affecting user state.
24558 * Prompting:: Annotations marking @value{GDBN}'s need for input.
24559 * Errors:: Annotations for error messages.
24560 * Invalidation:: Some annotations describe things now invalid.
24561 * Annotations for Running::
24562 Whether the program is running, how it stopped, etc.
24563 * Source Annotations:: Annotations describing source code.
24566 @node Annotations Overview
24567 @section What is an Annotation?
24568 @cindex annotations
24570 Annotations start with a newline character, two @samp{control-z}
24571 characters, and the name of the annotation. If there is no additional
24572 information associated with this annotation, the name of the annotation
24573 is followed immediately by a newline. If there is additional
24574 information, the name of the annotation is followed by a space, the
24575 additional information, and a newline. The additional information
24576 cannot contain newline characters.
24578 Any output not beginning with a newline and two @samp{control-z}
24579 characters denotes literal output from @value{GDBN}. Currently there is
24580 no need for @value{GDBN} to output a newline followed by two
24581 @samp{control-z} characters, but if there was such a need, the
24582 annotations could be extended with an @samp{escape} annotation which
24583 means those three characters as output.
24585 The annotation @var{level}, which is specified using the
24586 @option{--annotate} command line option (@pxref{Mode Options}), controls
24587 how much information @value{GDBN} prints together with its prompt,
24588 values of expressions, source lines, and other types of output. Level 0
24589 is for no annotations, level 1 is for use when @value{GDBN} is run as a
24590 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
24591 for programs that control @value{GDBN}, and level 2 annotations have
24592 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
24593 Interface, annotate, GDB's Obsolete Annotations}).
24596 @kindex set annotate
24597 @item set annotate @var{level}
24598 The @value{GDBN} command @code{set annotate} sets the level of
24599 annotations to the specified @var{level}.
24601 @item show annotate
24602 @kindex show annotate
24603 Show the current annotation level.
24606 This chapter describes level 3 annotations.
24608 A simple example of starting up @value{GDBN} with annotations is:
24611 $ @kbd{gdb --annotate=3}
24613 Copyright 2003 Free Software Foundation, Inc.
24614 GDB is free software, covered by the GNU General Public License,
24615 and you are welcome to change it and/or distribute copies of it
24616 under certain conditions.
24617 Type "show copying" to see the conditions.
24618 There is absolutely no warranty for GDB. Type "show warranty"
24620 This GDB was configured as "i386-pc-linux-gnu"
24631 Here @samp{quit} is input to @value{GDBN}; the rest is output from
24632 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
24633 denotes a @samp{control-z} character) are annotations; the rest is
24634 output from @value{GDBN}.
24636 @node Server Prefix
24637 @section The Server Prefix
24638 @cindex server prefix
24640 If you prefix a command with @samp{server } then it will not affect
24641 the command history, nor will it affect @value{GDBN}'s notion of which
24642 command to repeat if @key{RET} is pressed on a line by itself. This
24643 means that commands can be run behind a user's back by a front-end in
24644 a transparent manner.
24646 The server prefix does not affect the recording of values into the value
24647 history; to print a value without recording it into the value history,
24648 use the @code{output} command instead of the @code{print} command.
24651 @section Annotation for @value{GDBN} Input
24653 @cindex annotations for prompts
24654 When @value{GDBN} prompts for input, it annotates this fact so it is possible
24655 to know when to send output, when the output from a given command is
24658 Different kinds of input each have a different @dfn{input type}. Each
24659 input type has three annotations: a @code{pre-} annotation, which
24660 denotes the beginning of any prompt which is being output, a plain
24661 annotation, which denotes the end of the prompt, and then a @code{post-}
24662 annotation which denotes the end of any echo which may (or may not) be
24663 associated with the input. For example, the @code{prompt} input type
24664 features the following annotations:
24672 The input types are
24675 @findex pre-prompt annotation
24676 @findex prompt annotation
24677 @findex post-prompt annotation
24679 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
24681 @findex pre-commands annotation
24682 @findex commands annotation
24683 @findex post-commands annotation
24685 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
24686 command. The annotations are repeated for each command which is input.
24688 @findex pre-overload-choice annotation
24689 @findex overload-choice annotation
24690 @findex post-overload-choice annotation
24691 @item overload-choice
24692 When @value{GDBN} wants the user to select between various overloaded functions.
24694 @findex pre-query annotation
24695 @findex query annotation
24696 @findex post-query annotation
24698 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
24700 @findex pre-prompt-for-continue annotation
24701 @findex prompt-for-continue annotation
24702 @findex post-prompt-for-continue annotation
24703 @item prompt-for-continue
24704 When @value{GDBN} is asking the user to press return to continue. Note: Don't
24705 expect this to work well; instead use @code{set height 0} to disable
24706 prompting. This is because the counting of lines is buggy in the
24707 presence of annotations.
24712 @cindex annotations for errors, warnings and interrupts
24714 @findex quit annotation
24719 This annotation occurs right before @value{GDBN} responds to an interrupt.
24721 @findex error annotation
24726 This annotation occurs right before @value{GDBN} responds to an error.
24728 Quit and error annotations indicate that any annotations which @value{GDBN} was
24729 in the middle of may end abruptly. For example, if a
24730 @code{value-history-begin} annotation is followed by a @code{error}, one
24731 cannot expect to receive the matching @code{value-history-end}. One
24732 cannot expect not to receive it either, however; an error annotation
24733 does not necessarily mean that @value{GDBN} is immediately returning all the way
24736 @findex error-begin annotation
24737 A quit or error annotation may be preceded by
24743 Any output between that and the quit or error annotation is the error
24746 Warning messages are not yet annotated.
24747 @c If we want to change that, need to fix warning(), type_error(),
24748 @c range_error(), and possibly other places.
24751 @section Invalidation Notices
24753 @cindex annotations for invalidation messages
24754 The following annotations say that certain pieces of state may have
24758 @findex frames-invalid annotation
24759 @item ^Z^Zframes-invalid
24761 The frames (for example, output from the @code{backtrace} command) may
24764 @findex breakpoints-invalid annotation
24765 @item ^Z^Zbreakpoints-invalid
24767 The breakpoints may have changed. For example, the user just added or
24768 deleted a breakpoint.
24771 @node Annotations for Running
24772 @section Running the Program
24773 @cindex annotations for running programs
24775 @findex starting annotation
24776 @findex stopping annotation
24777 When the program starts executing due to a @value{GDBN} command such as
24778 @code{step} or @code{continue},
24784 is output. When the program stops,
24790 is output. Before the @code{stopped} annotation, a variety of
24791 annotations describe how the program stopped.
24794 @findex exited annotation
24795 @item ^Z^Zexited @var{exit-status}
24796 The program exited, and @var{exit-status} is the exit status (zero for
24797 successful exit, otherwise nonzero).
24799 @findex signalled annotation
24800 @findex signal-name annotation
24801 @findex signal-name-end annotation
24802 @findex signal-string annotation
24803 @findex signal-string-end annotation
24804 @item ^Z^Zsignalled
24805 The program exited with a signal. After the @code{^Z^Zsignalled}, the
24806 annotation continues:
24812 ^Z^Zsignal-name-end
24816 ^Z^Zsignal-string-end
24821 where @var{name} is the name of the signal, such as @code{SIGILL} or
24822 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
24823 as @code{Illegal Instruction} or @code{Segmentation fault}.
24824 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
24825 user's benefit and have no particular format.
24827 @findex signal annotation
24829 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
24830 just saying that the program received the signal, not that it was
24831 terminated with it.
24833 @findex breakpoint annotation
24834 @item ^Z^Zbreakpoint @var{number}
24835 The program hit breakpoint number @var{number}.
24837 @findex watchpoint annotation
24838 @item ^Z^Zwatchpoint @var{number}
24839 The program hit watchpoint number @var{number}.
24842 @node Source Annotations
24843 @section Displaying Source
24844 @cindex annotations for source display
24846 @findex source annotation
24847 The following annotation is used instead of displaying source code:
24850 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
24853 where @var{filename} is an absolute file name indicating which source
24854 file, @var{line} is the line number within that file (where 1 is the
24855 first line in the file), @var{character} is the character position
24856 within the file (where 0 is the first character in the file) (for most
24857 debug formats this will necessarily point to the beginning of a line),
24858 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
24859 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
24860 @var{addr} is the address in the target program associated with the
24861 source which is being displayed. @var{addr} is in the form @samp{0x}
24862 followed by one or more lowercase hex digits (note that this does not
24863 depend on the language).
24866 @chapter Reporting Bugs in @value{GDBN}
24867 @cindex bugs in @value{GDBN}
24868 @cindex reporting bugs in @value{GDBN}
24870 Your bug reports play an essential role in making @value{GDBN} reliable.
24872 Reporting a bug may help you by bringing a solution to your problem, or it
24873 may not. But in any case the principal function of a bug report is to help
24874 the entire community by making the next version of @value{GDBN} work better. Bug
24875 reports are your contribution to the maintenance of @value{GDBN}.
24877 In order for a bug report to serve its purpose, you must include the
24878 information that enables us to fix the bug.
24881 * Bug Criteria:: Have you found a bug?
24882 * Bug Reporting:: How to report bugs
24886 @section Have You Found a Bug?
24887 @cindex bug criteria
24889 If you are not sure whether you have found a bug, here are some guidelines:
24892 @cindex fatal signal
24893 @cindex debugger crash
24894 @cindex crash of debugger
24896 If the debugger gets a fatal signal, for any input whatever, that is a
24897 @value{GDBN} bug. Reliable debuggers never crash.
24899 @cindex error on valid input
24901 If @value{GDBN} produces an error message for valid input, that is a
24902 bug. (Note that if you're cross debugging, the problem may also be
24903 somewhere in the connection to the target.)
24905 @cindex invalid input
24907 If @value{GDBN} does not produce an error message for invalid input,
24908 that is a bug. However, you should note that your idea of
24909 ``invalid input'' might be our idea of ``an extension'' or ``support
24910 for traditional practice''.
24913 If you are an experienced user of debugging tools, your suggestions
24914 for improvement of @value{GDBN} are welcome in any case.
24917 @node Bug Reporting
24918 @section How to Report Bugs
24919 @cindex bug reports
24920 @cindex @value{GDBN} bugs, reporting
24922 A number of companies and individuals offer support for @sc{gnu} products.
24923 If you obtained @value{GDBN} from a support organization, we recommend you
24924 contact that organization first.
24926 You can find contact information for many support companies and
24927 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24929 @c should add a web page ref...
24932 @ifset BUGURL_DEFAULT
24933 In any event, we also recommend that you submit bug reports for
24934 @value{GDBN}. The preferred method is to submit them directly using
24935 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24936 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24939 @strong{Do not send bug reports to @samp{info-gdb}, or to
24940 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24941 not want to receive bug reports. Those that do have arranged to receive
24944 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24945 serves as a repeater. The mailing list and the newsgroup carry exactly
24946 the same messages. Often people think of posting bug reports to the
24947 newsgroup instead of mailing them. This appears to work, but it has one
24948 problem which can be crucial: a newsgroup posting often lacks a mail
24949 path back to the sender. Thus, if we need to ask for more information,
24950 we may be unable to reach you. For this reason, it is better to send
24951 bug reports to the mailing list.
24953 @ifclear BUGURL_DEFAULT
24954 In any event, we also recommend that you submit bug reports for
24955 @value{GDBN} to @value{BUGURL}.
24959 The fundamental principle of reporting bugs usefully is this:
24960 @strong{report all the facts}. If you are not sure whether to state a
24961 fact or leave it out, state it!
24963 Often people omit facts because they think they know what causes the
24964 problem and assume that some details do not matter. Thus, you might
24965 assume that the name of the variable you use in an example does not matter.
24966 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24967 stray memory reference which happens to fetch from the location where that
24968 name is stored in memory; perhaps, if the name were different, the contents
24969 of that location would fool the debugger into doing the right thing despite
24970 the bug. Play it safe and give a specific, complete example. That is the
24971 easiest thing for you to do, and the most helpful.
24973 Keep in mind that the purpose of a bug report is to enable us to fix the
24974 bug. It may be that the bug has been reported previously, but neither
24975 you nor we can know that unless your bug report is complete and
24978 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24979 bell?'' Those bug reports are useless, and we urge everyone to
24980 @emph{refuse to respond to them} except to chide the sender to report
24983 To enable us to fix the bug, you should include all these things:
24987 The version of @value{GDBN}. @value{GDBN} announces it if you start
24988 with no arguments; you can also print it at any time using @code{show
24991 Without this, we will not know whether there is any point in looking for
24992 the bug in the current version of @value{GDBN}.
24995 The type of machine you are using, and the operating system name and
24999 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
25000 ``@value{GCC}--2.8.1''.
25003 What compiler (and its version) was used to compile the program you are
25004 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
25005 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
25006 to get this information; for other compilers, see the documentation for
25010 The command arguments you gave the compiler to compile your example and
25011 observe the bug. For example, did you use @samp{-O}? To guarantee
25012 you will not omit something important, list them all. A copy of the
25013 Makefile (or the output from make) is sufficient.
25015 If we were to try to guess the arguments, we would probably guess wrong
25016 and then we might not encounter the bug.
25019 A complete input script, and all necessary source files, that will
25023 A description of what behavior you observe that you believe is
25024 incorrect. For example, ``It gets a fatal signal.''
25026 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
25027 will certainly notice it. But if the bug is incorrect output, we might
25028 not notice unless it is glaringly wrong. You might as well not give us
25029 a chance to make a mistake.
25031 Even if the problem you experience is a fatal signal, you should still
25032 say so explicitly. Suppose something strange is going on, such as, your
25033 copy of @value{GDBN} is out of synch, or you have encountered a bug in
25034 the C library on your system. (This has happened!) Your copy might
25035 crash and ours would not. If you told us to expect a crash, then when
25036 ours fails to crash, we would know that the bug was not happening for
25037 us. If you had not told us to expect a crash, then we would not be able
25038 to draw any conclusion from our observations.
25041 @cindex recording a session script
25042 To collect all this information, you can use a session recording program
25043 such as @command{script}, which is available on many Unix systems.
25044 Just run your @value{GDBN} session inside @command{script} and then
25045 include the @file{typescript} file with your bug report.
25047 Another way to record a @value{GDBN} session is to run @value{GDBN}
25048 inside Emacs and then save the entire buffer to a file.
25051 If you wish to suggest changes to the @value{GDBN} source, send us context
25052 diffs. If you even discuss something in the @value{GDBN} source, refer to
25053 it by context, not by line number.
25055 The line numbers in our development sources will not match those in your
25056 sources. Your line numbers would convey no useful information to us.
25060 Here are some things that are not necessary:
25064 A description of the envelope of the bug.
25066 Often people who encounter a bug spend a lot of time investigating
25067 which changes to the input file will make the bug go away and which
25068 changes will not affect it.
25070 This is often time consuming and not very useful, because the way we
25071 will find the bug is by running a single example under the debugger
25072 with breakpoints, not by pure deduction from a series of examples.
25073 We recommend that you save your time for something else.
25075 Of course, if you can find a simpler example to report @emph{instead}
25076 of the original one, that is a convenience for us. Errors in the
25077 output will be easier to spot, running under the debugger will take
25078 less time, and so on.
25080 However, simplification is not vital; if you do not want to do this,
25081 report the bug anyway and send us the entire test case you used.
25084 A patch for the bug.
25086 A patch for the bug does help us if it is a good one. But do not omit
25087 the necessary information, such as the test case, on the assumption that
25088 a patch is all we need. We might see problems with your patch and decide
25089 to fix the problem another way, or we might not understand it at all.
25091 Sometimes with a program as complicated as @value{GDBN} it is very hard to
25092 construct an example that will make the program follow a certain path
25093 through the code. If you do not send us the example, we will not be able
25094 to construct one, so we will not be able to verify that the bug is fixed.
25096 And if we cannot understand what bug you are trying to fix, or why your
25097 patch should be an improvement, we will not install it. A test case will
25098 help us to understand.
25101 A guess about what the bug is or what it depends on.
25103 Such guesses are usually wrong. Even we cannot guess right about such
25104 things without first using the debugger to find the facts.
25107 @c The readline documentation is distributed with the readline code
25108 @c and consists of the two following files:
25110 @c inc-hist.texinfo
25111 @c Use -I with makeinfo to point to the appropriate directory,
25112 @c environment var TEXINPUTS with TeX.
25113 @include rluser.texi
25114 @include inc-hist.texinfo
25117 @node Formatting Documentation
25118 @appendix Formatting Documentation
25120 @cindex @value{GDBN} reference card
25121 @cindex reference card
25122 The @value{GDBN} 4 release includes an already-formatted reference card, ready
25123 for printing with PostScript or Ghostscript, in the @file{gdb}
25124 subdirectory of the main source directory@footnote{In
25125 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
25126 release.}. If you can use PostScript or Ghostscript with your printer,
25127 you can print the reference card immediately with @file{refcard.ps}.
25129 The release also includes the source for the reference card. You
25130 can format it, using @TeX{}, by typing:
25136 The @value{GDBN} reference card is designed to print in @dfn{landscape}
25137 mode on US ``letter'' size paper;
25138 that is, on a sheet 11 inches wide by 8.5 inches
25139 high. You will need to specify this form of printing as an option to
25140 your @sc{dvi} output program.
25142 @cindex documentation
25144 All the documentation for @value{GDBN} comes as part of the machine-readable
25145 distribution. The documentation is written in Texinfo format, which is
25146 a documentation system that uses a single source file to produce both
25147 on-line information and a printed manual. You can use one of the Info
25148 formatting commands to create the on-line version of the documentation
25149 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
25151 @value{GDBN} includes an already formatted copy of the on-line Info
25152 version of this manual in the @file{gdb} subdirectory. The main Info
25153 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
25154 subordinate files matching @samp{gdb.info*} in the same directory. If
25155 necessary, you can print out these files, or read them with any editor;
25156 but they are easier to read using the @code{info} subsystem in @sc{gnu}
25157 Emacs or the standalone @code{info} program, available as part of the
25158 @sc{gnu} Texinfo distribution.
25160 If you want to format these Info files yourself, you need one of the
25161 Info formatting programs, such as @code{texinfo-format-buffer} or
25164 If you have @code{makeinfo} installed, and are in the top level
25165 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
25166 version @value{GDBVN}), you can make the Info file by typing:
25173 If you want to typeset and print copies of this manual, you need @TeX{},
25174 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
25175 Texinfo definitions file.
25177 @TeX{} is a typesetting program; it does not print files directly, but
25178 produces output files called @sc{dvi} files. To print a typeset
25179 document, you need a program to print @sc{dvi} files. If your system
25180 has @TeX{} installed, chances are it has such a program. The precise
25181 command to use depends on your system; @kbd{lpr -d} is common; another
25182 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
25183 require a file name without any extension or a @samp{.dvi} extension.
25185 @TeX{} also requires a macro definitions file called
25186 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
25187 written in Texinfo format. On its own, @TeX{} cannot either read or
25188 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
25189 and is located in the @file{gdb-@var{version-number}/texinfo}
25192 If you have @TeX{} and a @sc{dvi} printer program installed, you can
25193 typeset and print this manual. First switch to the @file{gdb}
25194 subdirectory of the main source directory (for example, to
25195 @file{gdb-@value{GDBVN}/gdb}) and type:
25201 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
25203 @node Installing GDB
25204 @appendix Installing @value{GDBN}
25205 @cindex installation
25208 * Requirements:: Requirements for building @value{GDBN}
25209 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
25210 * Separate Objdir:: Compiling @value{GDBN} in another directory
25211 * Config Names:: Specifying names for hosts and targets
25212 * Configure Options:: Summary of options for configure
25213 * System-wide configuration:: Having a system-wide init file
25217 @section Requirements for Building @value{GDBN}
25218 @cindex building @value{GDBN}, requirements for
25220 Building @value{GDBN} requires various tools and packages to be available.
25221 Other packages will be used only if they are found.
25223 @heading Tools/Packages Necessary for Building @value{GDBN}
25225 @item ISO C90 compiler
25226 @value{GDBN} is written in ISO C90. It should be buildable with any
25227 working C90 compiler, e.g.@: GCC.
