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
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 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 @ifset VERSION_PACKAGE
53 @value{VERSION_PACKAGE}
55 Version @value{GDBVN}.
57 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
58 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
59 Free Software Foundation, Inc.
61 Permission is granted to copy, distribute and/or modify this document
62 under the terms of the GNU Free Documentation License, Version 1.1 or
63 any later version published by the Free Software Foundation; with the
64 Invariant Sections being ``Free Software'' and ``Free Software Needs
65 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
66 and with the Back-Cover Texts as in (a) below.
68 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
69 this GNU Manual. Buying copies from GNU Press supports the FSF in
70 developing GNU and promoting software freedom.''
74 @title Debugging with @value{GDBN}
75 @subtitle The @sc{gnu} Source-Level Debugger
77 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
78 @ifset VERSION_PACKAGE
80 @subtitle @value{VERSION_PACKAGE}
82 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
86 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
87 \hfill {\it Debugging with @value{GDBN}}\par
88 \hfill \TeX{}info \texinfoversion\par
92 @vskip 0pt plus 1filll
93 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
94 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
95 Free Software Foundation, Inc.
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
102 Permission is granted to copy, distribute and/or modify this document
103 under the terms of the GNU Free Documentation License, Version 1.1 or
104 any later version published by the Free Software Foundation; with the
105 Invariant Sections being ``Free Software'' and ``Free Software Needs
106 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
107 and with the Back-Cover Texts as in (a) below.
109 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
110 this GNU Manual. Buying copies from GNU Press supports the FSF in
111 developing GNU and promoting software freedom.''
113 This edition of the GDB manual is dedicated to the memory of Fred
114 Fish. Fred was a long-standing contributor to GDB and to Free
115 software in general. We will miss him.
120 @node Top, Summary, (dir), (dir)
122 @top Debugging with @value{GDBN}
124 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
126 This is the @value{EDITION} Edition, for @value{GDBN}
127 @ifset VERSION_PACKAGE
128 @value{VERSION_PACKAGE}
130 Version @value{GDBVN}.
132 Copyright (C) 1988-2006 Free Software Foundation, Inc.
134 This edition of the GDB manual is dedicated to the memory of Fred
135 Fish. Fred was a long-standing contributor to GDB and to Free
136 software in general. We will miss him.
139 * Summary:: Summary of @value{GDBN}
140 * Sample Session:: A sample @value{GDBN} session
142 * Invocation:: Getting in and out of @value{GDBN}
143 * Commands:: @value{GDBN} commands
144 * Running:: Running programs under @value{GDBN}
145 * Stopping:: Stopping and continuing
146 * Reverse Execution:: Running programs backward
147 * Stack:: Examining the stack
148 * Source:: Examining source files
149 * Data:: Examining data
150 * Macros:: Preprocessor Macros
151 * Tracepoints:: Debugging remote targets non-intrusively
152 * Overlays:: Debugging programs that use overlays
154 * Languages:: Using @value{GDBN} with different languages
156 * Symbols:: Examining the symbol table
157 * Altering:: Altering execution
158 * GDB Files:: @value{GDBN} files
159 * Targets:: Specifying a debugging target
160 * Remote Debugging:: Debugging remote programs
161 * Configurations:: Configuration-specific information
162 * Controlling GDB:: Controlling @value{GDBN}
163 * Extending GDB:: Extending @value{GDBN}
164 * Interpreters:: Command Interpreters
165 * TUI:: @value{GDBN} Text User Interface
166 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
167 * GDB/MI:: @value{GDBN}'s Machine Interface.
168 * Annotations:: @value{GDBN}'s annotation interface.
170 * GDB Bugs:: Reporting bugs in @value{GDBN}
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
174 * Formatting Documentation:: How to format and print @value{GDBN} documentation
175 * Installing GDB:: Installing GDB
176 * Maintenance Commands:: Maintenance Commands
177 * Remote Protocol:: GDB Remote Serial Protocol
178 * Agent Expressions:: The GDB Agent Expression Mechanism
179 * Target Descriptions:: How targets can describe themselves to
181 * Operating System Information:: Getting additional information from
183 * Copying:: GNU General Public License says
184 how you can copy and share GDB
185 * GNU Free Documentation License:: The license for this documentation
194 @unnumbered Summary of @value{GDBN}
196 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
197 going on ``inside'' another program while it executes---or what another
198 program was doing at the moment it crashed.
200 @value{GDBN} can do four main kinds of things (plus other things in support of
201 these) to help you catch bugs in the act:
205 Start your program, specifying anything that might affect its behavior.
208 Make your program stop on specified conditions.
211 Examine what has happened, when your program has stopped.
214 Change things in your program, so you can experiment with correcting the
215 effects of one bug and go on to learn about another.
218 You can use @value{GDBN} to debug programs written in C and C@t{++}.
219 For more information, see @ref{Supported Languages,,Supported Languages}.
220 For more information, see @ref{C,,C and C++}.
223 Support for Modula-2 is partial. For information on Modula-2, see
224 @ref{Modula-2,,Modula-2}.
227 Debugging Pascal programs which use sets, subranges, file variables, or
228 nested functions does not currently work. @value{GDBN} does not support
229 entering expressions, printing values, or similar features using Pascal
233 @value{GDBN} can be used to debug programs written in Fortran, although
234 it may be necessary to refer to some variables with a trailing
237 @value{GDBN} can be used to debug programs written in Objective-C,
238 using either the Apple/NeXT or the GNU Objective-C runtime.
241 * Free Software:: Freely redistributable software
242 * Contributors:: Contributors to GDB
246 @unnumberedsec Free Software
248 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
249 General Public License
250 (GPL). The GPL gives you the freedom to copy or adapt a licensed
251 program---but every person getting a copy also gets with it the
252 freedom to modify that copy (which means that they must get access to
253 the source code), and the freedom to distribute further copies.
254 Typical software companies use copyrights to limit your freedoms; the
255 Free Software Foundation uses the GPL to preserve these freedoms.
257 Fundamentally, the General Public License is a license which says that
258 you have these freedoms and that you cannot take these freedoms away
261 @unnumberedsec Free Software Needs Free Documentation
263 The biggest deficiency in the free software community today is not in
264 the software---it is the lack of good free documentation that we can
265 include with the free software. Many of our most important
266 programs do not come with free reference manuals and free introductory
267 texts. Documentation is an essential part of any software package;
268 when an important free software package does not come with a free
269 manual and a free tutorial, that is a major gap. We have many such
272 Consider Perl, for instance. The tutorial manuals that people
273 normally use are non-free. How did this come about? Because the
274 authors of those manuals published them with restrictive terms---no
275 copying, no modification, source files not available---which exclude
276 them from the free software world.
278 That wasn't the first time this sort of thing happened, and it was far
279 from the last. Many times we have heard a GNU user eagerly describe a
280 manual that he is writing, his intended contribution to the community,
281 only to learn that he had ruined everything by signing a publication
282 contract to make it non-free.
284 Free documentation, like free software, is a matter of freedom, not
285 price. The problem with the non-free manual is not that publishers
286 charge a price for printed copies---that in itself is fine. (The Free
287 Software Foundation sells printed copies of manuals, too.) The
288 problem is the restrictions on the use of the manual. Free manuals
289 are available in source code form, and give you permission to copy and
290 modify. Non-free manuals do not allow this.
292 The criteria of freedom for a free manual are roughly the same as for
293 free software. Redistribution (including the normal kinds of
294 commercial redistribution) must be permitted, so that the manual can
295 accompany every copy of the program, both on-line and on paper.
297 Permission for modification of the technical content is crucial too.
298 When people modify the software, adding or changing features, if they
299 are conscientious they will change the manual too---so they can
300 provide accurate and clear documentation for the modified program. A
301 manual that leaves you no choice but to write a new manual to document
302 a changed version of the program is not really available to our
305 Some kinds of limits on the way modification is handled are
306 acceptable. For example, requirements to preserve the original
307 author's copyright notice, the distribution terms, or the list of
308 authors, are ok. It is also no problem to require modified versions
309 to include notice that they were modified. Even entire sections that
310 may not be deleted or changed are acceptable, as long as they deal
311 with nontechnical topics (like this one). These kinds of restrictions
312 are acceptable because they don't obstruct the community's normal use
315 However, it must be possible to modify all the @emph{technical}
316 content of the manual, and then distribute the result in all the usual
317 media, through all the usual channels. Otherwise, the restrictions
318 obstruct the use of the manual, it is not free, and we need another
319 manual to replace it.
321 Please spread the word about this issue. Our community continues to
322 lose manuals to proprietary publishing. If we spread the word that
323 free software needs free reference manuals and free tutorials, perhaps
324 the next person who wants to contribute by writing documentation will
325 realize, before it is too late, that only free manuals contribute to
326 the free software community.
328 If you are writing documentation, please insist on publishing it under
329 the GNU Free Documentation License or another free documentation
330 license. Remember that this decision requires your approval---you
331 don't have to let the publisher decide. Some commercial publishers
332 will use a free license if you insist, but they will not propose the
333 option; it is up to you to raise the issue and say firmly that this is
334 what you want. If the publisher you are dealing with refuses, please
335 try other publishers. If you're not sure whether a proposed license
336 is free, write to @email{licensing@@gnu.org}.
338 You can encourage commercial publishers to sell more free, copylefted
339 manuals and tutorials by buying them, and particularly by buying
340 copies from the publishers that paid for their writing or for major
341 improvements. Meanwhile, try to avoid buying non-free documentation
342 at all. Check the distribution terms of a manual before you buy it,
343 and insist that whoever seeks your business must respect your freedom.
344 Check the history of the book, and try to reward the publishers that
345 have paid or pay the authors to work on it.
347 The Free Software Foundation maintains a list of free documentation
348 published by other publishers, at
349 @url{http://www.fsf.org/doc/other-free-books.html}.
352 @unnumberedsec Contributors to @value{GDBN}
354 Richard Stallman was the original author of @value{GDBN}, and of many
355 other @sc{gnu} programs. Many others have contributed to its
356 development. This section attempts to credit major contributors. One
357 of the virtues of free software is that everyone is free to contribute
358 to it; with regret, we cannot actually acknowledge everyone here. The
359 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
360 blow-by-blow account.
362 Changes much prior to version 2.0 are lost in the mists of time.
365 @emph{Plea:} Additions to this section are particularly welcome. If you
366 or your friends (or enemies, to be evenhanded) have been unfairly
367 omitted from this list, we would like to add your names!
370 So that they may not regard their many labors as thankless, we
371 particularly thank those who shepherded @value{GDBN} through major
373 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
374 Jim Blandy (release 4.18);
375 Jason Molenda (release 4.17);
376 Stan Shebs (release 4.14);
377 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
378 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
379 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
380 Jim Kingdon (releases 3.5, 3.4, and 3.3);
381 and Randy Smith (releases 3.2, 3.1, and 3.0).
383 Richard Stallman, assisted at various times by Peter TerMaat, Chris
384 Hanson, and Richard Mlynarik, handled releases through 2.8.
386 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
387 in @value{GDBN}, with significant additional contributions from Per
388 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
389 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
390 much general update work leading to release 3.0).
392 @value{GDBN} uses the BFD subroutine library to examine multiple
393 object-file formats; BFD was a joint project of David V.
394 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
396 David Johnson wrote the original COFF support; Pace Willison did
397 the original support for encapsulated COFF.
399 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
401 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
402 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
404 Jean-Daniel Fekete contributed Sun 386i support.
405 Chris Hanson improved the HP9000 support.
406 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
407 David Johnson contributed Encore Umax support.
408 Jyrki Kuoppala contributed Altos 3068 support.
409 Jeff Law contributed HP PA and SOM support.
410 Keith Packard contributed NS32K support.
411 Doug Rabson contributed Acorn Risc Machine support.
412 Bob Rusk contributed Harris Nighthawk CX-UX support.
413 Chris Smith contributed Convex support (and Fortran debugging).
414 Jonathan Stone contributed Pyramid support.
415 Michael Tiemann contributed SPARC support.
416 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
417 Pace Willison contributed Intel 386 support.
418 Jay Vosburgh contributed Symmetry support.
419 Marko Mlinar contributed OpenRISC 1000 support.
421 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
423 Rich Schaefer and Peter Schauer helped with support of SunOS shared
426 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
427 about several machine instruction sets.
429 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
430 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
431 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
432 and RDI targets, respectively.
434 Brian Fox is the author of the readline libraries providing
435 command-line editing and command history.
437 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
438 Modula-2 support, and contributed the Languages chapter of this manual.
440 Fred Fish wrote most of the support for Unix System Vr4.
441 He also enhanced the command-completion support to cover C@t{++} overloaded
444 Hitachi America (now Renesas America), Ltd. sponsored the support for
445 H8/300, H8/500, and Super-H processors.
447 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
449 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
452 Toshiba sponsored the support for the TX39 Mips processor.
454 Matsushita sponsored the support for the MN10200 and MN10300 processors.
456 Fujitsu sponsored the support for SPARClite and FR30 processors.
458 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
461 Michael Snyder added support for tracepoints.
463 Stu Grossman wrote gdbserver.
465 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
466 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
468 The following people at the Hewlett-Packard Company contributed
469 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
470 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
471 compiler, and the Text User Interface (nee Terminal User Interface):
472 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
473 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
474 provided HP-specific information in this manual.
476 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
477 Robert Hoehne made significant contributions to the DJGPP port.
479 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
480 development since 1991. Cygnus engineers who have worked on @value{GDBN}
481 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
482 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
483 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
484 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
485 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
486 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
487 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
488 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
489 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
490 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
491 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
492 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
493 Zuhn have made contributions both large and small.
495 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
496 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
498 Jim Blandy added support for preprocessor macros, while working for Red
501 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
502 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
503 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
504 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
505 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
506 with the migration of old architectures to this new framework.
508 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
509 unwinder framework, this consisting of a fresh new design featuring
510 frame IDs, independent frame sniffers, and the sentinel frame. Mark
511 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
512 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
513 trad unwinders. The architecture-specific changes, each involving a
514 complete rewrite of the architecture's frame code, were carried out by
515 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
516 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
517 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
518 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
521 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
522 Tensilica, Inc.@: contributed support for Xtensa processors. Others
523 who have worked on the Xtensa port of @value{GDBN} in the past include
524 Steve Tjiang, John Newlin, and Scott Foehner.
527 @chapter A Sample @value{GDBN} Session
529 You can use this manual at your leisure to read all about @value{GDBN}.
530 However, a handful of commands are enough to get started using the
531 debugger. This chapter illustrates those commands.
534 In this sample session, we emphasize user input like this: @b{input},
535 to make it easier to pick out from the surrounding output.
538 @c FIXME: this example may not be appropriate for some configs, where
539 @c FIXME...primary interest is in remote use.
541 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
542 processor) exhibits the following bug: sometimes, when we change its
543 quote strings from the default, the commands used to capture one macro
544 definition within another stop working. In the following short @code{m4}
545 session, we define a macro @code{foo} which expands to @code{0000}; we
546 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
547 same thing. However, when we change the open quote string to
548 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
549 procedure fails to define a new synonym @code{baz}:
558 @b{define(bar,defn(`foo'))}
562 @b{changequote(<QUOTE>,<UNQUOTE>)}
564 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
567 m4: End of input: 0: fatal error: EOF in string
571 Let us use @value{GDBN} to try to see what is going on.
574 $ @b{@value{GDBP} m4}
575 @c FIXME: this falsifies the exact text played out, to permit smallbook
576 @c FIXME... format to come out better.
577 @value{GDBN} is free software and you are welcome to distribute copies
578 of it under certain conditions; type "show copying" to see
580 There is absolutely no warranty for @value{GDBN}; type "show warranty"
583 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
588 @value{GDBN} reads only enough symbol data to know where to find the
589 rest when needed; as a result, the first prompt comes up very quickly.
590 We now tell @value{GDBN} to use a narrower display width than usual, so
591 that examples fit in this manual.
594 (@value{GDBP}) @b{set width 70}
598 We need to see how the @code{m4} built-in @code{changequote} works.
599 Having looked at the source, we know the relevant subroutine is
600 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
601 @code{break} command.
604 (@value{GDBP}) @b{break m4_changequote}
605 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
609 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
610 control; as long as control does not reach the @code{m4_changequote}
611 subroutine, the program runs as usual:
614 (@value{GDBP}) @b{run}
615 Starting program: /work/Editorial/gdb/gnu/m4/m4
623 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
624 suspends execution of @code{m4}, displaying information about the
625 context where it stops.
628 @b{changequote(<QUOTE>,<UNQUOTE>)}
630 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
632 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
636 Now we use the command @code{n} (@code{next}) to advance execution to
637 the next line of the current function.
641 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
646 @code{set_quotes} looks like a promising subroutine. We can go into it
647 by using the command @code{s} (@code{step}) instead of @code{next}.
648 @code{step} goes to the next line to be executed in @emph{any}
649 subroutine, so it steps into @code{set_quotes}.
653 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
655 530 if (lquote != def_lquote)
659 The display that shows the subroutine where @code{m4} is now
660 suspended (and its arguments) is called a stack frame display. It
661 shows a summary of the stack. We can use the @code{backtrace}
662 command (which can also be spelled @code{bt}), to see where we are
663 in the stack as a whole: the @code{backtrace} command displays a
664 stack frame for each active subroutine.
667 (@value{GDBP}) @b{bt}
668 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
670 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
672 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
673 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
675 #4 0x79dc in expand_input () at macro.c:40
676 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
680 We step through a few more lines to see what happens. The first two
681 times, we can use @samp{s}; the next two times we use @code{n} to avoid
682 falling into the @code{xstrdup} subroutine.
686 0x3b5c 532 if (rquote != def_rquote)
688 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
689 def_lquote : xstrdup(lq);
691 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
694 538 len_lquote = strlen(rquote);
698 The last line displayed looks a little odd; we can examine the variables
699 @code{lquote} and @code{rquote} to see if they are in fact the new left
700 and right quotes we specified. We use the command @code{p}
701 (@code{print}) to see their values.
704 (@value{GDBP}) @b{p lquote}
705 $1 = 0x35d40 "<QUOTE>"
706 (@value{GDBP}) @b{p rquote}
707 $2 = 0x35d50 "<UNQUOTE>"
711 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
712 To look at some context, we can display ten lines of source
713 surrounding the current line with the @code{l} (@code{list}) command.
719 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
721 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
724 538 len_lquote = strlen(rquote);
725 539 len_rquote = strlen(lquote);
732 Let us step past the two lines that set @code{len_lquote} and
733 @code{len_rquote}, and then examine the values of those variables.
737 539 len_rquote = strlen(lquote);
740 (@value{GDBP}) @b{p len_lquote}
742 (@value{GDBP}) @b{p len_rquote}
747 That certainly looks wrong, assuming @code{len_lquote} and
748 @code{len_rquote} are meant to be the lengths of @code{lquote} and
749 @code{rquote} respectively. We can set them to better values using
750 the @code{p} command, since it can print the value of
751 any expression---and that expression can include subroutine calls and
755 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
757 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
762 Is that enough to fix the problem of using the new quotes with the
763 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
764 executing with the @code{c} (@code{continue}) command, and then try the
765 example that caused trouble initially:
771 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
778 Success! The new quotes now work just as well as the default ones. The
779 problem seems to have been just the two typos defining the wrong
780 lengths. We allow @code{m4} exit by giving it an EOF as input:
784 Program exited normally.
788 The message @samp{Program exited normally.} is from @value{GDBN}; it
789 indicates @code{m4} has finished executing. We can end our @value{GDBN}
790 session with the @value{GDBN} @code{quit} command.
793 (@value{GDBP}) @b{quit}
797 @chapter Getting In and Out of @value{GDBN}
799 This chapter discusses how to start @value{GDBN}, and how to get out of it.
803 type @samp{@value{GDBP}} to start @value{GDBN}.
805 type @kbd{quit} or @kbd{Ctrl-d} to exit.
809 * Invoking GDB:: How to start @value{GDBN}
810 * Quitting GDB:: How to quit @value{GDBN}
811 * Shell Commands:: How to use shell commands inside @value{GDBN}
812 * Logging Output:: How to log @value{GDBN}'s output to a file
816 @section Invoking @value{GDBN}
818 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
819 @value{GDBN} reads commands from the terminal until you tell it to exit.
821 You can also run @code{@value{GDBP}} with a variety of arguments and options,
822 to specify more of your debugging environment at the outset.
824 The command-line options described here are designed
825 to cover a variety of situations; in some environments, some of these
826 options may effectively be unavailable.
828 The most usual way to start @value{GDBN} is with one argument,
829 specifying an executable program:
832 @value{GDBP} @var{program}
836 You can also start with both an executable program and a core file
840 @value{GDBP} @var{program} @var{core}
843 You can, instead, specify a process ID as a second argument, if you want
844 to debug a running process:
847 @value{GDBP} @var{program} 1234
851 would attach @value{GDBN} to process @code{1234} (unless you also have a file
852 named @file{1234}; @value{GDBN} does check for a core file first).
854 Taking advantage of the second command-line argument requires a fairly
855 complete operating system; when you use @value{GDBN} as a remote
856 debugger attached to a bare board, there may not be any notion of
857 ``process'', and there is often no way to get a core dump. @value{GDBN}
858 will warn you if it is unable to attach or to read core dumps.
860 You can optionally have @code{@value{GDBP}} pass any arguments after the
861 executable file to the inferior using @code{--args}. This option stops
864 @value{GDBP} --args gcc -O2 -c foo.c
866 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
867 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
869 You can run @code{@value{GDBP}} without printing the front material, which describes
870 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
877 You can further control how @value{GDBN} starts up by using command-line
878 options. @value{GDBN} itself can remind you of the options available.
888 to display all available options and briefly describe their use
889 (@samp{@value{GDBP} -h} is a shorter equivalent).
891 All options and command line arguments you give are processed
892 in sequential order. The order makes a difference when the
893 @samp{-x} option is used.
897 * File Options:: Choosing files
898 * Mode Options:: Choosing modes
899 * Startup:: What @value{GDBN} does during startup
903 @subsection Choosing Files
905 When @value{GDBN} starts, it reads any arguments other than options as
906 specifying an executable file and core file (or process ID). This is
907 the same as if the arguments were specified by the @samp{-se} and
908 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
909 first argument that does not have an associated option flag as
910 equivalent to the @samp{-se} option followed by that argument; and the
911 second argument that does not have an associated option flag, if any, as
912 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
913 If the second argument begins with a decimal digit, @value{GDBN} will
914 first attempt to attach to it as a process, and if that fails, attempt
915 to open it as a corefile. If you have a corefile whose name begins with
916 a digit, you can prevent @value{GDBN} from treating it as a pid by
917 prefixing it with @file{./}, e.g.@: @file{./12345}.
919 If @value{GDBN} has not been configured to included core file support,
920 such as for most embedded targets, then it will complain about a second
921 argument and ignore it.
923 Many options have both long and short forms; both are shown in the
924 following list. @value{GDBN} also recognizes the long forms if you truncate
925 them, so long as enough of the option is present to be unambiguous.
926 (If you prefer, you can flag option arguments with @samp{--} rather
927 than @samp{-}, though we illustrate the more usual convention.)
929 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
930 @c way, both those who look for -foo and --foo in the index, will find
934 @item -symbols @var{file}
936 @cindex @code{--symbols}
938 Read symbol table from file @var{file}.
940 @item -exec @var{file}
942 @cindex @code{--exec}
944 Use file @var{file} as the executable file to execute when appropriate,
945 and for examining pure data in conjunction with a core dump.
949 Read symbol table from file @var{file} and use it as the executable
952 @item -core @var{file}
954 @cindex @code{--core}
956 Use file @var{file} as a core dump to examine.
958 @item -pid @var{number}
959 @itemx -p @var{number}
962 Connect to process ID @var{number}, as with the @code{attach} command.
964 @item -command @var{file}
966 @cindex @code{--command}
968 Execute @value{GDBN} commands from file @var{file}. @xref{Command
969 Files,, Command files}.
971 @item -eval-command @var{command}
972 @itemx -ex @var{command}
973 @cindex @code{--eval-command}
975 Execute a single @value{GDBN} command.
977 This option may be used multiple times to call multiple commands. It may
978 also be interleaved with @samp{-command} as required.
981 @value{GDBP} -ex 'target sim' -ex 'load' \
982 -x setbreakpoints -ex 'run' a.out
985 @item -directory @var{directory}
986 @itemx -d @var{directory}
987 @cindex @code{--directory}
989 Add @var{directory} to the path to search for source and script files.
993 @cindex @code{--readnow}
995 Read each symbol file's entire symbol table immediately, rather than
996 the default, which is to read it incrementally as it is needed.
997 This makes startup slower, but makes future operations faster.
1002 @subsection Choosing Modes
1004 You can run @value{GDBN} in various alternative modes---for example, in
1005 batch mode or quiet mode.
1012 Do not execute commands found in any initialization files. Normally,
1013 @value{GDBN} executes the commands in these files after all the command
1014 options and arguments have been processed. @xref{Command Files,,Command
1020 @cindex @code{--quiet}
1021 @cindex @code{--silent}
1023 ``Quiet''. Do not print the introductory and copyright messages. These
1024 messages are also suppressed in batch mode.
1027 @cindex @code{--batch}
1028 Run in batch mode. Exit with status @code{0} after processing all the
1029 command files specified with @samp{-x} (and all commands from
1030 initialization files, if not inhibited with @samp{-n}). Exit with
1031 nonzero status if an error occurs in executing the @value{GDBN} commands
1032 in the command files.
1034 Batch mode may be useful for running @value{GDBN} as a filter, for
1035 example to download and run a program on another computer; in order to
1036 make this more useful, the message
1039 Program exited normally.
1043 (which is ordinarily issued whenever a program running under
1044 @value{GDBN} control terminates) is not issued when running in batch
1048 @cindex @code{--batch-silent}
1049 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1050 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1051 unaffected). This is much quieter than @samp{-silent} and would be useless
1052 for an interactive session.
1054 This is particularly useful when using targets that give @samp{Loading section}
1055 messages, for example.
1057 Note that targets that give their output via @value{GDBN}, as opposed to
1058 writing directly to @code{stdout}, will also be made silent.
1060 @item -return-child-result
1061 @cindex @code{--return-child-result}
1062 The return code from @value{GDBN} will be the return code from the child
1063 process (the process being debugged), with the following exceptions:
1067 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1068 internal error. In this case the exit code is the same as it would have been
1069 without @samp{-return-child-result}.
1071 The user quits with an explicit value. E.g., @samp{quit 1}.
1073 The child process never runs, or is not allowed to terminate, in which case
1074 the exit code will be -1.
1077 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1078 when @value{GDBN} is being used as a remote program loader or simulator
1083 @cindex @code{--nowindows}
1085 ``No windows''. If @value{GDBN} comes with a graphical user interface
1086 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1087 interface. If no GUI is available, this option has no effect.
1091 @cindex @code{--windows}
1093 If @value{GDBN} includes a GUI, then this option requires it to be
1096 @item -cd @var{directory}
1098 Run @value{GDBN} using @var{directory} as its working directory,
1099 instead of the current directory.
1103 @cindex @code{--fullname}
1105 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1106 subprocess. It tells @value{GDBN} to output the full file name and line
1107 number in a standard, recognizable fashion each time a stack frame is
1108 displayed (which includes each time your program stops). This
1109 recognizable format looks like two @samp{\032} characters, followed by
1110 the file name, line number and character position separated by colons,
1111 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1112 @samp{\032} characters as a signal to display the source code for the
1116 @cindex @code{--epoch}
1117 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1118 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1119 routines so as to allow Epoch to display values of expressions in a
1122 @item -annotate @var{level}
1123 @cindex @code{--annotate}
1124 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1125 effect is identical to using @samp{set annotate @var{level}}
1126 (@pxref{Annotations}). The annotation @var{level} controls how much
1127 information @value{GDBN} prints together with its prompt, values of
1128 expressions, source lines, and other types of output. Level 0 is the
1129 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1130 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1131 that control @value{GDBN}, and level 2 has been deprecated.
1133 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1137 @cindex @code{--args}
1138 Change interpretation of command line so that arguments following the
1139 executable file are passed as command line arguments to the inferior.
1140 This option stops option processing.
1142 @item -baud @var{bps}
1144 @cindex @code{--baud}
1146 Set the line speed (baud rate or bits per second) of any serial
1147 interface used by @value{GDBN} for remote debugging.
1149 @item -l @var{timeout}
1151 Set the timeout (in seconds) of any communication used by @value{GDBN}
1152 for remote debugging.
1154 @item -tty @var{device}
1155 @itemx -t @var{device}
1156 @cindex @code{--tty}
1158 Run using @var{device} for your program's standard input and output.
1159 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1161 @c resolve the situation of these eventually
1163 @cindex @code{--tui}
1164 Activate the @dfn{Text User Interface} when starting. The Text User
1165 Interface manages several text windows on the terminal, showing
1166 source, assembly, registers and @value{GDBN} command outputs
1167 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1168 Text User Interface can be enabled by invoking the program
1169 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1170 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1173 @c @cindex @code{--xdb}
1174 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1175 @c For information, see the file @file{xdb_trans.html}, which is usually
1176 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1179 @item -interpreter @var{interp}
1180 @cindex @code{--interpreter}
1181 Use the interpreter @var{interp} for interface with the controlling
1182 program or device. This option is meant to be set by programs which
1183 communicate with @value{GDBN} using it as a back end.
1184 @xref{Interpreters, , Command Interpreters}.
1186 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1187 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1188 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1189 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1190 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1191 @sc{gdb/mi} interfaces are no longer supported.
1194 @cindex @code{--write}
1195 Open the executable and core files for both reading and writing. This
1196 is equivalent to the @samp{set write on} command inside @value{GDBN}
1200 @cindex @code{--statistics}
1201 This option causes @value{GDBN} to print statistics about time and
1202 memory usage after it completes each command and returns to the prompt.
1205 @cindex @code{--version}
1206 This option causes @value{GDBN} to print its version number and
1207 no-warranty blurb, and exit.
1212 @subsection What @value{GDBN} Does During Startup
1213 @cindex @value{GDBN} startup
1215 Here's the description of what @value{GDBN} does during session startup:
1219 Sets up the command interpreter as specified by the command line
1220 (@pxref{Mode Options, interpreter}).
1224 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1225 DOS/Windows systems, the home directory is the one pointed to by the
1226 @code{HOME} environment variable.} and executes all the commands in
1230 Processes command line options and operands.
1233 Reads and executes the commands from init file (if any) in the current
1234 working directory. This is only done if the current directory is
1235 different from your home directory. Thus, you can have more than one
1236 init file, one generic in your home directory, and another, specific
1237 to the program you are debugging, in the directory where you invoke
1241 Reads command files specified by the @samp{-x} option. @xref{Command
1242 Files}, for more details about @value{GDBN} command files.
1245 Reads the command history recorded in the @dfn{history file}.
1246 @xref{Command History}, for more details about the command history and the
1247 files where @value{GDBN} records it.
1250 Init files use the same syntax as @dfn{command files} (@pxref{Command
1251 Files}) and are processed by @value{GDBN} in the same way. The init
1252 file in your home directory can set options (such as @samp{set
1253 complaints}) that affect subsequent processing of command line options
1254 and operands. Init files are not executed if you use the @samp{-nx}
1255 option (@pxref{Mode Options, ,Choosing Modes}).
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
3056 When called without any arguments, @code{break} sets a breakpoint at
3057 the next instruction to be executed in the selected stack frame
3058 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3059 innermost, this makes your program stop as soon as control
3060 returns to that frame. This is similar to the effect of a
3061 @code{finish} command in the frame inside the selected frame---except
3062 that @code{finish} does not leave an active breakpoint. If you use
3063 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3064 the next time it reaches the current location; this may be useful
3067 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3068 least one instruction has been executed. If it did not do this, you
3069 would be unable to proceed past a breakpoint without first disabling the
3070 breakpoint. This rule applies whether or not the breakpoint already
3071 existed when your program stopped.
3073 @item break @dots{} if @var{cond}
3074 Set a breakpoint with condition @var{cond}; evaluate the expression
3075 @var{cond} each time the breakpoint is reached, and stop only if the
3076 value is nonzero---that is, if @var{cond} evaluates as true.
3077 @samp{@dots{}} stands for one of the possible arguments described
3078 above (or no argument) specifying where to break. @xref{Conditions,
3079 ,Break Conditions}, for more information on breakpoint conditions.
3082 @item tbreak @var{args}
3083 Set a breakpoint enabled only for one stop. @var{args} are the
3084 same as for the @code{break} command, and the breakpoint is set in the same
3085 way, but the breakpoint is automatically deleted after the first time your
3086 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3089 @cindex hardware breakpoints
3090 @item hbreak @var{args}
3091 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3092 @code{break} command and the breakpoint is set in the same way, but the
3093 breakpoint requires hardware support and some target hardware may not
3094 have this support. The main purpose of this is EPROM/ROM code
3095 debugging, so you can set a breakpoint at an instruction without
3096 changing the instruction. This can be used with the new trap-generation
3097 provided by SPARClite DSU and most x86-based targets. These targets
3098 will generate traps when a program accesses some data or instruction
3099 address that is assigned to the debug registers. However the hardware
3100 breakpoint registers can take a limited number of breakpoints. For
3101 example, on the DSU, only two data breakpoints can be set at a time, and
3102 @value{GDBN} will reject this command if more than two are used. Delete
3103 or disable unused hardware breakpoints before setting new ones
3104 (@pxref{Disabling, ,Disabling Breakpoints}).
3105 @xref{Conditions, ,Break Conditions}.
3106 For remote targets, you can restrict the number of hardware
3107 breakpoints @value{GDBN} will use, see @ref{set remote
3108 hardware-breakpoint-limit}.
3111 @item thbreak @var{args}
3112 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3113 are the same as for the @code{hbreak} command and the breakpoint is set in
3114 the same way. However, like the @code{tbreak} command,
3115 the breakpoint is automatically deleted after the
3116 first time your program stops there. Also, like the @code{hbreak}
3117 command, the breakpoint requires hardware support and some target hardware
3118 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3119 See also @ref{Conditions, ,Break Conditions}.
3122 @cindex regular expression
3123 @cindex breakpoints in functions matching a regexp
3124 @cindex set breakpoints in many functions
3125 @item rbreak @var{regex}
3126 Set breakpoints on all functions matching the regular expression
3127 @var{regex}. This command sets an unconditional breakpoint on all
3128 matches, printing a list of all breakpoints it set. Once these
3129 breakpoints are set, they are treated just like the breakpoints set with
3130 the @code{break} command. You can delete them, disable them, or make
3131 them conditional the same way as any other breakpoint.
3133 The syntax of the regular expression is the standard one used with tools
3134 like @file{grep}. Note that this is different from the syntax used by
3135 shells, so for instance @code{foo*} matches all functions that include
3136 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3137 @code{.*} leading and trailing the regular expression you supply, so to
3138 match only functions that begin with @code{foo}, use @code{^foo}.
3140 @cindex non-member C@t{++} functions, set breakpoint in
3141 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3142 breakpoints on overloaded functions that are not members of any special
3145 @cindex set breakpoints on all functions
3146 The @code{rbreak} command can be used to set breakpoints in
3147 @strong{all} the functions in a program, like this:
3150 (@value{GDBP}) rbreak .
3153 @kindex info breakpoints
3154 @cindex @code{$_} and @code{info breakpoints}
3155 @item info breakpoints @r{[}@var{n}@r{]}
3156 @itemx info break @r{[}@var{n}@r{]}
3157 @itemx info watchpoints @r{[}@var{n}@r{]}
3158 Print a table of all breakpoints, watchpoints, and catchpoints set and
3159 not deleted. Optional argument @var{n} means print information only
3160 about the specified breakpoint (or watchpoint or catchpoint). For
3161 each breakpoint, following columns are printed:
3164 @item Breakpoint Numbers
3166 Breakpoint, watchpoint, or catchpoint.
3168 Whether the breakpoint is marked to be disabled or deleted when hit.
3169 @item Enabled or Disabled
3170 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3171 that are not enabled.
3173 Where the breakpoint is in your program, as a memory address. For a
3174 pending breakpoint whose address is not yet known, this field will
3175 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3176 library that has the symbol or line referred by breakpoint is loaded.
3177 See below for details. A breakpoint with several locations will
3178 have @samp{<MULTIPLE>} in this field---see below for details.
3180 Where the breakpoint is in the source for your program, as a file and
3181 line number. For a pending breakpoint, the original string passed to
3182 the breakpoint command will be listed as it cannot be resolved until
3183 the appropriate shared library is loaded in the future.
3187 If a breakpoint is conditional, @code{info break} shows the condition on
3188 the line following the affected breakpoint; breakpoint commands, if any,
3189 are listed after that. A pending breakpoint is allowed to have a condition
3190 specified for it. The condition is not parsed for validity until a shared
3191 library is loaded that allows the pending breakpoint to resolve to a
3195 @code{info break} with a breakpoint
3196 number @var{n} as argument lists only that breakpoint. The
3197 convenience variable @code{$_} and the default examining-address for
3198 the @code{x} command are set to the address of the last breakpoint
3199 listed (@pxref{Memory, ,Examining Memory}).
3202 @code{info break} displays a count of the number of times the breakpoint
3203 has been hit. This is especially useful in conjunction with the
3204 @code{ignore} command. You can ignore a large number of breakpoint
3205 hits, look at the breakpoint info to see how many times the breakpoint
3206 was hit, and then run again, ignoring one less than that number. This
3207 will get you quickly to the last hit of that breakpoint.
3210 @value{GDBN} allows you to set any number of breakpoints at the same place in
3211 your program. There is nothing silly or meaningless about this. When
3212 the breakpoints are conditional, this is even useful
3213 (@pxref{Conditions, ,Break Conditions}).
3215 @cindex multiple locations, breakpoints
3216 @cindex breakpoints, multiple locations
3217 It is possible that a breakpoint corresponds to several locations
3218 in your program. Examples of this situation are:
3222 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3223 instances of the function body, used in different cases.
3226 For a C@t{++} template function, a given line in the function can
3227 correspond to any number of instantiations.
3230 For an inlined function, a given source line can correspond to
3231 several places where that function is inlined.
3234 In all those cases, @value{GDBN} will insert a breakpoint at all
3235 the relevant locations@footnote{
3236 As of this writing, multiple-location breakpoints work only if there's
3237 line number information for all the locations. This means that they
3238 will generally not work in system libraries, unless you have debug
3239 info with line numbers for them.}.
3241 A breakpoint with multiple locations is displayed in the breakpoint
3242 table using several rows---one header row, followed by one row for
3243 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3244 address column. The rows for individual locations contain the actual
3245 addresses for locations, and show the functions to which those
3246 locations belong. The number column for a location is of the form
3247 @var{breakpoint-number}.@var{location-number}.
3252 Num Type Disp Enb Address What
3253 1 breakpoint keep y <MULTIPLE>
3255 breakpoint already hit 1 time
3256 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3257 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3260 Each location can be individually enabled or disabled by passing
3261 @var{breakpoint-number}.@var{location-number} as argument to the
3262 @code{enable} and @code{disable} commands. Note that you cannot
3263 delete the individual locations from the list, you can only delete the
3264 entire list of locations that belong to their parent breakpoint (with
3265 the @kbd{delete @var{num}} command, where @var{num} is the number of
3266 the parent breakpoint, 1 in the above example). Disabling or enabling
3267 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3268 that belong to that breakpoint.
3270 @cindex pending breakpoints
3271 It's quite common to have a breakpoint inside a shared library.
3272 Shared libraries can be loaded and unloaded explicitly,
3273 and possibly repeatedly, as the program is executed. To support
3274 this use case, @value{GDBN} updates breakpoint locations whenever
3275 any shared library is loaded or unloaded. Typically, you would
3276 set a breakpoint in a shared library at the beginning of your
3277 debugging session, when the library is not loaded, and when the
3278 symbols from the library are not available. When you try to set
3279 breakpoint, @value{GDBN} will ask you if you want to set
3280 a so called @dfn{pending breakpoint}---breakpoint whose address
3281 is not yet resolved.
3283 After the program is run, whenever a new shared library is loaded,
3284 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3285 shared library contains the symbol or line referred to by some
3286 pending breakpoint, that breakpoint is resolved and becomes an
3287 ordinary breakpoint. When a library is unloaded, all breakpoints
3288 that refer to its symbols or source lines become pending again.
3290 This logic works for breakpoints with multiple locations, too. For
3291 example, if you have a breakpoint in a C@t{++} template function, and
3292 a newly loaded shared library has an instantiation of that template,
3293 a new location is added to the list of locations for the breakpoint.
3295 Except for having unresolved address, pending breakpoints do not
3296 differ from regular breakpoints. You can set conditions or commands,
3297 enable and disable them and perform other breakpoint operations.
3299 @value{GDBN} provides some additional commands for controlling what
3300 happens when the @samp{break} command cannot resolve breakpoint
3301 address specification to an address:
3303 @kindex set breakpoint pending
3304 @kindex show breakpoint pending
3306 @item set breakpoint pending auto
3307 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3308 location, it queries you whether a pending breakpoint should be created.
3310 @item set breakpoint pending on
3311 This indicates that an unrecognized breakpoint location should automatically
3312 result in a pending breakpoint being created.
3314 @item set breakpoint pending off
3315 This indicates that pending breakpoints are not to be created. Any
3316 unrecognized breakpoint location results in an error. This setting does
3317 not affect any pending breakpoints previously created.
3319 @item show breakpoint pending
3320 Show the current behavior setting for creating pending breakpoints.
3323 The settings above only affect the @code{break} command and its
3324 variants. Once breakpoint is set, it will be automatically updated
3325 as shared libraries are loaded and unloaded.
3327 @cindex automatic hardware breakpoints
3328 For some targets, @value{GDBN} can automatically decide if hardware or
3329 software breakpoints should be used, depending on whether the
3330 breakpoint address is read-only or read-write. This applies to
3331 breakpoints set with the @code{break} command as well as to internal
3332 breakpoints set by commands like @code{next} and @code{finish}. For
3333 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3336 You can control this automatic behaviour with the following commands::
3338 @kindex set breakpoint auto-hw
3339 @kindex show breakpoint auto-hw
3341 @item set breakpoint auto-hw on
3342 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3343 will try to use the target memory map to decide if software or hardware
3344 breakpoint must be used.
3346 @item set breakpoint auto-hw off
3347 This indicates @value{GDBN} should not automatically select breakpoint
3348 type. If the target provides a memory map, @value{GDBN} will warn when
3349 trying to set software breakpoint at a read-only address.
3352 @value{GDBN} normally implements breakpoints by replacing the program code
3353 at the breakpoint address with a special instruction, which, when
3354 executed, given control to the debugger. By default, the program
3355 code is so modified only when the program is resumed. As soon as
3356 the program stops, @value{GDBN} restores the original instructions. This
3357 behaviour guards against leaving breakpoints inserted in the
3358 target should gdb abrubptly disconnect. However, with slow remote
3359 targets, inserting and removing breakpoint can reduce the performance.
3360 This behavior can be controlled with the following commands::
3362 @kindex set breakpoint always-inserted
3363 @kindex show breakpoint always-inserted
3365 @item set breakpoint always-inserted off
3366 All breakpoints, including newly added by the user, are inserted in
3367 the target only when the target is resumed. All breakpoints are
3368 removed from the target when it stops.
3370 @item set breakpoint always-inserted on
3371 Causes all breakpoints to be inserted in the target at all times. If
3372 the user adds a new breakpoint, or changes an existing breakpoint, the
3373 breakpoints in the target are updated immediately. A breakpoint is
3374 removed from the target only when breakpoint itself is removed.
3376 @cindex non-stop mode, and @code{breakpoint always-inserted}
3377 @item set breakpoint always-inserted auto
3378 This is the default mode. If @value{GDBN} is controlling the inferior
3379 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3380 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3381 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3382 @code{breakpoint always-inserted} mode is off.
3385 @cindex negative breakpoint numbers
3386 @cindex internal @value{GDBN} breakpoints
3387 @value{GDBN} itself sometimes sets breakpoints in your program for
3388 special purposes, such as proper handling of @code{longjmp} (in C
3389 programs). These internal breakpoints are assigned negative numbers,
3390 starting with @code{-1}; @samp{info breakpoints} does not display them.
3391 You can see these breakpoints with the @value{GDBN} maintenance command
3392 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3395 @node Set Watchpoints
3396 @subsection Setting Watchpoints
3398 @cindex setting watchpoints
3399 You can use a watchpoint to stop execution whenever the value of an
3400 expression changes, without having to predict a particular place where
3401 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3402 The expression may be as simple as the value of a single variable, or
3403 as complex as many variables combined by operators. Examples include:
3407 A reference to the value of a single variable.
3410 An address cast to an appropriate data type. For example,
3411 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3412 address (assuming an @code{int} occupies 4 bytes).
3415 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3416 expression can use any operators valid in the program's native
3417 language (@pxref{Languages}).
3420 You can set a watchpoint on an expression even if the expression can
3421 not be evaluated yet. For instance, you can set a watchpoint on
3422 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3423 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3424 the expression produces a valid value. If the expression becomes
3425 valid in some other way than changing a variable (e.g.@: if the memory
3426 pointed to by @samp{*global_ptr} becomes readable as the result of a
3427 @code{malloc} call), @value{GDBN} may not stop until the next time
3428 the expression changes.
3430 @cindex software watchpoints
3431 @cindex hardware watchpoints
3432 Depending on your system, watchpoints may be implemented in software or
3433 hardware. @value{GDBN} does software watchpointing by single-stepping your
3434 program and testing the variable's value each time, which is hundreds of
3435 times slower than normal execution. (But this may still be worth it, to
3436 catch errors where you have no clue what part of your program is the
3439 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3440 x86-based targets, @value{GDBN} includes support for hardware
3441 watchpoints, which do not slow down the running of your program.
3445 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3446 Set a watchpoint for an expression. @value{GDBN} will break when the
3447 expression @var{expr} is written into by the program and its value
3448 changes. The simplest (and the most popular) use of this command is
3449 to watch the value of a single variable:
3452 (@value{GDBP}) watch foo
3455 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3456 clause, @value{GDBN} breaks only when the thread identified by
3457 @var{threadnum} changes the value of @var{expr}. If any other threads
3458 change the value of @var{expr}, @value{GDBN} will not break. Note
3459 that watchpoints restricted to a single thread in this way only work
3460 with Hardware Watchpoints.
3463 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3464 Set a watchpoint that will break when the value of @var{expr} is read
3468 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3469 Set a watchpoint that will break when @var{expr} is either read from
3470 or written into by the program.
3472 @kindex info watchpoints @r{[}@var{n}@r{]}
3473 @item info watchpoints
3474 This command prints a list of watchpoints, breakpoints, and catchpoints;
3475 it is the same as @code{info break} (@pxref{Set Breaks}).
3478 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3479 watchpoints execute very quickly, and the debugger reports a change in
3480 value at the exact instruction where the change occurs. If @value{GDBN}
3481 cannot set a hardware watchpoint, it sets a software watchpoint, which
3482 executes more slowly and reports the change in value at the next
3483 @emph{statement}, not the instruction, after the change occurs.
3485 @cindex use only software watchpoints
3486 You can force @value{GDBN} to use only software watchpoints with the
3487 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3488 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3489 the underlying system supports them. (Note that hardware-assisted
3490 watchpoints that were set @emph{before} setting
3491 @code{can-use-hw-watchpoints} to zero will still use the hardware
3492 mechanism of watching expression values.)
3495 @item set can-use-hw-watchpoints
3496 @kindex set can-use-hw-watchpoints
3497 Set whether or not to use hardware watchpoints.
3499 @item show can-use-hw-watchpoints
3500 @kindex show can-use-hw-watchpoints
3501 Show the current mode of using hardware watchpoints.
3504 For remote targets, you can restrict the number of hardware
3505 watchpoints @value{GDBN} will use, see @ref{set remote
3506 hardware-breakpoint-limit}.
3508 When you issue the @code{watch} command, @value{GDBN} reports
3511 Hardware watchpoint @var{num}: @var{expr}
3515 if it was able to set a hardware watchpoint.
3517 Currently, the @code{awatch} and @code{rwatch} commands can only set
3518 hardware watchpoints, because accesses to data that don't change the
3519 value of the watched expression cannot be detected without examining
3520 every instruction as it is being executed, and @value{GDBN} does not do
3521 that currently. If @value{GDBN} finds that it is unable to set a
3522 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3523 will print a message like this:
3526 Expression cannot be implemented with read/access watchpoint.
3529 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3530 data type of the watched expression is wider than what a hardware
3531 watchpoint on the target machine can handle. For example, some systems
3532 can only watch regions that are up to 4 bytes wide; on such systems you
3533 cannot set hardware watchpoints for an expression that yields a
3534 double-precision floating-point number (which is typically 8 bytes
3535 wide). As a work-around, it might be possible to break the large region
3536 into a series of smaller ones and watch them with separate watchpoints.
3538 If you set too many hardware watchpoints, @value{GDBN} might be unable
3539 to insert all of them when you resume the execution of your program.
3540 Since the precise number of active watchpoints is unknown until such
3541 time as the program is about to be resumed, @value{GDBN} might not be
3542 able to warn you about this when you set the watchpoints, and the
3543 warning will be printed only when the program is resumed:
3546 Hardware watchpoint @var{num}: Could not insert watchpoint
3550 If this happens, delete or disable some of the watchpoints.
3552 Watching complex expressions that reference many variables can also
3553 exhaust the resources available for hardware-assisted watchpoints.
3554 That's because @value{GDBN} needs to watch every variable in the
3555 expression with separately allocated resources.
3557 If you call a function interactively using @code{print} or @code{call},
3558 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3559 kind of breakpoint or the call completes.
3561 @value{GDBN} automatically deletes watchpoints that watch local
3562 (automatic) variables, or expressions that involve such variables, when
3563 they go out of scope, that is, when the execution leaves the block in
3564 which these variables were defined. In particular, when the program
3565 being debugged terminates, @emph{all} local variables go out of scope,
3566 and so only watchpoints that watch global variables remain set. If you
3567 rerun the program, you will need to set all such watchpoints again. One
3568 way of doing that would be to set a code breakpoint at the entry to the
3569 @code{main} function and when it breaks, set all the watchpoints.
3571 @cindex watchpoints and threads
3572 @cindex threads and watchpoints
3573 In multi-threaded programs, watchpoints will detect changes to the
3574 watched expression from every thread.
3577 @emph{Warning:} In multi-threaded programs, software watchpoints
3578 have only limited usefulness. If @value{GDBN} creates a software
3579 watchpoint, it can only watch the value of an expression @emph{in a
3580 single thread}. If you are confident that the expression can only
3581 change due to the current thread's activity (and if you are also
3582 confident that no other thread can become current), then you can use
3583 software watchpoints as usual. However, @value{GDBN} may not notice
3584 when a non-current thread's activity changes the expression. (Hardware
3585 watchpoints, in contrast, watch an expression in all threads.)
3588 @xref{set remote hardware-watchpoint-limit}.
3590 @node Set Catchpoints
3591 @subsection Setting Catchpoints
3592 @cindex catchpoints, setting
3593 @cindex exception handlers
3594 @cindex event handling
3596 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3597 kinds of program events, such as C@t{++} exceptions or the loading of a
3598 shared library. Use the @code{catch} command to set a catchpoint.
3602 @item catch @var{event}
3603 Stop when @var{event} occurs. @var{event} can be any of the following:
3606 @cindex stop on C@t{++} exceptions
3607 The throwing of a C@t{++} exception.
3610 The catching of a C@t{++} exception.
3613 @cindex Ada exception catching
3614 @cindex catch Ada exceptions
3615 An Ada exception being raised. If an exception name is specified
3616 at the end of the command (eg @code{catch exception Program_Error}),
3617 the debugger will stop only when this specific exception is raised.
3618 Otherwise, the debugger stops execution when any Ada exception is raised.
3620 When inserting an exception catchpoint on a user-defined exception whose
3621 name is identical to one of the exceptions defined by the language, the
3622 fully qualified name must be used as the exception name. Otherwise,
3623 @value{GDBN} will assume that it should stop on the pre-defined exception
3624 rather than the user-defined one. For instance, assuming an exception
3625 called @code{Constraint_Error} is defined in package @code{Pck}, then
3626 the command to use to catch such exceptions is @kbd{catch exception
3627 Pck.Constraint_Error}.
3629 @item exception unhandled
3630 An exception that was raised but is not handled by the program.
3633 A failed Ada assertion.
3636 @cindex break on fork/exec
3637 A call to @code{exec}. This is currently only available for HP-UX
3641 A call to @code{fork}. This is currently only available for HP-UX
3645 A call to @code{vfork}. This is currently only available for HP-UX
3650 @item tcatch @var{event}
3651 Set a catchpoint that is enabled only for one stop. The catchpoint is
3652 automatically deleted after the first time the event is caught.
3656 Use the @code{info break} command to list the current catchpoints.
3658 There are currently some limitations to C@t{++} exception handling
3659 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3663 If you call a function interactively, @value{GDBN} normally returns
3664 control to you when the function has finished executing. If the call
3665 raises an exception, however, the call may bypass the mechanism that
3666 returns control to you and cause your program either to abort or to
3667 simply continue running until it hits a breakpoint, catches a signal
3668 that @value{GDBN} is listening for, or exits. This is the case even if
3669 you set a catchpoint for the exception; catchpoints on exceptions are
3670 disabled within interactive calls.
3673 You cannot raise an exception interactively.
3676 You cannot install an exception handler interactively.
3679 @cindex raise exceptions
3680 Sometimes @code{catch} is not the best way to debug exception handling:
3681 if you need to know exactly where an exception is raised, it is better to
3682 stop @emph{before} the exception handler is called, since that way you
3683 can see the stack before any unwinding takes place. If you set a
3684 breakpoint in an exception handler instead, it may not be easy to find
3685 out where the exception was raised.
3687 To stop just before an exception handler is called, you need some
3688 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3689 raised by calling a library function named @code{__raise_exception}
3690 which has the following ANSI C interface:
3693 /* @var{addr} is where the exception identifier is stored.
3694 @var{id} is the exception identifier. */
3695 void __raise_exception (void **addr, void *id);
3699 To make the debugger catch all exceptions before any stack
3700 unwinding takes place, set a breakpoint on @code{__raise_exception}
3701 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3703 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3704 that depends on the value of @var{id}, you can stop your program when
3705 a specific exception is raised. You can use multiple conditional
3706 breakpoints to stop your program when any of a number of exceptions are
3711 @subsection Deleting Breakpoints
3713 @cindex clearing breakpoints, watchpoints, catchpoints
3714 @cindex deleting breakpoints, watchpoints, catchpoints
3715 It is often necessary to eliminate a breakpoint, watchpoint, or
3716 catchpoint once it has done its job and you no longer want your program
3717 to stop there. This is called @dfn{deleting} the breakpoint. A
3718 breakpoint that has been deleted no longer exists; it is forgotten.
3720 With the @code{clear} command you can delete breakpoints according to
3721 where they are in your program. With the @code{delete} command you can
3722 delete individual breakpoints, watchpoints, or catchpoints by specifying
3723 their breakpoint numbers.
3725 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3726 automatically ignores breakpoints on the first instruction to be executed
3727 when you continue execution without changing the execution address.
3732 Delete any breakpoints at the next instruction to be executed in the
3733 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3734 the innermost frame is selected, this is a good way to delete a
3735 breakpoint where your program just stopped.
3737 @item clear @var{location}
3738 Delete any breakpoints set at the specified @var{location}.
3739 @xref{Specify Location}, for the various forms of @var{location}; the
3740 most useful ones are listed below:
3743 @item clear @var{function}
3744 @itemx clear @var{filename}:@var{function}
3745 Delete any breakpoints set at entry to the named @var{function}.
3747 @item clear @var{linenum}
3748 @itemx clear @var{filename}:@var{linenum}
3749 Delete any breakpoints set at or within the code of the specified
3750 @var{linenum} of the specified @var{filename}.
3753 @cindex delete breakpoints
3755 @kindex d @r{(@code{delete})}
3756 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3757 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3758 ranges specified as arguments. If no argument is specified, delete all
3759 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3760 confirm off}). You can abbreviate this command as @code{d}.
3764 @subsection Disabling Breakpoints
3766 @cindex enable/disable a breakpoint
3767 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3768 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3769 it had been deleted, but remembers the information on the breakpoint so
3770 that you can @dfn{enable} it again later.
3772 You disable and enable breakpoints, watchpoints, and catchpoints with
3773 the @code{enable} and @code{disable} commands, optionally specifying one
3774 or more breakpoint numbers as arguments. Use @code{info break} or
3775 @code{info watch} to print a list of breakpoints, watchpoints, and
3776 catchpoints if you do not know which numbers to use.
3778 Disabling and enabling a breakpoint that has multiple locations
3779 affects all of its locations.
3781 A breakpoint, watchpoint, or catchpoint can have any of four different
3782 states of enablement:
3786 Enabled. The breakpoint stops your program. A breakpoint set
3787 with the @code{break} command starts out in this state.
3789 Disabled. The breakpoint has no effect on your program.
3791 Enabled once. The breakpoint stops your program, but then becomes
3794 Enabled for deletion. The breakpoint stops your program, but
3795 immediately after it does so it is deleted permanently. A breakpoint
3796 set with the @code{tbreak} command starts out in this state.
3799 You can use the following commands to enable or disable breakpoints,
3800 watchpoints, and catchpoints:
3804 @kindex dis @r{(@code{disable})}
3805 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3806 Disable the specified breakpoints---or all breakpoints, if none are
3807 listed. A disabled breakpoint has no effect but is not forgotten. All
3808 options such as ignore-counts, conditions and commands are remembered in
3809 case the breakpoint is enabled again later. You may abbreviate
3810 @code{disable} as @code{dis}.
3813 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3814 Enable the specified breakpoints (or all defined breakpoints). They
3815 become effective once again in stopping your program.
3817 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3818 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3819 of these breakpoints immediately after stopping your program.
3821 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3822 Enable the specified breakpoints to work once, then die. @value{GDBN}
3823 deletes any of these breakpoints as soon as your program stops there.
3824 Breakpoints set by the @code{tbreak} command start out in this state.
3827 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3828 @c confusing: tbreak is also initially enabled.
3829 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3830 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3831 subsequently, they become disabled or enabled only when you use one of
3832 the commands above. (The command @code{until} can set and delete a
3833 breakpoint of its own, but it does not change the state of your other
3834 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3838 @subsection Break Conditions
3839 @cindex conditional breakpoints
3840 @cindex breakpoint conditions
3842 @c FIXME what is scope of break condition expr? Context where wanted?
3843 @c in particular for a watchpoint?
3844 The simplest sort of breakpoint breaks every time your program reaches a
3845 specified place. You can also specify a @dfn{condition} for a
3846 breakpoint. A condition is just a Boolean expression in your
3847 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3848 a condition evaluates the expression each time your program reaches it,
3849 and your program stops only if the condition is @emph{true}.
3851 This is the converse of using assertions for program validation; in that
3852 situation, you want to stop when the assertion is violated---that is,
3853 when the condition is false. In C, if you want to test an assertion expressed
3854 by the condition @var{assert}, you should set the condition
3855 @samp{! @var{assert}} on the appropriate breakpoint.
3857 Conditions are also accepted for watchpoints; you may not need them,
3858 since a watchpoint is inspecting the value of an expression anyhow---but
3859 it might be simpler, say, to just set a watchpoint on a variable name,
3860 and specify a condition that tests whether the new value is an interesting
3863 Break conditions can have side effects, and may even call functions in
3864 your program. This can be useful, for example, to activate functions
3865 that log program progress, or to use your own print functions to
3866 format special data structures. The effects are completely predictable
3867 unless there is another enabled breakpoint at the same address. (In
3868 that case, @value{GDBN} might see the other breakpoint first and stop your
3869 program without checking the condition of this one.) Note that
3870 breakpoint commands are usually more convenient and flexible than break
3872 purpose of performing side effects when a breakpoint is reached
3873 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3875 Break conditions can be specified when a breakpoint is set, by using
3876 @samp{if} in the arguments to the @code{break} command. @xref{Set
3877 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3878 with the @code{condition} command.
3880 You can also use the @code{if} keyword with the @code{watch} command.
3881 The @code{catch} command does not recognize the @code{if} keyword;
3882 @code{condition} is the only way to impose a further condition on a
3887 @item condition @var{bnum} @var{expression}
3888 Specify @var{expression} as the break condition for breakpoint,
3889 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3890 breakpoint @var{bnum} stops your program only if the value of
3891 @var{expression} is true (nonzero, in C). When you use
3892 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3893 syntactic correctness, and to determine whether symbols in it have
3894 referents in the context of your breakpoint. If @var{expression} uses
3895 symbols not referenced in the context of the breakpoint, @value{GDBN}
3896 prints an error message:
3899 No symbol "foo" in current context.
3904 not actually evaluate @var{expression} at the time the @code{condition}
3905 command (or a command that sets a breakpoint with a condition, like
3906 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3908 @item condition @var{bnum}
3909 Remove the condition from breakpoint number @var{bnum}. It becomes
3910 an ordinary unconditional breakpoint.
3913 @cindex ignore count (of breakpoint)
3914 A special case of a breakpoint condition is to stop only when the
3915 breakpoint has been reached a certain number of times. This is so
3916 useful that there is a special way to do it, using the @dfn{ignore
3917 count} of the breakpoint. Every breakpoint has an ignore count, which
3918 is an integer. Most of the time, the ignore count is zero, and
3919 therefore has no effect. But if your program reaches a breakpoint whose
3920 ignore count is positive, then instead of stopping, it just decrements
3921 the ignore count by one and continues. As a result, if the ignore count
3922 value is @var{n}, the breakpoint does not stop the next @var{n} times
3923 your program reaches it.
3927 @item ignore @var{bnum} @var{count}
3928 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3929 The next @var{count} times the breakpoint is reached, your program's
3930 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3933 To make the breakpoint stop the next time it is reached, specify
3936 When you use @code{continue} to resume execution of your program from a
3937 breakpoint, you can specify an ignore count directly as an argument to
3938 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3939 Stepping,,Continuing and Stepping}.
3941 If a breakpoint has a positive ignore count and a condition, the
3942 condition is not checked. Once the ignore count reaches zero,
3943 @value{GDBN} resumes checking the condition.
3945 You could achieve the effect of the ignore count with a condition such
3946 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3947 is decremented each time. @xref{Convenience Vars, ,Convenience
3951 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3954 @node Break Commands
3955 @subsection Breakpoint Command Lists
3957 @cindex breakpoint commands
3958 You can give any breakpoint (or watchpoint or catchpoint) a series of
3959 commands to execute when your program stops due to that breakpoint. For
3960 example, you might want to print the values of certain expressions, or
3961 enable other breakpoints.
3965 @kindex end@r{ (breakpoint commands)}
3966 @item commands @r{[}@var{bnum}@r{]}
3967 @itemx @dots{} @var{command-list} @dots{}
3969 Specify a list of commands for breakpoint number @var{bnum}. The commands
3970 themselves appear on the following lines. Type a line containing just
3971 @code{end} to terminate the commands.
3973 To remove all commands from a breakpoint, type @code{commands} and
3974 follow it immediately with @code{end}; that is, give no commands.
3976 With no @var{bnum} argument, @code{commands} refers to the last
3977 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3978 recently encountered).
3981 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3982 disabled within a @var{command-list}.
3984 You can use breakpoint commands to start your program up again. Simply
3985 use the @code{continue} command, or @code{step}, or any other command
3986 that resumes execution.
3988 Any other commands in the command list, after a command that resumes
3989 execution, are ignored. This is because any time you resume execution
3990 (even with a simple @code{next} or @code{step}), you may encounter
3991 another breakpoint---which could have its own command list, leading to
3992 ambiguities about which list to execute.
3995 If the first command you specify in a command list is @code{silent}, the
3996 usual message about stopping at a breakpoint is not printed. This may
3997 be desirable for breakpoints that are to print a specific message and
3998 then continue. If none of the remaining commands print anything, you
3999 see no sign that the breakpoint was reached. @code{silent} is
4000 meaningful only at the beginning of a breakpoint command list.
4002 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4003 print precisely controlled output, and are often useful in silent
4004 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4006 For example, here is how you could use breakpoint commands to print the
4007 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4013 printf "x is %d\n",x
4018 One application for breakpoint commands is to compensate for one bug so
4019 you can test for another. Put a breakpoint just after the erroneous line
4020 of code, give it a condition to detect the case in which something
4021 erroneous has been done, and give it commands to assign correct values
4022 to any variables that need them. End with the @code{continue} command
4023 so that your program does not stop, and start with the @code{silent}
4024 command so that no output is produced. Here is an example:
4035 @c @ifclear BARETARGET
4036 @node Error in Breakpoints
4037 @subsection ``Cannot insert breakpoints''
4039 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
4041 Under some operating systems, breakpoints cannot be used in a program if
4042 any other process is running that program. In this situation,
4043 attempting to run or continue a program with a breakpoint causes
4044 @value{GDBN} to print an error message:
4047 Cannot insert breakpoints.
4048 The same program may be running in another process.
4051 When this happens, you have three ways to proceed:
4055 Remove or disable the breakpoints, then continue.
4058 Suspend @value{GDBN}, and copy the file containing your program to a new
4059 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
4060 that @value{GDBN} should run your program under that name.
4061 Then start your program again.
4064 Relink your program so that the text segment is nonsharable, using the
4065 linker option @samp{-N}. The operating system limitation may not apply
4066 to nonsharable executables.
4070 A similar message can be printed if you request too many active
4071 hardware-assisted breakpoints and watchpoints:
4073 @c FIXME: the precise wording of this message may change; the relevant
4074 @c source change is not committed yet (Sep 3, 1999).
4076 Stopped; cannot insert breakpoints.
4077 You may have requested too many hardware breakpoints and watchpoints.
4081 This message is printed when you attempt to resume the program, since
4082 only then @value{GDBN} knows exactly how many hardware breakpoints and
4083 watchpoints it needs to insert.
4085 When this message is printed, you need to disable or remove some of the
4086 hardware-assisted breakpoints and watchpoints, and then continue.
4088 @node Breakpoint-related Warnings
4089 @subsection ``Breakpoint address adjusted...''
4090 @cindex breakpoint address adjusted
4092 Some processor architectures place constraints on the addresses at
4093 which breakpoints may be placed. For architectures thus constrained,
4094 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4095 with the constraints dictated by the architecture.
4097 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4098 a VLIW architecture in which a number of RISC-like instructions may be
4099 bundled together for parallel execution. The FR-V architecture
4100 constrains the location of a breakpoint instruction within such a
4101 bundle to the instruction with the lowest address. @value{GDBN}
4102 honors this constraint by adjusting a breakpoint's address to the
4103 first in the bundle.
4105 It is not uncommon for optimized code to have bundles which contain
4106 instructions from different source statements, thus it may happen that
4107 a breakpoint's address will be adjusted from one source statement to
4108 another. Since this adjustment may significantly alter @value{GDBN}'s
4109 breakpoint related behavior from what the user expects, a warning is
4110 printed when the breakpoint is first set and also when the breakpoint
4113 A warning like the one below is printed when setting a breakpoint
4114 that's been subject to address adjustment:
4117 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4120 Such warnings are printed both for user settable and @value{GDBN}'s
4121 internal breakpoints. If you see one of these warnings, you should
4122 verify that a breakpoint set at the adjusted address will have the
4123 desired affect. If not, the breakpoint in question may be removed and
4124 other breakpoints may be set which will have the desired behavior.
4125 E.g., it may be sufficient to place the breakpoint at a later
4126 instruction. A conditional breakpoint may also be useful in some
4127 cases to prevent the breakpoint from triggering too often.
4129 @value{GDBN} will also issue a warning when stopping at one of these
4130 adjusted breakpoints:
4133 warning: Breakpoint 1 address previously adjusted from 0x00010414
4137 When this warning is encountered, it may be too late to take remedial
4138 action except in cases where the breakpoint is hit earlier or more
4139 frequently than expected.
4141 @node Continuing and Stepping
4142 @section Continuing and Stepping
4146 @cindex resuming execution
4147 @dfn{Continuing} means resuming program execution until your program
4148 completes normally. In contrast, @dfn{stepping} means executing just
4149 one more ``step'' of your program, where ``step'' may mean either one
4150 line of source code, or one machine instruction (depending on what
4151 particular command you use). Either when continuing or when stepping,
4152 your program may stop even sooner, due to a breakpoint or a signal. (If
4153 it stops due to a signal, you may want to use @code{handle}, or use
4154 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4158 @kindex c @r{(@code{continue})}
4159 @kindex fg @r{(resume foreground execution)}
4160 @item continue @r{[}@var{ignore-count}@r{]}
4161 @itemx c @r{[}@var{ignore-count}@r{]}
4162 @itemx fg @r{[}@var{ignore-count}@r{]}
4163 Resume program execution, at the address where your program last stopped;
4164 any breakpoints set at that address are bypassed. The optional argument
4165 @var{ignore-count} allows you to specify a further number of times to
4166 ignore a breakpoint at this location; its effect is like that of
4167 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4169 The argument @var{ignore-count} is meaningful only when your program
4170 stopped due to a breakpoint. At other times, the argument to
4171 @code{continue} is ignored.
4173 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4174 debugged program is deemed to be the foreground program) are provided
4175 purely for convenience, and have exactly the same behavior as
4179 To resume execution at a different place, you can use @code{return}
4180 (@pxref{Returning, ,Returning from a Function}) to go back to the
4181 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4182 Different Address}) to go to an arbitrary location in your program.
4184 A typical technique for using stepping is to set a breakpoint
4185 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4186 beginning of the function or the section of your program where a problem
4187 is believed to lie, run your program until it stops at that breakpoint,
4188 and then step through the suspect area, examining the variables that are
4189 interesting, until you see the problem happen.
4193 @kindex s @r{(@code{step})}
4195 Continue running your program until control reaches a different source
4196 line, then stop it and return control to @value{GDBN}. This command is
4197 abbreviated @code{s}.
4200 @c "without debugging information" is imprecise; actually "without line
4201 @c numbers in the debugging information". (gcc -g1 has debugging info but
4202 @c not line numbers). But it seems complex to try to make that
4203 @c distinction here.
4204 @emph{Warning:} If you use the @code{step} command while control is
4205 within a function that was compiled without debugging information,
4206 execution proceeds until control reaches a function that does have
4207 debugging information. Likewise, it will not step into a function which
4208 is compiled without debugging information. To step through functions
4209 without debugging information, use the @code{stepi} command, described
4213 The @code{step} command only stops at the first instruction of a source
4214 line. This prevents the multiple stops that could otherwise occur in
4215 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4216 to stop if a function that has debugging information is called within
4217 the line. In other words, @code{step} @emph{steps inside} any functions
4218 called within the line.
4220 Also, the @code{step} command only enters a function if there is line
4221 number information for the function. Otherwise it acts like the
4222 @code{next} command. This avoids problems when using @code{cc -gl}
4223 on MIPS machines. Previously, @code{step} entered subroutines if there
4224 was any debugging information about the routine.
4226 @item step @var{count}
4227 Continue running as in @code{step}, but do so @var{count} times. If a
4228 breakpoint is reached, or a signal not related to stepping occurs before
4229 @var{count} steps, stepping stops right away.
4232 @kindex n @r{(@code{next})}
4233 @item next @r{[}@var{count}@r{]}
4234 Continue to the next source line in the current (innermost) stack frame.
4235 This is similar to @code{step}, but function calls that appear within
4236 the line of code are executed without stopping. Execution stops when
4237 control reaches a different line of code at the original stack level
4238 that was executing when you gave the @code{next} command. This command
4239 is abbreviated @code{n}.
4241 An argument @var{count} is a repeat count, as for @code{step}.
4244 @c FIX ME!! Do we delete this, or is there a way it fits in with
4245 @c the following paragraph? --- Vctoria
4247 @c @code{next} within a function that lacks debugging information acts like
4248 @c @code{step}, but any function calls appearing within the code of the
4249 @c function are executed without stopping.
4251 The @code{next} command only stops at the first instruction of a
4252 source line. This prevents multiple stops that could otherwise occur in
4253 @code{switch} statements, @code{for} loops, etc.
4255 @kindex set step-mode
4257 @cindex functions without line info, and stepping
4258 @cindex stepping into functions with no line info
4259 @itemx set step-mode on
4260 The @code{set step-mode on} command causes the @code{step} command to
4261 stop at the first instruction of a function which contains no debug line
4262 information rather than stepping over it.
4264 This is useful in cases where you may be interested in inspecting the
4265 machine instructions of a function which has no symbolic info and do not
4266 want @value{GDBN} to automatically skip over this function.
4268 @item set step-mode off
4269 Causes the @code{step} command to step over any functions which contains no
4270 debug information. This is the default.
4272 @item show step-mode
4273 Show whether @value{GDBN} will stop in or step over functions without
4274 source line debug information.
4277 @kindex fin @r{(@code{finish})}
4279 Continue running until just after function in the selected stack frame
4280 returns. Print the returned value (if any). This command can be
4281 abbreviated as @code{fin}.
4283 Contrast this with the @code{return} command (@pxref{Returning,
4284 ,Returning from a Function}).
4287 @kindex u @r{(@code{until})}
4288 @cindex run until specified location
4291 Continue running until a source line past the current line, in the
4292 current stack frame, is reached. This command is used to avoid single
4293 stepping through a loop more than once. It is like the @code{next}
4294 command, except that when @code{until} encounters a jump, it
4295 automatically continues execution until the program counter is greater
4296 than the address of the jump.
4298 This means that when you reach the end of a loop after single stepping
4299 though it, @code{until} makes your program continue execution until it
4300 exits the loop. In contrast, a @code{next} command at the end of a loop
4301 simply steps back to the beginning of the loop, which forces you to step
4302 through the next iteration.
4304 @code{until} always stops your program if it attempts to exit the current
4307 @code{until} may produce somewhat counterintuitive results if the order
4308 of machine code does not match the order of the source lines. For
4309 example, in the following excerpt from a debugging session, the @code{f}
4310 (@code{frame}) command shows that execution is stopped at line
4311 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4315 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4317 (@value{GDBP}) until
4318 195 for ( ; argc > 0; NEXTARG) @{
4321 This happened because, for execution efficiency, the compiler had
4322 generated code for the loop closure test at the end, rather than the
4323 start, of the loop---even though the test in a C @code{for}-loop is
4324 written before the body of the loop. The @code{until} command appeared
4325 to step back to the beginning of the loop when it advanced to this
4326 expression; however, it has not really gone to an earlier
4327 statement---not in terms of the actual machine code.
4329 @code{until} with no argument works by means of single
4330 instruction stepping, and hence is slower than @code{until} with an
4333 @item until @var{location}
4334 @itemx u @var{location}
4335 Continue running your program until either the specified location is
4336 reached, or the current stack frame returns. @var{location} is any of
4337 the forms described in @ref{Specify Location}.
4338 This form of the command uses temporary breakpoints, and
4339 hence is quicker than @code{until} without an argument. The specified
4340 location is actually reached only if it is in the current frame. This
4341 implies that @code{until} can be used to skip over recursive function
4342 invocations. For instance in the code below, if the current location is
4343 line @code{96}, issuing @code{until 99} will execute the program up to
4344 line @code{99} in the same invocation of factorial, i.e., after the inner
4345 invocations have returned.
4348 94 int factorial (int value)
4350 96 if (value > 1) @{
4351 97 value *= factorial (value - 1);
4358 @kindex advance @var{location}
4359 @itemx advance @var{location}
4360 Continue running the program up to the given @var{location}. An argument is
4361 required, which should be of one of the forms described in
4362 @ref{Specify Location}.
4363 Execution will also stop upon exit from the current stack
4364 frame. This command is similar to @code{until}, but @code{advance} will
4365 not skip over recursive function calls, and the target location doesn't
4366 have to be in the same frame as the current one.
4370 @kindex si @r{(@code{stepi})}
4372 @itemx stepi @var{arg}
4374 Execute one machine instruction, then stop and return to the debugger.
4376 It is often useful to do @samp{display/i $pc} when stepping by machine
4377 instructions. This makes @value{GDBN} automatically display the next
4378 instruction to be executed, each time your program stops. @xref{Auto
4379 Display,, Automatic Display}.
4381 An argument is a repeat count, as in @code{step}.
4385 @kindex ni @r{(@code{nexti})}
4387 @itemx nexti @var{arg}
4389 Execute one machine instruction, but if it is a function call,
4390 proceed until the function returns.
4392 An argument is a repeat count, as in @code{next}.
4399 A signal is an asynchronous event that can happen in a program. The
4400 operating system defines the possible kinds of signals, and gives each
4401 kind a name and a number. For example, in Unix @code{SIGINT} is the
4402 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4403 @code{SIGSEGV} is the signal a program gets from referencing a place in
4404 memory far away from all the areas in use; @code{SIGALRM} occurs when
4405 the alarm clock timer goes off (which happens only if your program has
4406 requested an alarm).
4408 @cindex fatal signals
4409 Some signals, including @code{SIGALRM}, are a normal part of the
4410 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4411 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4412 program has not specified in advance some other way to handle the signal.
4413 @code{SIGINT} does not indicate an error in your program, but it is normally
4414 fatal so it can carry out the purpose of the interrupt: to kill the program.
4416 @value{GDBN} has the ability to detect any occurrence of a signal in your
4417 program. You can tell @value{GDBN} in advance what to do for each kind of
4420 @cindex handling signals
4421 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4422 @code{SIGALRM} be silently passed to your program
4423 (so as not to interfere with their role in the program's functioning)
4424 but to stop your program immediately whenever an error signal happens.
4425 You can change these settings with the @code{handle} command.
4428 @kindex info signals
4432 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4433 handle each one. You can use this to see the signal numbers of all
4434 the defined types of signals.
4436 @item info signals @var{sig}
4437 Similar, but print information only about the specified signal number.
4439 @code{info handle} is an alias for @code{info signals}.
4442 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4443 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4444 can be the number of a signal or its name (with or without the
4445 @samp{SIG} at the beginning); a list of signal numbers of the form
4446 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4447 known signals. Optional arguments @var{keywords}, described below,
4448 say what change to make.
4452 The keywords allowed by the @code{handle} command can be abbreviated.
4453 Their full names are:
4457 @value{GDBN} should not stop your program when this signal happens. It may
4458 still print a message telling you that the signal has come in.
4461 @value{GDBN} should stop your program when this signal happens. This implies
4462 the @code{print} keyword as well.
4465 @value{GDBN} should print a message when this signal happens.
4468 @value{GDBN} should not mention the occurrence of the signal at all. This
4469 implies the @code{nostop} keyword as well.
4473 @value{GDBN} should allow your program to see this signal; your program
4474 can handle the signal, or else it may terminate if the signal is fatal
4475 and not handled. @code{pass} and @code{noignore} are synonyms.
4479 @value{GDBN} should not allow your program to see this signal.
4480 @code{nopass} and @code{ignore} are synonyms.
4484 When a signal stops your program, the signal is not visible to the
4486 continue. Your program sees the signal then, if @code{pass} is in
4487 effect for the signal in question @emph{at that time}. In other words,
4488 after @value{GDBN} reports a signal, you can use the @code{handle}
4489 command with @code{pass} or @code{nopass} to control whether your
4490 program sees that signal when you continue.
4492 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4493 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4494 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4497 You can also use the @code{signal} command to prevent your program from
4498 seeing a signal, or cause it to see a signal it normally would not see,
4499 or to give it any signal at any time. For example, if your program stopped
4500 due to some sort of memory reference error, you might store correct
4501 values into the erroneous variables and continue, hoping to see more
4502 execution; but your program would probably terminate immediately as
4503 a result of the fatal signal once it saw the signal. To prevent this,
4504 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4508 @section Stopping and Starting Multi-thread Programs
4510 @cindex stopped threads
4511 @cindex threads, stopped
4513 @cindex continuing threads
4514 @cindex threads, continuing
4516 @value{GDBN} supports debugging programs with multiple threads
4517 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4518 are two modes of controlling execution of your program within the
4519 debugger. In the default mode, referred to as @dfn{all-stop mode},
4520 when any thread in your program stops (for example, at a breakpoint
4521 or while being stepped), all other threads in the program are also stopped by
4522 @value{GDBN}. On some targets, @value{GDBN} also supports
4523 @dfn{non-stop mode}, in which other threads can continue to run freely while
4524 you examine the stopped thread in the debugger.
4527 * All-Stop Mode:: All threads stop when GDB takes control
4528 * Non-Stop Mode:: Other threads continue to execute
4529 * Background Execution:: Running your program asynchronously
4530 * Thread-Specific Breakpoints:: Controlling breakpoints
4531 * Interrupted System Calls:: GDB may interfere with system calls
4535 @subsection All-Stop Mode
4537 @cindex all-stop mode
4539 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4540 @emph{all} threads of execution stop, not just the current thread. This
4541 allows you to examine the overall state of the program, including
4542 switching between threads, without worrying that things may change
4545 Conversely, whenever you restart the program, @emph{all} threads start
4546 executing. @emph{This is true even when single-stepping} with commands
4547 like @code{step} or @code{next}.
4549 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4550 Since thread scheduling is up to your debugging target's operating
4551 system (not controlled by @value{GDBN}), other threads may
4552 execute more than one statement while the current thread completes a
4553 single step. Moreover, in general other threads stop in the middle of a
4554 statement, rather than at a clean statement boundary, when the program
4557 You might even find your program stopped in another thread after
4558 continuing or even single-stepping. This happens whenever some other
4559 thread runs into a breakpoint, a signal, or an exception before the
4560 first thread completes whatever you requested.
4562 @cindex automatic thread selection
4563 @cindex switching threads automatically
4564 @cindex threads, automatic switching
4565 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4566 signal, it automatically selects the thread where that breakpoint or
4567 signal happened. @value{GDBN} alerts you to the context switch with a
4568 message such as @samp{[Switching to Thread @var{n}]} to identify the
4571 On some OSes, you can modify @value{GDBN}'s default behavior by
4572 locking the OS scheduler to allow only a single thread to run.
4575 @item set scheduler-locking @var{mode}
4576 @cindex scheduler locking mode
4577 @cindex lock scheduler
4578 Set the scheduler locking mode. If it is @code{off}, then there is no
4579 locking and any thread may run at any time. If @code{on}, then only the
4580 current thread may run when the inferior is resumed. The @code{step}
4581 mode optimizes for single-stepping; it prevents other threads
4582 from preempting the current thread while you are stepping, so that
4583 the focus of debugging does not change unexpectedly.
4584 Other threads only rarely (or never) get a chance to run
4585 when you step. They are more likely to run when you @samp{next} over a
4586 function call, and they are completely free to run when you use commands
4587 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4588 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4589 the current thread away from the thread that you are debugging.
4591 @item show scheduler-locking
4592 Display the current scheduler locking mode.
4596 @subsection Non-Stop Mode
4598 @cindex non-stop mode
4600 @c This section is really only a place-holder, and needs to be expanded
4601 @c with more details.
4603 For some multi-threaded targets, @value{GDBN} supports an optional
4604 mode of operation in which you can examine stopped program threads in
4605 the debugger while other threads continue to execute freely. This
4606 minimizes intrusion when debugging live systems, such as programs
4607 where some threads have real-time constraints or must continue to
4608 respond to external events. This is referred to as @dfn{non-stop} mode.
4610 In non-stop mode, when a thread stops to report a debugging event,
4611 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4612 threads as well, in contrast to the all-stop mode behavior. Additionally,
4613 execution commands such as @code{continue} and @code{step} apply by default
4614 only to the current thread in non-stop mode, rather than all threads as
4615 in all-stop mode. This allows you to control threads explicitly in
4616 ways that are not possible in all-stop mode --- for example, stepping
4617 one thread while allowing others to run freely, stepping
4618 one thread while holding all others stopped, or stepping several threads
4619 independently and simultaneously.
4621 To enter non-stop mode, use this sequence of commands before you run
4622 or attach to your program:
4625 # Enable the async interface.
4628 # If using the CLI, pagination breaks non-stop.
4631 # Finally, turn it on!
4635 You can use these commands to manipulate the non-stop mode setting:
4638 @kindex set non-stop
4639 @item set non-stop on
4640 Enable selection of non-stop mode.
4641 @item set non-stop off
4642 Disable selection of non-stop mode.
4643 @kindex show non-stop
4645 Show the current non-stop enablement setting.
4648 Note these commands only reflect whether non-stop mode is enabled,
4649 not whether the currently-executing program is being run in non-stop mode.
4650 In particular, the @code{set non-stop} preference is only consulted when
4651 @value{GDBN} starts or connects to the target program, and it is generally
4652 not possible to switch modes once debugging has started. Furthermore,
4653 since not all targets support non-stop mode, even when you have enabled
4654 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4657 In non-stop mode, all execution commands apply only to the current thread
4658 by default. That is, @code{continue} only continues one thread.
4659 To continue all threads, issue @code{continue -a} or @code{c -a}.
4661 You can use @value{GDBN}'s background execution commands
4662 (@pxref{Background Execution}) to run some threads in the background
4663 while you continue to examine or step others from @value{GDBN}.
4664 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4665 always executed asynchronously in non-stop mode.
4667 Suspending execution is done with the @code{interrupt} command when
4668 running in the background, or @kbd{Ctrl-c} during foreground execution.
4669 In all-stop mode, this stops the whole process;
4670 but in non-stop mode the interrupt applies only to the current thread.
4671 To stop the whole program, use @code{interrupt -a}.
4673 Other execution commands do not currently support the @code{-a} option.
4675 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4676 that thread current, as it does in all-stop mode. This is because the
4677 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4678 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4679 changed to a different thread just as you entered a command to operate on the
4680 previously current thread.
4682 @node Background Execution
4683 @subsection Background Execution
4685 @cindex foreground execution
4686 @cindex background execution
4687 @cindex asynchronous execution
4688 @cindex execution, foreground, background and asynchronous
4690 @value{GDBN}'s execution commands have two variants: the normal
4691 foreground (synchronous) behavior, and a background
4692 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4693 the program to report that some thread has stopped before prompting for
4694 another command. In background execution, @value{GDBN} immediately gives
4695 a command prompt so that you can issue other commands while your program runs.
4697 To specify background execution, add a @code{&} to the command. For example,
4698 the background form of the @code{continue} command is @code{continue&}, or
4699 just @code{c&}. The execution commands that accept background execution
4705 @xref{Starting, , Starting your Program}.
4709 @xref{Attach, , Debugging an Already-running Process}.
4713 @xref{Continuing and Stepping, step}.
4717 @xref{Continuing and Stepping, stepi}.
4721 @xref{Continuing and Stepping, next}.
4725 @xref{Continuing and Stepping, continue}.
4729 @xref{Continuing and Stepping, finish}.
4733 @xref{Continuing and Stepping, until}.
4737 Background execution is especially useful in conjunction with non-stop
4738 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4739 However, you can also use these commands in the normal all-stop mode with
4740 the restriction that you cannot issue another execution command until the
4741 previous one finishes. Examples of commands that are valid in all-stop
4742 mode while the program is running include @code{help} and @code{info break}.
4744 You can interrupt your program while it is running in the background by
4745 using the @code{interrupt} command.
4752 Suspend execution of the running program. In all-stop mode,
4753 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4754 only the current thread. To stop the whole program in non-stop mode,
4755 use @code{interrupt -a}.
4758 You may need to explicitly enable async mode before you can use background
4759 execution commands, with the @code{set target-async 1} command. If the
4760 target doesn't support async mode, @value{GDBN} issues an error message
4761 if you attempt to use the background execution commands.
4763 @node Thread-Specific Breakpoints
4764 @subsection Thread-Specific Breakpoints
4766 When your program has multiple threads (@pxref{Threads,, Debugging
4767 Programs with Multiple Threads}), you can choose whether to set
4768 breakpoints on all threads, or on a particular thread.
4771 @cindex breakpoints and threads
4772 @cindex thread breakpoints
4773 @kindex break @dots{} thread @var{threadno}
4774 @item break @var{linespec} thread @var{threadno}
4775 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4776 @var{linespec} specifies source lines; there are several ways of
4777 writing them (@pxref{Specify Location}), but the effect is always to
4778 specify some source line.
4780 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4781 to specify that you only want @value{GDBN} to stop the program when a
4782 particular thread reaches this breakpoint. @var{threadno} is one of the
4783 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4784 column of the @samp{info threads} display.
4786 If you do not specify @samp{thread @var{threadno}} when you set a
4787 breakpoint, the breakpoint applies to @emph{all} threads of your
4790 You can use the @code{thread} qualifier on conditional breakpoints as
4791 well; in this case, place @samp{thread @var{threadno}} before the
4792 breakpoint condition, like this:
4795 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4800 @node Interrupted System Calls
4801 @subsection Interrupted System Calls
4803 @cindex thread breakpoints and system calls
4804 @cindex system calls and thread breakpoints
4805 @cindex premature return from system calls
4806 There is an unfortunate side effect when using @value{GDBN} to debug
4807 multi-threaded programs. If one thread stops for a
4808 breakpoint, or for some other reason, and another thread is blocked in a
4809 system call, then the system call may return prematurely. This is a
4810 consequence of the interaction between multiple threads and the signals
4811 that @value{GDBN} uses to implement breakpoints and other events that
4814 To handle this problem, your program should check the return value of
4815 each system call and react appropriately. This is good programming
4818 For example, do not write code like this:
4824 The call to @code{sleep} will return early if a different thread stops
4825 at a breakpoint or for some other reason.
4827 Instead, write this:
4832 unslept = sleep (unslept);
4835 A system call is allowed to return early, so the system is still
4836 conforming to its specification. But @value{GDBN} does cause your
4837 multi-threaded program to behave differently than it would without
4840 Also, @value{GDBN} uses internal breakpoints in the thread library to
4841 monitor certain events such as thread creation and thread destruction.
4842 When such an event happens, a system call in another thread may return
4843 prematurely, even though your program does not appear to stop.
4846 @node Reverse Execution
4847 @chapter Running programs backward
4848 @cindex reverse execution
4849 @cindex running programs backward
4851 When you are debugging a program, it is not unusual to realize that
4852 you have gone too far, and some event of interest has already happened.
4853 If the target environment supports it, @value{GDBN} can allow you to
4854 ``rewind'' the program by running it backward.
4856 A target environment that supports reverse execution should be able
4857 to ``undo'' the changes in machine state that have taken place as the
4858 program was executing normally. Variables, registers etc.@: should
4859 revert to their previous values. Obviously this requires a great
4860 deal of sophistication on the part of the target environment; not
4861 all target environments can support reverse execution.
4863 When a program is executed in reverse, the instructions that
4864 have most recently been executed are ``un-executed'', in reverse
4865 order. The program counter runs backward, following the previous
4866 thread of execution in reverse. As each instruction is ``un-executed'',
4867 the values of memory and/or registers that were changed by that
4868 instruction are reverted to their previous states. After executing
4869 a piece of source code in reverse, all side effects of that code
4870 should be ``undone'', and all variables should be returned to their
4871 prior values@footnote{
4872 Note that some side effects are easier to undo than others. For instance,
4873 memory and registers are relatively easy, but device I/O is hard. Some
4874 targets may be able undo things like device I/O, and some may not.
4876 The contract between @value{GDBN} and the reverse executing target
4877 requires only that the target do something reasonable when
4878 @value{GDBN} tells it to execute backwards, and then report the
4879 results back to @value{GDBN}. Whatever the target reports back to
4880 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4881 assumes that the memory and registers that the target reports are in a
4882 consistant state, but @value{GDBN} accepts whatever it is given.
4885 If you are debugging in a target environment that supports
4886 reverse execution, @value{GDBN} provides the following commands.
4889 @kindex reverse-continue
4890 @kindex rc @r{(@code{reverse-continue})}
4891 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4892 @itemx rc @r{[}@var{ignore-count}@r{]}
4893 Beginning at the point where your program last stopped, start executing
4894 in reverse. Reverse execution will stop for breakpoints and synchronous
4895 exceptions (signals), just like normal execution. Behavior of
4896 asynchronous signals depends on the target environment.
