1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003
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 Programming & development tools.
43 * Gdb: (gdb). The @sc{gnu} debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
57 Permission is granted to copy, distribute and/or modify this document
58 under the terms of the GNU Free Documentation License, Version 1.1 or
59 any later version published by the Free Software Foundation; with the
60 Invariant Sections being ``Free Software'' and ``Free Software Needs
61 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
62 and with the Back-Cover Texts as in (a) below.
64 (a) The Free Software Foundation's Back-Cover Text is: ``You have
65 freedom to copy and modify this GNU Manual, like GNU software. Copies
66 published by the Free Software Foundation raise funds for GNU
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
89 Published by the Free Software Foundation @*
90 59 Temple Place - Suite 330, @*
91 Boston, MA 02111-1307 USA @*
94 Permission is granted to copy, distribute and/or modify this document
95 under the terms of the GNU Free Documentation License, Version 1.1 or
96 any later version published by the Free Software Foundation; with the
97 Invariant Sections being ``Free Software'' and ``Free Software Needs
98 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
99 and with the Back-Cover Texts as in (a) below.
101 (a) The Free Software Foundation's Back-Cover Text is: ``You have
102 freedom to copy and modify this GNU Manual, like GNU software. Copies
103 published by the Free Software Foundation raise funds for GNU
109 @node Top, Summary, (dir), (dir)
111 @top Debugging with @value{GDBN}
113 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
115 This is the @value{EDITION} Edition, for @value{GDBN} Version
118 Copyright (C) 1988-2003 Free Software Foundation, Inc.
121 * Summary:: Summary of @value{GDBN}
122 * Sample Session:: A sample @value{GDBN} session
124 * Invocation:: Getting in and out of @value{GDBN}
125 * Commands:: @value{GDBN} commands
126 * Running:: Running programs under @value{GDBN}
127 * Stopping:: Stopping and continuing
128 * Stack:: Examining the stack
129 * Source:: Examining source files
130 * Data:: Examining data
131 * Macros:: Preprocessor Macros
132 * Tracepoints:: Debugging remote targets non-intrusively
133 * Overlays:: Debugging programs that use overlays
135 * Languages:: Using @value{GDBN} with different languages
137 * Symbols:: Examining the symbol table
138 * Altering:: Altering execution
139 * GDB Files:: @value{GDBN} files
140 * Targets:: Specifying a debugging target
141 * Remote Debugging:: Debugging remote programs
142 * Configurations:: Configuration-specific information
143 * Controlling GDB:: Controlling @value{GDBN}
144 * Sequences:: Canned sequences of commands
145 * TUI:: @value{GDBN} Text User Interface
146 * Interpreters:: Command Interpreters
147 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
148 * Annotations:: @value{GDBN}'s annotation interface.
149 * GDB/MI:: @value{GDBN}'s Machine Interface.
151 * GDB Bugs:: Reporting bugs in @value{GDBN}
152 * Formatting Documentation:: How to format and print @value{GDBN} documentation
154 * Command Line Editing:: Command Line Editing
155 * Using History Interactively:: Using History Interactively
156 * Installing GDB:: Installing GDB
157 * Maintenance Commands:: Maintenance Commands
158 * Remote Protocol:: GDB Remote Serial Protocol
159 * Agent Expressions:: The GDB Agent Expression Mechanism
160 * Copying:: GNU General Public License says
161 how you can copy and share GDB
162 * GNU Free Documentation License:: The license for this documentation
171 @unnumbered Summary of @value{GDBN}
173 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
174 going on ``inside'' another program while it executes---or what another
175 program was doing at the moment it crashed.
177 @value{GDBN} can do four main kinds of things (plus other things in support of
178 these) to help you catch bugs in the act:
182 Start your program, specifying anything that might affect its behavior.
185 Make your program stop on specified conditions.
188 Examine what has happened, when your program has stopped.
191 Change things in your program, so you can experiment with correcting the
192 effects of one bug and go on to learn about another.
195 You can use @value{GDBN} to debug programs written in C and C++.
196 For more information, see @ref{Support,,Supported languages}.
197 For more information, see @ref{C,,C and C++}.
200 Support for Modula-2 is partial. For information on Modula-2, see
201 @ref{Modula-2,,Modula-2}.
204 Debugging Pascal programs which use sets, subranges, file variables, or
205 nested functions does not currently work. @value{GDBN} does not support
206 entering expressions, printing values, or similar features using Pascal
210 @value{GDBN} can be used to debug programs written in Fortran, although
211 it may be necessary to refer to some variables with a trailing
214 @value{GDBN} can be used to debug programs written in Objective-C,
215 using either the Apple/NeXT or the GNU Objective-C runtime.
218 * Free Software:: Freely redistributable software
219 * Contributors:: Contributors to GDB
223 @unnumberedsec Free software
225 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
226 General Public License
227 (GPL). The GPL gives you the freedom to copy or adapt a licensed
228 program---but every person getting a copy also gets with it the
229 freedom to modify that copy (which means that they must get access to
230 the source code), and the freedom to distribute further copies.
231 Typical software companies use copyrights to limit your freedoms; the
232 Free Software Foundation uses the GPL to preserve these freedoms.
234 Fundamentally, the General Public License is a license which says that
235 you have these freedoms and that you cannot take these freedoms away
238 @unnumberedsec Free Software Needs Free Documentation
240 The biggest deficiency in the free software community today is not in
241 the software---it is the lack of good free documentation that we can
242 include with the free software. Many of our most important
243 programs do not come with free reference manuals and free introductory
244 texts. Documentation is an essential part of any software package;
245 when an important free software package does not come with a free
246 manual and a free tutorial, that is a major gap. We have many such
249 Consider Perl, for instance. The tutorial manuals that people
250 normally use are non-free. How did this come about? Because the
251 authors of those manuals published them with restrictive terms---no
252 copying, no modification, source files not available---which exclude
253 them from the free software world.
255 That wasn't the first time this sort of thing happened, and it was far
256 from the last. Many times we have heard a GNU user eagerly describe a
257 manual that he is writing, his intended contribution to the community,
258 only to learn that he had ruined everything by signing a publication
259 contract to make it non-free.
261 Free documentation, like free software, is a matter of freedom, not
262 price. The problem with the non-free manual is not that publishers
263 charge a price for printed copies---that in itself is fine. (The Free
264 Software Foundation sells printed copies of manuals, too.) The
265 problem is the restrictions on the use of the manual. Free manuals
266 are available in source code form, and give you permission to copy and
267 modify. Non-free manuals do not allow this.
269 The criteria of freedom for a free manual are roughly the same as for
270 free software. Redistribution (including the normal kinds of
271 commercial redistribution) must be permitted, so that the manual can
272 accompany every copy of the program, both on-line and on paper.
274 Permission for modification of the technical content is crucial too.
275 When people modify the software, adding or changing features, if they
276 are conscientious they will change the manual too---so they can
277 provide accurate and clear documentation for the modified program. A
278 manual that leaves you no choice but to write a new manual to document
279 a changed version of the program is not really available to our
282 Some kinds of limits on the way modification is handled are
283 acceptable. For example, requirements to preserve the original
284 author's copyright notice, the distribution terms, or the list of
285 authors, are ok. It is also no problem to require modified versions
286 to include notice that they were modified. Even entire sections that
287 may not be deleted or changed are acceptable, as long as they deal
288 with nontechnical topics (like this one). These kinds of restrictions
289 are acceptable because they don't obstruct the community's normal use
292 However, it must be possible to modify all the @emph{technical}
293 content of the manual, and then distribute the result in all the usual
294 media, through all the usual channels. Otherwise, the restrictions
295 obstruct the use of the manual, it is not free, and we need another
296 manual to replace it.
298 Please spread the word about this issue. Our community continues to
299 lose manuals to proprietary publishing. If we spread the word that
300 free software needs free reference manuals and free tutorials, perhaps
301 the next person who wants to contribute by writing documentation will
302 realize, before it is too late, that only free manuals contribute to
303 the free software community.
305 If you are writing documentation, please insist on publishing it under
306 the GNU Free Documentation License or another free documentation
307 license. Remember that this decision requires your approval---you
308 don't have to let the publisher decide. Some commercial publishers
309 will use a free license if you insist, but they will not propose the
310 option; it is up to you to raise the issue and say firmly that this is
311 what you want. If the publisher you are dealing with refuses, please
312 try other publishers. If you're not sure whether a proposed license
313 is free, write to @email{licensing@@gnu.org}.
315 You can encourage commercial publishers to sell more free, copylefted
316 manuals and tutorials by buying them, and particularly by buying
317 copies from the publishers that paid for their writing or for major
318 improvements. Meanwhile, try to avoid buying non-free documentation
319 at all. Check the distribution terms of a manual before you buy it,
320 and insist that whoever seeks your business must respect your freedom.
321 Check the history of the book, and try to reward the publishers that
322 have paid or pay the authors to work on it.
324 The Free Software Foundation maintains a list of free documentation
325 published by other publishers, at
326 @url{http://www.fsf.org/doc/other-free-books.html}.
329 @unnumberedsec Contributors to @value{GDBN}
331 Richard Stallman was the original author of @value{GDBN}, and of many
332 other @sc{gnu} programs. Many others have contributed to its
333 development. This section attempts to credit major contributors. One
334 of the virtues of free software is that everyone is free to contribute
335 to it; with regret, we cannot actually acknowledge everyone here. The
336 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
337 blow-by-blow account.
339 Changes much prior to version 2.0 are lost in the mists of time.
342 @emph{Plea:} Additions to this section are particularly welcome. If you
343 or your friends (or enemies, to be evenhanded) have been unfairly
344 omitted from this list, we would like to add your names!
347 So that they may not regard their many labors as thankless, we
348 particularly thank those who shepherded @value{GDBN} through major
350 Andrew Cagney (releases 6.0, 5.3, 5.2, 5.1 and 5.0);
351 Jim Blandy (release 4.18);
352 Jason Molenda (release 4.17);
353 Stan Shebs (release 4.14);
354 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
355 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
356 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
357 Jim Kingdon (releases 3.5, 3.4, and 3.3);
358 and Randy Smith (releases 3.2, 3.1, and 3.0).
360 Richard Stallman, assisted at various times by Peter TerMaat, Chris
361 Hanson, and Richard Mlynarik, handled releases through 2.8.
363 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
364 in @value{GDBN}, with significant additional contributions from Per
365 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
366 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
367 much general update work leading to release 3.0).
369 @value{GDBN} uses the BFD subroutine library to examine multiple
370 object-file formats; BFD was a joint project of David V.
371 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
373 David Johnson wrote the original COFF support; Pace Willison did
374 the original support for encapsulated COFF.
376 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
378 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
379 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
381 Jean-Daniel Fekete contributed Sun 386i support.
382 Chris Hanson improved the HP9000 support.
383 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
384 David Johnson contributed Encore Umax support.
385 Jyrki Kuoppala contributed Altos 3068 support.
386 Jeff Law contributed HP PA and SOM support.
387 Keith Packard contributed NS32K support.
388 Doug Rabson contributed Acorn Risc Machine support.
389 Bob Rusk contributed Harris Nighthawk CX-UX support.
390 Chris Smith contributed Convex support (and Fortran debugging).
391 Jonathan Stone contributed Pyramid support.
392 Michael Tiemann contributed SPARC support.
393 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
394 Pace Willison contributed Intel 386 support.
395 Jay Vosburgh contributed Symmetry support.
396 Marko Mlinar contributed OpenRISC 1000 support.
398 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
400 Rich Schaefer and Peter Schauer helped with support of SunOS shared
403 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
404 about several machine instruction sets.
406 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
407 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
408 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
409 and RDI targets, respectively.
411 Brian Fox is the author of the readline libraries providing
412 command-line editing and command history.
414 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
415 Modula-2 support, and contributed the Languages chapter of this manual.
417 Fred Fish wrote most of the support for Unix System Vr4.
418 He also enhanced the command-completion support to cover C@t{++} overloaded
421 Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and
424 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
426 Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors.
428 Toshiba sponsored the support for the TX39 Mips processor.
430 Matsushita sponsored the support for the MN10200 and MN10300 processors.
432 Fujitsu sponsored the support for SPARClite and FR30 processors.
434 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
437 Michael Snyder added support for tracepoints.
439 Stu Grossman wrote gdbserver.
441 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
442 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
444 The following people at the Hewlett-Packard Company contributed
445 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
446 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
447 compiler, and the terminal user interface: Ben Krepp, Richard Title,
448 John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
449 Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
450 information in this manual.
452 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
453 Robert Hoehne made significant contributions to the DJGPP port.
455 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
456 development since 1991. Cygnus engineers who have worked on @value{GDBN}
457 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
458 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
459 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
460 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
461 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
462 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
463 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
464 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
465 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
466 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
467 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
468 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
469 Zuhn have made contributions both large and small.
471 Jim Blandy added support for preprocessor macros, while working for Red
475 @chapter A Sample @value{GDBN} Session
477 You can use this manual at your leisure to read all about @value{GDBN}.
478 However, a handful of commands are enough to get started using the
479 debugger. This chapter illustrates those commands.
482 In this sample session, we emphasize user input like this: @b{input},
483 to make it easier to pick out from the surrounding output.
486 @c FIXME: this example may not be appropriate for some configs, where
487 @c FIXME...primary interest is in remote use.
489 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
490 processor) exhibits the following bug: sometimes, when we change its
491 quote strings from the default, the commands used to capture one macro
492 definition within another stop working. In the following short @code{m4}
493 session, we define a macro @code{foo} which expands to @code{0000}; we
494 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
495 same thing. However, when we change the open quote string to
496 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
497 procedure fails to define a new synonym @code{baz}:
506 @b{define(bar,defn(`foo'))}
510 @b{changequote(<QUOTE>,<UNQUOTE>)}
512 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
515 m4: End of input: 0: fatal error: EOF in string
519 Let us use @value{GDBN} to try to see what is going on.
522 $ @b{@value{GDBP} m4}
523 @c FIXME: this falsifies the exact text played out, to permit smallbook
524 @c FIXME... format to come out better.
525 @value{GDBN} is free software and you are welcome to distribute copies
526 of it under certain conditions; type "show copying" to see
528 There is absolutely no warranty for @value{GDBN}; type "show warranty"
531 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
536 @value{GDBN} reads only enough symbol data to know where to find the
537 rest when needed; as a result, the first prompt comes up very quickly.
538 We now tell @value{GDBN} to use a narrower display width than usual, so
539 that examples fit in this manual.
542 (@value{GDBP}) @b{set width 70}
546 We need to see how the @code{m4} built-in @code{changequote} works.
547 Having looked at the source, we know the relevant subroutine is
548 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
549 @code{break} command.
552 (@value{GDBP}) @b{break m4_changequote}
553 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
557 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
558 control; as long as control does not reach the @code{m4_changequote}
559 subroutine, the program runs as usual:
562 (@value{GDBP}) @b{run}
563 Starting program: /work/Editorial/gdb/gnu/m4/m4
571 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
572 suspends execution of @code{m4}, displaying information about the
573 context where it stops.
576 @b{changequote(<QUOTE>,<UNQUOTE>)}
578 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
580 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
584 Now we use the command @code{n} (@code{next}) to advance execution to
585 the next line of the current function.
589 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
594 @code{set_quotes} looks like a promising subroutine. We can go into it
595 by using the command @code{s} (@code{step}) instead of @code{next}.
596 @code{step} goes to the next line to be executed in @emph{any}
597 subroutine, so it steps into @code{set_quotes}.
601 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
603 530 if (lquote != def_lquote)
607 The display that shows the subroutine where @code{m4} is now
608 suspended (and its arguments) is called a stack frame display. It
609 shows a summary of the stack. We can use the @code{backtrace}
610 command (which can also be spelled @code{bt}), to see where we are
611 in the stack as a whole: the @code{backtrace} command displays a
612 stack frame for each active subroutine.
615 (@value{GDBP}) @b{bt}
616 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
618 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
620 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
621 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
623 #4 0x79dc in expand_input () at macro.c:40
624 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
628 We step through a few more lines to see what happens. The first two
629 times, we can use @samp{s}; the next two times we use @code{n} to avoid
630 falling into the @code{xstrdup} subroutine.
634 0x3b5c 532 if (rquote != def_rquote)
636 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
637 def_lquote : xstrdup(lq);
639 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
642 538 len_lquote = strlen(rquote);
646 The last line displayed looks a little odd; we can examine the variables
647 @code{lquote} and @code{rquote} to see if they are in fact the new left
648 and right quotes we specified. We use the command @code{p}
649 (@code{print}) to see their values.
652 (@value{GDBP}) @b{p lquote}
653 $1 = 0x35d40 "<QUOTE>"
654 (@value{GDBP}) @b{p rquote}
655 $2 = 0x35d50 "<UNQUOTE>"
659 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
660 To look at some context, we can display ten lines of source
661 surrounding the current line with the @code{l} (@code{list}) command.
667 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
669 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
672 538 len_lquote = strlen(rquote);
673 539 len_rquote = strlen(lquote);
680 Let us step past the two lines that set @code{len_lquote} and
681 @code{len_rquote}, and then examine the values of those variables.
685 539 len_rquote = strlen(lquote);
688 (@value{GDBP}) @b{p len_lquote}
690 (@value{GDBP}) @b{p len_rquote}
695 That certainly looks wrong, assuming @code{len_lquote} and
696 @code{len_rquote} are meant to be the lengths of @code{lquote} and
697 @code{rquote} respectively. We can set them to better values using
698 the @code{p} command, since it can print the value of
699 any expression---and that expression can include subroutine calls and
703 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
705 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
710 Is that enough to fix the problem of using the new quotes with the
711 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
712 executing with the @code{c} (@code{continue}) command, and then try the
713 example that caused trouble initially:
719 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
726 Success! The new quotes now work just as well as the default ones. The
727 problem seems to have been just the two typos defining the wrong
728 lengths. We allow @code{m4} exit by giving it an EOF as input:
732 Program exited normally.
736 The message @samp{Program exited normally.} is from @value{GDBN}; it
737 indicates @code{m4} has finished executing. We can end our @value{GDBN}
738 session with the @value{GDBN} @code{quit} command.
741 (@value{GDBP}) @b{quit}
745 @chapter Getting In and Out of @value{GDBN}
747 This chapter discusses how to start @value{GDBN}, and how to get out of it.
751 type @samp{@value{GDBP}} to start @value{GDBN}.
753 type @kbd{quit} or @kbd{C-d} to exit.
757 * Invoking GDB:: How to start @value{GDBN}
758 * Quitting GDB:: How to quit @value{GDBN}
759 * Shell Commands:: How to use shell commands inside @value{GDBN}
763 @section Invoking @value{GDBN}
765 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
766 @value{GDBN} reads commands from the terminal until you tell it to exit.
768 You can also run @code{@value{GDBP}} with a variety of arguments and options,
769 to specify more of your debugging environment at the outset.
771 The command-line options described here are designed
772 to cover a variety of situations; in some environments, some of these
773 options may effectively be unavailable.
775 The most usual way to start @value{GDBN} is with one argument,
776 specifying an executable program:
779 @value{GDBP} @var{program}
783 You can also start with both an executable program and a core file
787 @value{GDBP} @var{program} @var{core}
790 You can, instead, specify a process ID as a second argument, if you want
791 to debug a running process:
794 @value{GDBP} @var{program} 1234
798 would attach @value{GDBN} to process @code{1234} (unless you also have a file
799 named @file{1234}; @value{GDBN} does check for a core file first).
801 Taking advantage of the second command-line argument requires a fairly
802 complete operating system; when you use @value{GDBN} as a remote
803 debugger attached to a bare board, there may not be any notion of
804 ``process'', and there is often no way to get a core dump. @value{GDBN}
805 will warn you if it is unable to attach or to read core dumps.
807 You can optionally have @code{@value{GDBP}} pass any arguments after the
808 executable file to the inferior using @code{--args}. This option stops
811 gdb --args gcc -O2 -c foo.c
813 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
814 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
816 You can run @code{@value{GDBP}} without printing the front material, which describes
817 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
824 You can further control how @value{GDBN} starts up by using command-line
825 options. @value{GDBN} itself can remind you of the options available.
835 to display all available options and briefly describe their use
836 (@samp{@value{GDBP} -h} is a shorter equivalent).
838 All options and command line arguments you give are processed
839 in sequential order. The order makes a difference when the
840 @samp{-x} option is used.
844 * File Options:: Choosing files
845 * Mode Options:: Choosing modes
849 @subsection Choosing files
851 When @value{GDBN} starts, it reads any arguments other than options as
852 specifying an executable file and core file (or process ID). This is
853 the same as if the arguments were specified by the @samp{-se} and
854 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
855 first argument that does not have an associated option flag as
856 equivalent to the @samp{-se} option followed by that argument; and the
857 second argument that does not have an associated option flag, if any, as
858 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
859 If the second argument begins with a decimal digit, @value{GDBN} will
860 first attempt to attach to it as a process, and if that fails, attempt
861 to open it as a corefile. If you have a corefile whose name begins with
862 a digit, you can prevent @value{GDBN} from treating it as a pid by
863 prefixing it with @file{./}, eg. @file{./12345}.
865 If @value{GDBN} has not been configured to included core file support,
866 such as for most embedded targets, then it will complain about a second
867 argument and ignore it.
869 Many options have both long and short forms; both are shown in the
870 following list. @value{GDBN} also recognizes the long forms if you truncate
871 them, so long as enough of the option is present to be unambiguous.
872 (If you prefer, you can flag option arguments with @samp{--} rather
873 than @samp{-}, though we illustrate the more usual convention.)
875 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
876 @c way, both those who look for -foo and --foo in the index, will find
880 @item -symbols @var{file}
882 @cindex @code{--symbols}
884 Read symbol table from file @var{file}.
886 @item -exec @var{file}
888 @cindex @code{--exec}
890 Use file @var{file} as the executable file to execute when appropriate,
891 and for examining pure data in conjunction with a core dump.
895 Read symbol table from file @var{file} and use it as the executable
898 @item -core @var{file}
900 @cindex @code{--core}
902 Use file @var{file} as a core dump to examine.
904 @item -c @var{number}
905 @item -pid @var{number}
906 @itemx -p @var{number}
909 Connect to process ID @var{number}, as with the @code{attach} command.
910 If there is no such process, @value{GDBN} will attempt to open a core
911 file named @var{number}.
913 @item -command @var{file}
915 @cindex @code{--command}
917 Execute @value{GDBN} commands from file @var{file}. @xref{Command
918 Files,, Command files}.
920 @item -directory @var{directory}
921 @itemx -d @var{directory}
922 @cindex @code{--directory}
924 Add @var{directory} to the path to search for source files.
928 @cindex @code{--mapped}
930 @emph{Warning: this option depends on operating system facilities that are not
931 supported on all systems.}@*
932 If memory-mapped files are available on your system through the @code{mmap}
933 system call, you can use this option
934 to have @value{GDBN} write the symbols from your
935 program into a reusable file in the current directory. If the program you are debugging is
936 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
937 Future @value{GDBN} debugging sessions notice the presence of this file,
938 and can quickly map in symbol information from it, rather than reading
939 the symbol table from the executable program.
941 The @file{.syms} file is specific to the host machine where @value{GDBN}
942 is run. It holds an exact image of the internal @value{GDBN} symbol
943 table. It cannot be shared across multiple host platforms.
947 @cindex @code{--readnow}
949 Read each symbol file's entire symbol table immediately, rather than
950 the default, which is to read it incrementally as it is needed.
951 This makes startup slower, but makes future operations faster.
955 You typically combine the @code{-mapped} and @code{-readnow} options in
956 order to build a @file{.syms} file that contains complete symbol
957 information. (@xref{Files,,Commands to specify files}, for information
958 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
959 but build a @file{.syms} file for future use is:
962 gdb -batch -nx -mapped -readnow programname
966 @subsection Choosing modes
968 You can run @value{GDBN} in various alternative modes---for example, in
969 batch mode or quiet mode.
976 Do not execute commands found in any initialization files. Normally,
977 @value{GDBN} executes the commands in these files after all the command
978 options and arguments have been processed. @xref{Command Files,,Command
984 @cindex @code{--quiet}
985 @cindex @code{--silent}
987 ``Quiet''. Do not print the introductory and copyright messages. These
988 messages are also suppressed in batch mode.
991 @cindex @code{--batch}
992 Run in batch mode. Exit with status @code{0} after processing all the
993 command files specified with @samp{-x} (and all commands from
994 initialization files, if not inhibited with @samp{-n}). Exit with
995 nonzero status if an error occurs in executing the @value{GDBN} commands
996 in the command files.
998 Batch mode may be useful for running @value{GDBN} as a filter, for
999 example to download and run a program on another computer; in order to
1000 make this more useful, the message
1003 Program exited normally.
1007 (which is ordinarily issued whenever a program running under
1008 @value{GDBN} control terminates) is not issued when running in batch
1013 @cindex @code{--nowindows}
1015 ``No windows''. If @value{GDBN} comes with a graphical user interface
1016 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1017 interface. If no GUI is available, this option has no effect.
1021 @cindex @code{--windows}
1023 If @value{GDBN} includes a GUI, then this option requires it to be
1026 @item -cd @var{directory}
1028 Run @value{GDBN} using @var{directory} as its working directory,
1029 instead of the current directory.
1033 @cindex @code{--fullname}
1035 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1036 subprocess. It tells @value{GDBN} to output the full file name and line
1037 number in a standard, recognizable fashion each time a stack frame is
1038 displayed (which includes each time your program stops). This
1039 recognizable format looks like two @samp{\032} characters, followed by
1040 the file name, line number and character position separated by colons,
1041 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1042 @samp{\032} characters as a signal to display the source code for the
1046 @cindex @code{--epoch}
1047 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1048 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1049 routines so as to allow Epoch to display values of expressions in a
1052 @item -annotate @var{level}
1053 @cindex @code{--annotate}
1054 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1055 effect is identical to using @samp{set annotate @var{level}}
1056 (@pxref{Annotations}).
1057 Annotation level controls how much information does @value{GDBN} print
1058 together with its prompt, values of expressions, source lines, and other
1059 types of output. Level 0 is the normal, level 1 is for use when
1060 @value{GDBN} is run as a subprocess of @sc{gnu} Emacs, level 2 is the
1061 maximum annotation suitable for programs that control @value{GDBN}.
1064 @cindex @code{--async}
1065 Use the asynchronous event loop for the command-line interface.
1066 @value{GDBN} processes all events, such as user keyboard input, via a
1067 special event loop. This allows @value{GDBN} to accept and process user
1068 commands in parallel with the debugged process being
1069 run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1070 MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1071 suspended when the debuggee runs.}, so you don't need to wait for
1072 control to return to @value{GDBN} before you type the next command.
1073 (@emph{Note:} as of version 5.1, the target side of the asynchronous
1074 operation is not yet in place, so @samp{-async} does not work fully
1076 @c FIXME: when the target side of the event loop is done, the above NOTE
1077 @c should be removed.
1079 When the standard input is connected to a terminal device, @value{GDBN}
1080 uses the asynchronous event loop by default, unless disabled by the
1081 @samp{-noasync} option.
1084 @cindex @code{--noasync}
1085 Disable the asynchronous event loop for the command-line interface.
1088 @cindex @code{--args}
1089 Change interpretation of command line so that arguments following the
1090 executable file are passed as command line arguments to the inferior.
1091 This option stops option processing.
1093 @item -baud @var{bps}
1095 @cindex @code{--baud}
1097 Set the line speed (baud rate or bits per second) of any serial
1098 interface used by @value{GDBN} for remote debugging.
1100 @item -tty @var{device}
1101 @itemx -t @var{device}
1102 @cindex @code{--tty}
1104 Run using @var{device} for your program's standard input and output.
1105 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1107 @c resolve the situation of these eventually
1109 @cindex @code{--tui}
1110 Activate the Terminal User Interface when starting.
1111 The Terminal User Interface manages several text windows on the terminal,
1112 showing source, assembly, registers and @value{GDBN} command outputs
1113 (@pxref{TUI, ,@value{GDBN} Text User Interface}).
1114 Do not use this option if you run @value{GDBN} from Emacs
1115 (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1118 @c @cindex @code{--xdb}
1119 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1120 @c For information, see the file @file{xdb_trans.html}, which is usually
1121 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1124 @item -interpreter @var{interp}
1125 @cindex @code{--interpreter}
1126 Use the interpreter @var{interp} for interface with the controlling
1127 program or device. This option is meant to be set by programs which
1128 communicate with @value{GDBN} using it as a back end.
1129 @xref{Interpreters, , Command Interpreters}.
1131 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1132 @value{GDBN} to use the current @dfn{@sc{gdb/mi} interface}
1133 (@pxref{GDB/MI, , The @sc{gdb/mi} Interface}). The previous @sc{gdb/mi}
1134 interface, included in @value{GDBN} version 5.3, can be selected with
1135 @samp{--interpreter=mi1}. Earlier @sc{gdb/mi} interfaces
1139 @cindex @code{--write}
1140 Open the executable and core files for both reading and writing. This
1141 is equivalent to the @samp{set write on} command inside @value{GDBN}
1145 @cindex @code{--statistics}
1146 This option causes @value{GDBN} to print statistics about time and
1147 memory usage after it completes each command and returns to the prompt.
1150 @cindex @code{--version}
1151 This option causes @value{GDBN} to print its version number and
1152 no-warranty blurb, and exit.
1157 @section Quitting @value{GDBN}
1158 @cindex exiting @value{GDBN}
1159 @cindex leaving @value{GDBN}
1162 @kindex quit @r{[}@var{expression}@r{]}
1163 @kindex q @r{(@code{quit})}
1164 @item quit @r{[}@var{expression}@r{]}
1166 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1167 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1168 do not supply @var{expression}, @value{GDBN} will terminate normally;
1169 otherwise it will terminate using the result of @var{expression} as the
1174 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1175 terminates the action of any @value{GDBN} command that is in progress and
1176 returns to @value{GDBN} command level. It is safe to type the interrupt
1177 character at any time because @value{GDBN} does not allow it to take effect
1178 until a time when it is safe.
1180 If you have been using @value{GDBN} to control an attached process or
1181 device, you can release it with the @code{detach} command
1182 (@pxref{Attach, ,Debugging an already-running process}).
1184 @node Shell Commands
1185 @section Shell commands
1187 If you need to execute occasional shell commands during your
1188 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1189 just use the @code{shell} command.
1193 @cindex shell escape
1194 @item shell @var{command string}
1195 Invoke a standard shell to execute @var{command string}.
1196 If it exists, the environment variable @code{SHELL} determines which
1197 shell to run. Otherwise @value{GDBN} uses the default shell
1198 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1201 The utility @code{make} is often needed in development environments.
1202 You do not have to use the @code{shell} command for this purpose in
1207 @cindex calling make
1208 @item make @var{make-args}
1209 Execute the @code{make} program with the specified
1210 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1214 @chapter @value{GDBN} Commands
1216 You can abbreviate a @value{GDBN} command to the first few letters of the command
1217 name, if that abbreviation is unambiguous; and you can repeat certain
1218 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1219 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1220 show you the alternatives available, if there is more than one possibility).
1223 * Command Syntax:: How to give commands to @value{GDBN}
1224 * Completion:: Command completion
1225 * Help:: How to ask @value{GDBN} for help
1228 @node Command Syntax
1229 @section Command syntax
1231 A @value{GDBN} command is a single line of input. There is no limit on
1232 how long it can be. It starts with a command name, which is followed by
1233 arguments whose meaning depends on the command name. For example, the
1234 command @code{step} accepts an argument which is the number of times to
1235 step, as in @samp{step 5}. You can also use the @code{step} command
1236 with no arguments. Some commands do not allow any arguments.
1238 @cindex abbreviation
1239 @value{GDBN} command names may always be truncated if that abbreviation is
1240 unambiguous. Other possible command abbreviations are listed in the
1241 documentation for individual commands. In some cases, even ambiguous
1242 abbreviations are allowed; for example, @code{s} is specially defined as
1243 equivalent to @code{step} even though there are other commands whose
1244 names start with @code{s}. You can test abbreviations by using them as
1245 arguments to the @code{help} command.
1247 @cindex repeating commands
1248 @kindex RET @r{(repeat last command)}
1249 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1250 repeat the previous command. Certain commands (for example, @code{run})
1251 will not repeat this way; these are commands whose unintentional
1252 repetition might cause trouble and which you are unlikely to want to
1255 The @code{list} and @code{x} commands, when you repeat them with
1256 @key{RET}, construct new arguments rather than repeating
1257 exactly as typed. This permits easy scanning of source or memory.
1259 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1260 output, in a way similar to the common utility @code{more}
1261 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1262 @key{RET} too many in this situation, @value{GDBN} disables command
1263 repetition after any command that generates this sort of display.
1265 @kindex # @r{(a comment)}
1267 Any text from a @kbd{#} to the end of the line is a comment; it does
1268 nothing. This is useful mainly in command files (@pxref{Command
1269 Files,,Command files}).
1271 @cindex repeating command sequences
1272 @kindex C-o @r{(operate-and-get-next)}
1273 The @kbd{C-o} binding is useful for repeating a complex sequence of
1274 commands. This command accepts the current line, like @kbd{RET}, and
1275 then fetches the next line relative to the current line from the history
1279 @section Command completion
1282 @cindex word completion
1283 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1284 only one possibility; it can also show you what the valid possibilities
1285 are for the next word in a command, at any time. This works for @value{GDBN}
1286 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1288 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1289 of a word. If there is only one possibility, @value{GDBN} fills in the
1290 word, and waits for you to finish the command (or press @key{RET} to
1291 enter it). For example, if you type
1293 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1294 @c complete accuracy in these examples; space introduced for clarity.
1295 @c If texinfo enhancements make it unnecessary, it would be nice to
1296 @c replace " @key" by "@key" in the following...
1298 (@value{GDBP}) info bre @key{TAB}
1302 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1303 the only @code{info} subcommand beginning with @samp{bre}:
1306 (@value{GDBP}) info breakpoints
1310 You can either press @key{RET} at this point, to run the @code{info
1311 breakpoints} command, or backspace and enter something else, if
1312 @samp{breakpoints} does not look like the command you expected. (If you
1313 were sure you wanted @code{info breakpoints} in the first place, you
1314 might as well just type @key{RET} immediately after @samp{info bre},
1315 to exploit command abbreviations rather than command completion).
1317 If there is more than one possibility for the next word when you press
1318 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1319 characters and try again, or just press @key{TAB} a second time;
1320 @value{GDBN} displays all the possible completions for that word. For
1321 example, you might want to set a breakpoint on a subroutine whose name
1322 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1323 just sounds the bell. Typing @key{TAB} again displays all the
1324 function names in your program that begin with those characters, for
1328 (@value{GDBP}) b make_ @key{TAB}
1329 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1330 make_a_section_from_file make_environ
1331 make_abs_section make_function_type
1332 make_blockvector make_pointer_type
1333 make_cleanup make_reference_type
1334 make_command make_symbol_completion_list
1335 (@value{GDBP}) b make_
1339 After displaying the available possibilities, @value{GDBN} copies your
1340 partial input (@samp{b make_} in the example) so you can finish the
1343 If you just want to see the list of alternatives in the first place, you
1344 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1345 means @kbd{@key{META} ?}. You can type this either by holding down a
1346 key designated as the @key{META} shift on your keyboard (if there is
1347 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1349 @cindex quotes in commands
1350 @cindex completion of quoted strings
1351 Sometimes the string you need, while logically a ``word'', may contain
1352 parentheses or other characters that @value{GDBN} normally excludes from
1353 its notion of a word. To permit word completion to work in this
1354 situation, you may enclose words in @code{'} (single quote marks) in
1355 @value{GDBN} commands.
1357 The most likely situation where you might need this is in typing the
1358 name of a C@t{++} function. This is because C@t{++} allows function
1359 overloading (multiple definitions of the same function, distinguished
1360 by argument type). For example, when you want to set a breakpoint you
1361 may need to distinguish whether you mean the version of @code{name}
1362 that takes an @code{int} parameter, @code{name(int)}, or the version
1363 that takes a @code{float} parameter, @code{name(float)}. To use the
1364 word-completion facilities in this situation, type a single quote
1365 @code{'} at the beginning of the function name. This alerts
1366 @value{GDBN} that it may need to consider more information than usual
1367 when you press @key{TAB} or @kbd{M-?} to request word completion:
1370 (@value{GDBP}) b 'bubble( @kbd{M-?}
1371 bubble(double,double) bubble(int,int)
1372 (@value{GDBP}) b 'bubble(
1375 In some cases, @value{GDBN} can tell that completing a name requires using
1376 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1377 completing as much as it can) if you do not type the quote in the first
1381 (@value{GDBP}) b bub @key{TAB}
1382 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1383 (@value{GDBP}) b 'bubble(
1387 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1388 you have not yet started typing the argument list when you ask for
1389 completion on an overloaded symbol.
1391 For more information about overloaded functions, see @ref{C plus plus
1392 expressions, ,C@t{++} expressions}. You can use the command @code{set
1393 overload-resolution off} to disable overload resolution;
1394 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1398 @section Getting help
1399 @cindex online documentation
1402 You can always ask @value{GDBN} itself for information on its commands,
1403 using the command @code{help}.
1406 @kindex h @r{(@code{help})}
1409 You can use @code{help} (abbreviated @code{h}) with no arguments to
1410 display a short list of named classes of commands:
1414 List of classes of commands:
1416 aliases -- Aliases of other commands
1417 breakpoints -- Making program stop at certain points
1418 data -- Examining data
1419 files -- Specifying and examining files
1420 internals -- Maintenance commands
1421 obscure -- Obscure features
1422 running -- Running the program
1423 stack -- Examining the stack
1424 status -- Status inquiries
1425 support -- Support facilities
1426 tracepoints -- Tracing of program execution without@*
1427 stopping the program
1428 user-defined -- User-defined commands
1430 Type "help" followed by a class name for a list of
1431 commands in that class.
1432 Type "help" followed by command name for full
1434 Command name abbreviations are allowed if unambiguous.
1437 @c the above line break eliminates huge line overfull...
1439 @item help @var{class}
1440 Using one of the general help classes as an argument, you can get a
1441 list of the individual commands in that class. For example, here is the
1442 help display for the class @code{status}:
1445 (@value{GDBP}) help status
1450 @c Line break in "show" line falsifies real output, but needed
1451 @c to fit in smallbook page size.
1452 info -- Generic command for showing things
1453 about the program being debugged
1454 show -- Generic command for showing things
1457 Type "help" followed by command name for full
1459 Command name abbreviations are allowed if unambiguous.
1463 @item help @var{command}
1464 With a command name as @code{help} argument, @value{GDBN} displays a
1465 short paragraph on how to use that command.
1468 @item apropos @var{args}
1469 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1470 commands, and their documentation, for the regular expression specified in
1471 @var{args}. It prints out all matches found. For example:
1482 set symbol-reloading -- Set dynamic symbol table reloading
1483 multiple times in one run
1484 show symbol-reloading -- Show dynamic symbol table reloading
1485 multiple times in one run
1490 @item complete @var{args}
1491 The @code{complete @var{args}} command lists all the possible completions
1492 for the beginning of a command. Use @var{args} to specify the beginning of the
1493 command you want completed. For example:
1499 @noindent results in:
1510 @noindent This is intended for use by @sc{gnu} Emacs.
1513 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1514 and @code{show} to inquire about the state of your program, or the state
1515 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1516 manual introduces each of them in the appropriate context. The listings
1517 under @code{info} and under @code{show} in the Index point to
1518 all the sub-commands. @xref{Index}.
1523 @kindex i @r{(@code{info})}
1525 This command (abbreviated @code{i}) is for describing the state of your
1526 program. For example, you can list the arguments given to your program
1527 with @code{info args}, list the registers currently in use with @code{info
1528 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1529 You can get a complete list of the @code{info} sub-commands with
1530 @w{@code{help info}}.
1534 You can assign the result of an expression to an environment variable with
1535 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1536 @code{set prompt $}.
1540 In contrast to @code{info}, @code{show} is for describing the state of
1541 @value{GDBN} itself.
