1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.1 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2009 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
175 * Operating System Information:: Getting additional information from
177 * Copying:: GNU General Public License says
178 how you can copy and share GDB
179 * GNU Free Documentation License:: The license for this documentation
188 @unnumbered Summary of @value{GDBN}
190 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
191 going on ``inside'' another program while it executes---or what another
192 program was doing at the moment it crashed.
194 @value{GDBN} can do four main kinds of things (plus other things in support of
195 these) to help you catch bugs in the act:
199 Start your program, specifying anything that might affect its behavior.
202 Make your program stop on specified conditions.
205 Examine what has happened, when your program has stopped.
208 Change things in your program, so you can experiment with correcting the
209 effects of one bug and go on to learn about another.
212 You can use @value{GDBN} to debug programs written in C and C@t{++}.
213 For more information, see @ref{Supported Languages,,Supported Languages}.
214 For more information, see @ref{C,,C and C++}.
217 Support for Modula-2 is partial. For information on Modula-2, see
218 @ref{Modula-2,,Modula-2}.
221 Debugging Pascal programs which use sets, subranges, file variables, or
222 nested functions does not currently work. @value{GDBN} does not support
223 entering expressions, printing values, or similar features using Pascal
227 @value{GDBN} can be used to debug programs written in Fortran, although
228 it may be necessary to refer to some variables with a trailing
231 @value{GDBN} can be used to debug programs written in Objective-C,
232 using either the Apple/NeXT or the GNU Objective-C runtime.
235 * Free Software:: Freely redistributable software
236 * Contributors:: Contributors to GDB
240 @unnumberedsec Free Software
242 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
243 General Public License
244 (GPL). The GPL gives you the freedom to copy or adapt a licensed
245 program---but every person getting a copy also gets with it the
246 freedom to modify that copy (which means that they must get access to
247 the source code), and the freedom to distribute further copies.
248 Typical software companies use copyrights to limit your freedoms; the
249 Free Software Foundation uses the GPL to preserve these freedoms.
251 Fundamentally, the General Public License is a license which says that
252 you have these freedoms and that you cannot take these freedoms away
255 @unnumberedsec Free Software Needs Free Documentation
257 The biggest deficiency in the free software community today is not in
258 the software---it is the lack of good free documentation that we can
259 include with the free software. Many of our most important
260 programs do not come with free reference manuals and free introductory
261 texts. Documentation is an essential part of any software package;
262 when an important free software package does not come with a free
263 manual and a free tutorial, that is a major gap. We have many such
266 Consider Perl, for instance. The tutorial manuals that people
267 normally use are non-free. How did this come about? Because the
268 authors of those manuals published them with restrictive terms---no
269 copying, no modification, source files not available---which exclude
270 them from the free software world.
272 That wasn't the first time this sort of thing happened, and it was far
273 from the last. Many times we have heard a GNU user eagerly describe a
274 manual that he is writing, his intended contribution to the community,
275 only to learn that he had ruined everything by signing a publication
276 contract to make it non-free.
278 Free documentation, like free software, is a matter of freedom, not
279 price. The problem with the non-free manual is not that publishers
280 charge a price for printed copies---that in itself is fine. (The Free
281 Software Foundation sells printed copies of manuals, too.) The
282 problem is the restrictions on the use of the manual. Free manuals
283 are available in source code form, and give you permission to copy and
284 modify. Non-free manuals do not allow this.
286 The criteria of freedom for a free manual are roughly the same as for
287 free software. Redistribution (including the normal kinds of
288 commercial redistribution) must be permitted, so that the manual can
289 accompany every copy of the program, both on-line and on paper.
291 Permission for modification of the technical content is crucial too.
292 When people modify the software, adding or changing features, if they
293 are conscientious they will change the manual too---so they can
294 provide accurate and clear documentation for the modified program. A
295 manual that leaves you no choice but to write a new manual to document
296 a changed version of the program is not really available to our
299 Some kinds of limits on the way modification is handled are
300 acceptable. For example, requirements to preserve the original
301 author's copyright notice, the distribution terms, or the list of
302 authors, are ok. It is also no problem to require modified versions
303 to include notice that they were modified. Even entire sections that
304 may not be deleted or changed are acceptable, as long as they deal
305 with nontechnical topics (like this one). These kinds of restrictions
306 are acceptable because they don't obstruct the community's normal use
309 However, it must be possible to modify all the @emph{technical}
310 content of the manual, and then distribute the result in all the usual
311 media, through all the usual channels. Otherwise, the restrictions
312 obstruct the use of the manual, it is not free, and we need another
313 manual to replace it.
315 Please spread the word about this issue. Our community continues to
316 lose manuals to proprietary publishing. If we spread the word that
317 free software needs free reference manuals and free tutorials, perhaps
318 the next person who wants to contribute by writing documentation will
319 realize, before it is too late, that only free manuals contribute to
320 the free software community.
322 If you are writing documentation, please insist on publishing it under
323 the GNU Free Documentation License or another free documentation
324 license. Remember that this decision requires your approval---you
325 don't have to let the publisher decide. Some commercial publishers
326 will use a free license if you insist, but they will not propose the
327 option; it is up to you to raise the issue and say firmly that this is
328 what you want. If the publisher you are dealing with refuses, please
329 try other publishers. If you're not sure whether a proposed license
330 is free, write to @email{licensing@@gnu.org}.
332 You can encourage commercial publishers to sell more free, copylefted
333 manuals and tutorials by buying them, and particularly by buying
334 copies from the publishers that paid for their writing or for major
335 improvements. Meanwhile, try to avoid buying non-free documentation
336 at all. Check the distribution terms of a manual before you buy it,
337 and insist that whoever seeks your business must respect your freedom.
338 Check the history of the book, and try to reward the publishers that
339 have paid or pay the authors to work on it.
341 The Free Software Foundation maintains a list of free documentation
342 published by other publishers, at
343 @url{http://www.fsf.org/doc/other-free-books.html}.
346 @unnumberedsec Contributors to @value{GDBN}
348 Richard Stallman was the original author of @value{GDBN}, and of many
349 other @sc{gnu} programs. Many others have contributed to its
350 development. This section attempts to credit major contributors. One
351 of the virtues of free software is that everyone is free to contribute
352 to it; with regret, we cannot actually acknowledge everyone here. The
353 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
354 blow-by-blow account.
356 Changes much prior to version 2.0 are lost in the mists of time.
359 @emph{Plea:} Additions to this section are particularly welcome. If you
360 or your friends (or enemies, to be evenhanded) have been unfairly
361 omitted from this list, we would like to add your names!
364 So that they may not regard their many labors as thankless, we
365 particularly thank those who shepherded @value{GDBN} through major
367 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
368 Jim Blandy (release 4.18);
369 Jason Molenda (release 4.17);
370 Stan Shebs (release 4.14);
371 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
372 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
373 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
374 Jim Kingdon (releases 3.5, 3.4, and 3.3);
375 and Randy Smith (releases 3.2, 3.1, and 3.0).
377 Richard Stallman, assisted at various times by Peter TerMaat, Chris
378 Hanson, and Richard Mlynarik, handled releases through 2.8.
380 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
381 in @value{GDBN}, with significant additional contributions from Per
382 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
383 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
384 much general update work leading to release 3.0).
386 @value{GDBN} uses the BFD subroutine library to examine multiple
387 object-file formats; BFD was a joint project of David V.
388 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
390 David Johnson wrote the original COFF support; Pace Willison did
391 the original support for encapsulated COFF.
393 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
395 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
396 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
398 Jean-Daniel Fekete contributed Sun 386i support.
399 Chris Hanson improved the HP9000 support.
400 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
401 David Johnson contributed Encore Umax support.
402 Jyrki Kuoppala contributed Altos 3068 support.
403 Jeff Law contributed HP PA and SOM support.
404 Keith Packard contributed NS32K support.
405 Doug Rabson contributed Acorn Risc Machine support.
406 Bob Rusk contributed Harris Nighthawk CX-UX support.
407 Chris Smith contributed Convex support (and Fortran debugging).
408 Jonathan Stone contributed Pyramid support.
409 Michael Tiemann contributed SPARC support.
410 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
411 Pace Willison contributed Intel 386 support.
412 Jay Vosburgh contributed Symmetry support.
413 Marko Mlinar contributed OpenRISC 1000 support.
415 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
417 Rich Schaefer and Peter Schauer helped with support of SunOS shared
420 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
421 about several machine instruction sets.
423 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
424 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
425 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
426 and RDI targets, respectively.
428 Brian Fox is the author of the readline libraries providing
429 command-line editing and command history.
431 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
432 Modula-2 support, and contributed the Languages chapter of this manual.
434 Fred Fish wrote most of the support for Unix System Vr4.
435 He also enhanced the command-completion support to cover C@t{++} overloaded
438 Hitachi America (now Renesas America), Ltd. sponsored the support for
439 H8/300, H8/500, and Super-H processors.
441 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
443 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
446 Toshiba sponsored the support for the TX39 Mips processor.
448 Matsushita sponsored the support for the MN10200 and MN10300 processors.
450 Fujitsu sponsored the support for SPARClite and FR30 processors.
452 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
455 Michael Snyder added support for tracepoints.
457 Stu Grossman wrote gdbserver.
459 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
460 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
462 The following people at the Hewlett-Packard Company contributed
463 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
464 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
465 compiler, and the Text User Interface (nee Terminal User Interface):
466 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
467 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
468 provided HP-specific information in this manual.
470 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
471 Robert Hoehne made significant contributions to the DJGPP port.
473 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
474 development since 1991. Cygnus engineers who have worked on @value{GDBN}
475 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
476 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
477 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
478 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
479 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
480 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
481 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
482 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
483 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
484 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
485 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
486 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
487 Zuhn have made contributions both large and small.
489 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
490 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
492 Jim Blandy added support for preprocessor macros, while working for Red
495 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
496 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
497 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
498 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
499 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
500 with the migration of old architectures to this new framework.
502 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
503 unwinder framework, this consisting of a fresh new design featuring
504 frame IDs, independent frame sniffers, and the sentinel frame. Mark
505 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
506 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
507 trad unwinders. The architecture-specific changes, each involving a
508 complete rewrite of the architecture's frame code, were carried out by
509 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
510 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
511 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
512 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
515 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
516 Tensilica, Inc.@: contributed support for Xtensa processors. Others
517 who have worked on the Xtensa port of @value{GDBN} in the past include
518 Steve Tjiang, John Newlin, and Scott Foehner.
521 @chapter A Sample @value{GDBN} Session
523 You can use this manual at your leisure to read all about @value{GDBN}.
524 However, a handful of commands are enough to get started using the
525 debugger. This chapter illustrates those commands.
528 In this sample session, we emphasize user input like this: @b{input},
529 to make it easier to pick out from the surrounding output.
532 @c FIXME: this example may not be appropriate for some configs, where
533 @c FIXME...primary interest is in remote use.
535 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
536 processor) exhibits the following bug: sometimes, when we change its
537 quote strings from the default, the commands used to capture one macro
538 definition within another stop working. In the following short @code{m4}
539 session, we define a macro @code{foo} which expands to @code{0000}; we
540 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
541 same thing. However, when we change the open quote string to
542 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
543 procedure fails to define a new synonym @code{baz}:
552 @b{define(bar,defn(`foo'))}
556 @b{changequote(<QUOTE>,<UNQUOTE>)}
558 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
561 m4: End of input: 0: fatal error: EOF in string
565 Let us use @value{GDBN} to try to see what is going on.
568 $ @b{@value{GDBP} m4}
569 @c FIXME: this falsifies the exact text played out, to permit smallbook
570 @c FIXME... format to come out better.
571 @value{GDBN} is free software and you are welcome to distribute copies
572 of it under certain conditions; type "show copying" to see
574 There is absolutely no warranty for @value{GDBN}; type "show warranty"
577 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
582 @value{GDBN} reads only enough symbol data to know where to find the
583 rest when needed; as a result, the first prompt comes up very quickly.
584 We now tell @value{GDBN} to use a narrower display width than usual, so
585 that examples fit in this manual.
588 (@value{GDBP}) @b{set width 70}
592 We need to see how the @code{m4} built-in @code{changequote} works.
593 Having looked at the source, we know the relevant subroutine is
594 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
595 @code{break} command.
598 (@value{GDBP}) @b{break m4_changequote}
599 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
603 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
604 control; as long as control does not reach the @code{m4_changequote}
605 subroutine, the program runs as usual:
608 (@value{GDBP}) @b{run}
609 Starting program: /work/Editorial/gdb/gnu/m4/m4
617 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
618 suspends execution of @code{m4}, displaying information about the
619 context where it stops.
622 @b{changequote(<QUOTE>,<UNQUOTE>)}
624 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
626 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
630 Now we use the command @code{n} (@code{next}) to advance execution to
631 the next line of the current function.
635 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
640 @code{set_quotes} looks like a promising subroutine. We can go into it
641 by using the command @code{s} (@code{step}) instead of @code{next}.
642 @code{step} goes to the next line to be executed in @emph{any}
643 subroutine, so it steps into @code{set_quotes}.
647 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
649 530 if (lquote != def_lquote)
653 The display that shows the subroutine where @code{m4} is now
654 suspended (and its arguments) is called a stack frame display. It
655 shows a summary of the stack. We can use the @code{backtrace}
656 command (which can also be spelled @code{bt}), to see where we are
657 in the stack as a whole: the @code{backtrace} command displays a
658 stack frame for each active subroutine.
661 (@value{GDBP}) @b{bt}
662 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
664 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
666 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
667 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
669 #4 0x79dc in expand_input () at macro.c:40
670 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
674 We step through a few more lines to see what happens. The first two
675 times, we can use @samp{s}; the next two times we use @code{n} to avoid
676 falling into the @code{xstrdup} subroutine.
680 0x3b5c 532 if (rquote != def_rquote)
682 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
683 def_lquote : xstrdup(lq);
685 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
688 538 len_lquote = strlen(rquote);
692 The last line displayed looks a little odd; we can examine the variables
693 @code{lquote} and @code{rquote} to see if they are in fact the new left
694 and right quotes we specified. We use the command @code{p}
695 (@code{print}) to see their values.
698 (@value{GDBP}) @b{p lquote}
699 $1 = 0x35d40 "<QUOTE>"
700 (@value{GDBP}) @b{p rquote}
701 $2 = 0x35d50 "<UNQUOTE>"
705 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
706 To look at some context, we can display ten lines of source
707 surrounding the current line with the @code{l} (@code{list}) command.
713 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
715 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
718 538 len_lquote = strlen(rquote);
719 539 len_rquote = strlen(lquote);
726 Let us step past the two lines that set @code{len_lquote} and
727 @code{len_rquote}, and then examine the values of those variables.
731 539 len_rquote = strlen(lquote);
734 (@value{GDBP}) @b{p len_lquote}
736 (@value{GDBP}) @b{p len_rquote}
741 That certainly looks wrong, assuming @code{len_lquote} and
742 @code{len_rquote} are meant to be the lengths of @code{lquote} and
743 @code{rquote} respectively. We can set them to better values using
744 the @code{p} command, since it can print the value of
745 any expression---and that expression can include subroutine calls and
749 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
751 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
756 Is that enough to fix the problem of using the new quotes with the
757 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
758 executing with the @code{c} (@code{continue}) command, and then try the
759 example that caused trouble initially:
765 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
772 Success! The new quotes now work just as well as the default ones. The
773 problem seems to have been just the two typos defining the wrong
774 lengths. We allow @code{m4} exit by giving it an EOF as input:
778 Program exited normally.
782 The message @samp{Program exited normally.} is from @value{GDBN}; it
783 indicates @code{m4} has finished executing. We can end our @value{GDBN}
784 session with the @value{GDBN} @code{quit} command.
787 (@value{GDBP}) @b{quit}
791 @chapter Getting In and Out of @value{GDBN}
793 This chapter discusses how to start @value{GDBN}, and how to get out of it.
797 type @samp{@value{GDBP}} to start @value{GDBN}.
799 type @kbd{quit} or @kbd{Ctrl-d} to exit.
803 * Invoking GDB:: How to start @value{GDBN}
804 * Quitting GDB:: How to quit @value{GDBN}
805 * Shell Commands:: How to use shell commands inside @value{GDBN}
806 * Logging Output:: How to log @value{GDBN}'s output to a file
810 @section Invoking @value{GDBN}
812 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
813 @value{GDBN} reads commands from the terminal until you tell it to exit.
815 You can also run @code{@value{GDBP}} with a variety of arguments and options,
816 to specify more of your debugging environment at the outset.
818 The command-line options described here are designed
819 to cover a variety of situations; in some environments, some of these
820 options may effectively be unavailable.
822 The most usual way to start @value{GDBN} is with one argument,
823 specifying an executable program:
826 @value{GDBP} @var{program}
830 You can also start with both an executable program and a core file
834 @value{GDBP} @var{program} @var{core}
837 You can, instead, specify a process ID as a second argument, if you want
838 to debug a running process:
841 @value{GDBP} @var{program} 1234
845 would attach @value{GDBN} to process @code{1234} (unless you also have a file
846 named @file{1234}; @value{GDBN} does check for a core file first).
848 Taking advantage of the second command-line argument requires a fairly
849 complete operating system; when you use @value{GDBN} as a remote
850 debugger attached to a bare board, there may not be any notion of
851 ``process'', and there is often no way to get a core dump. @value{GDBN}
852 will warn you if it is unable to attach or to read core dumps.
854 You can optionally have @code{@value{GDBP}} pass any arguments after the
855 executable file to the inferior using @code{--args}. This option stops
858 @value{GDBP} --args gcc -O2 -c foo.c
860 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
861 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
863 You can run @code{@value{GDBP}} without printing the front material, which describes
864 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
871 You can further control how @value{GDBN} starts up by using command-line
872 options. @value{GDBN} itself can remind you of the options available.
882 to display all available options and briefly describe their use
883 (@samp{@value{GDBP} -h} is a shorter equivalent).
885 All options and command line arguments you give are processed
886 in sequential order. The order makes a difference when the
887 @samp{-x} option is used.
891 * File Options:: Choosing files
892 * Mode Options:: Choosing modes
893 * Startup:: What @value{GDBN} does during startup
897 @subsection Choosing Files
899 When @value{GDBN} starts, it reads any arguments other than options as
900 specifying an executable file and core file (or process ID). This is
901 the same as if the arguments were specified by the @samp{-se} and
902 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
903 first argument that does not have an associated option flag as
904 equivalent to the @samp{-se} option followed by that argument; and the
905 second argument that does not have an associated option flag, if any, as
906 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
907 If the second argument begins with a decimal digit, @value{GDBN} will
908 first attempt to attach to it as a process, and if that fails, attempt
909 to open it as a corefile. If you have a corefile whose name begins with
910 a digit, you can prevent @value{GDBN} from treating it as a pid by
911 prefixing it with @file{./}, e.g.@: @file{./12345}.
913 If @value{GDBN} has not been configured to included core file support,
914 such as for most embedded targets, then it will complain about a second
915 argument and ignore it.
917 Many options have both long and short forms; both are shown in the
918 following list. @value{GDBN} also recognizes the long forms if you truncate
919 them, so long as enough of the option is present to be unambiguous.
920 (If you prefer, you can flag option arguments with @samp{--} rather
921 than @samp{-}, though we illustrate the more usual convention.)
923 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
924 @c way, both those who look for -foo and --foo in the index, will find
928 @item -symbols @var{file}
930 @cindex @code{--symbols}
932 Read symbol table from file @var{file}.
934 @item -exec @var{file}
936 @cindex @code{--exec}
938 Use file @var{file} as the executable file to execute when appropriate,
939 and for examining pure data in conjunction with a core dump.
943 Read symbol table from file @var{file} and use it as the executable
946 @item -core @var{file}
948 @cindex @code{--core}
950 Use file @var{file} as a core dump to examine.
952 @item -pid @var{number}
953 @itemx -p @var{number}
956 Connect to process ID @var{number}, as with the @code{attach} command.
958 @item -command @var{file}
960 @cindex @code{--command}
962 Execute @value{GDBN} commands from file @var{file}. @xref{Command
963 Files,, Command files}.
965 @item -eval-command @var{command}
966 @itemx -ex @var{command}
967 @cindex @code{--eval-command}
969 Execute a single @value{GDBN} command.
971 This option may be used multiple times to call multiple commands. It may
972 also be interleaved with @samp{-command} as required.
975 @value{GDBP} -ex 'target sim' -ex 'load' \
976 -x setbreakpoints -ex 'run' a.out
979 @item -directory @var{directory}
980 @itemx -d @var{directory}
981 @cindex @code{--directory}
983 Add @var{directory} to the path to search for source and script files.
987 @cindex @code{--readnow}
989 Read each symbol file's entire symbol table immediately, rather than
990 the default, which is to read it incrementally as it is needed.
991 This makes startup slower, but makes future operations faster.
996 @subsection Choosing Modes
998 You can run @value{GDBN} in various alternative modes---for example, in
999 batch mode or quiet mode.
1006 Do not execute commands found in any initialization files. Normally,
1007 @value{GDBN} executes the commands in these files after all the command
1008 options and arguments have been processed. @xref{Command Files,,Command
1014 @cindex @code{--quiet}
1015 @cindex @code{--silent}
1017 ``Quiet''. Do not print the introductory and copyright messages. These
1018 messages are also suppressed in batch mode.
1021 @cindex @code{--batch}
1022 Run in batch mode. Exit with status @code{0} after processing all the
1023 command files specified with @samp{-x} (and all commands from
1024 initialization files, if not inhibited with @samp{-n}). Exit with
1025 nonzero status if an error occurs in executing the @value{GDBN} commands
1026 in the command files.
1028 Batch mode may be useful for running @value{GDBN} as a filter, for
1029 example to download and run a program on another computer; in order to
1030 make this more useful, the message
1033 Program exited normally.
1037 (which is ordinarily issued whenever a program running under
1038 @value{GDBN} control terminates) is not issued when running in batch
1042 @cindex @code{--batch-silent}
1043 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1044 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1045 unaffected). This is much quieter than @samp{-silent} and would be useless
1046 for an interactive session.
1048 This is particularly useful when using targets that give @samp{Loading section}
1049 messages, for example.
1051 Note that targets that give their output via @value{GDBN}, as opposed to
1052 writing directly to @code{stdout}, will also be made silent.
1054 @item -return-child-result
1055 @cindex @code{--return-child-result}
1056 The return code from @value{GDBN} will be the return code from the child
1057 process (the process being debugged), with the following exceptions:
1061 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1062 internal error. In this case the exit code is the same as it would have been
1063 without @samp{-return-child-result}.
1065 The user quits with an explicit value. E.g., @samp{quit 1}.
1067 The child process never runs, or is not allowed to terminate, in which case
1068 the exit code will be -1.
1071 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1072 when @value{GDBN} is being used as a remote program loader or simulator
1077 @cindex @code{--nowindows}
1079 ``No windows''. If @value{GDBN} comes with a graphical user interface
1080 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1081 interface. If no GUI is available, this option has no effect.
1085 @cindex @code{--windows}
1087 If @value{GDBN} includes a GUI, then this option requires it to be
1090 @item -cd @var{directory}
1092 Run @value{GDBN} using @var{directory} as its working directory,
1093 instead of the current directory.
1097 @cindex @code{--fullname}
1099 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1100 subprocess. It tells @value{GDBN} to output the full file name and line
1101 number in a standard, recognizable fashion each time a stack frame is
1102 displayed (which includes each time your program stops). This
1103 recognizable format looks like two @samp{\032} characters, followed by
1104 the file name, line number and character position separated by colons,
1105 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1106 @samp{\032} characters as a signal to display the source code for the
1110 @cindex @code{--epoch}
1111 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1112 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1113 routines so as to allow Epoch to display values of expressions in a
1116 @item -annotate @var{level}
1117 @cindex @code{--annotate}
1118 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1119 effect is identical to using @samp{set annotate @var{level}}
1120 (@pxref{Annotations}). The annotation @var{level} controls how much
1121 information @value{GDBN} prints together with its prompt, values of
1122 expressions, source lines, and other types of output. Level 0 is the
1123 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1124 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1125 that control @value{GDBN}, and level 2 has been deprecated.
1127 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1131 @cindex @code{--args}
1132 Change interpretation of command line so that arguments following the
1133 executable file are passed as command line arguments to the inferior.
1134 This option stops option processing.
1136 @item -baud @var{bps}
1138 @cindex @code{--baud}
1140 Set the line speed (baud rate or bits per second) of any serial
1141 interface used by @value{GDBN} for remote debugging.
1143 @item -l @var{timeout}
1145 Set the timeout (in seconds) of any communication used by @value{GDBN}
1146 for remote debugging.
1148 @item -tty @var{device}
1149 @itemx -t @var{device}
1150 @cindex @code{--tty}
1152 Run using @var{device} for your program's standard input and output.
1153 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1155 @c resolve the situation of these eventually
1157 @cindex @code{--tui}
1158 Activate the @dfn{Text User Interface} when starting. The Text User
1159 Interface manages several text windows on the terminal, showing
1160 source, assembly, registers and @value{GDBN} command outputs
1161 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1162 Text User Interface can be enabled by invoking the program
1163 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1164 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1167 @c @cindex @code{--xdb}
1168 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1169 @c For information, see the file @file{xdb_trans.html}, which is usually
1170 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1173 @item -interpreter @var{interp}
1174 @cindex @code{--interpreter}
1175 Use the interpreter @var{interp} for interface with the controlling
1176 program or device. This option is meant to be set by programs which
1177 communicate with @value{GDBN} using it as a back end.
1178 @xref{Interpreters, , Command Interpreters}.
1180 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1181 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1182 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1183 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1184 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1185 @sc{gdb/mi} interfaces are no longer supported.
1188 @cindex @code{--write}
1189 Open the executable and core files for both reading and writing. This
1190 is equivalent to the @samp{set write on} command inside @value{GDBN}
1194 @cindex @code{--statistics}
1195 This option causes @value{GDBN} to print statistics about time and
1196 memory usage after it completes each command and returns to the prompt.
1199 @cindex @code{--version}
1200 This option causes @value{GDBN} to print its version number and
1201 no-warranty blurb, and exit.
1206 @subsection What @value{GDBN} Does During Startup
1207 @cindex @value{GDBN} startup
1209 Here's the description of what @value{GDBN} does during session startup:
1213 Sets up the command interpreter as specified by the command line
1214 (@pxref{Mode Options, interpreter}).
1218 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1219 used when building @value{GDBN}; @pxref{System-wide configuration,
1220 ,System-wide configuration and settings}) and executes all the commands in
1224 Reads the 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 To display the list of init files loaded by gdb at startup, you
1258 can use @kbd{gdb --help}.
1260 @cindex init file name
1261 @cindex @file{.gdbinit}
1262 @cindex @file{gdb.ini}
1263 The @value{GDBN} init files are normally called @file{.gdbinit}.
1264 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1265 the limitations of file names imposed by DOS filesystems. The Windows
1266 ports of @value{GDBN} use the standard name, but if they find a
1267 @file{gdb.ini} file, they warn you about that and suggest to rename
1268 the file to the standard name.
1272 @section Quitting @value{GDBN}
1273 @cindex exiting @value{GDBN}
1274 @cindex leaving @value{GDBN}
1277 @kindex quit @r{[}@var{expression}@r{]}
1278 @kindex q @r{(@code{quit})}
1279 @item quit @r{[}@var{expression}@r{]}
1281 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1282 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1283 do not supply @var{expression}, @value{GDBN} will terminate normally;
1284 otherwise it will terminate using the result of @var{expression} as the
1289 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1290 terminates the action of any @value{GDBN} command that is in progress and
1291 returns to @value{GDBN} command level. It is safe to type the interrupt
1292 character at any time because @value{GDBN} does not allow it to take effect
1293 until a time when it is safe.
1295 If you have been using @value{GDBN} to control an attached process or
1296 device, you can release it with the @code{detach} command
1297 (@pxref{Attach, ,Debugging an Already-running Process}).
1299 @node Shell Commands
1300 @section Shell Commands
1302 If you need to execute occasional shell commands during your
1303 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1304 just use the @code{shell} command.
1308 @cindex shell escape
1309 @item shell @var{command string}
1310 Invoke a standard shell to execute @var{command string}.
1311 If it exists, the environment variable @code{SHELL} determines which
1312 shell to run. Otherwise @value{GDBN} uses the default shell
1313 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1316 The utility @code{make} is often needed in development environments.
1317 You do not have to use the @code{shell} command for this purpose in
1322 @cindex calling make
1323 @item make @var{make-args}
1324 Execute the @code{make} program with the specified
1325 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1328 @node Logging Output
1329 @section Logging Output
1330 @cindex logging @value{GDBN} output
1331 @cindex save @value{GDBN} output to a file
1333 You may want to save the output of @value{GDBN} commands to a file.
1334 There are several commands to control @value{GDBN}'s logging.
1338 @item set logging on
1340 @item set logging off
1342 @cindex logging file name
1343 @item set logging file @var{file}
1344 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1345 @item set logging overwrite [on|off]
1346 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1347 you want @code{set logging on} to overwrite the logfile instead.
1348 @item set logging redirect [on|off]
1349 By default, @value{GDBN} output will go to both the terminal and the logfile.
1350 Set @code{redirect} if you want output to go only to the log file.
1351 @kindex show logging
1353 Show the current values of the logging settings.
1357 @chapter @value{GDBN} Commands
1359 You can abbreviate a @value{GDBN} command to the first few letters of the command
1360 name, if that abbreviation is unambiguous; and you can repeat certain
1361 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1362 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1363 show you the alternatives available, if there is more than one possibility).
1366 * Command Syntax:: How to give commands to @value{GDBN}
1367 * Completion:: Command completion
1368 * Help:: How to ask @value{GDBN} for help
1371 @node Command Syntax
1372 @section Command Syntax
1374 A @value{GDBN} command is a single line of input. There is no limit on
1375 how long it can be. It starts with a command name, which is followed by
1376 arguments whose meaning depends on the command name. For example, the
1377 command @code{step} accepts an argument which is the number of times to
1378 step, as in @samp{step 5}. You can also use the @code{step} command
1379 with no arguments. Some commands do not allow any arguments.
1381 @cindex abbreviation
1382 @value{GDBN} command names may always be truncated if that abbreviation is
1383 unambiguous. Other possible command abbreviations are listed in the
1384 documentation for individual commands. In some cases, even ambiguous
1385 abbreviations are allowed; for example, @code{s} is specially defined as
1386 equivalent to @code{step} even though there are other commands whose
1387 names start with @code{s}. You can test abbreviations by using them as
1388 arguments to the @code{help} command.
1390 @cindex repeating commands
1391 @kindex RET @r{(repeat last command)}
1392 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1393 repeat the previous command. Certain commands (for example, @code{run})
1394 will not repeat this way; these are commands whose unintentional
1395 repetition might cause trouble and which you are unlikely to want to
1396 repeat. User-defined commands can disable this feature; see
1397 @ref{Define, dont-repeat}.
1399 The @code{list} and @code{x} commands, when you repeat them with
1400 @key{RET}, construct new arguments rather than repeating
1401 exactly as typed. This permits easy scanning of source or memory.
1403 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1404 output, in a way similar to the common utility @code{more}
1405 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1406 @key{RET} too many in this situation, @value{GDBN} disables command
1407 repetition after any command that generates this sort of display.
1409 @kindex # @r{(a comment)}
1411 Any text from a @kbd{#} to the end of the line is a comment; it does
1412 nothing. This is useful mainly in command files (@pxref{Command
1413 Files,,Command Files}).
1415 @cindex repeating command sequences
1416 @kindex Ctrl-o @r{(operate-and-get-next)}
1417 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1418 commands. This command accepts the current line, like @key{RET}, and
1419 then fetches the next line relative to the current line from the history
1423 @section Command Completion
1426 @cindex word completion
1427 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1428 only one possibility; it can also show you what the valid possibilities
1429 are for the next word in a command, at any time. This works for @value{GDBN}
1430 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1432 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1433 of a word. If there is only one possibility, @value{GDBN} fills in the
1434 word, and waits for you to finish the command (or press @key{RET} to
1435 enter it). For example, if you type
1437 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1438 @c complete accuracy in these examples; space introduced for clarity.
1439 @c If texinfo enhancements make it unnecessary, it would be nice to
1440 @c replace " @key" by "@key" in the following...
1442 (@value{GDBP}) info bre @key{TAB}
1446 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1447 the only @code{info} subcommand beginning with @samp{bre}:
1450 (@value{GDBP}) info breakpoints
1454 You can either press @key{RET} at this point, to run the @code{info
1455 breakpoints} command, or backspace and enter something else, if
1456 @samp{breakpoints} does not look like the command you expected. (If you
1457 were sure you wanted @code{info breakpoints} in the first place, you
1458 might as well just type @key{RET} immediately after @samp{info bre},
1459 to exploit command abbreviations rather than command completion).
1461 If there is more than one possibility for the next word when you press
1462 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1463 characters and try again, or just press @key{TAB} a second time;
1464 @value{GDBN} displays all the possible completions for that word. For
1465 example, you might want to set a breakpoint on a subroutine whose name
1466 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1467 just sounds the bell. Typing @key{TAB} again displays all the
1468 function names in your program that begin with those characters, for
1472 (@value{GDBP}) b make_ @key{TAB}
1473 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1474 make_a_section_from_file make_environ
1475 make_abs_section make_function_type
1476 make_blockvector make_pointer_type
1477 make_cleanup make_reference_type
1478 make_command make_symbol_completion_list
1479 (@value{GDBP}) b make_
1483 After displaying the available possibilities, @value{GDBN} copies your
1484 partial input (@samp{b make_} in the example) so you can finish the
1487 If you just want to see the list of alternatives in the first place, you
1488 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1489 means @kbd{@key{META} ?}. You can type this either by holding down a
1490 key designated as the @key{META} shift on your keyboard (if there is
1491 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1493 @cindex quotes in commands
1494 @cindex completion of quoted strings
1495 Sometimes the string you need, while logically a ``word'', may contain
1496 parentheses or other characters that @value{GDBN} normally excludes from
1497 its notion of a word. To permit word completion to work in this
1498 situation, you may enclose words in @code{'} (single quote marks) in
1499 @value{GDBN} commands.
1501 The most likely situation where you might need this is in typing the
1502 name of a C@t{++} function. This is because C@t{++} allows function
1503 overloading (multiple definitions of the same function, distinguished
1504 by argument type). For example, when you want to set a breakpoint you
1505 may need to distinguish whether you mean the version of @code{name}
1506 that takes an @code{int} parameter, @code{name(int)}, or the version
1507 that takes a @code{float} parameter, @code{name(float)}. To use the
1508 word-completion facilities in this situation, type a single quote
1509 @code{'} at the beginning of the function name. This alerts
1510 @value{GDBN} that it may need to consider more information than usual
1511 when you press @key{TAB} or @kbd{M-?} to request word completion:
1514 (@value{GDBP}) b 'bubble( @kbd{M-?}
1515 bubble(double,double) bubble(int,int)
1516 (@value{GDBP}) b 'bubble(
1519 In some cases, @value{GDBN} can tell that completing a name requires using
1520 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1521 completing as much as it can) if you do not type the quote in the first
1525 (@value{GDBP}) b bub @key{TAB}
1526 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1527 (@value{GDBP}) b 'bubble(
1531 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1532 you have not yet started typing the argument list when you ask for
1533 completion on an overloaded symbol.
1535 For more information about overloaded functions, see @ref{C Plus Plus
1536 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1537 overload-resolution off} to disable overload resolution;
1538 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1540 @cindex completion of structure field names
1541 @cindex structure field name completion
1542 @cindex completion of union field names
1543 @cindex union field name completion
1544 When completing in an expression which looks up a field in a
1545 structure, @value{GDBN} also tries@footnote{The completer can be
1546 confused by certain kinds of invalid expressions. Also, it only
1547 examines the static type of the expression, not the dynamic type.} to
1548 limit completions to the field names available in the type of the
1552 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1553 magic to_delete to_fputs to_put to_rewind
1554 to_data to_flush to_isatty to_read to_write
1558 This is because the @code{gdb_stdout} is a variable of the type
1559 @code{struct ui_file} that is defined in @value{GDBN} sources as
1566 ui_file_flush_ftype *to_flush;
1567 ui_file_write_ftype *to_write;
1568 ui_file_fputs_ftype *to_fputs;
1569 ui_file_read_ftype *to_read;
1570 ui_file_delete_ftype *to_delete;
1571 ui_file_isatty_ftype *to_isatty;
1572 ui_file_rewind_ftype *to_rewind;
1573 ui_file_put_ftype *to_put;
1580 @section Getting Help
1581 @cindex online documentation
1584 You can always ask @value{GDBN} itself for information on its commands,
1585 using the command @code{help}.
1588 @kindex h @r{(@code{help})}
1591 You can use @code{help} (abbreviated @code{h}) with no arguments to
1592 display a short list of named classes of commands:
1596 List of classes of commands:
1598 aliases -- Aliases of other commands
1599 breakpoints -- Making program stop at certain points
1600 data -- Examining data
1601 files -- Specifying and examining files
1602 internals -- Maintenance commands
1603 obscure -- Obscure features
1604 running -- Running the program
1605 stack -- Examining the stack
1606 status -- Status inquiries
1607 support -- Support facilities
1608 tracepoints -- Tracing of program execution without
1609 stopping the program
1610 user-defined -- User-defined commands
1612 Type "help" followed by a class name for a list of
1613 commands in that class.
1614 Type "help" followed by command name for full
1616 Command name abbreviations are allowed if unambiguous.
1619 @c the above line break eliminates huge line overfull...
1621 @item help @var{class}
1622 Using one of the general help classes as an argument, you can get a
1623 list of the individual commands in that class. For example, here is the
1624 help display for the class @code{status}:
1627 (@value{GDBP}) help status
1632 @c Line break in "show" line falsifies real output, but needed
1633 @c to fit in smallbook page size.
1634 info -- Generic command for showing things
1635 about the program being debugged
1636 show -- Generic command for showing things
1639 Type "help" followed by command name for full
1641 Command name abbreviations are allowed if unambiguous.
1645 @item help @var{command}
1646 With a command name as @code{help} argument, @value{GDBN} displays a
1647 short paragraph on how to use that command.
1650 @item apropos @var{args}
1651 The @code{apropos} command searches through all of the @value{GDBN}
1652 commands, and their documentation, for the regular expression specified in
1653 @var{args}. It prints out all matches found. For example:
1664 set symbol-reloading -- Set dynamic symbol table reloading
1665 multiple times in one run
1666 show symbol-reloading -- Show dynamic symbol table reloading
1667 multiple times in one run
1672 @item complete @var{args}
1673 The @code{complete @var{args}} command lists all the possible completions
1674 for the beginning of a command. Use @var{args} to specify the beginning of the
1675 command you want completed. For example:
1681 @noindent results in:
1692 @noindent This is intended for use by @sc{gnu} Emacs.
1695 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1696 and @code{show} to inquire about the state of your program, or the state
1697 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1698 manual introduces each of them in the appropriate context. The listings
1699 under @code{info} and under @code{show} in the Index point to
1700 all the sub-commands. @xref{Index}.
1705 @kindex i @r{(@code{info})}
1707 This command (abbreviated @code{i}) is for describing the state of your
1708 program. For example, you can show the arguments passed to a function
1709 with @code{info args}, list the registers currently in use with @code{info
1710 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1711 You can get a complete list of the @code{info} sub-commands with
1712 @w{@code{help info}}.
1716 You can assign the result of an expression to an environment variable with
1717 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1718 @code{set prompt $}.
1722 In contrast to @code{info}, @code{show} is for describing the state of
1723 @value{GDBN} itself.
1724 You can change most of the things you can @code{show}, by using the
1725 related command @code{set}; for example, you can control what number
1726 system is used for displays with @code{set radix}, or simply inquire
1727 which is currently in use with @code{show radix}.
1730 To display all the settable parameters and their current
1731 values, you can use @code{show} with no arguments; you may also use
1732 @code{info set}. Both commands produce the same display.
1733 @c FIXME: "info set" violates the rule that "info" is for state of
1734 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1735 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1739 Here are three miscellaneous @code{show} subcommands, all of which are
1740 exceptional in lacking corresponding @code{set} commands:
1743 @kindex show version
1744 @cindex @value{GDBN} version number
1746 Show what version of @value{GDBN} is running. You should include this
1747 information in @value{GDBN} bug-reports. If multiple versions of
1748 @value{GDBN} are in use at your site, you may need to determine which
1749 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1750 commands are introduced, and old ones may wither away. Also, many
1751 system vendors ship variant versions of @value{GDBN}, and there are
1752 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1753 The version number is the same as the one announced when you start
1756 @kindex show copying
1757 @kindex info copying
1758 @cindex display @value{GDBN} copyright
1761 Display information about permission for copying @value{GDBN}.
1763 @kindex show warranty
1764 @kindex info warranty
1766 @itemx info warranty
1767 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1768 if your version of @value{GDBN} comes with one.
1773 @chapter Running Programs Under @value{GDBN}
1775 When you run a program under @value{GDBN}, you must first generate
1776 debugging information when you compile it.
1778 You may start @value{GDBN} with its arguments, if any, in an environment
1779 of your choice. If you are doing native debugging, you may redirect
1780 your program's input and output, debug an already running process, or
1781 kill a child process.
1784 * Compilation:: Compiling for debugging
1785 * Starting:: Starting your program
1786 * Arguments:: Your program's arguments
1787 * Environment:: Your program's environment
1789 * Working Directory:: Your program's working directory
1790 * Input/Output:: Your program's input and output
1791 * Attach:: Debugging an already-running process
1792 * Kill Process:: Killing the child process
1794 * Inferiors:: Debugging multiple inferiors
1795 * Threads:: Debugging programs with multiple threads
1796 * Processes:: Debugging programs with multiple processes
1797 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1801 @section Compiling for Debugging
1803 In order to debug a program effectively, you need to generate
1804 debugging information when you compile it. This debugging information
1805 is stored in the object file; it describes the data type of each
1806 variable or function and the correspondence between source line numbers
1807 and addresses in the executable code.
1809 To request debugging information, specify the @samp{-g} option when you run
1812 Programs that are to be shipped to your customers are compiled with
1813 optimizations, using the @samp{-O} compiler option. However, some
1814 compilers are unable to handle the @samp{-g} and @samp{-O} options
1815 together. Using those compilers, you cannot generate optimized
1816 executables containing debugging information.
1818 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1819 without @samp{-O}, making it possible to debug optimized code. We
1820 recommend that you @emph{always} use @samp{-g} whenever you compile a
1821 program. You may think your program is correct, but there is no sense
1822 in pushing your luck. For more information, see @ref{Optimized Code}.
1824 Older versions of the @sc{gnu} C compiler permitted a variant option
1825 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1826 format; if your @sc{gnu} C compiler has this option, do not use it.
1828 @value{GDBN} knows about preprocessor macros and can show you their
1829 expansion (@pxref{Macros}). Most compilers do not include information
1830 about preprocessor macros in the debugging information if you specify
1831 the @option{-g} flag alone, because this information is rather large.
1832 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1833 provides macro information if you specify the options
1834 @option{-gdwarf-2} and @option{-g3}; the former option requests
1835 debugging information in the Dwarf 2 format, and the latter requests
1836 ``extra information''. In the future, we hope to find more compact
1837 ways to represent macro information, so that it can be included with
1842 @section Starting your Program
1848 @kindex r @r{(@code{run})}
1851 Use the @code{run} command to start your program under @value{GDBN}.
1852 You must first specify the program name (except on VxWorks) with an
1853 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1854 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1855 (@pxref{Files, ,Commands to Specify Files}).
1859 If you are running your program in an execution environment that
1860 supports processes, @code{run} creates an inferior process and makes
1861 that process run your program. In some environments without processes,
1862 @code{run} jumps to the start of your program. Other targets,
1863 like @samp{remote}, are always running. If you get an error
1864 message like this one:
1867 The "remote" target does not support "run".
1868 Try "help target" or "continue".
1872 then use @code{continue} to run your program. You may need @code{load}
1873 first (@pxref{load}).
1875 The execution of a program is affected by certain information it
1876 receives from its superior. @value{GDBN} provides ways to specify this
1877 information, which you must do @emph{before} starting your program. (You
1878 can change it after starting your program, but such changes only affect
1879 your program the next time you start it.) This information may be
1880 divided into four categories:
1883 @item The @emph{arguments.}
1884 Specify the arguments to give your program as the arguments of the
1885 @code{run} command. If a shell is available on your target, the shell
1886 is used to pass the arguments, so that you may use normal conventions
1887 (such as wildcard expansion or variable substitution) in describing
1889 In Unix systems, you can control which shell is used with the
1890 @code{SHELL} environment variable.
1891 @xref{Arguments, ,Your Program's Arguments}.
1893 @item The @emph{environment.}
1894 Your program normally inherits its environment from @value{GDBN}, but you can
1895 use the @value{GDBN} commands @code{set environment} and @code{unset
1896 environment} to change parts of the environment that affect
1897 your program. @xref{Environment, ,Your Program's Environment}.
1899 @item The @emph{working directory.}
1900 Your program inherits its working directory from @value{GDBN}. You can set
1901 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1902 @xref{Working Directory, ,Your Program's Working Directory}.
1904 @item The @emph{standard input and output.}
1905 Your program normally uses the same device for standard input and
1906 standard output as @value{GDBN} is using. You can redirect input and output
1907 in the @code{run} command line, or you can use the @code{tty} command to
1908 set a different device for your program.
1909 @xref{Input/Output, ,Your Program's Input and Output}.
1912 @emph{Warning:} While input and output redirection work, you cannot use
1913 pipes to pass the output of the program you are debugging to another
1914 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1918 When you issue the @code{run} command, your program begins to execute
1919 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1920 of how to arrange for your program to stop. Once your program has
1921 stopped, you may call functions in your program, using the @code{print}
1922 or @code{call} commands. @xref{Data, ,Examining Data}.
1924 If the modification time of your symbol file has changed since the last
1925 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1926 table, and reads it again. When it does this, @value{GDBN} tries to retain
1927 your current breakpoints.
1932 @cindex run to main procedure
1933 The name of the main procedure can vary from language to language.
1934 With C or C@t{++}, the main procedure name is always @code{main}, but
1935 other languages such as Ada do not require a specific name for their
1936 main procedure. The debugger provides a convenient way to start the
1937 execution of the program and to stop at the beginning of the main
1938 procedure, depending on the language used.
1940 The @samp{start} command does the equivalent of setting a temporary
1941 breakpoint at the beginning of the main procedure and then invoking
1942 the @samp{run} command.
1944 @cindex elaboration phase
1945 Some programs contain an @dfn{elaboration} phase where some startup code is
1946 executed before the main procedure is called. This depends on the
1947 languages used to write your program. In C@t{++}, for instance,
1948 constructors for static and global objects are executed before
1949 @code{main} is called. It is therefore possible that the debugger stops
1950 before reaching the main procedure. However, the temporary breakpoint
1951 will remain to halt execution.
1953 Specify the arguments to give to your program as arguments to the
1954 @samp{start} command. These arguments will be given verbatim to the
1955 underlying @samp{run} command. Note that the same arguments will be
1956 reused if no argument is provided during subsequent calls to
1957 @samp{start} or @samp{run}.
1959 It is sometimes necessary to debug the program during elaboration. In
1960 these cases, using the @code{start} command would stop the execution of
1961 your program too late, as the program would have already completed the
1962 elaboration phase. Under these circumstances, insert breakpoints in your
1963 elaboration code before running your program.
1965 @kindex set exec-wrapper
1966 @item set exec-wrapper @var{wrapper}
1967 @itemx show exec-wrapper
1968 @itemx unset exec-wrapper
1969 When @samp{exec-wrapper} is set, the specified wrapper is used to
1970 launch programs for debugging. @value{GDBN} starts your program
1971 with a shell command of the form @kbd{exec @var{wrapper}
1972 @var{program}}. Quoting is added to @var{program} and its
1973 arguments, but not to @var{wrapper}, so you should add quotes if
1974 appropriate for your shell. The wrapper runs until it executes
1975 your program, and then @value{GDBN} takes control.
1977 You can use any program that eventually calls @code{execve} with
1978 its arguments as a wrapper. Several standard Unix utilities do
1979 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1980 with @code{exec "$@@"} will also work.
1982 For example, you can use @code{env} to pass an environment variable to
1983 the debugged program, without setting the variable in your shell's
1987 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1991 This command is available when debugging locally on most targets, excluding
1992 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
1994 @kindex set disable-randomization
1995 @item set disable-randomization
1996 @itemx set disable-randomization on
1997 This option (enabled by default in @value{GDBN}) will turn off the native
1998 randomization of the virtual address space of the started program. This option
1999 is useful for multiple debugging sessions to make the execution better
2000 reproducible and memory addresses reusable across debugging sessions.
2002 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2006 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2009 @item set disable-randomization off
2010 Leave the behavior of the started executable unchanged. Some bugs rear their
2011 ugly heads only when the program is loaded at certain addresses. If your bug
2012 disappears when you run the program under @value{GDBN}, that might be because
2013 @value{GDBN} by default disables the address randomization on platforms, such
2014 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2015 disable-randomization off} to try to reproduce such elusive bugs.
2017 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2018 It protects the programs against some kinds of security attacks. In these
2019 cases the attacker needs to know the exact location of a concrete executable
2020 code. Randomizing its location makes it impossible to inject jumps misusing
2021 a code at its expected addresses.
2023 Prelinking shared libraries provides a startup performance advantage but it
2024 makes addresses in these libraries predictable for privileged processes by
2025 having just unprivileged access at the target system. Reading the shared
2026 library binary gives enough information for assembling the malicious code
2027 misusing it. Still even a prelinked shared library can get loaded at a new
2028 random address just requiring the regular relocation process during the
2029 startup. Shared libraries not already prelinked are always loaded at
2030 a randomly chosen address.
2032 Position independent executables (PIE) contain position independent code
2033 similar to the shared libraries and therefore such executables get loaded at
2034 a randomly chosen address upon startup. PIE executables always load even
2035 already prelinked shared libraries at a random address. You can build such
2036 executable using @command{gcc -fPIE -pie}.
2038 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2039 (as long as the randomization is enabled).
2041 @item show disable-randomization
2042 Show the current setting of the explicit disable of the native randomization of
2043 the virtual address space of the started program.
2048 @section Your Program's Arguments
2050 @cindex arguments (to your program)
2051 The arguments to your program can be specified by the arguments of the
2053 They are passed to a shell, which expands wildcard characters and
2054 performs redirection of I/O, and thence to your program. Your
2055 @code{SHELL} environment variable (if it exists) specifies what shell
2056 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2057 the default shell (@file{/bin/sh} on Unix).
2059 On non-Unix systems, the program is usually invoked directly by
2060 @value{GDBN}, which emulates I/O redirection via the appropriate system
2061 calls, and the wildcard characters are expanded by the startup code of
2062 the program, not by the shell.
2064 @code{run} with no arguments uses the same arguments used by the previous
2065 @code{run}, or those set by the @code{set args} command.
2070 Specify the arguments to be used the next time your program is run. If
2071 @code{set args} has no arguments, @code{run} executes your program
2072 with no arguments. Once you have run your program with arguments,
2073 using @code{set args} before the next @code{run} is the only way to run
2074 it again without arguments.
2078 Show the arguments to give your program when it is started.
2082 @section Your Program's Environment
2084 @cindex environment (of your program)
2085 The @dfn{environment} consists of a set of environment variables and
2086 their values. Environment variables conventionally record such things as
2087 your user name, your home directory, your terminal type, and your search
2088 path for programs to run. Usually you set up environment variables with
2089 the shell and they are inherited by all the other programs you run. When
2090 debugging, it can be useful to try running your program with a modified
2091 environment without having to start @value{GDBN} over again.
2095 @item path @var{directory}
2096 Add @var{directory} to the front of the @code{PATH} environment variable
2097 (the search path for executables) that will be passed to your program.
2098 The value of @code{PATH} used by @value{GDBN} does not change.
2099 You may specify several directory names, separated by whitespace or by a
2100 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2101 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2102 is moved to the front, so it is searched sooner.
2104 You can use the string @samp{$cwd} to refer to whatever is the current
2105 working directory at the time @value{GDBN} searches the path. If you
2106 use @samp{.} instead, it refers to the directory where you executed the
2107 @code{path} command. @value{GDBN} replaces @samp{.} in the
2108 @var{directory} argument (with the current path) before adding
2109 @var{directory} to the search path.
2110 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2111 @c document that, since repeating it would be a no-op.
2115 Display the list of search paths for executables (the @code{PATH}
2116 environment variable).
2118 @kindex show environment
2119 @item show environment @r{[}@var{varname}@r{]}
2120 Print the value of environment variable @var{varname} to be given to
2121 your program when it starts. If you do not supply @var{varname},
2122 print the names and values of all environment variables to be given to
2123 your program. You can abbreviate @code{environment} as @code{env}.
2125 @kindex set environment
2126 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2127 Set environment variable @var{varname} to @var{value}. The value
2128 changes for your program only, not for @value{GDBN} itself. @var{value} may
2129 be any string; the values of environment variables are just strings, and
2130 any interpretation is supplied by your program itself. The @var{value}
2131 parameter is optional; if it is eliminated, the variable is set to a
2133 @c "any string" here does not include leading, trailing
2134 @c blanks. Gnu asks: does anyone care?
2136 For example, this command:
2143 tells the debugged program, when subsequently run, that its user is named
2144 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2145 are not actually required.)
2147 @kindex unset environment
2148 @item unset environment @var{varname}
2149 Remove variable @var{varname} from the environment to be passed to your
2150 program. This is different from @samp{set env @var{varname} =};
2151 @code{unset environment} removes the variable from the environment,
2152 rather than assigning it an empty value.
2155 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2157 by your @code{SHELL} environment variable if it exists (or
2158 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2159 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2160 @file{.bashrc} for BASH---any variables you set in that file affect
2161 your program. You may wish to move setting of environment variables to
2162 files that are only run when you sign on, such as @file{.login} or
2165 @node Working Directory
2166 @section Your Program's Working Directory
2168 @cindex working directory (of your program)
2169 Each time you start your program with @code{run}, it inherits its
2170 working directory from the current working directory of @value{GDBN}.
2171 The @value{GDBN} working directory is initially whatever it inherited
2172 from its parent process (typically the shell), but you can specify a new
2173 working directory in @value{GDBN} with the @code{cd} command.
2175 The @value{GDBN} working directory also serves as a default for the commands
2176 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2181 @cindex change working directory
2182 @item cd @var{directory}
2183 Set the @value{GDBN} working directory to @var{directory}.
2187 Print the @value{GDBN} working directory.
2190 It is generally impossible to find the current working directory of
2191 the process being debugged (since a program can change its directory
2192 during its run). If you work on a system where @value{GDBN} is
2193 configured with the @file{/proc} support, you can use the @code{info
2194 proc} command (@pxref{SVR4 Process Information}) to find out the
2195 current working directory of the debuggee.
2198 @section Your Program's Input and Output
2203 By default, the program you run under @value{GDBN} does input and output to
2204 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2205 to its own terminal modes to interact with you, but it records the terminal
2206 modes your program was using and switches back to them when you continue
2207 running your program.
2210 @kindex info terminal
2212 Displays information recorded by @value{GDBN} about the terminal modes your
2216 You can redirect your program's input and/or output using shell
2217 redirection with the @code{run} command. For example,
2224 starts your program, diverting its output to the file @file{outfile}.
2227 @cindex controlling terminal
2228 Another way to specify where your program should do input and output is
2229 with the @code{tty} command. This command accepts a file name as
2230 argument, and causes this file to be the default for future @code{run}
2231 commands. It also resets the controlling terminal for the child
2232 process, for future @code{run} commands. For example,
2239 directs that processes started with subsequent @code{run} commands
2240 default to do input and output on the terminal @file{/dev/ttyb} and have
2241 that as their controlling terminal.
2243 An explicit redirection in @code{run} overrides the @code{tty} command's
2244 effect on the input/output device, but not its effect on the controlling
2247 When you use the @code{tty} command or redirect input in the @code{run}
2248 command, only the input @emph{for your program} is affected. The input
2249 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2250 for @code{set inferior-tty}.
2252 @cindex inferior tty
2253 @cindex set inferior controlling terminal
2254 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2255 display the name of the terminal that will be used for future runs of your
2259 @item set inferior-tty /dev/ttyb
2260 @kindex set inferior-tty
2261 Set the tty for the program being debugged to /dev/ttyb.
2263 @item show inferior-tty
2264 @kindex show inferior-tty
2265 Show the current tty for the program being debugged.
2269 @section Debugging an Already-running Process
2274 @item attach @var{process-id}
2275 This command attaches to a running process---one that was started
2276 outside @value{GDBN}. (@code{info files} shows your active
2277 targets.) The command takes as argument a process ID. The usual way to
2278 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2279 or with the @samp{jobs -l} shell command.
2281 @code{attach} does not repeat if you press @key{RET} a second time after
2282 executing the command.
2285 To use @code{attach}, your program must be running in an environment
2286 which supports processes; for example, @code{attach} does not work for
2287 programs on bare-board targets that lack an operating system. You must
2288 also have permission to send the process a signal.
2290 When you use @code{attach}, the debugger finds the program running in
2291 the process first by looking in the current working directory, then (if
2292 the program is not found) by using the source file search path
2293 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2294 the @code{file} command to load the program. @xref{Files, ,Commands to
2297 The first thing @value{GDBN} does after arranging to debug the specified
2298 process is to stop it. You can examine and modify an attached process
2299 with all the @value{GDBN} commands that are ordinarily available when
2300 you start processes with @code{run}. You can insert breakpoints; you
2301 can step and continue; you can modify storage. If you would rather the
2302 process continue running, you may use the @code{continue} command after
2303 attaching @value{GDBN} to the process.
2308 When you have finished debugging the attached process, you can use the
2309 @code{detach} command to release it from @value{GDBN} control. Detaching
2310 the process continues its execution. After the @code{detach} command,
2311 that process and @value{GDBN} become completely independent once more, and you
2312 are ready to @code{attach} another process or start one with @code{run}.
2313 @code{detach} does not repeat if you press @key{RET} again after
2314 executing the command.
2317 If you exit @value{GDBN} while you have an attached process, you detach
2318 that process. If you use the @code{run} command, you kill that process.
2319 By default, @value{GDBN} asks for confirmation if you try to do either of these
2320 things; you can control whether or not you need to confirm by using the
2321 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2325 @section Killing the Child Process
2330 Kill the child process in which your program is running under @value{GDBN}.
2333 This command is useful if you wish to debug a core dump instead of a
2334 running process. @value{GDBN} ignores any core dump file while your program
2337 On some operating systems, a program cannot be executed outside @value{GDBN}
2338 while you have breakpoints set on it inside @value{GDBN}. You can use the
2339 @code{kill} command in this situation to permit running your program
2340 outside the debugger.
2342 The @code{kill} command is also useful if you wish to recompile and
2343 relink your program, since on many systems it is impossible to modify an
2344 executable file while it is running in a process. In this case, when you
2345 next type @code{run}, @value{GDBN} notices that the file has changed, and
2346 reads the symbol table again (while trying to preserve your current
2347 breakpoint settings).
2350 @section Debugging Multiple Inferiors
2352 Some @value{GDBN} targets are able to run multiple processes created
2353 from a single executable. This can happen, for instance, with an
2354 embedded system reporting back several processes via the remote
2358 @value{GDBN} represents the state of each program execution with an
2359 object called an @dfn{inferior}. An inferior typically corresponds to
2360 a process, but is more general and applies also to targets that do not
2361 have processes. Inferiors may be created before a process runs, and
2362 may (in future) be retained after a process exits. Each run of an
2363 executable creates a new inferior, as does each attachment to an
2364 existing process. Inferiors have unique identifiers that are
2365 different from process ids, and may optionally be named as well.
2366 Usually each inferior will also have its own distinct address space,
2367 although some embedded targets may have several inferiors running in
2368 different parts of a single space.
2370 Each inferior may in turn have multiple threads running in it.
2372 To find out what inferiors exist at any moment, use @code{info inferiors}:
2375 @kindex info inferiors
2376 @item info inferiors
2377 Print a list of all inferiors currently being managed by @value{GDBN}.
2379 @value{GDBN} displays for each inferior (in this order):
2383 the inferior number assigned by @value{GDBN}
2386 the target system's inferior identifier
2390 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2391 indicates the current inferior.
2395 @c end table here to get a little more width for example
2398 (@value{GDBP}) info inferiors
2404 To switch focus between inferiors, use the @code{inferior} command:
2407 @kindex inferior @var{infno}
2408 @item inferior @var{infno}
2409 Make inferior number @var{infno} the current inferior. The argument
2410 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2411 in the first field of the @samp{info inferiors} display.
2414 To quit debugging one of the inferiors, you can either detach from it
2415 by using the @w{@code{detach inferior}} command (allowing it to run
2416 independently), or kill it using the @w{@code{kill inferior}} command:
2419 @kindex detach inferior @var{infno}
2420 @item detach inferior @var{infno}
2421 Detach from the inferior identified by @value{GDBN} inferior number
2422 @var{infno}, and remove it from the inferior list.
2424 @kindex kill inferior @var{infno}
2425 @item kill inferior @var{infno}
2426 Kill the inferior identified by @value{GDBN} inferior number
2427 @var{infno}, and remove it from the inferior list.
2430 To be notified when inferiors are started or exit under @value{GDBN}'s
2431 control use @w{@code{set print inferior-events}}:
2434 @kindex set print inferior-events
2435 @cindex print messages on inferior start and exit
2436 @item set print inferior-events
2437 @itemx set print inferior-events on
2438 @itemx set print inferior-events off
2439 The @code{set print inferior-events} command allows you to enable or
2440 disable printing of messages when @value{GDBN} notices that new
2441 inferiors have started or that inferiors have exited or have been
2442 detached. By default, these messages will not be printed.
2444 @kindex show print inferior-events
2445 @item show print inferior-events
2446 Show whether messages will be printed when @value{GDBN} detects that
2447 inferiors have started, exited or have been detached.
2451 @section Debugging Programs with Multiple Threads
2453 @cindex threads of execution
2454 @cindex multiple threads
2455 @cindex switching threads
2456 In some operating systems, such as HP-UX and Solaris, a single program
2457 may have more than one @dfn{thread} of execution. The precise semantics
2458 of threads differ from one operating system to another, but in general
2459 the threads of a single program are akin to multiple processes---except
2460 that they share one address space (that is, they can all examine and
2461 modify the same variables). On the other hand, each thread has its own
2462 registers and execution stack, and perhaps private memory.
2464 @value{GDBN} provides these facilities for debugging multi-thread
2468 @item automatic notification of new threads
2469 @item @samp{thread @var{threadno}}, a command to switch among threads
2470 @item @samp{info threads}, a command to inquire about existing threads
2471 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2472 a command to apply a command to a list of threads
2473 @item thread-specific breakpoints
2474 @item @samp{set print thread-events}, which controls printing of
2475 messages on thread start and exit.
2476 @item @samp{set libthread-db-search-path @var{path}}, which lets
2477 the user specify which @code{libthread_db} to use if the default choice
2478 isn't compatible with the program.
2482 @emph{Warning:} These facilities are not yet available on every
2483 @value{GDBN} configuration where the operating system supports threads.
2484 If your @value{GDBN} does not support threads, these commands have no
2485 effect. For example, a system without thread support shows no output
2486 from @samp{info threads}, and always rejects the @code{thread} command,
2490 (@value{GDBP}) info threads
2491 (@value{GDBP}) thread 1
2492 Thread ID 1 not known. Use the "info threads" command to
2493 see the IDs of currently known threads.
2495 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2496 @c doesn't support threads"?
2499 @cindex focus of debugging
2500 @cindex current thread
2501 The @value{GDBN} thread debugging facility allows you to observe all
2502 threads while your program runs---but whenever @value{GDBN} takes
2503 control, one thread in particular is always the focus of debugging.
2504 This thread is called the @dfn{current thread}. Debugging commands show
2505 program information from the perspective of the current thread.
2507 @cindex @code{New} @var{systag} message
2508 @cindex thread identifier (system)
2509 @c FIXME-implementors!! It would be more helpful if the [New...] message
2510 @c included GDB's numeric thread handle, so you could just go to that
2511 @c thread without first checking `info threads'.
2512 Whenever @value{GDBN} detects a new thread in your program, it displays
2513 the target system's identification for the thread with a message in the
2514 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2515 whose form varies depending on the particular system. For example, on
2516 @sc{gnu}/Linux, you might see
2519 [New Thread 46912507313328 (LWP 25582)]
2523 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2524 the @var{systag} is simply something like @samp{process 368}, with no
2527 @c FIXME!! (1) Does the [New...] message appear even for the very first
2528 @c thread of a program, or does it only appear for the
2529 @c second---i.e.@: when it becomes obvious we have a multithread
2531 @c (2) *Is* there necessarily a first thread always? Or do some
2532 @c multithread systems permit starting a program with multiple
2533 @c threads ab initio?
2535 @cindex thread number
2536 @cindex thread identifier (GDB)
2537 For debugging purposes, @value{GDBN} associates its own thread
2538 number---always a single integer---with each thread in your program.
2541 @kindex info threads
2543 Display a summary of all threads currently in your
2544 program. @value{GDBN} displays for each thread (in this order):
2548 the thread number assigned by @value{GDBN}
2551 the target system's thread identifier (@var{systag})
2554 the current stack frame summary for that thread
2558 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2559 indicates the current thread.
2563 @c end table here to get a little more width for example
2566 (@value{GDBP}) info threads
2567 3 process 35 thread 27 0x34e5 in sigpause ()
2568 2 process 35 thread 23 0x34e5 in sigpause ()
2569 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2575 @cindex debugging multithreaded programs (on HP-UX)
2576 @cindex thread identifier (GDB), on HP-UX
2577 For debugging purposes, @value{GDBN} associates its own thread
2578 number---a small integer assigned in thread-creation order---with each
2579 thread in your program.
2581 @cindex @code{New} @var{systag} message, on HP-UX
2582 @cindex thread identifier (system), on HP-UX
2583 @c FIXME-implementors!! It would be more helpful if the [New...] message
2584 @c included GDB's numeric thread handle, so you could just go to that
2585 @c thread without first checking `info threads'.
2586 Whenever @value{GDBN} detects a new thread in your program, it displays
2587 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2588 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2589 whose form varies depending on the particular system. For example, on
2593 [New thread 2 (system thread 26594)]
2597 when @value{GDBN} notices a new thread.
2600 @kindex info threads (HP-UX)
2602 Display a summary of all threads currently in your
2603 program. @value{GDBN} displays for each thread (in this order):
2606 @item the thread number assigned by @value{GDBN}
2608 @item the target system's thread identifier (@var{systag})
2610 @item the current stack frame summary for that thread
2614 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2615 indicates the current thread.
2619 @c end table here to get a little more width for example
2622 (@value{GDBP}) info threads
2623 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2625 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2626 from /usr/lib/libc.2
2627 1 system thread 27905 0x7b003498 in _brk () \@*
2628 from /usr/lib/libc.2
2631 On Solaris, you can display more information about user threads with a
2632 Solaris-specific command:
2635 @item maint info sol-threads
2636 @kindex maint info sol-threads
2637 @cindex thread info (Solaris)
2638 Display info on Solaris user threads.
2642 @kindex thread @var{threadno}
2643 @item thread @var{threadno}
2644 Make thread number @var{threadno} the current thread. The command
2645 argument @var{threadno} is the internal @value{GDBN} thread number, as
2646 shown in the first field of the @samp{info threads} display.
2647 @value{GDBN} responds by displaying the system identifier of the thread
2648 you selected, and its current stack frame summary:
2651 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2652 (@value{GDBP}) thread 2
2653 [Switching to process 35 thread 23]
2654 0x34e5 in sigpause ()
2658 As with the @samp{[New @dots{}]} message, the form of the text after
2659 @samp{Switching to} depends on your system's conventions for identifying
2662 @kindex thread apply
2663 @cindex apply command to several threads
2664 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2665 The @code{thread apply} command allows you to apply the named
2666 @var{command} to one or more threads. Specify the numbers of the
2667 threads that you want affected with the command argument
2668 @var{threadno}. It can be a single thread number, one of the numbers
2669 shown in the first field of the @samp{info threads} display; or it
2670 could be a range of thread numbers, as in @code{2-4}. To apply a
2671 command to all threads, type @kbd{thread apply all @var{command}}.
2673 @kindex set print thread-events
2674 @cindex print messages on thread start and exit
2675 @item set print thread-events
2676 @itemx set print thread-events on
2677 @itemx set print thread-events off
2678 The @code{set print thread-events} command allows you to enable or
2679 disable printing of messages when @value{GDBN} notices that new threads have
2680 started or that threads have exited. By default, these messages will
2681 be printed if detection of these events is supported by the target.
2682 Note that these messages cannot be disabled on all targets.
2684 @kindex show print thread-events
2685 @item show print thread-events
2686 Show whether messages will be printed when @value{GDBN} detects that threads
2687 have started and exited.
2690 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2691 more information about how @value{GDBN} behaves when you stop and start
2692 programs with multiple threads.
2694 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2695 watchpoints in programs with multiple threads.
2698 @kindex set libthread-db-search-path
2699 @cindex search path for @code{libthread_db}
2700 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2701 If this variable is set, @var{path} is a colon-separated list of
2702 directories @value{GDBN} will use to search for @code{libthread_db}.
2703 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2706 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2707 @code{libthread_db} library to obtain information about threads in the
2708 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2709 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2710 with default system shared library directories, and finally the directory
2711 from which @code{libpthread} was loaded in the inferior process.
2713 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2714 @value{GDBN} attempts to initialize it with the current inferior process.
2715 If this initialization fails (which could happen because of a version
2716 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2717 will unload @code{libthread_db}, and continue with the next directory.
2718 If none of @code{libthread_db} libraries initialize successfully,
2719 @value{GDBN} will issue a warning and thread debugging will be disabled.
2721 Setting @code{libthread-db-search-path} is currently implemented
2722 only on some platforms.
2724 @kindex show libthread-db-search-path
2725 @item show libthread-db-search-path
2726 Display current libthread_db search path.
2730 @section Debugging Programs with Multiple Processes
2732 @cindex fork, debugging programs which call
2733 @cindex multiple processes
2734 @cindex processes, multiple
2735 On most systems, @value{GDBN} has no special support for debugging
2736 programs which create additional processes using the @code{fork}
2737 function. When a program forks, @value{GDBN} will continue to debug the
2738 parent process and the child process will run unimpeded. If you have
2739 set a breakpoint in any code which the child then executes, the child
2740 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2741 will cause it to terminate.
2743 However, if you want to debug the child process there is a workaround
2744 which isn't too painful. Put a call to @code{sleep} in the code which
2745 the child process executes after the fork. It may be useful to sleep
2746 only if a certain environment variable is set, or a certain file exists,
2747 so that the delay need not occur when you don't want to run @value{GDBN}
2748 on the child. While the child is sleeping, use the @code{ps} program to
2749 get its process ID. Then tell @value{GDBN} (a new invocation of
2750 @value{GDBN} if you are also debugging the parent process) to attach to
2751 the child process (@pxref{Attach}). From that point on you can debug
2752 the child process just like any other process which you attached to.
2754 On some systems, @value{GDBN} provides support for debugging programs that
2755 create additional processes using the @code{fork} or @code{vfork} functions.
2756 Currently, the only platforms with this feature are HP-UX (11.x and later
2757 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2759 By default, when a program forks, @value{GDBN} will continue to debug
2760 the parent process and the child process will run unimpeded.
2762 If you want to follow the child process instead of the parent process,
2763 use the command @w{@code{set follow-fork-mode}}.
2766 @kindex set follow-fork-mode
2767 @item set follow-fork-mode @var{mode}
2768 Set the debugger response to a program call of @code{fork} or
2769 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2770 process. The @var{mode} argument can be:
2774 The original process is debugged after a fork. The child process runs
2775 unimpeded. This is the default.
2778 The new process is debugged after a fork. The parent process runs
2783 @kindex show follow-fork-mode
2784 @item show follow-fork-mode
2785 Display the current debugger response to a @code{fork} or @code{vfork} call.
2788 @cindex debugging multiple processes
2789 On Linux, if you want to debug both the parent and child processes, use the
2790 command @w{@code{set detach-on-fork}}.
2793 @kindex set detach-on-fork
2794 @item set detach-on-fork @var{mode}
2795 Tells gdb whether to detach one of the processes after a fork, or
2796 retain debugger control over them both.
2800 The child process (or parent process, depending on the value of
2801 @code{follow-fork-mode}) will be detached and allowed to run
2802 independently. This is the default.
2805 Both processes will be held under the control of @value{GDBN}.
2806 One process (child or parent, depending on the value of
2807 @code{follow-fork-mode}) is debugged as usual, while the other
2812 @kindex show detach-on-fork
2813 @item show detach-on-fork
2814 Show whether detach-on-fork mode is on/off.
2817 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2818 will retain control of all forked processes (including nested forks).
2819 You can list the forked processes under the control of @value{GDBN} by
2820 using the @w{@code{info inferiors}} command, and switch from one fork
2821 to another by using the @code{inferior} command (@pxref{Inferiors,
2822 ,Debugging Multiple Inferiors}).
2824 To quit debugging one of the forked processes, you can either detach
2825 from it by using the @w{@code{detach inferior}} command (allowing it
2826 to run independently), or kill it using the @w{@code{kill inferior}}
2827 command. @xref{Inferiors, ,Debugging Multiple Inferiors}.
2829 If you ask to debug a child process and a @code{vfork} is followed by an
2830 @code{exec}, @value{GDBN} executes the new target up to the first
2831 breakpoint in the new target. If you have a breakpoint set on
2832 @code{main} in your original program, the breakpoint will also be set on
2833 the child process's @code{main}.
2835 On some systems, when a child process is spawned by @code{vfork}, you
2836 cannot debug the child or parent until an @code{exec} call completes.
2838 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2839 call executes, the new target restarts. To restart the parent process,
2840 use the @code{file} command with the parent executable name as its
2843 You can use the @code{catch} command to make @value{GDBN} stop whenever
2844 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2845 Catchpoints, ,Setting Catchpoints}.
2847 @node Checkpoint/Restart
2848 @section Setting a @emph{Bookmark} to Return to Later
2853 @cindex snapshot of a process
2854 @cindex rewind program state
2856 On certain operating systems@footnote{Currently, only
2857 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2858 program's state, called a @dfn{checkpoint}, and come back to it
2861 Returning to a checkpoint effectively undoes everything that has
2862 happened in the program since the @code{checkpoint} was saved. This
2863 includes changes in memory, registers, and even (within some limits)
2864 system state. Effectively, it is like going back in time to the
2865 moment when the checkpoint was saved.
2867 Thus, if you're stepping thru a program and you think you're
2868 getting close to the point where things go wrong, you can save
2869 a checkpoint. Then, if you accidentally go too far and miss
2870 the critical statement, instead of having to restart your program
2871 from the beginning, you can just go back to the checkpoint and
2872 start again from there.
2874 This can be especially useful if it takes a lot of time or
2875 steps to reach the point where you think the bug occurs.
2877 To use the @code{checkpoint}/@code{restart} method of debugging:
2882 Save a snapshot of the debugged program's current execution state.
2883 The @code{checkpoint} command takes no arguments, but each checkpoint
2884 is assigned a small integer id, similar to a breakpoint id.
2886 @kindex info checkpoints
2887 @item info checkpoints
2888 List the checkpoints that have been saved in the current debugging
2889 session. For each checkpoint, the following information will be
2896 @item Source line, or label
2899 @kindex restart @var{checkpoint-id}
2900 @item restart @var{checkpoint-id}
2901 Restore the program state that was saved as checkpoint number
2902 @var{checkpoint-id}. All program variables, registers, stack frames
2903 etc.@: will be returned to the values that they had when the checkpoint
2904 was saved. In essence, gdb will ``wind back the clock'' to the point
2905 in time when the checkpoint was saved.
2907 Note that breakpoints, @value{GDBN} variables, command history etc.
2908 are not affected by restoring a checkpoint. In general, a checkpoint
2909 only restores things that reside in the program being debugged, not in
2912 @kindex delete checkpoint @var{checkpoint-id}
2913 @item delete checkpoint @var{checkpoint-id}
2914 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2918 Returning to a previously saved checkpoint will restore the user state
2919 of the program being debugged, plus a significant subset of the system
2920 (OS) state, including file pointers. It won't ``un-write'' data from
2921 a file, but it will rewind the file pointer to the previous location,
2922 so that the previously written data can be overwritten. For files
2923 opened in read mode, the pointer will also be restored so that the
2924 previously read data can be read again.
2926 Of course, characters that have been sent to a printer (or other
2927 external device) cannot be ``snatched back'', and characters received
2928 from eg.@: a serial device can be removed from internal program buffers,
2929 but they cannot be ``pushed back'' into the serial pipeline, ready to
2930 be received again. Similarly, the actual contents of files that have
2931 been changed cannot be restored (at this time).
2933 However, within those constraints, you actually can ``rewind'' your
2934 program to a previously saved point in time, and begin debugging it
2935 again --- and you can change the course of events so as to debug a
2936 different execution path this time.
2938 @cindex checkpoints and process id
2939 Finally, there is one bit of internal program state that will be
2940 different when you return to a checkpoint --- the program's process
2941 id. Each checkpoint will have a unique process id (or @var{pid}),
2942 and each will be different from the program's original @var{pid}.
2943 If your program has saved a local copy of its process id, this could
2944 potentially pose a problem.
2946 @subsection A Non-obvious Benefit of Using Checkpoints
2948 On some systems such as @sc{gnu}/Linux, address space randomization
2949 is performed on new processes for security reasons. This makes it
2950 difficult or impossible to set a breakpoint, or watchpoint, on an
2951 absolute address if you have to restart the program, since the
2952 absolute location of a symbol will change from one execution to the
2955 A checkpoint, however, is an @emph{identical} copy of a process.
2956 Therefore if you create a checkpoint at (eg.@:) the start of main,
2957 and simply return to that checkpoint instead of restarting the
2958 process, you can avoid the effects of address randomization and
2959 your symbols will all stay in the same place.
2962 @chapter Stopping and Continuing
2964 The principal purposes of using a debugger are so that you can stop your
2965 program before it terminates; or so that, if your program runs into
2966 trouble, you can investigate and find out why.
2968 Inside @value{GDBN}, your program may stop for any of several reasons,
2969 such as a signal, a breakpoint, or reaching a new line after a
2970 @value{GDBN} command such as @code{step}. You may then examine and
2971 change variables, set new breakpoints or remove old ones, and then
2972 continue execution. Usually, the messages shown by @value{GDBN} provide
2973 ample explanation of the status of your program---but you can also
2974 explicitly request this information at any time.
2977 @kindex info program
2979 Display information about the status of your program: whether it is
2980 running or not, what process it is, and why it stopped.
2984 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2985 * Continuing and Stepping:: Resuming execution
2987 * Thread Stops:: Stopping and starting multi-thread programs
2991 @section Breakpoints, Watchpoints, and Catchpoints
2994 A @dfn{breakpoint} makes your program stop whenever a certain point in
2995 the program is reached. For each breakpoint, you can add conditions to
2996 control in finer detail whether your program stops. You can set
2997 breakpoints with the @code{break} command and its variants (@pxref{Set
2998 Breaks, ,Setting Breakpoints}), to specify the place where your program
2999 should stop by line number, function name or exact address in the
3002 On some systems, you can set breakpoints in shared libraries before
3003 the executable is run. There is a minor limitation on HP-UX systems:
3004 you must wait until the executable is run in order to set breakpoints
3005 in shared library routines that are not called directly by the program
3006 (for example, routines that are arguments in a @code{pthread_create}
3010 @cindex data breakpoints
3011 @cindex memory tracing
3012 @cindex breakpoint on memory address
3013 @cindex breakpoint on variable modification
3014 A @dfn{watchpoint} is a special breakpoint that stops your program
3015 when the value of an expression changes. The expression may be a value
3016 of a variable, or it could involve values of one or more variables
3017 combined by operators, such as @samp{a + b}. This is sometimes called
3018 @dfn{data breakpoints}. You must use a different command to set
3019 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3020 from that, you can manage a watchpoint like any other breakpoint: you
3021 enable, disable, and delete both breakpoints and watchpoints using the
3024 You can arrange to have values from your program displayed automatically
3025 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3029 @cindex breakpoint on events
3030 A @dfn{catchpoint} is another special breakpoint that stops your program
3031 when a certain kind of event occurs, such as the throwing of a C@t{++}
3032 exception or the loading of a library. As with watchpoints, you use a
3033 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3034 Catchpoints}), but aside from that, you can manage a catchpoint like any
3035 other breakpoint. (To stop when your program receives a signal, use the
3036 @code{handle} command; see @ref{Signals, ,Signals}.)
3038 @cindex breakpoint numbers
3039 @cindex numbers for breakpoints
3040 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3041 catchpoint when you create it; these numbers are successive integers
3042 starting with one. In many of the commands for controlling various
3043 features of breakpoints you use the breakpoint number to say which
3044 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3045 @dfn{disabled}; if disabled, it has no effect on your program until you
3048 @cindex breakpoint ranges
3049 @cindex ranges of breakpoints
3050 Some @value{GDBN} commands accept a range of breakpoints on which to
3051 operate. A breakpoint range is either a single breakpoint number, like
3052 @samp{5}, or two such numbers, in increasing order, separated by a
3053 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3054 all breakpoints in that range are operated on.
3057 * Set Breaks:: Setting breakpoints
3058 * Set Watchpoints:: Setting watchpoints
3059 * Set Catchpoints:: Setting catchpoints
3060 * Delete Breaks:: Deleting breakpoints
3061 * Disabling:: Disabling breakpoints
3062 * Conditions:: Break conditions
3063 * Break Commands:: Breakpoint command lists
3064 * Error in Breakpoints:: ``Cannot insert breakpoints''
3065 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3069 @subsection Setting Breakpoints
3071 @c FIXME LMB what does GDB do if no code on line of breakpt?
3072 @c consider in particular declaration with/without initialization.
3074 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3077 @kindex b @r{(@code{break})}
3078 @vindex $bpnum@r{, convenience variable}
3079 @cindex latest breakpoint
3080 Breakpoints are set with the @code{break} command (abbreviated
3081 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3082 number of the breakpoint you've set most recently; see @ref{Convenience
3083 Vars,, Convenience Variables}, for a discussion of what you can do with
3084 convenience variables.
3087 @item break @var{location}
3088 Set a breakpoint at the given @var{location}, which can specify a
3089 function name, a line number, or an address of an instruction.
3090 (@xref{Specify Location}, for a list of all the possible ways to
3091 specify a @var{location}.) The breakpoint will stop your program just
3092 before it executes any of the code in the specified @var{location}.
3094 When using source languages that permit overloading of symbols, such as
3095 C@t{++}, a function name may refer to more than one possible place to break.
3096 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3099 It is also possible to insert a breakpoint that will stop the program
3100 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3101 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3104 When called without any arguments, @code{break} sets a breakpoint at
3105 the next instruction to be executed in the selected stack frame
3106 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3107 innermost, this makes your program stop as soon as control
3108 returns to that frame. This is similar to the effect of a
3109 @code{finish} command in the frame inside the selected frame---except
3110 that @code{finish} does not leave an active breakpoint. If you use
3111 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3112 the next time it reaches the current location; this may be useful
3115 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3116 least one instruction has been executed. If it did not do this, you
3117 would be unable to proceed past a breakpoint without first disabling the
3118 breakpoint. This rule applies whether or not the breakpoint already
3119 existed when your program stopped.
3121 @item break @dots{} if @var{cond}
3122 Set a breakpoint with condition @var{cond}; evaluate the expression
3123 @var{cond} each time the breakpoint is reached, and stop only if the
3124 value is nonzero---that is, if @var{cond} evaluates as true.
3125 @samp{@dots{}} stands for one of the possible arguments described
3126 above (or no argument) specifying where to break. @xref{Conditions,
3127 ,Break Conditions}, for more information on breakpoint conditions.
3130 @item tbreak @var{args}
3131 Set a breakpoint enabled only for one stop. @var{args} are the
3132 same as for the @code{break} command, and the breakpoint is set in the same
3133 way, but the breakpoint is automatically deleted after the first time your
3134 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3137 @cindex hardware breakpoints
3138 @item hbreak @var{args}
3139 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3140 @code{break} command and the breakpoint is set in the same way, but the
3141 breakpoint requires hardware support and some target hardware may not
3142 have this support. The main purpose of this is EPROM/ROM code
3143 debugging, so you can set a breakpoint at an instruction without
3144 changing the instruction. This can be used with the new trap-generation
3145 provided by SPARClite DSU and most x86-based targets. These targets
3146 will generate traps when a program accesses some data or instruction
3147 address that is assigned to the debug registers. However the hardware
3148 breakpoint registers can take a limited number of breakpoints. For
3149 example, on the DSU, only two data breakpoints can be set at a time, and
3150 @value{GDBN} will reject this command if more than two are used. Delete
3151 or disable unused hardware breakpoints before setting new ones
3152 (@pxref{Disabling, ,Disabling Breakpoints}).
3153 @xref{Conditions, ,Break Conditions}.
3154 For remote targets, you can restrict the number of hardware
3155 breakpoints @value{GDBN} will use, see @ref{set remote
3156 hardware-breakpoint-limit}.
3159 @item thbreak @var{args}
3160 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3161 are the same as for the @code{hbreak} command and the breakpoint is set in
3162 the same way. However, like the @code{tbreak} command,
3163 the breakpoint is automatically deleted after the
3164 first time your program stops there. Also, like the @code{hbreak}
3165 command, the breakpoint requires hardware support and some target hardware
3166 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3167 See also @ref{Conditions, ,Break Conditions}.
3170 @cindex regular expression
3171 @cindex breakpoints in functions matching a regexp
3172 @cindex set breakpoints in many functions
3173 @item rbreak @var{regex}
3174 Set breakpoints on all functions matching the regular expression
3175 @var{regex}. This command sets an unconditional breakpoint on all
3176 matches, printing a list of all breakpoints it set. Once these
3177 breakpoints are set, they are treated just like the breakpoints set with
3178 the @code{break} command. You can delete them, disable them, or make
3179 them conditional the same way as any other breakpoint.
3181 The syntax of the regular expression is the standard one used with tools
3182 like @file{grep}. Note that this is different from the syntax used by
3183 shells, so for instance @code{foo*} matches all functions that include
3184 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3185 @code{.*} leading and trailing the regular expression you supply, so to
3186 match only functions that begin with @code{foo}, use @code{^foo}.
3188 @cindex non-member C@t{++} functions, set breakpoint in
3189 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3190 breakpoints on overloaded functions that are not members of any special
3193 @cindex set breakpoints on all functions
3194 The @code{rbreak} command can be used to set breakpoints in
3195 @strong{all} the functions in a program, like this:
3198 (@value{GDBP}) rbreak .
3201 @kindex info breakpoints
3202 @cindex @code{$_} and @code{info breakpoints}
3203 @item info breakpoints @r{[}@var{n}@r{]}
3204 @itemx info break @r{[}@var{n}@r{]}
3205 @itemx info watchpoints @r{[}@var{n}@r{]}
3206 Print a table of all breakpoints, watchpoints, and catchpoints set and
3207 not deleted. Optional argument @var{n} means print information only
3208 about the specified breakpoint (or watchpoint or catchpoint). For
3209 each breakpoint, following columns are printed:
3212 @item Breakpoint Numbers
3214 Breakpoint, watchpoint, or catchpoint.
3216 Whether the breakpoint is marked to be disabled or deleted when hit.
3217 @item Enabled or Disabled
3218 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3219 that are not enabled.
3221 Where the breakpoint is in your program, as a memory address. For a
3222 pending breakpoint whose address is not yet known, this field will
3223 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3224 library that has the symbol or line referred by breakpoint is loaded.
3225 See below for details. A breakpoint with several locations will
3226 have @samp{<MULTIPLE>} in this field---see below for details.
3228 Where the breakpoint is in the source for your program, as a file and
3229 line number. For a pending breakpoint, the original string passed to
3230 the breakpoint command will be listed as it cannot be resolved until
3231 the appropriate shared library is loaded in the future.
3235 If a breakpoint is conditional, @code{info break} shows the condition on
3236 the line following the affected breakpoint; breakpoint commands, if any,
3237 are listed after that. A pending breakpoint is allowed to have a condition
3238 specified for it. The condition is not parsed for validity until a shared
3239 library is loaded that allows the pending breakpoint to resolve to a
3243 @code{info break} with a breakpoint
3244 number @var{n} as argument lists only that breakpoint. The
3245 convenience variable @code{$_} and the default examining-address for
3246 the @code{x} command are set to the address of the last breakpoint
3247 listed (@pxref{Memory, ,Examining Memory}).
3250 @code{info break} displays a count of the number of times the breakpoint
3251 has been hit. This is especially useful in conjunction with the
3252 @code{ignore} command. You can ignore a large number of breakpoint
3253 hits, look at the breakpoint info to see how many times the breakpoint
3254 was hit, and then run again, ignoring one less than that number. This
3255 will get you quickly to the last hit of that breakpoint.
3258 @value{GDBN} allows you to set any number of breakpoints at the same place in
3259 your program. There is nothing silly or meaningless about this. When
3260 the breakpoints are conditional, this is even useful
3261 (@pxref{Conditions, ,Break Conditions}).
3263 @cindex multiple locations, breakpoints
3264 @cindex breakpoints, multiple locations
3265 It is possible that a breakpoint corresponds to several locations
3266 in your program. Examples of this situation are:
3270 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3271 instances of the function body, used in different cases.
3274 For a C@t{++} template function, a given line in the function can
3275 correspond to any number of instantiations.
3278 For an inlined function, a given source line can correspond to
3279 several places where that function is inlined.
3282 In all those cases, @value{GDBN} will insert a breakpoint at all
3283 the relevant locations@footnote{
3284 As of this writing, multiple-location breakpoints work only if there's
3285 line number information for all the locations. This means that they
3286 will generally not work in system libraries, unless you have debug
3287 info with line numbers for them.}.
3289 A breakpoint with multiple locations is displayed in the breakpoint
3290 table using several rows---one header row, followed by one row for
3291 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3292 address column. The rows for individual locations contain the actual
3293 addresses for locations, and show the functions to which those
3294 locations belong. The number column for a location is of the form
3295 @var{breakpoint-number}.@var{location-number}.
3300 Num Type Disp Enb Address What
3301 1 breakpoint keep y <MULTIPLE>
3303 breakpoint already hit 1 time
3304 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3305 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3308 Each location can be individually enabled or disabled by passing
3309 @var{breakpoint-number}.@var{location-number} as argument to the
3310 @code{enable} and @code{disable} commands. Note that you cannot
3311 delete the individual locations from the list, you can only delete the
3312 entire list of locations that belong to their parent breakpoint (with
3313 the @kbd{delete @var{num}} command, where @var{num} is the number of
3314 the parent breakpoint, 1 in the above example). Disabling or enabling
3315 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3316 that belong to that breakpoint.
3318 @cindex pending breakpoints
3319 It's quite common to have a breakpoint inside a shared library.
3320 Shared libraries can be loaded and unloaded explicitly,
3321 and possibly repeatedly, as the program is executed. To support
3322 this use case, @value{GDBN} updates breakpoint locations whenever
3323 any shared library is loaded or unloaded. Typically, you would
3324 set a breakpoint in a shared library at the beginning of your
3325 debugging session, when the library is not loaded, and when the
3326 symbols from the library are not available. When you try to set
3327 breakpoint, @value{GDBN} will ask you if you want to set
3328 a so called @dfn{pending breakpoint}---breakpoint whose address
3329 is not yet resolved.
3331 After the program is run, whenever a new shared library is loaded,
3332 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3333 shared library contains the symbol or line referred to by some
3334 pending breakpoint, that breakpoint is resolved and becomes an
3335 ordinary breakpoint. When a library is unloaded, all breakpoints
3336 that refer to its symbols or source lines become pending again.
3338 This logic works for breakpoints with multiple locations, too. For
3339 example, if you have a breakpoint in a C@t{++} template function, and
3340 a newly loaded shared library has an instantiation of that template,
3341 a new location is added to the list of locations for the breakpoint.
3343 Except for having unresolved address, pending breakpoints do not
3344 differ from regular breakpoints. You can set conditions or commands,
3345 enable and disable them and perform other breakpoint operations.
3347 @value{GDBN} provides some additional commands for controlling what
3348 happens when the @samp{break} command cannot resolve breakpoint
3349 address specification to an address:
3351 @kindex set breakpoint pending
3352 @kindex show breakpoint pending
3354 @item set breakpoint pending auto
3355 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3356 location, it queries you whether a pending breakpoint should be created.
3358 @item set breakpoint pending on
3359 This indicates that an unrecognized breakpoint location should automatically
3360 result in a pending breakpoint being created.
3362 @item set breakpoint pending off
3363 This indicates that pending breakpoints are not to be created. Any
3364 unrecognized breakpoint location results in an error. This setting does
3365 not affect any pending breakpoints previously created.
3367 @item show breakpoint pending
3368 Show the current behavior setting for creating pending breakpoints.
3371 The settings above only affect the @code{break} command and its
3372 variants. Once breakpoint is set, it will be automatically updated
3373 as shared libraries are loaded and unloaded.
3375 @cindex automatic hardware breakpoints
3376 For some targets, @value{GDBN} can automatically decide if hardware or
3377 software breakpoints should be used, depending on whether the
3378 breakpoint address is read-only or read-write. This applies to
3379 breakpoints set with the @code{break} command as well as to internal
3380 breakpoints set by commands like @code{next} and @code{finish}. For
3381 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3384 You can control this automatic behaviour with the following commands::
3386 @kindex set breakpoint auto-hw
3387 @kindex show breakpoint auto-hw
3389 @item set breakpoint auto-hw on
3390 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3391 will try to use the target memory map to decide if software or hardware
3392 breakpoint must be used.
3394 @item set breakpoint auto-hw off
3395 This indicates @value{GDBN} should not automatically select breakpoint
3396 type. If the target provides a memory map, @value{GDBN} will warn when
3397 trying to set software breakpoint at a read-only address.
3400 @value{GDBN} normally implements breakpoints by replacing the program code
3401 at the breakpoint address with a special instruction, which, when
3402 executed, given control to the debugger. By default, the program
3403 code is so modified only when the program is resumed. As soon as
3404 the program stops, @value{GDBN} restores the original instructions. This
3405 behaviour guards against leaving breakpoints inserted in the
3406 target should gdb abrubptly disconnect. However, with slow remote
3407 targets, inserting and removing breakpoint can reduce the performance.
3408 This behavior can be controlled with the following commands::
3410 @kindex set breakpoint always-inserted
3411 @kindex show breakpoint always-inserted
3413 @item set breakpoint always-inserted off
3414 All breakpoints, including newly added by the user, are inserted in
3415 the target only when the target is resumed. All breakpoints are
3416 removed from the target when it stops.
3418 @item set breakpoint always-inserted on
3419 Causes all breakpoints to be inserted in the target at all times. If
3420 the user adds a new breakpoint, or changes an existing breakpoint, the
3421 breakpoints in the target are updated immediately. A breakpoint is
3422 removed from the target only when breakpoint itself is removed.
3424 @cindex non-stop mode, and @code{breakpoint always-inserted}
3425 @item set breakpoint always-inserted auto
3426 This is the default mode. If @value{GDBN} is controlling the inferior
3427 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3428 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3429 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3430 @code{breakpoint always-inserted} mode is off.
3433 @cindex negative breakpoint numbers
3434 @cindex internal @value{GDBN} breakpoints
3435 @value{GDBN} itself sometimes sets breakpoints in your program for
3436 special purposes, such as proper handling of @code{longjmp} (in C
3437 programs). These internal breakpoints are assigned negative numbers,
3438 starting with @code{-1}; @samp{info breakpoints} does not display them.
3439 You can see these breakpoints with the @value{GDBN} maintenance command
3440 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3443 @node Set Watchpoints
3444 @subsection Setting Watchpoints
3446 @cindex setting watchpoints
3447 You can use a watchpoint to stop execution whenever the value of an
3448 expression changes, without having to predict a particular place where
3449 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3450 The expression may be as simple as the value of a single variable, or
3451 as complex as many variables combined by operators. Examples include:
3455 A reference to the value of a single variable.
3458 An address cast to an appropriate data type. For example,
3459 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3460 address (assuming an @code{int} occupies 4 bytes).
3463 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3464 expression can use any operators valid in the program's native
3465 language (@pxref{Languages}).
3468 You can set a watchpoint on an expression even if the expression can
3469 not be evaluated yet. For instance, you can set a watchpoint on
3470 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3471 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3472 the expression produces a valid value. If the expression becomes
3473 valid in some other way than changing a variable (e.g.@: if the memory
3474 pointed to by @samp{*global_ptr} becomes readable as the result of a
3475 @code{malloc} call), @value{GDBN} may not stop until the next time
3476 the expression changes.
3478 @cindex software watchpoints
3479 @cindex hardware watchpoints
3480 Depending on your system, watchpoints may be implemented in software or
3481 hardware. @value{GDBN} does software watchpointing by single-stepping your
3482 program and testing the variable's value each time, which is hundreds of
3483 times slower than normal execution. (But this may still be worth it, to
3484 catch errors where you have no clue what part of your program is the
3487 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3488 x86-based targets, @value{GDBN} includes support for hardware
3489 watchpoints, which do not slow down the running of your program.
3493 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3494 Set a watchpoint for an expression. @value{GDBN} will break when the
3495 expression @var{expr} is written into by the program and its value
3496 changes. The simplest (and the most popular) use of this command is
3497 to watch the value of a single variable:
3500 (@value{GDBP}) watch foo
3503 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3504 clause, @value{GDBN} breaks only when the thread identified by
3505 @var{threadnum} changes the value of @var{expr}. If any other threads
3506 change the value of @var{expr}, @value{GDBN} will not break. Note
3507 that watchpoints restricted to a single thread in this way only work
3508 with Hardware Watchpoints.
3511 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3512 Set a watchpoint that will break when the value of @var{expr} is read
3516 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3517 Set a watchpoint that will break when @var{expr} is either read from
3518 or written into by the program.
3520 @kindex info watchpoints @r{[}@var{n}@r{]}
3521 @item info watchpoints
3522 This command prints a list of watchpoints, breakpoints, and catchpoints;
3523 it is the same as @code{info break} (@pxref{Set Breaks}).
3526 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3527 watchpoints execute very quickly, and the debugger reports a change in
3528 value at the exact instruction where the change occurs. If @value{GDBN}
3529 cannot set a hardware watchpoint, it sets a software watchpoint, which
3530 executes more slowly and reports the change in value at the next
3531 @emph{statement}, not the instruction, after the change occurs.
3533 @cindex use only software watchpoints
3534 You can force @value{GDBN} to use only software watchpoints with the
3535 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3536 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3537 the underlying system supports them. (Note that hardware-assisted
3538 watchpoints that were set @emph{before} setting
3539 @code{can-use-hw-watchpoints} to zero will still use the hardware
3540 mechanism of watching expression values.)
3543 @item set can-use-hw-watchpoints
3544 @kindex set can-use-hw-watchpoints
3545 Set whether or not to use hardware watchpoints.
3547 @item show can-use-hw-watchpoints
3548 @kindex show can-use-hw-watchpoints
3549 Show the current mode of using hardware watchpoints.
3552 For remote targets, you can restrict the number of hardware
3553 watchpoints @value{GDBN} will use, see @ref{set remote
3554 hardware-breakpoint-limit}.
3556 When you issue the @code{watch} command, @value{GDBN} reports
3559 Hardware watchpoint @var{num}: @var{expr}
3563 if it was able to set a hardware watchpoint.
3565 Currently, the @code{awatch} and @code{rwatch} commands can only set
3566 hardware watchpoints, because accesses to data that don't change the
3567 value of the watched expression cannot be detected without examining
3568 every instruction as it is being executed, and @value{GDBN} does not do
3569 that currently. If @value{GDBN} finds that it is unable to set a
3570 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3571 will print a message like this:
3574 Expression cannot be implemented with read/access watchpoint.
3577 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3578 data type of the watched expression is wider than what a hardware
3579 watchpoint on the target machine can handle. For example, some systems
3580 can only watch regions that are up to 4 bytes wide; on such systems you
3581 cannot set hardware watchpoints for an expression that yields a
3582 double-precision floating-point number (which is typically 8 bytes
3583 wide). As a work-around, it might be possible to break the large region
3584 into a series of smaller ones and watch them with separate watchpoints.
3586 If you set too many hardware watchpoints, @value{GDBN} might be unable
3587 to insert all of them when you resume the execution of your program.
3588 Since the precise number of active watchpoints is unknown until such
3589 time as the program is about to be resumed, @value{GDBN} might not be
3590 able to warn you about this when you set the watchpoints, and the
3591 warning will be printed only when the program is resumed:
3594 Hardware watchpoint @var{num}: Could not insert watchpoint
3598 If this happens, delete or disable some of the watchpoints.
3600 Watching complex expressions that reference many variables can also
3601 exhaust the resources available for hardware-assisted watchpoints.
3602 That's because @value{GDBN} needs to watch every variable in the
3603 expression with separately allocated resources.
3605 If you call a function interactively using @code{print} or @code{call},
3606 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3607 kind of breakpoint or the call completes.
3609 @value{GDBN} automatically deletes watchpoints that watch local
3610 (automatic) variables, or expressions that involve such variables, when
3611 they go out of scope, that is, when the execution leaves the block in
3612 which these variables were defined. In particular, when the program
3613 being debugged terminates, @emph{all} local variables go out of scope,
3614 and so only watchpoints that watch global variables remain set. If you
3615 rerun the program, you will need to set all such watchpoints again. One
3616 way of doing that would be to set a code breakpoint at the entry to the
3617 @code{main} function and when it breaks, set all the watchpoints.
3619 @cindex watchpoints and threads
3620 @cindex threads and watchpoints
3621 In multi-threaded programs, watchpoints will detect changes to the
3622 watched expression from every thread.
3625 @emph{Warning:} In multi-threaded programs, software watchpoints
3626 have only limited usefulness. If @value{GDBN} creates a software
3627 watchpoint, it can only watch the value of an expression @emph{in a
3628 single thread}. If you are confident that the expression can only
3629 change due to the current thread's activity (and if you are also
3630 confident that no other thread can become current), then you can use
3631 software watchpoints as usual. However, @value{GDBN} may not notice
3632 when a non-current thread's activity changes the expression. (Hardware
3633 watchpoints, in contrast, watch an expression in all threads.)
3636 @xref{set remote hardware-watchpoint-limit}.
3638 @node Set Catchpoints
3639 @subsection Setting Catchpoints
3640 @cindex catchpoints, setting
3641 @cindex exception handlers
3642 @cindex event handling
3644 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3645 kinds of program events, such as C@t{++} exceptions or the loading of a
3646 shared library. Use the @code{catch} command to set a catchpoint.
3650 @item catch @var{event}
3651 Stop when @var{event} occurs. @var{event} can be any of the following:
3654 @cindex stop on C@t{++} exceptions
3655 The throwing of a C@t{++} exception.
3658 The catching of a C@t{++} exception.
3661 @cindex Ada exception catching
3662 @cindex catch Ada exceptions
3663 An Ada exception being raised. If an exception name is specified
3664 at the end of the command (eg @code{catch exception Program_Error}),
3665 the debugger will stop only when this specific exception is raised.
3666 Otherwise, the debugger stops execution when any Ada exception is raised.
3668 When inserting an exception catchpoint on a user-defined exception whose
3669 name is identical to one of the exceptions defined by the language, the
3670 fully qualified name must be used as the exception name. Otherwise,
3671 @value{GDBN} will assume that it should stop on the pre-defined exception
3672 rather than the user-defined one. For instance, assuming an exception
3673 called @code{Constraint_Error} is defined in package @code{Pck}, then
3674 the command to use to catch such exceptions is @kbd{catch exception
3675 Pck.Constraint_Error}.
3677 @item exception unhandled
3678 An exception that was raised but is not handled by the program.
3681 A failed Ada assertion.
3684 @cindex break on fork/exec
3685 A call to @code{exec}. This is currently only available for HP-UX
3689 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @r{...}
3690 @cindex break on a system call.
3691 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3692 syscall is a mechanism for application programs to request a service
3693 from the operating system (OS) or one of the OS system services.
3694 @value{GDBN} can catch some or all of the syscalls issued by the
3695 debuggee, and show the related information for each syscall. If no
3696 argument is specified, calls to and returns from all system calls
3699 @var{name} can be any system call name that is valid for the
3700 underlying OS. Just what syscalls are valid depends on the OS. On
3701 GNU and Unix systems, you can find the full list of valid syscall
3702 names on @file{/usr/include/asm/unistd.h}.
3704 @c For MS-Windows, the syscall names and the corresponding numbers
3705 @c can be found, e.g., on this URL:
3706 @c http://www.metasploit.com/users/opcode/syscalls.html
3707 @c but we don't support Windows syscalls yet.
3709 Normally, @value{GDBN} knows in advance which syscalls are valid for
3710 each OS, so you can use the @value{GDBN} command-line completion
3711 facilities (@pxref{Completion,, command completion}) to list the
3714 You may also specify the system call numerically. A syscall's
3715 number is the value passed to the OS's syscall dispatcher to
3716 identify the requested service. When you specify the syscall by its
3717 name, @value{GDBN} uses its database of syscalls to convert the name
3718 into the corresponding numeric code, but using the number directly
3719 may be useful if @value{GDBN}'s database does not have the complete
3720 list of syscalls on your system (e.g., because @value{GDBN} lags
3721 behind the OS upgrades).
3723 The example below illustrates how this command works if you don't provide
3727 (@value{GDBP}) catch syscall
3728 Catchpoint 1 (syscall)
3730 Starting program: /tmp/catch-syscall
3732 Catchpoint 1 (call to syscall 'close'), \
3733 0xffffe424 in __kernel_vsyscall ()
3737 Catchpoint 1 (returned from syscall 'close'), \
3738 0xffffe424 in __kernel_vsyscall ()
3742 Here is an example of catching a system call by name:
3745 (@value{GDBP}) catch syscall chroot
3746 Catchpoint 1 (syscall 'chroot' [61])
3748 Starting program: /tmp/catch-syscall
3750 Catchpoint 1 (call to syscall 'chroot'), \
3751 0xffffe424 in __kernel_vsyscall ()
3755 Catchpoint 1 (returned from syscall 'chroot'), \
3756 0xffffe424 in __kernel_vsyscall ()
3760 An example of specifying a system call numerically. In the case
3761 below, the syscall number has a corresponding entry in the XML
3762 file, so @value{GDBN} finds its name and prints it:
3765 (@value{GDBP}) catch syscall 252
3766 Catchpoint 1 (syscall(s) 'exit_group')
3768 Starting program: /tmp/catch-syscall
3770 Catchpoint 1 (call to syscall 'exit_group'), \
3771 0xffffe424 in __kernel_vsyscall ()
3775 Program exited normally.
3779 However, there can be situations when there is no corresponding name
3780 in XML file for that syscall number. In this case, @value{GDBN} prints
3781 a warning message saying that it was not able to find the syscall name,
3782 but the catchpoint will be set anyway. See the example below:
3785 (@value{GDBP}) catch syscall 764
3786 warning: The number '764' does not represent a known syscall.
3787 Catchpoint 2 (syscall 764)
3791 If you configure @value{GDBN} using the @samp{--without-expat} option,
3792 it will not be able to display syscall names. Also, if your
3793 architecture does not have an XML file describing its system calls,
3794 you will not be able to see the syscall names. It is important to
3795 notice that these two features are used for accessing the syscall
3796 name database. In either case, you will see a warning like this:
3799 (@value{GDBP}) catch syscall
3800 warning: Could not open "syscalls/i386-linux.xml"
3801 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
3802 GDB will not be able to display syscall names.
3803 Catchpoint 1 (syscall)
3807 Of course, the file name will change depending on your architecture and system.
3809 Still using the example above, you can also try to catch a syscall by its
3810 number. In this case, you would see something like:
3813 (@value{GDBP}) catch syscall 252
3814 Catchpoint 1 (syscall(s) 252)
3817 Again, in this case @value{GDBN} would not be able to display syscall's names.
3820 A call to @code{fork}. This is currently only available for HP-UX
3824 A call to @code{vfork}. This is currently only available for HP-UX
3829 @item tcatch @var{event}
3830 Set a catchpoint that is enabled only for one stop. The catchpoint is
3831 automatically deleted after the first time the event is caught.
3835 Use the @code{info break} command to list the current catchpoints.
3837 There are currently some limitations to C@t{++} exception handling
3838 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3842 If you call a function interactively, @value{GDBN} normally returns
3843 control to you when the function has finished executing. If the call
3844 raises an exception, however, the call may bypass the mechanism that
3845 returns control to you and cause your program either to abort or to
3846 simply continue running until it hits a breakpoint, catches a signal
3847 that @value{GDBN} is listening for, or exits. This is the case even if
3848 you set a catchpoint for the exception; catchpoints on exceptions are
3849 disabled within interactive calls.
3852 You cannot raise an exception interactively.
3855 You cannot install an exception handler interactively.
3858 @cindex raise exceptions
3859 Sometimes @code{catch} is not the best way to debug exception handling:
3860 if you need to know exactly where an exception is raised, it is better to
3861 stop @emph{before} the exception handler is called, since that way you
3862 can see the stack before any unwinding takes place. If you set a
3863 breakpoint in an exception handler instead, it may not be easy to find
3864 out where the exception was raised.
3866 To stop just before an exception handler is called, you need some
3867 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3868 raised by calling a library function named @code{__raise_exception}
3869 which has the following ANSI C interface:
3872 /* @var{addr} is where the exception identifier is stored.
3873 @var{id} is the exception identifier. */
3874 void __raise_exception (void **addr, void *id);
3878 To make the debugger catch all exceptions before any stack
3879 unwinding takes place, set a breakpoint on @code{__raise_exception}
3880 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3882 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3883 that depends on the value of @var{id}, you can stop your program when
3884 a specific exception is raised. You can use multiple conditional
3885 breakpoints to stop your program when any of a number of exceptions are
3890 @subsection Deleting Breakpoints
3892 @cindex clearing breakpoints, watchpoints, catchpoints
3893 @cindex deleting breakpoints, watchpoints, catchpoints
3894 It is often necessary to eliminate a breakpoint, watchpoint, or
3895 catchpoint once it has done its job and you no longer want your program
3896 to stop there. This is called @dfn{deleting} the breakpoint. A
3897 breakpoint that has been deleted no longer exists; it is forgotten.
3899 With the @code{clear} command you can delete breakpoints according to
3900 where they are in your program. With the @code{delete} command you can
3901 delete individual breakpoints, watchpoints, or catchpoints by specifying
3902 their breakpoint numbers.
3904 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3905 automatically ignores breakpoints on the first instruction to be executed
3906 when you continue execution without changing the execution address.
3911 Delete any breakpoints at the next instruction to be executed in the
3912 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3913 the innermost frame is selected, this is a good way to delete a
3914 breakpoint where your program just stopped.
