1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
48 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
49 Free Software Foundation, Inc.
51 Permission is granted to copy, distribute and/or modify this document
52 under the terms of the GNU Free Documentation License, Version 1.1 or
53 any later version published by the Free Software Foundation; with the
54 Invariant Sections being ``Free Software'' and ``Free Software Needs
55 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
56 and with the Back-Cover Texts as in (a) below.
58 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
59 this GNU Manual. Buying copies from GNU Press supports the FSF in
60 developing GNU and promoting software freedom.''
64 This file documents the @sc{gnu} debugger @value{GDBN}.
66 This is the @value{EDITION} Edition, of @cite{Debugging with
67 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
68 @ifset VERSION_PACKAGE
69 @value{VERSION_PACKAGE}
71 Version @value{GDBVN}.
77 @title Debugging with @value{GDBN}
78 @subtitle The @sc{gnu} Source-Level Debugger
80 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
81 @ifset VERSION_PACKAGE
83 @subtitle @value{VERSION_PACKAGE}
85 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
89 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
90 \hfill {\it Debugging with @value{GDBN}}\par
91 \hfill \TeX{}info \texinfoversion\par
95 @vskip 0pt plus 1filll
96 Published by the Free Software Foundation @*
97 51 Franklin Street, Fifth Floor,
98 Boston, MA 02110-1301, USA@*
103 This edition of the GDB manual is dedicated to the memory of Fred
104 Fish. Fred was a long-standing contributor to GDB and to Free
105 software in general. We will miss him.
110 @node Top, Summary, (dir), (dir)
112 @top Debugging with @value{GDBN}
114 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
116 This is the @value{EDITION} Edition, for @value{GDBN}
117 @ifset VERSION_PACKAGE
118 @value{VERSION_PACKAGE}
120 Version @value{GDBVN}.
122 Copyright (C) 1988-2009 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Reverse Execution:: Running programs backward
137 * Stack:: Examining the stack
138 * Source:: Examining source files
139 * Data:: Examining data
140 * Macros:: Preprocessor Macros
141 * Tracepoints:: Debugging remote targets non-intrusively
142 * Overlays:: Debugging programs that use overlays
144 * Languages:: Using @value{GDBN} with different languages
146 * Symbols:: Examining the symbol table
147 * Altering:: Altering execution
148 * GDB Files:: @value{GDBN} files
149 * Targets:: Specifying a debugging target
150 * Remote Debugging:: Debugging remote programs
151 * Configurations:: Configuration-specific information
152 * Controlling GDB:: Controlling @value{GDBN}
153 * Extending GDB:: Extending @value{GDBN}
154 * Interpreters:: Command Interpreters
155 * TUI:: @value{GDBN} Text User Interface
156 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
157 * GDB/MI:: @value{GDBN}'s Machine Interface.
158 * Annotations:: @value{GDBN}'s annotation interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 * Command Line Editing:: Command Line Editing
163 * Using History Interactively:: Using History Interactively
164 * Formatting Documentation:: How to format and print @value{GDBN} documentation
165 * Installing GDB:: Installing GDB
166 * Maintenance Commands:: Maintenance Commands
167 * Remote Protocol:: GDB Remote Serial Protocol
168 * Agent Expressions:: The GDB Agent Expression Mechanism
169 * Target Descriptions:: How targets can describe themselves to
171 * Operating System Information:: Getting additional information from
173 * Copying:: GNU General Public License says
174 how you can copy and share GDB
175 * GNU Free Documentation License:: The license for this documentation
184 @unnumbered Summary of @value{GDBN}
186 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
187 going on ``inside'' another program while it executes---or what another
188 program was doing at the moment it crashed.
190 @value{GDBN} can do four main kinds of things (plus other things in support of
191 these) to help you catch bugs in the act:
195 Start your program, specifying anything that might affect its behavior.
198 Make your program stop on specified conditions.
201 Examine what has happened, when your program has stopped.
204 Change things in your program, so you can experiment with correcting the
205 effects of one bug and go on to learn about another.
208 You can use @value{GDBN} to debug programs written in C and C@t{++}.
209 For more information, see @ref{Supported Languages,,Supported Languages}.
210 For more information, see @ref{C,,C and C++}.
213 Support for Modula-2 is partial. For information on Modula-2, see
214 @ref{Modula-2,,Modula-2}.
217 Debugging Pascal programs which use sets, subranges, file variables, or
218 nested functions does not currently work. @value{GDBN} does not support
219 entering expressions, printing values, or similar features using Pascal
223 @value{GDBN} can be used to debug programs written in Fortran, although
224 it may be necessary to refer to some variables with a trailing
227 @value{GDBN} can be used to debug programs written in Objective-C,
228 using either the Apple/NeXT or the GNU Objective-C runtime.
231 * Free Software:: Freely redistributable software
232 * Contributors:: Contributors to GDB
236 @unnumberedsec Free Software
238 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
239 General Public License
240 (GPL). The GPL gives you the freedom to copy or adapt a licensed
241 program---but every person getting a copy also gets with it the
242 freedom to modify that copy (which means that they must get access to
243 the source code), and the freedom to distribute further copies.
244 Typical software companies use copyrights to limit your freedoms; the
245 Free Software Foundation uses the GPL to preserve these freedoms.
247 Fundamentally, the General Public License is a license which says that
248 you have these freedoms and that you cannot take these freedoms away
251 @unnumberedsec Free Software Needs Free Documentation
253 The biggest deficiency in the free software community today is not in
254 the software---it is the lack of good free documentation that we can
255 include with the free software. Many of our most important
256 programs do not come with free reference manuals and free introductory
257 texts. Documentation is an essential part of any software package;
258 when an important free software package does not come with a free
259 manual and a free tutorial, that is a major gap. We have many such
262 Consider Perl, for instance. The tutorial manuals that people
263 normally use are non-free. How did this come about? Because the
264 authors of those manuals published them with restrictive terms---no
265 copying, no modification, source files not available---which exclude
266 them from the free software world.
268 That wasn't the first time this sort of thing happened, and it was far
269 from the last. Many times we have heard a GNU user eagerly describe a
270 manual that he is writing, his intended contribution to the community,
271 only to learn that he had ruined everything by signing a publication
272 contract to make it non-free.
274 Free documentation, like free software, is a matter of freedom, not
275 price. The problem with the non-free manual is not that publishers
276 charge a price for printed copies---that in itself is fine. (The Free
277 Software Foundation sells printed copies of manuals, too.) The
278 problem is the restrictions on the use of the manual. Free manuals
279 are available in source code form, and give you permission to copy and
280 modify. Non-free manuals do not allow this.
282 The criteria of freedom for a free manual are roughly the same as for
283 free software. Redistribution (including the normal kinds of
284 commercial redistribution) must be permitted, so that the manual can
285 accompany every copy of the program, both on-line and on paper.
287 Permission for modification of the technical content is crucial too.
288 When people modify the software, adding or changing features, if they
289 are conscientious they will change the manual too---so they can
290 provide accurate and clear documentation for the modified program. A
291 manual that leaves you no choice but to write a new manual to document
292 a changed version of the program is not really available to our
295 Some kinds of limits on the way modification is handled are
296 acceptable. For example, requirements to preserve the original
297 author's copyright notice, the distribution terms, or the list of
298 authors, are ok. It is also no problem to require modified versions
299 to include notice that they were modified. Even entire sections that
300 may not be deleted or changed are acceptable, as long as they deal
301 with nontechnical topics (like this one). These kinds of restrictions
302 are acceptable because they don't obstruct the community's normal use
305 However, it must be possible to modify all the @emph{technical}
306 content of the manual, and then distribute the result in all the usual
307 media, through all the usual channels. Otherwise, the restrictions
308 obstruct the use of the manual, it is not free, and we need another
309 manual to replace it.
311 Please spread the word about this issue. Our community continues to
312 lose manuals to proprietary publishing. If we spread the word that
313 free software needs free reference manuals and free tutorials, perhaps
314 the next person who wants to contribute by writing documentation will
315 realize, before it is too late, that only free manuals contribute to
316 the free software community.
318 If you are writing documentation, please insist on publishing it under
319 the GNU Free Documentation License or another free documentation
320 license. Remember that this decision requires your approval---you
321 don't have to let the publisher decide. Some commercial publishers
322 will use a free license if you insist, but they will not propose the
323 option; it is up to you to raise the issue and say firmly that this is
324 what you want. If the publisher you are dealing with refuses, please
325 try other publishers. If you're not sure whether a proposed license
326 is free, write to @email{licensing@@gnu.org}.
328 You can encourage commercial publishers to sell more free, copylefted
329 manuals and tutorials by buying them, and particularly by buying
330 copies from the publishers that paid for their writing or for major
331 improvements. Meanwhile, try to avoid buying non-free documentation
332 at all. Check the distribution terms of a manual before you buy it,
333 and insist that whoever seeks your business must respect your freedom.
334 Check the history of the book, and try to reward the publishers that
335 have paid or pay the authors to work on it.
337 The Free Software Foundation maintains a list of free documentation
338 published by other publishers, at
339 @url{http://www.fsf.org/doc/other-free-books.html}.
342 @unnumberedsec Contributors to @value{GDBN}
344 Richard Stallman was the original author of @value{GDBN}, and of many
345 other @sc{gnu} programs. Many others have contributed to its
346 development. This section attempts to credit major contributors. One
347 of the virtues of free software is that everyone is free to contribute
348 to it; with regret, we cannot actually acknowledge everyone here. The
349 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
350 blow-by-blow account.
352 Changes much prior to version 2.0 are lost in the mists of time.
355 @emph{Plea:} Additions to this section are particularly welcome. If you
356 or your friends (or enemies, to be evenhanded) have been unfairly
357 omitted from this list, we would like to add your names!
360 So that they may not regard their many labors as thankless, we
361 particularly thank those who shepherded @value{GDBN} through major
363 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
364 Jim Blandy (release 4.18);
365 Jason Molenda (release 4.17);
366 Stan Shebs (release 4.14);
367 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
368 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
369 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
370 Jim Kingdon (releases 3.5, 3.4, and 3.3);
371 and Randy Smith (releases 3.2, 3.1, and 3.0).
373 Richard Stallman, assisted at various times by Peter TerMaat, Chris
374 Hanson, and Richard Mlynarik, handled releases through 2.8.
376 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
377 in @value{GDBN}, with significant additional contributions from Per
378 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
379 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
380 much general update work leading to release 3.0).
382 @value{GDBN} uses the BFD subroutine library to examine multiple
383 object-file formats; BFD was a joint project of David V.
384 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
386 David Johnson wrote the original COFF support; Pace Willison did
387 the original support for encapsulated COFF.
389 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
391 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
392 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
394 Jean-Daniel Fekete contributed Sun 386i support.
395 Chris Hanson improved the HP9000 support.
396 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
397 David Johnson contributed Encore Umax support.
398 Jyrki Kuoppala contributed Altos 3068 support.
399 Jeff Law contributed HP PA and SOM support.
400 Keith Packard contributed NS32K support.
401 Doug Rabson contributed Acorn Risc Machine support.
402 Bob Rusk contributed Harris Nighthawk CX-UX support.
403 Chris Smith contributed Convex support (and Fortran debugging).
404 Jonathan Stone contributed Pyramid support.
405 Michael Tiemann contributed SPARC support.
406 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
407 Pace Willison contributed Intel 386 support.
408 Jay Vosburgh contributed Symmetry support.
409 Marko Mlinar contributed OpenRISC 1000 support.
411 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
413 Rich Schaefer and Peter Schauer helped with support of SunOS shared
416 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
417 about several machine instruction sets.
419 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
420 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
421 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
422 and RDI targets, respectively.
424 Brian Fox is the author of the readline libraries providing
425 command-line editing and command history.
427 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
428 Modula-2 support, and contributed the Languages chapter of this manual.
430 Fred Fish wrote most of the support for Unix System Vr4.
431 He also enhanced the command-completion support to cover C@t{++} overloaded
434 Hitachi America (now Renesas America), Ltd. sponsored the support for
435 H8/300, H8/500, and Super-H processors.
437 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
439 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
442 Toshiba sponsored the support for the TX39 Mips processor.
444 Matsushita sponsored the support for the MN10200 and MN10300 processors.
446 Fujitsu sponsored the support for SPARClite and FR30 processors.
448 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
451 Michael Snyder added support for tracepoints.
453 Stu Grossman wrote gdbserver.
455 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
456 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
458 The following people at the Hewlett-Packard Company contributed
459 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
460 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
461 compiler, and the Text User Interface (nee Terminal User Interface):
462 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
463 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
464 provided HP-specific information in this manual.
466 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
467 Robert Hoehne made significant contributions to the DJGPP port.
469 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
470 development since 1991. Cygnus engineers who have worked on @value{GDBN}
471 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
472 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
473 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
474 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
475 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
476 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
477 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
478 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
479 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
480 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
481 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
482 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
483 Zuhn have made contributions both large and small.
485 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
486 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
488 Jim Blandy added support for preprocessor macros, while working for Red
491 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
492 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
493 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
494 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
495 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
496 with the migration of old architectures to this new framework.
498 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
499 unwinder framework, this consisting of a fresh new design featuring
500 frame IDs, independent frame sniffers, and the sentinel frame. Mark
501 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
502 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
503 trad unwinders. The architecture-specific changes, each involving a
504 complete rewrite of the architecture's frame code, were carried out by
505 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
506 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
507 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
508 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
511 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
512 Tensilica, Inc.@: contributed support for Xtensa processors. Others
513 who have worked on the Xtensa port of @value{GDBN} in the past include
514 Steve Tjiang, John Newlin, and Scott Foehner.
517 @chapter A Sample @value{GDBN} Session
519 You can use this manual at your leisure to read all about @value{GDBN}.
520 However, a handful of commands are enough to get started using the
521 debugger. This chapter illustrates those commands.
524 In this sample session, we emphasize user input like this: @b{input},
525 to make it easier to pick out from the surrounding output.
528 @c FIXME: this example may not be appropriate for some configs, where
529 @c FIXME...primary interest is in remote use.
531 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
532 processor) exhibits the following bug: sometimes, when we change its
533 quote strings from the default, the commands used to capture one macro
534 definition within another stop working. In the following short @code{m4}
535 session, we define a macro @code{foo} which expands to @code{0000}; we
536 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
537 same thing. However, when we change the open quote string to
538 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
539 procedure fails to define a new synonym @code{baz}:
548 @b{define(bar,defn(`foo'))}
552 @b{changequote(<QUOTE>,<UNQUOTE>)}
554 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
557 m4: End of input: 0: fatal error: EOF in string
561 Let us use @value{GDBN} to try to see what is going on.
564 $ @b{@value{GDBP} m4}
565 @c FIXME: this falsifies the exact text played out, to permit smallbook
566 @c FIXME... format to come out better.
567 @value{GDBN} is free software and you are welcome to distribute copies
568 of it under certain conditions; type "show copying" to see
570 There is absolutely no warranty for @value{GDBN}; type "show warranty"
573 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
578 @value{GDBN} reads only enough symbol data to know where to find the
579 rest when needed; as a result, the first prompt comes up very quickly.
580 We now tell @value{GDBN} to use a narrower display width than usual, so
581 that examples fit in this manual.
584 (@value{GDBP}) @b{set width 70}
588 We need to see how the @code{m4} built-in @code{changequote} works.
589 Having looked at the source, we know the relevant subroutine is
590 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
591 @code{break} command.
594 (@value{GDBP}) @b{break m4_changequote}
595 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
599 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
600 control; as long as control does not reach the @code{m4_changequote}
601 subroutine, the program runs as usual:
604 (@value{GDBP}) @b{run}
605 Starting program: /work/Editorial/gdb/gnu/m4/m4
613 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
614 suspends execution of @code{m4}, displaying information about the
615 context where it stops.
618 @b{changequote(<QUOTE>,<UNQUOTE>)}
620 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
622 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
626 Now we use the command @code{n} (@code{next}) to advance execution to
627 the next line of the current function.
631 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
636 @code{set_quotes} looks like a promising subroutine. We can go into it
637 by using the command @code{s} (@code{step}) instead of @code{next}.
638 @code{step} goes to the next line to be executed in @emph{any}
639 subroutine, so it steps into @code{set_quotes}.
643 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
645 530 if (lquote != def_lquote)
649 The display that shows the subroutine where @code{m4} is now
650 suspended (and its arguments) is called a stack frame display. It
651 shows a summary of the stack. We can use the @code{backtrace}
652 command (which can also be spelled @code{bt}), to see where we are
653 in the stack as a whole: the @code{backtrace} command displays a
654 stack frame for each active subroutine.
657 (@value{GDBP}) @b{bt}
658 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
660 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
662 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
663 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
665 #4 0x79dc in expand_input () at macro.c:40
666 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
670 We step through a few more lines to see what happens. The first two
671 times, we can use @samp{s}; the next two times we use @code{n} to avoid
672 falling into the @code{xstrdup} subroutine.
676 0x3b5c 532 if (rquote != def_rquote)
678 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
679 def_lquote : xstrdup(lq);
681 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
684 538 len_lquote = strlen(rquote);
688 The last line displayed looks a little odd; we can examine the variables
689 @code{lquote} and @code{rquote} to see if they are in fact the new left
690 and right quotes we specified. We use the command @code{p}
691 (@code{print}) to see their values.
694 (@value{GDBP}) @b{p lquote}
695 $1 = 0x35d40 "<QUOTE>"
696 (@value{GDBP}) @b{p rquote}
697 $2 = 0x35d50 "<UNQUOTE>"
701 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
702 To look at some context, we can display ten lines of source
703 surrounding the current line with the @code{l} (@code{list}) command.
709 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
711 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
714 538 len_lquote = strlen(rquote);
715 539 len_rquote = strlen(lquote);
722 Let us step past the two lines that set @code{len_lquote} and
723 @code{len_rquote}, and then examine the values of those variables.
727 539 len_rquote = strlen(lquote);
730 (@value{GDBP}) @b{p len_lquote}
732 (@value{GDBP}) @b{p len_rquote}
737 That certainly looks wrong, assuming @code{len_lquote} and
738 @code{len_rquote} are meant to be the lengths of @code{lquote} and
739 @code{rquote} respectively. We can set them to better values using
740 the @code{p} command, since it can print the value of
741 any expression---and that expression can include subroutine calls and
745 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
747 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
752 Is that enough to fix the problem of using the new quotes with the
753 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
754 executing with the @code{c} (@code{continue}) command, and then try the
755 example that caused trouble initially:
761 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
768 Success! The new quotes now work just as well as the default ones. The
769 problem seems to have been just the two typos defining the wrong
770 lengths. We allow @code{m4} exit by giving it an EOF as input:
774 Program exited normally.
778 The message @samp{Program exited normally.} is from @value{GDBN}; it
779 indicates @code{m4} has finished executing. We can end our @value{GDBN}
780 session with the @value{GDBN} @code{quit} command.
783 (@value{GDBP}) @b{quit}
787 @chapter Getting In and Out of @value{GDBN}
789 This chapter discusses how to start @value{GDBN}, and how to get out of it.
793 type @samp{@value{GDBP}} to start @value{GDBN}.
795 type @kbd{quit} or @kbd{Ctrl-d} to exit.
799 * Invoking GDB:: How to start @value{GDBN}
800 * Quitting GDB:: How to quit @value{GDBN}
801 * Shell Commands:: How to use shell commands inside @value{GDBN}
802 * Logging Output:: How to log @value{GDBN}'s output to a file
806 @section Invoking @value{GDBN}
808 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
809 @value{GDBN} reads commands from the terminal until you tell it to exit.
811 You can also run @code{@value{GDBP}} with a variety of arguments and options,
812 to specify more of your debugging environment at the outset.
814 The command-line options described here are designed
815 to cover a variety of situations; in some environments, some of these
816 options may effectively be unavailable.
818 The most usual way to start @value{GDBN} is with one argument,
819 specifying an executable program:
822 @value{GDBP} @var{program}
826 You can also start with both an executable program and a core file
830 @value{GDBP} @var{program} @var{core}
833 You can, instead, specify a process ID as a second argument, if you want
834 to debug a running process:
837 @value{GDBP} @var{program} 1234
841 would attach @value{GDBN} to process @code{1234} (unless you also have a file
842 named @file{1234}; @value{GDBN} does check for a core file first).
844 Taking advantage of the second command-line argument requires a fairly
845 complete operating system; when you use @value{GDBN} as a remote
846 debugger attached to a bare board, there may not be any notion of
847 ``process'', and there is often no way to get a core dump. @value{GDBN}
848 will warn you if it is unable to attach or to read core dumps.
850 You can optionally have @code{@value{GDBP}} pass any arguments after the
851 executable file to the inferior using @code{--args}. This option stops
854 @value{GDBP} --args gcc -O2 -c foo.c
856 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
857 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
859 You can run @code{@value{GDBP}} without printing the front material, which describes
860 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
867 You can further control how @value{GDBN} starts up by using command-line
868 options. @value{GDBN} itself can remind you of the options available.
878 to display all available options and briefly describe their use
879 (@samp{@value{GDBP} -h} is a shorter equivalent).
881 All options and command line arguments you give are processed
882 in sequential order. The order makes a difference when the
883 @samp{-x} option is used.
887 * File Options:: Choosing files
888 * Mode Options:: Choosing modes
889 * Startup:: What @value{GDBN} does during startup
893 @subsection Choosing Files
895 When @value{GDBN} starts, it reads any arguments other than options as
896 specifying an executable file and core file (or process ID). This is
897 the same as if the arguments were specified by the @samp{-se} and
898 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
899 first argument that does not have an associated option flag as
900 equivalent to the @samp{-se} option followed by that argument; and the
901 second argument that does not have an associated option flag, if any, as
902 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
903 If the second argument begins with a decimal digit, @value{GDBN} will
904 first attempt to attach to it as a process, and if that fails, attempt
905 to open it as a corefile. If you have a corefile whose name begins with
906 a digit, you can prevent @value{GDBN} from treating it as a pid by
907 prefixing it with @file{./}, e.g.@: @file{./12345}.
909 If @value{GDBN} has not been configured to included core file support,
910 such as for most embedded targets, then it will complain about a second
911 argument and ignore it.
913 Many options have both long and short forms; both are shown in the
914 following list. @value{GDBN} also recognizes the long forms if you truncate
915 them, so long as enough of the option is present to be unambiguous.
916 (If you prefer, you can flag option arguments with @samp{--} rather
917 than @samp{-}, though we illustrate the more usual convention.)
919 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
920 @c way, both those who look for -foo and --foo in the index, will find
924 @item -symbols @var{file}
926 @cindex @code{--symbols}
928 Read symbol table from file @var{file}.
930 @item -exec @var{file}
932 @cindex @code{--exec}
934 Use file @var{file} as the executable file to execute when appropriate,
935 and for examining pure data in conjunction with a core dump.
939 Read symbol table from file @var{file} and use it as the executable
942 @item -core @var{file}
944 @cindex @code{--core}
946 Use file @var{file} as a core dump to examine.
948 @item -pid @var{number}
949 @itemx -p @var{number}
952 Connect to process ID @var{number}, as with the @code{attach} command.
954 @item -command @var{file}
956 @cindex @code{--command}
958 Execute @value{GDBN} commands from file @var{file}. @xref{Command
959 Files,, Command files}.
961 @item -eval-command @var{command}
962 @itemx -ex @var{command}
963 @cindex @code{--eval-command}
965 Execute a single @value{GDBN} command.
967 This option may be used multiple times to call multiple commands. It may
968 also be interleaved with @samp{-command} as required.
971 @value{GDBP} -ex 'target sim' -ex 'load' \
972 -x setbreakpoints -ex 'run' a.out
975 @item -directory @var{directory}
976 @itemx -d @var{directory}
977 @cindex @code{--directory}
979 Add @var{directory} to the path to search for source and script files.
983 @cindex @code{--readnow}
985 Read each symbol file's entire symbol table immediately, rather than
986 the default, which is to read it incrementally as it is needed.
987 This makes startup slower, but makes future operations faster.
992 @subsection Choosing Modes
994 You can run @value{GDBN} in various alternative modes---for example, in
995 batch mode or quiet mode.
1002 Do not execute commands found in any initialization files. Normally,
1003 @value{GDBN} executes the commands in these files after all the command
1004 options and arguments have been processed. @xref{Command Files,,Command
1010 @cindex @code{--quiet}
1011 @cindex @code{--silent}
1013 ``Quiet''. Do not print the introductory and copyright messages. These
1014 messages are also suppressed in batch mode.
1017 @cindex @code{--batch}
1018 Run in batch mode. Exit with status @code{0} after processing all the
1019 command files specified with @samp{-x} (and all commands from
1020 initialization files, if not inhibited with @samp{-n}). Exit with
1021 nonzero status if an error occurs in executing the @value{GDBN} commands
1022 in the command files.
1024 Batch mode may be useful for running @value{GDBN} as a filter, for
1025 example to download and run a program on another computer; in order to
1026 make this more useful, the message
1029 Program exited normally.
1033 (which is ordinarily issued whenever a program running under
1034 @value{GDBN} control terminates) is not issued when running in batch
1038 @cindex @code{--batch-silent}
1039 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1040 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1041 unaffected). This is much quieter than @samp{-silent} and would be useless
1042 for an interactive session.
1044 This is particularly useful when using targets that give @samp{Loading section}
1045 messages, for example.
1047 Note that targets that give their output via @value{GDBN}, as opposed to
1048 writing directly to @code{stdout}, will also be made silent.
1050 @item -return-child-result
1051 @cindex @code{--return-child-result}
1052 The return code from @value{GDBN} will be the return code from the child
1053 process (the process being debugged), with the following exceptions:
1057 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1058 internal error. In this case the exit code is the same as it would have been
1059 without @samp{-return-child-result}.
1061 The user quits with an explicit value. E.g., @samp{quit 1}.
1063 The child process never runs, or is not allowed to terminate, in which case
1064 the exit code will be -1.
1067 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1068 when @value{GDBN} is being used as a remote program loader or simulator
1073 @cindex @code{--nowindows}
1075 ``No windows''. If @value{GDBN} comes with a graphical user interface
1076 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1077 interface. If no GUI is available, this option has no effect.
1081 @cindex @code{--windows}
1083 If @value{GDBN} includes a GUI, then this option requires it to be
1086 @item -cd @var{directory}
1088 Run @value{GDBN} using @var{directory} as its working directory,
1089 instead of the current directory.
1093 @cindex @code{--fullname}
1095 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1096 subprocess. It tells @value{GDBN} to output the full file name and line
1097 number in a standard, recognizable fashion each time a stack frame is
1098 displayed (which includes each time your program stops). This
1099 recognizable format looks like two @samp{\032} characters, followed by
1100 the file name, line number and character position separated by colons,
1101 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1102 @samp{\032} characters as a signal to display the source code for the
1106 @cindex @code{--epoch}
1107 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1108 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1109 routines so as to allow Epoch to display values of expressions in a
1112 @item -annotate @var{level}
1113 @cindex @code{--annotate}
1114 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1115 effect is identical to using @samp{set annotate @var{level}}
1116 (@pxref{Annotations}). The annotation @var{level} controls how much
1117 information @value{GDBN} prints together with its prompt, values of
1118 expressions, source lines, and other types of output. Level 0 is the
1119 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1120 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1121 that control @value{GDBN}, and level 2 has been deprecated.
1123 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1127 @cindex @code{--args}
1128 Change interpretation of command line so that arguments following the
1129 executable file are passed as command line arguments to the inferior.
1130 This option stops option processing.
1132 @item -baud @var{bps}
1134 @cindex @code{--baud}
1136 Set the line speed (baud rate or bits per second) of any serial
1137 interface used by @value{GDBN} for remote debugging.
1139 @item -l @var{timeout}
1141 Set the timeout (in seconds) of any communication used by @value{GDBN}
1142 for remote debugging.
1144 @item -tty @var{device}
1145 @itemx -t @var{device}
1146 @cindex @code{--tty}
1148 Run using @var{device} for your program's standard input and output.
1149 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1151 @c resolve the situation of these eventually
1153 @cindex @code{--tui}
1154 Activate the @dfn{Text User Interface} when starting. The Text User
1155 Interface manages several text windows on the terminal, showing
1156 source, assembly, registers and @value{GDBN} command outputs
1157 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1158 Text User Interface can be enabled by invoking the program
1159 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1160 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1163 @c @cindex @code{--xdb}
1164 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1165 @c For information, see the file @file{xdb_trans.html}, which is usually
1166 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1169 @item -interpreter @var{interp}
1170 @cindex @code{--interpreter}
1171 Use the interpreter @var{interp} for interface with the controlling
1172 program or device. This option is meant to be set by programs which
1173 communicate with @value{GDBN} using it as a back end.
1174 @xref{Interpreters, , Command Interpreters}.
1176 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1177 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1178 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1179 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1180 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1181 @sc{gdb/mi} interfaces are no longer supported.
1184 @cindex @code{--write}
1185 Open the executable and core files for both reading and writing. This
1186 is equivalent to the @samp{set write on} command inside @value{GDBN}
1190 @cindex @code{--statistics}
1191 This option causes @value{GDBN} to print statistics about time and
1192 memory usage after it completes each command and returns to the prompt.
1195 @cindex @code{--version}
1196 This option causes @value{GDBN} to print its version number and
1197 no-warranty blurb, and exit.
1202 @subsection What @value{GDBN} Does During Startup
1203 @cindex @value{GDBN} startup
1205 Here's the description of what @value{GDBN} does during session startup:
1209 Sets up the command interpreter as specified by the command line
1210 (@pxref{Mode Options, interpreter}).
1214 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1215 used when building @value{GDBN}; @pxref{System-wide configuration,
1216 ,System-wide configuration and settings}) and executes all the commands in
1220 Reads the init file (if any) in your home directory@footnote{On
1221 DOS/Windows systems, the home directory is the one pointed to by the
1222 @code{HOME} environment variable.} and executes all the commands in
1226 Processes command line options and operands.
1229 Reads and executes the commands from init file (if any) in the current
1230 working directory. This is only done if the current directory is
1231 different from your home directory. Thus, you can have more than one
1232 init file, one generic in your home directory, and another, specific
1233 to the program you are debugging, in the directory where you invoke
1237 Reads command files specified by the @samp{-x} option. @xref{Command
1238 Files}, for more details about @value{GDBN} command files.
1241 Reads the command history recorded in the @dfn{history file}.
1242 @xref{Command History}, for more details about the command history and the
1243 files where @value{GDBN} records it.
1246 Init files use the same syntax as @dfn{command files} (@pxref{Command
1247 Files}) and are processed by @value{GDBN} in the same way. The init
1248 file in your home directory can set options (such as @samp{set
1249 complaints}) that affect subsequent processing of command line options
1250 and operands. Init files are not executed if you use the @samp{-nx}
1251 option (@pxref{Mode Options, ,Choosing Modes}).
1253 To display the list of init files loaded by gdb at startup, you
1254 can use @kbd{gdb --help}.
1256 @cindex init file name
1257 @cindex @file{.gdbinit}
1258 @cindex @file{gdb.ini}
1259 The @value{GDBN} init files are normally called @file{.gdbinit}.
1260 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1261 the limitations of file names imposed by DOS filesystems. The Windows
1262 ports of @value{GDBN} use the standard name, but if they find a
1263 @file{gdb.ini} file, they warn you about that and suggest to rename
1264 the file to the standard name.
1268 @section Quitting @value{GDBN}
1269 @cindex exiting @value{GDBN}
1270 @cindex leaving @value{GDBN}
1273 @kindex quit @r{[}@var{expression}@r{]}
1274 @kindex q @r{(@code{quit})}
1275 @item quit @r{[}@var{expression}@r{]}
1277 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1278 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1279 do not supply @var{expression}, @value{GDBN} will terminate normally;
1280 otherwise it will terminate using the result of @var{expression} as the
1285 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1286 terminates the action of any @value{GDBN} command that is in progress and
1287 returns to @value{GDBN} command level. It is safe to type the interrupt
1288 character at any time because @value{GDBN} does not allow it to take effect
1289 until a time when it is safe.
1291 If you have been using @value{GDBN} to control an attached process or
1292 device, you can release it with the @code{detach} command
1293 (@pxref{Attach, ,Debugging an Already-running Process}).
1295 @node Shell Commands
1296 @section Shell Commands
1298 If you need to execute occasional shell commands during your
1299 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1300 just use the @code{shell} command.
1304 @cindex shell escape
1305 @item shell @var{command string}
1306 Invoke a standard shell to execute @var{command string}.
1307 If it exists, the environment variable @code{SHELL} determines which
1308 shell to run. Otherwise @value{GDBN} uses the default shell
1309 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1312 The utility @code{make} is often needed in development environments.
1313 You do not have to use the @code{shell} command for this purpose in
1318 @cindex calling make
1319 @item make @var{make-args}
1320 Execute the @code{make} program with the specified
1321 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1324 @node Logging Output
1325 @section Logging Output
1326 @cindex logging @value{GDBN} output
1327 @cindex save @value{GDBN} output to a file
1329 You may want to save the output of @value{GDBN} commands to a file.
1330 There are several commands to control @value{GDBN}'s logging.
1334 @item set logging on
1336 @item set logging off
1338 @cindex logging file name
1339 @item set logging file @var{file}
1340 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1341 @item set logging overwrite [on|off]
1342 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1343 you want @code{set logging on} to overwrite the logfile instead.
1344 @item set logging redirect [on|off]
1345 By default, @value{GDBN} output will go to both the terminal and the logfile.
1346 Set @code{redirect} if you want output to go only to the log file.
1347 @kindex show logging
1349 Show the current values of the logging settings.
1353 @chapter @value{GDBN} Commands
1355 You can abbreviate a @value{GDBN} command to the first few letters of the command
1356 name, if that abbreviation is unambiguous; and you can repeat certain
1357 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1358 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1359 show you the alternatives available, if there is more than one possibility).
1362 * Command Syntax:: How to give commands to @value{GDBN}
1363 * Completion:: Command completion
1364 * Help:: How to ask @value{GDBN} for help
1367 @node Command Syntax
1368 @section Command Syntax
1370 A @value{GDBN} command is a single line of input. There is no limit on
1371 how long it can be. It starts with a command name, which is followed by
1372 arguments whose meaning depends on the command name. For example, the
1373 command @code{step} accepts an argument which is the number of times to
1374 step, as in @samp{step 5}. You can also use the @code{step} command
1375 with no arguments. Some commands do not allow any arguments.
1377 @cindex abbreviation
1378 @value{GDBN} command names may always be truncated if that abbreviation is
1379 unambiguous. Other possible command abbreviations are listed in the
1380 documentation for individual commands. In some cases, even ambiguous
1381 abbreviations are allowed; for example, @code{s} is specially defined as
1382 equivalent to @code{step} even though there are other commands whose
1383 names start with @code{s}. You can test abbreviations by using them as
1384 arguments to the @code{help} command.
1386 @cindex repeating commands
1387 @kindex RET @r{(repeat last command)}
1388 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1389 repeat the previous command. Certain commands (for example, @code{run})
1390 will not repeat this way; these are commands whose unintentional
1391 repetition might cause trouble and which you are unlikely to want to
1392 repeat. User-defined commands can disable this feature; see
1393 @ref{Define, dont-repeat}.
1395 The @code{list} and @code{x} commands, when you repeat them with
1396 @key{RET}, construct new arguments rather than repeating
1397 exactly as typed. This permits easy scanning of source or memory.
1399 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1400 output, in a way similar to the common utility @code{more}
1401 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1402 @key{RET} too many in this situation, @value{GDBN} disables command
1403 repetition after any command that generates this sort of display.
1405 @kindex # @r{(a comment)}
1407 Any text from a @kbd{#} to the end of the line is a comment; it does
1408 nothing. This is useful mainly in command files (@pxref{Command
1409 Files,,Command Files}).
1411 @cindex repeating command sequences
1412 @kindex Ctrl-o @r{(operate-and-get-next)}
1413 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1414 commands. This command accepts the current line, like @key{RET}, and
1415 then fetches the next line relative to the current line from the history
1419 @section Command Completion
1422 @cindex word completion
1423 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1424 only one possibility; it can also show you what the valid possibilities
1425 are for the next word in a command, at any time. This works for @value{GDBN}
1426 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1428 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1429 of a word. If there is only one possibility, @value{GDBN} fills in the
1430 word, and waits for you to finish the command (or press @key{RET} to
1431 enter it). For example, if you type
1433 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1434 @c complete accuracy in these examples; space introduced for clarity.
1435 @c If texinfo enhancements make it unnecessary, it would be nice to
1436 @c replace " @key" by "@key" in the following...
1438 (@value{GDBP}) info bre @key{TAB}
1442 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1443 the only @code{info} subcommand beginning with @samp{bre}:
1446 (@value{GDBP}) info breakpoints
1450 You can either press @key{RET} at this point, to run the @code{info
1451 breakpoints} command, or backspace and enter something else, if
1452 @samp{breakpoints} does not look like the command you expected. (If you
1453 were sure you wanted @code{info breakpoints} in the first place, you
1454 might as well just type @key{RET} immediately after @samp{info bre},
1455 to exploit command abbreviations rather than command completion).
1457 If there is more than one possibility for the next word when you press
1458 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1459 characters and try again, or just press @key{TAB} a second time;
1460 @value{GDBN} displays all the possible completions for that word. For
1461 example, you might want to set a breakpoint on a subroutine whose name
1462 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1463 just sounds the bell. Typing @key{TAB} again displays all the
1464 function names in your program that begin with those characters, for
1468 (@value{GDBP}) b make_ @key{TAB}
1469 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1470 make_a_section_from_file make_environ
1471 make_abs_section make_function_type
1472 make_blockvector make_pointer_type
1473 make_cleanup make_reference_type
1474 make_command make_symbol_completion_list
1475 (@value{GDBP}) b make_
1479 After displaying the available possibilities, @value{GDBN} copies your
1480 partial input (@samp{b make_} in the example) so you can finish the
1483 If you just want to see the list of alternatives in the first place, you
1484 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1485 means @kbd{@key{META} ?}. You can type this either by holding down a
1486 key designated as the @key{META} shift on your keyboard (if there is
1487 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1489 @cindex quotes in commands
1490 @cindex completion of quoted strings
1491 Sometimes the string you need, while logically a ``word'', may contain
1492 parentheses or other characters that @value{GDBN} normally excludes from
1493 its notion of a word. To permit word completion to work in this
1494 situation, you may enclose words in @code{'} (single quote marks) in
1495 @value{GDBN} commands.
1497 The most likely situation where you might need this is in typing the
1498 name of a C@t{++} function. This is because C@t{++} allows function
1499 overloading (multiple definitions of the same function, distinguished
1500 by argument type). For example, when you want to set a breakpoint you
1501 may need to distinguish whether you mean the version of @code{name}
1502 that takes an @code{int} parameter, @code{name(int)}, or the version
1503 that takes a @code{float} parameter, @code{name(float)}. To use the
1504 word-completion facilities in this situation, type a single quote
1505 @code{'} at the beginning of the function name. This alerts
1506 @value{GDBN} that it may need to consider more information than usual
1507 when you press @key{TAB} or @kbd{M-?} to request word completion:
1510 (@value{GDBP}) b 'bubble( @kbd{M-?}
1511 bubble(double,double) bubble(int,int)
1512 (@value{GDBP}) b 'bubble(
1515 In some cases, @value{GDBN} can tell that completing a name requires using
1516 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1517 completing as much as it can) if you do not type the quote in the first
1521 (@value{GDBP}) b bub @key{TAB}
1522 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1523 (@value{GDBP}) b 'bubble(
1527 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1528 you have not yet started typing the argument list when you ask for
1529 completion on an overloaded symbol.
1531 For more information about overloaded functions, see @ref{C Plus Plus
1532 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1533 overload-resolution off} to disable overload resolution;
1534 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1536 @cindex completion of structure field names
1537 @cindex structure field name completion
1538 @cindex completion of union field names
1539 @cindex union field name completion
1540 When completing in an expression which looks up a field in a
1541 structure, @value{GDBN} also tries@footnote{The completer can be
1542 confused by certain kinds of invalid expressions. Also, it only
1543 examines the static type of the expression, not the dynamic type.} to
1544 limit completions to the field names available in the type of the
1548 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1549 magic to_delete to_fputs to_put to_rewind
1550 to_data to_flush to_isatty to_read to_write
1554 This is because the @code{gdb_stdout} is a variable of the type
1555 @code{struct ui_file} that is defined in @value{GDBN} sources as
1562 ui_file_flush_ftype *to_flush;
1563 ui_file_write_ftype *to_write;
1564 ui_file_fputs_ftype *to_fputs;
1565 ui_file_read_ftype *to_read;
1566 ui_file_delete_ftype *to_delete;
1567 ui_file_isatty_ftype *to_isatty;
1568 ui_file_rewind_ftype *to_rewind;
1569 ui_file_put_ftype *to_put;
1576 @section Getting Help
1577 @cindex online documentation
1580 You can always ask @value{GDBN} itself for information on its commands,
1581 using the command @code{help}.
1584 @kindex h @r{(@code{help})}
1587 You can use @code{help} (abbreviated @code{h}) with no arguments to
1588 display a short list of named classes of commands:
1592 List of classes of commands:
1594 aliases -- Aliases of other commands
1595 breakpoints -- Making program stop at certain points
1596 data -- Examining data
1597 files -- Specifying and examining files
1598 internals -- Maintenance commands
1599 obscure -- Obscure features
1600 running -- Running the program
1601 stack -- Examining the stack
1602 status -- Status inquiries
1603 support -- Support facilities
1604 tracepoints -- Tracing of program execution without
1605 stopping the program
1606 user-defined -- User-defined commands
1608 Type "help" followed by a class name for a list of
1609 commands in that class.
1610 Type "help" followed by command name for full
1612 Command name abbreviations are allowed if unambiguous.
1615 @c the above line break eliminates huge line overfull...
1617 @item help @var{class}
1618 Using one of the general help classes as an argument, you can get a
1619 list of the individual commands in that class. For example, here is the
1620 help display for the class @code{status}:
1623 (@value{GDBP}) help status
1628 @c Line break in "show" line falsifies real output, but needed
1629 @c to fit in smallbook page size.
1630 info -- Generic command for showing things
1631 about the program being debugged
1632 show -- Generic command for showing things
1635 Type "help" followed by command name for full
1637 Command name abbreviations are allowed if unambiguous.
1641 @item help @var{command}
1642 With a command name as @code{help} argument, @value{GDBN} displays a
1643 short paragraph on how to use that command.
1646 @item apropos @var{args}
1647 The @code{apropos} command searches through all of the @value{GDBN}
1648 commands, and their documentation, for the regular expression specified in
1649 @var{args}. It prints out all matches found. For example:
1660 set symbol-reloading -- Set dynamic symbol table reloading
1661 multiple times in one run
1662 show symbol-reloading -- Show dynamic symbol table reloading
1663 multiple times in one run
1668 @item complete @var{args}
1669 The @code{complete @var{args}} command lists all the possible completions
1670 for the beginning of a command. Use @var{args} to specify the beginning of the
1671 command you want completed. For example:
1677 @noindent results in:
1688 @noindent This is intended for use by @sc{gnu} Emacs.
1691 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1692 and @code{show} to inquire about the state of your program, or the state
1693 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1694 manual introduces each of them in the appropriate context. The listings
1695 under @code{info} and under @code{show} in the Index point to
1696 all the sub-commands. @xref{Index}.
1701 @kindex i @r{(@code{info})}
1703 This command (abbreviated @code{i}) is for describing the state of your
1704 program. For example, you can show the arguments passed to a function
1705 with @code{info args}, list the registers currently in use with @code{info
1706 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1707 You can get a complete list of the @code{info} sub-commands with
1708 @w{@code{help info}}.
1712 You can assign the result of an expression to an environment variable with
1713 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1714 @code{set prompt $}.
1718 In contrast to @code{info}, @code{show} is for describing the state of
1719 @value{GDBN} itself.
1720 You can change most of the things you can @code{show}, by using the
1721 related command @code{set}; for example, you can control what number
1722 system is used for displays with @code{set radix}, or simply inquire
1723 which is currently in use with @code{show radix}.
1726 To display all the settable parameters and their current
1727 values, you can use @code{show} with no arguments; you may also use
1728 @code{info set}. Both commands produce the same display.
1729 @c FIXME: "info set" violates the rule that "info" is for state of
1730 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1731 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1735 Here are three miscellaneous @code{show} subcommands, all of which are
1736 exceptional in lacking corresponding @code{set} commands:
1739 @kindex show version
1740 @cindex @value{GDBN} version number
1742 Show what version of @value{GDBN} is running. You should include this
1743 information in @value{GDBN} bug-reports. If multiple versions of
1744 @value{GDBN} are in use at your site, you may need to determine which
1745 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1746 commands are introduced, and old ones may wither away. Also, many
1747 system vendors ship variant versions of @value{GDBN}, and there are
1748 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1749 The version number is the same as the one announced when you start
1752 @kindex show copying
1753 @kindex info copying
1754 @cindex display @value{GDBN} copyright
1757 Display information about permission for copying @value{GDBN}.
1759 @kindex show warranty
1760 @kindex info warranty
1762 @itemx info warranty
1763 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1764 if your version of @value{GDBN} comes with one.
1769 @chapter Running Programs Under @value{GDBN}
1771 When you run a program under @value{GDBN}, you must first generate
1772 debugging information when you compile it.
1774 You may start @value{GDBN} with its arguments, if any, in an environment
1775 of your choice. If you are doing native debugging, you may redirect
1776 your program's input and output, debug an already running process, or
1777 kill a child process.
1780 * Compilation:: Compiling for debugging
1781 * Starting:: Starting your program
1782 * Arguments:: Your program's arguments
1783 * Environment:: Your program's environment
1785 * Working Directory:: Your program's working directory
1786 * Input/Output:: Your program's input and output
1787 * Attach:: Debugging an already-running process
1788 * Kill Process:: Killing the child process
1790 * Inferiors:: Debugging multiple inferiors
1791 * Threads:: Debugging programs with multiple threads
1792 * Processes:: Debugging programs with multiple processes
1793 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1797 @section Compiling for Debugging
1799 In order to debug a program effectively, you need to generate
1800 debugging information when you compile it. This debugging information
1801 is stored in the object file; it describes the data type of each
1802 variable or function and the correspondence between source line numbers
1803 and addresses in the executable code.
1805 To request debugging information, specify the @samp{-g} option when you run
1808 Programs that are to be shipped to your customers are compiled with
1809 optimizations, using the @samp{-O} compiler option. However, many
1810 compilers are unable to handle the @samp{-g} and @samp{-O} options
1811 together. Using those compilers, you cannot generate optimized
1812 executables containing debugging information.
1814 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1815 without @samp{-O}, making it possible to debug optimized code. We
1816 recommend that you @emph{always} use @samp{-g} whenever you compile a
1817 program. You may think your program is correct, but there is no sense
1818 in pushing your luck.
1820 @cindex optimized code, debugging
1821 @cindex debugging optimized code
1822 When you debug a program compiled with @samp{-g -O}, remember that the
1823 optimizer is rearranging your code; the debugger shows you what is
1824 really there. Do not be too surprised when the execution path does not
1825 exactly match your source file! An extreme example: if you define a
1826 variable, but never use it, @value{GDBN} never sees that
1827 variable---because the compiler optimizes it out of existence.
1829 Some things do not work as well with @samp{-g -O} as with just
1830 @samp{-g}, particularly on machines with instruction scheduling. If in
1831 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1832 please report it to us as a bug (including a test case!).
1833 @xref{Variables}, for more information about debugging optimized code.
1835 Older versions of the @sc{gnu} C compiler permitted a variant option
1836 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1837 format; if your @sc{gnu} C compiler has this option, do not use it.
1839 @value{GDBN} knows about preprocessor macros and can show you their
1840 expansion (@pxref{Macros}). Most compilers do not include information
1841 about preprocessor macros in the debugging information if you specify
1842 the @option{-g} flag alone, because this information is rather large.
1843 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1844 provides macro information if you specify the options
1845 @option{-gdwarf-2} and @option{-g3}; the former option requests
1846 debugging information in the Dwarf 2 format, and the latter requests
1847 ``extra information''. In the future, we hope to find more compact
1848 ways to represent macro information, so that it can be included with
1853 @section Starting your Program
1859 @kindex r @r{(@code{run})}
1862 Use the @code{run} command to start your program under @value{GDBN}.
1863 You must first specify the program name (except on VxWorks) with an
1864 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1865 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1866 (@pxref{Files, ,Commands to Specify Files}).
1870 If you are running your program in an execution environment that
1871 supports processes, @code{run} creates an inferior process and makes
1872 that process run your program. In some environments without processes,
1873 @code{run} jumps to the start of your program. Other targets,
1874 like @samp{remote}, are always running. If you get an error
1875 message like this one:
1878 The "remote" target does not support "run".
1879 Try "help target" or "continue".
1883 then use @code{continue} to run your program. You may need @code{load}
1884 first (@pxref{load}).
1886 The execution of a program is affected by certain information it
1887 receives from its superior. @value{GDBN} provides ways to specify this
1888 information, which you must do @emph{before} starting your program. (You
1889 can change it after starting your program, but such changes only affect
1890 your program the next time you start it.) This information may be
1891 divided into four categories:
1894 @item The @emph{arguments.}
1895 Specify the arguments to give your program as the arguments of the
1896 @code{run} command. If a shell is available on your target, the shell
1897 is used to pass the arguments, so that you may use normal conventions
1898 (such as wildcard expansion or variable substitution) in describing
1900 In Unix systems, you can control which shell is used with the
1901 @code{SHELL} environment variable.
1902 @xref{Arguments, ,Your Program's Arguments}.
1904 @item The @emph{environment.}
1905 Your program normally inherits its environment from @value{GDBN}, but you can
1906 use the @value{GDBN} commands @code{set environment} and @code{unset
1907 environment} to change parts of the environment that affect
1908 your program. @xref{Environment, ,Your Program's Environment}.
1910 @item The @emph{working directory.}
1911 Your program inherits its working directory from @value{GDBN}. You can set
1912 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1913 @xref{Working Directory, ,Your Program's Working Directory}.
1915 @item The @emph{standard input and output.}
1916 Your program normally uses the same device for standard input and
1917 standard output as @value{GDBN} is using. You can redirect input and output
1918 in the @code{run} command line, or you can use the @code{tty} command to
1919 set a different device for your program.
1920 @xref{Input/Output, ,Your Program's Input and Output}.
1923 @emph{Warning:} While input and output redirection work, you cannot use
1924 pipes to pass the output of the program you are debugging to another
1925 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1929 When you issue the @code{run} command, your program begins to execute
1930 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1931 of how to arrange for your program to stop. Once your program has
1932 stopped, you may call functions in your program, using the @code{print}
1933 or @code{call} commands. @xref{Data, ,Examining Data}.
1935 If the modification time of your symbol file has changed since the last
1936 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1937 table, and reads it again. When it does this, @value{GDBN} tries to retain
1938 your current breakpoints.
1943 @cindex run to main procedure
1944 The name of the main procedure can vary from language to language.
1945 With C or C@t{++}, the main procedure name is always @code{main}, but
1946 other languages such as Ada do not require a specific name for their
1947 main procedure. The debugger provides a convenient way to start the
1948 execution of the program and to stop at the beginning of the main
1949 procedure, depending on the language used.
1951 The @samp{start} command does the equivalent of setting a temporary
1952 breakpoint at the beginning of the main procedure and then invoking
1953 the @samp{run} command.
1955 @cindex elaboration phase
1956 Some programs contain an @dfn{elaboration} phase where some startup code is
1957 executed before the main procedure is called. This depends on the
1958 languages used to write your program. In C@t{++}, for instance,
1959 constructors for static and global objects are executed before
1960 @code{main} is called. It is therefore possible that the debugger stops
1961 before reaching the main procedure. However, the temporary breakpoint
1962 will remain to halt execution.
1964 Specify the arguments to give to your program as arguments to the
1965 @samp{start} command. These arguments will be given verbatim to the
1966 underlying @samp{run} command. Note that the same arguments will be
1967 reused if no argument is provided during subsequent calls to
1968 @samp{start} or @samp{run}.
1970 It is sometimes necessary to debug the program during elaboration. In
1971 these cases, using the @code{start} command would stop the execution of
1972 your program too late, as the program would have already completed the
1973 elaboration phase. Under these circumstances, insert breakpoints in your
1974 elaboration code before running your program.
1976 @kindex set exec-wrapper
1977 @item set exec-wrapper @var{wrapper}
1978 @itemx show exec-wrapper
1979 @itemx unset exec-wrapper
1980 When @samp{exec-wrapper} is set, the specified wrapper is used to
1981 launch programs for debugging. @value{GDBN} starts your program
1982 with a shell command of the form @kbd{exec @var{wrapper}
1983 @var{program}}. Quoting is added to @var{program} and its
1984 arguments, but not to @var{wrapper}, so you should add quotes if
1985 appropriate for your shell. The wrapper runs until it executes
1986 your program, and then @value{GDBN} takes control.
1988 You can use any program that eventually calls @code{execve} with
1989 its arguments as a wrapper. Several standard Unix utilities do
1990 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1991 with @code{exec "$@@"} will also work.
1993 For example, you can use @code{env} to pass an environment variable to
1994 the debugged program, without setting the variable in your shell's
1998 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2002 This command is available when debugging locally on most targets, excluding
2003 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2005 @kindex set disable-randomization
2006 @item set disable-randomization
2007 @itemx set disable-randomization on
2008 This option (enabled by default in @value{GDBN}) will turn off the native
2009 randomization of the virtual address space of the started program. This option
2010 is useful for multiple debugging sessions to make the execution better
2011 reproducible and memory addresses reusable across debugging sessions.
2013 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2017 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2020 @item set disable-randomization off
2021 Leave the behavior of the started executable unchanged. Some bugs rear their
2022 ugly heads only when the program is loaded at certain addresses. If your bug
2023 disappears when you run the program under @value{GDBN}, that might be because
2024 @value{GDBN} by default disables the address randomization on platforms, such
2025 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2026 disable-randomization off} to try to reproduce such elusive bugs.
2028 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2029 It protects the programs against some kinds of security attacks. In these
2030 cases the attacker needs to know the exact location of a concrete executable
2031 code. Randomizing its location makes it impossible to inject jumps misusing
2032 a code at its expected addresses.
2034 Prelinking shared libraries provides a startup performance advantage but it
2035 makes addresses in these libraries predictable for privileged processes by
2036 having just unprivileged access at the target system. Reading the shared
2037 library binary gives enough information for assembling the malicious code
2038 misusing it. Still even a prelinked shared library can get loaded at a new
2039 random address just requiring the regular relocation process during the
2040 startup. Shared libraries not already prelinked are always loaded at
2041 a randomly chosen address.
2043 Position independent executables (PIE) contain position independent code
2044 similar to the shared libraries and therefore such executables get loaded at
2045 a randomly chosen address upon startup. PIE executables always load even
2046 already prelinked shared libraries at a random address. You can build such
2047 executable using @command{gcc -fPIE -pie}.
2049 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2050 (as long as the randomization is enabled).
2052 @item show disable-randomization
2053 Show the current setting of the explicit disable of the native randomization of
2054 the virtual address space of the started program.
2059 @section Your Program's Arguments
2061 @cindex arguments (to your program)
2062 The arguments to your program can be specified by the arguments of the
2064 They are passed to a shell, which expands wildcard characters and
2065 performs redirection of I/O, and thence to your program. Your
2066 @code{SHELL} environment variable (if it exists) specifies what shell
2067 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2068 the default shell (@file{/bin/sh} on Unix).
2070 On non-Unix systems, the program is usually invoked directly by
2071 @value{GDBN}, which emulates I/O redirection via the appropriate system
2072 calls, and the wildcard characters are expanded by the startup code of
2073 the program, not by the shell.
2075 @code{run} with no arguments uses the same arguments used by the previous
2076 @code{run}, or those set by the @code{set args} command.
2081 Specify the arguments to be used the next time your program is run. If
2082 @code{set args} has no arguments, @code{run} executes your program
2083 with no arguments. Once you have run your program with arguments,
2084 using @code{set args} before the next @code{run} is the only way to run
2085 it again without arguments.
2089 Show the arguments to give your program when it is started.
2093 @section Your Program's Environment
2095 @cindex environment (of your program)
2096 The @dfn{environment} consists of a set of environment variables and
2097 their values. Environment variables conventionally record such things as
2098 your user name, your home directory, your terminal type, and your search
2099 path for programs to run. Usually you set up environment variables with
2100 the shell and they are inherited by all the other programs you run. When
2101 debugging, it can be useful to try running your program with a modified
2102 environment without having to start @value{GDBN} over again.
2106 @item path @var{directory}
2107 Add @var{directory} to the front of the @code{PATH} environment variable
2108 (the search path for executables) that will be passed to your program.
2109 The value of @code{PATH} used by @value{GDBN} does not change.
2110 You may specify several directory names, separated by whitespace or by a
2111 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2112 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2113 is moved to the front, so it is searched sooner.
2115 You can use the string @samp{$cwd} to refer to whatever is the current
2116 working directory at the time @value{GDBN} searches the path. If you
2117 use @samp{.} instead, it refers to the directory where you executed the
2118 @code{path} command. @value{GDBN} replaces @samp{.} in the
2119 @var{directory} argument (with the current path) before adding
2120 @var{directory} to the search path.
2121 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2122 @c document that, since repeating it would be a no-op.
2126 Display the list of search paths for executables (the @code{PATH}
2127 environment variable).
2129 @kindex show environment
2130 @item show environment @r{[}@var{varname}@r{]}
2131 Print the value of environment variable @var{varname} to be given to
2132 your program when it starts. If you do not supply @var{varname},
2133 print the names and values of all environment variables to be given to
2134 your program. You can abbreviate @code{environment} as @code{env}.
2136 @kindex set environment
2137 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2138 Set environment variable @var{varname} to @var{value}. The value
2139 changes for your program only, not for @value{GDBN} itself. @var{value} may
2140 be any string; the values of environment variables are just strings, and
2141 any interpretation is supplied by your program itself. The @var{value}
2142 parameter is optional; if it is eliminated, the variable is set to a
2144 @c "any string" here does not include leading, trailing
2145 @c blanks. Gnu asks: does anyone care?
2147 For example, this command:
2154 tells the debugged program, when subsequently run, that its user is named
2155 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2156 are not actually required.)
2158 @kindex unset environment
2159 @item unset environment @var{varname}
2160 Remove variable @var{varname} from the environment to be passed to your
2161 program. This is different from @samp{set env @var{varname} =};
2162 @code{unset environment} removes the variable from the environment,
2163 rather than assigning it an empty value.
2166 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2168 by your @code{SHELL} environment variable if it exists (or
2169 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2170 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2171 @file{.bashrc} for BASH---any variables you set in that file affect
2172 your program. You may wish to move setting of environment variables to
2173 files that are only run when you sign on, such as @file{.login} or
2176 @node Working Directory
2177 @section Your Program's Working Directory
2179 @cindex working directory (of your program)
2180 Each time you start your program with @code{run}, it inherits its
2181 working directory from the current working directory of @value{GDBN}.
2182 The @value{GDBN} working directory is initially whatever it inherited
2183 from its parent process (typically the shell), but you can specify a new
2184 working directory in @value{GDBN} with the @code{cd} command.
2186 The @value{GDBN} working directory also serves as a default for the commands
2187 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2192 @cindex change working directory
2193 @item cd @var{directory}
2194 Set the @value{GDBN} working directory to @var{directory}.
2198 Print the @value{GDBN} working directory.
2201 It is generally impossible to find the current working directory of
2202 the process being debugged (since a program can change its directory
2203 during its run). If you work on a system where @value{GDBN} is
2204 configured with the @file{/proc} support, you can use the @code{info
2205 proc} command (@pxref{SVR4 Process Information}) to find out the
2206 current working directory of the debuggee.
2209 @section Your Program's Input and Output
2214 By default, the program you run under @value{GDBN} does input and output to
2215 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2216 to its own terminal modes to interact with you, but it records the terminal
2217 modes your program was using and switches back to them when you continue
2218 running your program.
2221 @kindex info terminal
2223 Displays information recorded by @value{GDBN} about the terminal modes your
2227 You can redirect your program's input and/or output using shell
2228 redirection with the @code{run} command. For example,
2235 starts your program, diverting its output to the file @file{outfile}.
2238 @cindex controlling terminal
2239 Another way to specify where your program should do input and output is
2240 with the @code{tty} command. This command accepts a file name as
2241 argument, and causes this file to be the default for future @code{run}
2242 commands. It also resets the controlling terminal for the child
2243 process, for future @code{run} commands. For example,
2250 directs that processes started with subsequent @code{run} commands
2251 default to do input and output on the terminal @file{/dev/ttyb} and have
2252 that as their controlling terminal.
2254 An explicit redirection in @code{run} overrides the @code{tty} command's
2255 effect on the input/output device, but not its effect on the controlling
2258 When you use the @code{tty} command or redirect input in the @code{run}
2259 command, only the input @emph{for your program} is affected. The input
2260 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2261 for @code{set inferior-tty}.
2263 @cindex inferior tty
2264 @cindex set inferior controlling terminal
2265 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2266 display the name of the terminal that will be used for future runs of your
2270 @item set inferior-tty /dev/ttyb
2271 @kindex set inferior-tty
2272 Set the tty for the program being debugged to /dev/ttyb.
2274 @item show inferior-tty
2275 @kindex show inferior-tty
2276 Show the current tty for the program being debugged.
2280 @section Debugging an Already-running Process
2285 @item attach @var{process-id}
2286 This command attaches to a running process---one that was started
2287 outside @value{GDBN}. (@code{info files} shows your active
2288 targets.) The command takes as argument a process ID. The usual way to
2289 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2290 or with the @samp{jobs -l} shell command.
2292 @code{attach} does not repeat if you press @key{RET} a second time after
2293 executing the command.
2296 To use @code{attach}, your program must be running in an environment
2297 which supports processes; for example, @code{attach} does not work for
2298 programs on bare-board targets that lack an operating system. You must
2299 also have permission to send the process a signal.
2301 When you use @code{attach}, the debugger finds the program running in
2302 the process first by looking in the current working directory, then (if
2303 the program is not found) by using the source file search path
2304 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2305 the @code{file} command to load the program. @xref{Files, ,Commands to
2308 The first thing @value{GDBN} does after arranging to debug the specified
2309 process is to stop it. You can examine and modify an attached process
2310 with all the @value{GDBN} commands that are ordinarily available when
2311 you start processes with @code{run}. You can insert breakpoints; you
2312 can step and continue; you can modify storage. If you would rather the
2313 process continue running, you may use the @code{continue} command after
2314 attaching @value{GDBN} to the process.
2319 When you have finished debugging the attached process, you can use the
2320 @code{detach} command to release it from @value{GDBN} control. Detaching
2321 the process continues its execution. After the @code{detach} command,
2322 that process and @value{GDBN} become completely independent once more, and you
2323 are ready to @code{attach} another process or start one with @code{run}.
2324 @code{detach} does not repeat if you press @key{RET} again after
2325 executing the command.
2328 If you exit @value{GDBN} while you have an attached process, you detach
2329 that process. If you use the @code{run} command, you kill that process.
2330 By default, @value{GDBN} asks for confirmation if you try to do either of these
2331 things; you can control whether or not you need to confirm by using the
2332 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2336 @section Killing the Child Process
2341 Kill the child process in which your program is running under @value{GDBN}.
2344 This command is useful if you wish to debug a core dump instead of a
2345 running process. @value{GDBN} ignores any core dump file while your program
2348 On some operating systems, a program cannot be executed outside @value{GDBN}
2349 while you have breakpoints set on it inside @value{GDBN}. You can use the
2350 @code{kill} command in this situation to permit running your program
2351 outside the debugger.
2353 The @code{kill} command is also useful if you wish to recompile and
2354 relink your program, since on many systems it is impossible to modify an
2355 executable file while it is running in a process. In this case, when you
2356 next type @code{run}, @value{GDBN} notices that the file has changed, and
2357 reads the symbol table again (while trying to preserve your current
2358 breakpoint settings).
2361 @section Debugging Multiple Inferiors
2363 Some @value{GDBN} targets are able to run multiple processes created
2364 from a single executable. This can happen, for instance, with an
2365 embedded system reporting back several processes via the remote
2369 @value{GDBN} represents the state of each program execution with an
2370 object called an @dfn{inferior}. An inferior typically corresponds to
2371 a process, but is more general and applies also to targets that do not
2372 have processes. Inferiors may be created before a process runs, and
2373 may (in future) be retained after a process exits. Each run of an
2374 executable creates a new inferior, as does each attachment to an
2375 existing process. Inferiors have unique identifiers that are
2376 different from process ids, and may optionally be named as well.
2377 Usually each inferior will also have its own distinct address space,
2378 although some embedded targets may have several inferiors running in
2379 different parts of a single space.
2381 Each inferior may in turn have multiple threads running in it.
2383 To find out what inferiors exist at any moment, use @code{info inferiors}:
2386 @kindex info inferiors
2387 @item info inferiors
2388 Print a list of all inferiors currently being managed by @value{GDBN}.
2390 @kindex set print inferior-events
2391 @cindex print messages on inferior start and exit
2392 @item set print inferior-events
2393 @itemx set print inferior-events on
2394 @itemx set print inferior-events off
2395 The @code{set print inferior-events} command allows you to enable or
2396 disable printing of messages when @value{GDBN} notices that new
2397 inferiors have started or that inferiors have exited or have been
2398 detached. By default, these messages will not be printed.
2400 @kindex show print inferior-events
2401 @item show print inferior-events
2402 Show whether messages will be printed when @value{GDBN} detects that
2403 inferiors have started, exited or have been detached.
2407 @section Debugging Programs with Multiple Threads
2409 @cindex threads of execution
2410 @cindex multiple threads
2411 @cindex switching threads
2412 In some operating systems, such as HP-UX and Solaris, a single program
2413 may have more than one @dfn{thread} of execution. The precise semantics
2414 of threads differ from one operating system to another, but in general
2415 the threads of a single program are akin to multiple processes---except
2416 that they share one address space (that is, they can all examine and
2417 modify the same variables). On the other hand, each thread has its own
2418 registers and execution stack, and perhaps private memory.
2420 @value{GDBN} provides these facilities for debugging multi-thread
2424 @item automatic notification of new threads
2425 @item @samp{thread @var{threadno}}, a command to switch among threads
2426 @item @samp{info threads}, a command to inquire about existing threads
2427 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2428 a command to apply a command to a list of threads
2429 @item thread-specific breakpoints
2430 @item @samp{set print thread-events}, which controls printing of
2431 messages on thread start and exit.
2435 @emph{Warning:} These facilities are not yet available on every
2436 @value{GDBN} configuration where the operating system supports threads.
2437 If your @value{GDBN} does not support threads, these commands have no
2438 effect. For example, a system without thread support shows no output
2439 from @samp{info threads}, and always rejects the @code{thread} command,
2443 (@value{GDBP}) info threads
2444 (@value{GDBP}) thread 1
2445 Thread ID 1 not known. Use the "info threads" command to
2446 see the IDs of currently known threads.
2448 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2449 @c doesn't support threads"?
2452 @cindex focus of debugging
2453 @cindex current thread
2454 The @value{GDBN} thread debugging facility allows you to observe all
2455 threads while your program runs---but whenever @value{GDBN} takes
2456 control, one thread in particular is always the focus of debugging.
2457 This thread is called the @dfn{current thread}. Debugging commands show
2458 program information from the perspective of the current thread.
2460 @cindex @code{New} @var{systag} message
2461 @cindex thread identifier (system)
2462 @c FIXME-implementors!! It would be more helpful if the [New...] message
2463 @c included GDB's numeric thread handle, so you could just go to that
2464 @c thread without first checking `info threads'.
2465 Whenever @value{GDBN} detects a new thread in your program, it displays
2466 the target system's identification for the thread with a message in the
2467 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2468 whose form varies depending on the particular system. For example, on
2469 @sc{gnu}/Linux, you might see
2472 [New Thread 46912507313328 (LWP 25582)]
2476 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2477 the @var{systag} is simply something like @samp{process 368}, with no
2480 @c FIXME!! (1) Does the [New...] message appear even for the very first
2481 @c thread of a program, or does it only appear for the
2482 @c second---i.e.@: when it becomes obvious we have a multithread
2484 @c (2) *Is* there necessarily a first thread always? Or do some
2485 @c multithread systems permit starting a program with multiple
2486 @c threads ab initio?
2488 @cindex thread number
2489 @cindex thread identifier (GDB)
2490 For debugging purposes, @value{GDBN} associates its own thread
2491 number---always a single integer---with each thread in your program.
2494 @kindex info threads
2496 Display a summary of all threads currently in your
2497 program. @value{GDBN} displays for each thread (in this order):
2501 the thread number assigned by @value{GDBN}
2504 the target system's thread identifier (@var{systag})
2507 the current stack frame summary for that thread
2511 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2512 indicates the current thread.
2516 @c end table here to get a little more width for example
2519 (@value{GDBP}) info threads
2520 3 process 35 thread 27 0x34e5 in sigpause ()
2521 2 process 35 thread 23 0x34e5 in sigpause ()
2522 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2528 @cindex debugging multithreaded programs (on HP-UX)
2529 @cindex thread identifier (GDB), on HP-UX
2530 For debugging purposes, @value{GDBN} associates its own thread
2531 number---a small integer assigned in thread-creation order---with each
2532 thread in your program.
2534 @cindex @code{New} @var{systag} message, on HP-UX
2535 @cindex thread identifier (system), on HP-UX
2536 @c FIXME-implementors!! It would be more helpful if the [New...] message
2537 @c included GDB's numeric thread handle, so you could just go to that
2538 @c thread without first checking `info threads'.
2539 Whenever @value{GDBN} detects a new thread in your program, it displays
2540 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2541 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2542 whose form varies depending on the particular system. For example, on
2546 [New thread 2 (system thread 26594)]
2550 when @value{GDBN} notices a new thread.
2553 @kindex info threads (HP-UX)
2555 Display a summary of all threads currently in your
2556 program. @value{GDBN} displays for each thread (in this order):
2559 @item the thread number assigned by @value{GDBN}
2561 @item the target system's thread identifier (@var{systag})
2563 @item the current stack frame summary for that thread
2567 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2568 indicates the current thread.
2572 @c end table here to get a little more width for example
2575 (@value{GDBP}) info threads
2576 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2578 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2579 from /usr/lib/libc.2
2580 1 system thread 27905 0x7b003498 in _brk () \@*
2581 from /usr/lib/libc.2
2584 On Solaris, you can display more information about user threads with a
2585 Solaris-specific command:
2588 @item maint info sol-threads
2589 @kindex maint info sol-threads
2590 @cindex thread info (Solaris)
2591 Display info on Solaris user threads.
2595 @kindex thread @var{threadno}
2596 @item thread @var{threadno}
2597 Make thread number @var{threadno} the current thread. The command
2598 argument @var{threadno} is the internal @value{GDBN} thread number, as
2599 shown in the first field of the @samp{info threads} display.
2600 @value{GDBN} responds by displaying the system identifier of the thread
2601 you selected, and its current stack frame summary:
2604 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2605 (@value{GDBP}) thread 2
2606 [Switching to process 35 thread 23]
2607 0x34e5 in sigpause ()
2611 As with the @samp{[New @dots{}]} message, the form of the text after
2612 @samp{Switching to} depends on your system's conventions for identifying
2615 @kindex thread apply
2616 @cindex apply command to several threads
2617 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2618 The @code{thread apply} command allows you to apply the named
2619 @var{command} to one or more threads. Specify the numbers of the
2620 threads that you want affected with the command argument
2621 @var{threadno}. It can be a single thread number, one of the numbers
2622 shown in the first field of the @samp{info threads} display; or it
2623 could be a range of thread numbers, as in @code{2-4}. To apply a
2624 command to all threads, type @kbd{thread apply all @var{command}}.
2626 @kindex set print thread-events
2627 @cindex print messages on thread start and exit
2628 @item set print thread-events
2629 @itemx set print thread-events on
2630 @itemx set print thread-events off
2631 The @code{set print thread-events} command allows you to enable or
2632 disable printing of messages when @value{GDBN} notices that new threads have
2633 started or that threads have exited. By default, these messages will
2634 be printed if detection of these events is supported by the target.
2635 Note that these messages cannot be disabled on all targets.
2637 @kindex show print thread-events
2638 @item show print thread-events
2639 Show whether messages will be printed when @value{GDBN} detects that threads
2640 have started and exited.
2643 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2644 more information about how @value{GDBN} behaves when you stop and start
2645 programs with multiple threads.
2647 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2648 watchpoints in programs with multiple threads.
2651 @section Debugging Programs with Multiple Processes
2653 @cindex fork, debugging programs which call
2654 @cindex multiple processes
2655 @cindex processes, multiple
2656 On most systems, @value{GDBN} has no special support for debugging
2657 programs which create additional processes using the @code{fork}
2658 function. When a program forks, @value{GDBN} will continue to debug the
2659 parent process and the child process will run unimpeded. If you have
2660 set a breakpoint in any code which the child then executes, the child
2661 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2662 will cause it to terminate.
2664 However, if you want to debug the child process there is a workaround
2665 which isn't too painful. Put a call to @code{sleep} in the code which
2666 the child process executes after the fork. It may be useful to sleep
2667 only if a certain environment variable is set, or a certain file exists,
2668 so that the delay need not occur when you don't want to run @value{GDBN}
2669 on the child. While the child is sleeping, use the @code{ps} program to
2670 get its process ID. Then tell @value{GDBN} (a new invocation of
2671 @value{GDBN} if you are also debugging the parent process) to attach to
2672 the child process (@pxref{Attach}). From that point on you can debug
2673 the child process just like any other process which you attached to.
2675 On some systems, @value{GDBN} provides support for debugging programs that
2676 create additional processes using the @code{fork} or @code{vfork} functions.
2677 Currently, the only platforms with this feature are HP-UX (11.x and later
2678 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2680 By default, when a program forks, @value{GDBN} will continue to debug
2681 the parent process and the child process will run unimpeded.
2683 If you want to follow the child process instead of the parent process,
2684 use the command @w{@code{set follow-fork-mode}}.
2687 @kindex set follow-fork-mode
2688 @item set follow-fork-mode @var{mode}
2689 Set the debugger response to a program call of @code{fork} or
2690 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2691 process. The @var{mode} argument can be:
2695 The original process is debugged after a fork. The child process runs
2696 unimpeded. This is the default.
2699 The new process is debugged after a fork. The parent process runs
2704 @kindex show follow-fork-mode
2705 @item show follow-fork-mode
2706 Display the current debugger response to a @code{fork} or @code{vfork} call.
2709 @cindex debugging multiple processes
2710 On Linux, if you want to debug both the parent and child processes, use the
2711 command @w{@code{set detach-on-fork}}.
2714 @kindex set detach-on-fork
2715 @item set detach-on-fork @var{mode}
2716 Tells gdb whether to detach one of the processes after a fork, or
2717 retain debugger control over them both.
2721 The child process (or parent process, depending on the value of
2722 @code{follow-fork-mode}) will be detached and allowed to run
2723 independently. This is the default.
2726 Both processes will be held under the control of @value{GDBN}.
2727 One process (child or parent, depending on the value of
2728 @code{follow-fork-mode}) is debugged as usual, while the other
2733 @kindex show detach-on-fork
2734 @item show detach-on-fork
2735 Show whether detach-on-fork mode is on/off.
2738 If you choose to set @samp{detach-on-fork} mode off, then
2739 @value{GDBN} will retain control of all forked processes (including
2740 nested forks). You can list the forked processes under the control of
2741 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2742 from one fork to another by using the @w{@code{fork}} command.
2747 Print a list of all forked processes under the control of @value{GDBN}.
2748 The listing will include a fork id, a process id, and the current
2749 position (program counter) of the process.
2751 @kindex fork @var{fork-id}
2752 @item fork @var{fork-id}
2753 Make fork number @var{fork-id} the current process. The argument
2754 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2755 as shown in the first field of the @samp{info forks} display.
2757 @kindex process @var{process-id}
2758 @item process @var{process-id}
2759 Make process number @var{process-id} the current process. The
2760 argument @var{process-id} must be one that is listed in the output of
2765 To quit debugging one of the forked processes, you can either detach
2766 from it by using the @w{@code{detach fork}} command (allowing it to
2767 run independently), or delete (and kill) it using the
2768 @w{@code{delete fork}} command.
2771 @kindex detach fork @var{fork-id}
2772 @item detach fork @var{fork-id}
2773 Detach from the process identified by @value{GDBN} fork number
2774 @var{fork-id}, and remove it from the fork list. The process will be
2775 allowed to run independently.
2777 @kindex delete fork @var{fork-id}
2778 @item delete fork @var{fork-id}
2779 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2780 and remove it from the fork list.
2784 If you ask to debug a child process and a @code{vfork} is followed by an
2785 @code{exec}, @value{GDBN} executes the new target up to the first
2786 breakpoint in the new target. If you have a breakpoint set on
2787 @code{main} in your original program, the breakpoint will also be set on
2788 the child process's @code{main}.
2790 When a child process is spawned by @code{vfork}, you cannot debug the
2791 child or parent until an @code{exec} call completes.
2793 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2794 call executes, the new target restarts. To restart the parent process,
2795 use the @code{file} command with the parent executable name as its
2798 You can use the @code{catch} command to make @value{GDBN} stop whenever
2799 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2800 Catchpoints, ,Setting Catchpoints}.
2802 @node Checkpoint/Restart
2803 @section Setting a @emph{Bookmark} to Return to Later
2808 @cindex snapshot of a process
2809 @cindex rewind program state
2811 On certain operating systems@footnote{Currently, only
2812 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2813 program's state, called a @dfn{checkpoint}, and come back to it
2816 Returning to a checkpoint effectively undoes everything that has
2817 happened in the program since the @code{checkpoint} was saved. This
2818 includes changes in memory, registers, and even (within some limits)
2819 system state. Effectively, it is like going back in time to the
2820 moment when the checkpoint was saved.
2822 Thus, if you're stepping thru a program and you think you're
2823 getting close to the point where things go wrong, you can save
2824 a checkpoint. Then, if you accidentally go too far and miss
2825 the critical statement, instead of having to restart your program
2826 from the beginning, you can just go back to the checkpoint and
2827 start again from there.
2829 This can be especially useful if it takes a lot of time or
2830 steps to reach the point where you think the bug occurs.
2832 To use the @code{checkpoint}/@code{restart} method of debugging:
2837 Save a snapshot of the debugged program's current execution state.
2838 The @code{checkpoint} command takes no arguments, but each checkpoint
2839 is assigned a small integer id, similar to a breakpoint id.
2841 @kindex info checkpoints
2842 @item info checkpoints
2843 List the checkpoints that have been saved in the current debugging
2844 session. For each checkpoint, the following information will be
2851 @item Source line, or label
2854 @kindex restart @var{checkpoint-id}
2855 @item restart @var{checkpoint-id}
2856 Restore the program state that was saved as checkpoint number
2857 @var{checkpoint-id}. All program variables, registers, stack frames
2858 etc.@: will be returned to the values that they had when the checkpoint
2859 was saved. In essence, gdb will ``wind back the clock'' to the point
2860 in time when the checkpoint was saved.
2862 Note that breakpoints, @value{GDBN} variables, command history etc.
2863 are not affected by restoring a checkpoint. In general, a checkpoint
2864 only restores things that reside in the program being debugged, not in
2867 @kindex delete checkpoint @var{checkpoint-id}
2868 @item delete checkpoint @var{checkpoint-id}
2869 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2873 Returning to a previously saved checkpoint will restore the user state
2874 of the program being debugged, plus a significant subset of the system
2875 (OS) state, including file pointers. It won't ``un-write'' data from
2876 a file, but it will rewind the file pointer to the previous location,
2877 so that the previously written data can be overwritten. For files
2878 opened in read mode, the pointer will also be restored so that the
2879 previously read data can be read again.
2881 Of course, characters that have been sent to a printer (or other
2882 external device) cannot be ``snatched back'', and characters received
2883 from eg.@: a serial device can be removed from internal program buffers,
2884 but they cannot be ``pushed back'' into the serial pipeline, ready to
2885 be received again. Similarly, the actual contents of files that have
2886 been changed cannot be restored (at this time).
2888 However, within those constraints, you actually can ``rewind'' your
2889 program to a previously saved point in time, and begin debugging it
2890 again --- and you can change the course of events so as to debug a
2891 different execution path this time.
2893 @cindex checkpoints and process id
2894 Finally, there is one bit of internal program state that will be
2895 different when you return to a checkpoint --- the program's process
2896 id. Each checkpoint will have a unique process id (or @var{pid}),
2897 and each will be different from the program's original @var{pid}.
2898 If your program has saved a local copy of its process id, this could
2899 potentially pose a problem.
2901 @subsection A Non-obvious Benefit of Using Checkpoints
2903 On some systems such as @sc{gnu}/Linux, address space randomization
2904 is performed on new processes for security reasons. This makes it
2905 difficult or impossible to set a breakpoint, or watchpoint, on an
2906 absolute address if you have to restart the program, since the
2907 absolute location of a symbol will change from one execution to the
2910 A checkpoint, however, is an @emph{identical} copy of a process.
2911 Therefore if you create a checkpoint at (eg.@:) the start of main,
2912 and simply return to that checkpoint instead of restarting the
2913 process, you can avoid the effects of address randomization and
2914 your symbols will all stay in the same place.
2917 @chapter Stopping and Continuing
2919 The principal purposes of using a debugger are so that you can stop your
2920 program before it terminates; or so that, if your program runs into
2921 trouble, you can investigate and find out why.
2923 Inside @value{GDBN}, your program may stop for any of several reasons,
2924 such as a signal, a breakpoint, or reaching a new line after a
2925 @value{GDBN} command such as @code{step}. You may then examine and
2926 change variables, set new breakpoints or remove old ones, and then
2927 continue execution. Usually, the messages shown by @value{GDBN} provide
2928 ample explanation of the status of your program---but you can also
2929 explicitly request this information at any time.
2932 @kindex info program
2934 Display information about the status of your program: whether it is
2935 running or not, what process it is, and why it stopped.
2939 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2940 * Continuing and Stepping:: Resuming execution
2942 * Thread Stops:: Stopping and starting multi-thread programs
2946 @section Breakpoints, Watchpoints, and Catchpoints
2949 A @dfn{breakpoint} makes your program stop whenever a certain point in
2950 the program is reached. For each breakpoint, you can add conditions to
2951 control in finer detail whether your program stops. You can set
2952 breakpoints with the @code{break} command and its variants (@pxref{Set
2953 Breaks, ,Setting Breakpoints}), to specify the place where your program
2954 should stop by line number, function name or exact address in the
2957 On some systems, you can set breakpoints in shared libraries before
2958 the executable is run. There is a minor limitation on HP-UX systems:
2959 you must wait until the executable is run in order to set breakpoints
2960 in shared library routines that are not called directly by the program
2961 (for example, routines that are arguments in a @code{pthread_create}
2965 @cindex data breakpoints
2966 @cindex memory tracing
2967 @cindex breakpoint on memory address
2968 @cindex breakpoint on variable modification
2969 A @dfn{watchpoint} is a special breakpoint that stops your program
2970 when the value of an expression changes. The expression may be a value
2971 of a variable, or it could involve values of one or more variables
2972 combined by operators, such as @samp{a + b}. This is sometimes called
2973 @dfn{data breakpoints}. You must use a different command to set
2974 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2975 from that, you can manage a watchpoint like any other breakpoint: you
2976 enable, disable, and delete both breakpoints and watchpoints using the
2979 You can arrange to have values from your program displayed automatically
2980 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2984 @cindex breakpoint on events
2985 A @dfn{catchpoint} is another special breakpoint that stops your program
2986 when a certain kind of event occurs, such as the throwing of a C@t{++}
2987 exception or the loading of a library. As with watchpoints, you use a
2988 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2989 Catchpoints}), but aside from that, you can manage a catchpoint like any
2990 other breakpoint. (To stop when your program receives a signal, use the
2991 @code{handle} command; see @ref{Signals, ,Signals}.)
2993 @cindex breakpoint numbers
2994 @cindex numbers for breakpoints
2995 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2996 catchpoint when you create it; these numbers are successive integers
2997 starting with one. In many of the commands for controlling various
2998 features of breakpoints you use the breakpoint number to say which
2999 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3000 @dfn{disabled}; if disabled, it has no effect on your program until you
3003 @cindex breakpoint ranges
3004 @cindex ranges of breakpoints
3005 Some @value{GDBN} commands accept a range of breakpoints on which to
3006 operate. A breakpoint range is either a single breakpoint number, like
3007 @samp{5}, or two such numbers, in increasing order, separated by a
3008 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3009 all breakpoints in that range are operated on.
3012 * Set Breaks:: Setting breakpoints
3013 * Set Watchpoints:: Setting watchpoints
3014 * Set Catchpoints:: Setting catchpoints
3015 * Delete Breaks:: Deleting breakpoints
3016 * Disabling:: Disabling breakpoints
3017 * Conditions:: Break conditions
3018 * Break Commands:: Breakpoint command lists
3019 * Error in Breakpoints:: ``Cannot insert breakpoints''
3020 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3024 @subsection Setting Breakpoints
3026 @c FIXME LMB what does GDB do if no code on line of breakpt?
3027 @c consider in particular declaration with/without initialization.
3029 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3032 @kindex b @r{(@code{break})}
3033 @vindex $bpnum@r{, convenience variable}
3034 @cindex latest breakpoint
3035 Breakpoints are set with the @code{break} command (abbreviated
3036 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3037 number of the breakpoint you've set most recently; see @ref{Convenience
3038 Vars,, Convenience Variables}, for a discussion of what you can do with
3039 convenience variables.
3042 @item break @var{location}
3043 Set a breakpoint at the given @var{location}, which can specify a
3044 function name, a line number, or an address of an instruction.
3045 (@xref{Specify Location}, for a list of all the possible ways to
3046 specify a @var{location}.) The breakpoint will stop your program just
3047 before it executes any of the code in the specified @var{location}.
3049 When using source languages that permit overloading of symbols, such as
3050 C@t{++}, a function name may refer to more than one possible place to break.
3051 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3054 It is also possible to insert a breakpoint that will stop the program
3055 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3056 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3059 When called without any arguments, @code{break} sets a breakpoint at
3060 the next instruction to be executed in the selected stack frame
3061 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3062 innermost, this makes your program stop as soon as control
3063 returns to that frame. This is similar to the effect of a
3064 @code{finish} command in the frame inside the selected frame---except
3065 that @code{finish} does not leave an active breakpoint. If you use
3066 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3067 the next time it reaches the current location; this may be useful
3070 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3071 least one instruction has been executed. If it did not do this, you
3072 would be unable to proceed past a breakpoint without first disabling the
3073 breakpoint. This rule applies whether or not the breakpoint already
3074 existed when your program stopped.
3076 @item break @dots{} if @var{cond}
3077 Set a breakpoint with condition @var{cond}; evaluate the expression
3078 @var{cond} each time the breakpoint is reached, and stop only if the
3079 value is nonzero---that is, if @var{cond} evaluates as true.
3080 @samp{@dots{}} stands for one of the possible arguments described
3081 above (or no argument) specifying where to break. @xref{Conditions,
3082 ,Break Conditions}, for more information on breakpoint conditions.
3085 @item tbreak @var{args}
3086 Set a breakpoint enabled only for one stop. @var{args} are the
3087 same as for the @code{break} command, and the breakpoint is set in the same
3088 way, but the breakpoint is automatically deleted after the first time your
3089 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3092 @cindex hardware breakpoints
3093 @item hbreak @var{args}
3094 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3095 @code{break} command and the breakpoint is set in the same way, but the
3096 breakpoint requires hardware support and some target hardware may not
3097 have this support. The main purpose of this is EPROM/ROM code
3098 debugging, so you can set a breakpoint at an instruction without
3099 changing the instruction. This can be used with the new trap-generation
3100 provided by SPARClite DSU and most x86-based targets. These targets
3101 will generate traps when a program accesses some data or instruction
3102 address that is assigned to the debug registers. However the hardware
3103 breakpoint registers can take a limited number of breakpoints. For
3104 example, on the DSU, only two data breakpoints can be set at a time, and
3105 @value{GDBN} will reject this command if more than two are used. Delete
3106 or disable unused hardware breakpoints before setting new ones
3107 (@pxref{Disabling, ,Disabling Breakpoints}).
3108 @xref{Conditions, ,Break Conditions}.
3109 For remote targets, you can restrict the number of hardware
3110 breakpoints @value{GDBN} will use, see @ref{set remote
3111 hardware-breakpoint-limit}.
3114 @item thbreak @var{args}
3115 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3116 are the same as for the @code{hbreak} command and the breakpoint is set in
3117 the same way. However, like the @code{tbreak} command,
3118 the breakpoint is automatically deleted after the
3119 first time your program stops there. Also, like the @code{hbreak}
3120 command, the breakpoint requires hardware support and some target hardware
3121 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3122 See also @ref{Conditions, ,Break Conditions}.
3125 @cindex regular expression
3126 @cindex breakpoints in functions matching a regexp
3127 @cindex set breakpoints in many functions
3128 @item rbreak @var{regex}
3129 Set breakpoints on all functions matching the regular expression
3130 @var{regex}. This command sets an unconditional breakpoint on all
3131 matches, printing a list of all breakpoints it set. Once these
3132 breakpoints are set, they are treated just like the breakpoints set with
3133 the @code{break} command. You can delete them, disable them, or make
3134 them conditional the same way as any other breakpoint.
3136 The syntax of the regular expression is the standard one used with tools
3137 like @file{grep}. Note that this is different from the syntax used by
3138 shells, so for instance @code{foo*} matches all functions that include
3139 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3140 @code{.*} leading and trailing the regular expression you supply, so to
3141 match only functions that begin with @code{foo}, use @code{^foo}.
3143 @cindex non-member C@t{++} functions, set breakpoint in
3144 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3145 breakpoints on overloaded functions that are not members of any special
3148 @cindex set breakpoints on all functions
3149 The @code{rbreak} command can be used to set breakpoints in
3150 @strong{all} the functions in a program, like this:
3153 (@value{GDBP}) rbreak .
3156 @kindex info breakpoints
3157 @cindex @code{$_} and @code{info breakpoints}
3158 @item info breakpoints @r{[}@var{n}@r{]}
3159 @itemx info break @r{[}@var{n}@r{]}
3160 @itemx info watchpoints @r{[}@var{n}@r{]}
3161 Print a table of all breakpoints, watchpoints, and catchpoints set and
3162 not deleted. Optional argument @var{n} means print information only
3163 about the specified breakpoint (or watchpoint or catchpoint). For
3164 each breakpoint, following columns are printed:
3167 @item Breakpoint Numbers
3169 Breakpoint, watchpoint, or catchpoint.
3171 Whether the breakpoint is marked to be disabled or deleted when hit.
3172 @item Enabled or Disabled
3173 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3174 that are not enabled.
3176 Where the breakpoint is in your program, as a memory address. For a
3177 pending breakpoint whose address is not yet known, this field will
3178 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3179 library that has the symbol or line referred by breakpoint is loaded.
3180 See below for details. A breakpoint with several locations will
3181 have @samp{<MULTIPLE>} in this field---see below for details.
3183 Where the breakpoint is in the source for your program, as a file and
3184 line number. For a pending breakpoint, the original string passed to
3185 the breakpoint command will be listed as it cannot be resolved until
3186 the appropriate shared library is loaded in the future.
3190 If a breakpoint is conditional, @code{info break} shows the condition on
3191 the line following the affected breakpoint; breakpoint commands, if any,
3192 are listed after that. A pending breakpoint is allowed to have a condition
3193 specified for it. The condition is not parsed for validity until a shared
3194 library is loaded that allows the pending breakpoint to resolve to a
3198 @code{info break} with a breakpoint
3199 number @var{n} as argument lists only that breakpoint. The
3200 convenience variable @code{$_} and the default examining-address for
3201 the @code{x} command are set to the address of the last breakpoint
3202 listed (@pxref{Memory, ,Examining Memory}).
3205 @code{info break} displays a count of the number of times the breakpoint
3206 has been hit. This is especially useful in conjunction with the
3207 @code{ignore} command. You can ignore a large number of breakpoint
3208 hits, look at the breakpoint info to see how many times the breakpoint
3209 was hit, and then run again, ignoring one less than that number. This
3210 will get you quickly to the last hit of that breakpoint.
3213 @value{GDBN} allows you to set any number of breakpoints at the same place in
3214 your program. There is nothing silly or meaningless about this. When
3215 the breakpoints are conditional, this is even useful
3216 (@pxref{Conditions, ,Break Conditions}).
3218 @cindex multiple locations, breakpoints
3219 @cindex breakpoints, multiple locations
3220 It is possible that a breakpoint corresponds to several locations
3221 in your program. Examples of this situation are:
3225 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3226 instances of the function body, used in different cases.
3229 For a C@t{++} template function, a given line in the function can
3230 correspond to any number of instantiations.
3233 For an inlined function, a given source line can correspond to
3234 several places where that function is inlined.
3237 In all those cases, @value{GDBN} will insert a breakpoint at all
3238 the relevant locations@footnote{
3239 As of this writing, multiple-location breakpoints work only if there's
3240 line number information for all the locations. This means that they
3241 will generally not work in system libraries, unless you have debug
3242 info with line numbers for them.}.
3244 A breakpoint with multiple locations is displayed in the breakpoint
3245 table using several rows---one header row, followed by one row for
3246 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3247 address column. The rows for individual locations contain the actual
3248 addresses for locations, and show the functions to which those
3249 locations belong. The number column for a location is of the form
3250 @var{breakpoint-number}.@var{location-number}.
3255 Num Type Disp Enb Address What
3256 1 breakpoint keep y <MULTIPLE>
3258 breakpoint already hit 1 time
3259 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3260 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3263 Each location can be individually enabled or disabled by passing
3264 @var{breakpoint-number}.@var{location-number} as argument to the
3265 @code{enable} and @code{disable} commands. Note that you cannot
3266 delete the individual locations from the list, you can only delete the
3267 entire list of locations that belong to their parent breakpoint (with
3268 the @kbd{delete @var{num}} command, where @var{num} is the number of
3269 the parent breakpoint, 1 in the above example). Disabling or enabling
3270 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3271 that belong to that breakpoint.
3273 @cindex pending breakpoints
3274 It's quite common to have a breakpoint inside a shared library.
3275 Shared libraries can be loaded and unloaded explicitly,
3276 and possibly repeatedly, as the program is executed. To support
3277 this use case, @value{GDBN} updates breakpoint locations whenever
3278 any shared library is loaded or unloaded. Typically, you would
3279 set a breakpoint in a shared library at the beginning of your
3280 debugging session, when the library is not loaded, and when the
3281 symbols from the library are not available. When you try to set
3282 breakpoint, @value{GDBN} will ask you if you want to set
3283 a so called @dfn{pending breakpoint}---breakpoint whose address
3284 is not yet resolved.
3286 After the program is run, whenever a new shared library is loaded,
3287 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3288 shared library contains the symbol or line referred to by some
3289 pending breakpoint, that breakpoint is resolved and becomes an
3290 ordinary breakpoint. When a library is unloaded, all breakpoints
3291 that refer to its symbols or source lines become pending again.
3293 This logic works for breakpoints with multiple locations, too. For
3294 example, if you have a breakpoint in a C@t{++} template function, and
3295 a newly loaded shared library has an instantiation of that template,
3296 a new location is added to the list of locations for the breakpoint.
3298 Except for having unresolved address, pending breakpoints do not
3299 differ from regular breakpoints. You can set conditions or commands,
3300 enable and disable them and perform other breakpoint operations.
3302 @value{GDBN} provides some additional commands for controlling what
3303 happens when the @samp{break} command cannot resolve breakpoint
3304 address specification to an address:
3306 @kindex set breakpoint pending
3307 @kindex show breakpoint pending
3309 @item set breakpoint pending auto
3310 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3311 location, it queries you whether a pending breakpoint should be created.
3313 @item set breakpoint pending on
3314 This indicates that an unrecognized breakpoint location should automatically
3315 result in a pending breakpoint being created.
3317 @item set breakpoint pending off
3318 This indicates that pending breakpoints are not to be created. Any
3319 unrecognized breakpoint location results in an error. This setting does
3320 not affect any pending breakpoints previously created.
3322 @item show breakpoint pending
3323 Show the current behavior setting for creating pending breakpoints.
3326 The settings above only affect the @code{break} command and its
3327 variants. Once breakpoint is set, it will be automatically updated
3328 as shared libraries are loaded and unloaded.
3330 @cindex automatic hardware breakpoints
3331 For some targets, @value{GDBN} can automatically decide if hardware or
3332 software breakpoints should be used, depending on whether the
3333 breakpoint address is read-only or read-write. This applies to
3334 breakpoints set with the @code{break} command as well as to internal
3335 breakpoints set by commands like @code{next} and @code{finish}. For
3336 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3339 You can control this automatic behaviour with the following commands::
3341 @kindex set breakpoint auto-hw
3342 @kindex show breakpoint auto-hw
3344 @item set breakpoint auto-hw on
3345 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3346 will try to use the target memory map to decide if software or hardware
3347 breakpoint must be used.
3349 @item set breakpoint auto-hw off
3350 This indicates @value{GDBN} should not automatically select breakpoint
3351 type. If the target provides a memory map, @value{GDBN} will warn when
3352 trying to set software breakpoint at a read-only address.
3355 @value{GDBN} normally implements breakpoints by replacing the program code
3356 at the breakpoint address with a special instruction, which, when
3357 executed, given control to the debugger. By default, the program
3358 code is so modified only when the program is resumed. As soon as
3359 the program stops, @value{GDBN} restores the original instructions. This
3360 behaviour guards against leaving breakpoints inserted in the
3361 target should gdb abrubptly disconnect. However, with slow remote
3362 targets, inserting and removing breakpoint can reduce the performance.
3363 This behavior can be controlled with the following commands::
3365 @kindex set breakpoint always-inserted
3366 @kindex show breakpoint always-inserted
3368 @item set breakpoint always-inserted off
3369 All breakpoints, including newly added by the user, are inserted in
3370 the target only when the target is resumed. All breakpoints are
3371 removed from the target when it stops.
3373 @item set breakpoint always-inserted on
3374 Causes all breakpoints to be inserted in the target at all times. If
3375 the user adds a new breakpoint, or changes an existing breakpoint, the
3376 breakpoints in the target are updated immediately. A breakpoint is
3377 removed from the target only when breakpoint itself is removed.
3379 @cindex non-stop mode, and @code{breakpoint always-inserted}
3380 @item set breakpoint always-inserted auto
3381 This is the default mode. If @value{GDBN} is controlling the inferior
3382 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3383 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3384 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3385 @code{breakpoint always-inserted} mode is off.
3388 @cindex negative breakpoint numbers
3389 @cindex internal @value{GDBN} breakpoints
3390 @value{GDBN} itself sometimes sets breakpoints in your program for
3391 special purposes, such as proper handling of @code{longjmp} (in C
3392 programs). These internal breakpoints are assigned negative numbers,
3393 starting with @code{-1}; @samp{info breakpoints} does not display them.
3394 You can see these breakpoints with the @value{GDBN} maintenance command
3395 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3398 @node Set Watchpoints
3399 @subsection Setting Watchpoints
3401 @cindex setting watchpoints
3402 You can use a watchpoint to stop execution whenever the value of an
3403 expression changes, without having to predict a particular place where
3404 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3405 The expression may be as simple as the value of a single variable, or
3406 as complex as many variables combined by operators. Examples include:
3410 A reference to the value of a single variable.
3413 An address cast to an appropriate data type. For example,
3414 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3415 address (assuming an @code{int} occupies 4 bytes).
3418 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3419 expression can use any operators valid in the program's native
3420 language (@pxref{Languages}).
3423 You can set a watchpoint on an expression even if the expression can
3424 not be evaluated yet. For instance, you can set a watchpoint on
3425 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3426 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3427 the expression produces a valid value. If the expression becomes
3428 valid in some other way than changing a variable (e.g.@: if the memory
3429 pointed to by @samp{*global_ptr} becomes readable as the result of a
3430 @code{malloc} call), @value{GDBN} may not stop until the next time
3431 the expression changes.
3433 @cindex software watchpoints
3434 @cindex hardware watchpoints
3435 Depending on your system, watchpoints may be implemented in software or
3436 hardware. @value{GDBN} does software watchpointing by single-stepping your
3437 program and testing the variable's value each time, which is hundreds of
3438 times slower than normal execution. (But this may still be worth it, to
3439 catch errors where you have no clue what part of your program is the
3442 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3443 x86-based targets, @value{GDBN} includes support for hardware
3444 watchpoints, which do not slow down the running of your program.
3448 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3449 Set a watchpoint for an expression. @value{GDBN} will break when the
3450 expression @var{expr} is written into by the program and its value
3451 changes. The simplest (and the most popular) use of this command is
3452 to watch the value of a single variable:
3455 (@value{GDBP}) watch foo
3458 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3459 clause, @value{GDBN} breaks only when the thread identified by
3460 @var{threadnum} changes the value of @var{expr}. If any other threads
3461 change the value of @var{expr}, @value{GDBN} will not break. Note
3462 that watchpoints restricted to a single thread in this way only work
3463 with Hardware Watchpoints.
3466 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3467 Set a watchpoint that will break when the value of @var{expr} is read
3471 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3472 Set a watchpoint that will break when @var{expr} is either read from
3473 or written into by the program.
3475 @kindex info watchpoints @r{[}@var{n}@r{]}
3476 @item info watchpoints
3477 This command prints a list of watchpoints, breakpoints, and catchpoints;
3478 it is the same as @code{info break} (@pxref{Set Breaks}).
3481 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3482 watchpoints execute very quickly, and the debugger reports a change in
3483 value at the exact instruction where the change occurs. If @value{GDBN}
3484 cannot set a hardware watchpoint, it sets a software watchpoint, which
3485 executes more slowly and reports the change in value at the next
3486 @emph{statement}, not the instruction, after the change occurs.
3488 @cindex use only software watchpoints
3489 You can force @value{GDBN} to use only software watchpoints with the
3490 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3491 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3492 the underlying system supports them. (Note that hardware-assisted
3493 watchpoints that were set @emph{before} setting
3494 @code{can-use-hw-watchpoints} to zero will still use the hardware
3495 mechanism of watching expression values.)
3498 @item set can-use-hw-watchpoints
3499 @kindex set can-use-hw-watchpoints
3500 Set whether or not to use hardware watchpoints.
3502 @item show can-use-hw-watchpoints
3503 @kindex show can-use-hw-watchpoints
3504 Show the current mode of using hardware watchpoints.
3507 For remote targets, you can restrict the number of hardware
3508 watchpoints @value{GDBN} will use, see @ref{set remote
3509 hardware-breakpoint-limit}.
3511 When you issue the @code{watch} command, @value{GDBN} reports
3514 Hardware watchpoint @var{num}: @var{expr}
3518 if it was able to set a hardware watchpoint.
3520 Currently, the @code{awatch} and @code{rwatch} commands can only set
3521 hardware watchpoints, because accesses to data that don't change the
3522 value of the watched expression cannot be detected without examining
3523 every instruction as it is being executed, and @value{GDBN} does not do
3524 that currently. If @value{GDBN} finds that it is unable to set a
3525 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3526 will print a message like this:
3529 Expression cannot be implemented with read/access watchpoint.
3532 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3533 data type of the watched expression is wider than what a hardware
3534 watchpoint on the target machine can handle. For example, some systems
3535 can only watch regions that are up to 4 bytes wide; on such systems you
3536 cannot set hardware watchpoints for an expression that yields a
3537 double-precision floating-point number (which is typically 8 bytes
3538 wide). As a work-around, it might be possible to break the large region
3539 into a series of smaller ones and watch them with separate watchpoints.
3541 If you set too many hardware watchpoints, @value{GDBN} might be unable
3542 to insert all of them when you resume the execution of your program.
3543 Since the precise number of active watchpoints is unknown until such
3544 time as the program is about to be resumed, @value{GDBN} might not be
3545 able to warn you about this when you set the watchpoints, and the
3546 warning will be printed only when the program is resumed:
3549 Hardware watchpoint @var{num}: Could not insert watchpoint
3553 If this happens, delete or disable some of the watchpoints.
3555 Watching complex expressions that reference many variables can also
3556 exhaust the resources available for hardware-assisted watchpoints.