1542 You can change most of the things you can @code{show}, by using the
1543 related command @code{set}; for example, you can control what number
1544 system is used for displays with @code{set radix}, or simply inquire
1545 which is currently in use with @code{show radix}.
1548 To display all the settable parameters and their current
1549 values, you can use @code{show} with no arguments; you may also use
1550 @code{info set}. Both commands produce the same display.
1551 @c FIXME: "info set" violates the rule that "info" is for state of
1552 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1553 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1557 Here are three miscellaneous @code{show} subcommands, all of which are
1558 exceptional in lacking corresponding @code{set} commands:
1561 @kindex show version
1562 @cindex version number
1564 Show what version of @value{GDBN} is running. You should include this
1565 information in @value{GDBN} bug-reports. If multiple versions of
1566 @value{GDBN} are in use at your site, you may need to determine which
1567 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1568 commands are introduced, and old ones may wither away. Also, many
1569 system vendors ship variant versions of @value{GDBN}, and there are
1570 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1571 The version number is the same as the one announced when you start
1574 @kindex show copying
1576 Display information about permission for copying @value{GDBN}.
1578 @kindex show warranty
1580 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1581 if your version of @value{GDBN} comes with one.
1586 @chapter Running Programs Under @value{GDBN}
1588 When you run a program under @value{GDBN}, you must first generate
1589 debugging information when you compile it.
1591 You may start @value{GDBN} with its arguments, if any, in an environment
1592 of your choice. If you are doing native debugging, you may redirect
1593 your program's input and output, debug an already running process, or
1594 kill a child process.
1597 * Compilation:: Compiling for debugging
1598 * Starting:: Starting your program
1599 * Arguments:: Your program's arguments
1600 * Environment:: Your program's environment
1602 * Working Directory:: Your program's working directory
1603 * Input/Output:: Your program's input and output
1604 * Attach:: Debugging an already-running process
1605 * Kill Process:: Killing the child process
1607 * Threads:: Debugging programs with multiple threads
1608 * Processes:: Debugging programs with multiple processes
1612 @section Compiling for debugging
1614 In order to debug a program effectively, you need to generate
1615 debugging information when you compile it. This debugging information
1616 is stored in the object file; it describes the data type of each
1617 variable or function and the correspondence between source line numbers
1618 and addresses in the executable code.
1620 To request debugging information, specify the @samp{-g} option when you run
1623 Most compilers do not include information about preprocessor macros in
1624 the debugging information if you specify the @option{-g} flag alone,
1625 because this information is rather large. Version 3.1 of @value{NGCC},
1626 the @sc{gnu} C compiler, provides macro information if you specify the
1627 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1628 debugging information in the Dwarf 2 format, and the latter requests
1629 ``extra information''. In the future, we hope to find more compact ways
1630 to represent macro information, so that it can be included with
1633 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1634 options together. Using those compilers, you cannot generate optimized
1635 executables containing debugging information.
1637 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1638 without @samp{-O}, making it possible to debug optimized code. We
1639 recommend that you @emph{always} use @samp{-g} whenever you compile a
1640 program. You may think your program is correct, but there is no sense
1641 in pushing your luck.
1643 @cindex optimized code, debugging
1644 @cindex debugging optimized code
1645 When you debug a program compiled with @samp{-g -O}, remember that the
1646 optimizer is rearranging your code; the debugger shows you what is
1647 really there. Do not be too surprised when the execution path does not
1648 exactly match your source file! An extreme example: if you define a
1649 variable, but never use it, @value{GDBN} never sees that
1650 variable---because the compiler optimizes it out of existence.
1652 Some things do not work as well with @samp{-g -O} as with just
1653 @samp{-g}, particularly on machines with instruction scheduling. If in
1654 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1655 please report it to us as a bug (including a test case!).
1657 Older versions of the @sc{gnu} C compiler permitted a variant option
1658 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1659 format; if your @sc{gnu} C compiler has this option, do not use it.
1663 @section Starting your program
1669 @kindex r @r{(@code{run})}
1672 Use the @code{run} command to start your program under @value{GDBN}.
1673 You must first specify the program name (except on VxWorks) with an
1674 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1675 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1676 (@pxref{Files, ,Commands to specify files}).
1680 If you are running your program in an execution environment that
1681 supports processes, @code{run} creates an inferior process and makes
1682 that process run your program. (In environments without processes,
1683 @code{run} jumps to the start of your program.)
1685 The execution of a program is affected by certain information it
1686 receives from its superior. @value{GDBN} provides ways to specify this
1687 information, which you must do @emph{before} starting your program. (You
1688 can change it after starting your program, but such changes only affect
1689 your program the next time you start it.) This information may be
1690 divided into four categories:
1693 @item The @emph{arguments.}
1694 Specify the arguments to give your program as the arguments of the
1695 @code{run} command. If a shell is available on your target, the shell
1696 is used to pass the arguments, so that you may use normal conventions
1697 (such as wildcard expansion or variable substitution) in describing
1699 In Unix systems, you can control which shell is used with the
1700 @code{SHELL} environment variable.
1701 @xref{Arguments, ,Your program's arguments}.
1703 @item The @emph{environment.}
1704 Your program normally inherits its environment from @value{GDBN}, but you can
1705 use the @value{GDBN} commands @code{set environment} and @code{unset
1706 environment} to change parts of the environment that affect
1707 your program. @xref{Environment, ,Your program's environment}.
1709 @item The @emph{working directory.}
1710 Your program inherits its working directory from @value{GDBN}. You can set
1711 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1712 @xref{Working Directory, ,Your program's working directory}.
1714 @item The @emph{standard input and output.}
1715 Your program normally uses the same device for standard input and
1716 standard output as @value{GDBN} is using. You can redirect input and output
1717 in the @code{run} command line, or you can use the @code{tty} command to
1718 set a different device for your program.
1719 @xref{Input/Output, ,Your program's input and output}.
1722 @emph{Warning:} While input and output redirection work, you cannot use
1723 pipes to pass the output of the program you are debugging to another
1724 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1728 When you issue the @code{run} command, your program begins to execute
1729 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1730 of how to arrange for your program to stop. Once your program has
1731 stopped, you may call functions in your program, using the @code{print}
1732 or @code{call} commands. @xref{Data, ,Examining Data}.
1734 If the modification time of your symbol file has changed since the last
1735 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1736 table, and reads it again. When it does this, @value{GDBN} tries to retain
1737 your current breakpoints.
1740 @section Your program's arguments
1742 @cindex arguments (to your program)
1743 The arguments to your program can be specified by the arguments of the
1745 They are passed to a shell, which expands wildcard characters and
1746 performs redirection of I/O, and thence to your program. Your
1747 @code{SHELL} environment variable (if it exists) specifies what shell
1748 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1749 the default shell (@file{/bin/sh} on Unix).
1751 On non-Unix systems, the program is usually invoked directly by
1752 @value{GDBN}, which emulates I/O redirection via the appropriate system
1753 calls, and the wildcard characters are expanded by the startup code of
1754 the program, not by the shell.
1756 @code{run} with no arguments uses the same arguments used by the previous
1757 @code{run}, or those set by the @code{set args} command.
1762 Specify the arguments to be used the next time your program is run. If
1763 @code{set args} has no arguments, @code{run} executes your program
1764 with no arguments. Once you have run your program with arguments,
1765 using @code{set args} before the next @code{run} is the only way to run
1766 it again without arguments.
1770 Show the arguments to give your program when it is started.
1774 @section Your program's environment
1776 @cindex environment (of your program)
1777 The @dfn{environment} consists of a set of environment variables and
1778 their values. Environment variables conventionally record such things as
1779 your user name, your home directory, your terminal type, and your search
1780 path for programs to run. Usually you set up environment variables with
1781 the shell and they are inherited by all the other programs you run. When
1782 debugging, it can be useful to try running your program with a modified
1783 environment without having to start @value{GDBN} over again.
1787 @item path @var{directory}
1788 Add @var{directory} to the front of the @code{PATH} environment variable
1789 (the search path for executables) that will be passed to your program.
1790 The value of @code{PATH} used by @value{GDBN} does not change.
1791 You may specify several directory names, separated by whitespace or by a
1792 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1793 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1794 is moved to the front, so it is searched sooner.
1796 You can use the string @samp{$cwd} to refer to whatever is the current
1797 working directory at the time @value{GDBN} searches the path. If you
1798 use @samp{.} instead, it refers to the directory where you executed the
1799 @code{path} command. @value{GDBN} replaces @samp{.} in the
1800 @var{directory} argument (with the current path) before adding
1801 @var{directory} to the search path.
1802 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1803 @c document that, since repeating it would be a no-op.
1807 Display the list of search paths for executables (the @code{PATH}
1808 environment variable).
1810 @kindex show environment
1811 @item show environment @r{[}@var{varname}@r{]}
1812 Print the value of environment variable @var{varname} to be given to
1813 your program when it starts. If you do not supply @var{varname},
1814 print the names and values of all environment variables to be given to
1815 your program. You can abbreviate @code{environment} as @code{env}.
1817 @kindex set environment
1818 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1819 Set environment variable @var{varname} to @var{value}. The value
1820 changes for your program only, not for @value{GDBN} itself. @var{value} may
1821 be any string; the values of environment variables are just strings, and
1822 any interpretation is supplied by your program itself. The @var{value}
1823 parameter is optional; if it is eliminated, the variable is set to a
1825 @c "any string" here does not include leading, trailing
1826 @c blanks. Gnu asks: does anyone care?
1828 For example, this command:
1835 tells the debugged program, when subsequently run, that its user is named
1836 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1837 are not actually required.)
1839 @kindex unset environment
1840 @item unset environment @var{varname}
1841 Remove variable @var{varname} from the environment to be passed to your
1842 program. This is different from @samp{set env @var{varname} =};
1843 @code{unset environment} removes the variable from the environment,
1844 rather than assigning it an empty value.
1847 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1849 by your @code{SHELL} environment variable if it exists (or
1850 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1851 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1852 @file{.bashrc} for BASH---any variables you set in that file affect
1853 your program. You may wish to move setting of environment variables to
1854 files that are only run when you sign on, such as @file{.login} or
1857 @node Working Directory
1858 @section Your program's working directory
1860 @cindex working directory (of your program)
1861 Each time you start your program with @code{run}, it inherits its
1862 working directory from the current working directory of @value{GDBN}.
1863 The @value{GDBN} working directory is initially whatever it inherited
1864 from its parent process (typically the shell), but you can specify a new
1865 working directory in @value{GDBN} with the @code{cd} command.
1867 The @value{GDBN} working directory also serves as a default for the commands
1868 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1873 @item cd @var{directory}
1874 Set the @value{GDBN} working directory to @var{directory}.
1878 Print the @value{GDBN} working directory.
1882 @section Your program's input and output
1887 By default, the program you run under @value{GDBN} does input and output to
1888 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1889 to its own terminal modes to interact with you, but it records the terminal
1890 modes your program was using and switches back to them when you continue
1891 running your program.
1894 @kindex info terminal
1896 Displays information recorded by @value{GDBN} about the terminal modes your
1900 You can redirect your program's input and/or output using shell
1901 redirection with the @code{run} command. For example,
1908 starts your program, diverting its output to the file @file{outfile}.
1911 @cindex controlling terminal
1912 Another way to specify where your program should do input and output is
1913 with the @code{tty} command. This command accepts a file name as
1914 argument, and causes this file to be the default for future @code{run}
1915 commands. It also resets the controlling terminal for the child
1916 process, for future @code{run} commands. For example,
1923 directs that processes started with subsequent @code{run} commands
1924 default to do input and output on the terminal @file{/dev/ttyb} and have
1925 that as their controlling terminal.
1927 An explicit redirection in @code{run} overrides the @code{tty} command's
1928 effect on the input/output device, but not its effect on the controlling
1931 When you use the @code{tty} command or redirect input in the @code{run}
1932 command, only the input @emph{for your program} is affected. The input
1933 for @value{GDBN} still comes from your terminal.
1936 @section Debugging an already-running process
1941 @item attach @var{process-id}
1942 This command attaches to a running process---one that was started
1943 outside @value{GDBN}. (@code{info files} shows your active
1944 targets.) The command takes as argument a process ID. The usual way to
1945 find out the process-id of a Unix process is with the @code{ps} utility,
1946 or with the @samp{jobs -l} shell command.
1948 @code{attach} does not repeat if you press @key{RET} a second time after
1949 executing the command.
1952 To use @code{attach}, your program must be running in an environment
1953 which supports processes; for example, @code{attach} does not work for
1954 programs on bare-board targets that lack an operating system. You must
1955 also have permission to send the process a signal.
1957 When you use @code{attach}, the debugger finds the program running in
1958 the process first by looking in the current working directory, then (if
1959 the program is not found) by using the source file search path
1960 (@pxref{Source Path, ,Specifying source directories}). You can also use
1961 the @code{file} command to load the program. @xref{Files, ,Commands to
1964 The first thing @value{GDBN} does after arranging to debug the specified
1965 process is to stop it. You can examine and modify an attached process
1966 with all the @value{GDBN} commands that are ordinarily available when
1967 you start processes with @code{run}. You can insert breakpoints; you
1968 can step and continue; you can modify storage. If you would rather the
1969 process continue running, you may use the @code{continue} command after
1970 attaching @value{GDBN} to the process.
1975 When you have finished debugging the attached process, you can use the
1976 @code{detach} command to release it from @value{GDBN} control. Detaching
1977 the process continues its execution. After the @code{detach} command,
1978 that process and @value{GDBN} become completely independent once more, and you
1979 are ready to @code{attach} another process or start one with @code{run}.
1980 @code{detach} does not repeat if you press @key{RET} again after
1981 executing the command.
1984 If you exit @value{GDBN} or use the @code{run} command while you have an
1985 attached process, you kill that process. By default, @value{GDBN} asks
1986 for confirmation if you try to do either of these things; you can
1987 control whether or not you need to confirm by using the @code{set
1988 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
1992 @section Killing the child process
1997 Kill the child process in which your program is running under @value{GDBN}.
2000 This command is useful if you wish to debug a core dump instead of a
2001 running process. @value{GDBN} ignores any core dump file while your program
2004 On some operating systems, a program cannot be executed outside @value{GDBN}
2005 while you have breakpoints set on it inside @value{GDBN}. You can use the
2006 @code{kill} command in this situation to permit running your program
2007 outside the debugger.
2009 The @code{kill} command is also useful if you wish to recompile and
2010 relink your program, since on many systems it is impossible to modify an
2011 executable file while it is running in a process. In this case, when you
2012 next type @code{run}, @value{GDBN} notices that the file has changed, and
2013 reads the symbol table again (while trying to preserve your current
2014 breakpoint settings).
2017 @section Debugging programs with multiple threads
2019 @cindex threads of execution
2020 @cindex multiple threads
2021 @cindex switching threads
2022 In some operating systems, such as HP-UX and Solaris, a single program
2023 may have more than one @dfn{thread} of execution. The precise semantics
2024 of threads differ from one operating system to another, but in general
2025 the threads of a single program are akin to multiple processes---except
2026 that they share one address space (that is, they can all examine and
2027 modify the same variables). On the other hand, each thread has its own
2028 registers and execution stack, and perhaps private memory.
2030 @value{GDBN} provides these facilities for debugging multi-thread
2034 @item automatic notification of new threads
2035 @item @samp{thread @var{threadno}}, a command to switch among threads
2036 @item @samp{info threads}, a command to inquire about existing threads
2037 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2038 a command to apply a command to a list of threads
2039 @item thread-specific breakpoints
2043 @emph{Warning:} These facilities are not yet available on every
2044 @value{GDBN} configuration where the operating system supports threads.
2045 If your @value{GDBN} does not support threads, these commands have no
2046 effect. For example, a system without thread support shows no output
2047 from @samp{info threads}, and always rejects the @code{thread} command,
2051 (@value{GDBP}) info threads
2052 (@value{GDBP}) thread 1
2053 Thread ID 1 not known. Use the "info threads" command to
2054 see the IDs of currently known threads.
2056 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2057 @c doesn't support threads"?
2060 @cindex focus of debugging
2061 @cindex current thread
2062 The @value{GDBN} thread debugging facility allows you to observe all
2063 threads while your program runs---but whenever @value{GDBN} takes
2064 control, one thread in particular is always the focus of debugging.
2065 This thread is called the @dfn{current thread}. Debugging commands show
2066 program information from the perspective of the current thread.
2068 @cindex @code{New} @var{systag} message
2069 @cindex thread identifier (system)
2070 @c FIXME-implementors!! It would be more helpful if the [New...] message
2071 @c included GDB's numeric thread handle, so you could just go to that
2072 @c thread without first checking `info threads'.
2073 Whenever @value{GDBN} detects a new thread in your program, it displays
2074 the target system's identification for the thread with a message in the
2075 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2076 whose form varies depending on the particular system. For example, on
2077 LynxOS, you might see
2080 [New process 35 thread 27]
2084 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2085 the @var{systag} is simply something like @samp{process 368}, with no
2088 @c FIXME!! (1) Does the [New...] message appear even for the very first
2089 @c thread of a program, or does it only appear for the
2090 @c second---i.e.@: when it becomes obvious we have a multithread
2092 @c (2) *Is* there necessarily a first thread always? Or do some
2093 @c multithread systems permit starting a program with multiple
2094 @c threads ab initio?
2096 @cindex thread number
2097 @cindex thread identifier (GDB)
2098 For debugging purposes, @value{GDBN} associates its own thread
2099 number---always a single integer---with each thread in your program.
2102 @kindex info threads
2104 Display a summary of all threads currently in your
2105 program. @value{GDBN} displays for each thread (in this order):
2108 @item the thread number assigned by @value{GDBN}
2110 @item the target system's thread identifier (@var{systag})
2112 @item the current stack frame summary for that thread
2116 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2117 indicates the current thread.
2121 @c end table here to get a little more width for example
2124 (@value{GDBP}) info threads
2125 3 process 35 thread 27 0x34e5 in sigpause ()
2126 2 process 35 thread 23 0x34e5 in sigpause ()
2127 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2133 @cindex thread number
2134 @cindex thread identifier (GDB)
2135 For debugging purposes, @value{GDBN} associates its own thread
2136 number---a small integer assigned in thread-creation order---with each
2137 thread in your program.
2139 @cindex @code{New} @var{systag} message, on HP-UX
2140 @cindex thread identifier (system), on HP-UX
2141 @c FIXME-implementors!! It would be more helpful if the [New...] message
2142 @c included GDB's numeric thread handle, so you could just go to that
2143 @c thread without first checking `info threads'.
2144 Whenever @value{GDBN} detects a new thread in your program, it displays
2145 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2146 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2147 whose form varies depending on the particular system. For example, on
2151 [New thread 2 (system thread 26594)]
2155 when @value{GDBN} notices a new thread.
2158 @kindex info threads
2160 Display a summary of all threads currently in your
2161 program. @value{GDBN} displays for each thread (in this order):
2164 @item the thread number assigned by @value{GDBN}
2166 @item the target system's thread identifier (@var{systag})
2168 @item the current stack frame summary for that thread
2172 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2173 indicates the current thread.
2177 @c end table here to get a little more width for example
2180 (@value{GDBP}) info threads
2181 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2183 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2184 from /usr/lib/libc.2
2185 1 system thread 27905 0x7b003498 in _brk () \@*
2186 from /usr/lib/libc.2
2190 @kindex thread @var{threadno}
2191 @item thread @var{threadno}
2192 Make thread number @var{threadno} the current thread. The command
2193 argument @var{threadno} is the internal @value{GDBN} thread number, as
2194 shown in the first field of the @samp{info threads} display.
2195 @value{GDBN} responds by displaying the system identifier of the thread
2196 you selected, and its current stack frame summary:
2199 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2200 (@value{GDBP}) thread 2
2201 [Switching to process 35 thread 23]
2202 0x34e5 in sigpause ()
2206 As with the @samp{[New @dots{}]} message, the form of the text after
2207 @samp{Switching to} depends on your system's conventions for identifying
2210 @kindex thread apply
2211 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2212 The @code{thread apply} command allows you to apply a command to one or
2213 more threads. Specify the numbers of the threads that you want affected
2214 with the command argument @var{threadno}. @var{threadno} is the internal
2215 @value{GDBN} thread number, as shown in the first field of the @samp{info
2216 threads} display. To apply a command to all threads, use
2217 @code{thread apply all} @var{args}.
2220 @cindex automatic thread selection
2221 @cindex switching threads automatically
2222 @cindex threads, automatic switching
2223 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2224 signal, it automatically selects the thread where that breakpoint or
2225 signal happened. @value{GDBN} alerts you to the context switch with a
2226 message of the form @samp{[Switching to @var{systag}]} to identify the
2229 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2230 more information about how @value{GDBN} behaves when you stop and start
2231 programs with multiple threads.
2233 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2234 watchpoints in programs with multiple threads.
2237 @section Debugging programs with multiple processes
2239 @cindex fork, debugging programs which call
2240 @cindex multiple processes
2241 @cindex processes, multiple
2242 On most systems, @value{GDBN} has no special support for debugging
2243 programs which create additional processes using the @code{fork}
2244 function. When a program forks, @value{GDBN} will continue to debug the
2245 parent process and the child process will run unimpeded. If you have
2246 set a breakpoint in any code which the child then executes, the child
2247 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2248 will cause it to terminate.
2250 However, if you want to debug the child process there is a workaround
2251 which isn't too painful. Put a call to @code{sleep} in the code which
2252 the child process executes after the fork. It may be useful to sleep
2253 only if a certain environment variable is set, or a certain file exists,
2254 so that the delay need not occur when you don't want to run @value{GDBN}
2255 on the child. While the child is sleeping, use the @code{ps} program to
2256 get its process ID. Then tell @value{GDBN} (a new invocation of
2257 @value{GDBN} if you are also debugging the parent process) to attach to
2258 the child process (@pxref{Attach}). From that point on you can debug
2259 the child process just like any other process which you attached to.
2261 On HP-UX (11.x and later only?), @value{GDBN} provides support for
2262 debugging programs that create additional processes using the
2263 @code{fork} or @code{vfork} function.
2265 By default, when a program forks, @value{GDBN} will continue to debug
2266 the parent process and the child process will run unimpeded.
2268 If you want to follow the child process instead of the parent process,
2269 use the command @w{@code{set follow-fork-mode}}.
2272 @kindex set follow-fork-mode
2273 @item set follow-fork-mode @var{mode}
2274 Set the debugger response to a program call of @code{fork} or
2275 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2276 process. The @var{mode} can be:
2280 The original process is debugged after a fork. The child process runs
2281 unimpeded. This is the default.
2284 The new process is debugged after a fork. The parent process runs
2288 The debugger will ask for one of the above choices.
2291 @item show follow-fork-mode
2292 Display the current debugger response to a @code{fork} or @code{vfork} call.
2295 If you ask to debug a child process and a @code{vfork} is followed by an
2296 @code{exec}, @value{GDBN} executes the new target up to the first
2297 breakpoint in the new target. If you have a breakpoint set on
2298 @code{main} in your original program, the breakpoint will also be set on
2299 the child process's @code{main}.
2301 When a child process is spawned by @code{vfork}, you cannot debug the
2302 child or parent until an @code{exec} call completes.
2304 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2305 call executes, the new target restarts. To restart the parent process,
2306 use the @code{file} command with the parent executable name as its
2309 You can use the @code{catch} command to make @value{GDBN} stop whenever
2310 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2311 Catchpoints, ,Setting catchpoints}.
2314 @chapter Stopping and Continuing
2316 The principal purposes of using a debugger are so that you can stop your
2317 program before it terminates; or so that, if your program runs into
2318 trouble, you can investigate and find out why.
2320 Inside @value{GDBN}, your program may stop for any of several reasons,
2321 such as a signal, a breakpoint, or reaching a new line after a
2322 @value{GDBN} command such as @code{step}. You may then examine and
2323 change variables, set new breakpoints or remove old ones, and then
2324 continue execution. Usually, the messages shown by @value{GDBN} provide
2325 ample explanation of the status of your program---but you can also
2326 explicitly request this information at any time.
2329 @kindex info program
2331 Display information about the status of your program: whether it is
2332 running or not, what process it is, and why it stopped.
2336 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2337 * Continuing and Stepping:: Resuming execution
2339 * Thread Stops:: Stopping and starting multi-thread programs
2343 @section Breakpoints, watchpoints, and catchpoints
2346 A @dfn{breakpoint} makes your program stop whenever a certain point in
2347 the program is reached. For each breakpoint, you can add conditions to
2348 control in finer detail whether your program stops. You can set
2349 breakpoints with the @code{break} command and its variants (@pxref{Set
2350 Breaks, ,Setting breakpoints}), to specify the place where your program
2351 should stop by line number, function name or exact address in the
2354 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2355 breakpoints in shared libraries before the executable is run. There is
2356 a minor limitation on HP-UX systems: you must wait until the executable
2357 is run in order to set breakpoints in shared library routines that are
2358 not called directly by the program (for example, routines that are
2359 arguments in a @code{pthread_create} call).
2362 @cindex memory tracing
2363 @cindex breakpoint on memory address
2364 @cindex breakpoint on variable modification
2365 A @dfn{watchpoint} is a special breakpoint that stops your program
2366 when the value of an expression changes. You must use a different
2367 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2368 watchpoints}), but aside from that, you can manage a watchpoint like
2369 any other breakpoint: you enable, disable, and delete both breakpoints
2370 and watchpoints using the same commands.
2372 You can arrange to have values from your program displayed automatically
2373 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2377 @cindex breakpoint on events
2378 A @dfn{catchpoint} is another special breakpoint that stops your program
2379 when a certain kind of event occurs, such as the throwing of a C@t{++}
2380 exception or the loading of a library. As with watchpoints, you use a
2381 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2382 catchpoints}), but aside from that, you can manage a catchpoint like any
2383 other breakpoint. (To stop when your program receives a signal, use the
2384 @code{handle} command; see @ref{Signals, ,Signals}.)
2386 @cindex breakpoint numbers
2387 @cindex numbers for breakpoints
2388 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2389 catchpoint when you create it; these numbers are successive integers
2390 starting with one. In many of the commands for controlling various
2391 features of breakpoints you use the breakpoint number to say which
2392 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2393 @dfn{disabled}; if disabled, it has no effect on your program until you
2396 @cindex breakpoint ranges
2397 @cindex ranges of breakpoints
2398 Some @value{GDBN} commands accept a range of breakpoints on which to
2399 operate. A breakpoint range is either a single breakpoint number, like
2400 @samp{5}, or two such numbers, in increasing order, separated by a
2401 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2402 all breakpoint in that range are operated on.
2405 * Set Breaks:: Setting breakpoints
2406 * Set Watchpoints:: Setting watchpoints
2407 * Set Catchpoints:: Setting catchpoints
2408 * Delete Breaks:: Deleting breakpoints
2409 * Disabling:: Disabling breakpoints
2410 * Conditions:: Break conditions
2411 * Break Commands:: Breakpoint command lists
2412 * Breakpoint Menus:: Breakpoint menus
2413 * Error in Breakpoints:: ``Cannot insert breakpoints''
2417 @subsection Setting breakpoints
2419 @c FIXME LMB what does GDB do if no code on line of breakpt?
2420 @c consider in particular declaration with/without initialization.
2422 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2425 @kindex b @r{(@code{break})}
2426 @vindex $bpnum@r{, convenience variable}
2427 @cindex latest breakpoint
2428 Breakpoints are set with the @code{break} command (abbreviated
2429 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2430 number of the breakpoint you've set most recently; see @ref{Convenience
2431 Vars,, Convenience variables}, for a discussion of what you can do with
2432 convenience variables.
2434 You have several ways to say where the breakpoint should go.
2437 @item break @var{function}
2438 Set a breakpoint at entry to function @var{function}.
2439 When using source languages that permit overloading of symbols, such as
2440 C@t{++}, @var{function} may refer to more than one possible place to break.
2441 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2443 @item break +@var{offset}
2444 @itemx break -@var{offset}
2445 Set a breakpoint some number of lines forward or back from the position
2446 at which execution stopped in the currently selected @dfn{stack frame}.
2447 (@xref{Frames, ,Frames}, for a description of stack frames.)
2449 @item break @var{linenum}
2450 Set a breakpoint at line @var{linenum} in the current source file.
2451 The current source file is the last file whose source text was printed.
2452 The breakpoint will stop your program just before it executes any of the
2455 @item break @var{filename}:@var{linenum}
2456 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2458 @item break @var{filename}:@var{function}
2459 Set a breakpoint at entry to function @var{function} found in file
2460 @var{filename}. Specifying a file name as well as a function name is
2461 superfluous except when multiple files contain similarly named
2464 @item break *@var{address}
2465 Set a breakpoint at address @var{address}. You can use this to set
2466 breakpoints in parts of your program which do not have debugging
2467 information or source files.
2470 When called without any arguments, @code{break} sets a breakpoint at
2471 the next instruction to be executed in the selected stack frame
2472 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2473 innermost, this makes your program stop as soon as control
2474 returns to that frame. This is similar to the effect of a
2475 @code{finish} command in the frame inside the selected frame---except
2476 that @code{finish} does not leave an active breakpoint. If you use
2477 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2478 the next time it reaches the current location; this may be useful
2481 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2482 least one instruction has been executed. If it did not do this, you
2483 would be unable to proceed past a breakpoint without first disabling the
2484 breakpoint. This rule applies whether or not the breakpoint already
2485 existed when your program stopped.
2487 @item break @dots{} if @var{cond}
2488 Set a breakpoint with condition @var{cond}; evaluate the expression
2489 @var{cond} each time the breakpoint is reached, and stop only if the
2490 value is nonzero---that is, if @var{cond} evaluates as true.
2491 @samp{@dots{}} stands for one of the possible arguments described
2492 above (or no argument) specifying where to break. @xref{Conditions,
2493 ,Break conditions}, for more information on breakpoint conditions.
2496 @item tbreak @var{args}
2497 Set a breakpoint enabled only for one stop. @var{args} are the
2498 same as for the @code{break} command, and the breakpoint is set in the same
2499 way, but the breakpoint is automatically deleted after the first time your
2500 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2503 @item hbreak @var{args}
2504 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2505 @code{break} command and the breakpoint is set in the same way, but the
2506 breakpoint requires hardware support and some target hardware may not
2507 have this support. The main purpose of this is EPROM/ROM code
2508 debugging, so you can set a breakpoint at an instruction without
2509 changing the instruction. This can be used with the new trap-generation
2510 provided by SPARClite DSU and some x86-based targets. These targets
2511 will generate traps when a program accesses some data or instruction
2512 address that is assigned to the debug registers. However the hardware
2513 breakpoint registers can take a limited number of breakpoints. For
2514 example, on the DSU, only two data breakpoints can be set at a time, and
2515 @value{GDBN} will reject this command if more than two are used. Delete
2516 or disable unused hardware breakpoints before setting new ones
2517 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2518 @xref{set remote hardware-breakpoint-limit}.
2522 @item thbreak @var{args}
2523 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2524 are the same as for the @code{hbreak} command and the breakpoint is set in
2525 the same way. However, like the @code{tbreak} command,
2526 the breakpoint is automatically deleted after the
2527 first time your program stops there. Also, like the @code{hbreak}
2528 command, the breakpoint requires hardware support and some target hardware
2529 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2530 See also @ref{Conditions, ,Break conditions}.
2533 @cindex regular expression
2534 @item rbreak @var{regex}
2535 Set breakpoints on all functions matching the regular expression
2536 @var{regex}. This command sets an unconditional breakpoint on all
2537 matches, printing a list of all breakpoints it set. Once these
2538 breakpoints are set, they are treated just like the breakpoints set with
2539 the @code{break} command. You can delete them, disable them, or make
2540 them conditional the same way as any other breakpoint.
2542 The syntax of the regular expression is the standard one used with tools
2543 like @file{grep}. Note that this is different from the syntax used by
2544 shells, so for instance @code{foo*} matches all functions that include
2545 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2546 @code{.*} leading and trailing the regular expression you supply, so to
2547 match only functions that begin with @code{foo}, use @code{^foo}.
2549 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2550 breakpoints on overloaded functions that are not members of any special
2553 @kindex info breakpoints
2554 @cindex @code{$_} and @code{info breakpoints}
2555 @item info breakpoints @r{[}@var{n}@r{]}
2556 @itemx info break @r{[}@var{n}@r{]}
2557 @itemx info watchpoints @r{[}@var{n}@r{]}
2558 Print a table of all breakpoints, watchpoints, and catchpoints set and
2559 not deleted, with the following columns for each breakpoint:
2562 @item Breakpoint Numbers
2564 Breakpoint, watchpoint, or catchpoint.
2566 Whether the breakpoint is marked to be disabled or deleted when hit.
2567 @item Enabled or Disabled
2568 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2569 that are not enabled.
2571 Where the breakpoint is in your program, as a memory address.
2573 Where the breakpoint is in the source for your program, as a file and
2578 If a breakpoint is conditional, @code{info break} shows the condition on
2579 the line following the affected breakpoint; breakpoint commands, if any,
2580 are listed after that.
2583 @code{info break} with a breakpoint
2584 number @var{n} as argument lists only that breakpoint. The
2585 convenience variable @code{$_} and the default examining-address for
2586 the @code{x} command are set to the address of the last breakpoint
2587 listed (@pxref{Memory, ,Examining memory}).
2590 @code{info break} displays a count of the number of times the breakpoint
2591 has been hit. This is especially useful in conjunction with the
2592 @code{ignore} command. You can ignore a large number of breakpoint
2593 hits, look at the breakpoint info to see how many times the breakpoint
2594 was hit, and then run again, ignoring one less than that number. This
2595 will get you quickly to the last hit of that breakpoint.
2598 @value{GDBN} allows you to set any number of breakpoints at the same place in
2599 your program. There is nothing silly or meaningless about this. When
2600 the breakpoints are conditional, this is even useful
2601 (@pxref{Conditions, ,Break conditions}).
2603 @cindex negative breakpoint numbers
2604 @cindex internal @value{GDBN} breakpoints
2605 @value{GDBN} itself sometimes sets breakpoints in your program for
2606 special purposes, such as proper handling of @code{longjmp} (in C
2607 programs). These internal breakpoints are assigned negative numbers,
2608 starting with @code{-1}; @samp{info breakpoints} does not display them.
2609 You can see these breakpoints with the @value{GDBN} maintenance command
2610 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2613 @node Set Watchpoints
2614 @subsection Setting watchpoints
2616 @cindex setting watchpoints
2617 @cindex software watchpoints
2618 @cindex hardware watchpoints
2619 You can use a watchpoint to stop execution whenever the value of an
2620 expression changes, without having to predict a particular place where
2623 Depending on your system, watchpoints may be implemented in software or
2624 hardware. @value{GDBN} does software watchpointing by single-stepping your
2625 program and testing the variable's value each time, which is hundreds of
2626 times slower than normal execution. (But this may still be worth it, to
2627 catch errors where you have no clue what part of your program is the
2630 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2631 @value{GDBN} includes support for
2632 hardware watchpoints, which do not slow down the running of your
2637 @item watch @var{expr}
2638 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2639 is written into by the program and its value changes.
2642 @item rwatch @var{expr}
2643 Set a watchpoint that will break when watch @var{expr} is read by the program.
2646 @item awatch @var{expr}
2647 Set a watchpoint that will break when @var{expr} is either read or written into
2650 @kindex info watchpoints
2651 @item info watchpoints
2652 This command prints a list of watchpoints, breakpoints, and catchpoints;
2653 it is the same as @code{info break}.
2656 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2657 watchpoints execute very quickly, and the debugger reports a change in
2658 value at the exact instruction where the change occurs. If @value{GDBN}
2659 cannot set a hardware watchpoint, it sets a software watchpoint, which
2660 executes more slowly and reports the change in value at the next
2661 statement, not the instruction, after the change occurs.
2663 When you issue the @code{watch} command, @value{GDBN} reports
2666 Hardware watchpoint @var{num}: @var{expr}
2670 if it was able to set a hardware watchpoint.
2672 Currently, the @code{awatch} and @code{rwatch} commands can only set
2673 hardware watchpoints, because accesses to data that don't change the
2674 value of the watched expression cannot be detected without examining
2675 every instruction as it is being executed, and @value{GDBN} does not do
2676 that currently. If @value{GDBN} finds that it is unable to set a
2677 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2678 will print a message like this:
2681 Expression cannot be implemented with read/access watchpoint.
2684 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2685 data type of the watched expression is wider than what a hardware
2686 watchpoint on the target machine can handle. For example, some systems
2687 can only watch regions that are up to 4 bytes wide; on such systems you
2688 cannot set hardware watchpoints for an expression that yields a
2689 double-precision floating-point number (which is typically 8 bytes
2690 wide). As a work-around, it might be possible to break the large region
2691 into a series of smaller ones and watch them with separate watchpoints.
2693 If you set too many hardware watchpoints, @value{GDBN} might be unable
2694 to insert all of them when you resume the execution of your program.
2695 Since the precise number of active watchpoints is unknown until such
2696 time as the program is about to be resumed, @value{GDBN} might not be
2697 able to warn you about this when you set the watchpoints, and the
2698 warning will be printed only when the program is resumed:
2701 Hardware watchpoint @var{num}: Could not insert watchpoint
2705 If this happens, delete or disable some of the watchpoints.
2707 The SPARClite DSU will generate traps when a program accesses some data
2708 or instruction address that is assigned to the debug registers. For the
2709 data addresses, DSU facilitates the @code{watch} command. However the
2710 hardware breakpoint registers can only take two data watchpoints, and
2711 both watchpoints must be the same kind. For example, you can set two
2712 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2713 @strong{or} two with @code{awatch} commands, but you cannot set one
2714 watchpoint with one command and the other with a different command.
2715 @value{GDBN} will reject the command if you try to mix watchpoints.
2716 Delete or disable unused watchpoint commands before setting new ones.
2718 If you call a function interactively using @code{print} or @code{call},
2719 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2720 kind of breakpoint or the call completes.
2722 @value{GDBN} automatically deletes watchpoints that watch local
2723 (automatic) variables, or expressions that involve such variables, when
2724 they go out of scope, that is, when the execution leaves the block in
2725 which these variables were defined. In particular, when the program
2726 being debugged terminates, @emph{all} local variables go out of scope,
2727 and so only watchpoints that watch global variables remain set. If you
2728 rerun the program, you will need to set all such watchpoints again. One
2729 way of doing that would be to set a code breakpoint at the entry to the
2730 @code{main} function and when it breaks, set all the watchpoints.
2733 @cindex watchpoints and threads
2734 @cindex threads and watchpoints
2735 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2736 usefulness. With the current watchpoint implementation, @value{GDBN}
2737 can only watch the value of an expression @emph{in a single thread}. If
2738 you are confident that the expression can only change due to the current
2739 thread's activity (and if you are also confident that no other thread
2740 can become current), then you can use watchpoints as usual. However,
2741 @value{GDBN} may not notice when a non-current thread's activity changes
2744 @c FIXME: this is almost identical to the previous paragraph.
2745 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2746 have only limited usefulness. If @value{GDBN} creates a software
2747 watchpoint, it can only watch the value of an expression @emph{in a
2748 single thread}. If you are confident that the expression can only
2749 change due to the current thread's activity (and if you are also
2750 confident that no other thread can become current), then you can use
2751 software watchpoints as usual. However, @value{GDBN} may not notice
2752 when a non-current thread's activity changes the expression. (Hardware
2753 watchpoints, in contrast, watch an expression in all threads.)
2756 @xref{set remote hardware-watchpoint-limit}.
2758 @node Set Catchpoints
2759 @subsection Setting catchpoints
2760 @cindex catchpoints, setting
2761 @cindex exception handlers
2762 @cindex event handling
2764 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2765 kinds of program events, such as C@t{++} exceptions or the loading of a
2766 shared library. Use the @code{catch} command to set a catchpoint.
