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 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11338 (@value{GDBP}) set An_Array := (1, others => 0)
11339 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11340 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11341 (@value{GDBP}) set A_Record := (1, "Peter", True);
11342 (@value{GDBP}) 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
11364 (@value{GDBP}) set A_Rec.Len := 4
11365 (@value{GDBP}) 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
11451 (@value{GDBP}) set x := y + 3
11452 (@value{GDBP}) 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:
11462 (@value{GDBP}) break f
11463 (@value{GDBP}) 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
11487 (@value{GDBP}) print 'max(x, y)
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 GNAT compiler never generates the prefix @code{Standard} for any of
11761 the standard symbols defined by the Ada language. @value{GDBN} knows about
11762 this: it will strip the prefix from names when you use it, and will never
11763 look for a name you have so qualified among local symbols, nor match against
11764 symbols in other packages or subprograms. If you have
11765 defined entities anywhere in your program other than parameters and
11766 local variables whose simple names match names in @code{Standard},
11767 GNAT's lack of qualification here can cause confusion. When this happens,
11768 you can usually resolve the confusion
11769 by qualifying the problematic names with package
11770 @code{Standard} explicitly.
11773 @node Unsupported Languages
11774 @section Unsupported Languages
11776 @cindex unsupported languages
11777 @cindex minimal language
11778 In addition to the other fully-supported programming languages,
11779 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11780 It does not represent a real programming language, but provides a set
11781 of capabilities close to what the C or assembly languages provide.
11782 This should allow most simple operations to be performed while debugging
11783 an application that uses a language currently not supported by @value{GDBN}.
11785 If the language is set to @code{auto}, @value{GDBN} will automatically
11786 select this language if the current frame corresponds to an unsupported
11790 @chapter Examining the Symbol Table
11792 The commands described in this chapter allow you to inquire about the
11793 symbols (names of variables, functions and types) defined in your
11794 program. This information is inherent in the text of your program and
11795 does not change as your program executes. @value{GDBN} finds it in your
11796 program's symbol table, in the file indicated when you started @value{GDBN}
11797 (@pxref{File Options, ,Choosing Files}), or by one of the
11798 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11800 @cindex symbol names
11801 @cindex names of symbols
11802 @cindex quoting names
11803 Occasionally, you may need to refer to symbols that contain unusual
11804 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11805 most frequent case is in referring to static variables in other
11806 source files (@pxref{Variables,,Program Variables}). File names
11807 are recorded in object files as debugging symbols, but @value{GDBN} would
11808 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11809 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11810 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11817 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11820 @cindex case-insensitive symbol names
11821 @cindex case sensitivity in symbol names
11822 @kindex set case-sensitive
11823 @item set case-sensitive on
11824 @itemx set case-sensitive off
11825 @itemx set case-sensitive auto
11826 Normally, when @value{GDBN} looks up symbols, it matches their names
11827 with case sensitivity determined by the current source language.
11828 Occasionally, you may wish to control that. The command @code{set
11829 case-sensitive} lets you do that by specifying @code{on} for
11830 case-sensitive matches or @code{off} for case-insensitive ones. If
11831 you specify @code{auto}, case sensitivity is reset to the default
11832 suitable for the source language. The default is case-sensitive
11833 matches for all languages except for Fortran, for which the default is
11834 case-insensitive matches.
11836 @kindex show case-sensitive
11837 @item show case-sensitive
11838 This command shows the current setting of case sensitivity for symbols
11841 @kindex info address
11842 @cindex address of a symbol
11843 @item info address @var{symbol}
11844 Describe where the data for @var{symbol} is stored. For a register
11845 variable, this says which register it is kept in. For a non-register
11846 local variable, this prints the stack-frame offset at which the variable
11849 Note the contrast with @samp{print &@var{symbol}}, which does not work
11850 at all for a register variable, and for a stack local variable prints
11851 the exact address of the current instantiation of the variable.
11853 @kindex info symbol
11854 @cindex symbol from address
11855 @cindex closest symbol and offset for an address
11856 @item info symbol @var{addr}
11857 Print the name of a symbol which is stored at the address @var{addr}.
11858 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11859 nearest symbol and an offset from it:
11862 (@value{GDBP}) info symbol 0x54320
11863 _initialize_vx + 396 in section .text
11867 This is the opposite of the @code{info address} command. You can use
11868 it to find out the name of a variable or a function given its address.
11870 For dynamically linked executables, the name of executable or shared
11871 library containing the symbol is also printed:
11874 (@value{GDBP}) info symbol 0x400225
11875 _start + 5 in section .text of /tmp/a.out
11876 (@value{GDBP}) info symbol 0x2aaaac2811cf
11877 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
11881 @item whatis [@var{arg}]
11882 Print the data type of @var{arg}, which can be either an expression or
11883 a data type. With no argument, print the data type of @code{$}, the
11884 last value in the value history. If @var{arg} is an expression, it is
11885 not actually evaluated, and any side-effecting operations (such as
11886 assignments or function calls) inside it do not take place. If
11887 @var{arg} is a type name, it may be the name of a type or typedef, or
11888 for C code it may have the form @samp{class @var{class-name}},
11889 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
11890 @samp{enum @var{enum-tag}}.
11891 @xref{Expressions, ,Expressions}.
11894 @item ptype [@var{arg}]
11895 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
11896 detailed description of the type, instead of just the name of the type.
11897 @xref{Expressions, ,Expressions}.
11899 For example, for this variable declaration:
11902 struct complex @{double real; double imag;@} v;
11906 the two commands give this output:
11910 (@value{GDBP}) whatis v
11911 type = struct complex
11912 (@value{GDBP}) ptype v
11913 type = struct complex @{
11921 As with @code{whatis}, using @code{ptype} without an argument refers to
11922 the type of @code{$}, the last value in the value history.
11924 @cindex incomplete type
11925 Sometimes, programs use opaque data types or incomplete specifications
11926 of complex data structure. If the debug information included in the
11927 program does not allow @value{GDBN} to display a full declaration of
11928 the data type, it will say @samp{<incomplete type>}. For example,
11929 given these declarations:
11933 struct foo *fooptr;
11937 but no definition for @code{struct foo} itself, @value{GDBN} will say:
11940 (@value{GDBP}) ptype foo
11941 $1 = <incomplete type>
11945 ``Incomplete type'' is C terminology for data types that are not
11946 completely specified.
11949 @item info types @var{regexp}
11951 Print a brief description of all types whose names match the regular
11952 expression @var{regexp} (or all types in your program, if you supply
11953 no argument). Each complete typename is matched as though it were a
11954 complete line; thus, @samp{i type value} gives information on all
11955 types in your program whose names include the string @code{value}, but
11956 @samp{i type ^value$} gives information only on types whose complete
11957 name is @code{value}.
11959 This command differs from @code{ptype} in two ways: first, like
11960 @code{whatis}, it does not print a detailed description; second, it
11961 lists all source files where a type is defined.
11964 @cindex local variables
11965 @item info scope @var{location}
11966 List all the variables local to a particular scope. This command
11967 accepts a @var{location} argument---a function name, a source line, or
11968 an address preceded by a @samp{*}, and prints all the variables local
11969 to the scope defined by that location. (@xref{Specify Location}, for
11970 details about supported forms of @var{location}.) For example:
11973 (@value{GDBP}) @b{info scope command_line_handler}
11974 Scope for command_line_handler:
11975 Symbol rl is an argument at stack/frame offset 8, length 4.
11976 Symbol linebuffer is in static storage at address 0x150a18, length 4.
11977 Symbol linelength is in static storage at address 0x150a1c, length 4.
11978 Symbol p is a local variable in register $esi, length 4.
11979 Symbol p1 is a local variable in register $ebx, length 4.
11980 Symbol nline is a local variable in register $edx, length 4.
11981 Symbol repeat is a local variable at frame offset -8, length 4.
11985 This command is especially useful for determining what data to collect
11986 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
11989 @kindex info source
11991 Show information about the current source file---that is, the source file for
11992 the function containing the current point of execution:
11995 the name of the source file, and the directory containing it,
11997 the directory it was compiled in,
11999 its length, in lines,
12001 which programming language it is written in,
12003 whether the executable includes debugging information for that file, and
12004 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12006 whether the debugging information includes information about
12007 preprocessor macros.
12011 @kindex info sources
12013 Print the names of all source files in your program for which there is
12014 debugging information, organized into two lists: files whose symbols
12015 have already been read, and files whose symbols will be read when needed.
12017 @kindex info functions
12018 @item info functions
12019 Print the names and data types of all defined functions.
12021 @item info functions @var{regexp}
12022 Print the names and data types of all defined functions
12023 whose names contain a match for regular expression @var{regexp}.
12024 Thus, @samp{info fun step} finds all functions whose names
12025 include @code{step}; @samp{info fun ^step} finds those whose names
12026 start with @code{step}. If a function name contains characters
12027 that conflict with the regular expression language (e.g.@:
12028 @samp{operator*()}), they may be quoted with a backslash.
12030 @kindex info variables
12031 @item info variables
12032 Print the names and data types of all variables that are declared
12033 outside of functions (i.e.@: excluding local variables).
12035 @item info variables @var{regexp}
12036 Print the names and data types of all variables (except for local
12037 variables) whose names contain a match for regular expression
12040 @kindex info classes
12041 @cindex Objective-C, classes and selectors
12043 @itemx info classes @var{regexp}
12044 Display all Objective-C classes in your program, or
12045 (with the @var{regexp} argument) all those matching a particular regular
12048 @kindex info selectors
12049 @item info selectors
12050 @itemx info selectors @var{regexp}
12051 Display all Objective-C selectors in your program, or
12052 (with the @var{regexp} argument) all those matching a particular regular
12056 This was never implemented.
12057 @kindex info methods
12059 @itemx info methods @var{regexp}
12060 The @code{info methods} command permits the user to examine all defined
12061 methods within C@t{++} program, or (with the @var{regexp} argument) a
12062 specific set of methods found in the various C@t{++} classes. Many
12063 C@t{++} classes provide a large number of methods. Thus, the output
12064 from the @code{ptype} command can be overwhelming and hard to use. The
12065 @code{info-methods} command filters the methods, printing only those
12066 which match the regular-expression @var{regexp}.
12069 @cindex reloading symbols
12070 Some systems allow individual object files that make up your program to
12071 be replaced without stopping and restarting your program. For example,
12072 in VxWorks you can simply recompile a defective object file and keep on
12073 running. If you are running on one of these systems, you can allow
12074 @value{GDBN} to reload the symbols for automatically relinked modules:
12077 @kindex set symbol-reloading
12078 @item set symbol-reloading on
12079 Replace symbol definitions for the corresponding source file when an
12080 object file with a particular name is seen again.
12082 @item set symbol-reloading off
12083 Do not replace symbol definitions when encountering object files of the
12084 same name more than once. This is the default state; if you are not
12085 running on a system that permits automatic relinking of modules, you
12086 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12087 may discard symbols when linking large programs, that may contain
12088 several modules (from different directories or libraries) with the same
12091 @kindex show symbol-reloading
12092 @item show symbol-reloading
12093 Show the current @code{on} or @code{off} setting.
12096 @cindex opaque data types
12097 @kindex set opaque-type-resolution
12098 @item set opaque-type-resolution on
12099 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12100 declared as a pointer to a @code{struct}, @code{class}, or
12101 @code{union}---for example, @code{struct MyType *}---that is used in one
12102 source file although the full declaration of @code{struct MyType} is in
12103 another source file. The default is on.
12105 A change in the setting of this subcommand will not take effect until
12106 the next time symbols for a file are loaded.
12108 @item set opaque-type-resolution off
12109 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12110 is printed as follows:
12112 @{<no data fields>@}
12115 @kindex show opaque-type-resolution
12116 @item show opaque-type-resolution
12117 Show whether opaque types are resolved or not.
12119 @kindex set print symbol-loading
12120 @cindex print messages when symbols are loaded
12121 @item set print symbol-loading
12122 @itemx set print symbol-loading on
12123 @itemx set print symbol-loading off
12124 The @code{set print symbol-loading} command allows you to enable or
12125 disable printing of messages when @value{GDBN} loads symbols.
12126 By default, these messages will be printed, and normally this is what
12127 you want. Disabling these messages is useful when debugging applications
12128 with lots of shared libraries where the quantity of output can be more
12129 annoying than useful.
12131 @kindex show print symbol-loading
12132 @item show print symbol-loading
12133 Show whether messages will be printed when @value{GDBN} loads symbols.
12135 @kindex maint print symbols
12136 @cindex symbol dump
12137 @kindex maint print psymbols
12138 @cindex partial symbol dump
12139 @item maint print symbols @var{filename}
12140 @itemx maint print psymbols @var{filename}
12141 @itemx maint print msymbols @var{filename}
12142 Write a dump of debugging symbol data into the file @var{filename}.
12143 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12144 symbols with debugging data are included. If you use @samp{maint print
12145 symbols}, @value{GDBN} includes all the symbols for which it has already
12146 collected full details: that is, @var{filename} reflects symbols for
12147 only those files whose symbols @value{GDBN} has read. You can use the
12148 command @code{info sources} to find out which files these are. If you
12149 use @samp{maint print psymbols} instead, the dump shows information about
12150 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12151 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12152 @samp{maint print msymbols} dumps just the minimal symbol information
12153 required for each object file from which @value{GDBN} has read some symbols.
12154 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12155 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12157 @kindex maint info symtabs
12158 @kindex maint info psymtabs
12159 @cindex listing @value{GDBN}'s internal symbol tables
12160 @cindex symbol tables, listing @value{GDBN}'s internal
12161 @cindex full symbol tables, listing @value{GDBN}'s internal
12162 @cindex partial symbol tables, listing @value{GDBN}'s internal
12163 @item maint info symtabs @r{[} @var{regexp} @r{]}
12164 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12166 List the @code{struct symtab} or @code{struct partial_symtab}
12167 structures whose names match @var{regexp}. If @var{regexp} is not
12168 given, list them all. The output includes expressions which you can
12169 copy into a @value{GDBN} debugging this one to examine a particular
12170 structure in more detail. For example:
12173 (@value{GDBP}) maint info psymtabs dwarf2read
12174 @{ objfile /home/gnu/build/gdb/gdb
12175 ((struct objfile *) 0x82e69d0)
12176 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12177 ((struct partial_symtab *) 0x8474b10)
12180 text addresses 0x814d3c8 -- 0x8158074
12181 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12182 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12183 dependencies (none)
12186 (@value{GDBP}) maint info symtabs
12190 We see that there is one partial symbol table whose filename contains
12191 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12192 and we see that @value{GDBN} has not read in any symtabs yet at all.
12193 If we set a breakpoint on a function, that will cause @value{GDBN} to
12194 read the symtab for the compilation unit containing that function:
12197 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12198 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12200 (@value{GDBP}) maint info symtabs
12201 @{ objfile /home/gnu/build/gdb/gdb
12202 ((struct objfile *) 0x82e69d0)
12203 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12204 ((struct symtab *) 0x86c1f38)
12207 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12208 linetable ((struct linetable *) 0x8370fa0)
12209 debugformat DWARF 2
12218 @chapter Altering Execution
12220 Once you think you have found an error in your program, you might want to
12221 find out for certain whether correcting the apparent error would lead to
12222 correct results in the rest of the run. You can find the answer by
12223 experiment, using the @value{GDBN} features for altering execution of the
12226 For example, you can store new values into variables or memory
12227 locations, give your program a signal, restart it at a different
12228 address, or even return prematurely from a function.
12231 * Assignment:: Assignment to variables
12232 * Jumping:: Continuing at a different address
12233 * Signaling:: Giving your program a signal
12234 * Returning:: Returning from a function
12235 * Calling:: Calling your program's functions
12236 * Patching:: Patching your program
12240 @section Assignment to Variables
12243 @cindex setting variables
12244 To alter the value of a variable, evaluate an assignment expression.
12245 @xref{Expressions, ,Expressions}. For example,
12252 stores the value 4 into the variable @code{x}, and then prints the
12253 value of the assignment expression (which is 4).
12254 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12255 information on operators in supported languages.
12257 @kindex set variable
12258 @cindex variables, setting
12259 If you are not interested in seeing the value of the assignment, use the
12260 @code{set} command instead of the @code{print} command. @code{set} is
12261 really the same as @code{print} except that the expression's value is
12262 not printed and is not put in the value history (@pxref{Value History,
12263 ,Value History}). The expression is evaluated only for its effects.
12265 If the beginning of the argument string of the @code{set} command
12266 appears identical to a @code{set} subcommand, use the @code{set
12267 variable} command instead of just @code{set}. This command is identical
12268 to @code{set} except for its lack of subcommands. For example, if your
12269 program has a variable @code{width}, you get an error if you try to set
12270 a new value with just @samp{set width=13}, because @value{GDBN} has the
12271 command @code{set width}:
12274 (@value{GDBP}) whatis width
12276 (@value{GDBP}) p width
12278 (@value{GDBP}) set width=47
12279 Invalid syntax in expression.
12283 The invalid expression, of course, is @samp{=47}. In
12284 order to actually set the program's variable @code{width}, use
12287 (@value{GDBP}) set var width=47
12290 Because the @code{set} command has many subcommands that can conflict
12291 with the names of program variables, it is a good idea to use the
12292 @code{set variable} command instead of just @code{set}. For example, if
12293 your program has a variable @code{g}, you run into problems if you try
12294 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12295 the command @code{set gnutarget}, abbreviated @code{set g}:
12299 (@value{GDBP}) whatis g
12303 (@value{GDBP}) set g=4
12307 The program being debugged has been started already.
12308 Start it from the beginning? (y or n) y
12309 Starting program: /home/smith/cc_progs/a.out
12310 "/home/smith/cc_progs/a.out": can't open to read symbols:
12311 Invalid bfd target.
12312 (@value{GDBP}) show g
12313 The current BFD target is "=4".
12318 The program variable @code{g} did not change, and you silently set the
12319 @code{gnutarget} to an invalid value. In order to set the variable
12323 (@value{GDBP}) set var g=4
12326 @value{GDBN} allows more implicit conversions in assignments than C; you can
12327 freely store an integer value into a pointer variable or vice versa,
12328 and you can convert any structure to any other structure that is the
12329 same length or shorter.
12330 @comment FIXME: how do structs align/pad in these conversions?
12331 @comment /doc@cygnus.com 18dec1990
12333 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12334 construct to generate a value of specified type at a specified address
12335 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12336 to memory location @code{0x83040} as an integer (which implies a certain size
12337 and representation in memory), and
12340 set @{int@}0x83040 = 4
12344 stores the value 4 into that memory location.
12347 @section Continuing at a Different Address
12349 Ordinarily, when you continue your program, you do so at the place where
12350 it stopped, with the @code{continue} command. You can instead continue at
12351 an address of your own choosing, with the following commands:
12355 @item jump @var{linespec}
12356 @itemx jump @var{location}
12357 Resume execution at line @var{linespec} or at address given by
12358 @var{location}. Execution stops again immediately if there is a
12359 breakpoint there. @xref{Specify Location}, for a description of the
12360 different forms of @var{linespec} and @var{location}. It is common
12361 practice to use the @code{tbreak} command in conjunction with
12362 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12364 The @code{jump} command does not change the current stack frame, or
12365 the stack pointer, or the contents of any memory location or any
12366 register other than the program counter. If line @var{linespec} is in
12367 a different function from the one currently executing, the results may
12368 be bizarre if the two functions expect different patterns of arguments or
12369 of local variables. For this reason, the @code{jump} command requests
12370 confirmation if the specified line is not in the function currently
12371 executing. However, even bizarre results are predictable if you are
12372 well acquainted with the machine-language code of your program.
12375 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12376 On many systems, you can get much the same effect as the @code{jump}
12377 command by storing a new value into the register @code{$pc}. The
12378 difference is that this does not start your program running; it only
12379 changes the address of where it @emph{will} run when you continue. For
12387 makes the next @code{continue} command or stepping command execute at
12388 address @code{0x485}, rather than at the address where your program stopped.
12389 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12391 The most common occasion to use the @code{jump} command is to back
12392 up---perhaps with more breakpoints set---over a portion of a program
12393 that has already executed, in order to examine its execution in more
12398 @section Giving your Program a Signal
12399 @cindex deliver a signal to a program
12403 @item signal @var{signal}
12404 Resume execution where your program stopped, but immediately give it the
12405 signal @var{signal}. @var{signal} can be the name or the number of a
12406 signal. For example, on many systems @code{signal 2} and @code{signal
12407 SIGINT} are both ways of sending an interrupt signal.
12409 Alternatively, if @var{signal} is zero, continue execution without
12410 giving a signal. This is useful when your program stopped on account of
12411 a signal and would ordinary see the signal when resumed with the
12412 @code{continue} command; @samp{signal 0} causes it to resume without a
12415 @code{signal} does not repeat when you press @key{RET} a second time
12416 after executing the command.
12420 Invoking the @code{signal} command is not the same as invoking the
12421 @code{kill} utility from the shell. Sending a signal with @code{kill}
12422 causes @value{GDBN} to decide what to do with the signal depending on
12423 the signal handling tables (@pxref{Signals}). The @code{signal} command
12424 passes the signal directly to your program.
12428 @section Returning from a Function
12431 @cindex returning from a function
12434 @itemx return @var{expression}
12435 You can cancel execution of a function call with the @code{return}
12436 command. If you give an
12437 @var{expression} argument, its value is used as the function's return
12441 When you use @code{return}, @value{GDBN} discards the selected stack frame
12442 (and all frames within it). You can think of this as making the
12443 discarded frame return prematurely. If you wish to specify a value to
12444 be returned, give that value as the argument to @code{return}.
12446 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12447 Frame}), and any other frames inside of it, leaving its caller as the
12448 innermost remaining frame. That frame becomes selected. The
12449 specified value is stored in the registers used for returning values
12452 The @code{return} command does not resume execution; it leaves the
12453 program stopped in the state that would exist if the function had just
12454 returned. In contrast, the @code{finish} command (@pxref{Continuing
12455 and Stepping, ,Continuing and Stepping}) resumes execution until the
12456 selected stack frame returns naturally.
12459 @section Calling Program Functions
12462 @cindex calling functions
12463 @cindex inferior functions, calling
12464 @item print @var{expr}
12465 Evaluate the expression @var{expr} and display the resulting value.
12466 @var{expr} may include calls to functions in the program being
12470 @item call @var{expr}
12471 Evaluate the expression @var{expr} without displaying @code{void}
12474 You can use this variant of the @code{print} command if you want to
12475 execute a function from your program that does not return anything
12476 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12477 with @code{void} returned values that @value{GDBN} will otherwise
12478 print. If the result is not void, it is printed and saved in the
12482 It is possible for the function you call via the @code{print} or
12483 @code{call} command to generate a signal (e.g., if there's a bug in
12484 the function, or if you passed it incorrect arguments). What happens
12485 in that case is controlled by the @code{set unwindonsignal} command.
12488 @item set unwindonsignal
12489 @kindex set unwindonsignal
12490 @cindex unwind stack in called functions
12491 @cindex call dummy stack unwinding
12492 Set unwinding of the stack if a signal is received while in a function
12493 that @value{GDBN} called in the program being debugged. If set to on,
12494 @value{GDBN} unwinds the stack it created for the call and restores
12495 the context to what it was before the call. If set to off (the
12496 default), @value{GDBN} stops in the frame where the signal was
12499 @item show unwindonsignal
12500 @kindex show unwindonsignal
12501 Show the current setting of stack unwinding in the functions called by
12505 @cindex weak alias functions
12506 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12507 for another function. In such case, @value{GDBN} might not pick up
12508 the type information, including the types of the function arguments,
12509 which causes @value{GDBN} to call the inferior function incorrectly.
12510 As a result, the called function will function erroneously and may
12511 even crash. A solution to that is to use the name of the aliased
12515 @section Patching Programs
12517 @cindex patching binaries
12518 @cindex writing into executables
12519 @cindex writing into corefiles
12521 By default, @value{GDBN} opens the file containing your program's
12522 executable code (or the corefile) read-only. This prevents accidental
12523 alterations to machine code; but it also prevents you from intentionally
12524 patching your program's binary.
12526 If you'd like to be able to patch the binary, you can specify that
12527 explicitly with the @code{set write} command. For example, you might
12528 want to turn on internal debugging flags, or even to make emergency
12534 @itemx set write off
12535 If you specify @samp{set write on}, @value{GDBN} opens executable and
12536 core files for both reading and writing; if you specify @kbd{set write
12537 off} (the default), @value{GDBN} opens them read-only.
12539 If you have already loaded a file, you must load it again (using the
12540 @code{exec-file} or @code{core-file} command) after changing @code{set
12541 write}, for your new setting to take effect.
12545 Display whether executable files and core files are opened for writing
12546 as well as reading.
12550 @chapter @value{GDBN} Files
12552 @value{GDBN} needs to know the file name of the program to be debugged,
12553 both in order to read its symbol table and in order to start your
12554 program. To debug a core dump of a previous run, you must also tell
12555 @value{GDBN} the name of the core dump file.
12558 * Files:: Commands to specify files
12559 * Separate Debug Files:: Debugging information in separate files
12560 * Symbol Errors:: Errors reading symbol files
12564 @section Commands to Specify Files
12566 @cindex symbol table
12567 @cindex core dump file
12569 You may want to specify executable and core dump file names. The usual
12570 way to do this is at start-up time, using the arguments to
12571 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12572 Out of @value{GDBN}}).
12574 Occasionally it is necessary to change to a different file during a
12575 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12576 specify a file you want to use. Or you are debugging a remote target
12577 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12578 Program}). In these situations the @value{GDBN} commands to specify
12579 new files are useful.
12582 @cindex executable file
12584 @item file @var{filename}
12585 Use @var{filename} as the program to be debugged. It is read for its
12586 symbols and for the contents of pure memory. It is also the program
12587 executed when you use the @code{run} command. If you do not specify a
12588 directory and the file is not found in the @value{GDBN} working directory,
12589 @value{GDBN} uses the environment variable @code{PATH} as a list of
12590 directories to search, just as the shell does when looking for a program
12591 to run. You can change the value of this variable, for both @value{GDBN}
12592 and your program, using the @code{path} command.
12594 @cindex unlinked object files
12595 @cindex patching object files
12596 You can load unlinked object @file{.o} files into @value{GDBN} using
12597 the @code{file} command. You will not be able to ``run'' an object
12598 file, but you can disassemble functions and inspect variables. Also,
12599 if the underlying BFD functionality supports it, you could use
12600 @kbd{gdb -write} to patch object files using this technique. Note
12601 that @value{GDBN} can neither interpret nor modify relocations in this
12602 case, so branches and some initialized variables will appear to go to
12603 the wrong place. But this feature is still handy from time to time.
12606 @code{file} with no argument makes @value{GDBN} discard any information it
12607 has on both executable file and the symbol table.
12610 @item exec-file @r{[} @var{filename} @r{]}
12611 Specify that the program to be run (but not the symbol table) is found
12612 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12613 if necessary to locate your program. Omitting @var{filename} means to
12614 discard information on the executable file.
12616 @kindex symbol-file
12617 @item symbol-file @r{[} @var{filename} @r{]}
12618 Read symbol table information from file @var{filename}. @code{PATH} is
12619 searched when necessary. Use the @code{file} command to get both symbol
12620 table and program to run from the same file.
12622 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12623 program's symbol table.
12625 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12626 some breakpoints and auto-display expressions. This is because they may
12627 contain pointers to the internal data recording symbols and data types,
12628 which are part of the old symbol table data being discarded inside
12631 @code{symbol-file} does not repeat if you press @key{RET} again after
12634 When @value{GDBN} is configured for a particular environment, it
12635 understands debugging information in whatever format is the standard
12636 generated for that environment; you may use either a @sc{gnu} compiler, or
12637 other compilers that adhere to the local conventions.
12638 Best results are usually obtained from @sc{gnu} compilers; for example,
12639 using @code{@value{NGCC}} you can generate debugging information for
12642 For most kinds of object files, with the exception of old SVR3 systems
12643 using COFF, the @code{symbol-file} command does not normally read the
12644 symbol table in full right away. Instead, it scans the symbol table
12645 quickly to find which source files and which symbols are present. The
12646 details are read later, one source file at a time, as they are needed.
12648 The purpose of this two-stage reading strategy is to make @value{GDBN}
12649 start up faster. For the most part, it is invisible except for
12650 occasional pauses while the symbol table details for a particular source
12651 file are being read. (The @code{set verbose} command can turn these
12652 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12653 Warnings and Messages}.)
12655 We have not implemented the two-stage strategy for COFF yet. When the
12656 symbol table is stored in COFF format, @code{symbol-file} reads the
12657 symbol table data in full right away. Note that ``stabs-in-COFF''
12658 still does the two-stage strategy, since the debug info is actually
12662 @cindex reading symbols immediately
12663 @cindex symbols, reading immediately
12664 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12665 @itemx file @var{filename} @r{[} -readnow @r{]}
12666 You can override the @value{GDBN} two-stage strategy for reading symbol
12667 tables by using the @samp{-readnow} option with any of the commands that
12668 load symbol table information, if you want to be sure @value{GDBN} has the
12669 entire symbol table available.
12671 @c FIXME: for now no mention of directories, since this seems to be in
12672 @c flux. 13mar1992 status is that in theory GDB would look either in
12673 @c current dir or in same dir as myprog; but issues like competing
12674 @c GDB's, or clutter in system dirs, mean that in practice right now
12675 @c only current dir is used. FFish says maybe a special GDB hierarchy
12676 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12680 @item core-file @r{[}@var{filename}@r{]}
12682 Specify the whereabouts of a core dump file to be used as the ``contents
12683 of memory''. Traditionally, core files contain only some parts of the
12684 address space of the process that generated them; @value{GDBN} can access the
12685 executable file itself for other parts.
12687 @code{core-file} with no argument specifies that no core file is
12690 Note that the core file is ignored when your program is actually running
12691 under @value{GDBN}. So, if you have been running your program and you
12692 wish to debug a core file instead, you must kill the subprocess in which
12693 the program is running. To do this, use the @code{kill} command
12694 (@pxref{Kill Process, ,Killing the Child Process}).
12696 @kindex add-symbol-file
12697 @cindex dynamic linking
12698 @item add-symbol-file @var{filename} @var{address}
12699 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12700 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12701 The @code{add-symbol-file} command reads additional symbol table
12702 information from the file @var{filename}. You would use this command
12703 when @var{filename} has been dynamically loaded (by some other means)
12704 into the program that is running. @var{address} should be the memory
12705 address at which the file has been loaded; @value{GDBN} cannot figure
12706 this out for itself. You can additionally specify an arbitrary number
12707 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12708 section name and base address for that section. You can specify any
12709 @var{address} as an expression.
12711 The symbol table of the file @var{filename} is added to the symbol table
12712 originally read with the @code{symbol-file} command. You can use the
12713 @code{add-symbol-file} command any number of times; the new symbol data
12714 thus read keeps adding to the old. To discard all old symbol data
12715 instead, use the @code{symbol-file} command without any arguments.
12717 @cindex relocatable object files, reading symbols from
12718 @cindex object files, relocatable, reading symbols from
12719 @cindex reading symbols from relocatable object files
12720 @cindex symbols, reading from relocatable object files
12721 @cindex @file{.o} files, reading symbols from
12722 Although @var{filename} is typically a shared library file, an
12723 executable file, or some other object file which has been fully
12724 relocated for loading into a process, you can also load symbolic
12725 information from relocatable @file{.o} files, as long as:
12729 the file's symbolic information refers only to linker symbols defined in
12730 that file, not to symbols defined by other object files,
12732 every section the file's symbolic information refers to has actually
12733 been loaded into the inferior, as it appears in the file, and
12735 you can determine the address at which every section was loaded, and
12736 provide these to the @code{add-symbol-file} command.
12740 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12741 relocatable files into an already running program; such systems
12742 typically make the requirements above easy to meet. However, it's
12743 important to recognize that many native systems use complex link
12744 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12745 assembly, for example) that make the requirements difficult to meet. In
12746 general, one cannot assume that using @code{add-symbol-file} to read a
12747 relocatable object file's symbolic information will have the same effect
12748 as linking the relocatable object file into the program in the normal
12751 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12753 @kindex add-symbol-file-from-memory
12754 @cindex @code{syscall DSO}
12755 @cindex load symbols from memory
12756 @item add-symbol-file-from-memory @var{address}
12757 Load symbols from the given @var{address} in a dynamically loaded
12758 object file whose image is mapped directly into the inferior's memory.
12759 For example, the Linux kernel maps a @code{syscall DSO} into each
12760 process's address space; this DSO provides kernel-specific code for
12761 some system calls. The argument can be any expression whose
12762 evaluation yields the address of the file's shared object file header.
12763 For this command to work, you must have used @code{symbol-file} or
12764 @code{exec-file} commands in advance.
12766 @kindex add-shared-symbol-files
12768 @item add-shared-symbol-files @var{library-file}
12769 @itemx assf @var{library-file}
12770 The @code{add-shared-symbol-files} command can currently be used only
12771 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12772 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12773 @value{GDBN} automatically looks for shared libraries, however if
12774 @value{GDBN} does not find yours, you can invoke
12775 @code{add-shared-symbol-files}. It takes one argument: the shared
12776 library's file name. @code{assf} is a shorthand alias for
12777 @code{add-shared-symbol-files}.
12780 @item section @var{section} @var{addr}
12781 The @code{section} command changes the base address of the named
12782 @var{section} of the exec file to @var{addr}. This can be used if the
12783 exec file does not contain section addresses, (such as in the
12784 @code{a.out} format), or when the addresses specified in the file
12785 itself are wrong. Each section must be changed separately. The
12786 @code{info files} command, described below, lists all the sections and
12790 @kindex info target
12793 @code{info files} and @code{info target} are synonymous; both print the
12794 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12795 including the names of the executable and core dump files currently in
12796 use by @value{GDBN}, and the files from which symbols were loaded. The
12797 command @code{help target} lists all possible targets rather than
12800 @kindex maint info sections
12801 @item maint info sections
12802 Another command that can give you extra information about program sections
12803 is @code{maint info sections}. In addition to the section information
12804 displayed by @code{info files}, this command displays the flags and file
12805 offset of each section in the executable and core dump files. In addition,
12806 @code{maint info sections} provides the following command options (which
12807 may be arbitrarily combined):
12811 Display sections for all loaded object files, including shared libraries.
12812 @item @var{sections}
12813 Display info only for named @var{sections}.
12814 @item @var{section-flags}
12815 Display info only for sections for which @var{section-flags} are true.
12816 The section flags that @value{GDBN} currently knows about are:
12819 Section will have space allocated in the process when loaded.
12820 Set for all sections except those containing debug information.
12822 Section will be loaded from the file into the child process memory.
12823 Set for pre-initialized code and data, clear for @code{.bss} sections.
12825 Section needs to be relocated before loading.
12827 Section cannot be modified by the child process.
12829 Section contains executable code only.
12831 Section contains data only (no executable code).
12833 Section will reside in ROM.
12835 Section contains data for constructor/destructor lists.
12837 Section is not empty.
12839 An instruction to the linker to not output the section.
12840 @item COFF_SHARED_LIBRARY
12841 A notification to the linker that the section contains
12842 COFF shared library information.
12844 Section contains common symbols.
12847 @kindex set trust-readonly-sections
12848 @cindex read-only sections
12849 @item set trust-readonly-sections on
12850 Tell @value{GDBN} that readonly sections in your object file
12851 really are read-only (i.e.@: that their contents will not change).
12852 In that case, @value{GDBN} can fetch values from these sections
12853 out of the object file, rather than from the target program.
12854 For some targets (notably embedded ones), this can be a significant
12855 enhancement to debugging performance.
12857 The default is off.
12859 @item set trust-readonly-sections off
12860 Tell @value{GDBN} not to trust readonly sections. This means that
12861 the contents of the section might change while the program is running,
12862 and must therefore be fetched from the target when needed.
12864 @item show trust-readonly-sections
12865 Show the current setting of trusting readonly sections.
12868 All file-specifying commands allow both absolute and relative file names
12869 as arguments. @value{GDBN} always converts the file name to an absolute file
12870 name and remembers it that way.
12872 @cindex shared libraries
12873 @anchor{Shared Libraries}
12874 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
12875 and IBM RS/6000 AIX shared libraries.
12877 On MS-Windows @value{GDBN} must be linked with the Expat library to support
12878 shared libraries. @xref{Expat}.
12880 @value{GDBN} automatically loads symbol definitions from shared libraries
12881 when you use the @code{run} command, or when you examine a core file.
12882 (Before you issue the @code{run} command, @value{GDBN} does not understand
12883 references to a function in a shared library, however---unless you are
12884 debugging a core file).
12886 On HP-UX, if the program loads a library explicitly, @value{GDBN}
12887 automatically loads the symbols at the time of the @code{shl_load} call.
12889 @c FIXME: some @value{GDBN} release may permit some refs to undef
12890 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
12891 @c FIXME...lib; check this from time to time when updating manual
12893 There are times, however, when you may wish to not automatically load
12894 symbol definitions from shared libraries, such as when they are
12895 particularly large or there are many of them.
12897 To control the automatic loading of shared library symbols, use the
12901 @kindex set auto-solib-add
12902 @item set auto-solib-add @var{mode}
12903 If @var{mode} is @code{on}, symbols from all shared object libraries
12904 will be loaded automatically when the inferior begins execution, you
12905 attach to an independently started inferior, or when the dynamic linker
12906 informs @value{GDBN} that a new library has been loaded. If @var{mode}
12907 is @code{off}, symbols must be loaded manually, using the
12908 @code{sharedlibrary} command. The default value is @code{on}.
12910 @cindex memory used for symbol tables
12911 If your program uses lots of shared libraries with debug info that
12912 takes large amounts of memory, you can decrease the @value{GDBN}
12913 memory footprint by preventing it from automatically loading the
12914 symbols from shared libraries. To that end, type @kbd{set
12915 auto-solib-add off} before running the inferior, then load each
12916 library whose debug symbols you do need with @kbd{sharedlibrary
12917 @var{regexp}}, where @var{regexp} is a regular expression that matches
12918 the libraries whose symbols you want to be loaded.
12920 @kindex show auto-solib-add
12921 @item show auto-solib-add
12922 Display the current autoloading mode.
12925 @cindex load shared library
12926 To explicitly load shared library symbols, use the @code{sharedlibrary}
12930 @kindex info sharedlibrary
12933 @itemx info sharedlibrary
12934 Print the names of the shared libraries which are currently loaded.
12936 @kindex sharedlibrary
12938 @item sharedlibrary @var{regex}
12939 @itemx share @var{regex}
12940 Load shared object library symbols for files matching a
12941 Unix regular expression.
12942 As with files loaded automatically, it only loads shared libraries
12943 required by your program for a core file or after typing @code{run}. If
12944 @var{regex} is omitted all shared libraries required by your program are
12947 @item nosharedlibrary
12948 @kindex nosharedlibrary
12949 @cindex unload symbols from shared libraries
12950 Unload all shared object library symbols. This discards all symbols
12951 that have been loaded from all shared libraries. Symbols from shared
12952 libraries that were loaded by explicit user requests are not
12956 Sometimes you may wish that @value{GDBN} stops and gives you control
12957 when any of shared library events happen. Use the @code{set
12958 stop-on-solib-events} command for this:
12961 @item set stop-on-solib-events
12962 @kindex set stop-on-solib-events
12963 This command controls whether @value{GDBN} should give you control
12964 when the dynamic linker notifies it about some shared library event.
12965 The most common event of interest is loading or unloading of a new
12968 @item show stop-on-solib-events
12969 @kindex show stop-on-solib-events
12970 Show whether @value{GDBN} stops and gives you control when shared
12971 library events happen.
12974 Shared libraries are also supported in many cross or remote debugging
12975 configurations. @value{GDBN} needs to have access to the target's libraries;
12976 this can be accomplished either by providing copies of the libraries
12977 on the host system, or by asking @value{GDBN} to automatically retrieve the
12978 libraries from the target. If copies of the target libraries are
12979 provided, they need to be the same as the target libraries, although the
12980 copies on the target can be stripped as long as the copies on the host are
12983 @cindex where to look for shared libraries
12984 For remote debugging, you need to tell @value{GDBN} where the target
12985 libraries are, so that it can load the correct copies---otherwise, it
12986 may try to load the host's libraries. @value{GDBN} has two variables
12987 to specify the search directories for target libraries.
12990 @cindex prefix for shared library file names
12991 @cindex system root, alternate
12992 @kindex set solib-absolute-prefix
12993 @kindex set sysroot
12994 @item set sysroot @var{path}
12995 Use @var{path} as the system root for the program being debugged. Any
12996 absolute shared library paths will be prefixed with @var{path}; many
12997 runtime loaders store the absolute paths to the shared library in the
12998 target program's memory. If you use @code{set sysroot} to find shared
12999 libraries, they need to be laid out in the same way that they are on
13000 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13003 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13004 retrieve the target libraries from the remote system. This is only
13005 supported when using a remote target that supports the @code{remote get}
13006 command (@pxref{File Transfer,,Sending files to a remote system}).
13007 The part of @var{path} following the initial @file{remote:}
13008 (if present) is used as system root prefix on the remote file system.
13009 @footnote{If you want to specify a local system root using a directory
13010 that happens to be named @file{remote:}, you need to use some equivalent
13011 variant of the name like @file{./remote:}.}
13013 The @code{set solib-absolute-prefix} command is an alias for @code{set
13016 @cindex default system root
13017 @cindex @samp{--with-sysroot}
13018 You can set the default system root by using the configure-time
13019 @samp{--with-sysroot} option. If the system root is inside
13020 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13021 @samp{--exec-prefix}), then the default system root will be updated
13022 automatically if the installed @value{GDBN} is moved to a new
13025 @kindex show sysroot
13027 Display the current shared library prefix.
13029 @kindex set solib-search-path
13030 @item set solib-search-path @var{path}
13031 If this variable is set, @var{path} is a colon-separated list of
13032 directories to search for shared libraries. @samp{solib-search-path}
13033 is used after @samp{sysroot} fails to locate the library, or if the
13034 path to the library is relative instead of absolute. If you want to
13035 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13036 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13037 finding your host's libraries. @samp{sysroot} is preferred; setting
13038 it to a nonexistent directory may interfere with automatic loading
13039 of shared library symbols.
13041 @kindex show solib-search-path
13042 @item show solib-search-path
13043 Display the current shared library search path.
13047 @node Separate Debug Files
13048 @section Debugging Information in Separate Files
13049 @cindex separate debugging information files
13050 @cindex debugging information in separate files
13051 @cindex @file{.debug} subdirectories
13052 @cindex debugging information directory, global
13053 @cindex global debugging information directory
13054 @cindex build ID, and separate debugging files
13055 @cindex @file{.build-id} directory
13057 @value{GDBN} allows you to put a program's debugging information in a
13058 file separate from the executable itself, in a way that allows
13059 @value{GDBN} to find and load the debugging information automatically.
13060 Since debugging information can be very large---sometimes larger
13061 than the executable code itself---some systems distribute debugging
13062 information for their executables in separate files, which users can
13063 install only when they need to debug a problem.
13065 @value{GDBN} supports two ways of specifying the separate debug info
13070 The executable contains a @dfn{debug link} that specifies the name of
13071 the separate debug info file. The separate debug file's name is
13072 usually @file{@var{executable}.debug}, where @var{executable} is the
13073 name of the corresponding executable file without leading directories
13074 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13075 debug link specifies a CRC32 checksum for the debug file, which
13076 @value{GDBN} uses to validate that the executable and the debug file
13077 came from the same build.
13080 The executable contains a @dfn{build ID}, a unique bit string that is
13081 also present in the corresponding debug info file. (This is supported
13082 only on some operating systems, notably those which use the ELF format
13083 for binary files and the @sc{gnu} Binutils.) For more details about
13084 this feature, see the description of the @option{--build-id}
13085 command-line option in @ref{Options, , Command Line Options, ld.info,
13086 The GNU Linker}. The debug info file's name is not specified
13087 explicitly by the build ID, but can be computed from the build ID, see
13091 Depending on the way the debug info file is specified, @value{GDBN}
13092 uses two different methods of looking for the debug file:
13096 For the ``debug link'' method, @value{GDBN} looks up the named file in
13097 the directory of the executable file, then in a subdirectory of that
13098 directory named @file{.debug}, and finally under the global debug
13099 directory, in a subdirectory whose name is identical to the leading
13100 directories of the executable's absolute file name.
13103 For the ``build ID'' method, @value{GDBN} looks in the
13104 @file{.build-id} subdirectory of the global debug directory for a file
13105 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13106 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13107 are the rest of the bit string. (Real build ID strings are 32 or more
13108 hex characters, not 10.)
13111 So, for example, suppose you ask @value{GDBN} to debug
13112 @file{/usr/bin/ls}, which has a debug link that specifies the
13113 file @file{ls.debug}, and a build ID whose value in hex is
13114 @code{abcdef1234}. If the global debug directory is
13115 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13116 debug information files, in the indicated order:
13120 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13122 @file{/usr/bin/ls.debug}
13124 @file{/usr/bin/.debug/ls.debug}
13126 @file{/usr/lib/debug/usr/bin/ls.debug}.
13129 You can set the global debugging info directory's name, and view the
13130 name @value{GDBN} is currently using.
13134 @kindex set debug-file-directory
13135 @item set debug-file-directory @var{directory}
13136 Set the directory which @value{GDBN} searches for separate debugging
13137 information files to @var{directory}.
13139 @kindex show debug-file-directory
13140 @item show debug-file-directory
13141 Show the directory @value{GDBN} searches for separate debugging
13146 @cindex @code{.gnu_debuglink} sections
13147 @cindex debug link sections
13148 A debug link is a special section of the executable file named
13149 @code{.gnu_debuglink}. The section must contain:
13153 A filename, with any leading directory components removed, followed by
13156 zero to three bytes of padding, as needed to reach the next four-byte
13157 boundary within the section, and
13159 a four-byte CRC checksum, stored in the same endianness used for the
13160 executable file itself. The checksum is computed on the debugging
13161 information file's full contents by the function given below, passing
13162 zero as the @var{crc} argument.
13165 Any executable file format can carry a debug link, as long as it can
13166 contain a section named @code{.gnu_debuglink} with the contents
13169 @cindex @code{.note.gnu.build-id} sections
13170 @cindex build ID sections
13171 The build ID is a special section in the executable file (and in other
13172 ELF binary files that @value{GDBN} may consider). This section is
13173 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13174 It contains unique identification for the built files---the ID remains
13175 the same across multiple builds of the same build tree. The default
13176 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13177 content for the build ID string. The same section with an identical
13178 value is present in the original built binary with symbols, in its
13179 stripped variant, and in the separate debugging information file.
13181 The debugging information file itself should be an ordinary
13182 executable, containing a full set of linker symbols, sections, and
13183 debugging information. The sections of the debugging information file
13184 should have the same names, addresses, and sizes as the original file,
13185 but they need not contain any data---much like a @code{.bss} section
13186 in an ordinary executable.
13188 The @sc{gnu} binary utilities (Binutils) package includes the
13189 @samp{objcopy} utility that can produce
13190 the separated executable / debugging information file pairs using the
13191 following commands:
13194 @kbd{objcopy --only-keep-debug foo foo.debug}
13199 These commands remove the debugging
13200 information from the executable file @file{foo} and place it in the file
13201 @file{foo.debug}. You can use the first, second or both methods to link the
13206 The debug link method needs the following additional command to also leave
13207 behind a debug link in @file{foo}:
13210 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13213 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13214 a version of the @code{strip} command such that the command @kbd{strip foo -f
13215 foo.debug} has the same functionality as the two @code{objcopy} commands and
13216 the @code{ln -s} command above, together.
13219 Build ID gets embedded into the main executable using @code{ld --build-id} or
13220 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13221 compatibility fixes for debug files separation are present in @sc{gnu} binary
13222 utilities (Binutils) package since version 2.18.
13227 Since there are many different ways to compute CRC's for the debug
13228 link (different polynomials, reversals, byte ordering, etc.), the
13229 simplest way to describe the CRC used in @code{.gnu_debuglink}
13230 sections is to give the complete code for a function that computes it:
13232 @kindex gnu_debuglink_crc32
13235 gnu_debuglink_crc32 (unsigned long crc,
13236 unsigned char *buf, size_t len)
13238 static const unsigned long crc32_table[256] =
13240 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13241 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13242 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13243 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13244 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13245 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13246 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13247 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13248 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13249 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13250 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13251 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13252 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13253 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13254 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13255 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13256 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13257 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13258 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13259 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13260 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13261 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13262 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13263 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13264 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13265 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13266 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13267 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13268 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13269 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13270 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13271 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13272 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13273 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13274 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13275 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13276 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13277 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13278 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13279 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13280 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13281 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13282 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13283 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13284 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13285 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13286 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13287 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13288 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13289 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13290 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13293 unsigned char *end;
13295 crc = ~crc & 0xffffffff;
13296 for (end = buf + len; buf < end; ++buf)
13297 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13298 return ~crc & 0xffffffff;
13303 This computation does not apply to the ``build ID'' method.
13306 @node Symbol Errors
13307 @section Errors Reading Symbol Files
13309 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13310 such as symbol types it does not recognize, or known bugs in compiler
13311 output. By default, @value{GDBN} does not notify you of such problems, since
13312 they are relatively common and primarily of interest to people
13313 debugging compilers. If you are interested in seeing information
13314 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13315 only one message about each such type of problem, no matter how many
13316 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13317 to see how many times the problems occur, with the @code{set
13318 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13321 The messages currently printed, and their meanings, include:
13324 @item inner block not inside outer block in @var{symbol}
13326 The symbol information shows where symbol scopes begin and end
13327 (such as at the start of a function or a block of statements). This
13328 error indicates that an inner scope block is not fully contained
13329 in its outer scope blocks.
13331 @value{GDBN} circumvents the problem by treating the inner block as if it had
13332 the same scope as the outer block. In the error message, @var{symbol}
13333 may be shown as ``@code{(don't know)}'' if the outer block is not a
13336 @item block at @var{address} out of order
13338 The symbol information for symbol scope blocks should occur in
13339 order of increasing addresses. This error indicates that it does not
13342 @value{GDBN} does not circumvent this problem, and has trouble
13343 locating symbols in the source file whose symbols it is reading. (You
13344 can often determine what source file is affected by specifying
13345 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13348 @item bad block start address patched
13350 The symbol information for a symbol scope block has a start address
13351 smaller than the address of the preceding source line. This is known
13352 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13354 @value{GDBN} circumvents the problem by treating the symbol scope block as
13355 starting on the previous source line.
13357 @item bad string table offset in symbol @var{n}
13360 Symbol number @var{n} contains a pointer into the string table which is
13361 larger than the size of the string table.
13363 @value{GDBN} circumvents the problem by considering the symbol to have the
13364 name @code{foo}, which may cause other problems if many symbols end up
13367 @item unknown symbol type @code{0x@var{nn}}
13369 The symbol information contains new data types that @value{GDBN} does
13370 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13371 uncomprehended information, in hexadecimal.
13373 @value{GDBN} circumvents the error by ignoring this symbol information.
13374 This usually allows you to debug your program, though certain symbols
13375 are not accessible. If you encounter such a problem and feel like
13376 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13377 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13378 and examine @code{*bufp} to see the symbol.
13380 @item stub type has NULL name
13382 @value{GDBN} could not find the full definition for a struct or class.
13384 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13385 The symbol information for a C@t{++} member function is missing some
13386 information that recent versions of the compiler should have output for
13389 @item info mismatch between compiler and debugger
13391 @value{GDBN} could not parse a type specification output by the compiler.
13396 @chapter Specifying a Debugging Target
13398 @cindex debugging target
13399 A @dfn{target} is the execution environment occupied by your program.
13401 Often, @value{GDBN} runs in the same host environment as your program;
13402 in that case, the debugging target is specified as a side effect when
13403 you use the @code{file} or @code{core} commands. When you need more
13404 flexibility---for example, running @value{GDBN} on a physically separate
13405 host, or controlling a standalone system over a serial port or a
13406 realtime system over a TCP/IP connection---you can use the @code{target}
13407 command to specify one of the target types configured for @value{GDBN}
13408 (@pxref{Target Commands, ,Commands for Managing Targets}).
13410 @cindex target architecture
13411 It is possible to build @value{GDBN} for several different @dfn{target
13412 architectures}. When @value{GDBN} is built like that, you can choose
13413 one of the available architectures with the @kbd{set architecture}
13417 @kindex set architecture
13418 @kindex show architecture
13419 @item set architecture @var{arch}
13420 This command sets the current target architecture to @var{arch}. The
13421 value of @var{arch} can be @code{"auto"}, in addition to one of the
13422 supported architectures.
13424 @item show architecture
13425 Show the current target architecture.
13427 @item set processor
13429 @kindex set processor
13430 @kindex show processor
13431 These are alias commands for, respectively, @code{set architecture}
13432 and @code{show architecture}.
13436 * Active Targets:: Active targets
13437 * Target Commands:: Commands for managing targets
13438 * Byte Order:: Choosing target byte order
13441 @node Active Targets
13442 @section Active Targets
13444 @cindex stacking targets
13445 @cindex active targets
13446 @cindex multiple targets
13448 There are three classes of targets: processes, core files, and
13449 executable files. @value{GDBN} can work concurrently on up to three
13450 active targets, one in each class. This allows you to (for example)
13451 start a process and inspect its activity without abandoning your work on
13454 For example, if you execute @samp{gdb a.out}, then the executable file
13455 @code{a.out} is the only active target. If you designate a core file as
13456 well---presumably from a prior run that crashed and coredumped---then
13457 @value{GDBN} has two active targets and uses them in tandem, looking
13458 first in the corefile target, then in the executable file, to satisfy
13459 requests for memory addresses. (Typically, these two classes of target
13460 are complementary, since core files contain only a program's
13461 read-write memory---variables and so on---plus machine status, while
13462 executable files contain only the program text and initialized data.)
13464 When you type @code{run}, your executable file becomes an active process
13465 target as well. When a process target is active, all @value{GDBN}
13466 commands requesting memory addresses refer to that target; addresses in
13467 an active core file or executable file target are obscured while the
13468 process target is active.
13470 Use the @code{core-file} and @code{exec-file} commands to select a new
13471 core file or executable target (@pxref{Files, ,Commands to Specify
13472 Files}). To specify as a target a process that is already running, use
13473 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13476 @node Target Commands
13477 @section Commands for Managing Targets
13480 @item target @var{type} @var{parameters}
13481 Connects the @value{GDBN} host environment to a target machine or
13482 process. A target is typically a protocol for talking to debugging
13483 facilities. You use the argument @var{type} to specify the type or
13484 protocol of the target machine.
13486 Further @var{parameters} are interpreted by the target protocol, but
13487 typically include things like device names or host names to connect
13488 with, process numbers, and baud rates.
13490 The @code{target} command does not repeat if you press @key{RET} again
13491 after executing the command.
13493 @kindex help target
13495 Displays the names of all targets available. To display targets
13496 currently selected, use either @code{info target} or @code{info files}
13497 (@pxref{Files, ,Commands to Specify Files}).
13499 @item help target @var{name}
13500 Describe a particular target, including any parameters necessary to
13503 @kindex set gnutarget
13504 @item set gnutarget @var{args}
13505 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13506 knows whether it is reading an @dfn{executable},
13507 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13508 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13509 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13512 @emph{Warning:} To specify a file format with @code{set gnutarget},
13513 you must know the actual BFD name.
13517 @xref{Files, , Commands to Specify Files}.
13519 @kindex show gnutarget
13520 @item show gnutarget
13521 Use the @code{show gnutarget} command to display what file format
13522 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13523 @value{GDBN} will determine the file format for each file automatically,
13524 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13527 @cindex common targets
13528 Here are some common targets (available, or not, depending on the GDB
13533 @item target exec @var{program}
13534 @cindex executable file target
13535 An executable file. @samp{target exec @var{program}} is the same as
13536 @samp{exec-file @var{program}}.
13538 @item target core @var{filename}
13539 @cindex core dump file target
13540 A core dump file. @samp{target core @var{filename}} is the same as
13541 @samp{core-file @var{filename}}.
13543 @item target remote @var{medium}
13544 @cindex remote target
13545 A remote system connected to @value{GDBN} via a serial line or network
13546 connection. This command tells @value{GDBN} to use its own remote
13547 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13549 For example, if you have a board connected to @file{/dev/ttya} on the
13550 machine running @value{GDBN}, you could say:
13553 target remote /dev/ttya
13556 @code{target remote} supports the @code{load} command. This is only
13557 useful if you have some other way of getting the stub to the target
13558 system, and you can put it somewhere in memory where it won't get
13559 clobbered by the download.
13562 @cindex built-in simulator target
13563 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13571 works; however, you cannot assume that a specific memory map, device
13572 drivers, or even basic I/O is available, although some simulators do
13573 provide these. For info about any processor-specific simulator details,
13574 see the appropriate section in @ref{Embedded Processors, ,Embedded
13579 Some configurations may include these targets as well:
13583 @item target nrom @var{dev}
13584 @cindex NetROM ROM emulator target
13585 NetROM ROM emulator. This target only supports downloading.
13589 Different targets are available on different configurations of @value{GDBN};
13590 your configuration may have more or fewer targets.
13592 Many remote targets require you to download the executable's code once
13593 you've successfully established a connection. You may wish to control
13594 various aspects of this process.
13599 @kindex set hash@r{, for remote monitors}
13600 @cindex hash mark while downloading
13601 This command controls whether a hash mark @samp{#} is displayed while
13602 downloading a file to the remote monitor. If on, a hash mark is
13603 displayed after each S-record is successfully downloaded to the
13607 @kindex show hash@r{, for remote monitors}
13608 Show the current status of displaying the hash mark.
13610 @item set debug monitor
13611 @kindex set debug monitor
13612 @cindex display remote monitor communications
13613 Enable or disable display of communications messages between
13614 @value{GDBN} and the remote monitor.
13616 @item show debug monitor
13617 @kindex show debug monitor
13618 Show the current status of displaying communications between
13619 @value{GDBN} and the remote monitor.
13624 @kindex load @var{filename}
13625 @item load @var{filename}
13627 Depending on what remote debugging facilities are configured into
13628 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13629 is meant to make @var{filename} (an executable) available for debugging
13630 on the remote system---by downloading, or dynamic linking, for example.
13631 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13632 the @code{add-symbol-file} command.