3557 That's because @value{GDBN} needs to watch every variable in the
3558 expression with separately allocated resources.
3560 If you call a function interactively using @code{print} or @code{call},
3561 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3562 kind of breakpoint or the call completes.
3564 @value{GDBN} automatically deletes watchpoints that watch local
3565 (automatic) variables, or expressions that involve such variables, when
3566 they go out of scope, that is, when the execution leaves the block in
3567 which these variables were defined. In particular, when the program
3568 being debugged terminates, @emph{all} local variables go out of scope,
3569 and so only watchpoints that watch global variables remain set. If you
3570 rerun the program, you will need to set all such watchpoints again. One
3571 way of doing that would be to set a code breakpoint at the entry to the
3572 @code{main} function and when it breaks, set all the watchpoints.
3574 @cindex watchpoints and threads
3575 @cindex threads and watchpoints
3576 In multi-threaded programs, watchpoints will detect changes to the
3577 watched expression from every thread.
3580 @emph{Warning:} In multi-threaded programs, software watchpoints
3581 have only limited usefulness. If @value{GDBN} creates a software
3582 watchpoint, it can only watch the value of an expression @emph{in a
3583 single thread}. If you are confident that the expression can only
3584 change due to the current thread's activity (and if you are also
3585 confident that no other thread can become current), then you can use
3586 software watchpoints as usual. However, @value{GDBN} may not notice
3587 when a non-current thread's activity changes the expression. (Hardware
3588 watchpoints, in contrast, watch an expression in all threads.)
3591 @xref{set remote hardware-watchpoint-limit}.
3593 @node Set Catchpoints
3594 @subsection Setting Catchpoints
3595 @cindex catchpoints, setting
3596 @cindex exception handlers
3597 @cindex event handling
3599 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3600 kinds of program events, such as C@t{++} exceptions or the loading of a
3601 shared library. Use the @code{catch} command to set a catchpoint.
3605 @item catch @var{event}
3606 Stop when @var{event} occurs. @var{event} can be any of the following:
3609 @cindex stop on C@t{++} exceptions
3610 The throwing of a C@t{++} exception.
3613 The catching of a C@t{++} exception.
3616 @cindex Ada exception catching
3617 @cindex catch Ada exceptions
3618 An Ada exception being raised. If an exception name is specified
3619 at the end of the command (eg @code{catch exception Program_Error}),
3620 the debugger will stop only when this specific exception is raised.
3621 Otherwise, the debugger stops execution when any Ada exception is raised.
3623 When inserting an exception catchpoint on a user-defined exception whose
3624 name is identical to one of the exceptions defined by the language, the
3625 fully qualified name must be used as the exception name. Otherwise,
3626 @value{GDBN} will assume that it should stop on the pre-defined exception
3627 rather than the user-defined one. For instance, assuming an exception
3628 called @code{Constraint_Error} is defined in package @code{Pck}, then
3629 the command to use to catch such exceptions is @kbd{catch exception
3630 Pck.Constraint_Error}.
3632 @item exception unhandled
3633 An exception that was raised but is not handled by the program.
3636 A failed Ada assertion.
3639 @cindex break on fork/exec
3640 A call to @code{exec}. This is currently only available for HP-UX
3644 A call to @code{fork}. This is currently only available for HP-UX
3648 A call to @code{vfork}. This is currently only available for HP-UX
3653 @item tcatch @var{event}
3654 Set a catchpoint that is enabled only for one stop. The catchpoint is
3655 automatically deleted after the first time the event is caught.
3659 Use the @code{info break} command to list the current catchpoints.
3661 There are currently some limitations to C@t{++} exception handling
3662 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3666 If you call a function interactively, @value{GDBN} normally returns
3667 control to you when the function has finished executing. If the call
3668 raises an exception, however, the call may bypass the mechanism that
3669 returns control to you and cause your program either to abort or to
3670 simply continue running until it hits a breakpoint, catches a signal
3671 that @value{GDBN} is listening for, or exits. This is the case even if
3672 you set a catchpoint for the exception; catchpoints on exceptions are
3673 disabled within interactive calls.
3676 You cannot raise an exception interactively.
3679 You cannot install an exception handler interactively.
3682 @cindex raise exceptions
3683 Sometimes @code{catch} is not the best way to debug exception handling:
3684 if you need to know exactly where an exception is raised, it is better to
3685 stop @emph{before} the exception handler is called, since that way you
3686 can see the stack before any unwinding takes place. If you set a
3687 breakpoint in an exception handler instead, it may not be easy to find
3688 out where the exception was raised.
3690 To stop just before an exception handler is called, you need some
3691 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3692 raised by calling a library function named @code{__raise_exception}
3693 which has the following ANSI C interface:
3696 /* @var{addr} is where the exception identifier is stored.
3697 @var{id} is the exception identifier. */
3698 void __raise_exception (void **addr, void *id);
3702 To make the debugger catch all exceptions before any stack
3703 unwinding takes place, set a breakpoint on @code{__raise_exception}
3704 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3706 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3707 that depends on the value of @var{id}, you can stop your program when
3708 a specific exception is raised. You can use multiple conditional
3709 breakpoints to stop your program when any of a number of exceptions are
3714 @subsection Deleting Breakpoints
3716 @cindex clearing breakpoints, watchpoints, catchpoints
3717 @cindex deleting breakpoints, watchpoints, catchpoints
3718 It is often necessary to eliminate a breakpoint, watchpoint, or
3719 catchpoint once it has done its job and you no longer want your program
3720 to stop there. This is called @dfn{deleting} the breakpoint. A
3721 breakpoint that has been deleted no longer exists; it is forgotten.
3723 With the @code{clear} command you can delete breakpoints according to
3724 where they are in your program. With the @code{delete} command you can
3725 delete individual breakpoints, watchpoints, or catchpoints by specifying
3726 their breakpoint numbers.
3728 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3729 automatically ignores breakpoints on the first instruction to be executed
3730 when you continue execution without changing the execution address.
3735 Delete any breakpoints at the next instruction to be executed in the
3736 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3737 the innermost frame is selected, this is a good way to delete a
3738 breakpoint where your program just stopped.
3740 @item clear @var{location}
3741 Delete any breakpoints set at the specified @var{location}.
3742 @xref{Specify Location}, for the various forms of @var{location}; the
3743 most useful ones are listed below:
3746 @item clear @var{function}
3747 @itemx clear @var{filename}:@var{function}
3748 Delete any breakpoints set at entry to the named @var{function}.
3750 @item clear @var{linenum}
3751 @itemx clear @var{filename}:@var{linenum}
3752 Delete any breakpoints set at or within the code of the specified
3753 @var{linenum} of the specified @var{filename}.
3756 @cindex delete breakpoints
3758 @kindex d @r{(@code{delete})}
3759 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3760 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3761 ranges specified as arguments. If no argument is specified, delete all
3762 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3763 confirm off}). You can abbreviate this command as @code{d}.
3767 @subsection Disabling Breakpoints
3769 @cindex enable/disable a breakpoint
3770 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3771 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3772 it had been deleted, but remembers the information on the breakpoint so
3773 that you can @dfn{enable} it again later.
3775 You disable and enable breakpoints, watchpoints, and catchpoints with
3776 the @code{enable} and @code{disable} commands, optionally specifying one
3777 or more breakpoint numbers as arguments. Use @code{info break} or
3778 @code{info watch} to print a list of breakpoints, watchpoints, and
3779 catchpoints if you do not know which numbers to use.
3781 Disabling and enabling a breakpoint that has multiple locations
3782 affects all of its locations.
3784 A breakpoint, watchpoint, or catchpoint can have any of four different
3785 states of enablement:
3789 Enabled. The breakpoint stops your program. A breakpoint set
3790 with the @code{break} command starts out in this state.
3792 Disabled. The breakpoint has no effect on your program.
3794 Enabled once. The breakpoint stops your program, but then becomes
3797 Enabled for deletion. The breakpoint stops your program, but
3798 immediately after it does so it is deleted permanently. A breakpoint
3799 set with the @code{tbreak} command starts out in this state.
3802 You can use the following commands to enable or disable breakpoints,
3803 watchpoints, and catchpoints:
3807 @kindex dis @r{(@code{disable})}
3808 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3809 Disable the specified breakpoints---or all breakpoints, if none are
3810 listed. A disabled breakpoint has no effect but is not forgotten. All
3811 options such as ignore-counts, conditions and commands are remembered in
3812 case the breakpoint is enabled again later. You may abbreviate
3813 @code{disable} as @code{dis}.
3816 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3817 Enable the specified breakpoints (or all defined breakpoints). They
3818 become effective once again in stopping your program.
3820 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3821 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3822 of these breakpoints immediately after stopping your program.
3824 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3825 Enable the specified breakpoints to work once, then die. @value{GDBN}
3826 deletes any of these breakpoints as soon as your program stops there.
3827 Breakpoints set by the @code{tbreak} command start out in this state.
3830 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3831 @c confusing: tbreak is also initially enabled.
3832 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3833 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3834 subsequently, they become disabled or enabled only when you use one of
3835 the commands above. (The command @code{until} can set and delete a
3836 breakpoint of its own, but it does not change the state of your other
3837 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3841 @subsection Break Conditions
3842 @cindex conditional breakpoints
3843 @cindex breakpoint conditions
3845 @c FIXME what is scope of break condition expr? Context where wanted?
3846 @c in particular for a watchpoint?
3847 The simplest sort of breakpoint breaks every time your program reaches a
3848 specified place. You can also specify a @dfn{condition} for a
3849 breakpoint. A condition is just a Boolean expression in your
3850 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3851 a condition evaluates the expression each time your program reaches it,
3852 and your program stops only if the condition is @emph{true}.
3854 This is the converse of using assertions for program validation; in that
3855 situation, you want to stop when the assertion is violated---that is,
3856 when the condition is false. In C, if you want to test an assertion expressed
3857 by the condition @var{assert}, you should set the condition
3858 @samp{! @var{assert}} on the appropriate breakpoint.
3860 Conditions are also accepted for watchpoints; you may not need them,
3861 since a watchpoint is inspecting the value of an expression anyhow---but
3862 it might be simpler, say, to just set a watchpoint on a variable name,
3863 and specify a condition that tests whether the new value is an interesting
3866 Break conditions can have side effects, and may even call functions in
3867 your program. This can be useful, for example, to activate functions
3868 that log program progress, or to use your own print functions to
3869 format special data structures. The effects are completely predictable
3870 unless there is another enabled breakpoint at the same address. (In
3871 that case, @value{GDBN} might see the other breakpoint first and stop your
3872 program without checking the condition of this one.) Note that
3873 breakpoint commands are usually more convenient and flexible than break
3875 purpose of performing side effects when a breakpoint is reached
3876 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3878 Break conditions can be specified when a breakpoint is set, by using
3879 @samp{if} in the arguments to the @code{break} command. @xref{Set
3880 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3881 with the @code{condition} command.
3883 You can also use the @code{if} keyword with the @code{watch} command.
3884 The @code{catch} command does not recognize the @code{if} keyword;
3885 @code{condition} is the only way to impose a further condition on a
3890 @item condition @var{bnum} @var{expression}
3891 Specify @var{expression} as the break condition for breakpoint,
3892 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3893 breakpoint @var{bnum} stops your program only if the value of
3894 @var{expression} is true (nonzero, in C). When you use
3895 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3896 syntactic correctness, and to determine whether symbols in it have
3897 referents in the context of your breakpoint. If @var{expression} uses
3898 symbols not referenced in the context of the breakpoint, @value{GDBN}
3899 prints an error message:
3902 No symbol "foo" in current context.
3907 not actually evaluate @var{expression} at the time the @code{condition}
3908 command (or a command that sets a breakpoint with a condition, like
3909 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3911 @item condition @var{bnum}
3912 Remove the condition from breakpoint number @var{bnum}. It becomes
3913 an ordinary unconditional breakpoint.
3916 @cindex ignore count (of breakpoint)
3917 A special case of a breakpoint condition is to stop only when the
3918 breakpoint has been reached a certain number of times. This is so
3919 useful that there is a special way to do it, using the @dfn{ignore
3920 count} of the breakpoint. Every breakpoint has an ignore count, which
3921 is an integer. Most of the time, the ignore count is zero, and
3922 therefore has no effect. But if your program reaches a breakpoint whose
3923 ignore count is positive, then instead of stopping, it just decrements
3924 the ignore count by one and continues. As a result, if the ignore count
3925 value is @var{n}, the breakpoint does not stop the next @var{n} times
3926 your program reaches it.
3930 @item ignore @var{bnum} @var{count}
3931 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3932 The next @var{count} times the breakpoint is reached, your program's
3933 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3936 To make the breakpoint stop the next time it is reached, specify
3939 When you use @code{continue} to resume execution of your program from a
3940 breakpoint, you can specify an ignore count directly as an argument to
3941 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3942 Stepping,,Continuing and Stepping}.
3944 If a breakpoint has a positive ignore count and a condition, the
3945 condition is not checked. Once the ignore count reaches zero,
3946 @value{GDBN} resumes checking the condition.
3948 You could achieve the effect of the ignore count with a condition such
3949 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3950 is decremented each time. @xref{Convenience Vars, ,Convenience
3954 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3957 @node Break Commands
3958 @subsection Breakpoint Command Lists
3960 @cindex breakpoint commands
3961 You can give any breakpoint (or watchpoint or catchpoint) a series of
3962 commands to execute when your program stops due to that breakpoint. For
3963 example, you might want to print the values of certain expressions, or
3964 enable other breakpoints.
3968 @kindex end@r{ (breakpoint commands)}
3969 @item commands @r{[}@var{bnum}@r{]}
3970 @itemx @dots{} @var{command-list} @dots{}
3972 Specify a list of commands for breakpoint number @var{bnum}. The commands
3973 themselves appear on the following lines. Type a line containing just
3974 @code{end} to terminate the commands.
3976 To remove all commands from a breakpoint, type @code{commands} and
3977 follow it immediately with @code{end}; that is, give no commands.
3979 With no @var{bnum} argument, @code{commands} refers to the last
3980 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3981 recently encountered).
3984 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3985 disabled within a @var{command-list}.
3987 You can use breakpoint commands to start your program up again. Simply
3988 use the @code{continue} command, or @code{step}, or any other command
3989 that resumes execution.
3991 Any other commands in the command list, after a command that resumes
3992 execution, are ignored. This is because any time you resume execution
3993 (even with a simple @code{next} or @code{step}), you may encounter
3994 another breakpoint---which could have its own command list, leading to
3995 ambiguities about which list to execute.
3998 If the first command you specify in a command list is @code{silent}, the
3999 usual message about stopping at a breakpoint is not printed. This may
4000 be desirable for breakpoints that are to print a specific message and
4001 then continue. If none of the remaining commands print anything, you
4002 see no sign that the breakpoint was reached. @code{silent} is
4003 meaningful only at the beginning of a breakpoint command list.
4005 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4006 print precisely controlled output, and are often useful in silent
4007 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4009 For example, here is how you could use breakpoint commands to print the
4010 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4016 printf "x is %d\n",x
4021 One application for breakpoint commands is to compensate for one bug so
4022 you can test for another. Put a breakpoint just after the erroneous line
4023 of code, give it a condition to detect the case in which something
4024 erroneous has been done, and give it commands to assign correct values
4025 to any variables that need them. End with the @code{continue} command
4026 so that your program does not stop, and start with the @code{silent}
4027 command so that no output is produced. Here is an example:
4038 @c @ifclear BARETARGET
4039 @node Error in Breakpoints
4040 @subsection ``Cannot insert breakpoints''
4042 If you request too many active hardware-assisted breakpoints and
4043 watchpoints, you will see this error message:
4045 @c FIXME: the precise wording of this message may change; the relevant
4046 @c source change is not committed yet (Sep 3, 1999).
4048 Stopped; cannot insert breakpoints.
4049 You may have requested too many hardware breakpoints and watchpoints.
4053 This message is printed when you attempt to resume the program, since
4054 only then @value{GDBN} knows exactly how many hardware breakpoints and
4055 watchpoints it needs to insert.
4057 When this message is printed, you need to disable or remove some of the
4058 hardware-assisted breakpoints and watchpoints, and then continue.
4060 @node Breakpoint-related Warnings
4061 @subsection ``Breakpoint address adjusted...''
4062 @cindex breakpoint address adjusted
4064 Some processor architectures place constraints on the addresses at
4065 which breakpoints may be placed. For architectures thus constrained,
4066 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4067 with the constraints dictated by the architecture.
4069 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4070 a VLIW architecture in which a number of RISC-like instructions may be
4071 bundled together for parallel execution. The FR-V architecture
4072 constrains the location of a breakpoint instruction within such a
4073 bundle to the instruction with the lowest address. @value{GDBN}
4074 honors this constraint by adjusting a breakpoint's address to the
4075 first in the bundle.
4077 It is not uncommon for optimized code to have bundles which contain
4078 instructions from different source statements, thus it may happen that
4079 a breakpoint's address will be adjusted from one source statement to
4080 another. Since this adjustment may significantly alter @value{GDBN}'s
4081 breakpoint related behavior from what the user expects, a warning is
4082 printed when the breakpoint is first set and also when the breakpoint
4085 A warning like the one below is printed when setting a breakpoint
4086 that's been subject to address adjustment:
4089 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4092 Such warnings are printed both for user settable and @value{GDBN}'s
4093 internal breakpoints. If you see one of these warnings, you should
4094 verify that a breakpoint set at the adjusted address will have the
4095 desired affect. If not, the breakpoint in question may be removed and
4096 other breakpoints may be set which will have the desired behavior.
4097 E.g., it may be sufficient to place the breakpoint at a later
4098 instruction. A conditional breakpoint may also be useful in some
4099 cases to prevent the breakpoint from triggering too often.
4101 @value{GDBN} will also issue a warning when stopping at one of these
4102 adjusted breakpoints:
4105 warning: Breakpoint 1 address previously adjusted from 0x00010414
4109 When this warning is encountered, it may be too late to take remedial
4110 action except in cases where the breakpoint is hit earlier or more
4111 frequently than expected.
4113 @node Continuing and Stepping
4114 @section Continuing and Stepping
4118 @cindex resuming execution
4119 @dfn{Continuing} means resuming program execution until your program
4120 completes normally. In contrast, @dfn{stepping} means executing just
4121 one more ``step'' of your program, where ``step'' may mean either one
4122 line of source code, or one machine instruction (depending on what
4123 particular command you use). Either when continuing or when stepping,
4124 your program may stop even sooner, due to a breakpoint or a signal. (If
4125 it stops due to a signal, you may want to use @code{handle}, or use
4126 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4130 @kindex c @r{(@code{continue})}
4131 @kindex fg @r{(resume foreground execution)}
4132 @item continue @r{[}@var{ignore-count}@r{]}
4133 @itemx c @r{[}@var{ignore-count}@r{]}
4134 @itemx fg @r{[}@var{ignore-count}@r{]}
4135 Resume program execution, at the address where your program last stopped;
4136 any breakpoints set at that address are bypassed. The optional argument
4137 @var{ignore-count} allows you to specify a further number of times to
4138 ignore a breakpoint at this location; its effect is like that of
4139 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4141 The argument @var{ignore-count} is meaningful only when your program
4142 stopped due to a breakpoint. At other times, the argument to
4143 @code{continue} is ignored.
4145 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4146 debugged program is deemed to be the foreground program) are provided
4147 purely for convenience, and have exactly the same behavior as
4151 To resume execution at a different place, you can use @code{return}
4152 (@pxref{Returning, ,Returning from a Function}) to go back to the
4153 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4154 Different Address}) to go to an arbitrary location in your program.
4156 A typical technique for using stepping is to set a breakpoint
4157 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4158 beginning of the function or the section of your program where a problem
4159 is believed to lie, run your program until it stops at that breakpoint,
4160 and then step through the suspect area, examining the variables that are
4161 interesting, until you see the problem happen.
4165 @kindex s @r{(@code{step})}
4167 Continue running your program until control reaches a different source
4168 line, then stop it and return control to @value{GDBN}. This command is
4169 abbreviated @code{s}.
4172 @c "without debugging information" is imprecise; actually "without line
4173 @c numbers in the debugging information". (gcc -g1 has debugging info but
4174 @c not line numbers). But it seems complex to try to make that
4175 @c distinction here.
4176 @emph{Warning:} If you use the @code{step} command while control is
4177 within a function that was compiled without debugging information,
4178 execution proceeds until control reaches a function that does have
4179 debugging information. Likewise, it will not step into a function which
4180 is compiled without debugging information. To step through functions
4181 without debugging information, use the @code{stepi} command, described
4185 The @code{step} command only stops at the first instruction of a source
4186 line. This prevents the multiple stops that could otherwise occur in
4187 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4188 to stop if a function that has debugging information is called within
4189 the line. In other words, @code{step} @emph{steps inside} any functions
4190 called within the line.
4192 Also, the @code{step} command only enters a function if there is line
4193 number information for the function. Otherwise it acts like the
4194 @code{next} command. This avoids problems when using @code{cc -gl}
4195 on MIPS machines. Previously, @code{step} entered subroutines if there
4196 was any debugging information about the routine.
4198 @item step @var{count}
4199 Continue running as in @code{step}, but do so @var{count} times. If a
4200 breakpoint is reached, or a signal not related to stepping occurs before
4201 @var{count} steps, stepping stops right away.
4204 @kindex n @r{(@code{next})}
4205 @item next @r{[}@var{count}@r{]}
4206 Continue to the next source line in the current (innermost) stack frame.
4207 This is similar to @code{step}, but function calls that appear within
4208 the line of code are executed without stopping. Execution stops when
4209 control reaches a different line of code at the original stack level
4210 that was executing when you gave the @code{next} command. This command
4211 is abbreviated @code{n}.
4213 An argument @var{count} is a repeat count, as for @code{step}.
4216 @c FIX ME!! Do we delete this, or is there a way it fits in with
4217 @c the following paragraph? --- Vctoria
4219 @c @code{next} within a function that lacks debugging information acts like
4220 @c @code{step}, but any function calls appearing within the code of the
4221 @c function are executed without stopping.
4223 The @code{next} command only stops at the first instruction of a
4224 source line. This prevents multiple stops that could otherwise occur in
4225 @code{switch} statements, @code{for} loops, etc.
4227 @kindex set step-mode
4229 @cindex functions without line info, and stepping
4230 @cindex stepping into functions with no line info
4231 @itemx set step-mode on
4232 The @code{set step-mode on} command causes the @code{step} command to
4233 stop at the first instruction of a function which contains no debug line
4234 information rather than stepping over it.
4236 This is useful in cases where you may be interested in inspecting the
4237 machine instructions of a function which has no symbolic info and do not
4238 want @value{GDBN} to automatically skip over this function.
4240 @item set step-mode off
4241 Causes the @code{step} command to step over any functions which contains no
4242 debug information. This is the default.
4244 @item show step-mode
4245 Show whether @value{GDBN} will stop in or step over functions without
4246 source line debug information.
4249 @kindex fin @r{(@code{finish})}
4251 Continue running until just after function in the selected stack frame
4252 returns. Print the returned value (if any). This command can be
4253 abbreviated as @code{fin}.
4255 Contrast this with the @code{return} command (@pxref{Returning,
4256 ,Returning from a Function}).
4259 @kindex u @r{(@code{until})}
4260 @cindex run until specified location
4263 Continue running until a source line past the current line, in the
4264 current stack frame, is reached. This command is used to avoid single
4265 stepping through a loop more than once. It is like the @code{next}
4266 command, except that when @code{until} encounters a jump, it
4267 automatically continues execution until the program counter is greater
4268 than the address of the jump.
4270 This means that when you reach the end of a loop after single stepping
4271 though it, @code{until} makes your program continue execution until it
4272 exits the loop. In contrast, a @code{next} command at the end of a loop
4273 simply steps back to the beginning of the loop, which forces you to step
4274 through the next iteration.
4276 @code{until} always stops your program if it attempts to exit the current
4279 @code{until} may produce somewhat counterintuitive results if the order
4280 of machine code does not match the order of the source lines. For
4281 example, in the following excerpt from a debugging session, the @code{f}
4282 (@code{frame}) command shows that execution is stopped at line
4283 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4287 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4289 (@value{GDBP}) until
4290 195 for ( ; argc > 0; NEXTARG) @{
4293 This happened because, for execution efficiency, the compiler had
4294 generated code for the loop closure test at the end, rather than the
4295 start, of the loop---even though the test in a C @code{for}-loop is
4296 written before the body of the loop. The @code{until} command appeared
4297 to step back to the beginning of the loop when it advanced to this
4298 expression; however, it has not really gone to an earlier
4299 statement---not in terms of the actual machine code.
4301 @code{until} with no argument works by means of single
4302 instruction stepping, and hence is slower than @code{until} with an
4305 @item until @var{location}
4306 @itemx u @var{location}
4307 Continue running your program until either the specified location is
4308 reached, or the current stack frame returns. @var{location} is any of
4309 the forms described in @ref{Specify Location}.
4310 This form of the command uses temporary breakpoints, and
4311 hence is quicker than @code{until} without an argument. The specified
4312 location is actually reached only if it is in the current frame. This
4313 implies that @code{until} can be used to skip over recursive function
4314 invocations. For instance in the code below, if the current location is
4315 line @code{96}, issuing @code{until 99} will execute the program up to
4316 line @code{99} in the same invocation of factorial, i.e., after the inner
4317 invocations have returned.
4320 94 int factorial (int value)
4322 96 if (value > 1) @{
4323 97 value *= factorial (value - 1);
4330 @kindex advance @var{location}
4331 @itemx advance @var{location}
4332 Continue running the program up to the given @var{location}. An argument is
4333 required, which should be of one of the forms described in
4334 @ref{Specify Location}.
4335 Execution will also stop upon exit from the current stack
4336 frame. This command is similar to @code{until}, but @code{advance} will
4337 not skip over recursive function calls, and the target location doesn't
4338 have to be in the same frame as the current one.
4342 @kindex si @r{(@code{stepi})}
4344 @itemx stepi @var{arg}
4346 Execute one machine instruction, then stop and return to the debugger.
4348 It is often useful to do @samp{display/i $pc} when stepping by machine
4349 instructions. This makes @value{GDBN} automatically display the next
4350 instruction to be executed, each time your program stops. @xref{Auto
4351 Display,, Automatic Display}.
4353 An argument is a repeat count, as in @code{step}.
4357 @kindex ni @r{(@code{nexti})}
4359 @itemx nexti @var{arg}
4361 Execute one machine instruction, but if it is a function call,
4362 proceed until the function returns.
4364 An argument is a repeat count, as in @code{next}.
4371 A signal is an asynchronous event that can happen in a program. The
4372 operating system defines the possible kinds of signals, and gives each
4373 kind a name and a number. For example, in Unix @code{SIGINT} is the
4374 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4375 @code{SIGSEGV} is the signal a program gets from referencing a place in
4376 memory far away from all the areas in use; @code{SIGALRM} occurs when
4377 the alarm clock timer goes off (which happens only if your program has
4378 requested an alarm).
4380 @cindex fatal signals
4381 Some signals, including @code{SIGALRM}, are a normal part of the
4382 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4383 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4384 program has not specified in advance some other way to handle the signal.
4385 @code{SIGINT} does not indicate an error in your program, but it is normally
4386 fatal so it can carry out the purpose of the interrupt: to kill the program.
4388 @value{GDBN} has the ability to detect any occurrence of a signal in your
4389 program. You can tell @value{GDBN} in advance what to do for each kind of
4392 @cindex handling signals
4393 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4394 @code{SIGALRM} be silently passed to your program
4395 (so as not to interfere with their role in the program's functioning)
4396 but to stop your program immediately whenever an error signal happens.
4397 You can change these settings with the @code{handle} command.
4400 @kindex info signals
4404 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4405 handle each one. You can use this to see the signal numbers of all
4406 the defined types of signals.
4408 @item info signals @var{sig}
4409 Similar, but print information only about the specified signal number.
4411 @code{info handle} is an alias for @code{info signals}.
4414 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4415 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4416 can be the number of a signal or its name (with or without the
4417 @samp{SIG} at the beginning); a list of signal numbers of the form
4418 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4419 known signals. Optional arguments @var{keywords}, described below,
4420 say what change to make.
4424 The keywords allowed by the @code{handle} command can be abbreviated.
4425 Their full names are:
4429 @value{GDBN} should not stop your program when this signal happens. It may
4430 still print a message telling you that the signal has come in.
4433 @value{GDBN} should stop your program when this signal happens. This implies
4434 the @code{print} keyword as well.
4437 @value{GDBN} should print a message when this signal happens.
4440 @value{GDBN} should not mention the occurrence of the signal at all. This
4441 implies the @code{nostop} keyword as well.
4445 @value{GDBN} should allow your program to see this signal; your program
4446 can handle the signal, or else it may terminate if the signal is fatal
4447 and not handled. @code{pass} and @code{noignore} are synonyms.
4451 @value{GDBN} should not allow your program to see this signal.
4452 @code{nopass} and @code{ignore} are synonyms.
4456 When a signal stops your program, the signal is not visible to the
4458 continue. Your program sees the signal then, if @code{pass} is in
4459 effect for the signal in question @emph{at that time}. In other words,
4460 after @value{GDBN} reports a signal, you can use the @code{handle}
4461 command with @code{pass} or @code{nopass} to control whether your
4462 program sees that signal when you continue.
4464 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4465 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4466 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4469 You can also use the @code{signal} command to prevent your program from
4470 seeing a signal, or cause it to see a signal it normally would not see,
4471 or to give it any signal at any time. For example, if your program stopped
4472 due to some sort of memory reference error, you might store correct
4473 values into the erroneous variables and continue, hoping to see more
4474 execution; but your program would probably terminate immediately as
4475 a result of the fatal signal once it saw the signal. To prevent this,
4476 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4479 @cindex extra signal information
4480 @anchor{extra signal information}
4482 On some targets, @value{GDBN} can inspect extra signal information
4483 associated with the intercepted signal, before it is actually
4484 delivered to the program being debugged. This information is exported
4485 by the convenience variable @code{$_siginfo}, and consists of data
4486 that is passed by the kernel to the signal handler at the time of the
4487 receipt of a signal. The data type of the information itself is
4488 target dependent. You can see the data type using the @code{ptype
4489 $_siginfo} command. On Unix systems, it typically corresponds to the
4490 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4493 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4494 referenced address that raised a segmentation fault.
4498 (@value{GDBP}) continue
4499 Program received signal SIGSEGV, Segmentation fault.
4500 0x0000000000400766 in main ()
4502 (@value{GDBP}) ptype $_siginfo
4509 struct @{...@} _kill;
4510 struct @{...@} _timer;
4512 struct @{...@} _sigchld;
4513 struct @{...@} _sigfault;
4514 struct @{...@} _sigpoll;
4517 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4521 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4522 $1 = (void *) 0x7ffff7ff7000
4526 Depending on target support, @code{$_siginfo} may also be writable.
4529 @section Stopping and Starting Multi-thread Programs
4531 @cindex stopped threads
4532 @cindex threads, stopped
4534 @cindex continuing threads
4535 @cindex threads, continuing
4537 @value{GDBN} supports debugging programs with multiple threads
4538 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4539 are two modes of controlling execution of your program within the
4540 debugger. In the default mode, referred to as @dfn{all-stop mode},
4541 when any thread in your program stops (for example, at a breakpoint
4542 or while being stepped), all other threads in the program are also stopped by
4543 @value{GDBN}. On some targets, @value{GDBN} also supports
4544 @dfn{non-stop mode}, in which other threads can continue to run freely while
4545 you examine the stopped thread in the debugger.
4548 * All-Stop Mode:: All threads stop when GDB takes control
4549 * Non-Stop Mode:: Other threads continue to execute
4550 * Background Execution:: Running your program asynchronously
4551 * Thread-Specific Breakpoints:: Controlling breakpoints
4552 * Interrupted System Calls:: GDB may interfere with system calls
4556 @subsection All-Stop Mode
4558 @cindex all-stop mode
4560 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4561 @emph{all} threads of execution stop, not just the current thread. This
4562 allows you to examine the overall state of the program, including
4563 switching between threads, without worrying that things may change
4566 Conversely, whenever you restart the program, @emph{all} threads start
4567 executing. @emph{This is true even when single-stepping} with commands
4568 like @code{step} or @code{next}.
4570 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4571 Since thread scheduling is up to your debugging target's operating
4572 system (not controlled by @value{GDBN}), other threads may
4573 execute more than one statement while the current thread completes a
4574 single step. Moreover, in general other threads stop in the middle of a
4575 statement, rather than at a clean statement boundary, when the program
4578 You might even find your program stopped in another thread after
4579 continuing or even single-stepping. This happens whenever some other
4580 thread runs into a breakpoint, a signal, or an exception before the
4581 first thread completes whatever you requested.
4583 @cindex automatic thread selection
4584 @cindex switching threads automatically
4585 @cindex threads, automatic switching
4586 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4587 signal, it automatically selects the thread where that breakpoint or
4588 signal happened. @value{GDBN} alerts you to the context switch with a
4589 message such as @samp{[Switching to Thread @var{n}]} to identify the
4592 On some OSes, you can modify @value{GDBN}'s default behavior by
4593 locking the OS scheduler to allow only a single thread to run.
4596 @item set scheduler-locking @var{mode}
4597 @cindex scheduler locking mode
4598 @cindex lock scheduler
4599 Set the scheduler locking mode. If it is @code{off}, then there is no
4600 locking and any thread may run at any time. If @code{on}, then only the
4601 current thread may run when the inferior is resumed. The @code{step}
4602 mode optimizes for single-stepping; it prevents other threads
4603 from preempting the current thread while you are stepping, so that
4604 the focus of debugging does not change unexpectedly.
4605 Other threads only rarely (or never) get a chance to run
4606 when you step. They are more likely to run when you @samp{next} over a
4607 function call, and they are completely free to run when you use commands
4608 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4609 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4610 the current thread away from the thread that you are debugging.
4612 @item show scheduler-locking
4613 Display the current scheduler locking mode.
4617 @subsection Non-Stop Mode
4619 @cindex non-stop mode
4621 @c This section is really only a place-holder, and needs to be expanded
4622 @c with more details.
4624 For some multi-threaded targets, @value{GDBN} supports an optional
4625 mode of operation in which you can examine stopped program threads in
4626 the debugger while other threads continue to execute freely. This
4627 minimizes intrusion when debugging live systems, such as programs
4628 where some threads have real-time constraints or must continue to
4629 respond to external events. This is referred to as @dfn{non-stop} mode.
4631 In non-stop mode, when a thread stops to report a debugging event,
4632 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4633 threads as well, in contrast to the all-stop mode behavior. Additionally,
4634 execution commands such as @code{continue} and @code{step} apply by default
4635 only to the current thread in non-stop mode, rather than all threads as
4636 in all-stop mode. This allows you to control threads explicitly in
4637 ways that are not possible in all-stop mode --- for example, stepping
4638 one thread while allowing others to run freely, stepping
4639 one thread while holding all others stopped, or stepping several threads
4640 independently and simultaneously.
4642 To enter non-stop mode, use this sequence of commands before you run
4643 or attach to your program:
4646 # Enable the async interface.
4649 # If using the CLI, pagination breaks non-stop.
4652 # Finally, turn it on!
4656 You can use these commands to manipulate the non-stop mode setting:
4659 @kindex set non-stop
4660 @item set non-stop on
4661 Enable selection of non-stop mode.
4662 @item set non-stop off
4663 Disable selection of non-stop mode.
4664 @kindex show non-stop
4666 Show the current non-stop enablement setting.
4669 Note these commands only reflect whether non-stop mode is enabled,
4670 not whether the currently-executing program is being run in non-stop mode.
4671 In particular, the @code{set non-stop} preference is only consulted when
4672 @value{GDBN} starts or connects to the target program, and it is generally
4673 not possible to switch modes once debugging has started. Furthermore,
4674 since not all targets support non-stop mode, even when you have enabled
4675 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4678 In non-stop mode, all execution commands apply only to the current thread
4679 by default. That is, @code{continue} only continues one thread.
4680 To continue all threads, issue @code{continue -a} or @code{c -a}.
4682 You can use @value{GDBN}'s background execution commands
4683 (@pxref{Background Execution}) to run some threads in the background
4684 while you continue to examine or step others from @value{GDBN}.
4685 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4686 always executed asynchronously in non-stop mode.
4688 Suspending execution is done with the @code{interrupt} command when
4689 running in the background, or @kbd{Ctrl-c} during foreground execution.
4690 In all-stop mode, this stops the whole process;
4691 but in non-stop mode the interrupt applies only to the current thread.
4692 To stop the whole program, use @code{interrupt -a}.
4694 Other execution commands do not currently support the @code{-a} option.
4696 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4697 that thread current, as it does in all-stop mode. This is because the
4698 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4699 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4700 changed to a different thread just as you entered a command to operate on the
4701 previously current thread.
4703 @node Background Execution
4704 @subsection Background Execution
4706 @cindex foreground execution
4707 @cindex background execution
4708 @cindex asynchronous execution
4709 @cindex execution, foreground, background and asynchronous
4711 @value{GDBN}'s execution commands have two variants: the normal
4712 foreground (synchronous) behavior, and a background
4713 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4714 the program to report that some thread has stopped before prompting for
4715 another command. In background execution, @value{GDBN} immediately gives
4716 a command prompt so that you can issue other commands while your program runs.
4718 You need to explicitly enable asynchronous mode before you can use
4719 background execution commands. You can use these commands to
4720 manipulate the asynchronous mode setting:
4723 @kindex set target-async
4724 @item set target-async on
4725 Enable asynchronous mode.
4726 @item set target-async off
4727 Disable asynchronous mode.
4728 @kindex show target-async
4729 @item show target-async
4730 Show the current target-async setting.
4733 If the target doesn't support async mode, @value{GDBN} issues an error
4734 message if you attempt to use the background execution commands.
4736 To specify background execution, add a @code{&} to the command. For example,
4737 the background form of the @code{continue} command is @code{continue&}, or
4738 just @code{c&}. The execution commands that accept background execution
4744 @xref{Starting, , Starting your Program}.
4748 @xref{Attach, , Debugging an Already-running Process}.
4752 @xref{Continuing and Stepping, step}.
4756 @xref{Continuing and Stepping, stepi}.
4760 @xref{Continuing and Stepping, next}.
4764 @xref{Continuing and Stepping, nexti}.
4768 @xref{Continuing and Stepping, continue}.
4772 @xref{Continuing and Stepping, finish}.
4776 @xref{Continuing and Stepping, until}.
4780 Background execution is especially useful in conjunction with non-stop
4781 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4782 However, you can also use these commands in the normal all-stop mode with
4783 the restriction that you cannot issue another execution command until the
4784 previous one finishes. Examples of commands that are valid in all-stop
4785 mode while the program is running include @code{help} and @code{info break}.
4787 You can interrupt your program while it is running in the background by
4788 using the @code{interrupt} command.
4795 Suspend execution of the running program. In all-stop mode,
4796 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4797 only the current thread. To stop the whole program in non-stop mode,
4798 use @code{interrupt -a}.
4801 @node Thread-Specific Breakpoints
4802 @subsection Thread-Specific Breakpoints
4804 When your program has multiple threads (@pxref{Threads,, Debugging
4805 Programs with Multiple Threads}), you can choose whether to set
4806 breakpoints on all threads, or on a particular thread.
4809 @cindex breakpoints and threads
4810 @cindex thread breakpoints
4811 @kindex break @dots{} thread @var{threadno}
4812 @item break @var{linespec} thread @var{threadno}
4813 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4814 @var{linespec} specifies source lines; there are several ways of
4815 writing them (@pxref{Specify Location}), but the effect is always to
4816 specify some source line.
4818 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4819 to specify that you only want @value{GDBN} to stop the program when a
4820 particular thread reaches this breakpoint. @var{threadno} is one of the
4821 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4822 column of the @samp{info threads} display.
4824 If you do not specify @samp{thread @var{threadno}} when you set a
4825 breakpoint, the breakpoint applies to @emph{all} threads of your
4828 You can use the @code{thread} qualifier on conditional breakpoints as
4829 well; in this case, place @samp{thread @var{threadno}} before the
4830 breakpoint condition, like this:
4833 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4838 @node Interrupted System Calls
4839 @subsection Interrupted System Calls
4841 @cindex thread breakpoints and system calls
4842 @cindex system calls and thread breakpoints
4843 @cindex premature return from system calls
4844 There is an unfortunate side effect when using @value{GDBN} to debug
4845 multi-threaded programs. If one thread stops for a
4846 breakpoint, or for some other reason, and another thread is blocked in a
4847 system call, then the system call may return prematurely. This is a
4848 consequence of the interaction between multiple threads and the signals
4849 that @value{GDBN} uses to implement breakpoints and other events that
4852 To handle this problem, your program should check the return value of
4853 each system call and react appropriately. This is good programming
4856 For example, do not write code like this:
4862 The call to @code{sleep} will return early if a different thread stops
4863 at a breakpoint or for some other reason.
4865 Instead, write this:
4870 unslept = sleep (unslept);
4873 A system call is allowed to return early, so the system is still
4874 conforming to its specification. But @value{GDBN} does cause your
4875 multi-threaded program to behave differently than it would without
4878 Also, @value{GDBN} uses internal breakpoints in the thread library to
4879 monitor certain events such as thread creation and thread destruction.
4880 When such an event happens, a system call in another thread may return
4881 prematurely, even though your program does not appear to stop.
4884 @node Reverse Execution
4885 @chapter Running programs backward
4886 @cindex reverse execution
4887 @cindex running programs backward
4889 When you are debugging a program, it is not unusual to realize that
4890 you have gone too far, and some event of interest has already happened.
4891 If the target environment supports it, @value{GDBN} can allow you to
4892 ``rewind'' the program by running it backward.
4894 A target environment that supports reverse execution should be able
4895 to ``undo'' the changes in machine state that have taken place as the
4896 program was executing normally. Variables, registers etc.@: should
4897 revert to their previous values. Obviously this requires a great
4898 deal of sophistication on the part of the target environment; not
4899 all target environments can support reverse execution.
4901 When a program is executed in reverse, the instructions that
4902 have most recently been executed are ``un-executed'', in reverse
4903 order. The program counter runs backward, following the previous
4904 thread of execution in reverse. As each instruction is ``un-executed'',
4905 the values of memory and/or registers that were changed by that
4906 instruction are reverted to their previous states. After executing
4907 a piece of source code in reverse, all side effects of that code
4908 should be ``undone'', and all variables should be returned to their
4909 prior values@footnote{
4910 Note that some side effects are easier to undo than others. For instance,
4911 memory and registers are relatively easy, but device I/O is hard. Some
4912 targets may be able undo things like device I/O, and some may not.
4914 The contract between @value{GDBN} and the reverse executing target
4915 requires only that the target do something reasonable when
4916 @value{GDBN} tells it to execute backwards, and then report the
4917 results back to @value{GDBN}. Whatever the target reports back to
4918 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4919 assumes that the memory and registers that the target reports are in a
4920 consistant state, but @value{GDBN} accepts whatever it is given.
4923 If you are debugging in a target environment that supports
4924 reverse execution, @value{GDBN} provides the following commands.
4927 @kindex reverse-continue
4928 @kindex rc @r{(@code{reverse-continue})}
4929 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4930 @itemx rc @r{[}@var{ignore-count}@r{]}
4931 Beginning at the point where your program last stopped, start executing
4932 in reverse. Reverse execution will stop for breakpoints and synchronous
4933 exceptions (signals), just like normal execution. Behavior of
4934 asynchronous signals depends on the target environment.
4936 @kindex reverse-step
4937 @kindex rs @r{(@code{step})}
4938 @item reverse-step @r{[}@var{count}@r{]}
4939 Run the program backward until control reaches the start of a
4940 different source line; then stop it, and return control to @value{GDBN}.
4942 Like the @code{step} command, @code{reverse-step} will only stop
4943 at the beginning of a source line. It ``un-executes'' the previously
4944 executed source line. If the previous source line included calls to
4945 debuggable functions, @code{reverse-step} will step (backward) into
4946 the called function, stopping at the beginning of the @emph{last}
4947 statement in the called function (typically a return statement).
4949 Also, as with the @code{step} command, if non-debuggable functions are
4950 called, @code{reverse-step} will run thru them backward without stopping.
4952 @kindex reverse-stepi
4953 @kindex rsi @r{(@code{reverse-stepi})}
4954 @item reverse-stepi @r{[}@var{count}@r{]}
4955 Reverse-execute one machine instruction. Note that the instruction
4956 to be reverse-executed is @emph{not} the one pointed to by the program
4957 counter, but the instruction executed prior to that one. For instance,
4958 if the last instruction was a jump, @code{reverse-stepi} will take you
4959 back from the destination of the jump to the jump instruction itself.
4961 @kindex reverse-next
4962 @kindex rn @r{(@code{reverse-next})}
4963 @item reverse-next @r{[}@var{count}@r{]}
4964 Run backward to the beginning of the previous line executed in
4965 the current (innermost) stack frame. If the line contains function
4966 calls, they will be ``un-executed'' without stopping. Starting from
4967 the first line of a function, @code{reverse-next} will take you back
4968 to the caller of that function, @emph{before} the function was called,
4969 just as the normal @code{next} command would take you from the last
4970 line of a function back to its return to its caller
4971 @footnote{Unles the code is too heavily optimized.}.
4973 @kindex reverse-nexti
4974 @kindex rni @r{(@code{reverse-nexti})}
4975 @item reverse-nexti @r{[}@var{count}@r{]}
4976 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
4977 in reverse, except that called functions are ``un-executed'' atomically.
4978 That is, if the previously executed instruction was a return from
4979 another instruction, @code{reverse-nexti} will continue to execute
4980 in reverse until the call to that function (from the current stack
4983 @kindex reverse-finish
4984 @item reverse-finish
4985 Just as the @code{finish} command takes you to the point where the
4986 current function returns, @code{reverse-finish} takes you to the point
4987 where it was called. Instead of ending up at the end of the current
4988 function invocation, you end up at the beginning.
4990 @kindex set exec-direction
4991 @item set exec-direction
4992 Set the direction of target execution.
4993 @itemx set exec-direction reverse
4994 @cindex execute forward or backward in time
4995 @value{GDBN} will perform all execution commands in reverse, until the
4996 exec-direction mode is changed to ``forward''. Affected commands include
4997 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
4998 command cannot be used in reverse mode.
4999 @item set exec-direction forward
5000 @value{GDBN} will perform all execution commands in the normal fashion.
5001 This is the default.
5006 @chapter Examining the Stack
5008 When your program has stopped, the first thing you need to know is where it
5009 stopped and how it got there.
5012 Each time your program performs a function call, information about the call
5014 That information includes the location of the call in your program,
5015 the arguments of the call,
5016 and the local variables of the function being called.
5017 The information is saved in a block of data called a @dfn{stack frame}.
5018 The stack frames are allocated in a region of memory called the @dfn{call
5021 When your program stops, the @value{GDBN} commands for examining the
5022 stack allow you to see all of this information.
5024 @cindex selected frame
5025 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5026 @value{GDBN} commands refer implicitly to the selected frame. In
5027 particular, whenever you ask @value{GDBN} for the value of a variable in
5028 your program, the value is found in the selected frame. There are
5029 special @value{GDBN} commands to select whichever frame you are
5030 interested in. @xref{Selection, ,Selecting a Frame}.
5032 When your program stops, @value{GDBN} automatically selects the
5033 currently executing frame and describes it briefly, similar to the
5034 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5037 * Frames:: Stack frames
5038 * Backtrace:: Backtraces
5039 * Selection:: Selecting a frame
5040 * Frame Info:: Information on a frame
5045 @section Stack Frames
5047 @cindex frame, definition
5049 The call stack is divided up into contiguous pieces called @dfn{stack
5050 frames}, or @dfn{frames} for short; each frame is the data associated
5051 with one call to one function. The frame contains the arguments given
5052 to the function, the function's local variables, and the address at
5053 which the function is executing.
5055 @cindex initial frame
5056 @cindex outermost frame
5057 @cindex innermost frame
5058 When your program is started, the stack has only one frame, that of the
5059 function @code{main}. This is called the @dfn{initial} frame or the
5060 @dfn{outermost} frame. Each time a function is called, a new frame is
5061 made. Each time a function returns, the frame for that function invocation
5062 is eliminated. If a function is recursive, there can be many frames for
5063 the same function. The frame for the function in which execution is
5064 actually occurring is called the @dfn{innermost} frame. This is the most
5065 recently created of all the stack frames that still exist.
5067 @cindex frame pointer
5068 Inside your program, stack frames are identified by their addresses. A
5069 stack frame consists of many bytes, each of which has its own address; each
5070 kind of computer has a convention for choosing one byte whose
5071 address serves as the address of the frame. Usually this address is kept
5072 in a register called the @dfn{frame pointer register}
5073 (@pxref{Registers, $fp}) while execution is going on in that frame.
5075 @cindex frame number
5076 @value{GDBN} assigns numbers to all existing stack frames, starting with
5077 zero for the innermost frame, one for the frame that called it,
5078 and so on upward. These numbers do not really exist in your program;
5079 they are assigned by @value{GDBN} to give you a way of designating stack
5080 frames in @value{GDBN} commands.
5082 @c The -fomit-frame-pointer below perennially causes hbox overflow
5083 @c underflow problems.
5084 @cindex frameless execution
5085 Some compilers provide a way to compile functions so that they operate
5086 without stack frames. (For example, the @value{NGCC} option
5088 @samp{-fomit-frame-pointer}
5090 generates functions without a frame.)
5091 This is occasionally done with heavily used library functions to save
5092 the frame setup time. @value{GDBN} has limited facilities for dealing
5093 with these function invocations. If the innermost function invocation
5094 has no stack frame, @value{GDBN} nevertheless regards it as though
5095 it had a separate frame, which is numbered zero as usual, allowing
5096 correct tracing of the function call chain. However, @value{GDBN} has
5097 no provision for frameless functions elsewhere in the stack.
5100 @kindex frame@r{, command}
5101 @cindex current stack frame
5102 @item frame @var{args}
5103 The @code{frame} command allows you to move from one stack frame to another,
5104 and to print the stack frame you select. @var{args} may be either the
5105 address of the frame or the stack frame number. Without an argument,
5106 @code{frame} prints the current stack frame.
5108 @kindex select-frame
5109 @cindex selecting frame silently
5111 The @code{select-frame} command allows you to move from one stack frame
5112 to another without printing the frame. This is the silent version of
5120 @cindex call stack traces
5121 A backtrace is a summary of how your program got where it is. It shows one
5122 line per frame, for many frames, starting with the currently executing
5123 frame (frame zero), followed by its caller (frame one), and on up the
5128 @kindex bt @r{(@code{backtrace})}
5131 Print a backtrace of the entire stack: one line per frame for all
5132 frames in the stack.
5134 You can stop the backtrace at any time by typing the system interrupt
5135 character, normally @kbd{Ctrl-c}.
5137 @item backtrace @var{n}
5139 Similar, but print only the innermost @var{n} frames.
5141 @item backtrace -@var{n}
5143 Similar, but print only the outermost @var{n} frames.
5145 @item backtrace full
5147 @itemx bt full @var{n}
5148 @itemx bt full -@var{n}
5149 Print the values of the local variables also. @var{n} specifies the
5150 number of frames to print, as described above.
5155 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5156 are additional aliases for @code{backtrace}.
5158 @cindex multiple threads, backtrace
5159 In a multi-threaded program, @value{GDBN} by default shows the
5160 backtrace only for the current thread. To display the backtrace for
5161 several or all of the threads, use the command @code{thread apply}
5162 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5163 apply all backtrace}, @value{GDBN} will display the backtrace for all
5164 the threads; this is handy when you debug a core dump of a
5165 multi-threaded program.
5167 Each line in the backtrace shows the frame number and the function name.
5168 The program counter value is also shown---unless you use @code{set
5169 print address off}. The backtrace also shows the source file name and
5170 line number, as well as the arguments to the function. The program
5171 counter value is omitted if it is at the beginning of the code for that
5174 Here is an example of a backtrace. It was made with the command
5175 @samp{bt 3}, so it shows the innermost three frames.
5179 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5181 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5182 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5184 (More stack frames follow...)
5189 The display for frame zero does not begin with a program counter
5190 value, indicating that your program has stopped at the beginning of the
5191 code for line @code{993} of @code{builtin.c}.
5194 The value of parameter @code{data} in frame 1 has been replaced by
5195 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5196 only if it is a scalar (integer, pointer, enumeration, etc). See command
5197 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5198 on how to configure the way function parameter values are printed.
5200 @cindex value optimized out, in backtrace
5201 @cindex function call arguments, optimized out
5202 If your program was compiled with optimizations, some compilers will
5203 optimize away arguments passed to functions if those arguments are
5204 never used after the call. Such optimizations generate code that
5205 passes arguments through registers, but doesn't store those arguments
5206 in the stack frame. @value{GDBN} has no way of displaying such
5207 arguments in stack frames other than the innermost one. Here's what
5208 such a backtrace might look like:
5212 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5214 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5215 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5217 (More stack frames follow...)
5222 The values of arguments that were not saved in their stack frames are
5223 shown as @samp{<value optimized out>}.
5225 If you need to display the values of such optimized-out arguments,
5226 either deduce that from other variables whose values depend on the one
5227 you are interested in, or recompile without optimizations.
5229 @cindex backtrace beyond @code{main} function
5230 @cindex program entry point
5231 @cindex startup code, and backtrace
5232 Most programs have a standard user entry point---a place where system
5233 libraries and startup code transition into user code. For C this is
5234 @code{main}@footnote{
5235 Note that embedded programs (the so-called ``free-standing''
5236 environment) are not required to have a @code{main} function as the
5237 entry point. They could even have multiple entry points.}.
5238 When @value{GDBN} finds the entry function in a backtrace
5239 it will terminate the backtrace, to avoid tracing into highly
5240 system-specific (and generally uninteresting) code.
5242 If you need to examine the startup code, or limit the number of levels
5243 in a backtrace, you can change this behavior:
5246 @item set backtrace past-main
5247 @itemx set backtrace past-main on
5248 @kindex set backtrace
5249 Backtraces will continue past the user entry point.
5251 @item set backtrace past-main off
5252 Backtraces will stop when they encounter the user entry point. This is the
5255 @item show backtrace past-main
5256 @kindex show backtrace
5257 Display the current user entry point backtrace policy.
5259 @item set backtrace past-entry
5260 @itemx set backtrace past-entry on
5261 Backtraces will continue past the internal entry point of an application.
5262 This entry point is encoded by the linker when the application is built,
5263 and is likely before the user entry point @code{main} (or equivalent) is called.
5265 @item set backtrace past-entry off
5266 Backtraces will stop when they encounter the internal entry point of an
5267 application. This is the default.
5269 @item show backtrace past-entry
5270 Display the current internal entry point backtrace policy.
5272 @item set backtrace limit @var{n}
5273 @itemx set backtrace limit 0
5274 @cindex backtrace limit
5275 Limit the backtrace to @var{n} levels. A value of zero means
5278 @item show backtrace limit
5279 Display the current limit on backtrace levels.
5283 @section Selecting a Frame
5285 Most commands for examining the stack and other data in your program work on
5286 whichever stack frame is selected at the moment. Here are the commands for
5287 selecting a stack frame; all of them finish by printing a brief description
5288 of the stack frame just selected.
5291 @kindex frame@r{, selecting}
5292 @kindex f @r{(@code{frame})}
5295 Select frame number @var{n}. Recall that frame zero is the innermost
5296 (currently executing) frame, frame one is the frame that called the
5297 innermost one, and so on. The highest-numbered frame is the one for
5300 @item frame @var{addr}
5302 Select the frame at address @var{addr}. This is useful mainly if the
5303 chaining of stack frames has been damaged by a bug, making it
5304 impossible for @value{GDBN} to assign numbers properly to all frames. In
5305 addition, this can be useful when your program has multiple stacks and
5306 switches between them.
5308 On the SPARC architecture, @code{frame} needs two addresses to
5309 select an arbitrary frame: a frame pointer and a stack pointer.
5311 On the MIPS and Alpha architecture, it needs two addresses: a stack
5312 pointer and a program counter.
5314 On the 29k architecture, it needs three addresses: a register stack
5315 pointer, a program counter, and a memory stack pointer.
5319 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5320 advances toward the outermost frame, to higher frame numbers, to frames
5321 that have existed longer. @var{n} defaults to one.
5324 @kindex do @r{(@code{down})}
5326 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5327 advances toward the innermost frame, to lower frame numbers, to frames
5328 that were created more recently. @var{n} defaults to one. You may
5329 abbreviate @code{down} as @code{do}.
5332 All of these commands end by printing two lines of output describing the
5333 frame. The first line shows the frame number, the function name, the
5334 arguments, and the source file and line number of execution in that
5335 frame. The second line shows the text of that source line.
5343 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5345 10 read_input_file (argv[i]);
5349 After such a printout, the @code{list} command with no arguments
5350 prints ten lines centered on the point of execution in the frame.
5351 You can also edit the program at the point of execution with your favorite
5352 editing program by typing @code{edit}.
5353 @xref{List, ,Printing Source Lines},
5357 @kindex down-silently
5359 @item up-silently @var{n}
5360 @itemx down-silently @var{n}
5361 These two commands are variants of @code{up} and @code{down},
5362 respectively; they differ in that they do their work silently, without
5363 causing display of the new frame. They are intended primarily for use
5364 in @value{GDBN} command scripts, where the output might be unnecessary and
5369 @section Information About a Frame
5371 There are several other commands to print information about the selected
5377 When used without any argument, this command does not change which
5378 frame is selected, but prints a brief description of the currently
5379 selected stack frame. It can be abbreviated @code{f}. With an
5380 argument, this command is used to select a stack frame.
5381 @xref{Selection, ,Selecting a Frame}.
5384 @kindex info f @r{(@code{info frame})}
5387 This command prints a verbose description of the selected stack frame,
5392 the address of the frame
5394 the address of the next frame down (called by this frame)
5396 the address of the next frame up (caller of this frame)
5398 the language in which the source code corresponding to this frame is written
5400 the address of the frame's arguments
5402 the address of the frame's local variables
5404 the program counter saved in it (the address of execution in the caller frame)
5406 which registers were saved in the frame
5409 @noindent The verbose description is useful when
5410 something has gone wrong that has made the stack format fail to fit
5411 the usual conventions.
5413 @item info frame @var{addr}
5414 @itemx info f @var{addr}
5415 Print a verbose description of the frame at address @var{addr}, without
5416 selecting that frame. The selected frame remains unchanged by this
5417 command. This requires the same kind of address (more than one for some
5418 architectures) that you specify in the @code{frame} command.
5419 @xref{Selection, ,Selecting a Frame}.
5423 Print the arguments of the selected frame, each on a separate line.
5427 Print the local variables of the selected frame, each on a separate
5428 line. These are all variables (declared either static or automatic)
5429 accessible at the point of execution of the selected frame.
5432 @cindex catch exceptions, list active handlers
5433 @cindex exception handlers, how to list
5435 Print a list of all the exception handlers that are active in the
5436 current stack frame at the current point of execution. To see other
5437 exception handlers, visit the associated frame (using the @code{up},
5438 @code{down}, or @code{frame} commands); then type @code{info catch}.
5439 @xref{Set Catchpoints, , Setting Catchpoints}.
5445 @chapter Examining Source Files
5447 @value{GDBN} can print parts of your program's source, since the debugging
5448 information recorded in the program tells @value{GDBN} what source files were
5449 used to build it. When your program stops, @value{GDBN} spontaneously prints
5450 the line where it stopped. Likewise, when you select a stack frame
5451 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5452 execution in that frame has stopped. You can print other portions of
5453 source files by explicit command.
5455 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5456 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5457 @value{GDBN} under @sc{gnu} Emacs}.
5460 * List:: Printing source lines
5461 * Specify Location:: How to specify code locations
5462 * Edit:: Editing source files
5463 * Search:: Searching source files
5464 * Source Path:: Specifying source directories
5465 * Machine Code:: Source and machine code
5469 @section Printing Source Lines
5472 @kindex l @r{(@code{list})}
5473 To print lines from a source file, use the @code{list} command
5474 (abbreviated @code{l}). By default, ten lines are printed.
5475 There are several ways to specify what part of the file you want to
5476 print; see @ref{Specify Location}, for the full list.
5478 Here are the forms of the @code{list} command most commonly used:
5481 @item list @var{linenum}
5482 Print lines centered around line number @var{linenum} in the
5483 current source file.
5485 @item list @var{function}
5486 Print lines centered around the beginning of function
5490 Print more lines. If the last lines printed were printed with a
5491 @code{list} command, this prints lines following the last lines
5492 printed; however, if the last line printed was a solitary line printed
5493 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5494 Stack}), this prints lines centered around that line.
5497 Print lines just before the lines last printed.
5500 @cindex @code{list}, how many lines to display
5501 By default, @value{GDBN} prints ten source lines with any of these forms of
5502 the @code{list} command. You can change this using @code{set listsize}:
5505 @kindex set listsize
5506 @item set listsize @var{count}
5507 Make the @code{list} command display @var{count} source lines (unless
5508 the @code{list} argument explicitly specifies some other number).
5510 @kindex show listsize
5512 Display the number of lines that @code{list} prints.
5515 Repeating a @code{list} command with @key{RET} discards the argument,
5516 so it is equivalent to typing just @code{list}. This is more useful
5517 than listing the same lines again. An exception is made for an
5518 argument of @samp{-}; that argument is preserved in repetition so that
5519 each repetition moves up in the source file.
5521 In general, the @code{list} command expects you to supply zero, one or two
5522 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5523 of writing them (@pxref{Specify Location}), but the effect is always
5524 to specify some source line.
5526 Here is a complete description of the possible arguments for @code{list}:
5529 @item list @var{linespec}
5530 Print lines centered around the line specified by @var{linespec}.
5532 @item list @var{first},@var{last}
5533 Print lines from @var{first} to @var{last}. Both arguments are
5534 linespecs. When a @code{list} command has two linespecs, and the
5535 source file of the second linespec is omitted, this refers to
5536 the same source file as the first linespec.
5538 @item list ,@var{last}
5539 Print lines ending with @var{last}.
5541 @item list @var{first},
5542 Print lines starting with @var{first}.
5545 Print lines just after the lines last printed.
5548 Print lines just before the lines last printed.
5551 As described in the preceding table.
5554 @node Specify Location
5555 @section Specifying a Location
5556 @cindex specifying location
5559 Several @value{GDBN} commands accept arguments that specify a location
5560 of your program's code. Since @value{GDBN} is a source-level
5561 debugger, a location usually specifies some line in the source code;
5562 for that reason, locations are also known as @dfn{linespecs}.
5564 Here are all the different ways of specifying a code location that
5565 @value{GDBN} understands:
5569 Specifies the line number @var{linenum} of the current source file.
5572 @itemx +@var{offset}
5573 Specifies the line @var{offset} lines before or after the @dfn{current
5574 line}. For the @code{list} command, the current line is the last one
5575 printed; for the breakpoint commands, this is the line at which
5576 execution stopped in the currently selected @dfn{stack frame}
5577 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5578 used as the second of the two linespecs in a @code{list} command,
5579 this specifies the line @var{offset} lines up or down from the first
5582 @item @var{filename}:@var{linenum}
5583 Specifies the line @var{linenum} in the source file @var{filename}.
5585 @item @var{function}
5586 Specifies the line that begins the body of the function @var{function}.
5587 For example, in C, this is the line with the open brace.
5589 @item @var{filename}:@var{function}
5590 Specifies the line that begins the body of the function @var{function}
5591 in the file @var{filename}. You only need the file name with a
5592 function name to avoid ambiguity when there are identically named
5593 functions in different source files.
5595 @item *@var{address}
5596 Specifies the program address @var{address}. For line-oriented
5597 commands, such as @code{list} and @code{edit}, this specifies a source
5598 line that contains @var{address}. For @code{break} and other
5599 breakpoint oriented commands, this can be used to set breakpoints in
5600 parts of your program which do not have debugging information or
5603 Here @var{address} may be any expression valid in the current working
5604 language (@pxref{Languages, working language}) that specifies a code
5605 address. In addition, as a convenience, @value{GDBN} extends the
5606 semantics of expressions used in locations to cover the situations
5607 that frequently happen during debugging. Here are the various forms
5611 @item @var{expression}
5612 Any expression valid in the current working language.
5614 @item @var{funcaddr}
5615 An address of a function or procedure derived from its name. In C,
5616 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5617 simply the function's name @var{function} (and actually a special case
5618 of a valid expression). In Pascal and Modula-2, this is
5619 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5620 (although the Pascal form also works).
5622 This form specifies the address of the function's first instruction,
5623 before the stack frame and arguments have been set up.
5625 @item '@var{filename}'::@var{funcaddr}
5626 Like @var{funcaddr} above, but also specifies the name of the source
5627 file explicitly. This is useful if the name of the function does not
5628 specify the function unambiguously, e.g., if there are several
5629 functions with identical names in different source files.
5636 @section Editing Source Files
5637 @cindex editing source files
5640 @kindex e @r{(@code{edit})}
5641 To edit the lines in a source file, use the @code{edit} command.
5642 The editing program of your choice
5643 is invoked with the current line set to
5644 the active line in the program.
5645 Alternatively, there are several ways to specify what part of the file you
5646 want to print if you want to see other parts of the program:
5649 @item edit @var{location}
5650 Edit the source file specified by @code{location}. Editing starts at
5651 that @var{location}, e.g., at the specified source line of the
5652 specified file. @xref{Specify Location}, for all the possible forms
5653 of the @var{location} argument; here are the forms of the @code{edit}
5654 command most commonly used:
5657 @item edit @var{number}
5658 Edit the current source file with @var{number} as the active line number.
5660 @item edit @var{function}
5661 Edit the file containing @var{function} at the beginning of its definition.
5666 @subsection Choosing your Editor
5667 You can customize @value{GDBN} to use any editor you want
5669 The only restriction is that your editor (say @code{ex}), recognizes the
5670 following command-line syntax:
5672 ex +@var{number} file
5674 The optional numeric value +@var{number} specifies the number of the line in
5675 the file where to start editing.}.
5676 By default, it is @file{@value{EDITOR}}, but you can change this
5677 by setting the environment variable @code{EDITOR} before using
5678 @value{GDBN}. For example, to configure @value{GDBN} to use the
5679 @code{vi} editor, you could use these commands with the @code{sh} shell:
5685 or in the @code{csh} shell,
5687 setenv EDITOR /usr/bin/vi
5692 @section Searching Source Files
5693 @cindex searching source files
5695 There are two commands for searching through the current source file for a
5700 @kindex forward-search
5701 @item forward-search @var{regexp}
5702 @itemx search @var{regexp}
5703 The command @samp{forward-search @var{regexp}} checks each line,
5704 starting with the one following the last line listed, for a match for
5705 @var{regexp}. It lists the line that is found. You can use the
5706 synonym @samp{search @var{regexp}} or abbreviate the command name as
5709 @kindex reverse-search
5710 @item reverse-search @var{regexp}
5711 The command @samp{reverse-search @var{regexp}} checks each line, starting
5712 with the one before the last line listed and going backward, for a match
5713 for @var{regexp}. It lists the line that is found. You can abbreviate
5714 this command as @code{rev}.
5718 @section Specifying Source Directories
5721 @cindex directories for source files
5722 Executable programs sometimes do not record the directories of the source
5723 files from which they were compiled, just the names. Even when they do,
5724 the directories could be moved between the compilation and your debugging
5725 session. @value{GDBN} has a list of directories to search for source files;
5726 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5727 it tries all the directories in the list, in the order they are present
5728 in the list, until it finds a file with the desired name.
5730 For example, suppose an executable references the file
5731 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5732 @file{/mnt/cross}. The file is first looked up literally; if this
5733 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5734 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5735 message is printed. @value{GDBN} does not look up the parts of the
5736 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5737 Likewise, the subdirectories of the source path are not searched: if
5738 the source path is @file{/mnt/cross}, and the binary refers to
5739 @file{foo.c}, @value{GDBN} would not find it under
5740 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5742 Plain file names, relative file names with leading directories, file
5743 names containing dots, etc.@: are all treated as described above; for
5744 instance, if the source path is @file{/mnt/cross}, and the source file
5745 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5746 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5747 that---@file{/mnt/cross/foo.c}.
5749 Note that the executable search path is @emph{not} used to locate the
5752 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5753 any information it has cached about where source files are found and where
5754 each line is in the file.
5758 When you start @value{GDBN}, its source path includes only @samp{cdir}
5759 and @samp{cwd}, in that order.
5760 To add other directories, use the @code{directory} command.
5762 The search path is used to find both program source files and @value{GDBN}
5763 script files (read using the @samp{-command} option and @samp{source} command).
5765 In addition to the source path, @value{GDBN} provides a set of commands
5766 that manage a list of source path substitution rules. A @dfn{substitution
5767 rule} specifies how to rewrite source directories stored in the program's
5768 debug information in case the sources were moved to a different
5769 directory between compilation and debugging. A rule is made of
5770 two strings, the first specifying what needs to be rewritten in
5771 the path, and the second specifying how it should be rewritten.
5772 In @ref{set substitute-path}, we name these two parts @var{from} and
5773 @var{to} respectively. @value{GDBN} does a simple string replacement
5774 of @var{from} with @var{to} at the start of the directory part of the
5775 source file name, and uses that result instead of the original file
5776 name to look up the sources.
5778 Using the previous example, suppose the @file{foo-1.0} tree has been
5779 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5780 @value{GDBN} to replace @file{/usr/src} in all source path names with
5781 @file{/mnt/cross}. The first lookup will then be
5782 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5783 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5784 substitution rule, use the @code{set substitute-path} command
5785 (@pxref{set substitute-path}).
5787 To avoid unexpected substitution results, a rule is applied only if the
5788 @var{from} part of the directory name ends at a directory separator.
5789 For instance, a rule substituting @file{/usr/source} into
5790 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5791 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5792 is applied only at the beginning of the directory name, this rule will
5793 not be applied to @file{/root/usr/source/baz.c} either.
5795 In many cases, you can achieve the same result using the @code{directory}
5796 command. However, @code{set substitute-path} can be more efficient in
5797 the case where the sources are organized in a complex tree with multiple
5798 subdirectories. With the @code{directory} command, you need to add each
5799 subdirectory of your project. If you moved the entire tree while
5800 preserving its internal organization, then @code{set substitute-path}
5801 allows you to direct the debugger to all the sources with one single
5804 @code{set substitute-path} is also more than just a shortcut command.
5805 The source path is only used if the file at the original location no
5806 longer exists. On the other hand, @code{set substitute-path} modifies
5807 the debugger behavior to look at the rewritten location instead. So, if
5808 for any reason a source file that is not relevant to your executable is
5809 located at the original location, a substitution rule is the only
5810 method available to point @value{GDBN} at the new location.
5813 @item directory @var{dirname} @dots{}
5814 @item dir @var{dirname} @dots{}
5815 Add directory @var{dirname} to the front of the source path. Several
5816 directory names may be given to this command, separated by @samp{:}
5817 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5818 part of absolute file names) or
5819 whitespace. You may specify a directory that is already in the source
5820 path; this moves it forward, so @value{GDBN} searches it sooner.
5824 @vindex $cdir@r{, convenience variable}
5825 @vindex $cwd@r{, convenience variable}
5826 @cindex compilation directory
5827 @cindex current directory
5828 @cindex working directory
5829 @cindex directory, current
5830 @cindex directory, compilation
5831 You can use the string @samp{$cdir} to refer to the compilation
5832 directory (if one is recorded), and @samp{$cwd} to refer to the current
5833 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5834 tracks the current working directory as it changes during your @value{GDBN}
5835 session, while the latter is immediately expanded to the current
5836 directory at the time you add an entry to the source path.
5839 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5841 @c RET-repeat for @code{directory} is explicitly disabled, but since
5842 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5844 @item show directories
5845 @kindex show directories
5846 Print the source path: show which directories it contains.
5848 @anchor{set substitute-path}
5849 @item set substitute-path @var{from} @var{to}
5850 @kindex set substitute-path
5851 Define a source path substitution rule, and add it at the end of the
5852 current list of existing substitution rules. If a rule with the same
5853 @var{from} was already defined, then the old rule is also deleted.
5855 For example, if the file @file{/foo/bar/baz.c} was moved to
5856 @file{/mnt/cross/baz.c}, then the command
5859 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5863 will tell @value{GDBN} to replace @samp{/usr/src} with
5864 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5865 @file{baz.c} even though it was moved.
5867 In the case when more than one substitution rule have been defined,
5868 the rules are evaluated one by one in the order where they have been
5869 defined. The first one matching, if any, is selected to perform
5872 For instance, if we had entered the following commands:
5875 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5876 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5880 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5881 @file{/mnt/include/defs.h} by using the first rule. However, it would
5882 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5883 @file{/mnt/src/lib/foo.c}.
5886 @item unset substitute-path [path]
5887 @kindex unset substitute-path
5888 If a path is specified, search the current list of substitution rules
5889 for a rule that would rewrite that path. Delete that rule if found.
5890 A warning is emitted by the debugger if no rule could be found.
5892 If no path is specified, then all substitution rules are deleted.
5894 @item show substitute-path [path]
5895 @kindex show substitute-path
5896 If a path is specified, then print the source path substitution rule
5897 which would rewrite that path, if any.
5899 If no path is specified, then print all existing source path substitution
5904 If your source path is cluttered with directories that are no longer of
5905 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5906 versions of source. You can correct the situation as follows:
5910 Use @code{directory} with no argument to reset the source path to its default value.
5913 Use @code{directory} with suitable arguments to reinstall the
5914 directories you want in the source path. You can add all the
5915 directories in one command.
5919 @section Source and Machine Code
5920 @cindex source line and its code address
5922 You can use the command @code{info line} to map source lines to program
5923 addresses (and vice versa), and the command @code{disassemble} to display
5924 a range of addresses as machine instructions. You can use the command
5925 @code{set disassemble-next-line} to set whether to disassemble next
5926 source line when execution stops. When run under @sc{gnu} Emacs
5927 mode, the @code{info line} command causes the arrow to point to the
5928 line specified. Also, @code{info line} prints addresses in symbolic form as
5933 @item info line @var{linespec}
5934 Print the starting and ending addresses of the compiled code for
5935 source line @var{linespec}. You can specify source lines in any of
5936 the ways documented in @ref{Specify Location}.
5939 For example, we can use @code{info line} to discover the location of
5940 the object code for the first line of function
5941 @code{m4_changequote}:
5943 @c FIXME: I think this example should also show the addresses in
5944 @c symbolic form, as they usually would be displayed.
5946 (@value{GDBP}) info line m4_changequote
5947 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5951 @cindex code address and its source line
5952 We can also inquire (using @code{*@var{addr}} as the form for
5953 @var{linespec}) what source line covers a particular address:
5955 (@value{GDBP}) info line *0x63ff
5956 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5959 @cindex @code{$_} and @code{info line}
5960 @cindex @code{x} command, default address
5961 @kindex x@r{(examine), and} info line
5962 After @code{info line}, the default address for the @code{x} command
5963 is changed to the starting address of the line, so that @samp{x/i} is
5964 sufficient to begin examining the machine code (@pxref{Memory,
5965 ,Examining Memory}). Also, this address is saved as the value of the
5966 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5971 @cindex assembly instructions
5972 @cindex instructions, assembly
5973 @cindex machine instructions
5974 @cindex listing machine instructions
5976 @itemx disassemble /m
5977 This specialized command dumps a range of memory as machine
5978 instructions. It can also print mixed source+disassembly by specifying
5979 the @code{/m} modifier.
5980 The default memory range is the function surrounding the
5981 program counter of the selected frame. A single argument to this
5982 command is a program counter value; @value{GDBN} dumps the function
5983 surrounding this value. Two arguments specify a range of addresses
5984 (first inclusive, second exclusive) to dump.
5987 The following example shows the disassembly of a range of addresses of
5988 HP PA-RISC 2.0 code:
5991 (@value{GDBP}) disas 0x32c4 0x32e4
5992 Dump of assembler code from 0x32c4 to 0x32e4:
5993 0x32c4 <main+204>: addil 0,dp
5994 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5995 0x32cc <main+212>: ldil 0x3000,r31
5996 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5997 0x32d4 <main+220>: ldo 0(r31),rp
5998 0x32d8 <main+224>: addil -0x800,dp
5999 0x32dc <main+228>: ldo 0x588(r1),r26
6000 0x32e0 <main+232>: ldil 0x3000,r31
6001 End of assembler dump.
6004 Here is an example showing mixed source+assembly for Intel x86:
6007 (@value{GDBP}) disas /m main
6008 Dump of assembler code for function main:
6010 0x08048330 <main+0>: push %ebp
6011 0x08048331 <main+1>: mov %esp,%ebp
6012 0x08048333 <main+3>: sub $0x8,%esp
6013 0x08048336 <main+6>: and $0xfffffff0,%esp
6014 0x08048339 <main+9>: sub $0x10,%esp
6016 6 printf ("Hello.\n");
6017 0x0804833c <main+12>: movl $0x8048440,(%esp)
6018 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6022 0x08048348 <main+24>: mov $0x0,%eax
6023 0x0804834d <main+29>: leave
6024 0x0804834e <main+30>: ret
6026 End of assembler dump.
6029 Some architectures have more than one commonly-used set of instruction
6030 mnemonics or other syntax.
6032 For programs that were dynamically linked and use shared libraries,
6033 instructions that call functions or branch to locations in the shared
6034 libraries might show a seemingly bogus location---it's actually a
6035 location of the relocation table. On some architectures, @value{GDBN}
6036 might be able to resolve these to actual function names.
6039 @kindex set disassembly-flavor
6040 @cindex Intel disassembly flavor
6041 @cindex AT&T disassembly flavor
6042 @item set disassembly-flavor @var{instruction-set}
6043 Select the instruction set to use when disassembling the
6044 program via the @code{disassemble} or @code{x/i} commands.
6046 Currently this command is only defined for the Intel x86 family. You
6047 can set @var{instruction-set} to either @code{intel} or @code{att}.
6048 The default is @code{att}, the AT&T flavor used by default by Unix
6049 assemblers for x86-based targets.
6051 @kindex show disassembly-flavor
6052 @item show disassembly-flavor
6053 Show the current setting of the disassembly flavor.
6057 @kindex set disassemble-next-line
6058 @kindex show disassemble-next-line
6059 @item set disassemble-next-line
6060 @itemx show disassemble-next-line
6061 Control whether or not @value{GDBN} will disassemble next source line
6062 when execution stops. If ON, GDB will display disassembly of the next
6063 source line when execution of the program being debugged stops.
6064 If AUTO (which is the default), or there's no line info to determine
6065 the source line of the next instruction, display disassembly of next
6066 instruction instead.
6071 @chapter Examining Data
6073 @cindex printing data
6074 @cindex examining data
6077 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6078 @c document because it is nonstandard... Under Epoch it displays in a
6079 @c different window or something like that.
6080 The usual way to examine data in your program is with the @code{print}
6081 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6082 evaluates and prints the value of an expression of the language your
6083 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6084 Different Languages}).
6087 @item print @var{expr}
6088 @itemx print /@var{f} @var{expr}
6089 @var{expr} is an expression (in the source language). By default the
6090 value of @var{expr} is printed in a format appropriate to its data type;
6091 you can choose a different format by specifying @samp{/@var{f}}, where
6092 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6096 @itemx print /@var{f}
6097 @cindex reprint the last value
6098 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6099 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6100 conveniently inspect the same value in an alternative format.
6103 A more low-level way of examining data is with the @code{x} command.
6104 It examines data in memory at a specified address and prints it in a
6105 specified format. @xref{Memory, ,Examining Memory}.
6107 If you are interested in information about types, or about how the
6108 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6109 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6113 * Expressions:: Expressions
6114 * Ambiguous Expressions:: Ambiguous Expressions
6115 * Variables:: Program variables
6116 * Arrays:: Artificial arrays
6117 * Output Formats:: Output formats
6118 * Memory:: Examining memory
6119 * Auto Display:: Automatic display
6120 * Print Settings:: Print settings
6121 * Value History:: Value history
6122 * Convenience Vars:: Convenience variables
6123 * Registers:: Registers
6124 * Floating Point Hardware:: Floating point hardware
6125 * Vector Unit:: Vector Unit
6126 * OS Information:: Auxiliary data provided by operating system
6127 * Memory Region Attributes:: Memory region attributes
6128 * Dump/Restore Files:: Copy between memory and a file
6129 * Core File Generation:: Cause a program dump its core
6130 * Character Sets:: Debugging programs that use a different
6131 character set than GDB does
6132 * Caching Remote Data:: Data caching for remote targets
6133 * Searching Memory:: Searching memory for a sequence of bytes
6137 @section Expressions
6140 @code{print} and many other @value{GDBN} commands accept an expression and
6141 compute its value. Any kind of constant, variable or operator defined
6142 by the programming language you are using is valid in an expression in
6143 @value{GDBN}. This includes conditional expressions, function calls,
6144 casts, and string constants. It also includes preprocessor macros, if
6145 you compiled your program to include this information; see
6148 @cindex arrays in expressions
6149 @value{GDBN} supports array constants in expressions input by
6150 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6151 you can use the command @code{print @{1, 2, 3@}} to create an array
6152 of three integers. If you pass an array to a function or assign it
6153 to a program variable, @value{GDBN} copies the array to memory that
6154 is @code{malloc}ed in the target program.
6156 Because C is so widespread, most of the expressions shown in examples in
6157 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6158 Languages}, for information on how to use expressions in other
6161 In this section, we discuss operators that you can use in @value{GDBN}
6162 expressions regardless of your programming language.
6164 @cindex casts, in expressions
6165 Casts are supported in all languages, not just in C, because it is so
6166 useful to cast a number into a pointer in order to examine a structure
6167 at that address in memory.
6168 @c FIXME: casts supported---Mod2 true?
6170 @value{GDBN} supports these operators, in addition to those common
6171 to programming languages:
6175 @samp{@@} is a binary operator for treating parts of memory as arrays.
6176 @xref{Arrays, ,Artificial Arrays}, for more information.
6179 @samp{::} allows you to specify a variable in terms of the file or
6180 function where it is defined. @xref{Variables, ,Program Variables}.
6182 @cindex @{@var{type}@}
6183 @cindex type casting memory
6184 @cindex memory, viewing as typed object
6185 @cindex casts, to view memory
6186 @item @{@var{type}@} @var{addr}
6187 Refers to an object of type @var{type} stored at address @var{addr} in
6188 memory. @var{addr} may be any expression whose value is an integer or
6189 pointer (but parentheses are required around binary operators, just as in
6190 a cast). This construct is allowed regardless of what kind of data is
6191 normally supposed to reside at @var{addr}.
6194 @node Ambiguous Expressions
6195 @section Ambiguous Expressions
6196 @cindex ambiguous expressions
6198 Expressions can sometimes contain some ambiguous elements. For instance,
6199 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6200 a single function name to be defined several times, for application in
6201 different contexts. This is called @dfn{overloading}. Another example
6202 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6203 templates and is typically instantiated several times, resulting in
6204 the same function name being defined in different contexts.
6206 In some cases and depending on the language, it is possible to adjust
6207 the expression to remove the ambiguity. For instance in C@t{++}, you
6208 can specify the signature of the function you want to break on, as in
6209 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6210 qualified name of your function often makes the expression unambiguous
6213 When an ambiguity that needs to be resolved is detected, the debugger
6214 has the capability to display a menu of numbered choices for each
6215 possibility, and then waits for the selection with the prompt @samp{>}.
6216 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6217 aborts the current command. If the command in which the expression was
6218 used allows more than one choice to be selected, the next option in the
6219 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6222 For example, the following session excerpt shows an attempt to set a
6223 breakpoint at the overloaded symbol @code{String::after}.
6224 We choose three particular definitions of that function name:
6226 @c FIXME! This is likely to change to show arg type lists, at least
6229 (@value{GDBP}) b String::after
6232 [2] file:String.cc; line number:867
6233 [3] file:String.cc; line number:860
6234 [4] file:String.cc; line number:875
6235 [5] file:String.cc; line number:853
6236 [6] file:String.cc; line number:846
6237 [7] file:String.cc; line number:735
6239 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6240 Breakpoint 2 at 0xb344: file String.cc, line 875.
6241 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6242 Multiple breakpoints were set.
6243 Use the "delete" command to delete unwanted
6250 @kindex set multiple-symbols
6251 @item set multiple-symbols @var{mode}
6252 @cindex multiple-symbols menu
6254 This option allows you to adjust the debugger behavior when an expression
6257 By default, @var{mode} is set to @code{all}. If the command with which
6258 the expression is used allows more than one choice, then @value{GDBN}
6259 automatically selects all possible choices. For instance, inserting
6260 a breakpoint on a function using an ambiguous name results in a breakpoint
6261 inserted on each possible match. However, if a unique choice must be made,
6262 then @value{GDBN} uses the menu to help you disambiguate the expression.
6263 For instance, printing the address of an overloaded function will result
6264 in the use of the menu.
6266 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6267 when an ambiguity is detected.
6269 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6270 an error due to the ambiguity and the command is aborted.
6272 @kindex show multiple-symbols
6273 @item show multiple-symbols
6274 Show the current value of the @code{multiple-symbols} setting.
6278 @section Program Variables
6280 The most common kind of expression to use is the name of a variable
6283 Variables in expressions are understood in the selected stack frame
6284 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6288 global (or file-static)
6295 visible according to the scope rules of the
6296 programming language from the point of execution in that frame
6299 @noindent This means that in the function
6314 you can examine and use the variable @code{a} whenever your program is
6315 executing within the function @code{foo}, but you can only use or
6316 examine the variable @code{b} while your program is executing inside
6317 the block where @code{b} is declared.
6319 @cindex variable name conflict
6320 There is an exception: you can refer to a variable or function whose
6321 scope is a single source file even if the current execution point is not
6322 in this file. But it is possible to have more than one such variable or
6323 function with the same name (in different source files). If that
6324 happens, referring to that name has unpredictable effects. If you wish,
6325 you can specify a static variable in a particular function or file,
6326 using the colon-colon (@code{::}) notation:
6328 @cindex colon-colon, context for variables/functions
6330 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6331 @cindex @code{::}, context for variables/functions
6334 @var{file}::@var{variable}
6335 @var{function}::@var{variable}
6339 Here @var{file} or @var{function} is the name of the context for the
6340 static @var{variable}. In the case of file names, you can use quotes to
6341 make sure @value{GDBN} parses the file name as a single word---for example,
6342 to print a global value of @code{x} defined in @file{f2.c}:
6345 (@value{GDBP}) p 'f2.c'::x
6348 @cindex C@t{++} scope resolution
6349 This use of @samp{::} is very rarely in conflict with the very similar
6350 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6351 scope resolution operator in @value{GDBN} expressions.
6352 @c FIXME: Um, so what happens in one of those rare cases where it's in
6355 @cindex wrong values
6356 @cindex variable values, wrong
6357 @cindex function entry/exit, wrong values of variables
6358 @cindex optimized code, wrong values of variables
6360 @emph{Warning:} Occasionally, a local variable may appear to have the
6361 wrong value at certain points in a function---just after entry to a new
6362 scope, and just before exit.
6364 You may see this problem when you are stepping by machine instructions.
6365 This is because, on most machines, it takes more than one instruction to
6366 set up a stack frame (including local variable definitions); if you are
6367 stepping by machine instructions, variables may appear to have the wrong
6368 values until the stack frame is completely built. On exit, it usually
6369 also takes more than one machine instruction to destroy a stack frame;
6370 after you begin stepping through that group of instructions, local
6371 variable definitions may be gone.
6373 This may also happen when the compiler does significant optimizations.
6374 To be sure of always seeing accurate values, turn off all optimization
6377 @cindex ``No symbol "foo" in current context''
6378 Another possible effect of compiler optimizations is to optimize
6379 unused variables out of existence, or assign variables to registers (as
6380 opposed to memory addresses). Depending on the support for such cases
6381 offered by the debug info format used by the compiler, @value{GDBN}
6382 might not be able to display values for such local variables. If that
6383 happens, @value{GDBN} will print a message like this:
6386 No symbol "foo" in current context.
6389 To solve such problems, either recompile without optimizations, or use a
6390 different debug info format, if the compiler supports several such
6391 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6392 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6393 produces debug info in a format that is superior to formats such as
6394 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6395 an effective form for debug info. @xref{Debugging Options,,Options
6396 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6397 Compiler Collection (GCC)}.
6398 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6399 that are best suited to C@t{++} programs.
6401 If you ask to print an object whose contents are unknown to
6402 @value{GDBN}, e.g., because its data type is not completely specified
6403 by the debug information, @value{GDBN} will say @samp{<incomplete
6404 type>}. @xref{Symbols, incomplete type}, for more about this.
6406 Strings are identified as arrays of @code{char} values without specified
6407 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6408 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6409 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6410 defines literal string type @code{"char"} as @code{char} without a sign.
6415 signed char var1[] = "A";
6418 You get during debugging
6423 $2 = @{65 'A', 0 '\0'@}
6427 @section Artificial Arrays
6429 @cindex artificial array
6431 @kindex @@@r{, referencing memory as an array}
6432 It is often useful to print out several successive objects of the
6433 same type in memory; a section of an array, or an array of
6434 dynamically determined size for which only a pointer exists in the
6437 You can do this by referring to a contiguous span of memory as an
6438 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6439 operand of @samp{@@} should be the first element of the desired array
6440 and be an individual object. The right operand should be the desired length
6441 of the array. The result is an array value whose elements are all of
6442 the type of the left argument. The first element is actually the left
6443 argument; the second element comes from bytes of memory immediately
6444 following those that hold the first element, and so on. Here is an
6445 example. If a program says
6448 int *array = (int *) malloc (len * sizeof (int));
6452 you can print the contents of @code{array} with
6458 The left operand of @samp{@@} must reside in memory. Array values made
6459 with @samp{@@} in this way behave just like other arrays in terms of
6460 subscripting, and are coerced to pointers when used in expressions.
6461 Artificial arrays most often appear in expressions via the value history
6462 (@pxref{Value History, ,Value History}), after printing one out.
6464 Another way to create an artificial array is to use a cast.
6465 This re-interprets a value as if it were an array.
6466 The value need not be in memory:
6468 (@value{GDBP}) p/x (short[2])0x12345678
6469 $1 = @{0x1234, 0x5678@}
6472 As a convenience, if you leave the array length out (as in
6473 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6474 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6476 (@value{GDBP}) p/x (short[])0x12345678
6477 $2 = @{0x1234, 0x5678@}
6480 Sometimes the artificial array mechanism is not quite enough; in
6481 moderately complex data structures, the elements of interest may not
6482 actually be adjacent---for example, if you are interested in the values
6483 of pointers in an array. One useful work-around in this situation is
6484 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6485 Variables}) as a counter in an expression that prints the first
6486 interesting value, and then repeat that expression via @key{RET}. For
6487 instance, suppose you have an array @code{dtab} of pointers to
6488 structures, and you are interested in the values of a field @code{fv}
6489 in each structure. Here is an example of what you might type:
6499 @node Output Formats
6500 @section Output Formats
6502 @cindex formatted output
6503 @cindex output formats
6504 By default, @value{GDBN} prints a value according to its data type. Sometimes
6505 this is not what you want. For example, you might want to print a number
6506 in hex, or a pointer in decimal. Or you might want to view data in memory
6507 at a certain address as a character string or as an instruction. To do
6508 these things, specify an @dfn{output format} when you print a value.
6510 The simplest use of output formats is to say how to print a value
6511 already computed. This is done by starting the arguments of the
6512 @code{print} command with a slash and a format letter. The format
6513 letters supported are:
6517 Regard the bits of the value as an integer, and print the integer in
6521 Print as integer in signed decimal.
6524 Print as integer in unsigned decimal.
6527 Print as integer in octal.
6530 Print as integer in binary. The letter @samp{t} stands for ``two''.
6531 @footnote{@samp{b} cannot be used because these format letters are also
6532 used with the @code{x} command, where @samp{b} stands for ``byte'';
6533 see @ref{Memory,,Examining Memory}.}
6536 @cindex unknown address, locating
6537 @cindex locate address
6538 Print as an address, both absolute in hexadecimal and as an offset from
6539 the nearest preceding symbol. You can use this format used to discover
6540 where (in what function) an unknown address is located:
6543 (@value{GDBP}) p/a 0x54320
6544 $3 = 0x54320 <_initialize_vx+396>
6548 The command @code{info symbol 0x54320} yields similar results.
6549 @xref{Symbols, info symbol}.
6552 Regard as an integer and print it as a character constant. This
6553 prints both the numerical value and its character representation. The
6554 character representation is replaced with the octal escape @samp{\nnn}
6555 for characters outside the 7-bit @sc{ascii} range.
6557 Without this format, @value{GDBN} displays @code{char},
6558 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6559 constants. Single-byte members of vectors are displayed as integer
6563 Regard the bits of the value as a floating point number and print
6564 using typical floating point syntax.
6567 @cindex printing strings
6568 @cindex printing byte arrays
6569 Regard as a string, if possible. With this format, pointers to single-byte
6570 data are displayed as null-terminated strings and arrays of single-byte data
6571 are displayed as fixed-length strings. Other values are displayed in their
6574 Without this format, @value{GDBN} displays pointers to and arrays of
6575 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6576 strings. Single-byte members of a vector are displayed as an integer
6580 For example, to print the program counter in hex (@pxref{Registers}), type
6587 Note that no space is required before the slash; this is because command
6588 names in @value{GDBN} cannot contain a slash.
6590 To reprint the last value in the value history with a different format,
6591 you can use the @code{print} command with just a format and no
6592 expression. For example, @samp{p/x} reprints the last value in hex.
6595 @section Examining Memory
6597 You can use the command @code{x} (for ``examine'') to examine memory in
6598 any of several formats, independently of your program's data types.
6600 @cindex examining memory
6602 @kindex x @r{(examine memory)}
6603 @item x/@var{nfu} @var{addr}
6606 Use the @code{x} command to examine memory.
6609 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6610 much memory to display and how to format it; @var{addr} is an
6611 expression giving the address where you want to start displaying memory.
6612 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6613 Several commands set convenient defaults for @var{addr}.
6616 @item @var{n}, the repeat count
6617 The repeat count is a decimal integer; the default is 1. It specifies
6618 how much memory (counting by units @var{u}) to display.
6619 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6622 @item @var{f}, the display format
6623 The display format is one of the formats used by @code{print}
6624 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6625 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6626 The default is @samp{x} (hexadecimal) initially. The default changes
6627 each time you use either @code{x} or @code{print}.
6629 @item @var{u}, the unit size
6630 The unit size is any of
6636 Halfwords (two bytes).
6638 Words (four bytes). This is the initial default.
6640 Giant words (eight bytes).
6643 Each time you specify a unit size with @code{x}, that size becomes the
6644 default unit the next time you use @code{x}. (For the @samp{s} and
6645 @samp{i} formats, the unit size is ignored and is normally not written.)
6647 @item @var{addr}, starting display address
6648 @var{addr} is the address where you want @value{GDBN} to begin displaying
6649 memory. The expression need not have a pointer value (though it may);
6650 it is always interpreted as an integer address of a byte of memory.
6651 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6652 @var{addr} is usually just after the last address examined---but several
6653 other commands also set the default address: @code{info breakpoints} (to
6654 the address of the last breakpoint listed), @code{info line} (to the
6655 starting address of a line), and @code{print} (if you use it to display
6656 a value from memory).
6659 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6660 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6661 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6662 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6663 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6665 Since the letters indicating unit sizes are all distinct from the
6666 letters specifying output formats, you do not have to remember whether
6667 unit size or format comes first; either order works. The output
6668 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6669 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6671 Even though the unit size @var{u} is ignored for the formats @samp{s}
6672 and @samp{i}, you might still want to use a count @var{n}; for example,
6673 @samp{3i} specifies that you want to see three machine instructions,
6674 including any operands. For convenience, especially when used with
6675 the @code{display} command, the @samp{i} format also prints branch delay
6676 slot instructions, if any, beyond the count specified, which immediately
6677 follow the last instruction that is within the count. The command
6678 @code{disassemble} gives an alternative way of inspecting machine
6679 instructions; see @ref{Machine Code,,Source and Machine Code}.
6681 All the defaults for the arguments to @code{x} are designed to make it
6682 easy to continue scanning memory with minimal specifications each time
6683 you use @code{x}. For example, after you have inspected three machine
6684 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6685 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6686 the repeat count @var{n} is used again; the other arguments default as
6687 for successive uses of @code{x}.
6689 @cindex @code{$_}, @code{$__}, and value history
6690 The addresses and contents printed by the @code{x} command are not saved
6691 in the value history because there is often too much of them and they
6692 would get in the way. Instead, @value{GDBN} makes these values available for
6693 subsequent use in expressions as values of the convenience variables
6694 @code{$_} and @code{$__}. After an @code{x} command, the last address
6695 examined is available for use in expressions in the convenience variable
6696 @code{$_}. The contents of that address, as examined, are available in
6697 the convenience variable @code{$__}.
6699 If the @code{x} command has a repeat count, the address and contents saved
6700 are from the last memory unit printed; this is not the same as the last
6701 address printed if several units were printed on the last line of output.
6703 @cindex remote memory comparison
6704 @cindex verify remote memory image
6705 When you are debugging a program running on a remote target machine
6706 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6707 remote machine's memory against the executable file you downloaded to
6708 the target. The @code{compare-sections} command is provided for such
6712 @kindex compare-sections
6713 @item compare-sections @r{[}@var{section-name}@r{]}
6714 Compare the data of a loadable section @var{section-name} in the
6715 executable file of the program being debugged with the same section in
6716 the remote machine's memory, and report any mismatches. With no
6717 arguments, compares all loadable sections. This command's
6718 availability depends on the target's support for the @code{"qCRC"}
6723 @section Automatic Display
6724 @cindex automatic display
6725 @cindex display of expressions
6727 If you find that you want to print the value of an expression frequently
6728 (to see how it changes), you might want to add it to the @dfn{automatic
6729 display list} so that @value{GDBN} prints its value each time your program stops.
6730 Each expression added to the list is given a number to identify it;
6731 to remove an expression from the list, you specify that number.
6732 The automatic display looks like this:
6736 3: bar[5] = (struct hack *) 0x3804
6740 This display shows item numbers, expressions and their current values. As with
6741 displays you request manually using @code{x} or @code{print}, you can
6742 specify the output format you prefer; in fact, @code{display} decides
6743 whether to use @code{print} or @code{x} depending your format
6744 specification---it uses @code{x} if you specify either the @samp{i}
6745 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6749 @item display @var{expr}
6750 Add the expression @var{expr} to the list of expressions to display
6751 each time your program stops. @xref{Expressions, ,Expressions}.
6753 @code{display} does not repeat if you press @key{RET} again after using it.
6755 @item display/@var{fmt} @var{expr}
6756 For @var{fmt} specifying only a display format and not a size or
6757 count, add the expression @var{expr} to the auto-display list but
6758 arrange to display it each time in the specified format @var{fmt}.
6759 @xref{Output Formats,,Output Formats}.
6761 @item display/@var{fmt} @var{addr}
6762 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6763 number of units, add the expression @var{addr} as a memory address to
6764 be examined each time your program stops. Examining means in effect
6765 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6768 For example, @samp{display/i $pc} can be helpful, to see the machine
6769 instruction about to be executed each time execution stops (@samp{$pc}
6770 is a common name for the program counter; @pxref{Registers, ,Registers}).
6773 @kindex delete display
6775 @item undisplay @var{dnums}@dots{}
6776 @itemx delete display @var{dnums}@dots{}
6777 Remove item numbers @var{dnums} from the list of expressions to display.
6779 @code{undisplay} does not repeat if you press @key{RET} after using it.
6780 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6782 @kindex disable display
6783 @item disable display @var{dnums}@dots{}
6784 Disable the display of item numbers @var{dnums}. A disabled display
6785 item is not printed automatically, but is not forgotten. It may be
6786 enabled again later.
6788 @kindex enable display
6789 @item enable display @var{dnums}@dots{}
6790 Enable display of item numbers @var{dnums}. It becomes effective once
6791 again in auto display of its expression, until you specify otherwise.
6794 Display the current values of the expressions on the list, just as is
6795 done when your program stops.
6797 @kindex info display
6799 Print the list of expressions previously set up to display
6800 automatically, each one with its item number, but without showing the
6801 values. This includes disabled expressions, which are marked as such.
6802 It also includes expressions which would not be displayed right now
6803 because they refer to automatic variables not currently available.
6806 @cindex display disabled out of scope
6807 If a display expression refers to local variables, then it does not make
6808 sense outside the lexical context for which it was set up. Such an
6809 expression is disabled when execution enters a context where one of its
6810 variables is not defined. For example, if you give the command
6811 @code{display last_char} while inside a function with an argument
6812 @code{last_char}, @value{GDBN} displays this argument while your program
6813 continues to stop inside that function. When it stops elsewhere---where
6814 there is no variable @code{last_char}---the display is disabled
6815 automatically. The next time your program stops where @code{last_char}
6816 is meaningful, you can enable the display expression once again.
6818 @node Print Settings
6819 @section Print Settings
6821 @cindex format options
6822 @cindex print settings
6823 @value{GDBN} provides the following ways to control how arrays, structures,
6824 and symbols are printed.
6827 These settings are useful for debugging programs in any language:
6831 @item set print address
6832 @itemx set print address on
6833 @cindex print/don't print memory addresses
6834 @value{GDBN} prints memory addresses showing the location of stack
6835 traces, structure values, pointer values, breakpoints, and so forth,
6836 even when it also displays the contents of those addresses. The default
6837 is @code{on}. For example, this is what a stack frame display looks like with
6838 @code{set print address on}:
6843 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6845 530 if (lquote != def_lquote)
6849 @item set print address off
6850 Do not print addresses when displaying their contents. For example,
6851 this is the same stack frame displayed with @code{set print address off}:
6855 (@value{GDBP}) set print addr off
6857 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6858 530 if (lquote != def_lquote)
6862 You can use @samp{set print address off} to eliminate all machine
6863 dependent displays from the @value{GDBN} interface. For example, with
6864 @code{print address off}, you should get the same text for backtraces on
6865 all machines---whether or not they involve pointer arguments.
6868 @item show print address
6869 Show whether or not addresses are to be printed.
6872 When @value{GDBN} prints a symbolic address, it normally prints the
6873 closest earlier symbol plus an offset. If that symbol does not uniquely
6874 identify the address (for example, it is a name whose scope is a single
6875 source file), you may need to clarify. One way to do this is with
6876 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6877 you can set @value{GDBN} to print the source file and line number when
6878 it prints a symbolic address:
6881 @item set print symbol-filename on
6882 @cindex source file and line of a symbol
6883 @cindex symbol, source file and line
6884 Tell @value{GDBN} to print the source file name and line number of a
6885 symbol in the symbolic form of an address.
6887 @item set print symbol-filename off
6888 Do not print source file name and line number of a symbol. This is the
6891 @item show print symbol-filename
6892 Show whether or not @value{GDBN} will print the source file name and
6893 line number of a symbol in the symbolic form of an address.
6896 Another situation where it is helpful to show symbol filenames and line
6897 numbers is when disassembling code; @value{GDBN} shows you the line
6898 number and source file that corresponds to each instruction.
6900 Also, you may wish to see the symbolic form only if the address being
6901 printed is reasonably close to the closest earlier symbol:
6904 @item set print max-symbolic-offset @var{max-offset}
6905 @cindex maximum value for offset of closest symbol
6906 Tell @value{GDBN} to only display the symbolic form of an address if the
6907 offset between the closest earlier symbol and the address is less than
6908 @var{max-offset}. The default is 0, which tells @value{GDBN}
6909 to always print the symbolic form of an address if any symbol precedes it.