4898 @kindex reverse-step
4899 @kindex rs @r{(@code{step})}
4900 @item reverse-step @r{[}@var{count}@r{]}
4901 Run the program backward until control reaches the start of a
4902 different source line; then stop it, and return control to @value{GDBN}.
4904 Like the @code{step} command, @code{reverse-step} will only stop
4905 at the beginning of a source line. It ``un-executes'' the previously
4906 executed source line. If the previous source line included calls to
4907 debuggable functions, @code{reverse-step} will step (backward) into
4908 the called function, stopping at the beginning of the @emph{last}
4909 statement in the called function (typically a return statement).
4911 Also, as with the @code{step} command, if non-debuggable functions are
4912 called, @code{reverse-step} will run thru them backward without stopping.
4914 @kindex reverse-stepi
4915 @kindex rsi @r{(@code{reverse-stepi})}
4916 @item reverse-stepi @r{[}@var{count}@r{]}
4917 Reverse-execute one machine instruction. Note that the instruction
4918 to be reverse-executed is @emph{not} the one pointed to by the program
4919 counter, but the instruction executed prior to that one. For instance,
4920 if the last instruction was a jump, @code{reverse-stepi} will take you
4921 back from the destination of the jump to the jump instruction itself.
4923 @kindex reverse-next
4924 @kindex rn @r{(@code{reverse-next})}
4925 @item reverse-next @r{[}@var{count}@r{]}
4926 Run backward to the beginning of the previous line executed in
4927 the current (innermost) stack frame. If the line contains function
4928 calls, they will be ``un-executed'' without stopping. Starting from
4929 the first line of a function, @code{reverse-next} will take you back
4930 to the caller of that function, @emph{before} the function was called,
4931 just as the normal @code{next} command would take you from the last
4932 line of a function back to its return to its caller
4933 @footnote{Unles the code is too heavily optimized.}.
4935 @kindex reverse-nexti
4936 @kindex rni @r{(@code{reverse-nexti})}
4937 @item reverse-nexti @r{[}@var{count}@r{]}
4938 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
4939 in reverse, except that called functions are ``un-executed'' atomically.
4940 That is, if the previously executed instruction was a return from
4941 another instruction, @code{reverse-nexti} will continue to execute
4942 in reverse until the call to that function (from the current stack
4945 @kindex reverse-finish
4946 @item reverse-finish
4947 Just as the @code{finish} command takes you to the point where the
4948 current function returns, @code{reverse-finish} takes you to the point
4949 where it was called. Instead of ending up at the end of the current
4950 function invocation, you end up at the beginning.
4952 @kindex set exec-direction
4953 @item set exec-direction
4954 Set the direction of target execution.
4955 @itemx set exec-direction reverse
4956 @cindex execute forward or backward in time
4957 @value{GDBN} will perform all execution commands in reverse, until the
4958 exec-direction mode is changed to ``forward''. Affected commands include
4959 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
4960 command cannot be used in reverse mode.
4961 @item set exec-direction forward
4962 @value{GDBN} will perform all execution commands in the normal fashion.
4963 This is the default.
4968 @chapter Examining the Stack
4970 When your program has stopped, the first thing you need to know is where it
4971 stopped and how it got there.
4974 Each time your program performs a function call, information about the call
4976 That information includes the location of the call in your program,
4977 the arguments of the call,
4978 and the local variables of the function being called.
4979 The information is saved in a block of data called a @dfn{stack frame}.
4980 The stack frames are allocated in a region of memory called the @dfn{call
4983 When your program stops, the @value{GDBN} commands for examining the
4984 stack allow you to see all of this information.
4986 @cindex selected frame
4987 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4988 @value{GDBN} commands refer implicitly to the selected frame. In
4989 particular, whenever you ask @value{GDBN} for the value of a variable in
4990 your program, the value is found in the selected frame. There are
4991 special @value{GDBN} commands to select whichever frame you are
4992 interested in. @xref{Selection, ,Selecting a Frame}.
4994 When your program stops, @value{GDBN} automatically selects the
4995 currently executing frame and describes it briefly, similar to the
4996 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4999 * Frames:: Stack frames
5000 * Backtrace:: Backtraces
5001 * Selection:: Selecting a frame
5002 * Frame Info:: Information on a frame
5007 @section Stack Frames
5009 @cindex frame, definition
5011 The call stack is divided up into contiguous pieces called @dfn{stack
5012 frames}, or @dfn{frames} for short; each frame is the data associated
5013 with one call to one function. The frame contains the arguments given
5014 to the function, the function's local variables, and the address at
5015 which the function is executing.
5017 @cindex initial frame
5018 @cindex outermost frame
5019 @cindex innermost frame
5020 When your program is started, the stack has only one frame, that of the
5021 function @code{main}. This is called the @dfn{initial} frame or the
5022 @dfn{outermost} frame. Each time a function is called, a new frame is
5023 made. Each time a function returns, the frame for that function invocation
5024 is eliminated. If a function is recursive, there can be many frames for
5025 the same function. The frame for the function in which execution is
5026 actually occurring is called the @dfn{innermost} frame. This is the most
5027 recently created of all the stack frames that still exist.
5029 @cindex frame pointer
5030 Inside your program, stack frames are identified by their addresses. A
5031 stack frame consists of many bytes, each of which has its own address; each
5032 kind of computer has a convention for choosing one byte whose
5033 address serves as the address of the frame. Usually this address is kept
5034 in a register called the @dfn{frame pointer register}
5035 (@pxref{Registers, $fp}) while execution is going on in that frame.
5037 @cindex frame number
5038 @value{GDBN} assigns numbers to all existing stack frames, starting with
5039 zero for the innermost frame, one for the frame that called it,
5040 and so on upward. These numbers do not really exist in your program;
5041 they are assigned by @value{GDBN} to give you a way of designating stack
5042 frames in @value{GDBN} commands.
5044 @c The -fomit-frame-pointer below perennially causes hbox overflow
5045 @c underflow problems.
5046 @cindex frameless execution
5047 Some compilers provide a way to compile functions so that they operate
5048 without stack frames. (For example, the @value{NGCC} option
5050 @samp{-fomit-frame-pointer}
5052 generates functions without a frame.)
5053 This is occasionally done with heavily used library functions to save
5054 the frame setup time. @value{GDBN} has limited facilities for dealing
5055 with these function invocations. If the innermost function invocation
5056 has no stack frame, @value{GDBN} nevertheless regards it as though
5057 it had a separate frame, which is numbered zero as usual, allowing
5058 correct tracing of the function call chain. However, @value{GDBN} has
5059 no provision for frameless functions elsewhere in the stack.
5062 @kindex frame@r{, command}
5063 @cindex current stack frame
5064 @item frame @var{args}
5065 The @code{frame} command allows you to move from one stack frame to another,
5066 and to print the stack frame you select. @var{args} may be either the
5067 address of the frame or the stack frame number. Without an argument,
5068 @code{frame} prints the current stack frame.
5070 @kindex select-frame
5071 @cindex selecting frame silently
5073 The @code{select-frame} command allows you to move from one stack frame
5074 to another without printing the frame. This is the silent version of
5082 @cindex call stack traces
5083 A backtrace is a summary of how your program got where it is. It shows one
5084 line per frame, for many frames, starting with the currently executing
5085 frame (frame zero), followed by its caller (frame one), and on up the
5090 @kindex bt @r{(@code{backtrace})}
5093 Print a backtrace of the entire stack: one line per frame for all
5094 frames in the stack.
5096 You can stop the backtrace at any time by typing the system interrupt
5097 character, normally @kbd{Ctrl-c}.
5099 @item backtrace @var{n}
5101 Similar, but print only the innermost @var{n} frames.
5103 @item backtrace -@var{n}
5105 Similar, but print only the outermost @var{n} frames.
5107 @item backtrace full
5109 @itemx bt full @var{n}
5110 @itemx bt full -@var{n}
5111 Print the values of the local variables also. @var{n} specifies the
5112 number of frames to print, as described above.
5117 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5118 are additional aliases for @code{backtrace}.
5120 @cindex multiple threads, backtrace
5121 In a multi-threaded program, @value{GDBN} by default shows the
5122 backtrace only for the current thread. To display the backtrace for
5123 several or all of the threads, use the command @code{thread apply}
5124 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5125 apply all backtrace}, @value{GDBN} will display the backtrace for all
5126 the threads; this is handy when you debug a core dump of a
5127 multi-threaded program.
5129 Each line in the backtrace shows the frame number and the function name.
5130 The program counter value is also shown---unless you use @code{set
5131 print address off}. The backtrace also shows the source file name and
5132 line number, as well as the arguments to the function. The program
5133 counter value is omitted if it is at the beginning of the code for that
5136 Here is an example of a backtrace. It was made with the command
5137 @samp{bt 3}, so it shows the innermost three frames.
5141 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5143 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
5144 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5146 (More stack frames follow...)
5151 The display for frame zero does not begin with a program counter
5152 value, indicating that your program has stopped at the beginning of the
5153 code for line @code{993} of @code{builtin.c}.
5155 @cindex value optimized out, in backtrace
5156 @cindex function call arguments, optimized out
5157 If your program was compiled with optimizations, some compilers will
5158 optimize away arguments passed to functions if those arguments are
5159 never used after the call. Such optimizations generate code that
5160 passes arguments through registers, but doesn't store those arguments
5161 in the stack frame. @value{GDBN} has no way of displaying such
5162 arguments in stack frames other than the innermost one. Here's what
5163 such a backtrace might look like:
5167 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5169 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5170 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5172 (More stack frames follow...)
5177 The values of arguments that were not saved in their stack frames are
5178 shown as @samp{<value optimized out>}.
5180 If you need to display the values of such optimized-out arguments,
5181 either deduce that from other variables whose values depend on the one
5182 you are interested in, or recompile without optimizations.
5184 @cindex backtrace beyond @code{main} function
5185 @cindex program entry point
5186 @cindex startup code, and backtrace
5187 Most programs have a standard user entry point---a place where system
5188 libraries and startup code transition into user code. For C this is
5189 @code{main}@footnote{
5190 Note that embedded programs (the so-called ``free-standing''
5191 environment) are not required to have a @code{main} function as the
5192 entry point. They could even have multiple entry points.}.
5193 When @value{GDBN} finds the entry function in a backtrace
5194 it will terminate the backtrace, to avoid tracing into highly
5195 system-specific (and generally uninteresting) code.
5197 If you need to examine the startup code, or limit the number of levels
5198 in a backtrace, you can change this behavior:
5201 @item set backtrace past-main
5202 @itemx set backtrace past-main on
5203 @kindex set backtrace
5204 Backtraces will continue past the user entry point.
5206 @item set backtrace past-main off
5207 Backtraces will stop when they encounter the user entry point. This is the
5210 @item show backtrace past-main
5211 @kindex show backtrace
5212 Display the current user entry point backtrace policy.
5214 @item set backtrace past-entry
5215 @itemx set backtrace past-entry on
5216 Backtraces will continue past the internal entry point of an application.
5217 This entry point is encoded by the linker when the application is built,
5218 and is likely before the user entry point @code{main} (or equivalent) is called.
5220 @item set backtrace past-entry off
5221 Backtraces will stop when they encounter the internal entry point of an
5222 application. This is the default.
5224 @item show backtrace past-entry
5225 Display the current internal entry point backtrace policy.
5227 @item set backtrace limit @var{n}
5228 @itemx set backtrace limit 0
5229 @cindex backtrace limit
5230 Limit the backtrace to @var{n} levels. A value of zero means
5233 @item show backtrace limit
5234 Display the current limit on backtrace levels.
5238 @section Selecting a Frame
5240 Most commands for examining the stack and other data in your program work on
5241 whichever stack frame is selected at the moment. Here are the commands for
5242 selecting a stack frame; all of them finish by printing a brief description
5243 of the stack frame just selected.
5246 @kindex frame@r{, selecting}
5247 @kindex f @r{(@code{frame})}
5250 Select frame number @var{n}. Recall that frame zero is the innermost
5251 (currently executing) frame, frame one is the frame that called the
5252 innermost one, and so on. The highest-numbered frame is the one for
5255 @item frame @var{addr}
5257 Select the frame at address @var{addr}. This is useful mainly if the
5258 chaining of stack frames has been damaged by a bug, making it
5259 impossible for @value{GDBN} to assign numbers properly to all frames. In
5260 addition, this can be useful when your program has multiple stacks and
5261 switches between them.
5263 On the SPARC architecture, @code{frame} needs two addresses to
5264 select an arbitrary frame: a frame pointer and a stack pointer.
5266 On the MIPS and Alpha architecture, it needs two addresses: a stack
5267 pointer and a program counter.
5269 On the 29k architecture, it needs three addresses: a register stack
5270 pointer, a program counter, and a memory stack pointer.
5274 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5275 advances toward the outermost frame, to higher frame numbers, to frames
5276 that have existed longer. @var{n} defaults to one.
5279 @kindex do @r{(@code{down})}
5281 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5282 advances toward the innermost frame, to lower frame numbers, to frames
5283 that were created more recently. @var{n} defaults to one. You may
5284 abbreviate @code{down} as @code{do}.
5287 All of these commands end by printing two lines of output describing the
5288 frame. The first line shows the frame number, the function name, the
5289 arguments, and the source file and line number of execution in that
5290 frame. The second line shows the text of that source line.
5298 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5300 10 read_input_file (argv[i]);
5304 After such a printout, the @code{list} command with no arguments
5305 prints ten lines centered on the point of execution in the frame.
5306 You can also edit the program at the point of execution with your favorite
5307 editing program by typing @code{edit}.
5308 @xref{List, ,Printing Source Lines},
5312 @kindex down-silently
5314 @item up-silently @var{n}
5315 @itemx down-silently @var{n}
5316 These two commands are variants of @code{up} and @code{down},
5317 respectively; they differ in that they do their work silently, without
5318 causing display of the new frame. They are intended primarily for use
5319 in @value{GDBN} command scripts, where the output might be unnecessary and
5324 @section Information About a Frame
5326 There are several other commands to print information about the selected
5332 When used without any argument, this command does not change which
5333 frame is selected, but prints a brief description of the currently
5334 selected stack frame. It can be abbreviated @code{f}. With an
5335 argument, this command is used to select a stack frame.
5336 @xref{Selection, ,Selecting a Frame}.
5339 @kindex info f @r{(@code{info frame})}
5342 This command prints a verbose description of the selected stack frame,
5347 the address of the frame
5349 the address of the next frame down (called by this frame)
5351 the address of the next frame up (caller of this frame)
5353 the language in which the source code corresponding to this frame is written
5355 the address of the frame's arguments
5357 the address of the frame's local variables
5359 the program counter saved in it (the address of execution in the caller frame)
5361 which registers were saved in the frame
5364 @noindent The verbose description is useful when
5365 something has gone wrong that has made the stack format fail to fit
5366 the usual conventions.
5368 @item info frame @var{addr}
5369 @itemx info f @var{addr}
5370 Print a verbose description of the frame at address @var{addr}, without
5371 selecting that frame. The selected frame remains unchanged by this
5372 command. This requires the same kind of address (more than one for some
5373 architectures) that you specify in the @code{frame} command.
5374 @xref{Selection, ,Selecting a Frame}.
5378 Print the arguments of the selected frame, each on a separate line.
5382 Print the local variables of the selected frame, each on a separate
5383 line. These are all variables (declared either static or automatic)
5384 accessible at the point of execution of the selected frame.
5387 @cindex catch exceptions, list active handlers
5388 @cindex exception handlers, how to list
5390 Print a list of all the exception handlers that are active in the
5391 current stack frame at the current point of execution. To see other
5392 exception handlers, visit the associated frame (using the @code{up},
5393 @code{down}, or @code{frame} commands); then type @code{info catch}.
5394 @xref{Set Catchpoints, , Setting Catchpoints}.
5400 @chapter Examining Source Files
5402 @value{GDBN} can print parts of your program's source, since the debugging
5403 information recorded in the program tells @value{GDBN} what source files were
5404 used to build it. When your program stops, @value{GDBN} spontaneously prints
5405 the line where it stopped. Likewise, when you select a stack frame
5406 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5407 execution in that frame has stopped. You can print other portions of
5408 source files by explicit command.
5410 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5411 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5412 @value{GDBN} under @sc{gnu} Emacs}.
5415 * List:: Printing source lines
5416 * Specify Location:: How to specify code locations
5417 * Edit:: Editing source files
5418 * Search:: Searching source files
5419 * Source Path:: Specifying source directories
5420 * Machine Code:: Source and machine code
5424 @section Printing Source Lines
5427 @kindex l @r{(@code{list})}
5428 To print lines from a source file, use the @code{list} command
5429 (abbreviated @code{l}). By default, ten lines are printed.
5430 There are several ways to specify what part of the file you want to
5431 print; see @ref{Specify Location}, for the full list.
5433 Here are the forms of the @code{list} command most commonly used:
5436 @item list @var{linenum}
5437 Print lines centered around line number @var{linenum} in the
5438 current source file.
5440 @item list @var{function}
5441 Print lines centered around the beginning of function
5445 Print more lines. If the last lines printed were printed with a
5446 @code{list} command, this prints lines following the last lines
5447 printed; however, if the last line printed was a solitary line printed
5448 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5449 Stack}), this prints lines centered around that line.
5452 Print lines just before the lines last printed.
5455 @cindex @code{list}, how many lines to display
5456 By default, @value{GDBN} prints ten source lines with any of these forms of
5457 the @code{list} command. You can change this using @code{set listsize}:
5460 @kindex set listsize
5461 @item set listsize @var{count}
5462 Make the @code{list} command display @var{count} source lines (unless
5463 the @code{list} argument explicitly specifies some other number).
5465 @kindex show listsize
5467 Display the number of lines that @code{list} prints.
5470 Repeating a @code{list} command with @key{RET} discards the argument,
5471 so it is equivalent to typing just @code{list}. This is more useful
5472 than listing the same lines again. An exception is made for an
5473 argument of @samp{-}; that argument is preserved in repetition so that
5474 each repetition moves up in the source file.
5476 In general, the @code{list} command expects you to supply zero, one or two
5477 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5478 of writing them (@pxref{Specify Location}), but the effect is always
5479 to specify some source line.
5481 Here is a complete description of the possible arguments for @code{list}:
5484 @item list @var{linespec}
5485 Print lines centered around the line specified by @var{linespec}.
5487 @item list @var{first},@var{last}
5488 Print lines from @var{first} to @var{last}. Both arguments are
5489 linespecs. When a @code{list} command has two linespecs, and the
5490 source file of the second linespec is omitted, this refers to
5491 the same source file as the first linespec.
5493 @item list ,@var{last}
5494 Print lines ending with @var{last}.
5496 @item list @var{first},
5497 Print lines starting with @var{first}.
5500 Print lines just after the lines last printed.
5503 Print lines just before the lines last printed.
5506 As described in the preceding table.
5509 @node Specify Location
5510 @section Specifying a Location
5511 @cindex specifying location
5514 Several @value{GDBN} commands accept arguments that specify a location
5515 of your program's code. Since @value{GDBN} is a source-level
5516 debugger, a location usually specifies some line in the source code;
5517 for that reason, locations are also known as @dfn{linespecs}.
5519 Here are all the different ways of specifying a code location that
5520 @value{GDBN} understands:
5524 Specifies the line number @var{linenum} of the current source file.
5527 @itemx +@var{offset}
5528 Specifies the line @var{offset} lines before or after the @dfn{current
5529 line}. For the @code{list} command, the current line is the last one
5530 printed; for the breakpoint commands, this is the line at which
5531 execution stopped in the currently selected @dfn{stack frame}
5532 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5533 used as the second of the two linespecs in a @code{list} command,
5534 this specifies the line @var{offset} lines up or down from the first
5537 @item @var{filename}:@var{linenum}
5538 Specifies the line @var{linenum} in the source file @var{filename}.
5540 @item @var{function}
5541 Specifies the line that begins the body of the function @var{function}.
5542 For example, in C, this is the line with the open brace.
5544 @item @var{filename}:@var{function}
5545 Specifies the line that begins the body of the function @var{function}
5546 in the file @var{filename}. You only need the file name with a
5547 function name to avoid ambiguity when there are identically named
5548 functions in different source files.
5550 @item *@var{address}
5551 Specifies the program address @var{address}. For line-oriented
5552 commands, such as @code{list} and @code{edit}, this specifies a source
5553 line that contains @var{address}. For @code{break} and other
5554 breakpoint oriented commands, this can be used to set breakpoints in
5555 parts of your program which do not have debugging information or
5558 Here @var{address} may be any expression valid in the current working
5559 language (@pxref{Languages, working language}) that specifies a code
5560 address. In addition, as a convenience, @value{GDBN} extends the
5561 semantics of expressions used in locations to cover the situations
5562 that frequently happen during debugging. Here are the various forms
5566 @item @var{expression}
5567 Any expression valid in the current working language.
5569 @item @var{funcaddr}
5570 An address of a function or procedure derived from its name. In C,
5571 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5572 simply the function's name @var{function} (and actually a special case
5573 of a valid expression). In Pascal and Modula-2, this is
5574 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5575 (although the Pascal form also works).
5577 This form specifies the address of the function's first instruction,
5578 before the stack frame and arguments have been set up.
5580 @item '@var{filename}'::@var{funcaddr}
5581 Like @var{funcaddr} above, but also specifies the name of the source
5582 file explicitly. This is useful if the name of the function does not
5583 specify the function unambiguously, e.g., if there are several
5584 functions with identical names in different source files.
5591 @section Editing Source Files
5592 @cindex editing source files
5595 @kindex e @r{(@code{edit})}
5596 To edit the lines in a source file, use the @code{edit} command.
5597 The editing program of your choice
5598 is invoked with the current line set to
5599 the active line in the program.
5600 Alternatively, there are several ways to specify what part of the file you
5601 want to print if you want to see other parts of the program:
5604 @item edit @var{location}
5605 Edit the source file specified by @code{location}. Editing starts at
5606 that @var{location}, e.g., at the specified source line of the
5607 specified file. @xref{Specify Location}, for all the possible forms
5608 of the @var{location} argument; here are the forms of the @code{edit}
5609 command most commonly used:
5612 @item edit @var{number}
5613 Edit the current source file with @var{number} as the active line number.
5615 @item edit @var{function}
5616 Edit the file containing @var{function} at the beginning of its definition.
5621 @subsection Choosing your Editor
5622 You can customize @value{GDBN} to use any editor you want
5624 The only restriction is that your editor (say @code{ex}), recognizes the
5625 following command-line syntax:
5627 ex +@var{number} file
5629 The optional numeric value +@var{number} specifies the number of the line in
5630 the file where to start editing.}.
5631 By default, it is @file{@value{EDITOR}}, but you can change this
5632 by setting the environment variable @code{EDITOR} before using
5633 @value{GDBN}. For example, to configure @value{GDBN} to use the
5634 @code{vi} editor, you could use these commands with the @code{sh} shell:
5640 or in the @code{csh} shell,
5642 setenv EDITOR /usr/bin/vi
5647 @section Searching Source Files
5648 @cindex searching source files
5650 There are two commands for searching through the current source file for a
5655 @kindex forward-search
5656 @item forward-search @var{regexp}
5657 @itemx search @var{regexp}
5658 The command @samp{forward-search @var{regexp}} checks each line,
5659 starting with the one following the last line listed, for a match for
5660 @var{regexp}. It lists the line that is found. You can use the
5661 synonym @samp{search @var{regexp}} or abbreviate the command name as
5664 @kindex reverse-search
5665 @item reverse-search @var{regexp}
5666 The command @samp{reverse-search @var{regexp}} checks each line, starting
5667 with the one before the last line listed and going backward, for a match
5668 for @var{regexp}. It lists the line that is found. You can abbreviate
5669 this command as @code{rev}.
5673 @section Specifying Source Directories
5676 @cindex directories for source files
5677 Executable programs sometimes do not record the directories of the source
5678 files from which they were compiled, just the names. Even when they do,
5679 the directories could be moved between the compilation and your debugging
5680 session. @value{GDBN} has a list of directories to search for source files;
5681 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5682 it tries all the directories in the list, in the order they are present
5683 in the list, until it finds a file with the desired name.
5685 For example, suppose an executable references the file
5686 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5687 @file{/mnt/cross}. The file is first looked up literally; if this
5688 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5689 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5690 message is printed. @value{GDBN} does not look up the parts of the
5691 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5692 Likewise, the subdirectories of the source path are not searched: if
5693 the source path is @file{/mnt/cross}, and the binary refers to
5694 @file{foo.c}, @value{GDBN} would not find it under
5695 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5697 Plain file names, relative file names with leading directories, file
5698 names containing dots, etc.@: are all treated as described above; for
5699 instance, if the source path is @file{/mnt/cross}, and the source file
5700 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5701 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5702 that---@file{/mnt/cross/foo.c}.
5704 Note that the executable search path is @emph{not} used to locate the
5707 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5708 any information it has cached about where source files are found and where
5709 each line is in the file.
5713 When you start @value{GDBN}, its source path includes only @samp{cdir}
5714 and @samp{cwd}, in that order.
5715 To add other directories, use the @code{directory} command.
5717 The search path is used to find both program source files and @value{GDBN}
5718 script files (read using the @samp{-command} option and @samp{source} command).
5720 In addition to the source path, @value{GDBN} provides a set of commands
5721 that manage a list of source path substitution rules. A @dfn{substitution
5722 rule} specifies how to rewrite source directories stored in the program's
5723 debug information in case the sources were moved to a different
5724 directory between compilation and debugging. A rule is made of
5725 two strings, the first specifying what needs to be rewritten in
5726 the path, and the second specifying how it should be rewritten.
5727 In @ref{set substitute-path}, we name these two parts @var{from} and
5728 @var{to} respectively. @value{GDBN} does a simple string replacement
5729 of @var{from} with @var{to} at the start of the directory part of the
5730 source file name, and uses that result instead of the original file
5731 name to look up the sources.
5733 Using the previous example, suppose the @file{foo-1.0} tree has been
5734 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5735 @value{GDBN} to replace @file{/usr/src} in all source path names with
5736 @file{/mnt/cross}. The first lookup will then be
5737 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5738 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5739 substitution rule, use the @code{set substitute-path} command
5740 (@pxref{set substitute-path}).
5742 To avoid unexpected substitution results, a rule is applied only if the
5743 @var{from} part of the directory name ends at a directory separator.
5744 For instance, a rule substituting @file{/usr/source} into
5745 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5746 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5747 is applied only at the beginning of the directory name, this rule will
5748 not be applied to @file{/root/usr/source/baz.c} either.
5750 In many cases, you can achieve the same result using the @code{directory}
5751 command. However, @code{set substitute-path} can be more efficient in
5752 the case where the sources are organized in a complex tree with multiple
5753 subdirectories. With the @code{directory} command, you need to add each
5754 subdirectory of your project. If you moved the entire tree while
5755 preserving its internal organization, then @code{set substitute-path}
5756 allows you to direct the debugger to all the sources with one single
5759 @code{set substitute-path} is also more than just a shortcut command.
5760 The source path is only used if the file at the original location no
5761 longer exists. On the other hand, @code{set substitute-path} modifies
5762 the debugger behavior to look at the rewritten location instead. So, if
5763 for any reason a source file that is not relevant to your executable is
5764 located at the original location, a substitution rule is the only
5765 method available to point @value{GDBN} at the new location.
5768 @item directory @var{dirname} @dots{}
5769 @item dir @var{dirname} @dots{}
5770 Add directory @var{dirname} to the front of the source path. Several
5771 directory names may be given to this command, separated by @samp{:}
5772 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5773 part of absolute file names) or
5774 whitespace. You may specify a directory that is already in the source
5775 path; this moves it forward, so @value{GDBN} searches it sooner.
5779 @vindex $cdir@r{, convenience variable}
5780 @vindex $cwd@r{, convenience variable}
5781 @cindex compilation directory
5782 @cindex current directory
5783 @cindex working directory
5784 @cindex directory, current
5785 @cindex directory, compilation
5786 You can use the string @samp{$cdir} to refer to the compilation
5787 directory (if one is recorded), and @samp{$cwd} to refer to the current
5788 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5789 tracks the current working directory as it changes during your @value{GDBN}
5790 session, while the latter is immediately expanded to the current
5791 directory at the time you add an entry to the source path.
5794 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5796 @c RET-repeat for @code{directory} is explicitly disabled, but since
5797 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5799 @item show directories
5800 @kindex show directories
5801 Print the source path: show which directories it contains.
5803 @anchor{set substitute-path}
5804 @item set substitute-path @var{from} @var{to}
5805 @kindex set substitute-path
5806 Define a source path substitution rule, and add it at the end of the
5807 current list of existing substitution rules. If a rule with the same
5808 @var{from} was already defined, then the old rule is also deleted.
5810 For example, if the file @file{/foo/bar/baz.c} was moved to
5811 @file{/mnt/cross/baz.c}, then the command
5814 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5818 will tell @value{GDBN} to replace @samp{/usr/src} with
5819 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5820 @file{baz.c} even though it was moved.
5822 In the case when more than one substitution rule have been defined,
5823 the rules are evaluated one by one in the order where they have been
5824 defined. The first one matching, if any, is selected to perform
5827 For instance, if we had entered the following commands:
5830 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5831 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5835 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5836 @file{/mnt/include/defs.h} by using the first rule. However, it would
5837 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5838 @file{/mnt/src/lib/foo.c}.
5841 @item unset substitute-path [path]
5842 @kindex unset substitute-path
5843 If a path is specified, search the current list of substitution rules
5844 for a rule that would rewrite that path. Delete that rule if found.
5845 A warning is emitted by the debugger if no rule could be found.
5847 If no path is specified, then all substitution rules are deleted.
5849 @item show substitute-path [path]
5850 @kindex show substitute-path
5851 If a path is specified, then print the source path substitution rule
5852 which would rewrite that path, if any.
5854 If no path is specified, then print all existing source path substitution
5859 If your source path is cluttered with directories that are no longer of
5860 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5861 versions of source. You can correct the situation as follows:
5865 Use @code{directory} with no argument to reset the source path to its default value.
5868 Use @code{directory} with suitable arguments to reinstall the
5869 directories you want in the source path. You can add all the
5870 directories in one command.
5874 @section Source and Machine Code
5875 @cindex source line and its code address
5877 You can use the command @code{info line} to map source lines to program
5878 addresses (and vice versa), and the command @code{disassemble} to display
5879 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5880 mode, the @code{info line} command causes the arrow to point to the
5881 line specified. Also, @code{info line} prints addresses in symbolic form as
5886 @item info line @var{linespec}
5887 Print the starting and ending addresses of the compiled code for
5888 source line @var{linespec}. You can specify source lines in any of
5889 the ways documented in @ref{Specify Location}.
5892 For example, we can use @code{info line} to discover the location of
5893 the object code for the first line of function
5894 @code{m4_changequote}:
5896 @c FIXME: I think this example should also show the addresses in
5897 @c symbolic form, as they usually would be displayed.
5899 (@value{GDBP}) info line m4_changequote
5900 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5904 @cindex code address and its source line
5905 We can also inquire (using @code{*@var{addr}} as the form for
5906 @var{linespec}) what source line covers a particular address:
5908 (@value{GDBP}) info line *0x63ff
5909 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5912 @cindex @code{$_} and @code{info line}
5913 @cindex @code{x} command, default address
5914 @kindex x@r{(examine), and} info line
5915 After @code{info line}, the default address for the @code{x} command
5916 is changed to the starting address of the line, so that @samp{x/i} is
5917 sufficient to begin examining the machine code (@pxref{Memory,
5918 ,Examining Memory}). Also, this address is saved as the value of the
5919 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5924 @cindex assembly instructions
5925 @cindex instructions, assembly
5926 @cindex machine instructions
5927 @cindex listing machine instructions
5929 @itemx disassemble /m
5930 This specialized command dumps a range of memory as machine
5931 instructions. It can also print mixed source+disassembly by specifying
5932 the @code{/m} modifier.
5933 The default memory range is the function surrounding the
5934 program counter of the selected frame. A single argument to this
5935 command is a program counter value; @value{GDBN} dumps the function
5936 surrounding this value. Two arguments specify a range of addresses
5937 (first inclusive, second exclusive) to dump.
5940 The following example shows the disassembly of a range of addresses of
5941 HP PA-RISC 2.0 code:
5944 (@value{GDBP}) disas 0x32c4 0x32e4
5945 Dump of assembler code from 0x32c4 to 0x32e4:
5946 0x32c4 <main+204>: addil 0,dp
5947 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5948 0x32cc <main+212>: ldil 0x3000,r31
5949 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5950 0x32d4 <main+220>: ldo 0(r31),rp
5951 0x32d8 <main+224>: addil -0x800,dp
5952 0x32dc <main+228>: ldo 0x588(r1),r26
5953 0x32e0 <main+232>: ldil 0x3000,r31
5954 End of assembler dump.
5957 Here is an example showing mixed source+assembly for Intel x86:
5960 (@value{GDBP}) disas /m main
5961 Dump of assembler code for function main:
5963 0x08048330 <main+0>: push %ebp
5964 0x08048331 <main+1>: mov %esp,%ebp
5965 0x08048333 <main+3>: sub $0x8,%esp
5966 0x08048336 <main+6>: and $0xfffffff0,%esp
5967 0x08048339 <main+9>: sub $0x10,%esp
5969 6 printf ("Hello.\n");
5970 0x0804833c <main+12>: movl $0x8048440,(%esp)
5971 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
5975 0x08048348 <main+24>: mov $0x0,%eax
5976 0x0804834d <main+29>: leave
5977 0x0804834e <main+30>: ret
5979 End of assembler dump.
5982 Some architectures have more than one commonly-used set of instruction
5983 mnemonics or other syntax.
5985 For programs that were dynamically linked and use shared libraries,
5986 instructions that call functions or branch to locations in the shared
5987 libraries might show a seemingly bogus location---it's actually a
5988 location of the relocation table. On some architectures, @value{GDBN}
5989 might be able to resolve these to actual function names.
5992 @kindex set disassembly-flavor
5993 @cindex Intel disassembly flavor
5994 @cindex AT&T disassembly flavor
5995 @item set disassembly-flavor @var{instruction-set}
5996 Select the instruction set to use when disassembling the
5997 program via the @code{disassemble} or @code{x/i} commands.
5999 Currently this command is only defined for the Intel x86 family. You
6000 can set @var{instruction-set} to either @code{intel} or @code{att}.
6001 The default is @code{att}, the AT&T flavor used by default by Unix
6002 assemblers for x86-based targets.
6004 @kindex show disassembly-flavor
6005 @item show disassembly-flavor
6006 Show the current setting of the disassembly flavor.
6011 @chapter Examining Data
6013 @cindex printing data
6014 @cindex examining data
6017 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6018 @c document because it is nonstandard... Under Epoch it displays in a
6019 @c different window or something like that.
6020 The usual way to examine data in your program is with the @code{print}
6021 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6022 evaluates and prints the value of an expression of the language your
6023 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6024 Different Languages}).
6027 @item print @var{expr}
6028 @itemx print /@var{f} @var{expr}
6029 @var{expr} is an expression (in the source language). By default the
6030 value of @var{expr} is printed in a format appropriate to its data type;
6031 you can choose a different format by specifying @samp{/@var{f}}, where
6032 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6036 @itemx print /@var{f}
6037 @cindex reprint the last value
6038 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6039 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6040 conveniently inspect the same value in an alternative format.
6043 A more low-level way of examining data is with the @code{x} command.
6044 It examines data in memory at a specified address and prints it in a
6045 specified format. @xref{Memory, ,Examining Memory}.
6047 If you are interested in information about types, or about how the
6048 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6049 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6053 * Expressions:: Expressions
6054 * Ambiguous Expressions:: Ambiguous Expressions
6055 * Variables:: Program variables
6056 * Arrays:: Artificial arrays
6057 * Output Formats:: Output formats
6058 * Memory:: Examining memory
6059 * Auto Display:: Automatic display
6060 * Print Settings:: Print settings
6061 * Value History:: Value history
6062 * Convenience Vars:: Convenience variables
6063 * Registers:: Registers
6064 * Floating Point Hardware:: Floating point hardware
6065 * Vector Unit:: Vector Unit
6066 * OS Information:: Auxiliary data provided by operating system
6067 * Memory Region Attributes:: Memory region attributes
6068 * Dump/Restore Files:: Copy between memory and a file
6069 * Core File Generation:: Cause a program dump its core
6070 * Character Sets:: Debugging programs that use a different
6071 character set than GDB does
6072 * Caching Remote Data:: Data caching for remote targets
6073 * Searching Memory:: Searching memory for a sequence of bytes
6077 @section Expressions
6080 @code{print} and many other @value{GDBN} commands accept an expression and
6081 compute its value. Any kind of constant, variable or operator defined
6082 by the programming language you are using is valid in an expression in
6083 @value{GDBN}. This includes conditional expressions, function calls,
6084 casts, and string constants. It also includes preprocessor macros, if
6085 you compiled your program to include this information; see
6088 @cindex arrays in expressions
6089 @value{GDBN} supports array constants in expressions input by
6090 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6091 you can use the command @code{print @{1, 2, 3@}} to create an array
6092 of three integers. If you pass an array to a function or assign it
6093 to a program variable, @value{GDBN} copies the array to memory that
6094 is @code{malloc}ed in the target program.
6096 Because C is so widespread, most of the expressions shown in examples in
6097 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6098 Languages}, for information on how to use expressions in other
6101 In this section, we discuss operators that you can use in @value{GDBN}
6102 expressions regardless of your programming language.
6104 @cindex casts, in expressions
6105 Casts are supported in all languages, not just in C, because it is so
6106 useful to cast a number into a pointer in order to examine a structure
6107 at that address in memory.
6108 @c FIXME: casts supported---Mod2 true?
6110 @value{GDBN} supports these operators, in addition to those common
6111 to programming languages:
6115 @samp{@@} is a binary operator for treating parts of memory as arrays.
6116 @xref{Arrays, ,Artificial Arrays}, for more information.
6119 @samp{::} allows you to specify a variable in terms of the file or
6120 function where it is defined. @xref{Variables, ,Program Variables}.
6122 @cindex @{@var{type}@}
6123 @cindex type casting memory
6124 @cindex memory, viewing as typed object
6125 @cindex casts, to view memory
6126 @item @{@var{type}@} @var{addr}
6127 Refers to an object of type @var{type} stored at address @var{addr} in
6128 memory. @var{addr} may be any expression whose value is an integer or
6129 pointer (but parentheses are required around binary operators, just as in
6130 a cast). This construct is allowed regardless of what kind of data is
6131 normally supposed to reside at @var{addr}.
6134 @node Ambiguous Expressions
6135 @section Ambiguous Expressions
6136 @cindex ambiguous expressions
6138 Expressions can sometimes contain some ambiguous elements. For instance,
6139 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6140 a single function name to be defined several times, for application in
6141 different contexts. This is called @dfn{overloading}. Another example
6142 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6143 templates and is typically instantiated several times, resulting in
6144 the same function name being defined in different contexts.
6146 In some cases and depending on the language, it is possible to adjust
6147 the expression to remove the ambiguity. For instance in C@t{++}, you
6148 can specify the signature of the function you want to break on, as in
6149 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6150 qualified name of your function often makes the expression unambiguous
6153 When an ambiguity that needs to be resolved is detected, the debugger
6154 has the capability to display a menu of numbered choices for each
6155 possibility, and then waits for the selection with the prompt @samp{>}.
6156 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6157 aborts the current command. If the command in which the expression was
6158 used allows more than one choice to be selected, the next option in the
6159 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6162 For example, the following session excerpt shows an attempt to set a
6163 breakpoint at the overloaded symbol @code{String::after}.
6164 We choose three particular definitions of that function name:
6166 @c FIXME! This is likely to change to show arg type lists, at least
6169 (@value{GDBP}) b String::after
6172 [2] file:String.cc; line number:867
6173 [3] file:String.cc; line number:860
6174 [4] file:String.cc; line number:875
6175 [5] file:String.cc; line number:853
6176 [6] file:String.cc; line number:846
6177 [7] file:String.cc; line number:735
6179 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6180 Breakpoint 2 at 0xb344: file String.cc, line 875.
6181 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6182 Multiple breakpoints were set.
6183 Use the "delete" command to delete unwanted
6190 @kindex set multiple-symbols
6191 @item set multiple-symbols @var{mode}
6192 @cindex multiple-symbols menu
6194 This option allows you to adjust the debugger behavior when an expression
6197 By default, @var{mode} is set to @code{all}. If the command with which
6198 the expression is used allows more than one choice, then @value{GDBN}
6199 automatically selects all possible choices. For instance, inserting
6200 a breakpoint on a function using an ambiguous name results in a breakpoint
6201 inserted on each possible match. However, if a unique choice must be made,
6202 then @value{GDBN} uses the menu to help you disambiguate the expression.
6203 For instance, printing the address of an overloaded function will result
6204 in the use of the menu.
6206 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6207 when an ambiguity is detected.
6209 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6210 an error due to the ambiguity and the command is aborted.
6212 @kindex show multiple-symbols
6213 @item show multiple-symbols
6214 Show the current value of the @code{multiple-symbols} setting.
6218 @section Program Variables
6220 The most common kind of expression to use is the name of a variable
6223 Variables in expressions are understood in the selected stack frame
6224 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6228 global (or file-static)
6235 visible according to the scope rules of the
6236 programming language from the point of execution in that frame
6239 @noindent This means that in the function
6254 you can examine and use the variable @code{a} whenever your program is
6255 executing within the function @code{foo}, but you can only use or
6256 examine the variable @code{b} while your program is executing inside
6257 the block where @code{b} is declared.
6259 @cindex variable name conflict
6260 There is an exception: you can refer to a variable or function whose
6261 scope is a single source file even if the current execution point is not
6262 in this file. But it is possible to have more than one such variable or
6263 function with the same name (in different source files). If that
6264 happens, referring to that name has unpredictable effects. If you wish,
6265 you can specify a static variable in a particular function or file,
6266 using the colon-colon (@code{::}) notation:
6268 @cindex colon-colon, context for variables/functions
6270 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6271 @cindex @code{::}, context for variables/functions
6274 @var{file}::@var{variable}
6275 @var{function}::@var{variable}
6279 Here @var{file} or @var{function} is the name of the context for the
6280 static @var{variable}. In the case of file names, you can use quotes to
6281 make sure @value{GDBN} parses the file name as a single word---for example,
6282 to print a global value of @code{x} defined in @file{f2.c}:
6285 (@value{GDBP}) p 'f2.c'::x
6288 @cindex C@t{++} scope resolution
6289 This use of @samp{::} is very rarely in conflict with the very similar
6290 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6291 scope resolution operator in @value{GDBN} expressions.
6292 @c FIXME: Um, so what happens in one of those rare cases where it's in
6295 @cindex wrong values
6296 @cindex variable values, wrong
6297 @cindex function entry/exit, wrong values of variables
6298 @cindex optimized code, wrong values of variables
6300 @emph{Warning:} Occasionally, a local variable may appear to have the
6301 wrong value at certain points in a function---just after entry to a new
6302 scope, and just before exit.
6304 You may see this problem when you are stepping by machine instructions.
6305 This is because, on most machines, it takes more than one instruction to
6306 set up a stack frame (including local variable definitions); if you are
6307 stepping by machine instructions, variables may appear to have the wrong
6308 values until the stack frame is completely built. On exit, it usually
6309 also takes more than one machine instruction to destroy a stack frame;
6310 after you begin stepping through that group of instructions, local
6311 variable definitions may be gone.
6313 This may also happen when the compiler does significant optimizations.
6314 To be sure of always seeing accurate values, turn off all optimization
6317 @cindex ``No symbol "foo" in current context''
6318 Another possible effect of compiler optimizations is to optimize
6319 unused variables out of existence, or assign variables to registers (as
6320 opposed to memory addresses). Depending on the support for such cases
6321 offered by the debug info format used by the compiler, @value{GDBN}
6322 might not be able to display values for such local variables. If that
6323 happens, @value{GDBN} will print a message like this:
6326 No symbol "foo" in current context.
6329 To solve such problems, either recompile without optimizations, or use a
6330 different debug info format, if the compiler supports several such
6331 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6332 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6333 produces debug info in a format that is superior to formats such as
6334 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6335 an effective form for debug info. @xref{Debugging Options,,Options
6336 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6337 Compiler Collection (GCC)}.
6338 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6339 that are best suited to C@t{++} programs.
6341 If you ask to print an object whose contents are unknown to
6342 @value{GDBN}, e.g., because its data type is not completely specified
6343 by the debug information, @value{GDBN} will say @samp{<incomplete
6344 type>}. @xref{Symbols, incomplete type}, for more about this.
6346 Strings are identified as arrays of @code{char} values without specified
6347 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6348 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6349 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6350 defines literal string type @code{"char"} as @code{char} without a sign.
6355 signed char var1[] = "A";
6358 You get during debugging
6363 $2 = @{65 'A', 0 '\0'@}
6367 @section Artificial Arrays
6369 @cindex artificial array
6371 @kindex @@@r{, referencing memory as an array}
6372 It is often useful to print out several successive objects of the
6373 same type in memory; a section of an array, or an array of
6374 dynamically determined size for which only a pointer exists in the
6377 You can do this by referring to a contiguous span of memory as an
6378 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6379 operand of @samp{@@} should be the first element of the desired array
6380 and be an individual object. The right operand should be the desired length
6381 of the array. The result is an array value whose elements are all of
6382 the type of the left argument. The first element is actually the left
6383 argument; the second element comes from bytes of memory immediately
6384 following those that hold the first element, and so on. Here is an
6385 example. If a program says
6388 int *array = (int *) malloc (len * sizeof (int));
6392 you can print the contents of @code{array} with
6398 The left operand of @samp{@@} must reside in memory. Array values made
6399 with @samp{@@} in this way behave just like other arrays in terms of
6400 subscripting, and are coerced to pointers when used in expressions.
6401 Artificial arrays most often appear in expressions via the value history
6402 (@pxref{Value History, ,Value History}), after printing one out.
6404 Another way to create an artificial array is to use a cast.
6405 This re-interprets a value as if it were an array.
6406 The value need not be in memory:
6408 (@value{GDBP}) p/x (short[2])0x12345678
6409 $1 = @{0x1234, 0x5678@}
6412 As a convenience, if you leave the array length out (as in
6413 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6414 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6416 (@value{GDBP}) p/x (short[])0x12345678
6417 $2 = @{0x1234, 0x5678@}
6420 Sometimes the artificial array mechanism is not quite enough; in
6421 moderately complex data structures, the elements of interest may not
6422 actually be adjacent---for example, if you are interested in the values
6423 of pointers in an array. One useful work-around in this situation is
6424 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6425 Variables}) as a counter in an expression that prints the first
6426 interesting value, and then repeat that expression via @key{RET}. For
6427 instance, suppose you have an array @code{dtab} of pointers to
6428 structures, and you are interested in the values of a field @code{fv}
6429 in each structure. Here is an example of what you might type:
6439 @node Output Formats
6440 @section Output Formats
6442 @cindex formatted output
6443 @cindex output formats
6444 By default, @value{GDBN} prints a value according to its data type. Sometimes
6445 this is not what you want. For example, you might want to print a number
6446 in hex, or a pointer in decimal. Or you might want to view data in memory
6447 at a certain address as a character string or as an instruction. To do
6448 these things, specify an @dfn{output format} when you print a value.
6450 The simplest use of output formats is to say how to print a value
6451 already computed. This is done by starting the arguments of the
6452 @code{print} command with a slash and a format letter. The format
6453 letters supported are:
6457 Regard the bits of the value as an integer, and print the integer in
6461 Print as integer in signed decimal.
6464 Print as integer in unsigned decimal.
6467 Print as integer in octal.
6470 Print as integer in binary. The letter @samp{t} stands for ``two''.
6471 @footnote{@samp{b} cannot be used because these format letters are also
6472 used with the @code{x} command, where @samp{b} stands for ``byte'';
6473 see @ref{Memory,,Examining Memory}.}
6476 @cindex unknown address, locating
6477 @cindex locate address
6478 Print as an address, both absolute in hexadecimal and as an offset from
6479 the nearest preceding symbol. You can use this format used to discover
6480 where (in what function) an unknown address is located:
6483 (@value{GDBP}) p/a 0x54320
6484 $3 = 0x54320 <_initialize_vx+396>
6488 The command @code{info symbol 0x54320} yields similar results.
6489 @xref{Symbols, info symbol}.
6492 Regard as an integer and print it as a character constant. This
6493 prints both the numerical value and its character representation. The
6494 character representation is replaced with the octal escape @samp{\nnn}
6495 for characters outside the 7-bit @sc{ascii} range.
6497 Without this format, @value{GDBN} displays @code{char},
6498 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6499 constants. Single-byte members of vectors are displayed as integer
6503 Regard the bits of the value as a floating point number and print
6504 using typical floating point syntax.
6507 @cindex printing strings
6508 @cindex printing byte arrays
6509 Regard as a string, if possible. With this format, pointers to single-byte
6510 data are displayed as null-terminated strings and arrays of single-byte data
6511 are displayed as fixed-length strings. Other values are displayed in their
6514 Without this format, @value{GDBN} displays pointers to and arrays of
6515 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6516 strings. Single-byte members of a vector are displayed as an integer
6520 For example, to print the program counter in hex (@pxref{Registers}), type
6527 Note that no space is required before the slash; this is because command
6528 names in @value{GDBN} cannot contain a slash.
6530 To reprint the last value in the value history with a different format,
6531 you can use the @code{print} command with just a format and no
6532 expression. For example, @samp{p/x} reprints the last value in hex.
6535 @section Examining Memory
6537 You can use the command @code{x} (for ``examine'') to examine memory in
6538 any of several formats, independently of your program's data types.
6540 @cindex examining memory
6542 @kindex x @r{(examine memory)}
6543 @item x/@var{nfu} @var{addr}
6546 Use the @code{x} command to examine memory.
6549 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6550 much memory to display and how to format it; @var{addr} is an
6551 expression giving the address where you want to start displaying memory.
6552 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6553 Several commands set convenient defaults for @var{addr}.
6556 @item @var{n}, the repeat count
6557 The repeat count is a decimal integer; the default is 1. It specifies
6558 how much memory (counting by units @var{u}) to display.
6559 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6562 @item @var{f}, the display format
6563 The display format is one of the formats used by @code{print}
6564 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6565 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6566 The default is @samp{x} (hexadecimal) initially. The default changes
6567 each time you use either @code{x} or @code{print}.
6569 @item @var{u}, the unit size
6570 The unit size is any of
6576 Halfwords (two bytes).
6578 Words (four bytes). This is the initial default.
6580 Giant words (eight bytes).
6583 Each time you specify a unit size with @code{x}, that size becomes the
6584 default unit the next time you use @code{x}. (For the @samp{s} and
6585 @samp{i} formats, the unit size is ignored and is normally not written.)
6587 @item @var{addr}, starting display address
6588 @var{addr} is the address where you want @value{GDBN} to begin displaying
6589 memory. The expression need not have a pointer value (though it may);
6590 it is always interpreted as an integer address of a byte of memory.
6591 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6592 @var{addr} is usually just after the last address examined---but several
6593 other commands also set the default address: @code{info breakpoints} (to
6594 the address of the last breakpoint listed), @code{info line} (to the
6595 starting address of a line), and @code{print} (if you use it to display
6596 a value from memory).
6599 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6600 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6601 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6602 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6603 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6605 Since the letters indicating unit sizes are all distinct from the
6606 letters specifying output formats, you do not have to remember whether
6607 unit size or format comes first; either order works. The output
6608 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6609 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6611 Even though the unit size @var{u} is ignored for the formats @samp{s}
6612 and @samp{i}, you might still want to use a count @var{n}; for example,
6613 @samp{3i} specifies that you want to see three machine instructions,
6614 including any operands. For convenience, especially when used with
6615 the @code{display} command, the @samp{i} format also prints branch delay
6616 slot instructions, if any, beyond the count specified, which immediately
6617 follow the last instruction that is within the count. The command
6618 @code{disassemble} gives an alternative way of inspecting machine
6619 instructions; see @ref{Machine Code,,Source and Machine Code}.
6621 All the defaults for the arguments to @code{x} are designed to make it
6622 easy to continue scanning memory with minimal specifications each time
6623 you use @code{x}. For example, after you have inspected three machine
6624 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6625 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6626 the repeat count @var{n} is used again; the other arguments default as
6627 for successive uses of @code{x}.
6629 @cindex @code{$_}, @code{$__}, and value history
6630 The addresses and contents printed by the @code{x} command are not saved
6631 in the value history because there is often too much of them and they
6632 would get in the way. Instead, @value{GDBN} makes these values available for
6633 subsequent use in expressions as values of the convenience variables
6634 @code{$_} and @code{$__}. After an @code{x} command, the last address
6635 examined is available for use in expressions in the convenience variable
6636 @code{$_}. The contents of that address, as examined, are available in
6637 the convenience variable @code{$__}.
6639 If the @code{x} command has a repeat count, the address and contents saved
6640 are from the last memory unit printed; this is not the same as the last
6641 address printed if several units were printed on the last line of output.
6643 @cindex remote memory comparison
6644 @cindex verify remote memory image
6645 When you are debugging a program running on a remote target machine
6646 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6647 remote machine's memory against the executable file you downloaded to
6648 the target. The @code{compare-sections} command is provided for such
6652 @kindex compare-sections
6653 @item compare-sections @r{[}@var{section-name}@r{]}
6654 Compare the data of a loadable section @var{section-name} in the
6655 executable file of the program being debugged with the same section in
6656 the remote machine's memory, and report any mismatches. With no
6657 arguments, compares all loadable sections. This command's
6658 availability depends on the target's support for the @code{"qCRC"}
6663 @section Automatic Display
6664 @cindex automatic display
6665 @cindex display of expressions
6667 If you find that you want to print the value of an expression frequently
6668 (to see how it changes), you might want to add it to the @dfn{automatic
6669 display list} so that @value{GDBN} prints its value each time your program stops.
6670 Each expression added to the list is given a number to identify it;
6671 to remove an expression from the list, you specify that number.
6672 The automatic display looks like this:
6676 3: bar[5] = (struct hack *) 0x3804
6680 This display shows item numbers, expressions and their current values. As with
6681 displays you request manually using @code{x} or @code{print}, you can
6682 specify the output format you prefer; in fact, @code{display} decides
6683 whether to use @code{print} or @code{x} depending your format
6684 specification---it uses @code{x} if you specify either the @samp{i}
6685 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6689 @item display @var{expr}
6690 Add the expression @var{expr} to the list of expressions to display
6691 each time your program stops. @xref{Expressions, ,Expressions}.
6693 @code{display} does not repeat if you press @key{RET} again after using it.
6695 @item display/@var{fmt} @var{expr}
6696 For @var{fmt} specifying only a display format and not a size or
6697 count, add the expression @var{expr} to the auto-display list but
6698 arrange to display it each time in the specified format @var{fmt}.
6699 @xref{Output Formats,,Output Formats}.
6701 @item display/@var{fmt} @var{addr}
6702 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6703 number of units, add the expression @var{addr} as a memory address to
6704 be examined each time your program stops. Examining means in effect
6705 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6708 For example, @samp{display/i $pc} can be helpful, to see the machine
6709 instruction about to be executed each time execution stops (@samp{$pc}
6710 is a common name for the program counter; @pxref{Registers, ,Registers}).
6713 @kindex delete display
6715 @item undisplay @var{dnums}@dots{}
6716 @itemx delete display @var{dnums}@dots{}
6717 Remove item numbers @var{dnums} from the list of expressions to display.
6719 @code{undisplay} does not repeat if you press @key{RET} after using it.
6720 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6722 @kindex disable display
6723 @item disable display @var{dnums}@dots{}
6724 Disable the display of item numbers @var{dnums}. A disabled display
6725 item is not printed automatically, but is not forgotten. It may be
6726 enabled again later.
6728 @kindex enable display
6729 @item enable display @var{dnums}@dots{}
6730 Enable display of item numbers @var{dnums}. It becomes effective once
6731 again in auto display of its expression, until you specify otherwise.
6734 Display the current values of the expressions on the list, just as is
6735 done when your program stops.
6737 @kindex info display
6739 Print the list of expressions previously set up to display
6740 automatically, each one with its item number, but without showing the
6741 values. This includes disabled expressions, which are marked as such.
6742 It also includes expressions which would not be displayed right now
6743 because they refer to automatic variables not currently available.
6746 @cindex display disabled out of scope
6747 If a display expression refers to local variables, then it does not make
6748 sense outside the lexical context for which it was set up. Such an
6749 expression is disabled when execution enters a context where one of its
6750 variables is not defined. For example, if you give the command
6751 @code{display last_char} while inside a function with an argument
6752 @code{last_char}, @value{GDBN} displays this argument while your program
6753 continues to stop inside that function. When it stops elsewhere---where
6754 there is no variable @code{last_char}---the display is disabled
6755 automatically. The next time your program stops where @code{last_char}
6756 is meaningful, you can enable the display expression once again.
6758 @node Print Settings
6759 @section Print Settings
6761 @cindex format options
6762 @cindex print settings
6763 @value{GDBN} provides the following ways to control how arrays, structures,
6764 and symbols are printed.
6767 These settings are useful for debugging programs in any language:
6771 @item set print address
6772 @itemx set print address on
6773 @cindex print/don't print memory addresses
6774 @value{GDBN} prints memory addresses showing the location of stack
6775 traces, structure values, pointer values, breakpoints, and so forth,
6776 even when it also displays the contents of those addresses. The default
6777 is @code{on}. For example, this is what a stack frame display looks like with
6778 @code{set print address on}:
6783 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6785 530 if (lquote != def_lquote)
6789 @item set print address off
6790 Do not print addresses when displaying their contents. For example,
6791 this is the same stack frame displayed with @code{set print address off}:
6795 (@value{GDBP}) set print addr off
6797 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6798 530 if (lquote != def_lquote)
6802 You can use @samp{set print address off} to eliminate all machine
6803 dependent displays from the @value{GDBN} interface. For example, with
6804 @code{print address off}, you should get the same text for backtraces on
6805 all machines---whether or not they involve pointer arguments.
6808 @item show print address
6809 Show whether or not addresses are to be printed.
6812 When @value{GDBN} prints a symbolic address, it normally prints the
6813 closest earlier symbol plus an offset. If that symbol does not uniquely
6814 identify the address (for example, it is a name whose scope is a single
6815 source file), you may need to clarify. One way to do this is with
6816 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6817 you can set @value{GDBN} to print the source file and line number when
6818 it prints a symbolic address:
6821 @item set print symbol-filename on
6822 @cindex source file and line of a symbol
6823 @cindex symbol, source file and line
6824 Tell @value{GDBN} to print the source file name and line number of a
6825 symbol in the symbolic form of an address.
6827 @item set print symbol-filename off
6828 Do not print source file name and line number of a symbol. This is the
6831 @item show print symbol-filename
6832 Show whether or not @value{GDBN} will print the source file name and
6833 line number of a symbol in the symbolic form of an address.
6836 Another situation where it is helpful to show symbol filenames and line
6837 numbers is when disassembling code; @value{GDBN} shows you the line
6838 number and source file that corresponds to each instruction.
6840 Also, you may wish to see the symbolic form only if the address being
6841 printed is reasonably close to the closest earlier symbol:
6844 @item set print max-symbolic-offset @var{max-offset}
6845 @cindex maximum value for offset of closest symbol
6846 Tell @value{GDBN} to only display the symbolic form of an address if the
6847 offset between the closest earlier symbol and the address is less than
6848 @var{max-offset}. The default is 0, which tells @value{GDBN}
6849 to always print the symbolic form of an address if any symbol precedes it.
6851 @item show print max-symbolic-offset
6852 Ask how large the maximum offset is that @value{GDBN} prints in a
6856 @cindex wild pointer, interpreting
6857 @cindex pointer, finding referent
6858 If you have a pointer and you are not sure where it points, try
6859 @samp{set print symbol-filename on}. Then you can determine the name
6860 and source file location of the variable where it points, using
6861 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6862 For example, here @value{GDBN} shows that a variable @code{ptt} points
6863 at another variable @code{t}, defined in @file{hi2.c}:
6866 (@value{GDBP}) set print symbol-filename on
6867 (@value{GDBP}) p/a ptt
6868 $4 = 0xe008 <t in hi2.c>
6872 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6873 does not show the symbol name and filename of the referent, even with
6874 the appropriate @code{set print} options turned on.
6877 Other settings control how different kinds of objects are printed:
6880 @item set print array
6881 @itemx set print array on
6882 @cindex pretty print arrays
6883 Pretty print arrays. This format is more convenient to read,
6884 but uses more space. The default is off.
6886 @item set print array off
6887 Return to compressed format for arrays.
6889 @item show print array
6890 Show whether compressed or pretty format is selected for displaying
6893 @cindex print array indexes
6894 @item set print array-indexes
6895 @itemx set print array-indexes on
6896 Print the index of each element when displaying arrays. May be more
6897 convenient to locate a given element in the array or quickly find the
6898 index of a given element in that printed array. The default is off.
6900 @item set print array-indexes off
6901 Stop printing element indexes when displaying arrays.
6903 @item show print array-indexes
6904 Show whether the index of each element is printed when displaying
6907 @item set print elements @var{number-of-elements}
6908 @cindex number of array elements to print
6909 @cindex limit on number of printed array elements
6910 Set a limit on how many elements of an array @value{GDBN} will print.
6911 If @value{GDBN} is printing a large array, it stops printing after it has
6912 printed the number of elements set by the @code{set print elements} command.
6913 This limit also applies to the display of strings.
6914 When @value{GDBN} starts, this limit is set to 200.
6915 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6917 @item show print elements
6918 Display the number of elements of a large array that @value{GDBN} will print.
6919 If the number is 0, then the printing is unlimited.
6921 @item set print frame-arguments @var{value}
6922 @cindex printing frame argument values
6923 @cindex print all frame argument values
6924 @cindex print frame argument values for scalars only
6925 @cindex do not print frame argument values
6926 This command allows to control how the values of arguments are printed
6927 when the debugger prints a frame (@pxref{Frames}). The possible
6932 The values of all arguments are printed. This is the default.
6935 Print the value of an argument only if it is a scalar. The value of more
6936 complex arguments such as arrays, structures, unions, etc, is replaced
6937 by @code{@dots{}}. Here is an example where only scalar arguments are shown:
6940 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
6945 None of the argument values are printed. Instead, the value of each argument
6946 is replaced by @code{@dots{}}. In this case, the example above now becomes:
6949 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
6954 By default, all argument values are always printed. But this command
6955 can be useful in several cases. For instance, it can be used to reduce
6956 the amount of information printed in each frame, making the backtrace
6957 more readable. Also, this command can be used to improve performance
6958 when displaying Ada frames, because the computation of large arguments
6959 can sometimes be CPU-intensive, especiallly in large applications.
6960 Setting @code{print frame-arguments} to @code{scalars} or @code{none}
6961 avoids this computation, thus speeding up the display of each Ada frame.
6963 @item show print frame-arguments
6964 Show how the value of arguments should be displayed when printing a frame.
6966 @item set print repeats
6967 @cindex repeated array elements
6968 Set the threshold for suppressing display of repeated array
6969 elements. When the number of consecutive identical elements of an
6970 array exceeds the threshold, @value{GDBN} prints the string
6971 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6972 identical repetitions, instead of displaying the identical elements
6973 themselves. Setting the threshold to zero will cause all elements to
6974 be individually printed. The default threshold is 10.
6976 @item show print repeats
6977 Display the current threshold for printing repeated identical
6980 @item set print null-stop
6981 @cindex @sc{null} elements in arrays
6982 Cause @value{GDBN} to stop printing the characters of an array when the first
6983 @sc{null} is encountered. This is useful when large arrays actually
6984 contain only short strings.
6987 @item show print null-stop
6988 Show whether @value{GDBN} stops printing an array on the first
6989 @sc{null} character.
6991 @item set print pretty on
6992 @cindex print structures in indented form
6993 @cindex indentation in structure display
6994 Cause @value{GDBN} to print structures in an indented format with one member
6995 per line, like this:
7010 @item set print pretty off
7011 Cause @value{GDBN} to print structures in a compact format, like this:
7015 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7016 meat = 0x54 "Pork"@}
7021 This is the default format.
7023 @item show print pretty
7024 Show which format @value{GDBN} is using to print structures.
7026 @item set print sevenbit-strings on
7027 @cindex eight-bit characters in strings
7028 @cindex octal escapes in strings
7029 Print using only seven-bit characters; if this option is set,
7030 @value{GDBN} displays any eight-bit characters (in strings or
7031 character values) using the notation @code{\}@var{nnn}. This setting is
7032 best if you are working in English (@sc{ascii}) and you use the
7033 high-order bit of characters as a marker or ``meta'' bit.
7035 @item set print sevenbit-strings off
7036 Print full eight-bit characters. This allows the use of more
7037 international character sets, and is the default.
7039 @item show print sevenbit-strings
7040 Show whether or not @value{GDBN} is printing only seven-bit characters.
7042 @item set print union on
7043 @cindex unions in structures, printing
7044 Tell @value{GDBN} to print unions which are contained in structures
7045 and other unions. This is the default setting.
7047 @item set print union off
7048 Tell @value{GDBN} not to print unions which are contained in
7049 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7052 @item show print union
7053 Ask @value{GDBN} whether or not it will print unions which are contained in
7054 structures and other unions.
7056 For example, given the declarations
7059 typedef enum @{Tree, Bug@} Species;
7060 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7061 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7072 struct thing foo = @{Tree, @{Acorn@}@};
7076 with @code{set print union on} in effect @samp{p foo} would print
7079 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7083 and with @code{set print union off} in effect it would print
7086 $1 = @{it = Tree, form = @{...@}@}
7090 @code{set print union} affects programs written in C-like languages
7096 These settings are of interest when debugging C@t{++} programs:
7099 @cindex demangling C@t{++} names
7100 @item set print demangle
7101 @itemx set print demangle on
7102 Print C@t{++} names in their source form rather than in the encoded
7103 (``mangled'') form passed to the assembler and linker for type-safe
7104 linkage. The default is on.
7106 @item show print demangle
7107 Show whether C@t{++} names are printed in mangled or demangled form.
7109 @item set print asm-demangle
7110 @itemx set print asm-demangle on
7111 Print C@t{++} names in their source form rather than their mangled form, even
7112 in assembler code printouts such as instruction disassemblies.
7115 @item show print asm-demangle
7116 Show whether C@t{++} names in assembly listings are printed in mangled
7119 @cindex C@t{++} symbol decoding style
7120 @cindex symbol decoding style, C@t{++}
7121 @kindex set demangle-style
7122 @item set demangle-style @var{style}
7123 Choose among several encoding schemes used by different compilers to
7124 represent C@t{++} names. The choices for @var{style} are currently:
7128 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7131 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7132 This is the default.
7135 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7138 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7141 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7142 @strong{Warning:} this setting alone is not sufficient to allow
7143 debugging @code{cfront}-generated executables. @value{GDBN} would
7144 require further enhancement to permit that.
7147 If you omit @var{style}, you will see a list of possible formats.
7149 @item show demangle-style
7150 Display the encoding style currently in use for decoding C@t{++} symbols.
7152 @item set print object
7153 @itemx set print object on
7154 @cindex derived type of an object, printing
7155 @cindex display derived types
7156 When displaying a pointer to an object, identify the @emph{actual}
7157 (derived) type of the object rather than the @emph{declared} type, using
7158 the virtual function table.
7160 @item set print object off
7161 Display only the declared type of objects, without reference to the
7162 virtual function table. This is the default setting.
7164 @item show print object
7165 Show whether actual, or declared, object types are displayed.
7167 @item set print static-members
7168 @itemx set print static-members on
7169 @cindex static members of C@t{++} objects
7170 Print static members when displaying a C@t{++} object. The default is on.
7172 @item set print static-members off
7173 Do not print static members when displaying a C@t{++} object.
7175 @item show print static-members
7176 Show whether C@t{++} static members are printed or not.
7178 @item set print pascal_static-members
7179 @itemx set print pascal_static-members on
7180 @cindex static members of Pascal objects
7181 @cindex Pascal objects, static members display
7182 Print static members when displaying a Pascal object. The default is on.
7184 @item set print pascal_static-members off
7185 Do not print static members when displaying a Pascal object.
7187 @item show print pascal_static-members
7188 Show whether Pascal static members are printed or not.
7190 @c These don't work with HP ANSI C++ yet.
7191 @item set print vtbl
7192 @itemx set print vtbl on
7193 @cindex pretty print C@t{++} virtual function tables
7194 @cindex virtual functions (C@t{++}) display
7195 @cindex VTBL display
7196 Pretty print C@t{++} virtual function tables. The default is off.
7197 (The @code{vtbl} commands do not work on programs compiled with the HP
7198 ANSI C@t{++} compiler (@code{aCC}).)
7200 @item set print vtbl off
7201 Do not pretty print C@t{++} virtual function tables.
7203 @item show print vtbl
7204 Show whether C@t{++} virtual function tables are pretty printed, or not.
7208 @section Value History
7210 @cindex value history
7211 @cindex history of values printed by @value{GDBN}
7212 Values printed by the @code{print} command are saved in the @value{GDBN}
7213 @dfn{value history}. This allows you to refer to them in other expressions.
7214 Values are kept until the symbol table is re-read or discarded
7215 (for example with the @code{file} or @code{symbol-file} commands).
7216 When the symbol table changes, the value history is discarded,
7217 since the values may contain pointers back to the types defined in the
7222 @cindex history number
7223 The values printed are given @dfn{history numbers} by which you can
7224 refer to them. These are successive integers starting with one.
7225 @code{print} shows you the history number assigned to a value by
7226 printing @samp{$@var{num} = } before the value; here @var{num} is the
7229 To refer to any previous value, use @samp{$} followed by the value's
7230 history number. The way @code{print} labels its output is designed to
7231 remind you of this. Just @code{$} refers to the most recent value in
7232 the history, and @code{$$} refers to the value before that.
7233 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7234 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7235 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7237 For example, suppose you have just printed a pointer to a structure and
7238 want to see the contents of the structure. It suffices to type
7244 If you have a chain of structures where the component @code{next} points
7245 to the next one, you can print the contents of the next one with this:
7252 You can print successive links in the chain by repeating this
7253 command---which you can do by just typing @key{RET}.
7255 Note that the history records values, not expressions. If the value of
7256 @code{x} is 4 and you type these commands:
7264 then the value recorded in the value history by the @code{print} command
7265 remains 4 even though the value of @code{x} has changed.
7270 Print the last ten values in the value history, with their item numbers.
7271 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7272 values} does not change the history.
7274 @item show values @var{n}
7275 Print ten history values centered on history item number @var{n}.
7278 Print ten history values just after the values last printed. If no more
7279 values are available, @code{show values +} produces no display.
7282 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7283 same effect as @samp{show values +}.
7285 @node Convenience Vars
7286 @section Convenience Variables
7288 @cindex convenience variables
7289 @cindex user-defined variables
7290 @value{GDBN} provides @dfn{convenience variables} that you can use within
7291 @value{GDBN} to hold on to a value and refer to it later. These variables
7292 exist entirely within @value{GDBN}; they are not part of your program, and
7293 setting a convenience variable has no direct effect on further execution
7294 of your program. That is why you can use them freely.
7296 Convenience variables are prefixed with @samp{$}. Any name preceded by
7297 @samp{$} can be used for a convenience variable, unless it is one of
7298 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7299 (Value history references, in contrast, are @emph{numbers} preceded
7300 by @samp{$}. @xref{Value History, ,Value History}.)
7302 You can save a value in a convenience variable with an assignment
7303 expression, just as you would set a variable in your program.
7307 set $foo = *object_ptr
7311 would save in @code{$foo} the value contained in the object pointed to by
7314 Using a convenience variable for the first time creates it, but its
7315 value is @code{void} until you assign a new value. You can alter the
7316 value with another assignment at any time.
7318 Convenience variables have no fixed types. You can assign a convenience
7319 variable any type of value, including structures and arrays, even if
7320 that variable already has a value of a different type. The convenience
7321 variable, when used as an expression, has the type of its current value.
7324 @kindex show convenience
7325 @cindex show all user variables
7326 @item show convenience
7327 Print a list of convenience variables used so far, and their values.
7328 Abbreviated @code{show conv}.
7330 @kindex init-if-undefined
7331 @cindex convenience variables, initializing
7332 @item init-if-undefined $@var{variable} = @var{expression}
7333 Set a convenience variable if it has not already been set. This is useful
7334 for user-defined commands that keep some state. It is similar, in concept,
7335 to using local static variables with initializers in C (except that
7336 convenience variables are global). It can also be used to allow users to
7337 override default values used in a command script.
7339 If the variable is already defined then the expression is not evaluated so
7340 any side-effects do not occur.
7343 One of the ways to use a convenience variable is as a counter to be
7344 incremented or a pointer to be advanced. For example, to print
7345 a field from successive elements of an array of structures:
7349 print bar[$i++]->contents
7353 Repeat that command by typing @key{RET}.
7355 Some convenience variables are created automatically by @value{GDBN} and given
7356 values likely to be useful.
7359 @vindex $_@r{, convenience variable}
7361 The variable @code{$_} is automatically set by the @code{x} command to
7362 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7363 commands which provide a default address for @code{x} to examine also
7364 set @code{$_} to that address; these commands include @code{info line}
7365 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7366 except when set by the @code{x} command, in which case it is a pointer
7367 to the type of @code{$__}.
7369 @vindex $__@r{, convenience variable}
7371 The variable @code{$__} is automatically set by the @code{x} command
7372 to the value found in the last address examined. Its type is chosen
7373 to match the format in which the data was printed.
7376 @vindex $_exitcode@r{, convenience variable}
7377 The variable @code{$_exitcode} is automatically set to the exit code when
7378 the program being debugged terminates.
7381 On HP-UX systems, if you refer to a function or variable name that
7382 begins with a dollar sign, @value{GDBN} searches for a user or system
7383 name first, before it searches for a convenience variable.
7389 You can refer to machine register contents, in expressions, as variables
7390 with names starting with @samp{$}. The names of registers are different
7391 for each machine; use @code{info registers} to see the names used on
7395 @kindex info registers
7396 @item info registers
7397 Print the names and values of all registers except floating-point
7398 and vector registers (in the selected stack frame).
7400 @kindex info all-registers
7401 @cindex floating point registers
7402 @item info all-registers
7403 Print the names and values of all registers, including floating-point
7404 and vector registers (in the selected stack frame).
7406 @item info registers @var{regname} @dots{}
7407 Print the @dfn{relativized} value of each specified register @var{regname}.
7408 As discussed in detail below, register values are normally relative to
7409 the selected stack frame. @var{regname} may be any register name valid on
7410 the machine you are using, with or without the initial @samp{$}.
7413 @cindex stack pointer register
7414 @cindex program counter register
7415 @cindex process status register
7416 @cindex frame pointer register
7417 @cindex standard registers
7418 @value{GDBN} has four ``standard'' register names that are available (in
7419 expressions) on most machines---whenever they do not conflict with an
7420 architecture's canonical mnemonics for registers. The register names
7421 @code{$pc} and @code{$sp} are used for the program counter register and
7422 the stack pointer. @code{$fp} is used for a register that contains a
7423 pointer to the current stack frame, and @code{$ps} is used for a
7424 register that contains the processor status. For example,
7425 you could print the program counter in hex with
7432 or print the instruction to be executed next with
7439 or add four to the stack pointer@footnote{This is a way of removing
7440 one word from the stack, on machines where stacks grow downward in
7441 memory (most machines, nowadays). This assumes that the innermost
7442 stack frame is selected; setting @code{$sp} is not allowed when other
7443 stack frames are selected. To pop entire frames off the stack,
7444 regardless of machine architecture, use @code{return};
7445 see @ref{Returning, ,Returning from a Function}.} with
7451 Whenever possible, these four standard register names are available on
7452 your machine even though the machine has different canonical mnemonics,
7453 so long as there is no conflict. The @code{info registers} command
7454 shows the canonical names. For example, on the SPARC, @code{info
7455 registers} displays the processor status register as @code{$psr} but you
7456 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7457 is an alias for the @sc{eflags} register.
7459 @value{GDBN} always considers the contents of an ordinary register as an
7460 integer when the register is examined in this way. Some machines have
7461 special registers which can hold nothing but floating point; these
7462 registers are considered to have floating point values. There is no way
7463 to refer to the contents of an ordinary register as floating point value
7464 (although you can @emph{print} it as a floating point value with
7465 @samp{print/f $@var{regname}}).
7467 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7468 means that the data format in which the register contents are saved by
7469 the operating system is not the same one that your program normally
7470 sees. For example, the registers of the 68881 floating point
7471 coprocessor are always saved in ``extended'' (raw) format, but all C
7472 programs expect to work with ``double'' (virtual) format. In such
7473 cases, @value{GDBN} normally works with the virtual format only (the format
7474 that makes sense for your program), but the @code{info registers} command
7475 prints the data in both formats.
7477 @cindex SSE registers (x86)
7478 @cindex MMX registers (x86)
7479 Some machines have special registers whose contents can be interpreted
7480 in several different ways. For example, modern x86-based machines
7481 have SSE and MMX registers that can hold several values packed
7482 together in several different formats. @value{GDBN} refers to such
7483 registers in @code{struct} notation:
7486 (@value{GDBP}) print $xmm1
7488 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7489 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7490 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7491 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7492 v4_int32 = @{0, 20657912, 11, 13@},
7493 v2_int64 = @{88725056443645952, 55834574859@},
7494 uint128 = 0x0000000d0000000b013b36f800000000
7499 To set values of such registers, you need to tell @value{GDBN} which
7500 view of the register you wish to change, as if you were assigning
7501 value to a @code{struct} member:
7504 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7507 Normally, register values are relative to the selected stack frame
7508 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7509 value that the register would contain if all stack frames farther in
7510 were exited and their saved registers restored. In order to see the
7511 true contents of hardware registers, you must select the innermost
7512 frame (with @samp{frame 0}).
7514 However, @value{GDBN} must deduce where registers are saved, from the machine
7515 code generated by your compiler. If some registers are not saved, or if
7516 @value{GDBN} is unable to locate the saved registers, the selected stack
7517 frame makes no difference.
7519 @node Floating Point Hardware
7520 @section Floating Point Hardware
7521 @cindex floating point
7523 Depending on the configuration, @value{GDBN} may be able to give
7524 you more information about the status of the floating point hardware.
7529 Display hardware-dependent information about the floating
7530 point unit. The exact contents and layout vary depending on the
7531 floating point chip. Currently, @samp{info float} is supported on
7532 the ARM and x86 machines.
7536 @section Vector Unit
7539 Depending on the configuration, @value{GDBN} may be able to give you
7540 more information about the status of the vector unit.
7545 Display information about the vector unit. The exact contents and
7546 layout vary depending on the hardware.
7549 @node OS Information
7550 @section Operating System Auxiliary Information
7551 @cindex OS information
7553 @value{GDBN} provides interfaces to useful OS facilities that can help
7554 you debug your program.
7556 @cindex @code{ptrace} system call
7557 @cindex @code{struct user} contents
7558 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7559 machines), it interfaces with the inferior via the @code{ptrace}
7560 system call. The operating system creates a special sata structure,
7561 called @code{struct user}, for this interface. You can use the
7562 command @code{info udot} to display the contents of this data
7568 Display the contents of the @code{struct user} maintained by the OS
7569 kernel for the program being debugged. @value{GDBN} displays the
7570 contents of @code{struct user} as a list of hex numbers, similar to
7571 the @code{examine} command.
7574 @cindex auxiliary vector
7575 @cindex vector, auxiliary
7576 Some operating systems supply an @dfn{auxiliary vector} to programs at
7577 startup. This is akin to the arguments and environment that you
7578 specify for a program, but contains a system-dependent variety of
7579 binary values that tell system libraries important details about the
7580 hardware, operating system, and process. Each value's purpose is
7581 identified by an integer tag; the meanings are well-known but system-specific.
7582 Depending on the configuration and operating system facilities,
7583 @value{GDBN} may be able to show you this information. For remote
7584 targets, this functionality may further depend on the remote stub's
7585 support of the @samp{qXfer:auxv:read} packet, see
7586 @ref{qXfer auxiliary vector read}.
7591 Display the auxiliary vector of the inferior, which can be either a
7592 live process or a core dump file. @value{GDBN} prints each tag value
7593 numerically, and also shows names and text descriptions for recognized
7594 tags. Some values in the vector are numbers, some bit masks, and some
7595 pointers to strings or other data. @value{GDBN} displays each value in the
7596 most appropriate form for a recognized tag, and in hexadecimal for
7597 an unrecognized tag.
7600 On some targets, @value{GDBN} can access operating-system-specific information
7601 and display it to user, without interpretation. For remote targets,
7602 this functionality depends on the remote stub's support of the
7603 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7606 @kindex info os processes
7607 @item info os processes
7608 Display the list of processes on the target. For each process,
7609 @value{GDBN} prints the process identifier, the name of the user, and
7610 the command corresponding to the process.
7613 @node Memory Region Attributes
7614 @section Memory Region Attributes
7615 @cindex memory region attributes
7617 @dfn{Memory region attributes} allow you to describe special handling
7618 required by regions of your target's memory. @value{GDBN} uses
7619 attributes to determine whether to allow certain types of memory
7620 accesses; whether to use specific width accesses; and whether to cache
7621 target memory. By default the description of memory regions is
7622 fetched from the target (if the current target supports this), but the
7623 user can override the fetched regions.
7625 Defined memory regions can be individually enabled and disabled. When a
7626 memory region is disabled, @value{GDBN} uses the default attributes when
7627 accessing memory in that region. Similarly, if no memory regions have
7628 been defined, @value{GDBN} uses the default attributes when accessing
7631 When a memory region is defined, it is given a number to identify it;
7632 to enable, disable, or remove a memory region, you specify that number.
7636 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7637 Define a memory region bounded by @var{lower} and @var{upper} with
7638 attributes @var{attributes}@dots{}, and add it to the list of regions
7639 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7640 case: it is treated as the target's maximum memory address.
7641 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7644 Discard any user changes to the memory regions and use target-supplied
7645 regions, if available, or no regions if the target does not support.
7648 @item delete mem @var{nums}@dots{}
7649 Remove memory regions @var{nums}@dots{} from the list of regions
7650 monitored by @value{GDBN}.
7653 @item disable mem @var{nums}@dots{}
7654 Disable monitoring of memory regions @var{nums}@dots{}.
7655 A disabled memory region is not forgotten.
7656 It may be enabled again later.
7659 @item enable mem @var{nums}@dots{}
7660 Enable monitoring of memory regions @var{nums}@dots{}.
7664 Print a table of all defined memory regions, with the following columns
7668 @item Memory Region Number
7669 @item Enabled or Disabled.
7670 Enabled memory regions are marked with @samp{y}.
7671 Disabled memory regions are marked with @samp{n}.
7674 The address defining the inclusive lower bound of the memory region.
7677 The address defining the exclusive upper bound of the memory region.
7680 The list of attributes set for this memory region.
7685 @subsection Attributes
7687 @subsubsection Memory Access Mode
7688 The access mode attributes set whether @value{GDBN} may make read or
7689 write accesses to a memory region.
7691 While these attributes prevent @value{GDBN} from performing invalid
7692 memory accesses, they do nothing to prevent the target system, I/O DMA,
7693 etc.@: from accessing memory.
7697 Memory is read only.
7699 Memory is write only.
7701 Memory is read/write. This is the default.
7704 @subsubsection Memory Access Size
7705 The access size attribute tells @value{GDBN} to use specific sized
7706 accesses in the memory region. Often memory mapped device registers
7707 require specific sized accesses. If no access size attribute is
7708 specified, @value{GDBN} may use accesses of any size.
7712 Use 8 bit memory accesses.
7714 Use 16 bit memory accesses.
7716 Use 32 bit memory accesses.
7718 Use 64 bit memory accesses.
7721 @c @subsubsection Hardware/Software Breakpoints
7722 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7723 @c will use hardware or software breakpoints for the internal breakpoints
7724 @c used by the step, next, finish, until, etc. commands.
7728 @c Always use hardware breakpoints
7729 @c @item swbreak (default)
7732 @subsubsection Data Cache
7733 The data cache attributes set whether @value{GDBN} will cache target
7734 memory. While this generally improves performance by reducing debug
7735 protocol overhead, it can lead to incorrect results because @value{GDBN}
7736 does not know about volatile variables or memory mapped device
7741 Enable @value{GDBN} to cache target memory.
7743 Disable @value{GDBN} from caching target memory. This is the default.
7746 @subsection Memory Access Checking
7747 @value{GDBN} can be instructed to refuse accesses to memory that is
7748 not explicitly described. This can be useful if accessing such
7749 regions has undesired effects for a specific target, or to provide
7750 better error checking. The following commands control this behaviour.
7753 @kindex set mem inaccessible-by-default
7754 @item set mem inaccessible-by-default [on|off]
7755 If @code{on} is specified, make @value{GDBN} treat memory not
7756 explicitly described by the memory ranges as non-existent and refuse accesses
7757 to such memory. The checks are only performed if there's at least one
7758 memory range defined. If @code{off} is specified, make @value{GDBN}
7759 treat the memory not explicitly described by the memory ranges as RAM.
7760 The default value is @code{on}.
7761 @kindex show mem inaccessible-by-default
7762 @item show mem inaccessible-by-default
7763 Show the current handling of accesses to unknown memory.
7767 @c @subsubsection Memory Write Verification
7768 @c The memory write verification attributes set whether @value{GDBN}
7769 @c will re-reads data after each write to verify the write was successful.
7773 @c @item noverify (default)
7776 @node Dump/Restore Files
7777 @section Copy Between Memory and a File
7778 @cindex dump/restore files
7779 @cindex append data to a file
7780 @cindex dump data to a file
7781 @cindex restore data from a file
7783 You can use the commands @code{dump}, @code{append}, and
7784 @code{restore} to copy data between target memory and a file. The
7785 @code{dump} and @code{append} commands write data to a file, and the
7786 @code{restore} command reads data from a file back into the inferior's
7787 memory. Files may be in binary, Motorola S-record, Intel hex, or
7788 Tektronix Hex format; however, @value{GDBN} can only append to binary
7794 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7795 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7796 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7797 or the value of @var{expr}, to @var{filename} in the given format.
7799 The @var{format} parameter may be any one of:
7806 Motorola S-record format.
7808 Tektronix Hex format.
7811 @value{GDBN} uses the same definitions of these formats as the
7812 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7813 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7817 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7818 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7819 Append the contents of memory from @var{start_addr} to @var{end_addr},
7820 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7821 (@value{GDBN} can only append data to files in raw binary form.)
7824 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7825 Restore the contents of file @var{filename} into memory. The
7826 @code{restore} command can automatically recognize any known @sc{bfd}
7827 file format, except for raw binary. To restore a raw binary file you
7828 must specify the optional keyword @code{binary} after the filename.
7830 If @var{bias} is non-zero, its value will be added to the addresses
7831 contained in the file. Binary files always start at address zero, so
7832 they will be restored at address @var{bias}. Other bfd files have
7833 a built-in location; they will be restored at offset @var{bias}
7836 If @var{start} and/or @var{end} are non-zero, then only data between
7837 file offset @var{start} and file offset @var{end} will be restored.
7838 These offsets are relative to the addresses in the file, before
7839 the @var{bias} argument is applied.
7843 @node Core File Generation
7844 @section How to Produce a Core File from Your Program
7845 @cindex dump core from inferior
7847 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7848 image of a running process and its process status (register values
7849 etc.). Its primary use is post-mortem debugging of a program that
7850 crashed while it ran outside a debugger. A program that crashes
7851 automatically produces a core file, unless this feature is disabled by
7852 the user. @xref{Files}, for information on invoking @value{GDBN} in
7853 the post-mortem debugging mode.
7855 Occasionally, you may wish to produce a core file of the program you
7856 are debugging in order to preserve a snapshot of its state.
7857 @value{GDBN} has a special command for that.
7861 @kindex generate-core-file
7862 @item generate-core-file [@var{file}]
7863 @itemx gcore [@var{file}]
7864 Produce a core dump of the inferior process. The optional argument
7865 @var{file} specifies the file name where to put the core dump. If not
7866 specified, the file name defaults to @file{core.@var{pid}}, where
7867 @var{pid} is the inferior process ID.
7869 Note that this command is implemented only for some systems (as of
7870 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7873 @node Character Sets
7874 @section Character Sets
7875 @cindex character sets
7877 @cindex translating between character sets
7878 @cindex host character set
7879 @cindex target character set
7881 If the program you are debugging uses a different character set to
7882 represent characters and strings than the one @value{GDBN} uses itself,
7883 @value{GDBN} can automatically translate between the character sets for
7884 you. The character set @value{GDBN} uses we call the @dfn{host
7885 character set}; the one the inferior program uses we call the
7886 @dfn{target character set}.
7888 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7889 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7890 remote protocol (@pxref{Remote Debugging}) to debug a program
7891 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7892 then the host character set is Latin-1, and the target character set is
7893 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7894 target-charset EBCDIC-US}, then @value{GDBN} translates between
7895 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7896 character and string literals in expressions.
7898 @value{GDBN} has no way to automatically recognize which character set
7899 the inferior program uses; you must tell it, using the @code{set
7900 target-charset} command, described below.
7902 Here are the commands for controlling @value{GDBN}'s character set
7906 @item set target-charset @var{charset}
7907 @kindex set target-charset
7908 Set the current target character set to @var{charset}. We list the
7909 character set names @value{GDBN} recognizes below, but if you type
7910 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7911 list the target character sets it supports.
7915 @item set host-charset @var{charset}
7916 @kindex set host-charset
7917 Set the current host character set to @var{charset}.
7919 By default, @value{GDBN} uses a host character set appropriate to the
7920 system it is running on; you can override that default using the
7921 @code{set host-charset} command.
7923 @value{GDBN} can only use certain character sets as its host character
7924 set. We list the character set names @value{GDBN} recognizes below, and
7925 indicate which can be host character sets, but if you type
7926 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7927 list the host character sets it supports.
7929 @item set charset @var{charset}
7931 Set the current host and target character sets to @var{charset}. As
7932 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7933 @value{GDBN} will list the name of the character sets that can be used
7934 for both host and target.
7938 @kindex show charset
7939 Show the names of the current host and target charsets.
7941 @itemx show host-charset
7942 @kindex show host-charset
7943 Show the name of the current host charset.
7945 @itemx show target-charset
7946 @kindex show target-charset
7947 Show the name of the current target charset.
7951 @value{GDBN} currently includes support for the following character
7957 @cindex ASCII character set
7958 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7962 @cindex ISO 8859-1 character set
7963 @cindex ISO Latin 1 character set
7964 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7965 characters needed for French, German, and Spanish. @value{GDBN} can use
7966 this as its host character set.
7970 @cindex EBCDIC character set
7971 @cindex IBM1047 character set
7972 Variants of the @sc{ebcdic} character set, used on some of IBM's
7973 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7974 @value{GDBN} cannot use these as its host character set.
7978 Note that these are all single-byte character sets. More work inside
7979 @value{GDBN} is needed to support multi-byte or variable-width character
7980 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7982 Here is an example of @value{GDBN}'s character set support in action.