13634 If your @value{GDBN} does not have a @code{load} command, attempting to
13635 execute it gets the error message ``@code{You can't do that when your
13636 target is @dots{}}''
13638 The file is loaded at whatever address is specified in the executable.
13639 For some object file formats, you can specify the load address when you
13640 link the program; for other formats, like a.out, the object file format
13641 specifies a fixed address.
13642 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13644 Depending on the remote side capabilities, @value{GDBN} may be able to
13645 load programs into flash memory.
13647 @code{load} does not repeat if you press @key{RET} again after using it.
13651 @section Choosing Target Byte Order
13653 @cindex choosing target byte order
13654 @cindex target byte order
13656 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13657 offer the ability to run either big-endian or little-endian byte
13658 orders. Usually the executable or symbol will include a bit to
13659 designate the endian-ness, and you will not need to worry about
13660 which to use. However, you may still find it useful to adjust
13661 @value{GDBN}'s idea of processor endian-ness manually.
13665 @item set endian big
13666 Instruct @value{GDBN} to assume the target is big-endian.
13668 @item set endian little
13669 Instruct @value{GDBN} to assume the target is little-endian.
13671 @item set endian auto
13672 Instruct @value{GDBN} to use the byte order associated with the
13676 Display @value{GDBN}'s current idea of the target byte order.
13680 Note that these commands merely adjust interpretation of symbolic
13681 data on the host, and that they have absolutely no effect on the
13685 @node Remote Debugging
13686 @chapter Debugging Remote Programs
13687 @cindex remote debugging
13689 If you are trying to debug a program running on a machine that cannot run
13690 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13691 For example, you might use remote debugging on an operating system kernel,
13692 or on a small system which does not have a general purpose operating system
13693 powerful enough to run a full-featured debugger.
13695 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13696 to make this work with particular debugging targets. In addition,
13697 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13698 but not specific to any particular target system) which you can use if you
13699 write the remote stubs---the code that runs on the remote system to
13700 communicate with @value{GDBN}.
13702 Other remote targets may be available in your
13703 configuration of @value{GDBN}; use @code{help target} to list them.
13706 * Connecting:: Connecting to a remote target
13707 * File Transfer:: Sending files to a remote system
13708 * Server:: Using the gdbserver program
13709 * Remote Configuration:: Remote configuration
13710 * Remote Stub:: Implementing a remote stub
13714 @section Connecting to a Remote Target
13716 On the @value{GDBN} host machine, you will need an unstripped copy of
13717 your program, since @value{GDBN} needs symbol and debugging information.
13718 Start up @value{GDBN} as usual, using the name of the local copy of your
13719 program as the first argument.
13721 @cindex @code{target remote}
13722 @value{GDBN} can communicate with the target over a serial line, or
13723 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13724 each case, @value{GDBN} uses the same protocol for debugging your
13725 program; only the medium carrying the debugging packets varies. The
13726 @code{target remote} command establishes a connection to the target.
13727 Its arguments indicate which medium to use:
13731 @item target remote @var{serial-device}
13732 @cindex serial line, @code{target remote}
13733 Use @var{serial-device} to communicate with the target. For example,
13734 to use a serial line connected to the device named @file{/dev/ttyb}:
13737 target remote /dev/ttyb
13740 If you're using a serial line, you may want to give @value{GDBN} the
13741 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13742 (@pxref{Remote Configuration, set remotebaud}) before the
13743 @code{target} command.
13745 @item target remote @code{@var{host}:@var{port}}
13746 @itemx target remote @code{tcp:@var{host}:@var{port}}
13747 @cindex @acronym{TCP} port, @code{target remote}
13748 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13749 The @var{host} may be either a host name or a numeric @acronym{IP}
13750 address; @var{port} must be a decimal number. The @var{host} could be
13751 the target machine itself, if it is directly connected to the net, or
13752 it might be a terminal server which in turn has a serial line to the
13755 For example, to connect to port 2828 on a terminal server named
13759 target remote manyfarms:2828
13762 If your remote target is actually running on the same machine as your
13763 debugger session (e.g.@: a simulator for your target running on the
13764 same host), you can omit the hostname. For example, to connect to
13765 port 1234 on your local machine:
13768 target remote :1234
13772 Note that the colon is still required here.
13774 @item target remote @code{udp:@var{host}:@var{port}}
13775 @cindex @acronym{UDP} port, @code{target remote}
13776 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13777 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13780 target remote udp:manyfarms:2828
13783 When using a @acronym{UDP} connection for remote debugging, you should
13784 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13785 can silently drop packets on busy or unreliable networks, which will
13786 cause havoc with your debugging session.
13788 @item target remote | @var{command}
13789 @cindex pipe, @code{target remote} to
13790 Run @var{command} in the background and communicate with it using a
13791 pipe. The @var{command} is a shell command, to be parsed and expanded
13792 by the system's command shell, @code{/bin/sh}; it should expect remote
13793 protocol packets on its standard input, and send replies on its
13794 standard output. You could use this to run a stand-alone simulator
13795 that speaks the remote debugging protocol, to make net connections
13796 using programs like @code{ssh}, or for other similar tricks.
13798 If @var{command} closes its standard output (perhaps by exiting),
13799 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13800 program has already exited, this will have no effect.)
13804 Once the connection has been established, you can use all the usual
13805 commands to examine and change data. The remote program is already
13806 running; you can use @kbd{step} and @kbd{continue}, and you do not
13807 need to use @kbd{run}.
13809 @cindex interrupting remote programs
13810 @cindex remote programs, interrupting
13811 Whenever @value{GDBN} is waiting for the remote program, if you type the
13812 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13813 program. This may or may not succeed, depending in part on the hardware
13814 and the serial drivers the remote system uses. If you type the
13815 interrupt character once again, @value{GDBN} displays this prompt:
13818 Interrupted while waiting for the program.
13819 Give up (and stop debugging it)? (y or n)
13822 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13823 (If you decide you want to try again later, you can use @samp{target
13824 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13825 goes back to waiting.
13828 @kindex detach (remote)
13830 When you have finished debugging the remote program, you can use the
13831 @code{detach} command to release it from @value{GDBN} control.
13832 Detaching from the target normally resumes its execution, but the results
13833 will depend on your particular remote stub. After the @code{detach}
13834 command, @value{GDBN} is free to connect to another target.
13838 The @code{disconnect} command behaves like @code{detach}, except that
13839 the target is generally not resumed. It will wait for @value{GDBN}
13840 (this instance or another one) to connect and continue debugging. After
13841 the @code{disconnect} command, @value{GDBN} is again free to connect to
13844 @cindex send command to remote monitor
13845 @cindex extend @value{GDBN} for remote targets
13846 @cindex add new commands for external monitor
13848 @item monitor @var{cmd}
13849 This command allows you to send arbitrary commands directly to the
13850 remote monitor. Since @value{GDBN} doesn't care about the commands it
13851 sends like this, this command is the way to extend @value{GDBN}---you
13852 can add new commands that only the external monitor will understand
13856 @node File Transfer
13857 @section Sending files to a remote system
13858 @cindex remote target, file transfer
13859 @cindex file transfer
13860 @cindex sending files to remote systems
13862 Some remote targets offer the ability to transfer files over the same
13863 connection used to communicate with @value{GDBN}. This is convenient
13864 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
13865 running @code{gdbserver} over a network interface. For other targets,
13866 e.g.@: embedded devices with only a single serial port, this may be
13867 the only way to upload or download files.
13869 Not all remote targets support these commands.
13873 @item remote put @var{hostfile} @var{targetfile}
13874 Copy file @var{hostfile} from the host system (the machine running
13875 @value{GDBN}) to @var{targetfile} on the target system.
13878 @item remote get @var{targetfile} @var{hostfile}
13879 Copy file @var{targetfile} from the target system to @var{hostfile}
13880 on the host system.
13882 @kindex remote delete
13883 @item remote delete @var{targetfile}
13884 Delete @var{targetfile} from the target system.
13889 @section Using the @code{gdbserver} Program
13892 @cindex remote connection without stubs
13893 @code{gdbserver} is a control program for Unix-like systems, which
13894 allows you to connect your program with a remote @value{GDBN} via
13895 @code{target remote}---but without linking in the usual debugging stub.
13897 @code{gdbserver} is not a complete replacement for the debugging stubs,
13898 because it requires essentially the same operating-system facilities
13899 that @value{GDBN} itself does. In fact, a system that can run
13900 @code{gdbserver} to connect to a remote @value{GDBN} could also run
13901 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
13902 because it is a much smaller program than @value{GDBN} itself. It is
13903 also easier to port than all of @value{GDBN}, so you may be able to get
13904 started more quickly on a new system by using @code{gdbserver}.
13905 Finally, if you develop code for real-time systems, you may find that
13906 the tradeoffs involved in real-time operation make it more convenient to
13907 do as much development work as possible on another system, for example
13908 by cross-compiling. You can use @code{gdbserver} to make a similar
13909 choice for debugging.
13911 @value{GDBN} and @code{gdbserver} communicate via either a serial line
13912 or a TCP connection, using the standard @value{GDBN} remote serial
13916 @emph{Warning:} @code{gdbserver} does not have any built-in security.
13917 Do not run @code{gdbserver} connected to any public network; a
13918 @value{GDBN} connection to @code{gdbserver} provides access to the
13919 target system with the same privileges as the user running
13923 @subsection Running @code{gdbserver}
13924 @cindex arguments, to @code{gdbserver}
13926 Run @code{gdbserver} on the target system. You need a copy of the
13927 program you want to debug, including any libraries it requires.
13928 @code{gdbserver} does not need your program's symbol table, so you can
13929 strip the program if necessary to save space. @value{GDBN} on the host
13930 system does all the symbol handling.
13932 To use the server, you must tell it how to communicate with @value{GDBN};
13933 the name of your program; and the arguments for your program. The usual
13937 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
13940 @var{comm} is either a device name (to use a serial line) or a TCP
13941 hostname and portnumber. For example, to debug Emacs with the argument
13942 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
13946 target> gdbserver /dev/com1 emacs foo.txt
13949 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
13952 To use a TCP connection instead of a serial line:
13955 target> gdbserver host:2345 emacs foo.txt
13958 The only difference from the previous example is the first argument,
13959 specifying that you are communicating with the host @value{GDBN} via
13960 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
13961 expect a TCP connection from machine @samp{host} to local TCP port 2345.
13962 (Currently, the @samp{host} part is ignored.) You can choose any number
13963 you want for the port number as long as it does not conflict with any
13964 TCP ports already in use on the target system (for example, @code{23} is
13965 reserved for @code{telnet}).@footnote{If you choose a port number that
13966 conflicts with another service, @code{gdbserver} prints an error message
13967 and exits.} You must use the same port number with the host @value{GDBN}
13968 @code{target remote} command.
13970 @subsubsection Attaching to a Running Program
13972 On some targets, @code{gdbserver} can also attach to running programs.
13973 This is accomplished via the @code{--attach} argument. The syntax is:
13976 target> gdbserver --attach @var{comm} @var{pid}
13979 @var{pid} is the process ID of a currently running process. It isn't necessary
13980 to point @code{gdbserver} at a binary for the running process.
13983 @cindex attach to a program by name
13984 You can debug processes by name instead of process ID if your target has the
13985 @code{pidof} utility:
13988 target> gdbserver --attach @var{comm} `pidof @var{program}`
13991 In case more than one copy of @var{program} is running, or @var{program}
13992 has multiple threads, most versions of @code{pidof} support the
13993 @code{-s} option to only return the first process ID.
13995 @subsubsection Multi-Process Mode for @code{gdbserver}
13996 @cindex gdbserver, multiple processes
13997 @cindex multiple processes with gdbserver
13999 When you connect to @code{gdbserver} using @code{target remote},
14000 @code{gdbserver} debugs the specified program only once. When the
14001 program exits, or you detach from it, @value{GDBN} closes the connection
14002 and @code{gdbserver} exits.
14004 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14005 enters multi-process mode. When the debugged program exits, or you
14006 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14007 though no program is running. The @code{run} and @code{attach}
14008 commands instruct @code{gdbserver} to run or attach to a new program.
14009 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14010 remote exec-file}) to select the program to run. Command line
14011 arguments are supported, except for wildcard expansion and I/O
14012 redirection (@pxref{Arguments}).
14014 To start @code{gdbserver} without supplying an initial command to run
14015 or process ID to attach, use the @option{--multi} command line option.
14016 Then you can connect using @kbd{target extended-remote} and start
14017 the program you want to debug.
14019 @code{gdbserver} does not automatically exit in multi-process mode.
14020 You can terminate it by using @code{monitor exit}
14021 (@pxref{Monitor Commands for gdbserver}).
14023 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14025 You can include @option{--debug} on the @code{gdbserver} command line.
14026 @code{gdbserver} will display extra status information about the debugging
14027 process. This option is intended for @code{gdbserver} development and
14028 for bug reports to the developers.
14030 The @option{--wrapper} option specifies a wrapper to launch programs
14031 for debugging. The option should be followed by the name of the
14032 wrapper, then any command-line arguments to pass to the wrapper, then
14033 @kbd{--} indicating the end of the wrapper arguments.
14035 @code{gdbserver} runs the specified wrapper program with a combined
14036 command line including the wrapper arguments, then the name of the
14037 program to debug, then any arguments to the program. The wrapper
14038 runs until it executes your program, and then @value{GDBN} gains control.
14040 You can use any program that eventually calls @code{execve} with
14041 its arguments as a wrapper. Several standard Unix utilities do
14042 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14043 with @code{exec "$@@"} will also work.
14045 For example, you can use @code{env} to pass an environment variable to
14046 the debugged program, without setting the variable in @code{gdbserver}'s
14050 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14053 @subsection Connecting to @code{gdbserver}
14055 Run @value{GDBN} on the host system.
14057 First make sure you have the necessary symbol files. Load symbols for
14058 your application using the @code{file} command before you connect. Use
14059 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14060 was compiled with the correct sysroot using @code{--with-sysroot}).
14062 The symbol file and target libraries must exactly match the executable
14063 and libraries on the target, with one exception: the files on the host
14064 system should not be stripped, even if the files on the target system
14065 are. Mismatched or missing files will lead to confusing results
14066 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14067 files may also prevent @code{gdbserver} from debugging multi-threaded
14070 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14071 For TCP connections, you must start up @code{gdbserver} prior to using
14072 the @code{target remote} command. Otherwise you may get an error whose
14073 text depends on the host system, but which usually looks something like
14074 @samp{Connection refused}. Don't use the @code{load}
14075 command in @value{GDBN} when using @code{gdbserver}, since the program is
14076 already on the target.
14078 @subsection Monitor Commands for @code{gdbserver}
14079 @cindex monitor commands, for @code{gdbserver}
14080 @anchor{Monitor Commands for gdbserver}
14082 During a @value{GDBN} session using @code{gdbserver}, you can use the
14083 @code{monitor} command to send special requests to @code{gdbserver}.
14084 Here are the available commands.
14088 List the available monitor commands.
14090 @item monitor set debug 0
14091 @itemx monitor set debug 1
14092 Disable or enable general debugging messages.
14094 @item monitor set remote-debug 0
14095 @itemx monitor set remote-debug 1
14096 Disable or enable specific debugging messages associated with the remote
14097 protocol (@pxref{Remote Protocol}).
14100 Tell gdbserver to exit immediately. This command should be followed by
14101 @code{disconnect} to close the debugging session. @code{gdbserver} will
14102 detach from any attached processes and kill any processes it created.
14103 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14104 of a multi-process mode debug session.
14108 @node Remote Configuration
14109 @section Remote Configuration
14112 @kindex show remote
14113 This section documents the configuration options available when
14114 debugging remote programs. For the options related to the File I/O
14115 extensions of the remote protocol, see @ref{system,
14116 system-call-allowed}.
14119 @item set remoteaddresssize @var{bits}
14120 @cindex address size for remote targets
14121 @cindex bits in remote address
14122 Set the maximum size of address in a memory packet to the specified
14123 number of bits. @value{GDBN} will mask off the address bits above
14124 that number, when it passes addresses to the remote target. The
14125 default value is the number of bits in the target's address.
14127 @item show remoteaddresssize
14128 Show the current value of remote address size in bits.
14130 @item set remotebaud @var{n}
14131 @cindex baud rate for remote targets
14132 Set the baud rate for the remote serial I/O to @var{n} baud. The
14133 value is used to set the speed of the serial port used for debugging
14136 @item show remotebaud
14137 Show the current speed of the remote connection.
14139 @item set remotebreak
14140 @cindex interrupt remote programs
14141 @cindex BREAK signal instead of Ctrl-C
14142 @anchor{set remotebreak}
14143 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14144 when you type @kbd{Ctrl-c} to interrupt the program running
14145 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14146 character instead. The default is off, since most remote systems
14147 expect to see @samp{Ctrl-C} as the interrupt signal.
14149 @item show remotebreak
14150 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14151 interrupt the remote program.
14153 @item set remoteflow on
14154 @itemx set remoteflow off
14155 @kindex set remoteflow
14156 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14157 on the serial port used to communicate to the remote target.
14159 @item show remoteflow
14160 @kindex show remoteflow
14161 Show the current setting of hardware flow control.
14163 @item set remotelogbase @var{base}
14164 Set the base (a.k.a.@: radix) of logging serial protocol
14165 communications to @var{base}. Supported values of @var{base} are:
14166 @code{ascii}, @code{octal}, and @code{hex}. The default is
14169 @item show remotelogbase
14170 Show the current setting of the radix for logging remote serial
14173 @item set remotelogfile @var{file}
14174 @cindex record serial communications on file
14175 Record remote serial communications on the named @var{file}. The
14176 default is not to record at all.
14178 @item show remotelogfile.
14179 Show the current setting of the file name on which to record the
14180 serial communications.
14182 @item set remotetimeout @var{num}
14183 @cindex timeout for serial communications
14184 @cindex remote timeout
14185 Set the timeout limit to wait for the remote target to respond to
14186 @var{num} seconds. The default is 2 seconds.
14188 @item show remotetimeout
14189 Show the current number of seconds to wait for the remote target
14192 @cindex limit hardware breakpoints and watchpoints
14193 @cindex remote target, limit break- and watchpoints
14194 @anchor{set remote hardware-watchpoint-limit}
14195 @anchor{set remote hardware-breakpoint-limit}
14196 @item set remote hardware-watchpoint-limit @var{limit}
14197 @itemx set remote hardware-breakpoint-limit @var{limit}
14198 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14199 watchpoints. A limit of -1, the default, is treated as unlimited.
14201 @item set remote exec-file @var{filename}
14202 @itemx show remote exec-file
14203 @anchor{set remote exec-file}
14204 @cindex executable file, for remote target
14205 Select the file used for @code{run} with @code{target
14206 extended-remote}. This should be set to a filename valid on the
14207 target system. If it is not set, the target will use a default
14208 filename (e.g.@: the last program run).
14211 @cindex remote packets, enabling and disabling
14212 The @value{GDBN} remote protocol autodetects the packets supported by
14213 your debugging stub. If you need to override the autodetection, you
14214 can use these commands to enable or disable individual packets. Each
14215 packet can be set to @samp{on} (the remote target supports this
14216 packet), @samp{off} (the remote target does not support this packet),
14217 or @samp{auto} (detect remote target support for this packet). They
14218 all default to @samp{auto}. For more information about each packet,
14219 see @ref{Remote Protocol}.
14221 During normal use, you should not have to use any of these commands.
14222 If you do, that may be a bug in your remote debugging stub, or a bug
14223 in @value{GDBN}. You may want to report the problem to the
14224 @value{GDBN} developers.
14226 For each packet @var{name}, the command to enable or disable the
14227 packet is @code{set remote @var{name}-packet}. The available settings
14230 @multitable @columnfractions 0.28 0.32 0.25
14233 @tab Related Features
14235 @item @code{fetch-register}
14237 @tab @code{info registers}
14239 @item @code{set-register}
14243 @item @code{binary-download}
14245 @tab @code{load}, @code{set}
14247 @item @code{read-aux-vector}
14248 @tab @code{qXfer:auxv:read}
14249 @tab @code{info auxv}
14251 @item @code{symbol-lookup}
14252 @tab @code{qSymbol}
14253 @tab Detecting multiple threads
14255 @item @code{attach}
14256 @tab @code{vAttach}
14259 @item @code{verbose-resume}
14261 @tab Stepping or resuming multiple threads
14267 @item @code{software-breakpoint}
14271 @item @code{hardware-breakpoint}
14275 @item @code{write-watchpoint}
14279 @item @code{read-watchpoint}
14283 @item @code{access-watchpoint}
14287 @item @code{target-features}
14288 @tab @code{qXfer:features:read}
14289 @tab @code{set architecture}
14291 @item @code{library-info}
14292 @tab @code{qXfer:libraries:read}
14293 @tab @code{info sharedlibrary}
14295 @item @code{memory-map}
14296 @tab @code{qXfer:memory-map:read}
14297 @tab @code{info mem}
14299 @item @code{read-spu-object}
14300 @tab @code{qXfer:spu:read}
14301 @tab @code{info spu}
14303 @item @code{write-spu-object}
14304 @tab @code{qXfer:spu:write}
14305 @tab @code{info spu}
14307 @item @code{get-thread-local-@*storage-address}
14308 @tab @code{qGetTLSAddr}
14309 @tab Displaying @code{__thread} variables
14311 @item @code{search-memory}
14312 @tab @code{qSearch:memory}
14315 @item @code{supported-packets}
14316 @tab @code{qSupported}
14317 @tab Remote communications parameters
14319 @item @code{pass-signals}
14320 @tab @code{QPassSignals}
14321 @tab @code{handle @var{signal}}
14323 @item @code{hostio-close-packet}
14324 @tab @code{vFile:close}
14325 @tab @code{remote get}, @code{remote put}
14327 @item @code{hostio-open-packet}
14328 @tab @code{vFile:open}
14329 @tab @code{remote get}, @code{remote put}
14331 @item @code{hostio-pread-packet}
14332 @tab @code{vFile:pread}
14333 @tab @code{remote get}, @code{remote put}
14335 @item @code{hostio-pwrite-packet}
14336 @tab @code{vFile:pwrite}
14337 @tab @code{remote get}, @code{remote put}
14339 @item @code{hostio-unlink-packet}
14340 @tab @code{vFile:unlink}
14341 @tab @code{remote delete}
14343 @item @code{noack-packet}
14344 @tab @code{QStartNoAckMode}
14345 @tab Packet acknowledgment
14347 @item @code{osdata}
14348 @tab @code{qXfer:osdata:read}
14349 @tab @code{info os}
14353 @section Implementing a Remote Stub
14355 @cindex debugging stub, example
14356 @cindex remote stub, example
14357 @cindex stub example, remote debugging
14358 The stub files provided with @value{GDBN} implement the target side of the
14359 communication protocol, and the @value{GDBN} side is implemented in the
14360 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14361 these subroutines to communicate, and ignore the details. (If you're
14362 implementing your own stub file, you can still ignore the details: start
14363 with one of the existing stub files. @file{sparc-stub.c} is the best
14364 organized, and therefore the easiest to read.)
14366 @cindex remote serial debugging, overview
14367 To debug a program running on another machine (the debugging
14368 @dfn{target} machine), you must first arrange for all the usual
14369 prerequisites for the program to run by itself. For example, for a C
14374 A startup routine to set up the C runtime environment; these usually
14375 have a name like @file{crt0}. The startup routine may be supplied by
14376 your hardware supplier, or you may have to write your own.
14379 A C subroutine library to support your program's
14380 subroutine calls, notably managing input and output.
14383 A way of getting your program to the other machine---for example, a
14384 download program. These are often supplied by the hardware
14385 manufacturer, but you may have to write your own from hardware
14389 The next step is to arrange for your program to use a serial port to
14390 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14391 machine). In general terms, the scheme looks like this:
14395 @value{GDBN} already understands how to use this protocol; when everything
14396 else is set up, you can simply use the @samp{target remote} command
14397 (@pxref{Targets,,Specifying a Debugging Target}).
14399 @item On the target,
14400 you must link with your program a few special-purpose subroutines that
14401 implement the @value{GDBN} remote serial protocol. The file containing these
14402 subroutines is called a @dfn{debugging stub}.
14404 On certain remote targets, you can use an auxiliary program
14405 @code{gdbserver} instead of linking a stub into your program.
14406 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14409 The debugging stub is specific to the architecture of the remote
14410 machine; for example, use @file{sparc-stub.c} to debug programs on
14413 @cindex remote serial stub list
14414 These working remote stubs are distributed with @value{GDBN}:
14419 @cindex @file{i386-stub.c}
14422 For Intel 386 and compatible architectures.
14425 @cindex @file{m68k-stub.c}
14426 @cindex Motorola 680x0
14428 For Motorola 680x0 architectures.
14431 @cindex @file{sh-stub.c}
14434 For Renesas SH architectures.
14437 @cindex @file{sparc-stub.c}
14439 For @sc{sparc} architectures.
14441 @item sparcl-stub.c
14442 @cindex @file{sparcl-stub.c}
14445 For Fujitsu @sc{sparclite} architectures.
14449 The @file{README} file in the @value{GDBN} distribution may list other
14450 recently added stubs.
14453 * Stub Contents:: What the stub can do for you
14454 * Bootstrapping:: What you must do for the stub
14455 * Debug Session:: Putting it all together
14458 @node Stub Contents
14459 @subsection What the Stub Can Do for You
14461 @cindex remote serial stub
14462 The debugging stub for your architecture supplies these three
14466 @item set_debug_traps
14467 @findex set_debug_traps
14468 @cindex remote serial stub, initialization
14469 This routine arranges for @code{handle_exception} to run when your
14470 program stops. You must call this subroutine explicitly near the
14471 beginning of your program.
14473 @item handle_exception
14474 @findex handle_exception
14475 @cindex remote serial stub, main routine
14476 This is the central workhorse, but your program never calls it
14477 explicitly---the setup code arranges for @code{handle_exception} to
14478 run when a trap is triggered.
14480 @code{handle_exception} takes control when your program stops during
14481 execution (for example, on a breakpoint), and mediates communications
14482 with @value{GDBN} on the host machine. This is where the communications
14483 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14484 representative on the target machine. It begins by sending summary
14485 information on the state of your program, then continues to execute,
14486 retrieving and transmitting any information @value{GDBN} needs, until you
14487 execute a @value{GDBN} command that makes your program resume; at that point,
14488 @code{handle_exception} returns control to your own code on the target
14492 @cindex @code{breakpoint} subroutine, remote
14493 Use this auxiliary subroutine to make your program contain a
14494 breakpoint. Depending on the particular situation, this may be the only
14495 way for @value{GDBN} to get control. For instance, if your target
14496 machine has some sort of interrupt button, you won't need to call this;
14497 pressing the interrupt button transfers control to
14498 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14499 simply receiving characters on the serial port may also trigger a trap;
14500 again, in that situation, you don't need to call @code{breakpoint} from
14501 your own program---simply running @samp{target remote} from the host
14502 @value{GDBN} session gets control.
14504 Call @code{breakpoint} if none of these is true, or if you simply want
14505 to make certain your program stops at a predetermined point for the
14506 start of your debugging session.
14509 @node Bootstrapping
14510 @subsection What You Must Do for the Stub
14512 @cindex remote stub, support routines
14513 The debugging stubs that come with @value{GDBN} are set up for a particular
14514 chip architecture, but they have no information about the rest of your
14515 debugging target machine.
14517 First of all you need to tell the stub how to communicate with the
14521 @item int getDebugChar()
14522 @findex getDebugChar
14523 Write this subroutine to read a single character from the serial port.
14524 It may be identical to @code{getchar} for your target system; a
14525 different name is used to allow you to distinguish the two if you wish.
14527 @item void putDebugChar(int)
14528 @findex putDebugChar
14529 Write this subroutine to write a single character to the serial port.
14530 It may be identical to @code{putchar} for your target system; a
14531 different name is used to allow you to distinguish the two if you wish.
14534 @cindex control C, and remote debugging
14535 @cindex interrupting remote targets
14536 If you want @value{GDBN} to be able to stop your program while it is
14537 running, you need to use an interrupt-driven serial driver, and arrange
14538 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14539 character). That is the character which @value{GDBN} uses to tell the
14540 remote system to stop.
14542 Getting the debugging target to return the proper status to @value{GDBN}
14543 probably requires changes to the standard stub; one quick and dirty way
14544 is to just execute a breakpoint instruction (the ``dirty'' part is that
14545 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14547 Other routines you need to supply are:
14550 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14551 @findex exceptionHandler
14552 Write this function to install @var{exception_address} in the exception
14553 handling tables. You need to do this because the stub does not have any
14554 way of knowing what the exception handling tables on your target system
14555 are like (for example, the processor's table might be in @sc{rom},
14556 containing entries which point to a table in @sc{ram}).
14557 @var{exception_number} is the exception number which should be changed;
14558 its meaning is architecture-dependent (for example, different numbers
14559 might represent divide by zero, misaligned access, etc). When this
14560 exception occurs, control should be transferred directly to
14561 @var{exception_address}, and the processor state (stack, registers,
14562 and so on) should be just as it is when a processor exception occurs. So if
14563 you want to use a jump instruction to reach @var{exception_address}, it
14564 should be a simple jump, not a jump to subroutine.
14566 For the 386, @var{exception_address} should be installed as an interrupt
14567 gate so that interrupts are masked while the handler runs. The gate
14568 should be at privilege level 0 (the most privileged level). The
14569 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14570 help from @code{exceptionHandler}.
14572 @item void flush_i_cache()
14573 @findex flush_i_cache
14574 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14575 instruction cache, if any, on your target machine. If there is no
14576 instruction cache, this subroutine may be a no-op.
14578 On target machines that have instruction caches, @value{GDBN} requires this
14579 function to make certain that the state of your program is stable.
14583 You must also make sure this library routine is available:
14586 @item void *memset(void *, int, int)
14588 This is the standard library function @code{memset} that sets an area of
14589 memory to a known value. If you have one of the free versions of
14590 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14591 either obtain it from your hardware manufacturer, or write your own.
14594 If you do not use the GNU C compiler, you may need other standard
14595 library subroutines as well; this varies from one stub to another,
14596 but in general the stubs are likely to use any of the common library
14597 subroutines which @code{@value{NGCC}} generates as inline code.
14600 @node Debug Session
14601 @subsection Putting it All Together
14603 @cindex remote serial debugging summary
14604 In summary, when your program is ready to debug, you must follow these
14609 Make sure you have defined the supporting low-level routines
14610 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14612 @code{getDebugChar}, @code{putDebugChar},
14613 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14617 Insert these lines near the top of your program:
14625 For the 680x0 stub only, you need to provide a variable called
14626 @code{exceptionHook}. Normally you just use:
14629 void (*exceptionHook)() = 0;
14633 but if before calling @code{set_debug_traps}, you set it to point to a
14634 function in your program, that function is called when
14635 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14636 error). The function indicated by @code{exceptionHook} is called with
14637 one parameter: an @code{int} which is the exception number.
14640 Compile and link together: your program, the @value{GDBN} debugging stub for
14641 your target architecture, and the supporting subroutines.
14644 Make sure you have a serial connection between your target machine and
14645 the @value{GDBN} host, and identify the serial port on the host.
14648 @c The "remote" target now provides a `load' command, so we should
14649 @c document that. FIXME.
14650 Download your program to your target machine (or get it there by
14651 whatever means the manufacturer provides), and start it.
14654 Start @value{GDBN} on the host, and connect to the target
14655 (@pxref{Connecting,,Connecting to a Remote Target}).
14659 @node Configurations
14660 @chapter Configuration-Specific Information
14662 While nearly all @value{GDBN} commands are available for all native and
14663 cross versions of the debugger, there are some exceptions. This chapter
14664 describes things that are only available in certain configurations.
14666 There are three major categories of configurations: native
14667 configurations, where the host and target are the same, embedded
14668 operating system configurations, which are usually the same for several
14669 different processor architectures, and bare embedded processors, which
14670 are quite different from each other.
14675 * Embedded Processors::
14682 This section describes details specific to particular native
14687 * BSD libkvm Interface:: Debugging BSD kernel memory images
14688 * SVR4 Process Information:: SVR4 process information
14689 * DJGPP Native:: Features specific to the DJGPP port
14690 * Cygwin Native:: Features specific to the Cygwin port
14691 * Hurd Native:: Features specific to @sc{gnu} Hurd
14692 * Neutrino:: Features specific to QNX Neutrino
14693 * Darwin:: Features specific to Darwin
14699 On HP-UX systems, if you refer to a function or variable name that
14700 begins with a dollar sign, @value{GDBN} searches for a user or system
14701 name first, before it searches for a convenience variable.
14704 @node BSD libkvm Interface
14705 @subsection BSD libkvm Interface
14708 @cindex kernel memory image
14709 @cindex kernel crash dump
14711 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14712 interface that provides a uniform interface for accessing kernel virtual
14713 memory images, including live systems and crash dumps. @value{GDBN}
14714 uses this interface to allow you to debug live kernels and kernel crash
14715 dumps on many native BSD configurations. This is implemented as a
14716 special @code{kvm} debugging target. For debugging a live system, load
14717 the currently running kernel into @value{GDBN} and connect to the
14721 (@value{GDBP}) @b{target kvm}
14724 For debugging crash dumps, provide the file name of the crash dump as an
14728 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14731 Once connected to the @code{kvm} target, the following commands are
14737 Set current context from the @dfn{Process Control Block} (PCB) address.
14740 Set current context from proc address. This command isn't available on
14741 modern FreeBSD systems.
14744 @node SVR4 Process Information
14745 @subsection SVR4 Process Information
14747 @cindex examine process image
14748 @cindex process info via @file{/proc}
14750 Many versions of SVR4 and compatible systems provide a facility called
14751 @samp{/proc} that can be used to examine the image of a running
14752 process using file-system subroutines. If @value{GDBN} is configured
14753 for an operating system with this facility, the command @code{info
14754 proc} is available to report information about the process running
14755 your program, or about any process running on your system. @code{info
14756 proc} works only on SVR4 systems that include the @code{procfs} code.
14757 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14758 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14764 @itemx info proc @var{process-id}
14765 Summarize available information about any running process. If a
14766 process ID is specified by @var{process-id}, display information about
14767 that process; otherwise display information about the program being
14768 debugged. The summary includes the debugged process ID, the command
14769 line used to invoke it, its current working directory, and its
14770 executable file's absolute file name.
14772 On some systems, @var{process-id} can be of the form
14773 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14774 within a process. If the optional @var{pid} part is missing, it means
14775 a thread from the process being debugged (the leading @samp{/} still
14776 needs to be present, or else @value{GDBN} will interpret the number as
14777 a process ID rather than a thread ID).
14779 @item info proc mappings
14780 @cindex memory address space mappings
14781 Report the memory address space ranges accessible in the program, with
14782 information on whether the process has read, write, or execute access
14783 rights to each range. On @sc{gnu}/Linux systems, each memory range
14784 includes the object file which is mapped to that range, instead of the
14785 memory access rights to that range.
14787 @item info proc stat
14788 @itemx info proc status
14789 @cindex process detailed status information
14790 These subcommands are specific to @sc{gnu}/Linux systems. They show
14791 the process-related information, including the user ID and group ID;
14792 how many threads are there in the process; its virtual memory usage;
14793 the signals that are pending, blocked, and ignored; its TTY; its
14794 consumption of system and user time; its stack size; its @samp{nice}
14795 value; etc. For more information, see the @samp{proc} man page
14796 (type @kbd{man 5 proc} from your shell prompt).
14798 @item info proc all
14799 Show all the information about the process described under all of the
14800 above @code{info proc} subcommands.
14803 @comment These sub-options of 'info proc' were not included when
14804 @comment procfs.c was re-written. Keep their descriptions around
14805 @comment against the day when someone finds the time to put them back in.
14806 @kindex info proc times
14807 @item info proc times
14808 Starting time, user CPU time, and system CPU time for your program and
14811 @kindex info proc id
14813 Report on the process IDs related to your program: its own process ID,
14814 the ID of its parent, the process group ID, and the session ID.
14817 @item set procfs-trace
14818 @kindex set procfs-trace
14819 @cindex @code{procfs} API calls
14820 This command enables and disables tracing of @code{procfs} API calls.
14822 @item show procfs-trace
14823 @kindex show procfs-trace
14824 Show the current state of @code{procfs} API call tracing.
14826 @item set procfs-file @var{file}
14827 @kindex set procfs-file
14828 Tell @value{GDBN} to write @code{procfs} API trace to the named
14829 @var{file}. @value{GDBN} appends the trace info to the previous
14830 contents of the file. The default is to display the trace on the
14833 @item show procfs-file
14834 @kindex show procfs-file
14835 Show the file to which @code{procfs} API trace is written.
14837 @item proc-trace-entry
14838 @itemx proc-trace-exit
14839 @itemx proc-untrace-entry
14840 @itemx proc-untrace-exit
14841 @kindex proc-trace-entry
14842 @kindex proc-trace-exit
14843 @kindex proc-untrace-entry
14844 @kindex proc-untrace-exit
14845 These commands enable and disable tracing of entries into and exits
14846 from the @code{syscall} interface.
14849 @kindex info pidlist
14850 @cindex process list, QNX Neutrino
14851 For QNX Neutrino only, this command displays the list of all the
14852 processes and all the threads within each process.
14855 @kindex info meminfo
14856 @cindex mapinfo list, QNX Neutrino
14857 For QNX Neutrino only, this command displays the list of all mapinfos.
14861 @subsection Features for Debugging @sc{djgpp} Programs
14862 @cindex @sc{djgpp} debugging
14863 @cindex native @sc{djgpp} debugging
14864 @cindex MS-DOS-specific commands
14867 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
14868 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
14869 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
14870 top of real-mode DOS systems and their emulations.
14872 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
14873 defines a few commands specific to the @sc{djgpp} port. This
14874 subsection describes those commands.
14879 This is a prefix of @sc{djgpp}-specific commands which print
14880 information about the target system and important OS structures.
14883 @cindex MS-DOS system info
14884 @cindex free memory information (MS-DOS)
14885 @item info dos sysinfo
14886 This command displays assorted information about the underlying
14887 platform: the CPU type and features, the OS version and flavor, the
14888 DPMI version, and the available conventional and DPMI memory.
14893 @cindex segment descriptor tables
14894 @cindex descriptor tables display
14896 @itemx info dos ldt
14897 @itemx info dos idt
14898 These 3 commands display entries from, respectively, Global, Local,
14899 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
14900 tables are data structures which store a descriptor for each segment
14901 that is currently in use. The segment's selector is an index into a
14902 descriptor table; the table entry for that index holds the
14903 descriptor's base address and limit, and its attributes and access
14906 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
14907 segment (used for both data and the stack), and a DOS segment (which
14908 allows access to DOS/BIOS data structures and absolute addresses in
14909 conventional memory). However, the DPMI host will usually define
14910 additional segments in order to support the DPMI environment.
14912 @cindex garbled pointers
14913 These commands allow to display entries from the descriptor tables.
14914 Without an argument, all entries from the specified table are
14915 displayed. An argument, which should be an integer expression, means
14916 display a single entry whose index is given by the argument. For
14917 example, here's a convenient way to display information about the
14918 debugged program's data segment:
14921 @exdent @code{(@value{GDBP}) info dos ldt $ds}
14922 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
14926 This comes in handy when you want to see whether a pointer is outside
14927 the data segment's limit (i.e.@: @dfn{garbled}).
14929 @cindex page tables display (MS-DOS)
14931 @itemx info dos pte
14932 These two commands display entries from, respectively, the Page
14933 Directory and the Page Tables. Page Directories and Page Tables are
14934 data structures which control how virtual memory addresses are mapped
14935 into physical addresses. A Page Table includes an entry for every
14936 page of memory that is mapped into the program's address space; there
14937 may be several Page Tables, each one holding up to 4096 entries. A
14938 Page Directory has up to 4096 entries, one each for every Page Table
14939 that is currently in use.
14941 Without an argument, @kbd{info dos pde} displays the entire Page
14942 Directory, and @kbd{info dos pte} displays all the entries in all of
14943 the Page Tables. An argument, an integer expression, given to the
14944 @kbd{info dos pde} command means display only that entry from the Page
14945 Directory table. An argument given to the @kbd{info dos pte} command
14946 means display entries from a single Page Table, the one pointed to by
14947 the specified entry in the Page Directory.
14949 @cindex direct memory access (DMA) on MS-DOS
14950 These commands are useful when your program uses @dfn{DMA} (Direct
14951 Memory Access), which needs physical addresses to program the DMA
14954 These commands are supported only with some DPMI servers.
14956 @cindex physical address from linear address
14957 @item info dos address-pte @var{addr}
14958 This command displays the Page Table entry for a specified linear
14959 address. The argument @var{addr} is a linear address which should
14960 already have the appropriate segment's base address added to it,
14961 because this command accepts addresses which may belong to @emph{any}
14962 segment. For example, here's how to display the Page Table entry for
14963 the page where a variable @code{i} is stored:
14966 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
14967 @exdent @code{Page Table entry for address 0x11a00d30:}
14968 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
14972 This says that @code{i} is stored at offset @code{0xd30} from the page
14973 whose physical base address is @code{0x02698000}, and shows all the
14974 attributes of that page.
14976 Note that you must cast the addresses of variables to a @code{char *},
14977 since otherwise the value of @code{__djgpp_base_address}, the base
14978 address of all variables and functions in a @sc{djgpp} program, will
14979 be added using the rules of C pointer arithmetics: if @code{i} is
14980 declared an @code{int}, @value{GDBN} will add 4 times the value of
14981 @code{__djgpp_base_address} to the address of @code{i}.
14983 Here's another example, it displays the Page Table entry for the
14987 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
14988 @exdent @code{Page Table entry for address 0x29110:}
14989 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
14993 (The @code{+ 3} offset is because the transfer buffer's address is the
14994 3rd member of the @code{_go32_info_block} structure.) The output
14995 clearly shows that this DPMI server maps the addresses in conventional
14996 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
14997 linear (@code{0x29110}) addresses are identical.
14999 This command is supported only with some DPMI servers.
15002 @cindex DOS serial data link, remote debugging
15003 In addition to native debugging, the DJGPP port supports remote
15004 debugging via a serial data link. The following commands are specific
15005 to remote serial debugging in the DJGPP port of @value{GDBN}.
15008 @kindex set com1base
15009 @kindex set com1irq
15010 @kindex set com2base
15011 @kindex set com2irq
15012 @kindex set com3base
15013 @kindex set com3irq
15014 @kindex set com4base
15015 @kindex set com4irq
15016 @item set com1base @var{addr}
15017 This command sets the base I/O port address of the @file{COM1} serial
15020 @item set com1irq @var{irq}
15021 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15022 for the @file{COM1} serial port.
15024 There are similar commands @samp{set com2base}, @samp{set com3irq},
15025 etc.@: for setting the port address and the @code{IRQ} lines for the
15028 @kindex show com1base
15029 @kindex show com1irq
15030 @kindex show com2base
15031 @kindex show com2irq
15032 @kindex show com3base
15033 @kindex show com3irq
15034 @kindex show com4base
15035 @kindex show com4irq
15036 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15037 display the current settings of the base address and the @code{IRQ}
15038 lines used by the COM ports.
15041 @kindex info serial
15042 @cindex DOS serial port status
15043 This command prints the status of the 4 DOS serial ports. For each
15044 port, it prints whether it's active or not, its I/O base address and
15045 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15046 counts of various errors encountered so far.
15050 @node Cygwin Native
15051 @subsection Features for Debugging MS Windows PE Executables
15052 @cindex MS Windows debugging
15053 @cindex native Cygwin debugging
15054 @cindex Cygwin-specific commands
15056 @value{GDBN} supports native debugging of MS Windows programs, including
15057 DLLs with and without symbolic debugging information. There are various
15058 additional Cygwin-specific commands, described in this section.
15059 Working with DLLs that have no debugging symbols is described in
15060 @ref{Non-debug DLL Symbols}.
15065 This is a prefix of MS Windows-specific commands which print
15066 information about the target system and important OS structures.
15068 @item info w32 selector
15069 This command displays information returned by
15070 the Win32 API @code{GetThreadSelectorEntry} function.
15071 It takes an optional argument that is evaluated to
15072 a long value to give the information about this given selector.
15073 Without argument, this command displays information
15074 about the six segment registers.
15078 This is a Cygwin-specific alias of @code{info shared}.
15080 @kindex dll-symbols
15082 This command loads symbols from a dll similarly to
15083 add-sym command but without the need to specify a base address.
15085 @kindex set cygwin-exceptions
15086 @cindex debugging the Cygwin DLL
15087 @cindex Cygwin DLL, debugging
15088 @item set cygwin-exceptions @var{mode}
15089 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15090 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15091 @value{GDBN} will delay recognition of exceptions, and may ignore some
15092 exceptions which seem to be caused by internal Cygwin DLL
15093 ``bookkeeping''. This option is meant primarily for debugging the
15094 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15095 @value{GDBN} users with false @code{SIGSEGV} signals.
15097 @kindex show cygwin-exceptions
15098 @item show cygwin-exceptions
15099 Displays whether @value{GDBN} will break on exceptions that happen
15100 inside the Cygwin DLL itself.
15102 @kindex set new-console
15103 @item set new-console @var{mode}
15104 If @var{mode} is @code{on} the debuggee will
15105 be started in a new console on next start.
15106 If @var{mode} is @code{off}i, the debuggee will
15107 be started in the same console as the debugger.
15109 @kindex show new-console
15110 @item show new-console
15111 Displays whether a new console is used
15112 when the debuggee is started.
15114 @kindex set new-group
15115 @item set new-group @var{mode}
15116 This boolean value controls whether the debuggee should
15117 start a new group or stay in the same group as the debugger.
15118 This affects the way the Windows OS handles
15121 @kindex show new-group
15122 @item show new-group
15123 Displays current value of new-group boolean.
15125 @kindex set debugevents
15126 @item set debugevents
15127 This boolean value adds debug output concerning kernel events related
15128 to the debuggee seen by the debugger. This includes events that
15129 signal thread and process creation and exit, DLL loading and
15130 unloading, console interrupts, and debugging messages produced by the
15131 Windows @code{OutputDebugString} API call.
15133 @kindex set debugexec
15134 @item set debugexec
15135 This boolean value adds debug output concerning execute events
15136 (such as resume thread) seen by the debugger.
15138 @kindex set debugexceptions
15139 @item set debugexceptions
15140 This boolean value adds debug output concerning exceptions in the
15141 debuggee seen by the debugger.
15143 @kindex set debugmemory
15144 @item set debugmemory
15145 This boolean value adds debug output concerning debuggee memory reads
15146 and writes by the debugger.
15150 This boolean values specifies whether the debuggee is called
15151 via a shell or directly (default value is on).
15155 Displays if the debuggee will be started with a shell.
15160 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15163 @node Non-debug DLL Symbols
15164 @subsubsection Support for DLLs without Debugging Symbols
15165 @cindex DLLs with no debugging symbols
15166 @cindex Minimal symbols and DLLs
15168 Very often on windows, some of the DLLs that your program relies on do
15169 not include symbolic debugging information (for example,
15170 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15171 symbols in a DLL, it relies on the minimal amount of symbolic
15172 information contained in the DLL's export table. This section
15173 describes working with such symbols, known internally to @value{GDBN} as
15174 ``minimal symbols''.
15176 Note that before the debugged program has started execution, no DLLs
15177 will have been loaded. The easiest way around this problem is simply to
15178 start the program --- either by setting a breakpoint or letting the
15179 program run once to completion. It is also possible to force
15180 @value{GDBN} to load a particular DLL before starting the executable ---
15181 see the shared library information in @ref{Files}, or the
15182 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15183 explicitly loading symbols from a DLL with no debugging information will
15184 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15185 which may adversely affect symbol lookup performance.
15187 @subsubsection DLL Name Prefixes
15189 In keeping with the naming conventions used by the Microsoft debugging
15190 tools, DLL export symbols are made available with a prefix based on the
15191 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15192 also entered into the symbol table, so @code{CreateFileA} is often
15193 sufficient. In some cases there will be name clashes within a program
15194 (particularly if the executable itself includes full debugging symbols)
15195 necessitating the use of the fully qualified name when referring to the
15196 contents of the DLL. Use single-quotes around the name to avoid the
15197 exclamation mark (``!'') being interpreted as a language operator.
15199 Note that the internal name of the DLL may be all upper-case, even
15200 though the file name of the DLL is lower-case, or vice-versa. Since
15201 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15202 some confusion. If in doubt, try the @code{info functions} and
15203 @code{info variables} commands or even @code{maint print msymbols}
15204 (@pxref{Symbols}). Here's an example:
15207 (@value{GDBP}) info function CreateFileA
15208 All functions matching regular expression "CreateFileA":
15210 Non-debugging symbols:
15211 0x77e885f4 CreateFileA
15212 0x77e885f4 KERNEL32!CreateFileA
15216 (@value{GDBP}) info function !
15217 All functions matching regular expression "!":
15219 Non-debugging symbols:
15220 0x6100114c cygwin1!__assert
15221 0x61004034 cygwin1!_dll_crt0@@0
15222 0x61004240 cygwin1!dll_crt0(per_process *)
15226 @subsubsection Working with Minimal Symbols
15228 Symbols extracted from a DLL's export table do not contain very much
15229 type information. All that @value{GDBN} can do is guess whether a symbol
15230 refers to a function or variable depending on the linker section that
15231 contains the symbol. Also note that the actual contents of the memory
15232 contained in a DLL are not available unless the program is running. This
15233 means that you cannot examine the contents of a variable or disassemble
15234 a function within a DLL without a running program.
15236 Variables are generally treated as pointers and dereferenced
15237 automatically. For this reason, it is often necessary to prefix a
15238 variable name with the address-of operator (``&'') and provide explicit
15239 type information in the command. Here's an example of the type of
15243 (@value{GDBP}) print 'cygwin1!__argv'
15248 (@value{GDBP}) x 'cygwin1!__argv'
15249 0x10021610: "\230y\""
15252 And two possible solutions:
15255 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15256 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15260 (@value{GDBP}) x/2x &'cygwin1!__argv'
15261 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15262 (@value{GDBP}) x/x 0x10021608
15263 0x10021608: 0x0022fd98
15264 (@value{GDBP}) x/s 0x0022fd98
15265 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15268 Setting a break point within a DLL is possible even before the program
15269 starts execution. However, under these circumstances, @value{GDBN} can't
15270 examine the initial instructions of the function in order to skip the
15271 function's frame set-up code. You can work around this by using ``*&''
15272 to set the breakpoint at a raw memory address:
15275 (@value{GDBP}) break *&'python22!PyOS_Readline'
15276 Breakpoint 1 at 0x1e04eff0
15279 The author of these extensions is not entirely convinced that setting a
15280 break point within a shared DLL like @file{kernel32.dll} is completely
15284 @subsection Commands Specific to @sc{gnu} Hurd Systems
15285 @cindex @sc{gnu} Hurd debugging
15287 This subsection describes @value{GDBN} commands specific to the
15288 @sc{gnu} Hurd native debugging.
15293 @kindex set signals@r{, Hurd command}
15294 @kindex set sigs@r{, Hurd command}
15295 This command toggles the state of inferior signal interception by
15296 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15297 affected by this command. @code{sigs} is a shorthand alias for
15302 @kindex show signals@r{, Hurd command}
15303 @kindex show sigs@r{, Hurd command}
15304 Show the current state of intercepting inferior's signals.
15306 @item set signal-thread
15307 @itemx set sigthread
15308 @kindex set signal-thread
15309 @kindex set sigthread
15310 This command tells @value{GDBN} which thread is the @code{libc} signal
15311 thread. That thread is run when a signal is delivered to a running
15312 process. @code{set sigthread} is the shorthand alias of @code{set
15315 @item show signal-thread
15316 @itemx show sigthread
15317 @kindex show signal-thread
15318 @kindex show sigthread
15319 These two commands show which thread will run when the inferior is
15320 delivered a signal.
15323 @kindex set stopped@r{, Hurd command}
15324 This commands tells @value{GDBN} that the inferior process is stopped,
15325 as with the @code{SIGSTOP} signal. The stopped process can be
15326 continued by delivering a signal to it.
15329 @kindex show stopped@r{, Hurd command}
15330 This command shows whether @value{GDBN} thinks the debuggee is
15333 @item set exceptions
15334 @kindex set exceptions@r{, Hurd command}
15335 Use this command to turn off trapping of exceptions in the inferior.
15336 When exception trapping is off, neither breakpoints nor
15337 single-stepping will work. To restore the default, set exception
15340 @item show exceptions
15341 @kindex show exceptions@r{, Hurd command}
15342 Show the current state of trapping exceptions in the inferior.
15344 @item set task pause
15345 @kindex set task@r{, Hurd commands}
15346 @cindex task attributes (@sc{gnu} Hurd)
15347 @cindex pause current task (@sc{gnu} Hurd)
15348 This command toggles task suspension when @value{GDBN} has control.
15349 Setting it to on takes effect immediately, and the task is suspended
15350 whenever @value{GDBN} gets control. Setting it to off will take
15351 effect the next time the inferior is continued. If this option is set
15352 to off, you can use @code{set thread default pause on} or @code{set
15353 thread pause on} (see below) to pause individual threads.
15355 @item show task pause
15356 @kindex show task@r{, Hurd commands}
15357 Show the current state of task suspension.
15359 @item set task detach-suspend-count
15360 @cindex task suspend count
15361 @cindex detach from task, @sc{gnu} Hurd
15362 This command sets the suspend count the task will be left with when
15363 @value{GDBN} detaches from it.
15365 @item show task detach-suspend-count
15366 Show the suspend count the task will be left with when detaching.
15368 @item set task exception-port
15369 @itemx set task excp
15370 @cindex task exception port, @sc{gnu} Hurd
15371 This command sets the task exception port to which @value{GDBN} will
15372 forward exceptions. The argument should be the value of the @dfn{send
15373 rights} of the task. @code{set task excp} is a shorthand alias.
15375 @item set noninvasive
15376 @cindex noninvasive task options
15377 This command switches @value{GDBN} to a mode that is the least
15378 invasive as far as interfering with the inferior is concerned. This
15379 is the same as using @code{set task pause}, @code{set exceptions}, and
15380 @code{set signals} to values opposite to the defaults.
15382 @item info send-rights
15383 @itemx info receive-rights
15384 @itemx info port-rights
15385 @itemx info port-sets
15386 @itemx info dead-names
15389 @cindex send rights, @sc{gnu} Hurd
15390 @cindex receive rights, @sc{gnu} Hurd
15391 @cindex port rights, @sc{gnu} Hurd
15392 @cindex port sets, @sc{gnu} Hurd
15393 @cindex dead names, @sc{gnu} Hurd
15394 These commands display information about, respectively, send rights,
15395 receive rights, port rights, port sets, and dead names of a task.
15396 There are also shorthand aliases: @code{info ports} for @code{info
15397 port-rights} and @code{info psets} for @code{info port-sets}.
15399 @item set thread pause
15400 @kindex set thread@r{, Hurd command}
15401 @cindex thread properties, @sc{gnu} Hurd
15402 @cindex pause current thread (@sc{gnu} Hurd)
15403 This command toggles current thread suspension when @value{GDBN} has
15404 control. Setting it to on takes effect immediately, and the current
15405 thread is suspended whenever @value{GDBN} gets control. Setting it to
15406 off will take effect the next time the inferior is continued.
15407 Normally, this command has no effect, since when @value{GDBN} has
15408 control, the whole task is suspended. However, if you used @code{set
15409 task pause off} (see above), this command comes in handy to suspend
15410 only the current thread.
15412 @item show thread pause
15413 @kindex show thread@r{, Hurd command}
15414 This command shows the state of current thread suspension.
15416 @item set thread run
15417 This command sets whether the current thread is allowed to run.
15419 @item show thread run
15420 Show whether the current thread is allowed to run.
15422 @item set thread detach-suspend-count
15423 @cindex thread suspend count, @sc{gnu} Hurd
15424 @cindex detach from thread, @sc{gnu} Hurd
15425 This command sets the suspend count @value{GDBN} will leave on a
15426 thread when detaching. This number is relative to the suspend count
15427 found by @value{GDBN} when it notices the thread; use @code{set thread
15428 takeover-suspend-count} to force it to an absolute value.
15430 @item show thread detach-suspend-count
15431 Show the suspend count @value{GDBN} will leave on the thread when
15434 @item set thread exception-port
15435 @itemx set thread excp
15436 Set the thread exception port to which to forward exceptions. This
15437 overrides the port set by @code{set task exception-port} (see above).
15438 @code{set thread excp} is the shorthand alias.
15440 @item set thread takeover-suspend-count
15441 Normally, @value{GDBN}'s thread suspend counts are relative to the
15442 value @value{GDBN} finds when it notices each thread. This command
15443 changes the suspend counts to be absolute instead.
15445 @item set thread default
15446 @itemx show thread default
15447 @cindex thread default settings, @sc{gnu} Hurd
15448 Each of the above @code{set thread} commands has a @code{set thread
15449 default} counterpart (e.g., @code{set thread default pause}, @code{set
15450 thread default exception-port}, etc.). The @code{thread default}
15451 variety of commands sets the default thread properties for all
15452 threads; you can then change the properties of individual threads with
15453 the non-default commands.
15458 @subsection QNX Neutrino
15459 @cindex QNX Neutrino
15461 @value{GDBN} provides the following commands specific to the QNX
15465 @item set debug nto-debug
15466 @kindex set debug nto-debug
15467 When set to on, enables debugging messages specific to the QNX
15470 @item show debug nto-debug
15471 @kindex show debug nto-debug
15472 Show the current state of QNX Neutrino messages.
15479 @value{GDBN} provides the following commands specific to the Darwin target:
15482 @item set debug darwin @var{num}
15483 @kindex set debug darwin
15484 When set to a non zero value, enables debugging messages specific to
15485 the Darwin support. Higher values produce more verbose output.
15487 @item show debug darwin
15488 @kindex show debug darwin
15489 Show the current state of Darwin messages.
15491 @item set debug mach-o @var{num}
15492 @kindex set debug mach-o
15493 When set to a non zero value, enables debugging messages while
15494 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15495 file format used on Darwin for object and executable files.) Higher
15496 values produce more verbose output. This is a command to diagnose
15497 problems internal to @value{GDBN} and should not be needed in normal
15500 @item show debug mach-o
15501 @kindex show debug mach-o
15502 Show the current state of Mach-O file messages.
15504 @item set mach-exceptions on
15505 @itemx set mach-exceptions off
15506 @kindex set mach-exceptions
15507 On Darwin, faults are first reported as a Mach exception and are then
15508 mapped to a Posix signal. Use this command to turn on trapping of
15509 Mach exceptions in the inferior. This might be sometimes useful to
15510 better understand the cause of a fault. The default is off.