6911 @item show print max-symbolic-offset
6912 Ask how large the maximum offset is that @value{GDBN} prints in a
6916 @cindex wild pointer, interpreting
6917 @cindex pointer, finding referent
6918 If you have a pointer and you are not sure where it points, try
6919 @samp{set print symbol-filename on}. Then you can determine the name
6920 and source file location of the variable where it points, using
6921 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6922 For example, here @value{GDBN} shows that a variable @code{ptt} points
6923 at another variable @code{t}, defined in @file{hi2.c}:
6926 (@value{GDBP}) set print symbol-filename on
6927 (@value{GDBP}) p/a ptt
6928 $4 = 0xe008 <t in hi2.c>
6932 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6933 does not show the symbol name and filename of the referent, even with
6934 the appropriate @code{set print} options turned on.
6937 Other settings control how different kinds of objects are printed:
6940 @item set print array
6941 @itemx set print array on
6942 @cindex pretty print arrays
6943 Pretty print arrays. This format is more convenient to read,
6944 but uses more space. The default is off.
6946 @item set print array off
6947 Return to compressed format for arrays.
6949 @item show print array
6950 Show whether compressed or pretty format is selected for displaying
6953 @cindex print array indexes
6954 @item set print array-indexes
6955 @itemx set print array-indexes on
6956 Print the index of each element when displaying arrays. May be more
6957 convenient to locate a given element in the array or quickly find the
6958 index of a given element in that printed array. The default is off.
6960 @item set print array-indexes off
6961 Stop printing element indexes when displaying arrays.
6963 @item show print array-indexes
6964 Show whether the index of each element is printed when displaying
6967 @item set print elements @var{number-of-elements}
6968 @cindex number of array elements to print
6969 @cindex limit on number of printed array elements
6970 Set a limit on how many elements of an array @value{GDBN} will print.
6971 If @value{GDBN} is printing a large array, it stops printing after it has
6972 printed the number of elements set by the @code{set print elements} command.
6973 This limit also applies to the display of strings.
6974 When @value{GDBN} starts, this limit is set to 200.
6975 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6977 @item show print elements
6978 Display the number of elements of a large array that @value{GDBN} will print.
6979 If the number is 0, then the printing is unlimited.
6981 @item set print frame-arguments @var{value}
6982 @kindex set print frame-arguments
6983 @cindex printing frame argument values
6984 @cindex print all frame argument values
6985 @cindex print frame argument values for scalars only
6986 @cindex do not print frame argument values
6987 This command allows to control how the values of arguments are printed
6988 when the debugger prints a frame (@pxref{Frames}). The possible
6993 The values of all arguments are printed.
6996 Print the value of an argument only if it is a scalar. The value of more
6997 complex arguments such as arrays, structures, unions, etc, is replaced
6998 by @code{@dots{}}. This is the default. Here is an example where
6999 only scalar arguments are shown:
7002 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7007 None of the argument values are printed. Instead, the value of each argument
7008 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7011 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7016 By default, only scalar arguments are printed. This command can be used
7017 to configure the debugger to print the value of all arguments, regardless
7018 of their type. However, it is often advantageous to not print the value
7019 of more complex parameters. For instance, it reduces the amount of
7020 information printed in each frame, making the backtrace more readable.
7021 Also, it improves performance when displaying Ada frames, because
7022 the computation of large arguments can sometimes be CPU-intensive,
7023 especially in large applications. Setting @code{print frame-arguments}
7024 to @code{scalars} (the default) or @code{none} avoids this computation,
7025 thus speeding up the display of each Ada frame.
7027 @item show print frame-arguments
7028 Show how the value of arguments should be displayed when printing a frame.
7030 @item set print repeats
7031 @cindex repeated array elements
7032 Set the threshold for suppressing display of repeated array
7033 elements. When the number of consecutive identical elements of an
7034 array exceeds the threshold, @value{GDBN} prints the string
7035 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7036 identical repetitions, instead of displaying the identical elements
7037 themselves. Setting the threshold to zero will cause all elements to
7038 be individually printed. The default threshold is 10.
7040 @item show print repeats
7041 Display the current threshold for printing repeated identical
7044 @item set print null-stop
7045 @cindex @sc{null} elements in arrays
7046 Cause @value{GDBN} to stop printing the characters of an array when the first
7047 @sc{null} is encountered. This is useful when large arrays actually
7048 contain only short strings.
7051 @item show print null-stop
7052 Show whether @value{GDBN} stops printing an array on the first
7053 @sc{null} character.
7055 @item set print pretty on
7056 @cindex print structures in indented form
7057 @cindex indentation in structure display
7058 Cause @value{GDBN} to print structures in an indented format with one member
7059 per line, like this:
7074 @item set print pretty off
7075 Cause @value{GDBN} to print structures in a compact format, like this:
7079 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7080 meat = 0x54 "Pork"@}
7085 This is the default format.
7087 @item show print pretty
7088 Show which format @value{GDBN} is using to print structures.
7090 @item set print sevenbit-strings on
7091 @cindex eight-bit characters in strings
7092 @cindex octal escapes in strings
7093 Print using only seven-bit characters; if this option is set,
7094 @value{GDBN} displays any eight-bit characters (in strings or
7095 character values) using the notation @code{\}@var{nnn}. This setting is
7096 best if you are working in English (@sc{ascii}) and you use the
7097 high-order bit of characters as a marker or ``meta'' bit.
7099 @item set print sevenbit-strings off
7100 Print full eight-bit characters. This allows the use of more
7101 international character sets, and is the default.
7103 @item show print sevenbit-strings
7104 Show whether or not @value{GDBN} is printing only seven-bit characters.
7106 @item set print union on
7107 @cindex unions in structures, printing
7108 Tell @value{GDBN} to print unions which are contained in structures
7109 and other unions. This is the default setting.
7111 @item set print union off
7112 Tell @value{GDBN} not to print unions which are contained in
7113 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7116 @item show print union
7117 Ask @value{GDBN} whether or not it will print unions which are contained in
7118 structures and other unions.
7120 For example, given the declarations
7123 typedef enum @{Tree, Bug@} Species;
7124 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7125 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7136 struct thing foo = @{Tree, @{Acorn@}@};
7140 with @code{set print union on} in effect @samp{p foo} would print
7143 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7147 and with @code{set print union off} in effect it would print
7150 $1 = @{it = Tree, form = @{...@}@}
7154 @code{set print union} affects programs written in C-like languages
7160 These settings are of interest when debugging C@t{++} programs:
7163 @cindex demangling C@t{++} names
7164 @item set print demangle
7165 @itemx set print demangle on
7166 Print C@t{++} names in their source form rather than in the encoded
7167 (``mangled'') form passed to the assembler and linker for type-safe
7168 linkage. The default is on.
7170 @item show print demangle
7171 Show whether C@t{++} names are printed in mangled or demangled form.
7173 @item set print asm-demangle
7174 @itemx set print asm-demangle on
7175 Print C@t{++} names in their source form rather than their mangled form, even
7176 in assembler code printouts such as instruction disassemblies.
7179 @item show print asm-demangle
7180 Show whether C@t{++} names in assembly listings are printed in mangled
7183 @cindex C@t{++} symbol decoding style
7184 @cindex symbol decoding style, C@t{++}
7185 @kindex set demangle-style
7186 @item set demangle-style @var{style}
7187 Choose among several encoding schemes used by different compilers to
7188 represent C@t{++} names. The choices for @var{style} are currently:
7192 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7195 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7196 This is the default.
7199 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7202 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7205 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7206 @strong{Warning:} this setting alone is not sufficient to allow
7207 debugging @code{cfront}-generated executables. @value{GDBN} would
7208 require further enhancement to permit that.
7211 If you omit @var{style}, you will see a list of possible formats.
7213 @item show demangle-style
7214 Display the encoding style currently in use for decoding C@t{++} symbols.
7216 @item set print object
7217 @itemx set print object on
7218 @cindex derived type of an object, printing
7219 @cindex display derived types
7220 When displaying a pointer to an object, identify the @emph{actual}
7221 (derived) type of the object rather than the @emph{declared} type, using
7222 the virtual function table.
7224 @item set print object off
7225 Display only the declared type of objects, without reference to the
7226 virtual function table. This is the default setting.
7228 @item show print object
7229 Show whether actual, or declared, object types are displayed.
7231 @item set print static-members
7232 @itemx set print static-members on
7233 @cindex static members of C@t{++} objects
7234 Print static members when displaying a C@t{++} object. The default is on.
7236 @item set print static-members off
7237 Do not print static members when displaying a C@t{++} object.
7239 @item show print static-members
7240 Show whether C@t{++} static members are printed or not.
7242 @item set print pascal_static-members
7243 @itemx set print pascal_static-members on
7244 @cindex static members of Pascal objects
7245 @cindex Pascal objects, static members display
7246 Print static members when displaying a Pascal object. The default is on.
7248 @item set print pascal_static-members off
7249 Do not print static members when displaying a Pascal object.
7251 @item show print pascal_static-members
7252 Show whether Pascal static members are printed or not.
7254 @c These don't work with HP ANSI C++ yet.
7255 @item set print vtbl
7256 @itemx set print vtbl on
7257 @cindex pretty print C@t{++} virtual function tables
7258 @cindex virtual functions (C@t{++}) display
7259 @cindex VTBL display
7260 Pretty print C@t{++} virtual function tables. The default is off.
7261 (The @code{vtbl} commands do not work on programs compiled with the HP
7262 ANSI C@t{++} compiler (@code{aCC}).)
7264 @item set print vtbl off
7265 Do not pretty print C@t{++} virtual function tables.
7267 @item show print vtbl
7268 Show whether C@t{++} virtual function tables are pretty printed, or not.
7272 @section Value History
7274 @cindex value history
7275 @cindex history of values printed by @value{GDBN}
7276 Values printed by the @code{print} command are saved in the @value{GDBN}
7277 @dfn{value history}. This allows you to refer to them in other expressions.
7278 Values are kept until the symbol table is re-read or discarded
7279 (for example with the @code{file} or @code{symbol-file} commands).
7280 When the symbol table changes, the value history is discarded,
7281 since the values may contain pointers back to the types defined in the
7286 @cindex history number
7287 The values printed are given @dfn{history numbers} by which you can
7288 refer to them. These are successive integers starting with one.
7289 @code{print} shows you the history number assigned to a value by
7290 printing @samp{$@var{num} = } before the value; here @var{num} is the
7293 To refer to any previous value, use @samp{$} followed by the value's
7294 history number. The way @code{print} labels its output is designed to
7295 remind you of this. Just @code{$} refers to the most recent value in
7296 the history, and @code{$$} refers to the value before that.
7297 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7298 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7299 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7301 For example, suppose you have just printed a pointer to a structure and
7302 want to see the contents of the structure. It suffices to type
7308 If you have a chain of structures where the component @code{next} points
7309 to the next one, you can print the contents of the next one with this:
7316 You can print successive links in the chain by repeating this
7317 command---which you can do by just typing @key{RET}.
7319 Note that the history records values, not expressions. If the value of
7320 @code{x} is 4 and you type these commands:
7328 then the value recorded in the value history by the @code{print} command
7329 remains 4 even though the value of @code{x} has changed.
7334 Print the last ten values in the value history, with their item numbers.
7335 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7336 values} does not change the history.
7338 @item show values @var{n}
7339 Print ten history values centered on history item number @var{n}.
7342 Print ten history values just after the values last printed. If no more
7343 values are available, @code{show values +} produces no display.
7346 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7347 same effect as @samp{show values +}.
7349 @node Convenience Vars
7350 @section Convenience Variables
7352 @cindex convenience variables
7353 @cindex user-defined variables
7354 @value{GDBN} provides @dfn{convenience variables} that you can use within
7355 @value{GDBN} to hold on to a value and refer to it later. These variables
7356 exist entirely within @value{GDBN}; they are not part of your program, and
7357 setting a convenience variable has no direct effect on further execution
7358 of your program. That is why you can use them freely.
7360 Convenience variables are prefixed with @samp{$}. Any name preceded by
7361 @samp{$} can be used for a convenience variable, unless it is one of
7362 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7363 (Value history references, in contrast, are @emph{numbers} preceded
7364 by @samp{$}. @xref{Value History, ,Value History}.)
7366 You can save a value in a convenience variable with an assignment
7367 expression, just as you would set a variable in your program.
7371 set $foo = *object_ptr
7375 would save in @code{$foo} the value contained in the object pointed to by
7378 Using a convenience variable for the first time creates it, but its
7379 value is @code{void} until you assign a new value. You can alter the
7380 value with another assignment at any time.
7382 Convenience variables have no fixed types. You can assign a convenience
7383 variable any type of value, including structures and arrays, even if
7384 that variable already has a value of a different type. The convenience
7385 variable, when used as an expression, has the type of its current value.
7388 @kindex show convenience
7389 @cindex show all user variables
7390 @item show convenience
7391 Print a list of convenience variables used so far, and their values.
7392 Abbreviated @code{show conv}.
7394 @kindex init-if-undefined
7395 @cindex convenience variables, initializing
7396 @item init-if-undefined $@var{variable} = @var{expression}
7397 Set a convenience variable if it has not already been set. This is useful
7398 for user-defined commands that keep some state. It is similar, in concept,
7399 to using local static variables with initializers in C (except that
7400 convenience variables are global). It can also be used to allow users to
7401 override default values used in a command script.
7403 If the variable is already defined then the expression is not evaluated so
7404 any side-effects do not occur.
7407 One of the ways to use a convenience variable is as a counter to be
7408 incremented or a pointer to be advanced. For example, to print
7409 a field from successive elements of an array of structures:
7413 print bar[$i++]->contents
7417 Repeat that command by typing @key{RET}.
7419 Some convenience variables are created automatically by @value{GDBN} and given
7420 values likely to be useful.
7423 @vindex $_@r{, convenience variable}
7425 The variable @code{$_} is automatically set by the @code{x} command to
7426 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7427 commands which provide a default address for @code{x} to examine also
7428 set @code{$_} to that address; these commands include @code{info line}
7429 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7430 except when set by the @code{x} command, in which case it is a pointer
7431 to the type of @code{$__}.
7433 @vindex $__@r{, convenience variable}
7435 The variable @code{$__} is automatically set by the @code{x} command
7436 to the value found in the last address examined. Its type is chosen
7437 to match the format in which the data was printed.
7440 @vindex $_exitcode@r{, convenience variable}
7441 The variable @code{$_exitcode} is automatically set to the exit code when
7442 the program being debugged terminates.
7445 @vindex $_siginfo@r{, convenience variable}
7446 The variable @code{$_siginfo} is bound to extra signal information
7447 inspection (@pxref{extra signal information}).
7450 On HP-UX systems, if you refer to a function or variable name that
7451 begins with a dollar sign, @value{GDBN} searches for a user or system
7452 name first, before it searches for a convenience variable.
7454 @cindex convenience functions
7455 @value{GDBN} also supplies some @dfn{convenience functions}. These
7456 have a syntax similar to convenience variables. A convenience
7457 function can be used in an expression just like an ordinary function;
7458 however, a convenience function is implemented internally to
7463 @kindex help function
7464 @cindex show all convenience functions
7465 Print a list of all convenience functions.
7472 You can refer to machine register contents, in expressions, as variables
7473 with names starting with @samp{$}. The names of registers are different
7474 for each machine; use @code{info registers} to see the names used on
7478 @kindex info registers
7479 @item info registers
7480 Print the names and values of all registers except floating-point
7481 and vector registers (in the selected stack frame).
7483 @kindex info all-registers
7484 @cindex floating point registers
7485 @item info all-registers
7486 Print the names and values of all registers, including floating-point
7487 and vector registers (in the selected stack frame).
7489 @item info registers @var{regname} @dots{}
7490 Print the @dfn{relativized} value of each specified register @var{regname}.
7491 As discussed in detail below, register values are normally relative to
7492 the selected stack frame. @var{regname} may be any register name valid on
7493 the machine you are using, with or without the initial @samp{$}.
7496 @cindex stack pointer register
7497 @cindex program counter register
7498 @cindex process status register
7499 @cindex frame pointer register
7500 @cindex standard registers
7501 @value{GDBN} has four ``standard'' register names that are available (in
7502 expressions) on most machines---whenever they do not conflict with an
7503 architecture's canonical mnemonics for registers. The register names
7504 @code{$pc} and @code{$sp} are used for the program counter register and
7505 the stack pointer. @code{$fp} is used for a register that contains a
7506 pointer to the current stack frame, and @code{$ps} is used for a
7507 register that contains the processor status. For example,
7508 you could print the program counter in hex with
7515 or print the instruction to be executed next with
7522 or add four to the stack pointer@footnote{This is a way of removing
7523 one word from the stack, on machines where stacks grow downward in
7524 memory (most machines, nowadays). This assumes that the innermost
7525 stack frame is selected; setting @code{$sp} is not allowed when other
7526 stack frames are selected. To pop entire frames off the stack,
7527 regardless of machine architecture, use @code{return};
7528 see @ref{Returning, ,Returning from a Function}.} with
7534 Whenever possible, these four standard register names are available on
7535 your machine even though the machine has different canonical mnemonics,
7536 so long as there is no conflict. The @code{info registers} command
7537 shows the canonical names. For example, on the SPARC, @code{info
7538 registers} displays the processor status register as @code{$psr} but you
7539 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7540 is an alias for the @sc{eflags} register.
7542 @value{GDBN} always considers the contents of an ordinary register as an
7543 integer when the register is examined in this way. Some machines have
7544 special registers which can hold nothing but floating point; these
7545 registers are considered to have floating point values. There is no way
7546 to refer to the contents of an ordinary register as floating point value
7547 (although you can @emph{print} it as a floating point value with
7548 @samp{print/f $@var{regname}}).
7550 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7551 means that the data format in which the register contents are saved by
7552 the operating system is not the same one that your program normally
7553 sees. For example, the registers of the 68881 floating point
7554 coprocessor are always saved in ``extended'' (raw) format, but all C
7555 programs expect to work with ``double'' (virtual) format. In such
7556 cases, @value{GDBN} normally works with the virtual format only (the format
7557 that makes sense for your program), but the @code{info registers} command
7558 prints the data in both formats.
7560 @cindex SSE registers (x86)
7561 @cindex MMX registers (x86)
7562 Some machines have special registers whose contents can be interpreted
7563 in several different ways. For example, modern x86-based machines
7564 have SSE and MMX registers that can hold several values packed
7565 together in several different formats. @value{GDBN} refers to such
7566 registers in @code{struct} notation:
7569 (@value{GDBP}) print $xmm1
7571 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7572 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7573 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7574 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7575 v4_int32 = @{0, 20657912, 11, 13@},
7576 v2_int64 = @{88725056443645952, 55834574859@},
7577 uint128 = 0x0000000d0000000b013b36f800000000
7582 To set values of such registers, you need to tell @value{GDBN} which
7583 view of the register you wish to change, as if you were assigning
7584 value to a @code{struct} member:
7587 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7590 Normally, register values are relative to the selected stack frame
7591 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7592 value that the register would contain if all stack frames farther in
7593 were exited and their saved registers restored. In order to see the
7594 true contents of hardware registers, you must select the innermost
7595 frame (with @samp{frame 0}).
7597 However, @value{GDBN} must deduce where registers are saved, from the machine
7598 code generated by your compiler. If some registers are not saved, or if
7599 @value{GDBN} is unable to locate the saved registers, the selected stack
7600 frame makes no difference.
7602 @node Floating Point Hardware
7603 @section Floating Point Hardware
7604 @cindex floating point
7606 Depending on the configuration, @value{GDBN} may be able to give
7607 you more information about the status of the floating point hardware.
7612 Display hardware-dependent information about the floating
7613 point unit. The exact contents and layout vary depending on the
7614 floating point chip. Currently, @samp{info float} is supported on
7615 the ARM and x86 machines.
7619 @section Vector Unit
7622 Depending on the configuration, @value{GDBN} may be able to give you
7623 more information about the status of the vector unit.
7628 Display information about the vector unit. The exact contents and
7629 layout vary depending on the hardware.
7632 @node OS Information
7633 @section Operating System Auxiliary Information
7634 @cindex OS information
7636 @value{GDBN} provides interfaces to useful OS facilities that can help
7637 you debug your program.
7639 @cindex @code{ptrace} system call
7640 @cindex @code{struct user} contents
7641 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7642 machines), it interfaces with the inferior via the @code{ptrace}
7643 system call. The operating system creates a special sata structure,
7644 called @code{struct user}, for this interface. You can use the
7645 command @code{info udot} to display the contents of this data
7651 Display the contents of the @code{struct user} maintained by the OS
7652 kernel for the program being debugged. @value{GDBN} displays the
7653 contents of @code{struct user} as a list of hex numbers, similar to
7654 the @code{examine} command.
7657 @cindex auxiliary vector
7658 @cindex vector, auxiliary
7659 Some operating systems supply an @dfn{auxiliary vector} to programs at
7660 startup. This is akin to the arguments and environment that you
7661 specify for a program, but contains a system-dependent variety of
7662 binary values that tell system libraries important details about the
7663 hardware, operating system, and process. Each value's purpose is
7664 identified by an integer tag; the meanings are well-known but system-specific.
7665 Depending on the configuration and operating system facilities,
7666 @value{GDBN} may be able to show you this information. For remote
7667 targets, this functionality may further depend on the remote stub's
7668 support of the @samp{qXfer:auxv:read} packet, see
7669 @ref{qXfer auxiliary vector read}.
7674 Display the auxiliary vector of the inferior, which can be either a
7675 live process or a core dump file. @value{GDBN} prints each tag value
7676 numerically, and also shows names and text descriptions for recognized
7677 tags. Some values in the vector are numbers, some bit masks, and some
7678 pointers to strings or other data. @value{GDBN} displays each value in the
7679 most appropriate form for a recognized tag, and in hexadecimal for
7680 an unrecognized tag.
7683 On some targets, @value{GDBN} can access operating-system-specific information
7684 and display it to user, without interpretation. For remote targets,
7685 this functionality depends on the remote stub's support of the
7686 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7689 @kindex info os processes
7690 @item info os processes
7691 Display the list of processes on the target. For each process,
7692 @value{GDBN} prints the process identifier, the name of the user, and
7693 the command corresponding to the process.
7696 @node Memory Region Attributes
7697 @section Memory Region Attributes
7698 @cindex memory region attributes
7700 @dfn{Memory region attributes} allow you to describe special handling
7701 required by regions of your target's memory. @value{GDBN} uses
7702 attributes to determine whether to allow certain types of memory
7703 accesses; whether to use specific width accesses; and whether to cache
7704 target memory. By default the description of memory regions is
7705 fetched from the target (if the current target supports this), but the
7706 user can override the fetched regions.
7708 Defined memory regions can be individually enabled and disabled. When a
7709 memory region is disabled, @value{GDBN} uses the default attributes when
7710 accessing memory in that region. Similarly, if no memory regions have
7711 been defined, @value{GDBN} uses the default attributes when accessing
7714 When a memory region is defined, it is given a number to identify it;
7715 to enable, disable, or remove a memory region, you specify that number.
7719 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7720 Define a memory region bounded by @var{lower} and @var{upper} with
7721 attributes @var{attributes}@dots{}, and add it to the list of regions
7722 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7723 case: it is treated as the target's maximum memory address.
7724 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7727 Discard any user changes to the memory regions and use target-supplied
7728 regions, if available, or no regions if the target does not support.
7731 @item delete mem @var{nums}@dots{}
7732 Remove memory regions @var{nums}@dots{} from the list of regions
7733 monitored by @value{GDBN}.
7736 @item disable mem @var{nums}@dots{}
7737 Disable monitoring of memory regions @var{nums}@dots{}.
7738 A disabled memory region is not forgotten.
7739 It may be enabled again later.
7742 @item enable mem @var{nums}@dots{}
7743 Enable monitoring of memory regions @var{nums}@dots{}.
7747 Print a table of all defined memory regions, with the following columns
7751 @item Memory Region Number
7752 @item Enabled or Disabled.
7753 Enabled memory regions are marked with @samp{y}.
7754 Disabled memory regions are marked with @samp{n}.
7757 The address defining the inclusive lower bound of the memory region.
7760 The address defining the exclusive upper bound of the memory region.
7763 The list of attributes set for this memory region.
7768 @subsection Attributes
7770 @subsubsection Memory Access Mode
7771 The access mode attributes set whether @value{GDBN} may make read or
7772 write accesses to a memory region.
7774 While these attributes prevent @value{GDBN} from performing invalid
7775 memory accesses, they do nothing to prevent the target system, I/O DMA,
7776 etc.@: from accessing memory.
7780 Memory is read only.
7782 Memory is write only.
7784 Memory is read/write. This is the default.
7787 @subsubsection Memory Access Size
7788 The access size attribute tells @value{GDBN} to use specific sized
7789 accesses in the memory region. Often memory mapped device registers
7790 require specific sized accesses. If no access size attribute is
7791 specified, @value{GDBN} may use accesses of any size.
7795 Use 8 bit memory accesses.
7797 Use 16 bit memory accesses.
7799 Use 32 bit memory accesses.
7801 Use 64 bit memory accesses.
7804 @c @subsubsection Hardware/Software Breakpoints
7805 @c The hardware/software breakpoint attributes set whether @value{GDBN}
7806 @c will use hardware or software breakpoints for the internal breakpoints
7807 @c used by the step, next, finish, until, etc. commands.
7811 @c Always use hardware breakpoints
7812 @c @item swbreak (default)
7815 @subsubsection Data Cache
7816 The data cache attributes set whether @value{GDBN} will cache target
7817 memory. While this generally improves performance by reducing debug
7818 protocol overhead, it can lead to incorrect results because @value{GDBN}
7819 does not know about volatile variables or memory mapped device
7824 Enable @value{GDBN} to cache target memory.
7826 Disable @value{GDBN} from caching target memory. This is the default.
7829 @subsection Memory Access Checking
7830 @value{GDBN} can be instructed to refuse accesses to memory that is
7831 not explicitly described. This can be useful if accessing such
7832 regions has undesired effects for a specific target, or to provide
7833 better error checking. The following commands control this behaviour.
7836 @kindex set mem inaccessible-by-default
7837 @item set mem inaccessible-by-default [on|off]
7838 If @code{on} is specified, make @value{GDBN} treat memory not
7839 explicitly described by the memory ranges as non-existent and refuse accesses
7840 to such memory. The checks are only performed if there's at least one
7841 memory range defined. If @code{off} is specified, make @value{GDBN}
7842 treat the memory not explicitly described by the memory ranges as RAM.
7843 The default value is @code{on}.
7844 @kindex show mem inaccessible-by-default
7845 @item show mem inaccessible-by-default
7846 Show the current handling of accesses to unknown memory.
7850 @c @subsubsection Memory Write Verification
7851 @c The memory write verification attributes set whether @value{GDBN}
7852 @c will re-reads data after each write to verify the write was successful.
7856 @c @item noverify (default)
7859 @node Dump/Restore Files
7860 @section Copy Between Memory and a File
7861 @cindex dump/restore files
7862 @cindex append data to a file
7863 @cindex dump data to a file
7864 @cindex restore data from a file
7866 You can use the commands @code{dump}, @code{append}, and
7867 @code{restore} to copy data between target memory and a file. The
7868 @code{dump} and @code{append} commands write data to a file, and the
7869 @code{restore} command reads data from a file back into the inferior's
7870 memory. Files may be in binary, Motorola S-record, Intel hex, or
7871 Tektronix Hex format; however, @value{GDBN} can only append to binary
7877 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7878 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7879 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7880 or the value of @var{expr}, to @var{filename} in the given format.
7882 The @var{format} parameter may be any one of:
7889 Motorola S-record format.
7891 Tektronix Hex format.
7894 @value{GDBN} uses the same definitions of these formats as the
7895 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7896 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7900 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7901 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7902 Append the contents of memory from @var{start_addr} to @var{end_addr},
7903 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7904 (@value{GDBN} can only append data to files in raw binary form.)
7907 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7908 Restore the contents of file @var{filename} into memory. The
7909 @code{restore} command can automatically recognize any known @sc{bfd}
7910 file format, except for raw binary. To restore a raw binary file you
7911 must specify the optional keyword @code{binary} after the filename.
7913 If @var{bias} is non-zero, its value will be added to the addresses
7914 contained in the file. Binary files always start at address zero, so
7915 they will be restored at address @var{bias}. Other bfd files have
7916 a built-in location; they will be restored at offset @var{bias}
7919 If @var{start} and/or @var{end} are non-zero, then only data between
7920 file offset @var{start} and file offset @var{end} will be restored.
7921 These offsets are relative to the addresses in the file, before
7922 the @var{bias} argument is applied.
7926 @node Core File Generation
7927 @section How to Produce a Core File from Your Program
7928 @cindex dump core from inferior
7930 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7931 image of a running process and its process status (register values
7932 etc.). Its primary use is post-mortem debugging of a program that
7933 crashed while it ran outside a debugger. A program that crashes
7934 automatically produces a core file, unless this feature is disabled by
7935 the user. @xref{Files}, for information on invoking @value{GDBN} in
7936 the post-mortem debugging mode.
7938 Occasionally, you may wish to produce a core file of the program you
7939 are debugging in order to preserve a snapshot of its state.
7940 @value{GDBN} has a special command for that.
7944 @kindex generate-core-file
7945 @item generate-core-file [@var{file}]
7946 @itemx gcore [@var{file}]
7947 Produce a core dump of the inferior process. The optional argument
7948 @var{file} specifies the file name where to put the core dump. If not
7949 specified, the file name defaults to @file{core.@var{pid}}, where
7950 @var{pid} is the inferior process ID.
7952 Note that this command is implemented only for some systems (as of
7953 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7956 @node Character Sets
7957 @section Character Sets
7958 @cindex character sets
7960 @cindex translating between character sets
7961 @cindex host character set
7962 @cindex target character set
7964 If the program you are debugging uses a different character set to
7965 represent characters and strings than the one @value{GDBN} uses itself,
7966 @value{GDBN} can automatically translate between the character sets for
7967 you. The character set @value{GDBN} uses we call the @dfn{host
7968 character set}; the one the inferior program uses we call the
7969 @dfn{target character set}.
7971 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7972 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7973 remote protocol (@pxref{Remote Debugging}) to debug a program
7974 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7975 then the host character set is Latin-1, and the target character set is
7976 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7977 target-charset EBCDIC-US}, then @value{GDBN} translates between
7978 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7979 character and string literals in expressions.
7981 @value{GDBN} has no way to automatically recognize which character set
7982 the inferior program uses; you must tell it, using the @code{set
7983 target-charset} command, described below.
7985 Here are the commands for controlling @value{GDBN}'s character set
7989 @item set target-charset @var{charset}
7990 @kindex set target-charset
7991 Set the current target character set to @var{charset}. To display the
7992 list of supported target character sets, type
7993 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
7995 @item set host-charset @var{charset}
7996 @kindex set host-charset
7997 Set the current host character set to @var{charset}.
7999 By default, @value{GDBN} uses a host character set appropriate to the
8000 system it is running on; you can override that default using the
8001 @code{set host-charset} command.
8003 @value{GDBN} can only use certain character sets as its host character
8004 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8005 @value{GDBN} will list the host character sets it supports.
8007 @item set charset @var{charset}
8009 Set the current host and target character sets to @var{charset}. As
8010 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8011 @value{GDBN} will list the names of the character sets that can be used
8012 for both host and target.
8015 @kindex show charset
8016 Show the names of the current host and target character sets.
8018 @item show host-charset
8019 @kindex show host-charset
8020 Show the name of the current host character set.
8022 @item show target-charset
8023 @kindex show target-charset
8024 Show the name of the current target character set.
8026 @item set target-wide-charset @var{charset}
8027 @kindex set target-wide-charset
8028 Set the current target's wide character set to @var{charset}. This is
8029 the character set used by the target's @code{wchar_t} type. To
8030 display the list of supported wide character sets, type
8031 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8033 @item show target-wide-charset
8034 @kindex show target-wide-charset
8035 Show the name of the current target's wide character set.
8038 Here is an example of @value{GDBN}'s character set support in action.
8039 Assume that the following source code has been placed in the file
8040 @file{charset-test.c}:
8046 = @{72, 101, 108, 108, 111, 44, 32, 119,
8047 111, 114, 108, 100, 33, 10, 0@};
8048 char ibm1047_hello[]
8049 = @{200, 133, 147, 147, 150, 107, 64, 166,
8050 150, 153, 147, 132, 90, 37, 0@};
8054 printf ("Hello, world!\n");
8058 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8059 containing the string @samp{Hello, world!} followed by a newline,
8060 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8062 We compile the program, and invoke the debugger on it:
8065 $ gcc -g charset-test.c -o charset-test
8066 $ gdb -nw charset-test
8067 GNU gdb 2001-12-19-cvs
8068 Copyright 2001 Free Software Foundation, Inc.
8073 We can use the @code{show charset} command to see what character sets
8074 @value{GDBN} is currently using to interpret and display characters and
8078 (@value{GDBP}) show charset
8079 The current host and target character set is `ISO-8859-1'.
8083 For the sake of printing this manual, let's use @sc{ascii} as our
8084 initial character set:
8086 (@value{GDBP}) set charset ASCII
8087 (@value{GDBP}) show charset
8088 The current host and target character set is `ASCII'.
8092 Let's assume that @sc{ascii} is indeed the correct character set for our
8093 host system --- in other words, let's assume that if @value{GDBN} prints
8094 characters using the @sc{ascii} character set, our terminal will display
8095 them properly. Since our current target character set is also
8096 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8099 (@value{GDBP}) print ascii_hello
8100 $1 = 0x401698 "Hello, world!\n"
8101 (@value{GDBP}) print ascii_hello[0]
8106 @value{GDBN} uses the target character set for character and string
8107 literals you use in expressions:
8110 (@value{GDBP}) print '+'
8115 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8118 @value{GDBN} relies on the user to tell it which character set the
8119 target program uses. If we print @code{ibm1047_hello} while our target
8120 character set is still @sc{ascii}, we get jibberish:
8123 (@value{GDBP}) print ibm1047_hello
8124 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8125 (@value{GDBP}) print ibm1047_hello[0]
8130 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8131 @value{GDBN} tells us the character sets it supports:
8134 (@value{GDBP}) set target-charset
8135 ASCII EBCDIC-US IBM1047 ISO-8859-1
8136 (@value{GDBP}) set target-charset
8139 We can select @sc{ibm1047} as our target character set, and examine the
8140 program's strings again. Now the @sc{ascii} string is wrong, but
8141 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8142 target character set, @sc{ibm1047}, to the host character set,
8143 @sc{ascii}, and they display correctly:
8146 (@value{GDBP}) set target-charset IBM1047
8147 (@value{GDBP}) show charset
8148 The current host character set is `ASCII'.
8149 The current target character set is `IBM1047'.
8150 (@value{GDBP}) print ascii_hello
8151 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8152 (@value{GDBP}) print ascii_hello[0]
8154 (@value{GDBP}) print ibm1047_hello
8155 $8 = 0x4016a8 "Hello, world!\n"
8156 (@value{GDBP}) print ibm1047_hello[0]
8161 As above, @value{GDBN} uses the target character set for character and
8162 string literals you use in expressions:
8165 (@value{GDBP}) print '+'
8170 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8173 @node Caching Remote Data
8174 @section Caching Data of Remote Targets
8175 @cindex caching data of remote targets
8177 @value{GDBN} can cache data exchanged between the debugger and a
8178 remote target (@pxref{Remote Debugging}). Such caching generally improves
8179 performance, because it reduces the overhead of the remote protocol by
8180 bundling memory reads and writes into large chunks. Unfortunately,
8181 @value{GDBN} does not currently know anything about volatile
8182 registers, and thus data caching will produce incorrect results when
8183 volatile registers are in use.
8186 @kindex set remotecache
8187 @item set remotecache on
8188 @itemx set remotecache off
8189 Set caching state for remote targets. When @code{ON}, use data
8190 caching. By default, this option is @code{OFF}.
8192 @kindex show remotecache
8193 @item show remotecache
8194 Show the current state of data caching for remote targets.
8198 Print the information about the data cache performance. The
8199 information displayed includes: the dcache width and depth; and for
8200 each cache line, how many times it was referenced, and its data and
8201 state (invalid, dirty, valid). This command is useful for debugging
8202 the data cache operation.
8205 @node Searching Memory
8206 @section Search Memory
8207 @cindex searching memory
8209 Memory can be searched for a particular sequence of bytes with the
8210 @code{find} command.
8214 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8215 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8216 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8217 etc. The search begins at address @var{start_addr} and continues for either
8218 @var{len} bytes or through to @var{end_addr} inclusive.
8221 @var{s} and @var{n} are optional parameters.
8222 They may be specified in either order, apart or together.
8225 @item @var{s}, search query size
8226 The size of each search query value.
8232 halfwords (two bytes)
8236 giant words (eight bytes)
8239 All values are interpreted in the current language.
8240 This means, for example, that if the current source language is C/C@t{++}
8241 then searching for the string ``hello'' includes the trailing '\0'.
8243 If the value size is not specified, it is taken from the
8244 value's type in the current language.
8245 This is useful when one wants to specify the search
8246 pattern as a mixture of types.
8247 Note that this means, for example, that in the case of C-like languages
8248 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8249 which is typically four bytes.
8251 @item @var{n}, maximum number of finds
8252 The maximum number of matches to print. The default is to print all finds.
8255 You can use strings as search values. Quote them with double-quotes
8257 The string value is copied into the search pattern byte by byte,
8258 regardless of the endianness of the target and the size specification.
8260 The address of each match found is printed as well as a count of the
8261 number of matches found.
8263 The address of the last value found is stored in convenience variable
8265 A count of the number of matches is stored in @samp{$numfound}.
8267 For example, if stopped at the @code{printf} in this function:
8273 static char hello[] = "hello-hello";
8274 static struct @{ char c; short s; int i; @}
8275 __attribute__ ((packed)) mixed
8276 = @{ 'c', 0x1234, 0x87654321 @};
8277 printf ("%s\n", hello);
8282 you get during debugging:
8285 (gdb) find &hello[0], +sizeof(hello), "hello"
8286 0x804956d <hello.1620+6>
8288 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8289 0x8049567 <hello.1620>
8290 0x804956d <hello.1620+6>
8292 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8293 0x8049567 <hello.1620>
8295 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8296 0x8049560 <mixed.1625>
8298 (gdb) print $numfound
8301 $2 = (void *) 0x8049560
8305 @chapter C Preprocessor Macros
8307 Some languages, such as C and C@t{++}, provide a way to define and invoke
8308 ``preprocessor macros'' which expand into strings of tokens.
8309 @value{GDBN} can evaluate expressions containing macro invocations, show
8310 the result of macro expansion, and show a macro's definition, including
8311 where it was defined.
8313 You may need to compile your program specially to provide @value{GDBN}
8314 with information about preprocessor macros. Most compilers do not
8315 include macros in their debugging information, even when you compile
8316 with the @option{-g} flag. @xref{Compilation}.
8318 A program may define a macro at one point, remove that definition later,
8319 and then provide a different definition after that. Thus, at different
8320 points in the program, a macro may have different definitions, or have
8321 no definition at all. If there is a current stack frame, @value{GDBN}
8322 uses the macros in scope at that frame's source code line. Otherwise,
8323 @value{GDBN} uses the macros in scope at the current listing location;
8326 Whenever @value{GDBN} evaluates an expression, it always expands any
8327 macro invocations present in the expression. @value{GDBN} also provides
8328 the following commands for working with macros explicitly.
8332 @kindex macro expand
8333 @cindex macro expansion, showing the results of preprocessor
8334 @cindex preprocessor macro expansion, showing the results of
8335 @cindex expanding preprocessor macros
8336 @item macro expand @var{expression}
8337 @itemx macro exp @var{expression}
8338 Show the results of expanding all preprocessor macro invocations in
8339 @var{expression}. Since @value{GDBN} simply expands macros, but does
8340 not parse the result, @var{expression} need not be a valid expression;
8341 it can be any string of tokens.
8344 @item macro expand-once @var{expression}
8345 @itemx macro exp1 @var{expression}
8346 @cindex expand macro once
8347 @i{(This command is not yet implemented.)} Show the results of
8348 expanding those preprocessor macro invocations that appear explicitly in
8349 @var{expression}. Macro invocations appearing in that expansion are
8350 left unchanged. This command allows you to see the effect of a
8351 particular macro more clearly, without being confused by further
8352 expansions. Since @value{GDBN} simply expands macros, but does not
8353 parse the result, @var{expression} need not be a valid expression; it
8354 can be any string of tokens.
8357 @cindex macro definition, showing
8358 @cindex definition, showing a macro's
8359 @item info macro @var{macro}
8360 Show the definition of the macro named @var{macro}, and describe the
8361 source location where that definition was established.
8363 @kindex macro define
8364 @cindex user-defined macros
8365 @cindex defining macros interactively
8366 @cindex macros, user-defined
8367 @item macro define @var{macro} @var{replacement-list}
8368 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8369 Introduce a definition for a preprocessor macro named @var{macro},
8370 invocations of which are replaced by the tokens given in
8371 @var{replacement-list}. The first form of this command defines an
8372 ``object-like'' macro, which takes no arguments; the second form
8373 defines a ``function-like'' macro, which takes the arguments given in
8376 A definition introduced by this command is in scope in every
8377 expression evaluated in @value{GDBN}, until it is removed with the
8378 @code{macro undef} command, described below. The definition overrides
8379 all definitions for @var{macro} present in the program being debugged,
8380 as well as any previous user-supplied definition.
8383 @item macro undef @var{macro}
8384 Remove any user-supplied definition for the macro named @var{macro}.
8385 This command only affects definitions provided with the @code{macro
8386 define} command, described above; it cannot remove definitions present
8387 in the program being debugged.
8391 List all the macros defined using the @code{macro define} command.
8394 @cindex macros, example of debugging with
8395 Here is a transcript showing the above commands in action. First, we
8396 show our source files:
8404 #define ADD(x) (M + x)
8409 printf ("Hello, world!\n");
8411 printf ("We're so creative.\n");
8413 printf ("Goodbye, world!\n");
8420 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8421 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8422 compiler includes information about preprocessor macros in the debugging
8426 $ gcc -gdwarf-2 -g3 sample.c -o sample
8430 Now, we start @value{GDBN} on our sample program:
8434 GNU gdb 2002-05-06-cvs
8435 Copyright 2002 Free Software Foundation, Inc.
8436 GDB is free software, @dots{}
8440 We can expand macros and examine their definitions, even when the
8441 program is not running. @value{GDBN} uses the current listing position
8442 to decide which macro definitions are in scope:
8445 (@value{GDBP}) list main
8448 5 #define ADD(x) (M + x)
8453 10 printf ("Hello, world!\n");
8455 12 printf ("We're so creative.\n");
8456 (@value{GDBP}) info macro ADD
8457 Defined at /home/jimb/gdb/macros/play/sample.c:5
8458 #define ADD(x) (M + x)
8459 (@value{GDBP}) info macro Q
8460 Defined at /home/jimb/gdb/macros/play/sample.h:1
8461 included at /home/jimb/gdb/macros/play/sample.c:2
8463 (@value{GDBP}) macro expand ADD(1)
8464 expands to: (42 + 1)
8465 (@value{GDBP}) macro expand-once ADD(1)
8466 expands to: once (M + 1)
8470 In the example above, note that @code{macro expand-once} expands only
8471 the macro invocation explicit in the original text --- the invocation of
8472 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8473 which was introduced by @code{ADD}.
8475 Once the program is running, @value{GDBN} uses the macro definitions in
8476 force at the source line of the current stack frame:
8479 (@value{GDBP}) break main
8480 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8482 Starting program: /home/jimb/gdb/macros/play/sample
8484 Breakpoint 1, main () at sample.c:10
8485 10 printf ("Hello, world!\n");
8489 At line 10, the definition of the macro @code{N} at line 9 is in force:
8492 (@value{GDBP}) info macro N
8493 Defined at /home/jimb/gdb/macros/play/sample.c:9
8495 (@value{GDBP}) macro expand N Q M
8497 (@value{GDBP}) print N Q M
8502 As we step over directives that remove @code{N}'s definition, and then
8503 give it a new definition, @value{GDBN} finds the definition (or lack
8504 thereof) in force at each point:
8509 12 printf ("We're so creative.\n");
8510 (@value{GDBP}) info macro N
8511 The symbol `N' has no definition as a C/C++ preprocessor macro
8512 at /home/jimb/gdb/macros/play/sample.c:12
8515 14 printf ("Goodbye, world!\n");
8516 (@value{GDBP}) info macro N
8517 Defined at /home/jimb/gdb/macros/play/sample.c:13
8519 (@value{GDBP}) macro expand N Q M
8520 expands to: 1729 < 42
8521 (@value{GDBP}) print N Q M
8528 @chapter Tracepoints
8529 @c This chapter is based on the documentation written by Michael
8530 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8533 In some applications, it is not feasible for the debugger to interrupt
8534 the program's execution long enough for the developer to learn
8535 anything helpful about its behavior. If the program's correctness
8536 depends on its real-time behavior, delays introduced by a debugger
8537 might cause the program to change its behavior drastically, or perhaps
8538 fail, even when the code itself is correct. It is useful to be able
8539 to observe the program's behavior without interrupting it.
8541 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8542 specify locations in the program, called @dfn{tracepoints}, and
8543 arbitrary expressions to evaluate when those tracepoints are reached.
8544 Later, using the @code{tfind} command, you can examine the values
8545 those expressions had when the program hit the tracepoints. The
8546 expressions may also denote objects in memory---structures or arrays,
8547 for example---whose values @value{GDBN} should record; while visiting
8548 a particular tracepoint, you may inspect those objects as if they were
8549 in memory at that moment. However, because @value{GDBN} records these
8550 values without interacting with you, it can do so quickly and
8551 unobtrusively, hopefully not disturbing the program's behavior.
8553 The tracepoint facility is currently available only for remote
8554 targets. @xref{Targets}. In addition, your remote target must know
8555 how to collect trace data. This functionality is implemented in the
8556 remote stub; however, none of the stubs distributed with @value{GDBN}
8557 support tracepoints as of this writing. The format of the remote
8558 packets used to implement tracepoints are described in @ref{Tracepoint
8561 This chapter describes the tracepoint commands and features.
8565 * Analyze Collected Data::
8566 * Tracepoint Variables::
8569 @node Set Tracepoints
8570 @section Commands to Set Tracepoints
8572 Before running such a @dfn{trace experiment}, an arbitrary number of
8573 tracepoints can be set. A tracepoint is actually a special type of
8574 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
8575 standard breakpoint commands. For instance, as with breakpoints,
8576 tracepoint numbers are successive integers starting from one, and many
8577 of the commands associated with tracepoints take the tracepoint number
8578 as their argument, to identify which tracepoint to work on.
8580 For each tracepoint, you can specify, in advance, some arbitrary set
8581 of data that you want the target to collect in the trace buffer when
8582 it hits that tracepoint. The collected data can include registers,
8583 local variables, or global data. Later, you can use @value{GDBN}
8584 commands to examine the values these data had at the time the
8587 Tracepoints do not support every breakpoint feature. Conditional
8588 expressions and ignore counts on tracepoints have no effect, and
8589 tracepoints cannot run @value{GDBN} commands when they are
8590 hit. Tracepoints may not be thread-specific either.
8592 This section describes commands to set tracepoints and associated
8593 conditions and actions.
8596 * Create and Delete Tracepoints::
8597 * Enable and Disable Tracepoints::
8598 * Tracepoint Passcounts::
8599 * Tracepoint Actions::
8600 * Listing Tracepoints::
8601 * Starting and Stopping Trace Experiments::
8604 @node Create and Delete Tracepoints
8605 @subsection Create and Delete Tracepoints
8608 @cindex set tracepoint
8610 @item trace @var{location}
8611 The @code{trace} command is very similar to the @code{break} command.
8612 Its argument @var{location} can be a source line, a function name, or
8613 an address in the target program. @xref{Specify Location}. The
8614 @code{trace} command defines a tracepoint, which is a point in the
8615 target program where the debugger will briefly stop, collect some
8616 data, and then allow the program to continue. Setting a tracepoint or
8617 changing its actions doesn't take effect until the next @code{tstart}
8618 command, and once a trace experiment is running, further changes will
8619 not have any effect until the next trace experiment starts.
8621 Here are some examples of using the @code{trace} command:
8624 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8626 (@value{GDBP}) @b{trace +2} // 2 lines forward
8628 (@value{GDBP}) @b{trace my_function} // first source line of function
8630 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8632 (@value{GDBP}) @b{trace *0x2117c4} // an address
8636 You can abbreviate @code{trace} as @code{tr}.
8639 @cindex last tracepoint number
8640 @cindex recent tracepoint number
8641 @cindex tracepoint number
8642 The convenience variable @code{$tpnum} records the tracepoint number
8643 of the most recently set tracepoint.
8645 @kindex delete tracepoint
8646 @cindex tracepoint deletion
8647 @item delete tracepoint @r{[}@var{num}@r{]}
8648 Permanently delete one or more tracepoints. With no argument, the
8649 default is to delete all tracepoints. Note that the regular
8650 @code{delete} command can remove tracepoints also.
8655 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
8657 (@value{GDBP}) @b{delete trace} // remove all tracepoints
8661 You can abbreviate this command as @code{del tr}.
8664 @node Enable and Disable Tracepoints
8665 @subsection Enable and Disable Tracepoints
8667 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
8670 @kindex disable tracepoint
8671 @item disable tracepoint @r{[}@var{num}@r{]}
8672 Disable tracepoint @var{num}, or all tracepoints if no argument
8673 @var{num} is given. A disabled tracepoint will have no effect during
8674 the next trace experiment, but it is not forgotten. You can re-enable
8675 a disabled tracepoint using the @code{enable tracepoint} command.
8677 @kindex enable tracepoint
8678 @item enable tracepoint @r{[}@var{num}@r{]}
8679 Enable tracepoint @var{num}, or all tracepoints. The enabled
8680 tracepoints will become effective the next time a trace experiment is
8684 @node Tracepoint Passcounts
8685 @subsection Tracepoint Passcounts
8689 @cindex tracepoint pass count
8690 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
8691 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
8692 automatically stop a trace experiment. If a tracepoint's passcount is
8693 @var{n}, then the trace experiment will be automatically stopped on
8694 the @var{n}'th time that tracepoint is hit. If the tracepoint number
8695 @var{num} is not specified, the @code{passcount} command sets the
8696 passcount of the most recently defined tracepoint. If no passcount is
8697 given, the trace experiment will run until stopped explicitly by the
8703 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
8704 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
8706 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
8707 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
8708 (@value{GDBP}) @b{trace foo}
8709 (@value{GDBP}) @b{pass 3}
8710 (@value{GDBP}) @b{trace bar}
8711 (@value{GDBP}) @b{pass 2}
8712 (@value{GDBP}) @b{trace baz}
8713 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
8714 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
8715 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
8716 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
8720 @node Tracepoint Actions
8721 @subsection Tracepoint Action Lists
8725 @cindex tracepoint actions
8726 @item actions @r{[}@var{num}@r{]}
8727 This command will prompt for a list of actions to be taken when the
8728 tracepoint is hit. If the tracepoint number @var{num} is not
8729 specified, this command sets the actions for the one that was most
8730 recently defined (so that you can define a tracepoint and then say
8731 @code{actions} without bothering about its number). You specify the
8732 actions themselves on the following lines, one action at a time, and
8733 terminate the actions list with a line containing just @code{end}. So
8734 far, the only defined actions are @code{collect} and
8735 @code{while-stepping}.
8737 @cindex remove actions from a tracepoint
8738 To remove all actions from a tracepoint, type @samp{actions @var{num}}
8739 and follow it immediately with @samp{end}.
8742 (@value{GDBP}) @b{collect @var{data}} // collect some data
8744 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
8746 (@value{GDBP}) @b{end} // signals the end of actions.
8749 In the following example, the action list begins with @code{collect}
8750 commands indicating the things to be collected when the tracepoint is
8751 hit. Then, in order to single-step and collect additional data
8752 following the tracepoint, a @code{while-stepping} command is used,
8753 followed by the list of things to be collected while stepping. The
8754 @code{while-stepping} command is terminated by its own separate
8755 @code{end} command. Lastly, the action list is terminated by an
8759 (@value{GDBP}) @b{trace foo}
8760 (@value{GDBP}) @b{actions}
8761 Enter actions for tracepoint 1, one per line:
8770 @kindex collect @r{(tracepoints)}
8771 @item collect @var{expr1}, @var{expr2}, @dots{}
8772 Collect values of the given expressions when the tracepoint is hit.
8773 This command accepts a comma-separated list of any valid expressions.
8774 In addition to global, static, or local variables, the following
8775 special arguments are supported:
8779 collect all registers
8782 collect all function arguments
8785 collect all local variables.
8788 You can give several consecutive @code{collect} commands, each one
8789 with a single argument, or one @code{collect} command with several
8790 arguments separated by commas: the effect is the same.
8792 The command @code{info scope} (@pxref{Symbols, info scope}) is
8793 particularly useful for figuring out what data to collect.
8795 @kindex while-stepping @r{(tracepoints)}
8796 @item while-stepping @var{n}
8797 Perform @var{n} single-step traces after the tracepoint, collecting
8798 new data at each step. The @code{while-stepping} command is
8799 followed by the list of what to collect while stepping (followed by
8800 its own @code{end} command):
8804 > collect $regs, myglobal
8810 You may abbreviate @code{while-stepping} as @code{ws} or
8814 @node Listing Tracepoints
8815 @subsection Listing Tracepoints
8818 @kindex info tracepoints
8820 @cindex information about tracepoints
8821 @item info tracepoints @r{[}@var{num}@r{]}
8822 Display information about the tracepoint @var{num}. If you don't
8823 specify a tracepoint number, displays information about all the
8824 tracepoints defined so far. The format is similar to that used for
8825 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
8826 command, simply restricting itself to tracepoints.
8828 A tracepoint's listing may include additional information specific to
8833 its passcount as given by the @code{passcount @var{n}} command
8835 its step count as given by the @code{while-stepping @var{n}} command
8837 its action list as given by the @code{actions} command. The actions
8838 are prefixed with an @samp{A} so as to distinguish them from commands.
8842 (@value{GDBP}) @b{info trace}
8843 Num Type Disp Enb Address What
8844 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
8848 A collect globfoo, $regs
8856 This command can be abbreviated @code{info tp}.
8859 @node Starting and Stopping Trace Experiments
8860 @subsection Starting and Stopping Trace Experiments
8864 @cindex start a new trace experiment
8865 @cindex collected data discarded
8867 This command takes no arguments. It starts the trace experiment, and
8868 begins collecting data. This has the side effect of discarding all
8869 the data collected in the trace buffer during the previous trace
8873 @cindex stop a running trace experiment
8875 This command takes no arguments. It ends the trace experiment, and
8876 stops collecting data.
8878 @strong{Note}: a trace experiment and data collection may stop
8879 automatically if any tracepoint's passcount is reached
8880 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
8883 @cindex status of trace data collection
8884 @cindex trace experiment, status of
8886 This command displays the status of the current trace data
8890 Here is an example of the commands we described so far:
8893 (@value{GDBP}) @b{trace gdb_c_test}
8894 (@value{GDBP}) @b{actions}
8895 Enter actions for tracepoint #1, one per line.
8896 > collect $regs,$locals,$args
8901 (@value{GDBP}) @b{tstart}
8902 [time passes @dots{}]
8903 (@value{GDBP}) @b{tstop}
8907 @node Analyze Collected Data
8908 @section Using the Collected Data
8910 After the tracepoint experiment ends, you use @value{GDBN} commands
8911 for examining the trace data. The basic idea is that each tracepoint
8912 collects a trace @dfn{snapshot} every time it is hit and another
8913 snapshot every time it single-steps. All these snapshots are
8914 consecutively numbered from zero and go into a buffer, and you can
8915 examine them later. The way you examine them is to @dfn{focus} on a
8916 specific trace snapshot. When the remote stub is focused on a trace
8917 snapshot, it will respond to all @value{GDBN} requests for memory and
8918 registers by reading from the buffer which belongs to that snapshot,
8919 rather than from @emph{real} memory or registers of the program being
8920 debugged. This means that @strong{all} @value{GDBN} commands
8921 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8922 behave as if we were currently debugging the program state as it was
8923 when the tracepoint occurred. Any requests for data that are not in
8924 the buffer will fail.
8927 * tfind:: How to select a trace snapshot
8928 * tdump:: How to display all data for a snapshot
8929 * save-tracepoints:: How to save tracepoints for a future run
8933 @subsection @code{tfind @var{n}}
8936 @cindex select trace snapshot
8937 @cindex find trace snapshot
8938 The basic command for selecting a trace snapshot from the buffer is
8939 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8940 counting from zero. If no argument @var{n} is given, the next
8941 snapshot is selected.
8943 Here are the various forms of using the @code{tfind} command.
8947 Find the first snapshot in the buffer. This is a synonym for
8948 @code{tfind 0} (since 0 is the number of the first snapshot).
8951 Stop debugging trace snapshots, resume @emph{live} debugging.
8954 Same as @samp{tfind none}.
8957 No argument means find the next trace snapshot.
8960 Find the previous trace snapshot before the current one. This permits
8961 retracing earlier steps.
8963 @item tfind tracepoint @var{num}
8964 Find the next snapshot associated with tracepoint @var{num}. Search
8965 proceeds forward from the last examined trace snapshot. If no
8966 argument @var{num} is given, it means find the next snapshot collected
8967 for the same tracepoint as the current snapshot.
8969 @item tfind pc @var{addr}
8970 Find the next snapshot associated with the value @var{addr} of the
8971 program counter. Search proceeds forward from the last examined trace
8972 snapshot. If no argument @var{addr} is given, it means find the next
8973 snapshot with the same value of PC as the current snapshot.
8975 @item tfind outside @var{addr1}, @var{addr2}
8976 Find the next snapshot whose PC is outside the given range of
8979 @item tfind range @var{addr1}, @var{addr2}
8980 Find the next snapshot whose PC is between @var{addr1} and
8981 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8983 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8984 Find the next snapshot associated with the source line @var{n}. If
8985 the optional argument @var{file} is given, refer to line @var{n} in
8986 that source file. Search proceeds forward from the last examined
8987 trace snapshot. If no argument @var{n} is given, it means find the
8988 next line other than the one currently being examined; thus saying
8989 @code{tfind line} repeatedly can appear to have the same effect as
8990 stepping from line to line in a @emph{live} debugging session.
8993 The default arguments for the @code{tfind} commands are specifically
8994 designed to make it easy to scan through the trace buffer. For
8995 instance, @code{tfind} with no argument selects the next trace
8996 snapshot, and @code{tfind -} with no argument selects the previous
8997 trace snapshot. So, by giving one @code{tfind} command, and then
8998 simply hitting @key{RET} repeatedly you can examine all the trace
8999 snapshots in order. Or, by saying @code{tfind -} and then hitting
9000 @key{RET} repeatedly you can examine the snapshots in reverse order.
9001 The @code{tfind line} command with no argument selects the snapshot
9002 for the next source line executed. The @code{tfind pc} command with
9003 no argument selects the next snapshot with the same program counter
9004 (PC) as the current frame. The @code{tfind tracepoint} command with
9005 no argument selects the next trace snapshot collected by the same
9006 tracepoint as the current one.
9008 In addition to letting you scan through the trace buffer manually,
9009 these commands make it easy to construct @value{GDBN} scripts that
9010 scan through the trace buffer and print out whatever collected data
9011 you are interested in. Thus, if we want to examine the PC, FP, and SP
9012 registers from each trace frame in the buffer, we can say this:
9015 (@value{GDBP}) @b{tfind start}
9016 (@value{GDBP}) @b{while ($trace_frame != -1)}
9017 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9018 $trace_frame, $pc, $sp, $fp
9022 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9023 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9024 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9025 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9026 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9027 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9028 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9029 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9030 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9031 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9032 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9035 Or, if we want to examine the variable @code{X} at each source line in
9039 (@value{GDBP}) @b{tfind start}
9040 (@value{GDBP}) @b{while ($trace_frame != -1)}
9041 > printf "Frame %d, X == %d\n", $trace_frame, X
9051 @subsection @code{tdump}
9053 @cindex dump all data collected at tracepoint
9054 @cindex tracepoint data, display
9056 This command takes no arguments. It prints all the data collected at
9057 the current trace snapshot.
9060 (@value{GDBP}) @b{trace 444}
9061 (@value{GDBP}) @b{actions}
9062 Enter actions for tracepoint #2, one per line:
9063 > collect $regs, $locals, $args, gdb_long_test
9066 (@value{GDBP}) @b{tstart}
9068 (@value{GDBP}) @b{tfind line 444}
9069 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9071 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9073 (@value{GDBP}) @b{tdump}
9074 Data collected at tracepoint 2, trace frame 1:
9075 d0 0xc4aa0085 -995491707
9079 d4 0x71aea3d 119204413
9084 a1 0x3000668 50333288
9087 a4 0x3000698 50333336
9089 fp 0x30bf3c 0x30bf3c
9090 sp 0x30bf34 0x30bf34
9092 pc 0x20b2c8 0x20b2c8
9096 p = 0x20e5b4 "gdb-test"
9103 gdb_long_test = 17 '\021'
9108 @node save-tracepoints
9109 @subsection @code{save-tracepoints @var{filename}}
9110 @kindex save-tracepoints
9111 @cindex save tracepoints for future sessions
9113 This command saves all current tracepoint definitions together with
9114 their actions and passcounts, into a file @file{@var{filename}}
9115 suitable for use in a later debugging session. To read the saved
9116 tracepoint definitions, use the @code{source} command (@pxref{Command
9119 @node Tracepoint Variables
9120 @section Convenience Variables for Tracepoints
9121 @cindex tracepoint variables
9122 @cindex convenience variables for tracepoints
9125 @vindex $trace_frame
9126 @item (int) $trace_frame
9127 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9128 snapshot is selected.
9131 @item (int) $tracepoint
9132 The tracepoint for the current trace snapshot.
9135 @item (int) $trace_line
9136 The line number for the current trace snapshot.
9139 @item (char []) $trace_file
9140 The source file for the current trace snapshot.
9143 @item (char []) $trace_func
9144 The name of the function containing @code{$tracepoint}.
9147 Note: @code{$trace_file} is not suitable for use in @code{printf},
9148 use @code{output} instead.
9150 Here's a simple example of using these convenience variables for
9151 stepping through all the trace snapshots and printing some of their
9155 (@value{GDBP}) @b{tfind start}
9157 (@value{GDBP}) @b{while $trace_frame != -1}
9158 > output $trace_file
9159 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9165 @chapter Debugging Programs That Use Overlays
9168 If your program is too large to fit completely in your target system's
9169 memory, you can sometimes use @dfn{overlays} to work around this
9170 problem. @value{GDBN} provides some support for debugging programs that
9174 * How Overlays Work:: A general explanation of overlays.
9175 * Overlay Commands:: Managing overlays in @value{GDBN}.
9176 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9177 mapped by asking the inferior.
9178 * Overlay Sample Program:: A sample program using overlays.
9181 @node How Overlays Work
9182 @section How Overlays Work
9183 @cindex mapped overlays
9184 @cindex unmapped overlays
9185 @cindex load address, overlay's
9186 @cindex mapped address
9187 @cindex overlay area
9189 Suppose you have a computer whose instruction address space is only 64
9190 kilobytes long, but which has much more memory which can be accessed by
9191 other means: special instructions, segment registers, or memory
9192 management hardware, for example. Suppose further that you want to
9193 adapt a program which is larger than 64 kilobytes to run on this system.
9195 One solution is to identify modules of your program which are relatively
9196 independent, and need not call each other directly; call these modules
9197 @dfn{overlays}. Separate the overlays from the main program, and place
9198 their machine code in the larger memory. Place your main program in
9199 instruction memory, but leave at least enough space there to hold the
9200 largest overlay as well.
9202 Now, to call a function located in an overlay, you must first copy that
9203 overlay's machine code from the large memory into the space set aside
9204 for it in the instruction memory, and then jump to its entry point
9207 @c NB: In the below the mapped area's size is greater or equal to the
9208 @c size of all overlays. This is intentional to remind the developer
9209 @c that overlays don't necessarily need to be the same size.
9213 Data Instruction Larger
9214 Address Space Address Space Address Space
9215 +-----------+ +-----------+ +-----------+
9217 +-----------+ +-----------+ +-----------+<-- overlay 1
9218 | program | | main | .----| overlay 1 | load address
9219 | variables | | program | | +-----------+
9220 | and heap | | | | | |
9221 +-----------+ | | | +-----------+<-- overlay 2
9222 | | +-----------+ | | | load address
9223 +-----------+ | | | .-| overlay 2 |
9225 mapped --->+-----------+ | | +-----------+
9227 | overlay | <-' | | |
9228 | area | <---' +-----------+<-- overlay 3
9229 | | <---. | | load address
9230 +-----------+ `--| overlay 3 |
9237 @anchor{A code overlay}A code overlay
9241 The diagram (@pxref{A code overlay}) shows a system with separate data
9242 and instruction address spaces. To map an overlay, the program copies
9243 its code from the larger address space to the instruction address space.
9244 Since the overlays shown here all use the same mapped address, only one
9245 may be mapped at a time. For a system with a single address space for
9246 data and instructions, the diagram would be similar, except that the
9247 program variables and heap would share an address space with the main
9248 program and the overlay area.
9250 An overlay loaded into instruction memory and ready for use is called a
9251 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9252 instruction memory. An overlay not present (or only partially present)
9253 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9254 is its address in the larger memory. The mapped address is also called
9255 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9256 called the @dfn{load memory address}, or @dfn{LMA}.
9258 Unfortunately, overlays are not a completely transparent way to adapt a
9259 program to limited instruction memory. They introduce a new set of
9260 global constraints you must keep in mind as you design your program:
9265 Before calling or returning to a function in an overlay, your program
9266 must make sure that overlay is actually mapped. Otherwise, the call or
9267 return will transfer control to the right address, but in the wrong
9268 overlay, and your program will probably crash.
9271 If the process of mapping an overlay is expensive on your system, you
9272 will need to choose your overlays carefully to minimize their effect on
9273 your program's performance.
9276 The executable file you load onto your system must contain each
9277 overlay's instructions, appearing at the overlay's load address, not its
9278 mapped address. However, each overlay's instructions must be relocated
9279 and its symbols defined as if the overlay were at its mapped address.
9280 You can use GNU linker scripts to specify different load and relocation
9281 addresses for pieces of your program; see @ref{Overlay Description,,,
9282 ld.info, Using ld: the GNU linker}.
9285 The procedure for loading executable files onto your system must be able
9286 to load their contents into the larger address space as well as the
9287 instruction and data spaces.
9291 The overlay system described above is rather simple, and could be
9292 improved in many ways:
9297 If your system has suitable bank switch registers or memory management
9298 hardware, you could use those facilities to make an overlay's load area
9299 contents simply appear at their mapped address in instruction space.
9300 This would probably be faster than copying the overlay to its mapped
9301 area in the usual way.
9304 If your overlays are small enough, you could set aside more than one
9305 overlay area, and have more than one overlay mapped at a time.
9308 You can use overlays to manage data, as well as instructions. In
9309 general, data overlays are even less transparent to your design than
9310 code overlays: whereas code overlays only require care when you call or
9311 return to functions, data overlays require care every time you access
9312 the data. Also, if you change the contents of a data overlay, you
9313 must copy its contents back out to its load address before you can copy a
9314 different data overlay into the same mapped area.
9319 @node Overlay Commands
9320 @section Overlay Commands
9322 To use @value{GDBN}'s overlay support, each overlay in your program must
9323 correspond to a separate section of the executable file. The section's
9324 virtual memory address and load memory address must be the overlay's
9325 mapped and load addresses. Identifying overlays with sections allows
9326 @value{GDBN} to determine the appropriate address of a function or
9327 variable, depending on whether the overlay is mapped or not.
9329 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9330 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9335 Disable @value{GDBN}'s overlay support. When overlay support is
9336 disabled, @value{GDBN} assumes that all functions and variables are
9337 always present at their mapped addresses. By default, @value{GDBN}'s
9338 overlay support is disabled.
9340 @item overlay manual
9341 @cindex manual overlay debugging
9342 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9343 relies on you to tell it which overlays are mapped, and which are not,
9344 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9345 commands described below.
9347 @item overlay map-overlay @var{overlay}
9348 @itemx overlay map @var{overlay}
9349 @cindex map an overlay
9350 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9351 be the name of the object file section containing the overlay. When an
9352 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9353 functions and variables at their mapped addresses. @value{GDBN} assumes
9354 that any other overlays whose mapped ranges overlap that of
9355 @var{overlay} are now unmapped.
9357 @item overlay unmap-overlay @var{overlay}
9358 @itemx overlay unmap @var{overlay}
9359 @cindex unmap an overlay
9360 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9361 must be the name of the object file section containing the overlay.
9362 When an overlay is unmapped, @value{GDBN} assumes it can find the
9363 overlay's functions and variables at their load addresses.
9366 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9367 consults a data structure the overlay manager maintains in the inferior
9368 to see which overlays are mapped. For details, see @ref{Automatic
9371 @item overlay load-target
9373 @cindex reloading the overlay table
9374 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9375 re-reads the table @value{GDBN} automatically each time the inferior
9376 stops, so this command should only be necessary if you have changed the
9377 overlay mapping yourself using @value{GDBN}. This command is only
9378 useful when using automatic overlay debugging.
9380 @item overlay list-overlays
9382 @cindex listing mapped overlays
9383 Display a list of the overlays currently mapped, along with their mapped
9384 addresses, load addresses, and sizes.
9388 Normally, when @value{GDBN} prints a code address, it includes the name
9389 of the function the address falls in:
9392 (@value{GDBP}) print main
9393 $3 = @{int ()@} 0x11a0 <main>
9396 When overlay debugging is enabled, @value{GDBN} recognizes code in
9397 unmapped overlays, and prints the names of unmapped functions with
9398 asterisks around them. For example, if @code{foo} is a function in an
9399 unmapped overlay, @value{GDBN} prints it this way:
9402 (@value{GDBP}) overlay list
9403 No sections are mapped.
9404 (@value{GDBP}) print foo
9405 $5 = @{int (int)@} 0x100000 <*foo*>
9408 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9412 (@value{GDBP}) overlay list
9413 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9414 mapped at 0x1016 - 0x104a
9415 (@value{GDBP}) print foo
9416 $6 = @{int (int)@} 0x1016 <foo>
9419 When overlay debugging is enabled, @value{GDBN} can find the correct
9420 address for functions and variables in an overlay, whether or not the
9421 overlay is mapped. This allows most @value{GDBN} commands, like
9422 @code{break} and @code{disassemble}, to work normally, even on unmapped
9423 code. However, @value{GDBN}'s breakpoint support has some limitations:
9427 @cindex breakpoints in overlays
9428 @cindex overlays, setting breakpoints in
9429 You can set breakpoints in functions in unmapped overlays, as long as
9430 @value{GDBN} can write to the overlay at its load address.
9432 @value{GDBN} can not set hardware or simulator-based breakpoints in
9433 unmapped overlays. However, if you set a breakpoint at the end of your
9434 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9435 you are using manual overlay management), @value{GDBN} will re-set its
9436 breakpoints properly.
9440 @node Automatic Overlay Debugging
9441 @section Automatic Overlay Debugging
9442 @cindex automatic overlay debugging
9444 @value{GDBN} can automatically track which overlays are mapped and which
9445 are not, given some simple co-operation from the overlay manager in the
9446 inferior. If you enable automatic overlay debugging with the
9447 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9448 looks in the inferior's memory for certain variables describing the
9449 current state of the overlays.
9451 Here are the variables your overlay manager must define to support
9452 @value{GDBN}'s automatic overlay debugging:
9456 @item @code{_ovly_table}:
9457 This variable must be an array of the following structures:
9462 /* The overlay's mapped address. */
9465 /* The size of the overlay, in bytes. */
9468 /* The overlay's load address. */
9471 /* Non-zero if the overlay is currently mapped;
9473 unsigned long mapped;
9477 @item @code{_novlys}:
9478 This variable must be a four-byte signed integer, holding the total
9479 number of elements in @code{_ovly_table}.
9483 To decide whether a particular overlay is mapped or not, @value{GDBN}
9484 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9485 @code{lma} members equal the VMA and LMA of the overlay's section in the
9486 executable file. When @value{GDBN} finds a matching entry, it consults
9487 the entry's @code{mapped} member to determine whether the overlay is
9490 In addition, your overlay manager may define a function called
9491 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9492 will silently set a breakpoint there. If the overlay manager then
9493 calls this function whenever it has changed the overlay table, this
9494 will enable @value{GDBN} to accurately keep track of which overlays
9495 are in program memory, and update any breakpoints that may be set
9496 in overlays. This will allow breakpoints to work even if the
9497 overlays are kept in ROM or other non-writable memory while they
9498 are not being executed.
9500 @node Overlay Sample Program
9501 @section Overlay Sample Program
9502 @cindex overlay example program
9504 When linking a program which uses overlays, you must place the overlays
9505 at their load addresses, while relocating them to run at their mapped
9506 addresses. To do this, you must write a linker script (@pxref{Overlay
9507 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9508 since linker scripts are specific to a particular host system, target
9509 architecture, and target memory layout, this manual cannot provide
9510 portable sample code demonstrating @value{GDBN}'s overlay support.
9512 However, the @value{GDBN} source distribution does contain an overlaid
9513 program, with linker scripts for a few systems, as part of its test
9514 suite. The program consists of the following files from
9515 @file{gdb/testsuite/gdb.base}:
9519 The main program file.
9521 A simple overlay manager, used by @file{overlays.c}.
9526 Overlay modules, loaded and used by @file{overlays.c}.
9529 Linker scripts for linking the test program on the @code{d10v-elf}
9530 and @code{m32r-elf} targets.
9533 You can build the test program using the @code{d10v-elf} GCC
9534 cross-compiler like this:
9537 $ d10v-elf-gcc -g -c overlays.c
9538 $ d10v-elf-gcc -g -c ovlymgr.c
9539 $ d10v-elf-gcc -g -c foo.c
9540 $ d10v-elf-gcc -g -c bar.c
9541 $ d10v-elf-gcc -g -c baz.c
9542 $ d10v-elf-gcc -g -c grbx.c
9543 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9544 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9547 The build process is identical for any other architecture, except that
9548 you must substitute the appropriate compiler and linker script for the
9549 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9553 @chapter Using @value{GDBN} with Different Languages
9556 Although programming languages generally have common aspects, they are
9557 rarely expressed in the same manner. For instance, in ANSI C,
9558 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9559 Modula-2, it is accomplished by @code{p^}. Values can also be
9560 represented (and displayed) differently. Hex numbers in C appear as
9561 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9563 @cindex working language
9564 Language-specific information is built into @value{GDBN} for some languages,
9565 allowing you to express operations like the above in your program's
9566 native language, and allowing @value{GDBN} to output values in a manner
9567 consistent with the syntax of your program's native language. The
9568 language you use to build expressions is called the @dfn{working
9572 * Setting:: Switching between source languages
9573 * Show:: Displaying the language
9574 * Checks:: Type and range checks
9575 * Supported Languages:: Supported languages
9576 * Unsupported Languages:: Unsupported languages
9580 @section Switching Between Source Languages
9582 There are two ways to control the working language---either have @value{GDBN}
9583 set it automatically, or select it manually yourself. You can use the
9584 @code{set language} command for either purpose. On startup, @value{GDBN}
9585 defaults to setting the language automatically. The working language is
9586 used to determine how expressions you type are interpreted, how values
9589 In addition to the working language, every source file that
9590 @value{GDBN} knows about has its own working language. For some object
9591 file formats, the compiler might indicate which language a particular
9592 source file is in. However, most of the time @value{GDBN} infers the
9593 language from the name of the file. The language of a source file
9594 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9595 show each frame appropriately for its own language. There is no way to
9596 set the language of a source file from within @value{GDBN}, but you can
9597 set the language associated with a filename extension. @xref{Show, ,
9598 Displaying the Language}.
9600 This is most commonly a problem when you use a program, such
9601 as @code{cfront} or @code{f2c}, that generates C but is written in
9602 another language. In that case, make the
9603 program use @code{#line} directives in its C output; that way
9604 @value{GDBN} will know the correct language of the source code of the original
9605 program, and will display that source code, not the generated C code.
9608 * Filenames:: Filename extensions and languages.
9609 * Manually:: Setting the working language manually
9610 * Automatically:: Having @value{GDBN} infer the source language
9614 @subsection List of Filename Extensions and Languages
9616 If a source file name ends in one of the following extensions, then
9617 @value{GDBN} infers that its language is the one indicated.
9638 Objective-C source file
9645 Modula-2 source file
9649 Assembler source file. This actually behaves almost like C, but
9650 @value{GDBN} does not skip over function prologues when stepping.
9653 In addition, you may set the language associated with a filename
9654 extension. @xref{Show, , Displaying the Language}.
9657 @subsection Setting the Working Language
9659 If you allow @value{GDBN} to set the language automatically,
9660 expressions are interpreted the same way in your debugging session and
9663 @kindex set language
9664 If you wish, you may set the language manually. To do this, issue the
9665 command @samp{set language @var{lang}}, where @var{lang} is the name of
9667 @code{c} or @code{modula-2}.
9668 For a list of the supported languages, type @samp{set language}.
9670 Setting the language manually prevents @value{GDBN} from updating the working
9671 language automatically. This can lead to confusion if you try
9672 to debug a program when the working language is not the same as the
9673 source language, when an expression is acceptable to both
9674 languages---but means different things. For instance, if the current
9675 source file were written in C, and @value{GDBN} was parsing Modula-2, a
9683 might not have the effect you intended. In C, this means to add
9684 @code{b} and @code{c} and place the result in @code{a}. The result
9685 printed would be the value of @code{a}. In Modula-2, this means to compare
9686 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
9689 @subsection Having @value{GDBN} Infer the Source Language
9691 To have @value{GDBN} set the working language automatically, use
9692 @samp{set language local} or @samp{set language auto}. @value{GDBN}
9693 then infers the working language. That is, when your program stops in a
9694 frame (usually by encountering a breakpoint), @value{GDBN} sets the
9695 working language to the language recorded for the function in that
9696 frame. If the language for a frame is unknown (that is, if the function
9697 or block corresponding to the frame was defined in a source file that
9698 does not have a recognized extension), the current working language is
9699 not changed, and @value{GDBN} issues a warning.
9701 This may not seem necessary for most programs, which are written
9702 entirely in one source language. However, program modules and libraries
9703 written in one source language can be used by a main program written in
9704 a different source language. Using @samp{set language auto} in this
9705 case frees you from having to set the working language manually.
9708 @section Displaying the Language
9710 The following commands help you find out which language is the
9711 working language, and also what language source files were written in.
9715 @kindex show language
9716 Display the current working language. This is the
9717 language you can use with commands such as @code{print} to
9718 build and compute expressions that may involve variables in your program.
9721 @kindex info frame@r{, show the source language}
9722 Display the source language for this frame. This language becomes the
9723 working language if you use an identifier from this frame.
9724 @xref{Frame Info, ,Information about a Frame}, to identify the other
9725 information listed here.
9728 @kindex info source@r{, show the source language}
9729 Display the source language of this source file.
9730 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
9731 information listed here.
9734 In unusual circumstances, you may have source files with extensions
9735 not in the standard list. You can then set the extension associated
9736 with a language explicitly:
9739 @item set extension-language @var{ext} @var{language}
9740 @kindex set extension-language
9741 Tell @value{GDBN} that source files with extension @var{ext} are to be
9742 assumed as written in the source language @var{language}.
9744 @item info extensions
9745 @kindex info extensions
9746 List all the filename extensions and the associated languages.
9750 @section Type and Range Checking
9753 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
9754 checking are included, but they do not yet have any effect. This
9755 section documents the intended facilities.
9757 @c FIXME remove warning when type/range code added
9759 Some languages are designed to guard you against making seemingly common
9760 errors through a series of compile- and run-time checks. These include
9761 checking the type of arguments to functions and operators, and making
9762 sure mathematical overflows are caught at run time. Checks such as
9763 these help to ensure a program's correctness once it has been compiled
9764 by eliminating type mismatches, and providing active checks for range
9765 errors when your program is running.
9767 @value{GDBN} can check for conditions like the above if you wish.
9768 Although @value{GDBN} does not check the statements in your program,
9769 it can check expressions entered directly into @value{GDBN} for
9770 evaluation via the @code{print} command, for example. As with the
9771 working language, @value{GDBN} can also decide whether or not to check
9772 automatically based on your program's source language.
9773 @xref{Supported Languages, ,Supported Languages}, for the default
9774 settings of supported languages.
9777 * Type Checking:: An overview of type checking
9778 * Range Checking:: An overview of range checking
9781 @cindex type checking
9782 @cindex checks, type
9784 @subsection An Overview of Type Checking
9786 Some languages, such as Modula-2, are strongly typed, meaning that the
9787 arguments to operators and functions have to be of the correct type,
9788 otherwise an error occurs. These checks prevent type mismatch
9789 errors from ever causing any run-time problems. For example,
9797 The second example fails because the @code{CARDINAL} 1 is not
9798 type-compatible with the @code{REAL} 2.3.
9800 For the expressions you use in @value{GDBN} commands, you can tell the
9801 @value{GDBN} type checker to skip checking;
9802 to treat any mismatches as errors and abandon the expression;
9803 or to only issue warnings when type mismatches occur,
9804 but evaluate the expression anyway. When you choose the last of
9805 these, @value{GDBN} evaluates expressions like the second example above, but
9806 also issues a warning.
9808 Even if you turn type checking off, there may be other reasons
9809 related to type that prevent @value{GDBN} from evaluating an expression.
9810 For instance, @value{GDBN} does not know how to add an @code{int} and
9811 a @code{struct foo}. These particular type errors have nothing to do
9812 with the language in use, and usually arise from expressions, such as
9813 the one described above, which make little sense to evaluate anyway.
9815 Each language defines to what degree it is strict about type. For
9816 instance, both Modula-2 and C require the arguments to arithmetical
9817 operators to be numbers. In C, enumerated types and pointers can be
9818 represented as numbers, so that they are valid arguments to mathematical
9819 operators. @xref{Supported Languages, ,Supported Languages}, for further
9820 details on specific languages.
9822 @value{GDBN} provides some additional commands for controlling the type checker:
9824 @kindex set check type
9825 @kindex show check type
9827 @item set check type auto
9828 Set type checking on or off based on the current working language.
9829 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9832 @item set check type on
9833 @itemx set check type off
9834 Set type checking on or off, overriding the default setting for the
9835 current working language. Issue a warning if the setting does not
9836 match the language default. If any type mismatches occur in
9837 evaluating an expression while type checking is on, @value{GDBN} prints a
9838 message and aborts evaluation of the expression.
9840 @item set check type warn
9841 Cause the type checker to issue warnings, but to always attempt to
9842 evaluate the expression. Evaluating the expression may still
9843 be impossible for other reasons. For example, @value{GDBN} cannot add
9844 numbers and structures.
9847 Show the current setting of the type checker, and whether or not @value{GDBN}
9848 is setting it automatically.
9851 @cindex range checking
9852 @cindex checks, range
9853 @node Range Checking
9854 @subsection An Overview of Range Checking
9856 In some languages (such as Modula-2), it is an error to exceed the
9857 bounds of a type; this is enforced with run-time checks. Such range
9858 checking is meant to ensure program correctness by making sure
9859 computations do not overflow, or indices on an array element access do
9860 not exceed the bounds of the array.
9862 For expressions you use in @value{GDBN} commands, you can tell
9863 @value{GDBN} to treat range errors in one of three ways: ignore them,
9864 always treat them as errors and abandon the expression, or issue
9865 warnings but evaluate the expression anyway.
9867 A range error can result from numerical overflow, from exceeding an
9868 array index bound, or when you type a constant that is not a member
9869 of any type. Some languages, however, do not treat overflows as an
9870 error. In many implementations of C, mathematical overflow causes the
9871 result to ``wrap around'' to lower values---for example, if @var{m} is
9872 the largest integer value, and @var{s} is the smallest, then
9875 @var{m} + 1 @result{} @var{s}
9878 This, too, is specific to individual languages, and in some cases
9879 specific to individual compilers or machines. @xref{Supported Languages, ,
9880 Supported Languages}, for further details on specific languages.
9882 @value{GDBN} provides some additional commands for controlling the range checker:
9884 @kindex set check range
9885 @kindex show check range
9887 @item set check range auto
9888 Set range checking on or off based on the current working language.
9889 @xref{Supported Languages, ,Supported Languages}, for the default settings for
9892 @item set check range on
9893 @itemx set check range off
9894 Set range checking on or off, overriding the default setting for the
9895 current working language. A warning is issued if the setting does not
9896 match the language default. If a range error occurs and range checking is on,
9897 then a message is printed and evaluation of the expression is aborted.
9899 @item set check range warn
9900 Output messages when the @value{GDBN} range checker detects a range error,
9901 but attempt to evaluate the expression anyway. Evaluating the
9902 expression may still be impossible for other reasons, such as accessing
9903 memory that the process does not own (a typical example from many Unix
9907 Show the current setting of the range checker, and whether or not it is
9908 being set automatically by @value{GDBN}.
9911 @node Supported Languages
9912 @section Supported Languages
9914 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9915 assembly, Modula-2, and Ada.
9916 @c This is false ...
9917 Some @value{GDBN} features may be used in expressions regardless of the
9918 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9919 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9920 ,Expressions}) can be used with the constructs of any supported
9923 The following sections detail to what degree each source language is
9924 supported by @value{GDBN}. These sections are not meant to be language
9925 tutorials or references, but serve only as a reference guide to what the
9926 @value{GDBN} expression parser accepts, and what input and output
9927 formats should look like for different languages. There are many good
9928 books written on each of these languages; please look to these for a
9929 language reference or tutorial.
9933 * Objective-C:: Objective-C
9936 * Modula-2:: Modula-2
9941 @subsection C and C@t{++}
9943 @cindex C and C@t{++}
9944 @cindex expressions in C or C@t{++}
9946 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9947 to both languages. Whenever this is the case, we discuss those languages
9951 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9952 @cindex @sc{gnu} C@t{++}
9953 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9954 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9955 effectively, you must compile your C@t{++} programs with a supported
9956 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9957 compiler (@code{aCC}).
9959 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9960 format; if it doesn't work on your system, try the stabs+ debugging
9961 format. You can select those formats explicitly with the @code{g++}
9962 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9963 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9964 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9967 * C Operators:: C and C@t{++} operators
9968 * C Constants:: C and C@t{++} constants
9969 * C Plus Plus Expressions:: C@t{++} expressions
9970 * C Defaults:: Default settings for C and C@t{++}
9971 * C Checks:: C and C@t{++} type and range checks
9972 * Debugging C:: @value{GDBN} and C
9973 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9974 * Decimal Floating Point:: Numbers in Decimal Floating Point format
9978 @subsubsection C and C@t{++} Operators
9980 @cindex C and C@t{++} operators
9982 Operators must be defined on values of specific types. For instance,
9983 @code{+} is defined on numbers, but not on structures. Operators are
9984 often defined on groups of types.
9986 For the purposes of C and C@t{++}, the following definitions hold:
9991 @emph{Integral types} include @code{int} with any of its storage-class
9992 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9995 @emph{Floating-point types} include @code{float}, @code{double}, and
9996 @code{long double} (if supported by the target platform).
9999 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10002 @emph{Scalar types} include all of the above.
10007 The following operators are supported. They are listed here
10008 in order of increasing precedence:
10012 The comma or sequencing operator. Expressions in a comma-separated list
10013 are evaluated from left to right, with the result of the entire
10014 expression being the last expression evaluated.
10017 Assignment. The value of an assignment expression is the value
10018 assigned. Defined on scalar types.
10021 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10022 and translated to @w{@code{@var{a} = @var{a op b}}}.
10023 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10024 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10025 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10028 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10029 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10033 Logical @sc{or}. Defined on integral types.
10036 Logical @sc{and}. Defined on integral types.
10039 Bitwise @sc{or}. Defined on integral types.
10042 Bitwise exclusive-@sc{or}. Defined on integral types.
10045 Bitwise @sc{and}. Defined on integral types.
10048 Equality and inequality. Defined on scalar types. The value of these
10049 expressions is 0 for false and non-zero for true.
10051 @item <@r{, }>@r{, }<=@r{, }>=
10052 Less than, greater than, less than or equal, greater than or equal.
10053 Defined on scalar types. The value of these expressions is 0 for false
10054 and non-zero for true.
10057 left shift, and right shift. Defined on integral types.
10060 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10063 Addition and subtraction. Defined on integral types, floating-point types and
10066 @item *@r{, }/@r{, }%
10067 Multiplication, division, and modulus. Multiplication and division are
10068 defined on integral and floating-point types. Modulus is defined on
10072 Increment and decrement. When appearing before a variable, the
10073 operation is performed before the variable is used in an expression;
10074 when appearing after it, the variable's value is used before the
10075 operation takes place.
10078 Pointer dereferencing. Defined on pointer types. Same precedence as
10082 Address operator. Defined on variables. Same precedence as @code{++}.
10084 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10085 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10086 to examine the address
10087 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10091 Negative. Defined on integral and floating-point types. Same
10092 precedence as @code{++}.
10095 Logical negation. Defined on integral types. Same precedence as
10099 Bitwise complement operator. Defined on integral types. Same precedence as
10104 Structure member, and pointer-to-structure member. For convenience,
10105 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10106 pointer based on the stored type information.
10107 Defined on @code{struct} and @code{union} data.
10110 Dereferences of pointers to members.
10113 Array indexing. @code{@var{a}[@var{i}]} is defined as
10114 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10117 Function parameter list. Same precedence as @code{->}.
10120 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10121 and @code{class} types.
10124 Doubled colons also represent the @value{GDBN} scope operator
10125 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10129 If an operator is redefined in the user code, @value{GDBN} usually
10130 attempts to invoke the redefined version instead of using the operator's
10131 predefined meaning.
10134 @subsubsection C and C@t{++} Constants
10136 @cindex C and C@t{++} constants
10138 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10143 Integer constants are a sequence of digits. Octal constants are
10144 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10145 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10146 @samp{l}, specifying that the constant should be treated as a
10150 Floating point constants are a sequence of digits, followed by a decimal
10151 point, followed by a sequence of digits, and optionally followed by an
10152 exponent. An exponent is of the form:
10153 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10154 sequence of digits. The @samp{+} is optional for positive exponents.
10155 A floating-point constant may also end with a letter @samp{f} or
10156 @samp{F}, specifying that the constant should be treated as being of
10157 the @code{float} (as opposed to the default @code{double}) type; or with
10158 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10162 Enumerated constants consist of enumerated identifiers, or their
10163 integral equivalents.
10166 Character constants are a single character surrounded by single quotes
10167 (@code{'}), or a number---the ordinal value of the corresponding character
10168 (usually its @sc{ascii} value). Within quotes, the single character may
10169 be represented by a letter or by @dfn{escape sequences}, which are of
10170 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10171 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10172 @samp{@var{x}} is a predefined special character---for example,
10173 @samp{\n} for newline.
10176 String constants are a sequence of character constants surrounded by
10177 double quotes (@code{"}). Any valid character constant (as described
10178 above) may appear. Double quotes within the string must be preceded by
10179 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10183 Pointer constants are an integral value. You can also write pointers
10184 to constants using the C operator @samp{&}.
10187 Array constants are comma-separated lists surrounded by braces @samp{@{}
10188 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10189 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10190 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10193 @node C Plus Plus Expressions
10194 @subsubsection C@t{++} Expressions
10196 @cindex expressions in C@t{++}
10197 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10199 @cindex debugging C@t{++} programs
10200 @cindex C@t{++} compilers
10201 @cindex debug formats and C@t{++}
10202 @cindex @value{NGCC} and C@t{++}
10204 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10205 proper compiler and the proper debug format. Currently, @value{GDBN}
10206 works best when debugging C@t{++} code that is compiled with
10207 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10208 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10209 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10210 stabs+ as their default debug format, so you usually don't need to
10211 specify a debug format explicitly. Other compilers and/or debug formats
10212 are likely to work badly or not at all when using @value{GDBN} to debug
10218 @cindex member functions
10220 Member function calls are allowed; you can use expressions like
10223 count = aml->GetOriginal(x, y)
10226 @vindex this@r{, inside C@t{++} member functions}
10227 @cindex namespace in C@t{++}
10229 While a member function is active (in the selected stack frame), your
10230 expressions have the same namespace available as the member function;
10231 that is, @value{GDBN} allows implicit references to the class instance
10232 pointer @code{this} following the same rules as C@t{++}.
10234 @cindex call overloaded functions
10235 @cindex overloaded functions, calling
10236 @cindex type conversions in C@t{++}
10238 You can call overloaded functions; @value{GDBN} resolves the function
10239 call to the right definition, with some restrictions. @value{GDBN} does not
10240 perform overload resolution involving user-defined type conversions,
10241 calls to constructors, or instantiations of templates that do not exist
10242 in the program. It also cannot handle ellipsis argument lists or
10245 It does perform integral conversions and promotions, floating-point
10246 promotions, arithmetic conversions, pointer conversions, conversions of
10247 class objects to base classes, and standard conversions such as those of
10248 functions or arrays to pointers; it requires an exact match on the
10249 number of function arguments.
10251 Overload resolution is always performed, unless you have specified
10252 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10253 ,@value{GDBN} Features for C@t{++}}.
10255 You must specify @code{set overload-resolution off} in order to use an
10256 explicit function signature to call an overloaded function, as in
10258 p 'foo(char,int)'('x', 13)
10261 The @value{GDBN} command-completion facility can simplify this;
10262 see @ref{Completion, ,Command Completion}.
10264 @cindex reference declarations
10266 @value{GDBN} understands variables declared as C@t{++} references; you can use
10267 them in expressions just as you do in C@t{++} source---they are automatically
10270 In the parameter list shown when @value{GDBN} displays a frame, the values of
10271 reference variables are not displayed (unlike other variables); this
10272 avoids clutter, since references are often used for large structures.
10273 The @emph{address} of a reference variable is always shown, unless
10274 you have specified @samp{set print address off}.
10277 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10278 expressions can use it just as expressions in your program do. Since
10279 one scope may be defined in another, you can use @code{::} repeatedly if
10280 necessary, for example in an expression like
10281 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10282 resolving name scope by reference to source files, in both C and C@t{++}
10283 debugging (@pxref{Variables, ,Program Variables}).
10286 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10287 calling virtual functions correctly, printing out virtual bases of
10288 objects, calling functions in a base subobject, casting objects, and
10289 invoking user-defined operators.
10292 @subsubsection C and C@t{++} Defaults
10294 @cindex C and C@t{++} defaults
10296 If you allow @value{GDBN} to set type and range checking automatically, they
10297 both default to @code{off} whenever the working language changes to
10298 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10299 selects the working language.
10301 If you allow @value{GDBN} to set the language automatically, it
10302 recognizes source files whose names end with @file{.c}, @file{.C}, or
10303 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10304 these files, it sets the working language to C or C@t{++}.
10305 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10306 for further details.
10308 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10309 @c unimplemented. If (b) changes, it might make sense to let this node
10310 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10313 @subsubsection C and C@t{++} Type and Range Checks
10315 @cindex C and C@t{++} checks
10317 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10318 is not used. However, if you turn type checking on, @value{GDBN}
10319 considers two variables type equivalent if:
10323 The two variables are structured and have the same structure, union, or
10327 The two variables have the same type name, or types that have been
10328 declared equivalent through @code{typedef}.
10331 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10334 The two @code{struct}, @code{union}, or @code{enum} variables are
10335 declared in the same declaration. (Note: this may not be true for all C
10340 Range checking, if turned on, is done on mathematical operations. Array
10341 indices are not checked, since they are often used to index a pointer
10342 that is not itself an array.
10345 @subsubsection @value{GDBN} and C
10347 The @code{set print union} and @code{show print union} commands apply to
10348 the @code{union} type. When set to @samp{on}, any @code{union} that is
10349 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10350 appears as @samp{@{...@}}.
10352 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10353 with pointers and a memory allocation function. @xref{Expressions,
10356 @node Debugging C Plus Plus
10357 @subsubsection @value{GDBN} Features for C@t{++}
10359 @cindex commands for C@t{++}
10361 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10362 designed specifically for use with C@t{++}. Here is a summary:
10365 @cindex break in overloaded functions
10366 @item @r{breakpoint menus}
10367 When you want a breakpoint in a function whose name is overloaded,
10368 @value{GDBN} has the capability to display a menu of possible breakpoint
10369 locations to help you specify which function definition you want.
10370 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10372 @cindex overloading in C@t{++}
10373 @item rbreak @var{regex}
10374 Setting breakpoints using regular expressions is helpful for setting
10375 breakpoints on overloaded functions that are not members of any special
10377 @xref{Set Breaks, ,Setting Breakpoints}.
10379 @cindex C@t{++} exception handling
10382 Debug C@t{++} exception handling using these commands. @xref{Set
10383 Catchpoints, , Setting Catchpoints}.
10385 @cindex inheritance
10386 @item ptype @var{typename}
10387 Print inheritance relationships as well as other information for type
10389 @xref{Symbols, ,Examining the Symbol Table}.
10391 @cindex C@t{++} symbol display
10392 @item set print demangle
10393 @itemx show print demangle
10394 @itemx set print asm-demangle
10395 @itemx show print asm-demangle
10396 Control whether C@t{++} symbols display in their source form, both when
10397 displaying code as C@t{++} source and when displaying disassemblies.
10398 @xref{Print Settings, ,Print Settings}.
10400 @item set print object
10401 @itemx show print object
10402 Choose whether to print derived (actual) or declared types of objects.
10403 @xref{Print Settings, ,Print Settings}.
10405 @item set print vtbl
10406 @itemx show print vtbl
10407 Control the format for printing virtual function tables.
10408 @xref{Print Settings, ,Print Settings}.
10409 (The @code{vtbl} commands do not work on programs compiled with the HP
10410 ANSI C@t{++} compiler (@code{aCC}).)
10412 @kindex set overload-resolution
10413 @cindex overloaded functions, overload resolution
10414 @item set overload-resolution on
10415 Enable overload resolution for C@t{++} expression evaluation. The default
10416 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10417 and searches for a function whose signature matches the argument types,
10418 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10419 Expressions, ,C@t{++} Expressions}, for details).
10420 If it cannot find a match, it emits a message.
10422 @item set overload-resolution off
10423 Disable overload resolution for C@t{++} expression evaluation. For
10424 overloaded functions that are not class member functions, @value{GDBN}
10425 chooses the first function of the specified name that it finds in the
10426 symbol table, whether or not its arguments are of the correct type. For
10427 overloaded functions that are class member functions, @value{GDBN}
10428 searches for a function whose signature @emph{exactly} matches the
10431 @kindex show overload-resolution
10432 @item show overload-resolution
10433 Show the current setting of overload resolution.
10435 @item @r{Overloaded symbol names}
10436 You can specify a particular definition of an overloaded symbol, using
10437 the same notation that is used to declare such symbols in C@t{++}: type
10438 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10439 also use the @value{GDBN} command-line word completion facilities to list the
10440 available choices, or to finish the type list for you.
10441 @xref{Completion,, Command Completion}, for details on how to do this.
10444 @node Decimal Floating Point
10445 @subsubsection Decimal Floating Point format
10446 @cindex decimal floating point format
10448 @value{GDBN} can examine, set and perform computations with numbers in
10449 decimal floating point format, which in the C language correspond to the
10450 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10451 specified by the extension to support decimal floating-point arithmetic.
10453 There are two encodings in use, depending on the architecture: BID (Binary
10454 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10455 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10458 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10459 to manipulate decimal floating point numbers, it is not possible to convert
10460 (using a cast, for example) integers wider than 32-bit to decimal float.
10462 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10463 point computations, error checking in decimal float operations ignores
10464 underflow, overflow and divide by zero exceptions.
10466 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10467 to inspect @code{_Decimal128} values stored in floating point registers. See
10468 @ref{PowerPC,,PowerPC} for more details.
10471 @subsection Objective-C
10473 @cindex Objective-C
10474 This section provides information about some commands and command
10475 options that are useful for debugging Objective-C code. See also
10476 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10477 few more commands specific to Objective-C support.
10480 * Method Names in Commands::
10481 * The Print Command with Objective-C::
10484 @node Method Names in Commands
10485 @subsubsection Method Names in Commands
10487 The following commands have been extended to accept Objective-C method
10488 names as line specifications:
10490 @kindex clear@r{, and Objective-C}
10491 @kindex break@r{, and Objective-C}
10492 @kindex info line@r{, and Objective-C}
10493 @kindex jump@r{, and Objective-C}
10494 @kindex list@r{, and Objective-C}
10498 @item @code{info line}
10503 A fully qualified Objective-C method name is specified as
10506 -[@var{Class} @var{methodName}]
10509 where the minus sign is used to indicate an instance method and a
10510 plus sign (not shown) is used to indicate a class method. The class
10511 name @var{Class} and method name @var{methodName} are enclosed in
10512 brackets, similar to the way messages are specified in Objective-C
10513 source code. For example, to set a breakpoint at the @code{create}
10514 instance method of class @code{Fruit} in the program currently being
10518 break -[Fruit create]
10521 To list ten program lines around the @code{initialize} class method,
10525 list +[NSText initialize]
10528 In the current version of @value{GDBN}, the plus or minus sign is
10529 required. In future versions of @value{GDBN}, the plus or minus
10530 sign will be optional, but you can use it to narrow the search. It
10531 is also possible to specify just a method name:
10537 You must specify the complete method name, including any colons. If
10538 your program's source files contain more than one @code{create} method,
10539 you'll be presented with a numbered list of classes that implement that
10540 method. Indicate your choice by number, or type @samp{0} to exit if
10543 As another example, to clear a breakpoint established at the
10544 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10547 clear -[NSWindow makeKeyAndOrderFront:]
10550 @node The Print Command with Objective-C
10551 @subsubsection The Print Command With Objective-C
10552 @cindex Objective-C, print objects
10553 @kindex print-object
10554 @kindex po @r{(@code{print-object})}
10556 The print command has also been extended to accept methods. For example:
10559 print -[@var{object} hash]
10562 @cindex print an Objective-C object description
10563 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10565 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10566 and print the result. Also, an additional command has been added,
10567 @code{print-object} or @code{po} for short, which is meant to print
10568 the description of an object. However, this command may only work
10569 with certain Objective-C libraries that have a particular hook
10570 function, @code{_NSPrintForDebugger}, defined.
10573 @subsection Fortran
10574 @cindex Fortran-specific support in @value{GDBN}
10576 @value{GDBN} can be used to debug programs written in Fortran, but it
10577 currently supports only the features of Fortran 77 language.
10579 @cindex trailing underscore, in Fortran symbols
10580 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10581 among them) append an underscore to the names of variables and
10582 functions. When you debug programs compiled by those compilers, you
10583 will need to refer to variables and functions with a trailing
10587 * Fortran Operators:: Fortran operators and expressions
10588 * Fortran Defaults:: Default settings for Fortran
10589 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10592 @node Fortran Operators
10593 @subsubsection Fortran Operators and Expressions
10595 @cindex Fortran operators and expressions
10597 Operators must be defined on values of specific types. For instance,
10598 @code{+} is defined on numbers, but not on characters or other non-
10599 arithmetic types. Operators are often defined on groups of types.
10603 The exponentiation operator. It raises the first operand to the power
10607 The range operator. Normally used in the form of array(low:high) to
10608 represent a section of array.
10611 The access component operator. Normally used to access elements in derived
10612 types. Also suitable for unions. As unions aren't part of regular Fortran,
10613 this can only happen when accessing a register that uses a gdbarch-defined
10617 @node Fortran Defaults
10618 @subsubsection Fortran Defaults
10620 @cindex Fortran Defaults
10622 Fortran symbols are usually case-insensitive, so @value{GDBN} by
10623 default uses case-insensitive matches for Fortran symbols. You can
10624 change that with the @samp{set case-insensitive} command, see
10625 @ref{Symbols}, for the details.
10627 @node Special Fortran Commands
10628 @subsubsection Special Fortran Commands
10630 @cindex Special Fortran commands
10632 @value{GDBN} has some commands to support Fortran-specific features,
10633 such as displaying common blocks.