7983 Assume that the following source code has been placed in the file
7984 @file{charset-test.c}:
7990 = @{72, 101, 108, 108, 111, 44, 32, 119,
7991 111, 114, 108, 100, 33, 10, 0@};
7992 char ibm1047_hello[]
7993 = @{200, 133, 147, 147, 150, 107, 64, 166,
7994 150, 153, 147, 132, 90, 37, 0@};
7998 printf ("Hello, world!\n");
8002 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8003 containing the string @samp{Hello, world!} followed by a newline,
8004 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8006 We compile the program, and invoke the debugger on it:
8009 $ gcc -g charset-test.c -o charset-test
8010 $ gdb -nw charset-test
8011 GNU gdb 2001-12-19-cvs
8012 Copyright 2001 Free Software Foundation, Inc.
8017 We can use the @code{show charset} command to see what character sets
8018 @value{GDBN} is currently using to interpret and display characters and
8022 (@value{GDBP}) show charset
8023 The current host and target character set is `ISO-8859-1'.
8027 For the sake of printing this manual, let's use @sc{ascii} as our
8028 initial character set:
8030 (@value{GDBP}) set charset ASCII
8031 (@value{GDBP}) show charset
8032 The current host and target character set is `ASCII'.
8036 Let's assume that @sc{ascii} is indeed the correct character set for our
8037 host system --- in other words, let's assume that if @value{GDBN} prints
8038 characters using the @sc{ascii} character set, our terminal will display
8039 them properly. Since our current target character set is also
8040 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8043 (@value{GDBP}) print ascii_hello
8044 $1 = 0x401698 "Hello, world!\n"
8045 (@value{GDBP}) print ascii_hello[0]
8050 @value{GDBN} uses the target character set for character and string
8051 literals you use in expressions:
8054 (@value{GDBP}) print '+'
8059 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8062 @value{GDBN} relies on the user to tell it which character set the
8063 target program uses. If we print @code{ibm1047_hello} while our target
8064 character set is still @sc{ascii}, we get jibberish:
8067 (@value{GDBP}) print ibm1047_hello
8068 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8069 (@value{GDBP}) print ibm1047_hello[0]
8074 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8075 @value{GDBN} tells us the character sets it supports:
8078 (@value{GDBP}) set target-charset
8079 ASCII EBCDIC-US IBM1047 ISO-8859-1
8080 (@value{GDBP}) set target-charset
8083 We can select @sc{ibm1047} as our target character set, and examine the
8084 program's strings again. Now the @sc{ascii} string is wrong, but
8085 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8086 target character set, @sc{ibm1047}, to the host character set,
8087 @sc{ascii}, and they display correctly:
8090 (@value{GDBP}) set target-charset IBM1047
8091 (@value{GDBP}) show charset
8092 The current host character set is `ASCII'.
8093 The current target character set is `IBM1047'.
8094 (@value{GDBP}) print ascii_hello
8095 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8096 (@value{GDBP}) print ascii_hello[0]
8098 (@value{GDBP}) print ibm1047_hello
8099 $8 = 0x4016a8 "Hello, world!\n"
8100 (@value{GDBP}) print ibm1047_hello[0]
8105 As above, @value{GDBN} uses the target character set for character and
8106 string literals you use in expressions:
8109 (@value{GDBP}) print '+'
8114 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8117 @node Caching Remote Data
8118 @section Caching Data of Remote Targets
8119 @cindex caching data of remote targets
8121 @value{GDBN} can cache data exchanged between the debugger and a
8122 remote target (@pxref{Remote Debugging}). Such caching generally improves
8123 performance, because it reduces the overhead of the remote protocol by
8124 bundling memory reads and writes into large chunks. Unfortunately,
8125 @value{GDBN} does not currently know anything about volatile
8126 registers, and thus data caching will produce incorrect results when
8127 volatile registers are in use.
8130 @kindex set remotecache
8131 @item set remotecache on
8132 @itemx set remotecache off
8133 Set caching state for remote targets. When @code{ON}, use data
8134 caching. By default, this option is @code{OFF}.
8136 @kindex show remotecache
8137 @item show remotecache
8138 Show the current state of data caching for remote targets.
8142 Print the information about the data cache performance. The
8143 information displayed includes: the dcache width and depth; and for
8144 each cache line, how many times it was referenced, and its data and
8145 state (invalid, dirty, valid). This command is useful for debugging
8146 the data cache operation.
8149 @node Searching Memory
8150 @section Search Memory
8151 @cindex searching memory
8153 Memory can be searched for a particular sequence of bytes with the
8154 @code{find} command.
8158 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8159 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8160 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8161 etc. The search begins at address @var{start_addr} and continues for either
8162 @var{len} bytes or through to @var{end_addr} inclusive.
8165 @var{s} and @var{n} are optional parameters.
8166 They may be specified in either order, apart or together.
8169 @item @var{s}, search query size
8170 The size of each search query value.
8176 halfwords (two bytes)
8180 giant words (eight bytes)
8183 All values are interpreted in the current language.
8184 This means, for example, that if the current source language is C/C@t{++}
8185 then searching for the string ``hello'' includes the trailing '\0'.
8187 If the value size is not specified, it is taken from the
8188 value's type in the current language.
8189 This is useful when one wants to specify the search
8190 pattern as a mixture of types.
8191 Note that this means, for example, that in the case of C-like languages
8192 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8193 which is typically four bytes.
8195 @item @var{n}, maximum number of finds
8196 The maximum number of matches to print. The default is to print all finds.
8199 You can use strings as search values. Quote them with double-quotes
8201 The string value is copied into the search pattern byte by byte,
8202 regardless of the endianness of the target and the size specification.
8204 The address of each match found is printed as well as a count of the
8205 number of matches found.
8207 The address of the last value found is stored in convenience variable
8209 A count of the number of matches is stored in @samp{$numfound}.
8211 For example, if stopped at the @code{printf} in this function:
8217 static char hello[] = "hello-hello";
8218 static struct @{ char c; short s; int i; @}
8219 __attribute__ ((packed)) mixed
8220 = @{ 'c', 0x1234, 0x87654321 @};
8221 printf ("%s\n", hello);
8226 you get during debugging:
8229 (gdb) find &hello[0], +sizeof(hello), "hello"
8230 0x804956d <hello.1620+6>
8232 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8233 0x8049567 <hello.1620>
8234 0x804956d <hello.1620+6>
8236 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8237 0x8049567 <hello.1620>
8239 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8240 0x8049560 <mixed.1625>
8242 (gdb) print $numfound
8245 $2 = (void *) 0x8049560
8249 @chapter C Preprocessor Macros
8251 Some languages, such as C and C@t{++}, provide a way to define and invoke
8252 ``preprocessor macros'' which expand into strings of tokens.
8253 @value{GDBN} can evaluate expressions containing macro invocations, show
8254 the result of macro expansion, and show a macro's definition, including
8255 where it was defined.
8257 You may need to compile your program specially to provide @value{GDBN}
8258 with information about preprocessor macros. Most compilers do not
8259 include macros in their debugging information, even when you compile
8260 with the @option{-g} flag. @xref{Compilation}.
8262 A program may define a macro at one point, remove that definition later,
8263 and then provide a different definition after that. Thus, at different
8264 points in the program, a macro may have different definitions, or have
8265 no definition at all. If there is a current stack frame, @value{GDBN}
8266 uses the macros in scope at that frame's source code line. Otherwise,
8267 @value{GDBN} uses the macros in scope at the current listing location;
8270 Whenever @value{GDBN} evaluates an expression, it always expands any
8271 macro invocations present in the expression. @value{GDBN} also provides
8272 the following commands for working with macros explicitly.
8276 @kindex macro expand
8277 @cindex macro expansion, showing the results of preprocessor
8278 @cindex preprocessor macro expansion, showing the results of
8279 @cindex expanding preprocessor macros
8280 @item macro expand @var{expression}
8281 @itemx macro exp @var{expression}
8282 Show the results of expanding all preprocessor macro invocations in
8283 @var{expression}. Since @value{GDBN} simply expands macros, but does
8284 not parse the result, @var{expression} need not be a valid expression;
8285 it can be any string of tokens.
8288 @item macro expand-once @var{expression}
8289 @itemx macro exp1 @var{expression}
8290 @cindex expand macro once
8291 @i{(This command is not yet implemented.)} Show the results of
8292 expanding those preprocessor macro invocations that appear explicitly in
8293 @var{expression}. Macro invocations appearing in that expansion are
8294 left unchanged. This command allows you to see the effect of a
8295 particular macro more clearly, without being confused by further
8296 expansions. Since @value{GDBN} simply expands macros, but does not
8297 parse the result, @var{expression} need not be a valid expression; it
8298 can be any string of tokens.
8301 @cindex macro definition, showing
8302 @cindex definition, showing a macro's
8303 @item info macro @var{macro}
8304 Show the definition of the macro named @var{macro}, and describe the
8305 source location where that definition was established.
8307 @kindex macro define
8308 @cindex user-defined macros
8309 @cindex defining macros interactively
8310 @cindex macros, user-defined
8311 @item macro define @var{macro} @var{replacement-list}
8312 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8313 Introduce a definition for a preprocessor macro named @var{macro},
8314 invocations of which are replaced by the tokens given in
8315 @var{replacement-list}. The first form of this command defines an
8316 ``object-like'' macro, which takes no arguments; the second form
8317 defines a ``function-like'' macro, which takes the arguments given in
8320 A definition introduced by this command is in scope in every
8321 expression evaluated in @value{GDBN}, until it is removed with the
8322 @code{macro undef} command, described below. The definition overrides
8323 all definitions for @var{macro} present in the program being debugged,
8324 as well as any previous user-supplied definition.
8327 @item macro undef @var{macro}
8328 Remove any user-supplied definition for the macro named @var{macro}.
8329 This command only affects definitions provided with the @code{macro
8330 define} command, described above; it cannot remove definitions present
8331 in the program being debugged.
8335 List all the macros defined using the @code{macro define} command.
8338 @cindex macros, example of debugging with
8339 Here is a transcript showing the above commands in action. First, we
8340 show our source files:
8348 #define ADD(x) (M + x)
8353 printf ("Hello, world!\n");
8355 printf ("We're so creative.\n");
8357 printf ("Goodbye, world!\n");
8364 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8365 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8366 compiler includes information about preprocessor macros in the debugging
8370 $ gcc -gdwarf-2 -g3 sample.c -o sample
8374 Now, we start @value{GDBN} on our sample program:
8378 GNU gdb 2002-05-06-cvs
8379 Copyright 2002 Free Software Foundation, Inc.
8380 GDB is free software, @dots{}
8384 We can expand macros and examine their definitions, even when the
8385 program is not running. @value{GDBN} uses the current listing position
8386 to decide which macro definitions are in scope:
8389 (@value{GDBP}) list main
8392 5 #define ADD(x) (M + x)
8397 10 printf ("Hello, world!\n");
8399 12 printf ("We're so creative.\n");
8400 (@value{GDBP}) info macro ADD
8401 Defined at /home/jimb/gdb/macros/play/sample.c:5
8402 #define ADD(x) (M + x)
8403 (@value{GDBP}) info macro Q
8404 Defined at /home/jimb/gdb/macros/play/sample.h:1
8405 included at /home/jimb/gdb/macros/play/sample.c:2
8407 (@value{GDBP}) macro expand ADD(1)
8408 expands to: (42 + 1)
8409 (@value{GDBP}) macro expand-once ADD(1)
8410 expands to: once (M + 1)
8414 In the example above, note that @code{macro expand-once} expands only
8415 the macro invocation explicit in the original text --- the invocation of
8416 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8417 which was introduced by @code{ADD}.
8419 Once the program is running, @value{GDBN} uses the macro definitions in
8420 force at the source line of the current stack frame:
8423 (@value{GDBP}) break main
8424 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8426 Starting program: /home/jimb/gdb/macros/play/sample
8428 Breakpoint 1, main () at sample.c:10
8429 10 printf ("Hello, world!\n");
8433 At line 10, the definition of the macro @code{N} at line 9 is in force:
8436 (@value{GDBP}) info macro N
8437 Defined at /home/jimb/gdb/macros/play/sample.c:9
8439 (@value{GDBP}) macro expand N Q M
8441 (@value{GDBP}) print N Q M
8446 As we step over directives that remove @code{N}'s definition, and then
8447 give it a new definition, @value{GDBN} finds the definition (or lack
8448 thereof) in force at each point:
8453 12 printf ("We're so creative.\n");
8454 (@value{GDBP}) info macro N
8455 The symbol `N' has no definition as a C/C++ preprocessor macro
8456 at /home/jimb/gdb/macros/play/sample.c:12
8459 14 printf ("Goodbye, world!\n");
8460 (@value{GDBP}) info macro N
8461 Defined at /home/jimb/gdb/macros/play/sample.c:13
8463 (@value{GDBP}) macro expand N Q M
8464 expands to: 1729 < 42
8465 (@value{GDBP}) print N Q M
8472 @chapter Tracepoints
8473 @c This chapter is based on the documentation written by Michael
8474 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8477 In some applications, it is not feasible for the debugger to interrupt
8478 the program's execution long enough for the developer to learn
8479 anything helpful about its behavior. If the program's correctness
8480 depends on its real-time behavior, delays introduced by a debugger
8481 might cause the program to change its behavior drastically, or perhaps
8482 fail, even when the code itself is correct. It is useful to be able
8483 to observe the program's behavior without interrupting it.
8485 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8486 specify locations in the program, called @dfn{tracepoints}, and
8487 arbitrary expressions to evaluate when those tracepoints are reached.
8488 Later, using the @code{tfind} command, you can examine the values
8489 those expressions had when the program hit the tracepoints. The
8490 expressions may also denote objects in memory---structures or arrays,
8491 for example---whose values @value{GDBN} should record; while visiting
8492 a particular tracepoint, you may inspect those objects as if they were
8493 in memory at that moment. However, because @value{GDBN} records these
8494 values without interacting with you, it can do so quickly and
8495 unobtrusively, hopefully not disturbing the program's behavior.
8497 The tracepoint facility is currently available only for remote
8498 targets. @xref{Targets}. In addition, your remote target must know
8499 how to collect trace data. This functionality is implemented in the
8500 remote stub; however, none of the stubs distributed with @value{GDBN}
8501 support tracepoints as of this writing. The format of the remote
8502 packets used to implement tracepoints are described in @ref{Tracepoint
8505 This chapter describes the tracepoint commands and features.
8509 * Analyze Collected Data::
8510 * Tracepoint Variables::
8513 @node Set Tracepoints
8514 @section Commands to Set Tracepoints
8516 Before running such a @dfn{trace experiment}, an arbitrary number of
8517 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
8518 tracepoint has a number assigned to it by @value{GDBN}. Like with
8519 breakpoints, tracepoint numbers are successive integers starting from
8520 one. Many of the commands associated with tracepoints take the
8521 tracepoint number as their argument, to identify which tracepoint to
8524 For each tracepoint, you can specify, in advance, some arbitrary set
8525 of data that you want the target to collect in the trace buffer when
8526 it hits that tracepoint. The collected data can include registers,
8527 local variables, or global data. Later, you can use @value{GDBN}
8528 commands to examine the values these data had at the time the
8531 This section describes commands to set tracepoints and associated
8532 conditions and actions.
8535 * Create and Delete Tracepoints::
8536 * Enable and Disable Tracepoints::
8537 * Tracepoint Passcounts::
8538 * Tracepoint Actions::
8539 * Listing Tracepoints::
8540 * Starting and Stopping Trace Experiments::
8543 @node Create and Delete Tracepoints
8544 @subsection Create and Delete Tracepoints
8547 @cindex set tracepoint
8550 The @code{trace} command is very similar to the @code{break} command.
8551 Its argument can be a source line, a function name, or an address in
8552 the target program. @xref{Set Breaks}. The @code{trace} command
8553 defines a tracepoint, which is a point in the target program where the
8554 debugger will briefly stop, collect some data, and then allow the
8555 program to continue. Setting a tracepoint or changing its commands
8556 doesn't take effect until the next @code{tstart} command; thus, you
8557 cannot change the tracepoint attributes once a trace experiment is
8560 Here are some examples of using the @code{trace} command:
8563 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8565 (@value{GDBP}) @b{trace +2} // 2 lines forward
8567 (@value{GDBP}) @b{trace my_function} // first source line of function
8569 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8571 (@value{GDBP}) @b{trace *0x2117c4} // an address
8575 You can abbreviate @code{trace} as @code{tr}.
8578 @cindex last tracepoint number
8579 @cindex recent tracepoint number
8580 @cindex tracepoint number
8581 The convenience variable @code{$tpnum} records the tracepoint number
8582 of the most recently set tracepoint.
8584 @kindex delete tracepoint
8585 @cindex tracepoint deletion
8586 @item delete tracepoint @r{[}@var{num}@r{]}
8587 Permanently delete one or more tracepoints. With no argument, the
8588 default is to delete all tracepoints.
8593 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8595 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8599 You can abbreviate this command as @code{del tr}.
8602 @node Enable and Disable Tracepoints
8603 @subsection Enable and Disable Tracepoints
8606 @kindex disable tracepoint
8607 @item disable tracepoint @r{[}@var{num}@r{]}
8608 Disable tracepoint @var{num}, or all tracepoints if no argument
8609 @var{num} is given. A disabled tracepoint will have no effect during
8610 the next trace experiment, but it is not forgotten. You can re-enable
8611 a disabled tracepoint using the @code{enable tracepoint} command.
8613 @kindex enable tracepoint
8614 @item enable tracepoint @r{[}@var{num}@r{]}
8615 Enable tracepoint @var{num}, or all tracepoints. The enabled
8616 tracepoints will become effective the next time a trace experiment is
8620 @node Tracepoint Passcounts
8621 @subsection Tracepoint Passcounts
8625 @cindex tracepoint pass count
8626 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8627 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8628 automatically stop a trace experiment. If a tracepoint's passcount is
8629 @var{n}, then the trace experiment will be automatically stopped on
8630 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8631 @var{num} is not specified, the @code{passcount} command sets the
8632 passcount of the most recently defined tracepoint. If no passcount is
8633 given, the trace experiment will run until stopped explicitly by the
8639 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8640 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8642 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8643 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8644 (@value{GDBP}) @b{trace foo}
8645 (@value{GDBP}) @b{pass 3}
8646 (@value{GDBP}) @b{trace bar}
8647 (@value{GDBP}) @b{pass 2}
8648 (@value{GDBP}) @b{trace baz}
8649 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8650 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8651 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8652 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8656 @node Tracepoint Actions
8657 @subsection Tracepoint Action Lists
8661 @cindex tracepoint actions
8662 @item actions @r{[}@var{num}@r{]}
8663 This command will prompt for a list of actions to be taken when the
8664 tracepoint is hit. If the tracepoint number @var{num} is not
8665 specified, this command sets the actions for the one that was most
8666 recently defined (so that you can define a tracepoint and then say
8667 @code{actions} without bothering about its number). You specify the
8668 actions themselves on the following lines, one action at a time, and
8669 terminate the actions list with a line containing just @code{end}. So
8670 far, the only defined actions are @code{collect} and
8671 @code{while-stepping}.
8673 @cindex remove actions from a tracepoint
8674 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8675 and follow it immediately with @samp{end}.
8678 (@value{GDBP}) @b{collect @var{data}} // collect some data
8680 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8682 (@value{GDBP}) @b{end} // signals the end of actions.
8685 In the following example, the action list begins with @code{collect}
8686 commands indicating the things to be collected when the tracepoint is
8687 hit. Then, in order to single-step and collect additional data
8688 following the tracepoint, a @code{while-stepping} command is used,
8689 followed by the list of things to be collected while stepping. The
8690 @code{while-stepping} command is terminated by its own separate
8691 @code{end} command. Lastly, the action list is terminated by an
8695 (@value{GDBP}) @b{trace foo}
8696 (@value{GDBP}) @b{actions}
8697 Enter actions for tracepoint 1, one per line:
8706 @kindex collect @r{(tracepoints)}
8707 @item collect @var{expr1}, @var{expr2}, @dots{}
8708 Collect values of the given expressions when the tracepoint is hit.
8709 This command accepts a comma-separated list of any valid expressions.
8710 In addition to global, static, or local variables, the following
8711 special arguments are supported:
8715 collect all registers
8718 collect all function arguments
8721 collect all local variables.
8724 You can give several consecutive @code{collect} commands, each one
8725 with a single argument, or one @code{collect} command with several
8726 arguments separated by commas: the effect is the same.
8728 The command @code{info scope} (@pxref{Symbols, info scope}) is
8729 particularly useful for figuring out what data to collect.
8731 @kindex while-stepping @r{(tracepoints)}
8732 @item while-stepping @var{n}
8733 Perform @var{n} single-step traces after the tracepoint, collecting
8734 new data at each step. The @code{while-stepping} command is
8735 followed by the list of what to collect while stepping (followed by
8736 its own @code{end} command):
8740 > collect $regs, myglobal
8746 You may abbreviate @code{while-stepping} as @code{ws} or
8750 @node Listing Tracepoints
8751 @subsection Listing Tracepoints
8754 @kindex info tracepoints
8756 @cindex information about tracepoints
8757 @item info tracepoints @r{[}@var{num}@r{]}
8758 Display information about the tracepoint @var{num}. If you don't specify
8759 a tracepoint number, displays information about all the tracepoints
8760 defined so far. For each tracepoint, the following information is
8767 whether it is enabled or disabled
8771 its passcount as given by the @code{passcount @var{n}} command
8773 its step count as given by the @code{while-stepping @var{n}} command
8775 where in the source files is the tracepoint set
8777 its action list as given by the @code{actions} command
8781 (@value{GDBP}) @b{info trace}
8782 Num Enb Address PassC StepC What
8783 1 y 0x002117c4 0 0 <gdb_asm>
8784 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
8785 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
8790 This command can be abbreviated @code{info tp}.
8793 @node Starting and Stopping Trace Experiments
8794 @subsection Starting and Stopping Trace Experiments
8798 @cindex start a new trace experiment
8799 @cindex collected data discarded
8801 This command takes no arguments. It starts the trace experiment, and
8802 begins collecting data. This has the side effect of discarding all
8803 the data collected in the trace buffer during the previous trace
8807 @cindex stop a running trace experiment
8809 This command takes no arguments. It ends the trace experiment, and
8810 stops collecting data.
8812 @strong{Note}: a trace experiment and data collection may stop
8813 automatically if any tracepoint's passcount is reached
8814 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8817 @cindex status of trace data collection
8818 @cindex trace experiment, status of
8820 This command displays the status of the current trace data
8824 Here is an example of the commands we described so far:
8827 (@value{GDBP}) @b{trace gdb_c_test}
8828 (@value{GDBP}) @b{actions}
8829 Enter actions for tracepoint #1, one per line.
8830 > collect $regs,$locals,$args
8835 (@value{GDBP}) @b{tstart}
8836 [time passes @dots{}]
8837 (@value{GDBP}) @b{tstop}
8841 @node Analyze Collected Data
8842 @section Using the Collected Data
8844 After the tracepoint experiment ends, you use @value{GDBN} commands
8845 for examining the trace data. The basic idea is that each tracepoint
8846 collects a trace @dfn{snapshot} every time it is hit and another
8847 snapshot every time it single-steps. All these snapshots are
8848 consecutively numbered from zero and go into a buffer, and you can
8849 examine them later. The way you examine them is to @dfn{focus} on a
8850 specific trace snapshot. When the remote stub is focused on a trace
8851 snapshot, it will respond to all @value{GDBN} requests for memory and
8852 registers by reading from the buffer which belongs to that snapshot,
8853 rather than from @emph{real} memory or registers of the program being
8854 debugged. This means that @strong{all} @value{GDBN} commands
8855 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8856 behave as if we were currently debugging the program state as it was
8857 when the tracepoint occurred. Any requests for data that are not in
8858 the buffer will fail.
8861 * tfind:: How to select a trace snapshot
8862 * tdump:: How to display all data for a snapshot
8863 * save-tracepoints:: How to save tracepoints for a future run
8867 @subsection @code{tfind @var{n}}
8870 @cindex select trace snapshot
8871 @cindex find trace snapshot
8872 The basic command for selecting a trace snapshot from the buffer is
8873 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8874 counting from zero. If no argument @var{n} is given, the next
8875 snapshot is selected.
8877 Here are the various forms of using the @code{tfind} command.
8881 Find the first snapshot in the buffer. This is a synonym for
8882 @code{tfind 0} (since 0 is the number of the first snapshot).
8885 Stop debugging trace snapshots, resume @emph{live} debugging.
8888 Same as @samp{tfind none}.
8891 No argument means find the next trace snapshot.
8894 Find the previous trace snapshot before the current one. This permits
8895 retracing earlier steps.
8897 @item tfind tracepoint @var{num}
8898 Find the next snapshot associated with tracepoint @var{num}. Search
8899 proceeds forward from the last examined trace snapshot. If no
8900 argument @var{num} is given, it means find the next snapshot collected
8901 for the same tracepoint as the current snapshot.
8903 @item tfind pc @var{addr}
8904 Find the next snapshot associated with the value @var{addr} of the
8905 program counter. Search proceeds forward from the last examined trace
8906 snapshot. If no argument @var{addr} is given, it means find the next
8907 snapshot with the same value of PC as the current snapshot.
8909 @item tfind outside @var{addr1}, @var{addr2}
8910 Find the next snapshot whose PC is outside the given range of
8913 @item tfind range @var{addr1}, @var{addr2}
8914 Find the next snapshot whose PC is between @var{addr1} and
8915 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8917 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8918 Find the next snapshot associated with the source line @var{n}. If
8919 the optional argument @var{file} is given, refer to line @var{n} in
8920 that source file. Search proceeds forward from the last examined
8921 trace snapshot. If no argument @var{n} is given, it means find the
8922 next line other than the one currently being examined; thus saying
8923 @code{tfind line} repeatedly can appear to have the same effect as
8924 stepping from line to line in a @emph{live} debugging session.
8927 The default arguments for the @code{tfind} commands are specifically
8928 designed to make it easy to scan through the trace buffer. For
8929 instance, @code{tfind} with no argument selects the next trace
8930 snapshot, and @code{tfind -} with no argument selects the previous
8931 trace snapshot. So, by giving one @code{tfind} command, and then
8932 simply hitting @key{RET} repeatedly you can examine all the trace
8933 snapshots in order. Or, by saying @code{tfind -} and then hitting
8934 @key{RET} repeatedly you can examine the snapshots in reverse order.
8935 The @code{tfind line} command with no argument selects the snapshot
8936 for the next source line executed. The @code{tfind pc} command with
8937 no argument selects the next snapshot with the same program counter
8938 (PC) as the current frame. The @code{tfind tracepoint} command with
8939 no argument selects the next trace snapshot collected by the same
8940 tracepoint as the current one.
8942 In addition to letting you scan through the trace buffer manually,
8943 these commands make it easy to construct @value{GDBN} scripts that
8944 scan through the trace buffer and print out whatever collected data
8945 you are interested in. Thus, if we want to examine the PC, FP, and SP
8946 registers from each trace frame in the buffer, we can say this:
8949 (@value{GDBP}) @b{tfind start}
8950 (@value{GDBP}) @b{while ($trace_frame != -1)}
8951 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8952 $trace_frame, $pc, $sp, $fp
8956 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8957 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8958 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8959 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8960 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8961 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8962 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8963 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8964 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8965 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8966 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8969 Or, if we want to examine the variable @code{X} at each source line in
8973 (@value{GDBP}) @b{tfind start}
8974 (@value{GDBP}) @b{while ($trace_frame != -1)}
8975 > printf "Frame %d, X == %d\n", $trace_frame, X
8985 @subsection @code{tdump}
8987 @cindex dump all data collected at tracepoint
8988 @cindex tracepoint data, display
8990 This command takes no arguments. It prints all the data collected at
8991 the current trace snapshot.
8994 (@value{GDBP}) @b{trace 444}
8995 (@value{GDBP}) @b{actions}
8996 Enter actions for tracepoint #2, one per line:
8997 > collect $regs, $locals, $args, gdb_long_test
9000 (@value{GDBP}) @b{tstart}
9002 (@value{GDBP}) @b{tfind line 444}
9003 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9005 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9007 (@value{GDBP}) @b{tdump}
9008 Data collected at tracepoint 2, trace frame 1:
9009 d0 0xc4aa0085 -995491707
9013 d4 0x71aea3d 119204413
9018 a1 0x3000668 50333288
9021 a4 0x3000698 50333336
9023 fp 0x30bf3c 0x30bf3c
9024 sp 0x30bf34 0x30bf34
9026 pc 0x20b2c8 0x20b2c8
9030 p = 0x20e5b4 "gdb-test"
9037 gdb_long_test = 17 '\021'
9042 @node save-tracepoints
9043 @subsection @code{save-tracepoints @var{filename}}
9044 @kindex save-tracepoints
9045 @cindex save tracepoints for future sessions
9047 This command saves all current tracepoint definitions together with
9048 their actions and passcounts, into a file @file{@var{filename}}
9049 suitable for use in a later debugging session. To read the saved
9050 tracepoint definitions, use the @code{source} command (@pxref{Command
9053 @node Tracepoint Variables
9054 @section Convenience Variables for Tracepoints
9055 @cindex tracepoint variables
9056 @cindex convenience variables for tracepoints
9059 @vindex $trace_frame
9060 @item (int) $trace_frame
9061 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9062 snapshot is selected.
9065 @item (int) $tracepoint
9066 The tracepoint for the current trace snapshot.
9069 @item (int) $trace_line
9070 The line number for the current trace snapshot.
9073 @item (char []) $trace_file
9074 The source file for the current trace snapshot.
9077 @item (char []) $trace_func
9078 The name of the function containing @code{$tracepoint}.
9081 Note: @code{$trace_file} is not suitable for use in @code{printf},
9082 use @code{output} instead.
9084 Here's a simple example of using these convenience variables for
9085 stepping through all the trace snapshots and printing some of their
9089 (@value{GDBP}) @b{tfind start}
9091 (@value{GDBP}) @b{while $trace_frame != -1}
9092 > output $trace_file
9093 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9099 @chapter Debugging Programs That Use Overlays
9102 If your program is too large to fit completely in your target system's
9103 memory, you can sometimes use @dfn{overlays} to work around this
9104 problem. @value{GDBN} provides some support for debugging programs that
9108 * How Overlays Work:: A general explanation of overlays.
9109 * Overlay Commands:: Managing overlays in @value{GDBN}.
9110 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9111 mapped by asking the inferior.
9112 * Overlay Sample Program:: A sample program using overlays.
9115 @node How Overlays Work
9116 @section How Overlays Work
9117 @cindex mapped overlays
9118 @cindex unmapped overlays
9119 @cindex load address, overlay's
9120 @cindex mapped address
9121 @cindex overlay area
9123 Suppose you have a computer whose instruction address space is only 64
9124 kilobytes long, but which has much more memory which can be accessed by
9125 other means: special instructions, segment registers, or memory
9126 management hardware, for example. Suppose further that you want to
9127 adapt a program which is larger than 64 kilobytes to run on this system.
9129 One solution is to identify modules of your program which are relatively
9130 independent, and need not call each other directly; call these modules
9131 @dfn{overlays}. Separate the overlays from the main program, and place
9132 their machine code in the larger memory. Place your main program in
9133 instruction memory, but leave at least enough space there to hold the
9134 largest overlay as well.
9136 Now, to call a function located in an overlay, you must first copy that
9137 overlay's machine code from the large memory into the space set aside
9138 for it in the instruction memory, and then jump to its entry point
9141 @c NB: In the below the mapped area's size is greater or equal to the
9142 @c size of all overlays. This is intentional to remind the developer
9143 @c that overlays don't necessarily need to be the same size.
9147 Data Instruction Larger
9148 Address Space Address Space Address Space
9149 +-----------+ +-----------+ +-----------+
9151 +-----------+ +-----------+ +-----------+<-- overlay 1
9152 | program | | main | .----| overlay 1 | load address
9153 | variables | | program | | +-----------+
9154 | and heap | | | | | |
9155 +-----------+ | | | +-----------+<-- overlay 2
9156 | | +-----------+ | | | load address
9157 +-----------+ | | | .-| overlay 2 |
9159 mapped --->+-----------+ | | +-----------+
9161 | overlay | <-' | | |
9162 | area | <---' +-----------+<-- overlay 3
9163 | | <---. | | load address
9164 +-----------+ `--| overlay 3 |
9171 @anchor{A code overlay}A code overlay
9175 The diagram (@pxref{A code overlay}) shows a system with separate data
9176 and instruction address spaces. To map an overlay, the program copies
9177 its code from the larger address space to the instruction address space.
9178 Since the overlays shown here all use the same mapped address, only one
9179 may be mapped at a time. For a system with a single address space for
9180 data and instructions, the diagram would be similar, except that the
9181 program variables and heap would share an address space with the main
9182 program and the overlay area.
9184 An overlay loaded into instruction memory and ready for use is called a
9185 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9186 instruction memory. An overlay not present (or only partially present)
9187 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9188 is its address in the larger memory. The mapped address is also called
9189 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9190 called the @dfn{load memory address}, or @dfn{LMA}.
9192 Unfortunately, overlays are not a completely transparent way to adapt a
9193 program to limited instruction memory. They introduce a new set of
9194 global constraints you must keep in mind as you design your program:
9199 Before calling or returning to a function in an overlay, your program
9200 must make sure that overlay is actually mapped. Otherwise, the call or
9201 return will transfer control to the right address, but in the wrong
9202 overlay, and your program will probably crash.
9205 If the process of mapping an overlay is expensive on your system, you
9206 will need to choose your overlays carefully to minimize their effect on
9207 your program's performance.
9210 The executable file you load onto your system must contain each
9211 overlay's instructions, appearing at the overlay's load address, not its
9212 mapped address. However, each overlay's instructions must be relocated
9213 and its symbols defined as if the overlay were at its mapped address.
9214 You can use GNU linker scripts to specify different load and relocation
9215 addresses for pieces of your program; see @ref{Overlay Description,,,
9216 ld.info, Using ld: the GNU linker}.
9219 The procedure for loading executable files onto your system must be able
9220 to load their contents into the larger address space as well as the
9221 instruction and data spaces.
9225 The overlay system described above is rather simple, and could be
9226 improved in many ways:
9231 If your system has suitable bank switch registers or memory management
9232 hardware, you could use those facilities to make an overlay's load area
9233 contents simply appear at their mapped address in instruction space.
9234 This would probably be faster than copying the overlay to its mapped
9235 area in the usual way.
9238 If your overlays are small enough, you could set aside more than one
9239 overlay area, and have more than one overlay mapped at a time.
9242 You can use overlays to manage data, as well as instructions. In
9243 general, data overlays are even less transparent to your design than
9244 code overlays: whereas code overlays only require care when you call or
9245 return to functions, data overlays require care every time you access
9246 the data. Also, if you change the contents of a data overlay, you
9247 must copy its contents back out to its load address before you can copy a
9248 different data overlay into the same mapped area.
9253 @node Overlay Commands
9254 @section Overlay Commands
9256 To use @value{GDBN}'s overlay support, each overlay in your program must
9257 correspond to a separate section of the executable file. The section's
9258 virtual memory address and load memory address must be the overlay's
9259 mapped and load addresses. Identifying overlays with sections allows
9260 @value{GDBN} to determine the appropriate address of a function or
9261 variable, depending on whether the overlay is mapped or not.
9263 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9264 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9269 Disable @value{GDBN}'s overlay support. When overlay support is
9270 disabled, @value{GDBN} assumes that all functions and variables are
9271 always present at their mapped addresses. By default, @value{GDBN}'s
9272 overlay support is disabled.
9274 @item overlay manual
9275 @cindex manual overlay debugging
9276 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9277 relies on you to tell it which overlays are mapped, and which are not,
9278 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9279 commands described below.
9281 @item overlay map-overlay @var{overlay}
9282 @itemx overlay map @var{overlay}
9283 @cindex map an overlay
9284 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9285 be the name of the object file section containing the overlay. When an
9286 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9287 functions and variables at their mapped addresses. @value{GDBN} assumes
9288 that any other overlays whose mapped ranges overlap that of
9289 @var{overlay} are now unmapped.
9291 @item overlay unmap-overlay @var{overlay}
9292 @itemx overlay unmap @var{overlay}
9293 @cindex unmap an overlay
9294 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9295 must be the name of the object file section containing the overlay.
9296 When an overlay is unmapped, @value{GDBN} assumes it can find the
9297 overlay's functions and variables at their load addresses.
9300 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9301 consults a data structure the overlay manager maintains in the inferior
9302 to see which overlays are mapped. For details, see @ref{Automatic
9305 @item overlay load-target
9307 @cindex reloading the overlay table
9308 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9309 re-reads the table @value{GDBN} automatically each time the inferior
9310 stops, so this command should only be necessary if you have changed the
9311 overlay mapping yourself using @value{GDBN}. This command is only
9312 useful when using automatic overlay debugging.
9314 @item overlay list-overlays
9316 @cindex listing mapped overlays
9317 Display a list of the overlays currently mapped, along with their mapped
9318 addresses, load addresses, and sizes.
9322 Normally, when @value{GDBN} prints a code address, it includes the name
9323 of the function the address falls in:
9326 (@value{GDBP}) print main
9327 $3 = @{int ()@} 0x11a0 <main>
9330 When overlay debugging is enabled, @value{GDBN} recognizes code in
9331 unmapped overlays, and prints the names of unmapped functions with
9332 asterisks around them. For example, if @code{foo} is a function in an
9333 unmapped overlay, @value{GDBN} prints it this way:
9336 (@value{GDBP}) overlay list
9337 No sections are mapped.
9338 (@value{GDBP}) print foo
9339 $5 = @{int (int)@} 0x100000 <*foo*>
9342 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9346 (@value{GDBP}) overlay list
9347 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9348 mapped at 0x1016 - 0x104a
9349 (@value{GDBP}) print foo
9350 $6 = @{int (int)@} 0x1016 <foo>
9353 When overlay debugging is enabled, @value{GDBN} can find the correct
9354 address for functions and variables in an overlay, whether or not the
9355 overlay is mapped. This allows most @value{GDBN} commands, like
9356 @code{break} and @code{disassemble}, to work normally, even on unmapped
9357 code. However, @value{GDBN}'s breakpoint support has some limitations:
9361 @cindex breakpoints in overlays
9362 @cindex overlays, setting breakpoints in
9363 You can set breakpoints in functions in unmapped overlays, as long as
9364 @value{GDBN} can write to the overlay at its load address.
9366 @value{GDBN} can not set hardware or simulator-based breakpoints in
9367 unmapped overlays. However, if you set a breakpoint at the end of your
9368 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9369 you are using manual overlay management), @value{GDBN} will re-set its
9370 breakpoints properly.
9374 @node Automatic Overlay Debugging
9375 @section Automatic Overlay Debugging
9376 @cindex automatic overlay debugging
9378 @value{GDBN} can automatically track which overlays are mapped and which
9379 are not, given some simple co-operation from the overlay manager in the
9380 inferior. If you enable automatic overlay debugging with the
9381 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9382 looks in the inferior's memory for certain variables describing the
9383 current state of the overlays.
9385 Here are the variables your overlay manager must define to support
9386 @value{GDBN}'s automatic overlay debugging:
9390 @item @code{_ovly_table}:
9391 This variable must be an array of the following structures:
9396 /* The overlay's mapped address. */
9399 /* The size of the overlay, in bytes. */
9402 /* The overlay's load address. */
9405 /* Non-zero if the overlay is currently mapped;
9407 unsigned long mapped;
9411 @item @code{_novlys}:
9412 This variable must be a four-byte signed integer, holding the total
9413 number of elements in @code{_ovly_table}.
9417 To decide whether a particular overlay is mapped or not, @value{GDBN}
9418 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9419 @code{lma} members equal the VMA and LMA of the overlay's section in the
9420 executable file. When @value{GDBN} finds a matching entry, it consults
9421 the entry's @code{mapped} member to determine whether the overlay is
9424 In addition, your overlay manager may define a function called
9425 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9426 will silently set a breakpoint there. If the overlay manager then
9427 calls this function whenever it has changed the overlay table, this
9428 will enable @value{GDBN} to accurately keep track of which overlays
9429 are in program memory, and update any breakpoints that may be set
9430 in overlays. This will allow breakpoints to work even if the
9431 overlays are kept in ROM or other non-writable memory while they
9432 are not being executed.
9434 @node Overlay Sample Program
9435 @section Overlay Sample Program
9436 @cindex overlay example program
9438 When linking a program which uses overlays, you must place the overlays
9439 at their load addresses, while relocating them to run at their mapped
9440 addresses. To do this, you must write a linker script (@pxref{Overlay
9441 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9442 since linker scripts are specific to a particular host system, target
9443 architecture, and target memory layout, this manual cannot provide
9444 portable sample code demonstrating @value{GDBN}'s overlay support.
9446 However, the @value{GDBN} source distribution does contain an overlaid
9447 program, with linker scripts for a few systems, as part of its test
9448 suite. The program consists of the following files from
9449 @file{gdb/testsuite/gdb.base}:
9453 The main program file.
9455 A simple overlay manager, used by @file{overlays.c}.
9460 Overlay modules, loaded and used by @file{overlays.c}.
9463 Linker scripts for linking the test program on the @code{d10v-elf}
9464 and @code{m32r-elf} targets.
9467 You can build the test program using the @code{d10v-elf} GCC
9468 cross-compiler like this:
9471 $ d10v-elf-gcc -g -c overlays.c
9472 $ d10v-elf-gcc -g -c ovlymgr.c
9473 $ d10v-elf-gcc -g -c foo.c
9474 $ d10v-elf-gcc -g -c bar.c
9475 $ d10v-elf-gcc -g -c baz.c
9476 $ d10v-elf-gcc -g -c grbx.c
9477 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9478 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9481 The build process is identical for any other architecture, except that
9482 you must substitute the appropriate compiler and linker script for the
9483 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9487 @chapter Using @value{GDBN} with Different Languages
9490 Although programming languages generally have common aspects, they are
9491 rarely expressed in the same manner. For instance, in ANSI C,
9492 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9493 Modula-2, it is accomplished by @code{p^}. Values can also be
9494 represented (and displayed) differently. Hex numbers in C appear as
9495 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9497 @cindex working language
9498 Language-specific information is built into @value{GDBN} for some languages,
9499 allowing you to express operations like the above in your program's
9500 native language, and allowing @value{GDBN} to output values in a manner
9501 consistent with the syntax of your program's native language. The
9502 language you use to build expressions is called the @dfn{working
9506 * Setting:: Switching between source languages
9507 * Show:: Displaying the language
9508 * Checks:: Type and range checks
9509 * Supported Languages:: Supported languages
9510 * Unsupported Languages:: Unsupported languages
9514 @section Switching Between Source Languages
9516 There are two ways to control the working language---either have @value{GDBN}
9517 set it automatically, or select it manually yourself. You can use the
9518 @code{set language} command for either purpose. On startup, @value{GDBN}
9519 defaults to setting the language automatically. The working language is
9520 used to determine how expressions you type are interpreted, how values
9523 In addition to the working language, every source file that
9524 @value{GDBN} knows about has its own working language. For some object
9525 file formats, the compiler might indicate which language a particular
9526 source file is in. However, most of the time @value{GDBN} infers the
9527 language from the name of the file. The language of a source file
9528 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9529 show each frame appropriately for its own language. There is no way to
9530 set the language of a source file from within @value{GDBN}, but you can
9531 set the language associated with a filename extension. @xref{Show, ,
9532 Displaying the Language}.
9534 This is most commonly a problem when you use a program, such
9535 as @code{cfront} or @code{f2c}, that generates C but is written in
9536 another language. In that case, make the
9537 program use @code{#line} directives in its C output; that way
9538 @value{GDBN} will know the correct language of the source code of the original
9539 program, and will display that source code, not the generated C code.
9542 * Filenames:: Filename extensions and languages.
9543 * Manually:: Setting the working language manually
9544 * Automatically:: Having @value{GDBN} infer the source language
9548 @subsection List of Filename Extensions and Languages
9550 If a source file name ends in one of the following extensions, then
9551 @value{GDBN} infers that its language is the one indicated.
9572 Objective-C source file
9579 Modula-2 source file
9583 Assembler source file. This actually behaves almost like C, but
9584 @value{GDBN} does not skip over function prologues when stepping.
9587 In addition, you may set the language associated with a filename
9588 extension. @xref{Show, , Displaying the Language}.
9591 @subsection Setting the Working Language
9593 If you allow @value{GDBN} to set the language automatically,
9594 expressions are interpreted the same way in your debugging session and
9597 @kindex set language
9598 If you wish, you may set the language manually. To do this, issue the
9599 command @samp{set language @var{lang}}, where @var{lang} is the name of
9601 @code{c} or @code{modula-2}.
9602 For a list of the supported languages, type @samp{set language}.
9604 Setting the language manually prevents @value{GDBN} from updating the working
9605 language automatically. This can lead to confusion if you try
9606 to debug a program when the working language is not the same as the
9607 source language, when an expression is acceptable to both
9608 languages---but means different things. For instance, if the current
9609 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9617 might not have the effect you intended. In C, this means to add
9618 @code{b} and @code{c} and place the result in @code{a}. The result
9619 printed would be the value of @code{a}. In Modula-2, this means to compare
9620 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9623 @subsection Having @value{GDBN} Infer the Source Language
9625 To have @value{GDBN} set the working language automatically, use
9626 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9627 then infers the working language. That is, when your program stops in a
9628 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9629 working language to the language recorded for the function in that
9630 frame. If the language for a frame is unknown (that is, if the function
9631 or block corresponding to the frame was defined in a source file that
9632 does not have a recognized extension), the current working language is
9633 not changed, and @value{GDBN} issues a warning.
9635 This may not seem necessary for most programs, which are written
9636 entirely in one source language. However, program modules and libraries
9637 written in one source language can be used by a main program written in
9638 a different source language. Using @samp{set language auto} in this
9639 case frees you from having to set the working language manually.
9642 @section Displaying the Language
9644 The following commands help you find out which language is the
9645 working language, and also what language source files were written in.
9649 @kindex show language
9650 Display the current working language. This is the
9651 language you can use with commands such as @code{print} to
9652 build and compute expressions that may involve variables in your program.
9655 @kindex info frame@r{, show the source language}
9656 Display the source language for this frame. This language becomes the
9657 working language if you use an identifier from this frame.
9658 @xref{Frame Info, ,Information about a Frame}, to identify the other
9659 information listed here.
9662 @kindex info source@r{, show the source language}
9663 Display the source language of this source file.
9664 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9665 information listed here.
9668 In unusual circumstances, you may have source files with extensions
9669 not in the standard list. You can then set the extension associated
9670 with a language explicitly:
9673 @item set extension-language @var{ext} @var{language}
9674 @kindex set extension-language
9675 Tell @value{GDBN} that source files with extension @var{ext} are to be
9676 assumed as written in the source language @var{language}.
9678 @item info extensions
9679 @kindex info extensions
9680 List all the filename extensions and the associated languages.
9684 @section Type and Range Checking
9687 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9688 checking are included, but they do not yet have any effect. This
9689 section documents the intended facilities.
9691 @c FIXME remove warning when type/range code added
9693 Some languages are designed to guard you against making seemingly common
9694 errors through a series of compile- and run-time checks. These include
9695 checking the type of arguments to functions and operators, and making
9696 sure mathematical overflows are caught at run time. Checks such as
9697 these help to ensure a program's correctness once it has been compiled
9698 by eliminating type mismatches, and providing active checks for range
9699 errors when your program is running.
9701 @value{GDBN} can check for conditions like the above if you wish.
9702 Although @value{GDBN} does not check the statements in your program,
9703 it can check expressions entered directly into @value{GDBN} for
9704 evaluation via the @code{print} command, for example. As with the
9705 working language, @value{GDBN} can also decide whether or not to check
9706 automatically based on your program's source language.
9707 @xref{Supported Languages, ,Supported Languages}, for the default
9708 settings of supported languages.
9711 * Type Checking:: An overview of type checking
9712 * Range Checking:: An overview of range checking
9715 @cindex type checking
9716 @cindex checks, type
9718 @subsection An Overview of Type Checking
9720 Some languages, such as Modula-2, are strongly typed, meaning that the
9721 arguments to operators and functions have to be of the correct type,
9722 otherwise an error occurs. These checks prevent type mismatch
9723 errors from ever causing any run-time problems. For example,
9731 The second example fails because the @code{CARDINAL} 1 is not
9732 type-compatible with the @code{REAL} 2.3.
9734 For the expressions you use in @value{GDBN} commands, you can tell the
9735 @value{GDBN} type checker to skip checking;
9736 to treat any mismatches as errors and abandon the expression;
9737 or to only issue warnings when type mismatches occur,
9738 but evaluate the expression anyway. When you choose the last of
9739 these, @value{GDBN} evaluates expressions like the second example above, but
9740 also issues a warning.
9742 Even if you turn type checking off, there may be other reasons
9743 related to type that prevent @value{GDBN} from evaluating an expression.
9744 For instance, @value{GDBN} does not know how to add an @code{int} and
9745 a @code{struct foo}. These particular type errors have nothing to do
9746 with the language in use, and usually arise from expressions, such as
9747 the one described above, which make little sense to evaluate anyway.
9749 Each language defines to what degree it is strict about type. For
9750 instance, both Modula-2 and C require the arguments to arithmetical
9751 operators to be numbers. In C, enumerated types and pointers can be
9752 represented as numbers, so that they are valid arguments to mathematical
9753 operators. @xref{Supported Languages, ,Supported Languages}, for further
9754 details on specific languages.
9756 @value{GDBN} provides some additional commands for controlling the type checker:
9758 @kindex set check type
9759 @kindex show check type
9761 @item set check type auto
9762 Set type checking on or off based on the current working language.
9763 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9766 @item set check type on
9767 @itemx set check type off
9768 Set type checking on or off, overriding the default setting for the
9769 current working language. Issue a warning if the setting does not
9770 match the language default. If any type mismatches occur in
9771 evaluating an expression while type checking is on, @value{GDBN} prints a
9772 message and aborts evaluation of the expression.
9774 @item set check type warn
9775 Cause the type checker to issue warnings, but to always attempt to
9776 evaluate the expression. Evaluating the expression may still
9777 be impossible for other reasons. For example, @value{GDBN} cannot add
9778 numbers and structures.
9781 Show the current setting of the type checker, and whether or not @value{GDBN}
9782 is setting it automatically.
9785 @cindex range checking
9786 @cindex checks, range
9787 @node Range Checking
9788 @subsection An Overview of Range Checking
9790 In some languages (such as Modula-2), it is an error to exceed the
9791 bounds of a type; this is enforced with run-time checks. Such range
9792 checking is meant to ensure program correctness by making sure
9793 computations do not overflow, or indices on an array element access do
9794 not exceed the bounds of the array.
9796 For expressions you use in @value{GDBN} commands, you can tell
9797 @value{GDBN} to treat range errors in one of three ways: ignore them,
9798 always treat them as errors and abandon the expression, or issue
9799 warnings but evaluate the expression anyway.
9801 A range error can result from numerical overflow, from exceeding an
9802 array index bound, or when you type a constant that is not a member
9803 of any type. Some languages, however, do not treat overflows as an
9804 error. In many implementations of C, mathematical overflow causes the
9805 result to ``wrap around'' to lower values---for example, if @var{m} is
9806 the largest integer value, and @var{s} is the smallest, then
9809 @var{m} + 1 @result{} @var{s}
9812 This, too, is specific to individual languages, and in some cases
9813 specific to individual compilers or machines. @xref{Supported Languages, ,
9814 Supported Languages}, for further details on specific languages.
9816 @value{GDBN} provides some additional commands for controlling the range checker:
9818 @kindex set check range
9819 @kindex show check range
9821 @item set check range auto
9822 Set range checking on or off based on the current working language.
9823 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9826 @item set check range on
9827 @itemx set check range off
9828 Set range checking on or off, overriding the default setting for the
9829 current working language. A warning is issued if the setting does not
9830 match the language default. If a range error occurs and range checking is on,
9831 then a message is printed and evaluation of the expression is aborted.
9833 @item set check range warn
9834 Output messages when the @value{GDBN} range checker detects a range error,
9835 but attempt to evaluate the expression anyway. Evaluating the
9836 expression may still be impossible for other reasons, such as accessing
9837 memory that the process does not own (a typical example from many Unix
9841 Show the current setting of the range checker, and whether or not it is
9842 being set automatically by @value{GDBN}.
9845 @node Supported Languages
9846 @section Supported Languages
9848 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9849 assembly, Modula-2, and Ada.
9850 @c This is false ...
9851 Some @value{GDBN} features may be used in expressions regardless of the
9852 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9853 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9854 ,Expressions}) can be used with the constructs of any supported
9857 The following sections detail to what degree each source language is
9858 supported by @value{GDBN}. These sections are not meant to be language
9859 tutorials or references, but serve only as a reference guide to what the
9860 @value{GDBN} expression parser accepts, and what input and output
9861 formats should look like for different languages. There are many good
9862 books written on each of these languages; please look to these for a
9863 language reference or tutorial.
9867 * Objective-C:: Objective-C
9870 * Modula-2:: Modula-2
9875 @subsection C and C@t{++}
9877 @cindex C and C@t{++}
9878 @cindex expressions in C or C@t{++}
9880 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9881 to both languages. Whenever this is the case, we discuss those languages
9885 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9886 @cindex @sc{gnu} C@t{++}
9887 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9888 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9889 effectively, you must compile your C@t{++} programs with a supported
9890 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9891 compiler (@code{aCC}).
9893 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9894 format; if it doesn't work on your system, try the stabs+ debugging
9895 format. You can select those formats explicitly with the @code{g++}
9896 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9897 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9898 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9901 * C Operators:: C and C@t{++} operators
9902 * C Constants:: C and C@t{++} constants
9903 * C Plus Plus Expressions:: C@t{++} expressions
9904 * C Defaults:: Default settings for C and C@t{++}
9905 * C Checks:: C and C@t{++} type and range checks
9906 * Debugging C:: @value{GDBN} and C
9907 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9908 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9912 @subsubsection C and C@t{++} Operators
9914 @cindex C and C@t{++} operators
9916 Operators must be defined on values of specific types. For instance,
9917 @code{+} is defined on numbers, but not on structures. Operators are
9918 often defined on groups of types.
9920 For the purposes of C and C@t{++}, the following definitions hold:
9925 @emph{Integral types} include @code{int} with any of its storage-class
9926 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9929 @emph{Floating-point types} include @code{float}, @code{double}, and
9930 @code{long double} (if supported by the target platform).
9933 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9936 @emph{Scalar types} include all of the above.
9941 The following operators are supported. They are listed here
9942 in order of increasing precedence:
9946 The comma or sequencing operator. Expressions in a comma-separated list
9947 are evaluated from left to right, with the result of the entire
9948 expression being the last expression evaluated.
9951 Assignment. The value of an assignment expression is the value
9952 assigned. Defined on scalar types.
9955 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9956 and translated to @w{@code{@var{a} = @var{a op b}}}.
9957 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9958 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9959 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9962 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9963 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9967 Logical @sc{or}. Defined on integral types.
9970 Logical @sc{and}. Defined on integral types.
9973 Bitwise @sc{or}. Defined on integral types.
9976 Bitwise exclusive-@sc{or}. Defined on integral types.
9979 Bitwise @sc{and}. Defined on integral types.
9982 Equality and inequality. Defined on scalar types. The value of these
9983 expressions is 0 for false and non-zero for true.
9985 @item <@r{, }>@r{, }<=@r{, }>=
9986 Less than, greater than, less than or equal, greater than or equal.
9987 Defined on scalar types. The value of these expressions is 0 for false
9988 and non-zero for true.
9991 left shift, and right shift. Defined on integral types.
9994 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9997 Addition and subtraction. Defined on integral types, floating-point types and
10000 @item *@r{, }/@r{, }%
10001 Multiplication, division, and modulus. Multiplication and division are
10002 defined on integral and floating-point types. Modulus is defined on
10006 Increment and decrement. When appearing before a variable, the
10007 operation is performed before the variable is used in an expression;
10008 when appearing after it, the variable's value is used before the
10009 operation takes place.
10012 Pointer dereferencing. Defined on pointer types. Same precedence as
10016 Address operator. Defined on variables. Same precedence as @code{++}.
10018 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10019 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10020 to examine the address
10021 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10025 Negative. Defined on integral and floating-point types. Same
10026 precedence as @code{++}.
10029 Logical negation. Defined on integral types. Same precedence as
10033 Bitwise complement operator. Defined on integral types. Same precedence as
10038 Structure member, and pointer-to-structure member. For convenience,
10039 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10040 pointer based on the stored type information.
10041 Defined on @code{struct} and @code{union} data.
10044 Dereferences of pointers to members.
10047 Array indexing. @code{@var{a}[@var{i}]} is defined as
10048 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10051 Function parameter list. Same precedence as @code{->}.
10054 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10055 and @code{class} types.
10058 Doubled colons also represent the @value{GDBN} scope operator
10059 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10063 If an operator is redefined in the user code, @value{GDBN} usually
10064 attempts to invoke the redefined version instead of using the operator's
10065 predefined meaning.
10068 @subsubsection C and C@t{++} Constants
10070 @cindex C and C@t{++} constants
10072 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10077 Integer constants are a sequence of digits. Octal constants are
10078 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10079 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10080 @samp{l}, specifying that the constant should be treated as a
10084 Floating point constants are a sequence of digits, followed by a decimal
10085 point, followed by a sequence of digits, and optionally followed by an
10086 exponent. An exponent is of the form:
10087 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10088 sequence of digits. The @samp{+} is optional for positive exponents.
10089 A floating-point constant may also end with a letter @samp{f} or
10090 @samp{F}, specifying that the constant should be treated as being of
10091 the @code{float} (as opposed to the default @code{double}) type; or with
10092 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10096 Enumerated constants consist of enumerated identifiers, or their
10097 integral equivalents.
10100 Character constants are a single character surrounded by single quotes
10101 (@code{'}), or a number---the ordinal value of the corresponding character
10102 (usually its @sc{ascii} value). Within quotes, the single character may
10103 be represented by a letter or by @dfn{escape sequences}, which are of
10104 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10105 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10106 @samp{@var{x}} is a predefined special character---for example,
10107 @samp{\n} for newline.
10110 String constants are a sequence of character constants surrounded by
10111 double quotes (@code{"}). Any valid character constant (as described
10112 above) may appear. Double quotes within the string must be preceded by
10113 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10117 Pointer constants are an integral value. You can also write pointers
10118 to constants using the C operator @samp{&}.
10121 Array constants are comma-separated lists surrounded by braces @samp{@{}
10122 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10123 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10124 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10127 @node C Plus Plus Expressions
10128 @subsubsection C@t{++} Expressions
10130 @cindex expressions in C@t{++}
10131 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10133 @cindex debugging C@t{++} programs
10134 @cindex C@t{++} compilers
10135 @cindex debug formats and C@t{++}
10136 @cindex @value{NGCC} and C@t{++}
10138 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10139 proper compiler and the proper debug format. Currently, @value{GDBN}
10140 works best when debugging C@t{++} code that is compiled with
10141 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10142 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10143 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10144 stabs+ as their default debug format, so you usually don't need to
10145 specify a debug format explicitly. Other compilers and/or debug formats
10146 are likely to work badly or not at all when using @value{GDBN} to debug
10152 @cindex member functions
10154 Member function calls are allowed; you can use expressions like
10157 count = aml->GetOriginal(x, y)
10160 @vindex this@r{, inside C@t{++} member functions}
10161 @cindex namespace in C@t{++}
10163 While a member function is active (in the selected stack frame), your
10164 expressions have the same namespace available as the member function;
10165 that is, @value{GDBN} allows implicit references to the class instance
10166 pointer @code{this} following the same rules as C@t{++}.
10168 @cindex call overloaded functions
10169 @cindex overloaded functions, calling
10170 @cindex type conversions in C@t{++}
10172 You can call overloaded functions; @value{GDBN} resolves the function
10173 call to the right definition, with some restrictions. @value{GDBN} does not
10174 perform overload resolution involving user-defined type conversions,
10175 calls to constructors, or instantiations of templates that do not exist
10176 in the program. It also cannot handle ellipsis argument lists or
10179 It does perform integral conversions and promotions, floating-point
10180 promotions, arithmetic conversions, pointer conversions, conversions of
10181 class objects to base classes, and standard conversions such as those of
10182 functions or arrays to pointers; it requires an exact match on the
10183 number of function arguments.
10185 Overload resolution is always performed, unless you have specified
10186 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10187 ,@value{GDBN} Features for C@t{++}}.
10189 You must specify @code{set overload-resolution off} in order to use an
10190 explicit function signature to call an overloaded function, as in
10192 p 'foo(char,int)'('x', 13)
10195 The @value{GDBN} command-completion facility can simplify this;
10196 see @ref{Completion, ,Command Completion}.
10198 @cindex reference declarations
10200 @value{GDBN} understands variables declared as C@t{++} references; you can use
10201 them in expressions just as you do in C@t{++} source---they are automatically
10204 In the parameter list shown when @value{GDBN} displays a frame, the values of
10205 reference variables are not displayed (unlike other variables); this
10206 avoids clutter, since references are often used for large structures.
10207 The @emph{address} of a reference variable is always shown, unless
10208 you have specified @samp{set print address off}.
10211 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10212 expressions can use it just as expressions in your program do. Since
10213 one scope may be defined in another, you can use @code{::} repeatedly if
10214 necessary, for example in an expression like
10215 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10216 resolving name scope by reference to source files, in both C and C@t{++}
10217 debugging (@pxref{Variables, ,Program Variables}).
10220 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10221 calling virtual functions correctly, printing out virtual bases of
10222 objects, calling functions in a base subobject, casting objects, and
10223 invoking user-defined operators.
10226 @subsubsection C and C@t{++} Defaults
10228 @cindex C and C@t{++} defaults
10230 If you allow @value{GDBN} to set type and range checking automatically, they
10231 both default to @code{off} whenever the working language changes to
10232 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10233 selects the working language.
10235 If you allow @value{GDBN} to set the language automatically, it
10236 recognizes source files whose names end with @file{.c}, @file{.C}, or
10237 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10238 these files, it sets the working language to C or C@t{++}.
10239 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10240 for further details.
10242 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10243 @c unimplemented. If (b) changes, it might make sense to let this node
10244 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10247 @subsubsection C and C@t{++} Type and Range Checks
10249 @cindex C and C@t{++} checks
10251 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10252 is not used. However, if you turn type checking on, @value{GDBN}
10253 considers two variables type equivalent if:
10257 The two variables are structured and have the same structure, union, or
10261 The two variables have the same type name, or types that have been
10262 declared equivalent through @code{typedef}.
10265 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10268 The two @code{struct}, @code{union}, or @code{enum} variables are
10269 declared in the same declaration. (Note: this may not be true for all C
10274 Range checking, if turned on, is done on mathematical operations. Array
10275 indices are not checked, since they are often used to index a pointer
10276 that is not itself an array.
10279 @subsubsection @value{GDBN} and C
10281 The @code{set print union} and @code{show print union} commands apply to
10282 the @code{union} type. When set to @samp{on}, any @code{union} that is
10283 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10284 appears as @samp{@{...@}}.
10286 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10287 with pointers and a memory allocation function. @xref{Expressions,
10290 @node Debugging C Plus Plus
10291 @subsubsection @value{GDBN} Features for C@t{++}
10293 @cindex commands for C@t{++}
10295 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10296 designed specifically for use with C@t{++}. Here is a summary:
10299 @cindex break in overloaded functions
10300 @item @r{breakpoint menus}
10301 When you want a breakpoint in a function whose name is overloaded,
10302 @value{GDBN} has the capability to display a menu of possible breakpoint
10303 locations to help you specify which function definition you want.
10304 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10306 @cindex overloading in C@t{++}
10307 @item rbreak @var{regex}
10308 Setting breakpoints using regular expressions is helpful for setting
10309 breakpoints on overloaded functions that are not members of any special
10311 @xref{Set Breaks, ,Setting Breakpoints}.
10313 @cindex C@t{++} exception handling
10316 Debug C@t{++} exception handling using these commands. @xref{Set
10317 Catchpoints, , Setting Catchpoints}.
10319 @cindex inheritance
10320 @item ptype @var{typename}
10321 Print inheritance relationships as well as other information for type
10323 @xref{Symbols, ,Examining the Symbol Table}.
10325 @cindex C@t{++} symbol display
10326 @item set print demangle
10327 @itemx show print demangle
10328 @itemx set print asm-demangle
10329 @itemx show print asm-demangle
10330 Control whether C@t{++} symbols display in their source form, both when
10331 displaying code as C@t{++} source and when displaying disassemblies.
10332 @xref{Print Settings, ,Print Settings}.
10334 @item set print object
10335 @itemx show print object
10336 Choose whether to print derived (actual) or declared types of objects.
10337 @xref{Print Settings, ,Print Settings}.
10339 @item set print vtbl
10340 @itemx show print vtbl
10341 Control the format for printing virtual function tables.
10342 @xref{Print Settings, ,Print Settings}.
10343 (The @code{vtbl} commands do not work on programs compiled with the HP
10344 ANSI C@t{++} compiler (@code{aCC}).)
10346 @kindex set overload-resolution
10347 @cindex overloaded functions, overload resolution
10348 @item set overload-resolution on
10349 Enable overload resolution for C@t{++} expression evaluation. The default
10350 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10351 and searches for a function whose signature matches the argument types,
10352 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10353 Expressions, ,C@t{++} Expressions}, for details).
10354 If it cannot find a match, it emits a message.
10356 @item set overload-resolution off
10357 Disable overload resolution for C@t{++} expression evaluation. For
10358 overloaded functions that are not class member functions, @value{GDBN}
10359 chooses the first function of the specified name that it finds in the
10360 symbol table, whether or not its arguments are of the correct type. For
10361 overloaded functions that are class member functions, @value{GDBN}
10362 searches for a function whose signature @emph{exactly} matches the
10365 @kindex show overload-resolution
10366 @item show overload-resolution
10367 Show the current setting of overload resolution.
10369 @item @r{Overloaded symbol names}
10370 You can specify a particular definition of an overloaded symbol, using
10371 the same notation that is used to declare such symbols in C@t{++}: type
10372 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10373 also use the @value{GDBN} command-line word completion facilities to list the
10374 available choices, or to finish the type list for you.
10375 @xref{Completion,, Command Completion}, for details on how to do this.
10378 @node Decimal Floating Point
10379 @subsubsection Decimal Floating Point format
10380 @cindex decimal floating point format
10382 @value{GDBN} can examine, set and perform computations with numbers in
10383 decimal floating point format, which in the C language correspond to the
10384 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10385 specified by the extension to support decimal floating-point arithmetic.
10387 There are two encodings in use, depending on the architecture: BID (Binary
10388 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10389 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10392 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10393 to manipulate decimal floating point numbers, it is not possible to convert
10394 (using a cast, for example) integers wider than 32-bit to decimal float.
10396 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10397 point computations, error checking in decimal float operations ignores
10398 underflow, overflow and divide by zero exceptions.
10400 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10401 to inspect @code{_Decimal128} values stored in floating point registers. See
10402 @ref{PowerPC,,PowerPC} for more details.
10405 @subsection Objective-C
10407 @cindex Objective-C
10408 This section provides information about some commands and command
10409 options that are useful for debugging Objective-C code. See also
10410 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10411 few more commands specific to Objective-C support.
10414 * Method Names in Commands::
10415 * The Print Command with Objective-C::
10418 @node Method Names in Commands
10419 @subsubsection Method Names in Commands
10421 The following commands have been extended to accept Objective-C method
10422 names as line specifications:
10424 @kindex clear@r{, and Objective-C}
10425 @kindex break@r{, and Objective-C}
10426 @kindex info line@r{, and Objective-C}
10427 @kindex jump@r{, and Objective-C}
10428 @kindex list@r{, and Objective-C}
10432 @item @code{info line}
10437 A fully qualified Objective-C method name is specified as
10440 -[@var{Class} @var{methodName}]
10443 where the minus sign is used to indicate an instance method and a
10444 plus sign (not shown) is used to indicate a class method. The class
10445 name @var{Class} and method name @var{methodName} are enclosed in
10446 brackets, similar to the way messages are specified in Objective-C
10447 source code. For example, to set a breakpoint at the @code{create}
10448 instance method of class @code{Fruit} in the program currently being
10452 break -[Fruit create]
10455 To list ten program lines around the @code{initialize} class method,
10459 list +[NSText initialize]
10462 In the current version of @value{GDBN}, the plus or minus sign is
10463 required. In future versions of @value{GDBN}, the plus or minus
10464 sign will be optional, but you can use it to narrow the search. It
10465 is also possible to specify just a method name:
10471 You must specify the complete method name, including any colons. If
10472 your program's source files contain more than one @code{create} method,
10473 you'll be presented with a numbered list of classes that implement that
10474 method. Indicate your choice by number, or type @samp{0} to exit if
10477 As another example, to clear a breakpoint established at the
10478 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10481 clear -[NSWindow makeKeyAndOrderFront:]
10484 @node The Print Command with Objective-C
10485 @subsubsection The Print Command With Objective-C
10486 @cindex Objective-C, print objects
10487 @kindex print-object
10488 @kindex po @r{(@code{print-object})}
10490 The print command has also been extended to accept methods. For example:
10493 print -[@var{object} hash]
10496 @cindex print an Objective-C object description
10497 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10499 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10500 and print the result. Also, an additional command has been added,
10501 @code{print-object} or @code{po} for short, which is meant to print
10502 the description of an object. However, this command may only work
10503 with certain Objective-C libraries that have a particular hook
10504 function, @code{_NSPrintForDebugger}, defined.
10507 @subsection Fortran
10508 @cindex Fortran-specific support in @value{GDBN}
10510 @value{GDBN} can be used to debug programs written in Fortran, but it
10511 currently supports only the features of Fortran 77 language.
10513 @cindex trailing underscore, in Fortran symbols
10514 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10515 among them) append an underscore to the names of variables and
10516 functions. When you debug programs compiled by those compilers, you
10517 will need to refer to variables and functions with a trailing
10521 * Fortran Operators:: Fortran operators and expressions
10522 * Fortran Defaults:: Default settings for Fortran
10523 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10526 @node Fortran Operators
10527 @subsubsection Fortran Operators and Expressions
10529 @cindex Fortran operators and expressions
10531 Operators must be defined on values of specific types. For instance,
10532 @code{+} is defined on numbers, but not on characters or other non-
10533 arithmetic types. Operators are often defined on groups of types.
10537 The exponentiation operator. It raises the first operand to the power
10541 The range operator. Normally used in the form of array(low:high) to
10542 represent a section of array.
10545 The access component operator. Normally used to access elements in derived
10546 types. Also suitable for unions. As unions aren't part of regular Fortran,
10547 this can only happen when accessing a register that uses a gdbarch-defined
10551 @node Fortran Defaults
10552 @subsubsection Fortran Defaults
10554 @cindex Fortran Defaults
10556 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10557 default uses case-insensitive matches for Fortran symbols. You can
10558 change that with the @samp{set case-insensitive} command, see
10559 @ref{Symbols}, for the details.
10561 @node Special Fortran Commands
10562 @subsubsection Special Fortran Commands
10564 @cindex Special Fortran commands
10566 @value{GDBN} has some commands to support Fortran-specific features,
10567 such as displaying common blocks.
10570 @cindex @code{COMMON} blocks, Fortran
10571 @kindex info common
10572 @item info common @r{[}@var{common-name}@r{]}
10573 This command prints the values contained in the Fortran @code{COMMON}
10574 block whose name is @var{common-name}. With no argument, the names of
10575 all @code{COMMON} blocks visible at the current program location are
10582 @cindex Pascal support in @value{GDBN}, limitations
10583 Debugging Pascal programs which use sets, subranges, file variables, or
10584 nested functions does not currently work. @value{GDBN} does not support
10585 entering expressions, printing values, or similar features using Pascal
10588 The Pascal-specific command @code{set print pascal_static-members}
10589 controls whether static members of Pascal objects are displayed.
10590 @xref{Print Settings, pascal_static-members}.
10593 @subsection Modula-2
10595 @cindex Modula-2, @value{GDBN} support
10597 The extensions made to @value{GDBN} to support Modula-2 only support
10598 output from the @sc{gnu} Modula-2 compiler (which is currently being
10599 developed). Other Modula-2 compilers are not currently supported, and
10600 attempting to debug executables produced by them is most likely
10601 to give an error as @value{GDBN} reads in the executable's symbol
10604 @cindex expressions in Modula-2
10606 * M2 Operators:: Built-in operators
10607 * Built-In Func/Proc:: Built-in functions and procedures
10608 * M2 Constants:: Modula-2 constants
10609 * M2 Types:: Modula-2 types
10610 * M2 Defaults:: Default settings for Modula-2
10611 * Deviations:: Deviations from standard Modula-2
10612 * M2 Checks:: Modula-2 type and range checks
10613 * M2 Scope:: The scope operators @code{::} and @code{.}
10614 * GDB/M2:: @value{GDBN} and Modula-2
10618 @subsubsection Operators
10619 @cindex Modula-2 operators
10621 Operators must be defined on values of specific types. For instance,
10622 @code{+} is defined on numbers, but not on structures. Operators are
10623 often defined on groups of types. For the purposes of Modula-2, the
10624 following definitions hold:
10629 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10633 @emph{Character types} consist of @code{CHAR} and its subranges.
10636 @emph{Floating-point types} consist of @code{REAL}.
10639 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10643 @emph{Scalar types} consist of all of the above.
10646 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10649 @emph{Boolean types} consist of @code{BOOLEAN}.
10653 The following operators are supported, and appear in order of
10654 increasing precedence:
10658 Function argument or array index separator.
10661 Assignment. The value of @var{var} @code{:=} @var{value} is
10665 Less than, greater than on integral, floating-point, or enumerated
10669 Less than or equal to, greater than or equal to
10670 on integral, floating-point and enumerated types, or set inclusion on
10671 set types. Same precedence as @code{<}.
10673 @item =@r{, }<>@r{, }#
10674 Equality and two ways of expressing inequality, valid on scalar types.
10675 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10676 available for inequality, since @code{#} conflicts with the script
10680 Set membership. Defined on set types and the types of their members.
10681 Same precedence as @code{<}.
10684 Boolean disjunction. Defined on boolean types.
10687 Boolean conjunction. Defined on boolean types.
10690 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10693 Addition and subtraction on integral and floating-point types, or union
10694 and difference on set types.
10697 Multiplication on integral and floating-point types, or set intersection
10701 Division on floating-point types, or symmetric set difference on set
10702 types. Same precedence as @code{*}.
10705 Integer division and remainder. Defined on integral types. Same
10706 precedence as @code{*}.
10709 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10712 Pointer dereferencing. Defined on pointer types.
10715 Boolean negation. Defined on boolean types. Same precedence as
10719 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10720 precedence as @code{^}.
10723 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10726 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10730 @value{GDBN} and Modula-2 scope operators.
10734 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10735 treats the use of the operator @code{IN}, or the use of operators
10736 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10737 @code{<=}, and @code{>=} on sets as an error.
10741 @node Built-In Func/Proc
10742 @subsubsection Built-in Functions and Procedures
10743 @cindex Modula-2 built-ins
10745 Modula-2 also makes available several built-in procedures and functions.
10746 In describing these, the following metavariables are used:
10751 represents an @code{ARRAY} variable.
10754 represents a @code{CHAR} constant or variable.
10757 represents a variable or constant of integral type.
10760 represents an identifier that belongs to a set. Generally used in the
10761 same function with the metavariable @var{s}. The type of @var{s} should
10762 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10765 represents a variable or constant of integral or floating-point type.
10768 represents a variable or constant of floating-point type.
10774 represents a variable.
10777 represents a variable or constant of one of many types. See the
10778 explanation of the function for details.
10781 All Modula-2 built-in procedures also return a result, described below.
10785 Returns the absolute value of @var{n}.
10788 If @var{c} is a lower case letter, it returns its upper case
10789 equivalent, otherwise it returns its argument.
10792 Returns the character whose ordinal value is @var{i}.
10795 Decrements the value in the variable @var{v} by one. Returns the new value.
10797 @item DEC(@var{v},@var{i})
10798 Decrements the value in the variable @var{v} by @var{i}. Returns the
10801 @item EXCL(@var{m},@var{s})
10802 Removes the element @var{m} from the set @var{s}. Returns the new
10805 @item FLOAT(@var{i})
10806 Returns the floating point equivalent of the integer @var{i}.
10808 @item HIGH(@var{a})
10809 Returns the index of the last member of @var{a}.
10812 Increments the value in the variable @var{v} by one. Returns the new value.
10814 @item INC(@var{v},@var{i})
10815 Increments the value in the variable @var{v} by @var{i}. Returns the
10818 @item INCL(@var{m},@var{s})
10819 Adds the element @var{m} to the set @var{s} if it is not already
10820 there. Returns the new set.
10823 Returns the maximum value of the type @var{t}.
10826 Returns the minimum value of the type @var{t}.
10829 Returns boolean TRUE if @var{i} is an odd number.
10832 Returns the ordinal value of its argument. For example, the ordinal
10833 value of a character is its @sc{ascii} value (on machines supporting the
10834 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10835 integral, character and enumerated types.
10837 @item SIZE(@var{x})
10838 Returns the size of its argument. @var{x} can be a variable or a type.
10840 @item TRUNC(@var{r})
10841 Returns the integral part of @var{r}.
10843 @item TSIZE(@var{x})
10844 Returns the size of its argument. @var{x} can be a variable or a type.
10846 @item VAL(@var{t},@var{i})
10847 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10851 @emph{Warning:} Sets and their operations are not yet supported, so
10852 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10856 @cindex Modula-2 constants
10858 @subsubsection Constants
10860 @value{GDBN} allows you to express the constants of Modula-2 in the following
10866 Integer constants are simply a sequence of digits. When used in an
10867 expression, a constant is interpreted to be type-compatible with the
10868 rest of the expression. Hexadecimal integers are specified by a
10869 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10872 Floating point constants appear as a sequence of digits, followed by a
10873 decimal point and another sequence of digits. An optional exponent can
10874 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10875 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10876 digits of the floating point constant must be valid decimal (base 10)
10880 Character constants consist of a single character enclosed by a pair of
10881 like quotes, either single (@code{'}) or double (@code{"}). They may
10882 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10883 followed by a @samp{C}.
10886 String constants consist of a sequence of characters enclosed by a
10887 pair of like quotes, either single (@code{'}) or double (@code{"}).
10888 Escape sequences in the style of C are also allowed. @xref{C
10889 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10893 Enumerated constants consist of an enumerated identifier.
10896 Boolean constants consist of the identifiers @code{TRUE} and
10900 Pointer constants consist of integral values only.
10903 Set constants are not yet supported.
10907 @subsubsection Modula-2 Types
10908 @cindex Modula-2 types
10910 Currently @value{GDBN} can print the following data types in Modula-2
10911 syntax: array types, record types, set types, pointer types, procedure
10912 types, enumerated types, subrange types and base types. You can also
10913 print the contents of variables declared using these type.
10914 This section gives a number of simple source code examples together with
10915 sample @value{GDBN} sessions.
10917 The first example contains the following section of code:
10926 and you can request @value{GDBN} to interrogate the type and value of
10927 @code{r} and @code{s}.
10930 (@value{GDBP}) print s
10932 (@value{GDBP}) ptype s
10934 (@value{GDBP}) print r
10936 (@value{GDBP}) ptype r
10941 Likewise if your source code declares @code{s} as:
10945 s: SET ['A'..'Z'] ;
10949 then you may query the type of @code{s} by:
10952 (@value{GDBP}) ptype s
10953 type = SET ['A'..'Z']
10957 Note that at present you cannot interactively manipulate set
10958 expressions using the debugger.
10960 The following example shows how you might declare an array in Modula-2
10961 and how you can interact with @value{GDBN} to print its type and contents:
10965 s: ARRAY [-10..10] OF CHAR ;
10969 (@value{GDBP}) ptype s
10970 ARRAY [-10..10] OF CHAR
10973 Note that the array handling is not yet complete and although the type
10974 is printed correctly, expression handling still assumes that all
10975 arrays have a lower bound of zero and not @code{-10} as in the example
10978 Here are some more type related Modula-2 examples:
10982 colour = (blue, red, yellow, green) ;
10983 t = [blue..yellow] ;
10991 The @value{GDBN} interaction shows how you can query the data type
10992 and value of a variable.
10995 (@value{GDBP}) print s
10997 (@value{GDBP}) ptype t
10998 type = [blue..yellow]
11002 In this example a Modula-2 array is declared and its contents
11003 displayed. Observe that the contents are written in the same way as
11004 their @code{C} counterparts.
11008 s: ARRAY [1..5] OF CARDINAL ;
11014 (@value{GDBP}) print s
11015 $1 = @{1, 0, 0, 0, 0@}
11016 (@value{GDBP}) ptype s
11017 type = ARRAY [1..5] OF CARDINAL
11020 The Modula-2 language interface to @value{GDBN} also understands
11021 pointer types as shown in this example:
11025 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11032 and you can request that @value{GDBN} describes the type of @code{s}.
11035 (@value{GDBP}) ptype s
11036 type = POINTER TO ARRAY [1..5] OF CARDINAL
11039 @value{GDBN} handles compound types as we can see in this example.
11040 Here we combine array types, record types, pointer types and subrange
11051 myarray = ARRAY myrange OF CARDINAL ;
11052 myrange = [-2..2] ;
11054 s: POINTER TO ARRAY myrange OF foo ;
11058 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11062 (@value{GDBP}) ptype s
11063 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11066 f3 : ARRAY [-2..2] OF CARDINAL;
11071 @subsubsection Modula-2 Defaults
11072 @cindex Modula-2 defaults
11074 If type and range checking are set automatically by @value{GDBN}, they
11075 both default to @code{on} whenever the working language changes to
11076 Modula-2. This happens regardless of whether you or @value{GDBN}
11077 selected the working language.
11079 If you allow @value{GDBN} to set the language automatically, then entering
11080 code compiled from a file whose name ends with @file{.mod} sets the
11081 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11082 Infer the Source Language}, for further details.
11085 @subsubsection Deviations from Standard Modula-2
11086 @cindex Modula-2, deviations from
11088 A few changes have been made to make Modula-2 programs easier to debug.
11089 This is done primarily via loosening its type strictness:
11093 Unlike in standard Modula-2, pointer constants can be formed by
11094 integers. This allows you to modify pointer variables during
11095 debugging. (In standard Modula-2, the actual address contained in a
11096 pointer variable is hidden from you; it can only be modified
11097 through direct assignment to another pointer variable or expression that
11098 returned a pointer.)
11101 C escape sequences can be used in strings and characters to represent
11102 non-printable characters. @value{GDBN} prints out strings with these
11103 escape sequences embedded. Single non-printable characters are
11104 printed using the @samp{CHR(@var{nnn})} format.
11107 The assignment operator (@code{:=}) returns the value of its right-hand
11111 All built-in procedures both modify @emph{and} return their argument.
11115 @subsubsection Modula-2 Type and Range Checks
11116 @cindex Modula-2 checks
11119 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11122 @c FIXME remove warning when type/range checks added
11124 @value{GDBN} considers two Modula-2 variables type equivalent if:
11128 They are of types that have been declared equivalent via a @code{TYPE
11129 @var{t1} = @var{t2}} statement
11132 They have been declared on the same line. (Note: This is true of the
11133 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11136 As long as type checking is enabled, any attempt to combine variables
11137 whose types are not equivalent is an error.
11139 Range checking is done on all mathematical operations, assignment, array
11140 index bounds, and all built-in functions and procedures.
11143 @subsubsection The Scope Operators @code{::} and @code{.}
11145 @cindex @code{.}, Modula-2 scope operator
11146 @cindex colon, doubled as scope operator
11148 @vindex colon-colon@r{, in Modula-2}
11149 @c Info cannot handle :: but TeX can.
11152 @vindex ::@r{, in Modula-2}
11155 There are a few subtle differences between the Modula-2 scope operator
11156 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11161 @var{module} . @var{id}
11162 @var{scope} :: @var{id}
11166 where @var{scope} is the name of a module or a procedure,
11167 @var{module} the name of a module, and @var{id} is any declared
11168 identifier within your program, except another module.
11170 Using the @code{::} operator makes @value{GDBN} search the scope
11171 specified by @var{scope} for the identifier @var{id}. If it is not
11172 found in the specified scope, then @value{GDBN} searches all scopes
11173 enclosing the one specified by @var{scope}.
11175 Using the @code{.} operator makes @value{GDBN} search the current scope for
11176 the identifier specified by @var{id} that was imported from the
11177 definition module specified by @var{module}. With this operator, it is
11178 an error if the identifier @var{id} was not imported from definition
11179 module @var{module}, or if @var{id} is not an identifier in
11183 @subsubsection @value{GDBN} and Modula-2
11185 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11186 Five subcommands of @code{set print} and @code{show print} apply
11187 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11188 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11189 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11190 analogue in Modula-2.
11192 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11193 with any language, is not useful with Modula-2. Its
11194 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11195 created in Modula-2 as they can in C or C@t{++}. However, because an
11196 address can be specified by an integral constant, the construct
11197 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11199 @cindex @code{#} in Modula-2
11200 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11201 interpreted as the beginning of a comment. Use @code{<>} instead.
11207 The extensions made to @value{GDBN} for Ada only support
11208 output from the @sc{gnu} Ada (GNAT) compiler.
11209 Other Ada compilers are not currently supported, and
11210 attempting to debug executables produced by them is most likely
11214 @cindex expressions in Ada
11216 * Ada Mode Intro:: General remarks on the Ada syntax
11217 and semantics supported by Ada mode
11219 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11220 * Additions to Ada:: Extensions of the Ada expression syntax.
11221 * Stopping Before Main Program:: Debugging the program during elaboration.
11222 * Ada Tasks:: Listing and setting breakpoints in tasks.
11223 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11224 * Ada Glitches:: Known peculiarities of Ada mode.
11227 @node Ada Mode Intro
11228 @subsubsection Introduction
11229 @cindex Ada mode, general
11231 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11232 syntax, with some extensions.
11233 The philosophy behind the design of this subset is
11237 That @value{GDBN} should provide basic literals and access to operations for
11238 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11239 leaving more sophisticated computations to subprograms written into the
11240 program (which therefore may be called from @value{GDBN}).
11243 That type safety and strict adherence to Ada language restrictions
11244 are not particularly important to the @value{GDBN} user.
11247 That brevity is important to the @value{GDBN} user.
11250 Thus, for brevity, the debugger acts as if all names declared in
11251 user-written packages are directly visible, even if they are not visible
11252 according to Ada rules, thus making it unnecessary to fully qualify most
11253 names with their packages, regardless of context. Where this causes
11254 ambiguity, @value{GDBN} asks the user's intent.
11256 The debugger will start in Ada mode if it detects an Ada main program.
11257 As for other languages, it will enter Ada mode when stopped in a program that
11258 was translated from an Ada source file.
11260 While in Ada mode, you may use `@t{--}' for comments. This is useful
11261 mostly for documenting command files. The standard @value{GDBN} comment
11262 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11263 middle (to allow based literals).
11265 The debugger supports limited overloading. Given a subprogram call in which
11266 the function symbol has multiple definitions, it will use the number of
11267 actual parameters and some information about their types to attempt to narrow
11268 the set of definitions. It also makes very limited use of context, preferring
11269 procedures to functions in the context of the @code{call} command, and
11270 functions to procedures elsewhere.
11272 @node Omissions from Ada
11273 @subsubsection Omissions from Ada
11274 @cindex Ada, omissions from
11276 Here are the notable omissions from the subset:
11280 Only a subset of the attributes are supported:
11284 @t{'First}, @t{'Last}, and @t{'Length}
11285 on array objects (not on types and subtypes).
11288 @t{'Min} and @t{'Max}.
11291 @t{'Pos} and @t{'Val}.
11297 @t{'Range} on array objects (not subtypes), but only as the right
11298 operand of the membership (@code{in}) operator.
11301 @t{'Access}, @t{'Unchecked_Access}, and
11302 @t{'Unrestricted_Access} (a GNAT extension).
11310 @code{Characters.Latin_1} are not available and
11311 concatenation is not implemented. Thus, escape characters in strings are
11312 not currently available.
11315 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11316 equality of representations. They will generally work correctly
11317 for strings and arrays whose elements have integer or enumeration types.
11318 They may not work correctly for arrays whose element
11319 types have user-defined equality, for arrays of real values
11320 (in particular, IEEE-conformant floating point, because of negative
11321 zeroes and NaNs), and for arrays whose elements contain unused bits with
11322 indeterminate values.
11325 The other component-by-component array operations (@code{and}, @code{or},
11326 @code{xor}, @code{not}, and relational tests other than equality)
11327 are not implemented.
11330 @cindex array aggregates (Ada)
11331 @cindex record aggregates (Ada)
11332 @cindex aggregates (Ada)
11333 There is limited support for array and record aggregates. They are
11334 permitted only on the right sides of assignments, as in these examples:
11337 set An_Array := (1, 2, 3, 4, 5, 6)
11338 set An_Array := (1, others => 0)
11339 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11340 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11341 set A_Record := (1, "Peter", True);
11342 set A_Record := (Name => "Peter", Id => 1, Alive => True)
11346 discriminant's value by assigning an aggregate has an
11347 undefined effect if that discriminant is used within the record.
11348 However, you can first modify discriminants by directly assigning to
11349 them (which normally would not be allowed in Ada), and then performing an
11350 aggregate assignment. For example, given a variable @code{A_Rec}
11351 declared to have a type such as:
11354 type Rec (Len : Small_Integer := 0) is record
11356 Vals : IntArray (1 .. Len);
11360 you can assign a value with a different size of @code{Vals} with two
11365 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11368 As this example also illustrates, @value{GDBN} is very loose about the usual
11369 rules concerning aggregates. You may leave out some of the
11370 components of an array or record aggregate (such as the @code{Len}
11371 component in the assignment to @code{A_Rec} above); they will retain their
11372 original values upon assignment. You may freely use dynamic values as
11373 indices in component associations. You may even use overlapping or
11374 redundant component associations, although which component values are
11375 assigned in such cases is not defined.
11378 Calls to dispatching subprograms are not implemented.
11381 The overloading algorithm is much more limited (i.e., less selective)
11382 than that of real Ada. It makes only limited use of the context in
11383 which a subexpression appears to resolve its meaning, and it is much
11384 looser in its rules for allowing type matches. As a result, some
11385 function calls will be ambiguous, and the user will be asked to choose
11386 the proper resolution.
11389 The @code{new} operator is not implemented.
11392 Entry calls are not implemented.
11395 Aside from printing, arithmetic operations on the native VAX floating-point
11396 formats are not supported.
11399 It is not possible to slice a packed array.
11402 The names @code{True} and @code{False}, when not part of a qualified name,
11403 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11405 Should your program
11406 redefine these names in a package or procedure (at best a dubious practice),
11407 you will have to use fully qualified names to access their new definitions.
11410 @node Additions to Ada
11411 @subsubsection Additions to Ada
11412 @cindex Ada, deviations from
11414 As it does for other languages, @value{GDBN} makes certain generic
11415 extensions to Ada (@pxref{Expressions}):
11419 If the expression @var{E} is a variable residing in memory (typically
11420 a local variable or array element) and @var{N} is a positive integer,
11421 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11422 @var{N}-1 adjacent variables following it in memory as an array. In
11423 Ada, this operator is generally not necessary, since its prime use is
11424 in displaying parts of an array, and slicing will usually do this in
11425 Ada. However, there are occasional uses when debugging programs in
11426 which certain debugging information has been optimized away.
11429 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11430 appears in function or file @var{B}.'' When @var{B} is a file name,
11431 you must typically surround it in single quotes.
11434 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11435 @var{type} that appears at address @var{addr}.''
11438 A name starting with @samp{$} is a convenience variable
11439 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11442 In addition, @value{GDBN} provides a few other shortcuts and outright
11443 additions specific to Ada:
11447 The assignment statement is allowed as an expression, returning
11448 its right-hand operand as its value. Thus, you may enter
11452 print A(tmp := y + 1)
11456 The semicolon is allowed as an ``operator,'' returning as its value
11457 the value of its right-hand operand.