3916 @item clear @var{location}
3917 Delete any breakpoints set at the specified @var{location}.
3918 @xref{Specify Location}, for the various forms of @var{location}; the
3919 most useful ones are listed below:
3922 @item clear @var{function}
3923 @itemx clear @var{filename}:@var{function}
3924 Delete any breakpoints set at entry to the named @var{function}.
3926 @item clear @var{linenum}
3927 @itemx clear @var{filename}:@var{linenum}
3928 Delete any breakpoints set at or within the code of the specified
3929 @var{linenum} of the specified @var{filename}.
3932 @cindex delete breakpoints
3934 @kindex d @r{(@code{delete})}
3935 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3936 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3937 ranges specified as arguments. If no argument is specified, delete all
3938 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3939 confirm off}). You can abbreviate this command as @code{d}.
3943 @subsection Disabling Breakpoints
3945 @cindex enable/disable a breakpoint
3946 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3947 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3948 it had been deleted, but remembers the information on the breakpoint so
3949 that you can @dfn{enable} it again later.
3951 You disable and enable breakpoints, watchpoints, and catchpoints with
3952 the @code{enable} and @code{disable} commands, optionally specifying one
3953 or more breakpoint numbers as arguments. Use @code{info break} or
3954 @code{info watch} to print a list of breakpoints, watchpoints, and
3955 catchpoints if you do not know which numbers to use.
3957 Disabling and enabling a breakpoint that has multiple locations
3958 affects all of its locations.
3960 A breakpoint, watchpoint, or catchpoint can have any of four different
3961 states of enablement:
3965 Enabled. The breakpoint stops your program. A breakpoint set
3966 with the @code{break} command starts out in this state.
3968 Disabled. The breakpoint has no effect on your program.
3970 Enabled once. The breakpoint stops your program, but then becomes
3973 Enabled for deletion. The breakpoint stops your program, but
3974 immediately after it does so it is deleted permanently. A breakpoint
3975 set with the @code{tbreak} command starts out in this state.
3978 You can use the following commands to enable or disable breakpoints,
3979 watchpoints, and catchpoints:
3983 @kindex dis @r{(@code{disable})}
3984 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3985 Disable the specified breakpoints---or all breakpoints, if none are
3986 listed. A disabled breakpoint has no effect but is not forgotten. All
3987 options such as ignore-counts, conditions and commands are remembered in
3988 case the breakpoint is enabled again later. You may abbreviate
3989 @code{disable} as @code{dis}.
3992 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3993 Enable the specified breakpoints (or all defined breakpoints). They
3994 become effective once again in stopping your program.
3996 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3997 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3998 of these breakpoints immediately after stopping your program.
4000 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4001 Enable the specified breakpoints to work once, then die. @value{GDBN}
4002 deletes any of these breakpoints as soon as your program stops there.
4003 Breakpoints set by the @code{tbreak} command start out in this state.
4006 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4007 @c confusing: tbreak is also initially enabled.
4008 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4009 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4010 subsequently, they become disabled or enabled only when you use one of
4011 the commands above. (The command @code{until} can set and delete a
4012 breakpoint of its own, but it does not change the state of your other
4013 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4017 @subsection Break Conditions
4018 @cindex conditional breakpoints
4019 @cindex breakpoint conditions
4021 @c FIXME what is scope of break condition expr? Context where wanted?
4022 @c in particular for a watchpoint?
4023 The simplest sort of breakpoint breaks every time your program reaches a
4024 specified place. You can also specify a @dfn{condition} for a
4025 breakpoint. A condition is just a Boolean expression in your
4026 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4027 a condition evaluates the expression each time your program reaches it,
4028 and your program stops only if the condition is @emph{true}.
4030 This is the converse of using assertions for program validation; in that
4031 situation, you want to stop when the assertion is violated---that is,
4032 when the condition is false. In C, if you want to test an assertion expressed
4033 by the condition @var{assert}, you should set the condition
4034 @samp{! @var{assert}} on the appropriate breakpoint.
4036 Conditions are also accepted for watchpoints; you may not need them,
4037 since a watchpoint is inspecting the value of an expression anyhow---but
4038 it might be simpler, say, to just set a watchpoint on a variable name,
4039 and specify a condition that tests whether the new value is an interesting
4042 Break conditions can have side effects, and may even call functions in
4043 your program. This can be useful, for example, to activate functions
4044 that log program progress, or to use your own print functions to
4045 format special data structures. The effects are completely predictable
4046 unless there is another enabled breakpoint at the same address. (In
4047 that case, @value{GDBN} might see the other breakpoint first and stop your
4048 program without checking the condition of this one.) Note that
4049 breakpoint commands are usually more convenient and flexible than break
4051 purpose of performing side effects when a breakpoint is reached
4052 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4054 Break conditions can be specified when a breakpoint is set, by using
4055 @samp{if} in the arguments to the @code{break} command. @xref{Set
4056 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4057 with the @code{condition} command.
4059 You can also use the @code{if} keyword with the @code{watch} command.
4060 The @code{catch} command does not recognize the @code{if} keyword;
4061 @code{condition} is the only way to impose a further condition on a
4066 @item condition @var{bnum} @var{expression}
4067 Specify @var{expression} as the break condition for breakpoint,
4068 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4069 breakpoint @var{bnum} stops your program only if the value of
4070 @var{expression} is true (nonzero, in C). When you use
4071 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4072 syntactic correctness, and to determine whether symbols in it have
4073 referents in the context of your breakpoint. If @var{expression} uses
4074 symbols not referenced in the context of the breakpoint, @value{GDBN}
4075 prints an error message:
4078 No symbol "foo" in current context.
4083 not actually evaluate @var{expression} at the time the @code{condition}
4084 command (or a command that sets a breakpoint with a condition, like
4085 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4087 @item condition @var{bnum}
4088 Remove the condition from breakpoint number @var{bnum}. It becomes
4089 an ordinary unconditional breakpoint.
4092 @cindex ignore count (of breakpoint)
4093 A special case of a breakpoint condition is to stop only when the
4094 breakpoint has been reached a certain number of times. This is so
4095 useful that there is a special way to do it, using the @dfn{ignore
4096 count} of the breakpoint. Every breakpoint has an ignore count, which
4097 is an integer. Most of the time, the ignore count is zero, and
4098 therefore has no effect. But if your program reaches a breakpoint whose
4099 ignore count is positive, then instead of stopping, it just decrements
4100 the ignore count by one and continues. As a result, if the ignore count
4101 value is @var{n}, the breakpoint does not stop the next @var{n} times
4102 your program reaches it.
4106 @item ignore @var{bnum} @var{count}
4107 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4108 The next @var{count} times the breakpoint is reached, your program's
4109 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4112 To make the breakpoint stop the next time it is reached, specify
4115 When you use @code{continue} to resume execution of your program from a
4116 breakpoint, you can specify an ignore count directly as an argument to
4117 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4118 Stepping,,Continuing and Stepping}.
4120 If a breakpoint has a positive ignore count and a condition, the
4121 condition is not checked. Once the ignore count reaches zero,
4122 @value{GDBN} resumes checking the condition.
4124 You could achieve the effect of the ignore count with a condition such
4125 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4126 is decremented each time. @xref{Convenience Vars, ,Convenience
4130 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4133 @node Break Commands
4134 @subsection Breakpoint Command Lists
4136 @cindex breakpoint commands
4137 You can give any breakpoint (or watchpoint or catchpoint) a series of
4138 commands to execute when your program stops due to that breakpoint. For
4139 example, you might want to print the values of certain expressions, or
4140 enable other breakpoints.
4144 @kindex end@r{ (breakpoint commands)}
4145 @item commands @r{[}@var{bnum}@r{]}
4146 @itemx @dots{} @var{command-list} @dots{}
4148 Specify a list of commands for breakpoint number @var{bnum}. The commands
4149 themselves appear on the following lines. Type a line containing just
4150 @code{end} to terminate the commands.
4152 To remove all commands from a breakpoint, type @code{commands} and
4153 follow it immediately with @code{end}; that is, give no commands.
4155 With no @var{bnum} argument, @code{commands} refers to the last
4156 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
4157 recently encountered).
4160 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4161 disabled within a @var{command-list}.
4163 You can use breakpoint commands to start your program up again. Simply
4164 use the @code{continue} command, or @code{step}, or any other command
4165 that resumes execution.
4167 Any other commands in the command list, after a command that resumes
4168 execution, are ignored. This is because any time you resume execution
4169 (even with a simple @code{next} or @code{step}), you may encounter
4170 another breakpoint---which could have its own command list, leading to
4171 ambiguities about which list to execute.
4174 If the first command you specify in a command list is @code{silent}, the
4175 usual message about stopping at a breakpoint is not printed. This may
4176 be desirable for breakpoints that are to print a specific message and
4177 then continue. If none of the remaining commands print anything, you
4178 see no sign that the breakpoint was reached. @code{silent} is
4179 meaningful only at the beginning of a breakpoint command list.
4181 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4182 print precisely controlled output, and are often useful in silent
4183 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4185 For example, here is how you could use breakpoint commands to print the
4186 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4192 printf "x is %d\n",x
4197 One application for breakpoint commands is to compensate for one bug so
4198 you can test for another. Put a breakpoint just after the erroneous line
4199 of code, give it a condition to detect the case in which something
4200 erroneous has been done, and give it commands to assign correct values
4201 to any variables that need them. End with the @code{continue} command
4202 so that your program does not stop, and start with the @code{silent}
4203 command so that no output is produced. Here is an example:
4214 @c @ifclear BARETARGET
4215 @node Error in Breakpoints
4216 @subsection ``Cannot insert breakpoints''
4218 If you request too many active hardware-assisted breakpoints and
4219 watchpoints, you will see this error message:
4221 @c FIXME: the precise wording of this message may change; the relevant
4222 @c source change is not committed yet (Sep 3, 1999).
4224 Stopped; cannot insert breakpoints.
4225 You may have requested too many hardware breakpoints and watchpoints.
4229 This message is printed when you attempt to resume the program, since
4230 only then @value{GDBN} knows exactly how many hardware breakpoints and
4231 watchpoints it needs to insert.
4233 When this message is printed, you need to disable or remove some of the
4234 hardware-assisted breakpoints and watchpoints, and then continue.
4236 @node Breakpoint-related Warnings
4237 @subsection ``Breakpoint address adjusted...''
4238 @cindex breakpoint address adjusted
4240 Some processor architectures place constraints on the addresses at
4241 which breakpoints may be placed. For architectures thus constrained,
4242 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4243 with the constraints dictated by the architecture.
4245 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4246 a VLIW architecture in which a number of RISC-like instructions may be
4247 bundled together for parallel execution. The FR-V architecture
4248 constrains the location of a breakpoint instruction within such a
4249 bundle to the instruction with the lowest address. @value{GDBN}
4250 honors this constraint by adjusting a breakpoint's address to the
4251 first in the bundle.
4253 It is not uncommon for optimized code to have bundles which contain
4254 instructions from different source statements, thus it may happen that
4255 a breakpoint's address will be adjusted from one source statement to
4256 another. Since this adjustment may significantly alter @value{GDBN}'s
4257 breakpoint related behavior from what the user expects, a warning is
4258 printed when the breakpoint is first set and also when the breakpoint
4261 A warning like the one below is printed when setting a breakpoint
4262 that's been subject to address adjustment:
4265 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4268 Such warnings are printed both for user settable and @value{GDBN}'s
4269 internal breakpoints. If you see one of these warnings, you should
4270 verify that a breakpoint set at the adjusted address will have the
4271 desired affect. If not, the breakpoint in question may be removed and
4272 other breakpoints may be set which will have the desired behavior.
4273 E.g., it may be sufficient to place the breakpoint at a later
4274 instruction. A conditional breakpoint may also be useful in some
4275 cases to prevent the breakpoint from triggering too often.
4277 @value{GDBN} will also issue a warning when stopping at one of these
4278 adjusted breakpoints:
4281 warning: Breakpoint 1 address previously adjusted from 0x00010414
4285 When this warning is encountered, it may be too late to take remedial
4286 action except in cases where the breakpoint is hit earlier or more
4287 frequently than expected.
4289 @node Continuing and Stepping
4290 @section Continuing and Stepping
4294 @cindex resuming execution
4295 @dfn{Continuing} means resuming program execution until your program
4296 completes normally. In contrast, @dfn{stepping} means executing just
4297 one more ``step'' of your program, where ``step'' may mean either one
4298 line of source code, or one machine instruction (depending on what
4299 particular command you use). Either when continuing or when stepping,
4300 your program may stop even sooner, due to a breakpoint or a signal. (If
4301 it stops due to a signal, you may want to use @code{handle}, or use
4302 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4306 @kindex c @r{(@code{continue})}
4307 @kindex fg @r{(resume foreground execution)}
4308 @item continue @r{[}@var{ignore-count}@r{]}
4309 @itemx c @r{[}@var{ignore-count}@r{]}
4310 @itemx fg @r{[}@var{ignore-count}@r{]}
4311 Resume program execution, at the address where your program last stopped;
4312 any breakpoints set at that address are bypassed. The optional argument
4313 @var{ignore-count} allows you to specify a further number of times to
4314 ignore a breakpoint at this location; its effect is like that of
4315 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4317 The argument @var{ignore-count} is meaningful only when your program
4318 stopped due to a breakpoint. At other times, the argument to
4319 @code{continue} is ignored.
4321 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4322 debugged program is deemed to be the foreground program) are provided
4323 purely for convenience, and have exactly the same behavior as
4327 To resume execution at a different place, you can use @code{return}
4328 (@pxref{Returning, ,Returning from a Function}) to go back to the
4329 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4330 Different Address}) to go to an arbitrary location in your program.
4332 A typical technique for using stepping is to set a breakpoint
4333 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4334 beginning of the function or the section of your program where a problem
4335 is believed to lie, run your program until it stops at that breakpoint,
4336 and then step through the suspect area, examining the variables that are
4337 interesting, until you see the problem happen.
4341 @kindex s @r{(@code{step})}
4343 Continue running your program until control reaches a different source
4344 line, then stop it and return control to @value{GDBN}. This command is
4345 abbreviated @code{s}.
4348 @c "without debugging information" is imprecise; actually "without line
4349 @c numbers in the debugging information". (gcc -g1 has debugging info but
4350 @c not line numbers). But it seems complex to try to make that
4351 @c distinction here.
4352 @emph{Warning:} If you use the @code{step} command while control is
4353 within a function that was compiled without debugging information,
4354 execution proceeds until control reaches a function that does have
4355 debugging information. Likewise, it will not step into a function which
4356 is compiled without debugging information. To step through functions
4357 without debugging information, use the @code{stepi} command, described
4361 The @code{step} command only stops at the first instruction of a source
4362 line. This prevents the multiple stops that could otherwise occur in
4363 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4364 to stop if a function that has debugging information is called within
4365 the line. In other words, @code{step} @emph{steps inside} any functions
4366 called within the line.
4368 Also, the @code{step} command only enters a function if there is line
4369 number information for the function. Otherwise it acts like the
4370 @code{next} command. This avoids problems when using @code{cc -gl}
4371 on MIPS machines. Previously, @code{step} entered subroutines if there
4372 was any debugging information about the routine.
4374 @item step @var{count}
4375 Continue running as in @code{step}, but do so @var{count} times. If a
4376 breakpoint is reached, or a signal not related to stepping occurs before
4377 @var{count} steps, stepping stops right away.
4380 @kindex n @r{(@code{next})}
4381 @item next @r{[}@var{count}@r{]}
4382 Continue to the next source line in the current (innermost) stack frame.
4383 This is similar to @code{step}, but function calls that appear within
4384 the line of code are executed without stopping. Execution stops when
4385 control reaches a different line of code at the original stack level
4386 that was executing when you gave the @code{next} command. This command
4387 is abbreviated @code{n}.
4389 An argument @var{count} is a repeat count, as for @code{step}.
4392 @c FIX ME!! Do we delete this, or is there a way it fits in with
4393 @c the following paragraph? --- Vctoria
4395 @c @code{next} within a function that lacks debugging information acts like
4396 @c @code{step}, but any function calls appearing within the code of the
4397 @c function are executed without stopping.
4399 The @code{next} command only stops at the first instruction of a
4400 source line. This prevents multiple stops that could otherwise occur in
4401 @code{switch} statements, @code{for} loops, etc.
4403 @kindex set step-mode
4405 @cindex functions without line info, and stepping
4406 @cindex stepping into functions with no line info
4407 @itemx set step-mode on
4408 The @code{set step-mode on} command causes the @code{step} command to
4409 stop at the first instruction of a function which contains no debug line
4410 information rather than stepping over it.
4412 This is useful in cases where you may be interested in inspecting the
4413 machine instructions of a function which has no symbolic info and do not
4414 want @value{GDBN} to automatically skip over this function.
4416 @item set step-mode off
4417 Causes the @code{step} command to step over any functions which contains no
4418 debug information. This is the default.
4420 @item show step-mode
4421 Show whether @value{GDBN} will stop in or step over functions without
4422 source line debug information.
4425 @kindex fin @r{(@code{finish})}
4427 Continue running until just after function in the selected stack frame
4428 returns. Print the returned value (if any). This command can be
4429 abbreviated as @code{fin}.
4431 Contrast this with the @code{return} command (@pxref{Returning,
4432 ,Returning from a Function}).
4435 @kindex u @r{(@code{until})}
4436 @cindex run until specified location
4439 Continue running until a source line past the current line, in the
4440 current stack frame, is reached. This command is used to avoid single
4441 stepping through a loop more than once. It is like the @code{next}
4442 command, except that when @code{until} encounters a jump, it
4443 automatically continues execution until the program counter is greater
4444 than the address of the jump.
4446 This means that when you reach the end of a loop after single stepping
4447 though it, @code{until} makes your program continue execution until it
4448 exits the loop. In contrast, a @code{next} command at the end of a loop
4449 simply steps back to the beginning of the loop, which forces you to step
4450 through the next iteration.
4452 @code{until} always stops your program if it attempts to exit the current
4455 @code{until} may produce somewhat counterintuitive results if the order
4456 of machine code does not match the order of the source lines. For
4457 example, in the following excerpt from a debugging session, the @code{f}
4458 (@code{frame}) command shows that execution is stopped at line
4459 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4463 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4465 (@value{GDBP}) until
4466 195 for ( ; argc > 0; NEXTARG) @{
4469 This happened because, for execution efficiency, the compiler had
4470 generated code for the loop closure test at the end, rather than the
4471 start, of the loop---even though the test in a C @code{for}-loop is
4472 written before the body of the loop. The @code{until} command appeared
4473 to step back to the beginning of the loop when it advanced to this
4474 expression; however, it has not really gone to an earlier
4475 statement---not in terms of the actual machine code.
4477 @code{until} with no argument works by means of single
4478 instruction stepping, and hence is slower than @code{until} with an
4481 @item until @var{location}
4482 @itemx u @var{location}
4483 Continue running your program until either the specified location is
4484 reached, or the current stack frame returns. @var{location} is any of
4485 the forms described in @ref{Specify Location}.
4486 This form of the command uses temporary breakpoints, and
4487 hence is quicker than @code{until} without an argument. The specified
4488 location is actually reached only if it is in the current frame. This
4489 implies that @code{until} can be used to skip over recursive function
4490 invocations. For instance in the code below, if the current location is
4491 line @code{96}, issuing @code{until 99} will execute the program up to
4492 line @code{99} in the same invocation of factorial, i.e., after the inner
4493 invocations have returned.
4496 94 int factorial (int value)
4498 96 if (value > 1) @{
4499 97 value *= factorial (value - 1);
4506 @kindex advance @var{location}
4507 @itemx advance @var{location}
4508 Continue running the program up to the given @var{location}. An argument is
4509 required, which should be of one of the forms described in
4510 @ref{Specify Location}.
4511 Execution will also stop upon exit from the current stack
4512 frame. This command is similar to @code{until}, but @code{advance} will
4513 not skip over recursive function calls, and the target location doesn't
4514 have to be in the same frame as the current one.
4518 @kindex si @r{(@code{stepi})}
4520 @itemx stepi @var{arg}
4522 Execute one machine instruction, then stop and return to the debugger.
4524 It is often useful to do @samp{display/i $pc} when stepping by machine
4525 instructions. This makes @value{GDBN} automatically display the next
4526 instruction to be executed, each time your program stops. @xref{Auto
4527 Display,, Automatic Display}.
4529 An argument is a repeat count, as in @code{step}.
4533 @kindex ni @r{(@code{nexti})}
4535 @itemx nexti @var{arg}
4537 Execute one machine instruction, but if it is a function call,
4538 proceed until the function returns.
4540 An argument is a repeat count, as in @code{next}.
4547 A signal is an asynchronous event that can happen in a program. The
4548 operating system defines the possible kinds of signals, and gives each
4549 kind a name and a number. For example, in Unix @code{SIGINT} is the
4550 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4551 @code{SIGSEGV} is the signal a program gets from referencing a place in
4552 memory far away from all the areas in use; @code{SIGALRM} occurs when
4553 the alarm clock timer goes off (which happens only if your program has
4554 requested an alarm).
4556 @cindex fatal signals
4557 Some signals, including @code{SIGALRM}, are a normal part of the
4558 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4559 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4560 program has not specified in advance some other way to handle the signal.
4561 @code{SIGINT} does not indicate an error in your program, but it is normally
4562 fatal so it can carry out the purpose of the interrupt: to kill the program.
4564 @value{GDBN} has the ability to detect any occurrence of a signal in your
4565 program. You can tell @value{GDBN} in advance what to do for each kind of
4568 @cindex handling signals
4569 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4570 @code{SIGALRM} be silently passed to your program
4571 (so as not to interfere with their role in the program's functioning)
4572 but to stop your program immediately whenever an error signal happens.
4573 You can change these settings with the @code{handle} command.
4576 @kindex info signals
4580 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4581 handle each one. You can use this to see the signal numbers of all
4582 the defined types of signals.
4584 @item info signals @var{sig}
4585 Similar, but print information only about the specified signal number.
4587 @code{info handle} is an alias for @code{info signals}.
4590 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4591 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4592 can be the number of a signal or its name (with or without the
4593 @samp{SIG} at the beginning); a list of signal numbers of the form
4594 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4595 known signals. Optional arguments @var{keywords}, described below,
4596 say what change to make.
4600 The keywords allowed by the @code{handle} command can be abbreviated.
4601 Their full names are:
4605 @value{GDBN} should not stop your program when this signal happens. It may
4606 still print a message telling you that the signal has come in.
4609 @value{GDBN} should stop your program when this signal happens. This implies
4610 the @code{print} keyword as well.
4613 @value{GDBN} should print a message when this signal happens.
4616 @value{GDBN} should not mention the occurrence of the signal at all. This
4617 implies the @code{nostop} keyword as well.
4621 @value{GDBN} should allow your program to see this signal; your program
4622 can handle the signal, or else it may terminate if the signal is fatal
4623 and not handled. @code{pass} and @code{noignore} are synonyms.
4627 @value{GDBN} should not allow your program to see this signal.
4628 @code{nopass} and @code{ignore} are synonyms.
4632 When a signal stops your program, the signal is not visible to the
4634 continue. Your program sees the signal then, if @code{pass} is in
4635 effect for the signal in question @emph{at that time}. In other words,
4636 after @value{GDBN} reports a signal, you can use the @code{handle}
4637 command with @code{pass} or @code{nopass} to control whether your
4638 program sees that signal when you continue.
4640 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4641 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4642 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4645 You can also use the @code{signal} command to prevent your program from
4646 seeing a signal, or cause it to see a signal it normally would not see,
4647 or to give it any signal at any time. For example, if your program stopped
4648 due to some sort of memory reference error, you might store correct
4649 values into the erroneous variables and continue, hoping to see more
4650 execution; but your program would probably terminate immediately as
4651 a result of the fatal signal once it saw the signal. To prevent this,
4652 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4655 @cindex extra signal information
4656 @anchor{extra signal information}
4658 On some targets, @value{GDBN} can inspect extra signal information
4659 associated with the intercepted signal, before it is actually
4660 delivered to the program being debugged. This information is exported
4661 by the convenience variable @code{$_siginfo}, and consists of data
4662 that is passed by the kernel to the signal handler at the time of the
4663 receipt of a signal. The data type of the information itself is
4664 target dependent. You can see the data type using the @code{ptype
4665 $_siginfo} command. On Unix systems, it typically corresponds to the
4666 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4669 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4670 referenced address that raised a segmentation fault.
4674 (@value{GDBP}) continue
4675 Program received signal SIGSEGV, Segmentation fault.
4676 0x0000000000400766 in main ()
4678 (@value{GDBP}) ptype $_siginfo
4685 struct @{...@} _kill;
4686 struct @{...@} _timer;
4688 struct @{...@} _sigchld;
4689 struct @{...@} _sigfault;
4690 struct @{...@} _sigpoll;
4693 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4697 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4698 $1 = (void *) 0x7ffff7ff7000
4702 Depending on target support, @code{$_siginfo} may also be writable.
4705 @section Stopping and Starting Multi-thread Programs
4707 @cindex stopped threads
4708 @cindex threads, stopped
4710 @cindex continuing threads
4711 @cindex threads, continuing
4713 @value{GDBN} supports debugging programs with multiple threads
4714 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4715 are two modes of controlling execution of your program within the
4716 debugger. In the default mode, referred to as @dfn{all-stop mode},
4717 when any thread in your program stops (for example, at a breakpoint
4718 or while being stepped), all other threads in the program are also stopped by
4719 @value{GDBN}. On some targets, @value{GDBN} also supports
4720 @dfn{non-stop mode}, in which other threads can continue to run freely while
4721 you examine the stopped thread in the debugger.
4724 * All-Stop Mode:: All threads stop when GDB takes control
4725 * Non-Stop Mode:: Other threads continue to execute
4726 * Background Execution:: Running your program asynchronously
4727 * Thread-Specific Breakpoints:: Controlling breakpoints
4728 * Interrupted System Calls:: GDB may interfere with system calls
4732 @subsection All-Stop Mode
4734 @cindex all-stop mode
4736 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4737 @emph{all} threads of execution stop, not just the current thread. This
4738 allows you to examine the overall state of the program, including
4739 switching between threads, without worrying that things may change
4742 Conversely, whenever you restart the program, @emph{all} threads start
4743 executing. @emph{This is true even when single-stepping} with commands
4744 like @code{step} or @code{next}.
4746 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4747 Since thread scheduling is up to your debugging target's operating
4748 system (not controlled by @value{GDBN}), other threads may
4749 execute more than one statement while the current thread completes a
4750 single step. Moreover, in general other threads stop in the middle of a
4751 statement, rather than at a clean statement boundary, when the program
4754 You might even find your program stopped in another thread after
4755 continuing or even single-stepping. This happens whenever some other
4756 thread runs into a breakpoint, a signal, or an exception before the
4757 first thread completes whatever you requested.
4759 @cindex automatic thread selection
4760 @cindex switching threads automatically
4761 @cindex threads, automatic switching
4762 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4763 signal, it automatically selects the thread where that breakpoint or
4764 signal happened. @value{GDBN} alerts you to the context switch with a
4765 message such as @samp{[Switching to Thread @var{n}]} to identify the
4768 On some OSes, you can modify @value{GDBN}'s default behavior by
4769 locking the OS scheduler to allow only a single thread to run.
4772 @item set scheduler-locking @var{mode}
4773 @cindex scheduler locking mode
4774 @cindex lock scheduler
4775 Set the scheduler locking mode. If it is @code{off}, then there is no
4776 locking and any thread may run at any time. If @code{on}, then only the
4777 current thread may run when the inferior is resumed. The @code{step}
4778 mode optimizes for single-stepping; it prevents other threads
4779 from preempting the current thread while you are stepping, so that
4780 the focus of debugging does not change unexpectedly.
4781 Other threads only rarely (or never) get a chance to run
4782 when you step. They are more likely to run when you @samp{next} over a
4783 function call, and they are completely free to run when you use commands
4784 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4785 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4786 the current thread away from the thread that you are debugging.
4788 @item show scheduler-locking
4789 Display the current scheduler locking mode.
4792 @cindex resume threads of multiple processes simultaneously
4793 By default, when you issue one of the execution commands such as
4794 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
4795 threads of the current inferior to run. For example, if @value{GDBN}
4796 is attached to two inferiors, each with two threads, the
4797 @code{continue} command resumes only the two threads of the current
4798 inferior. This is useful, for example, when you debug a program that
4799 forks and you want to hold the parent stopped (so that, for instance,
4800 it doesn't run to exit), while you debug the child. In other
4801 situations, you may not be interested in inspecting the current state
4802 of any of the processes @value{GDBN} is attached to, and you may want
4803 to resume them all until some breakpoint is hit. In the latter case,
4804 you can instruct @value{GDBN} to allow all threads of all the
4805 inferiors to run with the @w{@code{set schedule-multiple}} command.
4808 @kindex set schedule-multiple
4809 @item set schedule-multiple
4810 Set the mode for allowing threads of multiple processes to be resumed
4811 when an execution command is issued. When @code{on}, all threads of
4812 all processes are allowed to run. When @code{off}, only the threads
4813 of the current process are resumed. The default is @code{off}. The
4814 @code{scheduler-locking} mode takes precedence when set to @code{on},
4815 or while you are stepping and set to @code{step}.
4817 @item show schedule-multiple
4818 Display the current mode for resuming the execution of threads of
4823 @subsection Non-Stop Mode
4825 @cindex non-stop mode
4827 @c This section is really only a place-holder, and needs to be expanded
4828 @c with more details.
4830 For some multi-threaded targets, @value{GDBN} supports an optional
4831 mode of operation in which you can examine stopped program threads in
4832 the debugger while other threads continue to execute freely. This
4833 minimizes intrusion when debugging live systems, such as programs
4834 where some threads have real-time constraints or must continue to
4835 respond to external events. This is referred to as @dfn{non-stop} mode.
4837 In non-stop mode, when a thread stops to report a debugging event,
4838 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4839 threads as well, in contrast to the all-stop mode behavior. Additionally,
4840 execution commands such as @code{continue} and @code{step} apply by default
4841 only to the current thread in non-stop mode, rather than all threads as
4842 in all-stop mode. This allows you to control threads explicitly in
4843 ways that are not possible in all-stop mode --- for example, stepping
4844 one thread while allowing others to run freely, stepping
4845 one thread while holding all others stopped, or stepping several threads
4846 independently and simultaneously.
4848 To enter non-stop mode, use this sequence of commands before you run
4849 or attach to your program:
4852 # Enable the async interface.
4855 # If using the CLI, pagination breaks non-stop.
4858 # Finally, turn it on!
4862 You can use these commands to manipulate the non-stop mode setting:
4865 @kindex set non-stop
4866 @item set non-stop on
4867 Enable selection of non-stop mode.
4868 @item set non-stop off
4869 Disable selection of non-stop mode.
4870 @kindex show non-stop
4872 Show the current non-stop enablement setting.
4875 Note these commands only reflect whether non-stop mode is enabled,
4876 not whether the currently-executing program is being run in non-stop mode.
4877 In particular, the @code{set non-stop} preference is only consulted when
4878 @value{GDBN} starts or connects to the target program, and it is generally
4879 not possible to switch modes once debugging has started. Furthermore,
4880 since not all targets support non-stop mode, even when you have enabled
4881 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4884 In non-stop mode, all execution commands apply only to the current thread
4885 by default. That is, @code{continue} only continues one thread.
4886 To continue all threads, issue @code{continue -a} or @code{c -a}.
4888 You can use @value{GDBN}'s background execution commands
4889 (@pxref{Background Execution}) to run some threads in the background
4890 while you continue to examine or step others from @value{GDBN}.
4891 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4892 always executed asynchronously in non-stop mode.
4894 Suspending execution is done with the @code{interrupt} command when
4895 running in the background, or @kbd{Ctrl-c} during foreground execution.
4896 In all-stop mode, this stops the whole process;
4897 but in non-stop mode the interrupt applies only to the current thread.
4898 To stop the whole program, use @code{interrupt -a}.
4900 Other execution commands do not currently support the @code{-a} option.
4902 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4903 that thread current, as it does in all-stop mode. This is because the
4904 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4905 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4906 changed to a different thread just as you entered a command to operate on the
4907 previously current thread.
4909 @node Background Execution
4910 @subsection Background Execution
4912 @cindex foreground execution
4913 @cindex background execution
4914 @cindex asynchronous execution
4915 @cindex execution, foreground, background and asynchronous
4917 @value{GDBN}'s execution commands have two variants: the normal
4918 foreground (synchronous) behavior, and a background
4919 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4920 the program to report that some thread has stopped before prompting for
4921 another command. In background execution, @value{GDBN} immediately gives
4922 a command prompt so that you can issue other commands while your program runs.
4924 You need to explicitly enable asynchronous mode before you can use
4925 background execution commands. You can use these commands to
4926 manipulate the asynchronous mode setting:
4929 @kindex set target-async
4930 @item set target-async on
4931 Enable asynchronous mode.
4932 @item set target-async off
4933 Disable asynchronous mode.
4934 @kindex show target-async
4935 @item show target-async
4936 Show the current target-async setting.
4939 If the target doesn't support async mode, @value{GDBN} issues an error
4940 message if you attempt to use the background execution commands.
4942 To specify background execution, add a @code{&} to the command. For example,
4943 the background form of the @code{continue} command is @code{continue&}, or
4944 just @code{c&}. The execution commands that accept background execution
4950 @xref{Starting, , Starting your Program}.
4954 @xref{Attach, , Debugging an Already-running Process}.
4958 @xref{Continuing and Stepping, step}.
4962 @xref{Continuing and Stepping, stepi}.
4966 @xref{Continuing and Stepping, next}.
4970 @xref{Continuing and Stepping, nexti}.
4974 @xref{Continuing and Stepping, continue}.
4978 @xref{Continuing and Stepping, finish}.
4982 @xref{Continuing and Stepping, until}.
4986 Background execution is especially useful in conjunction with non-stop
4987 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4988 However, you can also use these commands in the normal all-stop mode with
4989 the restriction that you cannot issue another execution command until the
4990 previous one finishes. Examples of commands that are valid in all-stop
4991 mode while the program is running include @code{help} and @code{info break}.
4993 You can interrupt your program while it is running in the background by
4994 using the @code{interrupt} command.
5001 Suspend execution of the running program. In all-stop mode,
5002 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5003 only the current thread. To stop the whole program in non-stop mode,
5004 use @code{interrupt -a}.
5007 @node Thread-Specific Breakpoints
5008 @subsection Thread-Specific Breakpoints
5010 When your program has multiple threads (@pxref{Threads,, Debugging
5011 Programs with Multiple Threads}), you can choose whether to set
5012 breakpoints on all threads, or on a particular thread.
5015 @cindex breakpoints and threads
5016 @cindex thread breakpoints
5017 @kindex break @dots{} thread @var{threadno}
5018 @item break @var{linespec} thread @var{threadno}
5019 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5020 @var{linespec} specifies source lines; there are several ways of
5021 writing them (@pxref{Specify Location}), but the effect is always to
5022 specify some source line.
5024 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5025 to specify that you only want @value{GDBN} to stop the program when a
5026 particular thread reaches this breakpoint. @var{threadno} is one of the
5027 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5028 column of the @samp{info threads} display.
5030 If you do not specify @samp{thread @var{threadno}} when you set a
5031 breakpoint, the breakpoint applies to @emph{all} threads of your
5034 You can use the @code{thread} qualifier on conditional breakpoints as
5035 well; in this case, place @samp{thread @var{threadno}} before the
5036 breakpoint condition, like this:
5039 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5044 @node Interrupted System Calls
5045 @subsection Interrupted System Calls
5047 @cindex thread breakpoints and system calls
5048 @cindex system calls and thread breakpoints
5049 @cindex premature return from system calls
5050 There is an unfortunate side effect when using @value{GDBN} to debug
5051 multi-threaded programs. If one thread stops for a
5052 breakpoint, or for some other reason, and another thread is blocked in a
5053 system call, then the system call may return prematurely. This is a
5054 consequence of the interaction between multiple threads and the signals
5055 that @value{GDBN} uses to implement breakpoints and other events that
5058 To handle this problem, your program should check the return value of
5059 each system call and react appropriately. This is good programming
5062 For example, do not write code like this:
5068 The call to @code{sleep} will return early if a different thread stops
5069 at a breakpoint or for some other reason.
5071 Instead, write this:
5076 unslept = sleep (unslept);
5079 A system call is allowed to return early, so the system is still
5080 conforming to its specification. But @value{GDBN} does cause your
5081 multi-threaded program to behave differently than it would without
5084 Also, @value{GDBN} uses internal breakpoints in the thread library to
5085 monitor certain events such as thread creation and thread destruction.
5086 When such an event happens, a system call in another thread may return
5087 prematurely, even though your program does not appear to stop.
5090 @node Reverse Execution
5091 @chapter Running programs backward
5092 @cindex reverse execution
5093 @cindex running programs backward
5095 When you are debugging a program, it is not unusual to realize that
5096 you have gone too far, and some event of interest has already happened.
5097 If the target environment supports it, @value{GDBN} can allow you to
5098 ``rewind'' the program by running it backward.
5100 A target environment that supports reverse execution should be able
5101 to ``undo'' the changes in machine state that have taken place as the
5102 program was executing normally. Variables, registers etc.@: should
5103 revert to their previous values. Obviously this requires a great
5104 deal of sophistication on the part of the target environment; not
5105 all target environments can support reverse execution.
5107 When a program is executed in reverse, the instructions that
5108 have most recently been executed are ``un-executed'', in reverse
5109 order. The program counter runs backward, following the previous
5110 thread of execution in reverse. As each instruction is ``un-executed'',
5111 the values of memory and/or registers that were changed by that
5112 instruction are reverted to their previous states. After executing
5113 a piece of source code in reverse, all side effects of that code
5114 should be ``undone'', and all variables should be returned to their
5115 prior values@footnote{
5116 Note that some side effects are easier to undo than others. For instance,
5117 memory and registers are relatively easy, but device I/O is hard. Some
5118 targets may be able undo things like device I/O, and some may not.
5120 The contract between @value{GDBN} and the reverse executing target
5121 requires only that the target do something reasonable when
5122 @value{GDBN} tells it to execute backwards, and then report the
5123 results back to @value{GDBN}. Whatever the target reports back to
5124 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5125 assumes that the memory and registers that the target reports are in a
5126 consistant state, but @value{GDBN} accepts whatever it is given.
5129 If you are debugging in a target environment that supports
5130 reverse execution, @value{GDBN} provides the following commands.
5133 @kindex reverse-continue
5134 @kindex rc @r{(@code{reverse-continue})}
5135 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5136 @itemx rc @r{[}@var{ignore-count}@r{]}
5137 Beginning at the point where your program last stopped, start executing
5138 in reverse. Reverse execution will stop for breakpoints and synchronous
5139 exceptions (signals), just like normal execution. Behavior of
5140 asynchronous signals depends on the target environment.
5142 @kindex reverse-step
5143 @kindex rs @r{(@code{step})}
5144 @item reverse-step @r{[}@var{count}@r{]}
5145 Run the program backward until control reaches the start of a
5146 different source line; then stop it, and return control to @value{GDBN}.
5148 Like the @code{step} command, @code{reverse-step} will only stop
5149 at the beginning of a source line. It ``un-executes'' the previously
5150 executed source line. If the previous source line included calls to
5151 debuggable functions, @code{reverse-step} will step (backward) into
5152 the called function, stopping at the beginning of the @emph{last}
5153 statement in the called function (typically a return statement).
5155 Also, as with the @code{step} command, if non-debuggable functions are
5156 called, @code{reverse-step} will run thru them backward without stopping.
5158 @kindex reverse-stepi
5159 @kindex rsi @r{(@code{reverse-stepi})}
5160 @item reverse-stepi @r{[}@var{count}@r{]}
5161 Reverse-execute one machine instruction. Note that the instruction
5162 to be reverse-executed is @emph{not} the one pointed to by the program
5163 counter, but the instruction executed prior to that one. For instance,
5164 if the last instruction was a jump, @code{reverse-stepi} will take you
5165 back from the destination of the jump to the jump instruction itself.
5167 @kindex reverse-next
5168 @kindex rn @r{(@code{reverse-next})}
5169 @item reverse-next @r{[}@var{count}@r{]}
5170 Run backward to the beginning of the previous line executed in
5171 the current (innermost) stack frame. If the line contains function
5172 calls, they will be ``un-executed'' without stopping. Starting from
5173 the first line of a function, @code{reverse-next} will take you back
5174 to the caller of that function, @emph{before} the function was called,
5175 just as the normal @code{next} command would take you from the last
5176 line of a function back to its return to its caller
5177 @footnote{Unles the code is too heavily optimized.}.
5179 @kindex reverse-nexti
5180 @kindex rni @r{(@code{reverse-nexti})}
5181 @item reverse-nexti @r{[}@var{count}@r{]}
5182 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5183 in reverse, except that called functions are ``un-executed'' atomically.
5184 That is, if the previously executed instruction was a return from
5185 another instruction, @code{reverse-nexti} will continue to execute
5186 in reverse until the call to that function (from the current stack
5189 @kindex reverse-finish
5190 @item reverse-finish
5191 Just as the @code{finish} command takes you to the point where the
5192 current function returns, @code{reverse-finish} takes you to the point
5193 where it was called. Instead of ending up at the end of the current
5194 function invocation, you end up at the beginning.
5196 @kindex set exec-direction
5197 @item set exec-direction
5198 Set the direction of target execution.
5199 @itemx set exec-direction reverse
5200 @cindex execute forward or backward in time
5201 @value{GDBN} will perform all execution commands in reverse, until the
5202 exec-direction mode is changed to ``forward''. Affected commands include
5203 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5204 command cannot be used in reverse mode.
5205 @item set exec-direction forward
5206 @value{GDBN} will perform all execution commands in the normal fashion.
5207 This is the default.
5211 @node Process Record and Replay
5212 @chapter Recording Inferior's Execution and Replaying It
5213 @cindex process record and replay
5214 @cindex recording inferior's execution and replaying it
5216 On some platforms, @value{GDBN} provides a special @dfn{process record
5217 and replay} target that can record a log of the process execution, and
5218 replay it later with both forward and reverse execution commands.
5221 When this target is in use, if the execution log includes the record
5222 for the next instruction, @value{GDBN} will debug in @dfn{replay
5223 mode}. In the replay mode, the inferior does not really execute code
5224 instructions. Instead, all the events that normally happen during
5225 code execution are taken from the execution log. While code is not
5226 really executed in replay mode, the values of registers (including the
5227 program counter register) and the memory of the inferior are still
5228 changed as they normally would. Their contents are taken from the
5232 If the record for the next instruction is not in the execution log,
5233 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5234 inferior executes normally, and @value{GDBN} records the execution log
5237 The process record and replay target supports reverse execution
5238 (@pxref{Reverse Execution}), even if the platform on which the
5239 inferior runs does not. However, the reverse execution is limited in
5240 this case by the range of the instructions recorded in the execution
5241 log. In other words, reverse execution on platforms that don't
5242 support it directly can only be done in the replay mode.
5244 When debugging in the reverse direction, @value{GDBN} will work in
5245 replay mode as long as the execution log includes the record for the
5246 previous instruction; otherwise, it will work in record mode, if the
5247 platform supports reverse execution, or stop if not.
5249 For architecture environments that support process record and replay,
5250 @value{GDBN} provides the following commands:
5253 @kindex target record
5257 This command starts the process record and replay target. The process
5258 record and replay target can only debug a process that is already
5259 running. Therefore, you need first to start the process with the
5260 @kbd{run} or @kbd{start} commands, and then start the recording with
5261 the @kbd{target record} command.
5263 Both @code{record} and @code{rec} are aliases of @code{target record}.
5265 @cindex displaced stepping, and process record and replay
5266 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5267 will be automatically disabled when process record and replay target
5268 is started. That's because the process record and replay target
5269 doesn't support displaced stepping.
5271 @cindex non-stop mode, and process record and replay
5272 @cindex asynchronous execution, and process record and replay
5273 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5274 the asynchronous execution mode (@pxref{Background Execution}), the
5275 process record and replay target cannot be started because it doesn't
5276 support these two modes.
5281 Stop the process record and replay target. When process record and
5282 replay target stops, the entire execution log will be deleted and the
5283 inferior will either be terminated, or will remain in its final state.
5285 When you stop the process record and replay target in record mode (at
5286 the end of the execution log), the inferior will be stopped at the
5287 next instruction that would have been recorded. In other words, if
5288 you record for a while and then stop recording, the inferior process
5289 will be left in the same state as if the recording never happened.
5291 On the other hand, if the process record and replay target is stopped
5292 while in replay mode (that is, not at the end of the execution log,
5293 but at some earlier point), the inferior process will become ``live''
5294 at that earlier state, and it will then be possible to continue the
5295 usual ``live'' debugging of the process from that state.
5297 When the inferior process exits, or @value{GDBN} detaches from it,
5298 process record and replay target will automatically stop itself.
5300 @kindex set record insn-number-max
5301 @item set record insn-number-max @var{limit}
5302 Set the limit of instructions to be recorded. Default value is 200000.
5304 If @var{limit} is a positive number, then @value{GDBN} will start
5305 deleting instructions from the log once the number of the record
5306 instructions becomes greater than @var{limit}. For every new recorded
5307 instruction, @value{GDBN} will delete the earliest recorded
5308 instruction to keep the number of recorded instructions at the limit.
5309 (Since deleting recorded instructions loses information, @value{GDBN}
5310 lets you control what happens when the limit is reached, by means of
5311 the @code{stop-at-limit} option, described below.)
5313 If @var{limit} is zero, @value{GDBN} will never delete recorded
5314 instructions from the execution log. The number of recorded
5315 instructions is unlimited in this case.
5317 @kindex show record insn-number-max
5318 @item show record insn-number-max
5319 Show the limit of instructions to be recorded.
5321 @kindex set record stop-at-limit
5322 @item set record stop-at-limit
5323 Control the behavior when the number of recorded instructions reaches
5324 the limit. If ON (the default), @value{GDBN} will stop when the limit
5325 is reached for the first time and ask you whether you want to stop the
5326 inferior or continue running it and recording the execution log. If
5327 you decide to continue recording, each new recorded instruction will
5328 cause the oldest one to be deleted.
5330 If this option is OFF, @value{GDBN} will automatically delete the
5331 oldest record to make room for each new one, without asking.
5333 @kindex show record stop-at-limit
5334 @item show record stop-at-limit
5335 Show the current setting of @code{stop-at-limit}.
5337 @kindex info record insn-number
5338 @item info record insn-number
5339 Show the current number of recorded instructions.
5341 @kindex record delete
5344 When record target runs in replay mode (``in the past''), delete the
5345 subsequent execution log and begin to record a new execution log starting
5346 from the current address. This means you will abandon the previously
5347 recorded ``future'' and begin recording a new ``future''.
5352 @chapter Examining the Stack
5354 When your program has stopped, the first thing you need to know is where it
5355 stopped and how it got there.
5358 Each time your program performs a function call, information about the call
5360 That information includes the location of the call in your program,
5361 the arguments of the call,
5362 and the local variables of the function being called.
5363 The information is saved in a block of data called a @dfn{stack frame}.
5364 The stack frames are allocated in a region of memory called the @dfn{call
5367 When your program stops, the @value{GDBN} commands for examining the
5368 stack allow you to see all of this information.
5370 @cindex selected frame
5371 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5372 @value{GDBN} commands refer implicitly to the selected frame. In
5373 particular, whenever you ask @value{GDBN} for the value of a variable in
5374 your program, the value is found in the selected frame. There are
5375 special @value{GDBN} commands to select whichever frame you are
5376 interested in. @xref{Selection, ,Selecting a Frame}.
5378 When your program stops, @value{GDBN} automatically selects the
5379 currently executing frame and describes it briefly, similar to the
5380 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5383 * Frames:: Stack frames
5384 * Backtrace:: Backtraces
5385 * Selection:: Selecting a frame
5386 * Frame Info:: Information on a frame
5391 @section Stack Frames
5393 @cindex frame, definition
5395 The call stack is divided up into contiguous pieces called @dfn{stack
5396 frames}, or @dfn{frames} for short; each frame is the data associated
5397 with one call to one function. The frame contains the arguments given
5398 to the function, the function's local variables, and the address at
5399 which the function is executing.
5401 @cindex initial frame
5402 @cindex outermost frame
5403 @cindex innermost frame
5404 When your program is started, the stack has only one frame, that of the
5405 function @code{main}. This is called the @dfn{initial} frame or the
5406 @dfn{outermost} frame. Each time a function is called, a new frame is
5407 made. Each time a function returns, the frame for that function invocation
5408 is eliminated. If a function is recursive, there can be many frames for
5409 the same function. The frame for the function in which execution is
5410 actually occurring is called the @dfn{innermost} frame. This is the most
5411 recently created of all the stack frames that still exist.
5413 @cindex frame pointer
5414 Inside your program, stack frames are identified by their addresses. A
5415 stack frame consists of many bytes, each of which has its own address; each
5416 kind of computer has a convention for choosing one byte whose
5417 address serves as the address of the frame. Usually this address is kept
5418 in a register called the @dfn{frame pointer register}
5419 (@pxref{Registers, $fp}) while execution is going on in that frame.
5421 @cindex frame number
5422 @value{GDBN} assigns numbers to all existing stack frames, starting with
5423 zero for the innermost frame, one for the frame that called it,
5424 and so on upward. These numbers do not really exist in your program;
5425 they are assigned by @value{GDBN} to give you a way of designating stack
5426 frames in @value{GDBN} commands.
5428 @c The -fomit-frame-pointer below perennially causes hbox overflow
5429 @c underflow problems.
5430 @cindex frameless execution
5431 Some compilers provide a way to compile functions so that they operate
5432 without stack frames. (For example, the @value{NGCC} option
5434 @samp{-fomit-frame-pointer}
5436 generates functions without a frame.)
5437 This is occasionally done with heavily used library functions to save
5438 the frame setup time. @value{GDBN} has limited facilities for dealing
5439 with these function invocations. If the innermost function invocation
5440 has no stack frame, @value{GDBN} nevertheless regards it as though
5441 it had a separate frame, which is numbered zero as usual, allowing
5442 correct tracing of the function call chain. However, @value{GDBN} has
5443 no provision for frameless functions elsewhere in the stack.
5446 @kindex frame@r{, command}
5447 @cindex current stack frame
5448 @item frame @var{args}
5449 The @code{frame} command allows you to move from one stack frame to another,
5450 and to print the stack frame you select. @var{args} may be either the
5451 address of the frame or the stack frame number. Without an argument,
5452 @code{frame} prints the current stack frame.
5454 @kindex select-frame
5455 @cindex selecting frame silently
5457 The @code{select-frame} command allows you to move from one stack frame
5458 to another without printing the frame. This is the silent version of
5466 @cindex call stack traces
5467 A backtrace is a summary of how your program got where it is. It shows one
5468 line per frame, for many frames, starting with the currently executing
5469 frame (frame zero), followed by its caller (frame one), and on up the
5474 @kindex bt @r{(@code{backtrace})}
5477 Print a backtrace of the entire stack: one line per frame for all
5478 frames in the stack.
5480 You can stop the backtrace at any time by typing the system interrupt
5481 character, normally @kbd{Ctrl-c}.
5483 @item backtrace @var{n}
5485 Similar, but print only the innermost @var{n} frames.
5487 @item backtrace -@var{n}
5489 Similar, but print only the outermost @var{n} frames.
5491 @item backtrace full
5493 @itemx bt full @var{n}
5494 @itemx bt full -@var{n}
5495 Print the values of the local variables also. @var{n} specifies the
5496 number of frames to print, as described above.
5501 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5502 are additional aliases for @code{backtrace}.
5504 @cindex multiple threads, backtrace
5505 In a multi-threaded program, @value{GDBN} by default shows the
5506 backtrace only for the current thread. To display the backtrace for
5507 several or all of the threads, use the command @code{thread apply}
5508 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5509 apply all backtrace}, @value{GDBN} will display the backtrace for all
5510 the threads; this is handy when you debug a core dump of a
5511 multi-threaded program.
5513 Each line in the backtrace shows the frame number and the function name.
5514 The program counter value is also shown---unless you use @code{set
5515 print address off}. The backtrace also shows the source file name and
5516 line number, as well as the arguments to the function. The program
5517 counter value is omitted if it is at the beginning of the code for that
5520 Here is an example of a backtrace. It was made with the command
5521 @samp{bt 3}, so it shows the innermost three frames.
5525 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5527 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5528 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5530 (More stack frames follow...)
5535 The display for frame zero does not begin with a program counter
5536 value, indicating that your program has stopped at the beginning of the
5537 code for line @code{993} of @code{builtin.c}.
5540 The value of parameter @code{data} in frame 1 has been replaced by
5541 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5542 only if it is a scalar (integer, pointer, enumeration, etc). See command
5543 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5544 on how to configure the way function parameter values are printed.
5546 @cindex value optimized out, in backtrace
5547 @cindex function call arguments, optimized out
5548 If your program was compiled with optimizations, some compilers will
5549 optimize away arguments passed to functions if those arguments are
5550 never used after the call. Such optimizations generate code that
5551 passes arguments through registers, but doesn't store those arguments
5552 in the stack frame. @value{GDBN} has no way of displaying such
5553 arguments in stack frames other than the innermost one. Here's what
5554 such a backtrace might look like:
5558 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5560 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5561 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5563 (More stack frames follow...)
5568 The values of arguments that were not saved in their stack frames are
5569 shown as @samp{<value optimized out>}.
5571 If you need to display the values of such optimized-out arguments,
5572 either deduce that from other variables whose values depend on the one
5573 you are interested in, or recompile without optimizations.
5575 @cindex backtrace beyond @code{main} function
5576 @cindex program entry point
5577 @cindex startup code, and backtrace
5578 Most programs have a standard user entry point---a place where system
5579 libraries and startup code transition into user code. For C this is
5580 @code{main}@footnote{
5581 Note that embedded programs (the so-called ``free-standing''
5582 environment) are not required to have a @code{main} function as the
5583 entry point. They could even have multiple entry points.}.
5584 When @value{GDBN} finds the entry function in a backtrace
5585 it will terminate the backtrace, to avoid tracing into highly
5586 system-specific (and generally uninteresting) code.
5588 If you need to examine the startup code, or limit the number of levels
5589 in a backtrace, you can change this behavior:
5592 @item set backtrace past-main
5593 @itemx set backtrace past-main on
5594 @kindex set backtrace
5595 Backtraces will continue past the user entry point.
5597 @item set backtrace past-main off
5598 Backtraces will stop when they encounter the user entry point. This is the
5601 @item show backtrace past-main
5602 @kindex show backtrace
5603 Display the current user entry point backtrace policy.
5605 @item set backtrace past-entry
5606 @itemx set backtrace past-entry on
5607 Backtraces will continue past the internal entry point of an application.
5608 This entry point is encoded by the linker when the application is built,
5609 and is likely before the user entry point @code{main} (or equivalent) is called.
5611 @item set backtrace past-entry off
5612 Backtraces will stop when they encounter the internal entry point of an
5613 application. This is the default.
5615 @item show backtrace past-entry
5616 Display the current internal entry point backtrace policy.
5618 @item set backtrace limit @var{n}
5619 @itemx set backtrace limit 0
5620 @cindex backtrace limit
5621 Limit the backtrace to @var{n} levels. A value of zero means
5624 @item show backtrace limit
5625 Display the current limit on backtrace levels.
5629 @section Selecting a Frame
5631 Most commands for examining the stack and other data in your program work on
5632 whichever stack frame is selected at the moment. Here are the commands for
5633 selecting a stack frame; all of them finish by printing a brief description
5634 of the stack frame just selected.
5637 @kindex frame@r{, selecting}
5638 @kindex f @r{(@code{frame})}
5641 Select frame number @var{n}. Recall that frame zero is the innermost
5642 (currently executing) frame, frame one is the frame that called the
5643 innermost one, and so on. The highest-numbered frame is the one for
5646 @item frame @var{addr}
5648 Select the frame at address @var{addr}. This is useful mainly if the
5649 chaining of stack frames has been damaged by a bug, making it
5650 impossible for @value{GDBN} to assign numbers properly to all frames. In
5651 addition, this can be useful when your program has multiple stacks and
5652 switches between them.
5654 On the SPARC architecture, @code{frame} needs two addresses to
5655 select an arbitrary frame: a frame pointer and a stack pointer.
5657 On the MIPS and Alpha architecture, it needs two addresses: a stack
5658 pointer and a program counter.
5660 On the 29k architecture, it needs three addresses: a register stack
5661 pointer, a program counter, and a memory stack pointer.
5665 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5666 advances toward the outermost frame, to higher frame numbers, to frames
5667 that have existed longer. @var{n} defaults to one.
5670 @kindex do @r{(@code{down})}
5672 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5673 advances toward the innermost frame, to lower frame numbers, to frames
5674 that were created more recently. @var{n} defaults to one. You may
5675 abbreviate @code{down} as @code{do}.
5678 All of these commands end by printing two lines of output describing the
5679 frame. The first line shows the frame number, the function name, the
5680 arguments, and the source file and line number of execution in that
5681 frame. The second line shows the text of that source line.
5689 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5691 10 read_input_file (argv[i]);
5695 After such a printout, the @code{list} command with no arguments
5696 prints ten lines centered on the point of execution in the frame.
5697 You can also edit the program at the point of execution with your favorite
5698 editing program by typing @code{edit}.
5699 @xref{List, ,Printing Source Lines},
5703 @kindex down-silently
5705 @item up-silently @var{n}
5706 @itemx down-silently @var{n}
5707 These two commands are variants of @code{up} and @code{down},
5708 respectively; they differ in that they do their work silently, without
5709 causing display of the new frame. They are intended primarily for use
5710 in @value{GDBN} command scripts, where the output might be unnecessary and
5715 @section Information About a Frame
5717 There are several other commands to print information about the selected
5723 When used without any argument, this command does not change which
5724 frame is selected, but prints a brief description of the currently
5725 selected stack frame. It can be abbreviated @code{f}. With an
5726 argument, this command is used to select a stack frame.
5727 @xref{Selection, ,Selecting a Frame}.
5730 @kindex info f @r{(@code{info frame})}
5733 This command prints a verbose description of the selected stack frame,
5738 the address of the frame
5740 the address of the next frame down (called by this frame)
5742 the address of the next frame up (caller of this frame)
5744 the language in which the source code corresponding to this frame is written
5746 the address of the frame's arguments
5748 the address of the frame's local variables
5750 the program counter saved in it (the address of execution in the caller frame)
5752 which registers were saved in the frame
5755 @noindent The verbose description is useful when
5756 something has gone wrong that has made the stack format fail to fit
5757 the usual conventions.
5759 @item info frame @var{addr}
5760 @itemx info f @var{addr}
5761 Print a verbose description of the frame at address @var{addr}, without
5762 selecting that frame. The selected frame remains unchanged by this
5763 command. This requires the same kind of address (more than one for some
5764 architectures) that you specify in the @code{frame} command.
5765 @xref{Selection, ,Selecting a Frame}.
5769 Print the arguments of the selected frame, each on a separate line.
5773 Print the local variables of the selected frame, each on a separate
5774 line. These are all variables (declared either static or automatic)
5775 accessible at the point of execution of the selected frame.
5778 @cindex catch exceptions, list active handlers
5779 @cindex exception handlers, how to list
5781 Print a list of all the exception handlers that are active in the
5782 current stack frame at the current point of execution. To see other
5783 exception handlers, visit the associated frame (using the @code{up},
5784 @code{down}, or @code{frame} commands); then type @code{info catch}.
5785 @xref{Set Catchpoints, , Setting Catchpoints}.
5791 @chapter Examining Source Files
5793 @value{GDBN} can print parts of your program's source, since the debugging
5794 information recorded in the program tells @value{GDBN} what source files were
5795 used to build it. When your program stops, @value{GDBN} spontaneously prints
5796 the line where it stopped. Likewise, when you select a stack frame
5797 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5798 execution in that frame has stopped. You can print other portions of
5799 source files by explicit command.
5801 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5802 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5803 @value{GDBN} under @sc{gnu} Emacs}.
5806 * List:: Printing source lines
5807 * Specify Location:: How to specify code locations
5808 * Edit:: Editing source files
5809 * Search:: Searching source files
5810 * Source Path:: Specifying source directories
5811 * Machine Code:: Source and machine code
5815 @section Printing Source Lines
5818 @kindex l @r{(@code{list})}
5819 To print lines from a source file, use the @code{list} command
5820 (abbreviated @code{l}). By default, ten lines are printed.
5821 There are several ways to specify what part of the file you want to
5822 print; see @ref{Specify Location}, for the full list.
5824 Here are the forms of the @code{list} command most commonly used:
5827 @item list @var{linenum}
5828 Print lines centered around line number @var{linenum} in the
5829 current source file.
5831 @item list @var{function}
5832 Print lines centered around the beginning of function
5836 Print more lines. If the last lines printed were printed with a
5837 @code{list} command, this prints lines following the last lines
5838 printed; however, if the last line printed was a solitary line printed
5839 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5840 Stack}), this prints lines centered around that line.
5843 Print lines just before the lines last printed.
5846 @cindex @code{list}, how many lines to display
5847 By default, @value{GDBN} prints ten source lines with any of these forms of
5848 the @code{list} command. You can change this using @code{set listsize}:
5851 @kindex set listsize
5852 @item set listsize @var{count}
5853 Make the @code{list} command display @var{count} source lines (unless
5854 the @code{list} argument explicitly specifies some other number).
5856 @kindex show listsize
5858 Display the number of lines that @code{list} prints.
5861 Repeating a @code{list} command with @key{RET} discards the argument,
5862 so it is equivalent to typing just @code{list}. This is more useful
5863 than listing the same lines again. An exception is made for an
5864 argument of @samp{-}; that argument is preserved in repetition so that
5865 each repetition moves up in the source file.
5867 In general, the @code{list} command expects you to supply zero, one or two
5868 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5869 of writing them (@pxref{Specify Location}), but the effect is always
5870 to specify some source line.
5872 Here is a complete description of the possible arguments for @code{list}:
5875 @item list @var{linespec}
5876 Print lines centered around the line specified by @var{linespec}.
5878 @item list @var{first},@var{last}
5879 Print lines from @var{first} to @var{last}. Both arguments are
5880 linespecs. When a @code{list} command has two linespecs, and the
5881 source file of the second linespec is omitted, this refers to
5882 the same source file as the first linespec.
5884 @item list ,@var{last}
5885 Print lines ending with @var{last}.
5887 @item list @var{first},
5888 Print lines starting with @var{first}.
5891 Print lines just after the lines last printed.
5894 Print lines just before the lines last printed.
5897 As described in the preceding table.
5900 @node Specify Location
5901 @section Specifying a Location
5902 @cindex specifying location
5905 Several @value{GDBN} commands accept arguments that specify a location
5906 of your program's code. Since @value{GDBN} is a source-level
5907 debugger, a location usually specifies some line in the source code;
5908 for that reason, locations are also known as @dfn{linespecs}.
5910 Here are all the different ways of specifying a code location that
5911 @value{GDBN} understands:
5915 Specifies the line number @var{linenum} of the current source file.
5918 @itemx +@var{offset}
5919 Specifies the line @var{offset} lines before or after the @dfn{current
5920 line}. For the @code{list} command, the current line is the last one
5921 printed; for the breakpoint commands, this is the line at which
5922 execution stopped in the currently selected @dfn{stack frame}
5923 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5924 used as the second of the two linespecs in a @code{list} command,
5925 this specifies the line @var{offset} lines up or down from the first
5928 @item @var{filename}:@var{linenum}
5929 Specifies the line @var{linenum} in the source file @var{filename}.
5931 @item @var{function}
5932 Specifies the line that begins the body of the function @var{function}.
5933 For example, in C, this is the line with the open brace.
5935 @item @var{filename}:@var{function}
5936 Specifies the line that begins the body of the function @var{function}
5937 in the file @var{filename}. You only need the file name with a
5938 function name to avoid ambiguity when there are identically named
5939 functions in different source files.
5941 @item *@var{address}
5942 Specifies the program address @var{address}. For line-oriented
5943 commands, such as @code{list} and @code{edit}, this specifies a source
5944 line that contains @var{address}. For @code{break} and other
5945 breakpoint oriented commands, this can be used to set breakpoints in
5946 parts of your program which do not have debugging information or
5949 Here @var{address} may be any expression valid in the current working
5950 language (@pxref{Languages, working language}) that specifies a code
5951 address. In addition, as a convenience, @value{GDBN} extends the
5952 semantics of expressions used in locations to cover the situations
5953 that frequently happen during debugging. Here are the various forms
5957 @item @var{expression}
5958 Any expression valid in the current working language.
5960 @item @var{funcaddr}
5961 An address of a function or procedure derived from its name. In C,
5962 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5963 simply the function's name @var{function} (and actually a special case
5964 of a valid expression). In Pascal and Modula-2, this is
5965 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5966 (although the Pascal form also works).
5968 This form specifies the address of the function's first instruction,
5969 before the stack frame and arguments have been set up.
5971 @item '@var{filename}'::@var{funcaddr}
5972 Like @var{funcaddr} above, but also specifies the name of the source
5973 file explicitly. This is useful if the name of the function does not
5974 specify the function unambiguously, e.g., if there are several
5975 functions with identical names in different source files.
5982 @section Editing Source Files
5983 @cindex editing source files
5986 @kindex e @r{(@code{edit})}
5987 To edit the lines in a source file, use the @code{edit} command.
5988 The editing program of your choice
5989 is invoked with the current line set to
5990 the active line in the program.
5991 Alternatively, there are several ways to specify what part of the file you
5992 want to print if you want to see other parts of the program:
5995 @item edit @var{location}
5996 Edit the source file specified by @code{location}. Editing starts at
5997 that @var{location}, e.g., at the specified source line of the
5998 specified file. @xref{Specify Location}, for all the possible forms
5999 of the @var{location} argument; here are the forms of the @code{edit}
6000 command most commonly used:
6003 @item edit @var{number}
6004 Edit the current source file with @var{number} as the active line number.
6006 @item edit @var{function}
6007 Edit the file containing @var{function} at the beginning of its definition.
6012 @subsection Choosing your Editor
6013 You can customize @value{GDBN} to use any editor you want
6015 The only restriction is that your editor (say @code{ex}), recognizes the
6016 following command-line syntax:
6018 ex +@var{number} file
6020 The optional numeric value +@var{number} specifies the number of the line in
6021 the file where to start editing.}.
6022 By default, it is @file{@value{EDITOR}}, but you can change this
6023 by setting the environment variable @code{EDITOR} before using
6024 @value{GDBN}. For example, to configure @value{GDBN} to use the
6025 @code{vi} editor, you could use these commands with the @code{sh} shell:
6031 or in the @code{csh} shell,
6033 setenv EDITOR /usr/bin/vi
6038 @section Searching Source Files
6039 @cindex searching source files
6041 There are two commands for searching through the current source file for a
6046 @kindex forward-search
6047 @item forward-search @var{regexp}
6048 @itemx search @var{regexp}
6049 The command @samp{forward-search @var{regexp}} checks each line,
6050 starting with the one following the last line listed, for a match for
6051 @var{regexp}. It lists the line that is found. You can use the
6052 synonym @samp{search @var{regexp}} or abbreviate the command name as
6055 @kindex reverse-search
6056 @item reverse-search @var{regexp}
6057 The command @samp{reverse-search @var{regexp}} checks each line, starting
6058 with the one before the last line listed and going backward, for a match
6059 for @var{regexp}. It lists the line that is found. You can abbreviate
6060 this command as @code{rev}.
6064 @section Specifying Source Directories
6067 @cindex directories for source files
6068 Executable programs sometimes do not record the directories of the source
6069 files from which they were compiled, just the names. Even when they do,
6070 the directories could be moved between the compilation and your debugging
6071 session. @value{GDBN} has a list of directories to search for source files;
6072 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6073 it tries all the directories in the list, in the order they are present
6074 in the list, until it finds a file with the desired name.
6076 For example, suppose an executable references the file
6077 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6078 @file{/mnt/cross}. The file is first looked up literally; if this
6079 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6080 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6081 message is printed. @value{GDBN} does not look up the parts of the
6082 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6083 Likewise, the subdirectories of the source path are not searched: if
6084 the source path is @file{/mnt/cross}, and the binary refers to
6085 @file{foo.c}, @value{GDBN} would not find it under
6086 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6088 Plain file names, relative file names with leading directories, file
6089 names containing dots, etc.@: are all treated as described above; for
6090 instance, if the source path is @file{/mnt/cross}, and the source file
6091 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6092 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6093 that---@file{/mnt/cross/foo.c}.
6095 Note that the executable search path is @emph{not} used to locate the
6098 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6099 any information it has cached about where source files are found and where
6100 each line is in the file.
6104 When you start @value{GDBN}, its source path includes only @samp{cdir}
6105 and @samp{cwd}, in that order.
6106 To add other directories, use the @code{directory} command.
6108 The search path is used to find both program source files and @value{GDBN}
6109 script files (read using the @samp{-command} option and @samp{source} command).
6111 In addition to the source path, @value{GDBN} provides a set of commands
6112 that manage a list of source path substitution rules. A @dfn{substitution
6113 rule} specifies how to rewrite source directories stored in the program's
6114 debug information in case the sources were moved to a different
6115 directory between compilation and debugging. A rule is made of
6116 two strings, the first specifying what needs to be rewritten in
6117 the path, and the second specifying how it should be rewritten.
6118 In @ref{set substitute-path}, we name these two parts @var{from} and
6119 @var{to} respectively. @value{GDBN} does a simple string replacement
6120 of @var{from} with @var{to} at the start of the directory part of the
6121 source file name, and uses that result instead of the original file
6122 name to look up the sources.
6124 Using the previous example, suppose the @file{foo-1.0} tree has been
6125 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6126 @value{GDBN} to replace @file{/usr/src} in all source path names with
6127 @file{/mnt/cross}. The first lookup will then be
6128 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6129 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6130 substitution rule, use the @code{set substitute-path} command
6131 (@pxref{set substitute-path}).
6133 To avoid unexpected substitution results, a rule is applied only if the
6134 @var{from} part of the directory name ends at a directory separator.
6135 For instance, a rule substituting @file{/usr/source} into
6136 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6137 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6138 is applied only at the beginning of the directory name, this rule will
6139 not be applied to @file{/root/usr/source/baz.c} either.
6141 In many cases, you can achieve the same result using the @code{directory}
6142 command. However, @code{set substitute-path} can be more efficient in
6143 the case where the sources are organized in a complex tree with multiple
6144 subdirectories. With the @code{directory} command, you need to add each
6145 subdirectory of your project. If you moved the entire tree while
6146 preserving its internal organization, then @code{set substitute-path}
6147 allows you to direct the debugger to all the sources with one single
6150 @code{set substitute-path} is also more than just a shortcut command.
6151 The source path is only used if the file at the original location no
6152 longer exists. On the other hand, @code{set substitute-path} modifies
6153 the debugger behavior to look at the rewritten location instead. So, if
6154 for any reason a source file that is not relevant to your executable is
6155 located at the original location, a substitution rule is the only
6156 method available to point @value{GDBN} at the new location.
6158 @cindex @samp{--with-relocated-sources}
6159 @cindex default source path substitution
6160 You can configure a default source path substitution rule by
6161 configuring @value{GDBN} with the
6162 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6163 should be the name of a directory under @value{GDBN}'s configured
6164 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6165 directory names in debug information under @var{dir} will be adjusted
6166 automatically if the installed @value{GDBN} is moved to a new
6167 location. This is useful if @value{GDBN}, libraries or executables
6168 with debug information and corresponding source code are being moved
6172 @item directory @var{dirname} @dots{}
6173 @item dir @var{dirname} @dots{}
6174 Add directory @var{dirname} to the front of the source path. Several
6175 directory names may be given to this command, separated by @samp{:}
6176 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6177 part of absolute file names) or
6178 whitespace. You may specify a directory that is already in the source
6179 path; this moves it forward, so @value{GDBN} searches it sooner.
6183 @vindex $cdir@r{, convenience variable}
6184 @vindex $cwd@r{, convenience variable}
6185 @cindex compilation directory
6186 @cindex current directory
6187 @cindex working directory
6188 @cindex directory, current
6189 @cindex directory, compilation
6190 You can use the string @samp{$cdir} to refer to the compilation
6191 directory (if one is recorded), and @samp{$cwd} to refer to the current
6192 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6193 tracks the current working directory as it changes during your @value{GDBN}
6194 session, while the latter is immediately expanded to the current
6195 directory at the time you add an entry to the source path.
6198 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6200 @c RET-repeat for @code{directory} is explicitly disabled, but since
6201 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6203 @item show directories
6204 @kindex show directories
6205 Print the source path: show which directories it contains.
6207 @anchor{set substitute-path}
6208 @item set substitute-path @var{from} @var{to}
6209 @kindex set substitute-path
6210 Define a source path substitution rule, and add it at the end of the
6211 current list of existing substitution rules. If a rule with the same
6212 @var{from} was already defined, then the old rule is also deleted.
6214 For example, if the file @file{/foo/bar/baz.c} was moved to
6215 @file{/mnt/cross/baz.c}, then the command
6218 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6222 will tell @value{GDBN} to replace @samp{/usr/src} with
6223 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6224 @file{baz.c} even though it was moved.
6226 In the case when more than one substitution rule have been defined,
6227 the rules are evaluated one by one in the order where they have been
6228 defined. The first one matching, if any, is selected to perform
6231 For instance, if we had entered the following commands:
6234 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6235 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6239 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6240 @file{/mnt/include/defs.h} by using the first rule. However, it would
6241 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6242 @file{/mnt/src/lib/foo.c}.
6245 @item unset substitute-path [path]
6246 @kindex unset substitute-path
6247 If a path is specified, search the current list of substitution rules
6248 for a rule that would rewrite that path. Delete that rule if found.
6249 A warning is emitted by the debugger if no rule could be found.
6251 If no path is specified, then all substitution rules are deleted.
6253 @item show substitute-path [path]
6254 @kindex show substitute-path
6255 If a path is specified, then print the source path substitution rule
6256 which would rewrite that path, if any.
6258 If no path is specified, then print all existing source path substitution
6263 If your source path is cluttered with directories that are no longer of
6264 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6265 versions of source. You can correct the situation as follows:
6269 Use @code{directory} with no argument to reset the source path to its default value.
6272 Use @code{directory} with suitable arguments to reinstall the
6273 directories you want in the source path. You can add all the
6274 directories in one command.
6278 @section Source and Machine Code
6279 @cindex source line and its code address
6281 You can use the command @code{info line} to map source lines to program
6282 addresses (and vice versa), and the command @code{disassemble} to display
6283 a range of addresses as machine instructions. You can use the command
6284 @code{set disassemble-next-line} to set whether to disassemble next
6285 source line when execution stops. When run under @sc{gnu} Emacs
6286 mode, the @code{info line} command causes the arrow to point to the
6287 line specified. Also, @code{info line} prints addresses in symbolic form as
6292 @item info line @var{linespec}
6293 Print the starting and ending addresses of the compiled code for
6294 source line @var{linespec}. You can specify source lines in any of
6295 the ways documented in @ref{Specify Location}.
6298 For example, we can use @code{info line} to discover the location of
6299 the object code for the first line of function
6300 @code{m4_changequote}:
6302 @c FIXME: I think this example should also show the addresses in
6303 @c symbolic form, as they usually would be displayed.
6305 (@value{GDBP}) info line m4_changequote
6306 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6310 @cindex code address and its source line
6311 We can also inquire (using @code{*@var{addr}} as the form for
6312 @var{linespec}) what source line covers a particular address:
6314 (@value{GDBP}) info line *0x63ff
6315 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6318 @cindex @code{$_} and @code{info line}
6319 @cindex @code{x} command, default address
6320 @kindex x@r{(examine), and} info line
6321 After @code{info line}, the default address for the @code{x} command
6322 is changed to the starting address of the line, so that @samp{x/i} is
6323 sufficient to begin examining the machine code (@pxref{Memory,
6324 ,Examining Memory}). Also, this address is saved as the value of the
6325 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6330 @cindex assembly instructions
6331 @cindex instructions, assembly
6332 @cindex machine instructions
6333 @cindex listing machine instructions
6335 @itemx disassemble /m
6336 @itemx disassemble /r
6337 This specialized command dumps a range of memory as machine
6338 instructions. It can also print mixed source+disassembly by specifying
6339 the @code{/m} modifier and print the raw instructions in hex as well as
6340 in symbolic form by specifying the @code{/r}.
6341 The default memory range is the function surrounding the
6342 program counter of the selected frame. A single argument to this
6343 command is a program counter value; @value{GDBN} dumps the function
6344 surrounding this value. Two arguments specify a range of addresses
6345 (first inclusive, second exclusive) to dump.
6348 The following example shows the disassembly of a range of addresses of
6349 HP PA-RISC 2.0 code:
6352 (@value{GDBP}) disas 0x32c4 0x32e4
6353 Dump of assembler code from 0x32c4 to 0x32e4:
6354 0x32c4 <main+204>: addil 0,dp
6355 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6356 0x32cc <main+212>: ldil 0x3000,r31
6357 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6358 0x32d4 <main+220>: ldo 0(r31),rp
6359 0x32d8 <main+224>: addil -0x800,dp
6360 0x32dc <main+228>: ldo 0x588(r1),r26
6361 0x32e0 <main+232>: ldil 0x3000,r31
6362 End of assembler dump.
6365 Here is an example showing mixed source+assembly for Intel x86:
6368 (@value{GDBP}) disas /m main
6369 Dump of assembler code for function main:
6371 0x08048330 <main+0>: push %ebp
6372 0x08048331 <main+1>: mov %esp,%ebp
6373 0x08048333 <main+3>: sub $0x8,%esp
6374 0x08048336 <main+6>: and $0xfffffff0,%esp
6375 0x08048339 <main+9>: sub $0x10,%esp
6377 6 printf ("Hello.\n");
6378 0x0804833c <main+12>: movl $0x8048440,(%esp)
6379 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6383 0x08048348 <main+24>: mov $0x0,%eax
6384 0x0804834d <main+29>: leave
6385 0x0804834e <main+30>: ret
6387 End of assembler dump.
6390 Some architectures have more than one commonly-used set of instruction
6391 mnemonics or other syntax.
6393 For programs that were dynamically linked and use shared libraries,
6394 instructions that call functions or branch to locations in the shared
6395 libraries might show a seemingly bogus location---it's actually a
6396 location of the relocation table. On some architectures, @value{GDBN}
6397 might be able to resolve these to actual function names.
6400 @kindex set disassembly-flavor
6401 @cindex Intel disassembly flavor
6402 @cindex AT&T disassembly flavor
6403 @item set disassembly-flavor @var{instruction-set}
6404 Select the instruction set to use when disassembling the
6405 program via the @code{disassemble} or @code{x/i} commands.
6407 Currently this command is only defined for the Intel x86 family. You
6408 can set @var{instruction-set} to either @code{intel} or @code{att}.
6409 The default is @code{att}, the AT&T flavor used by default by Unix
6410 assemblers for x86-based targets.
6412 @kindex show disassembly-flavor
6413 @item show disassembly-flavor
6414 Show the current setting of the disassembly flavor.
6418 @kindex set disassemble-next-line
6419 @kindex show disassemble-next-line
6420 @item set disassemble-next-line
6421 @itemx show disassemble-next-line
6422 Control whether or not @value{GDBN} will disassemble the next source
6423 line or instruction when execution stops. If ON, @value{GDBN} will
6424 display disassembly of the next source line when execution of the
6425 program being debugged stops. This is @emph{in addition} to
6426 displaying the source line itself, which @value{GDBN} always does if
6427 possible. If the next source line cannot be displayed for some reason
6428 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6429 info in the debug info), @value{GDBN} will display disassembly of the
6430 next @emph{instruction} instead of showing the next source line. If
6431 AUTO, @value{GDBN} will display disassembly of next instruction only
6432 if the source line cannot be displayed. This setting causes
6433 @value{GDBN} to display some feedback when you step through a function
6434 with no line info or whose source file is unavailable. The default is
6435 OFF, which means never display the disassembly of the next line or
6441 @chapter Examining Data
6443 @cindex printing data
6444 @cindex examining data
6447 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6448 @c document because it is nonstandard... Under Epoch it displays in a
6449 @c different window or something like that.
6450 The usual way to examine data in your program is with the @code{print}
6451 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6452 evaluates and prints the value of an expression of the language your
6453 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6454 Different Languages}).
6457 @item print @var{expr}
6458 @itemx print /@var{f} @var{expr}
6459 @var{expr} is an expression (in the source language). By default the
6460 value of @var{expr} is printed in a format appropriate to its data type;
6461 you can choose a different format by specifying @samp{/@var{f}}, where
6462 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6466 @itemx print /@var{f}
6467 @cindex reprint the last value
6468 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6469 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6470 conveniently inspect the same value in an alternative format.
6473 A more low-level way of examining data is with the @code{x} command.
6474 It examines data in memory at a specified address and prints it in a
6475 specified format. @xref{Memory, ,Examining Memory}.
6477 If you are interested in information about types, or about how the
6478 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6479 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6483 * Expressions:: Expressions
6484 * Ambiguous Expressions:: Ambiguous Expressions
6485 * Variables:: Program variables
6486 * Arrays:: Artificial arrays
6487 * Output Formats:: Output formats
6488 * Memory:: Examining memory
6489 * Auto Display:: Automatic display
6490 * Print Settings:: Print settings
6491 * Value History:: Value history
6492 * Convenience Vars:: Convenience variables
6493 * Registers:: Registers
6494 * Floating Point Hardware:: Floating point hardware
6495 * Vector Unit:: Vector Unit
6496 * OS Information:: Auxiliary data provided by operating system
6497 * Memory Region Attributes:: Memory region attributes
6498 * Dump/Restore Files:: Copy between memory and a file
6499 * Core File Generation:: Cause a program dump its core
6500 * Character Sets:: Debugging programs that use a different
6501 character set than GDB does
6502 * Caching Remote Data:: Data caching for remote targets
6503 * Searching Memory:: Searching memory for a sequence of bytes
6507 @section Expressions
6510 @code{print} and many other @value{GDBN} commands accept an expression and
6511 compute its value. Any kind of constant, variable or operator defined
6512 by the programming language you are using is valid in an expression in
6513 @value{GDBN}. This includes conditional expressions, function calls,
6514 casts, and string constants. It also includes preprocessor macros, if
6515 you compiled your program to include this information; see
6518 @cindex arrays in expressions
6519 @value{GDBN} supports array constants in expressions input by
6520 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6521 you can use the command @code{print @{1, 2, 3@}} to create an array
6522 of three integers. If you pass an array to a function or assign it
6523 to a program variable, @value{GDBN} copies the array to memory that
6524 is @code{malloc}ed in the target program.
6526 Because C is so widespread, most of the expressions shown in examples in
6527 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6528 Languages}, for information on how to use expressions in other
6531 In this section, we discuss operators that you can use in @value{GDBN}
6532 expressions regardless of your programming language.
6534 @cindex casts, in expressions
6535 Casts are supported in all languages, not just in C, because it is so
6536 useful to cast a number into a pointer in order to examine a structure
6537 at that address in memory.
6538 @c FIXME: casts supported---Mod2 true?
6540 @value{GDBN} supports these operators, in addition to those common
6541 to programming languages:
6545 @samp{@@} is a binary operator for treating parts of memory as arrays.
6546 @xref{Arrays, ,Artificial Arrays}, for more information.
6549 @samp{::} allows you to specify a variable in terms of the file or
6550 function where it is defined. @xref{Variables, ,Program Variables}.
6552 @cindex @{@var{type}@}
6553 @cindex type casting memory
6554 @cindex memory, viewing as typed object
6555 @cindex casts, to view memory
6556 @item @{@var{type}@} @var{addr}
6557 Refers to an object of type @var{type} stored at address @var{addr} in
6558 memory. @var{addr} may be any expression whose value is an integer or
6559 pointer (but parentheses are required around binary operators, just as in
6560 a cast). This construct is allowed regardless of what kind of data is
6561 normally supposed to reside at @var{addr}.
6564 @node Ambiguous Expressions
6565 @section Ambiguous Expressions
6566 @cindex ambiguous expressions
6568 Expressions can sometimes contain some ambiguous elements. For instance,
6569 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6570 a single function name to be defined several times, for application in
6571 different contexts. This is called @dfn{overloading}. Another example
6572 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6573 templates and is typically instantiated several times, resulting in
6574 the same function name being defined in different contexts.
6576 In some cases and depending on the language, it is possible to adjust
6577 the expression to remove the ambiguity. For instance in C@t{++}, you
6578 can specify the signature of the function you want to break on, as in
6579 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6580 qualified name of your function often makes the expression unambiguous
6583 When an ambiguity that needs to be resolved is detected, the debugger
6584 has the capability to display a menu of numbered choices for each
6585 possibility, and then waits for the selection with the prompt @samp{>}.
6586 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6587 aborts the current command. If the command in which the expression was
6588 used allows more than one choice to be selected, the next option in the
6589 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6592 For example, the following session excerpt shows an attempt to set a
6593 breakpoint at the overloaded symbol @code{String::after}.
6594 We choose three particular definitions of that function name:
6596 @c FIXME! This is likely to change to show arg type lists, at least
6599 (@value{GDBP}) b String::after
6602 [2] file:String.cc; line number:867
6603 [3] file:String.cc; line number:860
6604 [4] file:String.cc; line number:875
6605 [5] file:String.cc; line number:853
6606 [6] file:String.cc; line number:846
6607 [7] file:String.cc; line number:735
6609 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6610 Breakpoint 2 at 0xb344: file String.cc, line 875.
6611 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6612 Multiple breakpoints were set.
6613 Use the "delete" command to delete unwanted
6620 @kindex set multiple-symbols
6621 @item set multiple-symbols @var{mode}
6622 @cindex multiple-symbols menu
6624 This option allows you to adjust the debugger behavior when an expression
6627 By default, @var{mode} is set to @code{all}. If the command with which
6628 the expression is used allows more than one choice, then @value{GDBN}
6629 automatically selects all possible choices. For instance, inserting
6630 a breakpoint on a function using an ambiguous name results in a breakpoint
6631 inserted on each possible match. However, if a unique choice must be made,
6632 then @value{GDBN} uses the menu to help you disambiguate the expression.
6633 For instance, printing the address of an overloaded function will result
6634 in the use of the menu.
6636 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6637 when an ambiguity is detected.
6639 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6640 an error due to the ambiguity and the command is aborted.
6642 @kindex show multiple-symbols
6643 @item show multiple-symbols
6644 Show the current value of the @code{multiple-symbols} setting.
6648 @section Program Variables
6650 The most common kind of expression to use is the name of a variable
6653 Variables in expressions are understood in the selected stack frame
6654 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6658 global (or file-static)
6665 visible according to the scope rules of the
6666 programming language from the point of execution in that frame
6669 @noindent This means that in the function
6684 you can examine and use the variable @code{a} whenever your program is
6685 executing within the function @code{foo}, but you can only use or
6686 examine the variable @code{b} while your program is executing inside
6687 the block where @code{b} is declared.
6689 @cindex variable name conflict
6690 There is an exception: you can refer to a variable or function whose
6691 scope is a single source file even if the current execution point is not
6692 in this file. But it is possible to have more than one such variable or
6693 function with the same name (in different source files). If that
6694 happens, referring to that name has unpredictable effects. If you wish,
6695 you can specify a static variable in a particular function or file,
6696 using the colon-colon (@code{::}) notation:
6698 @cindex colon-colon, context for variables/functions
6700 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6701 @cindex @code{::}, context for variables/functions
6704 @var{file}::@var{variable}
6705 @var{function}::@var{variable}
6709 Here @var{file} or @var{function} is the name of the context for the
6710 static @var{variable}. In the case of file names, you can use quotes to
6711 make sure @value{GDBN} parses the file name as a single word---for example,
6712 to print a global value of @code{x} defined in @file{f2.c}:
6715 (@value{GDBP}) p 'f2.c'::x
6718 @cindex C@t{++} scope resolution
6719 This use of @samp{::} is very rarely in conflict with the very similar
6720 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6721 scope resolution operator in @value{GDBN} expressions.
6722 @c FIXME: Um, so what happens in one of those rare cases where it's in
6725 @cindex wrong values
6726 @cindex variable values, wrong
6727 @cindex function entry/exit, wrong values of variables
6728 @cindex optimized code, wrong values of variables
6730 @emph{Warning:} Occasionally, a local variable may appear to have the
6731 wrong value at certain points in a function---just after entry to a new
6732 scope, and just before exit.
6734 You may see this problem when you are stepping by machine instructions.
6735 This is because, on most machines, it takes more than one instruction to
6736 set up a stack frame (including local variable definitions); if you are
6737 stepping by machine instructions, variables may appear to have the wrong
6738 values until the stack frame is completely built. On exit, it usually
6739 also takes more than one machine instruction to destroy a stack frame;
6740 after you begin stepping through that group of instructions, local
6741 variable definitions may be gone.
6743 This may also happen when the compiler does significant optimizations.
6744 To be sure of always seeing accurate values, turn off all optimization
6747 @cindex ``No symbol "foo" in current context''
6748 Another possible effect of compiler optimizations is to optimize
6749 unused variables out of existence, or assign variables to registers (as
6750 opposed to memory addresses). Depending on the support for such cases
6751 offered by the debug info format used by the compiler, @value{GDBN}
6752 might not be able to display values for such local variables. If that
6753 happens, @value{GDBN} will print a message like this:
6756 No symbol "foo" in current context.
6759 To solve such problems, either recompile without optimizations, or use a
6760 different debug info format, if the compiler supports several such
6761 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6762 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6763 produces debug info in a format that is superior to formats such as
6764 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6765 an effective form for debug info. @xref{Debugging Options,,Options
6766 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6767 Compiler Collection (GCC)}.
6768 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6769 that are best suited to C@t{++} programs.
6771 If you ask to print an object whose contents are unknown to
6772 @value{GDBN}, e.g., because its data type is not completely specified
6773 by the debug information, @value{GDBN} will say @samp{<incomplete
6774 type>}. @xref{Symbols, incomplete type}, for more about this.
6776 Strings are identified as arrays of @code{char} values without specified
6777 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6778 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6779 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6780 defines literal string type @code{"char"} as @code{char} without a sign.
6785 signed char var1[] = "A";
6788 You get during debugging
6793 $2 = @{65 'A', 0 '\0'@}
6797 @section Artificial Arrays
6799 @cindex artificial array
6801 @kindex @@@r{, referencing memory as an array}
6802 It is often useful to print out several successive objects of the
6803 same type in memory; a section of an array, or an array of
6804 dynamically determined size for which only a pointer exists in the
6807 You can do this by referring to a contiguous span of memory as an
6808 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6809 operand of @samp{@@} should be the first element of the desired array
6810 and be an individual object. The right operand should be the desired length
6811 of the array. The result is an array value whose elements are all of
6812 the type of the left argument. The first element is actually the left
6813 argument; the second element comes from bytes of memory immediately
6814 following those that hold the first element, and so on. Here is an
6815 example. If a program says
6818 int *array = (int *) malloc (len * sizeof (int));
6822 you can print the contents of @code{array} with
6828 The left operand of @samp{@@} must reside in memory. Array values made
6829 with @samp{@@} in this way behave just like other arrays in terms of
6830 subscripting, and are coerced to pointers when used in expressions.
6831 Artificial arrays most often appear in expressions via the value history
6832 (@pxref{Value History, ,Value History}), after printing one out.
6834 Another way to create an artificial array is to use a cast.
6835 This re-interprets a value as if it were an array.
6836 The value need not be in memory:
6838 (@value{GDBP}) p/x (short[2])0x12345678
6839 $1 = @{0x1234, 0x5678@}
6842 As a convenience, if you leave the array length out (as in
6843 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6844 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6846 (@value{GDBP}) p/x (short[])0x12345678
6847 $2 = @{0x1234, 0x5678@}
6850 Sometimes the artificial array mechanism is not quite enough; in
6851 moderately complex data structures, the elements of interest may not
6852 actually be adjacent---for example, if you are interested in the values
6853 of pointers in an array. One useful work-around in this situation is
6854 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6855 Variables}) as a counter in an expression that prints the first
6856 interesting value, and then repeat that expression via @key{RET}. For
6857 instance, suppose you have an array @code{dtab} of pointers to
6858 structures, and you are interested in the values of a field @code{fv}
6859 in each structure. Here is an example of what you might type:
6869 @node Output Formats
6870 @section Output Formats
6872 @cindex formatted output
6873 @cindex output formats
6874 By default, @value{GDBN} prints a value according to its data type. Sometimes
6875 this is not what you want. For example, you might want to print a number
6876 in hex, or a pointer in decimal. Or you might want to view data in memory
6877 at a certain address as a character string or as an instruction. To do
6878 these things, specify an @dfn{output format} when you print a value.
6880 The simplest use of output formats is to say how to print a value
6881 already computed. This is done by starting the arguments of the
6882 @code{print} command with a slash and a format letter. The format
6883 letters supported are:
6887 Regard the bits of the value as an integer, and print the integer in
6891 Print as integer in signed decimal.
6894 Print as integer in unsigned decimal.
6897 Print as integer in octal.
6900 Print as integer in binary. The letter @samp{t} stands for ``two''.
6901 @footnote{@samp{b} cannot be used because these format letters are also
6902 used with the @code{x} command, where @samp{b} stands for ``byte'';
6903 see @ref{Memory,,Examining Memory}.}
6906 @cindex unknown address, locating
6907 @cindex locate address
6908 Print as an address, both absolute in hexadecimal and as an offset from
6909 the nearest preceding symbol. You can use this format used to discover
6910 where (in what function) an unknown address is located:
6913 (@value{GDBP}) p/a 0x54320
6914 $3 = 0x54320 <_initialize_vx+396>
6918 The command @code{info symbol 0x54320} yields similar results.
6919 @xref{Symbols, info symbol}.
6922 Regard as an integer and print it as a character constant. This
6923 prints both the numerical value and its character representation. The
6924 character representation is replaced with the octal escape @samp{\nnn}
6925 for characters outside the 7-bit @sc{ascii} range.
6927 Without this format, @value{GDBN} displays @code{char},
6928 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6929 constants. Single-byte members of vectors are displayed as integer
6933 Regard the bits of the value as a floating point number and print
6934 using typical floating point syntax.
6937 @cindex printing strings
6938 @cindex printing byte arrays
6939 Regard as a string, if possible. With this format, pointers to single-byte
6940 data are displayed as null-terminated strings and arrays of single-byte data
6941 are displayed as fixed-length strings. Other values are displayed in their
6944 Without this format, @value{GDBN} displays pointers to and arrays of
6945 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6946 strings. Single-byte members of a vector are displayed as an integer
6950 @cindex raw printing
6951 Print using the @samp{raw} formatting. By default, @value{GDBN} will
6952 use a type-specific pretty-printer. The @samp{r} format bypasses any
6953 pretty-printer which might exist for the value's type.
6956 For example, to print the program counter in hex (@pxref{Registers}), type
6963 Note that no space is required before the slash; this is because command
6964 names in @value{GDBN} cannot contain a slash.
6966 To reprint the last value in the value history with a different format,
6967 you can use the @code{print} command with just a format and no
6968 expression. For example, @samp{p/x} reprints the last value in hex.
6971 @section Examining Memory
6973 You can use the command @code{x} (for ``examine'') to examine memory in
6974 any of several formats, independently of your program's data types.
6976 @cindex examining memory
6978 @kindex x @r{(examine memory)}
6979 @item x/@var{nfu} @var{addr}
6982 Use the @code{x} command to examine memory.
6985 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6986 much memory to display and how to format it; @var{addr} is an
6987 expression giving the address where you want to start displaying memory.
6988 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6989 Several commands set convenient defaults for @var{addr}.
6992 @item @var{n}, the repeat count
6993 The repeat count is a decimal integer; the default is 1. It specifies
6994 how much memory (counting by units @var{u}) to display.
6995 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6998 @item @var{f}, the display format
6999 The display format is one of the formats used by @code{print}
7000 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7001 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7002 The default is @samp{x} (hexadecimal) initially. The default changes
7003 each time you use either @code{x} or @code{print}.
7005 @item @var{u}, the unit size
7006 The unit size is any of
7012 Halfwords (two bytes).
7014 Words (four bytes). This is the initial default.
7016 Giant words (eight bytes).
7019 Each time you specify a unit size with @code{x}, that size becomes the
7020 default unit the next time you use @code{x}. (For the @samp{s} and
7021 @samp{i} formats, the unit size is ignored and is normally not written.)
7023 @item @var{addr}, starting display address
7024 @var{addr} is the address where you want @value{GDBN} to begin displaying
7025 memory. The expression need not have a pointer value (though it may);
7026 it is always interpreted as an integer address of a byte of memory.
7027 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7028 @var{addr} is usually just after the last address examined---but several
7029 other commands also set the default address: @code{info breakpoints} (to
7030 the address of the last breakpoint listed), @code{info line} (to the
7031 starting address of a line), and @code{print} (if you use it to display
7032 a value from memory).
7035 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7036 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7037 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7038 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7039 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7041 Since the letters indicating unit sizes are all distinct from the
7042 letters specifying output formats, you do not have to remember whether
7043 unit size or format comes first; either order works. The output
7044 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7045 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7047 Even though the unit size @var{u} is ignored for the formats @samp{s}
7048 and @samp{i}, you might still want to use a count @var{n}; for example,
7049 @samp{3i} specifies that you want to see three machine instructions,
7050 including any operands. For convenience, especially when used with
7051 the @code{display} command, the @samp{i} format also prints branch delay
7052 slot instructions, if any, beyond the count specified, which immediately
7053 follow the last instruction that is within the count. The command
7054 @code{disassemble} gives an alternative way of inspecting machine
7055 instructions; see @ref{Machine Code,,Source and Machine Code}.
7057 All the defaults for the arguments to @code{x} are designed to make it
7058 easy to continue scanning memory with minimal specifications each time
7059 you use @code{x}. For example, after you have inspected three machine
7060 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7061 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7062 the repeat count @var{n} is used again; the other arguments default as
7063 for successive uses of @code{x}.
7065 @cindex @code{$_}, @code{$__}, and value history
7066 The addresses and contents printed by the @code{x} command are not saved
7067 in the value history because there is often too much of them and they
7068 would get in the way. Instead, @value{GDBN} makes these values available for
7069 subsequent use in expressions as values of the convenience variables
7070 @code{$_} and @code{$__}. After an @code{x} command, the last address
7071 examined is available for use in expressions in the convenience variable
7072 @code{$_}. The contents of that address, as examined, are available in
7073 the convenience variable @code{$__}.
7075 If the @code{x} command has a repeat count, the address and contents saved
7076 are from the last memory unit printed; this is not the same as the last
7077 address printed if several units were printed on the last line of output.
7079 @cindex remote memory comparison
7080 @cindex verify remote memory image
7081 When you are debugging a program running on a remote target machine
7082 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7083 remote machine's memory against the executable file you downloaded to
7084 the target. The @code{compare-sections} command is provided for such
7088 @kindex compare-sections
7089 @item compare-sections @r{[}@var{section-name}@r{]}
7090 Compare the data of a loadable section @var{section-name} in the
7091 executable file of the program being debugged with the same section in
7092 the remote machine's memory, and report any mismatches. With no
7093 arguments, compares all loadable sections. This command's
7094 availability depends on the target's support for the @code{"qCRC"}
7099 @section Automatic Display
7100 @cindex automatic display
7101 @cindex display of expressions
7103 If you find that you want to print the value of an expression frequently
7104 (to see how it changes), you might want to add it to the @dfn{automatic
7105 display list} so that @value{GDBN} prints its value each time your program stops.
7106 Each expression added to the list is given a number to identify it;
7107 to remove an expression from the list, you specify that number.
7108 The automatic display looks like this:
7112 3: bar[5] = (struct hack *) 0x3804
7116 This display shows item numbers, expressions and their current values. As with
7117 displays you request manually using @code{x} or @code{print}, you can
7118 specify the output format you prefer; in fact, @code{display} decides
7119 whether to use @code{print} or @code{x} depending your format
7120 specification---it uses @code{x} if you specify either the @samp{i}
7121 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7125 @item display @var{expr}
7126 Add the expression @var{expr} to the list of expressions to display
7127 each time your program stops. @xref{Expressions, ,Expressions}.
7129 @code{display} does not repeat if you press @key{RET} again after using it.
7131 @item display/@var{fmt} @var{expr}
7132 For @var{fmt} specifying only a display format and not a size or
7133 count, add the expression @var{expr} to the auto-display list but
7134 arrange to display it each time in the specified format @var{fmt}.
7135 @xref{Output Formats,,Output Formats}.
7137 @item display/@var{fmt} @var{addr}
7138 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7139 number of units, add the expression @var{addr} as a memory address to
7140 be examined each time your program stops. Examining means in effect
7141 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7144 For example, @samp{display/i $pc} can be helpful, to see the machine
7145 instruction about to be executed each time execution stops (@samp{$pc}
7146 is a common name for the program counter; @pxref{Registers, ,Registers}).
7149 @kindex delete display
7151 @item undisplay @var{dnums}@dots{}
7152 @itemx delete display @var{dnums}@dots{}
7153 Remove item numbers @var{dnums} from the list of expressions to display.
7155 @code{undisplay} does not repeat if you press @key{RET} after using it.
7156 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7158 @kindex disable display
7159 @item disable display @var{dnums}@dots{}
7160 Disable the display of item numbers @var{dnums}. A disabled display
7161 item is not printed automatically, but is not forgotten. It may be
7162 enabled again later.
7164 @kindex enable display
7165 @item enable display @var{dnums}@dots{}
7166 Enable display of item numbers @var{dnums}. It becomes effective once
7167 again in auto display of its expression, until you specify otherwise.
7170 Display the current values of the expressions on the list, just as is
7171 done when your program stops.
7173 @kindex info display
7175 Print the list of expressions previously set up to display
7176 automatically, each one with its item number, but without showing the
7177 values. This includes disabled expressions, which are marked as such.
7178 It also includes expressions which would not be displayed right now
7179 because they refer to automatic variables not currently available.
7182 @cindex display disabled out of scope
7183 If a display expression refers to local variables, then it does not make
7184 sense outside the lexical context for which it was set up. Such an
7185 expression is disabled when execution enters a context where one of its
7186 variables is not defined. For example, if you give the command
7187 @code{display last_char} while inside a function with an argument
7188 @code{last_char}, @value{GDBN} displays this argument while your program
7189 continues to stop inside that function. When it stops elsewhere---where
7190 there is no variable @code{last_char}---the display is disabled
7191 automatically. The next time your program stops where @code{last_char}
7192 is meaningful, you can enable the display expression once again.
7194 @node Print Settings
7195 @section Print Settings
7197 @cindex format options
7198 @cindex print settings
7199 @value{GDBN} provides the following ways to control how arrays, structures,
7200 and symbols are printed.
7203 These settings are useful for debugging programs in any language:
7207 @item set print address
7208 @itemx set print address on
7209 @cindex print/don't print memory addresses
7210 @value{GDBN} prints memory addresses showing the location of stack
7211 traces, structure values, pointer values, breakpoints, and so forth,
7212 even when it also displays the contents of those addresses. The default
7213 is @code{on}. For example, this is what a stack frame display looks like with
7214 @code{set print address on}:
7219 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7221 530 if (lquote != def_lquote)
7225 @item set print address off
7226 Do not print addresses when displaying their contents. For example,
7227 this is the same stack frame displayed with @code{set print address off}:
7231 (@value{GDBP}) set print addr off
7233 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7234 530 if (lquote != def_lquote)
7238 You can use @samp{set print address off} to eliminate all machine
7239 dependent displays from the @value{GDBN} interface. For example, with
7240 @code{print address off}, you should get the same text for backtraces on
7241 all machines---whether or not they involve pointer arguments.
7244 @item show print address
7245 Show whether or not addresses are to be printed.
7248 When @value{GDBN} prints a symbolic address, it normally prints the
7249 closest earlier symbol plus an offset. If that symbol does not uniquely
7250 identify the address (for example, it is a name whose scope is a single
7251 source file), you may need to clarify. One way to do this is with
7252 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7253 you can set @value{GDBN} to print the source file and line number when
7254 it prints a symbolic address:
7257 @item set print symbol-filename on
7258 @cindex source file and line of a symbol
7259 @cindex symbol, source file and line
7260 Tell @value{GDBN} to print the source file name and line number of a
7261 symbol in the symbolic form of an address.
7263 @item set print symbol-filename off
7264 Do not print source file name and line number of a symbol. This is the
7267 @item show print symbol-filename
7268 Show whether or not @value{GDBN} will print the source file name and
7269 line number of a symbol in the symbolic form of an address.
7272 Another situation where it is helpful to show symbol filenames and line
7273 numbers is when disassembling code; @value{GDBN} shows you the line
7274 number and source file that corresponds to each instruction.
7276 Also, you may wish to see the symbolic form only if the address being
7277 printed is reasonably close to the closest earlier symbol:
7280 @item set print max-symbolic-offset @var{max-offset}
7281 @cindex maximum value for offset of closest symbol
7282 Tell @value{GDBN} to only display the symbolic form of an address if the
7283 offset between the closest earlier symbol and the address is less than
7284 @var{max-offset}. The default is 0, which tells @value{GDBN}
7285 to always print the symbolic form of an address if any symbol precedes it.
7287 @item show print max-symbolic-offset
7288 Ask how large the maximum offset is that @value{GDBN} prints in a
7292 @cindex wild pointer, interpreting
7293 @cindex pointer, finding referent
7294 If you have a pointer and you are not sure where it points, try
7295 @samp{set print symbol-filename on}. Then you can determine the name
7296 and source file location of the variable where it points, using
7297 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7298 For example, here @value{GDBN} shows that a variable @code{ptt} points
7299 at another variable @code{t}, defined in @file{hi2.c}:
7302 (@value{GDBP}) set print symbol-filename on
7303 (@value{GDBP}) p/a ptt
7304 $4 = 0xe008 <t in hi2.c>
7308 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7309 does not show the symbol name and filename of the referent, even with
7310 the appropriate @code{set print} options turned on.
7313 Other settings control how different kinds of objects are printed:
7316 @item set print array
7317 @itemx set print array on
7318 @cindex pretty print arrays
7319 Pretty print arrays. This format is more convenient to read,
7320 but uses more space. The default is off.
7322 @item set print array off
7323 Return to compressed format for arrays.
7325 @item show print array
7326 Show whether compressed or pretty format is selected for displaying
7329 @cindex print array indexes
7330 @item set print array-indexes
7331 @itemx set print array-indexes on
7332 Print the index of each element when displaying arrays. May be more
7333 convenient to locate a given element in the array or quickly find the
7334 index of a given element in that printed array. The default is off.
7336 @item set print array-indexes off
7337 Stop printing element indexes when displaying arrays.
7339 @item show print array-indexes
7340 Show whether the index of each element is printed when displaying
7343 @item set print elements @var{number-of-elements}
7344 @cindex number of array elements to print
7345 @cindex limit on number of printed array elements
7346 Set a limit on how many elements of an array @value{GDBN} will print.
7347 If @value{GDBN} is printing a large array, it stops printing after it has
7348 printed the number of elements set by the @code{set print elements} command.
7349 This limit also applies to the display of strings.
7350 When @value{GDBN} starts, this limit is set to 200.
7351 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7353 @item show print elements
7354 Display the number of elements of a large array that @value{GDBN} will print.
7355 If the number is 0, then the printing is unlimited.
7357 @item set print frame-arguments @var{value}
7358 @kindex set print frame-arguments
7359 @cindex printing frame argument values
7360 @cindex print all frame argument values
7361 @cindex print frame argument values for scalars only
7362 @cindex do not print frame argument values
7363 This command allows to control how the values of arguments are printed
7364 when the debugger prints a frame (@pxref{Frames}). The possible
7369 The values of all arguments are printed.
7372 Print the value of an argument only if it is a scalar. The value of more
7373 complex arguments such as arrays, structures, unions, etc, is replaced
7374 by @code{@dots{}}. This is the default. Here is an example where
7375 only scalar arguments are shown:
7378 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7383 None of the argument values are printed. Instead, the value of each argument
7384 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7387 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7392 By default, only scalar arguments are printed. This command can be used
7393 to configure the debugger to print the value of all arguments, regardless
7394 of their type. However, it is often advantageous to not print the value
7395 of more complex parameters. For instance, it reduces the amount of
7396 information printed in each frame, making the backtrace more readable.
7397 Also, it improves performance when displaying Ada frames, because
7398 the computation of large arguments can sometimes be CPU-intensive,
7399 especially in large applications. Setting @code{print frame-arguments}
7400 to @code{scalars} (the default) or @code{none} avoids this computation,
7401 thus speeding up the display of each Ada frame.
7403 @item show print frame-arguments
7404 Show how the value of arguments should be displayed when printing a frame.
7406 @item set print repeats
7407 @cindex repeated array elements
7408 Set the threshold for suppressing display of repeated array
7409 elements. When the number of consecutive identical elements of an
7410 array exceeds the threshold, @value{GDBN} prints the string
7411 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7412 identical repetitions, instead of displaying the identical elements
7413 themselves. Setting the threshold to zero will cause all elements to
7414 be individually printed. The default threshold is 10.
7416 @item show print repeats
7417 Display the current threshold for printing repeated identical
7420 @item set print null-stop
7421 @cindex @sc{null} elements in arrays
7422 Cause @value{GDBN} to stop printing the characters of an array when the first
7423 @sc{null} is encountered. This is useful when large arrays actually
7424 contain only short strings.
7427 @item show print null-stop
7428 Show whether @value{GDBN} stops printing an array on the first
7429 @sc{null} character.
7431 @item set print pretty on
7432 @cindex print structures in indented form
7433 @cindex indentation in structure display
7434 Cause @value{GDBN} to print structures in an indented format with one member
7435 per line, like this:
7450 @item set print pretty off
7451 Cause @value{GDBN} to print structures in a compact format, like this:
7455 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7456 meat = 0x54 "Pork"@}
7461 This is the default format.
7463 @item show print pretty
7464 Show which format @value{GDBN} is using to print structures.
7466 @item set print sevenbit-strings on
7467 @cindex eight-bit characters in strings
7468 @cindex octal escapes in strings
7469 Print using only seven-bit characters; if this option is set,
7470 @value{GDBN} displays any eight-bit characters (in strings or
7471 character values) using the notation @code{\}@var{nnn}. This setting is
7472 best if you are working in English (@sc{ascii}) and you use the
7473 high-order bit of characters as a marker or ``meta'' bit.
7475 @item set print sevenbit-strings off
7476 Print full eight-bit characters. This allows the use of more
7477 international character sets, and is the default.
7479 @item show print sevenbit-strings
7480 Show whether or not @value{GDBN} is printing only seven-bit characters.
7482 @item set print union on
7483 @cindex unions in structures, printing
7484 Tell @value{GDBN} to print unions which are contained in structures
7485 and other unions. This is the default setting.