15512 @item show mach-exceptions
15513 @kindex show mach-exceptions
15514 Show the current state of exceptions trapping.
15519 @section Embedded Operating Systems
15521 This section describes configurations involving the debugging of
15522 embedded operating systems that are available for several different
15526 * VxWorks:: Using @value{GDBN} with VxWorks
15529 @value{GDBN} includes the ability to debug programs running on
15530 various real-time operating systems.
15533 @subsection Using @value{GDBN} with VxWorks
15539 @kindex target vxworks
15540 @item target vxworks @var{machinename}
15541 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15542 is the target system's machine name or IP address.
15546 On VxWorks, @code{load} links @var{filename} dynamically on the
15547 current target system as well as adding its symbols in @value{GDBN}.
15549 @value{GDBN} enables developers to spawn and debug tasks running on networked
15550 VxWorks targets from a Unix host. Already-running tasks spawned from
15551 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15552 both the Unix host and on the VxWorks target. The program
15553 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15554 installed with the name @code{vxgdb}, to distinguish it from a
15555 @value{GDBN} for debugging programs on the host itself.)
15558 @item VxWorks-timeout @var{args}
15559 @kindex vxworks-timeout
15560 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15561 This option is set by the user, and @var{args} represents the number of
15562 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15563 your VxWorks target is a slow software simulator or is on the far side
15564 of a thin network line.
15567 The following information on connecting to VxWorks was current when
15568 this manual was produced; newer releases of VxWorks may use revised
15571 @findex INCLUDE_RDB
15572 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15573 to include the remote debugging interface routines in the VxWorks
15574 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15575 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15576 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15577 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15578 information on configuring and remaking VxWorks, see the manufacturer's
15580 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15582 Once you have included @file{rdb.a} in your VxWorks system image and set
15583 your Unix execution search path to find @value{GDBN}, you are ready to
15584 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15585 @code{vxgdb}, depending on your installation).
15587 @value{GDBN} comes up showing the prompt:
15594 * VxWorks Connection:: Connecting to VxWorks
15595 * VxWorks Download:: VxWorks download
15596 * VxWorks Attach:: Running tasks
15599 @node VxWorks Connection
15600 @subsubsection Connecting to VxWorks
15602 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15603 network. To connect to a target whose host name is ``@code{tt}'', type:
15606 (vxgdb) target vxworks tt
15610 @value{GDBN} displays messages like these:
15613 Attaching remote machine across net...
15618 @value{GDBN} then attempts to read the symbol tables of any object modules
15619 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15620 these files by searching the directories listed in the command search
15621 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15622 to find an object file, it displays a message such as:
15625 prog.o: No such file or directory.
15628 When this happens, add the appropriate directory to the search path with
15629 the @value{GDBN} command @code{path}, and execute the @code{target}
15632 @node VxWorks Download
15633 @subsubsection VxWorks Download
15635 @cindex download to VxWorks
15636 If you have connected to the VxWorks target and you want to debug an
15637 object that has not yet been loaded, you can use the @value{GDBN}
15638 @code{load} command to download a file from Unix to VxWorks
15639 incrementally. The object file given as an argument to the @code{load}
15640 command is actually opened twice: first by the VxWorks target in order
15641 to download the code, then by @value{GDBN} in order to read the symbol
15642 table. This can lead to problems if the current working directories on
15643 the two systems differ. If both systems have NFS mounted the same
15644 filesystems, you can avoid these problems by using absolute paths.
15645 Otherwise, it is simplest to set the working directory on both systems
15646 to the directory in which the object file resides, and then to reference
15647 the file by its name, without any path. For instance, a program
15648 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15649 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15650 program, type this on VxWorks:
15653 -> cd "@var{vxpath}/vw/demo/rdb"
15657 Then, in @value{GDBN}, type:
15660 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15661 (vxgdb) load prog.o
15664 @value{GDBN} displays a response similar to this:
15667 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15670 You can also use the @code{load} command to reload an object module
15671 after editing and recompiling the corresponding source file. Note that
15672 this makes @value{GDBN} delete all currently-defined breakpoints,
15673 auto-displays, and convenience variables, and to clear the value
15674 history. (This is necessary in order to preserve the integrity of
15675 debugger's data structures that reference the target system's symbol
15678 @node VxWorks Attach
15679 @subsubsection Running Tasks
15681 @cindex running VxWorks tasks
15682 You can also attach to an existing task using the @code{attach} command as
15686 (vxgdb) attach @var{task}
15690 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15691 or suspended when you attach to it. Running tasks are suspended at
15692 the time of attachment.
15694 @node Embedded Processors
15695 @section Embedded Processors
15697 This section goes into details specific to particular embedded
15700 @cindex send command to simulator
15701 Whenever a specific embedded processor has a simulator, @value{GDBN}
15702 allows to send an arbitrary command to the simulator.
15705 @item sim @var{command}
15706 @kindex sim@r{, a command}
15707 Send an arbitrary @var{command} string to the simulator. Consult the
15708 documentation for the specific simulator in use for information about
15709 acceptable commands.
15715 * M32R/D:: Renesas M32R/D
15716 * M68K:: Motorola M68K
15717 * MIPS Embedded:: MIPS Embedded
15718 * OpenRISC 1000:: OpenRisc 1000
15719 * PA:: HP PA Embedded
15720 * PowerPC Embedded:: PowerPC Embedded
15721 * Sparclet:: Tsqware Sparclet
15722 * Sparclite:: Fujitsu Sparclite
15723 * Z8000:: Zilog Z8000
15726 * Super-H:: Renesas Super-H
15735 @item target rdi @var{dev}
15736 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15737 use this target to communicate with both boards running the Angel
15738 monitor, or with the EmbeddedICE JTAG debug device.
15741 @item target rdp @var{dev}
15746 @value{GDBN} provides the following ARM-specific commands:
15749 @item set arm disassembler
15751 This commands selects from a list of disassembly styles. The
15752 @code{"std"} style is the standard style.
15754 @item show arm disassembler
15756 Show the current disassembly style.
15758 @item set arm apcs32
15759 @cindex ARM 32-bit mode
15760 This command toggles ARM operation mode between 32-bit and 26-bit.
15762 @item show arm apcs32
15763 Display the current usage of the ARM 32-bit mode.
15765 @item set arm fpu @var{fputype}
15766 This command sets the ARM floating-point unit (FPU) type. The
15767 argument @var{fputype} can be one of these:
15771 Determine the FPU type by querying the OS ABI.
15773 Software FPU, with mixed-endian doubles on little-endian ARM
15776 GCC-compiled FPA co-processor.
15778 Software FPU with pure-endian doubles.
15784 Show the current type of the FPU.
15787 This command forces @value{GDBN} to use the specified ABI.
15790 Show the currently used ABI.
15792 @item set arm fallback-mode (arm|thumb|auto)
15793 @value{GDBN} uses the symbol table, when available, to determine
15794 whether instructions are ARM or Thumb. This command controls
15795 @value{GDBN}'s default behavior when the symbol table is not
15796 available. The default is @samp{auto}, which causes @value{GDBN} to
15797 use the current execution mode (from the @code{T} bit in the @code{CPSR}
15800 @item show arm fallback-mode
15801 Show the current fallback instruction mode.
15803 @item set arm force-mode (arm|thumb|auto)
15804 This command overrides use of the symbol table to determine whether
15805 instructions are ARM or Thumb. The default is @samp{auto}, which
15806 causes @value{GDBN} to use the symbol table and then the setting
15807 of @samp{set arm fallback-mode}.
15809 @item show arm force-mode
15810 Show the current forced instruction mode.
15812 @item set debug arm
15813 Toggle whether to display ARM-specific debugging messages from the ARM
15814 target support subsystem.
15816 @item show debug arm
15817 Show whether ARM-specific debugging messages are enabled.
15820 The following commands are available when an ARM target is debugged
15821 using the RDI interface:
15824 @item rdilogfile @r{[}@var{file}@r{]}
15826 @cindex ADP (Angel Debugger Protocol) logging
15827 Set the filename for the ADP (Angel Debugger Protocol) packet log.
15828 With an argument, sets the log file to the specified @var{file}. With
15829 no argument, show the current log file name. The default log file is
15832 @item rdilogenable @r{[}@var{arg}@r{]}
15833 @kindex rdilogenable
15834 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
15835 enables logging, with an argument 0 or @code{"no"} disables it. With
15836 no arguments displays the current setting. When logging is enabled,
15837 ADP packets exchanged between @value{GDBN} and the RDI target device
15838 are logged to a file.
15840 @item set rdiromatzero
15841 @kindex set rdiromatzero
15842 @cindex ROM at zero address, RDI
15843 Tell @value{GDBN} whether the target has ROM at address 0. If on,
15844 vector catching is disabled, so that zero address can be used. If off
15845 (the default), vector catching is enabled. For this command to take
15846 effect, it needs to be invoked prior to the @code{target rdi} command.
15848 @item show rdiromatzero
15849 @kindex show rdiromatzero
15850 Show the current setting of ROM at zero address.
15852 @item set rdiheartbeat
15853 @kindex set rdiheartbeat
15854 @cindex RDI heartbeat
15855 Enable or disable RDI heartbeat packets. It is not recommended to
15856 turn on this option, since it confuses ARM and EPI JTAG interface, as
15857 well as the Angel monitor.
15859 @item show rdiheartbeat
15860 @kindex show rdiheartbeat
15861 Show the setting of RDI heartbeat packets.
15866 @subsection Renesas M32R/D and M32R/SDI
15869 @kindex target m32r
15870 @item target m32r @var{dev}
15871 Renesas M32R/D ROM monitor.
15873 @kindex target m32rsdi
15874 @item target m32rsdi @var{dev}
15875 Renesas M32R SDI server, connected via parallel port to the board.
15878 The following @value{GDBN} commands are specific to the M32R monitor:
15881 @item set download-path @var{path}
15882 @kindex set download-path
15883 @cindex find downloadable @sc{srec} files (M32R)
15884 Set the default path for finding downloadable @sc{srec} files.
15886 @item show download-path
15887 @kindex show download-path
15888 Show the default path for downloadable @sc{srec} files.
15890 @item set board-address @var{addr}
15891 @kindex set board-address
15892 @cindex M32-EVA target board address
15893 Set the IP address for the M32R-EVA target board.
15895 @item show board-address
15896 @kindex show board-address
15897 Show the current IP address of the target board.
15899 @item set server-address @var{addr}
15900 @kindex set server-address
15901 @cindex download server address (M32R)
15902 Set the IP address for the download server, which is the @value{GDBN}'s
15905 @item show server-address
15906 @kindex show server-address
15907 Display the IP address of the download server.
15909 @item upload @r{[}@var{file}@r{]}
15910 @kindex upload@r{, M32R}
15911 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
15912 upload capability. If no @var{file} argument is given, the current
15913 executable file is uploaded.
15915 @item tload @r{[}@var{file}@r{]}
15916 @kindex tload@r{, M32R}
15917 Test the @code{upload} command.
15920 The following commands are available for M32R/SDI:
15925 @cindex reset SDI connection, M32R
15926 This command resets the SDI connection.
15930 This command shows the SDI connection status.
15933 @kindex debug_chaos
15934 @cindex M32R/Chaos debugging
15935 Instructs the remote that M32R/Chaos debugging is to be used.
15937 @item use_debug_dma
15938 @kindex use_debug_dma
15939 Instructs the remote to use the DEBUG_DMA method of accessing memory.
15942 @kindex use_mon_code
15943 Instructs the remote to use the MON_CODE method of accessing memory.
15946 @kindex use_ib_break
15947 Instructs the remote to set breakpoints by IB break.
15949 @item use_dbt_break
15950 @kindex use_dbt_break
15951 Instructs the remote to set breakpoints by DBT.
15957 The Motorola m68k configuration includes ColdFire support, and a
15958 target command for the following ROM monitor.
15962 @kindex target dbug
15963 @item target dbug @var{dev}
15964 dBUG ROM monitor for Motorola ColdFire.
15968 @node MIPS Embedded
15969 @subsection MIPS Embedded
15971 @cindex MIPS boards
15972 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
15973 MIPS board attached to a serial line. This is available when
15974 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
15977 Use these @value{GDBN} commands to specify the connection to your target board:
15980 @item target mips @var{port}
15981 @kindex target mips @var{port}
15982 To run a program on the board, start up @code{@value{GDBP}} with the
15983 name of your program as the argument. To connect to the board, use the
15984 command @samp{target mips @var{port}}, where @var{port} is the name of
15985 the serial port connected to the board. If the program has not already
15986 been downloaded to the board, you may use the @code{load} command to
15987 download it. You can then use all the usual @value{GDBN} commands.
15989 For example, this sequence connects to the target board through a serial
15990 port, and loads and runs a program called @var{prog} through the
15994 host$ @value{GDBP} @var{prog}
15995 @value{GDBN} is free software and @dots{}
15996 (@value{GDBP}) target mips /dev/ttyb
15997 (@value{GDBP}) load @var{prog}
16001 @item target mips @var{hostname}:@var{portnumber}
16002 On some @value{GDBN} host configurations, you can specify a TCP
16003 connection (for instance, to a serial line managed by a terminal
16004 concentrator) instead of a serial port, using the syntax
16005 @samp{@var{hostname}:@var{portnumber}}.
16007 @item target pmon @var{port}
16008 @kindex target pmon @var{port}
16011 @item target ddb @var{port}
16012 @kindex target ddb @var{port}
16013 NEC's DDB variant of PMON for Vr4300.
16015 @item target lsi @var{port}
16016 @kindex target lsi @var{port}
16017 LSI variant of PMON.
16019 @kindex target r3900
16020 @item target r3900 @var{dev}
16021 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16023 @kindex target array
16024 @item target array @var{dev}
16025 Array Tech LSI33K RAID controller board.
16031 @value{GDBN} also supports these special commands for MIPS targets:
16034 @item set mipsfpu double
16035 @itemx set mipsfpu single
16036 @itemx set mipsfpu none
16037 @itemx set mipsfpu auto
16038 @itemx show mipsfpu
16039 @kindex set mipsfpu
16040 @kindex show mipsfpu
16041 @cindex MIPS remote floating point
16042 @cindex floating point, MIPS remote
16043 If your target board does not support the MIPS floating point
16044 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16045 need this, you may wish to put the command in your @value{GDBN} init
16046 file). This tells @value{GDBN} how to find the return value of
16047 functions which return floating point values. It also allows
16048 @value{GDBN} to avoid saving the floating point registers when calling
16049 functions on the board. If you are using a floating point coprocessor
16050 with only single precision floating point support, as on the @sc{r4650}
16051 processor, use the command @samp{set mipsfpu single}. The default
16052 double precision floating point coprocessor may be selected using
16053 @samp{set mipsfpu double}.
16055 In previous versions the only choices were double precision or no
16056 floating point, so @samp{set mipsfpu on} will select double precision
16057 and @samp{set mipsfpu off} will select no floating point.
16059 As usual, you can inquire about the @code{mipsfpu} variable with
16060 @samp{show mipsfpu}.
16062 @item set timeout @var{seconds}
16063 @itemx set retransmit-timeout @var{seconds}
16064 @itemx show timeout
16065 @itemx show retransmit-timeout
16066 @cindex @code{timeout}, MIPS protocol
16067 @cindex @code{retransmit-timeout}, MIPS protocol
16068 @kindex set timeout
16069 @kindex show timeout
16070 @kindex set retransmit-timeout
16071 @kindex show retransmit-timeout
16072 You can control the timeout used while waiting for a packet, in the MIPS
16073 remote protocol, with the @code{set timeout @var{seconds}} command. The
16074 default is 5 seconds. Similarly, you can control the timeout used while
16075 waiting for an acknowledgment of a packet with the @code{set
16076 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16077 You can inspect both values with @code{show timeout} and @code{show
16078 retransmit-timeout}. (These commands are @emph{only} available when
16079 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16081 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16082 is waiting for your program to stop. In that case, @value{GDBN} waits
16083 forever because it has no way of knowing how long the program is going
16084 to run before stopping.
16086 @item set syn-garbage-limit @var{num}
16087 @kindex set syn-garbage-limit@r{, MIPS remote}
16088 @cindex synchronize with remote MIPS target
16089 Limit the maximum number of characters @value{GDBN} should ignore when
16090 it tries to synchronize with the remote target. The default is 10
16091 characters. Setting the limit to -1 means there's no limit.
16093 @item show syn-garbage-limit
16094 @kindex show syn-garbage-limit@r{, MIPS remote}
16095 Show the current limit on the number of characters to ignore when
16096 trying to synchronize with the remote system.
16098 @item set monitor-prompt @var{prompt}
16099 @kindex set monitor-prompt@r{, MIPS remote}
16100 @cindex remote monitor prompt
16101 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16102 remote monitor. The default depends on the target:
16112 @item show monitor-prompt
16113 @kindex show monitor-prompt@r{, MIPS remote}
16114 Show the current strings @value{GDBN} expects as the prompt from the
16117 @item set monitor-warnings
16118 @kindex set monitor-warnings@r{, MIPS remote}
16119 Enable or disable monitor warnings about hardware breakpoints. This
16120 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16121 display warning messages whose codes are returned by the @code{lsi}
16122 PMON monitor for breakpoint commands.
16124 @item show monitor-warnings
16125 @kindex show monitor-warnings@r{, MIPS remote}
16126 Show the current setting of printing monitor warnings.
16128 @item pmon @var{command}
16129 @kindex pmon@r{, MIPS remote}
16130 @cindex send PMON command
16131 This command allows sending an arbitrary @var{command} string to the
16132 monitor. The monitor must be in debug mode for this to work.
16135 @node OpenRISC 1000
16136 @subsection OpenRISC 1000
16137 @cindex OpenRISC 1000
16139 @cindex or1k boards
16140 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16141 about platform and commands.
16145 @kindex target jtag
16146 @item target jtag jtag://@var{host}:@var{port}
16148 Connects to remote JTAG server.
16149 JTAG remote server can be either an or1ksim or JTAG server,
16150 connected via parallel port to the board.
16152 Example: @code{target jtag jtag://localhost:9999}
16155 @item or1ksim @var{command}
16156 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16157 Simulator, proprietary commands can be executed.
16159 @kindex info or1k spr
16160 @item info or1k spr
16161 Displays spr groups.
16163 @item info or1k spr @var{group}
16164 @itemx info or1k spr @var{groupno}
16165 Displays register names in selected group.
16167 @item info or1k spr @var{group} @var{register}
16168 @itemx info or1k spr @var{register}
16169 @itemx info or1k spr @var{groupno} @var{registerno}
16170 @itemx info or1k spr @var{registerno}
16171 Shows information about specified spr register.
16174 @item spr @var{group} @var{register} @var{value}
16175 @itemx spr @var{register @var{value}}
16176 @itemx spr @var{groupno} @var{registerno @var{value}}
16177 @itemx spr @var{registerno @var{value}}
16178 Writes @var{value} to specified spr register.
16181 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16182 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16183 program execution and is thus much faster. Hardware breakpoints/watchpoint
16184 triggers can be set using:
16187 Load effective address/data
16189 Store effective address/data
16191 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16196 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16197 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16199 @code{htrace} commands:
16200 @cindex OpenRISC 1000 htrace
16203 @item hwatch @var{conditional}
16204 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16205 or Data. For example:
16207 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16209 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16213 Display information about current HW trace configuration.
16215 @item htrace trigger @var{conditional}
16216 Set starting criteria for HW trace.
16218 @item htrace qualifier @var{conditional}
16219 Set acquisition qualifier for HW trace.
16221 @item htrace stop @var{conditional}
16222 Set HW trace stopping criteria.
16224 @item htrace record [@var{data}]*
16225 Selects the data to be recorded, when qualifier is met and HW trace was
16228 @item htrace enable
16229 @itemx htrace disable
16230 Enables/disables the HW trace.
16232 @item htrace rewind [@var{filename}]
16233 Clears currently recorded trace data.
16235 If filename is specified, new trace file is made and any newly collected data
16236 will be written there.
16238 @item htrace print [@var{start} [@var{len}]]
16239 Prints trace buffer, using current record configuration.
16241 @item htrace mode continuous
16242 Set continuous trace mode.
16244 @item htrace mode suspend
16245 Set suspend trace mode.
16249 @node PowerPC Embedded
16250 @subsection PowerPC Embedded
16252 @value{GDBN} provides the following PowerPC-specific commands:
16255 @kindex set powerpc
16256 @item set powerpc soft-float
16257 @itemx show powerpc soft-float
16258 Force @value{GDBN} to use (or not use) a software floating point calling
16259 convention. By default, @value{GDBN} selects the calling convention based
16260 on the selected architecture and the provided executable file.
16262 @item set powerpc vector-abi
16263 @itemx show powerpc vector-abi
16264 Force @value{GDBN} to use the specified calling convention for vector
16265 arguments and return values. The valid options are @samp{auto};
16266 @samp{generic}, to avoid vector registers even if they are present;
16267 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16268 registers. By default, @value{GDBN} selects the calling convention
16269 based on the selected architecture and the provided executable file.
16271 @kindex target dink32
16272 @item target dink32 @var{dev}
16273 DINK32 ROM monitor.
16275 @kindex target ppcbug
16276 @item target ppcbug @var{dev}
16277 @kindex target ppcbug1
16278 @item target ppcbug1 @var{dev}
16279 PPCBUG ROM monitor for PowerPC.
16282 @item target sds @var{dev}
16283 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16286 @cindex SDS protocol
16287 The following commands specific to the SDS protocol are supported
16291 @item set sdstimeout @var{nsec}
16292 @kindex set sdstimeout
16293 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16294 default is 2 seconds.
16296 @item show sdstimeout
16297 @kindex show sdstimeout
16298 Show the current value of the SDS timeout.
16300 @item sds @var{command}
16301 @kindex sds@r{, a command}
16302 Send the specified @var{command} string to the SDS monitor.
16307 @subsection HP PA Embedded
16311 @kindex target op50n
16312 @item target op50n @var{dev}
16313 OP50N monitor, running on an OKI HPPA board.
16315 @kindex target w89k
16316 @item target w89k @var{dev}
16317 W89K monitor, running on a Winbond HPPA board.
16322 @subsection Tsqware Sparclet
16326 @value{GDBN} enables developers to debug tasks running on
16327 Sparclet targets from a Unix host.
16328 @value{GDBN} uses code that runs on
16329 both the Unix host and on the Sparclet target. The program
16330 @code{@value{GDBP}} is installed and executed on the Unix host.
16333 @item remotetimeout @var{args}
16334 @kindex remotetimeout
16335 @value{GDBN} supports the option @code{remotetimeout}.
16336 This option is set by the user, and @var{args} represents the number of
16337 seconds @value{GDBN} waits for responses.
16340 @cindex compiling, on Sparclet
16341 When compiling for debugging, include the options @samp{-g} to get debug
16342 information and @samp{-Ttext} to relocate the program to where you wish to
16343 load it on the target. You may also want to add the options @samp{-n} or
16344 @samp{-N} in order to reduce the size of the sections. Example:
16347 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16350 You can use @code{objdump} to verify that the addresses are what you intended:
16353 sparclet-aout-objdump --headers --syms prog
16356 @cindex running, on Sparclet
16358 your Unix execution search path to find @value{GDBN}, you are ready to
16359 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16360 (or @code{sparclet-aout-gdb}, depending on your installation).
16362 @value{GDBN} comes up showing the prompt:
16369 * Sparclet File:: Setting the file to debug
16370 * Sparclet Connection:: Connecting to Sparclet
16371 * Sparclet Download:: Sparclet download
16372 * Sparclet Execution:: Running and debugging
16375 @node Sparclet File
16376 @subsubsection Setting File to Debug
16378 The @value{GDBN} command @code{file} lets you choose with program to debug.
16381 (gdbslet) file prog
16385 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16386 @value{GDBN} locates
16387 the file by searching the directories listed in the command search
16389 If the file was compiled with debug information (option @samp{-g}), source
16390 files will be searched as well.
16391 @value{GDBN} locates
16392 the source files by searching the directories listed in the directory search
16393 path (@pxref{Environment, ,Your Program's Environment}).
16395 to find a file, it displays a message such as:
16398 prog: No such file or directory.
16401 When this happens, add the appropriate directories to the search paths with
16402 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16403 @code{target} command again.
16405 @node Sparclet Connection
16406 @subsubsection Connecting to Sparclet
16408 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16409 To connect to a target on serial port ``@code{ttya}'', type:
16412 (gdbslet) target sparclet /dev/ttya
16413 Remote target sparclet connected to /dev/ttya
16414 main () at ../prog.c:3
16418 @value{GDBN} displays messages like these:
16424 @node Sparclet Download
16425 @subsubsection Sparclet Download
16427 @cindex download to Sparclet
16428 Once connected to the Sparclet target,
16429 you can use the @value{GDBN}
16430 @code{load} command to download the file from the host to the target.
16431 The file name and load offset should be given as arguments to the @code{load}
16433 Since the file format is aout, the program must be loaded to the starting
16434 address. You can use @code{objdump} to find out what this value is. The load
16435 offset is an offset which is added to the VMA (virtual memory address)
16436 of each of the file's sections.
16437 For instance, if the program
16438 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16439 and bss at 0x12010170, in @value{GDBN}, type:
16442 (gdbslet) load prog 0x12010000
16443 Loading section .text, size 0xdb0 vma 0x12010000
16446 If the code is loaded at a different address then what the program was linked
16447 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16448 to tell @value{GDBN} where to map the symbol table.
16450 @node Sparclet Execution
16451 @subsubsection Running and Debugging
16453 @cindex running and debugging Sparclet programs
16454 You can now begin debugging the task using @value{GDBN}'s execution control
16455 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16456 manual for the list of commands.
16460 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16462 Starting program: prog
16463 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16464 3 char *symarg = 0;
16466 4 char *execarg = "hello!";
16471 @subsection Fujitsu Sparclite
16475 @kindex target sparclite
16476 @item target sparclite @var{dev}
16477 Fujitsu sparclite boards, used only for the purpose of loading.
16478 You must use an additional command to debug the program.
16479 For example: target remote @var{dev} using @value{GDBN} standard
16485 @subsection Zilog Z8000
16488 @cindex simulator, Z8000
16489 @cindex Zilog Z8000 simulator
16491 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16494 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16495 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16496 segmented variant). The simulator recognizes which architecture is
16497 appropriate by inspecting the object code.
16500 @item target sim @var{args}
16502 @kindex target sim@r{, with Z8000}
16503 Debug programs on a simulated CPU. If the simulator supports setup
16504 options, specify them via @var{args}.
16508 After specifying this target, you can debug programs for the simulated
16509 CPU in the same style as programs for your host computer; use the
16510 @code{file} command to load a new program image, the @code{run} command
16511 to run your program, and so on.
16513 As well as making available all the usual machine registers
16514 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16515 additional items of information as specially named registers:
16520 Counts clock-ticks in the simulator.
16523 Counts instructions run in the simulator.
16526 Execution time in 60ths of a second.
16530 You can refer to these values in @value{GDBN} expressions with the usual
16531 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16532 conditional breakpoint that suspends only after at least 5000
16533 simulated clock ticks.
16536 @subsection Atmel AVR
16539 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16540 following AVR-specific commands:
16543 @item info io_registers
16544 @kindex info io_registers@r{, AVR}
16545 @cindex I/O registers (Atmel AVR)
16546 This command displays information about the AVR I/O registers. For
16547 each register, @value{GDBN} prints its number and value.
16554 When configured for debugging CRIS, @value{GDBN} provides the
16555 following CRIS-specific commands:
16558 @item set cris-version @var{ver}
16559 @cindex CRIS version
16560 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16561 The CRIS version affects register names and sizes. This command is useful in
16562 case autodetection of the CRIS version fails.
16564 @item show cris-version
16565 Show the current CRIS version.
16567 @item set cris-dwarf2-cfi
16568 @cindex DWARF-2 CFI and CRIS
16569 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16570 Change to @samp{off} when using @code{gcc-cris} whose version is below
16573 @item show cris-dwarf2-cfi
16574 Show the current state of using DWARF-2 CFI.
16576 @item set cris-mode @var{mode}
16578 Set the current CRIS mode to @var{mode}. It should only be changed when
16579 debugging in guru mode, in which case it should be set to
16580 @samp{guru} (the default is @samp{normal}).
16582 @item show cris-mode
16583 Show the current CRIS mode.
16587 @subsection Renesas Super-H
16590 For the Renesas Super-H processor, @value{GDBN} provides these
16595 @kindex regs@r{, Super-H}
16596 Show the values of all Super-H registers.
16598 @item set sh calling-convention @var{convention}
16599 @kindex set sh calling-convention
16600 Set the calling-convention used when calling functions from @value{GDBN}.
16601 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16602 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16603 convention. If the DWARF-2 information of the called function specifies
16604 that the function follows the Renesas calling convention, the function
16605 is called using the Renesas calling convention. If the calling convention
16606 is set to @samp{renesas}, the Renesas calling convention is always used,
16607 regardless of the DWARF-2 information. This can be used to override the
16608 default of @samp{gcc} if debug information is missing, or the compiler
16609 does not emit the DWARF-2 calling convention entry for a function.
16611 @item show sh calling-convention
16612 @kindex show sh calling-convention
16613 Show the current calling convention setting.
16618 @node Architectures
16619 @section Architectures
16621 This section describes characteristics of architectures that affect
16622 all uses of @value{GDBN} with the architecture, both native and cross.
16629 * HPPA:: HP PA architecture
16630 * SPU:: Cell Broadband Engine SPU architecture
16635 @subsection x86 Architecture-specific Issues
16638 @item set struct-convention @var{mode}
16639 @kindex set struct-convention
16640 @cindex struct return convention
16641 @cindex struct/union returned in registers
16642 Set the convention used by the inferior to return @code{struct}s and
16643 @code{union}s from functions to @var{mode}. Possible values of
16644 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16645 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16646 are returned on the stack, while @code{"reg"} means that a
16647 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16648 be returned in a register.
16650 @item show struct-convention
16651 @kindex show struct-convention
16652 Show the current setting of the convention to return @code{struct}s
16661 @kindex set rstack_high_address
16662 @cindex AMD 29K register stack
16663 @cindex register stack, AMD29K
16664 @item set rstack_high_address @var{address}
16665 On AMD 29000 family processors, registers are saved in a separate
16666 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16667 extent of this stack. Normally, @value{GDBN} just assumes that the
16668 stack is ``large enough''. This may result in @value{GDBN} referencing
16669 memory locations that do not exist. If necessary, you can get around
16670 this problem by specifying the ending address of the register stack with
16671 the @code{set rstack_high_address} command. The argument should be an
16672 address, which you probably want to precede with @samp{0x} to specify in
16675 @kindex show rstack_high_address
16676 @item show rstack_high_address
16677 Display the current limit of the register stack, on AMD 29000 family
16685 See the following section.
16690 @cindex stack on Alpha
16691 @cindex stack on MIPS
16692 @cindex Alpha stack
16694 Alpha- and MIPS-based computers use an unusual stack frame, which
16695 sometimes requires @value{GDBN} to search backward in the object code to
16696 find the beginning of a function.
16698 @cindex response time, MIPS debugging
16699 To improve response time (especially for embedded applications, where
16700 @value{GDBN} may be restricted to a slow serial line for this search)
16701 you may want to limit the size of this search, using one of these
16705 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16706 @item set heuristic-fence-post @var{limit}
16707 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16708 search for the beginning of a function. A value of @var{0} (the
16709 default) means there is no limit. However, except for @var{0}, the
16710 larger the limit the more bytes @code{heuristic-fence-post} must search
16711 and therefore the longer it takes to run. You should only need to use
16712 this command when debugging a stripped executable.
16714 @item show heuristic-fence-post
16715 Display the current limit.
16719 These commands are available @emph{only} when @value{GDBN} is configured
16720 for debugging programs on Alpha or MIPS processors.
16722 Several MIPS-specific commands are available when debugging MIPS
16726 @item set mips abi @var{arg}
16727 @kindex set mips abi
16728 @cindex set ABI for MIPS
16729 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16730 values of @var{arg} are:
16734 The default ABI associated with the current binary (this is the
16745 @item show mips abi
16746 @kindex show mips abi
16747 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16750 @itemx show mipsfpu
16751 @xref{MIPS Embedded, set mipsfpu}.
16753 @item set mips mask-address @var{arg}
16754 @kindex set mips mask-address
16755 @cindex MIPS addresses, masking
16756 This command determines whether the most-significant 32 bits of 64-bit
16757 MIPS addresses are masked off. The argument @var{arg} can be
16758 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16759 setting, which lets @value{GDBN} determine the correct value.
16761 @item show mips mask-address
16762 @kindex show mips mask-address
16763 Show whether the upper 32 bits of MIPS addresses are masked off or
16766 @item set remote-mips64-transfers-32bit-regs
16767 @kindex set remote-mips64-transfers-32bit-regs
16768 This command controls compatibility with 64-bit MIPS targets that
16769 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16770 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16771 and 64 bits for other registers, set this option to @samp{on}.
16773 @item show remote-mips64-transfers-32bit-regs
16774 @kindex show remote-mips64-transfers-32bit-regs
16775 Show the current setting of compatibility with older MIPS 64 targets.
16777 @item set debug mips
16778 @kindex set debug mips
16779 This command turns on and off debugging messages for the MIPS-specific
16780 target code in @value{GDBN}.
16782 @item show debug mips
16783 @kindex show debug mips
16784 Show the current setting of MIPS debugging messages.
16790 @cindex HPPA support
16792 When @value{GDBN} is debugging the HP PA architecture, it provides the
16793 following special commands:
16796 @item set debug hppa
16797 @kindex set debug hppa
16798 This command determines whether HPPA architecture-specific debugging
16799 messages are to be displayed.
16801 @item show debug hppa
16802 Show whether HPPA debugging messages are displayed.
16804 @item maint print unwind @var{address}
16805 @kindex maint print unwind@r{, HPPA}
16806 This command displays the contents of the unwind table entry at the
16807 given @var{address}.
16813 @subsection Cell Broadband Engine SPU architecture
16814 @cindex Cell Broadband Engine
16817 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
16818 it provides the following special commands:
16821 @item info spu event
16823 Display SPU event facility status. Shows current event mask
16824 and pending event status.
16826 @item info spu signal
16827 Display SPU signal notification facility status. Shows pending
16828 signal-control word and signal notification mode of both signal
16829 notification channels.
16831 @item info spu mailbox
16832 Display SPU mailbox facility status. Shows all pending entries,
16833 in order of processing, in each of the SPU Write Outbound,
16834 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
16837 Display MFC DMA status. Shows all pending commands in the MFC
16838 DMA queue. For each entry, opcode, tag, class IDs, effective
16839 and local store addresses and transfer size are shown.
16841 @item info spu proxydma
16842 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
16843 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
16844 and local store addresses and transfer size are shown.
16849 @subsection PowerPC
16850 @cindex PowerPC architecture
16852 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
16853 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
16854 numbers stored in the floating point registers. These values must be stored
16855 in two consecutive registers, always starting at an even register like
16856 @code{f0} or @code{f2}.
16858 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
16859 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
16860 @code{f2} and @code{f3} for @code{$dl1} and so on.
16862 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
16863 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
16866 @node Controlling GDB
16867 @chapter Controlling @value{GDBN}
16869 You can alter the way @value{GDBN} interacts with you by using the
16870 @code{set} command. For commands controlling how @value{GDBN} displays
16871 data, see @ref{Print Settings, ,Print Settings}. Other settings are
16876 * Editing:: Command editing
16877 * Command History:: Command history
16878 * Screen Size:: Screen size
16879 * Numbers:: Numbers
16880 * ABI:: Configuring the current ABI
16881 * Messages/Warnings:: Optional warnings and messages
16882 * Debugging Output:: Optional messages about internal happenings
16890 @value{GDBN} indicates its readiness to read a command by printing a string
16891 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
16892 can change the prompt string with the @code{set prompt} command. For
16893 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
16894 the prompt in one of the @value{GDBN} sessions so that you can always tell
16895 which one you are talking to.
16897 @emph{Note:} @code{set prompt} does not add a space for you after the
16898 prompt you set. This allows you to set a prompt which ends in a space
16899 or a prompt that does not.
16903 @item set prompt @var{newprompt}
16904 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
16906 @kindex show prompt
16908 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
16912 @section Command Editing
16914 @cindex command line editing
16916 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
16917 @sc{gnu} library provides consistent behavior for programs which provide a
16918 command line interface to the user. Advantages are @sc{gnu} Emacs-style
16919 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
16920 substitution, and a storage and recall of command history across
16921 debugging sessions.
16923 You may control the behavior of command line editing in @value{GDBN} with the
16924 command @code{set}.
16927 @kindex set editing
16930 @itemx set editing on
16931 Enable command line editing (enabled by default).
16933 @item set editing off
16934 Disable command line editing.
16936 @kindex show editing
16938 Show whether command line editing is enabled.
16941 @xref{Command Line Editing}, for more details about the Readline
16942 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
16943 encouraged to read that chapter.
16945 @node Command History
16946 @section Command History
16947 @cindex command history
16949 @value{GDBN} can keep track of the commands you type during your
16950 debugging sessions, so that you can be certain of precisely what
16951 happened. Use these commands to manage the @value{GDBN} command
16954 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
16955 package, to provide the history facility. @xref{Using History
16956 Interactively}, for the detailed description of the History library.
16958 To issue a command to @value{GDBN} without affecting certain aspects of
16959 the state which is seen by users, prefix it with @samp{server }
16960 (@pxref{Server Prefix}). This
16961 means that this command will not affect the command history, nor will it
16962 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
16963 pressed on a line by itself.
16965 @cindex @code{server}, command prefix
16966 The server prefix does not affect the recording of values into the value
16967 history; to print a value without recording it into the value history,
16968 use the @code{output} command instead of the @code{print} command.
16970 Here is the description of @value{GDBN} commands related to command
16974 @cindex history substitution
16975 @cindex history file
16976 @kindex set history filename
16977 @cindex @env{GDBHISTFILE}, environment variable
16978 @item set history filename @var{fname}
16979 Set the name of the @value{GDBN} command history file to @var{fname}.
16980 This is the file where @value{GDBN} reads an initial command history
16981 list, and where it writes the command history from this session when it
16982 exits. You can access this list through history expansion or through
16983 the history command editing characters listed below. This file defaults
16984 to the value of the environment variable @code{GDBHISTFILE}, or to
16985 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
16988 @cindex save command history
16989 @kindex set history save
16990 @item set history save
16991 @itemx set history save on
16992 Record command history in a file, whose name may be specified with the
16993 @code{set history filename} command. By default, this option is disabled.
16995 @item set history save off
16996 Stop recording command history in a file.
16998 @cindex history size
16999 @kindex set history size
17000 @cindex @env{HISTSIZE}, environment variable
17001 @item set history size @var{size}
17002 Set the number of commands which @value{GDBN} keeps in its history list.
17003 This defaults to the value of the environment variable
17004 @code{HISTSIZE}, or to 256 if this variable is not set.
17007 History expansion assigns special meaning to the character @kbd{!}.
17008 @xref{Event Designators}, for more details.
17010 @cindex history expansion, turn on/off
17011 Since @kbd{!} is also the logical not operator in C, history expansion
17012 is off by default. If you decide to enable history expansion with the
17013 @code{set history expansion on} command, you may sometimes need to
17014 follow @kbd{!} (when it is used as logical not, in an expression) with
17015 a space or a tab to prevent it from being expanded. The readline
17016 history facilities do not attempt substitution on the strings
17017 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17019 The commands to control history expansion are:
17022 @item set history expansion on
17023 @itemx set history expansion
17024 @kindex set history expansion
17025 Enable history expansion. History expansion is off by default.
17027 @item set history expansion off
17028 Disable history expansion.
17031 @kindex show history
17033 @itemx show history filename
17034 @itemx show history save
17035 @itemx show history size
17036 @itemx show history expansion
17037 These commands display the state of the @value{GDBN} history parameters.
17038 @code{show history} by itself displays all four states.
17043 @kindex show commands
17044 @cindex show last commands
17045 @cindex display command history
17046 @item show commands
17047 Display the last ten commands in the command history.
17049 @item show commands @var{n}
17050 Print ten commands centered on command number @var{n}.
17052 @item show commands +
17053 Print ten commands just after the commands last printed.
17057 @section Screen Size
17058 @cindex size of screen
17059 @cindex pauses in output
17061 Certain commands to @value{GDBN} may produce large amounts of
17062 information output to the screen. To help you read all of it,
17063 @value{GDBN} pauses and asks you for input at the end of each page of
17064 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17065 to discard the remaining output. Also, the screen width setting
17066 determines when to wrap lines of output. Depending on what is being
17067 printed, @value{GDBN} tries to break the line at a readable place,
17068 rather than simply letting it overflow onto the following line.
17070 Normally @value{GDBN} knows the size of the screen from the terminal
17071 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17072 together with the value of the @code{TERM} environment variable and the
17073 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17074 you can override it with the @code{set height} and @code{set
17081 @kindex show height
17082 @item set height @var{lpp}
17084 @itemx set width @var{cpl}
17086 These @code{set} commands specify a screen height of @var{lpp} lines and
17087 a screen width of @var{cpl} characters. The associated @code{show}
17088 commands display the current settings.
17090 If you specify a height of zero lines, @value{GDBN} does not pause during
17091 output no matter how long the output is. This is useful if output is to a
17092 file or to an editor buffer.
17094 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17095 from wrapping its output.
17097 @item set pagination on
17098 @itemx set pagination off
17099 @kindex set pagination
17100 Turn the output pagination on or off; the default is on. Turning
17101 pagination off is the alternative to @code{set height 0}.
17103 @item show pagination
17104 @kindex show pagination
17105 Show the current pagination mode.
17110 @cindex number representation
17111 @cindex entering numbers
17113 You can always enter numbers in octal, decimal, or hexadecimal in
17114 @value{GDBN} by the usual conventions: octal numbers begin with
17115 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17116 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17117 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17118 10; likewise, the default display for numbers---when no particular
17119 format is specified---is base 10. You can change the default base for
17120 both input and output with the commands described below.
17123 @kindex set input-radix
17124 @item set input-radix @var{base}
17125 Set the default base for numeric input. Supported choices
17126 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17127 specified either unambiguously or using the current input radix; for
17131 set input-radix 012
17132 set input-radix 10.
17133 set input-radix 0xa
17137 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17138 leaves the input radix unchanged, no matter what it was, since
17139 @samp{10}, being without any leading or trailing signs of its base, is
17140 interpreted in the current radix. Thus, if the current radix is 16,
17141 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17144 @kindex set output-radix
17145 @item set output-radix @var{base}
17146 Set the default base for numeric display. Supported choices
17147 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17148 specified either unambiguously or using the current input radix.
17150 @kindex show input-radix
17151 @item show input-radix
17152 Display the current default base for numeric input.
17154 @kindex show output-radix
17155 @item show output-radix
17156 Display the current default base for numeric display.
17158 @item set radix @r{[}@var{base}@r{]}
17162 These commands set and show the default base for both input and output
17163 of numbers. @code{set radix} sets the radix of input and output to
17164 the same base; without an argument, it resets the radix back to its
17165 default value of 10.
17170 @section Configuring the Current ABI
17172 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17173 application automatically. However, sometimes you need to override its
17174 conclusions. Use these commands to manage @value{GDBN}'s view of the
17181 One @value{GDBN} configuration can debug binaries for multiple operating
17182 system targets, either via remote debugging or native emulation.
17183 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17184 but you can override its conclusion using the @code{set osabi} command.
17185 One example where this is useful is in debugging of binaries which use
17186 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17187 not have the same identifying marks that the standard C library for your
17192 Show the OS ABI currently in use.
17195 With no argument, show the list of registered available OS ABI's.
17197 @item set osabi @var{abi}
17198 Set the current OS ABI to @var{abi}.
17201 @cindex float promotion
17203 Generally, the way that an argument of type @code{float} is passed to a
17204 function depends on whether the function is prototyped. For a prototyped
17205 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17206 according to the architecture's convention for @code{float}. For unprototyped
17207 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17208 @code{double} and then passed.
17210 Unfortunately, some forms of debug information do not reliably indicate whether
17211 a function is prototyped. If @value{GDBN} calls a function that is not marked
17212 as prototyped, it consults @kbd{set coerce-float-to-double}.
17215 @kindex set coerce-float-to-double
17216 @item set coerce-float-to-double
17217 @itemx set coerce-float-to-double on
17218 Arguments of type @code{float} will be promoted to @code{double} when passed
17219 to an unprototyped function. This is the default setting.
17221 @item set coerce-float-to-double off
17222 Arguments of type @code{float} will be passed directly to unprototyped
17225 @kindex show coerce-float-to-double
17226 @item show coerce-float-to-double
17227 Show the current setting of promoting @code{float} to @code{double}.
17231 @kindex show cp-abi
17232 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17233 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17234 used to build your application. @value{GDBN} only fully supports
17235 programs with a single C@t{++} ABI; if your program contains code using
17236 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17237 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17238 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17239 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17240 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17241 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17246 Show the C@t{++} ABI currently in use.
17249 With no argument, show the list of supported C@t{++} ABI's.
17251 @item set cp-abi @var{abi}
17252 @itemx set cp-abi auto
17253 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17256 @node Messages/Warnings
17257 @section Optional Warnings and Messages
17259 @cindex verbose operation
17260 @cindex optional warnings
17261 By default, @value{GDBN} is silent about its inner workings. If you are
17262 running on a slow machine, you may want to use the @code{set verbose}
17263 command. This makes @value{GDBN} tell you when it does a lengthy
17264 internal operation, so you will not think it has crashed.
17266 Currently, the messages controlled by @code{set verbose} are those
17267 which announce that the symbol table for a source file is being read;
17268 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17271 @kindex set verbose
17272 @item set verbose on
17273 Enables @value{GDBN} output of certain informational messages.
17275 @item set verbose off
17276 Disables @value{GDBN} output of certain informational messages.
17278 @kindex show verbose
17280 Displays whether @code{set verbose} is on or off.
17283 By default, if @value{GDBN} encounters bugs in the symbol table of an
17284 object file, it is silent; but if you are debugging a compiler, you may
17285 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17290 @kindex set complaints
17291 @item set complaints @var{limit}
17292 Permits @value{GDBN} to output @var{limit} complaints about each type of
17293 unusual symbols before becoming silent about the problem. Set
17294 @var{limit} to zero to suppress all complaints; set it to a large number
17295 to prevent complaints from being suppressed.
17297 @kindex show complaints
17298 @item show complaints
17299 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17303 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17304 lot of stupid questions to confirm certain commands. For example, if
17305 you try to run a program which is already running:
17309 The program being debugged has been started already.
17310 Start it from the beginning? (y or n)
17313 If you are willing to unflinchingly face the consequences of your own
17314 commands, you can disable this ``feature'':
17318 @kindex set confirm
17320 @cindex confirmation
17321 @cindex stupid questions
17322 @item set confirm off
17323 Disables confirmation requests.
17325 @item set confirm on
17326 Enables confirmation requests (the default).
17328 @kindex show confirm
17330 Displays state of confirmation requests.
17334 @cindex command tracing
17335 If you need to debug user-defined commands or sourced files you may find it
17336 useful to enable @dfn{command tracing}. In this mode each command will be
17337 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17338 quantity denoting the call depth of each command.
17341 @kindex set trace-commands
17342 @cindex command scripts, debugging
17343 @item set trace-commands on
17344 Enable command tracing.
17345 @item set trace-commands off
17346 Disable command tracing.
17347 @item show trace-commands
17348 Display the current state of command tracing.
17351 @node Debugging Output
17352 @section Optional Messages about Internal Happenings
17353 @cindex optional debugging messages
17355 @value{GDBN} has commands that enable optional debugging messages from
17356 various @value{GDBN} subsystems; normally these commands are of
17357 interest to @value{GDBN} maintainers, or when reporting a bug. This
17358 section documents those commands.
17361 @kindex set exec-done-display
17362 @item set exec-done-display
17363 Turns on or off the notification of asynchronous commands'
17364 completion. When on, @value{GDBN} will print a message when an
17365 asynchronous command finishes its execution. The default is off.
17366 @kindex show exec-done-display
17367 @item show exec-done-display
17368 Displays the current setting of asynchronous command completion
17371 @cindex gdbarch debugging info
17372 @cindex architecture debugging info
17373 @item set debug arch
17374 Turns on or off display of gdbarch debugging info. The default is off
17376 @item show debug arch
17377 Displays the current state of displaying gdbarch debugging info.
17378 @item set debug aix-thread
17379 @cindex AIX threads
17380 Display debugging messages about inner workings of the AIX thread
17382 @item show debug aix-thread
17383 Show the current state of AIX thread debugging info display.
17384 @item set debug dwarf2-die
17385 @cindex DWARF2 DIEs
17386 Dump DWARF2 DIEs after they are read in.
17387 The value is the number of nesting levels to print.
17388 A value of zero turns off the display.
17389 @item show debug dwarf2-die
17390 Show the current state of DWARF2 DIE debugging.
17391 @item set debug displaced
17392 @cindex displaced stepping debugging info
17393 Turns on or off display of @value{GDBN} debugging info for the
17394 displaced stepping support. The default is off.
17395 @item show debug displaced
17396 Displays the current state of displaying @value{GDBN} debugging info
17397 related to displaced stepping.
17398 @item set debug event
17399 @cindex event debugging info
17400 Turns on or off display of @value{GDBN} event debugging info. The
17402 @item show debug event
17403 Displays the current state of displaying @value{GDBN} event debugging
17405 @item set debug expression
17406 @cindex expression debugging info
17407 Turns on or off display of debugging info about @value{GDBN}
17408 expression parsing. The default is off.
17409 @item show debug expression
17410 Displays the current state of displaying debugging info about
17411 @value{GDBN} expression parsing.
17412 @item set debug frame
17413 @cindex frame debugging info
17414 Turns on or off display of @value{GDBN} frame debugging info. The
17416 @item show debug frame
17417 Displays the current state of displaying @value{GDBN} frame debugging
17419 @item set debug infrun
17420 @cindex inferior debugging info
17421 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17422 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17423 for implementing operations such as single-stepping the inferior.
17424 @item show debug infrun
17425 Displays the current state of @value{GDBN} inferior debugging.
17426 @item set debug lin-lwp
17427 @cindex @sc{gnu}/Linux LWP debug messages
17428 @cindex Linux lightweight processes
17429 Turns on or off debugging messages from the Linux LWP debug support.
17430 @item show debug lin-lwp
17431 Show the current state of Linux LWP debugging messages.
17432 @item set debug lin-lwp-async
17433 @cindex @sc{gnu}/Linux LWP async debug messages
17434 @cindex Linux lightweight processes
17435 Turns on or off debugging messages from the Linux LWP async debug support.
17436 @item show debug lin-lwp-async
17437 Show the current state of Linux LWP async debugging messages.
17438 @item set debug observer
17439 @cindex observer debugging info
17440 Turns on or off display of @value{GDBN} observer debugging. This
17441 includes info such as the notification of observable events.
17442 @item show debug observer
17443 Displays the current state of observer debugging.
17444 @item set debug overload
17445 @cindex C@t{++} overload debugging info
17446 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17447 info. This includes info such as ranking of functions, etc. The default
17449 @item show debug overload
17450 Displays the current state of displaying @value{GDBN} C@t{++} overload
17452 @cindex packets, reporting on stdout
17453 @cindex serial connections, debugging
17454 @cindex debug remote protocol
17455 @cindex remote protocol debugging
17456 @cindex display remote packets
17457 @item set debug remote
17458 Turns on or off display of reports on all packets sent back and forth across
17459 the serial line to the remote machine. The info is printed on the
17460 @value{GDBN} standard output stream. The default is off.
17461 @item show debug remote
17462 Displays the state of display of remote packets.
17463 @item set debug serial
17464 Turns on or off display of @value{GDBN} serial debugging info. The
17466 @item show debug serial
17467 Displays the current state of displaying @value{GDBN} serial debugging
17469 @item set debug solib-frv
17470 @cindex FR-V shared-library debugging
17471 Turns on or off debugging messages for FR-V shared-library code.
17472 @item show debug solib-frv
17473 Display the current state of FR-V shared-library code debugging
17475 @item set debug target
17476 @cindex target debugging info
17477 Turns on or off display of @value{GDBN} target debugging info. This info
17478 includes what is going on at the target level of GDB, as it happens. The
17479 default is 0. Set it to 1 to track events, and to 2 to also track the
17480 value of large memory transfers. Changes to this flag do not take effect
17481 until the next time you connect to a target or use the @code{run} command.
17482 @item show debug target
17483 Displays the current state of displaying @value{GDBN} target debugging
17485 @item set debug timestamp
17486 @cindex timestampping debugging info
17487 Turns on or off display of timestamps with @value{GDBN} debugging info.
17488 When enabled, seconds and microseconds are displayed before each debugging
17490 @item show debug timestamp
17491 Displays the current state of displaying timestamps with @value{GDBN}
17493 @item set debugvarobj
17494 @cindex variable object debugging info
17495 Turns on or off display of @value{GDBN} variable object debugging
17496 info. The default is off.
17497 @item show debugvarobj
17498 Displays the current state of displaying @value{GDBN} variable object
17500 @item set debug xml
17501 @cindex XML parser debugging
17502 Turns on or off debugging messages for built-in XML parsers.
17503 @item show debug xml
17504 Displays the current state of XML debugging messages.
17507 @node Extending GDB
17508 @chapter Extending @value{GDBN}
17509 @cindex extending GDB
17511 @value{GDBN} provides two mechanisms for extension. The first is based
17512 on composition of @value{GDBN} commands, and the second is based on the
17513 Python scripting language.
17516 * Sequences:: Canned Sequences of Commands
17517 * Python:: Scripting @value{GDBN} using Python
17521 @section Canned Sequences of Commands
17523 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17524 Command Lists}), @value{GDBN} provides two ways to store sequences of
17525 commands for execution as a unit: user-defined commands and command
17529 * Define:: How to define your own commands
17530 * Hooks:: Hooks for user-defined commands
17531 * Command Files:: How to write scripts of commands to be stored in a file
17532 * Output:: Commands for controlled output
17536 @subsection User-defined Commands
17538 @cindex user-defined command
17539 @cindex arguments, to user-defined commands
17540 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17541 which you assign a new name as a command. This is done with the
17542 @code{define} command. User commands may accept up to 10 arguments
17543 separated by whitespace. Arguments are accessed within the user command
17544 via @code{$arg0@dots{}$arg9}. A trivial example:
17548 print $arg0 + $arg1 + $arg2
17553 To execute the command use:
17560 This defines the command @code{adder}, which prints the sum of
17561 its three arguments. Note the arguments are text substitutions, so they may
17562 reference variables, use complex expressions, or even perform inferior
17565 @cindex argument count in user-defined commands
17566 @cindex how many arguments (user-defined commands)
17567 In addition, @code{$argc} may be used to find out how many arguments have
17568 been passed. This expands to a number in the range 0@dots{}10.
17573 print $arg0 + $arg1
17576 print $arg0 + $arg1 + $arg2
17584 @item define @var{commandname}
17585 Define a command named @var{commandname}. If there is already a command
17586 by that name, you are asked to confirm that you want to redefine it.
17588 The definition of the command is made up of other @value{GDBN} command lines,
17589 which are given following the @code{define} command. The end of these
17590 commands is marked by a line containing @code{end}.
17593 @kindex end@r{ (user-defined commands)}
17594 @item document @var{commandname}
17595 Document the user-defined command @var{commandname}, so that it can be
17596 accessed by @code{help}. The command @var{commandname} must already be
17597 defined. This command reads lines of documentation just as @code{define}
17598 reads the lines of the command definition, ending with @code{end}.
17599 After the @code{document} command is finished, @code{help} on command
17600 @var{commandname} displays the documentation you have written.
17602 You may use the @code{document} command again to change the
17603 documentation of a command. Redefining the command with @code{define}
17604 does not change the documentation.
17606 @kindex dont-repeat
17607 @cindex don't repeat command
17609 Used inside a user-defined command, this tells @value{GDBN} that this
17610 command should not be repeated when the user hits @key{RET}
17611 (@pxref{Command Syntax, repeat last command}).
17613 @kindex help user-defined
17614 @item help user-defined
17615 List all user-defined commands, with the first line of the documentation
17620 @itemx show user @var{commandname}
17621 Display the @value{GDBN} commands used to define @var{commandname} (but
17622 not its documentation). If no @var{commandname} is given, display the
17623 definitions for all user-defined commands.
17625 @cindex infinite recursion in user-defined commands
17626 @kindex show max-user-call-depth
17627 @kindex set max-user-call-depth
17628 @item show max-user-call-depth
17629 @itemx set max-user-call-depth
17630 The value of @code{max-user-call-depth} controls how many recursion
17631 levels are allowed in user-defined commands before @value{GDBN} suspects an
17632 infinite recursion and aborts the command.
17635 In addition to the above commands, user-defined commands frequently
17636 use control flow commands, described in @ref{Command Files}.
17638 When user-defined commands are executed, the
17639 commands of the definition are not printed. An error in any command
17640 stops execution of the user-defined command.
17642 If used interactively, commands that would ask for confirmation proceed
17643 without asking when used inside a user-defined command. Many @value{GDBN}
17644 commands that normally print messages to say what they are doing omit the
17645 messages when used in a user-defined command.
17648 @subsection User-defined Command Hooks
17649 @cindex command hooks
17650 @cindex hooks, for commands
17651 @cindex hooks, pre-command
17654 You may define @dfn{hooks}, which are a special kind of user-defined
17655 command. Whenever you run the command @samp{foo}, if the user-defined
17656 command @samp{hook-foo} exists, it is executed (with no arguments)
17657 before that command.
17659 @cindex hooks, post-command
17661 A hook may also be defined which is run after the command you executed.
17662 Whenever you run the command @samp{foo}, if the user-defined command
17663 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17664 that command. Post-execution hooks may exist simultaneously with
17665 pre-execution hooks, for the same command.
17667 It is valid for a hook to call the command which it hooks. If this
17668 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17670 @c It would be nice if hookpost could be passed a parameter indicating
17671 @c if the command it hooks executed properly or not. FIXME!