2770 @item catch @var{event}
2771 Stop when @var{event} occurs. @var{event} can be any of the following:
2775 The throwing of a C@t{++} exception.
2779 The catching of a C@t{++} exception.
2783 A call to @code{exec}. This is currently only available for HP-UX.
2787 A call to @code{fork}. This is currently only available for HP-UX.
2791 A call to @code{vfork}. This is currently only available for HP-UX.
2794 @itemx load @var{libname}
2796 The dynamic loading of any shared library, or the loading of the library
2797 @var{libname}. This is currently only available for HP-UX.
2800 @itemx unload @var{libname}
2801 @kindex catch unload
2802 The unloading of any dynamically loaded shared library, or the unloading
2803 of the library @var{libname}. This is currently only available for HP-UX.
2806 @item tcatch @var{event}
2807 Set a catchpoint that is enabled only for one stop. The catchpoint is
2808 automatically deleted after the first time the event is caught.
2812 Use the @code{info break} command to list the current catchpoints.
2814 There are currently some limitations to C@t{++} exception handling
2815 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2819 If you call a function interactively, @value{GDBN} normally returns
2820 control to you when the function has finished executing. If the call
2821 raises an exception, however, the call may bypass the mechanism that
2822 returns control to you and cause your program either to abort or to
2823 simply continue running until it hits a breakpoint, catches a signal
2824 that @value{GDBN} is listening for, or exits. This is the case even if
2825 you set a catchpoint for the exception; catchpoints on exceptions are
2826 disabled within interactive calls.
2829 You cannot raise an exception interactively.
2832 You cannot install an exception handler interactively.
2835 @cindex raise exceptions
2836 Sometimes @code{catch} is not the best way to debug exception handling:
2837 if you need to know exactly where an exception is raised, it is better to
2838 stop @emph{before} the exception handler is called, since that way you
2839 can see the stack before any unwinding takes place. If you set a
2840 breakpoint in an exception handler instead, it may not be easy to find
2841 out where the exception was raised.
2843 To stop just before an exception handler is called, you need some
2844 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2845 raised by calling a library function named @code{__raise_exception}
2846 which has the following ANSI C interface:
2849 /* @var{addr} is where the exception identifier is stored.
2850 @var{id} is the exception identifier. */
2851 void __raise_exception (void **addr, void *id);
2855 To make the debugger catch all exceptions before any stack
2856 unwinding takes place, set a breakpoint on @code{__raise_exception}
2857 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2859 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2860 that depends on the value of @var{id}, you can stop your program when
2861 a specific exception is raised. You can use multiple conditional
2862 breakpoints to stop your program when any of a number of exceptions are
2867 @subsection Deleting breakpoints
2869 @cindex clearing breakpoints, watchpoints, catchpoints
2870 @cindex deleting breakpoints, watchpoints, catchpoints
2871 It is often necessary to eliminate a breakpoint, watchpoint, or
2872 catchpoint once it has done its job and you no longer want your program
2873 to stop there. This is called @dfn{deleting} the breakpoint. A
2874 breakpoint that has been deleted no longer exists; it is forgotten.
2876 With the @code{clear} command you can delete breakpoints according to
2877 where they are in your program. With the @code{delete} command you can
2878 delete individual breakpoints, watchpoints, or catchpoints by specifying
2879 their breakpoint numbers.
2881 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2882 automatically ignores breakpoints on the first instruction to be executed
2883 when you continue execution without changing the execution address.
2888 Delete any breakpoints at the next instruction to be executed in the
2889 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2890 the innermost frame is selected, this is a good way to delete a
2891 breakpoint where your program just stopped.
2893 @item clear @var{function}
2894 @itemx clear @var{filename}:@var{function}
2895 Delete any breakpoints set at entry to the function @var{function}.
2897 @item clear @var{linenum}
2898 @itemx clear @var{filename}:@var{linenum}
2899 Delete any breakpoints set at or within the code of the specified line.
2901 @cindex delete breakpoints
2903 @kindex d @r{(@code{delete})}
2904 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2905 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2906 ranges specified as arguments. If no argument is specified, delete all
2907 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2908 confirm off}). You can abbreviate this command as @code{d}.
2912 @subsection Disabling breakpoints
2914 @kindex disable breakpoints
2915 @kindex enable breakpoints
2916 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2917 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2918 it had been deleted, but remembers the information on the breakpoint so
2919 that you can @dfn{enable} it again later.
2921 You disable and enable breakpoints, watchpoints, and catchpoints with
2922 the @code{enable} and @code{disable} commands, optionally specifying one
2923 or more breakpoint numbers as arguments. Use @code{info break} or
2924 @code{info watch} to print a list of breakpoints, watchpoints, and
2925 catchpoints if you do not know which numbers to use.
2927 A breakpoint, watchpoint, or catchpoint can have any of four different
2928 states of enablement:
2932 Enabled. The breakpoint stops your program. A breakpoint set
2933 with the @code{break} command starts out in this state.
2935 Disabled. The breakpoint has no effect on your program.
2937 Enabled once. The breakpoint stops your program, but then becomes
2940 Enabled for deletion. The breakpoint stops your program, but
2941 immediately after it does so it is deleted permanently. A breakpoint
2942 set with the @code{tbreak} command starts out in this state.
2945 You can use the following commands to enable or disable breakpoints,
2946 watchpoints, and catchpoints:
2949 @kindex disable breakpoints
2951 @kindex dis @r{(@code{disable})}
2952 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2953 Disable the specified breakpoints---or all breakpoints, if none are
2954 listed. A disabled breakpoint has no effect but is not forgotten. All
2955 options such as ignore-counts, conditions and commands are remembered in
2956 case the breakpoint is enabled again later. You may abbreviate
2957 @code{disable} as @code{dis}.
2959 @kindex enable breakpoints
2961 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2962 Enable the specified breakpoints (or all defined breakpoints). They
2963 become effective once again in stopping your program.
2965 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
2966 Enable the specified breakpoints temporarily. @value{GDBN} disables any
2967 of these breakpoints immediately after stopping your program.
2969 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
2970 Enable the specified breakpoints to work once, then die. @value{GDBN}
2971 deletes any of these breakpoints as soon as your program stops there.
2974 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
2975 @c confusing: tbreak is also initially enabled.
2976 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
2977 ,Setting breakpoints}), breakpoints that you set are initially enabled;
2978 subsequently, they become disabled or enabled only when you use one of
2979 the commands above. (The command @code{until} can set and delete a
2980 breakpoint of its own, but it does not change the state of your other
2981 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
2985 @subsection Break conditions
2986 @cindex conditional breakpoints
2987 @cindex breakpoint conditions
2989 @c FIXME what is scope of break condition expr? Context where wanted?
2990 @c in particular for a watchpoint?
2991 The simplest sort of breakpoint breaks every time your program reaches a
2992 specified place. You can also specify a @dfn{condition} for a
2993 breakpoint. A condition is just a Boolean expression in your
2994 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
2995 a condition evaluates the expression each time your program reaches it,
2996 and your program stops only if the condition is @emph{true}.
2998 This is the converse of using assertions for program validation; in that
2999 situation, you want to stop when the assertion is violated---that is,
3000 when the condition is false. In C, if you want to test an assertion expressed
3001 by the condition @var{assert}, you should set the condition
3002 @samp{! @var{assert}} on the appropriate breakpoint.
3004 Conditions are also accepted for watchpoints; you may not need them,
3005 since a watchpoint is inspecting the value of an expression anyhow---but
3006 it might be simpler, say, to just set a watchpoint on a variable name,
3007 and specify a condition that tests whether the new value is an interesting
3010 Break conditions can have side effects, and may even call functions in
3011 your program. This can be useful, for example, to activate functions
3012 that log program progress, or to use your own print functions to
3013 format special data structures. The effects are completely predictable
3014 unless there is another enabled breakpoint at the same address. (In
3015 that case, @value{GDBN} might see the other breakpoint first and stop your
3016 program without checking the condition of this one.) Note that
3017 breakpoint commands are usually more convenient and flexible than break
3019 purpose of performing side effects when a breakpoint is reached
3020 (@pxref{Break Commands, ,Breakpoint command lists}).
3022 Break conditions can be specified when a breakpoint is set, by using
3023 @samp{if} in the arguments to the @code{break} command. @xref{Set
3024 Breaks, ,Setting breakpoints}. They can also be changed at any time
3025 with the @code{condition} command.
3027 You can also use the @code{if} keyword with the @code{watch} command.
3028 The @code{catch} command does not recognize the @code{if} keyword;
3029 @code{condition} is the only way to impose a further condition on a
3034 @item condition @var{bnum} @var{expression}
3035 Specify @var{expression} as the break condition for breakpoint,
3036 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3037 breakpoint @var{bnum} stops your program only if the value of
3038 @var{expression} is true (nonzero, in C). When you use
3039 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3040 syntactic correctness, and to determine whether symbols in it have
3041 referents in the context of your breakpoint. If @var{expression} uses
3042 symbols not referenced in the context of the breakpoint, @value{GDBN}
3043 prints an error message:
3046 No symbol "foo" in current context.
3051 not actually evaluate @var{expression} at the time the @code{condition}
3052 command (or a command that sets a breakpoint with a condition, like
3053 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3055 @item condition @var{bnum}
3056 Remove the condition from breakpoint number @var{bnum}. It becomes
3057 an ordinary unconditional breakpoint.
3060 @cindex ignore count (of breakpoint)
3061 A special case of a breakpoint condition is to stop only when the
3062 breakpoint has been reached a certain number of times. This is so
3063 useful that there is a special way to do it, using the @dfn{ignore
3064 count} of the breakpoint. Every breakpoint has an ignore count, which
3065 is an integer. Most of the time, the ignore count is zero, and
3066 therefore has no effect. But if your program reaches a breakpoint whose
3067 ignore count is positive, then instead of stopping, it just decrements
3068 the ignore count by one and continues. As a result, if the ignore count
3069 value is @var{n}, the breakpoint does not stop the next @var{n} times
3070 your program reaches it.
3074 @item ignore @var{bnum} @var{count}
3075 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3076 The next @var{count} times the breakpoint is reached, your program's
3077 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3080 To make the breakpoint stop the next time it is reached, specify
3083 When you use @code{continue} to resume execution of your program from a
3084 breakpoint, you can specify an ignore count directly as an argument to
3085 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3086 Stepping,,Continuing and stepping}.
3088 If a breakpoint has a positive ignore count and a condition, the
3089 condition is not checked. Once the ignore count reaches zero,
3090 @value{GDBN} resumes checking the condition.
3092 You could achieve the effect of the ignore count with a condition such
3093 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3094 is decremented each time. @xref{Convenience Vars, ,Convenience
3098 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3101 @node Break Commands
3102 @subsection Breakpoint command lists
3104 @cindex breakpoint commands
3105 You can give any breakpoint (or watchpoint or catchpoint) a series of
3106 commands to execute when your program stops due to that breakpoint. For
3107 example, you might want to print the values of certain expressions, or
3108 enable other breakpoints.
3113 @item commands @r{[}@var{bnum}@r{]}
3114 @itemx @dots{} @var{command-list} @dots{}
3116 Specify a list of commands for breakpoint number @var{bnum}. The commands
3117 themselves appear on the following lines. Type a line containing just
3118 @code{end} to terminate the commands.
3120 To remove all commands from a breakpoint, type @code{commands} and
3121 follow it immediately with @code{end}; that is, give no commands.
3123 With no @var{bnum} argument, @code{commands} refers to the last
3124 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3125 recently encountered).
3128 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3129 disabled within a @var{command-list}.
3131 You can use breakpoint commands to start your program up again. Simply
3132 use the @code{continue} command, or @code{step}, or any other command
3133 that resumes execution.
3135 Any other commands in the command list, after a command that resumes
3136 execution, are ignored. This is because any time you resume execution
3137 (even with a simple @code{next} or @code{step}), you may encounter
3138 another breakpoint---which could have its own command list, leading to
3139 ambiguities about which list to execute.
3142 If the first command you specify in a command list is @code{silent}, the
3143 usual message about stopping at a breakpoint is not printed. This may
3144 be desirable for breakpoints that are to print a specific message and
3145 then continue. If none of the remaining commands print anything, you
3146 see no sign that the breakpoint was reached. @code{silent} is
3147 meaningful only at the beginning of a breakpoint command list.
3149 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3150 print precisely controlled output, and are often useful in silent
3151 breakpoints. @xref{Output, ,Commands for controlled output}.
3153 For example, here is how you could use breakpoint commands to print the
3154 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3160 printf "x is %d\n",x
3165 One application for breakpoint commands is to compensate for one bug so
3166 you can test for another. Put a breakpoint just after the erroneous line
3167 of code, give it a condition to detect the case in which something
3168 erroneous has been done, and give it commands to assign correct values
3169 to any variables that need them. End with the @code{continue} command
3170 so that your program does not stop, and start with the @code{silent}
3171 command so that no output is produced. Here is an example:
3182 @node Breakpoint Menus
3183 @subsection Breakpoint menus
3185 @cindex symbol overloading
3187 Some programming languages (notably C@t{++} and Objective-C) permit a
3188 single function name
3189 to be defined several times, for application in different contexts.
3190 This is called @dfn{overloading}. When a function name is overloaded,
3191 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3192 a breakpoint. If you realize this is a problem, you can use
3193 something like @samp{break @var{function}(@var{types})} to specify which
3194 particular version of the function you want. Otherwise, @value{GDBN} offers
3195 you a menu of numbered choices for different possible breakpoints, and
3196 waits for your selection with the prompt @samp{>}. The first two
3197 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3198 sets a breakpoint at each definition of @var{function}, and typing
3199 @kbd{0} aborts the @code{break} command without setting any new
3202 For example, the following session excerpt shows an attempt to set a
3203 breakpoint at the overloaded symbol @code{String::after}.
3204 We choose three particular definitions of that function name:
3206 @c FIXME! This is likely to change to show arg type lists, at least
3209 (@value{GDBP}) b String::after
3212 [2] file:String.cc; line number:867
3213 [3] file:String.cc; line number:860
3214 [4] file:String.cc; line number:875
3215 [5] file:String.cc; line number:853
3216 [6] file:String.cc; line number:846
3217 [7] file:String.cc; line number:735
3219 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3220 Breakpoint 2 at 0xb344: file String.cc, line 875.
3221 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3222 Multiple breakpoints were set.
3223 Use the "delete" command to delete unwanted
3229 @c @ifclear BARETARGET
3230 @node Error in Breakpoints
3231 @subsection ``Cannot insert breakpoints''
3233 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3235 Under some operating systems, breakpoints cannot be used in a program if
3236 any other process is running that program. In this situation,
3237 attempting to run or continue a program with a breakpoint causes
3238 @value{GDBN} to print an error message:
3241 Cannot insert breakpoints.
3242 The same program may be running in another process.
3245 When this happens, you have three ways to proceed:
3249 Remove or disable the breakpoints, then continue.
3252 Suspend @value{GDBN}, and copy the file containing your program to a new
3253 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3254 that @value{GDBN} should run your program under that name.
3255 Then start your program again.
3258 Relink your program so that the text segment is nonsharable, using the
3259 linker option @samp{-N}. The operating system limitation may not apply
3260 to nonsharable executables.
3264 A similar message can be printed if you request too many active
3265 hardware-assisted breakpoints and watchpoints:
3267 @c FIXME: the precise wording of this message may change; the relevant
3268 @c source change is not committed yet (Sep 3, 1999).
3270 Stopped; cannot insert breakpoints.
3271 You may have requested too many hardware breakpoints and watchpoints.
3275 This message is printed when you attempt to resume the program, since
3276 only then @value{GDBN} knows exactly how many hardware breakpoints and
3277 watchpoints it needs to insert.
3279 When this message is printed, you need to disable or remove some of the
3280 hardware-assisted breakpoints and watchpoints, and then continue.
3283 @node Continuing and Stepping
3284 @section Continuing and stepping
3288 @cindex resuming execution
3289 @dfn{Continuing} means resuming program execution until your program
3290 completes normally. In contrast, @dfn{stepping} means executing just
3291 one more ``step'' of your program, where ``step'' may mean either one
3292 line of source code, or one machine instruction (depending on what
3293 particular command you use). Either when continuing or when stepping,
3294 your program may stop even sooner, due to a breakpoint or a signal. (If
3295 it stops due to a signal, you may want to use @code{handle}, or use
3296 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3300 @kindex c @r{(@code{continue})}
3301 @kindex fg @r{(resume foreground execution)}
3302 @item continue @r{[}@var{ignore-count}@r{]}
3303 @itemx c @r{[}@var{ignore-count}@r{]}
3304 @itemx fg @r{[}@var{ignore-count}@r{]}
3305 Resume program execution, at the address where your program last stopped;
3306 any breakpoints set at that address are bypassed. The optional argument
3307 @var{ignore-count} allows you to specify a further number of times to
3308 ignore a breakpoint at this location; its effect is like that of
3309 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3311 The argument @var{ignore-count} is meaningful only when your program
3312 stopped due to a breakpoint. At other times, the argument to
3313 @code{continue} is ignored.
3315 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3316 debugged program is deemed to be the foreground program) are provided
3317 purely for convenience, and have exactly the same behavior as
3321 To resume execution at a different place, you can use @code{return}
3322 (@pxref{Returning, ,Returning from a function}) to go back to the
3323 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3324 different address}) to go to an arbitrary location in your program.
3326 A typical technique for using stepping is to set a breakpoint
3327 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3328 beginning of the function or the section of your program where a problem
3329 is believed to lie, run your program until it stops at that breakpoint,
3330 and then step through the suspect area, examining the variables that are
3331 interesting, until you see the problem happen.
3335 @kindex s @r{(@code{step})}
3337 Continue running your program until control reaches a different source
3338 line, then stop it and return control to @value{GDBN}. This command is
3339 abbreviated @code{s}.
3342 @c "without debugging information" is imprecise; actually "without line
3343 @c numbers in the debugging information". (gcc -g1 has debugging info but
3344 @c not line numbers). But it seems complex to try to make that
3345 @c distinction here.
3346 @emph{Warning:} If you use the @code{step} command while control is
3347 within a function that was compiled without debugging information,
3348 execution proceeds until control reaches a function that does have
3349 debugging information. Likewise, it will not step into a function which
3350 is compiled without debugging information. To step through functions
3351 without debugging information, use the @code{stepi} command, described
3355 The @code{step} command only stops at the first instruction of a source
3356 line. This prevents the multiple stops that could otherwise occur in
3357 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3358 to stop if a function that has debugging information is called within
3359 the line. In other words, @code{step} @emph{steps inside} any functions
3360 called within the line.
3362 Also, the @code{step} command only enters a function if there is line
3363 number information for the function. Otherwise it acts like the
3364 @code{next} command. This avoids problems when using @code{cc -gl}
3365 on MIPS machines. Previously, @code{step} entered subroutines if there
3366 was any debugging information about the routine.
3368 @item step @var{count}
3369 Continue running as in @code{step}, but do so @var{count} times. If a
3370 breakpoint is reached, or a signal not related to stepping occurs before
3371 @var{count} steps, stepping stops right away.
3374 @kindex n @r{(@code{next})}
3375 @item next @r{[}@var{count}@r{]}
3376 Continue to the next source line in the current (innermost) stack frame.
3377 This is similar to @code{step}, but function calls that appear within
3378 the line of code are executed without stopping. Execution stops when
3379 control reaches a different line of code at the original stack level
3380 that was executing when you gave the @code{next} command. This command
3381 is abbreviated @code{n}.
3383 An argument @var{count} is a repeat count, as for @code{step}.
3386 @c FIX ME!! Do we delete this, or is there a way it fits in with
3387 @c the following paragraph? --- Vctoria
3389 @c @code{next} within a function that lacks debugging information acts like
3390 @c @code{step}, but any function calls appearing within the code of the
3391 @c function are executed without stopping.
3393 The @code{next} command only stops at the first instruction of a
3394 source line. This prevents multiple stops that could otherwise occur in
3395 @code{switch} statements, @code{for} loops, etc.
3397 @kindex set step-mode
3399 @cindex functions without line info, and stepping
3400 @cindex stepping into functions with no line info
3401 @itemx set step-mode on
3402 The @code{set step-mode on} command causes the @code{step} command to
3403 stop at the first instruction of a function which contains no debug line
3404 information rather than stepping over it.
3406 This is useful in cases where you may be interested in inspecting the
3407 machine instructions of a function which has no symbolic info and do not
3408 want @value{GDBN} to automatically skip over this function.
3410 @item set step-mode off
3411 Causes the @code{step} command to step over any functions which contains no
3412 debug information. This is the default.
3416 Continue running until just after function in the selected stack frame
3417 returns. Print the returned value (if any).
3419 Contrast this with the @code{return} command (@pxref{Returning,
3420 ,Returning from a function}).
3423 @kindex u @r{(@code{until})}
3426 Continue running until a source line past the current line, in the
3427 current stack frame, is reached. This command is used to avoid single
3428 stepping through a loop more than once. It is like the @code{next}
3429 command, except that when @code{until} encounters a jump, it
3430 automatically continues execution until the program counter is greater
3431 than the address of the jump.
3433 This means that when you reach the end of a loop after single stepping
3434 though it, @code{until} makes your program continue execution until it
3435 exits the loop. In contrast, a @code{next} command at the end of a loop
3436 simply steps back to the beginning of the loop, which forces you to step
3437 through the next iteration.
3439 @code{until} always stops your program if it attempts to exit the current
3442 @code{until} may produce somewhat counterintuitive results if the order
3443 of machine code does not match the order of the source lines. For
3444 example, in the following excerpt from a debugging session, the @code{f}
3445 (@code{frame}) command shows that execution is stopped at line
3446 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3450 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3452 (@value{GDBP}) until
3453 195 for ( ; argc > 0; NEXTARG) @{
3456 This happened because, for execution efficiency, the compiler had
3457 generated code for the loop closure test at the end, rather than the
3458 start, of the loop---even though the test in a C @code{for}-loop is
3459 written before the body of the loop. The @code{until} command appeared
3460 to step back to the beginning of the loop when it advanced to this
3461 expression; however, it has not really gone to an earlier
3462 statement---not in terms of the actual machine code.
3464 @code{until} with no argument works by means of single
3465 instruction stepping, and hence is slower than @code{until} with an
3468 @item until @var{location}
3469 @itemx u @var{location}
3470 Continue running your program until either the specified location is
3471 reached, or the current stack frame returns. @var{location} is any of
3472 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3473 ,Setting breakpoints}). This form of the command uses breakpoints, and
3474 hence is quicker than @code{until} without an argument. The specified
3475 location is actually reached only if it is in the current frame. This
3476 implies that @code{until} can be used to skip over recursive function
3477 invocations. For instance in the code below, if the current location is
3478 line @code{96}, issuing @code{until 99} will execute the program up to
3479 line @code{99} in the same invocation of factorial, i.e. after the inner
3480 invocations have returned.
3483 94 int factorial (int value)
3485 96 if (value > 1) @{
3486 97 value *= factorial (value - 1);
3493 @kindex advance @var{location}
3494 @itemx advance @var{location}
3495 Continue running the program up to the given location. An argument is
3496 required, anything of the same form as arguments for the @code{break}
3497 command. Execution will also stop upon exit from the current stack
3498 frame. This command is similar to @code{until}, but @code{advance} will
3499 not skip over recursive function calls, and the target location doesn't
3500 have to be in the same frame as the current one.
3504 @kindex si @r{(@code{stepi})}
3506 @itemx stepi @var{arg}
3508 Execute one machine instruction, then stop and return to the debugger.
3510 It is often useful to do @samp{display/i $pc} when stepping by machine
3511 instructions. This makes @value{GDBN} automatically display the next
3512 instruction to be executed, each time your program stops. @xref{Auto
3513 Display,, Automatic display}.
3515 An argument is a repeat count, as in @code{step}.
3519 @kindex ni @r{(@code{nexti})}
3521 @itemx nexti @var{arg}
3523 Execute one machine instruction, but if it is a function call,
3524 proceed until the function returns.
3526 An argument is a repeat count, as in @code{next}.
3533 A signal is an asynchronous event that can happen in a program. The
3534 operating system defines the possible kinds of signals, and gives each
3535 kind a name and a number. For example, in Unix @code{SIGINT} is the
3536 signal a program gets when you type an interrupt character (often @kbd{C-c});
3537 @code{SIGSEGV} is the signal a program gets from referencing a place in
3538 memory far away from all the areas in use; @code{SIGALRM} occurs when
3539 the alarm clock timer goes off (which happens only if your program has
3540 requested an alarm).
3542 @cindex fatal signals
3543 Some signals, including @code{SIGALRM}, are a normal part of the
3544 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3545 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3546 program has not specified in advance some other way to handle the signal.
3547 @code{SIGINT} does not indicate an error in your program, but it is normally
3548 fatal so it can carry out the purpose of the interrupt: to kill the program.
3550 @value{GDBN} has the ability to detect any occurrence of a signal in your
3551 program. You can tell @value{GDBN} in advance what to do for each kind of
3554 @cindex handling signals
3555 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3556 @code{SIGALRM} be silently passed to your program
3557 (so as not to interfere with their role in the program's functioning)
3558 but to stop your program immediately whenever an error signal happens.
3559 You can change these settings with the @code{handle} command.
3562 @kindex info signals
3565 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3566 handle each one. You can use this to see the signal numbers of all
3567 the defined types of signals.
3569 @code{info handle} is an alias for @code{info signals}.
3572 @item handle @var{signal} @var{keywords}@dots{}
3573 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3574 can be the number of a signal or its name (with or without the
3575 @samp{SIG} at the beginning); a list of signal numbers of the form
3576 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3577 known signals. The @var{keywords} say what change to make.
3581 The keywords allowed by the @code{handle} command can be abbreviated.
3582 Their full names are:
3586 @value{GDBN} should not stop your program when this signal happens. It may
3587 still print a message telling you that the signal has come in.
3590 @value{GDBN} should stop your program when this signal happens. This implies
3591 the @code{print} keyword as well.
3594 @value{GDBN} should print a message when this signal happens.
3597 @value{GDBN} should not mention the occurrence of the signal at all. This
3598 implies the @code{nostop} keyword as well.
3602 @value{GDBN} should allow your program to see this signal; your program
3603 can handle the signal, or else it may terminate if the signal is fatal
3604 and not handled. @code{pass} and @code{noignore} are synonyms.
3608 @value{GDBN} should not allow your program to see this signal.
3609 @code{nopass} and @code{ignore} are synonyms.
3613 When a signal stops your program, the signal is not visible to the
3615 continue. Your program sees the signal then, if @code{pass} is in
3616 effect for the signal in question @emph{at that time}. In other words,
3617 after @value{GDBN} reports a signal, you can use the @code{handle}
3618 command with @code{pass} or @code{nopass} to control whether your
3619 program sees that signal when you continue.
3621 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3622 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3623 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3626 You can also use the @code{signal} command to prevent your program from
3627 seeing a signal, or cause it to see a signal it normally would not see,
3628 or to give it any signal at any time. For example, if your program stopped
3629 due to some sort of memory reference error, you might store correct
3630 values into the erroneous variables and continue, hoping to see more
3631 execution; but your program would probably terminate immediately as
3632 a result of the fatal signal once it saw the signal. To prevent this,
3633 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3637 @section Stopping and starting multi-thread programs
3639 When your program has multiple threads (@pxref{Threads,, Debugging
3640 programs with multiple threads}), you can choose whether to set
3641 breakpoints on all threads, or on a particular thread.
3644 @cindex breakpoints and threads
3645 @cindex thread breakpoints
3646 @kindex break @dots{} thread @var{threadno}
3647 @item break @var{linespec} thread @var{threadno}
3648 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3649 @var{linespec} specifies source lines; there are several ways of
3650 writing them, but the effect is always to specify some source line.
3652 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3653 to specify that you only want @value{GDBN} to stop the program when a
3654 particular thread reaches this breakpoint. @var{threadno} is one of the
3655 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3656 column of the @samp{info threads} display.
3658 If you do not specify @samp{thread @var{threadno}} when you set a
3659 breakpoint, the breakpoint applies to @emph{all} threads of your
3662 You can use the @code{thread} qualifier on conditional breakpoints as
3663 well; in this case, place @samp{thread @var{threadno}} before the
3664 breakpoint condition, like this:
3667 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3672 @cindex stopped threads
3673 @cindex threads, stopped
3674 Whenever your program stops under @value{GDBN} for any reason,
3675 @emph{all} threads of execution stop, not just the current thread. This
3676 allows you to examine the overall state of the program, including
3677 switching between threads, without worrying that things may change
3680 @cindex continuing threads
3681 @cindex threads, continuing
3682 Conversely, whenever you restart the program, @emph{all} threads start
3683 executing. @emph{This is true even when single-stepping} with commands
3684 like @code{step} or @code{next}.
3686 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3687 Since thread scheduling is up to your debugging target's operating
3688 system (not controlled by @value{GDBN}), other threads may
3689 execute more than one statement while the current thread completes a
3690 single step. Moreover, in general other threads stop in the middle of a
3691 statement, rather than at a clean statement boundary, when the program
3694 You might even find your program stopped in another thread after
3695 continuing or even single-stepping. This happens whenever some other
3696 thread runs into a breakpoint, a signal, or an exception before the
3697 first thread completes whatever you requested.
3699 On some OSes, you can lock the OS scheduler and thus allow only a single
3703 @item set scheduler-locking @var{mode}
3704 Set the scheduler locking mode. If it is @code{off}, then there is no
3705 locking and any thread may run at any time. If @code{on}, then only the
3706 current thread may run when the inferior is resumed. The @code{step}
3707 mode optimizes for single-stepping. It stops other threads from
3708 ``seizing the prompt'' by preempting the current thread while you are
3709 stepping. Other threads will only rarely (or never) get a chance to run
3710 when you step. They are more likely to run when you @samp{next} over a
3711 function call, and they are completely free to run when you use commands
3712 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3713 thread hits a breakpoint during its timeslice, they will never steal the
3714 @value{GDBN} prompt away from the thread that you are debugging.
3716 @item show scheduler-locking
3717 Display the current scheduler locking mode.
3722 @chapter Examining the Stack
3724 When your program has stopped, the first thing you need to know is where it
3725 stopped and how it got there.
3728 Each time your program performs a function call, information about the call
3730 That information includes the location of the call in your program,
3731 the arguments of the call,
3732 and the local variables of the function being called.
3733 The information is saved in a block of data called a @dfn{stack frame}.
3734 The stack frames are allocated in a region of memory called the @dfn{call
3737 When your program stops, the @value{GDBN} commands for examining the
3738 stack allow you to see all of this information.
3740 @cindex selected frame
3741 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3742 @value{GDBN} commands refer implicitly to the selected frame. In
3743 particular, whenever you ask @value{GDBN} for the value of a variable in
3744 your program, the value is found in the selected frame. There are
3745 special @value{GDBN} commands to select whichever frame you are
3746 interested in. @xref{Selection, ,Selecting a frame}.
3748 When your program stops, @value{GDBN} automatically selects the
3749 currently executing frame and describes it briefly, similar to the
3750 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3753 * Frames:: Stack frames
3754 * Backtrace:: Backtraces
3755 * Selection:: Selecting a frame
3756 * Frame Info:: Information on a frame
3761 @section Stack frames
3763 @cindex frame, definition
3765 The call stack is divided up into contiguous pieces called @dfn{stack
3766 frames}, or @dfn{frames} for short; each frame is the data associated
3767 with one call to one function. The frame contains the arguments given
3768 to the function, the function's local variables, and the address at
3769 which the function is executing.
3771 @cindex initial frame
3772 @cindex outermost frame
3773 @cindex innermost frame
3774 When your program is started, the stack has only one frame, that of the
3775 function @code{main}. This is called the @dfn{initial} frame or the
3776 @dfn{outermost} frame. Each time a function is called, a new frame is
3777 made. Each time a function returns, the frame for that function invocation
3778 is eliminated. If a function is recursive, there can be many frames for
3779 the same function. The frame for the function in which execution is
3780 actually occurring is called the @dfn{innermost} frame. This is the most
3781 recently created of all the stack frames that still exist.
3783 @cindex frame pointer
3784 Inside your program, stack frames are identified by their addresses. A
3785 stack frame consists of many bytes, each of which has its own address; each
3786 kind of computer has a convention for choosing one byte whose
3787 address serves as the address of the frame. Usually this address is kept
3788 in a register called the @dfn{frame pointer register} while execution is
3789 going on in that frame.
3791 @cindex frame number
3792 @value{GDBN} assigns numbers to all existing stack frames, starting with
3793 zero for the innermost frame, one for the frame that called it,
3794 and so on upward. These numbers do not really exist in your program;
3795 they are assigned by @value{GDBN} to give you a way of designating stack
3796 frames in @value{GDBN} commands.
3798 @c The -fomit-frame-pointer below perennially causes hbox overflow
3799 @c underflow problems.
3800 @cindex frameless execution
3801 Some compilers provide a way to compile functions so that they operate
3802 without stack frames. (For example, the @value{GCC} option
3804 @samp{-fomit-frame-pointer}
3806 generates functions without a frame.)
3807 This is occasionally done with heavily used library functions to save
3808 the frame setup time. @value{GDBN} has limited facilities for dealing
3809 with these function invocations. If the innermost function invocation
3810 has no stack frame, @value{GDBN} nevertheless regards it as though
3811 it had a separate frame, which is numbered zero as usual, allowing
3812 correct tracing of the function call chain. However, @value{GDBN} has
3813 no provision for frameless functions elsewhere in the stack.
3816 @kindex frame@r{, command}
3817 @cindex current stack frame
3818 @item frame @var{args}
3819 The @code{frame} command allows you to move from one stack frame to another,
3820 and to print the stack frame you select. @var{args} may be either the
3821 address of the frame or the stack frame number. Without an argument,
3822 @code{frame} prints the current stack frame.
3824 @kindex select-frame
3825 @cindex selecting frame silently
3827 The @code{select-frame} command allows you to move from one stack frame
3828 to another without printing the frame. This is the silent version of
3837 @cindex stack traces
3838 A backtrace is a summary of how your program got where it is. It shows one
3839 line per frame, for many frames, starting with the currently executing
3840 frame (frame zero), followed by its caller (frame one), and on up the
3845 @kindex bt @r{(@code{backtrace})}
3848 Print a backtrace of the entire stack: one line per frame for all
3849 frames in the stack.
3851 You can stop the backtrace at any time by typing the system interrupt
3852 character, normally @kbd{C-c}.
3854 @item backtrace @var{n}
3856 Similar, but print only the innermost @var{n} frames.
3858 @item backtrace -@var{n}
3860 Similar, but print only the outermost @var{n} frames.
3865 @kindex info s @r{(@code{info stack})}
3866 The names @code{where} and @code{info stack} (abbreviated @code{info s})
3867 are additional aliases for @code{backtrace}.
3869 Each line in the backtrace shows the frame number and the function name.
3870 The program counter value is also shown---unless you use @code{set
3871 print address off}. The backtrace also shows the source file name and
3872 line number, as well as the arguments to the function. The program
3873 counter value is omitted if it is at the beginning of the code for that
3876 Here is an example of a backtrace. It was made with the command
3877 @samp{bt 3}, so it shows the innermost three frames.
3881 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
3883 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
3884 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
3886 (More stack frames follow...)
3891 The display for frame zero does not begin with a program counter
3892 value, indicating that your program has stopped at the beginning of the
3893 code for line @code{993} of @code{builtin.c}.
3895 @kindex set backtrace-below-main
3896 @kindex show backtrace-below-main
3898 Most programs have a standard entry point---a place where system libraries
3899 and startup code transition into user code. For C this is @code{main}.
3900 When @value{GDBN} finds the entry function in a backtrace it will terminate
3901 the backtrace, to avoid tracing into highly system-specific (and generally
3902 uninteresting) code. If you need to examine the startup code, then you can
3903 change this behavior.
3906 @item set backtrace-below-main off
3907 Backtraces will stop when they encounter the user entry point. This is the
3910 @item set backtrace-below-main
3911 @itemx set backtrace-below-main on
3912 Backtraces will continue past the user entry point to the top of the stack.
3914 @item show backtrace-below-main
3915 Display the current backtrace policy.
3919 @section Selecting a frame
3921 Most commands for examining the stack and other data in your program work on
3922 whichever stack frame is selected at the moment. Here are the commands for
3923 selecting a stack frame; all of them finish by printing a brief description
3924 of the stack frame just selected.
3927 @kindex frame@r{, selecting}
3928 @kindex f @r{(@code{frame})}
3931 Select frame number @var{n}. Recall that frame zero is the innermost
3932 (currently executing) frame, frame one is the frame that called the
3933 innermost one, and so on. The highest-numbered frame is the one for
3936 @item frame @var{addr}
3938 Select the frame at address @var{addr}. This is useful mainly if the
3939 chaining of stack frames has been damaged by a bug, making it
3940 impossible for @value{GDBN} to assign numbers properly to all frames. In
3941 addition, this can be useful when your program has multiple stacks and
3942 switches between them.
3944 On the SPARC architecture, @code{frame} needs two addresses to
3945 select an arbitrary frame: a frame pointer and a stack pointer.
3947 On the MIPS and Alpha architecture, it needs two addresses: a stack
3948 pointer and a program counter.
3950 On the 29k architecture, it needs three addresses: a register stack
3951 pointer, a program counter, and a memory stack pointer.
3952 @c note to future updaters: this is conditioned on a flag
3953 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
3954 @c as of 27 Jan 1994.
3958 Move @var{n} frames up the stack. For positive numbers @var{n}, this
3959 advances toward the outermost frame, to higher frame numbers, to frames
3960 that have existed longer. @var{n} defaults to one.
3963 @kindex do @r{(@code{down})}
3965 Move @var{n} frames down the stack. For positive numbers @var{n}, this
3966 advances toward the innermost frame, to lower frame numbers, to frames
3967 that were created more recently. @var{n} defaults to one. You may
3968 abbreviate @code{down} as @code{do}.
3971 All of these commands end by printing two lines of output describing the
3972 frame. The first line shows the frame number, the function name, the
3973 arguments, and the source file and line number of execution in that
3974 frame. The second line shows the text of that source line.
3982 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
3984 10 read_input_file (argv[i]);
3988 After such a printout, the @code{list} command with no arguments
3989 prints ten lines centered on the point of execution in the frame.
3990 You can also edit the program at the point of execution with your favorite
3991 editing program by typing @code{edit}.
3992 @xref{List, ,Printing source lines},
3996 @kindex down-silently
3998 @item up-silently @var{n}
3999 @itemx down-silently @var{n}
4000 These two commands are variants of @code{up} and @code{down},
4001 respectively; they differ in that they do their work silently, without
4002 causing display of the new frame. They are intended primarily for use
4003 in @value{GDBN} command scripts, where the output might be unnecessary and
4008 @section Information about a frame
4010 There are several other commands to print information about the selected
4016 When used without any argument, this command does not change which
4017 frame is selected, but prints a brief description of the currently
4018 selected stack frame. It can be abbreviated @code{f}. With an
4019 argument, this command is used to select a stack frame.
4020 @xref{Selection, ,Selecting a frame}.
4023 @kindex info f @r{(@code{info frame})}
4026 This command prints a verbose description of the selected stack frame,
4031 the address of the frame
4033 the address of the next frame down (called by this frame)
4035 the address of the next frame up (caller of this frame)
4037 the language in which the source code corresponding to this frame is written
4039 the address of the frame's arguments
4041 the address of the frame's local variables
4043 the program counter saved in it (the address of execution in the caller frame)
4045 which registers were saved in the frame
4048 @noindent The verbose description is useful when
4049 something has gone wrong that has made the stack format fail to fit
4050 the usual conventions.
4052 @item info frame @var{addr}
4053 @itemx info f @var{addr}
4054 Print a verbose description of the frame at address @var{addr}, without
4055 selecting that frame. The selected frame remains unchanged by this
4056 command. This requires the same kind of address (more than one for some
4057 architectures) that you specify in the @code{frame} command.
4058 @xref{Selection, ,Selecting a frame}.
4062 Print the arguments of the selected frame, each on a separate line.
4066 Print the local variables of the selected frame, each on a separate
4067 line. These are all variables (declared either static or automatic)
4068 accessible at the point of execution of the selected frame.