7487 @item set print union off
7488 Tell @value{GDBN} not to print unions which are contained in
7489 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7492 @item show print union
7493 Ask @value{GDBN} whether or not it will print unions which are contained in
7494 structures and other unions.
7496 For example, given the declarations
7499 typedef enum @{Tree, Bug@} Species;
7500 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7501 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7512 struct thing foo = @{Tree, @{Acorn@}@};
7516 with @code{set print union on} in effect @samp{p foo} would print
7519 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7523 and with @code{set print union off} in effect it would print
7526 $1 = @{it = Tree, form = @{...@}@}
7530 @code{set print union} affects programs written in C-like languages
7536 These settings are of interest when debugging C@t{++} programs:
7539 @cindex demangling C@t{++} names
7540 @item set print demangle
7541 @itemx set print demangle on
7542 Print C@t{++} names in their source form rather than in the encoded
7543 (``mangled'') form passed to the assembler and linker for type-safe
7544 linkage. The default is on.
7546 @item show print demangle
7547 Show whether C@t{++} names are printed in mangled or demangled form.
7549 @item set print asm-demangle
7550 @itemx set print asm-demangle on
7551 Print C@t{++} names in their source form rather than their mangled form, even
7552 in assembler code printouts such as instruction disassemblies.
7555 @item show print asm-demangle
7556 Show whether C@t{++} names in assembly listings are printed in mangled
7559 @cindex C@t{++} symbol decoding style
7560 @cindex symbol decoding style, C@t{++}
7561 @kindex set demangle-style
7562 @item set demangle-style @var{style}
7563 Choose among several encoding schemes used by different compilers to
7564 represent C@t{++} names. The choices for @var{style} are currently:
7568 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7571 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7572 This is the default.
7575 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7578 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7581 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7582 @strong{Warning:} this setting alone is not sufficient to allow
7583 debugging @code{cfront}-generated executables. @value{GDBN} would
7584 require further enhancement to permit that.
7587 If you omit @var{style}, you will see a list of possible formats.
7589 @item show demangle-style
7590 Display the encoding style currently in use for decoding C@t{++} symbols.
7592 @item set print object
7593 @itemx set print object on
7594 @cindex derived type of an object, printing
7595 @cindex display derived types
7596 When displaying a pointer to an object, identify the @emph{actual}
7597 (derived) type of the object rather than the @emph{declared} type, using
7598 the virtual function table.
7600 @item set print object off
7601 Display only the declared type of objects, without reference to the
7602 virtual function table. This is the default setting.
7604 @item show print object
7605 Show whether actual, or declared, object types are displayed.
7607 @item set print static-members
7608 @itemx set print static-members on
7609 @cindex static members of C@t{++} objects
7610 Print static members when displaying a C@t{++} object. The default is on.
7612 @item set print static-members off
7613 Do not print static members when displaying a C@t{++} object.
7615 @item show print static-members
7616 Show whether C@t{++} static members are printed or not.
7618 @item set print pascal_static-members
7619 @itemx set print pascal_static-members on
7620 @cindex static members of Pascal objects
7621 @cindex Pascal objects, static members display
7622 Print static members when displaying a Pascal object. The default is on.
7624 @item set print pascal_static-members off
7625 Do not print static members when displaying a Pascal object.
7627 @item show print pascal_static-members
7628 Show whether Pascal static members are printed or not.
7630 @c These don't work with HP ANSI C++ yet.
7631 @item set print vtbl
7632 @itemx set print vtbl on
7633 @cindex pretty print C@t{++} virtual function tables
7634 @cindex virtual functions (C@t{++}) display
7635 @cindex VTBL display
7636 Pretty print C@t{++} virtual function tables. The default is off.
7637 (The @code{vtbl} commands do not work on programs compiled with the HP
7638 ANSI C@t{++} compiler (@code{aCC}).)
7640 @item set print vtbl off
7641 Do not pretty print C@t{++} virtual function tables.
7643 @item show print vtbl
7644 Show whether C@t{++} virtual function tables are pretty printed, or not.
7648 @section Value History
7650 @cindex value history
7651 @cindex history of values printed by @value{GDBN}
7652 Values printed by the @code{print} command are saved in the @value{GDBN}
7653 @dfn{value history}. This allows you to refer to them in other expressions.
7654 Values are kept until the symbol table is re-read or discarded
7655 (for example with the @code{file} or @code{symbol-file} commands).
7656 When the symbol table changes, the value history is discarded,
7657 since the values may contain pointers back to the types defined in the
7662 @cindex history number
7663 The values printed are given @dfn{history numbers} by which you can
7664 refer to them. These are successive integers starting with one.
7665 @code{print} shows you the history number assigned to a value by
7666 printing @samp{$@var{num} = } before the value; here @var{num} is the
7669 To refer to any previous value, use @samp{$} followed by the value's
7670 history number. The way @code{print} labels its output is designed to
7671 remind you of this. Just @code{$} refers to the most recent value in
7672 the history, and @code{$$} refers to the value before that.
7673 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7674 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7675 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7677 For example, suppose you have just printed a pointer to a structure and
7678 want to see the contents of the structure. It suffices to type
7684 If you have a chain of structures where the component @code{next} points
7685 to the next one, you can print the contents of the next one with this:
7692 You can print successive links in the chain by repeating this
7693 command---which you can do by just typing @key{RET}.
7695 Note that the history records values, not expressions. If the value of
7696 @code{x} is 4 and you type these commands:
7704 then the value recorded in the value history by the @code{print} command
7705 remains 4 even though the value of @code{x} has changed.
7710 Print the last ten values in the value history, with their item numbers.
7711 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7712 values} does not change the history.
7714 @item show values @var{n}
7715 Print ten history values centered on history item number @var{n}.
7718 Print ten history values just after the values last printed. If no more
7719 values are available, @code{show values +} produces no display.
7722 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7723 same effect as @samp{show values +}.
7725 @node Convenience Vars
7726 @section Convenience Variables
7728 @cindex convenience variables
7729 @cindex user-defined variables
7730 @value{GDBN} provides @dfn{convenience variables} that you can use within
7731 @value{GDBN} to hold on to a value and refer to it later. These variables
7732 exist entirely within @value{GDBN}; they are not part of your program, and
7733 setting a convenience variable has no direct effect on further execution
7734 of your program. That is why you can use them freely.
7736 Convenience variables are prefixed with @samp{$}. Any name preceded by
7737 @samp{$} can be used for a convenience variable, unless it is one of
7738 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7739 (Value history references, in contrast, are @emph{numbers} preceded
7740 by @samp{$}. @xref{Value History, ,Value History}.)
7742 You can save a value in a convenience variable with an assignment
7743 expression, just as you would set a variable in your program.
7747 set $foo = *object_ptr
7751 would save in @code{$foo} the value contained in the object pointed to by
7754 Using a convenience variable for the first time creates it, but its
7755 value is @code{void} until you assign a new value. You can alter the
7756 value with another assignment at any time.
7758 Convenience variables have no fixed types. You can assign a convenience
7759 variable any type of value, including structures and arrays, even if
7760 that variable already has a value of a different type. The convenience
7761 variable, when used as an expression, has the type of its current value.
7764 @kindex show convenience
7765 @cindex show all user variables
7766 @item show convenience
7767 Print a list of convenience variables used so far, and their values.
7768 Abbreviated @code{show conv}.
7770 @kindex init-if-undefined
7771 @cindex convenience variables, initializing
7772 @item init-if-undefined $@var{variable} = @var{expression}
7773 Set a convenience variable if it has not already been set. This is useful
7774 for user-defined commands that keep some state. It is similar, in concept,
7775 to using local static variables with initializers in C (except that
7776 convenience variables are global). It can also be used to allow users to
7777 override default values used in a command script.
7779 If the variable is already defined then the expression is not evaluated so
7780 any side-effects do not occur.
7783 One of the ways to use a convenience variable is as a counter to be
7784 incremented or a pointer to be advanced. For example, to print
7785 a field from successive elements of an array of structures:
7789 print bar[$i++]->contents
7793 Repeat that command by typing @key{RET}.
7795 Some convenience variables are created automatically by @value{GDBN} and given
7796 values likely to be useful.
7799 @vindex $_@r{, convenience variable}
7801 The variable @code{$_} is automatically set by the @code{x} command to
7802 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7803 commands which provide a default address for @code{x} to examine also
7804 set @code{$_} to that address; these commands include @code{info line}
7805 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7806 except when set by the @code{x} command, in which case it is a pointer
7807 to the type of @code{$__}.
7809 @vindex $__@r{, convenience variable}
7811 The variable @code{$__} is automatically set by the @code{x} command
7812 to the value found in the last address examined. Its type is chosen
7813 to match the format in which the data was printed.
7816 @vindex $_exitcode@r{, convenience variable}
7817 The variable @code{$_exitcode} is automatically set to the exit code when
7818 the program being debugged terminates.
7821 @vindex $_siginfo@r{, convenience variable}
7822 The variable @code{$_siginfo} contains extra signal information
7823 (@pxref{extra signal information}). Note that @code{$_siginfo}
7824 could be empty, if the application has not yet received any signals.
7825 For example, it will be empty before you execute the @code{run} command.
7828 On HP-UX systems, if you refer to a function or variable name that
7829 begins with a dollar sign, @value{GDBN} searches for a user or system
7830 name first, before it searches for a convenience variable.
7832 @cindex convenience functions
7833 @value{GDBN} also supplies some @dfn{convenience functions}. These
7834 have a syntax similar to convenience variables. A convenience
7835 function can be used in an expression just like an ordinary function;
7836 however, a convenience function is implemented internally to
7841 @kindex help function
7842 @cindex show all convenience functions
7843 Print a list of all convenience functions.
7850 You can refer to machine register contents, in expressions, as variables
7851 with names starting with @samp{$}. The names of registers are different
7852 for each machine; use @code{info registers} to see the names used on
7856 @kindex info registers
7857 @item info registers
7858 Print the names and values of all registers except floating-point
7859 and vector registers (in the selected stack frame).
7861 @kindex info all-registers
7862 @cindex floating point registers
7863 @item info all-registers
7864 Print the names and values of all registers, including floating-point
7865 and vector registers (in the selected stack frame).
7867 @item info registers @var{regname} @dots{}
7868 Print the @dfn{relativized} value of each specified register @var{regname}.
7869 As discussed in detail below, register values are normally relative to
7870 the selected stack frame. @var{regname} may be any register name valid on
7871 the machine you are using, with or without the initial @samp{$}.
7874 @cindex stack pointer register
7875 @cindex program counter register
7876 @cindex process status register
7877 @cindex frame pointer register
7878 @cindex standard registers
7879 @value{GDBN} has four ``standard'' register names that are available (in
7880 expressions) on most machines---whenever they do not conflict with an
7881 architecture's canonical mnemonics for registers. The register names
7882 @code{$pc} and @code{$sp} are used for the program counter register and
7883 the stack pointer. @code{$fp} is used for a register that contains a
7884 pointer to the current stack frame, and @code{$ps} is used for a
7885 register that contains the processor status. For example,
7886 you could print the program counter in hex with
7893 or print the instruction to be executed next with
7900 or add four to the stack pointer@footnote{This is a way of removing
7901 one word from the stack, on machines where stacks grow downward in
7902 memory (most machines, nowadays). This assumes that the innermost
7903 stack frame is selected; setting @code{$sp} is not allowed when other
7904 stack frames are selected. To pop entire frames off the stack,
7905 regardless of machine architecture, use @code{return};
7906 see @ref{Returning, ,Returning from a Function}.} with
7912 Whenever possible, these four standard register names are available on
7913 your machine even though the machine has different canonical mnemonics,
7914 so long as there is no conflict. The @code{info registers} command
7915 shows the canonical names. For example, on the SPARC, @code{info
7916 registers} displays the processor status register as @code{$psr} but you
7917 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7918 is an alias for the @sc{eflags} register.
7920 @value{GDBN} always considers the contents of an ordinary register as an
7921 integer when the register is examined in this way. Some machines have
7922 special registers which can hold nothing but floating point; these
7923 registers are considered to have floating point values. There is no way
7924 to refer to the contents of an ordinary register as floating point value
7925 (although you can @emph{print} it as a floating point value with
7926 @samp{print/f $@var{regname}}).
7928 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7929 means that the data format in which the register contents are saved by
7930 the operating system is not the same one that your program normally
7931 sees. For example, the registers of the 68881 floating point
7932 coprocessor are always saved in ``extended'' (raw) format, but all C
7933 programs expect to work with ``double'' (virtual) format. In such
7934 cases, @value{GDBN} normally works with the virtual format only (the format
7935 that makes sense for your program), but the @code{info registers} command
7936 prints the data in both formats.
7938 @cindex SSE registers (x86)
7939 @cindex MMX registers (x86)
7940 Some machines have special registers whose contents can be interpreted
7941 in several different ways. For example, modern x86-based machines
7942 have SSE and MMX registers that can hold several values packed
7943 together in several different formats. @value{GDBN} refers to such
7944 registers in @code{struct} notation:
7947 (@value{GDBP}) print $xmm1
7949 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7950 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7951 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7952 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7953 v4_int32 = @{0, 20657912, 11, 13@},
7954 v2_int64 = @{88725056443645952, 55834574859@},
7955 uint128 = 0x0000000d0000000b013b36f800000000
7960 To set values of such registers, you need to tell @value{GDBN} which
7961 view of the register you wish to change, as if you were assigning
7962 value to a @code{struct} member:
7965 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7968 Normally, register values are relative to the selected stack frame
7969 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7970 value that the register would contain if all stack frames farther in
7971 were exited and their saved registers restored. In order to see the
7972 true contents of hardware registers, you must select the innermost
7973 frame (with @samp{frame 0}).
7975 However, @value{GDBN} must deduce where registers are saved, from the machine
7976 code generated by your compiler. If some registers are not saved, or if
7977 @value{GDBN} is unable to locate the saved registers, the selected stack
7978 frame makes no difference.
7980 @node Floating Point Hardware
7981 @section Floating Point Hardware
7982 @cindex floating point
7984 Depending on the configuration, @value{GDBN} may be able to give
7985 you more information about the status of the floating point hardware.
7990 Display hardware-dependent information about the floating
7991 point unit. The exact contents and layout vary depending on the
7992 floating point chip. Currently, @samp{info float} is supported on
7993 the ARM and x86 machines.
7997 @section Vector Unit
8000 Depending on the configuration, @value{GDBN} may be able to give you
8001 more information about the status of the vector unit.
8006 Display information about the vector unit. The exact contents and
8007 layout vary depending on the hardware.
8010 @node OS Information
8011 @section Operating System Auxiliary Information
8012 @cindex OS information
8014 @value{GDBN} provides interfaces to useful OS facilities that can help
8015 you debug your program.
8017 @cindex @code{ptrace} system call
8018 @cindex @code{struct user} contents
8019 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8020 machines), it interfaces with the inferior via the @code{ptrace}
8021 system call. The operating system creates a special sata structure,
8022 called @code{struct user}, for this interface. You can use the
8023 command @code{info udot} to display the contents of this data
8029 Display the contents of the @code{struct user} maintained by the OS
8030 kernel for the program being debugged. @value{GDBN} displays the
8031 contents of @code{struct user} as a list of hex numbers, similar to
8032 the @code{examine} command.
8035 @cindex auxiliary vector
8036 @cindex vector, auxiliary
8037 Some operating systems supply an @dfn{auxiliary vector} to programs at
8038 startup. This is akin to the arguments and environment that you
8039 specify for a program, but contains a system-dependent variety of
8040 binary values that tell system libraries important details about the
8041 hardware, operating system, and process. Each value's purpose is
8042 identified by an integer tag; the meanings are well-known but system-specific.
8043 Depending on the configuration and operating system facilities,
8044 @value{GDBN} may be able to show you this information. For remote
8045 targets, this functionality may further depend on the remote stub's
8046 support of the @samp{qXfer:auxv:read} packet, see
8047 @ref{qXfer auxiliary vector read}.
8052 Display the auxiliary vector of the inferior, which can be either a
8053 live process or a core dump file. @value{GDBN} prints each tag value
8054 numerically, and also shows names and text descriptions for recognized
8055 tags. Some values in the vector are numbers, some bit masks, and some
8056 pointers to strings or other data. @value{GDBN} displays each value in the
8057 most appropriate form for a recognized tag, and in hexadecimal for
8058 an unrecognized tag.
8061 On some targets, @value{GDBN} can access operating-system-specific information
8062 and display it to user, without interpretation. For remote targets,
8063 this functionality depends on the remote stub's support of the
8064 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8067 @kindex info os processes
8068 @item info os processes
8069 Display the list of processes on the target. For each process,
8070 @value{GDBN} prints the process identifier, the name of the user, and
8071 the command corresponding to the process.
8074 @node Memory Region Attributes
8075 @section Memory Region Attributes
8076 @cindex memory region attributes
8078 @dfn{Memory region attributes} allow you to describe special handling
8079 required by regions of your target's memory. @value{GDBN} uses
8080 attributes to determine whether to allow certain types of memory
8081 accesses; whether to use specific width accesses; and whether to cache
8082 target memory. By default the description of memory regions is
8083 fetched from the target (if the current target supports this), but the
8084 user can override the fetched regions.
8086 Defined memory regions can be individually enabled and disabled. When a
8087 memory region is disabled, @value{GDBN} uses the default attributes when
8088 accessing memory in that region. Similarly, if no memory regions have
8089 been defined, @value{GDBN} uses the default attributes when accessing
8092 When a memory region is defined, it is given a number to identify it;
8093 to enable, disable, or remove a memory region, you specify that number.
8097 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8098 Define a memory region bounded by @var{lower} and @var{upper} with
8099 attributes @var{attributes}@dots{}, and add it to the list of regions
8100 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8101 case: it is treated as the target's maximum memory address.
8102 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8105 Discard any user changes to the memory regions and use target-supplied
8106 regions, if available, or no regions if the target does not support.
8109 @item delete mem @var{nums}@dots{}
8110 Remove memory regions @var{nums}@dots{} from the list of regions
8111 monitored by @value{GDBN}.
8114 @item disable mem @var{nums}@dots{}
8115 Disable monitoring of memory regions @var{nums}@dots{}.
8116 A disabled memory region is not forgotten.
8117 It may be enabled again later.
8120 @item enable mem @var{nums}@dots{}
8121 Enable monitoring of memory regions @var{nums}@dots{}.
8125 Print a table of all defined memory regions, with the following columns
8129 @item Memory Region Number
8130 @item Enabled or Disabled.
8131 Enabled memory regions are marked with @samp{y}.
8132 Disabled memory regions are marked with @samp{n}.
8135 The address defining the inclusive lower bound of the memory region.
8138 The address defining the exclusive upper bound of the memory region.
8141 The list of attributes set for this memory region.
8146 @subsection Attributes
8148 @subsubsection Memory Access Mode
8149 The access mode attributes set whether @value{GDBN} may make read or
8150 write accesses to a memory region.
8152 While these attributes prevent @value{GDBN} from performing invalid
8153 memory accesses, they do nothing to prevent the target system, I/O DMA,
8154 etc.@: from accessing memory.
8158 Memory is read only.
8160 Memory is write only.
8162 Memory is read/write. This is the default.
8165 @subsubsection Memory Access Size
8166 The access size attribute tells @value{GDBN} to use specific sized
8167 accesses in the memory region. Often memory mapped device registers
8168 require specific sized accesses. If no access size attribute is
8169 specified, @value{GDBN} may use accesses of any size.
8173 Use 8 bit memory accesses.
8175 Use 16 bit memory accesses.
8177 Use 32 bit memory accesses.
8179 Use 64 bit memory accesses.
8182 @c @subsubsection Hardware/Software Breakpoints
8183 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8184 @c will use hardware or software breakpoints for the internal breakpoints
8185 @c used by the step, next, finish, until, etc. commands.
8189 @c Always use hardware breakpoints
8190 @c @item swbreak (default)
8193 @subsubsection Data Cache
8194 The data cache attributes set whether @value{GDBN} will cache target
8195 memory. While this generally improves performance by reducing debug
8196 protocol overhead, it can lead to incorrect results because @value{GDBN}
8197 does not know about volatile variables or memory mapped device
8202 Enable @value{GDBN} to cache target memory.
8204 Disable @value{GDBN} from caching target memory. This is the default.
8207 @subsection Memory Access Checking
8208 @value{GDBN} can be instructed to refuse accesses to memory that is
8209 not explicitly described. This can be useful if accessing such
8210 regions has undesired effects for a specific target, or to provide
8211 better error checking. The following commands control this behaviour.
8214 @kindex set mem inaccessible-by-default
8215 @item set mem inaccessible-by-default [on|off]
8216 If @code{on} is specified, make @value{GDBN} treat memory not
8217 explicitly described by the memory ranges as non-existent and refuse accesses
8218 to such memory. The checks are only performed if there's at least one
8219 memory range defined. If @code{off} is specified, make @value{GDBN}
8220 treat the memory not explicitly described by the memory ranges as RAM.
8221 The default value is @code{on}.
8222 @kindex show mem inaccessible-by-default
8223 @item show mem inaccessible-by-default
8224 Show the current handling of accesses to unknown memory.
8228 @c @subsubsection Memory Write Verification
8229 @c The memory write verification attributes set whether @value{GDBN}
8230 @c will re-reads data after each write to verify the write was successful.
8234 @c @item noverify (default)
8237 @node Dump/Restore Files
8238 @section Copy Between Memory and a File
8239 @cindex dump/restore files
8240 @cindex append data to a file
8241 @cindex dump data to a file
8242 @cindex restore data from a file
8244 You can use the commands @code{dump}, @code{append}, and
8245 @code{restore} to copy data between target memory and a file. The
8246 @code{dump} and @code{append} commands write data to a file, and the
8247 @code{restore} command reads data from a file back into the inferior's
8248 memory. Files may be in binary, Motorola S-record, Intel hex, or
8249 Tektronix Hex format; however, @value{GDBN} can only append to binary
8255 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8256 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8257 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8258 or the value of @var{expr}, to @var{filename} in the given format.
8260 The @var{format} parameter may be any one of:
8267 Motorola S-record format.
8269 Tektronix Hex format.
8272 @value{GDBN} uses the same definitions of these formats as the
8273 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8274 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8278 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8279 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8280 Append the contents of memory from @var{start_addr} to @var{end_addr},
8281 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8282 (@value{GDBN} can only append data to files in raw binary form.)
8285 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8286 Restore the contents of file @var{filename} into memory. The
8287 @code{restore} command can automatically recognize any known @sc{bfd}
8288 file format, except for raw binary. To restore a raw binary file you
8289 must specify the optional keyword @code{binary} after the filename.
8291 If @var{bias} is non-zero, its value will be added to the addresses
8292 contained in the file. Binary files always start at address zero, so
8293 they will be restored at address @var{bias}. Other bfd files have
8294 a built-in location; they will be restored at offset @var{bias}
8297 If @var{start} and/or @var{end} are non-zero, then only data between
8298 file offset @var{start} and file offset @var{end} will be restored.
8299 These offsets are relative to the addresses in the file, before
8300 the @var{bias} argument is applied.
8304 @node Core File Generation
8305 @section How to Produce a Core File from Your Program
8306 @cindex dump core from inferior
8308 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8309 image of a running process and its process status (register values
8310 etc.). Its primary use is post-mortem debugging of a program that
8311 crashed while it ran outside a debugger. A program that crashes
8312 automatically produces a core file, unless this feature is disabled by
8313 the user. @xref{Files}, for information on invoking @value{GDBN} in
8314 the post-mortem debugging mode.
8316 Occasionally, you may wish to produce a core file of the program you
8317 are debugging in order to preserve a snapshot of its state.
8318 @value{GDBN} has a special command for that.
8322 @kindex generate-core-file
8323 @item generate-core-file [@var{file}]
8324 @itemx gcore [@var{file}]
8325 Produce a core dump of the inferior process. The optional argument
8326 @var{file} specifies the file name where to put the core dump. If not
8327 specified, the file name defaults to @file{core.@var{pid}}, where
8328 @var{pid} is the inferior process ID.
8330 Note that this command is implemented only for some systems (as of
8331 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8334 @node Character Sets
8335 @section Character Sets
8336 @cindex character sets
8338 @cindex translating between character sets
8339 @cindex host character set
8340 @cindex target character set
8342 If the program you are debugging uses a different character set to
8343 represent characters and strings than the one @value{GDBN} uses itself,
8344 @value{GDBN} can automatically translate between the character sets for
8345 you. The character set @value{GDBN} uses we call the @dfn{host
8346 character set}; the one the inferior program uses we call the
8347 @dfn{target character set}.
8349 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8350 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8351 remote protocol (@pxref{Remote Debugging}) to debug a program
8352 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8353 then the host character set is Latin-1, and the target character set is
8354 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8355 target-charset EBCDIC-US}, then @value{GDBN} translates between
8356 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8357 character and string literals in expressions.
8359 @value{GDBN} has no way to automatically recognize which character set
8360 the inferior program uses; you must tell it, using the @code{set
8361 target-charset} command, described below.
8363 Here are the commands for controlling @value{GDBN}'s character set
8367 @item set target-charset @var{charset}
8368 @kindex set target-charset
8369 Set the current target character set to @var{charset}. To display the
8370 list of supported target character sets, type
8371 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8373 @item set host-charset @var{charset}
8374 @kindex set host-charset
8375 Set the current host character set to @var{charset}.
8377 By default, @value{GDBN} uses a host character set appropriate to the
8378 system it is running on; you can override that default using the
8379 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8380 automatically determine the appropriate host character set. In this
8381 case, @value{GDBN} uses @samp{UTF-8}.
8383 @value{GDBN} can only use certain character sets as its host character
8384 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8385 @value{GDBN} will list the host character sets it supports.
8387 @item set charset @var{charset}
8389 Set the current host and target character sets to @var{charset}. As
8390 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8391 @value{GDBN} will list the names of the character sets that can be used
8392 for both host and target.
8395 @kindex show charset
8396 Show the names of the current host and target character sets.
8398 @item show host-charset
8399 @kindex show host-charset
8400 Show the name of the current host character set.
8402 @item show target-charset
8403 @kindex show target-charset
8404 Show the name of the current target character set.
8406 @item set target-wide-charset @var{charset}
8407 @kindex set target-wide-charset
8408 Set the current target's wide character set to @var{charset}. This is
8409 the character set used by the target's @code{wchar_t} type. To
8410 display the list of supported wide character sets, type
8411 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8413 @item show target-wide-charset
8414 @kindex show target-wide-charset
8415 Show the name of the current target's wide character set.
8418 Here is an example of @value{GDBN}'s character set support in action.
8419 Assume that the following source code has been placed in the file
8420 @file{charset-test.c}:
8426 = @{72, 101, 108, 108, 111, 44, 32, 119,
8427 111, 114, 108, 100, 33, 10, 0@};
8428 char ibm1047_hello[]
8429 = @{200, 133, 147, 147, 150, 107, 64, 166,
8430 150, 153, 147, 132, 90, 37, 0@};
8434 printf ("Hello, world!\n");
8438 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8439 containing the string @samp{Hello, world!} followed by a newline,
8440 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8442 We compile the program, and invoke the debugger on it:
8445 $ gcc -g charset-test.c -o charset-test
8446 $ gdb -nw charset-test
8447 GNU gdb 2001-12-19-cvs
8448 Copyright 2001 Free Software Foundation, Inc.
8453 We can use the @code{show charset} command to see what character sets
8454 @value{GDBN} is currently using to interpret and display characters and
8458 (@value{GDBP}) show charset
8459 The current host and target character set is `ISO-8859-1'.
8463 For the sake of printing this manual, let's use @sc{ascii} as our
8464 initial character set:
8466 (@value{GDBP}) set charset ASCII
8467 (@value{GDBP}) show charset
8468 The current host and target character set is `ASCII'.
8472 Let's assume that @sc{ascii} is indeed the correct character set for our
8473 host system --- in other words, let's assume that if @value{GDBN} prints
8474 characters using the @sc{ascii} character set, our terminal will display
8475 them properly. Since our current target character set is also
8476 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8479 (@value{GDBP}) print ascii_hello
8480 $1 = 0x401698 "Hello, world!\n"
8481 (@value{GDBP}) print ascii_hello[0]
8486 @value{GDBN} uses the target character set for character and string
8487 literals you use in expressions:
8490 (@value{GDBP}) print '+'
8495 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8498 @value{GDBN} relies on the user to tell it which character set the
8499 target program uses. If we print @code{ibm1047_hello} while our target
8500 character set is still @sc{ascii}, we get jibberish:
8503 (@value{GDBP}) print ibm1047_hello
8504 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8505 (@value{GDBP}) print ibm1047_hello[0]
8510 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8511 @value{GDBN} tells us the character sets it supports:
8514 (@value{GDBP}) set target-charset
8515 ASCII EBCDIC-US IBM1047 ISO-8859-1
8516 (@value{GDBP}) set target-charset
8519 We can select @sc{ibm1047} as our target character set, and examine the
8520 program's strings again. Now the @sc{ascii} string is wrong, but
8521 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8522 target character set, @sc{ibm1047}, to the host character set,
8523 @sc{ascii}, and they display correctly:
8526 (@value{GDBP}) set target-charset IBM1047
8527 (@value{GDBP}) show charset
8528 The current host character set is `ASCII'.
8529 The current target character set is `IBM1047'.
8530 (@value{GDBP}) print ascii_hello
8531 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8532 (@value{GDBP}) print ascii_hello[0]
8534 (@value{GDBP}) print ibm1047_hello
8535 $8 = 0x4016a8 "Hello, world!\n"
8536 (@value{GDBP}) print ibm1047_hello[0]
8541 As above, @value{GDBN} uses the target character set for character and
8542 string literals you use in expressions:
8545 (@value{GDBP}) print '+'
8550 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8553 @node Caching Remote Data
8554 @section Caching Data of Remote Targets
8555 @cindex caching data of remote targets
8557 @value{GDBN} caches data exchanged between the debugger and a
8558 remote target (@pxref{Remote Debugging}). Such caching generally improves
8559 performance, because it reduces the overhead of the remote protocol by
8560 bundling memory reads and writes into large chunks. Unfortunately, simply
8561 caching everything would lead to incorrect results, since @value{GDBN}
8562 does not necessarily know anything about volatile values, memory-mapped I/O
8563 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8564 memory can be changed @emph{while} a gdb command is executing.
8565 Therefore, by default, @value{GDBN} only caches data
8566 known to be on the stack@footnote{In non-stop mode, it is moderately
8567 rare for a running thread to modify the stack of a stopped thread
8568 in a way that would interfere with a backtrace, and caching of
8569 stack reads provides a significant speed up of remote backtraces.}.
8570 Other regions of memory can be explicitly marked as
8571 cacheable; see @pxref{Memory Region Attributes}.
8574 @kindex set remotecache
8575 @item set remotecache on
8576 @itemx set remotecache off
8577 This option no longer does anything; it exists for compatibility
8580 @kindex show remotecache
8581 @item show remotecache
8582 Show the current state of the obsolete remotecache flag.
8584 @kindex set stack-cache
8585 @item set stack-cache on
8586 @itemx set stack-cache off
8587 Enable or disable caching of stack accesses. When @code{ON}, use
8588 caching. By default, this option is @code{ON}.
8590 @kindex show stack-cache
8591 @item show stack-cache
8592 Show the current state of data caching for memory accesses.
8595 @item info dcache @r{[}line@r{]}
8596 Print the information about the data cache performance. The
8597 information displayed includes the dcache width and depth, and for
8598 each cache line, its number, address, and how many times it was
8599 referenced. This command is useful for debugging the data cache
8602 If a line number is specified, the contents of that line will be
8606 @node Searching Memory
8607 @section Search Memory
8608 @cindex searching memory
8610 Memory can be searched for a particular sequence of bytes with the
8611 @code{find} command.
8615 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8616 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8617 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8618 etc. The search begins at address @var{start_addr} and continues for either
8619 @var{len} bytes or through to @var{end_addr} inclusive.
8622 @var{s} and @var{n} are optional parameters.
8623 They may be specified in either order, apart or together.
8626 @item @var{s}, search query size
8627 The size of each search query value.
8633 halfwords (two bytes)
8637 giant words (eight bytes)
8640 All values are interpreted in the current language.
8641 This means, for example, that if the current source language is C/C@t{++}
8642 then searching for the string ``hello'' includes the trailing '\0'.
8644 If the value size is not specified, it is taken from the
8645 value's type in the current language.
8646 This is useful when one wants to specify the search
8647 pattern as a mixture of types.
8648 Note that this means, for example, that in the case of C-like languages
8649 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8650 which is typically four bytes.
8652 @item @var{n}, maximum number of finds
8653 The maximum number of matches to print. The default is to print all finds.
8656 You can use strings as search values. Quote them with double-quotes
8658 The string value is copied into the search pattern byte by byte,
8659 regardless of the endianness of the target and the size specification.
8661 The address of each match found is printed as well as a count of the
8662 number of matches found.
8664 The address of the last value found is stored in convenience variable
8666 A count of the number of matches is stored in @samp{$numfound}.
8668 For example, if stopped at the @code{printf} in this function:
8674 static char hello[] = "hello-hello";
8675 static struct @{ char c; short s; int i; @}
8676 __attribute__ ((packed)) mixed
8677 = @{ 'c', 0x1234, 0x87654321 @};
8678 printf ("%s\n", hello);
8683 you get during debugging:
8686 (gdb) find &hello[0], +sizeof(hello), "hello"
8687 0x804956d <hello.1620+6>
8689 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8690 0x8049567 <hello.1620>
8691 0x804956d <hello.1620+6>
8693 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8694 0x8049567 <hello.1620>
8696 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8697 0x8049560 <mixed.1625>
8699 (gdb) print $numfound
8702 $2 = (void *) 0x8049560
8705 @node Optimized Code
8706 @chapter Debugging Optimized Code
8707 @cindex optimized code, debugging
8708 @cindex debugging optimized code
8710 Almost all compilers support optimization. With optimization
8711 disabled, the compiler generates assembly code that corresponds
8712 directly to your source code, in a simplistic way. As the compiler
8713 applies more powerful optimizations, the generated assembly code
8714 diverges from your original source code. With help from debugging
8715 information generated by the compiler, @value{GDBN} can map from
8716 the running program back to constructs from your original source.
8718 @value{GDBN} is more accurate with optimization disabled. If you
8719 can recompile without optimization, it is easier to follow the
8720 progress of your program during debugging. But, there are many cases
8721 where you may need to debug an optimized version.
8723 When you debug a program compiled with @samp{-g -O}, remember that the
8724 optimizer has rearranged your code; the debugger shows you what is
8725 really there. Do not be too surprised when the execution path does not
8726 exactly match your source file! An extreme example: if you define a
8727 variable, but never use it, @value{GDBN} never sees that
8728 variable---because the compiler optimizes it out of existence.
8730 Some things do not work as well with @samp{-g -O} as with just
8731 @samp{-g}, particularly on machines with instruction scheduling. If in
8732 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
8733 please report it to us as a bug (including a test case!).
8734 @xref{Variables}, for more information about debugging optimized code.
8737 * Inline Functions:: How @value{GDBN} presents inlining
8740 @node Inline Functions
8741 @section Inline Functions
8742 @cindex inline functions, debugging
8744 @dfn{Inlining} is an optimization that inserts a copy of the function
8745 body directly at each call site, instead of jumping to a shared
8746 routine. @value{GDBN} displays inlined functions just like
8747 non-inlined functions. They appear in backtraces. You can view their
8748 arguments and local variables, step into them with @code{step}, skip
8749 them with @code{next}, and escape from them with @code{finish}.
8750 You can check whether a function was inlined by using the
8751 @code{info frame} command.
8753 For @value{GDBN} to support inlined functions, the compiler must
8754 record information about inlining in the debug information ---
8755 @value{NGCC} using the @sc{dwarf 2} format does this, and several
8756 other compilers do also. @value{GDBN} only supports inlined functions
8757 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
8758 do not emit two required attributes (@samp{DW_AT_call_file} and
8759 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
8760 function calls with earlier versions of @value{NGCC}. It instead
8761 displays the arguments and local variables of inlined functions as
8762 local variables in the caller.
8764 The body of an inlined function is directly included at its call site;
8765 unlike a non-inlined function, there are no instructions devoted to
8766 the call. @value{GDBN} still pretends that the call site and the
8767 start of the inlined function are different instructions. Stepping to
8768 the call site shows the call site, and then stepping again shows
8769 the first line of the inlined function, even though no additional
8770 instructions are executed.
8772 This makes source-level debugging much clearer; you can see both the
8773 context of the call and then the effect of the call. Only stepping by
8774 a single instruction using @code{stepi} or @code{nexti} does not do
8775 this; single instruction steps always show the inlined body.
8777 There are some ways that @value{GDBN} does not pretend that inlined
8778 function calls are the same as normal calls:
8782 You cannot set breakpoints on inlined functions. @value{GDBN}
8783 either reports that there is no symbol with that name, or else sets the
8784 breakpoint only on non-inlined copies of the function. This limitation
8785 will be removed in a future version of @value{GDBN}; until then,
8786 set a breakpoint by line number on the first line of the inlined
8790 Setting breakpoints at the call site of an inlined function may not
8791 work, because the call site does not contain any code. @value{GDBN}
8792 may incorrectly move the breakpoint to the next line of the enclosing
8793 function, after the call. This limitation will be removed in a future
8794 version of @value{GDBN}; until then, set a breakpoint on an earlier line
8795 or inside the inlined function instead.
8798 @value{GDBN} cannot locate the return value of inlined calls after
8799 using the @code{finish} command. This is a limitation of compiler-generated
8800 debugging information; after @code{finish}, you can step to the next line
8801 and print a variable where your program stored the return value.
8807 @chapter C Preprocessor Macros
8809 Some languages, such as C and C@t{++}, provide a way to define and invoke
8810 ``preprocessor macros'' which expand into strings of tokens.
8811 @value{GDBN} can evaluate expressions containing macro invocations, show
8812 the result of macro expansion, and show a macro's definition, including
8813 where it was defined.
8815 You may need to compile your program specially to provide @value{GDBN}
8816 with information about preprocessor macros. Most compilers do not
8817 include macros in their debugging information, even when you compile
8818 with the @option{-g} flag. @xref{Compilation}.
8820 A program may define a macro at one point, remove that definition later,
8821 and then provide a different definition after that. Thus, at different
8822 points in the program, a macro may have different definitions, or have
8823 no definition at all. If there is a current stack frame, @value{GDBN}
8824 uses the macros in scope at that frame's source code line. Otherwise,
8825 @value{GDBN} uses the macros in scope at the current listing location;
8828 Whenever @value{GDBN} evaluates an expression, it always expands any
8829 macro invocations present in the expression. @value{GDBN} also provides
8830 the following commands for working with macros explicitly.
8834 @kindex macro expand
8835 @cindex macro expansion, showing the results of preprocessor
8836 @cindex preprocessor macro expansion, showing the results of
8837 @cindex expanding preprocessor macros
8838 @item macro expand @var{expression}
8839 @itemx macro exp @var{expression}
8840 Show the results of expanding all preprocessor macro invocations in
8841 @var{expression}. Since @value{GDBN} simply expands macros, but does
8842 not parse the result, @var{expression} need not be a valid expression;
8843 it can be any string of tokens.
8846 @item macro expand-once @var{expression}
8847 @itemx macro exp1 @var{expression}
8848 @cindex expand macro once
8849 @i{(This command is not yet implemented.)} Show the results of
8850 expanding those preprocessor macro invocations that appear explicitly in
8851 @var{expression}. Macro invocations appearing in that expansion are
8852 left unchanged. This command allows you to see the effect of a
8853 particular macro more clearly, without being confused by further
8854 expansions. Since @value{GDBN} simply expands macros, but does not
8855 parse the result, @var{expression} need not be a valid expression; it
8856 can be any string of tokens.
8859 @cindex macro definition, showing
8860 @cindex definition, showing a macro's
8861 @item info macro @var{macro}
8862 Show the definition of the macro named @var{macro}, and describe the
8863 source location or compiler command-line where that definition was established.
8865 @kindex macro define
8866 @cindex user-defined macros
8867 @cindex defining macros interactively
8868 @cindex macros, user-defined
8869 @item macro define @var{macro} @var{replacement-list}
8870 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8871 Introduce a definition for a preprocessor macro named @var{macro},
8872 invocations of which are replaced by the tokens given in
8873 @var{replacement-list}. The first form of this command defines an
8874 ``object-like'' macro, which takes no arguments; the second form
8875 defines a ``function-like'' macro, which takes the arguments given in
8878 A definition introduced by this command is in scope in every
8879 expression evaluated in @value{GDBN}, until it is removed with the
8880 @code{macro undef} command, described below. The definition overrides
8881 all definitions for @var{macro} present in the program being debugged,
8882 as well as any previous user-supplied definition.
8885 @item macro undef @var{macro}
8886 Remove any user-supplied definition for the macro named @var{macro}.
8887 This command only affects definitions provided with the @code{macro
8888 define} command, described above; it cannot remove definitions present
8889 in the program being debugged.
8893 List all the macros defined using the @code{macro define} command.
8896 @cindex macros, example of debugging with
8897 Here is a transcript showing the above commands in action. First, we
8898 show our source files:
8906 #define ADD(x) (M + x)
8911 printf ("Hello, world!\n");
8913 printf ("We're so creative.\n");
8915 printf ("Goodbye, world!\n");
8922 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8923 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8924 compiler includes information about preprocessor macros in the debugging
8928 $ gcc -gdwarf-2 -g3 sample.c -o sample
8932 Now, we start @value{GDBN} on our sample program:
8936 GNU gdb 2002-05-06-cvs
8937 Copyright 2002 Free Software Foundation, Inc.
8938 GDB is free software, @dots{}
8942 We can expand macros and examine their definitions, even when the
8943 program is not running. @value{GDBN} uses the current listing position
8944 to decide which macro definitions are in scope:
8947 (@value{GDBP}) list main
8950 5 #define ADD(x) (M + x)
8955 10 printf ("Hello, world!\n");
8957 12 printf ("We're so creative.\n");
8958 (@value{GDBP}) info macro ADD
8959 Defined at /home/jimb/gdb/macros/play/sample.c:5
8960 #define ADD(x) (M + x)
8961 (@value{GDBP}) info macro Q
8962 Defined at /home/jimb/gdb/macros/play/sample.h:1
8963 included at /home/jimb/gdb/macros/play/sample.c:2
8965 (@value{GDBP}) macro expand ADD(1)
8966 expands to: (42 + 1)
8967 (@value{GDBP}) macro expand-once ADD(1)
8968 expands to: once (M + 1)
8972 In the example above, note that @code{macro expand-once} expands only
8973 the macro invocation explicit in the original text --- the invocation of
8974 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8975 which was introduced by @code{ADD}.
8977 Once the program is running, @value{GDBN} uses the macro definitions in
8978 force at the source line of the current stack frame:
8981 (@value{GDBP}) break main
8982 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8984 Starting program: /home/jimb/gdb/macros/play/sample
8986 Breakpoint 1, main () at sample.c:10
8987 10 printf ("Hello, world!\n");
8991 At line 10, the definition of the macro @code{N} at line 9 is in force:
8994 (@value{GDBP}) info macro N
8995 Defined at /home/jimb/gdb/macros/play/sample.c:9
8997 (@value{GDBP}) macro expand N Q M
8999 (@value{GDBP}) print N Q M
9004 As we step over directives that remove @code{N}'s definition, and then
9005 give it a new definition, @value{GDBN} finds the definition (or lack
9006 thereof) in force at each point:
9011 12 printf ("We're so creative.\n");
9012 (@value{GDBP}) info macro N
9013 The symbol `N' has no definition as a C/C++ preprocessor macro
9014 at /home/jimb/gdb/macros/play/sample.c:12
9017 14 printf ("Goodbye, world!\n");
9018 (@value{GDBP}) info macro N
9019 Defined at /home/jimb/gdb/macros/play/sample.c:13
9021 (@value{GDBP}) macro expand N Q M
9022 expands to: 1729 < 42
9023 (@value{GDBP}) print N Q M
9028 In addition to source files, macros can be defined on the compilation command
9029 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9030 such a way, @value{GDBN} displays the location of their definition as line zero
9031 of the source file submitted to the compiler.
9034 (@value{GDBP}) info macro __STDC__
9035 Defined at /home/jimb/gdb/macros/play/sample.c:0
9042 @chapter Tracepoints
9043 @c This chapter is based on the documentation written by Michael
9044 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9047 In some applications, it is not feasible for the debugger to interrupt
9048 the program's execution long enough for the developer to learn
9049 anything helpful about its behavior. If the program's correctness
9050 depends on its real-time behavior, delays introduced by a debugger
9051 might cause the program to change its behavior drastically, or perhaps
9052 fail, even when the code itself is correct. It is useful to be able
9053 to observe the program's behavior without interrupting it.
9055 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9056 specify locations in the program, called @dfn{tracepoints}, and
9057 arbitrary expressions to evaluate when those tracepoints are reached.
9058 Later, using the @code{tfind} command, you can examine the values
9059 those expressions had when the program hit the tracepoints. The
9060 expressions may also denote objects in memory---structures or arrays,
9061 for example---whose values @value{GDBN} should record; while visiting
9062 a particular tracepoint, you may inspect those objects as if they were
9063 in memory at that moment. However, because @value{GDBN} records these
9064 values without interacting with you, it can do so quickly and
9065 unobtrusively, hopefully not disturbing the program's behavior.
9067 The tracepoint facility is currently available only for remote
9068 targets. @xref{Targets}. In addition, your remote target must know
9069 how to collect trace data. This functionality is implemented in the
9070 remote stub; however, none of the stubs distributed with @value{GDBN}
9071 support tracepoints as of this writing. The format of the remote
9072 packets used to implement tracepoints are described in @ref{Tracepoint
9075 This chapter describes the tracepoint commands and features.
9079 * Analyze Collected Data::
9080 * Tracepoint Variables::
9083 @node Set Tracepoints
9084 @section Commands to Set Tracepoints
9086 Before running such a @dfn{trace experiment}, an arbitrary number of
9087 tracepoints can be set. A tracepoint is actually a special type of
9088 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9089 standard breakpoint commands. For instance, as with breakpoints,
9090 tracepoint numbers are successive integers starting from one, and many
9091 of the commands associated with tracepoints take the tracepoint number
9092 as their argument, to identify which tracepoint to work on.
9094 For each tracepoint, you can specify, in advance, some arbitrary set
9095 of data that you want the target to collect in the trace buffer when
9096 it hits that tracepoint. The collected data can include registers,
9097 local variables, or global data. Later, you can use @value{GDBN}
9098 commands to examine the values these data had at the time the
9101 Tracepoints do not support every breakpoint feature. Conditional
9102 expressions and ignore counts on tracepoints have no effect, and
9103 tracepoints cannot run @value{GDBN} commands when they are
9104 hit. Tracepoints may not be thread-specific either.
9106 This section describes commands to set tracepoints and associated
9107 conditions and actions.
9110 * Create and Delete Tracepoints::
9111 * Enable and Disable Tracepoints::
9112 * Tracepoint Passcounts::
9113 * Tracepoint Conditions::
9114 * Tracepoint Actions::
9115 * Listing Tracepoints::
9116 * Starting and Stopping Trace Experiments::
9119 @node Create and Delete Tracepoints
9120 @subsection Create and Delete Tracepoints
9123 @cindex set tracepoint
9125 @item trace @var{location}
9126 The @code{trace} command is very similar to the @code{break} command.
9127 Its argument @var{location} can be a source line, a function name, or
9128 an address in the target program. @xref{Specify Location}. The
9129 @code{trace} command defines a tracepoint, which is a point in the
9130 target program where the debugger will briefly stop, collect some
9131 data, and then allow the program to continue. Setting a tracepoint or
9132 changing its actions doesn't take effect until the next @code{tstart}
9133 command, and once a trace experiment is running, further changes will
9134 not have any effect until the next trace experiment starts.
9136 Here are some examples of using the @code{trace} command:
9139 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9141 (@value{GDBP}) @b{trace +2} // 2 lines forward
9143 (@value{GDBP}) @b{trace my_function} // first source line of function
9145 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9147 (@value{GDBP}) @b{trace *0x2117c4} // an address
9151 You can abbreviate @code{trace} as @code{tr}.
9153 @item trace @var{location} if @var{cond}
9154 Set a tracepoint with condition @var{cond}; evaluate the expression
9155 @var{cond} each time the tracepoint is reached, and collect data only
9156 if the value is nonzero---that is, if @var{cond} evaluates as true.
9157 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9158 information on tracepoint conditions.
9161 @cindex last tracepoint number
9162 @cindex recent tracepoint number
9163 @cindex tracepoint number
9164 The convenience variable @code{$tpnum} records the tracepoint number
9165 of the most recently set tracepoint.
9167 @kindex delete tracepoint
9168 @cindex tracepoint deletion
9169 @item delete tracepoint @r{[}@var{num}@r{]}
9170 Permanently delete one or more tracepoints. With no argument, the
9171 default is to delete all tracepoints. Note that the regular
9172 @code{delete} command can remove tracepoints also.
9177 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9179 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9183 You can abbreviate this command as @code{del tr}.
9186 @node Enable and Disable Tracepoints
9187 @subsection Enable and Disable Tracepoints
9189 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9192 @kindex disable tracepoint
9193 @item disable tracepoint @r{[}@var{num}@r{]}
9194 Disable tracepoint @var{num}, or all tracepoints if no argument
9195 @var{num} is given. A disabled tracepoint will have no effect during
9196 the next trace experiment, but it is not forgotten. You can re-enable
9197 a disabled tracepoint using the @code{enable tracepoint} command.
9199 @kindex enable tracepoint
9200 @item enable tracepoint @r{[}@var{num}@r{]}
9201 Enable tracepoint @var{num}, or all tracepoints. The enabled
9202 tracepoints will become effective the next time a trace experiment is
9206 @node Tracepoint Passcounts
9207 @subsection Tracepoint Passcounts
9211 @cindex tracepoint pass count
9212 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9213 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9214 automatically stop a trace experiment. If a tracepoint's passcount is
9215 @var{n}, then the trace experiment will be automatically stopped on
9216 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9217 @var{num} is not specified, the @code{passcount} command sets the
9218 passcount of the most recently defined tracepoint. If no passcount is
9219 given, the trace experiment will run until stopped explicitly by the
9225 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9226 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9228 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9229 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9230 (@value{GDBP}) @b{trace foo}
9231 (@value{GDBP}) @b{pass 3}
9232 (@value{GDBP}) @b{trace bar}
9233 (@value{GDBP}) @b{pass 2}
9234 (@value{GDBP}) @b{trace baz}
9235 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9236 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9237 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9238 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9242 @node Tracepoint Conditions
9243 @subsection Tracepoint Conditions
9244 @cindex conditional tracepoints
9245 @cindex tracepoint conditions
9247 The simplest sort of tracepoint collects data every time your program
9248 reaches a specified place. You can also specify a @dfn{condition} for
9249 a tracepoint. A condition is just a Boolean expression in your
9250 programming language (@pxref{Expressions, ,Expressions}). A
9251 tracepoint with a condition evaluates the expression each time your
9252 program reaches it, and data collection happens only if the condition
9255 Tracepoint conditions can be specified when a tracepoint is set, by
9256 using @samp{if} in the arguments to the @code{trace} command.
9257 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9258 also be set or changed at any time with the @code{condition} command,
9259 just as with breakpoints.
9261 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9262 the conditional expression itself. Instead, @value{GDBN} encodes the
9263 expression into an agent expression (@pxref{Agent Expressions}
9264 suitable for execution on the target, independently of @value{GDBN}.
9265 Global variables become raw memory locations, locals become stack
9266 accesses, and so forth.
9268 For instance, suppose you have a function that is usually called
9269 frequently, but should not be called after an error has occurred. You
9270 could use the following tracepoint command to collect data about calls
9271 of that function that happen while the error code is propagating
9272 through the program; an unconditional tracepoint could end up
9273 collecting thousands of useless trace frames that you would have to
9277 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9280 @node Tracepoint Actions
9281 @subsection Tracepoint Action Lists
9285 @cindex tracepoint actions
9286 @item actions @r{[}@var{num}@r{]}
9287 This command will prompt for a list of actions to be taken when the
9288 tracepoint is hit. If the tracepoint number @var{num} is not
9289 specified, this command sets the actions for the one that was most
9290 recently defined (so that you can define a tracepoint and then say
9291 @code{actions} without bothering about its number). You specify the
9292 actions themselves on the following lines, one action at a time, and
9293 terminate the actions list with a line containing just @code{end}. So
9294 far, the only defined actions are @code{collect} and
9295 @code{while-stepping}.
9297 @cindex remove actions from a tracepoint
9298 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9299 and follow it immediately with @samp{end}.
9302 (@value{GDBP}) @b{collect @var{data}} // collect some data
9304 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9306 (@value{GDBP}) @b{end} // signals the end of actions.
9309 In the following example, the action list begins with @code{collect}
9310 commands indicating the things to be collected when the tracepoint is
9311 hit. Then, in order to single-step and collect additional data
9312 following the tracepoint, a @code{while-stepping} command is used,
9313 followed by the list of things to be collected while stepping. The
9314 @code{while-stepping} command is terminated by its own separate
9315 @code{end} command. Lastly, the action list is terminated by an
9319 (@value{GDBP}) @b{trace foo}
9320 (@value{GDBP}) @b{actions}
9321 Enter actions for tracepoint 1, one per line:
9330 @kindex collect @r{(tracepoints)}
9331 @item collect @var{expr1}, @var{expr2}, @dots{}
9332 Collect values of the given expressions when the tracepoint is hit.
9333 This command accepts a comma-separated list of any valid expressions.
9334 In addition to global, static, or local variables, the following
9335 special arguments are supported:
9339 collect all registers
9342 collect all function arguments
9345 collect all local variables.
9348 You can give several consecutive @code{collect} commands, each one
9349 with a single argument, or one @code{collect} command with several
9350 arguments separated by commas: the effect is the same.
9352 The command @code{info scope} (@pxref{Symbols, info scope}) is
9353 particularly useful for figuring out what data to collect.
9355 @kindex while-stepping @r{(tracepoints)}
9356 @item while-stepping @var{n}
9357 Perform @var{n} single-step traces after the tracepoint, collecting
9358 new data at each step. The @code{while-stepping} command is
9359 followed by the list of what to collect while stepping (followed by
9360 its own @code{end} command):
9364 > collect $regs, myglobal
9370 You may abbreviate @code{while-stepping} as @code{ws} or
9374 @node Listing Tracepoints
9375 @subsection Listing Tracepoints
9378 @kindex info tracepoints
9380 @cindex information about tracepoints
9381 @item info tracepoints @r{[}@var{num}@r{]}
9382 Display information about the tracepoint @var{num}. If you don't
9383 specify a tracepoint number, displays information about all the
9384 tracepoints defined so far. The format is similar to that used for
9385 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9386 command, simply restricting itself to tracepoints.
9388 A tracepoint's listing may include additional information specific to
9393 its passcount as given by the @code{passcount @var{n}} command
9395 its step count as given by the @code{while-stepping @var{n}} command
9397 its action list as given by the @code{actions} command. The actions
9398 are prefixed with an @samp{A} so as to distinguish them from commands.
9402 (@value{GDBP}) @b{info trace}
9403 Num Type Disp Enb Address What
9404 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9408 A collect globfoo, $regs
9416 This command can be abbreviated @code{info tp}.
9419 @node Starting and Stopping Trace Experiments
9420 @subsection Starting and Stopping Trace Experiments
9424 @cindex start a new trace experiment
9425 @cindex collected data discarded
9427 This command takes no arguments. It starts the trace experiment, and
9428 begins collecting data. This has the side effect of discarding all
9429 the data collected in the trace buffer during the previous trace
9433 @cindex stop a running trace experiment
9435 This command takes no arguments. It ends the trace experiment, and
9436 stops collecting data.
9438 @strong{Note}: a trace experiment and data collection may stop
9439 automatically if any tracepoint's passcount is reached
9440 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9443 @cindex status of trace data collection
9444 @cindex trace experiment, status of
9446 This command displays the status of the current trace data
9450 Here is an example of the commands we described so far:
9453 (@value{GDBP}) @b{trace gdb_c_test}
9454 (@value{GDBP}) @b{actions}
9455 Enter actions for tracepoint #1, one per line.
9456 > collect $regs,$locals,$args
9461 (@value{GDBP}) @b{tstart}
9462 [time passes @dots{}]
9463 (@value{GDBP}) @b{tstop}
9467 @node Analyze Collected Data
9468 @section Using the Collected Data
9470 After the tracepoint experiment ends, you use @value{GDBN} commands
9471 for examining the trace data. The basic idea is that each tracepoint
9472 collects a trace @dfn{snapshot} every time it is hit and another
9473 snapshot every time it single-steps. All these snapshots are
9474 consecutively numbered from zero and go into a buffer, and you can
9475 examine them later. The way you examine them is to @dfn{focus} on a
9476 specific trace snapshot. When the remote stub is focused on a trace
9477 snapshot, it will respond to all @value{GDBN} requests for memory and
9478 registers by reading from the buffer which belongs to that snapshot,
9479 rather than from @emph{real} memory or registers of the program being
9480 debugged. This means that @strong{all} @value{GDBN} commands
9481 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9482 behave as if we were currently debugging the program state as it was
9483 when the tracepoint occurred. Any requests for data that are not in
9484 the buffer will fail.
9487 * tfind:: How to select a trace snapshot
9488 * tdump:: How to display all data for a snapshot
9489 * save-tracepoints:: How to save tracepoints for a future run
9493 @subsection @code{tfind @var{n}}
9496 @cindex select trace snapshot
9497 @cindex find trace snapshot
9498 The basic command for selecting a trace snapshot from the buffer is
9499 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9500 counting from zero. If no argument @var{n} is given, the next
9501 snapshot is selected.
9503 Here are the various forms of using the @code{tfind} command.
9507 Find the first snapshot in the buffer. This is a synonym for
9508 @code{tfind 0} (since 0 is the number of the first snapshot).
9511 Stop debugging trace snapshots, resume @emph{live} debugging.
9514 Same as @samp{tfind none}.
9517 No argument means find the next trace snapshot.
9520 Find the previous trace snapshot before the current one. This permits
9521 retracing earlier steps.
9523 @item tfind tracepoint @var{num}
9524 Find the next snapshot associated with tracepoint @var{num}. Search
9525 proceeds forward from the last examined trace snapshot. If no
9526 argument @var{num} is given, it means find the next snapshot collected
9527 for the same tracepoint as the current snapshot.
9529 @item tfind pc @var{addr}
9530 Find the next snapshot associated with the value @var{addr} of the
9531 program counter. Search proceeds forward from the last examined trace
9532 snapshot. If no argument @var{addr} is given, it means find the next
9533 snapshot with the same value of PC as the current snapshot.
9535 @item tfind outside @var{addr1}, @var{addr2}
9536 Find the next snapshot whose PC is outside the given range of
9539 @item tfind range @var{addr1}, @var{addr2}
9540 Find the next snapshot whose PC is between @var{addr1} and
9541 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
9543 @item tfind line @r{[}@var{file}:@r{]}@var{n}
9544 Find the next snapshot associated with the source line @var{n}. If
9545 the optional argument @var{file} is given, refer to line @var{n} in
9546 that source file. Search proceeds forward from the last examined
9547 trace snapshot. If no argument @var{n} is given, it means find the
9548 next line other than the one currently being examined; thus saying
9549 @code{tfind line} repeatedly can appear to have the same effect as
9550 stepping from line to line in a @emph{live} debugging session.
9553 The default arguments for the @code{tfind} commands are specifically
9554 designed to make it easy to scan through the trace buffer. For
9555 instance, @code{tfind} with no argument selects the next trace
9556 snapshot, and @code{tfind -} with no argument selects the previous
9557 trace snapshot. So, by giving one @code{tfind} command, and then
9558 simply hitting @key{RET} repeatedly you can examine all the trace
9559 snapshots in order. Or, by saying @code{tfind -} and then hitting
9560 @key{RET} repeatedly you can examine the snapshots in reverse order.
9561 The @code{tfind line} command with no argument selects the snapshot
9562 for the next source line executed. The @code{tfind pc} command with
9563 no argument selects the next snapshot with the same program counter
9564 (PC) as the current frame. The @code{tfind tracepoint} command with
9565 no argument selects the next trace snapshot collected by the same
9566 tracepoint as the current one.
9568 In addition to letting you scan through the trace buffer manually,
9569 these commands make it easy to construct @value{GDBN} scripts that
9570 scan through the trace buffer and print out whatever collected data
9571 you are interested in. Thus, if we want to examine the PC, FP, and SP
9572 registers from each trace frame in the buffer, we can say this:
9575 (@value{GDBP}) @b{tfind start}
9576 (@value{GDBP}) @b{while ($trace_frame != -1)}
9577 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9578 $trace_frame, $pc, $sp, $fp
9582 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9583 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9584 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9585 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9586 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9587 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9588 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9589 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9590 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9591 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9592 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9595 Or, if we want to examine the variable @code{X} at each source line in
9599 (@value{GDBP}) @b{tfind start}
9600 (@value{GDBP}) @b{while ($trace_frame != -1)}
9601 > printf "Frame %d, X == %d\n", $trace_frame, X
9611 @subsection @code{tdump}
9613 @cindex dump all data collected at tracepoint
9614 @cindex tracepoint data, display
9616 This command takes no arguments. It prints all the data collected at
9617 the current trace snapshot.
9620 (@value{GDBP}) @b{trace 444}
9621 (@value{GDBP}) @b{actions}
9622 Enter actions for tracepoint #2, one per line:
9623 > collect $regs, $locals, $args, gdb_long_test
9626 (@value{GDBP}) @b{tstart}
9628 (@value{GDBP}) @b{tfind line 444}
9629 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9631 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9633 (@value{GDBP}) @b{tdump}
9634 Data collected at tracepoint 2, trace frame 1:
9635 d0 0xc4aa0085 -995491707
9639 d4 0x71aea3d 119204413
9644 a1 0x3000668 50333288
9647 a4 0x3000698 50333336
9649 fp 0x30bf3c 0x30bf3c
9650 sp 0x30bf34 0x30bf34
9652 pc 0x20b2c8 0x20b2c8
9656 p = 0x20e5b4 "gdb-test"
9663 gdb_long_test = 17 '\021'
9668 @node save-tracepoints
9669 @subsection @code{save-tracepoints @var{filename}}
9670 @kindex save-tracepoints
9671 @cindex save tracepoints for future sessions
9673 This command saves all current tracepoint definitions together with
9674 their actions and passcounts, into a file @file{@var{filename}}
9675 suitable for use in a later debugging session. To read the saved
9676 tracepoint definitions, use the @code{source} command (@pxref{Command
9679 @node Tracepoint Variables
9680 @section Convenience Variables for Tracepoints
9681 @cindex tracepoint variables
9682 @cindex convenience variables for tracepoints
9685 @vindex $trace_frame
9686 @item (int) $trace_frame
9687 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9688 snapshot is selected.
9691 @item (int) $tracepoint
9692 The tracepoint for the current trace snapshot.
9695 @item (int) $trace_line
9696 The line number for the current trace snapshot.
9699 @item (char []) $trace_file
9700 The source file for the current trace snapshot.
9703 @item (char []) $trace_func
9704 The name of the function containing @code{$tracepoint}.
9707 Note: @code{$trace_file} is not suitable for use in @code{printf},
9708 use @code{output} instead.
9710 Here's a simple example of using these convenience variables for
9711 stepping through all the trace snapshots and printing some of their
9715 (@value{GDBP}) @b{tfind start}
9717 (@value{GDBP}) @b{while $trace_frame != -1}
9718 > output $trace_file
9719 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9725 @chapter Debugging Programs That Use Overlays
9728 If your program is too large to fit completely in your target system's
9729 memory, you can sometimes use @dfn{overlays} to work around this
9730 problem. @value{GDBN} provides some support for debugging programs that
9734 * How Overlays Work:: A general explanation of overlays.
9735 * Overlay Commands:: Managing overlays in @value{GDBN}.
9736 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9737 mapped by asking the inferior.
9738 * Overlay Sample Program:: A sample program using overlays.
9741 @node How Overlays Work
9742 @section How Overlays Work
9743 @cindex mapped overlays
9744 @cindex unmapped overlays
9745 @cindex load address, overlay's
9746 @cindex mapped address
9747 @cindex overlay area
9749 Suppose you have a computer whose instruction address space is only 64
9750 kilobytes long, but which has much more memory which can be accessed by
9751 other means: special instructions, segment registers, or memory
9752 management hardware, for example. Suppose further that you want to
9753 adapt a program which is larger than 64 kilobytes to run on this system.
9755 One solution is to identify modules of your program which are relatively
9756 independent, and need not call each other directly; call these modules
9757 @dfn{overlays}. Separate the overlays from the main program, and place
9758 their machine code in the larger memory. Place your main program in
9759 instruction memory, but leave at least enough space there to hold the
9760 largest overlay as well.
9762 Now, to call a function located in an overlay, you must first copy that
9763 overlay's machine code from the large memory into the space set aside
9764 for it in the instruction memory, and then jump to its entry point
9767 @c NB: In the below the mapped area's size is greater or equal to the
9768 @c size of all overlays. This is intentional to remind the developer
9769 @c that overlays don't necessarily need to be the same size.
9773 Data Instruction Larger
9774 Address Space Address Space Address Space
9775 +-----------+ +-----------+ +-----------+
9777 +-----------+ +-----------+ +-----------+<-- overlay 1
9778 | program | | main | .----| overlay 1 | load address
9779 | variables | | program | | +-----------+
9780 | and heap | | | | | |
9781 +-----------+ | | | +-----------+<-- overlay 2
9782 | | +-----------+ | | | load address
9783 +-----------+ | | | .-| overlay 2 |
9785 mapped --->+-----------+ | | +-----------+
9787 | overlay | <-' | | |
9788 | area | <---' +-----------+<-- overlay 3
9789 | | <---. | | load address
9790 +-----------+ `--| overlay 3 |
9797 @anchor{A code overlay}A code overlay
9801 The diagram (@pxref{A code overlay}) shows a system with separate data
9802 and instruction address spaces. To map an overlay, the program copies
9803 its code from the larger address space to the instruction address space.
9804 Since the overlays shown here all use the same mapped address, only one
9805 may be mapped at a time. For a system with a single address space for
9806 data and instructions, the diagram would be similar, except that the
9807 program variables and heap would share an address space with the main
9808 program and the overlay area.
9810 An overlay loaded into instruction memory and ready for use is called a
9811 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9812 instruction memory. An overlay not present (or only partially present)
9813 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9814 is its address in the larger memory. The mapped address is also called
9815 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9816 called the @dfn{load memory address}, or @dfn{LMA}.
9818 Unfortunately, overlays are not a completely transparent way to adapt a
9819 program to limited instruction memory. They introduce a new set of
9820 global constraints you must keep in mind as you design your program:
9825 Before calling or returning to a function in an overlay, your program
9826 must make sure that overlay is actually mapped. Otherwise, the call or
9827 return will transfer control to the right address, but in the wrong
9828 overlay, and your program will probably crash.
9831 If the process of mapping an overlay is expensive on your system, you
9832 will need to choose your overlays carefully to minimize their effect on
9833 your program's performance.
9836 The executable file you load onto your system must contain each
9837 overlay's instructions, appearing at the overlay's load address, not its
9838 mapped address. However, each overlay's instructions must be relocated
9839 and its symbols defined as if the overlay were at its mapped address.
9840 You can use GNU linker scripts to specify different load and relocation
9841 addresses for pieces of your program; see @ref{Overlay Description,,,
9842 ld.info, Using ld: the GNU linker}.
9845 The procedure for loading executable files onto your system must be able
9846 to load their contents into the larger address space as well as the
9847 instruction and data spaces.
9851 The overlay system described above is rather simple, and could be
9852 improved in many ways:
9857 If your system has suitable bank switch registers or memory management
9858 hardware, you could use those facilities to make an overlay's load area
9859 contents simply appear at their mapped address in instruction space.
9860 This would probably be faster than copying the overlay to its mapped
9861 area in the usual way.
9864 If your overlays are small enough, you could set aside more than one
9865 overlay area, and have more than one overlay mapped at a time.
9868 You can use overlays to manage data, as well as instructions. In
9869 general, data overlays are even less transparent to your design than
9870 code overlays: whereas code overlays only require care when you call or
9871 return to functions, data overlays require care every time you access
9872 the data. Also, if you change the contents of a data overlay, you
9873 must copy its contents back out to its load address before you can copy a
9874 different data overlay into the same mapped area.
9879 @node Overlay Commands
9880 @section Overlay Commands
9882 To use @value{GDBN}'s overlay support, each overlay in your program must
9883 correspond to a separate section of the executable file. The section's
9884 virtual memory address and load memory address must be the overlay's
9885 mapped and load addresses. Identifying overlays with sections allows
9886 @value{GDBN} to determine the appropriate address of a function or
9887 variable, depending on whether the overlay is mapped or not.
9889 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9890 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9895 Disable @value{GDBN}'s overlay support. When overlay support is
9896 disabled, @value{GDBN} assumes that all functions and variables are
9897 always present at their mapped addresses. By default, @value{GDBN}'s
9898 overlay support is disabled.
9900 @item overlay manual
9901 @cindex manual overlay debugging
9902 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9903 relies on you to tell it which overlays are mapped, and which are not,
9904 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9905 commands described below.
9907 @item overlay map-overlay @var{overlay}
9908 @itemx overlay map @var{overlay}
9909 @cindex map an overlay
9910 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9911 be the name of the object file section containing the overlay. When an
9912 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9913 functions and variables at their mapped addresses. @value{GDBN} assumes
9914 that any other overlays whose mapped ranges overlap that of
9915 @var{overlay} are now unmapped.
9917 @item overlay unmap-overlay @var{overlay}
9918 @itemx overlay unmap @var{overlay}
9919 @cindex unmap an overlay
9920 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9921 must be the name of the object file section containing the overlay.
9922 When an overlay is unmapped, @value{GDBN} assumes it can find the
9923 overlay's functions and variables at their load addresses.
9926 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9927 consults a data structure the overlay manager maintains in the inferior
9928 to see which overlays are mapped. For details, see @ref{Automatic
9931 @item overlay load-target
9933 @cindex reloading the overlay table
9934 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9935 re-reads the table @value{GDBN} automatically each time the inferior
9936 stops, so this command should only be necessary if you have changed the
9937 overlay mapping yourself using @value{GDBN}. This command is only
9938 useful when using automatic overlay debugging.
9940 @item overlay list-overlays
9942 @cindex listing mapped overlays
9943 Display a list of the overlays currently mapped, along with their mapped
9944 addresses, load addresses, and sizes.
9948 Normally, when @value{GDBN} prints a code address, it includes the name
9949 of the function the address falls in:
9952 (@value{GDBP}) print main
9953 $3 = @{int ()@} 0x11a0 <main>
9956 When overlay debugging is enabled, @value{GDBN} recognizes code in
9957 unmapped overlays, and prints the names of unmapped functions with
9958 asterisks around them. For example, if @code{foo} is a function in an
9959 unmapped overlay, @value{GDBN} prints it this way:
9962 (@value{GDBP}) overlay list
9963 No sections are mapped.
9964 (@value{GDBP}) print foo
9965 $5 = @{int (int)@} 0x100000 <*foo*>
9968 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9972 (@value{GDBP}) overlay list
9973 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9974 mapped at 0x1016 - 0x104a
9975 (@value{GDBP}) print foo
9976 $6 = @{int (int)@} 0x1016 <foo>
9979 When overlay debugging is enabled, @value{GDBN} can find the correct
9980 address for functions and variables in an overlay, whether or not the
9981 overlay is mapped. This allows most @value{GDBN} commands, like
9982 @code{break} and @code{disassemble}, to work normally, even on unmapped
9983 code. However, @value{GDBN}'s breakpoint support has some limitations:
9987 @cindex breakpoints in overlays
9988 @cindex overlays, setting breakpoints in
9989 You can set breakpoints in functions in unmapped overlays, as long as
9990 @value{GDBN} can write to the overlay at its load address.
9992 @value{GDBN} can not set hardware or simulator-based breakpoints in
9993 unmapped overlays. However, if you set a breakpoint at the end of your
9994 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9995 you are using manual overlay management), @value{GDBN} will re-set its
9996 breakpoints properly.
10000 @node Automatic Overlay Debugging
10001 @section Automatic Overlay Debugging
10002 @cindex automatic overlay debugging
10004 @value{GDBN} can automatically track which overlays are mapped and which
10005 are not, given some simple co-operation from the overlay manager in the
10006 inferior. If you enable automatic overlay debugging with the
10007 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10008 looks in the inferior's memory for certain variables describing the
10009 current state of the overlays.
10011 Here are the variables your overlay manager must define to support
10012 @value{GDBN}'s automatic overlay debugging:
10016 @item @code{_ovly_table}:
10017 This variable must be an array of the following structures:
10022 /* The overlay's mapped address. */
10025 /* The size of the overlay, in bytes. */
10026 unsigned long size;
10028 /* The overlay's load address. */
10031 /* Non-zero if the overlay is currently mapped;
10033 unsigned long mapped;
10037 @item @code{_novlys}:
10038 This variable must be a four-byte signed integer, holding the total
10039 number of elements in @code{_ovly_table}.
10043 To decide whether a particular overlay is mapped or not, @value{GDBN}
10044 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10045 @code{lma} members equal the VMA and LMA of the overlay's section in the
10046 executable file. When @value{GDBN} finds a matching entry, it consults
10047 the entry's @code{mapped} member to determine whether the overlay is
10050 In addition, your overlay manager may define a function called
10051 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10052 will silently set a breakpoint there. If the overlay manager then
10053 calls this function whenever it has changed the overlay table, this
10054 will enable @value{GDBN} to accurately keep track of which overlays
10055 are in program memory, and update any breakpoints that may be set
10056 in overlays. This will allow breakpoints to work even if the
10057 overlays are kept in ROM or other non-writable memory while they
10058 are not being executed.
10060 @node Overlay Sample Program
10061 @section Overlay Sample Program
10062 @cindex overlay example program
10064 When linking a program which uses overlays, you must place the overlays
10065 at their load addresses, while relocating them to run at their mapped
10066 addresses. To do this, you must write a linker script (@pxref{Overlay
10067 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10068 since linker scripts are specific to a particular host system, target
10069 architecture, and target memory layout, this manual cannot provide
10070 portable sample code demonstrating @value{GDBN}'s overlay support.
10072 However, the @value{GDBN} source distribution does contain an overlaid
10073 program, with linker scripts for a few systems, as part of its test
10074 suite. The program consists of the following files from
10075 @file{gdb/testsuite/gdb.base}:
10079 The main program file.
10081 A simple overlay manager, used by @file{overlays.c}.
10086 Overlay modules, loaded and used by @file{overlays.c}.
10089 Linker scripts for linking the test program on the @code{d10v-elf}
10090 and @code{m32r-elf} targets.
10093 You can build the test program using the @code{d10v-elf} GCC
10094 cross-compiler like this:
10097 $ d10v-elf-gcc -g -c overlays.c
10098 $ d10v-elf-gcc -g -c ovlymgr.c
10099 $ d10v-elf-gcc -g -c foo.c
10100 $ d10v-elf-gcc -g -c bar.c
10101 $ d10v-elf-gcc -g -c baz.c
10102 $ d10v-elf-gcc -g -c grbx.c
10103 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10104 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10107 The build process is identical for any other architecture, except that
10108 you must substitute the appropriate compiler and linker script for the
10109 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10113 @chapter Using @value{GDBN} with Different Languages
10116 Although programming languages generally have common aspects, they are
10117 rarely expressed in the same manner. For instance, in ANSI C,
10118 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10119 Modula-2, it is accomplished by @code{p^}. Values can also be
10120 represented (and displayed) differently. Hex numbers in C appear as
10121 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10123 @cindex working language
10124 Language-specific information is built into @value{GDBN} for some languages,
10125 allowing you to express operations like the above in your program's
10126 native language, and allowing @value{GDBN} to output values in a manner
10127 consistent with the syntax of your program's native language. The
10128 language you use to build expressions is called the @dfn{working
10132 * Setting:: Switching between source languages
10133 * Show:: Displaying the language
10134 * Checks:: Type and range checks
10135 * Supported Languages:: Supported languages
10136 * Unsupported Languages:: Unsupported languages
10140 @section Switching Between Source Languages
10142 There are two ways to control the working language---either have @value{GDBN}
10143 set it automatically, or select it manually yourself. You can use the
10144 @code{set language} command for either purpose. On startup, @value{GDBN}
10145 defaults to setting the language automatically. The working language is
10146 used to determine how expressions you type are interpreted, how values
10149 In addition to the working language, every source file that
10150 @value{GDBN} knows about has its own working language. For some object
10151 file formats, the compiler might indicate which language a particular
10152 source file is in. However, most of the time @value{GDBN} infers the
10153 language from the name of the file. The language of a source file
10154 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10155 show each frame appropriately for its own language. There is no way to
10156 set the language of a source file from within @value{GDBN}, but you can
10157 set the language associated with a filename extension. @xref{Show, ,
10158 Displaying the Language}.
10160 This is most commonly a problem when you use a program, such
10161 as @code{cfront} or @code{f2c}, that generates C but is written in
10162 another language. In that case, make the
10163 program use @code{#line} directives in its C output; that way
10164 @value{GDBN} will know the correct language of the source code of the original
10165 program, and will display that source code, not the generated C code.
10168 * Filenames:: Filename extensions and languages.
10169 * Manually:: Setting the working language manually
10170 * Automatically:: Having @value{GDBN} infer the source language
10174 @subsection List of Filename Extensions and Languages
10176 If a source file name ends in one of the following extensions, then
10177 @value{GDBN} infers that its language is the one indicated.
10195 C@t{++} source file
10198 Objective-C source file
10202 Fortran source file
10205 Modula-2 source file
10209 Assembler source file. This actually behaves almost like C, but
10210 @value{GDBN} does not skip over function prologues when stepping.
10213 In addition, you may set the language associated with a filename
10214 extension. @xref{Show, , Displaying the Language}.
10217 @subsection Setting the Working Language
10219 If you allow @value{GDBN} to set the language automatically,
10220 expressions are interpreted the same way in your debugging session and
10223 @kindex set language
10224 If you wish, you may set the language manually. To do this, issue the
10225 command @samp{set language @var{lang}}, where @var{lang} is the name of
10226 a language, such as
10227 @code{c} or @code{modula-2}.
10228 For a list of the supported languages, type @samp{set language}.
10230 Setting the language manually prevents @value{GDBN} from updating the working
10231 language automatically. This can lead to confusion if you try
10232 to debug a program when the working language is not the same as the
10233 source language, when an expression is acceptable to both
10234 languages---but means different things. For instance, if the current
10235 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10243 might not have the effect you intended. In C, this means to add
10244 @code{b} and @code{c} and place the result in @code{a}. The result
10245 printed would be the value of @code{a}. In Modula-2, this means to compare
10246 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10248 @node Automatically
10249 @subsection Having @value{GDBN} Infer the Source Language
10251 To have @value{GDBN} set the working language automatically, use
10252 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10253 then infers the working language. That is, when your program stops in a
10254 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10255 working language to the language recorded for the function in that
10256 frame. If the language for a frame is unknown (that is, if the function
10257 or block corresponding to the frame was defined in a source file that
10258 does not have a recognized extension), the current working language is
10259 not changed, and @value{GDBN} issues a warning.
10261 This may not seem necessary for most programs, which are written
10262 entirely in one source language. However, program modules and libraries
10263 written in one source language can be used by a main program written in
10264 a different source language. Using @samp{set language auto} in this
10265 case frees you from having to set the working language manually.
10268 @section Displaying the Language
10270 The following commands help you find out which language is the
10271 working language, and also what language source files were written in.
10274 @item show language
10275 @kindex show language
10276 Display the current working language. This is the
10277 language you can use with commands such as @code{print} to
10278 build and compute expressions that may involve variables in your program.
10281 @kindex info frame@r{, show the source language}
10282 Display the source language for this frame. This language becomes the
10283 working language if you use an identifier from this frame.
10284 @xref{Frame Info, ,Information about a Frame}, to identify the other
10285 information listed here.
10288 @kindex info source@r{, show the source language}
10289 Display the source language of this source file.
10290 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10291 information listed here.
10294 In unusual circumstances, you may have source files with extensions
10295 not in the standard list. You can then set the extension associated
10296 with a language explicitly:
10299 @item set extension-language @var{ext} @var{language}
10300 @kindex set extension-language
10301 Tell @value{GDBN} that source files with extension @var{ext} are to be
10302 assumed as written in the source language @var{language}.
10304 @item info extensions
10305 @kindex info extensions
10306 List all the filename extensions and the associated languages.
10310 @section Type and Range Checking
10313 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10314 checking are included, but they do not yet have any effect. This
10315 section documents the intended facilities.
10317 @c FIXME remove warning when type/range code added
10319 Some languages are designed to guard you against making seemingly common
10320 errors through a series of compile- and run-time checks. These include
10321 checking the type of arguments to functions and operators, and making
10322 sure mathematical overflows are caught at run time. Checks such as
10323 these help to ensure a program's correctness once it has been compiled
10324 by eliminating type mismatches, and providing active checks for range
10325 errors when your program is running.
10327 @value{GDBN} can check for conditions like the above if you wish.
10328 Although @value{GDBN} does not check the statements in your program,
10329 it can check expressions entered directly into @value{GDBN} for
10330 evaluation via the @code{print} command, for example. As with the
10331 working language, @value{GDBN} can also decide whether or not to check
10332 automatically based on your program's source language.
10333 @xref{Supported Languages, ,Supported Languages}, for the default
10334 settings of supported languages.
10337 * Type Checking:: An overview of type checking
10338 * Range Checking:: An overview of range checking
10341 @cindex type checking
10342 @cindex checks, type
10343 @node Type Checking
10344 @subsection An Overview of Type Checking
10346 Some languages, such as Modula-2, are strongly typed, meaning that the
10347 arguments to operators and functions have to be of the correct type,
10348 otherwise an error occurs. These checks prevent type mismatch
10349 errors from ever causing any run-time problems. For example,
10357 The second example fails because the @code{CARDINAL} 1 is not
10358 type-compatible with the @code{REAL} 2.3.
10360 For the expressions you use in @value{GDBN} commands, you can tell the
10361 @value{GDBN} type checker to skip checking;
10362 to treat any mismatches as errors and abandon the expression;
10363 or to only issue warnings when type mismatches occur,
10364 but evaluate the expression anyway. When you choose the last of
10365 these, @value{GDBN} evaluates expressions like the second example above, but
10366 also issues a warning.
10368 Even if you turn type checking off, there may be other reasons
10369 related to type that prevent @value{GDBN} from evaluating an expression.
10370 For instance, @value{GDBN} does not know how to add an @code{int} and
10371 a @code{struct foo}. These particular type errors have nothing to do
10372 with the language in use, and usually arise from expressions, such as
10373 the one described above, which make little sense to evaluate anyway.
10375 Each language defines to what degree it is strict about type. For
10376 instance, both Modula-2 and C require the arguments to arithmetical
10377 operators to be numbers. In C, enumerated types and pointers can be
10378 represented as numbers, so that they are valid arguments to mathematical
10379 operators. @xref{Supported Languages, ,Supported Languages}, for further
10380 details on specific languages.
10382 @value{GDBN} provides some additional commands for controlling the type checker:
10384 @kindex set check type
10385 @kindex show check type
10387 @item set check type auto
10388 Set type checking on or off based on the current working language.
10389 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10392 @item set check type on
10393 @itemx set check type off
10394 Set type checking on or off, overriding the default setting for the
10395 current working language. Issue a warning if the setting does not
10396 match the language default. If any type mismatches occur in
10397 evaluating an expression while type checking is on, @value{GDBN} prints a
10398 message and aborts evaluation of the expression.
10400 @item set check type warn
10401 Cause the type checker to issue warnings, but to always attempt to
10402 evaluate the expression. Evaluating the expression may still
10403 be impossible for other reasons. For example, @value{GDBN} cannot add
10404 numbers and structures.
10407 Show the current setting of the type checker, and whether or not @value{GDBN}
10408 is setting it automatically.
10411 @cindex range checking
10412 @cindex checks, range
10413 @node Range Checking
10414 @subsection An Overview of Range Checking
10416 In some languages (such as Modula-2), it is an error to exceed the
10417 bounds of a type; this is enforced with run-time checks. Such range
10418 checking is meant to ensure program correctness by making sure
10419 computations do not overflow, or indices on an array element access do
10420 not exceed the bounds of the array.
10422 For expressions you use in @value{GDBN} commands, you can tell
10423 @value{GDBN} to treat range errors in one of three ways: ignore them,
10424 always treat them as errors and abandon the expression, or issue
10425 warnings but evaluate the expression anyway.
10427 A range error can result from numerical overflow, from exceeding an
10428 array index bound, or when you type a constant that is not a member
10429 of any type. Some languages, however, do not treat overflows as an
10430 error. In many implementations of C, mathematical overflow causes the
10431 result to ``wrap around'' to lower values---for example, if @var{m} is
10432 the largest integer value, and @var{s} is the smallest, then
10435 @var{m} + 1 @result{} @var{s}
10438 This, too, is specific to individual languages, and in some cases
10439 specific to individual compilers or machines. @xref{Supported Languages, ,
10440 Supported Languages}, for further details on specific languages.
10442 @value{GDBN} provides some additional commands for controlling the range checker:
10444 @kindex set check range
10445 @kindex show check range
10447 @item set check range auto
10448 Set range checking on or off based on the current working language.
10449 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10452 @item set check range on
10453 @itemx set check range off
10454 Set range checking on or off, overriding the default setting for the
10455 current working language. A warning is issued if the setting does not
10456 match the language default. If a range error occurs and range checking is on,
10457 then a message is printed and evaluation of the expression is aborted.
10459 @item set check range warn
10460 Output messages when the @value{GDBN} range checker detects a range error,
10461 but attempt to evaluate the expression anyway. Evaluating the
10462 expression may still be impossible for other reasons, such as accessing
10463 memory that the process does not own (a typical example from many Unix
10467 Show the current setting of the range checker, and whether or not it is
10468 being set automatically by @value{GDBN}.
10471 @node Supported Languages
10472 @section Supported Languages
10474 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
10475 assembly, Modula-2, and Ada.
10476 @c This is false ...
10477 Some @value{GDBN} features may be used in expressions regardless of the
10478 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
10479 and the @samp{@{type@}addr} construct (@pxref{Expressions,
10480 ,Expressions}) can be used with the constructs of any supported
10483 The following sections detail to what degree each source language is
10484 supported by @value{GDBN}. These sections are not meant to be language
10485 tutorials or references, but serve only as a reference guide to what the
10486 @value{GDBN} expression parser accepts, and what input and output
10487 formats should look like for different languages. There are many good
10488 books written on each of these languages; please look to these for a
10489 language reference or tutorial.
10492 * C:: C and C@t{++}
10493 * Objective-C:: Objective-C
10494 * Fortran:: Fortran
10496 * Modula-2:: Modula-2
10501 @subsection C and C@t{++}
10503 @cindex C and C@t{++}
10504 @cindex expressions in C or C@t{++}
10506 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
10507 to both languages. Whenever this is the case, we discuss those languages
10511 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
10512 @cindex @sc{gnu} C@t{++}
10513 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
10514 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
10515 effectively, you must compile your C@t{++} programs with a supported
10516 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
10517 compiler (@code{aCC}).
10519 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
10520 format; if it doesn't work on your system, try the stabs+ debugging
10521 format. You can select those formats explicitly with the @code{g++}
10522 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
10523 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
10524 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
10527 * C Operators:: C and C@t{++} operators
10528 * C Constants:: C and C@t{++} constants
10529 * C Plus Plus Expressions:: C@t{++} expressions
10530 * C Defaults:: Default settings for C and C@t{++}
10531 * C Checks:: C and C@t{++} type and range checks
10532 * Debugging C:: @value{GDBN} and C
10533 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
10534 * Decimal Floating Point:: Numbers in Decimal Floating Point format
10538 @subsubsection C and C@t{++} Operators
10540 @cindex C and C@t{++} operators
10542 Operators must be defined on values of specific types. For instance,
10543 @code{+} is defined on numbers, but not on structures. Operators are
10544 often defined on groups of types.
10546 For the purposes of C and C@t{++}, the following definitions hold:
10551 @emph{Integral types} include @code{int} with any of its storage-class
10552 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
10555 @emph{Floating-point types} include @code{float}, @code{double}, and
10556 @code{long double} (if supported by the target platform).
10559 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10562 @emph{Scalar types} include all of the above.
10567 The following operators are supported. They are listed here
10568 in order of increasing precedence:
10572 The comma or sequencing operator. Expressions in a comma-separated list
10573 are evaluated from left to right, with the result of the entire
10574 expression being the last expression evaluated.
10577 Assignment. The value of an assignment expression is the value
10578 assigned. Defined on scalar types.
10581 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10582 and translated to @w{@code{@var{a} = @var{a op b}}}.
10583 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10584 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10585 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10588 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10589 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10593 Logical @sc{or}. Defined on integral types.
10596 Logical @sc{and}. Defined on integral types.
10599 Bitwise @sc{or}. Defined on integral types.
10602 Bitwise exclusive-@sc{or}. Defined on integral types.
10605 Bitwise @sc{and}. Defined on integral types.
10608 Equality and inequality. Defined on scalar types. The value of these
10609 expressions is 0 for false and non-zero for true.
10611 @item <@r{, }>@r{, }<=@r{, }>=
10612 Less than, greater than, less than or equal, greater than or equal.
10613 Defined on scalar types. The value of these expressions is 0 for false
10614 and non-zero for true.
10617 left shift, and right shift. Defined on integral types.
10620 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10623 Addition and subtraction. Defined on integral types, floating-point types and
10626 @item *@r{, }/@r{, }%
10627 Multiplication, division, and modulus. Multiplication and division are
10628 defined on integral and floating-point types. Modulus is defined on
10632 Increment and decrement. When appearing before a variable, the
10633 operation is performed before the variable is used in an expression;
10634 when appearing after it, the variable's value is used before the
10635 operation takes place.
10638 Pointer dereferencing. Defined on pointer types. Same precedence as
10642 Address operator. Defined on variables. Same precedence as @code{++}.
10644 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10645 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10646 to examine the address
10647 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10651 Negative. Defined on integral and floating-point types. Same
10652 precedence as @code{++}.
10655 Logical negation. Defined on integral types. Same precedence as
10659 Bitwise complement operator. Defined on integral types. Same precedence as
10664 Structure member, and pointer-to-structure member. For convenience,
10665 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10666 pointer based on the stored type information.
10667 Defined on @code{struct} and @code{union} data.
10670 Dereferences of pointers to members.
10673 Array indexing. @code{@var{a}[@var{i}]} is defined as
10674 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10677 Function parameter list. Same precedence as @code{->}.
10680 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10681 and @code{class} types.
10684 Doubled colons also represent the @value{GDBN} scope operator
10685 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10689 If an operator is redefined in the user code, @value{GDBN} usually
10690 attempts to invoke the redefined version instead of using the operator's
10691 predefined meaning.
10694 @subsubsection C and C@t{++} Constants
10696 @cindex C and C@t{++} constants
10698 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10703 Integer constants are a sequence of digits. Octal constants are
10704 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10705 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10706 @samp{l}, specifying that the constant should be treated as a
10710 Floating point constants are a sequence of digits, followed by a decimal
10711 point, followed by a sequence of digits, and optionally followed by an
10712 exponent. An exponent is of the form:
10713 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10714 sequence of digits. The @samp{+} is optional for positive exponents.
10715 A floating-point constant may also end with a letter @samp{f} or
10716 @samp{F}, specifying that the constant should be treated as being of
10717 the @code{float} (as opposed to the default @code{double}) type; or with
10718 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10722 Enumerated constants consist of enumerated identifiers, or their
10723 integral equivalents.
10726 Character constants are a single character surrounded by single quotes
10727 (@code{'}), or a number---the ordinal value of the corresponding character
10728 (usually its @sc{ascii} value). Within quotes, the single character may
10729 be represented by a letter or by @dfn{escape sequences}, which are of
10730 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10731 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10732 @samp{@var{x}} is a predefined special character---for example,
10733 @samp{\n} for newline.
10736 String constants are a sequence of character constants surrounded by
10737 double quotes (@code{"}). Any valid character constant (as described
10738 above) may appear. Double quotes within the string must be preceded by
10739 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10743 Pointer constants are an integral value. You can also write pointers
10744 to constants using the C operator @samp{&}.
10747 Array constants are comma-separated lists surrounded by braces @samp{@{}
10748 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10749 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10750 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10753 @node C Plus Plus Expressions
10754 @subsubsection C@t{++} Expressions
10756 @cindex expressions in C@t{++}
10757 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10759 @cindex debugging C@t{++} programs
10760 @cindex C@t{++} compilers
10761 @cindex debug formats and C@t{++}
10762 @cindex @value{NGCC} and C@t{++}
10764 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10765 proper compiler and the proper debug format. Currently, @value{GDBN}
10766 works best when debugging C@t{++} code that is compiled with
10767 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10768 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10769 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10770 stabs+ as their default debug format, so you usually don't need to
10771 specify a debug format explicitly. Other compilers and/or debug formats
10772 are likely to work badly or not at all when using @value{GDBN} to debug
10778 @cindex member functions
10780 Member function calls are allowed; you can use expressions like
10783 count = aml->GetOriginal(x, y)
10786 @vindex this@r{, inside C@t{++} member functions}
10787 @cindex namespace in C@t{++}
10789 While a member function is active (in the selected stack frame), your
10790 expressions have the same namespace available as the member function;
10791 that is, @value{GDBN} allows implicit references to the class instance
10792 pointer @code{this} following the same rules as C@t{++}.
10794 @cindex call overloaded functions
10795 @cindex overloaded functions, calling
10796 @cindex type conversions in C@t{++}
10798 You can call overloaded functions; @value{GDBN} resolves the function
10799 call to the right definition, with some restrictions. @value{GDBN} does not
10800 perform overload resolution involving user-defined type conversions,
10801 calls to constructors, or instantiations of templates that do not exist
10802 in the program. It also cannot handle ellipsis argument lists or
10805 It does perform integral conversions and promotions, floating-point
10806 promotions, arithmetic conversions, pointer conversions, conversions of
10807 class objects to base classes, and standard conversions such as those of
10808 functions or arrays to pointers; it requires an exact match on the
10809 number of function arguments.
10811 Overload resolution is always performed, unless you have specified
10812 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10813 ,@value{GDBN} Features for C@t{++}}.
10815 You must specify @code{set overload-resolution off} in order to use an
10816 explicit function signature to call an overloaded function, as in
10818 p 'foo(char,int)'('x', 13)
10821 The @value{GDBN} command-completion facility can simplify this;
10822 see @ref{Completion, ,Command Completion}.
10824 @cindex reference declarations
10826 @value{GDBN} understands variables declared as C@t{++} references; you can use
10827 them in expressions just as you do in C@t{++} source---they are automatically
10830 In the parameter list shown when @value{GDBN} displays a frame, the values of
10831 reference variables are not displayed (unlike other variables); this
10832 avoids clutter, since references are often used for large structures.
10833 The @emph{address} of a reference variable is always shown, unless
10834 you have specified @samp{set print address off}.
10837 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10838 expressions can use it just as expressions in your program do. Since
10839 one scope may be defined in another, you can use @code{::} repeatedly if
10840 necessary, for example in an expression like
10841 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10842 resolving name scope by reference to source files, in both C and C@t{++}
10843 debugging (@pxref{Variables, ,Program Variables}).
10846 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10847 calling virtual functions correctly, printing out virtual bases of
10848 objects, calling functions in a base subobject, casting objects, and
10849 invoking user-defined operators.
10852 @subsubsection C and C@t{++} Defaults
10854 @cindex C and C@t{++} defaults
10856 If you allow @value{GDBN} to set type and range checking automatically, they
10857 both default to @code{off} whenever the working language changes to
10858 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10859 selects the working language.
10861 If you allow @value{GDBN} to set the language automatically, it
10862 recognizes source files whose names end with @file{.c}, @file{.C}, or
10863 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10864 these files, it sets the working language to C or C@t{++}.
10865 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10866 for further details.
10868 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10869 @c unimplemented. If (b) changes, it might make sense to let this node
10870 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10873 @subsubsection C and C@t{++} Type and Range Checks
10875 @cindex C and C@t{++} checks
10877 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10878 is not used. However, if you turn type checking on, @value{GDBN}
10879 considers two variables type equivalent if:
10883 The two variables are structured and have the same structure, union, or
10887 The two variables have the same type name, or types that have been
10888 declared equivalent through @code{typedef}.
10891 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10894 The two @code{struct}, @code{union}, or @code{enum} variables are
10895 declared in the same declaration. (Note: this may not be true for all C
10900 Range checking, if turned on, is done on mathematical operations. Array
10901 indices are not checked, since they are often used to index a pointer
10902 that is not itself an array.
10905 @subsubsection @value{GDBN} and C
10907 The @code{set print union} and @code{show print union} commands apply to
10908 the @code{union} type. When set to @samp{on}, any @code{union} that is
10909 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10910 appears as @samp{@{...@}}.
10912 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10913 with pointers and a memory allocation function. @xref{Expressions,
10916 @node Debugging C Plus Plus
10917 @subsubsection @value{GDBN} Features for C@t{++}
10919 @cindex commands for C@t{++}
10921 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10922 designed specifically for use with C@t{++}. Here is a summary:
10925 @cindex break in overloaded functions
10926 @item @r{breakpoint menus}
10927 When you want a breakpoint in a function whose name is overloaded,
10928 @value{GDBN} has the capability to display a menu of possible breakpoint
10929 locations to help you specify which function definition you want.
10930 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10932 @cindex overloading in C@t{++}
10933 @item rbreak @var{regex}
10934 Setting breakpoints using regular expressions is helpful for setting
10935 breakpoints on overloaded functions that are not members of any special
10937 @xref{Set Breaks, ,Setting Breakpoints}.
10939 @cindex C@t{++} exception handling
10942 Debug C@t{++} exception handling using these commands. @xref{Set
10943 Catchpoints, , Setting Catchpoints}.
10945 @cindex inheritance
10946 @item ptype @var{typename}
10947 Print inheritance relationships as well as other information for type
10949 @xref{Symbols, ,Examining the Symbol Table}.
10951 @cindex C@t{++} symbol display
10952 @item set print demangle
10953 @itemx show print demangle
10954 @itemx set print asm-demangle
10955 @itemx show print asm-demangle
10956 Control whether C@t{++} symbols display in their source form, both when
10957 displaying code as C@t{++} source and when displaying disassemblies.
10958 @xref{Print Settings, ,Print Settings}.
10960 @item set print object
10961 @itemx show print object
10962 Choose whether to print derived (actual) or declared types of objects.
10963 @xref{Print Settings, ,Print Settings}.
10965 @item set print vtbl
10966 @itemx show print vtbl
10967 Control the format for printing virtual function tables.
10968 @xref{Print Settings, ,Print Settings}.
10969 (The @code{vtbl} commands do not work on programs compiled with the HP
10970 ANSI C@t{++} compiler (@code{aCC}).)
10972 @kindex set overload-resolution
10973 @cindex overloaded functions, overload resolution
10974 @item set overload-resolution on
10975 Enable overload resolution for C@t{++} expression evaluation. The default
10976 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10977 and searches for a function whose signature matches the argument types,
10978 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10979 Expressions, ,C@t{++} Expressions}, for details).
10980 If it cannot find a match, it emits a message.
10982 @item set overload-resolution off
10983 Disable overload resolution for C@t{++} expression evaluation. For
10984 overloaded functions that are not class member functions, @value{GDBN}
10985 chooses the first function of the specified name that it finds in the
10986 symbol table, whether or not its arguments are of the correct type. For
10987 overloaded functions that are class member functions, @value{GDBN}
10988 searches for a function whose signature @emph{exactly} matches the
10991 @kindex show overload-resolution
10992 @item show overload-resolution
10993 Show the current setting of overload resolution.
10995 @item @r{Overloaded symbol names}
10996 You can specify a particular definition of an overloaded symbol, using
10997 the same notation that is used to declare such symbols in C@t{++}: type
10998 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10999 also use the @value{GDBN} command-line word completion facilities to list the
11000 available choices, or to finish the type list for you.
11001 @xref{Completion,, Command Completion}, for details on how to do this.
11004 @node Decimal Floating Point
11005 @subsubsection Decimal Floating Point format
11006 @cindex decimal floating point format
11008 @value{GDBN} can examine, set and perform computations with numbers in
11009 decimal floating point format, which in the C language correspond to the
11010 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11011 specified by the extension to support decimal floating-point arithmetic.
11013 There are two encodings in use, depending on the architecture: BID (Binary
11014 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11015 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11018 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11019 to manipulate decimal floating point numbers, it is not possible to convert
11020 (using a cast, for example) integers wider than 32-bit to decimal float.
11022 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11023 point computations, error checking in decimal float operations ignores
11024 underflow, overflow and divide by zero exceptions.
11026 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11027 to inspect @code{_Decimal128} values stored in floating point registers.
11028 See @ref{PowerPC,,PowerPC} for more details.
11031 @subsection Objective-C
11033 @cindex Objective-C
11034 This section provides information about some commands and command
11035 options that are useful for debugging Objective-C code. See also
11036 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11037 few more commands specific to Objective-C support.
11040 * Method Names in Commands::
11041 * The Print Command with Objective-C::
11044 @node Method Names in Commands
11045 @subsubsection Method Names in Commands
11047 The following commands have been extended to accept Objective-C method
11048 names as line specifications:
11050 @kindex clear@r{, and Objective-C}
11051 @kindex break@r{, and Objective-C}
11052 @kindex info line@r{, and Objective-C}
11053 @kindex jump@r{, and Objective-C}
11054 @kindex list@r{, and Objective-C}
11058 @item @code{info line}
11063 A fully qualified Objective-C method name is specified as
11066 -[@var{Class} @var{methodName}]
11069 where the minus sign is used to indicate an instance method and a
11070 plus sign (not shown) is used to indicate a class method. The class
11071 name @var{Class} and method name @var{methodName} are enclosed in
11072 brackets, similar to the way messages are specified in Objective-C
11073 source code. For example, to set a breakpoint at the @code{create}
11074 instance method of class @code{Fruit} in the program currently being
11078 break -[Fruit create]
11081 To list ten program lines around the @code{initialize} class method,
11085 list +[NSText initialize]
11088 In the current version of @value{GDBN}, the plus or minus sign is
11089 required. In future versions of @value{GDBN}, the plus or minus
11090 sign will be optional, but you can use it to narrow the search. It
11091 is also possible to specify just a method name:
11097 You must specify the complete method name, including any colons. If
11098 your program's source files contain more than one @code{create} method,
11099 you'll be presented with a numbered list of classes that implement that
11100 method. Indicate your choice by number, or type @samp{0} to exit if
11103 As another example, to clear a breakpoint established at the
11104 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11107 clear -[NSWindow makeKeyAndOrderFront:]
11110 @node The Print Command with Objective-C
11111 @subsubsection The Print Command With Objective-C
11112 @cindex Objective-C, print objects
11113 @kindex print-object
11114 @kindex po @r{(@code{print-object})}
11116 The print command has also been extended to accept methods. For example:
11119 print -[@var{object} hash]
11122 @cindex print an Objective-C object description
11123 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11125 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11126 and print the result. Also, an additional command has been added,
11127 @code{print-object} or @code{po} for short, which is meant to print
11128 the description of an object. However, this command may only work
11129 with certain Objective-C libraries that have a particular hook
11130 function, @code{_NSPrintForDebugger}, defined.
11133 @subsection Fortran
11134 @cindex Fortran-specific support in @value{GDBN}
11136 @value{GDBN} can be used to debug programs written in Fortran, but it
11137 currently supports only the features of Fortran 77 language.
11139 @cindex trailing underscore, in Fortran symbols
11140 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11141 among them) append an underscore to the names of variables and
11142 functions. When you debug programs compiled by those compilers, you
11143 will need to refer to variables and functions with a trailing
11147 * Fortran Operators:: Fortran operators and expressions
11148 * Fortran Defaults:: Default settings for Fortran
11149 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11152 @node Fortran Operators
11153 @subsubsection Fortran Operators and Expressions
11155 @cindex Fortran operators and expressions
11157 Operators must be defined on values of specific types. For instance,
11158 @code{+} is defined on numbers, but not on characters or other non-
11159 arithmetic types. Operators are often defined on groups of types.
11163 The exponentiation operator. It raises the first operand to the power
11167 The range operator. Normally used in the form of array(low:high) to
11168 represent a section of array.
11171 The access component operator. Normally used to access elements in derived
11172 types. Also suitable for unions. As unions aren't part of regular Fortran,
11173 this can only happen when accessing a register that uses a gdbarch-defined
11177 @node Fortran Defaults
11178 @subsubsection Fortran Defaults
11180 @cindex Fortran Defaults
11182 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11183 default uses case-insensitive matches for Fortran symbols. You can
11184 change that with the @samp{set case-insensitive} command, see
11185 @ref{Symbols}, for the details.
11187 @node Special Fortran Commands
11188 @subsubsection Special Fortran Commands
11190 @cindex Special Fortran commands
11192 @value{GDBN} has some commands to support Fortran-specific features,
11193 such as displaying common blocks.
11196 @cindex @code{COMMON} blocks, Fortran
11197 @kindex info common
11198 @item info common @r{[}@var{common-name}@r{]}
11199 This command prints the values contained in the Fortran @code{COMMON}
11200 block whose name is @var{common-name}. With no argument, the names of
11201 all @code{COMMON} blocks visible at the current program location are
11208 @cindex Pascal support in @value{GDBN}, limitations
11209 Debugging Pascal programs which use sets, subranges, file variables, or
11210 nested functions does not currently work. @value{GDBN} does not support
11211 entering expressions, printing values, or similar features using Pascal
11214 The Pascal-specific command @code{set print pascal_static-members}
11215 controls whether static members of Pascal objects are displayed.
11216 @xref{Print Settings, pascal_static-members}.
11219 @subsection Modula-2
11221 @cindex Modula-2, @value{GDBN} support
11223 The extensions made to @value{GDBN} to support Modula-2 only support
11224 output from the @sc{gnu} Modula-2 compiler (which is currently being
11225 developed). Other Modula-2 compilers are not currently supported, and
11226 attempting to debug executables produced by them is most likely
11227 to give an error as @value{GDBN} reads in the executable's symbol
11230 @cindex expressions in Modula-2
11232 * M2 Operators:: Built-in operators
11233 * Built-In Func/Proc:: Built-in functions and procedures
11234 * M2 Constants:: Modula-2 constants
11235 * M2 Types:: Modula-2 types
11236 * M2 Defaults:: Default settings for Modula-2
11237 * Deviations:: Deviations from standard Modula-2
11238 * M2 Checks:: Modula-2 type and range checks
11239 * M2 Scope:: The scope operators @code{::} and @code{.}
11240 * GDB/M2:: @value{GDBN} and Modula-2
11244 @subsubsection Operators
11245 @cindex Modula-2 operators
11247 Operators must be defined on values of specific types. For instance,
11248 @code{+} is defined on numbers, but not on structures. Operators are
11249 often defined on groups of types. For the purposes of Modula-2, the
11250 following definitions hold:
11255 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11259 @emph{Character types} consist of @code{CHAR} and its subranges.
11262 @emph{Floating-point types} consist of @code{REAL}.
11265 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11269 @emph{Scalar types} consist of all of the above.
11272 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11275 @emph{Boolean types} consist of @code{BOOLEAN}.
11279 The following operators are supported, and appear in order of
11280 increasing precedence:
11284 Function argument or array index separator.
11287 Assignment. The value of @var{var} @code{:=} @var{value} is
11291 Less than, greater than on integral, floating-point, or enumerated
11295 Less than or equal to, greater than or equal to
11296 on integral, floating-point and enumerated types, or set inclusion on
11297 set types. Same precedence as @code{<}.
11299 @item =@r{, }<>@r{, }#
11300 Equality and two ways of expressing inequality, valid on scalar types.
11301 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11302 available for inequality, since @code{#} conflicts with the script
11306 Set membership. Defined on set types and the types of their members.
11307 Same precedence as @code{<}.
11310 Boolean disjunction. Defined on boolean types.
11313 Boolean conjunction. Defined on boolean types.
11316 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11319 Addition and subtraction on integral and floating-point types, or union
11320 and difference on set types.
11323 Multiplication on integral and floating-point types, or set intersection
11327 Division on floating-point types, or symmetric set difference on set
11328 types. Same precedence as @code{*}.
11331 Integer division and remainder. Defined on integral types. Same
11332 precedence as @code{*}.
11335 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11338 Pointer dereferencing. Defined on pointer types.
11341 Boolean negation. Defined on boolean types. Same precedence as
11345 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11346 precedence as @code{^}.
11349 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11352 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11356 @value{GDBN} and Modula-2 scope operators.
11360 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11361 treats the use of the operator @code{IN}, or the use of operators
11362 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11363 @code{<=}, and @code{>=} on sets as an error.
11367 @node Built-In Func/Proc
11368 @subsubsection Built-in Functions and Procedures
11369 @cindex Modula-2 built-ins
11371 Modula-2 also makes available several built-in procedures and functions.
11372 In describing these, the following metavariables are used:
11377 represents an @code{ARRAY} variable.
11380 represents a @code{CHAR} constant or variable.
11383 represents a variable or constant of integral type.
11386 represents an identifier that belongs to a set. Generally used in the
11387 same function with the metavariable @var{s}. The type of @var{s} should
11388 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11391 represents a variable or constant of integral or floating-point type.
11394 represents a variable or constant of floating-point type.
11400 represents a variable.
11403 represents a variable or constant of one of many types. See the
11404 explanation of the function for details.
11407 All Modula-2 built-in procedures also return a result, described below.
11411 Returns the absolute value of @var{n}.
11414 If @var{c} is a lower case letter, it returns its upper case
11415 equivalent, otherwise it returns its argument.
11418 Returns the character whose ordinal value is @var{i}.
11421 Decrements the value in the variable @var{v} by one. Returns the new value.
11423 @item DEC(@var{v},@var{i})
11424 Decrements the value in the variable @var{v} by @var{i}. Returns the
11427 @item EXCL(@var{m},@var{s})
11428 Removes the element @var{m} from the set @var{s}. Returns the new
11431 @item FLOAT(@var{i})
11432 Returns the floating point equivalent of the integer @var{i}.
11434 @item HIGH(@var{a})
11435 Returns the index of the last member of @var{a}.
11438 Increments the value in the variable @var{v} by one. Returns the new value.
11440 @item INC(@var{v},@var{i})
11441 Increments the value in the variable @var{v} by @var{i}. Returns the
11444 @item INCL(@var{m},@var{s})
11445 Adds the element @var{m} to the set @var{s} if it is not already
11446 there. Returns the new set.