11458 This allows, for example,
11459 complex conditional breaks:
11463 condition 1 (report(i); k += 1; A(k) > 100)
11467 Rather than use catenation and symbolic character names to introduce special
11468 characters into strings, one may instead use a special bracket notation,
11469 which is also used to print strings. A sequence of characters of the form
11470 @samp{["@var{XX}"]} within a string or character literal denotes the
11471 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11472 sequence of characters @samp{["""]} also denotes a single quotation mark
11473 in strings. For example,
11475 "One line.["0a"]Next line.["0a"]"
11478 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11482 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11483 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11491 When printing arrays, @value{GDBN} uses positional notation when the
11492 array has a lower bound of 1, and uses a modified named notation otherwise.
11493 For example, a one-dimensional array of three integers with a lower bound
11494 of 3 might print as
11501 That is, in contrast to valid Ada, only the first component has a @code{=>}
11505 You may abbreviate attributes in expressions with any unique,
11506 multi-character subsequence of
11507 their names (an exact match gets preference).
11508 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11509 in place of @t{a'length}.
11512 @cindex quoting Ada internal identifiers
11513 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11514 to lower case. The GNAT compiler uses upper-case characters for
11515 some of its internal identifiers, which are normally of no interest to users.
11516 For the rare occasions when you actually have to look at them,
11517 enclose them in angle brackets to avoid the lower-case mapping.
11520 @value{GDBP} print <JMPBUF_SAVE>[0]
11524 Printing an object of class-wide type or dereferencing an
11525 access-to-class-wide value will display all the components of the object's
11526 specific type (as indicated by its run-time tag). Likewise, component
11527 selection on such a value will operate on the specific type of the
11532 @node Stopping Before Main Program
11533 @subsubsection Stopping at the Very Beginning
11535 @cindex breakpointing Ada elaboration code
11536 It is sometimes necessary to debug the program during elaboration, and
11537 before reaching the main procedure.
11538 As defined in the Ada Reference
11539 Manual, the elaboration code is invoked from a procedure called
11540 @code{adainit}. To run your program up to the beginning of
11541 elaboration, simply use the following two commands:
11542 @code{tbreak adainit} and @code{run}.
11545 @subsubsection Extensions for Ada Tasks
11546 @cindex Ada, tasking
11548 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11549 @value{GDBN} provides the following task-related commands:
11554 This command shows a list of current Ada tasks, as in the following example:
11561 (@value{GDBP}) info tasks
11562 ID TID P-ID Pri State Name
11563 1 8088000 0 15 Child Activation Wait main_task
11564 2 80a4000 1 15 Accept Statement b
11565 3 809a800 1 15 Child Activation Wait a
11566 * 4 80ae800 3 15 Running c
11571 In this listing, the asterisk before the last task indicates it to be the
11572 task currently being inspected.
11576 Represents @value{GDBN}'s internal task number.
11582 The parent's task ID (@value{GDBN}'s internal task number).
11585 The base priority of the task.
11588 Current state of the task.
11592 The task has been created but has not been activated. It cannot be
11596 The task currently running.
11599 The task is not blocked for any reason known to Ada. (It may be waiting
11600 for a mutex, though.) It is conceptually "executing" in normal mode.
11603 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11604 that were waiting on terminate alternatives have been awakened and have
11605 terminated themselves.
11607 @item Child Activation Wait
11608 The task is waiting for created tasks to complete activation.
11610 @item Accept Statement
11611 The task is waiting on an accept or selective wait statement.
11613 @item Waiting on entry call
11614 The task is waiting on an entry call.
11616 @item Async Select Wait
11617 The task is waiting to start the abortable part of an asynchronous
11621 The task is waiting on a select statement with only a delay
11624 @item Child Termination Wait
11625 The task is sleeping having completed a master within itself, and is
11626 waiting for the tasks dependent on that master to become terminated or
11627 waiting on a terminate Phase.
11629 @item Wait Child in Term Alt
11630 The task is sleeping waiting for tasks on terminate alternatives to
11631 finish terminating.
11633 @item Accepting RV with @var{taskno}
11634 The task is accepting a rendez-vous with the task @var{taskno}.
11638 Name of the task in the program.
11642 @kindex info task @var{taskno}
11643 @item info task @var{taskno}
11644 This command shows detailled informations on the specified task, as in
11645 the following example:
11650 (@value{GDBP}) info tasks
11651 ID TID P-ID Pri State Name
11652 1 8077880 0 15 Child Activation Wait main_task
11653 * 2 807c468 1 15 Running task_1
11654 (@value{GDBP}) info task 2
11655 Ada Task: 0x807c468
11658 Parent: 1 (main_task)
11664 @kindex task@r{ (Ada)}
11665 @cindex current Ada task ID
11666 This command prints the ID of the current task.
11672 (@value{GDBP}) info tasks
11673 ID TID P-ID Pri State Name
11674 1 8077870 0 15 Child Activation Wait main_task
11675 * 2 807c458 1 15 Running t
11676 (@value{GDBP}) task
11677 [Current task is 2]
11680 @item task @var{taskno}
11681 @cindex Ada task switching
11682 This command is like the @code{thread @var{threadno}}
11683 command (@pxref{Threads}). It switches the context of debugging
11684 from the current task to the given task.
11690 (@value{GDBP}) info tasks
11691 ID TID P-ID Pri State Name
11692 1 8077870 0 15 Child Activation Wait main_task
11693 * 2 807c458 1 15 Running t
11694 (@value{GDBP}) task 1
11695 [Switching to task 1]
11696 #0 0x8067726 in pthread_cond_wait ()
11698 #0 0x8067726 in pthread_cond_wait ()
11699 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11700 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11701 #3 0x806153e in system.tasking.stages.activate_tasks ()
11702 #4 0x804aacc in un () at un.adb:5
11707 @node Ada Tasks and Core Files
11708 @subsubsection Tasking Support when Debugging Core Files
11709 @cindex Ada tasking and core file debugging
11711 When inspecting a core file, as opposed to debugging a live program,
11712 tasking support may be limited or even unavailable, depending on
11713 the platform being used.
11714 For instance, on x86-linux, the list of tasks is available, but task
11715 switching is not supported. On Tru64, however, task switching will work
11718 On certain platforms, including Tru64, the debugger needs to perform some
11719 memory writes in order to provide Ada tasking support. When inspecting
11720 a core file, this means that the core file must be opened with read-write
11721 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
11722 Under these circumstances, you should make a backup copy of the core
11723 file before inspecting it with @value{GDBN}.
11726 @subsubsection Known Peculiarities of Ada Mode
11727 @cindex Ada, problems
11729 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11730 we know of several problems with and limitations of Ada mode in
11732 some of which will be fixed with planned future releases of the debugger
11733 and the GNU Ada compiler.
11737 Currently, the debugger
11738 has insufficient information to determine whether certain pointers represent
11739 pointers to objects or the objects themselves.
11740 Thus, the user may have to tack an extra @code{.all} after an expression
11741 to get it printed properly.
11744 Static constants that the compiler chooses not to materialize as objects in
11745 storage are invisible to the debugger.
11748 Named parameter associations in function argument lists are ignored (the
11749 argument lists are treated as positional).
11752 Many useful library packages are currently invisible to the debugger.
11755 Fixed-point arithmetic, conversions, input, and output is carried out using
11756 floating-point arithmetic, and may give results that only approximate those on
11760 The type of the @t{'Address} attribute may not be @code{System.Address}.
11763 The GNAT compiler never generates the prefix @code{Standard} for any of
11764 the standard symbols defined by the Ada language. @value{GDBN} knows about
11765 this: it will strip the prefix from names when you use it, and will never
11766 look for a name you have so qualified among local symbols, nor match against
11767 symbols in other packages or subprograms. If you have
11768 defined entities anywhere in your program other than parameters and
11769 local variables whose simple names match names in @code{Standard},
11770 GNAT's lack of qualification here can cause confusion. When this happens,
11771 you can usually resolve the confusion
11772 by qualifying the problematic names with package
11773 @code{Standard} explicitly.
11776 @node Unsupported Languages
11777 @section Unsupported Languages
11779 @cindex unsupported languages
11780 @cindex minimal language
11781 In addition to the other fully-supported programming languages,
11782 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11783 It does not represent a real programming language, but provides a set
11784 of capabilities close to what the C or assembly languages provide.
11785 This should allow most simple operations to be performed while debugging
11786 an application that uses a language currently not supported by @value{GDBN}.
11788 If the language is set to @code{auto}, @value{GDBN} will automatically
11789 select this language if the current frame corresponds to an unsupported
11793 @chapter Examining the Symbol Table
11795 The commands described in this chapter allow you to inquire about the
11796 symbols (names of variables, functions and types) defined in your
11797 program. This information is inherent in the text of your program and
11798 does not change as your program executes. @value{GDBN} finds it in your
11799 program's symbol table, in the file indicated when you started @value{GDBN}
11800 (@pxref{File Options, ,Choosing Files}), or by one of the
11801 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11803 @cindex symbol names
11804 @cindex names of symbols
11805 @cindex quoting names
11806 Occasionally, you may need to refer to symbols that contain unusual
11807 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11808 most frequent case is in referring to static variables in other
11809 source files (@pxref{Variables,,Program Variables}). File names
11810 are recorded in object files as debugging symbols, but @value{GDBN} would
11811 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11812 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11813 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11820 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11823 @cindex case-insensitive symbol names
11824 @cindex case sensitivity in symbol names
11825 @kindex set case-sensitive
11826 @item set case-sensitive on
11827 @itemx set case-sensitive off
11828 @itemx set case-sensitive auto
11829 Normally, when @value{GDBN} looks up symbols, it matches their names
11830 with case sensitivity determined by the current source language.
11831 Occasionally, you may wish to control that. The command @code{set
11832 case-sensitive} lets you do that by specifying @code{on} for
11833 case-sensitive matches or @code{off} for case-insensitive ones. If
11834 you specify @code{auto}, case sensitivity is reset to the default
11835 suitable for the source language. The default is case-sensitive
11836 matches for all languages except for Fortran, for which the default is
11837 case-insensitive matches.
11839 @kindex show case-sensitive
11840 @item show case-sensitive
11841 This command shows the current setting of case sensitivity for symbols
11844 @kindex info address
11845 @cindex address of a symbol
11846 @item info address @var{symbol}
11847 Describe where the data for @var{symbol} is stored. For a register
11848 variable, this says which register it is kept in. For a non-register
11849 local variable, this prints the stack-frame offset at which the variable
11852 Note the contrast with @samp{print &@var{symbol}}, which does not work
11853 at all for a register variable, and for a stack local variable prints
11854 the exact address of the current instantiation of the variable.
11856 @kindex info symbol
11857 @cindex symbol from address
11858 @cindex closest symbol and offset for an address
11859 @item info symbol @var{addr}
11860 Print the name of a symbol which is stored at the address @var{addr}.
11861 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11862 nearest symbol and an offset from it:
11865 (@value{GDBP}) info symbol 0x54320
11866 _initialize_vx + 396 in section .text
11870 This is the opposite of the @code{info address} command. You can use
11871 it to find out the name of a variable or a function given its address.
11873 For dynamically linked executables, the name of executable or shared
11874 library containing the symbol is also printed:
11877 (@value{GDBP}) info symbol 0x400225
11878 _start + 5 in section .text of /tmp/a.out
11879 (@value{GDBP}) info symbol 0x2aaaac2811cf
11880 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
11884 @item whatis [@var{arg}]
11885 Print the data type of @var{arg}, which can be either an expression or
11886 a data type. With no argument, print the data type of @code{$}, the
11887 last value in the value history. If @var{arg} is an expression, it is
11888 not actually evaluated, and any side-effecting operations (such as
11889 assignments or function calls) inside it do not take place. If
11890 @var{arg} is a type name, it may be the name of a type or typedef, or
11891 for C code it may have the form @samp{class @var{class-name}},
11892 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11893 @samp{enum @var{enum-tag}}.
11894 @xref{Expressions, ,Expressions}.
11897 @item ptype [@var{arg}]
11898 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11899 detailed description of the type, instead of just the name of the type.
11900 @xref{Expressions, ,Expressions}.
11902 For example, for this variable declaration:
11905 struct complex @{double real; double imag;@} v;
11909 the two commands give this output:
11913 (@value{GDBP}) whatis v
11914 type = struct complex
11915 (@value{GDBP}) ptype v
11916 type = struct complex @{
11924 As with @code{whatis}, using @code{ptype} without an argument refers to
11925 the type of @code{$}, the last value in the value history.
11927 @cindex incomplete type
11928 Sometimes, programs use opaque data types or incomplete specifications
11929 of complex data structure. If the debug information included in the
11930 program does not allow @value{GDBN} to display a full declaration of
11931 the data type, it will say @samp{<incomplete type>}. For example,
11932 given these declarations:
11936 struct foo *fooptr;
11940 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11943 (@value{GDBP}) ptype foo
11944 $1 = <incomplete type>
11948 ``Incomplete type'' is C terminology for data types that are not
11949 completely specified.
11952 @item info types @var{regexp}
11954 Print a brief description of all types whose names match the regular
11955 expression @var{regexp} (or all types in your program, if you supply
11956 no argument). Each complete typename is matched as though it were a
11957 complete line; thus, @samp{i type value} gives information on all
11958 types in your program whose names include the string @code{value}, but
11959 @samp{i type ^value$} gives information only on types whose complete
11960 name is @code{value}.
11962 This command differs from @code{ptype} in two ways: first, like
11963 @code{whatis}, it does not print a detailed description; second, it
11964 lists all source files where a type is defined.
11967 @cindex local variables
11968 @item info scope @var{location}
11969 List all the variables local to a particular scope. This command
11970 accepts a @var{location} argument---a function name, a source line, or
11971 an address preceded by a @samp{*}, and prints all the variables local
11972 to the scope defined by that location. (@xref{Specify Location}, for
11973 details about supported forms of @var{location}.) For example:
11976 (@value{GDBP}) @b{info scope command_line_handler}
11977 Scope for command_line_handler:
11978 Symbol rl is an argument at stack/frame offset 8, length 4.
11979 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11980 Symbol linelength is in static storage at address 0x150a1c, length 4.
11981 Symbol p is a local variable in register $esi, length 4.
11982 Symbol p1 is a local variable in register $ebx, length 4.
11983 Symbol nline is a local variable in register $edx, length 4.
11984 Symbol repeat is a local variable at frame offset -8, length 4.
11988 This command is especially useful for determining what data to collect
11989 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11992 @kindex info source
11994 Show information about the current source file---that is, the source file for
11995 the function containing the current point of execution:
11998 the name of the source file, and the directory containing it,
12000 the directory it was compiled in,
12002 its length, in lines,
12004 which programming language it is written in,
12006 whether the executable includes debugging information for that file, and
12007 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12009 whether the debugging information includes information about
12010 preprocessor macros.
12014 @kindex info sources
12016 Print the names of all source files in your program for which there is
12017 debugging information, organized into two lists: files whose symbols
12018 have already been read, and files whose symbols will be read when needed.
12020 @kindex info functions
12021 @item info functions
12022 Print the names and data types of all defined functions.
12024 @item info functions @var{regexp}
12025 Print the names and data types of all defined functions
12026 whose names contain a match for regular expression @var{regexp}.
12027 Thus, @samp{info fun step} finds all functions whose names
12028 include @code{step}; @samp{info fun ^step} finds those whose names
12029 start with @code{step}. If a function name contains characters
12030 that conflict with the regular expression language (e.g.@:
12031 @samp{operator*()}), they may be quoted with a backslash.
12033 @kindex info variables
12034 @item info variables
12035 Print the names and data types of all variables that are declared
12036 outside of functions (i.e.@: excluding local variables).
12038 @item info variables @var{regexp}
12039 Print the names and data types of all variables (except for local
12040 variables) whose names contain a match for regular expression
12043 @kindex info classes
12044 @cindex Objective-C, classes and selectors
12046 @itemx info classes @var{regexp}
12047 Display all Objective-C classes in your program, or
12048 (with the @var{regexp} argument) all those matching a particular regular
12051 @kindex info selectors
12052 @item info selectors
12053 @itemx info selectors @var{regexp}
12054 Display all Objective-C selectors in your program, or
12055 (with the @var{regexp} argument) all those matching a particular regular
12059 This was never implemented.
12060 @kindex info methods
12062 @itemx info methods @var{regexp}
12063 The @code{info methods} command permits the user to examine all defined
12064 methods within C@t{++} program, or (with the @var{regexp} argument) a
12065 specific set of methods found in the various C@t{++} classes. Many
12066 C@t{++} classes provide a large number of methods. Thus, the output
12067 from the @code{ptype} command can be overwhelming and hard to use. The
12068 @code{info-methods} command filters the methods, printing only those
12069 which match the regular-expression @var{regexp}.
12072 @cindex reloading symbols
12073 Some systems allow individual object files that make up your program to
12074 be replaced without stopping and restarting your program. For example,
12075 in VxWorks you can simply recompile a defective object file and keep on
12076 running. If you are running on one of these systems, you can allow
12077 @value{GDBN} to reload the symbols for automatically relinked modules:
12080 @kindex set symbol-reloading
12081 @item set symbol-reloading on
12082 Replace symbol definitions for the corresponding source file when an
12083 object file with a particular name is seen again.
12085 @item set symbol-reloading off
12086 Do not replace symbol definitions when encountering object files of the
12087 same name more than once. This is the default state; if you are not
12088 running on a system that permits automatic relinking of modules, you
12089 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12090 may discard symbols when linking large programs, that may contain
12091 several modules (from different directories or libraries) with the same
12094 @kindex show symbol-reloading
12095 @item show symbol-reloading
12096 Show the current @code{on} or @code{off} setting.
12099 @cindex opaque data types
12100 @kindex set opaque-type-resolution
12101 @item set opaque-type-resolution on
12102 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12103 declared as a pointer to a @code{struct}, @code{class}, or
12104 @code{union}---for example, @code{struct MyType *}---that is used in one
12105 source file although the full declaration of @code{struct MyType} is in
12106 another source file. The default is on.
12108 A change in the setting of this subcommand will not take effect until
12109 the next time symbols for a file are loaded.
12111 @item set opaque-type-resolution off
12112 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12113 is printed as follows:
12115 @{<no data fields>@}
12118 @kindex show opaque-type-resolution
12119 @item show opaque-type-resolution
12120 Show whether opaque types are resolved or not.
12122 @kindex set print symbol-loading
12123 @cindex print messages when symbols are loaded
12124 @item set print symbol-loading
12125 @itemx set print symbol-loading on
12126 @itemx set print symbol-loading off
12127 The @code{set print symbol-loading} command allows you to enable or
12128 disable printing of messages when @value{GDBN} loads symbols.
12129 By default, these messages will be printed, and normally this is what
12130 you want. Disabling these messages is useful when debugging applications
12131 with lots of shared libraries where the quantity of output can be more
12132 annoying than useful.
12134 @kindex show print symbol-loading
12135 @item show print symbol-loading
12136 Show whether messages will be printed when @value{GDBN} loads symbols.
12138 @kindex maint print symbols
12139 @cindex symbol dump
12140 @kindex maint print psymbols
12141 @cindex partial symbol dump
12142 @item maint print symbols @var{filename}
12143 @itemx maint print psymbols @var{filename}
12144 @itemx maint print msymbols @var{filename}
12145 Write a dump of debugging symbol data into the file @var{filename}.
12146 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12147 symbols with debugging data are included. If you use @samp{maint print
12148 symbols}, @value{GDBN} includes all the symbols for which it has already
12149 collected full details: that is, @var{filename} reflects symbols for
12150 only those files whose symbols @value{GDBN} has read. You can use the
12151 command @code{info sources} to find out which files these are. If you
12152 use @samp{maint print psymbols} instead, the dump shows information about
12153 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12154 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12155 @samp{maint print msymbols} dumps just the minimal symbol information
12156 required for each object file from which @value{GDBN} has read some symbols.
12157 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12158 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12160 @kindex maint info symtabs
12161 @kindex maint info psymtabs
12162 @cindex listing @value{GDBN}'s internal symbol tables
12163 @cindex symbol tables, listing @value{GDBN}'s internal
12164 @cindex full symbol tables, listing @value{GDBN}'s internal
12165 @cindex partial symbol tables, listing @value{GDBN}'s internal
12166 @item maint info symtabs @r{[} @var{regexp} @r{]}
12167 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12169 List the @code{struct symtab} or @code{struct partial_symtab}
12170 structures whose names match @var{regexp}. If @var{regexp} is not
12171 given, list them all. The output includes expressions which you can
12172 copy into a @value{GDBN} debugging this one to examine a particular
12173 structure in more detail. For example:
12176 (@value{GDBP}) maint info psymtabs dwarf2read
12177 @{ objfile /home/gnu/build/gdb/gdb
12178 ((struct objfile *) 0x82e69d0)
12179 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12180 ((struct partial_symtab *) 0x8474b10)
12183 text addresses 0x814d3c8 -- 0x8158074
12184 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12185 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12186 dependencies (none)
12189 (@value{GDBP}) maint info symtabs
12193 We see that there is one partial symbol table whose filename contains
12194 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12195 and we see that @value{GDBN} has not read in any symtabs yet at all.
12196 If we set a breakpoint on a function, that will cause @value{GDBN} to
12197 read the symtab for the compilation unit containing that function:
12200 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12201 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12203 (@value{GDBP}) maint info symtabs
12204 @{ objfile /home/gnu/build/gdb/gdb
12205 ((struct objfile *) 0x82e69d0)
12206 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12207 ((struct symtab *) 0x86c1f38)
12210 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12211 linetable ((struct linetable *) 0x8370fa0)
12212 debugformat DWARF 2
12221 @chapter Altering Execution
12223 Once you think you have found an error in your program, you might want to
12224 find out for certain whether correcting the apparent error would lead to
12225 correct results in the rest of the run. You can find the answer by
12226 experiment, using the @value{GDBN} features for altering execution of the
12229 For example, you can store new values into variables or memory
12230 locations, give your program a signal, restart it at a different
12231 address, or even return prematurely from a function.
12234 * Assignment:: Assignment to variables
12235 * Jumping:: Continuing at a different address
12236 * Signaling:: Giving your program a signal
12237 * Returning:: Returning from a function
12238 * Calling:: Calling your program's functions
12239 * Patching:: Patching your program
12243 @section Assignment to Variables
12246 @cindex setting variables
12247 To alter the value of a variable, evaluate an assignment expression.
12248 @xref{Expressions, ,Expressions}. For example,
12255 stores the value 4 into the variable @code{x}, and then prints the
12256 value of the assignment expression (which is 4).
12257 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12258 information on operators in supported languages.
12260 @kindex set variable
12261 @cindex variables, setting
12262 If you are not interested in seeing the value of the assignment, use the
12263 @code{set} command instead of the @code{print} command. @code{set} is
12264 really the same as @code{print} except that the expression's value is
12265 not printed and is not put in the value history (@pxref{Value History,
12266 ,Value History}). The expression is evaluated only for its effects.
12268 If the beginning of the argument string of the @code{set} command
12269 appears identical to a @code{set} subcommand, use the @code{set
12270 variable} command instead of just @code{set}. This command is identical
12271 to @code{set} except for its lack of subcommands. For example, if your
12272 program has a variable @code{width}, you get an error if you try to set
12273 a new value with just @samp{set width=13}, because @value{GDBN} has the
12274 command @code{set width}:
12277 (@value{GDBP}) whatis width
12279 (@value{GDBP}) p width
12281 (@value{GDBP}) set width=47
12282 Invalid syntax in expression.
12286 The invalid expression, of course, is @samp{=47}. In
12287 order to actually set the program's variable @code{width}, use
12290 (@value{GDBP}) set var width=47
12293 Because the @code{set} command has many subcommands that can conflict
12294 with the names of program variables, it is a good idea to use the
12295 @code{set variable} command instead of just @code{set}. For example, if
12296 your program has a variable @code{g}, you run into problems if you try
12297 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12298 the command @code{set gnutarget}, abbreviated @code{set g}:
12302 (@value{GDBP}) whatis g
12306 (@value{GDBP}) set g=4
12310 The program being debugged has been started already.
12311 Start it from the beginning? (y or n) y
12312 Starting program: /home/smith/cc_progs/a.out
12313 "/home/smith/cc_progs/a.out": can't open to read symbols:
12314 Invalid bfd target.
12315 (@value{GDBP}) show g
12316 The current BFD target is "=4".
12321 The program variable @code{g} did not change, and you silently set the
12322 @code{gnutarget} to an invalid value. In order to set the variable
12326 (@value{GDBP}) set var g=4
12329 @value{GDBN} allows more implicit conversions in assignments than C; you can
12330 freely store an integer value into a pointer variable or vice versa,
12331 and you can convert any structure to any other structure that is the
12332 same length or shorter.
12333 @comment FIXME: how do structs align/pad in these conversions?
12334 @comment /doc@cygnus.com 18dec1990
12336 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12337 construct to generate a value of specified type at a specified address
12338 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12339 to memory location @code{0x83040} as an integer (which implies a certain size
12340 and representation in memory), and
12343 set @{int@}0x83040 = 4
12347 stores the value 4 into that memory location.
12350 @section Continuing at a Different Address
12352 Ordinarily, when you continue your program, you do so at the place where
12353 it stopped, with the @code{continue} command. You can instead continue at
12354 an address of your own choosing, with the following commands:
12358 @item jump @var{linespec}
12359 @itemx jump @var{location}
12360 Resume execution at line @var{linespec} or at address given by
12361 @var{location}. Execution stops again immediately if there is a
12362 breakpoint there. @xref{Specify Location}, for a description of the
12363 different forms of @var{linespec} and @var{location}. It is common
12364 practice to use the @code{tbreak} command in conjunction with
12365 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12367 The @code{jump} command does not change the current stack frame, or
12368 the stack pointer, or the contents of any memory location or any
12369 register other than the program counter. If line @var{linespec} is in
12370 a different function from the one currently executing, the results may
12371 be bizarre if the two functions expect different patterns of arguments or
12372 of local variables. For this reason, the @code{jump} command requests
12373 confirmation if the specified line is not in the function currently
12374 executing. However, even bizarre results are predictable if you are
12375 well acquainted with the machine-language code of your program.
12378 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12379 On many systems, you can get much the same effect as the @code{jump}
12380 command by storing a new value into the register @code{$pc}. The
12381 difference is that this does not start your program running; it only
12382 changes the address of where it @emph{will} run when you continue. For
12390 makes the next @code{continue} command or stepping command execute at
12391 address @code{0x485}, rather than at the address where your program stopped.
12392 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12394 The most common occasion to use the @code{jump} command is to back
12395 up---perhaps with more breakpoints set---over a portion of a program
12396 that has already executed, in order to examine its execution in more
12401 @section Giving your Program a Signal
12402 @cindex deliver a signal to a program
12406 @item signal @var{signal}
12407 Resume execution where your program stopped, but immediately give it the
12408 signal @var{signal}. @var{signal} can be the name or the number of a
12409 signal. For example, on many systems @code{signal 2} and @code{signal
12410 SIGINT} are both ways of sending an interrupt signal.
12412 Alternatively, if @var{signal} is zero, continue execution without
12413 giving a signal. This is useful when your program stopped on account of
12414 a signal and would ordinary see the signal when resumed with the
12415 @code{continue} command; @samp{signal 0} causes it to resume without a
12418 @code{signal} does not repeat when you press @key{RET} a second time
12419 after executing the command.
12423 Invoking the @code{signal} command is not the same as invoking the
12424 @code{kill} utility from the shell. Sending a signal with @code{kill}
12425 causes @value{GDBN} to decide what to do with the signal depending on
12426 the signal handling tables (@pxref{Signals}). The @code{signal} command
12427 passes the signal directly to your program.
12431 @section Returning from a Function
12434 @cindex returning from a function
12437 @itemx return @var{expression}
12438 You can cancel execution of a function call with the @code{return}
12439 command. If you give an
12440 @var{expression} argument, its value is used as the function's return
12444 When you use @code{return}, @value{GDBN} discards the selected stack frame
12445 (and all frames within it). You can think of this as making the
12446 discarded frame return prematurely. If you wish to specify a value to
12447 be returned, give that value as the argument to @code{return}.
12449 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12450 Frame}), and any other frames inside of it, leaving its caller as the
12451 innermost remaining frame. That frame becomes selected. The
12452 specified value is stored in the registers used for returning values
12455 The @code{return} command does not resume execution; it leaves the
12456 program stopped in the state that would exist if the function had just
12457 returned. In contrast, the @code{finish} command (@pxref{Continuing
12458 and Stepping, ,Continuing and Stepping}) resumes execution until the
12459 selected stack frame returns naturally.
12462 @section Calling Program Functions
12465 @cindex calling functions
12466 @cindex inferior functions, calling
12467 @item print @var{expr}
12468 Evaluate the expression @var{expr} and display the resulting value.
12469 @var{expr} may include calls to functions in the program being
12473 @item call @var{expr}
12474 Evaluate the expression @var{expr} without displaying @code{void}
12477 You can use this variant of the @code{print} command if you want to
12478 execute a function from your program that does not return anything
12479 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12480 with @code{void} returned values that @value{GDBN} will otherwise
12481 print. If the result is not void, it is printed and saved in the
12485 It is possible for the function you call via the @code{print} or
12486 @code{call} command to generate a signal (e.g., if there's a bug in
12487 the function, or if you passed it incorrect arguments). What happens
12488 in that case is controlled by the @code{set unwindonsignal} command.
12491 @item set unwindonsignal
12492 @kindex set unwindonsignal
12493 @cindex unwind stack in called functions
12494 @cindex call dummy stack unwinding
12495 Set unwinding of the stack if a signal is received while in a function
12496 that @value{GDBN} called in the program being debugged. If set to on,
12497 @value{GDBN} unwinds the stack it created for the call and restores
12498 the context to what it was before the call. If set to off (the
12499 default), @value{GDBN} stops in the frame where the signal was
12502 @item show unwindonsignal
12503 @kindex show unwindonsignal
12504 Show the current setting of stack unwinding in the functions called by
12508 @cindex weak alias functions
12509 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12510 for another function. In such case, @value{GDBN} might not pick up
12511 the type information, including the types of the function arguments,
12512 which causes @value{GDBN} to call the inferior function incorrectly.
12513 As a result, the called function will function erroneously and may
12514 even crash. A solution to that is to use the name of the aliased
12518 @section Patching Programs
12520 @cindex patching binaries
12521 @cindex writing into executables
12522 @cindex writing into corefiles
12524 By default, @value{GDBN} opens the file containing your program's
12525 executable code (or the corefile) read-only. This prevents accidental
12526 alterations to machine code; but it also prevents you from intentionally
12527 patching your program's binary.
12529 If you'd like to be able to patch the binary, you can specify that
12530 explicitly with the @code{set write} command. For example, you might
12531 want to turn on internal debugging flags, or even to make emergency
12537 @itemx set write off
12538 If you specify @samp{set write on}, @value{GDBN} opens executable and
12539 core files for both reading and writing; if you specify @kbd{set write
12540 off} (the default), @value{GDBN} opens them read-only.
12542 If you have already loaded a file, you must load it again (using the
12543 @code{exec-file} or @code{core-file} command) after changing @code{set
12544 write}, for your new setting to take effect.
12548 Display whether executable files and core files are opened for writing
12549 as well as reading.
12553 @chapter @value{GDBN} Files
12555 @value{GDBN} needs to know the file name of the program to be debugged,
12556 both in order to read its symbol table and in order to start your
12557 program. To debug a core dump of a previous run, you must also tell
12558 @value{GDBN} the name of the core dump file.
12561 * Files:: Commands to specify files
12562 * Separate Debug Files:: Debugging information in separate files
12563 * Symbol Errors:: Errors reading symbol files
12567 @section Commands to Specify Files
12569 @cindex symbol table
12570 @cindex core dump file
12572 You may want to specify executable and core dump file names. The usual
12573 way to do this is at start-up time, using the arguments to
12574 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12575 Out of @value{GDBN}}).
12577 Occasionally it is necessary to change to a different file during a
12578 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12579 specify a file you want to use. Or you are debugging a remote target
12580 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12581 Program}). In these situations the @value{GDBN} commands to specify
12582 new files are useful.
12585 @cindex executable file
12587 @item file @var{filename}
12588 Use @var{filename} as the program to be debugged. It is read for its
12589 symbols and for the contents of pure memory. It is also the program
12590 executed when you use the @code{run} command. If you do not specify a
12591 directory and the file is not found in the @value{GDBN} working directory,
12592 @value{GDBN} uses the environment variable @code{PATH} as a list of
12593 directories to search, just as the shell does when looking for a program
12594 to run. You can change the value of this variable, for both @value{GDBN}
12595 and your program, using the @code{path} command.
12597 @cindex unlinked object files
12598 @cindex patching object files
12599 You can load unlinked object @file{.o} files into @value{GDBN} using
12600 the @code{file} command. You will not be able to ``run'' an object
12601 file, but you can disassemble functions and inspect variables. Also,
12602 if the underlying BFD functionality supports it, you could use
12603 @kbd{gdb -write} to patch object files using this technique. Note
12604 that @value{GDBN} can neither interpret nor modify relocations in this
12605 case, so branches and some initialized variables will appear to go to
12606 the wrong place. But this feature is still handy from time to time.
12609 @code{file} with no argument makes @value{GDBN} discard any information it
12610 has on both executable file and the symbol table.
12613 @item exec-file @r{[} @var{filename} @r{]}
12614 Specify that the program to be run (but not the symbol table) is found
12615 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12616 if necessary to locate your program. Omitting @var{filename} means to
12617 discard information on the executable file.
12619 @kindex symbol-file
12620 @item symbol-file @r{[} @var{filename} @r{]}
12621 Read symbol table information from file @var{filename}. @code{PATH} is
12622 searched when necessary. Use the @code{file} command to get both symbol
12623 table and program to run from the same file.
12625 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12626 program's symbol table.
12628 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12629 some breakpoints and auto-display expressions. This is because they may
12630 contain pointers to the internal data recording symbols and data types,
12631 which are part of the old symbol table data being discarded inside
12634 @code{symbol-file} does not repeat if you press @key{RET} again after
12637 When @value{GDBN} is configured for a particular environment, it
12638 understands debugging information in whatever format is the standard
12639 generated for that environment; you may use either a @sc{gnu} compiler, or
12640 other compilers that adhere to the local conventions.
12641 Best results are usually obtained from @sc{gnu} compilers; for example,
12642 using @code{@value{NGCC}} you can generate debugging information for
12645 For most kinds of object files, with the exception of old SVR3 systems
12646 using COFF, the @code{symbol-file} command does not normally read the
12647 symbol table in full right away. Instead, it scans the symbol table
12648 quickly to find which source files and which symbols are present. The
12649 details are read later, one source file at a time, as they are needed.
12651 The purpose of this two-stage reading strategy is to make @value{GDBN}
12652 start up faster. For the most part, it is invisible except for
12653 occasional pauses while the symbol table details for a particular source
12654 file are being read. (The @code{set verbose} command can turn these
12655 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12656 Warnings and Messages}.)
12658 We have not implemented the two-stage strategy for COFF yet. When the
12659 symbol table is stored in COFF format, @code{symbol-file} reads the
12660 symbol table data in full right away. Note that ``stabs-in-COFF''
12661 still does the two-stage strategy, since the debug info is actually
12665 @cindex reading symbols immediately
12666 @cindex symbols, reading immediately
12667 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12668 @itemx file @var{filename} @r{[} -readnow @r{]}
12669 You can override the @value{GDBN} two-stage strategy for reading symbol
12670 tables by using the @samp{-readnow} option with any of the commands that
12671 load symbol table information, if you want to be sure @value{GDBN} has the
12672 entire symbol table available.
12674 @c FIXME: for now no mention of directories, since this seems to be in
12675 @c flux. 13mar1992 status is that in theory GDB would look either in
12676 @c current dir or in same dir as myprog; but issues like competing
12677 @c GDB's, or clutter in system dirs, mean that in practice right now
12678 @c only current dir is used. FFish says maybe a special GDB hierarchy
12679 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12683 @item core-file @r{[}@var{filename}@r{]}
12685 Specify the whereabouts of a core dump file to be used as the ``contents
12686 of memory''. Traditionally, core files contain only some parts of the
12687 address space of the process that generated them; @value{GDBN} can access the
12688 executable file itself for other parts.
12690 @code{core-file} with no argument specifies that no core file is
12693 Note that the core file is ignored when your program is actually running
12694 under @value{GDBN}. So, if you have been running your program and you
12695 wish to debug a core file instead, you must kill the subprocess in which
12696 the program is running. To do this, use the @code{kill} command
12697 (@pxref{Kill Process, ,Killing the Child Process}).
12699 @kindex add-symbol-file
12700 @cindex dynamic linking
12701 @item add-symbol-file @var{filename} @var{address}
12702 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12703 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12704 The @code{add-symbol-file} command reads additional symbol table
12705 information from the file @var{filename}. You would use this command
12706 when @var{filename} has been dynamically loaded (by some other means)
12707 into the program that is running. @var{address} should be the memory
12708 address at which the file has been loaded; @value{GDBN} cannot figure
12709 this out for itself. You can additionally specify an arbitrary number
12710 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12711 section name and base address for that section. You can specify any
12712 @var{address} as an expression.
12714 The symbol table of the file @var{filename} is added to the symbol table
12715 originally read with the @code{symbol-file} command. You can use the
12716 @code{add-symbol-file} command any number of times; the new symbol data
12717 thus read keeps adding to the old. To discard all old symbol data
12718 instead, use the @code{symbol-file} command without any arguments.
12720 @cindex relocatable object files, reading symbols from
12721 @cindex object files, relocatable, reading symbols from
12722 @cindex reading symbols from relocatable object files
12723 @cindex symbols, reading from relocatable object files
12724 @cindex @file{.o} files, reading symbols from
12725 Although @var{filename} is typically a shared library file, an
12726 executable file, or some other object file which has been fully
12727 relocated for loading into a process, you can also load symbolic
12728 information from relocatable @file{.o} files, as long as:
12732 the file's symbolic information refers only to linker symbols defined in
12733 that file, not to symbols defined by other object files,
12735 every section the file's symbolic information refers to has actually
12736 been loaded into the inferior, as it appears in the file, and
12738 you can determine the address at which every section was loaded, and
12739 provide these to the @code{add-symbol-file} command.
12743 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12744 relocatable files into an already running program; such systems
12745 typically make the requirements above easy to meet. However, it's
12746 important to recognize that many native systems use complex link
12747 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12748 assembly, for example) that make the requirements difficult to meet. In
12749 general, one cannot assume that using @code{add-symbol-file} to read a
12750 relocatable object file's symbolic information will have the same effect
12751 as linking the relocatable object file into the program in the normal
12754 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12756 @kindex add-symbol-file-from-memory
12757 @cindex @code{syscall DSO}
12758 @cindex load symbols from memory
12759 @item add-symbol-file-from-memory @var{address}
12760 Load symbols from the given @var{address} in a dynamically loaded
12761 object file whose image is mapped directly into the inferior's memory.
12762 For example, the Linux kernel maps a @code{syscall DSO} into each
12763 process's address space; this DSO provides kernel-specific code for
12764 some system calls. The argument can be any expression whose
12765 evaluation yields the address of the file's shared object file header.
12766 For this command to work, you must have used @code{symbol-file} or
12767 @code{exec-file} commands in advance.
12769 @kindex add-shared-symbol-files
12771 @item add-shared-symbol-files @var{library-file}
12772 @itemx assf @var{library-file}
12773 The @code{add-shared-symbol-files} command can currently be used only
12774 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12775 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12776 @value{GDBN} automatically looks for shared libraries, however if
12777 @value{GDBN} does not find yours, you can invoke
12778 @code{add-shared-symbol-files}. It takes one argument: the shared
12779 library's file name. @code{assf} is a shorthand alias for
12780 @code{add-shared-symbol-files}.
12783 @item section @var{section} @var{addr}
12784 The @code{section} command changes the base address of the named
12785 @var{section} of the exec file to @var{addr}. This can be used if the
12786 exec file does not contain section addresses, (such as in the
12787 @code{a.out} format), or when the addresses specified in the file
12788 itself are wrong. Each section must be changed separately. The
12789 @code{info files} command, described below, lists all the sections and
12793 @kindex info target
12796 @code{info files} and @code{info target} are synonymous; both print the
12797 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12798 including the names of the executable and core dump files currently in
12799 use by @value{GDBN}, and the files from which symbols were loaded. The
12800 command @code{help target} lists all possible targets rather than
12803 @kindex maint info sections
12804 @item maint info sections
12805 Another command that can give you extra information about program sections
12806 is @code{maint info sections}. In addition to the section information
12807 displayed by @code{info files}, this command displays the flags and file
12808 offset of each section in the executable and core dump files. In addition,
12809 @code{maint info sections} provides the following command options (which
12810 may be arbitrarily combined):
12814 Display sections for all loaded object files, including shared libraries.
12815 @item @var{sections}
12816 Display info only for named @var{sections}.
12817 @item @var{section-flags}
12818 Display info only for sections for which @var{section-flags} are true.
12819 The section flags that @value{GDBN} currently knows about are:
12822 Section will have space allocated in the process when loaded.
12823 Set for all sections except those containing debug information.
12825 Section will be loaded from the file into the child process memory.
12826 Set for pre-initialized code and data, clear for @code{.bss} sections.
12828 Section needs to be relocated before loading.
12830 Section cannot be modified by the child process.
12832 Section contains executable code only.
12834 Section contains data only (no executable code).
12836 Section will reside in ROM.
12838 Section contains data for constructor/destructor lists.
12840 Section is not empty.
12842 An instruction to the linker to not output the section.
12843 @item COFF_SHARED_LIBRARY
12844 A notification to the linker that the section contains
12845 COFF shared library information.
12847 Section contains common symbols.
12850 @kindex set trust-readonly-sections
12851 @cindex read-only sections
12852 @item set trust-readonly-sections on
12853 Tell @value{GDBN} that readonly sections in your object file
12854 really are read-only (i.e.@: that their contents will not change).
12855 In that case, @value{GDBN} can fetch values from these sections
12856 out of the object file, rather than from the target program.
12857 For some targets (notably embedded ones), this can be a significant
12858 enhancement to debugging performance.
12860 The default is off.
12862 @item set trust-readonly-sections off
12863 Tell @value{GDBN} not to trust readonly sections. This means that
12864 the contents of the section might change while the program is running,
12865 and must therefore be fetched from the target when needed.
12867 @item show trust-readonly-sections
12868 Show the current setting of trusting readonly sections.
12871 All file-specifying commands allow both absolute and relative file names
12872 as arguments. @value{GDBN} always converts the file name to an absolute file
12873 name and remembers it that way.
12875 @cindex shared libraries
12876 @anchor{Shared Libraries}
12877 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12878 and IBM RS/6000 AIX shared libraries.
12880 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12881 shared libraries. @xref{Expat}.
12883 @value{GDBN} automatically loads symbol definitions from shared libraries
12884 when you use the @code{run} command, or when you examine a core file.
12885 (Before you issue the @code{run} command, @value{GDBN} does not understand
12886 references to a function in a shared library, however---unless you are
12887 debugging a core file).
12889 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12890 automatically loads the symbols at the time of the @code{shl_load} call.
12892 @c FIXME: some @value{GDBN} release may permit some refs to undef
12893 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12894 @c FIXME...lib; check this from time to time when updating manual
12896 There are times, however, when you may wish to not automatically load
12897 symbol definitions from shared libraries, such as when they are
12898 particularly large or there are many of them.
12900 To control the automatic loading of shared library symbols, use the
12904 @kindex set auto-solib-add
12905 @item set auto-solib-add @var{mode}
12906 If @var{mode} is @code{on}, symbols from all shared object libraries
12907 will be loaded automatically when the inferior begins execution, you
12908 attach to an independently started inferior, or when the dynamic linker
12909 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12910 is @code{off}, symbols must be loaded manually, using the
12911 @code{sharedlibrary} command. The default value is @code{on}.
12913 @cindex memory used for symbol tables
12914 If your program uses lots of shared libraries with debug info that
12915 takes large amounts of memory, you can decrease the @value{GDBN}
12916 memory footprint by preventing it from automatically loading the
12917 symbols from shared libraries. To that end, type @kbd{set
12918 auto-solib-add off} before running the inferior, then load each
12919 library whose debug symbols you do need with @kbd{sharedlibrary
12920 @var{regexp}}, where @var{regexp} is a regular expression that matches
12921 the libraries whose symbols you want to be loaded.
12923 @kindex show auto-solib-add
12924 @item show auto-solib-add
12925 Display the current autoloading mode.
12928 @cindex load shared library
12929 To explicitly load shared library symbols, use the @code{sharedlibrary}
12933 @kindex info sharedlibrary
12936 @itemx info sharedlibrary
12937 Print the names of the shared libraries which are currently loaded.
12939 @kindex sharedlibrary
12941 @item sharedlibrary @var{regex}
12942 @itemx share @var{regex}
12943 Load shared object library symbols for files matching a
12944 Unix regular expression.
12945 As with files loaded automatically, it only loads shared libraries
12946 required by your program for a core file or after typing @code{run}. If
12947 @var{regex} is omitted all shared libraries required by your program are
12950 @item nosharedlibrary
12951 @kindex nosharedlibrary
12952 @cindex unload symbols from shared libraries
12953 Unload all shared object library symbols. This discards all symbols
12954 that have been loaded from all shared libraries. Symbols from shared
12955 libraries that were loaded by explicit user requests are not
12959 Sometimes you may wish that @value{GDBN} stops and gives you control
12960 when any of shared library events happen. Use the @code{set
12961 stop-on-solib-events} command for this:
12964 @item set stop-on-solib-events
12965 @kindex set stop-on-solib-events
12966 This command controls whether @value{GDBN} should give you control
12967 when the dynamic linker notifies it about some shared library event.
12968 The most common event of interest is loading or unloading of a new
12971 @item show stop-on-solib-events
12972 @kindex show stop-on-solib-events
12973 Show whether @value{GDBN} stops and gives you control when shared
12974 library events happen.
12977 Shared libraries are also supported in many cross or remote debugging
12978 configurations. @value{GDBN} needs to have access to the target's libraries;
12979 this can be accomplished either by providing copies of the libraries
12980 on the host system, or by asking @value{GDBN} to automatically retrieve the
12981 libraries from the target. If copies of the target libraries are
12982 provided, they need to be the same as the target libraries, although the
12983 copies on the target can be stripped as long as the copies on the host are
12986 @cindex where to look for shared libraries
12987 For remote debugging, you need to tell @value{GDBN} where the target
12988 libraries are, so that it can load the correct copies---otherwise, it
12989 may try to load the host's libraries. @value{GDBN} has two variables
12990 to specify the search directories for target libraries.
12993 @cindex prefix for shared library file names
12994 @cindex system root, alternate
12995 @kindex set solib-absolute-prefix
12996 @kindex set sysroot
12997 @item set sysroot @var{path}
12998 Use @var{path} as the system root for the program being debugged. Any
12999 absolute shared library paths will be prefixed with @var{path}; many
13000 runtime loaders store the absolute paths to the shared library in the
13001 target program's memory. If you use @code{set sysroot} to find shared
13002 libraries, they need to be laid out in the same way that they are on
13003 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13006 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13007 retrieve the target libraries from the remote system. This is only
13008 supported when using a remote target that supports the @code{remote get}
13009 command (@pxref{File Transfer,,Sending files to a remote system}).
13010 The part of @var{path} following the initial @file{remote:}
13011 (if present) is used as system root prefix on the remote file system.
13012 @footnote{If you want to specify a local system root using a directory
13013 that happens to be named @file{remote:}, you need to use some equivalent
13014 variant of the name like @file{./remote:}.}
13016 The @code{set solib-absolute-prefix} command is an alias for @code{set
13019 @cindex default system root
13020 @cindex @samp{--with-sysroot}
13021 You can set the default system root by using the configure-time
13022 @samp{--with-sysroot} option. If the system root is inside
13023 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13024 @samp{--exec-prefix}), then the default system root will be updated
13025 automatically if the installed @value{GDBN} is moved to a new
13028 @kindex show sysroot
13030 Display the current shared library prefix.
13032 @kindex set solib-search-path
13033 @item set solib-search-path @var{path}
13034 If this variable is set, @var{path} is a colon-separated list of
13035 directories to search for shared libraries. @samp{solib-search-path}
13036 is used after @samp{sysroot} fails to locate the library, or if the
13037 path to the library is relative instead of absolute. If you want to
13038 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13039 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13040 finding your host's libraries. @samp{sysroot} is preferred; setting
13041 it to a nonexistent directory may interfere with automatic loading
13042 of shared library symbols.
13044 @kindex show solib-search-path
13045 @item show solib-search-path
13046 Display the current shared library search path.
13050 @node Separate Debug Files
13051 @section Debugging Information in Separate Files
13052 @cindex separate debugging information files
13053 @cindex debugging information in separate files
13054 @cindex @file{.debug} subdirectories
13055 @cindex debugging information directory, global
13056 @cindex global debugging information directory
13057 @cindex build ID, and separate debugging files
13058 @cindex @file{.build-id} directory
13060 @value{GDBN} allows you to put a program's debugging information in a
13061 file separate from the executable itself, in a way that allows
13062 @value{GDBN} to find and load the debugging information automatically.
13063 Since debugging information can be very large---sometimes larger
13064 than the executable code itself---some systems distribute debugging
13065 information for their executables in separate files, which users can
13066 install only when they need to debug a problem.
13068 @value{GDBN} supports two ways of specifying the separate debug info
13073 The executable contains a @dfn{debug link} that specifies the name of
13074 the separate debug info file. The separate debug file's name is
13075 usually @file{@var{executable}.debug}, where @var{executable} is the
13076 name of the corresponding executable file without leading directories
13077 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13078 debug link specifies a CRC32 checksum for the debug file, which
13079 @value{GDBN} uses to validate that the executable and the debug file
13080 came from the same build.
13083 The executable contains a @dfn{build ID}, a unique bit string that is
13084 also present in the corresponding debug info file. (This is supported
13085 only on some operating systems, notably those which use the ELF format
13086 for binary files and the @sc{gnu} Binutils.) For more details about
13087 this feature, see the description of the @option{--build-id}
13088 command-line option in @ref{Options, , Command Line Options, ld.info,
13089 The GNU Linker}. The debug info file's name is not specified
13090 explicitly by the build ID, but can be computed from the build ID, see
13094 Depending on the way the debug info file is specified, @value{GDBN}
13095 uses two different methods of looking for the debug file:
13099 For the ``debug link'' method, @value{GDBN} looks up the named file in
13100 the directory of the executable file, then in a subdirectory of that
13101 directory named @file{.debug}, and finally under the global debug
13102 directory, in a subdirectory whose name is identical to the leading
13103 directories of the executable's absolute file name.
13106 For the ``build ID'' method, @value{GDBN} looks in the
13107 @file{.build-id} subdirectory of the global debug directory for a file
13108 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13109 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13110 are the rest of the bit string. (Real build ID strings are 32 or more
13111 hex characters, not 10.)
13114 So, for example, suppose you ask @value{GDBN} to debug
13115 @file{/usr/bin/ls}, which has a debug link that specifies the
13116 file @file{ls.debug}, and a build ID whose value in hex is
13117 @code{abcdef1234}. If the global debug directory is
13118 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13119 debug information files, in the indicated order:
13123 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13125 @file{/usr/bin/ls.debug}
13127 @file{/usr/bin/.debug/ls.debug}
13129 @file{/usr/lib/debug/usr/bin/ls.debug}.
13132 You can set the global debugging info directory's name, and view the
13133 name @value{GDBN} is currently using.
13137 @kindex set debug-file-directory
13138 @item set debug-file-directory @var{directory}
13139 Set the directory which @value{GDBN} searches for separate debugging
13140 information files to @var{directory}.
13142 @kindex show debug-file-directory
13143 @item show debug-file-directory
13144 Show the directory @value{GDBN} searches for separate debugging
13149 @cindex @code{.gnu_debuglink} sections
13150 @cindex debug link sections
13151 A debug link is a special section of the executable file named
13152 @code{.gnu_debuglink}. The section must contain:
13156 A filename, with any leading directory components removed, followed by
13159 zero to three bytes of padding, as needed to reach the next four-byte
13160 boundary within the section, and
13162 a four-byte CRC checksum, stored in the same endianness used for the
13163 executable file itself. The checksum is computed on the debugging
13164 information file's full contents by the function given below, passing
13165 zero as the @var{crc} argument.
13168 Any executable file format can carry a debug link, as long as it can
13169 contain a section named @code{.gnu_debuglink} with the contents
13172 @cindex @code{.note.gnu.build-id} sections
13173 @cindex build ID sections
13174 The build ID is a special section in the executable file (and in other
13175 ELF binary files that @value{GDBN} may consider). This section is
13176 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13177 It contains unique identification for the built files---the ID remains
13178 the same across multiple builds of the same build tree. The default
13179 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13180 content for the build ID string. The same section with an identical
13181 value is present in the original built binary with symbols, in its
13182 stripped variant, and in the separate debugging information file.
13184 The debugging information file itself should be an ordinary
13185 executable, containing a full set of linker symbols, sections, and
13186 debugging information. The sections of the debugging information file
13187 should have the same names, addresses, and sizes as the original file,
13188 but they need not contain any data---much like a @code{.bss} section
13189 in an ordinary executable.
13191 The @sc{gnu} binary utilities (Binutils) package includes the
13192 @samp{objcopy} utility that can produce
13193 the separated executable / debugging information file pairs using the
13194 following commands:
13197 @kbd{objcopy --only-keep-debug foo foo.debug}
13202 These commands remove the debugging
13203 information from the executable file @file{foo} and place it in the file
13204 @file{foo.debug}. You can use the first, second or both methods to link the
13209 The debug link method needs the following additional command to also leave
13210 behind a debug link in @file{foo}:
13213 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13216 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13217 a version of the @code{strip} command such that the command @kbd{strip foo -f
13218 foo.debug} has the same functionality as the two @code{objcopy} commands and
13219 the @code{ln -s} command above, together.
13222 Build ID gets embedded into the main executable using @code{ld --build-id} or
13223 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13224 compatibility fixes for debug files separation are present in @sc{gnu} binary
13225 utilities (Binutils) package since version 2.18.
13230 Since there are many different ways to compute CRC's for the debug
13231 link (different polynomials, reversals, byte ordering, etc.), the
13232 simplest way to describe the CRC used in @code{.gnu_debuglink}
13233 sections is to give the complete code for a function that computes it:
13235 @kindex gnu_debuglink_crc32
13238 gnu_debuglink_crc32 (unsigned long crc,
13239 unsigned char *buf, size_t len)
13241 static const unsigned long crc32_table[256] =
13243 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13244 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13245 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13246 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13247 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13248 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13249 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13250 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13251 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13252 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13253 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13254 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13255 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13256 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13257 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13258 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13259 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13260 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13261 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13262 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13263 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13264 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13265 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13266 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13267 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13268 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13269 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13270 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13271 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13272 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13273 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13274 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13275 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13276 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13277 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13278 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13279 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13280 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13281 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13282 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13283 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13284 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13285 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13286 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13287 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13288 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13289 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13290 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13291 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13292 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13293 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13296 unsigned char *end;
13298 crc = ~crc & 0xffffffff;
13299 for (end = buf + len; buf < end; ++buf)
13300 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13301 return ~crc & 0xffffffff;
13306 This computation does not apply to the ``build ID'' method.
13309 @node Symbol Errors
13310 @section Errors Reading Symbol Files
13312 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13313 such as symbol types it does not recognize, or known bugs in compiler
13314 output. By default, @value{GDBN} does not notify you of such problems, since
13315 they are relatively common and primarily of interest to people
13316 debugging compilers. If you are interested in seeing information
13317 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13318 only one message about each such type of problem, no matter how many
13319 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13320 to see how many times the problems occur, with the @code{set
13321 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13324 The messages currently printed, and their meanings, include:
13327 @item inner block not inside outer block in @var{symbol}
13329 The symbol information shows where symbol scopes begin and end
13330 (such as at the start of a function or a block of statements). This
13331 error indicates that an inner scope block is not fully contained
13332 in its outer scope blocks.
13334 @value{GDBN} circumvents the problem by treating the inner block as if it had
13335 the same scope as the outer block. In the error message, @var{symbol}
13336 may be shown as ``@code{(don't know)}'' if the outer block is not a
13339 @item block at @var{address} out of order
13341 The symbol information for symbol scope blocks should occur in
13342 order of increasing addresses. This error indicates that it does not
13345 @value{GDBN} does not circumvent this problem, and has trouble
13346 locating symbols in the source file whose symbols it is reading. (You
13347 can often determine what source file is affected by specifying
13348 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13351 @item bad block start address patched
13353 The symbol information for a symbol scope block has a start address
13354 smaller than the address of the preceding source line. This is known
13355 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13357 @value{GDBN} circumvents the problem by treating the symbol scope block as
13358 starting on the previous source line.
13360 @item bad string table offset in symbol @var{n}
13363 Symbol number @var{n} contains a pointer into the string table which is
13364 larger than the size of the string table.
13366 @value{GDBN} circumvents the problem by considering the symbol to have the
13367 name @code{foo}, which may cause other problems if many symbols end up
13370 @item unknown symbol type @code{0x@var{nn}}
13372 The symbol information contains new data types that @value{GDBN} does
13373 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13374 uncomprehended information, in hexadecimal.
13376 @value{GDBN} circumvents the error by ignoring this symbol information.
13377 This usually allows you to debug your program, though certain symbols
13378 are not accessible. If you encounter such a problem and feel like
13379 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13380 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13381 and examine @code{*bufp} to see the symbol.
13383 @item stub type has NULL name
13385 @value{GDBN} could not find the full definition for a struct or class.
13387 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13388 The symbol information for a C@t{++} member function is missing some
13389 information that recent versions of the compiler should have output for
13392 @item info mismatch between compiler and debugger
13394 @value{GDBN} could not parse a type specification output by the compiler.
13399 @chapter Specifying a Debugging Target
13401 @cindex debugging target
13402 A @dfn{target} is the execution environment occupied by your program.
13404 Often, @value{GDBN} runs in the same host environment as your program;
13405 in that case, the debugging target is specified as a side effect when
13406 you use the @code{file} or @code{core} commands. When you need more
13407 flexibility---for example, running @value{GDBN} on a physically separate
13408 host, or controlling a standalone system over a serial port or a
13409 realtime system over a TCP/IP connection---you can use the @code{target}
13410 command to specify one of the target types configured for @value{GDBN}
13411 (@pxref{Target Commands, ,Commands for Managing Targets}).
13413 @cindex target architecture
13414 It is possible to build @value{GDBN} for several different @dfn{target
13415 architectures}. When @value{GDBN} is built like that, you can choose
13416 one of the available architectures with the @kbd{set architecture}
13420 @kindex set architecture
13421 @kindex show architecture
13422 @item set architecture @var{arch}
13423 This command sets the current target architecture to @var{arch}. The
13424 value of @var{arch} can be @code{"auto"}, in addition to one of the
13425 supported architectures.
13427 @item show architecture
13428 Show the current target architecture.
13430 @item set processor
13432 @kindex set processor
13433 @kindex show processor
13434 These are alias commands for, respectively, @code{set architecture}
13435 and @code{show architecture}.
13439 * Active Targets:: Active targets
13440 * Target Commands:: Commands for managing targets
13441 * Byte Order:: Choosing target byte order
13444 @node Active Targets
13445 @section Active Targets
13447 @cindex stacking targets
13448 @cindex active targets
13449 @cindex multiple targets
13451 There are three classes of targets: processes, core files, and
13452 executable files. @value{GDBN} can work concurrently on up to three
13453 active targets, one in each class. This allows you to (for example)
13454 start a process and inspect its activity without abandoning your work on
13457 For example, if you execute @samp{gdb a.out}, then the executable file
13458 @code{a.out} is the only active target. If you designate a core file as
13459 well---presumably from a prior run that crashed and coredumped---then
13460 @value{GDBN} has two active targets and uses them in tandem, looking
13461 first in the corefile target, then in the executable file, to satisfy
13462 requests for memory addresses. (Typically, these two classes of target
13463 are complementary, since core files contain only a program's
13464 read-write memory---variables and so on---plus machine status, while
13465 executable files contain only the program text and initialized data.)
13467 When you type @code{run}, your executable file becomes an active process
13468 target as well. When a process target is active, all @value{GDBN}
13469 commands requesting memory addresses refer to that target; addresses in
13470 an active core file or executable file target are obscured while the
13471 process target is active.
13473 Use the @code{core-file} and @code{exec-file} commands to select a new
13474 core file or executable target (@pxref{Files, ,Commands to Specify
13475 Files}). To specify as a target a process that is already running, use
13476 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13479 @node Target Commands
13480 @section Commands for Managing Targets
13483 @item target @var{type} @var{parameters}
13484 Connects the @value{GDBN} host environment to a target machine or
13485 process. A target is typically a protocol for talking to debugging
13486 facilities. You use the argument @var{type} to specify the type or
13487 protocol of the target machine.
13489 Further @var{parameters} are interpreted by the target protocol, but
13490 typically include things like device names or host names to connect
13491 with, process numbers, and baud rates.
13493 The @code{target} command does not repeat if you press @key{RET} again
13494 after executing the command.
13496 @kindex help target
13498 Displays the names of all targets available. To display targets
13499 currently selected, use either @code{info target} or @code{info files}
13500 (@pxref{Files, ,Commands to Specify Files}).
13502 @item help target @var{name}
13503 Describe a particular target, including any parameters necessary to
13506 @kindex set gnutarget
13507 @item set gnutarget @var{args}
13508 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13509 knows whether it is reading an @dfn{executable},
13510 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13511 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13512 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13515 @emph{Warning:} To specify a file format with @code{set gnutarget},
13516 you must know the actual BFD name.
13520 @xref{Files, , Commands to Specify Files}.
13522 @kindex show gnutarget
13523 @item show gnutarget
13524 Use the @code{show gnutarget} command to display what file format
13525 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13526 @value{GDBN} will determine the file format for each file automatically,
13527 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13530 @cindex common targets
13531 Here are some common targets (available, or not, depending on the GDB
13536 @item target exec @var{program}
13537 @cindex executable file target
13538 An executable file. @samp{target exec @var{program}} is the same as
13539 @samp{exec-file @var{program}}.
13541 @item target core @var{filename}
13542 @cindex core dump file target
13543 A core dump file. @samp{target core @var{filename}} is the same as
13544 @samp{core-file @var{filename}}.
13546 @item target remote @var{medium}
13547 @cindex remote target
13548 A remote system connected to @value{GDBN} via a serial line or network
13549 connection. This command tells @value{GDBN} to use its own remote
13550 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13552 For example, if you have a board connected to @file{/dev/ttya} on the
13553 machine running @value{GDBN}, you could say:
13556 target remote /dev/ttya
13559 @code{target remote} supports the @code{load} command. This is only
13560 useful if you have some other way of getting the stub to the target
13561 system, and you can put it somewhere in memory where it won't get
13562 clobbered by the download.
13565 @cindex built-in simulator target
13566 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13574 works; however, you cannot assume that a specific memory map, device
13575 drivers, or even basic I/O is available, although some simulators do
13576 provide these. For info about any processor-specific simulator details,
13577 see the appropriate section in @ref{Embedded Processors, ,Embedded
13582 Some configurations may include these targets as well:
13586 @item target nrom @var{dev}
13587 @cindex NetROM ROM emulator target
13588 NetROM ROM emulator. This target only supports downloading.
13592 Different targets are available on different configurations of @value{GDBN};
13593 your configuration may have more or fewer targets.
13595 Many remote targets require you to download the executable's code once
13596 you've successfully established a connection. You may wish to control
13597 various aspects of this process.
13602 @kindex set hash@r{, for remote monitors}
13603 @cindex hash mark while downloading
13604 This command controls whether a hash mark @samp{#} is displayed while
13605 downloading a file to the remote monitor. If on, a hash mark is
13606 displayed after each S-record is successfully downloaded to the
13610 @kindex show hash@r{, for remote monitors}
13611 Show the current status of displaying the hash mark.
13613 @item set debug monitor
13614 @kindex set debug monitor
13615 @cindex display remote monitor communications
13616 Enable or disable display of communications messages between
13617 @value{GDBN} and the remote monitor.
13619 @item show debug monitor
13620 @kindex show debug monitor
13621 Show the current status of displaying communications between
13622 @value{GDBN} and the remote monitor.
13627 @kindex load @var{filename}
13628 @item load @var{filename}
13630 Depending on what remote debugging facilities are configured into
13631 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13632 is meant to make @var{filename} (an executable) available for debugging
13633 on the remote system---by downloading, or dynamic linking, for example.
13634 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13635 the @code{add-symbol-file} command.
13637 If your @value{GDBN} does not have a @code{load} command, attempting to
13638 execute it gets the error message ``@code{You can't do that when your
13639 target is @dots{}}''
13641 The file is loaded at whatever address is specified in the executable.
13642 For some object file formats, you can specify the load address when you
13643 link the program; for other formats, like a.out, the object file format
13644 specifies a fixed address.
13645 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13647 Depending on the remote side capabilities, @value{GDBN} may be able to
13648 load programs into flash memory.
13650 @code{load} does not repeat if you press @key{RET} again after using it.
13654 @section Choosing Target Byte Order
13656 @cindex choosing target byte order
13657 @cindex target byte order
13659 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13660 offer the ability to run either big-endian or little-endian byte
13661 orders. Usually the executable or symbol will include a bit to
13662 designate the endian-ness, and you will not need to worry about
13663 which to use. However, you may still find it useful to adjust
13664 @value{GDBN}'s idea of processor endian-ness manually.
13668 @item set endian big
13669 Instruct @value{GDBN} to assume the target is big-endian.
13671 @item set endian little
13672 Instruct @value{GDBN} to assume the target is little-endian.
13674 @item set endian auto
13675 Instruct @value{GDBN} to use the byte order associated with the
13679 Display @value{GDBN}'s current idea of the target byte order.
13683 Note that these commands merely adjust interpretation of symbolic
13684 data on the host, and that they have absolutely no effect on the
13688 @node Remote Debugging
13689 @chapter Debugging Remote Programs
13690 @cindex remote debugging
13692 If you are trying to debug a program running on a machine that cannot run
13693 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13694 For example, you might use remote debugging on an operating system kernel,
13695 or on a small system which does not have a general purpose operating system
13696 powerful enough to run a full-featured debugger.
13698 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13699 to make this work with particular debugging targets. In addition,
13700 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13701 but not specific to any particular target system) which you can use if you
13702 write the remote stubs---the code that runs on the remote system to
13703 communicate with @value{GDBN}.
13705 Other remote targets may be available in your
13706 configuration of @value{GDBN}; use @code{help target} to list them.
13709 * Connecting:: Connecting to a remote target
13710 * File Transfer:: Sending files to a remote system
13711 * Server:: Using the gdbserver program
13712 * Remote Configuration:: Remote configuration
13713 * Remote Stub:: Implementing a remote stub
13717 @section Connecting to a Remote Target
13719 On the @value{GDBN} host machine, you will need an unstripped copy of
13720 your program, since @value{GDBN} needs symbol and debugging information.
13721 Start up @value{GDBN} as usual, using the name of the local copy of your
13722 program as the first argument.
13724 @cindex @code{target remote}
13725 @value{GDBN} can communicate with the target over a serial line, or
13726 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13727 each case, @value{GDBN} uses the same protocol for debugging your
13728 program; only the medium carrying the debugging packets varies. The
13729 @code{target remote} command establishes a connection to the target.
13730 Its arguments indicate which medium to use:
13734 @item target remote @var{serial-device}
13735 @cindex serial line, @code{target remote}
13736 Use @var{serial-device} to communicate with the target. For example,
13737 to use a serial line connected to the device named @file{/dev/ttyb}:
13740 target remote /dev/ttyb
13743 If you're using a serial line, you may want to give @value{GDBN} the
13744 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13745 (@pxref{Remote Configuration, set remotebaud}) before the
13746 @code{target} command.
13748 @item target remote @code{@var{host}:@var{port}}
13749 @itemx target remote @code{tcp:@var{host}:@var{port}}
13750 @cindex @acronym{TCP} port, @code{target remote}
13751 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13752 The @var{host} may be either a host name or a numeric @acronym{IP}
13753 address; @var{port} must be a decimal number. The @var{host} could be
13754 the target machine itself, if it is directly connected to the net, or
13755 it might be a terminal server which in turn has a serial line to the
13758 For example, to connect to port 2828 on a terminal server named
13762 target remote manyfarms:2828
13765 If your remote target is actually running on the same machine as your
13766 debugger session (e.g.@: a simulator for your target running on the
13767 same host), you can omit the hostname. For example, to connect to
13768 port 1234 on your local machine:
13771 target remote :1234
13775 Note that the colon is still required here.
13777 @item target remote @code{udp:@var{host}:@var{port}}
13778 @cindex @acronym{UDP} port, @code{target remote}
13779 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13780 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13783 target remote udp:manyfarms:2828
13786 When using a @acronym{UDP} connection for remote debugging, you should
13787 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13788 can silently drop packets on busy or unreliable networks, which will
13789 cause havoc with your debugging session.
13791 @item target remote | @var{command}
13792 @cindex pipe, @code{target remote} to
13793 Run @var{command} in the background and communicate with it using a
13794 pipe. The @var{command} is a shell command, to be parsed and expanded
13795 by the system's command shell, @code{/bin/sh}; it should expect remote
13796 protocol packets on its standard input, and send replies on its
13797 standard output. You could use this to run a stand-alone simulator
13798 that speaks the remote debugging protocol, to make net connections
13799 using programs like @code{ssh}, or for other similar tricks.
13801 If @var{command} closes its standard output (perhaps by exiting),
13802 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13803 program has already exited, this will have no effect.)
13807 Once the connection has been established, you can use all the usual
13808 commands to examine and change data. The remote program is already
13809 running; you can use @kbd{step} and @kbd{continue}, and you do not
13810 need to use @kbd{run}.
13812 @cindex interrupting remote programs
13813 @cindex remote programs, interrupting
13814 Whenever @value{GDBN} is waiting for the remote program, if you type the
13815 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13816 program. This may or may not succeed, depending in part on the hardware
13817 and the serial drivers the remote system uses. If you type the
13818 interrupt character once again, @value{GDBN} displays this prompt:
13821 Interrupted while waiting for the program.
13822 Give up (and stop debugging it)? (y or n)
13825 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13826 (If you decide you want to try again later, you can use @samp{target
13827 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13828 goes back to waiting.
13831 @kindex detach (remote)
13833 When you have finished debugging the remote program, you can use the
13834 @code{detach} command to release it from @value{GDBN} control.
13835 Detaching from the target normally resumes its execution, but the results
13836 will depend on your particular remote stub. After the @code{detach}
13837 command, @value{GDBN} is free to connect to another target.
13841 The @code{disconnect} command behaves like @code{detach}, except that
13842 the target is generally not resumed. It will wait for @value{GDBN}
13843 (this instance or another one) to connect and continue debugging. After
13844 the @code{disconnect} command, @value{GDBN} is again free to connect to
13847 @cindex send command to remote monitor
13848 @cindex extend @value{GDBN} for remote targets
13849 @cindex add new commands for external monitor
13851 @item monitor @var{cmd}
13852 This command allows you to send arbitrary commands directly to the
13853 remote monitor. Since @value{GDBN} doesn't care about the commands it
13854 sends like this, this command is the way to extend @value{GDBN}---you
13855 can add new commands that only the external monitor will understand
13859 @node File Transfer
13860 @section Sending files to a remote system
13861 @cindex remote target, file transfer
13862 @cindex file transfer
13863 @cindex sending files to remote systems
13865 Some remote targets offer the ability to transfer files over the same
13866 connection used to communicate with @value{GDBN}. This is convenient
13867 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13868 running @code{gdbserver} over a network interface. For other targets,
13869 e.g.@: embedded devices with only a single serial port, this may be
13870 the only way to upload or download files.
13872 Not all remote targets support these commands.
13876 @item remote put @var{hostfile} @var{targetfile}
13877 Copy file @var{hostfile} from the host system (the machine running
13878 @value{GDBN}) to @var{targetfile} on the target system.
13881 @item remote get @var{targetfile} @var{hostfile}
13882 Copy file @var{targetfile} from the target system to @var{hostfile}
13883 on the host system.
13885 @kindex remote delete
13886 @item remote delete @var{targetfile}
13887 Delete @var{targetfile} from the target system.
13892 @section Using the @code{gdbserver} Program
13895 @cindex remote connection without stubs
13896 @code{gdbserver} is a control program for Unix-like systems, which
13897 allows you to connect your program with a remote @value{GDBN} via
13898 @code{target remote}---but without linking in the usual debugging stub.
13900 @code{gdbserver} is not a complete replacement for the debugging stubs,
13901 because it requires essentially the same operating-system facilities
13902 that @value{GDBN} itself does. In fact, a system that can run
13903 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13904 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13905 because it is a much smaller program than @value{GDBN} itself. It is
13906 also easier to port than all of @value{GDBN}, so you may be able to get
13907 started more quickly on a new system by using @code{gdbserver}.
13908 Finally, if you develop code for real-time systems, you may find that
13909 the tradeoffs involved in real-time operation make it more convenient to
13910 do as much development work as possible on another system, for example
13911 by cross-compiling. You can use @code{gdbserver} to make a similar
13912 choice for debugging.
13914 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13915 or a TCP connection, using the standard @value{GDBN} remote serial
13919 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13920 Do not run @code{gdbserver} connected to any public network; a
13921 @value{GDBN} connection to @code{gdbserver} provides access to the
13922 target system with the same privileges as the user running
13926 @subsection Running @code{gdbserver}
13927 @cindex arguments, to @code{gdbserver}
13929 Run @code{gdbserver} on the target system. You need a copy of the
13930 program you want to debug, including any libraries it requires.
13931 @code{gdbserver} does not need your program's symbol table, so you can
13932 strip the program if necessary to save space. @value{GDBN} on the host
13933 system does all the symbol handling.
13935 To use the server, you must tell it how to communicate with @value{GDBN};
13936 the name of your program; and the arguments for your program. The usual
13940 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13943 @var{comm} is either a device name (to use a serial line) or a TCP
13944 hostname and portnumber. For example, to debug Emacs with the argument
13945 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13949 target> gdbserver /dev/com1 emacs foo.txt
13952 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13955 To use a TCP connection instead of a serial line:
13958 target> gdbserver host:2345 emacs foo.txt
13961 The only difference from the previous example is the first argument,
13962 specifying that you are communicating with the host @value{GDBN} via
13963 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13964 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13965 (Currently, the @samp{host} part is ignored.) You can choose any number
13966 you want for the port number as long as it does not conflict with any
13967 TCP ports already in use on the target system (for example, @code{23} is
13968 reserved for @code{telnet}).@footnote{If you choose a port number that
13969 conflicts with another service, @code{gdbserver} prints an error message
13970 and exits.} You must use the same port number with the host @value{GDBN}
13971 @code{target remote} command.
13973 @subsubsection Attaching to a Running Program
13975 On some targets, @code{gdbserver} can also attach to running programs.
13976 This is accomplished via the @code{--attach} argument. The syntax is:
13979 target> gdbserver --attach @var{comm} @var{pid}
13982 @var{pid} is the process ID of a currently running process. It isn't necessary
13983 to point @code{gdbserver} at a binary for the running process.
13986 @cindex attach to a program by name
13987 You can debug processes by name instead of process ID if your target has the
13988 @code{pidof} utility:
13991 target> gdbserver --attach @var{comm} `pidof @var{program}`
13994 In case more than one copy of @var{program} is running, or @var{program}
13995 has multiple threads, most versions of @code{pidof} support the
13996 @code{-s} option to only return the first process ID.
13998 @subsubsection Multi-Process Mode for @code{gdbserver}
13999 @cindex gdbserver, multiple processes
14000 @cindex multiple processes with gdbserver
14002 When you connect to @code{gdbserver} using @code{target remote},
14003 @code{gdbserver} debugs the specified program only once. When the
14004 program exits, or you detach from it, @value{GDBN} closes the connection
14005 and @code{gdbserver} exits.
14007 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14008 enters multi-process mode. When the debugged program exits, or you
14009 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14010 though no program is running. The @code{run} and @code{attach}
14011 commands instruct @code{gdbserver} to run or attach to a new program.
14012 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14013 remote exec-file}) to select the program to run. Command line
14014 arguments are supported, except for wildcard expansion and I/O
14015 redirection (@pxref{Arguments}).
14017 To start @code{gdbserver} without supplying an initial command to run
14018 or process ID to attach, use the @option{--multi} command line option.
14019 Then you can connect using @kbd{target extended-remote} and start
14020 the program you want to debug.
14022 @code{gdbserver} does not automatically exit in multi-process mode.
14023 You can terminate it by using @code{monitor exit}
14024 (@pxref{Monitor Commands for gdbserver}).
14026 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14028 You can include @option{--debug} on the @code{gdbserver} command line.
14029 @code{gdbserver} will display extra status information about the debugging
14030 process. This option is intended for @code{gdbserver} development and
14031 for bug reports to the developers.
14033 The @option{--wrapper} option specifies a wrapper to launch programs
14034 for debugging. The option should be followed by the name of the
14035 wrapper, then any command-line arguments to pass to the wrapper, then
14036 @kbd{--} indicating the end of the wrapper arguments.
14038 @code{gdbserver} runs the specified wrapper program with a combined
14039 command line including the wrapper arguments, then the name of the
14040 program to debug, then any arguments to the program. The wrapper
14041 runs until it executes your program, and then @value{GDBN} gains control.
14043 You can use any program that eventually calls @code{execve} with
14044 its arguments as a wrapper. Several standard Unix utilities do
14045 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14046 with @code{exec "$@@"} will also work.
14048 For example, you can use @code{env} to pass an environment variable to
14049 the debugged program, without setting the variable in @code{gdbserver}'s
14053 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14056 @subsection Connecting to @code{gdbserver}
14058 Run @value{GDBN} on the host system.
14060 First make sure you have the necessary symbol files. Load symbols for
14061 your application using the @code{file} command before you connect. Use
14062 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14063 was compiled with the correct sysroot using @code{--with-sysroot}).
14065 The symbol file and target libraries must exactly match the executable
14066 and libraries on the target, with one exception: the files on the host
14067 system should not be stripped, even if the files on the target system
14068 are. Mismatched or missing files will lead to confusing results
14069 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14070 files may also prevent @code{gdbserver} from debugging multi-threaded
14073 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14074 For TCP connections, you must start up @code{gdbserver} prior to using
14075 the @code{target remote} command. Otherwise you may get an error whose
14076 text depends on the host system, but which usually looks something like
14077 @samp{Connection refused}. Don't use the @code{load}
14078 command in @value{GDBN} when using @code{gdbserver}, since the program is
14079 already on the target.
14081 @subsection Monitor Commands for @code{gdbserver}
14082 @cindex monitor commands, for @code{gdbserver}
14083 @anchor{Monitor Commands for gdbserver}
14085 During a @value{GDBN} session using @code{gdbserver}, you can use the
14086 @code{monitor} command to send special requests to @code{gdbserver}.
14087 Here are the available commands.
14091 List the available monitor commands.
14093 @item monitor set debug 0
14094 @itemx monitor set debug 1
14095 Disable or enable general debugging messages.
14097 @item monitor set remote-debug 0
14098 @itemx monitor set remote-debug 1
14099 Disable or enable specific debugging messages associated with the remote
14100 protocol (@pxref{Remote Protocol}).
14103 Tell gdbserver to exit immediately. This command should be followed by
14104 @code{disconnect} to close the debugging session. @code{gdbserver} will
14105 detach from any attached processes and kill any processes it created.
14106 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14107 of a multi-process mode debug session.
14111 @node Remote Configuration
14112 @section Remote Configuration
14115 @kindex show remote
14116 This section documents the configuration options available when
14117 debugging remote programs. For the options related to the File I/O
14118 extensions of the remote protocol, see @ref{system,
14119 system-call-allowed}.
14122 @item set remoteaddresssize @var{bits}
14123 @cindex address size for remote targets
14124 @cindex bits in remote address
14125 Set the maximum size of address in a memory packet to the specified
14126 number of bits. @value{GDBN} will mask off the address bits above
14127 that number, when it passes addresses to the remote target. The
14128 default value is the number of bits in the target's address.
14130 @item show remoteaddresssize
14131 Show the current value of remote address size in bits.
14133 @item set remotebaud @var{n}
14134 @cindex baud rate for remote targets
14135 Set the baud rate for the remote serial I/O to @var{n} baud. The
14136 value is used to set the speed of the serial port used for debugging
14139 @item show remotebaud
14140 Show the current speed of the remote connection.
14142 @item set remotebreak
14143 @cindex interrupt remote programs
14144 @cindex BREAK signal instead of Ctrl-C
14145 @anchor{set remotebreak}
14146 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14147 when you type @kbd{Ctrl-c} to interrupt the program running
14148 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14149 character instead. The default is off, since most remote systems
14150 expect to see @samp{Ctrl-C} as the interrupt signal.
14152 @item show remotebreak
14153 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14154 interrupt the remote program.
14156 @item set remoteflow on
14157 @itemx set remoteflow off
14158 @kindex set remoteflow
14159 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14160 on the serial port used to communicate to the remote target.
14162 @item show remoteflow
14163 @kindex show remoteflow
14164 Show the current setting of hardware flow control.
14166 @item set remotelogbase @var{base}
14167 Set the base (a.k.a.@: radix) of logging serial protocol
14168 communications to @var{base}. Supported values of @var{base} are:
14169 @code{ascii}, @code{octal}, and @code{hex}. The default is
14172 @item show remotelogbase
14173 Show the current setting of the radix for logging remote serial
14176 @item set remotelogfile @var{file}
14177 @cindex record serial communications on file
14178 Record remote serial communications on the named @var{file}. The
14179 default is not to record at all.
14181 @item show remotelogfile.
14182 Show the current setting of the file name on which to record the
14183 serial communications.
14185 @item set remotetimeout @var{num}
14186 @cindex timeout for serial communications
14187 @cindex remote timeout
14188 Set the timeout limit to wait for the remote target to respond to
14189 @var{num} seconds. The default is 2 seconds.
14191 @item show remotetimeout
14192 Show the current number of seconds to wait for the remote target
14195 @cindex limit hardware breakpoints and watchpoints
14196 @cindex remote target, limit break- and watchpoints
14197 @anchor{set remote hardware-watchpoint-limit}
14198 @anchor{set remote hardware-breakpoint-limit}
14199 @item set remote hardware-watchpoint-limit @var{limit}
14200 @itemx set remote hardware-breakpoint-limit @var{limit}
14201 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14202 watchpoints. A limit of -1, the default, is treated as unlimited.
14204 @item set remote exec-file @var{filename}
14205 @itemx show remote exec-file
14206 @anchor{set remote exec-file}
14207 @cindex executable file, for remote target
14208 Select the file used for @code{run} with @code{target
14209 extended-remote}. This should be set to a filename valid on the
14210 target system. If it is not set, the target will use a default
14211 filename (e.g.@: the last program run).
14214 @cindex remote packets, enabling and disabling
14215 The @value{GDBN} remote protocol autodetects the packets supported by
14216 your debugging stub. If you need to override the autodetection, you
14217 can use these commands to enable or disable individual packets. Each
14218 packet can be set to @samp{on} (the remote target supports this
14219 packet), @samp{off} (the remote target does not support this packet),
14220 or @samp{auto} (detect remote target support for this packet). They
14221 all default to @samp{auto}. For more information about each packet,
14222 see @ref{Remote Protocol}.
14224 During normal use, you should not have to use any of these commands.
14225 If you do, that may be a bug in your remote debugging stub, or a bug
14226 in @value{GDBN}. You may want to report the problem to the
14227 @value{GDBN} developers.
14229 For each packet @var{name}, the command to enable or disable the
14230 packet is @code{set remote @var{name}-packet}. The available settings
14233 @multitable @columnfractions 0.28 0.32 0.25
14236 @tab Related Features
14238 @item @code{fetch-register}
14240 @tab @code{info registers}
14242 @item @code{set-register}
14246 @item @code{binary-download}
14248 @tab @code{load}, @code{set}
14250 @item @code{read-aux-vector}
14251 @tab @code{qXfer:auxv:read}
14252 @tab @code{info auxv}
14254 @item @code{symbol-lookup}
14255 @tab @code{qSymbol}
14256 @tab Detecting multiple threads
14258 @item @code{attach}
14259 @tab @code{vAttach}
14262 @item @code{verbose-resume}
14264 @tab Stepping or resuming multiple threads
14270 @item @code{software-breakpoint}
14274 @item @code{hardware-breakpoint}
14278 @item @code{write-watchpoint}
14282 @item @code{read-watchpoint}
14286 @item @code{access-watchpoint}
14290 @item @code{target-features}
14291 @tab @code{qXfer:features:read}
14292 @tab @code{set architecture}
14294 @item @code{library-info}
14295 @tab @code{qXfer:libraries:read}
14296 @tab @code{info sharedlibrary}
14298 @item @code{memory-map}
14299 @tab @code{qXfer:memory-map:read}
14300 @tab @code{info mem}
14302 @item @code{read-spu-object}
14303 @tab @code{qXfer:spu:read}
14304 @tab @code{info spu}
14306 @item @code{write-spu-object}
14307 @tab @code{qXfer:spu:write}
14308 @tab @code{info spu}
14310 @item @code{get-thread-local-@*storage-address}
14311 @tab @code{qGetTLSAddr}
14312 @tab Displaying @code{__thread} variables
14314 @item @code{search-memory}
14315 @tab @code{qSearch:memory}
14318 @item @code{supported-packets}
14319 @tab @code{qSupported}
14320 @tab Remote communications parameters
14322 @item @code{pass-signals}
14323 @tab @code{QPassSignals}
14324 @tab @code{handle @var{signal}}
14326 @item @code{hostio-close-packet}
14327 @tab @code{vFile:close}
14328 @tab @code{remote get}, @code{remote put}
14330 @item @code{hostio-open-packet}
14331 @tab @code{vFile:open}
14332 @tab @code{remote get}, @code{remote put}
14334 @item @code{hostio-pread-packet}
14335 @tab @code{vFile:pread}
14336 @tab @code{remote get}, @code{remote put}
14338 @item @code{hostio-pwrite-packet}
14339 @tab @code{vFile:pwrite}
14340 @tab @code{remote get}, @code{remote put}
14342 @item @code{hostio-unlink-packet}
14343 @tab @code{vFile:unlink}
14344 @tab @code{remote delete}
14346 @item @code{noack-packet}
14347 @tab @code{QStartNoAckMode}
14348 @tab Packet acknowledgment
14350 @item @code{osdata}
14351 @tab @code{qXfer:osdata:read}
14352 @tab @code{info os}
14356 @section Implementing a Remote Stub
14358 @cindex debugging stub, example
14359 @cindex remote stub, example
14360 @cindex stub example, remote debugging
14361 The stub files provided with @value{GDBN} implement the target side of the
14362 communication protocol, and the @value{GDBN} side is implemented in the
14363 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14364 these subroutines to communicate, and ignore the details. (If you're
14365 implementing your own stub file, you can still ignore the details: start
14366 with one of the existing stub files. @file{sparc-stub.c} is the best
14367 organized, and therefore the easiest to read.)
14369 @cindex remote serial debugging, overview
14370 To debug a program running on another machine (the debugging
14371 @dfn{target} machine), you must first arrange for all the usual
14372 prerequisites for the program to run by itself. For example, for a C
14377 A startup routine to set up the C runtime environment; these usually
14378 have a name like @file{crt0}. The startup routine may be supplied by
14379 your hardware supplier, or you may have to write your own.
14382 A C subroutine library to support your program's
14383 subroutine calls, notably managing input and output.
14386 A way of getting your program to the other machine---for example, a
14387 download program. These are often supplied by the hardware
14388 manufacturer, but you may have to write your own from hardware
14392 The next step is to arrange for your program to use a serial port to
14393 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14394 machine). In general terms, the scheme looks like this:
14398 @value{GDBN} already understands how to use this protocol; when everything
14399 else is set up, you can simply use the @samp{target remote} command
14400 (@pxref{Targets,,Specifying a Debugging Target}).
14402 @item On the target,
14403 you must link with your program a few special-purpose subroutines that
14404 implement the @value{GDBN} remote serial protocol. The file containing these
14405 subroutines is called a @dfn{debugging stub}.
14407 On certain remote targets, you can use an auxiliary program
14408 @code{gdbserver} instead of linking a stub into your program.
14409 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14412 The debugging stub is specific to the architecture of the remote
14413 machine; for example, use @file{sparc-stub.c} to debug programs on
14416 @cindex remote serial stub list
14417 These working remote stubs are distributed with @value{GDBN}:
14422 @cindex @file{i386-stub.c}
14425 For Intel 386 and compatible architectures.
14428 @cindex @file{m68k-stub.c}
14429 @cindex Motorola 680x0
14431 For Motorola 680x0 architectures.
14434 @cindex @file{sh-stub.c}
14437 For Renesas SH architectures.
14440 @cindex @file{sparc-stub.c}
14442 For @sc{sparc} architectures.
14444 @item sparcl-stub.c
14445 @cindex @file{sparcl-stub.c}
14448 For Fujitsu @sc{sparclite} architectures.
14452 The @file{README} file in the @value{GDBN} distribution may list other
14453 recently added stubs.
14456 * Stub Contents:: What the stub can do for you
14457 * Bootstrapping:: What you must do for the stub
14458 * Debug Session:: Putting it all together
14461 @node Stub Contents
14462 @subsection What the Stub Can Do for You
14464 @cindex remote serial stub
14465 The debugging stub for your architecture supplies these three
14469 @item set_debug_traps
14470 @findex set_debug_traps
14471 @cindex remote serial stub, initialization
14472 This routine arranges for @code{handle_exception} to run when your
14473 program stops. You must call this subroutine explicitly near the
14474 beginning of your program.
14476 @item handle_exception
14477 @findex handle_exception
14478 @cindex remote serial stub, main routine
14479 This is the central workhorse, but your program never calls it
14480 explicitly---the setup code arranges for @code{handle_exception} to
14481 run when a trap is triggered.
14483 @code{handle_exception} takes control when your program stops during
14484 execution (for example, on a breakpoint), and mediates communications
14485 with @value{GDBN} on the host machine. This is where the communications
14486 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14487 representative on the target machine. It begins by sending summary
14488 information on the state of your program, then continues to execute,
14489 retrieving and transmitting any information @value{GDBN} needs, until you
14490 execute a @value{GDBN} command that makes your program resume; at that point,
14491 @code{handle_exception} returns control to your own code on the target
14495 @cindex @code{breakpoint} subroutine, remote
14496 Use this auxiliary subroutine to make your program contain a
14497 breakpoint. Depending on the particular situation, this may be the only
14498 way for @value{GDBN} to get control. For instance, if your target
14499 machine has some sort of interrupt button, you won't need to call this;
14500 pressing the interrupt button transfers control to
14501 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14502 simply receiving characters on the serial port may also trigger a trap;
14503 again, in that situation, you don't need to call @code{breakpoint} from
14504 your own program---simply running @samp{target remote} from the host
14505 @value{GDBN} session gets control.
14507 Call @code{breakpoint} if none of these is true, or if you simply want
14508 to make certain your program stops at a predetermined point for the
14509 start of your debugging session.
14512 @node Bootstrapping
14513 @subsection What You Must Do for the Stub
14515 @cindex remote stub, support routines
14516 The debugging stubs that come with @value{GDBN} are set up for a particular
14517 chip architecture, but they have no information about the rest of your
14518 debugging target machine.
14520 First of all you need to tell the stub how to communicate with the
14524 @item int getDebugChar()
14525 @findex getDebugChar
14526 Write this subroutine to read a single character from the serial port.
14527 It may be identical to @code{getchar} for your target system; a
14528 different name is used to allow you to distinguish the two if you wish.
14530 @item void putDebugChar(int)
14531 @findex putDebugChar
14532 Write this subroutine to write a single character to the serial port.
14533 It may be identical to @code{putchar} for your target system; a
14534 different name is used to allow you to distinguish the two if you wish.