10636 @cindex @code{COMMON} blocks, Fortran
10637 @kindex info common
10638 @item info common @r{[}@var{common-name}@r{]}
10639 This command prints the values contained in the Fortran @code{COMMON}
10640 block whose name is @var{common-name}. With no argument, the names of
10641 all @code{COMMON} blocks visible at the current program location are
10648 @cindex Pascal support in @value{GDBN}, limitations
10649 Debugging Pascal programs which use sets, subranges, file variables, or
10650 nested functions does not currently work. @value{GDBN} does not support
10651 entering expressions, printing values, or similar features using Pascal
10654 The Pascal-specific command @code{set print pascal_static-members}
10655 controls whether static members of Pascal objects are displayed.
10656 @xref{Print Settings, pascal_static-members}.
10659 @subsection Modula-2
10661 @cindex Modula-2, @value{GDBN} support
10663 The extensions made to @value{GDBN} to support Modula-2 only support
10664 output from the @sc{gnu} Modula-2 compiler (which is currently being
10665 developed). Other Modula-2 compilers are not currently supported, and
10666 attempting to debug executables produced by them is most likely
10667 to give an error as @value{GDBN} reads in the executable's symbol
10670 @cindex expressions in Modula-2
10672 * M2 Operators:: Built-in operators
10673 * Built-In Func/Proc:: Built-in functions and procedures
10674 * M2 Constants:: Modula-2 constants
10675 * M2 Types:: Modula-2 types
10676 * M2 Defaults:: Default settings for Modula-2
10677 * Deviations:: Deviations from standard Modula-2
10678 * M2 Checks:: Modula-2 type and range checks
10679 * M2 Scope:: The scope operators @code{::} and @code{.}
10680 * GDB/M2:: @value{GDBN} and Modula-2
10684 @subsubsection Operators
10685 @cindex Modula-2 operators
10687 Operators must be defined on values of specific types. For instance,
10688 @code{+} is defined on numbers, but not on structures. Operators are
10689 often defined on groups of types. For the purposes of Modula-2, the
10690 following definitions hold:
10695 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
10699 @emph{Character types} consist of @code{CHAR} and its subranges.
10702 @emph{Floating-point types} consist of @code{REAL}.
10705 @emph{Pointer types} consist of anything declared as @code{POINTER TO
10709 @emph{Scalar types} consist of all of the above.
10712 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
10715 @emph{Boolean types} consist of @code{BOOLEAN}.
10719 The following operators are supported, and appear in order of
10720 increasing precedence:
10724 Function argument or array index separator.
10727 Assignment. The value of @var{var} @code{:=} @var{value} is
10731 Less than, greater than on integral, floating-point, or enumerated
10735 Less than or equal to, greater than or equal to
10736 on integral, floating-point and enumerated types, or set inclusion on
10737 set types. Same precedence as @code{<}.
10739 @item =@r{, }<>@r{, }#
10740 Equality and two ways of expressing inequality, valid on scalar types.
10741 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
10742 available for inequality, since @code{#} conflicts with the script
10746 Set membership. Defined on set types and the types of their members.
10747 Same precedence as @code{<}.
10750 Boolean disjunction. Defined on boolean types.
10753 Boolean conjunction. Defined on boolean types.
10756 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10759 Addition and subtraction on integral and floating-point types, or union
10760 and difference on set types.
10763 Multiplication on integral and floating-point types, or set intersection
10767 Division on floating-point types, or symmetric set difference on set
10768 types. Same precedence as @code{*}.
10771 Integer division and remainder. Defined on integral types. Same
10772 precedence as @code{*}.
10775 Negative. Defined on @code{INTEGER} and @code{REAL} data.
10778 Pointer dereferencing. Defined on pointer types.
10781 Boolean negation. Defined on boolean types. Same precedence as
10785 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
10786 precedence as @code{^}.
10789 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
10792 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
10796 @value{GDBN} and Modula-2 scope operators.
10800 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
10801 treats the use of the operator @code{IN}, or the use of operators
10802 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
10803 @code{<=}, and @code{>=} on sets as an error.
10807 @node Built-In Func/Proc
10808 @subsubsection Built-in Functions and Procedures
10809 @cindex Modula-2 built-ins
10811 Modula-2 also makes available several built-in procedures and functions.
10812 In describing these, the following metavariables are used:
10817 represents an @code{ARRAY} variable.
10820 represents a @code{CHAR} constant or variable.
10823 represents a variable or constant of integral type.
10826 represents an identifier that belongs to a set. Generally used in the
10827 same function with the metavariable @var{s}. The type of @var{s} should
10828 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
10831 represents a variable or constant of integral or floating-point type.
10834 represents a variable or constant of floating-point type.
10840 represents a variable.
10843 represents a variable or constant of one of many types. See the
10844 explanation of the function for details.
10847 All Modula-2 built-in procedures also return a result, described below.
10851 Returns the absolute value of @var{n}.
10854 If @var{c} is a lower case letter, it returns its upper case
10855 equivalent, otherwise it returns its argument.
10858 Returns the character whose ordinal value is @var{i}.
10861 Decrements the value in the variable @var{v} by one. Returns the new value.
10863 @item DEC(@var{v},@var{i})
10864 Decrements the value in the variable @var{v} by @var{i}. Returns the
10867 @item EXCL(@var{m},@var{s})
10868 Removes the element @var{m} from the set @var{s}. Returns the new
10871 @item FLOAT(@var{i})
10872 Returns the floating point equivalent of the integer @var{i}.
10874 @item HIGH(@var{a})
10875 Returns the index of the last member of @var{a}.
10878 Increments the value in the variable @var{v} by one. Returns the new value.
10880 @item INC(@var{v},@var{i})
10881 Increments the value in the variable @var{v} by @var{i}. Returns the
10884 @item INCL(@var{m},@var{s})
10885 Adds the element @var{m} to the set @var{s} if it is not already
10886 there. Returns the new set.
10889 Returns the maximum value of the type @var{t}.
10892 Returns the minimum value of the type @var{t}.
10895 Returns boolean TRUE if @var{i} is an odd number.
10898 Returns the ordinal value of its argument. For example, the ordinal
10899 value of a character is its @sc{ascii} value (on machines supporting the
10900 @sc{ascii} character set). @var{x} must be of an ordered type, which include
10901 integral, character and enumerated types.
10903 @item SIZE(@var{x})
10904 Returns the size of its argument. @var{x} can be a variable or a type.
10906 @item TRUNC(@var{r})
10907 Returns the integral part of @var{r}.
10909 @item TSIZE(@var{x})
10910 Returns the size of its argument. @var{x} can be a variable or a type.
10912 @item VAL(@var{t},@var{i})
10913 Returns the member of the type @var{t} whose ordinal value is @var{i}.
10917 @emph{Warning:} Sets and their operations are not yet supported, so
10918 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
10922 @cindex Modula-2 constants
10924 @subsubsection Constants
10926 @value{GDBN} allows you to express the constants of Modula-2 in the following
10932 Integer constants are simply a sequence of digits. When used in an
10933 expression, a constant is interpreted to be type-compatible with the
10934 rest of the expression. Hexadecimal integers are specified by a
10935 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10938 Floating point constants appear as a sequence of digits, followed by a
10939 decimal point and another sequence of digits. An optional exponent can
10940 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10941 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10942 digits of the floating point constant must be valid decimal (base 10)
10946 Character constants consist of a single character enclosed by a pair of
10947 like quotes, either single (@code{'}) or double (@code{"}). They may
10948 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10949 followed by a @samp{C}.
10952 String constants consist of a sequence of characters enclosed by a
10953 pair of like quotes, either single (@code{'}) or double (@code{"}).
10954 Escape sequences in the style of C are also allowed. @xref{C
10955 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10959 Enumerated constants consist of an enumerated identifier.
10962 Boolean constants consist of the identifiers @code{TRUE} and
10966 Pointer constants consist of integral values only.
10969 Set constants are not yet supported.
10973 @subsubsection Modula-2 Types
10974 @cindex Modula-2 types
10976 Currently @value{GDBN} can print the following data types in Modula-2
10977 syntax: array types, record types, set types, pointer types, procedure
10978 types, enumerated types, subrange types and base types. You can also
10979 print the contents of variables declared using these type.
10980 This section gives a number of simple source code examples together with
10981 sample @value{GDBN} sessions.
10983 The first example contains the following section of code:
10992 and you can request @value{GDBN} to interrogate the type and value of
10993 @code{r} and @code{s}.
10996 (@value{GDBP}) print s
10998 (@value{GDBP}) ptype s
11000 (@value{GDBP}) print r
11002 (@value{GDBP}) ptype r
11007 Likewise if your source code declares @code{s} as:
11011 s: SET ['A'..'Z'] ;
11015 then you may query the type of @code{s} by:
11018 (@value{GDBP}) ptype s
11019 type = SET ['A'..'Z']
11023 Note that at present you cannot interactively manipulate set
11024 expressions using the debugger.
11026 The following example shows how you might declare an array in Modula-2
11027 and how you can interact with @value{GDBN} to print its type and contents:
11031 s: ARRAY [-10..10] OF CHAR ;
11035 (@value{GDBP}) ptype s
11036 ARRAY [-10..10] OF CHAR
11039 Note that the array handling is not yet complete and although the type
11040 is printed correctly, expression handling still assumes that all
11041 arrays have a lower bound of zero and not @code{-10} as in the example
11044 Here are some more type related Modula-2 examples:
11048 colour = (blue, red, yellow, green) ;
11049 t = [blue..yellow] ;
11057 The @value{GDBN} interaction shows how you can query the data type
11058 and value of a variable.
11061 (@value{GDBP}) print s
11063 (@value{GDBP}) ptype t
11064 type = [blue..yellow]
11068 In this example a Modula-2 array is declared and its contents
11069 displayed. Observe that the contents are written in the same way as
11070 their @code{C} counterparts.
11074 s: ARRAY [1..5] OF CARDINAL ;
11080 (@value{GDBP}) print s
11081 $1 = @{1, 0, 0, 0, 0@}
11082 (@value{GDBP}) ptype s
11083 type = ARRAY [1..5] OF CARDINAL
11086 The Modula-2 language interface to @value{GDBN} also understands
11087 pointer types as shown in this example:
11091 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11098 and you can request that @value{GDBN} describes the type of @code{s}.
11101 (@value{GDBP}) ptype s
11102 type = POINTER TO ARRAY [1..5] OF CARDINAL
11105 @value{GDBN} handles compound types as we can see in this example.
11106 Here we combine array types, record types, pointer types and subrange
11117 myarray = ARRAY myrange OF CARDINAL ;
11118 myrange = [-2..2] ;
11120 s: POINTER TO ARRAY myrange OF foo ;
11124 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11128 (@value{GDBP}) ptype s
11129 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11132 f3 : ARRAY [-2..2] OF CARDINAL;
11137 @subsubsection Modula-2 Defaults
11138 @cindex Modula-2 defaults
11140 If type and range checking are set automatically by @value{GDBN}, they
11141 both default to @code{on} whenever the working language changes to
11142 Modula-2. This happens regardless of whether you or @value{GDBN}
11143 selected the working language.
11145 If you allow @value{GDBN} to set the language automatically, then entering
11146 code compiled from a file whose name ends with @file{.mod} sets the
11147 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11148 Infer the Source Language}, for further details.
11151 @subsubsection Deviations from Standard Modula-2
11152 @cindex Modula-2, deviations from
11154 A few changes have been made to make Modula-2 programs easier to debug.
11155 This is done primarily via loosening its type strictness:
11159 Unlike in standard Modula-2, pointer constants can be formed by
11160 integers. This allows you to modify pointer variables during
11161 debugging. (In standard Modula-2, the actual address contained in a
11162 pointer variable is hidden from you; it can only be modified
11163 through direct assignment to another pointer variable or expression that
11164 returned a pointer.)
11167 C escape sequences can be used in strings and characters to represent
11168 non-printable characters. @value{GDBN} prints out strings with these
11169 escape sequences embedded. Single non-printable characters are
11170 printed using the @samp{CHR(@var{nnn})} format.
11173 The assignment operator (@code{:=}) returns the value of its right-hand
11177 All built-in procedures both modify @emph{and} return their argument.
11181 @subsubsection Modula-2 Type and Range Checks
11182 @cindex Modula-2 checks
11185 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11188 @c FIXME remove warning when type/range checks added
11190 @value{GDBN} considers two Modula-2 variables type equivalent if:
11194 They are of types that have been declared equivalent via a @code{TYPE
11195 @var{t1} = @var{t2}} statement
11198 They have been declared on the same line. (Note: This is true of the
11199 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11202 As long as type checking is enabled, any attempt to combine variables
11203 whose types are not equivalent is an error.
11205 Range checking is done on all mathematical operations, assignment, array
11206 index bounds, and all built-in functions and procedures.
11209 @subsubsection The Scope Operators @code{::} and @code{.}
11211 @cindex @code{.}, Modula-2 scope operator
11212 @cindex colon, doubled as scope operator
11214 @vindex colon-colon@r{, in Modula-2}
11215 @c Info cannot handle :: but TeX can.
11218 @vindex ::@r{, in Modula-2}
11221 There are a few subtle differences between the Modula-2 scope operator
11222 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11227 @var{module} . @var{id}
11228 @var{scope} :: @var{id}
11232 where @var{scope} is the name of a module or a procedure,
11233 @var{module} the name of a module, and @var{id} is any declared
11234 identifier within your program, except another module.
11236 Using the @code{::} operator makes @value{GDBN} search the scope
11237 specified by @var{scope} for the identifier @var{id}. If it is not
11238 found in the specified scope, then @value{GDBN} searches all scopes
11239 enclosing the one specified by @var{scope}.
11241 Using the @code{.} operator makes @value{GDBN} search the current scope for
11242 the identifier specified by @var{id} that was imported from the
11243 definition module specified by @var{module}. With this operator, it is
11244 an error if the identifier @var{id} was not imported from definition
11245 module @var{module}, or if @var{id} is not an identifier in
11249 @subsubsection @value{GDBN} and Modula-2
11251 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11252 Five subcommands of @code{set print} and @code{show print} apply
11253 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11254 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11255 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11256 analogue in Modula-2.
11258 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11259 with any language, is not useful with Modula-2. Its
11260 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11261 created in Modula-2 as they can in C or C@t{++}. However, because an
11262 address can be specified by an integral constant, the construct
11263 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11265 @cindex @code{#} in Modula-2
11266 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11267 interpreted as the beginning of a comment. Use @code{<>} instead.
11273 The extensions made to @value{GDBN} for Ada only support
11274 output from the @sc{gnu} Ada (GNAT) compiler.
11275 Other Ada compilers are not currently supported, and
11276 attempting to debug executables produced by them is most likely
11280 @cindex expressions in Ada
11282 * Ada Mode Intro:: General remarks on the Ada syntax
11283 and semantics supported by Ada mode
11285 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11286 * Additions to Ada:: Extensions of the Ada expression syntax.
11287 * Stopping Before Main Program:: Debugging the program during elaboration.
11288 * Ada Tasks:: Listing and setting breakpoints in tasks.
11289 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11290 * Ada Glitches:: Known peculiarities of Ada mode.
11293 @node Ada Mode Intro
11294 @subsubsection Introduction
11295 @cindex Ada mode, general
11297 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11298 syntax, with some extensions.
11299 The philosophy behind the design of this subset is
11303 That @value{GDBN} should provide basic literals and access to operations for
11304 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11305 leaving more sophisticated computations to subprograms written into the
11306 program (which therefore may be called from @value{GDBN}).
11309 That type safety and strict adherence to Ada language restrictions
11310 are not particularly important to the @value{GDBN} user.
11313 That brevity is important to the @value{GDBN} user.
11316 Thus, for brevity, the debugger acts as if all names declared in
11317 user-written packages are directly visible, even if they are not visible
11318 according to Ada rules, thus making it unnecessary to fully qualify most
11319 names with their packages, regardless of context. Where this causes
11320 ambiguity, @value{GDBN} asks the user's intent.
11322 The debugger will start in Ada mode if it detects an Ada main program.
11323 As for other languages, it will enter Ada mode when stopped in a program that
11324 was translated from an Ada source file.
11326 While in Ada mode, you may use `@t{--}' for comments. This is useful
11327 mostly for documenting command files. The standard @value{GDBN} comment
11328 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11329 middle (to allow based literals).
11331 The debugger supports limited overloading. Given a subprogram call in which
11332 the function symbol has multiple definitions, it will use the number of
11333 actual parameters and some information about their types to attempt to narrow
11334 the set of definitions. It also makes very limited use of context, preferring
11335 procedures to functions in the context of the @code{call} command, and
11336 functions to procedures elsewhere.
11338 @node Omissions from Ada
11339 @subsubsection Omissions from Ada
11340 @cindex Ada, omissions from
11342 Here are the notable omissions from the subset:
11346 Only a subset of the attributes are supported:
11350 @t{'First}, @t{'Last}, and @t{'Length}
11351 on array objects (not on types and subtypes).
11354 @t{'Min} and @t{'Max}.
11357 @t{'Pos} and @t{'Val}.
11363 @t{'Range} on array objects (not subtypes), but only as the right
11364 operand of the membership (@code{in}) operator.
11367 @t{'Access}, @t{'Unchecked_Access}, and
11368 @t{'Unrestricted_Access} (a GNAT extension).
11376 @code{Characters.Latin_1} are not available and
11377 concatenation is not implemented. Thus, escape characters in strings are
11378 not currently available.
11381 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11382 equality of representations. They will generally work correctly
11383 for strings and arrays whose elements have integer or enumeration types.
11384 They may not work correctly for arrays whose element
11385 types have user-defined equality, for arrays of real values
11386 (in particular, IEEE-conformant floating point, because of negative
11387 zeroes and NaNs), and for arrays whose elements contain unused bits with
11388 indeterminate values.
11391 The other component-by-component array operations (@code{and}, @code{or},
11392 @code{xor}, @code{not}, and relational tests other than equality)
11393 are not implemented.
11396 @cindex array aggregates (Ada)
11397 @cindex record aggregates (Ada)
11398 @cindex aggregates (Ada)
11399 There is limited support for array and record aggregates. They are
11400 permitted only on the right sides of assignments, as in these examples:
11403 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11404 (@value{GDBP}) set An_Array := (1, others => 0)
11405 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11406 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11407 (@value{GDBP}) set A_Record := (1, "Peter", True);
11408 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11412 discriminant's value by assigning an aggregate has an
11413 undefined effect if that discriminant is used within the record.
11414 However, you can first modify discriminants by directly assigning to
11415 them (which normally would not be allowed in Ada), and then performing an
11416 aggregate assignment. For example, given a variable @code{A_Rec}
11417 declared to have a type such as:
11420 type Rec (Len : Small_Integer := 0) is record
11422 Vals : IntArray (1 .. Len);
11426 you can assign a value with a different size of @code{Vals} with two
11430 (@value{GDBP}) set A_Rec.Len := 4
11431 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11434 As this example also illustrates, @value{GDBN} is very loose about the usual
11435 rules concerning aggregates. You may leave out some of the
11436 components of an array or record aggregate (such as the @code{Len}
11437 component in the assignment to @code{A_Rec} above); they will retain their
11438 original values upon assignment. You may freely use dynamic values as
11439 indices in component associations. You may even use overlapping or
11440 redundant component associations, although which component values are
11441 assigned in such cases is not defined.
11444 Calls to dispatching subprograms are not implemented.
11447 The overloading algorithm is much more limited (i.e., less selective)
11448 than that of real Ada. It makes only limited use of the context in
11449 which a subexpression appears to resolve its meaning, and it is much
11450 looser in its rules for allowing type matches. As a result, some
11451 function calls will be ambiguous, and the user will be asked to choose
11452 the proper resolution.
11455 The @code{new} operator is not implemented.
11458 Entry calls are not implemented.
11461 Aside from printing, arithmetic operations on the native VAX floating-point
11462 formats are not supported.
11465 It is not possible to slice a packed array.
11468 The names @code{True} and @code{False}, when not part of a qualified name,
11469 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11471 Should your program
11472 redefine these names in a package or procedure (at best a dubious practice),
11473 you will have to use fully qualified names to access their new definitions.
11476 @node Additions to Ada
11477 @subsubsection Additions to Ada
11478 @cindex Ada, deviations from
11480 As it does for other languages, @value{GDBN} makes certain generic
11481 extensions to Ada (@pxref{Expressions}):
11485 If the expression @var{E} is a variable residing in memory (typically
11486 a local variable or array element) and @var{N} is a positive integer,
11487 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11488 @var{N}-1 adjacent variables following it in memory as an array. In
11489 Ada, this operator is generally not necessary, since its prime use is
11490 in displaying parts of an array, and slicing will usually do this in
11491 Ada. However, there are occasional uses when debugging programs in
11492 which certain debugging information has been optimized away.
11495 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11496 appears in function or file @var{B}.'' When @var{B} is a file name,
11497 you must typically surround it in single quotes.
11500 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11501 @var{type} that appears at address @var{addr}.''
11504 A name starting with @samp{$} is a convenience variable
11505 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11508 In addition, @value{GDBN} provides a few other shortcuts and outright
11509 additions specific to Ada:
11513 The assignment statement is allowed as an expression, returning
11514 its right-hand operand as its value. Thus, you may enter
11517 (@value{GDBP}) set x := y + 3
11518 (@value{GDBP}) print A(tmp := y + 1)
11522 The semicolon is allowed as an ``operator,'' returning as its value
11523 the value of its right-hand operand.
11524 This allows, for example,
11525 complex conditional breaks:
11528 (@value{GDBP}) break f
11529 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11533 Rather than use catenation and symbolic character names to introduce special
11534 characters into strings, one may instead use a special bracket notation,
11535 which is also used to print strings. A sequence of characters of the form
11536 @samp{["@var{XX}"]} within a string or character literal denotes the
11537 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11538 sequence of characters @samp{["""]} also denotes a single quotation mark
11539 in strings. For example,
11541 "One line.["0a"]Next line.["0a"]"
11544 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11548 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11549 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11553 (@value{GDBP}) print 'max(x, y)
11557 When printing arrays, @value{GDBN} uses positional notation when the
11558 array has a lower bound of 1, and uses a modified named notation otherwise.
11559 For example, a one-dimensional array of three integers with a lower bound
11560 of 3 might print as
11567 That is, in contrast to valid Ada, only the first component has a @code{=>}
11571 You may abbreviate attributes in expressions with any unique,
11572 multi-character subsequence of
11573 their names (an exact match gets preference).
11574 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11575 in place of @t{a'length}.
11578 @cindex quoting Ada internal identifiers
11579 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11580 to lower case. The GNAT compiler uses upper-case characters for
11581 some of its internal identifiers, which are normally of no interest to users.
11582 For the rare occasions when you actually have to look at them,
11583 enclose them in angle brackets to avoid the lower-case mapping.
11586 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11590 Printing an object of class-wide type or dereferencing an
11591 access-to-class-wide value will display all the components of the object's
11592 specific type (as indicated by its run-time tag). Likewise, component
11593 selection on such a value will operate on the specific type of the
11598 @node Stopping Before Main Program
11599 @subsubsection Stopping at the Very Beginning
11601 @cindex breakpointing Ada elaboration code
11602 It is sometimes necessary to debug the program during elaboration, and
11603 before reaching the main procedure.
11604 As defined in the Ada Reference
11605 Manual, the elaboration code is invoked from a procedure called
11606 @code{adainit}. To run your program up to the beginning of
11607 elaboration, simply use the following two commands:
11608 @code{tbreak adainit} and @code{run}.
11611 @subsubsection Extensions for Ada Tasks
11612 @cindex Ada, tasking
11614 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11615 @value{GDBN} provides the following task-related commands:
11620 This command shows a list of current Ada tasks, as in the following example:
11627 (@value{GDBP}) info tasks
11628 ID TID P-ID Pri State Name
11629 1 8088000 0 15 Child Activation Wait main_task
11630 2 80a4000 1 15 Accept Statement b
11631 3 809a800 1 15 Child Activation Wait a
11632 * 4 80ae800 3 15 Runnable c
11637 In this listing, the asterisk before the last task indicates it to be the
11638 task currently being inspected.
11642 Represents @value{GDBN}'s internal task number.
11648 The parent's task ID (@value{GDBN}'s internal task number).
11651 The base priority of the task.
11654 Current state of the task.
11658 The task has been created but has not been activated. It cannot be
11662 The task is not blocked for any reason known to Ada. (It may be waiting
11663 for a mutex, though.) It is conceptually "executing" in normal mode.
11666 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
11667 that were waiting on terminate alternatives have been awakened and have
11668 terminated themselves.
11670 @item Child Activation Wait
11671 The task is waiting for created tasks to complete activation.
11673 @item Accept Statement
11674 The task is waiting on an accept or selective wait statement.
11676 @item Waiting on entry call
11677 The task is waiting on an entry call.
11679 @item Async Select Wait
11680 The task is waiting to start the abortable part of an asynchronous
11684 The task is waiting on a select statement with only a delay
11687 @item Child Termination Wait
11688 The task is sleeping having completed a master within itself, and is
11689 waiting for the tasks dependent on that master to become terminated or
11690 waiting on a terminate Phase.
11692 @item Wait Child in Term Alt
11693 The task is sleeping waiting for tasks on terminate alternatives to
11694 finish terminating.
11696 @item Accepting RV with @var{taskno}
11697 The task is accepting a rendez-vous with the task @var{taskno}.
11701 Name of the task in the program.
11705 @kindex info task @var{taskno}
11706 @item info task @var{taskno}
11707 This command shows detailled informations on the specified task, as in
11708 the following example:
11713 (@value{GDBP}) info tasks
11714 ID TID P-ID Pri State Name
11715 1 8077880 0 15 Child Activation Wait main_task
11716 * 2 807c468 1 15 Runnable task_1
11717 (@value{GDBP}) info task 2
11718 Ada Task: 0x807c468
11721 Parent: 1 (main_task)
11727 @kindex task@r{ (Ada)}
11728 @cindex current Ada task ID
11729 This command prints the ID of the current task.
11735 (@value{GDBP}) info tasks
11736 ID TID P-ID Pri State Name
11737 1 8077870 0 15 Child Activation Wait main_task
11738 * 2 807c458 1 15 Runnable t
11739 (@value{GDBP}) task
11740 [Current task is 2]
11743 @item task @var{taskno}
11744 @cindex Ada task switching
11745 This command is like the @code{thread @var{threadno}}
11746 command (@pxref{Threads}). It switches the context of debugging
11747 from the current task to the given task.
11753 (@value{GDBP}) info tasks
11754 ID TID P-ID Pri State Name
11755 1 8077870 0 15 Child Activation Wait main_task
11756 * 2 807c458 1 15 Runnable t
11757 (@value{GDBP}) task 1
11758 [Switching to task 1]
11759 #0 0x8067726 in pthread_cond_wait ()
11761 #0 0x8067726 in pthread_cond_wait ()
11762 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
11763 #2 0x805cb63 in system.task_primitives.operations.sleep ()
11764 #3 0x806153e in system.tasking.stages.activate_tasks ()
11765 #4 0x804aacc in un () at un.adb:5
11768 @item break @var{linespec} task @var{taskno}
11769 @itemx break @var{linespec} task @var{taskno} if @dots{}
11770 @cindex breakpoints and tasks, in Ada
11771 @cindex task breakpoints, in Ada
11772 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
11773 These commands are like the @code{break @dots{} thread @dots{}}
11774 command (@pxref{Thread Stops}).
11775 @var{linespec} specifies source lines, as described
11776 in @ref{Specify Location}.
11778 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
11779 to specify that you only want @value{GDBN} to stop the program when a
11780 particular Ada task reaches this breakpoint. @var{taskno} is one of the
11781 numeric task identifiers assigned by @value{GDBN}, shown in the first
11782 column of the @samp{info tasks} display.
11784 If you do not specify @samp{task @var{taskno}} when you set a
11785 breakpoint, the breakpoint applies to @emph{all} tasks of your
11788 You can use the @code{task} qualifier on conditional breakpoints as
11789 well; in this case, place @samp{task @var{taskno}} before the
11790 breakpoint condition (before the @code{if}).
11798 (@value{GDBP}) info tasks
11799 ID TID P-ID Pri State Name
11800 1 140022020 0 15 Child Activation Wait main_task
11801 2 140045060 1 15 Accept/Select Wait t2
11802 3 140044840 1 15 Runnable t1
11803 * 4 140056040 1 15 Runnable t3
11804 (@value{GDBP}) b 15 task 2
11805 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
11806 (@value{GDBP}) cont
11811 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
11813 (@value{GDBP}) info tasks
11814 ID TID P-ID Pri State Name
11815 1 140022020 0 15 Child Activation Wait main_task
11816 * 2 140045060 1 15 Runnable t2
11817 3 140044840 1 15 Runnable t1
11818 4 140056040 1 15 Delay Sleep t3
11822 @node Ada Tasks and Core Files
11823 @subsubsection Tasking Support when Debugging Core Files
11824 @cindex Ada tasking and core file debugging
11826 When inspecting a core file, as opposed to debugging a live program,
11827 tasking support may be limited or even unavailable, depending on
11828 the platform being used.
11829 For instance, on x86-linux, the list of tasks is available, but task
11830 switching is not supported. On Tru64, however, task switching will work
11833 On certain platforms, including Tru64, the debugger needs to perform some
11834 memory writes in order to provide Ada tasking support. When inspecting
11835 a core file, this means that the core file must be opened with read-write
11836 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
11837 Under these circumstances, you should make a backup copy of the core
11838 file before inspecting it with @value{GDBN}.
11841 @subsubsection Known Peculiarities of Ada Mode
11842 @cindex Ada, problems
11844 Besides the omissions listed previously (@pxref{Omissions from Ada}),
11845 we know of several problems with and limitations of Ada mode in
11847 some of which will be fixed with planned future releases of the debugger
11848 and the GNU Ada compiler.
11852 Currently, the debugger
11853 has insufficient information to determine whether certain pointers represent
11854 pointers to objects or the objects themselves.
11855 Thus, the user may have to tack an extra @code{.all} after an expression
11856 to get it printed properly.
11859 Static constants that the compiler chooses not to materialize as objects in
11860 storage are invisible to the debugger.
11863 Named parameter associations in function argument lists are ignored (the
11864 argument lists are treated as positional).
11867 Many useful library packages are currently invisible to the debugger.
11870 Fixed-point arithmetic, conversions, input, and output is carried out using
11871 floating-point arithmetic, and may give results that only approximate those on
11875 The GNAT compiler never generates the prefix @code{Standard} for any of
11876 the standard symbols defined by the Ada language. @value{GDBN} knows about
11877 this: it will strip the prefix from names when you use it, and will never
11878 look for a name you have so qualified among local symbols, nor match against
11879 symbols in other packages or subprograms. If you have
11880 defined entities anywhere in your program other than parameters and
11881 local variables whose simple names match names in @code{Standard},
11882 GNAT's lack of qualification here can cause confusion. When this happens,
11883 you can usually resolve the confusion
11884 by qualifying the problematic names with package
11885 @code{Standard} explicitly.
11888 @node Unsupported Languages
11889 @section Unsupported Languages
11891 @cindex unsupported languages
11892 @cindex minimal language
11893 In addition to the other fully-supported programming languages,
11894 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
11895 It does not represent a real programming language, but provides a set
11896 of capabilities close to what the C or assembly languages provide.
11897 This should allow most simple operations to be performed while debugging
11898 an application that uses a language currently not supported by @value{GDBN}.
11900 If the language is set to @code{auto}, @value{GDBN} will automatically
11901 select this language if the current frame corresponds to an unsupported
11905 @chapter Examining the Symbol Table
11907 The commands described in this chapter allow you to inquire about the
11908 symbols (names of variables, functions and types) defined in your
11909 program. This information is inherent in the text of your program and
11910 does not change as your program executes. @value{GDBN} finds it in your
11911 program's symbol table, in the file indicated when you started @value{GDBN}
11912 (@pxref{File Options, ,Choosing Files}), or by one of the
11913 file-management commands (@pxref{Files, ,Commands to Specify Files}).
11915 @cindex symbol names
11916 @cindex names of symbols
11917 @cindex quoting names
11918 Occasionally, you may need to refer to symbols that contain unusual
11919 characters, which @value{GDBN} ordinarily treats as word delimiters. The
11920 most frequent case is in referring to static variables in other
11921 source files (@pxref{Variables,,Program Variables}). File names
11922 are recorded in object files as debugging symbols, but @value{GDBN} would
11923 ordinarily parse a typical file name, like @file{foo.c}, as the three words
11924 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
11925 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
11932 looks up the value of @code{x} in the scope of the file @file{foo.c}.
11935 @cindex case-insensitive symbol names
11936 @cindex case sensitivity in symbol names
11937 @kindex set case-sensitive
11938 @item set case-sensitive on
11939 @itemx set case-sensitive off
11940 @itemx set case-sensitive auto
11941 Normally, when @value{GDBN} looks up symbols, it matches their names
11942 with case sensitivity determined by the current source language.
11943 Occasionally, you may wish to control that. The command @code{set
11944 case-sensitive} lets you do that by specifying @code{on} for
11945 case-sensitive matches or @code{off} for case-insensitive ones. If
11946 you specify @code{auto}, case sensitivity is reset to the default
11947 suitable for the source language. The default is case-sensitive
11948 matches for all languages except for Fortran, for which the default is
11949 case-insensitive matches.
11951 @kindex show case-sensitive
11952 @item show case-sensitive
11953 This command shows the current setting of case sensitivity for symbols
11956 @kindex info address
11957 @cindex address of a symbol
11958 @item info address @var{symbol}
11959 Describe where the data for @var{symbol} is stored. For a register
11960 variable, this says which register it is kept in. For a non-register
11961 local variable, this prints the stack-frame offset at which the variable
11964 Note the contrast with @samp{print &@var{symbol}}, which does not work
11965 at all for a register variable, and for a stack local variable prints
11966 the exact address of the current instantiation of the variable.
11968 @kindex info symbol
11969 @cindex symbol from address
11970 @cindex closest symbol and offset for an address
11971 @item info symbol @var{addr}
11972 Print the name of a symbol which is stored at the address @var{addr}.
11973 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
11974 nearest symbol and an offset from it:
11977 (@value{GDBP}) info symbol 0x54320
11978 _initialize_vx + 396 in section .text
11982 This is the opposite of the @code{info address} command. You can use
11983 it to find out the name of a variable or a function given its address.
11985 For dynamically linked executables, the name of executable or shared
11986 library containing the symbol is also printed:
11989 (@value{GDBP}) info symbol 0x400225
11990 _start + 5 in section .text of /tmp/a.out
11991 (@value{GDBP}) info symbol 0x2aaaac2811cf
11992 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
11996 @item whatis [@var{arg}]
11997 Print the data type of @var{arg}, which can be either an expression or
11998 a data type. With no argument, print the data type of @code{$}, the
11999 last value in the value history. If @var{arg} is an expression, it is
12000 not actually evaluated, and any side-effecting operations (such as
12001 assignments or function calls) inside it do not take place. If
12002 @var{arg} is a type name, it may be the name of a type or typedef, or
12003 for C code it may have the form @samp{class @var{class-name}},
12004 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12005 @samp{enum @var{enum-tag}}.
12006 @xref{Expressions, ,Expressions}.
12009 @item ptype [@var{arg}]
12010 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12011 detailed description of the type, instead of just the name of the type.
12012 @xref{Expressions, ,Expressions}.
12014 For example, for this variable declaration:
12017 struct complex @{double real; double imag;@} v;
12021 the two commands give this output:
12025 (@value{GDBP}) whatis v
12026 type = struct complex
12027 (@value{GDBP}) ptype v
12028 type = struct complex @{
12036 As with @code{whatis}, using @code{ptype} without an argument refers to
12037 the type of @code{$}, the last value in the value history.
12039 @cindex incomplete type
12040 Sometimes, programs use opaque data types or incomplete specifications
12041 of complex data structure. If the debug information included in the
12042 program does not allow @value{GDBN} to display a full declaration of
12043 the data type, it will say @samp{<incomplete type>}. For example,
12044 given these declarations:
12048 struct foo *fooptr;
12052 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12055 (@value{GDBP}) ptype foo
12056 $1 = <incomplete type>
12060 ``Incomplete type'' is C terminology for data types that are not
12061 completely specified.
12064 @item info types @var{regexp}
12066 Print a brief description of all types whose names match the regular
12067 expression @var{regexp} (or all types in your program, if you supply
12068 no argument). Each complete typename is matched as though it were a
12069 complete line; thus, @samp{i type value} gives information on all
12070 types in your program whose names include the string @code{value}, but
12071 @samp{i type ^value$} gives information only on types whose complete
12072 name is @code{value}.
12074 This command differs from @code{ptype} in two ways: first, like
12075 @code{whatis}, it does not print a detailed description; second, it
12076 lists all source files where a type is defined.
12079 @cindex local variables
12080 @item info scope @var{location}
12081 List all the variables local to a particular scope. This command
12082 accepts a @var{location} argument---a function name, a source line, or
12083 an address preceded by a @samp{*}, and prints all the variables local
12084 to the scope defined by that location. (@xref{Specify Location}, for
12085 details about supported forms of @var{location}.) For example:
12088 (@value{GDBP}) @b{info scope command_line_handler}
12089 Scope for command_line_handler:
12090 Symbol rl is an argument at stack/frame offset 8, length 4.
12091 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12092 Symbol linelength is in static storage at address 0x150a1c, length 4.
12093 Symbol p is a local variable in register $esi, length 4.
12094 Symbol p1 is a local variable in register $ebx, length 4.
12095 Symbol nline is a local variable in register $edx, length 4.
12096 Symbol repeat is a local variable at frame offset -8, length 4.
12100 This command is especially useful for determining what data to collect
12101 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12104 @kindex info source
12106 Show information about the current source file---that is, the source file for
12107 the function containing the current point of execution:
12110 the name of the source file, and the directory containing it,
12112 the directory it was compiled in,
12114 its length, in lines,
12116 which programming language it is written in,
12118 whether the executable includes debugging information for that file, and
12119 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12121 whether the debugging information includes information about
12122 preprocessor macros.
12126 @kindex info sources
12128 Print the names of all source files in your program for which there is
12129 debugging information, organized into two lists: files whose symbols
12130 have already been read, and files whose symbols will be read when needed.
12132 @kindex info functions
12133 @item info functions
12134 Print the names and data types of all defined functions.
12136 @item info functions @var{regexp}
12137 Print the names and data types of all defined functions
12138 whose names contain a match for regular expression @var{regexp}.
12139 Thus, @samp{info fun step} finds all functions whose names
12140 include @code{step}; @samp{info fun ^step} finds those whose names
12141 start with @code{step}. If a function name contains characters
12142 that conflict with the regular expression language (e.g.@:
12143 @samp{operator*()}), they may be quoted with a backslash.
12145 @kindex info variables
12146 @item info variables
12147 Print the names and data types of all variables that are declared
12148 outside of functions (i.e.@: excluding local variables).
12150 @item info variables @var{regexp}
12151 Print the names and data types of all variables (except for local
12152 variables) whose names contain a match for regular expression
12155 @kindex info classes
12156 @cindex Objective-C, classes and selectors
12158 @itemx info classes @var{regexp}
12159 Display all Objective-C classes in your program, or
12160 (with the @var{regexp} argument) all those matching a particular regular
12163 @kindex info selectors
12164 @item info selectors
12165 @itemx info selectors @var{regexp}
12166 Display all Objective-C selectors in your program, or
12167 (with the @var{regexp} argument) all those matching a particular regular
12171 This was never implemented.
12172 @kindex info methods
12174 @itemx info methods @var{regexp}
12175 The @code{info methods} command permits the user to examine all defined
12176 methods within C@t{++} program, or (with the @var{regexp} argument) a
12177 specific set of methods found in the various C@t{++} classes. Many
12178 C@t{++} classes provide a large number of methods. Thus, the output
12179 from the @code{ptype} command can be overwhelming and hard to use. The
12180 @code{info-methods} command filters the methods, printing only those
12181 which match the regular-expression @var{regexp}.
12184 @cindex reloading symbols
12185 Some systems allow individual object files that make up your program to
12186 be replaced without stopping and restarting your program. For example,
12187 in VxWorks you can simply recompile a defective object file and keep on
12188 running. If you are running on one of these systems, you can allow
12189 @value{GDBN} to reload the symbols for automatically relinked modules:
12192 @kindex set symbol-reloading
12193 @item set symbol-reloading on
12194 Replace symbol definitions for the corresponding source file when an
12195 object file with a particular name is seen again.
12197 @item set symbol-reloading off
12198 Do not replace symbol definitions when encountering object files of the
12199 same name more than once. This is the default state; if you are not
12200 running on a system that permits automatic relinking of modules, you
12201 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12202 may discard symbols when linking large programs, that may contain
12203 several modules (from different directories or libraries) with the same
12206 @kindex show symbol-reloading
12207 @item show symbol-reloading
12208 Show the current @code{on} or @code{off} setting.
12211 @cindex opaque data types
12212 @kindex set opaque-type-resolution
12213 @item set opaque-type-resolution on
12214 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12215 declared as a pointer to a @code{struct}, @code{class}, or
12216 @code{union}---for example, @code{struct MyType *}---that is used in one
12217 source file although the full declaration of @code{struct MyType} is in
12218 another source file. The default is on.
12220 A change in the setting of this subcommand will not take effect until
12221 the next time symbols for a file are loaded.
12223 @item set opaque-type-resolution off
12224 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12225 is printed as follows:
12227 @{<no data fields>@}
12230 @kindex show opaque-type-resolution
12231 @item show opaque-type-resolution
12232 Show whether opaque types are resolved or not.
12234 @kindex set print symbol-loading
12235 @cindex print messages when symbols are loaded
12236 @item set print symbol-loading
12237 @itemx set print symbol-loading on
12238 @itemx set print symbol-loading off
12239 The @code{set print symbol-loading} command allows you to enable or
12240 disable printing of messages when @value{GDBN} loads symbols.
12241 By default, these messages will be printed, and normally this is what
12242 you want. Disabling these messages is useful when debugging applications
12243 with lots of shared libraries where the quantity of output can be more
12244 annoying than useful.
12246 @kindex show print symbol-loading
12247 @item show print symbol-loading
12248 Show whether messages will be printed when @value{GDBN} loads symbols.
12250 @kindex maint print symbols
12251 @cindex symbol dump
12252 @kindex maint print psymbols
12253 @cindex partial symbol dump
12254 @item maint print symbols @var{filename}
12255 @itemx maint print psymbols @var{filename}
12256 @itemx maint print msymbols @var{filename}
12257 Write a dump of debugging symbol data into the file @var{filename}.
12258 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12259 symbols with debugging data are included. If you use @samp{maint print
12260 symbols}, @value{GDBN} includes all the symbols for which it has already
12261 collected full details: that is, @var{filename} reflects symbols for
12262 only those files whose symbols @value{GDBN} has read. You can use the
12263 command @code{info sources} to find out which files these are. If you
12264 use @samp{maint print psymbols} instead, the dump shows information about
12265 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12266 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12267 @samp{maint print msymbols} dumps just the minimal symbol information
12268 required for each object file from which @value{GDBN} has read some symbols.
12269 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12270 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12272 @kindex maint info symtabs
12273 @kindex maint info psymtabs
12274 @cindex listing @value{GDBN}'s internal symbol tables
12275 @cindex symbol tables, listing @value{GDBN}'s internal
12276 @cindex full symbol tables, listing @value{GDBN}'s internal
12277 @cindex partial symbol tables, listing @value{GDBN}'s internal
12278 @item maint info symtabs @r{[} @var{regexp} @r{]}
12279 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12281 List the @code{struct symtab} or @code{struct partial_symtab}
12282 structures whose names match @var{regexp}. If @var{regexp} is not
12283 given, list them all. The output includes expressions which you can
12284 copy into a @value{GDBN} debugging this one to examine a particular
12285 structure in more detail. For example:
12288 (@value{GDBP}) maint info psymtabs dwarf2read
12289 @{ objfile /home/gnu/build/gdb/gdb
12290 ((struct objfile *) 0x82e69d0)
12291 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12292 ((struct partial_symtab *) 0x8474b10)
12295 text addresses 0x814d3c8 -- 0x8158074
12296 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12297 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12298 dependencies (none)
12301 (@value{GDBP}) maint info symtabs
12305 We see that there is one partial symbol table whose filename contains
12306 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12307 and we see that @value{GDBN} has not read in any symtabs yet at all.
12308 If we set a breakpoint on a function, that will cause @value{GDBN} to
12309 read the symtab for the compilation unit containing that function:
12312 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12313 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12315 (@value{GDBP}) maint info symtabs
12316 @{ objfile /home/gnu/build/gdb/gdb
12317 ((struct objfile *) 0x82e69d0)
12318 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12319 ((struct symtab *) 0x86c1f38)
12322 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12323 linetable ((struct linetable *) 0x8370fa0)
12324 debugformat DWARF 2
12333 @chapter Altering Execution
12335 Once you think you have found an error in your program, you might want to
12336 find out for certain whether correcting the apparent error would lead to
12337 correct results in the rest of the run. You can find the answer by
12338 experiment, using the @value{GDBN} features for altering execution of the
12341 For example, you can store new values into variables or memory
12342 locations, give your program a signal, restart it at a different
12343 address, or even return prematurely from a function.
12346 * Assignment:: Assignment to variables
12347 * Jumping:: Continuing at a different address
12348 * Signaling:: Giving your program a signal
12349 * Returning:: Returning from a function
12350 * Calling:: Calling your program's functions
12351 * Patching:: Patching your program
12355 @section Assignment to Variables
12358 @cindex setting variables
12359 To alter the value of a variable, evaluate an assignment expression.
12360 @xref{Expressions, ,Expressions}. For example,
12367 stores the value 4 into the variable @code{x}, and then prints the
12368 value of the assignment expression (which is 4).
12369 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12370 information on operators in supported languages.
12372 @kindex set variable
12373 @cindex variables, setting
12374 If you are not interested in seeing the value of the assignment, use the
12375 @code{set} command instead of the @code{print} command. @code{set} is
12376 really the same as @code{print} except that the expression's value is
12377 not printed and is not put in the value history (@pxref{Value History,
12378 ,Value History}). The expression is evaluated only for its effects.
12380 If the beginning of the argument string of the @code{set} command
12381 appears identical to a @code{set} subcommand, use the @code{set
12382 variable} command instead of just @code{set}. This command is identical
12383 to @code{set} except for its lack of subcommands. For example, if your
12384 program has a variable @code{width}, you get an error if you try to set
12385 a new value with just @samp{set width=13}, because @value{GDBN} has the
12386 command @code{set width}:
12389 (@value{GDBP}) whatis width
12391 (@value{GDBP}) p width
12393 (@value{GDBP}) set width=47
12394 Invalid syntax in expression.
12398 The invalid expression, of course, is @samp{=47}. In
12399 order to actually set the program's variable @code{width}, use
12402 (@value{GDBP}) set var width=47
12405 Because the @code{set} command has many subcommands that can conflict
12406 with the names of program variables, it is a good idea to use the
12407 @code{set variable} command instead of just @code{set}. For example, if
12408 your program has a variable @code{g}, you run into problems if you try
12409 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12410 the command @code{set gnutarget}, abbreviated @code{set g}:
12414 (@value{GDBP}) whatis g
12418 (@value{GDBP}) set g=4
12422 The program being debugged has been started already.
12423 Start it from the beginning? (y or n) y
12424 Starting program: /home/smith/cc_progs/a.out
12425 "/home/smith/cc_progs/a.out": can't open to read symbols:
12426 Invalid bfd target.
12427 (@value{GDBP}) show g
12428 The current BFD target is "=4".
12433 The program variable @code{g} did not change, and you silently set the
12434 @code{gnutarget} to an invalid value. In order to set the variable
12438 (@value{GDBP}) set var g=4
12441 @value{GDBN} allows more implicit conversions in assignments than C; you can
12442 freely store an integer value into a pointer variable or vice versa,
12443 and you can convert any structure to any other structure that is the
12444 same length or shorter.
12445 @comment FIXME: how do structs align/pad in these conversions?
12446 @comment /doc@cygnus.com 18dec1990
12448 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12449 construct to generate a value of specified type at a specified address
12450 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12451 to memory location @code{0x83040} as an integer (which implies a certain size
12452 and representation in memory), and
12455 set @{int@}0x83040 = 4
12459 stores the value 4 into that memory location.
12462 @section Continuing at a Different Address
12464 Ordinarily, when you continue your program, you do so at the place where
12465 it stopped, with the @code{continue} command. You can instead continue at
12466 an address of your own choosing, with the following commands:
12470 @item jump @var{linespec}
12471 @itemx jump @var{location}
12472 Resume execution at line @var{linespec} or at address given by
12473 @var{location}. Execution stops again immediately if there is a
12474 breakpoint there. @xref{Specify Location}, for a description of the
12475 different forms of @var{linespec} and @var{location}. It is common
12476 practice to use the @code{tbreak} command in conjunction with
12477 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12479 The @code{jump} command does not change the current stack frame, or
12480 the stack pointer, or the contents of any memory location or any
12481 register other than the program counter. If line @var{linespec} is in
12482 a different function from the one currently executing, the results may
12483 be bizarre if the two functions expect different patterns of arguments or
12484 of local variables. For this reason, the @code{jump} command requests
12485 confirmation if the specified line is not in the function currently
12486 executing. However, even bizarre results are predictable if you are
12487 well acquainted with the machine-language code of your program.
12490 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12491 On many systems, you can get much the same effect as the @code{jump}
12492 command by storing a new value into the register @code{$pc}. The
12493 difference is that this does not start your program running; it only
12494 changes the address of where it @emph{will} run when you continue. For
12502 makes the next @code{continue} command or stepping command execute at
12503 address @code{0x485}, rather than at the address where your program stopped.
12504 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12506 The most common occasion to use the @code{jump} command is to back
12507 up---perhaps with more breakpoints set---over a portion of a program
12508 that has already executed, in order to examine its execution in more
12513 @section Giving your Program a Signal
12514 @cindex deliver a signal to a program
12518 @item signal @var{signal}
12519 Resume execution where your program stopped, but immediately give it the
12520 signal @var{signal}. @var{signal} can be the name or the number of a
12521 signal. For example, on many systems @code{signal 2} and @code{signal
12522 SIGINT} are both ways of sending an interrupt signal.
12524 Alternatively, if @var{signal} is zero, continue execution without
12525 giving a signal. This is useful when your program stopped on account of
12526 a signal and would ordinary see the signal when resumed with the
12527 @code{continue} command; @samp{signal 0} causes it to resume without a
12530 @code{signal} does not repeat when you press @key{RET} a second time
12531 after executing the command.
12535 Invoking the @code{signal} command is not the same as invoking the
12536 @code{kill} utility from the shell. Sending a signal with @code{kill}
12537 causes @value{GDBN} to decide what to do with the signal depending on
12538 the signal handling tables (@pxref{Signals}). The @code{signal} command
12539 passes the signal directly to your program.
12543 @section Returning from a Function
12546 @cindex returning from a function
12549 @itemx return @var{expression}
12550 You can cancel execution of a function call with the @code{return}
12551 command. If you give an
12552 @var{expression} argument, its value is used as the function's return
12556 When you use @code{return}, @value{GDBN} discards the selected stack frame
12557 (and all frames within it). You can think of this as making the
12558 discarded frame return prematurely. If you wish to specify a value to
12559 be returned, give that value as the argument to @code{return}.
12561 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12562 Frame}), and any other frames inside of it, leaving its caller as the
12563 innermost remaining frame. That frame becomes selected. The
12564 specified value is stored in the registers used for returning values
12567 The @code{return} command does not resume execution; it leaves the
12568 program stopped in the state that would exist if the function had just
12569 returned. In contrast, the @code{finish} command (@pxref{Continuing
12570 and Stepping, ,Continuing and Stepping}) resumes execution until the
12571 selected stack frame returns naturally.
12573 @value{GDBN} needs to know how the @var{expression} argument should be set for
12574 the inferior. The concrete registers assignment depends on the OS ABI and the
12575 type being returned by the selected stack frame. For example it is common for
12576 OS ABI to return floating point values in FPU registers while integer values in
12577 CPU registers. Still some ABIs return even floating point values in CPU
12578 registers. Larger integer widths (such as @code{long long int}) also have
12579 specific placement rules. @value{GDBN} already knows the OS ABI from its
12580 current target so it needs to find out also the type being returned to make the
12581 assignment into the right register(s).
12583 Normally, the selected stack frame has debug info. @value{GDBN} will always
12584 use the debug info instead of the implicit type of @var{expression} when the
12585 debug info is available. For example, if you type @kbd{return -1}, and the
12586 function in the current stack frame is declared to return a @code{long long
12587 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
12588 into a @code{long long int}:
12591 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
12593 (@value{GDBP}) return -1
12594 Make func return now? (y or n) y
12595 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
12596 43 printf ("result=%lld\n", func ());
12600 However, if the selected stack frame does not have a debug info, e.g., if the
12601 function was compiled without debug info, @value{GDBN} has to find out the type
12602 to return from user. Specifying a different type by mistake may set the value
12603 in different inferior registers than the caller code expects. For example,
12604 typing @kbd{return -1} with its implicit type @code{int} would set only a part
12605 of a @code{long long int} result for a debug info less function (on 32-bit
12606 architectures). Therefore the user is required to specify the return type by
12607 an appropriate cast explicitly:
12610 Breakpoint 2, 0x0040050b in func ()
12611 (@value{GDBP}) return -1
12612 Return value type not available for selected stack frame.
12613 Please use an explicit cast of the value to return.
12614 (@value{GDBP}) return (long long int) -1
12615 Make selected stack frame return now? (y or n) y
12616 #0 0x00400526 in main ()
12621 @section Calling Program Functions
12624 @cindex calling functions
12625 @cindex inferior functions, calling
12626 @item print @var{expr}
12627 Evaluate the expression @var{expr} and display the resulting value.
12628 @var{expr} may include calls to functions in the program being
12632 @item call @var{expr}
12633 Evaluate the expression @var{expr} without displaying @code{void}
12636 You can use this variant of the @code{print} command if you want to
12637 execute a function from your program that does not return anything
12638 (a.k.a.@: @dfn{a void function}), but without cluttering the output
12639 with @code{void} returned values that @value{GDBN} will otherwise
12640 print. If the result is not void, it is printed and saved in the
12644 It is possible for the function you call via the @code{print} or
12645 @code{call} command to generate a signal (e.g., if there's a bug in
12646 the function, or if you passed it incorrect arguments). What happens
12647 in that case is controlled by the @code{set unwindonsignal} command.
12650 @item set unwindonsignal
12651 @kindex set unwindonsignal
12652 @cindex unwind stack in called functions
12653 @cindex call dummy stack unwinding
12654 Set unwinding of the stack if a signal is received while in a function
12655 that @value{GDBN} called in the program being debugged. If set to on,
12656 @value{GDBN} unwinds the stack it created for the call and restores
12657 the context to what it was before the call. If set to off (the
12658 default), @value{GDBN} stops in the frame where the signal was
12661 @item show unwindonsignal
12662 @kindex show unwindonsignal
12663 Show the current setting of stack unwinding in the functions called by
12667 @cindex weak alias functions
12668 Sometimes, a function you wish to call is actually a @dfn{weak alias}
12669 for another function. In such case, @value{GDBN} might not pick up
12670 the type information, including the types of the function arguments,
12671 which causes @value{GDBN} to call the inferior function incorrectly.
12672 As a result, the called function will function erroneously and may
12673 even crash. A solution to that is to use the name of the aliased
12677 @section Patching Programs
12679 @cindex patching binaries
12680 @cindex writing into executables
12681 @cindex writing into corefiles
12683 By default, @value{GDBN} opens the file containing your program's
12684 executable code (or the corefile) read-only. This prevents accidental
12685 alterations to machine code; but it also prevents you from intentionally
12686 patching your program's binary.
12688 If you'd like to be able to patch the binary, you can specify that
12689 explicitly with the @code{set write} command. For example, you might
12690 want to turn on internal debugging flags, or even to make emergency
12696 @itemx set write off
12697 If you specify @samp{set write on}, @value{GDBN} opens executable and
12698 core files for both reading and writing; if you specify @kbd{set write
12699 off} (the default), @value{GDBN} opens them read-only.
12701 If you have already loaded a file, you must load it again (using the
12702 @code{exec-file} or @code{core-file} command) after changing @code{set
12703 write}, for your new setting to take effect.
12707 Display whether executable files and core files are opened for writing
12708 as well as reading.
12712 @chapter @value{GDBN} Files
12714 @value{GDBN} needs to know the file name of the program to be debugged,
12715 both in order to read its symbol table and in order to start your
12716 program. To debug a core dump of a previous run, you must also tell
12717 @value{GDBN} the name of the core dump file.
12720 * Files:: Commands to specify files
12721 * Separate Debug Files:: Debugging information in separate files
12722 * Symbol Errors:: Errors reading symbol files
12726 @section Commands to Specify Files
12728 @cindex symbol table
12729 @cindex core dump file
12731 You may want to specify executable and core dump file names. The usual
12732 way to do this is at start-up time, using the arguments to
12733 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
12734 Out of @value{GDBN}}).
12736 Occasionally it is necessary to change to a different file during a
12737 @value{GDBN} session. Or you may run @value{GDBN} and forget to
12738 specify a file you want to use. Or you are debugging a remote target
12739 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
12740 Program}). In these situations the @value{GDBN} commands to specify
12741 new files are useful.
12744 @cindex executable file
12746 @item file @var{filename}
12747 Use @var{filename} as the program to be debugged. It is read for its
12748 symbols and for the contents of pure memory. It is also the program
12749 executed when you use the @code{run} command. If you do not specify a
12750 directory and the file is not found in the @value{GDBN} working directory,
12751 @value{GDBN} uses the environment variable @code{PATH} as a list of
12752 directories to search, just as the shell does when looking for a program
12753 to run. You can change the value of this variable, for both @value{GDBN}
12754 and your program, using the @code{path} command.
12756 @cindex unlinked object files
12757 @cindex patching object files
12758 You can load unlinked object @file{.o} files into @value{GDBN} using
12759 the @code{file} command. You will not be able to ``run'' an object
12760 file, but you can disassemble functions and inspect variables. Also,
12761 if the underlying BFD functionality supports it, you could use
12762 @kbd{gdb -write} to patch object files using this technique. Note
12763 that @value{GDBN} can neither interpret nor modify relocations in this
12764 case, so branches and some initialized variables will appear to go to
12765 the wrong place. But this feature is still handy from time to time.
12768 @code{file} with no argument makes @value{GDBN} discard any information it
12769 has on both executable file and the symbol table.
12772 @item exec-file @r{[} @var{filename} @r{]}
12773 Specify that the program to be run (but not the symbol table) is found
12774 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
12775 if necessary to locate your program. Omitting @var{filename} means to
12776 discard information on the executable file.
12778 @kindex symbol-file
12779 @item symbol-file @r{[} @var{filename} @r{]}
12780 Read symbol table information from file @var{filename}. @code{PATH} is
12781 searched when necessary. Use the @code{file} command to get both symbol
12782 table and program to run from the same file.
12784 @code{symbol-file} with no argument clears out @value{GDBN} information on your
12785 program's symbol table.
12787 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
12788 some breakpoints and auto-display expressions. This is because they may
12789 contain pointers to the internal data recording symbols and data types,
12790 which are part of the old symbol table data being discarded inside
12793 @code{symbol-file} does not repeat if you press @key{RET} again after
12796 When @value{GDBN} is configured for a particular environment, it
12797 understands debugging information in whatever format is the standard
12798 generated for that environment; you may use either a @sc{gnu} compiler, or
12799 other compilers that adhere to the local conventions.
12800 Best results are usually obtained from @sc{gnu} compilers; for example,
12801 using @code{@value{NGCC}} you can generate debugging information for
12804 For most kinds of object files, with the exception of old SVR3 systems
12805 using COFF, the @code{symbol-file} command does not normally read the
12806 symbol table in full right away. Instead, it scans the symbol table
12807 quickly to find which source files and which symbols are present. The
12808 details are read later, one source file at a time, as they are needed.
12810 The purpose of this two-stage reading strategy is to make @value{GDBN}
12811 start up faster. For the most part, it is invisible except for
12812 occasional pauses while the symbol table details for a particular source
12813 file are being read. (The @code{set verbose} command can turn these
12814 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
12815 Warnings and Messages}.)
12817 We have not implemented the two-stage strategy for COFF yet. When the
12818 symbol table is stored in COFF format, @code{symbol-file} reads the
12819 symbol table data in full right away. Note that ``stabs-in-COFF''
12820 still does the two-stage strategy, since the debug info is actually
12824 @cindex reading symbols immediately
12825 @cindex symbols, reading immediately
12826 @item symbol-file @var{filename} @r{[} -readnow @r{]}
12827 @itemx file @var{filename} @r{[} -readnow @r{]}
12828 You can override the @value{GDBN} two-stage strategy for reading symbol
12829 tables by using the @samp{-readnow} option with any of the commands that
12830 load symbol table information, if you want to be sure @value{GDBN} has the
12831 entire symbol table available.
12833 @c FIXME: for now no mention of directories, since this seems to be in
12834 @c flux. 13mar1992 status is that in theory GDB would look either in
12835 @c current dir or in same dir as myprog; but issues like competing
12836 @c GDB's, or clutter in system dirs, mean that in practice right now
12837 @c only current dir is used. FFish says maybe a special GDB hierarchy
12838 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
12842 @item core-file @r{[}@var{filename}@r{]}
12844 Specify the whereabouts of a core dump file to be used as the ``contents
12845 of memory''. Traditionally, core files contain only some parts of the
12846 address space of the process that generated them; @value{GDBN} can access the
12847 executable file itself for other parts.
12849 @code{core-file} with no argument specifies that no core file is
12852 Note that the core file is ignored when your program is actually running
12853 under @value{GDBN}. So, if you have been running your program and you
12854 wish to debug a core file instead, you must kill the subprocess in which
12855 the program is running. To do this, use the @code{kill} command
12856 (@pxref{Kill Process, ,Killing the Child Process}).
12858 @kindex add-symbol-file
12859 @cindex dynamic linking
12860 @item add-symbol-file @var{filename} @var{address}
12861 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
12862 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
12863 The @code{add-symbol-file} command reads additional symbol table
12864 information from the file @var{filename}. You would use this command
12865 when @var{filename} has been dynamically loaded (by some other means)
12866 into the program that is running. @var{address} should be the memory
12867 address at which the file has been loaded; @value{GDBN} cannot figure
12868 this out for itself. You can additionally specify an arbitrary number
12869 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
12870 section name and base address for that section. You can specify any
12871 @var{address} as an expression.
12873 The symbol table of the file @var{filename} is added to the symbol table
12874 originally read with the @code{symbol-file} command. You can use the
12875 @code{add-symbol-file} command any number of times; the new symbol data
12876 thus read keeps adding to the old. To discard all old symbol data
12877 instead, use the @code{symbol-file} command without any arguments.
12879 @cindex relocatable object files, reading symbols from
12880 @cindex object files, relocatable, reading symbols from
12881 @cindex reading symbols from relocatable object files
12882 @cindex symbols, reading from relocatable object files
12883 @cindex @file{.o} files, reading symbols from
12884 Although @var{filename} is typically a shared library file, an
12885 executable file, or some other object file which has been fully
12886 relocated for loading into a process, you can also load symbolic
12887 information from relocatable @file{.o} files, as long as:
12891 the file's symbolic information refers only to linker symbols defined in
12892 that file, not to symbols defined by other object files,
12894 every section the file's symbolic information refers to has actually
12895 been loaded into the inferior, as it appears in the file, and
12897 you can determine the address at which every section was loaded, and
12898 provide these to the @code{add-symbol-file} command.
12902 Some embedded operating systems, like Sun Chorus and VxWorks, can load
12903 relocatable files into an already running program; such systems
12904 typically make the requirements above easy to meet. However, it's
12905 important to recognize that many native systems use complex link
12906 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
12907 assembly, for example) that make the requirements difficult to meet. In
12908 general, one cannot assume that using @code{add-symbol-file} to read a
12909 relocatable object file's symbolic information will have the same effect
12910 as linking the relocatable object file into the program in the normal
12913 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
12915 @kindex add-symbol-file-from-memory
12916 @cindex @code{syscall DSO}
12917 @cindex load symbols from memory
12918 @item add-symbol-file-from-memory @var{address}
12919 Load symbols from the given @var{address} in a dynamically loaded
12920 object file whose image is mapped directly into the inferior's memory.
12921 For example, the Linux kernel maps a @code{syscall DSO} into each
12922 process's address space; this DSO provides kernel-specific code for
12923 some system calls. The argument can be any expression whose
12924 evaluation yields the address of the file's shared object file header.
12925 For this command to work, you must have used @code{symbol-file} or
12926 @code{exec-file} commands in advance.
12928 @kindex add-shared-symbol-files
12930 @item add-shared-symbol-files @var{library-file}
12931 @itemx assf @var{library-file}
12932 The @code{add-shared-symbol-files} command can currently be used only
12933 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
12934 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
12935 @value{GDBN} automatically looks for shared libraries, however if
12936 @value{GDBN} does not find yours, you can invoke
12937 @code{add-shared-symbol-files}. It takes one argument: the shared
12938 library's file name. @code{assf} is a shorthand alias for
12939 @code{add-shared-symbol-files}.
12942 @item section @var{section} @var{addr}
12943 The @code{section} command changes the base address of the named
12944 @var{section} of the exec file to @var{addr}. This can be used if the
12945 exec file does not contain section addresses, (such as in the
12946 @code{a.out} format), or when the addresses specified in the file
12947 itself are wrong. Each section must be changed separately. The
12948 @code{info files} command, described below, lists all the sections and
12952 @kindex info target
12955 @code{info files} and @code{info target} are synonymous; both print the
12956 current target (@pxref{Targets, ,Specifying a Debugging Target}),
12957 including the names of the executable and core dump files currently in
12958 use by @value{GDBN}, and the files from which symbols were loaded. The
12959 command @code{help target} lists all possible targets rather than
12962 @kindex maint info sections
12963 @item maint info sections
12964 Another command that can give you extra information about program sections
12965 is @code{maint info sections}. In addition to the section information
12966 displayed by @code{info files}, this command displays the flags and file
12967 offset of each section in the executable and core dump files. In addition,
12968 @code{maint info sections} provides the following command options (which
12969 may be arbitrarily combined):
12973 Display sections for all loaded object files, including shared libraries.
12974 @item @var{sections}
12975 Display info only for named @var{sections}.
12976 @item @var{section-flags}
12977 Display info only for sections for which @var{section-flags} are true.
12978 The section flags that @value{GDBN} currently knows about are:
12981 Section will have space allocated in the process when loaded.
12982 Set for all sections except those containing debug information.
12984 Section will be loaded from the file into the child process memory.
12985 Set for pre-initialized code and data, clear for @code{.bss} sections.
12987 Section needs to be relocated before loading.
12989 Section cannot be modified by the child process.
12991 Section contains executable code only.
12993 Section contains data only (no executable code).
12995 Section will reside in ROM.
12997 Section contains data for constructor/destructor lists.
12999 Section is not empty.
13001 An instruction to the linker to not output the section.
13002 @item COFF_SHARED_LIBRARY
13003 A notification to the linker that the section contains
13004 COFF shared library information.
13006 Section contains common symbols.
13009 @kindex set trust-readonly-sections
13010 @cindex read-only sections
13011 @item set trust-readonly-sections on
13012 Tell @value{GDBN} that readonly sections in your object file
13013 really are read-only (i.e.@: that their contents will not change).
13014 In that case, @value{GDBN} can fetch values from these sections
13015 out of the object file, rather than from the target program.
13016 For some targets (notably embedded ones), this can be a significant
13017 enhancement to debugging performance.
13019 The default is off.
13021 @item set trust-readonly-sections off
13022 Tell @value{GDBN} not to trust readonly sections. This means that
13023 the contents of the section might change while the program is running,
13024 and must therefore be fetched from the target when needed.
13026 @item show trust-readonly-sections
13027 Show the current setting of trusting readonly sections.
13030 All file-specifying commands allow both absolute and relative file names
13031 as arguments. @value{GDBN} always converts the file name to an absolute file
13032 name and remembers it that way.
13034 @cindex shared libraries
13035 @anchor{Shared Libraries}
13036 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13037 and IBM RS/6000 AIX shared libraries.
13039 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13040 shared libraries. @xref{Expat}.
13042 @value{GDBN} automatically loads symbol definitions from shared libraries
13043 when you use the @code{run} command, or when you examine a core file.
13044 (Before you issue the @code{run} command, @value{GDBN} does not understand
13045 references to a function in a shared library, however---unless you are
13046 debugging a core file).
13048 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13049 automatically loads the symbols at the time of the @code{shl_load} call.
13051 @c FIXME: some @value{GDBN} release may permit some refs to undef
13052 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13053 @c FIXME...lib; check this from time to time when updating manual
13055 There are times, however, when you may wish to not automatically load
13056 symbol definitions from shared libraries, such as when they are
13057 particularly large or there are many of them.
13059 To control the automatic loading of shared library symbols, use the
13063 @kindex set auto-solib-add
13064 @item set auto-solib-add @var{mode}
13065 If @var{mode} is @code{on}, symbols from all shared object libraries
13066 will be loaded automatically when the inferior begins execution, you
13067 attach to an independently started inferior, or when the dynamic linker
13068 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13069 is @code{off}, symbols must be loaded manually, using the
13070 @code{sharedlibrary} command. The default value is @code{on}.
13072 @cindex memory used for symbol tables
13073 If your program uses lots of shared libraries with debug info that
13074 takes large amounts of memory, you can decrease the @value{GDBN}
13075 memory footprint by preventing it from automatically loading the
13076 symbols from shared libraries. To that end, type @kbd{set
13077 auto-solib-add off} before running the inferior, then load each
13078 library whose debug symbols you do need with @kbd{sharedlibrary
13079 @var{regexp}}, where @var{regexp} is a regular expression that matches
13080 the libraries whose symbols you want to be loaded.
13082 @kindex show auto-solib-add
13083 @item show auto-solib-add
13084 Display the current autoloading mode.
13087 @cindex load shared library
13088 To explicitly load shared library symbols, use the @code{sharedlibrary}
13092 @kindex info sharedlibrary
13095 @itemx info sharedlibrary
13096 Print the names of the shared libraries which are currently loaded.
13098 @kindex sharedlibrary
13100 @item sharedlibrary @var{regex}
13101 @itemx share @var{regex}
13102 Load shared object library symbols for files matching a
13103 Unix regular expression.
13104 As with files loaded automatically, it only loads shared libraries
13105 required by your program for a core file or after typing @code{run}. If
13106 @var{regex} is omitted all shared libraries required by your program are
13109 @item nosharedlibrary
13110 @kindex nosharedlibrary
13111 @cindex unload symbols from shared libraries
13112 Unload all shared object library symbols. This discards all symbols
13113 that have been loaded from all shared libraries. Symbols from shared
13114 libraries that were loaded by explicit user requests are not
13118 Sometimes you may wish that @value{GDBN} stops and gives you control
13119 when any of shared library events happen. Use the @code{set
13120 stop-on-solib-events} command for this:
13123 @item set stop-on-solib-events
13124 @kindex set stop-on-solib-events
13125 This command controls whether @value{GDBN} should give you control
13126 when the dynamic linker notifies it about some shared library event.
13127 The most common event of interest is loading or unloading of a new
13130 @item show stop-on-solib-events
13131 @kindex show stop-on-solib-events
13132 Show whether @value{GDBN} stops and gives you control when shared
13133 library events happen.
13136 Shared libraries are also supported in many cross or remote debugging
13137 configurations. @value{GDBN} needs to have access to the target's libraries;
13138 this can be accomplished either by providing copies of the libraries
13139 on the host system, or by asking @value{GDBN} to automatically retrieve the
13140 libraries from the target. If copies of the target libraries are
13141 provided, they need to be the same as the target libraries, although the
13142 copies on the target can be stripped as long as the copies on the host are
13145 @cindex where to look for shared libraries
13146 For remote debugging, you need to tell @value{GDBN} where the target
13147 libraries are, so that it can load the correct copies---otherwise, it
13148 may try to load the host's libraries. @value{GDBN} has two variables
13149 to specify the search directories for target libraries.
13152 @cindex prefix for shared library file names
13153 @cindex system root, alternate
13154 @kindex set solib-absolute-prefix
13155 @kindex set sysroot
13156 @item set sysroot @var{path}
13157 Use @var{path} as the system root for the program being debugged. Any
13158 absolute shared library paths will be prefixed with @var{path}; many
13159 runtime loaders store the absolute paths to the shared library in the
13160 target program's memory. If you use @code{set sysroot} to find shared
13161 libraries, they need to be laid out in the same way that they are on
13162 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13165 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13166 retrieve the target libraries from the remote system. This is only
13167 supported when using a remote target that supports the @code{remote get}
13168 command (@pxref{File Transfer,,Sending files to a remote system}).
13169 The part of @var{path} following the initial @file{remote:}
13170 (if present) is used as system root prefix on the remote file system.
13171 @footnote{If you want to specify a local system root using a directory
13172 that happens to be named @file{remote:}, you need to use some equivalent
13173 variant of the name like @file{./remote:}.}
13175 The @code{set solib-absolute-prefix} command is an alias for @code{set
13178 @cindex default system root
13179 @cindex @samp{--with-sysroot}
13180 You can set the default system root by using the configure-time
13181 @samp{--with-sysroot} option. If the system root is inside
13182 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13183 @samp{--exec-prefix}), then the default system root will be updated
13184 automatically if the installed @value{GDBN} is moved to a new
13187 @kindex show sysroot
13189 Display the current shared library prefix.
13191 @kindex set solib-search-path
13192 @item set solib-search-path @var{path}
13193 If this variable is set, @var{path} is a colon-separated list of
13194 directories to search for shared libraries. @samp{solib-search-path}
13195 is used after @samp{sysroot} fails to locate the library, or if the
13196 path to the library is relative instead of absolute. If you want to
13197 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13198 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13199 finding your host's libraries. @samp{sysroot} is preferred; setting
13200 it to a nonexistent directory may interfere with automatic loading
13201 of shared library symbols.
13203 @kindex show solib-search-path
13204 @item show solib-search-path
13205 Display the current shared library search path.
13209 @node Separate Debug Files
13210 @section Debugging Information in Separate Files
13211 @cindex separate debugging information files
13212 @cindex debugging information in separate files
13213 @cindex @file{.debug} subdirectories
13214 @cindex debugging information directory, global
13215 @cindex global debugging information directory
13216 @cindex build ID, and separate debugging files
13217 @cindex @file{.build-id} directory
13219 @value{GDBN} allows you to put a program's debugging information in a
13220 file separate from the executable itself, in a way that allows
13221 @value{GDBN} to find and load the debugging information automatically.
13222 Since debugging information can be very large---sometimes larger
13223 than the executable code itself---some systems distribute debugging
13224 information for their executables in separate files, which users can
13225 install only when they need to debug a problem.
13227 @value{GDBN} supports two ways of specifying the separate debug info
13232 The executable contains a @dfn{debug link} that specifies the name of
13233 the separate debug info file. The separate debug file's name is
13234 usually @file{@var{executable}.debug}, where @var{executable} is the
13235 name of the corresponding executable file without leading directories
13236 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13237 debug link specifies a CRC32 checksum for the debug file, which
13238 @value{GDBN} uses to validate that the executable and the debug file
13239 came from the same build.
13242 The executable contains a @dfn{build ID}, a unique bit string that is
13243 also present in the corresponding debug info file. (This is supported
13244 only on some operating systems, notably those which use the ELF format
13245 for binary files and the @sc{gnu} Binutils.) For more details about
13246 this feature, see the description of the @option{--build-id}
13247 command-line option in @ref{Options, , Command Line Options, ld.info,
13248 The GNU Linker}. The debug info file's name is not specified
13249 explicitly by the build ID, but can be computed from the build ID, see
13253 Depending on the way the debug info file is specified, @value{GDBN}
13254 uses two different methods of looking for the debug file:
13258 For the ``debug link'' method, @value{GDBN} looks up the named file in
13259 the directory of the executable file, then in a subdirectory of that
13260 directory named @file{.debug}, and finally under the global debug
13261 directory, in a subdirectory whose name is identical to the leading
13262 directories of the executable's absolute file name.
13265 For the ``build ID'' method, @value{GDBN} looks in the
13266 @file{.build-id} subdirectory of the global debug directory for a file
13267 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13268 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13269 are the rest of the bit string. (Real build ID strings are 32 or more
13270 hex characters, not 10.)
13273 So, for example, suppose you ask @value{GDBN} to debug
13274 @file{/usr/bin/ls}, which has a debug link that specifies the
13275 file @file{ls.debug}, and a build ID whose value in hex is
13276 @code{abcdef1234}. If the global debug directory is
13277 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13278 debug information files, in the indicated order:
13282 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13284 @file{/usr/bin/ls.debug}
13286 @file{/usr/bin/.debug/ls.debug}
13288 @file{/usr/lib/debug/usr/bin/ls.debug}.
13291 You can set the global debugging info directory's name, and view the
13292 name @value{GDBN} is currently using.
13296 @kindex set debug-file-directory
13297 @item set debug-file-directory @var{directory}
13298 Set the directory which @value{GDBN} searches for separate debugging
13299 information files to @var{directory}.
13301 @kindex show debug-file-directory
13302 @item show debug-file-directory
13303 Show the directory @value{GDBN} searches for separate debugging
13308 @cindex @code{.gnu_debuglink} sections
13309 @cindex debug link sections
13310 A debug link is a special section of the executable file named
13311 @code{.gnu_debuglink}. The section must contain:
13315 A filename, with any leading directory components removed, followed by
13318 zero to three bytes of padding, as needed to reach the next four-byte
13319 boundary within the section, and
13321 a four-byte CRC checksum, stored in the same endianness used for the
13322 executable file itself. The checksum is computed on the debugging
13323 information file's full contents by the function given below, passing
13324 zero as the @var{crc} argument.
13327 Any executable file format can carry a debug link, as long as it can
13328 contain a section named @code{.gnu_debuglink} with the contents
13331 @cindex @code{.note.gnu.build-id} sections
13332 @cindex build ID sections
13333 The build ID is a special section in the executable file (and in other
13334 ELF binary files that @value{GDBN} may consider). This section is
13335 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13336 It contains unique identification for the built files---the ID remains
13337 the same across multiple builds of the same build tree. The default
13338 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13339 content for the build ID string. The same section with an identical
13340 value is present in the original built binary with symbols, in its
13341 stripped variant, and in the separate debugging information file.
13343 The debugging information file itself should be an ordinary
13344 executable, containing a full set of linker symbols, sections, and
13345 debugging information. The sections of the debugging information file
13346 should have the same names, addresses, and sizes as the original file,
13347 but they need not contain any data---much like a @code{.bss} section
13348 in an ordinary executable.
13350 The @sc{gnu} binary utilities (Binutils) package includes the
13351 @samp{objcopy} utility that can produce
13352 the separated executable / debugging information file pairs using the
13353 following commands:
13356 @kbd{objcopy --only-keep-debug foo foo.debug}
13361 These commands remove the debugging
13362 information from the executable file @file{foo} and place it in the file
13363 @file{foo.debug}. You can use the first, second or both methods to link the
13368 The debug link method needs the following additional command to also leave
13369 behind a debug link in @file{foo}:
13372 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13375 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13376 a version of the @code{strip} command such that the command @kbd{strip foo -f
13377 foo.debug} has the same functionality as the two @code{objcopy} commands and
13378 the @code{ln -s} command above, together.
13381 Build ID gets embedded into the main executable using @code{ld --build-id} or
13382 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13383 compatibility fixes for debug files separation are present in @sc{gnu} binary
13384 utilities (Binutils) package since version 2.18.
13389 Since there are many different ways to compute CRC's for the debug
13390 link (different polynomials, reversals, byte ordering, etc.), the
13391 simplest way to describe the CRC used in @code{.gnu_debuglink}
13392 sections is to give the complete code for a function that computes it:
13394 @kindex gnu_debuglink_crc32
13397 gnu_debuglink_crc32 (unsigned long crc,
13398 unsigned char *buf, size_t len)
13400 static const unsigned long crc32_table[256] =
13402 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13403 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13404 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13405 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13406 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13407 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13408 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13409 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13410 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13411 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13412 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13413 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13414 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13415 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13416 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13417 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13418 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13419 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13420 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13421 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13422 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13423 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13424 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13425 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13426 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13427 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13428 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13429 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13430 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13431 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13432 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13433 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13434 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13435 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13436 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13437 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13438 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13439 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13440 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13441 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13442 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13443 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13444 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13445 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13446 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13447 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13448 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13449 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13450 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13451 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13452 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13455 unsigned char *end;
13457 crc = ~crc & 0xffffffff;
13458 for (end = buf + len; buf < end; ++buf)
13459 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13460 return ~crc & 0xffffffff;
13465 This computation does not apply to the ``build ID'' method.
13468 @node Symbol Errors
13469 @section Errors Reading Symbol Files
13471 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13472 such as symbol types it does not recognize, or known bugs in compiler
13473 output. By default, @value{GDBN} does not notify you of such problems, since
13474 they are relatively common and primarily of interest to people
13475 debugging compilers. If you are interested in seeing information
13476 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13477 only one message about each such type of problem, no matter how many
13478 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13479 to see how many times the problems occur, with the @code{set
13480 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13483 The messages currently printed, and their meanings, include:
13486 @item inner block not inside outer block in @var{symbol}
13488 The symbol information shows where symbol scopes begin and end
13489 (such as at the start of a function or a block of statements). This
13490 error indicates that an inner scope block is not fully contained
13491 in its outer scope blocks.
13493 @value{GDBN} circumvents the problem by treating the inner block as if it had
13494 the same scope as the outer block. In the error message, @var{symbol}
13495 may be shown as ``@code{(don't know)}'' if the outer block is not a
13498 @item block at @var{address} out of order
13500 The symbol information for symbol scope blocks should occur in
13501 order of increasing addresses. This error indicates that it does not
13504 @value{GDBN} does not circumvent this problem, and has trouble
13505 locating symbols in the source file whose symbols it is reading. (You
13506 can often determine what source file is affected by specifying
13507 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13510 @item bad block start address patched
13512 The symbol information for a symbol scope block has a start address
13513 smaller than the address of the preceding source line. This is known
13514 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13516 @value{GDBN} circumvents the problem by treating the symbol scope block as
13517 starting on the previous source line.
13519 @item bad string table offset in symbol @var{n}
13522 Symbol number @var{n} contains a pointer into the string table which is
13523 larger than the size of the string table.
13525 @value{GDBN} circumvents the problem by considering the symbol to have the
13526 name @code{foo}, which may cause other problems if many symbols end up
13529 @item unknown symbol type @code{0x@var{nn}}
13531 The symbol information contains new data types that @value{GDBN} does
13532 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13533 uncomprehended information, in hexadecimal.
13535 @value{GDBN} circumvents the error by ignoring this symbol information.
13536 This usually allows you to debug your program, though certain symbols
13537 are not accessible. If you encounter such a problem and feel like
13538 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13539 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13540 and examine @code{*bufp} to see the symbol.
13542 @item stub type has NULL name
13544 @value{GDBN} could not find the full definition for a struct or class.
13546 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13547 The symbol information for a C@t{++} member function is missing some
13548 information that recent versions of the compiler should have output for
13551 @item info mismatch between compiler and debugger
13553 @value{GDBN} could not parse a type specification output by the compiler.
13558 @chapter Specifying a Debugging Target
13560 @cindex debugging target
13561 A @dfn{target} is the execution environment occupied by your program.
13563 Often, @value{GDBN} runs in the same host environment as your program;
13564 in that case, the debugging target is specified as a side effect when
13565 you use the @code{file} or @code{core} commands. When you need more
13566 flexibility---for example, running @value{GDBN} on a physically separate
13567 host, or controlling a standalone system over a serial port or a
13568 realtime system over a TCP/IP connection---you can use the @code{target}
13569 command to specify one of the target types configured for @value{GDBN}
13570 (@pxref{Target Commands, ,Commands for Managing Targets}).
13572 @cindex target architecture
13573 It is possible to build @value{GDBN} for several different @dfn{target
13574 architectures}. When @value{GDBN} is built like that, you can choose
13575 one of the available architectures with the @kbd{set architecture}
13579 @kindex set architecture
13580 @kindex show architecture
13581 @item set architecture @var{arch}
13582 This command sets the current target architecture to @var{arch}. The
13583 value of @var{arch} can be @code{"auto"}, in addition to one of the
13584 supported architectures.
13586 @item show architecture
13587 Show the current target architecture.
13589 @item set processor
13591 @kindex set processor
13592 @kindex show processor
13593 These are alias commands for, respectively, @code{set architecture}
13594 and @code{show architecture}.
13598 * Active Targets:: Active targets
13599 * Target Commands:: Commands for managing targets
13600 * Byte Order:: Choosing target byte order
13603 @node Active Targets
13604 @section Active Targets
13606 @cindex stacking targets
13607 @cindex active targets
13608 @cindex multiple targets
13610 There are three classes of targets: processes, core files, and
13611 executable files. @value{GDBN} can work concurrently on up to three
13612 active targets, one in each class. This allows you to (for example)
13613 start a process and inspect its activity without abandoning your work on
13616 For example, if you execute @samp{gdb a.out}, then the executable file
13617 @code{a.out} is the only active target. If you designate a core file as
13618 well---presumably from a prior run that crashed and coredumped---then
13619 @value{GDBN} has two active targets and uses them in tandem, looking
13620 first in the corefile target, then in the executable file, to satisfy
13621 requests for memory addresses. (Typically, these two classes of target
13622 are complementary, since core files contain only a program's
13623 read-write memory---variables and so on---plus machine status, while
13624 executable files contain only the program text and initialized data.)
13626 When you type @code{run}, your executable file becomes an active process
13627 target as well. When a process target is active, all @value{GDBN}
13628 commands requesting memory addresses refer to that target; addresses in
13629 an active core file or executable file target are obscured while the
13630 process target is active.
13632 Use the @code{core-file} and @code{exec-file} commands to select a new
13633 core file or executable target (@pxref{Files, ,Commands to Specify
13634 Files}). To specify as a target a process that is already running, use
13635 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
13638 @node Target Commands
13639 @section Commands for Managing Targets
13642 @item target @var{type} @var{parameters}
13643 Connects the @value{GDBN} host environment to a target machine or
13644 process. A target is typically a protocol for talking to debugging
13645 facilities. You use the argument @var{type} to specify the type or
13646 protocol of the target machine.
13648 Further @var{parameters} are interpreted by the target protocol, but
13649 typically include things like device names or host names to connect
13650 with, process numbers, and baud rates.
13652 The @code{target} command does not repeat if you press @key{RET} again
13653 after executing the command.
13655 @kindex help target
13657 Displays the names of all targets available. To display targets
13658 currently selected, use either @code{info target} or @code{info files}
13659 (@pxref{Files, ,Commands to Specify Files}).
13661 @item help target @var{name}
13662 Describe a particular target, including any parameters necessary to
13665 @kindex set gnutarget
13666 @item set gnutarget @var{args}
13667 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
13668 knows whether it is reading an @dfn{executable},
13669 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
13670 with the @code{set gnutarget} command. Unlike most @code{target} commands,
13671 with @code{gnutarget} the @code{target} refers to a program, not a machine.
13674 @emph{Warning:} To specify a file format with @code{set gnutarget},
13675 you must know the actual BFD name.
13679 @xref{Files, , Commands to Specify Files}.
13681 @kindex show gnutarget
13682 @item show gnutarget
13683 Use the @code{show gnutarget} command to display what file format
13684 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
13685 @value{GDBN} will determine the file format for each file automatically,
13686 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
13689 @cindex common targets
13690 Here are some common targets (available, or not, depending on the GDB
13695 @item target exec @var{program}
13696 @cindex executable file target
13697 An executable file. @samp{target exec @var{program}} is the same as
13698 @samp{exec-file @var{program}}.
13700 @item target core @var{filename}
13701 @cindex core dump file target
13702 A core dump file. @samp{target core @var{filename}} is the same as
13703 @samp{core-file @var{filename}}.
13705 @item target remote @var{medium}
13706 @cindex remote target
13707 A remote system connected to @value{GDBN} via a serial line or network
13708 connection. This command tells @value{GDBN} to use its own remote
13709 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
13711 For example, if you have a board connected to @file{/dev/ttya} on the
13712 machine running @value{GDBN}, you could say:
13715 target remote /dev/ttya
13718 @code{target remote} supports the @code{load} command. This is only
13719 useful if you have some other way of getting the stub to the target
13720 system, and you can put it somewhere in memory where it won't get
13721 clobbered by the download.
13724 @cindex built-in simulator target
13725 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
13733 works; however, you cannot assume that a specific memory map, device
13734 drivers, or even basic I/O is available, although some simulators do
13735 provide these. For info about any processor-specific simulator details,
13736 see the appropriate section in @ref{Embedded Processors, ,Embedded
13741 Some configurations may include these targets as well:
13745 @item target nrom @var{dev}
13746 @cindex NetROM ROM emulator target
13747 NetROM ROM emulator. This target only supports downloading.
13751 Different targets are available on different configurations of @value{GDBN};
13752 your configuration may have more or fewer targets.
13754 Many remote targets require you to download the executable's code once
13755 you've successfully established a connection. You may wish to control
13756 various aspects of this process.
13761 @kindex set hash@r{, for remote monitors}
13762 @cindex hash mark while downloading
13763 This command controls whether a hash mark @samp{#} is displayed while
13764 downloading a file to the remote monitor. If on, a hash mark is
13765 displayed after each S-record is successfully downloaded to the
13769 @kindex show hash@r{, for remote monitors}
13770 Show the current status of displaying the hash mark.
13772 @item set debug monitor
13773 @kindex set debug monitor
13774 @cindex display remote monitor communications
13775 Enable or disable display of communications messages between
13776 @value{GDBN} and the remote monitor.
13778 @item show debug monitor
13779 @kindex show debug monitor
13780 Show the current status of displaying communications between
13781 @value{GDBN} and the remote monitor.
13786 @kindex load @var{filename}
13787 @item load @var{filename}
13789 Depending on what remote debugging facilities are configured into
13790 @value{GDBN}, the @code{load} command may be available. Where it exists, it
13791 is meant to make @var{filename} (an executable) available for debugging
13792 on the remote system---by downloading, or dynamic linking, for example.
13793 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
13794 the @code{add-symbol-file} command.
13796 If your @value{GDBN} does not have a @code{load} command, attempting to
13797 execute it gets the error message ``@code{You can't do that when your
13798 target is @dots{}}''
13800 The file is loaded at whatever address is specified in the executable.
13801 For some object file formats, you can specify the load address when you
13802 link the program; for other formats, like a.out, the object file format
13803 specifies a fixed address.
13804 @c FIXME! This would be a good place for an xref to the GNU linker doc.
13806 Depending on the remote side capabilities, @value{GDBN} may be able to
13807 load programs into flash memory.
13809 @code{load} does not repeat if you press @key{RET} again after using it.
13813 @section Choosing Target Byte Order
13815 @cindex choosing target byte order
13816 @cindex target byte order
13818 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
13819 offer the ability to run either big-endian or little-endian byte
13820 orders. Usually the executable or symbol will include a bit to
13821 designate the endian-ness, and you will not need to worry about
13822 which to use. However, you may still find it useful to adjust
13823 @value{GDBN}'s idea of processor endian-ness manually.
13827 @item set endian big
13828 Instruct @value{GDBN} to assume the target is big-endian.
13830 @item set endian little
13831 Instruct @value{GDBN} to assume the target is little-endian.
13833 @item set endian auto
13834 Instruct @value{GDBN} to use the byte order associated with the
13838 Display @value{GDBN}'s current idea of the target byte order.
13842 Note that these commands merely adjust interpretation of symbolic
13843 data on the host, and that they have absolutely no effect on the
13847 @node Remote Debugging
13848 @chapter Debugging Remote Programs
13849 @cindex remote debugging
13851 If you are trying to debug a program running on a machine that cannot run
13852 @value{GDBN} in the usual way, it is often useful to use remote debugging.
13853 For example, you might use remote debugging on an operating system kernel,
13854 or on a small system which does not have a general purpose operating system
13855 powerful enough to run a full-featured debugger.
13857 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
13858 to make this work with particular debugging targets. In addition,
13859 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
13860 but not specific to any particular target system) which you can use if you
13861 write the remote stubs---the code that runs on the remote system to
13862 communicate with @value{GDBN}.
13864 Other remote targets may be available in your
13865 configuration of @value{GDBN}; use @code{help target} to list them.
13868 * Connecting:: Connecting to a remote target
13869 * File Transfer:: Sending files to a remote system
13870 * Server:: Using the gdbserver program
13871 * Remote Configuration:: Remote configuration
13872 * Remote Stub:: Implementing a remote stub
13876 @section Connecting to a Remote Target
13878 On the @value{GDBN} host machine, you will need an unstripped copy of
13879 your program, since @value{GDBN} needs symbol and debugging information.
13880 Start up @value{GDBN} as usual, using the name of the local copy of your
13881 program as the first argument.
13883 @cindex @code{target remote}
13884 @value{GDBN} can communicate with the target over a serial line, or
13885 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
13886 each case, @value{GDBN} uses the same protocol for debugging your
13887 program; only the medium carrying the debugging packets varies. The
13888 @code{target remote} command establishes a connection to the target.
13889 Its arguments indicate which medium to use:
13893 @item target remote @var{serial-device}
13894 @cindex serial line, @code{target remote}
13895 Use @var{serial-device} to communicate with the target. For example,
13896 to use a serial line connected to the device named @file{/dev/ttyb}:
13899 target remote /dev/ttyb
13902 If you're using a serial line, you may want to give @value{GDBN} the
13903 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
13904 (@pxref{Remote Configuration, set remotebaud}) before the
13905 @code{target} command.
13907 @item target remote @code{@var{host}:@var{port}}
13908 @itemx target remote @code{tcp:@var{host}:@var{port}}
13909 @cindex @acronym{TCP} port, @code{target remote}
13910 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
13911 The @var{host} may be either a host name or a numeric @acronym{IP}
13912 address; @var{port} must be a decimal number. The @var{host} could be
13913 the target machine itself, if it is directly connected to the net, or
13914 it might be a terminal server which in turn has a serial line to the
13917 For example, to connect to port 2828 on a terminal server named
13921 target remote manyfarms:2828
13924 If your remote target is actually running on the same machine as your
13925 debugger session (e.g.@: a simulator for your target running on the
13926 same host), you can omit the hostname. For example, to connect to
13927 port 1234 on your local machine:
13930 target remote :1234
13934 Note that the colon is still required here.
13936 @item target remote @code{udp:@var{host}:@var{port}}
13937 @cindex @acronym{UDP} port, @code{target remote}
13938 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
13939 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
13942 target remote udp:manyfarms:2828
13945 When using a @acronym{UDP} connection for remote debugging, you should
13946 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
13947 can silently drop packets on busy or unreliable networks, which will
13948 cause havoc with your debugging session.
13950 @item target remote | @var{command}
13951 @cindex pipe, @code{target remote} to
13952 Run @var{command} in the background and communicate with it using a
13953 pipe. The @var{command} is a shell command, to be parsed and expanded
13954 by the system's command shell, @code{/bin/sh}; it should expect remote
13955 protocol packets on its standard input, and send replies on its
13956 standard output. You could use this to run a stand-alone simulator
13957 that speaks the remote debugging protocol, to make net connections
13958 using programs like @code{ssh}, or for other similar tricks.
13960 If @var{command} closes its standard output (perhaps by exiting),
13961 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
13962 program has already exited, this will have no effect.)
13966 Once the connection has been established, you can use all the usual
13967 commands to examine and change data. The remote program is already
13968 running; you can use @kbd{step} and @kbd{continue}, and you do not
13969 need to use @kbd{run}.
13971 @cindex interrupting remote programs
13972 @cindex remote programs, interrupting
13973 Whenever @value{GDBN} is waiting for the remote program, if you type the
13974 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
13975 program. This may or may not succeed, depending in part on the hardware
13976 and the serial drivers the remote system uses. If you type the
13977 interrupt character once again, @value{GDBN} displays this prompt:
13980 Interrupted while waiting for the program.
13981 Give up (and stop debugging it)? (y or n)
13984 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
13985 (If you decide you want to try again later, you can use @samp{target
13986 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
13987 goes back to waiting.
13990 @kindex detach (remote)
13992 When you have finished debugging the remote program, you can use the
13993 @code{detach} command to release it from @value{GDBN} control.
13994 Detaching from the target normally resumes its execution, but the results
13995 will depend on your particular remote stub. After the @code{detach}
13996 command, @value{GDBN} is free to connect to another target.
14000 The @code{disconnect} command behaves like @code{detach}, except that
14001 the target is generally not resumed. It will wait for @value{GDBN}
14002 (this instance or another one) to connect and continue debugging. After
14003 the @code{disconnect} command, @value{GDBN} is again free to connect to
14006 @cindex send command to remote monitor
14007 @cindex extend @value{GDBN} for remote targets
14008 @cindex add new commands for external monitor
14010 @item monitor @var{cmd}
14011 This command allows you to send arbitrary commands directly to the
14012 remote monitor. Since @value{GDBN} doesn't care about the commands it
14013 sends like this, this command is the way to extend @value{GDBN}---you
14014 can add new commands that only the external monitor will understand
14018 @node File Transfer
14019 @section Sending files to a remote system
14020 @cindex remote target, file transfer
14021 @cindex file transfer
14022 @cindex sending files to remote systems
14024 Some remote targets offer the ability to transfer files over the same
14025 connection used to communicate with @value{GDBN}. This is convenient
14026 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14027 running @code{gdbserver} over a network interface. For other targets,
14028 e.g.@: embedded devices with only a single serial port, this may be
14029 the only way to upload or download files.
14031 Not all remote targets support these commands.
14035 @item remote put @var{hostfile} @var{targetfile}
14036 Copy file @var{hostfile} from the host system (the machine running
14037 @value{GDBN}) to @var{targetfile} on the target system.
14040 @item remote get @var{targetfile} @var{hostfile}
14041 Copy file @var{targetfile} from the target system to @var{hostfile}
14042 on the host system.
14044 @kindex remote delete
14045 @item remote delete @var{targetfile}
14046 Delete @var{targetfile} from the target system.
14051 @section Using the @code{gdbserver} Program
14054 @cindex remote connection without stubs
14055 @code{gdbserver} is a control program for Unix-like systems, which
14056 allows you to connect your program with a remote @value{GDBN} via
14057 @code{target remote}---but without linking in the usual debugging stub.
14059 @code{gdbserver} is not a complete replacement for the debugging stubs,
14060 because it requires essentially the same operating-system facilities
14061 that @value{GDBN} itself does. In fact, a system that can run
14062 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14063 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14064 because it is a much smaller program than @value{GDBN} itself. It is
14065 also easier to port than all of @value{GDBN}, so you may be able to get
14066 started more quickly on a new system by using @code{gdbserver}.
14067 Finally, if you develop code for real-time systems, you may find that
14068 the tradeoffs involved in real-time operation make it more convenient to
14069 do as much development work as possible on another system, for example
14070 by cross-compiling. You can use @code{gdbserver} to make a similar
14071 choice for debugging.
14073 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14074 or a TCP connection, using the standard @value{GDBN} remote serial
14078 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14079 Do not run @code{gdbserver} connected to any public network; a
14080 @value{GDBN} connection to @code{gdbserver} provides access to the
14081 target system with the same privileges as the user running
14085 @subsection Running @code{gdbserver}
14086 @cindex arguments, to @code{gdbserver}
14088 Run @code{gdbserver} on the target system. You need a copy of the
14089 program you want to debug, including any libraries it requires.
14090 @code{gdbserver} does not need your program's symbol table, so you can
14091 strip the program if necessary to save space. @value{GDBN} on the host
14092 system does all the symbol handling.
14094 To use the server, you must tell it how to communicate with @value{GDBN};
14095 the name of your program; and the arguments for your program. The usual
14099 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14102 @var{comm} is either a device name (to use a serial line) or a TCP
14103 hostname and portnumber. For example, to debug Emacs with the argument
14104 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14108 target> gdbserver /dev/com1 emacs foo.txt
14111 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14114 To use a TCP connection instead of a serial line:
14117 target> gdbserver host:2345 emacs foo.txt
14120 The only difference from the previous example is the first argument,
14121 specifying that you are communicating with the host @value{GDBN} via
14122 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14123 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14124 (Currently, the @samp{host} part is ignored.) You can choose any number
14125 you want for the port number as long as it does not conflict with any
14126 TCP ports already in use on the target system (for example, @code{23} is
14127 reserved for @code{telnet}).@footnote{If you choose a port number that
14128 conflicts with another service, @code{gdbserver} prints an error message
14129 and exits.} You must use the same port number with the host @value{GDBN}
14130 @code{target remote} command.
14132 @subsubsection Attaching to a Running Program
14134 On some targets, @code{gdbserver} can also attach to running programs.
14135 This is accomplished via the @code{--attach} argument. The syntax is:
14138 target> gdbserver --attach @var{comm} @var{pid}
14141 @var{pid} is the process ID of a currently running process. It isn't necessary
14142 to point @code{gdbserver} at a binary for the running process.
14145 @cindex attach to a program by name
14146 You can debug processes by name instead of process ID if your target has the
14147 @code{pidof} utility:
14150 target> gdbserver --attach @var{comm} `pidof @var{program}`
14153 In case more than one copy of @var{program} is running, or @var{program}
14154 has multiple threads, most versions of @code{pidof} support the
14155 @code{-s} option to only return the first process ID.
14157 @subsubsection Multi-Process Mode for @code{gdbserver}
14158 @cindex gdbserver, multiple processes
14159 @cindex multiple processes with gdbserver
14161 When you connect to @code{gdbserver} using @code{target remote},
14162 @code{gdbserver} debugs the specified program only once. When the
14163 program exits, or you detach from it, @value{GDBN} closes the connection
14164 and @code{gdbserver} exits.
14166 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14167 enters multi-process mode. When the debugged program exits, or you
14168 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14169 though no program is running. The @code{run} and @code{attach}
14170 commands instruct @code{gdbserver} to run or attach to a new program.
14171 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14172 remote exec-file}) to select the program to run. Command line
14173 arguments are supported, except for wildcard expansion and I/O
14174 redirection (@pxref{Arguments}).
14176 To start @code{gdbserver} without supplying an initial command to run
14177 or process ID to attach, use the @option{--multi} command line option.
14178 Then you can connect using @kbd{target extended-remote} and start
14179 the program you want to debug.
14181 @code{gdbserver} does not automatically exit in multi-process mode.
14182 You can terminate it by using @code{monitor exit}
14183 (@pxref{Monitor Commands for gdbserver}).
14185 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14187 The @option{--debug} option tells @code{gdbserver} to display extra
14188 status information about the debugging process. The
14189 @option{--remote-debug} option tells @code{gdbserver} to display
14190 remote protocol debug output. These options are intended for
14191 @code{gdbserver} development and for bug reports to the developers.
14193 The @option{--wrapper} option specifies a wrapper to launch programs
14194 for debugging. The option should be followed by the name of the
14195 wrapper, then any command-line arguments to pass to the wrapper, then
14196 @kbd{--} indicating the end of the wrapper arguments.
14198 @code{gdbserver} runs the specified wrapper program with a combined
14199 command line including the wrapper arguments, then the name of the
14200 program to debug, then any arguments to the program. The wrapper
14201 runs until it executes your program, and then @value{GDBN} gains control.
14203 You can use any program that eventually calls @code{execve} with
14204 its arguments as a wrapper. Several standard Unix utilities do
14205 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14206 with @code{exec "$@@"} will also work.
14208 For example, you can use @code{env} to pass an environment variable to
14209 the debugged program, without setting the variable in @code{gdbserver}'s
14213 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14216 @subsection Connecting to @code{gdbserver}
14218 Run @value{GDBN} on the host system.
14220 First make sure you have the necessary symbol files. Load symbols for
14221 your application using the @code{file} command before you connect. Use
14222 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14223 was compiled with the correct sysroot using @code{--with-sysroot}).