25231 @heading Tools/Packages Optional for Building @value{GDBN}
25235 @value{GDBN} can use the Expat XML parsing library. This library may be
25236 included with your operating system distribution; if it is not, you
25237 can get the latest version from @url{http://expat.sourceforge.net}.
25238 The @file{configure} script will search for this library in several
25239 standard locations; if it is installed in an unusual path, you can
25240 use the @option{--with-libexpat-prefix} option to specify its location.
25246 Remote protocol memory maps (@pxref{Memory Map Format})
25248 Target descriptions (@pxref{Target Descriptions})
25250 Remote shared library lists (@pxref{Library List Format})
25252 MS-Windows shared libraries (@pxref{Shared Libraries})
25256 @cindex compressed debug sections
25257 @value{GDBN} will use the @samp{zlib} library, if available, to read
25258 compressed debug sections. Some linkers, such as GNU gold, are capable
25259 of producing binaries with compressed debug sections. If @value{GDBN}
25260 is compiled with @samp{zlib}, it will be able to read the debug
25261 information in such binaries.
25263 The @samp{zlib} library is likely included with your operating system
25264 distribution; if it is not, you can get the latest version from
25265 @url{http://zlib.net}.
25268 @value{GDBN}'s features related to character sets (@pxref{Character
25269 Sets}) require a functioning @code{iconv} implementation. If you are
25270 on a GNU system, then this is provided by the GNU C Library. Some
25271 other systems also provide a working @code{iconv}.
25273 On systems with @code{iconv}, you can install GNU Libiconv. If you
25274 have previously installed Libiconv, you can use the
25275 @option{--with-libiconv-prefix} option to configure.
25277 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
25278 arrange to build Libiconv if a directory named @file{libiconv} appears
25279 in the top-most source directory. If Libiconv is built this way, and
25280 if the operating system does not provide a suitable @code{iconv}
25281 implementation, then the just-built library will automatically be used
25282 by @value{GDBN}. One easy way to set this up is to download GNU
25283 Libiconv, unpack it, and then rename the directory holding the
25284 Libiconv source code to @samp{libiconv}.
25287 @node Running Configure
25288 @section Invoking the @value{GDBN} @file{configure} Script
25289 @cindex configuring @value{GDBN}
25290 @value{GDBN} comes with a @file{configure} script that automates the process
25291 of preparing @value{GDBN} for installation; you can then use @code{make} to
25292 build the @code{gdb} program.
25294 @c irrelevant in info file; it's as current as the code it lives with.
25295 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
25296 look at the @file{README} file in the sources; we may have improved the
25297 installation procedures since publishing this manual.}
25300 The @value{GDBN} distribution includes all the source code you need for
25301 @value{GDBN} in a single directory, whose name is usually composed by
25302 appending the version number to @samp{gdb}.
25304 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
25305 @file{gdb-@value{GDBVN}} directory. That directory contains:
25308 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
25309 script for configuring @value{GDBN} and all its supporting libraries
25311 @item gdb-@value{GDBVN}/gdb
25312 the source specific to @value{GDBN} itself
25314 @item gdb-@value{GDBVN}/bfd
25315 source for the Binary File Descriptor library
25317 @item gdb-@value{GDBVN}/include
25318 @sc{gnu} include files
25320 @item gdb-@value{GDBVN}/libiberty
25321 source for the @samp{-liberty} free software library
25323 @item gdb-@value{GDBVN}/opcodes
25324 source for the library of opcode tables and disassemblers
25326 @item gdb-@value{GDBVN}/readline
25327 source for the @sc{gnu} command-line interface
25329 @item gdb-@value{GDBVN}/glob
25330 source for the @sc{gnu} filename pattern-matching subroutine
25332 @item gdb-@value{GDBVN}/mmalloc
25333 source for the @sc{gnu} memory-mapped malloc package
25336 The simplest way to configure and build @value{GDBN} is to run @file{configure}
25337 from the @file{gdb-@var{version-number}} source directory, which in
25338 this example is the @file{gdb-@value{GDBVN}} directory.
25340 First switch to the @file{gdb-@var{version-number}} source directory
25341 if you are not already in it; then run @file{configure}. Pass the
25342 identifier for the platform on which @value{GDBN} will run as an
25348 cd gdb-@value{GDBVN}
25349 ./configure @var{host}
25354 where @var{host} is an identifier such as @samp{sun4} or
25355 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
25356 (You can often leave off @var{host}; @file{configure} tries to guess the
25357 correct value by examining your system.)
25359 Running @samp{configure @var{host}} and then running @code{make} builds the
25360 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
25361 libraries, then @code{gdb} itself. The configured source files, and the
25362 binaries, are left in the corresponding source directories.
25365 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
25366 system does not recognize this automatically when you run a different
25367 shell, you may need to run @code{sh} on it explicitly:
25370 sh configure @var{host}
25373 If you run @file{configure} from a directory that contains source
25374 directories for multiple libraries or programs, such as the
25375 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
25377 creates configuration files for every directory level underneath (unless
25378 you tell it not to, with the @samp{--norecursion} option).
25380 You should run the @file{configure} script from the top directory in the
25381 source tree, the @file{gdb-@var{version-number}} directory. If you run
25382 @file{configure} from one of the subdirectories, you will configure only
25383 that subdirectory. That is usually not what you want. In particular,
25384 if you run the first @file{configure} from the @file{gdb} subdirectory
25385 of the @file{gdb-@var{version-number}} directory, you will omit the
25386 configuration of @file{bfd}, @file{readline}, and other sibling
25387 directories of the @file{gdb} subdirectory. This leads to build errors
25388 about missing include files such as @file{bfd/bfd.h}.
25390 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
25391 However, you should make sure that the shell on your path (named by
25392 the @samp{SHELL} environment variable) is publicly readable. Remember
25393 that @value{GDBN} uses the shell to start your program---some systems refuse to
25394 let @value{GDBN} debug child processes whose programs are not readable.
25396 @node Separate Objdir
25397 @section Compiling @value{GDBN} in Another Directory
25399 If you want to run @value{GDBN} versions for several host or target machines,
25400 you need a different @code{gdb} compiled for each combination of
25401 host and target. @file{configure} is designed to make this easy by
25402 allowing you to generate each configuration in a separate subdirectory,
25403 rather than in the source directory. If your @code{make} program
25404 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
25405 @code{make} in each of these directories builds the @code{gdb}
25406 program specified there.
25408 To build @code{gdb} in a separate directory, run @file{configure}
25409 with the @samp{--srcdir} option to specify where to find the source.
25410 (You also need to specify a path to find @file{configure}
25411 itself from your working directory. If the path to @file{configure}
25412 would be the same as the argument to @samp{--srcdir}, you can leave out
25413 the @samp{--srcdir} option; it is assumed.)
25415 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
25416 separate directory for a Sun 4 like this:
25420 cd gdb-@value{GDBVN}
25423 ../gdb-@value{GDBVN}/configure sun4
25428 When @file{configure} builds a configuration using a remote source
25429 directory, it creates a tree for the binaries with the same structure
25430 (and using the same names) as the tree under the source directory. In
25431 the example, you'd find the Sun 4 library @file{libiberty.a} in the
25432 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
25433 @file{gdb-sun4/gdb}.
25435 Make sure that your path to the @file{configure} script has just one
25436 instance of @file{gdb} in it. If your path to @file{configure} looks
25437 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
25438 one subdirectory of @value{GDBN}, not the whole package. This leads to
25439 build errors about missing include files such as @file{bfd/bfd.h}.
25441 One popular reason to build several @value{GDBN} configurations in separate
25442 directories is to configure @value{GDBN} for cross-compiling (where
25443 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
25444 programs that run on another machine---the @dfn{target}).
25445 You specify a cross-debugging target by
25446 giving the @samp{--target=@var{target}} option to @file{configure}.
25448 When you run @code{make} to build a program or library, you must run
25449 it in a configured directory---whatever directory you were in when you
25450 called @file{configure} (or one of its subdirectories).
25452 The @code{Makefile} that @file{configure} generates in each source
25453 directory also runs recursively. If you type @code{make} in a source
25454 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
25455 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
25456 will build all the required libraries, and then build GDB.
25458 When you have multiple hosts or targets configured in separate
25459 directories, you can run @code{make} on them in parallel (for example,
25460 if they are NFS-mounted on each of the hosts); they will not interfere
25464 @section Specifying Names for Hosts and Targets
25466 The specifications used for hosts and targets in the @file{configure}
25467 script are based on a three-part naming scheme, but some short predefined
25468 aliases are also supported. The full naming scheme encodes three pieces
25469 of information in the following pattern:
25472 @var{architecture}-@var{vendor}-@var{os}
25475 For example, you can use the alias @code{sun4} as a @var{host} argument,
25476 or as the value for @var{target} in a @code{--target=@var{target}}
25477 option. The equivalent full name is @samp{sparc-sun-sunos4}.
25479 The @file{configure} script accompanying @value{GDBN} does not provide
25480 any query facility to list all supported host and target names or
25481 aliases. @file{configure} calls the Bourne shell script
25482 @code{config.sub} to map abbreviations to full names; you can read the
25483 script, if you wish, or you can use it to test your guesses on
25484 abbreviations---for example:
25487 % sh config.sub i386-linux
25489 % sh config.sub alpha-linux
25490 alpha-unknown-linux-gnu
25491 % sh config.sub hp9k700
25493 % sh config.sub sun4
25494 sparc-sun-sunos4.1.1
25495 % sh config.sub sun3
25496 m68k-sun-sunos4.1.1
25497 % sh config.sub i986v
25498 Invalid configuration `i986v': machine `i986v' not recognized
25502 @code{config.sub} is also distributed in the @value{GDBN} source
25503 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
25505 @node Configure Options
25506 @section @file{configure} Options
25508 Here is a summary of the @file{configure} options and arguments that
25509 are most often useful for building @value{GDBN}. @file{configure} also has
25510 several other options not listed here. @inforef{What Configure
25511 Does,,configure.info}, for a full explanation of @file{configure}.
25514 configure @r{[}--help@r{]}
25515 @r{[}--prefix=@var{dir}@r{]}
25516 @r{[}--exec-prefix=@var{dir}@r{]}
25517 @r{[}--srcdir=@var{dirname}@r{]}
25518 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
25519 @r{[}--target=@var{target}@r{]}
25524 You may introduce options with a single @samp{-} rather than
25525 @samp{--} if you prefer; but you may abbreviate option names if you use
25530 Display a quick summary of how to invoke @file{configure}.
25532 @item --prefix=@var{dir}
25533 Configure the source to install programs and files under directory
25536 @item --exec-prefix=@var{dir}
25537 Configure the source to install programs under directory
25540 @c avoid splitting the warning from the explanation:
25542 @item --srcdir=@var{dirname}
25543 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
25544 @code{make} that implements the @code{VPATH} feature.}@*
25545 Use this option to make configurations in directories separate from the
25546 @value{GDBN} source directories. Among other things, you can use this to
25547 build (or maintain) several configurations simultaneously, in separate
25548 directories. @file{configure} writes configuration-specific files in
25549 the current directory, but arranges for them to use the source in the
25550 directory @var{dirname}. @file{configure} creates directories under
25551 the working directory in parallel to the source directories below
25554 @item --norecursion
25555 Configure only the directory level where @file{configure} is executed; do not
25556 propagate configuration to subdirectories.
25558 @item --target=@var{target}
25559 Configure @value{GDBN} for cross-debugging programs running on the specified
25560 @var{target}. Without this option, @value{GDBN} is configured to debug
25561 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
25563 There is no convenient way to generate a list of all available targets.
25565 @item @var{host} @dots{}
25566 Configure @value{GDBN} to run on the specified @var{host}.
25568 There is no convenient way to generate a list of all available hosts.
25571 There are many other options available as well, but they are generally
25572 needed for special purposes only.
25574 @node System-wide configuration
25575 @section System-wide configuration and settings
25576 @cindex system-wide init file
25578 @value{GDBN} can be configured to have a system-wide init file;
25579 this file will be read and executed at startup (@pxref{Startup, , What
25580 @value{GDBN} does during startup}).
25582 Here is the corresponding configure option:
25585 @item --with-system-gdbinit=@var{file}
25586 Specify that the default location of the system-wide init file is
25590 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
25591 it may be subject to relocation. Two possible cases:
25595 If the default location of this init file contains @file{$prefix},
25596 it will be subject to relocation. Suppose that the configure options
25597 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
25598 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
25599 init file is looked for as @file{$install/etc/gdbinit} instead of
25600 @file{$prefix/etc/gdbinit}.
25603 By contrast, if the default location does not contain the prefix,
25604 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
25605 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
25606 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
25607 wherever @value{GDBN} is installed.
25610 @node Maintenance Commands
25611 @appendix Maintenance Commands
25612 @cindex maintenance commands
25613 @cindex internal commands
25615 In addition to commands intended for @value{GDBN} users, @value{GDBN}
25616 includes a number of commands intended for @value{GDBN} developers,
25617 that are not documented elsewhere in this manual. These commands are
25618 provided here for reference. (For commands that turn on debugging
25619 messages, see @ref{Debugging Output}.)
25622 @kindex maint agent
25623 @item maint agent @var{expression}
25624 Translate the given @var{expression} into remote agent bytecodes.
25625 This command is useful for debugging the Agent Expression mechanism
25626 (@pxref{Agent Expressions}).
25628 @kindex maint info breakpoints
25629 @item @anchor{maint info breakpoints}maint info breakpoints
25630 Using the same format as @samp{info breakpoints}, display both the
25631 breakpoints you've set explicitly, and those @value{GDBN} is using for
25632 internal purposes. Internal breakpoints are shown with negative
25633 breakpoint numbers. The type column identifies what kind of breakpoint
25638 Normal, explicitly set breakpoint.
25641 Normal, explicitly set watchpoint.
25644 Internal breakpoint, used to handle correctly stepping through
25645 @code{longjmp} calls.
25647 @item longjmp resume
25648 Internal breakpoint at the target of a @code{longjmp}.
25651 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
25654 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
25657 Shared library events.
25661 @kindex set displaced-stepping
25662 @kindex show displaced-stepping
25663 @cindex displaced stepping support
25664 @cindex out-of-line single-stepping
25665 @item set displaced-stepping
25666 @itemx show displaced-stepping
25667 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
25668 if the target supports it. Displaced stepping is a way to single-step
25669 over breakpoints without removing them from the inferior, by executing
25670 an out-of-line copy of the instruction that was originally at the
25671 breakpoint location. It is also known as out-of-line single-stepping.
25674 @item set displaced-stepping on
25675 If the target architecture supports it, @value{GDBN} will use
25676 displaced stepping to step over breakpoints.
25678 @item set displaced-stepping off
25679 @value{GDBN} will not use displaced stepping to step over breakpoints,
25680 even if such is supported by the target architecture.
25682 @cindex non-stop mode, and @samp{set displaced-stepping}
25683 @item set displaced-stepping auto
25684 This is the default mode. @value{GDBN} will use displaced stepping
25685 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
25686 architecture supports displaced stepping.
25689 @kindex maint check-symtabs
25690 @item maint check-symtabs
25691 Check the consistency of psymtabs and symtabs.
25693 @kindex maint cplus first_component
25694 @item maint cplus first_component @var{name}
25695 Print the first C@t{++} class/namespace component of @var{name}.
25697 @kindex maint cplus namespace
25698 @item maint cplus namespace
25699 Print the list of possible C@t{++} namespaces.
25701 @kindex maint demangle
25702 @item maint demangle @var{name}
25703 Demangle a C@t{++} or Objective-C mangled @var{name}.
25705 @kindex maint deprecate
25706 @kindex maint undeprecate
25707 @cindex deprecated commands
25708 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
25709 @itemx maint undeprecate @var{command}
25710 Deprecate or undeprecate the named @var{command}. Deprecated commands
25711 cause @value{GDBN} to issue a warning when you use them. The optional
25712 argument @var{replacement} says which newer command should be used in
25713 favor of the deprecated one; if it is given, @value{GDBN} will mention
25714 the replacement as part of the warning.
25716 @kindex maint dump-me
25717 @item maint dump-me
25718 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
25719 Cause a fatal signal in the debugger and force it to dump its core.
25720 This is supported only on systems which support aborting a program
25721 with the @code{SIGQUIT} signal.
25723 @kindex maint internal-error
25724 @kindex maint internal-warning
25725 @item maint internal-error @r{[}@var{message-text}@r{]}
25726 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
25727 Cause @value{GDBN} to call the internal function @code{internal_error}
25728 or @code{internal_warning} and hence behave as though an internal error
25729 or internal warning has been detected. In addition to reporting the
25730 internal problem, these functions give the user the opportunity to
25731 either quit @value{GDBN} or create a core file of the current
25732 @value{GDBN} session.
25734 These commands take an optional parameter @var{message-text} that is
25735 used as the text of the error or warning message.
25737 Here's an example of using @code{internal-error}:
25740 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
25741 @dots{}/maint.c:121: internal-error: testing, 1, 2
25742 A problem internal to GDB has been detected. Further
25743 debugging may prove unreliable.
25744 Quit this debugging session? (y or n) @kbd{n}
25745 Create a core file? (y or n) @kbd{n}
25749 @cindex @value{GDBN} internal error
25750 @cindex internal errors, control of @value{GDBN} behavior
25752 @kindex maint set internal-error
25753 @kindex maint show internal-error
25754 @kindex maint set internal-warning
25755 @kindex maint show internal-warning
25756 @item maint set internal-error @var{action} [ask|yes|no]
25757 @itemx maint show internal-error @var{action}
25758 @itemx maint set internal-warning @var{action} [ask|yes|no]
25759 @itemx maint show internal-warning @var{action}
25760 When @value{GDBN} reports an internal problem (error or warning) it
25761 gives the user the opportunity to both quit @value{GDBN} and create a
25762 core file of the current @value{GDBN} session. These commands let you
25763 override the default behaviour for each particular @var{action},
25764 described in the table below.
25768 You can specify that @value{GDBN} should always (yes) or never (no)
25769 quit. The default is to ask the user what to do.
25772 You can specify that @value{GDBN} should always (yes) or never (no)
25773 create a core file. The default is to ask the user what to do.
25776 @kindex maint packet
25777 @item maint packet @var{text}
25778 If @value{GDBN} is talking to an inferior via the serial protocol,
25779 then this command sends the string @var{text} to the inferior, and
25780 displays the response packet. @value{GDBN} supplies the initial
25781 @samp{$} character, the terminating @samp{#} character, and the
25784 @kindex maint print architecture
25785 @item maint print architecture @r{[}@var{file}@r{]}
25786 Print the entire architecture configuration. The optional argument
25787 @var{file} names the file where the output goes.
25789 @kindex maint print c-tdesc
25790 @item maint print c-tdesc
25791 Print the current target description (@pxref{Target Descriptions}) as
25792 a C source file. The created source file can be used in @value{GDBN}
25793 when an XML parser is not available to parse the description.
25795 @kindex maint print dummy-frames
25796 @item maint print dummy-frames
25797 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
25800 (@value{GDBP}) @kbd{b add}
25802 (@value{GDBP}) @kbd{print add(2,3)}
25803 Breakpoint 2, add (a=2, b=3) at @dots{}
25805 The program being debugged stopped while in a function called from GDB.
25807 (@value{GDBP}) @kbd{maint print dummy-frames}
25808 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
25809 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
25810 call_lo=0x01014000 call_hi=0x01014001
25814 Takes an optional file parameter.
25816 @kindex maint print registers
25817 @kindex maint print raw-registers
25818 @kindex maint print cooked-registers
25819 @kindex maint print register-groups
25820 @item maint print registers @r{[}@var{file}@r{]}
25821 @itemx maint print raw-registers @r{[}@var{file}@r{]}
25822 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
25823 @itemx maint print register-groups @r{[}@var{file}@r{]}
25824 Print @value{GDBN}'s internal register data structures.
25826 The command @code{maint print raw-registers} includes the contents of
25827 the raw register cache; the command @code{maint print cooked-registers}
25828 includes the (cooked) value of all registers; and the command
25829 @code{maint print register-groups} includes the groups that each
25830 register is a member of. @xref{Registers,, Registers, gdbint,
25831 @value{GDBN} Internals}.