17673 @kindex stop@r{, a pseudo-command}
17674 In addition, a pseudo-command, @samp{stop} exists. Defining
17675 (@samp{hook-stop}) makes the associated commands execute every time
17676 execution stops in your program: before breakpoint commands are run,
17677 displays are printed, or the stack frame is printed.
17679 For example, to ignore @code{SIGALRM} signals while
17680 single-stepping, but treat them normally during normal execution,
17685 handle SIGALRM nopass
17689 handle SIGALRM pass
17692 define hook-continue
17693 handle SIGALRM pass
17697 As a further example, to hook at the beginning and end of the @code{echo}
17698 command, and to add extra text to the beginning and end of the message,
17706 define hookpost-echo
17710 (@value{GDBP}) echo Hello World
17711 <<<---Hello World--->>>
17716 You can define a hook for any single-word command in @value{GDBN}, but
17717 not for command aliases; you should define a hook for the basic command
17718 name, e.g.@: @code{backtrace} rather than @code{bt}.
17719 @c FIXME! So how does Joe User discover whether a command is an alias
17721 If an error occurs during the execution of your hook, execution of
17722 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17723 (before the command that you actually typed had a chance to run).
17725 If you try to define a hook which does not match any known command, you
17726 get a warning from the @code{define} command.
17728 @node Command Files
17729 @subsection Command Files
17731 @cindex command files
17732 @cindex scripting commands
17733 A command file for @value{GDBN} is a text file made of lines that are
17734 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17735 also be included. An empty line in a command file does nothing; it
17736 does not mean to repeat the last command, as it would from the
17739 You can request the execution of a command file with the @code{source}
17744 @cindex execute commands from a file
17745 @item source [@code{-v}] @var{filename}
17746 Execute the command file @var{filename}.
17749 The lines in a command file are generally executed sequentially,
17750 unless the order of execution is changed by one of the
17751 @emph{flow-control commands} described below. The commands are not
17752 printed as they are executed. An error in any command terminates
17753 execution of the command file and control is returned to the console.
17755 @value{GDBN} searches for @var{filename} in the current directory and then
17756 on the search path (specified with the @samp{directory} command).
17758 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17759 each command as it is executed. The option must be given before
17760 @var{filename}, and is interpreted as part of the filename anywhere else.
17762 Commands that would ask for confirmation if used interactively proceed
17763 without asking when used in a command file. Many @value{GDBN} commands that
17764 normally print messages to say what they are doing omit the messages
17765 when called from command files.
17767 @value{GDBN} also accepts command input from standard input. In this
17768 mode, normal output goes to standard output and error output goes to
17769 standard error. Errors in a command file supplied on standard input do
17770 not terminate execution of the command file---execution continues with
17774 gdb < cmds > log 2>&1
17777 (The syntax above will vary depending on the shell used.) This example
17778 will execute commands from the file @file{cmds}. All output and errors
17779 would be directed to @file{log}.
17781 Since commands stored on command files tend to be more general than
17782 commands typed interactively, they frequently need to deal with
17783 complicated situations, such as different or unexpected values of
17784 variables and symbols, changes in how the program being debugged is
17785 built, etc. @value{GDBN} provides a set of flow-control commands to
17786 deal with these complexities. Using these commands, you can write
17787 complex scripts that loop over data structures, execute commands
17788 conditionally, etc.
17795 This command allows to include in your script conditionally executed
17796 commands. The @code{if} command takes a single argument, which is an
17797 expression to evaluate. It is followed by a series of commands that
17798 are executed only if the expression is true (its value is nonzero).
17799 There can then optionally be an @code{else} line, followed by a series
17800 of commands that are only executed if the expression was false. The
17801 end of the list is marked by a line containing @code{end}.
17805 This command allows to write loops. Its syntax is similar to
17806 @code{if}: the command takes a single argument, which is an expression
17807 to evaluate, and must be followed by the commands to execute, one per
17808 line, terminated by an @code{end}. These commands are called the
17809 @dfn{body} of the loop. The commands in the body of @code{while} are
17810 executed repeatedly as long as the expression evaluates to true.
17814 This command exits the @code{while} loop in whose body it is included.
17815 Execution of the script continues after that @code{while}s @code{end}
17818 @kindex loop_continue
17819 @item loop_continue
17820 This command skips the execution of the rest of the body of commands
17821 in the @code{while} loop in whose body it is included. Execution
17822 branches to the beginning of the @code{while} loop, where it evaluates
17823 the controlling expression.
17825 @kindex end@r{ (if/else/while commands)}
17827 Terminate the block of commands that are the body of @code{if},
17828 @code{else}, or @code{while} flow-control commands.
17833 @subsection Commands for Controlled Output
17835 During the execution of a command file or a user-defined command, normal
17836 @value{GDBN} output is suppressed; the only output that appears is what is
17837 explicitly printed by the commands in the definition. This section
17838 describes three commands useful for generating exactly the output you
17843 @item echo @var{text}
17844 @c I do not consider backslash-space a standard C escape sequence
17845 @c because it is not in ANSI.
17846 Print @var{text}. Nonprinting characters can be included in
17847 @var{text} using C escape sequences, such as @samp{\n} to print a
17848 newline. @strong{No newline is printed unless you specify one.}
17849 In addition to the standard C escape sequences, a backslash followed
17850 by a space stands for a space. This is useful for displaying a
17851 string with spaces at the beginning or the end, since leading and
17852 trailing spaces are otherwise trimmed from all arguments.
17853 To print @samp{@w{ }and foo =@w{ }}, use the command
17854 @samp{echo \@w{ }and foo = \@w{ }}.
17856 A backslash at the end of @var{text} can be used, as in C, to continue
17857 the command onto subsequent lines. For example,
17860 echo This is some text\n\
17861 which is continued\n\
17862 onto several lines.\n
17865 produces the same output as
17868 echo This is some text\n
17869 echo which is continued\n
17870 echo onto several lines.\n
17874 @item output @var{expression}
17875 Print the value of @var{expression} and nothing but that value: no
17876 newlines, no @samp{$@var{nn} = }. The value is not entered in the
17877 value history either. @xref{Expressions, ,Expressions}, for more information
17880 @item output/@var{fmt} @var{expression}
17881 Print the value of @var{expression} in format @var{fmt}. You can use
17882 the same formats as for @code{print}. @xref{Output Formats,,Output
17883 Formats}, for more information.
17886 @item printf @var{template}, @var{expressions}@dots{}
17887 Print the values of one or more @var{expressions} under the control of
17888 the string @var{template}. To print several values, make
17889 @var{expressions} be a comma-separated list of individual expressions,
17890 which may be either numbers or pointers. Their values are printed as
17891 specified by @var{template}, exactly as a C program would do by
17892 executing the code below:
17895 printf (@var{template}, @var{expressions}@dots{});
17898 As in @code{C} @code{printf}, ordinary characters in @var{template}
17899 are printed verbatim, while @dfn{conversion specification} introduced
17900 by the @samp{%} character cause subsequent @var{expressions} to be
17901 evaluated, their values converted and formatted according to type and
17902 style information encoded in the conversion specifications, and then
17905 For example, you can print two values in hex like this:
17908 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
17911 @code{printf} supports all the standard @code{C} conversion
17912 specifications, including the flags and modifiers between the @samp{%}
17913 character and the conversion letter, with the following exceptions:
17917 The argument-ordering modifiers, such as @samp{2$}, are not supported.
17920 The modifier @samp{*} is not supported for specifying precision or
17924 The @samp{'} flag (for separation of digits into groups according to
17925 @code{LC_NUMERIC'}) is not supported.
17928 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
17932 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
17935 The conversion letters @samp{a} and @samp{A} are not supported.
17939 Note that the @samp{ll} type modifier is supported only if the
17940 underlying @code{C} implementation used to build @value{GDBN} supports
17941 the @code{long long int} type, and the @samp{L} type modifier is
17942 supported only if @code{long double} type is available.
17944 As in @code{C}, @code{printf} supports simple backslash-escape
17945 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
17946 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
17947 single character. Octal and hexadecimal escape sequences are not
17950 Additionally, @code{printf} supports conversion specifications for DFP
17951 (@dfn{Decimal Floating Point}) types using the following length modifiers
17952 together with a floating point specifier.
17957 @samp{H} for printing @code{Decimal32} types.
17960 @samp{D} for printing @code{Decimal64} types.
17963 @samp{DD} for printing @code{Decimal128} types.
17966 If the underlying @code{C} implementation used to build @value{GDBN} has
17967 support for the three length modifiers for DFP types, other modifiers
17968 such as width and precision will also be available for @value{GDBN} to use.
17970 In case there is no such @code{C} support, no additional modifiers will be
17971 available and the value will be printed in the standard way.
17973 Here's an example of printing DFP types using the above conversion letters:
17975 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
17981 @section Scripting @value{GDBN} using Python
17982 @cindex python scripting
17983 @cindex scripting with python
17985 You can script @value{GDBN} using the @uref{http://www.python.org/,
17986 Python programming language}. This feature is available only if
17987 @value{GDBN} was configured using @option{--with-python}.
17990 * Python Commands:: Accessing Python from @value{GDBN}.
17991 * Python API:: Accessing @value{GDBN} from Python.
17994 @node Python Commands
17995 @subsection Python Commands
17996 @cindex python commands
17997 @cindex commands to access python
17999 @value{GDBN} provides one command for accessing the Python interpreter,
18000 and one related setting:
18004 @item python @r{[}@var{code}@r{]}
18005 The @code{python} command can be used to evaluate Python code.
18007 If given an argument, the @code{python} command will evaluate the
18008 argument as a Python command. For example:
18011 (@value{GDBP}) python print 23
18015 If you do not provide an argument to @code{python}, it will act as a
18016 multi-line command, like @code{define}. In this case, the Python
18017 script is made up of subsequent command lines, given after the
18018 @code{python} command. This command list is terminated using a line
18019 containing @code{end}. For example:
18022 (@value{GDBP}) python
18024 End with a line saying just "end".
18030 @kindex maint set python print-stack
18031 @item maint set python print-stack
18032 By default, @value{GDBN} will print a stack trace when an error occurs
18033 in a Python script. This can be controlled using @code{maint set
18034 python print-stack}: if @code{on}, the default, then Python stack
18035 printing is enabled; if @code{off}, then Python stack printing is
18040 @subsection Python API
18042 @cindex programming in python
18044 @cindex python stdout
18045 @cindex python pagination
18046 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18047 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18048 A Python program which outputs to one of these streams may have its
18049 output interrupted by the user (@pxref{Screen Size}). In this
18050 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18053 * Basic Python:: Basic Python Functions.
18054 * Exception Handling::
18055 * Values From Inferior::
18059 @subsubsection Basic Python
18061 @cindex python functions
18062 @cindex python module
18064 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18065 methods and classes added by @value{GDBN} are placed in this module.
18066 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18067 use in all scripts evaluated by the @code{python} command.
18069 @findex gdb.execute
18070 @defun execute command
18071 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18072 If a GDB exception happens while @var{command} runs, it is
18073 translated as described in @ref{Exception Handling,,Exception Handling}.
18074 If no exceptions occur, this function returns @code{None}.
18077 @findex gdb.get_parameter
18078 @defun get_parameter parameter
18079 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18080 string naming the parameter to look up; @var{parameter} may contain
18081 spaces if the parameter has a multi-part name. For example,
18082 @samp{print object} is a valid parameter name.
18084 If the named parameter does not exist, this function throws a
18085 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18086 a Python value of the appropriate type, and returned.
18090 @defun write string
18091 Print a string to @value{GDBN}'s paginated standard output stream.
18092 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18093 call this function.
18098 Flush @value{GDBN}'s paginated standard output stream. Flushing
18099 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18103 @node Exception Handling
18104 @subsubsection Exception Handling
18105 @cindex python exceptions
18106 @cindex exceptions, python
18108 When executing the @code{python} command, Python exceptions
18109 uncaught within the Python code are translated to calls to
18110 @value{GDBN} error-reporting mechanism. If the command that called
18111 @code{python} does not handle the error, @value{GDBN} will
18112 terminate it and print an error message containing the Python
18113 exception name, the associated value, and the Python call stack
18114 backtrace at the point where the exception was raised. Example:
18117 (@value{GDBP}) python print foo
18118 Traceback (most recent call last):
18119 File "<string>", line 1, in <module>
18120 NameError: name 'foo' is not defined
18123 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18124 code are converted to Python @code{RuntimeError} exceptions. User
18125 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18126 prompt) is translated to a Python @code{KeyboardInterrupt}
18127 exception. If you catch these exceptions in your Python code, your
18128 exception handler will see @code{RuntimeError} or
18129 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18130 message as its value, and the Python call stack backtrace at the
18131 Python statement closest to where the @value{GDBN} error occured as the
18134 @node Values From Inferior
18135 @subsubsection Values From Inferior
18136 @cindex values from inferior, with Python
18137 @cindex python, working with values from inferior
18139 @cindex @code{gdb.Value}
18140 @value{GDBN} provides values it obtains from the inferior program in
18141 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18142 for its internal bookkeeping of the inferior's values, and for
18143 fetching values when necessary.
18145 Inferior values that are simple scalars can be used directly in
18146 Python expressions that are valid for the value's data type. Here's
18147 an example for an integer or floating-point value @code{some_val}:
18154 As result of this, @code{bar} will also be a @code{gdb.Value} object
18155 whose values are of the same type as those of @code{some_val}.
18157 Inferior values that are structures or instances of some class can
18158 be accessed using the Python @dfn{dictionary syntax}. For example, if
18159 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18160 can access its @code{foo} element with:
18163 bar = some_val['foo']
18166 Again, @code{bar} will also be a @code{gdb.Value} object.
18168 For pointer data types, @code{gdb.Value} provides a method for
18169 dereferencing the pointer to obtain the object it points to.
18171 @defmethod Value dereference
18172 This method returns a new @code{gdb.Value} object whose contents is
18173 the object pointed to by the pointer. For example, if @code{foo} is
18174 a C pointer to an @code{int}, declared in your C program as
18181 then you can use the corresponding @code{gdb.Value} to access what
18182 @code{foo} points to like this:
18185 bar = foo.dereference ()
18188 The result @code{bar} will be a @code{gdb.Value} object holding the
18189 value pointed to by @code{foo}.
18193 @chapter Command Interpreters
18194 @cindex command interpreters
18196 @value{GDBN} supports multiple command interpreters, and some command
18197 infrastructure to allow users or user interface writers to switch
18198 between interpreters or run commands in other interpreters.
18200 @value{GDBN} currently supports two command interpreters, the console
18201 interpreter (sometimes called the command-line interpreter or @sc{cli})
18202 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18203 describes both of these interfaces in great detail.
18205 By default, @value{GDBN} will start with the console interpreter.
18206 However, the user may choose to start @value{GDBN} with another
18207 interpreter by specifying the @option{-i} or @option{--interpreter}
18208 startup options. Defined interpreters include:
18212 @cindex console interpreter
18213 The traditional console or command-line interpreter. This is the most often
18214 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18215 @value{GDBN} will use this interpreter.
18218 @cindex mi interpreter
18219 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18220 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18221 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18225 @cindex mi2 interpreter
18226 The current @sc{gdb/mi} interface.
18229 @cindex mi1 interpreter
18230 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18234 @cindex invoke another interpreter
18235 The interpreter being used by @value{GDBN} may not be dynamically
18236 switched at runtime. Although possible, this could lead to a very
18237 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18238 enters the command "interpreter-set console" in a console view,
18239 @value{GDBN} would switch to using the console interpreter, rendering
18240 the IDE inoperable!
18242 @kindex interpreter-exec
18243 Although you may only choose a single interpreter at startup, you may execute
18244 commands in any interpreter from the current interpreter using the appropriate
18245 command. If you are running the console interpreter, simply use the
18246 @code{interpreter-exec} command:
18249 interpreter-exec mi "-data-list-register-names"
18252 @sc{gdb/mi} has a similar command, although it is only available in versions of
18253 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18256 @chapter @value{GDBN} Text User Interface
18258 @cindex Text User Interface
18261 * TUI Overview:: TUI overview
18262 * TUI Keys:: TUI key bindings
18263 * TUI Single Key Mode:: TUI single key mode
18264 * TUI Commands:: TUI-specific commands
18265 * TUI Configuration:: TUI configuration variables
18268 The @value{GDBN} Text User Interface (TUI) is a terminal
18269 interface which uses the @code{curses} library to show the source
18270 file, the assembly output, the program registers and @value{GDBN}
18271 commands in separate text windows. The TUI mode is supported only
18272 on platforms where a suitable version of the @code{curses} library
18275 @pindex @value{GDBTUI}
18276 The TUI mode is enabled by default when you invoke @value{GDBN} as
18277 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
18278 You can also switch in and out of TUI mode while @value{GDBN} runs by
18279 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
18280 @xref{TUI Keys, ,TUI Key Bindings}.
18283 @section TUI Overview
18285 In TUI mode, @value{GDBN} can display several text windows:
18289 This window is the @value{GDBN} command window with the @value{GDBN}
18290 prompt and the @value{GDBN} output. The @value{GDBN} input is still
18291 managed using readline.
18294 The source window shows the source file of the program. The current
18295 line and active breakpoints are displayed in this window.
18298 The assembly window shows the disassembly output of the program.
18301 This window shows the processor registers. Registers are highlighted
18302 when their values change.
18305 The source and assembly windows show the current program position
18306 by highlighting the current line and marking it with a @samp{>} marker.
18307 Breakpoints are indicated with two markers. The first marker
18308 indicates the breakpoint type:
18312 Breakpoint which was hit at least once.
18315 Breakpoint which was never hit.
18318 Hardware breakpoint which was hit at least once.
18321 Hardware breakpoint which was never hit.
18324 The second marker indicates whether the breakpoint is enabled or not:
18328 Breakpoint is enabled.
18331 Breakpoint is disabled.
18334 The source, assembly and register windows are updated when the current
18335 thread changes, when the frame changes, or when the program counter
18338 These windows are not all visible at the same time. The command
18339 window is always visible. The others can be arranged in several
18350 source and assembly,
18353 source and registers, or
18356 assembly and registers.
18359 A status line above the command window shows the following information:
18363 Indicates the current @value{GDBN} target.
18364 (@pxref{Targets, ,Specifying a Debugging Target}).
18367 Gives the current process or thread number.
18368 When no process is being debugged, this field is set to @code{No process}.
18371 Gives the current function name for the selected frame.
18372 The name is demangled if demangling is turned on (@pxref{Print Settings}).
18373 When there is no symbol corresponding to the current program counter,
18374 the string @code{??} is displayed.
18377 Indicates the current line number for the selected frame.
18378 When the current line number is not known, the string @code{??} is displayed.
18381 Indicates the current program counter address.
18385 @section TUI Key Bindings
18386 @cindex TUI key bindings
18388 The TUI installs several key bindings in the readline keymaps
18389 (@pxref{Command Line Editing}). The following key bindings
18390 are installed for both TUI mode and the @value{GDBN} standard mode.
18399 Enter or leave the TUI mode. When leaving the TUI mode,
18400 the curses window management stops and @value{GDBN} operates using
18401 its standard mode, writing on the terminal directly. When reentering
18402 the TUI mode, control is given back to the curses windows.
18403 The screen is then refreshed.
18407 Use a TUI layout with only one window. The layout will
18408 either be @samp{source} or @samp{assembly}. When the TUI mode
18409 is not active, it will switch to the TUI mode.
18411 Think of this key binding as the Emacs @kbd{C-x 1} binding.
18415 Use a TUI layout with at least two windows. When the current
18416 layout already has two windows, the next layout with two windows is used.
18417 When a new layout is chosen, one window will always be common to the
18418 previous layout and the new one.
18420 Think of it as the Emacs @kbd{C-x 2} binding.
18424 Change the active window. The TUI associates several key bindings
18425 (like scrolling and arrow keys) with the active window. This command
18426 gives the focus to the next TUI window.
18428 Think of it as the Emacs @kbd{C-x o} binding.
18432 Switch in and out of the TUI SingleKey mode that binds single
18433 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
18436 The following key bindings only work in the TUI mode:
18441 Scroll the active window one page up.
18445 Scroll the active window one page down.
18449 Scroll the active window one line up.
18453 Scroll the active window one line down.
18457 Scroll the active window one column left.
18461 Scroll the active window one column right.
18465 Refresh the screen.
18468 Because the arrow keys scroll the active window in the TUI mode, they
18469 are not available for their normal use by readline unless the command
18470 window has the focus. When another window is active, you must use
18471 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
18472 and @kbd{C-f} to control the command window.
18474 @node TUI Single Key Mode
18475 @section TUI Single Key Mode
18476 @cindex TUI single key mode
18478 The TUI also provides a @dfn{SingleKey} mode, which binds several
18479 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
18480 switch into this mode, where the following key bindings are used:
18483 @kindex c @r{(SingleKey TUI key)}
18487 @kindex d @r{(SingleKey TUI key)}
18491 @kindex f @r{(SingleKey TUI key)}
18495 @kindex n @r{(SingleKey TUI key)}
18499 @kindex q @r{(SingleKey TUI key)}
18501 exit the SingleKey mode.
18503 @kindex r @r{(SingleKey TUI key)}
18507 @kindex s @r{(SingleKey TUI key)}
18511 @kindex u @r{(SingleKey TUI key)}
18515 @kindex v @r{(SingleKey TUI key)}
18519 @kindex w @r{(SingleKey TUI key)}
18524 Other keys temporarily switch to the @value{GDBN} command prompt.
18525 The key that was pressed is inserted in the editing buffer so that
18526 it is possible to type most @value{GDBN} commands without interaction
18527 with the TUI SingleKey mode. Once the command is entered the TUI
18528 SingleKey mode is restored. The only way to permanently leave
18529 this mode is by typing @kbd{q} or @kbd{C-x s}.
18533 @section TUI-specific Commands
18534 @cindex TUI commands
18536 The TUI has specific commands to control the text windows.
18537 These commands are always available, even when @value{GDBN} is not in
18538 the TUI mode. When @value{GDBN} is in the standard mode, most
18539 of these commands will automatically switch to the TUI mode.
18544 List and give the size of all displayed windows.
18548 Display the next layout.
18551 Display the previous layout.
18554 Display the source window only.
18557 Display the assembly window only.
18560 Display the source and assembly window.
18563 Display the register window together with the source or assembly window.
18567 Make the next window active for scrolling.
18570 Make the previous window active for scrolling.
18573 Make the source window active for scrolling.
18576 Make the assembly window active for scrolling.
18579 Make the register window active for scrolling.
18582 Make the command window active for scrolling.
18586 Refresh the screen. This is similar to typing @kbd{C-L}.
18588 @item tui reg float
18590 Show the floating point registers in the register window.
18592 @item tui reg general
18593 Show the general registers in the register window.
18596 Show the next register group. The list of register groups as well as
18597 their order is target specific. The predefined register groups are the
18598 following: @code{general}, @code{float}, @code{system}, @code{vector},
18599 @code{all}, @code{save}, @code{restore}.
18601 @item tui reg system
18602 Show the system registers in the register window.
18606 Update the source window and the current execution point.
18608 @item winheight @var{name} +@var{count}
18609 @itemx winheight @var{name} -@var{count}
18611 Change the height of the window @var{name} by @var{count}
18612 lines. Positive counts increase the height, while negative counts
18615 @item tabset @var{nchars}
18617 Set the width of tab stops to be @var{nchars} characters.
18620 @node TUI Configuration
18621 @section TUI Configuration Variables
18622 @cindex TUI configuration variables
18624 Several configuration variables control the appearance of TUI windows.
18627 @item set tui border-kind @var{kind}
18628 @kindex set tui border-kind
18629 Select the border appearance for the source, assembly and register windows.
18630 The possible values are the following:
18633 Use a space character to draw the border.
18636 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
18639 Use the Alternate Character Set to draw the border. The border is
18640 drawn using character line graphics if the terminal supports them.
18643 @item set tui border-mode @var{mode}
18644 @kindex set tui border-mode
18645 @itemx set tui active-border-mode @var{mode}
18646 @kindex set tui active-border-mode
18647 Select the display attributes for the borders of the inactive windows
18648 or the active window. The @var{mode} can be one of the following:
18651 Use normal attributes to display the border.
18657 Use reverse video mode.
18660 Use half bright mode.
18662 @item half-standout
18663 Use half bright and standout mode.
18666 Use extra bright or bold mode.
18668 @item bold-standout
18669 Use extra bright or bold and standout mode.
18674 @chapter Using @value{GDBN} under @sc{gnu} Emacs
18677 @cindex @sc{gnu} Emacs
18678 A special interface allows you to use @sc{gnu} Emacs to view (and
18679 edit) the source files for the program you are debugging with
18682 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
18683 executable file you want to debug as an argument. This command starts
18684 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
18685 created Emacs buffer.
18686 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
18688 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
18693 All ``terminal'' input and output goes through an Emacs buffer, called
18696 This applies both to @value{GDBN} commands and their output, and to the input
18697 and output done by the program you are debugging.
18699 This is useful because it means that you can copy the text of previous
18700 commands and input them again; you can even use parts of the output
18703 All the facilities of Emacs' Shell mode are available for interacting
18704 with your program. In particular, you can send signals the usual
18705 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
18709 @value{GDBN} displays source code through Emacs.
18711 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
18712 source file for that frame and puts an arrow (@samp{=>}) at the
18713 left margin of the current line. Emacs uses a separate buffer for
18714 source display, and splits the screen to show both your @value{GDBN} session
18717 Explicit @value{GDBN} @code{list} or search commands still produce output as
18718 usual, but you probably have no reason to use them from Emacs.
18721 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
18722 a graphical mode, enabled by default, which provides further buffers
18723 that can control the execution and describe the state of your program.
18724 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
18726 If you specify an absolute file name when prompted for the @kbd{M-x
18727 gdb} argument, then Emacs sets your current working directory to where
18728 your program resides. If you only specify the file name, then Emacs
18729 sets your current working directory to to the directory associated
18730 with the previous buffer. In this case, @value{GDBN} may find your
18731 program by searching your environment's @code{PATH} variable, but on
18732 some operating systems it might not find the source. So, although the
18733 @value{GDBN} input and output session proceeds normally, the auxiliary
18734 buffer does not display the current source and line of execution.
18736 The initial working directory of @value{GDBN} is printed on the top
18737 line of the GUD buffer and this serves as a default for the commands
18738 that specify files for @value{GDBN} to operate on. @xref{Files,
18739 ,Commands to Specify Files}.
18741 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
18742 need to call @value{GDBN} by a different name (for example, if you
18743 keep several configurations around, with different names) you can
18744 customize the Emacs variable @code{gud-gdb-command-name} to run the
18747 In the GUD buffer, you can use these special Emacs commands in
18748 addition to the standard Shell mode commands:
18752 Describe the features of Emacs' GUD Mode.
18755 Execute to another source line, like the @value{GDBN} @code{step} command; also
18756 update the display window to show the current file and location.
18759 Execute to next source line in this function, skipping all function
18760 calls, like the @value{GDBN} @code{next} command. Then update the display window
18761 to show the current file and location.
18764 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
18765 display window accordingly.
18768 Execute until exit from the selected stack frame, like the @value{GDBN}
18769 @code{finish} command.
18772 Continue execution of your program, like the @value{GDBN} @code{continue}
18776 Go up the number of frames indicated by the numeric argument
18777 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
18778 like the @value{GDBN} @code{up} command.
18781 Go down the number of frames indicated by the numeric argument, like the
18782 @value{GDBN} @code{down} command.
18785 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
18786 tells @value{GDBN} to set a breakpoint on the source line point is on.
18788 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
18789 separate frame which shows a backtrace when the GUD buffer is current.
18790 Move point to any frame in the stack and type @key{RET} to make it
18791 become the current frame and display the associated source in the
18792 source buffer. Alternatively, click @kbd{Mouse-2} to make the
18793 selected frame become the current one. In graphical mode, the
18794 speedbar displays watch expressions.
18796 If you accidentally delete the source-display buffer, an easy way to get
18797 it back is to type the command @code{f} in the @value{GDBN} buffer, to
18798 request a frame display; when you run under Emacs, this recreates
18799 the source buffer if necessary to show you the context of the current
18802 The source files displayed in Emacs are in ordinary Emacs buffers
18803 which are visiting the source files in the usual way. You can edit
18804 the files with these buffers if you wish; but keep in mind that @value{GDBN}
18805 communicates with Emacs in terms of line numbers. If you add or
18806 delete lines from the text, the line numbers that @value{GDBN} knows cease
18807 to correspond properly with the code.
18809 A more detailed description of Emacs' interaction with @value{GDBN} is
18810 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
18813 @c The following dropped because Epoch is nonstandard. Reactivate
18814 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
18816 @kindex Emacs Epoch environment
18820 Version 18 of @sc{gnu} Emacs has a built-in window system
18821 called the @code{epoch}
18822 environment. Users of this environment can use a new command,
18823 @code{inspect} which performs identically to @code{print} except that
18824 each value is printed in its own window.
18829 @chapter The @sc{gdb/mi} Interface
18831 @unnumberedsec Function and Purpose
18833 @cindex @sc{gdb/mi}, its purpose
18834 @sc{gdb/mi} is a line based machine oriented text interface to
18835 @value{GDBN} and is activated by specifying using the
18836 @option{--interpreter} command line option (@pxref{Mode Options}). It
18837 is specifically intended to support the development of systems which
18838 use the debugger as just one small component of a larger system.
18840 This chapter is a specification of the @sc{gdb/mi} interface. It is written
18841 in the form of a reference manual.
18843 Note that @sc{gdb/mi} is still under construction, so some of the
18844 features described below are incomplete and subject to change
18845 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
18847 @unnumberedsec Notation and Terminology
18849 @cindex notational conventions, for @sc{gdb/mi}
18850 This chapter uses the following notation:
18854 @code{|} separates two alternatives.
18857 @code{[ @var{something} ]} indicates that @var{something} is optional:
18858 it may or may not be given.
18861 @code{( @var{group} )*} means that @var{group} inside the parentheses
18862 may repeat zero or more times.
18865 @code{( @var{group} )+} means that @var{group} inside the parentheses
18866 may repeat one or more times.
18869 @code{"@var{string}"} means a literal @var{string}.
18873 @heading Dependencies
18877 * GDB/MI General Design::
18878 * GDB/MI Command Syntax::
18879 * GDB/MI Compatibility with CLI::
18880 * GDB/MI Development and Front Ends::
18881 * GDB/MI Output Records::
18882 * GDB/MI Simple Examples::
18883 * GDB/MI Command Description Format::
18884 * GDB/MI Breakpoint Commands::
18885 * GDB/MI Program Context::
18886 * GDB/MI Thread Commands::
18887 * GDB/MI Program Execution::
18888 * GDB/MI Stack Manipulation::
18889 * GDB/MI Variable Objects::
18890 * GDB/MI Data Manipulation::
18891 * GDB/MI Tracepoint Commands::
18892 * GDB/MI Symbol Query::
18893 * GDB/MI File Commands::
18895 * GDB/MI Kod Commands::
18896 * GDB/MI Memory Overlay Commands::
18897 * GDB/MI Signal Handling Commands::
18899 * GDB/MI Target Manipulation::
18900 * GDB/MI File Transfer Commands::
18901 * GDB/MI Miscellaneous Commands::
18904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18905 @node GDB/MI General Design
18906 @section @sc{gdb/mi} General Design
18907 @cindex GDB/MI General Design
18909 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
18910 parts---commands sent to @value{GDBN}, responses to those commands
18911 and notifications. Each command results in exactly one response,
18912 indicating either successful completion of the command, or an error.
18913 For the commands that do not resume the target, the response contains the
18914 requested information. For the commands that resume the target, the
18915 response only indicates whether the target was successfully resumed.
18916 Notifications is the mechanism for reporting changes in the state of the
18917 target, or in @value{GDBN} state, that cannot conveniently be associated with
18918 a command and reported as part of that command response.
18920 The important examples of notifications are:
18924 Exec notifications. These are used to report changes in
18925 target state---when a target is resumed, or stopped. It would not
18926 be feasible to include this information in response of resuming
18927 commands, because one resume commands can result in multiple events in
18928 different threads. Also, quite some time may pass before any event
18929 happens in the target, while a frontend needs to know whether the resuming
18930 command itself was successfully executed.
18933 Console output, and status notifications. Console output
18934 notifications are used to report output of CLI commands, as well as
18935 diagnostics for other commands. Status notifications are used to
18936 report the progress of a long-running operation. Naturally, including
18937 this information in command response would mean no output is produced
18938 until the command is finished, which is undesirable.
18941 General notifications. Commands may have various side effects on
18942 the @value{GDBN} or target state beyond their official purpose. For example,
18943 a command may change the selected thread. Although such changes can
18944 be included in command response, using notification allows for more
18945 orthogonal frontend design.
18949 There's no guarantee that whenever an MI command reports an error,
18950 @value{GDBN} or the target are in any specific state, and especially,
18951 the state is not reverted to the state before the MI command was
18952 processed. Therefore, whenever an MI command results in an error,
18953 we recommend that the frontend refreshes all the information shown in
18954 the user interface.
18956 @subsection Context management
18958 In most cases when @value{GDBN} accesses the target, this access is
18959 done in context of a specific thread and frame (@pxref{Frames}).
18960 Often, even when accessing global data, the target requires that a thread
18961 be specified. The CLI interface maintains the selected thread and frame,
18962 and supplies them to target on each command. This is convenient,
18963 because a command line user would not want to specify that information
18964 explicitly on each command, and because user interacts with
18965 @value{GDBN} via a single terminal, so no confusion is possible as
18966 to what thread and frame are the current ones.
18968 In the case of MI, the concept of selected thread and frame is less
18969 useful. First, a frontend can easily remember this information
18970 itself. Second, a graphical frontend can have more than one window,
18971 each one used for debugging a different thread, and the frontend might
18972 want to access additional threads for internal purposes. This
18973 increases the risk that by relying on implicitly selected thread, the
18974 frontend may be operating on a wrong one. Therefore, each MI command
18975 should explicitly specify which thread and frame to operate on. To
18976 make it possible, each MI command accepts the @samp{--thread} and
18977 @samp{--frame} options, the value to each is @value{GDBN} identifier
18978 for thread and frame to operate on.
18980 Usually, each top-level window in a frontend allows the user to select
18981 a thread and a frame, and remembers the user selection for further
18982 operations. However, in some cases @value{GDBN} may suggest that the
18983 current thread be changed. For example, when stopping on a breakpoint
18984 it is reasonable to switch to the thread where breakpoint is hit. For
18985 another example, if the user issues the CLI @samp{thread} command via
18986 the frontend, it is desirable to change the frontend's selected thread to the
18987 one specified by user. @value{GDBN} communicates the suggestion to
18988 change current thread using the @samp{=thread-selected} notification.
18989 No such notification is available for the selected frame at the moment.
18991 Note that historically, MI shares the selected thread with CLI, so
18992 frontends used the @code{-thread-select} to execute commands in the
18993 right context. However, getting this to work right is cumbersome. The
18994 simplest way is for frontend to emit @code{-thread-select} command
18995 before every command. This doubles the number of commands that need
18996 to be sent. The alternative approach is to suppress @code{-thread-select}
18997 if the selected thread in @value{GDBN} is supposed to be identical to the
18998 thread the frontend wants to operate on. However, getting this
18999 optimization right can be tricky. In particular, if the frontend
19000 sends several commands to @value{GDBN}, and one of the commands changes the
19001 selected thread, then the behaviour of subsequent commands will
19002 change. So, a frontend should either wait for response from such
19003 problematic commands, or explicitly add @code{-thread-select} for
19004 all subsequent commands. No frontend is known to do this exactly
19005 right, so it is suggested to just always pass the @samp{--thread} and
19006 @samp{--frame} options.
19008 @subsection Asynchronous command execution and non-stop mode
19010 On some targets, @value{GDBN} is capable of processing MI commands
19011 even while the target is running. This is called @dfn{asynchronous
19012 command execution} (@pxref{Background Execution}). The frontend may
19013 specify a preferrence for asynchronous execution using the
19014 @code{-gdb-set target-async 1} command, which should be emitted before
19015 either running the executable or attaching to the target. After the
19016 frontend has started the executable or attached to the target, it can
19017 find if asynchronous execution is enabled using the
19018 @code{-list-target-features} command.
19020 Even if @value{GDBN} can accept a command while target is running,
19021 many commands that access the target do not work when the target is
19022 running. Therefore, asynchronous command execution is most useful
19023 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19024 it is possible to examine the state of one thread, while other threads
19027 When a given thread is running, MI commands that try to access the
19028 target in the context of that thread may not work, or may work only on
19029 some targets. In particular, commands that try to operate on thread's
19030 stack will not work, on any target. Commands that read memory, or
19031 modify breakpoints, may work or not work, depending on the target. Note
19032 that even commands that operate on global state, such as @code{print},
19033 @code{set}, and breakpoint commands, still access the target in the
19034 context of a specific thread, so frontend should try to find a
19035 stopped thread and perform the operation on that thread (using the
19036 @samp{--thread} option).
19038 Which commands will work in the context of a running thread is
19039 highly target dependent. However, the two commands
19040 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19041 to find the state of a thread, will always work.
19043 @subsection Thread groups
19044 @value{GDBN} may be used to debug several processes at the same time.
19045 On some platfroms, @value{GDBN} may support debugging of several
19046 hardware systems, each one having several cores with several different
19047 processes running on each core. This section describes the MI
19048 mechanism to support such debugging scenarios.
19050 The key observation is that regardless of the structure of the
19051 target, MI can have a global list of threads, because most commands that
19052 accept the @samp{--thread} option do not need to know what process that
19053 thread belongs to. Therefore, it is not necessary to introduce
19054 neither additional @samp{--process} option, nor an notion of the
19055 current process in the MI interface. The only strictly new feature
19056 that is required is the ability to find how the threads are grouped
19059 To allow the user to discover such grouping, and to support arbitrary
19060 hierarchy of machines/cores/processes, MI introduces the concept of a
19061 @dfn{thread group}. Thread group is a collection of threads and other
19062 thread groups. A thread group always has a string identifier, a type,
19063 and may have additional attributes specific to the type. A new
19064 command, @code{-list-thread-groups}, returns the list of top-level
19065 thread groups, which correspond to processes that @value{GDBN} is
19066 debugging at the moment. By passing an identifier of a thread group
19067 to the @code{-list-thread-groups} command, it is possible to obtain
19068 the members of specific thread group.
19070 To allow the user to easily discover processes, and other objects, he
19071 wishes to debug, a concept of @dfn{available thread group} is
19072 introduced. Available thread group is an thread group that
19073 @value{GDBN} is not debugging, but that can be attached to, using the
19074 @code{-target-attach} command. The list of available top-level thread
19075 groups can be obtained using @samp{-list-thread-groups --available}.
19076 In general, the content of a thread group may be only retrieved only
19077 after attaching to that thread group.
19079 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19080 @node GDB/MI Command Syntax
19081 @section @sc{gdb/mi} Command Syntax
19084 * GDB/MI Input Syntax::
19085 * GDB/MI Output Syntax::
19088 @node GDB/MI Input Syntax
19089 @subsection @sc{gdb/mi} Input Syntax
19091 @cindex input syntax for @sc{gdb/mi}
19092 @cindex @sc{gdb/mi}, input syntax
19094 @item @var{command} @expansion{}
19095 @code{@var{cli-command} | @var{mi-command}}
19097 @item @var{cli-command} @expansion{}
19098 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19099 @var{cli-command} is any existing @value{GDBN} CLI command.
19101 @item @var{mi-command} @expansion{}
19102 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19103 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19105 @item @var{token} @expansion{}
19106 "any sequence of digits"
19108 @item @var{option} @expansion{}
19109 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19111 @item @var{parameter} @expansion{}
19112 @code{@var{non-blank-sequence} | @var{c-string}}
19114 @item @var{operation} @expansion{}
19115 @emph{any of the operations described in this chapter}
19117 @item @var{non-blank-sequence} @expansion{}
19118 @emph{anything, provided it doesn't contain special characters such as
19119 "-", @var{nl}, """ and of course " "}
19121 @item @var{c-string} @expansion{}
19122 @code{""" @var{seven-bit-iso-c-string-content} """}
19124 @item @var{nl} @expansion{}
19133 The CLI commands are still handled by the @sc{mi} interpreter; their
19134 output is described below.
19137 The @code{@var{token}}, when present, is passed back when the command
19141 Some @sc{mi} commands accept optional arguments as part of the parameter
19142 list. Each option is identified by a leading @samp{-} (dash) and may be
19143 followed by an optional argument parameter. Options occur first in the
19144 parameter list and can be delimited from normal parameters using
19145 @samp{--} (this is useful when some parameters begin with a dash).
19152 We want easy access to the existing CLI syntax (for debugging).
19155 We want it to be easy to spot a @sc{mi} operation.
19158 @node GDB/MI Output Syntax
19159 @subsection @sc{gdb/mi} Output Syntax
19161 @cindex output syntax of @sc{gdb/mi}
19162 @cindex @sc{gdb/mi}, output syntax
19163 The output from @sc{gdb/mi} consists of zero or more out-of-band records
19164 followed, optionally, by a single result record. This result record
19165 is for the most recent command. The sequence of output records is
19166 terminated by @samp{(gdb)}.
19168 If an input command was prefixed with a @code{@var{token}} then the
19169 corresponding output for that command will also be prefixed by that same
19173 @item @var{output} @expansion{}
19174 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
19176 @item @var{result-record} @expansion{}
19177 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
19179 @item @var{out-of-band-record} @expansion{}
19180 @code{@var{async-record} | @var{stream-record}}
19182 @item @var{async-record} @expansion{}
19183 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
19185 @item @var{exec-async-output} @expansion{}
19186 @code{[ @var{token} ] "*" @var{async-output}}
19188 @item @var{status-async-output} @expansion{}
19189 @code{[ @var{token} ] "+" @var{async-output}}
19191 @item @var{notify-async-output} @expansion{}
19192 @code{[ @var{token} ] "=" @var{async-output}}
19194 @item @var{async-output} @expansion{}
19195 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
19197 @item @var{result-class} @expansion{}
19198 @code{"done" | "running" | "connected" | "error" | "exit"}
19200 @item @var{async-class} @expansion{}
19201 @code{"stopped" | @var{others}} (where @var{others} will be added
19202 depending on the needs---this is still in development).
19204 @item @var{result} @expansion{}
19205 @code{ @var{variable} "=" @var{value}}
19207 @item @var{variable} @expansion{}
19208 @code{ @var{string} }
19210 @item @var{value} @expansion{}
19211 @code{ @var{const} | @var{tuple} | @var{list} }
19213 @item @var{const} @expansion{}
19214 @code{@var{c-string}}
19216 @item @var{tuple} @expansion{}
19217 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
19219 @item @var{list} @expansion{}
19220 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
19221 @var{result} ( "," @var{result} )* "]" }
19223 @item @var{stream-record} @expansion{}
19224 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
19226 @item @var{console-stream-output} @expansion{}
19227 @code{"~" @var{c-string}}
19229 @item @var{target-stream-output} @expansion{}
19230 @code{"@@" @var{c-string}}
19232 @item @var{log-stream-output} @expansion{}
19233 @code{"&" @var{c-string}}
19235 @item @var{nl} @expansion{}
19238 @item @var{token} @expansion{}
19239 @emph{any sequence of digits}.
19247 All output sequences end in a single line containing a period.
19250 The @code{@var{token}} is from the corresponding request. Note that
19251 for all async output, while the token is allowed by the grammar and
19252 may be output by future versions of @value{GDBN} for select async
19253 output messages, it is generally omitted. Frontends should treat
19254 all async output as reporting general changes in the state of the
19255 target and there should be no need to associate async output to any
19259 @cindex status output in @sc{gdb/mi}
19260 @var{status-async-output} contains on-going status information about the
19261 progress of a slow operation. It can be discarded. All status output is
19262 prefixed by @samp{+}.
19265 @cindex async output in @sc{gdb/mi}
19266 @var{exec-async-output} contains asynchronous state change on the target
19267 (stopped, started, disappeared). All async output is prefixed by
19271 @cindex notify output in @sc{gdb/mi}
19272 @var{notify-async-output} contains supplementary information that the
19273 client should handle (e.g., a new breakpoint information). All notify
19274 output is prefixed by @samp{=}.
19277 @cindex console output in @sc{gdb/mi}
19278 @var{console-stream-output} is output that should be displayed as is in the
19279 console. It is the textual response to a CLI command. All the console
19280 output is prefixed by @samp{~}.
19283 @cindex target output in @sc{gdb/mi}
19284 @var{target-stream-output} is the output produced by the target program.
19285 All the target output is prefixed by @samp{@@}.
19288 @cindex log output in @sc{gdb/mi}
19289 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
19290 instance messages that should be displayed as part of an error log. All
19291 the log output is prefixed by @samp{&}.
19294 @cindex list output in @sc{gdb/mi}
19295 New @sc{gdb/mi} commands should only output @var{lists} containing
19301 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
19302 details about the various output records.
19304 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19305 @node GDB/MI Compatibility with CLI
19306 @section @sc{gdb/mi} Compatibility with CLI
19308 @cindex compatibility, @sc{gdb/mi} and CLI
19309 @cindex @sc{gdb/mi}, compatibility with CLI
19311 For the developers convenience CLI commands can be entered directly,
19312 but there may be some unexpected behaviour. For example, commands
19313 that query the user will behave as if the user replied yes, breakpoint
19314 command lists are not executed and some CLI commands, such as
19315 @code{if}, @code{when} and @code{define}, prompt for further input with
19316 @samp{>}, which is not valid MI output.
19318 This feature may be removed at some stage in the future and it is
19319 recommended that front ends use the @code{-interpreter-exec} command
19320 (@pxref{-interpreter-exec}).
19322 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19323 @node GDB/MI Development and Front Ends
19324 @section @sc{gdb/mi} Development and Front Ends
19325 @cindex @sc{gdb/mi} development
19327 The application which takes the MI output and presents the state of the
19328 program being debugged to the user is called a @dfn{front end}.
19330 Although @sc{gdb/mi} is still incomplete, it is currently being used
19331 by a variety of front ends to @value{GDBN}. This makes it difficult
19332 to introduce new functionality without breaking existing usage. This
19333 section tries to minimize the problems by describing how the protocol
19336 Some changes in MI need not break a carefully designed front end, and
19337 for these the MI version will remain unchanged. The following is a
19338 list of changes that may occur within one level, so front ends should
19339 parse MI output in a way that can handle them:
19343 New MI commands may be added.
19346 New fields may be added to the output of any MI command.
19349 The range of values for fields with specified values, e.g.,
19350 @code{in_scope} (@pxref{-var-update}) may be extended.
19352 @c The format of field's content e.g type prefix, may change so parse it
19353 @c at your own risk. Yes, in general?
19355 @c The order of fields may change? Shouldn't really matter but it might
19356 @c resolve inconsistencies.
19359 If the changes are likely to break front ends, the MI version level
19360 will be increased by one. This will allow the front end to parse the
19361 output according to the MI version. Apart from mi0, new versions of
19362 @value{GDBN} will not support old versions of MI and it will be the
19363 responsibility of the front end to work with the new one.
19365 @c Starting with mi3, add a new command -mi-version that prints the MI
19368 The best way to avoid unexpected changes in MI that might break your front
19369 end is to make your project known to @value{GDBN} developers and
19370 follow development on @email{gdb@@sourceware.org} and
19371 @email{gdb-patches@@sourceware.org}.
19372 @cindex mailing lists
19374 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19375 @node GDB/MI Output Records
19376 @section @sc{gdb/mi} Output Records
19379 * GDB/MI Result Records::
19380 * GDB/MI Stream Records::
19381 * GDB/MI Async Records::
19382 * GDB/MI Frame Information::
19385 @node GDB/MI Result Records
19386 @subsection @sc{gdb/mi} Result Records
19388 @cindex result records in @sc{gdb/mi}
19389 @cindex @sc{gdb/mi}, result records
19390 In addition to a number of out-of-band notifications, the response to a
19391 @sc{gdb/mi} command includes one of the following result indications:
19395 @item "^done" [ "," @var{results} ]
19396 The synchronous operation was successful, @code{@var{results}} are the return
19401 @c Is this one correct? Should it be an out-of-band notification?
19402 The asynchronous operation was successfully started. The target is
19407 @value{GDBN} has connected to a remote target.
19409 @item "^error" "," @var{c-string}
19411 The operation failed. The @code{@var{c-string}} contains the corresponding
19416 @value{GDBN} has terminated.
19420 @node GDB/MI Stream Records
19421 @subsection @sc{gdb/mi} Stream Records
19423 @cindex @sc{gdb/mi}, stream records
19424 @cindex stream records in @sc{gdb/mi}
19425 @value{GDBN} internally maintains a number of output streams: the console, the
19426 target, and the log. The output intended for each of these streams is
19427 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
19429 Each stream record begins with a unique @dfn{prefix character} which
19430 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
19431 Syntax}). In addition to the prefix, each stream record contains a
19432 @code{@var{string-output}}. This is either raw text (with an implicit new
19433 line) or a quoted C string (which does not contain an implicit newline).
19436 @item "~" @var{string-output}
19437 The console output stream contains text that should be displayed in the
19438 CLI console window. It contains the textual responses to CLI commands.
19440 @item "@@" @var{string-output}
19441 The target output stream contains any textual output from the running
19442 target. This is only present when GDB's event loop is truly
19443 asynchronous, which is currently only the case for remote targets.
19445 @item "&" @var{string-output}
19446 The log stream contains debugging messages being produced by @value{GDBN}'s
19450 @node GDB/MI Async Records
19451 @subsection @sc{gdb/mi} Async Records
19453 @cindex async records in @sc{gdb/mi}
19454 @cindex @sc{gdb/mi}, async records
19455 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
19456 additional changes that have occurred. Those changes can either be a
19457 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
19458 target activity (e.g., target stopped).
19460 The following is the list of possible async records:
19464 @item *running,thread-id="@var{thread}"
19465 The target is now running. The @var{thread} field tells which
19466 specific thread is now running, and can be @samp{all} if all threads
19467 are running. The frontend should assume that no interaction with a
19468 running thread is possible after this notification is produced.
19469 The frontend should not assume that this notification is output
19470 only once for any command. @value{GDBN} may emit this notification
19471 several times, either for different threads, because it cannot resume
19472 all threads together, or even for a single thread, if the thread must
19473 be stepped though some code before letting it run freely.
19475 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
19476 The target has stopped. The @var{reason} field can have one of the
19480 @item breakpoint-hit
19481 A breakpoint was reached.
19482 @item watchpoint-trigger
19483 A watchpoint was triggered.
19484 @item read-watchpoint-trigger
19485 A read watchpoint was triggered.
19486 @item access-watchpoint-trigger
19487 An access watchpoint was triggered.
19488 @item function-finished
19489 An -exec-finish or similar CLI command was accomplished.
19490 @item location-reached
19491 An -exec-until or similar CLI command was accomplished.
19492 @item watchpoint-scope
19493 A watchpoint has gone out of scope.
19494 @item end-stepping-range
19495 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
19496 similar CLI command was accomplished.
19497 @item exited-signalled
19498 The inferior exited because of a signal.
19500 The inferior exited.
19501 @item exited-normally
19502 The inferior exited normally.
19503 @item signal-received
19504 A signal was received by the inferior.
19507 The @var{id} field identifies the thread that directly caused the stop
19508 -- for example by hitting a breakpoint. Depending on whether all-stop
19509 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
19510 stop all threads, or only the thread that directly triggered the stop.
19511 If all threads are stopped, the @var{stopped} field will have the
19512 value of @code{"all"}. Otherwise, the value of the @var{stopped}
19513 field will be a list of thread identifiers. Presently, this list will
19514 always include a single thread, but frontend should be prepared to see
19515 several threads in the list.
19517 @item =thread-group-created,id="@var{id}"
19518 @itemx =thread-group-exited,id="@var{id}"
19519 A thread thread group either was attached to, or has exited/detached
19520 from. The @var{id} field contains the @value{GDBN} identifier of the
19523 @item =thread-created,id="@var{id}",group-id="@var{gid}"
19524 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
19525 A thread either was created, or has exited. The @var{id} field
19526 contains the @value{GDBN} identifier of the thread. The @var{gid}
19527 field identifies the thread group this thread belongs to.
19529 @item =thread-selected,id="@var{id}"
19530 Informs that the selected thread was changed as result of the last
19531 command. This notification is not emitted as result of @code{-thread-select}
19532 command but is emitted whenever an MI command that is not documented
19533 to change the selected thread actually changes it. In particular,
19534 invoking, directly or indirectly (via user-defined command), the CLI
19535 @code{thread} command, will generate this notification.
19537 We suggest that in response to this notification, front ends
19538 highlight the selected thread and cause subsequent commands to apply to
19543 @node GDB/MI Frame Information
19544 @subsection @sc{gdb/mi} Frame Information
19546 Response from many MI commands includes an information about stack
19547 frame. This information is a tuple that may have the following
19552 The level of the stack frame. The innermost frame has the level of
19553 zero. This field is always present.
19556 The name of the function corresponding to the frame. This field may
19557 be absent if @value{GDBN} is unable to determine the function name.
19560 The code address for the frame. This field is always present.
19563 The name of the source files that correspond to the frame's code
19564 address. This field may be absent.
19567 The source line corresponding to the frames' code address. This field
19571 The name of the binary file (either executable or shared library) the
19572 corresponds to the frame's code address. This field may be absent.
19577 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19578 @node GDB/MI Simple Examples
19579 @section Simple Examples of @sc{gdb/mi} Interaction
19580 @cindex @sc{gdb/mi}, simple examples
19582 This subsection presents several simple examples of interaction using
19583 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
19584 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
19585 the output received from @sc{gdb/mi}.
19587 Note the line breaks shown in the examples are here only for
19588 readability, they don't appear in the real output.
19590 @subheading Setting a Breakpoint
19592 Setting a breakpoint generates synchronous output which contains detailed
19593 information of the breakpoint.
19596 -> -break-insert main
19597 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
19598 enabled="y",addr="0x08048564",func="main",file="myprog.c",
19599 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
19603 @subheading Program Execution
19605 Program execution generates asynchronous records and MI gives the
19606 reason that execution stopped.
19612 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
19613 frame=@{addr="0x08048564",func="main",
19614 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
19615 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
19620 <- *stopped,reason="exited-normally"
19624 @subheading Quitting @value{GDBN}
19626 Quitting @value{GDBN} just prints the result class @samp{^exit}.
19634 @subheading A Bad Command
19636 Here's what happens if you pass a non-existent command:
19640 <- ^error,msg="Undefined MI command: rubbish"
19645 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19646 @node GDB/MI Command Description Format
19647 @section @sc{gdb/mi} Command Description Format
19649 The remaining sections describe blocks of commands. Each block of
19650 commands is laid out in a fashion similar to this section.
19652 @subheading Motivation
19654 The motivation for this collection of commands.
19656 @subheading Introduction
19658 A brief introduction to this collection of commands as a whole.
19660 @subheading Commands
19662 For each command in the block, the following is described:
19664 @subsubheading Synopsis
19667 -command @var{args}@dots{}
19670 @subsubheading Result
19672 @subsubheading @value{GDBN} Command
19674 The corresponding @value{GDBN} CLI command(s), if any.
19676 @subsubheading Example
19678 Example(s) formatted for readability. Some of the described commands have
19679 not been implemented yet and these are labeled N.A.@: (not available).
19682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19683 @node GDB/MI Breakpoint Commands
19684 @section @sc{gdb/mi} Breakpoint Commands
19686 @cindex breakpoint commands for @sc{gdb/mi}
19687 @cindex @sc{gdb/mi}, breakpoint commands
19688 This section documents @sc{gdb/mi} commands for manipulating
19691 @subheading The @code{-break-after} Command
19692 @findex -break-after
19694 @subsubheading Synopsis
19697 -break-after @var{number} @var{count}
19700 The breakpoint number @var{number} is not in effect until it has been
19701 hit @var{count} times. To see how this is reflected in the output of
19702 the @samp{-break-list} command, see the description of the
19703 @samp{-break-list} command below.
19705 @subsubheading @value{GDBN} Command
19707 The corresponding @value{GDBN} command is @samp{ignore}.
19709 @subsubheading Example
19714 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
19715 enabled="y",addr="0x000100d0",func="main",file="hello.c",
19716 fullname="/home/foo/hello.c",line="5",times="0"@}
19723 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19724 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19725 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19726 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19727 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19728 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19729 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19730 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19731 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19732 line="5",times="0",ignore="3"@}]@}
19737 @subheading The @code{-break-catch} Command
19738 @findex -break-catch
19740 @subheading The @code{-break-commands} Command
19741 @findex -break-commands
19745 @subheading The @code{-break-condition} Command
19746 @findex -break-condition
19748 @subsubheading Synopsis
19751 -break-condition @var{number} @var{expr}
19754 Breakpoint @var{number} will stop the program only if the condition in
19755 @var{expr} is true. The condition becomes part of the
19756 @samp{-break-list} output (see the description of the @samp{-break-list}
19759 @subsubheading @value{GDBN} Command
19761 The corresponding @value{GDBN} command is @samp{condition}.
19763 @subsubheading Example
19767 -break-condition 1 1
19771 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19772 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19773 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19774 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19775 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19776 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19777 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19778 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
19779 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19780 line="5",cond="1",times="0",ignore="3"@}]@}
19784 @subheading The @code{-break-delete} Command
19785 @findex -break-delete
19787 @subsubheading Synopsis
19790 -break-delete ( @var{breakpoint} )+
19793 Delete the breakpoint(s) whose number(s) are specified in the argument
19794 list. This is obviously reflected in the breakpoint list.
19796 @subsubheading @value{GDBN} Command
19798 The corresponding @value{GDBN} command is @samp{delete}.
19800 @subsubheading Example
19808 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
19809 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19810 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19811 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19812 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19813 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19814 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19819 @subheading The @code{-break-disable} Command
19820 @findex -break-disable
19822 @subsubheading Synopsis
19825 -break-disable ( @var{breakpoint} )+
19828 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
19829 break list is now set to @samp{n} for the named @var{breakpoint}(s).