11449 Returns the maximum value of the type @var{t}.
11452 Returns the minimum value of the type @var{t}.
11455 Returns boolean TRUE if @var{i} is an odd number.
11458 Returns the ordinal value of its argument. For example, the ordinal
11459 value of a character is its @sc{ascii} value (on machines supporting the
11460 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11461 integral, character and enumerated types.
11463 @item SIZE(@var{x})
11464 Returns the size of its argument. @var{x} can be a variable or a type.
11466 @item TRUNC(@var{r})
11467 Returns the integral part of @var{r}.
11469 @item TSIZE(@var{x})
11470 Returns the size of its argument. @var{x} can be a variable or a type.
11472 @item VAL(@var{t},@var{i})
11473 Returns the member of the type @var{t} whose ordinal value is @var{i}.
11477 @emph{Warning:} Sets and their operations are not yet supported, so
11478 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
11482 @cindex Modula-2 constants
11484 @subsubsection Constants
11486 @value{GDBN} allows you to express the constants of Modula-2 in the following
11492 Integer constants are simply a sequence of digits. When used in an
11493 expression, a constant is interpreted to be type-compatible with the
11494 rest of the expression. Hexadecimal integers are specified by a
11495 trailing @samp{H}, and octal integers by a trailing @samp{B}.
11498 Floating point constants appear as a sequence of digits, followed by a
11499 decimal point and another sequence of digits. An optional exponent can
11500 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
11501 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
11502 digits of the floating point constant must be valid decimal (base 10)
11506 Character constants consist of a single character enclosed by a pair of
11507 like quotes, either single (@code{'}) or double (@code{"}). They may
11508 also be expressed by their ordinal value (their @sc{ascii} value, usually)
11509 followed by a @samp{C}.
11512 String constants consist of a sequence of characters enclosed by a
11513 pair of like quotes, either single (@code{'}) or double (@code{"}).
11514 Escape sequences in the style of C are also allowed. @xref{C
11515 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
11519 Enumerated constants consist of an enumerated identifier.
11522 Boolean constants consist of the identifiers @code{TRUE} and
11526 Pointer constants consist of integral values only.
11529 Set constants are not yet supported.
11533 @subsubsection Modula-2 Types
11534 @cindex Modula-2 types
11536 Currently @value{GDBN} can print the following data types in Modula-2
11537 syntax: array types, record types, set types, pointer types, procedure
11538 types, enumerated types, subrange types and base types. You can also
11539 print the contents of variables declared using these type.
11540 This section gives a number of simple source code examples together with
11541 sample @value{GDBN} sessions.
11543 The first example contains the following section of code:
11552 and you can request @value{GDBN} to interrogate the type and value of
11553 @code{r} and @code{s}.
11556 (@value{GDBP}) print s
11558 (@value{GDBP}) ptype s
11560 (@value{GDBP}) print r
11562 (@value{GDBP}) ptype r
11567 Likewise if your source code declares @code{s} as:
11571 s: SET ['A'..'Z'] ;
11575 then you may query the type of @code{s} by:
11578 (@value{GDBP}) ptype s
11579 type = SET ['A'..'Z']
11583 Note that at present you cannot interactively manipulate set
11584 expressions using the debugger.
11586 The following example shows how you might declare an array in Modula-2
11587 and how you can interact with @value{GDBN} to print its type and contents:
11591 s: ARRAY [-10..10] OF CHAR ;
11595 (@value{GDBP}) ptype s
11596 ARRAY [-10..10] OF CHAR
11599 Note that the array handling is not yet complete and although the type
11600 is printed correctly, expression handling still assumes that all
11601 arrays have a lower bound of zero and not @code{-10} as in the example
11604 Here are some more type related Modula-2 examples:
11608 colour = (blue, red, yellow, green) ;
11609 t = [blue..yellow] ;
11617 The @value{GDBN} interaction shows how you can query the data type
11618 and value of a variable.
11621 (@value{GDBP}) print s
11623 (@value{GDBP}) ptype t
11624 type = [blue..yellow]
11628 In this example a Modula-2 array is declared and its contents
11629 displayed. Observe that the contents are written in the same way as
11630 their @code{C} counterparts.
11634 s: ARRAY [1..5] OF CARDINAL ;
11640 (@value{GDBP}) print s
11641 $1 = @{1, 0, 0, 0, 0@}
11642 (@value{GDBP}) ptype s
11643 type = ARRAY [1..5] OF CARDINAL
11646 The Modula-2 language interface to @value{GDBN} also understands
11647 pointer types as shown in this example:
11651 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11658 and you can request that @value{GDBN} describes the type of @code{s}.
11661 (@value{GDBP}) ptype s
11662 type = POINTER TO ARRAY [1..5] OF CARDINAL
11665 @value{GDBN} handles compound types as we can see in this example.
11666 Here we combine array types, record types, pointer types and subrange
11677 myarray = ARRAY myrange OF CARDINAL ;
11678 myrange = [-2..2] ;
11680 s: POINTER TO ARRAY myrange OF foo ;
11684 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11688 (@value{GDBP}) ptype s
11689 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11692 f3 : ARRAY [-2..2] OF CARDINAL;
11697 @subsubsection Modula-2 Defaults
11698 @cindex Modula-2 defaults
11700 If type and range checking are set automatically by @value{GDBN}, they
11701 both default to @code{on} whenever the working language changes to
11702 Modula-2. This happens regardless of whether you or @value{GDBN}
11703 selected the working language.
11705 If you allow @value{GDBN} to set the language automatically, then entering
11706 code compiled from a file whose name ends with @file{.mod} sets the
11707 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11708 Infer the Source Language}, for further details.
11711 @subsubsection Deviations from Standard Modula-2
11712 @cindex Modula-2, deviations from
11714 A few changes have been made to make Modula-2 programs easier to debug.
11715 This is done primarily via loosening its type strictness:
11719 Unlike in standard Modula-2, pointer constants can be formed by
11720 integers. This allows you to modify pointer variables during
11721 debugging. (In standard Modula-2, the actual address contained in a
11722 pointer variable is hidden from you; it can only be modified
11723 through direct assignment to another pointer variable or expression that
11724 returned a pointer.)
11727 C escape sequences can be used in strings and characters to represent
11728 non-printable characters. @value{GDBN} prints out strings with these
11729 escape sequences embedded. Single non-printable characters are
11730 printed using the @samp{CHR(@var{nnn})} format.
11733 The assignment operator (@code{:=}) returns the value of its right-hand
11737 All built-in procedures both modify @emph{and} return their argument.
11741 @subsubsection Modula-2 Type and Range Checks
11742 @cindex Modula-2 checks
11745 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11748 @c FIXME remove warning when type/range checks added
11750 @value{GDBN} considers two Modula-2 variables type equivalent if:
11754 They are of types that have been declared equivalent via a @code{TYPE
11755 @var{t1} = @var{t2}} statement
11758 They have been declared on the same line. (Note: This is true of the
11759 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11762 As long as type checking is enabled, any attempt to combine variables
11763 whose types are not equivalent is an error.
11765 Range checking is done on all mathematical operations, assignment, array
11766 index bounds, and all built-in functions and procedures.
11769 @subsubsection The Scope Operators @code{::} and @code{.}
11771 @cindex @code{.}, Modula-2 scope operator
11772 @cindex colon, doubled as scope operator
11774 @vindex colon-colon@r{, in Modula-2}
11775 @c Info cannot handle :: but TeX can.
11778 @vindex ::@r{, in Modula-2}
11781 There are a few subtle differences between the Modula-2 scope operator
11782 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11787 @var{module} . @var{id}
11788 @var{scope} :: @var{id}
11792 where @var{scope} is the name of a module or a procedure,
11793 @var{module} the name of a module, and @var{id} is any declared
11794 identifier within your program, except another module.
11796 Using the @code{::} operator makes @value{GDBN} search the scope
11797 specified by @var{scope} for the identifier @var{id}. If it is not
11798 found in the specified scope, then @value{GDBN} searches all scopes
11799 enclosing the one specified by @var{scope}.
11801 Using the @code{.} operator makes @value{GDBN} search the current scope for
11802 the identifier specified by @var{id} that was imported from the
11803 definition module specified by @var{module}. With this operator, it is
11804 an error if the identifier @var{id} was not imported from definition
11805 module @var{module}, or if @var{id} is not an identifier in
11809 @subsubsection @value{GDBN} and Modula-2
11811 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11812 Five subcommands of @code{set print} and @code{show print} apply
11813 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11814 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11815 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11816 analogue in Modula-2.
11818 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11819 with any language, is not useful with Modula-2. Its
11820 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11821 created in Modula-2 as they can in C or C@t{++}. However, because an
11822 address can be specified by an integral constant, the construct
11823 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11825 @cindex @code{#} in Modula-2
11826 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11827 interpreted as the beginning of a comment. Use @code{<>} instead.
11833 The extensions made to @value{GDBN} for Ada only support
11834 output from the @sc{gnu} Ada (GNAT) compiler.
11835 Other Ada compilers are not currently supported, and
11836 attempting to debug executables produced by them is most likely
11840 @cindex expressions in Ada
11842 * Ada Mode Intro:: General remarks on the Ada syntax
11843 and semantics supported by Ada mode
11845 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11846 * Additions to Ada:: Extensions of the Ada expression syntax.
11847 * Stopping Before Main Program:: Debugging the program during elaboration.
11848 * Ada Tasks:: Listing and setting breakpoints in tasks.
11849 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11850 * Ada Glitches:: Known peculiarities of Ada mode.
11853 @node Ada Mode Intro
11854 @subsubsection Introduction
11855 @cindex Ada mode, general
11857 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11858 syntax, with some extensions.
11859 The philosophy behind the design of this subset is
11863 That @value{GDBN} should provide basic literals and access to operations for
11864 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11865 leaving more sophisticated computations to subprograms written into the
11866 program (which therefore may be called from @value{GDBN}).
11869 That type safety and strict adherence to Ada language restrictions
11870 are not particularly important to the @value{GDBN} user.
11873 That brevity is important to the @value{GDBN} user.
11876 Thus, for brevity, the debugger acts as if all names declared in
11877 user-written packages are directly visible, even if they are not visible
11878 according to Ada rules, thus making it unnecessary to fully qualify most
11879 names with their packages, regardless of context. Where this causes
11880 ambiguity, @value{GDBN} asks the user's intent.
11882 The debugger will start in Ada mode if it detects an Ada main program.
11883 As for other languages, it will enter Ada mode when stopped in a program that
11884 was translated from an Ada source file.
11886 While in Ada mode, you may use `@t{--}' for comments. This is useful
11887 mostly for documenting command files. The standard @value{GDBN} comment
11888 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11889 middle (to allow based literals).
11891 The debugger supports limited overloading. Given a subprogram call in which
11892 the function symbol has multiple definitions, it will use the number of
11893 actual parameters and some information about their types to attempt to narrow
11894 the set of definitions. It also makes very limited use of context, preferring
11895 procedures to functions in the context of the @code{call} command, and
11896 functions to procedures elsewhere.
11898 @node Omissions from Ada
11899 @subsubsection Omissions from Ada
11900 @cindex Ada, omissions from
11902 Here are the notable omissions from the subset:
11906 Only a subset of the attributes are supported:
11910 @t{'First}, @t{'Last}, and @t{'Length}
11911 on array objects (not on types and subtypes).
11914 @t{'Min} and @t{'Max}.
11917 @t{'Pos} and @t{'Val}.
11923 @t{'Range} on array objects (not subtypes), but only as the right
11924 operand of the membership (@code{in}) operator.
11927 @t{'Access}, @t{'Unchecked_Access}, and
11928 @t{'Unrestricted_Access} (a GNAT extension).
11936 @code{Characters.Latin_1} are not available and
11937 concatenation is not implemented. Thus, escape characters in strings are
11938 not currently available.
11941 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11942 equality of representations. They will generally work correctly
11943 for strings and arrays whose elements have integer or enumeration types.
11944 They may not work correctly for arrays whose element
11945 types have user-defined equality, for arrays of real values
11946 (in particular, IEEE-conformant floating point, because of negative
11947 zeroes and NaNs), and for arrays whose elements contain unused bits with
11948 indeterminate values.
11951 The other component-by-component array operations (@code{and}, @code{or},
11952 @code{xor}, @code{not}, and relational tests other than equality)
11953 are not implemented.
11956 @cindex array aggregates (Ada)
11957 @cindex record aggregates (Ada)
11958 @cindex aggregates (Ada)
11959 There is limited support for array and record aggregates. They are
11960 permitted only on the right sides of assignments, as in these examples:
11963 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11964 (@value{GDBP}) set An_Array := (1, others => 0)
11965 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11966 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11967 (@value{GDBP}) set A_Record := (1, "Peter", True);
11968 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11972 discriminant's value by assigning an aggregate has an
11973 undefined effect if that discriminant is used within the record.
11974 However, you can first modify discriminants by directly assigning to
11975 them (which normally would not be allowed in Ada), and then performing an
11976 aggregate assignment. For example, given a variable @code{A_Rec}
11977 declared to have a type such as:
11980 type Rec (Len : Small_Integer := 0) is record
11982 Vals : IntArray (1 .. Len);
11986 you can assign a value with a different size of @code{Vals} with two
11990 (@value{GDBP}) set A_Rec.Len := 4
11991 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11994 As this example also illustrates, @value{GDBN} is very loose about the usual
11995 rules concerning aggregates. You may leave out some of the
11996 components of an array or record aggregate (such as the @code{Len}
11997 component in the assignment to @code{A_Rec} above); they will retain their
11998 original values upon assignment. You may freely use dynamic values as
11999 indices in component associations. You may even use overlapping or
12000 redundant component associations, although which component values are
12001 assigned in such cases is not defined.
12004 Calls to dispatching subprograms are not implemented.
12007 The overloading algorithm is much more limited (i.e., less selective)
12008 than that of real Ada. It makes only limited use of the context in
12009 which a subexpression appears to resolve its meaning, and it is much
12010 looser in its rules for allowing type matches. As a result, some
12011 function calls will be ambiguous, and the user will be asked to choose
12012 the proper resolution.
12015 The @code{new} operator is not implemented.
12018 Entry calls are not implemented.
12021 Aside from printing, arithmetic operations on the native VAX floating-point
12022 formats are not supported.
12025 It is not possible to slice a packed array.
12028 The names @code{True} and @code{False}, when not part of a qualified name,
12029 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12031 Should your program
12032 redefine these names in a package or procedure (at best a dubious practice),
12033 you will have to use fully qualified names to access their new definitions.
12036 @node Additions to Ada
12037 @subsubsection Additions to Ada
12038 @cindex Ada, deviations from
12040 As it does for other languages, @value{GDBN} makes certain generic
12041 extensions to Ada (@pxref{Expressions}):
12045 If the expression @var{E} is a variable residing in memory (typically
12046 a local variable or array element) and @var{N} is a positive integer,
12047 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12048 @var{N}-1 adjacent variables following it in memory as an array. In
12049 Ada, this operator is generally not necessary, since its prime use is
12050 in displaying parts of an array, and slicing will usually do this in
12051 Ada. However, there are occasional uses when debugging programs in
12052 which certain debugging information has been optimized away.
12055 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12056 appears in function or file @var{B}.'' When @var{B} is a file name,
12057 you must typically surround it in single quotes.
12060 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12061 @var{type} that appears at address @var{addr}.''
12064 A name starting with @samp{$} is a convenience variable
12065 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12068 In addition, @value{GDBN} provides a few other shortcuts and outright
12069 additions specific to Ada:
12073 The assignment statement is allowed as an expression, returning
12074 its right-hand operand as its value. Thus, you may enter
12077 (@value{GDBP}) set x := y + 3
12078 (@value{GDBP}) print A(tmp := y + 1)
12082 The semicolon is allowed as an ``operator,'' returning as its value
12083 the value of its right-hand operand.
12084 This allows, for example,
12085 complex conditional breaks:
12088 (@value{GDBP}) break f
12089 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12093 Rather than use catenation and symbolic character names to introduce special
12094 characters into strings, one may instead use a special bracket notation,
12095 which is also used to print strings. A sequence of characters of the form
12096 @samp{["@var{XX}"]} within a string or character literal denotes the
12097 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12098 sequence of characters @samp{["""]} also denotes a single quotation mark
12099 in strings. For example,
12101 "One line.["0a"]Next line.["0a"]"
12104 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12108 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12109 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12113 (@value{GDBP}) print 'max(x, y)
12117 When printing arrays, @value{GDBN} uses positional notation when the
12118 array has a lower bound of 1, and uses a modified named notation otherwise.
12119 For example, a one-dimensional array of three integers with a lower bound
12120 of 3 might print as
12127 That is, in contrast to valid Ada, only the first component has a @code{=>}
12131 You may abbreviate attributes in expressions with any unique,
12132 multi-character subsequence of
12133 their names (an exact match gets preference).
12134 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12135 in place of @t{a'length}.
12138 @cindex quoting Ada internal identifiers
12139 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12140 to lower case. The GNAT compiler uses upper-case characters for
12141 some of its internal identifiers, which are normally of no interest to users.
12142 For the rare occasions when you actually have to look at them,
12143 enclose them in angle brackets to avoid the lower-case mapping.
12146 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12150 Printing an object of class-wide type or dereferencing an
12151 access-to-class-wide value will display all the components of the object's
12152 specific type (as indicated by its run-time tag). Likewise, component
12153 selection on such a value will operate on the specific type of the
12158 @node Stopping Before Main Program
12159 @subsubsection Stopping at the Very Beginning
12161 @cindex breakpointing Ada elaboration code
12162 It is sometimes necessary to debug the program during elaboration, and
12163 before reaching the main procedure.
12164 As defined in the Ada Reference
12165 Manual, the elaboration code is invoked from a procedure called
12166 @code{adainit}. To run your program up to the beginning of
12167 elaboration, simply use the following two commands:
12168 @code{tbreak adainit} and @code{run}.
12171 @subsubsection Extensions for Ada Tasks
12172 @cindex Ada, tasking
12174 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12175 @value{GDBN} provides the following task-related commands:
12180 This command shows a list of current Ada tasks, as in the following example:
12187 (@value{GDBP}) info tasks
12188 ID TID P-ID Pri State Name
12189 1 8088000 0 15 Child Activation Wait main_task
12190 2 80a4000 1 15 Accept Statement b
12191 3 809a800 1 15 Child Activation Wait a
12192 * 4 80ae800 3 15 Runnable c
12197 In this listing, the asterisk before the last task indicates it to be the
12198 task currently being inspected.
12202 Represents @value{GDBN}'s internal task number.
12208 The parent's task ID (@value{GDBN}'s internal task number).
12211 The base priority of the task.
12214 Current state of the task.
12218 The task has been created but has not been activated. It cannot be
12222 The task is not blocked for any reason known to Ada. (It may be waiting
12223 for a mutex, though.) It is conceptually "executing" in normal mode.
12226 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12227 that were waiting on terminate alternatives have been awakened and have
12228 terminated themselves.
12230 @item Child Activation Wait
12231 The task is waiting for created tasks to complete activation.
12233 @item Accept Statement
12234 The task is waiting on an accept or selective wait statement.
12236 @item Waiting on entry call
12237 The task is waiting on an entry call.
12239 @item Async Select Wait
12240 The task is waiting to start the abortable part of an asynchronous
12244 The task is waiting on a select statement with only a delay
12247 @item Child Termination Wait
12248 The task is sleeping having completed a master within itself, and is
12249 waiting for the tasks dependent on that master to become terminated or
12250 waiting on a terminate Phase.
12252 @item Wait Child in Term Alt
12253 The task is sleeping waiting for tasks on terminate alternatives to
12254 finish terminating.
12256 @item Accepting RV with @var{taskno}
12257 The task is accepting a rendez-vous with the task @var{taskno}.
12261 Name of the task in the program.
12265 @kindex info task @var{taskno}
12266 @item info task @var{taskno}
12267 This command shows detailled informations on the specified task, as in
12268 the following example:
12273 (@value{GDBP}) info tasks
12274 ID TID P-ID Pri State Name
12275 1 8077880 0 15 Child Activation Wait main_task
12276 * 2 807c468 1 15 Runnable task_1
12277 (@value{GDBP}) info task 2
12278 Ada Task: 0x807c468
12281 Parent: 1 (main_task)
12287 @kindex task@r{ (Ada)}
12288 @cindex current Ada task ID
12289 This command prints the ID of the current task.
12295 (@value{GDBP}) info tasks
12296 ID TID P-ID Pri State Name
12297 1 8077870 0 15 Child Activation Wait main_task
12298 * 2 807c458 1 15 Runnable t
12299 (@value{GDBP}) task
12300 [Current task is 2]
12303 @item task @var{taskno}
12304 @cindex Ada task switching
12305 This command is like the @code{thread @var{threadno}}
12306 command (@pxref{Threads}). It switches the context of debugging
12307 from the current task to the given task.
12313 (@value{GDBP}) info tasks
12314 ID TID P-ID Pri State Name
12315 1 8077870 0 15 Child Activation Wait main_task
12316 * 2 807c458 1 15 Runnable t
12317 (@value{GDBP}) task 1
12318 [Switching to task 1]
12319 #0 0x8067726 in pthread_cond_wait ()
12321 #0 0x8067726 in pthread_cond_wait ()
12322 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12323 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12324 #3 0x806153e in system.tasking.stages.activate_tasks ()
12325 #4 0x804aacc in un () at un.adb:5
12328 @item break @var{linespec} task @var{taskno}
12329 @itemx break @var{linespec} task @var{taskno} if @dots{}
12330 @cindex breakpoints and tasks, in Ada
12331 @cindex task breakpoints, in Ada
12332 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12333 These commands are like the @code{break @dots{} thread @dots{}}
12334 command (@pxref{Thread Stops}).
12335 @var{linespec} specifies source lines, as described
12336 in @ref{Specify Location}.
12338 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12339 to specify that you only want @value{GDBN} to stop the program when a
12340 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12341 numeric task identifiers assigned by @value{GDBN}, shown in the first
12342 column of the @samp{info tasks} display.
12344 If you do not specify @samp{task @var{taskno}} when you set a
12345 breakpoint, the breakpoint applies to @emph{all} tasks of your
12348 You can use the @code{task} qualifier on conditional breakpoints as
12349 well; in this case, place @samp{task @var{taskno}} before the
12350 breakpoint condition (before the @code{if}).
12358 (@value{GDBP}) info tasks
12359 ID TID P-ID Pri State Name
12360 1 140022020 0 15 Child Activation Wait main_task
12361 2 140045060 1 15 Accept/Select Wait t2
12362 3 140044840 1 15 Runnable t1
12363 * 4 140056040 1 15 Runnable t3
12364 (@value{GDBP}) b 15 task 2
12365 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12366 (@value{GDBP}) cont
12371 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
12373 (@value{GDBP}) info tasks
12374 ID TID P-ID Pri State Name
12375 1 140022020 0 15 Child Activation Wait main_task
12376 * 2 140045060 1 15 Runnable t2
12377 3 140044840 1 15 Runnable t1
12378 4 140056040 1 15 Delay Sleep t3
12382 @node Ada Tasks and Core Files
12383 @subsubsection Tasking Support when Debugging Core Files
12384 @cindex Ada tasking and core file debugging
12386 When inspecting a core file, as opposed to debugging a live program,
12387 tasking support may be limited or even unavailable, depending on
12388 the platform being used.
12389 For instance, on x86-linux, the list of tasks is available, but task
12390 switching is not supported. On Tru64, however, task switching will work
12393 On certain platforms, including Tru64, the debugger needs to perform some
12394 memory writes in order to provide Ada tasking support. When inspecting
12395 a core file, this means that the core file must be opened with read-write
12396 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12397 Under these circumstances, you should make a backup copy of the core
12398 file before inspecting it with @value{GDBN}.
12401 @subsubsection Known Peculiarities of Ada Mode
12402 @cindex Ada, problems
12404 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12405 we know of several problems with and limitations of Ada mode in
12407 some of which will be fixed with planned future releases of the debugger
12408 and the GNU Ada compiler.
12412 Currently, the debugger
12413 has insufficient information to determine whether certain pointers represent
12414 pointers to objects or the objects themselves.
12415 Thus, the user may have to tack an extra @code{.all} after an expression
12416 to get it printed properly.
12419 Static constants that the compiler chooses not to materialize as objects in
12420 storage are invisible to the debugger.
12423 Named parameter associations in function argument lists are ignored (the
12424 argument lists are treated as positional).
12427 Many useful library packages are currently invisible to the debugger.
12430 Fixed-point arithmetic, conversions, input, and output is carried out using
12431 floating-point arithmetic, and may give results that only approximate those on
12435 The GNAT compiler never generates the prefix @code{Standard} for any of
12436 the standard symbols defined by the Ada language. @value{GDBN} knows about
12437 this: it will strip the prefix from names when you use it, and will never
12438 look for a name you have so qualified among local symbols, nor match against
12439 symbols in other packages or subprograms. If you have
12440 defined entities anywhere in your program other than parameters and
12441 local variables whose simple names match names in @code{Standard},
12442 GNAT's lack of qualification here can cause confusion. When this happens,
12443 you can usually resolve the confusion
12444 by qualifying the problematic names with package
12445 @code{Standard} explicitly.
12448 @node Unsupported Languages
12449 @section Unsupported Languages
12451 @cindex unsupported languages
12452 @cindex minimal language
12453 In addition to the other fully-supported programming languages,
12454 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
12455 It does not represent a real programming language, but provides a set
12456 of capabilities close to what the C or assembly languages provide.
12457 This should allow most simple operations to be performed while debugging
12458 an application that uses a language currently not supported by @value{GDBN}.
12460 If the language is set to @code{auto}, @value{GDBN} will automatically
12461 select this language if the current frame corresponds to an unsupported
12465 @chapter Examining the Symbol Table
12467 The commands described in this chapter allow you to inquire about the
12468 symbols (names of variables, functions and types) defined in your
12469 program. This information is inherent in the text of your program and
12470 does not change as your program executes. @value{GDBN} finds it in your
12471 program's symbol table, in the file indicated when you started @value{GDBN}
12472 (@pxref{File Options, ,Choosing Files}), or by one of the
12473 file-management commands (@pxref{Files, ,Commands to Specify Files}).
12475 @cindex symbol names
12476 @cindex names of symbols
12477 @cindex quoting names
12478 Occasionally, you may need to refer to symbols that contain unusual
12479 characters, which @value{GDBN} ordinarily treats as word delimiters. The
12480 most frequent case is in referring to static variables in other
12481 source files (@pxref{Variables,,Program Variables}). File names
12482 are recorded in object files as debugging symbols, but @value{GDBN} would
12483 ordinarily parse a typical file name, like @file{foo.c}, as the three words
12484 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
12485 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
12492 looks up the value of @code{x} in the scope of the file @file{foo.c}.
12495 @cindex case-insensitive symbol names
12496 @cindex case sensitivity in symbol names
12497 @kindex set case-sensitive
12498 @item set case-sensitive on
12499 @itemx set case-sensitive off
12500 @itemx set case-sensitive auto
12501 Normally, when @value{GDBN} looks up symbols, it matches their names
12502 with case sensitivity determined by the current source language.
12503 Occasionally, you may wish to control that. The command @code{set
12504 case-sensitive} lets you do that by specifying @code{on} for
12505 case-sensitive matches or @code{off} for case-insensitive ones. If
12506 you specify @code{auto}, case sensitivity is reset to the default
12507 suitable for the source language. The default is case-sensitive
12508 matches for all languages except for Fortran, for which the default is
12509 case-insensitive matches.
12511 @kindex show case-sensitive
12512 @item show case-sensitive
12513 This command shows the current setting of case sensitivity for symbols
12516 @kindex info address
12517 @cindex address of a symbol
12518 @item info address @var{symbol}
12519 Describe where the data for @var{symbol} is stored. For a register
12520 variable, this says which register it is kept in. For a non-register
12521 local variable, this prints the stack-frame offset at which the variable
12524 Note the contrast with @samp{print &@var{symbol}}, which does not work
12525 at all for a register variable, and for a stack local variable prints
12526 the exact address of the current instantiation of the variable.
12528 @kindex info symbol
12529 @cindex symbol from address
12530 @cindex closest symbol and offset for an address
12531 @item info symbol @var{addr}
12532 Print the name of a symbol which is stored at the address @var{addr}.
12533 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
12534 nearest symbol and an offset from it:
12537 (@value{GDBP}) info symbol 0x54320
12538 _initialize_vx + 396 in section .text
12542 This is the opposite of the @code{info address} command. You can use
12543 it to find out the name of a variable or a function given its address.
12545 For dynamically linked executables, the name of executable or shared
12546 library containing the symbol is also printed:
12549 (@value{GDBP}) info symbol 0x400225
12550 _start + 5 in section .text of /tmp/a.out
12551 (@value{GDBP}) info symbol 0x2aaaac2811cf
12552 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
12556 @item whatis [@var{arg}]
12557 Print the data type of @var{arg}, which can be either an expression or
12558 a data type. With no argument, print the data type of @code{$}, the
12559 last value in the value history. If @var{arg} is an expression, it is
12560 not actually evaluated, and any side-effecting operations (such as
12561 assignments or function calls) inside it do not take place. If
12562 @var{arg} is a type name, it may be the name of a type or typedef, or
12563 for C code it may have the form @samp{class @var{class-name}},
12564 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12565 @samp{enum @var{enum-tag}}.
12566 @xref{Expressions, ,Expressions}.
12569 @item ptype [@var{arg}]
12570 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12571 detailed description of the type, instead of just the name of the type.
12572 @xref{Expressions, ,Expressions}.
12574 For example, for this variable declaration:
12577 struct complex @{double real; double imag;@} v;
12581 the two commands give this output:
12585 (@value{GDBP}) whatis v
12586 type = struct complex
12587 (@value{GDBP}) ptype v
12588 type = struct complex @{
12596 As with @code{whatis}, using @code{ptype} without an argument refers to
12597 the type of @code{$}, the last value in the value history.
12599 @cindex incomplete type
12600 Sometimes, programs use opaque data types or incomplete specifications
12601 of complex data structure. If the debug information included in the
12602 program does not allow @value{GDBN} to display a full declaration of
12603 the data type, it will say @samp{<incomplete type>}. For example,
12604 given these declarations:
12608 struct foo *fooptr;
12612 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12615 (@value{GDBP}) ptype foo
12616 $1 = <incomplete type>
12620 ``Incomplete type'' is C terminology for data types that are not
12621 completely specified.
12624 @item info types @var{regexp}
12626 Print a brief description of all types whose names match the regular
12627 expression @var{regexp} (or all types in your program, if you supply
12628 no argument). Each complete typename is matched as though it were a
12629 complete line; thus, @samp{i type value} gives information on all
12630 types in your program whose names include the string @code{value}, but
12631 @samp{i type ^value$} gives information only on types whose complete
12632 name is @code{value}.
12634 This command differs from @code{ptype} in two ways: first, like
12635 @code{whatis}, it does not print a detailed description; second, it
12636 lists all source files where a type is defined.
12639 @cindex local variables
12640 @item info scope @var{location}
12641 List all the variables local to a particular scope. This command
12642 accepts a @var{location} argument---a function name, a source line, or
12643 an address preceded by a @samp{*}, and prints all the variables local
12644 to the scope defined by that location. (@xref{Specify Location}, for
12645 details about supported forms of @var{location}.) For example:
12648 (@value{GDBP}) @b{info scope command_line_handler}
12649 Scope for command_line_handler:
12650 Symbol rl is an argument at stack/frame offset 8, length 4.
12651 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12652 Symbol linelength is in static storage at address 0x150a1c, length 4.
12653 Symbol p is a local variable in register $esi, length 4.
12654 Symbol p1 is a local variable in register $ebx, length 4.
12655 Symbol nline is a local variable in register $edx, length 4.
12656 Symbol repeat is a local variable at frame offset -8, length 4.
12660 This command is especially useful for determining what data to collect
12661 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12664 @kindex info source
12666 Show information about the current source file---that is, the source file for
12667 the function containing the current point of execution:
12670 the name of the source file, and the directory containing it,
12672 the directory it was compiled in,
12674 its length, in lines,
12676 which programming language it is written in,
12678 whether the executable includes debugging information for that file, and
12679 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12681 whether the debugging information includes information about
12682 preprocessor macros.
12686 @kindex info sources
12688 Print the names of all source files in your program for which there is
12689 debugging information, organized into two lists: files whose symbols
12690 have already been read, and files whose symbols will be read when needed.
12692 @kindex info functions
12693 @item info functions
12694 Print the names and data types of all defined functions.
12696 @item info functions @var{regexp}
12697 Print the names and data types of all defined functions
12698 whose names contain a match for regular expression @var{regexp}.
12699 Thus, @samp{info fun step} finds all functions whose names
12700 include @code{step}; @samp{info fun ^step} finds those whose names
12701 start with @code{step}. If a function name contains characters
12702 that conflict with the regular expression language (e.g.@:
12703 @samp{operator*()}), they may be quoted with a backslash.
12705 @kindex info variables
12706 @item info variables
12707 Print the names and data types of all variables that are declared
12708 outside of functions (i.e.@: excluding local variables).
12710 @item info variables @var{regexp}
12711 Print the names and data types of all variables (except for local
12712 variables) whose names contain a match for regular expression
12715 @kindex info classes
12716 @cindex Objective-C, classes and selectors
12718 @itemx info classes @var{regexp}
12719 Display all Objective-C classes in your program, or
12720 (with the @var{regexp} argument) all those matching a particular regular
12723 @kindex info selectors
12724 @item info selectors
12725 @itemx info selectors @var{regexp}
12726 Display all Objective-C selectors in your program, or
12727 (with the @var{regexp} argument) all those matching a particular regular
12731 This was never implemented.
12732 @kindex info methods
12734 @itemx info methods @var{regexp}
12735 The @code{info methods} command permits the user to examine all defined
12736 methods within C@t{++} program, or (with the @var{regexp} argument) a
12737 specific set of methods found in the various C@t{++} classes. Many
12738 C@t{++} classes provide a large number of methods. Thus, the output
12739 from the @code{ptype} command can be overwhelming and hard to use. The
12740 @code{info-methods} command filters the methods, printing only those
12741 which match the regular-expression @var{regexp}.
12744 @cindex reloading symbols
12745 Some systems allow individual object files that make up your program to
12746 be replaced without stopping and restarting your program. For example,
12747 in VxWorks you can simply recompile a defective object file and keep on
12748 running. If you are running on one of these systems, you can allow
12749 @value{GDBN} to reload the symbols for automatically relinked modules:
12752 @kindex set symbol-reloading
12753 @item set symbol-reloading on
12754 Replace symbol definitions for the corresponding source file when an
12755 object file with a particular name is seen again.
12757 @item set symbol-reloading off
12758 Do not replace symbol definitions when encountering object files of the
12759 same name more than once. This is the default state; if you are not
12760 running on a system that permits automatic relinking of modules, you
12761 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12762 may discard symbols when linking large programs, that may contain
12763 several modules (from different directories or libraries) with the same
12766 @kindex show symbol-reloading
12767 @item show symbol-reloading
12768 Show the current @code{on} or @code{off} setting.
12771 @cindex opaque data types
12772 @kindex set opaque-type-resolution
12773 @item set opaque-type-resolution on
12774 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12775 declared as a pointer to a @code{struct}, @code{class}, or
12776 @code{union}---for example, @code{struct MyType *}---that is used in one
12777 source file although the full declaration of @code{struct MyType} is in
12778 another source file. The default is on.
12780 A change in the setting of this subcommand will not take effect until
12781 the next time symbols for a file are loaded.
12783 @item set opaque-type-resolution off
12784 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12785 is printed as follows:
12787 @{<no data fields>@}
12790 @kindex show opaque-type-resolution
12791 @item show opaque-type-resolution
12792 Show whether opaque types are resolved or not.
12794 @kindex maint print symbols
12795 @cindex symbol dump
12796 @kindex maint print psymbols
12797 @cindex partial symbol dump
12798 @item maint print symbols @var{filename}
12799 @itemx maint print psymbols @var{filename}
12800 @itemx maint print msymbols @var{filename}
12801 Write a dump of debugging symbol data into the file @var{filename}.
12802 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12803 symbols with debugging data are included. If you use @samp{maint print
12804 symbols}, @value{GDBN} includes all the symbols for which it has already
12805 collected full details: that is, @var{filename} reflects symbols for
12806 only those files whose symbols @value{GDBN} has read. You can use the
12807 command @code{info sources} to find out which files these are. If you
12808 use @samp{maint print psymbols} instead, the dump shows information about
12809 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12810 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12811 @samp{maint print msymbols} dumps just the minimal symbol information
12812 required for each object file from which @value{GDBN} has read some symbols.
12813 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12814 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12816 @kindex maint info symtabs
12817 @kindex maint info psymtabs
12818 @cindex listing @value{GDBN}'s internal symbol tables
12819 @cindex symbol tables, listing @value{GDBN}'s internal
12820 @cindex full symbol tables, listing @value{GDBN}'s internal
12821 @cindex partial symbol tables, listing @value{GDBN}'s internal
12822 @item maint info symtabs @r{[} @var{regexp} @r{]}
12823 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12825 List the @code{struct symtab} or @code{struct partial_symtab}
12826 structures whose names match @var{regexp}. If @var{regexp} is not
12827 given, list them all. The output includes expressions which you can
12828 copy into a @value{GDBN} debugging this one to examine a particular
12829 structure in more detail. For example:
12832 (@value{GDBP}) maint info psymtabs dwarf2read
12833 @{ objfile /home/gnu/build/gdb/gdb
12834 ((struct objfile *) 0x82e69d0)
12835 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12836 ((struct partial_symtab *) 0x8474b10)
12839 text addresses 0x814d3c8 -- 0x8158074
12840 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12841 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12842 dependencies (none)
12845 (@value{GDBP}) maint info symtabs
12849 We see that there is one partial symbol table whose filename contains
12850 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12851 and we see that @value{GDBN} has not read in any symtabs yet at all.
12852 If we set a breakpoint on a function, that will cause @value{GDBN} to
12853 read the symtab for the compilation unit containing that function:
12856 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12857 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12859 (@value{GDBP}) maint info symtabs
12860 @{ objfile /home/gnu/build/gdb/gdb
12861 ((struct objfile *) 0x82e69d0)
12862 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12863 ((struct symtab *) 0x86c1f38)
12866 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12867 linetable ((struct linetable *) 0x8370fa0)
12868 debugformat DWARF 2
12877 @chapter Altering Execution
12879 Once you think you have found an error in your program, you might want to
12880 find out for certain whether correcting the apparent error would lead to
12881 correct results in the rest of the run. You can find the answer by
12882 experiment, using the @value{GDBN} features for altering execution of the
12885 For example, you can store new values into variables or memory
12886 locations, give your program a signal, restart it at a different
12887 address, or even return prematurely from a function.
12890 * Assignment:: Assignment to variables
12891 * Jumping:: Continuing at a different address
12892 * Signaling:: Giving your program a signal
12893 * Returning:: Returning from a function
12894 * Calling:: Calling your program's functions
12895 * Patching:: Patching your program
12899 @section Assignment to Variables
12902 @cindex setting variables
12903 To alter the value of a variable, evaluate an assignment expression.
12904 @xref{Expressions, ,Expressions}. For example,
12911 stores the value 4 into the variable @code{x}, and then prints the
12912 value of the assignment expression (which is 4).
12913 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12914 information on operators in supported languages.
12916 @kindex set variable
12917 @cindex variables, setting
12918 If you are not interested in seeing the value of the assignment, use the
12919 @code{set} command instead of the @code{print} command. @code{set} is
12920 really the same as @code{print} except that the expression's value is
12921 not printed and is not put in the value history (@pxref{Value History,
12922 ,Value History}). The expression is evaluated only for its effects.
12924 If the beginning of the argument string of the @code{set} command
12925 appears identical to a @code{set} subcommand, use the @code{set
12926 variable} command instead of just @code{set}. This command is identical
12927 to @code{set} except for its lack of subcommands. For example, if your
12928 program has a variable @code{width}, you get an error if you try to set
12929 a new value with just @samp{set width=13}, because @value{GDBN} has the
12930 command @code{set width}:
12933 (@value{GDBP}) whatis width
12935 (@value{GDBP}) p width
12937 (@value{GDBP}) set width=47
12938 Invalid syntax in expression.
12942 The invalid expression, of course, is @samp{=47}. In
12943 order to actually set the program's variable @code{width}, use
12946 (@value{GDBP}) set var width=47
12949 Because the @code{set} command has many subcommands that can conflict
12950 with the names of program variables, it is a good idea to use the
12951 @code{set variable} command instead of just @code{set}. For example, if
12952 your program has a variable @code{g}, you run into problems if you try
12953 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12954 the command @code{set gnutarget}, abbreviated @code{set g}:
12958 (@value{GDBP}) whatis g
12962 (@value{GDBP}) set g=4
12966 The program being debugged has been started already.
12967 Start it from the beginning? (y or n) y
12968 Starting program: /home/smith/cc_progs/a.out
12969 "/home/smith/cc_progs/a.out": can't open to read symbols:
12970 Invalid bfd target.
12971 (@value{GDBP}) show g
12972 The current BFD target is "=4".
12977 The program variable @code{g} did not change, and you silently set the
12978 @code{gnutarget} to an invalid value. In order to set the variable
12982 (@value{GDBP}) set var g=4
12985 @value{GDBN} allows more implicit conversions in assignments than C; you can
12986 freely store an integer value into a pointer variable or vice versa,
12987 and you can convert any structure to any other structure that is the
12988 same length or shorter.
12989 @comment FIXME: how do structs align/pad in these conversions?
12990 @comment /doc@cygnus.com 18dec1990
12992 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12993 construct to generate a value of specified type at a specified address
12994 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12995 to memory location @code{0x83040} as an integer (which implies a certain size
12996 and representation in memory), and
12999 set @{int@}0x83040 = 4
13003 stores the value 4 into that memory location.
13006 @section Continuing at a Different Address
13008 Ordinarily, when you continue your program, you do so at the place where
13009 it stopped, with the @code{continue} command. You can instead continue at
13010 an address of your own choosing, with the following commands:
13014 @item jump @var{linespec}
13015 @itemx jump @var{location}
13016 Resume execution at line @var{linespec} or at address given by
13017 @var{location}. Execution stops again immediately if there is a
13018 breakpoint there. @xref{Specify Location}, for a description of the
13019 different forms of @var{linespec} and @var{location}. It is common
13020 practice to use the @code{tbreak} command in conjunction with
13021 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13023 The @code{jump} command does not change the current stack frame, or
13024 the stack pointer, or the contents of any memory location or any
13025 register other than the program counter. If line @var{linespec} is in
13026 a different function from the one currently executing, the results may
13027 be bizarre if the two functions expect different patterns of arguments or
13028 of local variables. For this reason, the @code{jump} command requests
13029 confirmation if the specified line is not in the function currently
13030 executing. However, even bizarre results are predictable if you are
13031 well acquainted with the machine-language code of your program.
13034 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13035 On many systems, you can get much the same effect as the @code{jump}
13036 command by storing a new value into the register @code{$pc}. The
13037 difference is that this does not start your program running; it only
13038 changes the address of where it @emph{will} run when you continue. For
13046 makes the next @code{continue} command or stepping command execute at
13047 address @code{0x485}, rather than at the address where your program stopped.
13048 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13050 The most common occasion to use the @code{jump} command is to back
13051 up---perhaps with more breakpoints set---over a portion of a program
13052 that has already executed, in order to examine its execution in more
13057 @section Giving your Program a Signal
13058 @cindex deliver a signal to a program
13062 @item signal @var{signal}
13063 Resume execution where your program stopped, but immediately give it the
13064 signal @var{signal}. @var{signal} can be the name or the number of a
13065 signal. For example, on many systems @code{signal 2} and @code{signal
13066 SIGINT} are both ways of sending an interrupt signal.
13068 Alternatively, if @var{signal} is zero, continue execution without
13069 giving a signal. This is useful when your program stopped on account of
13070 a signal and would ordinary see the signal when resumed with the
13071 @code{continue} command; @samp{signal 0} causes it to resume without a
13074 @code{signal} does not repeat when you press @key{RET} a second time
13075 after executing the command.
13079 Invoking the @code{signal} command is not the same as invoking the
13080 @code{kill} utility from the shell. Sending a signal with @code{kill}
13081 causes @value{GDBN} to decide what to do with the signal depending on
13082 the signal handling tables (@pxref{Signals}). The @code{signal} command
13083 passes the signal directly to your program.
13087 @section Returning from a Function
13090 @cindex returning from a function
13093 @itemx return @var{expression}
13094 You can cancel execution of a function call with the @code{return}
13095 command. If you give an
13096 @var{expression} argument, its value is used as the function's return
13100 When you use @code{return}, @value{GDBN} discards the selected stack frame
13101 (and all frames within it). You can think of this as making the
13102 discarded frame return prematurely. If you wish to specify a value to
13103 be returned, give that value as the argument to @code{return}.
13105 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13106 Frame}), and any other frames inside of it, leaving its caller as the
13107 innermost remaining frame. That frame becomes selected. The
13108 specified value is stored in the registers used for returning values
13111 The @code{return} command does not resume execution; it leaves the
13112 program stopped in the state that would exist if the function had just
13113 returned. In contrast, the @code{finish} command (@pxref{Continuing
13114 and Stepping, ,Continuing and Stepping}) resumes execution until the
13115 selected stack frame returns naturally.
13117 @value{GDBN} needs to know how the @var{expression} argument should be set for
13118 the inferior. The concrete registers assignment depends on the OS ABI and the
13119 type being returned by the selected stack frame. For example it is common for
13120 OS ABI to return floating point values in FPU registers while integer values in
13121 CPU registers. Still some ABIs return even floating point values in CPU
13122 registers. Larger integer widths (such as @code{long long int}) also have
13123 specific placement rules. @value{GDBN} already knows the OS ABI from its
13124 current target so it needs to find out also the type being returned to make the
13125 assignment into the right register(s).
13127 Normally, the selected stack frame has debug info. @value{GDBN} will always
13128 use the debug info instead of the implicit type of @var{expression} when the
13129 debug info is available. For example, if you type @kbd{return -1}, and the
13130 function in the current stack frame is declared to return a @code{long long
13131 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13132 into a @code{long long int}:
13135 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13137 (@value{GDBP}) return -1
13138 Make func return now? (y or n) y
13139 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13140 43 printf ("result=%lld\n", func ());
13144 However, if the selected stack frame does not have a debug info, e.g., if the
13145 function was compiled without debug info, @value{GDBN} has to find out the type
13146 to return from user. Specifying a different type by mistake may set the value
13147 in different inferior registers than the caller code expects. For example,
13148 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13149 of a @code{long long int} result for a debug info less function (on 32-bit
13150 architectures). Therefore the user is required to specify the return type by
13151 an appropriate cast explicitly:
13154 Breakpoint 2, 0x0040050b in func ()
13155 (@value{GDBP}) return -1
13156 Return value type not available for selected stack frame.
13157 Please use an explicit cast of the value to return.
13158 (@value{GDBP}) return (long long int) -1
13159 Make selected stack frame return now? (y or n) y
13160 #0 0x00400526 in main ()
13165 @section Calling Program Functions
13168 @cindex calling functions
13169 @cindex inferior functions, calling
13170 @item print @var{expr}
13171 Evaluate the expression @var{expr} and display the resulting value.
13172 @var{expr} may include calls to functions in the program being
13176 @item call @var{expr}
13177 Evaluate the expression @var{expr} without displaying @code{void}
13180 You can use this variant of the @code{print} command if you want to
13181 execute a function from your program that does not return anything
13182 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13183 with @code{void} returned values that @value{GDBN} will otherwise
13184 print. If the result is not void, it is printed and saved in the
13188 It is possible for the function you call via the @code{print} or
13189 @code{call} command to generate a signal (e.g., if there's a bug in
13190 the function, or if you passed it incorrect arguments). What happens
13191 in that case is controlled by the @code{set unwindonsignal} command.
13193 Similarly, with a C@t{++} program it is possible for the function you
13194 call via the @code{print} or @code{call} command to generate an
13195 exception that is not handled due to the constraints of the dummy
13196 frame. In this case, any exception that is raised in the frame, but has
13197 an out-of-frame exception handler will not be found. GDB builds a
13198 dummy-frame for the inferior function call, and the unwinder cannot
13199 seek for exception handlers outside of this dummy-frame. What happens
13200 in that case is controlled by the
13201 @code{set unwind-on-terminating-exception} command.
13204 @item set unwindonsignal
13205 @kindex set unwindonsignal
13206 @cindex unwind stack in called functions
13207 @cindex call dummy stack unwinding
13208 Set unwinding of the stack if a signal is received while in a function
13209 that @value{GDBN} called in the program being debugged. If set to on,
13210 @value{GDBN} unwinds the stack it created for the call and restores
13211 the context to what it was before the call. If set to off (the
13212 default), @value{GDBN} stops in the frame where the signal was
13215 @item show unwindonsignal
13216 @kindex show unwindonsignal
13217 Show the current setting of stack unwinding in the functions called by
13220 @item set unwind-on-terminating-exception
13221 @kindex set unwind-on-terminating-exception
13222 @cindex unwind stack in called functions with unhandled exceptions
13223 @cindex call dummy stack unwinding on unhandled exception.
13224 Set unwinding of the stack if a C@t{++} exception is raised, but left
13225 unhandled while in a function that @value{GDBN} called in the program being
13226 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13227 it created for the call and restores the context to what it was before
13228 the call. If set to off, @value{GDBN} the exception is delivered to
13229 the default C@t{++} exception handler and the inferior terminated.
13231 @item show unwind-on-terminating-exception
13232 @kindex show unwind-on-terminating-exception
13233 Show the current setting of stack unwinding in the functions called by
13238 @cindex weak alias functions
13239 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13240 for another function. In such case, @value{GDBN} might not pick up
13241 the type information, including the types of the function arguments,
13242 which causes @value{GDBN} to call the inferior function incorrectly.
13243 As a result, the called function will function erroneously and may
13244 even crash. A solution to that is to use the name of the aliased
13248 @section Patching Programs
13250 @cindex patching binaries
13251 @cindex writing into executables
13252 @cindex writing into corefiles
13254 By default, @value{GDBN} opens the file containing your program's
13255 executable code (or the corefile) read-only. This prevents accidental
13256 alterations to machine code; but it also prevents you from intentionally
13257 patching your program's binary.
13259 If you'd like to be able to patch the binary, you can specify that
13260 explicitly with the @code{set write} command. For example, you might
13261 want to turn on internal debugging flags, or even to make emergency
13267 @itemx set write off
13268 If you specify @samp{set write on}, @value{GDBN} opens executable and
13269 core files for both reading and writing; if you specify @kbd{set write
13270 off} (the default), @value{GDBN} opens them read-only.
13272 If you have already loaded a file, you must load it again (using the
13273 @code{exec-file} or @code{core-file} command) after changing @code{set
13274 write}, for your new setting to take effect.
13278 Display whether executable files and core files are opened for writing
13279 as well as reading.
13283 @chapter @value{GDBN} Files
13285 @value{GDBN} needs to know the file name of the program to be debugged,
13286 both in order to read its symbol table and in order to start your
13287 program. To debug a core dump of a previous run, you must also tell
13288 @value{GDBN} the name of the core dump file.
13291 * Files:: Commands to specify files
13292 * Separate Debug Files:: Debugging information in separate files
13293 * Symbol Errors:: Errors reading symbol files
13294 * Data Files:: GDB data files
13298 @section Commands to Specify Files
13300 @cindex symbol table
13301 @cindex core dump file
13303 You may want to specify executable and core dump file names. The usual
13304 way to do this is at start-up time, using the arguments to
13305 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13306 Out of @value{GDBN}}).
13308 Occasionally it is necessary to change to a different file during a
13309 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13310 specify a file you want to use. Or you are debugging a remote target
13311 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13312 Program}). In these situations the @value{GDBN} commands to specify
13313 new files are useful.
13316 @cindex executable file
13318 @item file @var{filename}
13319 Use @var{filename} as the program to be debugged. It is read for its
13320 symbols and for the contents of pure memory. It is also the program
13321 executed when you use the @code{run} command. If you do not specify a
13322 directory and the file is not found in the @value{GDBN} working directory,
13323 @value{GDBN} uses the environment variable @code{PATH} as a list of
13324 directories to search, just as the shell does when looking for a program
13325 to run. You can change the value of this variable, for both @value{GDBN}
13326 and your program, using the @code{path} command.
13328 @cindex unlinked object files
13329 @cindex patching object files
13330 You can load unlinked object @file{.o} files into @value{GDBN} using
13331 the @code{file} command. You will not be able to ``run'' an object
13332 file, but you can disassemble functions and inspect variables. Also,
13333 if the underlying BFD functionality supports it, you could use
13334 @kbd{gdb -write} to patch object files using this technique. Note
13335 that @value{GDBN} can neither interpret nor modify relocations in this
13336 case, so branches and some initialized variables will appear to go to
13337 the wrong place. But this feature is still handy from time to time.
13340 @code{file} with no argument makes @value{GDBN} discard any information it
13341 has on both executable file and the symbol table.
13344 @item exec-file @r{[} @var{filename} @r{]}
13345 Specify that the program to be run (but not the symbol table) is found
13346 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
13347 if necessary to locate your program. Omitting @var{filename} means to
13348 discard information on the executable file.
13350 @kindex symbol-file
13351 @item symbol-file @r{[} @var{filename} @r{]}
13352 Read symbol table information from file @var{filename}. @code{PATH} is
13353 searched when necessary. Use the @code{file} command to get both symbol
13354 table and program to run from the same file.
13356 @code{symbol-file} with no argument clears out @value{GDBN} information on your
13357 program's symbol table.
13359 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
13360 some breakpoints and auto-display expressions. This is because they may
13361 contain pointers to the internal data recording symbols and data types,
13362 which are part of the old symbol table data being discarded inside
13365 @code{symbol-file} does not repeat if you press @key{RET} again after
13368 When @value{GDBN} is configured for a particular environment, it
13369 understands debugging information in whatever format is the standard
13370 generated for that environment; you may use either a @sc{gnu} compiler, or
13371 other compilers that adhere to the local conventions.
13372 Best results are usually obtained from @sc{gnu} compilers; for example,
13373 using @code{@value{NGCC}} you can generate debugging information for
13376 For most kinds of object files, with the exception of old SVR3 systems
13377 using COFF, the @code{symbol-file} command does not normally read the
13378 symbol table in full right away. Instead, it scans the symbol table
13379 quickly to find which source files and which symbols are present. The
13380 details are read later, one source file at a time, as they are needed.
13382 The purpose of this two-stage reading strategy is to make @value{GDBN}
13383 start up faster. For the most part, it is invisible except for
13384 occasional pauses while the symbol table details for a particular source
13385 file are being read. (The @code{set verbose} command can turn these
13386 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
13387 Warnings and Messages}.)
13389 We have not implemented the two-stage strategy for COFF yet. When the
13390 symbol table is stored in COFF format, @code{symbol-file} reads the
13391 symbol table data in full right away. Note that ``stabs-in-COFF''
13392 still does the two-stage strategy, since the debug info is actually
13396 @cindex reading symbols immediately
13397 @cindex symbols, reading immediately
13398 @item symbol-file @var{filename} @r{[} -readnow @r{]}
13399 @itemx file @var{filename} @r{[} -readnow @r{]}
13400 You can override the @value{GDBN} two-stage strategy for reading symbol
13401 tables by using the @samp{-readnow} option with any of the commands that
13402 load symbol table information, if you want to be sure @value{GDBN} has the
13403 entire symbol table available.
13405 @c FIXME: for now no mention of directories, since this seems to be in
13406 @c flux. 13mar1992 status is that in theory GDB would look either in
13407 @c current dir or in same dir as myprog; but issues like competing
13408 @c GDB's, or clutter in system dirs, mean that in practice right now
13409 @c only current dir is used. FFish says maybe a special GDB hierarchy
13410 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13414 @item core-file @r{[}@var{filename}@r{]}
13416 Specify the whereabouts of a core dump file to be used as the ``contents
13417 of memory''. Traditionally, core files contain only some parts of the
13418 address space of the process that generated them; @value{GDBN} can access the
13419 executable file itself for other parts.
13421 @code{core-file} with no argument specifies that no core file is
13424 Note that the core file is ignored when your program is actually running
13425 under @value{GDBN}. So, if you have been running your program and you
13426 wish to debug a core file instead, you must kill the subprocess in which
13427 the program is running. To do this, use the @code{kill} command
13428 (@pxref{Kill Process, ,Killing the Child Process}).
13430 @kindex add-symbol-file
13431 @cindex dynamic linking
13432 @item add-symbol-file @var{filename} @var{address}
13433 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13434 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
13435 The @code{add-symbol-file} command reads additional symbol table
13436 information from the file @var{filename}. You would use this command
13437 when @var{filename} has been dynamically loaded (by some other means)
13438 into the program that is running. @var{address} should be the memory
13439 address at which the file has been loaded; @value{GDBN} cannot figure
13440 this out for itself. You can additionally specify an arbitrary number
13441 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
13442 section name and base address for that section. You can specify any
13443 @var{address} as an expression.
13445 The symbol table of the file @var{filename} is added to the symbol table
13446 originally read with the @code{symbol-file} command. You can use the
13447 @code{add-symbol-file} command any number of times; the new symbol data
13448 thus read keeps adding to the old. To discard all old symbol data
13449 instead, use the @code{symbol-file} command without any arguments.
13451 @cindex relocatable object files, reading symbols from
13452 @cindex object files, relocatable, reading symbols from
13453 @cindex reading symbols from relocatable object files
13454 @cindex symbols, reading from relocatable object files
13455 @cindex @file{.o} files, reading symbols from
13456 Although @var{filename} is typically a shared library file, an
13457 executable file, or some other object file which has been fully
13458 relocated for loading into a process, you can also load symbolic
13459 information from relocatable @file{.o} files, as long as:
13463 the file's symbolic information refers only to linker symbols defined in
13464 that file, not to symbols defined by other object files,
13466 every section the file's symbolic information refers to has actually
13467 been loaded into the inferior, as it appears in the file, and
13469 you can determine the address at which every section was loaded, and
13470 provide these to the @code{add-symbol-file} command.
13474 Some embedded operating systems, like Sun Chorus and VxWorks, can load
13475 relocatable files into an already running program; such systems
13476 typically make the requirements above easy to meet. However, it's
13477 important to recognize that many native systems use complex link
13478 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
13479 assembly, for example) that make the requirements difficult to meet. In
13480 general, one cannot assume that using @code{add-symbol-file} to read a
13481 relocatable object file's symbolic information will have the same effect
13482 as linking the relocatable object file into the program in the normal
13485 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
13487 @kindex add-symbol-file-from-memory
13488 @cindex @code{syscall DSO}
13489 @cindex load symbols from memory
13490 @item add-symbol-file-from-memory @var{address}
13491 Load symbols from the given @var{address} in a dynamically loaded
13492 object file whose image is mapped directly into the inferior's memory.
13493 For example, the Linux kernel maps a @code{syscall DSO} into each
13494 process's address space; this DSO provides kernel-specific code for
13495 some system calls. The argument can be any expression whose
13496 evaluation yields the address of the file's shared object file header.
13497 For this command to work, you must have used @code{symbol-file} or
13498 @code{exec-file} commands in advance.
13500 @kindex add-shared-symbol-files
13502 @item add-shared-symbol-files @var{library-file}
13503 @itemx assf @var{library-file}
13504 The @code{add-shared-symbol-files} command can currently be used only
13505 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
13506 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
13507 @value{GDBN} automatically looks for shared libraries, however if
13508 @value{GDBN} does not find yours, you can invoke
13509 @code{add-shared-symbol-files}. It takes one argument: the shared
13510 library's file name. @code{assf} is a shorthand alias for
13511 @code{add-shared-symbol-files}.
13514 @item section @var{section} @var{addr}
13515 The @code{section} command changes the base address of the named
13516 @var{section} of the exec file to @var{addr}. This can be used if the
13517 exec file does not contain section addresses, (such as in the
13518 @code{a.out} format), or when the addresses specified in the file
13519 itself are wrong. Each section must be changed separately. The
13520 @code{info files} command, described below, lists all the sections and
13524 @kindex info target
13527 @code{info files} and @code{info target} are synonymous; both print the
13528 current target (@pxref{Targets, ,Specifying a Debugging Target}),
13529 including the names of the executable and core dump files currently in
13530 use by @value{GDBN}, and the files from which symbols were loaded. The
13531 command @code{help target} lists all possible targets rather than
13534 @kindex maint info sections
13535 @item maint info sections
13536 Another command that can give you extra information about program sections
13537 is @code{maint info sections}. In addition to the section information
13538 displayed by @code{info files}, this command displays the flags and file
13539 offset of each section in the executable and core dump files. In addition,
13540 @code{maint info sections} provides the following command options (which
13541 may be arbitrarily combined):
13545 Display sections for all loaded object files, including shared libraries.
13546 @item @var{sections}
13547 Display info only for named @var{sections}.
13548 @item @var{section-flags}
13549 Display info only for sections for which @var{section-flags} are true.
13550 The section flags that @value{GDBN} currently knows about are:
13553 Section will have space allocated in the process when loaded.
13554 Set for all sections except those containing debug information.
13556 Section will be loaded from the file into the child process memory.
13557 Set for pre-initialized code and data, clear for @code{.bss} sections.
13559 Section needs to be relocated before loading.
13561 Section cannot be modified by the child process.
13563 Section contains executable code only.
13565 Section contains data only (no executable code).
13567 Section will reside in ROM.
13569 Section contains data for constructor/destructor lists.
13571 Section is not empty.
13573 An instruction to the linker to not output the section.
13574 @item COFF_SHARED_LIBRARY
13575 A notification to the linker that the section contains
13576 COFF shared library information.
13578 Section contains common symbols.
13581 @kindex set trust-readonly-sections
13582 @cindex read-only sections
13583 @item set trust-readonly-sections on
13584 Tell @value{GDBN} that readonly sections in your object file
13585 really are read-only (i.e.@: that their contents will not change).
13586 In that case, @value{GDBN} can fetch values from these sections
13587 out of the object file, rather than from the target program.
13588 For some targets (notably embedded ones), this can be a significant
13589 enhancement to debugging performance.
13591 The default is off.
13593 @item set trust-readonly-sections off
13594 Tell @value{GDBN} not to trust readonly sections. This means that
13595 the contents of the section might change while the program is running,
13596 and must therefore be fetched from the target when needed.
13598 @item show trust-readonly-sections
13599 Show the current setting of trusting readonly sections.
13602 All file-specifying commands allow both absolute and relative file names
13603 as arguments. @value{GDBN} always converts the file name to an absolute file
13604 name and remembers it that way.
13606 @cindex shared libraries
13607 @anchor{Shared Libraries}
13608 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13609 and IBM RS/6000 AIX shared libraries.
13611 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13612 shared libraries. @xref{Expat}.
13614 @value{GDBN} automatically loads symbol definitions from shared libraries
13615 when you use the @code{run} command, or when you examine a core file.
13616 (Before you issue the @code{run} command, @value{GDBN} does not understand
13617 references to a function in a shared library, however---unless you are
13618 debugging a core file).
13620 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13621 automatically loads the symbols at the time of the @code{shl_load} call.
13623 @c FIXME: some @value{GDBN} release may permit some refs to undef
13624 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13625 @c FIXME...lib; check this from time to time when updating manual
13627 There are times, however, when you may wish to not automatically load
13628 symbol definitions from shared libraries, such as when they are
13629 particularly large or there are many of them.
13631 To control the automatic loading of shared library symbols, use the
13635 @kindex set auto-solib-add
13636 @item set auto-solib-add @var{mode}
13637 If @var{mode} is @code{on}, symbols from all shared object libraries
13638 will be loaded automatically when the inferior begins execution, you
13639 attach to an independently started inferior, or when the dynamic linker
13640 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13641 is @code{off}, symbols must be loaded manually, using the
13642 @code{sharedlibrary} command. The default value is @code{on}.
13644 @cindex memory used for symbol tables
13645 If your program uses lots of shared libraries with debug info that
13646 takes large amounts of memory, you can decrease the @value{GDBN}
13647 memory footprint by preventing it from automatically loading the
13648 symbols from shared libraries. To that end, type @kbd{set
13649 auto-solib-add off} before running the inferior, then load each
13650 library whose debug symbols you do need with @kbd{sharedlibrary
13651 @var{regexp}}, where @var{regexp} is a regular expression that matches
13652 the libraries whose symbols you want to be loaded.
13654 @kindex show auto-solib-add
13655 @item show auto-solib-add
13656 Display the current autoloading mode.
13659 @cindex load shared library
13660 To explicitly load shared library symbols, use the @code{sharedlibrary}
13664 @kindex info sharedlibrary
13666 @item info share @var{regex}
13667 @itemx info sharedlibrary @var{regex}
13668 Print the names of the shared libraries which are currently loaded
13669 that match @var{regex}. If @var{regex} is omitted then print
13670 all shared libraries that are loaded.
13672 @kindex sharedlibrary
13674 @item sharedlibrary @var{regex}
13675 @itemx share @var{regex}
13676 Load shared object library symbols for files matching a
13677 Unix regular expression.
13678 As with files loaded automatically, it only loads shared libraries
13679 required by your program for a core file or after typing @code{run}. If
13680 @var{regex} is omitted all shared libraries required by your program are
13683 @item nosharedlibrary
13684 @kindex nosharedlibrary
13685 @cindex unload symbols from shared libraries
13686 Unload all shared object library symbols. This discards all symbols
13687 that have been loaded from all shared libraries. Symbols from shared
13688 libraries that were loaded by explicit user requests are not
13692 Sometimes you may wish that @value{GDBN} stops and gives you control
13693 when any of shared library events happen. Use the @code{set
13694 stop-on-solib-events} command for this:
13697 @item set stop-on-solib-events
13698 @kindex set stop-on-solib-events
13699 This command controls whether @value{GDBN} should give you control
13700 when the dynamic linker notifies it about some shared library event.
13701 The most common event of interest is loading or unloading of a new
13704 @item show stop-on-solib-events
13705 @kindex show stop-on-solib-events
13706 Show whether @value{GDBN} stops and gives you control when shared
13707 library events happen.
13710 Shared libraries are also supported in many cross or remote debugging
13711 configurations. @value{GDBN} needs to have access to the target's libraries;
13712 this can be accomplished either by providing copies of the libraries
13713 on the host system, or by asking @value{GDBN} to automatically retrieve the
13714 libraries from the target. If copies of the target libraries are
13715 provided, they need to be the same as the target libraries, although the
13716 copies on the target can be stripped as long as the copies on the host are
13719 @cindex where to look for shared libraries
13720 For remote debugging, you need to tell @value{GDBN} where the target
13721 libraries are, so that it can load the correct copies---otherwise, it
13722 may try to load the host's libraries. @value{GDBN} has two variables
13723 to specify the search directories for target libraries.
13726 @cindex prefix for shared library file names
13727 @cindex system root, alternate
13728 @kindex set solib-absolute-prefix
13729 @kindex set sysroot
13730 @item set sysroot @var{path}
13731 Use @var{path} as the system root for the program being debugged. Any
13732 absolute shared library paths will be prefixed with @var{path}; many
13733 runtime loaders store the absolute paths to the shared library in the
13734 target program's memory. If you use @code{set sysroot} to find shared
13735 libraries, they need to be laid out in the same way that they are on
13736 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13739 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13740 retrieve the target libraries from the remote system. This is only
13741 supported when using a remote target that supports the @code{remote get}
13742 command (@pxref{File Transfer,,Sending files to a remote system}).
13743 The part of @var{path} following the initial @file{remote:}
13744 (if present) is used as system root prefix on the remote file system.
13745 @footnote{If you want to specify a local system root using a directory
13746 that happens to be named @file{remote:}, you need to use some equivalent
13747 variant of the name like @file{./remote:}.}
13749 The @code{set solib-absolute-prefix} command is an alias for @code{set
13752 @cindex default system root
13753 @cindex @samp{--with-sysroot}
13754 You can set the default system root by using the configure-time
13755 @samp{--with-sysroot} option. If the system root is inside
13756 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13757 @samp{--exec-prefix}), then the default system root will be updated
13758 automatically if the installed @value{GDBN} is moved to a new
13761 @kindex show sysroot
13763 Display the current shared library prefix.
13765 @kindex set solib-search-path
13766 @item set solib-search-path @var{path}
13767 If this variable is set, @var{path} is a colon-separated list of
13768 directories to search for shared libraries. @samp{solib-search-path}
13769 is used after @samp{sysroot} fails to locate the library, or if the
13770 path to the library is relative instead of absolute. If you want to
13771 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13772 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13773 finding your host's libraries. @samp{sysroot} is preferred; setting
13774 it to a nonexistent directory may interfere with automatic loading
13775 of shared library symbols.
13777 @kindex show solib-search-path
13778 @item show solib-search-path
13779 Display the current shared library search path.
13783 @node Separate Debug Files
13784 @section Debugging Information in Separate Files
13785 @cindex separate debugging information files
13786 @cindex debugging information in separate files
13787 @cindex @file{.debug} subdirectories
13788 @cindex debugging information directory, global
13789 @cindex global debugging information directory
13790 @cindex build ID, and separate debugging files
13791 @cindex @file{.build-id} directory
13793 @value{GDBN} allows you to put a program's debugging information in a
13794 file separate from the executable itself, in a way that allows
13795 @value{GDBN} to find and load the debugging information automatically.
13796 Since debugging information can be very large---sometimes larger
13797 than the executable code itself---some systems distribute debugging
13798 information for their executables in separate files, which users can
13799 install only when they need to debug a problem.
13801 @value{GDBN} supports two ways of specifying the separate debug info
13806 The executable contains a @dfn{debug link} that specifies the name of
13807 the separate debug info file. The separate debug file's name is
13808 usually @file{@var{executable}.debug}, where @var{executable} is the
13809 name of the corresponding executable file without leading directories
13810 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13811 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
13812 checksum for the debug file, which @value{GDBN} uses to validate that
13813 the executable and the debug file came from the same build.
13816 The executable contains a @dfn{build ID}, a unique bit string that is
13817 also present in the corresponding debug info file. (This is supported
13818 only on some operating systems, notably those which use the ELF format
13819 for binary files and the @sc{gnu} Binutils.) For more details about
13820 this feature, see the description of the @option{--build-id}
13821 command-line option in @ref{Options, , Command Line Options, ld.info,
13822 The GNU Linker}. The debug info file's name is not specified
13823 explicitly by the build ID, but can be computed from the build ID, see
13827 Depending on the way the debug info file is specified, @value{GDBN}
13828 uses two different methods of looking for the debug file:
13832 For the ``debug link'' method, @value{GDBN} looks up the named file in
13833 the directory of the executable file, then in a subdirectory of that
13834 directory named @file{.debug}, and finally under the global debug
13835 directory, in a subdirectory whose name is identical to the leading
13836 directories of the executable's absolute file name.
13839 For the ``build ID'' method, @value{GDBN} looks in the
13840 @file{.build-id} subdirectory of the global debug directory for a file
13841 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13842 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13843 are the rest of the bit string. (Real build ID strings are 32 or more
13844 hex characters, not 10.)
13847 So, for example, suppose you ask @value{GDBN} to debug
13848 @file{/usr/bin/ls}, which has a debug link that specifies the
13849 file @file{ls.debug}, and a build ID whose value in hex is
13850 @code{abcdef1234}. If the global debug directory is
13851 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13852 debug information files, in the indicated order:
13856 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13858 @file{/usr/bin/ls.debug}
13860 @file{/usr/bin/.debug/ls.debug}
13862 @file{/usr/lib/debug/usr/bin/ls.debug}.
13865 You can set the global debugging info directory's name, and view the
13866 name @value{GDBN} is currently using.
13870 @kindex set debug-file-directory
13871 @item set debug-file-directory @var{directory}
13872 Set the directory which @value{GDBN} searches for separate debugging
13873 information files to @var{directory}.
13875 @kindex show debug-file-directory
13876 @item show debug-file-directory
13877 Show the directory @value{GDBN} searches for separate debugging
13882 @cindex @code{.gnu_debuglink} sections
13883 @cindex debug link sections
13884 A debug link is a special section of the executable file named
13885 @code{.gnu_debuglink}. The section must contain:
13889 A filename, with any leading directory components removed, followed by
13892 zero to three bytes of padding, as needed to reach the next four-byte
13893 boundary within the section, and
13895 a four-byte CRC checksum, stored in the same endianness used for the
13896 executable file itself. The checksum is computed on the debugging
13897 information file's full contents by the function given below, passing
13898 zero as the @var{crc} argument.
13901 Any executable file format can carry a debug link, as long as it can
13902 contain a section named @code{.gnu_debuglink} with the contents
13905 @cindex @code{.note.gnu.build-id} sections
13906 @cindex build ID sections
13907 The build ID is a special section in the executable file (and in other
13908 ELF binary files that @value{GDBN} may consider). This section is
13909 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13910 It contains unique identification for the built files---the ID remains
13911 the same across multiple builds of the same build tree. The default
13912 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13913 content for the build ID string. The same section with an identical
13914 value is present in the original built binary with symbols, in its
13915 stripped variant, and in the separate debugging information file.
13917 The debugging information file itself should be an ordinary
13918 executable, containing a full set of linker symbols, sections, and
13919 debugging information. The sections of the debugging information file
13920 should have the same names, addresses, and sizes as the original file,
13921 but they need not contain any data---much like a @code{.bss} section
13922 in an ordinary executable.
13924 The @sc{gnu} binary utilities (Binutils) package includes the
13925 @samp{objcopy} utility that can produce
13926 the separated executable / debugging information file pairs using the
13927 following commands:
13930 @kbd{objcopy --only-keep-debug foo foo.debug}
13935 These commands remove the debugging
13936 information from the executable file @file{foo} and place it in the file
13937 @file{foo.debug}. You can use the first, second or both methods to link the
13942 The debug link method needs the following additional command to also leave
13943 behind a debug link in @file{foo}:
13946 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13949 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13950 a version of the @code{strip} command such that the command @kbd{strip foo -f
13951 foo.debug} has the same functionality as the two @code{objcopy} commands and
13952 the @code{ln -s} command above, together.
13955 Build ID gets embedded into the main executable using @code{ld --build-id} or
13956 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13957 compatibility fixes for debug files separation are present in @sc{gnu} binary
13958 utilities (Binutils) package since version 2.18.
13963 @cindex CRC algorithm definition
13964 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
13965 IEEE 802.3 using the polynomial:
13967 @c TexInfo requires naked braces for multi-digit exponents for Tex
13968 @c output, but this causes HTML output to barf. HTML has to be set using
13969 @c raw commands. So we end up having to specify this equation in 2
13974 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
13975 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
13981 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
13982 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
13986 The function is computed byte at a time, taking the least
13987 significant bit of each byte first. The initial pattern
13988 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
13989 the final result is inverted to ensure trailing zeros also affect the
13992 @emph{Note:} This is the same CRC polynomial as used in handling the
13993 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
13994 , @value{GDBN} Remote Serial Protocol}). However in the
13995 case of the Remote Serial Protocol, the CRC is computed @emph{most}
13996 significant bit first, and the result is not inverted, so trailing
13997 zeros have no effect on the CRC value.
13999 To complete the description, we show below the code of the function
14000 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14001 initially supplied @code{crc} argument means that an initial call to
14002 this function passing in zero will start computing the CRC using
14005 @kindex gnu_debuglink_crc32
14008 gnu_debuglink_crc32 (unsigned long crc,
14009 unsigned char *buf, size_t len)
14011 static const unsigned long crc32_table[256] =
14013 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14014 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14015 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14016 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14017 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14018 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14019 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14020 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14021 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14022 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14023 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14024 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14025 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14026 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14027 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14028 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14029 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14030 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14031 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14032 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14033 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14034 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14035 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14036 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14037 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14038 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14039 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14040 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14041 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14042 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14043 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14044 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14045 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14046 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14047 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14048 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14049 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14050 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14051 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14052 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14053 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14054 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14055 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14056 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14057 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14058 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14059 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14060 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14061 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14062 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14063 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14066 unsigned char *end;
14068 crc = ~crc & 0xffffffff;
14069 for (end = buf + len; buf < end; ++buf)
14070 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14071 return ~crc & 0xffffffff;
14076 This computation does not apply to the ``build ID'' method.
14079 @node Symbol Errors
14080 @section Errors Reading Symbol Files
14082 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14083 such as symbol types it does not recognize, or known bugs in compiler
14084 output. By default, @value{GDBN} does not notify you of such problems, since
14085 they are relatively common and primarily of interest to people
14086 debugging compilers. If you are interested in seeing information
14087 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14088 only one message about each such type of problem, no matter how many
14089 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14090 to see how many times the problems occur, with the @code{set
14091 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14094 The messages currently printed, and their meanings, include:
14097 @item inner block not inside outer block in @var{symbol}
14099 The symbol information shows where symbol scopes begin and end
14100 (such as at the start of a function or a block of statements). This
14101 error indicates that an inner scope block is not fully contained
14102 in its outer scope blocks.
14104 @value{GDBN} circumvents the problem by treating the inner block as if it had
14105 the same scope as the outer block. In the error message, @var{symbol}
14106 may be shown as ``@code{(don't know)}'' if the outer block is not a
14109 @item block at @var{address} out of order
14111 The symbol information for symbol scope blocks should occur in
14112 order of increasing addresses. This error indicates that it does not
14115 @value{GDBN} does not circumvent this problem, and has trouble
14116 locating symbols in the source file whose symbols it is reading. (You
14117 can often determine what source file is affected by specifying
14118 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14121 @item bad block start address patched
14123 The symbol information for a symbol scope block has a start address
14124 smaller than the address of the preceding source line. This is known
14125 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14127 @value{GDBN} circumvents the problem by treating the symbol scope block as
14128 starting on the previous source line.
14130 @item bad string table offset in symbol @var{n}
14133 Symbol number @var{n} contains a pointer into the string table which is
14134 larger than the size of the string table.
14136 @value{GDBN} circumvents the problem by considering the symbol to have the
14137 name @code{foo}, which may cause other problems if many symbols end up
14140 @item unknown symbol type @code{0x@var{nn}}
14142 The symbol information contains new data types that @value{GDBN} does
14143 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14144 uncomprehended information, in hexadecimal.
14146 @value{GDBN} circumvents the error by ignoring this symbol information.
14147 This usually allows you to debug your program, though certain symbols
14148 are not accessible. If you encounter such a problem and feel like
14149 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14150 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14151 and examine @code{*bufp} to see the symbol.
14153 @item stub type has NULL name
14155 @value{GDBN} could not find the full definition for a struct or class.
14157 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14158 The symbol information for a C@t{++} member function is missing some
14159 information that recent versions of the compiler should have output for
14162 @item info mismatch between compiler and debugger
14164 @value{GDBN} could not parse a type specification output by the compiler.
14169 @section GDB Data Files
14171 @cindex prefix for data files
14172 @value{GDBN} will sometimes read an auxiliary data file. These files
14173 are kept in a directory known as the @dfn{data directory}.
14175 You can set the data directory's name, and view the name @value{GDBN}
14176 is currently using.
14179 @kindex set data-directory
14180 @item set data-directory @var{directory}
14181 Set the directory which @value{GDBN} searches for auxiliary data files
14182 to @var{directory}.
14184 @kindex show data-directory
14185 @item show data-directory
14186 Show the directory @value{GDBN} searches for auxiliary data files.
14189 @cindex default data directory
14190 @cindex @samp{--with-gdb-datadir}
14191 You can set the default data directory by using the configure-time
14192 @samp{--with-gdb-datadir} option. If the data directory is inside
14193 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14194 @samp{--exec-prefix}), then the default data directory will be updated
14195 automatically if the installed @value{GDBN} is moved to a new
14199 @chapter Specifying a Debugging Target
14201 @cindex debugging target
14202 A @dfn{target} is the execution environment occupied by your program.
14204 Often, @value{GDBN} runs in the same host environment as your program;
14205 in that case, the debugging target is specified as a side effect when
14206 you use the @code{file} or @code{core} commands. When you need more
14207 flexibility---for example, running @value{GDBN} on a physically separate
14208 host, or controlling a standalone system over a serial port or a
14209 realtime system over a TCP/IP connection---you can use the @code{target}
14210 command to specify one of the target types configured for @value{GDBN}
14211 (@pxref{Target Commands, ,Commands for Managing Targets}).
14213 @cindex target architecture
14214 It is possible to build @value{GDBN} for several different @dfn{target
14215 architectures}. When @value{GDBN} is built like that, you can choose
14216 one of the available architectures with the @kbd{set architecture}
14220 @kindex set architecture
14221 @kindex show architecture
14222 @item set architecture @var{arch}
14223 This command sets the current target architecture to @var{arch}. The
14224 value of @var{arch} can be @code{"auto"}, in addition to one of the
14225 supported architectures.
14227 @item show architecture
14228 Show the current target architecture.
14230 @item set processor
14232 @kindex set processor
14233 @kindex show processor
14234 These are alias commands for, respectively, @code{set architecture}
14235 and @code{show architecture}.
14239 * Active Targets:: Active targets
14240 * Target Commands:: Commands for managing targets
14241 * Byte Order:: Choosing target byte order
14244 @node Active Targets
14245 @section Active Targets
14247 @cindex stacking targets
14248 @cindex active targets
14249 @cindex multiple targets
14251 There are three classes of targets: processes, core files, and
14252 executable files. @value{GDBN} can work concurrently on up to three
14253 active targets, one in each class. This allows you to (for example)
14254 start a process and inspect its activity without abandoning your work on
14257 For example, if you execute @samp{gdb a.out}, then the executable file
14258 @code{a.out} is the only active target. If you designate a core file as
14259 well---presumably from a prior run that crashed and coredumped---then
14260 @value{GDBN} has two active targets and uses them in tandem, looking
14261 first in the corefile target, then in the executable file, to satisfy
14262 requests for memory addresses. (Typically, these two classes of target
14263 are complementary, since core files contain only a program's
14264 read-write memory---variables and so on---plus machine status, while
14265 executable files contain only the program text and initialized data.)
14267 When you type @code{run}, your executable file becomes an active process
14268 target as well. When a process target is active, all @value{GDBN}
14269 commands requesting memory addresses refer to that target; addresses in
14270 an active core file or executable file target are obscured while the
14271 process target is active.
14273 Use the @code{core-file} and @code{exec-file} commands to select a new
14274 core file or executable target (@pxref{Files, ,Commands to Specify
14275 Files}). To specify as a target a process that is already running, use
14276 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
14279 @node Target Commands
14280 @section Commands for Managing Targets
14283 @item target @var{type} @var{parameters}
14284 Connects the @value{GDBN} host environment to a target machine or
14285 process. A target is typically a protocol for talking to debugging
14286 facilities. You use the argument @var{type} to specify the type or
14287 protocol of the target machine.
14289 Further @var{parameters} are interpreted by the target protocol, but
14290 typically include things like device names or host names to connect
14291 with, process numbers, and baud rates.
14293 The @code{target} command does not repeat if you press @key{RET} again
14294 after executing the command.
14296 @kindex help target
14298 Displays the names of all targets available. To display targets
14299 currently selected, use either @code{info target} or @code{info files}
14300 (@pxref{Files, ,Commands to Specify Files}).
14302 @item help target @var{name}
14303 Describe a particular target, including any parameters necessary to
14306 @kindex set gnutarget
14307 @item set gnutarget @var{args}
14308 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
14309 knows whether it is reading an @dfn{executable},
14310 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
14311 with the @code{set gnutarget} command. Unlike most @code{target} commands,
14312 with @code{gnutarget} the @code{target} refers to a program, not a machine.
14315 @emph{Warning:} To specify a file format with @code{set gnutarget},
14316 you must know the actual BFD name.
14320 @xref{Files, , Commands to Specify Files}.
14322 @kindex show gnutarget
14323 @item show gnutarget
14324 Use the @code{show gnutarget} command to display what file format
14325 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
14326 @value{GDBN} will determine the file format for each file automatically,
14327 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
14330 @cindex common targets
14331 Here are some common targets (available, or not, depending on the GDB
14336 @item target exec @var{program}
14337 @cindex executable file target
14338 An executable file. @samp{target exec @var{program}} is the same as
14339 @samp{exec-file @var{program}}.
14341 @item target core @var{filename}
14342 @cindex core dump file target
14343 A core dump file. @samp{target core @var{filename}} is the same as
14344 @samp{core-file @var{filename}}.
14346 @item target remote @var{medium}
14347 @cindex remote target
14348 A remote system connected to @value{GDBN} via a serial line or network
14349 connection. This command tells @value{GDBN} to use its own remote
14350 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
14352 For example, if you have a board connected to @file{/dev/ttya} on the
14353 machine running @value{GDBN}, you could say:
14356 target remote /dev/ttya
14359 @code{target remote} supports the @code{load} command. This is only
14360 useful if you have some other way of getting the stub to the target
14361 system, and you can put it somewhere in memory where it won't get
14362 clobbered by the download.
14365 @cindex built-in simulator target
14366 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
14374 works; however, you cannot assume that a specific memory map, device
14375 drivers, or even basic I/O is available, although some simulators do
14376 provide these. For info about any processor-specific simulator details,
14377 see the appropriate section in @ref{Embedded Processors, ,Embedded
14382 Some configurations may include these targets as well:
14386 @item target nrom @var{dev}
14387 @cindex NetROM ROM emulator target
14388 NetROM ROM emulator. This target only supports downloading.
14392 Different targets are available on different configurations of @value{GDBN};
14393 your configuration may have more or fewer targets.
14395 Many remote targets require you to download the executable's code once
14396 you've successfully established a connection. You may wish to control
14397 various aspects of this process.
14402 @kindex set hash@r{, for remote monitors}
14403 @cindex hash mark while downloading
14404 This command controls whether a hash mark @samp{#} is displayed while
14405 downloading a file to the remote monitor. If on, a hash mark is
14406 displayed after each S-record is successfully downloaded to the
14410 @kindex show hash@r{, for remote monitors}
14411 Show the current status of displaying the hash mark.
14413 @item set debug monitor
14414 @kindex set debug monitor
14415 @cindex display remote monitor communications
14416 Enable or disable display of communications messages between
14417 @value{GDBN} and the remote monitor.
14419 @item show debug monitor
14420 @kindex show debug monitor
14421 Show the current status of displaying communications between
14422 @value{GDBN} and the remote monitor.
14427 @kindex load @var{filename}
14428 @item load @var{filename}
14430 Depending on what remote debugging facilities are configured into
14431 @value{GDBN}, the @code{load} command may be available. Where it exists, it
14432 is meant to make @var{filename} (an executable) available for debugging
14433 on the remote system---by downloading, or dynamic linking, for example.
14434 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
14435 the @code{add-symbol-file} command.
14437 If your @value{GDBN} does not have a @code{load} command, attempting to
14438 execute it gets the error message ``@code{You can't do that when your
14439 target is @dots{}}''
14441 The file is loaded at whatever address is specified in the executable.
14442 For some object file formats, you can specify the load address when you
14443 link the program; for other formats, like a.out, the object file format
14444 specifies a fixed address.
14445 @c FIXME! This would be a good place for an xref to the GNU linker doc.
14447 Depending on the remote side capabilities, @value{GDBN} may be able to
14448 load programs into flash memory.
14450 @code{load} does not repeat if you press @key{RET} again after using it.
14454 @section Choosing Target Byte Order
14456 @cindex choosing target byte order
14457 @cindex target byte order
14459 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
14460 offer the ability to run either big-endian or little-endian byte
14461 orders. Usually the executable or symbol will include a bit to
14462 designate the endian-ness, and you will not need to worry about
14463 which to use. However, you may still find it useful to adjust
14464 @value{GDBN}'s idea of processor endian-ness manually.
14468 @item set endian big
14469 Instruct @value{GDBN} to assume the target is big-endian.
14471 @item set endian little
14472 Instruct @value{GDBN} to assume the target is little-endian.
14474 @item set endian auto
14475 Instruct @value{GDBN} to use the byte order associated with the
14479 Display @value{GDBN}'s current idea of the target byte order.
14483 Note that these commands merely adjust interpretation of symbolic
14484 data on the host, and that they have absolutely no effect on the
14488 @node Remote Debugging
14489 @chapter Debugging Remote Programs
14490 @cindex remote debugging
14492 If you are trying to debug a program running on a machine that cannot run
14493 @value{GDBN} in the usual way, it is often useful to use remote debugging.
14494 For example, you might use remote debugging on an operating system kernel,
14495 or on a small system which does not have a general purpose operating system
14496 powerful enough to run a full-featured debugger.
14498 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
14499 to make this work with particular debugging targets. In addition,
14500 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
14501 but not specific to any particular target system) which you can use if you
14502 write the remote stubs---the code that runs on the remote system to
14503 communicate with @value{GDBN}.
14505 Other remote targets may be available in your
14506 configuration of @value{GDBN}; use @code{help target} to list them.
14509 * Connecting:: Connecting to a remote target
14510 * File Transfer:: Sending files to a remote system
14511 * Server:: Using the gdbserver program
14512 * Remote Configuration:: Remote configuration
14513 * Remote Stub:: Implementing a remote stub
14517 @section Connecting to a Remote Target
14519 On the @value{GDBN} host machine, you will need an unstripped copy of
14520 your program, since @value{GDBN} needs symbol and debugging information.
14521 Start up @value{GDBN} as usual, using the name of the local copy of your
14522 program as the first argument.
14524 @cindex @code{target remote}
14525 @value{GDBN} can communicate with the target over a serial line, or
14526 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
14527 each case, @value{GDBN} uses the same protocol for debugging your
14528 program; only the medium carrying the debugging packets varies. The
14529 @code{target remote} command establishes a connection to the target.
14530 Its arguments indicate which medium to use:
14534 @item target remote @var{serial-device}
14535 @cindex serial line, @code{target remote}
14536 Use @var{serial-device} to communicate with the target. For example,
14537 to use a serial line connected to the device named @file{/dev/ttyb}:
14540 target remote /dev/ttyb
14543 If you're using a serial line, you may want to give @value{GDBN} the
14544 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
14545 (@pxref{Remote Configuration, set remotebaud}) before the
14546 @code{target} command.
14548 @item target remote @code{@var{host}:@var{port}}
14549 @itemx target remote @code{tcp:@var{host}:@var{port}}
14550 @cindex @acronym{TCP} port, @code{target remote}
14551 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
14552 The @var{host} may be either a host name or a numeric @acronym{IP}
14553 address; @var{port} must be a decimal number. The @var{host} could be
14554 the target machine itself, if it is directly connected to the net, or
14555 it might be a terminal server which in turn has a serial line to the
14558 For example, to connect to port 2828 on a terminal server named
14562 target remote manyfarms:2828
14565 If your remote target is actually running on the same machine as your
14566 debugger session (e.g.@: a simulator for your target running on the
14567 same host), you can omit the hostname. For example, to connect to
14568 port 1234 on your local machine:
14571 target remote :1234
14575 Note that the colon is still required here.
14577 @item target remote @code{udp:@var{host}:@var{port}}
14578 @cindex @acronym{UDP} port, @code{target remote}
14579 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
14580 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
14583 target remote udp:manyfarms:2828
14586 When using a @acronym{UDP} connection for remote debugging, you should
14587 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
14588 can silently drop packets on busy or unreliable networks, which will
14589 cause havoc with your debugging session.
14591 @item target remote | @var{command}
14592 @cindex pipe, @code{target remote} to
14593 Run @var{command} in the background and communicate with it using a
14594 pipe. The @var{command} is a shell command, to be parsed and expanded
14595 by the system's command shell, @code{/bin/sh}; it should expect remote
14596 protocol packets on its standard input, and send replies on its
14597 standard output. You could use this to run a stand-alone simulator
14598 that speaks the remote debugging protocol, to make net connections
14599 using programs like @code{ssh}, or for other similar tricks.
14601 If @var{command} closes its standard output (perhaps by exiting),
14602 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
14603 program has already exited, this will have no effect.)
14607 Once the connection has been established, you can use all the usual
14608 commands to examine and change data. The remote program is already
14609 running; you can use @kbd{step} and @kbd{continue}, and you do not
14610 need to use @kbd{run}.
14612 @cindex interrupting remote programs
14613 @cindex remote programs, interrupting
14614 Whenever @value{GDBN} is waiting for the remote program, if you type the
14615 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
14616 program. This may or may not succeed, depending in part on the hardware
14617 and the serial drivers the remote system uses. If you type the
14618 interrupt character once again, @value{GDBN} displays this prompt:
14621 Interrupted while waiting for the program.
14622 Give up (and stop debugging it)? (y or n)
14625 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
14626 (If you decide you want to try again later, you can use @samp{target
14627 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
14628 goes back to waiting.
14631 @kindex detach (remote)
14633 When you have finished debugging the remote program, you can use the
14634 @code{detach} command to release it from @value{GDBN} control.
14635 Detaching from the target normally resumes its execution, but the results
14636 will depend on your particular remote stub. After the @code{detach}
14637 command, @value{GDBN} is free to connect to another target.
14641 The @code{disconnect} command behaves like @code{detach}, except that
14642 the target is generally not resumed. It will wait for @value{GDBN}
14643 (this instance or another one) to connect and continue debugging. After
14644 the @code{disconnect} command, @value{GDBN} is again free to connect to
14647 @cindex send command to remote monitor
14648 @cindex extend @value{GDBN} for remote targets
14649 @cindex add new commands for external monitor
14651 @item monitor @var{cmd}
14652 This command allows you to send arbitrary commands directly to the
14653 remote monitor. Since @value{GDBN} doesn't care about the commands it
14654 sends like this, this command is the way to extend @value{GDBN}---you
14655 can add new commands that only the external monitor will understand
14659 @node File Transfer
14660 @section Sending files to a remote system
14661 @cindex remote target, file transfer
14662 @cindex file transfer
14663 @cindex sending files to remote systems
14665 Some remote targets offer the ability to transfer files over the same
14666 connection used to communicate with @value{GDBN}. This is convenient
14667 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14668 running @code{gdbserver} over a network interface. For other targets,
14669 e.g.@: embedded devices with only a single serial port, this may be
14670 the only way to upload or download files.
14672 Not all remote targets support these commands.
14676 @item remote put @var{hostfile} @var{targetfile}
14677 Copy file @var{hostfile} from the host system (the machine running
14678 @value{GDBN}) to @var{targetfile} on the target system.
14681 @item remote get @var{targetfile} @var{hostfile}
14682 Copy file @var{targetfile} from the target system to @var{hostfile}
14683 on the host system.
14685 @kindex remote delete
14686 @item remote delete @var{targetfile}
14687 Delete @var{targetfile} from the target system.
14692 @section Using the @code{gdbserver} Program
14695 @cindex remote connection without stubs
14696 @code{gdbserver} is a control program for Unix-like systems, which
14697 allows you to connect your program with a remote @value{GDBN} via
14698 @code{target remote}---but without linking in the usual debugging stub.
14700 @code{gdbserver} is not a complete replacement for the debugging stubs,
14701 because it requires essentially the same operating-system facilities
14702 that @value{GDBN} itself does. In fact, a system that can run
14703 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14704 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14705 because it is a much smaller program than @value{GDBN} itself. It is
14706 also easier to port than all of @value{GDBN}, so you may be able to get
14707 started more quickly on a new system by using @code{gdbserver}.
14708 Finally, if you develop code for real-time systems, you may find that
14709 the tradeoffs involved in real-time operation make it more convenient to
14710 do as much development work as possible on another system, for example
14711 by cross-compiling. You can use @code{gdbserver} to make a similar
14712 choice for debugging.
14714 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14715 or a TCP connection, using the standard @value{GDBN} remote serial
14719 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14720 Do not run @code{gdbserver} connected to any public network; a
14721 @value{GDBN} connection to @code{gdbserver} provides access to the
14722 target system with the same privileges as the user running
14726 @subsection Running @code{gdbserver}
14727 @cindex arguments, to @code{gdbserver}
14729 Run @code{gdbserver} on the target system. You need a copy of the
14730 program you want to debug, including any libraries it requires.
14731 @code{gdbserver} does not need your program's symbol table, so you can
14732 strip the program if necessary to save space. @value{GDBN} on the host
14733 system does all the symbol handling.
14735 To use the server, you must tell it how to communicate with @value{GDBN};
14736 the name of your program; and the arguments for your program. The usual
14740 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14743 @var{comm} is either a device name (to use a serial line) or a TCP
14744 hostname and portnumber. For example, to debug Emacs with the argument
14745 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14749 target> gdbserver /dev/com1 emacs foo.txt
14752 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14755 To use a TCP connection instead of a serial line:
14758 target> gdbserver host:2345 emacs foo.txt
14761 The only difference from the previous example is the first argument,
14762 specifying that you are communicating with the host @value{GDBN} via
14763 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14764 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14765 (Currently, the @samp{host} part is ignored.) You can choose any number
14766 you want for the port number as long as it does not conflict with any
14767 TCP ports already in use on the target system (for example, @code{23} is
14768 reserved for @code{telnet}).@footnote{If you choose a port number that
14769 conflicts with another service, @code{gdbserver} prints an error message
14770 and exits.} You must use the same port number with the host @value{GDBN}
14771 @code{target remote} command.
14773 @subsubsection Attaching to a Running Program
14775 On some targets, @code{gdbserver} can also attach to running programs.
14776 This is accomplished via the @code{--attach} argument. The syntax is:
14779 target> gdbserver --attach @var{comm} @var{pid}
14782 @var{pid} is the process ID of a currently running process. It isn't necessary
14783 to point @code{gdbserver} at a binary for the running process.
14786 @cindex attach to a program by name
14787 You can debug processes by name instead of process ID if your target has the
14788 @code{pidof} utility:
14791 target> gdbserver --attach @var{comm} `pidof @var{program}`
14794 In case more than one copy of @var{program} is running, or @var{program}
14795 has multiple threads, most versions of @code{pidof} support the
14796 @code{-s} option to only return the first process ID.
14798 @subsubsection Multi-Process Mode for @code{gdbserver}
14799 @cindex gdbserver, multiple processes
14800 @cindex multiple processes with gdbserver
14802 When you connect to @code{gdbserver} using @code{target remote},
14803 @code{gdbserver} debugs the specified program only once. When the
14804 program exits, or you detach from it, @value{GDBN} closes the connection
14805 and @code{gdbserver} exits.
14807 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14808 enters multi-process mode. When the debugged program exits, or you
14809 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14810 though no program is running. The @code{run} and @code{attach}
14811 commands instruct @code{gdbserver} to run or attach to a new program.
14812 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14813 remote exec-file}) to select the program to run. Command line
14814 arguments are supported, except for wildcard expansion and I/O
14815 redirection (@pxref{Arguments}).
14817 To start @code{gdbserver} without supplying an initial command to run
14818 or process ID to attach, use the @option{--multi} command line option.
14819 Then you can connect using @kbd{target extended-remote} and start
14820 the program you want to debug.
14822 @code{gdbserver} does not automatically exit in multi-process mode.
14823 You can terminate it by using @code{monitor exit}
14824 (@pxref{Monitor Commands for gdbserver}).
14826 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14828 The @option{--debug} option tells @code{gdbserver} to display extra
14829 status information about the debugging process. The
14830 @option{--remote-debug} option tells @code{gdbserver} to display
14831 remote protocol debug output. These options are intended for
14832 @code{gdbserver} development and for bug reports to the developers.
14834 The @option{--wrapper} option specifies a wrapper to launch programs
14835 for debugging. The option should be followed by the name of the
14836 wrapper, then any command-line arguments to pass to the wrapper, then
14837 @kbd{--} indicating the end of the wrapper arguments.
14839 @code{gdbserver} runs the specified wrapper program with a combined
14840 command line including the wrapper arguments, then the name of the
14841 program to debug, then any arguments to the program. The wrapper
14842 runs until it executes your program, and then @value{GDBN} gains control.
14844 You can use any program that eventually calls @code{execve} with
14845 its arguments as a wrapper. Several standard Unix utilities do
14846 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14847 with @code{exec "$@@"} will also work.
14849 For example, you can use @code{env} to pass an environment variable to
14850 the debugged program, without setting the variable in @code{gdbserver}'s
14854 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14857 @subsection Connecting to @code{gdbserver}
14859 Run @value{GDBN} on the host system.
14861 First make sure you have the necessary symbol files. Load symbols for
14862 your application using the @code{file} command before you connect. Use
14863 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14864 was compiled with the correct sysroot using @code{--with-sysroot}).
14866 The symbol file and target libraries must exactly match the executable
14867 and libraries on the target, with one exception: the files on the host
14868 system should not be stripped, even if the files on the target system
14869 are. Mismatched or missing files will lead to confusing results
14870 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14871 files may also prevent @code{gdbserver} from debugging multi-threaded
14874 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14875 For TCP connections, you must start up @code{gdbserver} prior to using
14876 the @code{target remote} command. Otherwise you may get an error whose
14877 text depends on the host system, but which usually looks something like
14878 @samp{Connection refused}. Don't use the @code{load}
14879 command in @value{GDBN} when using @code{gdbserver}, since the program is
14880 already on the target.
14882 @subsection Monitor Commands for @code{gdbserver}
14883 @cindex monitor commands, for @code{gdbserver}
14884 @anchor{Monitor Commands for gdbserver}
14886 During a @value{GDBN} session using @code{gdbserver}, you can use the
14887 @code{monitor} command to send special requests to @code{gdbserver}.
14888 Here are the available commands.
14892 List the available monitor commands.
14894 @item monitor set debug 0
14895 @itemx monitor set debug 1
14896 Disable or enable general debugging messages.
14898 @item monitor set remote-debug 0
14899 @itemx monitor set remote-debug 1
14900 Disable or enable specific debugging messages associated with the remote
14901 protocol (@pxref{Remote Protocol}).
14904 Tell gdbserver to exit immediately. This command should be followed by
14905 @code{disconnect} to close the debugging session. @code{gdbserver} will
14906 detach from any attached processes and kill any processes it created.
14907 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14908 of a multi-process mode debug session.
14912 @node Remote Configuration
14913 @section Remote Configuration
14916 @kindex show remote
14917 This section documents the configuration options available when
14918 debugging remote programs. For the options related to the File I/O
14919 extensions of the remote protocol, see @ref{system,
14920 system-call-allowed}.
14923 @item set remoteaddresssize @var{bits}
14924 @cindex address size for remote targets
14925 @cindex bits in remote address
14926 Set the maximum size of address in a memory packet to the specified
14927 number of bits. @value{GDBN} will mask off the address bits above
14928 that number, when it passes addresses to the remote target. The
14929 default value is the number of bits in the target's address.
14931 @item show remoteaddresssize
14932 Show the current value of remote address size in bits.
14934 @item set remotebaud @var{n}
14935 @cindex baud rate for remote targets
14936 Set the baud rate for the remote serial I/O to @var{n} baud. The
14937 value is used to set the speed of the serial port used for debugging
14940 @item show remotebaud
14941 Show the current speed of the remote connection.
14943 @item set remotebreak
14944 @cindex interrupt remote programs
14945 @cindex BREAK signal instead of Ctrl-C
14946 @anchor{set remotebreak}
14947 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14948 when you type @kbd{Ctrl-c} to interrupt the program running
14949 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14950 character instead. The default is off, since most remote systems
14951 expect to see @samp{Ctrl-C} as the interrupt signal.
14953 @item show remotebreak
14954 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14955 interrupt the remote program.
14957 @item set remoteflow on
14958 @itemx set remoteflow off
14959 @kindex set remoteflow
14960 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14961 on the serial port used to communicate to the remote target.
14963 @item show remoteflow
14964 @kindex show remoteflow
14965 Show the current setting of hardware flow control.
14967 @item set remotelogbase @var{base}
14968 Set the base (a.k.a.@: radix) of logging serial protocol
14969 communications to @var{base}. Supported values of @var{base} are:
14970 @code{ascii}, @code{octal}, and @code{hex}. The default is
14973 @item show remotelogbase
14974 Show the current setting of the radix for logging remote serial
14977 @item set remotelogfile @var{file}
14978 @cindex record serial communications on file
14979 Record remote serial communications on the named @var{file}. The
14980 default is not to record at all.
14982 @item show remotelogfile.
14983 Show the current setting of the file name on which to record the
14984 serial communications.
14986 @item set remotetimeout @var{num}
14987 @cindex timeout for serial communications
14988 @cindex remote timeout
14989 Set the timeout limit to wait for the remote target to respond to
14990 @var{num} seconds. The default is 2 seconds.
14992 @item show remotetimeout
14993 Show the current number of seconds to wait for the remote target
14996 @cindex limit hardware breakpoints and watchpoints
14997 @cindex remote target, limit break- and watchpoints
14998 @anchor{set remote hardware-watchpoint-limit}
14999 @anchor{set remote hardware-breakpoint-limit}
15000 @item set remote hardware-watchpoint-limit @var{limit}
15001 @itemx set remote hardware-breakpoint-limit @var{limit}
15002 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15003 watchpoints. A limit of -1, the default, is treated as unlimited.
15005 @item set remote exec-file @var{filename}
15006 @itemx show remote exec-file
15007 @anchor{set remote exec-file}
15008 @cindex executable file, for remote target
15009 Select the file used for @code{run} with @code{target
15010 extended-remote}. This should be set to a filename valid on the
15011 target system. If it is not set, the target will use a default
15012 filename (e.g.@: the last program run).
15016 @item set tcp auto-retry on
15017 @cindex auto-retry, for remote TCP target
15018 Enable auto-retry for remote TCP connections. This is useful if the remote
15019 debugging agent is launched in parallel with @value{GDBN}; there is a race
15020 condition because the agent may not become ready to accept the connection
15021 before @value{GDBN} attempts to connect. When auto-retry is
15022 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15023 to establish the connection using the timeout specified by
15024 @code{set tcp connect-timeout}.
15026 @item set tcp auto-retry off
15027 Do not auto-retry failed TCP connections.
15029 @item show tcp auto-retry
15030 Show the current auto-retry setting.
15032 @item set tcp connect-timeout @var{seconds}
15033 @cindex connection timeout, for remote TCP target
15034 @cindex timeout, for remote target connection
15035 Set the timeout for establishing a TCP connection to the remote target to
15036 @var{seconds}. The timeout affects both polling to retry failed connections
15037 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15038 that are merely slow to complete, and represents an approximate cumulative
15041 @item show tcp connect-timeout
15042 Show the current connection timeout setting.
15045 @cindex remote packets, enabling and disabling
15046 The @value{GDBN} remote protocol autodetects the packets supported by
15047 your debugging stub. If you need to override the autodetection, you
15048 can use these commands to enable or disable individual packets. Each
15049 packet can be set to @samp{on} (the remote target supports this
15050 packet), @samp{off} (the remote target does not support this packet),
15051 or @samp{auto} (detect remote target support for this packet). They
15052 all default to @samp{auto}. For more information about each packet,
15053 see @ref{Remote Protocol}.
15055 During normal use, you should not have to use any of these commands.
15056 If you do, that may be a bug in your remote debugging stub, or a bug
15057 in @value{GDBN}. You may want to report the problem to the
15058 @value{GDBN} developers.
15060 For each packet @var{name}, the command to enable or disable the
15061 packet is @code{set remote @var{name}-packet}. The available settings
15064 @multitable @columnfractions 0.28 0.32 0.25
15067 @tab Related Features
15069 @item @code{fetch-register}
15071 @tab @code{info registers}
15073 @item @code{set-register}
15077 @item @code{binary-download}
15079 @tab @code{load}, @code{set}
15081 @item @code{read-aux-vector}
15082 @tab @code{qXfer:auxv:read}
15083 @tab @code{info auxv}
15085 @item @code{symbol-lookup}
15086 @tab @code{qSymbol}
15087 @tab Detecting multiple threads
15089 @item @code{attach}
15090 @tab @code{vAttach}
15093 @item @code{verbose-resume}
15095 @tab Stepping or resuming multiple threads
15101 @item @code{software-breakpoint}
15105 @item @code{hardware-breakpoint}
15109 @item @code{write-watchpoint}
15113 @item @code{read-watchpoint}
15117 @item @code{access-watchpoint}
15121 @item @code{target-features}
15122 @tab @code{qXfer:features:read}
15123 @tab @code{set architecture}
15125 @item @code{library-info}
15126 @tab @code{qXfer:libraries:read}
15127 @tab @code{info sharedlibrary}
15129 @item @code{memory-map}
15130 @tab @code{qXfer:memory-map:read}
15131 @tab @code{info mem}
15133 @item @code{read-spu-object}
15134 @tab @code{qXfer:spu:read}
15135 @tab @code{info spu}
15137 @item @code{write-spu-object}
15138 @tab @code{qXfer:spu:write}
15139 @tab @code{info spu}
15141 @item @code{read-siginfo-object}
15142 @tab @code{qXfer:siginfo:read}
15143 @tab @code{print $_siginfo}
15145 @item @code{write-siginfo-object}
15146 @tab @code{qXfer:siginfo:write}
15147 @tab @code{set $_siginfo}
15149 @item @code{get-thread-local-@*storage-address}
15150 @tab @code{qGetTLSAddr}
15151 @tab Displaying @code{__thread} variables
15153 @item @code{search-memory}
15154 @tab @code{qSearch:memory}
15157 @item @code{supported-packets}
15158 @tab @code{qSupported}
15159 @tab Remote communications parameters
15161 @item @code{pass-signals}
15162 @tab @code{QPassSignals}
15163 @tab @code{handle @var{signal}}
15165 @item @code{hostio-close-packet}
15166 @tab @code{vFile:close}
15167 @tab @code{remote get}, @code{remote put}
15169 @item @code{hostio-open-packet}
15170 @tab @code{vFile:open}
15171 @tab @code{remote get}, @code{remote put}
15173 @item @code{hostio-pread-packet}
15174 @tab @code{vFile:pread}
15175 @tab @code{remote get}, @code{remote put}
15177 @item @code{hostio-pwrite-packet}
15178 @tab @code{vFile:pwrite}
15179 @tab @code{remote get}, @code{remote put}
15181 @item @code{hostio-unlink-packet}
15182 @tab @code{vFile:unlink}
15183 @tab @code{remote delete}
15185 @item @code{noack-packet}
15186 @tab @code{QStartNoAckMode}
15187 @tab Packet acknowledgment
15189 @item @code{osdata}
15190 @tab @code{qXfer:osdata:read}
15191 @tab @code{info os}
15193 @item @code{query-attached}
15194 @tab @code{qAttached}
15195 @tab Querying remote process attach state.
15199 @section Implementing a Remote Stub
15201 @cindex debugging stub, example
15202 @cindex remote stub, example
15203 @cindex stub example, remote debugging
15204 The stub files provided with @value{GDBN} implement the target side of the
15205 communication protocol, and the @value{GDBN} side is implemented in the
15206 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
15207 these subroutines to communicate, and ignore the details. (If you're
15208 implementing your own stub file, you can still ignore the details: start
15209 with one of the existing stub files. @file{sparc-stub.c} is the best
15210 organized, and therefore the easiest to read.)
15212 @cindex remote serial debugging, overview
15213 To debug a program running on another machine (the debugging
15214 @dfn{target} machine), you must first arrange for all the usual
15215 prerequisites for the program to run by itself. For example, for a C
15220 A startup routine to set up the C runtime environment; these usually
15221 have a name like @file{crt0}. The startup routine may be supplied by
15222 your hardware supplier, or you may have to write your own.