4071 @cindex catch exceptions, list active handlers
4072 @cindex exception handlers, how to list
4074 Print a list of all the exception handlers that are active in the
4075 current stack frame at the current point of execution. To see other
4076 exception handlers, visit the associated frame (using the @code{up},
4077 @code{down}, or @code{frame} commands); then type @code{info catch}.
4078 @xref{Set Catchpoints, , Setting catchpoints}.
4084 @chapter Examining Source Files
4086 @value{GDBN} can print parts of your program's source, since the debugging
4087 information recorded in the program tells @value{GDBN} what source files were
4088 used to build it. When your program stops, @value{GDBN} spontaneously prints
4089 the line where it stopped. Likewise, when you select a stack frame
4090 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4091 execution in that frame has stopped. You can print other portions of
4092 source files by explicit command.
4094 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4095 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4096 @value{GDBN} under @sc{gnu} Emacs}.
4099 * List:: Printing source lines
4100 * Edit:: Editing source files
4101 * Search:: Searching source files
4102 * Source Path:: Specifying source directories
4103 * Machine Code:: Source and machine code
4107 @section Printing source lines
4110 @kindex l @r{(@code{list})}
4111 To print lines from a source file, use the @code{list} command
4112 (abbreviated @code{l}). By default, ten lines are printed.
4113 There are several ways to specify what part of the file you want to print.
4115 Here are the forms of the @code{list} command most commonly used:
4118 @item list @var{linenum}
4119 Print lines centered around line number @var{linenum} in the
4120 current source file.
4122 @item list @var{function}
4123 Print lines centered around the beginning of function
4127 Print more lines. If the last lines printed were printed with a
4128 @code{list} command, this prints lines following the last lines
4129 printed; however, if the last line printed was a solitary line printed
4130 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4131 Stack}), this prints lines centered around that line.
4134 Print lines just before the lines last printed.
4137 By default, @value{GDBN} prints ten source lines with any of these forms of
4138 the @code{list} command. You can change this using @code{set listsize}:
4141 @kindex set listsize
4142 @item set listsize @var{count}
4143 Make the @code{list} command display @var{count} source lines (unless
4144 the @code{list} argument explicitly specifies some other number).
4146 @kindex show listsize
4148 Display the number of lines that @code{list} prints.
4151 Repeating a @code{list} command with @key{RET} discards the argument,
4152 so it is equivalent to typing just @code{list}. This is more useful
4153 than listing the same lines again. An exception is made for an
4154 argument of @samp{-}; that argument is preserved in repetition so that
4155 each repetition moves up in the source file.
4158 In general, the @code{list} command expects you to supply zero, one or two
4159 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4160 of writing them, but the effect is always to specify some source line.
4161 Here is a complete description of the possible arguments for @code{list}:
4164 @item list @var{linespec}
4165 Print lines centered around the line specified by @var{linespec}.
4167 @item list @var{first},@var{last}
4168 Print lines from @var{first} to @var{last}. Both arguments are
4171 @item list ,@var{last}
4172 Print lines ending with @var{last}.
4174 @item list @var{first},
4175 Print lines starting with @var{first}.
4178 Print lines just after the lines last printed.
4181 Print lines just before the lines last printed.
4184 As described in the preceding table.
4187 Here are the ways of specifying a single source line---all the
4192 Specifies line @var{number} of the current source file.
4193 When a @code{list} command has two linespecs, this refers to
4194 the same source file as the first linespec.
4197 Specifies the line @var{offset} lines after the last line printed.
4198 When used as the second linespec in a @code{list} command that has
4199 two, this specifies the line @var{offset} lines down from the
4203 Specifies the line @var{offset} lines before the last line printed.
4205 @item @var{filename}:@var{number}
4206 Specifies line @var{number} in the source file @var{filename}.
4208 @item @var{function}
4209 Specifies the line that begins the body of the function @var{function}.
4210 For example: in C, this is the line with the open brace.
4212 @item @var{filename}:@var{function}
4213 Specifies the line of the open-brace that begins the body of the
4214 function @var{function} in the file @var{filename}. You only need the
4215 file name with a function name to avoid ambiguity when there are
4216 identically named functions in different source files.
4218 @item *@var{address}
4219 Specifies the line containing the program address @var{address}.
4220 @var{address} may be any expression.
4224 @section Editing source files
4225 @cindex editing source files
4228 @kindex e @r{(@code{edit})}
4229 To edit the lines in a source file, use the @code{edit} command.
4230 The editing program of your choice
4231 is invoked with the current line set to
4232 the active line in the program.
4233 Alternatively, there are several ways to specify what part of the file you
4234 want to print if you want to see other parts of the program.
4236 Here are the forms of the @code{edit} command most commonly used:
4240 Edit the current source file at the active line number in the program.
4242 @item edit @var{number}
4243 Edit the current source file with @var{number} as the active line number.
4245 @item edit @var{function}
4246 Edit the file containing @var{function} at the beginning of its definition.
4248 @item edit @var{filename}:@var{number}
4249 Specifies line @var{number} in the source file @var{filename}.
4251 @item edit @var{filename}:@var{function}
4252 Specifies the line that begins the body of the
4253 function @var{function} in the file @var{filename}. You only need the
4254 file name with a function name to avoid ambiguity when there are
4255 identically named functions in different source files.
4257 @item edit *@var{address}
4258 Specifies the line containing the program address @var{address}.
4259 @var{address} may be any expression.
4262 @subsection Choosing your editor
4263 You can customize @value{GDBN} to use any editor you want
4265 The only restriction is that your editor (say @code{ex}), recognizes the
4266 following command-line syntax:
4268 ex +@var{number} file
4270 The optional numeric value +@var{number} designates the active line in
4271 the file.}. By default, it is @value{EDITOR}, but you can change this
4272 by setting the environment variable @code{EDITOR} before using
4273 @value{GDBN}. For example, to configure @value{GDBN} to use the
4274 @code{vi} editor, you could use these commands with the @code{sh} shell:
4280 or in the @code{csh} shell,
4282 setenv EDITOR /usr/bin/vi
4287 @section Searching source files
4289 @kindex reverse-search
4291 There are two commands for searching through the current source file for a
4296 @kindex forward-search
4297 @item forward-search @var{regexp}
4298 @itemx search @var{regexp}
4299 The command @samp{forward-search @var{regexp}} checks each line,
4300 starting with the one following the last line listed, for a match for
4301 @var{regexp}. It lists the line that is found. You can use the
4302 synonym @samp{search @var{regexp}} or abbreviate the command name as
4305 @item reverse-search @var{regexp}
4306 The command @samp{reverse-search @var{regexp}} checks each line, starting
4307 with the one before the last line listed and going backward, for a match
4308 for @var{regexp}. It lists the line that is found. You can abbreviate
4309 this command as @code{rev}.
4313 @section Specifying source directories
4316 @cindex directories for source files
4317 Executable programs sometimes do not record the directories of the source
4318 files from which they were compiled, just the names. Even when they do,
4319 the directories could be moved between the compilation and your debugging
4320 session. @value{GDBN} has a list of directories to search for source files;
4321 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4322 it tries all the directories in the list, in the order they are present
4323 in the list, until it finds a file with the desired name. Note that
4324 the executable search path is @emph{not} used for this purpose. Neither is
4325 the current working directory, unless it happens to be in the source
4328 If @value{GDBN} cannot find a source file in the source path, and the
4329 object program records a directory, @value{GDBN} tries that directory
4330 too. If the source path is empty, and there is no record of the
4331 compilation directory, @value{GDBN} looks in the current directory as a
4334 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4335 any information it has cached about where source files are found and where
4336 each line is in the file.
4340 When you start @value{GDBN}, its source path includes only @samp{cdir}
4341 and @samp{cwd}, in that order.
4342 To add other directories, use the @code{directory} command.
4345 @item directory @var{dirname} @dots{}
4346 @item dir @var{dirname} @dots{}
4347 Add directory @var{dirname} to the front of the source path. Several
4348 directory names may be given to this command, separated by @samp{:}
4349 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4350 part of absolute file names) or
4351 whitespace. You may specify a directory that is already in the source
4352 path; this moves it forward, so @value{GDBN} searches it sooner.
4356 @vindex $cdir@r{, convenience variable}
4357 @vindex $cwdr@r{, convenience variable}
4358 @cindex compilation directory
4359 @cindex current directory
4360 @cindex working directory
4361 @cindex directory, current
4362 @cindex directory, compilation
4363 You can use the string @samp{$cdir} to refer to the compilation
4364 directory (if one is recorded), and @samp{$cwd} to refer to the current
4365 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4366 tracks the current working directory as it changes during your @value{GDBN}
4367 session, while the latter is immediately expanded to the current
4368 directory at the time you add an entry to the source path.
4371 Reset the source path to empty again. This requires confirmation.
4373 @c RET-repeat for @code{directory} is explicitly disabled, but since
4374 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4376 @item show directories
4377 @kindex show directories
4378 Print the source path: show which directories it contains.
4381 If your source path is cluttered with directories that are no longer of
4382 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4383 versions of source. You can correct the situation as follows:
4387 Use @code{directory} with no argument to reset the source path to empty.
4390 Use @code{directory} with suitable arguments to reinstall the
4391 directories you want in the source path. You can add all the
4392 directories in one command.
4396 @section Source and machine code
4398 You can use the command @code{info line} to map source lines to program
4399 addresses (and vice versa), and the command @code{disassemble} to display
4400 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4401 mode, the @code{info line} command causes the arrow to point to the
4402 line specified. Also, @code{info line} prints addresses in symbolic form as
4407 @item info line @var{linespec}
4408 Print the starting and ending addresses of the compiled code for
4409 source line @var{linespec}. You can specify source lines in any of
4410 the ways understood by the @code{list} command (@pxref{List, ,Printing
4414 For example, we can use @code{info line} to discover the location of
4415 the object code for the first line of function
4416 @code{m4_changequote}:
4418 @c FIXME: I think this example should also show the addresses in
4419 @c symbolic form, as they usually would be displayed.
4421 (@value{GDBP}) info line m4_changequote
4422 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4426 We can also inquire (using @code{*@var{addr}} as the form for
4427 @var{linespec}) what source line covers a particular address:
4429 (@value{GDBP}) info line *0x63ff
4430 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4433 @cindex @code{$_} and @code{info line}
4434 @kindex x@r{(examine), and} info line
4435 After @code{info line}, the default address for the @code{x} command
4436 is changed to the starting address of the line, so that @samp{x/i} is
4437 sufficient to begin examining the machine code (@pxref{Memory,
4438 ,Examining memory}). Also, this address is saved as the value of the
4439 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4444 @cindex assembly instructions
4445 @cindex instructions, assembly
4446 @cindex machine instructions
4447 @cindex listing machine instructions
4449 This specialized command dumps a range of memory as machine
4450 instructions. The default memory range is the function surrounding the
4451 program counter of the selected frame. A single argument to this
4452 command is a program counter value; @value{GDBN} dumps the function
4453 surrounding this value. Two arguments specify a range of addresses
4454 (first inclusive, second exclusive) to dump.
4457 The following example shows the disassembly of a range of addresses of
4458 HP PA-RISC 2.0 code:
4461 (@value{GDBP}) disas 0x32c4 0x32e4
4462 Dump of assembler code from 0x32c4 to 0x32e4:
4463 0x32c4 <main+204>: addil 0,dp
4464 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4465 0x32cc <main+212>: ldil 0x3000,r31
4466 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4467 0x32d4 <main+220>: ldo 0(r31),rp
4468 0x32d8 <main+224>: addil -0x800,dp
4469 0x32dc <main+228>: ldo 0x588(r1),r26
4470 0x32e0 <main+232>: ldil 0x3000,r31
4471 End of assembler dump.
4474 Some architectures have more than one commonly-used set of instruction
4475 mnemonics or other syntax.
4478 @kindex set disassembly-flavor
4479 @cindex assembly instructions
4480 @cindex instructions, assembly
4481 @cindex machine instructions
4482 @cindex listing machine instructions
4483 @cindex Intel disassembly flavor
4484 @cindex AT&T disassembly flavor
4485 @item set disassembly-flavor @var{instruction-set}
4486 Select the instruction set to use when disassembling the
4487 program via the @code{disassemble} or @code{x/i} commands.
4489 Currently this command is only defined for the Intel x86 family. You
4490 can set @var{instruction-set} to either @code{intel} or @code{att}.
4491 The default is @code{att}, the AT&T flavor used by default by Unix
4492 assemblers for x86-based targets.
4497 @chapter Examining Data
4499 @cindex printing data
4500 @cindex examining data
4503 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4504 @c document because it is nonstandard... Under Epoch it displays in a
4505 @c different window or something like that.
4506 The usual way to examine data in your program is with the @code{print}
4507 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4508 evaluates and prints the value of an expression of the language your
4509 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4510 Different Languages}).
4513 @item print @var{expr}
4514 @itemx print /@var{f} @var{expr}
4515 @var{expr} is an expression (in the source language). By default the
4516 value of @var{expr} is printed in a format appropriate to its data type;
4517 you can choose a different format by specifying @samp{/@var{f}}, where
4518 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4522 @itemx print /@var{f}
4523 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4524 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4525 conveniently inspect the same value in an alternative format.
4528 A more low-level way of examining data is with the @code{x} command.
4529 It examines data in memory at a specified address and prints it in a
4530 specified format. @xref{Memory, ,Examining memory}.
4532 If you are interested in information about types, or about how the
4533 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4534 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4538 * Expressions:: Expressions
4539 * Variables:: Program variables
4540 * Arrays:: Artificial arrays
4541 * Output Formats:: Output formats
4542 * Memory:: Examining memory
4543 * Auto Display:: Automatic display
4544 * Print Settings:: Print settings
4545 * Value History:: Value history
4546 * Convenience Vars:: Convenience variables
4547 * Registers:: Registers
4548 * Floating Point Hardware:: Floating point hardware
4549 * Vector Unit:: Vector Unit
4550 * Memory Region Attributes:: Memory region attributes
4551 * Dump/Restore Files:: Copy between memory and a file
4552 * Character Sets:: Debugging programs that use a different
4553 character set than GDB does
4557 @section Expressions
4560 @code{print} and many other @value{GDBN} commands accept an expression and
4561 compute its value. Any kind of constant, variable or operator defined
4562 by the programming language you are using is valid in an expression in
4563 @value{GDBN}. This includes conditional expressions, function calls,
4564 casts, and string constants. It also includes preprocessor macros, if
4565 you compiled your program to include this information; see
4568 @value{GDBN} supports array constants in expressions input by
4569 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4570 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4571 memory that is @code{malloc}ed in the target program.
4573 Because C is so widespread, most of the expressions shown in examples in
4574 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4575 Languages}, for information on how to use expressions in other
4578 In this section, we discuss operators that you can use in @value{GDBN}
4579 expressions regardless of your programming language.
4581 Casts are supported in all languages, not just in C, because it is so
4582 useful to cast a number into a pointer in order to examine a structure
4583 at that address in memory.
4584 @c FIXME: casts supported---Mod2 true?
4586 @value{GDBN} supports these operators, in addition to those common
4587 to programming languages:
4591 @samp{@@} is a binary operator for treating parts of memory as arrays.
4592 @xref{Arrays, ,Artificial arrays}, for more information.
4595 @samp{::} allows you to specify a variable in terms of the file or
4596 function where it is defined. @xref{Variables, ,Program variables}.
4598 @cindex @{@var{type}@}
4599 @cindex type casting memory
4600 @cindex memory, viewing as typed object
4601 @cindex casts, to view memory
4602 @item @{@var{type}@} @var{addr}
4603 Refers to an object of type @var{type} stored at address @var{addr} in
4604 memory. @var{addr} may be any expression whose value is an integer or
4605 pointer (but parentheses are required around binary operators, just as in
4606 a cast). This construct is allowed regardless of what kind of data is
4607 normally supposed to reside at @var{addr}.
4611 @section Program variables
4613 The most common kind of expression to use is the name of a variable
4616 Variables in expressions are understood in the selected stack frame
4617 (@pxref{Selection, ,Selecting a frame}); they must be either:
4621 global (or file-static)
4628 visible according to the scope rules of the
4629 programming language from the point of execution in that frame
4632 @noindent This means that in the function
4647 you can examine and use the variable @code{a} whenever your program is
4648 executing within the function @code{foo}, but you can only use or
4649 examine the variable @code{b} while your program is executing inside
4650 the block where @code{b} is declared.
4652 @cindex variable name conflict
4653 There is an exception: you can refer to a variable or function whose
4654 scope is a single source file even if the current execution point is not
4655 in this file. But it is possible to have more than one such variable or
4656 function with the same name (in different source files). If that
4657 happens, referring to that name has unpredictable effects. If you wish,
4658 you can specify a static variable in a particular function or file,
4659 using the colon-colon notation:
4661 @cindex colon-colon, context for variables/functions
4663 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4664 @cindex @code{::}, context for variables/functions
4667 @var{file}::@var{variable}
4668 @var{function}::@var{variable}
4672 Here @var{file} or @var{function} is the name of the context for the
4673 static @var{variable}. In the case of file names, you can use quotes to
4674 make sure @value{GDBN} parses the file name as a single word---for example,
4675 to print a global value of @code{x} defined in @file{f2.c}:
4678 (@value{GDBP}) p 'f2.c'::x
4681 @cindex C@t{++} scope resolution
4682 This use of @samp{::} is very rarely in conflict with the very similar
4683 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4684 scope resolution operator in @value{GDBN} expressions.
4685 @c FIXME: Um, so what happens in one of those rare cases where it's in
4688 @cindex wrong values
4689 @cindex variable values, wrong
4691 @emph{Warning:} Occasionally, a local variable may appear to have the
4692 wrong value at certain points in a function---just after entry to a new
4693 scope, and just before exit.
4695 You may see this problem when you are stepping by machine instructions.
4696 This is because, on most machines, it takes more than one instruction to
4697 set up a stack frame (including local variable definitions); if you are
4698 stepping by machine instructions, variables may appear to have the wrong
4699 values until the stack frame is completely built. On exit, it usually
4700 also takes more than one machine instruction to destroy a stack frame;
4701 after you begin stepping through that group of instructions, local
4702 variable definitions may be gone.
4704 This may also happen when the compiler does significant optimizations.
4705 To be sure of always seeing accurate values, turn off all optimization
4708 @cindex ``No symbol "foo" in current context''
4709 Another possible effect of compiler optimizations is to optimize
4710 unused variables out of existence, or assign variables to registers (as
4711 opposed to memory addresses). Depending on the support for such cases
4712 offered by the debug info format used by the compiler, @value{GDBN}
4713 might not be able to display values for such local variables. If that
4714 happens, @value{GDBN} will print a message like this:
4717 No symbol "foo" in current context.
4720 To solve such problems, either recompile without optimizations, or use a
4721 different debug info format, if the compiler supports several such
4722 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler
4723 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4724 produces debug info in a format that is superior to formats such as
4725 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4726 an effective form for debug info. @xref{Debugging Options,,Options
4727 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4731 @section Artificial arrays
4733 @cindex artificial array
4734 @kindex @@@r{, referencing memory as an array}
4735 It is often useful to print out several successive objects of the
4736 same type in memory; a section of an array, or an array of
4737 dynamically determined size for which only a pointer exists in the
4740 You can do this by referring to a contiguous span of memory as an
4741 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4742 operand of @samp{@@} should be the first element of the desired array
4743 and be an individual object. The right operand should be the desired length
4744 of the array. The result is an array value whose elements are all of
4745 the type of the left argument. The first element is actually the left
4746 argument; the second element comes from bytes of memory immediately
4747 following those that hold the first element, and so on. Here is an
4748 example. If a program says
4751 int *array = (int *) malloc (len * sizeof (int));
4755 you can print the contents of @code{array} with
4761 The left operand of @samp{@@} must reside in memory. Array values made
4762 with @samp{@@} in this way behave just like other arrays in terms of
4763 subscripting, and are coerced to pointers when used in expressions.
4764 Artificial arrays most often appear in expressions via the value history
4765 (@pxref{Value History, ,Value history}), after printing one out.
4767 Another way to create an artificial array is to use a cast.
4768 This re-interprets a value as if it were an array.
4769 The value need not be in memory:
4771 (@value{GDBP}) p/x (short[2])0x12345678
4772 $1 = @{0x1234, 0x5678@}
4775 As a convenience, if you leave the array length out (as in
4776 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4777 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4779 (@value{GDBP}) p/x (short[])0x12345678
4780 $2 = @{0x1234, 0x5678@}
4783 Sometimes the artificial array mechanism is not quite enough; in
4784 moderately complex data structures, the elements of interest may not
4785 actually be adjacent---for example, if you are interested in the values
4786 of pointers in an array. One useful work-around in this situation is
4787 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4788 variables}) as a counter in an expression that prints the first
4789 interesting value, and then repeat that expression via @key{RET}. For
4790 instance, suppose you have an array @code{dtab} of pointers to
4791 structures, and you are interested in the values of a field @code{fv}
4792 in each structure. Here is an example of what you might type:
4802 @node Output Formats
4803 @section Output formats
4805 @cindex formatted output
4806 @cindex output formats
4807 By default, @value{GDBN} prints a value according to its data type. Sometimes
4808 this is not what you want. For example, you might want to print a number
4809 in hex, or a pointer in decimal. Or you might want to view data in memory
4810 at a certain address as a character string or as an instruction. To do
4811 these things, specify an @dfn{output format} when you print a value.
4813 The simplest use of output formats is to say how to print a value
4814 already computed. This is done by starting the arguments of the
4815 @code{print} command with a slash and a format letter. The format
4816 letters supported are:
4820 Regard the bits of the value as an integer, and print the integer in
4824 Print as integer in signed decimal.
4827 Print as integer in unsigned decimal.
4830 Print as integer in octal.
4833 Print as integer in binary. The letter @samp{t} stands for ``two''.
4834 @footnote{@samp{b} cannot be used because these format letters are also
4835 used with the @code{x} command, where @samp{b} stands for ``byte'';
4836 see @ref{Memory,,Examining memory}.}
4839 @cindex unknown address, locating
4840 @cindex locate address
4841 Print as an address, both absolute in hexadecimal and as an offset from
4842 the nearest preceding symbol. You can use this format used to discover
4843 where (in what function) an unknown address is located:
4846 (@value{GDBP}) p/a 0x54320
4847 $3 = 0x54320 <_initialize_vx+396>
4851 The command @code{info symbol 0x54320} yields similar results.
4852 @xref{Symbols, info symbol}.
4855 Regard as an integer and print it as a character constant.
4858 Regard the bits of the value as a floating point number and print
4859 using typical floating point syntax.
4862 For example, to print the program counter in hex (@pxref{Registers}), type
4869 Note that no space is required before the slash; this is because command
4870 names in @value{GDBN} cannot contain a slash.
4872 To reprint the last value in the value history with a different format,
4873 you can use the @code{print} command with just a format and no
4874 expression. For example, @samp{p/x} reprints the last value in hex.
4877 @section Examining memory
4879 You can use the command @code{x} (for ``examine'') to examine memory in
4880 any of several formats, independently of your program's data types.
4882 @cindex examining memory
4884 @kindex x @r{(examine memory)}
4885 @item x/@var{nfu} @var{addr}
4888 Use the @code{x} command to examine memory.
4891 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
4892 much memory to display and how to format it; @var{addr} is an
4893 expression giving the address where you want to start displaying memory.
4894 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
4895 Several commands set convenient defaults for @var{addr}.
4898 @item @var{n}, the repeat count
4899 The repeat count is a decimal integer; the default is 1. It specifies
4900 how much memory (counting by units @var{u}) to display.
4901 @c This really is **decimal**; unaffected by 'set radix' as of GDB
4904 @item @var{f}, the display format
4905 The display format is one of the formats used by @code{print},
4906 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
4907 The default is @samp{x} (hexadecimal) initially.
4908 The default changes each time you use either @code{x} or @code{print}.
4910 @item @var{u}, the unit size
4911 The unit size is any of
4917 Halfwords (two bytes).
4919 Words (four bytes). This is the initial default.
4921 Giant words (eight bytes).
4924 Each time you specify a unit size with @code{x}, that size becomes the
4925 default unit the next time you use @code{x}. (For the @samp{s} and
4926 @samp{i} formats, the unit size is ignored and is normally not written.)
4928 @item @var{addr}, starting display address
4929 @var{addr} is the address where you want @value{GDBN} to begin displaying
4930 memory. The expression need not have a pointer value (though it may);
4931 it is always interpreted as an integer address of a byte of memory.
4932 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
4933 @var{addr} is usually just after the last address examined---but several
4934 other commands also set the default address: @code{info breakpoints} (to
4935 the address of the last breakpoint listed), @code{info line} (to the
4936 starting address of a line), and @code{print} (if you use it to display
4937 a value from memory).
4940 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
4941 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
4942 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
4943 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
4944 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
4946 Since the letters indicating unit sizes are all distinct from the
4947 letters specifying output formats, you do not have to remember whether
4948 unit size or format comes first; either order works. The output
4949 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
4950 (However, the count @var{n} must come first; @samp{wx4} does not work.)
4952 Even though the unit size @var{u} is ignored for the formats @samp{s}
4953 and @samp{i}, you might still want to use a count @var{n}; for example,
4954 @samp{3i} specifies that you want to see three machine instructions,
4955 including any operands. The command @code{disassemble} gives an
4956 alternative way of inspecting machine instructions; see @ref{Machine
4957 Code,,Source and machine code}.
4959 All the defaults for the arguments to @code{x} are designed to make it
4960 easy to continue scanning memory with minimal specifications each time
4961 you use @code{x}. For example, after you have inspected three machine
4962 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
4963 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
4964 the repeat count @var{n} is used again; the other arguments default as
4965 for successive uses of @code{x}.
4967 @cindex @code{$_}, @code{$__}, and value history
4968 The addresses and contents printed by the @code{x} command are not saved
4969 in the value history because there is often too much of them and they
4970 would get in the way. Instead, @value{GDBN} makes these values available for
4971 subsequent use in expressions as values of the convenience variables
4972 @code{$_} and @code{$__}. After an @code{x} command, the last address
4973 examined is available for use in expressions in the convenience variable
4974 @code{$_}. The contents of that address, as examined, are available in
4975 the convenience variable @code{$__}.
4977 If the @code{x} command has a repeat count, the address and contents saved
4978 are from the last memory unit printed; this is not the same as the last
4979 address printed if several units were printed on the last line of output.
4982 @section Automatic display
4983 @cindex automatic display
4984 @cindex display of expressions
4986 If you find that you want to print the value of an expression frequently
4987 (to see how it changes), you might want to add it to the @dfn{automatic
4988 display list} so that @value{GDBN} prints its value each time your program stops.
4989 Each expression added to the list is given a number to identify it;
4990 to remove an expression from the list, you specify that number.
4991 The automatic display looks like this:
4995 3: bar[5] = (struct hack *) 0x3804
4999 This display shows item numbers, expressions and their current values. As with
5000 displays you request manually using @code{x} or @code{print}, you can
5001 specify the output format you prefer; in fact, @code{display} decides
5002 whether to use @code{print} or @code{x} depending on how elaborate your
5003 format specification is---it uses @code{x} if you specify a unit size,
5004 or one of the two formats (@samp{i} and @samp{s}) that are only
5005 supported by @code{x}; otherwise it uses @code{print}.
5009 @item display @var{expr}
5010 Add the expression @var{expr} to the list of expressions to display
5011 each time your program stops. @xref{Expressions, ,Expressions}.
5013 @code{display} does not repeat if you press @key{RET} again after using it.
5015 @item display/@var{fmt} @var{expr}
5016 For @var{fmt} specifying only a display format and not a size or
5017 count, add the expression @var{expr} to the auto-display list but
5018 arrange to display it each time in the specified format @var{fmt}.
5019 @xref{Output Formats,,Output formats}.
5021 @item display/@var{fmt} @var{addr}
5022 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5023 number of units, add the expression @var{addr} as a memory address to
5024 be examined each time your program stops. Examining means in effect
5025 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5028 For example, @samp{display/i $pc} can be helpful, to see the machine
5029 instruction about to be executed each time execution stops (@samp{$pc}
5030 is a common name for the program counter; @pxref{Registers, ,Registers}).
5033 @kindex delete display
5035 @item undisplay @var{dnums}@dots{}
5036 @itemx delete display @var{dnums}@dots{}
5037 Remove item numbers @var{dnums} from the list of expressions to display.
5039 @code{undisplay} does not repeat if you press @key{RET} after using it.
5040 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5042 @kindex disable display
5043 @item disable display @var{dnums}@dots{}
5044 Disable the display of item numbers @var{dnums}. A disabled display
5045 item is not printed automatically, but is not forgotten. It may be
5046 enabled again later.
5048 @kindex enable display
5049 @item enable display @var{dnums}@dots{}
5050 Enable display of item numbers @var{dnums}. It becomes effective once
5051 again in auto display of its expression, until you specify otherwise.
5054 Display the current values of the expressions on the list, just as is
5055 done when your program stops.
5057 @kindex info display
5059 Print the list of expressions previously set up to display
5060 automatically, each one with its item number, but without showing the
5061 values. This includes disabled expressions, which are marked as such.
5062 It also includes expressions which would not be displayed right now
5063 because they refer to automatic variables not currently available.
5066 If a display expression refers to local variables, then it does not make
5067 sense outside the lexical context for which it was set up. Such an
5068 expression is disabled when execution enters a context where one of its
5069 variables is not defined. For example, if you give the command
5070 @code{display last_char} while inside a function with an argument
5071 @code{last_char}, @value{GDBN} displays this argument while your program
5072 continues to stop inside that function. When it stops elsewhere---where
5073 there is no variable @code{last_char}---the display is disabled
5074 automatically. The next time your program stops where @code{last_char}
5075 is meaningful, you can enable the display expression once again.
5077 @node Print Settings
5078 @section Print settings
5080 @cindex format options
5081 @cindex print settings
5082 @value{GDBN} provides the following ways to control how arrays, structures,
5083 and symbols are printed.
5086 These settings are useful for debugging programs in any language:
5089 @kindex set print address
5090 @item set print address
5091 @itemx set print address on
5092 @value{GDBN} prints memory addresses showing the location of stack
5093 traces, structure values, pointer values, breakpoints, and so forth,
5094 even when it also displays the contents of those addresses. The default
5095 is @code{on}. For example, this is what a stack frame display looks like with
5096 @code{set print address on}:
5101 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5103 530 if (lquote != def_lquote)
5107 @item set print address off
5108 Do not print addresses when displaying their contents. For example,
5109 this is the same stack frame displayed with @code{set print address off}:
5113 (@value{GDBP}) set print addr off
5115 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5116 530 if (lquote != def_lquote)
5120 You can use @samp{set print address off} to eliminate all machine
5121 dependent displays from the @value{GDBN} interface. For example, with
5122 @code{print address off}, you should get the same text for backtraces on
5123 all machines---whether or not they involve pointer arguments.
5125 @kindex show print address
5126 @item show print address
5127 Show whether or not addresses are to be printed.
5130 When @value{GDBN} prints a symbolic address, it normally prints the
5131 closest earlier symbol plus an offset. If that symbol does not uniquely
5132 identify the address (for example, it is a name whose scope is a single
5133 source file), you may need to clarify. One way to do this is with
5134 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5135 you can set @value{GDBN} to print the source file and line number when
5136 it prints a symbolic address:
5139 @kindex set print symbol-filename
5140 @item set print symbol-filename on
5141 Tell @value{GDBN} to print the source file name and line number of a
5142 symbol in the symbolic form of an address.
5144 @item set print symbol-filename off
5145 Do not print source file name and line number of a symbol. This is the
5148 @kindex show print symbol-filename
5149 @item show print symbol-filename
5150 Show whether or not @value{GDBN} will print the source file name and
5151 line number of a symbol in the symbolic form of an address.
5154 Another situation where it is helpful to show symbol filenames and line
5155 numbers is when disassembling code; @value{GDBN} shows you the line
5156 number and source file that corresponds to each instruction.
5158 Also, you may wish to see the symbolic form only if the address being
5159 printed is reasonably close to the closest earlier symbol:
5162 @kindex set print max-symbolic-offset
5163 @item set print max-symbolic-offset @var{max-offset}
5164 Tell @value{GDBN} to only display the symbolic form of an address if the
5165 offset between the closest earlier symbol and the address is less than
5166 @var{max-offset}. The default is 0, which tells @value{GDBN}
5167 to always print the symbolic form of an address if any symbol precedes it.
5169 @kindex show print max-symbolic-offset
5170 @item show print max-symbolic-offset
5171 Ask how large the maximum offset is that @value{GDBN} prints in a
5175 @cindex wild pointer, interpreting
5176 @cindex pointer, finding referent
5177 If you have a pointer and you are not sure where it points, try
5178 @samp{set print symbol-filename on}. Then you can determine the name
5179 and source file location of the variable where it points, using
5180 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5181 For example, here @value{GDBN} shows that a variable @code{ptt} points
5182 at another variable @code{t}, defined in @file{hi2.c}:
5185 (@value{GDBP}) set print symbol-filename on
5186 (@value{GDBP}) p/a ptt
5187 $4 = 0xe008 <t in hi2.c>
5191 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5192 does not show the symbol name and filename of the referent, even with
5193 the appropriate @code{set print} options turned on.
5196 Other settings control how different kinds of objects are printed:
5199 @kindex set print array
5200 @item set print array
5201 @itemx set print array on
5202 Pretty print arrays. This format is more convenient to read,
5203 but uses more space. The default is off.
5205 @item set print array off
5206 Return to compressed format for arrays.
5208 @kindex show print array
5209 @item show print array
5210 Show whether compressed or pretty format is selected for displaying
5213 @kindex set print elements
5214 @item set print elements @var{number-of-elements}
5215 Set a limit on how many elements of an array @value{GDBN} will print.
5216 If @value{GDBN} is printing a large array, it stops printing after it has
5217 printed the number of elements set by the @code{set print elements} command.
5218 This limit also applies to the display of strings.
5219 When @value{GDBN} starts, this limit is set to 200.
5220 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5222 @kindex show print elements
5223 @item show print elements
5224 Display the number of elements of a large array that @value{GDBN} will print.
5225 If the number is 0, then the printing is unlimited.
5227 @kindex set print null-stop
5228 @item set print null-stop
5229 Cause @value{GDBN} to stop printing the characters of an array when the first
5230 @sc{null} is encountered. This is useful when large arrays actually
5231 contain only short strings.
5234 @kindex set print pretty
5235 @item set print pretty on
5236 Cause @value{GDBN} to print structures in an indented format with one member
5237 per line, like this:
5252 @item set print pretty off
5253 Cause @value{GDBN} to print structures in a compact format, like this:
5257 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5258 meat = 0x54 "Pork"@}
5263 This is the default format.
5265 @kindex show print pretty
5266 @item show print pretty
5267 Show which format @value{GDBN} is using to print structures.
5269 @kindex set print sevenbit-strings
5270 @item set print sevenbit-strings on
5271 Print using only seven-bit characters; if this option is set,
5272 @value{GDBN} displays any eight-bit characters (in strings or
5273 character values) using the notation @code{\}@var{nnn}. This setting is
5274 best if you are working in English (@sc{ascii}) and you use the
5275 high-order bit of characters as a marker or ``meta'' bit.
5277 @item set print sevenbit-strings off
5278 Print full eight-bit characters. This allows the use of more
5279 international character sets, and is the default.
5281 @kindex show print sevenbit-strings
5282 @item show print sevenbit-strings
5283 Show whether or not @value{GDBN} is printing only seven-bit characters.
5285 @kindex set print union
5286 @item set print union on
5287 Tell @value{GDBN} to print unions which are contained in structures. This
5288 is the default setting.
5290 @item set print union off
5291 Tell @value{GDBN} not to print unions which are contained in structures.
5293 @kindex show print union
5294 @item show print union
5295 Ask @value{GDBN} whether or not it will print unions which are contained in
5298 For example, given the declarations
5301 typedef enum @{Tree, Bug@} Species;
5302 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5303 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5314 struct thing foo = @{Tree, @{Acorn@}@};
5318 with @code{set print union on} in effect @samp{p foo} would print
5321 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5325 and with @code{set print union off} in effect it would print
5328 $1 = @{it = Tree, form = @{...@}@}
5334 These settings are of interest when debugging C@t{++} programs:
5338 @kindex set print demangle
5339 @item set print demangle
5340 @itemx set print demangle on
5341 Print C@t{++} names in their source form rather than in the encoded
5342 (``mangled'') form passed to the assembler and linker for type-safe
5343 linkage. The default is on.
5345 @kindex show print demangle
5346 @item show print demangle
5347 Show whether C@t{++} names are printed in mangled or demangled form.
5349 @kindex set print asm-demangle
5350 @item set print asm-demangle
5351 @itemx set print asm-demangle on
5352 Print C@t{++} names in their source form rather than their mangled form, even
5353 in assembler code printouts such as instruction disassemblies.
5356 @kindex show print asm-demangle
5357 @item show print asm-demangle
5358 Show whether C@t{++} names in assembly listings are printed in mangled
5361 @kindex set demangle-style
5362 @cindex C@t{++} symbol decoding style
5363 @cindex symbol decoding style, C@t{++}
5364 @item set demangle-style @var{style}
5365 Choose among several encoding schemes used by different compilers to
5366 represent C@t{++} names. The choices for @var{style} are currently:
5370 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5373 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5374 This is the default.
5377 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5380 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5383 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5384 @strong{Warning:} this setting alone is not sufficient to allow
5385 debugging @code{cfront}-generated executables. @value{GDBN} would
5386 require further enhancement to permit that.
5389 If you omit @var{style}, you will see a list of possible formats.
5391 @kindex show demangle-style
5392 @item show demangle-style
5393 Display the encoding style currently in use for decoding C@t{++} symbols.
5395 @kindex set print object
5396 @item set print object
5397 @itemx set print object on
5398 When displaying a pointer to an object, identify the @emph{actual}
5399 (derived) type of the object rather than the @emph{declared} type, using
5400 the virtual function table.
5402 @item set print object off
5403 Display only the declared type of objects, without reference to the
5404 virtual function table. This is the default setting.
5406 @kindex show print object
5407 @item show print object
5408 Show whether actual, or declared, object types are displayed.
5410 @kindex set print static-members
5411 @item set print static-members
5412 @itemx set print static-members on
5413 Print static members when displaying a C@t{++} object. The default is on.
5415 @item set print static-members off
5416 Do not print static members when displaying a C@t{++} object.
5418 @kindex show print static-members
5419 @item show print static-members
5420 Show whether C@t{++} static members are printed, or not.
5422 @c These don't work with HP ANSI C++ yet.
5423 @kindex set print vtbl
5424 @item set print vtbl
5425 @itemx set print vtbl on
5426 Pretty print C@t{++} virtual function tables. The default is off.
5427 (The @code{vtbl} commands do not work on programs compiled with the HP
5428 ANSI C@t{++} compiler (@code{aCC}).)
5430 @item set print vtbl off
5431 Do not pretty print C@t{++} virtual function tables.
5433 @kindex show print vtbl
5434 @item show print vtbl
5435 Show whether C@t{++} virtual function tables are pretty printed, or not.
5439 @section Value history
5441 @cindex value history
5442 Values printed by the @code{print} command are saved in the @value{GDBN}
5443 @dfn{value history}. This allows you to refer to them in other expressions.
5444 Values are kept until the symbol table is re-read or discarded
5445 (for example with the @code{file} or @code{symbol-file} commands).
5446 When the symbol table changes, the value history is discarded,
5447 since the values may contain pointers back to the types defined in the
5452 @cindex history number
5453 The values printed are given @dfn{history numbers} by which you can
5454 refer to them. These are successive integers starting with one.
5455 @code{print} shows you the history number assigned to a value by
5456 printing @samp{$@var{num} = } before the value; here @var{num} is the
5459 To refer to any previous value, use @samp{$} followed by the value's
5460 history number. The way @code{print} labels its output is designed to
5461 remind you of this. Just @code{$} refers to the most recent value in
5462 the history, and @code{$$} refers to the value before that.