19831 @subsubheading @value{GDBN} Command
19833 The corresponding @value{GDBN} command is @samp{disable}.
19835 @subsubheading Example
19843 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19844 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19845 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19846 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19847 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19848 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19849 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19850 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
19851 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19852 line="5",times="0"@}]@}
19856 @subheading The @code{-break-enable} Command
19857 @findex -break-enable
19859 @subsubheading Synopsis
19862 -break-enable ( @var{breakpoint} )+
19865 Enable (previously disabled) @var{breakpoint}(s).
19867 @subsubheading @value{GDBN} Command
19869 The corresponding @value{GDBN} command is @samp{enable}.
19871 @subsubheading Example
19879 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
19880 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19881 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19882 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19883 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
19884 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
19885 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
19886 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
19887 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
19888 line="5",times="0"@}]@}
19892 @subheading The @code{-break-info} Command
19893 @findex -break-info
19895 @subsubheading Synopsis
19898 -break-info @var{breakpoint}
19902 Get information about a single breakpoint.
19904 @subsubheading @value{GDBN} Command
19906 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
19908 @subsubheading Example
19911 @subheading The @code{-break-insert} Command
19912 @findex -break-insert
19914 @subsubheading Synopsis
19917 -break-insert [ -t ] [ -h ] [ -f ]
19918 [ -c @var{condition} ] [ -i @var{ignore-count} ]
19919 [ -p @var{thread} ] [ @var{location} ]
19923 If specified, @var{location}, can be one of:
19930 @item filename:linenum
19931 @item filename:function
19935 The possible optional parameters of this command are:
19939 Insert a temporary breakpoint.
19941 Insert a hardware breakpoint.
19942 @item -c @var{condition}
19943 Make the breakpoint conditional on @var{condition}.
19944 @item -i @var{ignore-count}
19945 Initialize the @var{ignore-count}.
19947 If @var{location} cannot be parsed (for example if it
19948 refers to unknown files or functions), create a pending
19949 breakpoint. Without this flag, @value{GDBN} will report
19950 an error, and won't create a breakpoint, if @var{location}
19954 @subsubheading Result
19956 The result is in the form:
19959 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
19960 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
19961 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
19962 times="@var{times}"@}
19966 where @var{number} is the @value{GDBN} number for this breakpoint,
19967 @var{funcname} is the name of the function where the breakpoint was
19968 inserted, @var{filename} is the name of the source file which contains
19969 this function, @var{lineno} is the source line number within that file
19970 and @var{times} the number of times that the breakpoint has been hit
19971 (always 0 for -break-insert but may be greater for -break-info or -break-list
19972 which use the same output).
19974 Note: this format is open to change.
19975 @c An out-of-band breakpoint instead of part of the result?
19977 @subsubheading @value{GDBN} Command
19979 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
19980 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
19982 @subsubheading Example
19987 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
19988 fullname="/home/foo/recursive2.c,line="4",times="0"@}
19990 -break-insert -t foo
19991 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
19992 fullname="/home/foo/recursive2.c,line="11",times="0"@}
19995 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
19996 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
19997 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
19998 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
19999 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20000 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20001 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20002 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20003 addr="0x0001072c", func="main",file="recursive2.c",
20004 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20005 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20006 addr="0x00010774",func="foo",file="recursive2.c",
20007 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20009 -break-insert -r foo.*
20010 ~int foo(int, int);
20011 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20012 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20016 @subheading The @code{-break-list} Command
20017 @findex -break-list
20019 @subsubheading Synopsis
20025 Displays the list of inserted breakpoints, showing the following fields:
20029 number of the breakpoint
20031 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20033 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20036 is the breakpoint enabled or no: @samp{y} or @samp{n}
20038 memory location at which the breakpoint is set
20040 logical location of the breakpoint, expressed by function name, file
20043 number of times the breakpoint has been hit
20046 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20047 @code{body} field is an empty list.
20049 @subsubheading @value{GDBN} Command
20051 The corresponding @value{GDBN} command is @samp{info break}.
20053 @subsubheading Example
20058 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20059 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20060 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20061 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20062 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20063 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20064 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20065 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20066 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20067 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20068 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20069 line="13",times="0"@}]@}
20073 Here's an example of the result when there are no breakpoints:
20078 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20079 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20080 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20081 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20082 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20083 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20084 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20089 @subheading The @code{-break-watch} Command
20090 @findex -break-watch
20092 @subsubheading Synopsis
20095 -break-watch [ -a | -r ]
20098 Create a watchpoint. With the @samp{-a} option it will create an
20099 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20100 read from or on a write to the memory location. With the @samp{-r}
20101 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
20102 trigger only when the memory location is accessed for reading. Without
20103 either of the options, the watchpoint created is a regular watchpoint,
20104 i.e., it will trigger when the memory location is accessed for writing.
20105 @xref{Set Watchpoints, , Setting Watchpoints}.
20107 Note that @samp{-break-list} will report a single list of watchpoints and
20108 breakpoints inserted.
20110 @subsubheading @value{GDBN} Command
20112 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
20115 @subsubheading Example
20117 Setting a watchpoint on a variable in the @code{main} function:
20122 ^done,wpt=@{number="2",exp="x"@}
20127 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
20128 value=@{old="-268439212",new="55"@},
20129 frame=@{func="main",args=[],file="recursive2.c",
20130 fullname="/home/foo/bar/recursive2.c",line="5"@}
20134 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
20135 the program execution twice: first for the variable changing value, then
20136 for the watchpoint going out of scope.
20141 ^done,wpt=@{number="5",exp="C"@}
20146 *stopped,reason="watchpoint-trigger",
20147 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
20148 frame=@{func="callee4",args=[],
20149 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20150 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20155 *stopped,reason="watchpoint-scope",wpnum="5",
20156 frame=@{func="callee3",args=[@{name="strarg",
20157 value="0x11940 \"A string argument.\""@}],
20158 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20159 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20163 Listing breakpoints and watchpoints, at different points in the program
20164 execution. Note that once the watchpoint goes out of scope, it is
20170 ^done,wpt=@{number="2",exp="C"@}
20173 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20174 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20175 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20176 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20177 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20178 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20179 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20180 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20181 addr="0x00010734",func="callee4",
20182 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20183 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
20184 bkpt=@{number="2",type="watchpoint",disp="keep",
20185 enabled="y",addr="",what="C",times="0"@}]@}
20190 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
20191 value=@{old="-276895068",new="3"@},
20192 frame=@{func="callee4",args=[],
20193 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20194 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20197 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20198 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20199 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20200 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20201 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20202 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20203 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20204 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20205 addr="0x00010734",func="callee4",
20206 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20207 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
20208 bkpt=@{number="2",type="watchpoint",disp="keep",
20209 enabled="y",addr="",what="C",times="-5"@}]@}
20213 ^done,reason="watchpoint-scope",wpnum="2",
20214 frame=@{func="callee3",args=[@{name="strarg",
20215 value="0x11940 \"A string argument.\""@}],
20216 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20217 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20220 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20221 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20222 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20223 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20224 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20225 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20226 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20227 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20228 addr="0x00010734",func="callee4",
20229 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20230 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
20235 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20236 @node GDB/MI Program Context
20237 @section @sc{gdb/mi} Program Context
20239 @subheading The @code{-exec-arguments} Command
20240 @findex -exec-arguments
20243 @subsubheading Synopsis
20246 -exec-arguments @var{args}
20249 Set the inferior program arguments, to be used in the next
20252 @subsubheading @value{GDBN} Command
20254 The corresponding @value{GDBN} command is @samp{set args}.
20256 @subsubheading Example
20260 -exec-arguments -v word
20266 @subheading The @code{-exec-show-arguments} Command
20267 @findex -exec-show-arguments
20269 @subsubheading Synopsis
20272 -exec-show-arguments
20275 Print the arguments of the program.
20277 @subsubheading @value{GDBN} Command
20279 The corresponding @value{GDBN} command is @samp{show args}.
20281 @subsubheading Example
20285 @subheading The @code{-environment-cd} Command
20286 @findex -environment-cd
20288 @subsubheading Synopsis
20291 -environment-cd @var{pathdir}
20294 Set @value{GDBN}'s working directory.
20296 @subsubheading @value{GDBN} Command
20298 The corresponding @value{GDBN} command is @samp{cd}.
20300 @subsubheading Example
20304 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20310 @subheading The @code{-environment-directory} Command
20311 @findex -environment-directory
20313 @subsubheading Synopsis
20316 -environment-directory [ -r ] [ @var{pathdir} ]+
20319 Add directories @var{pathdir} to beginning of search path for source files.
20320 If the @samp{-r} option is used, the search path is reset to the default
20321 search path. If directories @var{pathdir} are supplied in addition to the
20322 @samp{-r} option, the search path is first reset and then addition
20324 Multiple directories may be specified, separated by blanks. Specifying
20325 multiple directories in a single command
20326 results in the directories added to the beginning of the
20327 search path in the same order they were presented in the command.
20328 If blanks are needed as
20329 part of a directory name, double-quotes should be used around
20330 the name. In the command output, the path will show up separated
20331 by the system directory-separator character. The directory-separator
20332 character must not be used
20333 in any directory name.
20334 If no directories are specified, the current search path is displayed.
20336 @subsubheading @value{GDBN} Command
20338 The corresponding @value{GDBN} command is @samp{dir}.
20340 @subsubheading Example
20344 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20345 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20347 -environment-directory ""
20348 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
20350 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
20351 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
20353 -environment-directory -r
20354 ^done,source-path="$cdir:$cwd"
20359 @subheading The @code{-environment-path} Command
20360 @findex -environment-path
20362 @subsubheading Synopsis
20365 -environment-path [ -r ] [ @var{pathdir} ]+
20368 Add directories @var{pathdir} to beginning of search path for object files.
20369 If the @samp{-r} option is used, the search path is reset to the original
20370 search path that existed at gdb start-up. If directories @var{pathdir} are
20371 supplied in addition to the
20372 @samp{-r} option, the search path is first reset and then addition
20374 Multiple directories may be specified, separated by blanks. Specifying
20375 multiple directories in a single command
20376 results in the directories added to the beginning of the
20377 search path in the same order they were presented in the command.
20378 If blanks are needed as
20379 part of a directory name, double-quotes should be used around
20380 the name. In the command output, the path will show up separated
20381 by the system directory-separator character. The directory-separator
20382 character must not be used
20383 in any directory name.
20384 If no directories are specified, the current path is displayed.
20387 @subsubheading @value{GDBN} Command
20389 The corresponding @value{GDBN} command is @samp{path}.
20391 @subsubheading Example
20396 ^done,path="/usr/bin"
20398 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
20399 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
20401 -environment-path -r /usr/local/bin
20402 ^done,path="/usr/local/bin:/usr/bin"
20407 @subheading The @code{-environment-pwd} Command
20408 @findex -environment-pwd
20410 @subsubheading Synopsis
20416 Show the current working directory.
20418 @subsubheading @value{GDBN} Command
20420 The corresponding @value{GDBN} command is @samp{pwd}.
20422 @subsubheading Example
20427 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
20431 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20432 @node GDB/MI Thread Commands
20433 @section @sc{gdb/mi} Thread Commands
20436 @subheading The @code{-thread-info} Command
20437 @findex -thread-info
20439 @subsubheading Synopsis
20442 -thread-info [ @var{thread-id} ]
20445 Reports information about either a specific thread, if
20446 the @var{thread-id} parameter is present, or about all
20447 threads. When printing information about all threads,
20448 also reports the current thread.
20450 @subsubheading @value{GDBN} Command
20452 The @samp{info thread} command prints the same information
20455 @subsubheading Example
20460 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
20461 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
20462 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
20463 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
20464 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
20465 current-thread-id="1"
20469 The @samp{state} field may have the following values:
20473 The thread is stopped. Frame information is available for stopped
20477 The thread is running. There's no frame information for running
20482 @subheading The @code{-thread-list-ids} Command
20483 @findex -thread-list-ids
20485 @subsubheading Synopsis
20491 Produces a list of the currently known @value{GDBN} thread ids. At the
20492 end of the list it also prints the total number of such threads.
20494 This command is retained for historical reasons, the
20495 @code{-thread-info} command should be used instead.
20497 @subsubheading @value{GDBN} Command
20499 Part of @samp{info threads} supplies the same information.
20501 @subsubheading Example
20503 No threads present, besides the main process:
20508 ^done,thread-ids=@{@},number-of-threads="0"
20518 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20519 number-of-threads="3"
20524 @subheading The @code{-thread-select} Command
20525 @findex -thread-select
20527 @subsubheading Synopsis
20530 -thread-select @var{threadnum}
20533 Make @var{threadnum} the current thread. It prints the number of the new
20534 current thread, and the topmost frame for that thread.
20536 This command is deprecated in favor of explicitly using the
20537 @samp{--thread} option to each command.
20539 @subsubheading @value{GDBN} Command
20541 The corresponding @value{GDBN} command is @samp{thread}.
20543 @subsubheading Example
20550 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20551 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20555 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20556 number-of-threads="3"
20559 ^done,new-thread-id="3",
20560 frame=@{level="0",func="vprintf",
20561 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20562 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20566 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20567 @node GDB/MI Program Execution
20568 @section @sc{gdb/mi} Program Execution
20570 These are the asynchronous commands which generate the out-of-band
20571 record @samp{*stopped}. Currently @value{GDBN} only really executes
20572 asynchronously with remote targets and this interaction is mimicked in
20575 @subheading The @code{-exec-continue} Command
20576 @findex -exec-continue
20578 @subsubheading Synopsis
20581 -exec-continue [--all|--thread-group N]
20584 Resumes the execution of the inferior program until a breakpoint is
20585 encountered, or until the inferior exits. In all-stop mode
20586 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
20587 depending on the value of the @samp{scheduler-locking} variable. In
20588 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
20589 specified, only the thread specified with the @samp{--thread} option
20590 (or current thread, if no @samp{--thread} is provided) is resumed. If
20591 @samp{--all} is specified, all threads will be resumed. The
20592 @samp{--all} option is ignored in all-stop mode. If the
20593 @samp{--thread-group} options is specified, then all threads in that
20594 thread group are resumed.
20596 @subsubheading @value{GDBN} Command
20598 The corresponding @value{GDBN} corresponding is @samp{continue}.
20600 @subsubheading Example
20607 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
20608 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
20614 @subheading The @code{-exec-finish} Command
20615 @findex -exec-finish
20617 @subsubheading Synopsis
20623 Resumes the execution of the inferior program until the current
20624 function is exited. Displays the results returned by the function.
20626 @subsubheading @value{GDBN} Command
20628 The corresponding @value{GDBN} command is @samp{finish}.
20630 @subsubheading Example
20632 Function returning @code{void}.
20639 *stopped,reason="function-finished",frame=@{func="main",args=[],
20640 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
20644 Function returning other than @code{void}. The name of the internal
20645 @value{GDBN} variable storing the result is printed, together with the
20652 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
20653 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
20654 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
20655 gdb-result-var="$1",return-value="0"
20660 @subheading The @code{-exec-interrupt} Command
20661 @findex -exec-interrupt
20663 @subsubheading Synopsis
20666 -exec-interrupt [--all|--thread-group N]
20669 Interrupts the background execution of the target. Note how the token
20670 associated with the stop message is the one for the execution command
20671 that has been interrupted. The token for the interrupt itself only
20672 appears in the @samp{^done} output. If the user is trying to
20673 interrupt a non-running program, an error message will be printed.
20675 Note that when asynchronous execution is enabled, this command is
20676 asynchronous just like other execution commands. That is, first the
20677 @samp{^done} response will be printed, and the target stop will be
20678 reported after that using the @samp{*stopped} notification.
20680 In non-stop mode, only the context thread is interrupted by default.
20681 All threads will be interrupted if the @samp{--all} option is
20682 specified. If the @samp{--thread-group} option is specified, all
20683 threads in that group will be interrupted.
20685 @subsubheading @value{GDBN} Command
20687 The corresponding @value{GDBN} command is @samp{interrupt}.
20689 @subsubheading Example
20700 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
20701 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
20702 fullname="/home/foo/bar/try.c",line="13"@}
20707 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
20712 @subheading The @code{-exec-next} Command
20715 @subsubheading Synopsis
20721 Resumes execution of the inferior program, stopping when the beginning
20722 of the next source line is reached.
20724 @subsubheading @value{GDBN} Command
20726 The corresponding @value{GDBN} command is @samp{next}.
20728 @subsubheading Example
20734 *stopped,reason="end-stepping-range",line="8",file="hello.c"
20739 @subheading The @code{-exec-next-instruction} Command
20740 @findex -exec-next-instruction
20742 @subsubheading Synopsis
20745 -exec-next-instruction
20748 Executes one machine instruction. If the instruction is a function
20749 call, continues until the function returns. If the program stops at an
20750 instruction in the middle of a source line, the address will be
20753 @subsubheading @value{GDBN} Command
20755 The corresponding @value{GDBN} command is @samp{nexti}.
20757 @subsubheading Example
20761 -exec-next-instruction
20765 *stopped,reason="end-stepping-range",
20766 addr="0x000100d4",line="5",file="hello.c"
20771 @subheading The @code{-exec-return} Command
20772 @findex -exec-return
20774 @subsubheading Synopsis
20780 Makes current function return immediately. Doesn't execute the inferior.
20781 Displays the new current frame.
20783 @subsubheading @value{GDBN} Command
20785 The corresponding @value{GDBN} command is @samp{return}.
20787 @subsubheading Example
20791 200-break-insert callee4
20792 200^done,bkpt=@{number="1",addr="0x00010734",
20793 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20798 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20799 frame=@{func="callee4",args=[],
20800 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20801 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
20807 111^done,frame=@{level="0",func="callee3",
20808 args=[@{name="strarg",
20809 value="0x11940 \"A string argument.\""@}],
20810 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20811 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20816 @subheading The @code{-exec-run} Command
20819 @subsubheading Synopsis
20825 Starts execution of the inferior from the beginning. The inferior
20826 executes until either a breakpoint is encountered or the program
20827 exits. In the latter case the output will include an exit code, if
20828 the program has exited exceptionally.
20830 @subsubheading @value{GDBN} Command
20832 The corresponding @value{GDBN} command is @samp{run}.
20834 @subsubheading Examples
20839 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
20844 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
20845 frame=@{func="main",args=[],file="recursive2.c",
20846 fullname="/home/foo/bar/recursive2.c",line="4"@}
20851 Program exited normally:
20859 *stopped,reason="exited-normally"
20864 Program exited exceptionally:
20872 *stopped,reason="exited",exit-code="01"
20876 Another way the program can terminate is if it receives a signal such as
20877 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
20881 *stopped,reason="exited-signalled",signal-name="SIGINT",
20882 signal-meaning="Interrupt"
20886 @c @subheading -exec-signal
20889 @subheading The @code{-exec-step} Command
20892 @subsubheading Synopsis
20898 Resumes execution of the inferior program, stopping when the beginning
20899 of the next source line is reached, if the next source line is not a
20900 function call. If it is, stop at the first instruction of the called
20903 @subsubheading @value{GDBN} Command
20905 The corresponding @value{GDBN} command is @samp{step}.
20907 @subsubheading Example
20909 Stepping into a function:
20915 *stopped,reason="end-stepping-range",
20916 frame=@{func="foo",args=[@{name="a",value="10"@},
20917 @{name="b",value="0"@}],file="recursive2.c",
20918 fullname="/home/foo/bar/recursive2.c",line="11"@}
20928 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
20933 @subheading The @code{-exec-step-instruction} Command
20934 @findex -exec-step-instruction
20936 @subsubheading Synopsis
20939 -exec-step-instruction
20942 Resumes the inferior which executes one machine instruction. The
20943 output, once @value{GDBN} has stopped, will vary depending on whether
20944 we have stopped in the middle of a source line or not. In the former
20945 case, the address at which the program stopped will be printed as
20948 @subsubheading @value{GDBN} Command
20950 The corresponding @value{GDBN} command is @samp{stepi}.
20952 @subsubheading Example
20956 -exec-step-instruction
20960 *stopped,reason="end-stepping-range",
20961 frame=@{func="foo",args=[],file="try.c",
20962 fullname="/home/foo/bar/try.c",line="10"@}
20964 -exec-step-instruction
20968 *stopped,reason="end-stepping-range",
20969 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
20970 fullname="/home/foo/bar/try.c",line="10"@}
20975 @subheading The @code{-exec-until} Command
20976 @findex -exec-until
20978 @subsubheading Synopsis
20981 -exec-until [ @var{location} ]
20984 Executes the inferior until the @var{location} specified in the
20985 argument is reached. If there is no argument, the inferior executes
20986 until a source line greater than the current one is reached. The
20987 reason for stopping in this case will be @samp{location-reached}.
20989 @subsubheading @value{GDBN} Command
20991 The corresponding @value{GDBN} command is @samp{until}.
20993 @subsubheading Example
20997 -exec-until recursive2.c:6
21001 *stopped,reason="location-reached",frame=@{func="main",args=[],
21002 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21007 @subheading -file-clear
21008 Is this going away????
21011 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21012 @node GDB/MI Stack Manipulation
21013 @section @sc{gdb/mi} Stack Manipulation Commands
21016 @subheading The @code{-stack-info-frame} Command
21017 @findex -stack-info-frame
21019 @subsubheading Synopsis
21025 Get info on the selected frame.
21027 @subsubheading @value{GDBN} Command
21029 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21030 (without arguments).
21032 @subsubheading Example
21037 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21038 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21039 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21043 @subheading The @code{-stack-info-depth} Command
21044 @findex -stack-info-depth
21046 @subsubheading Synopsis
21049 -stack-info-depth [ @var{max-depth} ]
21052 Return the depth of the stack. If the integer argument @var{max-depth}
21053 is specified, do not count beyond @var{max-depth} frames.
21055 @subsubheading @value{GDBN} Command
21057 There's no equivalent @value{GDBN} command.
21059 @subsubheading Example
21061 For a stack with frame levels 0 through 11:
21068 -stack-info-depth 4
21071 -stack-info-depth 12
21074 -stack-info-depth 11
21077 -stack-info-depth 13
21082 @subheading The @code{-stack-list-arguments} Command
21083 @findex -stack-list-arguments
21085 @subsubheading Synopsis
21088 -stack-list-arguments @var{show-values}
21089 [ @var{low-frame} @var{high-frame} ]
21092 Display a list of the arguments for the frames between @var{low-frame}
21093 and @var{high-frame} (inclusive). If @var{low-frame} and
21094 @var{high-frame} are not provided, list the arguments for the whole
21095 call stack. If the two arguments are equal, show the single frame
21096 at the corresponding level. It is an error if @var{low-frame} is
21097 larger than the actual number of frames. On the other hand,
21098 @var{high-frame} may be larger than the actual number of frames, in
21099 which case only existing frames will be returned.
21101 The @var{show-values} argument must have a value of 0 or 1. A value of
21102 0 means that only the names of the arguments are listed, a value of 1
21103 means that both names and values of the arguments are printed.
21105 @subsubheading @value{GDBN} Command
21107 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
21108 @samp{gdb_get_args} command which partially overlaps with the
21109 functionality of @samp{-stack-list-arguments}.
21111 @subsubheading Example
21118 frame=@{level="0",addr="0x00010734",func="callee4",
21119 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21120 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
21121 frame=@{level="1",addr="0x0001076c",func="callee3",
21122 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21123 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
21124 frame=@{level="2",addr="0x0001078c",func="callee2",
21125 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21126 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
21127 frame=@{level="3",addr="0x000107b4",func="callee1",
21128 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21129 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
21130 frame=@{level="4",addr="0x000107e0",func="main",
21131 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21132 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
21134 -stack-list-arguments 0
21137 frame=@{level="0",args=[]@},
21138 frame=@{level="1",args=[name="strarg"]@},
21139 frame=@{level="2",args=[name="intarg",name="strarg"]@},
21140 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
21141 frame=@{level="4",args=[]@}]
21143 -stack-list-arguments 1
21146 frame=@{level="0",args=[]@},
21148 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21149 frame=@{level="2",args=[
21150 @{name="intarg",value="2"@},
21151 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21152 @{frame=@{level="3",args=[
21153 @{name="intarg",value="2"@},
21154 @{name="strarg",value="0x11940 \"A string argument.\""@},
21155 @{name="fltarg",value="3.5"@}]@},
21156 frame=@{level="4",args=[]@}]
21158 -stack-list-arguments 0 2 2
21159 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
21161 -stack-list-arguments 1 2 2
21162 ^done,stack-args=[frame=@{level="2",
21163 args=[@{name="intarg",value="2"@},
21164 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
21168 @c @subheading -stack-list-exception-handlers
21171 @subheading The @code{-stack-list-frames} Command
21172 @findex -stack-list-frames
21174 @subsubheading Synopsis
21177 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
21180 List the frames currently on the stack. For each frame it displays the
21185 The frame number, 0 being the topmost frame, i.e., the innermost function.
21187 The @code{$pc} value for that frame.
21191 File name of the source file where the function lives.
21193 Line number corresponding to the @code{$pc}.
21196 If invoked without arguments, this command prints a backtrace for the
21197 whole stack. If given two integer arguments, it shows the frames whose
21198 levels are between the two arguments (inclusive). If the two arguments
21199 are equal, it shows the single frame at the corresponding level. It is
21200 an error if @var{low-frame} is larger than the actual number of
21201 frames. On the other hand, @var{high-frame} may be larger than the
21202 actual number of frames, in which case only existing frames will be returned.
21204 @subsubheading @value{GDBN} Command
21206 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
21208 @subsubheading Example
21210 Full stack backtrace:
21216 [frame=@{level="0",addr="0x0001076c",func="foo",
21217 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
21218 frame=@{level="1",addr="0x000107a4",func="foo",
21219 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21220 frame=@{level="2",addr="0x000107a4",func="foo",
21221 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21222 frame=@{level="3",addr="0x000107a4",func="foo",
21223 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21224 frame=@{level="4",addr="0x000107a4",func="foo",
21225 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21226 frame=@{level="5",addr="0x000107a4",func="foo",
21227 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21228 frame=@{level="6",addr="0x000107a4",func="foo",
21229 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21230 frame=@{level="7",addr="0x000107a4",func="foo",
21231 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21232 frame=@{level="8",addr="0x000107a4",func="foo",
21233 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21234 frame=@{level="9",addr="0x000107a4",func="foo",
21235 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21236 frame=@{level="10",addr="0x000107a4",func="foo",
21237 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21238 frame=@{level="11",addr="0x00010738",func="main",
21239 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
21243 Show frames between @var{low_frame} and @var{high_frame}:
21247 -stack-list-frames 3 5
21249 [frame=@{level="3",addr="0x000107a4",func="foo",
21250 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21251 frame=@{level="4",addr="0x000107a4",func="foo",
21252 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21253 frame=@{level="5",addr="0x000107a4",func="foo",
21254 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21258 Show a single frame:
21262 -stack-list-frames 3 3
21264 [frame=@{level="3",addr="0x000107a4",func="foo",
21265 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21270 @subheading The @code{-stack-list-locals} Command
21271 @findex -stack-list-locals
21273 @subsubheading Synopsis
21276 -stack-list-locals @var{print-values}
21279 Display the local variable names for the selected frame. If
21280 @var{print-values} is 0 or @code{--no-values}, print only the names of
21281 the variables; if it is 1 or @code{--all-values}, print also their
21282 values; and if it is 2 or @code{--simple-values}, print the name,
21283 type and value for simple data types and the name and type for arrays,
21284 structures and unions. In this last case, a frontend can immediately
21285 display the value of simple data types and create variable objects for
21286 other data types when the user wishes to explore their values in
21289 @subsubheading @value{GDBN} Command
21291 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
21293 @subsubheading Example
21297 -stack-list-locals 0
21298 ^done,locals=[name="A",name="B",name="C"]
21300 -stack-list-locals --all-values
21301 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
21302 @{name="C",value="@{1, 2, 3@}"@}]
21303 -stack-list-locals --simple-values
21304 ^done,locals=[@{name="A",type="int",value="1"@},
21305 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
21310 @subheading The @code{-stack-select-frame} Command
21311 @findex -stack-select-frame
21313 @subsubheading Synopsis
21316 -stack-select-frame @var{framenum}
21319 Change the selected frame. Select a different frame @var{framenum} on
21322 This command in deprecated in favor of passing the @samp{--frame}
21323 option to every command.
21325 @subsubheading @value{GDBN} Command
21327 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
21328 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
21330 @subsubheading Example
21334 -stack-select-frame 2
21339 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21340 @node GDB/MI Variable Objects
21341 @section @sc{gdb/mi} Variable Objects
21345 @subheading Motivation for Variable Objects in @sc{gdb/mi}
21347 For the implementation of a variable debugger window (locals, watched
21348 expressions, etc.), we are proposing the adaptation of the existing code
21349 used by @code{Insight}.
21351 The two main reasons for that are:
21355 It has been proven in practice (it is already on its second generation).
21358 It will shorten development time (needless to say how important it is
21362 The original interface was designed to be used by Tcl code, so it was
21363 slightly changed so it could be used through @sc{gdb/mi}. This section
21364 describes the @sc{gdb/mi} operations that will be available and gives some
21365 hints about their use.
21367 @emph{Note}: In addition to the set of operations described here, we
21368 expect the @sc{gui} implementation of a variable window to require, at
21369 least, the following operations:
21372 @item @code{-gdb-show} @code{output-radix}
21373 @item @code{-stack-list-arguments}
21374 @item @code{-stack-list-locals}
21375 @item @code{-stack-select-frame}
21380 @subheading Introduction to Variable Objects
21382 @cindex variable objects in @sc{gdb/mi}
21384 Variable objects are "object-oriented" MI interface for examining and
21385 changing values of expressions. Unlike some other MI interfaces that
21386 work with expressions, variable objects are specifically designed for
21387 simple and efficient presentation in the frontend. A variable object
21388 is identified by string name. When a variable object is created, the
21389 frontend specifies the expression for that variable object. The
21390 expression can be a simple variable, or it can be an arbitrary complex
21391 expression, and can even involve CPU registers. After creating a
21392 variable object, the frontend can invoke other variable object
21393 operations---for example to obtain or change the value of a variable
21394 object, or to change display format.
21396 Variable objects have hierarchical tree structure. Any variable object
21397 that corresponds to a composite type, such as structure in C, has
21398 a number of child variable objects, for example corresponding to each
21399 element of a structure. A child variable object can itself have
21400 children, recursively. Recursion ends when we reach
21401 leaf variable objects, which always have built-in types. Child variable
21402 objects are created only by explicit request, so if a frontend
21403 is not interested in the children of a particular variable object, no
21404 child will be created.
21406 For a leaf variable object it is possible to obtain its value as a
21407 string, or set the value from a string. String value can be also
21408 obtained for a non-leaf variable object, but it's generally a string
21409 that only indicates the type of the object, and does not list its
21410 contents. Assignment to a non-leaf variable object is not allowed.
21412 A frontend does not need to read the values of all variable objects each time
21413 the program stops. Instead, MI provides an update command that lists all
21414 variable objects whose values has changed since the last update
21415 operation. This considerably reduces the amount of data that must
21416 be transferred to the frontend. As noted above, children variable
21417 objects are created on demand, and only leaf variable objects have a
21418 real value. As result, gdb will read target memory only for leaf
21419 variables that frontend has created.
21421 The automatic update is not always desirable. For example, a frontend
21422 might want to keep a value of some expression for future reference,
21423 and never update it. For another example, fetching memory is
21424 relatively slow for embedded targets, so a frontend might want
21425 to disable automatic update for the variables that are either not
21426 visible on the screen, or ``closed''. This is possible using so
21427 called ``frozen variable objects''. Such variable objects are never
21428 implicitly updated.
21430 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
21431 fixed variable object, the expression is parsed when the variable
21432 object is created, including associating identifiers to specific
21433 variables. The meaning of expression never changes. For a floating
21434 variable object the values of variables whose names appear in the
21435 expressions are re-evaluated every time in the context of the current
21436 frame. Consider this example:
21441 struct work_state state;
21448 If a fixed variable object for the @code{state} variable is created in
21449 this function, and we enter the recursive call, the the variable
21450 object will report the value of @code{state} in the top-level
21451 @code{do_work} invocation. On the other hand, a floating variable
21452 object will report the value of @code{state} in the current frame.
21454 If an expression specified when creating a fixed variable object
21455 refers to a local variable, the variable object becomes bound to the
21456 thread and frame in which the variable object is created. When such
21457 variable object is updated, @value{GDBN} makes sure that the
21458 thread/frame combination the variable object is bound to still exists,
21459 and re-evaluates the variable object in context of that thread/frame.
21461 The following is the complete set of @sc{gdb/mi} operations defined to
21462 access this functionality:
21464 @multitable @columnfractions .4 .6
21465 @item @strong{Operation}
21466 @tab @strong{Description}
21468 @item @code{-var-create}
21469 @tab create a variable object
21470 @item @code{-var-delete}
21471 @tab delete the variable object and/or its children
21472 @item @code{-var-set-format}
21473 @tab set the display format of this variable
21474 @item @code{-var-show-format}
21475 @tab show the display format of this variable
21476 @item @code{-var-info-num-children}
21477 @tab tells how many children this object has
21478 @item @code{-var-list-children}
21479 @tab return a list of the object's children
21480 @item @code{-var-info-type}
21481 @tab show the type of this variable object
21482 @item @code{-var-info-expression}
21483 @tab print parent-relative expression that this variable object represents
21484 @item @code{-var-info-path-expression}
21485 @tab print full expression that this variable object represents
21486 @item @code{-var-show-attributes}
21487 @tab is this variable editable? does it exist here?
21488 @item @code{-var-evaluate-expression}
21489 @tab get the value of this variable
21490 @item @code{-var-assign}
21491 @tab set the value of this variable
21492 @item @code{-var-update}
21493 @tab update the variable and its children
21494 @item @code{-var-set-frozen}
21495 @tab set frozeness attribute
21498 In the next subsection we describe each operation in detail and suggest
21499 how it can be used.
21501 @subheading Description And Use of Operations on Variable Objects
21503 @subheading The @code{-var-create} Command
21504 @findex -var-create
21506 @subsubheading Synopsis
21509 -var-create @{@var{name} | "-"@}
21510 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
21513 This operation creates a variable object, which allows the monitoring of
21514 a variable, the result of an expression, a memory cell or a CPU
21517 The @var{name} parameter is the string by which the object can be
21518 referenced. It must be unique. If @samp{-} is specified, the varobj
21519 system will generate a string ``varNNNNNN'' automatically. It will be
21520 unique provided that one does not specify @var{name} of that format.
21521 The command fails if a duplicate name is found.
21523 The frame under which the expression should be evaluated can be
21524 specified by @var{frame-addr}. A @samp{*} indicates that the current
21525 frame should be used. A @samp{@@} indicates that a floating variable
21526 object must be created.
21528 @var{expression} is any expression valid on the current language set (must not
21529 begin with a @samp{*}), or one of the following:
21533 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
21536 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
21539 @samp{$@var{regname}} --- a CPU register name
21542 @subsubheading Result
21544 This operation returns the name, number of children and the type of the
21545 object created. Type is returned as a string as the ones generated by
21546 the @value{GDBN} CLI. If a fixed variable object is bound to a
21547 specific thread, the thread is is also printed:
21550 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
21554 @subheading The @code{-var-delete} Command
21555 @findex -var-delete
21557 @subsubheading Synopsis
21560 -var-delete [ -c ] @var{name}
21563 Deletes a previously created variable object and all of its children.
21564 With the @samp{-c} option, just deletes the children.
21566 Returns an error if the object @var{name} is not found.
21569 @subheading The @code{-var-set-format} Command
21570 @findex -var-set-format
21572 @subsubheading Synopsis
21575 -var-set-format @var{name} @var{format-spec}
21578 Sets the output format for the value of the object @var{name} to be
21581 @anchor{-var-set-format}
21582 The syntax for the @var{format-spec} is as follows:
21585 @var{format-spec} @expansion{}
21586 @{binary | decimal | hexadecimal | octal | natural@}
21589 The natural format is the default format choosen automatically
21590 based on the variable type (like decimal for an @code{int}, hex
21591 for pointers, etc.).
21593 For a variable with children, the format is set only on the
21594 variable itself, and the children are not affected.
21596 @subheading The @code{-var-show-format} Command
21597 @findex -var-show-format
21599 @subsubheading Synopsis
21602 -var-show-format @var{name}
21605 Returns the format used to display the value of the object @var{name}.
21608 @var{format} @expansion{}
21613 @subheading The @code{-var-info-num-children} Command
21614 @findex -var-info-num-children
21616 @subsubheading Synopsis
21619 -var-info-num-children @var{name}
21622 Returns the number of children of a variable object @var{name}:
21629 @subheading The @code{-var-list-children} Command
21630 @findex -var-list-children
21632 @subsubheading Synopsis
21635 -var-list-children [@var{print-values}] @var{name}
21637 @anchor{-var-list-children}
21639 Return a list of the children of the specified variable object and
21640 create variable objects for them, if they do not already exist. With
21641 a single argument or if @var{print-values} has a value for of 0 or
21642 @code{--no-values}, print only the names of the variables; if
21643 @var{print-values} is 1 or @code{--all-values}, also print their
21644 values; and if it is 2 or @code{--simple-values} print the name and
21645 value for simple data types and just the name for arrays, structures
21648 @subsubheading Example
21652 -var-list-children n
21653 ^done,numchild=@var{n},children=[@{name=@var{name},
21654 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
21656 -var-list-children --all-values n
21657 ^done,numchild=@var{n},children=[@{name=@var{name},
21658 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
21662 @subheading The @code{-var-info-type} Command
21663 @findex -var-info-type
21665 @subsubheading Synopsis
21668 -var-info-type @var{name}
21671 Returns the type of the specified variable @var{name}. The type is
21672 returned as a string in the same format as it is output by the
21676 type=@var{typename}
21680 @subheading The @code{-var-info-expression} Command
21681 @findex -var-info-expression
21683 @subsubheading Synopsis
21686 -var-info-expression @var{name}
21689 Returns a string that is suitable for presenting this
21690 variable object in user interface. The string is generally
21691 not valid expression in the current language, and cannot be evaluated.
21693 For example, if @code{a} is an array, and variable object
21694 @code{A} was created for @code{a}, then we'll get this output:
21697 (gdb) -var-info-expression A.1
21698 ^done,lang="C",exp="1"
21702 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
21704 Note that the output of the @code{-var-list-children} command also
21705 includes those expressions, so the @code{-var-info-expression} command
21708 @subheading The @code{-var-info-path-expression} Command
21709 @findex -var-info-path-expression
21711 @subsubheading Synopsis
21714 -var-info-path-expression @var{name}
21717 Returns an expression that can be evaluated in the current
21718 context and will yield the same value that a variable object has.
21719 Compare this with the @code{-var-info-expression} command, which
21720 result can be used only for UI presentation. Typical use of
21721 the @code{-var-info-path-expression} command is creating a
21722 watchpoint from a variable object.
21724 For example, suppose @code{C} is a C@t{++} class, derived from class
21725 @code{Base}, and that the @code{Base} class has a member called
21726 @code{m_size}. Assume a variable @code{c} is has the type of
21727 @code{C} and a variable object @code{C} was created for variable
21728 @code{c}. Then, we'll get this output:
21730 (gdb) -var-info-path-expression C.Base.public.m_size
21731 ^done,path_expr=((Base)c).m_size)
21734 @subheading The @code{-var-show-attributes} Command
21735 @findex -var-show-attributes
21737 @subsubheading Synopsis
21740 -var-show-attributes @var{name}
21743 List attributes of the specified variable object @var{name}:
21746 status=@var{attr} [ ( ,@var{attr} )* ]
21750 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
21752 @subheading The @code{-var-evaluate-expression} Command
21753 @findex -var-evaluate-expression
21755 @subsubheading Synopsis
21758 -var-evaluate-expression [-f @var{format-spec}] @var{name}
21761 Evaluates the expression that is represented by the specified variable
21762 object and returns its value as a string. The format of the string
21763 can be specified with the @samp{-f} option. The possible values of
21764 this option are the same as for @code{-var-set-format}
21765 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
21766 the current display format will be used. The current display format
21767 can be changed using the @code{-var-set-format} command.
21773 Note that one must invoke @code{-var-list-children} for a variable
21774 before the value of a child variable can be evaluated.
21776 @subheading The @code{-var-assign} Command
21777 @findex -var-assign
21779 @subsubheading Synopsis
21782 -var-assign @var{name} @var{expression}
21785 Assigns the value of @var{expression} to the variable object specified
21786 by @var{name}. The object must be @samp{editable}. If the variable's
21787 value is altered by the assign, the variable will show up in any
21788 subsequent @code{-var-update} list.
21790 @subsubheading Example
21798 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
21802 @subheading The @code{-var-update} Command
21803 @findex -var-update
21805 @subsubheading Synopsis
21808 -var-update [@var{print-values}] @{@var{name} | "*"@}
21811 Reevaluate the expressions corresponding to the variable object
21812 @var{name} and all its direct and indirect children, and return the
21813 list of variable objects whose values have changed; @var{name} must
21814 be a root variable object. Here, ``changed'' means that the result of
21815 @code{-var-evaluate-expression} before and after the
21816 @code{-var-update} is different. If @samp{*} is used as the variable
21817 object names, all existing variable objects are updated, except
21818 for frozen ones (@pxref{-var-set-frozen}). The option
21819 @var{print-values} determines whether both names and values, or just
21820 names are printed. The possible values of this option are the same
21821 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
21822 recommended to use the @samp{--all-values} option, to reduce the
21823 number of MI commands needed on each program stop.
21825 With the @samp{*} parameter, if a variable object is bound to a
21826 currently running thread, it will not be updated, without any
21829 @subsubheading Example
21836 -var-update --all-values var1
21837 ^done,changelist=[@{name="var1",value="3",in_scope="true",
21838 type_changed="false"@}]
21842 @anchor{-var-update}
21843 The field in_scope may take three values:
21847 The variable object's current value is valid.
21850 The variable object does not currently hold a valid value but it may
21851 hold one in the future if its associated expression comes back into
21855 The variable object no longer holds a valid value.
21856 This can occur when the executable file being debugged has changed,
21857 either through recompilation or by using the @value{GDBN} @code{file}
21858 command. The front end should normally choose to delete these variable
21862 In the future new values may be added to this list so the front should
21863 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
21865 @subheading The @code{-var-set-frozen} Command
21866 @findex -var-set-frozen
21867 @anchor{-var-set-frozen}
21869 @subsubheading Synopsis
21872 -var-set-frozen @var{name} @var{flag}
21875 Set the frozenness flag on the variable object @var{name}. The
21876 @var{flag} parameter should be either @samp{1} to make the variable
21877 frozen or @samp{0} to make it unfrozen. If a variable object is
21878 frozen, then neither itself, nor any of its children, are
21879 implicitly updated by @code{-var-update} of
21880 a parent variable or by @code{-var-update *}. Only
21881 @code{-var-update} of the variable itself will update its value and
21882 values of its children. After a variable object is unfrozen, it is
21883 implicitly updated by all subsequent @code{-var-update} operations.
21884 Unfreezing a variable does not update it, only subsequent
21885 @code{-var-update} does.
21887 @subsubheading Example
21891 -var-set-frozen V 1
21897 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21898 @node GDB/MI Data Manipulation
21899 @section @sc{gdb/mi} Data Manipulation
21901 @cindex data manipulation, in @sc{gdb/mi}
21902 @cindex @sc{gdb/mi}, data manipulation
21903 This section describes the @sc{gdb/mi} commands that manipulate data:
21904 examine memory and registers, evaluate expressions, etc.
21906 @c REMOVED FROM THE INTERFACE.
21907 @c @subheading -data-assign
21908 @c Change the value of a program variable. Plenty of side effects.
21909 @c @subsubheading GDB Command
21911 @c @subsubheading Example
21914 @subheading The @code{-data-disassemble} Command
21915 @findex -data-disassemble
21917 @subsubheading Synopsis
21921 [ -s @var{start-addr} -e @var{end-addr} ]
21922 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
21930 @item @var{start-addr}
21931 is the beginning address (or @code{$pc})
21932 @item @var{end-addr}
21934 @item @var{filename}
21935 is the name of the file to disassemble
21936 @item @var{linenum}
21937 is the line number to disassemble around
21939 is the number of disassembly lines to be produced. If it is -1,
21940 the whole function will be disassembled, in case no @var{end-addr} is
21941 specified. If @var{end-addr} is specified as a non-zero value, and
21942 @var{lines} is lower than the number of disassembly lines between
21943 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
21944 displayed; if @var{lines} is higher than the number of lines between
21945 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
21948 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
21952 @subsubheading Result
21954 The output for each instruction is composed of four fields:
21963 Note that whatever included in the instruction field, is not manipulated
21964 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
21966 @subsubheading @value{GDBN} Command
21968 There's no direct mapping from this command to the CLI.
21970 @subsubheading Example
21972 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
21976 -data-disassemble -s $pc -e "$pc + 20" -- 0
21979 @{address="0x000107c0",func-name="main",offset="4",
21980 inst="mov 2, %o0"@},
21981 @{address="0x000107c4",func-name="main",offset="8",
21982 inst="sethi %hi(0x11800), %o2"@},
21983 @{address="0x000107c8",func-name="main",offset="12",
21984 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
21985 @{address="0x000107cc",func-name="main",offset="16",
21986 inst="sethi %hi(0x11800), %o2"@},
21987 @{address="0x000107d0",func-name="main",offset="20",
21988 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
21992 Disassemble the whole @code{main} function. Line 32 is part of
21996 -data-disassemble -f basics.c -l 32 -- 0
21998 @{address="0x000107bc",func-name="main",offset="0",
21999 inst="save %sp, -112, %sp"@},
22000 @{address="0x000107c0",func-name="main",offset="4",
22001 inst="mov 2, %o0"@},
22002 @{address="0x000107c4",func-name="main",offset="8",
22003 inst="sethi %hi(0x11800), %o2"@},
22005 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22006 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22010 Disassemble 3 instructions from the start of @code{main}:
22014 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22016 @{address="0x000107bc",func-name="main",offset="0",
22017 inst="save %sp, -112, %sp"@},
22018 @{address="0x000107c0",func-name="main",offset="4",
22019 inst="mov 2, %o0"@},
22020 @{address="0x000107c4",func-name="main",offset="8",
22021 inst="sethi %hi(0x11800), %o2"@}]
22025 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22029 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22031 src_and_asm_line=@{line="31",
22032 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22033 testsuite/gdb.mi/basics.c",line_asm_insn=[
22034 @{address="0x000107bc",func-name="main",offset="0",
22035 inst="save %sp, -112, %sp"@}]@},
22036 src_and_asm_line=@{line="32",
22037 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22038 testsuite/gdb.mi/basics.c",line_asm_insn=[
22039 @{address="0x000107c0",func-name="main",offset="4",
22040 inst="mov 2, %o0"@},
22041 @{address="0x000107c4",func-name="main",offset="8",
22042 inst="sethi %hi(0x11800), %o2"@}]@}]
22047 @subheading The @code{-data-evaluate-expression} Command
22048 @findex -data-evaluate-expression
22050 @subsubheading Synopsis
22053 -data-evaluate-expression @var{expr}
22056 Evaluate @var{expr} as an expression. The expression could contain an
22057 inferior function call. The function call will execute synchronously.
22058 If the expression contains spaces, it must be enclosed in double quotes.
22060 @subsubheading @value{GDBN} Command
22062 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22063 @samp{call}. In @code{gdbtk} only, there's a corresponding
22064 @samp{gdb_eval} command.
22066 @subsubheading Example
22068 In the following example, the numbers that precede the commands are the
22069 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22070 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22074 211-data-evaluate-expression A
22077 311-data-evaluate-expression &A
22078 311^done,value="0xefffeb7c"
22080 411-data-evaluate-expression A+3
22083 511-data-evaluate-expression "A + 3"
22089 @subheading The @code{-data-list-changed-registers} Command
22090 @findex -data-list-changed-registers
22092 @subsubheading Synopsis
22095 -data-list-changed-registers
22098 Display a list of the registers that have changed.
22100 @subsubheading @value{GDBN} Command
22102 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
22103 has the corresponding command @samp{gdb_changed_register_list}.
22105 @subsubheading Example
22107 On a PPC MBX board:
22115 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
22116 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
22119 -data-list-changed-registers
22120 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
22121 "10","11","13","14","15","16","17","18","19","20","21","22","23",
22122 "24","25","26","27","28","30","31","64","65","66","67","69"]
22127 @subheading The @code{-data-list-register-names} Command
22128 @findex -data-list-register-names
22130 @subsubheading Synopsis
22133 -data-list-register-names [ ( @var{regno} )+ ]
22136 Show a list of register names for the current target. If no arguments
22137 are given, it shows a list of the names of all the registers. If
22138 integer numbers are given as arguments, it will print a list of the
22139 names of the registers corresponding to the arguments. To ensure
22140 consistency between a register name and its number, the output list may
22141 include empty register names.
22143 @subsubheading @value{GDBN} Command
22145 @value{GDBN} does not have a command which corresponds to
22146 @samp{-data-list-register-names}. In @code{gdbtk} there is a
22147 corresponding command @samp{gdb_regnames}.
22149 @subsubheading Example
22151 For the PPC MBX board:
22154 -data-list-register-names
22155 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
22156 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
22157 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
22158 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
22159 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
22160 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
22161 "", "pc","ps","cr","lr","ctr","xer"]
22163 -data-list-register-names 1 2 3
22164 ^done,register-names=["r1","r2","r3"]
22168 @subheading The @code{-data-list-register-values} Command
22169 @findex -data-list-register-values
22171 @subsubheading Synopsis
22174 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
22177 Display the registers' contents. @var{fmt} is the format according to
22178 which the registers' contents are to be returned, followed by an optional
22179 list of numbers specifying the registers to display. A missing list of
22180 numbers indicates that the contents of all the registers must be returned.
22182 Allowed formats for @var{fmt} are:
22199 @subsubheading @value{GDBN} Command
22201 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
22202 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
22204 @subsubheading Example
22206 For a PPC MBX board (note: line breaks are for readability only, they
22207 don't appear in the actual output):
22211 -data-list-register-values r 64 65
22212 ^done,register-values=[@{number="64",value="0xfe00a300"@},
22213 @{number="65",value="0x00029002"@}]
22215 -data-list-register-values x
22216 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
22217 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
22218 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
22219 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
22220 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
22221 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
22222 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
22223 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
22224 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
22225 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
22226 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
22227 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
22228 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
22229 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
22230 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
22231 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
22232 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
22233 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
22234 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
22235 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
22236 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
22237 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
22238 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
22239 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
22240 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
22241 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
22242 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
22243 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
22244 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
22245 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
22246 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
22247 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
22248 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
22249 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
22250 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
22251 @{number="69",value="0x20002b03"@}]
22256 @subheading The @code{-data-read-memory} Command
22257 @findex -data-read-memory
22259 @subsubheading Synopsis
22262 -data-read-memory [ -o @var{byte-offset} ]
22263 @var{address} @var{word-format} @var{word-size}
22264 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
22271 @item @var{address}
22272 An expression specifying the address of the first memory word to be
22273 read. Complex expressions containing embedded white space should be
22274 quoted using the C convention.
22276 @item @var{word-format}
22277 The format to be used to print the memory words. The notation is the
22278 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
22281 @item @var{word-size}
22282 The size of each memory word in bytes.
22284 @item @var{nr-rows}
22285 The number of rows in the output table.
22287 @item @var{nr-cols}
22288 The number of columns in the output table.
22291 If present, indicates that each row should include an @sc{ascii} dump. The
22292 value of @var{aschar} is used as a padding character when a byte is not a
22293 member of the printable @sc{ascii} character set (printable @sc{ascii}
22294 characters are those whose code is between 32 and 126, inclusively).
22296 @item @var{byte-offset}
22297 An offset to add to the @var{address} before fetching memory.
22300 This command displays memory contents as a table of @var{nr-rows} by
22301 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
22302 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
22303 (returned as @samp{total-bytes}). Should less than the requested number
22304 of bytes be returned by the target, the missing words are identified
22305 using @samp{N/A}. The number of bytes read from the target is returned
22306 in @samp{nr-bytes} and the starting address used to read memory in
22309 The address of the next/previous row or page is available in
22310 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
22313 @subsubheading @value{GDBN} Command
22315 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
22316 @samp{gdb_get_mem} memory read command.
22318 @subsubheading Example
22320 Read six bytes of memory starting at @code{bytes+6} but then offset by
22321 @code{-6} bytes. Format as three rows of two columns. One byte per
22322 word. Display each word in hex.
22326 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
22327 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
22328 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
22329 prev-page="0x0000138a",memory=[
22330 @{addr="0x00001390",data=["0x00","0x01"]@},
22331 @{addr="0x00001392",data=["0x02","0x03"]@},
22332 @{addr="0x00001394",data=["0x04","0x05"]@}]
22336 Read two bytes of memory starting at address @code{shorts + 64} and
22337 display as a single word formatted in decimal.
22341 5-data-read-memory shorts+64 d 2 1 1
22342 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
22343 next-row="0x00001512",prev-row="0x0000150e",
22344 next-page="0x00001512",prev-page="0x0000150e",memory=[
22345 @{addr="0x00001510",data=["128"]@}]
22349 Read thirty two bytes of memory starting at @code{bytes+16} and format
22350 as eight rows of four columns. Include a string encoding with @samp{x}
22351 used as the non-printable character.
22355 4-data-read-memory bytes+16 x 1 8 4 x
22356 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
22357 next-row="0x000013c0",prev-row="0x0000139c",
22358 next-page="0x000013c0",prev-page="0x00001380",memory=[
22359 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
22360 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
22361 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
22362 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
22363 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
22364 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
22365 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
22366 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
22370 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22371 @node GDB/MI Tracepoint Commands
22372 @section @sc{gdb/mi} Tracepoint Commands
22374 The tracepoint commands are not yet implemented.
22376 @c @subheading -trace-actions
22378 @c @subheading -trace-delete
22380 @c @subheading -trace-disable
22382 @c @subheading -trace-dump
22384 @c @subheading -trace-enable
22386 @c @subheading -trace-exists
22388 @c @subheading -trace-find
22390 @c @subheading -trace-frame-number
22392 @c @subheading -trace-info
22394 @c @subheading -trace-insert
22396 @c @subheading -trace-list
22398 @c @subheading -trace-pass-count
22400 @c @subheading -trace-save
22402 @c @subheading -trace-start
22404 @c @subheading -trace-stop
22407 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22408 @node GDB/MI Symbol Query
22409 @section @sc{gdb/mi} Symbol Query Commands
22412 @subheading The @code{-symbol-info-address} Command
22413 @findex -symbol-info-address
22415 @subsubheading Synopsis
22418 -symbol-info-address @var{symbol}
22421 Describe where @var{symbol} is stored.
22423 @subsubheading @value{GDBN} Command
22425 The corresponding @value{GDBN} command is @samp{info address}.
22427 @subsubheading Example
22431 @subheading The @code{-symbol-info-file} Command
22432 @findex -symbol-info-file
22434 @subsubheading Synopsis
22440 Show the file for the symbol.
22442 @subsubheading @value{GDBN} Command
22444 There's no equivalent @value{GDBN} command. @code{gdbtk} has
22445 @samp{gdb_find_file}.
22447 @subsubheading Example
22451 @subheading The @code{-symbol-info-function} Command
22452 @findex -symbol-info-function
22454 @subsubheading Synopsis
22457 -symbol-info-function
22460 Show which function the symbol lives in.
22462 @subsubheading @value{GDBN} Command
22464 @samp{gdb_get_function} in @code{gdbtk}.
22466 @subsubheading Example
22470 @subheading The @code{-symbol-info-line} Command
22471 @findex -symbol-info-line
22473 @subsubheading Synopsis
22479 Show the core addresses of the code for a source line.
22481 @subsubheading @value{GDBN} Command
22483 The corresponding @value{GDBN} command is @samp{info line}.
22484 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
22486 @subsubheading Example
22490 @subheading The @code{-symbol-info-symbol} Command
22491 @findex -symbol-info-symbol
22493 @subsubheading Synopsis
22496 -symbol-info-symbol @var{addr}
22499 Describe what symbol is at location @var{addr}.
22501 @subsubheading @value{GDBN} Command
22503 The corresponding @value{GDBN} command is @samp{info symbol}.
22505 @subsubheading Example
22509 @subheading The @code{-symbol-list-functions} Command
22510 @findex -symbol-list-functions
22512 @subsubheading Synopsis
22515 -symbol-list-functions
22518 List the functions in the executable.
22520 @subsubheading @value{GDBN} Command
22522 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
22523 @samp{gdb_search} in @code{gdbtk}.
22525 @subsubheading Example
22529 @subheading The @code{-symbol-list-lines} Command
22530 @findex -symbol-list-lines
22532 @subsubheading Synopsis
22535 -symbol-list-lines @var{filename}
22538 Print the list of lines that contain code and their associated program
22539 addresses for the given source filename. The entries are sorted in
22540 ascending PC order.
22542 @subsubheading @value{GDBN} Command
22544 There is no corresponding @value{GDBN} command.
22546 @subsubheading Example
22549 -symbol-list-lines basics.c
22550 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
22555 @subheading The @code{-symbol-list-types} Command
22556 @findex -symbol-list-types
22558 @subsubheading Synopsis
22564 List all the type names.
22566 @subsubheading @value{GDBN} Command
22568 The corresponding commands are @samp{info types} in @value{GDBN},
22569 @samp{gdb_search} in @code{gdbtk}.
22571 @subsubheading Example
22575 @subheading The @code{-symbol-list-variables} Command
22576 @findex -symbol-list-variables
22578 @subsubheading Synopsis
22581 -symbol-list-variables
22584 List all the global and static variable names.
22586 @subsubheading @value{GDBN} Command
22588 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
22590 @subsubheading Example
22594 @subheading The @code{-symbol-locate} Command
22595 @findex -symbol-locate
22597 @subsubheading Synopsis
22603 @subsubheading @value{GDBN} Command
22605 @samp{gdb_loc} in @code{gdbtk}.
22607 @subsubheading Example
22611 @subheading The @code{-symbol-type} Command
22612 @findex -symbol-type
22614 @subsubheading Synopsis
22617 -symbol-type @var{variable}
22620 Show type of @var{variable}.
22622 @subsubheading @value{GDBN} Command
22624 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
22625 @samp{gdb_obj_variable}.
22627 @subsubheading Example
22631 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22632 @node GDB/MI File Commands
22633 @section @sc{gdb/mi} File Commands
22635 This section describes the GDB/MI commands to specify executable file names
22636 and to read in and obtain symbol table information.