25833 These commands take an optional parameter, a file name to which to
25834 write the information.
25836 @kindex maint print reggroups
25837 @item maint print reggroups @r{[}@var{file}@r{]}
25838 Print @value{GDBN}'s internal register group data structures. The
25839 optional argument @var{file} tells to what file to write the
25842 The register groups info looks like this:
25845 (@value{GDBP}) @kbd{maint print reggroups}
25858 This command forces @value{GDBN} to flush its internal register cache.
25860 @kindex maint print objfiles
25861 @cindex info for known object files
25862 @item maint print objfiles
25863 Print a dump of all known object files. For each object file, this
25864 command prints its name, address in memory, and all of its psymtabs
25867 @kindex maint print statistics
25868 @cindex bcache statistics
25869 @item maint print statistics
25870 This command prints, for each object file in the program, various data
25871 about that object file followed by the byte cache (@dfn{bcache})
25872 statistics for the object file. The objfile data includes the number
25873 of minimal, partial, full, and stabs symbols, the number of types
25874 defined by the objfile, the number of as yet unexpanded psym tables,
25875 the number of line tables and string tables, and the amount of memory
25876 used by the various tables. The bcache statistics include the counts,
25877 sizes, and counts of duplicates of all and unique objects, max,
25878 average, and median entry size, total memory used and its overhead and
25879 savings, and various measures of the hash table size and chain
25882 @kindex maint print target-stack
25883 @cindex target stack description
25884 @item maint print target-stack
25885 A @dfn{target} is an interface between the debugger and a particular
25886 kind of file or process. Targets can be stacked in @dfn{strata},
25887 so that more than one target can potentially respond to a request.
25888 In particular, memory accesses will walk down the stack of targets
25889 until they find a target that is interested in handling that particular
25892 This command prints a short description of each layer that was pushed on
25893 the @dfn{target stack}, starting from the top layer down to the bottom one.
25895 @kindex maint print type
25896 @cindex type chain of a data type
25897 @item maint print type @var{expr}
25898 Print the type chain for a type specified by @var{expr}. The argument
25899 can be either a type name or a symbol. If it is a symbol, the type of
25900 that symbol is described. The type chain produced by this command is
25901 a recursive definition of the data type as stored in @value{GDBN}'s
25902 data structures, including its flags and contained types.
25904 @kindex maint set dwarf2 max-cache-age
25905 @kindex maint show dwarf2 max-cache-age
25906 @item maint set dwarf2 max-cache-age
25907 @itemx maint show dwarf2 max-cache-age
25908 Control the DWARF 2 compilation unit cache.
25910 @cindex DWARF 2 compilation units cache
25911 In object files with inter-compilation-unit references, such as those
25912 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
25913 reader needs to frequently refer to previously read compilation units.
25914 This setting controls how long a compilation unit will remain in the
25915 cache if it is not referenced. A higher limit means that cached
25916 compilation units will be stored in memory longer, and more total
25917 memory will be used. Setting it to zero disables caching, which will
25918 slow down @value{GDBN} startup, but reduce memory consumption.
25920 @kindex maint set profile
25921 @kindex maint show profile
25922 @cindex profiling GDB
25923 @item maint set profile
25924 @itemx maint show profile
25925 Control profiling of @value{GDBN}.
25927 Profiling will be disabled until you use the @samp{maint set profile}
25928 command to enable it. When you enable profiling, the system will begin
25929 collecting timing and execution count data; when you disable profiling or
25930 exit @value{GDBN}, the results will be written to a log file. Remember that
25931 if you use profiling, @value{GDBN} will overwrite the profiling log file
25932 (often called @file{gmon.out}). If you have a record of important profiling
25933 data in a @file{gmon.out} file, be sure to move it to a safe location.
25935 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
25936 compiled with the @samp{-pg} compiler option.
25938 @kindex maint show-debug-regs
25939 @cindex hardware debug registers
25940 @item maint show-debug-regs
25941 Control whether to show variables that mirror the hardware debug
25942 registers. Use @code{ON} to enable, @code{OFF} to disable. If
25943 enabled, the debug registers values are shown when @value{GDBN} inserts or
25944 removes a hardware breakpoint or watchpoint, and when the inferior
25945 triggers a hardware-assisted breakpoint or watchpoint.
25947 @kindex maint space
25948 @cindex memory used by commands
25950 Control whether to display memory usage for each command. If set to a
25951 nonzero value, @value{GDBN} will display how much memory each command
25952 took, following the command's own output. This can also be requested
25953 by invoking @value{GDBN} with the @option{--statistics} command-line
25954 switch (@pxref{Mode Options}).
25957 @cindex time of command execution
25959 Control whether to display the execution time for each command. If
25960 set to a nonzero value, @value{GDBN} will display how much time it
25961 took to execute each command, following the command's own output.
25962 The time is not printed for the commands that run the target, since
25963 there's no mechanism currently to compute how much time was spend
25964 by @value{GDBN} and how much time was spend by the program been debugged.
25965 it's not possibly currently
25966 This can also be requested by invoking @value{GDBN} with the
25967 @option{--statistics} command-line switch (@pxref{Mode Options}).
25969 @kindex maint translate-address
25970 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25971 Find the symbol stored at the location specified by the address
25972 @var{addr} and an optional section name @var{section}. If found,
25973 @value{GDBN} prints the name of the closest symbol and an offset from
25974 the symbol's location to the specified address. This is similar to
25975 the @code{info address} command (@pxref{Symbols}), except that this
25976 command also allows to find symbols in other sections.
25978 If section was not specified, the section in which the symbol was found
25979 is also printed. For dynamically linked executables, the name of
25980 executable or shared library containing the symbol is printed as well.
25984 The following command is useful for non-interactive invocations of
25985 @value{GDBN}, such as in the test suite.
25988 @item set watchdog @var{nsec}
25989 @kindex set watchdog
25990 @cindex watchdog timer
25991 @cindex timeout for commands
25992 Set the maximum number of seconds @value{GDBN} will wait for the
25993 target operation to finish. If this time expires, @value{GDBN}
25994 reports and error and the command is aborted.
25996 @item show watchdog
25997 Show the current setting of the target wait timeout.
26000 @node Remote Protocol
26001 @appendix @value{GDBN} Remote Serial Protocol
26006 * Stop Reply Packets::
26007 * General Query Packets::
26008 * Register Packet Format::
26009 * Tracepoint Packets::
26010 * Host I/O Packets::
26012 * Notification Packets::
26013 * Remote Non-Stop::
26014 * Packet Acknowledgment::
26016 * File-I/O Remote Protocol Extension::
26017 * Library List Format::
26018 * Memory Map Format::
26024 There may be occasions when you need to know something about the
26025 protocol---for example, if there is only one serial port to your target
26026 machine, you might want your program to do something special if it
26027 recognizes a packet meant for @value{GDBN}.
26029 In the examples below, @samp{->} and @samp{<-} are used to indicate
26030 transmitted and received data, respectively.
26032 @cindex protocol, @value{GDBN} remote serial
26033 @cindex serial protocol, @value{GDBN} remote
26034 @cindex remote serial protocol
26035 All @value{GDBN} commands and responses (other than acknowledgments
26036 and notifications, see @ref{Notification Packets}) are sent as a
26037 @var{packet}. A @var{packet} is introduced with the character
26038 @samp{$}, the actual @var{packet-data}, and the terminating character
26039 @samp{#} followed by a two-digit @var{checksum}:
26042 @code{$}@var{packet-data}@code{#}@var{checksum}
26046 @cindex checksum, for @value{GDBN} remote
26048 The two-digit @var{checksum} is computed as the modulo 256 sum of all
26049 characters between the leading @samp{$} and the trailing @samp{#} (an
26050 eight bit unsigned checksum).
26052 Implementors should note that prior to @value{GDBN} 5.0 the protocol
26053 specification also included an optional two-digit @var{sequence-id}:
26056 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
26059 @cindex sequence-id, for @value{GDBN} remote
26061 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
26062 has never output @var{sequence-id}s. Stubs that handle packets added
26063 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
26065 When either the host or the target machine receives a packet, the first
26066 response expected is an acknowledgment: either @samp{+} (to indicate
26067 the package was received correctly) or @samp{-} (to request
26071 -> @code{$}@var{packet-data}@code{#}@var{checksum}
26076 The @samp{+}/@samp{-} acknowledgments can be disabled
26077 once a connection is established.
26078 @xref{Packet Acknowledgment}, for details.
26080 The host (@value{GDBN}) sends @var{command}s, and the target (the
26081 debugging stub incorporated in your program) sends a @var{response}. In
26082 the case of step and continue @var{command}s, the response is only sent
26083 when the operation has completed, and the target has again stopped all
26084 threads in all attached processes. This is the default all-stop mode
26085 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
26086 execution mode; see @ref{Remote Non-Stop}, for details.
26088 @var{packet-data} consists of a sequence of characters with the
26089 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
26092 @cindex remote protocol, field separator
26093 Fields within the packet should be separated using @samp{,} @samp{;} or
26094 @samp{:}. Except where otherwise noted all numbers are represented in
26095 @sc{hex} with leading zeros suppressed.
26097 Implementors should note that prior to @value{GDBN} 5.0, the character
26098 @samp{:} could not appear as the third character in a packet (as it
26099 would potentially conflict with the @var{sequence-id}).
26101 @cindex remote protocol, binary data
26102 @anchor{Binary Data}
26103 Binary data in most packets is encoded either as two hexadecimal
26104 digits per byte of binary data. This allowed the traditional remote
26105 protocol to work over connections which were only seven-bit clean.
26106 Some packets designed more recently assume an eight-bit clean
26107 connection, and use a more efficient encoding to send and receive
26110 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
26111 as an escape character. Any escaped byte is transmitted as the escape
26112 character followed by the original character XORed with @code{0x20}.
26113 For example, the byte @code{0x7d} would be transmitted as the two
26114 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
26115 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
26116 @samp{@}}) must always be escaped. Responses sent by the stub
26117 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
26118 is not interpreted as the start of a run-length encoded sequence
26121 Response @var{data} can be run-length encoded to save space.
26122 Run-length encoding replaces runs of identical characters with one
26123 instance of the repeated character, followed by a @samp{*} and a
26124 repeat count. The repeat count is itself sent encoded, to avoid
26125 binary characters in @var{data}: a value of @var{n} is sent as
26126 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
26127 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
26128 code 32) for a repeat count of 3. (This is because run-length
26129 encoding starts to win for counts 3 or more.) Thus, for example,
26130 @samp{0* } is a run-length encoding of ``0000'': the space character
26131 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
26134 The printable characters @samp{#} and @samp{$} or with a numeric value
26135 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
26136 seven repeats (@samp{$}) can be expanded using a repeat count of only
26137 five (@samp{"}). For example, @samp{00000000} can be encoded as
26140 The error response returned for some packets includes a two character
26141 error number. That number is not well defined.
26143 @cindex empty response, for unsupported packets
26144 For any @var{command} not supported by the stub, an empty response
26145 (@samp{$#00}) should be returned. That way it is possible to extend the
26146 protocol. A newer @value{GDBN} can tell if a packet is supported based
26149 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
26150 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
26156 The following table provides a complete list of all currently defined
26157 @var{command}s and their corresponding response @var{data}.
26158 @xref{File-I/O Remote Protocol Extension}, for details about the File
26159 I/O extension of the remote protocol.
26161 Each packet's description has a template showing the packet's overall
26162 syntax, followed by an explanation of the packet's meaning. We
26163 include spaces in some of the templates for clarity; these are not
26164 part of the packet's syntax. No @value{GDBN} packet uses spaces to
26165 separate its components. For example, a template like @samp{foo
26166 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
26167 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
26168 @var{baz}. @value{GDBN} does not transmit a space character between the
26169 @samp{foo} and the @var{bar}, or between the @var{bar} and the
26172 @cindex @var{thread-id}, in remote protocol
26173 @anchor{thread-id syntax}
26174 Several packets and replies include a @var{thread-id} field to identify
26175 a thread. Normally these are positive numbers with a target-specific
26176 interpretation, formatted as big-endian hex strings. A @var{thread-id}
26177 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
26180 In addition, the remote protocol supports a multiprocess feature in
26181 which the @var{thread-id} syntax is extended to optionally include both
26182 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
26183 The @var{pid} (process) and @var{tid} (thread) components each have the
26184 format described above: a positive number with target-specific
26185 interpretation formatted as a big-endian hex string, literal @samp{-1}
26186 to indicate all processes or threads (respectively), or @samp{0} to
26187 indicate an arbitrary process or thread. Specifying just a process, as
26188 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
26189 error to specify all processes but a specific thread, such as
26190 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
26191 for those packets and replies explicitly documented to include a process
26192 ID, rather than a @var{thread-id}.
26194 The multiprocess @var{thread-id} syntax extensions are only used if both
26195 @value{GDBN} and the stub report support for the @samp{multiprocess}
26196 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
26199 Note that all packet forms beginning with an upper- or lower-case
26200 letter, other than those described here, are reserved for future use.
26202 Here are the packet descriptions.
26207 @cindex @samp{!} packet
26208 @anchor{extended mode}
26209 Enable extended mode. In extended mode, the remote server is made
26210 persistent. The @samp{R} packet is used to restart the program being
26216 The remote target both supports and has enabled extended mode.
26220 @cindex @samp{?} packet
26221 Indicate the reason the target halted. The reply is the same as for
26222 step and continue. This packet has a special interpretation when the
26223 target is in non-stop mode; see @ref{Remote Non-Stop}.
26226 @xref{Stop Reply Packets}, for the reply specifications.
26228 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
26229 @cindex @samp{A} packet
26230 Initialized @code{argv[]} array passed into program. @var{arglen}
26231 specifies the number of bytes in the hex encoded byte stream
26232 @var{arg}. See @code{gdbserver} for more details.
26237 The arguments were set.
26243 @cindex @samp{b} packet
26244 (Don't use this packet; its behavior is not well-defined.)
26245 Change the serial line speed to @var{baud}.
26247 JTC: @emph{When does the transport layer state change? When it's
26248 received, or after the ACK is transmitted. In either case, there are
26249 problems if the command or the acknowledgment packet is dropped.}
26251 Stan: @emph{If people really wanted to add something like this, and get
26252 it working for the first time, they ought to modify ser-unix.c to send
26253 some kind of out-of-band message to a specially-setup stub and have the
26254 switch happen "in between" packets, so that from remote protocol's point
26255 of view, nothing actually happened.}
26257 @item B @var{addr},@var{mode}
26258 @cindex @samp{B} packet
26259 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
26260 breakpoint at @var{addr}.
26262 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
26263 (@pxref{insert breakpoint or watchpoint packet}).
26266 @cindex @samp{bc} packet
26267 Backward continue. Execute the target system in reverse. No parameter.
26268 @xref{Reverse Execution}, for more information.
26271 @xref{Stop Reply Packets}, for the reply specifications.
26274 @cindex @samp{bs} packet
26275 Backward single step. Execute one instruction in reverse. No parameter.
26276 @xref{Reverse Execution}, for more information.
26279 @xref{Stop Reply Packets}, for the reply specifications.
26281 @item c @r{[}@var{addr}@r{]}
26282 @cindex @samp{c} packet
26283 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
26284 resume at current address.
26287 @xref{Stop Reply Packets}, for the reply specifications.
26289 @item C @var{sig}@r{[};@var{addr}@r{]}
26290 @cindex @samp{C} packet
26291 Continue with signal @var{sig} (hex signal number). If
26292 @samp{;@var{addr}} is omitted, resume at same address.
26295 @xref{Stop Reply Packets}, for the reply specifications.
26298 @cindex @samp{d} packet
26301 Don't use this packet; instead, define a general set packet
26302 (@pxref{General Query Packets}).
26306 @cindex @samp{D} packet
26307 The first form of the packet is used to detach @value{GDBN} from the
26308 remote system. It is sent to the remote target
26309 before @value{GDBN} disconnects via the @code{detach} command.
26311 The second form, including a process ID, is used when multiprocess
26312 protocol extensions are enabled (@pxref{multiprocess extensions}), to
26313 detach only a specific process. The @var{pid} is specified as a
26314 big-endian hex string.
26324 @item F @var{RC},@var{EE},@var{CF};@var{XX}
26325 @cindex @samp{F} packet
26326 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
26327 This is part of the File-I/O protocol extension. @xref{File-I/O
26328 Remote Protocol Extension}, for the specification.
26331 @anchor{read registers packet}
26332 @cindex @samp{g} packet
26333 Read general registers.
26337 @item @var{XX@dots{}}
26338 Each byte of register data is described by two hex digits. The bytes
26339 with the register are transmitted in target byte order. The size of
26340 each register and their position within the @samp{g} packet are
26341 determined by the @value{GDBN} internal gdbarch functions
26342 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
26343 specification of several standard @samp{g} packets is specified below.
26348 @item G @var{XX@dots{}}
26349 @cindex @samp{G} packet
26350 Write general registers. @xref{read registers packet}, for a
26351 description of the @var{XX@dots{}} data.
26361 @item H @var{c} @var{thread-id}
26362 @cindex @samp{H} packet
26363 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
26364 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
26365 should be @samp{c} for step and continue operations, @samp{g} for other
26366 operations. The thread designator @var{thread-id} has the format and
26367 interpretation described in @ref{thread-id syntax}.
26378 @c 'H': How restrictive (or permissive) is the thread model. If a
26379 @c thread is selected and stopped, are other threads allowed
26380 @c to continue to execute? As I mentioned above, I think the
26381 @c semantics of each command when a thread is selected must be
26382 @c described. For example:
26384 @c 'g': If the stub supports threads and a specific thread is
26385 @c selected, returns the register block from that thread;
26386 @c otherwise returns current registers.
26388 @c 'G' If the stub supports threads and a specific thread is
26389 @c selected, sets the registers of the register block of
26390 @c that thread; otherwise sets current registers.
26392 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
26393 @anchor{cycle step packet}
26394 @cindex @samp{i} packet
26395 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
26396 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
26397 step starting at that address.
26400 @cindex @samp{I} packet
26401 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
26405 @cindex @samp{k} packet
26408 FIXME: @emph{There is no description of how to operate when a specific
26409 thread context has been selected (i.e.@: does 'k' kill only that
26412 @item m @var{addr},@var{length}
26413 @cindex @samp{m} packet
26414 Read @var{length} bytes of memory starting at address @var{addr}.
26415 Note that @var{addr} may not be aligned to any particular boundary.
26417 The stub need not use any particular size or alignment when gathering
26418 data from memory for the response; even if @var{addr} is word-aligned
26419 and @var{length} is a multiple of the word size, the stub is free to
26420 use byte accesses, or not. For this reason, this packet may not be
26421 suitable for accessing memory-mapped I/O devices.
26422 @cindex alignment of remote memory accesses
26423 @cindex size of remote memory accesses
26424 @cindex memory, alignment and size of remote accesses
26428 @item @var{XX@dots{}}
26429 Memory contents; each byte is transmitted as a two-digit hexadecimal
26430 number. The reply may contain fewer bytes than requested if the
26431 server was able to read only part of the region of memory.
26436 @item M @var{addr},@var{length}:@var{XX@dots{}}
26437 @cindex @samp{M} packet
26438 Write @var{length} bytes of memory starting at address @var{addr}.
26439 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
26440 hexadecimal number.
26447 for an error (this includes the case where only part of the data was
26452 @cindex @samp{p} packet
26453 Read the value of register @var{n}; @var{n} is in hex.
26454 @xref{read registers packet}, for a description of how the returned
26455 register value is encoded.