14537 @cindex control C, and remote debugging
14538 @cindex interrupting remote targets
14539 If you want @value{GDBN} to be able to stop your program while it is
14540 running, you need to use an interrupt-driven serial driver, and arrange
14541 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14542 character). That is the character which @value{GDBN} uses to tell the
14543 remote system to stop.
14545 Getting the debugging target to return the proper status to @value{GDBN}
14546 probably requires changes to the standard stub; one quick and dirty way
14547 is to just execute a breakpoint instruction (the ``dirty'' part is that
14548 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14550 Other routines you need to supply are:
14553 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14554 @findex exceptionHandler
14555 Write this function to install @var{exception_address} in the exception
14556 handling tables. You need to do this because the stub does not have any
14557 way of knowing what the exception handling tables on your target system
14558 are like (for example, the processor's table might be in @sc{rom},
14559 containing entries which point to a table in @sc{ram}).
14560 @var{exception_number} is the exception number which should be changed;
14561 its meaning is architecture-dependent (for example, different numbers
14562 might represent divide by zero, misaligned access, etc). When this
14563 exception occurs, control should be transferred directly to
14564 @var{exception_address}, and the processor state (stack, registers,
14565 and so on) should be just as it is when a processor exception occurs. So if
14566 you want to use a jump instruction to reach @var{exception_address}, it
14567 should be a simple jump, not a jump to subroutine.
14569 For the 386, @var{exception_address} should be installed as an interrupt
14570 gate so that interrupts are masked while the handler runs. The gate
14571 should be at privilege level 0 (the most privileged level). The
14572 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14573 help from @code{exceptionHandler}.
14575 @item void flush_i_cache()
14576 @findex flush_i_cache
14577 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14578 instruction cache, if any, on your target machine. If there is no
14579 instruction cache, this subroutine may be a no-op.
14581 On target machines that have instruction caches, @value{GDBN} requires this
14582 function to make certain that the state of your program is stable.
14586 You must also make sure this library routine is available:
14589 @item void *memset(void *, int, int)
14591 This is the standard library function @code{memset} that sets an area of
14592 memory to a known value. If you have one of the free versions of
14593 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14594 either obtain it from your hardware manufacturer, or write your own.
14597 If you do not use the GNU C compiler, you may need other standard
14598 library subroutines as well; this varies from one stub to another,
14599 but in general the stubs are likely to use any of the common library
14600 subroutines which @code{@value{NGCC}} generates as inline code.
14603 @node Debug Session
14604 @subsection Putting it All Together
14606 @cindex remote serial debugging summary
14607 In summary, when your program is ready to debug, you must follow these
14612 Make sure you have defined the supporting low-level routines
14613 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14615 @code{getDebugChar}, @code{putDebugChar},
14616 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14620 Insert these lines near the top of your program:
14628 For the 680x0 stub only, you need to provide a variable called
14629 @code{exceptionHook}. Normally you just use:
14632 void (*exceptionHook)() = 0;
14636 but if before calling @code{set_debug_traps}, you set it to point to a
14637 function in your program, that function is called when
14638 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14639 error). The function indicated by @code{exceptionHook} is called with
14640 one parameter: an @code{int} which is the exception number.
14643 Compile and link together: your program, the @value{GDBN} debugging stub for
14644 your target architecture, and the supporting subroutines.
14647 Make sure you have a serial connection between your target machine and
14648 the @value{GDBN} host, and identify the serial port on the host.
14651 @c The "remote" target now provides a `load' command, so we should
14652 @c document that. FIXME.
14653 Download your program to your target machine (or get it there by
14654 whatever means the manufacturer provides), and start it.
14657 Start @value{GDBN} on the host, and connect to the target
14658 (@pxref{Connecting,,Connecting to a Remote Target}).
14662 @node Configurations
14663 @chapter Configuration-Specific Information
14665 While nearly all @value{GDBN} commands are available for all native and
14666 cross versions of the debugger, there are some exceptions. This chapter
14667 describes things that are only available in certain configurations.
14669 There are three major categories of configurations: native
14670 configurations, where the host and target are the same, embedded
14671 operating system configurations, which are usually the same for several
14672 different processor architectures, and bare embedded processors, which
14673 are quite different from each other.
14678 * Embedded Processors::
14685 This section describes details specific to particular native
14690 * BSD libkvm Interface:: Debugging BSD kernel memory images
14691 * SVR4 Process Information:: SVR4 process information
14692 * DJGPP Native:: Features specific to the DJGPP port
14693 * Cygwin Native:: Features specific to the Cygwin port
14694 * Hurd Native:: Features specific to @sc{gnu} Hurd
14695 * Neutrino:: Features specific to QNX Neutrino
14696 * Darwin:: Features specific to Darwin
14702 On HP-UX systems, if you refer to a function or variable name that
14703 begins with a dollar sign, @value{GDBN} searches for a user or system
14704 name first, before it searches for a convenience variable.
14707 @node BSD libkvm Interface
14708 @subsection BSD libkvm Interface
14711 @cindex kernel memory image
14712 @cindex kernel crash dump
14714 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14715 interface that provides a uniform interface for accessing kernel virtual
14716 memory images, including live systems and crash dumps. @value{GDBN}
14717 uses this interface to allow you to debug live kernels and kernel crash
14718 dumps on many native BSD configurations. This is implemented as a
14719 special @code{kvm} debugging target. For debugging a live system, load
14720 the currently running kernel into @value{GDBN} and connect to the
14724 (@value{GDBP}) @b{target kvm}
14727 For debugging crash dumps, provide the file name of the crash dump as an
14731 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14734 Once connected to the @code{kvm} target, the following commands are
14740 Set current context from the @dfn{Process Control Block} (PCB) address.
14743 Set current context from proc address. This command isn't available on
14744 modern FreeBSD systems.
14747 @node SVR4 Process Information
14748 @subsection SVR4 Process Information
14750 @cindex examine process image
14751 @cindex process info via @file{/proc}
14753 Many versions of SVR4 and compatible systems provide a facility called
14754 @samp{/proc} that can be used to examine the image of a running
14755 process using file-system subroutines. If @value{GDBN} is configured
14756 for an operating system with this facility, the command @code{info
14757 proc} is available to report information about the process running
14758 your program, or about any process running on your system. @code{info
14759 proc} works only on SVR4 systems that include the @code{procfs} code.
14760 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14761 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14767 @itemx info proc @var{process-id}
14768 Summarize available information about any running process. If a
14769 process ID is specified by @var{process-id}, display information about
14770 that process; otherwise display information about the program being
14771 debugged. The summary includes the debugged process ID, the command
14772 line used to invoke it, its current working directory, and its
14773 executable file's absolute file name.
14775 On some systems, @var{process-id} can be of the form
14776 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14777 within a process. If the optional @var{pid} part is missing, it means
14778 a thread from the process being debugged (the leading @samp{/} still
14779 needs to be present, or else @value{GDBN} will interpret the number as
14780 a process ID rather than a thread ID).
14782 @item info proc mappings
14783 @cindex memory address space mappings
14784 Report the memory address space ranges accessible in the program, with
14785 information on whether the process has read, write, or execute access
14786 rights to each range. On @sc{gnu}/Linux systems, each memory range
14787 includes the object file which is mapped to that range, instead of the
14788 memory access rights to that range.
14790 @item info proc stat
14791 @itemx info proc status
14792 @cindex process detailed status information
14793 These subcommands are specific to @sc{gnu}/Linux systems. They show
14794 the process-related information, including the user ID and group ID;
14795 how many threads are there in the process; its virtual memory usage;
14796 the signals that are pending, blocked, and ignored; its TTY; its
14797 consumption of system and user time; its stack size; its @samp{nice}
14798 value; etc. For more information, see the @samp{proc} man page
14799 (type @kbd{man 5 proc} from your shell prompt).
14801 @item info proc all
14802 Show all the information about the process described under all of the
14803 above @code{info proc} subcommands.
14806 @comment These sub-options of 'info proc' were not included when
14807 @comment procfs.c was re-written. Keep their descriptions around
14808 @comment against the day when someone finds the time to put them back in.
14809 @kindex info proc times
14810 @item info proc times
14811 Starting time, user CPU time, and system CPU time for your program and
14814 @kindex info proc id
14816 Report on the process IDs related to your program: its own process ID,
14817 the ID of its parent, the process group ID, and the session ID.
14820 @item set procfs-trace
14821 @kindex set procfs-trace
14822 @cindex @code{procfs} API calls
14823 This command enables and disables tracing of @code{procfs} API calls.
14825 @item show procfs-trace
14826 @kindex show procfs-trace
14827 Show the current state of @code{procfs} API call tracing.
14829 @item set procfs-file @var{file}
14830 @kindex set procfs-file
14831 Tell @value{GDBN} to write @code{procfs} API trace to the named
14832 @var{file}. @value{GDBN} appends the trace info to the previous
14833 contents of the file. The default is to display the trace on the
14836 @item show procfs-file
14837 @kindex show procfs-file
14838 Show the file to which @code{procfs} API trace is written.
14840 @item proc-trace-entry
14841 @itemx proc-trace-exit
14842 @itemx proc-untrace-entry
14843 @itemx proc-untrace-exit
14844 @kindex proc-trace-entry
14845 @kindex proc-trace-exit
14846 @kindex proc-untrace-entry
14847 @kindex proc-untrace-exit
14848 These commands enable and disable tracing of entries into and exits
14849 from the @code{syscall} interface.
14852 @kindex info pidlist
14853 @cindex process list, QNX Neutrino
14854 For QNX Neutrino only, this command displays the list of all the
14855 processes and all the threads within each process.
14858 @kindex info meminfo
14859 @cindex mapinfo list, QNX Neutrino
14860 For QNX Neutrino only, this command displays the list of all mapinfos.
14864 @subsection Features for Debugging @sc{djgpp} Programs
14865 @cindex @sc{djgpp} debugging
14866 @cindex native @sc{djgpp} debugging
14867 @cindex MS-DOS-specific commands
14870 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14871 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14872 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14873 top of real-mode DOS systems and their emulations.
14875 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14876 defines a few commands specific to the @sc{djgpp} port. This
14877 subsection describes those commands.
14882 This is a prefix of @sc{djgpp}-specific commands which print
14883 information about the target system and important OS structures.
14886 @cindex MS-DOS system info
14887 @cindex free memory information (MS-DOS)
14888 @item info dos sysinfo
14889 This command displays assorted information about the underlying
14890 platform: the CPU type and features, the OS version and flavor, the
14891 DPMI version, and the available conventional and DPMI memory.
14896 @cindex segment descriptor tables
14897 @cindex descriptor tables display
14899 @itemx info dos ldt
14900 @itemx info dos idt
14901 These 3 commands display entries from, respectively, Global, Local,
14902 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14903 tables are data structures which store a descriptor for each segment
14904 that is currently in use. The segment's selector is an index into a
14905 descriptor table; the table entry for that index holds the
14906 descriptor's base address and limit, and its attributes and access
14909 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14910 segment (used for both data and the stack), and a DOS segment (which
14911 allows access to DOS/BIOS data structures and absolute addresses in
14912 conventional memory). However, the DPMI host will usually define
14913 additional segments in order to support the DPMI environment.
14915 @cindex garbled pointers
14916 These commands allow to display entries from the descriptor tables.
14917 Without an argument, all entries from the specified table are
14918 displayed. An argument, which should be an integer expression, means
14919 display a single entry whose index is given by the argument. For
14920 example, here's a convenient way to display information about the
14921 debugged program's data segment:
14924 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14925 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14929 This comes in handy when you want to see whether a pointer is outside
14930 the data segment's limit (i.e.@: @dfn{garbled}).
14932 @cindex page tables display (MS-DOS)
14934 @itemx info dos pte
14935 These two commands display entries from, respectively, the Page
14936 Directory and the Page Tables. Page Directories and Page Tables are
14937 data structures which control how virtual memory addresses are mapped
14938 into physical addresses. A Page Table includes an entry for every
14939 page of memory that is mapped into the program's address space; there
14940 may be several Page Tables, each one holding up to 4096 entries. A
14941 Page Directory has up to 4096 entries, one each for every Page Table
14942 that is currently in use.
14944 Without an argument, @kbd{info dos pde} displays the entire Page
14945 Directory, and @kbd{info dos pte} displays all the entries in all of
14946 the Page Tables. An argument, an integer expression, given to the
14947 @kbd{info dos pde} command means display only that entry from the Page
14948 Directory table. An argument given to the @kbd{info dos pte} command
14949 means display entries from a single Page Table, the one pointed to by
14950 the specified entry in the Page Directory.
14952 @cindex direct memory access (DMA) on MS-DOS
14953 These commands are useful when your program uses @dfn{DMA} (Direct
14954 Memory Access), which needs physical addresses to program the DMA
14957 These commands are supported only with some DPMI servers.
14959 @cindex physical address from linear address
14960 @item info dos address-pte @var{addr}
14961 This command displays the Page Table entry for a specified linear
14962 address. The argument @var{addr} is a linear address which should
14963 already have the appropriate segment's base address added to it,
14964 because this command accepts addresses which may belong to @emph{any}
14965 segment. For example, here's how to display the Page Table entry for
14966 the page where a variable @code{i} is stored:
14969 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14970 @exdent @code{Page Table entry for address 0x11a00d30:}
14971 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14975 This says that @code{i} is stored at offset @code{0xd30} from the page
14976 whose physical base address is @code{0x02698000}, and shows all the
14977 attributes of that page.
14979 Note that you must cast the addresses of variables to a @code{char *},
14980 since otherwise the value of @code{__djgpp_base_address}, the base
14981 address of all variables and functions in a @sc{djgpp} program, will
14982 be added using the rules of C pointer arithmetics: if @code{i} is
14983 declared an @code{int}, @value{GDBN} will add 4 times the value of
14984 @code{__djgpp_base_address} to the address of @code{i}.
14986 Here's another example, it displays the Page Table entry for the
14990 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14991 @exdent @code{Page Table entry for address 0x29110:}
14992 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14996 (The @code{+ 3} offset is because the transfer buffer's address is the
14997 3rd member of the @code{_go32_info_block} structure.) The output
14998 clearly shows that this DPMI server maps the addresses in conventional
14999 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15000 linear (@code{0x29110}) addresses are identical.
15002 This command is supported only with some DPMI servers.
15005 @cindex DOS serial data link, remote debugging
15006 In addition to native debugging, the DJGPP port supports remote
15007 debugging via a serial data link. The following commands are specific
15008 to remote serial debugging in the DJGPP port of @value{GDBN}.
15011 @kindex set com1base
15012 @kindex set com1irq
15013 @kindex set com2base
15014 @kindex set com2irq
15015 @kindex set com3base
15016 @kindex set com3irq
15017 @kindex set com4base
15018 @kindex set com4irq
15019 @item set com1base @var{addr}
15020 This command sets the base I/O port address of the @file{COM1} serial
15023 @item set com1irq @var{irq}
15024 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15025 for the @file{COM1} serial port.
15027 There are similar commands @samp{set com2base}, @samp{set com3irq},
15028 etc.@: for setting the port address and the @code{IRQ} lines for the
15031 @kindex show com1base
15032 @kindex show com1irq
15033 @kindex show com2base
15034 @kindex show com2irq
15035 @kindex show com3base
15036 @kindex show com3irq
15037 @kindex show com4base
15038 @kindex show com4irq
15039 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15040 display the current settings of the base address and the @code{IRQ}
15041 lines used by the COM ports.
15044 @kindex info serial
15045 @cindex DOS serial port status
15046 This command prints the status of the 4 DOS serial ports. For each
15047 port, it prints whether it's active or not, its I/O base address and
15048 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15049 counts of various errors encountered so far.
15053 @node Cygwin Native
15054 @subsection Features for Debugging MS Windows PE Executables
15055 @cindex MS Windows debugging
15056 @cindex native Cygwin debugging
15057 @cindex Cygwin-specific commands
15059 @value{GDBN} supports native debugging of MS Windows programs, including
15060 DLLs with and without symbolic debugging information. There are various
15061 additional Cygwin-specific commands, described in this section.
15062 Working with DLLs that have no debugging symbols is described in
15063 @ref{Non-debug DLL Symbols}.
15068 This is a prefix of MS Windows-specific commands which print
15069 information about the target system and important OS structures.
15071 @item info w32 selector
15072 This command displays information returned by
15073 the Win32 API @code{GetThreadSelectorEntry} function.
15074 It takes an optional argument that is evaluated to
15075 a long value to give the information about this given selector.
15076 Without argument, this command displays information
15077 about the six segment registers.
15081 This is a Cygwin-specific alias of @code{info shared}.
15083 @kindex dll-symbols
15085 This command loads symbols from a dll similarly to
15086 add-sym command but without the need to specify a base address.
15088 @kindex set cygwin-exceptions
15089 @cindex debugging the Cygwin DLL
15090 @cindex Cygwin DLL, debugging
15091 @item set cygwin-exceptions @var{mode}
15092 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15093 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15094 @value{GDBN} will delay recognition of exceptions, and may ignore some
15095 exceptions which seem to be caused by internal Cygwin DLL
15096 ``bookkeeping''. This option is meant primarily for debugging the
15097 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15098 @value{GDBN} users with false @code{SIGSEGV} signals.
15100 @kindex show cygwin-exceptions
15101 @item show cygwin-exceptions
15102 Displays whether @value{GDBN} will break on exceptions that happen
15103 inside the Cygwin DLL itself.
15105 @kindex set new-console
15106 @item set new-console @var{mode}
15107 If @var{mode} is @code{on} the debuggee will
15108 be started in a new console on next start.
15109 If @var{mode} is @code{off}i, the debuggee will
15110 be started in the same console as the debugger.
15112 @kindex show new-console
15113 @item show new-console
15114 Displays whether a new console is used
15115 when the debuggee is started.
15117 @kindex set new-group
15118 @item set new-group @var{mode}
15119 This boolean value controls whether the debuggee should
15120 start a new group or stay in the same group as the debugger.
15121 This affects the way the Windows OS handles
15124 @kindex show new-group
15125 @item show new-group
15126 Displays current value of new-group boolean.
15128 @kindex set debugevents
15129 @item set debugevents
15130 This boolean value adds debug output concerning kernel events related
15131 to the debuggee seen by the debugger. This includes events that
15132 signal thread and process creation and exit, DLL loading and
15133 unloading, console interrupts, and debugging messages produced by the
15134 Windows @code{OutputDebugString} API call.
15136 @kindex set debugexec
15137 @item set debugexec
15138 This boolean value adds debug output concerning execute events
15139 (such as resume thread) seen by the debugger.
15141 @kindex set debugexceptions
15142 @item set debugexceptions
15143 This boolean value adds debug output concerning exceptions in the
15144 debuggee seen by the debugger.
15146 @kindex set debugmemory
15147 @item set debugmemory
15148 This boolean value adds debug output concerning debuggee memory reads
15149 and writes by the debugger.
15153 This boolean values specifies whether the debuggee is called
15154 via a shell or directly (default value is on).
15158 Displays if the debuggee will be started with a shell.
15163 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15166 @node Non-debug DLL Symbols
15167 @subsubsection Support for DLLs without Debugging Symbols
15168 @cindex DLLs with no debugging symbols
15169 @cindex Minimal symbols and DLLs
15171 Very often on windows, some of the DLLs that your program relies on do
15172 not include symbolic debugging information (for example,
15173 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15174 symbols in a DLL, it relies on the minimal amount of symbolic
15175 information contained in the DLL's export table. This section
15176 describes working with such symbols, known internally to @value{GDBN} as
15177 ``minimal symbols''.
15179 Note that before the debugged program has started execution, no DLLs
15180 will have been loaded. The easiest way around this problem is simply to
15181 start the program --- either by setting a breakpoint or letting the
15182 program run once to completion. It is also possible to force
15183 @value{GDBN} to load a particular DLL before starting the executable ---
15184 see the shared library information in @ref{Files}, or the
15185 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15186 explicitly loading symbols from a DLL with no debugging information will
15187 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15188 which may adversely affect symbol lookup performance.
15190 @subsubsection DLL Name Prefixes
15192 In keeping with the naming conventions used by the Microsoft debugging
15193 tools, DLL export symbols are made available with a prefix based on the
15194 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15195 also entered into the symbol table, so @code{CreateFileA} is often
15196 sufficient. In some cases there will be name clashes within a program
15197 (particularly if the executable itself includes full debugging symbols)
15198 necessitating the use of the fully qualified name when referring to the
15199 contents of the DLL. Use single-quotes around the name to avoid the
15200 exclamation mark (``!'') being interpreted as a language operator.
15202 Note that the internal name of the DLL may be all upper-case, even
15203 though the file name of the DLL is lower-case, or vice-versa. Since
15204 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15205 some confusion. If in doubt, try the @code{info functions} and
15206 @code{info variables} commands or even @code{maint print msymbols}
15207 (@pxref{Symbols}). Here's an example:
15210 (@value{GDBP}) info function CreateFileA
15211 All functions matching regular expression "CreateFileA":
15213 Non-debugging symbols:
15214 0x77e885f4 CreateFileA
15215 0x77e885f4 KERNEL32!CreateFileA
15219 (@value{GDBP}) info function !
15220 All functions matching regular expression "!":
15222 Non-debugging symbols:
15223 0x6100114c cygwin1!__assert
15224 0x61004034 cygwin1!_dll_crt0@@0
15225 0x61004240 cygwin1!dll_crt0(per_process *)
15229 @subsubsection Working with Minimal Symbols
15231 Symbols extracted from a DLL's export table do not contain very much
15232 type information. All that @value{GDBN} can do is guess whether a symbol
15233 refers to a function or variable depending on the linker section that
15234 contains the symbol. Also note that the actual contents of the memory
15235 contained in a DLL are not available unless the program is running. This
15236 means that you cannot examine the contents of a variable or disassemble
15237 a function within a DLL without a running program.
15239 Variables are generally treated as pointers and dereferenced
15240 automatically. For this reason, it is often necessary to prefix a
15241 variable name with the address-of operator (``&'') and provide explicit
15242 type information in the command. Here's an example of the type of
15246 (@value{GDBP}) print 'cygwin1!__argv'
15251 (@value{GDBP}) x 'cygwin1!__argv'
15252 0x10021610: "\230y\""
15255 And two possible solutions:
15258 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15259 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15263 (@value{GDBP}) x/2x &'cygwin1!__argv'
15264 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15265 (@value{GDBP}) x/x 0x10021608
15266 0x10021608: 0x0022fd98
15267 (@value{GDBP}) x/s 0x0022fd98
15268 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15271 Setting a break point within a DLL is possible even before the program
15272 starts execution. However, under these circumstances, @value{GDBN} can't
15273 examine the initial instructions of the function in order to skip the
15274 function's frame set-up code. You can work around this by using ``*&''
15275 to set the breakpoint at a raw memory address:
15278 (@value{GDBP}) break *&'python22!PyOS_Readline'
15279 Breakpoint 1 at 0x1e04eff0
15282 The author of these extensions is not entirely convinced that setting a
15283 break point within a shared DLL like @file{kernel32.dll} is completely
15287 @subsection Commands Specific to @sc{gnu} Hurd Systems
15288 @cindex @sc{gnu} Hurd debugging
15290 This subsection describes @value{GDBN} commands specific to the
15291 @sc{gnu} Hurd native debugging.
15296 @kindex set signals@r{, Hurd command}
15297 @kindex set sigs@r{, Hurd command}
15298 This command toggles the state of inferior signal interception by
15299 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15300 affected by this command. @code{sigs} is a shorthand alias for
15305 @kindex show signals@r{, Hurd command}
15306 @kindex show sigs@r{, Hurd command}
15307 Show the current state of intercepting inferior's signals.
15309 @item set signal-thread
15310 @itemx set sigthread
15311 @kindex set signal-thread
15312 @kindex set sigthread
15313 This command tells @value{GDBN} which thread is the @code{libc} signal
15314 thread. That thread is run when a signal is delivered to a running
15315 process. @code{set sigthread} is the shorthand alias of @code{set
15318 @item show signal-thread
15319 @itemx show sigthread
15320 @kindex show signal-thread
15321 @kindex show sigthread
15322 These two commands show which thread will run when the inferior is
15323 delivered a signal.
15326 @kindex set stopped@r{, Hurd command}
15327 This commands tells @value{GDBN} that the inferior process is stopped,
15328 as with the @code{SIGSTOP} signal. The stopped process can be
15329 continued by delivering a signal to it.
15332 @kindex show stopped@r{, Hurd command}
15333 This command shows whether @value{GDBN} thinks the debuggee is
15336 @item set exceptions
15337 @kindex set exceptions@r{, Hurd command}
15338 Use this command to turn off trapping of exceptions in the inferior.
15339 When exception trapping is off, neither breakpoints nor
15340 single-stepping will work. To restore the default, set exception
15343 @item show exceptions
15344 @kindex show exceptions@r{, Hurd command}
15345 Show the current state of trapping exceptions in the inferior.
15347 @item set task pause
15348 @kindex set task@r{, Hurd commands}
15349 @cindex task attributes (@sc{gnu} Hurd)
15350 @cindex pause current task (@sc{gnu} Hurd)
15351 This command toggles task suspension when @value{GDBN} has control.
15352 Setting it to on takes effect immediately, and the task is suspended
15353 whenever @value{GDBN} gets control. Setting it to off will take
15354 effect the next time the inferior is continued. If this option is set
15355 to off, you can use @code{set thread default pause on} or @code{set
15356 thread pause on} (see below) to pause individual threads.
15358 @item show task pause
15359 @kindex show task@r{, Hurd commands}
15360 Show the current state of task suspension.
15362 @item set task detach-suspend-count
15363 @cindex task suspend count
15364 @cindex detach from task, @sc{gnu} Hurd
15365 This command sets the suspend count the task will be left with when
15366 @value{GDBN} detaches from it.
15368 @item show task detach-suspend-count
15369 Show the suspend count the task will be left with when detaching.
15371 @item set task exception-port
15372 @itemx set task excp
15373 @cindex task exception port, @sc{gnu} Hurd
15374 This command sets the task exception port to which @value{GDBN} will
15375 forward exceptions. The argument should be the value of the @dfn{send
15376 rights} of the task. @code{set task excp} is a shorthand alias.
15378 @item set noninvasive
15379 @cindex noninvasive task options
15380 This command switches @value{GDBN} to a mode that is the least
15381 invasive as far as interfering with the inferior is concerned. This
15382 is the same as using @code{set task pause}, @code{set exceptions}, and
15383 @code{set signals} to values opposite to the defaults.
15385 @item info send-rights
15386 @itemx info receive-rights
15387 @itemx info port-rights
15388 @itemx info port-sets
15389 @itemx info dead-names
15392 @cindex send rights, @sc{gnu} Hurd
15393 @cindex receive rights, @sc{gnu} Hurd
15394 @cindex port rights, @sc{gnu} Hurd
15395 @cindex port sets, @sc{gnu} Hurd
15396 @cindex dead names, @sc{gnu} Hurd
15397 These commands display information about, respectively, send rights,
15398 receive rights, port rights, port sets, and dead names of a task.
15399 There are also shorthand aliases: @code{info ports} for @code{info
15400 port-rights} and @code{info psets} for @code{info port-sets}.
15402 @item set thread pause
15403 @kindex set thread@r{, Hurd command}
15404 @cindex thread properties, @sc{gnu} Hurd
15405 @cindex pause current thread (@sc{gnu} Hurd)
15406 This command toggles current thread suspension when @value{GDBN} has
15407 control. Setting it to on takes effect immediately, and the current
15408 thread is suspended whenever @value{GDBN} gets control. Setting it to
15409 off will take effect the next time the inferior is continued.
15410 Normally, this command has no effect, since when @value{GDBN} has
15411 control, the whole task is suspended. However, if you used @code{set
15412 task pause off} (see above), this command comes in handy to suspend
15413 only the current thread.
15415 @item show thread pause
15416 @kindex show thread@r{, Hurd command}
15417 This command shows the state of current thread suspension.
15419 @item set thread run
15420 This command sets whether the current thread is allowed to run.
15422 @item show thread run
15423 Show whether the current thread is allowed to run.
15425 @item set thread detach-suspend-count
15426 @cindex thread suspend count, @sc{gnu} Hurd
15427 @cindex detach from thread, @sc{gnu} Hurd
15428 This command sets the suspend count @value{GDBN} will leave on a
15429 thread when detaching. This number is relative to the suspend count
15430 found by @value{GDBN} when it notices the thread; use @code{set thread
15431 takeover-suspend-count} to force it to an absolute value.
15433 @item show thread detach-suspend-count
15434 Show the suspend count @value{GDBN} will leave on the thread when
15437 @item set thread exception-port
15438 @itemx set thread excp
15439 Set the thread exception port to which to forward exceptions. This
15440 overrides the port set by @code{set task exception-port} (see above).
15441 @code{set thread excp} is the shorthand alias.
15443 @item set thread takeover-suspend-count
15444 Normally, @value{GDBN}'s thread suspend counts are relative to the
15445 value @value{GDBN} finds when it notices each thread. This command
15446 changes the suspend counts to be absolute instead.
15448 @item set thread default
15449 @itemx show thread default
15450 @cindex thread default settings, @sc{gnu} Hurd
15451 Each of the above @code{set thread} commands has a @code{set thread
15452 default} counterpart (e.g., @code{set thread default pause}, @code{set
15453 thread default exception-port}, etc.). The @code{thread default}
15454 variety of commands sets the default thread properties for all
15455 threads; you can then change the properties of individual threads with
15456 the non-default commands.
15461 @subsection QNX Neutrino
15462 @cindex QNX Neutrino
15464 @value{GDBN} provides the following commands specific to the QNX
15468 @item set debug nto-debug
15469 @kindex set debug nto-debug
15470 When set to on, enables debugging messages specific to the QNX
15473 @item show debug nto-debug
15474 @kindex show debug nto-debug
15475 Show the current state of QNX Neutrino messages.
15482 @value{GDBN} provides the following commands specific to the Darwin target:
15485 @item set debug darwin @var{num}
15486 @kindex set debug darwin
15487 When set to a non zero value, enables debugging messages specific to
15488 the Darwin support. Higher values produce more verbose output.
15490 @item show debug darwin
15491 @kindex show debug darwin
15492 Show the current state of Darwin messages.
15494 @item set debug mach-o @var{num}
15495 @kindex set debug mach-o
15496 When set to a non zero value, enables debugging messages while
15497 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15498 file format used on Darwin for object and executable files.) Higher
15499 values produce more verbose output. This is a command to diagnose
15500 problems internal to @value{GDBN} and should not be needed in normal
15503 @item show debug mach-o
15504 @kindex show debug mach-o
15505 Show the current state of Mach-O file messages.
15507 @item set mach-exceptions on
15508 @itemx set mach-exceptions off
15509 @kindex set mach-exceptions
15510 On Darwin, faults are first reported as a Mach exception and are then
15511 mapped to a Posix signal. Use this command to turn on trapping of
15512 Mach exceptions in the inferior. This might be sometimes useful to
15513 better understand the cause of a fault. The default is off.
15515 @item show mach-exceptions
15516 @kindex show mach-exceptions
15517 Show the current state of exceptions trapping.
15522 @section Embedded Operating Systems
15524 This section describes configurations involving the debugging of
15525 embedded operating systems that are available for several different
15529 * VxWorks:: Using @value{GDBN} with VxWorks
15532 @value{GDBN} includes the ability to debug programs running on
15533 various real-time operating systems.
15536 @subsection Using @value{GDBN} with VxWorks
15542 @kindex target vxworks
15543 @item target vxworks @var{machinename}
15544 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15545 is the target system's machine name or IP address.
15549 On VxWorks, @code{load} links @var{filename} dynamically on the
15550 current target system as well as adding its symbols in @value{GDBN}.
15552 @value{GDBN} enables developers to spawn and debug tasks running on networked
15553 VxWorks targets from a Unix host. Already-running tasks spawned from
15554 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15555 both the Unix host and on the VxWorks target. The program
15556 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15557 installed with the name @code{vxgdb}, to distinguish it from a
15558 @value{GDBN} for debugging programs on the host itself.)
15561 @item VxWorks-timeout @var{args}
15562 @kindex vxworks-timeout
15563 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15564 This option is set by the user, and @var{args} represents the number of
15565 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15566 your VxWorks target is a slow software simulator or is on the far side
15567 of a thin network line.
15570 The following information on connecting to VxWorks was current when
15571 this manual was produced; newer releases of VxWorks may use revised
15574 @findex INCLUDE_RDB
15575 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15576 to include the remote debugging interface routines in the VxWorks
15577 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15578 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15579 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15580 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15581 information on configuring and remaking VxWorks, see the manufacturer's
15583 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15585 Once you have included @file{rdb.a} in your VxWorks system image and set
15586 your Unix execution search path to find @value{GDBN}, you are ready to
15587 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15588 @code{vxgdb}, depending on your installation).
15590 @value{GDBN} comes up showing the prompt:
15597 * VxWorks Connection:: Connecting to VxWorks
15598 * VxWorks Download:: VxWorks download
15599 * VxWorks Attach:: Running tasks
15602 @node VxWorks Connection
15603 @subsubsection Connecting to VxWorks
15605 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15606 network. To connect to a target whose host name is ``@code{tt}'', type:
15609 (vxgdb) target vxworks tt
15613 @value{GDBN} displays messages like these:
15616 Attaching remote machine across net...
15621 @value{GDBN} then attempts to read the symbol tables of any object modules
15622 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15623 these files by searching the directories listed in the command search
15624 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15625 to find an object file, it displays a message such as:
15628 prog.o: No such file or directory.
15631 When this happens, add the appropriate directory to the search path with
15632 the @value{GDBN} command @code{path}, and execute the @code{target}
15635 @node VxWorks Download
15636 @subsubsection VxWorks Download
15638 @cindex download to VxWorks
15639 If you have connected to the VxWorks target and you want to debug an
15640 object that has not yet been loaded, you can use the @value{GDBN}
15641 @code{load} command to download a file from Unix to VxWorks
15642 incrementally. The object file given as an argument to the @code{load}
15643 command is actually opened twice: first by the VxWorks target in order
15644 to download the code, then by @value{GDBN} in order to read the symbol
15645 table. This can lead to problems if the current working directories on
15646 the two systems differ. If both systems have NFS mounted the same
15647 filesystems, you can avoid these problems by using absolute paths.
15648 Otherwise, it is simplest to set the working directory on both systems
15649 to the directory in which the object file resides, and then to reference
15650 the file by its name, without any path. For instance, a program
15651 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15652 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15653 program, type this on VxWorks:
15656 -> cd "@var{vxpath}/vw/demo/rdb"
15660 Then, in @value{GDBN}, type:
15663 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15664 (vxgdb) load prog.o
15667 @value{GDBN} displays a response similar to this:
15670 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15673 You can also use the @code{load} command to reload an object module
15674 after editing and recompiling the corresponding source file. Note that
15675 this makes @value{GDBN} delete all currently-defined breakpoints,
15676 auto-displays, and convenience variables, and to clear the value
15677 history. (This is necessary in order to preserve the integrity of
15678 debugger's data structures that reference the target system's symbol
15681 @node VxWorks Attach
15682 @subsubsection Running Tasks
15684 @cindex running VxWorks tasks
15685 You can also attach to an existing task using the @code{attach} command as
15689 (vxgdb) attach @var{task}
15693 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15694 or suspended when you attach to it. Running tasks are suspended at
15695 the time of attachment.
15697 @node Embedded Processors
15698 @section Embedded Processors
15700 This section goes into details specific to particular embedded
15703 @cindex send command to simulator
15704 Whenever a specific embedded processor has a simulator, @value{GDBN}
15705 allows to send an arbitrary command to the simulator.
15708 @item sim @var{command}
15709 @kindex sim@r{, a command}
15710 Send an arbitrary @var{command} string to the simulator. Consult the
15711 documentation for the specific simulator in use for information about
15712 acceptable commands.
15718 * M32R/D:: Renesas M32R/D
15719 * M68K:: Motorola M68K
15720 * MIPS Embedded:: MIPS Embedded
15721 * OpenRISC 1000:: OpenRisc 1000
15722 * PA:: HP PA Embedded
15723 * PowerPC Embedded:: PowerPC Embedded
15724 * Sparclet:: Tsqware Sparclet
15725 * Sparclite:: Fujitsu Sparclite
15726 * Z8000:: Zilog Z8000
15729 * Super-H:: Renesas Super-H
15738 @item target rdi @var{dev}
15739 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15740 use this target to communicate with both boards running the Angel
15741 monitor, or with the EmbeddedICE JTAG debug device.
15744 @item target rdp @var{dev}
15749 @value{GDBN} provides the following ARM-specific commands:
15752 @item set arm disassembler
15754 This commands selects from a list of disassembly styles. The
15755 @code{"std"} style is the standard style.
15757 @item show arm disassembler
15759 Show the current disassembly style.
15761 @item set arm apcs32
15762 @cindex ARM 32-bit mode
15763 This command toggles ARM operation mode between 32-bit and 26-bit.
15765 @item show arm apcs32
15766 Display the current usage of the ARM 32-bit mode.
15768 @item set arm fpu @var{fputype}
15769 This command sets the ARM floating-point unit (FPU) type. The
15770 argument @var{fputype} can be one of these:
15774 Determine the FPU type by querying the OS ABI.
15776 Software FPU, with mixed-endian doubles on little-endian ARM
15779 GCC-compiled FPA co-processor.
15781 Software FPU with pure-endian doubles.
15787 Show the current type of the FPU.
15790 This command forces @value{GDBN} to use the specified ABI.
15793 Show the currently used ABI.
15795 @item set arm fallback-mode (arm|thumb|auto)
15796 @value{GDBN} uses the symbol table, when available, to determine
15797 whether instructions are ARM or Thumb. This command controls
15798 @value{GDBN}'s default behavior when the symbol table is not
15799 available. The default is @samp{auto}, which causes @value{GDBN} to
15800 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15803 @item show arm fallback-mode
15804 Show the current fallback instruction mode.
15806 @item set arm force-mode (arm|thumb|auto)
15807 This command overrides use of the symbol table to determine whether
15808 instructions are ARM or Thumb. The default is @samp{auto}, which
15809 causes @value{GDBN} to use the symbol table and then the setting
15810 of @samp{set arm fallback-mode}.
15812 @item show arm force-mode
15813 Show the current forced instruction mode.
15815 @item set debug arm
15816 Toggle whether to display ARM-specific debugging messages from the ARM
15817 target support subsystem.
15819 @item show debug arm
15820 Show whether ARM-specific debugging messages are enabled.
15823 The following commands are available when an ARM target is debugged
15824 using the RDI interface:
15827 @item rdilogfile @r{[}@var{file}@r{]}
15829 @cindex ADP (Angel Debugger Protocol) logging
15830 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15831 With an argument, sets the log file to the specified @var{file}. With
15832 no argument, show the current log file name. The default log file is
15835 @item rdilogenable @r{[}@var{arg}@r{]}
15836 @kindex rdilogenable
15837 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15838 enables logging, with an argument 0 or @code{"no"} disables it. With
15839 no arguments displays the current setting. When logging is enabled,
15840 ADP packets exchanged between @value{GDBN} and the RDI target device
15841 are logged to a file.
15843 @item set rdiromatzero
15844 @kindex set rdiromatzero
15845 @cindex ROM at zero address, RDI
15846 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15847 vector catching is disabled, so that zero address can be used. If off
15848 (the default), vector catching is enabled. For this command to take
15849 effect, it needs to be invoked prior to the @code{target rdi} command.
15851 @item show rdiromatzero
15852 @kindex show rdiromatzero
15853 Show the current setting of ROM at zero address.
15855 @item set rdiheartbeat
15856 @kindex set rdiheartbeat
15857 @cindex RDI heartbeat
15858 Enable or disable RDI heartbeat packets. It is not recommended to
15859 turn on this option, since it confuses ARM and EPI JTAG interface, as
15860 well as the Angel monitor.
15862 @item show rdiheartbeat
15863 @kindex show rdiheartbeat
15864 Show the setting of RDI heartbeat packets.
15869 @subsection Renesas M32R/D and M32R/SDI
15872 @kindex target m32r
15873 @item target m32r @var{dev}
15874 Renesas M32R/D ROM monitor.
15876 @kindex target m32rsdi
15877 @item target m32rsdi @var{dev}
15878 Renesas M32R SDI server, connected via parallel port to the board.
15881 The following @value{GDBN} commands are specific to the M32R monitor:
15884 @item set download-path @var{path}
15885 @kindex set download-path
15886 @cindex find downloadable @sc{srec} files (M32R)
15887 Set the default path for finding downloadable @sc{srec} files.
15889 @item show download-path
15890 @kindex show download-path
15891 Show the default path for downloadable @sc{srec} files.
15893 @item set board-address @var{addr}
15894 @kindex set board-address
15895 @cindex M32-EVA target board address
15896 Set the IP address for the M32R-EVA target board.
15898 @item show board-address
15899 @kindex show board-address
15900 Show the current IP address of the target board.
15902 @item set server-address @var{addr}
15903 @kindex set server-address
15904 @cindex download server address (M32R)
15905 Set the IP address for the download server, which is the @value{GDBN}'s
15908 @item show server-address
15909 @kindex show server-address
15910 Display the IP address of the download server.
15912 @item upload @r{[}@var{file}@r{]}
15913 @kindex upload@r{, M32R}
15914 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15915 upload capability. If no @var{file} argument is given, the current
15916 executable file is uploaded.
15918 @item tload @r{[}@var{file}@r{]}
15919 @kindex tload@r{, M32R}
15920 Test the @code{upload} command.
15923 The following commands are available for M32R/SDI:
15928 @cindex reset SDI connection, M32R
15929 This command resets the SDI connection.
15933 This command shows the SDI connection status.
15936 @kindex debug_chaos
15937 @cindex M32R/Chaos debugging
15938 Instructs the remote that M32R/Chaos debugging is to be used.
15940 @item use_debug_dma
15941 @kindex use_debug_dma
15942 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15945 @kindex use_mon_code
15946 Instructs the remote to use the MON_CODE method of accessing memory.
15949 @kindex use_ib_break
15950 Instructs the remote to set breakpoints by IB break.
15952 @item use_dbt_break
15953 @kindex use_dbt_break
15954 Instructs the remote to set breakpoints by DBT.
15960 The Motorola m68k configuration includes ColdFire support, and a
15961 target command for the following ROM monitor.
15965 @kindex target dbug
15966 @item target dbug @var{dev}
15967 dBUG ROM monitor for Motorola ColdFire.
15971 @node MIPS Embedded
15972 @subsection MIPS Embedded
15974 @cindex MIPS boards
15975 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15976 MIPS board attached to a serial line. This is available when
15977 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15980 Use these @value{GDBN} commands to specify the connection to your target board:
15983 @item target mips @var{port}
15984 @kindex target mips @var{port}
15985 To run a program on the board, start up @code{@value{GDBP}} with the
15986 name of your program as the argument. To connect to the board, use the
15987 command @samp{target mips @var{port}}, where @var{port} is the name of
15988 the serial port connected to the board. If the program has not already
15989 been downloaded to the board, you may use the @code{load} command to
15990 download it. You can then use all the usual @value{GDBN} commands.
15992 For example, this sequence connects to the target board through a serial
15993 port, and loads and runs a program called @var{prog} through the
15997 host$ @value{GDBP} @var{prog}
15998 @value{GDBN} is free software and @dots{}
15999 (@value{GDBP}) target mips /dev/ttyb
16000 (@value{GDBP}) load @var{prog}
16004 @item target mips @var{hostname}:@var{portnumber}
16005 On some @value{GDBN} host configurations, you can specify a TCP
16006 connection (for instance, to a serial line managed by a terminal
16007 concentrator) instead of a serial port, using the syntax
16008 @samp{@var{hostname}:@var{portnumber}}.
16010 @item target pmon @var{port}
16011 @kindex target pmon @var{port}
16014 @item target ddb @var{port}
16015 @kindex target ddb @var{port}
16016 NEC's DDB variant of PMON for Vr4300.
16018 @item target lsi @var{port}
16019 @kindex target lsi @var{port}
16020 LSI variant of PMON.
16022 @kindex target r3900
16023 @item target r3900 @var{dev}
16024 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16026 @kindex target array
16027 @item target array @var{dev}
16028 Array Tech LSI33K RAID controller board.
16034 @value{GDBN} also supports these special commands for MIPS targets:
16037 @item set mipsfpu double
16038 @itemx set mipsfpu single
16039 @itemx set mipsfpu none
16040 @itemx set mipsfpu auto
16041 @itemx show mipsfpu
16042 @kindex set mipsfpu
16043 @kindex show mipsfpu
16044 @cindex MIPS remote floating point
16045 @cindex floating point, MIPS remote
16046 If your target board does not support the MIPS floating point
16047 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16048 need this, you may wish to put the command in your @value{GDBN} init
16049 file). This tells @value{GDBN} how to find the return value of
16050 functions which return floating point values. It also allows
16051 @value{GDBN} to avoid saving the floating point registers when calling
16052 functions on the board. If you are using a floating point coprocessor
16053 with only single precision floating point support, as on the @sc{r4650}
16054 processor, use the command @samp{set mipsfpu single}. The default
16055 double precision floating point coprocessor may be selected using
16056 @samp{set mipsfpu double}.
16058 In previous versions the only choices were double precision or no
16059 floating point, so @samp{set mipsfpu on} will select double precision
16060 and @samp{set mipsfpu off} will select no floating point.
16062 As usual, you can inquire about the @code{mipsfpu} variable with
16063 @samp{show mipsfpu}.
16065 @item set timeout @var{seconds}
16066 @itemx set retransmit-timeout @var{seconds}
16067 @itemx show timeout
16068 @itemx show retransmit-timeout
16069 @cindex @code{timeout}, MIPS protocol
16070 @cindex @code{retransmit-timeout}, MIPS protocol
16071 @kindex set timeout
16072 @kindex show timeout
16073 @kindex set retransmit-timeout
16074 @kindex show retransmit-timeout
16075 You can control the timeout used while waiting for a packet, in the MIPS
16076 remote protocol, with the @code{set timeout @var{seconds}} command. The
16077 default is 5 seconds. Similarly, you can control the timeout used while
16078 waiting for an acknowledgment of a packet with the @code{set
16079 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16080 You can inspect both values with @code{show timeout} and @code{show
16081 retransmit-timeout}. (These commands are @emph{only} available when
16082 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16084 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16085 is waiting for your program to stop. In that case, @value{GDBN} waits
16086 forever because it has no way of knowing how long the program is going
16087 to run before stopping.
16089 @item set syn-garbage-limit @var{num}
16090 @kindex set syn-garbage-limit@r{, MIPS remote}
16091 @cindex synchronize with remote MIPS target
16092 Limit the maximum number of characters @value{GDBN} should ignore when
16093 it tries to synchronize with the remote target. The default is 10
16094 characters. Setting the limit to -1 means there's no limit.
16096 @item show syn-garbage-limit
16097 @kindex show syn-garbage-limit@r{, MIPS remote}
16098 Show the current limit on the number of characters to ignore when
16099 trying to synchronize with the remote system.
16101 @item set monitor-prompt @var{prompt}
16102 @kindex set monitor-prompt@r{, MIPS remote}
16103 @cindex remote monitor prompt
16104 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16105 remote monitor. The default depends on the target:
16115 @item show monitor-prompt
16116 @kindex show monitor-prompt@r{, MIPS remote}
16117 Show the current strings @value{GDBN} expects as the prompt from the
16120 @item set monitor-warnings
16121 @kindex set monitor-warnings@r{, MIPS remote}
16122 Enable or disable monitor warnings about hardware breakpoints. This
16123 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16124 display warning messages whose codes are returned by the @code{lsi}
16125 PMON monitor for breakpoint commands.
16127 @item show monitor-warnings
16128 @kindex show monitor-warnings@r{, MIPS remote}
16129 Show the current setting of printing monitor warnings.
16131 @item pmon @var{command}
16132 @kindex pmon@r{, MIPS remote}
16133 @cindex send PMON command
16134 This command allows sending an arbitrary @var{command} string to the
16135 monitor. The monitor must be in debug mode for this to work.
16138 @node OpenRISC 1000
16139 @subsection OpenRISC 1000
16140 @cindex OpenRISC 1000
16142 @cindex or1k boards
16143 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16144 about platform and commands.
16148 @kindex target jtag
16149 @item target jtag jtag://@var{host}:@var{port}
16151 Connects to remote JTAG server.
16152 JTAG remote server can be either an or1ksim or JTAG server,
16153 connected via parallel port to the board.
16155 Example: @code{target jtag jtag://localhost:9999}
16158 @item or1ksim @var{command}
16159 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16160 Simulator, proprietary commands can be executed.
16162 @kindex info or1k spr
16163 @item info or1k spr
16164 Displays spr groups.
16166 @item info or1k spr @var{group}
16167 @itemx info or1k spr @var{groupno}
16168 Displays register names in selected group.
16170 @item info or1k spr @var{group} @var{register}
16171 @itemx info or1k spr @var{register}
16172 @itemx info or1k spr @var{groupno} @var{registerno}
16173 @itemx info or1k spr @var{registerno}
16174 Shows information about specified spr register.
16177 @item spr @var{group} @var{register} @var{value}
16178 @itemx spr @var{register @var{value}}
16179 @itemx spr @var{groupno} @var{registerno @var{value}}
16180 @itemx spr @var{registerno @var{value}}
16181 Writes @var{value} to specified spr register.
16184 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16185 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16186 program execution and is thus much faster. Hardware breakpoints/watchpoint
16187 triggers can be set using:
16190 Load effective address/data
16192 Store effective address/data
16194 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16199 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16200 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16202 @code{htrace} commands:
16203 @cindex OpenRISC 1000 htrace
16206 @item hwatch @var{conditional}
16207 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16208 or Data. For example:
16210 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16212 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16216 Display information about current HW trace configuration.
16218 @item htrace trigger @var{conditional}
16219 Set starting criteria for HW trace.
16221 @item htrace qualifier @var{conditional}
16222 Set acquisition qualifier for HW trace.
16224 @item htrace stop @var{conditional}
16225 Set HW trace stopping criteria.
16227 @item htrace record [@var{data}]*
16228 Selects the data to be recorded, when qualifier is met and HW trace was
16231 @item htrace enable
16232 @itemx htrace disable
16233 Enables/disables the HW trace.
16235 @item htrace rewind [@var{filename}]
16236 Clears currently recorded trace data.
16238 If filename is specified, new trace file is made and any newly collected data
16239 will be written there.
16241 @item htrace print [@var{start} [@var{len}]]
16242 Prints trace buffer, using current record configuration.
16244 @item htrace mode continuous
16245 Set continuous trace mode.
16247 @item htrace mode suspend
16248 Set suspend trace mode.
16252 @node PowerPC Embedded
16253 @subsection PowerPC Embedded
16255 @value{GDBN} provides the following PowerPC-specific commands:
16258 @kindex set powerpc
16259 @item set powerpc soft-float
16260 @itemx show powerpc soft-float
16261 Force @value{GDBN} to use (or not use) a software floating point calling
16262 convention. By default, @value{GDBN} selects the calling convention based
16263 on the selected architecture and the provided executable file.
16265 @item set powerpc vector-abi
16266 @itemx show powerpc vector-abi
16267 Force @value{GDBN} to use the specified calling convention for vector
16268 arguments and return values. The valid options are @samp{auto};
16269 @samp{generic}, to avoid vector registers even if they are present;
16270 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16271 registers. By default, @value{GDBN} selects the calling convention
16272 based on the selected architecture and the provided executable file.
16274 @kindex target dink32
16275 @item target dink32 @var{dev}
16276 DINK32 ROM monitor.
16278 @kindex target ppcbug
16279 @item target ppcbug @var{dev}
16280 @kindex target ppcbug1
16281 @item target ppcbug1 @var{dev}
16282 PPCBUG ROM monitor for PowerPC.
16285 @item target sds @var{dev}
16286 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16289 @cindex SDS protocol
16290 The following commands specific to the SDS protocol are supported
16294 @item set sdstimeout @var{nsec}
16295 @kindex set sdstimeout
16296 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16297 default is 2 seconds.
16299 @item show sdstimeout
16300 @kindex show sdstimeout
16301 Show the current value of the SDS timeout.
16303 @item sds @var{command}
16304 @kindex sds@r{, a command}
16305 Send the specified @var{command} string to the SDS monitor.
16310 @subsection HP PA Embedded
16314 @kindex target op50n
16315 @item target op50n @var{dev}
16316 OP50N monitor, running on an OKI HPPA board.
16318 @kindex target w89k
16319 @item target w89k @var{dev}
16320 W89K monitor, running on a Winbond HPPA board.
16325 @subsection Tsqware Sparclet
16329 @value{GDBN} enables developers to debug tasks running on
16330 Sparclet targets from a Unix host.
16331 @value{GDBN} uses code that runs on
16332 both the Unix host and on the Sparclet target. The program
16333 @code{@value{GDBP}} is installed and executed on the Unix host.
16336 @item remotetimeout @var{args}
16337 @kindex remotetimeout
16338 @value{GDBN} supports the option @code{remotetimeout}.
16339 This option is set by the user, and @var{args} represents the number of
16340 seconds @value{GDBN} waits for responses.
16343 @cindex compiling, on Sparclet
16344 When compiling for debugging, include the options @samp{-g} to get debug
16345 information and @samp{-Ttext} to relocate the program to where you wish to
16346 load it on the target. You may also want to add the options @samp{-n} or
16347 @samp{-N} in order to reduce the size of the sections. Example:
16350 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16353 You can use @code{objdump} to verify that the addresses are what you intended:
16356 sparclet-aout-objdump --headers --syms prog
16359 @cindex running, on Sparclet
16361 your Unix execution search path to find @value{GDBN}, you are ready to
16362 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16363 (or @code{sparclet-aout-gdb}, depending on your installation).
16365 @value{GDBN} comes up showing the prompt:
16372 * Sparclet File:: Setting the file to debug
16373 * Sparclet Connection:: Connecting to Sparclet
16374 * Sparclet Download:: Sparclet download
16375 * Sparclet Execution:: Running and debugging
16378 @node Sparclet File
16379 @subsubsection Setting File to Debug
16381 The @value{GDBN} command @code{file} lets you choose with program to debug.
16384 (gdbslet) file prog
16388 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16389 @value{GDBN} locates
16390 the file by searching the directories listed in the command search
16392 If the file was compiled with debug information (option @samp{-g}), source
16393 files will be searched as well.
16394 @value{GDBN} locates
16395 the source files by searching the directories listed in the directory search
16396 path (@pxref{Environment, ,Your Program's Environment}).
16398 to find a file, it displays a message such as:
16401 prog: No such file or directory.
16404 When this happens, add the appropriate directories to the search paths with
16405 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16406 @code{target} command again.
16408 @node Sparclet Connection
16409 @subsubsection Connecting to Sparclet
16411 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16412 To connect to a target on serial port ``@code{ttya}'', type:
16415 (gdbslet) target sparclet /dev/ttya
16416 Remote target sparclet connected to /dev/ttya
16417 main () at ../prog.c:3
16421 @value{GDBN} displays messages like these:
16427 @node Sparclet Download
16428 @subsubsection Sparclet Download
16430 @cindex download to Sparclet
16431 Once connected to the Sparclet target,
16432 you can use the @value{GDBN}
16433 @code{load} command to download the file from the host to the target.
16434 The file name and load offset should be given as arguments to the @code{load}
16436 Since the file format is aout, the program must be loaded to the starting
16437 address. You can use @code{objdump} to find out what this value is. The load
16438 offset is an offset which is added to the VMA (virtual memory address)
16439 of each of the file's sections.
16440 For instance, if the program
16441 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16442 and bss at 0x12010170, in @value{GDBN}, type:
16445 (gdbslet) load prog 0x12010000
16446 Loading section .text, size 0xdb0 vma 0x12010000
16449 If the code is loaded at a different address then what the program was linked
16450 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16451 to tell @value{GDBN} where to map the symbol table.
16453 @node Sparclet Execution
16454 @subsubsection Running and Debugging
16456 @cindex running and debugging Sparclet programs
16457 You can now begin debugging the task using @value{GDBN}'s execution control
16458 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16459 manual for the list of commands.
16463 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16465 Starting program: prog
16466 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16467 3 char *symarg = 0;
16469 4 char *execarg = "hello!";
16474 @subsection Fujitsu Sparclite
16478 @kindex target sparclite
16479 @item target sparclite @var{dev}
16480 Fujitsu sparclite boards, used only for the purpose of loading.
16481 You must use an additional command to debug the program.
16482 For example: target remote @var{dev} using @value{GDBN} standard
16488 @subsection Zilog Z8000
16491 @cindex simulator, Z8000
16492 @cindex Zilog Z8000 simulator
16494 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16497 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16498 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16499 segmented variant). The simulator recognizes which architecture is
16500 appropriate by inspecting the object code.
16503 @item target sim @var{args}
16505 @kindex target sim@r{, with Z8000}
16506 Debug programs on a simulated CPU. If the simulator supports setup
16507 options, specify them via @var{args}.
16511 After specifying this target, you can debug programs for the simulated
16512 CPU in the same style as programs for your host computer; use the
16513 @code{file} command to load a new program image, the @code{run} command
16514 to run your program, and so on.
16516 As well as making available all the usual machine registers
16517 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16518 additional items of information as specially named registers:
16523 Counts clock-ticks in the simulator.
16526 Counts instructions run in the simulator.
16529 Execution time in 60ths of a second.
16533 You can refer to these values in @value{GDBN} expressions with the usual
16534 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16535 conditional breakpoint that suspends only after at least 5000
16536 simulated clock ticks.
16539 @subsection Atmel AVR
16542 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16543 following AVR-specific commands:
16546 @item info io_registers
16547 @kindex info io_registers@r{, AVR}
16548 @cindex I/O registers (Atmel AVR)
16549 This command displays information about the AVR I/O registers. For
16550 each register, @value{GDBN} prints its number and value.
16557 When configured for debugging CRIS, @value{GDBN} provides the
16558 following CRIS-specific commands:
16561 @item set cris-version @var{ver}
16562 @cindex CRIS version
16563 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16564 The CRIS version affects register names and sizes. This command is useful in
16565 case autodetection of the CRIS version fails.
16567 @item show cris-version
16568 Show the current CRIS version.
16570 @item set cris-dwarf2-cfi
16571 @cindex DWARF-2 CFI and CRIS
16572 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16573 Change to @samp{off} when using @code{gcc-cris} whose version is below
16576 @item show cris-dwarf2-cfi
16577 Show the current state of using DWARF-2 CFI.
16579 @item set cris-mode @var{mode}
16581 Set the current CRIS mode to @var{mode}. It should only be changed when
16582 debugging in guru mode, in which case it should be set to
16583 @samp{guru} (the default is @samp{normal}).
16585 @item show cris-mode
16586 Show the current CRIS mode.
16590 @subsection Renesas Super-H
16593 For the Renesas Super-H processor, @value{GDBN} provides these
16598 @kindex regs@r{, Super-H}
16599 Show the values of all Super-H registers.
16601 @item set sh calling-convention @var{convention}
16602 @kindex set sh calling-convention
16603 Set the calling-convention used when calling functions from @value{GDBN}.
16604 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16605 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16606 convention. If the DWARF-2 information of the called function specifies
16607 that the function follows the Renesas calling convention, the function
16608 is called using the Renesas calling convention. If the calling convention
16609 is set to @samp{renesas}, the Renesas calling convention is always used,
16610 regardless of the DWARF-2 information. This can be used to override the
16611 default of @samp{gcc} if debug information is missing, or the compiler
16612 does not emit the DWARF-2 calling convention entry for a function.
16614 @item show sh calling-convention
16615 @kindex show sh calling-convention
16616 Show the current calling convention setting.
16621 @node Architectures
16622 @section Architectures
16624 This section describes characteristics of architectures that affect
16625 all uses of @value{GDBN} with the architecture, both native and cross.
16632 * HPPA:: HP PA architecture
16633 * SPU:: Cell Broadband Engine SPU architecture
16638 @subsection x86 Architecture-specific Issues
16641 @item set struct-convention @var{mode}
16642 @kindex set struct-convention
16643 @cindex struct return convention
16644 @cindex struct/union returned in registers
16645 Set the convention used by the inferior to return @code{struct}s and
16646 @code{union}s from functions to @var{mode}. Possible values of
16647 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16648 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16649 are returned on the stack, while @code{"reg"} means that a
16650 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16651 be returned in a register.
16653 @item show struct-convention
16654 @kindex show struct-convention
16655 Show the current setting of the convention to return @code{struct}s
16664 @kindex set rstack_high_address
16665 @cindex AMD 29K register stack
16666 @cindex register stack, AMD29K
16667 @item set rstack_high_address @var{address}
16668 On AMD 29000 family processors, registers are saved in a separate
16669 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16670 extent of this stack. Normally, @value{GDBN} just assumes that the
16671 stack is ``large enough''. This may result in @value{GDBN} referencing
16672 memory locations that do not exist. If necessary, you can get around
16673 this problem by specifying the ending address of the register stack with
16674 the @code{set rstack_high_address} command. The argument should be an
16675 address, which you probably want to precede with @samp{0x} to specify in
16678 @kindex show rstack_high_address
16679 @item show rstack_high_address
16680 Display the current limit of the register stack, on AMD 29000 family
16688 See the following section.
16693 @cindex stack on Alpha
16694 @cindex stack on MIPS
16695 @cindex Alpha stack
16697 Alpha- and MIPS-based computers use an unusual stack frame, which
16698 sometimes requires @value{GDBN} to search backward in the object code to
16699 find the beginning of a function.
16701 @cindex response time, MIPS debugging
16702 To improve response time (especially for embedded applications, where
16703 @value{GDBN} may be restricted to a slow serial line for this search)
16704 you may want to limit the size of this search, using one of these
16708 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16709 @item set heuristic-fence-post @var{limit}
16710 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16711 search for the beginning of a function. A value of @var{0} (the
16712 default) means there is no limit. However, except for @var{0}, the
16713 larger the limit the more bytes @code{heuristic-fence-post} must search
16714 and therefore the longer it takes to run. You should only need to use
16715 this command when debugging a stripped executable.
16717 @item show heuristic-fence-post
16718 Display the current limit.
16722 These commands are available @emph{only} when @value{GDBN} is configured
16723 for debugging programs on Alpha or MIPS processors.
16725 Several MIPS-specific commands are available when debugging MIPS
16729 @item set mips abi @var{arg}
16730 @kindex set mips abi
16731 @cindex set ABI for MIPS
16732 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16733 values of @var{arg} are:
16737 The default ABI associated with the current binary (this is the
16748 @item show mips abi
16749 @kindex show mips abi
16750 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16753 @itemx show mipsfpu
16754 @xref{MIPS Embedded, set mipsfpu}.
16756 @item set mips mask-address @var{arg}
16757 @kindex set mips mask-address
16758 @cindex MIPS addresses, masking
16759 This command determines whether the most-significant 32 bits of 64-bit
16760 MIPS addresses are masked off. The argument @var{arg} can be
16761 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16762 setting, which lets @value{GDBN} determine the correct value.
16764 @item show mips mask-address
16765 @kindex show mips mask-address
16766 Show whether the upper 32 bits of MIPS addresses are masked off or
16769 @item set remote-mips64-transfers-32bit-regs
16770 @kindex set remote-mips64-transfers-32bit-regs
16771 This command controls compatibility with 64-bit MIPS targets that
16772 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16773 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16774 and 64 bits for other registers, set this option to @samp{on}.
16776 @item show remote-mips64-transfers-32bit-regs
16777 @kindex show remote-mips64-transfers-32bit-regs
16778 Show the current setting of compatibility with older MIPS 64 targets.
16780 @item set debug mips
16781 @kindex set debug mips
16782 This command turns on and off debugging messages for the MIPS-specific
16783 target code in @value{GDBN}.
16785 @item show debug mips
16786 @kindex show debug mips
16787 Show the current setting of MIPS debugging messages.
16793 @cindex HPPA support
16795 When @value{GDBN} is debugging the HP PA architecture, it provides the
16796 following special commands:
16799 @item set debug hppa
16800 @kindex set debug hppa
16801 This command determines whether HPPA architecture-specific debugging
16802 messages are to be displayed.
16804 @item show debug hppa
16805 Show whether HPPA debugging messages are displayed.
16807 @item maint print unwind @var{address}
16808 @kindex maint print unwind@r{, HPPA}
16809 This command displays the contents of the unwind table entry at the
16810 given @var{address}.
16816 @subsection Cell Broadband Engine SPU architecture
16817 @cindex Cell Broadband Engine
16820 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16821 it provides the following special commands:
16824 @item info spu event
16826 Display SPU event facility status. Shows current event mask
16827 and pending event status.
16829 @item info spu signal
16830 Display SPU signal notification facility status. Shows pending
16831 signal-control word and signal notification mode of both signal
16832 notification channels.
16834 @item info spu mailbox
16835 Display SPU mailbox facility status. Shows all pending entries,
16836 in order of processing, in each of the SPU Write Outbound,
16837 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16840 Display MFC DMA status. Shows all pending commands in the MFC
16841 DMA queue. For each entry, opcode, tag, class IDs, effective
16842 and local store addresses and transfer size are shown.
16844 @item info spu proxydma
16845 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16846 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16847 and local store addresses and transfer size are shown.
16852 @subsection PowerPC
16853 @cindex PowerPC architecture
16855 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16856 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16857 numbers stored in the floating point registers. These values must be stored
16858 in two consecutive registers, always starting at an even register like
16859 @code{f0} or @code{f2}.
16861 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16862 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16863 @code{f2} and @code{f3} for @code{$dl1} and so on.
16865 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
16866 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
16869 @node Controlling GDB
16870 @chapter Controlling @value{GDBN}
16872 You can alter the way @value{GDBN} interacts with you by using the
16873 @code{set} command. For commands controlling how @value{GDBN} displays
16874 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16879 * Editing:: Command editing
16880 * Command History:: Command history
16881 * Screen Size:: Screen size
16882 * Numbers:: Numbers
16883 * ABI:: Configuring the current ABI
16884 * Messages/Warnings:: Optional warnings and messages
16885 * Debugging Output:: Optional messages about internal happenings
16893 @value{GDBN} indicates its readiness to read a command by printing a string
16894 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16895 can change the prompt string with the @code{set prompt} command. For
16896 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16897 the prompt in one of the @value{GDBN} sessions so that you can always tell
16898 which one you are talking to.
16900 @emph{Note:} @code{set prompt} does not add a space for you after the
16901 prompt you set. This allows you to set a prompt which ends in a space
16902 or a prompt that does not.
16906 @item set prompt @var{newprompt}
16907 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16909 @kindex show prompt
16911 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16915 @section Command Editing
16917 @cindex command line editing
16919 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16920 @sc{gnu} library provides consistent behavior for programs which provide a
16921 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16922 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16923 substitution, and a storage and recall of command history across
16924 debugging sessions.
16926 You may control the behavior of command line editing in @value{GDBN} with the
16927 command @code{set}.
16930 @kindex set editing
16933 @itemx set editing on
16934 Enable command line editing (enabled by default).
16936 @item set editing off
16937 Disable command line editing.
16939 @kindex show editing
16941 Show whether command line editing is enabled.
16944 @xref{Command Line Editing}, for more details about the Readline
16945 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16946 encouraged to read that chapter.
16948 @node Command History
16949 @section Command History
16950 @cindex command history
16952 @value{GDBN} can keep track of the commands you type during your
16953 debugging sessions, so that you can be certain of precisely what
16954 happened. Use these commands to manage the @value{GDBN} command
16957 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16958 package, to provide the history facility. @xref{Using History
16959 Interactively}, for the detailed description of the History library.
16961 To issue a command to @value{GDBN} without affecting certain aspects of
16962 the state which is seen by users, prefix it with @samp{server }
16963 (@pxref{Server Prefix}). This
16964 means that this command will not affect the command history, nor will it
16965 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16966 pressed on a line by itself.
16968 @cindex @code{server}, command prefix
16969 The server prefix does not affect the recording of values into the value
16970 history; to print a value without recording it into the value history,
16971 use the @code{output} command instead of the @code{print} command.
16973 Here is the description of @value{GDBN} commands related to command
16977 @cindex history substitution
16978 @cindex history file
16979 @kindex set history filename
16980 @cindex @env{GDBHISTFILE}, environment variable
16981 @item set history filename @var{fname}
16982 Set the name of the @value{GDBN} command history file to @var{fname}.
16983 This is the file where @value{GDBN} reads an initial command history
16984 list, and where it writes the command history from this session when it
16985 exits. You can access this list through history expansion or through
16986 the history command editing characters listed below. This file defaults
16987 to the value of the environment variable @code{GDBHISTFILE}, or to
16988 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16991 @cindex save command history
16992 @kindex set history save
16993 @item set history save
16994 @itemx set history save on
16995 Record command history in a file, whose name may be specified with the
16996 @code{set history filename} command. By default, this option is disabled.
16998 @item set history save off
16999 Stop recording command history in a file.
17001 @cindex history size
17002 @kindex set history size
17003 @cindex @env{HISTSIZE}, environment variable
17004 @item set history size @var{size}
17005 Set the number of commands which @value{GDBN} keeps in its history list.
17006 This defaults to the value of the environment variable
17007 @code{HISTSIZE}, or to 256 if this variable is not set.
17010 History expansion assigns special meaning to the character @kbd{!}.
17011 @xref{Event Designators}, for more details.
17013 @cindex history expansion, turn on/off
17014 Since @kbd{!} is also the logical not operator in C, history expansion
17015 is off by default. If you decide to enable history expansion with the
17016 @code{set history expansion on} command, you may sometimes need to
17017 follow @kbd{!} (when it is used as logical not, in an expression) with
17018 a space or a tab to prevent it from being expanded. The readline
17019 history facilities do not attempt substitution on the strings
17020 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17022 The commands to control history expansion are:
17025 @item set history expansion on
17026 @itemx set history expansion
17027 @kindex set history expansion
17028 Enable history expansion. History expansion is off by default.
17030 @item set history expansion off
17031 Disable history expansion.
17034 @kindex show history
17036 @itemx show history filename
17037 @itemx show history save
17038 @itemx show history size
17039 @itemx show history expansion
17040 These commands display the state of the @value{GDBN} history parameters.
17041 @code{show history} by itself displays all four states.
17046 @kindex show commands
17047 @cindex show last commands
17048 @cindex display command history
17049 @item show commands
17050 Display the last ten commands in the command history.
17052 @item show commands @var{n}
17053 Print ten commands centered on command number @var{n}.
17055 @item show commands +
17056 Print ten commands just after the commands last printed.
17060 @section Screen Size
17061 @cindex size of screen
17062 @cindex pauses in output
17064 Certain commands to @value{GDBN} may produce large amounts of
17065 information output to the screen. To help you read all of it,
17066 @value{GDBN} pauses and asks you for input at the end of each page of
17067 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17068 to discard the remaining output. Also, the screen width setting
17069 determines when to wrap lines of output. Depending on what is being
17070 printed, @value{GDBN} tries to break the line at a readable place,
17071 rather than simply letting it overflow onto the following line.
17073 Normally @value{GDBN} knows the size of the screen from the terminal
17074 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17075 together with the value of the @code{TERM} environment variable and the
17076 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17077 you can override it with the @code{set height} and @code{set
17084 @kindex show height
17085 @item set height @var{lpp}
17087 @itemx set width @var{cpl}
17089 These @code{set} commands specify a screen height of @var{lpp} lines and
17090 a screen width of @var{cpl} characters. The associated @code{show}
17091 commands display the current settings.
17093 If you specify a height of zero lines, @value{GDBN} does not pause during
17094 output no matter how long the output is. This is useful if output is to a
17095 file or to an editor buffer.
17097 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17098 from wrapping its output.
17100 @item set pagination on
17101 @itemx set pagination off
17102 @kindex set pagination
17103 Turn the output pagination on or off; the default is on. Turning
17104 pagination off is the alternative to @code{set height 0}.
17106 @item show pagination
17107 @kindex show pagination
17108 Show the current pagination mode.
17113 @cindex number representation
17114 @cindex entering numbers
17116 You can always enter numbers in octal, decimal, or hexadecimal in
17117 @value{GDBN} by the usual conventions: octal numbers begin with
17118 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17119 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17120 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17121 10; likewise, the default display for numbers---when no particular
17122 format is specified---is base 10. You can change the default base for
17123 both input and output with the commands described below.
17126 @kindex set input-radix
17127 @item set input-radix @var{base}
17128 Set the default base for numeric input. Supported choices
17129 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17130 specified either unambiguously or using the current input radix; for
17134 set input-radix 012
17135 set input-radix 10.
17136 set input-radix 0xa
17140 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17141 leaves the input radix unchanged, no matter what it was, since
17142 @samp{10}, being without any leading or trailing signs of its base, is
17143 interpreted in the current radix. Thus, if the current radix is 16,
17144 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17147 @kindex set output-radix
17148 @item set output-radix @var{base}
17149 Set the default base for numeric display. Supported choices
17150 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17151 specified either unambiguously or using the current input radix.
17153 @kindex show input-radix
17154 @item show input-radix
17155 Display the current default base for numeric input.
17157 @kindex show output-radix
17158 @item show output-radix
17159 Display the current default base for numeric display.
17161 @item set radix @r{[}@var{base}@r{]}
17165 These commands set and show the default base for both input and output
17166 of numbers. @code{set radix} sets the radix of input and output to
17167 the same base; without an argument, it resets the radix back to its
17168 default value of 10.
17173 @section Configuring the Current ABI
17175 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17176 application automatically. However, sometimes you need to override its
17177 conclusions. Use these commands to manage @value{GDBN}'s view of the
17184 One @value{GDBN} configuration can debug binaries for multiple operating
17185 system targets, either via remote debugging or native emulation.
17186 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17187 but you can override its conclusion using the @code{set osabi} command.
17188 One example where this is useful is in debugging of binaries which use
17189 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17190 not have the same identifying marks that the standard C library for your
17195 Show the OS ABI currently in use.
17198 With no argument, show the list of registered available OS ABI's.
17200 @item set osabi @var{abi}
17201 Set the current OS ABI to @var{abi}.
17204 @cindex float promotion
17206 Generally, the way that an argument of type @code{float} is passed to a
17207 function depends on whether the function is prototyped. For a prototyped
17208 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17209 according to the architecture's convention for @code{float}. For unprototyped
17210 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17211 @code{double} and then passed.
17213 Unfortunately, some forms of debug information do not reliably indicate whether
17214 a function is prototyped. If @value{GDBN} calls a function that is not marked
17215 as prototyped, it consults @kbd{set coerce-float-to-double}.
17218 @kindex set coerce-float-to-double
17219 @item set coerce-float-to-double
17220 @itemx set coerce-float-to-double on
17221 Arguments of type @code{float} will be promoted to @code{double} when passed
17222 to an unprototyped function. This is the default setting.
17224 @item set coerce-float-to-double off
17225 Arguments of type @code{float} will be passed directly to unprototyped
17228 @kindex show coerce-float-to-double
17229 @item show coerce-float-to-double
17230 Show the current setting of promoting @code{float} to @code{double}.
17234 @kindex show cp-abi
17235 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17236 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17237 used to build your application. @value{GDBN} only fully supports
17238 programs with a single C@t{++} ABI; if your program contains code using
17239 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17240 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17241 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17242 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17243 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17244 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17249 Show the C@t{++} ABI currently in use.
17252 With no argument, show the list of supported C@t{++} ABI's.
17254 @item set cp-abi @var{abi}
17255 @itemx set cp-abi auto
17256 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17259 @node Messages/Warnings
17260 @section Optional Warnings and Messages
17262 @cindex verbose operation
17263 @cindex optional warnings
17264 By default, @value{GDBN} is silent about its inner workings. If you are
17265 running on a slow machine, you may want to use the @code{set verbose}
17266 command. This makes @value{GDBN} tell you when it does a lengthy
17267 internal operation, so you will not think it has crashed.
17269 Currently, the messages controlled by @code{set verbose} are those
17270 which announce that the symbol table for a source file is being read;
17271 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17274 @kindex set verbose
17275 @item set verbose on
17276 Enables @value{GDBN} output of certain informational messages.
17278 @item set verbose off
17279 Disables @value{GDBN} output of certain informational messages.
17281 @kindex show verbose
17283 Displays whether @code{set verbose} is on or off.
17286 By default, if @value{GDBN} encounters bugs in the symbol table of an
17287 object file, it is silent; but if you are debugging a compiler, you may
17288 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17293 @kindex set complaints
17294 @item set complaints @var{limit}
17295 Permits @value{GDBN} to output @var{limit} complaints about each type of
17296 unusual symbols before becoming silent about the problem. Set
17297 @var{limit} to zero to suppress all complaints; set it to a large number
17298 to prevent complaints from being suppressed.
17300 @kindex show complaints
17301 @item show complaints
17302 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17306 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17307 lot of stupid questions to confirm certain commands. For example, if
17308 you try to run a program which is already running:
17312 The program being debugged has been started already.
17313 Start it from the beginning? (y or n)
17316 If you are willing to unflinchingly face the consequences of your own
17317 commands, you can disable this ``feature'':
17321 @kindex set confirm
17323 @cindex confirmation
17324 @cindex stupid questions
17325 @item set confirm off
17326 Disables confirmation requests.
17328 @item set confirm on
17329 Enables confirmation requests (the default).
17331 @kindex show confirm
17333 Displays state of confirmation requests.
17337 @cindex command tracing
17338 If you need to debug user-defined commands or sourced files you may find it
17339 useful to enable @dfn{command tracing}. In this mode each command will be
17340 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17341 quantity denoting the call depth of each command.
17344 @kindex set trace-commands
17345 @cindex command scripts, debugging
17346 @item set trace-commands on
17347 Enable command tracing.
17348 @item set trace-commands off
17349 Disable command tracing.
17350 @item show trace-commands
17351 Display the current state of command tracing.
17354 @node Debugging Output
17355 @section Optional Messages about Internal Happenings
17356 @cindex optional debugging messages
17358 @value{GDBN} has commands that enable optional debugging messages from
17359 various @value{GDBN} subsystems; normally these commands are of
17360 interest to @value{GDBN} maintainers, or when reporting a bug. This
17361 section documents those commands.
17364 @kindex set exec-done-display
17365 @item set exec-done-display
17366 Turns on or off the notification of asynchronous commands'
17367 completion. When on, @value{GDBN} will print a message when an
17368 asynchronous command finishes its execution. The default is off.
17369 @kindex show exec-done-display
17370 @item show exec-done-display
17371 Displays the current setting of asynchronous command completion
17374 @cindex gdbarch debugging info
17375 @cindex architecture debugging info
17376 @item set debug arch
17377 Turns on or off display of gdbarch debugging info. The default is off
17379 @item show debug arch
17380 Displays the current state of displaying gdbarch debugging info.
17381 @item set debug aix-thread
17382 @cindex AIX threads
17383 Display debugging messages about inner workings of the AIX thread
17385 @item show debug aix-thread
17386 Show the current state of AIX thread debugging info display.
17387 @item set debug dwarf2-die
17388 @cindex DWARF2 DIEs
17389 Dump DWARF2 DIEs after they are read in.
17390 The value is the number of nesting levels to print.
17391 A value of zero turns off the display.
17392 @item show debug dwarf2-die
17393 Show the current state of DWARF2 DIE debugging.
17394 @item set debug displaced
17395 @cindex displaced stepping debugging info
17396 Turns on or off display of @value{GDBN} debugging info for the
17397 displaced stepping support. The default is off.
17398 @item show debug displaced
17399 Displays the current state of displaying @value{GDBN} debugging info
17400 related to displaced stepping.
17401 @item set debug event
17402 @cindex event debugging info
17403 Turns on or off display of @value{GDBN} event debugging info. The
17405 @item show debug event
17406 Displays the current state of displaying @value{GDBN} event debugging
17408 @item set debug expression
17409 @cindex expression debugging info
17410 Turns on or off display of debugging info about @value{GDBN}
17411 expression parsing. The default is off.
17412 @item show debug expression
17413 Displays the current state of displaying debugging info about
17414 @value{GDBN} expression parsing.
17415 @item set debug frame
17416 @cindex frame debugging info
17417 Turns on or off display of @value{GDBN} frame debugging info. The
17419 @item show debug frame
17420 Displays the current state of displaying @value{GDBN} frame debugging
17422 @item set debug infrun
17423 @cindex inferior debugging info
17424 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17425 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17426 for implementing operations such as single-stepping the inferior.
17427 @item show debug infrun
17428 Displays the current state of @value{GDBN} inferior debugging.
17429 @item set debug lin-lwp
17430 @cindex @sc{gnu}/Linux LWP debug messages
17431 @cindex Linux lightweight processes
17432 Turns on or off debugging messages from the Linux LWP debug support.
17433 @item show debug lin-lwp
17434 Show the current state of Linux LWP debugging messages.
17435 @item set debug lin-lwp-async
17436 @cindex @sc{gnu}/Linux LWP async debug messages
17437 @cindex Linux lightweight processes
17438 Turns on or off debugging messages from the Linux LWP async debug support.
17439 @item show debug lin-lwp-async
17440 Show the current state of Linux LWP async debugging messages.
17441 @item set debug observer
17442 @cindex observer debugging info
17443 Turns on or off display of @value{GDBN} observer debugging. This
17444 includes info such as the notification of observable events.
17445 @item show debug observer
17446 Displays the current state of observer debugging.
17447 @item set debug overload
17448 @cindex C@t{++} overload debugging info
17449 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17450 info. This includes info such as ranking of functions, etc. The default
17452 @item show debug overload
17453 Displays the current state of displaying @value{GDBN} C@t{++} overload
17455 @cindex packets, reporting on stdout
17456 @cindex serial connections, debugging
17457 @cindex debug remote protocol
17458 @cindex remote protocol debugging
17459 @cindex display remote packets
17460 @item set debug remote
17461 Turns on or off display of reports on all packets sent back and forth across
17462 the serial line to the remote machine. The info is printed on the
17463 @value{GDBN} standard output stream. The default is off.
17464 @item show debug remote
17465 Displays the state of display of remote packets.
17466 @item set debug serial
17467 Turns on or off display of @value{GDBN} serial debugging info. The
17469 @item show debug serial
17470 Displays the current state of displaying @value{GDBN} serial debugging
17472 @item set debug solib-frv
17473 @cindex FR-V shared-library debugging
17474 Turns on or off debugging messages for FR-V shared-library code.
17475 @item show debug solib-frv
17476 Display the current state of FR-V shared-library code debugging
17478 @item set debug target
17479 @cindex target debugging info
17480 Turns on or off display of @value{GDBN} target debugging info. This info
17481 includes what is going on at the target level of GDB, as it happens. The
17482 default is 0. Set it to 1 to track events, and to 2 to also track the
17483 value of large memory transfers. Changes to this flag do not take effect
17484 until the next time you connect to a target or use the @code{run} command.
17485 @item show debug target
17486 Displays the current state of displaying @value{GDBN} target debugging
17488 @item set debug timestamp
17489 @cindex timestampping debugging info
17490 Turns on or off display of timestamps with @value{GDBN} debugging info.
17491 When enabled, seconds and microseconds are displayed before each debugging
17493 @item show debug timestamp
17494 Displays the current state of displaying timestamps with @value{GDBN}
17496 @item set debugvarobj
17497 @cindex variable object debugging info
17498 Turns on or off display of @value{GDBN} variable object debugging
17499 info. The default is off.
17500 @item show debugvarobj
17501 Displays the current state of displaying @value{GDBN} variable object
17503 @item set debug xml
17504 @cindex XML parser debugging
17505 Turns on or off debugging messages for built-in XML parsers.
17506 @item show debug xml
17507 Displays the current state of XML debugging messages.
17510 @node Extending GDB
17511 @chapter Extending @value{GDBN}
17512 @cindex extending GDB
17514 @value{GDBN} provides two mechanisms for extension. The first is based
17515 on composition of @value{GDBN} commands, and the second is based on the
17516 Python scripting language.
17519 * Sequences:: Canned Sequences of Commands
17520 * Python:: Scripting @value{GDBN} using Python
17524 @section Canned Sequences of Commands
17526 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17527 Command Lists}), @value{GDBN} provides two ways to store sequences of
17528 commands for execution as a unit: user-defined commands and command
17532 * Define:: How to define your own commands
17533 * Hooks:: Hooks for user-defined commands
17534 * Command Files:: How to write scripts of commands to be stored in a file
17535 * Output:: Commands for controlled output
17539 @subsection User-defined Commands
17541 @cindex user-defined command
17542 @cindex arguments, to user-defined commands
17543 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17544 which you assign a new name as a command. This is done with the
17545 @code{define} command. User commands may accept up to 10 arguments
17546 separated by whitespace. Arguments are accessed within the user command
17547 via @code{$arg0@dots{}$arg9}. A trivial example:
17551 print $arg0 + $arg1 + $arg2
17556 To execute the command use:
17563 This defines the command @code{adder}, which prints the sum of
17564 its three arguments. Note the arguments are text substitutions, so they may
17565 reference variables, use complex expressions, or even perform inferior
17568 @cindex argument count in user-defined commands
17569 @cindex how many arguments (user-defined commands)
17570 In addition, @code{$argc} may be used to find out how many arguments have
17571 been passed. This expands to a number in the range 0@dots{}10.
17576 print $arg0 + $arg1
17579 print $arg0 + $arg1 + $arg2
17587 @item define @var{commandname}
17588 Define a command named @var{commandname}. If there is already a command
17589 by that name, you are asked to confirm that you want to redefine it.
17591 The definition of the command is made up of other @value{GDBN} command lines,
17592 which are given following the @code{define} command. The end of these
17593 commands is marked by a line containing @code{end}.
17596 @kindex end@r{ (user-defined commands)}
17597 @item document @var{commandname}
17598 Document the user-defined command @var{commandname}, so that it can be
17599 accessed by @code{help}. The command @var{commandname} must already be
17600 defined. This command reads lines of documentation just as @code{define}
17601 reads the lines of the command definition, ending with @code{end}.
17602 After the @code{document} command is finished, @code{help} on command
17603 @var{commandname} displays the documentation you have written.
17605 You may use the @code{document} command again to change the
17606 documentation of a command. Redefining the command with @code{define}
17607 does not change the documentation.
17609 @kindex dont-repeat
17610 @cindex don't repeat command
17612 Used inside a user-defined command, this tells @value{GDBN} that this
17613 command should not be repeated when the user hits @key{RET}
17614 (@pxref{Command Syntax, repeat last command}).
17616 @kindex help user-defined
17617 @item help user-defined
17618 List all user-defined commands, with the first line of the documentation
17623 @itemx show user @var{commandname}
17624 Display the @value{GDBN} commands used to define @var{commandname} (but
17625 not its documentation). If no @var{commandname} is given, display the
17626 definitions for all user-defined commands.
17628 @cindex infinite recursion in user-defined commands
17629 @kindex show max-user-call-depth
17630 @kindex set max-user-call-depth
17631 @item show max-user-call-depth
17632 @itemx set max-user-call-depth
17633 The value of @code{max-user-call-depth} controls how many recursion
17634 levels are allowed in user-defined commands before @value{GDBN} suspects an
17635 infinite recursion and aborts the command.
17638 In addition to the above commands, user-defined commands frequently
17639 use control flow commands, described in @ref{Command Files}.
17641 When user-defined commands are executed, the
17642 commands of the definition are not printed. An error in any command
17643 stops execution of the user-defined command.
17645 If used interactively, commands that would ask for confirmation proceed
17646 without asking when used inside a user-defined command. Many @value{GDBN}
17647 commands that normally print messages to say what they are doing omit the
17648 messages when used in a user-defined command.
17651 @subsection User-defined Command Hooks
17652 @cindex command hooks
17653 @cindex hooks, for commands
17654 @cindex hooks, pre-command
17657 You may define @dfn{hooks}, which are a special kind of user-defined
17658 command. Whenever you run the command @samp{foo}, if the user-defined
17659 command @samp{hook-foo} exists, it is executed (with no arguments)
17660 before that command.
17662 @cindex hooks, post-command
17664 A hook may also be defined which is run after the command you executed.
17665 Whenever you run the command @samp{foo}, if the user-defined command
17666 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17667 that command. Post-execution hooks may exist simultaneously with
17668 pre-execution hooks, for the same command.
17670 It is valid for a hook to call the command which it hooks. If this
17671 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17673 @c It would be nice if hookpost could be passed a parameter indicating
17674 @c if the command it hooks executed properly or not. FIXME!
17676 @kindex stop@r{, a pseudo-command}
17677 In addition, a pseudo-command, @samp{stop} exists. Defining
17678 (@samp{hook-stop}) makes the associated commands execute every time
17679 execution stops in your program: before breakpoint commands are run,
17680 displays are printed, or the stack frame is printed.
17682 For example, to ignore @code{SIGALRM} signals while
17683 single-stepping, but treat them normally during normal execution,
17688 handle SIGALRM nopass
17692 handle SIGALRM pass
17695 define hook-continue
17696 handle SIGALRM pass
17700 As a further example, to hook at the beginning and end of the @code{echo}
17701 command, and to add extra text to the beginning and end of the message,
17709 define hookpost-echo
17713 (@value{GDBP}) echo Hello World
17714 <<<---Hello World--->>>
17719 You can define a hook for any single-word command in @value{GDBN}, but
17720 not for command aliases; you should define a hook for the basic command
17721 name, e.g.@: @code{backtrace} rather than @code{bt}.
17722 @c FIXME! So how does Joe User discover whether a command is an alias
17724 If an error occurs during the execution of your hook, execution of
17725 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17726 (before the command that you actually typed had a chance to run).
17728 If you try to define a hook which does not match any known command, you
17729 get a warning from the @code{define} command.
17731 @node Command Files
17732 @subsection Command Files
17734 @cindex command files
17735 @cindex scripting commands
17736 A command file for @value{GDBN} is a text file made of lines that are
17737 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17738 also be included. An empty line in a command file does nothing; it
17739 does not mean to repeat the last command, as it would from the
17742 You can request the execution of a command file with the @code{source}
17747 @cindex execute commands from a file
17748 @item source [@code{-v}] @var{filename}
17749 Execute the command file @var{filename}.
17752 The lines in a command file are generally executed sequentially,
17753 unless the order of execution is changed by one of the
17754 @emph{flow-control commands} described below. The commands are not
17755 printed as they are executed. An error in any command terminates
17756 execution of the command file and control is returned to the console.
17758 @value{GDBN} searches for @var{filename} in the current directory and then
17759 on the search path (specified with the @samp{directory} command).
17761 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17762 each command as it is executed. The option must be given before
17763 @var{filename}, and is interpreted as part of the filename anywhere else.
17765 Commands that would ask for confirmation if used interactively proceed
17766 without asking when used in a command file. Many @value{GDBN} commands that
17767 normally print messages to say what they are doing omit the messages
17768 when called from command files.
17770 @value{GDBN} also accepts command input from standard input. In this
17771 mode, normal output goes to standard output and error output goes to
17772 standard error. Errors in a command file supplied on standard input do
17773 not terminate execution of the command file---execution continues with
17777 gdb < cmds > log 2>&1
17780 (The syntax above will vary depending on the shell used.) This example
17781 will execute commands from the file @file{cmds}. All output and errors
17782 would be directed to @file{log}.
17784 Since commands stored on command files tend to be more general than
17785 commands typed interactively, they frequently need to deal with
17786 complicated situations, such as different or unexpected values of
17787 variables and symbols, changes in how the program being debugged is
17788 built, etc. @value{GDBN} provides a set of flow-control commands to
17789 deal with these complexities. Using these commands, you can write
17790 complex scripts that loop over data structures, execute commands
17791 conditionally, etc.
17798 This command allows to include in your script conditionally executed
17799 commands. The @code{if} command takes a single argument, which is an
17800 expression to evaluate. It is followed by a series of commands that
17801 are executed only if the expression is true (its value is nonzero).
17802 There can then optionally be an @code{else} line, followed by a series
17803 of commands that are only executed if the expression was false. The
17804 end of the list is marked by a line containing @code{end}.