22638 @subheading The @code{-file-exec-and-symbols} Command
22639 @findex -file-exec-and-symbols
22641 @subsubheading Synopsis
22644 -file-exec-and-symbols @var{file}
22647 Specify the executable file to be debugged. This file is the one from
22648 which the symbol table is also read. If no file is specified, the
22649 command clears the executable and symbol information. If breakpoints
22650 are set when using this command with no arguments, @value{GDBN} will produce
22651 error messages. Otherwise, no output is produced, except a completion
22654 @subsubheading @value{GDBN} Command
22656 The corresponding @value{GDBN} command is @samp{file}.
22658 @subsubheading Example
22662 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22668 @subheading The @code{-file-exec-file} Command
22669 @findex -file-exec-file
22671 @subsubheading Synopsis
22674 -file-exec-file @var{file}
22677 Specify the executable file to be debugged. Unlike
22678 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
22679 from this file. If used without argument, @value{GDBN} clears the information
22680 about the executable file. No output is produced, except a completion
22683 @subsubheading @value{GDBN} Command
22685 The corresponding @value{GDBN} command is @samp{exec-file}.
22687 @subsubheading Example
22691 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22697 @subheading The @code{-file-list-exec-sections} Command
22698 @findex -file-list-exec-sections
22700 @subsubheading Synopsis
22703 -file-list-exec-sections
22706 List the sections of the current executable file.
22708 @subsubheading @value{GDBN} Command
22710 The @value{GDBN} command @samp{info file} shows, among the rest, the same
22711 information as this command. @code{gdbtk} has a corresponding command
22712 @samp{gdb_load_info}.
22714 @subsubheading Example
22718 @subheading The @code{-file-list-exec-source-file} Command
22719 @findex -file-list-exec-source-file
22721 @subsubheading Synopsis
22724 -file-list-exec-source-file
22727 List the line number, the current source file, and the absolute path
22728 to the current source file for the current executable. The macro
22729 information field has a value of @samp{1} or @samp{0} depending on
22730 whether or not the file includes preprocessor macro information.
22732 @subsubheading @value{GDBN} Command
22734 The @value{GDBN} equivalent is @samp{info source}
22736 @subsubheading Example
22740 123-file-list-exec-source-file
22741 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
22746 @subheading The @code{-file-list-exec-source-files} Command
22747 @findex -file-list-exec-source-files
22749 @subsubheading Synopsis
22752 -file-list-exec-source-files
22755 List the source files for the current executable.
22757 It will always output the filename, but only when @value{GDBN} can find
22758 the absolute file name of a source file, will it output the fullname.
22760 @subsubheading @value{GDBN} Command
22762 The @value{GDBN} equivalent is @samp{info sources}.
22763 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
22765 @subsubheading Example
22768 -file-list-exec-source-files
22770 @{file=foo.c,fullname=/home/foo.c@},
22771 @{file=/home/bar.c,fullname=/home/bar.c@},
22772 @{file=gdb_could_not_find_fullpath.c@}]
22776 @subheading The @code{-file-list-shared-libraries} Command
22777 @findex -file-list-shared-libraries
22779 @subsubheading Synopsis
22782 -file-list-shared-libraries
22785 List the shared libraries in the program.
22787 @subsubheading @value{GDBN} Command
22789 The corresponding @value{GDBN} command is @samp{info shared}.
22791 @subsubheading Example
22795 @subheading The @code{-file-list-symbol-files} Command
22796 @findex -file-list-symbol-files
22798 @subsubheading Synopsis
22801 -file-list-symbol-files
22806 @subsubheading @value{GDBN} Command
22808 The corresponding @value{GDBN} command is @samp{info file} (part of it).
22810 @subsubheading Example
22814 @subheading The @code{-file-symbol-file} Command
22815 @findex -file-symbol-file
22817 @subsubheading Synopsis
22820 -file-symbol-file @var{file}
22823 Read symbol table info from the specified @var{file} argument. When
22824 used without arguments, clears @value{GDBN}'s symbol table info. No output is
22825 produced, except for a completion notification.
22827 @subsubheading @value{GDBN} Command
22829 The corresponding @value{GDBN} command is @samp{symbol-file}.
22831 @subsubheading Example
22835 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
22841 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22842 @node GDB/MI Memory Overlay Commands
22843 @section @sc{gdb/mi} Memory Overlay Commands
22845 The memory overlay commands are not implemented.
22847 @c @subheading -overlay-auto
22849 @c @subheading -overlay-list-mapping-state
22851 @c @subheading -overlay-list-overlays
22853 @c @subheading -overlay-map
22855 @c @subheading -overlay-off
22857 @c @subheading -overlay-on
22859 @c @subheading -overlay-unmap
22861 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22862 @node GDB/MI Signal Handling Commands
22863 @section @sc{gdb/mi} Signal Handling Commands
22865 Signal handling commands are not implemented.
22867 @c @subheading -signal-handle
22869 @c @subheading -signal-list-handle-actions
22871 @c @subheading -signal-list-signal-types
22875 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22876 @node GDB/MI Target Manipulation
22877 @section @sc{gdb/mi} Target Manipulation Commands
22880 @subheading The @code{-target-attach} Command
22881 @findex -target-attach
22883 @subsubheading Synopsis
22886 -target-attach @var{pid} | @var{gid} | @var{file}
22889 Attach to a process @var{pid} or a file @var{file} outside of
22890 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
22891 group, the id previously returned by
22892 @samp{-list-thread-groups --available} must be used.
22894 @subsubheading @value{GDBN} Command
22896 The corresponding @value{GDBN} command is @samp{attach}.
22898 @subsubheading Example
22902 =thread-created,id="1"
22903 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
22908 @subheading The @code{-target-compare-sections} Command
22909 @findex -target-compare-sections
22911 @subsubheading Synopsis
22914 -target-compare-sections [ @var{section} ]
22917 Compare data of section @var{section} on target to the exec file.
22918 Without the argument, all sections are compared.
22920 @subsubheading @value{GDBN} Command
22922 The @value{GDBN} equivalent is @samp{compare-sections}.
22924 @subsubheading Example
22928 @subheading The @code{-target-detach} Command
22929 @findex -target-detach
22931 @subsubheading Synopsis
22934 -target-detach [ @var{pid} | @var{gid} ]
22937 Detach from the remote target which normally resumes its execution.
22938 If either @var{pid} or @var{gid} is specified, detaches from either
22939 the specified process, or specified thread group. There's no output.
22941 @subsubheading @value{GDBN} Command
22943 The corresponding @value{GDBN} command is @samp{detach}.
22945 @subsubheading Example
22955 @subheading The @code{-target-disconnect} Command
22956 @findex -target-disconnect
22958 @subsubheading Synopsis
22964 Disconnect from the remote target. There's no output and the target is
22965 generally not resumed.
22967 @subsubheading @value{GDBN} Command
22969 The corresponding @value{GDBN} command is @samp{disconnect}.
22971 @subsubheading Example
22981 @subheading The @code{-target-download} Command
22982 @findex -target-download
22984 @subsubheading Synopsis
22990 Loads the executable onto the remote target.
22991 It prints out an update message every half second, which includes the fields:
22995 The name of the section.
22997 The size of what has been sent so far for that section.
22999 The size of the section.
23001 The total size of what was sent so far (the current and the previous sections).
23003 The size of the overall executable to download.
23007 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23008 @sc{gdb/mi} Output Syntax}).
23010 In addition, it prints the name and size of the sections, as they are
23011 downloaded. These messages include the following fields:
23015 The name of the section.
23017 The size of the section.
23019 The size of the overall executable to download.
23023 At the end, a summary is printed.
23025 @subsubheading @value{GDBN} Command
23027 The corresponding @value{GDBN} command is @samp{load}.
23029 @subsubheading Example
23031 Note: each status message appears on a single line. Here the messages
23032 have been broken down so that they can fit onto a page.
23037 +download,@{section=".text",section-size="6668",total-size="9880"@}
23038 +download,@{section=".text",section-sent="512",section-size="6668",
23039 total-sent="512",total-size="9880"@}
23040 +download,@{section=".text",section-sent="1024",section-size="6668",
23041 total-sent="1024",total-size="9880"@}
23042 +download,@{section=".text",section-sent="1536",section-size="6668",
23043 total-sent="1536",total-size="9880"@}
23044 +download,@{section=".text",section-sent="2048",section-size="6668",
23045 total-sent="2048",total-size="9880"@}
23046 +download,@{section=".text",section-sent="2560",section-size="6668",
23047 total-sent="2560",total-size="9880"@}
23048 +download,@{section=".text",section-sent="3072",section-size="6668",
23049 total-sent="3072",total-size="9880"@}
23050 +download,@{section=".text",section-sent="3584",section-size="6668",
23051 total-sent="3584",total-size="9880"@}
23052 +download,@{section=".text",section-sent="4096",section-size="6668",
23053 total-sent="4096",total-size="9880"@}
23054 +download,@{section=".text",section-sent="4608",section-size="6668",
23055 total-sent="4608",total-size="9880"@}
23056 +download,@{section=".text",section-sent="5120",section-size="6668",
23057 total-sent="5120",total-size="9880"@}
23058 +download,@{section=".text",section-sent="5632",section-size="6668",
23059 total-sent="5632",total-size="9880"@}
23060 +download,@{section=".text",section-sent="6144",section-size="6668",
23061 total-sent="6144",total-size="9880"@}
23062 +download,@{section=".text",section-sent="6656",section-size="6668",
23063 total-sent="6656",total-size="9880"@}
23064 +download,@{section=".init",section-size="28",total-size="9880"@}
23065 +download,@{section=".fini",section-size="28",total-size="9880"@}
23066 +download,@{section=".data",section-size="3156",total-size="9880"@}
23067 +download,@{section=".data",section-sent="512",section-size="3156",
23068 total-sent="7236",total-size="9880"@}
23069 +download,@{section=".data",section-sent="1024",section-size="3156",
23070 total-sent="7748",total-size="9880"@}
23071 +download,@{section=".data",section-sent="1536",section-size="3156",
23072 total-sent="8260",total-size="9880"@}
23073 +download,@{section=".data",section-sent="2048",section-size="3156",
23074 total-sent="8772",total-size="9880"@}
23075 +download,@{section=".data",section-sent="2560",section-size="3156",
23076 total-sent="9284",total-size="9880"@}
23077 +download,@{section=".data",section-sent="3072",section-size="3156",
23078 total-sent="9796",total-size="9880"@}
23079 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23085 @subheading The @code{-target-exec-status} Command
23086 @findex -target-exec-status
23088 @subsubheading Synopsis
23091 -target-exec-status
23094 Provide information on the state of the target (whether it is running or
23095 not, for instance).
23097 @subsubheading @value{GDBN} Command
23099 There's no equivalent @value{GDBN} command.
23101 @subsubheading Example
23105 @subheading The @code{-target-list-available-targets} Command
23106 @findex -target-list-available-targets
23108 @subsubheading Synopsis
23111 -target-list-available-targets
23114 List the possible targets to connect to.
23116 @subsubheading @value{GDBN} Command
23118 The corresponding @value{GDBN} command is @samp{help target}.
23120 @subsubheading Example
23124 @subheading The @code{-target-list-current-targets} Command
23125 @findex -target-list-current-targets
23127 @subsubheading Synopsis
23130 -target-list-current-targets
23133 Describe the current target.
23135 @subsubheading @value{GDBN} Command
23137 The corresponding information is printed by @samp{info file} (among
23140 @subsubheading Example
23144 @subheading The @code{-target-list-parameters} Command
23145 @findex -target-list-parameters
23147 @subsubheading Synopsis
23150 -target-list-parameters
23155 @subsubheading @value{GDBN} Command
23159 @subsubheading Example
23163 @subheading The @code{-target-select} Command
23164 @findex -target-select
23166 @subsubheading Synopsis
23169 -target-select @var{type} @var{parameters @dots{}}
23172 Connect @value{GDBN} to the remote target. This command takes two args:
23176 The type of target, for instance @samp{remote}, etc.
23177 @item @var{parameters}
23178 Device names, host names and the like. @xref{Target Commands, ,
23179 Commands for Managing Targets}, for more details.
23182 The output is a connection notification, followed by the address at
23183 which the target program is, in the following form:
23186 ^connected,addr="@var{address}",func="@var{function name}",
23187 args=[@var{arg list}]
23190 @subsubheading @value{GDBN} Command
23192 The corresponding @value{GDBN} command is @samp{target}.
23194 @subsubheading Example
23198 -target-select remote /dev/ttya
23199 ^connected,addr="0xfe00a300",func="??",args=[]
23203 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23204 @node GDB/MI File Transfer Commands
23205 @section @sc{gdb/mi} File Transfer Commands
23208 @subheading The @code{-target-file-put} Command
23209 @findex -target-file-put
23211 @subsubheading Synopsis
23214 -target-file-put @var{hostfile} @var{targetfile}
23217 Copy file @var{hostfile} from the host system (the machine running
23218 @value{GDBN}) to @var{targetfile} on the target system.
23220 @subsubheading @value{GDBN} Command
23222 The corresponding @value{GDBN} command is @samp{remote put}.
23224 @subsubheading Example
23228 -target-file-put localfile remotefile
23234 @subheading The @code{-target-file-get} Command
23235 @findex -target-file-get
23237 @subsubheading Synopsis
23240 -target-file-get @var{targetfile} @var{hostfile}
23243 Copy file @var{targetfile} from the target system to @var{hostfile}
23244 on the host system.
23246 @subsubheading @value{GDBN} Command
23248 The corresponding @value{GDBN} command is @samp{remote get}.
23250 @subsubheading Example
23254 -target-file-get remotefile localfile
23260 @subheading The @code{-target-file-delete} Command
23261 @findex -target-file-delete
23263 @subsubheading Synopsis
23266 -target-file-delete @var{targetfile}
23269 Delete @var{targetfile} from the target system.
23271 @subsubheading @value{GDBN} Command
23273 The corresponding @value{GDBN} command is @samp{remote delete}.
23275 @subsubheading Example
23279 -target-file-delete remotefile
23285 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23286 @node GDB/MI Miscellaneous Commands
23287 @section Miscellaneous @sc{gdb/mi} Commands
23289 @c @subheading -gdb-complete
23291 @subheading The @code{-gdb-exit} Command
23294 @subsubheading Synopsis
23300 Exit @value{GDBN} immediately.
23302 @subsubheading @value{GDBN} Command
23304 Approximately corresponds to @samp{quit}.
23306 @subsubheading Example
23315 @subheading The @code{-exec-abort} Command
23316 @findex -exec-abort
23318 @subsubheading Synopsis
23324 Kill the inferior running program.
23326 @subsubheading @value{GDBN} Command
23328 The corresponding @value{GDBN} command is @samp{kill}.
23330 @subsubheading Example
23334 @subheading The @code{-gdb-set} Command
23337 @subsubheading Synopsis
23343 Set an internal @value{GDBN} variable.
23344 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
23346 @subsubheading @value{GDBN} Command
23348 The corresponding @value{GDBN} command is @samp{set}.
23350 @subsubheading Example
23360 @subheading The @code{-gdb-show} Command
23363 @subsubheading Synopsis
23369 Show the current value of a @value{GDBN} variable.
23371 @subsubheading @value{GDBN} Command
23373 The corresponding @value{GDBN} command is @samp{show}.
23375 @subsubheading Example
23384 @c @subheading -gdb-source
23387 @subheading The @code{-gdb-version} Command
23388 @findex -gdb-version
23390 @subsubheading Synopsis
23396 Show version information for @value{GDBN}. Used mostly in testing.
23398 @subsubheading @value{GDBN} Command
23400 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
23401 default shows this information when you start an interactive session.
23403 @subsubheading Example
23405 @c This example modifies the actual output from GDB to avoid overfull
23411 ~Copyright 2000 Free Software Foundation, Inc.
23412 ~GDB is free software, covered by the GNU General Public License, and
23413 ~you are welcome to change it and/or distribute copies of it under
23414 ~ certain conditions.
23415 ~Type "show copying" to see the conditions.
23416 ~There is absolutely no warranty for GDB. Type "show warranty" for
23418 ~This GDB was configured as
23419 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
23424 @subheading The @code{-list-features} Command
23425 @findex -list-features
23427 Returns a list of particular features of the MI protocol that
23428 this version of gdb implements. A feature can be a command,
23429 or a new field in an output of some command, or even an
23430 important bugfix. While a frontend can sometimes detect presence
23431 of a feature at runtime, it is easier to perform detection at debugger
23434 The command returns a list of strings, with each string naming an
23435 available feature. Each returned string is just a name, it does not
23436 have any internal structure. The list of possible feature names
23442 (gdb) -list-features
23443 ^done,result=["feature1","feature2"]
23446 The current list of features is:
23449 @item frozen-varobjs
23450 Indicates presence of the @code{-var-set-frozen} command, as well
23451 as possible presense of the @code{frozen} field in the output
23452 of @code{-varobj-create}.
23453 @item pending-breakpoints
23454 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
23456 Indicates presence of the @code{-thread-info} command.
23460 @subheading The @code{-list-target-features} Command
23461 @findex -list-target-features
23463 Returns a list of particular features that are supported by the
23464 target. Those features affect the permitted MI commands, but
23465 unlike the features reported by the @code{-list-features} command, the
23466 features depend on which target GDB is using at the moment. Whenever
23467 a target can change, due to commands such as @code{-target-select},
23468 @code{-target-attach} or @code{-exec-run}, the list of target features
23469 may change, and the frontend should obtain it again.
23473 (gdb) -list-features
23474 ^done,result=["async"]
23477 The current list of features is:
23481 Indicates that the target is capable of asynchronous command
23482 execution, which means that @value{GDBN} will accept further commands
23483 while the target is running.
23487 @subheading The @code{-list-thread-groups} Command
23488 @findex -list-thread-groups
23490 @subheading Synopsis
23493 -list-thread-groups [ --available ] [ @var{group} ]
23496 When used without the @var{group} parameter, lists top-level thread
23497 groups that are being debugged. When used with the @var{group}
23498 parameter, the children of the specified group are listed. The
23499 children can be either threads, or other groups. At present,
23500 @value{GDBN} will not report both threads and groups as children at
23501 the same time, but it may change in future.
23503 With the @samp{--available} option, instead of reporting groups that
23504 are been debugged, GDB will report all thread groups available on the
23505 target. Using the @samp{--available} option together with @var{group}
23508 @subheading Example
23512 -list-thread-groups
23513 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
23514 -list-thread-groups 17
23515 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
23516 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
23517 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
23518 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
23519 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
23522 @subheading The @code{-interpreter-exec} Command
23523 @findex -interpreter-exec
23525 @subheading Synopsis
23528 -interpreter-exec @var{interpreter} @var{command}
23530 @anchor{-interpreter-exec}
23532 Execute the specified @var{command} in the given @var{interpreter}.
23534 @subheading @value{GDBN} Command
23536 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
23538 @subheading Example
23542 -interpreter-exec console "break main"
23543 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
23544 &"During symbol reading, bad structure-type format.\n"
23545 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
23550 @subheading The @code{-inferior-tty-set} Command
23551 @findex -inferior-tty-set
23553 @subheading Synopsis
23556 -inferior-tty-set /dev/pts/1
23559 Set terminal for future runs of the program being debugged.
23561 @subheading @value{GDBN} Command
23563 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
23565 @subheading Example
23569 -inferior-tty-set /dev/pts/1
23574 @subheading The @code{-inferior-tty-show} Command
23575 @findex -inferior-tty-show
23577 @subheading Synopsis
23583 Show terminal for future runs of program being debugged.
23585 @subheading @value{GDBN} Command
23587 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
23589 @subheading Example
23593 -inferior-tty-set /dev/pts/1
23597 ^done,inferior_tty_terminal="/dev/pts/1"
23601 @subheading The @code{-enable-timings} Command
23602 @findex -enable-timings
23604 @subheading Synopsis
23607 -enable-timings [yes | no]
23610 Toggle the printing of the wallclock, user and system times for an MI
23611 command as a field in its output. This command is to help frontend
23612 developers optimize the performance of their code. No argument is
23613 equivalent to @samp{yes}.
23615 @subheading @value{GDBN} Command
23619 @subheading Example
23627 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23628 addr="0x080484ed",func="main",file="myprog.c",
23629 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
23630 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
23638 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
23639 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
23640 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
23641 fullname="/home/nickrob/myprog.c",line="73"@}
23646 @chapter @value{GDBN} Annotations
23648 This chapter describes annotations in @value{GDBN}. Annotations were
23649 designed to interface @value{GDBN} to graphical user interfaces or other
23650 similar programs which want to interact with @value{GDBN} at a
23651 relatively high level.
23653 The annotation mechanism has largely been superseded by @sc{gdb/mi}
23657 This is Edition @value{EDITION}, @value{DATE}.
23661 * Annotations Overview:: What annotations are; the general syntax.
23662 * Server Prefix:: Issuing a command without affecting user state.
23663 * Prompting:: Annotations marking @value{GDBN}'s need for input.
23664 * Errors:: Annotations for error messages.
23665 * Invalidation:: Some annotations describe things now invalid.
23666 * Annotations for Running::
23667 Whether the program is running, how it stopped, etc.
23668 * Source Annotations:: Annotations describing source code.
23671 @node Annotations Overview
23672 @section What is an Annotation?
23673 @cindex annotations
23675 Annotations start with a newline character, two @samp{control-z}
23676 characters, and the name of the annotation. If there is no additional
23677 information associated with this annotation, the name of the annotation
23678 is followed immediately by a newline. If there is additional
23679 information, the name of the annotation is followed by a space, the
23680 additional information, and a newline. The additional information
23681 cannot contain newline characters.
23683 Any output not beginning with a newline and two @samp{control-z}
23684 characters denotes literal output from @value{GDBN}. Currently there is
23685 no need for @value{GDBN} to output a newline followed by two
23686 @samp{control-z} characters, but if there was such a need, the
23687 annotations could be extended with an @samp{escape} annotation which
23688 means those three characters as output.
23690 The annotation @var{level}, which is specified using the
23691 @option{--annotate} command line option (@pxref{Mode Options}), controls
23692 how much information @value{GDBN} prints together with its prompt,
23693 values of expressions, source lines, and other types of output. Level 0
23694 is for no annotations, level 1 is for use when @value{GDBN} is run as a
23695 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
23696 for programs that control @value{GDBN}, and level 2 annotations have
23697 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
23698 Interface, annotate, GDB's Obsolete Annotations}).
23701 @kindex set annotate
23702 @item set annotate @var{level}
23703 The @value{GDBN} command @code{set annotate} sets the level of
23704 annotations to the specified @var{level}.
23706 @item show annotate
23707 @kindex show annotate
23708 Show the current annotation level.
23711 This chapter describes level 3 annotations.
23713 A simple example of starting up @value{GDBN} with annotations is:
23716 $ @kbd{gdb --annotate=3}
23718 Copyright 2003 Free Software Foundation, Inc.
23719 GDB is free software, covered by the GNU General Public License,
23720 and you are welcome to change it and/or distribute copies of it
23721 under certain conditions.
23722 Type "show copying" to see the conditions.
23723 There is absolutely no warranty for GDB. Type "show warranty"
23725 This GDB was configured as "i386-pc-linux-gnu"
23736 Here @samp{quit} is input to @value{GDBN}; the rest is output from
23737 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
23738 denotes a @samp{control-z} character) are annotations; the rest is
23739 output from @value{GDBN}.
23741 @node Server Prefix
23742 @section The Server Prefix
23743 @cindex server prefix
23745 If you prefix a command with @samp{server } then it will not affect
23746 the command history, nor will it affect @value{GDBN}'s notion of which
23747 command to repeat if @key{RET} is pressed on a line by itself. This
23748 means that commands can be run behind a user's back by a front-end in
23749 a transparent manner.
23751 The server prefix does not affect the recording of values into the value
23752 history; to print a value without recording it into the value history,
23753 use the @code{output} command instead of the @code{print} command.
23756 @section Annotation for @value{GDBN} Input
23758 @cindex annotations for prompts
23759 When @value{GDBN} prompts for input, it annotates this fact so it is possible
23760 to know when to send output, when the output from a given command is
23763 Different kinds of input each have a different @dfn{input type}. Each
23764 input type has three annotations: a @code{pre-} annotation, which
23765 denotes the beginning of any prompt which is being output, a plain
23766 annotation, which denotes the end of the prompt, and then a @code{post-}
23767 annotation which denotes the end of any echo which may (or may not) be
23768 associated with the input. For example, the @code{prompt} input type
23769 features the following annotations:
23777 The input types are
23780 @findex pre-prompt annotation
23781 @findex prompt annotation
23782 @findex post-prompt annotation
23784 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
23786 @findex pre-commands annotation
23787 @findex commands annotation
23788 @findex post-commands annotation
23790 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
23791 command. The annotations are repeated for each command which is input.
23793 @findex pre-overload-choice annotation
23794 @findex overload-choice annotation
23795 @findex post-overload-choice annotation
23796 @item overload-choice
23797 When @value{GDBN} wants the user to select between various overloaded functions.
23799 @findex pre-query annotation
23800 @findex query annotation
23801 @findex post-query annotation
23803 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
23805 @findex pre-prompt-for-continue annotation
23806 @findex prompt-for-continue annotation
23807 @findex post-prompt-for-continue annotation
23808 @item prompt-for-continue
23809 When @value{GDBN} is asking the user to press return to continue. Note: Don't
23810 expect this to work well; instead use @code{set height 0} to disable
23811 prompting. This is because the counting of lines is buggy in the
23812 presence of annotations.
23817 @cindex annotations for errors, warnings and interrupts
23819 @findex quit annotation
23824 This annotation occurs right before @value{GDBN} responds to an interrupt.
23826 @findex error annotation
23831 This annotation occurs right before @value{GDBN} responds to an error.
23833 Quit and error annotations indicate that any annotations which @value{GDBN} was
23834 in the middle of may end abruptly. For example, if a
23835 @code{value-history-begin} annotation is followed by a @code{error}, one
23836 cannot expect to receive the matching @code{value-history-end}. One
23837 cannot expect not to receive it either, however; an error annotation
23838 does not necessarily mean that @value{GDBN} is immediately returning all the way
23841 @findex error-begin annotation
23842 A quit or error annotation may be preceded by
23848 Any output between that and the quit or error annotation is the error
23851 Warning messages are not yet annotated.
23852 @c If we want to change that, need to fix warning(), type_error(),
23853 @c range_error(), and possibly other places.
23856 @section Invalidation Notices
23858 @cindex annotations for invalidation messages
23859 The following annotations say that certain pieces of state may have
23863 @findex frames-invalid annotation
23864 @item ^Z^Zframes-invalid
23866 The frames (for example, output from the @code{backtrace} command) may
23869 @findex breakpoints-invalid annotation
23870 @item ^Z^Zbreakpoints-invalid
23872 The breakpoints may have changed. For example, the user just added or
23873 deleted a breakpoint.
23876 @node Annotations for Running
23877 @section Running the Program
23878 @cindex annotations for running programs
23880 @findex starting annotation
23881 @findex stopping annotation
23882 When the program starts executing due to a @value{GDBN} command such as
23883 @code{step} or @code{continue},
23889 is output. When the program stops,
23895 is output. Before the @code{stopped} annotation, a variety of
23896 annotations describe how the program stopped.
23899 @findex exited annotation
23900 @item ^Z^Zexited @var{exit-status}
23901 The program exited, and @var{exit-status} is the exit status (zero for
23902 successful exit, otherwise nonzero).
23904 @findex signalled annotation
23905 @findex signal-name annotation
23906 @findex signal-name-end annotation
23907 @findex signal-string annotation
23908 @findex signal-string-end annotation
23909 @item ^Z^Zsignalled
23910 The program exited with a signal. After the @code{^Z^Zsignalled}, the
23911 annotation continues:
23917 ^Z^Zsignal-name-end
23921 ^Z^Zsignal-string-end
23926 where @var{name} is the name of the signal, such as @code{SIGILL} or
23927 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
23928 as @code{Illegal Instruction} or @code{Segmentation fault}.
23929 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
23930 user's benefit and have no particular format.
23932 @findex signal annotation
23934 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
23935 just saying that the program received the signal, not that it was
23936 terminated with it.
23938 @findex breakpoint annotation
23939 @item ^Z^Zbreakpoint @var{number}
23940 The program hit breakpoint number @var{number}.
23942 @findex watchpoint annotation
23943 @item ^Z^Zwatchpoint @var{number}
23944 The program hit watchpoint number @var{number}.
23947 @node Source Annotations
23948 @section Displaying Source
23949 @cindex annotations for source display
23951 @findex source annotation
23952 The following annotation is used instead of displaying source code:
23955 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
23958 where @var{filename} is an absolute file name indicating which source
23959 file, @var{line} is the line number within that file (where 1 is the
23960 first line in the file), @var{character} is the character position
23961 within the file (where 0 is the first character in the file) (for most
23962 debug formats this will necessarily point to the beginning of a line),
23963 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
23964 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
23965 @var{addr} is the address in the target program associated with the
23966 source which is being displayed. @var{addr} is in the form @samp{0x}
23967 followed by one or more lowercase hex digits (note that this does not
23968 depend on the language).
23971 @chapter Reporting Bugs in @value{GDBN}
23972 @cindex bugs in @value{GDBN}
23973 @cindex reporting bugs in @value{GDBN}
23975 Your bug reports play an essential role in making @value{GDBN} reliable.
23977 Reporting a bug may help you by bringing a solution to your problem, or it
23978 may not. But in any case the principal function of a bug report is to help
23979 the entire community by making the next version of @value{GDBN} work better. Bug
23980 reports are your contribution to the maintenance of @value{GDBN}.
23982 In order for a bug report to serve its purpose, you must include the
23983 information that enables us to fix the bug.
23986 * Bug Criteria:: Have you found a bug?
23987 * Bug Reporting:: How to report bugs
23991 @section Have You Found a Bug?
23992 @cindex bug criteria
23994 If you are not sure whether you have found a bug, here are some guidelines:
23997 @cindex fatal signal
23998 @cindex debugger crash
23999 @cindex crash of debugger
24001 If the debugger gets a fatal signal, for any input whatever, that is a
24002 @value{GDBN} bug. Reliable debuggers never crash.
24004 @cindex error on valid input
24006 If @value{GDBN} produces an error message for valid input, that is a
24007 bug. (Note that if you're cross debugging, the problem may also be
24008 somewhere in the connection to the target.)
24010 @cindex invalid input
24012 If @value{GDBN} does not produce an error message for invalid input,
24013 that is a bug. However, you should note that your idea of
24014 ``invalid input'' might be our idea of ``an extension'' or ``support
24015 for traditional practice''.
24018 If you are an experienced user of debugging tools, your suggestions
24019 for improvement of @value{GDBN} are welcome in any case.
24022 @node Bug Reporting
24023 @section How to Report Bugs
24024 @cindex bug reports
24025 @cindex @value{GDBN} bugs, reporting
24027 A number of companies and individuals offer support for @sc{gnu} products.
24028 If you obtained @value{GDBN} from a support organization, we recommend you
24029 contact that organization first.
24031 You can find contact information for many support companies and
24032 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24034 @c should add a web page ref...
24037 @ifset BUGURL_DEFAULT
24038 In any event, we also recommend that you submit bug reports for
24039 @value{GDBN}. The preferred method is to submit them directly using
24040 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24041 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24044 @strong{Do not send bug reports to @samp{info-gdb}, or to
24045 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24046 not want to receive bug reports. Those that do have arranged to receive
24049 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24050 serves as a repeater. The mailing list and the newsgroup carry exactly
24051 the same messages. Often people think of posting bug reports to the
24052 newsgroup instead of mailing them. This appears to work, but it has one
24053 problem which can be crucial: a newsgroup posting often lacks a mail
24054 path back to the sender. Thus, if we need to ask for more information,
24055 we may be unable to reach you. For this reason, it is better to send
24056 bug reports to the mailing list.
24058 @ifclear BUGURL_DEFAULT
24059 In any event, we also recommend that you submit bug reports for
24060 @value{GDBN} to @value{BUGURL}.
24064 The fundamental principle of reporting bugs usefully is this:
24065 @strong{report all the facts}. If you are not sure whether to state a
24066 fact or leave it out, state it!
24068 Often people omit facts because they think they know what causes the
24069 problem and assume that some details do not matter. Thus, you might
24070 assume that the name of the variable you use in an example does not matter.
24071 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24072 stray memory reference which happens to fetch from the location where that
24073 name is stored in memory; perhaps, if the name were different, the contents
24074 of that location would fool the debugger into doing the right thing despite
24075 the bug. Play it safe and give a specific, complete example. That is the
24076 easiest thing for you to do, and the most helpful.
24078 Keep in mind that the purpose of a bug report is to enable us to fix the
24079 bug. It may be that the bug has been reported previously, but neither
24080 you nor we can know that unless your bug report is complete and
24083 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24084 bell?'' Those bug reports are useless, and we urge everyone to
24085 @emph{refuse to respond to them} except to chide the sender to report
24088 To enable us to fix the bug, you should include all these things:
24092 The version of @value{GDBN}. @value{GDBN} announces it if you start
24093 with no arguments; you can also print it at any time using @code{show
24096 Without this, we will not know whether there is any point in looking for
24097 the bug in the current version of @value{GDBN}.
24100 The type of machine you are using, and the operating system name and
24104 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
24105 ``@value{GCC}--2.8.1''.
24108 What compiler (and its version) was used to compile the program you are
24109 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
24110 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
24111 to get this information; for other compilers, see the documentation for
24115 The command arguments you gave the compiler to compile your example and
24116 observe the bug. For example, did you use @samp{-O}? To guarantee
24117 you will not omit something important, list them all. A copy of the
24118 Makefile (or the output from make) is sufficient.
24120 If we were to try to guess the arguments, we would probably guess wrong
24121 and then we might not encounter the bug.
24124 A complete input script, and all necessary source files, that will
24128 A description of what behavior you observe that you believe is
24129 incorrect. For example, ``It gets a fatal signal.''
24131 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
24132 will certainly notice it. But if the bug is incorrect output, we might
24133 not notice unless it is glaringly wrong. You might as well not give us
24134 a chance to make a mistake.
24136 Even if the problem you experience is a fatal signal, you should still
24137 say so explicitly. Suppose something strange is going on, such as, your
24138 copy of @value{GDBN} is out of synch, or you have encountered a bug in
24139 the C library on your system. (This has happened!) Your copy might
24140 crash and ours would not. If you told us to expect a crash, then when
24141 ours fails to crash, we would know that the bug was not happening for
24142 us. If you had not told us to expect a crash, then we would not be able
24143 to draw any conclusion from our observations.
24146 @cindex recording a session script
24147 To collect all this information, you can use a session recording program
24148 such as @command{script}, which is available on many Unix systems.
24149 Just run your @value{GDBN} session inside @command{script} and then
24150 include the @file{typescript} file with your bug report.
24152 Another way to record a @value{GDBN} session is to run @value{GDBN}
24153 inside Emacs and then save the entire buffer to a file.
24156 If you wish to suggest changes to the @value{GDBN} source, send us context
24157 diffs. If you even discuss something in the @value{GDBN} source, refer to
24158 it by context, not by line number.
24160 The line numbers in our development sources will not match those in your
24161 sources. Your line numbers would convey no useful information to us.
24165 Here are some things that are not necessary:
24169 A description of the envelope of the bug.
24171 Often people who encounter a bug spend a lot of time investigating
24172 which changes to the input file will make the bug go away and which
24173 changes will not affect it.
24175 This is often time consuming and not very useful, because the way we
24176 will find the bug is by running a single example under the debugger
24177 with breakpoints, not by pure deduction from a series of examples.
24178 We recommend that you save your time for something else.
24180 Of course, if you can find a simpler example to report @emph{instead}
24181 of the original one, that is a convenience for us. Errors in the
24182 output will be easier to spot, running under the debugger will take
24183 less time, and so on.
24185 However, simplification is not vital; if you do not want to do this,
24186 report the bug anyway and send us the entire test case you used.
24189 A patch for the bug.
24191 A patch for the bug does help us if it is a good one. But do not omit
24192 the necessary information, such as the test case, on the assumption that
24193 a patch is all we need. We might see problems with your patch and decide
24194 to fix the problem another way, or we might not understand it at all.
24196 Sometimes with a program as complicated as @value{GDBN} it is very hard to
24197 construct an example that will make the program follow a certain path
24198 through the code. If you do not send us the example, we will not be able
24199 to construct one, so we will not be able to verify that the bug is fixed.
24201 And if we cannot understand what bug you are trying to fix, or why your
24202 patch should be an improvement, we will not install it. A test case will
24203 help us to understand.
24206 A guess about what the bug is or what it depends on.
24208 Such guesses are usually wrong. Even we cannot guess right about such
24209 things without first using the debugger to find the facts.
24212 @c The readline documentation is distributed with the readline code
24213 @c and consists of the two following files:
24215 @c inc-hist.texinfo
24216 @c Use -I with makeinfo to point to the appropriate directory,
24217 @c environment var TEXINPUTS with TeX.
24218 @include rluser.texi
24219 @include inc-hist.texinfo
24222 @node Formatting Documentation
24223 @appendix Formatting Documentation
24225 @cindex @value{GDBN} reference card
24226 @cindex reference card
24227 The @value{GDBN} 4 release includes an already-formatted reference card, ready
24228 for printing with PostScript or Ghostscript, in the @file{gdb}
24229 subdirectory of the main source directory@footnote{In
24230 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
24231 release.}. If you can use PostScript or Ghostscript with your printer,
24232 you can print the reference card immediately with @file{refcard.ps}.
24234 The release also includes the source for the reference card. You
24235 can format it, using @TeX{}, by typing:
24241 The @value{GDBN} reference card is designed to print in @dfn{landscape}
24242 mode on US ``letter'' size paper;
24243 that is, on a sheet 11 inches wide by 8.5 inches
24244 high. You will need to specify this form of printing as an option to
24245 your @sc{dvi} output program.
24247 @cindex documentation
24249 All the documentation for @value{GDBN} comes as part of the machine-readable
24250 distribution. The documentation is written in Texinfo format, which is
24251 a documentation system that uses a single source file to produce both
24252 on-line information and a printed manual. You can use one of the Info
24253 formatting commands to create the on-line version of the documentation
24254 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
24256 @value{GDBN} includes an already formatted copy of the on-line Info
24257 version of this manual in the @file{gdb} subdirectory. The main Info
24258 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
24259 subordinate files matching @samp{gdb.info*} in the same directory. If
24260 necessary, you can print out these files, or read them with any editor;
24261 but they are easier to read using the @code{info} subsystem in @sc{gnu}
24262 Emacs or the standalone @code{info} program, available as part of the
24263 @sc{gnu} Texinfo distribution.
24265 If you want to format these Info files yourself, you need one of the
24266 Info formatting programs, such as @code{texinfo-format-buffer} or
24269 If you have @code{makeinfo} installed, and are in the top level
24270 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
24271 version @value{GDBVN}), you can make the Info file by typing:
24278 If you want to typeset and print copies of this manual, you need @TeX{},
24279 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
24280 Texinfo definitions file.
24282 @TeX{} is a typesetting program; it does not print files directly, but
24283 produces output files called @sc{dvi} files. To print a typeset
24284 document, you need a program to print @sc{dvi} files. If your system
24285 has @TeX{} installed, chances are it has such a program. The precise
24286 command to use depends on your system; @kbd{lpr -d} is common; another
24287 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
24288 require a file name without any extension or a @samp{.dvi} extension.
24290 @TeX{} also requires a macro definitions file called
24291 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
24292 written in Texinfo format. On its own, @TeX{} cannot either read or
24293 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
24294 and is located in the @file{gdb-@var{version-number}/texinfo}
24297 If you have @TeX{} and a @sc{dvi} printer program installed, you can
24298 typeset and print this manual. First switch to the @file{gdb}
24299 subdirectory of the main source directory (for example, to
24300 @file{gdb-@value{GDBVN}/gdb}) and type:
24306 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
24308 @node Installing GDB
24309 @appendix Installing @value{GDBN}
24310 @cindex installation
24313 * Requirements:: Requirements for building @value{GDBN}
24314 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
24315 * Separate Objdir:: Compiling @value{GDBN} in another directory
24316 * Config Names:: Specifying names for hosts and targets
24317 * Configure Options:: Summary of options for configure
24321 @section Requirements for Building @value{GDBN}
24322 @cindex building @value{GDBN}, requirements for
24324 Building @value{GDBN} requires various tools and packages to be available.
24325 Other packages will be used only if they are found.
24327 @heading Tools/Packages Necessary for Building @value{GDBN}
24329 @item ISO C90 compiler
24330 @value{GDBN} is written in ISO C90. It should be buildable with any
24331 working C90 compiler, e.g.@: GCC.
24335 @heading Tools/Packages Optional for Building @value{GDBN}
24339 @value{GDBN} can use the Expat XML parsing library. This library may be
24340 included with your operating system distribution; if it is not, you
24341 can get the latest version from @url{http://expat.sourceforge.net}.
24342 The @file{configure} script will search for this library in several
24343 standard locations; if it is installed in an unusual path, you can
24344 use the @option{--with-libexpat-prefix} option to specify its location.
24350 Remote protocol memory maps (@pxref{Memory Map Format})
24352 Target descriptions (@pxref{Target Descriptions})
24354 Remote shared library lists (@pxref{Library List Format})
24356 MS-Windows shared libraries (@pxref{Shared Libraries})
24360 @cindex compressed debug sections
24361 @value{GDBN} will use the @samp{zlib} library, if available, to read
24362 compressed debug sections. Some linkers, such as GNU gold, are capable
24363 of producing binaries with compressed debug sections. If @value{GDBN}
24364 is compiled with @samp{zlib}, it will be able to read the debug
24365 information in such binaries.
24367 The @samp{zlib} library is likely included with your operating system
24368 distribution; if it is not, you can get the latest version from
24369 @url{http://zlib.net}.
24373 @node Running Configure
24374 @section Invoking the @value{GDBN} @file{configure} Script
24375 @cindex configuring @value{GDBN}
24376 @value{GDBN} comes with a @file{configure} script that automates the process
24377 of preparing @value{GDBN} for installation; you can then use @code{make} to
24378 build the @code{gdb} program.
24380 @c irrelevant in info file; it's as current as the code it lives with.
24381 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
24382 look at the @file{README} file in the sources; we may have improved the
24383 installation procedures since publishing this manual.}
24386 The @value{GDBN} distribution includes all the source code you need for
24387 @value{GDBN} in a single directory, whose name is usually composed by
24388 appending the version number to @samp{gdb}.
24390 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
24391 @file{gdb-@value{GDBVN}} directory. That directory contains:
24394 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
24395 script for configuring @value{GDBN} and all its supporting libraries
24397 @item gdb-@value{GDBVN}/gdb
24398 the source specific to @value{GDBN} itself
24400 @item gdb-@value{GDBVN}/bfd
24401 source for the Binary File Descriptor library
24403 @item gdb-@value{GDBVN}/include
24404 @sc{gnu} include files
24406 @item gdb-@value{GDBVN}/libiberty
24407 source for the @samp{-liberty} free software library
24409 @item gdb-@value{GDBVN}/opcodes
24410 source for the library of opcode tables and disassemblers
24412 @item gdb-@value{GDBVN}/readline
24413 source for the @sc{gnu} command-line interface
24415 @item gdb-@value{GDBVN}/glob
24416 source for the @sc{gnu} filename pattern-matching subroutine
24418 @item gdb-@value{GDBVN}/mmalloc
24419 source for the @sc{gnu} memory-mapped malloc package
24422 The simplest way to configure and build @value{GDBN} is to run @file{configure}
24423 from the @file{gdb-@var{version-number}} source directory, which in
24424 this example is the @file{gdb-@value{GDBVN}} directory.
24426 First switch to the @file{gdb-@var{version-number}} source directory
24427 if you are not already in it; then run @file{configure}. Pass the
24428 identifier for the platform on which @value{GDBN} will run as an
24434 cd gdb-@value{GDBVN}
24435 ./configure @var{host}
24440 where @var{host} is an identifier such as @samp{sun4} or
24441 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
24442 (You can often leave off @var{host}; @file{configure} tries to guess the
24443 correct value by examining your system.)
24445 Running @samp{configure @var{host}} and then running @code{make} builds the
24446 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
24447 libraries, then @code{gdb} itself. The configured source files, and the
24448 binaries, are left in the corresponding source directories.
24451 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
24452 system does not recognize this automatically when you run a different
24453 shell, you may need to run @code{sh} on it explicitly:
24456 sh configure @var{host}
24459 If you run @file{configure} from a directory that contains source
24460 directories for multiple libraries or programs, such as the
24461 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
24463 creates configuration files for every directory level underneath (unless
24464 you tell it not to, with the @samp{--norecursion} option).
24466 You should run the @file{configure} script from the top directory in the
24467 source tree, the @file{gdb-@var{version-number}} directory. If you run
24468 @file{configure} from one of the subdirectories, you will configure only
24469 that subdirectory. That is usually not what you want. In particular,
24470 if you run the first @file{configure} from the @file{gdb} subdirectory
24471 of the @file{gdb-@var{version-number}} directory, you will omit the
24472 configuration of @file{bfd}, @file{readline}, and other sibling
24473 directories of the @file{gdb} subdirectory. This leads to build errors
24474 about missing include files such as @file{bfd/bfd.h}.
24476 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
24477 However, you should make sure that the shell on your path (named by
24478 the @samp{SHELL} environment variable) is publicly readable. Remember
24479 that @value{GDBN} uses the shell to start your program---some systems refuse to
24480 let @value{GDBN} debug child processes whose programs are not readable.
24482 @node Separate Objdir
24483 @section Compiling @value{GDBN} in Another Directory
24485 If you want to run @value{GDBN} versions for several host or target machines,
24486 you need a different @code{gdb} compiled for each combination of
24487 host and target. @file{configure} is designed to make this easy by
24488 allowing you to generate each configuration in a separate subdirectory,
24489 rather than in the source directory. If your @code{make} program
24490 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
24491 @code{make} in each of these directories builds the @code{gdb}
24492 program specified there.
24494 To build @code{gdb} in a separate directory, run @file{configure}
24495 with the @samp{--srcdir} option to specify where to find the source.
24496 (You also need to specify a path to find @file{configure}
24497 itself from your working directory. If the path to @file{configure}
24498 would be the same as the argument to @samp{--srcdir}, you can leave out
24499 the @samp{--srcdir} option; it is assumed.)
24501 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
24502 separate directory for a Sun 4 like this:
24506 cd gdb-@value{GDBVN}
24509 ../gdb-@value{GDBVN}/configure sun4
24514 When @file{configure} builds a configuration using a remote source
24515 directory, it creates a tree for the binaries with the same structure
24516 (and using the same names) as the tree under the source directory. In
24517 the example, you'd find the Sun 4 library @file{libiberty.a} in the
24518 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
24519 @file{gdb-sun4/gdb}.
24521 Make sure that your path to the @file{configure} script has just one
24522 instance of @file{gdb} in it. If your path to @file{configure} looks
24523 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
24524 one subdirectory of @value{GDBN}, not the whole package. This leads to
24525 build errors about missing include files such as @file{bfd/bfd.h}.
24527 One popular reason to build several @value{GDBN} configurations in separate
24528 directories is to configure @value{GDBN} for cross-compiling (where
24529 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
24530 programs that run on another machine---the @dfn{target}).
24531 You specify a cross-debugging target by
24532 giving the @samp{--target=@var{target}} option to @file{configure}.
24534 When you run @code{make} to build a program or library, you must run
24535 it in a configured directory---whatever directory you were in when you
24536 called @file{configure} (or one of its subdirectories).
24538 The @code{Makefile} that @file{configure} generates in each source
24539 directory also runs recursively. If you type @code{make} in a source
24540 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
24541 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
24542 will build all the required libraries, and then build GDB.
24544 When you have multiple hosts or targets configured in separate
24545 directories, you can run @code{make} on them in parallel (for example,
24546 if they are NFS-mounted on each of the hosts); they will not interfere
24550 @section Specifying Names for Hosts and Targets
24552 The specifications used for hosts and targets in the @file{configure}
24553 script are based on a three-part naming scheme, but some short predefined
24554 aliases are also supported. The full naming scheme encodes three pieces
24555 of information in the following pattern:
24558 @var{architecture}-@var{vendor}-@var{os}
24561 For example, you can use the alias @code{sun4} as a @var{host} argument,
24562 or as the value for @var{target} in a @code{--target=@var{target}}
24563 option. The equivalent full name is @samp{sparc-sun-sunos4}.
24565 The @file{configure} script accompanying @value{GDBN} does not provide
24566 any query facility to list all supported host and target names or
24567 aliases. @file{configure} calls the Bourne shell script
24568 @code{config.sub} to map abbreviations to full names; you can read the
24569 script, if you wish, or you can use it to test your guesses on
24570 abbreviations---for example:
24573 % sh config.sub i386-linux
24575 % sh config.sub alpha-linux
24576 alpha-unknown-linux-gnu
24577 % sh config.sub hp9k700
24579 % sh config.sub sun4
24580 sparc-sun-sunos4.1.1
24581 % sh config.sub sun3
24582 m68k-sun-sunos4.1.1
24583 % sh config.sub i986v
24584 Invalid configuration `i986v': machine `i986v' not recognized
24588 @code{config.sub} is also distributed in the @value{GDBN} source
24589 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
24591 @node Configure Options
24592 @section @file{configure} Options
24594 Here is a summary of the @file{configure} options and arguments that
24595 are most often useful for building @value{GDBN}. @file{configure} also has
24596 several other options not listed here. @inforef{What Configure
24597 Does,,configure.info}, for a full explanation of @file{configure}.
24600 configure @r{[}--help@r{]}
24601 @r{[}--prefix=@var{dir}@r{]}
24602 @r{[}--exec-prefix=@var{dir}@r{]}
24603 @r{[}--srcdir=@var{dirname}@r{]}
24604 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
24605 @r{[}--target=@var{target}@r{]}
24610 You may introduce options with a single @samp{-} rather than
24611 @samp{--} if you prefer; but you may abbreviate option names if you use
24616 Display a quick summary of how to invoke @file{configure}.
24618 @item --prefix=@var{dir}
24619 Configure the source to install programs and files under directory
24622 @item --exec-prefix=@var{dir}
24623 Configure the source to install programs under directory
24626 @c avoid splitting the warning from the explanation:
24628 @item --srcdir=@var{dirname}
24629 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
24630 @code{make} that implements the @code{VPATH} feature.}@*
24631 Use this option to make configurations in directories separate from the
24632 @value{GDBN} source directories. Among other things, you can use this to
24633 build (or maintain) several configurations simultaneously, in separate
24634 directories. @file{configure} writes configuration-specific files in
24635 the current directory, but arranges for them to use the source in the
24636 directory @var{dirname}. @file{configure} creates directories under
24637 the working directory in parallel to the source directories below
24640 @item --norecursion
24641 Configure only the directory level where @file{configure} is executed; do not
24642 propagate configuration to subdirectories.
24644 @item --target=@var{target}
24645 Configure @value{GDBN} for cross-debugging programs running on the specified
24646 @var{target}. Without this option, @value{GDBN} is configured to debug
24647 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
24649 There is no convenient way to generate a list of all available targets.
24651 @item @var{host} @dots{}
24652 Configure @value{GDBN} to run on the specified @var{host}.
24654 There is no convenient way to generate a list of all available hosts.
24657 There are many other options available as well, but they are generally
24658 needed for special purposes only.
24660 @node Maintenance Commands
24661 @appendix Maintenance Commands
24662 @cindex maintenance commands
24663 @cindex internal commands
24665 In addition to commands intended for @value{GDBN} users, @value{GDBN}
24666 includes a number of commands intended for @value{GDBN} developers,
24667 that are not documented elsewhere in this manual. These commands are
24668 provided here for reference. (For commands that turn on debugging
24669 messages, see @ref{Debugging Output}.)
24672 @kindex maint agent
24673 @item maint agent @var{expression}
24674 Translate the given @var{expression} into remote agent bytecodes.
24675 This command is useful for debugging the Agent Expression mechanism
24676 (@pxref{Agent Expressions}).
24678 @kindex maint info breakpoints
24679 @item @anchor{maint info breakpoints}maint info breakpoints
24680 Using the same format as @samp{info breakpoints}, display both the
24681 breakpoints you've set explicitly, and those @value{GDBN} is using for
24682 internal purposes. Internal breakpoints are shown with negative
24683 breakpoint numbers. The type column identifies what kind of breakpoint
24688 Normal, explicitly set breakpoint.
24691 Normal, explicitly set watchpoint.
24694 Internal breakpoint, used to handle correctly stepping through
24695 @code{longjmp} calls.
24697 @item longjmp resume
24698 Internal breakpoint at the target of a @code{longjmp}.
24701 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
24704 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
24707 Shared library events.
24711 @kindex set displaced-stepping
24712 @kindex show displaced-stepping
24713 @cindex displaced stepping support
24714 @cindex out-of-line single-stepping
24715 @item set displaced-stepping
24716 @itemx show displaced-stepping
24717 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
24718 if the target supports it. Displaced stepping is a way to single-step
24719 over breakpoints without removing them from the inferior, by executing
24720 an out-of-line copy of the instruction that was originally at the
24721 breakpoint location. It is also known as out-of-line single-stepping.
24724 @item set displaced-stepping on
24725 If the target architecture supports it, @value{GDBN} will use
24726 displaced stepping to step over breakpoints.
24728 @item set displaced-stepping off
24729 @value{GDBN} will not use displaced stepping to step over breakpoints,
24730 even if such is supported by the target architecture.
24732 @cindex non-stop mode, and @samp{set displaced-stepping}
24733 @item set displaced-stepping auto
24734 This is the default mode. @value{GDBN} will use displaced stepping
24735 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
24736 architecture supports displaced stepping.
24739 @kindex maint check-symtabs
24740 @item maint check-symtabs
24741 Check the consistency of psymtabs and symtabs.
24743 @kindex maint cplus first_component
24744 @item maint cplus first_component @var{name}
24745 Print the first C@t{++} class/namespace component of @var{name}.
24747 @kindex maint cplus namespace
24748 @item maint cplus namespace
24749 Print the list of possible C@t{++} namespaces.
24751 @kindex maint demangle
24752 @item maint demangle @var{name}
24753 Demangle a C@t{++} or Objective-C mangled @var{name}.
24755 @kindex maint deprecate
24756 @kindex maint undeprecate
24757 @cindex deprecated commands
24758 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
24759 @itemx maint undeprecate @var{command}
24760 Deprecate or undeprecate the named @var{command}. Deprecated commands
24761 cause @value{GDBN} to issue a warning when you use them. The optional
24762 argument @var{replacement} says which newer command should be used in
24763 favor of the deprecated one; if it is given, @value{GDBN} will mention
24764 the replacement as part of the warning.
24766 @kindex maint dump-me
24767 @item maint dump-me
24768 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
24769 Cause a fatal signal in the debugger and force it to dump its core.
24770 This is supported only on systems which support aborting a program
24771 with the @code{SIGQUIT} signal.
24773 @kindex maint internal-error
24774 @kindex maint internal-warning
24775 @item maint internal-error @r{[}@var{message-text}@r{]}
24776 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
24777 Cause @value{GDBN} to call the internal function @code{internal_error}
24778 or @code{internal_warning} and hence behave as though an internal error
24779 or internal warning has been detected. In addition to reporting the
24780 internal problem, these functions give the user the opportunity to
24781 either quit @value{GDBN} or create a core file of the current
24782 @value{GDBN} session.
24784 These commands take an optional parameter @var{message-text} that is
24785 used as the text of the error or warning message.
24787 Here's an example of using @code{internal-error}:
24790 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
24791 @dots{}/maint.c:121: internal-error: testing, 1, 2
24792 A problem internal to GDB has been detected. Further
24793 debugging may prove unreliable.
24794 Quit this debugging session? (y or n) @kbd{n}
24795 Create a core file? (y or n) @kbd{n}
24799 @kindex maint packet
24800 @item maint packet @var{text}
24801 If @value{GDBN} is talking to an inferior via the serial protocol,
24802 then this command sends the string @var{text} to the inferior, and
24803 displays the response packet. @value{GDBN} supplies the initial
24804 @samp{$} character, the terminating @samp{#} character, and the
24807 @kindex maint print architecture
24808 @item maint print architecture @r{[}@var{file}@r{]}
24809 Print the entire architecture configuration. The optional argument
24810 @var{file} names the file where the output goes.
24812 @kindex maint print c-tdesc
24813 @item maint print c-tdesc
24814 Print the current target description (@pxref{Target Descriptions}) as
24815 a C source file. The created source file can be used in @value{GDBN}
24816 when an XML parser is not available to parse the description.
24818 @kindex maint print dummy-frames
24819 @item maint print dummy-frames
24820 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
24823 (@value{GDBP}) @kbd{b add}
24825 (@value{GDBP}) @kbd{print add(2,3)}
24826 Breakpoint 2, add (a=2, b=3) at @dots{}
24828 The program being debugged stopped while in a function called from GDB.
24830 (@value{GDBP}) @kbd{maint print dummy-frames}
24831 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
24832 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
24833 call_lo=0x01014000 call_hi=0x01014001
24837 Takes an optional file parameter.
24839 @kindex maint print registers
24840 @kindex maint print raw-registers
24841 @kindex maint print cooked-registers
24842 @kindex maint print register-groups
24843 @item maint print registers @r{[}@var{file}@r{]}
24844 @itemx maint print raw-registers @r{[}@var{file}@r{]}
24845 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
24846 @itemx maint print register-groups @r{[}@var{file}@r{]}
24847 Print @value{GDBN}'s internal register data structures.
24849 The command @code{maint print raw-registers} includes the contents of
24850 the raw register cache; the command @code{maint print cooked-registers}
24851 includes the (cooked) value of all registers; and the command
24852 @code{maint print register-groups} includes the groups that each
24853 register is a member of. @xref{Registers,, Registers, gdbint,
24854 @value{GDBN} Internals}.
24856 These commands take an optional parameter, a file name to which to
24857 write the information.