5463 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5464 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5465 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5467 For example, suppose you have just printed a pointer to a structure and
5468 want to see the contents of the structure. It suffices to type
5474 If you have a chain of structures where the component @code{next} points
5475 to the next one, you can print the contents of the next one with this:
5482 You can print successive links in the chain by repeating this
5483 command---which you can do by just typing @key{RET}.
5485 Note that the history records values, not expressions. If the value of
5486 @code{x} is 4 and you type these commands:
5494 then the value recorded in the value history by the @code{print} command
5495 remains 4 even though the value of @code{x} has changed.
5500 Print the last ten values in the value history, with their item numbers.
5501 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5502 values} does not change the history.
5504 @item show values @var{n}
5505 Print ten history values centered on history item number @var{n}.
5508 Print ten history values just after the values last printed. If no more
5509 values are available, @code{show values +} produces no display.
5512 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5513 same effect as @samp{show values +}.
5515 @node Convenience Vars
5516 @section Convenience variables
5518 @cindex convenience variables
5519 @value{GDBN} provides @dfn{convenience variables} that you can use within
5520 @value{GDBN} to hold on to a value and refer to it later. These variables
5521 exist entirely within @value{GDBN}; they are not part of your program, and
5522 setting a convenience variable has no direct effect on further execution
5523 of your program. That is why you can use them freely.
5525 Convenience variables are prefixed with @samp{$}. Any name preceded by
5526 @samp{$} can be used for a convenience variable, unless it is one of
5527 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5528 (Value history references, in contrast, are @emph{numbers} preceded
5529 by @samp{$}. @xref{Value History, ,Value history}.)
5531 You can save a value in a convenience variable with an assignment
5532 expression, just as you would set a variable in your program.
5536 set $foo = *object_ptr
5540 would save in @code{$foo} the value contained in the object pointed to by
5543 Using a convenience variable for the first time creates it, but its
5544 value is @code{void} until you assign a new value. You can alter the
5545 value with another assignment at any time.
5547 Convenience variables have no fixed types. You can assign a convenience
5548 variable any type of value, including structures and arrays, even if
5549 that variable already has a value of a different type. The convenience
5550 variable, when used as an expression, has the type of its current value.
5553 @kindex show convenience
5554 @item show convenience
5555 Print a list of convenience variables used so far, and their values.
5556 Abbreviated @code{show conv}.
5559 One of the ways to use a convenience variable is as a counter to be
5560 incremented or a pointer to be advanced. For example, to print
5561 a field from successive elements of an array of structures:
5565 print bar[$i++]->contents
5569 Repeat that command by typing @key{RET}.
5571 Some convenience variables are created automatically by @value{GDBN} and given
5572 values likely to be useful.
5575 @vindex $_@r{, convenience variable}
5577 The variable @code{$_} is automatically set by the @code{x} command to
5578 the last address examined (@pxref{Memory, ,Examining memory}). Other
5579 commands which provide a default address for @code{x} to examine also
5580 set @code{$_} to that address; these commands include @code{info line}
5581 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5582 except when set by the @code{x} command, in which case it is a pointer
5583 to the type of @code{$__}.
5585 @vindex $__@r{, convenience variable}
5587 The variable @code{$__} is automatically set by the @code{x} command
5588 to the value found in the last address examined. Its type is chosen
5589 to match the format in which the data was printed.
5592 @vindex $_exitcode@r{, convenience variable}
5593 The variable @code{$_exitcode} is automatically set to the exit code when
5594 the program being debugged terminates.
5597 On HP-UX systems, if you refer to a function or variable name that
5598 begins with a dollar sign, @value{GDBN} searches for a user or system
5599 name first, before it searches for a convenience variable.
5605 You can refer to machine register contents, in expressions, as variables
5606 with names starting with @samp{$}. The names of registers are different
5607 for each machine; use @code{info registers} to see the names used on
5611 @kindex info registers
5612 @item info registers
5613 Print the names and values of all registers except floating-point
5614 and vector registers (in the selected stack frame).
5616 @kindex info all-registers
5617 @cindex floating point registers
5618 @item info all-registers
5619 Print the names and values of all registers, including floating-point
5620 and vector registers (in the selected stack frame).
5622 @item info registers @var{regname} @dots{}
5623 Print the @dfn{relativized} value of each specified register @var{regname}.
5624 As discussed in detail below, register values are normally relative to
5625 the selected stack frame. @var{regname} may be any register name valid on
5626 the machine you are using, with or without the initial @samp{$}.
5629 @value{GDBN} has four ``standard'' register names that are available (in
5630 expressions) on most machines---whenever they do not conflict with an
5631 architecture's canonical mnemonics for registers. The register names
5632 @code{$pc} and @code{$sp} are used for the program counter register and
5633 the stack pointer. @code{$fp} is used for a register that contains a
5634 pointer to the current stack frame, and @code{$ps} is used for a
5635 register that contains the processor status. For example,
5636 you could print the program counter in hex with
5643 or print the instruction to be executed next with
5650 or add four to the stack pointer@footnote{This is a way of removing
5651 one word from the stack, on machines where stacks grow downward in
5652 memory (most machines, nowadays). This assumes that the innermost
5653 stack frame is selected; setting @code{$sp} is not allowed when other
5654 stack frames are selected. To pop entire frames off the stack,
5655 regardless of machine architecture, use @code{return};
5656 see @ref{Returning, ,Returning from a function}.} with
5662 Whenever possible, these four standard register names are available on
5663 your machine even though the machine has different canonical mnemonics,
5664 so long as there is no conflict. The @code{info registers} command
5665 shows the canonical names. For example, on the SPARC, @code{info
5666 registers} displays the processor status register as @code{$psr} but you
5667 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5668 is an alias for the @sc{eflags} register.
5670 @value{GDBN} always considers the contents of an ordinary register as an
5671 integer when the register is examined in this way. Some machines have
5672 special registers which can hold nothing but floating point; these
5673 registers are considered to have floating point values. There is no way
5674 to refer to the contents of an ordinary register as floating point value
5675 (although you can @emph{print} it as a floating point value with
5676 @samp{print/f $@var{regname}}).
5678 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5679 means that the data format in which the register contents are saved by
5680 the operating system is not the same one that your program normally
5681 sees. For example, the registers of the 68881 floating point
5682 coprocessor are always saved in ``extended'' (raw) format, but all C
5683 programs expect to work with ``double'' (virtual) format. In such
5684 cases, @value{GDBN} normally works with the virtual format only (the format
5685 that makes sense for your program), but the @code{info registers} command
5686 prints the data in both formats.
5688 Normally, register values are relative to the selected stack frame
5689 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5690 value that the register would contain if all stack frames farther in
5691 were exited and their saved registers restored. In order to see the
5692 true contents of hardware registers, you must select the innermost
5693 frame (with @samp{frame 0}).
5695 However, @value{GDBN} must deduce where registers are saved, from the machine
5696 code generated by your compiler. If some registers are not saved, or if
5697 @value{GDBN} is unable to locate the saved registers, the selected stack
5698 frame makes no difference.
5700 @node Floating Point Hardware
5701 @section Floating point hardware
5702 @cindex floating point
5704 Depending on the configuration, @value{GDBN} may be able to give
5705 you more information about the status of the floating point hardware.
5710 Display hardware-dependent information about the floating
5711 point unit. The exact contents and layout vary depending on the
5712 floating point chip. Currently, @samp{info float} is supported on
5713 the ARM and x86 machines.
5717 @section Vector Unit
5720 Depending on the configuration, @value{GDBN} may be able to give you
5721 more information about the status of the vector unit.
5726 Display information about the vector unit. The exact contents and
5727 layout vary depending on the hardware.
5730 @node Memory Region Attributes
5731 @section Memory region attributes
5732 @cindex memory region attributes
5734 @dfn{Memory region attributes} allow you to describe special handling
5735 required by regions of your target's memory. @value{GDBN} uses attributes
5736 to determine whether to allow certain types of memory accesses; whether to
5737 use specific width accesses; and whether to cache target memory.
5739 Defined memory regions can be individually enabled and disabled. When a
5740 memory region is disabled, @value{GDBN} uses the default attributes when
5741 accessing memory in that region. Similarly, if no memory regions have
5742 been defined, @value{GDBN} uses the default attributes when accessing
5745 When a memory region is defined, it is given a number to identify it;
5746 to enable, disable, or remove a memory region, you specify that number.
5750 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5751 Define memory region bounded by @var{lower} and @var{upper} with
5752 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5753 special case: it is treated as the the target's maximum memory address.
5754 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5757 @item delete mem @var{nums}@dots{}
5758 Remove memory regions @var{nums}@dots{}.
5761 @item disable mem @var{nums}@dots{}
5762 Disable memory regions @var{nums}@dots{}.
5763 A disabled memory region is not forgotten.
5764 It may be enabled again later.
5767 @item enable mem @var{nums}@dots{}
5768 Enable memory regions @var{nums}@dots{}.
5772 Print a table of all defined memory regions, with the following columns
5776 @item Memory Region Number
5777 @item Enabled or Disabled.
5778 Enabled memory regions are marked with @samp{y}.
5779 Disabled memory regions are marked with @samp{n}.
5782 The address defining the inclusive lower bound of the memory region.
5785 The address defining the exclusive upper bound of the memory region.
5788 The list of attributes set for this memory region.
5793 @subsection Attributes
5795 @subsubsection Memory Access Mode
5796 The access mode attributes set whether @value{GDBN} may make read or
5797 write accesses to a memory region.
5799 While these attributes prevent @value{GDBN} from performing invalid
5800 memory accesses, they do nothing to prevent the target system, I/O DMA,
5801 etc. from accessing memory.
5805 Memory is read only.
5807 Memory is write only.
5809 Memory is read/write. This is the default.
5812 @subsubsection Memory Access Size
5813 The acccess size attributes tells @value{GDBN} to use specific sized
5814 accesses in the memory region. Often memory mapped device registers
5815 require specific sized accesses. If no access size attribute is
5816 specified, @value{GDBN} may use accesses of any size.
5820 Use 8 bit memory accesses.
5822 Use 16 bit memory accesses.
5824 Use 32 bit memory accesses.
5826 Use 64 bit memory accesses.
5829 @c @subsubsection Hardware/Software Breakpoints
5830 @c The hardware/software breakpoint attributes set whether @value{GDBN}
5831 @c will use hardware or software breakpoints for the internal breakpoints
5832 @c used by the step, next, finish, until, etc. commands.
5836 @c Always use hardware breakpoints
5837 @c @item swbreak (default)
5840 @subsubsection Data Cache
5841 The data cache attributes set whether @value{GDBN} will cache target
5842 memory. While this generally improves performance by reducing debug
5843 protocol overhead, it can lead to incorrect results because @value{GDBN}
5844 does not know about volatile variables or memory mapped device
5849 Enable @value{GDBN} to cache target memory.
5851 Disable @value{GDBN} from caching target memory. This is the default.
5854 @c @subsubsection Memory Write Verification
5855 @c The memory write verification attributes set whether @value{GDBN}
5856 @c will re-reads data after each write to verify the write was successful.
5860 @c @item noverify (default)
5863 @node Dump/Restore Files
5864 @section Copy between memory and a file
5865 @cindex dump/restore files
5866 @cindex append data to a file
5867 @cindex dump data to a file
5868 @cindex restore data from a file
5870 You can use the commands @code{dump}, @code{append}, and
5871 @code{restore} to copy data between target memory and a file. The
5872 @code{dump} and @code{append} commands write data to a file, and the
5873 @code{restore} command reads data from a file back into the inferior's
5874 memory. Files may be in binary, Motorola S-record, Intel hex, or
5875 Tektronix Hex format; however, @value{GDBN} can only append to binary
5881 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
5882 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
5883 Dump the contents of memory from @var{start_addr} to @var{end_addr},
5884 or the value of @var{expr}, to @var{filename} in the given format.
5886 The @var{format} parameter may be any one of:
5893 Motorola S-record format.
5895 Tektronix Hex format.
5898 @value{GDBN} uses the same definitions of these formats as the
5899 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
5900 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
5904 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
5905 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
5906 Append the contents of memory from @var{start_addr} to @var{end_addr},
5907 or the value of @var{expr}, to @var{filename}, in raw binary form.
5908 (@value{GDBN} can only append data to files in raw binary form.)
5911 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
5912 Restore the contents of file @var{filename} into memory. The
5913 @code{restore} command can automatically recognize any known @sc{bfd}
5914 file format, except for raw binary. To restore a raw binary file you
5915 must specify the optional keyword @code{binary} after the filename.
5917 If @var{bias} is non-zero, its value will be added to the addresses
5918 contained in the file. Binary files always start at address zero, so
5919 they will be restored at address @var{bias}. Other bfd files have
5920 a built-in location; they will be restored at offset @var{bias}
5923 If @var{start} and/or @var{end} are non-zero, then only data between
5924 file offset @var{start} and file offset @var{end} will be restored.
5925 These offsets are relative to the addresses in the file, before
5926 the @var{bias} argument is applied.
5930 @node Character Sets
5931 @section Character Sets
5932 @cindex character sets
5934 @cindex translating between character sets
5935 @cindex host character set
5936 @cindex target character set
5938 If the program you are debugging uses a different character set to
5939 represent characters and strings than the one @value{GDBN} uses itself,
5940 @value{GDBN} can automatically translate between the character sets for
5941 you. The character set @value{GDBN} uses we call the @dfn{host
5942 character set}; the one the inferior program uses we call the
5943 @dfn{target character set}.
5945 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
5946 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
5947 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
5948 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
5949 then the host character set is Latin-1, and the target character set is
5950 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
5951 target-charset EBCDIC-US}, then @value{GDBN} translates between
5952 @sc{ebcdic} and Latin 1 as you print character or string values, or use
5953 character and string literals in expressions.
5955 @value{GDBN} has no way to automatically recognize which character set
5956 the inferior program uses; you must tell it, using the @code{set
5957 target-charset} command, described below.
5959 Here are the commands for controlling @value{GDBN}'s character set
5963 @item set target-charset @var{charset}
5964 @kindex set target-charset
5965 Set the current target character set to @var{charset}. We list the
5966 character set names @value{GDBN} recognizes below, but if you type
5967 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
5968 list the target character sets it supports.
5972 @item set host-charset @var{charset}
5973 @kindex set host-charset
5974 Set the current host character set to @var{charset}.
5976 By default, @value{GDBN} uses a host character set appropriate to the
5977 system it is running on; you can override that default using the
5978 @code{set host-charset} command.
5980 @value{GDBN} can only use certain character sets as its host character
5981 set. We list the character set names @value{GDBN} recognizes below, and
5982 indicate which can be host character sets, but if you type
5983 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
5984 list the host character sets it supports.
5986 @item set charset @var{charset}
5988 Set the current host and target character sets to @var{charset}. As
5989 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
5990 @value{GDBN} will list the name of the character sets that can be used
5991 for both host and target.
5995 @kindex show charset
5996 Show the names of the current host and target charsets.
5998 @itemx show host-charset
5999 @kindex show host-charset
6000 Show the name of the current host charset.
6002 @itemx show target-charset
6003 @kindex show target-charset
6004 Show the name of the current target charset.
6008 @value{GDBN} currently includes support for the following character
6014 @cindex ASCII character set
6015 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6019 @cindex ISO 8859-1 character set
6020 @cindex ISO Latin 1 character set
6021 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6022 characters needed for French, German, and Spanish. @value{GDBN} can use
6023 this as its host character set.
6027 @cindex EBCDIC character set
6028 @cindex IBM1047 character set
6029 Variants of the @sc{ebcdic} character set, used on some of IBM's
6030 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6031 @value{GDBN} cannot use these as its host character set.
6035 Note that these are all single-byte character sets. More work inside
6036 GDB is needed to support multi-byte or variable-width character
6037 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6039 Here is an example of @value{GDBN}'s character set support in action.
6040 Assume that the following source code has been placed in the file
6041 @file{charset-test.c}:
6047 = @{72, 101, 108, 108, 111, 44, 32, 119,
6048 111, 114, 108, 100, 33, 10, 0@};
6049 char ibm1047_hello[]
6050 = @{200, 133, 147, 147, 150, 107, 64, 166,
6051 150, 153, 147, 132, 90, 37, 0@};
6055 printf ("Hello, world!\n");
6059 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6060 containing the string @samp{Hello, world!} followed by a newline,
6061 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6063 We compile the program, and invoke the debugger on it:
6066 $ gcc -g charset-test.c -o charset-test
6067 $ gdb -nw charset-test
6068 GNU gdb 2001-12-19-cvs
6069 Copyright 2001 Free Software Foundation, Inc.
6074 We can use the @code{show charset} command to see what character sets
6075 @value{GDBN} is currently using to interpret and display characters and
6080 The current host and target character set is `ISO-8859-1'.
6084 For the sake of printing this manual, let's use @sc{ascii} as our
6085 initial character set:
6087 (gdb) set charset ASCII
6089 The current host and target character set is `ASCII'.
6093 Let's assume that @sc{ascii} is indeed the correct character set for our
6094 host system --- in other words, let's assume that if @value{GDBN} prints
6095 characters using the @sc{ascii} character set, our terminal will display
6096 them properly. Since our current target character set is also
6097 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6100 (gdb) print ascii_hello
6101 $1 = 0x401698 "Hello, world!\n"
6102 (gdb) print ascii_hello[0]
6107 @value{GDBN} uses the target character set for character and string
6108 literals you use in expressions:
6116 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6119 @value{GDBN} relies on the user to tell it which character set the
6120 target program uses. If we print @code{ibm1047_hello} while our target
6121 character set is still @sc{ascii}, we get jibberish:
6124 (gdb) print ibm1047_hello
6125 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6126 (gdb) print ibm1047_hello[0]
6131 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6132 @value{GDBN} tells us the character sets it supports:
6135 (gdb) set target-charset
6136 ASCII EBCDIC-US IBM1047 ISO-8859-1
6137 (gdb) set target-charset
6140 We can select @sc{ibm1047} as our target character set, and examine the
6141 program's strings again. Now the @sc{ascii} string is wrong, but
6142 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6143 target character set, @sc{ibm1047}, to the host character set,
6144 @sc{ascii}, and they display correctly:
6147 (gdb) set target-charset IBM1047
6149 The current host character set is `ASCII'.
6150 The current target character set is `IBM1047'.
6151 (gdb) print ascii_hello
6152 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6153 (gdb) print ascii_hello[0]
6155 (gdb) print ibm1047_hello
6156 $8 = 0x4016a8 "Hello, world!\n"
6157 (gdb) print ibm1047_hello[0]
6162 As above, @value{GDBN} uses the target character set for character and
6163 string literals you use in expressions:
6171 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6176 @chapter C Preprocessor Macros
6178 Some languages, such as C and C++, provide a way to define and invoke
6179 ``preprocessor macros'' which expand into strings of tokens.
6180 @value{GDBN} can evaluate expressions containing macro invocations, show
6181 the result of macro expansion, and show a macro's definition, including
6182 where it was defined.
6184 You may need to compile your program specially to provide @value{GDBN}
6185 with information about preprocessor macros. Most compilers do not
6186 include macros in their debugging information, even when you compile
6187 with the @option{-g} flag. @xref{Compilation}.
6189 A program may define a macro at one point, remove that definition later,
6190 and then provide a different definition after that. Thus, at different
6191 points in the program, a macro may have different definitions, or have
6192 no definition at all. If there is a current stack frame, @value{GDBN}
6193 uses the macros in scope at that frame's source code line. Otherwise,
6194 @value{GDBN} uses the macros in scope at the current listing location;
6197 At the moment, @value{GDBN} does not support the @code{##}
6198 token-splicing operator, the @code{#} stringification operator, or
6199 variable-arity macros.
6201 Whenever @value{GDBN} evaluates an expression, it always expands any
6202 macro invocations present in the expression. @value{GDBN} also provides
6203 the following commands for working with macros explicitly.
6207 @kindex macro expand
6208 @cindex macro expansion, showing the results of preprocessor
6209 @cindex preprocessor macro expansion, showing the results of
6210 @cindex expanding preprocessor macros
6211 @item macro expand @var{expression}
6212 @itemx macro exp @var{expression}
6213 Show the results of expanding all preprocessor macro invocations in
6214 @var{expression}. Since @value{GDBN} simply expands macros, but does
6215 not parse the result, @var{expression} need not be a valid expression;
6216 it can be any string of tokens.
6218 @kindex macro expand-once
6219 @item macro expand-once @var{expression}
6220 @itemx macro exp1 @var{expression}
6221 @i{(This command is not yet implemented.)} Show the results of
6222 expanding those preprocessor macro invocations that appear explicitly in
6223 @var{expression}. Macro invocations appearing in that expansion are
6224 left unchanged. This command allows you to see the effect of a
6225 particular macro more clearly, without being confused by further
6226 expansions. Since @value{GDBN} simply expands macros, but does not
6227 parse the result, @var{expression} need not be a valid expression; it
6228 can be any string of tokens.
6231 @cindex macro definition, showing
6232 @cindex definition, showing a macro's
6233 @item info macro @var{macro}
6234 Show the definition of the macro named @var{macro}, and describe the
6235 source location where that definition was established.
6237 @kindex macro define
6238 @cindex user-defined macros
6239 @cindex defining macros interactively
6240 @cindex macros, user-defined
6241 @item macro define @var{macro} @var{replacement-list}
6242 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6243 @i{(This command is not yet implemented.)} Introduce a definition for a
6244 preprocessor macro named @var{macro}, invocations of which are replaced
6245 by the tokens given in @var{replacement-list}. The first form of this
6246 command defines an ``object-like'' macro, which takes no arguments; the
6247 second form defines a ``function-like'' macro, which takes the arguments
6248 given in @var{arglist}.
6250 A definition introduced by this command is in scope in every expression
6251 evaluated in @value{GDBN}, until it is removed with the @command{macro
6252 undef} command, described below. The definition overrides all
6253 definitions for @var{macro} present in the program being debugged, as
6254 well as any previous user-supplied definition.
6257 @item macro undef @var{macro}
6258 @i{(This command is not yet implemented.)} Remove any user-supplied
6259 definition for the macro named @var{macro}. This command only affects
6260 definitions provided with the @command{macro define} command, described
6261 above; it cannot remove definitions present in the program being
6266 @cindex macros, example of debugging with
6267 Here is a transcript showing the above commands in action. First, we
6268 show our source files:
6276 #define ADD(x) (M + x)
6281 printf ("Hello, world!\n");
6283 printf ("We're so creative.\n");
6285 printf ("Goodbye, world!\n");
6292 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6293 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6294 compiler includes information about preprocessor macros in the debugging
6298 $ gcc -gdwarf-2 -g3 sample.c -o sample
6302 Now, we start @value{GDBN} on our sample program:
6306 GNU gdb 2002-05-06-cvs
6307 Copyright 2002 Free Software Foundation, Inc.
6308 GDB is free software, @dots{}
6312 We can expand macros and examine their definitions, even when the
6313 program is not running. @value{GDBN} uses the current listing position
6314 to decide which macro definitions are in scope:
6320 5 #define ADD(x) (M + x)
6325 10 printf ("Hello, world!\n");
6327 12 printf ("We're so creative.\n");
6328 (gdb) info macro ADD
6329 Defined at /home/jimb/gdb/macros/play/sample.c:5
6330 #define ADD(x) (M + x)
6332 Defined at /home/jimb/gdb/macros/play/sample.h:1
6333 included at /home/jimb/gdb/macros/play/sample.c:2
6335 (gdb) macro expand ADD(1)
6336 expands to: (42 + 1)
6337 (gdb) macro expand-once ADD(1)
6338 expands to: once (M + 1)
6342 In the example above, note that @command{macro expand-once} expands only
6343 the macro invocation explicit in the original text --- the invocation of
6344 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6345 which was introduced by @code{ADD}.
6347 Once the program is running, GDB uses the macro definitions in force at
6348 the source line of the current stack frame:
6352 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6354 Starting program: /home/jimb/gdb/macros/play/sample
6356 Breakpoint 1, main () at sample.c:10
6357 10 printf ("Hello, world!\n");
6361 At line 10, the definition of the macro @code{N} at line 9 is in force:
6365 Defined at /home/jimb/gdb/macros/play/sample.c:9
6367 (gdb) macro expand N Q M
6374 As we step over directives that remove @code{N}'s definition, and then
6375 give it a new definition, @value{GDBN} finds the definition (or lack
6376 thereof) in force at each point:
6381 12 printf ("We're so creative.\n");
6383 The symbol `N' has no definition as a C/C++ preprocessor macro
6384 at /home/jimb/gdb/macros/play/sample.c:12
6387 14 printf ("Goodbye, world!\n");
6389 Defined at /home/jimb/gdb/macros/play/sample.c:13
6391 (gdb) macro expand N Q M
6392 expands to: 1729 < 42
6400 @chapter Tracepoints
6401 @c This chapter is based on the documentation written by Michael
6402 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6405 In some applications, it is not feasible for the debugger to interrupt
6406 the program's execution long enough for the developer to learn
6407 anything helpful about its behavior. If the program's correctness
6408 depends on its real-time behavior, delays introduced by a debugger
6409 might cause the program to change its behavior drastically, or perhaps
6410 fail, even when the code itself is correct. It is useful to be able
6411 to observe the program's behavior without interrupting it.
6413 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6414 specify locations in the program, called @dfn{tracepoints}, and
6415 arbitrary expressions to evaluate when those tracepoints are reached.
6416 Later, using the @code{tfind} command, you can examine the values
6417 those expressions had when the program hit the tracepoints. The
6418 expressions may also denote objects in memory---structures or arrays,
6419 for example---whose values @value{GDBN} should record; while visiting
6420 a particular tracepoint, you may inspect those objects as if they were
6421 in memory at that moment. However, because @value{GDBN} records these
6422 values without interacting with you, it can do so quickly and
6423 unobtrusively, hopefully not disturbing the program's behavior.
6425 The tracepoint facility is currently available only for remote
6426 targets. @xref{Targets}. In addition, your remote target must know how
6427 to collect trace data. This functionality is implemented in the remote
6428 stub; however, none of the stubs distributed with @value{GDBN} support
6429 tracepoints as of this writing.
6431 This chapter describes the tracepoint commands and features.
6435 * Analyze Collected Data::
6436 * Tracepoint Variables::
6439 @node Set Tracepoints
6440 @section Commands to Set Tracepoints
6442 Before running such a @dfn{trace experiment}, an arbitrary number of
6443 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6444 tracepoint has a number assigned to it by @value{GDBN}. Like with
6445 breakpoints, tracepoint numbers are successive integers starting from
6446 one. Many of the commands associated with tracepoints take the
6447 tracepoint number as their argument, to identify which tracepoint to
6450 For each tracepoint, you can specify, in advance, some arbitrary set
6451 of data that you want the target to collect in the trace buffer when
6452 it hits that tracepoint. The collected data can include registers,
6453 local variables, or global data. Later, you can use @value{GDBN}
6454 commands to examine the values these data had at the time the
6457 This section describes commands to set tracepoints and associated
6458 conditions and actions.
6461 * Create and Delete Tracepoints::
6462 * Enable and Disable Tracepoints::
6463 * Tracepoint Passcounts::
6464 * Tracepoint Actions::
6465 * Listing Tracepoints::
6466 * Starting and Stopping Trace Experiment::
6469 @node Create and Delete Tracepoints
6470 @subsection Create and Delete Tracepoints
6473 @cindex set tracepoint
6476 The @code{trace} command is very similar to the @code{break} command.
6477 Its argument can be a source line, a function name, or an address in
6478 the target program. @xref{Set Breaks}. The @code{trace} command
6479 defines a tracepoint, which is a point in the target program where the
6480 debugger will briefly stop, collect some data, and then allow the
6481 program to continue. Setting a tracepoint or changing its commands
6482 doesn't take effect until the next @code{tstart} command; thus, you
6483 cannot change the tracepoint attributes once a trace experiment is
6486 Here are some examples of using the @code{trace} command:
6489 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6491 (@value{GDBP}) @b{trace +2} // 2 lines forward
6493 (@value{GDBP}) @b{trace my_function} // first source line of function
6495 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6497 (@value{GDBP}) @b{trace *0x2117c4} // an address
6501 You can abbreviate @code{trace} as @code{tr}.
6504 @cindex last tracepoint number
6505 @cindex recent tracepoint number
6506 @cindex tracepoint number
6507 The convenience variable @code{$tpnum} records the tracepoint number
6508 of the most recently set tracepoint.
6510 @kindex delete tracepoint
6511 @cindex tracepoint deletion
6512 @item delete tracepoint @r{[}@var{num}@r{]}
6513 Permanently delete one or more tracepoints. With no argument, the
6514 default is to delete all tracepoints.
6519 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6521 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6525 You can abbreviate this command as @code{del tr}.
6528 @node Enable and Disable Tracepoints
6529 @subsection Enable and Disable Tracepoints
6532 @kindex disable tracepoint
6533 @item disable tracepoint @r{[}@var{num}@r{]}
6534 Disable tracepoint @var{num}, or all tracepoints if no argument
6535 @var{num} is given. A disabled tracepoint will have no effect during
6536 the next trace experiment, but it is not forgotten. You can re-enable
6537 a disabled tracepoint using the @code{enable tracepoint} command.
6539 @kindex enable tracepoint
6540 @item enable tracepoint @r{[}@var{num}@r{]}
6541 Enable tracepoint @var{num}, or all tracepoints. The enabled
6542 tracepoints will become effective the next time a trace experiment is
6546 @node Tracepoint Passcounts
6547 @subsection Tracepoint Passcounts
6551 @cindex tracepoint pass count
6552 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6553 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6554 automatically stop a trace experiment. If a tracepoint's passcount is
6555 @var{n}, then the trace experiment will be automatically stopped on
6556 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6557 @var{num} is not specified, the @code{passcount} command sets the
6558 passcount of the most recently defined tracepoint. If no passcount is
6559 given, the trace experiment will run until stopped explicitly by the
6565 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6566 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6568 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6569 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6570 (@value{GDBP}) @b{trace foo}
6571 (@value{GDBP}) @b{pass 3}
6572 (@value{GDBP}) @b{trace bar}
6573 (@value{GDBP}) @b{pass 2}
6574 (@value{GDBP}) @b{trace baz}
6575 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6576 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6577 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6578 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6582 @node Tracepoint Actions
6583 @subsection Tracepoint Action Lists
6587 @cindex tracepoint actions
6588 @item actions @r{[}@var{num}@r{]}
6589 This command will prompt for a list of actions to be taken when the
6590 tracepoint is hit. If the tracepoint number @var{num} is not
6591 specified, this command sets the actions for the one that was most
6592 recently defined (so that you can define a tracepoint and then say
6593 @code{actions} without bothering about its number). You specify the
6594 actions themselves on the following lines, one action at a time, and
6595 terminate the actions list with a line containing just @code{end}. So
6596 far, the only defined actions are @code{collect} and
6597 @code{while-stepping}.
6599 @cindex remove actions from a tracepoint
6600 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6601 and follow it immediately with @samp{end}.
6604 (@value{GDBP}) @b{collect @var{data}} // collect some data
6606 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6608 (@value{GDBP}) @b{end} // signals the end of actions.
6611 In the following example, the action list begins with @code{collect}
6612 commands indicating the things to be collected when the tracepoint is
6613 hit. Then, in order to single-step and collect additional data
6614 following the tracepoint, a @code{while-stepping} command is used,
6615 followed by the list of things to be collected while stepping. The
6616 @code{while-stepping} command is terminated by its own separate
6617 @code{end} command. Lastly, the action list is terminated by an
6621 (@value{GDBP}) @b{trace foo}
6622 (@value{GDBP}) @b{actions}
6623 Enter actions for tracepoint 1, one per line:
6632 @kindex collect @r{(tracepoints)}
6633 @item collect @var{expr1}, @var{expr2}, @dots{}
6634 Collect values of the given expressions when the tracepoint is hit.
6635 This command accepts a comma-separated list of any valid expressions.
6636 In addition to global, static, or local variables, the following
6637 special arguments are supported:
6641 collect all registers
6644 collect all function arguments
6647 collect all local variables.
6650 You can give several consecutive @code{collect} commands, each one
6651 with a single argument, or one @code{collect} command with several
6652 arguments separated by commas: the effect is the same.
6654 The command @code{info scope} (@pxref{Symbols, info scope}) is
6655 particularly useful for figuring out what data to collect.
6657 @kindex while-stepping @r{(tracepoints)}
6658 @item while-stepping @var{n}
6659 Perform @var{n} single-step traces after the tracepoint, collecting
6660 new data at each step. The @code{while-stepping} command is
6661 followed by the list of what to collect while stepping (followed by
6662 its own @code{end} command):
6666 > collect $regs, myglobal
6672 You may abbreviate @code{while-stepping} as @code{ws} or
6676 @node Listing Tracepoints
6677 @subsection Listing Tracepoints
6680 @kindex info tracepoints
6681 @cindex information about tracepoints
6682 @item info tracepoints @r{[}@var{num}@r{]}
6683 Display information about the tracepoint @var{num}. If you don't specify
6684 a tracepoint number, displays information about all the tracepoints
6685 defined so far. For each tracepoint, the following information is
6692 whether it is enabled or disabled
6696 its passcount as given by the @code{passcount @var{n}} command
6698 its step count as given by the @code{while-stepping @var{n}} command
6700 where in the source files is the tracepoint set
6702 its action list as given by the @code{actions} command
6706 (@value{GDBP}) @b{info trace}
6707 Num Enb Address PassC StepC What
6708 1 y 0x002117c4 0 0 <gdb_asm>
6709 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6710 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6715 This command can be abbreviated @code{info tp}.
6718 @node Starting and Stopping Trace Experiment
6719 @subsection Starting and Stopping Trace Experiment
6723 @cindex start a new trace experiment
6724 @cindex collected data discarded
6726 This command takes no arguments. It starts the trace experiment, and
6727 begins collecting data. This has the side effect of discarding all
6728 the data collected in the trace buffer during the previous trace
6732 @cindex stop a running trace experiment
6734 This command takes no arguments. It ends the trace experiment, and
6735 stops collecting data.
6737 @strong{Note:} a trace experiment and data collection may stop
6738 automatically if any tracepoint's passcount is reached
6739 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6742 @cindex status of trace data collection
6743 @cindex trace experiment, status of
6745 This command displays the status of the current trace data
6749 Here is an example of the commands we described so far:
6752 (@value{GDBP}) @b{trace gdb_c_test}
6753 (@value{GDBP}) @b{actions}
6754 Enter actions for tracepoint #1, one per line.
6755 > collect $regs,$locals,$args
6760 (@value{GDBP}) @b{tstart}
6761 [time passes @dots{}]
6762 (@value{GDBP}) @b{tstop}
6766 @node Analyze Collected Data
6767 @section Using the collected data
6769 After the tracepoint experiment ends, you use @value{GDBN} commands
6770 for examining the trace data. The basic idea is that each tracepoint
6771 collects a trace @dfn{snapshot} every time it is hit and another
6772 snapshot every time it single-steps. All these snapshots are
6773 consecutively numbered from zero and go into a buffer, and you can
6774 examine them later. The way you examine them is to @dfn{focus} on a
6775 specific trace snapshot. When the remote stub is focused on a trace
6776 snapshot, it will respond to all @value{GDBN} requests for memory and
6777 registers by reading from the buffer which belongs to that snapshot,
6778 rather than from @emph{real} memory or registers of the program being
6779 debugged. This means that @strong{all} @value{GDBN} commands
6780 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6781 behave as if we were currently debugging the program state as it was
6782 when the tracepoint occurred. Any requests for data that are not in
6783 the buffer will fail.
6786 * tfind:: How to select a trace snapshot
6787 * tdump:: How to display all data for a snapshot
6788 * save-tracepoints:: How to save tracepoints for a future run
6792 @subsection @code{tfind @var{n}}
6795 @cindex select trace snapshot
6796 @cindex find trace snapshot
6797 The basic command for selecting a trace snapshot from the buffer is
6798 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6799 counting from zero. If no argument @var{n} is given, the next
6800 snapshot is selected.
6802 Here are the various forms of using the @code{tfind} command.
6806 Find the first snapshot in the buffer. This is a synonym for
6807 @code{tfind 0} (since 0 is the number of the first snapshot).
6810 Stop debugging trace snapshots, resume @emph{live} debugging.
6813 Same as @samp{tfind none}.
6816 No argument means find the next trace snapshot.
6819 Find the previous trace snapshot before the current one. This permits
6820 retracing earlier steps.
6822 @item tfind tracepoint @var{num}
6823 Find the next snapshot associated with tracepoint @var{num}. Search
6824 proceeds forward from the last examined trace snapshot. If no
6825 argument @var{num} is given, it means find the next snapshot collected
6826 for the same tracepoint as the current snapshot.
6828 @item tfind pc @var{addr}
6829 Find the next snapshot associated with the value @var{addr} of the
6830 program counter. Search proceeds forward from the last examined trace
6831 snapshot. If no argument @var{addr} is given, it means find the next
6832 snapshot with the same value of PC as the current snapshot.
6834 @item tfind outside @var{addr1}, @var{addr2}
6835 Find the next snapshot whose PC is outside the given range of
6838 @item tfind range @var{addr1}, @var{addr2}
6839 Find the next snapshot whose PC is between @var{addr1} and
6840 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6842 @item tfind line @r{[}@var{file}:@r{]}@var{n}
6843 Find the next snapshot associated with the source line @var{n}. If
6844 the optional argument @var{file} is given, refer to line @var{n} in
6845 that source file. Search proceeds forward from the last examined
6846 trace snapshot. If no argument @var{n} is given, it means find the
6847 next line other than the one currently being examined; thus saying
6848 @code{tfind line} repeatedly can appear to have the same effect as
6849 stepping from line to line in a @emph{live} debugging session.
6852 The default arguments for the @code{tfind} commands are specifically
6853 designed to make it easy to scan through the trace buffer. For
6854 instance, @code{tfind} with no argument selects the next trace
6855 snapshot, and @code{tfind -} with no argument selects the previous
6856 trace snapshot. So, by giving one @code{tfind} command, and then
6857 simply hitting @key{RET} repeatedly you can examine all the trace
6858 snapshots in order. Or, by saying @code{tfind -} and then hitting
6859 @key{RET} repeatedly you can examine the snapshots in reverse order.
6860 The @code{tfind line} command with no argument selects the snapshot
6861 for the next source line executed. The @code{tfind pc} command with
6862 no argument selects the next snapshot with the same program counter
6863 (PC) as the current frame. The @code{tfind tracepoint} command with
6864 no argument selects the next trace snapshot collected by the same
6865 tracepoint as the current one.
6867 In addition to letting you scan through the trace buffer manually,
6868 these commands make it easy to construct @value{GDBN} scripts that
6869 scan through the trace buffer and print out whatever collected data
6870 you are interested in. Thus, if we want to examine the PC, FP, and SP
6871 registers from each trace frame in the buffer, we can say this:
6874 (@value{GDBP}) @b{tfind start}
6875 (@value{GDBP}) @b{while ($trace_frame != -1)}
6876 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
6877 $trace_frame, $pc, $sp, $fp
6881 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
6882 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
6883 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
6884 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
6885 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
6886 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
6887 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
6888 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
6889 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
6890 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
6891 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
6894 Or, if we want to examine the variable @code{X} at each source line in
6898 (@value{GDBP}) @b{tfind start}
6899 (@value{GDBP}) @b{while ($trace_frame != -1)}
6900 > printf "Frame %d, X == %d\n", $trace_frame, X
6910 @subsection @code{tdump}
6912 @cindex dump all data collected at tracepoint
6913 @cindex tracepoint data, display
6915 This command takes no arguments. It prints all the data collected at
6916 the current trace snapshot.