26459 @item @var{XX@dots{}}
26460 the register's value
26464 Indicating an unrecognized @var{query}.
26467 @item P @var{n@dots{}}=@var{r@dots{}}
26468 @anchor{write register packet}
26469 @cindex @samp{P} packet
26470 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
26471 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
26472 digits for each byte in the register (target byte order).
26482 @item q @var{name} @var{params}@dots{}
26483 @itemx Q @var{name} @var{params}@dots{}
26484 @cindex @samp{q} packet
26485 @cindex @samp{Q} packet
26486 General query (@samp{q}) and set (@samp{Q}). These packets are
26487 described fully in @ref{General Query Packets}.
26490 @cindex @samp{r} packet
26491 Reset the entire system.
26493 Don't use this packet; use the @samp{R} packet instead.
26496 @cindex @samp{R} packet
26497 Restart the program being debugged. @var{XX}, while needed, is ignored.
26498 This packet is only available in extended mode (@pxref{extended mode}).
26500 The @samp{R} packet has no reply.
26502 @item s @r{[}@var{addr}@r{]}
26503 @cindex @samp{s} packet
26504 Single step. @var{addr} is the address at which to resume. If
26505 @var{addr} is omitted, resume at same address.
26508 @xref{Stop Reply Packets}, for the reply specifications.
26510 @item S @var{sig}@r{[};@var{addr}@r{]}
26511 @anchor{step with signal packet}
26512 @cindex @samp{S} packet
26513 Step with signal. This is analogous to the @samp{C} packet, but
26514 requests a single-step, rather than a normal resumption of execution.
26517 @xref{Stop Reply Packets}, for the reply specifications.
26519 @item t @var{addr}:@var{PP},@var{MM}
26520 @cindex @samp{t} packet
26521 Search backwards starting at address @var{addr} for a match with pattern
26522 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
26523 @var{addr} must be at least 3 digits.
26525 @item T @var{thread-id}
26526 @cindex @samp{T} packet
26527 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
26532 thread is still alive
26538 Packets starting with @samp{v} are identified by a multi-letter name,
26539 up to the first @samp{;} or @samp{?} (or the end of the packet).
26541 @item vAttach;@var{pid}
26542 @cindex @samp{vAttach} packet
26543 Attach to a new process with the specified process ID @var{pid}.
26544 The process ID is a
26545 hexadecimal integer identifying the process. In all-stop mode, all
26546 threads in the attached process are stopped; in non-stop mode, it may be
26547 attached without being stopped if that is supported by the target.
26549 @c In non-stop mode, on a successful vAttach, the stub should set the
26550 @c current thread to a thread of the newly-attached process. After
26551 @c attaching, GDB queries for the attached process's thread ID with qC.
26552 @c Also note that, from a user perspective, whether or not the
26553 @c target is stopped on attach in non-stop mode depends on whether you
26554 @c use the foreground or background version of the attach command, not
26555 @c on what vAttach does; GDB does the right thing with respect to either
26556 @c stopping or restarting threads.
26558 This packet is only available in extended mode (@pxref{extended mode}).
26564 @item @r{Any stop packet}
26565 for success in all-stop mode (@pxref{Stop Reply Packets})
26567 for success in non-stop mode (@pxref{Remote Non-Stop})
26570 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
26571 @cindex @samp{vCont} packet
26572 Resume the inferior, specifying different actions for each thread.
26573 If an action is specified with no @var{thread-id}, then it is applied to any
26574 threads that don't have a specific action specified; if no default action is
26575 specified then other threads should remain stopped in all-stop mode and
26576 in their current state in non-stop mode.
26577 Specifying multiple
26578 default actions is an error; specifying no actions is also an error.
26579 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
26581 Currently supported actions are:
26587 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
26591 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
26595 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
26598 The optional argument @var{addr} normally associated with the
26599 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
26600 not supported in @samp{vCont}.
26602 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
26603 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
26604 A stop reply should be generated for any affected thread not already stopped.
26605 When a thread is stopped by means of a @samp{t} action,
26606 the corresponding stop reply should indicate that the thread has stopped with
26607 signal @samp{0}, regardless of whether the target uses some other signal
26608 as an implementation detail.
26611 @xref{Stop Reply Packets}, for the reply specifications.
26614 @cindex @samp{vCont?} packet
26615 Request a list of actions supported by the @samp{vCont} packet.
26619 @item vCont@r{[};@var{action}@dots{}@r{]}
26620 The @samp{vCont} packet is supported. Each @var{action} is a supported
26621 command in the @samp{vCont} packet.
26623 The @samp{vCont} packet is not supported.
26626 @item vFile:@var{operation}:@var{parameter}@dots{}
26627 @cindex @samp{vFile} packet
26628 Perform a file operation on the target system. For details,
26629 see @ref{Host I/O Packets}.
26631 @item vFlashErase:@var{addr},@var{length}
26632 @cindex @samp{vFlashErase} packet
26633 Direct the stub to erase @var{length} bytes of flash starting at
26634 @var{addr}. The region may enclose any number of flash blocks, but
26635 its start and end must fall on block boundaries, as indicated by the
26636 flash block size appearing in the memory map (@pxref{Memory Map
26637 Format}). @value{GDBN} groups flash memory programming operations
26638 together, and sends a @samp{vFlashDone} request after each group; the
26639 stub is allowed to delay erase operation until the @samp{vFlashDone}
26640 packet is received.
26642 The stub must support @samp{vCont} if it reports support for
26643 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
26644 this case @samp{vCont} actions can be specified to apply to all threads
26645 in a process by using the @samp{p@var{pid}.-1} form of the
26656 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
26657 @cindex @samp{vFlashWrite} packet
26658 Direct the stub to write data to flash address @var{addr}. The data
26659 is passed in binary form using the same encoding as for the @samp{X}
26660 packet (@pxref{Binary Data}). The memory ranges specified by
26661 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
26662 not overlap, and must appear in order of increasing addresses
26663 (although @samp{vFlashErase} packets for higher addresses may already
26664 have been received; the ordering is guaranteed only between
26665 @samp{vFlashWrite} packets). If a packet writes to an address that was
26666 neither erased by a preceding @samp{vFlashErase} packet nor by some other
26667 target-specific method, the results are unpredictable.
26675 for vFlashWrite addressing non-flash memory
26681 @cindex @samp{vFlashDone} packet
26682 Indicate to the stub that flash programming operation is finished.
26683 The stub is permitted to delay or batch the effects of a group of
26684 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
26685 @samp{vFlashDone} packet is received. The contents of the affected
26686 regions of flash memory are unpredictable until the @samp{vFlashDone}
26687 request is completed.
26689 @item vKill;@var{pid}
26690 @cindex @samp{vKill} packet
26691 Kill the process with the specified process ID. @var{pid} is a
26692 hexadecimal integer identifying the process. This packet is used in
26693 preference to @samp{k} when multiprocess protocol extensions are
26694 supported; see @ref{multiprocess extensions}.
26704 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
26705 @cindex @samp{vRun} packet
26706 Run the program @var{filename}, passing it each @var{argument} on its
26707 command line. The file and arguments are hex-encoded strings. If
26708 @var{filename} is an empty string, the stub may use a default program
26709 (e.g.@: the last program run). The program is created in the stopped
26712 @c FIXME: What about non-stop mode?
26714 This packet is only available in extended mode (@pxref{extended mode}).
26720 @item @r{Any stop packet}
26721 for success (@pxref{Stop Reply Packets})
26725 @anchor{vStopped packet}
26726 @cindex @samp{vStopped} packet
26728 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
26729 reply and prompt for the stub to report another one.
26733 @item @r{Any stop packet}
26734 if there is another unreported stop event (@pxref{Stop Reply Packets})
26736 if there are no unreported stop events
26739 @item X @var{addr},@var{length}:@var{XX@dots{}}
26741 @cindex @samp{X} packet
26742 Write data to memory, where the data is transmitted in binary.
26743 @var{addr} is address, @var{length} is number of bytes,
26744 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
26754 @item z @var{type},@var{addr},@var{length}
26755 @itemx Z @var{type},@var{addr},@var{length}
26756 @anchor{insert breakpoint or watchpoint packet}
26757 @cindex @samp{z} packet
26758 @cindex @samp{Z} packets
26759 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
26760 watchpoint starting at address @var{address} and covering the next
26761 @var{length} bytes.
26763 Each breakpoint and watchpoint packet @var{type} is documented
26766 @emph{Implementation notes: A remote target shall return an empty string
26767 for an unrecognized breakpoint or watchpoint packet @var{type}. A
26768 remote target shall support either both or neither of a given
26769 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
26770 avoid potential problems with duplicate packets, the operations should
26771 be implemented in an idempotent way.}
26773 @item z0,@var{addr},@var{length}
26774 @itemx Z0,@var{addr},@var{length}
26775 @cindex @samp{z0} packet
26776 @cindex @samp{Z0} packet
26777 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
26778 @var{addr} of size @var{length}.
26780 A memory breakpoint is implemented by replacing the instruction at
26781 @var{addr} with a software breakpoint or trap instruction. The
26782 @var{length} is used by targets that indicates the size of the
26783 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
26784 @sc{mips} can insert either a 2 or 4 byte breakpoint).
26786 @emph{Implementation note: It is possible for a target to copy or move
26787 code that contains memory breakpoints (e.g., when implementing
26788 overlays). The behavior of this packet, in the presence of such a
26789 target, is not defined.}
26801 @item z1,@var{addr},@var{length}
26802 @itemx Z1,@var{addr},@var{length}
26803 @cindex @samp{z1} packet
26804 @cindex @samp{Z1} packet
26805 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
26806 address @var{addr} of size @var{length}.
26808 A hardware breakpoint is implemented using a mechanism that is not
26809 dependant on being able to modify the target's memory.
26811 @emph{Implementation note: A hardware breakpoint is not affected by code
26824 @item z2,@var{addr},@var{length}
26825 @itemx Z2,@var{addr},@var{length}
26826 @cindex @samp{z2} packet
26827 @cindex @samp{Z2} packet
26828 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
26840 @item z3,@var{addr},@var{length}
26841 @itemx Z3,@var{addr},@var{length}
26842 @cindex @samp{z3} packet
26843 @cindex @samp{Z3} packet
26844 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
26856 @item z4,@var{addr},@var{length}
26857 @itemx Z4,@var{addr},@var{length}
26858 @cindex @samp{z4} packet
26859 @cindex @samp{Z4} packet
26860 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
26874 @node Stop Reply Packets
26875 @section Stop Reply Packets
26876 @cindex stop reply packets
26878 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
26879 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
26880 receive any of the below as a reply. Except for @samp{?}
26881 and @samp{vStopped}, that reply is only returned
26882 when the target halts. In the below the exact meaning of @dfn{signal
26883 number} is defined by the header @file{include/gdb/signals.h} in the
26884 @value{GDBN} source code.
26886 As in the description of request packets, we include spaces in the
26887 reply templates for clarity; these are not part of the reply packet's
26888 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
26894 The program received signal number @var{AA} (a two-digit hexadecimal
26895 number). This is equivalent to a @samp{T} response with no
26896 @var{n}:@var{r} pairs.
26898 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
26899 @cindex @samp{T} packet reply
26900 The program received signal number @var{AA} (a two-digit hexadecimal
26901 number). This is equivalent to an @samp{S} response, except that the
26902 @samp{@var{n}:@var{r}} pairs can carry values of important registers
26903 and other information directly in the stop reply packet, reducing
26904 round-trip latency. Single-step and breakpoint traps are reported
26905 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
26909 If @var{n} is a hexadecimal number, it is a register number, and the
26910 corresponding @var{r} gives that register's value. @var{r} is a
26911 series of bytes in target byte order, with each byte given by a
26912 two-digit hex number.
26915 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
26916 the stopped thread, as specified in @ref{thread-id syntax}.
26919 If @var{n} is a recognized @dfn{stop reason}, it describes a more
26920 specific event that stopped the target. The currently defined stop
26921 reasons are listed below. @var{aa} should be @samp{05}, the trap
26922 signal. At most one stop reason should be present.
26925 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
26926 and go on to the next; this allows us to extend the protocol in the
26930 The currently defined stop reasons are:
26936 The packet indicates a watchpoint hit, and @var{r} is the data address, in
26939 @cindex shared library events, remote reply
26941 The packet indicates that the loaded libraries have changed.
26942 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
26943 list of loaded libraries. @var{r} is ignored.
26945 @cindex replay log events, remote reply
26947 The packet indicates that the target cannot continue replaying
26948 logged execution events, because it has reached the end (or the
26949 beginning when executing backward) of the log. The value of @var{r}
26950 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
26951 for more information.
26957 @itemx W @var{AA} ; process:@var{pid}
26958 The process exited, and @var{AA} is the exit status. This is only
26959 applicable to certain targets.
26961 The second form of the response, including the process ID of the exited
26962 process, can be used only when @value{GDBN} has reported support for
26963 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26964 The @var{pid} is formatted as a big-endian hex string.
26967 @itemx X @var{AA} ; process:@var{pid}
26968 The process terminated with signal @var{AA}.
26970 The second form of the response, including the process ID of the
26971 terminated process, can be used only when @value{GDBN} has reported
26972 support for multiprocess protocol extensions; see @ref{multiprocess
26973 extensions}. The @var{pid} is formatted as a big-endian hex string.
26975 @item O @var{XX}@dots{}
26976 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26977 written as the program's console output. This can happen at any time
26978 while the program is running and the debugger should continue to wait
26979 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
26981 @item F @var{call-id},@var{parameter}@dots{}
26982 @var{call-id} is the identifier which says which host system call should
26983 be called. This is just the name of the function. Translation into the
26984 correct system call is only applicable as it's defined in @value{GDBN}.
26985 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
26988 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
26989 this very system call.
26991 The target replies with this packet when it expects @value{GDBN} to
26992 call a host system call on behalf of the target. @value{GDBN} replies
26993 with an appropriate @samp{F} packet and keeps up waiting for the next
26994 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
26995 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
26996 Protocol Extension}, for more details.
27000 @node General Query Packets
27001 @section General Query Packets
27002 @cindex remote query requests
27004 Packets starting with @samp{q} are @dfn{general query packets};
27005 packets starting with @samp{Q} are @dfn{general set packets}. General
27006 query and set packets are a semi-unified form for retrieving and
27007 sending information to and from the stub.
27009 The initial letter of a query or set packet is followed by a name
27010 indicating what sort of thing the packet applies to. For example,
27011 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
27012 definitions with the stub. These packet names follow some
27017 The name must not contain commas, colons or semicolons.
27019 Most @value{GDBN} query and set packets have a leading upper case
27022 The names of custom vendor packets should use a company prefix, in
27023 lower case, followed by a period. For example, packets designed at
27024 the Acme Corporation might begin with @samp{qacme.foo} (for querying
27025 foos) or @samp{Qacme.bar} (for setting bars).
27028 The name of a query or set packet should be separated from any
27029 parameters by a @samp{:}; the parameters themselves should be
27030 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
27031 full packet name, and check for a separator or the end of the packet,
27032 in case two packet names share a common prefix. New packets should not begin
27033 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
27034 packets predate these conventions, and have arguments without any terminator
27035 for the packet name; we suspect they are in widespread use in places that
27036 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
27037 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
27040 Like the descriptions of the other packets, each description here
27041 has a template showing the packet's overall syntax, followed by an
27042 explanation of the packet's meaning. We include spaces in some of the
27043 templates for clarity; these are not part of the packet's syntax. No
27044 @value{GDBN} packet uses spaces to separate its components.
27046 Here are the currently defined query and set packets:
27051 @cindex current thread, remote request
27052 @cindex @samp{qC} packet
27053 Return the current thread ID.
27057 @item QC @var{thread-id}
27058 Where @var{thread-id} is a thread ID as documented in
27059 @ref{thread-id syntax}.
27060 @item @r{(anything else)}
27061 Any other reply implies the old thread ID.
27064 @item qCRC:@var{addr},@var{length}
27065 @cindex CRC of memory block, remote request
27066 @cindex @samp{qCRC} packet
27067 Compute the CRC checksum of a block of memory.
27071 An error (such as memory fault)
27072 @item C @var{crc32}
27073 The specified memory region's checksum is @var{crc32}.
27077 @itemx qsThreadInfo
27078 @cindex list active threads, remote request
27079 @cindex @samp{qfThreadInfo} packet
27080 @cindex @samp{qsThreadInfo} packet
27081 Obtain a list of all active thread IDs from the target (OS). Since there
27082 may be too many active threads to fit into one reply packet, this query
27083 works iteratively: it may require more than one query/reply sequence to
27084 obtain the entire list of threads. The first query of the sequence will
27085 be the @samp{qfThreadInfo} query; subsequent queries in the
27086 sequence will be the @samp{qsThreadInfo} query.
27088 NOTE: This packet replaces the @samp{qL} query (see below).
27092 @item m @var{thread-id}
27094 @item m @var{thread-id},@var{thread-id}@dots{}
27095 a comma-separated list of thread IDs
27097 (lower case letter @samp{L}) denotes end of list.
27100 In response to each query, the target will reply with a list of one or
27101 more thread IDs, separated by commas.
27102 @value{GDBN} will respond to each reply with a request for more thread
27103 ids (using the @samp{qs} form of the query), until the target responds
27104 with @samp{l} (lower-case el, for @dfn{last}).
27105 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
27108 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
27109 @cindex get thread-local storage address, remote request
27110 @cindex @samp{qGetTLSAddr} packet
27111 Fetch the address associated with thread local storage specified
27112 by @var{thread-id}, @var{offset}, and @var{lm}.
27114 @var{thread-id} is the thread ID associated with the
27115 thread for which to fetch the TLS address. @xref{thread-id syntax}.
27117 @var{offset} is the (big endian, hex encoded) offset associated with the
27118 thread local variable. (This offset is obtained from the debug
27119 information associated with the variable.)
27121 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
27122 the load module associated with the thread local storage. For example,
27123 a @sc{gnu}/Linux system will pass the link map address of the shared
27124 object associated with the thread local storage under consideration.
27125 Other operating environments may choose to represent the load module
27126 differently, so the precise meaning of this parameter will vary.
27130 @item @var{XX}@dots{}
27131 Hex encoded (big endian) bytes representing the address of the thread
27132 local storage requested.
27135 An error occurred. @var{nn} are hex digits.
27138 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
27141 @item qL @var{startflag} @var{threadcount} @var{nextthread}
27142 Obtain thread information from RTOS. Where: @var{startflag} (one hex
27143 digit) is one to indicate the first query and zero to indicate a
27144 subsequent query; @var{threadcount} (two hex digits) is the maximum
27145 number of threads the response packet can contain; and @var{nextthread}
27146 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
27147 returned in the response as @var{argthread}.
27149 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
27153 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
27154 Where: @var{count} (two hex digits) is the number of threads being
27155 returned; @var{done} (one hex digit) is zero to indicate more threads
27156 and one indicates no further threads; @var{argthreadid} (eight hex
27157 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
27158 is a sequence of thread IDs from the target. @var{threadid} (eight hex
27159 digits). See @code{remote.c:parse_threadlist_response()}.
27163 @cindex section offsets, remote request
27164 @cindex @samp{qOffsets} packet
27165 Get section offsets that the target used when relocating the downloaded
27170 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
27171 Relocate the @code{Text} section by @var{xxx} from its original address.
27172 Relocate the @code{Data} section by @var{yyy} from its original address.
27173 If the object file format provides segment information (e.g.@: @sc{elf}
27174 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
27175 segments by the supplied offsets.
27177 @emph{Note: while a @code{Bss} offset may be included in the response,
27178 @value{GDBN} ignores this and instead applies the @code{Data} offset
27179 to the @code{Bss} section.}
27181 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
27182 Relocate the first segment of the object file, which conventionally
27183 contains program code, to a starting address of @var{xxx}. If
27184 @samp{DataSeg} is specified, relocate the second segment, which
27185 conventionally contains modifiable data, to a starting address of
27186 @var{yyy}. @value{GDBN} will report an error if the object file
27187 does not contain segment information, or does not contain at least
27188 as many segments as mentioned in the reply. Extra segments are
27189 kept at fixed offsets relative to the last relocated segment.