24859 @kindex maint print reggroups
24860 @item maint print reggroups @r{[}@var{file}@r{]}
24861 Print @value{GDBN}'s internal register group data structures. The
24862 optional argument @var{file} tells to what file to write the
24865 The register groups info looks like this:
24868 (@value{GDBP}) @kbd{maint print reggroups}
24881 This command forces @value{GDBN} to flush its internal register cache.
24883 @kindex maint print objfiles
24884 @cindex info for known object files
24885 @item maint print objfiles
24886 Print a dump of all known object files. For each object file, this
24887 command prints its name, address in memory, and all of its psymtabs
24890 @kindex maint print statistics
24891 @cindex bcache statistics
24892 @item maint print statistics
24893 This command prints, for each object file in the program, various data
24894 about that object file followed by the byte cache (@dfn{bcache})
24895 statistics for the object file. The objfile data includes the number
24896 of minimal, partial, full, and stabs symbols, the number of types
24897 defined by the objfile, the number of as yet unexpanded psym tables,
24898 the number of line tables and string tables, and the amount of memory
24899 used by the various tables. The bcache statistics include the counts,
24900 sizes, and counts of duplicates of all and unique objects, max,
24901 average, and median entry size, total memory used and its overhead and
24902 savings, and various measures of the hash table size and chain
24905 @kindex maint print target-stack
24906 @cindex target stack description
24907 @item maint print target-stack
24908 A @dfn{target} is an interface between the debugger and a particular
24909 kind of file or process. Targets can be stacked in @dfn{strata},
24910 so that more than one target can potentially respond to a request.
24911 In particular, memory accesses will walk down the stack of targets
24912 until they find a target that is interested in handling that particular
24915 This command prints a short description of each layer that was pushed on
24916 the @dfn{target stack}, starting from the top layer down to the bottom one.
24918 @kindex maint print type
24919 @cindex type chain of a data type
24920 @item maint print type @var{expr}
24921 Print the type chain for a type specified by @var{expr}. The argument
24922 can be either a type name or a symbol. If it is a symbol, the type of
24923 that symbol is described. The type chain produced by this command is
24924 a recursive definition of the data type as stored in @value{GDBN}'s
24925 data structures, including its flags and contained types.
24927 @kindex maint set dwarf2 max-cache-age
24928 @kindex maint show dwarf2 max-cache-age
24929 @item maint set dwarf2 max-cache-age
24930 @itemx maint show dwarf2 max-cache-age
24931 Control the DWARF 2 compilation unit cache.
24933 @cindex DWARF 2 compilation units cache
24934 In object files with inter-compilation-unit references, such as those
24935 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
24936 reader needs to frequently refer to previously read compilation units.
24937 This setting controls how long a compilation unit will remain in the
24938 cache if it is not referenced. A higher limit means that cached
24939 compilation units will be stored in memory longer, and more total
24940 memory will be used. Setting it to zero disables caching, which will
24941 slow down @value{GDBN} startup, but reduce memory consumption.
24943 @kindex maint set profile
24944 @kindex maint show profile
24945 @cindex profiling GDB
24946 @item maint set profile
24947 @itemx maint show profile
24948 Control profiling of @value{GDBN}.
24950 Profiling will be disabled until you use the @samp{maint set profile}
24951 command to enable it. When you enable profiling, the system will begin
24952 collecting timing and execution count data; when you disable profiling or
24953 exit @value{GDBN}, the results will be written to a log file. Remember that
24954 if you use profiling, @value{GDBN} will overwrite the profiling log file
24955 (often called @file{gmon.out}). If you have a record of important profiling
24956 data in a @file{gmon.out} file, be sure to move it to a safe location.
24958 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
24959 compiled with the @samp{-pg} compiler option.
24961 @kindex maint set linux-async
24962 @kindex maint show linux-async
24963 @cindex asynchronous support
24964 @item maint set linux-async
24965 @itemx maint show linux-async
24966 Control the GNU/Linux native asynchronous support
24967 (@pxref{Background Execution}) of @value{GDBN}.
24969 GNU/Linux native asynchronous support will be disabled until you use
24970 the @samp{maint set linux-async} command to enable it.
24972 @kindex maint set remote-async
24973 @kindex maint show remote-async
24974 @cindex asynchronous support
24975 @item maint set remote-async
24976 @itemx maint show remote-async
24977 Control the remote asynchronous support
24978 (@pxref{Background Execution}) of @value{GDBN}.
24980 Remote asynchronous support will be disabled until you use
24981 the @samp{maint set remote-async} command to enable it.
24983 @kindex maint show-debug-regs
24984 @cindex x86 hardware debug registers
24985 @item maint show-debug-regs
24986 Control whether to show variables that mirror the x86 hardware debug
24987 registers. Use @code{ON} to enable, @code{OFF} to disable. If
24988 enabled, the debug registers values are shown when @value{GDBN} inserts or
24989 removes a hardware breakpoint or watchpoint, and when the inferior
24990 triggers a hardware-assisted breakpoint or watchpoint.
24992 @kindex maint space
24993 @cindex memory used by commands
24995 Control whether to display memory usage for each command. If set to a
24996 nonzero value, @value{GDBN} will display how much memory each command
24997 took, following the command's own output. This can also be requested
24998 by invoking @value{GDBN} with the @option{--statistics} command-line
24999 switch (@pxref{Mode Options}).
25002 @cindex time of command execution
25004 Control whether to display the execution time for each command. If
25005 set to a nonzero value, @value{GDBN} will display how much time it
25006 took to execute each command, following the command's own output.
25007 The time is not printed for the commands that run the target, since
25008 there's no mechanism currently to compute how much time was spend
25009 by @value{GDBN} and how much time was spend by the program been debugged.
25010 it's not possibly currently
25011 This can also be requested by invoking @value{GDBN} with the
25012 @option{--statistics} command-line switch (@pxref{Mode Options}).
25014 @kindex maint translate-address
25015 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25016 Find the symbol stored at the location specified by the address
25017 @var{addr} and an optional section name @var{section}. If found,
25018 @value{GDBN} prints the name of the closest symbol and an offset from
25019 the symbol's location to the specified address. This is similar to
25020 the @code{info address} command (@pxref{Symbols}), except that this
25021 command also allows to find symbols in other sections.
25023 If section was not specified, the section in which the symbol was found
25024 is also printed. For dynamically linked executables, the name of
25025 executable or shared library containing the symbol is printed as well.
25029 The following command is useful for non-interactive invocations of
25030 @value{GDBN}, such as in the test suite.
25033 @item set watchdog @var{nsec}
25034 @kindex set watchdog
25035 @cindex watchdog timer
25036 @cindex timeout for commands
25037 Set the maximum number of seconds @value{GDBN} will wait for the
25038 target operation to finish. If this time expires, @value{GDBN}
25039 reports and error and the command is aborted.
25041 @item show watchdog
25042 Show the current setting of the target wait timeout.
25045 @node Remote Protocol
25046 @appendix @value{GDBN} Remote Serial Protocol
25051 * Stop Reply Packets::
25052 * General Query Packets::
25053 * Register Packet Format::
25054 * Tracepoint Packets::
25055 * Host I/O Packets::
25057 * Notification Packets::
25058 * Remote Non-Stop::
25059 * Packet Acknowledgment::
25061 * File-I/O Remote Protocol Extension::
25062 * Library List Format::
25063 * Memory Map Format::
25069 There may be occasions when you need to know something about the
25070 protocol---for example, if there is only one serial port to your target
25071 machine, you might want your program to do something special if it
25072 recognizes a packet meant for @value{GDBN}.
25074 In the examples below, @samp{->} and @samp{<-} are used to indicate
25075 transmitted and received data, respectively.
25077 @cindex protocol, @value{GDBN} remote serial
25078 @cindex serial protocol, @value{GDBN} remote
25079 @cindex remote serial protocol
25080 All @value{GDBN} commands and responses (other than acknowledgments
25081 and notifications, see @ref{Notification Packets}) are sent as a
25082 @var{packet}. A @var{packet} is introduced with the character
25083 @samp{$}, the actual @var{packet-data}, and the terminating character
25084 @samp{#} followed by a two-digit @var{checksum}:
25087 @code{$}@var{packet-data}@code{#}@var{checksum}
25091 @cindex checksum, for @value{GDBN} remote
25093 The two-digit @var{checksum} is computed as the modulo 256 sum of all
25094 characters between the leading @samp{$} and the trailing @samp{#} (an
25095 eight bit unsigned checksum).
25097 Implementors should note that prior to @value{GDBN} 5.0 the protocol
25098 specification also included an optional two-digit @var{sequence-id}:
25101 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
25104 @cindex sequence-id, for @value{GDBN} remote
25106 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
25107 has never output @var{sequence-id}s. Stubs that handle packets added
25108 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
25110 When either the host or the target machine receives a packet, the first
25111 response expected is an acknowledgment: either @samp{+} (to indicate
25112 the package was received correctly) or @samp{-} (to request
25116 -> @code{$}@var{packet-data}@code{#}@var{checksum}
25121 The @samp{+}/@samp{-} acknowledgments can be disabled
25122 once a connection is established.
25123 @xref{Packet Acknowledgment}, for details.
25125 The host (@value{GDBN}) sends @var{command}s, and the target (the
25126 debugging stub incorporated in your program) sends a @var{response}. In
25127 the case of step and continue @var{command}s, the response is only sent
25128 when the operation has completed, and the target has again stopped all
25129 threads in all attached processes. This is the default all-stop mode
25130 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
25131 execution mode; see @ref{Remote Non-Stop}, for details.
25133 @var{packet-data} consists of a sequence of characters with the
25134 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
25137 @cindex remote protocol, field separator
25138 Fields within the packet should be separated using @samp{,} @samp{;} or
25139 @samp{:}. Except where otherwise noted all numbers are represented in
25140 @sc{hex} with leading zeros suppressed.
25142 Implementors should note that prior to @value{GDBN} 5.0, the character
25143 @samp{:} could not appear as the third character in a packet (as it
25144 would potentially conflict with the @var{sequence-id}).
25146 @cindex remote protocol, binary data
25147 @anchor{Binary Data}
25148 Binary data in most packets is encoded either as two hexadecimal
25149 digits per byte of binary data. This allowed the traditional remote
25150 protocol to work over connections which were only seven-bit clean.
25151 Some packets designed more recently assume an eight-bit clean
25152 connection, and use a more efficient encoding to send and receive
25155 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
25156 as an escape character. Any escaped byte is transmitted as the escape
25157 character followed by the original character XORed with @code{0x20}.
25158 For example, the byte @code{0x7d} would be transmitted as the two
25159 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
25160 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
25161 @samp{@}}) must always be escaped. Responses sent by the stub
25162 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
25163 is not interpreted as the start of a run-length encoded sequence
25166 Response @var{data} can be run-length encoded to save space.
25167 Run-length encoding replaces runs of identical characters with one
25168 instance of the repeated character, followed by a @samp{*} and a
25169 repeat count. The repeat count is itself sent encoded, to avoid
25170 binary characters in @var{data}: a value of @var{n} is sent as
25171 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
25172 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
25173 code 32) for a repeat count of 3. (This is because run-length
25174 encoding starts to win for counts 3 or more.) Thus, for example,
25175 @samp{0* } is a run-length encoding of ``0000'': the space character
25176 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
25179 The printable characters @samp{#} and @samp{$} or with a numeric value
25180 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
25181 seven repeats (@samp{$}) can be expanded using a repeat count of only
25182 five (@samp{"}). For example, @samp{00000000} can be encoded as
25185 The error response returned for some packets includes a two character
25186 error number. That number is not well defined.
25188 @cindex empty response, for unsupported packets
25189 For any @var{command} not supported by the stub, an empty response
25190 (@samp{$#00}) should be returned. That way it is possible to extend the
25191 protocol. A newer @value{GDBN} can tell if a packet is supported based
25194 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
25195 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
25201 The following table provides a complete list of all currently defined
25202 @var{command}s and their corresponding response @var{data}.
25203 @xref{File-I/O Remote Protocol Extension}, for details about the File
25204 I/O extension of the remote protocol.
25206 Each packet's description has a template showing the packet's overall
25207 syntax, followed by an explanation of the packet's meaning. We
25208 include spaces in some of the templates for clarity; these are not
25209 part of the packet's syntax. No @value{GDBN} packet uses spaces to
25210 separate its components. For example, a template like @samp{foo
25211 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
25212 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
25213 @var{baz}. @value{GDBN} does not transmit a space character between the
25214 @samp{foo} and the @var{bar}, or between the @var{bar} and the
25217 @cindex @var{thread-id}, in remote protocol
25218 @anchor{thread-id syntax}
25219 Several packets and replies include a @var{thread-id} field to identify
25220 a thread. Normally these are positive numbers with a target-specific
25221 interpretation, formatted as big-endian hex strings. A @var{thread-id}
25222 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
25225 In addition, the remote protocol supports a multiprocess feature in
25226 which the @var{thread-id} syntax is extended to optionally include both
25227 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
25228 The @var{pid} (process) and @var{tid} (thread) components each have the
25229 format described above: a positive number with target-specific
25230 interpretation formatted as a big-endian hex string, literal @samp{-1}
25231 to indicate all processes or threads (respectively), or @samp{0} to
25232 indicate an arbitrary process or thread. Specifying just a process, as
25233 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
25234 error to specify all processes but a specific thread, such as
25235 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
25236 for those packets and replies explicitly documented to include a process
25237 ID, rather than a @var{thread-id}.
25239 The multiprocess @var{thread-id} syntax extensions are only used if both
25240 @value{GDBN} and the stub report support for the @samp{multiprocess}
25241 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
25244 Note that all packet forms beginning with an upper- or lower-case
25245 letter, other than those described here, are reserved for future use.
25247 Here are the packet descriptions.
25252 @cindex @samp{!} packet
25253 @anchor{extended mode}
25254 Enable extended mode. In extended mode, the remote server is made
25255 persistent. The @samp{R} packet is used to restart the program being
25261 The remote target both supports and has enabled extended mode.
25265 @cindex @samp{?} packet
25266 Indicate the reason the target halted. The reply is the same as for
25267 step and continue. This packet has a special interpretation when the
25268 target is in non-stop mode; see @ref{Remote Non-Stop}.
25271 @xref{Stop Reply Packets}, for the reply specifications.
25273 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
25274 @cindex @samp{A} packet
25275 Initialized @code{argv[]} array passed into program. @var{arglen}
25276 specifies the number of bytes in the hex encoded byte stream
25277 @var{arg}. See @code{gdbserver} for more details.
25282 The arguments were set.
25288 @cindex @samp{b} packet
25289 (Don't use this packet; its behavior is not well-defined.)
25290 Change the serial line speed to @var{baud}.
25292 JTC: @emph{When does the transport layer state change? When it's
25293 received, or after the ACK is transmitted. In either case, there are
25294 problems if the command or the acknowledgment packet is dropped.}
25296 Stan: @emph{If people really wanted to add something like this, and get
25297 it working for the first time, they ought to modify ser-unix.c to send
25298 some kind of out-of-band message to a specially-setup stub and have the
25299 switch happen "in between" packets, so that from remote protocol's point
25300 of view, nothing actually happened.}
25302 @item B @var{addr},@var{mode}
25303 @cindex @samp{B} packet
25304 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
25305 breakpoint at @var{addr}.
25307 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
25308 (@pxref{insert breakpoint or watchpoint packet}).
25311 @cindex @samp{bc} packet
25312 Backward continue. Execute the target system in reverse. No parameter.
25313 @xref{Reverse Execution}, for more information.
25316 @xref{Stop Reply Packets}, for the reply specifications.
25319 @cindex @samp{bs} packet
25320 Backward single step. Execute one instruction in reverse. No parameter.
25321 @xref{Reverse Execution}, for more information.
25324 @xref{Stop Reply Packets}, for the reply specifications.
25326 @item c @r{[}@var{addr}@r{]}
25327 @cindex @samp{c} packet
25328 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
25329 resume at current address.
25332 @xref{Stop Reply Packets}, for the reply specifications.
25334 @item C @var{sig}@r{[};@var{addr}@r{]}
25335 @cindex @samp{C} packet
25336 Continue with signal @var{sig} (hex signal number). If
25337 @samp{;@var{addr}} is omitted, resume at same address.
25340 @xref{Stop Reply Packets}, for the reply specifications.
25343 @cindex @samp{d} packet
25346 Don't use this packet; instead, define a general set packet
25347 (@pxref{General Query Packets}).
25351 @cindex @samp{D} packet
25352 The first form of the packet is used to detach @value{GDBN} from the
25353 remote system. It is sent to the remote target
25354 before @value{GDBN} disconnects via the @code{detach} command.
25356 The second form, including a process ID, is used when multiprocess
25357 protocol extensions are enabled (@pxref{multiprocess extensions}), to
25358 detach only a specific process. The @var{pid} is specified as a
25359 big-endian hex string.
25369 @item F @var{RC},@var{EE},@var{CF};@var{XX}
25370 @cindex @samp{F} packet
25371 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
25372 This is part of the File-I/O protocol extension. @xref{File-I/O
25373 Remote Protocol Extension}, for the specification.
25376 @anchor{read registers packet}
25377 @cindex @samp{g} packet
25378 Read general registers.
25382 @item @var{XX@dots{}}
25383 Each byte of register data is described by two hex digits. The bytes
25384 with the register are transmitted in target byte order. The size of
25385 each register and their position within the @samp{g} packet are
25386 determined by the @value{GDBN} internal gdbarch functions
25387 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
25388 specification of several standard @samp{g} packets is specified below.
25393 @item G @var{XX@dots{}}
25394 @cindex @samp{G} packet
25395 Write general registers. @xref{read registers packet}, for a
25396 description of the @var{XX@dots{}} data.
25406 @item H @var{c} @var{thread-id}
25407 @cindex @samp{H} packet
25408 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
25409 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
25410 should be @samp{c} for step and continue operations, @samp{g} for other
25411 operations. The thread designator @var{thread-id} has the format and
25412 interpretation described in @ref{thread-id syntax}.
25423 @c 'H': How restrictive (or permissive) is the thread model. If a
25424 @c thread is selected and stopped, are other threads allowed
25425 @c to continue to execute? As I mentioned above, I think the
25426 @c semantics of each command when a thread is selected must be
25427 @c described. For example:
25429 @c 'g': If the stub supports threads and a specific thread is
25430 @c selected, returns the register block from that thread;
25431 @c otherwise returns current registers.
25433 @c 'G' If the stub supports threads and a specific thread is
25434 @c selected, sets the registers of the register block of
25435 @c that thread; otherwise sets current registers.
25437 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
25438 @anchor{cycle step packet}
25439 @cindex @samp{i} packet
25440 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
25441 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
25442 step starting at that address.
25445 @cindex @samp{I} packet
25446 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
25450 @cindex @samp{k} packet
25453 FIXME: @emph{There is no description of how to operate when a specific
25454 thread context has been selected (i.e.@: does 'k' kill only that
25457 @item m @var{addr},@var{length}
25458 @cindex @samp{m} packet
25459 Read @var{length} bytes of memory starting at address @var{addr}.
25460 Note that @var{addr} may not be aligned to any particular boundary.
25462 The stub need not use any particular size or alignment when gathering
25463 data from memory for the response; even if @var{addr} is word-aligned
25464 and @var{length} is a multiple of the word size, the stub is free to
25465 use byte accesses, or not. For this reason, this packet may not be
25466 suitable for accessing memory-mapped I/O devices.
25467 @cindex alignment of remote memory accesses
25468 @cindex size of remote memory accesses
25469 @cindex memory, alignment and size of remote accesses
25473 @item @var{XX@dots{}}
25474 Memory contents; each byte is transmitted as a two-digit hexadecimal
25475 number. The reply may contain fewer bytes than requested if the
25476 server was able to read only part of the region of memory.
25481 @item M @var{addr},@var{length}:@var{XX@dots{}}
25482 @cindex @samp{M} packet
25483 Write @var{length} bytes of memory starting at address @var{addr}.
25484 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
25485 hexadecimal number.
25492 for an error (this includes the case where only part of the data was
25497 @cindex @samp{p} packet
25498 Read the value of register @var{n}; @var{n} is in hex.
25499 @xref{read registers packet}, for a description of how the returned
25500 register value is encoded.
25504 @item @var{XX@dots{}}
25505 the register's value
25509 Indicating an unrecognized @var{query}.
25512 @item P @var{n@dots{}}=@var{r@dots{}}
25513 @anchor{write register packet}
25514 @cindex @samp{P} packet
25515 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
25516 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
25517 digits for each byte in the register (target byte order).
25527 @item q @var{name} @var{params}@dots{}
25528 @itemx Q @var{name} @var{params}@dots{}
25529 @cindex @samp{q} packet
25530 @cindex @samp{Q} packet
25531 General query (@samp{q}) and set (@samp{Q}). These packets are
25532 described fully in @ref{General Query Packets}.
25535 @cindex @samp{r} packet
25536 Reset the entire system.
25538 Don't use this packet; use the @samp{R} packet instead.
25541 @cindex @samp{R} packet
25542 Restart the program being debugged. @var{XX}, while needed, is ignored.
25543 This packet is only available in extended mode (@pxref{extended mode}).
25545 The @samp{R} packet has no reply.
25547 @item s @r{[}@var{addr}@r{]}
25548 @cindex @samp{s} packet
25549 Single step. @var{addr} is the address at which to resume. If
25550 @var{addr} is omitted, resume at same address.
25553 @xref{Stop Reply Packets}, for the reply specifications.
25555 @item S @var{sig}@r{[};@var{addr}@r{]}
25556 @anchor{step with signal packet}
25557 @cindex @samp{S} packet
25558 Step with signal. This is analogous to the @samp{C} packet, but
25559 requests a single-step, rather than a normal resumption of execution.
25562 @xref{Stop Reply Packets}, for the reply specifications.
25564 @item t @var{addr}:@var{PP},@var{MM}
25565 @cindex @samp{t} packet
25566 Search backwards starting at address @var{addr} for a match with pattern
25567 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
25568 @var{addr} must be at least 3 digits.
25570 @item T @var{thread-id}
25571 @cindex @samp{T} packet
25572 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
25577 thread is still alive
25583 Packets starting with @samp{v} are identified by a multi-letter name,
25584 up to the first @samp{;} or @samp{?} (or the end of the packet).
25586 @item vAttach;@var{pid}
25587 @cindex @samp{vAttach} packet
25588 Attach to a new process with the specified process ID @var{pid}.
25589 The process ID is a
25590 hexadecimal integer identifying the process. In all-stop mode, all
25591 threads in the attached process are stopped; in non-stop mode, it may be
25592 attached without being stopped if that is supported by the target.
25594 @c In non-stop mode, on a successful vAttach, the stub should set the
25595 @c current thread to a thread of the newly-attached process. After
25596 @c attaching, GDB queries for the attached process's thread ID with qC.
25597 @c Also note that, from a user perspective, whether or not the
25598 @c target is stopped on attach in non-stop mode depends on whether you
25599 @c use the foreground or background version of the attach command, not
25600 @c on what vAttach does; GDB does the right thing with respect to either
25601 @c stopping or restarting threads.
25603 This packet is only available in extended mode (@pxref{extended mode}).
25609 @item @r{Any stop packet}
25610 for success in all-stop mode (@pxref{Stop Reply Packets})
25612 for success in non-stop mode (@pxref{Remote Non-Stop})
25615 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
25616 @cindex @samp{vCont} packet
25617 Resume the inferior, specifying different actions for each thread.
25618 If an action is specified with no @var{thread-id}, then it is applied to any
25619 threads that don't have a specific action specified; if no default action is
25620 specified then other threads should remain stopped in all-stop mode and
25621 in their current state in non-stop mode.
25622 Specifying multiple
25623 default actions is an error; specifying no actions is also an error.
25624 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
25626 Currently supported actions are:
25632 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
25636 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
25640 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
25643 The optional argument @var{addr} normally associated with the
25644 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
25645 not supported in @samp{vCont}.
25647 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
25648 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
25649 A stop reply should be generated for any affected thread not already stopped.
25650 When a thread is stopped by means of a @samp{t} action,
25651 the corresponding stop reply should indicate that the thread has stopped with
25652 signal @samp{0}, regardless of whether the target uses some other signal
25653 as an implementation detail.
25656 @xref{Stop Reply Packets}, for the reply specifications.
25659 @cindex @samp{vCont?} packet
25660 Request a list of actions supported by the @samp{vCont} packet.
25664 @item vCont@r{[};@var{action}@dots{}@r{]}
25665 The @samp{vCont} packet is supported. Each @var{action} is a supported
25666 command in the @samp{vCont} packet.
25668 The @samp{vCont} packet is not supported.
25671 @item vFile:@var{operation}:@var{parameter}@dots{}
25672 @cindex @samp{vFile} packet
25673 Perform a file operation on the target system. For details,
25674 see @ref{Host I/O Packets}.
25676 @item vFlashErase:@var{addr},@var{length}
25677 @cindex @samp{vFlashErase} packet
25678 Direct the stub to erase @var{length} bytes of flash starting at
25679 @var{addr}. The region may enclose any number of flash blocks, but
25680 its start and end must fall on block boundaries, as indicated by the
25681 flash block size appearing in the memory map (@pxref{Memory Map
25682 Format}). @value{GDBN} groups flash memory programming operations
25683 together, and sends a @samp{vFlashDone} request after each group; the
25684 stub is allowed to delay erase operation until the @samp{vFlashDone}
25685 packet is received.
25687 The stub must support @samp{vCont} if it reports support for
25688 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
25689 this case @samp{vCont} actions can be specified to apply to all threads
25690 in a process by using the @samp{p@var{pid}.-1} form of the
25701 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
25702 @cindex @samp{vFlashWrite} packet
25703 Direct the stub to write data to flash address @var{addr}. The data
25704 is passed in binary form using the same encoding as for the @samp{X}
25705 packet (@pxref{Binary Data}). The memory ranges specified by
25706 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
25707 not overlap, and must appear in order of increasing addresses
25708 (although @samp{vFlashErase} packets for higher addresses may already
25709 have been received; the ordering is guaranteed only between
25710 @samp{vFlashWrite} packets). If a packet writes to an address that was
25711 neither erased by a preceding @samp{vFlashErase} packet nor by some other
25712 target-specific method, the results are unpredictable.
25720 for vFlashWrite addressing non-flash memory
25726 @cindex @samp{vFlashDone} packet
25727 Indicate to the stub that flash programming operation is finished.
25728 The stub is permitted to delay or batch the effects of a group of
25729 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
25730 @samp{vFlashDone} packet is received. The contents of the affected
25731 regions of flash memory are unpredictable until the @samp{vFlashDone}
25732 request is completed.
25734 @item vKill;@var{pid}
25735 @cindex @samp{vKill} packet
25736 Kill the process with the specified process ID. @var{pid} is a
25737 hexadecimal integer identifying the process. This packet is used in
25738 preference to @samp{k} when multiprocess protocol extensions are
25739 supported; see @ref{multiprocess extensions}.
25749 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
25750 @cindex @samp{vRun} packet
25751 Run the program @var{filename}, passing it each @var{argument} on its
25752 command line. The file and arguments are hex-encoded strings. If
25753 @var{filename} is an empty string, the stub may use a default program
25754 (e.g.@: the last program run). The program is created in the stopped
25757 @c FIXME: What about non-stop mode?
25759 This packet is only available in extended mode (@pxref{extended mode}).
25765 @item @r{Any stop packet}
25766 for success (@pxref{Stop Reply Packets})
25770 @anchor{vStopped packet}
25771 @cindex @samp{vStopped} packet
25773 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
25774 reply and prompt for the stub to report another one.
25778 @item @r{Any stop packet}
25779 if there is another unreported stop event (@pxref{Stop Reply Packets})
25781 if there are no unreported stop events
25784 @item X @var{addr},@var{length}:@var{XX@dots{}}
25786 @cindex @samp{X} packet
25787 Write data to memory, where the data is transmitted in binary.
25788 @var{addr} is address, @var{length} is number of bytes,
25789 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
25799 @item z @var{type},@var{addr},@var{length}
25800 @itemx Z @var{type},@var{addr},@var{length}
25801 @anchor{insert breakpoint or watchpoint packet}
25802 @cindex @samp{z} packet
25803 @cindex @samp{Z} packets
25804 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
25805 watchpoint starting at address @var{address} and covering the next
25806 @var{length} bytes.
25808 Each breakpoint and watchpoint packet @var{type} is documented
25811 @emph{Implementation notes: A remote target shall return an empty string
25812 for an unrecognized breakpoint or watchpoint packet @var{type}. A
25813 remote target shall support either both or neither of a given
25814 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
25815 avoid potential problems with duplicate packets, the operations should
25816 be implemented in an idempotent way.}
25818 @item z0,@var{addr},@var{length}
25819 @itemx Z0,@var{addr},@var{length}
25820 @cindex @samp{z0} packet
25821 @cindex @samp{Z0} packet
25822 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
25823 @var{addr} of size @var{length}.
25825 A memory breakpoint is implemented by replacing the instruction at
25826 @var{addr} with a software breakpoint or trap instruction. The
25827 @var{length} is used by targets that indicates the size of the
25828 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
25829 @sc{mips} can insert either a 2 or 4 byte breakpoint).
25831 @emph{Implementation note: It is possible for a target to copy or move
25832 code that contains memory breakpoints (e.g., when implementing
25833 overlays). The behavior of this packet, in the presence of such a
25834 target, is not defined.}
25846 @item z1,@var{addr},@var{length}
25847 @itemx Z1,@var{addr},@var{length}
25848 @cindex @samp{z1} packet
25849 @cindex @samp{Z1} packet
25850 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
25851 address @var{addr} of size @var{length}.
25853 A hardware breakpoint is implemented using a mechanism that is not
25854 dependant on being able to modify the target's memory.
25856 @emph{Implementation note: A hardware breakpoint is not affected by code
25869 @item z2,@var{addr},@var{length}
25870 @itemx Z2,@var{addr},@var{length}
25871 @cindex @samp{z2} packet
25872 @cindex @samp{Z2} packet
25873 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
25885 @item z3,@var{addr},@var{length}
25886 @itemx Z3,@var{addr},@var{length}
25887 @cindex @samp{z3} packet
25888 @cindex @samp{Z3} packet
25889 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
25901 @item z4,@var{addr},@var{length}
25902 @itemx Z4,@var{addr},@var{length}
25903 @cindex @samp{z4} packet
25904 @cindex @samp{Z4} packet
25905 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
25919 @node Stop Reply Packets
25920 @section Stop Reply Packets
25921 @cindex stop reply packets
25923 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
25924 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
25925 receive any of the below as a reply. Except for @samp{?}
25926 and @samp{vStopped}, that reply is only returned
25927 when the target halts. In the below the exact meaning of @dfn{signal
25928 number} is defined by the header @file{include/gdb/signals.h} in the
25929 @value{GDBN} source code.
25931 As in the description of request packets, we include spaces in the
25932 reply templates for clarity; these are not part of the reply packet's
25933 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
25939 The program received signal number @var{AA} (a two-digit hexadecimal
25940 number). This is equivalent to a @samp{T} response with no
25941 @var{n}:@var{r} pairs.
25943 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
25944 @cindex @samp{T} packet reply
25945 The program received signal number @var{AA} (a two-digit hexadecimal
25946 number). This is equivalent to an @samp{S} response, except that the
25947 @samp{@var{n}:@var{r}} pairs can carry values of important registers
25948 and other information directly in the stop reply packet, reducing
25949 round-trip latency. Single-step and breakpoint traps are reported
25950 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
25954 If @var{n} is a hexadecimal number, it is a register number, and the
25955 corresponding @var{r} gives that register's value. @var{r} is a
25956 series of bytes in target byte order, with each byte given by a
25957 two-digit hex number.
25960 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
25961 the stopped thread, as specified in @ref{thread-id syntax}.
25964 If @var{n} is a recognized @dfn{stop reason}, it describes a more
25965 specific event that stopped the target. The currently defined stop
25966 reasons are listed below. @var{aa} should be @samp{05}, the trap
25967 signal. At most one stop reason should be present.
25970 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
25971 and go on to the next; this allows us to extend the protocol in the
25975 The currently defined stop reasons are:
25981 The packet indicates a watchpoint hit, and @var{r} is the data address, in
25984 @cindex shared library events, remote reply
25986 The packet indicates that the loaded libraries have changed.
25987 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
25988 list of loaded libraries. @var{r} is ignored.
25990 @cindex replay log events, remote reply
25992 The packet indicates that the target cannot continue replaying
25993 logged execution events, because it has reached the end (or the
25994 beginning when executing backward) of the log. The value of @var{r}
25995 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
25996 for more information.
26002 @itemx W @var{AA} ; process:@var{pid}
26003 The process exited, and @var{AA} is the exit status. This is only
26004 applicable to certain targets.
26006 The second form of the response, including the process ID of the exited
26007 process, can be used only when @value{GDBN} has reported support for
26008 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26009 The @var{pid} is formatted as a big-endian hex string.
26012 @itemx X @var{AA} ; process:@var{pid}
26013 The process terminated with signal @var{AA}.
26015 The second form of the response, including the process ID of the
26016 terminated process, can be used only when @value{GDBN} has reported
26017 support for multiprocess protocol extensions; see @ref{multiprocess
26018 extensions}. The @var{pid} is formatted as a big-endian hex string.
26020 @item O @var{XX}@dots{}
26021 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26022 written as the program's console output. This can happen at any time
26023 while the program is running and the debugger should continue to wait
26024 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
26026 @item F @var{call-id},@var{parameter}@dots{}
26027 @var{call-id} is the identifier which says which host system call should
26028 be called. This is just the name of the function. Translation into the
26029 correct system call is only applicable as it's defined in @value{GDBN}.
26030 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
26033 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
26034 this very system call.
26036 The target replies with this packet when it expects @value{GDBN} to
26037 call a host system call on behalf of the target. @value{GDBN} replies
26038 with an appropriate @samp{F} packet and keeps up waiting for the next
26039 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
26040 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
26041 Protocol Extension}, for more details.
26045 @node General Query Packets
26046 @section General Query Packets
26047 @cindex remote query requests
26049 Packets starting with @samp{q} are @dfn{general query packets};
26050 packets starting with @samp{Q} are @dfn{general set packets}. General
26051 query and set packets are a semi-unified form for retrieving and
26052 sending information to and from the stub.
26054 The initial letter of a query or set packet is followed by a name
26055 indicating what sort of thing the packet applies to. For example,
26056 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
26057 definitions with the stub. These packet names follow some
26062 The name must not contain commas, colons or semicolons.
26064 Most @value{GDBN} query and set packets have a leading upper case
26067 The names of custom vendor packets should use a company prefix, in
26068 lower case, followed by a period. For example, packets designed at
26069 the Acme Corporation might begin with @samp{qacme.foo} (for querying
26070 foos) or @samp{Qacme.bar} (for setting bars).
26073 The name of a query or set packet should be separated from any
26074 parameters by a @samp{:}; the parameters themselves should be
26075 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
26076 full packet name, and check for a separator or the end of the packet,
26077 in case two packet names share a common prefix. New packets should not begin
26078 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
26079 packets predate these conventions, and have arguments without any terminator
26080 for the packet name; we suspect they are in widespread use in places that
26081 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
26082 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
26085 Like the descriptions of the other packets, each description here
26086 has a template showing the packet's overall syntax, followed by an
26087 explanation of the packet's meaning. We include spaces in some of the
26088 templates for clarity; these are not part of the packet's syntax. No
26089 @value{GDBN} packet uses spaces to separate its components.
26091 Here are the currently defined query and set packets:
26096 @cindex current thread, remote request
26097 @cindex @samp{qC} packet
26098 Return the current thread ID.
26102 @item QC @var{thread-id}
26103 Where @var{thread-id} is a thread ID as documented in
26104 @ref{thread-id syntax}.
26105 @item @r{(anything else)}
26106 Any other reply implies the old thread ID.
26109 @item qCRC:@var{addr},@var{length}
26110 @cindex CRC of memory block, remote request
26111 @cindex @samp{qCRC} packet
26112 Compute the CRC checksum of a block of memory.
26116 An error (such as memory fault)
26117 @item C @var{crc32}
26118 The specified memory region's checksum is @var{crc32}.
26122 @itemx qsThreadInfo
26123 @cindex list active threads, remote request
26124 @cindex @samp{qfThreadInfo} packet
26125 @cindex @samp{qsThreadInfo} packet
26126 Obtain a list of all active thread IDs from the target (OS). Since there
26127 may be too many active threads to fit into one reply packet, this query
26128 works iteratively: it may require more than one query/reply sequence to
26129 obtain the entire list of threads. The first query of the sequence will
26130 be the @samp{qfThreadInfo} query; subsequent queries in the
26131 sequence will be the @samp{qsThreadInfo} query.
26133 NOTE: This packet replaces the @samp{qL} query (see below).
26137 @item m @var{thread-id}
26139 @item m @var{thread-id},@var{thread-id}@dots{}
26140 a comma-separated list of thread IDs
26142 (lower case letter @samp{L}) denotes end of list.
26145 In response to each query, the target will reply with a list of one or
26146 more thread IDs, separated by commas.
26147 @value{GDBN} will respond to each reply with a request for more thread
26148 ids (using the @samp{qs} form of the query), until the target responds
26149 with @samp{l} (lower-case el, for @dfn{last}).
26150 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
26153 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
26154 @cindex get thread-local storage address, remote request
26155 @cindex @samp{qGetTLSAddr} packet
26156 Fetch the address associated with thread local storage specified
26157 by @var{thread-id}, @var{offset}, and @var{lm}.
26159 @var{thread-id} is the thread ID associated with the
26160 thread for which to fetch the TLS address. @xref{thread-id syntax}.
26162 @var{offset} is the (big endian, hex encoded) offset associated with the
26163 thread local variable. (This offset is obtained from the debug
26164 information associated with the variable.)
26166 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
26167 the load module associated with the thread local storage. For example,
26168 a @sc{gnu}/Linux system will pass the link map address of the shared
26169 object associated with the thread local storage under consideration.
26170 Other operating environments may choose to represent the load module
26171 differently, so the precise meaning of this parameter will vary.
26175 @item @var{XX}@dots{}
26176 Hex encoded (big endian) bytes representing the address of the thread
26177 local storage requested.
26180 An error occurred. @var{nn} are hex digits.
26183 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
26186 @item qL @var{startflag} @var{threadcount} @var{nextthread}
26187 Obtain thread information from RTOS. Where: @var{startflag} (one hex
26188 digit) is one to indicate the first query and zero to indicate a
26189 subsequent query; @var{threadcount} (two hex digits) is the maximum
26190 number of threads the response packet can contain; and @var{nextthread}
26191 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
26192 returned in the response as @var{argthread}.
26194 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
26198 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
26199 Where: @var{count} (two hex digits) is the number of threads being
26200 returned; @var{done} (one hex digit) is zero to indicate more threads
26201 and one indicates no further threads; @var{argthreadid} (eight hex
26202 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
26203 is a sequence of thread IDs from the target. @var{threadid} (eight hex
26204 digits). See @code{remote.c:parse_threadlist_response()}.
26208 @cindex section offsets, remote request
26209 @cindex @samp{qOffsets} packet
26210 Get section offsets that the target used when relocating the downloaded
26215 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
26216 Relocate the @code{Text} section by @var{xxx} from its original address.
26217 Relocate the @code{Data} section by @var{yyy} from its original address.
26218 If the object file format provides segment information (e.g.@: @sc{elf}
26219 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
26220 segments by the supplied offsets.
26222 @emph{Note: while a @code{Bss} offset may be included in the response,
26223 @value{GDBN} ignores this and instead applies the @code{Data} offset
26224 to the @code{Bss} section.}
26226 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
26227 Relocate the first segment of the object file, which conventionally
26228 contains program code, to a starting address of @var{xxx}. If
26229 @samp{DataSeg} is specified, relocate the second segment, which
26230 conventionally contains modifiable data, to a starting address of
26231 @var{yyy}. @value{GDBN} will report an error if the object file
26232 does not contain segment information, or does not contain at least
26233 as many segments as mentioned in the reply. Extra segments are
26234 kept at fixed offsets relative to the last relocated segment.
26237 @item qP @var{mode} @var{thread-id}
26238 @cindex thread information, remote request
26239 @cindex @samp{qP} packet
26240 Returns information on @var{thread-id}. Where: @var{mode} is a hex
26241 encoded 32 bit mode; @var{thread-id} is a thread ID
26242 (@pxref{thread-id syntax}).
26244 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
26247 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
26251 @cindex non-stop mode, remote request
26252 @cindex @samp{QNonStop} packet
26254 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
26255 @xref{Remote Non-Stop}, for more information.
26260 The request succeeded.
26263 An error occurred. @var{nn} are hex digits.
26266 An empty reply indicates that @samp{QNonStop} is not supported by
26270 This packet is not probed by default; the remote stub must request it,
26271 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26272 Use of this packet is controlled by the @code{set non-stop} command;
26273 @pxref{Non-Stop Mode}.
26275 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
26276 @cindex pass signals to inferior, remote request
26277 @cindex @samp{QPassSignals} packet
26278 @anchor{QPassSignals}
26279 Each listed @var{signal} should be passed directly to the inferior process.
26280 Signals are numbered identically to continue packets and stop replies
26281 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
26282 strictly greater than the previous item. These signals do not need to stop
26283 the inferior, or be reported to @value{GDBN}. All other signals should be
26284 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
26285 combine; any earlier @samp{QPassSignals} list is completely replaced by the
26286 new list. This packet improves performance when using @samp{handle
26287 @var{signal} nostop noprint pass}.
26292 The request succeeded.
26295 An error occurred. @var{nn} are hex digits.
26298 An empty reply indicates that @samp{QPassSignals} is not supported by
26302 Use of this packet is controlled by the @code{set remote pass-signals}
26303 command (@pxref{Remote Configuration, set remote pass-signals}).
26304 This packet is not probed by default; the remote stub must request it,
26305 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26307 @item qRcmd,@var{command}
26308 @cindex execute remote command, remote request
26309 @cindex @samp{qRcmd} packet
26310 @var{command} (hex encoded) is passed to the local interpreter for
26311 execution. Invalid commands should be reported using the output
26312 string. Before the final result packet, the target may also respond
26313 with a number of intermediate @samp{O@var{output}} console output
26314 packets. @emph{Implementors should note that providing access to a
26315 stubs's interpreter may have security implications}.
26320 A command response with no output.
26322 A command response with the hex encoded output string @var{OUTPUT}.
26324 Indicate a badly formed request.
26326 An empty reply indicates that @samp{qRcmd} is not recognized.
26329 (Note that the @code{qRcmd} packet's name is separated from the
26330 command by a @samp{,}, not a @samp{:}, contrary to the naming
26331 conventions above. Please don't use this packet as a model for new
26334 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
26335 @cindex searching memory, in remote debugging
26336 @cindex @samp{qSearch:memory} packet
26337 @anchor{qSearch memory}
26338 Search @var{length} bytes at @var{address} for @var{search-pattern}.
26339 @var{address} and @var{length} are encoded in hex.
26340 @var{search-pattern} is a sequence of bytes, hex encoded.
26345 The pattern was not found.
26347 The pattern was found at @var{address}.
26349 A badly formed request or an error was encountered while searching memory.
26351 An empty reply indicates that @samp{qSearch:memory} is not recognized.
26354 @item QStartNoAckMode
26355 @cindex @samp{QStartNoAckMode} packet
26356 @anchor{QStartNoAckMode}
26357 Request that the remote stub disable the normal @samp{+}/@samp{-}
26358 protocol acknowledgments (@pxref{Packet Acknowledgment}).
26363 The stub has switched to no-acknowledgment mode.
26364 @value{GDBN} acknowledges this reponse,
26365 but neither the stub nor @value{GDBN} shall send or expect further
26366 @samp{+}/@samp{-} acknowledgments in the current connection.
26368 An empty reply indicates that the stub does not support no-acknowledgment mode.
26371 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
26372 @cindex supported packets, remote query
26373 @cindex features of the remote protocol
26374 @cindex @samp{qSupported} packet
26375 @anchor{qSupported}
26376 Tell the remote stub about features supported by @value{GDBN}, and
26377 query the stub for features it supports. This packet allows
26378 @value{GDBN} and the remote stub to take advantage of each others'
26379 features. @samp{qSupported} also consolidates multiple feature probes
26380 at startup, to improve @value{GDBN} performance---a single larger
26381 packet performs better than multiple smaller probe packets on
26382 high-latency links. Some features may enable behavior which must not
26383 be on by default, e.g.@: because it would confuse older clients or
26384 stubs. Other features may describe packets which could be
26385 automatically probed for, but are not. These features must be
26386 reported before @value{GDBN} will use them. This ``default
26387 unsupported'' behavior is not appropriate for all packets, but it
26388 helps to keep the initial connection time under control with new
26389 versions of @value{GDBN} which support increasing numbers of packets.
26393 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
26394 The stub supports or does not support each returned @var{stubfeature},
26395 depending on the form of each @var{stubfeature} (see below for the
26398 An empty reply indicates that @samp{qSupported} is not recognized,
26399 or that no features needed to be reported to @value{GDBN}.
26402 The allowed forms for each feature (either a @var{gdbfeature} in the
26403 @samp{qSupported} packet, or a @var{stubfeature} in the response)
26407 @item @var{name}=@var{value}
26408 The remote protocol feature @var{name} is supported, and associated
26409 with the specified @var{value}. The format of @var{value} depends
26410 on the feature, but it must not include a semicolon.
26412 The remote protocol feature @var{name} is supported, and does not
26413 need an associated value.
26415 The remote protocol feature @var{name} is not supported.
26417 The remote protocol feature @var{name} may be supported, and
26418 @value{GDBN} should auto-detect support in some other way when it is
26419 needed. This form will not be used for @var{gdbfeature} notifications,
26420 but may be used for @var{stubfeature} responses.
26423 Whenever the stub receives a @samp{qSupported} request, the
26424 supplied set of @value{GDBN} features should override any previous
26425 request. This allows @value{GDBN} to put the stub in a known
26426 state, even if the stub had previously been communicating with
26427 a different version of @value{GDBN}.
26429 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
26434 This feature indicates whether @value{GDBN} supports multiprocess
26435 extensions to the remote protocol. @value{GDBN} does not use such
26436 extensions unless the stub also reports that it supports them by
26437 including @samp{multiprocess+} in its @samp{qSupported} reply.
26438 @xref{multiprocess extensions}, for details.
26441 Stubs should ignore any unknown values for
26442 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
26443 packet supports receiving packets of unlimited length (earlier
26444 versions of @value{GDBN} may reject overly long responses). Additional values
26445 for @var{gdbfeature} may be defined in the future to let the stub take
26446 advantage of new features in @value{GDBN}, e.g.@: incompatible
26447 improvements in the remote protocol---the @samp{multiprocess} feature is
26448 an example of such a feature. The stub's reply should be independent
26449 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
26450 describes all the features it supports, and then the stub replies with
26451 all the features it supports.
26453 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
26454 responses, as long as each response uses one of the standard forms.
26456 Some features are flags. A stub which supports a flag feature
26457 should respond with a @samp{+} form response. Other features
26458 require values, and the stub should respond with an @samp{=}
26461 Each feature has a default value, which @value{GDBN} will use if
26462 @samp{qSupported} is not available or if the feature is not mentioned
26463 in the @samp{qSupported} response. The default values are fixed; a
26464 stub is free to omit any feature responses that match the defaults.
26466 Not all features can be probed, but for those which can, the probing
26467 mechanism is useful: in some cases, a stub's internal
26468 architecture may not allow the protocol layer to know some information
26469 about the underlying target in advance. This is especially common in
26470 stubs which may be configured for multiple targets.
26472 These are the currently defined stub features and their properties:
26474 @multitable @columnfractions 0.35 0.2 0.12 0.2
26475 @c NOTE: The first row should be @headitem, but we do not yet require
26476 @c a new enough version of Texinfo (4.7) to use @headitem.
26478 @tab Value Required
26482 @item @samp{PacketSize}
26487 @item @samp{qXfer:auxv:read}
26492 @item @samp{qXfer:features:read}
26497 @item @samp{qXfer:libraries:read}
26502 @item @samp{qXfer:memory-map:read}
26507 @item @samp{qXfer:spu:read}
26512 @item @samp{qXfer:spu:write}
26517 @item @samp{QNonStop}
26522 @item @samp{QPassSignals}
26527 @item @samp{QStartNoAckMode}
26532 @item @samp{multiprocess}
26539 These are the currently defined stub features, in more detail:
26542 @cindex packet size, remote protocol
26543 @item PacketSize=@var{bytes}
26544 The remote stub can accept packets up to at least @var{bytes} in
26545 length. @value{GDBN} will send packets up to this size for bulk
26546 transfers, and will never send larger packets. This is a limit on the
26547 data characters in the packet, including the frame and checksum.
26548 There is no trailing NUL byte in a remote protocol packet; if the stub
26549 stores packets in a NUL-terminated format, it should allow an extra
26550 byte in its buffer for the NUL. If this stub feature is not supported,
26551 @value{GDBN} guesses based on the size of the @samp{g} packet response.
26553 @item qXfer:auxv:read
26554 The remote stub understands the @samp{qXfer:auxv:read} packet
26555 (@pxref{qXfer auxiliary vector read}).
26557 @item qXfer:features:read
26558 The remote stub understands the @samp{qXfer:features:read} packet
26559 (@pxref{qXfer target description read}).
26561 @item qXfer:libraries:read
26562 The remote stub understands the @samp{qXfer:libraries:read} packet
26563 (@pxref{qXfer library list read}).
26565 @item qXfer:memory-map:read
26566 The remote stub understands the @samp{qXfer:memory-map:read} packet
26567 (@pxref{qXfer memory map read}).
26569 @item qXfer:spu:read
26570 The remote stub understands the @samp{qXfer:spu:read} packet
26571 (@pxref{qXfer spu read}).
26573 @item qXfer:spu:write
26574 The remote stub understands the @samp{qXfer:spu:write} packet
26575 (@pxref{qXfer spu write}).
26578 The remote stub understands the @samp{QNonStop} packet
26579 (@pxref{QNonStop}).
26582 The remote stub understands the @samp{QPassSignals} packet
26583 (@pxref{QPassSignals}).
26585 @item QStartNoAckMode
26586 The remote stub understands the @samp{QStartNoAckMode} packet and
26587 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
26590 @anchor{multiprocess extensions}
26591 @cindex multiprocess extensions, in remote protocol
26592 The remote stub understands the multiprocess extensions to the remote
26593 protocol syntax. The multiprocess extensions affect the syntax of
26594 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
26595 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
26596 replies. Note that reporting this feature indicates support for the
26597 syntactic extensions only, not that the stub necessarily supports
26598 debugging of more than one process at a time. The stub must not use
26599 multiprocess extensions in packet replies unless @value{GDBN} has also
26600 indicated it supports them in its @samp{qSupported} request.
26602 @item qXfer:osdata:read
26603 The remote stub understands the @samp{qXfer:osdata:read} packet
26604 ((@pxref{qXfer osdata read}).
26609 @cindex symbol lookup, remote request
26610 @cindex @samp{qSymbol} packet
26611 Notify the target that @value{GDBN} is prepared to serve symbol lookup
26612 requests. Accept requests from the target for the values of symbols.
26617 The target does not need to look up any (more) symbols.
26618 @item qSymbol:@var{sym_name}
26619 The target requests the value of symbol @var{sym_name} (hex encoded).
26620 @value{GDBN} may provide the value by using the
26621 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
26625 @item qSymbol:@var{sym_value}:@var{sym_name}
26626 Set the value of @var{sym_name} to @var{sym_value}.
26628 @var{sym_name} (hex encoded) is the name of a symbol whose value the
26629 target has previously requested.
26631 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
26632 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
26638 The target does not need to look up any (more) symbols.
26639 @item qSymbol:@var{sym_name}
26640 The target requests the value of a new symbol @var{sym_name} (hex
26641 encoded). @value{GDBN} will continue to supply the values of symbols
26642 (if available), until the target ceases to request them.
26647 @xref{Tracepoint Packets}.
26649 @item qThreadExtraInfo,@var{thread-id}
26650 @cindex thread attributes info, remote request
26651 @cindex @samp{qThreadExtraInfo} packet
26652 Obtain a printable string description of a thread's attributes from
26653 the target OS. @var{thread-id} is a thread ID;
26654 see @ref{thread-id syntax}. This
26655 string may contain anything that the target OS thinks is interesting
26656 for @value{GDBN} to tell the user about the thread. The string is
26657 displayed in @value{GDBN}'s @code{info threads} display. Some
26658 examples of possible thread extra info strings are @samp{Runnable}, or
26659 @samp{Blocked on Mutex}.
26663 @item @var{XX}@dots{}
26664 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
26665 comprising the printable string containing the extra information about
26666 the thread's attributes.
26669 (Note that the @code{qThreadExtraInfo} packet's name is separated from
26670 the command by a @samp{,}, not a @samp{:}, contrary to the naming
26671 conventions above. Please don't use this packet as a model for new
26679 @xref{Tracepoint Packets}.
26681 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
26682 @cindex read special object, remote request
26683 @cindex @samp{qXfer} packet
26684 @anchor{qXfer read}
26685 Read uninterpreted bytes from the target's special data area
26686 identified by the keyword @var{object}. Request @var{length} bytes
26687 starting at @var{offset} bytes into the data. The content and
26688 encoding of @var{annex} is specific to @var{object}; it can supply
26689 additional details about what data to access.
26691 Here are the specific requests of this form defined so far. All
26692 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
26693 formats, listed below.
26696 @item qXfer:auxv:read::@var{offset},@var{length}
26697 @anchor{qXfer auxiliary vector read}
26698 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
26699 auxiliary vector}. Note @var{annex} must be empty.
26701 This packet is not probed by default; the remote stub must request it,
26702 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26704 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
26705 @anchor{qXfer target description read}
26706 Access the @dfn{target description}. @xref{Target Descriptions}. The
26707 annex specifies which XML document to access. The main description is
26708 always loaded from the @samp{target.xml} annex.
26710 This packet is not probed by default; the remote stub must request it,
26711 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26713 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
26714 @anchor{qXfer library list read}
26715 Access the target's list of loaded libraries. @xref{Library List Format}.
26716 The annex part of the generic @samp{qXfer} packet must be empty
26717 (@pxref{qXfer read}).
26719 Targets which maintain a list of libraries in the program's memory do
26720 not need to implement this packet; it is designed for platforms where
26721 the operating system manages the list of loaded libraries.
26723 This packet is not probed by default; the remote stub must request it,
26724 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26726 @item qXfer:memory-map:read::@var{offset},@var{length}
26727 @anchor{qXfer memory map read}
26728 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
26729 annex part of the generic @samp{qXfer} packet must be empty
26730 (@pxref{qXfer read}).
26732 This packet is not probed by default; the remote stub must request it,
26733 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26735 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
26736 @anchor{qXfer spu read}
26737 Read contents of an @code{spufs} file on the target system. The
26738 annex specifies which file to read; it must be of the form
26739 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
26740 in the target process, and @var{name} identifes the @code{spufs} file
26741 in that context to be accessed.
26743 This packet is not probed by default; the remote stub must request it,
26744 by supplying an appropriate @samp{qSupported} response
26745 (@pxref{qSupported}).
26747 @item qXfer:osdata:read::@var{offset},@var{length}
26748 @anchor{qXfer osdata read}
26749 Access the target's @dfn{operating system information}.
26750 @xref{Operating System Information}.
26757 Data @var{data} (@pxref{Binary Data}) has been read from the
26758 target. There may be more data at a higher address (although
26759 it is permitted to return @samp{m} even for the last valid
26760 block of data, as long as at least one byte of data was read).
26761 @var{data} may have fewer bytes than the @var{length} in the
26765 Data @var{data} (@pxref{Binary Data}) has been read from the target.
26766 There is no more data to be read. @var{data} may have fewer bytes
26767 than the @var{length} in the request.
26770 The @var{offset} in the request is at the end of the data.
26771 There is no more data to be read.
26774 The request was malformed, or @var{annex} was invalid.
26777 The offset was invalid, or there was an error encountered reading the data.
26778 @var{nn} is a hex-encoded @code{errno} value.
26781 An empty reply indicates the @var{object} string was not recognized by
26782 the stub, or that the object does not support reading.
26785 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
26786 @cindex write data into object, remote request
26787 Write uninterpreted bytes into the target's special data area
26788 identified by the keyword @var{object}, starting at @var{offset} bytes
26789 into the data. @var{data}@dots{} is the binary-encoded data
26790 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
26791 is specific to @var{object}; it can supply additional details about what data
26794 Here are the specific requests of this form defined so far. All
26795 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
26796 formats, listed below.
26799 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
26800 @anchor{qXfer spu write}
26801 Write @var{data} to an @code{spufs} file on the target system. The
26802 annex specifies which file to write; it must be of the form
26803 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
26804 in the target process, and @var{name} identifes the @code{spufs} file
26805 in that context to be accessed.
26807 This packet is not probed by default; the remote stub must request it,
26808 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
26814 @var{nn} (hex encoded) is the number of bytes written.
26815 This may be fewer bytes than supplied in the request.
26818 The request was malformed, or @var{annex} was invalid.
26821 The offset was invalid, or there was an error encountered writing the data.
26822 @var{nn} is a hex-encoded @code{errno} value.
26825 An empty reply indicates the @var{object} string was not
26826 recognized by the stub, or that the object does not support writing.
26829 @item qXfer:@var{object}:@var{operation}:@dots{}
26830 Requests of this form may be added in the future. When a stub does
26831 not recognize the @var{object} keyword, or its support for
26832 @var{object} does not recognize the @var{operation} keyword, the stub
26833 must respond with an empty packet.
26837 @node Register Packet Format
26838 @section Register Packet Format
26840 The following @code{g}/@code{G} packets have previously been defined.
26841 In the below, some thirty-two bit registers are transferred as
26842 sixty-four bits. Those registers should be zero/sign extended (which?)
26843 to fill the space allocated. Register bytes are transferred in target
26844 byte order. The two nibbles within a register byte are transferred
26845 most-significant - least-significant.
26851 All registers are transferred as thirty-two bit quantities in the order:
26852 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
26853 registers; fsr; fir; fp.
26857 All registers are transferred as sixty-four bit quantities (including
26858 thirty-two bit registers such as @code{sr}). The ordering is the same
26863 @node Tracepoint Packets
26864 @section Tracepoint Packets
26865 @cindex tracepoint packets
26866 @cindex packets, tracepoint
26868 Here we describe the packets @value{GDBN} uses to implement
26869 tracepoints (@pxref{Tracepoints}).
26873 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
26874 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
26875 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
26876 the tracepoint is disabled. @var{step} is the tracepoint's step
26877 count, and @var{pass} is its pass count. If the trailing @samp{-} is
26878 present, further @samp{QTDP} packets will follow to specify this
26879 tracepoint's actions.