6919 (@value{GDBP}) @b{trace 444}
6920 (@value{GDBP}) @b{actions}
6921 Enter actions for tracepoint #2, one per line:
6922 > collect $regs, $locals, $args, gdb_long_test
6925 (@value{GDBP}) @b{tstart}
6927 (@value{GDBP}) @b{tfind line 444}
6928 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
6930 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
6932 (@value{GDBP}) @b{tdump}
6933 Data collected at tracepoint 2, trace frame 1:
6934 d0 0xc4aa0085 -995491707
6938 d4 0x71aea3d 119204413
6943 a1 0x3000668 50333288
6946 a4 0x3000698 50333336
6948 fp 0x30bf3c 0x30bf3c
6949 sp 0x30bf34 0x30bf34
6951 pc 0x20b2c8 0x20b2c8
6955 p = 0x20e5b4 "gdb-test"
6962 gdb_long_test = 17 '\021'
6967 @node save-tracepoints
6968 @subsection @code{save-tracepoints @var{filename}}
6969 @kindex save-tracepoints
6970 @cindex save tracepoints for future sessions
6972 This command saves all current tracepoint definitions together with
6973 their actions and passcounts, into a file @file{@var{filename}}
6974 suitable for use in a later debugging session. To read the saved
6975 tracepoint definitions, use the @code{source} command (@pxref{Command
6978 @node Tracepoint Variables
6979 @section Convenience Variables for Tracepoints
6980 @cindex tracepoint variables
6981 @cindex convenience variables for tracepoints
6984 @vindex $trace_frame
6985 @item (int) $trace_frame
6986 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
6987 snapshot is selected.
6990 @item (int) $tracepoint
6991 The tracepoint for the current trace snapshot.
6994 @item (int) $trace_line
6995 The line number for the current trace snapshot.
6998 @item (char []) $trace_file
6999 The source file for the current trace snapshot.
7002 @item (char []) $trace_func
7003 The name of the function containing @code{$tracepoint}.
7006 Note: @code{$trace_file} is not suitable for use in @code{printf},
7007 use @code{output} instead.
7009 Here's a simple example of using these convenience variables for
7010 stepping through all the trace snapshots and printing some of their
7014 (@value{GDBP}) @b{tfind start}
7016 (@value{GDBP}) @b{while $trace_frame != -1}
7017 > output $trace_file
7018 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7024 @chapter Debugging Programs That Use Overlays
7027 If your program is too large to fit completely in your target system's
7028 memory, you can sometimes use @dfn{overlays} to work around this
7029 problem. @value{GDBN} provides some support for debugging programs that
7033 * How Overlays Work:: A general explanation of overlays.
7034 * Overlay Commands:: Managing overlays in @value{GDBN}.
7035 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7036 mapped by asking the inferior.
7037 * Overlay Sample Program:: A sample program using overlays.
7040 @node How Overlays Work
7041 @section How Overlays Work
7042 @cindex mapped overlays
7043 @cindex unmapped overlays
7044 @cindex load address, overlay's
7045 @cindex mapped address
7046 @cindex overlay area
7048 Suppose you have a computer whose instruction address space is only 64
7049 kilobytes long, but which has much more memory which can be accessed by
7050 other means: special instructions, segment registers, or memory
7051 management hardware, for example. Suppose further that you want to
7052 adapt a program which is larger than 64 kilobytes to run on this system.
7054 One solution is to identify modules of your program which are relatively
7055 independent, and need not call each other directly; call these modules
7056 @dfn{overlays}. Separate the overlays from the main program, and place
7057 their machine code in the larger memory. Place your main program in
7058 instruction memory, but leave at least enough space there to hold the
7059 largest overlay as well.
7061 Now, to call a function located in an overlay, you must first copy that
7062 overlay's machine code from the large memory into the space set aside
7063 for it in the instruction memory, and then jump to its entry point
7066 @c NB: In the below the mapped area's size is greater or equal to the
7067 @c size of all overlays. This is intentional to remind the developer
7068 @c that overlays don't necessarily need to be the same size.
7072 Data Instruction Larger
7073 Address Space Address Space Address Space
7074 +-----------+ +-----------+ +-----------+
7076 +-----------+ +-----------+ +-----------+<-- overlay 1
7077 | program | | main | .----| overlay 1 | load address
7078 | variables | | program | | +-----------+
7079 | and heap | | | | | |
7080 +-----------+ | | | +-----------+<-- overlay 2
7081 | | +-----------+ | | | load address
7082 +-----------+ | | | .-| overlay 2 |
7084 mapped --->+-----------+ | | +-----------+
7086 | overlay | <-' | | |
7087 | area | <---' +-----------+<-- overlay 3
7088 | | <---. | | load address
7089 +-----------+ `--| overlay 3 |
7096 @anchor{A code overlay}A code overlay
7100 The diagram (@pxref{A code overlay}) shows a system with separate data
7101 and instruction address spaces. To map an overlay, the program copies
7102 its code from the larger address space to the instruction address space.
7103 Since the overlays shown here all use the same mapped address, only one
7104 may be mapped at a time. For a system with a single address space for
7105 data and instructions, the diagram would be similar, except that the
7106 program variables and heap would share an address space with the main
7107 program and the overlay area.
7109 An overlay loaded into instruction memory and ready for use is called a
7110 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7111 instruction memory. An overlay not present (or only partially present)
7112 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7113 is its address in the larger memory. The mapped address is also called
7114 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7115 called the @dfn{load memory address}, or @dfn{LMA}.
7117 Unfortunately, overlays are not a completely transparent way to adapt a
7118 program to limited instruction memory. They introduce a new set of
7119 global constraints you must keep in mind as you design your program:
7124 Before calling or returning to a function in an overlay, your program
7125 must make sure that overlay is actually mapped. Otherwise, the call or
7126 return will transfer control to the right address, but in the wrong
7127 overlay, and your program will probably crash.
7130 If the process of mapping an overlay is expensive on your system, you
7131 will need to choose your overlays carefully to minimize their effect on
7132 your program's performance.
7135 The executable file you load onto your system must contain each
7136 overlay's instructions, appearing at the overlay's load address, not its
7137 mapped address. However, each overlay's instructions must be relocated
7138 and its symbols defined as if the overlay were at its mapped address.
7139 You can use GNU linker scripts to specify different load and relocation
7140 addresses for pieces of your program; see @ref{Overlay Description,,,
7141 ld.info, Using ld: the GNU linker}.
7144 The procedure for loading executable files onto your system must be able
7145 to load their contents into the larger address space as well as the
7146 instruction and data spaces.
7150 The overlay system described above is rather simple, and could be
7151 improved in many ways:
7156 If your system has suitable bank switch registers or memory management
7157 hardware, you could use those facilities to make an overlay's load area
7158 contents simply appear at their mapped address in instruction space.
7159 This would probably be faster than copying the overlay to its mapped
7160 area in the usual way.
7163 If your overlays are small enough, you could set aside more than one
7164 overlay area, and have more than one overlay mapped at a time.
7167 You can use overlays to manage data, as well as instructions. In
7168 general, data overlays are even less transparent to your design than
7169 code overlays: whereas code overlays only require care when you call or
7170 return to functions, data overlays require care every time you access
7171 the data. Also, if you change the contents of a data overlay, you
7172 must copy its contents back out to its load address before you can copy a
7173 different data overlay into the same mapped area.
7178 @node Overlay Commands
7179 @section Overlay Commands
7181 To use @value{GDBN}'s overlay support, each overlay in your program must
7182 correspond to a separate section of the executable file. The section's
7183 virtual memory address and load memory address must be the overlay's
7184 mapped and load addresses. Identifying overlays with sections allows
7185 @value{GDBN} to determine the appropriate address of a function or
7186 variable, depending on whether the overlay is mapped or not.
7188 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7189 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7194 Disable @value{GDBN}'s overlay support. When overlay support is
7195 disabled, @value{GDBN} assumes that all functions and variables are
7196 always present at their mapped addresses. By default, @value{GDBN}'s
7197 overlay support is disabled.
7199 @item overlay manual
7200 @kindex overlay manual
7201 @cindex manual overlay debugging
7202 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7203 relies on you to tell it which overlays are mapped, and which are not,
7204 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7205 commands described below.
7207 @item overlay map-overlay @var{overlay}
7208 @itemx overlay map @var{overlay}
7209 @kindex overlay map-overlay
7210 @cindex map an overlay
7211 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7212 be the name of the object file section containing the overlay. When an
7213 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7214 functions and variables at their mapped addresses. @value{GDBN} assumes
7215 that any other overlays whose mapped ranges overlap that of
7216 @var{overlay} are now unmapped.
7218 @item overlay unmap-overlay @var{overlay}
7219 @itemx overlay unmap @var{overlay}
7220 @kindex overlay unmap-overlay
7221 @cindex unmap an overlay
7222 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7223 must be the name of the object file section containing the overlay.
7224 When an overlay is unmapped, @value{GDBN} assumes it can find the
7225 overlay's functions and variables at their load addresses.
7228 @kindex overlay auto
7229 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7230 consults a data structure the overlay manager maintains in the inferior
7231 to see which overlays are mapped. For details, see @ref{Automatic
7234 @item overlay load-target
7236 @kindex overlay load-target
7237 @cindex reloading the overlay table
7238 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7239 re-reads the table @value{GDBN} automatically each time the inferior
7240 stops, so this command should only be necessary if you have changed the
7241 overlay mapping yourself using @value{GDBN}. This command is only
7242 useful when using automatic overlay debugging.
7244 @item overlay list-overlays
7246 @cindex listing mapped overlays
7247 Display a list of the overlays currently mapped, along with their mapped
7248 addresses, load addresses, and sizes.
7252 Normally, when @value{GDBN} prints a code address, it includes the name
7253 of the function the address falls in:
7257 $3 = @{int ()@} 0x11a0 <main>
7260 When overlay debugging is enabled, @value{GDBN} recognizes code in
7261 unmapped overlays, and prints the names of unmapped functions with
7262 asterisks around them. For example, if @code{foo} is a function in an
7263 unmapped overlay, @value{GDBN} prints it this way:
7267 No sections are mapped.
7269 $5 = @{int (int)@} 0x100000 <*foo*>
7272 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7277 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7278 mapped at 0x1016 - 0x104a
7280 $6 = @{int (int)@} 0x1016 <foo>
7283 When overlay debugging is enabled, @value{GDBN} can find the correct
7284 address for functions and variables in an overlay, whether or not the
7285 overlay is mapped. This allows most @value{GDBN} commands, like
7286 @code{break} and @code{disassemble}, to work normally, even on unmapped
7287 code. However, @value{GDBN}'s breakpoint support has some limitations:
7291 @cindex breakpoints in overlays
7292 @cindex overlays, setting breakpoints in
7293 You can set breakpoints in functions in unmapped overlays, as long as
7294 @value{GDBN} can write to the overlay at its load address.
7296 @value{GDBN} can not set hardware or simulator-based breakpoints in
7297 unmapped overlays. However, if you set a breakpoint at the end of your
7298 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7299 you are using manual overlay management), @value{GDBN} will re-set its
7300 breakpoints properly.
7304 @node Automatic Overlay Debugging
7305 @section Automatic Overlay Debugging
7306 @cindex automatic overlay debugging
7308 @value{GDBN} can automatically track which overlays are mapped and which
7309 are not, given some simple co-operation from the overlay manager in the
7310 inferior. If you enable automatic overlay debugging with the
7311 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7312 looks in the inferior's memory for certain variables describing the
7313 current state of the overlays.
7315 Here are the variables your overlay manager must define to support
7316 @value{GDBN}'s automatic overlay debugging:
7320 @item @code{_ovly_table}:
7321 This variable must be an array of the following structures:
7326 /* The overlay's mapped address. */
7329 /* The size of the overlay, in bytes. */
7332 /* The overlay's load address. */
7335 /* Non-zero if the overlay is currently mapped;
7337 unsigned long mapped;
7341 @item @code{_novlys}:
7342 This variable must be a four-byte signed integer, holding the total
7343 number of elements in @code{_ovly_table}.
7347 To decide whether a particular overlay is mapped or not, @value{GDBN}
7348 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7349 @code{lma} members equal the VMA and LMA of the overlay's section in the
7350 executable file. When @value{GDBN} finds a matching entry, it consults
7351 the entry's @code{mapped} member to determine whether the overlay is
7354 In addition, your overlay manager may define a function called
7355 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7356 will silently set a breakpoint there. If the overlay manager then
7357 calls this function whenever it has changed the overlay table, this
7358 will enable @value{GDBN} to accurately keep track of which overlays
7359 are in program memory, and update any breakpoints that may be set
7360 in overlays. This will allow breakpoints to work even if the
7361 overlays are kept in ROM or other non-writable memory while they
7362 are not being executed.
7364 @node Overlay Sample Program
7365 @section Overlay Sample Program
7366 @cindex overlay example program
7368 When linking a program which uses overlays, you must place the overlays
7369 at their load addresses, while relocating them to run at their mapped
7370 addresses. To do this, you must write a linker script (@pxref{Overlay
7371 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7372 since linker scripts are specific to a particular host system, target
7373 architecture, and target memory layout, this manual cannot provide
7374 portable sample code demonstrating @value{GDBN}'s overlay support.
7376 However, the @value{GDBN} source distribution does contain an overlaid
7377 program, with linker scripts for a few systems, as part of its test
7378 suite. The program consists of the following files from
7379 @file{gdb/testsuite/gdb.base}:
7383 The main program file.
7385 A simple overlay manager, used by @file{overlays.c}.
7390 Overlay modules, loaded and used by @file{overlays.c}.
7393 Linker scripts for linking the test program on the @code{d10v-elf}
7394 and @code{m32r-elf} targets.
7397 You can build the test program using the @code{d10v-elf} GCC
7398 cross-compiler like this:
7401 $ d10v-elf-gcc -g -c overlays.c
7402 $ d10v-elf-gcc -g -c ovlymgr.c
7403 $ d10v-elf-gcc -g -c foo.c
7404 $ d10v-elf-gcc -g -c bar.c
7405 $ d10v-elf-gcc -g -c baz.c
7406 $ d10v-elf-gcc -g -c grbx.c
7407 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7408 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7411 The build process is identical for any other architecture, except that
7412 you must substitute the appropriate compiler and linker script for the
7413 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7417 @chapter Using @value{GDBN} with Different Languages
7420 Although programming languages generally have common aspects, they are
7421 rarely expressed in the same manner. For instance, in ANSI C,
7422 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7423 Modula-2, it is accomplished by @code{p^}. Values can also be
7424 represented (and displayed) differently. Hex numbers in C appear as
7425 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7427 @cindex working language
7428 Language-specific information is built into @value{GDBN} for some languages,
7429 allowing you to express operations like the above in your program's
7430 native language, and allowing @value{GDBN} to output values in a manner
7431 consistent with the syntax of your program's native language. The
7432 language you use to build expressions is called the @dfn{working
7436 * Setting:: Switching between source languages
7437 * Show:: Displaying the language
7438 * Checks:: Type and range checks
7439 * Support:: Supported languages
7443 @section Switching between source languages
7445 There are two ways to control the working language---either have @value{GDBN}
7446 set it automatically, or select it manually yourself. You can use the
7447 @code{set language} command for either purpose. On startup, @value{GDBN}
7448 defaults to setting the language automatically. The working language is
7449 used to determine how expressions you type are interpreted, how values
7452 In addition to the working language, every source file that
7453 @value{GDBN} knows about has its own working language. For some object
7454 file formats, the compiler might indicate which language a particular
7455 source file is in. However, most of the time @value{GDBN} infers the
7456 language from the name of the file. The language of a source file
7457 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7458 show each frame appropriately for its own language. There is no way to
7459 set the language of a source file from within @value{GDBN}, but you can
7460 set the language associated with a filename extension. @xref{Show, ,
7461 Displaying the language}.
7463 This is most commonly a problem when you use a program, such
7464 as @code{cfront} or @code{f2c}, that generates C but is written in
7465 another language. In that case, make the
7466 program use @code{#line} directives in its C output; that way
7467 @value{GDBN} will know the correct language of the source code of the original
7468 program, and will display that source code, not the generated C code.
7471 * Filenames:: Filename extensions and languages.
7472 * Manually:: Setting the working language manually
7473 * Automatically:: Having @value{GDBN} infer the source language
7477 @subsection List of filename extensions and languages
7479 If a source file name ends in one of the following extensions, then
7480 @value{GDBN} infers that its language is the one indicated.
7496 Objective-C source file
7503 Modula-2 source file
7507 Assembler source file. This actually behaves almost like C, but
7508 @value{GDBN} does not skip over function prologues when stepping.
7511 In addition, you may set the language associated with a filename
7512 extension. @xref{Show, , Displaying the language}.
7515 @subsection Setting the working language
7517 If you allow @value{GDBN} to set the language automatically,
7518 expressions are interpreted the same way in your debugging session and
7521 @kindex set language
7522 If you wish, you may set the language manually. To do this, issue the
7523 command @samp{set language @var{lang}}, where @var{lang} is the name of
7525 @code{c} or @code{modula-2}.
7526 For a list of the supported languages, type @samp{set language}.
7528 Setting the language manually prevents @value{GDBN} from updating the working
7529 language automatically. This can lead to confusion if you try
7530 to debug a program when the working language is not the same as the
7531 source language, when an expression is acceptable to both
7532 languages---but means different things. For instance, if the current
7533 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7541 might not have the effect you intended. In C, this means to add
7542 @code{b} and @code{c} and place the result in @code{a}. The result
7543 printed would be the value of @code{a}. In Modula-2, this means to compare
7544 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7547 @subsection Having @value{GDBN} infer the source language
7549 To have @value{GDBN} set the working language automatically, use
7550 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7551 then infers the working language. That is, when your program stops in a
7552 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7553 working language to the language recorded for the function in that
7554 frame. If the language for a frame is unknown (that is, if the function
7555 or block corresponding to the frame was defined in a source file that
7556 does not have a recognized extension), the current working language is
7557 not changed, and @value{GDBN} issues a warning.
7559 This may not seem necessary for most programs, which are written
7560 entirely in one source language. However, program modules and libraries
7561 written in one source language can be used by a main program written in
7562 a different source language. Using @samp{set language auto} in this
7563 case frees you from having to set the working language manually.
7566 @section Displaying the language
7568 The following commands help you find out which language is the
7569 working language, and also what language source files were written in.
7571 @kindex show language
7572 @kindex info frame@r{, show the source language}
7573 @kindex info source@r{, show the source language}
7576 Display the current working language. This is the
7577 language you can use with commands such as @code{print} to
7578 build and compute expressions that may involve variables in your program.
7581 Display the source language for this frame. This language becomes the
7582 working language if you use an identifier from this frame.
7583 @xref{Frame Info, ,Information about a frame}, to identify the other
7584 information listed here.
7587 Display the source language of this source file.
7588 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7589 information listed here.
7592 In unusual circumstances, you may have source files with extensions
7593 not in the standard list. You can then set the extension associated
7594 with a language explicitly:
7596 @kindex set extension-language
7597 @kindex info extensions
7599 @item set extension-language @var{.ext} @var{language}
7600 Set source files with extension @var{.ext} to be assumed to be in
7601 the source language @var{language}.
7603 @item info extensions
7604 List all the filename extensions and the associated languages.
7608 @section Type and range checking
7611 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7612 checking are included, but they do not yet have any effect. This
7613 section documents the intended facilities.
7615 @c FIXME remove warning when type/range code added
7617 Some languages are designed to guard you against making seemingly common
7618 errors through a series of compile- and run-time checks. These include
7619 checking the type of arguments to functions and operators, and making
7620 sure mathematical overflows are caught at run time. Checks such as
7621 these help to ensure a program's correctness once it has been compiled
7622 by eliminating type mismatches, and providing active checks for range
7623 errors when your program is running.
7625 @value{GDBN} can check for conditions like the above if you wish.
7626 Although @value{GDBN} does not check the statements in your program, it
7627 can check expressions entered directly into @value{GDBN} for evaluation via
7628 the @code{print} command, for example. As with the working language,
7629 @value{GDBN} can also decide whether or not to check automatically based on
7630 your program's source language. @xref{Support, ,Supported languages},
7631 for the default settings of supported languages.
7634 * Type Checking:: An overview of type checking
7635 * Range Checking:: An overview of range checking
7638 @cindex type checking
7639 @cindex checks, type
7641 @subsection An overview of type checking
7643 Some languages, such as Modula-2, are strongly typed, meaning that the
7644 arguments to operators and functions have to be of the correct type,
7645 otherwise an error occurs. These checks prevent type mismatch
7646 errors from ever causing any run-time problems. For example,
7654 The second example fails because the @code{CARDINAL} 1 is not
7655 type-compatible with the @code{REAL} 2.3.
7657 For the expressions you use in @value{GDBN} commands, you can tell the
7658 @value{GDBN} type checker to skip checking;
7659 to treat any mismatches as errors and abandon the expression;
7660 or to only issue warnings when type mismatches occur,
7661 but evaluate the expression anyway. When you choose the last of
7662 these, @value{GDBN} evaluates expressions like the second example above, but
7663 also issues a warning.
7665 Even if you turn type checking off, there may be other reasons
7666 related to type that prevent @value{GDBN} from evaluating an expression.
7667 For instance, @value{GDBN} does not know how to add an @code{int} and
7668 a @code{struct foo}. These particular type errors have nothing to do
7669 with the language in use, and usually arise from expressions, such as
7670 the one described above, which make little sense to evaluate anyway.
7672 Each language defines to what degree it is strict about type. For
7673 instance, both Modula-2 and C require the arguments to arithmetical
7674 operators to be numbers. In C, enumerated types and pointers can be
7675 represented as numbers, so that they are valid arguments to mathematical
7676 operators. @xref{Support, ,Supported languages}, for further
7677 details on specific languages.
7679 @value{GDBN} provides some additional commands for controlling the type checker:
7681 @kindex set check@r{, type}
7682 @kindex set check type
7683 @kindex show check type
7685 @item set check type auto
7686 Set type checking on or off based on the current working language.
7687 @xref{Support, ,Supported languages}, for the default settings for
7690 @item set check type on
7691 @itemx set check type off
7692 Set type checking on or off, overriding the default setting for the
7693 current working language. Issue a warning if the setting does not
7694 match the language default. If any type mismatches occur in
7695 evaluating an expression while type checking is on, @value{GDBN} prints a
7696 message and aborts evaluation of the expression.
7698 @item set check type warn
7699 Cause the type checker to issue warnings, but to always attempt to
7700 evaluate the expression. Evaluating the expression may still
7701 be impossible for other reasons. For example, @value{GDBN} cannot add
7702 numbers and structures.
7705 Show the current setting of the type checker, and whether or not @value{GDBN}
7706 is setting it automatically.
7709 @cindex range checking
7710 @cindex checks, range
7711 @node Range Checking
7712 @subsection An overview of range checking
7714 In some languages (such as Modula-2), it is an error to exceed the
7715 bounds of a type; this is enforced with run-time checks. Such range
7716 checking is meant to ensure program correctness by making sure
7717 computations do not overflow, or indices on an array element access do
7718 not exceed the bounds of the array.
7720 For expressions you use in @value{GDBN} commands, you can tell
7721 @value{GDBN} to treat range errors in one of three ways: ignore them,
7722 always treat them as errors and abandon the expression, or issue
7723 warnings but evaluate the expression anyway.
7725 A range error can result from numerical overflow, from exceeding an
7726 array index bound, or when you type a constant that is not a member
7727 of any type. Some languages, however, do not treat overflows as an
7728 error. In many implementations of C, mathematical overflow causes the
7729 result to ``wrap around'' to lower values---for example, if @var{m} is
7730 the largest integer value, and @var{s} is the smallest, then
7733 @var{m} + 1 @result{} @var{s}
7736 This, too, is specific to individual languages, and in some cases
7737 specific to individual compilers or machines. @xref{Support, ,
7738 Supported languages}, for further details on specific languages.
7740 @value{GDBN} provides some additional commands for controlling the range checker:
7742 @kindex set check@r{, range}
7743 @kindex set check range
7744 @kindex show check range
7746 @item set check range auto
7747 Set range checking on or off based on the current working language.
7748 @xref{Support, ,Supported languages}, for the default settings for
7751 @item set check range on
7752 @itemx set check range off
7753 Set range checking on or off, overriding the default setting for the
7754 current working language. A warning is issued if the setting does not
7755 match the language default. If a range error occurs and range checking is on,
7756 then a message is printed and evaluation of the expression is aborted.
7758 @item set check range warn
7759 Output messages when the @value{GDBN} range checker detects a range error,
7760 but attempt to evaluate the expression anyway. Evaluating the
7761 expression may still be impossible for other reasons, such as accessing
7762 memory that the process does not own (a typical example from many Unix
7766 Show the current setting of the range checker, and whether or not it is
7767 being set automatically by @value{GDBN}.
7771 @section Supported languages
7773 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, assembly, and Modula-2.
7774 @c This is false ...
7775 Some @value{GDBN} features may be used in expressions regardless of the
7776 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7777 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7778 ,Expressions}) can be used with the constructs of any supported
7781 The following sections detail to what degree each source language is
7782 supported by @value{GDBN}. These sections are not meant to be language
7783 tutorials or references, but serve only as a reference guide to what the
7784 @value{GDBN} expression parser accepts, and what input and output
7785 formats should look like for different languages. There are many good
7786 books written on each of these languages; please look to these for a
7787 language reference or tutorial.
7791 * Objective-C:: Objective-C
7792 * Modula-2:: Modula-2
7796 @subsection C and C@t{++}
7798 @cindex C and C@t{++}
7799 @cindex expressions in C or C@t{++}
7801 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7802 to both languages. Whenever this is the case, we discuss those languages
7806 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
7807 @cindex @sc{gnu} C@t{++}
7808 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7809 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7810 effectively, you must compile your C@t{++} programs with a supported
7811 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
7812 compiler (@code{aCC}).
7814 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
7815 format; if it doesn't work on your system, try the stabs+ debugging
7816 format. You can select those formats explicitly with the @code{g++}
7817 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
7818 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7819 CC, gcc.info, Using @sc{gnu} CC}.
7822 * C Operators:: C and C@t{++} operators
7823 * C Constants:: C and C@t{++} constants
7824 * C plus plus expressions:: C@t{++} expressions
7825 * C Defaults:: Default settings for C and C@t{++}
7826 * C Checks:: C and C@t{++} type and range checks
7827 * Debugging C:: @value{GDBN} and C
7828 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
7832 @subsubsection C and C@t{++} operators
7834 @cindex C and C@t{++} operators
7836 Operators must be defined on values of specific types. For instance,
7837 @code{+} is defined on numbers, but not on structures. Operators are
7838 often defined on groups of types.
7840 For the purposes of C and C@t{++}, the following definitions hold:
7845 @emph{Integral types} include @code{int} with any of its storage-class
7846 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
7849 @emph{Floating-point types} include @code{float}, @code{double}, and
7850 @code{long double} (if supported by the target platform).
7853 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
7856 @emph{Scalar types} include all of the above.
7861 The following operators are supported. They are listed here
7862 in order of increasing precedence:
7866 The comma or sequencing operator. Expressions in a comma-separated list
7867 are evaluated from left to right, with the result of the entire
7868 expression being the last expression evaluated.
7871 Assignment. The value of an assignment expression is the value
7872 assigned. Defined on scalar types.
7875 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
7876 and translated to @w{@code{@var{a} = @var{a op b}}}.
7877 @w{@code{@var{op}=}} and @code{=} have the same precedence.
7878 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
7879 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
7882 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
7883 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
7887 Logical @sc{or}. Defined on integral types.
7890 Logical @sc{and}. Defined on integral types.
7893 Bitwise @sc{or}. Defined on integral types.
7896 Bitwise exclusive-@sc{or}. Defined on integral types.
7899 Bitwise @sc{and}. Defined on integral types.
7902 Equality and inequality. Defined on scalar types. The value of these
7903 expressions is 0 for false and non-zero for true.
7905 @item <@r{, }>@r{, }<=@r{, }>=
7906 Less than, greater than, less than or equal, greater than or equal.
7907 Defined on scalar types. The value of these expressions is 0 for false
7908 and non-zero for true.
7911 left shift, and right shift. Defined on integral types.
7914 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
7917 Addition and subtraction. Defined on integral types, floating-point types and
7920 @item *@r{, }/@r{, }%
7921 Multiplication, division, and modulus. Multiplication and division are
7922 defined on integral and floating-point types. Modulus is defined on
7926 Increment and decrement. When appearing before a variable, the
7927 operation is performed before the variable is used in an expression;
7928 when appearing after it, the variable's value is used before the
7929 operation takes place.
7932 Pointer dereferencing. Defined on pointer types. Same precedence as
7936 Address operator. Defined on variables. Same precedence as @code{++}.
7938 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
7939 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
7940 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
7941 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
7945 Negative. Defined on integral and floating-point types. Same
7946 precedence as @code{++}.
7949 Logical negation. Defined on integral types. Same precedence as
7953 Bitwise complement operator. Defined on integral types. Same precedence as
7958 Structure member, and pointer-to-structure member. For convenience,
7959 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
7960 pointer based on the stored type information.
7961 Defined on @code{struct} and @code{union} data.
7964 Dereferences of pointers to members.
7967 Array indexing. @code{@var{a}[@var{i}]} is defined as
7968 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
7971 Function parameter list. Same precedence as @code{->}.
7974 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
7975 and @code{class} types.
7978 Doubled colons also represent the @value{GDBN} scope operator
7979 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
7983 If an operator is redefined in the user code, @value{GDBN} usually
7984 attempts to invoke the redefined version instead of using the operator's
7992 @subsubsection C and C@t{++} constants
7994 @cindex C and C@t{++} constants
7996 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8001 Integer constants are a sequence of digits. Octal constants are
8002 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8003 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8004 @samp{l}, specifying that the constant should be treated as a
8008 Floating point constants are a sequence of digits, followed by a decimal
8009 point, followed by a sequence of digits, and optionally followed by an
8010 exponent. An exponent is of the form:
8011 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8012 sequence of digits. The @samp{+} is optional for positive exponents.
8013 A floating-point constant may also end with a letter @samp{f} or
8014 @samp{F}, specifying that the constant should be treated as being of
8015 the @code{float} (as opposed to the default @code{double}) type; or with
8016 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8020 Enumerated constants consist of enumerated identifiers, or their
8021 integral equivalents.
8024 Character constants are a single character surrounded by single quotes
8025 (@code{'}), or a number---the ordinal value of the corresponding character
8026 (usually its @sc{ascii} value). Within quotes, the single character may
8027 be represented by a letter or by @dfn{escape sequences}, which are of
8028 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8029 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8030 @samp{@var{x}} is a predefined special character---for example,
8031 @samp{\n} for newline.
8034 String constants are a sequence of character constants surrounded by
8035 double quotes (@code{"}). Any valid character constant (as described
8036 above) may appear. Double quotes within the string must be preceded by
8037 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8041 Pointer constants are an integral value. You can also write pointers
8042 to constants using the C operator @samp{&}.
8045 Array constants are comma-separated lists surrounded by braces @samp{@{}
8046 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8047 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8048 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8052 * C plus plus expressions::
8059 @node C plus plus expressions
8060 @subsubsection C@t{++} expressions
8062 @cindex expressions in C@t{++}
8063 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8065 @cindex debugging C@t{++} programs
8066 @cindex C@t{++} compilers
8067 @cindex debug formats and C@t{++}
8068 @cindex @value{NGCC} and C@t{++}
8070 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8071 proper compiler and the proper debug format. Currently, @value{GDBN}
8072 works best when debugging C@t{++} code that is compiled with
8073 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8074 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8075 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8076 stabs+ as their default debug format, so you usually don't need to
8077 specify a debug format explicitly. Other compilers and/or debug formats
8078 are likely to work badly or not at all when using @value{GDBN} to debug
8084 @cindex member functions
8086 Member function calls are allowed; you can use expressions like
8089 count = aml->GetOriginal(x, y)
8092 @vindex this@r{, inside C@t{++} member functions}
8093 @cindex namespace in C@t{++}
8095 While a member function is active (in the selected stack frame), your
8096 expressions have the same namespace available as the member function;
8097 that is, @value{GDBN} allows implicit references to the class instance
8098 pointer @code{this} following the same rules as C@t{++}.
8100 @cindex call overloaded functions
8101 @cindex overloaded functions, calling
8102 @cindex type conversions in C@t{++}
8104 You can call overloaded functions; @value{GDBN} resolves the function
8105 call to the right definition, with some restrictions. @value{GDBN} does not
8106 perform overload resolution involving user-defined type conversions,
8107 calls to constructors, or instantiations of templates that do not exist
8108 in the program. It also cannot handle ellipsis argument lists or
8111 It does perform integral conversions and promotions, floating-point
8112 promotions, arithmetic conversions, pointer conversions, conversions of
8113 class objects to base classes, and standard conversions such as those of
8114 functions or arrays to pointers; it requires an exact match on the
8115 number of function arguments.
8117 Overload resolution is always performed, unless you have specified
8118 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8119 ,@value{GDBN} features for C@t{++}}.
8121 You must specify @code{set overload-resolution off} in order to use an
8122 explicit function signature to call an overloaded function, as in
8124 p 'foo(char,int)'('x', 13)
8127 The @value{GDBN} command-completion facility can simplify this;
8128 see @ref{Completion, ,Command completion}.
8130 @cindex reference declarations
8132 @value{GDBN} understands variables declared as C@t{++} references; you can use
8133 them in expressions just as you do in C@t{++} source---they are automatically
8136 In the parameter list shown when @value{GDBN} displays a frame, the values of
8137 reference variables are not displayed (unlike other variables); this
8138 avoids clutter, since references are often used for large structures.
8139 The @emph{address} of a reference variable is always shown, unless
8140 you have specified @samp{set print address off}.
8143 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8144 expressions can use it just as expressions in your program do. Since
8145 one scope may be defined in another, you can use @code{::} repeatedly if
8146 necessary, for example in an expression like
8147 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8148 resolving name scope by reference to source files, in both C and C@t{++}
8149 debugging (@pxref{Variables, ,Program variables}).
8152 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8153 calling virtual functions correctly, printing out virtual bases of
8154 objects, calling functions in a base subobject, casting objects, and
8155 invoking user-defined operators.
8158 @subsubsection C and C@t{++} defaults
8160 @cindex C and C@t{++} defaults
8162 If you allow @value{GDBN} to set type and range checking automatically, they
8163 both default to @code{off} whenever the working language changes to
8164 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8165 selects the working language.
8167 If you allow @value{GDBN} to set the language automatically, it
8168 recognizes source files whose names end with @file{.c}, @file{.C}, or
8169 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8170 these files, it sets the working language to C or C@t{++}.
8171 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8172 for further details.
8174 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8175 @c unimplemented. If (b) changes, it might make sense to let this node
8176 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8179 @subsubsection C and C@t{++} type and range checks
8181 @cindex C and C@t{++} checks
8183 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8184 is not used. However, if you turn type checking on, @value{GDBN}
8185 considers two variables type equivalent if:
8189 The two variables are structured and have the same structure, union, or
8193 The two variables have the same type name, or types that have been
8194 declared equivalent through @code{typedef}.
8197 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8200 The two @code{struct}, @code{union}, or @code{enum} variables are
8201 declared in the same declaration. (Note: this may not be true for all C
8206 Range checking, if turned on, is done on mathematical operations. Array
8207 indices are not checked, since they are often used to index a pointer
8208 that is not itself an array.
8211 @subsubsection @value{GDBN} and C
8213 The @code{set print union} and @code{show print union} commands apply to
8214 the @code{union} type. When set to @samp{on}, any @code{union} that is
8215 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8216 appears as @samp{@{...@}}.
8218 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8219 with pointers and a memory allocation function. @xref{Expressions,
8223 * Debugging C plus plus::
8226 @node Debugging C plus plus
8227 @subsubsection @value{GDBN} features for C@t{++}
8229 @cindex commands for C@t{++}
8231 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8232 designed specifically for use with C@t{++}. Here is a summary:
8235 @cindex break in overloaded functions
8236 @item @r{breakpoint menus}
8237 When you want a breakpoint in a function whose name is overloaded,
8238 @value{GDBN} breakpoint menus help you specify which function definition
8239 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8241 @cindex overloading in C@t{++}
8242 @item rbreak @var{regex}
8243 Setting breakpoints using regular expressions is helpful for setting
8244 breakpoints on overloaded functions that are not members of any special
8246 @xref{Set Breaks, ,Setting breakpoints}.
8248 @cindex C@t{++} exception handling
8251 Debug C@t{++} exception handling using these commands. @xref{Set
8252 Catchpoints, , Setting catchpoints}.
8255 @item ptype @var{typename}
8256 Print inheritance relationships as well as other information for type
8258 @xref{Symbols, ,Examining the Symbol Table}.
8260 @cindex C@t{++} symbol display
8261 @item set print demangle
8262 @itemx show print demangle
8263 @itemx set print asm-demangle
8264 @itemx show print asm-demangle
8265 Control whether C@t{++} symbols display in their source form, both when
8266 displaying code as C@t{++} source and when displaying disassemblies.
8267 @xref{Print Settings, ,Print settings}.
8269 @item set print object
8270 @itemx show print object
8271 Choose whether to print derived (actual) or declared types of objects.
8272 @xref{Print Settings, ,Print settings}.
8274 @item set print vtbl
8275 @itemx show print vtbl
8276 Control the format for printing virtual function tables.
8277 @xref{Print Settings, ,Print settings}.
8278 (The @code{vtbl} commands do not work on programs compiled with the HP
8279 ANSI C@t{++} compiler (@code{aCC}).)
8281 @kindex set overload-resolution
8282 @cindex overloaded functions, overload resolution
8283 @item set overload-resolution on
8284 Enable overload resolution for C@t{++} expression evaluation. The default
8285 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8286 and searches for a function whose signature matches the argument types,
8287 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8288 expressions}, for details). If it cannot find a match, it emits a
8291 @item set overload-resolution off
8292 Disable overload resolution for C@t{++} expression evaluation. For
8293 overloaded functions that are not class member functions, @value{GDBN}
8294 chooses the first function of the specified name that it finds in the
8295 symbol table, whether or not its arguments are of the correct type. For
8296 overloaded functions that are class member functions, @value{GDBN}
8297 searches for a function whose signature @emph{exactly} matches the
8300 @item @r{Overloaded symbol names}
8301 You can specify a particular definition of an overloaded symbol, using
8302 the same notation that is used to declare such symbols in C@t{++}: type
8303 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8304 also use the @value{GDBN} command-line word completion facilities to list the
8305 available choices, or to finish the type list for you.
8306 @xref{Completion,, Command completion}, for details on how to do this.
8310 @subsection Objective-C
8313 This section provides information about some commands and command
8314 options that are useful for debugging Objective-C code.
8317 * Method Names in Commands::
8318 * The Print Command with Objective-C::
8321 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8322 @subsubsection Method Names in Commands
8324 The following commands have been extended to accept Objective-C method
8325 names as line specifications:
8327 @kindex clear@r{, and Objective-C}
8328 @kindex break@r{, and Objective-C}
8329 @kindex info line@r{, and Objective-C}
8330 @kindex jump@r{, and Objective-C}
8331 @kindex list@r{, and Objective-C}
8335 @item @code{info line}
8340 A fully qualified Objective-C method name is specified as
8343 -[@var{Class} @var{methodName}]
8346 where the minus sign is used to indicate an instance method and a plus
8347 sign (not shown) is used to indicate a class method. The
8348 class name @var{Class} and method name @var{methoName} are enclosed in
8349 brackets, similar to the way messages are specified in Objective-C source
8350 code. For example, to set a breakpoint at the @code{create} instance method of
8351 class @code{Fruit} in the program currently being debugged, enter:
8354 break -[Fruit create]
8357 To list ten program lines around the @code{initialize} class method,
8361 list +[NSText initialize]
8364 In the current version of GDB, the plus or minus sign is required. In
8365 future versions of GDB, the plus or minus sign will be optional, but you
8366 can use it to narrow the search. It is also possible to specify just a
8373 You must specify the complete method name, including any colons. If
8374 your program's source files contain more than one @code{create} method,
8375 you'll be presented with a numbered list of classes that implement that
8376 method. Indicate your choice by number, or type @samp{0} to exit if
8379 As another example, to clear a breakpoint established at the
8380 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
8383 clear -[NSWindow makeKeyAndOrderFront:]
8386 @node The Print Command with Objective-C
8387 @subsubsection The Print Command With Objective-C
8389 The print command has also been extended to accept methods. For example:
8392 print -[object hash]
8395 @cindex print an Objective-C object description
8396 will tell gdb to send the -hash message to object and print the
8397 result. Also an additional command has been added, @code{print-object}
8398 or @code{po} for short, which is meant to print the description of an
8399 object. However, this command may only work with certain Objective-C
8400 libraries that have a particular hook function, called
8401 @code{_NSPrintForDebugger} defined.