27192 @item qP @var{mode} @var{thread-id}
27193 @cindex thread information, remote request
27194 @cindex @samp{qP} packet
27195 Returns information on @var{thread-id}. Where: @var{mode} is a hex
27196 encoded 32 bit mode; @var{thread-id} is a thread ID
27197 (@pxref{thread-id syntax}).
27199 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
27202 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
27206 @cindex non-stop mode, remote request
27207 @cindex @samp{QNonStop} packet
27209 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
27210 @xref{Remote Non-Stop}, for more information.
27215 The request succeeded.
27218 An error occurred. @var{nn} are hex digits.
27221 An empty reply indicates that @samp{QNonStop} is not supported by
27225 This packet is not probed by default; the remote stub must request it,
27226 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27227 Use of this packet is controlled by the @code{set non-stop} command;
27228 @pxref{Non-Stop Mode}.
27230 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
27231 @cindex pass signals to inferior, remote request
27232 @cindex @samp{QPassSignals} packet
27233 @anchor{QPassSignals}
27234 Each listed @var{signal} should be passed directly to the inferior process.
27235 Signals are numbered identically to continue packets and stop replies
27236 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
27237 strictly greater than the previous item. These signals do not need to stop
27238 the inferior, or be reported to @value{GDBN}. All other signals should be
27239 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
27240 combine; any earlier @samp{QPassSignals} list is completely replaced by the
27241 new list. This packet improves performance when using @samp{handle
27242 @var{signal} nostop noprint pass}.
27247 The request succeeded.
27250 An error occurred. @var{nn} are hex digits.
27253 An empty reply indicates that @samp{QPassSignals} is not supported by
27257 Use of this packet is controlled by the @code{set remote pass-signals}
27258 command (@pxref{Remote Configuration, set remote pass-signals}).
27259 This packet is not probed by default; the remote stub must request it,
27260 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27262 @item qRcmd,@var{command}
27263 @cindex execute remote command, remote request
27264 @cindex @samp{qRcmd} packet
27265 @var{command} (hex encoded) is passed to the local interpreter for
27266 execution. Invalid commands should be reported using the output
27267 string. Before the final result packet, the target may also respond
27268 with a number of intermediate @samp{O@var{output}} console output
27269 packets. @emph{Implementors should note that providing access to a
27270 stubs's interpreter may have security implications}.
27275 A command response with no output.
27277 A command response with the hex encoded output string @var{OUTPUT}.
27279 Indicate a badly formed request.
27281 An empty reply indicates that @samp{qRcmd} is not recognized.
27284 (Note that the @code{qRcmd} packet's name is separated from the
27285 command by a @samp{,}, not a @samp{:}, contrary to the naming
27286 conventions above. Please don't use this packet as a model for new
27289 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
27290 @cindex searching memory, in remote debugging
27291 @cindex @samp{qSearch:memory} packet
27292 @anchor{qSearch memory}
27293 Search @var{length} bytes at @var{address} for @var{search-pattern}.
27294 @var{address} and @var{length} are encoded in hex.
27295 @var{search-pattern} is a sequence of bytes, hex encoded.
27300 The pattern was not found.
27302 The pattern was found at @var{address}.
27304 A badly formed request or an error was encountered while searching memory.
27306 An empty reply indicates that @samp{qSearch:memory} is not recognized.
27309 @item QStartNoAckMode
27310 @cindex @samp{QStartNoAckMode} packet
27311 @anchor{QStartNoAckMode}
27312 Request that the remote stub disable the normal @samp{+}/@samp{-}
27313 protocol acknowledgments (@pxref{Packet Acknowledgment}).
27318 The stub has switched to no-acknowledgment mode.
27319 @value{GDBN} acknowledges this reponse,
27320 but neither the stub nor @value{GDBN} shall send or expect further
27321 @samp{+}/@samp{-} acknowledgments in the current connection.
27323 An empty reply indicates that the stub does not support no-acknowledgment mode.
27326 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
27327 @cindex supported packets, remote query
27328 @cindex features of the remote protocol
27329 @cindex @samp{qSupported} packet
27330 @anchor{qSupported}
27331 Tell the remote stub about features supported by @value{GDBN}, and
27332 query the stub for features it supports. This packet allows
27333 @value{GDBN} and the remote stub to take advantage of each others'
27334 features. @samp{qSupported} also consolidates multiple feature probes
27335 at startup, to improve @value{GDBN} performance---a single larger
27336 packet performs better than multiple smaller probe packets on
27337 high-latency links. Some features may enable behavior which must not
27338 be on by default, e.g.@: because it would confuse older clients or
27339 stubs. Other features may describe packets which could be
27340 automatically probed for, but are not. These features must be
27341 reported before @value{GDBN} will use them. This ``default
27342 unsupported'' behavior is not appropriate for all packets, but it
27343 helps to keep the initial connection time under control with new
27344 versions of @value{GDBN} which support increasing numbers of packets.
27348 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
27349 The stub supports or does not support each returned @var{stubfeature},
27350 depending on the form of each @var{stubfeature} (see below for the
27353 An empty reply indicates that @samp{qSupported} is not recognized,
27354 or that no features needed to be reported to @value{GDBN}.
27357 The allowed forms for each feature (either a @var{gdbfeature} in the
27358 @samp{qSupported} packet, or a @var{stubfeature} in the response)
27362 @item @var{name}=@var{value}
27363 The remote protocol feature @var{name} is supported, and associated
27364 with the specified @var{value}. The format of @var{value} depends
27365 on the feature, but it must not include a semicolon.
27367 The remote protocol feature @var{name} is supported, and does not
27368 need an associated value.
27370 The remote protocol feature @var{name} is not supported.
27372 The remote protocol feature @var{name} may be supported, and
27373 @value{GDBN} should auto-detect support in some other way when it is
27374 needed. This form will not be used for @var{gdbfeature} notifications,
27375 but may be used for @var{stubfeature} responses.
27378 Whenever the stub receives a @samp{qSupported} request, the
27379 supplied set of @value{GDBN} features should override any previous
27380 request. This allows @value{GDBN} to put the stub in a known
27381 state, even if the stub had previously been communicating with
27382 a different version of @value{GDBN}.
27384 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
27389 This feature indicates whether @value{GDBN} supports multiprocess
27390 extensions to the remote protocol. @value{GDBN} does not use such
27391 extensions unless the stub also reports that it supports them by
27392 including @samp{multiprocess+} in its @samp{qSupported} reply.
27393 @xref{multiprocess extensions}, for details.
27396 Stubs should ignore any unknown values for
27397 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
27398 packet supports receiving packets of unlimited length (earlier
27399 versions of @value{GDBN} may reject overly long responses). Additional values
27400 for @var{gdbfeature} may be defined in the future to let the stub take
27401 advantage of new features in @value{GDBN}, e.g.@: incompatible
27402 improvements in the remote protocol---the @samp{multiprocess} feature is
27403 an example of such a feature. The stub's reply should be independent
27404 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
27405 describes all the features it supports, and then the stub replies with
27406 all the features it supports.
27408 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
27409 responses, as long as each response uses one of the standard forms.
27411 Some features are flags. A stub which supports a flag feature
27412 should respond with a @samp{+} form response. Other features
27413 require values, and the stub should respond with an @samp{=}
27416 Each feature has a default value, which @value{GDBN} will use if
27417 @samp{qSupported} is not available or if the feature is not mentioned
27418 in the @samp{qSupported} response. The default values are fixed; a
27419 stub is free to omit any feature responses that match the defaults.
27421 Not all features can be probed, but for those which can, the probing
27422 mechanism is useful: in some cases, a stub's internal
27423 architecture may not allow the protocol layer to know some information
27424 about the underlying target in advance. This is especially common in
27425 stubs which may be configured for multiple targets.
27427 These are the currently defined stub features and their properties:
27429 @multitable @columnfractions 0.35 0.2 0.12 0.2
27430 @c NOTE: The first row should be @headitem, but we do not yet require
27431 @c a new enough version of Texinfo (4.7) to use @headitem.
27433 @tab Value Required
27437 @item @samp{PacketSize}
27442 @item @samp{qXfer:auxv:read}
27447 @item @samp{qXfer:features:read}
27452 @item @samp{qXfer:libraries:read}
27457 @item @samp{qXfer:memory-map:read}
27462 @item @samp{qXfer:spu:read}
27467 @item @samp{qXfer:spu:write}
27472 @item @samp{qXfer:siginfo:read}
27477 @item @samp{qXfer:siginfo:write}
27482 @item @samp{QNonStop}
27487 @item @samp{QPassSignals}
27492 @item @samp{QStartNoAckMode}
27497 @item @samp{multiprocess}
27504 These are the currently defined stub features, in more detail:
27507 @cindex packet size, remote protocol
27508 @item PacketSize=@var{bytes}
27509 The remote stub can accept packets up to at least @var{bytes} in
27510 length. @value{GDBN} will send packets up to this size for bulk
27511 transfers, and will never send larger packets. This is a limit on the
27512 data characters in the packet, including the frame and checksum.
27513 There is no trailing NUL byte in a remote protocol packet; if the stub
27514 stores packets in a NUL-terminated format, it should allow an extra
27515 byte in its buffer for the NUL. If this stub feature is not supported,
27516 @value{GDBN} guesses based on the size of the @samp{g} packet response.
27518 @item qXfer:auxv:read
27519 The remote stub understands the @samp{qXfer:auxv:read} packet
27520 (@pxref{qXfer auxiliary vector read}).
27522 @item qXfer:features:read
27523 The remote stub understands the @samp{qXfer:features:read} packet
27524 (@pxref{qXfer target description read}).
27526 @item qXfer:libraries:read
27527 The remote stub understands the @samp{qXfer:libraries:read} packet
27528 (@pxref{qXfer library list read}).
27530 @item qXfer:memory-map:read
27531 The remote stub understands the @samp{qXfer:memory-map:read} packet
27532 (@pxref{qXfer memory map read}).
27534 @item qXfer:spu:read
27535 The remote stub understands the @samp{qXfer:spu:read} packet
27536 (@pxref{qXfer spu read}).
27538 @item qXfer:spu:write
27539 The remote stub understands the @samp{qXfer:spu:write} packet
27540 (@pxref{qXfer spu write}).
27542 @item qXfer:siginfo:read
27543 The remote stub understands the @samp{qXfer:siginfo:read} packet
27544 (@pxref{qXfer siginfo read}).
27546 @item qXfer:siginfo:write
27547 The remote stub understands the @samp{qXfer:siginfo:write} packet
27548 (@pxref{qXfer siginfo write}).
27551 The remote stub understands the @samp{QNonStop} packet
27552 (@pxref{QNonStop}).
27555 The remote stub understands the @samp{QPassSignals} packet
27556 (@pxref{QPassSignals}).
27558 @item QStartNoAckMode
27559 The remote stub understands the @samp{QStartNoAckMode} packet and
27560 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
27563 @anchor{multiprocess extensions}
27564 @cindex multiprocess extensions, in remote protocol
27565 The remote stub understands the multiprocess extensions to the remote
27566 protocol syntax. The multiprocess extensions affect the syntax of
27567 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
27568 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
27569 replies. Note that reporting this feature indicates support for the
27570 syntactic extensions only, not that the stub necessarily supports
27571 debugging of more than one process at a time. The stub must not use
27572 multiprocess extensions in packet replies unless @value{GDBN} has also
27573 indicated it supports them in its @samp{qSupported} request.
27575 @item qXfer:osdata:read
27576 The remote stub understands the @samp{qXfer:osdata:read} packet
27577 ((@pxref{qXfer osdata read}).
27582 @cindex symbol lookup, remote request
27583 @cindex @samp{qSymbol} packet
27584 Notify the target that @value{GDBN} is prepared to serve symbol lookup
27585 requests. Accept requests from the target for the values of symbols.
27590 The target does not need to look up any (more) symbols.
27591 @item qSymbol:@var{sym_name}
27592 The target requests the value of symbol @var{sym_name} (hex encoded).
27593 @value{GDBN} may provide the value by using the
27594 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
27598 @item qSymbol:@var{sym_value}:@var{sym_name}
27599 Set the value of @var{sym_name} to @var{sym_value}.
27601 @var{sym_name} (hex encoded) is the name of a symbol whose value the
27602 target has previously requested.
27604 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
27605 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
27611 The target does not need to look up any (more) symbols.
27612 @item qSymbol:@var{sym_name}
27613 The target requests the value of a new symbol @var{sym_name} (hex
27614 encoded). @value{GDBN} will continue to supply the values of symbols
27615 (if available), until the target ceases to request them.
27620 @xref{Tracepoint Packets}.
27622 @item qThreadExtraInfo,@var{thread-id}
27623 @cindex thread attributes info, remote request
27624 @cindex @samp{qThreadExtraInfo} packet
27625 Obtain a printable string description of a thread's attributes from
27626 the target OS. @var{thread-id} is a thread ID;
27627 see @ref{thread-id syntax}. This
27628 string may contain anything that the target OS thinks is interesting
27629 for @value{GDBN} to tell the user about the thread. The string is
27630 displayed in @value{GDBN}'s @code{info threads} display. Some
27631 examples of possible thread extra info strings are @samp{Runnable}, or
27632 @samp{Blocked on Mutex}.
27636 @item @var{XX}@dots{}
27637 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
27638 comprising the printable string containing the extra information about
27639 the thread's attributes.
27642 (Note that the @code{qThreadExtraInfo} packet's name is separated from
27643 the command by a @samp{,}, not a @samp{:}, contrary to the naming
27644 conventions above. Please don't use this packet as a model for new
27652 @xref{Tracepoint Packets}.
27654 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
27655 @cindex read special object, remote request
27656 @cindex @samp{qXfer} packet
27657 @anchor{qXfer read}
27658 Read uninterpreted bytes from the target's special data area
27659 identified by the keyword @var{object}. Request @var{length} bytes
27660 starting at @var{offset} bytes into the data. The content and
27661 encoding of @var{annex} is specific to @var{object}; it can supply
27662 additional details about what data to access.
27664 Here are the specific requests of this form defined so far. All
27665 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
27666 formats, listed below.
27669 @item qXfer:auxv:read::@var{offset},@var{length}
27670 @anchor{qXfer auxiliary vector read}
27671 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
27672 auxiliary vector}. Note @var{annex} must be empty.
27674 This packet is not probed by default; the remote stub must request it,
27675 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27677 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
27678 @anchor{qXfer target description read}
27679 Access the @dfn{target description}. @xref{Target Descriptions}. The
27680 annex specifies which XML document to access. The main description is
27681 always loaded from the @samp{target.xml} annex.
27683 This packet is not probed by default; the remote stub must request it,
27684 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27686 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
27687 @anchor{qXfer library list read}
27688 Access the target's list of loaded libraries. @xref{Library List Format}.
27689 The annex part of the generic @samp{qXfer} packet must be empty
27690 (@pxref{qXfer read}).
27692 Targets which maintain a list of libraries in the program's memory do
27693 not need to implement this packet; it is designed for platforms where
27694 the operating system manages the list of loaded libraries.
27696 This packet is not probed by default; the remote stub must request it,
27697 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27699 @item qXfer:memory-map:read::@var{offset},@var{length}
27700 @anchor{qXfer memory map read}
27701 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
27702 annex part of the generic @samp{qXfer} packet must be empty
27703 (@pxref{qXfer read}).
27705 This packet is not probed by default; the remote stub must request it,
27706 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27708 @item qXfer:siginfo:read::@var{offset},@var{length}
27709 @anchor{qXfer siginfo read}
27710 Read contents of the extra signal information on the target
27711 system. The annex part of the generic @samp{qXfer} packet must be
27712 empty (@pxref{qXfer read}).
27714 This packet is not probed by default; the remote stub must request it,
27715 by supplying an appropriate @samp{qSupported} response
27716 (@pxref{qSupported}).
27718 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
27719 @anchor{qXfer spu read}
27720 Read contents of an @code{spufs} file on the target system. The
27721 annex specifies which file to read; it must be of the form
27722 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27723 in the target process, and @var{name} identifes the @code{spufs} file
27724 in that context to be accessed.
27726 This packet is not probed by default; the remote stub must request it,
27727 by supplying an appropriate @samp{qSupported} response
27728 (@pxref{qSupported}).
27730 @item qXfer:osdata:read::@var{offset},@var{length}
27731 @anchor{qXfer osdata read}
27732 Access the target's @dfn{operating system information}.
27733 @xref{Operating System Information}.
27740 Data @var{data} (@pxref{Binary Data}) has been read from the
27741 target. There may be more data at a higher address (although
27742 it is permitted to return @samp{m} even for the last valid
27743 block of data, as long as at least one byte of data was read).
27744 @var{data} may have fewer bytes than the @var{length} in the
27748 Data @var{data} (@pxref{Binary Data}) has been read from the target.
27749 There is no more data to be read. @var{data} may have fewer bytes
27750 than the @var{length} in the request.
27753 The @var{offset} in the request is at the end of the data.
27754 There is no more data to be read.
27757 The request was malformed, or @var{annex} was invalid.
27760 The offset was invalid, or there was an error encountered reading the data.
27761 @var{nn} is a hex-encoded @code{errno} value.
27764 An empty reply indicates the @var{object} string was not recognized by
27765 the stub, or that the object does not support reading.
27768 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
27769 @cindex write data into object, remote request
27770 @anchor{qXfer write}
27771 Write uninterpreted bytes into the target's special data area
27772 identified by the keyword @var{object}, starting at @var{offset} bytes
27773 into the data. @var{data}@dots{} is the binary-encoded data
27774 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
27775 is specific to @var{object}; it can supply additional details about what data
27778 Here are the specific requests of this form defined so far. All
27779 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
27780 formats, listed below.
27783 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
27784 @anchor{qXfer siginfo write}
27785 Write @var{data} to the extra signal information on the target system.
27786 The annex part of the generic @samp{qXfer} packet must be
27787 empty (@pxref{qXfer write}).
27789 This packet is not probed by default; the remote stub must request it,
27790 by supplying an appropriate @samp{qSupported} response
27791 (@pxref{qSupported}).
27793 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
27794 @anchor{qXfer spu write}
27795 Write @var{data} to an @code{spufs} file on the target system. The
27796 annex specifies which file to write; it must be of the form
27797 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27798 in the target process, and @var{name} identifes the @code{spufs} file
27799 in that context to be accessed.
27801 This packet is not probed by default; the remote stub must request it,
27802 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27808 @var{nn} (hex encoded) is the number of bytes written.
27809 This may be fewer bytes than supplied in the request.
27812 The request was malformed, or @var{annex} was invalid.
27815 The offset was invalid, or there was an error encountered writing the data.
27816 @var{nn} is a hex-encoded @code{errno} value.
27819 An empty reply indicates the @var{object} string was not
27820 recognized by the stub, or that the object does not support writing.
27823 @item qXfer:@var{object}:@var{operation}:@dots{}
27824 Requests of this form may be added in the future. When a stub does
27825 not recognize the @var{object} keyword, or its support for
27826 @var{object} does not recognize the @var{operation} keyword, the stub
27827 must respond with an empty packet.
27829 @item qAttached:@var{pid}
27830 @cindex query attached, remote request
27831 @cindex @samp{qAttached} packet
27832 Return an indication of whether the remote server attached to an
27833 existing process or created a new process. When the multiprocess
27834 protocol extensions are supported (@pxref{multiprocess extensions}),
27835 @var{pid} is an integer in hexadecimal format identifying the target
27836 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
27837 the query packet will be simplified as @samp{qAttached}.
27839 This query is used, for example, to know whether the remote process
27840 should be detached or killed when a @value{GDBN} session is ended with
27841 the @code{quit} command.
27846 The remote server attached to an existing process.
27848 The remote server created a new process.
27850 A badly formed request or an error was encountered.
27855 @node Register Packet Format
27856 @section Register Packet Format
27858 The following @code{g}/@code{G} packets have previously been defined.
27859 In the below, some thirty-two bit registers are transferred as
27860 sixty-four bits. Those registers should be zero/sign extended (which?)