17808 This command allows to write loops. Its syntax is similar to
17809 @code{if}: the command takes a single argument, which is an expression
17810 to evaluate, and must be followed by the commands to execute, one per
17811 line, terminated by an @code{end}. These commands are called the
17812 @dfn{body} of the loop. The commands in the body of @code{while} are
17813 executed repeatedly as long as the expression evaluates to true.
17817 This command exits the @code{while} loop in whose body it is included.
17818 Execution of the script continues after that @code{while}s @code{end}
17821 @kindex loop_continue
17822 @item loop_continue
17823 This command skips the execution of the rest of the body of commands
17824 in the @code{while} loop in whose body it is included. Execution
17825 branches to the beginning of the @code{while} loop, where it evaluates
17826 the controlling expression.
17828 @kindex end@r{ (if/else/while commands)}
17830 Terminate the block of commands that are the body of @code{if},
17831 @code{else}, or @code{while} flow-control commands.
17836 @subsection Commands for Controlled Output
17838 During the execution of a command file or a user-defined command, normal
17839 @value{GDBN} output is suppressed; the only output that appears is what is
17840 explicitly printed by the commands in the definition. This section
17841 describes three commands useful for generating exactly the output you
17846 @item echo @var{text}
17847 @c I do not consider backslash-space a standard C escape sequence
17848 @c because it is not in ANSI.
17849 Print @var{text}. Nonprinting characters can be included in
17850 @var{text} using C escape sequences, such as @samp{\n} to print a
17851 newline. @strong{No newline is printed unless you specify one.}
17852 In addition to the standard C escape sequences, a backslash followed
17853 by a space stands for a space. This is useful for displaying a
17854 string with spaces at the beginning or the end, since leading and
17855 trailing spaces are otherwise trimmed from all arguments.
17856 To print @samp{@w{ }and foo =@w{ }}, use the command
17857 @samp{echo \@w{ }and foo = \@w{ }}.
17859 A backslash at the end of @var{text} can be used, as in C, to continue
17860 the command onto subsequent lines. For example,
17863 echo This is some text\n\
17864 which is continued\n\
17865 onto several lines.\n
17868 produces the same output as
17871 echo This is some text\n
17872 echo which is continued\n
17873 echo onto several lines.\n
17877 @item output @var{expression}
17878 Print the value of @var{expression} and nothing but that value: no
17879 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17880 value history either. @xref{Expressions, ,Expressions}, for more information
17883 @item output/@var{fmt} @var{expression}
17884 Print the value of @var{expression} in format @var{fmt}. You can use
17885 the same formats as for @code{print}. @xref{Output Formats,,Output
17886 Formats}, for more information.
17889 @item printf @var{template}, @var{expressions}@dots{}
17890 Print the values of one or more @var{expressions} under the control of
17891 the string @var{template}. To print several values, make
17892 @var{expressions} be a comma-separated list of individual expressions,
17893 which may be either numbers or pointers. Their values are printed as
17894 specified by @var{template}, exactly as a C program would do by
17895 executing the code below:
17898 printf (@var{template}, @var{expressions}@dots{});
17901 As in @code{C} @code{printf}, ordinary characters in @var{template}
17902 are printed verbatim, while @dfn{conversion specification} introduced
17903 by the @samp{%} character cause subsequent @var{expressions} to be
17904 evaluated, their values converted and formatted according to type and
17905 style information encoded in the conversion specifications, and then
17908 For example, you can print two values in hex like this:
17911 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17914 @code{printf} supports all the standard @code{C} conversion
17915 specifications, including the flags and modifiers between the @samp{%}
17916 character and the conversion letter, with the following exceptions:
17920 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17923 The modifier @samp{*} is not supported for specifying precision or
17927 The @samp{'} flag (for separation of digits into groups according to
17928 @code{LC_NUMERIC'}) is not supported.
17931 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17935 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17938 The conversion letters @samp{a} and @samp{A} are not supported.
17942 Note that the @samp{ll} type modifier is supported only if the
17943 underlying @code{C} implementation used to build @value{GDBN} supports
17944 the @code{long long int} type, and the @samp{L} type modifier is
17945 supported only if @code{long double} type is available.
17947 As in @code{C}, @code{printf} supports simple backslash-escape
17948 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17949 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17950 single character. Octal and hexadecimal escape sequences are not
17953 Additionally, @code{printf} supports conversion specifications for DFP
17954 (@dfn{Decimal Floating Point}) types using the following length modifiers
17955 together with a floating point specifier.
17960 @samp{H} for printing @code{Decimal32} types.
17963 @samp{D} for printing @code{Decimal64} types.
17966 @samp{DD} for printing @code{Decimal128} types.
17969 If the underlying @code{C} implementation used to build @value{GDBN} has
17970 support for the three length modifiers for DFP types, other modifiers
17971 such as width and precision will also be available for @value{GDBN} to use.
17973 In case there is no such @code{C} support, no additional modifiers will be
17974 available and the value will be printed in the standard way.
17976 Here's an example of printing DFP types using the above conversion letters:
17978 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17984 @section Scripting @value{GDBN} using Python
17985 @cindex python scripting
17986 @cindex scripting with python
17988 You can script @value{GDBN} using the @uref{http://www.python.org/,
17989 Python programming language}. This feature is available only if
17990 @value{GDBN} was configured using @option{--with-python}.
17993 * Python Commands:: Accessing Python from @value{GDBN}.
17994 * Python API:: Accessing @value{GDBN} from Python.
17997 @node Python Commands
17998 @subsection Python Commands
17999 @cindex python commands
18000 @cindex commands to access python
18002 @value{GDBN} provides one command for accessing the Python interpreter,
18003 and one related setting:
18007 @item python @r{[}@var{code}@r{]}
18008 The @code{python} command can be used to evaluate Python code.
18010 If given an argument, the @code{python} command will evaluate the
18011 argument as a Python command. For example:
18014 (@value{GDBP}) python print 23
18018 If you do not provide an argument to @code{python}, it will act as a
18019 multi-line command, like @code{define}. In this case, the Python
18020 script is made up of subsequent command lines, given after the
18021 @code{python} command. This command list is terminated using a line
18022 containing @code{end}. For example:
18025 (@value{GDBP}) python
18027 End with a line saying just "end".
18033 @kindex maint set python print-stack
18034 @item maint set python print-stack
18035 By default, @value{GDBN} will print a stack trace when an error occurs
18036 in a Python script. This can be controlled using @code{maint set
18037 python print-stack}: if @code{on}, the default, then Python stack
18038 printing is enabled; if @code{off}, then Python stack printing is
18043 @subsection Python API
18045 @cindex programming in python
18047 @cindex python stdout
18048 @cindex python pagination
18049 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18050 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18051 A Python program which outputs to one of these streams may have its
18052 output interrupted by the user (@pxref{Screen Size}). In this
18053 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18056 * Basic Python:: Basic Python Functions.
18057 * Exception Handling::
18058 * Values From Inferior::
18062 @subsubsection Basic Python
18064 @cindex python functions
18065 @cindex python module
18067 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18068 methods and classes added by @value{GDBN} are placed in this module.
18069 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18070 use in all scripts evaluated by the @code{python} command.
18072 @findex gdb.execute
18073 @defun execute command
18074 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18075 If a GDB exception happens while @var{command} runs, it is
18076 translated as described in @ref{Exception Handling,,Exception Handling}.
18077 If no exceptions occur, this function returns @code{None}.
18080 @findex gdb.get_parameter
18081 @defun get_parameter parameter
18082 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18083 string naming the parameter to look up; @var{parameter} may contain
18084 spaces if the parameter has a multi-part name. For example,
18085 @samp{print object} is a valid parameter name.
18087 If the named parameter does not exist, this function throws a
18088 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18089 a Python value of the appropriate type, and returned.
18093 @defun write string
18094 Print a string to @value{GDBN}'s paginated standard output stream.
18095 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18096 call this function.
18101 Flush @value{GDBN}'s paginated standard output stream. Flushing
18102 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18106 @node Exception Handling
18107 @subsubsection Exception Handling
18108 @cindex python exceptions
18109 @cindex exceptions, python
18111 When executing the @code{python} command, Python exceptions
18112 uncaught within the Python code are translated to calls to
18113 @value{GDBN} error-reporting mechanism. If the command that called
18114 @code{python} does not handle the error, @value{GDBN} will
18115 terminate it and print an error message containing the Python
18116 exception name, the associated value, and the Python call stack
18117 backtrace at the point where the exception was raised. Example:
18120 (@value{GDBP}) python print foo
18121 Traceback (most recent call last):
18122 File "<string>", line 1, in <module>
18123 NameError: name 'foo' is not defined
18126 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18127 code are converted to Python @code{RuntimeError} exceptions. User
18128 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18129 prompt) is translated to a Python @code{KeyboardInterrupt}
18130 exception. If you catch these exceptions in your Python code, your
18131 exception handler will see @code{RuntimeError} or
18132 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18133 message as its value, and the Python call stack backtrace at the
18134 Python statement closest to where the @value{GDBN} error occured as the
18137 @node Values From Inferior
18138 @subsubsection Values From Inferior
18139 @cindex values from inferior, with Python
18140 @cindex python, working with values from inferior
18142 @cindex @code{gdb.Value}
18143 @value{GDBN} provides values it obtains from the inferior program in
18144 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18145 for its internal bookkeeping of the inferior's values, and for
18146 fetching values when necessary.
18148 Inferior values that are simple scalars can be used directly in
18149 Python expressions that are valid for the value's data type. Here's
18150 an example for an integer or floating-point value @code{some_val}:
18157 As result of this, @code{bar} will also be a @code{gdb.Value} object
18158 whose values are of the same type as those of @code{some_val}.
18160 Inferior values that are structures or instances of some class can
18161 be accessed using the Python @dfn{dictionary syntax}. For example, if
18162 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18163 can access its @code{foo} element with:
18166 bar = some_val['foo']
18169 Again, @code{bar} will also be a @code{gdb.Value} object.
18171 For pointer data types, @code{gdb.Value} provides a method for
18172 dereferencing the pointer to obtain the object it points to.
18174 @defmethod Value dereference
18175 This method returns a new @code{gdb.Value} object whose contents is
18176 the object pointed to by the pointer. For example, if @code{foo} is
18177 a C pointer to an @code{int}, declared in your C program as
18184 then you can use the corresponding @code{gdb.Value} to access what
18185 @code{foo} points to like this:
18188 bar = foo.dereference ()
18191 The result @code{bar} will be a @code{gdb.Value} object holding the
18192 value pointed to by @code{foo}.
18196 @chapter Command Interpreters
18197 @cindex command interpreters
18199 @value{GDBN} supports multiple command interpreters, and some command
18200 infrastructure to allow users or user interface writers to switch
18201 between interpreters or run commands in other interpreters.
18203 @value{GDBN} currently supports two command interpreters, the console
18204 interpreter (sometimes called the command-line interpreter or @sc{cli})
18205 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18206 describes both of these interfaces in great detail.
18208 By default, @value{GDBN} will start with the console interpreter.
18209 However, the user may choose to start @value{GDBN} with another
18210 interpreter by specifying the @option{-i} or @option{--interpreter}
18211 startup options. Defined interpreters include:
18215 @cindex console interpreter
18216 The traditional console or command-line interpreter. This is the most often
18217 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18218 @value{GDBN} will use this interpreter.
18221 @cindex mi interpreter
18222 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18223 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18224 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18228 @cindex mi2 interpreter
18229 The current @sc{gdb/mi} interface.
18232 @cindex mi1 interpreter
18233 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18237 @cindex invoke another interpreter
18238 The interpreter being used by @value{GDBN} may not be dynamically
18239 switched at runtime. Although possible, this could lead to a very
18240 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18241 enters the command "interpreter-set console" in a console view,
18242 @value{GDBN} would switch to using the console interpreter, rendering
18243 the IDE inoperable!
18245 @kindex interpreter-exec
18246 Although you may only choose a single interpreter at startup, you may execute
18247 commands in any interpreter from the current interpreter using the appropriate
18248 command. If you are running the console interpreter, simply use the
18249 @code{interpreter-exec} command:
18252 interpreter-exec mi "-data-list-register-names"
18255 @sc{gdb/mi} has a similar command, although it is only available in versions of
18256 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18259 @chapter @value{GDBN} Text User Interface
18261 @cindex Text User Interface
18264 * TUI Overview:: TUI overview
18265 * TUI Keys:: TUI key bindings
18266 * TUI Single Key Mode:: TUI single key mode
18267 * TUI Commands:: TUI-specific commands
18268 * TUI Configuration:: TUI configuration variables
18271 The @value{GDBN} Text User Interface (TUI) is a terminal
18272 interface which uses the @code{curses} library to show the source
18273 file, the assembly output, the program registers and @value{GDBN}
18274 commands in separate text windows. The TUI mode is supported only
18275 on platforms where a suitable version of the @code{curses} library
18278 @pindex @value{GDBTUI}
18279 The TUI mode is enabled by default when you invoke @value{GDBN} as
18280 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
18281 You can also switch in and out of TUI mode while @value{GDBN} runs by
18282 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
18283 @xref{TUI Keys, ,TUI Key Bindings}.
18286 @section TUI Overview
18288 In TUI mode, @value{GDBN} can display several text windows:
18292 This window is the @value{GDBN} command window with the @value{GDBN}
18293 prompt and the @value{GDBN} output. The @value{GDBN} input is still
18294 managed using readline.
18297 The source window shows the source file of the program. The current
18298 line and active breakpoints are displayed in this window.
18301 The assembly window shows the disassembly output of the program.
18304 This window shows the processor registers. Registers are highlighted
18305 when their values change.
18308 The source and assembly windows show the current program position
18309 by highlighting the current line and marking it with a @samp{>} marker.
18310 Breakpoints are indicated with two markers. The first marker
18311 indicates the breakpoint type:
18315 Breakpoint which was hit at least once.
18318 Breakpoint which was never hit.
18321 Hardware breakpoint which was hit at least once.
18324 Hardware breakpoint which was never hit.
18327 The second marker indicates whether the breakpoint is enabled or not:
18331 Breakpoint is enabled.
18334 Breakpoint is disabled.
18337 The source, assembly and register windows are updated when the current
18338 thread changes, when the frame changes, or when the program counter
18341 These windows are not all visible at the same time. The command
18342 window is always visible. The others can be arranged in several
18353 source and assembly,
18356 source and registers, or
18359 assembly and registers.
18362 A status line above the command window shows the following information:
18366 Indicates the current @value{GDBN} target.
18367 (@pxref{Targets, ,Specifying a Debugging Target}).
18370 Gives the current process or thread number.
18371 When no process is being debugged, this field is set to @code{No process}.
18374 Gives the current function name for the selected frame.
18375 The name is demangled if demangling is turned on (@pxref{Print Settings}).
18376 When there is no symbol corresponding to the current program counter,
18377 the string @code{??} is displayed.
18380 Indicates the current line number for the selected frame.
18381 When the current line number is not known, the string @code{??} is displayed.
18384 Indicates the current program counter address.
18388 @section TUI Key Bindings
18389 @cindex TUI key bindings
18391 The TUI installs several key bindings in the readline keymaps
18392 (@pxref{Command Line Editing}). The following key bindings
18393 are installed for both TUI mode and the @value{GDBN} standard mode.
18402 Enter or leave the TUI mode. When leaving the TUI mode,
18403 the curses window management stops and @value{GDBN} operates using
18404 its standard mode, writing on the terminal directly. When reentering
18405 the TUI mode, control is given back to the curses windows.
18406 The screen is then refreshed.
18410 Use a TUI layout with only one window. The layout will
18411 either be @samp{source} or @samp{assembly}. When the TUI mode
18412 is not active, it will switch to the TUI mode.
18414 Think of this key binding as the Emacs @kbd{C-x 1} binding.
18418 Use a TUI layout with at least two windows. When the current
18419 layout already has two windows, the next layout with two windows is used.
18420 When a new layout is chosen, one window will always be common to the
18421 previous layout and the new one.
18423 Think of it as the Emacs @kbd{C-x 2} binding.
18427 Change the active window. The TUI associates several key bindings
18428 (like scrolling and arrow keys) with the active window. This command
18429 gives the focus to the next TUI window.
18431 Think of it as the Emacs @kbd{C-x o} binding.
18435 Switch in and out of the TUI SingleKey mode that binds single
18436 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
18439 The following key bindings only work in the TUI mode:
18444 Scroll the active window one page up.
18448 Scroll the active window one page down.
18452 Scroll the active window one line up.
18456 Scroll the active window one line down.
18460 Scroll the active window one column left.
18464 Scroll the active window one column right.
18468 Refresh the screen.
18471 Because the arrow keys scroll the active window in the TUI mode, they
18472 are not available for their normal use by readline unless the command
18473 window has the focus. When another window is active, you must use
18474 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
18475 and @kbd{C-f} to control the command window.
18477 @node TUI Single Key Mode
18478 @section TUI Single Key Mode
18479 @cindex TUI single key mode
18481 The TUI also provides a @dfn{SingleKey} mode, which binds several
18482 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
18483 switch into this mode, where the following key bindings are used:
18486 @kindex c @r{(SingleKey TUI key)}
18490 @kindex d @r{(SingleKey TUI key)}
18494 @kindex f @r{(SingleKey TUI key)}
18498 @kindex n @r{(SingleKey TUI key)}
18502 @kindex q @r{(SingleKey TUI key)}
18504 exit the SingleKey mode.
18506 @kindex r @r{(SingleKey TUI key)}
18510 @kindex s @r{(SingleKey TUI key)}
18514 @kindex u @r{(SingleKey TUI key)}
18518 @kindex v @r{(SingleKey TUI key)}
18522 @kindex w @r{(SingleKey TUI key)}
18527 Other keys temporarily switch to the @value{GDBN} command prompt.
18528 The key that was pressed is inserted in the editing buffer so that
18529 it is possible to type most @value{GDBN} commands without interaction
18530 with the TUI SingleKey mode. Once the command is entered the TUI
18531 SingleKey mode is restored. The only way to permanently leave
18532 this mode is by typing @kbd{q} or @kbd{C-x s}.
18536 @section TUI-specific Commands
18537 @cindex TUI commands
18539 The TUI has specific commands to control the text windows.
18540 These commands are always available, even when @value{GDBN} is not in
18541 the TUI mode. When @value{GDBN} is in the standard mode, most
18542 of these commands will automatically switch to the TUI mode.
18547 List and give the size of all displayed windows.
18551 Display the next layout.
18554 Display the previous layout.
18557 Display the source window only.
18560 Display the assembly window only.
18563 Display the source and assembly window.
18566 Display the register window together with the source or assembly window.
18570 Make the next window active for scrolling.
18573 Make the previous window active for scrolling.
18576 Make the source window active for scrolling.
18579 Make the assembly window active for scrolling.
18582 Make the register window active for scrolling.
18585 Make the command window active for scrolling.
18589 Refresh the screen. This is similar to typing @kbd{C-L}.
18591 @item tui reg float
18593 Show the floating point registers in the register window.
18595 @item tui reg general
18596 Show the general registers in the register window.
18599 Show the next register group. The list of register groups as well as
18600 their order is target specific. The predefined register groups are the
18601 following: @code{general}, @code{float}, @code{system}, @code{vector},
18602 @code{all}, @code{save}, @code{restore}.
18604 @item tui reg system
18605 Show the system registers in the register window.
18609 Update the source window and the current execution point.
18611 @item winheight @var{name} +@var{count}
18612 @itemx winheight @var{name} -@var{count}
18614 Change the height of the window @var{name} by @var{count}
18615 lines. Positive counts increase the height, while negative counts
18618 @item tabset @var{nchars}
18620 Set the width of tab stops to be @var{nchars} characters.
18623 @node TUI Configuration
18624 @section TUI Configuration Variables
18625 @cindex TUI configuration variables
18627 Several configuration variables control the appearance of TUI windows.
18630 @item set tui border-kind @var{kind}
18631 @kindex set tui border-kind
18632 Select the border appearance for the source, assembly and register windows.
18633 The possible values are the following:
18636 Use a space character to draw the border.
18639 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
18642 Use the Alternate Character Set to draw the border. The border is
18643 drawn using character line graphics if the terminal supports them.
18646 @item set tui border-mode @var{mode}
18647 @kindex set tui border-mode
18648 @itemx set tui active-border-mode @var{mode}
18649 @kindex set tui active-border-mode
18650 Select the display attributes for the borders of the inactive windows
18651 or the active window. The @var{mode} can be one of the following:
18654 Use normal attributes to display the border.
18660 Use reverse video mode.
18663 Use half bright mode.
18665 @item half-standout
18666 Use half bright and standout mode.
18669 Use extra bright or bold mode.
18671 @item bold-standout
18672 Use extra bright or bold and standout mode.
18677 @chapter Using @value{GDBN} under @sc{gnu} Emacs
18680 @cindex @sc{gnu} Emacs
18681 A special interface allows you to use @sc{gnu} Emacs to view (and
18682 edit) the source files for the program you are debugging with
18685 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
18686 executable file you want to debug as an argument. This command starts
18687 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
18688 created Emacs buffer.
18689 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
18691 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
18696 All ``terminal'' input and output goes through an Emacs buffer, called
18699 This applies both to @value{GDBN} commands and their output, and to the input
18700 and output done by the program you are debugging.
18702 This is useful because it means that you can copy the text of previous
18703 commands and input them again; you can even use parts of the output
18706 All the facilities of Emacs' Shell mode are available for interacting
18707 with your program. In particular, you can send signals the usual
18708 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
18712 @value{GDBN} displays source code through Emacs.
18714 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
18715 source file for that frame and puts an arrow (@samp{=>}) at the
18716 left margin of the current line. Emacs uses a separate buffer for
18717 source display, and splits the screen to show both your @value{GDBN} session
18720 Explicit @value{GDBN} @code{list} or search commands still produce output as
18721 usual, but you probably have no reason to use them from Emacs.
18724 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
18725 a graphical mode, enabled by default, which provides further buffers
18726 that can control the execution and describe the state of your program.
18727 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
18729 If you specify an absolute file name when prompted for the @kbd{M-x
18730 gdb} argument, then Emacs sets your current working directory to where
18731 your program resides. If you only specify the file name, then Emacs
18732 sets your current working directory to to the directory associated
18733 with the previous buffer. In this case, @value{GDBN} may find your
18734 program by searching your environment's @code{PATH} variable, but on
18735 some operating systems it might not find the source. So, although the
18736 @value{GDBN} input and output session proceeds normally, the auxiliary
18737 buffer does not display the current source and line of execution.
18739 The initial working directory of @value{GDBN} is printed on the top
18740 line of the GUD buffer and this serves as a default for the commands
18741 that specify files for @value{GDBN} to operate on. @xref{Files,
18742 ,Commands to Specify Files}.
18744 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
18745 need to call @value{GDBN} by a different name (for example, if you
18746 keep several configurations around, with different names) you can
18747 customize the Emacs variable @code{gud-gdb-command-name} to run the
18750 In the GUD buffer, you can use these special Emacs commands in
18751 addition to the standard Shell mode commands:
18755 Describe the features of Emacs' GUD Mode.
18758 Execute to another source line, like the @value{GDBN} @code{step} command; also
18759 update the display window to show the current file and location.
18762 Execute to next source line in this function, skipping all function
18763 calls, like the @value{GDBN} @code{next} command. Then update the display window
18764 to show the current file and location.
18767 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
18768 display window accordingly.
18771 Execute until exit from the selected stack frame, like the @value{GDBN}
18772 @code{finish} command.
18775 Continue execution of your program, like the @value{GDBN} @code{continue}
18779 Go up the number of frames indicated by the numeric argument
18780 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
18781 like the @value{GDBN} @code{up} command.
18784 Go down the number of frames indicated by the numeric argument, like the
18785 @value{GDBN} @code{down} command.
18788 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
18789 tells @value{GDBN} to set a breakpoint on the source line point is on.
18791 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
18792 separate frame which shows a backtrace when the GUD buffer is current.
18793 Move point to any frame in the stack and type @key{RET} to make it
18794 become the current frame and display the associated source in the
18795 source buffer. Alternatively, click @kbd{Mouse-2} to make the
18796 selected frame become the current one. In graphical mode, the
18797 speedbar displays watch expressions.
18799 If you accidentally delete the source-display buffer, an easy way to get
18800 it back is to type the command @code{f} in the @value{GDBN} buffer, to
18801 request a frame display; when you run under Emacs, this recreates
18802 the source buffer if necessary to show you the context of the current
18805 The source files displayed in Emacs are in ordinary Emacs buffers
18806 which are visiting the source files in the usual way. You can edit
18807 the files with these buffers if you wish; but keep in mind that @value{GDBN}
18808 communicates with Emacs in terms of line numbers. If you add or
18809 delete lines from the text, the line numbers that @value{GDBN} knows cease
18810 to correspond properly with the code.
18812 A more detailed description of Emacs' interaction with @value{GDBN} is
18813 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
18816 @c The following dropped because Epoch is nonstandard. Reactivate
18817 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
18819 @kindex Emacs Epoch environment
18823 Version 18 of @sc{gnu} Emacs has a built-in window system
18824 called the @code{epoch}
18825 environment. Users of this environment can use a new command,
18826 @code{inspect} which performs identically to @code{print} except that
18827 each value is printed in its own window.
18832 @chapter The @sc{gdb/mi} Interface
18834 @unnumberedsec Function and Purpose
18836 @cindex @sc{gdb/mi}, its purpose
18837 @sc{gdb/mi} is a line based machine oriented text interface to
18838 @value{GDBN} and is activated by specifying using the
18839 @option{--interpreter} command line option (@pxref{Mode Options}). It
18840 is specifically intended to support the development of systems which
18841 use the debugger as just one small component of a larger system.
18843 This chapter is a specification of the @sc{gdb/mi} interface. It is written
18844 in the form of a reference manual.
18846 Note that @sc{gdb/mi} is still under construction, so some of the
18847 features described below are incomplete and subject to change
18848 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
18850 @unnumberedsec Notation and Terminology
18852 @cindex notational conventions, for @sc{gdb/mi}
18853 This chapter uses the following notation:
18857 @code{|} separates two alternatives.
18860 @code{[ @var{something} ]} indicates that @var{something} is optional:
18861 it may or may not be given.
18864 @code{( @var{group} )*} means that @var{group} inside the parentheses
18865 may repeat zero or more times.
18868 @code{( @var{group} )+} means that @var{group} inside the parentheses
18869 may repeat one or more times.
18872 @code{"@var{string}"} means a literal @var{string}.
18876 @heading Dependencies
18880 * GDB/MI Command Syntax::
18881 * GDB/MI Compatibility with CLI::
18882 * GDB/MI Development and Front Ends::
18883 * GDB/MI Output Records::
18884 * GDB/MI Simple Examples::
18885 * GDB/MI Command Description Format::
18886 * GDB/MI Breakpoint Commands::
18887 * GDB/MI Program Context::
18888 * GDB/MI Thread Commands::
18889 * GDB/MI Program Execution::
18890 * GDB/MI Stack Manipulation::
18891 * GDB/MI Variable Objects::
18892 * GDB/MI Data Manipulation::
18893 * GDB/MI Tracepoint Commands::
18894 * GDB/MI Symbol Query::
18895 * GDB/MI File Commands::
18897 * GDB/MI Kod Commands::
18898 * GDB/MI Memory Overlay Commands::
18899 * GDB/MI Signal Handling Commands::
18901 * GDB/MI Target Manipulation::
18902 * GDB/MI File Transfer Commands::
18903 * GDB/MI Miscellaneous Commands::
18906 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18907 @node GDB/MI Command Syntax
18908 @section @sc{gdb/mi} Command Syntax
18911 * GDB/MI Input Syntax::
18912 * GDB/MI Output Syntax::
18915 @node GDB/MI Input Syntax
18916 @subsection @sc{gdb/mi} Input Syntax
18918 @cindex input syntax for @sc{gdb/mi}
18919 @cindex @sc{gdb/mi}, input syntax
18921 @item @var{command} @expansion{}
18922 @code{@var{cli-command} | @var{mi-command}}
18924 @item @var{cli-command} @expansion{}
18925 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
18926 @var{cli-command} is any existing @value{GDBN} CLI command.
18928 @item @var{mi-command} @expansion{}
18929 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
18930 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
18932 @item @var{token} @expansion{}
18933 "any sequence of digits"
18935 @item @var{option} @expansion{}
18936 @code{"-" @var{parameter} [ " " @var{parameter} ]}
18938 @item @var{parameter} @expansion{}
18939 @code{@var{non-blank-sequence} | @var{c-string}}
18941 @item @var{operation} @expansion{}
18942 @emph{any of the operations described in this chapter}
18944 @item @var{non-blank-sequence} @expansion{}
18945 @emph{anything, provided it doesn't contain special characters such as
18946 "-", @var{nl}, """ and of course " "}
18948 @item @var{c-string} @expansion{}
18949 @code{""" @var{seven-bit-iso-c-string-content} """}
18951 @item @var{nl} @expansion{}
18960 The CLI commands are still handled by the @sc{mi} interpreter; their
18961 output is described below.
18964 The @code{@var{token}}, when present, is passed back when the command
18968 Some @sc{mi} commands accept optional arguments as part of the parameter
18969 list. Each option is identified by a leading @samp{-} (dash) and may be
18970 followed by an optional argument parameter. Options occur first in the
18971 parameter list and can be delimited from normal parameters using
18972 @samp{--} (this is useful when some parameters begin with a dash).
18979 We want easy access to the existing CLI syntax (for debugging).
18982 We want it to be easy to spot a @sc{mi} operation.
18985 @node GDB/MI Output Syntax
18986 @subsection @sc{gdb/mi} Output Syntax
18988 @cindex output syntax of @sc{gdb/mi}
18989 @cindex @sc{gdb/mi}, output syntax
18990 The output from @sc{gdb/mi} consists of zero or more out-of-band records
18991 followed, optionally, by a single result record. This result record
18992 is for the most recent command. The sequence of output records is
18993 terminated by @samp{(gdb)}.
18995 If an input command was prefixed with a @code{@var{token}} then the
18996 corresponding output for that command will also be prefixed by that same
19000 @item @var{output} @expansion{}
19001 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
19003 @item @var{result-record} @expansion{}
19004 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
19006 @item @var{out-of-band-record} @expansion{}
19007 @code{@var{async-record} | @var{stream-record}}
19009 @item @var{async-record} @expansion{}
19010 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
19012 @item @var{exec-async-output} @expansion{}
19013 @code{[ @var{token} ] "*" @var{async-output}}
19015 @item @var{status-async-output} @expansion{}
19016 @code{[ @var{token} ] "+" @var{async-output}}
19018 @item @var{notify-async-output} @expansion{}
19019 @code{[ @var{token} ] "=" @var{async-output}}
19021 @item @var{async-output} @expansion{}
19022 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
19024 @item @var{result-class} @expansion{}
19025 @code{"done" | "running" | "connected" | "error" | "exit"}
19027 @item @var{async-class} @expansion{}
19028 @code{"stopped" | @var{others}} (where @var{others} will be added
19029 depending on the needs---this is still in development).
19031 @item @var{result} @expansion{}
19032 @code{ @var{variable} "=" @var{value}}
19034 @item @var{variable} @expansion{}
19035 @code{ @var{string} }
19037 @item @var{value} @expansion{}
19038 @code{ @var{const} | @var{tuple} | @var{list} }
19040 @item @var{const} @expansion{}
19041 @code{@var{c-string}}
19043 @item @var{tuple} @expansion{}
19044 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
19046 @item @var{list} @expansion{}
19047 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
19048 @var{result} ( "," @var{result} )* "]" }
19050 @item @var{stream-record} @expansion{}
19051 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
19053 @item @var{console-stream-output} @expansion{}
19054 @code{"~" @var{c-string}}
19056 @item @var{target-stream-output} @expansion{}
19057 @code{"@@" @var{c-string}}
19059 @item @var{log-stream-output} @expansion{}
19060 @code{"&" @var{c-string}}
19062 @item @var{nl} @expansion{}
19065 @item @var{token} @expansion{}
19066 @emph{any sequence of digits}.
19074 All output sequences end in a single line containing a period.
19077 The @code{@var{token}} is from the corresponding request. Note that
19078 for all async output, while the token is allowed by the grammar and
19079 may be output by future versions of @value{GDBN} for select async
19080 output messages, it is generally omitted. Frontends should treat
19081 all async output as reporting general changes in the state of the
19082 target and there should be no need to associate async output to any
19086 @cindex status output in @sc{gdb/mi}
19087 @var{status-async-output} contains on-going status information about the
19088 progress of a slow operation. It can be discarded. All status output is
19089 prefixed by @samp{+}.
19092 @cindex async output in @sc{gdb/mi}
19093 @var{exec-async-output} contains asynchronous state change on the target
19094 (stopped, started, disappeared). All async output is prefixed by
19098 @cindex notify output in @sc{gdb/mi}
19099 @var{notify-async-output} contains supplementary information that the
19100 client should handle (e.g., a new breakpoint information). All notify
19101 output is prefixed by @samp{=}.
19104 @cindex console output in @sc{gdb/mi}
19105 @var{console-stream-output} is output that should be displayed as is in the
19106 console. It is the textual response to a CLI command. All the console
19107 output is prefixed by @samp{~}.
19110 @cindex target output in @sc{gdb/mi}
19111 @var{target-stream-output} is the output produced by the target program.
19112 All the target output is prefixed by @samp{@@}.
19115 @cindex log output in @sc{gdb/mi}
19116 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
19117 instance messages that should be displayed as part of an error log. All
19118 the log output is prefixed by @samp{&}.
19121 @cindex list output in @sc{gdb/mi}
19122 New @sc{gdb/mi} commands should only output @var{lists} containing
19128 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
19129 details about the various output records.
19131 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19132 @node GDB/MI Compatibility with CLI
19133 @section @sc{gdb/mi} Compatibility with CLI
19135 @cindex compatibility, @sc{gdb/mi} and CLI
19136 @cindex @sc{gdb/mi}, compatibility with CLI
19138 For the developers convenience CLI commands can be entered directly,
19139 but there may be some unexpected behaviour. For example, commands
19140 that query the user will behave as if the user replied yes, breakpoint
19141 command lists are not executed and some CLI commands, such as
19142 @code{if}, @code{when} and @code{define}, prompt for further input with
19143 @samp{>}, which is not valid MI output.
19145 This feature may be removed at some stage in the future and it is
19146 recommended that front ends use the @code{-interpreter-exec} command
19147 (@pxref{-interpreter-exec}).
19149 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19150 @node GDB/MI Development and Front Ends
19151 @section @sc{gdb/mi} Development and Front Ends
19152 @cindex @sc{gdb/mi} development
19154 The application which takes the MI output and presents the state of the
19155 program being debugged to the user is called a @dfn{front end}.
19157 Although @sc{gdb/mi} is still incomplete, it is currently being used
19158 by a variety of front ends to @value{GDBN}. This makes it difficult
19159 to introduce new functionality without breaking existing usage. This
19160 section tries to minimize the problems by describing how the protocol
19163 Some changes in MI need not break a carefully designed front end, and
19164 for these the MI version will remain unchanged. The following is a
19165 list of changes that may occur within one level, so front ends should
19166 parse MI output in a way that can handle them:
19170 New MI commands may be added.
19173 New fields may be added to the output of any MI command.
19176 The range of values for fields with specified values, e.g.,
19177 @code{in_scope} (@pxref{-var-update}) may be extended.
19179 @c The format of field's content e.g type prefix, may change so parse it
19180 @c at your own risk. Yes, in general?
19182 @c The order of fields may change? Shouldn't really matter but it might
19183 @c resolve inconsistencies.
19186 If the changes are likely to break front ends, the MI version level
19187 will be increased by one. This will allow the front end to parse the
19188 output according to the MI version. Apart from mi0, new versions of
19189 @value{GDBN} will not support old versions of MI and it will be the
19190 responsibility of the front end to work with the new one.
19192 @c Starting with mi3, add a new command -mi-version that prints the MI
19195 The best way to avoid unexpected changes in MI that might break your front
19196 end is to make your project known to @value{GDBN} developers and
19197 follow development on @email{gdb@@sourceware.org} and
19198 @email{gdb-patches@@sourceware.org}.
19199 @cindex mailing lists
19201 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19202 @node GDB/MI Output Records
19203 @section @sc{gdb/mi} Output Records
19206 * GDB/MI Result Records::
19207 * GDB/MI Stream Records::
19208 * GDB/MI Async Records::
19211 @node GDB/MI Result Records
19212 @subsection @sc{gdb/mi} Result Records
19214 @cindex result records in @sc{gdb/mi}
19215 @cindex @sc{gdb/mi}, result records
19216 In addition to a number of out-of-band notifications, the response to a
19217 @sc{gdb/mi} command includes one of the following result indications:
19221 @item "^done" [ "," @var{results} ]
19222 The synchronous operation was successful, @code{@var{results}} are the return
19227 @c Is this one correct? Should it be an out-of-band notification?
19228 The asynchronous operation was successfully started. The target is
19233 @value{GDBN} has connected to a remote target.
19235 @item "^error" "," @var{c-string}
19237 The operation failed. The @code{@var{c-string}} contains the corresponding
19242 @value{GDBN} has terminated.
19246 @node GDB/MI Stream Records
19247 @subsection @sc{gdb/mi} Stream Records
19249 @cindex @sc{gdb/mi}, stream records
19250 @cindex stream records in @sc{gdb/mi}
19251 @value{GDBN} internally maintains a number of output streams: the console, the
19252 target, and the log. The output intended for each of these streams is
19253 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
19255 Each stream record begins with a unique @dfn{prefix character} which
19256 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
19257 Syntax}). In addition to the prefix, each stream record contains a
19258 @code{@var{string-output}}. This is either raw text (with an implicit new
19259 line) or a quoted C string (which does not contain an implicit newline).
19262 @item "~" @var{string-output}
19263 The console output stream contains text that should be displayed in the
19264 CLI console window. It contains the textual responses to CLI commands.
19266 @item "@@" @var{string-output}
19267 The target output stream contains any textual output from the running
19268 target. This is only present when GDB's event loop is truly
19269 asynchronous, which is currently only the case for remote targets.
19271 @item "&" @var{string-output}
19272 The log stream contains debugging messages being produced by @value{GDBN}'s
19276 @node GDB/MI Async Records
19277 @subsection @sc{gdb/mi} Async Records
19279 @cindex async records in @sc{gdb/mi}
19280 @cindex @sc{gdb/mi}, async records
19281 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
19282 additional changes that have occurred. Those changes can either be a
19283 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
19284 target activity (e.g., target stopped).
19286 The following is the list of possible async records:
19290 @item *running,thread-id="@var{thread}"
19291 The target is now running. The @var{thread} field tells which
19292 specific thread is now running, and can be @samp{all} if all threads
19293 are running. The frontend should assume that no interaction with a
19294 running thread is possible after this notification is produced.
19295 The frontend should not assume that this notification is output
19296 only once for any command. @value{GDBN} may emit this notification
19297 several times, either for different threads, because it cannot resume
19298 all threads together, or even for a single thread, if the thread must
19299 be stepped though some code before letting it run freely.
19301 @item *stopped,reason="@var{reason}"
19302 The target has stopped. The @var{reason} field can have one of the
19306 @item breakpoint-hit
19307 A breakpoint was reached.
19308 @item watchpoint-trigger
19309 A watchpoint was triggered.
19310 @item read-watchpoint-trigger
19311 A read watchpoint was triggered.
19312 @item access-watchpoint-trigger
19313 An access watchpoint was triggered.
19314 @item function-finished
19315 An -exec-finish or similar CLI command was accomplished.
19316 @item location-reached
19317 An -exec-until or similar CLI command was accomplished.
19318 @item watchpoint-scope
19319 A watchpoint has gone out of scope.
19320 @item end-stepping-range
19321 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
19322 similar CLI command was accomplished.
19323 @item exited-signalled
19324 The inferior exited because of a signal.
19326 The inferior exited.
19327 @item exited-normally
19328 The inferior exited normally.
19329 @item signal-received
19330 A signal was received by the inferior.
19333 @item =thread-created,id="@var{id}"
19334 @itemx =thread-exited,id="@var{id}"
19335 A thread either was created, or has exited. The @var{id} field
19336 contains the @value{GDBN} identifier of the thread.
19338 @item =thread-selected,id="@var{id}"
19339 Informs that the selected thread was changed as result of the last
19340 command. This notification is not emitted as result of @code{-thread-select}
19341 command but is emitted whenever an MI command that is not documented
19342 to change the selected thread actually changes it. In particular,
19343 invoking, directly or indirectly (via user-defined command), the CLI
19344 @code{thread} command, will generate this notification.
19346 We suggest that in response to this notification, front ends
19347 highlight the selected thread and cause subsequent commands to apply to
19354 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19355 @node GDB/MI Simple Examples
19356 @section Simple Examples of @sc{gdb/mi} Interaction
19357 @cindex @sc{gdb/mi}, simple examples
19359 This subsection presents several simple examples of interaction using
19360 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
19361 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
19362 the output received from @sc{gdb/mi}.
19364 Note the line breaks shown in the examples are here only for
19365 readability, they don't appear in the real output.
19367 @subheading Setting a Breakpoint
19369 Setting a breakpoint generates synchronous output which contains detailed
19370 information of the breakpoint.
19373 -> -break-insert main
19374 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
19375 enabled="y",addr="0x08048564",func="main",file="myprog.c",
19376 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
19380 @subheading Program Execution
19382 Program execution generates asynchronous records and MI gives the
19383 reason that execution stopped.
19389 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
19390 frame=@{addr="0x08048564",func="main",
19391 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
19392 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
19397 <- *stopped,reason="exited-normally"
19401 @subheading Quitting @value{GDBN}
19403 Quitting @value{GDBN} just prints the result class @samp{^exit}.
19411 @subheading A Bad Command
19413 Here's what happens if you pass a non-existent command:
19417 <- ^error,msg="Undefined MI command: rubbish"
19422 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19423 @node GDB/MI Command Description Format
19424 @section @sc{gdb/mi} Command Description Format
19426 The remaining sections describe blocks of commands. Each block of
19427 commands is laid out in a fashion similar to this section.
19429 @subheading Motivation
19431 The motivation for this collection of commands.
19433 @subheading Introduction
19435 A brief introduction to this collection of commands as a whole.
19437 @subheading Commands
19439 For each command in the block, the following is described:
19441 @subsubheading Synopsis
19444 -command @var{args}@dots{}
19447 @subsubheading Result
19449 @subsubheading @value{GDBN} Command
19451 The corresponding @value{GDBN} CLI command(s), if any.
19453 @subsubheading Example
19455 Example(s) formatted for readability. Some of the described commands have
19456 not been implemented yet and these are labeled N.A.@: (not available).
19459 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19460 @node GDB/MI Breakpoint Commands
19461 @section @sc{gdb/mi} Breakpoint Commands
19463 @cindex breakpoint commands for @sc{gdb/mi}
19464 @cindex @sc{gdb/mi}, breakpoint commands
19465 This section documents @sc{gdb/mi} commands for manipulating
19468 @subheading The @code{-break-after} Command
19469 @findex -break-after
19471 @subsubheading Synopsis
19474 -break-after @var{number} @var{count}
19477 The breakpoint number @var{number} is not in effect until it has been
19478 hit @var{count} times. To see how this is reflected in the output of
19479 the @samp{-break-list} command, see the description of the
19480 @samp{-break-list} command below.
19482 @subsubheading @value{GDBN} Command
19484 The corresponding @value{GDBN} command is @samp{ignore}.
19486 @subsubheading Example
19491 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
19492 enabled="y",addr="0x000100d0",func="main",file="hello.c",
19493 fullname="/home/foo/hello.c",line="5",times="0"@}
19500 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19501 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19502 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19503 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19504 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19505 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19506 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19507 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19508 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19509 line="5",times="0",ignore="3"@}]@}
19514 @subheading The @code{-break-catch} Command
19515 @findex -break-catch
19517 @subheading The @code{-break-commands} Command
19518 @findex -break-commands
19522 @subheading The @code{-break-condition} Command
19523 @findex -break-condition
19525 @subsubheading Synopsis
19528 -break-condition @var{number} @var{expr}
19531 Breakpoint @var{number} will stop the program only if the condition in
19532 @var{expr} is true. The condition becomes part of the
19533 @samp{-break-list} output (see the description of the @samp{-break-list}
19536 @subsubheading @value{GDBN} Command
19538 The corresponding @value{GDBN} command is @samp{condition}.
19540 @subsubheading Example
19544 -break-condition 1 1
19548 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19549 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19550 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19551 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19552 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19553 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19554 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19555 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19556 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19557 line="5",cond="1",times="0",ignore="3"@}]@}
19561 @subheading The @code{-break-delete} Command
19562 @findex -break-delete
19564 @subsubheading Synopsis
19567 -break-delete ( @var{breakpoint} )+
19570 Delete the breakpoint(s) whose number(s) are specified in the argument
19571 list. This is obviously reflected in the breakpoint list.
19573 @subsubheading @value{GDBN} Command
19575 The corresponding @value{GDBN} command is @samp{delete}.
19577 @subsubheading Example
19585 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19586 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19587 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19588 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19589 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19590 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19591 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19596 @subheading The @code{-break-disable} Command
19597 @findex -break-disable
19599 @subsubheading Synopsis
19602 -break-disable ( @var{breakpoint} )+
19605 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
19606 break list is now set to @samp{n} for the named @var{breakpoint}(s).
19608 @subsubheading @value{GDBN} Command
19610 The corresponding @value{GDBN} command is @samp{disable}.
19612 @subsubheading Example
19620 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19621 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19622 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19623 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19624 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19625 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19626 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19627 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
19628 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19629 line="5",times="0"@}]@}
19633 @subheading The @code{-break-enable} Command
19634 @findex -break-enable
19636 @subsubheading Synopsis
19639 -break-enable ( @var{breakpoint} )+
19642 Enable (previously disabled) @var{breakpoint}(s).
19644 @subsubheading @value{GDBN} Command
19646 The corresponding @value{GDBN} command is @samp{enable}.
19648 @subsubheading Example
19656 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19657 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19658 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19659 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19660 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19661 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19662 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19663 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19664 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19665 line="5",times="0"@}]@}
19669 @subheading The @code{-break-info} Command
19670 @findex -break-info
19672 @subsubheading Synopsis
19675 -break-info @var{breakpoint}
19679 Get information about a single breakpoint.
19681 @subsubheading @value{GDBN} Command
19683 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
19685 @subsubheading Example
19688 @subheading The @code{-break-insert} Command
19689 @findex -break-insert
19691 @subsubheading Synopsis
19694 -break-insert [ -t ] [ -h ] [ -f ]
19695 [ -c @var{condition} ] [ -i @var{ignore-count} ]
19696 [ -p @var{thread} ] [ @var{location} ]
19700 If specified, @var{location}, can be one of:
19707 @item filename:linenum
19708 @item filename:function
19712 The possible optional parameters of this command are:
19716 Insert a temporary breakpoint.
19718 Insert a hardware breakpoint.
19719 @item -c @var{condition}
19720 Make the breakpoint conditional on @var{condition}.
19721 @item -i @var{ignore-count}
19722 Initialize the @var{ignore-count}.
19724 If @var{location} cannot be parsed (for example if it
19725 refers to unknown files or functions), create a pending
19726 breakpoint. Without this flag, @value{GDBN} will report
19727 an error, and won't create a breakpoint, if @var{location}
19731 @subsubheading Result
19733 The result is in the form:
19736 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
19737 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
19738 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
19739 times="@var{times}"@}
19743 where @var{number} is the @value{GDBN} number for this breakpoint,
19744 @var{funcname} is the name of the function where the breakpoint was
19745 inserted, @var{filename} is the name of the source file which contains
19746 this function, @var{lineno} is the source line number within that file
19747 and @var{times} the number of times that the breakpoint has been hit
19748 (always 0 for -break-insert but may be greater for -break-info or -break-list
19749 which use the same output).
19751 Note: this format is open to change.
19752 @c An out-of-band breakpoint instead of part of the result?
19754 @subsubheading @value{GDBN} Command
19756 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
19757 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
19759 @subsubheading Example
19764 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
19765 fullname="/home/foo/recursive2.c,line="4",times="0"@}
19767 -break-insert -t foo
19768 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
19769 fullname="/home/foo/recursive2.c,line="11",times="0"@}
19772 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19773 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19774 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19775 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19776 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19777 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19778 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19779 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19780 addr="0x0001072c", func="main",file="recursive2.c",
19781 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
19782 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
19783 addr="0x00010774",func="foo",file="recursive2.c",
19784 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
19786 -break-insert -r foo.*
19787 ~int foo(int, int);
19788 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
19789 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
19793 @subheading The @code{-break-list} Command
19794 @findex -break-list
19796 @subsubheading Synopsis
19802 Displays the list of inserted breakpoints, showing the following fields:
19806 number of the breakpoint
19808 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
19810 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
19813 is the breakpoint enabled or no: @samp{y} or @samp{n}
19815 memory location at which the breakpoint is set
19817 logical location of the breakpoint, expressed by function name, file
19820 number of times the breakpoint has been hit
19823 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
19824 @code{body} field is an empty list.
19826 @subsubheading @value{GDBN} Command
19828 The corresponding @value{GDBN} command is @samp{info break}.
19830 @subsubheading Example
19835 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19836 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19837 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19838 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19839 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19840 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19841 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19842 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19843 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
19844 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19845 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
19846 line="13",times="0"@}]@}
19850 Here's an example of the result when there are no breakpoints:
19855 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19856 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19857 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19858 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19859 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19860 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19861 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19866 @subheading The @code{-break-watch} Command
19867 @findex -break-watch
19869 @subsubheading Synopsis
19872 -break-watch [ -a | -r ]
19875 Create a watchpoint. With the @samp{-a} option it will create an
19876 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
19877 read from or on a write to the memory location. With the @samp{-r}
19878 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
19879 trigger only when the memory location is accessed for reading. Without
19880 either of the options, the watchpoint created is a regular watchpoint,
19881 i.e., it will trigger when the memory location is accessed for writing.
19882 @xref{Set Watchpoints, , Setting Watchpoints}.
19884 Note that @samp{-break-list} will report a single list of watchpoints and
19885 breakpoints inserted.
19887 @subsubheading @value{GDBN} Command
19889 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
19892 @subsubheading Example
19894 Setting a watchpoint on a variable in the @code{main} function:
19899 ^done,wpt=@{number="2",exp="x"@}
19904 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
19905 value=@{old="-268439212",new="55"@},
19906 frame=@{func="main",args=[],file="recursive2.c",
19907 fullname="/home/foo/bar/recursive2.c",line="5"@}
19911 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
19912 the program execution twice: first for the variable changing value, then
19913 for the watchpoint going out of scope.
19918 ^done,wpt=@{number="5",exp="C"@}
19923 *stopped,reason="watchpoint-trigger",
19924 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
19925 frame=@{func="callee4",args=[],
19926 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19927 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19932 *stopped,reason="watchpoint-scope",wpnum="5",
19933 frame=@{func="callee3",args=[@{name="strarg",
19934 value="0x11940 \"A string argument.\""@}],
19935 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19936 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19940 Listing breakpoints and watchpoints, at different points in the program
19941 execution. Note that once the watchpoint goes out of scope, it is
19947 ^done,wpt=@{number="2",exp="C"@}
19950 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19951 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19952 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19953 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19954 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19955 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19956 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19957 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19958 addr="0x00010734",func="callee4",
19959 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19960 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
19961 bkpt=@{number="2",type="watchpoint",disp="keep",
19962 enabled="y",addr="",what="C",times="0"@}]@}
19967 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
19968 value=@{old="-276895068",new="3"@},
19969 frame=@{func="callee4",args=[],
19970 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19971 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
19974 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19975 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19976 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19977 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19978 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19979 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19980 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19981 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19982 addr="0x00010734",func="callee4",
19983 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19984 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
19985 bkpt=@{number="2",type="watchpoint",disp="keep",
19986 enabled="y",addr="",what="C",times="-5"@}]@}
19990 ^done,reason="watchpoint-scope",wpnum="2",
19991 frame=@{func="callee3",args=[@{name="strarg",
19992 value="0x11940 \"A string argument.\""@}],
19993 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19994 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19997 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19998 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19999 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20000 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20001 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20002 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20003 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20004 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20005 addr="0x00010734",func="callee4",
20006 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20007 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
20012 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20013 @node GDB/MI Program Context
20014 @section @sc{gdb/mi} Program Context
20016 @subheading The @code{-exec-arguments} Command
20017 @findex -exec-arguments
20020 @subsubheading Synopsis
20023 -exec-arguments @var{args}
20026 Set the inferior program arguments, to be used in the next
20029 @subsubheading @value{GDBN} Command
20031 The corresponding @value{GDBN} command is @samp{set args}.
20033 @subsubheading Example
20037 -exec-arguments -v word
20043 @subheading The @code{-exec-show-arguments} Command
20044 @findex -exec-show-arguments
20046 @subsubheading Synopsis
20049 -exec-show-arguments
20052 Print the arguments of the program.
20054 @subsubheading @value{GDBN} Command
20056 The corresponding @value{GDBN} command is @samp{show args}.
20058 @subsubheading Example
20062 @subheading The @code{-environment-cd} Command
20063 @findex -environment-cd
20065 @subsubheading Synopsis
20068 -environment-cd @var{pathdir}
20071 Set @value{GDBN}'s working directory.
20073 @subsubheading @value{GDBN} Command
20075 The corresponding @value{GDBN} command is @samp{cd}.
20077 @subsubheading Example
20081 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20087 @subheading The @code{-environment-directory} Command
20088 @findex -environment-directory
20090 @subsubheading Synopsis
20093 -environment-directory [ -r ] [ @var{pathdir} ]+
20096 Add directories @var{pathdir} to beginning of search path for source files.
20097 If the @samp{-r} option is used, the search path is reset to the default
20098 search path. If directories @var{pathdir} are supplied in addition to the
20099 @samp{-r} option, the search path is first reset and then addition
20101 Multiple directories may be specified, separated by blanks. Specifying
20102 multiple directories in a single command
20103 results in the directories added to the beginning of the
20104 search path in the same order they were presented in the command.
20105 If blanks are needed as
20106 part of a directory name, double-quotes should be used around
20107 the name. In the command output, the path will show up separated
20108 by the system directory-separator character. The directory-separator
20109 character must not be used
20110 in any directory name.
20111 If no directories are specified, the current search path is displayed.
20113 @subsubheading @value{GDBN} Command
20115 The corresponding @value{GDBN} command is @samp{dir}.
20117 @subsubheading Example
20121 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20122 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20124 -environment-directory ""
20125 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20127 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
20128 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
20130 -environment-directory -r
20131 ^done,source-path="$cdir:$cwd"
20136 @subheading The @code{-environment-path} Command
20137 @findex -environment-path
20139 @subsubheading Synopsis
20142 -environment-path [ -r ] [ @var{pathdir} ]+
20145 Add directories @var{pathdir} to beginning of search path for object files.
20146 If the @samp{-r} option is used, the search path is reset to the original
20147 search path that existed at gdb start-up. If directories @var{pathdir} are
20148 supplied in addition to the
20149 @samp{-r} option, the search path is first reset and then addition
20151 Multiple directories may be specified, separated by blanks. Specifying
20152 multiple directories in a single command
20153 results in the directories added to the beginning of the
20154 search path in the same order they were presented in the command.
20155 If blanks are needed as
20156 part of a directory name, double-quotes should be used around
20157 the name. In the command output, the path will show up separated
20158 by the system directory-separator character. The directory-separator
20159 character must not be used
20160 in any directory name.
20161 If no directories are specified, the current path is displayed.
20164 @subsubheading @value{GDBN} Command
20166 The corresponding @value{GDBN} command is @samp{path}.
20168 @subsubheading Example
20173 ^done,path="/usr/bin"
20175 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
20176 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
20178 -environment-path -r /usr/local/bin
20179 ^done,path="/usr/local/bin:/usr/bin"
20184 @subheading The @code{-environment-pwd} Command
20185 @findex -environment-pwd
20187 @subsubheading Synopsis
20193 Show the current working directory.
20195 @subsubheading @value{GDBN} Command
20197 The corresponding @value{GDBN} command is @samp{pwd}.
20199 @subsubheading Example
20204 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
20208 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20209 @node GDB/MI Thread Commands
20210 @section @sc{gdb/mi} Thread Commands
20213 @subheading The @code{-thread-info} Command
20214 @findex -thread-info
20216 @subsubheading Synopsis
20219 -thread-info [ @var{thread-id} ]
20222 Reports information about either a specific thread, if
20223 the @var{thread-id} parameter is present, or about all
20224 threads. When printing information about all threads,
20225 also reports the current thread.
20227 @subsubheading @value{GDBN} Command
20229 The @samp{info thread} command prints the same information
20232 @subsubheading Example
20237 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
20238 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},
20239 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
20240 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
20241 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@}@}],
20242 current-thread-id="1"
20246 @subheading The @code{-thread-list-ids} Command
20247 @findex -thread-list-ids
20249 @subsubheading Synopsis
20255 Produces a list of the currently known @value{GDBN} thread ids. At the
20256 end of the list it also prints the total number of such threads.
20258 @subsubheading @value{GDBN} Command
20260 Part of @samp{info threads} supplies the same information.
20262 @subsubheading Example
20264 No threads present, besides the main process:
20269 ^done,thread-ids=@{@},number-of-threads="0"
20279 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20280 number-of-threads="3"
20285 @subheading The @code{-thread-select} Command
20286 @findex -thread-select
20288 @subsubheading Synopsis
20291 -thread-select @var{threadnum}
20294 Make @var{threadnum} the current thread. It prints the number of the new
20295 current thread, and the topmost frame for that thread.
20297 @subsubheading @value{GDBN} Command
20299 The corresponding @value{GDBN} command is @samp{thread}.
20301 @subsubheading Example
20308 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20309 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20313 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20314 number-of-threads="3"
20317 ^done,new-thread-id="3",
20318 frame=@{level="0",func="vprintf",
20319 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20320 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20324 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20325 @node GDB/MI Program Execution
20326 @section @sc{gdb/mi} Program Execution
20328 These are the asynchronous commands which generate the out-of-band
20329 record @samp{*stopped}. Currently @value{GDBN} only really executes
20330 asynchronously with remote targets and this interaction is mimicked in
20333 @subheading The @code{-exec-continue} Command
20334 @findex -exec-continue
20336 @subsubheading Synopsis
20342 Resumes the execution of the inferior program until a breakpoint is
20343 encountered, or until the inferior exits.
20345 @subsubheading @value{GDBN} Command
20347 The corresponding @value{GDBN} corresponding is @samp{continue}.
20349 @subsubheading Example
20356 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
20357 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
20363 @subheading The @code{-exec-finish} Command
20364 @findex -exec-finish
20366 @subsubheading Synopsis
20372 Resumes the execution of the inferior program until the current
20373 function is exited. Displays the results returned by the function.
20375 @subsubheading @value{GDBN} Command
20377 The corresponding @value{GDBN} command is @samp{finish}.
20379 @subsubheading Example
20381 Function returning @code{void}.
20388 *stopped,reason="function-finished",frame=@{func="main",args=[],
20389 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
20393 Function returning other than @code{void}. The name of the internal
20394 @value{GDBN} variable storing the result is printed, together with the
20401 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
20402 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
20403 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20404 gdb-result-var="$1",return-value="0"
20409 @subheading The @code{-exec-interrupt} Command
20410 @findex -exec-interrupt
20412 @subsubheading Synopsis
20418 Interrupts the background execution of the target. Note how the token
20419 associated with the stop message is the one for the execution command
20420 that has been interrupted. The token for the interrupt itself only
20421 appears in the @samp{^done} output. If the user is trying to
20422 interrupt a non-running program, an error message will be printed.
20424 @subsubheading @value{GDBN} Command
20426 The corresponding @value{GDBN} command is @samp{interrupt}.
20428 @subsubheading Example
20439 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
20440 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
20441 fullname="/home/foo/bar/try.c",line="13"@}
20446 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
20451 @subheading The @code{-exec-next} Command
20454 @subsubheading Synopsis
20460 Resumes execution of the inferior program, stopping when the beginning
20461 of the next source line is reached.
20463 @subsubheading @value{GDBN} Command
20465 The corresponding @value{GDBN} command is @samp{next}.
20467 @subsubheading Example
20473 *stopped,reason="end-stepping-range",line="8",file="hello.c"
20478 @subheading The @code{-exec-next-instruction} Command
20479 @findex -exec-next-instruction
20481 @subsubheading Synopsis
20484 -exec-next-instruction
20487 Executes one machine instruction. If the instruction is a function
20488 call, continues until the function returns. If the program stops at an
20489 instruction in the middle of a source line, the address will be
20492 @subsubheading @value{GDBN} Command
20494 The corresponding @value{GDBN} command is @samp{nexti}.
20496 @subsubheading Example
20500 -exec-next-instruction
20504 *stopped,reason="end-stepping-range",
20505 addr="0x000100d4",line="5",file="hello.c"
20510 @subheading The @code{-exec-return} Command
20511 @findex -exec-return
20513 @subsubheading Synopsis
20519 Makes current function return immediately. Doesn't execute the inferior.
20520 Displays the new current frame.
20522 @subsubheading @value{GDBN} Command
20524 The corresponding @value{GDBN} command is @samp{return}.
20526 @subsubheading Example
20530 200-break-insert callee4
20531 200^done,bkpt=@{number="1",addr="0x00010734",
20532 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20537 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20538 frame=@{func="callee4",args=[],
20539 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20540 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20546 111^done,frame=@{level="0",func="callee3",
20547 args=[@{name="strarg",
20548 value="0x11940 \"A string argument.\""@}],
20549 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20550 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20555 @subheading The @code{-exec-run} Command
20558 @subsubheading Synopsis
20564 Starts execution of the inferior from the beginning. The inferior
20565 executes until either a breakpoint is encountered or the program
20566 exits. In the latter case the output will include an exit code, if
20567 the program has exited exceptionally.
20569 @subsubheading @value{GDBN} Command
20571 The corresponding @value{GDBN} command is @samp{run}.
20573 @subsubheading Examples
20578 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
20583 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20584 frame=@{func="main",args=[],file="recursive2.c",
20585 fullname="/home/foo/bar/recursive2.c",line="4"@}
20590 Program exited normally:
20598 *stopped,reason="exited-normally"
20603 Program exited exceptionally:
20611 *stopped,reason="exited",exit-code="01"
20615 Another way the program can terminate is if it receives a signal such as
20616 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
20620 *stopped,reason="exited-signalled",signal-name="SIGINT",
20621 signal-meaning="Interrupt"
20625 @c @subheading -exec-signal
20628 @subheading The @code{-exec-step} Command
20631 @subsubheading Synopsis
20637 Resumes execution of the inferior program, stopping when the beginning
20638 of the next source line is reached, if the next source line is not a
20639 function call. If it is, stop at the first instruction of the called
20642 @subsubheading @value{GDBN} Command
20644 The corresponding @value{GDBN} command is @samp{step}.
20646 @subsubheading Example
20648 Stepping into a function:
20654 *stopped,reason="end-stepping-range",
20655 frame=@{func="foo",args=[@{name="a",value="10"@},
20656 @{name="b",value="0"@}],file="recursive2.c",
20657 fullname="/home/foo/bar/recursive2.c",line="11"@}
20667 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
20672 @subheading The @code{-exec-step-instruction} Command
20673 @findex -exec-step-instruction
20675 @subsubheading Synopsis
20678 -exec-step-instruction
20681 Resumes the inferior which executes one machine instruction. The
20682 output, once @value{GDBN} has stopped, will vary depending on whether
20683 we have stopped in the middle of a source line or not. In the former
20684 case, the address at which the program stopped will be printed as
20687 @subsubheading @value{GDBN} Command
20689 The corresponding @value{GDBN} command is @samp{stepi}.
20691 @subsubheading Example
20695 -exec-step-instruction
20699 *stopped,reason="end-stepping-range",
20700 frame=@{func="foo",args=[],file="try.c",
20701 fullname="/home/foo/bar/try.c",line="10"@}
20703 -exec-step-instruction
20707 *stopped,reason="end-stepping-range",
20708 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
20709 fullname="/home/foo/bar/try.c",line="10"@}
20714 @subheading The @code{-exec-until} Command
20715 @findex -exec-until
20717 @subsubheading Synopsis
20720 -exec-until [ @var{location} ]
20723 Executes the inferior until the @var{location} specified in the
20724 argument is reached. If there is no argument, the inferior executes
20725 until a source line greater than the current one is reached. The
20726 reason for stopping in this case will be @samp{location-reached}.
20728 @subsubheading @value{GDBN} Command
20730 The corresponding @value{GDBN} command is @samp{until}.
20732 @subsubheading Example
20736 -exec-until recursive2.c:6
20740 *stopped,reason="location-reached",frame=@{func="main",args=[],
20741 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
20746 @subheading -file-clear
20747 Is this going away????
20750 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20751 @node GDB/MI Stack Manipulation
20752 @section @sc{gdb/mi} Stack Manipulation Commands
20755 @subheading The @code{-stack-info-frame} Command
20756 @findex -stack-info-frame
20758 @subsubheading Synopsis
20764 Get info on the selected frame.
20766 @subsubheading @value{GDBN} Command
20768 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
20769 (without arguments).
20771 @subsubheading Example
20776 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
20777 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20778 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
20782 @subheading The @code{-stack-info-depth} Command
20783 @findex -stack-info-depth
20785 @subsubheading Synopsis
20788 -stack-info-depth [ @var{max-depth} ]
20791 Return the depth of the stack. If the integer argument @var{max-depth}
20792 is specified, do not count beyond @var{max-depth} frames.
20794 @subsubheading @value{GDBN} Command
20796 There's no equivalent @value{GDBN} command.
20798 @subsubheading Example
20800 For a stack with frame levels 0 through 11:
20807 -stack-info-depth 4
20810 -stack-info-depth 12
20813 -stack-info-depth 11
20816 -stack-info-depth 13
20821 @subheading The @code{-stack-list-arguments} Command
20822 @findex -stack-list-arguments
20824 @subsubheading Synopsis
20827 -stack-list-arguments @var{show-values}
20828 [ @var{low-frame} @var{high-frame} ]
20831 Display a list of the arguments for the frames between @var{low-frame}
20832 and @var{high-frame} (inclusive). If @var{low-frame} and
20833 @var{high-frame} are not provided, list the arguments for the whole
20834 call stack. If the two arguments are equal, show the single frame
20835 at the corresponding level. It is an error if @var{low-frame} is
20836 larger than the actual number of frames. On the other hand,
20837 @var{high-frame} may be larger than the actual number of frames, in
20838 which case only existing frames will be returned.
20840 The @var{show-values} argument must have a value of 0 or 1. A value of
20841 0 means that only the names of the arguments are listed, a value of 1
20842 means that both names and values of the arguments are printed.
20844 @subsubheading @value{GDBN} Command
20846 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
20847 @samp{gdb_get_args} command which partially overlaps with the
20848 functionality of @samp{-stack-list-arguments}.
20850 @subsubheading Example
20857 frame=@{level="0",addr="0x00010734",func="callee4",
20858 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20859 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
20860 frame=@{level="1",addr="0x0001076c",func="callee3",
20861 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20862 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
20863 frame=@{level="2",addr="0x0001078c",func="callee2",
20864 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20865 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
20866 frame=@{level="3",addr="0x000107b4",func="callee1",
20867 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20868 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
20869 frame=@{level="4",addr="0x000107e0",func="main",
20870 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20871 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
20873 -stack-list-arguments 0
20876 frame=@{level="0",args=[]@},
20877 frame=@{level="1",args=[name="strarg"]@},
20878 frame=@{level="2",args=[name="intarg",name="strarg"]@},
20879 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
20880 frame=@{level="4",args=[]@}]
20882 -stack-list-arguments 1
20885 frame=@{level="0",args=[]@},
20887 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
20888 frame=@{level="2",args=[
20889 @{name="intarg",value="2"@},
20890 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
20891 @{frame=@{level="3",args=[
20892 @{name="intarg",value="2"@},
20893 @{name="strarg",value="0x11940 \"A string argument.\""@},
20894 @{name="fltarg",value="3.5"@}]@},
20895 frame=@{level="4",args=[]@}]
20897 -stack-list-arguments 0 2 2
20898 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
20900 -stack-list-arguments 1 2 2
20901 ^done,stack-args=[frame=@{level="2",
20902 args=[@{name="intarg",value="2"@},
20903 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
20907 @c @subheading -stack-list-exception-handlers
20910 @subheading The @code{-stack-list-frames} Command
20911 @findex -stack-list-frames
20913 @subsubheading Synopsis
20916 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
20919 List the frames currently on the stack. For each frame it displays the
20924 The frame number, 0 being the topmost frame, i.e., the innermost function.
20926 The @code{$pc} value for that frame.
20930 File name of the source file where the function lives.
20932 Line number corresponding to the @code{$pc}.
20935 If invoked without arguments, this command prints a backtrace for the
20936 whole stack. If given two integer arguments, it shows the frames whose
20937 levels are between the two arguments (inclusive). If the two arguments
20938 are equal, it shows the single frame at the corresponding level. It is
20939 an error if @var{low-frame} is larger than the actual number of
20940 frames. On the other hand, @var{high-frame} may be larger than the
20941 actual number of frames, in which case only existing frames will be returned.
20943 @subsubheading @value{GDBN} Command
20945 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
20947 @subsubheading Example
20949 Full stack backtrace:
20955 [frame=@{level="0",addr="0x0001076c",func="foo",
20956 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
20957 frame=@{level="1",addr="0x000107a4",func="foo",
20958 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20959 frame=@{level="2",addr="0x000107a4",func="foo",
20960 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20961 frame=@{level="3",addr="0x000107a4",func="foo",
20962 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20963 frame=@{level="4",addr="0x000107a4",func="foo",
20964 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20965 frame=@{level="5",addr="0x000107a4",func="foo",
20966 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20967 frame=@{level="6",addr="0x000107a4",func="foo",
20968 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20969 frame=@{level="7",addr="0x000107a4",func="foo",
20970 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20971 frame=@{level="8",addr="0x000107a4",func="foo",
20972 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20973 frame=@{level="9",addr="0x000107a4",func="foo",
20974 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20975 frame=@{level="10",addr="0x000107a4",func="foo",
20976 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20977 frame=@{level="11",addr="0x00010738",func="main",
20978 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
20982 Show frames between @var{low_frame} and @var{high_frame}:
20986 -stack-list-frames 3 5
20988 [frame=@{level="3",addr="0x000107a4",func="foo",
20989 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20990 frame=@{level="4",addr="0x000107a4",func="foo",
20991 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20992 frame=@{level="5",addr="0x000107a4",func="foo",
20993 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
20997 Show a single frame:
21001 -stack-list-frames 3 3
21003 [frame=@{level="3",addr="0x000107a4",func="foo",
21004 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21009 @subheading The @code{-stack-list-locals} Command
21010 @findex -stack-list-locals
21012 @subsubheading Synopsis
21015 -stack-list-locals @var{print-values}
21018 Display the local variable names for the selected frame. If
21019 @var{print-values} is 0 or @code{--no-values}, print only the names of
21020 the variables; if it is 1 or @code{--all-values}, print also their
21021 values; and if it is 2 or @code{--simple-values}, print the name,
21022 type and value for simple data types and the name and type for arrays,
21023 structures and unions. In this last case, a frontend can immediately
21024 display the value of simple data types and create variable objects for
21025 other data types when the user wishes to explore their values in
21028 @subsubheading @value{GDBN} Command
21030 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
21032 @subsubheading Example
21036 -stack-list-locals 0
21037 ^done,locals=[name="A",name="B",name="C"]
21039 -stack-list-locals --all-values
21040 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
21041 @{name="C",value="@{1, 2, 3@}"@}]
21042 -stack-list-locals --simple-values
21043 ^done,locals=[@{name="A",type="int",value="1"@},
21044 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
21049 @subheading The @code{-stack-select-frame} Command
21050 @findex -stack-select-frame
21052 @subsubheading Synopsis
21055 -stack-select-frame @var{framenum}
21058 Change the selected frame. Select a different frame @var{framenum} on
21061 @subsubheading @value{GDBN} Command
21063 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
21064 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
21066 @subsubheading Example
21070 -stack-select-frame 2
21075 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21076 @node GDB/MI Variable Objects
21077 @section @sc{gdb/mi} Variable Objects
21081 @subheading Motivation for Variable Objects in @sc{gdb/mi}
21083 For the implementation of a variable debugger window (locals, watched
21084 expressions, etc.), we are proposing the adaptation of the existing code
21085 used by @code{Insight}.
21087 The two main reasons for that are:
21091 It has been proven in practice (it is already on its second generation).
21094 It will shorten development time (needless to say how important it is
21098 The original interface was designed to be used by Tcl code, so it was
21099 slightly changed so it could be used through @sc{gdb/mi}. This section
21100 describes the @sc{gdb/mi} operations that will be available and gives some
21101 hints about their use.
21103 @emph{Note}: In addition to the set of operations described here, we
21104 expect the @sc{gui} implementation of a variable window to require, at
21105 least, the following operations:
21108 @item @code{-gdb-show} @code{output-radix}
21109 @item @code{-stack-list-arguments}
21110 @item @code{-stack-list-locals}
21111 @item @code{-stack-select-frame}
21116 @subheading Introduction to Variable Objects
21118 @cindex variable objects in @sc{gdb/mi}
21120 Variable objects are "object-oriented" MI interface for examining and
21121 changing values of expressions. Unlike some other MI interfaces that
21122 work with expressions, variable objects are specifically designed for
21123 simple and efficient presentation in the frontend. A variable object
21124 is identified by string name. When a variable object is created, the
21125 frontend specifies the expression for that variable object. The
21126 expression can be a simple variable, or it can be an arbitrary complex
21127 expression, and can even involve CPU registers. After creating a
21128 variable object, the frontend can invoke other variable object
21129 operations---for example to obtain or change the value of a variable
21130 object, or to change display format.
21132 Variable objects have hierarchical tree structure. Any variable object
21133 that corresponds to a composite type, such as structure in C, has
21134 a number of child variable objects, for example corresponding to each
21135 element of a structure. A child variable object can itself have
21136 children, recursively. Recursion ends when we reach
21137 leaf variable objects, which always have built-in types. Child variable
21138 objects are created only by explicit request, so if a frontend
21139 is not interested in the children of a particular variable object, no
21140 child will be created.
21142 For a leaf variable object it is possible to obtain its value as a
21143 string, or set the value from a string. String value can be also
21144 obtained for a non-leaf variable object, but it's generally a string
21145 that only indicates the type of the object, and does not list its
21146 contents. Assignment to a non-leaf variable object is not allowed.
21148 A frontend does not need to read the values of all variable objects each time
21149 the program stops. Instead, MI provides an update command that lists all
21150 variable objects whose values has changed since the last update
21151 operation. This considerably reduces the amount of data that must
21152 be transferred to the frontend. As noted above, children variable
21153 objects are created on demand, and only leaf variable objects have a
21154 real value. As result, gdb will read target memory only for leaf
21155 variables that frontend has created.
21157 The automatic update is not always desirable. For example, a frontend
21158 might want to keep a value of some expression for future reference,
21159 and never update it. For another example, fetching memory is
21160 relatively slow for embedded targets, so a frontend might want
21161 to disable automatic update for the variables that are either not
21162 visible on the screen, or ``closed''. This is possible using so
21163 called ``frozen variable objects''. Such variable objects are never
21164 implicitly updated.
21166 The following is the complete set of @sc{gdb/mi} operations defined to
21167 access this functionality:
21169 @multitable @columnfractions .4 .6
21170 @item @strong{Operation}
21171 @tab @strong{Description}
21173 @item @code{-var-create}
21174 @tab create a variable object
21175 @item @code{-var-delete}
21176 @tab delete the variable object and/or its children
21177 @item @code{-var-set-format}
21178 @tab set the display format of this variable
21179 @item @code{-var-show-format}
21180 @tab show the display format of this variable
21181 @item @code{-var-info-num-children}
21182 @tab tells how many children this object has
21183 @item @code{-var-list-children}
21184 @tab return a list of the object's children
21185 @item @code{-var-info-type}
21186 @tab show the type of this variable object
21187 @item @code{-var-info-expression}
21188 @tab print parent-relative expression that this variable object represents
21189 @item @code{-var-info-path-expression}
21190 @tab print full expression that this variable object represents
21191 @item @code{-var-show-attributes}
21192 @tab is this variable editable? does it exist here?
21193 @item @code{-var-evaluate-expression}
21194 @tab get the value of this variable
21195 @item @code{-var-assign}
21196 @tab set the value of this variable
21197 @item @code{-var-update}
21198 @tab update the variable and its children
21199 @item @code{-var-set-frozen}
21200 @tab set frozeness attribute
21203 In the next subsection we describe each operation in detail and suggest
21204 how it can be used.
21206 @subheading Description And Use of Operations on Variable Objects
21208 @subheading The @code{-var-create} Command
21209 @findex -var-create
21211 @subsubheading Synopsis
21214 -var-create @{@var{name} | "-"@}
21215 @{@var{frame-addr} | "*"@} @var{expression}
21218 This operation creates a variable object, which allows the monitoring of
21219 a variable, the result of an expression, a memory cell or a CPU
21222 The @var{name} parameter is the string by which the object can be
21223 referenced. It must be unique. If @samp{-} is specified, the varobj
21224 system will generate a string ``varNNNNNN'' automatically. It will be
21225 unique provided that one does not specify @var{name} on that format.
21226 The command fails if a duplicate name is found.
21228 The frame under which the expression should be evaluated can be
21229 specified by @var{frame-addr}. A @samp{*} indicates that the current
21230 frame should be used.
21232 @var{expression} is any expression valid on the current language set (must not
21233 begin with a @samp{*}), or one of the following:
21237 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
21240 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
21243 @samp{$@var{regname}} --- a CPU register name
21246 @subsubheading Result
21248 This operation returns the name, number of children and the type of the
21249 object created. Type is returned as a string as the ones generated by
21250 the @value{GDBN} CLI:
21253 name="@var{name}",numchild="N",type="@var{type}"
21257 @subheading The @code{-var-delete} Command
21258 @findex -var-delete
21260 @subsubheading Synopsis
21263 -var-delete [ -c ] @var{name}
21266 Deletes a previously created variable object and all of its children.
21267 With the @samp{-c} option, just deletes the children.
21269 Returns an error if the object @var{name} is not found.
21272 @subheading The @code{-var-set-format} Command
21273 @findex -var-set-format
21275 @subsubheading Synopsis
21278 -var-set-format @var{name} @var{format-spec}
21281 Sets the output format for the value of the object @var{name} to be
21284 @anchor{-var-set-format}
21285 The syntax for the @var{format-spec} is as follows:
21288 @var{format-spec} @expansion{}
21289 @{binary | decimal | hexadecimal | octal | natural@}
21292 The natural format is the default format choosen automatically
21293 based on the variable type (like decimal for an @code{int}, hex
21294 for pointers, etc.).
21296 For a variable with children, the format is set only on the
21297 variable itself, and the children are not affected.
21299 @subheading The @code{-var-show-format} Command
21300 @findex -var-show-format
21302 @subsubheading Synopsis
21305 -var-show-format @var{name}
21308 Returns the format used to display the value of the object @var{name}.
21311 @var{format} @expansion{}
21316 @subheading The @code{-var-info-num-children} Command
21317 @findex -var-info-num-children
21319 @subsubheading Synopsis
21322 -var-info-num-children @var{name}
21325 Returns the number of children of a variable object @var{name}:
21332 @subheading The @code{-var-list-children} Command
21333 @findex -var-list-children
21335 @subsubheading Synopsis
21338 -var-list-children [@var{print-values}] @var{name}
21340 @anchor{-var-list-children}
21342 Return a list of the children of the specified variable object and
21343 create variable objects for them, if they do not already exist. With
21344 a single argument or if @var{print-values} has a value for of 0 or
21345 @code{--no-values}, print only the names of the variables; if
21346 @var{print-values} is 1 or @code{--all-values}, also print their
21347 values; and if it is 2 or @code{--simple-values} print the name and
21348 value for simple data types and just the name for arrays, structures
21351 @subsubheading Example
21355 -var-list-children n
21356 ^done,numchild=@var{n},children=[@{name=@var{name},
21357 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
21359 -var-list-children --all-values n
21360 ^done,numchild=@var{n},children=[@{name=@var{name},
21361 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
21365 @subheading The @code{-var-info-type} Command
21366 @findex -var-info-type
21368 @subsubheading Synopsis
21371 -var-info-type @var{name}
21374 Returns the type of the specified variable @var{name}. The type is
21375 returned as a string in the same format as it is output by the
21379 type=@var{typename}
21383 @subheading The @code{-var-info-expression} Command
21384 @findex -var-info-expression
21386 @subsubheading Synopsis
21389 -var-info-expression @var{name}
21392 Returns a string that is suitable for presenting this
21393 variable object in user interface. The string is generally
21394 not valid expression in the current language, and cannot be evaluated.
21396 For example, if @code{a} is an array, and variable object
21397 @code{A} was created for @code{a}, then we'll get this output:
21400 (gdb) -var-info-expression A.1
21401 ^done,lang="C",exp="1"
21405 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
21407 Note that the output of the @code{-var-list-children} command also
21408 includes those expressions, so the @code{-var-info-expression} command
21411 @subheading The @code{-var-info-path-expression} Command
21412 @findex -var-info-path-expression
21414 @subsubheading Synopsis
21417 -var-info-path-expression @var{name}
21420 Returns an expression that can be evaluated in the current
21421 context and will yield the same value that a variable object has.
21422 Compare this with the @code{-var-info-expression} command, which
21423 result can be used only for UI presentation. Typical use of
21424 the @code{-var-info-path-expression} command is creating a
21425 watchpoint from a variable object.
21427 For example, suppose @code{C} is a C@t{++} class, derived from class
21428 @code{Base}, and that the @code{Base} class has a member called
21429 @code{m_size}. Assume a variable @code{c} is has the type of
21430 @code{C} and a variable object @code{C} was created for variable
21431 @code{c}. Then, we'll get this output:
21433 (gdb) -var-info-path-expression C.Base.public.m_size
21434 ^done,path_expr=((Base)c).m_size)
21437 @subheading The @code{-var-show-attributes} Command
21438 @findex -var-show-attributes
21440 @subsubheading Synopsis
21443 -var-show-attributes @var{name}
21446 List attributes of the specified variable object @var{name}:
21449 status=@var{attr} [ ( ,@var{attr} )* ]
21453 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
21455 @subheading The @code{-var-evaluate-expression} Command
21456 @findex -var-evaluate-expression
21458 @subsubheading Synopsis
21461 -var-evaluate-expression [-f @var{format-spec}] @var{name}
21464 Evaluates the expression that is represented by the specified variable
21465 object and returns its value as a string. The format of the string
21466 can be specified with the @samp{-f} option. The possible values of
21467 this option are the same as for @code{-var-set-format}
21468 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
21469 the current display format will be used. The current display format
21470 can be changed using the @code{-var-set-format} command.
21476 Note that one must invoke @code{-var-list-children} for a variable
21477 before the value of a child variable can be evaluated.
21479 @subheading The @code{-var-assign} Command
21480 @findex -var-assign
21482 @subsubheading Synopsis
21485 -var-assign @var{name} @var{expression}
21488 Assigns the value of @var{expression} to the variable object specified
21489 by @var{name}. The object must be @samp{editable}. If the variable's
21490 value is altered by the assign, the variable will show up in any
21491 subsequent @code{-var-update} list.
21493 @subsubheading Example
21501 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
21505 @subheading The @code{-var-update} Command
21506 @findex -var-update
21508 @subsubheading Synopsis
21511 -var-update [@var{print-values}] @{@var{name} | "*"@}
21514 Reevaluate the expressions corresponding to the variable object
21515 @var{name} and all its direct and indirect children, and return the
21516 list of variable objects whose values have changed; @var{name} must
21517 be a root variable object. Here, ``changed'' means that the result of
21518 @code{-var-evaluate-expression} before and after the
21519 @code{-var-update} is different. If @samp{*} is used as the variable
21520 object names, all existing variable objects are updated, except
21521 for frozen ones (@pxref{-var-set-frozen}). The option
21522 @var{print-values} determines whether both names and values, or just
21523 names are printed. The possible values of this option are the same
21524 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
21525 recommended to use the @samp{--all-values} option, to reduce the
21526 number of MI commands needed on each program stop.
21529 @subsubheading Example
21536 -var-update --all-values var1
21537 ^done,changelist=[@{name="var1",value="3",in_scope="true",
21538 type_changed="false"@}]
21542 @anchor{-var-update}
21543 The field in_scope may take three values:
21547 The variable object's current value is valid.
21550 The variable object does not currently hold a valid value but it may
21551 hold one in the future if its associated expression comes back into
21555 The variable object no longer holds a valid value.
21556 This can occur when the executable file being debugged has changed,
21557 either through recompilation or by using the @value{GDBN} @code{file}
21558 command. The front end should normally choose to delete these variable
21562 In the future new values may be added to this list so the front should
21563 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
21565 @subheading The @code{-var-set-frozen} Command
21566 @findex -var-set-frozen
21567 @anchor{-var-set-frozen}
21569 @subsubheading Synopsis
21572 -var-set-frozen @var{name} @var{flag}
21575 Set the frozenness flag on the variable object @var{name}. The
21576 @var{flag} parameter should be either @samp{1} to make the variable
21577 frozen or @samp{0} to make it unfrozen. If a variable object is
21578 frozen, then neither itself, nor any of its children, are
21579 implicitly updated by @code{-var-update} of
21580 a parent variable or by @code{-var-update *}. Only
21581 @code{-var-update} of the variable itself will update its value and
21582 values of its children. After a variable object is unfrozen, it is
21583 implicitly updated by all subsequent @code{-var-update} operations.
21584 Unfreezing a variable does not update it, only subsequent
21585 @code{-var-update} does.
21587 @subsubheading Example
21591 -var-set-frozen V 1
21597 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21598 @node GDB/MI Data Manipulation
21599 @section @sc{gdb/mi} Data Manipulation
21601 @cindex data manipulation, in @sc{gdb/mi}
21602 @cindex @sc{gdb/mi}, data manipulation
21603 This section describes the @sc{gdb/mi} commands that manipulate data:
21604 examine memory and registers, evaluate expressions, etc.
21606 @c REMOVED FROM THE INTERFACE.
21607 @c @subheading -data-assign
21608 @c Change the value of a program variable. Plenty of side effects.
21609 @c @subsubheading GDB Command
21611 @c @subsubheading Example
21614 @subheading The @code{-data-disassemble} Command
21615 @findex -data-disassemble
21617 @subsubheading Synopsis
21621 [ -s @var{start-addr} -e @var{end-addr} ]
21622 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
21630 @item @var{start-addr}
21631 is the beginning address (or @code{$pc})
21632 @item @var{end-addr}
21634 @item @var{filename}
21635 is the name of the file to disassemble
21636 @item @var{linenum}
21637 is the line number to disassemble around
21639 is the number of disassembly lines to be produced. If it is -1,
21640 the whole function will be disassembled, in case no @var{end-addr} is
21641 specified. If @var{end-addr} is specified as a non-zero value, and
21642 @var{lines} is lower than the number of disassembly lines between
21643 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
21644 displayed; if @var{lines} is higher than the number of lines between
21645 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
21648 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
21652 @subsubheading Result
21654 The output for each instruction is composed of four fields:
21663 Note that whatever included in the instruction field, is not manipulated
21664 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
21666 @subsubheading @value{GDBN} Command
21668 There's no direct mapping from this command to the CLI.
21670 @subsubheading Example
21672 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
21676 -data-disassemble -s $pc -e "$pc + 20" -- 0
21679 @{address="0x000107c0",func-name="main",offset="4",
21680 inst="mov 2, %o0"@},
21681 @{address="0x000107c4",func-name="main",offset="8",
21682 inst="sethi %hi(0x11800), %o2"@},
21683 @{address="0x000107c8",func-name="main",offset="12",
21684 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
21685 @{address="0x000107cc",func-name="main",offset="16",
21686 inst="sethi %hi(0x11800), %o2"@},
21687 @{address="0x000107d0",func-name="main",offset="20",
21688 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
21692 Disassemble the whole @code{main} function. Line 32 is part of
21696 -data-disassemble -f basics.c -l 32 -- 0
21698 @{address="0x000107bc",func-name="main",offset="0",
21699 inst="save %sp, -112, %sp"@},
21700 @{address="0x000107c0",func-name="main",offset="4",
21701 inst="mov 2, %o0"@},
21702 @{address="0x000107c4",func-name="main",offset="8",
21703 inst="sethi %hi(0x11800), %o2"@},
21705 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
21706 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
21710 Disassemble 3 instructions from the start of @code{main}:
21714 -data-disassemble -f basics.c -l 32 -n 3 -- 0
21716 @{address="0x000107bc",func-name="main",offset="0",
21717 inst="save %sp, -112, %sp"@},
21718 @{address="0x000107c0",func-name="main",offset="4",
21719 inst="mov 2, %o0"@},
21720 @{address="0x000107c4",func-name="main",offset="8",
21721 inst="sethi %hi(0x11800), %o2"@}]
21725 Disassemble 3 instructions from the start of @code{main} in mixed mode:
21729 -data-disassemble -f basics.c -l 32 -n 3 -- 1
21731 src_and_asm_line=@{line="31",
21732 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
21733 testsuite/gdb.mi/basics.c",line_asm_insn=[
21734 @{address="0x000107bc",func-name="main",offset="0",
21735 inst="save %sp, -112, %sp"@}]@},
21736 src_and_asm_line=@{line="32",
21737 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
21738 testsuite/gdb.mi/basics.c",line_asm_insn=[
21739 @{address="0x000107c0",func-name="main",offset="4",
21740 inst="mov 2, %o0"@},
21741 @{address="0x000107c4",func-name="main",offset="8",
21742 inst="sethi %hi(0x11800), %o2"@}]@}]
21747 @subheading The @code{-data-evaluate-expression} Command
21748 @findex -data-evaluate-expression
21750 @subsubheading Synopsis
21753 -data-evaluate-expression @var{expr}
21756 Evaluate @var{expr} as an expression. The expression could contain an
21757 inferior function call. The function call will execute synchronously.
21758 If the expression contains spaces, it must be enclosed in double quotes.
21760 @subsubheading @value{GDBN} Command
21762 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
21763 @samp{call}. In @code{gdbtk} only, there's a corresponding
21764 @samp{gdb_eval} command.
21766 @subsubheading Example
21768 In the following example, the numbers that precede the commands are the
21769 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
21770 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
21774 211-data-evaluate-expression A
21777 311-data-evaluate-expression &A
21778 311^done,value="0xefffeb7c"
21780 411-data-evaluate-expression A+3
21783 511-data-evaluate-expression "A + 3"
21789 @subheading The @code{-data-list-changed-registers} Command
21790 @findex -data-list-changed-registers
21792 @subsubheading Synopsis
21795 -data-list-changed-registers
21798 Display a list of the registers that have changed.
21800 @subsubheading @value{GDBN} Command
21802 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
21803 has the corresponding command @samp{gdb_changed_register_list}.
21805 @subsubheading Example
21807 On a PPC MBX board:
21815 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
21816 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
21819 -data-list-changed-registers
21820 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
21821 "10","11","13","14","15","16","17","18","19","20","21","22","23",
21822 "24","25","26","27","28","30","31","64","65","66","67","69"]
21827 @subheading The @code{-data-list-register-names} Command
21828 @findex -data-list-register-names
21830 @subsubheading Synopsis
21833 -data-list-register-names [ ( @var{regno} )+ ]
21836 Show a list of register names for the current target. If no arguments
21837 are given, it shows a list of the names of all the registers. If
21838 integer numbers are given as arguments, it will print a list of the
21839 names of the registers corresponding to the arguments. To ensure
21840 consistency between a register name and its number, the output list may
21841 include empty register names.