15225 A C subroutine library to support your program's
15226 subroutine calls, notably managing input and output.
15229 A way of getting your program to the other machine---for example, a
15230 download program. These are often supplied by the hardware
15231 manufacturer, but you may have to write your own from hardware
15235 The next step is to arrange for your program to use a serial port to
15236 communicate with the machine where @value{GDBN} is running (the @dfn{host}
15237 machine). In general terms, the scheme looks like this:
15241 @value{GDBN} already understands how to use this protocol; when everything
15242 else is set up, you can simply use the @samp{target remote} command
15243 (@pxref{Targets,,Specifying a Debugging Target}).
15245 @item On the target,
15246 you must link with your program a few special-purpose subroutines that
15247 implement the @value{GDBN} remote serial protocol. The file containing these
15248 subroutines is called a @dfn{debugging stub}.
15250 On certain remote targets, you can use an auxiliary program
15251 @code{gdbserver} instead of linking a stub into your program.
15252 @xref{Server,,Using the @code{gdbserver} Program}, for details.
15255 The debugging stub is specific to the architecture of the remote
15256 machine; for example, use @file{sparc-stub.c} to debug programs on
15259 @cindex remote serial stub list
15260 These working remote stubs are distributed with @value{GDBN}:
15265 @cindex @file{i386-stub.c}
15268 For Intel 386 and compatible architectures.
15271 @cindex @file{m68k-stub.c}
15272 @cindex Motorola 680x0
15274 For Motorola 680x0 architectures.
15277 @cindex @file{sh-stub.c}
15280 For Renesas SH architectures.
15283 @cindex @file{sparc-stub.c}
15285 For @sc{sparc} architectures.
15287 @item sparcl-stub.c
15288 @cindex @file{sparcl-stub.c}
15291 For Fujitsu @sc{sparclite} architectures.
15295 The @file{README} file in the @value{GDBN} distribution may list other
15296 recently added stubs.
15299 * Stub Contents:: What the stub can do for you
15300 * Bootstrapping:: What you must do for the stub
15301 * Debug Session:: Putting it all together
15304 @node Stub Contents
15305 @subsection What the Stub Can Do for You
15307 @cindex remote serial stub
15308 The debugging stub for your architecture supplies these three
15312 @item set_debug_traps
15313 @findex set_debug_traps
15314 @cindex remote serial stub, initialization
15315 This routine arranges for @code{handle_exception} to run when your
15316 program stops. You must call this subroutine explicitly near the
15317 beginning of your program.
15319 @item handle_exception
15320 @findex handle_exception
15321 @cindex remote serial stub, main routine
15322 This is the central workhorse, but your program never calls it
15323 explicitly---the setup code arranges for @code{handle_exception} to
15324 run when a trap is triggered.
15326 @code{handle_exception} takes control when your program stops during
15327 execution (for example, on a breakpoint), and mediates communications
15328 with @value{GDBN} on the host machine. This is where the communications
15329 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
15330 representative on the target machine. It begins by sending summary
15331 information on the state of your program, then continues to execute,
15332 retrieving and transmitting any information @value{GDBN} needs, until you
15333 execute a @value{GDBN} command that makes your program resume; at that point,
15334 @code{handle_exception} returns control to your own code on the target
15338 @cindex @code{breakpoint} subroutine, remote
15339 Use this auxiliary subroutine to make your program contain a
15340 breakpoint. Depending on the particular situation, this may be the only
15341 way for @value{GDBN} to get control. For instance, if your target
15342 machine has some sort of interrupt button, you won't need to call this;
15343 pressing the interrupt button transfers control to
15344 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
15345 simply receiving characters on the serial port may also trigger a trap;
15346 again, in that situation, you don't need to call @code{breakpoint} from
15347 your own program---simply running @samp{target remote} from the host
15348 @value{GDBN} session gets control.
15350 Call @code{breakpoint} if none of these is true, or if you simply want
15351 to make certain your program stops at a predetermined point for the
15352 start of your debugging session.
15355 @node Bootstrapping
15356 @subsection What You Must Do for the Stub
15358 @cindex remote stub, support routines
15359 The debugging stubs that come with @value{GDBN} are set up for a particular
15360 chip architecture, but they have no information about the rest of your
15361 debugging target machine.
15363 First of all you need to tell the stub how to communicate with the
15367 @item int getDebugChar()
15368 @findex getDebugChar
15369 Write this subroutine to read a single character from the serial port.
15370 It may be identical to @code{getchar} for your target system; a
15371 different name is used to allow you to distinguish the two if you wish.
15373 @item void putDebugChar(int)
15374 @findex putDebugChar
15375 Write this subroutine to write a single character to the serial port.
15376 It may be identical to @code{putchar} for your target system; a
15377 different name is used to allow you to distinguish the two if you wish.
15380 @cindex control C, and remote debugging
15381 @cindex interrupting remote targets
15382 If you want @value{GDBN} to be able to stop your program while it is
15383 running, you need to use an interrupt-driven serial driver, and arrange
15384 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
15385 character). That is the character which @value{GDBN} uses to tell the
15386 remote system to stop.
15388 Getting the debugging target to return the proper status to @value{GDBN}
15389 probably requires changes to the standard stub; one quick and dirty way
15390 is to just execute a breakpoint instruction (the ``dirty'' part is that
15391 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
15393 Other routines you need to supply are:
15396 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
15397 @findex exceptionHandler
15398 Write this function to install @var{exception_address} in the exception
15399 handling tables. You need to do this because the stub does not have any
15400 way of knowing what the exception handling tables on your target system
15401 are like (for example, the processor's table might be in @sc{rom},
15402 containing entries which point to a table in @sc{ram}).
15403 @var{exception_number} is the exception number which should be changed;
15404 its meaning is architecture-dependent (for example, different numbers
15405 might represent divide by zero, misaligned access, etc). When this
15406 exception occurs, control should be transferred directly to
15407 @var{exception_address}, and the processor state (stack, registers,
15408 and so on) should be just as it is when a processor exception occurs. So if
15409 you want to use a jump instruction to reach @var{exception_address}, it
15410 should be a simple jump, not a jump to subroutine.
15412 For the 386, @var{exception_address} should be installed as an interrupt
15413 gate so that interrupts are masked while the handler runs. The gate
15414 should be at privilege level 0 (the most privileged level). The
15415 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
15416 help from @code{exceptionHandler}.
15418 @item void flush_i_cache()
15419 @findex flush_i_cache
15420 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
15421 instruction cache, if any, on your target machine. If there is no
15422 instruction cache, this subroutine may be a no-op.
15424 On target machines that have instruction caches, @value{GDBN} requires this
15425 function to make certain that the state of your program is stable.
15429 You must also make sure this library routine is available:
15432 @item void *memset(void *, int, int)
15434 This is the standard library function @code{memset} that sets an area of
15435 memory to a known value. If you have one of the free versions of
15436 @code{libc.a}, @code{memset} can be found there; otherwise, you must
15437 either obtain it from your hardware manufacturer, or write your own.
15440 If you do not use the GNU C compiler, you may need other standard
15441 library subroutines as well; this varies from one stub to another,
15442 but in general the stubs are likely to use any of the common library
15443 subroutines which @code{@value{NGCC}} generates as inline code.
15446 @node Debug Session
15447 @subsection Putting it All Together
15449 @cindex remote serial debugging summary
15450 In summary, when your program is ready to debug, you must follow these
15455 Make sure you have defined the supporting low-level routines
15456 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
15458 @code{getDebugChar}, @code{putDebugChar},
15459 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
15463 Insert these lines near the top of your program:
15471 For the 680x0 stub only, you need to provide a variable called
15472 @code{exceptionHook}. Normally you just use:
15475 void (*exceptionHook)() = 0;
15479 but if before calling @code{set_debug_traps}, you set it to point to a
15480 function in your program, that function is called when
15481 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
15482 error). The function indicated by @code{exceptionHook} is called with
15483 one parameter: an @code{int} which is the exception number.
15486 Compile and link together: your program, the @value{GDBN} debugging stub for
15487 your target architecture, and the supporting subroutines.
15490 Make sure you have a serial connection between your target machine and
15491 the @value{GDBN} host, and identify the serial port on the host.
15494 @c The "remote" target now provides a `load' command, so we should
15495 @c document that. FIXME.
15496 Download your program to your target machine (or get it there by
15497 whatever means the manufacturer provides), and start it.
15500 Start @value{GDBN} on the host, and connect to the target
15501 (@pxref{Connecting,,Connecting to a Remote Target}).
15505 @node Configurations
15506 @chapter Configuration-Specific Information
15508 While nearly all @value{GDBN} commands are available for all native and
15509 cross versions of the debugger, there are some exceptions. This chapter
15510 describes things that are only available in certain configurations.
15512 There are three major categories of configurations: native
15513 configurations, where the host and target are the same, embedded
15514 operating system configurations, which are usually the same for several
15515 different processor architectures, and bare embedded processors, which
15516 are quite different from each other.
15521 * Embedded Processors::
15528 This section describes details specific to particular native
15533 * BSD libkvm Interface:: Debugging BSD kernel memory images
15534 * SVR4 Process Information:: SVR4 process information
15535 * DJGPP Native:: Features specific to the DJGPP port
15536 * Cygwin Native:: Features specific to the Cygwin port
15537 * Hurd Native:: Features specific to @sc{gnu} Hurd
15538 * Neutrino:: Features specific to QNX Neutrino
15539 * Darwin:: Features specific to Darwin
15545 On HP-UX systems, if you refer to a function or variable name that
15546 begins with a dollar sign, @value{GDBN} searches for a user or system
15547 name first, before it searches for a convenience variable.
15550 @node BSD libkvm Interface
15551 @subsection BSD libkvm Interface
15554 @cindex kernel memory image
15555 @cindex kernel crash dump
15557 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
15558 interface that provides a uniform interface for accessing kernel virtual
15559 memory images, including live systems and crash dumps. @value{GDBN}
15560 uses this interface to allow you to debug live kernels and kernel crash
15561 dumps on many native BSD configurations. This is implemented as a
15562 special @code{kvm} debugging target. For debugging a live system, load
15563 the currently running kernel into @value{GDBN} and connect to the
15567 (@value{GDBP}) @b{target kvm}
15570 For debugging crash dumps, provide the file name of the crash dump as an
15574 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
15577 Once connected to the @code{kvm} target, the following commands are
15583 Set current context from the @dfn{Process Control Block} (PCB) address.
15586 Set current context from proc address. This command isn't available on
15587 modern FreeBSD systems.
15590 @node SVR4 Process Information
15591 @subsection SVR4 Process Information
15593 @cindex examine process image
15594 @cindex process info via @file{/proc}
15596 Many versions of SVR4 and compatible systems provide a facility called
15597 @samp{/proc} that can be used to examine the image of a running
15598 process using file-system subroutines. If @value{GDBN} is configured
15599 for an operating system with this facility, the command @code{info
15600 proc} is available to report information about the process running
15601 your program, or about any process running on your system. @code{info
15602 proc} works only on SVR4 systems that include the @code{procfs} code.
15603 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
15604 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
15610 @itemx info proc @var{process-id}
15611 Summarize available information about any running process. If a
15612 process ID is specified by @var{process-id}, display information about
15613 that process; otherwise display information about the program being
15614 debugged. The summary includes the debugged process ID, the command
15615 line used to invoke it, its current working directory, and its
15616 executable file's absolute file name.
15618 On some systems, @var{process-id} can be of the form
15619 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
15620 within a process. If the optional @var{pid} part is missing, it means
15621 a thread from the process being debugged (the leading @samp{/} still
15622 needs to be present, or else @value{GDBN} will interpret the number as
15623 a process ID rather than a thread ID).
15625 @item info proc mappings
15626 @cindex memory address space mappings
15627 Report the memory address space ranges accessible in the program, with
15628 information on whether the process has read, write, or execute access
15629 rights to each range. On @sc{gnu}/Linux systems, each memory range
15630 includes the object file which is mapped to that range, instead of the
15631 memory access rights to that range.
15633 @item info proc stat
15634 @itemx info proc status
15635 @cindex process detailed status information
15636 These subcommands are specific to @sc{gnu}/Linux systems. They show
15637 the process-related information, including the user ID and group ID;
15638 how many threads are there in the process; its virtual memory usage;
15639 the signals that are pending, blocked, and ignored; its TTY; its
15640 consumption of system and user time; its stack size; its @samp{nice}
15641 value; etc. For more information, see the @samp{proc} man page
15642 (type @kbd{man 5 proc} from your shell prompt).
15644 @item info proc all
15645 Show all the information about the process described under all of the
15646 above @code{info proc} subcommands.
15649 @comment These sub-options of 'info proc' were not included when
15650 @comment procfs.c was re-written. Keep their descriptions around
15651 @comment against the day when someone finds the time to put them back in.
15652 @kindex info proc times
15653 @item info proc times
15654 Starting time, user CPU time, and system CPU time for your program and
15657 @kindex info proc id
15659 Report on the process IDs related to your program: its own process ID,
15660 the ID of its parent, the process group ID, and the session ID.
15663 @item set procfs-trace
15664 @kindex set procfs-trace
15665 @cindex @code{procfs} API calls
15666 This command enables and disables tracing of @code{procfs} API calls.
15668 @item show procfs-trace
15669 @kindex show procfs-trace
15670 Show the current state of @code{procfs} API call tracing.
15672 @item set procfs-file @var{file}
15673 @kindex set procfs-file
15674 Tell @value{GDBN} to write @code{procfs} API trace to the named
15675 @var{file}. @value{GDBN} appends the trace info to the previous
15676 contents of the file. The default is to display the trace on the
15679 @item show procfs-file
15680 @kindex show procfs-file
15681 Show the file to which @code{procfs} API trace is written.
15683 @item proc-trace-entry
15684 @itemx proc-trace-exit
15685 @itemx proc-untrace-entry
15686 @itemx proc-untrace-exit
15687 @kindex proc-trace-entry
15688 @kindex proc-trace-exit
15689 @kindex proc-untrace-entry
15690 @kindex proc-untrace-exit
15691 These commands enable and disable tracing of entries into and exits
15692 from the @code{syscall} interface.
15695 @kindex info pidlist
15696 @cindex process list, QNX Neutrino
15697 For QNX Neutrino only, this command displays the list of all the
15698 processes and all the threads within each process.
15701 @kindex info meminfo
15702 @cindex mapinfo list, QNX Neutrino
15703 For QNX Neutrino only, this command displays the list of all mapinfos.
15707 @subsection Features for Debugging @sc{djgpp} Programs
15708 @cindex @sc{djgpp} debugging
15709 @cindex native @sc{djgpp} debugging
15710 @cindex MS-DOS-specific commands
15713 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15714 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15715 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15716 top of real-mode DOS systems and their emulations.
15718 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15719 defines a few commands specific to the @sc{djgpp} port. This
15720 subsection describes those commands.
15725 This is a prefix of @sc{djgpp}-specific commands which print
15726 information about the target system and important OS structures.
15729 @cindex MS-DOS system info
15730 @cindex free memory information (MS-DOS)
15731 @item info dos sysinfo
15732 This command displays assorted information about the underlying
15733 platform: the CPU type and features, the OS version and flavor, the
15734 DPMI version, and the available conventional and DPMI memory.
15739 @cindex segment descriptor tables
15740 @cindex descriptor tables display
15742 @itemx info dos ldt
15743 @itemx info dos idt
15744 These 3 commands display entries from, respectively, Global, Local,
15745 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15746 tables are data structures which store a descriptor for each segment
15747 that is currently in use. The segment's selector is an index into a
15748 descriptor table; the table entry for that index holds the
15749 descriptor's base address and limit, and its attributes and access
15752 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15753 segment (used for both data and the stack), and a DOS segment (which
15754 allows access to DOS/BIOS data structures and absolute addresses in
15755 conventional memory). However, the DPMI host will usually define
15756 additional segments in order to support the DPMI environment.
15758 @cindex garbled pointers
15759 These commands allow to display entries from the descriptor tables.
15760 Without an argument, all entries from the specified table are
15761 displayed. An argument, which should be an integer expression, means
15762 display a single entry whose index is given by the argument. For
15763 example, here's a convenient way to display information about the
15764 debugged program's data segment:
15767 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15768 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15772 This comes in handy when you want to see whether a pointer is outside
15773 the data segment's limit (i.e.@: @dfn{garbled}).
15775 @cindex page tables display (MS-DOS)
15777 @itemx info dos pte
15778 These two commands display entries from, respectively, the Page
15779 Directory and the Page Tables. Page Directories and Page Tables are
15780 data structures which control how virtual memory addresses are mapped
15781 into physical addresses. A Page Table includes an entry for every
15782 page of memory that is mapped into the program's address space; there
15783 may be several Page Tables, each one holding up to 4096 entries. A
15784 Page Directory has up to 4096 entries, one each for every Page Table
15785 that is currently in use.
15787 Without an argument, @kbd{info dos pde} displays the entire Page
15788 Directory, and @kbd{info dos pte} displays all the entries in all of
15789 the Page Tables. An argument, an integer expression, given to the
15790 @kbd{info dos pde} command means display only that entry from the Page
15791 Directory table. An argument given to the @kbd{info dos pte} command
15792 means display entries from a single Page Table, the one pointed to by
15793 the specified entry in the Page Directory.
15795 @cindex direct memory access (DMA) on MS-DOS
15796 These commands are useful when your program uses @dfn{DMA} (Direct
15797 Memory Access), which needs physical addresses to program the DMA
15800 These commands are supported only with some DPMI servers.
15802 @cindex physical address from linear address
15803 @item info dos address-pte @var{addr}
15804 This command displays the Page Table entry for a specified linear
15805 address. The argument @var{addr} is a linear address which should
15806 already have the appropriate segment's base address added to it,
15807 because this command accepts addresses which may belong to @emph{any}
15808 segment. For example, here's how to display the Page Table entry for
15809 the page where a variable @code{i} is stored:
15812 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15813 @exdent @code{Page Table entry for address 0x11a00d30:}
15814 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15818 This says that @code{i} is stored at offset @code{0xd30} from the page
15819 whose physical base address is @code{0x02698000}, and shows all the
15820 attributes of that page.
15822 Note that you must cast the addresses of variables to a @code{char *},
15823 since otherwise the value of @code{__djgpp_base_address}, the base
15824 address of all variables and functions in a @sc{djgpp} program, will
15825 be added using the rules of C pointer arithmetics: if @code{i} is
15826 declared an @code{int}, @value{GDBN} will add 4 times the value of
15827 @code{__djgpp_base_address} to the address of @code{i}.
15829 Here's another example, it displays the Page Table entry for the
15833 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15834 @exdent @code{Page Table entry for address 0x29110:}
15835 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15839 (The @code{+ 3} offset is because the transfer buffer's address is the
15840 3rd member of the @code{_go32_info_block} structure.) The output
15841 clearly shows that this DPMI server maps the addresses in conventional
15842 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15843 linear (@code{0x29110}) addresses are identical.
15845 This command is supported only with some DPMI servers.
15848 @cindex DOS serial data link, remote debugging
15849 In addition to native debugging, the DJGPP port supports remote
15850 debugging via a serial data link. The following commands are specific
15851 to remote serial debugging in the DJGPP port of @value{GDBN}.
15854 @kindex set com1base
15855 @kindex set com1irq
15856 @kindex set com2base
15857 @kindex set com2irq
15858 @kindex set com3base
15859 @kindex set com3irq
15860 @kindex set com4base
15861 @kindex set com4irq
15862 @item set com1base @var{addr}
15863 This command sets the base I/O port address of the @file{COM1} serial
15866 @item set com1irq @var{irq}
15867 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15868 for the @file{COM1} serial port.
15870 There are similar commands @samp{set com2base}, @samp{set com3irq},
15871 etc.@: for setting the port address and the @code{IRQ} lines for the
15874 @kindex show com1base
15875 @kindex show com1irq
15876 @kindex show com2base
15877 @kindex show com2irq
15878 @kindex show com3base
15879 @kindex show com3irq
15880 @kindex show com4base
15881 @kindex show com4irq
15882 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15883 display the current settings of the base address and the @code{IRQ}
15884 lines used by the COM ports.
15887 @kindex info serial
15888 @cindex DOS serial port status
15889 This command prints the status of the 4 DOS serial ports. For each
15890 port, it prints whether it's active or not, its I/O base address and
15891 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15892 counts of various errors encountered so far.
15896 @node Cygwin Native
15897 @subsection Features for Debugging MS Windows PE Executables
15898 @cindex MS Windows debugging
15899 @cindex native Cygwin debugging
15900 @cindex Cygwin-specific commands
15902 @value{GDBN} supports native debugging of MS Windows programs, including
15903 DLLs with and without symbolic debugging information. There are various
15904 additional Cygwin-specific commands, described in this section.
15905 Working with DLLs that have no debugging symbols is described in
15906 @ref{Non-debug DLL Symbols}.
15911 This is a prefix of MS Windows-specific commands which print
15912 information about the target system and important OS structures.
15914 @item info w32 selector
15915 This command displays information returned by
15916 the Win32 API @code{GetThreadSelectorEntry} function.
15917 It takes an optional argument that is evaluated to
15918 a long value to give the information about this given selector.
15919 Without argument, this command displays information
15920 about the six segment registers.
15924 This is a Cygwin-specific alias of @code{info shared}.
15926 @kindex dll-symbols
15928 This command loads symbols from a dll similarly to
15929 add-sym command but without the need to specify a base address.
15931 @kindex set cygwin-exceptions
15932 @cindex debugging the Cygwin DLL
15933 @cindex Cygwin DLL, debugging
15934 @item set cygwin-exceptions @var{mode}
15935 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15936 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15937 @value{GDBN} will delay recognition of exceptions, and may ignore some
15938 exceptions which seem to be caused by internal Cygwin DLL
15939 ``bookkeeping''. This option is meant primarily for debugging the
15940 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15941 @value{GDBN} users with false @code{SIGSEGV} signals.
15943 @kindex show cygwin-exceptions
15944 @item show cygwin-exceptions
15945 Displays whether @value{GDBN} will break on exceptions that happen
15946 inside the Cygwin DLL itself.
15948 @kindex set new-console
15949 @item set new-console @var{mode}
15950 If @var{mode} is @code{on} the debuggee will
15951 be started in a new console on next start.
15952 If @var{mode} is @code{off}i, the debuggee will
15953 be started in the same console as the debugger.
15955 @kindex show new-console
15956 @item show new-console
15957 Displays whether a new console is used
15958 when the debuggee is started.
15960 @kindex set new-group
15961 @item set new-group @var{mode}
15962 This boolean value controls whether the debuggee should
15963 start a new group or stay in the same group as the debugger.
15964 This affects the way the Windows OS handles
15967 @kindex show new-group
15968 @item show new-group
15969 Displays current value of new-group boolean.
15971 @kindex set debugevents
15972 @item set debugevents
15973 This boolean value adds debug output concerning kernel events related
15974 to the debuggee seen by the debugger. This includes events that
15975 signal thread and process creation and exit, DLL loading and
15976 unloading, console interrupts, and debugging messages produced by the
15977 Windows @code{OutputDebugString} API call.
15979 @kindex set debugexec
15980 @item set debugexec
15981 This boolean value adds debug output concerning execute events
15982 (such as resume thread) seen by the debugger.
15984 @kindex set debugexceptions
15985 @item set debugexceptions
15986 This boolean value adds debug output concerning exceptions in the
15987 debuggee seen by the debugger.
15989 @kindex set debugmemory
15990 @item set debugmemory
15991 This boolean value adds debug output concerning debuggee memory reads
15992 and writes by the debugger.
15996 This boolean values specifies whether the debuggee is called
15997 via a shell or directly (default value is on).
16001 Displays if the debuggee will be started with a shell.
16006 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16009 @node Non-debug DLL Symbols
16010 @subsubsection Support for DLLs without Debugging Symbols
16011 @cindex DLLs with no debugging symbols
16012 @cindex Minimal symbols and DLLs
16014 Very often on windows, some of the DLLs that your program relies on do
16015 not include symbolic debugging information (for example,
16016 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16017 symbols in a DLL, it relies on the minimal amount of symbolic
16018 information contained in the DLL's export table. This section
16019 describes working with such symbols, known internally to @value{GDBN} as
16020 ``minimal symbols''.
16022 Note that before the debugged program has started execution, no DLLs
16023 will have been loaded. The easiest way around this problem is simply to
16024 start the program --- either by setting a breakpoint or letting the
16025 program run once to completion. It is also possible to force
16026 @value{GDBN} to load a particular DLL before starting the executable ---
16027 see the shared library information in @ref{Files}, or the
16028 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16029 explicitly loading symbols from a DLL with no debugging information will
16030 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16031 which may adversely affect symbol lookup performance.
16033 @subsubsection DLL Name Prefixes
16035 In keeping with the naming conventions used by the Microsoft debugging
16036 tools, DLL export symbols are made available with a prefix based on the
16037 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16038 also entered into the symbol table, so @code{CreateFileA} is often
16039 sufficient. In some cases there will be name clashes within a program
16040 (particularly if the executable itself includes full debugging symbols)
16041 necessitating the use of the fully qualified name when referring to the
16042 contents of the DLL. Use single-quotes around the name to avoid the
16043 exclamation mark (``!'') being interpreted as a language operator.
16045 Note that the internal name of the DLL may be all upper-case, even
16046 though the file name of the DLL is lower-case, or vice-versa. Since
16047 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16048 some confusion. If in doubt, try the @code{info functions} and
16049 @code{info variables} commands or even @code{maint print msymbols}
16050 (@pxref{Symbols}). Here's an example:
16053 (@value{GDBP}) info function CreateFileA
16054 All functions matching regular expression "CreateFileA":
16056 Non-debugging symbols:
16057 0x77e885f4 CreateFileA
16058 0x77e885f4 KERNEL32!CreateFileA
16062 (@value{GDBP}) info function !
16063 All functions matching regular expression "!":
16065 Non-debugging symbols:
16066 0x6100114c cygwin1!__assert
16067 0x61004034 cygwin1!_dll_crt0@@0
16068 0x61004240 cygwin1!dll_crt0(per_process *)
16072 @subsubsection Working with Minimal Symbols
16074 Symbols extracted from a DLL's export table do not contain very much
16075 type information. All that @value{GDBN} can do is guess whether a symbol
16076 refers to a function or variable depending on the linker section that
16077 contains the symbol. Also note that the actual contents of the memory
16078 contained in a DLL are not available unless the program is running. This
16079 means that you cannot examine the contents of a variable or disassemble
16080 a function within a DLL without a running program.
16082 Variables are generally treated as pointers and dereferenced
16083 automatically. For this reason, it is often necessary to prefix a
16084 variable name with the address-of operator (``&'') and provide explicit
16085 type information in the command. Here's an example of the type of
16089 (@value{GDBP}) print 'cygwin1!__argv'
16094 (@value{GDBP}) x 'cygwin1!__argv'
16095 0x10021610: "\230y\""
16098 And two possible solutions:
16101 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16102 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16106 (@value{GDBP}) x/2x &'cygwin1!__argv'
16107 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16108 (@value{GDBP}) x/x 0x10021608
16109 0x10021608: 0x0022fd98
16110 (@value{GDBP}) x/s 0x0022fd98
16111 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16114 Setting a break point within a DLL is possible even before the program
16115 starts execution. However, under these circumstances, @value{GDBN} can't
16116 examine the initial instructions of the function in order to skip the
16117 function's frame set-up code. You can work around this by using ``*&''
16118 to set the breakpoint at a raw memory address:
16121 (@value{GDBP}) break *&'python22!PyOS_Readline'
16122 Breakpoint 1 at 0x1e04eff0
16125 The author of these extensions is not entirely convinced that setting a
16126 break point within a shared DLL like @file{kernel32.dll} is completely
16130 @subsection Commands Specific to @sc{gnu} Hurd Systems
16131 @cindex @sc{gnu} Hurd debugging
16133 This subsection describes @value{GDBN} commands specific to the
16134 @sc{gnu} Hurd native debugging.
16139 @kindex set signals@r{, Hurd command}
16140 @kindex set sigs@r{, Hurd command}
16141 This command toggles the state of inferior signal interception by
16142 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16143 affected by this command. @code{sigs} is a shorthand alias for
16148 @kindex show signals@r{, Hurd command}
16149 @kindex show sigs@r{, Hurd command}
16150 Show the current state of intercepting inferior's signals.
16152 @item set signal-thread
16153 @itemx set sigthread
16154 @kindex set signal-thread
16155 @kindex set sigthread
16156 This command tells @value{GDBN} which thread is the @code{libc} signal
16157 thread. That thread is run when a signal is delivered to a running
16158 process. @code{set sigthread} is the shorthand alias of @code{set
16161 @item show signal-thread
16162 @itemx show sigthread
16163 @kindex show signal-thread
16164 @kindex show sigthread
16165 These two commands show which thread will run when the inferior is
16166 delivered a signal.
16169 @kindex set stopped@r{, Hurd command}
16170 This commands tells @value{GDBN} that the inferior process is stopped,
16171 as with the @code{SIGSTOP} signal. The stopped process can be
16172 continued by delivering a signal to it.
16175 @kindex show stopped@r{, Hurd command}
16176 This command shows whether @value{GDBN} thinks the debuggee is
16179 @item set exceptions
16180 @kindex set exceptions@r{, Hurd command}
16181 Use this command to turn off trapping of exceptions in the inferior.
16182 When exception trapping is off, neither breakpoints nor
16183 single-stepping will work. To restore the default, set exception
16186 @item show exceptions
16187 @kindex show exceptions@r{, Hurd command}
16188 Show the current state of trapping exceptions in the inferior.
16190 @item set task pause
16191 @kindex set task@r{, Hurd commands}
16192 @cindex task attributes (@sc{gnu} Hurd)
16193 @cindex pause current task (@sc{gnu} Hurd)
16194 This command toggles task suspension when @value{GDBN} has control.
16195 Setting it to on takes effect immediately, and the task is suspended
16196 whenever @value{GDBN} gets control. Setting it to off will take
16197 effect the next time the inferior is continued. If this option is set
16198 to off, you can use @code{set thread default pause on} or @code{set
16199 thread pause on} (see below) to pause individual threads.
16201 @item show task pause
16202 @kindex show task@r{, Hurd commands}
16203 Show the current state of task suspension.
16205 @item set task detach-suspend-count
16206 @cindex task suspend count
16207 @cindex detach from task, @sc{gnu} Hurd
16208 This command sets the suspend count the task will be left with when
16209 @value{GDBN} detaches from it.
16211 @item show task detach-suspend-count
16212 Show the suspend count the task will be left with when detaching.
16214 @item set task exception-port
16215 @itemx set task excp
16216 @cindex task exception port, @sc{gnu} Hurd
16217 This command sets the task exception port to which @value{GDBN} will
16218 forward exceptions. The argument should be the value of the @dfn{send
16219 rights} of the task. @code{set task excp} is a shorthand alias.
16221 @item set noninvasive
16222 @cindex noninvasive task options
16223 This command switches @value{GDBN} to a mode that is the least
16224 invasive as far as interfering with the inferior is concerned. This
16225 is the same as using @code{set task pause}, @code{set exceptions}, and
16226 @code{set signals} to values opposite to the defaults.
16228 @item info send-rights
16229 @itemx info receive-rights
16230 @itemx info port-rights
16231 @itemx info port-sets
16232 @itemx info dead-names
16235 @cindex send rights, @sc{gnu} Hurd
16236 @cindex receive rights, @sc{gnu} Hurd
16237 @cindex port rights, @sc{gnu} Hurd
16238 @cindex port sets, @sc{gnu} Hurd
16239 @cindex dead names, @sc{gnu} Hurd
16240 These commands display information about, respectively, send rights,
16241 receive rights, port rights, port sets, and dead names of a task.
16242 There are also shorthand aliases: @code{info ports} for @code{info
16243 port-rights} and @code{info psets} for @code{info port-sets}.
16245 @item set thread pause
16246 @kindex set thread@r{, Hurd command}
16247 @cindex thread properties, @sc{gnu} Hurd
16248 @cindex pause current thread (@sc{gnu} Hurd)
16249 This command toggles current thread suspension when @value{GDBN} has
16250 control. Setting it to on takes effect immediately, and the current
16251 thread is suspended whenever @value{GDBN} gets control. Setting it to
16252 off will take effect the next time the inferior is continued.
16253 Normally, this command has no effect, since when @value{GDBN} has
16254 control, the whole task is suspended. However, if you used @code{set
16255 task pause off} (see above), this command comes in handy to suspend
16256 only the current thread.
16258 @item show thread pause
16259 @kindex show thread@r{, Hurd command}
16260 This command shows the state of current thread suspension.
16262 @item set thread run
16263 This command sets whether the current thread is allowed to run.
16265 @item show thread run
16266 Show whether the current thread is allowed to run.
16268 @item set thread detach-suspend-count
16269 @cindex thread suspend count, @sc{gnu} Hurd
16270 @cindex detach from thread, @sc{gnu} Hurd
16271 This command sets the suspend count @value{GDBN} will leave on a
16272 thread when detaching. This number is relative to the suspend count
16273 found by @value{GDBN} when it notices the thread; use @code{set thread
16274 takeover-suspend-count} to force it to an absolute value.
16276 @item show thread detach-suspend-count
16277 Show the suspend count @value{GDBN} will leave on the thread when
16280 @item set thread exception-port
16281 @itemx set thread excp
16282 Set the thread exception port to which to forward exceptions. This
16283 overrides the port set by @code{set task exception-port} (see above).
16284 @code{set thread excp} is the shorthand alias.
16286 @item set thread takeover-suspend-count
16287 Normally, @value{GDBN}'s thread suspend counts are relative to the
16288 value @value{GDBN} finds when it notices each thread. This command
16289 changes the suspend counts to be absolute instead.
16291 @item set thread default
16292 @itemx show thread default
16293 @cindex thread default settings, @sc{gnu} Hurd
16294 Each of the above @code{set thread} commands has a @code{set thread
16295 default} counterpart (e.g., @code{set thread default pause}, @code{set
16296 thread default exception-port}, etc.). The @code{thread default}
16297 variety of commands sets the default thread properties for all
16298 threads; you can then change the properties of individual threads with
16299 the non-default commands.
16304 @subsection QNX Neutrino
16305 @cindex QNX Neutrino
16307 @value{GDBN} provides the following commands specific to the QNX
16311 @item set debug nto-debug
16312 @kindex set debug nto-debug
16313 When set to on, enables debugging messages specific to the QNX
16316 @item show debug nto-debug
16317 @kindex show debug nto-debug
16318 Show the current state of QNX Neutrino messages.
16325 @value{GDBN} provides the following commands specific to the Darwin target:
16328 @item set debug darwin @var{num}
16329 @kindex set debug darwin
16330 When set to a non zero value, enables debugging messages specific to
16331 the Darwin support. Higher values produce more verbose output.
16333 @item show debug darwin
16334 @kindex show debug darwin
16335 Show the current state of Darwin messages.
16337 @item set debug mach-o @var{num}
16338 @kindex set debug mach-o
16339 When set to a non zero value, enables debugging messages while
16340 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
16341 file format used on Darwin for object and executable files.) Higher
16342 values produce more verbose output. This is a command to diagnose
16343 problems internal to @value{GDBN} and should not be needed in normal
16346 @item show debug mach-o
16347 @kindex show debug mach-o
16348 Show the current state of Mach-O file messages.
16350 @item set mach-exceptions on
16351 @itemx set mach-exceptions off
16352 @kindex set mach-exceptions
16353 On Darwin, faults are first reported as a Mach exception and are then
16354 mapped to a Posix signal. Use this command to turn on trapping of
16355 Mach exceptions in the inferior. This might be sometimes useful to
16356 better understand the cause of a fault. The default is off.
16358 @item show mach-exceptions
16359 @kindex show mach-exceptions
16360 Show the current state of exceptions trapping.
16365 @section Embedded Operating Systems
16367 This section describes configurations involving the debugging of
16368 embedded operating systems that are available for several different
16372 * VxWorks:: Using @value{GDBN} with VxWorks
16375 @value{GDBN} includes the ability to debug programs running on
16376 various real-time operating systems.
16379 @subsection Using @value{GDBN} with VxWorks
16385 @kindex target vxworks
16386 @item target vxworks @var{machinename}
16387 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
16388 is the target system's machine name or IP address.
16392 On VxWorks, @code{load} links @var{filename} dynamically on the
16393 current target system as well as adding its symbols in @value{GDBN}.
16395 @value{GDBN} enables developers to spawn and debug tasks running on networked
16396 VxWorks targets from a Unix host. Already-running tasks spawned from
16397 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
16398 both the Unix host and on the VxWorks target. The program
16399 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
16400 installed with the name @code{vxgdb}, to distinguish it from a
16401 @value{GDBN} for debugging programs on the host itself.)
16404 @item VxWorks-timeout @var{args}
16405 @kindex vxworks-timeout
16406 All VxWorks-based targets now support the option @code{vxworks-timeout}.
16407 This option is set by the user, and @var{args} represents the number of
16408 seconds @value{GDBN} waits for responses to rpc's. You might use this if
16409 your VxWorks target is a slow software simulator or is on the far side
16410 of a thin network line.
16413 The following information on connecting to VxWorks was current when
16414 this manual was produced; newer releases of VxWorks may use revised
16417 @findex INCLUDE_RDB
16418 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
16419 to include the remote debugging interface routines in the VxWorks
16420 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
16421 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
16422 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
16423 source debugging task @code{tRdbTask} when VxWorks is booted. For more
16424 information on configuring and remaking VxWorks, see the manufacturer's
16426 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
16428 Once you have included @file{rdb.a} in your VxWorks system image and set
16429 your Unix execution search path to find @value{GDBN}, you are ready to
16430 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
16431 @code{vxgdb}, depending on your installation).
16433 @value{GDBN} comes up showing the prompt:
16440 * VxWorks Connection:: Connecting to VxWorks
16441 * VxWorks Download:: VxWorks download
16442 * VxWorks Attach:: Running tasks
16445 @node VxWorks Connection
16446 @subsubsection Connecting to VxWorks
16448 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
16449 network. To connect to a target whose host name is ``@code{tt}'', type:
16452 (vxgdb) target vxworks tt
16456 @value{GDBN} displays messages like these:
16459 Attaching remote machine across net...
16464 @value{GDBN} then attempts to read the symbol tables of any object modules
16465 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
16466 these files by searching the directories listed in the command search
16467 path (@pxref{Environment, ,Your Program's Environment}); if it fails
16468 to find an object file, it displays a message such as:
16471 prog.o: No such file or directory.
16474 When this happens, add the appropriate directory to the search path with
16475 the @value{GDBN} command @code{path}, and execute the @code{target}
16478 @node VxWorks Download
16479 @subsubsection VxWorks Download
16481 @cindex download to VxWorks
16482 If you have connected to the VxWorks target and you want to debug an
16483 object that has not yet been loaded, you can use the @value{GDBN}
16484 @code{load} command to download a file from Unix to VxWorks
16485 incrementally. The object file given as an argument to the @code{load}
16486 command is actually opened twice: first by the VxWorks target in order
16487 to download the code, then by @value{GDBN} in order to read the symbol
16488 table. This can lead to problems if the current working directories on
16489 the two systems differ. If both systems have NFS mounted the same
16490 filesystems, you can avoid these problems by using absolute paths.
16491 Otherwise, it is simplest to set the working directory on both systems
16492 to the directory in which the object file resides, and then to reference
16493 the file by its name, without any path. For instance, a program
16494 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
16495 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
16496 program, type this on VxWorks:
16499 -> cd "@var{vxpath}/vw/demo/rdb"
16503 Then, in @value{GDBN}, type:
16506 (vxgdb) cd @var{hostpath}/vw/demo/rdb
16507 (vxgdb) load prog.o
16510 @value{GDBN} displays a response similar to this:
16513 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
16516 You can also use the @code{load} command to reload an object module
16517 after editing and recompiling the corresponding source file. Note that
16518 this makes @value{GDBN} delete all currently-defined breakpoints,
16519 auto-displays, and convenience variables, and to clear the value
16520 history. (This is necessary in order to preserve the integrity of
16521 debugger's data structures that reference the target system's symbol
16524 @node VxWorks Attach
16525 @subsubsection Running Tasks
16527 @cindex running VxWorks tasks
16528 You can also attach to an existing task using the @code{attach} command as
16532 (vxgdb) attach @var{task}
16536 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
16537 or suspended when you attach to it. Running tasks are suspended at
16538 the time of attachment.
16540 @node Embedded Processors
16541 @section Embedded Processors
16543 This section goes into details specific to particular embedded
16546 @cindex send command to simulator
16547 Whenever a specific embedded processor has a simulator, @value{GDBN}
16548 allows to send an arbitrary command to the simulator.
16551 @item sim @var{command}
16552 @kindex sim@r{, a command}
16553 Send an arbitrary @var{command} string to the simulator. Consult the
16554 documentation for the specific simulator in use for information about
16555 acceptable commands.
16561 * M32R/D:: Renesas M32R/D
16562 * M68K:: Motorola M68K
16563 * MIPS Embedded:: MIPS Embedded
16564 * OpenRISC 1000:: OpenRisc 1000
16565 * PA:: HP PA Embedded
16566 * PowerPC Embedded:: PowerPC Embedded
16567 * Sparclet:: Tsqware Sparclet
16568 * Sparclite:: Fujitsu Sparclite
16569 * Z8000:: Zilog Z8000
16572 * Super-H:: Renesas Super-H
16581 @item target rdi @var{dev}
16582 ARM Angel monitor, via RDI library interface to ADP protocol. You may
16583 use this target to communicate with both boards running the Angel
16584 monitor, or with the EmbeddedICE JTAG debug device.
16587 @item target rdp @var{dev}
16592 @value{GDBN} provides the following ARM-specific commands:
16595 @item set arm disassembler
16597 This commands selects from a list of disassembly styles. The
16598 @code{"std"} style is the standard style.
16600 @item show arm disassembler
16602 Show the current disassembly style.
16604 @item set arm apcs32
16605 @cindex ARM 32-bit mode
16606 This command toggles ARM operation mode between 32-bit and 26-bit.
16608 @item show arm apcs32
16609 Display the current usage of the ARM 32-bit mode.
16611 @item set arm fpu @var{fputype}
16612 This command sets the ARM floating-point unit (FPU) type. The
16613 argument @var{fputype} can be one of these:
16617 Determine the FPU type by querying the OS ABI.
16619 Software FPU, with mixed-endian doubles on little-endian ARM
16622 GCC-compiled FPA co-processor.
16624 Software FPU with pure-endian doubles.
16630 Show the current type of the FPU.
16633 This command forces @value{GDBN} to use the specified ABI.
16636 Show the currently used ABI.
16638 @item set arm fallback-mode (arm|thumb|auto)
16639 @value{GDBN} uses the symbol table, when available, to determine
16640 whether instructions are ARM or Thumb. This command controls
16641 @value{GDBN}'s default behavior when the symbol table is not
16642 available. The default is @samp{auto}, which causes @value{GDBN} to
16643 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16646 @item show arm fallback-mode
16647 Show the current fallback instruction mode.
16649 @item set arm force-mode (arm|thumb|auto)
16650 This command overrides use of the symbol table to determine whether
16651 instructions are ARM or Thumb. The default is @samp{auto}, which
16652 causes @value{GDBN} to use the symbol table and then the setting
16653 of @samp{set arm fallback-mode}.
16655 @item show arm force-mode
16656 Show the current forced instruction mode.
16658 @item set debug arm
16659 Toggle whether to display ARM-specific debugging messages from the ARM
16660 target support subsystem.
16662 @item show debug arm
16663 Show whether ARM-specific debugging messages are enabled.
16666 The following commands are available when an ARM target is debugged
16667 using the RDI interface:
16670 @item rdilogfile @r{[}@var{file}@r{]}
16672 @cindex ADP (Angel Debugger Protocol) logging
16673 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16674 With an argument, sets the log file to the specified @var{file}. With
16675 no argument, show the current log file name. The default log file is
16678 @item rdilogenable @r{[}@var{arg}@r{]}
16679 @kindex rdilogenable
16680 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16681 enables logging, with an argument 0 or @code{"no"} disables it. With
16682 no arguments displays the current setting. When logging is enabled,
16683 ADP packets exchanged between @value{GDBN} and the RDI target device
16684 are logged to a file.
16686 @item set rdiromatzero
16687 @kindex set rdiromatzero
16688 @cindex ROM at zero address, RDI
16689 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16690 vector catching is disabled, so that zero address can be used. If off
16691 (the default), vector catching is enabled. For this command to take
16692 effect, it needs to be invoked prior to the @code{target rdi} command.
16694 @item show rdiromatzero
16695 @kindex show rdiromatzero
16696 Show the current setting of ROM at zero address.
16698 @item set rdiheartbeat
16699 @kindex set rdiheartbeat
16700 @cindex RDI heartbeat
16701 Enable or disable RDI heartbeat packets. It is not recommended to
16702 turn on this option, since it confuses ARM and EPI JTAG interface, as
16703 well as the Angel monitor.
16705 @item show rdiheartbeat
16706 @kindex show rdiheartbeat
16707 Show the setting of RDI heartbeat packets.
16712 @subsection Renesas M32R/D and M32R/SDI
16715 @kindex target m32r
16716 @item target m32r @var{dev}
16717 Renesas M32R/D ROM monitor.
16719 @kindex target m32rsdi
16720 @item target m32rsdi @var{dev}
16721 Renesas M32R SDI server, connected via parallel port to the board.
16724 The following @value{GDBN} commands are specific to the M32R monitor:
16727 @item set download-path @var{path}
16728 @kindex set download-path
16729 @cindex find downloadable @sc{srec} files (M32R)
16730 Set the default path for finding downloadable @sc{srec} files.
16732 @item show download-path
16733 @kindex show download-path
16734 Show the default path for downloadable @sc{srec} files.
16736 @item set board-address @var{addr}
16737 @kindex set board-address
16738 @cindex M32-EVA target board address
16739 Set the IP address for the M32R-EVA target board.
16741 @item show board-address
16742 @kindex show board-address
16743 Show the current IP address of the target board.
16745 @item set server-address @var{addr}
16746 @kindex set server-address
16747 @cindex download server address (M32R)
16748 Set the IP address for the download server, which is the @value{GDBN}'s
16751 @item show server-address
16752 @kindex show server-address
16753 Display the IP address of the download server.
16755 @item upload @r{[}@var{file}@r{]}
16756 @kindex upload@r{, M32R}
16757 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16758 upload capability. If no @var{file} argument is given, the current
16759 executable file is uploaded.
16761 @item tload @r{[}@var{file}@r{]}
16762 @kindex tload@r{, M32R}
16763 Test the @code{upload} command.
16766 The following commands are available for M32R/SDI:
16771 @cindex reset SDI connection, M32R
16772 This command resets the SDI connection.
16776 This command shows the SDI connection status.
16779 @kindex debug_chaos
16780 @cindex M32R/Chaos debugging
16781 Instructs the remote that M32R/Chaos debugging is to be used.
16783 @item use_debug_dma
16784 @kindex use_debug_dma
16785 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16788 @kindex use_mon_code
16789 Instructs the remote to use the MON_CODE method of accessing memory.
16792 @kindex use_ib_break
16793 Instructs the remote to set breakpoints by IB break.
16795 @item use_dbt_break
16796 @kindex use_dbt_break
16797 Instructs the remote to set breakpoints by DBT.
16803 The Motorola m68k configuration includes ColdFire support, and a
16804 target command for the following ROM monitor.
16808 @kindex target dbug
16809 @item target dbug @var{dev}
16810 dBUG ROM monitor for Motorola ColdFire.
16814 @node MIPS Embedded
16815 @subsection MIPS Embedded
16817 @cindex MIPS boards
16818 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16819 MIPS board attached to a serial line. This is available when
16820 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16823 Use these @value{GDBN} commands to specify the connection to your target board:
16826 @item target mips @var{port}
16827 @kindex target mips @var{port}
16828 To run a program on the board, start up @code{@value{GDBP}} with the
16829 name of your program as the argument. To connect to the board, use the
16830 command @samp{target mips @var{port}}, where @var{port} is the name of
16831 the serial port connected to the board. If the program has not already
16832 been downloaded to the board, you may use the @code{load} command to
16833 download it. You can then use all the usual @value{GDBN} commands.
16835 For example, this sequence connects to the target board through a serial
16836 port, and loads and runs a program called @var{prog} through the
16840 host$ @value{GDBP} @var{prog}
16841 @value{GDBN} is free software and @dots{}
16842 (@value{GDBP}) target mips /dev/ttyb
16843 (@value{GDBP}) load @var{prog}
16847 @item target mips @var{hostname}:@var{portnumber}
16848 On some @value{GDBN} host configurations, you can specify a TCP
16849 connection (for instance, to a serial line managed by a terminal
16850 concentrator) instead of a serial port, using the syntax
16851 @samp{@var{hostname}:@var{portnumber}}.
16853 @item target pmon @var{port}
16854 @kindex target pmon @var{port}
16857 @item target ddb @var{port}
16858 @kindex target ddb @var{port}
16859 NEC's DDB variant of PMON for Vr4300.
16861 @item target lsi @var{port}
16862 @kindex target lsi @var{port}
16863 LSI variant of PMON.
16865 @kindex target r3900
16866 @item target r3900 @var{dev}
16867 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16869 @kindex target array
16870 @item target array @var{dev}
16871 Array Tech LSI33K RAID controller board.
16877 @value{GDBN} also supports these special commands for MIPS targets:
16880 @item set mipsfpu double
16881 @itemx set mipsfpu single
16882 @itemx set mipsfpu none
16883 @itemx set mipsfpu auto
16884 @itemx show mipsfpu
16885 @kindex set mipsfpu
16886 @kindex show mipsfpu
16887 @cindex MIPS remote floating point
16888 @cindex floating point, MIPS remote
16889 If your target board does not support the MIPS floating point
16890 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16891 need this, you may wish to put the command in your @value{GDBN} init
16892 file). This tells @value{GDBN} how to find the return value of
16893 functions which return floating point values. It also allows
16894 @value{GDBN} to avoid saving the floating point registers when calling
16895 functions on the board. If you are using a floating point coprocessor
16896 with only single precision floating point support, as on the @sc{r4650}
16897 processor, use the command @samp{set mipsfpu single}. The default
16898 double precision floating point coprocessor may be selected using
16899 @samp{set mipsfpu double}.
16901 In previous versions the only choices were double precision or no
16902 floating point, so @samp{set mipsfpu on} will select double precision
16903 and @samp{set mipsfpu off} will select no floating point.
16905 As usual, you can inquire about the @code{mipsfpu} variable with
16906 @samp{show mipsfpu}.
16908 @item set timeout @var{seconds}
16909 @itemx set retransmit-timeout @var{seconds}
16910 @itemx show timeout
16911 @itemx show retransmit-timeout
16912 @cindex @code{timeout}, MIPS protocol
16913 @cindex @code{retransmit-timeout}, MIPS protocol
16914 @kindex set timeout
16915 @kindex show timeout
16916 @kindex set retransmit-timeout
16917 @kindex show retransmit-timeout
16918 You can control the timeout used while waiting for a packet, in the MIPS
16919 remote protocol, with the @code{set timeout @var{seconds}} command. The
16920 default is 5 seconds. Similarly, you can control the timeout used while
16921 waiting for an acknowledgment of a packet with the @code{set
16922 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16923 You can inspect both values with @code{show timeout} and @code{show
16924 retransmit-timeout}. (These commands are @emph{only} available when
16925 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16927 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16928 is waiting for your program to stop. In that case, @value{GDBN} waits
16929 forever because it has no way of knowing how long the program is going
16930 to run before stopping.
16932 @item set syn-garbage-limit @var{num}
16933 @kindex set syn-garbage-limit@r{, MIPS remote}
16934 @cindex synchronize with remote MIPS target
16935 Limit the maximum number of characters @value{GDBN} should ignore when
16936 it tries to synchronize with the remote target. The default is 10
16937 characters. Setting the limit to -1 means there's no limit.
16939 @item show syn-garbage-limit
16940 @kindex show syn-garbage-limit@r{, MIPS remote}
16941 Show the current limit on the number of characters to ignore when
16942 trying to synchronize with the remote system.
16944 @item set monitor-prompt @var{prompt}
16945 @kindex set monitor-prompt@r{, MIPS remote}
16946 @cindex remote monitor prompt
16947 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16948 remote monitor. The default depends on the target:
16958 @item show monitor-prompt
16959 @kindex show monitor-prompt@r{, MIPS remote}
16960 Show the current strings @value{GDBN} expects as the prompt from the
16963 @item set monitor-warnings
16964 @kindex set monitor-warnings@r{, MIPS remote}
16965 Enable or disable monitor warnings about hardware breakpoints. This
16966 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16967 display warning messages whose codes are returned by the @code{lsi}
16968 PMON monitor for breakpoint commands.
16970 @item show monitor-warnings
16971 @kindex show monitor-warnings@r{, MIPS remote}
16972 Show the current setting of printing monitor warnings.
16974 @item pmon @var{command}
16975 @kindex pmon@r{, MIPS remote}
16976 @cindex send PMON command
16977 This command allows sending an arbitrary @var{command} string to the
16978 monitor. The monitor must be in debug mode for this to work.
16981 @node OpenRISC 1000
16982 @subsection OpenRISC 1000
16983 @cindex OpenRISC 1000
16985 @cindex or1k boards
16986 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16987 about platform and commands.
16991 @kindex target jtag
16992 @item target jtag jtag://@var{host}:@var{port}
16994 Connects to remote JTAG server.
16995 JTAG remote server can be either an or1ksim or JTAG server,
16996 connected via parallel port to the board.
16998 Example: @code{target jtag jtag://localhost:9999}
17001 @item or1ksim @var{command}
17002 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17003 Simulator, proprietary commands can be executed.
17005 @kindex info or1k spr
17006 @item info or1k spr
17007 Displays spr groups.
17009 @item info or1k spr @var{group}
17010 @itemx info or1k spr @var{groupno}
17011 Displays register names in selected group.
17013 @item info or1k spr @var{group} @var{register}
17014 @itemx info or1k spr @var{register}
17015 @itemx info or1k spr @var{groupno} @var{registerno}
17016 @itemx info or1k spr @var{registerno}
17017 Shows information about specified spr register.
17020 @item spr @var{group} @var{register} @var{value}
17021 @itemx spr @var{register @var{value}}
17022 @itemx spr @var{groupno} @var{registerno @var{value}}
17023 @itemx spr @var{registerno @var{value}}
17024 Writes @var{value} to specified spr register.
17027 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17028 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17029 program execution and is thus much faster. Hardware breakpoints/watchpoint
17030 triggers can be set using:
17033 Load effective address/data
17035 Store effective address/data
17037 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17042 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17043 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17045 @code{htrace} commands:
17046 @cindex OpenRISC 1000 htrace
17049 @item hwatch @var{conditional}
17050 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17051 or Data. For example:
17053 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17055 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17059 Display information about current HW trace configuration.
17061 @item htrace trigger @var{conditional}
17062 Set starting criteria for HW trace.
17064 @item htrace qualifier @var{conditional}
17065 Set acquisition qualifier for HW trace.
17067 @item htrace stop @var{conditional}
17068 Set HW trace stopping criteria.
17070 @item htrace record [@var{data}]*
17071 Selects the data to be recorded, when qualifier is met and HW trace was
17074 @item htrace enable
17075 @itemx htrace disable
17076 Enables/disables the HW trace.
17078 @item htrace rewind [@var{filename}]
17079 Clears currently recorded trace data.
17081 If filename is specified, new trace file is made and any newly collected data
17082 will be written there.
17084 @item htrace print [@var{start} [@var{len}]]
17085 Prints trace buffer, using current record configuration.
17087 @item htrace mode continuous
17088 Set continuous trace mode.
17090 @item htrace mode suspend
17091 Set suspend trace mode.
17095 @node PowerPC Embedded
17096 @subsection PowerPC Embedded
17098 @value{GDBN} provides the following PowerPC-specific commands:
17101 @kindex set powerpc
17102 @item set powerpc soft-float
17103 @itemx show powerpc soft-float
17104 Force @value{GDBN} to use (or not use) a software floating point calling
17105 convention. By default, @value{GDBN} selects the calling convention based
17106 on the selected architecture and the provided executable file.
17108 @item set powerpc vector-abi
17109 @itemx show powerpc vector-abi
17110 Force @value{GDBN} to use the specified calling convention for vector
17111 arguments and return values. The valid options are @samp{auto};
17112 @samp{generic}, to avoid vector registers even if they are present;
17113 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
17114 registers. By default, @value{GDBN} selects the calling convention
17115 based on the selected architecture and the provided executable file.
17117 @kindex target dink32
17118 @item target dink32 @var{dev}
17119 DINK32 ROM monitor.
17121 @kindex target ppcbug
17122 @item target ppcbug @var{dev}
17123 @kindex target ppcbug1
17124 @item target ppcbug1 @var{dev}
17125 PPCBUG ROM monitor for PowerPC.
17128 @item target sds @var{dev}
17129 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
17132 @cindex SDS protocol
17133 The following commands specific to the SDS protocol are supported
17137 @item set sdstimeout @var{nsec}
17138 @kindex set sdstimeout
17139 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
17140 default is 2 seconds.
17142 @item show sdstimeout
17143 @kindex show sdstimeout
17144 Show the current value of the SDS timeout.
17146 @item sds @var{command}
17147 @kindex sds@r{, a command}
17148 Send the specified @var{command} string to the SDS monitor.
17153 @subsection HP PA Embedded
17157 @kindex target op50n
17158 @item target op50n @var{dev}
17159 OP50N monitor, running on an OKI HPPA board.
17161 @kindex target w89k
17162 @item target w89k @var{dev}
17163 W89K monitor, running on a Winbond HPPA board.
17168 @subsection Tsqware Sparclet
17172 @value{GDBN} enables developers to debug tasks running on
17173 Sparclet targets from a Unix host.
17174 @value{GDBN} uses code that runs on
17175 both the Unix host and on the Sparclet target. The program
17176 @code{@value{GDBP}} is installed and executed on the Unix host.
17179 @item remotetimeout @var{args}
17180 @kindex remotetimeout
17181 @value{GDBN} supports the option @code{remotetimeout}.
17182 This option is set by the user, and @var{args} represents the number of
17183 seconds @value{GDBN} waits for responses.
17186 @cindex compiling, on Sparclet
17187 When compiling for debugging, include the options @samp{-g} to get debug
17188 information and @samp{-Ttext} to relocate the program to where you wish to
17189 load it on the target. You may also want to add the options @samp{-n} or
17190 @samp{-N} in order to reduce the size of the sections. Example:
17193 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
17196 You can use @code{objdump} to verify that the addresses are what you intended:
17199 sparclet-aout-objdump --headers --syms prog
17202 @cindex running, on Sparclet
17204 your Unix execution search path to find @value{GDBN}, you are ready to
17205 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
17206 (or @code{sparclet-aout-gdb}, depending on your installation).
17208 @value{GDBN} comes up showing the prompt:
17215 * Sparclet File:: Setting the file to debug
17216 * Sparclet Connection:: Connecting to Sparclet
17217 * Sparclet Download:: Sparclet download
17218 * Sparclet Execution:: Running and debugging
17221 @node Sparclet File
17222 @subsubsection Setting File to Debug
17224 The @value{GDBN} command @code{file} lets you choose with program to debug.
17227 (gdbslet) file prog
17231 @value{GDBN} then attempts to read the symbol table of @file{prog}.
17232 @value{GDBN} locates
17233 the file by searching the directories listed in the command search
17235 If the file was compiled with debug information (option @samp{-g}), source
17236 files will be searched as well.
17237 @value{GDBN} locates
17238 the source files by searching the directories listed in the directory search
17239 path (@pxref{Environment, ,Your Program's Environment}).
17241 to find a file, it displays a message such as:
17244 prog: No such file or directory.
17247 When this happens, add the appropriate directories to the search paths with
17248 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
17249 @code{target} command again.
17251 @node Sparclet Connection
17252 @subsubsection Connecting to Sparclet
17254 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
17255 To connect to a target on serial port ``@code{ttya}'', type:
17258 (gdbslet) target sparclet /dev/ttya
17259 Remote target sparclet connected to /dev/ttya
17260 main () at ../prog.c:3
17264 @value{GDBN} displays messages like these:
17270 @node Sparclet Download
17271 @subsubsection Sparclet Download
17273 @cindex download to Sparclet
17274 Once connected to the Sparclet target,
17275 you can use the @value{GDBN}
17276 @code{load} command to download the file from the host to the target.
17277 The file name and load offset should be given as arguments to the @code{load}
17279 Since the file format is aout, the program must be loaded to the starting
17280 address. You can use @code{objdump} to find out what this value is. The load
17281 offset is an offset which is added to the VMA (virtual memory address)
17282 of each of the file's sections.
17283 For instance, if the program
17284 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
17285 and bss at 0x12010170, in @value{GDBN}, type:
17288 (gdbslet) load prog 0x12010000
17289 Loading section .text, size 0xdb0 vma 0x12010000
17292 If the code is loaded at a different address then what the program was linked
17293 to, you may need to use the @code{section} and @code{add-symbol-file} commands
17294 to tell @value{GDBN} where to map the symbol table.
17296 @node Sparclet Execution
17297 @subsubsection Running and Debugging
17299 @cindex running and debugging Sparclet programs
17300 You can now begin debugging the task using @value{GDBN}'s execution control
17301 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
17302 manual for the list of commands.
17306 Breakpoint 1 at 0x12010000: file prog.c, line 3.
17308 Starting program: prog
17309 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
17310 3 char *symarg = 0;
17312 4 char *execarg = "hello!";
17317 @subsection Fujitsu Sparclite
17321 @kindex target sparclite
17322 @item target sparclite @var{dev}
17323 Fujitsu sparclite boards, used only for the purpose of loading.
17324 You must use an additional command to debug the program.
17325 For example: target remote @var{dev} using @value{GDBN} standard
17331 @subsection Zilog Z8000
17334 @cindex simulator, Z8000
17335 @cindex Zilog Z8000 simulator
17337 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
17340 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
17341 unsegmented variant of the Z8000 architecture) or the Z8001 (the
17342 segmented variant). The simulator recognizes which architecture is
17343 appropriate by inspecting the object code.
17346 @item target sim @var{args}
17348 @kindex target sim@r{, with Z8000}
17349 Debug programs on a simulated CPU. If the simulator supports setup
17350 options, specify them via @var{args}.
17354 After specifying this target, you can debug programs for the simulated
17355 CPU in the same style as programs for your host computer; use the
17356 @code{file} command to load a new program image, the @code{run} command
17357 to run your program, and so on.
17359 As well as making available all the usual machine registers
17360 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
17361 additional items of information as specially named registers:
17366 Counts clock-ticks in the simulator.
17369 Counts instructions run in the simulator.
17372 Execution time in 60ths of a second.
17376 You can refer to these values in @value{GDBN} expressions with the usual
17377 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
17378 conditional breakpoint that suspends only after at least 5000
17379 simulated clock ticks.
17382 @subsection Atmel AVR
17385 When configured for debugging the Atmel AVR, @value{GDBN} supports the
17386 following AVR-specific commands:
17389 @item info io_registers
17390 @kindex info io_registers@r{, AVR}
17391 @cindex I/O registers (Atmel AVR)
17392 This command displays information about the AVR I/O registers. For
17393 each register, @value{GDBN} prints its number and value.
17400 When configured for debugging CRIS, @value{GDBN} provides the
17401 following CRIS-specific commands:
17404 @item set cris-version @var{ver}
17405 @cindex CRIS version
17406 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
17407 The CRIS version affects register names and sizes. This command is useful in
17408 case autodetection of the CRIS version fails.
17410 @item show cris-version
17411 Show the current CRIS version.
17413 @item set cris-dwarf2-cfi
17414 @cindex DWARF-2 CFI and CRIS
17415 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
17416 Change to @samp{off} when using @code{gcc-cris} whose version is below
17419 @item show cris-dwarf2-cfi
17420 Show the current state of using DWARF-2 CFI.
17422 @item set cris-mode @var{mode}
17424 Set the current CRIS mode to @var{mode}. It should only be changed when
17425 debugging in guru mode, in which case it should be set to
17426 @samp{guru} (the default is @samp{normal}).
17428 @item show cris-mode
17429 Show the current CRIS mode.
17433 @subsection Renesas Super-H
17436 For the Renesas Super-H processor, @value{GDBN} provides these
17441 @kindex regs@r{, Super-H}
17442 Show the values of all Super-H registers.
17444 @item set sh calling-convention @var{convention}
17445 @kindex set sh calling-convention
17446 Set the calling-convention used when calling functions from @value{GDBN}.
17447 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
17448 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
17449 convention. If the DWARF-2 information of the called function specifies
17450 that the function follows the Renesas calling convention, the function
17451 is called using the Renesas calling convention. If the calling convention
17452 is set to @samp{renesas}, the Renesas calling convention is always used,
17453 regardless of the DWARF-2 information. This can be used to override the
17454 default of @samp{gcc} if debug information is missing, or the compiler
17455 does not emit the DWARF-2 calling convention entry for a function.
17457 @item show sh calling-convention
17458 @kindex show sh calling-convention
17459 Show the current calling convention setting.
17464 @node Architectures
17465 @section Architectures
17467 This section describes characteristics of architectures that affect
17468 all uses of @value{GDBN} with the architecture, both native and cross.
17475 * HPPA:: HP PA architecture
17476 * SPU:: Cell Broadband Engine SPU architecture
17481 @subsection x86 Architecture-specific Issues
17484 @item set struct-convention @var{mode}
17485 @kindex set struct-convention
17486 @cindex struct return convention
17487 @cindex struct/union returned in registers
17488 Set the convention used by the inferior to return @code{struct}s and
17489 @code{union}s from functions to @var{mode}. Possible values of
17490 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
17491 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
17492 are returned on the stack, while @code{"reg"} means that a
17493 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
17494 be returned in a register.
17496 @item show struct-convention
17497 @kindex show struct-convention
17498 Show the current setting of the convention to return @code{struct}s
17507 @kindex set rstack_high_address
17508 @cindex AMD 29K register stack
17509 @cindex register stack, AMD29K
17510 @item set rstack_high_address @var{address}
17511 On AMD 29000 family processors, registers are saved in a separate
17512 @dfn{register stack}. There is no way for @value{GDBN} to determine the
17513 extent of this stack. Normally, @value{GDBN} just assumes that the
17514 stack is ``large enough''. This may result in @value{GDBN} referencing
17515 memory locations that do not exist. If necessary, you can get around
17516 this problem by specifying the ending address of the register stack with
17517 the @code{set rstack_high_address} command. The argument should be an
17518 address, which you probably want to precede with @samp{0x} to specify in
17521 @kindex show rstack_high_address
17522 @item show rstack_high_address
17523 Display the current limit of the register stack, on AMD 29000 family
17531 See the following section.
17536 @cindex stack on Alpha
17537 @cindex stack on MIPS
17538 @cindex Alpha stack
17540 Alpha- and MIPS-based computers use an unusual stack frame, which
17541 sometimes requires @value{GDBN} to search backward in the object code to
17542 find the beginning of a function.
17544 @cindex response time, MIPS debugging
17545 To improve response time (especially for embedded applications, where
17546 @value{GDBN} may be restricted to a slow serial line for this search)
17547 you may want to limit the size of this search, using one of these
17551 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
17552 @item set heuristic-fence-post @var{limit}
17553 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
17554 search for the beginning of a function. A value of @var{0} (the
17555 default) means there is no limit. However, except for @var{0}, the
17556 larger the limit the more bytes @code{heuristic-fence-post} must search
17557 and therefore the longer it takes to run. You should only need to use
17558 this command when debugging a stripped executable.
17560 @item show heuristic-fence-post
17561 Display the current limit.
17565 These commands are available @emph{only} when @value{GDBN} is configured
17566 for debugging programs on Alpha or MIPS processors.
17568 Several MIPS-specific commands are available when debugging MIPS
17572 @item set mips abi @var{arg}
17573 @kindex set mips abi
17574 @cindex set ABI for MIPS
17575 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
17576 values of @var{arg} are:
17580 The default ABI associated with the current binary (this is the
17591 @item show mips abi
17592 @kindex show mips abi
17593 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
17596 @itemx show mipsfpu
17597 @xref{MIPS Embedded, set mipsfpu}.
17599 @item set mips mask-address @var{arg}
17600 @kindex set mips mask-address
17601 @cindex MIPS addresses, masking
17602 This command determines whether the most-significant 32 bits of 64-bit
17603 MIPS addresses are masked off. The argument @var{arg} can be
17604 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
17605 setting, which lets @value{GDBN} determine the correct value.
17607 @item show mips mask-address
17608 @kindex show mips mask-address
17609 Show whether the upper 32 bits of MIPS addresses are masked off or
17612 @item set remote-mips64-transfers-32bit-regs
17613 @kindex set remote-mips64-transfers-32bit-regs
17614 This command controls compatibility with 64-bit MIPS targets that
17615 transfer data in 32-bit quantities. If you have an old MIPS 64 target
17616 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
17617 and 64 bits for other registers, set this option to @samp{on}.
17619 @item show remote-mips64-transfers-32bit-regs
17620 @kindex show remote-mips64-transfers-32bit-regs
17621 Show the current setting of compatibility with older MIPS 64 targets.
17623 @item set debug mips
17624 @kindex set debug mips
17625 This command turns on and off debugging messages for the MIPS-specific
17626 target code in @value{GDBN}.
17628 @item show debug mips
17629 @kindex show debug mips
17630 Show the current setting of MIPS debugging messages.
17636 @cindex HPPA support
17638 When @value{GDBN} is debugging the HP PA architecture, it provides the
17639 following special commands:
17642 @item set debug hppa
17643 @kindex set debug hppa
17644 This command determines whether HPPA architecture-specific debugging
17645 messages are to be displayed.
17647 @item show debug hppa
17648 Show whether HPPA debugging messages are displayed.
17650 @item maint print unwind @var{address}
17651 @kindex maint print unwind@r{, HPPA}
17652 This command displays the contents of the unwind table entry at the
17653 given @var{address}.
17659 @subsection Cell Broadband Engine SPU architecture
17660 @cindex Cell Broadband Engine
17663 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17664 it provides the following special commands:
17667 @item info spu event
17669 Display SPU event facility status. Shows current event mask
17670 and pending event status.
17672 @item info spu signal
17673 Display SPU signal notification facility status. Shows pending
17674 signal-control word and signal notification mode of both signal
17675 notification channels.
17677 @item info spu mailbox
17678 Display SPU mailbox facility status. Shows all pending entries,
17679 in order of processing, in each of the SPU Write Outbound,
17680 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17683 Display MFC DMA status. Shows all pending commands in the MFC
17684 DMA queue. For each entry, opcode, tag, class IDs, effective
17685 and local store addresses and transfer size are shown.
17687 @item info spu proxydma
17688 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17689 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17690 and local store addresses and transfer size are shown.
17694 When @value{GDBN} is debugging a combined PowerPC/SPU application
17695 on the Cell Broadband Engine, it provides in addition the following
17699 @item set spu stop-on-load @var{arg}
17701 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
17702 will give control to the user when a new SPE thread enters its @code{main}
17703 function. The default is @code{off}.
17705 @item show spu stop-on-load
17707 Show whether to stop for new SPE threads.
17709 @item set spu auto-flush-cache @var{arg}
17710 Set whether to automatically flush the software-managed cache. When set to
17711 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
17712 cache to be flushed whenever SPE execution stops. This provides a consistent
17713 view of PowerPC memory that is accessed via the cache. If an application
17714 does not use the software-managed cache, this option has no effect.
17716 @item show spu auto-flush-cache
17717 Show whether to automatically flush the software-managed cache.
17722 @subsection PowerPC
17723 @cindex PowerPC architecture
17725 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17726 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17727 numbers stored in the floating point registers. These values must be stored
17728 in two consecutive registers, always starting at an even register like
17729 @code{f0} or @code{f2}.
17731 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
17732 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
17733 @code{f2} and @code{f3} for @code{$dl1} and so on.
17735 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
17736 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
17739 @node Controlling GDB
17740 @chapter Controlling @value{GDBN}
17742 You can alter the way @value{GDBN} interacts with you by using the
17743 @code{set} command. For commands controlling how @value{GDBN} displays
17744 data, see @ref{Print Settings, ,Print Settings}. Other settings are
17749 * Editing:: Command editing
17750 * Command History:: Command history
17751 * Screen Size:: Screen size
17752 * Numbers:: Numbers
17753 * ABI:: Configuring the current ABI
17754 * Messages/Warnings:: Optional warnings and messages
17755 * Debugging Output:: Optional messages about internal happenings
17756 * Other Misc Settings:: Other Miscellaneous Settings
17764 @value{GDBN} indicates its readiness to read a command by printing a string
17765 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17766 can change the prompt string with the @code{set prompt} command. For
17767 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17768 the prompt in one of the @value{GDBN} sessions so that you can always tell
17769 which one you are talking to.
17771 @emph{Note:} @code{set prompt} does not add a space for you after the
17772 prompt you set. This allows you to set a prompt which ends in a space
17773 or a prompt that does not.
17777 @item set prompt @var{newprompt}
17778 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17780 @kindex show prompt
17782 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17786 @section Command Editing
17788 @cindex command line editing
17790 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17791 @sc{gnu} library provides consistent behavior for programs which provide a
17792 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17793 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17794 substitution, and a storage and recall of command history across
17795 debugging sessions.
17797 You may control the behavior of command line editing in @value{GDBN} with the
17798 command @code{set}.
17801 @kindex set editing
17804 @itemx set editing on
17805 Enable command line editing (enabled by default).
17807 @item set editing off
17808 Disable command line editing.
17810 @kindex show editing
17812 Show whether command line editing is enabled.
17815 @xref{Command Line Editing}, for more details about the Readline
17816 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17817 encouraged to read that chapter.
17819 @node Command History
17820 @section Command History
17821 @cindex command history
17823 @value{GDBN} can keep track of the commands you type during your
17824 debugging sessions, so that you can be certain of precisely what
17825 happened. Use these commands to manage the @value{GDBN} command
17828 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17829 package, to provide the history facility. @xref{Using History
17830 Interactively}, for the detailed description of the History library.
17832 To issue a command to @value{GDBN} without affecting certain aspects of
17833 the state which is seen by users, prefix it with @samp{server }
17834 (@pxref{Server Prefix}). This
17835 means that this command will not affect the command history, nor will it
17836 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17837 pressed on a line by itself.
17839 @cindex @code{server}, command prefix
17840 The server prefix does not affect the recording of values into the value
17841 history; to print a value without recording it into the value history,
17842 use the @code{output} command instead of the @code{print} command.
17844 Here is the description of @value{GDBN} commands related to command
17848 @cindex history substitution
17849 @cindex history file
17850 @kindex set history filename
17851 @cindex @env{GDBHISTFILE}, environment variable
17852 @item set history filename @var{fname}
17853 Set the name of the @value{GDBN} command history file to @var{fname}.
17854 This is the file where @value{GDBN} reads an initial command history
17855 list, and where it writes the command history from this session when it
17856 exits. You can access this list through history expansion or through
17857 the history command editing characters listed below. This file defaults
17858 to the value of the environment variable @code{GDBHISTFILE}, or to
17859 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17862 @cindex save command history
17863 @kindex set history save
17864 @item set history save
17865 @itemx set history save on
17866 Record command history in a file, whose name may be specified with the
17867 @code{set history filename} command. By default, this option is disabled.
17869 @item set history save off
17870 Stop recording command history in a file.
17872 @cindex history size
17873 @kindex set history size
17874 @cindex @env{HISTSIZE}, environment variable
17875 @item set history size @var{size}
17876 Set the number of commands which @value{GDBN} keeps in its history list.
17877 This defaults to the value of the environment variable
17878 @code{HISTSIZE}, or to 256 if this variable is not set.
17881 History expansion assigns special meaning to the character @kbd{!}.
17882 @xref{Event Designators}, for more details.
17884 @cindex history expansion, turn on/off
17885 Since @kbd{!} is also the logical not operator in C, history expansion
17886 is off by default. If you decide to enable history expansion with the
17887 @code{set history expansion on} command, you may sometimes need to
17888 follow @kbd{!} (when it is used as logical not, in an expression) with
17889 a space or a tab to prevent it from being expanded. The readline
17890 history facilities do not attempt substitution on the strings
17891 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17893 The commands to control history expansion are:
17896 @item set history expansion on
17897 @itemx set history expansion
17898 @kindex set history expansion
17899 Enable history expansion. History expansion is off by default.
17901 @item set history expansion off
17902 Disable history expansion.
17905 @kindex show history
17907 @itemx show history filename
17908 @itemx show history save
17909 @itemx show history size
17910 @itemx show history expansion
17911 These commands display the state of the @value{GDBN} history parameters.
17912 @code{show history} by itself displays all four states.
17917 @kindex show commands
17918 @cindex show last commands
17919 @cindex display command history
17920 @item show commands
17921 Display the last ten commands in the command history.
17923 @item show commands @var{n}
17924 Print ten commands centered on command number @var{n}.
17926 @item show commands +
17927 Print ten commands just after the commands last printed.
17931 @section Screen Size
17932 @cindex size of screen
17933 @cindex pauses in output
17935 Certain commands to @value{GDBN} may produce large amounts of
17936 information output to the screen. To help you read all of it,
17937 @value{GDBN} pauses and asks you for input at the end of each page of
17938 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17939 to discard the remaining output. Also, the screen width setting
17940 determines when to wrap lines of output. Depending on what is being
17941 printed, @value{GDBN} tries to break the line at a readable place,
17942 rather than simply letting it overflow onto the following line.
17944 Normally @value{GDBN} knows the size of the screen from the terminal
17945 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17946 together with the value of the @code{TERM} environment variable and the
17947 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17948 you can override it with the @code{set height} and @code{set
17955 @kindex show height
17956 @item set height @var{lpp}
17958 @itemx set width @var{cpl}
17960 These @code{set} commands specify a screen height of @var{lpp} lines and
17961 a screen width of @var{cpl} characters. The associated @code{show}
17962 commands display the current settings.
17964 If you specify a height of zero lines, @value{GDBN} does not pause during
17965 output no matter how long the output is. This is useful if output is to a
17966 file or to an editor buffer.
17968 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17969 from wrapping its output.
17971 @item set pagination on
17972 @itemx set pagination off
17973 @kindex set pagination
17974 Turn the output pagination on or off; the default is on. Turning
17975 pagination off is the alternative to @code{set height 0}.
17977 @item show pagination
17978 @kindex show pagination
17979 Show the current pagination mode.
17984 @cindex number representation
17985 @cindex entering numbers
17987 You can always enter numbers in octal, decimal, or hexadecimal in
17988 @value{GDBN} by the usual conventions: octal numbers begin with
17989 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17990 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17991 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17992 10; likewise, the default display for numbers---when no particular
17993 format is specified---is base 10. You can change the default base for
17994 both input and output with the commands described below.
17997 @kindex set input-radix
17998 @item set input-radix @var{base}
17999 Set the default base for numeric input. Supported choices
18000 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18001 specified either unambiguously or using the current input radix; for
18005 set input-radix 012
18006 set input-radix 10.
18007 set input-radix 0xa
18011 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18012 leaves the input radix unchanged, no matter what it was, since
18013 @samp{10}, being without any leading or trailing signs of its base, is
18014 interpreted in the current radix. Thus, if the current radix is 16,
18015 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18018 @kindex set output-radix
18019 @item set output-radix @var{base}
18020 Set the default base for numeric display. Supported choices
18021 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18022 specified either unambiguously or using the current input radix.
18024 @kindex show input-radix
18025 @item show input-radix
18026 Display the current default base for numeric input.
18028 @kindex show output-radix
18029 @item show output-radix
18030 Display the current default base for numeric display.
18032 @item set radix @r{[}@var{base}@r{]}
18036 These commands set and show the default base for both input and output
18037 of numbers. @code{set radix} sets the radix of input and output to
18038 the same base; without an argument, it resets the radix back to its
18039 default value of 10.
18044 @section Configuring the Current ABI
18046 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18047 application automatically. However, sometimes you need to override its
18048 conclusions. Use these commands to manage @value{GDBN}'s view of the
18055 One @value{GDBN} configuration can debug binaries for multiple operating
18056 system targets, either via remote debugging or native emulation.
18057 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18058 but you can override its conclusion using the @code{set osabi} command.
18059 One example where this is useful is in debugging of binaries which use
18060 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18061 not have the same identifying marks that the standard C library for your
18066 Show the OS ABI currently in use.
18069 With no argument, show the list of registered available OS ABI's.
18071 @item set osabi @var{abi}
18072 Set the current OS ABI to @var{abi}.
18075 @cindex float promotion
18077 Generally, the way that an argument of type @code{float} is passed to a
18078 function depends on whether the function is prototyped. For a prototyped
18079 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18080 according to the architecture's convention for @code{float}. For unprototyped
18081 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18082 @code{double} and then passed.
18084 Unfortunately, some forms of debug information do not reliably indicate whether
18085 a function is prototyped. If @value{GDBN} calls a function that is not marked
18086 as prototyped, it consults @kbd{set coerce-float-to-double}.
18089 @kindex set coerce-float-to-double
18090 @item set coerce-float-to-double
18091 @itemx set coerce-float-to-double on
18092 Arguments of type @code{float} will be promoted to @code{double} when passed
18093 to an unprototyped function. This is the default setting.
18095 @item set coerce-float-to-double off
18096 Arguments of type @code{float} will be passed directly to unprototyped
18099 @kindex show coerce-float-to-double
18100 @item show coerce-float-to-double
18101 Show the current setting of promoting @code{float} to @code{double}.
18105 @kindex show cp-abi
18106 @value{GDBN} needs to know the ABI used for your program's C@t{++}
18107 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
18108 used to build your application. @value{GDBN} only fully supports
18109 programs with a single C@t{++} ABI; if your program contains code using
18110 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
18111 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
18112 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
18113 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
18114 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
18115 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
18120 Show the C@t{++} ABI currently in use.
18123 With no argument, show the list of supported C@t{++} ABI's.
18125 @item set cp-abi @var{abi}
18126 @itemx set cp-abi auto
18127 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
18130 @node Messages/Warnings
18131 @section Optional Warnings and Messages
18133 @cindex verbose operation
18134 @cindex optional warnings
18135 By default, @value{GDBN} is silent about its inner workings. If you are
18136 running on a slow machine, you may want to use the @code{set verbose}
18137 command. This makes @value{GDBN} tell you when it does a lengthy
18138 internal operation, so you will not think it has crashed.
18140 Currently, the messages controlled by @code{set verbose} are those
18141 which announce that the symbol table for a source file is being read;
18142 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
18145 @kindex set verbose
18146 @item set verbose on
18147 Enables @value{GDBN} output of certain informational messages.
18149 @item set verbose off
18150 Disables @value{GDBN} output of certain informational messages.
18152 @kindex show verbose
18154 Displays whether @code{set verbose} is on or off.
18157 By default, if @value{GDBN} encounters bugs in the symbol table of an
18158 object file, it is silent; but if you are debugging a compiler, you may
18159 find this information useful (@pxref{Symbol Errors, ,Errors Reading
18164 @kindex set complaints
18165 @item set complaints @var{limit}
18166 Permits @value{GDBN} to output @var{limit} complaints about each type of
18167 unusual symbols before becoming silent about the problem. Set
18168 @var{limit} to zero to suppress all complaints; set it to a large number
18169 to prevent complaints from being suppressed.
18171 @kindex show complaints
18172 @item show complaints
18173 Displays how many symbol complaints @value{GDBN} is permitted to produce.
18177 @anchor{confirmation requests}
18178 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
18179 lot of stupid questions to confirm certain commands. For example, if
18180 you try to run a program which is already running:
18184 The program being debugged has been started already.
18185 Start it from the beginning? (y or n)
18188 If you are willing to unflinchingly face the consequences of your own
18189 commands, you can disable this ``feature'':
18193 @kindex set confirm
18195 @cindex confirmation
18196 @cindex stupid questions
18197 @item set confirm off
18198 Disables confirmation requests.
18200 @item set confirm on
18201 Enables confirmation requests (the default).
18203 @kindex show confirm
18205 Displays state of confirmation requests.
18209 @cindex command tracing
18210 If you need to debug user-defined commands or sourced files you may find it
18211 useful to enable @dfn{command tracing}. In this mode each command will be
18212 printed as it is executed, prefixed with one or more @samp{+} symbols, the
18213 quantity denoting the call depth of each command.
18216 @kindex set trace-commands
18217 @cindex command scripts, debugging
18218 @item set trace-commands on
18219 Enable command tracing.
18220 @item set trace-commands off
18221 Disable command tracing.
18222 @item show trace-commands
18223 Display the current state of command tracing.
18226 @node Debugging Output
18227 @section Optional Messages about Internal Happenings
18228 @cindex optional debugging messages
18230 @value{GDBN} has commands that enable optional debugging messages from
18231 various @value{GDBN} subsystems; normally these commands are of
18232 interest to @value{GDBN} maintainers, or when reporting a bug. This
18233 section documents those commands.
18236 @kindex set exec-done-display
18237 @item set exec-done-display
18238 Turns on or off the notification of asynchronous commands'
18239 completion. When on, @value{GDBN} will print a message when an
18240 asynchronous command finishes its execution. The default is off.
18241 @kindex show exec-done-display
18242 @item show exec-done-display
18243 Displays the current setting of asynchronous command completion
18246 @cindex gdbarch debugging info
18247 @cindex architecture debugging info
18248 @item set debug arch
18249 Turns on or off display of gdbarch debugging info. The default is off
18251 @item show debug arch
18252 Displays the current state of displaying gdbarch debugging info.
18253 @item set debug aix-thread
18254 @cindex AIX threads
18255 Display debugging messages about inner workings of the AIX thread
18257 @item show debug aix-thread
18258 Show the current state of AIX thread debugging info display.
18259 @item set debug dwarf2-die
18260 @cindex DWARF2 DIEs
18261 Dump DWARF2 DIEs after they are read in.
18262 The value is the number of nesting levels to print.
18263 A value of zero turns off the display.
18264 @item show debug dwarf2-die
18265 Show the current state of DWARF2 DIE debugging.
18266 @item set debug displaced
18267 @cindex displaced stepping debugging info
18268 Turns on or off display of @value{GDBN} debugging info for the
18269 displaced stepping support. The default is off.
18270 @item show debug displaced
18271 Displays the current state of displaying @value{GDBN} debugging info
18272 related to displaced stepping.
18273 @item set debug event
18274 @cindex event debugging info
18275 Turns on or off display of @value{GDBN} event debugging info. The
18277 @item show debug event
18278 Displays the current state of displaying @value{GDBN} event debugging
18280 @item set debug expression
18281 @cindex expression debugging info
18282 Turns on or off display of debugging info about @value{GDBN}
18283 expression parsing. The default is off.
18284 @item show debug expression
18285 Displays the current state of displaying debugging info about
18286 @value{GDBN} expression parsing.
18287 @item set debug frame
18288 @cindex frame debugging info
18289 Turns on or off display of @value{GDBN} frame debugging info. The
18291 @item show debug frame
18292 Displays the current state of displaying @value{GDBN} frame debugging
18294 @item set debug gnu-nat
18295 @cindex @sc{gnu}/Hurd debug messages
18296 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
18297 @item show debug gnu-nat
18298 Show the current state of @sc{gnu}/Hurd debugging messages.
18299 @item set debug infrun
18300 @cindex inferior debugging info
18301 Turns on or off display of @value{GDBN} debugging info for running the inferior.
18302 The default is off. @file{infrun.c} contains GDB's runtime state machine used
18303 for implementing operations such as single-stepping the inferior.
18304 @item show debug infrun
18305 Displays the current state of @value{GDBN} inferior debugging.
18306 @item set debug lin-lwp
18307 @cindex @sc{gnu}/Linux LWP debug messages
18308 @cindex Linux lightweight processes
18309 Turns on or off debugging messages from the Linux LWP debug support.
18310 @item show debug lin-lwp
18311 Show the current state of Linux LWP debugging messages.
18312 @item set debug lin-lwp-async
18313 @cindex @sc{gnu}/Linux LWP async debug messages
18314 @cindex Linux lightweight processes
18315 Turns on or off debugging messages from the Linux LWP async debug support.
18316 @item show debug lin-lwp-async
18317 Show the current state of Linux LWP async debugging messages.
18318 @item set debug observer
18319 @cindex observer debugging info
18320 Turns on or off display of @value{GDBN} observer debugging. This
18321 includes info such as the notification of observable events.
18322 @item show debug observer
18323 Displays the current state of observer debugging.
18324 @item set debug overload
18325 @cindex C@t{++} overload debugging info
18326 Turns on or off display of @value{GDBN} C@t{++} overload debugging
18327 info. This includes info such as ranking of functions, etc. The default
18329 @item show debug overload
18330 Displays the current state of displaying @value{GDBN} C@t{++} overload
18332 @cindex packets, reporting on stdout
18333 @cindex serial connections, debugging
18334 @cindex debug remote protocol
18335 @cindex remote protocol debugging
18336 @cindex display remote packets
18337 @item set debug remote
18338 Turns on or off display of reports on all packets sent back and forth across
18339 the serial line to the remote machine. The info is printed on the
18340 @value{GDBN} standard output stream. The default is off.
18341 @item show debug remote
18342 Displays the state of display of remote packets.
18343 @item set debug serial
18344 Turns on or off display of @value{GDBN} serial debugging info. The
18346 @item show debug serial
18347 Displays the current state of displaying @value{GDBN} serial debugging
18349 @item set debug solib-frv
18350 @cindex FR-V shared-library debugging
18351 Turns on or off debugging messages for FR-V shared-library code.
18352 @item show debug solib-frv
18353 Display the current state of FR-V shared-library code debugging
18355 @item set debug target
18356 @cindex target debugging info
18357 Turns on or off display of @value{GDBN} target debugging info. This info
18358 includes what is going on at the target level of GDB, as it happens. The
18359 default is 0. Set it to 1 to track events, and to 2 to also track the
18360 value of large memory transfers. Changes to this flag do not take effect
18361 until the next time you connect to a target or use the @code{run} command.
18362 @item show debug target
18363 Displays the current state of displaying @value{GDBN} target debugging
18365 @item set debug timestamp
18366 @cindex timestampping debugging info
18367 Turns on or off display of timestamps with @value{GDBN} debugging info.
18368 When enabled, seconds and microseconds are displayed before each debugging
18370 @item show debug timestamp
18371 Displays the current state of displaying timestamps with @value{GDBN}
18373 @item set debugvarobj
18374 @cindex variable object debugging info
18375 Turns on or off display of @value{GDBN} variable object debugging
18376 info. The default is off.
18377 @item show debugvarobj
18378 Displays the current state of displaying @value{GDBN} variable object
18380 @item set debug xml
18381 @cindex XML parser debugging
18382 Turns on or off debugging messages for built-in XML parsers.
18383 @item show debug xml
18384 Displays the current state of XML debugging messages.
18387 @node Other Misc Settings
18388 @section Other Miscellaneous Settings
18389 @cindex miscellaneous settings
18392 @kindex set interactive-mode
18393 @item set interactive-mode
18394 If @code{on}, forces @value{GDBN} to operate interactively.
18395 If @code{off}, forces @value{GDBN} to operate non-interactively,
18396 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
18397 based on whether the debugger was started in a terminal or not.
18399 In the vast majority of cases, the debugger should be able to guess
18400 correctly which mode should be used. But this setting can be useful
18401 in certain specific cases, such as running a MinGW @value{GDBN}
18402 inside a cygwin window.
18404 @kindex show interactive-mode
18405 @item show interactive-mode
18406 Displays whether the debugger is operating in interactive mode or not.
18409 @node Extending GDB
18410 @chapter Extending @value{GDBN}
18411 @cindex extending GDB
18413 @value{GDBN} provides two mechanisms for extension. The first is based
18414 on composition of @value{GDBN} commands, and the second is based on the
18415 Python scripting language.
18418 * Sequences:: Canned Sequences of Commands
18419 * Python:: Scripting @value{GDBN} using Python
18423 @section Canned Sequences of Commands
18425 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
18426 Command Lists}), @value{GDBN} provides two ways to store sequences of
18427 commands for execution as a unit: user-defined commands and command
18431 * Define:: How to define your own commands
18432 * Hooks:: Hooks for user-defined commands
18433 * Command Files:: How to write scripts of commands to be stored in a file
18434 * Output:: Commands for controlled output
18438 @subsection User-defined Commands
18440 @cindex user-defined command
18441 @cindex arguments, to user-defined commands
18442 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
18443 which you assign a new name as a command. This is done with the
18444 @code{define} command. User commands may accept up to 10 arguments
18445 separated by whitespace. Arguments are accessed within the user command
18446 via @code{$arg0@dots{}$arg9}. A trivial example:
18450 print $arg0 + $arg1 + $arg2
18455 To execute the command use:
18462 This defines the command @code{adder}, which prints the sum of
18463 its three arguments. Note the arguments are text substitutions, so they may
18464 reference variables, use complex expressions, or even perform inferior
18467 @cindex argument count in user-defined commands
18468 @cindex how many arguments (user-defined commands)
18469 In addition, @code{$argc} may be used to find out how many arguments have
18470 been passed. This expands to a number in the range 0@dots{}10.
18475 print $arg0 + $arg1
18478 print $arg0 + $arg1 + $arg2
18486 @item define @var{commandname}
18487 Define a command named @var{commandname}. If there is already a command
18488 by that name, you are asked to confirm that you want to redefine it.
18489 @var{commandname} may be a bare command name consisting of letters,
18490 numbers, dashes, and underscores. It may also start with any predefined
18491 prefix command. For example, @samp{define target my-target} creates
18492 a user-defined @samp{target my-target} command.
18494 The definition of the command is made up of other @value{GDBN} command lines,
18495 which are given following the @code{define} command. The end of these
18496 commands is marked by a line containing @code{end}.
18499 @kindex end@r{ (user-defined commands)}
18500 @item document @var{commandname}
18501 Document the user-defined command @var{commandname}, so that it can be
18502 accessed by @code{help}. The command @var{commandname} must already be
18503 defined. This command reads lines of documentation just as @code{define}
18504 reads the lines of the command definition, ending with @code{end}.
18505 After the @code{document} command is finished, @code{help} on command
18506 @var{commandname} displays the documentation you have written.
18508 You may use the @code{document} command again to change the
18509 documentation of a command. Redefining the command with @code{define}
18510 does not change the documentation.
18512 @kindex dont-repeat
18513 @cindex don't repeat command
18515 Used inside a user-defined command, this tells @value{GDBN} that this
18516 command should not be repeated when the user hits @key{RET}
18517 (@pxref{Command Syntax, repeat last command}).
18519 @kindex help user-defined
18520 @item help user-defined
18521 List all user-defined commands, with the first line of the documentation
18526 @itemx show user @var{commandname}
18527 Display the @value{GDBN} commands used to define @var{commandname} (but
18528 not its documentation). If no @var{commandname} is given, display the
18529 definitions for all user-defined commands.
18531 @cindex infinite recursion in user-defined commands
18532 @kindex show max-user-call-depth
18533 @kindex set max-user-call-depth
18534 @item show max-user-call-depth
18535 @itemx set max-user-call-depth
18536 The value of @code{max-user-call-depth} controls how many recursion
18537 levels are allowed in user-defined commands before @value{GDBN} suspects an
18538 infinite recursion and aborts the command.
18541 In addition to the above commands, user-defined commands frequently
18542 use control flow commands, described in @ref{Command Files}.
18544 When user-defined commands are executed, the
18545 commands of the definition are not printed. An error in any command
18546 stops execution of the user-defined command.
18548 If used interactively, commands that would ask for confirmation proceed
18549 without asking when used inside a user-defined command. Many @value{GDBN}
18550 commands that normally print messages to say what they are doing omit the
18551 messages when used in a user-defined command.
18554 @subsection User-defined Command Hooks
18555 @cindex command hooks
18556 @cindex hooks, for commands
18557 @cindex hooks, pre-command
18560 You may define @dfn{hooks}, which are a special kind of user-defined
18561 command. Whenever you run the command @samp{foo}, if the user-defined
18562 command @samp{hook-foo} exists, it is executed (with no arguments)
18563 before that command.
18565 @cindex hooks, post-command
18567 A hook may also be defined which is run after the command you executed.
18568 Whenever you run the command @samp{foo}, if the user-defined command
18569 @samp{hookpost-foo} exists, it is executed (with no arguments) after
18570 that command. Post-execution hooks may exist simultaneously with
18571 pre-execution hooks, for the same command.
18573 It is valid for a hook to call the command which it hooks. If this
18574 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
18576 @c It would be nice if hookpost could be passed a parameter indicating
18577 @c if the command it hooks executed properly or not. FIXME!
18579 @kindex stop@r{, a pseudo-command}
18580 In addition, a pseudo-command, @samp{stop} exists. Defining
18581 (@samp{hook-stop}) makes the associated commands execute every time
18582 execution stops in your program: before breakpoint commands are run,
18583 displays are printed, or the stack frame is printed.
18585 For example, to ignore @code{SIGALRM} signals while
18586 single-stepping, but treat them normally during normal execution,
18591 handle SIGALRM nopass
18595 handle SIGALRM pass
18598 define hook-continue
18599 handle SIGALRM pass
18603 As a further example, to hook at the beginning and end of the @code{echo}
18604 command, and to add extra text to the beginning and end of the message,
18612 define hookpost-echo
18616 (@value{GDBP}) echo Hello World
18617 <<<---Hello World--->>>
18622 You can define a hook for any single-word command in @value{GDBN}, but
18623 not for command aliases; you should define a hook for the basic command
18624 name, e.g.@: @code{backtrace} rather than @code{bt}.
18625 @c FIXME! So how does Joe User discover whether a command is an alias
18627 You can hook a multi-word command by adding @code{hook-} or
18628 @code{hookpost-} to the last word of the command, e.g.@:
18629 @samp{define target hook-remote} to add a hook to @samp{target remote}.
18631 If an error occurs during the execution of your hook, execution of
18632 @value{GDBN} commands stops and @value{GDBN} issues a prompt
18633 (before the command that you actually typed had a chance to run).
18635 If you try to define a hook which does not match any known command, you
18636 get a warning from the @code{define} command.
18638 @node Command Files
18639 @subsection Command Files
18641 @cindex command files
18642 @cindex scripting commands
18643 A command file for @value{GDBN} is a text file made of lines that are
18644 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
18645 also be included. An empty line in a command file does nothing; it
18646 does not mean to repeat the last command, as it would from the
18649 You can request the execution of a command file with the @code{source}
18654 @cindex execute commands from a file
18655 @item source [@code{-v}] @var{filename}
18656 Execute the command file @var{filename}.
18659 The lines in a command file are generally executed sequentially,
18660 unless the order of execution is changed by one of the
18661 @emph{flow-control commands} described below. The commands are not
18662 printed as they are executed. An error in any command terminates
18663 execution of the command file and control is returned to the console.
18665 @value{GDBN} searches for @var{filename} in the current directory and then
18666 on the search path (specified with the @samp{directory} command).
18668 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
18669 each command as it is executed. The option must be given before
18670 @var{filename}, and is interpreted as part of the filename anywhere else.
18672 Commands that would ask for confirmation if used interactively proceed
18673 without asking when used in a command file. Many @value{GDBN} commands that
18674 normally print messages to say what they are doing omit the messages
18675 when called from command files.
18677 @value{GDBN} also accepts command input from standard input. In this
18678 mode, normal output goes to standard output and error output goes to
18679 standard error. Errors in a command file supplied on standard input do
18680 not terminate execution of the command file---execution continues with
18684 gdb < cmds > log 2>&1
18687 (The syntax above will vary depending on the shell used.) This example
18688 will execute commands from the file @file{cmds}. All output and errors
18689 would be directed to @file{log}.
18691 Since commands stored on command files tend to be more general than
18692 commands typed interactively, they frequently need to deal with
18693 complicated situations, such as different or unexpected values of
18694 variables and symbols, changes in how the program being debugged is
18695 built, etc. @value{GDBN} provides a set of flow-control commands to
18696 deal with these complexities. Using these commands, you can write
18697 complex scripts that loop over data structures, execute commands
18698 conditionally, etc.
18705 This command allows to include in your script conditionally executed
18706 commands. The @code{if} command takes a single argument, which is an
18707 expression to evaluate. It is followed by a series of commands that
18708 are executed only if the expression is true (its value is nonzero).
18709 There can then optionally be an @code{else} line, followed by a series
18710 of commands that are only executed if the expression was false. The
18711 end of the list is marked by a line containing @code{end}.
18715 This command allows to write loops. Its syntax is similar to
18716 @code{if}: the command takes a single argument, which is an expression
18717 to evaluate, and must be followed by the commands to execute, one per
18718 line, terminated by an @code{end}. These commands are called the
18719 @dfn{body} of the loop. The commands in the body of @code{while} are
18720 executed repeatedly as long as the expression evaluates to true.
18724 This command exits the @code{while} loop in whose body it is included.
18725 Execution of the script continues after that @code{while}s @code{end}
18728 @kindex loop_continue
18729 @item loop_continue
18730 This command skips the execution of the rest of the body of commands
18731 in the @code{while} loop in whose body it is included. Execution
18732 branches to the beginning of the @code{while} loop, where it evaluates
18733 the controlling expression.
18735 @kindex end@r{ (if/else/while commands)}
18737 Terminate the block of commands that are the body of @code{if},
18738 @code{else}, or @code{while} flow-control commands.
18743 @subsection Commands for Controlled Output
18745 During the execution of a command file or a user-defined command, normal
18746 @value{GDBN} output is suppressed; the only output that appears is what is
18747 explicitly printed by the commands in the definition. This section
18748 describes three commands useful for generating exactly the output you
18753 @item echo @var{text}
18754 @c I do not consider backslash-space a standard C escape sequence
18755 @c because it is not in ANSI.
18756 Print @var{text}. Nonprinting characters can be included in
18757 @var{text} using C escape sequences, such as @samp{\n} to print a
18758 newline. @strong{No newline is printed unless you specify one.}
18759 In addition to the standard C escape sequences, a backslash followed
18760 by a space stands for a space. This is useful for displaying a
18761 string with spaces at the beginning or the end, since leading and
18762 trailing spaces are otherwise trimmed from all arguments.
18763 To print @samp{@w{ }and foo =@w{ }}, use the command
18764 @samp{echo \@w{ }and foo = \@w{ }}.
18766 A backslash at the end of @var{text} can be used, as in C, to continue
18767 the command onto subsequent lines. For example,
18770 echo This is some text\n\
18771 which is continued\n\
18772 onto several lines.\n
18775 produces the same output as
18778 echo This is some text\n
18779 echo which is continued\n
18780 echo onto several lines.\n
18784 @item output @var{expression}
18785 Print the value of @var{expression} and nothing but that value: no
18786 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18787 value history either. @xref{Expressions, ,Expressions}, for more information
18790 @item output/@var{fmt} @var{expression}
18791 Print the value of @var{expression} in format @var{fmt}. You can use
18792 the same formats as for @code{print}. @xref{Output Formats,,Output
18793 Formats}, for more information.
18796 @item printf @var{template}, @var{expressions}@dots{}
18797 Print the values of one or more @var{expressions} under the control of
18798 the string @var{template}. To print several values, make
18799 @var{expressions} be a comma-separated list of individual expressions,
18800 which may be either numbers or pointers. Their values are printed as
18801 specified by @var{template}, exactly as a C program would do by
18802 executing the code below:
18805 printf (@var{template}, @var{expressions}@dots{});
18808 As in @code{C} @code{printf}, ordinary characters in @var{template}
18809 are printed verbatim, while @dfn{conversion specification} introduced
18810 by the @samp{%} character cause subsequent @var{expressions} to be
18811 evaluated, their values converted and formatted according to type and
18812 style information encoded in the conversion specifications, and then
18815 For example, you can print two values in hex like this:
18818 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18821 @code{printf} supports all the standard @code{C} conversion
18822 specifications, including the flags and modifiers between the @samp{%}
18823 character and the conversion letter, with the following exceptions:
18827 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18830 The modifier @samp{*} is not supported for specifying precision or
18834 The @samp{'} flag (for separation of digits into groups according to
18835 @code{LC_NUMERIC'}) is not supported.
18838 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18842 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18845 The conversion letters @samp{a} and @samp{A} are not supported.
18849 Note that the @samp{ll} type modifier is supported only if the
18850 underlying @code{C} implementation used to build @value{GDBN} supports
18851 the @code{long long int} type, and the @samp{L} type modifier is
18852 supported only if @code{long double} type is available.
18854 As in @code{C}, @code{printf} supports simple backslash-escape
18855 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18856 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18857 single character. Octal and hexadecimal escape sequences are not
18860 Additionally, @code{printf} supports conversion specifications for DFP
18861 (@dfn{Decimal Floating Point}) types using the following length modifiers
18862 together with a floating point specifier.
18867 @samp{H} for printing @code{Decimal32} types.
18870 @samp{D} for printing @code{Decimal64} types.
18873 @samp{DD} for printing @code{Decimal128} types.
18876 If the underlying @code{C} implementation used to build @value{GDBN} has
18877 support for the three length modifiers for DFP types, other modifiers
18878 such as width and precision will also be available for @value{GDBN} to use.
18880 In case there is no such @code{C} support, no additional modifiers will be
18881 available and the value will be printed in the standard way.
18883 Here's an example of printing DFP types using the above conversion letters:
18885 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18891 @section Scripting @value{GDBN} using Python
18892 @cindex python scripting
18893 @cindex scripting with python
18895 You can script @value{GDBN} using the @uref{http://www.python.org/,
18896 Python programming language}. This feature is available only if
18897 @value{GDBN} was configured using @option{--with-python}.
18900 * Python Commands:: Accessing Python from @value{GDBN}.
18901 * Python API:: Accessing @value{GDBN} from Python.
18904 @node Python Commands
18905 @subsection Python Commands
18906 @cindex python commands
18907 @cindex commands to access python
18909 @value{GDBN} provides one command for accessing the Python interpreter,
18910 and one related setting:
18914 @item python @r{[}@var{code}@r{]}
18915 The @code{python} command can be used to evaluate Python code.
18917 If given an argument, the @code{python} command will evaluate the
18918 argument as a Python command. For example:
18921 (@value{GDBP}) python print 23
18925 If you do not provide an argument to @code{python}, it will act as a
18926 multi-line command, like @code{define}. In this case, the Python
18927 script is made up of subsequent command lines, given after the
18928 @code{python} command. This command list is terminated using a line
18929 containing @code{end}. For example:
18932 (@value{GDBP}) python
18934 End with a line saying just "end".
18940 @kindex maint set python print-stack
18941 @item maint set python print-stack
18942 By default, @value{GDBN} will print a stack trace when an error occurs
18943 in a Python script. This can be controlled using @code{maint set
18944 python print-stack}: if @code{on}, the default, then Python stack
18945 printing is enabled; if @code{off}, then Python stack printing is
18950 @subsection Python API
18952 @cindex programming in python
18954 @cindex python stdout
18955 @cindex python pagination
18956 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18957 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18958 A Python program which outputs to one of these streams may have its
18959 output interrupted by the user (@pxref{Screen Size}). In this
18960 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18963 * Basic Python:: Basic Python Functions.
18964 * Exception Handling::
18965 * Auto-loading:: Automatically loading Python code.
18966 * Values From Inferior::
18967 * Types In Python:: Python representation of types.
18968 * Pretty Printing:: Pretty-printing values.
18969 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
18970 * Commands In Python:: Implementing new commands in Python.
18971 * Functions In Python:: Writing new convenience functions.
18972 * Objfiles In Python:: Object files.
18973 * Frames In Python:: Acessing inferior stack frames from Python.
18977 @subsubsection Basic Python
18979 @cindex python functions
18980 @cindex python module
18982 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18983 methods and classes added by @value{GDBN} are placed in this module.
18984 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18985 use in all scripts evaluated by the @code{python} command.
18987 @findex gdb.execute
18988 @defun execute command [from_tty]
18989 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18990 If a GDB exception happens while @var{command} runs, it is
18991 translated as described in @ref{Exception Handling,,Exception Handling}.
18992 If no exceptions occur, this function returns @code{None}.
18994 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18995 command as having originated from the user invoking it interactively.
18996 It must be a boolean value. If omitted, it defaults to @code{False}.
18999 @findex gdb.parameter
19000 @defun parameter parameter
19001 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19002 string naming the parameter to look up; @var{parameter} may contain
19003 spaces if the parameter has a multi-part name. For example,
19004 @samp{print object} is a valid parameter name.
19006 If the named parameter does not exist, this function throws a
19007 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19008 a Python value of the appropriate type, and returned.
19011 @findex gdb.history
19012 @defun history number
19013 Return a value from @value{GDBN}'s value history (@pxref{Value
19014 History}). @var{number} indicates which history element to return.
19015 If @var{number} is negative, then @value{GDBN} will take its absolute value
19016 and count backward from the last element (i.e., the most recent element) to
19017 find the value to return. If @var{number} is zero, then @value{GDBN} will
19018 return the most recent element. If the element specified by @var{number}
19019 doesn't exist in the value history, a @code{RuntimeError} exception will be
19022 If no exception is raised, the return value is always an instance of
19023 @code{gdb.Value} (@pxref{Values From Inferior}).
19027 @defun write string
19028 Print a string to @value{GDBN}'s paginated standard output stream.
19029 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
19030 call this function.
19035 Flush @value{GDBN}'s paginated standard output stream. Flushing
19036 @code{sys.stdout} or @code{sys.stderr} will automatically call this
19040 @node Exception Handling
19041 @subsubsection Exception Handling
19042 @cindex python exceptions
19043 @cindex exceptions, python
19045 When executing the @code{python} command, Python exceptions
19046 uncaught within the Python code are translated to calls to
19047 @value{GDBN} error-reporting mechanism. If the command that called
19048 @code{python} does not handle the error, @value{GDBN} will
19049 terminate it and print an error message containing the Python
19050 exception name, the associated value, and the Python call stack
19051 backtrace at the point where the exception was raised. Example:
19054 (@value{GDBP}) python print foo
19055 Traceback (most recent call last):
19056 File "<string>", line 1, in <module>
19057 NameError: name 'foo' is not defined
19060 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
19061 code are converted to Python @code{RuntimeError} exceptions. User
19062 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
19063 prompt) is translated to a Python @code{KeyboardInterrupt}
19064 exception. If you catch these exceptions in your Python code, your
19065 exception handler will see @code{RuntimeError} or
19066 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
19067 message as its value, and the Python call stack backtrace at the
19068 Python statement closest to where the @value{GDBN} error occured as the
19072 @subsubsection Auto-loading
19073 @cindex auto-loading, Python
19075 When a new object file is read (for example, due to the @code{file}
19076 command, or because the inferior has loaded a shared library),
19077 @value{GDBN} will look for a file named @file{@var{objfile}-gdb.py},
19078 where @var{objfile} is the object file's real name, formed by ensuring
19079 that the file name is absolute, following all symlinks, and resolving
19080 @code{.} and @code{..} components. If this file exists and is
19081 readable, @value{GDBN} will evaluate it as a Python script.