27861 to fill the space allocated. Register bytes are transferred in target
27862 byte order. The two nibbles within a register byte are transferred
27863 most-significant - least-significant.
27869 All registers are transferred as thirty-two bit quantities in the order:
27870 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
27871 registers; fsr; fir; fp.
27875 All registers are transferred as sixty-four bit quantities (including
27876 thirty-two bit registers such as @code{sr}). The ordering is the same
27881 @node Tracepoint Packets
27882 @section Tracepoint Packets
27883 @cindex tracepoint packets
27884 @cindex packets, tracepoint
27886 Here we describe the packets @value{GDBN} uses to implement
27887 tracepoints (@pxref{Tracepoints}).
27891 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
27892 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
27893 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
27894 the tracepoint is disabled. @var{step} is the tracepoint's step
27895 count, and @var{pass} is its pass count. If the trailing @samp{-} is
27896 present, further @samp{QTDP} packets will follow to specify this
27897 tracepoint's actions.
27902 The packet was understood and carried out.
27904 The packet was not recognized.
27907 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
27908 Define actions to be taken when a tracepoint is hit. @var{n} and
27909 @var{addr} must be the same as in the initial @samp{QTDP} packet for
27910 this tracepoint. This packet may only be sent immediately after
27911 another @samp{QTDP} packet that ended with a @samp{-}. If the
27912 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
27913 specifying more actions for this tracepoint.
27915 In the series of action packets for a given tracepoint, at most one
27916 can have an @samp{S} before its first @var{action}. If such a packet
27917 is sent, it and the following packets define ``while-stepping''
27918 actions. Any prior packets define ordinary actions --- that is, those
27919 taken when the tracepoint is first hit. If no action packet has an
27920 @samp{S}, then all the packets in the series specify ordinary
27921 tracepoint actions.
27923 The @samp{@var{action}@dots{}} portion of the packet is a series of
27924 actions, concatenated without separators. Each action has one of the
27930 Collect the registers whose bits are set in @var{mask}. @var{mask} is
27931 a hexadecimal number whose @var{i}'th bit is set if register number
27932 @var{i} should be collected. (The least significant bit is numbered
27933 zero.) Note that @var{mask} may be any number of digits long; it may
27934 not fit in a 32-bit word.
27936 @item M @var{basereg},@var{offset},@var{len}
27937 Collect @var{len} bytes of memory starting at the address in register
27938 number @var{basereg}, plus @var{offset}. If @var{basereg} is
27939 @samp{-1}, then the range has a fixed address: @var{offset} is the
27940 address of the lowest byte to collect. The @var{basereg},
27941 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
27942 values (the @samp{-1} value for @var{basereg} is a special case).
27944 @item X @var{len},@var{expr}
27945 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
27946 it directs. @var{expr} is an agent expression, as described in
27947 @ref{Agent Expressions}. Each byte of the expression is encoded as a
27948 two-digit hex number in the packet; @var{len} is the number of bytes
27949 in the expression (and thus one-half the number of hex digits in the
27954 Any number of actions may be packed together in a single @samp{QTDP}
27955 packet, as long as the packet does not exceed the maximum packet
27956 length (400 bytes, for many stubs). There may be only one @samp{R}
27957 action per tracepoint, and it must precede any @samp{M} or @samp{X}
27958 actions. Any registers referred to by @samp{M} and @samp{X} actions
27959 must be collected by a preceding @samp{R} action. (The
27960 ``while-stepping'' actions are treated as if they were attached to a
27961 separate tracepoint, as far as these restrictions are concerned.)
27966 The packet was understood and carried out.
27968 The packet was not recognized.
27971 @item QTFrame:@var{n}
27972 Select the @var{n}'th tracepoint frame from the buffer, and use the
27973 register and memory contents recorded there to answer subsequent
27974 request packets from @value{GDBN}.
27976 A successful reply from the stub indicates that the stub has found the
27977 requested frame. The response is a series of parts, concatenated
27978 without separators, describing the frame we selected. Each part has
27979 one of the following forms:
27983 The selected frame is number @var{n} in the trace frame buffer;
27984 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
27985 was no frame matching the criteria in the request packet.
27988 The selected trace frame records a hit of tracepoint number @var{t};
27989 @var{t} is a hexadecimal number.
27993 @item QTFrame:pc:@var{addr}
27994 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27995 currently selected frame whose PC is @var{addr};
27996 @var{addr} is a hexadecimal number.
27998 @item QTFrame:tdp:@var{t}
27999 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
28000 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
28001 is a hexadecimal number.
28003 @item QTFrame:range:@var{start}:@var{end}
28004 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
28005 currently selected frame whose PC is between @var{start} (inclusive)
28006 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
28009 @item QTFrame:outside:@var{start}:@var{end}
28010 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
28011 frame @emph{outside} the given range of addresses.
28014 Begin the tracepoint experiment. Begin collecting data from tracepoint
28015 hits in the trace frame buffer.
28018 End the tracepoint experiment. Stop collecting trace frames.
28021 Clear the table of tracepoints, and empty the trace frame buffer.
28023 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
28024 Establish the given ranges of memory as ``transparent''. The stub
28025 will answer requests for these ranges from memory's current contents,
28026 if they were not collected as part of the tracepoint hit.
28028 @value{GDBN} uses this to mark read-only regions of memory, like those
28029 containing program code. Since these areas never change, they should
28030 still have the same contents they did when the tracepoint was hit, so
28031 there's no reason for the stub to refuse to provide their contents.
28034 Ask the stub if there is a trace experiment running right now.
28039 There is no trace experiment running.
28041 There is a trace experiment running.
28047 @node Host I/O Packets
28048 @section Host I/O Packets
28049 @cindex Host I/O, remote protocol
28050 @cindex file transfer, remote protocol
28052 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
28053 operations on the far side of a remote link. For example, Host I/O is
28054 used to upload and download files to a remote target with its own
28055 filesystem. Host I/O uses the same constant values and data structure
28056 layout as the target-initiated File-I/O protocol. However, the
28057 Host I/O packets are structured differently. The target-initiated
28058 protocol relies on target memory to store parameters and buffers.
28059 Host I/O requests are initiated by @value{GDBN}, and the
28060 target's memory is not involved. @xref{File-I/O Remote Protocol
28061 Extension}, for more details on the target-initiated protocol.
28063 The Host I/O request packets all encode a single operation along with
28064 its arguments. They have this format:
28068 @item vFile:@var{operation}: @var{parameter}@dots{}
28069 @var{operation} is the name of the particular request; the target
28070 should compare the entire packet name up to the second colon when checking
28071 for a supported operation. The format of @var{parameter} depends on
28072 the operation. Numbers are always passed in hexadecimal. Negative
28073 numbers have an explicit minus sign (i.e.@: two's complement is not
28074 used). Strings (e.g.@: filenames) are encoded as a series of
28075 hexadecimal bytes. The last argument to a system call may be a
28076 buffer of escaped binary data (@pxref{Binary Data}).
28080 The valid responses to Host I/O packets are:
28084 @item F @var{result} [, @var{errno}] [; @var{attachment}]
28085 @var{result} is the integer value returned by this operation, usually
28086 non-negative for success and -1 for errors. If an error has occured,
28087 @var{errno} will be included in the result. @var{errno} will have a
28088 value defined by the File-I/O protocol (@pxref{Errno Values}). For
28089 operations which return data, @var{attachment} supplies the data as a
28090 binary buffer. Binary buffers in response packets are escaped in the
28091 normal way (@pxref{Binary Data}). See the individual packet
28092 documentation for the interpretation of @var{result} and
28096 An empty response indicates that this operation is not recognized.
28100 These are the supported Host I/O operations:
28103 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
28104 Open a file at @var{pathname} and return a file descriptor for it, or
28105 return -1 if an error occurs. @var{pathname} is a string,
28106 @var{flags} is an integer indicating a mask of open flags
28107 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
28108 of mode bits to use if the file is created (@pxref{mode_t Values}).
28109 @xref{open}, for details of the open flags and mode values.
28111 @item vFile:close: @var{fd}
28112 Close the open file corresponding to @var{fd} and return 0, or
28113 -1 if an error occurs.
28115 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
28116 Read data from the open file corresponding to @var{fd}. Up to
28117 @var{count} bytes will be read from the file, starting at @var{offset}
28118 relative to the start of the file. The target may read fewer bytes;
28119 common reasons include packet size limits and an end-of-file
28120 condition. The number of bytes read is returned. Zero should only be
28121 returned for a successful read at the end of the file, or if
28122 @var{count} was zero.
28124 The data read should be returned as a binary attachment on success.
28125 If zero bytes were read, the response should include an empty binary
28126 attachment (i.e.@: a trailing semicolon). The return value is the
28127 number of target bytes read; the binary attachment may be longer if
28128 some characters were escaped.
28130 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
28131 Write @var{data} (a binary buffer) to the open file corresponding
28132 to @var{fd}. Start the write at @var{offset} from the start of the
28133 file. Unlike many @code{write} system calls, there is no
28134 separate @var{count} argument; the length of @var{data} in the
28135 packet is used. @samp{vFile:write} returns the number of bytes written,
28136 which may be shorter than the length of @var{data}, or -1 if an
28139 @item vFile:unlink: @var{pathname}
28140 Delete the file at @var{pathname} on the target. Return 0,
28141 or -1 if an error occurs. @var{pathname} is a string.
28146 @section Interrupts
28147 @cindex interrupts (remote protocol)
28149 When a program on the remote target is running, @value{GDBN} may
28150 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
28151 control of which is specified via @value{GDBN}'s @samp{remotebreak}
28152 setting (@pxref{set remotebreak}).
28154 The precise meaning of @code{BREAK} is defined by the transport
28155 mechanism and may, in fact, be undefined. @value{GDBN} does not
28156 currently define a @code{BREAK} mechanism for any of the network
28157 interfaces except for TCP, in which case @value{GDBN} sends the
28158 @code{telnet} BREAK sequence.
28160 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
28161 transport mechanisms. It is represented by sending the single byte
28162 @code{0x03} without any of the usual packet overhead described in
28163 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
28164 transmitted as part of a packet, it is considered to be packet data
28165 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
28166 (@pxref{X packet}), used for binary downloads, may include an unescaped
28167 @code{0x03} as part of its packet.
28169 Stubs are not required to recognize these interrupt mechanisms and the
28170 precise meaning associated with receipt of the interrupt is
28171 implementation defined. If the target supports debugging of multiple
28172 threads and/or processes, it should attempt to interrupt all
28173 currently-executing threads and processes.
28174 If the stub is successful at interrupting the
28175 running program, it should send one of the stop
28176 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
28177 of successfully stopping the program in all-stop mode, and a stop reply
28178 for each stopped thread in non-stop mode.
28179 Interrupts received while the
28180 program is stopped are discarded.
28182 @node Notification Packets
28183 @section Notification Packets
28184 @cindex notification packets
28185 @cindex packets, notification
28187 The @value{GDBN} remote serial protocol includes @dfn{notifications},
28188 packets that require no acknowledgment. Both the GDB and the stub
28189 may send notifications (although the only notifications defined at
28190 present are sent by the stub). Notifications carry information
28191 without incurring the round-trip latency of an acknowledgment, and so
28192 are useful for low-impact communications where occasional packet loss
28195 A notification packet has the form @samp{% @var{data} #
28196 @var{checksum}}, where @var{data} is the content of the notification,
28197 and @var{checksum} is a checksum of @var{data}, computed and formatted
28198 as for ordinary @value{GDBN} packets. A notification's @var{data}
28199 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
28200 receiving a notification, the recipient sends no @samp{+} or @samp{-}
28201 to acknowledge the notification's receipt or to report its corruption.
28203 Every notification's @var{data} begins with a name, which contains no
28204 colon characters, followed by a colon character.
28206 Recipients should silently ignore corrupted notifications and
28207 notifications they do not understand. Recipients should restart
28208 timeout periods on receipt of a well-formed notification, whether or
28209 not they understand it.
28211 Senders should only send the notifications described here when this
28212 protocol description specifies that they are permitted. In the
28213 future, we may extend the protocol to permit existing notifications in
28214 new contexts; this rule helps older senders avoid confusing newer
28217 (Older versions of @value{GDBN} ignore bytes received until they see
28218 the @samp{$} byte that begins an ordinary packet, so new stubs may
28219 transmit notifications without fear of confusing older clients. There
28220 are no notifications defined for @value{GDBN} to send at the moment, but we
28221 assume that most older stubs would ignore them, as well.)
28223 The following notification packets from the stub to @value{GDBN} are
28227 @item Stop: @var{reply}
28228 Report an asynchronous stop event in non-stop mode.
28229 The @var{reply} has the form of a stop reply, as
28230 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
28231 for information on how these notifications are acknowledged by
28235 @node Remote Non-Stop
28236 @section Remote Protocol Support for Non-Stop Mode
28238 @value{GDBN}'s remote protocol supports non-stop debugging of
28239 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
28240 supports non-stop mode, it should report that to @value{GDBN} by including
28241 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
28243 @value{GDBN} typically sends a @samp{QNonStop} packet only when
28244 establishing a new connection with the stub. Entering non-stop mode
28245 does not alter the state of any currently-running threads, but targets
28246 must stop all threads in any already-attached processes when entering
28247 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
28248 probe the target state after a mode change.
28250 In non-stop mode, when an attached process encounters an event that
28251 would otherwise be reported with a stop reply, it uses the
28252 asynchronous notification mechanism (@pxref{Notification Packets}) to
28253 inform @value{GDBN}. In contrast to all-stop mode, where all threads
28254 in all processes are stopped when a stop reply is sent, in non-stop
28255 mode only the thread reporting the stop event is stopped. That is,
28256 when reporting a @samp{S} or @samp{T} response to indicate completion
28257 of a step operation, hitting a breakpoint, or a fault, only the
28258 affected thread is stopped; any other still-running threads continue
28259 to run. When reporting a @samp{W} or @samp{X} response, all running
28260 threads belonging to other attached processes continue to run.
28262 Only one stop reply notification at a time may be pending; if
28263 additional stop events occur before @value{GDBN} has acknowledged the
28264 previous notification, they must be queued by the stub for later
28265 synchronous transmission in response to @samp{vStopped} packets from
28266 @value{GDBN}. Because the notification mechanism is unreliable,
28267 the stub is permitted to resend a stop reply notification
28268 if it believes @value{GDBN} may not have received it. @value{GDBN}
28269 ignores additional stop reply notifications received before it has
28270 finished processing a previous notification and the stub has completed
28271 sending any queued stop events.
28273 Otherwise, @value{GDBN} must be prepared to receive a stop reply
28274 notification at any time. Specifically, they may appear when
28275 @value{GDBN} is not otherwise reading input from the stub, or when
28276 @value{GDBN} is expecting to read a normal synchronous response or a
28277 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
28278 Notification packets are distinct from any other communication from
28279 the stub so there is no ambiguity.
28281 After receiving a stop reply notification, @value{GDBN} shall
28282 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
28283 as a regular, synchronous request to the stub. Such acknowledgment
28284 is not required to happen immediately, as @value{GDBN} is permitted to
28285 send other, unrelated packets to the stub first, which the stub should
28288 Upon receiving a @samp{vStopped} packet, if the stub has other queued
28289 stop events to report to @value{GDBN}, it shall respond by sending a
28290 normal stop reply response. @value{GDBN} shall then send another
28291 @samp{vStopped} packet to solicit further responses; again, it is
28292 permitted to send other, unrelated packets as well which the stub
28293 should process normally.
28295 If the stub receives a @samp{vStopped} packet and there are no
28296 additional stop events to report, the stub shall return an @samp{OK}
28297 response. At this point, if further stop events occur, the stub shall
28298 send a new stop reply notification, @value{GDBN} shall accept the
28299 notification, and the process shall be repeated.
28301 In non-stop mode, the target shall respond to the @samp{?} packet as
28302 follows. First, any incomplete stop reply notification/@samp{vStopped}
28303 sequence in progress is abandoned. The target must begin a new
28304 sequence reporting stop events for all stopped threads, whether or not
28305 it has previously reported those events to @value{GDBN}. The first
28306 stop reply is sent as a synchronous reply to the @samp{?} packet, and
28307 subsequent stop replies are sent as responses to @samp{vStopped} packets
28308 using the mechanism described above. The target must not send
28309 asynchronous stop reply notifications until the sequence is complete.
28310 If all threads are running when the target receives the @samp{?} packet,
28311 or if the target is not attached to any process, it shall respond
28314 @node Packet Acknowledgment
28315 @section Packet Acknowledgment
28317 @cindex acknowledgment, for @value{GDBN} remote
28318 @cindex packet acknowledgment, for @value{GDBN} remote
28319 By default, when either the host or the target machine receives a packet,
28320 the first response expected is an acknowledgment: either @samp{+} (to indicate
28321 the package was received correctly) or @samp{-} (to request retransmission).
28322 This mechanism allows the @value{GDBN} remote protocol to operate over
28323 unreliable transport mechanisms, such as a serial line.
28325 In cases where the transport mechanism is itself reliable (such as a pipe or
28326 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
28327 It may be desirable to disable them in that case to reduce communication
28328 overhead, or for other reasons. This can be accomplished by means of the
28329 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
28331 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
28332 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
28333 and response format still includes the normal checksum, as described in
28334 @ref{Overview}, but the checksum may be ignored by the receiver.
28336 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
28337 no-acknowledgment mode, it should report that to @value{GDBN}
28338 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
28339 @pxref{qSupported}.
28340 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
28341 disabled via the @code{set remote noack-packet off} command
28342 (@pxref{Remote Configuration}),
28343 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
28344 Only then may the stub actually turn off packet acknowledgments.
28345 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
28346 response, which can be safely ignored by the stub.
28348 Note that @code{set remote noack-packet} command only affects negotiation
28349 between @value{GDBN} and the stub when subsequent connections are made;
28350 it does not affect the protocol acknowledgment state for any current
28352 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
28353 new connection is established,
28354 there is also no protocol request to re-enable the acknowledgments
28355 for the current connection, once disabled.
28360 Example sequence of a target being re-started. Notice how the restart
28361 does not get any direct output:
28366 @emph{target restarts}
28369 <- @code{T001:1234123412341234}
28373 Example sequence of a target being stepped by a single instruction:
28376 -> @code{G1445@dots{}}
28381 <- @code{T001:1234123412341234}
28385 <- @code{1455@dots{}}
28389 @node File-I/O Remote Protocol Extension
28390 @section File-I/O Remote Protocol Extension
28391 @cindex File-I/O remote protocol extension
28394 * File-I/O Overview::
28395 * Protocol Basics::
28396 * The F Request Packet::
28397 * The F Reply Packet::
28398 * The Ctrl-C Message::
28400 * List of Supported Calls::
28401 * Protocol-specific Representation of Datatypes::
28403 * File-I/O Examples::
28406 @node File-I/O Overview
28407 @subsection File-I/O Overview
28408 @cindex file-i/o overview
28410 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
28411 target to use the host's file system and console I/O to perform various
28412 system calls. System calls on the target system are translated into a
28413 remote protocol packet to the host system, which then performs the needed
28414 actions and returns a response packet to the target system.
28415 This simulates file system operations even on targets that lack file systems.
28417 The protocol is defined to be independent of both the host and target systems.
28418 It uses its own internal representation of datatypes and values. Both
28419 @value{GDBN} and the target's @value{GDBN} stub are responsible for
28420 translating the system-dependent value representations into the internal
28421 protocol representations when data is transmitted.
28423 The communication is synchronous. A system call is possible only when
28424 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
28425 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
28426 the target is stopped to allow deterministic access to the target's
28427 memory. Therefore File-I/O is not interruptible by target signals. On
28428 the other hand, it is possible to interrupt File-I/O by a user interrupt
28429 (@samp{Ctrl-C}) within @value{GDBN}.
28431 The target's request to perform a host system call does not finish
28432 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
28433 after finishing the system call, the target returns to continuing the
28434 previous activity (continue, step). No additional continue or step
28435 request from @value{GDBN} is required.