14225 The symbol file and target libraries must exactly match the executable
14226 and libraries on the target, with one exception: the files on the host
14227 system should not be stripped, even if the files on the target system
14228 are. Mismatched or missing files will lead to confusing results
14229 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14230 files may also prevent @code{gdbserver} from debugging multi-threaded
14233 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14234 For TCP connections, you must start up @code{gdbserver} prior to using
14235 the @code{target remote} command. Otherwise you may get an error whose
14236 text depends on the host system, but which usually looks something like
14237 @samp{Connection refused}. Don't use the @code{load}
14238 command in @value{GDBN} when using @code{gdbserver}, since the program is
14239 already on the target.
14241 @subsection Monitor Commands for @code{gdbserver}
14242 @cindex monitor commands, for @code{gdbserver}
14243 @anchor{Monitor Commands for gdbserver}
14245 During a @value{GDBN} session using @code{gdbserver}, you can use the
14246 @code{monitor} command to send special requests to @code{gdbserver}.
14247 Here are the available commands.
14251 List the available monitor commands.
14253 @item monitor set debug 0
14254 @itemx monitor set debug 1
14255 Disable or enable general debugging messages.
14257 @item monitor set remote-debug 0
14258 @itemx monitor set remote-debug 1
14259 Disable or enable specific debugging messages associated with the remote
14260 protocol (@pxref{Remote Protocol}).
14263 Tell gdbserver to exit immediately. This command should be followed by
14264 @code{disconnect} to close the debugging session. @code{gdbserver} will
14265 detach from any attached processes and kill any processes it created.
14266 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14267 of a multi-process mode debug session.
14271 @node Remote Configuration
14272 @section Remote Configuration
14275 @kindex show remote
14276 This section documents the configuration options available when
14277 debugging remote programs. For the options related to the File I/O
14278 extensions of the remote protocol, see @ref{system,
14279 system-call-allowed}.
14282 @item set remoteaddresssize @var{bits}
14283 @cindex address size for remote targets
14284 @cindex bits in remote address
14285 Set the maximum size of address in a memory packet to the specified
14286 number of bits. @value{GDBN} will mask off the address bits above
14287 that number, when it passes addresses to the remote target. The
14288 default value is the number of bits in the target's address.
14290 @item show remoteaddresssize
14291 Show the current value of remote address size in bits.
14293 @item set remotebaud @var{n}
14294 @cindex baud rate for remote targets
14295 Set the baud rate for the remote serial I/O to @var{n} baud. The
14296 value is used to set the speed of the serial port used for debugging
14299 @item show remotebaud
14300 Show the current speed of the remote connection.
14302 @item set remotebreak
14303 @cindex interrupt remote programs
14304 @cindex BREAK signal instead of Ctrl-C
14305 @anchor{set remotebreak}
14306 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14307 when you type @kbd{Ctrl-c} to interrupt the program running
14308 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14309 character instead. The default is off, since most remote systems
14310 expect to see @samp{Ctrl-C} as the interrupt signal.
14312 @item show remotebreak
14313 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14314 interrupt the remote program.
14316 @item set remoteflow on
14317 @itemx set remoteflow off
14318 @kindex set remoteflow
14319 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14320 on the serial port used to communicate to the remote target.
14322 @item show remoteflow
14323 @kindex show remoteflow
14324 Show the current setting of hardware flow control.
14326 @item set remotelogbase @var{base}
14327 Set the base (a.k.a.@: radix) of logging serial protocol
14328 communications to @var{base}. Supported values of @var{base} are:
14329 @code{ascii}, @code{octal}, and @code{hex}. The default is
14332 @item show remotelogbase
14333 Show the current setting of the radix for logging remote serial
14336 @item set remotelogfile @var{file}
14337 @cindex record serial communications on file
14338 Record remote serial communications on the named @var{file}. The
14339 default is not to record at all.
14341 @item show remotelogfile.
14342 Show the current setting of the file name on which to record the
14343 serial communications.
14345 @item set remotetimeout @var{num}
14346 @cindex timeout for serial communications
14347 @cindex remote timeout
14348 Set the timeout limit to wait for the remote target to respond to
14349 @var{num} seconds. The default is 2 seconds.
14351 @item show remotetimeout
14352 Show the current number of seconds to wait for the remote target
14355 @cindex limit hardware breakpoints and watchpoints
14356 @cindex remote target, limit break- and watchpoints
14357 @anchor{set remote hardware-watchpoint-limit}
14358 @anchor{set remote hardware-breakpoint-limit}
14359 @item set remote hardware-watchpoint-limit @var{limit}
14360 @itemx set remote hardware-breakpoint-limit @var{limit}
14361 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14362 watchpoints. A limit of -1, the default, is treated as unlimited.
14364 @item set remote exec-file @var{filename}
14365 @itemx show remote exec-file
14366 @anchor{set remote exec-file}
14367 @cindex executable file, for remote target
14368 Select the file used for @code{run} with @code{target
14369 extended-remote}. This should be set to a filename valid on the
14370 target system. If it is not set, the target will use a default
14371 filename (e.g.@: the last program run).
14375 @item set tcp auto-retry on
14376 @cindex auto-retry, for remote TCP target
14377 Enable auto-retry for remote TCP connections. This is useful if the remote
14378 debugging agent is launched in parallel with @value{GDBN}; there is a race
14379 condition because the agent may not become ready to accept the connection
14380 before @value{GDBN} attempts to connect. When auto-retry is
14381 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14382 to establish the connection using the timeout specified by
14383 @code{set tcp connect-timeout}.
14385 @item set tcp auto-retry off
14386 Do not auto-retry failed TCP connections.
14388 @item show tcp auto-retry
14389 Show the current auto-retry setting.
14391 @item set tcp connect-timeout @var{seconds}
14392 @cindex connection timeout, for remote TCP target
14393 @cindex timeout, for remote target connection
14394 Set the timeout for establishing a TCP connection to the remote target to
14395 @var{seconds}. The timeout affects both polling to retry failed connections
14396 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14397 that are merely slow to complete, and represents an approximate cumulative
14400 @item show tcp connect-timeout
14401 Show the current connection timeout setting.
14404 @cindex remote packets, enabling and disabling
14405 The @value{GDBN} remote protocol autodetects the packets supported by
14406 your debugging stub. If you need to override the autodetection, you
14407 can use these commands to enable or disable individual packets. Each
14408 packet can be set to @samp{on} (the remote target supports this
14409 packet), @samp{off} (the remote target does not support this packet),
14410 or @samp{auto} (detect remote target support for this packet). They
14411 all default to @samp{auto}. For more information about each packet,
14412 see @ref{Remote Protocol}.
14414 During normal use, you should not have to use any of these commands.
14415 If you do, that may be a bug in your remote debugging stub, or a bug
14416 in @value{GDBN}. You may want to report the problem to the
14417 @value{GDBN} developers.
14419 For each packet @var{name}, the command to enable or disable the
14420 packet is @code{set remote @var{name}-packet}. The available settings
14423 @multitable @columnfractions 0.28 0.32 0.25
14426 @tab Related Features
14428 @item @code{fetch-register}
14430 @tab @code{info registers}
14432 @item @code{set-register}
14436 @item @code{binary-download}
14438 @tab @code{load}, @code{set}
14440 @item @code{read-aux-vector}
14441 @tab @code{qXfer:auxv:read}
14442 @tab @code{info auxv}
14444 @item @code{symbol-lookup}
14445 @tab @code{qSymbol}
14446 @tab Detecting multiple threads
14448 @item @code{attach}
14449 @tab @code{vAttach}
14452 @item @code{verbose-resume}
14454 @tab Stepping or resuming multiple threads
14460 @item @code{software-breakpoint}
14464 @item @code{hardware-breakpoint}
14468 @item @code{write-watchpoint}
14472 @item @code{read-watchpoint}
14476 @item @code{access-watchpoint}
14480 @item @code{target-features}
14481 @tab @code{qXfer:features:read}
14482 @tab @code{set architecture}
14484 @item @code{library-info}
14485 @tab @code{qXfer:libraries:read}
14486 @tab @code{info sharedlibrary}
14488 @item @code{memory-map}
14489 @tab @code{qXfer:memory-map:read}
14490 @tab @code{info mem}
14492 @item @code{read-spu-object}
14493 @tab @code{qXfer:spu:read}
14494 @tab @code{info spu}
14496 @item @code{write-spu-object}
14497 @tab @code{qXfer:spu:write}
14498 @tab @code{info spu}
14500 @item @code{read-siginfo-object}
14501 @tab @code{qXfer:siginfo:read}
14502 @tab @code{print $_siginfo}
14504 @item @code{write-siginfo-object}
14505 @tab @code{qXfer:siginfo:write}
14506 @tab @code{set $_siginfo}
14508 @item @code{get-thread-local-@*storage-address}
14509 @tab @code{qGetTLSAddr}
14510 @tab Displaying @code{__thread} variables
14512 @item @code{search-memory}
14513 @tab @code{qSearch:memory}
14516 @item @code{supported-packets}
14517 @tab @code{qSupported}
14518 @tab Remote communications parameters
14520 @item @code{pass-signals}
14521 @tab @code{QPassSignals}
14522 @tab @code{handle @var{signal}}
14524 @item @code{hostio-close-packet}
14525 @tab @code{vFile:close}
14526 @tab @code{remote get}, @code{remote put}
14528 @item @code{hostio-open-packet}
14529 @tab @code{vFile:open}
14530 @tab @code{remote get}, @code{remote put}
14532 @item @code{hostio-pread-packet}
14533 @tab @code{vFile:pread}
14534 @tab @code{remote get}, @code{remote put}
14536 @item @code{hostio-pwrite-packet}
14537 @tab @code{vFile:pwrite}
14538 @tab @code{remote get}, @code{remote put}
14540 @item @code{hostio-unlink-packet}
14541 @tab @code{vFile:unlink}
14542 @tab @code{remote delete}
14544 @item @code{noack-packet}
14545 @tab @code{QStartNoAckMode}
14546 @tab Packet acknowledgment
14548 @item @code{osdata}
14549 @tab @code{qXfer:osdata:read}
14550 @tab @code{info os}
14552 @item @code{query-attached}
14553 @tab @code{qAttached}
14554 @tab Querying remote process attach state.
14558 @section Implementing a Remote Stub
14560 @cindex debugging stub, example
14561 @cindex remote stub, example
14562 @cindex stub example, remote debugging
14563 The stub files provided with @value{GDBN} implement the target side of the
14564 communication protocol, and the @value{GDBN} side is implemented in the
14565 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
14566 these subroutines to communicate, and ignore the details. (If you're
14567 implementing your own stub file, you can still ignore the details: start
14568 with one of the existing stub files. @file{sparc-stub.c} is the best
14569 organized, and therefore the easiest to read.)
14571 @cindex remote serial debugging, overview
14572 To debug a program running on another machine (the debugging
14573 @dfn{target} machine), you must first arrange for all the usual
14574 prerequisites for the program to run by itself. For example, for a C
14579 A startup routine to set up the C runtime environment; these usually
14580 have a name like @file{crt0}. The startup routine may be supplied by
14581 your hardware supplier, or you may have to write your own.
14584 A C subroutine library to support your program's
14585 subroutine calls, notably managing input and output.
14588 A way of getting your program to the other machine---for example, a
14589 download program. These are often supplied by the hardware
14590 manufacturer, but you may have to write your own from hardware
14594 The next step is to arrange for your program to use a serial port to
14595 communicate with the machine where @value{GDBN} is running (the @dfn{host}
14596 machine). In general terms, the scheme looks like this:
14600 @value{GDBN} already understands how to use this protocol; when everything
14601 else is set up, you can simply use the @samp{target remote} command
14602 (@pxref{Targets,,Specifying a Debugging Target}).
14604 @item On the target,
14605 you must link with your program a few special-purpose subroutines that
14606 implement the @value{GDBN} remote serial protocol. The file containing these
14607 subroutines is called a @dfn{debugging stub}.
14609 On certain remote targets, you can use an auxiliary program
14610 @code{gdbserver} instead of linking a stub into your program.
14611 @xref{Server,,Using the @code{gdbserver} Program}, for details.
14614 The debugging stub is specific to the architecture of the remote
14615 machine; for example, use @file{sparc-stub.c} to debug programs on
14618 @cindex remote serial stub list
14619 These working remote stubs are distributed with @value{GDBN}:
14624 @cindex @file{i386-stub.c}
14627 For Intel 386 and compatible architectures.
14630 @cindex @file{m68k-stub.c}
14631 @cindex Motorola 680x0
14633 For Motorola 680x0 architectures.
14636 @cindex @file{sh-stub.c}
14639 For Renesas SH architectures.
14642 @cindex @file{sparc-stub.c}
14644 For @sc{sparc} architectures.
14646 @item sparcl-stub.c
14647 @cindex @file{sparcl-stub.c}
14650 For Fujitsu @sc{sparclite} architectures.
14654 The @file{README} file in the @value{GDBN} distribution may list other
14655 recently added stubs.
14658 * Stub Contents:: What the stub can do for you
14659 * Bootstrapping:: What you must do for the stub
14660 * Debug Session:: Putting it all together
14663 @node Stub Contents
14664 @subsection What the Stub Can Do for You
14666 @cindex remote serial stub
14667 The debugging stub for your architecture supplies these three
14671 @item set_debug_traps
14672 @findex set_debug_traps
14673 @cindex remote serial stub, initialization
14674 This routine arranges for @code{handle_exception} to run when your
14675 program stops. You must call this subroutine explicitly near the
14676 beginning of your program.
14678 @item handle_exception
14679 @findex handle_exception
14680 @cindex remote serial stub, main routine
14681 This is the central workhorse, but your program never calls it
14682 explicitly---the setup code arranges for @code{handle_exception} to
14683 run when a trap is triggered.
14685 @code{handle_exception} takes control when your program stops during
14686 execution (for example, on a breakpoint), and mediates communications
14687 with @value{GDBN} on the host machine. This is where the communications
14688 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
14689 representative on the target machine. It begins by sending summary
14690 information on the state of your program, then continues to execute,
14691 retrieving and transmitting any information @value{GDBN} needs, until you
14692 execute a @value{GDBN} command that makes your program resume; at that point,
14693 @code{handle_exception} returns control to your own code on the target
14697 @cindex @code{breakpoint} subroutine, remote
14698 Use this auxiliary subroutine to make your program contain a
14699 breakpoint. Depending on the particular situation, this may be the only
14700 way for @value{GDBN} to get control. For instance, if your target
14701 machine has some sort of interrupt button, you won't need to call this;
14702 pressing the interrupt button transfers control to
14703 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
14704 simply receiving characters on the serial port may also trigger a trap;
14705 again, in that situation, you don't need to call @code{breakpoint} from
14706 your own program---simply running @samp{target remote} from the host
14707 @value{GDBN} session gets control.
14709 Call @code{breakpoint} if none of these is true, or if you simply want
14710 to make certain your program stops at a predetermined point for the
14711 start of your debugging session.
14714 @node Bootstrapping
14715 @subsection What You Must Do for the Stub
14717 @cindex remote stub, support routines
14718 The debugging stubs that come with @value{GDBN} are set up for a particular
14719 chip architecture, but they have no information about the rest of your
14720 debugging target machine.
14722 First of all you need to tell the stub how to communicate with the
14726 @item int getDebugChar()
14727 @findex getDebugChar
14728 Write this subroutine to read a single character from the serial port.
14729 It may be identical to @code{getchar} for your target system; a
14730 different name is used to allow you to distinguish the two if you wish.
14732 @item void putDebugChar(int)
14733 @findex putDebugChar
14734 Write this subroutine to write a single character to the serial port.
14735 It may be identical to @code{putchar} for your target system; a
14736 different name is used to allow you to distinguish the two if you wish.
14739 @cindex control C, and remote debugging
14740 @cindex interrupting remote targets
14741 If you want @value{GDBN} to be able to stop your program while it is
14742 running, you need to use an interrupt-driven serial driver, and arrange
14743 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
14744 character). That is the character which @value{GDBN} uses to tell the
14745 remote system to stop.
14747 Getting the debugging target to return the proper status to @value{GDBN}
14748 probably requires changes to the standard stub; one quick and dirty way
14749 is to just execute a breakpoint instruction (the ``dirty'' part is that
14750 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
14752 Other routines you need to supply are:
14755 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
14756 @findex exceptionHandler
14757 Write this function to install @var{exception_address} in the exception
14758 handling tables. You need to do this because the stub does not have any
14759 way of knowing what the exception handling tables on your target system
14760 are like (for example, the processor's table might be in @sc{rom},
14761 containing entries which point to a table in @sc{ram}).
14762 @var{exception_number} is the exception number which should be changed;
14763 its meaning is architecture-dependent (for example, different numbers
14764 might represent divide by zero, misaligned access, etc). When this
14765 exception occurs, control should be transferred directly to
14766 @var{exception_address}, and the processor state (stack, registers,
14767 and so on) should be just as it is when a processor exception occurs. So if
14768 you want to use a jump instruction to reach @var{exception_address}, it
14769 should be a simple jump, not a jump to subroutine.
14771 For the 386, @var{exception_address} should be installed as an interrupt
14772 gate so that interrupts are masked while the handler runs. The gate
14773 should be at privilege level 0 (the most privileged level). The
14774 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
14775 help from @code{exceptionHandler}.
14777 @item void flush_i_cache()
14778 @findex flush_i_cache
14779 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
14780 instruction cache, if any, on your target machine. If there is no
14781 instruction cache, this subroutine may be a no-op.
14783 On target machines that have instruction caches, @value{GDBN} requires this
14784 function to make certain that the state of your program is stable.
14788 You must also make sure this library routine is available:
14791 @item void *memset(void *, int, int)
14793 This is the standard library function @code{memset} that sets an area of
14794 memory to a known value. If you have one of the free versions of
14795 @code{libc.a}, @code{memset} can be found there; otherwise, you must
14796 either obtain it from your hardware manufacturer, or write your own.
14799 If you do not use the GNU C compiler, you may need other standard
14800 library subroutines as well; this varies from one stub to another,
14801 but in general the stubs are likely to use any of the common library
14802 subroutines which @code{@value{NGCC}} generates as inline code.
14805 @node Debug Session
14806 @subsection Putting it All Together
14808 @cindex remote serial debugging summary
14809 In summary, when your program is ready to debug, you must follow these
14814 Make sure you have defined the supporting low-level routines
14815 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
14817 @code{getDebugChar}, @code{putDebugChar},
14818 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
14822 Insert these lines near the top of your program:
14830 For the 680x0 stub only, you need to provide a variable called
14831 @code{exceptionHook}. Normally you just use:
14834 void (*exceptionHook)() = 0;
14838 but if before calling @code{set_debug_traps}, you set it to point to a
14839 function in your program, that function is called when
14840 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
14841 error). The function indicated by @code{exceptionHook} is called with
14842 one parameter: an @code{int} which is the exception number.
14845 Compile and link together: your program, the @value{GDBN} debugging stub for
14846 your target architecture, and the supporting subroutines.
14849 Make sure you have a serial connection between your target machine and
14850 the @value{GDBN} host, and identify the serial port on the host.
14853 @c The "remote" target now provides a `load' command, so we should
14854 @c document that. FIXME.
14855 Download your program to your target machine (or get it there by
14856 whatever means the manufacturer provides), and start it.
14859 Start @value{GDBN} on the host, and connect to the target
14860 (@pxref{Connecting,,Connecting to a Remote Target}).
14864 @node Configurations
14865 @chapter Configuration-Specific Information
14867 While nearly all @value{GDBN} commands are available for all native and
14868 cross versions of the debugger, there are some exceptions. This chapter
14869 describes things that are only available in certain configurations.
14871 There are three major categories of configurations: native
14872 configurations, where the host and target are the same, embedded
14873 operating system configurations, which are usually the same for several
14874 different processor architectures, and bare embedded processors, which
14875 are quite different from each other.
14880 * Embedded Processors::
14887 This section describes details specific to particular native
14892 * BSD libkvm Interface:: Debugging BSD kernel memory images
14893 * SVR4 Process Information:: SVR4 process information
14894 * DJGPP Native:: Features specific to the DJGPP port
14895 * Cygwin Native:: Features specific to the Cygwin port
14896 * Hurd Native:: Features specific to @sc{gnu} Hurd
14897 * Neutrino:: Features specific to QNX Neutrino
14898 * Darwin:: Features specific to Darwin
14904 On HP-UX systems, if you refer to a function or variable name that
14905 begins with a dollar sign, @value{GDBN} searches for a user or system
14906 name first, before it searches for a convenience variable.
14909 @node BSD libkvm Interface
14910 @subsection BSD libkvm Interface
14913 @cindex kernel memory image
14914 @cindex kernel crash dump
14916 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
14917 interface that provides a uniform interface for accessing kernel virtual
14918 memory images, including live systems and crash dumps. @value{GDBN}
14919 uses this interface to allow you to debug live kernels and kernel crash
14920 dumps on many native BSD configurations. This is implemented as a
14921 special @code{kvm} debugging target. For debugging a live system, load
14922 the currently running kernel into @value{GDBN} and connect to the
14926 (@value{GDBP}) @b{target kvm}
14929 For debugging crash dumps, provide the file name of the crash dump as an
14933 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
14936 Once connected to the @code{kvm} target, the following commands are
14942 Set current context from the @dfn{Process Control Block} (PCB) address.
14945 Set current context from proc address. This command isn't available on
14946 modern FreeBSD systems.
14949 @node SVR4 Process Information
14950 @subsection SVR4 Process Information
14952 @cindex examine process image
14953 @cindex process info via @file{/proc}
14955 Many versions of SVR4 and compatible systems provide a facility called
14956 @samp{/proc} that can be used to examine the image of a running
14957 process using file-system subroutines. If @value{GDBN} is configured
14958 for an operating system with this facility, the command @code{info
14959 proc} is available to report information about the process running
14960 your program, or about any process running on your system. @code{info
14961 proc} works only on SVR4 systems that include the @code{procfs} code.
14962 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
14963 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
14969 @itemx info proc @var{process-id}
14970 Summarize available information about any running process. If a
14971 process ID is specified by @var{process-id}, display information about
14972 that process; otherwise display information about the program being
14973 debugged. The summary includes the debugged process ID, the command
14974 line used to invoke it, its current working directory, and its
14975 executable file's absolute file name.
14977 On some systems, @var{process-id} can be of the form
14978 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
14979 within a process. If the optional @var{pid} part is missing, it means
14980 a thread from the process being debugged (the leading @samp{/} still
14981 needs to be present, or else @value{GDBN} will interpret the number as
14982 a process ID rather than a thread ID).
14984 @item info proc mappings
14985 @cindex memory address space mappings
14986 Report the memory address space ranges accessible in the program, with
14987 information on whether the process has read, write, or execute access
14988 rights to each range. On @sc{gnu}/Linux systems, each memory range
14989 includes the object file which is mapped to that range, instead of the
14990 memory access rights to that range.
14992 @item info proc stat
14993 @itemx info proc status
14994 @cindex process detailed status information
14995 These subcommands are specific to @sc{gnu}/Linux systems. They show
14996 the process-related information, including the user ID and group ID;
14997 how many threads are there in the process; its virtual memory usage;
14998 the signals that are pending, blocked, and ignored; its TTY; its
14999 consumption of system and user time; its stack size; its @samp{nice}
15000 value; etc. For more information, see the @samp{proc} man page
15001 (type @kbd{man 5 proc} from your shell prompt).
15003 @item info proc all
15004 Show all the information about the process described under all of the
15005 above @code{info proc} subcommands.
15008 @comment These sub-options of 'info proc' were not included when
15009 @comment procfs.c was re-written. Keep their descriptions around
15010 @comment against the day when someone finds the time to put them back in.
15011 @kindex info proc times
15012 @item info proc times
15013 Starting time, user CPU time, and system CPU time for your program and
15016 @kindex info proc id
15018 Report on the process IDs related to your program: its own process ID,
15019 the ID of its parent, the process group ID, and the session ID.
15022 @item set procfs-trace
15023 @kindex set procfs-trace
15024 @cindex @code{procfs} API calls
15025 This command enables and disables tracing of @code{procfs} API calls.
15027 @item show procfs-trace
15028 @kindex show procfs-trace
15029 Show the current state of @code{procfs} API call tracing.
15031 @item set procfs-file @var{file}
15032 @kindex set procfs-file
15033 Tell @value{GDBN} to write @code{procfs} API trace to the named
15034 @var{file}. @value{GDBN} appends the trace info to the previous
15035 contents of the file. The default is to display the trace on the
15038 @item show procfs-file
15039 @kindex show procfs-file
15040 Show the file to which @code{procfs} API trace is written.
15042 @item proc-trace-entry
15043 @itemx proc-trace-exit
15044 @itemx proc-untrace-entry
15045 @itemx proc-untrace-exit
15046 @kindex proc-trace-entry
15047 @kindex proc-trace-exit
15048 @kindex proc-untrace-entry
15049 @kindex proc-untrace-exit
15050 These commands enable and disable tracing of entries into and exits
15051 from the @code{syscall} interface.
15054 @kindex info pidlist
15055 @cindex process list, QNX Neutrino
15056 For QNX Neutrino only, this command displays the list of all the
15057 processes and all the threads within each process.
15060 @kindex info meminfo
15061 @cindex mapinfo list, QNX Neutrino
15062 For QNX Neutrino only, this command displays the list of all mapinfos.
15066 @subsection Features for Debugging @sc{djgpp} Programs
15067 @cindex @sc{djgpp} debugging
15068 @cindex native @sc{djgpp} debugging
15069 @cindex MS-DOS-specific commands
15072 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15073 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15074 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15075 top of real-mode DOS systems and their emulations.
15077 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15078 defines a few commands specific to the @sc{djgpp} port. This
15079 subsection describes those commands.
15084 This is a prefix of @sc{djgpp}-specific commands which print
15085 information about the target system and important OS structures.
15088 @cindex MS-DOS system info
15089 @cindex free memory information (MS-DOS)
15090 @item info dos sysinfo
15091 This command displays assorted information about the underlying
15092 platform: the CPU type and features, the OS version and flavor, the
15093 DPMI version, and the available conventional and DPMI memory.
15098 @cindex segment descriptor tables
15099 @cindex descriptor tables display
15101 @itemx info dos ldt
15102 @itemx info dos idt
15103 These 3 commands display entries from, respectively, Global, Local,
15104 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15105 tables are data structures which store a descriptor for each segment
15106 that is currently in use. The segment's selector is an index into a
15107 descriptor table; the table entry for that index holds the
15108 descriptor's base address and limit, and its attributes and access
15111 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15112 segment (used for both data and the stack), and a DOS segment (which
15113 allows access to DOS/BIOS data structures and absolute addresses in
15114 conventional memory). However, the DPMI host will usually define
15115 additional segments in order to support the DPMI environment.
15117 @cindex garbled pointers
15118 These commands allow to display entries from the descriptor tables.
15119 Without an argument, all entries from the specified table are
15120 displayed. An argument, which should be an integer expression, means
15121 display a single entry whose index is given by the argument. For
15122 example, here's a convenient way to display information about the
15123 debugged program's data segment:
15126 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15127 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15131 This comes in handy when you want to see whether a pointer is outside
15132 the data segment's limit (i.e.@: @dfn{garbled}).
15134 @cindex page tables display (MS-DOS)
15136 @itemx info dos pte
15137 These two commands display entries from, respectively, the Page
15138 Directory and the Page Tables. Page Directories and Page Tables are
15139 data structures which control how virtual memory addresses are mapped
15140 into physical addresses. A Page Table includes an entry for every
15141 page of memory that is mapped into the program's address space; there
15142 may be several Page Tables, each one holding up to 4096 entries. A
15143 Page Directory has up to 4096 entries, one each for every Page Table
15144 that is currently in use.
15146 Without an argument, @kbd{info dos pde} displays the entire Page
15147 Directory, and @kbd{info dos pte} displays all the entries in all of
15148 the Page Tables. An argument, an integer expression, given to the
15149 @kbd{info dos pde} command means display only that entry from the Page
15150 Directory table. An argument given to the @kbd{info dos pte} command
15151 means display entries from a single Page Table, the one pointed to by
15152 the specified entry in the Page Directory.
15154 @cindex direct memory access (DMA) on MS-DOS
15155 These commands are useful when your program uses @dfn{DMA} (Direct
15156 Memory Access), which needs physical addresses to program the DMA
15159 These commands are supported only with some DPMI servers.
15161 @cindex physical address from linear address
15162 @item info dos address-pte @var{addr}
15163 This command displays the Page Table entry for a specified linear
15164 address. The argument @var{addr} is a linear address which should
15165 already have the appropriate segment's base address added to it,
15166 because this command accepts addresses which may belong to @emph{any}
15167 segment. For example, here's how to display the Page Table entry for
15168 the page where a variable @code{i} is stored:
15171 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15172 @exdent @code{Page Table entry for address 0x11a00d30:}
15173 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15177 This says that @code{i} is stored at offset @code{0xd30} from the page
15178 whose physical base address is @code{0x02698000}, and shows all the
15179 attributes of that page.
15181 Note that you must cast the addresses of variables to a @code{char *},
15182 since otherwise the value of @code{__djgpp_base_address}, the base
15183 address of all variables and functions in a @sc{djgpp} program, will
15184 be added using the rules of C pointer arithmetics: if @code{i} is
15185 declared an @code{int}, @value{GDBN} will add 4 times the value of
15186 @code{__djgpp_base_address} to the address of @code{i}.
15188 Here's another example, it displays the Page Table entry for the
15192 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15193 @exdent @code{Page Table entry for address 0x29110:}
15194 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15198 (The @code{+ 3} offset is because the transfer buffer's address is the
15199 3rd member of the @code{_go32_info_block} structure.) The output
15200 clearly shows that this DPMI server maps the addresses in conventional
15201 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15202 linear (@code{0x29110}) addresses are identical.
15204 This command is supported only with some DPMI servers.
15207 @cindex DOS serial data link, remote debugging
15208 In addition to native debugging, the DJGPP port supports remote
15209 debugging via a serial data link. The following commands are specific
15210 to remote serial debugging in the DJGPP port of @value{GDBN}.
15213 @kindex set com1base
15214 @kindex set com1irq
15215 @kindex set com2base
15216 @kindex set com2irq
15217 @kindex set com3base
15218 @kindex set com3irq
15219 @kindex set com4base
15220 @kindex set com4irq
15221 @item set com1base @var{addr}
15222 This command sets the base I/O port address of the @file{COM1} serial
15225 @item set com1irq @var{irq}
15226 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15227 for the @file{COM1} serial port.
15229 There are similar commands @samp{set com2base}, @samp{set com3irq},
15230 etc.@: for setting the port address and the @code{IRQ} lines for the
15233 @kindex show com1base
15234 @kindex show com1irq
15235 @kindex show com2base
15236 @kindex show com2irq
15237 @kindex show com3base
15238 @kindex show com3irq
15239 @kindex show com4base
15240 @kindex show com4irq
15241 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15242 display the current settings of the base address and the @code{IRQ}
15243 lines used by the COM ports.
15246 @kindex info serial
15247 @cindex DOS serial port status
15248 This command prints the status of the 4 DOS serial ports. For each
15249 port, it prints whether it's active or not, its I/O base address and
15250 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15251 counts of various errors encountered so far.
15255 @node Cygwin Native
15256 @subsection Features for Debugging MS Windows PE Executables
15257 @cindex MS Windows debugging
15258 @cindex native Cygwin debugging
15259 @cindex Cygwin-specific commands
15261 @value{GDBN} supports native debugging of MS Windows programs, including
15262 DLLs with and without symbolic debugging information. There are various
15263 additional Cygwin-specific commands, described in this section.
15264 Working with DLLs that have no debugging symbols is described in
15265 @ref{Non-debug DLL Symbols}.
15270 This is a prefix of MS Windows-specific commands which print
15271 information about the target system and important OS structures.
15273 @item info w32 selector
15274 This command displays information returned by
15275 the Win32 API @code{GetThreadSelectorEntry} function.
15276 It takes an optional argument that is evaluated to
15277 a long value to give the information about this given selector.
15278 Without argument, this command displays information
15279 about the six segment registers.
15283 This is a Cygwin-specific alias of @code{info shared}.
15285 @kindex dll-symbols
15287 This command loads symbols from a dll similarly to
15288 add-sym command but without the need to specify a base address.
15290 @kindex set cygwin-exceptions
15291 @cindex debugging the Cygwin DLL
15292 @cindex Cygwin DLL, debugging
15293 @item set cygwin-exceptions @var{mode}
15294 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15295 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15296 @value{GDBN} will delay recognition of exceptions, and may ignore some
15297 exceptions which seem to be caused by internal Cygwin DLL
15298 ``bookkeeping''. This option is meant primarily for debugging the
15299 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15300 @value{GDBN} users with false @code{SIGSEGV} signals.
15302 @kindex show cygwin-exceptions
15303 @item show cygwin-exceptions
15304 Displays whether @value{GDBN} will break on exceptions that happen
15305 inside the Cygwin DLL itself.
15307 @kindex set new-console
15308 @item set new-console @var{mode}
15309 If @var{mode} is @code{on} the debuggee will
15310 be started in a new console on next start.
15311 If @var{mode} is @code{off}i, the debuggee will
15312 be started in the same console as the debugger.
15314 @kindex show new-console
15315 @item show new-console
15316 Displays whether a new console is used
15317 when the debuggee is started.
15319 @kindex set new-group
15320 @item set new-group @var{mode}
15321 This boolean value controls whether the debuggee should
15322 start a new group or stay in the same group as the debugger.
15323 This affects the way the Windows OS handles
15326 @kindex show new-group
15327 @item show new-group
15328 Displays current value of new-group boolean.
15330 @kindex set debugevents
15331 @item set debugevents
15332 This boolean value adds debug output concerning kernel events related
15333 to the debuggee seen by the debugger. This includes events that
15334 signal thread and process creation and exit, DLL loading and
15335 unloading, console interrupts, and debugging messages produced by the
15336 Windows @code{OutputDebugString} API call.
15338 @kindex set debugexec
15339 @item set debugexec
15340 This boolean value adds debug output concerning execute events
15341 (such as resume thread) seen by the debugger.
15343 @kindex set debugexceptions
15344 @item set debugexceptions
15345 This boolean value adds debug output concerning exceptions in the
15346 debuggee seen by the debugger.
15348 @kindex set debugmemory
15349 @item set debugmemory
15350 This boolean value adds debug output concerning debuggee memory reads
15351 and writes by the debugger.
15355 This boolean values specifies whether the debuggee is called
15356 via a shell or directly (default value is on).
15360 Displays if the debuggee will be started with a shell.
15365 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15368 @node Non-debug DLL Symbols
15369 @subsubsection Support for DLLs without Debugging Symbols
15370 @cindex DLLs with no debugging symbols
15371 @cindex Minimal symbols and DLLs
15373 Very often on windows, some of the DLLs that your program relies on do
15374 not include symbolic debugging information (for example,
15375 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15376 symbols in a DLL, it relies on the minimal amount of symbolic
15377 information contained in the DLL's export table. This section
15378 describes working with such symbols, known internally to @value{GDBN} as
15379 ``minimal symbols''.
15381 Note that before the debugged program has started execution, no DLLs
15382 will have been loaded. The easiest way around this problem is simply to
15383 start the program --- either by setting a breakpoint or letting the
15384 program run once to completion. It is also possible to force
15385 @value{GDBN} to load a particular DLL before starting the executable ---
15386 see the shared library information in @ref{Files}, or the
15387 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15388 explicitly loading symbols from a DLL with no debugging information will
15389 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15390 which may adversely affect symbol lookup performance.
15392 @subsubsection DLL Name Prefixes
15394 In keeping with the naming conventions used by the Microsoft debugging
15395 tools, DLL export symbols are made available with a prefix based on the
15396 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15397 also entered into the symbol table, so @code{CreateFileA} is often
15398 sufficient. In some cases there will be name clashes within a program
15399 (particularly if the executable itself includes full debugging symbols)
15400 necessitating the use of the fully qualified name when referring to the
15401 contents of the DLL. Use single-quotes around the name to avoid the
15402 exclamation mark (``!'') being interpreted as a language operator.
15404 Note that the internal name of the DLL may be all upper-case, even
15405 though the file name of the DLL is lower-case, or vice-versa. Since
15406 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15407 some confusion. If in doubt, try the @code{info functions} and
15408 @code{info variables} commands or even @code{maint print msymbols}
15409 (@pxref{Symbols}). Here's an example:
15412 (@value{GDBP}) info function CreateFileA
15413 All functions matching regular expression "CreateFileA":
15415 Non-debugging symbols:
15416 0x77e885f4 CreateFileA
15417 0x77e885f4 KERNEL32!CreateFileA
15421 (@value{GDBP}) info function !
15422 All functions matching regular expression "!":
15424 Non-debugging symbols:
15425 0x6100114c cygwin1!__assert
15426 0x61004034 cygwin1!_dll_crt0@@0
15427 0x61004240 cygwin1!dll_crt0(per_process *)
15431 @subsubsection Working with Minimal Symbols
15433 Symbols extracted from a DLL's export table do not contain very much
15434 type information. All that @value{GDBN} can do is guess whether a symbol
15435 refers to a function or variable depending on the linker section that
15436 contains the symbol. Also note that the actual contents of the memory
15437 contained in a DLL are not available unless the program is running. This
15438 means that you cannot examine the contents of a variable or disassemble
15439 a function within a DLL without a running program.
15441 Variables are generally treated as pointers and dereferenced
15442 automatically. For this reason, it is often necessary to prefix a
15443 variable name with the address-of operator (``&'') and provide explicit
15444 type information in the command. Here's an example of the type of
15448 (@value{GDBP}) print 'cygwin1!__argv'
15453 (@value{GDBP}) x 'cygwin1!__argv'
15454 0x10021610: "\230y\""
15457 And two possible solutions:
15460 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15461 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15465 (@value{GDBP}) x/2x &'cygwin1!__argv'
15466 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15467 (@value{GDBP}) x/x 0x10021608
15468 0x10021608: 0x0022fd98
15469 (@value{GDBP}) x/s 0x0022fd98
15470 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15473 Setting a break point within a DLL is possible even before the program
15474 starts execution. However, under these circumstances, @value{GDBN} can't
15475 examine the initial instructions of the function in order to skip the
15476 function's frame set-up code. You can work around this by using ``*&''
15477 to set the breakpoint at a raw memory address:
15480 (@value{GDBP}) break *&'python22!PyOS_Readline'
15481 Breakpoint 1 at 0x1e04eff0
15484 The author of these extensions is not entirely convinced that setting a
15485 break point within a shared DLL like @file{kernel32.dll} is completely
15489 @subsection Commands Specific to @sc{gnu} Hurd Systems
15490 @cindex @sc{gnu} Hurd debugging
15492 This subsection describes @value{GDBN} commands specific to the
15493 @sc{gnu} Hurd native debugging.
15498 @kindex set signals@r{, Hurd command}
15499 @kindex set sigs@r{, Hurd command}
15500 This command toggles the state of inferior signal interception by
15501 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15502 affected by this command. @code{sigs} is a shorthand alias for
15507 @kindex show signals@r{, Hurd command}
15508 @kindex show sigs@r{, Hurd command}
15509 Show the current state of intercepting inferior's signals.
15511 @item set signal-thread
15512 @itemx set sigthread
15513 @kindex set signal-thread
15514 @kindex set sigthread
15515 This command tells @value{GDBN} which thread is the @code{libc} signal
15516 thread. That thread is run when a signal is delivered to a running
15517 process. @code{set sigthread} is the shorthand alias of @code{set
15520 @item show signal-thread
15521 @itemx show sigthread
15522 @kindex show signal-thread
15523 @kindex show sigthread
15524 These two commands show which thread will run when the inferior is
15525 delivered a signal.
15528 @kindex set stopped@r{, Hurd command}
15529 This commands tells @value{GDBN} that the inferior process is stopped,
15530 as with the @code{SIGSTOP} signal. The stopped process can be
15531 continued by delivering a signal to it.
15534 @kindex show stopped@r{, Hurd command}
15535 This command shows whether @value{GDBN} thinks the debuggee is
15538 @item set exceptions
15539 @kindex set exceptions@r{, Hurd command}
15540 Use this command to turn off trapping of exceptions in the inferior.
15541 When exception trapping is off, neither breakpoints nor
15542 single-stepping will work. To restore the default, set exception
15545 @item show exceptions
15546 @kindex show exceptions@r{, Hurd command}
15547 Show the current state of trapping exceptions in the inferior.
15549 @item set task pause
15550 @kindex set task@r{, Hurd commands}
15551 @cindex task attributes (@sc{gnu} Hurd)
15552 @cindex pause current task (@sc{gnu} Hurd)
15553 This command toggles task suspension when @value{GDBN} has control.
15554 Setting it to on takes effect immediately, and the task is suspended
15555 whenever @value{GDBN} gets control. Setting it to off will take
15556 effect the next time the inferior is continued. If this option is set
15557 to off, you can use @code{set thread default pause on} or @code{set
15558 thread pause on} (see below) to pause individual threads.
15560 @item show task pause
15561 @kindex show task@r{, Hurd commands}
15562 Show the current state of task suspension.
15564 @item set task detach-suspend-count
15565 @cindex task suspend count
15566 @cindex detach from task, @sc{gnu} Hurd
15567 This command sets the suspend count the task will be left with when
15568 @value{GDBN} detaches from it.
15570 @item show task detach-suspend-count
15571 Show the suspend count the task will be left with when detaching.
15573 @item set task exception-port
15574 @itemx set task excp
15575 @cindex task exception port, @sc{gnu} Hurd
15576 This command sets the task exception port to which @value{GDBN} will
15577 forward exceptions. The argument should be the value of the @dfn{send
15578 rights} of the task. @code{set task excp} is a shorthand alias.
15580 @item set noninvasive
15581 @cindex noninvasive task options
15582 This command switches @value{GDBN} to a mode that is the least
15583 invasive as far as interfering with the inferior is concerned. This
15584 is the same as using @code{set task pause}, @code{set exceptions}, and
15585 @code{set signals} to values opposite to the defaults.
15587 @item info send-rights
15588 @itemx info receive-rights
15589 @itemx info port-rights
15590 @itemx info port-sets
15591 @itemx info dead-names
15594 @cindex send rights, @sc{gnu} Hurd
15595 @cindex receive rights, @sc{gnu} Hurd
15596 @cindex port rights, @sc{gnu} Hurd
15597 @cindex port sets, @sc{gnu} Hurd
15598 @cindex dead names, @sc{gnu} Hurd
15599 These commands display information about, respectively, send rights,
15600 receive rights, port rights, port sets, and dead names of a task.
15601 There are also shorthand aliases: @code{info ports} for @code{info
15602 port-rights} and @code{info psets} for @code{info port-sets}.
15604 @item set thread pause
15605 @kindex set thread@r{, Hurd command}
15606 @cindex thread properties, @sc{gnu} Hurd
15607 @cindex pause current thread (@sc{gnu} Hurd)
15608 This command toggles current thread suspension when @value{GDBN} has
15609 control. Setting it to on takes effect immediately, and the current
15610 thread is suspended whenever @value{GDBN} gets control. Setting it to
15611 off will take effect the next time the inferior is continued.
15612 Normally, this command has no effect, since when @value{GDBN} has
15613 control, the whole task is suspended. However, if you used @code{set
15614 task pause off} (see above), this command comes in handy to suspend
15615 only the current thread.
15617 @item show thread pause
15618 @kindex show thread@r{, Hurd command}
15619 This command shows the state of current thread suspension.
15621 @item set thread run
15622 This command sets whether the current thread is allowed to run.
15624 @item show thread run
15625 Show whether the current thread is allowed to run.
15627 @item set thread detach-suspend-count
15628 @cindex thread suspend count, @sc{gnu} Hurd
15629 @cindex detach from thread, @sc{gnu} Hurd
15630 This command sets the suspend count @value{GDBN} will leave on a
15631 thread when detaching. This number is relative to the suspend count
15632 found by @value{GDBN} when it notices the thread; use @code{set thread
15633 takeover-suspend-count} to force it to an absolute value.
15635 @item show thread detach-suspend-count
15636 Show the suspend count @value{GDBN} will leave on the thread when
15639 @item set thread exception-port
15640 @itemx set thread excp
15641 Set the thread exception port to which to forward exceptions. This
15642 overrides the port set by @code{set task exception-port} (see above).
15643 @code{set thread excp} is the shorthand alias.
15645 @item set thread takeover-suspend-count
15646 Normally, @value{GDBN}'s thread suspend counts are relative to the
15647 value @value{GDBN} finds when it notices each thread. This command
15648 changes the suspend counts to be absolute instead.
15650 @item set thread default
15651 @itemx show thread default
15652 @cindex thread default settings, @sc{gnu} Hurd
15653 Each of the above @code{set thread} commands has a @code{set thread
15654 default} counterpart (e.g., @code{set thread default pause}, @code{set
15655 thread default exception-port}, etc.). The @code{thread default}
15656 variety of commands sets the default thread properties for all
15657 threads; you can then change the properties of individual threads with
15658 the non-default commands.
15663 @subsection QNX Neutrino
15664 @cindex QNX Neutrino
15666 @value{GDBN} provides the following commands specific to the QNX
15670 @item set debug nto-debug
15671 @kindex set debug nto-debug
15672 When set to on, enables debugging messages specific to the QNX
15675 @item show debug nto-debug
15676 @kindex show debug nto-debug
15677 Show the current state of QNX Neutrino messages.
15684 @value{GDBN} provides the following commands specific to the Darwin target:
15687 @item set debug darwin @var{num}
15688 @kindex set debug darwin
15689 When set to a non zero value, enables debugging messages specific to
15690 the Darwin support. Higher values produce more verbose output.
15692 @item show debug darwin
15693 @kindex show debug darwin
15694 Show the current state of Darwin messages.
15696 @item set debug mach-o @var{num}
15697 @kindex set debug mach-o
15698 When set to a non zero value, enables debugging messages while
15699 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
15700 file format used on Darwin for object and executable files.) Higher
15701 values produce more verbose output. This is a command to diagnose
15702 problems internal to @value{GDBN} and should not be needed in normal
15705 @item show debug mach-o
15706 @kindex show debug mach-o
15707 Show the current state of Mach-O file messages.
15709 @item set mach-exceptions on
15710 @itemx set mach-exceptions off
15711 @kindex set mach-exceptions
15712 On Darwin, faults are first reported as a Mach exception and are then
15713 mapped to a Posix signal. Use this command to turn on trapping of
15714 Mach exceptions in the inferior. This might be sometimes useful to
15715 better understand the cause of a fault. The default is off.
15717 @item show mach-exceptions
15718 @kindex show mach-exceptions
15719 Show the current state of exceptions trapping.
15724 @section Embedded Operating Systems
15726 This section describes configurations involving the debugging of
15727 embedded operating systems that are available for several different
15731 * VxWorks:: Using @value{GDBN} with VxWorks
15734 @value{GDBN} includes the ability to debug programs running on
15735 various real-time operating systems.
15738 @subsection Using @value{GDBN} with VxWorks
15744 @kindex target vxworks
15745 @item target vxworks @var{machinename}
15746 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
15747 is the target system's machine name or IP address.
15751 On VxWorks, @code{load} links @var{filename} dynamically on the
15752 current target system as well as adding its symbols in @value{GDBN}.
15754 @value{GDBN} enables developers to spawn and debug tasks running on networked
15755 VxWorks targets from a Unix host. Already-running tasks spawned from
15756 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
15757 both the Unix host and on the VxWorks target. The program
15758 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
15759 installed with the name @code{vxgdb}, to distinguish it from a
15760 @value{GDBN} for debugging programs on the host itself.)
15763 @item VxWorks-timeout @var{args}
15764 @kindex vxworks-timeout
15765 All VxWorks-based targets now support the option @code{vxworks-timeout}.
15766 This option is set by the user, and @var{args} represents the number of
15767 seconds @value{GDBN} waits for responses to rpc's. You might use this if
15768 your VxWorks target is a slow software simulator or is on the far side
15769 of a thin network line.
15772 The following information on connecting to VxWorks was current when
15773 this manual was produced; newer releases of VxWorks may use revised
15776 @findex INCLUDE_RDB
15777 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
15778 to include the remote debugging interface routines in the VxWorks
15779 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
15780 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
15781 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
15782 source debugging task @code{tRdbTask} when VxWorks is booted. For more
15783 information on configuring and remaking VxWorks, see the manufacturer's
15785 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
15787 Once you have included @file{rdb.a} in your VxWorks system image and set
15788 your Unix execution search path to find @value{GDBN}, you are ready to
15789 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
15790 @code{vxgdb}, depending on your installation).
15792 @value{GDBN} comes up showing the prompt:
15799 * VxWorks Connection:: Connecting to VxWorks
15800 * VxWorks Download:: VxWorks download
15801 * VxWorks Attach:: Running tasks
15804 @node VxWorks Connection
15805 @subsubsection Connecting to VxWorks
15807 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
15808 network. To connect to a target whose host name is ``@code{tt}'', type:
15811 (vxgdb) target vxworks tt
15815 @value{GDBN} displays messages like these:
15818 Attaching remote machine across net...
15823 @value{GDBN} then attempts to read the symbol tables of any object modules
15824 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
15825 these files by searching the directories listed in the command search
15826 path (@pxref{Environment, ,Your Program's Environment}); if it fails
15827 to find an object file, it displays a message such as:
15830 prog.o: No such file or directory.
15833 When this happens, add the appropriate directory to the search path with
15834 the @value{GDBN} command @code{path}, and execute the @code{target}
15837 @node VxWorks Download
15838 @subsubsection VxWorks Download
15840 @cindex download to VxWorks
15841 If you have connected to the VxWorks target and you want to debug an
15842 object that has not yet been loaded, you can use the @value{GDBN}
15843 @code{load} command to download a file from Unix to VxWorks
15844 incrementally. The object file given as an argument to the @code{load}
15845 command is actually opened twice: first by the VxWorks target in order
15846 to download the code, then by @value{GDBN} in order to read the symbol
15847 table. This can lead to problems if the current working directories on
15848 the two systems differ. If both systems have NFS mounted the same
15849 filesystems, you can avoid these problems by using absolute paths.
15850 Otherwise, it is simplest to set the working directory on both systems
15851 to the directory in which the object file resides, and then to reference
15852 the file by its name, without any path. For instance, a program
15853 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
15854 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
15855 program, type this on VxWorks:
15858 -> cd "@var{vxpath}/vw/demo/rdb"
15862 Then, in @value{GDBN}, type:
15865 (vxgdb) cd @var{hostpath}/vw/demo/rdb
15866 (vxgdb) load prog.o
15869 @value{GDBN} displays a response similar to this:
15872 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
15875 You can also use the @code{load} command to reload an object module
15876 after editing and recompiling the corresponding source file. Note that
15877 this makes @value{GDBN} delete all currently-defined breakpoints,
15878 auto-displays, and convenience variables, and to clear the value
15879 history. (This is necessary in order to preserve the integrity of
15880 debugger's data structures that reference the target system's symbol
15883 @node VxWorks Attach
15884 @subsubsection Running Tasks
15886 @cindex running VxWorks tasks
15887 You can also attach to an existing task using the @code{attach} command as
15891 (vxgdb) attach @var{task}
15895 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
15896 or suspended when you attach to it. Running tasks are suspended at
15897 the time of attachment.
15899 @node Embedded Processors
15900 @section Embedded Processors
15902 This section goes into details specific to particular embedded
15905 @cindex send command to simulator
15906 Whenever a specific embedded processor has a simulator, @value{GDBN}
15907 allows to send an arbitrary command to the simulator.
15910 @item sim @var{command}
15911 @kindex sim@r{, a command}
15912 Send an arbitrary @var{command} string to the simulator. Consult the
15913 documentation for the specific simulator in use for information about
15914 acceptable commands.
15920 * M32R/D:: Renesas M32R/D
15921 * M68K:: Motorola M68K
15922 * MIPS Embedded:: MIPS Embedded
15923 * OpenRISC 1000:: OpenRisc 1000
15924 * PA:: HP PA Embedded
15925 * PowerPC Embedded:: PowerPC Embedded
15926 * Sparclet:: Tsqware Sparclet
15927 * Sparclite:: Fujitsu Sparclite
15928 * Z8000:: Zilog Z8000
15931 * Super-H:: Renesas Super-H
15940 @item target rdi @var{dev}
15941 ARM Angel monitor, via RDI library interface to ADP protocol. You may
15942 use this target to communicate with both boards running the Angel
15943 monitor, or with the EmbeddedICE JTAG debug device.
15946 @item target rdp @var{dev}
15951 @value{GDBN} provides the following ARM-specific commands:
15954 @item set arm disassembler
15956 This commands selects from a list of disassembly styles. The
15957 @code{"std"} style is the standard style.
15959 @item show arm disassembler
15961 Show the current disassembly style.
15963 @item set arm apcs32
15964 @cindex ARM 32-bit mode
15965 This command toggles ARM operation mode between 32-bit and 26-bit.
15967 @item show arm apcs32
15968 Display the current usage of the ARM 32-bit mode.
15970 @item set arm fpu @var{fputype}
15971 This command sets the ARM floating-point unit (FPU) type. The
15972 argument @var{fputype} can be one of these:
15976 Determine the FPU type by querying the OS ABI.
15978 Software FPU, with mixed-endian doubles on little-endian ARM
15981 GCC-compiled FPA co-processor.
15983 Software FPU with pure-endian doubles.
15989 Show the current type of the FPU.
15992 This command forces @value{GDBN} to use the specified ABI.
15995 Show the currently used ABI.
15997 @item set arm fallback-mode (arm|thumb|auto)
15998 @value{GDBN} uses the symbol table, when available, to determine
15999 whether instructions are ARM or Thumb. This command controls
16000 @value{GDBN}'s default behavior when the symbol table is not
16001 available. The default is @samp{auto}, which causes @value{GDBN} to
16002 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16005 @item show arm fallback-mode
16006 Show the current fallback instruction mode.
16008 @item set arm force-mode (arm|thumb|auto)
16009 This command overrides use of the symbol table to determine whether
16010 instructions are ARM or Thumb. The default is @samp{auto}, which
16011 causes @value{GDBN} to use the symbol table and then the setting
16012 of @samp{set arm fallback-mode}.
16014 @item show arm force-mode
16015 Show the current forced instruction mode.
16017 @item set debug arm
16018 Toggle whether to display ARM-specific debugging messages from the ARM
16019 target support subsystem.
16021 @item show debug arm
16022 Show whether ARM-specific debugging messages are enabled.
16025 The following commands are available when an ARM target is debugged
16026 using the RDI interface:
16029 @item rdilogfile @r{[}@var{file}@r{]}
16031 @cindex ADP (Angel Debugger Protocol) logging
16032 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16033 With an argument, sets the log file to the specified @var{file}. With
16034 no argument, show the current log file name. The default log file is
16037 @item rdilogenable @r{[}@var{arg}@r{]}
16038 @kindex rdilogenable
16039 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16040 enables logging, with an argument 0 or @code{"no"} disables it. With
16041 no arguments displays the current setting. When logging is enabled,
16042 ADP packets exchanged between @value{GDBN} and the RDI target device
16043 are logged to a file.
16045 @item set rdiromatzero
16046 @kindex set rdiromatzero
16047 @cindex ROM at zero address, RDI
16048 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16049 vector catching is disabled, so that zero address can be used. If off
16050 (the default), vector catching is enabled. For this command to take
16051 effect, it needs to be invoked prior to the @code{target rdi} command.
16053 @item show rdiromatzero
16054 @kindex show rdiromatzero
16055 Show the current setting of ROM at zero address.
16057 @item set rdiheartbeat
16058 @kindex set rdiheartbeat
16059 @cindex RDI heartbeat
16060 Enable or disable RDI heartbeat packets. It is not recommended to
16061 turn on this option, since it confuses ARM and EPI JTAG interface, as
16062 well as the Angel monitor.
16064 @item show rdiheartbeat
16065 @kindex show rdiheartbeat
16066 Show the setting of RDI heartbeat packets.
16071 @subsection Renesas M32R/D and M32R/SDI
16074 @kindex target m32r
16075 @item target m32r @var{dev}
16076 Renesas M32R/D ROM monitor.
16078 @kindex target m32rsdi
16079 @item target m32rsdi @var{dev}
16080 Renesas M32R SDI server, connected via parallel port to the board.
16083 The following @value{GDBN} commands are specific to the M32R monitor:
16086 @item set download-path @var{path}
16087 @kindex set download-path
16088 @cindex find downloadable @sc{srec} files (M32R)
16089 Set the default path for finding downloadable @sc{srec} files.
16091 @item show download-path
16092 @kindex show download-path
16093 Show the default path for downloadable @sc{srec} files.
16095 @item set board-address @var{addr}
16096 @kindex set board-address
16097 @cindex M32-EVA target board address
16098 Set the IP address for the M32R-EVA target board.
16100 @item show board-address
16101 @kindex show board-address
16102 Show the current IP address of the target board.
16104 @item set server-address @var{addr}
16105 @kindex set server-address
16106 @cindex download server address (M32R)
16107 Set the IP address for the download server, which is the @value{GDBN}'s
16110 @item show server-address
16111 @kindex show server-address
16112 Display the IP address of the download server.
16114 @item upload @r{[}@var{file}@r{]}
16115 @kindex upload@r{, M32R}
16116 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16117 upload capability. If no @var{file} argument is given, the current
16118 executable file is uploaded.
16120 @item tload @r{[}@var{file}@r{]}
16121 @kindex tload@r{, M32R}
16122 Test the @code{upload} command.
16125 The following commands are available for M32R/SDI:
16130 @cindex reset SDI connection, M32R
16131 This command resets the SDI connection.
16135 This command shows the SDI connection status.
16138 @kindex debug_chaos
16139 @cindex M32R/Chaos debugging
16140 Instructs the remote that M32R/Chaos debugging is to be used.
16142 @item use_debug_dma
16143 @kindex use_debug_dma
16144 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16147 @kindex use_mon_code
16148 Instructs the remote to use the MON_CODE method of accessing memory.
16151 @kindex use_ib_break
16152 Instructs the remote to set breakpoints by IB break.
16154 @item use_dbt_break
16155 @kindex use_dbt_break
16156 Instructs the remote to set breakpoints by DBT.
16162 The Motorola m68k configuration includes ColdFire support, and a
16163 target command for the following ROM monitor.
16167 @kindex target dbug
16168 @item target dbug @var{dev}
16169 dBUG ROM monitor for Motorola ColdFire.
16173 @node MIPS Embedded
16174 @subsection MIPS Embedded
16176 @cindex MIPS boards
16177 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16178 MIPS board attached to a serial line. This is available when
16179 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16182 Use these @value{GDBN} commands to specify the connection to your target board:
16185 @item target mips @var{port}
16186 @kindex target mips @var{port}
16187 To run a program on the board, start up @code{@value{GDBP}} with the
16188 name of your program as the argument. To connect to the board, use the
16189 command @samp{target mips @var{port}}, where @var{port} is the name of
16190 the serial port connected to the board. If the program has not already
16191 been downloaded to the board, you may use the @code{load} command to
16192 download it. You can then use all the usual @value{GDBN} commands.
16194 For example, this sequence connects to the target board through a serial
16195 port, and loads and runs a program called @var{prog} through the
16199 host$ @value{GDBP} @var{prog}
16200 @value{GDBN} is free software and @dots{}
16201 (@value{GDBP}) target mips /dev/ttyb
16202 (@value{GDBP}) load @var{prog}
16206 @item target mips @var{hostname}:@var{portnumber}
16207 On some @value{GDBN} host configurations, you can specify a TCP
16208 connection (for instance, to a serial line managed by a terminal
16209 concentrator) instead of a serial port, using the syntax
16210 @samp{@var{hostname}:@var{portnumber}}.
16212 @item target pmon @var{port}
16213 @kindex target pmon @var{port}
16216 @item target ddb @var{port}
16217 @kindex target ddb @var{port}
16218 NEC's DDB variant of PMON for Vr4300.
16220 @item target lsi @var{port}
16221 @kindex target lsi @var{port}
16222 LSI variant of PMON.
16224 @kindex target r3900
16225 @item target r3900 @var{dev}
16226 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16228 @kindex target array
16229 @item target array @var{dev}
16230 Array Tech LSI33K RAID controller board.
16236 @value{GDBN} also supports these special commands for MIPS targets:
16239 @item set mipsfpu double
16240 @itemx set mipsfpu single
16241 @itemx set mipsfpu none
16242 @itemx set mipsfpu auto
16243 @itemx show mipsfpu
16244 @kindex set mipsfpu
16245 @kindex show mipsfpu
16246 @cindex MIPS remote floating point
16247 @cindex floating point, MIPS remote
16248 If your target board does not support the MIPS floating point
16249 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16250 need this, you may wish to put the command in your @value{GDBN} init
16251 file). This tells @value{GDBN} how to find the return value of
16252 functions which return floating point values. It also allows
16253 @value{GDBN} to avoid saving the floating point registers when calling
16254 functions on the board. If you are using a floating point coprocessor
16255 with only single precision floating point support, as on the @sc{r4650}
16256 processor, use the command @samp{set mipsfpu single}. The default
16257 double precision floating point coprocessor may be selected using
16258 @samp{set mipsfpu double}.
16260 In previous versions the only choices were double precision or no
16261 floating point, so @samp{set mipsfpu on} will select double precision
16262 and @samp{set mipsfpu off} will select no floating point.
16264 As usual, you can inquire about the @code{mipsfpu} variable with
16265 @samp{show mipsfpu}.
16267 @item set timeout @var{seconds}
16268 @itemx set retransmit-timeout @var{seconds}
16269 @itemx show timeout
16270 @itemx show retransmit-timeout
16271 @cindex @code{timeout}, MIPS protocol
16272 @cindex @code{retransmit-timeout}, MIPS protocol
16273 @kindex set timeout
16274 @kindex show timeout
16275 @kindex set retransmit-timeout
16276 @kindex show retransmit-timeout
16277 You can control the timeout used while waiting for a packet, in the MIPS
16278 remote protocol, with the @code{set timeout @var{seconds}} command. The
16279 default is 5 seconds. Similarly, you can control the timeout used while
16280 waiting for an acknowledgment of a packet with the @code{set
16281 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16282 You can inspect both values with @code{show timeout} and @code{show
16283 retransmit-timeout}. (These commands are @emph{only} available when
16284 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16286 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16287 is waiting for your program to stop. In that case, @value{GDBN} waits
16288 forever because it has no way of knowing how long the program is going
16289 to run before stopping.
16291 @item set syn-garbage-limit @var{num}
16292 @kindex set syn-garbage-limit@r{, MIPS remote}
16293 @cindex synchronize with remote MIPS target
16294 Limit the maximum number of characters @value{GDBN} should ignore when
16295 it tries to synchronize with the remote target. The default is 10
16296 characters. Setting the limit to -1 means there's no limit.
16298 @item show syn-garbage-limit
16299 @kindex show syn-garbage-limit@r{, MIPS remote}
16300 Show the current limit on the number of characters to ignore when
16301 trying to synchronize with the remote system.
16303 @item set monitor-prompt @var{prompt}
16304 @kindex set monitor-prompt@r{, MIPS remote}
16305 @cindex remote monitor prompt
16306 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16307 remote monitor. The default depends on the target:
16317 @item show monitor-prompt
16318 @kindex show monitor-prompt@r{, MIPS remote}
16319 Show the current strings @value{GDBN} expects as the prompt from the
16322 @item set monitor-warnings
16323 @kindex set monitor-warnings@r{, MIPS remote}
16324 Enable or disable monitor warnings about hardware breakpoints. This
16325 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16326 display warning messages whose codes are returned by the @code{lsi}
16327 PMON monitor for breakpoint commands.
16329 @item show monitor-warnings
16330 @kindex show monitor-warnings@r{, MIPS remote}
16331 Show the current setting of printing monitor warnings.
16333 @item pmon @var{command}
16334 @kindex pmon@r{, MIPS remote}
16335 @cindex send PMON command
16336 This command allows sending an arbitrary @var{command} string to the
16337 monitor. The monitor must be in debug mode for this to work.
16340 @node OpenRISC 1000
16341 @subsection OpenRISC 1000
16342 @cindex OpenRISC 1000
16344 @cindex or1k boards
16345 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16346 about platform and commands.
16350 @kindex target jtag
16351 @item target jtag jtag://@var{host}:@var{port}
16353 Connects to remote JTAG server.
16354 JTAG remote server can be either an or1ksim or JTAG server,
16355 connected via parallel port to the board.
16357 Example: @code{target jtag jtag://localhost:9999}
16360 @item or1ksim @var{command}
16361 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16362 Simulator, proprietary commands can be executed.
16364 @kindex info or1k spr
16365 @item info or1k spr
16366 Displays spr groups.
16368 @item info or1k spr @var{group}
16369 @itemx info or1k spr @var{groupno}
16370 Displays register names in selected group.
16372 @item info or1k spr @var{group} @var{register}
16373 @itemx info or1k spr @var{register}
16374 @itemx info or1k spr @var{groupno} @var{registerno}
16375 @itemx info or1k spr @var{registerno}
16376 Shows information about specified spr register.
16379 @item spr @var{group} @var{register} @var{value}
16380 @itemx spr @var{register @var{value}}
16381 @itemx spr @var{groupno} @var{registerno @var{value}}
16382 @itemx spr @var{registerno @var{value}}
16383 Writes @var{value} to specified spr register.
16386 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16387 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16388 program execution and is thus much faster. Hardware breakpoints/watchpoint
16389 triggers can be set using:
16392 Load effective address/data
16394 Store effective address/data
16396 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16401 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16402 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16404 @code{htrace} commands:
16405 @cindex OpenRISC 1000 htrace
16408 @item hwatch @var{conditional}
16409 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16410 or Data. For example:
16412 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16414 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16418 Display information about current HW trace configuration.
16420 @item htrace trigger @var{conditional}
16421 Set starting criteria for HW trace.
16423 @item htrace qualifier @var{conditional}
16424 Set acquisition qualifier for HW trace.
16426 @item htrace stop @var{conditional}
16427 Set HW trace stopping criteria.
16429 @item htrace record [@var{data}]*
16430 Selects the data to be recorded, when qualifier is met and HW trace was
16433 @item htrace enable
16434 @itemx htrace disable
16435 Enables/disables the HW trace.
16437 @item htrace rewind [@var{filename}]
16438 Clears currently recorded trace data.
16440 If filename is specified, new trace file is made and any newly collected data
16441 will be written there.
16443 @item htrace print [@var{start} [@var{len}]]
16444 Prints trace buffer, using current record configuration.
16446 @item htrace mode continuous
16447 Set continuous trace mode.
16449 @item htrace mode suspend
16450 Set suspend trace mode.
16454 @node PowerPC Embedded
16455 @subsection PowerPC Embedded
16457 @value{GDBN} provides the following PowerPC-specific commands:
16460 @kindex set powerpc
16461 @item set powerpc soft-float
16462 @itemx show powerpc soft-float
16463 Force @value{GDBN} to use (or not use) a software floating point calling
16464 convention. By default, @value{GDBN} selects the calling convention based
16465 on the selected architecture and the provided executable file.
16467 @item set powerpc vector-abi
16468 @itemx show powerpc vector-abi
16469 Force @value{GDBN} to use the specified calling convention for vector
16470 arguments and return values. The valid options are @samp{auto};
16471 @samp{generic}, to avoid vector registers even if they are present;
16472 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16473 registers. By default, @value{GDBN} selects the calling convention
16474 based on the selected architecture and the provided executable file.
16476 @kindex target dink32
16477 @item target dink32 @var{dev}
16478 DINK32 ROM monitor.
16480 @kindex target ppcbug
16481 @item target ppcbug @var{dev}
16482 @kindex target ppcbug1
16483 @item target ppcbug1 @var{dev}
16484 PPCBUG ROM monitor for PowerPC.
16487 @item target sds @var{dev}
16488 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16491 @cindex SDS protocol
16492 The following commands specific to the SDS protocol are supported
16496 @item set sdstimeout @var{nsec}
16497 @kindex set sdstimeout
16498 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16499 default is 2 seconds.
16501 @item show sdstimeout
16502 @kindex show sdstimeout
16503 Show the current value of the SDS timeout.
16505 @item sds @var{command}
16506 @kindex sds@r{, a command}
16507 Send the specified @var{command} string to the SDS monitor.
16512 @subsection HP PA Embedded
16516 @kindex target op50n
16517 @item target op50n @var{dev}
16518 OP50N monitor, running on an OKI HPPA board.
16520 @kindex target w89k
16521 @item target w89k @var{dev}
16522 W89K monitor, running on a Winbond HPPA board.
16527 @subsection Tsqware Sparclet
16531 @value{GDBN} enables developers to debug tasks running on
16532 Sparclet targets from a Unix host.
16533 @value{GDBN} uses code that runs on
16534 both the Unix host and on the Sparclet target. The program
16535 @code{@value{GDBP}} is installed and executed on the Unix host.
16538 @item remotetimeout @var{args}
16539 @kindex remotetimeout
16540 @value{GDBN} supports the option @code{remotetimeout}.
16541 This option is set by the user, and @var{args} represents the number of
16542 seconds @value{GDBN} waits for responses.
16545 @cindex compiling, on Sparclet
16546 When compiling for debugging, include the options @samp{-g} to get debug
16547 information and @samp{-Ttext} to relocate the program to where you wish to
16548 load it on the target. You may also want to add the options @samp{-n} or
16549 @samp{-N} in order to reduce the size of the sections. Example:
16552 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16555 You can use @code{objdump} to verify that the addresses are what you intended:
16558 sparclet-aout-objdump --headers --syms prog
16561 @cindex running, on Sparclet
16563 your Unix execution search path to find @value{GDBN}, you are ready to
16564 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
16565 (or @code{sparclet-aout-gdb}, depending on your installation).
16567 @value{GDBN} comes up showing the prompt:
16574 * Sparclet File:: Setting the file to debug
16575 * Sparclet Connection:: Connecting to Sparclet
16576 * Sparclet Download:: Sparclet download
16577 * Sparclet Execution:: Running and debugging
16580 @node Sparclet File
16581 @subsubsection Setting File to Debug
16583 The @value{GDBN} command @code{file} lets you choose with program to debug.
16586 (gdbslet) file prog
16590 @value{GDBN} then attempts to read the symbol table of @file{prog}.
16591 @value{GDBN} locates
16592 the file by searching the directories listed in the command search
16594 If the file was compiled with debug information (option @samp{-g}), source
16595 files will be searched as well.
16596 @value{GDBN} locates
16597 the source files by searching the directories listed in the directory search
16598 path (@pxref{Environment, ,Your Program's Environment}).
16600 to find a file, it displays a message such as:
16603 prog: No such file or directory.
16606 When this happens, add the appropriate directories to the search paths with
16607 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
16608 @code{target} command again.
16610 @node Sparclet Connection
16611 @subsubsection Connecting to Sparclet
16613 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
16614 To connect to a target on serial port ``@code{ttya}'', type:
16617 (gdbslet) target sparclet /dev/ttya
16618 Remote target sparclet connected to /dev/ttya
16619 main () at ../prog.c:3
16623 @value{GDBN} displays messages like these:
16629 @node Sparclet Download
16630 @subsubsection Sparclet Download
16632 @cindex download to Sparclet
16633 Once connected to the Sparclet target,
16634 you can use the @value{GDBN}
16635 @code{load} command to download the file from the host to the target.
16636 The file name and load offset should be given as arguments to the @code{load}
16638 Since the file format is aout, the program must be loaded to the starting
16639 address. You can use @code{objdump} to find out what this value is. The load
16640 offset is an offset which is added to the VMA (virtual memory address)
16641 of each of the file's sections.
16642 For instance, if the program
16643 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
16644 and bss at 0x12010170, in @value{GDBN}, type:
16647 (gdbslet) load prog 0x12010000
16648 Loading section .text, size 0xdb0 vma 0x12010000
16651 If the code is loaded at a different address then what the program was linked
16652 to, you may need to use the @code{section} and @code{add-symbol-file} commands
16653 to tell @value{GDBN} where to map the symbol table.
16655 @node Sparclet Execution
16656 @subsubsection Running and Debugging
16658 @cindex running and debugging Sparclet programs
16659 You can now begin debugging the task using @value{GDBN}'s execution control
16660 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
16661 manual for the list of commands.
16665 Breakpoint 1 at 0x12010000: file prog.c, line 3.
16667 Starting program: prog
16668 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
16669 3 char *symarg = 0;
16671 4 char *execarg = "hello!";
16676 @subsection Fujitsu Sparclite
16680 @kindex target sparclite
16681 @item target sparclite @var{dev}
16682 Fujitsu sparclite boards, used only for the purpose of loading.
16683 You must use an additional command to debug the program.
16684 For example: target remote @var{dev} using @value{GDBN} standard
16690 @subsection Zilog Z8000
16693 @cindex simulator, Z8000
16694 @cindex Zilog Z8000 simulator
16696 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
16699 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
16700 unsegmented variant of the Z8000 architecture) or the Z8001 (the
16701 segmented variant). The simulator recognizes which architecture is
16702 appropriate by inspecting the object code.
16705 @item target sim @var{args}
16707 @kindex target sim@r{, with Z8000}
16708 Debug programs on a simulated CPU. If the simulator supports setup
16709 options, specify them via @var{args}.
16713 After specifying this target, you can debug programs for the simulated
16714 CPU in the same style as programs for your host computer; use the
16715 @code{file} command to load a new program image, the @code{run} command
16716 to run your program, and so on.
16718 As well as making available all the usual machine registers
16719 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
16720 additional items of information as specially named registers:
16725 Counts clock-ticks in the simulator.
16728 Counts instructions run in the simulator.
16731 Execution time in 60ths of a second.
16735 You can refer to these values in @value{GDBN} expressions with the usual
16736 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
16737 conditional breakpoint that suspends only after at least 5000
16738 simulated clock ticks.
16741 @subsection Atmel AVR
16744 When configured for debugging the Atmel AVR, @value{GDBN} supports the
16745 following AVR-specific commands:
16748 @item info io_registers
16749 @kindex info io_registers@r{, AVR}
16750 @cindex I/O registers (Atmel AVR)
16751 This command displays information about the AVR I/O registers. For
16752 each register, @value{GDBN} prints its number and value.
16759 When configured for debugging CRIS, @value{GDBN} provides the
16760 following CRIS-specific commands:
16763 @item set cris-version @var{ver}
16764 @cindex CRIS version
16765 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
16766 The CRIS version affects register names and sizes. This command is useful in
16767 case autodetection of the CRIS version fails.
16769 @item show cris-version
16770 Show the current CRIS version.
16772 @item set cris-dwarf2-cfi
16773 @cindex DWARF-2 CFI and CRIS
16774 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
16775 Change to @samp{off} when using @code{gcc-cris} whose version is below
16778 @item show cris-dwarf2-cfi
16779 Show the current state of using DWARF-2 CFI.
16781 @item set cris-mode @var{mode}
16783 Set the current CRIS mode to @var{mode}. It should only be changed when
16784 debugging in guru mode, in which case it should be set to
16785 @samp{guru} (the default is @samp{normal}).
16787 @item show cris-mode
16788 Show the current CRIS mode.
16792 @subsection Renesas Super-H
16795 For the Renesas Super-H processor, @value{GDBN} provides these
16800 @kindex regs@r{, Super-H}
16801 Show the values of all Super-H registers.
16803 @item set sh calling-convention @var{convention}
16804 @kindex set sh calling-convention
16805 Set the calling-convention used when calling functions from @value{GDBN}.
16806 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
16807 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
16808 convention. If the DWARF-2 information of the called function specifies
16809 that the function follows the Renesas calling convention, the function
16810 is called using the Renesas calling convention. If the calling convention
16811 is set to @samp{renesas}, the Renesas calling convention is always used,
16812 regardless of the DWARF-2 information. This can be used to override the
16813 default of @samp{gcc} if debug information is missing, or the compiler
16814 does not emit the DWARF-2 calling convention entry for a function.
16816 @item show sh calling-convention
16817 @kindex show sh calling-convention
16818 Show the current calling convention setting.
16823 @node Architectures
16824 @section Architectures
16826 This section describes characteristics of architectures that affect
16827 all uses of @value{GDBN} with the architecture, both native and cross.
16834 * HPPA:: HP PA architecture
16835 * SPU:: Cell Broadband Engine SPU architecture
16840 @subsection x86 Architecture-specific Issues
16843 @item set struct-convention @var{mode}
16844 @kindex set struct-convention
16845 @cindex struct return convention
16846 @cindex struct/union returned in registers
16847 Set the convention used by the inferior to return @code{struct}s and
16848 @code{union}s from functions to @var{mode}. Possible values of
16849 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
16850 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
16851 are returned on the stack, while @code{"reg"} means that a
16852 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
16853 be returned in a register.
16855 @item show struct-convention
16856 @kindex show struct-convention
16857 Show the current setting of the convention to return @code{struct}s
16866 @kindex set rstack_high_address
16867 @cindex AMD 29K register stack
16868 @cindex register stack, AMD29K
16869 @item set rstack_high_address @var{address}
16870 On AMD 29000 family processors, registers are saved in a separate
16871 @dfn{register stack}. There is no way for @value{GDBN} to determine the
16872 extent of this stack. Normally, @value{GDBN} just assumes that the
16873 stack is ``large enough''. This may result in @value{GDBN} referencing
16874 memory locations that do not exist. If necessary, you can get around
16875 this problem by specifying the ending address of the register stack with
16876 the @code{set rstack_high_address} command. The argument should be an
16877 address, which you probably want to precede with @samp{0x} to specify in
16880 @kindex show rstack_high_address
16881 @item show rstack_high_address
16882 Display the current limit of the register stack, on AMD 29000 family
16890 See the following section.
16895 @cindex stack on Alpha
16896 @cindex stack on MIPS
16897 @cindex Alpha stack
16899 Alpha- and MIPS-based computers use an unusual stack frame, which
16900 sometimes requires @value{GDBN} to search backward in the object code to
16901 find the beginning of a function.
16903 @cindex response time, MIPS debugging
16904 To improve response time (especially for embedded applications, where
16905 @value{GDBN} may be restricted to a slow serial line for this search)
16906 you may want to limit the size of this search, using one of these
16910 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
16911 @item set heuristic-fence-post @var{limit}
16912 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
16913 search for the beginning of a function. A value of @var{0} (the
16914 default) means there is no limit. However, except for @var{0}, the
16915 larger the limit the more bytes @code{heuristic-fence-post} must search
16916 and therefore the longer it takes to run. You should only need to use
16917 this command when debugging a stripped executable.
16919 @item show heuristic-fence-post
16920 Display the current limit.
16924 These commands are available @emph{only} when @value{GDBN} is configured
16925 for debugging programs on Alpha or MIPS processors.
16927 Several MIPS-specific commands are available when debugging MIPS
16931 @item set mips abi @var{arg}
16932 @kindex set mips abi
16933 @cindex set ABI for MIPS
16934 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
16935 values of @var{arg} are:
16939 The default ABI associated with the current binary (this is the
16950 @item show mips abi
16951 @kindex show mips abi
16952 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
16955 @itemx show mipsfpu
16956 @xref{MIPS Embedded, set mipsfpu}.
16958 @item set mips mask-address @var{arg}
16959 @kindex set mips mask-address
16960 @cindex MIPS addresses, masking
16961 This command determines whether the most-significant 32 bits of 64-bit
16962 MIPS addresses are masked off. The argument @var{arg} can be
16963 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
16964 setting, which lets @value{GDBN} determine the correct value.
16966 @item show mips mask-address
16967 @kindex show mips mask-address
16968 Show whether the upper 32 bits of MIPS addresses are masked off or
16971 @item set remote-mips64-transfers-32bit-regs
16972 @kindex set remote-mips64-transfers-32bit-regs
16973 This command controls compatibility with 64-bit MIPS targets that
16974 transfer data in 32-bit quantities. If you have an old MIPS 64 target
16975 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
16976 and 64 bits for other registers, set this option to @samp{on}.
16978 @item show remote-mips64-transfers-32bit-regs
16979 @kindex show remote-mips64-transfers-32bit-regs
16980 Show the current setting of compatibility with older MIPS 64 targets.
16982 @item set debug mips
16983 @kindex set debug mips
16984 This command turns on and off debugging messages for the MIPS-specific
16985 target code in @value{GDBN}.
16987 @item show debug mips
16988 @kindex show debug mips
16989 Show the current setting of MIPS debugging messages.
16995 @cindex HPPA support
16997 When @value{GDBN} is debugging the HP PA architecture, it provides the
16998 following special commands:
17001 @item set debug hppa
17002 @kindex set debug hppa
17003 This command determines whether HPPA architecture-specific debugging
17004 messages are to be displayed.
17006 @item show debug hppa
17007 Show whether HPPA debugging messages are displayed.
17009 @item maint print unwind @var{address}
17010 @kindex maint print unwind@r{, HPPA}
17011 This command displays the contents of the unwind table entry at the
17012 given @var{address}.
17018 @subsection Cell Broadband Engine SPU architecture
17019 @cindex Cell Broadband Engine
17022 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17023 it provides the following special commands:
17026 @item info spu event
17028 Display SPU event facility status. Shows current event mask
17029 and pending event status.
17031 @item info spu signal
17032 Display SPU signal notification facility status. Shows pending
17033 signal-control word and signal notification mode of both signal
17034 notification channels.
17036 @item info spu mailbox
17037 Display SPU mailbox facility status. Shows all pending entries,
17038 in order of processing, in each of the SPU Write Outbound,
17039 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17042 Display MFC DMA status. Shows all pending commands in the MFC
17043 DMA queue. For each entry, opcode, tag, class IDs, effective
17044 and local store addresses and transfer size are shown.
17046 @item info spu proxydma
17047 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17048 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17049 and local store addresses and transfer size are shown.
17054 @subsection PowerPC
17055 @cindex PowerPC architecture
17057 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17058 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17059 numbers stored in the floating point registers. These values must be stored
17060 in two consecutive registers, always starting at an even register like
17061 @code{f0} or @code{f2}.
17063 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
17064 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
17065 @code{f2} and @code{f3} for @code{$dl1} and so on.
17067 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
17068 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
17071 @node Controlling GDB
17072 @chapter Controlling @value{GDBN}
17074 You can alter the way @value{GDBN} interacts with you by using the
17075 @code{set} command. For commands controlling how @value{GDBN} displays
17076 data, see @ref{Print Settings, ,Print Settings}. Other settings are
17081 * Editing:: Command editing
17082 * Command History:: Command history
17083 * Screen Size:: Screen size
17084 * Numbers:: Numbers
17085 * ABI:: Configuring the current ABI
17086 * Messages/Warnings:: Optional warnings and messages
17087 * Debugging Output:: Optional messages about internal happenings
17095 @value{GDBN} indicates its readiness to read a command by printing a string
17096 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17097 can change the prompt string with the @code{set prompt} command. For
17098 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17099 the prompt in one of the @value{GDBN} sessions so that you can always tell
17100 which one you are talking to.
17102 @emph{Note:} @code{set prompt} does not add a space for you after the
17103 prompt you set. This allows you to set a prompt which ends in a space
17104 or a prompt that does not.
17108 @item set prompt @var{newprompt}
17109 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17111 @kindex show prompt
17113 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17117 @section Command Editing
17119 @cindex command line editing
17121 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17122 @sc{gnu} library provides consistent behavior for programs which provide a
17123 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17124 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17125 substitution, and a storage and recall of command history across
17126 debugging sessions.
17128 You may control the behavior of command line editing in @value{GDBN} with the
17129 command @code{set}.
17132 @kindex set editing
17135 @itemx set editing on
17136 Enable command line editing (enabled by default).
17138 @item set editing off
17139 Disable command line editing.
17141 @kindex show editing
17143 Show whether command line editing is enabled.
17146 @xref{Command Line Editing}, for more details about the Readline
17147 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17148 encouraged to read that chapter.
17150 @node Command History
17151 @section Command History
17152 @cindex command history
17154 @value{GDBN} can keep track of the commands you type during your
17155 debugging sessions, so that you can be certain of precisely what
17156 happened. Use these commands to manage the @value{GDBN} command
17159 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17160 package, to provide the history facility. @xref{Using History
17161 Interactively}, for the detailed description of the History library.
17163 To issue a command to @value{GDBN} without affecting certain aspects of
17164 the state which is seen by users, prefix it with @samp{server }
17165 (@pxref{Server Prefix}). This
17166 means that this command will not affect the command history, nor will it
17167 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17168 pressed on a line by itself.
17170 @cindex @code{server}, command prefix
17171 The server prefix does not affect the recording of values into the value
17172 history; to print a value without recording it into the value history,
17173 use the @code{output} command instead of the @code{print} command.
17175 Here is the description of @value{GDBN} commands related to command
17179 @cindex history substitution
17180 @cindex history file
17181 @kindex set history filename
17182 @cindex @env{GDBHISTFILE}, environment variable
17183 @item set history filename @var{fname}
17184 Set the name of the @value{GDBN} command history file to @var{fname}.
17185 This is the file where @value{GDBN} reads an initial command history
17186 list, and where it writes the command history from this session when it
17187 exits. You can access this list through history expansion or through
17188 the history command editing characters listed below. This file defaults
17189 to the value of the environment variable @code{GDBHISTFILE}, or to
17190 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17193 @cindex save command history
17194 @kindex set history save
17195 @item set history save
17196 @itemx set history save on
17197 Record command history in a file, whose name may be specified with the
17198 @code{set history filename} command. By default, this option is disabled.
17200 @item set history save off
17201 Stop recording command history in a file.
17203 @cindex history size
17204 @kindex set history size
17205 @cindex @env{HISTSIZE}, environment variable
17206 @item set history size @var{size}
17207 Set the number of commands which @value{GDBN} keeps in its history list.
17208 This defaults to the value of the environment variable
17209 @code{HISTSIZE}, or to 256 if this variable is not set.
17212 History expansion assigns special meaning to the character @kbd{!}.
17213 @xref{Event Designators}, for more details.
17215 @cindex history expansion, turn on/off
17216 Since @kbd{!} is also the logical not operator in C, history expansion
17217 is off by default. If you decide to enable history expansion with the
17218 @code{set history expansion on} command, you may sometimes need to
17219 follow @kbd{!} (when it is used as logical not, in an expression) with
17220 a space or a tab to prevent it from being expanded. The readline
17221 history facilities do not attempt substitution on the strings
17222 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17224 The commands to control history expansion are:
17227 @item set history expansion on
17228 @itemx set history expansion
17229 @kindex set history expansion
17230 Enable history expansion. History expansion is off by default.
17232 @item set history expansion off
17233 Disable history expansion.
17236 @kindex show history
17238 @itemx show history filename
17239 @itemx show history save
17240 @itemx show history size
17241 @itemx show history expansion
17242 These commands display the state of the @value{GDBN} history parameters.
17243 @code{show history} by itself displays all four states.
17248 @kindex show commands
17249 @cindex show last commands
17250 @cindex display command history
17251 @item show commands
17252 Display the last ten commands in the command history.
17254 @item show commands @var{n}
17255 Print ten commands centered on command number @var{n}.
17257 @item show commands +
17258 Print ten commands just after the commands last printed.
17262 @section Screen Size
17263 @cindex size of screen
17264 @cindex pauses in output
17266 Certain commands to @value{GDBN} may produce large amounts of
17267 information output to the screen. To help you read all of it,
17268 @value{GDBN} pauses and asks you for input at the end of each page of
17269 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17270 to discard the remaining output. Also, the screen width setting
17271 determines when to wrap lines of output. Depending on what is being
17272 printed, @value{GDBN} tries to break the line at a readable place,
17273 rather than simply letting it overflow onto the following line.
17275 Normally @value{GDBN} knows the size of the screen from the terminal
17276 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17277 together with the value of the @code{TERM} environment variable and the
17278 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17279 you can override it with the @code{set height} and @code{set
17286 @kindex show height
17287 @item set height @var{lpp}
17289 @itemx set width @var{cpl}
17291 These @code{set} commands specify a screen height of @var{lpp} lines and
17292 a screen width of @var{cpl} characters. The associated @code{show}
17293 commands display the current settings.
17295 If you specify a height of zero lines, @value{GDBN} does not pause during
17296 output no matter how long the output is. This is useful if output is to a
17297 file or to an editor buffer.
17299 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17300 from wrapping its output.
17302 @item set pagination on
17303 @itemx set pagination off
17304 @kindex set pagination
17305 Turn the output pagination on or off; the default is on. Turning
17306 pagination off is the alternative to @code{set height 0}.
17308 @item show pagination
17309 @kindex show pagination
17310 Show the current pagination mode.
17315 @cindex number representation
17316 @cindex entering numbers
17318 You can always enter numbers in octal, decimal, or hexadecimal in
17319 @value{GDBN} by the usual conventions: octal numbers begin with
17320 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17321 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17322 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17323 10; likewise, the default display for numbers---when no particular
17324 format is specified---is base 10. You can change the default base for
17325 both input and output with the commands described below.
17328 @kindex set input-radix
17329 @item set input-radix @var{base}
17330 Set the default base for numeric input. Supported choices
17331 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17332 specified either unambiguously or using the current input radix; for
17336 set input-radix 012
17337 set input-radix 10.
17338 set input-radix 0xa
17342 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17343 leaves the input radix unchanged, no matter what it was, since
17344 @samp{10}, being without any leading or trailing signs of its base, is
17345 interpreted in the current radix. Thus, if the current radix is 16,
17346 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17349 @kindex set output-radix
17350 @item set output-radix @var{base}
17351 Set the default base for numeric display. Supported choices
17352 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17353 specified either unambiguously or using the current input radix.
17355 @kindex show input-radix
17356 @item show input-radix
17357 Display the current default base for numeric input.
17359 @kindex show output-radix
17360 @item show output-radix
17361 Display the current default base for numeric display.
17363 @item set radix @r{[}@var{base}@r{]}
17367 These commands set and show the default base for both input and output
17368 of numbers. @code{set radix} sets the radix of input and output to
17369 the same base; without an argument, it resets the radix back to its
17370 default value of 10.
17375 @section Configuring the Current ABI
17377 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17378 application automatically. However, sometimes you need to override its
17379 conclusions. Use these commands to manage @value{GDBN}'s view of the
17386 One @value{GDBN} configuration can debug binaries for multiple operating
17387 system targets, either via remote debugging or native emulation.
17388 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17389 but you can override its conclusion using the @code{set osabi} command.
17390 One example where this is useful is in debugging of binaries which use
17391 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17392 not have the same identifying marks that the standard C library for your
17397 Show the OS ABI currently in use.
17400 With no argument, show the list of registered available OS ABI's.
17402 @item set osabi @var{abi}
17403 Set the current OS ABI to @var{abi}.
17406 @cindex float promotion
17408 Generally, the way that an argument of type @code{float} is passed to a
17409 function depends on whether the function is prototyped. For a prototyped
17410 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17411 according to the architecture's convention for @code{float}. For unprototyped
17412 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17413 @code{double} and then passed.
17415 Unfortunately, some forms of debug information do not reliably indicate whether
17416 a function is prototyped. If @value{GDBN} calls a function that is not marked
17417 as prototyped, it consults @kbd{set coerce-float-to-double}.
17420 @kindex set coerce-float-to-double
17421 @item set coerce-float-to-double
17422 @itemx set coerce-float-to-double on
17423 Arguments of type @code{float} will be promoted to @code{double} when passed
17424 to an unprototyped function. This is the default setting.
17426 @item set coerce-float-to-double off
17427 Arguments of type @code{float} will be passed directly to unprototyped
17430 @kindex show coerce-float-to-double
17431 @item show coerce-float-to-double
17432 Show the current setting of promoting @code{float} to @code{double}.
17436 @kindex show cp-abi
17437 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17438 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17439 used to build your application. @value{GDBN} only fully supports
17440 programs with a single C@t{++} ABI; if your program contains code using
17441 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17442 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17443 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17444 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17445 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17446 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17451 Show the C@t{++} ABI currently in use.
17454 With no argument, show the list of supported C@t{++} ABI's.
17456 @item set cp-abi @var{abi}
17457 @itemx set cp-abi auto
17458 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17461 @node Messages/Warnings
17462 @section Optional Warnings and Messages
17464 @cindex verbose operation
17465 @cindex optional warnings
17466 By default, @value{GDBN} is silent about its inner workings. If you are
17467 running on a slow machine, you may want to use the @code{set verbose}
17468 command. This makes @value{GDBN} tell you when it does a lengthy
17469 internal operation, so you will not think it has crashed.
17471 Currently, the messages controlled by @code{set verbose} are those
17472 which announce that the symbol table for a source file is being read;
17473 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17476 @kindex set verbose
17477 @item set verbose on
17478 Enables @value{GDBN} output of certain informational messages.
17480 @item set verbose off
17481 Disables @value{GDBN} output of certain informational messages.
17483 @kindex show verbose
17485 Displays whether @code{set verbose} is on or off.
17488 By default, if @value{GDBN} encounters bugs in the symbol table of an
17489 object file, it is silent; but if you are debugging a compiler, you may
17490 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17495 @kindex set complaints
17496 @item set complaints @var{limit}
17497 Permits @value{GDBN} to output @var{limit} complaints about each type of
17498 unusual symbols before becoming silent about the problem. Set
17499 @var{limit} to zero to suppress all complaints; set it to a large number
17500 to prevent complaints from being suppressed.
17502 @kindex show complaints
17503 @item show complaints
17504 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17508 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17509 lot of stupid questions to confirm certain commands. For example, if
17510 you try to run a program which is already running:
17514 The program being debugged has been started already.
17515 Start it from the beginning? (y or n)
17518 If you are willing to unflinchingly face the consequences of your own
17519 commands, you can disable this ``feature'':
17523 @kindex set confirm
17525 @cindex confirmation
17526 @cindex stupid questions
17527 @item set confirm off
17528 Disables confirmation requests.
17530 @item set confirm on
17531 Enables confirmation requests (the default).
17533 @kindex show confirm
17535 Displays state of confirmation requests.
17539 @cindex command tracing
17540 If you need to debug user-defined commands or sourced files you may find it
17541 useful to enable @dfn{command tracing}. In this mode each command will be
17542 printed as it is executed, prefixed with one or more @samp{+} symbols, the
17543 quantity denoting the call depth of each command.
17546 @kindex set trace-commands
17547 @cindex command scripts, debugging
17548 @item set trace-commands on
17549 Enable command tracing.
17550 @item set trace-commands off
17551 Disable command tracing.
17552 @item show trace-commands
17553 Display the current state of command tracing.
17556 @node Debugging Output
17557 @section Optional Messages about Internal Happenings
17558 @cindex optional debugging messages
17560 @value{GDBN} has commands that enable optional debugging messages from
17561 various @value{GDBN} subsystems; normally these commands are of
17562 interest to @value{GDBN} maintainers, or when reporting a bug. This
17563 section documents those commands.
17566 @kindex set exec-done-display
17567 @item set exec-done-display
17568 Turns on or off the notification of asynchronous commands'
17569 completion. When on, @value{GDBN} will print a message when an
17570 asynchronous command finishes its execution. The default is off.
17571 @kindex show exec-done-display
17572 @item show exec-done-display
17573 Displays the current setting of asynchronous command completion
17576 @cindex gdbarch debugging info
17577 @cindex architecture debugging info
17578 @item set debug arch
17579 Turns on or off display of gdbarch debugging info. The default is off
17581 @item show debug arch
17582 Displays the current state of displaying gdbarch debugging info.
17583 @item set debug aix-thread
17584 @cindex AIX threads
17585 Display debugging messages about inner workings of the AIX thread
17587 @item show debug aix-thread
17588 Show the current state of AIX thread debugging info display.
17589 @item set debug dwarf2-die
17590 @cindex DWARF2 DIEs
17591 Dump DWARF2 DIEs after they are read in.
17592 The value is the number of nesting levels to print.
17593 A value of zero turns off the display.
17594 @item show debug dwarf2-die
17595 Show the current state of DWARF2 DIE debugging.
17596 @item set debug displaced
17597 @cindex displaced stepping debugging info
17598 Turns on or off display of @value{GDBN} debugging info for the
17599 displaced stepping support. The default is off.
17600 @item show debug displaced
17601 Displays the current state of displaying @value{GDBN} debugging info
17602 related to displaced stepping.
17603 @item set debug event
17604 @cindex event debugging info
17605 Turns on or off display of @value{GDBN} event debugging info. The
17607 @item show debug event
17608 Displays the current state of displaying @value{GDBN} event debugging
17610 @item set debug expression
17611 @cindex expression debugging info
17612 Turns on or off display of debugging info about @value{GDBN}
17613 expression parsing. The default is off.
17614 @item show debug expression
17615 Displays the current state of displaying debugging info about
17616 @value{GDBN} expression parsing.
17617 @item set debug frame
17618 @cindex frame debugging info
17619 Turns on or off display of @value{GDBN} frame debugging info. The
17621 @item show debug frame
17622 Displays the current state of displaying @value{GDBN} frame debugging
17624 @item set debug infrun
17625 @cindex inferior debugging info
17626 Turns on or off display of @value{GDBN} debugging info for running the inferior.
17627 The default is off. @file{infrun.c} contains GDB's runtime state machine used
17628 for implementing operations such as single-stepping the inferior.
17629 @item show debug infrun
17630 Displays the current state of @value{GDBN} inferior debugging.
17631 @item set debug lin-lwp
17632 @cindex @sc{gnu}/Linux LWP debug messages
17633 @cindex Linux lightweight processes
17634 Turns on or off debugging messages from the Linux LWP debug support.
17635 @item show debug lin-lwp
17636 Show the current state of Linux LWP debugging messages.
17637 @item set debug lin-lwp-async
17638 @cindex @sc{gnu}/Linux LWP async debug messages
17639 @cindex Linux lightweight processes
17640 Turns on or off debugging messages from the Linux LWP async debug support.
17641 @item show debug lin-lwp-async
17642 Show the current state of Linux LWP async debugging messages.
17643 @item set debug observer
17644 @cindex observer debugging info
17645 Turns on or off display of @value{GDBN} observer debugging. This
17646 includes info such as the notification of observable events.
17647 @item show debug observer
17648 Displays the current state of observer debugging.
17649 @item set debug overload
17650 @cindex C@t{++} overload debugging info
17651 Turns on or off display of @value{GDBN} C@t{++} overload debugging
17652 info. This includes info such as ranking of functions, etc. The default
17654 @item show debug overload
17655 Displays the current state of displaying @value{GDBN} C@t{++} overload
17657 @cindex packets, reporting on stdout
17658 @cindex serial connections, debugging
17659 @cindex debug remote protocol
17660 @cindex remote protocol debugging
17661 @cindex display remote packets
17662 @item set debug remote
17663 Turns on or off display of reports on all packets sent back and forth across
17664 the serial line to the remote machine. The info is printed on the
17665 @value{GDBN} standard output stream. The default is off.
17666 @item show debug remote
17667 Displays the state of display of remote packets.
17668 @item set debug serial
17669 Turns on or off display of @value{GDBN} serial debugging info. The
17671 @item show debug serial
17672 Displays the current state of displaying @value{GDBN} serial debugging
17674 @item set debug solib-frv
17675 @cindex FR-V shared-library debugging
17676 Turns on or off debugging messages for FR-V shared-library code.
17677 @item show debug solib-frv
17678 Display the current state of FR-V shared-library code debugging
17680 @item set debug target
17681 @cindex target debugging info
17682 Turns on or off display of @value{GDBN} target debugging info. This info
17683 includes what is going on at the target level of GDB, as it happens. The
17684 default is 0. Set it to 1 to track events, and to 2 to also track the
17685 value of large memory transfers. Changes to this flag do not take effect
17686 until the next time you connect to a target or use the @code{run} command.
17687 @item show debug target
17688 Displays the current state of displaying @value{GDBN} target debugging
17690 @item set debug timestamp
17691 @cindex timestampping debugging info
17692 Turns on or off display of timestamps with @value{GDBN} debugging info.
17693 When enabled, seconds and microseconds are displayed before each debugging
17695 @item show debug timestamp
17696 Displays the current state of displaying timestamps with @value{GDBN}
17698 @item set debugvarobj
17699 @cindex variable object debugging info
17700 Turns on or off display of @value{GDBN} variable object debugging
17701 info. The default is off.
17702 @item show debugvarobj
17703 Displays the current state of displaying @value{GDBN} variable object
17705 @item set debug xml
17706 @cindex XML parser debugging
17707 Turns on or off debugging messages for built-in XML parsers.
17708 @item show debug xml
17709 Displays the current state of XML debugging messages.
17712 @node Extending GDB
17713 @chapter Extending @value{GDBN}
17714 @cindex extending GDB
17716 @value{GDBN} provides two mechanisms for extension. The first is based
17717 on composition of @value{GDBN} commands, and the second is based on the
17718 Python scripting language.
17721 * Sequences:: Canned Sequences of Commands
17722 * Python:: Scripting @value{GDBN} using Python
17726 @section Canned Sequences of Commands
17728 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
17729 Command Lists}), @value{GDBN} provides two ways to store sequences of
17730 commands for execution as a unit: user-defined commands and command
17734 * Define:: How to define your own commands
17735 * Hooks:: Hooks for user-defined commands
17736 * Command Files:: How to write scripts of commands to be stored in a file
17737 * Output:: Commands for controlled output
17741 @subsection User-defined Commands
17743 @cindex user-defined command
17744 @cindex arguments, to user-defined commands
17745 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
17746 which you assign a new name as a command. This is done with the
17747 @code{define} command. User commands may accept up to 10 arguments
17748 separated by whitespace. Arguments are accessed within the user command
17749 via @code{$arg0@dots{}$arg9}. A trivial example:
17753 print $arg0 + $arg1 + $arg2
17758 To execute the command use:
17765 This defines the command @code{adder}, which prints the sum of
17766 its three arguments. Note the arguments are text substitutions, so they may
17767 reference variables, use complex expressions, or even perform inferior
17770 @cindex argument count in user-defined commands
17771 @cindex how many arguments (user-defined commands)
17772 In addition, @code{$argc} may be used to find out how many arguments have
17773 been passed. This expands to a number in the range 0@dots{}10.
17778 print $arg0 + $arg1
17781 print $arg0 + $arg1 + $arg2
17789 @item define @var{commandname}
17790 Define a command named @var{commandname}. If there is already a command
17791 by that name, you are asked to confirm that you want to redefine it.
17792 @var{commandname} may be a bare command name consisting of letters,
17793 numbers, dashes, and underscores. It may also start with any predefined
17794 prefix command. For example, @samp{define target my-target} creates
17795 a user-defined @samp{target my-target} command.
17797 The definition of the command is made up of other @value{GDBN} command lines,
17798 which are given following the @code{define} command. The end of these
17799 commands is marked by a line containing @code{end}.
17802 @kindex end@r{ (user-defined commands)}
17803 @item document @var{commandname}
17804 Document the user-defined command @var{commandname}, so that it can be
17805 accessed by @code{help}. The command @var{commandname} must already be
17806 defined. This command reads lines of documentation just as @code{define}
17807 reads the lines of the command definition, ending with @code{end}.
17808 After the @code{document} command is finished, @code{help} on command
17809 @var{commandname} displays the documentation you have written.
17811 You may use the @code{document} command again to change the
17812 documentation of a command. Redefining the command with @code{define}
17813 does not change the documentation.
17815 @kindex dont-repeat
17816 @cindex don't repeat command
17818 Used inside a user-defined command, this tells @value{GDBN} that this
17819 command should not be repeated when the user hits @key{RET}
17820 (@pxref{Command Syntax, repeat last command}).
17822 @kindex help user-defined
17823 @item help user-defined
17824 List all user-defined commands, with the first line of the documentation
17829 @itemx show user @var{commandname}
17830 Display the @value{GDBN} commands used to define @var{commandname} (but
17831 not its documentation). If no @var{commandname} is given, display the
17832 definitions for all user-defined commands.
17834 @cindex infinite recursion in user-defined commands
17835 @kindex show max-user-call-depth
17836 @kindex set max-user-call-depth
17837 @item show max-user-call-depth
17838 @itemx set max-user-call-depth
17839 The value of @code{max-user-call-depth} controls how many recursion
17840 levels are allowed in user-defined commands before @value{GDBN} suspects an
17841 infinite recursion and aborts the command.
17844 In addition to the above commands, user-defined commands frequently
17845 use control flow commands, described in @ref{Command Files}.
17847 When user-defined commands are executed, the
17848 commands of the definition are not printed. An error in any command
17849 stops execution of the user-defined command.