19083 If this file does not exist, and if the parameter
19084 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
19085 then @value{GDBN} will use the file named
19086 @file{@var{debug-file-directory}/@var{real-name}}, where
19087 @var{real-name} is the object file's real name, as described above.
19089 Finally, if this file does not exist, then @value{GDBN} will look for
19090 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
19091 @var{data-directory} is @value{GDBN}'s data directory (available via
19092 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
19093 is the object file's real name, as described above.
19095 When reading an auto-loaded file, @value{GDBN} sets the ``current
19096 objfile''. This is available via the @code{gdb.current_objfile}
19097 function (@pxref{Objfiles In Python}). This can be useful for
19098 registering objfile-specific pretty-printers.
19100 The auto-loading feature is useful for supplying application-specific
19101 debugging commands and scripts. You can enable or disable this
19102 feature, and view its current state.
19105 @kindex maint set python auto-load
19106 @item maint set python auto-load [yes|no]
19107 Enable or disable the Python auto-loading feature.
19109 @kindex show python auto-load
19110 @item show python auto-load
19111 Show whether Python auto-loading is enabled or disabled.
19114 @value{GDBN} does not track which files it has already auto-loaded.
19115 So, your @samp{-gdb.py} file should take care to ensure that it may be
19116 evaluated multiple times without error.
19118 @node Values From Inferior
19119 @subsubsection Values From Inferior
19120 @cindex values from inferior, with Python
19121 @cindex python, working with values from inferior
19123 @cindex @code{gdb.Value}
19124 @value{GDBN} provides values it obtains from the inferior program in
19125 an object of type @code{gdb.Value}. @value{GDBN} uses this object
19126 for its internal bookkeeping of the inferior's values, and for
19127 fetching values when necessary.
19129 Inferior values that are simple scalars can be used directly in
19130 Python expressions that are valid for the value's data type. Here's
19131 an example for an integer or floating-point value @code{some_val}:
19138 As result of this, @code{bar} will also be a @code{gdb.Value} object
19139 whose values are of the same type as those of @code{some_val}.
19141 Inferior values that are structures or instances of some class can
19142 be accessed using the Python @dfn{dictionary syntax}. For example, if
19143 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
19144 can access its @code{foo} element with:
19147 bar = some_val['foo']
19150 Again, @code{bar} will also be a @code{gdb.Value} object.
19152 The following attributes are provided:
19155 @defivar Value address
19156 If this object is addressable, this read-only attribute holds a
19157 @code{gdb.Value} object representing the address. Otherwise,
19158 this attribute holds @code{None}.
19161 @cindex optimized out value in Python
19162 @defivar Value is_optimized_out
19163 This read-only boolean attribute is true if the compiler optimized out
19164 this value, thus it is not available for fetching from the inferior.
19167 @defivar Value type
19168 The type of this @code{gdb.Value}. The value of this attribute is a
19169 @code{gdb.Type} object.
19173 The following methods are provided:
19176 @defmethod Value dereference
19177 For pointer data types, this method returns a new @code{gdb.Value} object
19178 whose contents is the object pointed to by the pointer. For example, if
19179 @code{foo} is a C pointer to an @code{int}, declared in your C program as
19186 then you can use the corresponding @code{gdb.Value} to access what
19187 @code{foo} points to like this:
19190 bar = foo.dereference ()
19193 The result @code{bar} will be a @code{gdb.Value} object holding the
19194 value pointed to by @code{foo}.
19197 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
19198 If this @code{gdb.Value} represents a string, then this method
19199 converts the contents to a Python string. Otherwise, this method will
19200 throw an exception.
19202 Strings are recognized in a language-specific way; whether a given
19203 @code{gdb.Value} represents a string is determined by the current
19206 For C-like languages, a value is a string if it is a pointer to or an
19207 array of characters or ints. The string is assumed to be terminated
19208 by a zero of the appropriate width. However if the optional length
19209 argument is given, the string will be converted to that given length,
19210 ignoring any embedded zeros that the string may contain.
19212 If the optional @var{encoding} argument is given, it must be a string
19213 naming the encoding of the string in the @code{gdb.Value}, such as
19214 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
19215 the same encodings as the corresponding argument to Python's
19216 @code{string.decode} method, and the Python codec machinery will be used
19217 to convert the string. If @var{encoding} is not given, or if
19218 @var{encoding} is the empty string, then either the @code{target-charset}
19219 (@pxref{Character Sets}) will be used, or a language-specific encoding
19220 will be used, if the current language is able to supply one.
19222 The optional @var{errors} argument is the same as the corresponding
19223 argument to Python's @code{string.decode} method.
19225 If the optional @var{length} argument is given, the string will be
19226 fetched and converted to the given length.
19230 @node Types In Python
19231 @subsubsection Types In Python
19232 @cindex types in Python
19233 @cindex Python, working with types
19236 @value{GDBN} represents types from the inferior using the class
19239 The following type-related functions are available in the @code{gdb}
19242 @findex gdb.lookup_type
19243 @defun lookup_type name [block]
19244 This function looks up a type by name. @var{name} is the name of the
19245 type to look up. It must be a string.
19247 Ordinarily, this function will return an instance of @code{gdb.Type}.
19248 If the named type cannot be found, it will throw an exception.
19251 An instance of @code{Type} has the following attributes:
19255 The type code for this type. The type code will be one of the
19256 @code{TYPE_CODE_} constants defined below.
19259 @defivar Type sizeof
19260 The size of this type, in target @code{char} units. Usually, a
19261 target's @code{char} type will be an 8-bit byte. However, on some
19262 unusual platforms, this type may have a different size.
19266 The tag name for this type. The tag name is the name after
19267 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
19268 languages have this concept. If this type has no tag name, then
19269 @code{None} is returned.
19273 The following methods are provided:
19276 @defmethod Type fields
19277 For structure and union types, this method returns the fields. Range
19278 types have two fields, the minimum and maximum values. Enum types
19279 have one field per enum constant. Function and method types have one
19280 field per parameter. The base types of C@t{++} classes are also
19281 represented as fields. If the type has no fields, or does not fit
19282 into one of these categories, an empty sequence will be returned.
19284 Each field is an object, with some pre-defined attributes:
19287 This attribute is not available for @code{static} fields (as in
19288 C@t{++} or Java). For non-@code{static} fields, the value is the bit
19289 position of the field.
19292 The name of the field, or @code{None} for anonymous fields.
19295 This is @code{True} if the field is artificial, usually meaning that
19296 it was provided by the compiler and not the user. This attribute is
19297 always provided, and is @code{False} if the field is not artificial.
19300 If the field is packed, or is a bitfield, then this will have a
19301 non-zero value, which is the size of the field in bits. Otherwise,
19302 this will be zero; in this case the field's size is given by its type.
19305 The type of the field. This is usually an instance of @code{Type},
19306 but it can be @code{None} in some situations.
19310 @defmethod Type const
19311 Return a new @code{gdb.Type} object which represents a
19312 @code{const}-qualified variant of this type.
19315 @defmethod Type volatile
19316 Return a new @code{gdb.Type} object which represents a
19317 @code{volatile}-qualified variant of this type.
19320 @defmethod Type unqualified
19321 Return a new @code{gdb.Type} object which represents an unqualified
19322 variant of this type. That is, the result is neither @code{const} nor
19326 @defmethod Type reference
19327 Return a new @code{gdb.Type} object which represents a reference to this
19331 @defmethod Type strip_typedefs
19332 Return a new @code{gdb.Type} that represents the real type,
19333 after removing all layers of typedefs.
19336 @defmethod Type target
19337 Return a new @code{gdb.Type} object which represents the target type
19340 For a pointer type, the target type is the type of the pointed-to
19341 object. For an array type (meaning C-like arrays), the target type is
19342 the type of the elements of the array. For a function or method type,
19343 the target type is the type of the return value. For a complex type,
19344 the target type is the type of the elements. For a typedef, the
19345 target type is the aliased type.
19347 If the type does not have a target, this method will throw an
19351 @defmethod Type template_argument n
19352 If this @code{gdb.Type} is an instantiation of a template, this will
19353 return a new @code{gdb.Type} which represents the type of the
19354 @var{n}th template argument.
19356 If this @code{gdb.Type} is not a template type, this will throw an
19357 exception. Ordinarily, only C@t{++} code will have template types.
19359 @var{name} is searched for globally.
19364 Each type has a code, which indicates what category this type falls
19365 into. The available type categories are represented by constants
19366 defined in the @code{gdb} module:
19369 @findex TYPE_CODE_PTR
19370 @findex gdb.TYPE_CODE_PTR
19371 @item TYPE_CODE_PTR
19372 The type is a pointer.
19374 @findex TYPE_CODE_ARRAY
19375 @findex gdb.TYPE_CODE_ARRAY
19376 @item TYPE_CODE_ARRAY
19377 The type is an array.
19379 @findex TYPE_CODE_STRUCT
19380 @findex gdb.TYPE_CODE_STRUCT
19381 @item TYPE_CODE_STRUCT
19382 The type is a structure.
19384 @findex TYPE_CODE_UNION
19385 @findex gdb.TYPE_CODE_UNION
19386 @item TYPE_CODE_UNION
19387 The type is a union.
19389 @findex TYPE_CODE_ENUM
19390 @findex gdb.TYPE_CODE_ENUM
19391 @item TYPE_CODE_ENUM
19392 The type is an enum.
19394 @findex TYPE_CODE_FLAGS
19395 @findex gdb.TYPE_CODE_FLAGS
19396 @item TYPE_CODE_FLAGS
19397 A bit flags type, used for things such as status registers.
19399 @findex TYPE_CODE_FUNC
19400 @findex gdb.TYPE_CODE_FUNC
19401 @item TYPE_CODE_FUNC
19402 The type is a function.
19404 @findex TYPE_CODE_INT
19405 @findex gdb.TYPE_CODE_INT
19406 @item TYPE_CODE_INT
19407 The type is an integer type.
19409 @findex TYPE_CODE_FLT
19410 @findex gdb.TYPE_CODE_FLT
19411 @item TYPE_CODE_FLT
19412 A floating point type.
19414 @findex TYPE_CODE_VOID
19415 @findex gdb.TYPE_CODE_VOID
19416 @item TYPE_CODE_VOID
19417 The special type @code{void}.
19419 @findex TYPE_CODE_SET
19420 @findex gdb.TYPE_CODE_SET
19421 @item TYPE_CODE_SET
19424 @findex TYPE_CODE_RANGE
19425 @findex gdb.TYPE_CODE_RANGE
19426 @item TYPE_CODE_RANGE
19427 A range type, that is, an integer type with bounds.
19429 @findex TYPE_CODE_STRING
19430 @findex gdb.TYPE_CODE_STRING
19431 @item TYPE_CODE_STRING
19432 A string type. Note that this is only used for certain languages with
19433 language-defined string types; C strings are not represented this way.
19435 @findex TYPE_CODE_BITSTRING
19436 @findex gdb.TYPE_CODE_BITSTRING
19437 @item TYPE_CODE_BITSTRING
19440 @findex TYPE_CODE_ERROR
19441 @findex gdb.TYPE_CODE_ERROR
19442 @item TYPE_CODE_ERROR
19443 An unknown or erroneous type.
19445 @findex TYPE_CODE_METHOD
19446 @findex gdb.TYPE_CODE_METHOD
19447 @item TYPE_CODE_METHOD
19448 A method type, as found in C@t{++} or Java.
19450 @findex TYPE_CODE_METHODPTR
19451 @findex gdb.TYPE_CODE_METHODPTR
19452 @item TYPE_CODE_METHODPTR
19453 A pointer-to-member-function.
19455 @findex TYPE_CODE_MEMBERPTR
19456 @findex gdb.TYPE_CODE_MEMBERPTR
19457 @item TYPE_CODE_MEMBERPTR
19458 A pointer-to-member.
19460 @findex TYPE_CODE_REF
19461 @findex gdb.TYPE_CODE_REF
19462 @item TYPE_CODE_REF
19465 @findex TYPE_CODE_CHAR
19466 @findex gdb.TYPE_CODE_CHAR
19467 @item TYPE_CODE_CHAR
19470 @findex TYPE_CODE_BOOL
19471 @findex gdb.TYPE_CODE_BOOL
19472 @item TYPE_CODE_BOOL
19475 @findex TYPE_CODE_COMPLEX
19476 @findex gdb.TYPE_CODE_COMPLEX
19477 @item TYPE_CODE_COMPLEX
19478 A complex float type.
19480 @findex TYPE_CODE_TYPEDEF
19481 @findex gdb.TYPE_CODE_TYPEDEF
19482 @item TYPE_CODE_TYPEDEF
19483 A typedef to some other type.
19485 @findex TYPE_CODE_NAMESPACE
19486 @findex gdb.TYPE_CODE_NAMESPACE
19487 @item TYPE_CODE_NAMESPACE
19488 A C@t{++} namespace.
19490 @findex TYPE_CODE_DECFLOAT
19491 @findex gdb.TYPE_CODE_DECFLOAT
19492 @item TYPE_CODE_DECFLOAT
19493 A decimal floating point type.
19495 @findex TYPE_CODE_INTERNAL_FUNCTION
19496 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
19497 @item TYPE_CODE_INTERNAL_FUNCTION
19498 A function internal to @value{GDBN}. This is the type used to represent
19499 convenience functions.
19502 @node Pretty Printing
19503 @subsubsection Pretty Printing
19505 @value{GDBN} provides a mechanism to allow pretty-printing of values
19506 using Python code. The pretty-printer API allows application-specific
19507 code to greatly simplify the display of complex objects. This
19508 mechanism works for both MI and the CLI.
19510 For example, here is how a C@t{++} @code{std::string} looks without a
19514 (@value{GDBP}) print s
19516 static npos = 4294967295,
19518 <std::allocator<char>> = @{
19519 <__gnu_cxx::new_allocator<char>> = @{<No data fields>@}, <No data fields>@},
19520 members of std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider:
19521 _M_p = 0x804a014 "abcd"
19526 After a pretty-printer for @code{std::string} has been installed, only
19527 the contents are printed:
19530 (@value{GDBP}) print s
19534 A pretty-printer is just an object that holds a value and implements a
19535 specific interface, defined here.
19537 @defop Operation {pretty printer} children (self)
19538 @value{GDBN} will call this method on a pretty-printer to compute the
19539 children of the pretty-printer's value.
19541 This method must return an object conforming to the Python iterator
19542 protocol. Each item returned by the iterator must be a tuple holding
19543 two elements. The first element is the ``name'' of the child; the
19544 second element is the child's value. The value can be any Python
19545 object which is convertible to a @value{GDBN} value.
19547 This method is optional. If it does not exist, @value{GDBN} will act
19548 as though the value has no children.
19551 @defop Operation {pretty printer} display_hint (self)
19552 The CLI may call this method and use its result to change the
19553 formatting of a value. The result will also be supplied to an MI
19554 consumer as a @samp{displayhint} attribute of the variable being
19557 This method is optional. If it does exist, this method must return a
19560 Some display hints are predefined by @value{GDBN}:
19564 Indicate that the object being printed is ``array-like''. The CLI
19565 uses this to respect parameters such as @code{set print elements} and
19566 @code{set print array}.
19569 Indicate that the object being printed is ``map-like'', and that the
19570 children of this value can be assumed to alternate between keys and
19574 Indicate that the object being printed is ``string-like''. If the
19575 printer's @code{to_string} method returns a Python string of some
19576 kind, then @value{GDBN} will call its internal language-specific
19577 string-printing function to format the string. For the CLI this means
19578 adding quotation marks, possibly escaping some characters, respecting
19579 @code{set print elements}, and the like.
19583 @defop Operation {pretty printer} to_string (self)
19584 @value{GDBN} will call this method to display the string
19585 representation of the value passed to the object's constructor.
19587 When printing from the CLI, if the @code{to_string} method exists,
19588 then @value{GDBN} will prepend its result to the values returned by
19589 @code{children}. Exactly how this formatting is done is dependent on
19590 the display hint, and may change as more hints are added. Also,
19591 depending on the print settings (@pxref{Print Settings}), the CLI may
19592 print just the result of @code{to_string} in a stack trace, omitting
19593 the result of @code{children}.
19595 If this method returns a string, it is printed verbatim.
19597 Otherwise, if this method returns an instance of @code{gdb.Value},
19598 then @value{GDBN} prints this value. This may result in a call to
19599 another pretty-printer.
19601 If instead the method returns a Python value which is convertible to a
19602 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
19603 the resulting value. Again, this may result in a call to another
19604 pretty-printer. Python scalars (integers, floats, and booleans) and
19605 strings are convertible to @code{gdb.Value}; other types are not.
19607 If the result is not one of these types, an exception is raised.
19610 @node Selecting Pretty-Printers
19611 @subsubsection Selecting Pretty-Printers
19613 The Python list @code{gdb.pretty_printers} contains an array of
19614 functions that have been registered via addition as a pretty-printer.
19615 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
19618 A function on one of these lists is passed a single @code{gdb.Value}
19619 argument and should return a pretty-printer object conforming to the
19620 interface definition above (@pxref{Pretty Printing}). If a function
19621 cannot create a pretty-printer for the value, it should return
19624 @value{GDBN} first checks the @code{pretty_printers} attribute of each
19625 @code{gdb.Objfile} and iteratively calls each function in the list for
19626 that @code{gdb.Objfile} until it receives a pretty-printer object.
19627 After these lists have been exhausted, it tries the global
19628 @code{gdb.pretty-printers} list, again calling each function until an
19629 object is returned.
19631 The order in which the objfiles are searched is not specified. For a
19632 given list, functions are always invoked from the head of the list,
19633 and iterated over sequentially until the end of the list, or a printer
19634 object is returned.
19636 Here is an example showing how a @code{std::string} printer might be
19640 class StdStringPrinter:
19641 "Print a std::string"
19643 def __init__ (self, val):
19646 def to_string (self):
19647 return self.val['_M_dataplus']['_M_p']
19649 def display_hint (self):
19653 And here is an example showing how a lookup function for the printer
19654 example above might be written.
19657 def str_lookup_function (val):
19659 lookup_tag = val.type.tag
19660 regex = re.compile ("^std::basic_string<char,.*>$")
19661 if lookup_tag == None:
19663 if regex.match (lookup_tag):
19664 return StdStringPrinter (val)
19669 The example lookup function extracts the value's type, and attempts to
19670 match it to a type that it can pretty-print. If it is a type the
19671 printer can pretty-print, it will return a printer object. If not, it
19672 returns @code{None}.
19674 We recommend that you put your core pretty-printers into a Python
19675 package. If your pretty-printers are for use with a library, we
19676 further recommend embedding a version number into the package name.
19677 This practice will enable @value{GDBN} to load multiple versions of
19678 your pretty-printers at the same time, because they will have
19681 You should write auto-loaded code (@pxref{Auto-loading}) such that it
19682 can be evaluated multiple times without changing its meaning. An
19683 ideal auto-load file will consist solely of @code{import}s of your
19684 printer modules, followed by a call to a register pretty-printers with
19685 the current objfile.
19687 Taken as a whole, this approach will scale nicely to multiple
19688 inferiors, each potentially using a different library version.
19689 Embedding a version number in the Python package name will ensure that
19690 @value{GDBN} is able to load both sets of printers simultaneously.
19691 Then, because the search for pretty-printers is done by objfile, and
19692 because your auto-loaded code took care to register your library's
19693 printers with a specific objfile, @value{GDBN} will find the correct
19694 printers for the specific version of the library used by each
19697 To continue the @code{std::string} example (@pxref{Pretty Printing}),
19698 this code might appear in @code{gdb.libstdcxx.v6}:
19701 def register_printers (objfile):
19702 objfile.pretty_printers.add (str_lookup_function)
19706 And then the corresponding contents of the auto-load file would be:
19709 import gdb.libstdcxx.v6
19710 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
19713 @node Commands In Python
19714 @subsubsection Commands In Python
19716 @cindex commands in python
19717 @cindex python commands
19718 You can implement new @value{GDBN} CLI commands in Python. A CLI
19719 command is implemented using an instance of the @code{gdb.Command}
19720 class, most commonly using a subclass.
19722 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
19723 The object initializer for @code{Command} registers the new command
19724 with @value{GDBN}. This initializer is normally invoked from the
19725 subclass' own @code{__init__} method.
19727 @var{name} is the name of the command. If @var{name} consists of
19728 multiple words, then the initial words are looked for as prefix
19729 commands. In this case, if one of the prefix commands does not exist,
19730 an exception is raised.
19732 There is no support for multi-line commands.
19734 @var{command_class} should be one of the @samp{COMMAND_} constants
19735 defined below. This argument tells @value{GDBN} how to categorize the
19736 new command in the help system.
19738 @var{completer_class} is an optional argument. If given, it should be
19739 one of the @samp{COMPLETE_} constants defined below. This argument
19740 tells @value{GDBN} how to perform completion for this command. If not
19741 given, @value{GDBN} will attempt to complete using the object's
19742 @code{complete} method (see below); if no such method is found, an
19743 error will occur when completion is attempted.
19745 @var{prefix} is an optional argument. If @code{True}, then the new
19746 command is a prefix command; sub-commands of this command may be
19749 The help text for the new command is taken from the Python
19750 documentation string for the command's class, if there is one. If no
19751 documentation string is provided, the default value ``This command is
19752 not documented.'' is used.
19755 @cindex don't repeat Python command
19756 @defmethod Command dont_repeat
19757 By default, a @value{GDBN} command is repeated when the user enters a
19758 blank line at the command prompt. A command can suppress this
19759 behavior by invoking the @code{dont_repeat} method. This is similar
19760 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
19763 @defmethod Command invoke argument from_tty
19764 This method is called by @value{GDBN} when this command is invoked.
19766 @var{argument} is a string. It is the argument to the command, after
19767 leading and trailing whitespace has been stripped.
19769 @var{from_tty} is a boolean argument. When true, this means that the
19770 command was entered by the user at the terminal; when false it means
19771 that the command came from elsewhere.
19773 If this method throws an exception, it is turned into a @value{GDBN}
19774 @code{error} call. Otherwise, the return value is ignored.
19777 @cindex completion of Python commands
19778 @defmethod Command complete text word
19779 This method is called by @value{GDBN} when the user attempts
19780 completion on this command. All forms of completion are handled by
19781 this method, that is, the @key{TAB} and @key{M-?} key bindings
19782 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
19785 The arguments @var{text} and @var{word} are both strings. @var{text}
19786 holds the complete command line up to the cursor's location.
19787 @var{word} holds the last word of the command line; this is computed
19788 using a word-breaking heuristic.
19790 The @code{complete} method can return several values:
19793 If the return value is a sequence, the contents of the sequence are
19794 used as the completions. It is up to @code{complete} to ensure that the
19795 contents actually do complete the word. A zero-length sequence is
19796 allowed, it means that there were no completions available. Only
19797 string elements of the sequence are used; other elements in the
19798 sequence are ignored.
19801 If the return value is one of the @samp{COMPLETE_} constants defined
19802 below, then the corresponding @value{GDBN}-internal completion
19803 function is invoked, and its result is used.
19806 All other results are treated as though there were no available
19811 When a new command is registered, it must be declared as a member of
19812 some general class of commands. This is used to classify top-level
19813 commands in the on-line help system; note that prefix commands are not
19814 listed under their own category but rather that of their top-level
19815 command. The available classifications are represented by constants
19816 defined in the @code{gdb} module:
19819 @findex COMMAND_NONE
19820 @findex gdb.COMMAND_NONE
19822 The command does not belong to any particular class. A command in
19823 this category will not be displayed in any of the help categories.
19825 @findex COMMAND_RUNNING
19826 @findex gdb.COMMAND_RUNNING
19827 @item COMMAND_RUNNING
19828 The command is related to running the inferior. For example,
19829 @code{start}, @code{step}, and @code{continue} are in this category.
19830 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
19831 commands in this category.
19833 @findex COMMAND_DATA
19834 @findex gdb.COMMAND_DATA
19836 The command is related to data or variables. For example,
19837 @code{call}, @code{find}, and @code{print} are in this category. Type
19838 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
19841 @findex COMMAND_STACK
19842 @findex gdb.COMMAND_STACK
19843 @item COMMAND_STACK
19844 The command has to do with manipulation of the stack. For example,
19845 @code{backtrace}, @code{frame}, and @code{return} are in this
19846 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
19847 list of commands in this category.
19849 @findex COMMAND_FILES
19850 @findex gdb.COMMAND_FILES
19851 @item COMMAND_FILES
19852 This class is used for file-related commands. For example,
19853 @code{file}, @code{list} and @code{section} are in this category.
19854 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
19855 commands in this category.
19857 @findex COMMAND_SUPPORT
19858 @findex gdb.COMMAND_SUPPORT
19859 @item COMMAND_SUPPORT
19860 This should be used for ``support facilities'', generally meaning
19861 things that are useful to the user when interacting with @value{GDBN},
19862 but not related to the state of the inferior. For example,
19863 @code{help}, @code{make}, and @code{shell} are in this category. Type
19864 @kbd{help support} at the @value{GDBN} prompt to see a list of
19865 commands in this category.
19867 @findex COMMAND_STATUS
19868 @findex gdb.COMMAND_STATUS
19869 @item COMMAND_STATUS
19870 The command is an @samp{info}-related command, that is, related to the
19871 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
19872 and @code{show} are in this category. Type @kbd{help status} at the
19873 @value{GDBN} prompt to see a list of commands in this category.
19875 @findex COMMAND_BREAKPOINTS
19876 @findex gdb.COMMAND_BREAKPOINTS
19877 @item COMMAND_BREAKPOINTS
19878 The command has to do with breakpoints. For example, @code{break},
19879 @code{clear}, and @code{delete} are in this category. Type @kbd{help
19880 breakpoints} at the @value{GDBN} prompt to see a list of commands in
19883 @findex COMMAND_TRACEPOINTS
19884 @findex gdb.COMMAND_TRACEPOINTS
19885 @item COMMAND_TRACEPOINTS
19886 The command has to do with tracepoints. For example, @code{trace},
19887 @code{actions}, and @code{tfind} are in this category. Type
19888 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
19889 commands in this category.
19891 @findex COMMAND_OBSCURE
19892 @findex gdb.COMMAND_OBSCURE
19893 @item COMMAND_OBSCURE
19894 The command is only used in unusual circumstances, or is not of
19895 general interest to users. For example, @code{checkpoint},
19896 @code{fork}, and @code{stop} are in this category. Type @kbd{help
19897 obscure} at the @value{GDBN} prompt to see a list of commands in this
19900 @findex COMMAND_MAINTENANCE
19901 @findex gdb.COMMAND_MAINTENANCE
19902 @item COMMAND_MAINTENANCE
19903 The command is only useful to @value{GDBN} maintainers. The
19904 @code{maintenance} and @code{flushregs} commands are in this category.
19905 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
19906 commands in this category.
19909 A new command can use a predefined completion function, either by
19910 specifying it via an argument at initialization, or by returning it
19911 from the @code{complete} method. These predefined completion
19912 constants are all defined in the @code{gdb} module:
19915 @findex COMPLETE_NONE
19916 @findex gdb.COMPLETE_NONE
19917 @item COMPLETE_NONE
19918 This constant means that no completion should be done.
19920 @findex COMPLETE_FILENAME
19921 @findex gdb.COMPLETE_FILENAME
19922 @item COMPLETE_FILENAME
19923 This constant means that filename completion should be performed.
19925 @findex COMPLETE_LOCATION
19926 @findex gdb.COMPLETE_LOCATION
19927 @item COMPLETE_LOCATION
19928 This constant means that location completion should be done.
19929 @xref{Specify Location}.
19931 @findex COMPLETE_COMMAND
19932 @findex gdb.COMPLETE_COMMAND
19933 @item COMPLETE_COMMAND
19934 This constant means that completion should examine @value{GDBN}
19937 @findex COMPLETE_SYMBOL
19938 @findex gdb.COMPLETE_SYMBOL
19939 @item COMPLETE_SYMBOL
19940 This constant means that completion should be done using symbol names
19944 The following code snippet shows how a trivial CLI command can be
19945 implemented in Python:
19948 class HelloWorld (gdb.Command):
19949 """Greet the whole world."""
19951 def __init__ (self):
19952 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
19954 def invoke (self, arg, from_tty):
19955 print "Hello, World!"
19960 The last line instantiates the class, and is necessary to trigger the
19961 registration of the command with @value{GDBN}. Depending on how the
19962 Python code is read into @value{GDBN}, you may need to import the
19963 @code{gdb} module explicitly.
19965 @node Functions In Python
19966 @subsubsection Writing new convenience functions
19968 @cindex writing convenience functions
19969 @cindex convenience functions in python
19970 @cindex python convenience functions
19971 @tindex gdb.Function
19973 You can implement new convenience functions (@pxref{Convenience Vars})
19974 in Python. A convenience function is an instance of a subclass of the
19975 class @code{gdb.Function}.
19977 @defmethod Function __init__ name
19978 The initializer for @code{Function} registers the new function with
19979 @value{GDBN}. The argument @var{name} is the name of the function,
19980 a string. The function will be visible to the user as a convenience
19981 variable of type @code{internal function}, whose name is the same as
19982 the given @var{name}.
19984 The documentation for the new function is taken from the documentation
19985 string for the new class.
19988 @defmethod Function invoke @var{*args}
19989 When a convenience function is evaluated, its arguments are converted
19990 to instances of @code{gdb.Value}, and then the function's
19991 @code{invoke} method is called. Note that @value{GDBN} does not
19992 predetermine the arity of convenience functions. Instead, all
19993 available arguments are passed to @code{invoke}, following the
19994 standard Python calling convention. In particular, a convenience
19995 function can have default values for parameters without ill effect.
19997 The return value of this method is used as its value in the enclosing
19998 expression. If an ordinary Python value is returned, it is converted
19999 to a @code{gdb.Value} following the usual rules.
20002 The following code snippet shows how a trivial convenience function can
20003 be implemented in Python:
20006 class Greet (gdb.Function):
20007 """Return string to greet someone.
20008 Takes a name as argument."""
20010 def __init__ (self):
20011 super (Greet, self).__init__ ("greet")
20013 def invoke (self, name):
20014 return "Hello, %s!" % name.string ()
20019 The last line instantiates the class, and is necessary to trigger the
20020 registration of the function with @value{GDBN}. Depending on how the
20021 Python code is read into @value{GDBN}, you may need to import the
20022 @code{gdb} module explicitly.
20024 @node Objfiles In Python
20025 @subsubsection Objfiles In Python
20027 @cindex objfiles in python
20028 @tindex gdb.Objfile
20030 @value{GDBN} loads symbols for an inferior from various
20031 symbol-containing files (@pxref{Files}). These include the primary
20032 executable file, any shared libraries used by the inferior, and any
20033 separate debug info files (@pxref{Separate Debug Files}).
20034 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
20036 The following objfile-related functions are available in the
20039 @findex gdb.current_objfile
20040 @defun current_objfile
20041 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
20042 sets the ``current objfile'' to the corresponding objfile. This
20043 function returns the current objfile. If there is no current objfile,
20044 this function returns @code{None}.
20047 @findex gdb.objfiles
20049 Return a sequence of all the objfiles current known to @value{GDBN}.
20050 @xref{Objfiles In Python}.
20053 Each objfile is represented by an instance of the @code{gdb.Objfile}
20056 @defivar Objfile filename
20057 The file name of the objfile as a string.
20060 @defivar Objfile pretty_printers
20061 The @code{pretty_printers} attribute is a list of functions. It is
20062 used to look up pretty-printers. A @code{Value} is passed to each
20063 function in order; if the function returns @code{None}, then the
20064 search continues. Otherwise, the return value should be an object
20065 which is used to format the value. @xref{Pretty Printing}, for more
20069 @node Frames In Python
20070 @subsubsection Acessing inferior stack frames from Python.
20072 @cindex frames in python
20073 When the debugged program stops, @value{GDBN} is able to analyze its call
20074 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
20075 represents a frame in the stack. A @code{gdb.Frame} object is only valid
20076 while its corresponding frame exists in the inferior's stack. If you try
20077 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
20080 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
20084 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
20088 The following frame-related functions are available in the @code{gdb} module:
20090 @findex gdb.selected_frame
20091 @defun selected_frame
20092 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
20095 @defun frame_stop_reason_string reason
20096 Return a string explaining the reason why @value{GDBN} stopped unwinding
20097 frames, as expressed by the given @var{reason} code (an integer, see the
20098 @code{unwind_stop_reason} method further down in this section).
20101 A @code{gdb.Frame} object has the following methods:
20104 @defmethod Frame is_valid
20105 Returns true if the @code{gdb.Frame} object is valid, false if not.
20106 A frame object can become invalid if the frame it refers to doesn't
20107 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
20108 an exception if it is invalid at the time the method is called.
20111 @defmethod Frame name
20112 Returns the function name of the frame, or @code{None} if it can't be
20116 @defmethod Frame type
20117 Returns the type of the frame. The value can be one of
20118 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
20119 or @code{gdb.SENTINEL_FRAME}.
20122 @defmethod Frame unwind_stop_reason
20123 Return an integer representing the reason why it's not possible to find
20124 more frames toward the outermost frame. Use
20125 @code{gdb.frame_stop_reason_string} to convert the value returned by this
20126 function to a string.
20129 @defmethod Frame pc
20130 Returns the frame's resume address.
20133 @defmethod Frame older
20134 Return the frame that called this frame.
20137 @defmethod Frame newer
20138 Return the frame called by this frame.
20141 @defmethod Frame read_var variable
20142 Return the value of the given variable in this frame. @var{variable} must
20148 @chapter Command Interpreters
20149 @cindex command interpreters
20151 @value{GDBN} supports multiple command interpreters, and some command
20152 infrastructure to allow users or user interface writers to switch
20153 between interpreters or run commands in other interpreters.
20155 @value{GDBN} currently supports two command interpreters, the console
20156 interpreter (sometimes called the command-line interpreter or @sc{cli})
20157 and the machine interface interpreter (or @sc{gdb/mi}). This manual
20158 describes both of these interfaces in great detail.
20160 By default, @value{GDBN} will start with the console interpreter.
20161 However, the user may choose to start @value{GDBN} with another
20162 interpreter by specifying the @option{-i} or @option{--interpreter}
20163 startup options. Defined interpreters include:
20167 @cindex console interpreter
20168 The traditional console or command-line interpreter. This is the most often
20169 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
20170 @value{GDBN} will use this interpreter.
20173 @cindex mi interpreter
20174 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
20175 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
20176 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
20180 @cindex mi2 interpreter
20181 The current @sc{gdb/mi} interface.
20184 @cindex mi1 interpreter
20185 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
20189 @cindex invoke another interpreter
20190 The interpreter being used by @value{GDBN} may not be dynamically
20191 switched at runtime. Although possible, this could lead to a very
20192 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
20193 enters the command "interpreter-set console" in a console view,
20194 @value{GDBN} would switch to using the console interpreter, rendering
20195 the IDE inoperable!
20197 @kindex interpreter-exec
20198 Although you may only choose a single interpreter at startup, you may execute
20199 commands in any interpreter from the current interpreter using the appropriate
20200 command. If you are running the console interpreter, simply use the
20201 @code{interpreter-exec} command:
20204 interpreter-exec mi "-data-list-register-names"
20207 @sc{gdb/mi} has a similar command, although it is only available in versions of
20208 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
20211 @chapter @value{GDBN} Text User Interface
20213 @cindex Text User Interface
20216 * TUI Overview:: TUI overview
20217 * TUI Keys:: TUI key bindings
20218 * TUI Single Key Mode:: TUI single key mode
20219 * TUI Commands:: TUI-specific commands
20220 * TUI Configuration:: TUI configuration variables
20223 The @value{GDBN} Text User Interface (TUI) is a terminal
20224 interface which uses the @code{curses} library to show the source
20225 file, the assembly output, the program registers and @value{GDBN}
20226 commands in separate text windows. The TUI mode is supported only
20227 on platforms where a suitable version of the @code{curses} library
20230 @pindex @value{GDBTUI}
20231 The TUI mode is enabled by default when you invoke @value{GDBN} as
20232 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
20233 You can also switch in and out of TUI mode while @value{GDBN} runs by
20234 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
20235 @xref{TUI Keys, ,TUI Key Bindings}.
20238 @section TUI Overview
20240 In TUI mode, @value{GDBN} can display several text windows:
20244 This window is the @value{GDBN} command window with the @value{GDBN}
20245 prompt and the @value{GDBN} output. The @value{GDBN} input is still
20246 managed using readline.
20249 The source window shows the source file of the program. The current
20250 line and active breakpoints are displayed in this window.
20253 The assembly window shows the disassembly output of the program.
20256 This window shows the processor registers. Registers are highlighted
20257 when their values change.
20260 The source and assembly windows show the current program position
20261 by highlighting the current line and marking it with a @samp{>} marker.
20262 Breakpoints are indicated with two markers. The first marker
20263 indicates the breakpoint type:
20267 Breakpoint which was hit at least once.
20270 Breakpoint which was never hit.
20273 Hardware breakpoint which was hit at least once.
20276 Hardware breakpoint which was never hit.
20279 The second marker indicates whether the breakpoint is enabled or not:
20283 Breakpoint is enabled.
20286 Breakpoint is disabled.
20289 The source, assembly and register windows are updated when the current
20290 thread changes, when the frame changes, or when the program counter
20293 These windows are not all visible at the same time. The command
20294 window is always visible. The others can be arranged in several
20305 source and assembly,
20308 source and registers, or
20311 assembly and registers.
20314 A status line above the command window shows the following information:
20318 Indicates the current @value{GDBN} target.
20319 (@pxref{Targets, ,Specifying a Debugging Target}).
20322 Gives the current process or thread number.
20323 When no process is being debugged, this field is set to @code{No process}.
20326 Gives the current function name for the selected frame.
20327 The name is demangled if demangling is turned on (@pxref{Print Settings}).
20328 When there is no symbol corresponding to the current program counter,
20329 the string @code{??} is displayed.
20332 Indicates the current line number for the selected frame.
20333 When the current line number is not known, the string @code{??} is displayed.
20336 Indicates the current program counter address.
20340 @section TUI Key Bindings
20341 @cindex TUI key bindings
20343 The TUI installs several key bindings in the readline keymaps
20344 (@pxref{Command Line Editing}). The following key bindings
20345 are installed for both TUI mode and the @value{GDBN} standard mode.
20354 Enter or leave the TUI mode. When leaving the TUI mode,
20355 the curses window management stops and @value{GDBN} operates using
20356 its standard mode, writing on the terminal directly. When reentering
20357 the TUI mode, control is given back to the curses windows.
20358 The screen is then refreshed.
20362 Use a TUI layout with only one window. The layout will
20363 either be @samp{source} or @samp{assembly}. When the TUI mode
20364 is not active, it will switch to the TUI mode.
20366 Think of this key binding as the Emacs @kbd{C-x 1} binding.
20370 Use a TUI layout with at least two windows. When the current
20371 layout already has two windows, the next layout with two windows is used.
20372 When a new layout is chosen, one window will always be common to the
20373 previous layout and the new one.
20375 Think of it as the Emacs @kbd{C-x 2} binding.
20379 Change the active window. The TUI associates several key bindings
20380 (like scrolling and arrow keys) with the active window. This command
20381 gives the focus to the next TUI window.
20383 Think of it as the Emacs @kbd{C-x o} binding.
20387 Switch in and out of the TUI SingleKey mode that binds single
20388 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
20391 The following key bindings only work in the TUI mode:
20396 Scroll the active window one page up.
20400 Scroll the active window one page down.
20404 Scroll the active window one line up.
20408 Scroll the active window one line down.
20412 Scroll the active window one column left.
20416 Scroll the active window one column right.
20420 Refresh the screen.
20423 Because the arrow keys scroll the active window in the TUI mode, they
20424 are not available for their normal use by readline unless the command
20425 window has the focus. When another window is active, you must use
20426 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
20427 and @kbd{C-f} to control the command window.
20429 @node TUI Single Key Mode
20430 @section TUI Single Key Mode
20431 @cindex TUI single key mode
20433 The TUI also provides a @dfn{SingleKey} mode, which binds several
20434 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
20435 switch into this mode, where the following key bindings are used:
20438 @kindex c @r{(SingleKey TUI key)}
20442 @kindex d @r{(SingleKey TUI key)}
20446 @kindex f @r{(SingleKey TUI key)}
20450 @kindex n @r{(SingleKey TUI key)}
20454 @kindex q @r{(SingleKey TUI key)}
20456 exit the SingleKey mode.
20458 @kindex r @r{(SingleKey TUI key)}
20462 @kindex s @r{(SingleKey TUI key)}
20466 @kindex u @r{(SingleKey TUI key)}
20470 @kindex v @r{(SingleKey TUI key)}
20474 @kindex w @r{(SingleKey TUI key)}
20479 Other keys temporarily switch to the @value{GDBN} command prompt.
20480 The key that was pressed is inserted in the editing buffer so that
20481 it is possible to type most @value{GDBN} commands without interaction
20482 with the TUI SingleKey mode. Once the command is entered the TUI
20483 SingleKey mode is restored. The only way to permanently leave
20484 this mode is by typing @kbd{q} or @kbd{C-x s}.
20488 @section TUI-specific Commands
20489 @cindex TUI commands
20491 The TUI has specific commands to control the text windows.
20492 These commands are always available, even when @value{GDBN} is not in
20493 the TUI mode. When @value{GDBN} is in the standard mode, most
20494 of these commands will automatically switch to the TUI mode.
20499 List and give the size of all displayed windows.
20503 Display the next layout.
20506 Display the previous layout.
20509 Display the source window only.
20512 Display the assembly window only.
20515 Display the source and assembly window.
20518 Display the register window together with the source or assembly window.
20522 Make the next window active for scrolling.
20525 Make the previous window active for scrolling.
20528 Make the source window active for scrolling.
20531 Make the assembly window active for scrolling.
20534 Make the register window active for scrolling.
20537 Make the command window active for scrolling.
20541 Refresh the screen. This is similar to typing @kbd{C-L}.
20543 @item tui reg float
20545 Show the floating point registers in the register window.
20547 @item tui reg general
20548 Show the general registers in the register window.
20551 Show the next register group. The list of register groups as well as
20552 their order is target specific. The predefined register groups are the
20553 following: @code{general}, @code{float}, @code{system}, @code{vector},
20554 @code{all}, @code{save}, @code{restore}.
20556 @item tui reg system
20557 Show the system registers in the register window.
20561 Update the source window and the current execution point.
20563 @item winheight @var{name} +@var{count}
20564 @itemx winheight @var{name} -@var{count}
20566 Change the height of the window @var{name} by @var{count}
20567 lines. Positive counts increase the height, while negative counts
20570 @item tabset @var{nchars}
20572 Set the width of tab stops to be @var{nchars} characters.
20575 @node TUI Configuration
20576 @section TUI Configuration Variables
20577 @cindex TUI configuration variables
20579 Several configuration variables control the appearance of TUI windows.
20582 @item set tui border-kind @var{kind}
20583 @kindex set tui border-kind
20584 Select the border appearance for the source, assembly and register windows.
20585 The possible values are the following:
20588 Use a space character to draw the border.
20591 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
20594 Use the Alternate Character Set to draw the border. The border is
20595 drawn using character line graphics if the terminal supports them.
20598 @item set tui border-mode @var{mode}
20599 @kindex set tui border-mode
20600 @itemx set tui active-border-mode @var{mode}
20601 @kindex set tui active-border-mode
20602 Select the display attributes for the borders of the inactive windows
20603 or the active window. The @var{mode} can be one of the following:
20606 Use normal attributes to display the border.
20612 Use reverse video mode.
20615 Use half bright mode.
20617 @item half-standout
20618 Use half bright and standout mode.
20621 Use extra bright or bold mode.
20623 @item bold-standout
20624 Use extra bright or bold and standout mode.
20629 @chapter Using @value{GDBN} under @sc{gnu} Emacs
20632 @cindex @sc{gnu} Emacs
20633 A special interface allows you to use @sc{gnu} Emacs to view (and
20634 edit) the source files for the program you are debugging with
20637 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
20638 executable file you want to debug as an argument. This command starts
20639 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
20640 created Emacs buffer.
20641 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
20643 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
20648 All ``terminal'' input and output goes through an Emacs buffer, called
20651 This applies both to @value{GDBN} commands and their output, and to the input
20652 and output done by the program you are debugging.
20654 This is useful because it means that you can copy the text of previous
20655 commands and input them again; you can even use parts of the output
20658 All the facilities of Emacs' Shell mode are available for interacting
20659 with your program. In particular, you can send signals the usual
20660 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
20664 @value{GDBN} displays source code through Emacs.
20666 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
20667 source file for that frame and puts an arrow (@samp{=>}) at the
20668 left margin of the current line. Emacs uses a separate buffer for
20669 source display, and splits the screen to show both your @value{GDBN} session
20672 Explicit @value{GDBN} @code{list} or search commands still produce output as
20673 usual, but you probably have no reason to use them from Emacs.
20676 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
20677 a graphical mode, enabled by default, which provides further buffers
20678 that can control the execution and describe the state of your program.
20679 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
20681 If you specify an absolute file name when prompted for the @kbd{M-x
20682 gdb} argument, then Emacs sets your current working directory to where
20683 your program resides. If you only specify the file name, then Emacs
20684 sets your current working directory to to the directory associated
20685 with the previous buffer. In this case, @value{GDBN} may find your
20686 program by searching your environment's @code{PATH} variable, but on
20687 some operating systems it might not find the source. So, although the
20688 @value{GDBN} input and output session proceeds normally, the auxiliary
20689 buffer does not display the current source and line of execution.
20691 The initial working directory of @value{GDBN} is printed on the top
20692 line of the GUD buffer and this serves as a default for the commands
20693 that specify files for @value{GDBN} to operate on. @xref{Files,
20694 ,Commands to Specify Files}.
20696 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
20697 need to call @value{GDBN} by a different name (for example, if you
20698 keep several configurations around, with different names) you can
20699 customize the Emacs variable @code{gud-gdb-command-name} to run the
20702 In the GUD buffer, you can use these special Emacs commands in
20703 addition to the standard Shell mode commands:
20707 Describe the features of Emacs' GUD Mode.
20710 Execute to another source line, like the @value{GDBN} @code{step} command; also
20711 update the display window to show the current file and location.
20714 Execute to next source line in this function, skipping all function
20715 calls, like the @value{GDBN} @code{next} command. Then update the display window
20716 to show the current file and location.
20719 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
20720 display window accordingly.
20723 Execute until exit from the selected stack frame, like the @value{GDBN}
20724 @code{finish} command.
20727 Continue execution of your program, like the @value{GDBN} @code{continue}
20731 Go up the number of frames indicated by the numeric argument
20732 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
20733 like the @value{GDBN} @code{up} command.
20736 Go down the number of frames indicated by the numeric argument, like the
20737 @value{GDBN} @code{down} command.
20740 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
20741 tells @value{GDBN} to set a breakpoint on the source line point is on.
20743 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
20744 separate frame which shows a backtrace when the GUD buffer is current.
20745 Move point to any frame in the stack and type @key{RET} to make it
20746 become the current frame and display the associated source in the
20747 source buffer. Alternatively, click @kbd{Mouse-2} to make the
20748 selected frame become the current one. In graphical mode, the
20749 speedbar displays watch expressions.
20751 If you accidentally delete the source-display buffer, an easy way to get
20752 it back is to type the command @code{f} in the @value{GDBN} buffer, to
20753 request a frame display; when you run under Emacs, this recreates
20754 the source buffer if necessary to show you the context of the current
20757 The source files displayed in Emacs are in ordinary Emacs buffers
20758 which are visiting the source files in the usual way. You can edit
20759 the files with these buffers if you wish; but keep in mind that @value{GDBN}
20760 communicates with Emacs in terms of line numbers. If you add or
20761 delete lines from the text, the line numbers that @value{GDBN} knows cease
20762 to correspond properly with the code.
20764 A more detailed description of Emacs' interaction with @value{GDBN} is
20765 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
20768 @c The following dropped because Epoch is nonstandard. Reactivate
20769 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
20771 @kindex Emacs Epoch environment
20775 Version 18 of @sc{gnu} Emacs has a built-in window system
20776 called the @code{epoch}
20777 environment. Users of this environment can use a new command,
20778 @code{inspect} which performs identically to @code{print} except that
20779 each value is printed in its own window.
20784 @chapter The @sc{gdb/mi} Interface
20786 @unnumberedsec Function and Purpose
20788 @cindex @sc{gdb/mi}, its purpose
20789 @sc{gdb/mi} is a line based machine oriented text interface to
20790 @value{GDBN} and is activated by specifying using the
20791 @option{--interpreter} command line option (@pxref{Mode Options}). It
20792 is specifically intended to support the development of systems which
20793 use the debugger as just one small component of a larger system.
20795 This chapter is a specification of the @sc{gdb/mi} interface. It is written
20796 in the form of a reference manual.
20798 Note that @sc{gdb/mi} is still under construction, so some of the
20799 features described below are incomplete and subject to change
20800 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
20802 @unnumberedsec Notation and Terminology
20804 @cindex notational conventions, for @sc{gdb/mi}
20805 This chapter uses the following notation:
20809 @code{|} separates two alternatives.
20812 @code{[ @var{something} ]} indicates that @var{something} is optional:
20813 it may or may not be given.
20816 @code{( @var{group} )*} means that @var{group} inside the parentheses
20817 may repeat zero or more times.
20820 @code{( @var{group} )+} means that @var{group} inside the parentheses
20821 may repeat one or more times.
20824 @code{"@var{string}"} means a literal @var{string}.
20828 @heading Dependencies
20832 * GDB/MI General Design::
20833 * GDB/MI Command Syntax::
20834 * GDB/MI Compatibility with CLI::
20835 * GDB/MI Development and Front Ends::
20836 * GDB/MI Output Records::
20837 * GDB/MI Simple Examples::
20838 * GDB/MI Command Description Format::
20839 * GDB/MI Breakpoint Commands::
20840 * GDB/MI Program Context::
20841 * GDB/MI Thread Commands::
20842 * GDB/MI Program Execution::
20843 * GDB/MI Stack Manipulation::
20844 * GDB/MI Variable Objects::
20845 * GDB/MI Data Manipulation::
20846 * GDB/MI Tracepoint Commands::
20847 * GDB/MI Symbol Query::
20848 * GDB/MI File Commands::
20850 * GDB/MI Kod Commands::
20851 * GDB/MI Memory Overlay Commands::
20852 * GDB/MI Signal Handling Commands::
20854 * GDB/MI Target Manipulation::
20855 * GDB/MI File Transfer Commands::
20856 * GDB/MI Miscellaneous Commands::
20859 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20860 @node GDB/MI General Design
20861 @section @sc{gdb/mi} General Design
20862 @cindex GDB/MI General Design
20864 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
20865 parts---commands sent to @value{GDBN}, responses to those commands
20866 and notifications. Each command results in exactly one response,
20867 indicating either successful completion of the command, or an error.
20868 For the commands that do not resume the target, the response contains the
20869 requested information. For the commands that resume the target, the
20870 response only indicates whether the target was successfully resumed.
20871 Notifications is the mechanism for reporting changes in the state of the
20872 target, or in @value{GDBN} state, that cannot conveniently be associated with
20873 a command and reported as part of that command response.
20875 The important examples of notifications are:
20879 Exec notifications. These are used to report changes in
20880 target state---when a target is resumed, or stopped. It would not
20881 be feasible to include this information in response of resuming
20882 commands, because one resume commands can result in multiple events in
20883 different threads. Also, quite some time may pass before any event
20884 happens in the target, while a frontend needs to know whether the resuming
20885 command itself was successfully executed.
20888 Console output, and status notifications. Console output
20889 notifications are used to report output of CLI commands, as well as
20890 diagnostics for other commands. Status notifications are used to
20891 report the progress of a long-running operation. Naturally, including
20892 this information in command response would mean no output is produced
20893 until the command is finished, which is undesirable.
20896 General notifications. Commands may have various side effects on
20897 the @value{GDBN} or target state beyond their official purpose. For example,
20898 a command may change the selected thread. Although such changes can
20899 be included in command response, using notification allows for more
20900 orthogonal frontend design.
20904 There's no guarantee that whenever an MI command reports an error,
20905 @value{GDBN} or the target are in any specific state, and especially,
20906 the state is not reverted to the state before the MI command was
20907 processed. Therefore, whenever an MI command results in an error,
20908 we recommend that the frontend refreshes all the information shown in
20909 the user interface.
20913 * Context management::
20914 * Asynchronous and non-stop modes::
20918 @node Context management
20919 @subsection Context management
20921 In most cases when @value{GDBN} accesses the target, this access is
20922 done in context of a specific thread and frame (@pxref{Frames}).
20923 Often, even when accessing global data, the target requires that a thread
20924 be specified. The CLI interface maintains the selected thread and frame,
20925 and supplies them to target on each command. This is convenient,
20926 because a command line user would not want to specify that information
20927 explicitly on each command, and because user interacts with
20928 @value{GDBN} via a single terminal, so no confusion is possible as
20929 to what thread and frame are the current ones.
20931 In the case of MI, the concept of selected thread and frame is less
20932 useful. First, a frontend can easily remember this information
20933 itself. Second, a graphical frontend can have more than one window,
20934 each one used for debugging a different thread, and the frontend might
20935 want to access additional threads for internal purposes. This
20936 increases the risk that by relying on implicitly selected thread, the
20937 frontend may be operating on a wrong one. Therefore, each MI command
20938 should explicitly specify which thread and frame to operate on. To
20939 make it possible, each MI command accepts the @samp{--thread} and
20940 @samp{--frame} options, the value to each is @value{GDBN} identifier
20941 for thread and frame to operate on.
20943 Usually, each top-level window in a frontend allows the user to select
20944 a thread and a frame, and remembers the user selection for further
20945 operations. However, in some cases @value{GDBN} may suggest that the
20946 current thread be changed. For example, when stopping on a breakpoint
20947 it is reasonable to switch to the thread where breakpoint is hit. For
20948 another example, if the user issues the CLI @samp{thread} command via
20949 the frontend, it is desirable to change the frontend's selected thread to the
20950 one specified by user. @value{GDBN} communicates the suggestion to
20951 change current thread using the @samp{=thread-selected} notification.
20952 No such notification is available for the selected frame at the moment.
20954 Note that historically, MI shares the selected thread with CLI, so
20955 frontends used the @code{-thread-select} to execute commands in the
20956 right context. However, getting this to work right is cumbersome. The
20957 simplest way is for frontend to emit @code{-thread-select} command
20958 before every command. This doubles the number of commands that need
20959 to be sent. The alternative approach is to suppress @code{-thread-select}
20960 if the selected thread in @value{GDBN} is supposed to be identical to the
20961 thread the frontend wants to operate on. However, getting this
20962 optimization right can be tricky. In particular, if the frontend
20963 sends several commands to @value{GDBN}, and one of the commands changes the
20964 selected thread, then the behaviour of subsequent commands will
20965 change. So, a frontend should either wait for response from such
20966 problematic commands, or explicitly add @code{-thread-select} for
20967 all subsequent commands. No frontend is known to do this exactly
20968 right, so it is suggested to just always pass the @samp{--thread} and
20969 @samp{--frame} options.
20971 @node Asynchronous and non-stop modes
20972 @subsection Asynchronous command execution and non-stop mode
20974 On some targets, @value{GDBN} is capable of processing MI commands
20975 even while the target is running. This is called @dfn{asynchronous
20976 command execution} (@pxref{Background Execution}). The frontend may
20977 specify a preferrence for asynchronous execution using the
20978 @code{-gdb-set target-async 1} command, which should be emitted before
20979 either running the executable or attaching to the target. After the
20980 frontend has started the executable or attached to the target, it can
20981 find if asynchronous execution is enabled using the
20982 @code{-list-target-features} command.
20984 Even if @value{GDBN} can accept a command while target is running,
20985 many commands that access the target do not work when the target is
20986 running. Therefore, asynchronous command execution is most useful
20987 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
20988 it is possible to examine the state of one thread, while other threads
20991 When a given thread is running, MI commands that try to access the
20992 target in the context of that thread may not work, or may work only on
20993 some targets. In particular, commands that try to operate on thread's
20994 stack will not work, on any target. Commands that read memory, or
20995 modify breakpoints, may work or not work, depending on the target. Note
20996 that even commands that operate on global state, such as @code{print},
20997 @code{set}, and breakpoint commands, still access the target in the
20998 context of a specific thread, so frontend should try to find a
20999 stopped thread and perform the operation on that thread (using the
21000 @samp{--thread} option).
21002 Which commands will work in the context of a running thread is
21003 highly target dependent. However, the two commands
21004 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
21005 to find the state of a thread, will always work.
21007 @node Thread groups
21008 @subsection Thread groups
21009 @value{GDBN} may be used to debug several processes at the same time.
21010 On some platfroms, @value{GDBN} may support debugging of several
21011 hardware systems, each one having several cores with several different
21012 processes running on each core. This section describes the MI
21013 mechanism to support such debugging scenarios.
21015 The key observation is that regardless of the structure of the
21016 target, MI can have a global list of threads, because most commands that
21017 accept the @samp{--thread} option do not need to know what process that
21018 thread belongs to. Therefore, it is not necessary to introduce
21019 neither additional @samp{--process} option, nor an notion of the
21020 current process in the MI interface. The only strictly new feature
21021 that is required is the ability to find how the threads are grouped
21024 To allow the user to discover such grouping, and to support arbitrary
21025 hierarchy of machines/cores/processes, MI introduces the concept of a
21026 @dfn{thread group}. Thread group is a collection of threads and other
21027 thread groups. A thread group always has a string identifier, a type,
21028 and may have additional attributes specific to the type. A new
21029 command, @code{-list-thread-groups}, returns the list of top-level
21030 thread groups, which correspond to processes that @value{GDBN} is
21031 debugging at the moment. By passing an identifier of a thread group
21032 to the @code{-list-thread-groups} command, it is possible to obtain
21033 the members of specific thread group.
21035 To allow the user to easily discover processes, and other objects, he
21036 wishes to debug, a concept of @dfn{available thread group} is
21037 introduced. Available thread group is an thread group that
21038 @value{GDBN} is not debugging, but that can be attached to, using the
21039 @code{-target-attach} command. The list of available top-level thread
21040 groups can be obtained using @samp{-list-thread-groups --available}.
21041 In general, the content of a thread group may be only retrieved only
21042 after attaching to that thread group.
21044 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21045 @node GDB/MI Command Syntax
21046 @section @sc{gdb/mi} Command Syntax
21049 * GDB/MI Input Syntax::
21050 * GDB/MI Output Syntax::
21053 @node GDB/MI Input Syntax
21054 @subsection @sc{gdb/mi} Input Syntax
21056 @cindex input syntax for @sc{gdb/mi}
21057 @cindex @sc{gdb/mi}, input syntax
21059 @item @var{command} @expansion{}
21060 @code{@var{cli-command} | @var{mi-command}}
21062 @item @var{cli-command} @expansion{}
21063 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
21064 @var{cli-command} is any existing @value{GDBN} CLI command.
21066 @item @var{mi-command} @expansion{}
21067 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
21068 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
21070 @item @var{token} @expansion{}
21071 "any sequence of digits"
21073 @item @var{option} @expansion{}
21074 @code{"-" @var{parameter} [ " " @var{parameter} ]}
21076 @item @var{parameter} @expansion{}
21077 @code{@var{non-blank-sequence} | @var{c-string}}
21079 @item @var{operation} @expansion{}
21080 @emph{any of the operations described in this chapter}
21082 @item @var{non-blank-sequence} @expansion{}
21083 @emph{anything, provided it doesn't contain special characters such as
21084 "-", @var{nl}, """ and of course " "}
21086 @item @var{c-string} @expansion{}
21087 @code{""" @var{seven-bit-iso-c-string-content} """}
21089 @item @var{nl} @expansion{}
21098 The CLI commands are still handled by the @sc{mi} interpreter; their
21099 output is described below.
21102 The @code{@var{token}}, when present, is passed back when the command
21106 Some @sc{mi} commands accept optional arguments as part of the parameter
21107 list. Each option is identified by a leading @samp{-} (dash) and may be
21108 followed by an optional argument parameter. Options occur first in the
21109 parameter list and can be delimited from normal parameters using
21110 @samp{--} (this is useful when some parameters begin with a dash).
21117 We want easy access to the existing CLI syntax (for debugging).
21120 We want it to be easy to spot a @sc{mi} operation.
21123 @node GDB/MI Output Syntax
21124 @subsection @sc{gdb/mi} Output Syntax
21126 @cindex output syntax of @sc{gdb/mi}
21127 @cindex @sc{gdb/mi}, output syntax
21128 The output from @sc{gdb/mi} consists of zero or more out-of-band records
21129 followed, optionally, by a single result record. This result record
21130 is for the most recent command. The sequence of output records is
21131 terminated by @samp{(gdb)}.
21133 If an input command was prefixed with a @code{@var{token}} then the
21134 corresponding output for that command will also be prefixed by that same
21138 @item @var{output} @expansion{}
21139 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
21141 @item @var{result-record} @expansion{}
21142 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
21144 @item @var{out-of-band-record} @expansion{}
21145 @code{@var{async-record} | @var{stream-record}}
21147 @item @var{async-record} @expansion{}
21148 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
21150 @item @var{exec-async-output} @expansion{}
21151 @code{[ @var{token} ] "*" @var{async-output}}
21153 @item @var{status-async-output} @expansion{}
21154 @code{[ @var{token} ] "+" @var{async-output}}
21156 @item @var{notify-async-output} @expansion{}
21157 @code{[ @var{token} ] "=" @var{async-output}}
21159 @item @var{async-output} @expansion{}
21160 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
21162 @item @var{result-class} @expansion{}
21163 @code{"done" | "running" | "connected" | "error" | "exit"}
21165 @item @var{async-class} @expansion{}
21166 @code{"stopped" | @var{others}} (where @var{others} will be added
21167 depending on the needs---this is still in development).
21169 @item @var{result} @expansion{}
21170 @code{ @var{variable} "=" @var{value}}
21172 @item @var{variable} @expansion{}
21173 @code{ @var{string} }
21175 @item @var{value} @expansion{}
21176 @code{ @var{const} | @var{tuple} | @var{list} }
21178 @item @var{const} @expansion{}
21179 @code{@var{c-string}}
21181 @item @var{tuple} @expansion{}
21182 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
21184 @item @var{list} @expansion{}
21185 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
21186 @var{result} ( "," @var{result} )* "]" }
21188 @item @var{stream-record} @expansion{}
21189 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
21191 @item @var{console-stream-output} @expansion{}
21192 @code{"~" @var{c-string}}
21194 @item @var{target-stream-output} @expansion{}
21195 @code{"@@" @var{c-string}}
21197 @item @var{log-stream-output} @expansion{}
21198 @code{"&" @var{c-string}}
21200 @item @var{nl} @expansion{}
21203 @item @var{token} @expansion{}
21204 @emph{any sequence of digits}.
21212 All output sequences end in a single line containing a period.
21215 The @code{@var{token}} is from the corresponding request. Note that
21216 for all async output, while the token is allowed by the grammar and
21217 may be output by future versions of @value{GDBN} for select async
21218 output messages, it is generally omitted. Frontends should treat
21219 all async output as reporting general changes in the state of the
21220 target and there should be no need to associate async output to any
21224 @cindex status output in @sc{gdb/mi}
21225 @var{status-async-output} contains on-going status information about the
21226 progress of a slow operation. It can be discarded. All status output is
21227 prefixed by @samp{+}.
21230 @cindex async output in @sc{gdb/mi}
21231 @var{exec-async-output} contains asynchronous state change on the target
21232 (stopped, started, disappeared). All async output is prefixed by
21236 @cindex notify output in @sc{gdb/mi}
21237 @var{notify-async-output} contains supplementary information that the
21238 client should handle (e.g., a new breakpoint information). All notify
21239 output is prefixed by @samp{=}.
21242 @cindex console output in @sc{gdb/mi}
21243 @var{console-stream-output} is output that should be displayed as is in the
21244 console. It is the textual response to a CLI command. All the console
21245 output is prefixed by @samp{~}.
21248 @cindex target output in @sc{gdb/mi}
21249 @var{target-stream-output} is the output produced by the target program.
21250 All the target output is prefixed by @samp{@@}.
21253 @cindex log output in @sc{gdb/mi}
21254 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
21255 instance messages that should be displayed as part of an error log. All
21256 the log output is prefixed by @samp{&}.
21259 @cindex list output in @sc{gdb/mi}
21260 New @sc{gdb/mi} commands should only output @var{lists} containing
21266 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
21267 details about the various output records.
21269 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21270 @node GDB/MI Compatibility with CLI
21271 @section @sc{gdb/mi} Compatibility with CLI
21273 @cindex compatibility, @sc{gdb/mi} and CLI
21274 @cindex @sc{gdb/mi}, compatibility with CLI
21276 For the developers convenience CLI commands can be entered directly,
21277 but there may be some unexpected behaviour. For example, commands
21278 that query the user will behave as if the user replied yes, breakpoint
21279 command lists are not executed and some CLI commands, such as
21280 @code{if}, @code{when} and @code{define}, prompt for further input with
21281 @samp{>}, which is not valid MI output.
21283 This feature may be removed at some stage in the future and it is
21284 recommended that front ends use the @code{-interpreter-exec} command
21285 (@pxref{-interpreter-exec}).
21287 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21288 @node GDB/MI Development and Front Ends
21289 @section @sc{gdb/mi} Development and Front Ends
21290 @cindex @sc{gdb/mi} development
21292 The application which takes the MI output and presents the state of the
21293 program being debugged to the user is called a @dfn{front end}.
21295 Although @sc{gdb/mi} is still incomplete, it is currently being used
21296 by a variety of front ends to @value{GDBN}. This makes it difficult
21297 to introduce new functionality without breaking existing usage. This
21298 section tries to minimize the problems by describing how the protocol
21301 Some changes in MI need not break a carefully designed front end, and
21302 for these the MI version will remain unchanged. The following is a
21303 list of changes that may occur within one level, so front ends should
21304 parse MI output in a way that can handle them:
21308 New MI commands may be added.
21311 New fields may be added to the output of any MI command.
21314 The range of values for fields with specified values, e.g.,
21315 @code{in_scope} (@pxref{-var-update}) may be extended.
21317 @c The format of field's content e.g type prefix, may change so parse it
21318 @c at your own risk. Yes, in general?
21320 @c The order of fields may change? Shouldn't really matter but it might
21321 @c resolve inconsistencies.
21324 If the changes are likely to break front ends, the MI version level
21325 will be increased by one. This will allow the front end to parse the
21326 output according to the MI version. Apart from mi0, new versions of
21327 @value{GDBN} will not support old versions of MI and it will be the
21328 responsibility of the front end to work with the new one.
21330 @c Starting with mi3, add a new command -mi-version that prints the MI
21333 The best way to avoid unexpected changes in MI that might break your front
21334 end is to make your project known to @value{GDBN} developers and
21335 follow development on @email{gdb@@sourceware.org} and
21336 @email{gdb-patches@@sourceware.org}.
21337 @cindex mailing lists
21339 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21340 @node GDB/MI Output Records
21341 @section @sc{gdb/mi} Output Records
21344 * GDB/MI Result Records::
21345 * GDB/MI Stream Records::
21346 * GDB/MI Async Records::
21347 * GDB/MI Frame Information::
21350 @node GDB/MI Result Records
21351 @subsection @sc{gdb/mi} Result Records
21353 @cindex result records in @sc{gdb/mi}
21354 @cindex @sc{gdb/mi}, result records
21355 In addition to a number of out-of-band notifications, the response to a
21356 @sc{gdb/mi} command includes one of the following result indications:
21360 @item "^done" [ "," @var{results} ]
21361 The synchronous operation was successful, @code{@var{results}} are the return
21366 @c Is this one correct? Should it be an out-of-band notification?
21367 The asynchronous operation was successfully started. The target is
21372 @value{GDBN} has connected to a remote target.
21374 @item "^error" "," @var{c-string}
21376 The operation failed. The @code{@var{c-string}} contains the corresponding
21381 @value{GDBN} has terminated.
21385 @node GDB/MI Stream Records
21386 @subsection @sc{gdb/mi} Stream Records
21388 @cindex @sc{gdb/mi}, stream records
21389 @cindex stream records in @sc{gdb/mi}
21390 @value{GDBN} internally maintains a number of output streams: the console, the
21391 target, and the log. The output intended for each of these streams is
21392 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
21394 Each stream record begins with a unique @dfn{prefix character} which
21395 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
21396 Syntax}). In addition to the prefix, each stream record contains a
21397 @code{@var{string-output}}. This is either raw text (with an implicit new
21398 line) or a quoted C string (which does not contain an implicit newline).
21401 @item "~" @var{string-output}
21402 The console output stream contains text that should be displayed in the
21403 CLI console window. It contains the textual responses to CLI commands.
21405 @item "@@" @var{string-output}
21406 The target output stream contains any textual output from the running
21407 target. This is only present when GDB's event loop is truly
21408 asynchronous, which is currently only the case for remote targets.
21410 @item "&" @var{string-output}
21411 The log stream contains debugging messages being produced by @value{GDBN}'s
21415 @node GDB/MI Async Records
21416 @subsection @sc{gdb/mi} Async Records
21418 @cindex async records in @sc{gdb/mi}
21419 @cindex @sc{gdb/mi}, async records
21420 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
21421 additional changes that have occurred. Those changes can either be a
21422 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
21423 target activity (e.g., target stopped).
21425 The following is the list of possible async records:
21429 @item *running,thread-id="@var{thread}"
21430 The target is now running. The @var{thread} field tells which
21431 specific thread is now running, and can be @samp{all} if all threads
21432 are running. The frontend should assume that no interaction with a
21433 running thread is possible after this notification is produced.
21434 The frontend should not assume that this notification is output
21435 only once for any command. @value{GDBN} may emit this notification
21436 several times, either for different threads, because it cannot resume
21437 all threads together, or even for a single thread, if the thread must
21438 be stepped though some code before letting it run freely.
21440 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
21441 The target has stopped. The @var{reason} field can have one of the
21445 @item breakpoint-hit
21446 A breakpoint was reached.
21447 @item watchpoint-trigger
21448 A watchpoint was triggered.
21449 @item read-watchpoint-trigger
21450 A read watchpoint was triggered.
21451 @item access-watchpoint-trigger
21452 An access watchpoint was triggered.
21453 @item function-finished
21454 An -exec-finish or similar CLI command was accomplished.
21455 @item location-reached
21456 An -exec-until or similar CLI command was accomplished.
21457 @item watchpoint-scope
21458 A watchpoint has gone out of scope.
21459 @item end-stepping-range
21460 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
21461 similar CLI command was accomplished.
21462 @item exited-signalled
21463 The inferior exited because of a signal.
21465 The inferior exited.
21466 @item exited-normally
21467 The inferior exited normally.
21468 @item signal-received
21469 A signal was received by the inferior.
21472 The @var{id} field identifies the thread that directly caused the stop
21473 -- for example by hitting a breakpoint. Depending on whether all-stop
21474 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
21475 stop all threads, or only the thread that directly triggered the stop.
21476 If all threads are stopped, the @var{stopped} field will have the
21477 value of @code{"all"}. Otherwise, the value of the @var{stopped}
21478 field will be a list of thread identifiers. Presently, this list will
21479 always include a single thread, but frontend should be prepared to see
21480 several threads in the list.
21482 @item =thread-group-created,id="@var{id}"
21483 @itemx =thread-group-exited,id="@var{id}"
21484 A thread thread group either was attached to, or has exited/detached
21485 from. The @var{id} field contains the @value{GDBN} identifier of the
21488 @item =thread-created,id="@var{id}",group-id="@var{gid}"
21489 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
21490 A thread either was created, or has exited. The @var{id} field
21491 contains the @value{GDBN} identifier of the thread. The @var{gid}
21492 field identifies the thread group this thread belongs to.
21494 @item =thread-selected,id="@var{id}"
21495 Informs that the selected thread was changed as result of the last
21496 command. This notification is not emitted as result of @code{-thread-select}
21497 command but is emitted whenever an MI command that is not documented
21498 to change the selected thread actually changes it. In particular,
21499 invoking, directly or indirectly (via user-defined command), the CLI
21500 @code{thread} command, will generate this notification.
21502 We suggest that in response to this notification, front ends
21503 highlight the selected thread and cause subsequent commands to apply to
21506 @item =library-loaded,...
21507 Reports that a new library file was loaded by the program. This
21508 notification has 4 fields---@var{id}, @var{target-name},
21509 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
21510 opaque identifier of the library. For remote debugging case,
21511 @var{target-name} and @var{host-name} fields give the name of the
21512 library file on the target, and on the host respectively. For native
21513 debugging, both those fields have the same value. The
21514 @var{symbols-loaded} field reports if the debug symbols for this
21515 library are loaded.
21517 @item =library-unloaded,...
21518 Reports that a library was unloaded by the program. This notification
21519 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
21520 the same meaning as for the @code{=library-loaded} notification
21524 @node GDB/MI Frame Information
21525 @subsection @sc{gdb/mi} Frame Information
21527 Response from many MI commands includes an information about stack
21528 frame. This information is a tuple that may have the following
21533 The level of the stack frame. The innermost frame has the level of
21534 zero. This field is always present.
21537 The name of the function corresponding to the frame. This field may
21538 be absent if @value{GDBN} is unable to determine the function name.
21541 The code address for the frame. This field is always present.
21544 The name of the source files that correspond to the frame's code
21545 address. This field may be absent.
21548 The source line corresponding to the frames' code address. This field
21552 The name of the binary file (either executable or shared library) the
21553 corresponds to the frame's code address. This field may be absent.
21558 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21559 @node GDB/MI Simple Examples
21560 @section Simple Examples of @sc{gdb/mi} Interaction
21561 @cindex @sc{gdb/mi}, simple examples
21563 This subsection presents several simple examples of interaction using
21564 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
21565 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
21566 the output received from @sc{gdb/mi}.
21568 Note the line breaks shown in the examples are here only for
21569 readability, they don't appear in the real output.
21571 @subheading Setting a Breakpoint
21573 Setting a breakpoint generates synchronous output which contains detailed
21574 information of the breakpoint.
21577 -> -break-insert main
21578 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21579 enabled="y",addr="0x08048564",func="main",file="myprog.c",
21580 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
21584 @subheading Program Execution
21586 Program execution generates asynchronous records and MI gives the
21587 reason that execution stopped.
21593 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
21594 frame=@{addr="0x08048564",func="main",
21595 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
21596 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
21601 <- *stopped,reason="exited-normally"
21605 @subheading Quitting @value{GDBN}
21607 Quitting @value{GDBN} just prints the result class @samp{^exit}.
21615 @subheading A Bad Command
21617 Here's what happens if you pass a non-existent command:
21621 <- ^error,msg="Undefined MI command: rubbish"
21626 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21627 @node GDB/MI Command Description Format
21628 @section @sc{gdb/mi} Command Description Format
21630 The remaining sections describe blocks of commands. Each block of
21631 commands is laid out in a fashion similar to this section.
21633 @subheading Motivation
21635 The motivation for this collection of commands.
21637 @subheading Introduction
21639 A brief introduction to this collection of commands as a whole.
21641 @subheading Commands
21643 For each command in the block, the following is described:
21645 @subsubheading Synopsis
21648 -command @var{args}@dots{}
21651 @subsubheading Result
21653 @subsubheading @value{GDBN} Command
21655 The corresponding @value{GDBN} CLI command(s), if any.
21657 @subsubheading Example
21659 Example(s) formatted for readability. Some of the described commands have
21660 not been implemented yet and these are labeled N.A.@: (not available).
21663 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21664 @node GDB/MI Breakpoint Commands
21665 @section @sc{gdb/mi} Breakpoint Commands
21667 @cindex breakpoint commands for @sc{gdb/mi}
21668 @cindex @sc{gdb/mi}, breakpoint commands
21669 This section documents @sc{gdb/mi} commands for manipulating
21672 @subheading The @code{-break-after} Command
21673 @findex -break-after
21675 @subsubheading Synopsis
21678 -break-after @var{number} @var{count}
21681 The breakpoint number @var{number} is not in effect until it has been
21682 hit @var{count} times. To see how this is reflected in the output of
21683 the @samp{-break-list} command, see the description of the
21684 @samp{-break-list} command below.
21686 @subsubheading @value{GDBN} Command
21688 The corresponding @value{GDBN} command is @samp{ignore}.
21690 @subsubheading Example
21695 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21696 enabled="y",addr="0x000100d0",func="main",file="hello.c",
21697 fullname="/home/foo/hello.c",line="5",times="0"@}
21704 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21705 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21706 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21707 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21708 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21709 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21710 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21711 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21712 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21713 line="5",times="0",ignore="3"@}]@}
21718 @subheading The @code{-break-catch} Command
21719 @findex -break-catch
21722 @subheading The @code{-break-commands} Command
21723 @findex -break-commands
21725 @subsubheading Synopsis
21728 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
21731 Specifies the CLI commands that should be executed when breakpoint
21732 @var{number} is hit. The parameters @var{command1} to @var{commandN}
21733 are the commands. If no command is specified, any previously-set
21734 commands are cleared. @xref{Break Commands}. Typical use of this
21735 functionality is tracing a program, that is, printing of values of
21736 some variables whenever breakpoint is hit and then continuing.
21738 @subsubheading @value{GDBN} Command
21740 The corresponding @value{GDBN} command is @samp{commands}.
21742 @subsubheading Example
21747 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21748 enabled="y",addr="0x000100d0",func="main",file="hello.c",
21749 fullname="/home/foo/hello.c",line="5",times="0"@}
21751 -break-commands 1 "print v" "continue"
21756 @subheading The @code{-break-condition} Command
21757 @findex -break-condition
21759 @subsubheading Synopsis
21762 -break-condition @var{number} @var{expr}
21765 Breakpoint @var{number} will stop the program only if the condition in
21766 @var{expr} is true. The condition becomes part of the
21767 @samp{-break-list} output (see the description of the @samp{-break-list}
21770 @subsubheading @value{GDBN} Command
21772 The corresponding @value{GDBN} command is @samp{condition}.
21774 @subsubheading Example
21778 -break-condition 1 1
21782 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21783 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21784 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21785 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21786 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21787 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21788 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21789 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21790 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21791 line="5",cond="1",times="0",ignore="3"@}]@}
21795 @subheading The @code{-break-delete} Command
21796 @findex -break-delete
21798 @subsubheading Synopsis
21801 -break-delete ( @var{breakpoint} )+
21804 Delete the breakpoint(s) whose number(s) are specified in the argument
21805 list. This is obviously reflected in the breakpoint list.
21807 @subsubheading @value{GDBN} Command
21809 The corresponding @value{GDBN} command is @samp{delete}.
21811 @subsubheading Example
21819 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
21820 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21821 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21822 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21823 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21824 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21825 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21830 @subheading The @code{-break-disable} Command
21831 @findex -break-disable
21833 @subsubheading Synopsis
21836 -break-disable ( @var{breakpoint} )+
21839 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
21840 break list is now set to @samp{n} for the named @var{breakpoint}(s).
21842 @subsubheading @value{GDBN} Command
21844 The corresponding @value{GDBN} command is @samp{disable}.
21846 @subsubheading Example
21854 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21855 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21856 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21857 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21858 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21859 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21860 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21861 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
21862 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21863 line="5",times="0"@}]@}
21867 @subheading The @code{-break-enable} Command
21868 @findex -break-enable
21870 @subsubheading Synopsis
21873 -break-enable ( @var{breakpoint} )+
21876 Enable (previously disabled) @var{breakpoint}(s).
21878 @subsubheading @value{GDBN} Command
21880 The corresponding @value{GDBN} command is @samp{enable}.
21882 @subsubheading Example
21890 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21891 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21892 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21893 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21894 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21895 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21896 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21897 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
21898 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21899 line="5",times="0"@}]@}
21903 @subheading The @code{-break-info} Command
21904 @findex -break-info
21906 @subsubheading Synopsis
21909 -break-info @var{breakpoint}
21913 Get information about a single breakpoint.
21915 @subsubheading @value{GDBN} Command
21917 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
21919 @subsubheading Example
21922 @subheading The @code{-break-insert} Command
21923 @findex -break-insert
21925 @subsubheading Synopsis
21928 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
21929 [ -c @var{condition} ] [ -i @var{ignore-count} ]
21930 [ -p @var{thread} ] [ @var{location} ]
21934 If specified, @var{location}, can be one of:
21941 @item filename:linenum
21942 @item filename:function
21946 The possible optional parameters of this command are:
21950 Insert a temporary breakpoint.
21952 Insert a hardware breakpoint.
21953 @item -c @var{condition}
21954 Make the breakpoint conditional on @var{condition}.
21955 @item -i @var{ignore-count}
21956 Initialize the @var{ignore-count}.
21958 If @var{location} cannot be parsed (for example if it
21959 refers to unknown files or functions), create a pending
21960 breakpoint. Without this flag, @value{GDBN} will report
21961 an error, and won't create a breakpoint, if @var{location}
21964 Create a disabled breakpoint.
21967 @subsubheading Result
21969 The result is in the form:
21972 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
21973 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
21974 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
21975 times="@var{times}"@}
21979 where @var{number} is the @value{GDBN} number for this breakpoint,
21980 @var{funcname} is the name of the function where the breakpoint was
21981 inserted, @var{filename} is the name of the source file which contains
21982 this function, @var{lineno} is the source line number within that file
21983 and @var{times} the number of times that the breakpoint has been hit
21984 (always 0 for -break-insert but may be greater for -break-info or -break-list
21985 which use the same output).
21987 Note: this format is open to change.
21988 @c An out-of-band breakpoint instead of part of the result?
21990 @subsubheading @value{GDBN} Command
21992 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
21993 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
21995 @subsubheading Example
22000 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
22001 fullname="/home/foo/recursive2.c,line="4",times="0"@}
22003 -break-insert -t foo
22004 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
22005 fullname="/home/foo/recursive2.c,line="11",times="0"@}
22008 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22009 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22010 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22011 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22012 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22013 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22014 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22015 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22016 addr="0x0001072c", func="main",file="recursive2.c",
22017 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
22018 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
22019 addr="0x00010774",func="foo",file="recursive2.c",
22020 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
22022 -break-insert -r foo.*
22023 ~int foo(int, int);
22024 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
22025 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
22029 @subheading The @code{-break-list} Command
22030 @findex -break-list
22032 @subsubheading Synopsis
22038 Displays the list of inserted breakpoints, showing the following fields:
22042 number of the breakpoint
22044 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
22046 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
22049 is the breakpoint enabled or no: @samp{y} or @samp{n}
22051 memory location at which the breakpoint is set
22053 logical location of the breakpoint, expressed by function name, file
22056 number of times the breakpoint has been hit
22059 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
22060 @code{body} field is an empty list.
22062 @subsubheading @value{GDBN} Command
22064 The corresponding @value{GDBN} command is @samp{info break}.
22066 @subsubheading Example
22071 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22072 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22073 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22074 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22075 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22076 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22077 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22078 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22079 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
22080 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
22081 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
22082 line="13",times="0"@}]@}
22086 Here's an example of the result when there are no breakpoints:
22091 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
22092 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22093 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22094 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22095 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22096 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22097 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22102 @subheading The @code{-break-watch} Command
22103 @findex -break-watch
22105 @subsubheading Synopsis
22108 -break-watch [ -a | -r ]
22111 Create a watchpoint. With the @samp{-a} option it will create an
22112 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
22113 read from or on a write to the memory location. With the @samp{-r}
22114 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
22115 trigger only when the memory location is accessed for reading. Without
22116 either of the options, the watchpoint created is a regular watchpoint,
22117 i.e., it will trigger when the memory location is accessed for writing.
22118 @xref{Set Watchpoints, , Setting Watchpoints}.
22120 Note that @samp{-break-list} will report a single list of watchpoints and
22121 breakpoints inserted.
22123 @subsubheading @value{GDBN} Command
22125 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
22128 @subsubheading Example
22130 Setting a watchpoint on a variable in the @code{main} function:
22135 ^done,wpt=@{number="2",exp="x"@}
22140 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
22141 value=@{old="-268439212",new="55"@},
22142 frame=@{func="main",args=[],file="recursive2.c",
22143 fullname="/home/foo/bar/recursive2.c",line="5"@}
22147 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
22148 the program execution twice: first for the variable changing value, then
22149 for the watchpoint going out of scope.
22154 ^done,wpt=@{number="5",exp="C"@}
22159 *stopped,reason="watchpoint-trigger",
22160 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
22161 frame=@{func="callee4",args=[],
22162 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22163 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
22168 *stopped,reason="watchpoint-scope",wpnum="5",
22169 frame=@{func="callee3",args=[@{name="strarg",
22170 value="0x11940 \"A string argument.\""@}],
22171 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22172 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22176 Listing breakpoints and watchpoints, at different points in the program
22177 execution. Note that once the watchpoint goes out of scope, it is
22183 ^done,wpt=@{number="2",exp="C"@}
22186 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22187 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22188 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22189 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22190 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22191 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22192 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22193 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22194 addr="0x00010734",func="callee4",
22195 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22196 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
22197 bkpt=@{number="2",type="watchpoint",disp="keep",
22198 enabled="y",addr="",what="C",times="0"@}]@}
22203 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
22204 value=@{old="-276895068",new="3"@},
22205 frame=@{func="callee4",args=[],
22206 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22207 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
22210 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22211 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22212 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22213 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22214 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22215 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22216 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22217 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22218 addr="0x00010734",func="callee4",
22219 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22220 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
22221 bkpt=@{number="2",type="watchpoint",disp="keep",
22222 enabled="y",addr="",what="C",times="-5"@}]@}
22226 ^done,reason="watchpoint-scope",wpnum="2",
22227 frame=@{func="callee3",args=[@{name="strarg",
22228 value="0x11940 \"A string argument.\""@}],
22229 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22230 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22233 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22234 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22235 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22236 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22237 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22238 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22239 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22240 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22241 addr="0x00010734",func="callee4",
22242 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22243 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
22248 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22249 @node GDB/MI Program Context
22250 @section @sc{gdb/mi} Program Context
22252 @subheading The @code{-exec-arguments} Command
22253 @findex -exec-arguments
22256 @subsubheading Synopsis
22259 -exec-arguments @var{args}
22262 Set the inferior program arguments, to be used in the next
22265 @subsubheading @value{GDBN} Command
22267 The corresponding @value{GDBN} command is @samp{set args}.
22269 @subsubheading Example
22273 -exec-arguments -v word
22280 @subheading The @code{-exec-show-arguments} Command
22281 @findex -exec-show-arguments
22283 @subsubheading Synopsis
22286 -exec-show-arguments
22289 Print the arguments of the program.
22291 @subsubheading @value{GDBN} Command
22293 The corresponding @value{GDBN} command is @samp{show args}.
22295 @subsubheading Example
22300 @subheading The @code{-environment-cd} Command
22301 @findex -environment-cd
22303 @subsubheading Synopsis
22306 -environment-cd @var{pathdir}
22309 Set @value{GDBN}'s working directory.
22311 @subsubheading @value{GDBN} Command
22313 The corresponding @value{GDBN} command is @samp{cd}.
22315 @subsubheading Example
22319 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
22325 @subheading The @code{-environment-directory} Command
22326 @findex -environment-directory
22328 @subsubheading Synopsis
22331 -environment-directory [ -r ] [ @var{pathdir} ]+
22334 Add directories @var{pathdir} to beginning of search path for source files.
22335 If the @samp{-r} option is used, the search path is reset to the default
22336 search path. If directories @var{pathdir} are supplied in addition to the
22337 @samp{-r} option, the search path is first reset and then addition
22339 Multiple directories may be specified, separated by blanks. Specifying
22340 multiple directories in a single command
22341 results in the directories added to the beginning of the
22342 search path in the same order they were presented in the command.
22343 If blanks are needed as
22344 part of a directory name, double-quotes should be used around
22345 the name. In the command output, the path will show up separated
22346 by the system directory-separator character. The directory-separator
22347 character must not be used
22348 in any directory name.
22349 If no directories are specified, the current search path is displayed.
22351 @subsubheading @value{GDBN} Command
22353 The corresponding @value{GDBN} command is @samp{dir}.
22355 @subsubheading Example
22359 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
22360 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
22362 -environment-directory ""
22363 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
22365 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
22366 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
22368 -environment-directory -r
22369 ^done,source-path="$cdir:$cwd"
22374 @subheading The @code{-environment-path} Command
22375 @findex -environment-path
22377 @subsubheading Synopsis
22380 -environment-path [ -r ] [ @var{pathdir} ]+
22383 Add directories @var{pathdir} to beginning of search path for object files.
22384 If the @samp{-r} option is used, the search path is reset to the original
22385 search path that existed at gdb start-up. If directories @var{pathdir} are
22386 supplied in addition to the
22387 @samp{-r} option, the search path is first reset and then addition
22389 Multiple directories may be specified, separated by blanks. Specifying
22390 multiple directories in a single command
22391 results in the directories added to the beginning of the
22392 search path in the same order they were presented in the command.
22393 If blanks are needed as
22394 part of a directory name, double-quotes should be used around
22395 the name. In the command output, the path will show up separated
22396 by the system directory-separator character. The directory-separator
22397 character must not be used
22398 in any directory name.
22399 If no directories are specified, the current path is displayed.
22402 @subsubheading @value{GDBN} Command
22404 The corresponding @value{GDBN} command is @samp{path}.
22406 @subsubheading Example
22411 ^done,path="/usr/bin"
22413 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
22414 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
22416 -environment-path -r /usr/local/bin
22417 ^done,path="/usr/local/bin:/usr/bin"
22422 @subheading The @code{-environment-pwd} Command
22423 @findex -environment-pwd
22425 @subsubheading Synopsis
22431 Show the current working directory.
22433 @subsubheading @value{GDBN} Command
22435 The corresponding @value{GDBN} command is @samp{pwd}.
22437 @subsubheading Example
22442 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
22446 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22447 @node GDB/MI Thread Commands
22448 @section @sc{gdb/mi} Thread Commands
22451 @subheading The @code{-thread-info} Command
22452 @findex -thread-info
22454 @subsubheading Synopsis
22457 -thread-info [ @var{thread-id} ]
22460 Reports information about either a specific thread, if
22461 the @var{thread-id} parameter is present, or about all
22462 threads. When printing information about all threads,
22463 also reports the current thread.
22465 @subsubheading @value{GDBN} Command
22467 The @samp{info thread} command prints the same information
22470 @subsubheading Example
22475 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
22476 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
22477 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
22478 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
22479 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
22480 current-thread-id="1"
22484 The @samp{state} field may have the following values:
22488 The thread is stopped. Frame information is available for stopped
22492 The thread is running. There's no frame information for running
22497 @subheading The @code{-thread-list-ids} Command
22498 @findex -thread-list-ids
22500 @subsubheading Synopsis
22506 Produces a list of the currently known @value{GDBN} thread ids. At the
22507 end of the list it also prints the total number of such threads.
22509 This command is retained for historical reasons, the
22510 @code{-thread-info} command should be used instead.
22512 @subsubheading @value{GDBN} Command
22514 Part of @samp{info threads} supplies the same information.
22516 @subsubheading Example
22521 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
22522 current-thread-id="1",number-of-threads="3"
22527 @subheading The @code{-thread-select} Command
22528 @findex -thread-select
22530 @subsubheading Synopsis
22533 -thread-select @var{threadnum}
22536 Make @var{threadnum} the current thread. It prints the number of the new
22537 current thread, and the topmost frame for that thread.
22539 This command is deprecated in favor of explicitly using the
22540 @samp{--thread} option to each command.
22542 @subsubheading @value{GDBN} Command
22544 The corresponding @value{GDBN} command is @samp{thread}.
22546 @subsubheading Example
22553 *stopped,reason="end-stepping-range",thread-id="2",line="187",
22554 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
22558 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
22559 number-of-threads="3"
22562 ^done,new-thread-id="3",
22563 frame=@{level="0",func="vprintf",
22564 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
22565 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
22569 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22570 @node GDB/MI Program Execution
22571 @section @sc{gdb/mi} Program Execution
22573 These are the asynchronous commands which generate the out-of-band
22574 record @samp{*stopped}. Currently @value{GDBN} only really executes
22575 asynchronously with remote targets and this interaction is mimicked in
22578 @subheading The @code{-exec-continue} Command
22579 @findex -exec-continue
22581 @subsubheading Synopsis
22584 -exec-continue [--all|--thread-group N]
22587 Resumes the execution of the inferior program until a breakpoint is
22588 encountered, or until the inferior exits. In all-stop mode
22589 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
22590 depending on the value of the @samp{scheduler-locking} variable. In
22591 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
22592 specified, only the thread specified with the @samp{--thread} option
22593 (or current thread, if no @samp{--thread} is provided) is resumed. If
22594 @samp{--all} is specified, all threads will be resumed. The
22595 @samp{--all} option is ignored in all-stop mode. If the
22596 @samp{--thread-group} options is specified, then all threads in that
22597 thread group are resumed.
22599 @subsubheading @value{GDBN} Command
22601 The corresponding @value{GDBN} corresponding is @samp{continue}.
22603 @subsubheading Example
22610 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
22611 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
22617 @subheading The @code{-exec-finish} Command
22618 @findex -exec-finish
22620 @subsubheading Synopsis
22626 Resumes the execution of the inferior program until the current
22627 function is exited. Displays the results returned by the function.
22629 @subsubheading @value{GDBN} Command
22631 The corresponding @value{GDBN} command is @samp{finish}.
22633 @subsubheading Example
22635 Function returning @code{void}.
22642 *stopped,reason="function-finished",frame=@{func="main",args=[],
22643 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
22647 Function returning other than @code{void}. The name of the internal
22648 @value{GDBN} variable storing the result is printed, together with the
22655 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
22656 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
22657 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22658 gdb-result-var="$1",return-value="0"
22663 @subheading The @code{-exec-interrupt} Command
22664 @findex -exec-interrupt
22666 @subsubheading Synopsis
22669 -exec-interrupt [--all|--thread-group N]
22672 Interrupts the background execution of the target. Note how the token
22673 associated with the stop message is the one for the execution command
22674 that has been interrupted. The token for the interrupt itself only
22675 appears in the @samp{^done} output. If the user is trying to
22676 interrupt a non-running program, an error message will be printed.
22678 Note that when asynchronous execution is enabled, this command is
22679 asynchronous just like other execution commands. That is, first the
22680 @samp{^done} response will be printed, and the target stop will be
22681 reported after that using the @samp{*stopped} notification.
22683 In non-stop mode, only the context thread is interrupted by default.
22684 All threads will be interrupted if the @samp{--all} option is
22685 specified. If the @samp{--thread-group} option is specified, all
22686 threads in that group will be interrupted.
22688 @subsubheading @value{GDBN} Command
22690 The corresponding @value{GDBN} command is @samp{interrupt}.
22692 @subsubheading Example
22703 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
22704 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
22705 fullname="/home/foo/bar/try.c",line="13"@}
22710 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
22714 @subheading The @code{-exec-jump} Command
22717 @subsubheading Synopsis
22720 -exec-jump @var{location}
22723 Resumes execution of the inferior program at the location specified by
22724 parameter. @xref{Specify Location}, for a description of the
22725 different forms of @var{location}.
22727 @subsubheading @value{GDBN} Command
22729 The corresponding @value{GDBN} command is @samp{jump}.
22731 @subsubheading Example
22734 -exec-jump foo.c:10
22735 *running,thread-id="all"
22740 @subheading The @code{-exec-next} Command
22743 @subsubheading Synopsis
22749 Resumes execution of the inferior program, stopping when the beginning
22750 of the next source line is reached.
22752 @subsubheading @value{GDBN} Command
22754 The corresponding @value{GDBN} command is @samp{next}.
22756 @subsubheading Example
22762 *stopped,reason="end-stepping-range",line="8",file="hello.c"
22767 @subheading The @code{-exec-next-instruction} Command
22768 @findex -exec-next-instruction
22770 @subsubheading Synopsis
22773 -exec-next-instruction
22776 Executes one machine instruction. If the instruction is a function
22777 call, continues until the function returns. If the program stops at an
22778 instruction in the middle of a source line, the address will be
22781 @subsubheading @value{GDBN} Command
22783 The corresponding @value{GDBN} command is @samp{nexti}.
22785 @subsubheading Example
22789 -exec-next-instruction
22793 *stopped,reason="end-stepping-range",
22794 addr="0x000100d4",line="5",file="hello.c"
22799 @subheading The @code{-exec-return} Command
22800 @findex -exec-return
22802 @subsubheading Synopsis
22808 Makes current function return immediately. Doesn't execute the inferior.
22809 Displays the new current frame.
22811 @subsubheading @value{GDBN} Command
22813 The corresponding @value{GDBN} command is @samp{return}.
22815 @subsubheading Example
22819 200-break-insert callee4
22820 200^done,bkpt=@{number="1",addr="0x00010734",
22821 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
22826 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
22827 frame=@{func="callee4",args=[],
22828 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22829 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
22835 111^done,frame=@{level="0",func="callee3",
22836 args=[@{name="strarg",
22837 value="0x11940 \"A string argument.\""@}],
22838 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22839 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22844 @subheading The @code{-exec-run} Command
22847 @subsubheading Synopsis
22853 Starts execution of the inferior from the beginning. The inferior
22854 executes until either a breakpoint is encountered or the program
22855 exits. In the latter case the output will include an exit code, if
22856 the program has exited exceptionally.
22858 @subsubheading @value{GDBN} Command
22860 The corresponding @value{GDBN} command is @samp{run}.
22862 @subsubheading Examples
22867 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
22872 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
22873 frame=@{func="main",args=[],file="recursive2.c",
22874 fullname="/home/foo/bar/recursive2.c",line="4"@}
22879 Program exited normally:
22887 *stopped,reason="exited-normally"
22892 Program exited exceptionally:
22900 *stopped,reason="exited",exit-code="01"
22904 Another way the program can terminate is if it receives a signal such as
22905 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
22909 *stopped,reason="exited-signalled",signal-name="SIGINT",
22910 signal-meaning="Interrupt"
22914 @c @subheading -exec-signal
22917 @subheading The @code{-exec-step} Command
22920 @subsubheading Synopsis
22926 Resumes execution of the inferior program, stopping when the beginning
22927 of the next source line is reached, if the next source line is not a
22928 function call. If it is, stop at the first instruction of the called
22931 @subsubheading @value{GDBN} Command
22933 The corresponding @value{GDBN} command is @samp{step}.
22935 @subsubheading Example
22937 Stepping into a function:
22943 *stopped,reason="end-stepping-range",
22944 frame=@{func="foo",args=[@{name="a",value="10"@},
22945 @{name="b",value="0"@}],file="recursive2.c",
22946 fullname="/home/foo/bar/recursive2.c",line="11"@}
22956 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
22961 @subheading The @code{-exec-step-instruction} Command
22962 @findex -exec-step-instruction
22964 @subsubheading Synopsis
22967 -exec-step-instruction
22970 Resumes the inferior which executes one machine instruction. The
22971 output, once @value{GDBN} has stopped, will vary depending on whether
22972 we have stopped in the middle of a source line or not. In the former
22973 case, the address at which the program stopped will be printed as
22976 @subsubheading @value{GDBN} Command
22978 The corresponding @value{GDBN} command is @samp{stepi}.
22980 @subsubheading Example
22984 -exec-step-instruction
22988 *stopped,reason="end-stepping-range",
22989 frame=@{func="foo",args=[],file="try.c",
22990 fullname="/home/foo/bar/try.c",line="10"@}
22992 -exec-step-instruction
22996 *stopped,reason="end-stepping-range",
22997 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
22998 fullname="/home/foo/bar/try.c",line="10"@}
23003 @subheading The @code{-exec-until} Command
23004 @findex -exec-until
23006 @subsubheading Synopsis
23009 -exec-until [ @var{location} ]
23012 Executes the inferior until the @var{location} specified in the
23013 argument is reached. If there is no argument, the inferior executes
23014 until a source line greater than the current one is reached. The
23015 reason for stopping in this case will be @samp{location-reached}.
23017 @subsubheading @value{GDBN} Command
23019 The corresponding @value{GDBN} command is @samp{until}.
23021 @subsubheading Example
23025 -exec-until recursive2.c:6
23029 *stopped,reason="location-reached",frame=@{func="main",args=[],
23030 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
23035 @subheading -file-clear
23036 Is this going away????
23039 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23040 @node GDB/MI Stack Manipulation
23041 @section @sc{gdb/mi} Stack Manipulation Commands
23044 @subheading The @code{-stack-info-frame} Command
23045 @findex -stack-info-frame
23047 @subsubheading Synopsis
23053 Get info on the selected frame.
23055 @subsubheading @value{GDBN} Command
23057 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
23058 (without arguments).
23060 @subsubheading Example
23065 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
23066 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23067 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
23071 @subheading The @code{-stack-info-depth} Command
23072 @findex -stack-info-depth
23074 @subsubheading Synopsis
23077 -stack-info-depth [ @var{max-depth} ]
23080 Return the depth of the stack. If the integer argument @var{max-depth}
23081 is specified, do not count beyond @var{max-depth} frames.
23083 @subsubheading @value{GDBN} Command
23085 There's no equivalent @value{GDBN} command.
23087 @subsubheading Example
23089 For a stack with frame levels 0 through 11:
23096 -stack-info-depth 4
23099 -stack-info-depth 12
23102 -stack-info-depth 11
23105 -stack-info-depth 13
23110 @subheading The @code{-stack-list-arguments} Command
23111 @findex -stack-list-arguments
23113 @subsubheading Synopsis
23116 -stack-list-arguments @var{show-values}
23117 [ @var{low-frame} @var{high-frame} ]
23120 Display a list of the arguments for the frames between @var{low-frame}
23121 and @var{high-frame} (inclusive). If @var{low-frame} and
23122 @var{high-frame} are not provided, list the arguments for the whole
23123 call stack. If the two arguments are equal, show the single frame
23124 at the corresponding level. It is an error if @var{low-frame} is
23125 larger than the actual number of frames. On the other hand,
23126 @var{high-frame} may be larger than the actual number of frames, in
23127 which case only existing frames will be returned.
23129 The @var{show-values} argument must have a value of 0 or 1. A value of
23130 0 means that only the names of the arguments are listed, a value of 1
23131 means that both names and values of the arguments are printed.
23133 Use of this command to obtain arguments in a single frame is
23134 deprecated in favor of the @samp{-stack-list-variables} command.
23136 @subsubheading @value{GDBN} Command
23138 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
23139 @samp{gdb_get_args} command which partially overlaps with the
23140 functionality of @samp{-stack-list-arguments}.
23142 @subsubheading Example
23149 frame=@{level="0",addr="0x00010734",func="callee4",
23150 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23151 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
23152 frame=@{level="1",addr="0x0001076c",func="callee3",
23153 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23154 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
23155 frame=@{level="2",addr="0x0001078c",func="callee2",
23156 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23157 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
23158 frame=@{level="3",addr="0x000107b4",func="callee1",
23159 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23160 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
23161 frame=@{level="4",addr="0x000107e0",func="main",
23162 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23163 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
23165 -stack-list-arguments 0
23168 frame=@{level="0",args=[]@},
23169 frame=@{level="1",args=[name="strarg"]@},
23170 frame=@{level="2",args=[name="intarg",name="strarg"]@},
23171 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
23172 frame=@{level="4",args=[]@}]
23174 -stack-list-arguments 1
23177 frame=@{level="0",args=[]@},
23179 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
23180 frame=@{level="2",args=[
23181 @{name="intarg",value="2"@},
23182 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
23183 @{frame=@{level="3",args=[
23184 @{name="intarg",value="2"@},
23185 @{name="strarg",value="0x11940 \"A string argument.\""@},
23186 @{name="fltarg",value="3.5"@}]@},
23187 frame=@{level="4",args=[]@}]
23189 -stack-list-arguments 0 2 2
23190 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
23192 -stack-list-arguments 1 2 2
23193 ^done,stack-args=[frame=@{level="2",
23194 args=[@{name="intarg",value="2"@},
23195 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
23199 @c @subheading -stack-list-exception-handlers
23202 @subheading The @code{-stack-list-frames} Command
23203 @findex -stack-list-frames
23205 @subsubheading Synopsis
23208 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
23211 List the frames currently on the stack. For each frame it displays the
23216 The frame number, 0 being the topmost frame, i.e., the innermost function.
23218 The @code{$pc} value for that frame.
23222 File name of the source file where the function lives.
23224 Line number corresponding to the @code{$pc}.
23227 If invoked without arguments, this command prints a backtrace for the
23228 whole stack. If given two integer arguments, it shows the frames whose
23229 levels are between the two arguments (inclusive). If the two arguments
23230 are equal, it shows the single frame at the corresponding level. It is
23231 an error if @var{low-frame} is larger than the actual number of
23232 frames. On the other hand, @var{high-frame} may be larger than the
23233 actual number of frames, in which case only existing frames will be returned.
23235 @subsubheading @value{GDBN} Command
23237 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
23239 @subsubheading Example
23241 Full stack backtrace:
23247 [frame=@{level="0",addr="0x0001076c",func="foo",
23248 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
23249 frame=@{level="1",addr="0x000107a4",func="foo",
23250 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23251 frame=@{level="2",addr="0x000107a4",func="foo",
23252 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23253 frame=@{level="3",addr="0x000107a4",func="foo",
23254 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23255 frame=@{level="4",addr="0x000107a4",func="foo",
23256 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23257 frame=@{level="5",addr="0x000107a4",func="foo",
23258 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23259 frame=@{level="6",addr="0x000107a4",func="foo",
23260 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23261 frame=@{level="7",addr="0x000107a4",func="foo",
23262 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23263 frame=@{level="8",addr="0x000107a4",func="foo",
23264 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23265 frame=@{level="9",addr="0x000107a4",func="foo",
23266 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23267 frame=@{level="10",addr="0x000107a4",func="foo",
23268 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23269 frame=@{level="11",addr="0x00010738",func="main",
23270 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
23274 Show frames between @var{low_frame} and @var{high_frame}:
23278 -stack-list-frames 3 5
23280 [frame=@{level="3",addr="0x000107a4",func="foo",
23281 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23282 frame=@{level="4",addr="0x000107a4",func="foo",
23283 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23284 frame=@{level="5",addr="0x000107a4",func="foo",
23285 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
23289 Show a single frame:
23293 -stack-list-frames 3 3
23295 [frame=@{level="3",addr="0x000107a4",func="foo",
23296 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
23301 @subheading The @code{-stack-list-locals} Command
23302 @findex -stack-list-locals
23304 @subsubheading Synopsis
23307 -stack-list-locals @var{print-values}
23310 Display the local variable names for the selected frame. If
23311 @var{print-values} is 0 or @code{--no-values}, print only the names of
23312 the variables; if it is 1 or @code{--all-values}, print also their
23313 values; and if it is 2 or @code{--simple-values}, print the name,
23314 type and value for simple data types and the name and type for arrays,
23315 structures and unions. In this last case, a frontend can immediately
23316 display the value of simple data types and create variable objects for
23317 other data types when the user wishes to explore their values in
23320 This command is deprecated in favor of the
23321 @samp{-stack-list-variables} command.
23323 @subsubheading @value{GDBN} Command
23325 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
23327 @subsubheading Example
23331 -stack-list-locals 0
23332 ^done,locals=[name="A",name="B",name="C"]
23334 -stack-list-locals --all-values
23335 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
23336 @{name="C",value="@{1, 2, 3@}"@}]
23337 -stack-list-locals --simple-values
23338 ^done,locals=[@{name="A",type="int",value="1"@},
23339 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
23343 @subheading The @code{-stack-list-variables} Command
23344 @findex -stack-list-variables
23346 @subsubheading Synopsis
23349 -stack-list-variables @var{print-values}
23352 Display the names of local variables and function arguments for the selected frame. If
23353 @var{print-values} is 0 or @code{--no-values}, print only the names of
23354 the variables; if it is 1 or @code{--all-values}, print also their
23355 values; and if it is 2 or @code{--simple-values}, print the name,
23356 type and value for simple data types and the name and type for arrays,
23357 structures and unions.
23359 @subsubheading Example
23363 -stack-list-variables --thread 1 --frame 0 --all-values
23364 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
23369 @subheading The @code{-stack-select-frame} Command
23370 @findex -stack-select-frame
23372 @subsubheading Synopsis
23375 -stack-select-frame @var{framenum}
23378 Change the selected frame. Select a different frame @var{framenum} on
23381 This command in deprecated in favor of passing the @samp{--frame}
23382 option to every command.
23384 @subsubheading @value{GDBN} Command
23386 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
23387 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
23389 @subsubheading Example
23393 -stack-select-frame 2
23398 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23399 @node GDB/MI Variable Objects
23400 @section @sc{gdb/mi} Variable Objects
23404 @subheading Motivation for Variable Objects in @sc{gdb/mi}
23406 For the implementation of a variable debugger window (locals, watched
23407 expressions, etc.), we are proposing the adaptation of the existing code
23408 used by @code{Insight}.
23410 The two main reasons for that are:
23414 It has been proven in practice (it is already on its second generation).
23417 It will shorten development time (needless to say how important it is
23421 The original interface was designed to be used by Tcl code, so it was
23422 slightly changed so it could be used through @sc{gdb/mi}. This section
23423 describes the @sc{gdb/mi} operations that will be available and gives some
23424 hints about their use.
23426 @emph{Note}: In addition to the set of operations described here, we
23427 expect the @sc{gui} implementation of a variable window to require, at
23428 least, the following operations:
23431 @item @code{-gdb-show} @code{output-radix}
23432 @item @code{-stack-list-arguments}
23433 @item @code{-stack-list-locals}
23434 @item @code{-stack-select-frame}
23439 @subheading Introduction to Variable Objects
23441 @cindex variable objects in @sc{gdb/mi}
23443 Variable objects are "object-oriented" MI interface for examining and
23444 changing values of expressions. Unlike some other MI interfaces that
23445 work with expressions, variable objects are specifically designed for
23446 simple and efficient presentation in the frontend. A variable object
23447 is identified by string name. When a variable object is created, the
23448 frontend specifies the expression for that variable object. The
23449 expression can be a simple variable, or it can be an arbitrary complex
23450 expression, and can even involve CPU registers. After creating a
23451 variable object, the frontend can invoke other variable object
23452 operations---for example to obtain or change the value of a variable
23453 object, or to change display format.
23455 Variable objects have hierarchical tree structure. Any variable object
23456 that corresponds to a composite type, such as structure in C, has
23457 a number of child variable objects, for example corresponding to each
23458 element of a structure. A child variable object can itself have
23459 children, recursively. Recursion ends when we reach
23460 leaf variable objects, which always have built-in types. Child variable
23461 objects are created only by explicit request, so if a frontend
23462 is not interested in the children of a particular variable object, no
23463 child will be created.