28438 (@value{GDBP}) continue
28439 <- target requests 'system call X'
28440 target is stopped, @value{GDBN} executes system call
28441 -> @value{GDBN} returns result
28442 ... target continues, @value{GDBN} returns to wait for the target
28443 <- target hits breakpoint and sends a Txx packet
28446 The protocol only supports I/O on the console and to regular files on
28447 the host file system. Character or block special devices, pipes,
28448 named pipes, sockets or any other communication method on the host
28449 system are not supported by this protocol.
28451 File I/O is not supported in non-stop mode.
28453 @node Protocol Basics
28454 @subsection Protocol Basics
28455 @cindex protocol basics, file-i/o
28457 The File-I/O protocol uses the @code{F} packet as the request as well
28458 as reply packet. Since a File-I/O system call can only occur when
28459 @value{GDBN} is waiting for a response from the continuing or stepping target,
28460 the File-I/O request is a reply that @value{GDBN} has to expect as a result
28461 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
28462 This @code{F} packet contains all information needed to allow @value{GDBN}
28463 to call the appropriate host system call:
28467 A unique identifier for the requested system call.
28470 All parameters to the system call. Pointers are given as addresses
28471 in the target memory address space. Pointers to strings are given as
28472 pointer/length pair. Numerical values are given as they are.
28473 Numerical control flags are given in a protocol-specific representation.
28477 At this point, @value{GDBN} has to perform the following actions.
28481 If the parameters include pointer values to data needed as input to a
28482 system call, @value{GDBN} requests this data from the target with a
28483 standard @code{m} packet request. This additional communication has to be
28484 expected by the target implementation and is handled as any other @code{m}
28488 @value{GDBN} translates all value from protocol representation to host
28489 representation as needed. Datatypes are coerced into the host types.
28492 @value{GDBN} calls the system call.
28495 It then coerces datatypes back to protocol representation.
28498 If the system call is expected to return data in buffer space specified
28499 by pointer parameters to the call, the data is transmitted to the
28500 target using a @code{M} or @code{X} packet. This packet has to be expected
28501 by the target implementation and is handled as any other @code{M} or @code{X}
28506 Eventually @value{GDBN} replies with another @code{F} packet which contains all
28507 necessary information for the target to continue. This at least contains
28514 @code{errno}, if has been changed by the system call.
28521 After having done the needed type and value coercion, the target continues
28522 the latest continue or step action.
28524 @node The F Request Packet
28525 @subsection The @code{F} Request Packet
28526 @cindex file-i/o request packet
28527 @cindex @code{F} request packet
28529 The @code{F} request packet has the following format:
28532 @item F@var{call-id},@var{parameter@dots{}}
28534 @var{call-id} is the identifier to indicate the host system call to be called.
28535 This is just the name of the function.
28537 @var{parameter@dots{}} are the parameters to the system call.
28538 Parameters are hexadecimal integer values, either the actual values in case
28539 of scalar datatypes, pointers to target buffer space in case of compound
28540 datatypes and unspecified memory areas, or pointer/length pairs in case
28541 of string parameters. These are appended to the @var{call-id} as a
28542 comma-delimited list. All values are transmitted in ASCII
28543 string representation, pointer/length pairs separated by a slash.
28549 @node The F Reply Packet
28550 @subsection The @code{F} Reply Packet
28551 @cindex file-i/o reply packet
28552 @cindex @code{F} reply packet
28554 The @code{F} reply packet has the following format:
28558 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
28560 @var{retcode} is the return code of the system call as hexadecimal value.
28562 @var{errno} is the @code{errno} set by the call, in protocol-specific
28564 This parameter can be omitted if the call was successful.
28566 @var{Ctrl-C flag} is only sent if the user requested a break. In this
28567 case, @var{errno} must be sent as well, even if the call was successful.
28568 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
28575 or, if the call was interrupted before the host call has been performed:
28582 assuming 4 is the protocol-specific representation of @code{EINTR}.
28587 @node The Ctrl-C Message
28588 @subsection The @samp{Ctrl-C} Message
28589 @cindex ctrl-c message, in file-i/o protocol
28591 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
28592 reply packet (@pxref{The F Reply Packet}),
28593 the target should behave as if it had
28594 gotten a break message. The meaning for the target is ``system call
28595 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
28596 (as with a break message) and return to @value{GDBN} with a @code{T02}
28599 It's important for the target to know in which
28600 state the system call was interrupted. There are two possible cases:
28604 The system call hasn't been performed on the host yet.
28607 The system call on the host has been finished.
28611 These two states can be distinguished by the target by the value of the
28612 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
28613 call hasn't been performed. This is equivalent to the @code{EINTR} handling
28614 on POSIX systems. In any other case, the target may presume that the
28615 system call has been finished --- successfully or not --- and should behave
28616 as if the break message arrived right after the system call.
28618 @value{GDBN} must behave reliably. If the system call has not been called
28619 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
28620 @code{errno} in the packet. If the system call on the host has been finished
28621 before the user requests a break, the full action must be finished by
28622 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
28623 The @code{F} packet may only be sent when either nothing has happened
28624 or the full action has been completed.
28627 @subsection Console I/O
28628 @cindex console i/o as part of file-i/o
28630 By default and if not explicitly closed by the target system, the file
28631 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
28632 on the @value{GDBN} console is handled as any other file output operation
28633 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
28634 by @value{GDBN} so that after the target read request from file descriptor
28635 0 all following typing is buffered until either one of the following
28640 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
28642 system call is treated as finished.
28645 The user presses @key{RET}. This is treated as end of input with a trailing
28649 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
28650 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
28654 If the user has typed more characters than fit in the buffer given to
28655 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
28656 either another @code{read(0, @dots{})} is requested by the target, or debugging
28657 is stopped at the user's request.
28660 @node List of Supported Calls
28661 @subsection List of Supported Calls
28662 @cindex list of supported file-i/o calls
28679 @unnumberedsubsubsec open
28680 @cindex open, file-i/o system call
28685 int open(const char *pathname, int flags);
28686 int open(const char *pathname, int flags, mode_t mode);
28690 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
28693 @var{flags} is the bitwise @code{OR} of the following values:
28697 If the file does not exist it will be created. The host
28698 rules apply as far as file ownership and time stamps
28702 When used with @code{O_CREAT}, if the file already exists it is
28703 an error and open() fails.
28706 If the file already exists and the open mode allows
28707 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
28708 truncated to zero length.
28711 The file is opened in append mode.
28714 The file is opened for reading only.
28717 The file is opened for writing only.
28720 The file is opened for reading and writing.
28724 Other bits are silently ignored.
28728 @var{mode} is the bitwise @code{OR} of the following values:
28732 User has read permission.
28735 User has write permission.
28738 Group has read permission.
28741 Group has write permission.
28744 Others have read permission.
28747 Others have write permission.
28751 Other bits are silently ignored.
28754 @item Return value:
28755 @code{open} returns the new file descriptor or -1 if an error
28762 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
28765 @var{pathname} refers to a directory.
28768 The requested access is not allowed.
28771 @var{pathname} was too long.
28774 A directory component in @var{pathname} does not exist.
28777 @var{pathname} refers to a device, pipe, named pipe or socket.
28780 @var{pathname} refers to a file on a read-only filesystem and
28781 write access was requested.
28784 @var{pathname} is an invalid pointer value.
28787 No space on device to create the file.
28790 The process already has the maximum number of files open.
28793 The limit on the total number of files open on the system
28797 The call was interrupted by the user.
28803 @unnumberedsubsubsec close
28804 @cindex close, file-i/o system call
28813 @samp{Fclose,@var{fd}}
28815 @item Return value:
28816 @code{close} returns zero on success, or -1 if an error occurred.
28822 @var{fd} isn't a valid open file descriptor.
28825 The call was interrupted by the user.
28831 @unnumberedsubsubsec read
28832 @cindex read, file-i/o system call
28837 int read(int fd, void *buf, unsigned int count);
28841 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
28843 @item Return value:
28844 On success, the number of bytes read is returned.
28845 Zero indicates end of file. If count is zero, read
28846 returns zero as well. On error, -1 is returned.
28852 @var{fd} is not a valid file descriptor or is not open for
28856 @var{bufptr} is an invalid pointer value.
28859 The call was interrupted by the user.
28865 @unnumberedsubsubsec write
28866 @cindex write, file-i/o system call
28871 int write(int fd, const void *buf, unsigned int count);
28875 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
28877 @item Return value:
28878 On success, the number of bytes written are returned.
28879 Zero indicates nothing was written. On error, -1
28886 @var{fd} is not a valid file descriptor or is not open for
28890 @var{bufptr} is an invalid pointer value.
28893 An attempt was made to write a file that exceeds the
28894 host-specific maximum file size allowed.
28897 No space on device to write the data.
28900 The call was interrupted by the user.
28906 @unnumberedsubsubsec lseek
28907 @cindex lseek, file-i/o system call
28912 long lseek (int fd, long offset, int flag);
28916 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
28918 @var{flag} is one of:
28922 The offset is set to @var{offset} bytes.
28925 The offset is set to its current location plus @var{offset}
28929 The offset is set to the size of the file plus @var{offset}
28933 @item Return value:
28934 On success, the resulting unsigned offset in bytes from
28935 the beginning of the file is returned. Otherwise, a
28936 value of -1 is returned.
28942 @var{fd} is not a valid open file descriptor.
28945 @var{fd} is associated with the @value{GDBN} console.
28948 @var{flag} is not a proper value.
28951 The call was interrupted by the user.
28957 @unnumberedsubsubsec rename
28958 @cindex rename, file-i/o system call
28963 int rename(const char *oldpath, const char *newpath);
28967 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
28969 @item Return value:
28970 On success, zero is returned. On error, -1 is returned.
28976 @var{newpath} is an existing directory, but @var{oldpath} is not a
28980 @var{newpath} is a non-empty directory.
28983 @var{oldpath} or @var{newpath} is a directory that is in use by some
28987 An attempt was made to make a directory a subdirectory
28991 A component used as a directory in @var{oldpath} or new
28992 path is not a directory. Or @var{oldpath} is a directory
28993 and @var{newpath} exists but is not a directory.
28996 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
28999 No access to the file or the path of the file.
29003 @var{oldpath} or @var{newpath} was too long.
29006 A directory component in @var{oldpath} or @var{newpath} does not exist.
29009 The file is on a read-only filesystem.
29012 The device containing the file has no room for the new
29016 The call was interrupted by the user.
29022 @unnumberedsubsubsec unlink
29023 @cindex unlink, file-i/o system call
29028 int unlink(const char *pathname);
29032 @samp{Funlink,@var{pathnameptr}/@var{len}}
29034 @item Return value:
29035 On success, zero is returned. On error, -1 is returned.
29041 No access to the file or the path of the file.
29044 The system does not allow unlinking of directories.
29047 The file @var{pathname} cannot be unlinked because it's
29048 being used by another process.
29051 @var{pathnameptr} is an invalid pointer value.
29054 @var{pathname} was too long.
29057 A directory component in @var{pathname} does not exist.
29060 A component of the path is not a directory.
29063 The file is on a read-only filesystem.
29066 The call was interrupted by the user.
29072 @unnumberedsubsubsec stat/fstat
29073 @cindex fstat, file-i/o system call
29074 @cindex stat, file-i/o system call
29079 int stat(const char *pathname, struct stat *buf);
29080 int fstat(int fd, struct stat *buf);
29084 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
29085 @samp{Ffstat,@var{fd},@var{bufptr}}
29087 @item Return value:
29088 On success, zero is returned. On error, -1 is returned.
29094 @var{fd} is not a valid open file.
29097 A directory component in @var{pathname} does not exist or the
29098 path is an empty string.
29101 A component of the path is not a directory.
29104 @var{pathnameptr} is an invalid pointer value.
29107 No access to the file or the path of the file.
29110 @var{pathname} was too long.
29113 The call was interrupted by the user.
29119 @unnumberedsubsubsec gettimeofday
29120 @cindex gettimeofday, file-i/o system call
29125 int gettimeofday(struct timeval *tv, void *tz);
29129 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
29131 @item Return value:
29132 On success, 0 is returned, -1 otherwise.
29138 @var{tz} is a non-NULL pointer.
29141 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
29147 @unnumberedsubsubsec isatty
29148 @cindex isatty, file-i/o system call
29153 int isatty(int fd);
29157 @samp{Fisatty,@var{fd}}
29159 @item Return value:
29160 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
29166 The call was interrupted by the user.
29171 Note that the @code{isatty} call is treated as a special case: it returns
29172 1 to the target if the file descriptor is attached
29173 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
29174 would require implementing @code{ioctl} and would be more complex than
29179 @unnumberedsubsubsec system
29180 @cindex system, file-i/o system call
29185 int system(const char *command);
29189 @samp{Fsystem,@var{commandptr}/@var{len}}
29191 @item Return value:
29192 If @var{len} is zero, the return value indicates whether a shell is
29193 available. A zero return value indicates a shell is not available.
29194 For non-zero @var{len}, the value returned is -1 on error and the
29195 return status of the command otherwise. Only the exit status of the
29196 command is returned, which is extracted from the host's @code{system}
29197 return value by calling @code{WEXITSTATUS(retval)}. In case
29198 @file{/bin/sh} could not be executed, 127 is returned.
29204 The call was interrupted by the user.
29209 @value{GDBN} takes over the full task of calling the necessary host calls
29210 to perform the @code{system} call. The return value of @code{system} on
29211 the host is simplified before it's returned
29212 to the target. Any termination signal information from the child process
29213 is discarded, and the return value consists
29214 entirely of the exit status of the called command.
29216 Due to security concerns, the @code{system} call is by default refused
29217 by @value{GDBN}. The user has to allow this call explicitly with the
29218 @code{set remote system-call-allowed 1} command.
29221 @item set remote system-call-allowed
29222 @kindex set remote system-call-allowed
29223 Control whether to allow the @code{system} calls in the File I/O
29224 protocol for the remote target. The default is zero (disabled).
29226 @item show remote system-call-allowed
29227 @kindex show remote system-call-allowed
29228 Show whether the @code{system} calls are allowed in the File I/O
29232 @node Protocol-specific Representation of Datatypes
29233 @subsection Protocol-specific Representation of Datatypes
29234 @cindex protocol-specific representation of datatypes, in file-i/o protocol
29237 * Integral Datatypes::
29239 * Memory Transfer::
29244 @node Integral Datatypes
29245 @unnumberedsubsubsec Integral Datatypes
29246 @cindex integral datatypes, in file-i/o protocol
29248 The integral datatypes used in the system calls are @code{int},
29249 @code{unsigned int}, @code{long}, @code{unsigned long},
29250 @code{mode_t}, and @code{time_t}.
29252 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
29253 implemented as 32 bit values in this protocol.
29255 @code{long} and @code{unsigned long} are implemented as 64 bit types.
29257 @xref{Limits}, for corresponding MIN and MAX values (similar to those
29258 in @file{limits.h}) to allow range checking on host and target.
29260 @code{time_t} datatypes are defined as seconds since the Epoch.
29262 All integral datatypes transferred as part of a memory read or write of a
29263 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
29266 @node Pointer Values
29267 @unnumberedsubsubsec Pointer Values
29268 @cindex pointer values, in file-i/o protocol
29270 Pointers to target data are transmitted as they are. An exception
29271 is made for pointers to buffers for which the length isn't
29272 transmitted as part of the function call, namely strings. Strings
29273 are transmitted as a pointer/length pair, both as hex values, e.g.@:
29280 which is a pointer to data of length 18 bytes at position 0x1aaf.
29281 The length is defined as the full string length in bytes, including
29282 the trailing null byte. For example, the string @code{"hello world"}
29283 at address 0x123456 is transmitted as
29289 @node Memory Transfer
29290 @unnumberedsubsubsec Memory Transfer
29291 @cindex memory transfer, in file-i/o protocol
29293 Structured data which is transferred using a memory read or write (for
29294 example, a @code{struct stat}) is expected to be in a protocol-specific format
29295 with all scalar multibyte datatypes being big endian. Translation to
29296 this representation needs to be done both by the target before the @code{F}
29297 packet is sent, and by @value{GDBN} before
29298 it transfers memory to the target. Transferred pointers to structured
29299 data should point to the already-coerced data at any time.
29303 @unnumberedsubsubsec struct stat
29304 @cindex struct stat, in file-i/o protocol
29306 The buffer of type @code{struct stat} used by the target and @value{GDBN}
29307 is defined as follows:
29311 unsigned int st_dev; /* device */
29312 unsigned int st_ino; /* inode */
29313 mode_t st_mode; /* protection */
29314 unsigned int st_nlink; /* number of hard links */
29315 unsigned int st_uid; /* user ID of owner */
29316 unsigned int st_gid; /* group ID of owner */
29317 unsigned int st_rdev; /* device type (if inode device) */
29318 unsigned long st_size; /* total size, in bytes */
29319 unsigned long st_blksize; /* blocksize for filesystem I/O */
29320 unsigned long st_blocks; /* number of blocks allocated */
29321 time_t st_atime; /* time of last access */
29322 time_t st_mtime; /* time of last modification */
29323 time_t st_ctime; /* time of last change */
29327 The integral datatypes conform to the definitions given in the
29328 appropriate section (see @ref{Integral Datatypes}, for details) so this
29329 structure is of size 64 bytes.
29331 The values of several fields have a restricted meaning and/or
29337 A value of 0 represents a file, 1 the console.
29340 No valid meaning for the target. Transmitted unchanged.
29343 Valid mode bits are described in @ref{Constants}. Any other
29344 bits have currently no meaning for the target.
29349 No valid meaning for the target. Transmitted unchanged.
29354 These values have a host and file system dependent
29355 accuracy. Especially on Windows hosts, the file system may not
29356 support exact timing values.
29359 The target gets a @code{struct stat} of the above representation and is
29360 responsible for coercing it to the target representation before
29363 Note that due to size differences between the host, target, and protocol
29364 representations of @code{struct stat} members, these members could eventually
29365 get truncated on the target.
29367 @node struct timeval
29368 @unnumberedsubsubsec struct timeval
29369 @cindex struct timeval, in file-i/o protocol
29371 The buffer of type @code{struct timeval} used by the File-I/O protocol
29372 is defined as follows:
29376 time_t tv_sec; /* second */
29377 long tv_usec; /* microsecond */
29381 The integral datatypes conform to the definitions given in the
29382 appropriate section (see @ref{Integral Datatypes}, for details) so this
29383 structure is of size 8 bytes.
29386 @subsection Constants
29387 @cindex constants, in file-i/o protocol
29389 The following values are used for the constants inside of the
29390 protocol. @value{GDBN} and target are responsible for translating these
29391 values before and after the call as needed.
29402 @unnumberedsubsubsec Open Flags
29403 @cindex open flags, in file-i/o protocol
29405 All values are given in hexadecimal representation.
29417 @node mode_t Values
29418 @unnumberedsubsubsec mode_t Values
29419 @cindex mode_t values, in file-i/o protocol
29421 All values are given in octal representation.
29438 @unnumberedsubsubsec Errno Values
29439 @cindex errno values, in file-i/o protocol
29441 All values are given in decimal representation.
29466 @code{EUNKNOWN} is used as a fallback error value if a host system returns
29467 any error value not in the list of supported error numbers.