8403 @node Modula-2, , Objective-C, Support
8404 @subsection Modula-2
8406 @cindex Modula-2, @value{GDBN} support
8408 The extensions made to @value{GDBN} to support Modula-2 only support
8409 output from the @sc{gnu} Modula-2 compiler (which is currently being
8410 developed). Other Modula-2 compilers are not currently supported, and
8411 attempting to debug executables produced by them is most likely
8412 to give an error as @value{GDBN} reads in the executable's symbol
8415 @cindex expressions in Modula-2
8417 * M2 Operators:: Built-in operators
8418 * Built-In Func/Proc:: Built-in functions and procedures
8419 * M2 Constants:: Modula-2 constants
8420 * M2 Defaults:: Default settings for Modula-2
8421 * Deviations:: Deviations from standard Modula-2
8422 * M2 Checks:: Modula-2 type and range checks
8423 * M2 Scope:: The scope operators @code{::} and @code{.}
8424 * GDB/M2:: @value{GDBN} and Modula-2
8428 @subsubsection Operators
8429 @cindex Modula-2 operators
8431 Operators must be defined on values of specific types. For instance,
8432 @code{+} is defined on numbers, but not on structures. Operators are
8433 often defined on groups of types. For the purposes of Modula-2, the
8434 following definitions hold:
8439 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8443 @emph{Character types} consist of @code{CHAR} and its subranges.
8446 @emph{Floating-point types} consist of @code{REAL}.
8449 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8453 @emph{Scalar types} consist of all of the above.
8456 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8459 @emph{Boolean types} consist of @code{BOOLEAN}.
8463 The following operators are supported, and appear in order of
8464 increasing precedence:
8468 Function argument or array index separator.
8471 Assignment. The value of @var{var} @code{:=} @var{value} is
8475 Less than, greater than on integral, floating-point, or enumerated
8479 Less than or equal to, greater than or equal to
8480 on integral, floating-point and enumerated types, or set inclusion on
8481 set types. Same precedence as @code{<}.
8483 @item =@r{, }<>@r{, }#
8484 Equality and two ways of expressing inequality, valid on scalar types.
8485 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8486 available for inequality, since @code{#} conflicts with the script
8490 Set membership. Defined on set types and the types of their members.
8491 Same precedence as @code{<}.
8494 Boolean disjunction. Defined on boolean types.
8497 Boolean conjunction. Defined on boolean types.
8500 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8503 Addition and subtraction on integral and floating-point types, or union
8504 and difference on set types.
8507 Multiplication on integral and floating-point types, or set intersection
8511 Division on floating-point types, or symmetric set difference on set
8512 types. Same precedence as @code{*}.
8515 Integer division and remainder. Defined on integral types. Same
8516 precedence as @code{*}.
8519 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8522 Pointer dereferencing. Defined on pointer types.
8525 Boolean negation. Defined on boolean types. Same precedence as
8529 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8530 precedence as @code{^}.
8533 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8536 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8540 @value{GDBN} and Modula-2 scope operators.
8544 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8545 treats the use of the operator @code{IN}, or the use of operators
8546 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8547 @code{<=}, and @code{>=} on sets as an error.
8551 @node Built-In Func/Proc
8552 @subsubsection Built-in functions and procedures
8553 @cindex Modula-2 built-ins
8555 Modula-2 also makes available several built-in procedures and functions.
8556 In describing these, the following metavariables are used:
8561 represents an @code{ARRAY} variable.
8564 represents a @code{CHAR} constant or variable.
8567 represents a variable or constant of integral type.
8570 represents an identifier that belongs to a set. Generally used in the
8571 same function with the metavariable @var{s}. The type of @var{s} should
8572 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8575 represents a variable or constant of integral or floating-point type.
8578 represents a variable or constant of floating-point type.
8584 represents a variable.
8587 represents a variable or constant of one of many types. See the
8588 explanation of the function for details.
8591 All Modula-2 built-in procedures also return a result, described below.
8595 Returns the absolute value of @var{n}.
8598 If @var{c} is a lower case letter, it returns its upper case
8599 equivalent, otherwise it returns its argument.
8602 Returns the character whose ordinal value is @var{i}.
8605 Decrements the value in the variable @var{v} by one. Returns the new value.
8607 @item DEC(@var{v},@var{i})
8608 Decrements the value in the variable @var{v} by @var{i}. Returns the
8611 @item EXCL(@var{m},@var{s})
8612 Removes the element @var{m} from the set @var{s}. Returns the new
8615 @item FLOAT(@var{i})
8616 Returns the floating point equivalent of the integer @var{i}.
8619 Returns the index of the last member of @var{a}.
8622 Increments the value in the variable @var{v} by one. Returns the new value.
8624 @item INC(@var{v},@var{i})
8625 Increments the value in the variable @var{v} by @var{i}. Returns the
8628 @item INCL(@var{m},@var{s})
8629 Adds the element @var{m} to the set @var{s} if it is not already
8630 there. Returns the new set.
8633 Returns the maximum value of the type @var{t}.
8636 Returns the minimum value of the type @var{t}.
8639 Returns boolean TRUE if @var{i} is an odd number.
8642 Returns the ordinal value of its argument. For example, the ordinal
8643 value of a character is its @sc{ascii} value (on machines supporting the
8644 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8645 integral, character and enumerated types.
8648 Returns the size of its argument. @var{x} can be a variable or a type.
8650 @item TRUNC(@var{r})
8651 Returns the integral part of @var{r}.
8653 @item VAL(@var{t},@var{i})
8654 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8658 @emph{Warning:} Sets and their operations are not yet supported, so
8659 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8663 @cindex Modula-2 constants
8665 @subsubsection Constants
8667 @value{GDBN} allows you to express the constants of Modula-2 in the following
8673 Integer constants are simply a sequence of digits. When used in an
8674 expression, a constant is interpreted to be type-compatible with the
8675 rest of the expression. Hexadecimal integers are specified by a
8676 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8679 Floating point constants appear as a sequence of digits, followed by a
8680 decimal point and another sequence of digits. An optional exponent can
8681 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8682 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8683 digits of the floating point constant must be valid decimal (base 10)
8687 Character constants consist of a single character enclosed by a pair of
8688 like quotes, either single (@code{'}) or double (@code{"}). They may
8689 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8690 followed by a @samp{C}.
8693 String constants consist of a sequence of characters enclosed by a
8694 pair of like quotes, either single (@code{'}) or double (@code{"}).
8695 Escape sequences in the style of C are also allowed. @xref{C
8696 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8700 Enumerated constants consist of an enumerated identifier.
8703 Boolean constants consist of the identifiers @code{TRUE} and
8707 Pointer constants consist of integral values only.
8710 Set constants are not yet supported.
8714 @subsubsection Modula-2 defaults
8715 @cindex Modula-2 defaults
8717 If type and range checking are set automatically by @value{GDBN}, they
8718 both default to @code{on} whenever the working language changes to
8719 Modula-2. This happens regardless of whether you or @value{GDBN}
8720 selected the working language.
8722 If you allow @value{GDBN} to set the language automatically, then entering
8723 code compiled from a file whose name ends with @file{.mod} sets the
8724 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8725 the language automatically}, for further details.
8728 @subsubsection Deviations from standard Modula-2
8729 @cindex Modula-2, deviations from
8731 A few changes have been made to make Modula-2 programs easier to debug.
8732 This is done primarily via loosening its type strictness:
8736 Unlike in standard Modula-2, pointer constants can be formed by
8737 integers. This allows you to modify pointer variables during
8738 debugging. (In standard Modula-2, the actual address contained in a
8739 pointer variable is hidden from you; it can only be modified
8740 through direct assignment to another pointer variable or expression that
8741 returned a pointer.)
8744 C escape sequences can be used in strings and characters to represent
8745 non-printable characters. @value{GDBN} prints out strings with these
8746 escape sequences embedded. Single non-printable characters are
8747 printed using the @samp{CHR(@var{nnn})} format.
8750 The assignment operator (@code{:=}) returns the value of its right-hand
8754 All built-in procedures both modify @emph{and} return their argument.
8758 @subsubsection Modula-2 type and range checks
8759 @cindex Modula-2 checks
8762 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8765 @c FIXME remove warning when type/range checks added
8767 @value{GDBN} considers two Modula-2 variables type equivalent if:
8771 They are of types that have been declared equivalent via a @code{TYPE
8772 @var{t1} = @var{t2}} statement
8775 They have been declared on the same line. (Note: This is true of the
8776 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8779 As long as type checking is enabled, any attempt to combine variables
8780 whose types are not equivalent is an error.
8782 Range checking is done on all mathematical operations, assignment, array
8783 index bounds, and all built-in functions and procedures.
8786 @subsubsection The scope operators @code{::} and @code{.}
8788 @cindex @code{.}, Modula-2 scope operator
8789 @cindex colon, doubled as scope operator
8791 @vindex colon-colon@r{, in Modula-2}
8792 @c Info cannot handle :: but TeX can.
8795 @vindex ::@r{, in Modula-2}
8798 There are a few subtle differences between the Modula-2 scope operator
8799 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8804 @var{module} . @var{id}
8805 @var{scope} :: @var{id}
8809 where @var{scope} is the name of a module or a procedure,
8810 @var{module} the name of a module, and @var{id} is any declared
8811 identifier within your program, except another module.
8813 Using the @code{::} operator makes @value{GDBN} search the scope
8814 specified by @var{scope} for the identifier @var{id}. If it is not
8815 found in the specified scope, then @value{GDBN} searches all scopes
8816 enclosing the one specified by @var{scope}.
8818 Using the @code{.} operator makes @value{GDBN} search the current scope for
8819 the identifier specified by @var{id} that was imported from the
8820 definition module specified by @var{module}. With this operator, it is
8821 an error if the identifier @var{id} was not imported from definition
8822 module @var{module}, or if @var{id} is not an identifier in
8826 @subsubsection @value{GDBN} and Modula-2
8828 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
8829 Five subcommands of @code{set print} and @code{show print} apply
8830 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
8831 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
8832 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
8833 analogue in Modula-2.
8835 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
8836 with any language, is not useful with Modula-2. Its
8837 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
8838 created in Modula-2 as they can in C or C@t{++}. However, because an
8839 address can be specified by an integral constant, the construct
8840 @samp{@{@var{type}@}@var{adrexp}} is still useful.
8842 @cindex @code{#} in Modula-2
8843 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
8844 interpreted as the beginning of a comment. Use @code{<>} instead.
8847 @chapter Examining the Symbol Table
8849 The commands described in this chapter allow you to inquire about the
8850 symbols (names of variables, functions and types) defined in your
8851 program. This information is inherent in the text of your program and
8852 does not change as your program executes. @value{GDBN} finds it in your
8853 program's symbol table, in the file indicated when you started @value{GDBN}
8854 (@pxref{File Options, ,Choosing files}), or by one of the
8855 file-management commands (@pxref{Files, ,Commands to specify files}).
8857 @cindex symbol names
8858 @cindex names of symbols
8859 @cindex quoting names
8860 Occasionally, you may need to refer to symbols that contain unusual
8861 characters, which @value{GDBN} ordinarily treats as word delimiters. The
8862 most frequent case is in referring to static variables in other
8863 source files (@pxref{Variables,,Program variables}). File names
8864 are recorded in object files as debugging symbols, but @value{GDBN} would
8865 ordinarily parse a typical file name, like @file{foo.c}, as the three words
8866 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
8867 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
8874 looks up the value of @code{x} in the scope of the file @file{foo.c}.
8877 @kindex info address
8878 @cindex address of a symbol
8879 @item info address @var{symbol}
8880 Describe where the data for @var{symbol} is stored. For a register
8881 variable, this says which register it is kept in. For a non-register
8882 local variable, this prints the stack-frame offset at which the variable
8885 Note the contrast with @samp{print &@var{symbol}}, which does not work
8886 at all for a register variable, and for a stack local variable prints
8887 the exact address of the current instantiation of the variable.
8890 @cindex symbol from address
8891 @item info symbol @var{addr}
8892 Print the name of a symbol which is stored at the address @var{addr}.
8893 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
8894 nearest symbol and an offset from it:
8897 (@value{GDBP}) info symbol 0x54320
8898 _initialize_vx + 396 in section .text
8902 This is the opposite of the @code{info address} command. You can use
8903 it to find out the name of a variable or a function given its address.
8906 @item whatis @var{expr}
8907 Print the data type of expression @var{expr}. @var{expr} is not
8908 actually evaluated, and any side-effecting operations (such as
8909 assignments or function calls) inside it do not take place.
8910 @xref{Expressions, ,Expressions}.
8913 Print the data type of @code{$}, the last value in the value history.
8916 @item ptype @var{typename}
8917 Print a description of data type @var{typename}. @var{typename} may be
8918 the name of a type, or for C code it may have the form @samp{class
8919 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
8920 @var{union-tag}} or @samp{enum @var{enum-tag}}.
8922 @item ptype @var{expr}
8924 Print a description of the type of expression @var{expr}. @code{ptype}
8925 differs from @code{whatis} by printing a detailed description, instead
8926 of just the name of the type.
8928 For example, for this variable declaration:
8931 struct complex @{double real; double imag;@} v;
8935 the two commands give this output:
8939 (@value{GDBP}) whatis v
8940 type = struct complex
8941 (@value{GDBP}) ptype v
8942 type = struct complex @{
8950 As with @code{whatis}, using @code{ptype} without an argument refers to
8951 the type of @code{$}, the last value in the value history.
8954 @item info types @var{regexp}
8956 Print a brief description of all types whose names match @var{regexp}
8957 (or all types in your program, if you supply no argument). Each
8958 complete typename is matched as though it were a complete line; thus,
8959 @samp{i type value} gives information on all types in your program whose
8960 names include the string @code{value}, but @samp{i type ^value$} gives
8961 information only on types whose complete name is @code{value}.
8963 This command differs from @code{ptype} in two ways: first, like
8964 @code{whatis}, it does not print a detailed description; second, it
8965 lists all source files where a type is defined.
8968 @cindex local variables
8969 @item info scope @var{addr}
8970 List all the variables local to a particular scope. This command
8971 accepts a location---a function name, a source line, or an address
8972 preceded by a @samp{*}, and prints all the variables local to the
8973 scope defined by that location. For example:
8976 (@value{GDBP}) @b{info scope command_line_handler}
8977 Scope for command_line_handler:
8978 Symbol rl is an argument at stack/frame offset 8, length 4.
8979 Symbol linebuffer is in static storage at address 0x150a18, length 4.
8980 Symbol linelength is in static storage at address 0x150a1c, length 4.
8981 Symbol p is a local variable in register $esi, length 4.
8982 Symbol p1 is a local variable in register $ebx, length 4.
8983 Symbol nline is a local variable in register $edx, length 4.
8984 Symbol repeat is a local variable at frame offset -8, length 4.
8988 This command is especially useful for determining what data to collect
8989 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
8994 Show information about the current source file---that is, the source file for
8995 the function containing the current point of execution:
8998 the name of the source file, and the directory containing it,
9000 the directory it was compiled in,
9002 its length, in lines,
9004 which programming language it is written in,
9006 whether the executable includes debugging information for that file, and
9007 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9009 whether the debugging information includes information about
9010 preprocessor macros.
9014 @kindex info sources
9016 Print the names of all source files in your program for which there is
9017 debugging information, organized into two lists: files whose symbols
9018 have already been read, and files whose symbols will be read when needed.
9020 @kindex info functions
9021 @item info functions
9022 Print the names and data types of all defined functions.
9024 @item info functions @var{regexp}
9025 Print the names and data types of all defined functions
9026 whose names contain a match for regular expression @var{regexp}.
9027 Thus, @samp{info fun step} finds all functions whose names
9028 include @code{step}; @samp{info fun ^step} finds those whose names
9029 start with @code{step}. If a function name contains characters
9030 that conflict with the regular expression language (eg.
9031 @samp{operator*()}), they may be quoted with a backslash.
9033 @kindex info variables
9034 @item info variables
9035 Print the names and data types of all variables that are declared
9036 outside of functions (i.e.@: excluding local variables).
9038 @item info variables @var{regexp}
9039 Print the names and data types of all variables (except for local
9040 variables) whose names contain a match for regular expression
9043 @kindex info classes
9045 @itemx info classes @var{regexp}
9046 Display all Objective-C classes in your program, or
9047 (with the @var{regexp} argument) all those matching a particular regular
9050 @kindex info selectors
9051 @item info selectors
9052 @itemx info selectors @var{regexp}
9053 Display all Objective-C selectors in your program, or
9054 (with the @var{regexp} argument) all those matching a particular regular
9058 This was never implemented.
9059 @kindex info methods
9061 @itemx info methods @var{regexp}
9062 The @code{info methods} command permits the user to examine all defined
9063 methods within C@t{++} program, or (with the @var{regexp} argument) a
9064 specific set of methods found in the various C@t{++} classes. Many
9065 C@t{++} classes provide a large number of methods. Thus, the output
9066 from the @code{ptype} command can be overwhelming and hard to use. The
9067 @code{info-methods} command filters the methods, printing only those
9068 which match the regular-expression @var{regexp}.
9071 @cindex reloading symbols
9072 Some systems allow individual object files that make up your program to
9073 be replaced without stopping and restarting your program. For example,
9074 in VxWorks you can simply recompile a defective object file and keep on
9075 running. If you are running on one of these systems, you can allow
9076 @value{GDBN} to reload the symbols for automatically relinked modules:
9079 @kindex set symbol-reloading
9080 @item set symbol-reloading on
9081 Replace symbol definitions for the corresponding source file when an
9082 object file with a particular name is seen again.
9084 @item set symbol-reloading off
9085 Do not replace symbol definitions when encountering object files of the
9086 same name more than once. This is the default state; if you are not
9087 running on a system that permits automatic relinking of modules, you
9088 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9089 may discard symbols when linking large programs, that may contain
9090 several modules (from different directories or libraries) with the same
9093 @kindex show symbol-reloading
9094 @item show symbol-reloading
9095 Show the current @code{on} or @code{off} setting.
9098 @kindex set opaque-type-resolution
9099 @item set opaque-type-resolution on
9100 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9101 declared as a pointer to a @code{struct}, @code{class}, or
9102 @code{union}---for example, @code{struct MyType *}---that is used in one
9103 source file although the full declaration of @code{struct MyType} is in
9104 another source file. The default is on.
9106 A change in the setting of this subcommand will not take effect until
9107 the next time symbols for a file are loaded.
9109 @item set opaque-type-resolution off
9110 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9111 is printed as follows:
9113 @{<no data fields>@}
9116 @kindex show opaque-type-resolution
9117 @item show opaque-type-resolution
9118 Show whether opaque types are resolved or not.
9120 @kindex maint print symbols
9122 @kindex maint print psymbols
9123 @cindex partial symbol dump
9124 @item maint print symbols @var{filename}
9125 @itemx maint print psymbols @var{filename}
9126 @itemx maint print msymbols @var{filename}
9127 Write a dump of debugging symbol data into the file @var{filename}.
9128 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9129 symbols with debugging data are included. If you use @samp{maint print
9130 symbols}, @value{GDBN} includes all the symbols for which it has already
9131 collected full details: that is, @var{filename} reflects symbols for
9132 only those files whose symbols @value{GDBN} has read. You can use the
9133 command @code{info sources} to find out which files these are. If you
9134 use @samp{maint print psymbols} instead, the dump shows information about
9135 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9136 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9137 @samp{maint print msymbols} dumps just the minimal symbol information
9138 required for each object file from which @value{GDBN} has read some symbols.
9139 @xref{Files, ,Commands to specify files}, for a discussion of how
9140 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9142 @kindex maint info symtabs
9143 @kindex maint info psymtabs
9144 @cindex listing @value{GDBN}'s internal symbol tables
9145 @cindex symbol tables, listing @value{GDBN}'s internal
9146 @cindex full symbol tables, listing @value{GDBN}'s internal
9147 @cindex partial symbol tables, listing @value{GDBN}'s internal
9148 @item maint info symtabs @r{[} @var{regexp} @r{]}
9149 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9151 List the @code{struct symtab} or @code{struct partial_symtab}
9152 structures whose names match @var{regexp}. If @var{regexp} is not
9153 given, list them all. The output includes expressions which you can
9154 copy into a @value{GDBN} debugging this one to examine a particular
9155 structure in more detail. For example:
9158 (@value{GDBP}) maint info psymtabs dwarf2read
9159 @{ objfile /home/gnu/build/gdb/gdb
9160 ((struct objfile *) 0x82e69d0)
9161 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9162 ((struct partial_symtab *) 0x8474b10)
9165 text addresses 0x814d3c8 -- 0x8158074
9166 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9167 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9171 (@value{GDBP}) maint info symtabs
9175 We see that there is one partial symbol table whose filename contains
9176 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9177 and we see that @value{GDBN} has not read in any symtabs yet at all.
9178 If we set a breakpoint on a function, that will cause @value{GDBN} to
9179 read the symtab for the compilation unit containing that function:
9182 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9183 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9185 (@value{GDBP}) maint info symtabs
9186 @{ objfile /home/gnu/build/gdb/gdb
9187 ((struct objfile *) 0x82e69d0)
9188 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9189 ((struct symtab *) 0x86c1f38)
9192 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9202 @chapter Altering Execution
9204 Once you think you have found an error in your program, you might want to
9205 find out for certain whether correcting the apparent error would lead to
9206 correct results in the rest of the run. You can find the answer by
9207 experiment, using the @value{GDBN} features for altering execution of the
9210 For example, you can store new values into variables or memory
9211 locations, give your program a signal, restart it at a different
9212 address, or even return prematurely from a function.
9215 * Assignment:: Assignment to variables
9216 * Jumping:: Continuing at a different address
9217 * Signaling:: Giving your program a signal
9218 * Returning:: Returning from a function
9219 * Calling:: Calling your program's functions
9220 * Patching:: Patching your program
9224 @section Assignment to variables
9227 @cindex setting variables
9228 To alter the value of a variable, evaluate an assignment expression.
9229 @xref{Expressions, ,Expressions}. For example,
9236 stores the value 4 into the variable @code{x}, and then prints the
9237 value of the assignment expression (which is 4).
9238 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9239 information on operators in supported languages.
9241 @kindex set variable
9242 @cindex variables, setting
9243 If you are not interested in seeing the value of the assignment, use the
9244 @code{set} command instead of the @code{print} command. @code{set} is
9245 really the same as @code{print} except that the expression's value is
9246 not printed and is not put in the value history (@pxref{Value History,
9247 ,Value history}). The expression is evaluated only for its effects.
9249 If the beginning of the argument string of the @code{set} command
9250 appears identical to a @code{set} subcommand, use the @code{set
9251 variable} command instead of just @code{set}. This command is identical
9252 to @code{set} except for its lack of subcommands. For example, if your
9253 program has a variable @code{width}, you get an error if you try to set
9254 a new value with just @samp{set width=13}, because @value{GDBN} has the
9255 command @code{set width}:
9258 (@value{GDBP}) whatis width
9260 (@value{GDBP}) p width
9262 (@value{GDBP}) set width=47
9263 Invalid syntax in expression.
9267 The invalid expression, of course, is @samp{=47}. In
9268 order to actually set the program's variable @code{width}, use
9271 (@value{GDBP}) set var width=47
9274 Because the @code{set} command has many subcommands that can conflict
9275 with the names of program variables, it is a good idea to use the
9276 @code{set variable} command instead of just @code{set}. For example, if
9277 your program has a variable @code{g}, you run into problems if you try
9278 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9279 the command @code{set gnutarget}, abbreviated @code{set g}:
9283 (@value{GDBP}) whatis g
9287 (@value{GDBP}) set g=4
9291 The program being debugged has been started already.
9292 Start it from the beginning? (y or n) y
9293 Starting program: /home/smith/cc_progs/a.out
9294 "/home/smith/cc_progs/a.out": can't open to read symbols:
9296 (@value{GDBP}) show g
9297 The current BFD target is "=4".
9302 The program variable @code{g} did not change, and you silently set the
9303 @code{gnutarget} to an invalid value. In order to set the variable
9307 (@value{GDBP}) set var g=4
9310 @value{GDBN} allows more implicit conversions in assignments than C; you can
9311 freely store an integer value into a pointer variable or vice versa,
9312 and you can convert any structure to any other structure that is the
9313 same length or shorter.
9314 @comment FIXME: how do structs align/pad in these conversions?
9315 @comment /doc@cygnus.com 18dec1990
9317 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9318 construct to generate a value of specified type at a specified address
9319 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9320 to memory location @code{0x83040} as an integer (which implies a certain size
9321 and representation in memory), and
9324 set @{int@}0x83040 = 4
9328 stores the value 4 into that memory location.
9331 @section Continuing at a different address
9333 Ordinarily, when you continue your program, you do so at the place where
9334 it stopped, with the @code{continue} command. You can instead continue at
9335 an address of your own choosing, with the following commands:
9339 @item jump @var{linespec}
9340 Resume execution at line @var{linespec}. Execution stops again
9341 immediately if there is a breakpoint there. @xref{List, ,Printing
9342 source lines}, for a description of the different forms of
9343 @var{linespec}. It is common practice to use the @code{tbreak} command
9344 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9347 The @code{jump} command does not change the current stack frame, or
9348 the stack pointer, or the contents of any memory location or any
9349 register other than the program counter. If line @var{linespec} is in
9350 a different function from the one currently executing, the results may
9351 be bizarre if the two functions expect different patterns of arguments or
9352 of local variables. For this reason, the @code{jump} command requests
9353 confirmation if the specified line is not in the function currently
9354 executing. However, even bizarre results are predictable if you are
9355 well acquainted with the machine-language code of your program.
9357 @item jump *@var{address}
9358 Resume execution at the instruction at address @var{address}.
9361 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9362 On many systems, you can get much the same effect as the @code{jump}
9363 command by storing a new value into the register @code{$pc}. The
9364 difference is that this does not start your program running; it only
9365 changes the address of where it @emph{will} run when you continue. For
9373 makes the next @code{continue} command or stepping command execute at
9374 address @code{0x485}, rather than at the address where your program stopped.
9375 @xref{Continuing and Stepping, ,Continuing and stepping}.
9377 The most common occasion to use the @code{jump} command is to back
9378 up---perhaps with more breakpoints set---over a portion of a program
9379 that has already executed, in order to examine its execution in more
9384 @section Giving your program a signal
9388 @item signal @var{signal}
9389 Resume execution where your program stopped, but immediately give it the
9390 signal @var{signal}. @var{signal} can be the name or the number of a
9391 signal. For example, on many systems @code{signal 2} and @code{signal
9392 SIGINT} are both ways of sending an interrupt signal.
9394 Alternatively, if @var{signal} is zero, continue execution without
9395 giving a signal. This is useful when your program stopped on account of
9396 a signal and would ordinary see the signal when resumed with the
9397 @code{continue} command; @samp{signal 0} causes it to resume without a
9400 @code{signal} does not repeat when you press @key{RET} a second time
9401 after executing the command.
9405 Invoking the @code{signal} command is not the same as invoking the
9406 @code{kill} utility from the shell. Sending a signal with @code{kill}
9407 causes @value{GDBN} to decide what to do with the signal depending on
9408 the signal handling tables (@pxref{Signals}). The @code{signal} command
9409 passes the signal directly to your program.
9413 @section Returning from a function
9416 @cindex returning from a function
9419 @itemx return @var{expression}
9420 You can cancel execution of a function call with the @code{return}
9421 command. If you give an
9422 @var{expression} argument, its value is used as the function's return
9426 When you use @code{return}, @value{GDBN} discards the selected stack frame
9427 (and all frames within it). You can think of this as making the
9428 discarded frame return prematurely. If you wish to specify a value to
9429 be returned, give that value as the argument to @code{return}.
9431 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9432 frame}), and any other frames inside of it, leaving its caller as the
9433 innermost remaining frame. That frame becomes selected. The
9434 specified value is stored in the registers used for returning values
9437 The @code{return} command does not resume execution; it leaves the
9438 program stopped in the state that would exist if the function had just
9439 returned. In contrast, the @code{finish} command (@pxref{Continuing
9440 and Stepping, ,Continuing and stepping}) resumes execution until the
9441 selected stack frame returns naturally.
9444 @section Calling program functions
9446 @cindex calling functions
9449 @item call @var{expr}
9450 Evaluate the expression @var{expr} without displaying @code{void}
9454 You can use this variant of the @code{print} command if you want to
9455 execute a function from your program, but without cluttering the output
9456 with @code{void} returned values. If the result is not void, it
9457 is printed and saved in the value history.
9460 @section Patching programs
9462 @cindex patching binaries
9463 @cindex writing into executables
9464 @cindex writing into corefiles
9466 By default, @value{GDBN} opens the file containing your program's
9467 executable code (or the corefile) read-only. This prevents accidental
9468 alterations to machine code; but it also prevents you from intentionally
9469 patching your program's binary.
9471 If you'd like to be able to patch the binary, you can specify that
9472 explicitly with the @code{set write} command. For example, you might
9473 want to turn on internal debugging flags, or even to make emergency
9479 @itemx set write off
9480 If you specify @samp{set write on}, @value{GDBN} opens executable and
9481 core files for both reading and writing; if you specify @samp{set write
9482 off} (the default), @value{GDBN} opens them read-only.
9484 If you have already loaded a file, you must load it again (using the
9485 @code{exec-file} or @code{core-file} command) after changing @code{set
9486 write}, for your new setting to take effect.
9490 Display whether executable files and core files are opened for writing
9495 @chapter @value{GDBN} Files
9497 @value{GDBN} needs to know the file name of the program to be debugged,
9498 both in order to read its symbol table and in order to start your
9499 program. To debug a core dump of a previous run, you must also tell
9500 @value{GDBN} the name of the core dump file.
9503 * Files:: Commands to specify files
9504 * Separate Debug Files:: Debugging information in separate files
9505 * Symbol Errors:: Errors reading symbol files
9509 @section Commands to specify files
9511 @cindex symbol table
9512 @cindex core dump file
9514 You may want to specify executable and core dump file names. The usual
9515 way to do this is at start-up time, using the arguments to
9516 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9517 Out of @value{GDBN}}).
9519 Occasionally it is necessary to change to a different file during a
9520 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9521 a file you want to use. In these situations the @value{GDBN} commands
9522 to specify new files are useful.
9525 @cindex executable file
9527 @item file @var{filename}
9528 Use @var{filename} as the program to be debugged. It is read for its
9529 symbols and for the contents of pure memory. It is also the program
9530 executed when you use the @code{run} command. If you do not specify a
9531 directory and the file is not found in the @value{GDBN} working directory,
9532 @value{GDBN} uses the environment variable @code{PATH} as a list of
9533 directories to search, just as the shell does when looking for a program
9534 to run. You can change the value of this variable, for both @value{GDBN}
9535 and your program, using the @code{path} command.
9537 On systems with memory-mapped files, an auxiliary file named
9538 @file{@var{filename}.syms} may hold symbol table information for
9539 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9540 @file{@var{filename}.syms}, starting up more quickly. See the
9541 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9542 (available on the command line, and with the commands @code{file},
9543 @code{symbol-file}, or @code{add-symbol-file}, described below),
9544 for more information.
9547 @code{file} with no argument makes @value{GDBN} discard any information it
9548 has on both executable file and the symbol table.
9551 @item exec-file @r{[} @var{filename} @r{]}
9552 Specify that the program to be run (but not the symbol table) is found
9553 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9554 if necessary to locate your program. Omitting @var{filename} means to
9555 discard information on the executable file.
9558 @item symbol-file @r{[} @var{filename} @r{]}
9559 Read symbol table information from file @var{filename}. @code{PATH} is
9560 searched when necessary. Use the @code{file} command to get both symbol
9561 table and program to run from the same file.
9563 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9564 program's symbol table.
9566 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9567 of its convenience variables, the value history, and all breakpoints and
9568 auto-display expressions. This is because they may contain pointers to
9569 the internal data recording symbols and data types, which are part of
9570 the old symbol table data being discarded inside @value{GDBN}.
9572 @code{symbol-file} does not repeat if you press @key{RET} again after
9575 When @value{GDBN} is configured for a particular environment, it
9576 understands debugging information in whatever format is the standard
9577 generated for that environment; you may use either a @sc{gnu} compiler, or
9578 other compilers that adhere to the local conventions.
9579 Best results are usually obtained from @sc{gnu} compilers; for example,
9580 using @code{@value{GCC}} you can generate debugging information for
9583 For most kinds of object files, with the exception of old SVR3 systems
9584 using COFF, the @code{symbol-file} command does not normally read the
9585 symbol table in full right away. Instead, it scans the symbol table
9586 quickly to find which source files and which symbols are present. The
9587 details are read later, one source file at a time, as they are needed.
9589 The purpose of this two-stage reading strategy is to make @value{GDBN}
9590 start up faster. For the most part, it is invisible except for
9591 occasional pauses while the symbol table details for a particular source
9592 file are being read. (The @code{set verbose} command can turn these
9593 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9594 warnings and messages}.)
9596 We have not implemented the two-stage strategy for COFF yet. When the
9597 symbol table is stored in COFF format, @code{symbol-file} reads the
9598 symbol table data in full right away. Note that ``stabs-in-COFF''
9599 still does the two-stage strategy, since the debug info is actually
9603 @cindex reading symbols immediately
9604 @cindex symbols, reading immediately
9606 @cindex memory-mapped symbol file
9607 @cindex saving symbol table
9608 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9609 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9610 You can override the @value{GDBN} two-stage strategy for reading symbol
9611 tables by using the @samp{-readnow} option with any of the commands that
9612 load symbol table information, if you want to be sure @value{GDBN} has the
9613 entire symbol table available.
9615 If memory-mapped files are available on your system through the
9616 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9617 cause @value{GDBN} to write the symbols for your program into a reusable
9618 file. Future @value{GDBN} debugging sessions map in symbol information
9619 from this auxiliary symbol file (if the program has not changed), rather
9620 than spending time reading the symbol table from the executable
9621 program. Using the @samp{-mapped} option has the same effect as
9622 starting @value{GDBN} with the @samp{-mapped} command-line option.
9624 You can use both options together, to make sure the auxiliary symbol
9625 file has all the symbol information for your program.
9627 The auxiliary symbol file for a program called @var{myprog} is called
9628 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9629 than the corresponding executable), @value{GDBN} always attempts to use
9630 it when you debug @var{myprog}; no special options or commands are
9633 The @file{.syms} file is specific to the host machine where you run
9634 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9635 symbol table. It cannot be shared across multiple host platforms.
9637 @c FIXME: for now no mention of directories, since this seems to be in
9638 @c flux. 13mar1992 status is that in theory GDB would look either in
9639 @c current dir or in same dir as myprog; but issues like competing
9640 @c GDB's, or clutter in system dirs, mean that in practice right now
9641 @c only current dir is used. FFish says maybe a special GDB hierarchy
9642 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9647 @item core-file @r{[} @var{filename} @r{]}
9648 Specify the whereabouts of a core dump file to be used as the ``contents
9649 of memory''. Traditionally, core files contain only some parts of the
9650 address space of the process that generated them; @value{GDBN} can access the
9651 executable file itself for other parts.
9653 @code{core-file} with no argument specifies that no core file is
9656 Note that the core file is ignored when your program is actually running
9657 under @value{GDBN}. So, if you have been running your program and you
9658 wish to debug a core file instead, you must kill the subprocess in which
9659 the program is running. To do this, use the @code{kill} command
9660 (@pxref{Kill Process, ,Killing the child process}).
9662 @kindex add-symbol-file
9663 @cindex dynamic linking
9664 @item add-symbol-file @var{filename} @var{address}
9665 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9666 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9667 The @code{add-symbol-file} command reads additional symbol table
9668 information from the file @var{filename}. You would use this command
9669 when @var{filename} has been dynamically loaded (by some other means)
9670 into the program that is running. @var{address} should be the memory
9671 address at which the file has been loaded; @value{GDBN} cannot figure
9672 this out for itself. You can additionally specify an arbitrary number
9673 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9674 section name and base address for that section. You can specify any
9675 @var{address} as an expression.
9677 The symbol table of the file @var{filename} is added to the symbol table
9678 originally read with the @code{symbol-file} command. You can use the
9679 @code{add-symbol-file} command any number of times; the new symbol data
9680 thus read keeps adding to the old. To discard all old symbol data
9681 instead, use the @code{symbol-file} command without any arguments.
9683 @cindex relocatable object files, reading symbols from
9684 @cindex object files, relocatable, reading symbols from
9685 @cindex reading symbols from relocatable object files
9686 @cindex symbols, reading from relocatable object files
9687 @cindex @file{.o} files, reading symbols from
9688 Although @var{filename} is typically a shared library file, an
9689 executable file, or some other object file which has been fully
9690 relocated for loading into a process, you can also load symbolic
9691 information from relocatable @file{.o} files, as long as:
9695 the file's symbolic information refers only to linker symbols defined in
9696 that file, not to symbols defined by other object files,
9698 every section the file's symbolic information refers to has actually
9699 been loaded into the inferior, as it appears in the file, and
9701 you can determine the address at which every section was loaded, and
9702 provide these to the @code{add-symbol-file} command.
9706 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9707 relocatable files into an already running program; such systems
9708 typically make the requirements above easy to meet. However, it's
9709 important to recognize that many native systems use complex link
9710 procedures (@code{.linkonce} section factoring and C++ constructor table
9711 assembly, for example) that make the requirements difficult to meet. In
9712 general, one cannot assume that using @code{add-symbol-file} to read a
9713 relocatable object file's symbolic information will have the same effect
9714 as linking the relocatable object file into the program in the normal
9717 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9719 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9720 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9721 table information for @var{filename}.
9723 @kindex add-shared-symbol-file
9724 @item add-shared-symbol-file
9725 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9726 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9727 shared libraries, however if @value{GDBN} does not find yours, you can run
9728 @code{add-shared-symbol-file}. It takes no arguments.
9732 The @code{section} command changes the base address of section SECTION of
9733 the exec file to ADDR. This can be used if the exec file does not contain
9734 section addresses, (such as in the a.out format), or when the addresses
9735 specified in the file itself are wrong. Each section must be changed
9736 separately. The @code{info files} command, described below, lists all
9737 the sections and their addresses.
9743 @code{info files} and @code{info target} are synonymous; both print the
9744 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9745 including the names of the executable and core dump files currently in
9746 use by @value{GDBN}, and the files from which symbols were loaded. The
9747 command @code{help target} lists all possible targets rather than
9750 @kindex maint info sections
9751 @item maint info sections
9752 Another command that can give you extra information about program sections
9753 is @code{maint info sections}. In addition to the section information
9754 displayed by @code{info files}, this command displays the flags and file
9755 offset of each section in the executable and core dump files. In addition,
9756 @code{maint info sections} provides the following command options (which
9757 may be arbitrarily combined):
9761 Display sections for all loaded object files, including shared libraries.
9762 @item @var{sections}
9763 Display info only for named @var{sections}.
9764 @item @var{section-flags}
9765 Display info only for sections for which @var{section-flags} are true.
9766 The section flags that @value{GDBN} currently knows about are:
9769 Section will have space allocated in the process when loaded.
9770 Set for all sections except those containing debug information.
9772 Section will be loaded from the file into the child process memory.
9773 Set for pre-initialized code and data, clear for @code{.bss} sections.
9775 Section needs to be relocated before loading.
9777 Section cannot be modified by the child process.
9779 Section contains executable code only.
9781 Section contains data only (no executable code).
9783 Section will reside in ROM.
9785 Section contains data for constructor/destructor lists.
9787 Section is not empty.
9789 An instruction to the linker to not output the section.
9790 @item COFF_SHARED_LIBRARY
9791 A notification to the linker that the section contains
9792 COFF shared library information.
9794 Section contains common symbols.
9797 @kindex set trust-readonly-sections
9798 @item set trust-readonly-sections on
9799 Tell @value{GDBN} that readonly sections in your object file
9800 really are read-only (i.e.@: that their contents will not change).