26884 The packet was understood and carried out.
26886 The packet was not recognized.
26889 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
26890 Define actions to be taken when a tracepoint is hit. @var{n} and
26891 @var{addr} must be the same as in the initial @samp{QTDP} packet for
26892 this tracepoint. This packet may only be sent immediately after
26893 another @samp{QTDP} packet that ended with a @samp{-}. If the
26894 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
26895 specifying more actions for this tracepoint.
26897 In the series of action packets for a given tracepoint, at most one
26898 can have an @samp{S} before its first @var{action}. If such a packet
26899 is sent, it and the following packets define ``while-stepping''
26900 actions. Any prior packets define ordinary actions --- that is, those
26901 taken when the tracepoint is first hit. If no action packet has an
26902 @samp{S}, then all the packets in the series specify ordinary
26903 tracepoint actions.
26905 The @samp{@var{action}@dots{}} portion of the packet is a series of
26906 actions, concatenated without separators. Each action has one of the
26912 Collect the registers whose bits are set in @var{mask}. @var{mask} is
26913 a hexadecimal number whose @var{i}'th bit is set if register number
26914 @var{i} should be collected. (The least significant bit is numbered
26915 zero.) Note that @var{mask} may be any number of digits long; it may
26916 not fit in a 32-bit word.
26918 @item M @var{basereg},@var{offset},@var{len}
26919 Collect @var{len} bytes of memory starting at the address in register
26920 number @var{basereg}, plus @var{offset}. If @var{basereg} is
26921 @samp{-1}, then the range has a fixed address: @var{offset} is the
26922 address of the lowest byte to collect. The @var{basereg},
26923 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
26924 values (the @samp{-1} value for @var{basereg} is a special case).
26926 @item X @var{len},@var{expr}
26927 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
26928 it directs. @var{expr} is an agent expression, as described in
26929 @ref{Agent Expressions}. Each byte of the expression is encoded as a
26930 two-digit hex number in the packet; @var{len} is the number of bytes
26931 in the expression (and thus one-half the number of hex digits in the
26936 Any number of actions may be packed together in a single @samp{QTDP}
26937 packet, as long as the packet does not exceed the maximum packet
26938 length (400 bytes, for many stubs). There may be only one @samp{R}
26939 action per tracepoint, and it must precede any @samp{M} or @samp{X}
26940 actions. Any registers referred to by @samp{M} and @samp{X} actions
26941 must be collected by a preceding @samp{R} action. (The
26942 ``while-stepping'' actions are treated as if they were attached to a
26943 separate tracepoint, as far as these restrictions are concerned.)
26948 The packet was understood and carried out.
26950 The packet was not recognized.
26953 @item QTFrame:@var{n}
26954 Select the @var{n}'th tracepoint frame from the buffer, and use the
26955 register and memory contents recorded there to answer subsequent
26956 request packets from @value{GDBN}.
26958 A successful reply from the stub indicates that the stub has found the
26959 requested frame. The response is a series of parts, concatenated
26960 without separators, describing the frame we selected. Each part has
26961 one of the following forms:
26965 The selected frame is number @var{n} in the trace frame buffer;
26966 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
26967 was no frame matching the criteria in the request packet.
26970 The selected trace frame records a hit of tracepoint number @var{t};
26971 @var{t} is a hexadecimal number.
26975 @item QTFrame:pc:@var{addr}
26976 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26977 currently selected frame whose PC is @var{addr};
26978 @var{addr} is a hexadecimal number.
26980 @item QTFrame:tdp:@var{t}
26981 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26982 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
26983 is a hexadecimal number.
26985 @item QTFrame:range:@var{start}:@var{end}
26986 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
26987 currently selected frame whose PC is between @var{start} (inclusive)
26988 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
26991 @item QTFrame:outside:@var{start}:@var{end}
26992 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
26993 frame @emph{outside} the given range of addresses.
26996 Begin the tracepoint experiment. Begin collecting data from tracepoint
26997 hits in the trace frame buffer.
27000 End the tracepoint experiment. Stop collecting trace frames.
27003 Clear the table of tracepoints, and empty the trace frame buffer.
27005 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
27006 Establish the given ranges of memory as ``transparent''. The stub
27007 will answer requests for these ranges from memory's current contents,
27008 if they were not collected as part of the tracepoint hit.
27010 @value{GDBN} uses this to mark read-only regions of memory, like those
27011 containing program code. Since these areas never change, they should
27012 still have the same contents they did when the tracepoint was hit, so
27013 there's no reason for the stub to refuse to provide their contents.
27016 Ask the stub if there is a trace experiment running right now.
27021 There is no trace experiment running.
27023 There is a trace experiment running.
27029 @node Host I/O Packets
27030 @section Host I/O Packets
27031 @cindex Host I/O, remote protocol
27032 @cindex file transfer, remote protocol
27034 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
27035 operations on the far side of a remote link. For example, Host I/O is
27036 used to upload and download files to a remote target with its own
27037 filesystem. Host I/O uses the same constant values and data structure
27038 layout as the target-initiated File-I/O protocol. However, the
27039 Host I/O packets are structured differently. The target-initiated
27040 protocol relies on target memory to store parameters and buffers.
27041 Host I/O requests are initiated by @value{GDBN}, and the
27042 target's memory is not involved. @xref{File-I/O Remote Protocol
27043 Extension}, for more details on the target-initiated protocol.
27045 The Host I/O request packets all encode a single operation along with
27046 its arguments. They have this format:
27050 @item vFile:@var{operation}: @var{parameter}@dots{}
27051 @var{operation} is the name of the particular request; the target
27052 should compare the entire packet name up to the second colon when checking
27053 for a supported operation. The format of @var{parameter} depends on
27054 the operation. Numbers are always passed in hexadecimal. Negative
27055 numbers have an explicit minus sign (i.e.@: two's complement is not
27056 used). Strings (e.g.@: filenames) are encoded as a series of
27057 hexadecimal bytes. The last argument to a system call may be a
27058 buffer of escaped binary data (@pxref{Binary Data}).
27062 The valid responses to Host I/O packets are:
27066 @item F @var{result} [, @var{errno}] [; @var{attachment}]
27067 @var{result} is the integer value returned by this operation, usually
27068 non-negative for success and -1 for errors. If an error has occured,
27069 @var{errno} will be included in the result. @var{errno} will have a
27070 value defined by the File-I/O protocol (@pxref{Errno Values}). For
27071 operations which return data, @var{attachment} supplies the data as a
27072 binary buffer. Binary buffers in response packets are escaped in the
27073 normal way (@pxref{Binary Data}). See the individual packet
27074 documentation for the interpretation of @var{result} and
27078 An empty response indicates that this operation is not recognized.
27082 These are the supported Host I/O operations:
27085 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
27086 Open a file at @var{pathname} and return a file descriptor for it, or
27087 return -1 if an error occurs. @var{pathname} is a string,
27088 @var{flags} is an integer indicating a mask of open flags
27089 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
27090 of mode bits to use if the file is created (@pxref{mode_t Values}).
27091 @xref{open}, for details of the open flags and mode values.
27093 @item vFile:close: @var{fd}
27094 Close the open file corresponding to @var{fd} and return 0, or
27095 -1 if an error occurs.
27097 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
27098 Read data from the open file corresponding to @var{fd}. Up to
27099 @var{count} bytes will be read from the file, starting at @var{offset}
27100 relative to the start of the file. The target may read fewer bytes;
27101 common reasons include packet size limits and an end-of-file
27102 condition. The number of bytes read is returned. Zero should only be
27103 returned for a successful read at the end of the file, or if
27104 @var{count} was zero.
27106 The data read should be returned as a binary attachment on success.
27107 If zero bytes were read, the response should include an empty binary
27108 attachment (i.e.@: a trailing semicolon). The return value is the
27109 number of target bytes read; the binary attachment may be longer if
27110 some characters were escaped.
27112 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
27113 Write @var{data} (a binary buffer) to the open file corresponding
27114 to @var{fd}. Start the write at @var{offset} from the start of the
27115 file. Unlike many @code{write} system calls, there is no
27116 separate @var{count} argument; the length of @var{data} in the
27117 packet is used. @samp{vFile:write} returns the number of bytes written,
27118 which may be shorter than the length of @var{data}, or -1 if an
27121 @item vFile:unlink: @var{pathname}
27122 Delete the file at @var{pathname} on the target. Return 0,
27123 or -1 if an error occurs. @var{pathname} is a string.
27128 @section Interrupts
27129 @cindex interrupts (remote protocol)
27131 When a program on the remote target is running, @value{GDBN} may
27132 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
27133 control of which is specified via @value{GDBN}'s @samp{remotebreak}
27134 setting (@pxref{set remotebreak}).
27136 The precise meaning of @code{BREAK} is defined by the transport
27137 mechanism and may, in fact, be undefined. @value{GDBN} does not
27138 currently define a @code{BREAK} mechanism for any of the network
27139 interfaces except for TCP, in which case @value{GDBN} sends the
27140 @code{telnet} BREAK sequence.
27142 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
27143 transport mechanisms. It is represented by sending the single byte
27144 @code{0x03} without any of the usual packet overhead described in
27145 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
27146 transmitted as part of a packet, it is considered to be packet data
27147 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
27148 (@pxref{X packet}), used for binary downloads, may include an unescaped
27149 @code{0x03} as part of its packet.
27151 Stubs are not required to recognize these interrupt mechanisms and the
27152 precise meaning associated with receipt of the interrupt is
27153 implementation defined. If the target supports debugging of multiple
27154 threads and/or processes, it should attempt to interrupt all
27155 currently-executing threads and processes.
27156 If the stub is successful at interrupting the
27157 running program, it should send one of the stop
27158 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
27159 of successfully stopping the program in all-stop mode, and a stop reply
27160 for each stopped thread in non-stop mode.
27161 Interrupts received while the
27162 program is stopped are discarded.
27164 @node Notification Packets
27165 @section Notification Packets
27166 @cindex notification packets
27167 @cindex packets, notification
27169 The @value{GDBN} remote serial protocol includes @dfn{notifications},
27170 packets that require no acknowledgment. Both the GDB and the stub
27171 may send notifications (although the only notifications defined at
27172 present are sent by the stub). Notifications carry information
27173 without incurring the round-trip latency of an acknowledgment, and so
27174 are useful for low-impact communications where occasional packet loss
27177 A notification packet has the form @samp{% @var{data} #
27178 @var{checksum}}, where @var{data} is the content of the notification,
27179 and @var{checksum} is a checksum of @var{data}, computed and formatted
27180 as for ordinary @value{GDBN} packets. A notification's @var{data}
27181 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
27182 receiving a notification, the recipient sends no @samp{+} or @samp{-}
27183 to acknowledge the notification's receipt or to report its corruption.
27185 Every notification's @var{data} begins with a name, which contains no
27186 colon characters, followed by a colon character.
27188 Recipients should silently ignore corrupted notifications and
27189 notifications they do not understand. Recipients should restart
27190 timeout periods on receipt of a well-formed notification, whether or
27191 not they understand it.
27193 Senders should only send the notifications described here when this
27194 protocol description specifies that they are permitted. In the
27195 future, we may extend the protocol to permit existing notifications in
27196 new contexts; this rule helps older senders avoid confusing newer
27199 (Older versions of @value{GDBN} ignore bytes received until they see
27200 the @samp{$} byte that begins an ordinary packet, so new stubs may
27201 transmit notifications without fear of confusing older clients. There
27202 are no notifications defined for @value{GDBN} to send at the moment, but we
27203 assume that most older stubs would ignore them, as well.)
27205 The following notification packets from the stub to @value{GDBN} are
27209 @item Stop: @var{reply}
27210 Report an asynchronous stop event in non-stop mode.
27211 The @var{reply} has the form of a stop reply, as
27212 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
27213 for information on how these notifications are acknowledged by
27217 @node Remote Non-Stop
27218 @section Remote Protocol Support for Non-Stop Mode
27220 @value{GDBN}'s remote protocol supports non-stop debugging of
27221 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
27222 supports non-stop mode, it should report that to @value{GDBN} by including
27223 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
27225 @value{GDBN} typically sends a @samp{QNonStop} packet only when
27226 establishing a new connection with the stub. Entering non-stop mode
27227 does not alter the state of any currently-running threads, but targets
27228 must stop all threads in any already-attached processes when entering
27229 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
27230 probe the target state after a mode change.
27232 In non-stop mode, when an attached process encounters an event that
27233 would otherwise be reported with a stop reply, it uses the
27234 asynchronous notification mechanism (@pxref{Notification Packets}) to
27235 inform @value{GDBN}. In contrast to all-stop mode, where all threads
27236 in all processes are stopped when a stop reply is sent, in non-stop
27237 mode only the thread reporting the stop event is stopped. That is,
27238 when reporting a @samp{S} or @samp{T} response to indicate completion
27239 of a step operation, hitting a breakpoint, or a fault, only the
27240 affected thread is stopped; any other still-running threads continue
27241 to run. When reporting a @samp{W} or @samp{X} response, all running
27242 threads belonging to other attached processes continue to run.
27244 Only one stop reply notification at a time may be pending; if
27245 additional stop events occur before @value{GDBN} has acknowledged the
27246 previous notification, they must be queued by the stub for later
27247 synchronous transmission in response to @samp{vStopped} packets from
27248 @value{GDBN}. Because the notification mechanism is unreliable,
27249 the stub is permitted to resend a stop reply notification
27250 if it believes @value{GDBN} may not have received it. @value{GDBN}
27251 ignores additional stop reply notifications received before it has
27252 finished processing a previous notification and the stub has completed
27253 sending any queued stop events.
27255 Otherwise, @value{GDBN} must be prepared to receive a stop reply
27256 notification at any time. Specifically, they may appear when
27257 @value{GDBN} is not otherwise reading input from the stub, or when
27258 @value{GDBN} is expecting to read a normal synchronous response or a
27259 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
27260 Notification packets are distinct from any other communication from
27261 the stub so there is no ambiguity.
27263 After receiving a stop reply notification, @value{GDBN} shall
27264 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
27265 as a regular, synchronous request to the stub. Such acknowledgment
27266 is not required to happen immediately, as @value{GDBN} is permitted to
27267 send other, unrelated packets to the stub first, which the stub should
27270 Upon receiving a @samp{vStopped} packet, if the stub has other queued
27271 stop events to report to @value{GDBN}, it shall respond by sending a
27272 normal stop reply response. @value{GDBN} shall then send another
27273 @samp{vStopped} packet to solicit further responses; again, it is
27274 permitted to send other, unrelated packets as well which the stub
27275 should process normally.
27277 If the stub receives a @samp{vStopped} packet and there are no
27278 additional stop events to report, the stub shall return an @samp{OK}
27279 response. At this point, if further stop events occur, the stub shall
27280 send a new stop reply notification, @value{GDBN} shall accept the
27281 notification, and the process shall be repeated.
27283 In non-stop mode, the target shall respond to the @samp{?} packet as
27284 follows. First, any incomplete stop reply notification/@samp{vStopped}
27285 sequence in progress is abandoned. The target must begin a new
27286 sequence reporting stop events for all stopped threads, whether or not
27287 it has previously reported those events to @value{GDBN}. The first
27288 stop reply is sent as a synchronous reply to the @samp{?} packet, and
27289 subsequent stop replies are sent as responses to @samp{vStopped} packets
27290 using the mechanism described above. The target must not send
27291 asynchronous stop reply notifications until the sequence is complete.
27292 If all threads are running when the target receives the @samp{?} packet,
27293 or if the target is not attached to any process, it shall respond
27296 @node Packet Acknowledgment
27297 @section Packet Acknowledgment
27299 @cindex acknowledgment, for @value{GDBN} remote
27300 @cindex packet acknowledgment, for @value{GDBN} remote
27301 By default, when either the host or the target machine receives a packet,
27302 the first response expected is an acknowledgment: either @samp{+} (to indicate
27303 the package was received correctly) or @samp{-} (to request retransmission).
27304 This mechanism allows the @value{GDBN} remote protocol to operate over
27305 unreliable transport mechanisms, such as a serial line.
27307 In cases where the transport mechanism is itself reliable (such as a pipe or
27308 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
27309 It may be desirable to disable them in that case to reduce communication
27310 overhead, or for other reasons. This can be accomplished by means of the
27311 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
27313 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
27314 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
27315 and response format still includes the normal checksum, as described in
27316 @ref{Overview}, but the checksum may be ignored by the receiver.
27318 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
27319 no-acknowledgment mode, it should report that to @value{GDBN}
27320 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
27321 @pxref{qSupported}.
27322 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
27323 disabled via the @code{set remote noack-packet off} command
27324 (@pxref{Remote Configuration}),
27325 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
27326 Only then may the stub actually turn off packet acknowledgments.
27327 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
27328 response, which can be safely ignored by the stub.
27330 Note that @code{set remote noack-packet} command only affects negotiation
27331 between @value{GDBN} and the stub when subsequent connections are made;
27332 it does not affect the protocol acknowledgment state for any current
27334 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
27335 new connection is established,
27336 there is also no protocol request to re-enable the acknowledgments
27337 for the current connection, once disabled.
27342 Example sequence of a target being re-started. Notice how the restart
27343 does not get any direct output:
27348 @emph{target restarts}
27351 <- @code{T001:1234123412341234}
27355 Example sequence of a target being stepped by a single instruction:
27358 -> @code{G1445@dots{}}
27363 <- @code{T001:1234123412341234}
27367 <- @code{1455@dots{}}
27371 @node File-I/O Remote Protocol Extension
27372 @section File-I/O Remote Protocol Extension
27373 @cindex File-I/O remote protocol extension
27376 * File-I/O Overview::
27377 * Protocol Basics::
27378 * The F Request Packet::
27379 * The F Reply Packet::
27380 * The Ctrl-C Message::
27382 * List of Supported Calls::
27383 * Protocol-specific Representation of Datatypes::
27385 * File-I/O Examples::
27388 @node File-I/O Overview
27389 @subsection File-I/O Overview
27390 @cindex file-i/o overview
27392 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
27393 target to use the host's file system and console I/O to perform various
27394 system calls. System calls on the target system are translated into a
27395 remote protocol packet to the host system, which then performs the needed
27396 actions and returns a response packet to the target system.
27397 This simulates file system operations even on targets that lack file systems.
27399 The protocol is defined to be independent of both the host and target systems.
27400 It uses its own internal representation of datatypes and values. Both
27401 @value{GDBN} and the target's @value{GDBN} stub are responsible for
27402 translating the system-dependent value representations into the internal
27403 protocol representations when data is transmitted.
27405 The communication is synchronous. A system call is possible only when
27406 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
27407 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
27408 the target is stopped to allow deterministic access to the target's
27409 memory. Therefore File-I/O is not interruptible by target signals. On
27410 the other hand, it is possible to interrupt File-I/O by a user interrupt
27411 (@samp{Ctrl-C}) within @value{GDBN}.
27413 The target's request to perform a host system call does not finish
27414 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
27415 after finishing the system call, the target returns to continuing the
27416 previous activity (continue, step). No additional continue or step
27417 request from @value{GDBN} is required.
27420 (@value{GDBP}) continue
27421 <- target requests 'system call X'
27422 target is stopped, @value{GDBN} executes system call
27423 -> @value{GDBN} returns result
27424 ... target continues, @value{GDBN} returns to wait for the target
27425 <- target hits breakpoint and sends a Txx packet
27428 The protocol only supports I/O on the console and to regular files on
27429 the host file system. Character or block special devices, pipes,
27430 named pipes, sockets or any other communication method on the host
27431 system are not supported by this protocol.
27433 File I/O is not supported in non-stop mode.
27435 @node Protocol Basics
27436 @subsection Protocol Basics
27437 @cindex protocol basics, file-i/o
27439 The File-I/O protocol uses the @code{F} packet as the request as well
27440 as reply packet. Since a File-I/O system call can only occur when
27441 @value{GDBN} is waiting for a response from the continuing or stepping target,
27442 the File-I/O request is a reply that @value{GDBN} has to expect as a result
27443 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
27444 This @code{F} packet contains all information needed to allow @value{GDBN}
27445 to call the appropriate host system call:
27449 A unique identifier for the requested system call.
27452 All parameters to the system call. Pointers are given as addresses
27453 in the target memory address space. Pointers to strings are given as
27454 pointer/length pair. Numerical values are given as they are.
27455 Numerical control flags are given in a protocol-specific representation.
27459 At this point, @value{GDBN} has to perform the following actions.
27463 If the parameters include pointer values to data needed as input to a
27464 system call, @value{GDBN} requests this data from the target with a
27465 standard @code{m} packet request. This additional communication has to be
27466 expected by the target implementation and is handled as any other @code{m}
27470 @value{GDBN} translates all value from protocol representation to host
27471 representation as needed. Datatypes are coerced into the host types.
27474 @value{GDBN} calls the system call.
27477 It then coerces datatypes back to protocol representation.
27480 If the system call is expected to return data in buffer space specified
27481 by pointer parameters to the call, the data is transmitted to the
27482 target using a @code{M} or @code{X} packet. This packet has to be expected
27483 by the target implementation and is handled as any other @code{M} or @code{X}
27488 Eventually @value{GDBN} replies with another @code{F} packet which contains all
27489 necessary information for the target to continue. This at least contains
27496 @code{errno}, if has been changed by the system call.
27503 After having done the needed type and value coercion, the target continues
27504 the latest continue or step action.
27506 @node The F Request Packet
27507 @subsection The @code{F} Request Packet
27508 @cindex file-i/o request packet
27509 @cindex @code{F} request packet
27511 The @code{F} request packet has the following format:
27514 @item F@var{call-id},@var{parameter@dots{}}
27516 @var{call-id} is the identifier to indicate the host system call to be called.
27517 This is just the name of the function.
27519 @var{parameter@dots{}} are the parameters to the system call.
27520 Parameters are hexadecimal integer values, either the actual values in case
27521 of scalar datatypes, pointers to target buffer space in case of compound
27522 datatypes and unspecified memory areas, or pointer/length pairs in case
27523 of string parameters. These are appended to the @var{call-id} as a
27524 comma-delimited list. All values are transmitted in ASCII
27525 string representation, pointer/length pairs separated by a slash.
27531 @node The F Reply Packet
27532 @subsection The @code{F} Reply Packet
27533 @cindex file-i/o reply packet
27534 @cindex @code{F} reply packet
27536 The @code{F} reply packet has the following format:
27540 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
27542 @var{retcode} is the return code of the system call as hexadecimal value.
27544 @var{errno} is the @code{errno} set by the call, in protocol-specific
27546 This parameter can be omitted if the call was successful.
27548 @var{Ctrl-C flag} is only sent if the user requested a break. In this
27549 case, @var{errno} must be sent as well, even if the call was successful.
27550 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
27557 or, if the call was interrupted before the host call has been performed:
27564 assuming 4 is the protocol-specific representation of @code{EINTR}.
27569 @node The Ctrl-C Message
27570 @subsection The @samp{Ctrl-C} Message
27571 @cindex ctrl-c message, in file-i/o protocol
27573 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
27574 reply packet (@pxref{The F Reply Packet}),
27575 the target should behave as if it had
27576 gotten a break message. The meaning for the target is ``system call
27577 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
27578 (as with a break message) and return to @value{GDBN} with a @code{T02}
27581 It's important for the target to know in which
27582 state the system call was interrupted. There are two possible cases:
27586 The system call hasn't been performed on the host yet.
27589 The system call on the host has been finished.
27593 These two states can be distinguished by the target by the value of the
27594 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
27595 call hasn't been performed. This is equivalent to the @code{EINTR} handling
27596 on POSIX systems. In any other case, the target may presume that the
27597 system call has been finished --- successfully or not --- and should behave
27598 as if the break message arrived right after the system call.
27600 @value{GDBN} must behave reliably. If the system call has not been called
27601 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
27602 @code{errno} in the packet. If the system call on the host has been finished
27603 before the user requests a break, the full action must be finished by
27604 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
27605 The @code{F} packet may only be sent when either nothing has happened
27606 or the full action has been completed.
27609 @subsection Console I/O
27610 @cindex console i/o as part of file-i/o
27612 By default and if not explicitly closed by the target system, the file
27613 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
27614 on the @value{GDBN} console is handled as any other file output operation
27615 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
27616 by @value{GDBN} so that after the target read request from file descriptor
27617 0 all following typing is buffered until either one of the following
27622 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
27624 system call is treated as finished.
27627 The user presses @key{RET}. This is treated as end of input with a trailing
27631 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
27632 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
27636 If the user has typed more characters than fit in the buffer given to
27637 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
27638 either another @code{read(0, @dots{})} is requested by the target, or debugging
27639 is stopped at the user's request.
27642 @node List of Supported Calls
27643 @subsection List of Supported Calls
27644 @cindex list of supported file-i/o calls
27661 @unnumberedsubsubsec open
27662 @cindex open, file-i/o system call
27667 int open(const char *pathname, int flags);
27668 int open(const char *pathname, int flags, mode_t mode);
27672 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
27675 @var{flags} is the bitwise @code{OR} of the following values:
27679 If the file does not exist it will be created. The host
27680 rules apply as far as file ownership and time stamps
27684 When used with @code{O_CREAT}, if the file already exists it is
27685 an error and open() fails.
27688 If the file already exists and the open mode allows
27689 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
27690 truncated to zero length.
27693 The file is opened in append mode.
27696 The file is opened for reading only.
27699 The file is opened for writing only.
27702 The file is opened for reading and writing.
27706 Other bits are silently ignored.
27710 @var{mode} is the bitwise @code{OR} of the following values:
27714 User has read permission.
27717 User has write permission.
27720 Group has read permission.
27723 Group has write permission.
27726 Others have read permission.
27729 Others have write permission.
27733 Other bits are silently ignored.
27736 @item Return value:
27737 @code{open} returns the new file descriptor or -1 if an error
27744 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
27747 @var{pathname} refers to a directory.
27750 The requested access is not allowed.
27753 @var{pathname} was too long.
27756 A directory component in @var{pathname} does not exist.
27759 @var{pathname} refers to a device, pipe, named pipe or socket.
27762 @var{pathname} refers to a file on a read-only filesystem and
27763 write access was requested.
27766 @var{pathname} is an invalid pointer value.
27769 No space on device to create the file.
27772 The process already has the maximum number of files open.
27775 The limit on the total number of files open on the system
27779 The call was interrupted by the user.
27785 @unnumberedsubsubsec close
27786 @cindex close, file-i/o system call
27795 @samp{Fclose,@var{fd}}
27797 @item Return value:
27798 @code{close} returns zero on success, or -1 if an error occurred.
27804 @var{fd} isn't a valid open file descriptor.
27807 The call was interrupted by the user.
27813 @unnumberedsubsubsec read
27814 @cindex read, file-i/o system call
27819 int read(int fd, void *buf, unsigned int count);
27823 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
27825 @item Return value:
27826 On success, the number of bytes read is returned.
27827 Zero indicates end of file. If count is zero, read
27828 returns zero as well. On error, -1 is returned.
27834 @var{fd} is not a valid file descriptor or is not open for
27838 @var{bufptr} is an invalid pointer value.
27841 The call was interrupted by the user.
27847 @unnumberedsubsubsec write
27848 @cindex write, file-i/o system call
27853 int write(int fd, const void *buf, unsigned int count);
27857 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
27859 @item Return value:
27860 On success, the number of bytes written are returned.
27861 Zero indicates nothing was written. On error, -1
27868 @var{fd} is not a valid file descriptor or is not open for
27872 @var{bufptr} is an invalid pointer value.
27875 An attempt was made to write a file that exceeds the
27876 host-specific maximum file size allowed.
27879 No space on device to write the data.
27882 The call was interrupted by the user.
27888 @unnumberedsubsubsec lseek
27889 @cindex lseek, file-i/o system call
27894 long lseek (int fd, long offset, int flag);
27898 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
27900 @var{flag} is one of:
27904 The offset is set to @var{offset} bytes.
27907 The offset is set to its current location plus @var{offset}
27911 The offset is set to the size of the file plus @var{offset}
27915 @item Return value:
27916 On success, the resulting unsigned offset in bytes from
27917 the beginning of the file is returned. Otherwise, a
27918 value of -1 is returned.
27924 @var{fd} is not a valid open file descriptor.
27927 @var{fd} is associated with the @value{GDBN} console.
27930 @var{flag} is not a proper value.
27933 The call was interrupted by the user.
27939 @unnumberedsubsubsec rename
27940 @cindex rename, file-i/o system call
27945 int rename(const char *oldpath, const char *newpath);
27949 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
27951 @item Return value:
27952 On success, zero is returned. On error, -1 is returned.
27958 @var{newpath} is an existing directory, but @var{oldpath} is not a
27962 @var{newpath} is a non-empty directory.
27965 @var{oldpath} or @var{newpath} is a directory that is in use by some
27969 An attempt was made to make a directory a subdirectory
27973 A component used as a directory in @var{oldpath} or new
27974 path is not a directory. Or @var{oldpath} is a directory
27975 and @var{newpath} exists but is not a directory.
27978 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
27981 No access to the file or the path of the file.
27985 @var{oldpath} or @var{newpath} was too long.
27988 A directory component in @var{oldpath} or @var{newpath} does not exist.
27991 The file is on a read-only filesystem.
27994 The device containing the file has no room for the new
27998 The call was interrupted by the user.
28004 @unnumberedsubsubsec unlink
28005 @cindex unlink, file-i/o system call
28010 int unlink(const char *pathname);
28014 @samp{Funlink,@var{pathnameptr}/@var{len}}
28016 @item Return value:
28017 On success, zero is returned. On error, -1 is returned.
28023 No access to the file or the path of the file.
28026 The system does not allow unlinking of directories.
28029 The file @var{pathname} cannot be unlinked because it's
28030 being used by another process.
28033 @var{pathnameptr} is an invalid pointer value.
28036 @var{pathname} was too long.
28039 A directory component in @var{pathname} does not exist.
28042 A component of the path is not a directory.
28045 The file is on a read-only filesystem.
28048 The call was interrupted by the user.
28054 @unnumberedsubsubsec stat/fstat
28055 @cindex fstat, file-i/o system call
28056 @cindex stat, file-i/o system call
28061 int stat(const char *pathname, struct stat *buf);
28062 int fstat(int fd, struct stat *buf);
28066 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
28067 @samp{Ffstat,@var{fd},@var{bufptr}}
28069 @item Return value:
28070 On success, zero is returned. On error, -1 is returned.
28076 @var{fd} is not a valid open file.
28079 A directory component in @var{pathname} does not exist or the
28080 path is an empty string.
28083 A component of the path is not a directory.
28086 @var{pathnameptr} is an invalid pointer value.
28089 No access to the file or the path of the file.
28092 @var{pathname} was too long.
28095 The call was interrupted by the user.
28101 @unnumberedsubsubsec gettimeofday
28102 @cindex gettimeofday, file-i/o system call
28107 int gettimeofday(struct timeval *tv, void *tz);
28111 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
28113 @item Return value:
28114 On success, 0 is returned, -1 otherwise.
28120 @var{tz} is a non-NULL pointer.
28123 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
28129 @unnumberedsubsubsec isatty
28130 @cindex isatty, file-i/o system call
28135 int isatty(int fd);
28139 @samp{Fisatty,@var{fd}}
28141 @item Return value:
28142 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
28148 The call was interrupted by the user.
28153 Note that the @code{isatty} call is treated as a special case: it returns
28154 1 to the target if the file descriptor is attached
28155 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
28156 would require implementing @code{ioctl} and would be more complex than
28161 @unnumberedsubsubsec system
28162 @cindex system, file-i/o system call
28167 int system(const char *command);
28171 @samp{Fsystem,@var{commandptr}/@var{len}}
28173 @item Return value:
28174 If @var{len} is zero, the return value indicates whether a shell is
28175 available. A zero return value indicates a shell is not available.
28176 For non-zero @var{len}, the value returned is -1 on error and the
28177 return status of the command otherwise. Only the exit status of the
28178 command is returned, which is extracted from the host's @code{system}
28179 return value by calling @code{WEXITSTATUS(retval)}. In case
28180 @file{/bin/sh} could not be executed, 127 is returned.
28186 The call was interrupted by the user.
28191 @value{GDBN} takes over the full task of calling the necessary host calls
28192 to perform the @code{system} call. The return value of @code{system} on
28193 the host is simplified before it's returned
28194 to the target. Any termination signal information from the child process
28195 is discarded, and the return value consists
28196 entirely of the exit status of the called command.
28198 Due to security concerns, the @code{system} call is by default refused
28199 by @value{GDBN}. The user has to allow this call explicitly with the
28200 @code{set remote system-call-allowed 1} command.
28203 @item set remote system-call-allowed
28204 @kindex set remote system-call-allowed
28205 Control whether to allow the @code{system} calls in the File I/O
28206 protocol for the remote target. The default is zero (disabled).
28208 @item show remote system-call-allowed
28209 @kindex show remote system-call-allowed
28210 Show whether the @code{system} calls are allowed in the File I/O
28214 @node Protocol-specific Representation of Datatypes
28215 @subsection Protocol-specific Representation of Datatypes
28216 @cindex protocol-specific representation of datatypes, in file-i/o protocol
28219 * Integral Datatypes::
28221 * Memory Transfer::
28226 @node Integral Datatypes
28227 @unnumberedsubsubsec Integral Datatypes
28228 @cindex integral datatypes, in file-i/o protocol
28230 The integral datatypes used in the system calls are @code{int},
28231 @code{unsigned int}, @code{long}, @code{unsigned long},
28232 @code{mode_t}, and @code{time_t}.
28234 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
28235 implemented as 32 bit values in this protocol.
28237 @code{long} and @code{unsigned long} are implemented as 64 bit types.
28239 @xref{Limits}, for corresponding MIN and MAX values (similar to those
28240 in @file{limits.h}) to allow range checking on host and target.
28242 @code{time_t} datatypes are defined as seconds since the Epoch.
28244 All integral datatypes transferred as part of a memory read or write of a
28245 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
28248 @node Pointer Values
28249 @unnumberedsubsubsec Pointer Values
28250 @cindex pointer values, in file-i/o protocol
28252 Pointers to target data are transmitted as they are. An exception
28253 is made for pointers to buffers for which the length isn't
28254 transmitted as part of the function call, namely strings. Strings
28255 are transmitted as a pointer/length pair, both as hex values, e.g.@:
28262 which is a pointer to data of length 18 bytes at position 0x1aaf.
28263 The length is defined as the full string length in bytes, including
28264 the trailing null byte. For example, the string @code{"hello world"}
28265 at address 0x123456 is transmitted as
28271 @node Memory Transfer
28272 @unnumberedsubsubsec Memory Transfer
28273 @cindex memory transfer, in file-i/o protocol
28275 Structured data which is transferred using a memory read or write (for
28276 example, a @code{struct stat}) is expected to be in a protocol-specific format
28277 with all scalar multibyte datatypes being big endian. Translation to
28278 this representation needs to be done both by the target before the @code{F}
28279 packet is sent, and by @value{GDBN} before
28280 it transfers memory to the target. Transferred pointers to structured
28281 data should point to the already-coerced data at any time.
28285 @unnumberedsubsubsec struct stat
28286 @cindex struct stat, in file-i/o protocol
28288 The buffer of type @code{struct stat} used by the target and @value{GDBN}
28289 is defined as follows:
28293 unsigned int st_dev; /* device */
28294 unsigned int st_ino; /* inode */
28295 mode_t st_mode; /* protection */
28296 unsigned int st_nlink; /* number of hard links */
28297 unsigned int st_uid; /* user ID of owner */
28298 unsigned int st_gid; /* group ID of owner */
28299 unsigned int st_rdev; /* device type (if inode device) */
28300 unsigned long st_size; /* total size, in bytes */
28301 unsigned long st_blksize; /* blocksize for filesystem I/O */
28302 unsigned long st_blocks; /* number of blocks allocated */
28303 time_t st_atime; /* time of last access */
28304 time_t st_mtime; /* time of last modification */
28305 time_t st_ctime; /* time of last change */
28309 The integral datatypes conform to the definitions given in the
28310 appropriate section (see @ref{Integral Datatypes}, for details) so this
28311 structure is of size 64 bytes.
28313 The values of several fields have a restricted meaning and/or
28319 A value of 0 represents a file, 1 the console.
28322 No valid meaning for the target. Transmitted unchanged.
28325 Valid mode bits are described in @ref{Constants}. Any other
28326 bits have currently no meaning for the target.
28331 No valid meaning for the target. Transmitted unchanged.
28336 These values have a host and file system dependent
28337 accuracy. Especially on Windows hosts, the file system may not
28338 support exact timing values.
28341 The target gets a @code{struct stat} of the above representation and is
28342 responsible for coercing it to the target representation before
28345 Note that due to size differences between the host, target, and protocol
28346 representations of @code{struct stat} members, these members could eventually
28347 get truncated on the target.
28349 @node struct timeval
28350 @unnumberedsubsubsec struct timeval
28351 @cindex struct timeval, in file-i/o protocol
28353 The buffer of type @code{struct timeval} used by the File-I/O protocol
28354 is defined as follows:
28358 time_t tv_sec; /* second */
28359 long tv_usec; /* microsecond */
28363 The integral datatypes conform to the definitions given in the
28364 appropriate section (see @ref{Integral Datatypes}, for details) so this
28365 structure is of size 8 bytes.
28368 @subsection Constants
28369 @cindex constants, in file-i/o protocol
28371 The following values are used for the constants inside of the
28372 protocol. @value{GDBN} and target are responsible for translating these
28373 values before and after the call as needed.
28384 @unnumberedsubsubsec Open Flags
28385 @cindex open flags, in file-i/o protocol
28387 All values are given in hexadecimal representation.
28399 @node mode_t Values
28400 @unnumberedsubsubsec mode_t Values
28401 @cindex mode_t values, in file-i/o protocol
28403 All values are given in octal representation.
28420 @unnumberedsubsubsec Errno Values
28421 @cindex errno values, in file-i/o protocol
28423 All values are given in decimal representation.
28448 @code{EUNKNOWN} is used as a fallback error value if a host system returns
28449 any error value not in the list of supported error numbers.
28452 @unnumberedsubsubsec Lseek Flags
28453 @cindex lseek flags, in file-i/o protocol
28462 @unnumberedsubsubsec Limits
28463 @cindex limits, in file-i/o protocol
28465 All values are given in decimal representation.
28468 INT_MIN -2147483648
28470 UINT_MAX 4294967295
28471 LONG_MIN -9223372036854775808
28472 LONG_MAX 9223372036854775807
28473 ULONG_MAX 18446744073709551615
28476 @node File-I/O Examples
28477 @subsection File-I/O Examples
28478 @cindex file-i/o examples
28480 Example sequence of a write call, file descriptor 3, buffer is at target
28481 address 0x1234, 6 bytes should be written:
28484 <- @code{Fwrite,3,1234,6}
28485 @emph{request memory read from target}
28488 @emph{return "6 bytes written"}
28492 Example sequence of a read call, file descriptor 3, buffer is at target
28493 address 0x1234, 6 bytes should be read:
28496 <- @code{Fread,3,1234,6}
28497 @emph{request memory write to target}
28498 -> @code{X1234,6:XXXXXX}
28499 @emph{return "6 bytes read"}
28503 Example sequence of a read call, call fails on the host due to invalid
28504 file descriptor (@code{EBADF}):
28507 <- @code{Fread,3,1234,6}
28511 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
28515 <- @code{Fread,3,1234,6}
28520 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
28524 <- @code{Fread,3,1234,6}
28525 -> @code{X1234,6:XXXXXX}
28529 @node Library List Format
28530 @section Library List Format
28531 @cindex library list format, remote protocol
28533 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
28534 same process as your application to manage libraries. In this case,
28535 @value{GDBN} can use the loader's symbol table and normal memory
28536 operations to maintain a list of shared libraries. On other
28537 platforms, the operating system manages loaded libraries.
28538 @value{GDBN} can not retrieve the list of currently loaded libraries
28539 through memory operations, so it uses the @samp{qXfer:libraries:read}
28540 packet (@pxref{qXfer library list read}) instead. The remote stub
28541 queries the target's operating system and reports which libraries
28544 The @samp{qXfer:libraries:read} packet returns an XML document which
28545 lists loaded libraries and their offsets. Each library has an
28546 associated name and one or more segment or section base addresses,
28547 which report where the library was loaded in memory.
28549 For the common case of libraries that are fully linked binaries, the
28550 library should have a list of segments. If the target supports
28551 dynamic linking of a relocatable object file, its library XML element
28552 should instead include a list of allocated sections. The segment or
28553 section bases are start addresses, not relocation offsets; they do not
28554 depend on the library's link-time base addresses.
28556 @value{GDBN} must be linked with the Expat library to support XML
28557 library lists. @xref{Expat}.
28559 A simple memory map, with one loaded library relocated by a single
28560 offset, looks like this:
28564 <library name="/lib/libc.so.6">
28565 <segment address="0x10000000"/>
28570 Another simple memory map, with one loaded library with three
28571 allocated sections (.text, .data, .bss), looks like this:
28575 <library name="sharedlib.o">
28576 <section address="0x10000000"/>
28577 <section address="0x20000000"/>
28578 <section address="0x30000000"/>
28583 The format of a library list is described by this DTD:
28586 <!-- library-list: Root element with versioning -->
28587 <!ELEMENT library-list (library)*>
28588 <!ATTLIST library-list version CDATA #FIXED "1.0">
28589 <!ELEMENT library (segment*, section*)>
28590 <!ATTLIST library name CDATA #REQUIRED>
28591 <!ELEMENT segment EMPTY>
28592 <!ATTLIST segment address CDATA #REQUIRED>
28593 <!ELEMENT section EMPTY>
28594 <!ATTLIST section address CDATA #REQUIRED>
28597 In addition, segments and section descriptors cannot be mixed within a
28598 single library element, and you must supply at least one segment or
28599 section for each library.
28601 @node Memory Map Format
28602 @section Memory Map Format
28603 @cindex memory map format
28605 To be able to write into flash memory, @value{GDBN} needs to obtain a
28606 memory map from the target. This section describes the format of the
28609 The memory map is obtained using the @samp{qXfer:memory-map:read}
28610 (@pxref{qXfer memory map read}) packet and is an XML document that
28611 lists memory regions.
28613 @value{GDBN} must be linked with the Expat library to support XML
28614 memory maps. @xref{Expat}.
28616 The top-level structure of the document is shown below:
28619 <?xml version="1.0"?>
28620 <!DOCTYPE memory-map
28621 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
28622 "http://sourceware.org/gdb/gdb-memory-map.dtd">
28628 Each region can be either:
28633 A region of RAM starting at @var{addr} and extending for @var{length}
28637 <memory type="ram" start="@var{addr}" length="@var{length}"/>
28642 A region of read-only memory:
28645 <memory type="rom" start="@var{addr}" length="@var{length}"/>
28650 A region of flash memory, with erasure blocks @var{blocksize}
28654 <memory type="flash" start="@var{addr}" length="@var{length}">
28655 <property name="blocksize">@var{blocksize}</property>
28661 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
28662 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
28663 packets to write to addresses in such ranges.
28665 The formal DTD for memory map format is given below:
28668 <!-- ................................................... -->
28669 <!-- Memory Map XML DTD ................................ -->
28670 <!-- File: memory-map.dtd .............................. -->
28671 <!-- .................................... .............. -->
28672 <!-- memory-map.dtd -->
28673 <!-- memory-map: Root element with versioning -->
28674 <!ELEMENT memory-map (memory | property)>
28675 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
28676 <!ELEMENT memory (property)>
28677 <!-- memory: Specifies a memory region,
28678 and its type, or device. -->
28679 <!ATTLIST memory type CDATA #REQUIRED
28680 start CDATA #REQUIRED
28681 length CDATA #REQUIRED
28682 device CDATA #IMPLIED>
28683 <!-- property: Generic attribute tag -->
28684 <!ELEMENT property (#PCDATA | property)*>
28685 <!ATTLIST property name CDATA #REQUIRED>
28688 @include agentexpr.texi
28690 @node Target Descriptions
28691 @appendix Target Descriptions
28692 @cindex target descriptions
28694 @strong{Warning:} target descriptions are still under active development,
28695 and the contents and format may change between @value{GDBN} releases.
28696 The format is expected to stabilize in the future.
28698 One of the challenges of using @value{GDBN} to debug embedded systems
28699 is that there are so many minor variants of each processor
28700 architecture in use. It is common practice for vendors to start with
28701 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
28702 and then make changes to adapt it to a particular market niche. Some
28703 architectures have hundreds of variants, available from dozens of
28704 vendors. This leads to a number of problems:
28708 With so many different customized processors, it is difficult for
28709 the @value{GDBN} maintainers to keep up with the changes.
28711 Since individual variants may have short lifetimes or limited
28712 audiences, it may not be worthwhile to carry information about every
28713 variant in the @value{GDBN} source tree.
28715 When @value{GDBN} does support the architecture of the embedded system
28716 at hand, the task of finding the correct architecture name to give the
28717 @command{set architecture} command can be error-prone.
28720 To address these problems, the @value{GDBN} remote protocol allows a
28721 target system to not only identify itself to @value{GDBN}, but to
28722 actually describe its own features. This lets @value{GDBN} support
28723 processor variants it has never seen before --- to the extent that the
28724 descriptions are accurate, and that @value{GDBN} understands them.
28726 @value{GDBN} must be linked with the Expat library to support XML
28727 target descriptions. @xref{Expat}.
28730 * Retrieving Descriptions:: How descriptions are fetched from a target.
28731 * Target Description Format:: The contents of a target description.
28732 * Predefined Target Types:: Standard types available for target
28734 * Standard Target Features:: Features @value{GDBN} knows about.
28737 @node Retrieving Descriptions
28738 @section Retrieving Descriptions
28740 Target descriptions can be read from the target automatically, or
28741 specified by the user manually. The default behavior is to read the
28742 description from the target. @value{GDBN} retrieves it via the remote
28743 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
28744 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
28745 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
28746 XML document, of the form described in @ref{Target Description
28749 Alternatively, you can specify a file to read for the target description.
28750 If a file is set, the target will not be queried. The commands to
28751 specify a file are:
28754 @cindex set tdesc filename
28755 @item set tdesc filename @var{path}
28756 Read the target description from @var{path}.
28758 @cindex unset tdesc filename
28759 @item unset tdesc filename
28760 Do not read the XML target description from a file. @value{GDBN}
28761 will use the description supplied by the current target.
28763 @cindex show tdesc filename
28764 @item show tdesc filename
28765 Show the filename to read for a target description, if any.
28769 @node Target Description Format
28770 @section Target Description Format
28771 @cindex target descriptions, XML format
28773 A target description annex is an @uref{http://www.w3.org/XML/, XML}
28774 document which complies with the Document Type Definition provided in
28775 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
28776 means you can use generally available tools like @command{xmllint} to
28777 check that your feature descriptions are well-formed and valid.
28778 However, to help people unfamiliar with XML write descriptions for
28779 their targets, we also describe the grammar here.
28781 Target descriptions can identify the architecture of the remote target
28782 and (for some architectures) provide information about custom register
28783 sets. @value{GDBN} can use this information to autoconfigure for your
28784 target, or to warn you if you connect to an unsupported target.
28786 Here is a simple target description:
28789 <target version="1.0">
28790 <architecture>i386:x86-64</architecture>
28795 This minimal description only says that the target uses
28796 the x86-64 architecture.
28798 A target description has the following overall form, with [ ] marking
28799 optional elements and @dots{} marking repeatable elements. The elements
28800 are explained further below.
28803 <?xml version="1.0"?>
28804 <!DOCTYPE target SYSTEM "gdb-target.dtd">
28805 <target version="1.0">
28806 @r{[}@var{architecture}@r{]}
28807 @r{[}@var{feature}@dots{}@r{]}
28812 The description is generally insensitive to whitespace and line
28813 breaks, under the usual common-sense rules. The XML version
28814 declaration and document type declaration can generally be omitted
28815 (@value{GDBN} does not require them), but specifying them may be
28816 useful for XML validation tools. The @samp{version} attribute for
28817 @samp{<target>} may also be omitted, but we recommend
28818 including it; if future versions of @value{GDBN} use an incompatible
28819 revision of @file{gdb-target.dtd}, they will detect and report
28820 the version mismatch.
28822 @subsection Inclusion
28823 @cindex target descriptions, inclusion
28826 @cindex <xi:include>
28829 It can sometimes be valuable to split a target description up into
28830 several different annexes, either for organizational purposes, or to
28831 share files between different possible target descriptions. You can
28832 divide a description into multiple files by replacing any element of
28833 the target description with an inclusion directive of the form:
28836 <xi:include href="@var{document}"/>
28840 When @value{GDBN} encounters an element of this form, it will retrieve
28841 the named XML @var{document}, and replace the inclusion directive with
28842 the contents of that document. If the current description was read
28843 using @samp{qXfer}, then so will be the included document;
28844 @var{document} will be interpreted as the name of an annex. If the
28845 current description was read from a file, @value{GDBN} will look for
28846 @var{document} as a file in the same directory where it found the
28847 original description.
28849 @subsection Architecture
28850 @cindex <architecture>
28852 An @samp{<architecture>} element has this form:
28855 <architecture>@var{arch}</architecture>
28858 @var{arch} is an architecture name from the same selection
28859 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
28860 Debugging Target}).
28862 @subsection Features
28865 Each @samp{<feature>} describes some logical portion of the target
28866 system. Features are currently used to describe available CPU
28867 registers and the types of their contents. A @samp{<feature>} element
28871 <feature name="@var{name}">
28872 @r{[}@var{type}@dots{}@r{]}
28878 Each feature's name should be unique within the description. The name
28879 of a feature does not matter unless @value{GDBN} has some special
28880 knowledge of the contents of that feature; if it does, the feature
28881 should have its standard name. @xref{Standard Target Features}.
28885 Any register's value is a collection of bits which @value{GDBN} must
28886 interpret. The default interpretation is a two's complement integer,
28887 but other types can be requested by name in the register description.
28888 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
28889 Target Types}), and the description can define additional composite types.
28891 Each type element must have an @samp{id} attribute, which gives
28892 a unique (within the containing @samp{<feature>}) name to the type.
28893 Types must be defined before they are used.
28896 Some targets offer vector registers, which can be treated as arrays
28897 of scalar elements. These types are written as @samp{<vector>} elements,
28898 specifying the array element type, @var{type}, and the number of elements,
28902 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
28906 If a register's value is usefully viewed in multiple ways, define it
28907 with a union type containing the useful representations. The
28908 @samp{<union>} element contains one or more @samp{<field>} elements,
28909 each of which has a @var{name} and a @var{type}:
28912 <union id="@var{id}">
28913 <field name="@var{name}" type="@var{type}"/>
28918 @subsection Registers
28921 Each register is represented as an element with this form:
28924 <reg name="@var{name}"
28925 bitsize="@var{size}"
28926 @r{[}regnum="@var{num}"@r{]}
28927 @r{[}save-restore="@var{save-restore}"@r{]}
28928 @r{[}type="@var{type}"@r{]}
28929 @r{[}group="@var{group}"@r{]}/>
28933 The components are as follows:
28938 The register's name; it must be unique within the target description.
28941 The register's size, in bits.
28944 The register's number. If omitted, a register's number is one greater
28945 than that of the previous register (either in the current feature or in
28946 a preceeding feature); the first register in the target description
28947 defaults to zero. This register number is used to read or write
28948 the register; e.g.@: it is used in the remote @code{p} and @code{P}
28949 packets, and registers appear in the @code{g} and @code{G} packets
28950 in order of increasing register number.
28953 Whether the register should be preserved across inferior function
28954 calls; this must be either @code{yes} or @code{no}. The default is
28955 @code{yes}, which is appropriate for most registers except for
28956 some system control registers; this is not related to the target's
28960 The type of the register. @var{type} may be a predefined type, a type
28961 defined in the current feature, or one of the special types @code{int}
28962 and @code{float}. @code{int} is an integer type of the correct size
28963 for @var{bitsize}, and @code{float} is a floating point type (in the
28964 architecture's normal floating point format) of the correct size for
28965 @var{bitsize}. The default is @code{int}.
28968 The register group to which this register belongs. @var{group} must
28969 be either @code{general}, @code{float}, or @code{vector}. If no
28970 @var{group} is specified, @value{GDBN} will not display the register
28971 in @code{info registers}.
28975 @node Predefined Target Types
28976 @section Predefined Target Types
28977 @cindex target descriptions, predefined types
28979 Type definitions in the self-description can build up composite types
28980 from basic building blocks, but can not define fundamental types. Instead,
28981 standard identifiers are provided by @value{GDBN} for the fundamental
28982 types. The currently supported types are:
28991 Signed integer types holding the specified number of bits.
28998 Unsigned integer types holding the specified number of bits.
29002 Pointers to unspecified code and data. The program counter and
29003 any dedicated return address register may be marked as code
29004 pointers; printing a code pointer converts it into a symbolic
29005 address. The stack pointer and any dedicated address registers
29006 may be marked as data pointers.
29009 Single precision IEEE floating point.
29012 Double precision IEEE floating point.
29015 The 12-byte extended precision format used by ARM FPA registers.
29019 @node Standard Target Features
29020 @section Standard Target Features
29021 @cindex target descriptions, standard features
29023 A target description must contain either no registers or all the
29024 target's registers. If the description contains no registers, then
29025 @value{GDBN} will assume a default register layout, selected based on
29026 the architecture. If the description contains any registers, the
29027 default layout will not be used; the standard registers must be
29028 described in the target description, in such a way that @value{GDBN}
29029 can recognize them.
29031 This is accomplished by giving specific names to feature elements
29032 which contain standard registers. @value{GDBN} will look for features
29033 with those names and verify that they contain the expected registers;
29034 if any known feature is missing required registers, or if any required
29035 feature is missing, @value{GDBN} will reject the target
29036 description. You can add additional registers to any of the
29037 standard features --- @value{GDBN} will display them just as if
29038 they were added to an unrecognized feature.
29040 This section lists the known features and their expected contents.
29041 Sample XML documents for these features are included in the
29042 @value{GDBN} source tree, in the directory @file{gdb/features}.
29044 Names recognized by @value{GDBN} should include the name of the
29045 company or organization which selected the name, and the overall
29046 architecture to which the feature applies; so e.g.@: the feature
29047 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
29049 The names of registers are not case sensitive for the purpose
29050 of recognizing standard features, but @value{GDBN} will only display
29051 registers using the capitalization used in the description.
29057 * PowerPC Features::
29062 @subsection ARM Features
29063 @cindex target descriptions, ARM features
29065 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
29066 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
29067 @samp{lr}, @samp{pc}, and @samp{cpsr}.
29069 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
29070 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
29072 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
29073 it should contain at least registers @samp{wR0} through @samp{wR15} and
29074 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
29075 @samp{wCSSF}, and @samp{wCASF} registers are optional.
29077 @node MIPS Features
29078 @subsection MIPS Features
29079 @cindex target descriptions, MIPS features
29081 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
29082 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
29083 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
29086 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
29087 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
29088 registers. They may be 32-bit or 64-bit depending on the target.
29090 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
29091 it may be optional in a future version of @value{GDBN}. It should
29092 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
29093 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
29095 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
29096 contain a single register, @samp{restart}, which is used by the
29097 Linux kernel to control restartable syscalls.
29099 @node M68K Features
29100 @subsection M68K Features
29101 @cindex target descriptions, M68K features
29104 @item @samp{org.gnu.gdb.m68k.core}
29105 @itemx @samp{org.gnu.gdb.coldfire.core}
29106 @itemx @samp{org.gnu.gdb.fido.core}
29107 One of those features must be always present.
29108 The feature that is present determines which flavor of m68k is
29109 used. The feature that is present should contain registers
29110 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
29111 @samp{sp}, @samp{ps} and @samp{pc}.
29113 @item @samp{org.gnu.gdb.coldfire.fp}
29114 This feature is optional. If present, it should contain registers
29115 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
29119 @node PowerPC Features
29120 @subsection PowerPC Features
29121 @cindex target descriptions, PowerPC features
29123 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
29124 targets. It should contain registers @samp{r0} through @samp{r31},
29125 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
29126 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
29128 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
29129 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
29131 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
29132 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
29135 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
29136 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
29137 will combine these registers with the floating point registers
29138 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
29139 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
29140 through @samp{vs63}, the set of vector registers for POWER7.
29142 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
29143 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
29144 @samp{spefscr}. SPE targets should provide 32-bit registers in
29145 @samp{org.gnu.gdb.power.core} and provide the upper halves in
29146 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
29147 these to present registers @samp{ev0} through @samp{ev31} to the
29150 @node Operating System Information
29151 @appendix Operating System Information
29152 @cindex operating system information
29158 Users of @value{GDBN} often wish to obtain information about the state of
29159 the operating system running on the target---for example the list of
29160 processes, or the list of open files. This section describes the
29161 mechanism that makes it possible. This mechanism is similar to the
29162 target features mechanism (@pxref{Target Descriptions}), but focuses
29163 on a different aspect of target.
29165 Operating system information is retrived from the target via the
29166 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
29167 read}). The object name in the request should be @samp{osdata}, and
29168 the @var{annex} identifies the data to be fetched.
29171 @appendixsection Process list
29172 @cindex operating system information, process list
29174 When requesting the process list, the @var{annex} field in the
29175 @samp{qXfer} request should be @samp{processes}. The returned data is
29176 an XML document. The formal syntax of this document is defined in
29177 @file{gdb/features/osdata.dtd}.
29179 An example document is:
29182 <?xml version="1.0"?>
29183 <!DOCTYPE target SYSTEM "osdata.dtd">
29184 <osdata type="processes">
29186 <column name="pid">1</column>
29187 <column name="user">root</column>
29188 <column name="command">/sbin/init</column>
29193 Each item should include a column whose name is @samp{pid}. The value
29194 of that column should identify the process on the target. The
29195 @samp{user} and @samp{command} columns are optional, and will be
29196 displayed by @value{GDBN}. Target may provide additional columns,
29197 which @value{GDBN} currently ignores.
29211 % I think something like @colophon should be in texinfo. In the
29213 \long\def\colophon{\hbox to0pt{}\vfill
29214 \centerline{The body of this manual is set in}
29215 \centerline{\fontname\tenrm,}
29216 \centerline{with headings in {\bf\fontname\tenbf}}
29217 \centerline{and examples in {\tt\fontname\tentt}.}
29218 \centerline{{\it\fontname\tenit\/},}
29219 \centerline{{\bf\fontname\tenbf}, and}
29220 \centerline{{\sl\fontname\tensl\/}}
29221 \centerline{are used for emphasis.}\vfill}
29223 % Blame: doc@cygnus.com, 1991.