23465 For a leaf variable object it is possible to obtain its value as a
23466 string, or set the value from a string. String value can be also
23467 obtained for a non-leaf variable object, but it's generally a string
23468 that only indicates the type of the object, and does not list its
23469 contents. Assignment to a non-leaf variable object is not allowed.
23471 A frontend does not need to read the values of all variable objects each time
23472 the program stops. Instead, MI provides an update command that lists all
23473 variable objects whose values has changed since the last update
23474 operation. This considerably reduces the amount of data that must
23475 be transferred to the frontend. As noted above, children variable
23476 objects are created on demand, and only leaf variable objects have a
23477 real value. As result, gdb will read target memory only for leaf
23478 variables that frontend has created.
23480 The automatic update is not always desirable. For example, a frontend
23481 might want to keep a value of some expression for future reference,
23482 and never update it. For another example, fetching memory is
23483 relatively slow for embedded targets, so a frontend might want
23484 to disable automatic update for the variables that are either not
23485 visible on the screen, or ``closed''. This is possible using so
23486 called ``frozen variable objects''. Such variable objects are never
23487 implicitly updated.
23489 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
23490 fixed variable object, the expression is parsed when the variable
23491 object is created, including associating identifiers to specific
23492 variables. The meaning of expression never changes. For a floating
23493 variable object the values of variables whose names appear in the
23494 expressions are re-evaluated every time in the context of the current
23495 frame. Consider this example:
23500 struct work_state state;
23507 If a fixed variable object for the @code{state} variable is created in
23508 this function, and we enter the recursive call, the the variable
23509 object will report the value of @code{state} in the top-level
23510 @code{do_work} invocation. On the other hand, a floating variable
23511 object will report the value of @code{state} in the current frame.
23513 If an expression specified when creating a fixed variable object
23514 refers to a local variable, the variable object becomes bound to the
23515 thread and frame in which the variable object is created. When such
23516 variable object is updated, @value{GDBN} makes sure that the
23517 thread/frame combination the variable object is bound to still exists,
23518 and re-evaluates the variable object in context of that thread/frame.
23520 The following is the complete set of @sc{gdb/mi} operations defined to
23521 access this functionality:
23523 @multitable @columnfractions .4 .6
23524 @item @strong{Operation}
23525 @tab @strong{Description}
23527 @item @code{-enable-pretty-printing}
23528 @tab enable Python-based pretty-printing
23529 @item @code{-var-create}
23530 @tab create a variable object
23531 @item @code{-var-delete}
23532 @tab delete the variable object and/or its children
23533 @item @code{-var-set-format}
23534 @tab set the display format of this variable
23535 @item @code{-var-show-format}
23536 @tab show the display format of this variable
23537 @item @code{-var-info-num-children}
23538 @tab tells how many children this object has
23539 @item @code{-var-list-children}
23540 @tab return a list of the object's children
23541 @item @code{-var-info-type}
23542 @tab show the type of this variable object
23543 @item @code{-var-info-expression}
23544 @tab print parent-relative expression that this variable object represents
23545 @item @code{-var-info-path-expression}
23546 @tab print full expression that this variable object represents
23547 @item @code{-var-show-attributes}
23548 @tab is this variable editable? does it exist here?
23549 @item @code{-var-evaluate-expression}
23550 @tab get the value of this variable
23551 @item @code{-var-assign}
23552 @tab set the value of this variable
23553 @item @code{-var-update}
23554 @tab update the variable and its children
23555 @item @code{-var-set-frozen}
23556 @tab set frozeness attribute
23557 @item @code{-var-set-update-range}
23558 @tab set range of children to display on update
23561 In the next subsection we describe each operation in detail and suggest
23562 how it can be used.
23564 @subheading Description And Use of Operations on Variable Objects
23566 @subheading The @code{-enable-pretty-printing} Command
23567 @findex -enable-pretty-printing
23570 -enable-pretty-printing
23573 @value{GDBN} allows Python-based visualizers to affect the output of the
23574 MI variable object commands. However, because there was no way to
23575 implement this in a fully backward-compatible way, a front end must
23576 request that this functionality be enabled.
23578 Once enabled, this feature cannot be disabled.
23580 Note that if Python support has not been compiled into @value{GDBN},
23581 this command will still succeed (and do nothing).
23583 This feature is currently (as of @value{GDBN} 7.0) experimental, and
23584 may work differently in future versions of @value{GDBN}.
23586 @subheading The @code{-var-create} Command
23587 @findex -var-create
23589 @subsubheading Synopsis
23592 -var-create @{@var{name} | "-"@}
23593 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
23596 This operation creates a variable object, which allows the monitoring of
23597 a variable, the result of an expression, a memory cell or a CPU
23600 The @var{name} parameter is the string by which the object can be
23601 referenced. It must be unique. If @samp{-} is specified, the varobj
23602 system will generate a string ``varNNNNNN'' automatically. It will be
23603 unique provided that one does not specify @var{name} of that format.
23604 The command fails if a duplicate name is found.
23606 The frame under which the expression should be evaluated can be
23607 specified by @var{frame-addr}. A @samp{*} indicates that the current
23608 frame should be used. A @samp{@@} indicates that a floating variable
23609 object must be created.
23611 @var{expression} is any expression valid on the current language set (must not
23612 begin with a @samp{*}), or one of the following:
23616 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
23619 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
23622 @samp{$@var{regname}} --- a CPU register name
23625 @cindex dynamic varobj
23626 A varobj's contents may be provided by a Python-based pretty-printer. In this
23627 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
23628 have slightly different semantics in some cases. If the
23629 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
23630 will never create a dynamic varobj. This ensures backward
23631 compatibility for existing clients.
23633 @subsubheading Result
23635 This operation returns attributes of the newly-created varobj. These
23640 The name of the varobj.
23643 The number of children of the varobj. This number is not necessarily
23644 reliable for a dynamic varobj. Instead, you must examine the
23645 @samp{has_more} attribute.
23648 The varobj's scalar value. For a varobj whose type is some sort of
23649 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
23650 will not be interesting.
23653 The varobj's type. This is a string representation of the type, as
23654 would be printed by the @value{GDBN} CLI.
23657 If a variable object is bound to a specific thread, then this is the
23658 thread's identifier.
23661 For a dynamic varobj, this indicates whether there appear to be any
23662 children available. For a non-dynamic varobj, this will be 0.
23665 This attribute will be present and have the value @samp{1} if the
23666 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
23667 then this attribute will not be present.
23670 A dynamic varobj can supply a display hint to the front end. The
23671 value comes directly from the Python pretty-printer object's
23672 @code{display_hint} method. @xref{Pretty Printing}.
23675 Typical output will look like this:
23678 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
23679 has_more="@var{has_more}"
23683 @subheading The @code{-var-delete} Command
23684 @findex -var-delete
23686 @subsubheading Synopsis
23689 -var-delete [ -c ] @var{name}
23692 Deletes a previously created variable object and all of its children.
23693 With the @samp{-c} option, just deletes the children.
23695 Returns an error if the object @var{name} is not found.
23698 @subheading The @code{-var-set-format} Command
23699 @findex -var-set-format
23701 @subsubheading Synopsis
23704 -var-set-format @var{name} @var{format-spec}
23707 Sets the output format for the value of the object @var{name} to be
23710 @anchor{-var-set-format}
23711 The syntax for the @var{format-spec} is as follows:
23714 @var{format-spec} @expansion{}
23715 @{binary | decimal | hexadecimal | octal | natural@}
23718 The natural format is the default format choosen automatically
23719 based on the variable type (like decimal for an @code{int}, hex
23720 for pointers, etc.).
23722 For a variable with children, the format is set only on the
23723 variable itself, and the children are not affected.
23725 @subheading The @code{-var-show-format} Command
23726 @findex -var-show-format
23728 @subsubheading Synopsis
23731 -var-show-format @var{name}
23734 Returns the format used to display the value of the object @var{name}.
23737 @var{format} @expansion{}
23742 @subheading The @code{-var-info-num-children} Command
23743 @findex -var-info-num-children
23745 @subsubheading Synopsis
23748 -var-info-num-children @var{name}
23751 Returns the number of children of a variable object @var{name}:
23757 Note that this number is not completely reliable for a dynamic varobj.
23758 It will return the current number of children, but more children may
23762 @subheading The @code{-var-list-children} Command
23763 @findex -var-list-children
23765 @subsubheading Synopsis
23768 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
23770 @anchor{-var-list-children}
23772 Return a list of the children of the specified variable object and
23773 create variable objects for them, if they do not already exist. With
23774 a single argument or if @var{print-values} has a value for of 0 or
23775 @code{--no-values}, print only the names of the variables; if
23776 @var{print-values} is 1 or @code{--all-values}, also print their
23777 values; and if it is 2 or @code{--simple-values} print the name and
23778 value for simple data types and just the name for arrays, structures
23781 @var{from} and @var{to}, if specified, indicate the range of children
23782 to report. If @var{from} or @var{to} is less than zero, the range is
23783 reset and all children will be reported. Otherwise, children starting
23784 at @var{from} (zero-based) and up to and excluding @var{to} will be
23787 If a child range is requested, it will only affect the current call to
23788 @code{-var-list-children}, but not future calls to @code{-var-update}.
23789 For this, you must instead use @code{-var-set-update-range}. The
23790 intent of this approach is to enable a front end to implement any
23791 update approach it likes; for example, scrolling a view may cause the
23792 front end to request more children with @code{-var-list-children}, and
23793 then the front end could call @code{-var-set-update-range} with a
23794 different range to ensure that future updates are restricted to just
23797 For each child the following results are returned:
23802 Name of the variable object created for this child.
23805 The expression to be shown to the user by the front end to designate this child.
23806 For example this may be the name of a structure member.
23808 For a dynamic varobj, this value cannot be used to form an
23809 expression. There is no way to do this at all with a dynamic varobj.
23811 For C/C@t{++} structures there are several pseudo children returned to
23812 designate access qualifiers. For these pseudo children @var{exp} is
23813 @samp{public}, @samp{private}, or @samp{protected}. In this case the
23814 type and value are not present.
23816 A dynamic varobj will not report the access qualifying
23817 pseudo-children, regardless of the language. This information is not
23818 available at all with a dynamic varobj.
23821 Number of children this child has. For a dynamic varobj, this will be
23825 The type of the child.
23828 If values were requested, this is the value.
23831 If this variable object is associated with a thread, this is the thread id.
23832 Otherwise this result is not present.
23835 If the variable object is frozen, this variable will be present with a value of 1.
23838 The result may have its own attributes:
23842 A dynamic varobj can supply a display hint to the front end. The
23843 value comes directly from the Python pretty-printer object's
23844 @code{display_hint} method. @xref{Pretty Printing}.
23847 This is an integer attribute which is nonzero if there are children
23848 remaining after the end of the selected range.
23851 @subsubheading Example
23855 -var-list-children n
23856 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
23857 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
23859 -var-list-children --all-values n
23860 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
23861 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
23865 @subheading The @code{-var-info-type} Command
23866 @findex -var-info-type
23868 @subsubheading Synopsis
23871 -var-info-type @var{name}
23874 Returns the type of the specified variable @var{name}. The type is
23875 returned as a string in the same format as it is output by the
23879 type=@var{typename}
23883 @subheading The @code{-var-info-expression} Command
23884 @findex -var-info-expression
23886 @subsubheading Synopsis
23889 -var-info-expression @var{name}
23892 Returns a string that is suitable for presenting this
23893 variable object in user interface. The string is generally
23894 not valid expression in the current language, and cannot be evaluated.
23896 For example, if @code{a} is an array, and variable object
23897 @code{A} was created for @code{a}, then we'll get this output:
23900 (gdb) -var-info-expression A.1
23901 ^done,lang="C",exp="1"
23905 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
23907 Note that the output of the @code{-var-list-children} command also
23908 includes those expressions, so the @code{-var-info-expression} command
23911 @subheading The @code{-var-info-path-expression} Command
23912 @findex -var-info-path-expression
23914 @subsubheading Synopsis
23917 -var-info-path-expression @var{name}
23920 Returns an expression that can be evaluated in the current
23921 context and will yield the same value that a variable object has.
23922 Compare this with the @code{-var-info-expression} command, which
23923 result can be used only for UI presentation. Typical use of
23924 the @code{-var-info-path-expression} command is creating a
23925 watchpoint from a variable object.
23927 This command is currently not valid for children of a dynamic varobj,
23928 and will give an error when invoked on one.
23930 For example, suppose @code{C} is a C@t{++} class, derived from class
23931 @code{Base}, and that the @code{Base} class has a member called
23932 @code{m_size}. Assume a variable @code{c} is has the type of
23933 @code{C} and a variable object @code{C} was created for variable
23934 @code{c}. Then, we'll get this output:
23936 (gdb) -var-info-path-expression C.Base.public.m_size
23937 ^done,path_expr=((Base)c).m_size)
23940 @subheading The @code{-var-show-attributes} Command
23941 @findex -var-show-attributes
23943 @subsubheading Synopsis
23946 -var-show-attributes @var{name}
23949 List attributes of the specified variable object @var{name}:
23952 status=@var{attr} [ ( ,@var{attr} )* ]
23956 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
23958 @subheading The @code{-var-evaluate-expression} Command
23959 @findex -var-evaluate-expression
23961 @subsubheading Synopsis
23964 -var-evaluate-expression [-f @var{format-spec}] @var{name}
23967 Evaluates the expression that is represented by the specified variable
23968 object and returns its value as a string. The format of the string
23969 can be specified with the @samp{-f} option. The possible values of
23970 this option are the same as for @code{-var-set-format}
23971 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
23972 the current display format will be used. The current display format
23973 can be changed using the @code{-var-set-format} command.
23979 Note that one must invoke @code{-var-list-children} for a variable
23980 before the value of a child variable can be evaluated.
23982 @subheading The @code{-var-assign} Command
23983 @findex -var-assign
23985 @subsubheading Synopsis
23988 -var-assign @var{name} @var{expression}
23991 Assigns the value of @var{expression} to the variable object specified
23992 by @var{name}. The object must be @samp{editable}. If the variable's
23993 value is altered by the assign, the variable will show up in any
23994 subsequent @code{-var-update} list.
23996 @subsubheading Example
24004 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
24008 @subheading The @code{-var-update} Command
24009 @findex -var-update
24011 @subsubheading Synopsis
24014 -var-update [@var{print-values}] @{@var{name} | "*"@}
24017 Reevaluate the expressions corresponding to the variable object
24018 @var{name} and all its direct and indirect children, and return the
24019 list of variable objects whose values have changed; @var{name} must
24020 be a root variable object. Here, ``changed'' means that the result of
24021 @code{-var-evaluate-expression} before and after the
24022 @code{-var-update} is different. If @samp{*} is used as the variable
24023 object names, all existing variable objects are updated, except
24024 for frozen ones (@pxref{-var-set-frozen}). The option
24025 @var{print-values} determines whether both names and values, or just
24026 names are printed. The possible values of this option are the same
24027 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
24028 recommended to use the @samp{--all-values} option, to reduce the
24029 number of MI commands needed on each program stop.
24031 With the @samp{*} parameter, if a variable object is bound to a
24032 currently running thread, it will not be updated, without any
24035 If @code{-var-set-update-range} was previously used on a varobj, then
24036 only the selected range of children will be reported.
24038 @code{-var-update} reports all the changed varobjs in a tuple named
24041 Each item in the change list is itself a tuple holding:
24045 The name of the varobj.
24048 If values were requested for this update, then this field will be
24049 present and will hold the value of the varobj.
24052 @anchor{-var-update}
24053 This field is a string which may take one of three values:
24057 The variable object's current value is valid.
24060 The variable object does not currently hold a valid value but it may
24061 hold one in the future if its associated expression comes back into
24065 The variable object no longer holds a valid value.
24066 This can occur when the executable file being debugged has changed,
24067 either through recompilation or by using the @value{GDBN} @code{file}
24068 command. The front end should normally choose to delete these variable
24072 In the future new values may be added to this list so the front should
24073 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
24076 This is only present if the varobj is still valid. If the type
24077 changed, then this will be the string @samp{true}; otherwise it will
24081 If the varobj's type changed, then this field will be present and will
24084 @item new_num_children
24085 For a dynamic varobj, if the number of children changed, or if the
24086 type changed, this will be the new number of children.
24088 The @samp{numchild} field in other varobj responses is generally not
24089 valid for a dynamic varobj -- it will show the number of children that
24090 @value{GDBN} knows about, but because dynamic varobjs lazily
24091 instantiate their children, this will not reflect the number of
24092 children which may be available.
24094 The @samp{new_num_children} attribute only reports changes to the
24095 number of children known by @value{GDBN}. This is the only way to
24096 detect whether an update has removed children (which necessarily can
24097 only happen at the end of the update range).
24100 The display hint, if any.
24103 This is an integer value, which will be 1 if there are more children
24104 available outside the varobj's update range.
24107 This attribute will be present and have the value @samp{1} if the
24108 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
24109 then this attribute will not be present.
24112 If new children were added to a dynamic varobj within the selected
24113 update range (as set by @code{-var-set-update-range}), then they will
24114 be listed in this attribute.
24117 @subsubheading Example
24124 -var-update --all-values var1
24125 ^done,changelist=[@{name="var1",value="3",in_scope="true",
24126 type_changed="false"@}]
24130 @subheading The @code{-var-set-frozen} Command
24131 @findex -var-set-frozen
24132 @anchor{-var-set-frozen}
24134 @subsubheading Synopsis
24137 -var-set-frozen @var{name} @var{flag}
24140 Set the frozenness flag on the variable object @var{name}. The
24141 @var{flag} parameter should be either @samp{1} to make the variable
24142 frozen or @samp{0} to make it unfrozen. If a variable object is
24143 frozen, then neither itself, nor any of its children, are
24144 implicitly updated by @code{-var-update} of
24145 a parent variable or by @code{-var-update *}. Only
24146 @code{-var-update} of the variable itself will update its value and
24147 values of its children. After a variable object is unfrozen, it is
24148 implicitly updated by all subsequent @code{-var-update} operations.
24149 Unfreezing a variable does not update it, only subsequent
24150 @code{-var-update} does.
24152 @subsubheading Example
24156 -var-set-frozen V 1
24161 @subheading The @code{-var-set-update-range} command
24162 @findex -var-set-update-range
24163 @anchor{-var-set-update-range}
24165 @subsubheading Synopsis
24168 -var-set-update-range @var{name} @var{from} @var{to}
24171 Set the range of children to be returned by future invocations of
24172 @code{-var-update}.
24174 @var{from} and @var{to} indicate the range of children to report. If
24175 @var{from} or @var{to} is less than zero, the range is reset and all
24176 children will be reported. Otherwise, children starting at @var{from}
24177 (zero-based) and up to and excluding @var{to} will be reported.
24179 @subsubheading Example
24183 -var-set-update-range V 1 2
24187 @subheading The @code{-var-set-visualizer} command
24188 @findex -var-set-visualizer
24189 @anchor{-var-set-visualizer}
24191 @subsubheading Synopsis
24194 -var-set-visualizer @var{name} @var{visualizer}
24197 Set a visualizer for the variable object @var{name}.
24199 @var{visualizer} is the visualizer to use. The special value
24200 @samp{None} means to disable any visualizer in use.
24202 If not @samp{None}, @var{visualizer} must be a Python expression.
24203 This expression must evaluate to a callable object which accepts a
24204 single argument. @value{GDBN} will call this object with the value of
24205 the varobj @var{name} as an argument (this is done so that the same
24206 Python pretty-printing code can be used for both the CLI and MI).
24207 When called, this object must return an object which conforms to the
24208 pretty-printing interface (@pxref{Pretty Printing}).
24210 The pre-defined function @code{gdb.default_visualizer} may be used to
24211 select a visualizer by following the built-in process
24212 (@pxref{Selecting Pretty-Printers}). This is done automatically when
24213 a varobj is created, and so ordinarily is not needed.
24215 This feature is only available if Python support is enabled. The MI
24216 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
24217 can be used to check this.
24219 @subsubheading Example
24221 Resetting the visualizer:
24225 -var-set-visualizer V None
24229 Reselecting the default (type-based) visualizer:
24233 -var-set-visualizer V gdb.default_visualizer
24237 Suppose @code{SomeClass} is a visualizer class. A lambda expression
24238 can be used to instantiate this class for a varobj:
24242 -var-set-visualizer V "lambda val: SomeClass()"
24246 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24247 @node GDB/MI Data Manipulation
24248 @section @sc{gdb/mi} Data Manipulation
24250 @cindex data manipulation, in @sc{gdb/mi}
24251 @cindex @sc{gdb/mi}, data manipulation
24252 This section describes the @sc{gdb/mi} commands that manipulate data:
24253 examine memory and registers, evaluate expressions, etc.
24255 @c REMOVED FROM THE INTERFACE.
24256 @c @subheading -data-assign
24257 @c Change the value of a program variable. Plenty of side effects.
24258 @c @subsubheading GDB Command
24260 @c @subsubheading Example
24263 @subheading The @code{-data-disassemble} Command
24264 @findex -data-disassemble
24266 @subsubheading Synopsis
24270 [ -s @var{start-addr} -e @var{end-addr} ]
24271 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
24279 @item @var{start-addr}
24280 is the beginning address (or @code{$pc})
24281 @item @var{end-addr}
24283 @item @var{filename}
24284 is the name of the file to disassemble
24285 @item @var{linenum}
24286 is the line number to disassemble around
24288 is the number of disassembly lines to be produced. If it is -1,
24289 the whole function will be disassembled, in case no @var{end-addr} is
24290 specified. If @var{end-addr} is specified as a non-zero value, and
24291 @var{lines} is lower than the number of disassembly lines between
24292 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
24293 displayed; if @var{lines} is higher than the number of lines between
24294 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
24297 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
24301 @subsubheading Result
24303 The output for each instruction is composed of four fields:
24312 Note that whatever included in the instruction field, is not manipulated
24313 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
24315 @subsubheading @value{GDBN} Command
24317 There's no direct mapping from this command to the CLI.
24319 @subsubheading Example
24321 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
24325 -data-disassemble -s $pc -e "$pc + 20" -- 0
24328 @{address="0x000107c0",func-name="main",offset="4",
24329 inst="mov 2, %o0"@},
24330 @{address="0x000107c4",func-name="main",offset="8",
24331 inst="sethi %hi(0x11800), %o2"@},
24332 @{address="0x000107c8",func-name="main",offset="12",
24333 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
24334 @{address="0x000107cc",func-name="main",offset="16",
24335 inst="sethi %hi(0x11800), %o2"@},
24336 @{address="0x000107d0",func-name="main",offset="20",
24337 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
24341 Disassemble the whole @code{main} function. Line 32 is part of
24345 -data-disassemble -f basics.c -l 32 -- 0
24347 @{address="0x000107bc",func-name="main",offset="0",
24348 inst="save %sp, -112, %sp"@},
24349 @{address="0x000107c0",func-name="main",offset="4",
24350 inst="mov 2, %o0"@},
24351 @{address="0x000107c4",func-name="main",offset="8",
24352 inst="sethi %hi(0x11800), %o2"@},
24354 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
24355 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
24359 Disassemble 3 instructions from the start of @code{main}:
24363 -data-disassemble -f basics.c -l 32 -n 3 -- 0
24365 @{address="0x000107bc",func-name="main",offset="0",
24366 inst="save %sp, -112, %sp"@},
24367 @{address="0x000107c0",func-name="main",offset="4",
24368 inst="mov 2, %o0"@},
24369 @{address="0x000107c4",func-name="main",offset="8",
24370 inst="sethi %hi(0x11800), %o2"@}]
24374 Disassemble 3 instructions from the start of @code{main} in mixed mode:
24378 -data-disassemble -f basics.c -l 32 -n 3 -- 1
24380 src_and_asm_line=@{line="31",
24381 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
24382 testsuite/gdb.mi/basics.c",line_asm_insn=[
24383 @{address="0x000107bc",func-name="main",offset="0",
24384 inst="save %sp, -112, %sp"@}]@},
24385 src_and_asm_line=@{line="32",
24386 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
24387 testsuite/gdb.mi/basics.c",line_asm_insn=[
24388 @{address="0x000107c0",func-name="main",offset="4",
24389 inst="mov 2, %o0"@},
24390 @{address="0x000107c4",func-name="main",offset="8",
24391 inst="sethi %hi(0x11800), %o2"@}]@}]
24396 @subheading The @code{-data-evaluate-expression} Command
24397 @findex -data-evaluate-expression
24399 @subsubheading Synopsis
24402 -data-evaluate-expression @var{expr}
24405 Evaluate @var{expr} as an expression. The expression could contain an
24406 inferior function call. The function call will execute synchronously.
24407 If the expression contains spaces, it must be enclosed in double quotes.
24409 @subsubheading @value{GDBN} Command
24411 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
24412 @samp{call}. In @code{gdbtk} only, there's a corresponding
24413 @samp{gdb_eval} command.
24415 @subsubheading Example
24417 In the following example, the numbers that precede the commands are the
24418 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
24419 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
24423 211-data-evaluate-expression A
24426 311-data-evaluate-expression &A
24427 311^done,value="0xefffeb7c"
24429 411-data-evaluate-expression A+3
24432 511-data-evaluate-expression "A + 3"
24438 @subheading The @code{-data-list-changed-registers} Command
24439 @findex -data-list-changed-registers
24441 @subsubheading Synopsis
24444 -data-list-changed-registers
24447 Display a list of the registers that have changed.
24449 @subsubheading @value{GDBN} Command
24451 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
24452 has the corresponding command @samp{gdb_changed_register_list}.
24454 @subsubheading Example
24456 On a PPC MBX board:
24464 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
24465 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
24468 -data-list-changed-registers
24469 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
24470 "10","11","13","14","15","16","17","18","19","20","21","22","23",
24471 "24","25","26","27","28","30","31","64","65","66","67","69"]
24476 @subheading The @code{-data-list-register-names} Command
24477 @findex -data-list-register-names
24479 @subsubheading Synopsis
24482 -data-list-register-names [ ( @var{regno} )+ ]
24485 Show a list of register names for the current target. If no arguments
24486 are given, it shows a list of the names of all the registers. If
24487 integer numbers are given as arguments, it will print a list of the
24488 names of the registers corresponding to the arguments. To ensure
24489 consistency between a register name and its number, the output list may
24490 include empty register names.
24492 @subsubheading @value{GDBN} Command
24494 @value{GDBN} does not have a command which corresponds to
24495 @samp{-data-list-register-names}. In @code{gdbtk} there is a
24496 corresponding command @samp{gdb_regnames}.
24498 @subsubheading Example
24500 For the PPC MBX board:
24503 -data-list-register-names
24504 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
24505 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
24506 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
24507 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
24508 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
24509 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
24510 "", "pc","ps","cr","lr","ctr","xer"]
24512 -data-list-register-names 1 2 3
24513 ^done,register-names=["r1","r2","r3"]
24517 @subheading The @code{-data-list-register-values} Command
24518 @findex -data-list-register-values
24520 @subsubheading Synopsis
24523 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
24526 Display the registers' contents. @var{fmt} is the format according to
24527 which the registers' contents are to be returned, followed by an optional
24528 list of numbers specifying the registers to display. A missing list of
24529 numbers indicates that the contents of all the registers must be returned.
24531 Allowed formats for @var{fmt} are:
24548 @subsubheading @value{GDBN} Command
24550 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
24551 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
24553 @subsubheading Example
24555 For a PPC MBX board (note: line breaks are for readability only, they
24556 don't appear in the actual output):
24560 -data-list-register-values r 64 65
24561 ^done,register-values=[@{number="64",value="0xfe00a300"@},
24562 @{number="65",value="0x00029002"@}]
24564 -data-list-register-values x
24565 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
24566 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
24567 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
24568 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
24569 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
24570 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
24571 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
24572 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
24573 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
24574 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
24575 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
24576 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
24577 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
24578 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
24579 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
24580 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
24581 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
24582 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
24583 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
24584 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
24585 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
24586 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
24587 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
24588 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
24589 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
24590 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
24591 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
24592 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
24593 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
24594 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
24595 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
24596 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
24597 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
24598 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
24599 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
24600 @{number="69",value="0x20002b03"@}]
24605 @subheading The @code{-data-read-memory} Command
24606 @findex -data-read-memory
24608 @subsubheading Synopsis
24611 -data-read-memory [ -o @var{byte-offset} ]
24612 @var{address} @var{word-format} @var{word-size}
24613 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
24620 @item @var{address}
24621 An expression specifying the address of the first memory word to be
24622 read. Complex expressions containing embedded white space should be
24623 quoted using the C convention.
24625 @item @var{word-format}
24626 The format to be used to print the memory words. The notation is the
24627 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
24630 @item @var{word-size}
24631 The size of each memory word in bytes.
24633 @item @var{nr-rows}
24634 The number of rows in the output table.
24636 @item @var{nr-cols}
24637 The number of columns in the output table.
24640 If present, indicates that each row should include an @sc{ascii} dump. The
24641 value of @var{aschar} is used as a padding character when a byte is not a
24642 member of the printable @sc{ascii} character set (printable @sc{ascii}
24643 characters are those whose code is between 32 and 126, inclusively).
24645 @item @var{byte-offset}
24646 An offset to add to the @var{address} before fetching memory.
24649 This command displays memory contents as a table of @var{nr-rows} by
24650 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
24651 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
24652 (returned as @samp{total-bytes}). Should less than the requested number
24653 of bytes be returned by the target, the missing words are identified
24654 using @samp{N/A}. The number of bytes read from the target is returned
24655 in @samp{nr-bytes} and the starting address used to read memory in
24658 The address of the next/previous row or page is available in
24659 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
24662 @subsubheading @value{GDBN} Command
24664 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
24665 @samp{gdb_get_mem} memory read command.
24667 @subsubheading Example
24669 Read six bytes of memory starting at @code{bytes+6} but then offset by
24670 @code{-6} bytes. Format as three rows of two columns. One byte per
24671 word. Display each word in hex.
24675 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
24676 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
24677 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
24678 prev-page="0x0000138a",memory=[
24679 @{addr="0x00001390",data=["0x00","0x01"]@},
24680 @{addr="0x00001392",data=["0x02","0x03"]@},
24681 @{addr="0x00001394",data=["0x04","0x05"]@}]
24685 Read two bytes of memory starting at address @code{shorts + 64} and
24686 display as a single word formatted in decimal.
24690 5-data-read-memory shorts+64 d 2 1 1
24691 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
24692 next-row="0x00001512",prev-row="0x0000150e",
24693 next-page="0x00001512",prev-page="0x0000150e",memory=[
24694 @{addr="0x00001510",data=["128"]@}]
24698 Read thirty two bytes of memory starting at @code{bytes+16} and format
24699 as eight rows of four columns. Include a string encoding with @samp{x}
24700 used as the non-printable character.
24704 4-data-read-memory bytes+16 x 1 8 4 x
24705 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
24706 next-row="0x000013c0",prev-row="0x0000139c",
24707 next-page="0x000013c0",prev-page="0x00001380",memory=[
24708 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
24709 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
24710 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
24711 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
24712 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
24713 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
24714 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
24715 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
24719 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24720 @node GDB/MI Tracepoint Commands
24721 @section @sc{gdb/mi} Tracepoint Commands
24723 The tracepoint commands are not yet implemented.
24725 @c @subheading -trace-actions
24727 @c @subheading -trace-delete
24729 @c @subheading -trace-disable
24731 @c @subheading -trace-dump
24733 @c @subheading -trace-enable
24735 @c @subheading -trace-exists
24737 @c @subheading -trace-find
24739 @c @subheading -trace-frame-number
24741 @c @subheading -trace-info
24743 @c @subheading -trace-insert
24745 @c @subheading -trace-list
24747 @c @subheading -trace-pass-count
24749 @c @subheading -trace-save
24751 @c @subheading -trace-start
24753 @c @subheading -trace-stop
24756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24757 @node GDB/MI Symbol Query
24758 @section @sc{gdb/mi} Symbol Query Commands
24762 @subheading The @code{-symbol-info-address} Command
24763 @findex -symbol-info-address
24765 @subsubheading Synopsis
24768 -symbol-info-address @var{symbol}
24771 Describe where @var{symbol} is stored.
24773 @subsubheading @value{GDBN} Command
24775 The corresponding @value{GDBN} command is @samp{info address}.
24777 @subsubheading Example
24781 @subheading The @code{-symbol-info-file} Command
24782 @findex -symbol-info-file
24784 @subsubheading Synopsis
24790 Show the file for the symbol.
24792 @subsubheading @value{GDBN} Command
24794 There's no equivalent @value{GDBN} command. @code{gdbtk} has
24795 @samp{gdb_find_file}.
24797 @subsubheading Example
24801 @subheading The @code{-symbol-info-function} Command
24802 @findex -symbol-info-function
24804 @subsubheading Synopsis
24807 -symbol-info-function
24810 Show which function the symbol lives in.
24812 @subsubheading @value{GDBN} Command
24814 @samp{gdb_get_function} in @code{gdbtk}.
24816 @subsubheading Example
24820 @subheading The @code{-symbol-info-line} Command
24821 @findex -symbol-info-line
24823 @subsubheading Synopsis
24829 Show the core addresses of the code for a source line.
24831 @subsubheading @value{GDBN} Command
24833 The corresponding @value{GDBN} command is @samp{info line}.
24834 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
24836 @subsubheading Example
24840 @subheading The @code{-symbol-info-symbol} Command
24841 @findex -symbol-info-symbol
24843 @subsubheading Synopsis
24846 -symbol-info-symbol @var{addr}
24849 Describe what symbol is at location @var{addr}.
24851 @subsubheading @value{GDBN} Command
24853 The corresponding @value{GDBN} command is @samp{info symbol}.
24855 @subsubheading Example
24859 @subheading The @code{-symbol-list-functions} Command
24860 @findex -symbol-list-functions
24862 @subsubheading Synopsis
24865 -symbol-list-functions
24868 List the functions in the executable.
24870 @subsubheading @value{GDBN} Command
24872 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
24873 @samp{gdb_search} in @code{gdbtk}.
24875 @subsubheading Example
24880 @subheading The @code{-symbol-list-lines} Command
24881 @findex -symbol-list-lines
24883 @subsubheading Synopsis
24886 -symbol-list-lines @var{filename}
24889 Print the list of lines that contain code and their associated program
24890 addresses for the given source filename. The entries are sorted in
24891 ascending PC order.
24893 @subsubheading @value{GDBN} Command
24895 There is no corresponding @value{GDBN} command.
24897 @subsubheading Example
24900 -symbol-list-lines basics.c
24901 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
24907 @subheading The @code{-symbol-list-types} Command
24908 @findex -symbol-list-types
24910 @subsubheading Synopsis
24916 List all the type names.
24918 @subsubheading @value{GDBN} Command
24920 The corresponding commands are @samp{info types} in @value{GDBN},
24921 @samp{gdb_search} in @code{gdbtk}.
24923 @subsubheading Example
24927 @subheading The @code{-symbol-list-variables} Command
24928 @findex -symbol-list-variables
24930 @subsubheading Synopsis
24933 -symbol-list-variables
24936 List all the global and static variable names.
24938 @subsubheading @value{GDBN} Command
24940 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
24942 @subsubheading Example
24946 @subheading The @code{-symbol-locate} Command
24947 @findex -symbol-locate
24949 @subsubheading Synopsis
24955 @subsubheading @value{GDBN} Command
24957 @samp{gdb_loc} in @code{gdbtk}.
24959 @subsubheading Example
24963 @subheading The @code{-symbol-type} Command
24964 @findex -symbol-type
24966 @subsubheading Synopsis
24969 -symbol-type @var{variable}
24972 Show type of @var{variable}.
24974 @subsubheading @value{GDBN} Command
24976 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
24977 @samp{gdb_obj_variable}.
24979 @subsubheading Example
24984 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24985 @node GDB/MI File Commands
24986 @section @sc{gdb/mi} File Commands
24988 This section describes the GDB/MI commands to specify executable file names
24989 and to read in and obtain symbol table information.
24991 @subheading The @code{-file-exec-and-symbols} Command
24992 @findex -file-exec-and-symbols
24994 @subsubheading Synopsis
24997 -file-exec-and-symbols @var{file}
25000 Specify the executable file to be debugged. This file is the one from
25001 which the symbol table is also read. If no file is specified, the
25002 command clears the executable and symbol information. If breakpoints
25003 are set when using this command with no arguments, @value{GDBN} will produce
25004 error messages. Otherwise, no output is produced, except a completion
25007 @subsubheading @value{GDBN} Command
25009 The corresponding @value{GDBN} command is @samp{file}.
25011 @subsubheading Example
25015 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
25021 @subheading The @code{-file-exec-file} Command
25022 @findex -file-exec-file
25024 @subsubheading Synopsis
25027 -file-exec-file @var{file}
25030 Specify the executable file to be debugged. Unlike
25031 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
25032 from this file. If used without argument, @value{GDBN} clears the information
25033 about the executable file. No output is produced, except a completion
25036 @subsubheading @value{GDBN} Command
25038 The corresponding @value{GDBN} command is @samp{exec-file}.
25040 @subsubheading Example
25044 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
25051 @subheading The @code{-file-list-exec-sections} Command
25052 @findex -file-list-exec-sections
25054 @subsubheading Synopsis
25057 -file-list-exec-sections
25060 List the sections of the current executable file.
25062 @subsubheading @value{GDBN} Command
25064 The @value{GDBN} command @samp{info file} shows, among the rest, the same
25065 information as this command. @code{gdbtk} has a corresponding command
25066 @samp{gdb_load_info}.
25068 @subsubheading Example
25073 @subheading The @code{-file-list-exec-source-file} Command
25074 @findex -file-list-exec-source-file
25076 @subsubheading Synopsis
25079 -file-list-exec-source-file
25082 List the line number, the current source file, and the absolute path
25083 to the current source file for the current executable. The macro
25084 information field has a value of @samp{1} or @samp{0} depending on
25085 whether or not the file includes preprocessor macro information.
25087 @subsubheading @value{GDBN} Command
25089 The @value{GDBN} equivalent is @samp{info source}
25091 @subsubheading Example
25095 123-file-list-exec-source-file
25096 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
25101 @subheading The @code{-file-list-exec-source-files} Command
25102 @findex -file-list-exec-source-files
25104 @subsubheading Synopsis
25107 -file-list-exec-source-files
25110 List the source files for the current executable.
25112 It will always output the filename, but only when @value{GDBN} can find
25113 the absolute file name of a source file, will it output the fullname.
25115 @subsubheading @value{GDBN} Command
25117 The @value{GDBN} equivalent is @samp{info sources}.
25118 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
25120 @subsubheading Example
25123 -file-list-exec-source-files
25125 @{file=foo.c,fullname=/home/foo.c@},
25126 @{file=/home/bar.c,fullname=/home/bar.c@},
25127 @{file=gdb_could_not_find_fullpath.c@}]
25132 @subheading The @code{-file-list-shared-libraries} Command
25133 @findex -file-list-shared-libraries
25135 @subsubheading Synopsis
25138 -file-list-shared-libraries
25141 List the shared libraries in the program.
25143 @subsubheading @value{GDBN} Command
25145 The corresponding @value{GDBN} command is @samp{info shared}.
25147 @subsubheading Example
25151 @subheading The @code{-file-list-symbol-files} Command
25152 @findex -file-list-symbol-files
25154 @subsubheading Synopsis
25157 -file-list-symbol-files
25162 @subsubheading @value{GDBN} Command
25164 The corresponding @value{GDBN} command is @samp{info file} (part of it).
25166 @subsubheading Example
25171 @subheading The @code{-file-symbol-file} Command
25172 @findex -file-symbol-file
25174 @subsubheading Synopsis
25177 -file-symbol-file @var{file}
25180 Read symbol table info from the specified @var{file} argument. When
25181 used without arguments, clears @value{GDBN}'s symbol table info. No output is
25182 produced, except for a completion notification.
25184 @subsubheading @value{GDBN} Command
25186 The corresponding @value{GDBN} command is @samp{symbol-file}.
25188 @subsubheading Example
25192 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
25198 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25199 @node GDB/MI Memory Overlay Commands
25200 @section @sc{gdb/mi} Memory Overlay Commands
25202 The memory overlay commands are not implemented.
25204 @c @subheading -overlay-auto
25206 @c @subheading -overlay-list-mapping-state
25208 @c @subheading -overlay-list-overlays
25210 @c @subheading -overlay-map
25212 @c @subheading -overlay-off
25214 @c @subheading -overlay-on
25216 @c @subheading -overlay-unmap
25218 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25219 @node GDB/MI Signal Handling Commands
25220 @section @sc{gdb/mi} Signal Handling Commands
25222 Signal handling commands are not implemented.
25224 @c @subheading -signal-handle
25226 @c @subheading -signal-list-handle-actions
25228 @c @subheading -signal-list-signal-types
25232 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25233 @node GDB/MI Target Manipulation
25234 @section @sc{gdb/mi} Target Manipulation Commands
25237 @subheading The @code{-target-attach} Command
25238 @findex -target-attach
25240 @subsubheading Synopsis
25243 -target-attach @var{pid} | @var{gid} | @var{file}
25246 Attach to a process @var{pid} or a file @var{file} outside of
25247 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
25248 group, the id previously returned by
25249 @samp{-list-thread-groups --available} must be used.
25251 @subsubheading @value{GDBN} Command
25253 The corresponding @value{GDBN} command is @samp{attach}.
25255 @subsubheading Example
25259 =thread-created,id="1"
25260 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
25266 @subheading The @code{-target-compare-sections} Command
25267 @findex -target-compare-sections
25269 @subsubheading Synopsis
25272 -target-compare-sections [ @var{section} ]
25275 Compare data of section @var{section} on target to the exec file.
25276 Without the argument, all sections are compared.
25278 @subsubheading @value{GDBN} Command
25280 The @value{GDBN} equivalent is @samp{compare-sections}.
25282 @subsubheading Example
25287 @subheading The @code{-target-detach} Command
25288 @findex -target-detach
25290 @subsubheading Synopsis
25293 -target-detach [ @var{pid} | @var{gid} ]
25296 Detach from the remote target which normally resumes its execution.
25297 If either @var{pid} or @var{gid} is specified, detaches from either
25298 the specified process, or specified thread group. There's no output.
25300 @subsubheading @value{GDBN} Command
25302 The corresponding @value{GDBN} command is @samp{detach}.
25304 @subsubheading Example
25314 @subheading The @code{-target-disconnect} Command
25315 @findex -target-disconnect
25317 @subsubheading Synopsis
25323 Disconnect from the remote target. There's no output and the target is
25324 generally not resumed.
25326 @subsubheading @value{GDBN} Command
25328 The corresponding @value{GDBN} command is @samp{disconnect}.
25330 @subsubheading Example
25340 @subheading The @code{-target-download} Command
25341 @findex -target-download
25343 @subsubheading Synopsis
25349 Loads the executable onto the remote target.
25350 It prints out an update message every half second, which includes the fields:
25354 The name of the section.
25356 The size of what has been sent so far for that section.
25358 The size of the section.
25360 The total size of what was sent so far (the current and the previous sections).
25362 The size of the overall executable to download.
25366 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
25367 @sc{gdb/mi} Output Syntax}).
25369 In addition, it prints the name and size of the sections, as they are
25370 downloaded. These messages include the following fields:
25374 The name of the section.
25376 The size of the section.
25378 The size of the overall executable to download.
25382 At the end, a summary is printed.
25384 @subsubheading @value{GDBN} Command
25386 The corresponding @value{GDBN} command is @samp{load}.
25388 @subsubheading Example
25390 Note: each status message appears on a single line. Here the messages
25391 have been broken down so that they can fit onto a page.
25396 +download,@{section=".text",section-size="6668",total-size="9880"@}
25397 +download,@{section=".text",section-sent="512",section-size="6668",
25398 total-sent="512",total-size="9880"@}
25399 +download,@{section=".text",section-sent="1024",section-size="6668",
25400 total-sent="1024",total-size="9880"@}
25401 +download,@{section=".text",section-sent="1536",section-size="6668",
25402 total-sent="1536",total-size="9880"@}
25403 +download,@{section=".text",section-sent="2048",section-size="6668",
25404 total-sent="2048",total-size="9880"@}
25405 +download,@{section=".text",section-sent="2560",section-size="6668",
25406 total-sent="2560",total-size="9880"@}
25407 +download,@{section=".text",section-sent="3072",section-size="6668",
25408 total-sent="3072",total-size="9880"@}
25409 +download,@{section=".text",section-sent="3584",section-size="6668",
25410 total-sent="3584",total-size="9880"@}
25411 +download,@{section=".text",section-sent="4096",section-size="6668",
25412 total-sent="4096",total-size="9880"@}
25413 +download,@{section=".text",section-sent="4608",section-size="6668",
25414 total-sent="4608",total-size="9880"@}
25415 +download,@{section=".text",section-sent="5120",section-size="6668",
25416 total-sent="5120",total-size="9880"@}
25417 +download,@{section=".text",section-sent="5632",section-size="6668",
25418 total-sent="5632",total-size="9880"@}
25419 +download,@{section=".text",section-sent="6144",section-size="6668",
25420 total-sent="6144",total-size="9880"@}
25421 +download,@{section=".text",section-sent="6656",section-size="6668",
25422 total-sent="6656",total-size="9880"@}
25423 +download,@{section=".init",section-size="28",total-size="9880"@}
25424 +download,@{section=".fini",section-size="28",total-size="9880"@}
25425 +download,@{section=".data",section-size="3156",total-size="9880"@}
25426 +download,@{section=".data",section-sent="512",section-size="3156",
25427 total-sent="7236",total-size="9880"@}
25428 +download,@{section=".data",section-sent="1024",section-size="3156",
25429 total-sent="7748",total-size="9880"@}
25430 +download,@{section=".data",section-sent="1536",section-size="3156",
25431 total-sent="8260",total-size="9880"@}
25432 +download,@{section=".data",section-sent="2048",section-size="3156",
25433 total-sent="8772",total-size="9880"@}
25434 +download,@{section=".data",section-sent="2560",section-size="3156",
25435 total-sent="9284",total-size="9880"@}
25436 +download,@{section=".data",section-sent="3072",section-size="3156",
25437 total-sent="9796",total-size="9880"@}
25438 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
25445 @subheading The @code{-target-exec-status} Command
25446 @findex -target-exec-status
25448 @subsubheading Synopsis
25451 -target-exec-status
25454 Provide information on the state of the target (whether it is running or
25455 not, for instance).
25457 @subsubheading @value{GDBN} Command
25459 There's no equivalent @value{GDBN} command.
25461 @subsubheading Example
25465 @subheading The @code{-target-list-available-targets} Command
25466 @findex -target-list-available-targets
25468 @subsubheading Synopsis
25471 -target-list-available-targets
25474 List the possible targets to connect to.
25476 @subsubheading @value{GDBN} Command
25478 The corresponding @value{GDBN} command is @samp{help target}.
25480 @subsubheading Example
25484 @subheading The @code{-target-list-current-targets} Command
25485 @findex -target-list-current-targets
25487 @subsubheading Synopsis
25490 -target-list-current-targets
25493 Describe the current target.
25495 @subsubheading @value{GDBN} Command
25497 The corresponding information is printed by @samp{info file} (among
25500 @subsubheading Example
25504 @subheading The @code{-target-list-parameters} Command
25505 @findex -target-list-parameters
25507 @subsubheading Synopsis
25510 -target-list-parameters
25516 @subsubheading @value{GDBN} Command
25520 @subsubheading Example
25524 @subheading The @code{-target-select} Command
25525 @findex -target-select
25527 @subsubheading Synopsis
25530 -target-select @var{type} @var{parameters @dots{}}
25533 Connect @value{GDBN} to the remote target. This command takes two args:
25537 The type of target, for instance @samp{remote}, etc.
25538 @item @var{parameters}
25539 Device names, host names and the like. @xref{Target Commands, ,
25540 Commands for Managing Targets}, for more details.
25543 The output is a connection notification, followed by the address at
25544 which the target program is, in the following form:
25547 ^connected,addr="@var{address}",func="@var{function name}",
25548 args=[@var{arg list}]
25551 @subsubheading @value{GDBN} Command
25553 The corresponding @value{GDBN} command is @samp{target}.
25555 @subsubheading Example
25559 -target-select remote /dev/ttya
25560 ^connected,addr="0xfe00a300",func="??",args=[]
25564 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25565 @node GDB/MI File Transfer Commands
25566 @section @sc{gdb/mi} File Transfer Commands
25569 @subheading The @code{-target-file-put} Command
25570 @findex -target-file-put
25572 @subsubheading Synopsis
25575 -target-file-put @var{hostfile} @var{targetfile}
25578 Copy file @var{hostfile} from the host system (the machine running
25579 @value{GDBN}) to @var{targetfile} on the target system.
25581 @subsubheading @value{GDBN} Command
25583 The corresponding @value{GDBN} command is @samp{remote put}.
25585 @subsubheading Example
25589 -target-file-put localfile remotefile
25595 @subheading The @code{-target-file-get} Command
25596 @findex -target-file-get
25598 @subsubheading Synopsis
25601 -target-file-get @var{targetfile} @var{hostfile}
25604 Copy file @var{targetfile} from the target system to @var{hostfile}
25605 on the host system.
25607 @subsubheading @value{GDBN} Command
25609 The corresponding @value{GDBN} command is @samp{remote get}.
25611 @subsubheading Example
25615 -target-file-get remotefile localfile
25621 @subheading The @code{-target-file-delete} Command
25622 @findex -target-file-delete
25624 @subsubheading Synopsis
25627 -target-file-delete @var{targetfile}
25630 Delete @var{targetfile} from the target system.
25632 @subsubheading @value{GDBN} Command
25634 The corresponding @value{GDBN} command is @samp{remote delete}.
25636 @subsubheading Example
25640 -target-file-delete remotefile
25646 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25647 @node GDB/MI Miscellaneous Commands
25648 @section Miscellaneous @sc{gdb/mi} Commands
25650 @c @subheading -gdb-complete
25652 @subheading The @code{-gdb-exit} Command
25655 @subsubheading Synopsis
25661 Exit @value{GDBN} immediately.
25663 @subsubheading @value{GDBN} Command
25665 Approximately corresponds to @samp{quit}.
25667 @subsubheading Example
25677 @subheading The @code{-exec-abort} Command
25678 @findex -exec-abort
25680 @subsubheading Synopsis
25686 Kill the inferior running program.
25688 @subsubheading @value{GDBN} Command
25690 The corresponding @value{GDBN} command is @samp{kill}.
25692 @subsubheading Example
25697 @subheading The @code{-gdb-set} Command
25700 @subsubheading Synopsis
25706 Set an internal @value{GDBN} variable.
25707 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
25709 @subsubheading @value{GDBN} Command
25711 The corresponding @value{GDBN} command is @samp{set}.
25713 @subsubheading Example
25723 @subheading The @code{-gdb-show} Command
25726 @subsubheading Synopsis
25732 Show the current value of a @value{GDBN} variable.
25734 @subsubheading @value{GDBN} Command
25736 The corresponding @value{GDBN} command is @samp{show}.
25738 @subsubheading Example
25747 @c @subheading -gdb-source
25750 @subheading The @code{-gdb-version} Command
25751 @findex -gdb-version
25753 @subsubheading Synopsis
25759 Show version information for @value{GDBN}. Used mostly in testing.
25761 @subsubheading @value{GDBN} Command
25763 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
25764 default shows this information when you start an interactive session.
25766 @subsubheading Example
25768 @c This example modifies the actual output from GDB to avoid overfull
25774 ~Copyright 2000 Free Software Foundation, Inc.
25775 ~GDB is free software, covered by the GNU General Public License, and
25776 ~you are welcome to change it and/or distribute copies of it under
25777 ~ certain conditions.
25778 ~Type "show copying" to see the conditions.
25779 ~There is absolutely no warranty for GDB. Type "show warranty" for
25781 ~This GDB was configured as
25782 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
25787 @subheading The @code{-list-features} Command
25788 @findex -list-features
25790 Returns a list of particular features of the MI protocol that
25791 this version of gdb implements. A feature can be a command,
25792 or a new field in an output of some command, or even an
25793 important bugfix. While a frontend can sometimes detect presence
25794 of a feature at runtime, it is easier to perform detection at debugger
25797 The command returns a list of strings, with each string naming an
25798 available feature. Each returned string is just a name, it does not
25799 have any internal structure. The list of possible feature names
25805 (gdb) -list-features
25806 ^done,result=["feature1","feature2"]
25809 The current list of features is:
25812 @item frozen-varobjs
25813 Indicates presence of the @code{-var-set-frozen} command, as well
25814 as possible presense of the @code{frozen} field in the output
25815 of @code{-varobj-create}.
25816 @item pending-breakpoints
25817 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
25819 Indicates presence of Python scripting support, Python-based
25820 pretty-printing commands, and possible presence of the
25821 @samp{display_hint} field in the output of @code{-var-list-children}
25823 Indicates presence of the @code{-thread-info} command.
25827 @subheading The @code{-list-target-features} Command
25828 @findex -list-target-features
25830 Returns a list of particular features that are supported by the
25831 target. Those features affect the permitted MI commands, but
25832 unlike the features reported by the @code{-list-features} command, the
25833 features depend on which target GDB is using at the moment. Whenever
25834 a target can change, due to commands such as @code{-target-select},
25835 @code{-target-attach} or @code{-exec-run}, the list of target features
25836 may change, and the frontend should obtain it again.
25840 (gdb) -list-features
25841 ^done,result=["async"]
25844 The current list of features is:
25848 Indicates that the target is capable of asynchronous command
25849 execution, which means that @value{GDBN} will accept further commands
25850 while the target is running.
25854 @subheading The @code{-list-thread-groups} Command
25855 @findex -list-thread-groups
25857 @subheading Synopsis
25860 -list-thread-groups [ --available ] [ @var{group} ]
25863 When used without the @var{group} parameter, lists top-level thread
25864 groups that are being debugged. When used with the @var{group}
25865 parameter, the children of the specified group are listed. The
25866 children can be either threads, or other groups. At present,
25867 @value{GDBN} will not report both threads and groups as children at
25868 the same time, but it may change in future.
25870 With the @samp{--available} option, instead of reporting groups that
25871 are been debugged, GDB will report all thread groups available on the
25872 target. Using the @samp{--available} option together with @var{group}
25875 @subheading Example
25879 -list-thread-groups
25880 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
25881 -list-thread-groups 17
25882 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25883 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25884 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25885 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25886 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
25889 @subheading The @code{-interpreter-exec} Command
25890 @findex -interpreter-exec
25892 @subheading Synopsis
25895 -interpreter-exec @var{interpreter} @var{command}
25897 @anchor{-interpreter-exec}
25899 Execute the specified @var{command} in the given @var{interpreter}.
25901 @subheading @value{GDBN} Command
25903 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
25905 @subheading Example
25909 -interpreter-exec console "break main"
25910 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
25911 &"During symbol reading, bad structure-type format.\n"
25912 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
25917 @subheading The @code{-inferior-tty-set} Command
25918 @findex -inferior-tty-set
25920 @subheading Synopsis
25923 -inferior-tty-set /dev/pts/1
25926 Set terminal for future runs of the program being debugged.
25928 @subheading @value{GDBN} Command
25930 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
25932 @subheading Example
25936 -inferior-tty-set /dev/pts/1
25941 @subheading The @code{-inferior-tty-show} Command
25942 @findex -inferior-tty-show
25944 @subheading Synopsis
25950 Show terminal for future runs of program being debugged.
25952 @subheading @value{GDBN} Command
25954 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
25956 @subheading Example
25960 -inferior-tty-set /dev/pts/1
25964 ^done,inferior_tty_terminal="/dev/pts/1"
25968 @subheading The @code{-enable-timings} Command
25969 @findex -enable-timings
25971 @subheading Synopsis
25974 -enable-timings [yes | no]
25977 Toggle the printing of the wallclock, user and system times for an MI
25978 command as a field in its output. This command is to help frontend
25979 developers optimize the performance of their code. No argument is
25980 equivalent to @samp{yes}.
25982 @subheading @value{GDBN} Command
25986 @subheading Example
25994 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25995 addr="0x080484ed",func="main",file="myprog.c",
25996 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
25997 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
26005 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26006 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
26007 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
26008 fullname="/home/nickrob/myprog.c",line="73"@}
26013 @chapter @value{GDBN} Annotations
26015 This chapter describes annotations in @value{GDBN}. Annotations were
26016 designed to interface @value{GDBN} to graphical user interfaces or other
26017 similar programs which want to interact with @value{GDBN} at a
26018 relatively high level.
26020 The annotation mechanism has largely been superseded by @sc{gdb/mi}
26024 This is Edition @value{EDITION}, @value{DATE}.
26028 * Annotations Overview:: What annotations are; the general syntax.
26029 * Server Prefix:: Issuing a command without affecting user state.
26030 * Prompting:: Annotations marking @value{GDBN}'s need for input.
26031 * Errors:: Annotations for error messages.
26032 * Invalidation:: Some annotations describe things now invalid.
26033 * Annotations for Running::
26034 Whether the program is running, how it stopped, etc.
26035 * Source Annotations:: Annotations describing source code.
26038 @node Annotations Overview
26039 @section What is an Annotation?
26040 @cindex annotations
26042 Annotations start with a newline character, two @samp{control-z}
26043 characters, and the name of the annotation. If there is no additional
26044 information associated with this annotation, the name of the annotation
26045 is followed immediately by a newline. If there is additional
26046 information, the name of the annotation is followed by a space, the
26047 additional information, and a newline. The additional information
26048 cannot contain newline characters.
26050 Any output not beginning with a newline and two @samp{control-z}
26051 characters denotes literal output from @value{GDBN}. Currently there is
26052 no need for @value{GDBN} to output a newline followed by two
26053 @samp{control-z} characters, but if there was such a need, the
26054 annotations could be extended with an @samp{escape} annotation which
26055 means those three characters as output.
26057 The annotation @var{level}, which is specified using the
26058 @option{--annotate} command line option (@pxref{Mode Options}), controls
26059 how much information @value{GDBN} prints together with its prompt,
26060 values of expressions, source lines, and other types of output. Level 0
26061 is for no annotations, level 1 is for use when @value{GDBN} is run as a
26062 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
26063 for programs that control @value{GDBN}, and level 2 annotations have
26064 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
26065 Interface, annotate, GDB's Obsolete Annotations}).
26068 @kindex set annotate
26069 @item set annotate @var{level}
26070 The @value{GDBN} command @code{set annotate} sets the level of
26071 annotations to the specified @var{level}.
26073 @item show annotate
26074 @kindex show annotate
26075 Show the current annotation level.
26078 This chapter describes level 3 annotations.
26080 A simple example of starting up @value{GDBN} with annotations is:
26083 $ @kbd{gdb --annotate=3}
26085 Copyright 2003 Free Software Foundation, Inc.
26086 GDB is free software, covered by the GNU General Public License,
26087 and you are welcome to change it and/or distribute copies of it
26088 under certain conditions.
26089 Type "show copying" to see the conditions.
26090 There is absolutely no warranty for GDB. Type "show warranty"
26092 This GDB was configured as "i386-pc-linux-gnu"
26103 Here @samp{quit} is input to @value{GDBN}; the rest is output from
26104 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
26105 denotes a @samp{control-z} character) are annotations; the rest is
26106 output from @value{GDBN}.
26108 @node Server Prefix
26109 @section The Server Prefix
26110 @cindex server prefix
26112 If you prefix a command with @samp{server } then it will not affect
26113 the command history, nor will it affect @value{GDBN}'s notion of which
26114 command to repeat if @key{RET} is pressed on a line by itself. This
26115 means that commands can be run behind a user's back by a front-end in
26116 a transparent manner.
26118 The @code{server } prefix does not affect the recording of values into
26119 the value history; to print a value without recording it into the
26120 value history, use the @code{output} command instead of the
26121 @code{print} command.
26123 Using this prefix also disables confirmation requests
26124 (@pxref{confirmation requests}).
26127 @section Annotation for @value{GDBN} Input
26129 @cindex annotations for prompts
26130 When @value{GDBN} prompts for input, it annotates this fact so it is possible
26131 to know when to send output, when the output from a given command is
26134 Different kinds of input each have a different @dfn{input type}. Each
26135 input type has three annotations: a @code{pre-} annotation, which
26136 denotes the beginning of any prompt which is being output, a plain
26137 annotation, which denotes the end of the prompt, and then a @code{post-}
26138 annotation which denotes the end of any echo which may (or may not) be
26139 associated with the input. For example, the @code{prompt} input type
26140 features the following annotations:
26148 The input types are
26151 @findex pre-prompt annotation
26152 @findex prompt annotation
26153 @findex post-prompt annotation
26155 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
26157 @findex pre-commands annotation
26158 @findex commands annotation
26159 @findex post-commands annotation
26161 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
26162 command. The annotations are repeated for each command which is input.
26164 @findex pre-overload-choice annotation
26165 @findex overload-choice annotation
26166 @findex post-overload-choice annotation
26167 @item overload-choice
26168 When @value{GDBN} wants the user to select between various overloaded functions.
26170 @findex pre-query annotation
26171 @findex query annotation
26172 @findex post-query annotation
26174 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
26176 @findex pre-prompt-for-continue annotation
26177 @findex prompt-for-continue annotation
26178 @findex post-prompt-for-continue annotation
26179 @item prompt-for-continue
26180 When @value{GDBN} is asking the user to press return to continue. Note: Don't
26181 expect this to work well; instead use @code{set height 0} to disable
26182 prompting. This is because the counting of lines is buggy in the
26183 presence of annotations.
26188 @cindex annotations for errors, warnings and interrupts
26190 @findex quit annotation
26195 This annotation occurs right before @value{GDBN} responds to an interrupt.
26197 @findex error annotation
26202 This annotation occurs right before @value{GDBN} responds to an error.
26204 Quit and error annotations indicate that any annotations which @value{GDBN} was
26205 in the middle of may end abruptly. For example, if a
26206 @code{value-history-begin} annotation is followed by a @code{error}, one
26207 cannot expect to receive the matching @code{value-history-end}. One
26208 cannot expect not to receive it either, however; an error annotation
26209 does not necessarily mean that @value{GDBN} is immediately returning all the way
26212 @findex error-begin annotation
26213 A quit or error annotation may be preceded by
26219 Any output between that and the quit or error annotation is the error
26222 Warning messages are not yet annotated.
26223 @c If we want to change that, need to fix warning(), type_error(),
26224 @c range_error(), and possibly other places.
26227 @section Invalidation Notices
26229 @cindex annotations for invalidation messages
26230 The following annotations say that certain pieces of state may have
26234 @findex frames-invalid annotation
26235 @item ^Z^Zframes-invalid
26237 The frames (for example, output from the @code{backtrace} command) may
26240 @findex breakpoints-invalid annotation
26241 @item ^Z^Zbreakpoints-invalid
26243 The breakpoints may have changed. For example, the user just added or
26244 deleted a breakpoint.
26247 @node Annotations for Running
26248 @section Running the Program
26249 @cindex annotations for running programs
26251 @findex starting annotation
26252 @findex stopping annotation
26253 When the program starts executing due to a @value{GDBN} command such as
26254 @code{step} or @code{continue},
26260 is output. When the program stops,
26266 is output. Before the @code{stopped} annotation, a variety of
26267 annotations describe how the program stopped.
26270 @findex exited annotation
26271 @item ^Z^Zexited @var{exit-status}
26272 The program exited, and @var{exit-status} is the exit status (zero for
26273 successful exit, otherwise nonzero).
26275 @findex signalled annotation
26276 @findex signal-name annotation
26277 @findex signal-name-end annotation
26278 @findex signal-string annotation
26279 @findex signal-string-end annotation
26280 @item ^Z^Zsignalled
26281 The program exited with a signal. After the @code{^Z^Zsignalled}, the
26282 annotation continues:
26288 ^Z^Zsignal-name-end
26292 ^Z^Zsignal-string-end
26297 where @var{name} is the name of the signal, such as @code{SIGILL} or
26298 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
26299 as @code{Illegal Instruction} or @code{Segmentation fault}.
26300 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
26301 user's benefit and have no particular format.
26303 @findex signal annotation
26305 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
26306 just saying that the program received the signal, not that it was
26307 terminated with it.
26309 @findex breakpoint annotation
26310 @item ^Z^Zbreakpoint @var{number}
26311 The program hit breakpoint number @var{number}.
26313 @findex watchpoint annotation
26314 @item ^Z^Zwatchpoint @var{number}
26315 The program hit watchpoint number @var{number}.
26318 @node Source Annotations
26319 @section Displaying Source
26320 @cindex annotations for source display
26322 @findex source annotation
26323 The following annotation is used instead of displaying source code:
26326 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
26329 where @var{filename} is an absolute file name indicating which source
26330 file, @var{line} is the line number within that file (where 1 is the
26331 first line in the file), @var{character} is the character position
26332 within the file (where 0 is the first character in the file) (for most
26333 debug formats this will necessarily point to the beginning of a line),
26334 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
26335 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
26336 @var{addr} is the address in the target program associated with the
26337 source which is being displayed. @var{addr} is in the form @samp{0x}
26338 followed by one or more lowercase hex digits (note that this does not
26339 depend on the language).
26341 @node JIT Interface
26342 @chapter JIT Compilation Interface
26343 @cindex just-in-time compilation
26344 @cindex JIT compilation interface
26346 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
26347 interface. A JIT compiler is a program or library that generates native
26348 executable code at runtime and executes it, usually in order to achieve good
26349 performance while maintaining platform independence.
26351 Programs that use JIT compilation are normally difficult to debug because
26352 portions of their code are generated at runtime, instead of being loaded from
26353 object files, which is where @value{GDBN} normally finds the program's symbols
26354 and debug information. In order to debug programs that use JIT compilation,
26355 @value{GDBN} has an interface that allows the program to register in-memory
26356 symbol files with @value{GDBN} at runtime.
26358 If you are using @value{GDBN} to debug a program that uses this interface, then
26359 it should work transparently so long as you have not stripped the binary. If
26360 you are developing a JIT compiler, then the interface is documented in the rest
26361 of this chapter. At this time, the only known client of this interface is the
26364 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
26365 JIT compiler communicates with @value{GDBN} by writing data into a global
26366 variable and calling a fuction at a well-known symbol. When @value{GDBN}
26367 attaches, it reads a linked list of symbol files from the global variable to
26368 find existing code, and puts a breakpoint in the function so that it can find
26369 out about additional code.
26372 * Declarations:: Relevant C struct declarations
26373 * Registering Code:: Steps to register code
26374 * Unregistering Code:: Steps to unregister code
26378 @section JIT Declarations
26380 These are the relevant struct declarations that a C program should include to
26381 implement the interface:
26391 struct jit_code_entry
26393 struct jit_code_entry *next_entry;
26394 struct jit_code_entry *prev_entry;
26395 const char *symfile_addr;
26396 uint64_t symfile_size;
26399 struct jit_descriptor
26402 /* This type should be jit_actions_t, but we use uint32_t
26403 to be explicit about the bitwidth. */
26404 uint32_t action_flag;
26405 struct jit_code_entry *relevant_entry;
26406 struct jit_code_entry *first_entry;
26409 /* GDB puts a breakpoint in this function. */
26410 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
26412 /* Make sure to specify the version statically, because the
26413 debugger may check the version before we can set it. */
26414 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
26417 If the JIT is multi-threaded, then it is important that the JIT synchronize any
26418 modifications to this global data properly, which can easily be done by putting
26419 a global mutex around modifications to these structures.
26421 @node Registering Code
26422 @section Registering Code
26424 To register code with @value{GDBN}, the JIT should follow this protocol:
26428 Generate an object file in memory with symbols and other desired debug
26429 information. The file must include the virtual addresses of the sections.
26432 Create a code entry for the file, which gives the start and size of the symbol
26436 Add it to the linked list in the JIT descriptor.
26439 Point the relevant_entry field of the descriptor at the entry.
26442 Set @code{action_flag} to @code{JIT_REGISTER} and call
26443 @code{__jit_debug_register_code}.
26446 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
26447 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
26448 new code. However, the linked list must still be maintained in order to allow
26449 @value{GDBN} to attach to a running process and still find the symbol files.
26451 @node Unregistering Code
26452 @section Unregistering Code
26454 If code is freed, then the JIT should use the following protocol:
26458 Remove the code entry corresponding to the code from the linked list.
26461 Point the @code{relevant_entry} field of the descriptor at the code entry.
26464 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
26465 @code{__jit_debug_register_code}.
26468 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
26469 and the JIT will leak the memory used for the associated symbol files.
26472 @chapter Reporting Bugs in @value{GDBN}
26473 @cindex bugs in @value{GDBN}
26474 @cindex reporting bugs in @value{GDBN}
26476 Your bug reports play an essential role in making @value{GDBN} reliable.
26478 Reporting a bug may help you by bringing a solution to your problem, or it
26479 may not. But in any case the principal function of a bug report is to help
26480 the entire community by making the next version of @value{GDBN} work better. Bug
26481 reports are your contribution to the maintenance of @value{GDBN}.
26483 In order for a bug report to serve its purpose, you must include the
26484 information that enables us to fix the bug.
26487 * Bug Criteria:: Have you found a bug?
26488 * Bug Reporting:: How to report bugs
26492 @section Have You Found a Bug?
26493 @cindex bug criteria
26495 If you are not sure whether you have found a bug, here are some guidelines:
26498 @cindex fatal signal
26499 @cindex debugger crash
26500 @cindex crash of debugger
26502 If the debugger gets a fatal signal, for any input whatever, that is a
26503 @value{GDBN} bug. Reliable debuggers never crash.
26505 @cindex error on valid input
26507 If @value{GDBN} produces an error message for valid input, that is a
26508 bug. (Note that if you're cross debugging, the problem may also be
26509 somewhere in the connection to the target.)
26511 @cindex invalid input
26513 If @value{GDBN} does not produce an error message for invalid input,
26514 that is a bug. However, you should note that your idea of
26515 ``invalid input'' might be our idea of ``an extension'' or ``support
26516 for traditional practice''.
26519 If you are an experienced user of debugging tools, your suggestions
26520 for improvement of @value{GDBN} are welcome in any case.
26523 @node Bug Reporting
26524 @section How to Report Bugs
26525 @cindex bug reports
26526 @cindex @value{GDBN} bugs, reporting
26528 A number of companies and individuals offer support for @sc{gnu} products.
26529 If you obtained @value{GDBN} from a support organization, we recommend you
26530 contact that organization first.
26532 You can find contact information for many support companies and
26533 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
26535 @c should add a web page ref...
26538 @ifset BUGURL_DEFAULT
26539 In any event, we also recommend that you submit bug reports for
26540 @value{GDBN}. The preferred method is to submit them directly using
26541 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
26542 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
26545 @strong{Do not send bug reports to @samp{info-gdb}, or to
26546 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
26547 not want to receive bug reports. Those that do have arranged to receive
26550 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
26551 serves as a repeater. The mailing list and the newsgroup carry exactly
26552 the same messages. Often people think of posting bug reports to the
26553 newsgroup instead of mailing them. This appears to work, but it has one
26554 problem which can be crucial: a newsgroup posting often lacks a mail
26555 path back to the sender. Thus, if we need to ask for more information,
26556 we may be unable to reach you. For this reason, it is better to send
26557 bug reports to the mailing list.
26559 @ifclear BUGURL_DEFAULT
26560 In any event, we also recommend that you submit bug reports for
26561 @value{GDBN} to @value{BUGURL}.
26565 The fundamental principle of reporting bugs usefully is this:
26566 @strong{report all the facts}. If you are not sure whether to state a
26567 fact or leave it out, state it!
26569 Often people omit facts because they think they know what causes the
26570 problem and assume that some details do not matter. Thus, you might
26571 assume that the name of the variable you use in an example does not matter.
26572 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
26573 stray memory reference which happens to fetch from the location where that
26574 name is stored in memory; perhaps, if the name were different, the contents
26575 of that location would fool the debugger into doing the right thing despite
26576 the bug. Play it safe and give a specific, complete example. That is the
26577 easiest thing for you to do, and the most helpful.
26579 Keep in mind that the purpose of a bug report is to enable us to fix the
26580 bug. It may be that the bug has been reported previously, but neither
26581 you nor we can know that unless your bug report is complete and
26584 Sometimes people give a few sketchy facts and ask, ``Does this ring a
26585 bell?'' Those bug reports are useless, and we urge everyone to
26586 @emph{refuse to respond to them} except to chide the sender to report
26589 To enable us to fix the bug, you should include all these things:
26593 The version of @value{GDBN}. @value{GDBN} announces it if you start
26594 with no arguments; you can also print it at any time using @code{show
26597 Without this, we will not know whether there is any point in looking for
26598 the bug in the current version of @value{GDBN}.
26601 The type of machine you are using, and the operating system name and
26605 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
26606 ``@value{GCC}--2.8.1''.
26609 What compiler (and its version) was used to compile the program you are
26610 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
26611 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
26612 to get this information; for other compilers, see the documentation for
26616 The command arguments you gave the compiler to compile your example and
26617 observe the bug. For example, did you use @samp{-O}? To guarantee
26618 you will not omit something important, list them all. A copy of the
26619 Makefile (or the output from make) is sufficient.
26621 If we were to try to guess the arguments, we would probably guess wrong
26622 and then we might not encounter the bug.
26625 A complete input script, and all necessary source files, that will
26629 A description of what behavior you observe that you believe is
26630 incorrect. For example, ``It gets a fatal signal.''
26632 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
26633 will certainly notice it. But if the bug is incorrect output, we might
26634 not notice unless it is glaringly wrong. You might as well not give us
26635 a chance to make a mistake.
26637 Even if the problem you experience is a fatal signal, you should still
26638 say so explicitly. Suppose something strange is going on, such as, your
26639 copy of @value{GDBN} is out of synch, or you have encountered a bug in
26640 the C library on your system. (This has happened!) Your copy might
26641 crash and ours would not. If you told us to expect a crash, then when
26642 ours fails to crash, we would know that the bug was not happening for
26643 us. If you had not told us to expect a crash, then we would not be able
26644 to draw any conclusion from our observations.
26647 @cindex recording a session script
26648 To collect all this information, you can use a session recording program
26649 such as @command{script}, which is available on many Unix systems.
26650 Just run your @value{GDBN} session inside @command{script} and then
26651 include the @file{typescript} file with your bug report.
26653 Another way to record a @value{GDBN} session is to run @value{GDBN}
26654 inside Emacs and then save the entire buffer to a file.
26657 If you wish to suggest changes to the @value{GDBN} source, send us context
26658 diffs. If you even discuss something in the @value{GDBN} source, refer to
26659 it by context, not by line number.
26661 The line numbers in our development sources will not match those in your
26662 sources. Your line numbers would convey no useful information to us.
26666 Here are some things that are not necessary:
26670 A description of the envelope of the bug.
26672 Often people who encounter a bug spend a lot of time investigating
26673 which changes to the input file will make the bug go away and which
26674 changes will not affect it.
26676 This is often time consuming and not very useful, because the way we
26677 will find the bug is by running a single example under the debugger
26678 with breakpoints, not by pure deduction from a series of examples.
26679 We recommend that you save your time for something else.
26681 Of course, if you can find a simpler example to report @emph{instead}
26682 of the original one, that is a convenience for us. Errors in the
26683 output will be easier to spot, running under the debugger will take
26684 less time, and so on.
26686 However, simplification is not vital; if you do not want to do this,
26687 report the bug anyway and send us the entire test case you used.
26690 A patch for the bug.
26692 A patch for the bug does help us if it is a good one. But do not omit
26693 the necessary information, such as the test case, on the assumption that
26694 a patch is all we need. We might see problems with your patch and decide
26695 to fix the problem another way, or we might not understand it at all.
26697 Sometimes with a program as complicated as @value{GDBN} it is very hard to
26698 construct an example that will make the program follow a certain path
26699 through the code. If you do not send us the example, we will not be able
26700 to construct one, so we will not be able to verify that the bug is fixed.
26702 And if we cannot understand what bug you are trying to fix, or why your
26703 patch should be an improvement, we will not install it. A test case will
26704 help us to understand.
26707 A guess about what the bug is or what it depends on.
26709 Such guesses are usually wrong. Even we cannot guess right about such
26710 things without first using the debugger to find the facts.
26713 @c The readline documentation is distributed with the readline code
26714 @c and consists of the two following files:
26716 @c inc-hist.texinfo
26717 @c Use -I with makeinfo to point to the appropriate directory,
26718 @c environment var TEXINPUTS with TeX.
26719 @include rluser.texi
26720 @include inc-hist.texinfo
26723 @node Formatting Documentation
26724 @appendix Formatting Documentation
26726 @cindex @value{GDBN} reference card
26727 @cindex reference card
26728 The @value{GDBN} 4 release includes an already-formatted reference card, ready
26729 for printing with PostScript or Ghostscript, in the @file{gdb}
26730 subdirectory of the main source directory@footnote{In
26731 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
26732 release.}. If you can use PostScript or Ghostscript with your printer,
26733 you can print the reference card immediately with @file{refcard.ps}.
26735 The release also includes the source for the reference card. You
26736 can format it, using @TeX{}, by typing:
26742 The @value{GDBN} reference card is designed to print in @dfn{landscape}
26743 mode on US ``letter'' size paper;
26744 that is, on a sheet 11 inches wide by 8.5 inches
26745 high. You will need to specify this form of printing as an option to
26746 your @sc{dvi} output program.
26748 @cindex documentation
26750 All the documentation for @value{GDBN} comes as part of the machine-readable
26751 distribution. The documentation is written in Texinfo format, which is
26752 a documentation system that uses a single source file to produce both
26753 on-line information and a printed manual. You can use one of the Info
26754 formatting commands to create the on-line version of the documentation
26755 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
26757 @value{GDBN} includes an already formatted copy of the on-line Info
26758 version of this manual in the @file{gdb} subdirectory. The main Info
26759 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
26760 subordinate files matching @samp{gdb.info*} in the same directory. If
26761 necessary, you can print out these files, or read them with any editor;
26762 but they are easier to read using the @code{info} subsystem in @sc{gnu}
26763 Emacs or the standalone @code{info} program, available as part of the
26764 @sc{gnu} Texinfo distribution.
26766 If you want to format these Info files yourself, you need one of the
26767 Info formatting programs, such as @code{texinfo-format-buffer} or
26770 If you have @code{makeinfo} installed, and are in the top level
26771 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
26772 version @value{GDBVN}), you can make the Info file by typing:
26779 If you want to typeset and print copies of this manual, you need @TeX{},
26780 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
26781 Texinfo definitions file.
26783 @TeX{} is a typesetting program; it does not print files directly, but
26784 produces output files called @sc{dvi} files. To print a typeset
26785 document, you need a program to print @sc{dvi} files. If your system
26786 has @TeX{} installed, chances are it has such a program. The precise
26787 command to use depends on your system; @kbd{lpr -d} is common; another
26788 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
26789 require a file name without any extension or a @samp{.dvi} extension.
26791 @TeX{} also requires a macro definitions file called
26792 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
26793 written in Texinfo format. On its own, @TeX{} cannot either read or
26794 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
26795 and is located in the @file{gdb-@var{version-number}/texinfo}
26798 If you have @TeX{} and a @sc{dvi} printer program installed, you can
26799 typeset and print this manual. First switch to the @file{gdb}
26800 subdirectory of the main source directory (for example, to
26801 @file{gdb-@value{GDBVN}/gdb}) and type:
26807 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
26809 @node Installing GDB
26810 @appendix Installing @value{GDBN}
26811 @cindex installation
26814 * Requirements:: Requirements for building @value{GDBN}
26815 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
26816 * Separate Objdir:: Compiling @value{GDBN} in another directory
26817 * Config Names:: Specifying names for hosts and targets
26818 * Configure Options:: Summary of options for configure
26819 * System-wide configuration:: Having a system-wide init file
26823 @section Requirements for Building @value{GDBN}
26824 @cindex building @value{GDBN}, requirements for
26826 Building @value{GDBN} requires various tools and packages to be available.
26827 Other packages will be used only if they are found.
26829 @heading Tools/Packages Necessary for Building @value{GDBN}
26831 @item ISO C90 compiler
26832 @value{GDBN} is written in ISO C90. It should be buildable with any
26833 working C90 compiler, e.g.@: GCC.
26837 @heading Tools/Packages Optional for Building @value{GDBN}
26841 @value{GDBN} can use the Expat XML parsing library. This library may be
26842 included with your operating system distribution; if it is not, you
26843 can get the latest version from @url{http://expat.sourceforge.net}.
26844 The @file{configure} script will search for this library in several
26845 standard locations; if it is installed in an unusual path, you can
26846 use the @option{--with-libexpat-prefix} option to specify its location.
26852 Remote protocol memory maps (@pxref{Memory Map Format})
26854 Target descriptions (@pxref{Target Descriptions})
26856 Remote shared library lists (@pxref{Library List Format})
26858 MS-Windows shared libraries (@pxref{Shared Libraries})
26862 @cindex compressed debug sections
26863 @value{GDBN} will use the @samp{zlib} library, if available, to read
26864 compressed debug sections. Some linkers, such as GNU gold, are capable
26865 of producing binaries with compressed debug sections. If @value{GDBN}
26866 is compiled with @samp{zlib}, it will be able to read the debug
26867 information in such binaries.
26869 The @samp{zlib} library is likely included with your operating system
26870 distribution; if it is not, you can get the latest version from
26871 @url{http://zlib.net}.
26874 @value{GDBN}'s features related to character sets (@pxref{Character
26875 Sets}) require a functioning @code{iconv} implementation. If you are
26876 on a GNU system, then this is provided by the GNU C Library. Some
26877 other systems also provide a working @code{iconv}.
26879 On systems with @code{iconv}, you can install GNU Libiconv. If you
26880 have previously installed Libiconv, you can use the
26881 @option{--with-libiconv-prefix} option to configure.
26883 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
26884 arrange to build Libiconv if a directory named @file{libiconv} appears
26885 in the top-most source directory. If Libiconv is built this way, and
26886 if the operating system does not provide a suitable @code{iconv}
26887 implementation, then the just-built library will automatically be used
26888 by @value{GDBN}. One easy way to set this up is to download GNU
26889 Libiconv, unpack it, and then rename the directory holding the
26890 Libiconv source code to @samp{libiconv}.
26893 @node Running Configure
26894 @section Invoking the @value{GDBN} @file{configure} Script
26895 @cindex configuring @value{GDBN}
26896 @value{GDBN} comes with a @file{configure} script that automates the process
26897 of preparing @value{GDBN} for installation; you can then use @code{make} to
26898 build the @code{gdb} program.
26900 @c irrelevant in info file; it's as current as the code it lives with.
26901 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
26902 look at the @file{README} file in the sources; we may have improved the
26903 installation procedures since publishing this manual.}
26906 The @value{GDBN} distribution includes all the source code you need for
26907 @value{GDBN} in a single directory, whose name is usually composed by
26908 appending the version number to @samp{gdb}.
26910 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
26911 @file{gdb-@value{GDBVN}} directory. That directory contains:
26914 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
26915 script for configuring @value{GDBN} and all its supporting libraries
26917 @item gdb-@value{GDBVN}/gdb
26918 the source specific to @value{GDBN} itself
26920 @item gdb-@value{GDBVN}/bfd
26921 source for the Binary File Descriptor library
26923 @item gdb-@value{GDBVN}/include
26924 @sc{gnu} include files
26926 @item gdb-@value{GDBVN}/libiberty
26927 source for the @samp{-liberty} free software library
26929 @item gdb-@value{GDBVN}/opcodes
26930 source for the library of opcode tables and disassemblers
26932 @item gdb-@value{GDBVN}/readline
26933 source for the @sc{gnu} command-line interface
26935 @item gdb-@value{GDBVN}/glob
26936 source for the @sc{gnu} filename pattern-matching subroutine
26938 @item gdb-@value{GDBVN}/mmalloc
26939 source for the @sc{gnu} memory-mapped malloc package
26942 The simplest way to configure and build @value{GDBN} is to run @file{configure}
26943 from the @file{gdb-@var{version-number}} source directory, which in
26944 this example is the @file{gdb-@value{GDBVN}} directory.
26946 First switch to the @file{gdb-@var{version-number}} source directory
26947 if you are not already in it; then run @file{configure}. Pass the
26948 identifier for the platform on which @value{GDBN} will run as an
26954 cd gdb-@value{GDBVN}
26955 ./configure @var{host}
26960 where @var{host} is an identifier such as @samp{sun4} or
26961 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
26962 (You can often leave off @var{host}; @file{configure} tries to guess the
26963 correct value by examining your system.)
26965 Running @samp{configure @var{host}} and then running @code{make} builds the
26966 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
26967 libraries, then @code{gdb} itself. The configured source files, and the
26968 binaries, are left in the corresponding source directories.
26971 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
26972 system does not recognize this automatically when you run a different
26973 shell, you may need to run @code{sh} on it explicitly:
26976 sh configure @var{host}
26979 If you run @file{configure} from a directory that contains source
26980 directories for multiple libraries or programs, such as the
26981 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
26983 creates configuration files for every directory level underneath (unless
26984 you tell it not to, with the @samp{--norecursion} option).
26986 You should run the @file{configure} script from the top directory in the
26987 source tree, the @file{gdb-@var{version-number}} directory. If you run
26988 @file{configure} from one of the subdirectories, you will configure only
26989 that subdirectory. That is usually not what you want. In particular,
26990 if you run the first @file{configure} from the @file{gdb} subdirectory
26991 of the @file{gdb-@var{version-number}} directory, you will omit the
26992 configuration of @file{bfd}, @file{readline}, and other sibling
26993 directories of the @file{gdb} subdirectory. This leads to build errors
26994 about missing include files such as @file{bfd/bfd.h}.
26996 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
26997 However, you should make sure that the shell on your path (named by
26998 the @samp{SHELL} environment variable) is publicly readable. Remember
26999 that @value{GDBN} uses the shell to start your program---some systems refuse to
27000 let @value{GDBN} debug child processes whose programs are not readable.
27002 @node Separate Objdir
27003 @section Compiling @value{GDBN} in Another Directory
27005 If you want to run @value{GDBN} versions for several host or target machines,
27006 you need a different @code{gdb} compiled for each combination of
27007 host and target. @file{configure} is designed to make this easy by
27008 allowing you to generate each configuration in a separate subdirectory,
27009 rather than in the source directory. If your @code{make} program
27010 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
27011 @code{make} in each of these directories builds the @code{gdb}
27012 program specified there.
27014 To build @code{gdb} in a separate directory, run @file{configure}
27015 with the @samp{--srcdir} option to specify where to find the source.
27016 (You also need to specify a path to find @file{configure}
27017 itself from your working directory. If the path to @file{configure}
27018 would be the same as the argument to @samp{--srcdir}, you can leave out
27019 the @samp{--srcdir} option; it is assumed.)
27021 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
27022 separate directory for a Sun 4 like this:
27026 cd gdb-@value{GDBVN}
27029 ../gdb-@value{GDBVN}/configure sun4
27034 When @file{configure} builds a configuration using a remote source
27035 directory, it creates a tree for the binaries with the same structure
27036 (and using the same names) as the tree under the source directory. In
27037 the example, you'd find the Sun 4 library @file{libiberty.a} in the
27038 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
27039 @file{gdb-sun4/gdb}.
27041 Make sure that your path to the @file{configure} script has just one
27042 instance of @file{gdb} in it. If your path to @file{configure} looks
27043 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
27044 one subdirectory of @value{GDBN}, not the whole package. This leads to
27045 build errors about missing include files such as @file{bfd/bfd.h}.
27047 One popular reason to build several @value{GDBN} configurations in separate
27048 directories is to configure @value{GDBN} for cross-compiling (where
27049 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
27050 programs that run on another machine---the @dfn{target}).
27051 You specify a cross-debugging target by
27052 giving the @samp{--target=@var{target}} option to @file{configure}.
27054 When you run @code{make} to build a program or library, you must run
27055 it in a configured directory---whatever directory you were in when you
27056 called @file{configure} (or one of its subdirectories).
27058 The @code{Makefile} that @file{configure} generates in each source
27059 directory also runs recursively. If you type @code{make} in a source
27060 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
27061 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
27062 will build all the required libraries, and then build GDB.
27064 When you have multiple hosts or targets configured in separate
27065 directories, you can run @code{make} on them in parallel (for example,
27066 if they are NFS-mounted on each of the hosts); they will not interfere
27070 @section Specifying Names for Hosts and Targets
27072 The specifications used for hosts and targets in the @file{configure}
27073 script are based on a three-part naming scheme, but some short predefined
27074 aliases are also supported. The full naming scheme encodes three pieces
27075 of information in the following pattern:
27078 @var{architecture}-@var{vendor}-@var{os}
27081 For example, you can use the alias @code{sun4} as a @var{host} argument,
27082 or as the value for @var{target} in a @code{--target=@var{target}}
27083 option. The equivalent full name is @samp{sparc-sun-sunos4}.
27085 The @file{configure} script accompanying @value{GDBN} does not provide
27086 any query facility to list all supported host and target names or
27087 aliases. @file{configure} calls the Bourne shell script
27088 @code{config.sub} to map abbreviations to full names; you can read the
27089 script, if you wish, or you can use it to test your guesses on
27090 abbreviations---for example:
27093 % sh config.sub i386-linux
27095 % sh config.sub alpha-linux
27096 alpha-unknown-linux-gnu
27097 % sh config.sub hp9k700
27099 % sh config.sub sun4
27100 sparc-sun-sunos4.1.1
27101 % sh config.sub sun3
27102 m68k-sun-sunos4.1.1
27103 % sh config.sub i986v
27104 Invalid configuration `i986v': machine `i986v' not recognized
27108 @code{config.sub} is also distributed in the @value{GDBN} source
27109 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
27111 @node Configure Options
27112 @section @file{configure} Options
27114 Here is a summary of the @file{configure} options and arguments that
27115 are most often useful for building @value{GDBN}. @file{configure} also has
27116 several other options not listed here. @inforef{What Configure
27117 Does,,configure.info}, for a full explanation of @file{configure}.
27120 configure @r{[}--help@r{]}
27121 @r{[}--prefix=@var{dir}@r{]}
27122 @r{[}--exec-prefix=@var{dir}@r{]}
27123 @r{[}--srcdir=@var{dirname}@r{]}
27124 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
27125 @r{[}--target=@var{target}@r{]}
27130 You may introduce options with a single @samp{-} rather than
27131 @samp{--} if you prefer; but you may abbreviate option names if you use
27136 Display a quick summary of how to invoke @file{configure}.
27138 @item --prefix=@var{dir}
27139 Configure the source to install programs and files under directory
27142 @item --exec-prefix=@var{dir}
27143 Configure the source to install programs under directory
27146 @c avoid splitting the warning from the explanation:
27148 @item --srcdir=@var{dirname}
27149 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
27150 @code{make} that implements the @code{VPATH} feature.}@*
27151 Use this option to make configurations in directories separate from the
27152 @value{GDBN} source directories. Among other things, you can use this to
27153 build (or maintain) several configurations simultaneously, in separate
27154 directories. @file{configure} writes configuration-specific files in
27155 the current directory, but arranges for them to use the source in the
27156 directory @var{dirname}. @file{configure} creates directories under
27157 the working directory in parallel to the source directories below
27160 @item --norecursion
27161 Configure only the directory level where @file{configure} is executed; do not
27162 propagate configuration to subdirectories.
27164 @item --target=@var{target}
27165 Configure @value{GDBN} for cross-debugging programs running on the specified
27166 @var{target}. Without this option, @value{GDBN} is configured to debug
27167 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
27169 There is no convenient way to generate a list of all available targets.
27171 @item @var{host} @dots{}
27172 Configure @value{GDBN} to run on the specified @var{host}.
27174 There is no convenient way to generate a list of all available hosts.
27177 There are many other options available as well, but they are generally
27178 needed for special purposes only.
27180 @node System-wide configuration
27181 @section System-wide configuration and settings
27182 @cindex system-wide init file
27184 @value{GDBN} can be configured to have a system-wide init file;
27185 this file will be read and executed at startup (@pxref{Startup, , What
27186 @value{GDBN} does during startup}).
27188 Here is the corresponding configure option:
27191 @item --with-system-gdbinit=@var{file}
27192 Specify that the default location of the system-wide init file is
27196 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
27197 it may be subject to relocation. Two possible cases:
27201 If the default location of this init file contains @file{$prefix},
27202 it will be subject to relocation. Suppose that the configure options
27203 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
27204 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
27205 init file is looked for as @file{$install/etc/gdbinit} instead of
27206 @file{$prefix/etc/gdbinit}.
27209 By contrast, if the default location does not contain the prefix,
27210 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
27211 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
27212 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
27213 wherever @value{GDBN} is installed.
27216 @node Maintenance Commands
27217 @appendix Maintenance Commands
27218 @cindex maintenance commands
27219 @cindex internal commands
27221 In addition to commands intended for @value{GDBN} users, @value{GDBN}
27222 includes a number of commands intended for @value{GDBN} developers,
27223 that are not documented elsewhere in this manual. These commands are
27224 provided here for reference. (For commands that turn on debugging
27225 messages, see @ref{Debugging Output}.)
27228 @kindex maint agent
27229 @kindex maint agent-eval
27230 @item maint agent @var{expression}
27231 @itemx maint agent-eval @var{expression}
27232 Translate the given @var{expression} into remote agent bytecodes.
27233 This command is useful for debugging the Agent Expression mechanism
27234 (@pxref{Agent Expressions}). The @samp{agent} version produces an
27235 expression useful for data collection, such as by tracepoints, while
27236 @samp{maint agent-eval} produces an expression that evaluates directly
27237 to a result. For instance, a collection expression for @code{globa +
27238 globb} will include bytecodes to record four bytes of memory at each
27239 of the addresses of @code{globa} and @code{globb}, while discarding
27240 the result of the addition, while an evaluation expression will do the
27241 addition and return the sum.
27243 @kindex maint info breakpoints
27244 @item @anchor{maint info breakpoints}maint info breakpoints
27245 Using the same format as @samp{info breakpoints}, display both the
27246 breakpoints you've set explicitly, and those @value{GDBN} is using for
27247 internal purposes. Internal breakpoints are shown with negative
27248 breakpoint numbers. The type column identifies what kind of breakpoint
27253 Normal, explicitly set breakpoint.
27256 Normal, explicitly set watchpoint.
27259 Internal breakpoint, used to handle correctly stepping through
27260 @code{longjmp} calls.
27262 @item longjmp resume
27263 Internal breakpoint at the target of a @code{longjmp}.
27266 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
27269 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
27272 Shared library events.
27276 @kindex set displaced-stepping
27277 @kindex show displaced-stepping
27278 @cindex displaced stepping support
27279 @cindex out-of-line single-stepping
27280 @item set displaced-stepping
27281 @itemx show displaced-stepping
27282 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
27283 if the target supports it. Displaced stepping is a way to single-step
27284 over breakpoints without removing them from the inferior, by executing
27285 an out-of-line copy of the instruction that was originally at the
27286 breakpoint location. It is also known as out-of-line single-stepping.
27289 @item set displaced-stepping on
27290 If the target architecture supports it, @value{GDBN} will use
27291 displaced stepping to step over breakpoints.
27293 @item set displaced-stepping off
27294 @value{GDBN} will not use displaced stepping to step over breakpoints,
27295 even if such is supported by the target architecture.
27297 @cindex non-stop mode, and @samp{set displaced-stepping}
27298 @item set displaced-stepping auto
27299 This is the default mode. @value{GDBN} will use displaced stepping
27300 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
27301 architecture supports displaced stepping.
27304 @kindex maint check-symtabs
27305 @item maint check-symtabs
27306 Check the consistency of psymtabs and symtabs.
27308 @kindex maint cplus first_component
27309 @item maint cplus first_component @var{name}
27310 Print the first C@t{++} class/namespace component of @var{name}.
27312 @kindex maint cplus namespace
27313 @item maint cplus namespace
27314 Print the list of possible C@t{++} namespaces.
27316 @kindex maint demangle
27317 @item maint demangle @var{name}
27318 Demangle a C@t{++} or Objective-C mangled @var{name}.
27320 @kindex maint deprecate
27321 @kindex maint undeprecate
27322 @cindex deprecated commands
27323 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
27324 @itemx maint undeprecate @var{command}
27325 Deprecate or undeprecate the named @var{command}. Deprecated commands
27326 cause @value{GDBN} to issue a warning when you use them. The optional
27327 argument @var{replacement} says which newer command should be used in
27328 favor of the deprecated one; if it is given, @value{GDBN} will mention
27329 the replacement as part of the warning.
27331 @kindex maint dump-me
27332 @item maint dump-me
27333 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
27334 Cause a fatal signal in the debugger and force it to dump its core.
27335 This is supported only on systems which support aborting a program
27336 with the @code{SIGQUIT} signal.
27338 @kindex maint internal-error
27339 @kindex maint internal-warning
27340 @item maint internal-error @r{[}@var{message-text}@r{]}
27341 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
27342 Cause @value{GDBN} to call the internal function @code{internal_error}
27343 or @code{internal_warning} and hence behave as though an internal error
27344 or internal warning has been detected. In addition to reporting the
27345 internal problem, these functions give the user the opportunity to
27346 either quit @value{GDBN} or create a core file of the current
27347 @value{GDBN} session.
27349 These commands take an optional parameter @var{message-text} that is
27350 used as the text of the error or warning message.
27352 Here's an example of using @code{internal-error}:
27355 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
27356 @dots{}/maint.c:121: internal-error: testing, 1, 2
27357 A problem internal to GDB has been detected. Further
27358 debugging may prove unreliable.
27359 Quit this debugging session? (y or n) @kbd{n}
27360 Create a core file? (y or n) @kbd{n}
27364 @cindex @value{GDBN} internal error
27365 @cindex internal errors, control of @value{GDBN} behavior
27367 @kindex maint set internal-error
27368 @kindex maint show internal-error
27369 @kindex maint set internal-warning
27370 @kindex maint show internal-warning
27371 @item maint set internal-error @var{action} [ask|yes|no]
27372 @itemx maint show internal-error @var{action}
27373 @itemx maint set internal-warning @var{action} [ask|yes|no]
27374 @itemx maint show internal-warning @var{action}
27375 When @value{GDBN} reports an internal problem (error or warning) it
27376 gives the user the opportunity to both quit @value{GDBN} and create a
27377 core file of the current @value{GDBN} session. These commands let you
27378 override the default behaviour for each particular @var{action},
27379 described in the table below.
27383 You can specify that @value{GDBN} should always (yes) or never (no)
27384 quit. The default is to ask the user what to do.
27387 You can specify that @value{GDBN} should always (yes) or never (no)
27388 create a core file. The default is to ask the user what to do.
27391 @kindex maint packet
27392 @item maint packet @var{text}
27393 If @value{GDBN} is talking to an inferior via the serial protocol,
27394 then this command sends the string @var{text} to the inferior, and
27395 displays the response packet. @value{GDBN} supplies the initial
27396 @samp{$} character, the terminating @samp{#} character, and the
27399 @kindex maint print architecture
27400 @item maint print architecture @r{[}@var{file}@r{]}
27401 Print the entire architecture configuration. The optional argument
27402 @var{file} names the file where the output goes.
27404 @kindex maint print c-tdesc
27405 @item maint print c-tdesc
27406 Print the current target description (@pxref{Target Descriptions}) as
27407 a C source file. The created source file can be used in @value{GDBN}
27408 when an XML parser is not available to parse the description.
27410 @kindex maint print dummy-frames
27411 @item maint print dummy-frames
27412 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
27415 (@value{GDBP}) @kbd{b add}
27417 (@value{GDBP}) @kbd{print add(2,3)}
27418 Breakpoint 2, add (a=2, b=3) at @dots{}
27420 The program being debugged stopped while in a function called from GDB.
27422 (@value{GDBP}) @kbd{maint print dummy-frames}
27423 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
27424 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
27425 call_lo=0x01014000 call_hi=0x01014001
27429 Takes an optional file parameter.
27431 @kindex maint print registers
27432 @kindex maint print raw-registers
27433 @kindex maint print cooked-registers
27434 @kindex maint print register-groups
27435 @item maint print registers @r{[}@var{file}@r{]}
27436 @itemx maint print raw-registers @r{[}@var{file}@r{]}
27437 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
27438 @itemx maint print register-groups @r{[}@var{file}@r{]}
27439 Print @value{GDBN}'s internal register data structures.
27441 The command @code{maint print raw-registers} includes the contents of
27442 the raw register cache; the command @code{maint print cooked-registers}
27443 includes the (cooked) value of all registers; and the command
27444 @code{maint print register-groups} includes the groups that each
27445 register is a member of. @xref{Registers,, Registers, gdbint,
27446 @value{GDBN} Internals}.
27448 These commands take an optional parameter, a file name to which to
27449 write the information.
27451 @kindex maint print reggroups
27452 @item maint print reggroups @r{[}@var{file}@r{]}
27453 Print @value{GDBN}'s internal register group data structures. The
27454 optional argument @var{file} tells to what file to write the
27457 The register groups info looks like this:
27460 (@value{GDBP}) @kbd{maint print reggroups}
27473 This command forces @value{GDBN} to flush its internal register cache.
27475 @kindex maint print objfiles
27476 @cindex info for known object files
27477 @item maint print objfiles
27478 Print a dump of all known object files. For each object file, this
27479 command prints its name, address in memory, and all of its psymtabs
27482 @kindex maint print statistics
27483 @cindex bcache statistics
27484 @item maint print statistics
27485 This command prints, for each object file in the program, various data
27486 about that object file followed by the byte cache (@dfn{bcache})
27487 statistics for the object file. The objfile data includes the number
27488 of minimal, partial, full, and stabs symbols, the number of types
27489 defined by the objfile, the number of as yet unexpanded psym tables,
27490 the number of line tables and string tables, and the amount of memory
27491 used by the various tables. The bcache statistics include the counts,
27492 sizes, and counts of duplicates of all and unique objects, max,
27493 average, and median entry size, total memory used and its overhead and
27494 savings, and various measures of the hash table size and chain
27497 @kindex maint print target-stack
27498 @cindex target stack description
27499 @item maint print target-stack
27500 A @dfn{target} is an interface between the debugger and a particular
27501 kind of file or process. Targets can be stacked in @dfn{strata},
27502 so that more than one target can potentially respond to a request.
27503 In particular, memory accesses will walk down the stack of targets
27504 until they find a target that is interested in handling that particular
27507 This command prints a short description of each layer that was pushed on
27508 the @dfn{target stack}, starting from the top layer down to the bottom one.
27510 @kindex maint print type
27511 @cindex type chain of a data type
27512 @item maint print type @var{expr}
27513 Print the type chain for a type specified by @var{expr}. The argument
27514 can be either a type name or a symbol. If it is a symbol, the type of
27515 that symbol is described. The type chain produced by this command is
27516 a recursive definition of the data type as stored in @value{GDBN}'s
27517 data structures, including its flags and contained types.
27519 @kindex maint set dwarf2 max-cache-age
27520 @kindex maint show dwarf2 max-cache-age
27521 @item maint set dwarf2 max-cache-age
27522 @itemx maint show dwarf2 max-cache-age
27523 Control the DWARF 2 compilation unit cache.
27525 @cindex DWARF 2 compilation units cache
27526 In object files with inter-compilation-unit references, such as those
27527 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
27528 reader needs to frequently refer to previously read compilation units.
27529 This setting controls how long a compilation unit will remain in the
27530 cache if it is not referenced. A higher limit means that cached
27531 compilation units will be stored in memory longer, and more total
27532 memory will be used. Setting it to zero disables caching, which will
27533 slow down @value{GDBN} startup, but reduce memory consumption.
27535 @kindex maint set profile
27536 @kindex maint show profile
27537 @cindex profiling GDB
27538 @item maint set profile
27539 @itemx maint show profile
27540 Control profiling of @value{GDBN}.
27542 Profiling will be disabled until you use the @samp{maint set profile}
27543 command to enable it. When you enable profiling, the system will begin
27544 collecting timing and execution count data; when you disable profiling or
27545 exit @value{GDBN}, the results will be written to a log file. Remember that
27546 if you use profiling, @value{GDBN} will overwrite the profiling log file
27547 (often called @file{gmon.out}). If you have a record of important profiling
27548 data in a @file{gmon.out} file, be sure to move it to a safe location.
27550 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
27551 compiled with the @samp{-pg} compiler option.
27553 @kindex maint set show-debug-regs
27554 @kindex maint show show-debug-regs
27555 @cindex hardware debug registers
27556 @item maint set show-debug-regs
27557 @itemx maint show show-debug-regs
27558 Control whether to show variables that mirror the hardware debug
27559 registers. Use @code{ON} to enable, @code{OFF} to disable. If
27560 enabled, the debug registers values are shown when @value{GDBN} inserts or
27561 removes a hardware breakpoint or watchpoint, and when the inferior
27562 triggers a hardware-assisted breakpoint or watchpoint.
27564 @kindex maint space
27565 @cindex memory used by commands
27567 Control whether to display memory usage for each command. If set to a
27568 nonzero value, @value{GDBN} will display how much memory each command
27569 took, following the command's own output. This can also be requested
27570 by invoking @value{GDBN} with the @option{--statistics} command-line
27571 switch (@pxref{Mode Options}).
27574 @cindex time of command execution
27576 Control whether to display the execution time for each command. If
27577 set to a nonzero value, @value{GDBN} will display how much time it
27578 took to execute each command, following the command's own output.
27579 The time is not printed for the commands that run the target, since
27580 there's no mechanism currently to compute how much time was spend
27581 by @value{GDBN} and how much time was spend by the program been debugged.
27582 it's not possibly currently
27583 This can also be requested by invoking @value{GDBN} with the
27584 @option{--statistics} command-line switch (@pxref{Mode Options}).
27586 @kindex maint translate-address
27587 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
27588 Find the symbol stored at the location specified by the address
27589 @var{addr} and an optional section name @var{section}. If found,
27590 @value{GDBN} prints the name of the closest symbol and an offset from
27591 the symbol's location to the specified address. This is similar to
27592 the @code{info address} command (@pxref{Symbols}), except that this
27593 command also allows to find symbols in other sections.
27595 If section was not specified, the section in which the symbol was found
27596 is also printed. For dynamically linked executables, the name of
27597 executable or shared library containing the symbol is printed as well.
27601 The following command is useful for non-interactive invocations of
27602 @value{GDBN}, such as in the test suite.
27605 @item set watchdog @var{nsec}
27606 @kindex set watchdog
27607 @cindex watchdog timer
27608 @cindex timeout for commands
27609 Set the maximum number of seconds @value{GDBN} will wait for the
27610 target operation to finish. If this time expires, @value{GDBN}
27611 reports and error and the command is aborted.
27613 @item show watchdog
27614 Show the current setting of the target wait timeout.
27617 @node Remote Protocol
27618 @appendix @value{GDBN} Remote Serial Protocol
27623 * Stop Reply Packets::
27624 * General Query Packets::
27625 * Register Packet Format::
27626 * Tracepoint Packets::
27627 * Host I/O Packets::
27629 * Notification Packets::
27630 * Remote Non-Stop::
27631 * Packet Acknowledgment::
27633 * File-I/O Remote Protocol Extension::
27634 * Library List Format::
27635 * Memory Map Format::
27641 There may be occasions when you need to know something about the
27642 protocol---for example, if there is only one serial port to your target
27643 machine, you might want your program to do something special if it
27644 recognizes a packet meant for @value{GDBN}.
27646 In the examples below, @samp{->} and @samp{<-} are used to indicate
27647 transmitted and received data, respectively.
27649 @cindex protocol, @value{GDBN} remote serial
27650 @cindex serial protocol, @value{GDBN} remote
27651 @cindex remote serial protocol
27652 All @value{GDBN} commands and responses (other than acknowledgments
27653 and notifications, see @ref{Notification Packets}) are sent as a
27654 @var{packet}. A @var{packet} is introduced with the character
27655 @samp{$}, the actual @var{packet-data}, and the terminating character
27656 @samp{#} followed by a two-digit @var{checksum}:
27659 @code{$}@var{packet-data}@code{#}@var{checksum}
27663 @cindex checksum, for @value{GDBN} remote
27665 The two-digit @var{checksum} is computed as the modulo 256 sum of all
27666 characters between the leading @samp{$} and the trailing @samp{#} (an
27667 eight bit unsigned checksum).
27669 Implementors should note that prior to @value{GDBN} 5.0 the protocol
27670 specification also included an optional two-digit @var{sequence-id}:
27673 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
27676 @cindex sequence-id, for @value{GDBN} remote
27678 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
27679 has never output @var{sequence-id}s. Stubs that handle packets added
27680 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
27682 When either the host or the target machine receives a packet, the first
27683 response expected is an acknowledgment: either @samp{+} (to indicate
27684 the package was received correctly) or @samp{-} (to request
27688 -> @code{$}@var{packet-data}@code{#}@var{checksum}
27693 The @samp{+}/@samp{-} acknowledgments can be disabled
27694 once a connection is established.
27695 @xref{Packet Acknowledgment}, for details.
27697 The host (@value{GDBN}) sends @var{command}s, and the target (the
27698 debugging stub incorporated in your program) sends a @var{response}. In
27699 the case of step and continue @var{command}s, the response is only sent
27700 when the operation has completed, and the target has again stopped all
27701 threads in all attached processes. This is the default all-stop mode
27702 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
27703 execution mode; see @ref{Remote Non-Stop}, for details.
27705 @var{packet-data} consists of a sequence of characters with the
27706 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
27709 @cindex remote protocol, field separator
27710 Fields within the packet should be separated using @samp{,} @samp{;} or
27711 @samp{:}. Except where otherwise noted all numbers are represented in
27712 @sc{hex} with leading zeros suppressed.
27714 Implementors should note that prior to @value{GDBN} 5.0, the character
27715 @samp{:} could not appear as the third character in a packet (as it
27716 would potentially conflict with the @var{sequence-id}).
27718 @cindex remote protocol, binary data
27719 @anchor{Binary Data}
27720 Binary data in most packets is encoded either as two hexadecimal
27721 digits per byte of binary data. This allowed the traditional remote
27722 protocol to work over connections which were only seven-bit clean.
27723 Some packets designed more recently assume an eight-bit clean
27724 connection, and use a more efficient encoding to send and receive
27727 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
27728 as an escape character. Any escaped byte is transmitted as the escape
27729 character followed by the original character XORed with @code{0x20}.
27730 For example, the byte @code{0x7d} would be transmitted as the two
27731 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
27732 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
27733 @samp{@}}) must always be escaped. Responses sent by the stub
27734 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
27735 is not interpreted as the start of a run-length encoded sequence
27738 Response @var{data} can be run-length encoded to save space.
27739 Run-length encoding replaces runs of identical characters with one
27740 instance of the repeated character, followed by a @samp{*} and a
27741 repeat count. The repeat count is itself sent encoded, to avoid
27742 binary characters in @var{data}: a value of @var{n} is sent as
27743 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
27744 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
27745 code 32) for a repeat count of 3. (This is because run-length
27746 encoding starts to win for counts 3 or more.) Thus, for example,
27747 @samp{0* } is a run-length encoding of ``0000'': the space character
27748 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
27751 The printable characters @samp{#} and @samp{$} or with a numeric value
27752 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
27753 seven repeats (@samp{$}) can be expanded using a repeat count of only
27754 five (@samp{"}). For example, @samp{00000000} can be encoded as
27757 The error response returned for some packets includes a two character
27758 error number. That number is not well defined.