17851 If used interactively, commands that would ask for confirmation proceed
17852 without asking when used inside a user-defined command. Many @value{GDBN}
17853 commands that normally print messages to say what they are doing omit the
17854 messages when used in a user-defined command.
17857 @subsection User-defined Command Hooks
17858 @cindex command hooks
17859 @cindex hooks, for commands
17860 @cindex hooks, pre-command
17863 You may define @dfn{hooks}, which are a special kind of user-defined
17864 command. Whenever you run the command @samp{foo}, if the user-defined
17865 command @samp{hook-foo} exists, it is executed (with no arguments)
17866 before that command.
17868 @cindex hooks, post-command
17870 A hook may also be defined which is run after the command you executed.
17871 Whenever you run the command @samp{foo}, if the user-defined command
17872 @samp{hookpost-foo} exists, it is executed (with no arguments) after
17873 that command. Post-execution hooks may exist simultaneously with
17874 pre-execution hooks, for the same command.
17876 It is valid for a hook to call the command which it hooks. If this
17877 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
17879 @c It would be nice if hookpost could be passed a parameter indicating
17880 @c if the command it hooks executed properly or not. FIXME!
17882 @kindex stop@r{, a pseudo-command}
17883 In addition, a pseudo-command, @samp{stop} exists. Defining
17884 (@samp{hook-stop}) makes the associated commands execute every time
17885 execution stops in your program: before breakpoint commands are run,
17886 displays are printed, or the stack frame is printed.
17888 For example, to ignore @code{SIGALRM} signals while
17889 single-stepping, but treat them normally during normal execution,
17894 handle SIGALRM nopass
17898 handle SIGALRM pass
17901 define hook-continue
17902 handle SIGALRM pass
17906 As a further example, to hook at the beginning and end of the @code{echo}
17907 command, and to add extra text to the beginning and end of the message,
17915 define hookpost-echo
17919 (@value{GDBP}) echo Hello World
17920 <<<---Hello World--->>>
17925 You can define a hook for any single-word command in @value{GDBN}, but
17926 not for command aliases; you should define a hook for the basic command
17927 name, e.g.@: @code{backtrace} rather than @code{bt}.
17928 @c FIXME! So how does Joe User discover whether a command is an alias
17930 You can hook a multi-word command by adding @code{hook-} or
17931 @code{hookpost-} to the last word of the command, e.g.@:
17932 @samp{define target hook-remote} to add a hook to @samp{target remote}.
17934 If an error occurs during the execution of your hook, execution of
17935 @value{GDBN} commands stops and @value{GDBN} issues a prompt
17936 (before the command that you actually typed had a chance to run).
17938 If you try to define a hook which does not match any known command, you
17939 get a warning from the @code{define} command.
17941 @node Command Files
17942 @subsection Command Files
17944 @cindex command files
17945 @cindex scripting commands
17946 A command file for @value{GDBN} is a text file made of lines that are
17947 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
17948 also be included. An empty line in a command file does nothing; it
17949 does not mean to repeat the last command, as it would from the
17952 You can request the execution of a command file with the @code{source}
17957 @cindex execute commands from a file
17958 @item source [@code{-v}] @var{filename}
17959 Execute the command file @var{filename}.
17962 The lines in a command file are generally executed sequentially,
17963 unless the order of execution is changed by one of the
17964 @emph{flow-control commands} described below. The commands are not
17965 printed as they are executed. An error in any command terminates
17966 execution of the command file and control is returned to the console.
17968 @value{GDBN} searches for @var{filename} in the current directory and then
17969 on the search path (specified with the @samp{directory} command).
17971 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
17972 each command as it is executed. The option must be given before
17973 @var{filename}, and is interpreted as part of the filename anywhere else.
17975 Commands that would ask for confirmation if used interactively proceed
17976 without asking when used in a command file. Many @value{GDBN} commands that
17977 normally print messages to say what they are doing omit the messages
17978 when called from command files.
17980 @value{GDBN} also accepts command input from standard input. In this
17981 mode, normal output goes to standard output and error output goes to
17982 standard error. Errors in a command file supplied on standard input do
17983 not terminate execution of the command file---execution continues with
17987 gdb < cmds > log 2>&1
17990 (The syntax above will vary depending on the shell used.) This example
17991 will execute commands from the file @file{cmds}. All output and errors
17992 would be directed to @file{log}.
17994 Since commands stored on command files tend to be more general than
17995 commands typed interactively, they frequently need to deal with
17996 complicated situations, such as different or unexpected values of
17997 variables and symbols, changes in how the program being debugged is
17998 built, etc. @value{GDBN} provides a set of flow-control commands to
17999 deal with these complexities. Using these commands, you can write
18000 complex scripts that loop over data structures, execute commands
18001 conditionally, etc.
18008 This command allows to include in your script conditionally executed
18009 commands. The @code{if} command takes a single argument, which is an
18010 expression to evaluate. It is followed by a series of commands that
18011 are executed only if the expression is true (its value is nonzero).
18012 There can then optionally be an @code{else} line, followed by a series
18013 of commands that are only executed if the expression was false. The
18014 end of the list is marked by a line containing @code{end}.
18018 This command allows to write loops. Its syntax is similar to
18019 @code{if}: the command takes a single argument, which is an expression
18020 to evaluate, and must be followed by the commands to execute, one per
18021 line, terminated by an @code{end}. These commands are called the
18022 @dfn{body} of the loop. The commands in the body of @code{while} are
18023 executed repeatedly as long as the expression evaluates to true.
18027 This command exits the @code{while} loop in whose body it is included.
18028 Execution of the script continues after that @code{while}s @code{end}
18031 @kindex loop_continue
18032 @item loop_continue
18033 This command skips the execution of the rest of the body of commands
18034 in the @code{while} loop in whose body it is included. Execution
18035 branches to the beginning of the @code{while} loop, where it evaluates
18036 the controlling expression.
18038 @kindex end@r{ (if/else/while commands)}
18040 Terminate the block of commands that are the body of @code{if},
18041 @code{else}, or @code{while} flow-control commands.
18046 @subsection Commands for Controlled Output
18048 During the execution of a command file or a user-defined command, normal
18049 @value{GDBN} output is suppressed; the only output that appears is what is
18050 explicitly printed by the commands in the definition. This section
18051 describes three commands useful for generating exactly the output you
18056 @item echo @var{text}
18057 @c I do not consider backslash-space a standard C escape sequence
18058 @c because it is not in ANSI.
18059 Print @var{text}. Nonprinting characters can be included in
18060 @var{text} using C escape sequences, such as @samp{\n} to print a
18061 newline. @strong{No newline is printed unless you specify one.}
18062 In addition to the standard C escape sequences, a backslash followed
18063 by a space stands for a space. This is useful for displaying a
18064 string with spaces at the beginning or the end, since leading and
18065 trailing spaces are otherwise trimmed from all arguments.
18066 To print @samp{@w{ }and foo =@w{ }}, use the command
18067 @samp{echo \@w{ }and foo = \@w{ }}.
18069 A backslash at the end of @var{text} can be used, as in C, to continue
18070 the command onto subsequent lines. For example,
18073 echo This is some text\n\
18074 which is continued\n\
18075 onto several lines.\n
18078 produces the same output as
18081 echo This is some text\n
18082 echo which is continued\n
18083 echo onto several lines.\n
18087 @item output @var{expression}
18088 Print the value of @var{expression} and nothing but that value: no
18089 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18090 value history either. @xref{Expressions, ,Expressions}, for more information
18093 @item output/@var{fmt} @var{expression}
18094 Print the value of @var{expression} in format @var{fmt}. You can use
18095 the same formats as for @code{print}. @xref{Output Formats,,Output
18096 Formats}, for more information.
18099 @item printf @var{template}, @var{expressions}@dots{}
18100 Print the values of one or more @var{expressions} under the control of
18101 the string @var{template}. To print several values, make
18102 @var{expressions} be a comma-separated list of individual expressions,
18103 which may be either numbers or pointers. Their values are printed as
18104 specified by @var{template}, exactly as a C program would do by
18105 executing the code below:
18108 printf (@var{template}, @var{expressions}@dots{});
18111 As in @code{C} @code{printf}, ordinary characters in @var{template}
18112 are printed verbatim, while @dfn{conversion specification} introduced
18113 by the @samp{%} character cause subsequent @var{expressions} to be
18114 evaluated, their values converted and formatted according to type and
18115 style information encoded in the conversion specifications, and then
18118 For example, you can print two values in hex like this:
18121 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18124 @code{printf} supports all the standard @code{C} conversion
18125 specifications, including the flags and modifiers between the @samp{%}
18126 character and the conversion letter, with the following exceptions:
18130 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18133 The modifier @samp{*} is not supported for specifying precision or
18137 The @samp{'} flag (for separation of digits into groups according to
18138 @code{LC_NUMERIC'}) is not supported.
18141 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18145 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18148 The conversion letters @samp{a} and @samp{A} are not supported.
18152 Note that the @samp{ll} type modifier is supported only if the
18153 underlying @code{C} implementation used to build @value{GDBN} supports
18154 the @code{long long int} type, and the @samp{L} type modifier is
18155 supported only if @code{long double} type is available.
18157 As in @code{C}, @code{printf} supports simple backslash-escape
18158 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18159 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18160 single character. Octal and hexadecimal escape sequences are not
18163 Additionally, @code{printf} supports conversion specifications for DFP
18164 (@dfn{Decimal Floating Point}) types using the following length modifiers
18165 together with a floating point specifier.
18170 @samp{H} for printing @code{Decimal32} types.
18173 @samp{D} for printing @code{Decimal64} types.
18176 @samp{DD} for printing @code{Decimal128} types.
18179 If the underlying @code{C} implementation used to build @value{GDBN} has
18180 support for the three length modifiers for DFP types, other modifiers
18181 such as width and precision will also be available for @value{GDBN} to use.
18183 In case there is no such @code{C} support, no additional modifiers will be
18184 available and the value will be printed in the standard way.
18186 Here's an example of printing DFP types using the above conversion letters:
18188 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18194 @section Scripting @value{GDBN} using Python
18195 @cindex python scripting
18196 @cindex scripting with python
18198 You can script @value{GDBN} using the @uref{http://www.python.org/,
18199 Python programming language}. This feature is available only if
18200 @value{GDBN} was configured using @option{--with-python}.
18203 * Python Commands:: Accessing Python from @value{GDBN}.
18204 * Python API:: Accessing @value{GDBN} from Python.
18207 @node Python Commands
18208 @subsection Python Commands
18209 @cindex python commands
18210 @cindex commands to access python
18212 @value{GDBN} provides one command for accessing the Python interpreter,
18213 and one related setting:
18217 @item python @r{[}@var{code}@r{]}
18218 The @code{python} command can be used to evaluate Python code.
18220 If given an argument, the @code{python} command will evaluate the
18221 argument as a Python command. For example:
18224 (@value{GDBP}) python print 23
18228 If you do not provide an argument to @code{python}, it will act as a
18229 multi-line command, like @code{define}. In this case, the Python
18230 script is made up of subsequent command lines, given after the
18231 @code{python} command. This command list is terminated using a line
18232 containing @code{end}. For example:
18235 (@value{GDBP}) python
18237 End with a line saying just "end".
18243 @kindex maint set python print-stack
18244 @item maint set python print-stack
18245 By default, @value{GDBN} will print a stack trace when an error occurs
18246 in a Python script. This can be controlled using @code{maint set
18247 python print-stack}: if @code{on}, the default, then Python stack
18248 printing is enabled; if @code{off}, then Python stack printing is
18253 @subsection Python API
18255 @cindex programming in python
18257 @cindex python stdout
18258 @cindex python pagination
18259 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18260 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18261 A Python program which outputs to one of these streams may have its
18262 output interrupted by the user (@pxref{Screen Size}). In this
18263 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18266 * Basic Python:: Basic Python Functions.
18267 * Exception Handling::
18268 * Values From Inferior::
18269 * Commands In Python:: Implementing new commands in Python.
18270 * Functions In Python:: Writing new convenience functions.
18271 * Frames In Python:: Acessing inferior stack frames from Python.
18275 @subsubsection Basic Python
18277 @cindex python functions
18278 @cindex python module
18280 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18281 methods and classes added by @value{GDBN} are placed in this module.
18282 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18283 use in all scripts evaluated by the @code{python} command.
18285 @findex gdb.execute
18286 @defun execute command [from_tty]
18287 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18288 If a GDB exception happens while @var{command} runs, it is
18289 translated as described in @ref{Exception Handling,,Exception Handling}.
18290 If no exceptions occur, this function returns @code{None}.
18292 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18293 command as having originated from the user invoking it interactively.
18294 It must be a boolean value. If omitted, it defaults to @code{False}.
18297 @findex gdb.get_parameter
18298 @defun get_parameter parameter
18299 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18300 string naming the parameter to look up; @var{parameter} may contain
18301 spaces if the parameter has a multi-part name. For example,
18302 @samp{print object} is a valid parameter name.
18304 If the named parameter does not exist, this function throws a
18305 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18306 a Python value of the appropriate type, and returned.
18309 @findex gdb.history
18310 @defun history number
18311 Return a value from @value{GDBN}'s value history (@pxref{Value
18312 History}). @var{number} indicates which history element to return.
18313 If @var{number} is negative, then @value{GDBN} will take its absolute value
18314 and count backward from the last element (i.e., the most recent element) to
18315 find the value to return. If @var{number} is zero, then @value{GDBN} will
18316 return the most recent element. If the element specified by @var{number}
18317 doesn't exist in the value history, a @code{RuntimeError} exception will be
18320 If no exception is raised, the return value is always an instance of
18321 @code{gdb.Value} (@pxref{Values From Inferior}).
18325 @defun write string
18326 Print a string to @value{GDBN}'s paginated standard output stream.
18327 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18328 call this function.
18333 Flush @value{GDBN}'s paginated standard output stream. Flushing
18334 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18338 @node Exception Handling
18339 @subsubsection Exception Handling
18340 @cindex python exceptions
18341 @cindex exceptions, python
18343 When executing the @code{python} command, Python exceptions
18344 uncaught within the Python code are translated to calls to
18345 @value{GDBN} error-reporting mechanism. If the command that called
18346 @code{python} does not handle the error, @value{GDBN} will
18347 terminate it and print an error message containing the Python
18348 exception name, the associated value, and the Python call stack
18349 backtrace at the point where the exception was raised. Example:
18352 (@value{GDBP}) python print foo
18353 Traceback (most recent call last):
18354 File "<string>", line 1, in <module>
18355 NameError: name 'foo' is not defined
18358 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18359 code are converted to Python @code{RuntimeError} exceptions. User
18360 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18361 prompt) is translated to a Python @code{KeyboardInterrupt}
18362 exception. If you catch these exceptions in your Python code, your
18363 exception handler will see @code{RuntimeError} or
18364 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18365 message as its value, and the Python call stack backtrace at the
18366 Python statement closest to where the @value{GDBN} error occured as the
18369 @node Values From Inferior
18370 @subsubsection Values From Inferior
18371 @cindex values from inferior, with Python
18372 @cindex python, working with values from inferior
18374 @cindex @code{gdb.Value}
18375 @value{GDBN} provides values it obtains from the inferior program in
18376 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18377 for its internal bookkeeping of the inferior's values, and for
18378 fetching values when necessary.
18380 Inferior values that are simple scalars can be used directly in
18381 Python expressions that are valid for the value's data type. Here's
18382 an example for an integer or floating-point value @code{some_val}:
18389 As result of this, @code{bar} will also be a @code{gdb.Value} object
18390 whose values are of the same type as those of @code{some_val}.
18392 Inferior values that are structures or instances of some class can
18393 be accessed using the Python @dfn{dictionary syntax}. For example, if
18394 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18395 can access its @code{foo} element with:
18398 bar = some_val['foo']
18401 Again, @code{bar} will also be a @code{gdb.Value} object.
18403 The following attributes are provided:
18406 @defmethod Value address
18407 If this object is addressable, this read-only attribute holds a
18408 @code{gdb.Value} object representing the address. Otherwise,
18409 this attribute holds @code{None}.
18412 @cindex optimized out value in Python
18413 @defmethod Value is_optimized_out
18414 This read-only boolean attribute is true if the compiler optimized out
18415 this value, thus it is not available for fetching from the inferior.
18419 The following methods are provided:
18422 @defmethod Value dereference
18423 For pointer data types, this method returns a new @code{gdb.Value} object
18424 whose contents is the object pointed to by the pointer. For example, if
18425 @code{foo} is a C pointer to an @code{int}, declared in your C program as
18432 then you can use the corresponding @code{gdb.Value} to access what
18433 @code{foo} points to like this:
18436 bar = foo.dereference ()
18439 The result @code{bar} will be a @code{gdb.Value} object holding the
18440 value pointed to by @code{foo}.
18443 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]}
18444 If this @code{gdb.Value} represents a string, then this method
18445 converts the contents to a Python string. Otherwise, this method will
18446 throw an exception.
18448 Strings are recognized in a language-specific way; whether a given
18449 @code{gdb.Value} represents a string is determined by the current
18452 For C-like languages, a value is a string if it is a pointer to or an
18453 array of characters or ints. The string is assumed to be terminated
18454 by a zero of the appropriate width.
18456 If the optional @var{encoding} argument is given, it must be a string
18457 naming the encoding of the string in the @code{gdb.Value}, such as
18458 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18459 the same encodings as the corresponding argument to Python's
18460 @code{string.decode} method, and the Python codec machinery will be used
18461 to convert the string. If @var{encoding} is not given, or if
18462 @var{encoding} is the empty string, then either the @code{target-charset}
18463 (@pxref{Character Sets}) will be used, or a language-specific encoding
18464 will be used, if the current language is able to supply one.
18466 The optional @var{errors} argument is the same as the corresponding
18467 argument to Python's @code{string.decode} method.
18471 @node Commands In Python
18472 @subsubsection Commands In Python
18474 @cindex commands in python
18475 @cindex python commands
18476 You can implement new @value{GDBN} CLI commands in Python. A CLI
18477 command is implemented using an instance of the @code{gdb.Command}
18478 class, most commonly using a subclass.
18480 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
18481 The object initializer for @code{Command} registers the new command
18482 with @value{GDBN}. This initializer is normally invoked from the
18483 subclass' own @code{__init__} method.
18485 @var{name} is the name of the command. If @var{name} consists of
18486 multiple words, then the initial words are looked for as prefix
18487 commands. In this case, if one of the prefix commands does not exist,
18488 an exception is raised.
18490 There is no support for multi-line commands.
18492 @var{command_class} should be one of the @samp{COMMAND_} constants
18493 defined below. This argument tells @value{GDBN} how to categorize the
18494 new command in the help system.
18496 @var{completer_class} is an optional argument. If given, it should be
18497 one of the @samp{COMPLETE_} constants defined below. This argument
18498 tells @value{GDBN} how to perform completion for this command. If not
18499 given, @value{GDBN} will attempt to complete using the object's
18500 @code{complete} method (see below); if no such method is found, an
18501 error will occur when completion is attempted.
18503 @var{prefix} is an optional argument. If @code{True}, then the new
18504 command is a prefix command; sub-commands of this command may be
18507 The help text for the new command is taken from the Python
18508 documentation string for the command's class, if there is one. If no
18509 documentation string is provided, the default value ``This command is
18510 not documented.'' is used.
18513 @cindex don't repeat Python command
18514 @defmethod Command dont_repeat
18515 By default, a @value{GDBN} command is repeated when the user enters a
18516 blank line at the command prompt. A command can suppress this
18517 behavior by invoking the @code{dont_repeat} method. This is similar
18518 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
18521 @defmethod Command invoke argument from_tty
18522 This method is called by @value{GDBN} when this command is invoked.
18524 @var{argument} is a string. It is the argument to the command, after
18525 leading and trailing whitespace has been stripped.
18527 @var{from_tty} is a boolean argument. When true, this means that the
18528 command was entered by the user at the terminal; when false it means
18529 that the command came from elsewhere.
18531 If this method throws an exception, it is turned into a @value{GDBN}
18532 @code{error} call. Otherwise, the return value is ignored.
18535 @cindex completion of Python commands
18536 @defmethod Command complete text word
18537 This method is called by @value{GDBN} when the user attempts
18538 completion on this command. All forms of completion are handled by
18539 this method, that is, the @key{TAB} and @key{M-?} key bindings
18540 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
18543 The arguments @var{text} and @var{word} are both strings. @var{text}
18544 holds the complete command line up to the cursor's location.
18545 @var{word} holds the last word of the command line; this is computed
18546 using a word-breaking heuristic.
18548 The @code{complete} method can return several values:
18551 If the return value is a sequence, the contents of the sequence are
18552 used as the completions. It is up to @code{complete} to ensure that the
18553 contents actually do complete the word. A zero-length sequence is
18554 allowed, it means that there were no completions available. Only
18555 string elements of the sequence are used; other elements in the
18556 sequence are ignored.
18559 If the return value is one of the @samp{COMPLETE_} constants defined
18560 below, then the corresponding @value{GDBN}-internal completion
18561 function is invoked, and its result is used.
18564 All other results are treated as though there were no available
18569 When a new command is registered, it must be declared as a member of
18570 some general class of commands. This is used to classify top-level
18571 commands in the on-line help system; note that prefix commands are not
18572 listed under their own category but rather that of their top-level
18573 command. The available classifications are represented by constants
18574 defined in the @code{gdb} module:
18577 @findex COMMAND_NONE
18578 @findex gdb.COMMAND_NONE
18580 The command does not belong to any particular class. A command in
18581 this category will not be displayed in any of the help categories.
18583 @findex COMMAND_RUNNING
18584 @findex gdb.COMMAND_RUNNING
18585 @item COMMAND_RUNNING
18586 The command is related to running the inferior. For example,
18587 @code{start}, @code{step}, and @code{continue} are in this category.
18588 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
18589 commands in this category.
18591 @findex COMMAND_DATA
18592 @findex gdb.COMMAND_DATA
18594 The command is related to data or variables. For example,
18595 @code{call}, @code{find}, and @code{print} are in this category. Type
18596 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
18599 @findex COMMAND_STACK
18600 @findex gdb.COMMAND_STACK
18601 @item COMMAND_STACK
18602 The command has to do with manipulation of the stack. For example,
18603 @code{backtrace}, @code{frame}, and @code{return} are in this
18604 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
18605 list of commands in this category.
18607 @findex COMMAND_FILES
18608 @findex gdb.COMMAND_FILES
18609 @item COMMAND_FILES
18610 This class is used for file-related commands. For example,
18611 @code{file}, @code{list} and @code{section} are in this category.
18612 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
18613 commands in this category.
18615 @findex COMMAND_SUPPORT
18616 @findex gdb.COMMAND_SUPPORT
18617 @item COMMAND_SUPPORT
18618 This should be used for ``support facilities'', generally meaning
18619 things that are useful to the user when interacting with @value{GDBN},
18620 but not related to the state of the inferior. For example,
18621 @code{help}, @code{make}, and @code{shell} are in this category. Type
18622 @kbd{help support} at the @value{GDBN} prompt to see a list of
18623 commands in this category.
18625 @findex COMMAND_STATUS
18626 @findex gdb.COMMAND_STATUS
18627 @item COMMAND_STATUS
18628 The command is an @samp{info}-related command, that is, related to the
18629 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
18630 and @code{show} are in this category. Type @kbd{help status} at the
18631 @value{GDBN} prompt to see a list of commands in this category.
18633 @findex COMMAND_BREAKPOINTS
18634 @findex gdb.COMMAND_BREAKPOINTS
18635 @item COMMAND_BREAKPOINTS
18636 The command has to do with breakpoints. For example, @code{break},
18637 @code{clear}, and @code{delete} are in this category. Type @kbd{help
18638 breakpoints} at the @value{GDBN} prompt to see a list of commands in
18641 @findex COMMAND_TRACEPOINTS
18642 @findex gdb.COMMAND_TRACEPOINTS
18643 @item COMMAND_TRACEPOINTS
18644 The command has to do with tracepoints. For example, @code{trace},
18645 @code{actions}, and @code{tfind} are in this category. Type
18646 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
18647 commands in this category.
18649 @findex COMMAND_OBSCURE
18650 @findex gdb.COMMAND_OBSCURE
18651 @item COMMAND_OBSCURE
18652 The command is only used in unusual circumstances, or is not of
18653 general interest to users. For example, @code{checkpoint},
18654 @code{fork}, and @code{stop} are in this category. Type @kbd{help
18655 obscure} at the @value{GDBN} prompt to see a list of commands in this
18658 @findex COMMAND_MAINTENANCE
18659 @findex gdb.COMMAND_MAINTENANCE
18660 @item COMMAND_MAINTENANCE
18661 The command is only useful to @value{GDBN} maintainers. The
18662 @code{maintenance} and @code{flushregs} commands are in this category.
18663 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
18664 commands in this category.
18667 A new command can use a predefined completion function, either by
18668 specifying it via an argument at initialization, or by returning it
18669 from the @code{complete} method. These predefined completion
18670 constants are all defined in the @code{gdb} module:
18673 @findex COMPLETE_NONE
18674 @findex gdb.COMPLETE_NONE
18675 @item COMPLETE_NONE
18676 This constant means that no completion should be done.
18678 @findex COMPLETE_FILENAME
18679 @findex gdb.COMPLETE_FILENAME
18680 @item COMPLETE_FILENAME
18681 This constant means that filename completion should be performed.
18683 @findex COMPLETE_LOCATION
18684 @findex gdb.COMPLETE_LOCATION
18685 @item COMPLETE_LOCATION
18686 This constant means that location completion should be done.
18687 @xref{Specify Location}.
18689 @findex COMPLETE_COMMAND
18690 @findex gdb.COMPLETE_COMMAND
18691 @item COMPLETE_COMMAND
18692 This constant means that completion should examine @value{GDBN}
18695 @findex COMPLETE_SYMBOL
18696 @findex gdb.COMPLETE_SYMBOL
18697 @item COMPLETE_SYMBOL
18698 This constant means that completion should be done using symbol names
18702 The following code snippet shows how a trivial CLI command can be
18703 implemented in Python:
18706 class HelloWorld (gdb.Command):
18707 """Greet the whole world."""
18709 def __init__ (self):
18710 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
18712 def invoke (self, arg, from_tty):
18713 print "Hello, World!"
18718 The last line instantiates the class, and is necessary to trigger the
18719 registration of the command with @value{GDBN}. Depending on how the
18720 Python code is read into @value{GDBN}, you may need to import the
18721 @code{gdb} module explicitly.
18723 @node Functions In Python
18724 @subsubsection Writing new convenience functions
18726 @cindex writing convenience functions
18727 @cindex convenience functions in python
18728 @cindex python convenience functions
18729 @tindex gdb.Function
18731 You can implement new convenience functions (@pxref{Convenience Vars})
18732 in Python. A convenience function is an instance of a subclass of the
18733 class @code{gdb.Function}.
18735 @defmethod Function __init__ name
18736 The initializer for @code{Function} registers the new function with
18737 @value{GDBN}. The argument @var{name} is the name of the function,
18738 a string. The function will be visible to the user as a convenience
18739 variable of type @code{internal function}, whose name is the same as
18740 the given @var{name}.
18742 The documentation for the new function is taken from the documentation
18743 string for the new class.
18746 @defmethod Function invoke @var{*args}
18747 When a convenience function is evaluated, its arguments are converted
18748 to instances of @code{gdb.Value}, and then the function's
18749 @code{invoke} method is called. Note that @value{GDBN} does not
18750 predetermine the arity of convenience functions. Instead, all
18751 available arguments are passed to @code{invoke}, following the
18752 standard Python calling convention. In particular, a convenience
18753 function can have default values for parameters without ill effect.
18755 The return value of this method is used as its value in the enclosing
18756 expression. If an ordinary Python value is returned, it is converted
18757 to a @code{gdb.Value} following the usual rules.
18760 The following code snippet shows how a trivial convenience function can
18761 be implemented in Python:
18764 class Greet (gdb.Function):
18765 """Return string to greet someone.
18766 Takes a name as argument."""
18768 def __init__ (self):
18769 super (Greet, self).__init__ ("greet")
18771 def invoke (self, name):
18772 return "Hello, %s!" % name.string ()
18777 The last line instantiates the class, and is necessary to trigger the
18778 registration of the function with @value{GDBN}. Depending on how the
18779 Python code is read into @value{GDBN}, you may need to import the
18780 @code{gdb} module explicitly.
18782 @node Frames In Python
18783 @subsubsection Acessing inferior stack frames from Python.
18785 @cindex frames in python
18786 When the debugged program stops, @value{GDBN} is able to analyze its call
18787 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
18788 represents a frame in the stack. A @code{gdb.Frame} object is only valid
18789 while its corresponding frame exists in the inferior's stack. If you try
18790 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
18793 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
18797 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
18801 The following frame-related functions are available in the @code{gdb} module:
18803 @findex gdb.selected_frame
18804 @defun selected_frame
18805 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
18808 @defun frame_stop_reason_string reason
18809 Return a string explaining the reason why @value{GDBN} stopped unwinding
18810 frames, as expressed by the given @var{reason} code (an integer, see the
18811 @code{unwind_stop_reason} method further down in this section).
18814 A @code{gdb.Frame} object has the following methods:
18817 @defmethod Frame is_valid
18818 Returns true if the @code{gdb.Frame} object is valid, false if not.
18819 A frame object can become invalid if the frame it refers to doesn't
18820 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
18821 an exception if it is invalid at the time the method is called.
18824 @defmethod Frame name
18825 Returns the function name of the frame, or @code{None} if it can't be
18829 @defmethod Frame type
18830 Returns the type of the frame. The value can be one of
18831 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
18832 or @code{gdb.SENTINEL_FRAME}.
18835 @defmethod Frame unwind_stop_reason
18836 Return an integer representing the reason why it's not possible to find
18837 more frames toward the outermost frame. Use
18838 @code{gdb.frame_stop_reason_string} to convert the value returned by this
18839 function to a string.
18842 @defmethod Frame pc
18843 Returns the frame's resume address.
18846 @defmethod Frame older
18847 Return the frame that called this frame.
18850 @defmethod Frame newer
18851 Return the frame called by this frame.
18854 @defmethod Frame read_var variable
18855 Return the value of the given variable in this frame. @var{variable} must
18861 @chapter Command Interpreters
18862 @cindex command interpreters
18864 @value{GDBN} supports multiple command interpreters, and some command
18865 infrastructure to allow users or user interface writers to switch
18866 between interpreters or run commands in other interpreters.
18868 @value{GDBN} currently supports two command interpreters, the console
18869 interpreter (sometimes called the command-line interpreter or @sc{cli})
18870 and the machine interface interpreter (or @sc{gdb/mi}). This manual
18871 describes both of these interfaces in great detail.
18873 By default, @value{GDBN} will start with the console interpreter.
18874 However, the user may choose to start @value{GDBN} with another
18875 interpreter by specifying the @option{-i} or @option{--interpreter}
18876 startup options. Defined interpreters include:
18880 @cindex console interpreter
18881 The traditional console or command-line interpreter. This is the most often
18882 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
18883 @value{GDBN} will use this interpreter.
18886 @cindex mi interpreter
18887 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
18888 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
18889 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
18893 @cindex mi2 interpreter
18894 The current @sc{gdb/mi} interface.
18897 @cindex mi1 interpreter
18898 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
18902 @cindex invoke another interpreter
18903 The interpreter being used by @value{GDBN} may not be dynamically
18904 switched at runtime. Although possible, this could lead to a very
18905 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
18906 enters the command "interpreter-set console" in a console view,
18907 @value{GDBN} would switch to using the console interpreter, rendering
18908 the IDE inoperable!
18910 @kindex interpreter-exec
18911 Although you may only choose a single interpreter at startup, you may execute
18912 commands in any interpreter from the current interpreter using the appropriate
18913 command. If you are running the console interpreter, simply use the
18914 @code{interpreter-exec} command:
18917 interpreter-exec mi "-data-list-register-names"
18920 @sc{gdb/mi} has a similar command, although it is only available in versions of
18921 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
18924 @chapter @value{GDBN} Text User Interface
18926 @cindex Text User Interface
18929 * TUI Overview:: TUI overview
18930 * TUI Keys:: TUI key bindings
18931 * TUI Single Key Mode:: TUI single key mode
18932 * TUI Commands:: TUI-specific commands
18933 * TUI Configuration:: TUI configuration variables
18936 The @value{GDBN} Text User Interface (TUI) is a terminal
18937 interface which uses the @code{curses} library to show the source
18938 file, the assembly output, the program registers and @value{GDBN}
18939 commands in separate text windows. The TUI mode is supported only
18940 on platforms where a suitable version of the @code{curses} library
18943 @pindex @value{GDBTUI}
18944 The TUI mode is enabled by default when you invoke @value{GDBN} as
18945 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
18946 You can also switch in and out of TUI mode while @value{GDBN} runs by
18947 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
18948 @xref{TUI Keys, ,TUI Key Bindings}.
18951 @section TUI Overview
18953 In TUI mode, @value{GDBN} can display several text windows:
18957 This window is the @value{GDBN} command window with the @value{GDBN}
18958 prompt and the @value{GDBN} output. The @value{GDBN} input is still
18959 managed using readline.
18962 The source window shows the source file of the program. The current
18963 line and active breakpoints are displayed in this window.
18966 The assembly window shows the disassembly output of the program.
18969 This window shows the processor registers. Registers are highlighted
18970 when their values change.
18973 The source and assembly windows show the current program position
18974 by highlighting the current line and marking it with a @samp{>} marker.
18975 Breakpoints are indicated with two markers. The first marker
18976 indicates the breakpoint type:
18980 Breakpoint which was hit at least once.
18983 Breakpoint which was never hit.
18986 Hardware breakpoint which was hit at least once.
18989 Hardware breakpoint which was never hit.
18992 The second marker indicates whether the breakpoint is enabled or not:
18996 Breakpoint is enabled.
18999 Breakpoint is disabled.
19002 The source, assembly and register windows are updated when the current
19003 thread changes, when the frame changes, or when the program counter
19006 These windows are not all visible at the same time. The command
19007 window is always visible. The others can be arranged in several
19018 source and assembly,
19021 source and registers, or
19024 assembly and registers.
19027 A status line above the command window shows the following information:
19031 Indicates the current @value{GDBN} target.
19032 (@pxref{Targets, ,Specifying a Debugging Target}).
19035 Gives the current process or thread number.
19036 When no process is being debugged, this field is set to @code{No process}.
19039 Gives the current function name for the selected frame.
19040 The name is demangled if demangling is turned on (@pxref{Print Settings}).
19041 When there is no symbol corresponding to the current program counter,
19042 the string @code{??} is displayed.
19045 Indicates the current line number for the selected frame.
19046 When the current line number is not known, the string @code{??} is displayed.
19049 Indicates the current program counter address.
19053 @section TUI Key Bindings
19054 @cindex TUI key bindings
19056 The TUI installs several key bindings in the readline keymaps
19057 (@pxref{Command Line Editing}). The following key bindings
19058 are installed for both TUI mode and the @value{GDBN} standard mode.
19067 Enter or leave the TUI mode. When leaving the TUI mode,
19068 the curses window management stops and @value{GDBN} operates using
19069 its standard mode, writing on the terminal directly. When reentering
19070 the TUI mode, control is given back to the curses windows.
19071 The screen is then refreshed.
19075 Use a TUI layout with only one window. The layout will
19076 either be @samp{source} or @samp{assembly}. When the TUI mode
19077 is not active, it will switch to the TUI mode.
19079 Think of this key binding as the Emacs @kbd{C-x 1} binding.
19083 Use a TUI layout with at least two windows. When the current
19084 layout already has two windows, the next layout with two windows is used.
19085 When a new layout is chosen, one window will always be common to the
19086 previous layout and the new one.
19088 Think of it as the Emacs @kbd{C-x 2} binding.
19092 Change the active window. The TUI associates several key bindings
19093 (like scrolling and arrow keys) with the active window. This command
19094 gives the focus to the next TUI window.
19096 Think of it as the Emacs @kbd{C-x o} binding.
19100 Switch in and out of the TUI SingleKey mode that binds single
19101 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
19104 The following key bindings only work in the TUI mode:
19109 Scroll the active window one page up.
19113 Scroll the active window one page down.
19117 Scroll the active window one line up.
19121 Scroll the active window one line down.
19125 Scroll the active window one column left.
19129 Scroll the active window one column right.
19133 Refresh the screen.
19136 Because the arrow keys scroll the active window in the TUI mode, they
19137 are not available for their normal use by readline unless the command
19138 window has the focus. When another window is active, you must use
19139 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
19140 and @kbd{C-f} to control the command window.
19142 @node TUI Single Key Mode
19143 @section TUI Single Key Mode
19144 @cindex TUI single key mode
19146 The TUI also provides a @dfn{SingleKey} mode, which binds several
19147 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
19148 switch into this mode, where the following key bindings are used:
19151 @kindex c @r{(SingleKey TUI key)}
19155 @kindex d @r{(SingleKey TUI key)}
19159 @kindex f @r{(SingleKey TUI key)}
19163 @kindex n @r{(SingleKey TUI key)}
19167 @kindex q @r{(SingleKey TUI key)}
19169 exit the SingleKey mode.
19171 @kindex r @r{(SingleKey TUI key)}
19175 @kindex s @r{(SingleKey TUI key)}
19179 @kindex u @r{(SingleKey TUI key)}
19183 @kindex v @r{(SingleKey TUI key)}
19187 @kindex w @r{(SingleKey TUI key)}
19192 Other keys temporarily switch to the @value{GDBN} command prompt.
19193 The key that was pressed is inserted in the editing buffer so that
19194 it is possible to type most @value{GDBN} commands without interaction
19195 with the TUI SingleKey mode. Once the command is entered the TUI
19196 SingleKey mode is restored. The only way to permanently leave
19197 this mode is by typing @kbd{q} or @kbd{C-x s}.
19201 @section TUI-specific Commands
19202 @cindex TUI commands
19204 The TUI has specific commands to control the text windows.
19205 These commands are always available, even when @value{GDBN} is not in
19206 the TUI mode. When @value{GDBN} is in the standard mode, most
19207 of these commands will automatically switch to the TUI mode.
19212 List and give the size of all displayed windows.
19216 Display the next layout.
19219 Display the previous layout.
19222 Display the source window only.
19225 Display the assembly window only.
19228 Display the source and assembly window.
19231 Display the register window together with the source or assembly window.
19235 Make the next window active for scrolling.
19238 Make the previous window active for scrolling.
19241 Make the source window active for scrolling.
19244 Make the assembly window active for scrolling.
19247 Make the register window active for scrolling.
19250 Make the command window active for scrolling.
19254 Refresh the screen. This is similar to typing @kbd{C-L}.
19256 @item tui reg float
19258 Show the floating point registers in the register window.
19260 @item tui reg general
19261 Show the general registers in the register window.
19264 Show the next register group. The list of register groups as well as
19265 their order is target specific. The predefined register groups are the
19266 following: @code{general}, @code{float}, @code{system}, @code{vector},
19267 @code{all}, @code{save}, @code{restore}.
19269 @item tui reg system
19270 Show the system registers in the register window.
19274 Update the source window and the current execution point.
19276 @item winheight @var{name} +@var{count}
19277 @itemx winheight @var{name} -@var{count}
19279 Change the height of the window @var{name} by @var{count}
19280 lines. Positive counts increase the height, while negative counts
19283 @item tabset @var{nchars}
19285 Set the width of tab stops to be @var{nchars} characters.
19288 @node TUI Configuration
19289 @section TUI Configuration Variables
19290 @cindex TUI configuration variables
19292 Several configuration variables control the appearance of TUI windows.
19295 @item set tui border-kind @var{kind}
19296 @kindex set tui border-kind
19297 Select the border appearance for the source, assembly and register windows.
19298 The possible values are the following:
19301 Use a space character to draw the border.
19304 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
19307 Use the Alternate Character Set to draw the border. The border is
19308 drawn using character line graphics if the terminal supports them.
19311 @item set tui border-mode @var{mode}
19312 @kindex set tui border-mode
19313 @itemx set tui active-border-mode @var{mode}
19314 @kindex set tui active-border-mode
19315 Select the display attributes for the borders of the inactive windows
19316 or the active window. The @var{mode} can be one of the following:
19319 Use normal attributes to display the border.
19325 Use reverse video mode.
19328 Use half bright mode.
19330 @item half-standout
19331 Use half bright and standout mode.
19334 Use extra bright or bold mode.
19336 @item bold-standout
19337 Use extra bright or bold and standout mode.
19342 @chapter Using @value{GDBN} under @sc{gnu} Emacs
19345 @cindex @sc{gnu} Emacs
19346 A special interface allows you to use @sc{gnu} Emacs to view (and
19347 edit) the source files for the program you are debugging with
19350 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
19351 executable file you want to debug as an argument. This command starts
19352 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
19353 created Emacs buffer.
19354 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
19356 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
19361 All ``terminal'' input and output goes through an Emacs buffer, called
19364 This applies both to @value{GDBN} commands and their output, and to the input
19365 and output done by the program you are debugging.
19367 This is useful because it means that you can copy the text of previous
19368 commands and input them again; you can even use parts of the output
19371 All the facilities of Emacs' Shell mode are available for interacting
19372 with your program. In particular, you can send signals the usual
19373 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
19377 @value{GDBN} displays source code through Emacs.
19379 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
19380 source file for that frame and puts an arrow (@samp{=>}) at the
19381 left margin of the current line. Emacs uses a separate buffer for
19382 source display, and splits the screen to show both your @value{GDBN} session
19385 Explicit @value{GDBN} @code{list} or search commands still produce output as
19386 usual, but you probably have no reason to use them from Emacs.
19389 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
19390 a graphical mode, enabled by default, which provides further buffers
19391 that can control the execution and describe the state of your program.
19392 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
19394 If you specify an absolute file name when prompted for the @kbd{M-x
19395 gdb} argument, then Emacs sets your current working directory to where
19396 your program resides. If you only specify the file name, then Emacs
19397 sets your current working directory to to the directory associated
19398 with the previous buffer. In this case, @value{GDBN} may find your
19399 program by searching your environment's @code{PATH} variable, but on
19400 some operating systems it might not find the source. So, although the
19401 @value{GDBN} input and output session proceeds normally, the auxiliary
19402 buffer does not display the current source and line of execution.
19404 The initial working directory of @value{GDBN} is printed on the top
19405 line of the GUD buffer and this serves as a default for the commands
19406 that specify files for @value{GDBN} to operate on. @xref{Files,
19407 ,Commands to Specify Files}.
19409 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
19410 need to call @value{GDBN} by a different name (for example, if you
19411 keep several configurations around, with different names) you can
19412 customize the Emacs variable @code{gud-gdb-command-name} to run the
19415 In the GUD buffer, you can use these special Emacs commands in
19416 addition to the standard Shell mode commands:
19420 Describe the features of Emacs' GUD Mode.
19423 Execute to another source line, like the @value{GDBN} @code{step} command; also
19424 update the display window to show the current file and location.
19427 Execute to next source line in this function, skipping all function
19428 calls, like the @value{GDBN} @code{next} command. Then update the display window
19429 to show the current file and location.
19432 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
19433 display window accordingly.
19436 Execute until exit from the selected stack frame, like the @value{GDBN}
19437 @code{finish} command.
19440 Continue execution of your program, like the @value{GDBN} @code{continue}
19444 Go up the number of frames indicated by the numeric argument
19445 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
19446 like the @value{GDBN} @code{up} command.
19449 Go down the number of frames indicated by the numeric argument, like the
19450 @value{GDBN} @code{down} command.
19453 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
19454 tells @value{GDBN} to set a breakpoint on the source line point is on.
19456 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
19457 separate frame which shows a backtrace when the GUD buffer is current.
19458 Move point to any frame in the stack and type @key{RET} to make it
19459 become the current frame and display the associated source in the
19460 source buffer. Alternatively, click @kbd{Mouse-2} to make the
19461 selected frame become the current one. In graphical mode, the
19462 speedbar displays watch expressions.
19464 If you accidentally delete the source-display buffer, an easy way to get
19465 it back is to type the command @code{f} in the @value{GDBN} buffer, to
19466 request a frame display; when you run under Emacs, this recreates
19467 the source buffer if necessary to show you the context of the current
19470 The source files displayed in Emacs are in ordinary Emacs buffers
19471 which are visiting the source files in the usual way. You can edit
19472 the files with these buffers if you wish; but keep in mind that @value{GDBN}
19473 communicates with Emacs in terms of line numbers. If you add or
19474 delete lines from the text, the line numbers that @value{GDBN} knows cease
19475 to correspond properly with the code.
19477 A more detailed description of Emacs' interaction with @value{GDBN} is
19478 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
19481 @c The following dropped because Epoch is nonstandard. Reactivate
19482 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
19484 @kindex Emacs Epoch environment
19488 Version 18 of @sc{gnu} Emacs has a built-in window system
19489 called the @code{epoch}
19490 environment. Users of this environment can use a new command,
19491 @code{inspect} which performs identically to @code{print} except that
19492 each value is printed in its own window.
19497 @chapter The @sc{gdb/mi} Interface
19499 @unnumberedsec Function and Purpose
19501 @cindex @sc{gdb/mi}, its purpose
19502 @sc{gdb/mi} is a line based machine oriented text interface to
19503 @value{GDBN} and is activated by specifying using the
19504 @option{--interpreter} command line option (@pxref{Mode Options}). It
19505 is specifically intended to support the development of systems which
19506 use the debugger as just one small component of a larger system.
19508 This chapter is a specification of the @sc{gdb/mi} interface. It is written
19509 in the form of a reference manual.
19511 Note that @sc{gdb/mi} is still under construction, so some of the
19512 features described below are incomplete and subject to change
19513 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
19515 @unnumberedsec Notation and Terminology
19517 @cindex notational conventions, for @sc{gdb/mi}
19518 This chapter uses the following notation:
19522 @code{|} separates two alternatives.
19525 @code{[ @var{something} ]} indicates that @var{something} is optional:
19526 it may or may not be given.
19529 @code{( @var{group} )*} means that @var{group} inside the parentheses
19530 may repeat zero or more times.
19533 @code{( @var{group} )+} means that @var{group} inside the parentheses
19534 may repeat one or more times.
19537 @code{"@var{string}"} means a literal @var{string}.
19541 @heading Dependencies
19545 * GDB/MI General Design::
19546 * GDB/MI Command Syntax::
19547 * GDB/MI Compatibility with CLI::
19548 * GDB/MI Development and Front Ends::
19549 * GDB/MI Output Records::
19550 * GDB/MI Simple Examples::
19551 * GDB/MI Command Description Format::
19552 * GDB/MI Breakpoint Commands::
19553 * GDB/MI Program Context::
19554 * GDB/MI Thread Commands::
19555 * GDB/MI Program Execution::
19556 * GDB/MI Stack Manipulation::
19557 * GDB/MI Variable Objects::
19558 * GDB/MI Data Manipulation::
19559 * GDB/MI Tracepoint Commands::
19560 * GDB/MI Symbol Query::
19561 * GDB/MI File Commands::
19563 * GDB/MI Kod Commands::
19564 * GDB/MI Memory Overlay Commands::
19565 * GDB/MI Signal Handling Commands::
19567 * GDB/MI Target Manipulation::
19568 * GDB/MI File Transfer Commands::
19569 * GDB/MI Miscellaneous Commands::
19572 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19573 @node GDB/MI General Design
19574 @section @sc{gdb/mi} General Design
19575 @cindex GDB/MI General Design
19577 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
19578 parts---commands sent to @value{GDBN}, responses to those commands
19579 and notifications. Each command results in exactly one response,
19580 indicating either successful completion of the command, or an error.
19581 For the commands that do not resume the target, the response contains the
19582 requested information. For the commands that resume the target, the
19583 response only indicates whether the target was successfully resumed.
19584 Notifications is the mechanism for reporting changes in the state of the
19585 target, or in @value{GDBN} state, that cannot conveniently be associated with
19586 a command and reported as part of that command response.
19588 The important examples of notifications are:
19592 Exec notifications. These are used to report changes in
19593 target state---when a target is resumed, or stopped. It would not
19594 be feasible to include this information in response of resuming
19595 commands, because one resume commands can result in multiple events in
19596 different threads. Also, quite some time may pass before any event
19597 happens in the target, while a frontend needs to know whether the resuming
19598 command itself was successfully executed.
19601 Console output, and status notifications. Console output
19602 notifications are used to report output of CLI commands, as well as
19603 diagnostics for other commands. Status notifications are used to
19604 report the progress of a long-running operation. Naturally, including
19605 this information in command response would mean no output is produced
19606 until the command is finished, which is undesirable.
19609 General notifications. Commands may have various side effects on
19610 the @value{GDBN} or target state beyond their official purpose. For example,
19611 a command may change the selected thread. Although such changes can
19612 be included in command response, using notification allows for more
19613 orthogonal frontend design.
19617 There's no guarantee that whenever an MI command reports an error,
19618 @value{GDBN} or the target are in any specific state, and especially,
19619 the state is not reverted to the state before the MI command was
19620 processed. Therefore, whenever an MI command results in an error,
19621 we recommend that the frontend refreshes all the information shown in
19622 the user interface.
19624 @subsection Context management
19626 In most cases when @value{GDBN} accesses the target, this access is
19627 done in context of a specific thread and frame (@pxref{Frames}).
19628 Often, even when accessing global data, the target requires that a thread
19629 be specified. The CLI interface maintains the selected thread and frame,
19630 and supplies them to target on each command. This is convenient,
19631 because a command line user would not want to specify that information
19632 explicitly on each command, and because user interacts with
19633 @value{GDBN} via a single terminal, so no confusion is possible as
19634 to what thread and frame are the current ones.
19636 In the case of MI, the concept of selected thread and frame is less
19637 useful. First, a frontend can easily remember this information
19638 itself. Second, a graphical frontend can have more than one window,
19639 each one used for debugging a different thread, and the frontend might
19640 want to access additional threads for internal purposes. This
19641 increases the risk that by relying on implicitly selected thread, the
19642 frontend may be operating on a wrong one. Therefore, each MI command
19643 should explicitly specify which thread and frame to operate on. To
19644 make it possible, each MI command accepts the @samp{--thread} and
19645 @samp{--frame} options, the value to each is @value{GDBN} identifier
19646 for thread and frame to operate on.
19648 Usually, each top-level window in a frontend allows the user to select
19649 a thread and a frame, and remembers the user selection for further
19650 operations. However, in some cases @value{GDBN} may suggest that the
19651 current thread be changed. For example, when stopping on a breakpoint
19652 it is reasonable to switch to the thread where breakpoint is hit. For
19653 another example, if the user issues the CLI @samp{thread} command via
19654 the frontend, it is desirable to change the frontend's selected thread to the
19655 one specified by user. @value{GDBN} communicates the suggestion to
19656 change current thread using the @samp{=thread-selected} notification.
19657 No such notification is available for the selected frame at the moment.
19659 Note that historically, MI shares the selected thread with CLI, so
19660 frontends used the @code{-thread-select} to execute commands in the
19661 right context. However, getting this to work right is cumbersome. The
19662 simplest way is for frontend to emit @code{-thread-select} command
19663 before every command. This doubles the number of commands that need
19664 to be sent. The alternative approach is to suppress @code{-thread-select}
19665 if the selected thread in @value{GDBN} is supposed to be identical to the
19666 thread the frontend wants to operate on. However, getting this
19667 optimization right can be tricky. In particular, if the frontend
19668 sends several commands to @value{GDBN}, and one of the commands changes the
19669 selected thread, then the behaviour of subsequent commands will
19670 change. So, a frontend should either wait for response from such
19671 problematic commands, or explicitly add @code{-thread-select} for
19672 all subsequent commands. No frontend is known to do this exactly
19673 right, so it is suggested to just always pass the @samp{--thread} and
19674 @samp{--frame} options.
19676 @subsection Asynchronous command execution and non-stop mode
19678 On some targets, @value{GDBN} is capable of processing MI commands
19679 even while the target is running. This is called @dfn{asynchronous
19680 command execution} (@pxref{Background Execution}). The frontend may
19681 specify a preferrence for asynchronous execution using the
19682 @code{-gdb-set target-async 1} command, which should be emitted before
19683 either running the executable or attaching to the target. After the
19684 frontend has started the executable or attached to the target, it can
19685 find if asynchronous execution is enabled using the
19686 @code{-list-target-features} command.
19688 Even if @value{GDBN} can accept a command while target is running,
19689 many commands that access the target do not work when the target is
19690 running. Therefore, asynchronous command execution is most useful
19691 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
19692 it is possible to examine the state of one thread, while other threads
19695 When a given thread is running, MI commands that try to access the
19696 target in the context of that thread may not work, or may work only on
19697 some targets. In particular, commands that try to operate on thread's
19698 stack will not work, on any target. Commands that read memory, or
19699 modify breakpoints, may work or not work, depending on the target. Note
19700 that even commands that operate on global state, such as @code{print},
19701 @code{set}, and breakpoint commands, still access the target in the
19702 context of a specific thread, so frontend should try to find a
19703 stopped thread and perform the operation on that thread (using the
19704 @samp{--thread} option).
19706 Which commands will work in the context of a running thread is
19707 highly target dependent. However, the two commands
19708 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
19709 to find the state of a thread, will always work.
19711 @subsection Thread groups
19712 @value{GDBN} may be used to debug several processes at the same time.
19713 On some platfroms, @value{GDBN} may support debugging of several
19714 hardware systems, each one having several cores with several different
19715 processes running on each core. This section describes the MI
19716 mechanism to support such debugging scenarios.
19718 The key observation is that regardless of the structure of the
19719 target, MI can have a global list of threads, because most commands that
19720 accept the @samp{--thread} option do not need to know what process that
19721 thread belongs to. Therefore, it is not necessary to introduce
19722 neither additional @samp{--process} option, nor an notion of the
19723 current process in the MI interface. The only strictly new feature
19724 that is required is the ability to find how the threads are grouped
19727 To allow the user to discover such grouping, and to support arbitrary
19728 hierarchy of machines/cores/processes, MI introduces the concept of a
19729 @dfn{thread group}. Thread group is a collection of threads and other
19730 thread groups. A thread group always has a string identifier, a type,
19731 and may have additional attributes specific to the type. A new
19732 command, @code{-list-thread-groups}, returns the list of top-level
19733 thread groups, which correspond to processes that @value{GDBN} is
19734 debugging at the moment. By passing an identifier of a thread group
19735 to the @code{-list-thread-groups} command, it is possible to obtain
19736 the members of specific thread group.
19738 To allow the user to easily discover processes, and other objects, he
19739 wishes to debug, a concept of @dfn{available thread group} is
19740 introduced. Available thread group is an thread group that
19741 @value{GDBN} is not debugging, but that can be attached to, using the
19742 @code{-target-attach} command. The list of available top-level thread
19743 groups can be obtained using @samp{-list-thread-groups --available}.
19744 In general, the content of a thread group may be only retrieved only
19745 after attaching to that thread group.
19747 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19748 @node GDB/MI Command Syntax
19749 @section @sc{gdb/mi} Command Syntax
19752 * GDB/MI Input Syntax::
19753 * GDB/MI Output Syntax::
19756 @node GDB/MI Input Syntax
19757 @subsection @sc{gdb/mi} Input Syntax
19759 @cindex input syntax for @sc{gdb/mi}
19760 @cindex @sc{gdb/mi}, input syntax
19762 @item @var{command} @expansion{}
19763 @code{@var{cli-command} | @var{mi-command}}
19765 @item @var{cli-command} @expansion{}
19766 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
19767 @var{cli-command} is any existing @value{GDBN} CLI command.
19769 @item @var{mi-command} @expansion{}
19770 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
19771 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
19773 @item @var{token} @expansion{}
19774 "any sequence of digits"
19776 @item @var{option} @expansion{}
19777 @code{"-" @var{parameter} [ " " @var{parameter} ]}
19779 @item @var{parameter} @expansion{}
19780 @code{@var{non-blank-sequence} | @var{c-string}}
19782 @item @var{operation} @expansion{}
19783 @emph{any of the operations described in this chapter}
19785 @item @var{non-blank-sequence} @expansion{}
19786 @emph{anything, provided it doesn't contain special characters such as
19787 "-", @var{nl}, """ and of course " "}
19789 @item @var{c-string} @expansion{}
19790 @code{""" @var{seven-bit-iso-c-string-content} """}
19792 @item @var{nl} @expansion{}
19801 The CLI commands are still handled by the @sc{mi} interpreter; their
19802 output is described below.
19805 The @code{@var{token}}, when present, is passed back when the command
19809 Some @sc{mi} commands accept optional arguments as part of the parameter
19810 list. Each option is identified by a leading @samp{-} (dash) and may be
19811 followed by an optional argument parameter. Options occur first in the
19812 parameter list and can be delimited from normal parameters using
19813 @samp{--} (this is useful when some parameters begin with a dash).
19820 We want easy access to the existing CLI syntax (for debugging).
19823 We want it to be easy to spot a @sc{mi} operation.
19826 @node GDB/MI Output Syntax
19827 @subsection @sc{gdb/mi} Output Syntax
19829 @cindex output syntax of @sc{gdb/mi}
19830 @cindex @sc{gdb/mi}, output syntax
19831 The output from @sc{gdb/mi} consists of zero or more out-of-band records
19832 followed, optionally, by a single result record. This result record
19833 is for the most recent command. The sequence of output records is
19834 terminated by @samp{(gdb)}.
19836 If an input command was prefixed with a @code{@var{token}} then the
19837 corresponding output for that command will also be prefixed by that same
19841 @item @var{output} @expansion{}
19842 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
19844 @item @var{result-record} @expansion{}
19845 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
19847 @item @var{out-of-band-record} @expansion{}
19848 @code{@var{async-record} | @var{stream-record}}
19850 @item @var{async-record} @expansion{}
19851 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
19853 @item @var{exec-async-output} @expansion{}
19854 @code{[ @var{token} ] "*" @var{async-output}}
19856 @item @var{status-async-output} @expansion{}
19857 @code{[ @var{token} ] "+" @var{async-output}}
19859 @item @var{notify-async-output} @expansion{}
19860 @code{[ @var{token} ] "=" @var{async-output}}
19862 @item @var{async-output} @expansion{}
19863 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
19865 @item @var{result-class} @expansion{}
19866 @code{"done" | "running" | "connected" | "error" | "exit"}
19868 @item @var{async-class} @expansion{}
19869 @code{"stopped" | @var{others}} (where @var{others} will be added
19870 depending on the needs---this is still in development).
19872 @item @var{result} @expansion{}
19873 @code{ @var{variable} "=" @var{value}}
19875 @item @var{variable} @expansion{}
19876 @code{ @var{string} }
19878 @item @var{value} @expansion{}
19879 @code{ @var{const} | @var{tuple} | @var{list} }
19881 @item @var{const} @expansion{}
19882 @code{@var{c-string}}
19884 @item @var{tuple} @expansion{}
19885 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
19887 @item @var{list} @expansion{}
19888 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
19889 @var{result} ( "," @var{result} )* "]" }
19891 @item @var{stream-record} @expansion{}
19892 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
19894 @item @var{console-stream-output} @expansion{}
19895 @code{"~" @var{c-string}}
19897 @item @var{target-stream-output} @expansion{}
19898 @code{"@@" @var{c-string}}
19900 @item @var{log-stream-output} @expansion{}
19901 @code{"&" @var{c-string}}
19903 @item @var{nl} @expansion{}
19906 @item @var{token} @expansion{}
19907 @emph{any sequence of digits}.
19915 All output sequences end in a single line containing a period.
19918 The @code{@var{token}} is from the corresponding request. Note that
19919 for all async output, while the token is allowed by the grammar and
19920 may be output by future versions of @value{GDBN} for select async
19921 output messages, it is generally omitted. Frontends should treat
19922 all async output as reporting general changes in the state of the
19923 target and there should be no need to associate async output to any
19927 @cindex status output in @sc{gdb/mi}
19928 @var{status-async-output} contains on-going status information about the
19929 progress of a slow operation. It can be discarded. All status output is
19930 prefixed by @samp{+}.
19933 @cindex async output in @sc{gdb/mi}
19934 @var{exec-async-output} contains asynchronous state change on the target
19935 (stopped, started, disappeared). All async output is prefixed by
19939 @cindex notify output in @sc{gdb/mi}
19940 @var{notify-async-output} contains supplementary information that the
19941 client should handle (e.g., a new breakpoint information). All notify
19942 output is prefixed by @samp{=}.
19945 @cindex console output in @sc{gdb/mi}
19946 @var{console-stream-output} is output that should be displayed as is in the
19947 console. It is the textual response to a CLI command. All the console
19948 output is prefixed by @samp{~}.
19951 @cindex target output in @sc{gdb/mi}
19952 @var{target-stream-output} is the output produced by the target program.
19953 All the target output is prefixed by @samp{@@}.
19956 @cindex log output in @sc{gdb/mi}
19957 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
19958 instance messages that should be displayed as part of an error log. All
19959 the log output is prefixed by @samp{&}.
19962 @cindex list output in @sc{gdb/mi}
19963 New @sc{gdb/mi} commands should only output @var{lists} containing
19969 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
19970 details about the various output records.
19972 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19973 @node GDB/MI Compatibility with CLI
19974 @section @sc{gdb/mi} Compatibility with CLI
19976 @cindex compatibility, @sc{gdb/mi} and CLI
19977 @cindex @sc{gdb/mi}, compatibility with CLI
19979 For the developers convenience CLI commands can be entered directly,
19980 but there may be some unexpected behaviour. For example, commands
19981 that query the user will behave as if the user replied yes, breakpoint
19982 command lists are not executed and some CLI commands, such as
19983 @code{if}, @code{when} and @code{define}, prompt for further input with
19984 @samp{>}, which is not valid MI output.
19986 This feature may be removed at some stage in the future and it is
19987 recommended that front ends use the @code{-interpreter-exec} command
19988 (@pxref{-interpreter-exec}).
19990 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19991 @node GDB/MI Development and Front Ends
19992 @section @sc{gdb/mi} Development and Front Ends
19993 @cindex @sc{gdb/mi} development
19995 The application which takes the MI output and presents the state of the
19996 program being debugged to the user is called a @dfn{front end}.
19998 Although @sc{gdb/mi} is still incomplete, it is currently being used
19999 by a variety of front ends to @value{GDBN}. This makes it difficult
20000 to introduce new functionality without breaking existing usage. This
20001 section tries to minimize the problems by describing how the protocol
20004 Some changes in MI need not break a carefully designed front end, and
20005 for these the MI version will remain unchanged. The following is a
20006 list of changes that may occur within one level, so front ends should
20007 parse MI output in a way that can handle them:
20011 New MI commands may be added.
20014 New fields may be added to the output of any MI command.
20017 The range of values for fields with specified values, e.g.,
20018 @code{in_scope} (@pxref{-var-update}) may be extended.
20020 @c The format of field's content e.g type prefix, may change so parse it
20021 @c at your own risk. Yes, in general?
20023 @c The order of fields may change? Shouldn't really matter but it might
20024 @c resolve inconsistencies.
20027 If the changes are likely to break front ends, the MI version level
20028 will be increased by one. This will allow the front end to parse the
20029 output according to the MI version. Apart from mi0, new versions of
20030 @value{GDBN} will not support old versions of MI and it will be the
20031 responsibility of the front end to work with the new one.
20033 @c Starting with mi3, add a new command -mi-version that prints the MI
20036 The best way to avoid unexpected changes in MI that might break your front
20037 end is to make your project known to @value{GDBN} developers and
20038 follow development on @email{gdb@@sourceware.org} and
20039 @email{gdb-patches@@sourceware.org}.
20040 @cindex mailing lists
20042 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20043 @node GDB/MI Output Records
20044 @section @sc{gdb/mi} Output Records
20047 * GDB/MI Result Records::
20048 * GDB/MI Stream Records::
20049 * GDB/MI Async Records::
20050 * GDB/MI Frame Information::
20053 @node GDB/MI Result Records
20054 @subsection @sc{gdb/mi} Result Records
20056 @cindex result records in @sc{gdb/mi}
20057 @cindex @sc{gdb/mi}, result records
20058 In addition to a number of out-of-band notifications, the response to a
20059 @sc{gdb/mi} command includes one of the following result indications:
20063 @item "^done" [ "," @var{results} ]
20064 The synchronous operation was successful, @code{@var{results}} are the return
20069 @c Is this one correct? Should it be an out-of-band notification?
20070 The asynchronous operation was successfully started. The target is
20075 @value{GDBN} has connected to a remote target.
20077 @item "^error" "," @var{c-string}
20079 The operation failed. The @code{@var{c-string}} contains the corresponding
20084 @value{GDBN} has terminated.
20088 @node GDB/MI Stream Records
20089 @subsection @sc{gdb/mi} Stream Records
20091 @cindex @sc{gdb/mi}, stream records
20092 @cindex stream records in @sc{gdb/mi}
20093 @value{GDBN} internally maintains a number of output streams: the console, the
20094 target, and the log. The output intended for each of these streams is
20095 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
20097 Each stream record begins with a unique @dfn{prefix character} which
20098 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
20099 Syntax}). In addition to the prefix, each stream record contains a
20100 @code{@var{string-output}}. This is either raw text (with an implicit new
20101 line) or a quoted C string (which does not contain an implicit newline).
20104 @item "~" @var{string-output}
20105 The console output stream contains text that should be displayed in the
20106 CLI console window. It contains the textual responses to CLI commands.
20108 @item "@@" @var{string-output}
20109 The target output stream contains any textual output from the running
20110 target. This is only present when GDB's event loop is truly
20111 asynchronous, which is currently only the case for remote targets.
20113 @item "&" @var{string-output}
20114 The log stream contains debugging messages being produced by @value{GDBN}'s
20118 @node GDB/MI Async Records
20119 @subsection @sc{gdb/mi} Async Records
20121 @cindex async records in @sc{gdb/mi}
20122 @cindex @sc{gdb/mi}, async records
20123 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
20124 additional changes that have occurred. Those changes can either be a
20125 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
20126 target activity (e.g., target stopped).
20128 The following is the list of possible async records:
20132 @item *running,thread-id="@var{thread}"
20133 The target is now running. The @var{thread} field tells which
20134 specific thread is now running, and can be @samp{all} if all threads
20135 are running. The frontend should assume that no interaction with a
20136 running thread is possible after this notification is produced.
20137 The frontend should not assume that this notification is output
20138 only once for any command. @value{GDBN} may emit this notification
20139 several times, either for different threads, because it cannot resume
20140 all threads together, or even for a single thread, if the thread must
20141 be stepped though some code before letting it run freely.
20143 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
20144 The target has stopped. The @var{reason} field can have one of the
20148 @item breakpoint-hit
20149 A breakpoint was reached.
20150 @item watchpoint-trigger
20151 A watchpoint was triggered.
20152 @item read-watchpoint-trigger
20153 A read watchpoint was triggered.
20154 @item access-watchpoint-trigger
20155 An access watchpoint was triggered.
20156 @item function-finished
20157 An -exec-finish or similar CLI command was accomplished.
20158 @item location-reached
20159 An -exec-until or similar CLI command was accomplished.
20160 @item watchpoint-scope
20161 A watchpoint has gone out of scope.
20162 @item end-stepping-range
20163 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
20164 similar CLI command was accomplished.
20165 @item exited-signalled
20166 The inferior exited because of a signal.
20168 The inferior exited.
20169 @item exited-normally
20170 The inferior exited normally.
20171 @item signal-received
20172 A signal was received by the inferior.
20175 The @var{id} field identifies the thread that directly caused the stop
20176 -- for example by hitting a breakpoint. Depending on whether all-stop
20177 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
20178 stop all threads, or only the thread that directly triggered the stop.
20179 If all threads are stopped, the @var{stopped} field will have the
20180 value of @code{"all"}. Otherwise, the value of the @var{stopped}
20181 field will be a list of thread identifiers. Presently, this list will
20182 always include a single thread, but frontend should be prepared to see
20183 several threads in the list.
20185 @item =thread-group-created,id="@var{id}"
20186 @itemx =thread-group-exited,id="@var{id}"
20187 A thread thread group either was attached to, or has exited/detached
20188 from. The @var{id} field contains the @value{GDBN} identifier of the
20191 @item =thread-created,id="@var{id}",group-id="@var{gid}"
20192 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
20193 A thread either was created, or has exited. The @var{id} field
20194 contains the @value{GDBN} identifier of the thread. The @var{gid}
20195 field identifies the thread group this thread belongs to.
20197 @item =thread-selected,id="@var{id}"
20198 Informs that the selected thread was changed as result of the last
20199 command. This notification is not emitted as result of @code{-thread-select}
20200 command but is emitted whenever an MI command that is not documented
20201 to change the selected thread actually changes it. In particular,
20202 invoking, directly or indirectly (via user-defined command), the CLI
20203 @code{thread} command, will generate this notification.
20205 We suggest that in response to this notification, front ends
20206 highlight the selected thread and cause subsequent commands to apply to
20209 @item =library-loaded,...
20210 Reports that a new library file was loaded by the program. This
20211 notification has 4 fields---@var{id}, @var{target-name},
20212 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
20213 opaque identifier of the library. For remote debugging case,
20214 @var{target-name} and @var{host-name} fields give the name of the
20215 library file on the target, and on the host respectively. For native
20216 debugging, both those fields have the same value. The
20217 @var{symbols-loaded} field reports if the debug symbols for this
20218 library are loaded.
20220 @item =library-unloaded,...
20221 Reports that a library was unloaded by the program. This notification
20222 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
20223 the same meaning as for the @code{=library-loaded} notification
20227 @node GDB/MI Frame Information
20228 @subsection @sc{gdb/mi} Frame Information
20230 Response from many MI commands includes an information about stack
20231 frame. This information is a tuple that may have the following
20236 The level of the stack frame. The innermost frame has the level of
20237 zero. This field is always present.
20240 The name of the function corresponding to the frame. This field may
20241 be absent if @value{GDBN} is unable to determine the function name.
20244 The code address for the frame. This field is always present.
20247 The name of the source files that correspond to the frame's code
20248 address. This field may be absent.
20251 The source line corresponding to the frames' code address. This field
20255 The name of the binary file (either executable or shared library) the
20256 corresponds to the frame's code address. This field may be absent.
20261 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20262 @node GDB/MI Simple Examples
20263 @section Simple Examples of @sc{gdb/mi} Interaction
20264 @cindex @sc{gdb/mi}, simple examples
20266 This subsection presents several simple examples of interaction using
20267 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
20268 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
20269 the output received from @sc{gdb/mi}.
20271 Note the line breaks shown in the examples are here only for
20272 readability, they don't appear in the real output.
20274 @subheading Setting a Breakpoint
20276 Setting a breakpoint generates synchronous output which contains detailed
20277 information of the breakpoint.
20280 -> -break-insert main
20281 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20282 enabled="y",addr="0x08048564",func="main",file="myprog.c",
20283 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
20287 @subheading Program Execution
20289 Program execution generates asynchronous records and MI gives the
20290 reason that execution stopped.
20296 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
20297 frame=@{addr="0x08048564",func="main",
20298 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
20299 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
20304 <- *stopped,reason="exited-normally"
20308 @subheading Quitting @value{GDBN}
20310 Quitting @value{GDBN} just prints the result class @samp{^exit}.
20318 @subheading A Bad Command
20320 Here's what happens if you pass a non-existent command:
20324 <- ^error,msg="Undefined MI command: rubbish"
20329 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20330 @node GDB/MI Command Description Format
20331 @section @sc{gdb/mi} Command Description Format
20333 The remaining sections describe blocks of commands. Each block of
20334 commands is laid out in a fashion similar to this section.
20336 @subheading Motivation
20338 The motivation for this collection of commands.
20340 @subheading Introduction
20342 A brief introduction to this collection of commands as a whole.
20344 @subheading Commands
20346 For each command in the block, the following is described:
20348 @subsubheading Synopsis
20351 -command @var{args}@dots{}
20354 @subsubheading Result
20356 @subsubheading @value{GDBN} Command
20358 The corresponding @value{GDBN} CLI command(s), if any.
20360 @subsubheading Example
20362 Example(s) formatted for readability. Some of the described commands have
20363 not been implemented yet and these are labeled N.A.@: (not available).
20366 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20367 @node GDB/MI Breakpoint Commands
20368 @section @sc{gdb/mi} Breakpoint Commands
20370 @cindex breakpoint commands for @sc{gdb/mi}
20371 @cindex @sc{gdb/mi}, breakpoint commands
20372 This section documents @sc{gdb/mi} commands for manipulating
20375 @subheading The @code{-break-after} Command
20376 @findex -break-after
20378 @subsubheading Synopsis
20381 -break-after @var{number} @var{count}
20384 The breakpoint number @var{number} is not in effect until it has been
20385 hit @var{count} times. To see how this is reflected in the output of
20386 the @samp{-break-list} command, see the description of the
20387 @samp{-break-list} command below.
20389 @subsubheading @value{GDBN} Command
20391 The corresponding @value{GDBN} command is @samp{ignore}.
20393 @subsubheading Example
20398 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
20399 enabled="y",addr="0x000100d0",func="main",file="hello.c",
20400 fullname="/home/foo/hello.c",line="5",times="0"@}
20407 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20408 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20409 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20410 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20411 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20412 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20413 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20414 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20415 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20416 line="5",times="0",ignore="3"@}]@}
20421 @subheading The @code{-break-catch} Command
20422 @findex -break-catch
20424 @subheading The @code{-break-commands} Command
20425 @findex -break-commands
20429 @subheading The @code{-break-condition} Command
20430 @findex -break-condition
20432 @subsubheading Synopsis
20435 -break-condition @var{number} @var{expr}
20438 Breakpoint @var{number} will stop the program only if the condition in
20439 @var{expr} is true. The condition becomes part of the
20440 @samp{-break-list} output (see the description of the @samp{-break-list}
20443 @subsubheading @value{GDBN} Command
20445 The corresponding @value{GDBN} command is @samp{condition}.
20447 @subsubheading Example
20451 -break-condition 1 1
20455 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20456 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20457 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20458 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20459 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20460 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20461 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20462 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20463 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20464 line="5",cond="1",times="0",ignore="3"@}]@}
20468 @subheading The @code{-break-delete} Command
20469 @findex -break-delete
20471 @subsubheading Synopsis
20474 -break-delete ( @var{breakpoint} )+
20477 Delete the breakpoint(s) whose number(s) are specified in the argument
20478 list. This is obviously reflected in the breakpoint list.
20480 @subsubheading @value{GDBN} Command
20482 The corresponding @value{GDBN} command is @samp{delete}.
20484 @subsubheading Example
20492 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20493 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20494 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20495 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20496 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20497 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20498 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20503 @subheading The @code{-break-disable} Command
20504 @findex -break-disable
20506 @subsubheading Synopsis
20509 -break-disable ( @var{breakpoint} )+
20512 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
20513 break list is now set to @samp{n} for the named @var{breakpoint}(s).
20515 @subsubheading @value{GDBN} Command
20517 The corresponding @value{GDBN} command is @samp{disable}.
20519 @subsubheading Example
20527 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20528 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20529 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20530 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20531 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20532 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20533 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20534 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
20535 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20536 line="5",times="0"@}]@}
20540 @subheading The @code{-break-enable} Command
20541 @findex -break-enable
20543 @subsubheading Synopsis
20546 -break-enable ( @var{breakpoint} )+
20549 Enable (previously disabled) @var{breakpoint}(s).
20551 @subsubheading @value{GDBN} Command
20553 The corresponding @value{GDBN} command is @samp{enable}.
20555 @subsubheading Example
20563 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20564 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20565 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20566 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20567 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20568 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20569 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20570 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20571 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
20572 line="5",times="0"@}]@}
20576 @subheading The @code{-break-info} Command
20577 @findex -break-info
20579 @subsubheading Synopsis
20582 -break-info @var{breakpoint}
20586 Get information about a single breakpoint.
20588 @subsubheading @value{GDBN} Command
20590 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
20592 @subsubheading Example
20595 @subheading The @code{-break-insert} Command
20596 @findex -break-insert
20598 @subsubheading Synopsis
20601 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
20602 [ -c @var{condition} ] [ -i @var{ignore-count} ]
20603 [ -p @var{thread} ] [ @var{location} ]
20607 If specified, @var{location}, can be one of:
20614 @item filename:linenum
20615 @item filename:function
20619 The possible optional parameters of this command are:
20623 Insert a temporary breakpoint.
20625 Insert a hardware breakpoint.
20626 @item -c @var{condition}
20627 Make the breakpoint conditional on @var{condition}.
20628 @item -i @var{ignore-count}
20629 Initialize the @var{ignore-count}.
20631 If @var{location} cannot be parsed (for example if it
20632 refers to unknown files or functions), create a pending
20633 breakpoint. Without this flag, @value{GDBN} will report
20634 an error, and won't create a breakpoint, if @var{location}
20637 Create a disabled breakpoint.
20640 @subsubheading Result
20642 The result is in the form:
20645 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
20646 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
20647 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
20648 times="@var{times}"@}
20652 where @var{number} is the @value{GDBN} number for this breakpoint,
20653 @var{funcname} is the name of the function where the breakpoint was
20654 inserted, @var{filename} is the name of the source file which contains
20655 this function, @var{lineno} is the source line number within that file
20656 and @var{times} the number of times that the breakpoint has been hit
20657 (always 0 for -break-insert but may be greater for -break-info or -break-list
20658 which use the same output).
20660 Note: this format is open to change.
20661 @c An out-of-band breakpoint instead of part of the result?
20663 @subsubheading @value{GDBN} Command
20665 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
20666 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
20668 @subsubheading Example
20673 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
20674 fullname="/home/foo/recursive2.c,line="4",times="0"@}
20676 -break-insert -t foo
20677 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
20678 fullname="/home/foo/recursive2.c,line="11",times="0"@}
20681 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20682 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20683 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20684 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20685 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20686 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20687 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20688 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20689 addr="0x0001072c", func="main",file="recursive2.c",
20690 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
20691 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
20692 addr="0x00010774",func="foo",file="recursive2.c",
20693 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
20695 -break-insert -r foo.*
20696 ~int foo(int, int);
20697 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
20698 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
20702 @subheading The @code{-break-list} Command
20703 @findex -break-list
20705 @subsubheading Synopsis
20711 Displays the list of inserted breakpoints, showing the following fields:
20715 number of the breakpoint
20717 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
20719 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
20722 is the breakpoint enabled or no: @samp{y} or @samp{n}
20724 memory location at which the breakpoint is set
20726 logical location of the breakpoint, expressed by function name, file
20729 number of times the breakpoint has been hit
20732 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
20733 @code{body} field is an empty list.
20735 @subsubheading @value{GDBN} Command
20737 The corresponding @value{GDBN} command is @samp{info break}.
20739 @subsubheading Example
20744 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20745 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20746 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20747 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20748 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20749 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20750 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20751 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20752 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
20753 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
20754 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
20755 line="13",times="0"@}]@}
20759 Here's an example of the result when there are no breakpoints:
20764 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
20765 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20766 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20767 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20768 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20769 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20770 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20775 @subheading The @code{-break-watch} Command
20776 @findex -break-watch
20778 @subsubheading Synopsis
20781 -break-watch [ -a | -r ]
20784 Create a watchpoint. With the @samp{-a} option it will create an
20785 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
20786 read from or on a write to the memory location. With the @samp{-r}
20787 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
20788 trigger only when the memory location is accessed for reading. Without
20789 either of the options, the watchpoint created is a regular watchpoint,
20790 i.e., it will trigger when the memory location is accessed for writing.
20791 @xref{Set Watchpoints, , Setting Watchpoints}.
20793 Note that @samp{-break-list} will report a single list of watchpoints and
20794 breakpoints inserted.
20796 @subsubheading @value{GDBN} Command
20798 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
20801 @subsubheading Example
20803 Setting a watchpoint on a variable in the @code{main} function:
20808 ^done,wpt=@{number="2",exp="x"@}
20813 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
20814 value=@{old="-268439212",new="55"@},
20815 frame=@{func="main",args=[],file="recursive2.c",
20816 fullname="/home/foo/bar/recursive2.c",line="5"@}
20820 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
20821 the program execution twice: first for the variable changing value, then
20822 for the watchpoint going out of scope.
20827 ^done,wpt=@{number="5",exp="C"@}
20832 *stopped,reason="watchpoint-trigger",
20833 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
20834 frame=@{func="callee4",args=[],
20835 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20836 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20841 *stopped,reason="watchpoint-scope",wpnum="5",
20842 frame=@{func="callee3",args=[@{name="strarg",
20843 value="0x11940 \"A string argument.\""@}],
20844 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20845 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20849 Listing breakpoints and watchpoints, at different points in the program
20850 execution. Note that once the watchpoint goes out of scope, it is
20856 ^done,wpt=@{number="2",exp="C"@}
20859 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20860 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20861 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20862 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20863 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20864 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20865 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20866 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20867 addr="0x00010734",func="callee4",
20868 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20869 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
20870 bkpt=@{number="2",type="watchpoint",disp="keep",
20871 enabled="y",addr="",what="C",times="0"@}]@}
20876 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
20877 value=@{old="-276895068",new="3"@},
20878 frame=@{func="callee4",args=[],
20879 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20880 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
20883 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
20884 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20885 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20886 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20887 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20888 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20889 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20890 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20891 addr="0x00010734",func="callee4",
20892 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20893 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
20894 bkpt=@{number="2",type="watchpoint",disp="keep",
20895 enabled="y",addr="",what="C",times="-5"@}]@}
20899 ^done,reason="watchpoint-scope",wpnum="2",
20900 frame=@{func="callee3",args=[@{name="strarg",
20901 value="0x11940 \"A string argument.\""@}],
20902 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20903 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
20906 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
20907 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
20908 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
20909 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
20910 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
20911 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
20912 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
20913 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
20914 addr="0x00010734",func="callee4",
20915 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
20916 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
20921 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20922 @node GDB/MI Program Context
20923 @section @sc{gdb/mi} Program Context
20925 @subheading The @code{-exec-arguments} Command
20926 @findex -exec-arguments
20929 @subsubheading Synopsis
20932 -exec-arguments @var{args}
20935 Set the inferior program arguments, to be used in the next
20938 @subsubheading @value{GDBN} Command
20940 The corresponding @value{GDBN} command is @samp{set args}.
20942 @subsubheading Example
20946 -exec-arguments -v word
20952 @subheading The @code{-exec-show-arguments} Command
20953 @findex -exec-show-arguments
20955 @subsubheading Synopsis
20958 -exec-show-arguments
20961 Print the arguments of the program.
20963 @subsubheading @value{GDBN} Command
20965 The corresponding @value{GDBN} command is @samp{show args}.
20967 @subsubheading Example
20971 @subheading The @code{-environment-cd} Command
20972 @findex -environment-cd
20974 @subsubheading Synopsis
20977 -environment-cd @var{pathdir}
20980 Set @value{GDBN}'s working directory.
20982 @subsubheading @value{GDBN} Command
20984 The corresponding @value{GDBN} command is @samp{cd}.
20986 @subsubheading Example
20990 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
20996 @subheading The @code{-environment-directory} Command
20997 @findex -environment-directory
20999 @subsubheading Synopsis
21002 -environment-directory [ -r ] [ @var{pathdir} ]+
21005 Add directories @var{pathdir} to beginning of search path for source files.
21006 If the @samp{-r} option is used, the search path is reset to the default
21007 search path. If directories @var{pathdir} are supplied in addition to the
21008 @samp{-r} option, the search path is first reset and then addition
21010 Multiple directories may be specified, separated by blanks. Specifying
21011 multiple directories in a single command
21012 results in the directories added to the beginning of the
21013 search path in the same order they were presented in the command.
21014 If blanks are needed as
21015 part of a directory name, double-quotes should be used around
21016 the name. In the command output, the path will show up separated
21017 by the system directory-separator character. The directory-separator
21018 character must not be used
21019 in any directory name.
21020 If no directories are specified, the current search path is displayed.
21022 @subsubheading @value{GDBN} Command
21024 The corresponding @value{GDBN} command is @samp{dir}.
21026 @subsubheading Example
21030 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
21031 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21033 -environment-directory ""
21034 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
21036 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
21037 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
21039 -environment-directory -r
21040 ^done,source-path="$cdir:$cwd"
21045 @subheading The @code{-environment-path} Command
21046 @findex -environment-path
21048 @subsubheading Synopsis
21051 -environment-path [ -r ] [ @var{pathdir} ]+
21054 Add directories @var{pathdir} to beginning of search path for object files.
21055 If the @samp{-r} option is used, the search path is reset to the original
21056 search path that existed at gdb start-up. If directories @var{pathdir} are
21057 supplied in addition to the
21058 @samp{-r} option, the search path is first reset and then addition
21060 Multiple directories may be specified, separated by blanks. Specifying
21061 multiple directories in a single command
21062 results in the directories added to the beginning of the
21063 search path in the same order they were presented in the command.
21064 If blanks are needed as
21065 part of a directory name, double-quotes should be used around
21066 the name. In the command output, the path will show up separated
21067 by the system directory-separator character. The directory-separator
21068 character must not be used
21069 in any directory name.
21070 If no directories are specified, the current path is displayed.
21073 @subsubheading @value{GDBN} Command
21075 The corresponding @value{GDBN} command is @samp{path}.
21077 @subsubheading Example
21082 ^done,path="/usr/bin"
21084 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
21085 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
21087 -environment-path -r /usr/local/bin
21088 ^done,path="/usr/local/bin:/usr/bin"
21093 @subheading The @code{-environment-pwd} Command
21094 @findex -environment-pwd
21096 @subsubheading Synopsis
21102 Show the current working directory.
21104 @subsubheading @value{GDBN} Command
21106 The corresponding @value{GDBN} command is @samp{pwd}.
21108 @subsubheading Example
21113 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
21117 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21118 @node GDB/MI Thread Commands
21119 @section @sc{gdb/mi} Thread Commands
21122 @subheading The @code{-thread-info} Command
21123 @findex -thread-info
21125 @subsubheading Synopsis
21128 -thread-info [ @var{thread-id} ]
21131 Reports information about either a specific thread, if
21132 the @var{thread-id} parameter is present, or about all
21133 threads. When printing information about all threads,
21134 also reports the current thread.
21136 @subsubheading @value{GDBN} Command
21138 The @samp{info thread} command prints the same information
21141 @subsubheading Example
21146 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
21147 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
21148 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
21149 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
21150 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
21151 current-thread-id="1"
21155 The @samp{state} field may have the following values:
21159 The thread is stopped. Frame information is available for stopped
21163 The thread is running. There's no frame information for running
21168 @subheading The @code{-thread-list-ids} Command
21169 @findex -thread-list-ids
21171 @subsubheading Synopsis
21177 Produces a list of the currently known @value{GDBN} thread ids. At the
21178 end of the list it also prints the total number of such threads.
21180 This command is retained for historical reasons, the
21181 @code{-thread-info} command should be used instead.
21183 @subsubheading @value{GDBN} Command
21185 Part of @samp{info threads} supplies the same information.
21187 @subsubheading Example
21192 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21193 current-thread-id="1",number-of-threads="3"
21198 @subheading The @code{-thread-select} Command
21199 @findex -thread-select
21201 @subsubheading Synopsis
21204 -thread-select @var{threadnum}
21207 Make @var{threadnum} the current thread. It prints the number of the new
21208 current thread, and the topmost frame for that thread.
21210 This command is deprecated in favor of explicitly using the
21211 @samp{--thread} option to each command.
21213 @subsubheading @value{GDBN} Command
21215 The corresponding @value{GDBN} command is @samp{thread}.
21217 @subsubheading Example
21224 *stopped,reason="end-stepping-range",thread-id="2",line="187",
21225 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
21229 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
21230 number-of-threads="3"
21233 ^done,new-thread-id="3",
21234 frame=@{level="0",func="vprintf",
21235 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
21236 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
21240 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21241 @node GDB/MI Program Execution
21242 @section @sc{gdb/mi} Program Execution
21244 These are the asynchronous commands which generate the out-of-band
21245 record @samp{*stopped}. Currently @value{GDBN} only really executes
21246 asynchronously with remote targets and this interaction is mimicked in
21249 @subheading The @code{-exec-continue} Command
21250 @findex -exec-continue
21252 @subsubheading Synopsis
21255 -exec-continue [--all|--thread-group N]
21258 Resumes the execution of the inferior program until a breakpoint is
21259 encountered, or until the inferior exits. In all-stop mode
21260 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
21261 depending on the value of the @samp{scheduler-locking} variable. In
21262 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
21263 specified, only the thread specified with the @samp{--thread} option
21264 (or current thread, if no @samp{--thread} is provided) is resumed. If
21265 @samp{--all} is specified, all threads will be resumed. The
21266 @samp{--all} option is ignored in all-stop mode. If the
21267 @samp{--thread-group} options is specified, then all threads in that
21268 thread group are resumed.
21270 @subsubheading @value{GDBN} Command
21272 The corresponding @value{GDBN} corresponding is @samp{continue}.
21274 @subsubheading Example
21281 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
21282 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
21288 @subheading The @code{-exec-finish} Command
21289 @findex -exec-finish
21291 @subsubheading Synopsis
21297 Resumes the execution of the inferior program until the current
21298 function is exited. Displays the results returned by the function.
21300 @subsubheading @value{GDBN} Command
21302 The corresponding @value{GDBN} command is @samp{finish}.
21304 @subsubheading Example
21306 Function returning @code{void}.
21313 *stopped,reason="function-finished",frame=@{func="main",args=[],
21314 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
21318 Function returning other than @code{void}. The name of the internal
21319 @value{GDBN} variable storing the result is printed, together with the
21326 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
21327 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
21328 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21329 gdb-result-var="$1",return-value="0"
21334 @subheading The @code{-exec-interrupt} Command
21335 @findex -exec-interrupt
21337 @subsubheading Synopsis
21340 -exec-interrupt [--all|--thread-group N]
21343 Interrupts the background execution of the target. Note how the token
21344 associated with the stop message is the one for the execution command
21345 that has been interrupted. The token for the interrupt itself only
21346 appears in the @samp{^done} output. If the user is trying to
21347 interrupt a non-running program, an error message will be printed.
21349 Note that when asynchronous execution is enabled, this command is
21350 asynchronous just like other execution commands. That is, first the
21351 @samp{^done} response will be printed, and the target stop will be
21352 reported after that using the @samp{*stopped} notification.
21354 In non-stop mode, only the context thread is interrupted by default.
21355 All threads will be interrupted if the @samp{--all} option is
21356 specified. If the @samp{--thread-group} option is specified, all
21357 threads in that group will be interrupted.
21359 @subsubheading @value{GDBN} Command
21361 The corresponding @value{GDBN} command is @samp{interrupt}.
21363 @subsubheading Example
21374 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
21375 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
21376 fullname="/home/foo/bar/try.c",line="13"@}
21381 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
21386 @subheading The @code{-exec-next} Command
21389 @subsubheading Synopsis
21395 Resumes execution of the inferior program, stopping when the beginning
21396 of the next source line is reached.
21398 @subsubheading @value{GDBN} Command
21400 The corresponding @value{GDBN} command is @samp{next}.
21402 @subsubheading Example
21408 *stopped,reason="end-stepping-range",line="8",file="hello.c"
21413 @subheading The @code{-exec-next-instruction} Command
21414 @findex -exec-next-instruction
21416 @subsubheading Synopsis
21419 -exec-next-instruction
21422 Executes one machine instruction. If the instruction is a function
21423 call, continues until the function returns. If the program stops at an
21424 instruction in the middle of a source line, the address will be
21427 @subsubheading @value{GDBN} Command
21429 The corresponding @value{GDBN} command is @samp{nexti}.
21431 @subsubheading Example
21435 -exec-next-instruction
21439 *stopped,reason="end-stepping-range",
21440 addr="0x000100d4",line="5",file="hello.c"
21445 @subheading The @code{-exec-return} Command
21446 @findex -exec-return
21448 @subsubheading Synopsis
21454 Makes current function return immediately. Doesn't execute the inferior.
21455 Displays the new current frame.
21457 @subsubheading @value{GDBN} Command
21459 The corresponding @value{GDBN} command is @samp{return}.
21461 @subsubheading Example
21465 200-break-insert callee4
21466 200^done,bkpt=@{number="1",addr="0x00010734",
21467 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21472 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21473 frame=@{func="callee4",args=[],
21474 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21475 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
21481 111^done,frame=@{level="0",func="callee3",
21482 args=[@{name="strarg",
21483 value="0x11940 \"A string argument.\""@}],
21484 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21485 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21490 @subheading The @code{-exec-run} Command
21493 @subsubheading Synopsis
21499 Starts execution of the inferior from the beginning. The inferior
21500 executes until either a breakpoint is encountered or the program
21501 exits. In the latter case the output will include an exit code, if
21502 the program has exited exceptionally.
21504 @subsubheading @value{GDBN} Command
21506 The corresponding @value{GDBN} command is @samp{run}.
21508 @subsubheading Examples
21513 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
21518 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
21519 frame=@{func="main",args=[],file="recursive2.c",
21520 fullname="/home/foo/bar/recursive2.c",line="4"@}
21525 Program exited normally:
21533 *stopped,reason="exited-normally"
21538 Program exited exceptionally:
21546 *stopped,reason="exited",exit-code="01"
21550 Another way the program can terminate is if it receives a signal such as
21551 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
21555 *stopped,reason="exited-signalled",signal-name="SIGINT",
21556 signal-meaning="Interrupt"
21560 @c @subheading -exec-signal
21563 @subheading The @code{-exec-step} Command
21566 @subsubheading Synopsis
21572 Resumes execution of the inferior program, stopping when the beginning
21573 of the next source line is reached, if the next source line is not a
21574 function call. If it is, stop at the first instruction of the called
21577 @subsubheading @value{GDBN} Command
21579 The corresponding @value{GDBN} command is @samp{step}.
21581 @subsubheading Example
21583 Stepping into a function:
21589 *stopped,reason="end-stepping-range",
21590 frame=@{func="foo",args=[@{name="a",value="10"@},
21591 @{name="b",value="0"@}],file="recursive2.c",
21592 fullname="/home/foo/bar/recursive2.c",line="11"@}
21602 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
21607 @subheading The @code{-exec-step-instruction} Command
21608 @findex -exec-step-instruction
21610 @subsubheading Synopsis
21613 -exec-step-instruction
21616 Resumes the inferior which executes one machine instruction. The
21617 output, once @value{GDBN} has stopped, will vary depending on whether
21618 we have stopped in the middle of a source line or not. In the former
21619 case, the address at which the program stopped will be printed as
21622 @subsubheading @value{GDBN} Command
21624 The corresponding @value{GDBN} command is @samp{stepi}.
21626 @subsubheading Example
21630 -exec-step-instruction
21634 *stopped,reason="end-stepping-range",
21635 frame=@{func="foo",args=[],file="try.c",
21636 fullname="/home/foo/bar/try.c",line="10"@}
21638 -exec-step-instruction
21642 *stopped,reason="end-stepping-range",
21643 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
21644 fullname="/home/foo/bar/try.c",line="10"@}
21649 @subheading The @code{-exec-until} Command
21650 @findex -exec-until
21652 @subsubheading Synopsis
21655 -exec-until [ @var{location} ]
21658 Executes the inferior until the @var{location} specified in the
21659 argument is reached. If there is no argument, the inferior executes
21660 until a source line greater than the current one is reached. The
21661 reason for stopping in this case will be @samp{location-reached}.
21663 @subsubheading @value{GDBN} Command
21665 The corresponding @value{GDBN} command is @samp{until}.
21667 @subsubheading Example
21671 -exec-until recursive2.c:6
21675 *stopped,reason="location-reached",frame=@{func="main",args=[],
21676 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
21681 @subheading -file-clear
21682 Is this going away????
21685 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21686 @node GDB/MI Stack Manipulation
21687 @section @sc{gdb/mi} Stack Manipulation Commands
21690 @subheading The @code{-stack-info-frame} Command
21691 @findex -stack-info-frame
21693 @subsubheading Synopsis
21699 Get info on the selected frame.
21701 @subsubheading @value{GDBN} Command
21703 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
21704 (without arguments).
21706 @subsubheading Example
21711 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
21712 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21713 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
21717 @subheading The @code{-stack-info-depth} Command
21718 @findex -stack-info-depth
21720 @subsubheading Synopsis
21723 -stack-info-depth [ @var{max-depth} ]
21726 Return the depth of the stack. If the integer argument @var{max-depth}
21727 is specified, do not count beyond @var{max-depth} frames.
21729 @subsubheading @value{GDBN} Command
21731 There's no equivalent @value{GDBN} command.
21733 @subsubheading Example
21735 For a stack with frame levels 0 through 11:
21742 -stack-info-depth 4
21745 -stack-info-depth 12
21748 -stack-info-depth 11
21751 -stack-info-depth 13
21756 @subheading The @code{-stack-list-arguments} Command
21757 @findex -stack-list-arguments
21759 @subsubheading Synopsis
21762 -stack-list-arguments @var{show-values}
21763 [ @var{low-frame} @var{high-frame} ]
21766 Display a list of the arguments for the frames between @var{low-frame}
21767 and @var{high-frame} (inclusive). If @var{low-frame} and
21768 @var{high-frame} are not provided, list the arguments for the whole
21769 call stack. If the two arguments are equal, show the single frame
21770 at the corresponding level. It is an error if @var{low-frame} is
21771 larger than the actual number of frames. On the other hand,
21772 @var{high-frame} may be larger than the actual number of frames, in
21773 which case only existing frames will be returned.
21775 The @var{show-values} argument must have a value of 0 or 1. A value of
21776 0 means that only the names of the arguments are listed, a value of 1
21777 means that both names and values of the arguments are printed.
21779 @subsubheading @value{GDBN} Command
21781 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
21782 @samp{gdb_get_args} command which partially overlaps with the
21783 functionality of @samp{-stack-list-arguments}.
21785 @subsubheading Example
21792 frame=@{level="0",addr="0x00010734",func="callee4",
21793 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21794 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
21795 frame=@{level="1",addr="0x0001076c",func="callee3",
21796 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21797 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
21798 frame=@{level="2",addr="0x0001078c",func="callee2",
21799 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21800 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
21801 frame=@{level="3",addr="0x000107b4",func="callee1",
21802 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21803 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
21804 frame=@{level="4",addr="0x000107e0",func="main",
21805 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21806 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
21808 -stack-list-arguments 0
21811 frame=@{level="0",args=[]@},
21812 frame=@{level="1",args=[name="strarg"]@},
21813 frame=@{level="2",args=[name="intarg",name="strarg"]@},
21814 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
21815 frame=@{level="4",args=[]@}]
21817 -stack-list-arguments 1
21820 frame=@{level="0",args=[]@},
21822 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21823 frame=@{level="2",args=[
21824 @{name="intarg",value="2"@},
21825 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
21826 @{frame=@{level="3",args=[
21827 @{name="intarg",value="2"@},
21828 @{name="strarg",value="0x11940 \"A string argument.\""@},
21829 @{name="fltarg",value="3.5"@}]@},
21830 frame=@{level="4",args=[]@}]
21832 -stack-list-arguments 0 2 2
21833 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
21835 -stack-list-arguments 1 2 2
21836 ^done,stack-args=[frame=@{level="2",
21837 args=[@{name="intarg",value="2"@},
21838 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
21842 @c @subheading -stack-list-exception-handlers
21845 @subheading The @code{-stack-list-frames} Command
21846 @findex -stack-list-frames
21848 @subsubheading Synopsis
21851 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
21854 List the frames currently on the stack. For each frame it displays the
21859 The frame number, 0 being the topmost frame, i.e., the innermost function.
21861 The @code{$pc} value for that frame.
21865 File name of the source file where the function lives.
21867 Line number corresponding to the @code{$pc}.
21870 If invoked without arguments, this command prints a backtrace for the
21871 whole stack. If given two integer arguments, it shows the frames whose
21872 levels are between the two arguments (inclusive). If the two arguments
21873 are equal, it shows the single frame at the corresponding level. It is
21874 an error if @var{low-frame} is larger than the actual number of
21875 frames. On the other hand, @var{high-frame} may be larger than the
21876 actual number of frames, in which case only existing frames will be returned.
21878 @subsubheading @value{GDBN} Command
21880 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
21882 @subsubheading Example
21884 Full stack backtrace:
21890 [frame=@{level="0",addr="0x0001076c",func="foo",
21891 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
21892 frame=@{level="1",addr="0x000107a4",func="foo",
21893 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21894 frame=@{level="2",addr="0x000107a4",func="foo",
21895 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21896 frame=@{level="3",addr="0x000107a4",func="foo",
21897 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21898 frame=@{level="4",addr="0x000107a4",func="foo",
21899 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21900 frame=@{level="5",addr="0x000107a4",func="foo",
21901 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21902 frame=@{level="6",addr="0x000107a4",func="foo",
21903 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21904 frame=@{level="7",addr="0x000107a4",func="foo",
21905 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21906 frame=@{level="8",addr="0x000107a4",func="foo",
21907 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21908 frame=@{level="9",addr="0x000107a4",func="foo",
21909 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21910 frame=@{level="10",addr="0x000107a4",func="foo",
21911 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21912 frame=@{level="11",addr="0x00010738",func="main",
21913 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
21917 Show frames between @var{low_frame} and @var{high_frame}:
21921 -stack-list-frames 3 5
21923 [frame=@{level="3",addr="0x000107a4",func="foo",
21924 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21925 frame=@{level="4",addr="0x000107a4",func="foo",
21926 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
21927 frame=@{level="5",addr="0x000107a4",func="foo",
21928 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21932 Show a single frame:
21936 -stack-list-frames 3 3
21938 [frame=@{level="3",addr="0x000107a4",func="foo",
21939 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
21944 @subheading The @code{-stack-list-locals} Command
21945 @findex -stack-list-locals
21947 @subsubheading Synopsis
21950 -stack-list-locals @var{print-values}
21953 Display the local variable names for the selected frame. If
21954 @var{print-values} is 0 or @code{--no-values}, print only the names of
21955 the variables; if it is 1 or @code{--all-values}, print also their
21956 values; and if it is 2 or @code{--simple-values}, print the name,
21957 type and value for simple data types and the name and type for arrays,
21958 structures and unions. In this last case, a frontend can immediately
21959 display the value of simple data types and create variable objects for
21960 other data types when the user wishes to explore their values in
21963 @subsubheading @value{GDBN} Command
21965 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
21967 @subsubheading Example
21971 -stack-list-locals 0
21972 ^done,locals=[name="A",name="B",name="C"]
21974 -stack-list-locals --all-values
21975 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
21976 @{name="C",value="@{1, 2, 3@}"@}]
21977 -stack-list-locals --simple-values
21978 ^done,locals=[@{name="A",type="int",value="1"@},
21979 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
21984 @subheading The @code{-stack-select-frame} Command
21985 @findex -stack-select-frame
21987 @subsubheading Synopsis
21990 -stack-select-frame @var{framenum}
21993 Change the selected frame. Select a different frame @var{framenum} on
21996 This command in deprecated in favor of passing the @samp{--frame}
21997 option to every command.
21999 @subsubheading @value{GDBN} Command
22001 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
22002 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
22004 @subsubheading Example
22008 -stack-select-frame 2
22013 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22014 @node GDB/MI Variable Objects
22015 @section @sc{gdb/mi} Variable Objects
22019 @subheading Motivation for Variable Objects in @sc{gdb/mi}
22021 For the implementation of a variable debugger window (locals, watched
22022 expressions, etc.), we are proposing the adaptation of the existing code
22023 used by @code{Insight}.
22025 The two main reasons for that are:
22029 It has been proven in practice (it is already on its second generation).
22032 It will shorten development time (needless to say how important it is
22036 The original interface was designed to be used by Tcl code, so it was
22037 slightly changed so it could be used through @sc{gdb/mi}. This section
22038 describes the @sc{gdb/mi} operations that will be available and gives some
22039 hints about their use.