21843 @subsubheading @value{GDBN} Command
21845 @value{GDBN} does not have a command which corresponds to
21846 @samp{-data-list-register-names}. In @code{gdbtk} there is a
21847 corresponding command @samp{gdb_regnames}.
21849 @subsubheading Example
21851 For the PPC MBX board:
21854 -data-list-register-names
21855 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
21856 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
21857 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
21858 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
21859 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
21860 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
21861 "", "pc","ps","cr","lr","ctr","xer"]
21863 -data-list-register-names 1 2 3
21864 ^done,register-names=["r1","r2","r3"]
21868 @subheading The @code{-data-list-register-values} Command
21869 @findex -data-list-register-values
21871 @subsubheading Synopsis
21874 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
21877 Display the registers' contents. @var{fmt} is the format according to
21878 which the registers' contents are to be returned, followed by an optional
21879 list of numbers specifying the registers to display. A missing list of
21880 numbers indicates that the contents of all the registers must be returned.
21882 Allowed formats for @var{fmt} are:
21899 @subsubheading @value{GDBN} Command
21901 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
21902 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
21904 @subsubheading Example
21906 For a PPC MBX board (note: line breaks are for readability only, they
21907 don't appear in the actual output):
21911 -data-list-register-values r 64 65
21912 ^done,register-values=[@{number="64",value="0xfe00a300"@},
21913 @{number="65",value="0x00029002"@}]
21915 -data-list-register-values x
21916 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
21917 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
21918 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
21919 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
21920 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
21921 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
21922 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
21923 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
21924 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
21925 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
21926 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
21927 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
21928 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
21929 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
21930 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
21931 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
21932 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
21933 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
21934 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
21935 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
21936 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
21937 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
21938 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
21939 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
21940 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
21941 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
21942 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
21943 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
21944 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
21945 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
21946 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
21947 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
21948 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
21949 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
21950 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
21951 @{number="69",value="0x20002b03"@}]
21956 @subheading The @code{-data-read-memory} Command
21957 @findex -data-read-memory
21959 @subsubheading Synopsis
21962 -data-read-memory [ -o @var{byte-offset} ]
21963 @var{address} @var{word-format} @var{word-size}
21964 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
21971 @item @var{address}
21972 An expression specifying the address of the first memory word to be
21973 read. Complex expressions containing embedded white space should be
21974 quoted using the C convention.
21976 @item @var{word-format}
21977 The format to be used to print the memory words. The notation is the
21978 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
21981 @item @var{word-size}
21982 The size of each memory word in bytes.
21984 @item @var{nr-rows}
21985 The number of rows in the output table.
21987 @item @var{nr-cols}
21988 The number of columns in the output table.
21991 If present, indicates that each row should include an @sc{ascii} dump. The
21992 value of @var{aschar} is used as a padding character when a byte is not a
21993 member of the printable @sc{ascii} character set (printable @sc{ascii}
21994 characters are those whose code is between 32 and 126, inclusively).
21996 @item @var{byte-offset}
21997 An offset to add to the @var{address} before fetching memory.
22000 This command displays memory contents as a table of @var{nr-rows} by
22001 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
22002 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
22003 (returned as @samp{total-bytes}). Should less than the requested number
22004 of bytes be returned by the target, the missing words are identified
22005 using @samp{N/A}. The number of bytes read from the target is returned
22006 in @samp{nr-bytes} and the starting address used to read memory in
22009 The address of the next/previous row or page is available in
22010 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
22013 @subsubheading @value{GDBN} Command
22015 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
22016 @samp{gdb_get_mem} memory read command.
22018 @subsubheading Example
22020 Read six bytes of memory starting at @code{bytes+6} but then offset by
22021 @code{-6} bytes. Format as three rows of two columns. One byte per
22022 word. Display each word in hex.
22026 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
22027 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
22028 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
22029 prev-page="0x0000138a",memory=[
22030 @{addr="0x00001390",data=["0x00","0x01"]@},
22031 @{addr="0x00001392",data=["0x02","0x03"]@},
22032 @{addr="0x00001394",data=["0x04","0x05"]@}]
22036 Read two bytes of memory starting at address @code{shorts + 64} and
22037 display as a single word formatted in decimal.
22041 5-data-read-memory shorts+64 d 2 1 1
22042 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
22043 next-row="0x00001512",prev-row="0x0000150e",
22044 next-page="0x00001512",prev-page="0x0000150e",memory=[
22045 @{addr="0x00001510",data=["128"]@}]
22049 Read thirty two bytes of memory starting at @code{bytes+16} and format
22050 as eight rows of four columns. Include a string encoding with @samp{x}
22051 used as the non-printable character.
22055 4-data-read-memory bytes+16 x 1 8 4 x
22056 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
22057 next-row="0x000013c0",prev-row="0x0000139c",
22058 next-page="0x000013c0",prev-page="0x00001380",memory=[
22059 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
22060 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
22061 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
22062 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
22063 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
22064 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
22065 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
22066 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
22070 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22071 @node GDB/MI Tracepoint Commands
22072 @section @sc{gdb/mi} Tracepoint Commands
22074 The tracepoint commands are not yet implemented.
22076 @c @subheading -trace-actions
22078 @c @subheading -trace-delete
22080 @c @subheading -trace-disable
22082 @c @subheading -trace-dump
22084 @c @subheading -trace-enable
22086 @c @subheading -trace-exists
22088 @c @subheading -trace-find
22090 @c @subheading -trace-frame-number
22092 @c @subheading -trace-info
22094 @c @subheading -trace-insert
22096 @c @subheading -trace-list
22098 @c @subheading -trace-pass-count
22100 @c @subheading -trace-save
22102 @c @subheading -trace-start
22104 @c @subheading -trace-stop
22107 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22108 @node GDB/MI Symbol Query
22109 @section @sc{gdb/mi} Symbol Query Commands
22112 @subheading The @code{-symbol-info-address} Command
22113 @findex -symbol-info-address
22115 @subsubheading Synopsis
22118 -symbol-info-address @var{symbol}
22121 Describe where @var{symbol} is stored.
22123 @subsubheading @value{GDBN} Command
22125 The corresponding @value{GDBN} command is @samp{info address}.
22127 @subsubheading Example
22131 @subheading The @code{-symbol-info-file} Command
22132 @findex -symbol-info-file
22134 @subsubheading Synopsis
22140 Show the file for the symbol.
22142 @subsubheading @value{GDBN} Command
22144 There's no equivalent @value{GDBN} command. @code{gdbtk} has
22145 @samp{gdb_find_file}.
22147 @subsubheading Example
22151 @subheading The @code{-symbol-info-function} Command
22152 @findex -symbol-info-function
22154 @subsubheading Synopsis
22157 -symbol-info-function
22160 Show which function the symbol lives in.
22162 @subsubheading @value{GDBN} Command
22164 @samp{gdb_get_function} in @code{gdbtk}.
22166 @subsubheading Example
22170 @subheading The @code{-symbol-info-line} Command
22171 @findex -symbol-info-line
22173 @subsubheading Synopsis
22179 Show the core addresses of the code for a source line.
22181 @subsubheading @value{GDBN} Command
22183 The corresponding @value{GDBN} command is @samp{info line}.
22184 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
22186 @subsubheading Example
22190 @subheading The @code{-symbol-info-symbol} Command
22191 @findex -symbol-info-symbol
22193 @subsubheading Synopsis
22196 -symbol-info-symbol @var{addr}
22199 Describe what symbol is at location @var{addr}.
22201 @subsubheading @value{GDBN} Command
22203 The corresponding @value{GDBN} command is @samp{info symbol}.
22205 @subsubheading Example
22209 @subheading The @code{-symbol-list-functions} Command
22210 @findex -symbol-list-functions
22212 @subsubheading Synopsis
22215 -symbol-list-functions
22218 List the functions in the executable.
22220 @subsubheading @value{GDBN} Command
22222 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
22223 @samp{gdb_search} in @code{gdbtk}.
22225 @subsubheading Example
22229 @subheading The @code{-symbol-list-lines} Command
22230 @findex -symbol-list-lines
22232 @subsubheading Synopsis
22235 -symbol-list-lines @var{filename}
22238 Print the list of lines that contain code and their associated program
22239 addresses for the given source filename. The entries are sorted in
22240 ascending PC order.
22242 @subsubheading @value{GDBN} Command
22244 There is no corresponding @value{GDBN} command.
22246 @subsubheading Example
22249 -symbol-list-lines basics.c
22250 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
22255 @subheading The @code{-symbol-list-types} Command
22256 @findex -symbol-list-types
22258 @subsubheading Synopsis
22264 List all the type names.
22266 @subsubheading @value{GDBN} Command
22268 The corresponding commands are @samp{info types} in @value{GDBN},
22269 @samp{gdb_search} in @code{gdbtk}.
22271 @subsubheading Example
22275 @subheading The @code{-symbol-list-variables} Command
22276 @findex -symbol-list-variables
22278 @subsubheading Synopsis
22281 -symbol-list-variables
22284 List all the global and static variable names.
22286 @subsubheading @value{GDBN} Command
22288 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
22290 @subsubheading Example
22294 @subheading The @code{-symbol-locate} Command
22295 @findex -symbol-locate
22297 @subsubheading Synopsis
22303 @subsubheading @value{GDBN} Command
22305 @samp{gdb_loc} in @code{gdbtk}.
22307 @subsubheading Example
22311 @subheading The @code{-symbol-type} Command
22312 @findex -symbol-type
22314 @subsubheading Synopsis
22317 -symbol-type @var{variable}
22320 Show type of @var{variable}.
22322 @subsubheading @value{GDBN} Command
22324 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
22325 @samp{gdb_obj_variable}.
22327 @subsubheading Example
22331 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22332 @node GDB/MI File Commands
22333 @section @sc{gdb/mi} File Commands
22335 This section describes the GDB/MI commands to specify executable file names
22336 and to read in and obtain symbol table information.
22338 @subheading The @code{-file-exec-and-symbols} Command
22339 @findex -file-exec-and-symbols
22341 @subsubheading Synopsis
22344 -file-exec-and-symbols @var{file}
22347 Specify the executable file to be debugged. This file is the one from
22348 which the symbol table is also read. If no file is specified, the
22349 command clears the executable and symbol information. If breakpoints
22350 are set when using this command with no arguments, @value{GDBN} will produce
22351 error messages. Otherwise, no output is produced, except a completion
22354 @subsubheading @value{GDBN} Command
22356 The corresponding @value{GDBN} command is @samp{file}.
22358 @subsubheading Example
22362 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22368 @subheading The @code{-file-exec-file} Command
22369 @findex -file-exec-file
22371 @subsubheading Synopsis
22374 -file-exec-file @var{file}
22377 Specify the executable file to be debugged. Unlike
22378 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
22379 from this file. If used without argument, @value{GDBN} clears the information
22380 about the executable file. No output is produced, except a completion
22383 @subsubheading @value{GDBN} Command
22385 The corresponding @value{GDBN} command is @samp{exec-file}.
22387 @subsubheading Example
22391 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22397 @subheading The @code{-file-list-exec-sections} Command
22398 @findex -file-list-exec-sections
22400 @subsubheading Synopsis
22403 -file-list-exec-sections
22406 List the sections of the current executable file.
22408 @subsubheading @value{GDBN} Command
22410 The @value{GDBN} command @samp{info file} shows, among the rest, the same
22411 information as this command. @code{gdbtk} has a corresponding command
22412 @samp{gdb_load_info}.
22414 @subsubheading Example
22418 @subheading The @code{-file-list-exec-source-file} Command
22419 @findex -file-list-exec-source-file
22421 @subsubheading Synopsis
22424 -file-list-exec-source-file
22427 List the line number, the current source file, and the absolute path
22428 to the current source file for the current executable. The macro
22429 information field has a value of @samp{1} or @samp{0} depending on
22430 whether or not the file includes preprocessor macro information.
22432 @subsubheading @value{GDBN} Command
22434 The @value{GDBN} equivalent is @samp{info source}
22436 @subsubheading Example
22440 123-file-list-exec-source-file
22441 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
22446 @subheading The @code{-file-list-exec-source-files} Command
22447 @findex -file-list-exec-source-files
22449 @subsubheading Synopsis
22452 -file-list-exec-source-files
22455 List the source files for the current executable.
22457 It will always output the filename, but only when @value{GDBN} can find
22458 the absolute file name of a source file, will it output the fullname.
22460 @subsubheading @value{GDBN} Command
22462 The @value{GDBN} equivalent is @samp{info sources}.
22463 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
22465 @subsubheading Example
22468 -file-list-exec-source-files
22470 @{file=foo.c,fullname=/home/foo.c@},
22471 @{file=/home/bar.c,fullname=/home/bar.c@},
22472 @{file=gdb_could_not_find_fullpath.c@}]
22476 @subheading The @code{-file-list-shared-libraries} Command
22477 @findex -file-list-shared-libraries
22479 @subsubheading Synopsis
22482 -file-list-shared-libraries
22485 List the shared libraries in the program.
22487 @subsubheading @value{GDBN} Command
22489 The corresponding @value{GDBN} command is @samp{info shared}.
22491 @subsubheading Example
22495 @subheading The @code{-file-list-symbol-files} Command
22496 @findex -file-list-symbol-files
22498 @subsubheading Synopsis
22501 -file-list-symbol-files
22506 @subsubheading @value{GDBN} Command
22508 The corresponding @value{GDBN} command is @samp{info file} (part of it).
22510 @subsubheading Example
22514 @subheading The @code{-file-symbol-file} Command
22515 @findex -file-symbol-file
22517 @subsubheading Synopsis
22520 -file-symbol-file @var{file}
22523 Read symbol table info from the specified @var{file} argument. When
22524 used without arguments, clears @value{GDBN}'s symbol table info. No output is
22525 produced, except for a completion notification.
22527 @subsubheading @value{GDBN} Command
22529 The corresponding @value{GDBN} command is @samp{symbol-file}.
22531 @subsubheading Example
22535 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22541 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22542 @node GDB/MI Memory Overlay Commands
22543 @section @sc{gdb/mi} Memory Overlay Commands
22545 The memory overlay commands are not implemented.
22547 @c @subheading -overlay-auto
22549 @c @subheading -overlay-list-mapping-state
22551 @c @subheading -overlay-list-overlays
22553 @c @subheading -overlay-map
22555 @c @subheading -overlay-off
22557 @c @subheading -overlay-on
22559 @c @subheading -overlay-unmap
22561 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22562 @node GDB/MI Signal Handling Commands
22563 @section @sc{gdb/mi} Signal Handling Commands
22565 Signal handling commands are not implemented.
22567 @c @subheading -signal-handle
22569 @c @subheading -signal-list-handle-actions
22571 @c @subheading -signal-list-signal-types
22575 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22576 @node GDB/MI Target Manipulation
22577 @section @sc{gdb/mi} Target Manipulation Commands
22580 @subheading The @code{-target-attach} Command
22581 @findex -target-attach
22583 @subsubheading Synopsis
22586 -target-attach @var{pid} | @var{file}
22589 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
22591 @subsubheading @value{GDBN} Command
22593 The corresponding @value{GDBN} command is @samp{attach}.
22595 @subsubheading Example
22599 =thread-created,id="1"
22600 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
22605 @subheading The @code{-target-compare-sections} Command
22606 @findex -target-compare-sections
22608 @subsubheading Synopsis
22611 -target-compare-sections [ @var{section} ]
22614 Compare data of section @var{section} on target to the exec file.
22615 Without the argument, all sections are compared.
22617 @subsubheading @value{GDBN} Command
22619 The @value{GDBN} equivalent is @samp{compare-sections}.
22621 @subsubheading Example
22625 @subheading The @code{-target-detach} Command
22626 @findex -target-detach
22628 @subsubheading Synopsis
22634 Detach from the remote target which normally resumes its execution.
22637 @subsubheading @value{GDBN} Command
22639 The corresponding @value{GDBN} command is @samp{detach}.
22641 @subsubheading Example
22651 @subheading The @code{-target-disconnect} Command
22652 @findex -target-disconnect
22654 @subsubheading Synopsis
22660 Disconnect from the remote target. There's no output and the target is
22661 generally not resumed.
22663 @subsubheading @value{GDBN} Command
22665 The corresponding @value{GDBN} command is @samp{disconnect}.
22667 @subsubheading Example
22677 @subheading The @code{-target-download} Command
22678 @findex -target-download
22680 @subsubheading Synopsis
22686 Loads the executable onto the remote target.
22687 It prints out an update message every half second, which includes the fields:
22691 The name of the section.
22693 The size of what has been sent so far for that section.
22695 The size of the section.
22697 The total size of what was sent so far (the current and the previous sections).
22699 The size of the overall executable to download.
22703 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
22704 @sc{gdb/mi} Output Syntax}).
22706 In addition, it prints the name and size of the sections, as they are
22707 downloaded. These messages include the following fields:
22711 The name of the section.
22713 The size of the section.
22715 The size of the overall executable to download.
22719 At the end, a summary is printed.
22721 @subsubheading @value{GDBN} Command
22723 The corresponding @value{GDBN} command is @samp{load}.
22725 @subsubheading Example
22727 Note: each status message appears on a single line. Here the messages
22728 have been broken down so that they can fit onto a page.
22733 +download,@{section=".text",section-size="6668",total-size="9880"@}
22734 +download,@{section=".text",section-sent="512",section-size="6668",
22735 total-sent="512",total-size="9880"@}
22736 +download,@{section=".text",section-sent="1024",section-size="6668",
22737 total-sent="1024",total-size="9880"@}
22738 +download,@{section=".text",section-sent="1536",section-size="6668",
22739 total-sent="1536",total-size="9880"@}
22740 +download,@{section=".text",section-sent="2048",section-size="6668",
22741 total-sent="2048",total-size="9880"@}
22742 +download,@{section=".text",section-sent="2560",section-size="6668",
22743 total-sent="2560",total-size="9880"@}
22744 +download,@{section=".text",section-sent="3072",section-size="6668",
22745 total-sent="3072",total-size="9880"@}
22746 +download,@{section=".text",section-sent="3584",section-size="6668",
22747 total-sent="3584",total-size="9880"@}
22748 +download,@{section=".text",section-sent="4096",section-size="6668",
22749 total-sent="4096",total-size="9880"@}
22750 +download,@{section=".text",section-sent="4608",section-size="6668",
22751 total-sent="4608",total-size="9880"@}
22752 +download,@{section=".text",section-sent="5120",section-size="6668",
22753 total-sent="5120",total-size="9880"@}
22754 +download,@{section=".text",section-sent="5632",section-size="6668",
22755 total-sent="5632",total-size="9880"@}
22756 +download,@{section=".text",section-sent="6144",section-size="6668",
22757 total-sent="6144",total-size="9880"@}
22758 +download,@{section=".text",section-sent="6656",section-size="6668",
22759 total-sent="6656",total-size="9880"@}
22760 +download,@{section=".init",section-size="28",total-size="9880"@}
22761 +download,@{section=".fini",section-size="28",total-size="9880"@}
22762 +download,@{section=".data",section-size="3156",total-size="9880"@}
22763 +download,@{section=".data",section-sent="512",section-size="3156",
22764 total-sent="7236",total-size="9880"@}
22765 +download,@{section=".data",section-sent="1024",section-size="3156",
22766 total-sent="7748",total-size="9880"@}
22767 +download,@{section=".data",section-sent="1536",section-size="3156",
22768 total-sent="8260",total-size="9880"@}
22769 +download,@{section=".data",section-sent="2048",section-size="3156",
22770 total-sent="8772",total-size="9880"@}
22771 +download,@{section=".data",section-sent="2560",section-size="3156",
22772 total-sent="9284",total-size="9880"@}
22773 +download,@{section=".data",section-sent="3072",section-size="3156",
22774 total-sent="9796",total-size="9880"@}
22775 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
22781 @subheading The @code{-target-exec-status} Command
22782 @findex -target-exec-status
22784 @subsubheading Synopsis
22787 -target-exec-status
22790 Provide information on the state of the target (whether it is running or
22791 not, for instance).
22793 @subsubheading @value{GDBN} Command
22795 There's no equivalent @value{GDBN} command.
22797 @subsubheading Example
22801 @subheading The @code{-target-list-available-targets} Command
22802 @findex -target-list-available-targets
22804 @subsubheading Synopsis
22807 -target-list-available-targets
22810 List the possible targets to connect to.
22812 @subsubheading @value{GDBN} Command
22814 The corresponding @value{GDBN} command is @samp{help target}.
22816 @subsubheading Example
22820 @subheading The @code{-target-list-current-targets} Command
22821 @findex -target-list-current-targets
22823 @subsubheading Synopsis
22826 -target-list-current-targets
22829 Describe the current target.
22831 @subsubheading @value{GDBN} Command
22833 The corresponding information is printed by @samp{info file} (among
22836 @subsubheading Example
22840 @subheading The @code{-target-list-parameters} Command
22841 @findex -target-list-parameters
22843 @subsubheading Synopsis
22846 -target-list-parameters
22851 @subsubheading @value{GDBN} Command
22855 @subsubheading Example
22859 @subheading The @code{-target-select} Command
22860 @findex -target-select
22862 @subsubheading Synopsis
22865 -target-select @var{type} @var{parameters @dots{}}
22868 Connect @value{GDBN} to the remote target. This command takes two args:
22872 The type of target, for instance @samp{remote}, etc.
22873 @item @var{parameters}
22874 Device names, host names and the like. @xref{Target Commands, ,
22875 Commands for Managing Targets}, for more details.
22878 The output is a connection notification, followed by the address at
22879 which the target program is, in the following form:
22882 ^connected,addr="@var{address}",func="@var{function name}",
22883 args=[@var{arg list}]
22886 @subsubheading @value{GDBN} Command
22888 The corresponding @value{GDBN} command is @samp{target}.
22890 @subsubheading Example
22894 -target-select remote /dev/ttya
22895 ^connected,addr="0xfe00a300",func="??",args=[]
22899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22900 @node GDB/MI File Transfer Commands
22901 @section @sc{gdb/mi} File Transfer Commands
22904 @subheading The @code{-target-file-put} Command
22905 @findex -target-file-put
22907 @subsubheading Synopsis
22910 -target-file-put @var{hostfile} @var{targetfile}
22913 Copy file @var{hostfile} from the host system (the machine running
22914 @value{GDBN}) to @var{targetfile} on the target system.
22916 @subsubheading @value{GDBN} Command
22918 The corresponding @value{GDBN} command is @samp{remote put}.
22920 @subsubheading Example
22924 -target-file-put localfile remotefile
22930 @subheading The @code{-target-file-get} Command
22931 @findex -target-file-get
22933 @subsubheading Synopsis
22936 -target-file-get @var{targetfile} @var{hostfile}
22939 Copy file @var{targetfile} from the target system to @var{hostfile}
22940 on the host system.
22942 @subsubheading @value{GDBN} Command
22944 The corresponding @value{GDBN} command is @samp{remote get}.
22946 @subsubheading Example
22950 -target-file-get remotefile localfile
22956 @subheading The @code{-target-file-delete} Command
22957 @findex -target-file-delete
22959 @subsubheading Synopsis
22962 -target-file-delete @var{targetfile}
22965 Delete @var{targetfile} from the target system.
22967 @subsubheading @value{GDBN} Command
22969 The corresponding @value{GDBN} command is @samp{remote delete}.
22971 @subsubheading Example
22975 -target-file-delete remotefile
22981 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22982 @node GDB/MI Miscellaneous Commands
22983 @section Miscellaneous @sc{gdb/mi} Commands
22985 @c @subheading -gdb-complete
22987 @subheading The @code{-gdb-exit} Command
22990 @subsubheading Synopsis
22996 Exit @value{GDBN} immediately.
22998 @subsubheading @value{GDBN} Command
23000 Approximately corresponds to @samp{quit}.
23002 @subsubheading Example
23011 @subheading The @code{-exec-abort} Command
23012 @findex -exec-abort
23014 @subsubheading Synopsis
23020 Kill the inferior running program.
23022 @subsubheading @value{GDBN} Command
23024 The corresponding @value{GDBN} command is @samp{kill}.
23026 @subsubheading Example
23030 @subheading The @code{-gdb-set} Command
23033 @subsubheading Synopsis
23039 Set an internal @value{GDBN} variable.
23040 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
23042 @subsubheading @value{GDBN} Command
23044 The corresponding @value{GDBN} command is @samp{set}.
23046 @subsubheading Example
23056 @subheading The @code{-gdb-show} Command
23059 @subsubheading Synopsis
23065 Show the current value of a @value{GDBN} variable.
23067 @subsubheading @value{GDBN} Command
23069 The corresponding @value{GDBN} command is @samp{show}.
23071 @subsubheading Example
23080 @c @subheading -gdb-source
23083 @subheading The @code{-gdb-version} Command
23084 @findex -gdb-version
23086 @subsubheading Synopsis
23092 Show version information for @value{GDBN}. Used mostly in testing.
23094 @subsubheading @value{GDBN} Command
23096 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
23097 default shows this information when you start an interactive session.
23099 @subsubheading Example
23101 @c This example modifies the actual output from GDB to avoid overfull
23107 ~Copyright 2000 Free Software Foundation, Inc.
23108 ~GDB is free software, covered by the GNU General Public License, and
23109 ~you are welcome to change it and/or distribute copies of it under
23110 ~ certain conditions.
23111 ~Type "show copying" to see the conditions.
23112 ~There is absolutely no warranty for GDB. Type "show warranty" for
23114 ~This GDB was configured as
23115 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
23120 @subheading The @code{-list-features} Command
23121 @findex -list-features
23123 Returns a list of particular features of the MI protocol that
23124 this version of gdb implements. A feature can be a command,
23125 or a new field in an output of some command, or even an
23126 important bugfix. While a frontend can sometimes detect presence
23127 of a feature at runtime, it is easier to perform detection at debugger
23130 The command returns a list of strings, with each string naming an
23131 available feature. Each returned string is just a name, it does not
23132 have any internal structure. The list of possible feature names
23138 (gdb) -list-features
23139 ^done,result=["feature1","feature2"]
23142 The current list of features is:
23145 @item frozen-varobjs
23146 Indicates presence of the @code{-var-set-frozen} command, as well
23147 as possible presense of the @code{frozen} field in the output
23148 of @code{-varobj-create}.
23149 @item pending-breakpoints
23150 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
23152 Indicates presence of the @code{-thread-info} command.
23156 @subheading The @code{-list-target-features} Command
23157 @findex -list-target-features
23159 Returns a list of particular features that are supported by the
23160 target. Those features affect the permitted MI commands, but
23161 unlike the features reported by the @code{-list-features} command, the
23162 features depend on which target GDB is using at the moment. Whenever
23163 a target can change, due to commands such as @code{-target-select},
23164 @code{-target-attach} or @code{-exec-run}, the list of target features
23165 may change, and the frontend should obtain it again.
23169 (gdb) -list-features
23170 ^done,result=["async"]
23173 The current list of features is:
23177 Indicates that the target is capable of asynchronous command
23178 execution, which means that @value{GDBN} will accept further commands
23179 while the target is running.
23184 @subheading The @code{-interpreter-exec} Command
23185 @findex -interpreter-exec
23187 @subheading Synopsis
23190 -interpreter-exec @var{interpreter} @var{command}
23192 @anchor{-interpreter-exec}
23194 Execute the specified @var{command} in the given @var{interpreter}.
23196 @subheading @value{GDBN} Command
23198 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
23200 @subheading Example
23204 -interpreter-exec console "break main"
23205 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
23206 &"During symbol reading, bad structure-type format.\n"
23207 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
23212 @subheading The @code{-inferior-tty-set} Command
23213 @findex -inferior-tty-set
23215 @subheading Synopsis
23218 -inferior-tty-set /dev/pts/1
23221 Set terminal for future runs of the program being debugged.
23223 @subheading @value{GDBN} Command
23225 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
23227 @subheading Example
23231 -inferior-tty-set /dev/pts/1
23236 @subheading The @code{-inferior-tty-show} Command
23237 @findex -inferior-tty-show
23239 @subheading Synopsis
23245 Show terminal for future runs of program being debugged.
23247 @subheading @value{GDBN} Command
23249 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
23251 @subheading Example
23255 -inferior-tty-set /dev/pts/1
23259 ^done,inferior_tty_terminal="/dev/pts/1"
23263 @subheading The @code{-enable-timings} Command
23264 @findex -enable-timings
23266 @subheading Synopsis
23269 -enable-timings [yes | no]
23272 Toggle the printing of the wallclock, user and system times for an MI
23273 command as a field in its output. This command is to help frontend
23274 developers optimize the performance of their code. No argument is
23275 equivalent to @samp{yes}.
23277 @subheading @value{GDBN} Command
23281 @subheading Example
23289 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23290 addr="0x080484ed",func="main",file="myprog.c",
23291 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
23292 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
23300 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
23301 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
23302 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
23303 fullname="/home/nickrob/myprog.c",line="73"@}
23308 @chapter @value{GDBN} Annotations
23310 This chapter describes annotations in @value{GDBN}. Annotations were
23311 designed to interface @value{GDBN} to graphical user interfaces or other
23312 similar programs which want to interact with @value{GDBN} at a
23313 relatively high level.
23315 The annotation mechanism has largely been superseded by @sc{gdb/mi}
23319 This is Edition @value{EDITION}, @value{DATE}.
23323 * Annotations Overview:: What annotations are; the general syntax.
23324 * Server Prefix:: Issuing a command without affecting user state.
23325 * Prompting:: Annotations marking @value{GDBN}'s need for input.
23326 * Errors:: Annotations for error messages.
23327 * Invalidation:: Some annotations describe things now invalid.
23328 * Annotations for Running::
23329 Whether the program is running, how it stopped, etc.
23330 * Source Annotations:: Annotations describing source code.
23333 @node Annotations Overview
23334 @section What is an Annotation?
23335 @cindex annotations
23337 Annotations start with a newline character, two @samp{control-z}
23338 characters, and the name of the annotation. If there is no additional
23339 information associated with this annotation, the name of the annotation
23340 is followed immediately by a newline. If there is additional
23341 information, the name of the annotation is followed by a space, the
23342 additional information, and a newline. The additional information
23343 cannot contain newline characters.
23345 Any output not beginning with a newline and two @samp{control-z}
23346 characters denotes literal output from @value{GDBN}. Currently there is
23347 no need for @value{GDBN} to output a newline followed by two
23348 @samp{control-z} characters, but if there was such a need, the
23349 annotations could be extended with an @samp{escape} annotation which
23350 means those three characters as output.
23352 The annotation @var{level}, which is specified using the
23353 @option{--annotate} command line option (@pxref{Mode Options}), controls
23354 how much information @value{GDBN} prints together with its prompt,
23355 values of expressions, source lines, and other types of output. Level 0
23356 is for no annotations, level 1 is for use when @value{GDBN} is run as a
23357 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
23358 for programs that control @value{GDBN}, and level 2 annotations have
23359 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
23360 Interface, annotate, GDB's Obsolete Annotations}).
23363 @kindex set annotate
23364 @item set annotate @var{level}
23365 The @value{GDBN} command @code{set annotate} sets the level of
23366 annotations to the specified @var{level}.
23368 @item show annotate
23369 @kindex show annotate
23370 Show the current annotation level.
23373 This chapter describes level 3 annotations.
23375 A simple example of starting up @value{GDBN} with annotations is:
23378 $ @kbd{gdb --annotate=3}
23380 Copyright 2003 Free Software Foundation, Inc.
23381 GDB is free software, covered by the GNU General Public License,
23382 and you are welcome to change it and/or distribute copies of it
23383 under certain conditions.
23384 Type "show copying" to see the conditions.
23385 There is absolutely no warranty for GDB. Type "show warranty"
23387 This GDB was configured as "i386-pc-linux-gnu"
23398 Here @samp{quit} is input to @value{GDBN}; the rest is output from
23399 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
23400 denotes a @samp{control-z} character) are annotations; the rest is
23401 output from @value{GDBN}.
23403 @node Server Prefix
23404 @section The Server Prefix
23405 @cindex server prefix
23407 If you prefix a command with @samp{server } then it will not affect
23408 the command history, nor will it affect @value{GDBN}'s notion of which
23409 command to repeat if @key{RET} is pressed on a line by itself. This
23410 means that commands can be run behind a user's back by a front-end in
23411 a transparent manner.
23413 The server prefix does not affect the recording of values into the value
23414 history; to print a value without recording it into the value history,
23415 use the @code{output} command instead of the @code{print} command.
23418 @section Annotation for @value{GDBN} Input
23420 @cindex annotations for prompts
23421 When @value{GDBN} prompts for input, it annotates this fact so it is possible
23422 to know when to send output, when the output from a given command is
23425 Different kinds of input each have a different @dfn{input type}. Each
23426 input type has three annotations: a @code{pre-} annotation, which
23427 denotes the beginning of any prompt which is being output, a plain
23428 annotation, which denotes the end of the prompt, and then a @code{post-}
23429 annotation which denotes the end of any echo which may (or may not) be
23430 associated with the input. For example, the @code{prompt} input type
23431 features the following annotations:
23439 The input types are
23442 @findex pre-prompt annotation
23443 @findex prompt annotation
23444 @findex post-prompt annotation
23446 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
23448 @findex pre-commands annotation
23449 @findex commands annotation
23450 @findex post-commands annotation
23452 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
23453 command. The annotations are repeated for each command which is input.
23455 @findex pre-overload-choice annotation
23456 @findex overload-choice annotation
23457 @findex post-overload-choice annotation
23458 @item overload-choice
23459 When @value{GDBN} wants the user to select between various overloaded functions.
23461 @findex pre-query annotation
23462 @findex query annotation
23463 @findex post-query annotation
23465 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
23467 @findex pre-prompt-for-continue annotation
23468 @findex prompt-for-continue annotation
23469 @findex post-prompt-for-continue annotation
23470 @item prompt-for-continue
23471 When @value{GDBN} is asking the user to press return to continue. Note: Don't
23472 expect this to work well; instead use @code{set height 0} to disable
23473 prompting. This is because the counting of lines is buggy in the
23474 presence of annotations.
23479 @cindex annotations for errors, warnings and interrupts
23481 @findex quit annotation
23486 This annotation occurs right before @value{GDBN} responds to an interrupt.
23488 @findex error annotation
23493 This annotation occurs right before @value{GDBN} responds to an error.
23495 Quit and error annotations indicate that any annotations which @value{GDBN} was
23496 in the middle of may end abruptly. For example, if a
23497 @code{value-history-begin} annotation is followed by a @code{error}, one
23498 cannot expect to receive the matching @code{value-history-end}. One
23499 cannot expect not to receive it either, however; an error annotation
23500 does not necessarily mean that @value{GDBN} is immediately returning all the way
23503 @findex error-begin annotation
23504 A quit or error annotation may be preceded by
23510 Any output between that and the quit or error annotation is the error
23513 Warning messages are not yet annotated.
23514 @c If we want to change that, need to fix warning(), type_error(),
23515 @c range_error(), and possibly other places.
23518 @section Invalidation Notices
23520 @cindex annotations for invalidation messages
23521 The following annotations say that certain pieces of state may have
23525 @findex frames-invalid annotation
23526 @item ^Z^Zframes-invalid
23528 The frames (for example, output from the @code{backtrace} command) may
23531 @findex breakpoints-invalid annotation
23532 @item ^Z^Zbreakpoints-invalid
23534 The breakpoints may have changed. For example, the user just added or
23535 deleted a breakpoint.
23538 @node Annotations for Running
23539 @section Running the Program
23540 @cindex annotations for running programs
23542 @findex starting annotation
23543 @findex stopping annotation
23544 When the program starts executing due to a @value{GDBN} command such as
23545 @code{step} or @code{continue},
23551 is output. When the program stops,
23557 is output. Before the @code{stopped} annotation, a variety of
23558 annotations describe how the program stopped.
23561 @findex exited annotation
23562 @item ^Z^Zexited @var{exit-status}
23563 The program exited, and @var{exit-status} is the exit status (zero for
23564 successful exit, otherwise nonzero).
23566 @findex signalled annotation
23567 @findex signal-name annotation
23568 @findex signal-name-end annotation
23569 @findex signal-string annotation
23570 @findex signal-string-end annotation
23571 @item ^Z^Zsignalled
23572 The program exited with a signal. After the @code{^Z^Zsignalled}, the
23573 annotation continues:
23579 ^Z^Zsignal-name-end
23583 ^Z^Zsignal-string-end
23588 where @var{name} is the name of the signal, such as @code{SIGILL} or
23589 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
23590 as @code{Illegal Instruction} or @code{Segmentation fault}.
23591 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
23592 user's benefit and have no particular format.
23594 @findex signal annotation
23596 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
23597 just saying that the program received the signal, not that it was
23598 terminated with it.
23600 @findex breakpoint annotation
23601 @item ^Z^Zbreakpoint @var{number}
23602 The program hit breakpoint number @var{number}.
23604 @findex watchpoint annotation
23605 @item ^Z^Zwatchpoint @var{number}
23606 The program hit watchpoint number @var{number}.
23609 @node Source Annotations
23610 @section Displaying Source
23611 @cindex annotations for source display
23613 @findex source annotation
23614 The following annotation is used instead of displaying source code:
23617 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
23620 where @var{filename} is an absolute file name indicating which source
23621 file, @var{line} is the line number within that file (where 1 is the
23622 first line in the file), @var{character} is the character position
23623 within the file (where 0 is the first character in the file) (for most
23624 debug formats this will necessarily point to the beginning of a line),
23625 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
23626 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
23627 @var{addr} is the address in the target program associated with the
23628 source which is being displayed. @var{addr} is in the form @samp{0x}
23629 followed by one or more lowercase hex digits (note that this does not
23630 depend on the language).
23633 @chapter Reporting Bugs in @value{GDBN}
23634 @cindex bugs in @value{GDBN}
23635 @cindex reporting bugs in @value{GDBN}
23637 Your bug reports play an essential role in making @value{GDBN} reliable.
23639 Reporting a bug may help you by bringing a solution to your problem, or it
23640 may not. But in any case the principal function of a bug report is to help
23641 the entire community by making the next version of @value{GDBN} work better. Bug
23642 reports are your contribution to the maintenance of @value{GDBN}.
23644 In order for a bug report to serve its purpose, you must include the
23645 information that enables us to fix the bug.
23648 * Bug Criteria:: Have you found a bug?
23649 * Bug Reporting:: How to report bugs
23653 @section Have You Found a Bug?
23654 @cindex bug criteria
23656 If you are not sure whether you have found a bug, here are some guidelines:
23659 @cindex fatal signal
23660 @cindex debugger crash
23661 @cindex crash of debugger
23663 If the debugger gets a fatal signal, for any input whatever, that is a
23664 @value{GDBN} bug. Reliable debuggers never crash.
23666 @cindex error on valid input
23668 If @value{GDBN} produces an error message for valid input, that is a
23669 bug. (Note that if you're cross debugging, the problem may also be
23670 somewhere in the connection to the target.)
23672 @cindex invalid input
23674 If @value{GDBN} does not produce an error message for invalid input,
23675 that is a bug. However, you should note that your idea of
23676 ``invalid input'' might be our idea of ``an extension'' or ``support
23677 for traditional practice''.
23680 If you are an experienced user of debugging tools, your suggestions
23681 for improvement of @value{GDBN} are welcome in any case.
23684 @node Bug Reporting
23685 @section How to Report Bugs
23686 @cindex bug reports
23687 @cindex @value{GDBN} bugs, reporting
23689 A number of companies and individuals offer support for @sc{gnu} products.
23690 If you obtained @value{GDBN} from a support organization, we recommend you
23691 contact that organization first.
23693 You can find contact information for many support companies and
23694 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
23696 @c should add a web page ref...
23699 @ifset BUGURL_DEFAULT
23700 In any event, we also recommend that you submit bug reports for
23701 @value{GDBN}. The preferred method is to submit them directly using
23702 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
23703 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
23706 @strong{Do not send bug reports to @samp{info-gdb}, or to
23707 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
23708 not want to receive bug reports. Those that do have arranged to receive
23711 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
23712 serves as a repeater. The mailing list and the newsgroup carry exactly
23713 the same messages. Often people think of posting bug reports to the
23714 newsgroup instead of mailing them. This appears to work, but it has one
23715 problem which can be crucial: a newsgroup posting often lacks a mail
23716 path back to the sender. Thus, if we need to ask for more information,
23717 we may be unable to reach you. For this reason, it is better to send
23718 bug reports to the mailing list.
23720 @ifclear BUGURL_DEFAULT
23721 In any event, we also recommend that you submit bug reports for
23722 @value{GDBN} to @value{BUGURL}.
23726 The fundamental principle of reporting bugs usefully is this:
23727 @strong{report all the facts}. If you are not sure whether to state a
23728 fact or leave it out, state it!
23730 Often people omit facts because they think they know what causes the
23731 problem and assume that some details do not matter. Thus, you might
23732 assume that the name of the variable you use in an example does not matter.
23733 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
23734 stray memory reference which happens to fetch from the location where that
23735 name is stored in memory; perhaps, if the name were different, the contents
23736 of that location would fool the debugger into doing the right thing despite
23737 the bug. Play it safe and give a specific, complete example. That is the
23738 easiest thing for you to do, and the most helpful.
23740 Keep in mind that the purpose of a bug report is to enable us to fix the
23741 bug. It may be that the bug has been reported previously, but neither
23742 you nor we can know that unless your bug report is complete and
23745 Sometimes people give a few sketchy facts and ask, ``Does this ring a
23746 bell?'' Those bug reports are useless, and we urge everyone to
23747 @emph{refuse to respond to them} except to chide the sender to report
23750 To enable us to fix the bug, you should include all these things:
23754 The version of @value{GDBN}. @value{GDBN} announces it if you start
23755 with no arguments; you can also print it at any time using @code{show
23758 Without this, we will not know whether there is any point in looking for
23759 the bug in the current version of @value{GDBN}.
23762 The type of machine you are using, and the operating system name and
23766 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
23767 ``@value{GCC}--2.8.1''.
23770 What compiler (and its version) was used to compile the program you are
23771 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
23772 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
23773 to get this information; for other compilers, see the documentation for
23777 The command arguments you gave the compiler to compile your example and
23778 observe the bug. For example, did you use @samp{-O}? To guarantee
23779 you will not omit something important, list them all. A copy of the
23780 Makefile (or the output from make) is sufficient.
23782 If we were to try to guess the arguments, we would probably guess wrong
23783 and then we might not encounter the bug.
23786 A complete input script, and all necessary source files, that will
23790 A description of what behavior you observe that you believe is
23791 incorrect. For example, ``It gets a fatal signal.''
23793 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
23794 will certainly notice it. But if the bug is incorrect output, we might
23795 not notice unless it is glaringly wrong. You might as well not give us
23796 a chance to make a mistake.
23798 Even if the problem you experience is a fatal signal, you should still
23799 say so explicitly. Suppose something strange is going on, such as, your
23800 copy of @value{GDBN} is out of synch, or you have encountered a bug in
23801 the C library on your system. (This has happened!) Your copy might
23802 crash and ours would not. If you told us to expect a crash, then when
23803 ours fails to crash, we would know that the bug was not happening for
23804 us. If you had not told us to expect a crash, then we would not be able
23805 to draw any conclusion from our observations.
23808 @cindex recording a session script
23809 To collect all this information, you can use a session recording program
23810 such as @command{script}, which is available on many Unix systems.
23811 Just run your @value{GDBN} session inside @command{script} and then
23812 include the @file{typescript} file with your bug report.
23814 Another way to record a @value{GDBN} session is to run @value{GDBN}
23815 inside Emacs and then save the entire buffer to a file.
23818 If you wish to suggest changes to the @value{GDBN} source, send us context
23819 diffs. If you even discuss something in the @value{GDBN} source, refer to
23820 it by context, not by line number.
23822 The line numbers in our development sources will not match those in your
23823 sources. Your line numbers would convey no useful information to us.
23827 Here are some things that are not necessary:
23831 A description of the envelope of the bug.
23833 Often people who encounter a bug spend a lot of time investigating
23834 which changes to the input file will make the bug go away and which
23835 changes will not affect it.
23837 This is often time consuming and not very useful, because the way we
23838 will find the bug is by running a single example under the debugger
23839 with breakpoints, not by pure deduction from a series of examples.
23840 We recommend that you save your time for something else.
23842 Of course, if you can find a simpler example to report @emph{instead}
23843 of the original one, that is a convenience for us. Errors in the
23844 output will be easier to spot, running under the debugger will take
23845 less time, and so on.
23847 However, simplification is not vital; if you do not want to do this,
23848 report the bug anyway and send us the entire test case you used.
23851 A patch for the bug.
23853 A patch for the bug does help us if it is a good one. But do not omit
23854 the necessary information, such as the test case, on the assumption that
23855 a patch is all we need. We might see problems with your patch and decide
23856 to fix the problem another way, or we might not understand it at all.
23858 Sometimes with a program as complicated as @value{GDBN} it is very hard to
23859 construct an example that will make the program follow a certain path
23860 through the code. If you do not send us the example, we will not be able
23861 to construct one, so we will not be able to verify that the bug is fixed.
23863 And if we cannot understand what bug you are trying to fix, or why your
23864 patch should be an improvement, we will not install it. A test case will
23865 help us to understand.
23868 A guess about what the bug is or what it depends on.
23870 Such guesses are usually wrong. Even we cannot guess right about such
23871 things without first using the debugger to find the facts.
23874 @c The readline documentation is distributed with the readline code
23875 @c and consists of the two following files:
23877 @c inc-hist.texinfo
23878 @c Use -I with makeinfo to point to the appropriate directory,
23879 @c environment var TEXINPUTS with TeX.
23880 @include rluser.texi
23881 @include inc-hist.texinfo
23884 @node Formatting Documentation
23885 @appendix Formatting Documentation
23887 @cindex @value{GDBN} reference card
23888 @cindex reference card
23889 The @value{GDBN} 4 release includes an already-formatted reference card, ready
23890 for printing with PostScript or Ghostscript, in the @file{gdb}
23891 subdirectory of the main source directory@footnote{In
23892 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
23893 release.}. If you can use PostScript or Ghostscript with your printer,
23894 you can print the reference card immediately with @file{refcard.ps}.
23896 The release also includes the source for the reference card. You
23897 can format it, using @TeX{}, by typing:
23903 The @value{GDBN} reference card is designed to print in @dfn{landscape}
23904 mode on US ``letter'' size paper;
23905 that is, on a sheet 11 inches wide by 8.5 inches
23906 high. You will need to specify this form of printing as an option to
23907 your @sc{dvi} output program.
23909 @cindex documentation
23911 All the documentation for @value{GDBN} comes as part of the machine-readable
23912 distribution. The documentation is written in Texinfo format, which is
23913 a documentation system that uses a single source file to produce both
23914 on-line information and a printed manual. You can use one of the Info
23915 formatting commands to create the on-line version of the documentation
23916 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
23918 @value{GDBN} includes an already formatted copy of the on-line Info
23919 version of this manual in the @file{gdb} subdirectory. The main Info
23920 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
23921 subordinate files matching @samp{gdb.info*} in the same directory. If
23922 necessary, you can print out these files, or read them with any editor;
23923 but they are easier to read using the @code{info} subsystem in @sc{gnu}
23924 Emacs or the standalone @code{info} program, available as part of the
23925 @sc{gnu} Texinfo distribution.
23927 If you want to format these Info files yourself, you need one of the
23928 Info formatting programs, such as @code{texinfo-format-buffer} or
23931 If you have @code{makeinfo} installed, and are in the top level
23932 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
23933 version @value{GDBVN}), you can make the Info file by typing:
23940 If you want to typeset and print copies of this manual, you need @TeX{},
23941 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
23942 Texinfo definitions file.
23944 @TeX{} is a typesetting program; it does not print files directly, but
23945 produces output files called @sc{dvi} files. To print a typeset
23946 document, you need a program to print @sc{dvi} files. If your system
23947 has @TeX{} installed, chances are it has such a program. The precise
23948 command to use depends on your system; @kbd{lpr -d} is common; another
23949 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
23950 require a file name without any extension or a @samp{.dvi} extension.
23952 @TeX{} also requires a macro definitions file called
23953 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
23954 written in Texinfo format. On its own, @TeX{} cannot either read or
23955 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
23956 and is located in the @file{gdb-@var{version-number}/texinfo}
23959 If you have @TeX{} and a @sc{dvi} printer program installed, you can
23960 typeset and print this manual. First switch to the @file{gdb}
23961 subdirectory of the main source directory (for example, to
23962 @file{gdb-@value{GDBVN}/gdb}) and type:
23968 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
23970 @node Installing GDB
23971 @appendix Installing @value{GDBN}
23972 @cindex installation
23975 * Requirements:: Requirements for building @value{GDBN}
23976 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
23977 * Separate Objdir:: Compiling @value{GDBN} in another directory
23978 * Config Names:: Specifying names for hosts and targets
23979 * Configure Options:: Summary of options for configure
23983 @section Requirements for Building @value{GDBN}
23984 @cindex building @value{GDBN}, requirements for
23986 Building @value{GDBN} requires various tools and packages to be available.
23987 Other packages will be used only if they are found.
23989 @heading Tools/Packages Necessary for Building @value{GDBN}
23991 @item ISO C90 compiler
23992 @value{GDBN} is written in ISO C90. It should be buildable with any
23993 working C90 compiler, e.g.@: GCC.
23997 @heading Tools/Packages Optional for Building @value{GDBN}
24001 @value{GDBN} can use the Expat XML parsing library. This library may be
24002 included with your operating system distribution; if it is not, you
24003 can get the latest version from @url{http://expat.sourceforge.net}.
24004 The @file{configure} script will search for this library in several
24005 standard locations; if it is installed in an unusual path, you can
24006 use the @option{--with-libexpat-prefix} option to specify its location.
24012 Remote protocol memory maps (@pxref{Memory Map Format})
24014 Target descriptions (@pxref{Target Descriptions})
24016 Remote shared library lists (@pxref{Library List Format})
24018 MS-Windows shared libraries (@pxref{Shared Libraries})
24022 @cindex compressed debug sections
24023 @value{GDBN} will use the @samp{zlib} library, if available, to read
24024 compressed debug sections. Some linkers, such as GNU gold, are capable
24025 of producing binaries with compressed debug sections. If @value{GDBN}
24026 is compiled with @samp{zlib}, it will be able to read the debug
24027 information in such binaries.
24029 The @samp{zlib} library is likely included with your operating system
24030 distribution; if it is not, you can get the latest version from
24031 @url{http://zlib.net}.
24035 @node Running Configure
24036 @section Invoking the @value{GDBN} @file{configure} Script
24037 @cindex configuring @value{GDBN}
24038 @value{GDBN} comes with a @file{configure} script that automates the process
24039 of preparing @value{GDBN} for installation; you can then use @code{make} to
24040 build the @code{gdb} program.
24042 @c irrelevant in info file; it's as current as the code it lives with.
24043 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
24044 look at the @file{README} file in the sources; we may have improved the
24045 installation procedures since publishing this manual.}
24048 The @value{GDBN} distribution includes all the source code you need for
24049 @value{GDBN} in a single directory, whose name is usually composed by
24050 appending the version number to @samp{gdb}.
24052 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
24053 @file{gdb-@value{GDBVN}} directory. That directory contains:
24056 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
24057 script for configuring @value{GDBN} and all its supporting libraries
24059 @item gdb-@value{GDBVN}/gdb
24060 the source specific to @value{GDBN} itself
24062 @item gdb-@value{GDBVN}/bfd
24063 source for the Binary File Descriptor library
24065 @item gdb-@value{GDBVN}/include
24066 @sc{gnu} include files
24068 @item gdb-@value{GDBVN}/libiberty
24069 source for the @samp{-liberty} free software library
24071 @item gdb-@value{GDBVN}/opcodes
24072 source for the library of opcode tables and disassemblers
24074 @item gdb-@value{GDBVN}/readline
24075 source for the @sc{gnu} command-line interface
24077 @item gdb-@value{GDBVN}/glob
24078 source for the @sc{gnu} filename pattern-matching subroutine
24080 @item gdb-@value{GDBVN}/mmalloc
24081 source for the @sc{gnu} memory-mapped malloc package
24084 The simplest way to configure and build @value{GDBN} is to run @file{configure}
24085 from the @file{gdb-@var{version-number}} source directory, which in
24086 this example is the @file{gdb-@value{GDBVN}} directory.
24088 First switch to the @file{gdb-@var{version-number}} source directory
24089 if you are not already in it; then run @file{configure}. Pass the
24090 identifier for the platform on which @value{GDBN} will run as an
24096 cd gdb-@value{GDBVN}
24097 ./configure @var{host}
24102 where @var{host} is an identifier such as @samp{sun4} or
24103 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
24104 (You can often leave off @var{host}; @file{configure} tries to guess the
24105 correct value by examining your system.)
24107 Running @samp{configure @var{host}} and then running @code{make} builds the
24108 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
24109 libraries, then @code{gdb} itself. The configured source files, and the
24110 binaries, are left in the corresponding source directories.
24113 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
24114 system does not recognize this automatically when you run a different
24115 shell, you may need to run @code{sh} on it explicitly:
24118 sh configure @var{host}
24121 If you run @file{configure} from a directory that contains source
24122 directories for multiple libraries or programs, such as the
24123 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
24125 creates configuration files for every directory level underneath (unless
24126 you tell it not to, with the @samp{--norecursion} option).
24128 You should run the @file{configure} script from the top directory in the
24129 source tree, the @file{gdb-@var{version-number}} directory. If you run
24130 @file{configure} from one of the subdirectories, you will configure only
24131 that subdirectory. That is usually not what you want. In particular,
24132 if you run the first @file{configure} from the @file{gdb} subdirectory
24133 of the @file{gdb-@var{version-number}} directory, you will omit the
24134 configuration of @file{bfd}, @file{readline}, and other sibling
24135 directories of the @file{gdb} subdirectory. This leads to build errors
24136 about missing include files such as @file{bfd/bfd.h}.
24138 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
24139 However, you should make sure that the shell on your path (named by
24140 the @samp{SHELL} environment variable) is publicly readable. Remember
24141 that @value{GDBN} uses the shell to start your program---some systems refuse to
24142 let @value{GDBN} debug child processes whose programs are not readable.
24144 @node Separate Objdir
24145 @section Compiling @value{GDBN} in Another Directory
24147 If you want to run @value{GDBN} versions for several host or target machines,
24148 you need a different @code{gdb} compiled for each combination of
24149 host and target. @file{configure} is designed to make this easy by
24150 allowing you to generate each configuration in a separate subdirectory,
24151 rather than in the source directory. If your @code{make} program
24152 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
24153 @code{make} in each of these directories builds the @code{gdb}
24154 program specified there.
24156 To build @code{gdb} in a separate directory, run @file{configure}
24157 with the @samp{--srcdir} option to specify where to find the source.
24158 (You also need to specify a path to find @file{configure}
24159 itself from your working directory. If the path to @file{configure}
24160 would be the same as the argument to @samp{--srcdir}, you can leave out
24161 the @samp{--srcdir} option; it is assumed.)
24163 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
24164 separate directory for a Sun 4 like this:
24168 cd gdb-@value{GDBVN}
24171 ../gdb-@value{GDBVN}/configure sun4
24176 When @file{configure} builds a configuration using a remote source
24177 directory, it creates a tree for the binaries with the same structure
24178 (and using the same names) as the tree under the source directory. In
24179 the example, you'd find the Sun 4 library @file{libiberty.a} in the
24180 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
24181 @file{gdb-sun4/gdb}.
24183 Make sure that your path to the @file{configure} script has just one
24184 instance of @file{gdb} in it. If your path to @file{configure} looks
24185 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
24186 one subdirectory of @value{GDBN}, not the whole package. This leads to
24187 build errors about missing include files such as @file{bfd/bfd.h}.
24189 One popular reason to build several @value{GDBN} configurations in separate
24190 directories is to configure @value{GDBN} for cross-compiling (where
24191 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
24192 programs that run on another machine---the @dfn{target}).
24193 You specify a cross-debugging target by
24194 giving the @samp{--target=@var{target}} option to @file{configure}.
24196 When you run @code{make} to build a program or library, you must run
24197 it in a configured directory---whatever directory you were in when you
24198 called @file{configure} (or one of its subdirectories).
24200 The @code{Makefile} that @file{configure} generates in each source
24201 directory also runs recursively. If you type @code{make} in a source
24202 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
24203 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
24204 will build all the required libraries, and then build GDB.
24206 When you have multiple hosts or targets configured in separate
24207 directories, you can run @code{make} on them in parallel (for example,
24208 if they are NFS-mounted on each of the hosts); they will not interfere
24212 @section Specifying Names for Hosts and Targets
24214 The specifications used for hosts and targets in the @file{configure}
24215 script are based on a three-part naming scheme, but some short predefined
24216 aliases are also supported. The full naming scheme encodes three pieces
24217 of information in the following pattern:
24220 @var{architecture}-@var{vendor}-@var{os}
24223 For example, you can use the alias @code{sun4} as a @var{host} argument,
24224 or as the value for @var{target} in a @code{--target=@var{target}}
24225 option. The equivalent full name is @samp{sparc-sun-sunos4}.
24227 The @file{configure} script accompanying @value{GDBN} does not provide
24228 any query facility to list all supported host and target names or
24229 aliases. @file{configure} calls the Bourne shell script
24230 @code{config.sub} to map abbreviations to full names; you can read the
24231 script, if you wish, or you can use it to test your guesses on
24232 abbreviations---for example:
24235 % sh config.sub i386-linux
24237 % sh config.sub alpha-linux
24238 alpha-unknown-linux-gnu
24239 % sh config.sub hp9k700
24241 % sh config.sub sun4
24242 sparc-sun-sunos4.1.1
24243 % sh config.sub sun3
24244 m68k-sun-sunos4.1.1
24245 % sh config.sub i986v
24246 Invalid configuration `i986v': machine `i986v' not recognized
24250 @code{config.sub} is also distributed in the @value{GDBN} source
24251 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
24253 @node Configure Options
24254 @section @file{configure} Options
24256 Here is a summary of the @file{configure} options and arguments that
24257 are most often useful for building @value{GDBN}. @file{configure} also has
24258 several other options not listed here. @inforef{What Configure
24259 Does,,configure.info}, for a full explanation of @file{configure}.
24262 configure @r{[}--help@r{]}
24263 @r{[}--prefix=@var{dir}@r{]}
24264 @r{[}--exec-prefix=@var{dir}@r{]}
24265 @r{[}--srcdir=@var{dirname}@r{]}
24266 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
24267 @r{[}--target=@var{target}@r{]}
24272 You may introduce options with a single @samp{-} rather than
24273 @samp{--} if you prefer; but you may abbreviate option names if you use
24278 Display a quick summary of how to invoke @file{configure}.
24280 @item --prefix=@var{dir}
24281 Configure the source to install programs and files under directory
24284 @item --exec-prefix=@var{dir}
24285 Configure the source to install programs under directory
24288 @c avoid splitting the warning from the explanation:
24290 @item --srcdir=@var{dirname}
24291 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
24292 @code{make} that implements the @code{VPATH} feature.}@*
24293 Use this option to make configurations in directories separate from the
24294 @value{GDBN} source directories. Among other things, you can use this to
24295 build (or maintain) several configurations simultaneously, in separate
24296 directories. @file{configure} writes configuration-specific files in
24297 the current directory, but arranges for them to use the source in the
24298 directory @var{dirname}. @file{configure} creates directories under
24299 the working directory in parallel to the source directories below
24302 @item --norecursion
24303 Configure only the directory level where @file{configure} is executed; do not
24304 propagate configuration to subdirectories.
24306 @item --target=@var{target}
24307 Configure @value{GDBN} for cross-debugging programs running on the specified
24308 @var{target}. Without this option, @value{GDBN} is configured to debug
24309 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
24311 There is no convenient way to generate a list of all available targets.
24313 @item @var{host} @dots{}
24314 Configure @value{GDBN} to run on the specified @var{host}.
24316 There is no convenient way to generate a list of all available hosts.
24319 There are many other options available as well, but they are generally
24320 needed for special purposes only.
24322 @node Maintenance Commands
24323 @appendix Maintenance Commands
24324 @cindex maintenance commands
24325 @cindex internal commands
24327 In addition to commands intended for @value{GDBN} users, @value{GDBN}
24328 includes a number of commands intended for @value{GDBN} developers,
24329 that are not documented elsewhere in this manual. These commands are
24330 provided here for reference. (For commands that turn on debugging
24331 messages, see @ref{Debugging Output}.)
24334 @kindex maint agent
24335 @item maint agent @var{expression}
24336 Translate the given @var{expression} into remote agent bytecodes.
24337 This command is useful for debugging the Agent Expression mechanism
24338 (@pxref{Agent Expressions}).
24340 @kindex maint info breakpoints
24341 @item @anchor{maint info breakpoints}maint info breakpoints
24342 Using the same format as @samp{info breakpoints}, display both the
24343 breakpoints you've set explicitly, and those @value{GDBN} is using for
24344 internal purposes. Internal breakpoints are shown with negative
24345 breakpoint numbers. The type column identifies what kind of breakpoint
24350 Normal, explicitly set breakpoint.
24353 Normal, explicitly set watchpoint.
24356 Internal breakpoint, used to handle correctly stepping through
24357 @code{longjmp} calls.
24359 @item longjmp resume
24360 Internal breakpoint at the target of a @code{longjmp}.
24363 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
24366 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
24369 Shared library events.
24373 @kindex set displaced-stepping
24374 @kindex show displaced-stepping
24375 @cindex displaced stepping support
24376 @cindex out-of-line single-stepping
24377 @item set displaced-stepping
24378 @itemx show displaced-stepping
24379 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
24380 if the target supports it. Displaced stepping is a way to single-step
24381 over breakpoints without removing them from the inferior, by executing
24382 an out-of-line copy of the instruction that was originally at the
24383 breakpoint location. It is also known as out-of-line single-stepping.
24386 @item set displaced-stepping on
24387 If the target architecture supports it, @value{GDBN} will use
24388 displaced stepping to step over breakpoints.
24390 @item set displaced-stepping off
24391 @value{GDBN} will not use displaced stepping to step over breakpoints,
24392 even if such is supported by the target architecture.
24394 @cindex non-stop mode, and @samp{set displaced-stepping}
24395 @item set displaced-stepping auto
24396 This is the default mode. @value{GDBN} will use displaced stepping
24397 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
24398 architecture supports displaced stepping.
24401 @kindex maint check-symtabs
24402 @item maint check-symtabs
24403 Check the consistency of psymtabs and symtabs.
24405 @kindex maint cplus first_component
24406 @item maint cplus first_component @var{name}
24407 Print the first C@t{++} class/namespace component of @var{name}.
24409 @kindex maint cplus namespace
24410 @item maint cplus namespace
24411 Print the list of possible C@t{++} namespaces.
24413 @kindex maint demangle
24414 @item maint demangle @var{name}
24415 Demangle a C@t{++} or Objective-C mangled @var{name}.
24417 @kindex maint deprecate
24418 @kindex maint undeprecate
24419 @cindex deprecated commands
24420 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
24421 @itemx maint undeprecate @var{command}
24422 Deprecate or undeprecate the named @var{command}. Deprecated commands
24423 cause @value{GDBN} to issue a warning when you use them. The optional
24424 argument @var{replacement} says which newer command should be used in
24425 favor of the deprecated one; if it is given, @value{GDBN} will mention
24426 the replacement as part of the warning.
24428 @kindex maint dump-me
24429 @item maint dump-me
24430 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
24431 Cause a fatal signal in the debugger and force it to dump its core.
24432 This is supported only on systems which support aborting a program
24433 with the @code{SIGQUIT} signal.
24435 @kindex maint internal-error
24436 @kindex maint internal-warning
24437 @item maint internal-error @r{[}@var{message-text}@r{]}
24438 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
24439 Cause @value{GDBN} to call the internal function @code{internal_error}
24440 or @code{internal_warning} and hence behave as though an internal error
24441 or internal warning has been detected. In addition to reporting the
24442 internal problem, these functions give the user the opportunity to
24443 either quit @value{GDBN} or create a core file of the current
24444 @value{GDBN} session.
24446 These commands take an optional parameter @var{message-text} that is
24447 used as the text of the error or warning message.
24449 Here's an example of using @code{internal-error}:
24452 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
24453 @dots{}/maint.c:121: internal-error: testing, 1, 2
24454 A problem internal to GDB has been detected. Further
24455 debugging may prove unreliable.
24456 Quit this debugging session? (y or n) @kbd{n}
24457 Create a core file? (y or n) @kbd{n}
24461 @kindex maint packet
24462 @item maint packet @var{text}
24463 If @value{GDBN} is talking to an inferior via the serial protocol,
24464 then this command sends the string @var{text} to the inferior, and
24465 displays the response packet. @value{GDBN} supplies the initial
24466 @samp{$} character, the terminating @samp{#} character, and the
24469 @kindex maint print architecture
24470 @item maint print architecture @r{[}@var{file}@r{]}
24471 Print the entire architecture configuration. The optional argument
24472 @var{file} names the file where the output goes.
24474 @kindex maint print c-tdesc
24475 @item maint print c-tdesc
24476 Print the current target description (@pxref{Target Descriptions}) as
24477 a C source file. The created source file can be used in @value{GDBN}
24478 when an XML parser is not available to parse the description.
24480 @kindex maint print dummy-frames
24481 @item maint print dummy-frames
24482 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
24485 (@value{GDBP}) @kbd{b add}
24487 (@value{GDBP}) @kbd{print add(2,3)}
24488 Breakpoint 2, add (a=2, b=3) at @dots{}
24490 The program being debugged stopped while in a function called from GDB.
24492 (@value{GDBP}) @kbd{maint print dummy-frames}
24493 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
24494 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
24495 call_lo=0x01014000 call_hi=0x01014001
24499 Takes an optional file parameter.
24501 @kindex maint print registers
24502 @kindex maint print raw-registers
24503 @kindex maint print cooked-registers
24504 @kindex maint print register-groups
24505 @item maint print registers @r{[}@var{file}@r{]}
24506 @itemx maint print raw-registers @r{[}@var{file}@r{]}
24507 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
24508 @itemx maint print register-groups @r{[}@var{file}@r{]}
24509 Print @value{GDBN}'s internal register data structures.
24511 The command @code{maint print raw-registers} includes the contents of
24512 the raw register cache; the command @code{maint print cooked-registers}
24513 includes the (cooked) value of all registers; and the command
24514 @code{maint print register-groups} includes the groups that each
24515 register is a member of. @xref{Registers,, Registers, gdbint,
24516 @value{GDBN} Internals}.
24518 These commands take an optional parameter, a file name to which to
24519 write the information.
24521 @kindex maint print reggroups
24522 @item maint print reggroups @r{[}@var{file}@r{]}
24523 Print @value{GDBN}'s internal register group data structures. The
24524 optional argument @var{file} tells to what file to write the
24527 The register groups info looks like this:
24530 (@value{GDBP}) @kbd{maint print reggroups}
24543 This command forces @value{GDBN} to flush its internal register cache.
24545 @kindex maint print objfiles
24546 @cindex info for known object files
24547 @item maint print objfiles
24548 Print a dump of all known object files. For each object file, this
24549 command prints its name, address in memory, and all of its psymtabs
24552 @kindex maint print statistics
24553 @cindex bcache statistics
24554 @item maint print statistics
24555 This command prints, for each object file in the program, various data
24556 about that object file followed by the byte cache (@dfn{bcache})
24557 statistics for the object file. The objfile data includes the number
24558 of minimal, partial, full, and stabs symbols, the number of types
24559 defined by the objfile, the number of as yet unexpanded psym tables,
24560 the number of line tables and string tables, and the amount of memory
24561 used by the various tables. The bcache statistics include the counts,
24562 sizes, and counts of duplicates of all and unique objects, max,
24563 average, and median entry size, total memory used and its overhead and
24564 savings, and various measures of the hash table size and chain
24567 @kindex maint print target-stack
24568 @cindex target stack description
24569 @item maint print target-stack
24570 A @dfn{target} is an interface between the debugger and a particular
24571 kind of file or process. Targets can be stacked in @dfn{strata},
24572 so that more than one target can potentially respond to a request.
24573 In particular, memory accesses will walk down the stack of targets
24574 until they find a target that is interested in handling that particular
24577 This command prints a short description of each layer that was pushed on
24578 the @dfn{target stack}, starting from the top layer down to the bottom one.
24580 @kindex maint print type
24581 @cindex type chain of a data type
24582 @item maint print type @var{expr}
24583 Print the type chain for a type specified by @var{expr}. The argument
24584 can be either a type name or a symbol. If it is a symbol, the type of
24585 that symbol is described. The type chain produced by this command is
24586 a recursive definition of the data type as stored in @value{GDBN}'s
24587 data structures, including its flags and contained types.
24589 @kindex maint set dwarf2 max-cache-age
24590 @kindex maint show dwarf2 max-cache-age
24591 @item maint set dwarf2 max-cache-age
24592 @itemx maint show dwarf2 max-cache-age
24593 Control the DWARF 2 compilation unit cache.
24595 @cindex DWARF 2 compilation units cache
24596 In object files with inter-compilation-unit references, such as those
24597 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
24598 reader needs to frequently refer to previously read compilation units.
24599 This setting controls how long a compilation unit will remain in the
24600 cache if it is not referenced. A higher limit means that cached
24601 compilation units will be stored in memory longer, and more total
24602 memory will be used. Setting it to zero disables caching, which will
24603 slow down @value{GDBN} startup, but reduce memory consumption.
24605 @kindex maint set profile
24606 @kindex maint show profile
24607 @cindex profiling GDB
24608 @item maint set profile
24609 @itemx maint show profile
24610 Control profiling of @value{GDBN}.
24612 Profiling will be disabled until you use the @samp{maint set profile}
24613 command to enable it. When you enable profiling, the system will begin
24614 collecting timing and execution count data; when you disable profiling or
24615 exit @value{GDBN}, the results will be written to a log file. Remember that
24616 if you use profiling, @value{GDBN} will overwrite the profiling log file
24617 (often called @file{gmon.out}). If you have a record of important profiling
24618 data in a @file{gmon.out} file, be sure to move it to a safe location.
24620 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
24621 compiled with the @samp{-pg} compiler option.
24623 @kindex maint set linux-async
24624 @kindex maint show linux-async
24625 @cindex asynchronous support
24626 @item maint set linux-async
24627 @itemx maint show linux-async
24628 Control the GNU/Linux native asynchronous support
24629 (@pxref{Background Execution}) of @value{GDBN}.
24631 GNU/Linux native asynchronous support will be disabled until you use
24632 the @samp{maint set linux-async} command to enable it.
24634 @kindex maint set remote-async
24635 @kindex maint show remote-async
24636 @cindex asynchronous support
24637 @item maint set remote-async
24638 @itemx maint show remote-async
24639 Control the remote asynchronous support
24640 (@pxref{Background Execution}) of @value{GDBN}.
24642 Remote asynchronous support will be disabled until you use
24643 the @samp{maint set remote-async} command to enable it.
24645 @kindex maint show-debug-regs
24646 @cindex x86 hardware debug registers
24647 @item maint show-debug-regs
24648 Control whether to show variables that mirror the x86 hardware debug
24649 registers. Use @code{ON} to enable, @code{OFF} to disable. If
24650 enabled, the debug registers values are shown when @value{GDBN} inserts or
24651 removes a hardware breakpoint or watchpoint, and when the inferior
24652 triggers a hardware-assisted breakpoint or watchpoint.
24654 @kindex maint space
24655 @cindex memory used by commands
24657 Control whether to display memory usage for each command. If set to a
24658 nonzero value, @value{GDBN} will display how much memory each command
24659 took, following the command's own output. This can also be requested
24660 by invoking @value{GDBN} with the @option{--statistics} command-line
24661 switch (@pxref{Mode Options}).
24664 @cindex time of command execution
24666 Control whether to display the execution time for each command. If
24667 set to a nonzero value, @value{GDBN} will display how much time it
24668 took to execute each command, following the command's own output.
24669 The time is not printed for the commands that run the target, since
24670 there's no mechanism currently to compute how much time was spend
24671 by @value{GDBN} and how much time was spend by the program been debugged.
24672 it's not possibly currently
24673 This can also be requested by invoking @value{GDBN} with the
24674 @option{--statistics} command-line switch (@pxref{Mode Options}).
24676 @kindex maint translate-address
24677 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
24678 Find the symbol stored at the location specified by the address
24679 @var{addr} and an optional section name @var{section}. If found,
24680 @value{GDBN} prints the name of the closest symbol and an offset from
24681 the symbol's location to the specified address. This is similar to
24682 the @code{info address} command (@pxref{Symbols}), except that this
24683 command also allows to find symbols in other sections.
24685 If section was not specified, the section in which the symbol was found
24686 is also printed. For dynamically linked executables, the name of
24687 executable or shared library containing the symbol is printed as well.
24691 The following command is useful for non-interactive invocations of
24692 @value{GDBN}, such as in the test suite.
24695 @item set watchdog @var{nsec}
24696 @kindex set watchdog
24697 @cindex watchdog timer
24698 @cindex timeout for commands
24699 Set the maximum number of seconds @value{GDBN} will wait for the
24700 target operation to finish. If this time expires, @value{GDBN}
24701 reports and error and the command is aborted.
24703 @item show watchdog
24704 Show the current setting of the target wait timeout.
24707 @node Remote Protocol
24708 @appendix @value{GDBN} Remote Serial Protocol
24713 * Stop Reply Packets::
24714 * General Query Packets::
24715 * Register Packet Format::
24716 * Tracepoint Packets::
24717 * Host I/O Packets::
24719 * Notification Packets::
24720 * Remote Non-Stop::
24721 * Packet Acknowledgment::
24723 * File-I/O Remote Protocol Extension::
24724 * Library List Format::
24725 * Memory Map Format::
24731 There may be occasions when you need to know something about the
24732 protocol---for example, if there is only one serial port to your target
24733 machine, you might want your program to do something special if it
24734 recognizes a packet meant for @value{GDBN}.
24736 In the examples below, @samp{->} and @samp{<-} are used to indicate
24737 transmitted and received data, respectively.
24739 @cindex protocol, @value{GDBN} remote serial
24740 @cindex serial protocol, @value{GDBN} remote
24741 @cindex remote serial protocol
24742 All @value{GDBN} commands and responses (other than acknowledgments
24743 and notifications, see @ref{Notification Packets}) are sent as a
24744 @var{packet}. A @var{packet} is introduced with the character
24745 @samp{$}, the actual @var{packet-data}, and the terminating character
24746 @samp{#} followed by a two-digit @var{checksum}:
24749 @code{$}@var{packet-data}@code{#}@var{checksum}
24753 @cindex checksum, for @value{GDBN} remote
24755 The two-digit @var{checksum} is computed as the modulo 256 sum of all
24756 characters between the leading @samp{$} and the trailing @samp{#} (an
24757 eight bit unsigned checksum).
24759 Implementors should note that prior to @value{GDBN} 5.0 the protocol
24760 specification also included an optional two-digit @var{sequence-id}:
24763 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
24766 @cindex sequence-id, for @value{GDBN} remote
24768 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
24769 has never output @var{sequence-id}s. Stubs that handle packets added
24770 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
24772 When either the host or the target machine receives a packet, the first
24773 response expected is an acknowledgment: either @samp{+} (to indicate
24774 the package was received correctly) or @samp{-} (to request
24778 -> @code{$}@var{packet-data}@code{#}@var{checksum}
24783 The @samp{+}/@samp{-} acknowledgments can be disabled
24784 once a connection is established.
24785 @xref{Packet Acknowledgment}, for details.
24787 The host (@value{GDBN}) sends @var{command}s, and the target (the
24788 debugging stub incorporated in your program) sends a @var{response}. In
24789 the case of step and continue @var{command}s, the response is only sent
24790 when the operation has completed, and the target has again stopped all
24791 threads in all attached processes. This is the default all-stop mode
24792 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
24793 execution mode; see @ref{Remote Non-Stop}, for details.
24795 @var{packet-data} consists of a sequence of characters with the
24796 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
24799 @cindex remote protocol, field separator
24800 Fields within the packet should be separated using @samp{,} @samp{;} or
24801 @samp{:}. Except where otherwise noted all numbers are represented in
24802 @sc{hex} with leading zeros suppressed.
24804 Implementors should note that prior to @value{GDBN} 5.0, the character
24805 @samp{:} could not appear as the third character in a packet (as it
24806 would potentially conflict with the @var{sequence-id}).
24808 @cindex remote protocol, binary data
24809 @anchor{Binary Data}
24810 Binary data in most packets is encoded either as two hexadecimal
24811 digits per byte of binary data. This allowed the traditional remote
24812 protocol to work over connections which were only seven-bit clean.
24813 Some packets designed more recently assume an eight-bit clean
24814 connection, and use a more efficient encoding to send and receive
24817 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
24818 as an escape character. Any escaped byte is transmitted as the escape
24819 character followed by the original character XORed with @code{0x20}.
24820 For example, the byte @code{0x7d} would be transmitted as the two
24821 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
24822 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
24823 @samp{@}}) must always be escaped. Responses sent by the stub
24824 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
24825 is not interpreted as the start of a run-length encoded sequence
24828 Response @var{data} can be run-length encoded to save space.
24829 Run-length encoding replaces runs of identical characters with one
24830 instance of the repeated character, followed by a @samp{*} and a
24831 repeat count. The repeat count is itself sent encoded, to avoid
24832 binary characters in @var{data}: a value of @var{n} is sent as
24833 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
24834 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
24835 code 32) for a repeat count of 3. (This is because run-length
24836 encoding starts to win for counts 3 or more.) Thus, for example,
24837 @samp{0* } is a run-length encoding of ``0000'': the space character
24838 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
24841 The printable characters @samp{#} and @samp{$} or with a numeric value
24842 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
24843 seven repeats (@samp{$}) can be expanded using a repeat count of only
24844 five (@samp{"}). For example, @samp{00000000} can be encoded as
24847 The error response returned for some packets includes a two character
24848 error number. That number is not well defined.
24850 @cindex empty response, for unsupported packets
24851 For any @var{command} not supported by the stub, an empty response
24852 (@samp{$#00}) should be returned. That way it is possible to extend the
24853 protocol. A newer @value{GDBN} can tell if a packet is supported based
24856 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
24857 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
24863 The following table provides a complete list of all currently defined
24864 @var{command}s and their corresponding response @var{data}.
24865 @xref{File-I/O Remote Protocol Extension}, for details about the File
24866 I/O extension of the remote protocol.
24868 Each packet's description has a template showing the packet's overall
24869 syntax, followed by an explanation of the packet's meaning. We
24870 include spaces in some of the templates for clarity; these are not
24871 part of the packet's syntax. No @value{GDBN} packet uses spaces to
24872 separate its components. For example, a template like @samp{foo
24873 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
24874 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
24875 @var{baz}. @value{GDBN} does not transmit a space character between the
24876 @samp{foo} and the @var{bar}, or between the @var{bar} and the
24879 @cindex @var{thread-id}, in remote protocol
24880 @anchor{thread-id syntax}
24881 Several packets and replies include a @var{thread-id} field to identify
24882 a thread. Normally these are positive numbers with a target-specific
24883 interpretation, formatted as big-endian hex strings. A @var{thread-id}
24884 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
24887 In addition, the remote protocol supports a multiprocess feature in
24888 which the @var{thread-id} syntax is extended to optionally include both
24889 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
24890 The @var{pid} (process) and @var{tid} (thread) components each have the
24891 format described above: a positive number with target-specific
24892 interpretation formatted as a big-endian hex string, literal @samp{-1}
24893 to indicate all processes or threads (respectively), or @samp{0} to
24894 indicate an arbitrary process or thread. Specifying just a process, as
24895 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
24896 error to specify all processes but a specific thread, such as
24897 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
24898 for those packets and replies explicitly documented to include a process
24899 ID, rather than a @var{thread-id}.
24901 The multiprocess @var{thread-id} syntax extensions are only used if both
24902 @value{GDBN} and the stub report support for the @samp{multiprocess}
24903 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
24906 Note that all packet forms beginning with an upper- or lower-case
24907 letter, other than those described here, are reserved for future use.
24909 Here are the packet descriptions.
24914 @cindex @samp{!} packet
24915 @anchor{extended mode}
24916 Enable extended mode. In extended mode, the remote server is made
24917 persistent. The @samp{R} packet is used to restart the program being
24923 The remote target both supports and has enabled extended mode.
24927 @cindex @samp{?} packet
24928 Indicate the reason the target halted. The reply is the same as for
24929 step and continue. This packet has a special interpretation when the
24930 target is in non-stop mode; see @ref{Remote Non-Stop}.
24933 @xref{Stop Reply Packets}, for the reply specifications.
24935 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
24936 @cindex @samp{A} packet
24937 Initialized @code{argv[]} array passed into program. @var{arglen}
24938 specifies the number of bytes in the hex encoded byte stream
24939 @var{arg}. See @code{gdbserver} for more details.
24944 The arguments were set.
24950 @cindex @samp{b} packet
24951 (Don't use this packet; its behavior is not well-defined.)
24952 Change the serial line speed to @var{baud}.
24954 JTC: @emph{When does the transport layer state change? When it's
24955 received, or after the ACK is transmitted. In either case, there are
24956 problems if the command or the acknowledgment packet is dropped.}
24958 Stan: @emph{If people really wanted to add something like this, and get
24959 it working for the first time, they ought to modify ser-unix.c to send
24960 some kind of out-of-band message to a specially-setup stub and have the
24961 switch happen "in between" packets, so that from remote protocol's point
24962 of view, nothing actually happened.}
24964 @item B @var{addr},@var{mode}
24965 @cindex @samp{B} packet
24966 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
24967 breakpoint at @var{addr}.
24969 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
24970 (@pxref{insert breakpoint or watchpoint packet}).
24973 @cindex @samp{bc} packet
24974 Backward continue. Execute the target system in reverse. No parameter.
24975 @xref{Reverse Execution}, for more information.
24978 @xref{Stop Reply Packets}, for the reply specifications.
24981 @cindex @samp{bs} packet
24982 Backward single step. Execute one instruction in reverse. No parameter.
24983 @xref{Reverse Execution}, for more information.
24986 @xref{Stop Reply Packets}, for the reply specifications.
24988 @item c @r{[}@var{addr}@r{]}
24989 @cindex @samp{c} packet
24990 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
24991 resume at current address.
24994 @xref{Stop Reply Packets}, for the reply specifications.
24996 @item C @var{sig}@r{[};@var{addr}@r{]}
24997 @cindex @samp{C} packet
24998 Continue with signal @var{sig} (hex signal number). If
24999 @samp{;@var{addr}} is omitted, resume at same address.
25002 @xref{Stop Reply Packets}, for the reply specifications.
25005 @cindex @samp{d} packet
25008 Don't use this packet; instead, define a general set packet
25009 (@pxref{General Query Packets}).
25013 @cindex @samp{D} packet
25014 The first form of the packet is used to detach @value{GDBN} from the
25015 remote system. It is sent to the remote target
25016 before @value{GDBN} disconnects via the @code{detach} command.
25018 The second form, including a process ID, is used when multiprocess
25019 protocol extensions are enabled (@pxref{multiprocess extensions}), to
25020 detach only a specific process. The @var{pid} is specified as a
25021 big-endian hex string.
25031 @item F @var{RC},@var{EE},@var{CF};@var{XX}
25032 @cindex @samp{F} packet
25033 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
25034 This is part of the File-I/O protocol extension. @xref{File-I/O
25035 Remote Protocol Extension}, for the specification.
25038 @anchor{read registers packet}
25039 @cindex @samp{g} packet
25040 Read general registers.
25044 @item @var{XX@dots{}}
25045 Each byte of register data is described by two hex digits. The bytes
25046 with the register are transmitted in target byte order. The size of
25047 each register and their position within the @samp{g} packet are
25048 determined by the @value{GDBN} internal gdbarch functions
25049 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
25050 specification of several standard @samp{g} packets is specified below.
25055 @item G @var{XX@dots{}}
25056 @cindex @samp{G} packet
25057 Write general registers. @xref{read registers packet}, for a
25058 description of the @var{XX@dots{}} data.
25068 @item H @var{c} @var{thread-id}
25069 @cindex @samp{H} packet
25070 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
25071 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
25072 should be @samp{c} for step and continue operations, @samp{g} for other
25073 operations. The thread designator @var{thread-id} has the format and
25074 interpretation described in @ref{thread-id syntax}.
25085 @c 'H': How restrictive (or permissive) is the thread model. If a
25086 @c thread is selected and stopped, are other threads allowed
25087 @c to continue to execute? As I mentioned above, I think the
25088 @c semantics of each command when a thread is selected must be
25089 @c described. For example:
25091 @c 'g': If the stub supports threads and a specific thread is
25092 @c selected, returns the register block from that thread;
25093 @c otherwise returns current registers.
25095 @c 'G' If the stub supports threads and a specific thread is
25096 @c selected, sets the registers of the register block of
25097 @c that thread; otherwise sets current registers.
25099 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
25100 @anchor{cycle step packet}
25101 @cindex @samp{i} packet
25102 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
25103 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
25104 step starting at that address.
25107 @cindex @samp{I} packet
25108 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
25112 @cindex @samp{k} packet
25115 FIXME: @emph{There is no description of how to operate when a specific
25116 thread context has been selected (i.e.@: does 'k' kill only that
25119 @item m @var{addr},@var{length}
25120 @cindex @samp{m} packet
25121 Read @var{length} bytes of memory starting at address @var{addr}.
25122 Note that @var{addr} may not be aligned to any particular boundary.
25124 The stub need not use any particular size or alignment when gathering
25125 data from memory for the response; even if @var{addr} is word-aligned
25126 and @var{length} is a multiple of the word size, the stub is free to
25127 use byte accesses, or not. For this reason, this packet may not be
25128 suitable for accessing memory-mapped I/O devices.
25129 @cindex alignment of remote memory accesses
25130 @cindex size of remote memory accesses
25131 @cindex memory, alignment and size of remote accesses
25135 @item @var{XX@dots{}}
25136 Memory contents; each byte is transmitted as a two-digit hexadecimal
25137 number. The reply may contain fewer bytes than requested if the
25138 server was able to read only part of the region of memory.
25143 @item M @var{addr},@var{length}:@var{XX@dots{}}
25144 @cindex @samp{M} packet
25145 Write @var{length} bytes of memory starting at address @var{addr}.
25146 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
25147 hexadecimal number.
25154 for an error (this includes the case where only part of the data was
25159 @cindex @samp{p} packet
25160 Read the value of register @var{n}; @var{n} is in hex.
25161 @xref{read registers packet}, for a description of how the returned
25162 register value is encoded.
25166 @item @var{XX@dots{}}
25167 the register's value
25171 Indicating an unrecognized @var{query}.
25174 @item P @var{n@dots{}}=@var{r@dots{}}
25175 @anchor{write register packet}
25176 @cindex @samp{P} packet
25177 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
25178 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
25179 digits for each byte in the register (target byte order).
25189 @item q @var{name} @var{params}@dots{}
25190 @itemx Q @var{name} @var{params}@dots{}
25191 @cindex @samp{q} packet
25192 @cindex @samp{Q} packet
25193 General query (@samp{q}) and set (@samp{Q}). These packets are
25194 described fully in @ref{General Query Packets}.
25197 @cindex @samp{r} packet
25198 Reset the entire system.
25200 Don't use this packet; use the @samp{R} packet instead.
25203 @cindex @samp{R} packet
25204 Restart the program being debugged. @var{XX}, while needed, is ignored.
25205 This packet is only available in extended mode (@pxref{extended mode}).
25207 The @samp{R} packet has no reply.
25209 @item s @r{[}@var{addr}@r{]}
25210 @cindex @samp{s} packet
25211 Single step. @var{addr} is the address at which to resume. If
25212 @var{addr} is omitted, resume at same address.
25215 @xref{Stop Reply Packets}, for the reply specifications.
25217 @item S @var{sig}@r{[};@var{addr}@r{]}
25218 @anchor{step with signal packet}
25219 @cindex @samp{S} packet
25220 Step with signal. This is analogous to the @samp{C} packet, but
25221 requests a single-step, rather than a normal resumption of execution.
25224 @xref{Stop Reply Packets}, for the reply specifications.
25226 @item t @var{addr}:@var{PP},@var{MM}
25227 @cindex @samp{t} packet
25228 Search backwards starting at address @var{addr} for a match with pattern
25229 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
25230 @var{addr} must be at least 3 digits.
25232 @item T @var{thread-id}
25233 @cindex @samp{T} packet
25234 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
25239 thread is still alive
25245 Packets starting with @samp{v} are identified by a multi-letter name,
25246 up to the first @samp{;} or @samp{?} (or the end of the packet).
25248 @item vAttach;@var{pid}
25249 @cindex @samp{vAttach} packet
25250 Attach to a new process with the specified process ID @var{pid}.
25251 The process ID is a
25252 hexadecimal integer identifying the process. In all-stop mode, all
25253 threads in the attached process are stopped; in non-stop mode, it may be
25254 attached without being stopped if that is supported by the target.
25256 @c In non-stop mode, on a successful vAttach, the stub should set the
25257 @c current thread to a thread of the newly-attached process. After
25258 @c attaching, GDB queries for the attached process's thread ID with qC.
25259 @c Also note that, from a user perspective, whether or not the
25260 @c target is stopped on attach in non-stop mode depends on whether you
25261 @c use the foreground or background version of the attach command, not
25262 @c on what vAttach does; GDB does the right thing with respect to either
25263 @c stopping or restarting threads.
25265 This packet is only available in extended mode (@pxref{extended mode}).
25271 @item @r{Any stop packet}
25272 for success in all-stop mode (@pxref{Stop Reply Packets})
25274 for success in non-stop mode (@pxref{Remote Non-Stop})
25277 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
25278 @cindex @samp{vCont} packet
25279 Resume the inferior, specifying different actions for each thread.
25280 If an action is specified with no @var{thread-id}, then it is applied to any
25281 threads that don't have a specific action specified; if no default action is
25282 specified then other threads should remain stopped in all-stop mode and
25283 in their current state in non-stop mode.
25284 Specifying multiple
25285 default actions is an error; specifying no actions is also an error.
25286 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
25288 Currently supported actions are:
25294 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
25298 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
25302 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
25305 The optional argument @var{addr} normally associated with the
25306 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
25307 not supported in @samp{vCont}.
25309 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
25310 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
25311 A stop reply should be generated for any affected thread not already stopped.
25312 When a thread is stopped by means of a @samp{t} action,
25313 the corresponding stop reply should indicate that the thread has stopped with
25314 signal @samp{0}, regardless of whether the target uses some other signal
25315 as an implementation detail.
25318 @xref{Stop Reply Packets}, for the reply specifications.
25321 @cindex @samp{vCont?} packet
25322 Request a list of actions supported by the @samp{vCont} packet.
25326 @item vCont@r{[};@var{action}@dots{}@r{]}
25327 The @samp{vCont} packet is supported. Each @var{action} is a supported
25328 command in the @samp{vCont} packet.
25330 The @samp{vCont} packet is not supported.
25333 @item vFile:@var{operation}:@var{parameter}@dots{}
25334 @cindex @samp{vFile} packet
25335 Perform a file operation on the target system. For details,
25336 see @ref{Host I/O Packets}.
25338 @item vFlashErase:@var{addr},@var{length}
25339 @cindex @samp{vFlashErase} packet
25340 Direct the stub to erase @var{length} bytes of flash starting at
25341 @var{addr}. The region may enclose any number of flash blocks, but
25342 its start and end must fall on block boundaries, as indicated by the
25343 flash block size appearing in the memory map (@pxref{Memory Map
25344 Format}). @value{GDBN} groups flash memory programming operations
25345 together, and sends a @samp{vFlashDone} request after each group; the
25346 stub is allowed to delay erase operation until the @samp{vFlashDone}
25347 packet is received.