27760 @cindex empty response, for unsupported packets
27761 For any @var{command} not supported by the stub, an empty response
27762 (@samp{$#00}) should be returned. That way it is possible to extend the
27763 protocol. A newer @value{GDBN} can tell if a packet is supported based
27766 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
27767 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
27773 The following table provides a complete list of all currently defined
27774 @var{command}s and their corresponding response @var{data}.
27775 @xref{File-I/O Remote Protocol Extension}, for details about the File
27776 I/O extension of the remote protocol.
27778 Each packet's description has a template showing the packet's overall
27779 syntax, followed by an explanation of the packet's meaning. We
27780 include spaces in some of the templates for clarity; these are not
27781 part of the packet's syntax. No @value{GDBN} packet uses spaces to
27782 separate its components. For example, a template like @samp{foo
27783 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
27784 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
27785 @var{baz}. @value{GDBN} does not transmit a space character between the
27786 @samp{foo} and the @var{bar}, or between the @var{bar} and the
27789 @cindex @var{thread-id}, in remote protocol
27790 @anchor{thread-id syntax}
27791 Several packets and replies include a @var{thread-id} field to identify
27792 a thread. Normally these are positive numbers with a target-specific
27793 interpretation, formatted as big-endian hex strings. A @var{thread-id}
27794 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
27797 In addition, the remote protocol supports a multiprocess feature in
27798 which the @var{thread-id} syntax is extended to optionally include both
27799 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
27800 The @var{pid} (process) and @var{tid} (thread) components each have the
27801 format described above: a positive number with target-specific
27802 interpretation formatted as a big-endian hex string, literal @samp{-1}
27803 to indicate all processes or threads (respectively), or @samp{0} to
27804 indicate an arbitrary process or thread. Specifying just a process, as
27805 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
27806 error to specify all processes but a specific thread, such as
27807 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
27808 for those packets and replies explicitly documented to include a process
27809 ID, rather than a @var{thread-id}.
27811 The multiprocess @var{thread-id} syntax extensions are only used if both
27812 @value{GDBN} and the stub report support for the @samp{multiprocess}
27813 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
27816 Note that all packet forms beginning with an upper- or lower-case
27817 letter, other than those described here, are reserved for future use.
27819 Here are the packet descriptions.
27824 @cindex @samp{!} packet
27825 @anchor{extended mode}
27826 Enable extended mode. In extended mode, the remote server is made
27827 persistent. The @samp{R} packet is used to restart the program being
27833 The remote target both supports and has enabled extended mode.
27837 @cindex @samp{?} packet
27838 Indicate the reason the target halted. The reply is the same as for
27839 step and continue. This packet has a special interpretation when the
27840 target is in non-stop mode; see @ref{Remote Non-Stop}.
27843 @xref{Stop Reply Packets}, for the reply specifications.
27845 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
27846 @cindex @samp{A} packet
27847 Initialized @code{argv[]} array passed into program. @var{arglen}
27848 specifies the number of bytes in the hex encoded byte stream
27849 @var{arg}. See @code{gdbserver} for more details.
27854 The arguments were set.
27860 @cindex @samp{b} packet
27861 (Don't use this packet; its behavior is not well-defined.)
27862 Change the serial line speed to @var{baud}.
27864 JTC: @emph{When does the transport layer state change? When it's
27865 received, or after the ACK is transmitted. In either case, there are
27866 problems if the command or the acknowledgment packet is dropped.}
27868 Stan: @emph{If people really wanted to add something like this, and get
27869 it working for the first time, they ought to modify ser-unix.c to send
27870 some kind of out-of-band message to a specially-setup stub and have the
27871 switch happen "in between" packets, so that from remote protocol's point
27872 of view, nothing actually happened.}
27874 @item B @var{addr},@var{mode}
27875 @cindex @samp{B} packet
27876 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
27877 breakpoint at @var{addr}.
27879 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
27880 (@pxref{insert breakpoint or watchpoint packet}).
27882 @cindex @samp{bc} packet
27885 Backward continue. Execute the target system in reverse. No parameter.
27886 @xref{Reverse Execution}, for more information.
27889 @xref{Stop Reply Packets}, for the reply specifications.
27891 @cindex @samp{bs} packet
27894 Backward single step. Execute one instruction in reverse. No parameter.
27895 @xref{Reverse Execution}, for more information.
27898 @xref{Stop Reply Packets}, for the reply specifications.
27900 @item c @r{[}@var{addr}@r{]}
27901 @cindex @samp{c} packet
27902 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
27903 resume at current address.
27906 @xref{Stop Reply Packets}, for the reply specifications.
27908 @item C @var{sig}@r{[};@var{addr}@r{]}
27909 @cindex @samp{C} packet
27910 Continue with signal @var{sig} (hex signal number). If
27911 @samp{;@var{addr}} is omitted, resume at same address.
27914 @xref{Stop Reply Packets}, for the reply specifications.
27917 @cindex @samp{d} packet
27920 Don't use this packet; instead, define a general set packet
27921 (@pxref{General Query Packets}).
27925 @cindex @samp{D} packet
27926 The first form of the packet is used to detach @value{GDBN} from the
27927 remote system. It is sent to the remote target
27928 before @value{GDBN} disconnects via the @code{detach} command.
27930 The second form, including a process ID, is used when multiprocess
27931 protocol extensions are enabled (@pxref{multiprocess extensions}), to
27932 detach only a specific process. The @var{pid} is specified as a
27933 big-endian hex string.
27943 @item F @var{RC},@var{EE},@var{CF};@var{XX}
27944 @cindex @samp{F} packet
27945 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
27946 This is part of the File-I/O protocol extension. @xref{File-I/O
27947 Remote Protocol Extension}, for the specification.
27950 @anchor{read registers packet}
27951 @cindex @samp{g} packet
27952 Read general registers.
27956 @item @var{XX@dots{}}
27957 Each byte of register data is described by two hex digits. The bytes
27958 with the register are transmitted in target byte order. The size of
27959 each register and their position within the @samp{g} packet are
27960 determined by the @value{GDBN} internal gdbarch functions
27961 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
27962 specification of several standard @samp{g} packets is specified below.
27967 @item G @var{XX@dots{}}
27968 @cindex @samp{G} packet
27969 Write general registers. @xref{read registers packet}, for a
27970 description of the @var{XX@dots{}} data.
27980 @item H @var{c} @var{thread-id}
27981 @cindex @samp{H} packet
27982 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
27983 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
27984 should be @samp{c} for step and continue operations, @samp{g} for other
27985 operations. The thread designator @var{thread-id} has the format and
27986 interpretation described in @ref{thread-id syntax}.
27997 @c 'H': How restrictive (or permissive) is the thread model. If a
27998 @c thread is selected and stopped, are other threads allowed
27999 @c to continue to execute? As I mentioned above, I think the
28000 @c semantics of each command when a thread is selected must be
28001 @c described. For example:
28003 @c 'g': If the stub supports threads and a specific thread is
28004 @c selected, returns the register block from that thread;
28005 @c otherwise returns current registers.
28007 @c 'G' If the stub supports threads and a specific thread is
28008 @c selected, sets the registers of the register block of
28009 @c that thread; otherwise sets current registers.
28011 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
28012 @anchor{cycle step packet}
28013 @cindex @samp{i} packet
28014 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
28015 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
28016 step starting at that address.
28019 @cindex @samp{I} packet
28020 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
28024 @cindex @samp{k} packet
28027 FIXME: @emph{There is no description of how to operate when a specific
28028 thread context has been selected (i.e.@: does 'k' kill only that
28031 @item m @var{addr},@var{length}
28032 @cindex @samp{m} packet
28033 Read @var{length} bytes of memory starting at address @var{addr}.
28034 Note that @var{addr} may not be aligned to any particular boundary.
28036 The stub need not use any particular size or alignment when gathering
28037 data from memory for the response; even if @var{addr} is word-aligned
28038 and @var{length} is a multiple of the word size, the stub is free to
28039 use byte accesses, or not. For this reason, this packet may not be
28040 suitable for accessing memory-mapped I/O devices.
28041 @cindex alignment of remote memory accesses
28042 @cindex size of remote memory accesses
28043 @cindex memory, alignment and size of remote accesses
28047 @item @var{XX@dots{}}
28048 Memory contents; each byte is transmitted as a two-digit hexadecimal
28049 number. The reply may contain fewer bytes than requested if the
28050 server was able to read only part of the region of memory.
28055 @item M @var{addr},@var{length}:@var{XX@dots{}}
28056 @cindex @samp{M} packet
28057 Write @var{length} bytes of memory starting at address @var{addr}.
28058 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
28059 hexadecimal number.
28066 for an error (this includes the case where only part of the data was
28071 @cindex @samp{p} packet
28072 Read the value of register @var{n}; @var{n} is in hex.
28073 @xref{read registers packet}, for a description of how the returned
28074 register value is encoded.
28078 @item @var{XX@dots{}}
28079 the register's value
28083 Indicating an unrecognized @var{query}.
28086 @item P @var{n@dots{}}=@var{r@dots{}}
28087 @anchor{write register packet}
28088 @cindex @samp{P} packet
28089 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
28090 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
28091 digits for each byte in the register (target byte order).
28101 @item q @var{name} @var{params}@dots{}
28102 @itemx Q @var{name} @var{params}@dots{}
28103 @cindex @samp{q} packet
28104 @cindex @samp{Q} packet
28105 General query (@samp{q}) and set (@samp{Q}). These packets are
28106 described fully in @ref{General Query Packets}.
28109 @cindex @samp{r} packet
28110 Reset the entire system.
28112 Don't use this packet; use the @samp{R} packet instead.
28115 @cindex @samp{R} packet
28116 Restart the program being debugged. @var{XX}, while needed, is ignored.
28117 This packet is only available in extended mode (@pxref{extended mode}).
28119 The @samp{R} packet has no reply.
28121 @item s @r{[}@var{addr}@r{]}
28122 @cindex @samp{s} packet
28123 Single step. @var{addr} is the address at which to resume. If
28124 @var{addr} is omitted, resume at same address.
28127 @xref{Stop Reply Packets}, for the reply specifications.
28129 @item S @var{sig}@r{[};@var{addr}@r{]}
28130 @anchor{step with signal packet}
28131 @cindex @samp{S} packet
28132 Step with signal. This is analogous to the @samp{C} packet, but
28133 requests a single-step, rather than a normal resumption of execution.
28136 @xref{Stop Reply Packets}, for the reply specifications.
28138 @item t @var{addr}:@var{PP},@var{MM}
28139 @cindex @samp{t} packet
28140 Search backwards starting at address @var{addr} for a match with pattern
28141 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
28142 @var{addr} must be at least 3 digits.
28144 @item T @var{thread-id}
28145 @cindex @samp{T} packet
28146 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
28151 thread is still alive
28157 Packets starting with @samp{v} are identified by a multi-letter name,
28158 up to the first @samp{;} or @samp{?} (or the end of the packet).
28160 @item vAttach;@var{pid}
28161 @cindex @samp{vAttach} packet
28162 Attach to a new process with the specified process ID @var{pid}.
28163 The process ID is a
28164 hexadecimal integer identifying the process. In all-stop mode, all
28165 threads in the attached process are stopped; in non-stop mode, it may be
28166 attached without being stopped if that is supported by the target.
28168 @c In non-stop mode, on a successful vAttach, the stub should set the
28169 @c current thread to a thread of the newly-attached process. After
28170 @c attaching, GDB queries for the attached process's thread ID with qC.
28171 @c Also note that, from a user perspective, whether or not the
28172 @c target is stopped on attach in non-stop mode depends on whether you
28173 @c use the foreground or background version of the attach command, not
28174 @c on what vAttach does; GDB does the right thing with respect to either
28175 @c stopping or restarting threads.
28177 This packet is only available in extended mode (@pxref{extended mode}).
28183 @item @r{Any stop packet}
28184 for success in all-stop mode (@pxref{Stop Reply Packets})
28186 for success in non-stop mode (@pxref{Remote Non-Stop})
28189 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
28190 @cindex @samp{vCont} packet
28191 Resume the inferior, specifying different actions for each thread.
28192 If an action is specified with no @var{thread-id}, then it is applied to any
28193 threads that don't have a specific action specified; if no default action is
28194 specified then other threads should remain stopped in all-stop mode and
28195 in their current state in non-stop mode.
28196 Specifying multiple
28197 default actions is an error; specifying no actions is also an error.
28198 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
28200 Currently supported actions are:
28206 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
28210 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
28214 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
28217 The optional argument @var{addr} normally associated with the
28218 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
28219 not supported in @samp{vCont}.
28221 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
28222 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
28223 A stop reply should be generated for any affected thread not already stopped.
28224 When a thread is stopped by means of a @samp{t} action,
28225 the corresponding stop reply should indicate that the thread has stopped with
28226 signal @samp{0}, regardless of whether the target uses some other signal
28227 as an implementation detail.
28230 @xref{Stop Reply Packets}, for the reply specifications.
28233 @cindex @samp{vCont?} packet
28234 Request a list of actions supported by the @samp{vCont} packet.
28238 @item vCont@r{[};@var{action}@dots{}@r{]}
28239 The @samp{vCont} packet is supported. Each @var{action} is a supported
28240 command in the @samp{vCont} packet.
28242 The @samp{vCont} packet is not supported.
28245 @item vFile:@var{operation}:@var{parameter}@dots{}
28246 @cindex @samp{vFile} packet
28247 Perform a file operation on the target system. For details,
28248 see @ref{Host I/O Packets}.
28250 @item vFlashErase:@var{addr},@var{length}
28251 @cindex @samp{vFlashErase} packet
28252 Direct the stub to erase @var{length} bytes of flash starting at
28253 @var{addr}. The region may enclose any number of flash blocks, but
28254 its start and end must fall on block boundaries, as indicated by the
28255 flash block size appearing in the memory map (@pxref{Memory Map
28256 Format}). @value{GDBN} groups flash memory programming operations
28257 together, and sends a @samp{vFlashDone} request after each group; the
28258 stub is allowed to delay erase operation until the @samp{vFlashDone}
28259 packet is received.
28261 The stub must support @samp{vCont} if it reports support for
28262 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
28263 this case @samp{vCont} actions can be specified to apply to all threads
28264 in a process by using the @samp{p@var{pid}.-1} form of the
28275 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
28276 @cindex @samp{vFlashWrite} packet
28277 Direct the stub to write data to flash address @var{addr}. The data
28278 is passed in binary form using the same encoding as for the @samp{X}
28279 packet (@pxref{Binary Data}). The memory ranges specified by
28280 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
28281 not overlap, and must appear in order of increasing addresses
28282 (although @samp{vFlashErase} packets for higher addresses may already
28283 have been received; the ordering is guaranteed only between
28284 @samp{vFlashWrite} packets). If a packet writes to an address that was
28285 neither erased by a preceding @samp{vFlashErase} packet nor by some other
28286 target-specific method, the results are unpredictable.
28294 for vFlashWrite addressing non-flash memory
28300 @cindex @samp{vFlashDone} packet
28301 Indicate to the stub that flash programming operation is finished.
28302 The stub is permitted to delay or batch the effects of a group of
28303 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
28304 @samp{vFlashDone} packet is received. The contents of the affected
28305 regions of flash memory are unpredictable until the @samp{vFlashDone}
28306 request is completed.
28308 @item vKill;@var{pid}
28309 @cindex @samp{vKill} packet
28310 Kill the process with the specified process ID. @var{pid} is a
28311 hexadecimal integer identifying the process. This packet is used in
28312 preference to @samp{k} when multiprocess protocol extensions are
28313 supported; see @ref{multiprocess extensions}.
28323 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
28324 @cindex @samp{vRun} packet
28325 Run the program @var{filename}, passing it each @var{argument} on its
28326 command line. The file and arguments are hex-encoded strings. If
28327 @var{filename} is an empty string, the stub may use a default program
28328 (e.g.@: the last program run). The program is created in the stopped
28331 @c FIXME: What about non-stop mode?
28333 This packet is only available in extended mode (@pxref{extended mode}).
28339 @item @r{Any stop packet}
28340 for success (@pxref{Stop Reply Packets})
28344 @anchor{vStopped packet}
28345 @cindex @samp{vStopped} packet
28347 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
28348 reply and prompt for the stub to report another one.
28352 @item @r{Any stop packet}
28353 if there is another unreported stop event (@pxref{Stop Reply Packets})
28355 if there are no unreported stop events
28358 @item X @var{addr},@var{length}:@var{XX@dots{}}
28360 @cindex @samp{X} packet
28361 Write data to memory, where the data is transmitted in binary.
28362 @var{addr} is address, @var{length} is number of bytes,
28363 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
28373 @item z @var{type},@var{addr},@var{length}
28374 @itemx Z @var{type},@var{addr},@var{length}
28375 @anchor{insert breakpoint or watchpoint packet}
28376 @cindex @samp{z} packet
28377 @cindex @samp{Z} packets
28378 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
28379 watchpoint starting at address @var{address} and covering the next
28380 @var{length} bytes.
28382 Each breakpoint and watchpoint packet @var{type} is documented
28385 @emph{Implementation notes: A remote target shall return an empty string
28386 for an unrecognized breakpoint or watchpoint packet @var{type}. A
28387 remote target shall support either both or neither of a given
28388 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
28389 avoid potential problems with duplicate packets, the operations should
28390 be implemented in an idempotent way.}
28392 @item z0,@var{addr},@var{length}
28393 @itemx Z0,@var{addr},@var{length}
28394 @cindex @samp{z0} packet
28395 @cindex @samp{Z0} packet
28396 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
28397 @var{addr} of size @var{length}.
28399 A memory breakpoint is implemented by replacing the instruction at
28400 @var{addr} with a software breakpoint or trap instruction. The
28401 @var{length} is used by targets that indicates the size of the
28402 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
28403 @sc{mips} can insert either a 2 or 4 byte breakpoint).
28405 @emph{Implementation note: It is possible for a target to copy or move
28406 code that contains memory breakpoints (e.g., when implementing
28407 overlays). The behavior of this packet, in the presence of such a
28408 target, is not defined.}
28420 @item z1,@var{addr},@var{length}
28421 @itemx Z1,@var{addr},@var{length}
28422 @cindex @samp{z1} packet
28423 @cindex @samp{Z1} packet
28424 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
28425 address @var{addr} of size @var{length}.
28427 A hardware breakpoint is implemented using a mechanism that is not
28428 dependant on being able to modify the target's memory.
28430 @emph{Implementation note: A hardware breakpoint is not affected by code
28443 @item z2,@var{addr},@var{length}
28444 @itemx Z2,@var{addr},@var{length}
28445 @cindex @samp{z2} packet
28446 @cindex @samp{Z2} packet
28447 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
28459 @item z3,@var{addr},@var{length}
28460 @itemx Z3,@var{addr},@var{length}
28461 @cindex @samp{z3} packet
28462 @cindex @samp{Z3} packet
28463 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
28475 @item z4,@var{addr},@var{length}
28476 @itemx Z4,@var{addr},@var{length}
28477 @cindex @samp{z4} packet
28478 @cindex @samp{Z4} packet
28479 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
28493 @node Stop Reply Packets
28494 @section Stop Reply Packets
28495 @cindex stop reply packets
28497 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
28498 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
28499 receive any of the below as a reply. Except for @samp{?}
28500 and @samp{vStopped}, that reply is only returned
28501 when the target halts. In the below the exact meaning of @dfn{signal
28502 number} is defined by the header @file{include/gdb/signals.h} in the
28503 @value{GDBN} source code.
28505 As in the description of request packets, we include spaces in the
28506 reply templates for clarity; these are not part of the reply packet's
28507 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
28513 The program received signal number @var{AA} (a two-digit hexadecimal
28514 number). This is equivalent to a @samp{T} response with no
28515 @var{n}:@var{r} pairs.
28517 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
28518 @cindex @samp{T} packet reply
28519 The program received signal number @var{AA} (a two-digit hexadecimal
28520 number). This is equivalent to an @samp{S} response, except that the
28521 @samp{@var{n}:@var{r}} pairs can carry values of important registers
28522 and other information directly in the stop reply packet, reducing
28523 round-trip latency. Single-step and breakpoint traps are reported
28524 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
28528 If @var{n} is a hexadecimal number, it is a register number, and the
28529 corresponding @var{r} gives that register's value. @var{r} is a
28530 series of bytes in target byte order, with each byte given by a
28531 two-digit hex number.
28534 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
28535 the stopped thread, as specified in @ref{thread-id syntax}.
28538 If @var{n} is a recognized @dfn{stop reason}, it describes a more
28539 specific event that stopped the target. The currently defined stop
28540 reasons are listed below. @var{aa} should be @samp{05}, the trap
28541 signal. At most one stop reason should be present.
28544 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
28545 and go on to the next; this allows us to extend the protocol in the
28549 The currently defined stop reasons are:
28555 The packet indicates a watchpoint hit, and @var{r} is the data address, in
28558 @cindex shared library events, remote reply
28560 The packet indicates that the loaded libraries have changed.
28561 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
28562 list of loaded libraries. @var{r} is ignored.
28564 @cindex replay log events, remote reply
28566 The packet indicates that the target cannot continue replaying
28567 logged execution events, because it has reached the end (or the
28568 beginning when executing backward) of the log. The value of @var{r}
28569 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
28570 for more information.
28576 @itemx W @var{AA} ; process:@var{pid}
28577 The process exited, and @var{AA} is the exit status. This is only
28578 applicable to certain targets.
28580 The second form of the response, including the process ID of the exited
28581 process, can be used only when @value{GDBN} has reported support for
28582 multiprocess protocol extensions; see @ref{multiprocess extensions}.
28583 The @var{pid} is formatted as a big-endian hex string.
28586 @itemx X @var{AA} ; process:@var{pid}
28587 The process terminated with signal @var{AA}.
28589 The second form of the response, including the process ID of the
28590 terminated process, can be used only when @value{GDBN} has reported
28591 support for multiprocess protocol extensions; see @ref{multiprocess
28592 extensions}. The @var{pid} is formatted as a big-endian hex string.
28594 @item O @var{XX}@dots{}
28595 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
28596 written as the program's console output. This can happen at any time
28597 while the program is running and the debugger should continue to wait
28598 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
28600 @item F @var{call-id},@var{parameter}@dots{}
28601 @var{call-id} is the identifier which says which host system call should
28602 be called. This is just the name of the function. Translation into the
28603 correct system call is only applicable as it's defined in @value{GDBN}.
28604 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
28607 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
28608 this very system call.
28610 The target replies with this packet when it expects @value{GDBN} to
28611 call a host system call on behalf of the target. @value{GDBN} replies
28612 with an appropriate @samp{F} packet and keeps up waiting for the next
28613 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
28614 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
28615 Protocol Extension}, for more details.
28619 @node General Query Packets
28620 @section General Query Packets
28621 @cindex remote query requests
28623 Packets starting with @samp{q} are @dfn{general query packets};
28624 packets starting with @samp{Q} are @dfn{general set packets}. General
28625 query and set packets are a semi-unified form for retrieving and
28626 sending information to and from the stub.
28628 The initial letter of a query or set packet is followed by a name
28629 indicating what sort of thing the packet applies to. For example,
28630 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
28631 definitions with the stub. These packet names follow some
28636 The name must not contain commas, colons or semicolons.
28638 Most @value{GDBN} query and set packets have a leading upper case
28641 The names of custom vendor packets should use a company prefix, in
28642 lower case, followed by a period. For example, packets designed at
28643 the Acme Corporation might begin with @samp{qacme.foo} (for querying
28644 foos) or @samp{Qacme.bar} (for setting bars).
28647 The name of a query or set packet should be separated from any
28648 parameters by a @samp{:}; the parameters themselves should be
28649 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
28650 full packet name, and check for a separator or the end of the packet,
28651 in case two packet names share a common prefix. New packets should not begin
28652 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
28653 packets predate these conventions, and have arguments without any terminator
28654 for the packet name; we suspect they are in widespread use in places that
28655 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
28656 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
28659 Like the descriptions of the other packets, each description here
28660 has a template showing the packet's overall syntax, followed by an
28661 explanation of the packet's meaning. We include spaces in some of the
28662 templates for clarity; these are not part of the packet's syntax. No
28663 @value{GDBN} packet uses spaces to separate its components.
28665 Here are the currently defined query and set packets:
28670 @cindex current thread, remote request
28671 @cindex @samp{qC} packet
28672 Return the current thread ID.
28676 @item QC @var{thread-id}
28677 Where @var{thread-id} is a thread ID as documented in
28678 @ref{thread-id syntax}.
28679 @item @r{(anything else)}
28680 Any other reply implies the old thread ID.
28683 @item qCRC:@var{addr},@var{length}
28684 @cindex CRC of memory block, remote request
28685 @cindex @samp{qCRC} packet
28686 Compute the CRC checksum of a block of memory using CRC-32 defined in
28687 IEEE 802.3. The CRC is computed byte at a time, taking the most
28688 significant bit of each byte first. The initial pattern code
28689 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
28691 @emph{Note:} This is the same CRC used in validating separate debug
28692 files (@pxref{Separate Debug Files, , Debugging Information in Separate
28693 Files}). However the algorithm is slightly different. When validating
28694 separate debug files, the CRC is computed taking the @emph{least}
28695 significant bit of each byte first, and the final result is inverted to
28696 detect trailing zeros.
28701 An error (such as memory fault)
28702 @item C @var{crc32}
28703 The specified memory region's checksum is @var{crc32}.
28707 @itemx qsThreadInfo
28708 @cindex list active threads, remote request
28709 @cindex @samp{qfThreadInfo} packet
28710 @cindex @samp{qsThreadInfo} packet
28711 Obtain a list of all active thread IDs from the target (OS). Since there
28712 may be too many active threads to fit into one reply packet, this query
28713 works iteratively: it may require more than one query/reply sequence to
28714 obtain the entire list of threads. The first query of the sequence will
28715 be the @samp{qfThreadInfo} query; subsequent queries in the
28716 sequence will be the @samp{qsThreadInfo} query.
28718 NOTE: This packet replaces the @samp{qL} query (see below).
28722 @item m @var{thread-id}
28724 @item m @var{thread-id},@var{thread-id}@dots{}
28725 a comma-separated list of thread IDs
28727 (lower case letter @samp{L}) denotes end of list.
28730 In response to each query, the target will reply with a list of one or
28731 more thread IDs, separated by commas.
28732 @value{GDBN} will respond to each reply with a request for more thread
28733 ids (using the @samp{qs} form of the query), until the target responds
28734 with @samp{l} (lower-case el, for @dfn{last}).
28735 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
28738 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
28739 @cindex get thread-local storage address, remote request
28740 @cindex @samp{qGetTLSAddr} packet
28741 Fetch the address associated with thread local storage specified
28742 by @var{thread-id}, @var{offset}, and @var{lm}.
28744 @var{thread-id} is the thread ID associated with the
28745 thread for which to fetch the TLS address. @xref{thread-id syntax}.
28747 @var{offset} is the (big endian, hex encoded) offset associated with the
28748 thread local variable. (This offset is obtained from the debug
28749 information associated with the variable.)
28751 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
28752 the load module associated with the thread local storage. For example,
28753 a @sc{gnu}/Linux system will pass the link map address of the shared
28754 object associated with the thread local storage under consideration.
28755 Other operating environments may choose to represent the load module
28756 differently, so the precise meaning of this parameter will vary.
28760 @item @var{XX}@dots{}
28761 Hex encoded (big endian) bytes representing the address of the thread
28762 local storage requested.
28765 An error occurred. @var{nn} are hex digits.
28768 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
28771 @item qL @var{startflag} @var{threadcount} @var{nextthread}
28772 Obtain thread information from RTOS. Where: @var{startflag} (one hex
28773 digit) is one to indicate the first query and zero to indicate a
28774 subsequent query; @var{threadcount} (two hex digits) is the maximum
28775 number of threads the response packet can contain; and @var{nextthread}
28776 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
28777 returned in the response as @var{argthread}.
28779 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
28783 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
28784 Where: @var{count} (two hex digits) is the number of threads being
28785 returned; @var{done} (one hex digit) is zero to indicate more threads
28786 and one indicates no further threads; @var{argthreadid} (eight hex
28787 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
28788 is a sequence of thread IDs from the target. @var{threadid} (eight hex
28789 digits). See @code{remote.c:parse_threadlist_response()}.
28793 @cindex section offsets, remote request
28794 @cindex @samp{qOffsets} packet
28795 Get section offsets that the target used when relocating the downloaded
28800 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
28801 Relocate the @code{Text} section by @var{xxx} from its original address.
28802 Relocate the @code{Data} section by @var{yyy} from its original address.
28803 If the object file format provides segment information (e.g.@: @sc{elf}
28804 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
28805 segments by the supplied offsets.
28807 @emph{Note: while a @code{Bss} offset may be included in the response,
28808 @value{GDBN} ignores this and instead applies the @code{Data} offset
28809 to the @code{Bss} section.}
28811 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
28812 Relocate the first segment of the object file, which conventionally
28813 contains program code, to a starting address of @var{xxx}. If
28814 @samp{DataSeg} is specified, relocate the second segment, which
28815 conventionally contains modifiable data, to a starting address of
28816 @var{yyy}. @value{GDBN} will report an error if the object file
28817 does not contain segment information, or does not contain at least
28818 as many segments as mentioned in the reply. Extra segments are
28819 kept at fixed offsets relative to the last relocated segment.
28822 @item qP @var{mode} @var{thread-id}
28823 @cindex thread information, remote request
28824 @cindex @samp{qP} packet
28825 Returns information on @var{thread-id}. Where: @var{mode} is a hex
28826 encoded 32 bit mode; @var{thread-id} is a thread ID
28827 (@pxref{thread-id syntax}).
28829 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
28832 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
28836 @cindex non-stop mode, remote request
28837 @cindex @samp{QNonStop} packet
28839 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
28840 @xref{Remote Non-Stop}, for more information.
28845 The request succeeded.
28848 An error occurred. @var{nn} are hex digits.
28851 An empty reply indicates that @samp{QNonStop} is not supported by
28855 This packet is not probed by default; the remote stub must request it,
28856 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28857 Use of this packet is controlled by the @code{set non-stop} command;
28858 @pxref{Non-Stop Mode}.
28860 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
28861 @cindex pass signals to inferior, remote request
28862 @cindex @samp{QPassSignals} packet
28863 @anchor{QPassSignals}
28864 Each listed @var{signal} should be passed directly to the inferior process.
28865 Signals are numbered identically to continue packets and stop replies
28866 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
28867 strictly greater than the previous item. These signals do not need to stop
28868 the inferior, or be reported to @value{GDBN}. All other signals should be
28869 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
28870 combine; any earlier @samp{QPassSignals} list is completely replaced by the
28871 new list. This packet improves performance when using @samp{handle
28872 @var{signal} nostop noprint pass}.
28877 The request succeeded.
28880 An error occurred. @var{nn} are hex digits.
28883 An empty reply indicates that @samp{QPassSignals} is not supported by
28887 Use of this packet is controlled by the @code{set remote pass-signals}
28888 command (@pxref{Remote Configuration, set remote pass-signals}).
28889 This packet is not probed by default; the remote stub must request it,
28890 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28892 @item qRcmd,@var{command}
28893 @cindex execute remote command, remote request
28894 @cindex @samp{qRcmd} packet
28895 @var{command} (hex encoded) is passed to the local interpreter for
28896 execution. Invalid commands should be reported using the output
28897 string. Before the final result packet, the target may also respond
28898 with a number of intermediate @samp{O@var{output}} console output
28899 packets. @emph{Implementors should note that providing access to a
28900 stubs's interpreter may have security implications}.
28905 A command response with no output.
28907 A command response with the hex encoded output string @var{OUTPUT}.
28909 Indicate a badly formed request.
28911 An empty reply indicates that @samp{qRcmd} is not recognized.
28914 (Note that the @code{qRcmd} packet's name is separated from the
28915 command by a @samp{,}, not a @samp{:}, contrary to the naming
28916 conventions above. Please don't use this packet as a model for new
28919 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
28920 @cindex searching memory, in remote debugging
28921 @cindex @samp{qSearch:memory} packet
28922 @anchor{qSearch memory}
28923 Search @var{length} bytes at @var{address} for @var{search-pattern}.
28924 @var{address} and @var{length} are encoded in hex.
28925 @var{search-pattern} is a sequence of bytes, hex encoded.
28930 The pattern was not found.
28932 The pattern was found at @var{address}.
28934 A badly formed request or an error was encountered while searching memory.
28936 An empty reply indicates that @samp{qSearch:memory} is not recognized.
28939 @item QStartNoAckMode
28940 @cindex @samp{QStartNoAckMode} packet
28941 @anchor{QStartNoAckMode}
28942 Request that the remote stub disable the normal @samp{+}/@samp{-}
28943 protocol acknowledgments (@pxref{Packet Acknowledgment}).
28948 The stub has switched to no-acknowledgment mode.
28949 @value{GDBN} acknowledges this reponse,
28950 but neither the stub nor @value{GDBN} shall send or expect further
28951 @samp{+}/@samp{-} acknowledgments in the current connection.
28953 An empty reply indicates that the stub does not support no-acknowledgment mode.
28956 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
28957 @cindex supported packets, remote query
28958 @cindex features of the remote protocol
28959 @cindex @samp{qSupported} packet
28960 @anchor{qSupported}
28961 Tell the remote stub about features supported by @value{GDBN}, and
28962 query the stub for features it supports. This packet allows
28963 @value{GDBN} and the remote stub to take advantage of each others'
28964 features. @samp{qSupported} also consolidates multiple feature probes
28965 at startup, to improve @value{GDBN} performance---a single larger
28966 packet performs better than multiple smaller probe packets on
28967 high-latency links. Some features may enable behavior which must not
28968 be on by default, e.g.@: because it would confuse older clients or
28969 stubs. Other features may describe packets which could be
28970 automatically probed for, but are not. These features must be
28971 reported before @value{GDBN} will use them. This ``default
28972 unsupported'' behavior is not appropriate for all packets, but it
28973 helps to keep the initial connection time under control with new
28974 versions of @value{GDBN} which support increasing numbers of packets.
28978 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
28979 The stub supports or does not support each returned @var{stubfeature},
28980 depending on the form of each @var{stubfeature} (see below for the
28983 An empty reply indicates that @samp{qSupported} is not recognized,
28984 or that no features needed to be reported to @value{GDBN}.
28987 The allowed forms for each feature (either a @var{gdbfeature} in the
28988 @samp{qSupported} packet, or a @var{stubfeature} in the response)
28992 @item @var{name}=@var{value}
28993 The remote protocol feature @var{name} is supported, and associated
28994 with the specified @var{value}. The format of @var{value} depends
28995 on the feature, but it must not include a semicolon.
28997 The remote protocol feature @var{name} is supported, and does not
28998 need an associated value.
29000 The remote protocol feature @var{name} is not supported.
29002 The remote protocol feature @var{name} may be supported, and
29003 @value{GDBN} should auto-detect support in some other way when it is
29004 needed. This form will not be used for @var{gdbfeature} notifications,
29005 but may be used for @var{stubfeature} responses.
29008 Whenever the stub receives a @samp{qSupported} request, the
29009 supplied set of @value{GDBN} features should override any previous
29010 request. This allows @value{GDBN} to put the stub in a known
29011 state, even if the stub had previously been communicating with
29012 a different version of @value{GDBN}.
29014 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
29019 This feature indicates whether @value{GDBN} supports multiprocess
29020 extensions to the remote protocol. @value{GDBN} does not use such
29021 extensions unless the stub also reports that it supports them by
29022 including @samp{multiprocess+} in its @samp{qSupported} reply.
29023 @xref{multiprocess extensions}, for details.
29026 Stubs should ignore any unknown values for
29027 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
29028 packet supports receiving packets of unlimited length (earlier
29029 versions of @value{GDBN} may reject overly long responses). Additional values
29030 for @var{gdbfeature} may be defined in the future to let the stub take
29031 advantage of new features in @value{GDBN}, e.g.@: incompatible
29032 improvements in the remote protocol---the @samp{multiprocess} feature is
29033 an example of such a feature. The stub's reply should be independent
29034 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
29035 describes all the features it supports, and then the stub replies with
29036 all the features it supports.
29038 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
29039 responses, as long as each response uses one of the standard forms.
29041 Some features are flags. A stub which supports a flag feature
29042 should respond with a @samp{+} form response. Other features
29043 require values, and the stub should respond with an @samp{=}
29046 Each feature has a default value, which @value{GDBN} will use if
29047 @samp{qSupported} is not available or if the feature is not mentioned
29048 in the @samp{qSupported} response. The default values are fixed; a
29049 stub is free to omit any feature responses that match the defaults.
29051 Not all features can be probed, but for those which can, the probing
29052 mechanism is useful: in some cases, a stub's internal
29053 architecture may not allow the protocol layer to know some information
29054 about the underlying target in advance. This is especially common in
29055 stubs which may be configured for multiple targets.
29057 These are the currently defined stub features and their properties:
29059 @multitable @columnfractions 0.35 0.2 0.12 0.2
29060 @c NOTE: The first row should be @headitem, but we do not yet require
29061 @c a new enough version of Texinfo (4.7) to use @headitem.
29063 @tab Value Required
29067 @item @samp{PacketSize}
29072 @item @samp{qXfer:auxv:read}
29077 @item @samp{qXfer:features:read}
29082 @item @samp{qXfer:libraries:read}
29087 @item @samp{qXfer:memory-map:read}
29092 @item @samp{qXfer:spu:read}
29097 @item @samp{qXfer:spu:write}
29102 @item @samp{qXfer:siginfo:read}
29107 @item @samp{qXfer:siginfo:write}
29112 @item @samp{QNonStop}
29117 @item @samp{QPassSignals}
29122 @item @samp{QStartNoAckMode}
29127 @item @samp{multiprocess}
29132 @item @samp{ConditionalTracepoints}
29137 @item @samp{ReverseContinue}
29142 @item @samp{ReverseStep}
29149 These are the currently defined stub features, in more detail:
29152 @cindex packet size, remote protocol
29153 @item PacketSize=@var{bytes}
29154 The remote stub can accept packets up to at least @var{bytes} in
29155 length. @value{GDBN} will send packets up to this size for bulk
29156 transfers, and will never send larger packets. This is a limit on the
29157 data characters in the packet, including the frame and checksum.
29158 There is no trailing NUL byte in a remote protocol packet; if the stub
29159 stores packets in a NUL-terminated format, it should allow an extra
29160 byte in its buffer for the NUL. If this stub feature is not supported,
29161 @value{GDBN} guesses based on the size of the @samp{g} packet response.
29163 @item qXfer:auxv:read
29164 The remote stub understands the @samp{qXfer:auxv:read} packet
29165 (@pxref{qXfer auxiliary vector read}).
29167 @item qXfer:features:read
29168 The remote stub understands the @samp{qXfer:features:read} packet
29169 (@pxref{qXfer target description read}).
29171 @item qXfer:libraries:read
29172 The remote stub understands the @samp{qXfer:libraries:read} packet
29173 (@pxref{qXfer library list read}).
29175 @item qXfer:memory-map:read
29176 The remote stub understands the @samp{qXfer:memory-map:read} packet
29177 (@pxref{qXfer memory map read}).
29179 @item qXfer:spu:read
29180 The remote stub understands the @samp{qXfer:spu:read} packet
29181 (@pxref{qXfer spu read}).
29183 @item qXfer:spu:write
29184 The remote stub understands the @samp{qXfer:spu:write} packet
29185 (@pxref{qXfer spu write}).
29187 @item qXfer:siginfo:read
29188 The remote stub understands the @samp{qXfer:siginfo:read} packet
29189 (@pxref{qXfer siginfo read}).
29191 @item qXfer:siginfo:write
29192 The remote stub understands the @samp{qXfer:siginfo:write} packet
29193 (@pxref{qXfer siginfo write}).
29196 The remote stub understands the @samp{QNonStop} packet
29197 (@pxref{QNonStop}).
29200 The remote stub understands the @samp{QPassSignals} packet
29201 (@pxref{QPassSignals}).
29203 @item QStartNoAckMode
29204 The remote stub understands the @samp{QStartNoAckMode} packet and
29205 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
29208 @anchor{multiprocess extensions}
29209 @cindex multiprocess extensions, in remote protocol
29210 The remote stub understands the multiprocess extensions to the remote
29211 protocol syntax. The multiprocess extensions affect the syntax of
29212 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
29213 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
29214 replies. Note that reporting this feature indicates support for the
29215 syntactic extensions only, not that the stub necessarily supports
29216 debugging of more than one process at a time. The stub must not use
29217 multiprocess extensions in packet replies unless @value{GDBN} has also
29218 indicated it supports them in its @samp{qSupported} request.
29220 @item qXfer:osdata:read
29221 The remote stub understands the @samp{qXfer:osdata:read} packet
29222 ((@pxref{qXfer osdata read}).
29224 @item ConditionalTracepoints
29225 The remote stub accepts and implements conditional expressions defined
29226 for tracepoints (@pxref{Tracepoint Conditions}).
29228 @item ReverseContinue
29229 The remote stub accepts and implements the reverse continue packet
29233 The remote stub accepts and implements the reverse step packet
29239 @cindex symbol lookup, remote request
29240 @cindex @samp{qSymbol} packet
29241 Notify the target that @value{GDBN} is prepared to serve symbol lookup
29242 requests. Accept requests from the target for the values of symbols.
29247 The target does not need to look up any (more) symbols.
29248 @item qSymbol:@var{sym_name}
29249 The target requests the value of symbol @var{sym_name} (hex encoded).
29250 @value{GDBN} may provide the value by using the
29251 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
29255 @item qSymbol:@var{sym_value}:@var{sym_name}
29256 Set the value of @var{sym_name} to @var{sym_value}.
29258 @var{sym_name} (hex encoded) is the name of a symbol whose value the
29259 target has previously requested.
29261 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
29262 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
29268 The target does not need to look up any (more) symbols.
29269 @item qSymbol:@var{sym_name}
29270 The target requests the value of a new symbol @var{sym_name} (hex
29271 encoded). @value{GDBN} will continue to supply the values of symbols
29272 (if available), until the target ceases to request them.
29277 @xref{Tracepoint Packets}.
29279 @item qThreadExtraInfo,@var{thread-id}
29280 @cindex thread attributes info, remote request
29281 @cindex @samp{qThreadExtraInfo} packet
29282 Obtain a printable string description of a thread's attributes from
29283 the target OS. @var{thread-id} is a thread ID;
29284 see @ref{thread-id syntax}. This
29285 string may contain anything that the target OS thinks is interesting
29286 for @value{GDBN} to tell the user about the thread. The string is
29287 displayed in @value{GDBN}'s @code{info threads} display. Some
29288 examples of possible thread extra info strings are @samp{Runnable}, or
29289 @samp{Blocked on Mutex}.
29293 @item @var{XX}@dots{}
29294 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
29295 comprising the printable string containing the extra information about
29296 the thread's attributes.
29299 (Note that the @code{qThreadExtraInfo} packet's name is separated from
29300 the command by a @samp{,}, not a @samp{:}, contrary to the naming
29301 conventions above. Please don't use this packet as a model for new
29309 @xref{Tracepoint Packets}.
29311 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
29312 @cindex read special object, remote request
29313 @cindex @samp{qXfer} packet
29314 @anchor{qXfer read}
29315 Read uninterpreted bytes from the target's special data area
29316 identified by the keyword @var{object}. Request @var{length} bytes
29317 starting at @var{offset} bytes into the data. The content and
29318 encoding of @var{annex} is specific to @var{object}; it can supply
29319 additional details about what data to access.
29321 Here are the specific requests of this form defined so far. All
29322 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
29323 formats, listed below.
29326 @item qXfer:auxv:read::@var{offset},@var{length}
29327 @anchor{qXfer auxiliary vector read}
29328 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
29329 auxiliary vector}. Note @var{annex} must be empty.
29331 This packet is not probed by default; the remote stub must request it,
29332 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29334 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
29335 @anchor{qXfer target description read}
29336 Access the @dfn{target description}. @xref{Target Descriptions}. The
29337 annex specifies which XML document to access. The main description is
29338 always loaded from the @samp{target.xml} annex.
29340 This packet is not probed by default; the remote stub must request it,
29341 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29343 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
29344 @anchor{qXfer library list read}
29345 Access the target's list of loaded libraries. @xref{Library List Format}.
29346 The annex part of the generic @samp{qXfer} packet must be empty
29347 (@pxref{qXfer read}).
29349 Targets which maintain a list of libraries in the program's memory do
29350 not need to implement this packet; it is designed for platforms where
29351 the operating system manages the list of loaded libraries.
29353 This packet is not probed by default; the remote stub must request it,
29354 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29356 @item qXfer:memory-map:read::@var{offset},@var{length}
29357 @anchor{qXfer memory map read}
29358 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
29359 annex part of the generic @samp{qXfer} packet must be empty
29360 (@pxref{qXfer read}).
29362 This packet is not probed by default; the remote stub must request it,
29363 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29365 @item qXfer:siginfo:read::@var{offset},@var{length}
29366 @anchor{qXfer siginfo read}
29367 Read contents of the extra signal information on the target
29368 system. The annex part of the generic @samp{qXfer} packet must be
29369 empty (@pxref{qXfer read}).
29371 This packet is not probed by default; the remote stub must request it,
29372 by supplying an appropriate @samp{qSupported} response
29373 (@pxref{qSupported}).
29375 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
29376 @anchor{qXfer spu read}
29377 Read contents of an @code{spufs} file on the target system. The
29378 annex specifies which file to read; it must be of the form
29379 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
29380 in the target process, and @var{name} identifes the @code{spufs} file
29381 in that context to be accessed.
29383 This packet is not probed by default; the remote stub must request it,
29384 by supplying an appropriate @samp{qSupported} response
29385 (@pxref{qSupported}).
29387 @item qXfer:osdata:read::@var{offset},@var{length}
29388 @anchor{qXfer osdata read}
29389 Access the target's @dfn{operating system information}.
29390 @xref{Operating System Information}.
29397 Data @var{data} (@pxref{Binary Data}) has been read from the
29398 target. There may be more data at a higher address (although
29399 it is permitted to return @samp{m} even for the last valid
29400 block of data, as long as at least one byte of data was read).
29401 @var{data} may have fewer bytes than the @var{length} in the
29405 Data @var{data} (@pxref{Binary Data}) has been read from the target.
29406 There is no more data to be read. @var{data} may have fewer bytes
29407 than the @var{length} in the request.
29410 The @var{offset} in the request is at the end of the data.
29411 There is no more data to be read.
29414 The request was malformed, or @var{annex} was invalid.
29417 The offset was invalid, or there was an error encountered reading the data.
29418 @var{nn} is a hex-encoded @code{errno} value.
29421 An empty reply indicates the @var{object} string was not recognized by
29422 the stub, or that the object does not support reading.
29425 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
29426 @cindex write data into object, remote request
29427 @anchor{qXfer write}
29428 Write uninterpreted bytes into the target's special data area
29429 identified by the keyword @var{object}, starting at @var{offset} bytes
29430 into the data. @var{data}@dots{} is the binary-encoded data
29431 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
29432 is specific to @var{object}; it can supply additional details about what data
29435 Here are the specific requests of this form defined so far. All
29436 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
29437 formats, listed below.
29440 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
29441 @anchor{qXfer siginfo write}
29442 Write @var{data} to the extra signal information on the target system.
29443 The annex part of the generic @samp{qXfer} packet must be
29444 empty (@pxref{qXfer write}).
29446 This packet is not probed by default; the remote stub must request it,
29447 by supplying an appropriate @samp{qSupported} response
29448 (@pxref{qSupported}).
29450 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
29451 @anchor{qXfer spu write}
29452 Write @var{data} to an @code{spufs} file on the target system. The
29453 annex specifies which file to write; it must be of the form
29454 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
29455 in the target process, and @var{name} identifes the @code{spufs} file
29456 in that context to be accessed.
29458 This packet is not probed by default; the remote stub must request it,
29459 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29465 @var{nn} (hex encoded) is the number of bytes written.
29466 This may be fewer bytes than supplied in the request.
29469 The request was malformed, or @var{annex} was invalid.
29472 The offset was invalid, or there was an error encountered writing the data.
29473 @var{nn} is a hex-encoded @code{errno} value.
29476 An empty reply indicates the @var{object} string was not
29477 recognized by the stub, or that the object does not support writing.
29480 @item qXfer:@var{object}:@var{operation}:@dots{}
29481 Requests of this form may be added in the future. When a stub does
29482 not recognize the @var{object} keyword, or its support for
29483 @var{object} does not recognize the @var{operation} keyword, the stub
29484 must respond with an empty packet.
29486 @item qAttached:@var{pid}
29487 @cindex query attached, remote request
29488 @cindex @samp{qAttached} packet
29489 Return an indication of whether the remote server attached to an
29490 existing process or created a new process. When the multiprocess
29491 protocol extensions are supported (@pxref{multiprocess extensions}),
29492 @var{pid} is an integer in hexadecimal format identifying the target
29493 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
29494 the query packet will be simplified as @samp{qAttached}.
29496 This query is used, for example, to know whether the remote process
29497 should be detached or killed when a @value{GDBN} session is ended with
29498 the @code{quit} command.
29503 The remote server attached to an existing process.
29505 The remote server created a new process.
29507 A badly formed request or an error was encountered.
29512 @node Register Packet Format
29513 @section Register Packet Format
29515 The following @code{g}/@code{G} packets have previously been defined.
29516 In the below, some thirty-two bit registers are transferred as
29517 sixty-four bits. Those registers should be zero/sign extended (which?)
29518 to fill the space allocated. Register bytes are transferred in target
29519 byte order. The two nibbles within a register byte are transferred
29520 most-significant - least-significant.
29526 All registers are transferred as thirty-two bit quantities in the order:
29527 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
29528 registers; fsr; fir; fp.
29532 All registers are transferred as sixty-four bit quantities (including
29533 thirty-two bit registers such as @code{sr}). The ordering is the same
29538 @node Tracepoint Packets
29539 @section Tracepoint Packets
29540 @cindex tracepoint packets
29541 @cindex packets, tracepoint
29543 Here we describe the packets @value{GDBN} uses to implement
29544 tracepoints (@pxref{Tracepoints}).
29548 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:X@var{len},@var{bytes}]@r{[}-@r{]}
29549 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
29550 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
29551 the tracepoint is disabled. @var{step} is the tracepoint's step
29552 count, and @var{pass} is its pass count. If an @samp{X} is present,
29553 it introduces a tracepoint condition, which consists of a hexadecimal
29554 length, followed by a comma and hex-encoded bytes, in a manner similar
29555 to action encodings as described below. If the trailing @samp{-} is
29556 present, further @samp{QTDP} packets will follow to specify this
29557 tracepoint's actions.
29562 The packet was understood and carried out.
29564 The packet was not recognized.
29567 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
29568 Define actions to be taken when a tracepoint is hit. @var{n} and
29569 @var{addr} must be the same as in the initial @samp{QTDP} packet for
29570 this tracepoint. This packet may only be sent immediately after
29571 another @samp{QTDP} packet that ended with a @samp{-}. If the
29572 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
29573 specifying more actions for this tracepoint.
29575 In the series of action packets for a given tracepoint, at most one
29576 can have an @samp{S} before its first @var{action}. If such a packet
29577 is sent, it and the following packets define ``while-stepping''
29578 actions. Any prior packets define ordinary actions --- that is, those
29579 taken when the tracepoint is first hit. If no action packet has an
29580 @samp{S}, then all the packets in the series specify ordinary
29581 tracepoint actions.
29583 The @samp{@var{action}@dots{}} portion of the packet is a series of
29584 actions, concatenated without separators. Each action has one of the
29590 Collect the registers whose bits are set in @var{mask}. @var{mask} is
29591 a hexadecimal number whose @var{i}'th bit is set if register number
29592 @var{i} should be collected. (The least significant bit is numbered
29593 zero.) Note that @var{mask} may be any number of digits long; it may
29594 not fit in a 32-bit word.
29596 @item M @var{basereg},@var{offset},@var{len}
29597 Collect @var{len} bytes of memory starting at the address in register
29598 number @var{basereg}, plus @var{offset}. If @var{basereg} is
29599 @samp{-1}, then the range has a fixed address: @var{offset} is the
29600 address of the lowest byte to collect. The @var{basereg},
29601 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
29602 values (the @samp{-1} value for @var{basereg} is a special case).
29604 @item X @var{len},@var{expr}
29605 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
29606 it directs. @var{expr} is an agent expression, as described in
29607 @ref{Agent Expressions}. Each byte of the expression is encoded as a
29608 two-digit hex number in the packet; @var{len} is the number of bytes
29609 in the expression (and thus one-half the number of hex digits in the
29614 Any number of actions may be packed together in a single @samp{QTDP}
29615 packet, as long as the packet does not exceed the maximum packet
29616 length (400 bytes, for many stubs). There may be only one @samp{R}
29617 action per tracepoint, and it must precede any @samp{M} or @samp{X}
29618 actions. Any registers referred to by @samp{M} and @samp{X} actions
29619 must be collected by a preceding @samp{R} action. (The
29620 ``while-stepping'' actions are treated as if they were attached to a
29621 separate tracepoint, as far as these restrictions are concerned.)
29626 The packet was understood and carried out.
29628 The packet was not recognized.
29631 @item QTFrame:@var{n}
29632 Select the @var{n}'th tracepoint frame from the buffer, and use the
29633 register and memory contents recorded there to answer subsequent
29634 request packets from @value{GDBN}.
29636 A successful reply from the stub indicates that the stub has found the
29637 requested frame. The response is a series of parts, concatenated
29638 without separators, describing the frame we selected. Each part has
29639 one of the following forms:
29643 The selected frame is number @var{n} in the trace frame buffer;
29644 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
29645 was no frame matching the criteria in the request packet.
29648 The selected trace frame records a hit of tracepoint number @var{t};
29649 @var{t} is a hexadecimal number.
29653 @item QTFrame:pc:@var{addr}
29654 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29655 currently selected frame whose PC is @var{addr};
29656 @var{addr} is a hexadecimal number.
29658 @item QTFrame:tdp:@var{t}
29659 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29660 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
29661 is a hexadecimal number.
29663 @item QTFrame:range:@var{start}:@var{end}
29664 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29665 currently selected frame whose PC is between @var{start} (inclusive)
29666 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
29669 @item QTFrame:outside:@var{start}:@var{end}
29670 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
29671 frame @emph{outside} the given range of addresses.
29674 Begin the tracepoint experiment. Begin collecting data from tracepoint
29675 hits in the trace frame buffer.
29678 End the tracepoint experiment. Stop collecting trace frames.
29681 Clear the table of tracepoints, and empty the trace frame buffer.
29683 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
29684 Establish the given ranges of memory as ``transparent''. The stub
29685 will answer requests for these ranges from memory's current contents,
29686 if they were not collected as part of the tracepoint hit.
29688 @value{GDBN} uses this to mark read-only regions of memory, like those
29689 containing program code. Since these areas never change, they should
29690 still have the same contents they did when the tracepoint was hit, so
29691 there's no reason for the stub to refuse to provide their contents.
29694 Ask the stub if there is a trace experiment running right now.
29699 There is no trace experiment running.
29701 There is a trace experiment running.
29707 @node Host I/O Packets
29708 @section Host I/O Packets
29709 @cindex Host I/O, remote protocol
29710 @cindex file transfer, remote protocol
29712 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
29713 operations on the far side of a remote link. For example, Host I/O is
29714 used to upload and download files to a remote target with its own
29715 filesystem. Host I/O uses the same constant values and data structure
29716 layout as the target-initiated File-I/O protocol. However, the
29717 Host I/O packets are structured differently. The target-initiated
29718 protocol relies on target memory to store parameters and buffers.
29719 Host I/O requests are initiated by @value{GDBN}, and the
29720 target's memory is not involved. @xref{File-I/O Remote Protocol
29721 Extension}, for more details on the target-initiated protocol.
29723 The Host I/O request packets all encode a single operation along with
29724 its arguments. They have this format:
29728 @item vFile:@var{operation}: @var{parameter}@dots{}
29729 @var{operation} is the name of the particular request; the target
29730 should compare the entire packet name up to the second colon when checking
29731 for a supported operation. The format of @var{parameter} depends on
29732 the operation. Numbers are always passed in hexadecimal. Negative
29733 numbers have an explicit minus sign (i.e.@: two's complement is not
29734 used). Strings (e.g.@: filenames) are encoded as a series of
29735 hexadecimal bytes. The last argument to a system call may be a
29736 buffer of escaped binary data (@pxref{Binary Data}).
29740 The valid responses to Host I/O packets are:
29744 @item F @var{result} [, @var{errno}] [; @var{attachment}]
29745 @var{result} is the integer value returned by this operation, usually
29746 non-negative for success and -1 for errors. If an error has occured,
29747 @var{errno} will be included in the result. @var{errno} will have a
29748 value defined by the File-I/O protocol (@pxref{Errno Values}). For
29749 operations which return data, @var{attachment} supplies the data as a
29750 binary buffer. Binary buffers in response packets are escaped in the
29751 normal way (@pxref{Binary Data}). See the individual packet
29752 documentation for the interpretation of @var{result} and
29756 An empty response indicates that this operation is not recognized.
29760 These are the supported Host I/O operations:
29763 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
29764 Open a file at @var{pathname} and return a file descriptor for it, or
29765 return -1 if an error occurs. @var{pathname} is a string,
29766 @var{flags} is an integer indicating a mask of open flags
29767 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
29768 of mode bits to use if the file is created (@pxref{mode_t Values}).
29769 @xref{open}, for details of the open flags and mode values.
29771 @item vFile:close: @var{fd}
29772 Close the open file corresponding to @var{fd} and return 0, or
29773 -1 if an error occurs.
29775 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
29776 Read data from the open file corresponding to @var{fd}. Up to
29777 @var{count} bytes will be read from the file, starting at @var{offset}
29778 relative to the start of the file. The target may read fewer bytes;
29779 common reasons include packet size limits and an end-of-file
29780 condition. The number of bytes read is returned. Zero should only be
29781 returned for a successful read at the end of the file, or if
29782 @var{count} was zero.
29784 The data read should be returned as a binary attachment on success.
29785 If zero bytes were read, the response should include an empty binary
29786 attachment (i.e.@: a trailing semicolon). The return value is the
29787 number of target bytes read; the binary attachment may be longer if
29788 some characters were escaped.
29790 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
29791 Write @var{data} (a binary buffer) to the open file corresponding
29792 to @var{fd}. Start the write at @var{offset} from the start of the
29793 file. Unlike many @code{write} system calls, there is no
29794 separate @var{count} argument; the length of @var{data} in the
29795 packet is used. @samp{vFile:write} returns the number of bytes written,
29796 which may be shorter than the length of @var{data}, or -1 if an
29799 @item vFile:unlink: @var{pathname}
29800 Delete the file at @var{pathname} on the target. Return 0,
29801 or -1 if an error occurs. @var{pathname} is a string.
29806 @section Interrupts
29807 @cindex interrupts (remote protocol)
29809 When a program on the remote target is running, @value{GDBN} may
29810 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
29811 control of which is specified via @value{GDBN}'s @samp{remotebreak}
29812 setting (@pxref{set remotebreak}).
29814 The precise meaning of @code{BREAK} is defined by the transport
29815 mechanism and may, in fact, be undefined. @value{GDBN} does not
29816 currently define a @code{BREAK} mechanism for any of the network
29817 interfaces except for TCP, in which case @value{GDBN} sends the
29818 @code{telnet} BREAK sequence.
29820 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
29821 transport mechanisms. It is represented by sending the single byte
29822 @code{0x03} without any of the usual packet overhead described in
29823 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
29824 transmitted as part of a packet, it is considered to be packet data
29825 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
29826 (@pxref{X packet}), used for binary downloads, may include an unescaped
29827 @code{0x03} as part of its packet.
29829 Stubs are not required to recognize these interrupt mechanisms and the
29830 precise meaning associated with receipt of the interrupt is
29831 implementation defined. If the target supports debugging of multiple
29832 threads and/or processes, it should attempt to interrupt all
29833 currently-executing threads and processes.
29834 If the stub is successful at interrupting the
29835 running program, it should send one of the stop
29836 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
29837 of successfully stopping the program in all-stop mode, and a stop reply
29838 for each stopped thread in non-stop mode.
29839 Interrupts received while the
29840 program is stopped are discarded.
29842 @node Notification Packets
29843 @section Notification Packets
29844 @cindex notification packets
29845 @cindex packets, notification
29847 The @value{GDBN} remote serial protocol includes @dfn{notifications},
29848 packets that require no acknowledgment. Both the GDB and the stub
29849 may send notifications (although the only notifications defined at
29850 present are sent by the stub). Notifications carry information
29851 without incurring the round-trip latency of an acknowledgment, and so
29852 are useful for low-impact communications where occasional packet loss
29855 A notification packet has the form @samp{% @var{data} #
29856 @var{checksum}}, where @var{data} is the content of the notification,
29857 and @var{checksum} is a checksum of @var{data}, computed and formatted
29858 as for ordinary @value{GDBN} packets. A notification's @var{data}
29859 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
29860 receiving a notification, the recipient sends no @samp{+} or @samp{-}
29861 to acknowledge the notification's receipt or to report its corruption.
29863 Every notification's @var{data} begins with a name, which contains no
29864 colon characters, followed by a colon character.
29866 Recipients should silently ignore corrupted notifications and
29867 notifications they do not understand. Recipients should restart
29868 timeout periods on receipt of a well-formed notification, whether or
29869 not they understand it.
29871 Senders should only send the notifications described here when this
29872 protocol description specifies that they are permitted. In the
29873 future, we may extend the protocol to permit existing notifications in
29874 new contexts; this rule helps older senders avoid confusing newer
29877 (Older versions of @value{GDBN} ignore bytes received until they see
29878 the @samp{$} byte that begins an ordinary packet, so new stubs may
29879 transmit notifications without fear of confusing older clients. There
29880 are no notifications defined for @value{GDBN} to send at the moment, but we
29881 assume that most older stubs would ignore them, as well.)
29883 The following notification packets from the stub to @value{GDBN} are
29887 @item Stop: @var{reply}
29888 Report an asynchronous stop event in non-stop mode.
29889 The @var{reply} has the form of a stop reply, as
29890 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
29891 for information on how these notifications are acknowledged by
29895 @node Remote Non-Stop
29896 @section Remote Protocol Support for Non-Stop Mode
29898 @value{GDBN}'s remote protocol supports non-stop debugging of
29899 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
29900 supports non-stop mode, it should report that to @value{GDBN} by including
29901 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
29903 @value{GDBN} typically sends a @samp{QNonStop} packet only when
29904 establishing a new connection with the stub. Entering non-stop mode
29905 does not alter the state of any currently-running threads, but targets
29906 must stop all threads in any already-attached processes when entering
29907 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
29908 probe the target state after a mode change.
29910 In non-stop mode, when an attached process encounters an event that
29911 would otherwise be reported with a stop reply, it uses the
29912 asynchronous notification mechanism (@pxref{Notification Packets}) to
29913 inform @value{GDBN}. In contrast to all-stop mode, where all threads
29914 in all processes are stopped when a stop reply is sent, in non-stop
29915 mode only the thread reporting the stop event is stopped. That is,
29916 when reporting a @samp{S} or @samp{T} response to indicate completion
29917 of a step operation, hitting a breakpoint, or a fault, only the
29918 affected thread is stopped; any other still-running threads continue
29919 to run. When reporting a @samp{W} or @samp{X} response, all running
29920 threads belonging to other attached processes continue to run.
29922 Only one stop reply notification at a time may be pending; if
29923 additional stop events occur before @value{GDBN} has acknowledged the
29924 previous notification, they must be queued by the stub for later
29925 synchronous transmission in response to @samp{vStopped} packets from
29926 @value{GDBN}. Because the notification mechanism is unreliable,
29927 the stub is permitted to resend a stop reply notification
29928 if it believes @value{GDBN} may not have received it. @value{GDBN}
29929 ignores additional stop reply notifications received before it has
29930 finished processing a previous notification and the stub has completed
29931 sending any queued stop events.
29933 Otherwise, @value{GDBN} must be prepared to receive a stop reply
29934 notification at any time. Specifically, they may appear when
29935 @value{GDBN} is not otherwise reading input from the stub, or when
29936 @value{GDBN} is expecting to read a normal synchronous response or a
29937 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
29938 Notification packets are distinct from any other communication from
29939 the stub so there is no ambiguity.
29941 After receiving a stop reply notification, @value{GDBN} shall
29942 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
29943 as a regular, synchronous request to the stub. Such acknowledgment
29944 is not required to happen immediately, as @value{GDBN} is permitted to
29945 send other, unrelated packets to the stub first, which the stub should
29948 Upon receiving a @samp{vStopped} packet, if the stub has other queued
29949 stop events to report to @value{GDBN}, it shall respond by sending a
29950 normal stop reply response. @value{GDBN} shall then send another
29951 @samp{vStopped} packet to solicit further responses; again, it is
29952 permitted to send other, unrelated packets as well which the stub
29953 should process normally.
29955 If the stub receives a @samp{vStopped} packet and there are no
29956 additional stop events to report, the stub shall return an @samp{OK}
29957 response. At this point, if further stop events occur, the stub shall
29958 send a new stop reply notification, @value{GDBN} shall accept the
29959 notification, and the process shall be repeated.
29961 In non-stop mode, the target shall respond to the @samp{?} packet as
29962 follows. First, any incomplete stop reply notification/@samp{vStopped}
29963 sequence in progress is abandoned. The target must begin a new
29964 sequence reporting stop events for all stopped threads, whether or not
29965 it has previously reported those events to @value{GDBN}. The first
29966 stop reply is sent as a synchronous reply to the @samp{?} packet, and
29967 subsequent stop replies are sent as responses to @samp{vStopped} packets
29968 using the mechanism described above. The target must not send
29969 asynchronous stop reply notifications until the sequence is complete.
29970 If all threads are running when the target receives the @samp{?} packet,
29971 or if the target is not attached to any process, it shall respond
29974 @node Packet Acknowledgment
29975 @section Packet Acknowledgment
29977 @cindex acknowledgment, for @value{GDBN} remote
29978 @cindex packet acknowledgment, for @value{GDBN} remote
29979 By default, when either the host or the target machine receives a packet,
29980 the first response expected is an acknowledgment: either @samp{+} (to indicate
29981 the package was received correctly) or @samp{-} (to request retransmission).
29982 This mechanism allows the @value{GDBN} remote protocol to operate over
29983 unreliable transport mechanisms, such as a serial line.
29985 In cases where the transport mechanism is itself reliable (such as a pipe or
29986 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
29987 It may be desirable to disable them in that case to reduce communication
29988 overhead, or for other reasons. This can be accomplished by means of the
29989 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
29991 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
29992 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
29993 and response format still includes the normal checksum, as described in
29994 @ref{Overview}, but the checksum may be ignored by the receiver.
29996 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
29997 no-acknowledgment mode, it should report that to @value{GDBN}
29998 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
29999 @pxref{qSupported}.
30000 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
30001 disabled via the @code{set remote noack-packet off} command
30002 (@pxref{Remote Configuration}),
30003 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
30004 Only then may the stub actually turn off packet acknowledgments.
30005 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
30006 response, which can be safely ignored by the stub.
30008 Note that @code{set remote noack-packet} command only affects negotiation
30009 between @value{GDBN} and the stub when subsequent connections are made;
30010 it does not affect the protocol acknowledgment state for any current
30012 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
30013 new connection is established,
30014 there is also no protocol request to re-enable the acknowledgments
30015 for the current connection, once disabled.
30020 Example sequence of a target being re-started. Notice how the restart
30021 does not get any direct output:
30026 @emph{target restarts}
30029 <- @code{T001:1234123412341234}
30033 Example sequence of a target being stepped by a single instruction:
30036 -> @code{G1445@dots{}}
30041 <- @code{T001:1234123412341234}
30045 <- @code{1455@dots{}}
30049 @node File-I/O Remote Protocol Extension
30050 @section File-I/O Remote Protocol Extension
30051 @cindex File-I/O remote protocol extension
30054 * File-I/O Overview::
30055 * Protocol Basics::
30056 * The F Request Packet::
30057 * The F Reply Packet::
30058 * The Ctrl-C Message::
30060 * List of Supported Calls::
30061 * Protocol-specific Representation of Datatypes::
30063 * File-I/O Examples::
30066 @node File-I/O Overview
30067 @subsection File-I/O Overview
30068 @cindex file-i/o overview
30070 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
30071 target to use the host's file system and console I/O to perform various
30072 system calls. System calls on the target system are translated into a
30073 remote protocol packet to the host system, which then performs the needed
30074 actions and returns a response packet to the target system.
30075 This simulates file system operations even on targets that lack file systems.
30077 The protocol is defined to be independent of both the host and target systems.
30078 It uses its own internal representation of datatypes and values. Both
30079 @value{GDBN} and the target's @value{GDBN} stub are responsible for
30080 translating the system-dependent value representations into the internal
30081 protocol representations when data is transmitted.
30083 The communication is synchronous. A system call is possible only when
30084 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
30085 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
30086 the target is stopped to allow deterministic access to the target's
30087 memory. Therefore File-I/O is not interruptible by target signals. On
30088 the other hand, it is possible to interrupt File-I/O by a user interrupt
30089 (@samp{Ctrl-C}) within @value{GDBN}.
30091 The target's request to perform a host system call does not finish
30092 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
30093 after finishing the system call, the target returns to continuing the
30094 previous activity (continue, step). No additional continue or step
30095 request from @value{GDBN} is required.
30098 (@value{GDBP}) continue
30099 <- target requests 'system call X'
30100 target is stopped, @value{GDBN} executes system call
30101 -> @value{GDBN} returns result
30102 ... target continues, @value{GDBN} returns to wait for the target
30103 <- target hits breakpoint and sends a Txx packet
30106 The protocol only supports I/O on the console and to regular files on
30107 the host file system. Character or block special devices, pipes,
30108 named pipes, sockets or any other communication method on the host
30109 system are not supported by this protocol.
30111 File I/O is not supported in non-stop mode.
30113 @node Protocol Basics
30114 @subsection Protocol Basics
30115 @cindex protocol basics, file-i/o
30117 The File-I/O protocol uses the @code{F} packet as the request as well
30118 as reply packet. Since a File-I/O system call can only occur when
30119 @value{GDBN} is waiting for a response from the continuing or stepping target,
30120 the File-I/O request is a reply that @value{GDBN} has to expect as a result
30121 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
30122 This @code{F} packet contains all information needed to allow @value{GDBN}
30123 to call the appropriate host system call:
30127 A unique identifier for the requested system call.
30130 All parameters to the system call. Pointers are given as addresses
30131 in the target memory address space. Pointers to strings are given as
30132 pointer/length pair. Numerical values are given as they are.
30133 Numerical control flags are given in a protocol-specific representation.
30137 At this point, @value{GDBN} has to perform the following actions.
30141 If the parameters include pointer values to data needed as input to a
30142 system call, @value{GDBN} requests this data from the target with a
30143 standard @code{m} packet request. This additional communication has to be
30144 expected by the target implementation and is handled as any other @code{m}
30148 @value{GDBN} translates all value from protocol representation to host
30149 representation as needed. Datatypes are coerced into the host types.
30152 @value{GDBN} calls the system call.
30155 It then coerces datatypes back to protocol representation.
30158 If the system call is expected to return data in buffer space specified
30159 by pointer parameters to the call, the data is transmitted to the
30160 target using a @code{M} or @code{X} packet. This packet has to be expected
30161 by the target implementation and is handled as any other @code{M} or @code{X}
30166 Eventually @value{GDBN} replies with another @code{F} packet which contains all
30167 necessary information for the target to continue. This at least contains
30174 @code{errno}, if has been changed by the system call.
30181 After having done the needed type and value coercion, the target continues
30182 the latest continue or step action.
30184 @node The F Request Packet
30185 @subsection The @code{F} Request Packet
30186 @cindex file-i/o request packet
30187 @cindex @code{F} request packet
30189 The @code{F} request packet has the following format:
30192 @item F@var{call-id},@var{parameter@dots{}}
30194 @var{call-id} is the identifier to indicate the host system call to be called.
30195 This is just the name of the function.
30197 @var{parameter@dots{}} are the parameters to the system call.
30198 Parameters are hexadecimal integer values, either the actual values in case
30199 of scalar datatypes, pointers to target buffer space in case of compound
30200 datatypes and unspecified memory areas, or pointer/length pairs in case
30201 of string parameters. These are appended to the @var{call-id} as a
30202 comma-delimited list. All values are transmitted in ASCII
30203 string representation, pointer/length pairs separated by a slash.
30209 @node The F Reply Packet
30210 @subsection The @code{F} Reply Packet
30211 @cindex file-i/o reply packet
30212 @cindex @code{F} reply packet
30214 The @code{F} reply packet has the following format:
30218 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
30220 @var{retcode} is the return code of the system call as hexadecimal value.
30222 @var{errno} is the @code{errno} set by the call, in protocol-specific
30224 This parameter can be omitted if the call was successful.
30226 @var{Ctrl-C flag} is only sent if the user requested a break. In this
30227 case, @var{errno} must be sent as well, even if the call was successful.
30228 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
30235 or, if the call was interrupted before the host call has been performed:
30242 assuming 4 is the protocol-specific representation of @code{EINTR}.
30247 @node The Ctrl-C Message
30248 @subsection The @samp{Ctrl-C} Message
30249 @cindex ctrl-c message, in file-i/o protocol
30251 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
30252 reply packet (@pxref{The F Reply Packet}),
30253 the target should behave as if it had
30254 gotten a break message. The meaning for the target is ``system call
30255 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
30256 (as with a break message) and return to @value{GDBN} with a @code{T02}
30259 It's important for the target to know in which
30260 state the system call was interrupted. There are two possible cases:
30264 The system call hasn't been performed on the host yet.
30267 The system call on the host has been finished.
30271 These two states can be distinguished by the target by the value of the
30272 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
30273 call hasn't been performed. This is equivalent to the @code{EINTR} handling
30274 on POSIX systems. In any other case, the target may presume that the
30275 system call has been finished --- successfully or not --- and should behave
30276 as if the break message arrived right after the system call.
30278 @value{GDBN} must behave reliably. If the system call has not been called
30279 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
30280 @code{errno} in the packet. If the system call on the host has been finished
30281 before the user requests a break, the full action must be finished by
30282 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
30283 The @code{F} packet may only be sent when either nothing has happened
30284 or the full action has been completed.
30287 @subsection Console I/O
30288 @cindex console i/o as part of file-i/o
30290 By default and if not explicitly closed by the target system, the file
30291 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
30292 on the @value{GDBN} console is handled as any other file output operation
30293 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
30294 by @value{GDBN} so that after the target read request from file descriptor
30295 0 all following typing is buffered until either one of the following
30300 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
30302 system call is treated as finished.
30305 The user presses @key{RET}. This is treated as end of input with a trailing
30309 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
30310 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
30314 If the user has typed more characters than fit in the buffer given to
30315 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
30316 either another @code{read(0, @dots{})} is requested by the target, or debugging
30317 is stopped at the user's request.
30320 @node List of Supported Calls
30321 @subsection List of Supported Calls
30322 @cindex list of supported file-i/o calls
30339 @unnumberedsubsubsec open
30340 @cindex open, file-i/o system call
30345 int open(const char *pathname, int flags);
30346 int open(const char *pathname, int flags, mode_t mode);
30350 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
30353 @var{flags} is the bitwise @code{OR} of the following values:
30357 If the file does not exist it will be created. The host
30358 rules apply as far as file ownership and time stamps
30362 When used with @code{O_CREAT}, if the file already exists it is
30363 an error and open() fails.
30366 If the file already exists and the open mode allows
30367 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
30368 truncated to zero length.
30371 The file is opened in append mode.
30374 The file is opened for reading only.
30377 The file is opened for writing only.
30380 The file is opened for reading and writing.
30384 Other bits are silently ignored.
30388 @var{mode} is the bitwise @code{OR} of the following values:
30392 User has read permission.
30395 User has write permission.
30398 Group has read permission.
30401 Group has write permission.
30404 Others have read permission.
30407 Others have write permission.
30411 Other bits are silently ignored.
30414 @item Return value:
30415 @code{open} returns the new file descriptor or -1 if an error
30422 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
30425 @var{pathname} refers to a directory.
30428 The requested access is not allowed.
30431 @var{pathname} was too long.
30434 A directory component in @var{pathname} does not exist.
30437 @var{pathname} refers to a device, pipe, named pipe or socket.
30440 @var{pathname} refers to a file on a read-only filesystem and
30441 write access was requested.
30444 @var{pathname} is an invalid pointer value.
30447 No space on device to create the file.
30450 The process already has the maximum number of files open.
30453 The limit on the total number of files open on the system
30457 The call was interrupted by the user.
30463 @unnumberedsubsubsec close
30464 @cindex close, file-i/o system call
30473 @samp{Fclose,@var{fd}}
30475 @item Return value:
30476 @code{close} returns zero on success, or -1 if an error occurred.
30482 @var{fd} isn't a valid open file descriptor.
30485 The call was interrupted by the user.
30491 @unnumberedsubsubsec read
30492 @cindex read, file-i/o system call
30497 int read(int fd, void *buf, unsigned int count);
30501 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
30503 @item Return value:
30504 On success, the number of bytes read is returned.
30505 Zero indicates end of file. If count is zero, read
30506 returns zero as well. On error, -1 is returned.
30512 @var{fd} is not a valid file descriptor or is not open for
30516 @var{bufptr} is an invalid pointer value.
30519 The call was interrupted by the user.
30525 @unnumberedsubsubsec write
30526 @cindex write, file-i/o system call
30531 int write(int fd, const void *buf, unsigned int count);
30535 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
30537 @item Return value:
30538 On success, the number of bytes written are returned.
30539 Zero indicates nothing was written. On error, -1
30546 @var{fd} is not a valid file descriptor or is not open for
30550 @var{bufptr} is an invalid pointer value.
30553 An attempt was made to write a file that exceeds the
30554 host-specific maximum file size allowed.
30557 No space on device to write the data.
30560 The call was interrupted by the user.
30566 @unnumberedsubsubsec lseek
30567 @cindex lseek, file-i/o system call
30572 long lseek (int fd, long offset, int flag);
30576 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
30578 @var{flag} is one of:
30582 The offset is set to @var{offset} bytes.
30585 The offset is set to its current location plus @var{offset}
30589 The offset is set to the size of the file plus @var{offset}
30593 @item Return value:
30594 On success, the resulting unsigned offset in bytes from
30595 the beginning of the file is returned. Otherwise, a
30596 value of -1 is returned.
30602 @var{fd} is not a valid open file descriptor.
30605 @var{fd} is associated with the @value{GDBN} console.
30608 @var{flag} is not a proper value.
30611 The call was interrupted by the user.
30617 @unnumberedsubsubsec rename
30618 @cindex rename, file-i/o system call
30623 int rename(const char *oldpath, const char *newpath);
30627 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
30629 @item Return value:
30630 On success, zero is returned. On error, -1 is returned.
30636 @var{newpath} is an existing directory, but @var{oldpath} is not a
30640 @var{newpath} is a non-empty directory.
30643 @var{oldpath} or @var{newpath} is a directory that is in use by some
30647 An attempt was made to make a directory a subdirectory
30651 A component used as a directory in @var{oldpath} or new
30652 path is not a directory. Or @var{oldpath} is a directory
30653 and @var{newpath} exists but is not a directory.
30656 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
30659 No access to the file or the path of the file.
30663 @var{oldpath} or @var{newpath} was too long.
30666 A directory component in @var{oldpath} or @var{newpath} does not exist.
30669 The file is on a read-only filesystem.
30672 The device containing the file has no room for the new
30676 The call was interrupted by the user.
30682 @unnumberedsubsubsec unlink
30683 @cindex unlink, file-i/o system call
30688 int unlink(const char *pathname);
30692 @samp{Funlink,@var{pathnameptr}/@var{len}}
30694 @item Return value:
30695 On success, zero is returned. On error, -1 is returned.
30701 No access to the file or the path of the file.
30704 The system does not allow unlinking of directories.
30707 The file @var{pathname} cannot be unlinked because it's
30708 being used by another process.
30711 @var{pathnameptr} is an invalid pointer value.
30714 @var{pathname} was too long.
30717 A directory component in @var{pathname} does not exist.
30720 A component of the path is not a directory.
30723 The file is on a read-only filesystem.
30726 The call was interrupted by the user.
30732 @unnumberedsubsubsec stat/fstat
30733 @cindex fstat, file-i/o system call
30734 @cindex stat, file-i/o system call
30739 int stat(const char *pathname, struct stat *buf);
30740 int fstat(int fd, struct stat *buf);
30744 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
30745 @samp{Ffstat,@var{fd},@var{bufptr}}
30747 @item Return value:
30748 On success, zero is returned. On error, -1 is returned.
30754 @var{fd} is not a valid open file.
30757 A directory component in @var{pathname} does not exist or the
30758 path is an empty string.
30761 A component of the path is not a directory.
30764 @var{pathnameptr} is an invalid pointer value.
30767 No access to the file or the path of the file.
30770 @var{pathname} was too long.
30773 The call was interrupted by the user.
30779 @unnumberedsubsubsec gettimeofday
30780 @cindex gettimeofday, file-i/o system call
30785 int gettimeofday(struct timeval *tv, void *tz);
30789 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
30791 @item Return value:
30792 On success, 0 is returned, -1 otherwise.
30798 @var{tz} is a non-NULL pointer.
30801 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
30807 @unnumberedsubsubsec isatty
30808 @cindex isatty, file-i/o system call
30813 int isatty(int fd);
30817 @samp{Fisatty,@var{fd}}
30819 @item Return value:
30820 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
30826 The call was interrupted by the user.
30831 Note that the @code{isatty} call is treated as a special case: it returns
30832 1 to the target if the file descriptor is attached
30833 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
30834 would require implementing @code{ioctl} and would be more complex than
30839 @unnumberedsubsubsec system
30840 @cindex system, file-i/o system call
30845 int system(const char *command);
30849 @samp{Fsystem,@var{commandptr}/@var{len}}
30851 @item Return value:
30852 If @var{len} is zero, the return value indicates whether a shell is
30853 available. A zero return value indicates a shell is not available.
30854 For non-zero @var{len}, the value returned is -1 on error and the
30855 return status of the command otherwise. Only the exit status of the
30856 command is returned, which is extracted from the host's @code{system}
30857 return value by calling @code{WEXITSTATUS(retval)}. In case
30858 @file{/bin/sh} could not be executed, 127 is returned.
30864 The call was interrupted by the user.
30869 @value{GDBN} takes over the full task of calling the necessary host calls
30870 to perform the @code{system} call. The return value of @code{system} on
30871 the host is simplified before it's returned
30872 to the target. Any termination signal information from the child process
30873 is discarded, and the return value consists
30874 entirely of the exit status of the called command.
30876 Due to security concerns, the @code{system} call is by default refused
30877 by @value{GDBN}. The user has to allow this call explicitly with the
30878 @code{set remote system-call-allowed 1} command.
30881 @item set remote system-call-allowed
30882 @kindex set remote system-call-allowed
30883 Control whether to allow the @code{system} calls in the File I/O
30884 protocol for the remote target. The default is zero (disabled).
30886 @item show remote system-call-allowed
30887 @kindex show remote system-call-allowed
30888 Show whether the @code{system} calls are allowed in the File I/O
30892 @node Protocol-specific Representation of Datatypes
30893 @subsection Protocol-specific Representation of Datatypes
30894 @cindex protocol-specific representation of datatypes, in file-i/o protocol
30897 * Integral Datatypes::
30899 * Memory Transfer::
30904 @node Integral Datatypes
30905 @unnumberedsubsubsec Integral Datatypes
30906 @cindex integral datatypes, in file-i/o protocol
30908 The integral datatypes used in the system calls are @code{int},
30909 @code{unsigned int}, @code{long}, @code{unsigned long},
30910 @code{mode_t}, and @code{time_t}.
30912 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
30913 implemented as 32 bit values in this protocol.
30915 @code{long} and @code{unsigned long} are implemented as 64 bit types.
30917 @xref{Limits}, for corresponding MIN and MAX values (similar to those
30918 in @file{limits.h}) to allow range checking on host and target.
30920 @code{time_t} datatypes are defined as seconds since the Epoch.
30922 All integral datatypes transferred as part of a memory read or write of a
30923 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
30926 @node Pointer Values
30927 @unnumberedsubsubsec Pointer Values
30928 @cindex pointer values, in file-i/o protocol
30930 Pointers to target data are transmitted as they are. An exception
30931 is made for pointers to buffers for which the length isn't
30932 transmitted as part of the function call, namely strings. Strings
30933 are transmitted as a pointer/length pair, both as hex values, e.g.@:
30940 which is a pointer to data of length 18 bytes at position 0x1aaf.
30941 The length is defined as the full string length in bytes, including
30942 the trailing null byte. For example, the string @code{"hello world"}
30943 at address 0x123456 is transmitted as
30949 @node Memory Transfer
30950 @unnumberedsubsubsec Memory Transfer
30951 @cindex memory transfer, in file-i/o protocol
30953 Structured data which is transferred using a memory read or write (for
30954 example, a @code{struct stat}) is expected to be in a protocol-specific format
30955 with all scalar multibyte datatypes being big endian. Translation to
30956 this representation needs to be done both by the target before the @code{F}
30957 packet is sent, and by @value{GDBN} before
30958 it transfers memory to the target. Transferred pointers to structured
30959 data should point to the already-coerced data at any time.
30963 @unnumberedsubsubsec struct stat
30964 @cindex struct stat, in file-i/o protocol
30966 The buffer of type @code{struct stat} used by the target and @value{GDBN}
30967 is defined as follows:
30971 unsigned int st_dev; /* device */
30972 unsigned int st_ino; /* inode */
30973 mode_t st_mode; /* protection */
30974 unsigned int st_nlink; /* number of hard links */
30975 unsigned int st_uid; /* user ID of owner */
30976 unsigned int st_gid; /* group ID of owner */
30977 unsigned int st_rdev; /* device type (if inode device) */
30978 unsigned long st_size; /* total size, in bytes */
30979 unsigned long st_blksize; /* blocksize for filesystem I/O */
30980 unsigned long st_blocks; /* number of blocks allocated */
30981 time_t st_atime; /* time of last access */
30982 time_t st_mtime; /* time of last modification */
30983 time_t st_ctime; /* time of last change */
30987 The integral datatypes conform to the definitions given in the
30988 appropriate section (see @ref{Integral Datatypes}, for details) so this
30989 structure is of size 64 bytes.
30991 The values of several fields have a restricted meaning and/or
30997 A value of 0 represents a file, 1 the console.
31000 No valid meaning for the target. Transmitted unchanged.
31003 Valid mode bits are described in @ref{Constants}. Any other
31004 bits have currently no meaning for the target.
31009 No valid meaning for the target. Transmitted unchanged.
31014 These values have a host and file system dependent
31015 accuracy. Especially on Windows hosts, the file system may not
31016 support exact timing values.
31019 The target gets a @code{struct stat} of the above representation and is
31020 responsible for coercing it to the target representation before
31023 Note that due to size differences between the host, target, and protocol
31024 representations of @code{struct stat} members, these members could eventually
31025 get truncated on the target.
31027 @node struct timeval
31028 @unnumberedsubsubsec struct timeval
31029 @cindex struct timeval, in file-i/o protocol
31031 The buffer of type @code{struct timeval} used by the File-I/O protocol
31032 is defined as follows:
31036 time_t tv_sec; /* second */
31037 long tv_usec; /* microsecond */
31041 The integral datatypes conform to the definitions given in the
31042 appropriate section (see @ref{Integral Datatypes}, for details) so this
31043 structure is of size 8 bytes.
31046 @subsection Constants
31047 @cindex constants, in file-i/o protocol
31049 The following values are used for the constants inside of the
31050 protocol. @value{GDBN} and target are responsible for translating these
31051 values before and after the call as needed.
31062 @unnumberedsubsubsec Open Flags
31063 @cindex open flags, in file-i/o protocol
31065 All values are given in hexadecimal representation.
31077 @node mode_t Values
31078 @unnumberedsubsubsec mode_t Values
31079 @cindex mode_t values, in file-i/o protocol
31081 All values are given in octal representation.
31098 @unnumberedsubsubsec Errno Values
31099 @cindex errno values, in file-i/o protocol
31101 All values are given in decimal representation.
31126 @code{EUNKNOWN} is used as a fallback error value if a host system returns
31127 any error value not in the list of supported error numbers.
31130 @unnumberedsubsubsec Lseek Flags
31131 @cindex lseek flags, in file-i/o protocol
31140 @unnumberedsubsubsec Limits
31141 @cindex limits, in file-i/o protocol
31143 All values are given in decimal representation.
31146 INT_MIN -2147483648
31148 UINT_MAX 4294967295
31149 LONG_MIN -9223372036854775808
31150 LONG_MAX 9223372036854775807
31151 ULONG_MAX 18446744073709551615
31154 @node File-I/O Examples
31155 @subsection File-I/O Examples
31156 @cindex file-i/o examples
31158 Example sequence of a write call, file descriptor 3, buffer is at target
31159 address 0x1234, 6 bytes should be written:
31162 <- @code{Fwrite,3,1234,6}
31163 @emph{request memory read from target}
31166 @emph{return "6 bytes written"}
31170 Example sequence of a read call, file descriptor 3, buffer is at target
31171 address 0x1234, 6 bytes should be read:
31174 <- @code{Fread,3,1234,6}
31175 @emph{request memory write to target}
31176 -> @code{X1234,6:XXXXXX}
31177 @emph{return "6 bytes read"}
31181 Example sequence of a read call, call fails on the host due to invalid
31182 file descriptor (@code{EBADF}):
31185 <- @code{Fread,3,1234,6}
31189 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
31193 <- @code{Fread,3,1234,6}
31198 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
31202 <- @code{Fread,3,1234,6}
31203 -> @code{X1234,6:XXXXXX}
31207 @node Library List Format
31208 @section Library List Format
31209 @cindex library list format, remote protocol
31211 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
31212 same process as your application to manage libraries. In this case,
31213 @value{GDBN} can use the loader's symbol table and normal memory
31214 operations to maintain a list of shared libraries. On other
31215 platforms, the operating system manages loaded libraries.
31216 @value{GDBN} can not retrieve the list of currently loaded libraries
31217 through memory operations, so it uses the @samp{qXfer:libraries:read}
31218 packet (@pxref{qXfer library list read}) instead. The remote stub
31219 queries the target's operating system and reports which libraries
31222 The @samp{qXfer:libraries:read} packet returns an XML document which
31223 lists loaded libraries and their offsets. Each library has an
31224 associated name and one or more segment or section base addresses,
31225 which report where the library was loaded in memory.
31227 For the common case of libraries that are fully linked binaries, the
31228 library should have a list of segments. If the target supports
31229 dynamic linking of a relocatable object file, its library XML element
31230 should instead include a list of allocated sections. The segment or
31231 section bases are start addresses, not relocation offsets; they do not
31232 depend on the library's link-time base addresses.
31234 @value{GDBN} must be linked with the Expat library to support XML
31235 library lists. @xref{Expat}.
31237 A simple memory map, with one loaded library relocated by a single
31238 offset, looks like this:
31242 <library name="/lib/libc.so.6">
31243 <segment address="0x10000000"/>
31248 Another simple memory map, with one loaded library with three
31249 allocated sections (.text, .data, .bss), looks like this:
31253 <library name="sharedlib.o">
31254 <section address="0x10000000"/>
31255 <section address="0x20000000"/>
31256 <section address="0x30000000"/>
31261 The format of a library list is described by this DTD:
31264 <!-- library-list: Root element with versioning -->
31265 <!ELEMENT library-list (library)*>
31266 <!ATTLIST library-list version CDATA #FIXED "1.0">
31267 <!ELEMENT library (segment*, section*)>
31268 <!ATTLIST library name CDATA #REQUIRED>
31269 <!ELEMENT segment EMPTY>
31270 <!ATTLIST segment address CDATA #REQUIRED>
31271 <!ELEMENT section EMPTY>
31272 <!ATTLIST section address CDATA #REQUIRED>
31275 In addition, segments and section descriptors cannot be mixed within a
31276 single library element, and you must supply at least one segment or
31277 section for each library.
31279 @node Memory Map Format
31280 @section Memory Map Format
31281 @cindex memory map format
31283 To be able to write into flash memory, @value{GDBN} needs to obtain a
31284 memory map from the target. This section describes the format of the
31287 The memory map is obtained using the @samp{qXfer:memory-map:read}
31288 (@pxref{qXfer memory map read}) packet and is an XML document that
31289 lists memory regions.
31291 @value{GDBN} must be linked with the Expat library to support XML
31292 memory maps. @xref{Expat}.
31294 The top-level structure of the document is shown below:
31297 <?xml version="1.0"?>
31298 <!DOCTYPE memory-map
31299 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
31300 "http://sourceware.org/gdb/gdb-memory-map.dtd">
31306 Each region can be either:
31311 A region of RAM starting at @var{addr} and extending for @var{length}
31315 <memory type="ram" start="@var{addr}" length="@var{length}"/>
31320 A region of read-only memory:
31323 <memory type="rom" start="@var{addr}" length="@var{length}"/>
31328 A region of flash memory, with erasure blocks @var{blocksize}
31332 <memory type="flash" start="@var{addr}" length="@var{length}">
31333 <property name="blocksize">@var{blocksize}</property>
31339 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
31340 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
31341 packets to write to addresses in such ranges.
31343 The formal DTD for memory map format is given below:
31346 <!-- ................................................... -->
31347 <!-- Memory Map XML DTD ................................ -->
31348 <!-- File: memory-map.dtd .............................. -->
31349 <!-- .................................... .............. -->
31350 <!-- memory-map.dtd -->
31351 <!-- memory-map: Root element with versioning -->
31352 <!ELEMENT memory-map (memory | property)>
31353 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
31354 <!ELEMENT memory (property)>
31355 <!-- memory: Specifies a memory region,
31356 and its type, or device. -->
31357 <!ATTLIST memory type CDATA #REQUIRED
31358 start CDATA #REQUIRED
31359 length CDATA #REQUIRED
31360 device CDATA #IMPLIED>
31361 <!-- property: Generic attribute tag -->
31362 <!ELEMENT property (#PCDATA | property)*>
31363 <!ATTLIST property name CDATA #REQUIRED>
31366 @include agentexpr.texi
31368 @node Target Descriptions
31369 @appendix Target Descriptions
31370 @cindex target descriptions
31372 @strong{Warning:} target descriptions are still under active development,
31373 and the contents and format may change between @value{GDBN} releases.
31374 The format is expected to stabilize in the future.
31376 One of the challenges of using @value{GDBN} to debug embedded systems
31377 is that there are so many minor variants of each processor
31378 architecture in use. It is common practice for vendors to start with
31379 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
31380 and then make changes to adapt it to a particular market niche. Some
31381 architectures have hundreds of variants, available from dozens of
31382 vendors. This leads to a number of problems:
31386 With so many different customized processors, it is difficult for
31387 the @value{GDBN} maintainers to keep up with the changes.
31389 Since individual variants may have short lifetimes or limited
31390 audiences, it may not be worthwhile to carry information about every
31391 variant in the @value{GDBN} source tree.
31393 When @value{GDBN} does support the architecture of the embedded system
31394 at hand, the task of finding the correct architecture name to give the
31395 @command{set architecture} command can be error-prone.
31398 To address these problems, the @value{GDBN} remote protocol allows a
31399 target system to not only identify itself to @value{GDBN}, but to
31400 actually describe its own features. This lets @value{GDBN} support
31401 processor variants it has never seen before --- to the extent that the
31402 descriptions are accurate, and that @value{GDBN} understands them.
31404 @value{GDBN} must be linked with the Expat library to support XML
31405 target descriptions. @xref{Expat}.
31408 * Retrieving Descriptions:: How descriptions are fetched from a target.
31409 * Target Description Format:: The contents of a target description.
31410 * Predefined Target Types:: Standard types available for target
31412 * Standard Target Features:: Features @value{GDBN} knows about.
31415 @node Retrieving Descriptions
31416 @section Retrieving Descriptions
31418 Target descriptions can be read from the target automatically, or
31419 specified by the user manually. The default behavior is to read the
31420 description from the target. @value{GDBN} retrieves it via the remote
31421 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
31422 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
31423 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
31424 XML document, of the form described in @ref{Target Description
31427 Alternatively, you can specify a file to read for the target description.
31428 If a file is set, the target will not be queried. The commands to
31429 specify a file are:
31432 @cindex set tdesc filename
31433 @item set tdesc filename @var{path}
31434 Read the target description from @var{path}.
31436 @cindex unset tdesc filename
31437 @item unset tdesc filename
31438 Do not read the XML target description from a file. @value{GDBN}
31439 will use the description supplied by the current target.
31441 @cindex show tdesc filename
31442 @item show tdesc filename
31443 Show the filename to read for a target description, if any.
31447 @node Target Description Format
31448 @section Target Description Format
31449 @cindex target descriptions, XML format
31451 A target description annex is an @uref{http://www.w3.org/XML/, XML}
31452 document which complies with the Document Type Definition provided in
31453 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
31454 means you can use generally available tools like @command{xmllint} to
31455 check that your feature descriptions are well-formed and valid.
31456 However, to help people unfamiliar with XML write descriptions for
31457 their targets, we also describe the grammar here.
31459 Target descriptions can identify the architecture of the remote target
31460 and (for some architectures) provide information about custom register
31461 sets. They can also identify the OS ABI of the remote target.
31462 @value{GDBN} can use this information to autoconfigure for your
31463 target, or to warn you if you connect to an unsupported target.
31465 Here is a simple target description:
31468 <target version="1.0">
31469 <architecture>i386:x86-64</architecture>
31474 This minimal description only says that the target uses
31475 the x86-64 architecture.
31477 A target description has the following overall form, with [ ] marking
31478 optional elements and @dots{} marking repeatable elements. The elements
31479 are explained further below.
31482 <?xml version="1.0"?>
31483 <!DOCTYPE target SYSTEM "gdb-target.dtd">
31484 <target version="1.0">
31485 @r{[}@var{architecture}@r{]}
31486 @r{[}@var{osabi}@r{]}
31487 @r{[}@var{compatible}@r{]}
31488 @r{[}@var{feature}@dots{}@r{]}
31493 The description is generally insensitive to whitespace and line
31494 breaks, under the usual common-sense rules. The XML version
31495 declaration and document type declaration can generally be omitted
31496 (@value{GDBN} does not require them), but specifying them may be
31497 useful for XML validation tools. The @samp{version} attribute for
31498 @samp{<target>} may also be omitted, but we recommend
31499 including it; if future versions of @value{GDBN} use an incompatible
31500 revision of @file{gdb-target.dtd}, they will detect and report
31501 the version mismatch.
31503 @subsection Inclusion
31504 @cindex target descriptions, inclusion
31507 @cindex <xi:include>
31510 It can sometimes be valuable to split a target description up into
31511 several different annexes, either for organizational purposes, or to
31512 share files between different possible target descriptions. You can
31513 divide a description into multiple files by replacing any element of
31514 the target description with an inclusion directive of the form:
31517 <xi:include href="@var{document}"/>
31521 When @value{GDBN} encounters an element of this form, it will retrieve
31522 the named XML @var{document}, and replace the inclusion directive with
31523 the contents of that document. If the current description was read
31524 using @samp{qXfer}, then so will be the included document;
31525 @var{document} will be interpreted as the name of an annex. If the
31526 current description was read from a file, @value{GDBN} will look for
31527 @var{document} as a file in the same directory where it found the
31528 original description.
31530 @subsection Architecture
31531 @cindex <architecture>
31533 An @samp{<architecture>} element has this form:
31536 <architecture>@var{arch}</architecture>
31539 @var{arch} is one of the architectures from the set accepted by
31540 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
31543 @cindex @code{<osabi>}
31545 This optional field was introduced in @value{GDBN} version 7.0.
31546 Previous versions of @value{GDBN} ignore it.
31548 An @samp{<osabi>} element has this form:
31551 <osabi>@var{abi-name}</osabi>
31554 @var{abi-name} is an OS ABI name from the same selection accepted by
31555 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
31557 @subsection Compatible Architecture
31558 @cindex @code{<compatible>}
31560 This optional field was introduced in @value{GDBN} version 7.0.
31561 Previous versions of @value{GDBN} ignore it.
31563 A @samp{<compatible>} element has this form:
31566 <compatible>@var{arch}</compatible>
31569 @var{arch} is one of the architectures from the set accepted by
31570 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
31572 A @samp{<compatible>} element is used to specify that the target
31573 is able to run binaries in some other than the main target architecture
31574 given by the @samp{<architecture>} element. For example, on the
31575 Cell Broadband Engine, the main architecture is @code{powerpc:common}
31576 or @code{powerpc:common64}, but the system is able to run binaries
31577 in the @code{spu} architecture as well. The way to describe this
31578 capability with @samp{<compatible>} is as follows:
31581 <architecture>powerpc:common</architecture>
31582 <compatible>spu</compatible>
31585 @subsection Features
31588 Each @samp{<feature>} describes some logical portion of the target
31589 system. Features are currently used to describe available CPU
31590 registers and the types of their contents. A @samp{<feature>} element
31594 <feature name="@var{name}">
31595 @r{[}@var{type}@dots{}@r{]}
31601 Each feature's name should be unique within the description. The name
31602 of a feature does not matter unless @value{GDBN} has some special
31603 knowledge of the contents of that feature; if it does, the feature
31604 should have its standard name. @xref{Standard Target Features}.
31608 Any register's value is a collection of bits which @value{GDBN} must
31609 interpret. The default interpretation is a two's complement integer,
31610 but other types can be requested by name in the register description.
31611 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
31612 Target Types}), and the description can define additional composite types.
31614 Each type element must have an @samp{id} attribute, which gives
31615 a unique (within the containing @samp{<feature>}) name to the type.
31616 Types must be defined before they are used.
31619 Some targets offer vector registers, which can be treated as arrays
31620 of scalar elements. These types are written as @samp{<vector>} elements,
31621 specifying the array element type, @var{type}, and the number of elements,
31625 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
31629 If a register's value is usefully viewed in multiple ways, define it
31630 with a union type containing the useful representations. The
31631 @samp{<union>} element contains one or more @samp{<field>} elements,
31632 each of which has a @var{name} and a @var{type}:
31635 <union id="@var{id}">
31636 <field name="@var{name}" type="@var{type}"/>
31641 @subsection Registers
31644 Each register is represented as an element with this form:
31647 <reg name="@var{name}"
31648 bitsize="@var{size}"
31649 @r{[}regnum="@var{num}"@r{]}
31650 @r{[}save-restore="@var{save-restore}"@r{]}
31651 @r{[}type="@var{type}"@r{]}
31652 @r{[}group="@var{group}"@r{]}/>
31656 The components are as follows:
31661 The register's name; it must be unique within the target description.
31664 The register's size, in bits.
31667 The register's number. If omitted, a register's number is one greater
31668 than that of the previous register (either in the current feature or in
31669 a preceeding feature); the first register in the target description
31670 defaults to zero. This register number is used to read or write
31671 the register; e.g.@: it is used in the remote @code{p} and @code{P}
31672 packets, and registers appear in the @code{g} and @code{G} packets
31673 in order of increasing register number.
31676 Whether the register should be preserved across inferior function
31677 calls; this must be either @code{yes} or @code{no}. The default is
31678 @code{yes}, which is appropriate for most registers except for
31679 some system control registers; this is not related to the target's
31683 The type of the register. @var{type} may be a predefined type, a type
31684 defined in the current feature, or one of the special types @code{int}
31685 and @code{float}. @code{int} is an integer type of the correct size
31686 for @var{bitsize}, and @code{float} is a floating point type (in the
31687 architecture's normal floating point format) of the correct size for
31688 @var{bitsize}. The default is @code{int}.
31691 The register group to which this register belongs. @var{group} must
31692 be either @code{general}, @code{float}, or @code{vector}. If no
31693 @var{group} is specified, @value{GDBN} will not display the register
31694 in @code{info registers}.
31698 @node Predefined Target Types
31699 @section Predefined Target Types
31700 @cindex target descriptions, predefined types
31702 Type definitions in the self-description can build up composite types
31703 from basic building blocks, but can not define fundamental types. Instead,
31704 standard identifiers are provided by @value{GDBN} for the fundamental
31705 types. The currently supported types are:
31714 Signed integer types holding the specified number of bits.
31721 Unsigned integer types holding the specified number of bits.
31725 Pointers to unspecified code and data. The program counter and
31726 any dedicated return address register may be marked as code
31727 pointers; printing a code pointer converts it into a symbolic
31728 address. The stack pointer and any dedicated address registers
31729 may be marked as data pointers.
31732 Single precision IEEE floating point.
31735 Double precision IEEE floating point.
31738 The 12-byte extended precision format used by ARM FPA registers.
31742 @node Standard Target Features
31743 @section Standard Target Features
31744 @cindex target descriptions, standard features
31746 A target description must contain either no registers or all the
31747 target's registers. If the description contains no registers, then
31748 @value{GDBN} will assume a default register layout, selected based on
31749 the architecture. If the description contains any registers, the
31750 default layout will not be used; the standard registers must be
31751 described in the target description, in such a way that @value{GDBN}
31752 can recognize them.
31754 This is accomplished by giving specific names to feature elements
31755 which contain standard registers. @value{GDBN} will look for features
31756 with those names and verify that they contain the expected registers;
31757 if any known feature is missing required registers, or if any required
31758 feature is missing, @value{GDBN} will reject the target
31759 description. You can add additional registers to any of the
31760 standard features --- @value{GDBN} will display them just as if
31761 they were added to an unrecognized feature.
31763 This section lists the known features and their expected contents.
31764 Sample XML documents for these features are included in the
31765 @value{GDBN} source tree, in the directory @file{gdb/features}.
31767 Names recognized by @value{GDBN} should include the name of the
31768 company or organization which selected the name, and the overall
31769 architecture to which the feature applies; so e.g.@: the feature
31770 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
31772 The names of registers are not case sensitive for the purpose
31773 of recognizing standard features, but @value{GDBN} will only display
31774 registers using the capitalization used in the description.
31780 * PowerPC Features::
31785 @subsection ARM Features
31786 @cindex target descriptions, ARM features
31788 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
31789 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
31790 @samp{lr}, @samp{pc}, and @samp{cpsr}.
31792 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
31793 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
31795 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
31796 it should contain at least registers @samp{wR0} through @samp{wR15} and
31797 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
31798 @samp{wCSSF}, and @samp{wCASF} registers are optional.
31800 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
31801 should contain at least registers @samp{d0} through @samp{d15}. If
31802 they are present, @samp{d16} through @samp{d31} should also be included.
31803 @value{GDBN} will synthesize the single-precision registers from
31804 halves of the double-precision registers.
31806 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
31807 need to contain registers; it instructs @value{GDBN} to display the
31808 VFP double-precision registers as vectors and to synthesize the
31809 quad-precision registers from pairs of double-precision registers.
31810 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
31811 be present and include 32 double-precision registers.
31813 @node MIPS Features
31814 @subsection MIPS Features
31815 @cindex target descriptions, MIPS features
31817 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
31818 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
31819 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
31822 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
31823 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
31824 registers. They may be 32-bit or 64-bit depending on the target.
31826 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
31827 it may be optional in a future version of @value{GDBN}. It should
31828 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
31829 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
31831 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
31832 contain a single register, @samp{restart}, which is used by the
31833 Linux kernel to control restartable syscalls.
31835 @node M68K Features
31836 @subsection M68K Features
31837 @cindex target descriptions, M68K features
31840 @item @samp{org.gnu.gdb.m68k.core}
31841 @itemx @samp{org.gnu.gdb.coldfire.core}
31842 @itemx @samp{org.gnu.gdb.fido.core}
31843 One of those features must be always present.
31844 The feature that is present determines which flavor of m68k is
31845 used. The feature that is present should contain registers
31846 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
31847 @samp{sp}, @samp{ps} and @samp{pc}.
31849 @item @samp{org.gnu.gdb.coldfire.fp}
31850 This feature is optional. If present, it should contain registers
31851 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
31855 @node PowerPC Features
31856 @subsection PowerPC Features
31857 @cindex target descriptions, PowerPC features
31859 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
31860 targets. It should contain registers @samp{r0} through @samp{r31},
31861 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
31862 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
31864 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
31865 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
31867 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
31868 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
31871 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
31872 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
31873 will combine these registers with the floating point registers
31874 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
31875 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
31876 through @samp{vs63}, the set of vector registers for POWER7.
31878 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
31879 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
31880 @samp{spefscr}. SPE targets should provide 32-bit registers in
31881 @samp{org.gnu.gdb.power.core} and provide the upper halves in
31882 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
31883 these to present registers @samp{ev0} through @samp{ev31} to the
31886 @node Operating System Information
31887 @appendix Operating System Information
31888 @cindex operating system information
31894 Users of @value{GDBN} often wish to obtain information about the state of
31895 the operating system running on the target---for example the list of
31896 processes, or the list of open files. This section describes the
31897 mechanism that makes it possible. This mechanism is similar to the
31898 target features mechanism (@pxref{Target Descriptions}), but focuses
31899 on a different aspect of target.
31901 Operating system information is retrived from the target via the
31902 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
31903 read}). The object name in the request should be @samp{osdata}, and
31904 the @var{annex} identifies the data to be fetched.
31907 @appendixsection Process list
31908 @cindex operating system information, process list
31910 When requesting the process list, the @var{annex} field in the
31911 @samp{qXfer} request should be @samp{processes}. The returned data is
31912 an XML document. The formal syntax of this document is defined in
31913 @file{gdb/features/osdata.dtd}.
31915 An example document is:
31918 <?xml version="1.0"?>
31919 <!DOCTYPE target SYSTEM "osdata.dtd">
31920 <osdata type="processes">
31922 <column name="pid">1</column>
31923 <column name="user">root</column>
31924 <column name="command">/sbin/init</column>
31929 Each item should include a column whose name is @samp{pid}. The value
31930 of that column should identify the process on the target. The
31931 @samp{user} and @samp{command} columns are optional, and will be
31932 displayed by @value{GDBN}. Target may provide additional columns,
31933 which @value{GDBN} currently ignores.
31947 % I think something like @colophon should be in texinfo. In the
31949 \long\def\colophon{\hbox to0pt{}\vfill
31950 \centerline{The body of this manual is set in}
31951 \centerline{\fontname\tenrm,}
31952 \centerline{with headings in {\bf\fontname\tenbf}}
31953 \centerline{and examples in {\tt\fontname\tentt}.}
31954 \centerline{{\it\fontname\tenit\/},}
31955 \centerline{{\bf\fontname\tenbf}, and}
31956 \centerline{{\sl\fontname\tensl\/}}
31957 \centerline{are used for emphasis.}\vfill}
31959 % Blame: doc@cygnus.com, 1991.