22041 @emph{Note}: In addition to the set of operations described here, we
22042 expect the @sc{gui} implementation of a variable window to require, at
22043 least, the following operations:
22046 @item @code{-gdb-show} @code{output-radix}
22047 @item @code{-stack-list-arguments}
22048 @item @code{-stack-list-locals}
22049 @item @code{-stack-select-frame}
22054 @subheading Introduction to Variable Objects
22056 @cindex variable objects in @sc{gdb/mi}
22058 Variable objects are "object-oriented" MI interface for examining and
22059 changing values of expressions. Unlike some other MI interfaces that
22060 work with expressions, variable objects are specifically designed for
22061 simple and efficient presentation in the frontend. A variable object
22062 is identified by string name. When a variable object is created, the
22063 frontend specifies the expression for that variable object. The
22064 expression can be a simple variable, or it can be an arbitrary complex
22065 expression, and can even involve CPU registers. After creating a
22066 variable object, the frontend can invoke other variable object
22067 operations---for example to obtain or change the value of a variable
22068 object, or to change display format.
22070 Variable objects have hierarchical tree structure. Any variable object
22071 that corresponds to a composite type, such as structure in C, has
22072 a number of child variable objects, for example corresponding to each
22073 element of a structure. A child variable object can itself have
22074 children, recursively. Recursion ends when we reach
22075 leaf variable objects, which always have built-in types. Child variable
22076 objects are created only by explicit request, so if a frontend
22077 is not interested in the children of a particular variable object, no
22078 child will be created.
22080 For a leaf variable object it is possible to obtain its value as a
22081 string, or set the value from a string. String value can be also
22082 obtained for a non-leaf variable object, but it's generally a string
22083 that only indicates the type of the object, and does not list its
22084 contents. Assignment to a non-leaf variable object is not allowed.
22086 A frontend does not need to read the values of all variable objects each time
22087 the program stops. Instead, MI provides an update command that lists all
22088 variable objects whose values has changed since the last update
22089 operation. This considerably reduces the amount of data that must
22090 be transferred to the frontend. As noted above, children variable
22091 objects are created on demand, and only leaf variable objects have a
22092 real value. As result, gdb will read target memory only for leaf
22093 variables that frontend has created.
22095 The automatic update is not always desirable. For example, a frontend
22096 might want to keep a value of some expression for future reference,
22097 and never update it. For another example, fetching memory is
22098 relatively slow for embedded targets, so a frontend might want
22099 to disable automatic update for the variables that are either not
22100 visible on the screen, or ``closed''. This is possible using so
22101 called ``frozen variable objects''. Such variable objects are never
22102 implicitly updated.
22104 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
22105 fixed variable object, the expression is parsed when the variable
22106 object is created, including associating identifiers to specific
22107 variables. The meaning of expression never changes. For a floating
22108 variable object the values of variables whose names appear in the
22109 expressions are re-evaluated every time in the context of the current
22110 frame. Consider this example:
22115 struct work_state state;
22122 If a fixed variable object for the @code{state} variable is created in
22123 this function, and we enter the recursive call, the the variable
22124 object will report the value of @code{state} in the top-level
22125 @code{do_work} invocation. On the other hand, a floating variable
22126 object will report the value of @code{state} in the current frame.
22128 If an expression specified when creating a fixed variable object
22129 refers to a local variable, the variable object becomes bound to the
22130 thread and frame in which the variable object is created. When such
22131 variable object is updated, @value{GDBN} makes sure that the
22132 thread/frame combination the variable object is bound to still exists,
22133 and re-evaluates the variable object in context of that thread/frame.
22135 The following is the complete set of @sc{gdb/mi} operations defined to
22136 access this functionality:
22138 @multitable @columnfractions .4 .6
22139 @item @strong{Operation}
22140 @tab @strong{Description}
22142 @item @code{-var-create}
22143 @tab create a variable object
22144 @item @code{-var-delete}
22145 @tab delete the variable object and/or its children
22146 @item @code{-var-set-format}
22147 @tab set the display format of this variable
22148 @item @code{-var-show-format}
22149 @tab show the display format of this variable
22150 @item @code{-var-info-num-children}
22151 @tab tells how many children this object has
22152 @item @code{-var-list-children}
22153 @tab return a list of the object's children
22154 @item @code{-var-info-type}
22155 @tab show the type of this variable object
22156 @item @code{-var-info-expression}
22157 @tab print parent-relative expression that this variable object represents
22158 @item @code{-var-info-path-expression}
22159 @tab print full expression that this variable object represents
22160 @item @code{-var-show-attributes}
22161 @tab is this variable editable? does it exist here?
22162 @item @code{-var-evaluate-expression}
22163 @tab get the value of this variable
22164 @item @code{-var-assign}
22165 @tab set the value of this variable
22166 @item @code{-var-update}
22167 @tab update the variable and its children
22168 @item @code{-var-set-frozen}
22169 @tab set frozeness attribute
22172 In the next subsection we describe each operation in detail and suggest
22173 how it can be used.
22175 @subheading Description And Use of Operations on Variable Objects
22177 @subheading The @code{-var-create} Command
22178 @findex -var-create
22180 @subsubheading Synopsis
22183 -var-create @{@var{name} | "-"@}
22184 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
22187 This operation creates a variable object, which allows the monitoring of
22188 a variable, the result of an expression, a memory cell or a CPU
22191 The @var{name} parameter is the string by which the object can be
22192 referenced. It must be unique. If @samp{-} is specified, the varobj
22193 system will generate a string ``varNNNNNN'' automatically. It will be
22194 unique provided that one does not specify @var{name} of that format.
22195 The command fails if a duplicate name is found.
22197 The frame under which the expression should be evaluated can be
22198 specified by @var{frame-addr}. A @samp{*} indicates that the current
22199 frame should be used. A @samp{@@} indicates that a floating variable
22200 object must be created.
22202 @var{expression} is any expression valid on the current language set (must not
22203 begin with a @samp{*}), or one of the following:
22207 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
22210 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
22213 @samp{$@var{regname}} --- a CPU register name
22216 @subsubheading Result
22218 This operation returns the name, number of children and the type of the
22219 object created. Type is returned as a string as the ones generated by
22220 the @value{GDBN} CLI. If a fixed variable object is bound to a
22221 specific thread, the thread is is also printed:
22224 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
22228 @subheading The @code{-var-delete} Command
22229 @findex -var-delete
22231 @subsubheading Synopsis
22234 -var-delete [ -c ] @var{name}
22237 Deletes a previously created variable object and all of its children.
22238 With the @samp{-c} option, just deletes the children.
22240 Returns an error if the object @var{name} is not found.
22243 @subheading The @code{-var-set-format} Command
22244 @findex -var-set-format
22246 @subsubheading Synopsis
22249 -var-set-format @var{name} @var{format-spec}
22252 Sets the output format for the value of the object @var{name} to be
22255 @anchor{-var-set-format}
22256 The syntax for the @var{format-spec} is as follows:
22259 @var{format-spec} @expansion{}
22260 @{binary | decimal | hexadecimal | octal | natural@}
22263 The natural format is the default format choosen automatically
22264 based on the variable type (like decimal for an @code{int}, hex
22265 for pointers, etc.).
22267 For a variable with children, the format is set only on the
22268 variable itself, and the children are not affected.
22270 @subheading The @code{-var-show-format} Command
22271 @findex -var-show-format
22273 @subsubheading Synopsis
22276 -var-show-format @var{name}
22279 Returns the format used to display the value of the object @var{name}.
22282 @var{format} @expansion{}
22287 @subheading The @code{-var-info-num-children} Command
22288 @findex -var-info-num-children
22290 @subsubheading Synopsis
22293 -var-info-num-children @var{name}
22296 Returns the number of children of a variable object @var{name}:
22303 @subheading The @code{-var-list-children} Command
22304 @findex -var-list-children
22306 @subsubheading Synopsis
22309 -var-list-children [@var{print-values}] @var{name}
22311 @anchor{-var-list-children}
22313 Return a list of the children of the specified variable object and
22314 create variable objects for them, if they do not already exist. With
22315 a single argument or if @var{print-values} has a value for of 0 or
22316 @code{--no-values}, print only the names of the variables; if
22317 @var{print-values} is 1 or @code{--all-values}, also print their
22318 values; and if it is 2 or @code{--simple-values} print the name and
22319 value for simple data types and just the name for arrays, structures
22322 @subsubheading Example
22326 -var-list-children n
22327 ^done,numchild=@var{n},children=[@{name=@var{name},
22328 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
22330 -var-list-children --all-values n
22331 ^done,numchild=@var{n},children=[@{name=@var{name},
22332 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
22336 @subheading The @code{-var-info-type} Command
22337 @findex -var-info-type
22339 @subsubheading Synopsis
22342 -var-info-type @var{name}
22345 Returns the type of the specified variable @var{name}. The type is
22346 returned as a string in the same format as it is output by the
22350 type=@var{typename}
22354 @subheading The @code{-var-info-expression} Command
22355 @findex -var-info-expression
22357 @subsubheading Synopsis
22360 -var-info-expression @var{name}
22363 Returns a string that is suitable for presenting this
22364 variable object in user interface. The string is generally
22365 not valid expression in the current language, and cannot be evaluated.
22367 For example, if @code{a} is an array, and variable object
22368 @code{A} was created for @code{a}, then we'll get this output:
22371 (gdb) -var-info-expression A.1
22372 ^done,lang="C",exp="1"
22376 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
22378 Note that the output of the @code{-var-list-children} command also
22379 includes those expressions, so the @code{-var-info-expression} command
22382 @subheading The @code{-var-info-path-expression} Command
22383 @findex -var-info-path-expression
22385 @subsubheading Synopsis
22388 -var-info-path-expression @var{name}
22391 Returns an expression that can be evaluated in the current
22392 context and will yield the same value that a variable object has.
22393 Compare this with the @code{-var-info-expression} command, which
22394 result can be used only for UI presentation. Typical use of
22395 the @code{-var-info-path-expression} command is creating a
22396 watchpoint from a variable object.
22398 For example, suppose @code{C} is a C@t{++} class, derived from class
22399 @code{Base}, and that the @code{Base} class has a member called
22400 @code{m_size}. Assume a variable @code{c} is has the type of
22401 @code{C} and a variable object @code{C} was created for variable
22402 @code{c}. Then, we'll get this output:
22404 (gdb) -var-info-path-expression C.Base.public.m_size
22405 ^done,path_expr=((Base)c).m_size)
22408 @subheading The @code{-var-show-attributes} Command
22409 @findex -var-show-attributes
22411 @subsubheading Synopsis
22414 -var-show-attributes @var{name}
22417 List attributes of the specified variable object @var{name}:
22420 status=@var{attr} [ ( ,@var{attr} )* ]
22424 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
22426 @subheading The @code{-var-evaluate-expression} Command
22427 @findex -var-evaluate-expression
22429 @subsubheading Synopsis
22432 -var-evaluate-expression [-f @var{format-spec}] @var{name}
22435 Evaluates the expression that is represented by the specified variable
22436 object and returns its value as a string. The format of the string
22437 can be specified with the @samp{-f} option. The possible values of
22438 this option are the same as for @code{-var-set-format}
22439 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
22440 the current display format will be used. The current display format
22441 can be changed using the @code{-var-set-format} command.
22447 Note that one must invoke @code{-var-list-children} for a variable
22448 before the value of a child variable can be evaluated.
22450 @subheading The @code{-var-assign} Command
22451 @findex -var-assign
22453 @subsubheading Synopsis
22456 -var-assign @var{name} @var{expression}
22459 Assigns the value of @var{expression} to the variable object specified
22460 by @var{name}. The object must be @samp{editable}. If the variable's
22461 value is altered by the assign, the variable will show up in any
22462 subsequent @code{-var-update} list.
22464 @subsubheading Example
22472 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
22476 @subheading The @code{-var-update} Command
22477 @findex -var-update
22479 @subsubheading Synopsis
22482 -var-update [@var{print-values}] @{@var{name} | "*"@}
22485 Reevaluate the expressions corresponding to the variable object
22486 @var{name} and all its direct and indirect children, and return the
22487 list of variable objects whose values have changed; @var{name} must
22488 be a root variable object. Here, ``changed'' means that the result of
22489 @code{-var-evaluate-expression} before and after the
22490 @code{-var-update} is different. If @samp{*} is used as the variable
22491 object names, all existing variable objects are updated, except
22492 for frozen ones (@pxref{-var-set-frozen}). The option
22493 @var{print-values} determines whether both names and values, or just
22494 names are printed. The possible values of this option are the same
22495 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
22496 recommended to use the @samp{--all-values} option, to reduce the
22497 number of MI commands needed on each program stop.
22499 With the @samp{*} parameter, if a variable object is bound to a
22500 currently running thread, it will not be updated, without any
22503 @subsubheading Example
22510 -var-update --all-values var1
22511 ^done,changelist=[@{name="var1",value="3",in_scope="true",
22512 type_changed="false"@}]
22516 @anchor{-var-update}
22517 The field in_scope may take three values:
22521 The variable object's current value is valid.
22524 The variable object does not currently hold a valid value but it may
22525 hold one in the future if its associated expression comes back into
22529 The variable object no longer holds a valid value.
22530 This can occur when the executable file being debugged has changed,
22531 either through recompilation or by using the @value{GDBN} @code{file}
22532 command. The front end should normally choose to delete these variable
22536 In the future new values may be added to this list so the front should
22537 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
22539 @subheading The @code{-var-set-frozen} Command
22540 @findex -var-set-frozen
22541 @anchor{-var-set-frozen}
22543 @subsubheading Synopsis
22546 -var-set-frozen @var{name} @var{flag}
22549 Set the frozenness flag on the variable object @var{name}. The
22550 @var{flag} parameter should be either @samp{1} to make the variable
22551 frozen or @samp{0} to make it unfrozen. If a variable object is
22552 frozen, then neither itself, nor any of its children, are
22553 implicitly updated by @code{-var-update} of
22554 a parent variable or by @code{-var-update *}. Only
22555 @code{-var-update} of the variable itself will update its value and
22556 values of its children. After a variable object is unfrozen, it is
22557 implicitly updated by all subsequent @code{-var-update} operations.
22558 Unfreezing a variable does not update it, only subsequent
22559 @code{-var-update} does.
22561 @subsubheading Example
22565 -var-set-frozen V 1
22571 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22572 @node GDB/MI Data Manipulation
22573 @section @sc{gdb/mi} Data Manipulation
22575 @cindex data manipulation, in @sc{gdb/mi}
22576 @cindex @sc{gdb/mi}, data manipulation
22577 This section describes the @sc{gdb/mi} commands that manipulate data:
22578 examine memory and registers, evaluate expressions, etc.
22580 @c REMOVED FROM THE INTERFACE.
22581 @c @subheading -data-assign
22582 @c Change the value of a program variable. Plenty of side effects.
22583 @c @subsubheading GDB Command
22585 @c @subsubheading Example
22588 @subheading The @code{-data-disassemble} Command
22589 @findex -data-disassemble
22591 @subsubheading Synopsis
22595 [ -s @var{start-addr} -e @var{end-addr} ]
22596 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
22604 @item @var{start-addr}
22605 is the beginning address (or @code{$pc})
22606 @item @var{end-addr}
22608 @item @var{filename}
22609 is the name of the file to disassemble
22610 @item @var{linenum}
22611 is the line number to disassemble around
22613 is the number of disassembly lines to be produced. If it is -1,
22614 the whole function will be disassembled, in case no @var{end-addr} is
22615 specified. If @var{end-addr} is specified as a non-zero value, and
22616 @var{lines} is lower than the number of disassembly lines between
22617 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
22618 displayed; if @var{lines} is higher than the number of lines between
22619 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
22622 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
22626 @subsubheading Result
22628 The output for each instruction is composed of four fields:
22637 Note that whatever included in the instruction field, is not manipulated
22638 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
22640 @subsubheading @value{GDBN} Command
22642 There's no direct mapping from this command to the CLI.
22644 @subsubheading Example
22646 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
22650 -data-disassemble -s $pc -e "$pc + 20" -- 0
22653 @{address="0x000107c0",func-name="main",offset="4",
22654 inst="mov 2, %o0"@},
22655 @{address="0x000107c4",func-name="main",offset="8",
22656 inst="sethi %hi(0x11800), %o2"@},
22657 @{address="0x000107c8",func-name="main",offset="12",
22658 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
22659 @{address="0x000107cc",func-name="main",offset="16",
22660 inst="sethi %hi(0x11800), %o2"@},
22661 @{address="0x000107d0",func-name="main",offset="20",
22662 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
22666 Disassemble the whole @code{main} function. Line 32 is part of
22670 -data-disassemble -f basics.c -l 32 -- 0
22672 @{address="0x000107bc",func-name="main",offset="0",
22673 inst="save %sp, -112, %sp"@},
22674 @{address="0x000107c0",func-name="main",offset="4",
22675 inst="mov 2, %o0"@},
22676 @{address="0x000107c4",func-name="main",offset="8",
22677 inst="sethi %hi(0x11800), %o2"@},
22679 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
22680 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
22684 Disassemble 3 instructions from the start of @code{main}:
22688 -data-disassemble -f basics.c -l 32 -n 3 -- 0
22690 @{address="0x000107bc",func-name="main",offset="0",
22691 inst="save %sp, -112, %sp"@},
22692 @{address="0x000107c0",func-name="main",offset="4",
22693 inst="mov 2, %o0"@},
22694 @{address="0x000107c4",func-name="main",offset="8",
22695 inst="sethi %hi(0x11800), %o2"@}]
22699 Disassemble 3 instructions from the start of @code{main} in mixed mode:
22703 -data-disassemble -f basics.c -l 32 -n 3 -- 1
22705 src_and_asm_line=@{line="31",
22706 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22707 testsuite/gdb.mi/basics.c",line_asm_insn=[
22708 @{address="0x000107bc",func-name="main",offset="0",
22709 inst="save %sp, -112, %sp"@}]@},
22710 src_and_asm_line=@{line="32",
22711 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
22712 testsuite/gdb.mi/basics.c",line_asm_insn=[
22713 @{address="0x000107c0",func-name="main",offset="4",
22714 inst="mov 2, %o0"@},
22715 @{address="0x000107c4",func-name="main",offset="8",
22716 inst="sethi %hi(0x11800), %o2"@}]@}]
22721 @subheading The @code{-data-evaluate-expression} Command
22722 @findex -data-evaluate-expression
22724 @subsubheading Synopsis
22727 -data-evaluate-expression @var{expr}
22730 Evaluate @var{expr} as an expression. The expression could contain an
22731 inferior function call. The function call will execute synchronously.
22732 If the expression contains spaces, it must be enclosed in double quotes.
22734 @subsubheading @value{GDBN} Command
22736 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
22737 @samp{call}. In @code{gdbtk} only, there's a corresponding
22738 @samp{gdb_eval} command.
22740 @subsubheading Example
22742 In the following example, the numbers that precede the commands are the
22743 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
22744 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
22748 211-data-evaluate-expression A
22751 311-data-evaluate-expression &A
22752 311^done,value="0xefffeb7c"
22754 411-data-evaluate-expression A+3
22757 511-data-evaluate-expression "A + 3"
22763 @subheading The @code{-data-list-changed-registers} Command
22764 @findex -data-list-changed-registers
22766 @subsubheading Synopsis
22769 -data-list-changed-registers
22772 Display a list of the registers that have changed.
22774 @subsubheading @value{GDBN} Command
22776 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
22777 has the corresponding command @samp{gdb_changed_register_list}.
22779 @subsubheading Example
22781 On a PPC MBX board:
22789 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
22790 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
22793 -data-list-changed-registers
22794 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
22795 "10","11","13","14","15","16","17","18","19","20","21","22","23",
22796 "24","25","26","27","28","30","31","64","65","66","67","69"]
22801 @subheading The @code{-data-list-register-names} Command
22802 @findex -data-list-register-names
22804 @subsubheading Synopsis
22807 -data-list-register-names [ ( @var{regno} )+ ]
22810 Show a list of register names for the current target. If no arguments
22811 are given, it shows a list of the names of all the registers. If
22812 integer numbers are given as arguments, it will print a list of the
22813 names of the registers corresponding to the arguments. To ensure
22814 consistency between a register name and its number, the output list may
22815 include empty register names.
22817 @subsubheading @value{GDBN} Command
22819 @value{GDBN} does not have a command which corresponds to
22820 @samp{-data-list-register-names}. In @code{gdbtk} there is a
22821 corresponding command @samp{gdb_regnames}.
22823 @subsubheading Example
22825 For the PPC MBX board:
22828 -data-list-register-names
22829 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
22830 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
22831 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
22832 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
22833 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
22834 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
22835 "", "pc","ps","cr","lr","ctr","xer"]
22837 -data-list-register-names 1 2 3
22838 ^done,register-names=["r1","r2","r3"]
22842 @subheading The @code{-data-list-register-values} Command
22843 @findex -data-list-register-values
22845 @subsubheading Synopsis
22848 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
22851 Display the registers' contents. @var{fmt} is the format according to
22852 which the registers' contents are to be returned, followed by an optional
22853 list of numbers specifying the registers to display. A missing list of
22854 numbers indicates that the contents of all the registers must be returned.
22856 Allowed formats for @var{fmt} are:
22873 @subsubheading @value{GDBN} Command
22875 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
22876 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
22878 @subsubheading Example
22880 For a PPC MBX board (note: line breaks are for readability only, they
22881 don't appear in the actual output):
22885 -data-list-register-values r 64 65
22886 ^done,register-values=[@{number="64",value="0xfe00a300"@},
22887 @{number="65",value="0x00029002"@}]
22889 -data-list-register-values x
22890 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
22891 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
22892 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
22893 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
22894 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
22895 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
22896 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
22897 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
22898 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
22899 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
22900 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
22901 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
22902 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
22903 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
22904 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
22905 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
22906 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
22907 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
22908 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
22909 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
22910 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
22911 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
22912 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
22913 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
22914 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
22915 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
22916 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
22917 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
22918 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
22919 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
22920 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
22921 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
22922 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
22923 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
22924 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
22925 @{number="69",value="0x20002b03"@}]
22930 @subheading The @code{-data-read-memory} Command
22931 @findex -data-read-memory
22933 @subsubheading Synopsis
22936 -data-read-memory [ -o @var{byte-offset} ]
22937 @var{address} @var{word-format} @var{word-size}
22938 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
22945 @item @var{address}
22946 An expression specifying the address of the first memory word to be
22947 read. Complex expressions containing embedded white space should be
22948 quoted using the C convention.
22950 @item @var{word-format}
22951 The format to be used to print the memory words. The notation is the
22952 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
22955 @item @var{word-size}
22956 The size of each memory word in bytes.
22958 @item @var{nr-rows}
22959 The number of rows in the output table.
22961 @item @var{nr-cols}
22962 The number of columns in the output table.
22965 If present, indicates that each row should include an @sc{ascii} dump. The
22966 value of @var{aschar} is used as a padding character when a byte is not a
22967 member of the printable @sc{ascii} character set (printable @sc{ascii}
22968 characters are those whose code is between 32 and 126, inclusively).
22970 @item @var{byte-offset}
22971 An offset to add to the @var{address} before fetching memory.
22974 This command displays memory contents as a table of @var{nr-rows} by
22975 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
22976 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
22977 (returned as @samp{total-bytes}). Should less than the requested number
22978 of bytes be returned by the target, the missing words are identified
22979 using @samp{N/A}. The number of bytes read from the target is returned
22980 in @samp{nr-bytes} and the starting address used to read memory in
22983 The address of the next/previous row or page is available in
22984 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
22987 @subsubheading @value{GDBN} Command
22989 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
22990 @samp{gdb_get_mem} memory read command.
22992 @subsubheading Example
22994 Read six bytes of memory starting at @code{bytes+6} but then offset by
22995 @code{-6} bytes. Format as three rows of two columns. One byte per
22996 word. Display each word in hex.
23000 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
23001 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
23002 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
23003 prev-page="0x0000138a",memory=[
23004 @{addr="0x00001390",data=["0x00","0x01"]@},
23005 @{addr="0x00001392",data=["0x02","0x03"]@},
23006 @{addr="0x00001394",data=["0x04","0x05"]@}]
23010 Read two bytes of memory starting at address @code{shorts + 64} and
23011 display as a single word formatted in decimal.
23015 5-data-read-memory shorts+64 d 2 1 1
23016 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
23017 next-row="0x00001512",prev-row="0x0000150e",
23018 next-page="0x00001512",prev-page="0x0000150e",memory=[
23019 @{addr="0x00001510",data=["128"]@}]
23023 Read thirty two bytes of memory starting at @code{bytes+16} and format
23024 as eight rows of four columns. Include a string encoding with @samp{x}
23025 used as the non-printable character.
23029 4-data-read-memory bytes+16 x 1 8 4 x
23030 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
23031 next-row="0x000013c0",prev-row="0x0000139c",
23032 next-page="0x000013c0",prev-page="0x00001380",memory=[
23033 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
23034 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
23035 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
23036 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
23037 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
23038 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
23039 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
23040 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
23044 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23045 @node GDB/MI Tracepoint Commands
23046 @section @sc{gdb/mi} Tracepoint Commands
23048 The tracepoint commands are not yet implemented.
23050 @c @subheading -trace-actions
23052 @c @subheading -trace-delete
23054 @c @subheading -trace-disable
23056 @c @subheading -trace-dump
23058 @c @subheading -trace-enable
23060 @c @subheading -trace-exists
23062 @c @subheading -trace-find
23064 @c @subheading -trace-frame-number
23066 @c @subheading -trace-info
23068 @c @subheading -trace-insert
23070 @c @subheading -trace-list
23072 @c @subheading -trace-pass-count
23074 @c @subheading -trace-save
23076 @c @subheading -trace-start
23078 @c @subheading -trace-stop
23081 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23082 @node GDB/MI Symbol Query
23083 @section @sc{gdb/mi} Symbol Query Commands
23086 @subheading The @code{-symbol-info-address} Command
23087 @findex -symbol-info-address
23089 @subsubheading Synopsis
23092 -symbol-info-address @var{symbol}
23095 Describe where @var{symbol} is stored.
23097 @subsubheading @value{GDBN} Command
23099 The corresponding @value{GDBN} command is @samp{info address}.
23101 @subsubheading Example
23105 @subheading The @code{-symbol-info-file} Command
23106 @findex -symbol-info-file
23108 @subsubheading Synopsis
23114 Show the file for the symbol.
23116 @subsubheading @value{GDBN} Command
23118 There's no equivalent @value{GDBN} command. @code{gdbtk} has
23119 @samp{gdb_find_file}.
23121 @subsubheading Example
23125 @subheading The @code{-symbol-info-function} Command
23126 @findex -symbol-info-function
23128 @subsubheading Synopsis
23131 -symbol-info-function
23134 Show which function the symbol lives in.
23136 @subsubheading @value{GDBN} Command
23138 @samp{gdb_get_function} in @code{gdbtk}.
23140 @subsubheading Example
23144 @subheading The @code{-symbol-info-line} Command
23145 @findex -symbol-info-line
23147 @subsubheading Synopsis
23153 Show the core addresses of the code for a source line.
23155 @subsubheading @value{GDBN} Command
23157 The corresponding @value{GDBN} command is @samp{info line}.
23158 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
23160 @subsubheading Example
23164 @subheading The @code{-symbol-info-symbol} Command
23165 @findex -symbol-info-symbol
23167 @subsubheading Synopsis
23170 -symbol-info-symbol @var{addr}
23173 Describe what symbol is at location @var{addr}.
23175 @subsubheading @value{GDBN} Command
23177 The corresponding @value{GDBN} command is @samp{info symbol}.
23179 @subsubheading Example
23183 @subheading The @code{-symbol-list-functions} Command
23184 @findex -symbol-list-functions
23186 @subsubheading Synopsis
23189 -symbol-list-functions
23192 List the functions in the executable.
23194 @subsubheading @value{GDBN} Command
23196 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
23197 @samp{gdb_search} in @code{gdbtk}.
23199 @subsubheading Example
23203 @subheading The @code{-symbol-list-lines} Command
23204 @findex -symbol-list-lines
23206 @subsubheading Synopsis
23209 -symbol-list-lines @var{filename}
23212 Print the list of lines that contain code and their associated program
23213 addresses for the given source filename. The entries are sorted in
23214 ascending PC order.
23216 @subsubheading @value{GDBN} Command
23218 There is no corresponding @value{GDBN} command.
23220 @subsubheading Example
23223 -symbol-list-lines basics.c
23224 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
23229 @subheading The @code{-symbol-list-types} Command
23230 @findex -symbol-list-types
23232 @subsubheading Synopsis
23238 List all the type names.
23240 @subsubheading @value{GDBN} Command
23242 The corresponding commands are @samp{info types} in @value{GDBN},
23243 @samp{gdb_search} in @code{gdbtk}.
23245 @subsubheading Example
23249 @subheading The @code{-symbol-list-variables} Command
23250 @findex -symbol-list-variables
23252 @subsubheading Synopsis
23255 -symbol-list-variables
23258 List all the global and static variable names.
23260 @subsubheading @value{GDBN} Command
23262 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
23264 @subsubheading Example
23268 @subheading The @code{-symbol-locate} Command
23269 @findex -symbol-locate
23271 @subsubheading Synopsis
23277 @subsubheading @value{GDBN} Command
23279 @samp{gdb_loc} in @code{gdbtk}.
23281 @subsubheading Example
23285 @subheading The @code{-symbol-type} Command
23286 @findex -symbol-type
23288 @subsubheading Synopsis
23291 -symbol-type @var{variable}
23294 Show type of @var{variable}.
23296 @subsubheading @value{GDBN} Command
23298 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
23299 @samp{gdb_obj_variable}.
23301 @subsubheading Example
23305 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23306 @node GDB/MI File Commands
23307 @section @sc{gdb/mi} File Commands
23309 This section describes the GDB/MI commands to specify executable file names
23310 and to read in and obtain symbol table information.
23312 @subheading The @code{-file-exec-and-symbols} Command
23313 @findex -file-exec-and-symbols
23315 @subsubheading Synopsis
23318 -file-exec-and-symbols @var{file}
23321 Specify the executable file to be debugged. This file is the one from
23322 which the symbol table is also read. If no file is specified, the
23323 command clears the executable and symbol information. If breakpoints
23324 are set when using this command with no arguments, @value{GDBN} will produce
23325 error messages. Otherwise, no output is produced, except a completion
23328 @subsubheading @value{GDBN} Command
23330 The corresponding @value{GDBN} command is @samp{file}.
23332 @subsubheading Example
23336 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23342 @subheading The @code{-file-exec-file} Command
23343 @findex -file-exec-file
23345 @subsubheading Synopsis
23348 -file-exec-file @var{file}
23351 Specify the executable file to be debugged. Unlike
23352 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
23353 from this file. If used without argument, @value{GDBN} clears the information
23354 about the executable file. No output is produced, except a completion
23357 @subsubheading @value{GDBN} Command
23359 The corresponding @value{GDBN} command is @samp{exec-file}.
23361 @subsubheading Example
23365 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23371 @subheading The @code{-file-list-exec-sections} Command
23372 @findex -file-list-exec-sections
23374 @subsubheading Synopsis
23377 -file-list-exec-sections
23380 List the sections of the current executable file.
23382 @subsubheading @value{GDBN} Command
23384 The @value{GDBN} command @samp{info file} shows, among the rest, the same
23385 information as this command. @code{gdbtk} has a corresponding command
23386 @samp{gdb_load_info}.
23388 @subsubheading Example
23392 @subheading The @code{-file-list-exec-source-file} Command
23393 @findex -file-list-exec-source-file
23395 @subsubheading Synopsis
23398 -file-list-exec-source-file
23401 List the line number, the current source file, and the absolute path
23402 to the current source file for the current executable. The macro
23403 information field has a value of @samp{1} or @samp{0} depending on
23404 whether or not the file includes preprocessor macro information.
23406 @subsubheading @value{GDBN} Command
23408 The @value{GDBN} equivalent is @samp{info source}
23410 @subsubheading Example
23414 123-file-list-exec-source-file
23415 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
23420 @subheading The @code{-file-list-exec-source-files} Command
23421 @findex -file-list-exec-source-files
23423 @subsubheading Synopsis
23426 -file-list-exec-source-files
23429 List the source files for the current executable.
23431 It will always output the filename, but only when @value{GDBN} can find
23432 the absolute file name of a source file, will it output the fullname.
23434 @subsubheading @value{GDBN} Command
23436 The @value{GDBN} equivalent is @samp{info sources}.
23437 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
23439 @subsubheading Example
23442 -file-list-exec-source-files
23444 @{file=foo.c,fullname=/home/foo.c@},
23445 @{file=/home/bar.c,fullname=/home/bar.c@},
23446 @{file=gdb_could_not_find_fullpath.c@}]
23450 @subheading The @code{-file-list-shared-libraries} Command
23451 @findex -file-list-shared-libraries
23453 @subsubheading Synopsis
23456 -file-list-shared-libraries
23459 List the shared libraries in the program.
23461 @subsubheading @value{GDBN} Command
23463 The corresponding @value{GDBN} command is @samp{info shared}.
23465 @subsubheading Example
23469 @subheading The @code{-file-list-symbol-files} Command
23470 @findex -file-list-symbol-files
23472 @subsubheading Synopsis
23475 -file-list-symbol-files
23480 @subsubheading @value{GDBN} Command
23482 The corresponding @value{GDBN} command is @samp{info file} (part of it).
23484 @subsubheading Example
23488 @subheading The @code{-file-symbol-file} Command
23489 @findex -file-symbol-file
23491 @subsubheading Synopsis
23494 -file-symbol-file @var{file}
23497 Read symbol table info from the specified @var{file} argument. When
23498 used without arguments, clears @value{GDBN}'s symbol table info. No output is
23499 produced, except for a completion notification.
23501 @subsubheading @value{GDBN} Command
23503 The corresponding @value{GDBN} command is @samp{symbol-file}.
23505 @subsubheading Example
23509 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
23515 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23516 @node GDB/MI Memory Overlay Commands
23517 @section @sc{gdb/mi} Memory Overlay Commands
23519 The memory overlay commands are not implemented.
23521 @c @subheading -overlay-auto
23523 @c @subheading -overlay-list-mapping-state
23525 @c @subheading -overlay-list-overlays
23527 @c @subheading -overlay-map
23529 @c @subheading -overlay-off
23531 @c @subheading -overlay-on
23533 @c @subheading -overlay-unmap
23535 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23536 @node GDB/MI Signal Handling Commands
23537 @section @sc{gdb/mi} Signal Handling Commands
23539 Signal handling commands are not implemented.
23541 @c @subheading -signal-handle
23543 @c @subheading -signal-list-handle-actions
23545 @c @subheading -signal-list-signal-types
23549 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23550 @node GDB/MI Target Manipulation
23551 @section @sc{gdb/mi} Target Manipulation Commands
23554 @subheading The @code{-target-attach} Command
23555 @findex -target-attach
23557 @subsubheading Synopsis
23560 -target-attach @var{pid} | @var{gid} | @var{file}
23563 Attach to a process @var{pid} or a file @var{file} outside of
23564 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
23565 group, the id previously returned by
23566 @samp{-list-thread-groups --available} must be used.
23568 @subsubheading @value{GDBN} Command
23570 The corresponding @value{GDBN} command is @samp{attach}.
23572 @subsubheading Example
23576 =thread-created,id="1"
23577 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
23582 @subheading The @code{-target-compare-sections} Command
23583 @findex -target-compare-sections
23585 @subsubheading Synopsis
23588 -target-compare-sections [ @var{section} ]
23591 Compare data of section @var{section} on target to the exec file.
23592 Without the argument, all sections are compared.
23594 @subsubheading @value{GDBN} Command
23596 The @value{GDBN} equivalent is @samp{compare-sections}.
23598 @subsubheading Example
23602 @subheading The @code{-target-detach} Command
23603 @findex -target-detach
23605 @subsubheading Synopsis
23608 -target-detach [ @var{pid} | @var{gid} ]
23611 Detach from the remote target which normally resumes its execution.
23612 If either @var{pid} or @var{gid} is specified, detaches from either
23613 the specified process, or specified thread group. There's no output.
23615 @subsubheading @value{GDBN} Command
23617 The corresponding @value{GDBN} command is @samp{detach}.
23619 @subsubheading Example
23629 @subheading The @code{-target-disconnect} Command
23630 @findex -target-disconnect
23632 @subsubheading Synopsis
23638 Disconnect from the remote target. There's no output and the target is
23639 generally not resumed.
23641 @subsubheading @value{GDBN} Command
23643 The corresponding @value{GDBN} command is @samp{disconnect}.
23645 @subsubheading Example
23655 @subheading The @code{-target-download} Command
23656 @findex -target-download
23658 @subsubheading Synopsis
23664 Loads the executable onto the remote target.
23665 It prints out an update message every half second, which includes the fields:
23669 The name of the section.
23671 The size of what has been sent so far for that section.
23673 The size of the section.
23675 The total size of what was sent so far (the current and the previous sections).
23677 The size of the overall executable to download.
23681 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
23682 @sc{gdb/mi} Output Syntax}).
23684 In addition, it prints the name and size of the sections, as they are
23685 downloaded. These messages include the following fields:
23689 The name of the section.
23691 The size of the section.
23693 The size of the overall executable to download.
23697 At the end, a summary is printed.
23699 @subsubheading @value{GDBN} Command
23701 The corresponding @value{GDBN} command is @samp{load}.
23703 @subsubheading Example
23705 Note: each status message appears on a single line. Here the messages
23706 have been broken down so that they can fit onto a page.
23711 +download,@{section=".text",section-size="6668",total-size="9880"@}
23712 +download,@{section=".text",section-sent="512",section-size="6668",
23713 total-sent="512",total-size="9880"@}
23714 +download,@{section=".text",section-sent="1024",section-size="6668",
23715 total-sent="1024",total-size="9880"@}
23716 +download,@{section=".text",section-sent="1536",section-size="6668",
23717 total-sent="1536",total-size="9880"@}
23718 +download,@{section=".text",section-sent="2048",section-size="6668",
23719 total-sent="2048",total-size="9880"@}
23720 +download,@{section=".text",section-sent="2560",section-size="6668",
23721 total-sent="2560",total-size="9880"@}
23722 +download,@{section=".text",section-sent="3072",section-size="6668",
23723 total-sent="3072",total-size="9880"@}
23724 +download,@{section=".text",section-sent="3584",section-size="6668",
23725 total-sent="3584",total-size="9880"@}
23726 +download,@{section=".text",section-sent="4096",section-size="6668",
23727 total-sent="4096",total-size="9880"@}
23728 +download,@{section=".text",section-sent="4608",section-size="6668",
23729 total-sent="4608",total-size="9880"@}
23730 +download,@{section=".text",section-sent="5120",section-size="6668",
23731 total-sent="5120",total-size="9880"@}
23732 +download,@{section=".text",section-sent="5632",section-size="6668",
23733 total-sent="5632",total-size="9880"@}
23734 +download,@{section=".text",section-sent="6144",section-size="6668",
23735 total-sent="6144",total-size="9880"@}
23736 +download,@{section=".text",section-sent="6656",section-size="6668",
23737 total-sent="6656",total-size="9880"@}
23738 +download,@{section=".init",section-size="28",total-size="9880"@}
23739 +download,@{section=".fini",section-size="28",total-size="9880"@}
23740 +download,@{section=".data",section-size="3156",total-size="9880"@}
23741 +download,@{section=".data",section-sent="512",section-size="3156",
23742 total-sent="7236",total-size="9880"@}
23743 +download,@{section=".data",section-sent="1024",section-size="3156",
23744 total-sent="7748",total-size="9880"@}
23745 +download,@{section=".data",section-sent="1536",section-size="3156",
23746 total-sent="8260",total-size="9880"@}
23747 +download,@{section=".data",section-sent="2048",section-size="3156",
23748 total-sent="8772",total-size="9880"@}
23749 +download,@{section=".data",section-sent="2560",section-size="3156",
23750 total-sent="9284",total-size="9880"@}
23751 +download,@{section=".data",section-sent="3072",section-size="3156",
23752 total-sent="9796",total-size="9880"@}
23753 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
23759 @subheading The @code{-target-exec-status} Command
23760 @findex -target-exec-status
23762 @subsubheading Synopsis
23765 -target-exec-status
23768 Provide information on the state of the target (whether it is running or
23769 not, for instance).
23771 @subsubheading @value{GDBN} Command
23773 There's no equivalent @value{GDBN} command.
23775 @subsubheading Example
23779 @subheading The @code{-target-list-available-targets} Command
23780 @findex -target-list-available-targets
23782 @subsubheading Synopsis
23785 -target-list-available-targets
23788 List the possible targets to connect to.
23790 @subsubheading @value{GDBN} Command
23792 The corresponding @value{GDBN} command is @samp{help target}.
23794 @subsubheading Example
23798 @subheading The @code{-target-list-current-targets} Command
23799 @findex -target-list-current-targets
23801 @subsubheading Synopsis
23804 -target-list-current-targets
23807 Describe the current target.
23809 @subsubheading @value{GDBN} Command
23811 The corresponding information is printed by @samp{info file} (among
23814 @subsubheading Example
23818 @subheading The @code{-target-list-parameters} Command
23819 @findex -target-list-parameters
23821 @subsubheading Synopsis
23824 -target-list-parameters
23829 @subsubheading @value{GDBN} Command
23833 @subsubheading Example
23837 @subheading The @code{-target-select} Command
23838 @findex -target-select
23840 @subsubheading Synopsis
23843 -target-select @var{type} @var{parameters @dots{}}
23846 Connect @value{GDBN} to the remote target. This command takes two args:
23850 The type of target, for instance @samp{remote}, etc.
23851 @item @var{parameters}
23852 Device names, host names and the like. @xref{Target Commands, ,
23853 Commands for Managing Targets}, for more details.
23856 The output is a connection notification, followed by the address at
23857 which the target program is, in the following form:
23860 ^connected,addr="@var{address}",func="@var{function name}",
23861 args=[@var{arg list}]
23864 @subsubheading @value{GDBN} Command
23866 The corresponding @value{GDBN} command is @samp{target}.
23868 @subsubheading Example
23872 -target-select remote /dev/ttya
23873 ^connected,addr="0xfe00a300",func="??",args=[]
23877 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23878 @node GDB/MI File Transfer Commands
23879 @section @sc{gdb/mi} File Transfer Commands
23882 @subheading The @code{-target-file-put} Command
23883 @findex -target-file-put
23885 @subsubheading Synopsis
23888 -target-file-put @var{hostfile} @var{targetfile}
23891 Copy file @var{hostfile} from the host system (the machine running
23892 @value{GDBN}) to @var{targetfile} on the target system.
23894 @subsubheading @value{GDBN} Command
23896 The corresponding @value{GDBN} command is @samp{remote put}.
23898 @subsubheading Example
23902 -target-file-put localfile remotefile
23908 @subheading The @code{-target-file-get} Command
23909 @findex -target-file-get
23911 @subsubheading Synopsis
23914 -target-file-get @var{targetfile} @var{hostfile}
23917 Copy file @var{targetfile} from the target system to @var{hostfile}
23918 on the host system.
23920 @subsubheading @value{GDBN} Command
23922 The corresponding @value{GDBN} command is @samp{remote get}.
23924 @subsubheading Example
23928 -target-file-get remotefile localfile
23934 @subheading The @code{-target-file-delete} Command
23935 @findex -target-file-delete
23937 @subsubheading Synopsis
23940 -target-file-delete @var{targetfile}
23943 Delete @var{targetfile} from the target system.
23945 @subsubheading @value{GDBN} Command
23947 The corresponding @value{GDBN} command is @samp{remote delete}.
23949 @subsubheading Example
23953 -target-file-delete remotefile
23959 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23960 @node GDB/MI Miscellaneous Commands
23961 @section Miscellaneous @sc{gdb/mi} Commands
23963 @c @subheading -gdb-complete
23965 @subheading The @code{-gdb-exit} Command
23968 @subsubheading Synopsis
23974 Exit @value{GDBN} immediately.
23976 @subsubheading @value{GDBN} Command
23978 Approximately corresponds to @samp{quit}.
23980 @subsubheading Example
23989 @subheading The @code{-exec-abort} Command
23990 @findex -exec-abort
23992 @subsubheading Synopsis
23998 Kill the inferior running program.
24000 @subsubheading @value{GDBN} Command
24002 The corresponding @value{GDBN} command is @samp{kill}.
24004 @subsubheading Example
24008 @subheading The @code{-gdb-set} Command
24011 @subsubheading Synopsis
24017 Set an internal @value{GDBN} variable.
24018 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
24020 @subsubheading @value{GDBN} Command
24022 The corresponding @value{GDBN} command is @samp{set}.
24024 @subsubheading Example
24034 @subheading The @code{-gdb-show} Command
24037 @subsubheading Synopsis
24043 Show the current value of a @value{GDBN} variable.
24045 @subsubheading @value{GDBN} Command
24047 The corresponding @value{GDBN} command is @samp{show}.
24049 @subsubheading Example
24058 @c @subheading -gdb-source
24061 @subheading The @code{-gdb-version} Command
24062 @findex -gdb-version
24064 @subsubheading Synopsis
24070 Show version information for @value{GDBN}. Used mostly in testing.
24072 @subsubheading @value{GDBN} Command
24074 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
24075 default shows this information when you start an interactive session.
24077 @subsubheading Example
24079 @c This example modifies the actual output from GDB to avoid overfull
24085 ~Copyright 2000 Free Software Foundation, Inc.
24086 ~GDB is free software, covered by the GNU General Public License, and
24087 ~you are welcome to change it and/or distribute copies of it under
24088 ~ certain conditions.
24089 ~Type "show copying" to see the conditions.
24090 ~There is absolutely no warranty for GDB. Type "show warranty" for
24092 ~This GDB was configured as
24093 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
24098 @subheading The @code{-list-features} Command
24099 @findex -list-features
24101 Returns a list of particular features of the MI protocol that
24102 this version of gdb implements. A feature can be a command,
24103 or a new field in an output of some command, or even an
24104 important bugfix. While a frontend can sometimes detect presence
24105 of a feature at runtime, it is easier to perform detection at debugger
24108 The command returns a list of strings, with each string naming an
24109 available feature. Each returned string is just a name, it does not
24110 have any internal structure. The list of possible feature names
24116 (gdb) -list-features
24117 ^done,result=["feature1","feature2"]
24120 The current list of features is:
24123 @item frozen-varobjs
24124 Indicates presence of the @code{-var-set-frozen} command, as well
24125 as possible presense of the @code{frozen} field in the output
24126 of @code{-varobj-create}.
24127 @item pending-breakpoints
24128 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
24130 Indicates presence of the @code{-thread-info} command.
24134 @subheading The @code{-list-target-features} Command
24135 @findex -list-target-features
24137 Returns a list of particular features that are supported by the
24138 target. Those features affect the permitted MI commands, but
24139 unlike the features reported by the @code{-list-features} command, the
24140 features depend on which target GDB is using at the moment. Whenever
24141 a target can change, due to commands such as @code{-target-select},
24142 @code{-target-attach} or @code{-exec-run}, the list of target features
24143 may change, and the frontend should obtain it again.
24147 (gdb) -list-features
24148 ^done,result=["async"]
24151 The current list of features is:
24155 Indicates that the target is capable of asynchronous command
24156 execution, which means that @value{GDBN} will accept further commands
24157 while the target is running.
24161 @subheading The @code{-list-thread-groups} Command
24162 @findex -list-thread-groups
24164 @subheading Synopsis
24167 -list-thread-groups [ --available ] [ @var{group} ]
24170 When used without the @var{group} parameter, lists top-level thread
24171 groups that are being debugged. When used with the @var{group}
24172 parameter, the children of the specified group are listed. The
24173 children can be either threads, or other groups. At present,
24174 @value{GDBN} will not report both threads and groups as children at
24175 the same time, but it may change in future.
24177 With the @samp{--available} option, instead of reporting groups that
24178 are been debugged, GDB will report all thread groups available on the
24179 target. Using the @samp{--available} option together with @var{group}
24182 @subheading Example
24186 -list-thread-groups
24187 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
24188 -list-thread-groups 17
24189 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24190 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24191 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24192 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24193 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
24196 @subheading The @code{-interpreter-exec} Command
24197 @findex -interpreter-exec
24199 @subheading Synopsis
24202 -interpreter-exec @var{interpreter} @var{command}
24204 @anchor{-interpreter-exec}
24206 Execute the specified @var{command} in the given @var{interpreter}.
24208 @subheading @value{GDBN} Command
24210 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
24212 @subheading Example
24216 -interpreter-exec console "break main"
24217 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
24218 &"During symbol reading, bad structure-type format.\n"
24219 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
24224 @subheading The @code{-inferior-tty-set} Command
24225 @findex -inferior-tty-set
24227 @subheading Synopsis
24230 -inferior-tty-set /dev/pts/1
24233 Set terminal for future runs of the program being debugged.
24235 @subheading @value{GDBN} Command
24237 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
24239 @subheading Example
24243 -inferior-tty-set /dev/pts/1
24248 @subheading The @code{-inferior-tty-show} Command
24249 @findex -inferior-tty-show
24251 @subheading Synopsis
24257 Show terminal for future runs of program being debugged.
24259 @subheading @value{GDBN} Command
24261 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
24263 @subheading Example
24267 -inferior-tty-set /dev/pts/1
24271 ^done,inferior_tty_terminal="/dev/pts/1"
24275 @subheading The @code{-enable-timings} Command
24276 @findex -enable-timings
24278 @subheading Synopsis
24281 -enable-timings [yes | no]
24284 Toggle the printing of the wallclock, user and system times for an MI
24285 command as a field in its output. This command is to help frontend
24286 developers optimize the performance of their code. No argument is
24287 equivalent to @samp{yes}.
24289 @subheading @value{GDBN} Command
24293 @subheading Example
24301 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24302 addr="0x080484ed",func="main",file="myprog.c",
24303 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
24304 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
24312 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24313 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
24314 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
24315 fullname="/home/nickrob/myprog.c",line="73"@}
24320 @chapter @value{GDBN} Annotations
24322 This chapter describes annotations in @value{GDBN}. Annotations were
24323 designed to interface @value{GDBN} to graphical user interfaces or other
24324 similar programs which want to interact with @value{GDBN} at a
24325 relatively high level.
24327 The annotation mechanism has largely been superseded by @sc{gdb/mi}
24331 This is Edition @value{EDITION}, @value{DATE}.
24335 * Annotations Overview:: What annotations are; the general syntax.
24336 * Server Prefix:: Issuing a command without affecting user state.
24337 * Prompting:: Annotations marking @value{GDBN}'s need for input.
24338 * Errors:: Annotations for error messages.
24339 * Invalidation:: Some annotations describe things now invalid.
24340 * Annotations for Running::
24341 Whether the program is running, how it stopped, etc.
24342 * Source Annotations:: Annotations describing source code.
24345 @node Annotations Overview
24346 @section What is an Annotation?
24347 @cindex annotations
24349 Annotations start with a newline character, two @samp{control-z}
24350 characters, and the name of the annotation. If there is no additional
24351 information associated with this annotation, the name of the annotation
24352 is followed immediately by a newline. If there is additional
24353 information, the name of the annotation is followed by a space, the
24354 additional information, and a newline. The additional information
24355 cannot contain newline characters.
24357 Any output not beginning with a newline and two @samp{control-z}
24358 characters denotes literal output from @value{GDBN}. Currently there is
24359 no need for @value{GDBN} to output a newline followed by two
24360 @samp{control-z} characters, but if there was such a need, the
24361 annotations could be extended with an @samp{escape} annotation which
24362 means those three characters as output.
24364 The annotation @var{level}, which is specified using the
24365 @option{--annotate} command line option (@pxref{Mode Options}), controls
24366 how much information @value{GDBN} prints together with its prompt,
24367 values of expressions, source lines, and other types of output. Level 0
24368 is for no annotations, level 1 is for use when @value{GDBN} is run as a
24369 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
24370 for programs that control @value{GDBN}, and level 2 annotations have
24371 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
24372 Interface, annotate, GDB's Obsolete Annotations}).
24375 @kindex set annotate
24376 @item set annotate @var{level}
24377 The @value{GDBN} command @code{set annotate} sets the level of
24378 annotations to the specified @var{level}.
24380 @item show annotate
24381 @kindex show annotate
24382 Show the current annotation level.
24385 This chapter describes level 3 annotations.
24387 A simple example of starting up @value{GDBN} with annotations is:
24390 $ @kbd{gdb --annotate=3}
24392 Copyright 2003 Free Software Foundation, Inc.
24393 GDB is free software, covered by the GNU General Public License,
24394 and you are welcome to change it and/or distribute copies of it
24395 under certain conditions.
24396 Type "show copying" to see the conditions.
24397 There is absolutely no warranty for GDB. Type "show warranty"
24399 This GDB was configured as "i386-pc-linux-gnu"
24410 Here @samp{quit} is input to @value{GDBN}; the rest is output from
24411 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
24412 denotes a @samp{control-z} character) are annotations; the rest is
24413 output from @value{GDBN}.
24415 @node Server Prefix
24416 @section The Server Prefix
24417 @cindex server prefix
24419 If you prefix a command with @samp{server } then it will not affect
24420 the command history, nor will it affect @value{GDBN}'s notion of which
24421 command to repeat if @key{RET} is pressed on a line by itself. This
24422 means that commands can be run behind a user's back by a front-end in
24423 a transparent manner.
24425 The server prefix does not affect the recording of values into the value
24426 history; to print a value without recording it into the value history,
24427 use the @code{output} command instead of the @code{print} command.
24430 @section Annotation for @value{GDBN} Input
24432 @cindex annotations for prompts
24433 When @value{GDBN} prompts for input, it annotates this fact so it is possible
24434 to know when to send output, when the output from a given command is
24437 Different kinds of input each have a different @dfn{input type}. Each
24438 input type has three annotations: a @code{pre-} annotation, which
24439 denotes the beginning of any prompt which is being output, a plain
24440 annotation, which denotes the end of the prompt, and then a @code{post-}
24441 annotation which denotes the end of any echo which may (or may not) be
24442 associated with the input. For example, the @code{prompt} input type
24443 features the following annotations:
24451 The input types are
24454 @findex pre-prompt annotation
24455 @findex prompt annotation
24456 @findex post-prompt annotation
24458 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
24460 @findex pre-commands annotation
24461 @findex commands annotation
24462 @findex post-commands annotation
24464 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
24465 command. The annotations are repeated for each command which is input.
24467 @findex pre-overload-choice annotation
24468 @findex overload-choice annotation
24469 @findex post-overload-choice annotation
24470 @item overload-choice
24471 When @value{GDBN} wants the user to select between various overloaded functions.
24473 @findex pre-query annotation
24474 @findex query annotation
24475 @findex post-query annotation
24477 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
24479 @findex pre-prompt-for-continue annotation
24480 @findex prompt-for-continue annotation
24481 @findex post-prompt-for-continue annotation
24482 @item prompt-for-continue
24483 When @value{GDBN} is asking the user to press return to continue. Note: Don't
24484 expect this to work well; instead use @code{set height 0} to disable
24485 prompting. This is because the counting of lines is buggy in the
24486 presence of annotations.
24491 @cindex annotations for errors, warnings and interrupts
24493 @findex quit annotation
24498 This annotation occurs right before @value{GDBN} responds to an interrupt.
24500 @findex error annotation
24505 This annotation occurs right before @value{GDBN} responds to an error.
24507 Quit and error annotations indicate that any annotations which @value{GDBN} was
24508 in the middle of may end abruptly. For example, if a
24509 @code{value-history-begin} annotation is followed by a @code{error}, one
24510 cannot expect to receive the matching @code{value-history-end}. One
24511 cannot expect not to receive it either, however; an error annotation
24512 does not necessarily mean that @value{GDBN} is immediately returning all the way
24515 @findex error-begin annotation
24516 A quit or error annotation may be preceded by
24522 Any output between that and the quit or error annotation is the error
24525 Warning messages are not yet annotated.
24526 @c If we want to change that, need to fix warning(), type_error(),
24527 @c range_error(), and possibly other places.
24530 @section Invalidation Notices
24532 @cindex annotations for invalidation messages
24533 The following annotations say that certain pieces of state may have
24537 @findex frames-invalid annotation
24538 @item ^Z^Zframes-invalid
24540 The frames (for example, output from the @code{backtrace} command) may
24543 @findex breakpoints-invalid annotation
24544 @item ^Z^Zbreakpoints-invalid
24546 The breakpoints may have changed. For example, the user just added or
24547 deleted a breakpoint.
24550 @node Annotations for Running
24551 @section Running the Program
24552 @cindex annotations for running programs
24554 @findex starting annotation
24555 @findex stopping annotation
24556 When the program starts executing due to a @value{GDBN} command such as
24557 @code{step} or @code{continue},
24563 is output. When the program stops,
24569 is output. Before the @code{stopped} annotation, a variety of
24570 annotations describe how the program stopped.
24573 @findex exited annotation
24574 @item ^Z^Zexited @var{exit-status}
24575 The program exited, and @var{exit-status} is the exit status (zero for
24576 successful exit, otherwise nonzero).
24578 @findex signalled annotation
24579 @findex signal-name annotation
24580 @findex signal-name-end annotation
24581 @findex signal-string annotation
24582 @findex signal-string-end annotation
24583 @item ^Z^Zsignalled
24584 The program exited with a signal. After the @code{^Z^Zsignalled}, the
24585 annotation continues:
24591 ^Z^Zsignal-name-end
24595 ^Z^Zsignal-string-end
24600 where @var{name} is the name of the signal, such as @code{SIGILL} or
24601 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
24602 as @code{Illegal Instruction} or @code{Segmentation fault}.
24603 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
24604 user's benefit and have no particular format.
24606 @findex signal annotation
24608 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
24609 just saying that the program received the signal, not that it was
24610 terminated with it.
24612 @findex breakpoint annotation
24613 @item ^Z^Zbreakpoint @var{number}
24614 The program hit breakpoint number @var{number}.
24616 @findex watchpoint annotation
24617 @item ^Z^Zwatchpoint @var{number}
24618 The program hit watchpoint number @var{number}.
24621 @node Source Annotations
24622 @section Displaying Source
24623 @cindex annotations for source display
24625 @findex source annotation
24626 The following annotation is used instead of displaying source code:
24629 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
24632 where @var{filename} is an absolute file name indicating which source
24633 file, @var{line} is the line number within that file (where 1 is the
24634 first line in the file), @var{character} is the character position
24635 within the file (where 0 is the first character in the file) (for most
24636 debug formats this will necessarily point to the beginning of a line),
24637 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
24638 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
24639 @var{addr} is the address in the target program associated with the
24640 source which is being displayed. @var{addr} is in the form @samp{0x}
24641 followed by one or more lowercase hex digits (note that this does not
24642 depend on the language).
24645 @chapter Reporting Bugs in @value{GDBN}
24646 @cindex bugs in @value{GDBN}
24647 @cindex reporting bugs in @value{GDBN}
24649 Your bug reports play an essential role in making @value{GDBN} reliable.
24651 Reporting a bug may help you by bringing a solution to your problem, or it
24652 may not. But in any case the principal function of a bug report is to help
24653 the entire community by making the next version of @value{GDBN} work better. Bug
24654 reports are your contribution to the maintenance of @value{GDBN}.
24656 In order for a bug report to serve its purpose, you must include the
24657 information that enables us to fix the bug.
24660 * Bug Criteria:: Have you found a bug?
24661 * Bug Reporting:: How to report bugs
24665 @section Have You Found a Bug?
24666 @cindex bug criteria
24668 If you are not sure whether you have found a bug, here are some guidelines:
24671 @cindex fatal signal
24672 @cindex debugger crash
24673 @cindex crash of debugger
24675 If the debugger gets a fatal signal, for any input whatever, that is a
24676 @value{GDBN} bug. Reliable debuggers never crash.
24678 @cindex error on valid input
24680 If @value{GDBN} produces an error message for valid input, that is a
24681 bug. (Note that if you're cross debugging, the problem may also be
24682 somewhere in the connection to the target.)
24684 @cindex invalid input
24686 If @value{GDBN} does not produce an error message for invalid input,
24687 that is a bug. However, you should note that your idea of
24688 ``invalid input'' might be our idea of ``an extension'' or ``support
24689 for traditional practice''.
24692 If you are an experienced user of debugging tools, your suggestions
24693 for improvement of @value{GDBN} are welcome in any case.
24696 @node Bug Reporting
24697 @section How to Report Bugs
24698 @cindex bug reports
24699 @cindex @value{GDBN} bugs, reporting
24701 A number of companies and individuals offer support for @sc{gnu} products.
24702 If you obtained @value{GDBN} from a support organization, we recommend you
24703 contact that organization first.
24705 You can find contact information for many support companies and
24706 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
24708 @c should add a web page ref...
24711 @ifset BUGURL_DEFAULT
24712 In any event, we also recommend that you submit bug reports for
24713 @value{GDBN}. The preferred method is to submit them directly using
24714 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
24715 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
24718 @strong{Do not send bug reports to @samp{info-gdb}, or to
24719 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
24720 not want to receive bug reports. Those that do have arranged to receive
24723 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
24724 serves as a repeater. The mailing list and the newsgroup carry exactly
24725 the same messages. Often people think of posting bug reports to the
24726 newsgroup instead of mailing them. This appears to work, but it has one
24727 problem which can be crucial: a newsgroup posting often lacks a mail
24728 path back to the sender. Thus, if we need to ask for more information,
24729 we may be unable to reach you. For this reason, it is better to send
24730 bug reports to the mailing list.
24732 @ifclear BUGURL_DEFAULT
24733 In any event, we also recommend that you submit bug reports for
24734 @value{GDBN} to @value{BUGURL}.
24738 The fundamental principle of reporting bugs usefully is this:
24739 @strong{report all the facts}. If you are not sure whether to state a
24740 fact or leave it out, state it!
24742 Often people omit facts because they think they know what causes the
24743 problem and assume that some details do not matter. Thus, you might
24744 assume that the name of the variable you use in an example does not matter.
24745 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
24746 stray memory reference which happens to fetch from the location where that
24747 name is stored in memory; perhaps, if the name were different, the contents
24748 of that location would fool the debugger into doing the right thing despite
24749 the bug. Play it safe and give a specific, complete example. That is the
24750 easiest thing for you to do, and the most helpful.
24752 Keep in mind that the purpose of a bug report is to enable us to fix the
24753 bug. It may be that the bug has been reported previously, but neither
24754 you nor we can know that unless your bug report is complete and
24757 Sometimes people give a few sketchy facts and ask, ``Does this ring a
24758 bell?'' Those bug reports are useless, and we urge everyone to
24759 @emph{refuse to respond to them} except to chide the sender to report
24762 To enable us to fix the bug, you should include all these things:
24766 The version of @value{GDBN}. @value{GDBN} announces it if you start
24767 with no arguments; you can also print it at any time using @code{show
24770 Without this, we will not know whether there is any point in looking for
24771 the bug in the current version of @value{GDBN}.
24774 The type of machine you are using, and the operating system name and
24778 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
24779 ``@value{GCC}--2.8.1''.
24782 What compiler (and its version) was used to compile the program you are
24783 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
24784 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
24785 to get this information; for other compilers, see the documentation for
24789 The command arguments you gave the compiler to compile your example and
24790 observe the bug. For example, did you use @samp{-O}? To guarantee
24791 you will not omit something important, list them all. A copy of the
24792 Makefile (or the output from make) is sufficient.
24794 If we were to try to guess the arguments, we would probably guess wrong
24795 and then we might not encounter the bug.
24798 A complete input script, and all necessary source files, that will
24802 A description of what behavior you observe that you believe is
24803 incorrect. For example, ``It gets a fatal signal.''
24805 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
24806 will certainly notice it. But if the bug is incorrect output, we might
24807 not notice unless it is glaringly wrong. You might as well not give us
24808 a chance to make a mistake.
24810 Even if the problem you experience is a fatal signal, you should still
24811 say so explicitly. Suppose something strange is going on, such as, your
24812 copy of @value{GDBN} is out of synch, or you have encountered a bug in
24813 the C library on your system. (This has happened!) Your copy might
24814 crash and ours would not. If you told us to expect a crash, then when
24815 ours fails to crash, we would know that the bug was not happening for
24816 us. If you had not told us to expect a crash, then we would not be able
24817 to draw any conclusion from our observations.
24820 @cindex recording a session script
24821 To collect all this information, you can use a session recording program
24822 such as @command{script}, which is available on many Unix systems.
24823 Just run your @value{GDBN} session inside @command{script} and then
24824 include the @file{typescript} file with your bug report.
24826 Another way to record a @value{GDBN} session is to run @value{GDBN}
24827 inside Emacs and then save the entire buffer to a file.
24830 If you wish to suggest changes to the @value{GDBN} source, send us context
24831 diffs. If you even discuss something in the @value{GDBN} source, refer to
24832 it by context, not by line number.
24834 The line numbers in our development sources will not match those in your
24835 sources. Your line numbers would convey no useful information to us.
24839 Here are some things that are not necessary:
24843 A description of the envelope of the bug.
24845 Often people who encounter a bug spend a lot of time investigating
24846 which changes to the input file will make the bug go away and which
24847 changes will not affect it.
24849 This is often time consuming and not very useful, because the way we
24850 will find the bug is by running a single example under the debugger
24851 with breakpoints, not by pure deduction from a series of examples.
24852 We recommend that you save your time for something else.
24854 Of course, if you can find a simpler example to report @emph{instead}
24855 of the original one, that is a convenience for us. Errors in the
24856 output will be easier to spot, running under the debugger will take
24857 less time, and so on.
24859 However, simplification is not vital; if you do not want to do this,
24860 report the bug anyway and send us the entire test case you used.
24863 A patch for the bug.
24865 A patch for the bug does help us if it is a good one. But do not omit
24866 the necessary information, such as the test case, on the assumption that
24867 a patch is all we need. We might see problems with your patch and decide
24868 to fix the problem another way, or we might not understand it at all.
24870 Sometimes with a program as complicated as @value{GDBN} it is very hard to
24871 construct an example that will make the program follow a certain path
24872 through the code. If you do not send us the example, we will not be able
24873 to construct one, so we will not be able to verify that the bug is fixed.
24875 And if we cannot understand what bug you are trying to fix, or why your
24876 patch should be an improvement, we will not install it. A test case will
24877 help us to understand.
24880 A guess about what the bug is or what it depends on.
24882 Such guesses are usually wrong. Even we cannot guess right about such
24883 things without first using the debugger to find the facts.
24886 @c The readline documentation is distributed with the readline code
24887 @c and consists of the two following files:
24889 @c inc-hist.texinfo
24890 @c Use -I with makeinfo to point to the appropriate directory,
24891 @c environment var TEXINPUTS with TeX.
24892 @include rluser.texi
24893 @include inc-hist.texinfo
24896 @node Formatting Documentation
24897 @appendix Formatting Documentation
24899 @cindex @value{GDBN} reference card
24900 @cindex reference card
24901 The @value{GDBN} 4 release includes an already-formatted reference card, ready
24902 for printing with PostScript or Ghostscript, in the @file{gdb}
24903 subdirectory of the main source directory@footnote{In
24904 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
24905 release.}. If you can use PostScript or Ghostscript with your printer,
24906 you can print the reference card immediately with @file{refcard.ps}.
24908 The release also includes the source for the reference card. You
24909 can format it, using @TeX{}, by typing:
24915 The @value{GDBN} reference card is designed to print in @dfn{landscape}
24916 mode on US ``letter'' size paper;
24917 that is, on a sheet 11 inches wide by 8.5 inches
24918 high. You will need to specify this form of printing as an option to
24919 your @sc{dvi} output program.
24921 @cindex documentation
24923 All the documentation for @value{GDBN} comes as part of the machine-readable
24924 distribution. The documentation is written in Texinfo format, which is
24925 a documentation system that uses a single source file to produce both
24926 on-line information and a printed manual. You can use one of the Info
24927 formatting commands to create the on-line version of the documentation
24928 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
24930 @value{GDBN} includes an already formatted copy of the on-line Info
24931 version of this manual in the @file{gdb} subdirectory. The main Info
24932 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
24933 subordinate files matching @samp{gdb.info*} in the same directory. If
24934 necessary, you can print out these files, or read them with any editor;
24935 but they are easier to read using the @code{info} subsystem in @sc{gnu}
24936 Emacs or the standalone @code{info} program, available as part of the
24937 @sc{gnu} Texinfo distribution.
24939 If you want to format these Info files yourself, you need one of the
24940 Info formatting programs, such as @code{texinfo-format-buffer} or
24943 If you have @code{makeinfo} installed, and are in the top level
24944 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
24945 version @value{GDBVN}), you can make the Info file by typing:
24952 If you want to typeset and print copies of this manual, you need @TeX{},
24953 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
24954 Texinfo definitions file.
24956 @TeX{} is a typesetting program; it does not print files directly, but
24957 produces output files called @sc{dvi} files. To print a typeset
24958 document, you need a program to print @sc{dvi} files. If your system
24959 has @TeX{} installed, chances are it has such a program. The precise
24960 command to use depends on your system; @kbd{lpr -d} is common; another
24961 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
24962 require a file name without any extension or a @samp{.dvi} extension.
24964 @TeX{} also requires a macro definitions file called
24965 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
24966 written in Texinfo format. On its own, @TeX{} cannot either read or
24967 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
24968 and is located in the @file{gdb-@var{version-number}/texinfo}
24971 If you have @TeX{} and a @sc{dvi} printer program installed, you can
24972 typeset and print this manual. First switch to the @file{gdb}
24973 subdirectory of the main source directory (for example, to
24974 @file{gdb-@value{GDBVN}/gdb}) and type:
24980 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
24982 @node Installing GDB
24983 @appendix Installing @value{GDBN}
24984 @cindex installation
24987 * Requirements:: Requirements for building @value{GDBN}
24988 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
24989 * Separate Objdir:: Compiling @value{GDBN} in another directory
24990 * Config Names:: Specifying names for hosts and targets
24991 * Configure Options:: Summary of options for configure
24992 * System-wide configuration:: Having a system-wide init file
24996 @section Requirements for Building @value{GDBN}
24997 @cindex building @value{GDBN}, requirements for
24999 Building @value{GDBN} requires various tools and packages to be available.
25000 Other packages will be used only if they are found.
25002 @heading Tools/Packages Necessary for Building @value{GDBN}
25004 @item ISO C90 compiler
25005 @value{GDBN} is written in ISO C90. It should be buildable with any
25006 working C90 compiler, e.g.@: GCC.
25010 @heading Tools/Packages Optional for Building @value{GDBN}
25014 @value{GDBN} can use the Expat XML parsing library. This library may be
25015 included with your operating system distribution; if it is not, you
25016 can get the latest version from @url{http://expat.sourceforge.net}.
25017 The @file{configure} script will search for this library in several
25018 standard locations; if it is installed in an unusual path, you can
25019 use the @option{--with-libexpat-prefix} option to specify its location.
25025 Remote protocol memory maps (@pxref{Memory Map Format})
25027 Target descriptions (@pxref{Target Descriptions})
25029 Remote shared library lists (@pxref{Library List Format})
25031 MS-Windows shared libraries (@pxref{Shared Libraries})
25035 @cindex compressed debug sections
25036 @value{GDBN} will use the @samp{zlib} library, if available, to read
25037 compressed debug sections. Some linkers, such as GNU gold, are capable
25038 of producing binaries with compressed debug sections. If @value{GDBN}
25039 is compiled with @samp{zlib}, it will be able to read the debug
25040 information in such binaries.
25042 The @samp{zlib} library is likely included with your operating system
25043 distribution; if it is not, you can get the latest version from
25044 @url{http://zlib.net}.
25047 @value{GDBN}'s features related to character sets (@pxref{Character
25048 Sets}) require a functioning @code{iconv} implementation. If you are
25049 on a GNU system, then this is provided by the GNU C Library. Some
25050 other systems also provide a working @code{iconv}.
25052 On systems with @code{iconv}, you can install GNU Libiconv. If you
25053 have previously installed Libiconv, you can use the
25054 @option{--with-libiconv-prefix} option to configure.
25056 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
25057 arrange to build Libiconv if a directory named @file{libiconv} appears
25058 in the top-most source directory. If Libiconv is built this way, and
25059 if the operating system does not provide a suitable @code{iconv}
25060 implementation, then the just-built library will automatically be used
25061 by @value{GDBN}. One easy way to set this up is to download GNU
25062 Libiconv, unpack it, and then rename the directory holding the
25063 Libiconv source code to @samp{libiconv}.
25066 @node Running Configure
25067 @section Invoking the @value{GDBN} @file{configure} Script
25068 @cindex configuring @value{GDBN}
25069 @value{GDBN} comes with a @file{configure} script that automates the process
25070 of preparing @value{GDBN} for installation; you can then use @code{make} to
25071 build the @code{gdb} program.
25073 @c irrelevant in info file; it's as current as the code it lives with.
25074 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
25075 look at the @file{README} file in the sources; we may have improved the
25076 installation procedures since publishing this manual.}
25079 The @value{GDBN} distribution includes all the source code you need for
25080 @value{GDBN} in a single directory, whose name is usually composed by
25081 appending the version number to @samp{gdb}.
25083 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
25084 @file{gdb-@value{GDBVN}} directory. That directory contains:
25087 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
25088 script for configuring @value{GDBN} and all its supporting libraries
25090 @item gdb-@value{GDBVN}/gdb
25091 the source specific to @value{GDBN} itself
25093 @item gdb-@value{GDBVN}/bfd
25094 source for the Binary File Descriptor library
25096 @item gdb-@value{GDBVN}/include
25097 @sc{gnu} include files
25099 @item gdb-@value{GDBVN}/libiberty
25100 source for the @samp{-liberty} free software library
25102 @item gdb-@value{GDBVN}/opcodes
25103 source for the library of opcode tables and disassemblers
25105 @item gdb-@value{GDBVN}/readline
25106 source for the @sc{gnu} command-line interface
25108 @item gdb-@value{GDBVN}/glob
25109 source for the @sc{gnu} filename pattern-matching subroutine
25111 @item gdb-@value{GDBVN}/mmalloc
25112 source for the @sc{gnu} memory-mapped malloc package
25115 The simplest way to configure and build @value{GDBN} is to run @file{configure}
25116 from the @file{gdb-@var{version-number}} source directory, which in
25117 this example is the @file{gdb-@value{GDBVN}} directory.
25119 First switch to the @file{gdb-@var{version-number}} source directory
25120 if you are not already in it; then run @file{configure}. Pass the
25121 identifier for the platform on which @value{GDBN} will run as an
25127 cd gdb-@value{GDBVN}
25128 ./configure @var{host}
25133 where @var{host} is an identifier such as @samp{sun4} or
25134 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
25135 (You can often leave off @var{host}; @file{configure} tries to guess the
25136 correct value by examining your system.)
25138 Running @samp{configure @var{host}} and then running @code{make} builds the
25139 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
25140 libraries, then @code{gdb} itself. The configured source files, and the
25141 binaries, are left in the corresponding source directories.
25144 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
25145 system does not recognize this automatically when you run a different
25146 shell, you may need to run @code{sh} on it explicitly:
25149 sh configure @var{host}
25152 If you run @file{configure} from a directory that contains source
25153 directories for multiple libraries or programs, such as the
25154 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
25156 creates configuration files for every directory level underneath (unless
25157 you tell it not to, with the @samp{--norecursion} option).
25159 You should run the @file{configure} script from the top directory in the
25160 source tree, the @file{gdb-@var{version-number}} directory. If you run
25161 @file{configure} from one of the subdirectories, you will configure only
25162 that subdirectory. That is usually not what you want. In particular,
25163 if you run the first @file{configure} from the @file{gdb} subdirectory
25164 of the @file{gdb-@var{version-number}} directory, you will omit the
25165 configuration of @file{bfd}, @file{readline}, and other sibling
25166 directories of the @file{gdb} subdirectory. This leads to build errors
25167 about missing include files such as @file{bfd/bfd.h}.
25169 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
25170 However, you should make sure that the shell on your path (named by
25171 the @samp{SHELL} environment variable) is publicly readable. Remember
25172 that @value{GDBN} uses the shell to start your program---some systems refuse to
25173 let @value{GDBN} debug child processes whose programs are not readable.
25175 @node Separate Objdir
25176 @section Compiling @value{GDBN} in Another Directory
25178 If you want to run @value{GDBN} versions for several host or target machines,
25179 you need a different @code{gdb} compiled for each combination of
25180 host and target. @file{configure} is designed to make this easy by
25181 allowing you to generate each configuration in a separate subdirectory,
25182 rather than in the source directory. If your @code{make} program
25183 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
25184 @code{make} in each of these directories builds the @code{gdb}
25185 program specified there.
25187 To build @code{gdb} in a separate directory, run @file{configure}
25188 with the @samp{--srcdir} option to specify where to find the source.
25189 (You also need to specify a path to find @file{configure}
25190 itself from your working directory. If the path to @file{configure}
25191 would be the same as the argument to @samp{--srcdir}, you can leave out
25192 the @samp{--srcdir} option; it is assumed.)
25194 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
25195 separate directory for a Sun 4 like this:
25199 cd gdb-@value{GDBVN}
25202 ../gdb-@value{GDBVN}/configure sun4
25207 When @file{configure} builds a configuration using a remote source
25208 directory, it creates a tree for the binaries with the same structure
25209 (and using the same names) as the tree under the source directory. In
25210 the example, you'd find the Sun 4 library @file{libiberty.a} in the
25211 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
25212 @file{gdb-sun4/gdb}.
25214 Make sure that your path to the @file{configure} script has just one
25215 instance of @file{gdb} in it. If your path to @file{configure} looks
25216 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
25217 one subdirectory of @value{GDBN}, not the whole package. This leads to
25218 build errors about missing include files such as @file{bfd/bfd.h}.
25220 One popular reason to build several @value{GDBN} configurations in separate
25221 directories is to configure @value{GDBN} for cross-compiling (where
25222 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
25223 programs that run on another machine---the @dfn{target}).
25224 You specify a cross-debugging target by
25225 giving the @samp{--target=@var{target}} option to @file{configure}.
25227 When you run @code{make} to build a program or library, you must run
25228 it in a configured directory---whatever directory you were in when you
25229 called @file{configure} (or one of its subdirectories).
25231 The @code{Makefile} that @file{configure} generates in each source
25232 directory also runs recursively. If you type @code{make} in a source
25233 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
25234 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
25235 will build all the required libraries, and then build GDB.
25237 When you have multiple hosts or targets configured in separate
25238 directories, you can run @code{make} on them in parallel (for example,
25239 if they are NFS-mounted on each of the hosts); they will not interfere
25243 @section Specifying Names for Hosts and Targets
25245 The specifications used for hosts and targets in the @file{configure}
25246 script are based on a three-part naming scheme, but some short predefined
25247 aliases are also supported. The full naming scheme encodes three pieces
25248 of information in the following pattern:
25251 @var{architecture}-@var{vendor}-@var{os}
25254 For example, you can use the alias @code{sun4} as a @var{host} argument,
25255 or as the value for @var{target} in a @code{--target=@var{target}}
25256 option. The equivalent full name is @samp{sparc-sun-sunos4}.
25258 The @file{configure} script accompanying @value{GDBN} does not provide
25259 any query facility to list all supported host and target names or
25260 aliases. @file{configure} calls the Bourne shell script
25261 @code{config.sub} to map abbreviations to full names; you can read the
25262 script, if you wish, or you can use it to test your guesses on
25263 abbreviations---for example:
25266 % sh config.sub i386-linux
25268 % sh config.sub alpha-linux
25269 alpha-unknown-linux-gnu
25270 % sh config.sub hp9k700
25272 % sh config.sub sun4
25273 sparc-sun-sunos4.1.1
25274 % sh config.sub sun3
25275 m68k-sun-sunos4.1.1
25276 % sh config.sub i986v
25277 Invalid configuration `i986v': machine `i986v' not recognized
25281 @code{config.sub} is also distributed in the @value{GDBN} source
25282 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
25284 @node Configure Options
25285 @section @file{configure} Options
25287 Here is a summary of the @file{configure} options and arguments that
25288 are most often useful for building @value{GDBN}. @file{configure} also has
25289 several other options not listed here. @inforef{What Configure
25290 Does,,configure.info}, for a full explanation of @file{configure}.
25293 configure @r{[}--help@r{]}
25294 @r{[}--prefix=@var{dir}@r{]}
25295 @r{[}--exec-prefix=@var{dir}@r{]}
25296 @r{[}--srcdir=@var{dirname}@r{]}
25297 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
25298 @r{[}--target=@var{target}@r{]}
25303 You may introduce options with a single @samp{-} rather than
25304 @samp{--} if you prefer; but you may abbreviate option names if you use
25309 Display a quick summary of how to invoke @file{configure}.
25311 @item --prefix=@var{dir}
25312 Configure the source to install programs and files under directory
25315 @item --exec-prefix=@var{dir}
25316 Configure the source to install programs under directory
25319 @c avoid splitting the warning from the explanation:
25321 @item --srcdir=@var{dirname}
25322 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
25323 @code{make} that implements the @code{VPATH} feature.}@*
25324 Use this option to make configurations in directories separate from the
25325 @value{GDBN} source directories. Among other things, you can use this to
25326 build (or maintain) several configurations simultaneously, in separate
25327 directories. @file{configure} writes configuration-specific files in
25328 the current directory, but arranges for them to use the source in the
25329 directory @var{dirname}. @file{configure} creates directories under
25330 the working directory in parallel to the source directories below
25333 @item --norecursion
25334 Configure only the directory level where @file{configure} is executed; do not
25335 propagate configuration to subdirectories.
25337 @item --target=@var{target}
25338 Configure @value{GDBN} for cross-debugging programs running on the specified
25339 @var{target}. Without this option, @value{GDBN} is configured to debug
25340 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
25342 There is no convenient way to generate a list of all available targets.
25344 @item @var{host} @dots{}
25345 Configure @value{GDBN} to run on the specified @var{host}.
25347 There is no convenient way to generate a list of all available hosts.
25350 There are many other options available as well, but they are generally
25351 needed for special purposes only.
25353 @node System-wide configuration
25354 @section System-wide configuration and settings
25355 @cindex system-wide init file
25357 @value{GDBN} can be configured to have a system-wide init file;
25358 this file will be read and executed at startup (@pxref{Startup, , What
25359 @value{GDBN} does during startup}).
25361 Here is the corresponding configure option:
25364 @item --with-system-gdbinit=@var{file}
25365 Specify that the default location of the system-wide init file is
25369 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
25370 it may be subject to relocation. Two possible cases:
25374 If the default location of this init file contains @file{$prefix},
25375 it will be subject to relocation. Suppose that the configure options
25376 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
25377 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
25378 init file is looked for as @file{$install/etc/gdbinit} instead of
25379 @file{$prefix/etc/gdbinit}.
25382 By contrast, if the default location does not contain the prefix,
25383 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
25384 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
25385 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
25386 wherever @value{GDBN} is installed.
25389 @node Maintenance Commands
25390 @appendix Maintenance Commands
25391 @cindex maintenance commands
25392 @cindex internal commands
25394 In addition to commands intended for @value{GDBN} users, @value{GDBN}
25395 includes a number of commands intended for @value{GDBN} developers,
25396 that are not documented elsewhere in this manual. These commands are
25397 provided here for reference. (For commands that turn on debugging
25398 messages, see @ref{Debugging Output}.)
25401 @kindex maint agent
25402 @item maint agent @var{expression}
25403 Translate the given @var{expression} into remote agent bytecodes.
25404 This command is useful for debugging the Agent Expression mechanism
25405 (@pxref{Agent Expressions}).
25407 @kindex maint info breakpoints
25408 @item @anchor{maint info breakpoints}maint info breakpoints
25409 Using the same format as @samp{info breakpoints}, display both the
25410 breakpoints you've set explicitly, and those @value{GDBN} is using for
25411 internal purposes. Internal breakpoints are shown with negative
25412 breakpoint numbers. The type column identifies what kind of breakpoint
25417 Normal, explicitly set breakpoint.
25420 Normal, explicitly set watchpoint.
25423 Internal breakpoint, used to handle correctly stepping through
25424 @code{longjmp} calls.
25426 @item longjmp resume
25427 Internal breakpoint at the target of a @code{longjmp}.
25430 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
25433 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
25436 Shared library events.
25440 @kindex set displaced-stepping
25441 @kindex show displaced-stepping
25442 @cindex displaced stepping support
25443 @cindex out-of-line single-stepping
25444 @item set displaced-stepping
25445 @itemx show displaced-stepping
25446 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
25447 if the target supports it. Displaced stepping is a way to single-step
25448 over breakpoints without removing them from the inferior, by executing
25449 an out-of-line copy of the instruction that was originally at the
25450 breakpoint location. It is also known as out-of-line single-stepping.
25453 @item set displaced-stepping on
25454 If the target architecture supports it, @value{GDBN} will use
25455 displaced stepping to step over breakpoints.
25457 @item set displaced-stepping off
25458 @value{GDBN} will not use displaced stepping to step over breakpoints,
25459 even if such is supported by the target architecture.
25461 @cindex non-stop mode, and @samp{set displaced-stepping}
25462 @item set displaced-stepping auto
25463 This is the default mode. @value{GDBN} will use displaced stepping
25464 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
25465 architecture supports displaced stepping.
25468 @kindex maint check-symtabs
25469 @item maint check-symtabs
25470 Check the consistency of psymtabs and symtabs.
25472 @kindex maint cplus first_component
25473 @item maint cplus first_component @var{name}
25474 Print the first C@t{++} class/namespace component of @var{name}.
25476 @kindex maint cplus namespace
25477 @item maint cplus namespace
25478 Print the list of possible C@t{++} namespaces.
25480 @kindex maint demangle
25481 @item maint demangle @var{name}
25482 Demangle a C@t{++} or Objective-C mangled @var{name}.
25484 @kindex maint deprecate
25485 @kindex maint undeprecate
25486 @cindex deprecated commands
25487 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
25488 @itemx maint undeprecate @var{command}
25489 Deprecate or undeprecate the named @var{command}. Deprecated commands
25490 cause @value{GDBN} to issue a warning when you use them. The optional
25491 argument @var{replacement} says which newer command should be used in
25492 favor of the deprecated one; if it is given, @value{GDBN} will mention
25493 the replacement as part of the warning.
25495 @kindex maint dump-me
25496 @item maint dump-me
25497 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
25498 Cause a fatal signal in the debugger and force it to dump its core.
25499 This is supported only on systems which support aborting a program
25500 with the @code{SIGQUIT} signal.
25502 @kindex maint internal-error
25503 @kindex maint internal-warning
25504 @item maint internal-error @r{[}@var{message-text}@r{]}
25505 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
25506 Cause @value{GDBN} to call the internal function @code{internal_error}
25507 or @code{internal_warning} and hence behave as though an internal error
25508 or internal warning has been detected. In addition to reporting the
25509 internal problem, these functions give the user the opportunity to
25510 either quit @value{GDBN} or create a core file of the current
25511 @value{GDBN} session.
25513 These commands take an optional parameter @var{message-text} that is
25514 used as the text of the error or warning message.
25516 Here's an example of using @code{internal-error}:
25519 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
25520 @dots{}/maint.c:121: internal-error: testing, 1, 2
25521 A problem internal to GDB has been detected. Further
25522 debugging may prove unreliable.
25523 Quit this debugging session? (y or n) @kbd{n}
25524 Create a core file? (y or n) @kbd{n}
25528 @cindex @value{GDBN} internal error
25529 @cindex internal errors, control of @value{GDBN} behavior
25531 @kindex maint set internal-error
25532 @kindex maint show internal-error
25533 @kindex maint set internal-warning
25534 @kindex maint show internal-warning
25535 @item maint set internal-error @var{action} [ask|yes|no]
25536 @itemx maint show internal-error @var{action}
25537 @itemx maint set internal-warning @var{action} [ask|yes|no]
25538 @itemx maint show internal-warning @var{action}
25539 When @value{GDBN} reports an internal problem (error or warning) it
25540 gives the user the opportunity to both quit @value{GDBN} and create a
25541 core file of the current @value{GDBN} session. These commands let you
25542 override the default behaviour for each particular @var{action},
25543 described in the table below.
25547 You can specify that @value{GDBN} should always (yes) or never (no)
25548 quit. The default is to ask the user what to do.
25551 You can specify that @value{GDBN} should always (yes) or never (no)
25552 create a core file. The default is to ask the user what to do.
25555 @kindex maint packet
25556 @item maint packet @var{text}
25557 If @value{GDBN} is talking to an inferior via the serial protocol,
25558 then this command sends the string @var{text} to the inferior, and
25559 displays the response packet. @value{GDBN} supplies the initial
25560 @samp{$} character, the terminating @samp{#} character, and the
25563 @kindex maint print architecture
25564 @item maint print architecture @r{[}@var{file}@r{]}
25565 Print the entire architecture configuration. The optional argument
25566 @var{file} names the file where the output goes.
25568 @kindex maint print c-tdesc
25569 @item maint print c-tdesc
25570 Print the current target description (@pxref{Target Descriptions}) as
25571 a C source file. The created source file can be used in @value{GDBN}
25572 when an XML parser is not available to parse the description.
25574 @kindex maint print dummy-frames
25575 @item maint print dummy-frames
25576 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
25579 (@value{GDBP}) @kbd{b add}
25581 (@value{GDBP}) @kbd{print add(2,3)}
25582 Breakpoint 2, add (a=2, b=3) at @dots{}
25584 The program being debugged stopped while in a function called from GDB.
25586 (@value{GDBP}) @kbd{maint print dummy-frames}
25587 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
25588 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
25589 call_lo=0x01014000 call_hi=0x01014001
25593 Takes an optional file parameter.
25595 @kindex maint print registers
25596 @kindex maint print raw-registers
25597 @kindex maint print cooked-registers
25598 @kindex maint print register-groups
25599 @item maint print registers @r{[}@var{file}@r{]}
25600 @itemx maint print raw-registers @r{[}@var{file}@r{]}
25601 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
25602 @itemx maint print register-groups @r{[}@var{file}@r{]}
25603 Print @value{GDBN}'s internal register data structures.
25605 The command @code{maint print raw-registers} includes the contents of
25606 the raw register cache; the command @code{maint print cooked-registers}
25607 includes the (cooked) value of all registers; and the command
25608 @code{maint print register-groups} includes the groups that each
25609 register is a member of. @xref{Registers,, Registers, gdbint,
25610 @value{GDBN} Internals}.
25612 These commands take an optional parameter, a file name to which to
25613 write the information.
25615 @kindex maint print reggroups
25616 @item maint print reggroups @r{[}@var{file}@r{]}
25617 Print @value{GDBN}'s internal register group data structures. The
25618 optional argument @var{file} tells to what file to write the
25621 The register groups info looks like this:
25624 (@value{GDBP}) @kbd{maint print reggroups}
25637 This command forces @value{GDBN} to flush its internal register cache.
25639 @kindex maint print objfiles
25640 @cindex info for known object files
25641 @item maint print objfiles
25642 Print a dump of all known object files. For each object file, this
25643 command prints its name, address in memory, and all of its psymtabs
25646 @kindex maint print statistics
25647 @cindex bcache statistics
25648 @item maint print statistics
25649 This command prints, for each object file in the program, various data
25650 about that object file followed by the byte cache (@dfn{bcache})
25651 statistics for the object file. The objfile data includes the number
25652 of minimal, partial, full, and stabs symbols, the number of types
25653 defined by the objfile, the number of as yet unexpanded psym tables,
25654 the number of line tables and string tables, and the amount of memory
25655 used by the various tables. The bcache statistics include the counts,
25656 sizes, and counts of duplicates of all and unique objects, max,
25657 average, and median entry size, total memory used and its overhead and
25658 savings, and various measures of the hash table size and chain
25661 @kindex maint print target-stack
25662 @cindex target stack description
25663 @item maint print target-stack
25664 A @dfn{target} is an interface between the debugger and a particular
25665 kind of file or process. Targets can be stacked in @dfn{strata},
25666 so that more than one target can potentially respond to a request.
25667 In particular, memory accesses will walk down the stack of targets
25668 until they find a target that is interested in handling that particular
25671 This command prints a short description of each layer that was pushed on
25672 the @dfn{target stack}, starting from the top layer down to the bottom one.
25674 @kindex maint print type
25675 @cindex type chain of a data type
25676 @item maint print type @var{expr}
25677 Print the type chain for a type specified by @var{expr}. The argument
25678 can be either a type name or a symbol. If it is a symbol, the type of
25679 that symbol is described. The type chain produced by this command is
25680 a recursive definition of the data type as stored in @value{GDBN}'s
25681 data structures, including its flags and contained types.
25683 @kindex maint set dwarf2 max-cache-age
25684 @kindex maint show dwarf2 max-cache-age
25685 @item maint set dwarf2 max-cache-age
25686 @itemx maint show dwarf2 max-cache-age
25687 Control the DWARF 2 compilation unit cache.
25689 @cindex DWARF 2 compilation units cache
25690 In object files with inter-compilation-unit references, such as those
25691 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
25692 reader needs to frequently refer to previously read compilation units.
25693 This setting controls how long a compilation unit will remain in the
25694 cache if it is not referenced. A higher limit means that cached
25695 compilation units will be stored in memory longer, and more total
25696 memory will be used. Setting it to zero disables caching, which will
25697 slow down @value{GDBN} startup, but reduce memory consumption.
25699 @kindex maint set profile
25700 @kindex maint show profile
25701 @cindex profiling GDB
25702 @item maint set profile
25703 @itemx maint show profile
25704 Control profiling of @value{GDBN}.
25706 Profiling will be disabled until you use the @samp{maint set profile}
25707 command to enable it. When you enable profiling, the system will begin
25708 collecting timing and execution count data; when you disable profiling or
25709 exit @value{GDBN}, the results will be written to a log file. Remember that
25710 if you use profiling, @value{GDBN} will overwrite the profiling log file
25711 (often called @file{gmon.out}). If you have a record of important profiling
25712 data in a @file{gmon.out} file, be sure to move it to a safe location.
25714 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
25715 compiled with the @samp{-pg} compiler option.
25717 @kindex maint show-debug-regs
25718 @cindex x86 hardware debug registers
25719 @item maint show-debug-regs
25720 Control whether to show variables that mirror the x86 hardware debug
25721 registers. Use @code{ON} to enable, @code{OFF} to disable. If
25722 enabled, the debug registers values are shown when @value{GDBN} inserts or
25723 removes a hardware breakpoint or watchpoint, and when the inferior
25724 triggers a hardware-assisted breakpoint or watchpoint.
25726 @kindex maint space
25727 @cindex memory used by commands
25729 Control whether to display memory usage for each command. If set to a
25730 nonzero value, @value{GDBN} will display how much memory each command
25731 took, following the command's own output. This can also be requested
25732 by invoking @value{GDBN} with the @option{--statistics} command-line
25733 switch (@pxref{Mode Options}).
25736 @cindex time of command execution
25738 Control whether to display the execution time for each command. If
25739 set to a nonzero value, @value{GDBN} will display how much time it
25740 took to execute each command, following the command's own output.
25741 The time is not printed for the commands that run the target, since
25742 there's no mechanism currently to compute how much time was spend
25743 by @value{GDBN} and how much time was spend by the program been debugged.
25744 it's not possibly currently
25745 This can also be requested by invoking @value{GDBN} with the
25746 @option{--statistics} command-line switch (@pxref{Mode Options}).
25748 @kindex maint translate-address
25749 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
25750 Find the symbol stored at the location specified by the address
25751 @var{addr} and an optional section name @var{section}. If found,
25752 @value{GDBN} prints the name of the closest symbol and an offset from
25753 the symbol's location to the specified address. This is similar to
25754 the @code{info address} command (@pxref{Symbols}), except that this
25755 command also allows to find symbols in other sections.
25757 If section was not specified, the section in which the symbol was found
25758 is also printed. For dynamically linked executables, the name of
25759 executable or shared library containing the symbol is printed as well.
25763 The following command is useful for non-interactive invocations of
25764 @value{GDBN}, such as in the test suite.
25767 @item set watchdog @var{nsec}
25768 @kindex set watchdog
25769 @cindex watchdog timer
25770 @cindex timeout for commands
25771 Set the maximum number of seconds @value{GDBN} will wait for the
25772 target operation to finish. If this time expires, @value{GDBN}
25773 reports and error and the command is aborted.
25775 @item show watchdog
25776 Show the current setting of the target wait timeout.
25779 @node Remote Protocol
25780 @appendix @value{GDBN} Remote Serial Protocol
25785 * Stop Reply Packets::
25786 * General Query Packets::
25787 * Register Packet Format::
25788 * Tracepoint Packets::
25789 * Host I/O Packets::
25791 * Notification Packets::
25792 * Remote Non-Stop::
25793 * Packet Acknowledgment::
25795 * File-I/O Remote Protocol Extension::
25796 * Library List Format::
25797 * Memory Map Format::
25803 There may be occasions when you need to know something about the
25804 protocol---for example, if there is only one serial port to your target
25805 machine, you might want your program to do something special if it
25806 recognizes a packet meant for @value{GDBN}.
25808 In the examples below, @samp{->} and @samp{<-} are used to indicate
25809 transmitted and received data, respectively.
25811 @cindex protocol, @value{GDBN} remote serial
25812 @cindex serial protocol, @value{GDBN} remote
25813 @cindex remote serial protocol
25814 All @value{GDBN} commands and responses (other than acknowledgments
25815 and notifications, see @ref{Notification Packets}) are sent as a
25816 @var{packet}. A @var{packet} is introduced with the character
25817 @samp{$}, the actual @var{packet-data}, and the terminating character
25818 @samp{#} followed by a two-digit @var{checksum}:
25821 @code{$}@var{packet-data}@code{#}@var{checksum}
25825 @cindex checksum, for @value{GDBN} remote
25827 The two-digit @var{checksum} is computed as the modulo 256 sum of all
25828 characters between the leading @samp{$} and the trailing @samp{#} (an
25829 eight bit unsigned checksum).
25831 Implementors should note that prior to @value{GDBN} 5.0 the protocol
25832 specification also included an optional two-digit @var{sequence-id}:
25835 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
25838 @cindex sequence-id, for @value{GDBN} remote
25840 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
25841 has never output @var{sequence-id}s. Stubs that handle packets added
25842 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
25844 When either the host or the target machine receives a packet, the first
25845 response expected is an acknowledgment: either @samp{+} (to indicate
25846 the package was received correctly) or @samp{-} (to request
25850 -> @code{$}@var{packet-data}@code{#}@var{checksum}
25855 The @samp{+}/@samp{-} acknowledgments can be disabled
25856 once a connection is established.
25857 @xref{Packet Acknowledgment}, for details.
25859 The host (@value{GDBN}) sends @var{command}s, and the target (the
25860 debugging stub incorporated in your program) sends a @var{response}. In
25861 the case of step and continue @var{command}s, the response is only sent
25862 when the operation has completed, and the target has again stopped all
25863 threads in all attached processes. This is the default all-stop mode
25864 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
25865 execution mode; see @ref{Remote Non-Stop}, for details.
25867 @var{packet-data} consists of a sequence of characters with the
25868 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
25871 @cindex remote protocol, field separator
25872 Fields within the packet should be separated using @samp{,} @samp{;} or
25873 @samp{:}. Except where otherwise noted all numbers are represented in
25874 @sc{hex} with leading zeros suppressed.
25876 Implementors should note that prior to @value{GDBN} 5.0, the character
25877 @samp{:} could not appear as the third character in a packet (as it
25878 would potentially conflict with the @var{sequence-id}).
25880 @cindex remote protocol, binary data
25881 @anchor{Binary Data}
25882 Binary data in most packets is encoded either as two hexadecimal
25883 digits per byte of binary data. This allowed the traditional remote
25884 protocol to work over connections which were only seven-bit clean.
25885 Some packets designed more recently assume an eight-bit clean
25886 connection, and use a more efficient encoding to send and receive
25889 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
25890 as an escape character. Any escaped byte is transmitted as the escape
25891 character followed by the original character XORed with @code{0x20}.
25892 For example, the byte @code{0x7d} would be transmitted as the two
25893 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
25894 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
25895 @samp{@}}) must always be escaped. Responses sent by the stub
25896 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
25897 is not interpreted as the start of a run-length encoded sequence
25900 Response @var{data} can be run-length encoded to save space.
25901 Run-length encoding replaces runs of identical characters with one
25902 instance of the repeated character, followed by a @samp{*} and a
25903 repeat count. The repeat count is itself sent encoded, to avoid
25904 binary characters in @var{data}: a value of @var{n} is sent as
25905 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
25906 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
25907 code 32) for a repeat count of 3. (This is because run-length
25908 encoding starts to win for counts 3 or more.) Thus, for example,
25909 @samp{0* } is a run-length encoding of ``0000'': the space character
25910 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
25913 The printable characters @samp{#} and @samp{$} or with a numeric value
25914 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
25915 seven repeats (@samp{$}) can be expanded using a repeat count of only
25916 five (@samp{"}). For example, @samp{00000000} can be encoded as
25919 The error response returned for some packets includes a two character
25920 error number. That number is not well defined.
25922 @cindex empty response, for unsupported packets
25923 For any @var{command} not supported by the stub, an empty response
25924 (@samp{$#00}) should be returned. That way it is possible to extend the
25925 protocol. A newer @value{GDBN} can tell if a packet is supported based
25928 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
25929 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
25935 The following table provides a complete list of all currently defined
25936 @var{command}s and their corresponding response @var{data}.
25937 @xref{File-I/O Remote Protocol Extension}, for details about the File
25938 I/O extension of the remote protocol.
25940 Each packet's description has a template showing the packet's overall
25941 syntax, followed by an explanation of the packet's meaning. We
25942 include spaces in some of the templates for clarity; these are not
25943 part of the packet's syntax. No @value{GDBN} packet uses spaces to
25944 separate its components. For example, a template like @samp{foo
25945 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
25946 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
25947 @var{baz}. @value{GDBN} does not transmit a space character between the
25948 @samp{foo} and the @var{bar}, or between the @var{bar} and the
25951 @cindex @var{thread-id}, in remote protocol
25952 @anchor{thread-id syntax}
25953 Several packets and replies include a @var{thread-id} field to identify
25954 a thread. Normally these are positive numbers with a target-specific
25955 interpretation, formatted as big-endian hex strings. A @var{thread-id}
25956 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
25959 In addition, the remote protocol supports a multiprocess feature in
25960 which the @var{thread-id} syntax is extended to optionally include both
25961 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
25962 The @var{pid} (process) and @var{tid} (thread) components each have the
25963 format described above: a positive number with target-specific
25964 interpretation formatted as a big-endian hex string, literal @samp{-1}
25965 to indicate all processes or threads (respectively), or @samp{0} to
25966 indicate an arbitrary process or thread. Specifying just a process, as
25967 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
25968 error to specify all processes but a specific thread, such as
25969 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
25970 for those packets and replies explicitly documented to include a process
25971 ID, rather than a @var{thread-id}.
25973 The multiprocess @var{thread-id} syntax extensions are only used if both
25974 @value{GDBN} and the stub report support for the @samp{multiprocess}
25975 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
25978 Note that all packet forms beginning with an upper- or lower-case
25979 letter, other than those described here, are reserved for future use.
25981 Here are the packet descriptions.
25986 @cindex @samp{!} packet
25987 @anchor{extended mode}
25988 Enable extended mode. In extended mode, the remote server is made
25989 persistent. The @samp{R} packet is used to restart the program being
25995 The remote target both supports and has enabled extended mode.
25999 @cindex @samp{?} packet
26000 Indicate the reason the target halted. The reply is the same as for
26001 step and continue. This packet has a special interpretation when the
26002 target is in non-stop mode; see @ref{Remote Non-Stop}.
26005 @xref{Stop Reply Packets}, for the reply specifications.
26007 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
26008 @cindex @samp{A} packet
26009 Initialized @code{argv[]} array passed into program. @var{arglen}
26010 specifies the number of bytes in the hex encoded byte stream
26011 @var{arg}. See @code{gdbserver} for more details.
26016 The arguments were set.
26022 @cindex @samp{b} packet
26023 (Don't use this packet; its behavior is not well-defined.)
26024 Change the serial line speed to @var{baud}.
26026 JTC: @emph{When does the transport layer state change? When it's
26027 received, or after the ACK is transmitted. In either case, there are
26028 problems if the command or the acknowledgment packet is dropped.}
26030 Stan: @emph{If people really wanted to add something like this, and get
26031 it working for the first time, they ought to modify ser-unix.c to send
26032 some kind of out-of-band message to a specially-setup stub and have the
26033 switch happen "in between" packets, so that from remote protocol's point
26034 of view, nothing actually happened.}
26036 @item B @var{addr},@var{mode}
26037 @cindex @samp{B} packet
26038 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
26039 breakpoint at @var{addr}.