29470 @unnumberedsubsubsec Lseek Flags
29471 @cindex lseek flags, in file-i/o protocol
29480 @unnumberedsubsubsec Limits
29481 @cindex limits, in file-i/o protocol
29483 All values are given in decimal representation.
29486 INT_MIN -2147483648
29488 UINT_MAX 4294967295
29489 LONG_MIN -9223372036854775808
29490 LONG_MAX 9223372036854775807
29491 ULONG_MAX 18446744073709551615
29494 @node File-I/O Examples
29495 @subsection File-I/O Examples
29496 @cindex file-i/o examples
29498 Example sequence of a write call, file descriptor 3, buffer is at target
29499 address 0x1234, 6 bytes should be written:
29502 <- @code{Fwrite,3,1234,6}
29503 @emph{request memory read from target}
29506 @emph{return "6 bytes written"}
29510 Example sequence of a read call, file descriptor 3, buffer is at target
29511 address 0x1234, 6 bytes should be read:
29514 <- @code{Fread,3,1234,6}
29515 @emph{request memory write to target}
29516 -> @code{X1234,6:XXXXXX}
29517 @emph{return "6 bytes read"}
29521 Example sequence of a read call, call fails on the host due to invalid
29522 file descriptor (@code{EBADF}):
29525 <- @code{Fread,3,1234,6}
29529 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
29533 <- @code{Fread,3,1234,6}
29538 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
29542 <- @code{Fread,3,1234,6}
29543 -> @code{X1234,6:XXXXXX}
29547 @node Library List Format
29548 @section Library List Format
29549 @cindex library list format, remote protocol
29551 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
29552 same process as your application to manage libraries. In this case,
29553 @value{GDBN} can use the loader's symbol table and normal memory
29554 operations to maintain a list of shared libraries. On other
29555 platforms, the operating system manages loaded libraries.
29556 @value{GDBN} can not retrieve the list of currently loaded libraries
29557 through memory operations, so it uses the @samp{qXfer:libraries:read}
29558 packet (@pxref{qXfer library list read}) instead. The remote stub
29559 queries the target's operating system and reports which libraries
29562 The @samp{qXfer:libraries:read} packet returns an XML document which
29563 lists loaded libraries and their offsets. Each library has an
29564 associated name and one or more segment or section base addresses,
29565 which report where the library was loaded in memory.
29567 For the common case of libraries that are fully linked binaries, the
29568 library should have a list of segments. If the target supports
29569 dynamic linking of a relocatable object file, its library XML element
29570 should instead include a list of allocated sections. The segment or
29571 section bases are start addresses, not relocation offsets; they do not
29572 depend on the library's link-time base addresses.
29574 @value{GDBN} must be linked with the Expat library to support XML
29575 library lists. @xref{Expat}.
29577 A simple memory map, with one loaded library relocated by a single
29578 offset, looks like this:
29582 <library name="/lib/libc.so.6">
29583 <segment address="0x10000000"/>
29588 Another simple memory map, with one loaded library with three
29589 allocated sections (.text, .data, .bss), looks like this:
29593 <library name="sharedlib.o">
29594 <section address="0x10000000"/>
29595 <section address="0x20000000"/>
29596 <section address="0x30000000"/>
29601 The format of a library list is described by this DTD:
29604 <!-- library-list: Root element with versioning -->
29605 <!ELEMENT library-list (library)*>
29606 <!ATTLIST library-list version CDATA #FIXED "1.0">
29607 <!ELEMENT library (segment*, section*)>
29608 <!ATTLIST library name CDATA #REQUIRED>
29609 <!ELEMENT segment EMPTY>
29610 <!ATTLIST segment address CDATA #REQUIRED>
29611 <!ELEMENT section EMPTY>
29612 <!ATTLIST section address CDATA #REQUIRED>
29615 In addition, segments and section descriptors cannot be mixed within a
29616 single library element, and you must supply at least one segment or
29617 section for each library.
29619 @node Memory Map Format
29620 @section Memory Map Format
29621 @cindex memory map format
29623 To be able to write into flash memory, @value{GDBN} needs to obtain a
29624 memory map from the target. This section describes the format of the
29627 The memory map is obtained using the @samp{qXfer:memory-map:read}
29628 (@pxref{qXfer memory map read}) packet and is an XML document that
29629 lists memory regions.
29631 @value{GDBN} must be linked with the Expat library to support XML
29632 memory maps. @xref{Expat}.
29634 The top-level structure of the document is shown below:
29637 <?xml version="1.0"?>
29638 <!DOCTYPE memory-map
29639 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
29640 "http://sourceware.org/gdb/gdb-memory-map.dtd">
29646 Each region can be either:
29651 A region of RAM starting at @var{addr} and extending for @var{length}
29655 <memory type="ram" start="@var{addr}" length="@var{length}"/>
29660 A region of read-only memory:
29663 <memory type="rom" start="@var{addr}" length="@var{length}"/>
29668 A region of flash memory, with erasure blocks @var{blocksize}
29672 <memory type="flash" start="@var{addr}" length="@var{length}">
29673 <property name="blocksize">@var{blocksize}</property>
29679 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
29680 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
29681 packets to write to addresses in such ranges.
29683 The formal DTD for memory map format is given below:
29686 <!-- ................................................... -->
29687 <!-- Memory Map XML DTD ................................ -->
29688 <!-- File: memory-map.dtd .............................. -->
29689 <!-- .................................... .............. -->
29690 <!-- memory-map.dtd -->
29691 <!-- memory-map: Root element with versioning -->
29692 <!ELEMENT memory-map (memory | property)>
29693 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
29694 <!ELEMENT memory (property)>
29695 <!-- memory: Specifies a memory region,
29696 and its type, or device. -->
29697 <!ATTLIST memory type CDATA #REQUIRED
29698 start CDATA #REQUIRED
29699 length CDATA #REQUIRED
29700 device CDATA #IMPLIED>
29701 <!-- property: Generic attribute tag -->
29702 <!ELEMENT property (#PCDATA | property)*>
29703 <!ATTLIST property name CDATA #REQUIRED>
29706 @include agentexpr.texi
29708 @node Target Descriptions
29709 @appendix Target Descriptions
29710 @cindex target descriptions
29712 @strong{Warning:} target descriptions are still under active development,
29713 and the contents and format may change between @value{GDBN} releases.
29714 The format is expected to stabilize in the future.
29716 One of the challenges of using @value{GDBN} to debug embedded systems
29717 is that there are so many minor variants of each processor
29718 architecture in use. It is common practice for vendors to start with
29719 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
29720 and then make changes to adapt it to a particular market niche. Some
29721 architectures have hundreds of variants, available from dozens of
29722 vendors. This leads to a number of problems:
29726 With so many different customized processors, it is difficult for
29727 the @value{GDBN} maintainers to keep up with the changes.
29729 Since individual variants may have short lifetimes or limited
29730 audiences, it may not be worthwhile to carry information about every
29731 variant in the @value{GDBN} source tree.
29733 When @value{GDBN} does support the architecture of the embedded system
29734 at hand, the task of finding the correct architecture name to give the
29735 @command{set architecture} command can be error-prone.
29738 To address these problems, the @value{GDBN} remote protocol allows a
29739 target system to not only identify itself to @value{GDBN}, but to
29740 actually describe its own features. This lets @value{GDBN} support
29741 processor variants it has never seen before --- to the extent that the
29742 descriptions are accurate, and that @value{GDBN} understands them.
29744 @value{GDBN} must be linked with the Expat library to support XML
29745 target descriptions. @xref{Expat}.
29748 * Retrieving Descriptions:: How descriptions are fetched from a target.
29749 * Target Description Format:: The contents of a target description.
29750 * Predefined Target Types:: Standard types available for target
29752 * Standard Target Features:: Features @value{GDBN} knows about.
29755 @node Retrieving Descriptions
29756 @section Retrieving Descriptions
29758 Target descriptions can be read from the target automatically, or
29759 specified by the user manually. The default behavior is to read the
29760 description from the target. @value{GDBN} retrieves it via the remote
29761 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
29762 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
29763 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
29764 XML document, of the form described in @ref{Target Description
29767 Alternatively, you can specify a file to read for the target description.
29768 If a file is set, the target will not be queried. The commands to
29769 specify a file are:
29772 @cindex set tdesc filename
29773 @item set tdesc filename @var{path}
29774 Read the target description from @var{path}.
29776 @cindex unset tdesc filename
29777 @item unset tdesc filename
29778 Do not read the XML target description from a file. @value{GDBN}
29779 will use the description supplied by the current target.
29781 @cindex show tdesc filename
29782 @item show tdesc filename
29783 Show the filename to read for a target description, if any.
29787 @node Target Description Format
29788 @section Target Description Format
29789 @cindex target descriptions, XML format
29791 A target description annex is an @uref{http://www.w3.org/XML/, XML}
29792 document which complies with the Document Type Definition provided in
29793 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
29794 means you can use generally available tools like @command{xmllint} to
29795 check that your feature descriptions are well-formed and valid.
29796 However, to help people unfamiliar with XML write descriptions for
29797 their targets, we also describe the grammar here.
29799 Target descriptions can identify the architecture of the remote target
29800 and (for some architectures) provide information about custom register
29801 sets. @value{GDBN} can use this information to autoconfigure for your
29802 target, or to warn you if you connect to an unsupported target.
29804 Here is a simple target description:
29807 <target version="1.0">
29808 <architecture>i386:x86-64</architecture>
29813 This minimal description only says that the target uses
29814 the x86-64 architecture.
29816 A target description has the following overall form, with [ ] marking
29817 optional elements and @dots{} marking repeatable elements. The elements
29818 are explained further below.
29821 <?xml version="1.0"?>
29822 <!DOCTYPE target SYSTEM "gdb-target.dtd">
29823 <target version="1.0">
29824 @r{[}@var{architecture}@r{]}
29825 @r{[}@var{feature}@dots{}@r{]}
29830 The description is generally insensitive to whitespace and line
29831 breaks, under the usual common-sense rules. The XML version
29832 declaration and document type declaration can generally be omitted
29833 (@value{GDBN} does not require them), but specifying them may be
29834 useful for XML validation tools. The @samp{version} attribute for
29835 @samp{<target>} may also be omitted, but we recommend
29836 including it; if future versions of @value{GDBN} use an incompatible
29837 revision of @file{gdb-target.dtd}, they will detect and report
29838 the version mismatch.
29840 @subsection Inclusion
29841 @cindex target descriptions, inclusion
29844 @cindex <xi:include>
29847 It can sometimes be valuable to split a target description up into
29848 several different annexes, either for organizational purposes, or to
29849 share files between different possible target descriptions. You can
29850 divide a description into multiple files by replacing any element of
29851 the target description with an inclusion directive of the form:
29854 <xi:include href="@var{document}"/>
29858 When @value{GDBN} encounters an element of this form, it will retrieve
29859 the named XML @var{document}, and replace the inclusion directive with
29860 the contents of that document. If the current description was read
29861 using @samp{qXfer}, then so will be the included document;
29862 @var{document} will be interpreted as the name of an annex. If the
29863 current description was read from a file, @value{GDBN} will look for
29864 @var{document} as a file in the same directory where it found the
29865 original description.
29867 @subsection Architecture
29868 @cindex <architecture>
29870 An @samp{<architecture>} element has this form:
29873 <architecture>@var{arch}</architecture>
29876 @var{arch} is an architecture name from the same selection
29877 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
29878 Debugging Target}).
29880 @subsection Features
29883 Each @samp{<feature>} describes some logical portion of the target
29884 system. Features are currently used to describe available CPU
29885 registers and the types of their contents. A @samp{<feature>} element
29889 <feature name="@var{name}">
29890 @r{[}@var{type}@dots{}@r{]}
29896 Each feature's name should be unique within the description. The name
29897 of a feature does not matter unless @value{GDBN} has some special
29898 knowledge of the contents of that feature; if it does, the feature
29899 should have its standard name. @xref{Standard Target Features}.
29903 Any register's value is a collection of bits which @value{GDBN} must
29904 interpret. The default interpretation is a two's complement integer,
29905 but other types can be requested by name in the register description.
29906 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
29907 Target Types}), and the description can define additional composite types.
29909 Each type element must have an @samp{id} attribute, which gives
29910 a unique (within the containing @samp{<feature>}) name to the type.
29911 Types must be defined before they are used.
29914 Some targets offer vector registers, which can be treated as arrays
29915 of scalar elements. These types are written as @samp{<vector>} elements,
29916 specifying the array element type, @var{type}, and the number of elements,
29920 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
29924 If a register's value is usefully viewed in multiple ways, define it
29925 with a union type containing the useful representations. The
29926 @samp{<union>} element contains one or more @samp{<field>} elements,
29927 each of which has a @var{name} and a @var{type}:
29930 <union id="@var{id}">
29931 <field name="@var{name}" type="@var{type}"/>
29936 @subsection Registers
29939 Each register is represented as an element with this form:
29942 <reg name="@var{name}"
29943 bitsize="@var{size}"
29944 @r{[}regnum="@var{num}"@r{]}
29945 @r{[}save-restore="@var{save-restore}"@r{]}
29946 @r{[}type="@var{type}"@r{]}
29947 @r{[}group="@var{group}"@r{]}/>
29951 The components are as follows:
29956 The register's name; it must be unique within the target description.
29959 The register's size, in bits.
29962 The register's number. If omitted, a register's number is one greater
29963 than that of the previous register (either in the current feature or in
29964 a preceeding feature); the first register in the target description
29965 defaults to zero. This register number is used to read or write
29966 the register; e.g.@: it is used in the remote @code{p} and @code{P}
29967 packets, and registers appear in the @code{g} and @code{G} packets
29968 in order of increasing register number.
29971 Whether the register should be preserved across inferior function
29972 calls; this must be either @code{yes} or @code{no}. The default is
29973 @code{yes}, which is appropriate for most registers except for
29974 some system control registers; this is not related to the target's
29978 The type of the register. @var{type} may be a predefined type, a type
29979 defined in the current feature, or one of the special types @code{int}
29980 and @code{float}. @code{int} is an integer type of the correct size
29981 for @var{bitsize}, and @code{float} is a floating point type (in the
29982 architecture's normal floating point format) of the correct size for
29983 @var{bitsize}. The default is @code{int}.
29986 The register group to which this register belongs. @var{group} must
29987 be either @code{general}, @code{float}, or @code{vector}. If no
29988 @var{group} is specified, @value{GDBN} will not display the register
29989 in @code{info registers}.
29993 @node Predefined Target Types
29994 @section Predefined Target Types
29995 @cindex target descriptions, predefined types
29997 Type definitions in the self-description can build up composite types
29998 from basic building blocks, but can not define fundamental types. Instead,
29999 standard identifiers are provided by @value{GDBN} for the fundamental
30000 types. The currently supported types are:
30009 Signed integer types holding the specified number of bits.
30016 Unsigned integer types holding the specified number of bits.
30020 Pointers to unspecified code and data. The program counter and
30021 any dedicated return address register may be marked as code
30022 pointers; printing a code pointer converts it into a symbolic
30023 address. The stack pointer and any dedicated address registers
30024 may be marked as data pointers.
30027 Single precision IEEE floating point.
30030 Double precision IEEE floating point.
30033 The 12-byte extended precision format used by ARM FPA registers.
30037 @node Standard Target Features
30038 @section Standard Target Features
30039 @cindex target descriptions, standard features
30041 A target description must contain either no registers or all the
30042 target's registers. If the description contains no registers, then
30043 @value{GDBN} will assume a default register layout, selected based on
30044 the architecture. If the description contains any registers, the
30045 default layout will not be used; the standard registers must be
30046 described in the target description, in such a way that @value{GDBN}
30047 can recognize them.
30049 This is accomplished by giving specific names to feature elements
30050 which contain standard registers. @value{GDBN} will look for features
30051 with those names and verify that they contain the expected registers;
30052 if any known feature is missing required registers, or if any required
30053 feature is missing, @value{GDBN} will reject the target
30054 description. You can add additional registers to any of the
30055 standard features --- @value{GDBN} will display them just as if
30056 they were added to an unrecognized feature.
30058 This section lists the known features and their expected contents.
30059 Sample XML documents for these features are included in the
30060 @value{GDBN} source tree, in the directory @file{gdb/features}.
30062 Names recognized by @value{GDBN} should include the name of the
30063 company or organization which selected the name, and the overall
30064 architecture to which the feature applies; so e.g.@: the feature
30065 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
30067 The names of registers are not case sensitive for the purpose
30068 of recognizing standard features, but @value{GDBN} will only display
30069 registers using the capitalization used in the description.
30075 * PowerPC Features::
30080 @subsection ARM Features
30081 @cindex target descriptions, ARM features
30083 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
30084 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
30085 @samp{lr}, @samp{pc}, and @samp{cpsr}.
30087 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
30088 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
30090 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
30091 it should contain at least registers @samp{wR0} through @samp{wR15} and
30092 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
30093 @samp{wCSSF}, and @samp{wCASF} registers are optional.
30095 @node MIPS Features
30096 @subsection MIPS Features
30097 @cindex target descriptions, MIPS features
30099 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
30100 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
30101 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
30104 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
30105 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
30106 registers. They may be 32-bit or 64-bit depending on the target.
30108 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
30109 it may be optional in a future version of @value{GDBN}. It should
30110 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
30111 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
30113 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
30114 contain a single register, @samp{restart}, which is used by the
30115 Linux kernel to control restartable syscalls.
30117 @node M68K Features
30118 @subsection M68K Features
30119 @cindex target descriptions, M68K features
30122 @item @samp{org.gnu.gdb.m68k.core}
30123 @itemx @samp{org.gnu.gdb.coldfire.core}
30124 @itemx @samp{org.gnu.gdb.fido.core}
30125 One of those features must be always present.
30126 The feature that is present determines which flavor of m68k is
30127 used. The feature that is present should contain registers
30128 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
30129 @samp{sp}, @samp{ps} and @samp{pc}.
30131 @item @samp{org.gnu.gdb.coldfire.fp}
30132 This feature is optional. If present, it should contain registers
30133 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
30137 @node PowerPC Features
30138 @subsection PowerPC Features
30139 @cindex target descriptions, PowerPC features
30141 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
30142 targets. It should contain registers @samp{r0} through @samp{r31},
30143 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
30144 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
30146 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
30147 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
30149 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
30150 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
30153 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
30154 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
30155 will combine these registers with the floating point registers
30156 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
30157 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
30158 through @samp{vs63}, the set of vector registers for POWER7.
30160 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
30161 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
30162 @samp{spefscr}. SPE targets should provide 32-bit registers in
30163 @samp{org.gnu.gdb.power.core} and provide the upper halves in
30164 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
30165 these to present registers @samp{ev0} through @samp{ev31} to the
30168 @node Operating System Information
30169 @appendix Operating System Information
30170 @cindex operating system information
30176 Users of @value{GDBN} often wish to obtain information about the state of
30177 the operating system running on the target---for example the list of
30178 processes, or the list of open files. This section describes the
30179 mechanism that makes it possible. This mechanism is similar to the
30180 target features mechanism (@pxref{Target Descriptions}), but focuses
30181 on a different aspect of target.
30183 Operating system information is retrived from the target via the
30184 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
30185 read}). The object name in the request should be @samp{osdata}, and
30186 the @var{annex} identifies the data to be fetched.
30189 @appendixsection Process list
30190 @cindex operating system information, process list
30192 When requesting the process list, the @var{annex} field in the
30193 @samp{qXfer} request should be @samp{processes}. The returned data is
30194 an XML document. The formal syntax of this document is defined in
30195 @file{gdb/features/osdata.dtd}.
30197 An example document is:
30200 <?xml version="1.0"?>
30201 <!DOCTYPE target SYSTEM "osdata.dtd">
30202 <osdata type="processes">
30204 <column name="pid">1</column>
30205 <column name="user">root</column>
30206 <column name="command">/sbin/init</column>
30211 Each item should include a column whose name is @samp{pid}. The value
30212 of that column should identify the process on the target. The
30213 @samp{user} and @samp{command} columns are optional, and will be
30214 displayed by @value{GDBN}. Target may provide additional columns,
30215 which @value{GDBN} currently ignores.
30229 % I think something like @colophon should be in texinfo. In the
30231 \long\def\colophon{\hbox to0pt{}\vfill
30232 \centerline{The body of this manual is set in}
30233 \centerline{\fontname\tenrm,}
30234 \centerline{with headings in {\bf\fontname\tenbf}}
30235 \centerline{and examples in {\tt\fontname\tentt}.}
30236 \centerline{{\it\fontname\tenit\/},}
30237 \centerline{{\bf\fontname\tenbf}, and}
30238 \centerline{{\sl\fontname\tensl\/}}
30239 \centerline{are used for emphasis.}\vfill}
30241 % Blame: doc@cygnus.com, 1991.