25349 The stub must support @samp{vCont} if it reports support for
25350 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
25351 this case @samp{vCont} actions can be specified to apply to all threads
25352 in a process by using the @samp{p@var{pid}.-1} form of the
25363 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
25364 @cindex @samp{vFlashWrite} packet
25365 Direct the stub to write data to flash address @var{addr}. The data
25366 is passed in binary form using the same encoding as for the @samp{X}
25367 packet (@pxref{Binary Data}). The memory ranges specified by
25368 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
25369 not overlap, and must appear in order of increasing addresses
25370 (although @samp{vFlashErase} packets for higher addresses may already
25371 have been received; the ordering is guaranteed only between
25372 @samp{vFlashWrite} packets). If a packet writes to an address that was
25373 neither erased by a preceding @samp{vFlashErase} packet nor by some other
25374 target-specific method, the results are unpredictable.
25382 for vFlashWrite addressing non-flash memory
25388 @cindex @samp{vFlashDone} packet
25389 Indicate to the stub that flash programming operation is finished.
25390 The stub is permitted to delay or batch the effects of a group of
25391 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
25392 @samp{vFlashDone} packet is received. The contents of the affected
25393 regions of flash memory are unpredictable until the @samp{vFlashDone}
25394 request is completed.
25396 @item vKill;@var{pid}
25397 @cindex @samp{vKill} packet
25398 Kill the process with the specified process ID. @var{pid} is a
25399 hexadecimal integer identifying the process. This packet is used in
25400 preference to @samp{k} when multiprocess protocol extensions are
25401 supported; see @ref{multiprocess extensions}.
25411 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
25412 @cindex @samp{vRun} packet
25413 Run the program @var{filename}, passing it each @var{argument} on its
25414 command line. The file and arguments are hex-encoded strings. If
25415 @var{filename} is an empty string, the stub may use a default program
25416 (e.g.@: the last program run). The program is created in the stopped
25419 @c FIXME: What about non-stop mode?
25421 This packet is only available in extended mode (@pxref{extended mode}).
25427 @item @r{Any stop packet}
25428 for success (@pxref{Stop Reply Packets})
25432 @anchor{vStopped packet}
25433 @cindex @samp{vStopped} packet
25435 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
25436 reply and prompt for the stub to report another one.
25440 @item @r{Any stop packet}
25441 if there is another unreported stop event (@pxref{Stop Reply Packets})
25443 if there are no unreported stop events
25446 @item X @var{addr},@var{length}:@var{XX@dots{}}
25448 @cindex @samp{X} packet
25449 Write data to memory, where the data is transmitted in binary.
25450 @var{addr} is address, @var{length} is number of bytes,
25451 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
25461 @item z @var{type},@var{addr},@var{length}
25462 @itemx Z @var{type},@var{addr},@var{length}
25463 @anchor{insert breakpoint or watchpoint packet}
25464 @cindex @samp{z} packet
25465 @cindex @samp{Z} packets
25466 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
25467 watchpoint starting at address @var{address} and covering the next
25468 @var{length} bytes.
25470 Each breakpoint and watchpoint packet @var{type} is documented
25473 @emph{Implementation notes: A remote target shall return an empty string
25474 for an unrecognized breakpoint or watchpoint packet @var{type}. A
25475 remote target shall support either both or neither of a given
25476 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
25477 avoid potential problems with duplicate packets, the operations should
25478 be implemented in an idempotent way.}
25480 @item z0,@var{addr},@var{length}
25481 @itemx Z0,@var{addr},@var{length}
25482 @cindex @samp{z0} packet
25483 @cindex @samp{Z0} packet
25484 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
25485 @var{addr} of size @var{length}.
25487 A memory breakpoint is implemented by replacing the instruction at
25488 @var{addr} with a software breakpoint or trap instruction. The
25489 @var{length} is used by targets that indicates the size of the
25490 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
25491 @sc{mips} can insert either a 2 or 4 byte breakpoint).
25493 @emph{Implementation note: It is possible for a target to copy or move
25494 code that contains memory breakpoints (e.g., when implementing
25495 overlays). The behavior of this packet, in the presence of such a
25496 target, is not defined.}
25508 @item z1,@var{addr},@var{length}
25509 @itemx Z1,@var{addr},@var{length}
25510 @cindex @samp{z1} packet
25511 @cindex @samp{Z1} packet
25512 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
25513 address @var{addr} of size @var{length}.
25515 A hardware breakpoint is implemented using a mechanism that is not
25516 dependant on being able to modify the target's memory.
25518 @emph{Implementation note: A hardware breakpoint is not affected by code
25531 @item z2,@var{addr},@var{length}
25532 @itemx Z2,@var{addr},@var{length}
25533 @cindex @samp{z2} packet
25534 @cindex @samp{Z2} packet
25535 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
25547 @item z3,@var{addr},@var{length}
25548 @itemx Z3,@var{addr},@var{length}
25549 @cindex @samp{z3} packet
25550 @cindex @samp{Z3} packet
25551 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
25563 @item z4,@var{addr},@var{length}
25564 @itemx Z4,@var{addr},@var{length}
25565 @cindex @samp{z4} packet
25566 @cindex @samp{Z4} packet
25567 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
25581 @node Stop Reply Packets
25582 @section Stop Reply Packets
25583 @cindex stop reply packets
25585 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
25586 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
25587 receive any of the below as a reply. Except for @samp{?}
25588 and @samp{vStopped}, that reply is only returned
25589 when the target halts. In the below the exact meaning of @dfn{signal
25590 number} is defined by the header @file{include/gdb/signals.h} in the
25591 @value{GDBN} source code.
25593 As in the description of request packets, we include spaces in the
25594 reply templates for clarity; these are not part of the reply packet's
25595 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
25601 The program received signal number @var{AA} (a two-digit hexadecimal
25602 number). This is equivalent to a @samp{T} response with no
25603 @var{n}:@var{r} pairs.
25605 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
25606 @cindex @samp{T} packet reply
25607 The program received signal number @var{AA} (a two-digit hexadecimal
25608 number). This is equivalent to an @samp{S} response, except that the
25609 @samp{@var{n}:@var{r}} pairs can carry values of important registers
25610 and other information directly in the stop reply packet, reducing
25611 round-trip latency. Single-step and breakpoint traps are reported
25612 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
25616 If @var{n} is a hexadecimal number, it is a register number, and the
25617 corresponding @var{r} gives that register's value. @var{r} is a
25618 series of bytes in target byte order, with each byte given by a
25619 two-digit hex number.
25622 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
25623 the stopped thread, as specified in @ref{thread-id syntax}.
25626 If @var{n} is a recognized @dfn{stop reason}, it describes a more
25627 specific event that stopped the target. The currently defined stop
25628 reasons are listed below. @var{aa} should be @samp{05}, the trap
25629 signal. At most one stop reason should be present.
25632 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
25633 and go on to the next; this allows us to extend the protocol in the
25637 The currently defined stop reasons are:
25643 The packet indicates a watchpoint hit, and @var{r} is the data address, in
25646 @cindex shared library events, remote reply
25648 The packet indicates that the loaded libraries have changed.
25649 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
25650 list of loaded libraries. @var{r} is ignored.
25652 @cindex replay log events, remote reply
25654 The packet indicates that the target cannot continue replaying
25655 logged execution events, because it has reached the end (or the
25656 beginning when executing backward) of the log. The value of @var{r}
25657 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
25658 for more information.
25664 @itemx W @var{AA} ; process:@var{pid}
25665 The process exited, and @var{AA} is the exit status. This is only
25666 applicable to certain targets.
25668 The second form of the response, including the process ID of the exited
25669 process, can be used only when @value{GDBN} has reported support for
25670 multiprocess protocol extensions; see @ref{multiprocess extensions}.
25671 The @var{pid} is formatted as a big-endian hex string.
25674 @itemx X @var{AA} ; process:@var{pid}
25675 The process terminated with signal @var{AA}.
25677 The second form of the response, including the process ID of the
25678 terminated process, can be used only when @value{GDBN} has reported
25679 support for multiprocess protocol extensions; see @ref{multiprocess
25680 extensions}. The @var{pid} is formatted as a big-endian hex string.
25682 @item O @var{XX}@dots{}
25683 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
25684 written as the program's console output. This can happen at any time
25685 while the program is running and the debugger should continue to wait
25686 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
25688 @item F @var{call-id},@var{parameter}@dots{}
25689 @var{call-id} is the identifier which says which host system call should
25690 be called. This is just the name of the function. Translation into the
25691 correct system call is only applicable as it's defined in @value{GDBN}.
25692 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
25695 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
25696 this very system call.
25698 The target replies with this packet when it expects @value{GDBN} to
25699 call a host system call on behalf of the target. @value{GDBN} replies
25700 with an appropriate @samp{F} packet and keeps up waiting for the next
25701 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
25702 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
25703 Protocol Extension}, for more details.
25707 @node General Query Packets
25708 @section General Query Packets
25709 @cindex remote query requests
25711 Packets starting with @samp{q} are @dfn{general query packets};
25712 packets starting with @samp{Q} are @dfn{general set packets}. General
25713 query and set packets are a semi-unified form for retrieving and
25714 sending information to and from the stub.
25716 The initial letter of a query or set packet is followed by a name
25717 indicating what sort of thing the packet applies to. For example,
25718 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
25719 definitions with the stub. These packet names follow some
25724 The name must not contain commas, colons or semicolons.
25726 Most @value{GDBN} query and set packets have a leading upper case
25729 The names of custom vendor packets should use a company prefix, in
25730 lower case, followed by a period. For example, packets designed at
25731 the Acme Corporation might begin with @samp{qacme.foo} (for querying
25732 foos) or @samp{Qacme.bar} (for setting bars).
25735 The name of a query or set packet should be separated from any
25736 parameters by a @samp{:}; the parameters themselves should be
25737 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
25738 full packet name, and check for a separator or the end of the packet,
25739 in case two packet names share a common prefix. New packets should not begin
25740 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
25741 packets predate these conventions, and have arguments without any terminator
25742 for the packet name; we suspect they are in widespread use in places that
25743 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
25744 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
25747 Like the descriptions of the other packets, each description here
25748 has a template showing the packet's overall syntax, followed by an
25749 explanation of the packet's meaning. We include spaces in some of the
25750 templates for clarity; these are not part of the packet's syntax. No
25751 @value{GDBN} packet uses spaces to separate its components.
25753 Here are the currently defined query and set packets:
25758 @cindex current thread, remote request
25759 @cindex @samp{qC} packet
25760 Return the current thread ID.
25764 @item QC @var{thread-id}
25765 Where @var{thread-id} is a thread ID as documented in
25766 @ref{thread-id syntax}.
25767 @item @r{(anything else)}
25768 Any other reply implies the old thread ID.
25771 @item qCRC:@var{addr},@var{length}
25772 @cindex CRC of memory block, remote request
25773 @cindex @samp{qCRC} packet
25774 Compute the CRC checksum of a block of memory.
25778 An error (such as memory fault)
25779 @item C @var{crc32}
25780 The specified memory region's checksum is @var{crc32}.
25784 @itemx qsThreadInfo
25785 @cindex list active threads, remote request
25786 @cindex @samp{qfThreadInfo} packet
25787 @cindex @samp{qsThreadInfo} packet
25788 Obtain a list of all active thread IDs from the target (OS). Since there
25789 may be too many active threads to fit into one reply packet, this query
25790 works iteratively: it may require more than one query/reply sequence to
25791 obtain the entire list of threads. The first query of the sequence will
25792 be the @samp{qfThreadInfo} query; subsequent queries in the
25793 sequence will be the @samp{qsThreadInfo} query.
25795 NOTE: This packet replaces the @samp{qL} query (see below).
25799 @item m @var{thread-id}
25801 @item m @var{thread-id},@var{thread-id}@dots{}
25802 a comma-separated list of thread IDs
25804 (lower case letter @samp{L}) denotes end of list.
25807 In response to each query, the target will reply with a list of one or
25808 more thread IDs, separated by commas.
25809 @value{GDBN} will respond to each reply with a request for more thread
25810 ids (using the @samp{qs} form of the query), until the target responds
25811 with @samp{l} (lower-case el, for @dfn{last}).
25812 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
25815 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
25816 @cindex get thread-local storage address, remote request
25817 @cindex @samp{qGetTLSAddr} packet
25818 Fetch the address associated with thread local storage specified
25819 by @var{thread-id}, @var{offset}, and @var{lm}.
25821 @var{thread-id} is the thread ID associated with the
25822 thread for which to fetch the TLS address. @xref{thread-id syntax}.
25824 @var{offset} is the (big endian, hex encoded) offset associated with the
25825 thread local variable. (This offset is obtained from the debug
25826 information associated with the variable.)
25828 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
25829 the load module associated with the thread local storage. For example,
25830 a @sc{gnu}/Linux system will pass the link map address of the shared
25831 object associated with the thread local storage under consideration.
25832 Other operating environments may choose to represent the load module
25833 differently, so the precise meaning of this parameter will vary.
25837 @item @var{XX}@dots{}
25838 Hex encoded (big endian) bytes representing the address of the thread
25839 local storage requested.
25842 An error occurred. @var{nn} are hex digits.
25845 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
25848 @item qL @var{startflag} @var{threadcount} @var{nextthread}
25849 Obtain thread information from RTOS. Where: @var{startflag} (one hex
25850 digit) is one to indicate the first query and zero to indicate a
25851 subsequent query; @var{threadcount} (two hex digits) is the maximum
25852 number of threads the response packet can contain; and @var{nextthread}
25853 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
25854 returned in the response as @var{argthread}.
25856 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
25860 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
25861 Where: @var{count} (two hex digits) is the number of threads being
25862 returned; @var{done} (one hex digit) is zero to indicate more threads
25863 and one indicates no further threads; @var{argthreadid} (eight hex
25864 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
25865 is a sequence of thread IDs from the target. @var{threadid} (eight hex
25866 digits). See @code{remote.c:parse_threadlist_response()}.
25870 @cindex section offsets, remote request
25871 @cindex @samp{qOffsets} packet
25872 Get section offsets that the target used when relocating the downloaded
25877 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
25878 Relocate the @code{Text} section by @var{xxx} from its original address.
25879 Relocate the @code{Data} section by @var{yyy} from its original address.
25880 If the object file format provides segment information (e.g.@: @sc{elf}
25881 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
25882 segments by the supplied offsets.
25884 @emph{Note: while a @code{Bss} offset may be included in the response,
25885 @value{GDBN} ignores this and instead applies the @code{Data} offset
25886 to the @code{Bss} section.}
25888 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
25889 Relocate the first segment of the object file, which conventionally
25890 contains program code, to a starting address of @var{xxx}. If
25891 @samp{DataSeg} is specified, relocate the second segment, which
25892 conventionally contains modifiable data, to a starting address of
25893 @var{yyy}. @value{GDBN} will report an error if the object file
25894 does not contain segment information, or does not contain at least
25895 as many segments as mentioned in the reply. Extra segments are
25896 kept at fixed offsets relative to the last relocated segment.
25899 @item qP @var{mode} @var{thread-id}
25900 @cindex thread information, remote request
25901 @cindex @samp{qP} packet
25902 Returns information on @var{thread-id}. Where: @var{mode} is a hex
25903 encoded 32 bit mode; @var{thread-id} is a thread ID
25904 (@pxref{thread-id syntax}).
25906 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
25909 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
25913 @cindex non-stop mode, remote request
25914 @cindex @samp{QNonStop} packet
25916 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
25917 @xref{Remote Non-Stop}, for more information.
25922 The request succeeded.
25925 An error occurred. @var{nn} are hex digits.
25928 An empty reply indicates that @samp{QNonStop} is not supported by
25932 This packet is not probed by default; the remote stub must request it,
25933 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25934 Use of this packet is controlled by the @code{set non-stop} command;
25935 @pxref{Non-Stop Mode}.
25937 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
25938 @cindex pass signals to inferior, remote request
25939 @cindex @samp{QPassSignals} packet
25940 @anchor{QPassSignals}
25941 Each listed @var{signal} should be passed directly to the inferior process.
25942 Signals are numbered identically to continue packets and stop replies
25943 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
25944 strictly greater than the previous item. These signals do not need to stop
25945 the inferior, or be reported to @value{GDBN}. All other signals should be
25946 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
25947 combine; any earlier @samp{QPassSignals} list is completely replaced by the
25948 new list. This packet improves performance when using @samp{handle
25949 @var{signal} nostop noprint pass}.
25954 The request succeeded.
25957 An error occurred. @var{nn} are hex digits.
25960 An empty reply indicates that @samp{QPassSignals} is not supported by
25964 Use of this packet is controlled by the @code{set remote pass-signals}
25965 command (@pxref{Remote Configuration, set remote pass-signals}).
25966 This packet is not probed by default; the remote stub must request it,
25967 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
25969 @item qRcmd,@var{command}
25970 @cindex execute remote command, remote request
25971 @cindex @samp{qRcmd} packet
25972 @var{command} (hex encoded) is passed to the local interpreter for
25973 execution. Invalid commands should be reported using the output
25974 string. Before the final result packet, the target may also respond
25975 with a number of intermediate @samp{O@var{output}} console output
25976 packets. @emph{Implementors should note that providing access to a
25977 stubs's interpreter may have security implications}.
25982 A command response with no output.
25984 A command response with the hex encoded output string @var{OUTPUT}.
25986 Indicate a badly formed request.
25988 An empty reply indicates that @samp{qRcmd} is not recognized.
25991 (Note that the @code{qRcmd} packet's name is separated from the
25992 command by a @samp{,}, not a @samp{:}, contrary to the naming
25993 conventions above. Please don't use this packet as a model for new
25996 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
25997 @cindex searching memory, in remote debugging
25998 @cindex @samp{qSearch:memory} packet
25999 @anchor{qSearch memory}
26000 Search @var{length} bytes at @var{address} for @var{search-pattern}.
26001 @var{address} and @var{length} are encoded in hex.
26002 @var{search-pattern} is a sequence of bytes, hex encoded.
26007 The pattern was not found.
26009 The pattern was found at @var{address}.
26011 A badly formed request or an error was encountered while searching memory.
26013 An empty reply indicates that @samp{qSearch:memory} is not recognized.
26016 @item QStartNoAckMode
26017 @cindex @samp{QStartNoAckMode} packet
26018 @anchor{QStartNoAckMode}
26019 Request that the remote stub disable the normal @samp{+}/@samp{-}
26020 protocol acknowledgments (@pxref{Packet Acknowledgment}).
26025 The stub has switched to no-acknowledgment mode.
26026 @value{GDBN} acknowledges this reponse,
26027 but neither the stub nor @value{GDBN} shall send or expect further
26028 @samp{+}/@samp{-} acknowledgments in the current connection.
26030 An empty reply indicates that the stub does not support no-acknowledgment mode.
26033 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
26034 @cindex supported packets, remote query
26035 @cindex features of the remote protocol
26036 @cindex @samp{qSupported} packet
26037 @anchor{qSupported}
26038 Tell the remote stub about features supported by @value{GDBN}, and
26039 query the stub for features it supports. This packet allows
26040 @value{GDBN} and the remote stub to take advantage of each others'
26041 features. @samp{qSupported} also consolidates multiple feature probes
26042 at startup, to improve @value{GDBN} performance---a single larger
26043 packet performs better than multiple smaller probe packets on
26044 high-latency links. Some features may enable behavior which must not
26045 be on by default, e.g.@: because it would confuse older clients or
26046 stubs. Other features may describe packets which could be
26047 automatically probed for, but are not. These features must be
26048 reported before @value{GDBN} will use them. This ``default
26049 unsupported'' behavior is not appropriate for all packets, but it
26050 helps to keep the initial connection time under control with new
26051 versions of @value{GDBN} which support increasing numbers of packets.
26055 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
26056 The stub supports or does not support each returned @var{stubfeature},
26057 depending on the form of each @var{stubfeature} (see below for the
26060 An empty reply indicates that @samp{qSupported} is not recognized,
26061 or that no features needed to be reported to @value{GDBN}.
26064 The allowed forms for each feature (either a @var{gdbfeature} in the
26065 @samp{qSupported} packet, or a @var{stubfeature} in the response)
26069 @item @var{name}=@var{value}
26070 The remote protocol feature @var{name} is supported, and associated
26071 with the specified @var{value}. The format of @var{value} depends
26072 on the feature, but it must not include a semicolon.
26074 The remote protocol feature @var{name} is supported, and does not
26075 need an associated value.
26077 The remote protocol feature @var{name} is not supported.
26079 The remote protocol feature @var{name} may be supported, and
26080 @value{GDBN} should auto-detect support in some other way when it is
26081 needed. This form will not be used for @var{gdbfeature} notifications,
26082 but may be used for @var{stubfeature} responses.
26085 Whenever the stub receives a @samp{qSupported} request, the
26086 supplied set of @value{GDBN} features should override any previous
26087 request. This allows @value{GDBN} to put the stub in a known
26088 state, even if the stub had previously been communicating with
26089 a different version of @value{GDBN}.
26091 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
26096 This feature indicates whether @value{GDBN} supports multiprocess
26097 extensions to the remote protocol. @value{GDBN} does not use such
26098 extensions unless the stub also reports that it supports them by
26099 including @samp{multiprocess+} in its @samp{qSupported} reply.
26100 @xref{multiprocess extensions}, for details.
26103 Stubs should ignore any unknown values for
26104 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
26105 packet supports receiving packets of unlimited length (earlier
26106 versions of @value{GDBN} may reject overly long responses). Additional values
26107 for @var{gdbfeature} may be defined in the future to let the stub take
26108 advantage of new features in @value{GDBN}, e.g.@: incompatible
26109 improvements in the remote protocol---the @samp{multiprocess} feature is
26110 an example of such a feature. The stub's reply should be independent
26111 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
26112 describes all the features it supports, and then the stub replies with
26113 all the features it supports.
26115 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
26116 responses, as long as each response uses one of the standard forms.
26118 Some features are flags. A stub which supports a flag feature
26119 should respond with a @samp{+} form response. Other features
26120 require values, and the stub should respond with an @samp{=}
26123 Each feature has a default value, which @value{GDBN} will use if
26124 @samp{qSupported} is not available or if the feature is not mentioned
26125 in the @samp{qSupported} response. The default values are fixed; a
26126 stub is free to omit any feature responses that match the defaults.
26128 Not all features can be probed, but for those which can, the probing
26129 mechanism is useful: in some cases, a stub's internal
26130 architecture may not allow the protocol layer to know some information
26131 about the underlying target in advance. This is especially common in
26132 stubs which may be configured for multiple targets.
26134 These are the currently defined stub features and their properties:
26136 @multitable @columnfractions 0.35 0.2 0.12 0.2
26137 @c NOTE: The first row should be @headitem, but we do not yet require
26138 @c a new enough version of Texinfo (4.7) to use @headitem.
26140 @tab Value Required
26144 @item @samp{PacketSize}
26149 @item @samp{qXfer:auxv:read}
26154 @item @samp{qXfer:features:read}
26159 @item @samp{qXfer:libraries:read}
26164 @item @samp{qXfer:memory-map:read}
26169 @item @samp{qXfer:spu:read}
26174 @item @samp{qXfer:spu:write}
26179 @item @samp{QNonStop}
26184 @item @samp{QPassSignals}
26189 @item @samp{QStartNoAckMode}
26194 @item @samp{multiprocess}
26201 These are the currently defined stub features, in more detail:
26204 @cindex packet size, remote protocol
26205 @item PacketSize=@var{bytes}
26206 The remote stub can accept packets up to at least @var{bytes} in
26207 length. @value{GDBN} will send packets up to this size for bulk
26208 transfers, and will never send larger packets. This is a limit on the
26209 data characters in the packet, including the frame and checksum.
26210 There is no trailing NUL byte in a remote protocol packet; if the stub
26211 stores packets in a NUL-terminated format, it should allow an extra
26212 byte in its buffer for the NUL. If this stub feature is not supported,
26213 @value{GDBN} guesses based on the size of the @samp{g} packet response.
26215 @item qXfer:auxv:read
26216 The remote stub understands the @samp{qXfer:auxv:read} packet
26217 (@pxref{qXfer auxiliary vector read}).
26219 @item qXfer:features:read
26220 The remote stub understands the @samp{qXfer:features:read} packet
26221 (@pxref{qXfer target description read}).
26223 @item qXfer:libraries:read
26224 The remote stub understands the @samp{qXfer:libraries:read} packet
26225 (@pxref{qXfer library list read}).
26227 @item qXfer:memory-map:read
26228 The remote stub understands the @samp{qXfer:memory-map:read} packet
26229 (@pxref{qXfer memory map read}).
26231 @item qXfer:spu:read
26232 The remote stub understands the @samp{qXfer:spu:read} packet
26233 (@pxref{qXfer spu read}).
26235 @item qXfer:spu:write
26236 The remote stub understands the @samp{qXfer:spu:write} packet
26237 (@pxref{qXfer spu write}).
26240 The remote stub understands the @samp{QNonStop} packet
26241 (@pxref{QNonStop}).
26244 The remote stub understands the @samp{QPassSignals} packet
26245 (@pxref{QPassSignals}).
26247 @item QStartNoAckMode
26248 The remote stub understands the @samp{QStartNoAckMode} packet and
26249 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
26252 @anchor{multiprocess extensions}
26253 @cindex multiprocess extensions, in remote protocol
26254 The remote stub understands the multiprocess extensions to the remote
26255 protocol syntax. The multiprocess extensions affect the syntax of
26256 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
26257 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
26258 replies. Note that reporting this feature indicates support for the
26259 syntactic extensions only, not that the stub necessarily supports
26260 debugging of more than one process at a time. The stub must not use
26261 multiprocess extensions in packet replies unless @value{GDBN} has also
26262 indicated it supports them in its @samp{qSupported} request.
26264 @item qXfer:osdata:read
26265 The remote stub understands the @samp{qXfer:osdata:read} packet
26266 ((@pxref{qXfer osdata read}).
26271 @cindex symbol lookup, remote request
26272 @cindex @samp{qSymbol} packet
26273 Notify the target that @value{GDBN} is prepared to serve symbol lookup
26274 requests. Accept requests from the target for the values of symbols.
26279 The target does not need to look up any (more) symbols.
26280 @item qSymbol:@var{sym_name}
26281 The target requests the value of symbol @var{sym_name} (hex encoded).
26282 @value{GDBN} may provide the value by using the
26283 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
26287 @item qSymbol:@var{sym_value}:@var{sym_name}
26288 Set the value of @var{sym_name} to @var{sym_value}.
26290 @var{sym_name} (hex encoded) is the name of a symbol whose value the
26291 target has previously requested.
26293 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
26294 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
26300 The target does not need to look up any (more) symbols.
26301 @item qSymbol:@var{sym_name}
26302 The target requests the value of a new symbol @var{sym_name} (hex
26303 encoded). @value{GDBN} will continue to supply the values of symbols
26304 (if available), until the target ceases to request them.
26309 @xref{Tracepoint Packets}.
26311 @item qThreadExtraInfo,@var{thread-id}
26312 @cindex thread attributes info, remote request
26313 @cindex @samp{qThreadExtraInfo} packet
26314 Obtain a printable string description of a thread's attributes from
26315 the target OS. @var{thread-id} is a thread ID;
26316 see @ref{thread-id syntax}. This
26317 string may contain anything that the target OS thinks is interesting
26318 for @value{GDBN} to tell the user about the thread. The string is
26319 displayed in @value{GDBN}'s @code{info threads} display. Some
26320 examples of possible thread extra info strings are @samp{Runnable}, or
26321 @samp{Blocked on Mutex}.
26325 @item @var{XX}@dots{}
26326 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
26327 comprising the printable string containing the extra information about
26328 the thread's attributes.
26331 (Note that the @code{qThreadExtraInfo} packet's name is separated from
26332 the command by a @samp{,}, not a @samp{:}, contrary to the naming
26333 conventions above. Please don't use this packet as a model for new
26341 @xref{Tracepoint Packets}.
26343 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
26344 @cindex read special object, remote request
26345 @cindex @samp{qXfer} packet
26346 @anchor{qXfer read}
26347 Read uninterpreted bytes from the target's special data area
26348 identified by the keyword @var{object}. Request @var{length} bytes
26349 starting at @var{offset} bytes into the data. The content and
26350 encoding of @var{annex} is specific to @var{object}; it can supply
26351 additional details about what data to access.
26353 Here are the specific requests of this form defined so far. All
26354 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
26355 formats, listed below.
26358 @item qXfer:auxv:read::@var{offset},@var{length}
26359 @anchor{qXfer auxiliary vector read}
26360 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
26361 auxiliary vector}. Note @var{annex} must be empty.
26363 This packet is not probed by default; the remote stub must request it,
26364 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26366 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
26367 @anchor{qXfer target description read}
26368 Access the @dfn{target description}. @xref{Target Descriptions}. The
26369 annex specifies which XML document to access. The main description is
26370 always loaded from the @samp{target.xml} annex.
26372 This packet is not probed by default; the remote stub must request it,
26373 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26375 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
26376 @anchor{qXfer library list read}
26377 Access the target's list of loaded libraries. @xref{Library List Format}.
26378 The annex part of the generic @samp{qXfer} packet must be empty
26379 (@pxref{qXfer read}).
26381 Targets which maintain a list of libraries in the program's memory do
26382 not need to implement this packet; it is designed for platforms where
26383 the operating system manages the list of loaded libraries.
26385 This packet is not probed by default; the remote stub must request it,
26386 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26388 @item qXfer:memory-map:read::@var{offset},@var{length}
26389 @anchor{qXfer memory map read}
26390 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
26391 annex part of the generic @samp{qXfer} packet must be empty
26392 (@pxref{qXfer read}).
26394 This packet is not probed by default; the remote stub must request it,
26395 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26397 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
26398 @anchor{qXfer spu read}
26399 Read contents of an @code{spufs} file on the target system. The
26400 annex specifies which file to read; it must be of the form
26401 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
26402 in the target process, and @var{name} identifes the @code{spufs} file
26403 in that context to be accessed.
26405 This packet is not probed by default; the remote stub must request it,
26406 by supplying an appropriate @samp{qSupported} response
26407 (@pxref{qSupported}).
26409 @item qXfer:osdata:read::@var{offset},@var{length}
26410 @anchor{qXfer osdata read}
26411 Access the target's @dfn{operating system information}.
26412 @xref{Operating System Information}.
26419 Data @var{data} (@pxref{Binary Data}) has been read from the
26420 target. There may be more data at a higher address (although
26421 it is permitted to return @samp{m} even for the last valid
26422 block of data, as long as at least one byte of data was read).
26423 @var{data} may have fewer bytes than the @var{length} in the
26427 Data @var{data} (@pxref{Binary Data}) has been read from the target.
26428 There is no more data to be read. @var{data} may have fewer bytes
26429 than the @var{length} in the request.
26432 The @var{offset} in the request is at the end of the data.
26433 There is no more data to be read.
26436 The request was malformed, or @var{annex} was invalid.
26439 The offset was invalid, or there was an error encountered reading the data.
26440 @var{nn} is a hex-encoded @code{errno} value.
26443 An empty reply indicates the @var{object} string was not recognized by
26444 the stub, or that the object does not support reading.
26447 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
26448 @cindex write data into object, remote request
26449 Write uninterpreted bytes into the target's special data area
26450 identified by the keyword @var{object}, starting at @var{offset} bytes
26451 into the data. @var{data}@dots{} is the binary-encoded data
26452 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
26453 is specific to @var{object}; it can supply additional details about what data
26456 Here are the specific requests of this form defined so far. All
26457 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
26458 formats, listed below.
26461 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
26462 @anchor{qXfer spu write}
26463 Write @var{data} to an @code{spufs} file on the target system. The
26464 annex specifies which file to write; it must be of the form
26465 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
26466 in the target process, and @var{name} identifes the @code{spufs} file
26467 in that context to be accessed.
26469 This packet is not probed by default; the remote stub must request it,
26470 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26476 @var{nn} (hex encoded) is the number of bytes written.
26477 This may be fewer bytes than supplied in the request.
26480 The request was malformed, or @var{annex} was invalid.
26483 The offset was invalid, or there was an error encountered writing the data.
26484 @var{nn} is a hex-encoded @code{errno} value.
26487 An empty reply indicates the @var{object} string was not
26488 recognized by the stub, or that the object does not support writing.
26491 @item qXfer:@var{object}:@var{operation}:@dots{}
26492 Requests of this form may be added in the future. When a stub does
26493 not recognize the @var{object} keyword, or its support for
26494 @var{object} does not recognize the @var{operation} keyword, the stub
26495 must respond with an empty packet.
26499 @node Register Packet Format
26500 @section Register Packet Format
26502 The following @code{g}/@code{G} packets have previously been defined.
26503 In the below, some thirty-two bit registers are transferred as
26504 sixty-four bits. Those registers should be zero/sign extended (which?)
26505 to fill the space allocated. Register bytes are transferred in target
26506 byte order. The two nibbles within a register byte are transferred
26507 most-significant - least-significant.
26513 All registers are transferred as thirty-two bit quantities in the order:
26514 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
26515 registers; fsr; fir; fp.
26519 All registers are transferred as sixty-four bit quantities (including
26520 thirty-two bit registers such as @code{sr}). The ordering is the same
26525 @node Tracepoint Packets
26526 @section Tracepoint Packets
26527 @cindex tracepoint packets
26528 @cindex packets, tracepoint
26530 Here we describe the packets @value{GDBN} uses to implement
26531 tracepoints (@pxref{Tracepoints}).
26535 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
26536 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
26537 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
26538 the tracepoint is disabled. @var{step} is the tracepoint's step
26539 count, and @var{pass} is its pass count. If the trailing @samp{-} is
26540 present, further @samp{QTDP} packets will follow to specify this
26541 tracepoint's actions.
26546 The packet was understood and carried out.
26548 The packet was not recognized.
26551 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
26552 Define actions to be taken when a tracepoint is hit. @var{n} and
26553 @var{addr} must be the same as in the initial @samp{QTDP} packet for
26554 this tracepoint. This packet may only be sent immediately after
26555 another @samp{QTDP} packet that ended with a @samp{-}. If the
26556 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
26557 specifying more actions for this tracepoint.
26559 In the series of action packets for a given tracepoint, at most one
26560 can have an @samp{S} before its first @var{action}. If such a packet
26561 is sent, it and the following packets define ``while-stepping''
26562 actions. Any prior packets define ordinary actions --- that is, those
26563 taken when the tracepoint is first hit. If no action packet has an
26564 @samp{S}, then all the packets in the series specify ordinary
26565 tracepoint actions.
26567 The @samp{@var{action}@dots{}} portion of the packet is a series of
26568 actions, concatenated without separators. Each action has one of the
26574 Collect the registers whose bits are set in @var{mask}. @var{mask} is
26575 a hexadecimal number whose @var{i}'th bit is set if register number
26576 @var{i} should be collected. (The least significant bit is numbered
26577 zero.) Note that @var{mask} may be any number of digits long; it may
26578 not fit in a 32-bit word.
26580 @item M @var{basereg},@var{offset},@var{len}
26581 Collect @var{len} bytes of memory starting at the address in register
26582 number @var{basereg}, plus @var{offset}. If @var{basereg} is
26583 @samp{-1}, then the range has a fixed address: @var{offset} is the
26584 address of the lowest byte to collect. The @var{basereg},
26585 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
26586 values (the @samp{-1} value for @var{basereg} is a special case).
26588 @item X @var{len},@var{expr}
26589 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
26590 it directs. @var{expr} is an agent expression, as described in
26591 @ref{Agent Expressions}. Each byte of the expression is encoded as a
26592 two-digit hex number in the packet; @var{len} is the number of bytes
26593 in the expression (and thus one-half the number of hex digits in the
26598 Any number of actions may be packed together in a single @samp{QTDP}
26599 packet, as long as the packet does not exceed the maximum packet
26600 length (400 bytes, for many stubs). There may be only one @samp{R}
26601 action per tracepoint, and it must precede any @samp{M} or @samp{X}
26602 actions. Any registers referred to by @samp{M} and @samp{X} actions
26603 must be collected by a preceding @samp{R} action. (The
26604 ``while-stepping'' actions are treated as if they were attached to a
26605 separate tracepoint, as far as these restrictions are concerned.)
26610 The packet was understood and carried out.
26612 The packet was not recognized.
26615 @item QTFrame:@var{n}
26616 Select the @var{n}'th tracepoint frame from the buffer, and use the
26617 register and memory contents recorded there to answer subsequent
26618 request packets from @value{GDBN}.
26620 A successful reply from the stub indicates that the stub has found the
26621 requested frame. The response is a series of parts, concatenated
26622 without separators, describing the frame we selected. Each part has
26623 one of the following forms:
26627 The selected frame is number @var{n} in the trace frame buffer;
26628 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
26629 was no frame matching the criteria in the request packet.
26632 The selected trace frame records a hit of tracepoint number @var{t};
26633 @var{t} is a hexadecimal number.
26637 @item QTFrame:pc:@var{addr}
26638 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26639 currently selected frame whose PC is @var{addr};
26640 @var{addr} is a hexadecimal number.
26642 @item QTFrame:tdp:@var{t}
26643 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26644 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
26645 is a hexadecimal number.
26647 @item QTFrame:range:@var{start}:@var{end}
26648 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26649 currently selected frame whose PC is between @var{start} (inclusive)
26650 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
26653 @item QTFrame:outside:@var{start}:@var{end}
26654 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
26655 frame @emph{outside} the given range of addresses.
26658 Begin the tracepoint experiment. Begin collecting data from tracepoint
26659 hits in the trace frame buffer.
26662 End the tracepoint experiment. Stop collecting trace frames.
26665 Clear the table of tracepoints, and empty the trace frame buffer.
26667 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
26668 Establish the given ranges of memory as ``transparent''. The stub
26669 will answer requests for these ranges from memory's current contents,
26670 if they were not collected as part of the tracepoint hit.
26672 @value{GDBN} uses this to mark read-only regions of memory, like those
26673 containing program code. Since these areas never change, they should
26674 still have the same contents they did when the tracepoint was hit, so
26675 there's no reason for the stub to refuse to provide their contents.
26678 Ask the stub if there is a trace experiment running right now.
26683 There is no trace experiment running.
26685 There is a trace experiment running.
26691 @node Host I/O Packets
26692 @section Host I/O Packets
26693 @cindex Host I/O, remote protocol
26694 @cindex file transfer, remote protocol
26696 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
26697 operations on the far side of a remote link. For example, Host I/O is
26698 used to upload and download files to a remote target with its own
26699 filesystem. Host I/O uses the same constant values and data structure
26700 layout as the target-initiated File-I/O protocol. However, the
26701 Host I/O packets are structured differently. The target-initiated
26702 protocol relies on target memory to store parameters and buffers.
26703 Host I/O requests are initiated by @value{GDBN}, and the
26704 target's memory is not involved. @xref{File-I/O Remote Protocol
26705 Extension}, for more details on the target-initiated protocol.
26707 The Host I/O request packets all encode a single operation along with
26708 its arguments. They have this format:
26712 @item vFile:@var{operation}: @var{parameter}@dots{}
26713 @var{operation} is the name of the particular request; the target
26714 should compare the entire packet name up to the second colon when checking
26715 for a supported operation. The format of @var{parameter} depends on
26716 the operation. Numbers are always passed in hexadecimal. Negative
26717 numbers have an explicit minus sign (i.e.@: two's complement is not
26718 used). Strings (e.g.@: filenames) are encoded as a series of
26719 hexadecimal bytes. The last argument to a system call may be a
26720 buffer of escaped binary data (@pxref{Binary Data}).
26724 The valid responses to Host I/O packets are:
26728 @item F @var{result} [, @var{errno}] [; @var{attachment}]
26729 @var{result} is the integer value returned by this operation, usually
26730 non-negative for success and -1 for errors. If an error has occured,
26731 @var{errno} will be included in the result. @var{errno} will have a
26732 value defined by the File-I/O protocol (@pxref{Errno Values}). For
26733 operations which return data, @var{attachment} supplies the data as a
26734 binary buffer. Binary buffers in response packets are escaped in the
26735 normal way (@pxref{Binary Data}). See the individual packet
26736 documentation for the interpretation of @var{result} and
26740 An empty response indicates that this operation is not recognized.
26744 These are the supported Host I/O operations:
26747 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
26748 Open a file at @var{pathname} and return a file descriptor for it, or
26749 return -1 if an error occurs. @var{pathname} is a string,
26750 @var{flags} is an integer indicating a mask of open flags
26751 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
26752 of mode bits to use if the file is created (@pxref{mode_t Values}).
26753 @xref{open}, for details of the open flags and mode values.
26755 @item vFile:close: @var{fd}
26756 Close the open file corresponding to @var{fd} and return 0, or
26757 -1 if an error occurs.
26759 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
26760 Read data from the open file corresponding to @var{fd}. Up to
26761 @var{count} bytes will be read from the file, starting at @var{offset}
26762 relative to the start of the file. The target may read fewer bytes;
26763 common reasons include packet size limits and an end-of-file
26764 condition. The number of bytes read is returned. Zero should only be
26765 returned for a successful read at the end of the file, or if
26766 @var{count} was zero.
26768 The data read should be returned as a binary attachment on success.
26769 If zero bytes were read, the response should include an empty binary
26770 attachment (i.e.@: a trailing semicolon). The return value is the
26771 number of target bytes read; the binary attachment may be longer if
26772 some characters were escaped.
26774 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
26775 Write @var{data} (a binary buffer) to the open file corresponding
26776 to @var{fd}. Start the write at @var{offset} from the start of the
26777 file. Unlike many @code{write} system calls, there is no
26778 separate @var{count} argument; the length of @var{data} in the
26779 packet is used. @samp{vFile:write} returns the number of bytes written,
26780 which may be shorter than the length of @var{data}, or -1 if an
26783 @item vFile:unlink: @var{pathname}
26784 Delete the file at @var{pathname} on the target. Return 0,
26785 or -1 if an error occurs. @var{pathname} is a string.
26790 @section Interrupts
26791 @cindex interrupts (remote protocol)
26793 When a program on the remote target is running, @value{GDBN} may
26794 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
26795 control of which is specified via @value{GDBN}'s @samp{remotebreak}
26796 setting (@pxref{set remotebreak}).
26798 The precise meaning of @code{BREAK} is defined by the transport
26799 mechanism and may, in fact, be undefined. @value{GDBN} does not
26800 currently define a @code{BREAK} mechanism for any of the network
26801 interfaces except for TCP, in which case @value{GDBN} sends the
26802 @code{telnet} BREAK sequence.
26804 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
26805 transport mechanisms. It is represented by sending the single byte
26806 @code{0x03} without any of the usual packet overhead described in
26807 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
26808 transmitted as part of a packet, it is considered to be packet data
26809 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
26810 (@pxref{X packet}), used for binary downloads, may include an unescaped
26811 @code{0x03} as part of its packet.
26813 Stubs are not required to recognize these interrupt mechanisms and the
26814 precise meaning associated with receipt of the interrupt is
26815 implementation defined. If the target supports debugging of multiple
26816 threads and/or processes, it should attempt to interrupt all
26817 currently-executing threads and processes.
26818 If the stub is successful at interrupting the
26819 running program, it should send one of the stop
26820 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
26821 of successfully stopping the program in all-stop mode, and a stop reply
26822 for each stopped thread in non-stop mode.
26823 Interrupts received while the
26824 program is stopped are discarded.
26826 @node Notification Packets
26827 @section Notification Packets
26828 @cindex notification packets
26829 @cindex packets, notification
26831 The @value{GDBN} remote serial protocol includes @dfn{notifications},
26832 packets that require no acknowledgment. Both the GDB and the stub
26833 may send notifications (although the only notifications defined at
26834 present are sent by the stub). Notifications carry information
26835 without incurring the round-trip latency of an acknowledgment, and so
26836 are useful for low-impact communications where occasional packet loss
26839 A notification packet has the form @samp{% @var{data} #
26840 @var{checksum}}, where @var{data} is the content of the notification,
26841 and @var{checksum} is a checksum of @var{data}, computed and formatted
26842 as for ordinary @value{GDBN} packets. A notification's @var{data}
26843 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
26844 receiving a notification, the recipient sends no @samp{+} or @samp{-}
26845 to acknowledge the notification's receipt or to report its corruption.
26847 Every notification's @var{data} begins with a name, which contains no
26848 colon characters, followed by a colon character.
26850 Recipients should silently ignore corrupted notifications and
26851 notifications they do not understand. Recipients should restart
26852 timeout periods on receipt of a well-formed notification, whether or
26853 not they understand it.
26855 Senders should only send the notifications described here when this
26856 protocol description specifies that they are permitted. In the
26857 future, we may extend the protocol to permit existing notifications in
26858 new contexts; this rule helps older senders avoid confusing newer
26861 (Older versions of @value{GDBN} ignore bytes received until they see
26862 the @samp{$} byte that begins an ordinary packet, so new stubs may
26863 transmit notifications without fear of confusing older clients. There
26864 are no notifications defined for @value{GDBN} to send at the moment, but we
26865 assume that most older stubs would ignore them, as well.)
26867 The following notification packets from the stub to @value{GDBN} are
26871 @item Stop: @var{reply}
26872 Report an asynchronous stop event in non-stop mode.
26873 The @var{reply} has the form of a stop reply, as
26874 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
26875 for information on how these notifications are acknowledged by
26879 @node Remote Non-Stop
26880 @section Remote Protocol Support for Non-Stop Mode
26882 @value{GDBN}'s remote protocol supports non-stop debugging of
26883 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
26884 supports non-stop mode, it should report that to @value{GDBN} by including
26885 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
26887 @value{GDBN} typically sends a @samp{QNonStop} packet only when
26888 establishing a new connection with the stub. Entering non-stop mode
26889 does not alter the state of any currently-running threads, but targets
26890 must stop all threads in any already-attached processes when entering
26891 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
26892 probe the target state after a mode change.
26894 In non-stop mode, when an attached process encounters an event that
26895 would otherwise be reported with a stop reply, it uses the
26896 asynchronous notification mechanism (@pxref{Notification Packets}) to
26897 inform @value{GDBN}. In contrast to all-stop mode, where all threads
26898 in all processes are stopped when a stop reply is sent, in non-stop
26899 mode only the thread reporting the stop event is stopped. That is,
26900 when reporting a @samp{S} or @samp{T} response to indicate completion
26901 of a step operation, hitting a breakpoint, or a fault, only the
26902 affected thread is stopped; any other still-running threads continue
26903 to run. When reporting a @samp{W} or @samp{X} response, all running
26904 threads belonging to other attached processes continue to run.
26906 Only one stop reply notification at a time may be pending; if
26907 additional stop events occur before @value{GDBN} has acknowledged the
26908 previous notification, they must be queued by the stub for later
26909 synchronous transmission in response to @samp{vStopped} packets from
26910 @value{GDBN}. Because the notification mechanism is unreliable,
26911 the stub is permitted to resend a stop reply notification
26912 if it believes @value{GDBN} may not have received it. @value{GDBN}
26913 ignores additional stop reply notifications received before it has
26914 finished processing a previous notification and the stub has completed
26915 sending any queued stop events.
26917 Otherwise, @value{GDBN} must be prepared to receive a stop reply
26918 notification at any time. Specifically, they may appear when
26919 @value{GDBN} is not otherwise reading input from the stub, or when
26920 @value{GDBN} is expecting to read a normal synchronous response or a
26921 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
26922 Notification packets are distinct from any other communication from
26923 the stub so there is no ambiguity.
26925 After receiving a stop reply notification, @value{GDBN} shall
26926 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
26927 as a regular, synchronous request to the stub. Such acknowledgment
26928 is not required to happen immediately, as @value{GDBN} is permitted to
26929 send other, unrelated packets to the stub first, which the stub should
26932 Upon receiving a @samp{vStopped} packet, if the stub has other queued
26933 stop events to report to @value{GDBN}, it shall respond by sending a
26934 normal stop reply response. @value{GDBN} shall then send another
26935 @samp{vStopped} packet to solicit further responses; again, it is
26936 permitted to send other, unrelated packets as well which the stub
26937 should process normally.
26939 If the stub receives a @samp{vStopped} packet and there are no
26940 additional stop events to report, the stub shall return an @samp{OK}
26941 response. At this point, if further stop events occur, the stub shall
26942 send a new stop reply notification, @value{GDBN} shall accept the
26943 notification, and the process shall be repeated.
26945 In non-stop mode, the target shall respond to the @samp{?} packet as
26946 follows. First, any incomplete stop reply notification/@samp{vStopped}
26947 sequence in progress is abandoned. The target must begin a new
26948 sequence reporting stop events for all stopped threads, whether or not
26949 it has previously reported those events to @value{GDBN}. The first
26950 stop reply is sent as a synchronous reply to the @samp{?} packet, and
26951 subsequent stop replies are sent as responses to @samp{vStopped} packets
26952 using the mechanism described above. The target must not send
26953 asynchronous stop reply notifications until the sequence is complete.
26954 If all threads are running when the target receives the @samp{?} packet,
26955 or if the target is not attached to any process, it shall respond
26958 @node Packet Acknowledgment
26959 @section Packet Acknowledgment
26961 @cindex acknowledgment, for @value{GDBN} remote
26962 @cindex packet acknowledgment, for @value{GDBN} remote
26963 By default, when either the host or the target machine receives a packet,
26964 the first response expected is an acknowledgment: either @samp{+} (to indicate
26965 the package was received correctly) or @samp{-} (to request retransmission).
26966 This mechanism allows the @value{GDBN} remote protocol to operate over
26967 unreliable transport mechanisms, such as a serial line.
26969 In cases where the transport mechanism is itself reliable (such as a pipe or
26970 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
26971 It may be desirable to disable them in that case to reduce communication
26972 overhead, or for other reasons. This can be accomplished by means of the
26973 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
26975 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
26976 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
26977 and response format still includes the normal checksum, as described in
26978 @ref{Overview}, but the checksum may be ignored by the receiver.
26980 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
26981 no-acknowledgment mode, it should report that to @value{GDBN}
26982 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
26983 @pxref{qSupported}.
26984 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
26985 disabled via the @code{set remote noack-packet off} command
26986 (@pxref{Remote Configuration}),
26987 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
26988 Only then may the stub actually turn off packet acknowledgments.
26989 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
26990 response, which can be safely ignored by the stub.
26992 Note that @code{set remote noack-packet} command only affects negotiation
26993 between @value{GDBN} and the stub when subsequent connections are made;
26994 it does not affect the protocol acknowledgment state for any current
26996 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
26997 new connection is established,
26998 there is also no protocol request to re-enable the acknowledgments
26999 for the current connection, once disabled.
27004 Example sequence of a target being re-started. Notice how the restart
27005 does not get any direct output:
27010 @emph{target restarts}
27013 <- @code{T001:1234123412341234}
27017 Example sequence of a target being stepped by a single instruction:
27020 -> @code{G1445@dots{}}
27025 <- @code{T001:1234123412341234}
27029 <- @code{1455@dots{}}
27033 @node File-I/O Remote Protocol Extension
27034 @section File-I/O Remote Protocol Extension
27035 @cindex File-I/O remote protocol extension
27038 * File-I/O Overview::
27039 * Protocol Basics::
27040 * The F Request Packet::
27041 * The F Reply Packet::
27042 * The Ctrl-C Message::
27044 * List of Supported Calls::
27045 * Protocol-specific Representation of Datatypes::
27047 * File-I/O Examples::
27050 @node File-I/O Overview
27051 @subsection File-I/O Overview
27052 @cindex file-i/o overview
27054 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
27055 target to use the host's file system and console I/O to perform various
27056 system calls. System calls on the target system are translated into a
27057 remote protocol packet to the host system, which then performs the needed
27058 actions and returns a response packet to the target system.
27059 This simulates file system operations even on targets that lack file systems.
27061 The protocol is defined to be independent of both the host and target systems.
27062 It uses its own internal representation of datatypes and values. Both
27063 @value{GDBN} and the target's @value{GDBN} stub are responsible for
27064 translating the system-dependent value representations into the internal
27065 protocol representations when data is transmitted.
27067 The communication is synchronous. A system call is possible only when
27068 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
27069 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
27070 the target is stopped to allow deterministic access to the target's
27071 memory. Therefore File-I/O is not interruptible by target signals. On
27072 the other hand, it is possible to interrupt File-I/O by a user interrupt
27073 (@samp{Ctrl-C}) within @value{GDBN}.
27075 The target's request to perform a host system call does not finish
27076 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
27077 after finishing the system call, the target returns to continuing the
27078 previous activity (continue, step). No additional continue or step
27079 request from @value{GDBN} is required.
27082 (@value{GDBP}) continue
27083 <- target requests 'system call X'
27084 target is stopped, @value{GDBN} executes system call
27085 -> @value{GDBN} returns result
27086 ... target continues, @value{GDBN} returns to wait for the target
27087 <- target hits breakpoint and sends a Txx packet
27090 The protocol only supports I/O on the console and to regular files on
27091 the host file system. Character or block special devices, pipes,
27092 named pipes, sockets or any other communication method on the host
27093 system are not supported by this protocol.
27095 File I/O is not supported in non-stop mode.
27097 @node Protocol Basics
27098 @subsection Protocol Basics
27099 @cindex protocol basics, file-i/o
27101 The File-I/O protocol uses the @code{F} packet as the request as well
27102 as reply packet. Since a File-I/O system call can only occur when
27103 @value{GDBN} is waiting for a response from the continuing or stepping target,
27104 the File-I/O request is a reply that @value{GDBN} has to expect as a result
27105 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
27106 This @code{F} packet contains all information needed to allow @value{GDBN}
27107 to call the appropriate host system call:
27111 A unique identifier for the requested system call.
27114 All parameters to the system call. Pointers are given as addresses
27115 in the target memory address space. Pointers to strings are given as
27116 pointer/length pair. Numerical values are given as they are.
27117 Numerical control flags are given in a protocol-specific representation.
27121 At this point, @value{GDBN} has to perform the following actions.
27125 If the parameters include pointer values to data needed as input to a
27126 system call, @value{GDBN} requests this data from the target with a
27127 standard @code{m} packet request. This additional communication has to be
27128 expected by the target implementation and is handled as any other @code{m}
27132 @value{GDBN} translates all value from protocol representation to host
27133 representation as needed. Datatypes are coerced into the host types.
27136 @value{GDBN} calls the system call.
27139 It then coerces datatypes back to protocol representation.
27142 If the system call is expected to return data in buffer space specified
27143 by pointer parameters to the call, the data is transmitted to the
27144 target using a @code{M} or @code{X} packet. This packet has to be expected
27145 by the target implementation and is handled as any other @code{M} or @code{X}
27150 Eventually @value{GDBN} replies with another @code{F} packet which contains all
27151 necessary information for the target to continue. This at least contains
27158 @code{errno}, if has been changed by the system call.
27165 After having done the needed type and value coercion, the target continues
27166 the latest continue or step action.
27168 @node The F Request Packet
27169 @subsection The @code{F} Request Packet
27170 @cindex file-i/o request packet
27171 @cindex @code{F} request packet
27173 The @code{F} request packet has the following format:
27176 @item F@var{call-id},@var{parameter@dots{}}
27178 @var{call-id} is the identifier to indicate the host system call to be called.
27179 This is just the name of the function.
27181 @var{parameter@dots{}} are the parameters to the system call.
27182 Parameters are hexadecimal integer values, either the actual values in case
27183 of scalar datatypes, pointers to target buffer space in case of compound
27184 datatypes and unspecified memory areas, or pointer/length pairs in case
27185 of string parameters. These are appended to the @var{call-id} as a
27186 comma-delimited list. All values are transmitted in ASCII
27187 string representation, pointer/length pairs separated by a slash.
27193 @node The F Reply Packet
27194 @subsection The @code{F} Reply Packet
27195 @cindex file-i/o reply packet
27196 @cindex @code{F} reply packet
27198 The @code{F} reply packet has the following format:
27202 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
27204 @var{retcode} is the return code of the system call as hexadecimal value.
27206 @var{errno} is the @code{errno} set by the call, in protocol-specific
27208 This parameter can be omitted if the call was successful.
27210 @var{Ctrl-C flag} is only sent if the user requested a break. In this
27211 case, @var{errno} must be sent as well, even if the call was successful.
27212 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
27219 or, if the call was interrupted before the host call has been performed:
27226 assuming 4 is the protocol-specific representation of @code{EINTR}.
27231 @node The Ctrl-C Message
27232 @subsection The @samp{Ctrl-C} Message
27233 @cindex ctrl-c message, in file-i/o protocol
27235 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
27236 reply packet (@pxref{The F Reply Packet}),
27237 the target should behave as if it had
27238 gotten a break message. The meaning for the target is ``system call
27239 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
27240 (as with a break message) and return to @value{GDBN} with a @code{T02}
27243 It's important for the target to know in which
27244 state the system call was interrupted. There are two possible cases:
27248 The system call hasn't been performed on the host yet.
27251 The system call on the host has been finished.
27255 These two states can be distinguished by the target by the value of the
27256 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
27257 call hasn't been performed. This is equivalent to the @code{EINTR} handling
27258 on POSIX systems. In any other case, the target may presume that the
27259 system call has been finished --- successfully or not --- and should behave
27260 as if the break message arrived right after the system call.
27262 @value{GDBN} must behave reliably. If the system call has not been called
27263 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
27264 @code{errno} in the packet. If the system call on the host has been finished
27265 before the user requests a break, the full action must be finished by
27266 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
27267 The @code{F} packet may only be sent when either nothing has happened
27268 or the full action has been completed.
27271 @subsection Console I/O
27272 @cindex console i/o as part of file-i/o
27274 By default and if not explicitly closed by the target system, the file
27275 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
27276 on the @value{GDBN} console is handled as any other file output operation
27277 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
27278 by @value{GDBN} so that after the target read request from file descriptor
27279 0 all following typing is buffered until either one of the following
27284 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
27286 system call is treated as finished.
27289 The user presses @key{RET}. This is treated as end of input with a trailing
27293 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
27294 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
27298 If the user has typed more characters than fit in the buffer given to
27299 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
27300 either another @code{read(0, @dots{})} is requested by the target, or debugging
27301 is stopped at the user's request.
27304 @node List of Supported Calls
27305 @subsection List of Supported Calls
27306 @cindex list of supported file-i/o calls
27323 @unnumberedsubsubsec open
27324 @cindex open, file-i/o system call
27329 int open(const char *pathname, int flags);
27330 int open(const char *pathname, int flags, mode_t mode);
27334 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
27337 @var{flags} is the bitwise @code{OR} of the following values:
27341 If the file does not exist it will be created. The host
27342 rules apply as far as file ownership and time stamps
27346 When used with @code{O_CREAT}, if the file already exists it is
27347 an error and open() fails.
27350 If the file already exists and the open mode allows
27351 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
27352 truncated to zero length.
27355 The file is opened in append mode.
27358 The file is opened for reading only.
27361 The file is opened for writing only.
27364 The file is opened for reading and writing.
27368 Other bits are silently ignored.
27372 @var{mode} is the bitwise @code{OR} of the following values:
27376 User has read permission.
27379 User has write permission.
27382 Group has read permission.
27385 Group has write permission.
27388 Others have read permission.
27391 Others have write permission.
27395 Other bits are silently ignored.
27398 @item Return value:
27399 @code{open} returns the new file descriptor or -1 if an error
27406 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
27409 @var{pathname} refers to a directory.
27412 The requested access is not allowed.
27415 @var{pathname} was too long.
27418 A directory component in @var{pathname} does not exist.
27421 @var{pathname} refers to a device, pipe, named pipe or socket.
27424 @var{pathname} refers to a file on a read-only filesystem and
27425 write access was requested.
27428 @var{pathname} is an invalid pointer value.
27431 No space on device to create the file.
27434 The process already has the maximum number of files open.
27437 The limit on the total number of files open on the system
27441 The call was interrupted by the user.
27447 @unnumberedsubsubsec close
27448 @cindex close, file-i/o system call
27457 @samp{Fclose,@var{fd}}
27459 @item Return value:
27460 @code{close} returns zero on success, or -1 if an error occurred.
27466 @var{fd} isn't a valid open file descriptor.
27469 The call was interrupted by the user.
27475 @unnumberedsubsubsec read
27476 @cindex read, file-i/o system call
27481 int read(int fd, void *buf, unsigned int count);
27485 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
27487 @item Return value:
27488 On success, the number of bytes read is returned.
27489 Zero indicates end of file. If count is zero, read
27490 returns zero as well. On error, -1 is returned.
27496 @var{fd} is not a valid file descriptor or is not open for
27500 @var{bufptr} is an invalid pointer value.
27503 The call was interrupted by the user.
27509 @unnumberedsubsubsec write
27510 @cindex write, file-i/o system call
27515 int write(int fd, const void *buf, unsigned int count);
27519 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
27521 @item Return value:
27522 On success, the number of bytes written are returned.
27523 Zero indicates nothing was written. On error, -1
27530 @var{fd} is not a valid file descriptor or is not open for
27534 @var{bufptr} is an invalid pointer value.
27537 An attempt was made to write a file that exceeds the
27538 host-specific maximum file size allowed.
27541 No space on device to write the data.
27544 The call was interrupted by the user.
27550 @unnumberedsubsubsec lseek
27551 @cindex lseek, file-i/o system call
27556 long lseek (int fd, long offset, int flag);
27560 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
27562 @var{flag} is one of:
27566 The offset is set to @var{offset} bytes.
27569 The offset is set to its current location plus @var{offset}
27573 The offset is set to the size of the file plus @var{offset}
27577 @item Return value:
27578 On success, the resulting unsigned offset in bytes from
27579 the beginning of the file is returned. Otherwise, a
27580 value of -1 is returned.
27586 @var{fd} is not a valid open file descriptor.
27589 @var{fd} is associated with the @value{GDBN} console.
27592 @var{flag} is not a proper value.
27595 The call was interrupted by the user.
27601 @unnumberedsubsubsec rename
27602 @cindex rename, file-i/o system call
27607 int rename(const char *oldpath, const char *newpath);
27611 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
27613 @item Return value:
27614 On success, zero is returned. On error, -1 is returned.
27620 @var{newpath} is an existing directory, but @var{oldpath} is not a
27624 @var{newpath} is a non-empty directory.
27627 @var{oldpath} or @var{newpath} is a directory that is in use by some
27631 An attempt was made to make a directory a subdirectory
27635 A component used as a directory in @var{oldpath} or new
27636 path is not a directory. Or @var{oldpath} is a directory
27637 and @var{newpath} exists but is not a directory.
27640 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
27643 No access to the file or the path of the file.
27647 @var{oldpath} or @var{newpath} was too long.
27650 A directory component in @var{oldpath} or @var{newpath} does not exist.
27653 The file is on a read-only filesystem.
27656 The device containing the file has no room for the new
27660 The call was interrupted by the user.
27666 @unnumberedsubsubsec unlink
27667 @cindex unlink, file-i/o system call
27672 int unlink(const char *pathname);
27676 @samp{Funlink,@var{pathnameptr}/@var{len}}
27678 @item Return value:
27679 On success, zero is returned. On error, -1 is returned.
27685 No access to the file or the path of the file.
27688 The system does not allow unlinking of directories.
27691 The file @var{pathname} cannot be unlinked because it's
27692 being used by another process.
27695 @var{pathnameptr} is an invalid pointer value.
27698 @var{pathname} was too long.
27701 A directory component in @var{pathname} does not exist.
27704 A component of the path is not a directory.
27707 The file is on a read-only filesystem.
27710 The call was interrupted by the user.
27716 @unnumberedsubsubsec stat/fstat
27717 @cindex fstat, file-i/o system call
27718 @cindex stat, file-i/o system call
27723 int stat(const char *pathname, struct stat *buf);
27724 int fstat(int fd, struct stat *buf);
27728 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
27729 @samp{Ffstat,@var{fd},@var{bufptr}}
27731 @item Return value:
27732 On success, zero is returned. On error, -1 is returned.
27738 @var{fd} is not a valid open file.
27741 A directory component in @var{pathname} does not exist or the
27742 path is an empty string.
27745 A component of the path is not a directory.
27748 @var{pathnameptr} is an invalid pointer value.
27751 No access to the file or the path of the file.
27754 @var{pathname} was too long.
27757 The call was interrupted by the user.
27763 @unnumberedsubsubsec gettimeofday
27764 @cindex gettimeofday, file-i/o system call
27769 int gettimeofday(struct timeval *tv, void *tz);
27773 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
27775 @item Return value:
27776 On success, 0 is returned, -1 otherwise.
27782 @var{tz} is a non-NULL pointer.
27785 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
27791 @unnumberedsubsubsec isatty
27792 @cindex isatty, file-i/o system call
27797 int isatty(int fd);
27801 @samp{Fisatty,@var{fd}}
27803 @item Return value:
27804 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
27810 The call was interrupted by the user.
27815 Note that the @code{isatty} call is treated as a special case: it returns
27816 1 to the target if the file descriptor is attached
27817 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
27818 would require implementing @code{ioctl} and would be more complex than
27823 @unnumberedsubsubsec system
27824 @cindex system, file-i/o system call
27829 int system(const char *command);
27833 @samp{Fsystem,@var{commandptr}/@var{len}}
27835 @item Return value:
27836 If @var{len} is zero, the return value indicates whether a shell is
27837 available. A zero return value indicates a shell is not available.
27838 For non-zero @var{len}, the value returned is -1 on error and the
27839 return status of the command otherwise. Only the exit status of the
27840 command is returned, which is extracted from the host's @code{system}
27841 return value by calling @code{WEXITSTATUS(retval)}. In case
27842 @file{/bin/sh} could not be executed, 127 is returned.
27848 The call was interrupted by the user.
27853 @value{GDBN} takes over the full task of calling the necessary host calls
27854 to perform the @code{system} call. The return value of @code{system} on
27855 the host is simplified before it's returned
27856 to the target. Any termination signal information from the child process
27857 is discarded, and the return value consists
27858 entirely of the exit status of the called command.
27860 Due to security concerns, the @code{system} call is by default refused
27861 by @value{GDBN}. The user has to allow this call explicitly with the
27862 @code{set remote system-call-allowed 1} command.
27865 @item set remote system-call-allowed
27866 @kindex set remote system-call-allowed
27867 Control whether to allow the @code{system} calls in the File I/O
27868 protocol for the remote target. The default is zero (disabled).
27870 @item show remote system-call-allowed
27871 @kindex show remote system-call-allowed
27872 Show whether the @code{system} calls are allowed in the File I/O
27876 @node Protocol-specific Representation of Datatypes
27877 @subsection Protocol-specific Representation of Datatypes
27878 @cindex protocol-specific representation of datatypes, in file-i/o protocol
27881 * Integral Datatypes::
27883 * Memory Transfer::
27888 @node Integral Datatypes
27889 @unnumberedsubsubsec Integral Datatypes
27890 @cindex integral datatypes, in file-i/o protocol
27892 The integral datatypes used in the system calls are @code{int},
27893 @code{unsigned int}, @code{long}, @code{unsigned long},
27894 @code{mode_t}, and @code{time_t}.
27896 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
27897 implemented as 32 bit values in this protocol.
27899 @code{long} and @code{unsigned long} are implemented as 64 bit types.
27901 @xref{Limits}, for corresponding MIN and MAX values (similar to those
27902 in @file{limits.h}) to allow range checking on host and target.
27904 @code{time_t} datatypes are defined as seconds since the Epoch.
27906 All integral datatypes transferred as part of a memory read or write of a
27907 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
27910 @node Pointer Values
27911 @unnumberedsubsubsec Pointer Values
27912 @cindex pointer values, in file-i/o protocol
27914 Pointers to target data are transmitted as they are. An exception
27915 is made for pointers to buffers for which the length isn't
27916 transmitted as part of the function call, namely strings. Strings
27917 are transmitted as a pointer/length pair, both as hex values, e.g.@:
27924 which is a pointer to data of length 18 bytes at position 0x1aaf.
27925 The length is defined as the full string length in bytes, including
27926 the trailing null byte. For example, the string @code{"hello world"}
27927 at address 0x123456 is transmitted as
27933 @node Memory Transfer
27934 @unnumberedsubsubsec Memory Transfer
27935 @cindex memory transfer, in file-i/o protocol
27937 Structured data which is transferred using a memory read or write (for
27938 example, a @code{struct stat}) is expected to be in a protocol-specific format
27939 with all scalar multibyte datatypes being big endian. Translation to
27940 this representation needs to be done both by the target before the @code{F}
27941 packet is sent, and by @value{GDBN} before
27942 it transfers memory to the target. Transferred pointers to structured
27943 data should point to the already-coerced data at any time.
27947 @unnumberedsubsubsec struct stat
27948 @cindex struct stat, in file-i/o protocol
27950 The buffer of type @code{struct stat} used by the target and @value{GDBN}
27951 is defined as follows:
27955 unsigned int st_dev; /* device */
27956 unsigned int st_ino; /* inode */
27957 mode_t st_mode; /* protection */
27958 unsigned int st_nlink; /* number of hard links */
27959 unsigned int st_uid; /* user ID of owner */
27960 unsigned int st_gid; /* group ID of owner */
27961 unsigned int st_rdev; /* device type (if inode device) */
27962 unsigned long st_size; /* total size, in bytes */
27963 unsigned long st_blksize; /* blocksize for filesystem I/O */
27964 unsigned long st_blocks; /* number of blocks allocated */
27965 time_t st_atime; /* time of last access */
27966 time_t st_mtime; /* time of last modification */
27967 time_t st_ctime; /* time of last change */
27971 The integral datatypes conform to the definitions given in the
27972 appropriate section (see @ref{Integral Datatypes}, for details) so this
27973 structure is of size 64 bytes.
27975 The values of several fields have a restricted meaning and/or
27981 A value of 0 represents a file, 1 the console.
27984 No valid meaning for the target. Transmitted unchanged.
27987 Valid mode bits are described in @ref{Constants}. Any other
27988 bits have currently no meaning for the target.
27993 No valid meaning for the target. Transmitted unchanged.
27998 These values have a host and file system dependent
27999 accuracy. Especially on Windows hosts, the file system may not
28000 support exact timing values.
28003 The target gets a @code{struct stat} of the above representation and is
28004 responsible for coercing it to the target representation before
28007 Note that due to size differences between the host, target, and protocol
28008 representations of @code{struct stat} members, these members could eventually
28009 get truncated on the target.
28011 @node struct timeval
28012 @unnumberedsubsubsec struct timeval
28013 @cindex struct timeval, in file-i/o protocol
28015 The buffer of type @code{struct timeval} used by the File-I/O protocol
28016 is defined as follows:
28020 time_t tv_sec; /* second */
28021 long tv_usec; /* microsecond */
28025 The integral datatypes conform to the definitions given in the
28026 appropriate section (see @ref{Integral Datatypes}, for details) so this
28027 structure is of size 8 bytes.
28030 @subsection Constants
28031 @cindex constants, in file-i/o protocol
28033 The following values are used for the constants inside of the
28034 protocol. @value{GDBN} and target are responsible for translating these
28035 values before and after the call as needed.
28046 @unnumberedsubsubsec Open Flags
28047 @cindex open flags, in file-i/o protocol
28049 All values are given in hexadecimal representation.
28061 @node mode_t Values
28062 @unnumberedsubsubsec mode_t Values
28063 @cindex mode_t values, in file-i/o protocol
28065 All values are given in octal representation.
28082 @unnumberedsubsubsec Errno Values
28083 @cindex errno values, in file-i/o protocol
28085 All values are given in decimal representation.
28110 @code{EUNKNOWN} is used as a fallback error value if a host system returns
28111 any error value not in the list of supported error numbers.
28114 @unnumberedsubsubsec Lseek Flags
28115 @cindex lseek flags, in file-i/o protocol
28124 @unnumberedsubsubsec Limits
28125 @cindex limits, in file-i/o protocol
28127 All values are given in decimal representation.
28130 INT_MIN -2147483648
28132 UINT_MAX 4294967295
28133 LONG_MIN -9223372036854775808
28134 LONG_MAX 9223372036854775807
28135 ULONG_MAX 18446744073709551615
28138 @node File-I/O Examples
28139 @subsection File-I/O Examples
28140 @cindex file-i/o examples
28142 Example sequence of a write call, file descriptor 3, buffer is at target
28143 address 0x1234, 6 bytes should be written:
28146 <- @code{Fwrite,3,1234,6}
28147 @emph{request memory read from target}
28150 @emph{return "6 bytes written"}
28154 Example sequence of a read call, file descriptor 3, buffer is at target
28155 address 0x1234, 6 bytes should be read:
28158 <- @code{Fread,3,1234,6}
28159 @emph{request memory write to target}
28160 -> @code{X1234,6:XXXXXX}
28161 @emph{return "6 bytes read"}
28165 Example sequence of a read call, call fails on the host due to invalid
28166 file descriptor (@code{EBADF}):
28169 <- @code{Fread,3,1234,6}
28173 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
28177 <- @code{Fread,3,1234,6}
28182 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
28186 <- @code{Fread,3,1234,6}
28187 -> @code{X1234,6:XXXXXX}
28191 @node Library List Format
28192 @section Library List Format
28193 @cindex library list format, remote protocol
28195 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
28196 same process as your application to manage libraries. In this case,
28197 @value{GDBN} can use the loader's symbol table and normal memory
28198 operations to maintain a list of shared libraries. On other
28199 platforms, the operating system manages loaded libraries.
28200 @value{GDBN} can not retrieve the list of currently loaded libraries
28201 through memory operations, so it uses the @samp{qXfer:libraries:read}
28202 packet (@pxref{qXfer library list read}) instead. The remote stub
28203 queries the target's operating system and reports which libraries
28206 The @samp{qXfer:libraries:read} packet returns an XML document which
28207 lists loaded libraries and their offsets. Each library has an
28208 associated name and one or more segment or section base addresses,
28209 which report where the library was loaded in memory.
28211 For the common case of libraries that are fully linked binaries, the
28212 library should have a list of segments. If the target supports
28213 dynamic linking of a relocatable object file, its library XML element
28214 should instead include a list of allocated sections. The segment or
28215 section bases are start addresses, not relocation offsets; they do not
28216 depend on the library's link-time base addresses.
28218 @value{GDBN} must be linked with the Expat library to support XML
28219 library lists. @xref{Expat}.
28221 A simple memory map, with one loaded library relocated by a single
28222 offset, looks like this:
28226 <library name="/lib/libc.so.6">
28227 <segment address="0x10000000"/>
28232 Another simple memory map, with one loaded library with three
28233 allocated sections (.text, .data, .bss), looks like this:
28237 <library name="sharedlib.o">
28238 <section address="0x10000000"/>
28239 <section address="0x20000000"/>
28240 <section address="0x30000000"/>
28245 The format of a library list is described by this DTD:
28248 <!-- library-list: Root element with versioning -->
28249 <!ELEMENT library-list (library)*>
28250 <!ATTLIST library-list version CDATA #FIXED "1.0">
28251 <!ELEMENT library (segment*, section*)>
28252 <!ATTLIST library name CDATA #REQUIRED>
28253 <!ELEMENT segment EMPTY>
28254 <!ATTLIST segment address CDATA #REQUIRED>
28255 <!ELEMENT section EMPTY>
28256 <!ATTLIST section address CDATA #REQUIRED>
28259 In addition, segments and section descriptors cannot be mixed within a
28260 single library element, and you must supply at least one segment or
28261 section for each library.
28263 @node Memory Map Format
28264 @section Memory Map Format
28265 @cindex memory map format
28267 To be able to write into flash memory, @value{GDBN} needs to obtain a
28268 memory map from the target. This section describes the format of the
28271 The memory map is obtained using the @samp{qXfer:memory-map:read}
28272 (@pxref{qXfer memory map read}) packet and is an XML document that
28273 lists memory regions.
28275 @value{GDBN} must be linked with the Expat library to support XML
28276 memory maps. @xref{Expat}.
28278 The top-level structure of the document is shown below:
28281 <?xml version="1.0"?>
28282 <!DOCTYPE memory-map
28283 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
28284 "http://sourceware.org/gdb/gdb-memory-map.dtd">
28290 Each region can be either:
28295 A region of RAM starting at @var{addr} and extending for @var{length}
28299 <memory type="ram" start="@var{addr}" length="@var{length}"/>
28304 A region of read-only memory:
28307 <memory type="rom" start="@var{addr}" length="@var{length}"/>
28312 A region of flash memory, with erasure blocks @var{blocksize}
28316 <memory type="flash" start="@var{addr}" length="@var{length}">
28317 <property name="blocksize">@var{blocksize}</property>
28323 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
28324 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
28325 packets to write to addresses in such ranges.
28327 The formal DTD for memory map format is given below:
28330 <!-- ................................................... -->
28331 <!-- Memory Map XML DTD ................................ -->
28332 <!-- File: memory-map.dtd .............................. -->
28333 <!-- .................................... .............. -->
28334 <!-- memory-map.dtd -->
28335 <!-- memory-map: Root element with versioning -->
28336 <!ELEMENT memory-map (memory | property)>
28337 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
28338 <!ELEMENT memory (property)>
28339 <!-- memory: Specifies a memory region,
28340 and its type, or device. -->
28341 <!ATTLIST memory type CDATA #REQUIRED
28342 start CDATA #REQUIRED
28343 length CDATA #REQUIRED
28344 device CDATA #IMPLIED>
28345 <!-- property: Generic attribute tag -->
28346 <!ELEMENT property (#PCDATA | property)*>
28347 <!ATTLIST property name CDATA #REQUIRED>
28350 @include agentexpr.texi
28352 @node Target Descriptions
28353 @appendix Target Descriptions
28354 @cindex target descriptions
28356 @strong{Warning:} target descriptions are still under active development,
28357 and the contents and format may change between @value{GDBN} releases.
28358 The format is expected to stabilize in the future.
28360 One of the challenges of using @value{GDBN} to debug embedded systems
28361 is that there are so many minor variants of each processor
28362 architecture in use. It is common practice for vendors to start with
28363 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
28364 and then make changes to adapt it to a particular market niche. Some
28365 architectures have hundreds of variants, available from dozens of
28366 vendors. This leads to a number of problems:
28370 With so many different customized processors, it is difficult for
28371 the @value{GDBN} maintainers to keep up with the changes.
28373 Since individual variants may have short lifetimes or limited
28374 audiences, it may not be worthwhile to carry information about every
28375 variant in the @value{GDBN} source tree.
28377 When @value{GDBN} does support the architecture of the embedded system
28378 at hand, the task of finding the correct architecture name to give the
28379 @command{set architecture} command can be error-prone.
28382 To address these problems, the @value{GDBN} remote protocol allows a
28383 target system to not only identify itself to @value{GDBN}, but to
28384 actually describe its own features. This lets @value{GDBN} support
28385 processor variants it has never seen before --- to the extent that the
28386 descriptions are accurate, and that @value{GDBN} understands them.
28388 @value{GDBN} must be linked with the Expat library to support XML
28389 target descriptions. @xref{Expat}.
28392 * Retrieving Descriptions:: How descriptions are fetched from a target.
28393 * Target Description Format:: The contents of a target description.
28394 * Predefined Target Types:: Standard types available for target
28396 * Standard Target Features:: Features @value{GDBN} knows about.
28399 @node Retrieving Descriptions
28400 @section Retrieving Descriptions
28402 Target descriptions can be read from the target automatically, or
28403 specified by the user manually. The default behavior is to read the
28404 description from the target. @value{GDBN} retrieves it via the remote
28405 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
28406 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
28407 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
28408 XML document, of the form described in @ref{Target Description
28411 Alternatively, you can specify a file to read for the target description.
28412 If a file is set, the target will not be queried. The commands to
28413 specify a file are:
28416 @cindex set tdesc filename
28417 @item set tdesc filename @var{path}
28418 Read the target description from @var{path}.
28420 @cindex unset tdesc filename
28421 @item unset tdesc filename
28422 Do not read the XML target description from a file. @value{GDBN}
28423 will use the description supplied by the current target.
28425 @cindex show tdesc filename
28426 @item show tdesc filename
28427 Show the filename to read for a target description, if any.
28431 @node Target Description Format
28432 @section Target Description Format
28433 @cindex target descriptions, XML format
28435 A target description annex is an @uref{http://www.w3.org/XML/, XML}
28436 document which complies with the Document Type Definition provided in
28437 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
28438 means you can use generally available tools like @command{xmllint} to
28439 check that your feature descriptions are well-formed and valid.
28440 However, to help people unfamiliar with XML write descriptions for
28441 their targets, we also describe the grammar here.
28443 Target descriptions can identify the architecture of the remote target
28444 and (for some architectures) provide information about custom register
28445 sets. @value{GDBN} can use this information to autoconfigure for your
28446 target, or to warn you if you connect to an unsupported target.
28448 Here is a simple target description:
28451 <target version="1.0">
28452 <architecture>i386:x86-64</architecture>
28457 This minimal description only says that the target uses
28458 the x86-64 architecture.
28460 A target description has the following overall form, with [ ] marking
28461 optional elements and @dots{} marking repeatable elements. The elements
28462 are explained further below.
28465 <?xml version="1.0"?>
28466 <!DOCTYPE target SYSTEM "gdb-target.dtd">
28467 <target version="1.0">
28468 @r{[}@var{architecture}@r{]}
28469 @r{[}@var{feature}@dots{}@r{]}
28474 The description is generally insensitive to whitespace and line
28475 breaks, under the usual common-sense rules. The XML version
28476 declaration and document type declaration can generally be omitted
28477 (@value{GDBN} does not require them), but specifying them may be
28478 useful for XML validation tools. The @samp{version} attribute for
28479 @samp{<target>} may also be omitted, but we recommend
28480 including it; if future versions of @value{GDBN} use an incompatible
28481 revision of @file{gdb-target.dtd}, they will detect and report
28482 the version mismatch.
28484 @subsection Inclusion
28485 @cindex target descriptions, inclusion
28488 @cindex <xi:include>
28491 It can sometimes be valuable to split a target description up into
28492 several different annexes, either for organizational purposes, or to
28493 share files between different possible target descriptions. You can
28494 divide a description into multiple files by replacing any element of
28495 the target description with an inclusion directive of the form:
28498 <xi:include href="@var{document}"/>
28502 When @value{GDBN} encounters an element of this form, it will retrieve
28503 the named XML @var{document}, and replace the inclusion directive with
28504 the contents of that document. If the current description was read
28505 using @samp{qXfer}, then so will be the included document;
28506 @var{document} will be interpreted as the name of an annex. If the
28507 current description was read from a file, @value{GDBN} will look for
28508 @var{document} as a file in the same directory where it found the
28509 original description.
28511 @subsection Architecture
28512 @cindex <architecture>
28514 An @samp{<architecture>} element has this form:
28517 <architecture>@var{arch}</architecture>
28520 @var{arch} is an architecture name from the same selection
28521 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
28522 Debugging Target}).
28524 @subsection Features
28527 Each @samp{<feature>} describes some logical portion of the target
28528 system. Features are currently used to describe available CPU
28529 registers and the types of their contents. A @samp{<feature>} element
28533 <feature name="@var{name}">
28534 @r{[}@var{type}@dots{}@r{]}
28540 Each feature's name should be unique within the description. The name
28541 of a feature does not matter unless @value{GDBN} has some special
28542 knowledge of the contents of that feature; if it does, the feature
28543 should have its standard name. @xref{Standard Target Features}.
28547 Any register's value is a collection of bits which @value{GDBN} must
28548 interpret. The default interpretation is a two's complement integer,
28549 but other types can be requested by name in the register description.
28550 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
28551 Target Types}), and the description can define additional composite types.
28553 Each type element must have an @samp{id} attribute, which gives
28554 a unique (within the containing @samp{<feature>}) name to the type.
28555 Types must be defined before they are used.
28558 Some targets offer vector registers, which can be treated as arrays
28559 of scalar elements. These types are written as @samp{<vector>} elements,
28560 specifying the array element type, @var{type}, and the number of elements,
28564 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
28568 If a register's value is usefully viewed in multiple ways, define it
28569 with a union type containing the useful representations. The
28570 @samp{<union>} element contains one or more @samp{<field>} elements,
28571 each of which has a @var{name} and a @var{type}:
28574 <union id="@var{id}">
28575 <field name="@var{name}" type="@var{type}"/>
28580 @subsection Registers
28583 Each register is represented as an element with this form:
28586 <reg name="@var{name}"
28587 bitsize="@var{size}"
28588 @r{[}regnum="@var{num}"@r{]}
28589 @r{[}save-restore="@var{save-restore}"@r{]}
28590 @r{[}type="@var{type}"@r{]}
28591 @r{[}group="@var{group}"@r{]}/>
28595 The components are as follows:
28600 The register's name; it must be unique within the target description.
28603 The register's size, in bits.
28606 The register's number. If omitted, a register's number is one greater
28607 than that of the previous register (either in the current feature or in
28608 a preceeding feature); the first register in the target description
28609 defaults to zero. This register number is used to read or write
28610 the register; e.g.@: it is used in the remote @code{p} and @code{P}
28611 packets, and registers appear in the @code{g} and @code{G} packets
28612 in order of increasing register number.
28615 Whether the register should be preserved across inferior function
28616 calls; this must be either @code{yes} or @code{no}. The default is
28617 @code{yes}, which is appropriate for most registers except for
28618 some system control registers; this is not related to the target's
28622 The type of the register. @var{type} may be a predefined type, a type
28623 defined in the current feature, or one of the special types @code{int}
28624 and @code{float}. @code{int} is an integer type of the correct size
28625 for @var{bitsize}, and @code{float} is a floating point type (in the
28626 architecture's normal floating point format) of the correct size for
28627 @var{bitsize}. The default is @code{int}.
28630 The register group to which this register belongs. @var{group} must
28631 be either @code{general}, @code{float}, or @code{vector}. If no
28632 @var{group} is specified, @value{GDBN} will not display the register
28633 in @code{info registers}.
28637 @node Predefined Target Types
28638 @section Predefined Target Types
28639 @cindex target descriptions, predefined types
28641 Type definitions in the self-description can build up composite types
28642 from basic building blocks, but can not define fundamental types. Instead,
28643 standard identifiers are provided by @value{GDBN} for the fundamental
28644 types. The currently supported types are:
28653 Signed integer types holding the specified number of bits.
28660 Unsigned integer types holding the specified number of bits.
28664 Pointers to unspecified code and data. The program counter and
28665 any dedicated return address register may be marked as code
28666 pointers; printing a code pointer converts it into a symbolic
28667 address. The stack pointer and any dedicated address registers
28668 may be marked as data pointers.
28671 Single precision IEEE floating point.
28674 Double precision IEEE floating point.
28677 The 12-byte extended precision format used by ARM FPA registers.
28681 @node Standard Target Features
28682 @section Standard Target Features
28683 @cindex target descriptions, standard features
28685 A target description must contain either no registers or all the
28686 target's registers. If the description contains no registers, then
28687 @value{GDBN} will assume a default register layout, selected based on
28688 the architecture. If the description contains any registers, the
28689 default layout will not be used; the standard registers must be
28690 described in the target description, in such a way that @value{GDBN}
28691 can recognize them.
28693 This is accomplished by giving specific names to feature elements
28694 which contain standard registers. @value{GDBN} will look for features
28695 with those names and verify that they contain the expected registers;
28696 if any known feature is missing required registers, or if any required
28697 feature is missing, @value{GDBN} will reject the target
28698 description. You can add additional registers to any of the
28699 standard features --- @value{GDBN} will display them just as if
28700 they were added to an unrecognized feature.
28702 This section lists the known features and their expected contents.
28703 Sample XML documents for these features are included in the
28704 @value{GDBN} source tree, in the directory @file{gdb/features}.
28706 Names recognized by @value{GDBN} should include the name of the
28707 company or organization which selected the name, and the overall
28708 architecture to which the feature applies; so e.g.@: the feature
28709 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
28711 The names of registers are not case sensitive for the purpose
28712 of recognizing standard features, but @value{GDBN} will only display
28713 registers using the capitalization used in the description.
28719 * PowerPC Features::
28724 @subsection ARM Features
28725 @cindex target descriptions, ARM features
28727 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
28728 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
28729 @samp{lr}, @samp{pc}, and @samp{cpsr}.
28731 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
28732 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
28734 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
28735 it should contain at least registers @samp{wR0} through @samp{wR15} and
28736 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
28737 @samp{wCSSF}, and @samp{wCASF} registers are optional.
28739 @node MIPS Features
28740 @subsection MIPS Features
28741 @cindex target descriptions, MIPS features
28743 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
28744 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
28745 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
28748 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
28749 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
28750 registers. They may be 32-bit or 64-bit depending on the target.
28752 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
28753 it may be optional in a future version of @value{GDBN}. It should
28754 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
28755 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
28757 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
28758 contain a single register, @samp{restart}, which is used by the
28759 Linux kernel to control restartable syscalls.
28761 @node M68K Features
28762 @subsection M68K Features
28763 @cindex target descriptions, M68K features
28766 @item @samp{org.gnu.gdb.m68k.core}
28767 @itemx @samp{org.gnu.gdb.coldfire.core}
28768 @itemx @samp{org.gnu.gdb.fido.core}
28769 One of those features must be always present.
28770 The feature that is present determines which flavor of m68k is
28771 used. The feature that is present should contain registers
28772 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
28773 @samp{sp}, @samp{ps} and @samp{pc}.
28775 @item @samp{org.gnu.gdb.coldfire.fp}
28776 This feature is optional. If present, it should contain registers
28777 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
28781 @node PowerPC Features
28782 @subsection PowerPC Features
28783 @cindex target descriptions, PowerPC features
28785 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
28786 targets. It should contain registers @samp{r0} through @samp{r31},
28787 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
28788 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
28790 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
28791 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
28793 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
28794 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
28797 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
28798 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
28799 will combine these registers with the floating point registers
28800 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
28801 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
28802 through @samp{vs63}, the set of vector registers for POWER7.
28804 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
28805 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
28806 @samp{spefscr}. SPE targets should provide 32-bit registers in
28807 @samp{org.gnu.gdb.power.core} and provide the upper halves in
28808 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
28809 these to present registers @samp{ev0} through @samp{ev31} to the
28812 @node Operating System Information
28813 @appendix Operating System Information
28814 @cindex operating system information
28820 Users of @value{GDBN} often wish to obtain information about the state of
28821 the operating system running on the target---for example the list of
28822 processes, or the list of open files. This section describes the
28823 mechanism that makes it possible. This mechanism is similar to the
28824 target features mechanism (@pxref{Target Descriptions}), but focuses
28825 on a different aspect of target.
28827 Operating system information is retrived from the target via the
28828 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
28829 read}). The object name in the request should be @samp{osdata}, and
28830 the @var{annex} identifies the data to be fetched.
28833 @appendixsection Process list
28834 @cindex operating system information, process list
28836 When requesting the process list, the @var{annex} field in the
28837 @samp{qXfer} request should be @samp{processes}. The returned data is
28838 an XML document. The formal syntax of this document is defined in
28839 @file{gdb/features/osdata.dtd}.
28841 An example document is:
28844 <?xml version="1.0"?>
28845 <!DOCTYPE target SYSTEM "osdata.dtd">
28846 <osdata type="processes">
28848 <column name="pid">1</column>
28849 <column name="user">root</column>
28850 <column name="command">/sbin/init</column>
28855 Each item should include a column whose name is @samp{pid}. The value
28856 of that column should identify the process on the target. The
28857 @samp{user} and @samp{command} columns are optional, and will be
28858 displayed by @value{GDBN}. Target may provide additional columns,
28859 which @value{GDBN} currently ignores.
28873 % I think something like @colophon should be in texinfo. In the
28875 \long\def\colophon{\hbox to0pt{}\vfill
28876 \centerline{The body of this manual is set in}
28877 \centerline{\fontname\tenrm,}
28878 \centerline{with headings in {\bf\fontname\tenbf}}
28879 \centerline{and examples in {\tt\fontname\tentt}.}
28880 \centerline{{\it\fontname\tenit\/},}
28881 \centerline{{\bf\fontname\tenbf}, and}
28882 \centerline{{\sl\fontname\tensl\/}}
28883 \centerline{are used for emphasis.}\vfill}
28885 % Blame: doc@cygnus.com, 1991.