26041 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
26042 (@pxref{insert breakpoint or watchpoint packet}).
26045 @cindex @samp{bc} packet
26046 Backward continue. Execute the target system in reverse. No parameter.
26047 @xref{Reverse Execution}, for more information.
26050 @xref{Stop Reply Packets}, for the reply specifications.
26053 @cindex @samp{bs} packet
26054 Backward single step. Execute one instruction in reverse. No parameter.
26055 @xref{Reverse Execution}, for more information.
26058 @xref{Stop Reply Packets}, for the reply specifications.
26060 @item c @r{[}@var{addr}@r{]}
26061 @cindex @samp{c} packet
26062 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
26063 resume at current address.
26066 @xref{Stop Reply Packets}, for the reply specifications.
26068 @item C @var{sig}@r{[};@var{addr}@r{]}
26069 @cindex @samp{C} packet
26070 Continue with signal @var{sig} (hex signal number). If
26071 @samp{;@var{addr}} is omitted, resume at same address.
26074 @xref{Stop Reply Packets}, for the reply specifications.
26077 @cindex @samp{d} packet
26080 Don't use this packet; instead, define a general set packet
26081 (@pxref{General Query Packets}).
26085 @cindex @samp{D} packet
26086 The first form of the packet is used to detach @value{GDBN} from the
26087 remote system. It is sent to the remote target
26088 before @value{GDBN} disconnects via the @code{detach} command.
26090 The second form, including a process ID, is used when multiprocess
26091 protocol extensions are enabled (@pxref{multiprocess extensions}), to
26092 detach only a specific process. The @var{pid} is specified as a
26093 big-endian hex string.
26103 @item F @var{RC},@var{EE},@var{CF};@var{XX}
26104 @cindex @samp{F} packet
26105 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
26106 This is part of the File-I/O protocol extension. @xref{File-I/O
26107 Remote Protocol Extension}, for the specification.
26110 @anchor{read registers packet}
26111 @cindex @samp{g} packet
26112 Read general registers.
26116 @item @var{XX@dots{}}
26117 Each byte of register data is described by two hex digits. The bytes
26118 with the register are transmitted in target byte order. The size of
26119 each register and their position within the @samp{g} packet are
26120 determined by the @value{GDBN} internal gdbarch functions
26121 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
26122 specification of several standard @samp{g} packets is specified below.
26127 @item G @var{XX@dots{}}
26128 @cindex @samp{G} packet
26129 Write general registers. @xref{read registers packet}, for a
26130 description of the @var{XX@dots{}} data.
26140 @item H @var{c} @var{thread-id}
26141 @cindex @samp{H} packet
26142 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
26143 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
26144 should be @samp{c} for step and continue operations, @samp{g} for other
26145 operations. The thread designator @var{thread-id} has the format and
26146 interpretation described in @ref{thread-id syntax}.
26157 @c 'H': How restrictive (or permissive) is the thread model. If a
26158 @c thread is selected and stopped, are other threads allowed
26159 @c to continue to execute? As I mentioned above, I think the
26160 @c semantics of each command when a thread is selected must be
26161 @c described. For example:
26163 @c 'g': If the stub supports threads and a specific thread is
26164 @c selected, returns the register block from that thread;
26165 @c otherwise returns current registers.
26167 @c 'G' If the stub supports threads and a specific thread is
26168 @c selected, sets the registers of the register block of
26169 @c that thread; otherwise sets current registers.
26171 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
26172 @anchor{cycle step packet}
26173 @cindex @samp{i} packet
26174 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
26175 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
26176 step starting at that address.
26179 @cindex @samp{I} packet
26180 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
26184 @cindex @samp{k} packet
26187 FIXME: @emph{There is no description of how to operate when a specific
26188 thread context has been selected (i.e.@: does 'k' kill only that
26191 @item m @var{addr},@var{length}
26192 @cindex @samp{m} packet
26193 Read @var{length} bytes of memory starting at address @var{addr}.
26194 Note that @var{addr} may not be aligned to any particular boundary.
26196 The stub need not use any particular size or alignment when gathering
26197 data from memory for the response; even if @var{addr} is word-aligned
26198 and @var{length} is a multiple of the word size, the stub is free to
26199 use byte accesses, or not. For this reason, this packet may not be
26200 suitable for accessing memory-mapped I/O devices.
26201 @cindex alignment of remote memory accesses
26202 @cindex size of remote memory accesses
26203 @cindex memory, alignment and size of remote accesses
26207 @item @var{XX@dots{}}
26208 Memory contents; each byte is transmitted as a two-digit hexadecimal
26209 number. The reply may contain fewer bytes than requested if the
26210 server was able to read only part of the region of memory.
26215 @item M @var{addr},@var{length}:@var{XX@dots{}}
26216 @cindex @samp{M} packet
26217 Write @var{length} bytes of memory starting at address @var{addr}.
26218 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
26219 hexadecimal number.
26226 for an error (this includes the case where only part of the data was
26231 @cindex @samp{p} packet
26232 Read the value of register @var{n}; @var{n} is in hex.
26233 @xref{read registers packet}, for a description of how the returned
26234 register value is encoded.
26238 @item @var{XX@dots{}}
26239 the register's value
26243 Indicating an unrecognized @var{query}.
26246 @item P @var{n@dots{}}=@var{r@dots{}}
26247 @anchor{write register packet}
26248 @cindex @samp{P} packet
26249 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
26250 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
26251 digits for each byte in the register (target byte order).
26261 @item q @var{name} @var{params}@dots{}
26262 @itemx Q @var{name} @var{params}@dots{}
26263 @cindex @samp{q} packet
26264 @cindex @samp{Q} packet
26265 General query (@samp{q}) and set (@samp{Q}). These packets are
26266 described fully in @ref{General Query Packets}.
26269 @cindex @samp{r} packet
26270 Reset the entire system.
26272 Don't use this packet; use the @samp{R} packet instead.
26275 @cindex @samp{R} packet
26276 Restart the program being debugged. @var{XX}, while needed, is ignored.
26277 This packet is only available in extended mode (@pxref{extended mode}).
26279 The @samp{R} packet has no reply.
26281 @item s @r{[}@var{addr}@r{]}
26282 @cindex @samp{s} packet
26283 Single step. @var{addr} is the address at which to resume. If
26284 @var{addr} is omitted, resume at same address.
26287 @xref{Stop Reply Packets}, for the reply specifications.
26289 @item S @var{sig}@r{[};@var{addr}@r{]}
26290 @anchor{step with signal packet}
26291 @cindex @samp{S} packet
26292 Step with signal. This is analogous to the @samp{C} packet, but
26293 requests a single-step, rather than a normal resumption of execution.
26296 @xref{Stop Reply Packets}, for the reply specifications.
26298 @item t @var{addr}:@var{PP},@var{MM}
26299 @cindex @samp{t} packet
26300 Search backwards starting at address @var{addr} for a match with pattern
26301 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
26302 @var{addr} must be at least 3 digits.
26304 @item T @var{thread-id}
26305 @cindex @samp{T} packet
26306 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
26311 thread is still alive
26317 Packets starting with @samp{v} are identified by a multi-letter name,
26318 up to the first @samp{;} or @samp{?} (or the end of the packet).
26320 @item vAttach;@var{pid}
26321 @cindex @samp{vAttach} packet
26322 Attach to a new process with the specified process ID @var{pid}.
26323 The process ID is a
26324 hexadecimal integer identifying the process. In all-stop mode, all
26325 threads in the attached process are stopped; in non-stop mode, it may be
26326 attached without being stopped if that is supported by the target.
26328 @c In non-stop mode, on a successful vAttach, the stub should set the
26329 @c current thread to a thread of the newly-attached process. After
26330 @c attaching, GDB queries for the attached process's thread ID with qC.
26331 @c Also note that, from a user perspective, whether or not the
26332 @c target is stopped on attach in non-stop mode depends on whether you
26333 @c use the foreground or background version of the attach command, not
26334 @c on what vAttach does; GDB does the right thing with respect to either
26335 @c stopping or restarting threads.
26337 This packet is only available in extended mode (@pxref{extended mode}).
26343 @item @r{Any stop packet}
26344 for success in all-stop mode (@pxref{Stop Reply Packets})
26346 for success in non-stop mode (@pxref{Remote Non-Stop})
26349 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
26350 @cindex @samp{vCont} packet
26351 Resume the inferior, specifying different actions for each thread.
26352 If an action is specified with no @var{thread-id}, then it is applied to any
26353 threads that don't have a specific action specified; if no default action is
26354 specified then other threads should remain stopped in all-stop mode and
26355 in their current state in non-stop mode.
26356 Specifying multiple
26357 default actions is an error; specifying no actions is also an error.
26358 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
26360 Currently supported actions are:
26366 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
26370 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
26374 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
26377 The optional argument @var{addr} normally associated with the
26378 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
26379 not supported in @samp{vCont}.
26381 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
26382 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
26383 A stop reply should be generated for any affected thread not already stopped.
26384 When a thread is stopped by means of a @samp{t} action,
26385 the corresponding stop reply should indicate that the thread has stopped with
26386 signal @samp{0}, regardless of whether the target uses some other signal
26387 as an implementation detail.
26390 @xref{Stop Reply Packets}, for the reply specifications.
26393 @cindex @samp{vCont?} packet
26394 Request a list of actions supported by the @samp{vCont} packet.
26398 @item vCont@r{[};@var{action}@dots{}@r{]}
26399 The @samp{vCont} packet is supported. Each @var{action} is a supported
26400 command in the @samp{vCont} packet.
26402 The @samp{vCont} packet is not supported.
26405 @item vFile:@var{operation}:@var{parameter}@dots{}
26406 @cindex @samp{vFile} packet
26407 Perform a file operation on the target system. For details,
26408 see @ref{Host I/O Packets}.
26410 @item vFlashErase:@var{addr},@var{length}
26411 @cindex @samp{vFlashErase} packet
26412 Direct the stub to erase @var{length} bytes of flash starting at
26413 @var{addr}. The region may enclose any number of flash blocks, but
26414 its start and end must fall on block boundaries, as indicated by the
26415 flash block size appearing in the memory map (@pxref{Memory Map
26416 Format}). @value{GDBN} groups flash memory programming operations
26417 together, and sends a @samp{vFlashDone} request after each group; the
26418 stub is allowed to delay erase operation until the @samp{vFlashDone}
26419 packet is received.
26421 The stub must support @samp{vCont} if it reports support for
26422 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
26423 this case @samp{vCont} actions can be specified to apply to all threads
26424 in a process by using the @samp{p@var{pid}.-1} form of the
26435 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
26436 @cindex @samp{vFlashWrite} packet
26437 Direct the stub to write data to flash address @var{addr}. The data
26438 is passed in binary form using the same encoding as for the @samp{X}
26439 packet (@pxref{Binary Data}). The memory ranges specified by
26440 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
26441 not overlap, and must appear in order of increasing addresses
26442 (although @samp{vFlashErase} packets for higher addresses may already
26443 have been received; the ordering is guaranteed only between
26444 @samp{vFlashWrite} packets). If a packet writes to an address that was
26445 neither erased by a preceding @samp{vFlashErase} packet nor by some other
26446 target-specific method, the results are unpredictable.
26454 for vFlashWrite addressing non-flash memory
26460 @cindex @samp{vFlashDone} packet
26461 Indicate to the stub that flash programming operation is finished.
26462 The stub is permitted to delay or batch the effects of a group of
26463 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
26464 @samp{vFlashDone} packet is received. The contents of the affected
26465 regions of flash memory are unpredictable until the @samp{vFlashDone}
26466 request is completed.
26468 @item vKill;@var{pid}
26469 @cindex @samp{vKill} packet
26470 Kill the process with the specified process ID. @var{pid} is a
26471 hexadecimal integer identifying the process. This packet is used in
26472 preference to @samp{k} when multiprocess protocol extensions are
26473 supported; see @ref{multiprocess extensions}.
26483 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
26484 @cindex @samp{vRun} packet
26485 Run the program @var{filename}, passing it each @var{argument} on its
26486 command line. The file and arguments are hex-encoded strings. If
26487 @var{filename} is an empty string, the stub may use a default program
26488 (e.g.@: the last program run). The program is created in the stopped
26491 @c FIXME: What about non-stop mode?
26493 This packet is only available in extended mode (@pxref{extended mode}).
26499 @item @r{Any stop packet}
26500 for success (@pxref{Stop Reply Packets})
26504 @anchor{vStopped packet}
26505 @cindex @samp{vStopped} packet
26507 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
26508 reply and prompt for the stub to report another one.
26512 @item @r{Any stop packet}
26513 if there is another unreported stop event (@pxref{Stop Reply Packets})
26515 if there are no unreported stop events
26518 @item X @var{addr},@var{length}:@var{XX@dots{}}
26520 @cindex @samp{X} packet
26521 Write data to memory, where the data is transmitted in binary.
26522 @var{addr} is address, @var{length} is number of bytes,
26523 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
26533 @item z @var{type},@var{addr},@var{length}
26534 @itemx Z @var{type},@var{addr},@var{length}
26535 @anchor{insert breakpoint or watchpoint packet}
26536 @cindex @samp{z} packet
26537 @cindex @samp{Z} packets
26538 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
26539 watchpoint starting at address @var{address} and covering the next
26540 @var{length} bytes.
26542 Each breakpoint and watchpoint packet @var{type} is documented
26545 @emph{Implementation notes: A remote target shall return an empty string
26546 for an unrecognized breakpoint or watchpoint packet @var{type}. A
26547 remote target shall support either both or neither of a given
26548 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
26549 avoid potential problems with duplicate packets, the operations should
26550 be implemented in an idempotent way.}
26552 @item z0,@var{addr},@var{length}
26553 @itemx Z0,@var{addr},@var{length}
26554 @cindex @samp{z0} packet
26555 @cindex @samp{Z0} packet
26556 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
26557 @var{addr} of size @var{length}.
26559 A memory breakpoint is implemented by replacing the instruction at
26560 @var{addr} with a software breakpoint or trap instruction. The
26561 @var{length} is used by targets that indicates the size of the
26562 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
26563 @sc{mips} can insert either a 2 or 4 byte breakpoint).
26565 @emph{Implementation note: It is possible for a target to copy or move
26566 code that contains memory breakpoints (e.g., when implementing
26567 overlays). The behavior of this packet, in the presence of such a
26568 target, is not defined.}
26580 @item z1,@var{addr},@var{length}
26581 @itemx Z1,@var{addr},@var{length}
26582 @cindex @samp{z1} packet
26583 @cindex @samp{Z1} packet
26584 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
26585 address @var{addr} of size @var{length}.
26587 A hardware breakpoint is implemented using a mechanism that is not
26588 dependant on being able to modify the target's memory.
26590 @emph{Implementation note: A hardware breakpoint is not affected by code
26603 @item z2,@var{addr},@var{length}
26604 @itemx Z2,@var{addr},@var{length}
26605 @cindex @samp{z2} packet
26606 @cindex @samp{Z2} packet
26607 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
26619 @item z3,@var{addr},@var{length}
26620 @itemx Z3,@var{addr},@var{length}
26621 @cindex @samp{z3} packet
26622 @cindex @samp{Z3} packet
26623 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
26635 @item z4,@var{addr},@var{length}
26636 @itemx Z4,@var{addr},@var{length}
26637 @cindex @samp{z4} packet
26638 @cindex @samp{Z4} packet
26639 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
26653 @node Stop Reply Packets
26654 @section Stop Reply Packets
26655 @cindex stop reply packets
26657 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
26658 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
26659 receive any of the below as a reply. Except for @samp{?}
26660 and @samp{vStopped}, that reply is only returned
26661 when the target halts. In the below the exact meaning of @dfn{signal
26662 number} is defined by the header @file{include/gdb/signals.h} in the
26663 @value{GDBN} source code.
26665 As in the description of request packets, we include spaces in the
26666 reply templates for clarity; these are not part of the reply packet's
26667 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
26673 The program received signal number @var{AA} (a two-digit hexadecimal
26674 number). This is equivalent to a @samp{T} response with no
26675 @var{n}:@var{r} pairs.
26677 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
26678 @cindex @samp{T} packet reply
26679 The program received signal number @var{AA} (a two-digit hexadecimal
26680 number). This is equivalent to an @samp{S} response, except that the
26681 @samp{@var{n}:@var{r}} pairs can carry values of important registers
26682 and other information directly in the stop reply packet, reducing
26683 round-trip latency. Single-step and breakpoint traps are reported
26684 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
26688 If @var{n} is a hexadecimal number, it is a register number, and the
26689 corresponding @var{r} gives that register's value. @var{r} is a
26690 series of bytes in target byte order, with each byte given by a
26691 two-digit hex number.
26694 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
26695 the stopped thread, as specified in @ref{thread-id syntax}.
26698 If @var{n} is a recognized @dfn{stop reason}, it describes a more
26699 specific event that stopped the target. The currently defined stop
26700 reasons are listed below. @var{aa} should be @samp{05}, the trap
26701 signal. At most one stop reason should be present.
26704 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
26705 and go on to the next; this allows us to extend the protocol in the
26709 The currently defined stop reasons are:
26715 The packet indicates a watchpoint hit, and @var{r} is the data address, in
26718 @cindex shared library events, remote reply
26720 The packet indicates that the loaded libraries have changed.
26721 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
26722 list of loaded libraries. @var{r} is ignored.
26724 @cindex replay log events, remote reply
26726 The packet indicates that the target cannot continue replaying
26727 logged execution events, because it has reached the end (or the
26728 beginning when executing backward) of the log. The value of @var{r}
26729 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
26730 for more information.
26736 @itemx W @var{AA} ; process:@var{pid}
26737 The process exited, and @var{AA} is the exit status. This is only
26738 applicable to certain targets.
26740 The second form of the response, including the process ID of the exited
26741 process, can be used only when @value{GDBN} has reported support for
26742 multiprocess protocol extensions; see @ref{multiprocess extensions}.
26743 The @var{pid} is formatted as a big-endian hex string.
26746 @itemx X @var{AA} ; process:@var{pid}
26747 The process terminated with signal @var{AA}.
26749 The second form of the response, including the process ID of the
26750 terminated process, can be used only when @value{GDBN} has reported
26751 support for multiprocess protocol extensions; see @ref{multiprocess
26752 extensions}. The @var{pid} is formatted as a big-endian hex string.
26754 @item O @var{XX}@dots{}
26755 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
26756 written as the program's console output. This can happen at any time
26757 while the program is running and the debugger should continue to wait
26758 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
26760 @item F @var{call-id},@var{parameter}@dots{}
26761 @var{call-id} is the identifier which says which host system call should
26762 be called. This is just the name of the function. Translation into the
26763 correct system call is only applicable as it's defined in @value{GDBN}.
26764 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
26767 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
26768 this very system call.
26770 The target replies with this packet when it expects @value{GDBN} to
26771 call a host system call on behalf of the target. @value{GDBN} replies
26772 with an appropriate @samp{F} packet and keeps up waiting for the next
26773 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
26774 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
26775 Protocol Extension}, for more details.
26779 @node General Query Packets
26780 @section General Query Packets
26781 @cindex remote query requests
26783 Packets starting with @samp{q} are @dfn{general query packets};
26784 packets starting with @samp{Q} are @dfn{general set packets}. General
26785 query and set packets are a semi-unified form for retrieving and
26786 sending information to and from the stub.
26788 The initial letter of a query or set packet is followed by a name
26789 indicating what sort of thing the packet applies to. For example,
26790 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
26791 definitions with the stub. These packet names follow some
26796 The name must not contain commas, colons or semicolons.
26798 Most @value{GDBN} query and set packets have a leading upper case
26801 The names of custom vendor packets should use a company prefix, in
26802 lower case, followed by a period. For example, packets designed at
26803 the Acme Corporation might begin with @samp{qacme.foo} (for querying
26804 foos) or @samp{Qacme.bar} (for setting bars).
26807 The name of a query or set packet should be separated from any
26808 parameters by a @samp{:}; the parameters themselves should be
26809 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
26810 full packet name, and check for a separator or the end of the packet,
26811 in case two packet names share a common prefix. New packets should not begin
26812 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
26813 packets predate these conventions, and have arguments without any terminator
26814 for the packet name; we suspect they are in widespread use in places that
26815 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
26816 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
26819 Like the descriptions of the other packets, each description here
26820 has a template showing the packet's overall syntax, followed by an
26821 explanation of the packet's meaning. We include spaces in some of the
26822 templates for clarity; these are not part of the packet's syntax. No
26823 @value{GDBN} packet uses spaces to separate its components.
26825 Here are the currently defined query and set packets:
26830 @cindex current thread, remote request
26831 @cindex @samp{qC} packet
26832 Return the current thread ID.
26836 @item QC @var{thread-id}
26837 Where @var{thread-id} is a thread ID as documented in
26838 @ref{thread-id syntax}.
26839 @item @r{(anything else)}
26840 Any other reply implies the old thread ID.
26843 @item qCRC:@var{addr},@var{length}
26844 @cindex CRC of memory block, remote request
26845 @cindex @samp{qCRC} packet
26846 Compute the CRC checksum of a block of memory.
26850 An error (such as memory fault)
26851 @item C @var{crc32}
26852 The specified memory region's checksum is @var{crc32}.
26856 @itemx qsThreadInfo
26857 @cindex list active threads, remote request
26858 @cindex @samp{qfThreadInfo} packet
26859 @cindex @samp{qsThreadInfo} packet
26860 Obtain a list of all active thread IDs from the target (OS). Since there
26861 may be too many active threads to fit into one reply packet, this query
26862 works iteratively: it may require more than one query/reply sequence to
26863 obtain the entire list of threads. The first query of the sequence will
26864 be the @samp{qfThreadInfo} query; subsequent queries in the
26865 sequence will be the @samp{qsThreadInfo} query.
26867 NOTE: This packet replaces the @samp{qL} query (see below).
26871 @item m @var{thread-id}
26873 @item m @var{thread-id},@var{thread-id}@dots{}
26874 a comma-separated list of thread IDs
26876 (lower case letter @samp{L}) denotes end of list.
26879 In response to each query, the target will reply with a list of one or
26880 more thread IDs, separated by commas.
26881 @value{GDBN} will respond to each reply with a request for more thread
26882 ids (using the @samp{qs} form of the query), until the target responds
26883 with @samp{l} (lower-case el, for @dfn{last}).
26884 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
26887 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
26888 @cindex get thread-local storage address, remote request
26889 @cindex @samp{qGetTLSAddr} packet
26890 Fetch the address associated with thread local storage specified
26891 by @var{thread-id}, @var{offset}, and @var{lm}.
26893 @var{thread-id} is the thread ID associated with the
26894 thread for which to fetch the TLS address. @xref{thread-id syntax}.
26896 @var{offset} is the (big endian, hex encoded) offset associated with the
26897 thread local variable. (This offset is obtained from the debug
26898 information associated with the variable.)
26900 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
26901 the load module associated with the thread local storage. For example,
26902 a @sc{gnu}/Linux system will pass the link map address of the shared
26903 object associated with the thread local storage under consideration.
26904 Other operating environments may choose to represent the load module
26905 differently, so the precise meaning of this parameter will vary.
26909 @item @var{XX}@dots{}
26910 Hex encoded (big endian) bytes representing the address of the thread
26911 local storage requested.
26914 An error occurred. @var{nn} are hex digits.
26917 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
26920 @item qL @var{startflag} @var{threadcount} @var{nextthread}
26921 Obtain thread information from RTOS. Where: @var{startflag} (one hex
26922 digit) is one to indicate the first query and zero to indicate a
26923 subsequent query; @var{threadcount} (two hex digits) is the maximum
26924 number of threads the response packet can contain; and @var{nextthread}
26925 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
26926 returned in the response as @var{argthread}.
26928 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
26932 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
26933 Where: @var{count} (two hex digits) is the number of threads being
26934 returned; @var{done} (one hex digit) is zero to indicate more threads
26935 and one indicates no further threads; @var{argthreadid} (eight hex
26936 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
26937 is a sequence of thread IDs from the target. @var{threadid} (eight hex
26938 digits). See @code{remote.c:parse_threadlist_response()}.
26942 @cindex section offsets, remote request
26943 @cindex @samp{qOffsets} packet
26944 Get section offsets that the target used when relocating the downloaded
26949 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
26950 Relocate the @code{Text} section by @var{xxx} from its original address.
26951 Relocate the @code{Data} section by @var{yyy} from its original address.
26952 If the object file format provides segment information (e.g.@: @sc{elf}
26953 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
26954 segments by the supplied offsets.
26956 @emph{Note: while a @code{Bss} offset may be included in the response,
26957 @value{GDBN} ignores this and instead applies the @code{Data} offset
26958 to the @code{Bss} section.}
26960 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
26961 Relocate the first segment of the object file, which conventionally
26962 contains program code, to a starting address of @var{xxx}. If
26963 @samp{DataSeg} is specified, relocate the second segment, which
26964 conventionally contains modifiable data, to a starting address of
26965 @var{yyy}. @value{GDBN} will report an error if the object file
26966 does not contain segment information, or does not contain at least
26967 as many segments as mentioned in the reply. Extra segments are
26968 kept at fixed offsets relative to the last relocated segment.
26971 @item qP @var{mode} @var{thread-id}
26972 @cindex thread information, remote request
26973 @cindex @samp{qP} packet
26974 Returns information on @var{thread-id}. Where: @var{mode} is a hex
26975 encoded 32 bit mode; @var{thread-id} is a thread ID
26976 (@pxref{thread-id syntax}).
26978 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
26981 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
26985 @cindex non-stop mode, remote request
26986 @cindex @samp{QNonStop} packet
26988 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
26989 @xref{Remote Non-Stop}, for more information.
26994 The request succeeded.
26997 An error occurred. @var{nn} are hex digits.
27000 An empty reply indicates that @samp{QNonStop} is not supported by
27004 This packet is not probed by default; the remote stub must request it,
27005 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27006 Use of this packet is controlled by the @code{set non-stop} command;
27007 @pxref{Non-Stop Mode}.
27009 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
27010 @cindex pass signals to inferior, remote request
27011 @cindex @samp{QPassSignals} packet
27012 @anchor{QPassSignals}
27013 Each listed @var{signal} should be passed directly to the inferior process.
27014 Signals are numbered identically to continue packets and stop replies
27015 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
27016 strictly greater than the previous item. These signals do not need to stop
27017 the inferior, or be reported to @value{GDBN}. All other signals should be
27018 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
27019 combine; any earlier @samp{QPassSignals} list is completely replaced by the
27020 new list. This packet improves performance when using @samp{handle
27021 @var{signal} nostop noprint pass}.
27026 The request succeeded.
27029 An error occurred. @var{nn} are hex digits.
27032 An empty reply indicates that @samp{QPassSignals} is not supported by
27036 Use of this packet is controlled by the @code{set remote pass-signals}
27037 command (@pxref{Remote Configuration, set remote pass-signals}).
27038 This packet is not probed by default; the remote stub must request it,
27039 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27041 @item qRcmd,@var{command}
27042 @cindex execute remote command, remote request
27043 @cindex @samp{qRcmd} packet
27044 @var{command} (hex encoded) is passed to the local interpreter for
27045 execution. Invalid commands should be reported using the output
27046 string. Before the final result packet, the target may also respond
27047 with a number of intermediate @samp{O@var{output}} console output
27048 packets. @emph{Implementors should note that providing access to a
27049 stubs's interpreter may have security implications}.
27054 A command response with no output.
27056 A command response with the hex encoded output string @var{OUTPUT}.
27058 Indicate a badly formed request.
27060 An empty reply indicates that @samp{qRcmd} is not recognized.
27063 (Note that the @code{qRcmd} packet's name is separated from the
27064 command by a @samp{,}, not a @samp{:}, contrary to the naming
27065 conventions above. Please don't use this packet as a model for new
27068 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
27069 @cindex searching memory, in remote debugging
27070 @cindex @samp{qSearch:memory} packet
27071 @anchor{qSearch memory}
27072 Search @var{length} bytes at @var{address} for @var{search-pattern}.
27073 @var{address} and @var{length} are encoded in hex.
27074 @var{search-pattern} is a sequence of bytes, hex encoded.
27079 The pattern was not found.
27081 The pattern was found at @var{address}.
27083 A badly formed request or an error was encountered while searching memory.
27085 An empty reply indicates that @samp{qSearch:memory} is not recognized.
27088 @item QStartNoAckMode
27089 @cindex @samp{QStartNoAckMode} packet
27090 @anchor{QStartNoAckMode}
27091 Request that the remote stub disable the normal @samp{+}/@samp{-}
27092 protocol acknowledgments (@pxref{Packet Acknowledgment}).
27097 The stub has switched to no-acknowledgment mode.
27098 @value{GDBN} acknowledges this reponse,
27099 but neither the stub nor @value{GDBN} shall send or expect further
27100 @samp{+}/@samp{-} acknowledgments in the current connection.
27102 An empty reply indicates that the stub does not support no-acknowledgment mode.
27105 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
27106 @cindex supported packets, remote query
27107 @cindex features of the remote protocol
27108 @cindex @samp{qSupported} packet
27109 @anchor{qSupported}
27110 Tell the remote stub about features supported by @value{GDBN}, and
27111 query the stub for features it supports. This packet allows
27112 @value{GDBN} and the remote stub to take advantage of each others'
27113 features. @samp{qSupported} also consolidates multiple feature probes
27114 at startup, to improve @value{GDBN} performance---a single larger
27115 packet performs better than multiple smaller probe packets on
27116 high-latency links. Some features may enable behavior which must not
27117 be on by default, e.g.@: because it would confuse older clients or
27118 stubs. Other features may describe packets which could be
27119 automatically probed for, but are not. These features must be
27120 reported before @value{GDBN} will use them. This ``default
27121 unsupported'' behavior is not appropriate for all packets, but it
27122 helps to keep the initial connection time under control with new
27123 versions of @value{GDBN} which support increasing numbers of packets.
27127 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
27128 The stub supports or does not support each returned @var{stubfeature},
27129 depending on the form of each @var{stubfeature} (see below for the
27132 An empty reply indicates that @samp{qSupported} is not recognized,
27133 or that no features needed to be reported to @value{GDBN}.
27136 The allowed forms for each feature (either a @var{gdbfeature} in the
27137 @samp{qSupported} packet, or a @var{stubfeature} in the response)
27141 @item @var{name}=@var{value}
27142 The remote protocol feature @var{name} is supported, and associated
27143 with the specified @var{value}. The format of @var{value} depends
27144 on the feature, but it must not include a semicolon.
27146 The remote protocol feature @var{name} is supported, and does not
27147 need an associated value.
27149 The remote protocol feature @var{name} is not supported.
27151 The remote protocol feature @var{name} may be supported, and
27152 @value{GDBN} should auto-detect support in some other way when it is
27153 needed. This form will not be used for @var{gdbfeature} notifications,
27154 but may be used for @var{stubfeature} responses.
27157 Whenever the stub receives a @samp{qSupported} request, the
27158 supplied set of @value{GDBN} features should override any previous
27159 request. This allows @value{GDBN} to put the stub in a known
27160 state, even if the stub had previously been communicating with
27161 a different version of @value{GDBN}.
27163 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
27168 This feature indicates whether @value{GDBN} supports multiprocess
27169 extensions to the remote protocol. @value{GDBN} does not use such
27170 extensions unless the stub also reports that it supports them by
27171 including @samp{multiprocess+} in its @samp{qSupported} reply.
27172 @xref{multiprocess extensions}, for details.
27175 Stubs should ignore any unknown values for
27176 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
27177 packet supports receiving packets of unlimited length (earlier
27178 versions of @value{GDBN} may reject overly long responses). Additional values
27179 for @var{gdbfeature} may be defined in the future to let the stub take
27180 advantage of new features in @value{GDBN}, e.g.@: incompatible
27181 improvements in the remote protocol---the @samp{multiprocess} feature is
27182 an example of such a feature. The stub's reply should be independent
27183 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
27184 describes all the features it supports, and then the stub replies with
27185 all the features it supports.
27187 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
27188 responses, as long as each response uses one of the standard forms.
27190 Some features are flags. A stub which supports a flag feature
27191 should respond with a @samp{+} form response. Other features
27192 require values, and the stub should respond with an @samp{=}
27195 Each feature has a default value, which @value{GDBN} will use if
27196 @samp{qSupported} is not available or if the feature is not mentioned
27197 in the @samp{qSupported} response. The default values are fixed; a
27198 stub is free to omit any feature responses that match the defaults.
27200 Not all features can be probed, but for those which can, the probing
27201 mechanism is useful: in some cases, a stub's internal
27202 architecture may not allow the protocol layer to know some information
27203 about the underlying target in advance. This is especially common in
27204 stubs which may be configured for multiple targets.
27206 These are the currently defined stub features and their properties:
27208 @multitable @columnfractions 0.35 0.2 0.12 0.2
27209 @c NOTE: The first row should be @headitem, but we do not yet require
27210 @c a new enough version of Texinfo (4.7) to use @headitem.
27212 @tab Value Required
27216 @item @samp{PacketSize}
27221 @item @samp{qXfer:auxv:read}
27226 @item @samp{qXfer:features:read}
27231 @item @samp{qXfer:libraries:read}
27236 @item @samp{qXfer:memory-map:read}
27241 @item @samp{qXfer:spu:read}
27246 @item @samp{qXfer:spu:write}
27251 @item @samp{qXfer:siginfo:read}
27256 @item @samp{qXfer:siginfo:write}
27261 @item @samp{QNonStop}
27266 @item @samp{QPassSignals}
27271 @item @samp{QStartNoAckMode}
27276 @item @samp{multiprocess}
27283 These are the currently defined stub features, in more detail:
27286 @cindex packet size, remote protocol
27287 @item PacketSize=@var{bytes}
27288 The remote stub can accept packets up to at least @var{bytes} in
27289 length. @value{GDBN} will send packets up to this size for bulk
27290 transfers, and will never send larger packets. This is a limit on the
27291 data characters in the packet, including the frame and checksum.
27292 There is no trailing NUL byte in a remote protocol packet; if the stub
27293 stores packets in a NUL-terminated format, it should allow an extra
27294 byte in its buffer for the NUL. If this stub feature is not supported,
27295 @value{GDBN} guesses based on the size of the @samp{g} packet response.
27297 @item qXfer:auxv:read
27298 The remote stub understands the @samp{qXfer:auxv:read} packet
27299 (@pxref{qXfer auxiliary vector read}).
27301 @item qXfer:features:read
27302 The remote stub understands the @samp{qXfer:features:read} packet
27303 (@pxref{qXfer target description read}).
27305 @item qXfer:libraries:read
27306 The remote stub understands the @samp{qXfer:libraries:read} packet
27307 (@pxref{qXfer library list read}).
27309 @item qXfer:memory-map:read
27310 The remote stub understands the @samp{qXfer:memory-map:read} packet
27311 (@pxref{qXfer memory map read}).
27313 @item qXfer:spu:read
27314 The remote stub understands the @samp{qXfer:spu:read} packet
27315 (@pxref{qXfer spu read}).
27317 @item qXfer:spu:write
27318 The remote stub understands the @samp{qXfer:spu:write} packet
27319 (@pxref{qXfer spu write}).
27321 @item qXfer:siginfo:read
27322 The remote stub understands the @samp{qXfer:siginfo:read} packet
27323 (@pxref{qXfer siginfo read}).
27325 @item qXfer:siginfo:write
27326 The remote stub understands the @samp{qXfer:siginfo:write} packet
27327 (@pxref{qXfer siginfo write}).
27330 The remote stub understands the @samp{QNonStop} packet
27331 (@pxref{QNonStop}).
27334 The remote stub understands the @samp{QPassSignals} packet
27335 (@pxref{QPassSignals}).
27337 @item QStartNoAckMode
27338 The remote stub understands the @samp{QStartNoAckMode} packet and
27339 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
27342 @anchor{multiprocess extensions}
27343 @cindex multiprocess extensions, in remote protocol
27344 The remote stub understands the multiprocess extensions to the remote
27345 protocol syntax. The multiprocess extensions affect the syntax of
27346 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
27347 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
27348 replies. Note that reporting this feature indicates support for the
27349 syntactic extensions only, not that the stub necessarily supports
27350 debugging of more than one process at a time. The stub must not use
27351 multiprocess extensions in packet replies unless @value{GDBN} has also
27352 indicated it supports them in its @samp{qSupported} request.
27354 @item qXfer:osdata:read
27355 The remote stub understands the @samp{qXfer:osdata:read} packet
27356 ((@pxref{qXfer osdata read}).
27361 @cindex symbol lookup, remote request
27362 @cindex @samp{qSymbol} packet
27363 Notify the target that @value{GDBN} is prepared to serve symbol lookup
27364 requests. Accept requests from the target for the values of symbols.
27369 The target does not need to look up any (more) symbols.
27370 @item qSymbol:@var{sym_name}
27371 The target requests the value of symbol @var{sym_name} (hex encoded).
27372 @value{GDBN} may provide the value by using the
27373 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
27377 @item qSymbol:@var{sym_value}:@var{sym_name}
27378 Set the value of @var{sym_name} to @var{sym_value}.
27380 @var{sym_name} (hex encoded) is the name of a symbol whose value the
27381 target has previously requested.
27383 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
27384 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
27390 The target does not need to look up any (more) symbols.
27391 @item qSymbol:@var{sym_name}
27392 The target requests the value of a new symbol @var{sym_name} (hex
27393 encoded). @value{GDBN} will continue to supply the values of symbols
27394 (if available), until the target ceases to request them.
27399 @xref{Tracepoint Packets}.
27401 @item qThreadExtraInfo,@var{thread-id}
27402 @cindex thread attributes info, remote request
27403 @cindex @samp{qThreadExtraInfo} packet
27404 Obtain a printable string description of a thread's attributes from
27405 the target OS. @var{thread-id} is a thread ID;
27406 see @ref{thread-id syntax}. This
27407 string may contain anything that the target OS thinks is interesting
27408 for @value{GDBN} to tell the user about the thread. The string is
27409 displayed in @value{GDBN}'s @code{info threads} display. Some
27410 examples of possible thread extra info strings are @samp{Runnable}, or
27411 @samp{Blocked on Mutex}.
27415 @item @var{XX}@dots{}
27416 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
27417 comprising the printable string containing the extra information about
27418 the thread's attributes.
27421 (Note that the @code{qThreadExtraInfo} packet's name is separated from
27422 the command by a @samp{,}, not a @samp{:}, contrary to the naming
27423 conventions above. Please don't use this packet as a model for new
27431 @xref{Tracepoint Packets}.
27433 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
27434 @cindex read special object, remote request
27435 @cindex @samp{qXfer} packet
27436 @anchor{qXfer read}
27437 Read uninterpreted bytes from the target's special data area
27438 identified by the keyword @var{object}. Request @var{length} bytes
27439 starting at @var{offset} bytes into the data. The content and
27440 encoding of @var{annex} is specific to @var{object}; it can supply
27441 additional details about what data to access.
27443 Here are the specific requests of this form defined so far. All
27444 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
27445 formats, listed below.
27448 @item qXfer:auxv:read::@var{offset},@var{length}
27449 @anchor{qXfer auxiliary vector read}
27450 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
27451 auxiliary vector}. Note @var{annex} must be empty.
27453 This packet is not probed by default; the remote stub must request it,
27454 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27456 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
27457 @anchor{qXfer target description read}
27458 Access the @dfn{target description}. @xref{Target Descriptions}. The
27459 annex specifies which XML document to access. The main description is
27460 always loaded from the @samp{target.xml} annex.
27462 This packet is not probed by default; the remote stub must request it,
27463 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27465 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
27466 @anchor{qXfer library list read}
27467 Access the target's list of loaded libraries. @xref{Library List Format}.
27468 The annex part of the generic @samp{qXfer} packet must be empty
27469 (@pxref{qXfer read}).
27471 Targets which maintain a list of libraries in the program's memory do
27472 not need to implement this packet; it is designed for platforms where
27473 the operating system manages the list of loaded libraries.
27475 This packet is not probed by default; the remote stub must request it,
27476 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27478 @item qXfer:memory-map:read::@var{offset},@var{length}
27479 @anchor{qXfer memory map read}
27480 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
27481 annex part of the generic @samp{qXfer} packet must be empty
27482 (@pxref{qXfer read}).
27484 This packet is not probed by default; the remote stub must request it,
27485 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27487 @item qXfer:siginfo:read::@var{offset},@var{length}
27488 @anchor{qXfer siginfo read}
27489 Read contents of the extra signal information on the target
27490 system. The annex part of the generic @samp{qXfer} packet must be
27491 empty (@pxref{qXfer read}).
27493 This packet is not probed by default; the remote stub must request it,
27494 by supplying an appropriate @samp{qSupported} response
27495 (@pxref{qSupported}).
27497 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
27498 @anchor{qXfer spu read}
27499 Read contents of an @code{spufs} file on the target system. The
27500 annex specifies which file to read; it must be of the form
27501 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27502 in the target process, and @var{name} identifes the @code{spufs} file
27503 in that context to be accessed.
27505 This packet is not probed by default; the remote stub must request it,
27506 by supplying an appropriate @samp{qSupported} response
27507 (@pxref{qSupported}).
27509 @item qXfer:osdata:read::@var{offset},@var{length}
27510 @anchor{qXfer osdata read}
27511 Access the target's @dfn{operating system information}.
27512 @xref{Operating System Information}.
27519 Data @var{data} (@pxref{Binary Data}) has been read from the
27520 target. There may be more data at a higher address (although
27521 it is permitted to return @samp{m} even for the last valid
27522 block of data, as long as at least one byte of data was read).
27523 @var{data} may have fewer bytes than the @var{length} in the
27527 Data @var{data} (@pxref{Binary Data}) has been read from the target.
27528 There is no more data to be read. @var{data} may have fewer bytes
27529 than the @var{length} in the request.
27532 The @var{offset} in the request is at the end of the data.
27533 There is no more data to be read.
27536 The request was malformed, or @var{annex} was invalid.
27539 The offset was invalid, or there was an error encountered reading the data.
27540 @var{nn} is a hex-encoded @code{errno} value.
27543 An empty reply indicates the @var{object} string was not recognized by
27544 the stub, or that the object does not support reading.
27547 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
27548 @cindex write data into object, remote request
27549 @anchor{qXfer write}
27550 Write uninterpreted bytes into the target's special data area
27551 identified by the keyword @var{object}, starting at @var{offset} bytes
27552 into the data. @var{data}@dots{} is the binary-encoded data
27553 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
27554 is specific to @var{object}; it can supply additional details about what data
27557 Here are the specific requests of this form defined so far. All
27558 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
27559 formats, listed below.
27562 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
27563 @anchor{qXfer siginfo write}
27564 Write @var{data} to the extra signal information on the target system.
27565 The annex part of the generic @samp{qXfer} packet must be
27566 empty (@pxref{qXfer write}).
27568 This packet is not probed by default; the remote stub must request it,
27569 by supplying an appropriate @samp{qSupported} response
27570 (@pxref{qSupported}).
27572 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
27573 @anchor{qXfer spu write}
27574 Write @var{data} to an @code{spufs} file on the target system. The
27575 annex specifies which file to write; it must be of the form
27576 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
27577 in the target process, and @var{name} identifes the @code{spufs} file
27578 in that context to be accessed.
27580 This packet is not probed by default; the remote stub must request it,
27581 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
27587 @var{nn} (hex encoded) is the number of bytes written.
27588 This may be fewer bytes than supplied in the request.
27591 The request was malformed, or @var{annex} was invalid.
27594 The offset was invalid, or there was an error encountered writing the data.
27595 @var{nn} is a hex-encoded @code{errno} value.
27598 An empty reply indicates the @var{object} string was not
27599 recognized by the stub, or that the object does not support writing.
27602 @item qXfer:@var{object}:@var{operation}:@dots{}
27603 Requests of this form may be added in the future. When a stub does
27604 not recognize the @var{object} keyword, or its support for
27605 @var{object} does not recognize the @var{operation} keyword, the stub
27606 must respond with an empty packet.
27608 @item qAttached:@var{pid}
27609 @cindex query attached, remote request
27610 @cindex @samp{qAttached} packet
27611 Return an indication of whether the remote server attached to an
27612 existing process or created a new process. When the multiprocess
27613 protocol extensions are supported (@pxref{multiprocess extensions}),
27614 @var{pid} is an integer in hexadecimal format identifying the target
27615 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
27616 the query packet will be simplified as @samp{qAttached}.
27618 This query is used, for example, to know whether the remote process
27619 should be detached or killed when a @value{GDBN} session is ended with
27620 the @code{quit} command.
27625 The remote server attached to an existing process.
27627 The remote server created a new process.
27629 A badly formed request or an error was encountered.
27634 @node Register Packet Format
27635 @section Register Packet Format
27637 The following @code{g}/@code{G} packets have previously been defined.
27638 In the below, some thirty-two bit registers are transferred as
27639 sixty-four bits. Those registers should be zero/sign extended (which?)
27640 to fill the space allocated. Register bytes are transferred in target
27641 byte order. The two nibbles within a register byte are transferred
27642 most-significant - least-significant.
27648 All registers are transferred as thirty-two bit quantities in the order:
27649 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
27650 registers; fsr; fir; fp.
27654 All registers are transferred as sixty-four bit quantities (including
27655 thirty-two bit registers such as @code{sr}). The ordering is the same
27660 @node Tracepoint Packets
27661 @section Tracepoint Packets
27662 @cindex tracepoint packets
27663 @cindex packets, tracepoint
27665 Here we describe the packets @value{GDBN} uses to implement
27666 tracepoints (@pxref{Tracepoints}).
27670 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
27671 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
27672 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
27673 the tracepoint is disabled. @var{step} is the tracepoint's step
27674 count, and @var{pass} is its pass count. If the trailing @samp{-} is
27675 present, further @samp{QTDP} packets will follow to specify this
27676 tracepoint's actions.
27681 The packet was understood and carried out.
27683 The packet was not recognized.
27686 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
27687 Define actions to be taken when a tracepoint is hit. @var{n} and
27688 @var{addr} must be the same as in the initial @samp{QTDP} packet for
27689 this tracepoint. This packet may only be sent immediately after
27690 another @samp{QTDP} packet that ended with a @samp{-}. If the
27691 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
27692 specifying more actions for this tracepoint.
27694 In the series of action packets for a given tracepoint, at most one
27695 can have an @samp{S} before its first @var{action}. If such a packet
27696 is sent, it and the following packets define ``while-stepping''
27697 actions. Any prior packets define ordinary actions --- that is, those
27698 taken when the tracepoint is first hit. If no action packet has an
27699 @samp{S}, then all the packets in the series specify ordinary
27700 tracepoint actions.
27702 The @samp{@var{action}@dots{}} portion of the packet is a series of
27703 actions, concatenated without separators. Each action has one of the
27709 Collect the registers whose bits are set in @var{mask}. @var{mask} is
27710 a hexadecimal number whose @var{i}'th bit is set if register number
27711 @var{i} should be collected. (The least significant bit is numbered
27712 zero.) Note that @var{mask} may be any number of digits long; it may
27713 not fit in a 32-bit word.
27715 @item M @var{basereg},@var{offset},@var{len}
27716 Collect @var{len} bytes of memory starting at the address in register
27717 number @var{basereg}, plus @var{offset}. If @var{basereg} is
27718 @samp{-1}, then the range has a fixed address: @var{offset} is the
27719 address of the lowest byte to collect. The @var{basereg},
27720 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
27721 values (the @samp{-1} value for @var{basereg} is a special case).
27723 @item X @var{len},@var{expr}
27724 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
27725 it directs. @var{expr} is an agent expression, as described in
27726 @ref{Agent Expressions}. Each byte of the expression is encoded as a
27727 two-digit hex number in the packet; @var{len} is the number of bytes
27728 in the expression (and thus one-half the number of hex digits in the
27733 Any number of actions may be packed together in a single @samp{QTDP}
27734 packet, as long as the packet does not exceed the maximum packet
27735 length (400 bytes, for many stubs). There may be only one @samp{R}
27736 action per tracepoint, and it must precede any @samp{M} or @samp{X}
27737 actions. Any registers referred to by @samp{M} and @samp{X} actions
27738 must be collected by a preceding @samp{R} action. (The
27739 ``while-stepping'' actions are treated as if they were attached to a
27740 separate tracepoint, as far as these restrictions are concerned.)
27745 The packet was understood and carried out.
27747 The packet was not recognized.
27750 @item QTFrame:@var{n}
27751 Select the @var{n}'th tracepoint frame from the buffer, and use the
27752 register and memory contents recorded there to answer subsequent
27753 request packets from @value{GDBN}.
27755 A successful reply from the stub indicates that the stub has found the
27756 requested frame. The response is a series of parts, concatenated
27757 without separators, describing the frame we selected. Each part has
27758 one of the following forms:
27762 The selected frame is number @var{n} in the trace frame buffer;
27763 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
27764 was no frame matching the criteria in the request packet.
27767 The selected trace frame records a hit of tracepoint number @var{t};
27768 @var{t} is a hexadecimal number.
27772 @item QTFrame:pc:@var{addr}
27773 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27774 currently selected frame whose PC is @var{addr};
27775 @var{addr} is a hexadecimal number.
27777 @item QTFrame:tdp:@var{t}
27778 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27779 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
27780 is a hexadecimal number.
27782 @item QTFrame:range:@var{start}:@var{end}
27783 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
27784 currently selected frame whose PC is between @var{start} (inclusive)
27785 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
27788 @item QTFrame:outside:@var{start}:@var{end}
27789 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
27790 frame @emph{outside} the given range of addresses.
27793 Begin the tracepoint experiment. Begin collecting data from tracepoint
27794 hits in the trace frame buffer.
27797 End the tracepoint experiment. Stop collecting trace frames.
27800 Clear the table of tracepoints, and empty the trace frame buffer.
27802 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
27803 Establish the given ranges of memory as ``transparent''. The stub
27804 will answer requests for these ranges from memory's current contents,
27805 if they were not collected as part of the tracepoint hit.
27807 @value{GDBN} uses this to mark read-only regions of memory, like those
27808 containing program code. Since these areas never change, they should
27809 still have the same contents they did when the tracepoint was hit, so
27810 there's no reason for the stub to refuse to provide their contents.
27813 Ask the stub if there is a trace experiment running right now.
27818 There is no trace experiment running.
27820 There is a trace experiment running.
27826 @node Host I/O Packets
27827 @section Host I/O Packets
27828 @cindex Host I/O, remote protocol
27829 @cindex file transfer, remote protocol
27831 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
27832 operations on the far side of a remote link. For example, Host I/O is
27833 used to upload and download files to a remote target with its own
27834 filesystem. Host I/O uses the same constant values and data structure
27835 layout as the target-initiated File-I/O protocol. However, the
27836 Host I/O packets are structured differently. The target-initiated
27837 protocol relies on target memory to store parameters and buffers.
27838 Host I/O requests are initiated by @value{GDBN}, and the
27839 target's memory is not involved. @xref{File-I/O Remote Protocol
27840 Extension}, for more details on the target-initiated protocol.
27842 The Host I/O request packets all encode a single operation along with
27843 its arguments. They have this format:
27847 @item vFile:@var{operation}: @var{parameter}@dots{}
27848 @var{operation} is the name of the particular request; the target
27849 should compare the entire packet name up to the second colon when checking
27850 for a supported operation. The format of @var{parameter} depends on
27851 the operation. Numbers are always passed in hexadecimal. Negative
27852 numbers have an explicit minus sign (i.e.@: two's complement is not
27853 used). Strings (e.g.@: filenames) are encoded as a series of
27854 hexadecimal bytes. The last argument to a system call may be a
27855 buffer of escaped binary data (@pxref{Binary Data}).
27859 The valid responses to Host I/O packets are:
27863 @item F @var{result} [, @var{errno}] [; @var{attachment}]
27864 @var{result} is the integer value returned by this operation, usually
27865 non-negative for success and -1 for errors. If an error has occured,
27866 @var{errno} will be included in the result. @var{errno} will have a
27867 value defined by the File-I/O protocol (@pxref{Errno Values}). For
27868 operations which return data, @var{attachment} supplies the data as a
27869 binary buffer. Binary buffers in response packets are escaped in the
27870 normal way (@pxref{Binary Data}). See the individual packet
27871 documentation for the interpretation of @var{result} and
27875 An empty response indicates that this operation is not recognized.
27879 These are the supported Host I/O operations:
27882 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
27883 Open a file at @var{pathname} and return a file descriptor for it, or
27884 return -1 if an error occurs. @var{pathname} is a string,
27885 @var{flags} is an integer indicating a mask of open flags
27886 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
27887 of mode bits to use if the file is created (@pxref{mode_t Values}).
27888 @xref{open}, for details of the open flags and mode values.
27890 @item vFile:close: @var{fd}
27891 Close the open file corresponding to @var{fd} and return 0, or
27892 -1 if an error occurs.
27894 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
27895 Read data from the open file corresponding to @var{fd}. Up to
27896 @var{count} bytes will be read from the file, starting at @var{offset}
27897 relative to the start of the file. The target may read fewer bytes;
27898 common reasons include packet size limits and an end-of-file
27899 condition. The number of bytes read is returned. Zero should only be
27900 returned for a successful read at the end of the file, or if
27901 @var{count} was zero.
27903 The data read should be returned as a binary attachment on success.
27904 If zero bytes were read, the response should include an empty binary
27905 attachment (i.e.@: a trailing semicolon). The return value is the
27906 number of target bytes read; the binary attachment may be longer if
27907 some characters were escaped.
27909 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
27910 Write @var{data} (a binary buffer) to the open file corresponding
27911 to @var{fd}. Start the write at @var{offset} from the start of the
27912 file. Unlike many @code{write} system calls, there is no
27913 separate @var{count} argument; the length of @var{data} in the
27914 packet is used. @samp{vFile:write} returns the number of bytes written,
27915 which may be shorter than the length of @var{data}, or -1 if an
27918 @item vFile:unlink: @var{pathname}
27919 Delete the file at @var{pathname} on the target. Return 0,
27920 or -1 if an error occurs. @var{pathname} is a string.
27925 @section Interrupts
27926 @cindex interrupts (remote protocol)
27928 When a program on the remote target is running, @value{GDBN} may
27929 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
27930 control of which is specified via @value{GDBN}'s @samp{remotebreak}
27931 setting (@pxref{set remotebreak}).
27933 The precise meaning of @code{BREAK} is defined by the transport
27934 mechanism and may, in fact, be undefined. @value{GDBN} does not
27935 currently define a @code{BREAK} mechanism for any of the network
27936 interfaces except for TCP, in which case @value{GDBN} sends the
27937 @code{telnet} BREAK sequence.
27939 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
27940 transport mechanisms. It is represented by sending the single byte
27941 @code{0x03} without any of the usual packet overhead described in
27942 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
27943 transmitted as part of a packet, it is considered to be packet data
27944 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
27945 (@pxref{X packet}), used for binary downloads, may include an unescaped
27946 @code{0x03} as part of its packet.
27948 Stubs are not required to recognize these interrupt mechanisms and the
27949 precise meaning associated with receipt of the interrupt is
27950 implementation defined. If the target supports debugging of multiple
27951 threads and/or processes, it should attempt to interrupt all
27952 currently-executing threads and processes.
27953 If the stub is successful at interrupting the
27954 running program, it should send one of the stop
27955 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
27956 of successfully stopping the program in all-stop mode, and a stop reply
27957 for each stopped thread in non-stop mode.
27958 Interrupts received while the
27959 program is stopped are discarded.
27961 @node Notification Packets
27962 @section Notification Packets
27963 @cindex notification packets
27964 @cindex packets, notification
27966 The @value{GDBN} remote serial protocol includes @dfn{notifications},
27967 packets that require no acknowledgment. Both the GDB and the stub
27968 may send notifications (although the only notifications defined at
27969 present are sent by the stub). Notifications carry information
27970 without incurring the round-trip latency of an acknowledgment, and so
27971 are useful for low-impact communications where occasional packet loss
27974 A notification packet has the form @samp{% @var{data} #
27975 @var{checksum}}, where @var{data} is the content of the notification,
27976 and @var{checksum} is a checksum of @var{data}, computed and formatted
27977 as for ordinary @value{GDBN} packets. A notification's @var{data}
27978 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
27979 receiving a notification, the recipient sends no @samp{+} or @samp{-}
27980 to acknowledge the notification's receipt or to report its corruption.
27982 Every notification's @var{data} begins with a name, which contains no
27983 colon characters, followed by a colon character.
27985 Recipients should silently ignore corrupted notifications and
27986 notifications they do not understand. Recipients should restart
27987 timeout periods on receipt of a well-formed notification, whether or
27988 not they understand it.
27990 Senders should only send the notifications described here when this
27991 protocol description specifies that they are permitted. In the
27992 future, we may extend the protocol to permit existing notifications in
27993 new contexts; this rule helps older senders avoid confusing newer
27996 (Older versions of @value{GDBN} ignore bytes received until they see
27997 the @samp{$} byte that begins an ordinary packet, so new stubs may
27998 transmit notifications without fear of confusing older clients. There
27999 are no notifications defined for @value{GDBN} to send at the moment, but we
28000 assume that most older stubs would ignore them, as well.)
28002 The following notification packets from the stub to @value{GDBN} are
28006 @item Stop: @var{reply}
28007 Report an asynchronous stop event in non-stop mode.
28008 The @var{reply} has the form of a stop reply, as
28009 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
28010 for information on how these notifications are acknowledged by
28014 @node Remote Non-Stop
28015 @section Remote Protocol Support for Non-Stop Mode
28017 @value{GDBN}'s remote protocol supports non-stop debugging of
28018 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
28019 supports non-stop mode, it should report that to @value{GDBN} by including
28020 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
28022 @value{GDBN} typically sends a @samp{QNonStop} packet only when
28023 establishing a new connection with the stub. Entering non-stop mode
28024 does not alter the state of any currently-running threads, but targets
28025 must stop all threads in any already-attached processes when entering
28026 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
28027 probe the target state after a mode change.
28029 In non-stop mode, when an attached process encounters an event that
28030 would otherwise be reported with a stop reply, it uses the
28031 asynchronous notification mechanism (@pxref{Notification Packets}) to
28032 inform @value{GDBN}. In contrast to all-stop mode, where all threads
28033 in all processes are stopped when a stop reply is sent, in non-stop
28034 mode only the thread reporting the stop event is stopped. That is,
28035 when reporting a @samp{S} or @samp{T} response to indicate completion
28036 of a step operation, hitting a breakpoint, or a fault, only the
28037 affected thread is stopped; any other still-running threads continue
28038 to run. When reporting a @samp{W} or @samp{X} response, all running
28039 threads belonging to other attached processes continue to run.
28041 Only one stop reply notification at a time may be pending; if
28042 additional stop events occur before @value{GDBN} has acknowledged the
28043 previous notification, they must be queued by the stub for later
28044 synchronous transmission in response to @samp{vStopped} packets from
28045 @value{GDBN}. Because the notification mechanism is unreliable,
28046 the stub is permitted to resend a stop reply notification
28047 if it believes @value{GDBN} may not have received it. @value{GDBN}
28048 ignores additional stop reply notifications received before it has
28049 finished processing a previous notification and the stub has completed
28050 sending any queued stop events.
28052 Otherwise, @value{GDBN} must be prepared to receive a stop reply
28053 notification at any time. Specifically, they may appear when
28054 @value{GDBN} is not otherwise reading input from the stub, or when
28055 @value{GDBN} is expecting to read a normal synchronous response or a
28056 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
28057 Notification packets are distinct from any other communication from
28058 the stub so there is no ambiguity.
28060 After receiving a stop reply notification, @value{GDBN} shall
28061 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
28062 as a regular, synchronous request to the stub. Such acknowledgment
28063 is not required to happen immediately, as @value{GDBN} is permitted to
28064 send other, unrelated packets to the stub first, which the stub should
28067 Upon receiving a @samp{vStopped} packet, if the stub has other queued
28068 stop events to report to @value{GDBN}, it shall respond by sending a
28069 normal stop reply response. @value{GDBN} shall then send another
28070 @samp{vStopped} packet to solicit further responses; again, it is
28071 permitted to send other, unrelated packets as well which the stub
28072 should process normally.
28074 If the stub receives a @samp{vStopped} packet and there are no
28075 additional stop events to report, the stub shall return an @samp{OK}
28076 response. At this point, if further stop events occur, the stub shall
28077 send a new stop reply notification, @value{GDBN} shall accept the
28078 notification, and the process shall be repeated.
28080 In non-stop mode, the target shall respond to the @samp{?} packet as
28081 follows. First, any incomplete stop reply notification/@samp{vStopped}
28082 sequence in progress is abandoned. The target must begin a new
28083 sequence reporting stop events for all stopped threads, whether or not
28084 it has previously reported those events to @value{GDBN}. The first
28085 stop reply is sent as a synchronous reply to the @samp{?} packet, and
28086 subsequent stop replies are sent as responses to @samp{vStopped} packets
28087 using the mechanism described above. The target must not send
28088 asynchronous stop reply notifications until the sequence is complete.
28089 If all threads are running when the target receives the @samp{?} packet,
28090 or if the target is not attached to any process, it shall respond
28093 @node Packet Acknowledgment
28094 @section Packet Acknowledgment
28096 @cindex acknowledgment, for @value{GDBN} remote
28097 @cindex packet acknowledgment, for @value{GDBN} remote
28098 By default, when either the host or the target machine receives a packet,
28099 the first response expected is an acknowledgment: either @samp{+} (to indicate
28100 the package was received correctly) or @samp{-} (to request retransmission).
28101 This mechanism allows the @value{GDBN} remote protocol to operate over
28102 unreliable transport mechanisms, such as a serial line.
28104 In cases where the transport mechanism is itself reliable (such as a pipe or
28105 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
28106 It may be desirable to disable them in that case to reduce communication
28107 overhead, or for other reasons. This can be accomplished by means of the
28108 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
28110 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
28111 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
28112 and response format still includes the normal checksum, as described in
28113 @ref{Overview}, but the checksum may be ignored by the receiver.
28115 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
28116 no-acknowledgment mode, it should report that to @value{GDBN}
28117 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
28118 @pxref{qSupported}.
28119 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
28120 disabled via the @code{set remote noack-packet off} command
28121 (@pxref{Remote Configuration}),
28122 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
28123 Only then may the stub actually turn off packet acknowledgments.
28124 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
28125 response, which can be safely ignored by the stub.
28127 Note that @code{set remote noack-packet} command only affects negotiation
28128 between @value{GDBN} and the stub when subsequent connections are made;
28129 it does not affect the protocol acknowledgment state for any current
28131 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
28132 new connection is established,
28133 there is also no protocol request to re-enable the acknowledgments
28134 for the current connection, once disabled.
28139 Example sequence of a target being re-started. Notice how the restart
28140 does not get any direct output:
28145 @emph{target restarts}
28148 <- @code{T001:1234123412341234}
28152 Example sequence of a target being stepped by a single instruction:
28155 -> @code{G1445@dots{}}
28160 <- @code{T001:1234123412341234}
28164 <- @code{1455@dots{}}
28168 @node File-I/O Remote Protocol Extension
28169 @section File-I/O Remote Protocol Extension
28170 @cindex File-I/O remote protocol extension
28173 * File-I/O Overview::
28174 * Protocol Basics::
28175 * The F Request Packet::
28176 * The F Reply Packet::
28177 * The Ctrl-C Message::
28179 * List of Supported Calls::
28180 * Protocol-specific Representation of Datatypes::
28182 * File-I/O Examples::
28185 @node File-I/O Overview
28186 @subsection File-I/O Overview
28187 @cindex file-i/o overview
28189 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
28190 target to use the host's file system and console I/O to perform various
28191 system calls. System calls on the target system are translated into a
28192 remote protocol packet to the host system, which then performs the needed
28193 actions and returns a response packet to the target system.
28194 This simulates file system operations even on targets that lack file systems.
28196 The protocol is defined to be independent of both the host and target systems.
28197 It uses its own internal representation of datatypes and values. Both
28198 @value{GDBN} and the target's @value{GDBN} stub are responsible for
28199 translating the system-dependent value representations into the internal
28200 protocol representations when data is transmitted.
28202 The communication is synchronous. A system call is possible only when
28203 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
28204 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
28205 the target is stopped to allow deterministic access to the target's
28206 memory. Therefore File-I/O is not interruptible by target signals. On
28207 the other hand, it is possible to interrupt File-I/O by a user interrupt
28208 (@samp{Ctrl-C}) within @value{GDBN}.
28210 The target's request to perform a host system call does not finish
28211 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
28212 after finishing the system call, the target returns to continuing the
28213 previous activity (continue, step). No additional continue or step
28214 request from @value{GDBN} is required.
28217 (@value{GDBP}) continue
28218 <- target requests 'system call X'
28219 target is stopped, @value{GDBN} executes system call
28220 -> @value{GDBN} returns result
28221 ... target continues, @value{GDBN} returns to wait for the target
28222 <- target hits breakpoint and sends a Txx packet
28225 The protocol only supports I/O on the console and to regular files on
28226 the host file system. Character or block special devices, pipes,
28227 named pipes, sockets or any other communication method on the host
28228 system are not supported by this protocol.
28230 File I/O is not supported in non-stop mode.
28232 @node Protocol Basics
28233 @subsection Protocol Basics
28234 @cindex protocol basics, file-i/o
28236 The File-I/O protocol uses the @code{F} packet as the request as well
28237 as reply packet. Since a File-I/O system call can only occur when
28238 @value{GDBN} is waiting for a response from the continuing or stepping target,
28239 the File-I/O request is a reply that @value{GDBN} has to expect as a result
28240 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
28241 This @code{F} packet contains all information needed to allow @value{GDBN}
28242 to call the appropriate host system call:
28246 A unique identifier for the requested system call.
28249 All parameters to the system call. Pointers are given as addresses
28250 in the target memory address space. Pointers to strings are given as
28251 pointer/length pair. Numerical values are given as they are.
28252 Numerical control flags are given in a protocol-specific representation.
28256 At this point, @value{GDBN} has to perform the following actions.
28260 If the parameters include pointer values to data needed as input to a
28261 system call, @value{GDBN} requests this data from the target with a
28262 standard @code{m} packet request. This additional communication has to be
28263 expected by the target implementation and is handled as any other @code{m}
28267 @value{GDBN} translates all value from protocol representation to host
28268 representation as needed. Datatypes are coerced into the host types.
28271 @value{GDBN} calls the system call.
28274 It then coerces datatypes back to protocol representation.
28277 If the system call is expected to return data in buffer space specified
28278 by pointer parameters to the call, the data is transmitted to the
28279 target using a @code{M} or @code{X} packet. This packet has to be expected
28280 by the target implementation and is handled as any other @code{M} or @code{X}
28285 Eventually @value{GDBN} replies with another @code{F} packet which contains all
28286 necessary information for the target to continue. This at least contains
28293 @code{errno}, if has been changed by the system call.
28300 After having done the needed type and value coercion, the target continues
28301 the latest continue or step action.
28303 @node The F Request Packet
28304 @subsection The @code{F} Request Packet
28305 @cindex file-i/o request packet
28306 @cindex @code{F} request packet
28308 The @code{F} request packet has the following format:
28311 @item F@var{call-id},@var{parameter@dots{}}
28313 @var{call-id} is the identifier to indicate the host system call to be called.
28314 This is just the name of the function.
28316 @var{parameter@dots{}} are the parameters to the system call.
28317 Parameters are hexadecimal integer values, either the actual values in case
28318 of scalar datatypes, pointers to target buffer space in case of compound
28319 datatypes and unspecified memory areas, or pointer/length pairs in case
28320 of string parameters. These are appended to the @var{call-id} as a
28321 comma-delimited list. All values are transmitted in ASCII
28322 string representation, pointer/length pairs separated by a slash.
28328 @node The F Reply Packet
28329 @subsection The @code{F} Reply Packet
28330 @cindex file-i/o reply packet
28331 @cindex @code{F} reply packet
28333 The @code{F} reply packet has the following format:
28337 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
28339 @var{retcode} is the return code of the system call as hexadecimal value.
28341 @var{errno} is the @code{errno} set by the call, in protocol-specific
28343 This parameter can be omitted if the call was successful.
28345 @var{Ctrl-C flag} is only sent if the user requested a break. In this
28346 case, @var{errno} must be sent as well, even if the call was successful.
28347 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
28354 or, if the call was interrupted before the host call has been performed:
28361 assuming 4 is the protocol-specific representation of @code{EINTR}.
28366 @node The Ctrl-C Message
28367 @subsection The @samp{Ctrl-C} Message
28368 @cindex ctrl-c message, in file-i/o protocol
28370 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
28371 reply packet (@pxref{The F Reply Packet}),
28372 the target should behave as if it had
28373 gotten a break message. The meaning for the target is ``system call
28374 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
28375 (as with a break message) and return to @value{GDBN} with a @code{T02}
28378 It's important for the target to know in which
28379 state the system call was interrupted. There are two possible cases:
28383 The system call hasn't been performed on the host yet.
28386 The system call on the host has been finished.
28390 These two states can be distinguished by the target by the value of the
28391 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
28392 call hasn't been performed. This is equivalent to the @code{EINTR} handling
28393 on POSIX systems. In any other case, the target may presume that the
28394 system call has been finished --- successfully or not --- and should behave
28395 as if the break message arrived right after the system call.
28397 @value{GDBN} must behave reliably. If the system call has not been called
28398 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
28399 @code{errno} in the packet. If the system call on the host has been finished
28400 before the user requests a break, the full action must be finished by
28401 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
28402 The @code{F} packet may only be sent when either nothing has happened
28403 or the full action has been completed.
28406 @subsection Console I/O
28407 @cindex console i/o as part of file-i/o
28409 By default and if not explicitly closed by the target system, the file
28410 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
28411 on the @value{GDBN} console is handled as any other file output operation
28412 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
28413 by @value{GDBN} so that after the target read request from file descriptor
28414 0 all following typing is buffered until either one of the following
28419 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
28421 system call is treated as finished.
28424 The user presses @key{RET}. This is treated as end of input with a trailing
28428 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
28429 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
28433 If the user has typed more characters than fit in the buffer given to
28434 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
28435 either another @code{read(0, @dots{})} is requested by the target, or debugging
28436 is stopped at the user's request.
28439 @node List of Supported Calls
28440 @subsection List of Supported Calls
28441 @cindex list of supported file-i/o calls
28458 @unnumberedsubsubsec open
28459 @cindex open, file-i/o system call
28464 int open(const char *pathname, int flags);
28465 int open(const char *pathname, int flags, mode_t mode);
28469 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
28472 @var{flags} is the bitwise @code{OR} of the following values:
28476 If the file does not exist it will be created. The host
28477 rules apply as far as file ownership and time stamps
28481 When used with @code{O_CREAT}, if the file already exists it is
28482 an error and open() fails.
28485 If the file already exists and the open mode allows
28486 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
28487 truncated to zero length.
28490 The file is opened in append mode.
28493 The file is opened for reading only.
28496 The file is opened for writing only.
28499 The file is opened for reading and writing.
28503 Other bits are silently ignored.
28507 @var{mode} is the bitwise @code{OR} of the following values:
28511 User has read permission.
28514 User has write permission.
28517 Group has read permission.
28520 Group has write permission.
28523 Others have read permission.
28526 Others have write permission.
28530 Other bits are silently ignored.
28533 @item Return value:
28534 @code{open} returns the new file descriptor or -1 if an error
28541 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
28544 @var{pathname} refers to a directory.
28547 The requested access is not allowed.
28550 @var{pathname} was too long.
28553 A directory component in @var{pathname} does not exist.
28556 @var{pathname} refers to a device, pipe, named pipe or socket.
28559 @var{pathname} refers to a file on a read-only filesystem and
28560 write access was requested.
28563 @var{pathname} is an invalid pointer value.
28566 No space on device to create the file.
28569 The process already has the maximum number of files open.
28572 The limit on the total number of files open on the system
28576 The call was interrupted by the user.
28582 @unnumberedsubsubsec close
28583 @cindex close, file-i/o system call
28592 @samp{Fclose,@var{fd}}
28594 @item Return value:
28595 @code{close} returns zero on success, or -1 if an error occurred.
28601 @var{fd} isn't a valid open file descriptor.
28604 The call was interrupted by the user.
28610 @unnumberedsubsubsec read
28611 @cindex read, file-i/o system call
28616 int read(int fd, void *buf, unsigned int count);
28620 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
28622 @item Return value:
28623 On success, the number of bytes read is returned.
28624 Zero indicates end of file. If count is zero, read
28625 returns zero as well. On error, -1 is returned.
28631 @var{fd} is not a valid file descriptor or is not open for
28635 @var{bufptr} is an invalid pointer value.
28638 The call was interrupted by the user.
28644 @unnumberedsubsubsec write
28645 @cindex write, file-i/o system call
28650 int write(int fd, const void *buf, unsigned int count);
28654 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
28656 @item Return value:
28657 On success, the number of bytes written are returned.
28658 Zero indicates nothing was written. On error, -1
28665 @var{fd} is not a valid file descriptor or is not open for
28669 @var{bufptr} is an invalid pointer value.
28672 An attempt was made to write a file that exceeds the
28673 host-specific maximum file size allowed.
28676 No space on device to write the data.
28679 The call was interrupted by the user.
28685 @unnumberedsubsubsec lseek
28686 @cindex lseek, file-i/o system call
28691 long lseek (int fd, long offset, int flag);
28695 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
28697 @var{flag} is one of:
28701 The offset is set to @var{offset} bytes.
28704 The offset is set to its current location plus @var{offset}
28708 The offset is set to the size of the file plus @var{offset}
28712 @item Return value:
28713 On success, the resulting unsigned offset in bytes from
28714 the beginning of the file is returned. Otherwise, a
28715 value of -1 is returned.
28721 @var{fd} is not a valid open file descriptor.
28724 @var{fd} is associated with the @value{GDBN} console.
28727 @var{flag} is not a proper value.
28730 The call was interrupted by the user.
28736 @unnumberedsubsubsec rename
28737 @cindex rename, file-i/o system call
28742 int rename(const char *oldpath, const char *newpath);
28746 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
28748 @item Return value:
28749 On success, zero is returned. On error, -1 is returned.
28755 @var{newpath} is an existing directory, but @var{oldpath} is not a
28759 @var{newpath} is a non-empty directory.
28762 @var{oldpath} or @var{newpath} is a directory that is in use by some
28766 An attempt was made to make a directory a subdirectory
28770 A component used as a directory in @var{oldpath} or new
28771 path is not a directory. Or @var{oldpath} is a directory
28772 and @var{newpath} exists but is not a directory.
28775 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
28778 No access to the file or the path of the file.
28782 @var{oldpath} or @var{newpath} was too long.
28785 A directory component in @var{oldpath} or @var{newpath} does not exist.
28788 The file is on a read-only filesystem.
28791 The device containing the file has no room for the new
28795 The call was interrupted by the user.
28801 @unnumberedsubsubsec unlink
28802 @cindex unlink, file-i/o system call
28807 int unlink(const char *pathname);
28811 @samp{Funlink,@var{pathnameptr}/@var{len}}
28813 @item Return value:
28814 On success, zero is returned. On error, -1 is returned.
28820 No access to the file or the path of the file.
28823 The system does not allow unlinking of directories.
28826 The file @var{pathname} cannot be unlinked because it's
28827 being used by another process.
28830 @var{pathnameptr} is an invalid pointer value.
28833 @var{pathname} was too long.
28836 A directory component in @var{pathname} does not exist.
28839 A component of the path is not a directory.
28842 The file is on a read-only filesystem.
28845 The call was interrupted by the user.
28851 @unnumberedsubsubsec stat/fstat
28852 @cindex fstat, file-i/o system call
28853 @cindex stat, file-i/o system call
28858 int stat(const char *pathname, struct stat *buf);
28859 int fstat(int fd, struct stat *buf);
28863 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
28864 @samp{Ffstat,@var{fd},@var{bufptr}}
28866 @item Return value:
28867 On success, zero is returned. On error, -1 is returned.
28873 @var{fd} is not a valid open file.
28876 A directory component in @var{pathname} does not exist or the
28877 path is an empty string.
28880 A component of the path is not a directory.
28883 @var{pathnameptr} is an invalid pointer value.
28886 No access to the file or the path of the file.
28889 @var{pathname} was too long.
28892 The call was interrupted by the user.
28898 @unnumberedsubsubsec gettimeofday
28899 @cindex gettimeofday, file-i/o system call
28904 int gettimeofday(struct timeval *tv, void *tz);
28908 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
28910 @item Return value:
28911 On success, 0 is returned, -1 otherwise.
28917 @var{tz} is a non-NULL pointer.
28920 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
28926 @unnumberedsubsubsec isatty
28927 @cindex isatty, file-i/o system call
28932 int isatty(int fd);
28936 @samp{Fisatty,@var{fd}}
28938 @item Return value:
28939 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
28945 The call was interrupted by the user.
28950 Note that the @code{isatty} call is treated as a special case: it returns
28951 1 to the target if the file descriptor is attached
28952 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
28953 would require implementing @code{ioctl} and would be more complex than
28958 @unnumberedsubsubsec system
28959 @cindex system, file-i/o system call
28964 int system(const char *command);
28968 @samp{Fsystem,@var{commandptr}/@var{len}}
28970 @item Return value:
28971 If @var{len} is zero, the return value indicates whether a shell is
28972 available. A zero return value indicates a shell is not available.
28973 For non-zero @var{len}, the value returned is -1 on error and the
28974 return status of the command otherwise. Only the exit status of the
28975 command is returned, which is extracted from the host's @code{system}
28976 return value by calling @code{WEXITSTATUS(retval)}. In case
28977 @file{/bin/sh} could not be executed, 127 is returned.
28983 The call was interrupted by the user.
28988 @value{GDBN} takes over the full task of calling the necessary host calls
28989 to perform the @code{system} call. The return value of @code{system} on
28990 the host is simplified before it's returned
28991 to the target. Any termination signal information from the child process
28992 is discarded, and the return value consists
28993 entirely of the exit status of the called command.
28995 Due to security concerns, the @code{system} call is by default refused
28996 by @value{GDBN}. The user has to allow this call explicitly with the
28997 @code{set remote system-call-allowed 1} command.
29000 @item set remote system-call-allowed
29001 @kindex set remote system-call-allowed
29002 Control whether to allow the @code{system} calls in the File I/O
29003 protocol for the remote target. The default is zero (disabled).
29005 @item show remote system-call-allowed
29006 @kindex show remote system-call-allowed
29007 Show whether the @code{system} calls are allowed in the File I/O
29011 @node Protocol-specific Representation of Datatypes
29012 @subsection Protocol-specific Representation of Datatypes
29013 @cindex protocol-specific representation of datatypes, in file-i/o protocol
29016 * Integral Datatypes::
29018 * Memory Transfer::
29023 @node Integral Datatypes
29024 @unnumberedsubsubsec Integral Datatypes
29025 @cindex integral datatypes, in file-i/o protocol
29027 The integral datatypes used in the system calls are @code{int},
29028 @code{unsigned int}, @code{long}, @code{unsigned long},
29029 @code{mode_t}, and @code{time_t}.
29031 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
29032 implemented as 32 bit values in this protocol.
29034 @code{long} and @code{unsigned long} are implemented as 64 bit types.
29036 @xref{Limits}, for corresponding MIN and MAX values (similar to those
29037 in @file{limits.h}) to allow range checking on host and target.
29039 @code{time_t} datatypes are defined as seconds since the Epoch.
29041 All integral datatypes transferred as part of a memory read or write of a
29042 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
29045 @node Pointer Values
29046 @unnumberedsubsubsec Pointer Values
29047 @cindex pointer values, in file-i/o protocol
29049 Pointers to target data are transmitted as they are. An exception
29050 is made for pointers to buffers for which the length isn't
29051 transmitted as part of the function call, namely strings. Strings
29052 are transmitted as a pointer/length pair, both as hex values, e.g.@:
29059 which is a pointer to data of length 18 bytes at position 0x1aaf.
29060 The length is defined as the full string length in bytes, including
29061 the trailing null byte. For example, the string @code{"hello world"}
29062 at address 0x123456 is transmitted as
29068 @node Memory Transfer
29069 @unnumberedsubsubsec Memory Transfer
29070 @cindex memory transfer, in file-i/o protocol
29072 Structured data which is transferred using a memory read or write (for
29073 example, a @code{struct stat}) is expected to be in a protocol-specific format
29074 with all scalar multibyte datatypes being big endian. Translation to
29075 this representation needs to be done both by the target before the @code{F}
29076 packet is sent, and by @value{GDBN} before
29077 it transfers memory to the target. Transferred pointers to structured
29078 data should point to the already-coerced data at any time.
29082 @unnumberedsubsubsec struct stat
29083 @cindex struct stat, in file-i/o protocol
29085 The buffer of type @code{struct stat} used by the target and @value{GDBN}
29086 is defined as follows:
29090 unsigned int st_dev; /* device */
29091 unsigned int st_ino; /* inode */
29092 mode_t st_mode; /* protection */
29093 unsigned int st_nlink; /* number of hard links */
29094 unsigned int st_uid; /* user ID of owner */
29095 unsigned int st_gid; /* group ID of owner */
29096 unsigned int st_rdev; /* device type (if inode device) */
29097 unsigned long st_size; /* total size, in bytes */
29098 unsigned long st_blksize; /* blocksize for filesystem I/O */
29099 unsigned long st_blocks; /* number of blocks allocated */
29100 time_t st_atime; /* time of last access */
29101 time_t st_mtime; /* time of last modification */
29102 time_t st_ctime; /* time of last change */
29106 The integral datatypes conform to the definitions given in the
29107 appropriate section (see @ref{Integral Datatypes}, for details) so this
29108 structure is of size 64 bytes.
29110 The values of several fields have a restricted meaning and/or
29116 A value of 0 represents a file, 1 the console.
29119 No valid meaning for the target. Transmitted unchanged.
29122 Valid mode bits are described in @ref{Constants}. Any other
29123 bits have currently no meaning for the target.
29128 No valid meaning for the target. Transmitted unchanged.
29133 These values have a host and file system dependent
29134 accuracy. Especially on Windows hosts, the file system may not
29135 support exact timing values.
29138 The target gets a @code{struct stat} of the above representation and is
29139 responsible for coercing it to the target representation before
29142 Note that due to size differences between the host, target, and protocol
29143 representations of @code{struct stat} members, these members could eventually
29144 get truncated on the target.
29146 @node struct timeval
29147 @unnumberedsubsubsec struct timeval
29148 @cindex struct timeval, in file-i/o protocol
29150 The buffer of type @code{struct timeval} used by the File-I/O protocol
29151 is defined as follows:
29155 time_t tv_sec; /* second */
29156 long tv_usec; /* microsecond */
29160 The integral datatypes conform to the definitions given in the
29161 appropriate section (see @ref{Integral Datatypes}, for details) so this
29162 structure is of size 8 bytes.
29165 @subsection Constants
29166 @cindex constants, in file-i/o protocol
29168 The following values are used for the constants inside of the
29169 protocol. @value{GDBN} and target are responsible for translating these
29170 values before and after the call as needed.
29181 @unnumberedsubsubsec Open Flags
29182 @cindex open flags, in file-i/o protocol
29184 All values are given in hexadecimal representation.
29196 @node mode_t Values
29197 @unnumberedsubsubsec mode_t Values
29198 @cindex mode_t values, in file-i/o protocol
29200 All values are given in octal representation.
29217 @unnumberedsubsubsec Errno Values
29218 @cindex errno values, in file-i/o protocol
29220 All values are given in decimal representation.
29245 @code{EUNKNOWN} is used as a fallback error value if a host system returns
29246 any error value not in the list of supported error numbers.
29249 @unnumberedsubsubsec Lseek Flags
29250 @cindex lseek flags, in file-i/o protocol
29259 @unnumberedsubsubsec Limits
29260 @cindex limits, in file-i/o protocol
29262 All values are given in decimal representation.
29265 INT_MIN -2147483648
29267 UINT_MAX 4294967295
29268 LONG_MIN -9223372036854775808
29269 LONG_MAX 9223372036854775807
29270 ULONG_MAX 18446744073709551615
29273 @node File-I/O Examples
29274 @subsection File-I/O Examples
29275 @cindex file-i/o examples
29277 Example sequence of a write call, file descriptor 3, buffer is at target
29278 address 0x1234, 6 bytes should be written:
29281 <- @code{Fwrite,3,1234,6}
29282 @emph{request memory read from target}
29285 @emph{return "6 bytes written"}
29289 Example sequence of a read call, file descriptor 3, buffer is at target
29290 address 0x1234, 6 bytes should be read:
29293 <- @code{Fread,3,1234,6}
29294 @emph{request memory write to target}
29295 -> @code{X1234,6:XXXXXX}
29296 @emph{return "6 bytes read"}
29300 Example sequence of a read call, call fails on the host due to invalid
29301 file descriptor (@code{EBADF}):
29304 <- @code{Fread,3,1234,6}
29308 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
29312 <- @code{Fread,3,1234,6}
29317 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
29321 <- @code{Fread,3,1234,6}
29322 -> @code{X1234,6:XXXXXX}
29326 @node Library List Format
29327 @section Library List Format
29328 @cindex library list format, remote protocol
29330 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
29331 same process as your application to manage libraries. In this case,
29332 @value{GDBN} can use the loader's symbol table and normal memory
29333 operations to maintain a list of shared libraries. On other
29334 platforms, the operating system manages loaded libraries.
29335 @value{GDBN} can not retrieve the list of currently loaded libraries
29336 through memory operations, so it uses the @samp{qXfer:libraries:read}
29337 packet (@pxref{qXfer library list read}) instead. The remote stub
29338 queries the target's operating system and reports which libraries
29341 The @samp{qXfer:libraries:read} packet returns an XML document which
29342 lists loaded libraries and their offsets. Each library has an
29343 associated name and one or more segment or section base addresses,
29344 which report where the library was loaded in memory.
29346 For the common case of libraries that are fully linked binaries, the
29347 library should have a list of segments. If the target supports
29348 dynamic linking of a relocatable object file, its library XML element
29349 should instead include a list of allocated sections. The segment or
29350 section bases are start addresses, not relocation offsets; they do not
29351 depend on the library's link-time base addresses.
29353 @value{GDBN} must be linked with the Expat library to support XML
29354 library lists. @xref{Expat}.
29356 A simple memory map, with one loaded library relocated by a single
29357 offset, looks like this:
29361 <library name="/lib/libc.so.6">
29362 <segment address="0x10000000"/>
29367 Another simple memory map, with one loaded library with three
29368 allocated sections (.text, .data, .bss), looks like this:
29372 <library name="sharedlib.o">
29373 <section address="0x10000000"/>
29374 <section address="0x20000000"/>
29375 <section address="0x30000000"/>
29380 The format of a library list is described by this DTD:
29383 <!-- library-list: Root element with versioning -->
29384 <!ELEMENT library-list (library)*>
29385 <!ATTLIST library-list version CDATA #FIXED "1.0">
29386 <!ELEMENT library (segment*, section*)>
29387 <!ATTLIST library name CDATA #REQUIRED>
29388 <!ELEMENT segment EMPTY>
29389 <!ATTLIST segment address CDATA #REQUIRED>
29390 <!ELEMENT section EMPTY>
29391 <!ATTLIST section address CDATA #REQUIRED>
29394 In addition, segments and section descriptors cannot be mixed within a
29395 single library element, and you must supply at least one segment or
29396 section for each library.
29398 @node Memory Map Format
29399 @section Memory Map Format
29400 @cindex memory map format
29402 To be able to write into flash memory, @value{GDBN} needs to obtain a
29403 memory map from the target. This section describes the format of the
29406 The memory map is obtained using the @samp{qXfer:memory-map:read}
29407 (@pxref{qXfer memory map read}) packet and is an XML document that
29408 lists memory regions.
29410 @value{GDBN} must be linked with the Expat library to support XML
29411 memory maps. @xref{Expat}.
29413 The top-level structure of the document is shown below:
29416 <?xml version="1.0"?>
29417 <!DOCTYPE memory-map
29418 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
29419 "http://sourceware.org/gdb/gdb-memory-map.dtd">
29425 Each region can be either:
29430 A region of RAM starting at @var{addr} and extending for @var{length}
29434 <memory type="ram" start="@var{addr}" length="@var{length}"/>
29439 A region of read-only memory:
29442 <memory type="rom" start="@var{addr}" length="@var{length}"/>
29447 A region of flash memory, with erasure blocks @var{blocksize}
29451 <memory type="flash" start="@var{addr}" length="@var{length}">
29452 <property name="blocksize">@var{blocksize}</property>
29458 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
29459 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
29460 packets to write to addresses in such ranges.
29462 The formal DTD for memory map format is given below:
29465 <!-- ................................................... -->
29466 <!-- Memory Map XML DTD ................................ -->
29467 <!-- File: memory-map.dtd .............................. -->
29468 <!-- .................................... .............. -->
29469 <!-- memory-map.dtd -->
29470 <!-- memory-map: Root element with versioning -->
29471 <!ELEMENT memory-map (memory | property)>
29472 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
29473 <!ELEMENT memory (property)>
29474 <!-- memory: Specifies a memory region,
29475 and its type, or device. -->
29476 <!ATTLIST memory type CDATA #REQUIRED
29477 start CDATA #REQUIRED
29478 length CDATA #REQUIRED
29479 device CDATA #IMPLIED>
29480 <!-- property: Generic attribute tag -->
29481 <!ELEMENT property (#PCDATA | property)*>
29482 <!ATTLIST property name CDATA #REQUIRED>
29485 @include agentexpr.texi
29487 @node Target Descriptions
29488 @appendix Target Descriptions
29489 @cindex target descriptions
29491 @strong{Warning:} target descriptions are still under active development,
29492 and the contents and format may change between @value{GDBN} releases.
29493 The format is expected to stabilize in the future.
29495 One of the challenges of using @value{GDBN} to debug embedded systems
29496 is that there are so many minor variants of each processor
29497 architecture in use. It is common practice for vendors to start with
29498 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
29499 and then make changes to adapt it to a particular market niche. Some
29500 architectures have hundreds of variants, available from dozens of
29501 vendors. This leads to a number of problems:
29505 With so many different customized processors, it is difficult for
29506 the @value{GDBN} maintainers to keep up with the changes.
29508 Since individual variants may have short lifetimes or limited
29509 audiences, it may not be worthwhile to carry information about every
29510 variant in the @value{GDBN} source tree.
29512 When @value{GDBN} does support the architecture of the embedded system
29513 at hand, the task of finding the correct architecture name to give the
29514 @command{set architecture} command can be error-prone.
29517 To address these problems, the @value{GDBN} remote protocol allows a
29518 target system to not only identify itself to @value{GDBN}, but to
29519 actually describe its own features. This lets @value{GDBN} support
29520 processor variants it has never seen before --- to the extent that the
29521 descriptions are accurate, and that @value{GDBN} understands them.
29523 @value{GDBN} must be linked with the Expat library to support XML
29524 target descriptions. @xref{Expat}.
29527 * Retrieving Descriptions:: How descriptions are fetched from a target.
29528 * Target Description Format:: The contents of a target description.
29529 * Predefined Target Types:: Standard types available for target
29531 * Standard Target Features:: Features @value{GDBN} knows about.
29534 @node Retrieving Descriptions
29535 @section Retrieving Descriptions
29537 Target descriptions can be read from the target automatically, or
29538 specified by the user manually. The default behavior is to read the
29539 description from the target. @value{GDBN} retrieves it via the remote
29540 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
29541 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
29542 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
29543 XML document, of the form described in @ref{Target Description
29546 Alternatively, you can specify a file to read for the target description.
29547 If a file is set, the target will not be queried. The commands to
29548 specify a file are:
29551 @cindex set tdesc filename
29552 @item set tdesc filename @var{path}
29553 Read the target description from @var{path}.
29555 @cindex unset tdesc filename
29556 @item unset tdesc filename
29557 Do not read the XML target description from a file. @value{GDBN}
29558 will use the description supplied by the current target.
29560 @cindex show tdesc filename
29561 @item show tdesc filename
29562 Show the filename to read for a target description, if any.
29566 @node Target Description Format
29567 @section Target Description Format
29568 @cindex target descriptions, XML format
29570 A target description annex is an @uref{http://www.w3.org/XML/, XML}
29571 document which complies with the Document Type Definition provided in
29572 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
29573 means you can use generally available tools like @command{xmllint} to
29574 check that your feature descriptions are well-formed and valid.
29575 However, to help people unfamiliar with XML write descriptions for
29576 their targets, we also describe the grammar here.
29578 Target descriptions can identify the architecture of the remote target
29579 and (for some architectures) provide information about custom register
29580 sets. @value{GDBN} can use this information to autoconfigure for your
29581 target, or to warn you if you connect to an unsupported target.
29583 Here is a simple target description:
29586 <target version="1.0">
29587 <architecture>i386:x86-64</architecture>
29592 This minimal description only says that the target uses
29593 the x86-64 architecture.
29595 A target description has the following overall form, with [ ] marking
29596 optional elements and @dots{} marking repeatable elements. The elements
29597 are explained further below.
29600 <?xml version="1.0"?>
29601 <!DOCTYPE target SYSTEM "gdb-target.dtd">
29602 <target version="1.0">
29603 @r{[}@var{architecture}@r{]}
29604 @r{[}@var{feature}@dots{}@r{]}
29609 The description is generally insensitive to whitespace and line
29610 breaks, under the usual common-sense rules. The XML version
29611 declaration and document type declaration can generally be omitted
29612 (@value{GDBN} does not require them), but specifying them may be
29613 useful for XML validation tools. The @samp{version} attribute for
29614 @samp{<target>} may also be omitted, but we recommend
29615 including it; if future versions of @value{GDBN} use an incompatible
29616 revision of @file{gdb-target.dtd}, they will detect and report
29617 the version mismatch.
29619 @subsection Inclusion
29620 @cindex target descriptions, inclusion
29623 @cindex <xi:include>
29626 It can sometimes be valuable to split a target description up into
29627 several different annexes, either for organizational purposes, or to
29628 share files between different possible target descriptions. You can
29629 divide a description into multiple files by replacing any element of
29630 the target description with an inclusion directive of the form:
29633 <xi:include href="@var{document}"/>
29637 When @value{GDBN} encounters an element of this form, it will retrieve
29638 the named XML @var{document}, and replace the inclusion directive with
29639 the contents of that document. If the current description was read
29640 using @samp{qXfer}, then so will be the included document;
29641 @var{document} will be interpreted as the name of an annex. If the
29642 current description was read from a file, @value{GDBN} will look for
29643 @var{document} as a file in the same directory where it found the
29644 original description.
29646 @subsection Architecture
29647 @cindex <architecture>
29649 An @samp{<architecture>} element has this form:
29652 <architecture>@var{arch}</architecture>
29655 @var{arch} is an architecture name from the same selection
29656 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
29657 Debugging Target}).
29659 @subsection Features
29662 Each @samp{<feature>} describes some logical portion of the target
29663 system. Features are currently used to describe available CPU
29664 registers and the types of their contents. A @samp{<feature>} element
29668 <feature name="@var{name}">
29669 @r{[}@var{type}@dots{}@r{]}
29675 Each feature's name should be unique within the description. The name
29676 of a feature does not matter unless @value{GDBN} has some special
29677 knowledge of the contents of that feature; if it does, the feature
29678 should have its standard name. @xref{Standard Target Features}.
29682 Any register's value is a collection of bits which @value{GDBN} must
29683 interpret. The default interpretation is a two's complement integer,
29684 but other types can be requested by name in the register description.
29685 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
29686 Target Types}), and the description can define additional composite types.
29688 Each type element must have an @samp{id} attribute, which gives
29689 a unique (within the containing @samp{<feature>}) name to the type.
29690 Types must be defined before they are used.
29693 Some targets offer vector registers, which can be treated as arrays
29694 of scalar elements. These types are written as @samp{<vector>} elements,
29695 specifying the array element type, @var{type}, and the number of elements,
29699 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
29703 If a register's value is usefully viewed in multiple ways, define it
29704 with a union type containing the useful representations. The
29705 @samp{<union>} element contains one or more @samp{<field>} elements,
29706 each of which has a @var{name} and a @var{type}:
29709 <union id="@var{id}">
29710 <field name="@var{name}" type="@var{type}"/>
29715 @subsection Registers
29718 Each register is represented as an element with this form:
29721 <reg name="@var{name}"
29722 bitsize="@var{size}"
29723 @r{[}regnum="@var{num}"@r{]}
29724 @r{[}save-restore="@var{save-restore}"@r{]}
29725 @r{[}type="@var{type}"@r{]}
29726 @r{[}group="@var{group}"@r{]}/>
29730 The components are as follows:
29735 The register's name; it must be unique within the target description.
29738 The register's size, in bits.
29741 The register's number. If omitted, a register's number is one greater
29742 than that of the previous register (either in the current feature or in
29743 a preceeding feature); the first register in the target description
29744 defaults to zero. This register number is used to read or write
29745 the register; e.g.@: it is used in the remote @code{p} and @code{P}
29746 packets, and registers appear in the @code{g} and @code{G} packets
29747 in order of increasing register number.
29750 Whether the register should be preserved across inferior function
29751 calls; this must be either @code{yes} or @code{no}. The default is
29752 @code{yes}, which is appropriate for most registers except for
29753 some system control registers; this is not related to the target's
29757 The type of the register. @var{type} may be a predefined type, a type
29758 defined in the current feature, or one of the special types @code{int}
29759 and @code{float}. @code{int} is an integer type of the correct size
29760 for @var{bitsize}, and @code{float} is a floating point type (in the
29761 architecture's normal floating point format) of the correct size for
29762 @var{bitsize}. The default is @code{int}.
29765 The register group to which this register belongs. @var{group} must
29766 be either @code{general}, @code{float}, or @code{vector}. If no
29767 @var{group} is specified, @value{GDBN} will not display the register
29768 in @code{info registers}.
29772 @node Predefined Target Types
29773 @section Predefined Target Types
29774 @cindex target descriptions, predefined types
29776 Type definitions in the self-description can build up composite types
29777 from basic building blocks, but can not define fundamental types. Instead,
29778 standard identifiers are provided by @value{GDBN} for the fundamental
29779 types. The currently supported types are:
29788 Signed integer types holding the specified number of bits.
29795 Unsigned integer types holding the specified number of bits.
29799 Pointers to unspecified code and data. The program counter and
29800 any dedicated return address register may be marked as code
29801 pointers; printing a code pointer converts it into a symbolic
29802 address. The stack pointer and any dedicated address registers
29803 may be marked as data pointers.
29806 Single precision IEEE floating point.
29809 Double precision IEEE floating point.
29812 The 12-byte extended precision format used by ARM FPA registers.
29816 @node Standard Target Features
29817 @section Standard Target Features
29818 @cindex target descriptions, standard features
29820 A target description must contain either no registers or all the
29821 target's registers. If the description contains no registers, then
29822 @value{GDBN} will assume a default register layout, selected based on
29823 the architecture. If the description contains any registers, the
29824 default layout will not be used; the standard registers must be
29825 described in the target description, in such a way that @value{GDBN}
29826 can recognize them.
29828 This is accomplished by giving specific names to feature elements
29829 which contain standard registers. @value{GDBN} will look for features
29830 with those names and verify that they contain the expected registers;
29831 if any known feature is missing required registers, or if any required
29832 feature is missing, @value{GDBN} will reject the target
29833 description. You can add additional registers to any of the
29834 standard features --- @value{GDBN} will display them just as if
29835 they were added to an unrecognized feature.
29837 This section lists the known features and their expected contents.
29838 Sample XML documents for these features are included in the
29839 @value{GDBN} source tree, in the directory @file{gdb/features}.
29841 Names recognized by @value{GDBN} should include the name of the
29842 company or organization which selected the name, and the overall
29843 architecture to which the feature applies; so e.g.@: the feature
29844 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
29846 The names of registers are not case sensitive for the purpose
29847 of recognizing standard features, but @value{GDBN} will only display
29848 registers using the capitalization used in the description.
29854 * PowerPC Features::
29859 @subsection ARM Features
29860 @cindex target descriptions, ARM features
29862 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
29863 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
29864 @samp{lr}, @samp{pc}, and @samp{cpsr}.
29866 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
29867 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
29869 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
29870 it should contain at least registers @samp{wR0} through @samp{wR15} and
29871 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
29872 @samp{wCSSF}, and @samp{wCASF} registers are optional.
29874 @node MIPS Features
29875 @subsection MIPS Features
29876 @cindex target descriptions, MIPS features
29878 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
29879 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
29880 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
29883 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
29884 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
29885 registers. They may be 32-bit or 64-bit depending on the target.
29887 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
29888 it may be optional in a future version of @value{GDBN}. It should
29889 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
29890 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
29892 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
29893 contain a single register, @samp{restart}, which is used by the
29894 Linux kernel to control restartable syscalls.
29896 @node M68K Features
29897 @subsection M68K Features
29898 @cindex target descriptions, M68K features
29901 @item @samp{org.gnu.gdb.m68k.core}
29902 @itemx @samp{org.gnu.gdb.coldfire.core}
29903 @itemx @samp{org.gnu.gdb.fido.core}
29904 One of those features must be always present.
29905 The feature that is present determines which flavor of m68k is
29906 used. The feature that is present should contain registers
29907 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
29908 @samp{sp}, @samp{ps} and @samp{pc}.
29910 @item @samp{org.gnu.gdb.coldfire.fp}
29911 This feature is optional. If present, it should contain registers
29912 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
29916 @node PowerPC Features
29917 @subsection PowerPC Features
29918 @cindex target descriptions, PowerPC features
29920 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
29921 targets. It should contain registers @samp{r0} through @samp{r31},
29922 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
29923 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
29925 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
29926 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
29928 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
29929 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
29932 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
29933 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
29934 will combine these registers with the floating point registers
29935 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
29936 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
29937 through @samp{vs63}, the set of vector registers for POWER7.
29939 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
29940 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
29941 @samp{spefscr}. SPE targets should provide 32-bit registers in
29942 @samp{org.gnu.gdb.power.core} and provide the upper halves in
29943 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
29944 these to present registers @samp{ev0} through @samp{ev31} to the
29947 @node Operating System Information
29948 @appendix Operating System Information
29949 @cindex operating system information
29955 Users of @value{GDBN} often wish to obtain information about the state of
29956 the operating system running on the target---for example the list of
29957 processes, or the list of open files. This section describes the
29958 mechanism that makes it possible. This mechanism is similar to the
29959 target features mechanism (@pxref{Target Descriptions}), but focuses
29960 on a different aspect of target.
29962 Operating system information is retrived from the target via the
29963 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
29964 read}). The object name in the request should be @samp{osdata}, and
29965 the @var{annex} identifies the data to be fetched.
29968 @appendixsection Process list
29969 @cindex operating system information, process list
29971 When requesting the process list, the @var{annex} field in the
29972 @samp{qXfer} request should be @samp{processes}. The returned data is
29973 an XML document. The formal syntax of this document is defined in
29974 @file{gdb/features/osdata.dtd}.
29976 An example document is:
29979 <?xml version="1.0"?>
29980 <!DOCTYPE target SYSTEM "osdata.dtd">
29981 <osdata type="processes">
29983 <column name="pid">1</column>
29984 <column name="user">root</column>
29985 <column name="command">/sbin/init</column>
29990 Each item should include a column whose name is @samp{pid}. The value
29991 of that column should identify the process on the target. The
29992 @samp{user} and @samp{command} columns are optional, and will be
29993 displayed by @value{GDBN}. Target may provide additional columns,
29994 which @value{GDBN} currently ignores.
30008 % I think something like @colophon should be in texinfo. In the
30010 \long\def\colophon{\hbox to0pt{}\vfill
30011 \centerline{The body of this manual is set in}
30012 \centerline{\fontname\tenrm,}
30013 \centerline{with headings in {\bf\fontname\tenbf}}
30014 \centerline{and examples in {\tt\fontname\tentt}.}
30015 \centerline{{\it\fontname\tenit\/},}
30016 \centerline{{\bf\fontname\tenbf}, and}
30017 \centerline{{\sl\fontname\tensl\/}}
30018 \centerline{are used for emphasis.}\vfill}
30020 % Blame: doc@cygnus.com, 1991.