9801 In that case, @value{GDBN} can fetch values from these sections
9802 out of the object file, rather than from the target program.
9803 For some targets (notably embedded ones), this can be a significant
9804 enhancement to debugging performance.
9808 @item set trust-readonly-sections off
9809 Tell @value{GDBN} not to trust readonly sections. This means that
9810 the contents of the section might change while the program is running,
9811 and must therefore be fetched from the target when needed.
9814 All file-specifying commands allow both absolute and relative file names
9815 as arguments. @value{GDBN} always converts the file name to an absolute file
9816 name and remembers it that way.
9818 @cindex shared libraries
9819 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
9822 @value{GDBN} automatically loads symbol definitions from shared libraries
9823 when you use the @code{run} command, or when you examine a core file.
9824 (Before you issue the @code{run} command, @value{GDBN} does not understand
9825 references to a function in a shared library, however---unless you are
9826 debugging a core file).
9828 On HP-UX, if the program loads a library explicitly, @value{GDBN}
9829 automatically loads the symbols at the time of the @code{shl_load} call.
9831 @c FIXME: some @value{GDBN} release may permit some refs to undef
9832 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
9833 @c FIXME...lib; check this from time to time when updating manual
9835 There are times, however, when you may wish to not automatically load
9836 symbol definitions from shared libraries, such as when they are
9837 particularly large or there are many of them.
9839 To control the automatic loading of shared library symbols, use the
9843 @kindex set auto-solib-add
9844 @item set auto-solib-add @var{mode}
9845 If @var{mode} is @code{on}, symbols from all shared object libraries
9846 will be loaded automatically when the inferior begins execution, you
9847 attach to an independently started inferior, or when the dynamic linker
9848 informs @value{GDBN} that a new library has been loaded. If @var{mode}
9849 is @code{off}, symbols must be loaded manually, using the
9850 @code{sharedlibrary} command. The default value is @code{on}.
9852 @kindex show auto-solib-add
9853 @item show auto-solib-add
9854 Display the current autoloading mode.
9857 To explicitly load shared library symbols, use the @code{sharedlibrary}
9861 @kindex info sharedlibrary
9864 @itemx info sharedlibrary
9865 Print the names of the shared libraries which are currently loaded.
9867 @kindex sharedlibrary
9869 @item sharedlibrary @var{regex}
9870 @itemx share @var{regex}
9871 Load shared object library symbols for files matching a
9872 Unix regular expression.
9873 As with files loaded automatically, it only loads shared libraries
9874 required by your program for a core file or after typing @code{run}. If
9875 @var{regex} is omitted all shared libraries required by your program are
9879 On some systems, such as HP-UX systems, @value{GDBN} supports
9880 autoloading shared library symbols until a limiting threshold size is
9881 reached. This provides the benefit of allowing autoloading to remain on
9882 by default, but avoids autoloading excessively large shared libraries,
9883 up to a threshold that is initially set, but which you can modify if you
9886 Beyond that threshold, symbols from shared libraries must be explicitly
9887 loaded. To load these symbols, use the command @code{sharedlibrary
9888 @var{filename}}. The base address of the shared library is determined
9889 automatically by @value{GDBN} and need not be specified.
9891 To display or set the threshold, use the commands:
9894 @kindex set auto-solib-limit
9895 @item set auto-solib-limit @var{threshold}
9896 Set the autoloading size threshold, in an integral number of megabytes.
9897 If @var{threshold} is nonzero and shared library autoloading is enabled,
9898 symbols from all shared object libraries will be loaded until the total
9899 size of the loaded shared library symbols exceeds this threshold.
9900 Otherwise, symbols must be loaded manually, using the
9901 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
9904 @kindex show auto-solib-limit
9905 @item show auto-solib-limit
9906 Display the current autoloading size threshold, in megabytes.
9909 Shared libraries are also supported in many cross or remote debugging
9910 configurations. A copy of the target's libraries need to be present on the
9911 host system; they need to be the same as the target libraries, although the
9912 copies on the target can be stripped as long as the copies on the host are
9915 You need to tell @value{GDBN} where the target libraries are, so that it can
9916 load the correct copies---otherwise, it may try to load the host's libraries.
9917 @value{GDBN} has two variables to specify the search directories for target
9921 @kindex set solib-absolute-prefix
9922 @item set solib-absolute-prefix @var{path}
9923 If this variable is set, @var{path} will be used as a prefix for any
9924 absolute shared library paths; many runtime loaders store the absolute
9925 paths to the shared library in the target program's memory. If you use
9926 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
9927 out in the same way that they are on the target, with e.g.@: a
9928 @file{/usr/lib} hierarchy under @var{path}.
9930 You can set the default value of @samp{solib-absolute-prefix} by using the
9931 configure-time @samp{--with-sysroot} option.
9933 @kindex show solib-absolute-prefix
9934 @item show solib-absolute-prefix
9935 Display the current shared library prefix.
9937 @kindex set solib-search-path
9938 @item set solib-search-path @var{path}
9939 If this variable is set, @var{path} is a colon-separated list of directories
9940 to search for shared libraries. @samp{solib-search-path} is used after
9941 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
9942 the library is relative instead of absolute. If you want to use
9943 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
9944 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
9945 @value{GDBN} from finding your host's libraries.
9947 @kindex show solib-search-path
9948 @item show solib-search-path
9949 Display the current shared library search path.
9953 @node Separate Debug Files
9954 @section Debugging Information in Separate Files
9955 @cindex separate debugging information files
9956 @cindex debugging information in separate files
9957 @cindex @file{.debug} subdirectories
9958 @cindex debugging information directory, global
9959 @cindex global debugging information directory
9961 @value{GDBN} allows you to put a program's debugging information in a
9962 file separate from the executable itself, in a way that allows
9963 @value{GDBN} to find and load the debugging information automatically.
9964 Since debugging information can be very large --- sometimes larger
9965 than the executable code itself --- some systems distribute debugging
9966 information for their executables in separate files, which users can
9967 install only when they need to debug a problem.
9969 If an executable's debugging information has been extracted to a
9970 separate file, the executable should contain a @dfn{debug link} giving
9971 the name of the debugging information file (with no directory
9972 components), and a checksum of its contents. (The exact form of a
9973 debug link is described below.) If the full name of the directory
9974 containing the executable is @var{execdir}, and the executable has a
9975 debug link that specifies the name @var{debugfile}, then @value{GDBN}
9976 will automatically search for the debugging information file in three
9981 the directory containing the executable file (that is, it will look
9982 for a file named @file{@var{execdir}/@var{debugfile}},
9984 a subdirectory of that directory named @file{.debug} (that is, the
9985 file @file{@var{execdir}/.debug/@var{debugfile}}, and
9987 a subdirectory of the global debug file directory that includes the
9988 executable's full path, and the name from the link (that is, the file
9989 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
9990 @var{globaldebugdir} is the global debug file directory, and
9991 @var{execdir} has been turned into a relative path).
9994 @value{GDBN} checks under each of these names for a debugging
9995 information file whose checksum matches that given in the link, and
9996 reads the debugging information from the first one it finds.
9998 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
9999 which has a link containing the name @file{ls.debug}, and the global
10000 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
10001 for debug information in @file{/usr/bin/ls.debug},
10002 @file{/usr/bin/.debug/ls.debug}, and
10003 @file{/usr/lib/debug/usr/bin/ls.debug}.
10005 You can set the global debugging info directory's name, and view the
10006 name @value{GDBN} is currently using.
10010 @kindex set debug-file-directory
10011 @item set debug-file-directory @var{directory}
10012 Set the directory which @value{GDBN} searches for separate debugging
10013 information files to @var{directory}.
10015 @kindex show debug-file-directory
10016 @item show debug-file-directory
10017 Show the directory @value{GDBN} searches for separate debugging
10022 @cindex @code{.gnu_debuglink} sections
10023 @cindex debug links
10024 A debug link is a special section of the executable file named
10025 @code{.gnu_debuglink}. The section must contain:
10029 A filename, with any leading directory components removed, followed by
10032 zero to three bytes of padding, as needed to reach the next four-byte
10033 boundary within the section, and
10035 a four-byte CRC checksum, stored in the same endianness used for the
10036 executable file itself. The checksum is computed on the debugging
10037 information file's full contents by the function given below, passing
10038 zero as the @var{crc} argument.
10041 Any executable file format can carry a debug link, as long as it can
10042 contain a section named @code{.gnu_debuglink} with the contents
10045 The debugging information file itself should be an ordinary
10046 executable, containing a full set of linker symbols, sections, and
10047 debugging information. The sections of the debugging information file
10048 should have the same names, addresses and sizes as the original file,
10049 but they need not contain any data --- much like a @code{.bss} section
10050 in an ordinary executable.
10052 As of December 2002, there is no standard GNU utility to produce
10053 separated executable / debugging information file pairs. Ulrich
10054 Drepper's @file{elfutils} package, starting with version 0.53,
10055 contains a version of the @code{strip} command such that the command
10056 @kbd{strip foo -f foo.debug} removes the debugging information from
10057 the executable file @file{foo}, places it in the file
10058 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
10060 Since there are many different ways to compute CRC's (different
10061 polynomials, reversals, byte ordering, etc.), the simplest way to
10062 describe the CRC used in @code{.gnu_debuglink} sections is to give the
10063 complete code for a function that computes it:
10065 @kindex @code{gnu_debuglink_crc32}
10068 gnu_debuglink_crc32 (unsigned long crc,
10069 unsigned char *buf, size_t len)
10071 static const unsigned long crc32_table[256] =
10073 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
10074 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
10075 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
10076 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
10077 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
10078 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
10079 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
10080 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
10081 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
10082 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
10083 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
10084 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
10085 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
10086 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
10087 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
10088 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
10089 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
10090 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
10091 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
10092 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
10093 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
10094 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
10095 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
10096 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
10097 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
10098 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
10099 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
10100 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
10101 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
10102 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
10103 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
10104 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
10105 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
10106 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
10107 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
10108 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
10109 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
10110 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
10111 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
10112 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
10113 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
10114 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
10115 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
10116 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10117 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10118 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10119 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10120 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10121 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10122 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10123 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10126 unsigned char *end;
10128 crc = ~crc & 0xffffffff;
10129 for (end = buf + len; buf < end; ++buf)
10130 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10131 return ~crc & 0xffffffff;
10136 @node Symbol Errors
10137 @section Errors reading symbol files
10139 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10140 such as symbol types it does not recognize, or known bugs in compiler
10141 output. By default, @value{GDBN} does not notify you of such problems, since
10142 they are relatively common and primarily of interest to people
10143 debugging compilers. If you are interested in seeing information
10144 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10145 only one message about each such type of problem, no matter how many
10146 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10147 to see how many times the problems occur, with the @code{set
10148 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10151 The messages currently printed, and their meanings, include:
10154 @item inner block not inside outer block in @var{symbol}
10156 The symbol information shows where symbol scopes begin and end
10157 (such as at the start of a function or a block of statements). This
10158 error indicates that an inner scope block is not fully contained
10159 in its outer scope blocks.
10161 @value{GDBN} circumvents the problem by treating the inner block as if it had
10162 the same scope as the outer block. In the error message, @var{symbol}
10163 may be shown as ``@code{(don't know)}'' if the outer block is not a
10166 @item block at @var{address} out of order
10168 The symbol information for symbol scope blocks should occur in
10169 order of increasing addresses. This error indicates that it does not
10172 @value{GDBN} does not circumvent this problem, and has trouble
10173 locating symbols in the source file whose symbols it is reading. (You
10174 can often determine what source file is affected by specifying
10175 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10178 @item bad block start address patched
10180 The symbol information for a symbol scope block has a start address
10181 smaller than the address of the preceding source line. This is known
10182 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10184 @value{GDBN} circumvents the problem by treating the symbol scope block as
10185 starting on the previous source line.
10187 @item bad string table offset in symbol @var{n}
10190 Symbol number @var{n} contains a pointer into the string table which is
10191 larger than the size of the string table.
10193 @value{GDBN} circumvents the problem by considering the symbol to have the
10194 name @code{foo}, which may cause other problems if many symbols end up
10197 @item unknown symbol type @code{0x@var{nn}}
10199 The symbol information contains new data types that @value{GDBN} does
10200 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10201 uncomprehended information, in hexadecimal.
10203 @value{GDBN} circumvents the error by ignoring this symbol information.
10204 This usually allows you to debug your program, though certain symbols
10205 are not accessible. If you encounter such a problem and feel like
10206 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10207 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10208 and examine @code{*bufp} to see the symbol.
10210 @item stub type has NULL name
10212 @value{GDBN} could not find the full definition for a struct or class.
10214 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10215 The symbol information for a C@t{++} member function is missing some
10216 information that recent versions of the compiler should have output for
10219 @item info mismatch between compiler and debugger
10221 @value{GDBN} could not parse a type specification output by the compiler.
10226 @chapter Specifying a Debugging Target
10228 @cindex debugging target
10231 A @dfn{target} is the execution environment occupied by your program.
10233 Often, @value{GDBN} runs in the same host environment as your program;
10234 in that case, the debugging target is specified as a side effect when
10235 you use the @code{file} or @code{core} commands. When you need more
10236 flexibility---for example, running @value{GDBN} on a physically separate
10237 host, or controlling a standalone system over a serial port or a
10238 realtime system over a TCP/IP connection---you can use the @code{target}
10239 command to specify one of the target types configured for @value{GDBN}
10240 (@pxref{Target Commands, ,Commands for managing targets}).
10243 * Active Targets:: Active targets
10244 * Target Commands:: Commands for managing targets
10245 * Byte Order:: Choosing target byte order
10246 * Remote:: Remote debugging
10247 * KOD:: Kernel Object Display
10251 @node Active Targets
10252 @section Active targets
10254 @cindex stacking targets
10255 @cindex active targets
10256 @cindex multiple targets
10258 There are three classes of targets: processes, core files, and
10259 executable files. @value{GDBN} can work concurrently on up to three
10260 active targets, one in each class. This allows you to (for example)
10261 start a process and inspect its activity without abandoning your work on
10264 For example, if you execute @samp{gdb a.out}, then the executable file
10265 @code{a.out} is the only active target. If you designate a core file as
10266 well---presumably from a prior run that crashed and coredumped---then
10267 @value{GDBN} has two active targets and uses them in tandem, looking
10268 first in the corefile target, then in the executable file, to satisfy
10269 requests for memory addresses. (Typically, these two classes of target
10270 are complementary, since core files contain only a program's
10271 read-write memory---variables and so on---plus machine status, while
10272 executable files contain only the program text and initialized data.)
10274 When you type @code{run}, your executable file becomes an active process
10275 target as well. When a process target is active, all @value{GDBN}
10276 commands requesting memory addresses refer to that target; addresses in
10277 an active core file or executable file target are obscured while the
10278 process target is active.
10280 Use the @code{core-file} and @code{exec-file} commands to select a new
10281 core file or executable target (@pxref{Files, ,Commands to specify
10282 files}). To specify as a target a process that is already running, use
10283 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10286 @node Target Commands
10287 @section Commands for managing targets
10290 @item target @var{type} @var{parameters}
10291 Connects the @value{GDBN} host environment to a target machine or
10292 process. A target is typically a protocol for talking to debugging
10293 facilities. You use the argument @var{type} to specify the type or
10294 protocol of the target machine.
10296 Further @var{parameters} are interpreted by the target protocol, but
10297 typically include things like device names or host names to connect
10298 with, process numbers, and baud rates.
10300 The @code{target} command does not repeat if you press @key{RET} again
10301 after executing the command.
10303 @kindex help target
10305 Displays the names of all targets available. To display targets
10306 currently selected, use either @code{info target} or @code{info files}
10307 (@pxref{Files, ,Commands to specify files}).
10309 @item help target @var{name}
10310 Describe a particular target, including any parameters necessary to
10313 @kindex set gnutarget
10314 @item set gnutarget @var{args}
10315 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10316 knows whether it is reading an @dfn{executable},
10317 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10318 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10319 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10322 @emph{Warning:} To specify a file format with @code{set gnutarget},
10323 you must know the actual BFD name.
10327 @xref{Files, , Commands to specify files}.
10329 @kindex show gnutarget
10330 @item show gnutarget
10331 Use the @code{show gnutarget} command to display what file format
10332 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10333 @value{GDBN} will determine the file format for each file automatically,
10334 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10337 Here are some common targets (available, or not, depending on the GDB
10341 @kindex target exec
10342 @item target exec @var{program}
10343 An executable file. @samp{target exec @var{program}} is the same as
10344 @samp{exec-file @var{program}}.
10346 @kindex target core
10347 @item target core @var{filename}
10348 A core dump file. @samp{target core @var{filename}} is the same as
10349 @samp{core-file @var{filename}}.
10351 @kindex target remote
10352 @item target remote @var{dev}
10353 Remote serial target in GDB-specific protocol. The argument @var{dev}
10354 specifies what serial device to use for the connection (e.g.
10355 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10356 supports the @code{load} command. This is only useful if you have
10357 some other way of getting the stub to the target system, and you can put
10358 it somewhere in memory where it won't get clobbered by the download.
10362 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10370 works; however, you cannot assume that a specific memory map, device
10371 drivers, or even basic I/O is available, although some simulators do
10372 provide these. For info about any processor-specific simulator details,
10373 see the appropriate section in @ref{Embedded Processors, ,Embedded
10378 Some configurations may include these targets as well:
10382 @kindex target nrom
10383 @item target nrom @var{dev}
10384 NetROM ROM emulator. This target only supports downloading.
10388 Different targets are available on different configurations of @value{GDBN};
10389 your configuration may have more or fewer targets.
10391 Many remote targets require you to download the executable's code
10392 once you've successfully established a connection.
10396 @kindex load @var{filename}
10397 @item load @var{filename}
10398 Depending on what remote debugging facilities are configured into
10399 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10400 is meant to make @var{filename} (an executable) available for debugging
10401 on the remote system---by downloading, or dynamic linking, for example.
10402 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10403 the @code{add-symbol-file} command.
10405 If your @value{GDBN} does not have a @code{load} command, attempting to
10406 execute it gets the error message ``@code{You can't do that when your
10407 target is @dots{}}''
10409 The file is loaded at whatever address is specified in the executable.
10410 For some object file formats, you can specify the load address when you
10411 link the program; for other formats, like a.out, the object file format
10412 specifies a fixed address.
10413 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10415 @code{load} does not repeat if you press @key{RET} again after using it.
10419 @section Choosing target byte order
10421 @cindex choosing target byte order
10422 @cindex target byte order
10424 Some types of processors, such as the MIPS, PowerPC, and Hitachi SH,
10425 offer the ability to run either big-endian or little-endian byte
10426 orders. Usually the executable or symbol will include a bit to
10427 designate the endian-ness, and you will not need to worry about
10428 which to use. However, you may still find it useful to adjust
10429 @value{GDBN}'s idea of processor endian-ness manually.
10432 @kindex set endian big
10433 @item set endian big
10434 Instruct @value{GDBN} to assume the target is big-endian.
10436 @kindex set endian little
10437 @item set endian little
10438 Instruct @value{GDBN} to assume the target is little-endian.
10440 @kindex set endian auto
10441 @item set endian auto
10442 Instruct @value{GDBN} to use the byte order associated with the
10446 Display @value{GDBN}'s current idea of the target byte order.
10450 Note that these commands merely adjust interpretation of symbolic
10451 data on the host, and that they have absolutely no effect on the
10455 @section Remote debugging
10456 @cindex remote debugging
10458 If you are trying to debug a program running on a machine that cannot run
10459 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10460 For example, you might use remote debugging on an operating system kernel,
10461 or on a small system which does not have a general purpose operating system
10462 powerful enough to run a full-featured debugger.
10464 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10465 to make this work with particular debugging targets. In addition,
10466 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10467 but not specific to any particular target system) which you can use if you
10468 write the remote stubs---the code that runs on the remote system to
10469 communicate with @value{GDBN}.
10471 Other remote targets may be available in your
10472 configuration of @value{GDBN}; use @code{help target} to list them.
10475 @section Kernel Object Display
10477 @cindex kernel object display
10478 @cindex kernel object
10481 Some targets support kernel object display. Using this facility,
10482 @value{GDBN} communicates specially with the underlying operating system
10483 and can display information about operating system-level objects such as
10484 mutexes and other synchronization objects. Exactly which objects can be
10485 displayed is determined on a per-OS basis.
10487 Use the @code{set os} command to set the operating system. This tells
10488 @value{GDBN} which kernel object display module to initialize:
10491 (@value{GDBP}) set os cisco
10494 If @code{set os} succeeds, @value{GDBN} will display some information
10495 about the operating system, and will create a new @code{info} command
10496 which can be used to query the target. The @code{info} command is named
10497 after the operating system:
10500 (@value{GDBP}) info cisco
10501 List of Cisco Kernel Objects
10503 any Any and all objects
10506 Further subcommands can be used to query about particular objects known
10509 There is currently no way to determine whether a given operating system
10510 is supported other than to try it.
10513 @node Remote Debugging
10514 @chapter Debugging remote programs
10517 * Connecting:: Connecting to a remote target
10518 * Server:: Using the gdbserver program
10519 * NetWare:: Using the gdbserve.nlm program
10520 * Remote configuration:: Remote configuration
10521 * remote stub:: Implementing a remote stub
10525 @section Connecting to a remote target
10527 On the @value{GDBN} host machine, you will need an unstripped copy of
10528 your program, since @value{GDBN} needs symobl and debugging information.
10529 Start up @value{GDBN} as usual, using the name of the local copy of your
10530 program as the first argument.
10532 @cindex serial line, @code{target remote}
10533 If you're using a serial line, you may want to give @value{GDBN} the
10534 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
10535 before the @code{target} command.
10537 After that, use @code{target remote} to establish communications with
10538 the target machine. Its argument specifies how to communicate---either
10539 via a devicename attached to a direct serial line, or a TCP or UDP port
10540 (possibly to a terminal server which in turn has a serial line to the
10541 target). For example, to use a serial line connected to the device
10542 named @file{/dev/ttyb}:
10545 target remote /dev/ttyb
10548 @cindex TCP port, @code{target remote}
10549 To use a TCP connection, use an argument of the form
10550 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10551 For example, to connect to port 2828 on a
10552 terminal server named @code{manyfarms}:
10555 target remote manyfarms:2828
10558 If your remote target is actually running on the same machine as
10559 your debugger session (e.g.@: a simulator of your target running on
10560 the same host), you can omit the hostname. For example, to connect
10561 to port 1234 on your local machine:
10564 target remote :1234
10568 Note that the colon is still required here.
10570 @cindex UDP port, @code{target remote}
10571 To use a UDP connection, use an argument of the form
10572 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10573 on a terminal server named @code{manyfarms}:
10576 target remote udp:manyfarms:2828
10579 When using a UDP connection for remote debugging, you should keep in mind
10580 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10581 busy or unreliable networks, which will cause havoc with your debugging
10584 Now you can use all the usual commands to examine and change data and to
10585 step and continue the remote program.
10587 @cindex interrupting remote programs
10588 @cindex remote programs, interrupting
10589 Whenever @value{GDBN} is waiting for the remote program, if you type the
10590 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10591 program. This may or may not succeed, depending in part on the hardware
10592 and the serial drivers the remote system uses. If you type the
10593 interrupt character once again, @value{GDBN} displays this prompt:
10596 Interrupted while waiting for the program.
10597 Give up (and stop debugging it)? (y or n)
10600 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10601 (If you decide you want to try again later, you can use @samp{target
10602 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10603 goes back to waiting.
10606 @kindex detach (remote)
10608 When you have finished debugging the remote program, you can use the
10609 @code{detach} command to release it from @value{GDBN} control.
10610 Detaching from the target normally resumes its execution, but the results
10611 will depend on your particular remote stub. After the @code{detach}
10612 command, @value{GDBN} is free to connect to another target.
10616 The @code{disconnect} command behaves like @code{detach}, except that
10617 the target is generally not resumed. It will wait for @value{GDBN}
10618 (this instance or another one) to connect and continue debugging. After
10619 the @code{disconnect} command, @value{GDBN} is again free to connect to
10624 @section Using the @code{gdbserver} program
10627 @cindex remote connection without stubs
10628 @code{gdbserver} is a control program for Unix-like systems, which
10629 allows you to connect your program with a remote @value{GDBN} via
10630 @code{target remote}---but without linking in the usual debugging stub.
10632 @code{gdbserver} is not a complete replacement for the debugging stubs,
10633 because it requires essentially the same operating-system facilities
10634 that @value{GDBN} itself does. In fact, a system that can run
10635 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10636 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10637 because it is a much smaller program than @value{GDBN} itself. It is
10638 also easier to port than all of @value{GDBN}, so you may be able to get
10639 started more quickly on a new system by using @code{gdbserver}.
10640 Finally, if you develop code for real-time systems, you may find that
10641 the tradeoffs involved in real-time operation make it more convenient to
10642 do as much development work as possible on another system, for example
10643 by cross-compiling. You can use @code{gdbserver} to make a similar
10644 choice for debugging.
10646 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10647 or a TCP connection, using the standard @value{GDBN} remote serial
10651 @item On the target machine,
10652 you need to have a copy of the program you want to debug.
10653 @code{gdbserver} does not need your program's symbol table, so you can
10654 strip the program if necessary to save space. @value{GDBN} on the host
10655 system does all the symbol handling.
10657 To use the server, you must tell it how to communicate with @value{GDBN};
10658 the name of your program; and the arguments for your program. The usual
10662 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10665 @var{comm} is either a device name (to use a serial line) or a TCP
10666 hostname and portnumber. For example, to debug Emacs with the argument
10667 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10671 target> gdbserver /dev/com1 emacs foo.txt
10674 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10677 To use a TCP connection instead of a serial line:
10680 target> gdbserver host:2345 emacs foo.txt
10683 The only difference from the previous example is the first argument,
10684 specifying that you are communicating with the host @value{GDBN} via
10685 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10686 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10687 (Currently, the @samp{host} part is ignored.) You can choose any number
10688 you want for the port number as long as it does not conflict with any
10689 TCP ports already in use on the target system (for example, @code{23} is
10690 reserved for @code{telnet}).@footnote{If you choose a port number that
10691 conflicts with another service, @code{gdbserver} prints an error message
10692 and exits.} You must use the same port number with the host @value{GDBN}
10693 @code{target remote} command.
10695 On some targets, @code{gdbserver} can also attach to running programs.
10696 This is accomplished via the @code{--attach} argument. The syntax is:
10699 target> gdbserver @var{comm} --attach @var{pid}
10702 @var{pid} is the process ID of a currently running process. It isn't necessary
10703 to point @code{gdbserver} at a binary for the running process.
10705 @item On the host machine,
10706 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
10707 For TCP connections, you must start up @code{gdbserver} prior to using
10708 the @code{target remote} command. Otherwise you may get an error whose
10709 text depends on the host system, but which usually looks something like
10710 @samp{Connection refused}. You don't need to use the @code{load}
10711 command in @value{GDBN} when using gdbserver, since the program is
10712 already on the target.
10717 @section Using the @code{gdbserve.nlm} program
10719 @kindex gdbserve.nlm
10720 @code{gdbserve.nlm} is a control program for NetWare systems, which
10721 allows you to connect your program with a remote @value{GDBN} via
10722 @code{target remote}.
10724 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10725 using the standard @value{GDBN} remote serial protocol.
10728 @item On the target machine,
10729 you need to have a copy of the program you want to debug.
10730 @code{gdbserve.nlm} does not need your program's symbol table, so you
10731 can strip the program if necessary to save space. @value{GDBN} on the
10732 host system does all the symbol handling.
10734 To use the server, you must tell it how to communicate with
10735 @value{GDBN}; the name of your program; and the arguments for your
10736 program. The syntax is:
10739 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10740 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10743 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10744 the baud rate used by the connection. @var{port} and @var{node} default
10745 to 0, @var{baud} defaults to 9600@dmn{bps}.
10747 For example, to debug Emacs with the argument @samp{foo.txt}and
10748 communicate with @value{GDBN} over serial port number 2 or board 1
10749 using a 19200@dmn{bps} connection:
10752 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10756 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
10757 Connecting to a remote target}).
10761 @node Remote configuration
10762 @section Remote configuration
10764 The following configuration options are available when debugging remote
10768 @kindex set remote hardware-watchpoint-limit
10769 @kindex set remote hardware-breakpoint-limit
10770 @anchor{set remote hardware-watchpoint-limit}
10771 @anchor{set remote hardware-breakpoint-limit}
10772 @item set remote hardware-watchpoint-limit @var{limit}
10773 @itemx set remote hardware-breakpoint-limit @var{limit}
10774 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
10775 watchpoints. A limit of -1, the default, is treated as unlimited.
10779 @section Implementing a remote stub
10781 @cindex debugging stub, example
10782 @cindex remote stub, example
10783 @cindex stub example, remote debugging
10784 The stub files provided with @value{GDBN} implement the target side of the
10785 communication protocol, and the @value{GDBN} side is implemented in the
10786 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10787 these subroutines to communicate, and ignore the details. (If you're
10788 implementing your own stub file, you can still ignore the details: start
10789 with one of the existing stub files. @file{sparc-stub.c} is the best
10790 organized, and therefore the easiest to read.)
10792 @cindex remote serial debugging, overview
10793 To debug a program running on another machine (the debugging
10794 @dfn{target} machine), you must first arrange for all the usual
10795 prerequisites for the program to run by itself. For example, for a C
10800 A startup routine to set up the C runtime environment; these usually
10801 have a name like @file{crt0}. The startup routine may be supplied by
10802 your hardware supplier, or you may have to write your own.
10805 A C subroutine library to support your program's
10806 subroutine calls, notably managing input and output.
10809 A way of getting your program to the other machine---for example, a
10810 download program. These are often supplied by the hardware
10811 manufacturer, but you may have to write your own from hardware
10815 The next step is to arrange for your program to use a serial port to
10816 communicate with the machine where @value{GDBN} is running (the @dfn{host}
10817 machine). In general terms, the scheme looks like this:
10821 @value{GDBN} already understands how to use this protocol; when everything
10822 else is set up, you can simply use the @samp{target remote} command
10823 (@pxref{Targets,,Specifying a Debugging Target}).
10825 @item On the target,
10826 you must link with your program a few special-purpose subroutines that
10827 implement the @value{GDBN} remote serial protocol. The file containing these
10828 subroutines is called a @dfn{debugging stub}.
10830 On certain remote targets, you can use an auxiliary program
10831 @code{gdbserver} instead of linking a stub into your program.
10832 @xref{Server,,Using the @code{gdbserver} program}, for details.
10835 The debugging stub is specific to the architecture of the remote
10836 machine; for example, use @file{sparc-stub.c} to debug programs on
10839 @cindex remote serial stub list
10840 These working remote stubs are distributed with @value{GDBN}:
10845 @cindex @file{i386-stub.c}
10848 For Intel 386 and compatible architectures.
10851 @cindex @file{m68k-stub.c}
10852 @cindex Motorola 680x0
10854 For Motorola 680x0 architectures.
10857 @cindex @file{sh-stub.c}
10860 For Hitachi SH architectures.
10863 @cindex @file{sparc-stub.c}
10865 For @sc{sparc} architectures.
10867 @item sparcl-stub.c
10868 @cindex @file{sparcl-stub.c}
10871 For Fujitsu @sc{sparclite} architectures.
10875 The @file{README} file in the @value{GDBN} distribution may list other
10876 recently added stubs.
10879 * Stub Contents:: What the stub can do for you
10880 * Bootstrapping:: What you must do for the stub
10881 * Debug Session:: Putting it all together
10884 @node Stub Contents
10885 @subsection What the stub can do for you
10887 @cindex remote serial stub
10888 The debugging stub for your architecture supplies these three
10892 @item set_debug_traps
10893 @kindex set_debug_traps
10894 @cindex remote serial stub, initialization
10895 This routine arranges for @code{handle_exception} to run when your
10896 program stops. You must call this subroutine explicitly near the
10897 beginning of your program.
10899 @item handle_exception
10900 @kindex handle_exception
10901 @cindex remote serial stub, main routine
10902 This is the central workhorse, but your program never calls it
10903 explicitly---the setup code arranges for @code{handle_exception} to
10904 run when a trap is triggered.
10906 @code{handle_exception} takes control when your program stops during
10907 execution (for example, on a breakpoint), and mediates communications
10908 with @value{GDBN} on the host machine. This is where the communications
10909 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
10910 representative on the target machine. It begins by sending summary
10911 information on the state of your program, then continues to execute,
10912 retrieving and transmitting any information @value{GDBN} needs, until you
10913 execute a @value{GDBN} command that makes your program resume; at that point,
10914 @code{handle_exception} returns control to your own code on the target
10918 @cindex @code{breakpoint} subroutine, remote
10919 Use this auxiliary subroutine to make your program contain a
10920 breakpoint. Depending on the particular situation, this may be the only
10921 way for @value{GDBN} to get control. For instance, if your target
10922 machine has some sort of interrupt button, you won't need to call this;
10923 pressing the interrupt button transfers control to
10924 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
10925 simply receiving characters on the serial port may also trigger a trap;
10926 again, in that situation, you don't need to call @code{breakpoint} from
10927 your own program---simply running @samp{target remote} from the host
10928 @value{GDBN} session gets control.
10930 Call @code{breakpoint} if none of these is true, or if you simply want
10931 to make certain your program stops at a predetermined point for the
10932 start of your debugging session.
10935 @node Bootstrapping
10936 @subsection What you must do for the stub
10938 @cindex remote stub, support routines
10939 The debugging stubs that come with @value{GDBN} are set up for a particular
10940 chip architecture, but they have no information about the rest of your
10941 debugging target machine.
10943 First of all you need to tell the stub how to communicate with the
10947 @item int getDebugChar()
10948 @kindex getDebugChar
10949 Write this subroutine to read a single character from the serial port.
10950 It may be identical to @code{getchar} for your target system; a
10951 different name is used to allow you to distinguish the two if you wish.
10953 @item void putDebugChar(int)
10954 @kindex putDebugChar
10955 Write this subroutine to write a single character to the serial port.
10956 It may be identical to @code{putchar} for your target system; a
10957 different name is used to allow you to distinguish the two if you wish.
10960 @cindex control C, and remote debugging
10961 @cindex interrupting remote targets
10962 If you want @value{GDBN} to be able to stop your program while it is
10963 running, you need to use an interrupt-driven serial driver, and arrange
10964 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
10965 character). That is the character which @value{GDBN} uses to tell the
10966 remote system to stop.
10968 Getting the debugging target to return the proper status to @value{GDBN}
10969 probably requires changes to the standard stub; one quick and dirty way
10970 is to just execute a breakpoint instruction (the ``dirty'' part is that
10971 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
10973 Other routines you need to supply are:
10976 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
10977 @kindex exceptionHandler
10978 Write this function to install @var{exception_address} in the exception
10979 handling tables. You need to do this because the stub does not have any
10980 way of knowing what the exception handling tables on your target system
10981 are like (for example, the processor's table might be in @sc{rom},
10982 containing entries which point to a table in @sc{ram}).
10983 @var{exception_number} is the exception number which should be changed;
10984 its meaning is architecture-dependent (for example, different numbers
10985 might represent divide by zero, misaligned access, etc). When this
10986 exception occurs, control should be transferred directly to
10987 @var{exception_address}, and the processor state (stack, registers,
10988 and so on) should be just as it is when a processor exception occurs. So if
10989 you want to use a jump instruction to reach @var{exception_address}, it
10990 should be a simple jump, not a jump to subroutine.
10992 For the 386, @var{exception_address} should be installed as an interrupt
10993 gate so that interrupts are masked while the handler runs. The gate
10994 should be at privilege level 0 (the most privileged level). The
10995 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
10996 help from @code{exceptionHandler}.
10998 @item void flush_i_cache()
10999 @kindex flush_i_cache
11000 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
11001 instruction cache, if any, on your target machine. If there is no
11002 instruction cache, this subroutine may be a no-op.
11004 On target machines that have instruction caches, @value{GDBN} requires this
11005 function to make certain that the state of your program is stable.
11009 You must also make sure this library routine is available:
11012 @item void *memset(void *, int, int)
11014 This is the standard library function @code{memset} that sets an area of
11015 memory to a known value. If you have one of the free versions of
11016 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11017 either obtain it from your hardware manufacturer, or write your own.
11020 If you do not use the GNU C compiler, you may need other standard
11021 library subroutines as well; this varies from one stub to another,
11022 but in general the stubs are likely to use any of the common library
11023 subroutines which @code{@value{GCC}} generates as inline code.
11026 @node Debug Session
11027 @subsection Putting it all together
11029 @cindex remote serial debugging summary
11030 In summary, when your program is ready to debug, you must follow these
11035 Make sure you have defined the supporting low-level routines
11036 (@pxref{Bootstrapping,,What you must do for the stub}):
11038 @code{getDebugChar}, @code{putDebugChar},
11039 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11043 Insert these lines near the top of your program:
11051 For the 680x0 stub only, you need to provide a variable called
11052 @code{exceptionHook}. Normally you just use:
11055 void (*exceptionHook)() = 0;
11059 but if before calling @code{set_debug_traps}, you set it to point to a
11060 function in your program, that function is called when
11061 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11062 error). The function indicated by @code{exceptionHook} is called with
11063 one parameter: an @code{int} which is the exception number.
11066 Compile and link together: your program, the @value{GDBN} debugging stub for
11067 your target architecture, and the supporting subroutines.
11070 Make sure you have a serial connection between your target machine and
11071 the @value{GDBN} host, and identify the serial port on the host.
11074 @c The "remote" target now provides a `load' command, so we should
11075 @c document that. FIXME.
11076 Download your program to your target machine (or get it there by
11077 whatever means the manufacturer provides), and start it.
11080 Start @value{GDBN} on the host, and connect to the target
11081 (@pxref{Connecting,,Connecting to a remote target}).
11085 @node Configurations
11086 @chapter Configuration-Specific Information
11088 While nearly all @value{GDBN} commands are available for all native and
11089 cross versions of the debugger, there are some exceptions. This chapter
11090 describes things that are only available in certain configurations.
11092 There are three major categories of configurations: native
11093 configurations, where the host and target are the same, embedded
11094 operating system configurations, which are usually the same for several
11095 different processor architectures, and bare embedded processors, which
11096 are quite different from each other.
11101 * Embedded Processors::
11108 This section describes details specific to particular native
11113 * SVR4 Process Information:: SVR4 process information
11114 * DJGPP Native:: Features specific to the DJGPP port
11115 * Cygwin Native:: Features specific to the Cygwin port
11121 On HP-UX systems, if you refer to a function or variable name that
11122 begins with a dollar sign, @value{GDBN} searches for a user or system
11123 name first, before it searches for a convenience variable.
11125 @node SVR4 Process Information
11126 @subsection SVR4 process information
11129 @cindex process image
11131 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11132 used to examine the image of a running process using file-system
11133 subroutines. If @value{GDBN} is configured for an operating system with
11134 this facility, the command @code{info proc} is available to report on
11135 several kinds of information about the process running your program.
11136 @code{info proc} works only on SVR4 systems that include the
11137 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11138 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11143 Summarize available information about the process.
11145 @kindex info proc mappings
11146 @item info proc mappings
11147 Report on the address ranges accessible in the program, with information
11148 on whether your program may read, write, or execute each range.
11150 @comment These sub-options of 'info proc' were not included when
11151 @comment procfs.c was re-written. Keep their descriptions around
11152 @comment against the day when someone finds the time to put them back in.
11153 @kindex info proc times
11154 @item info proc times
11155 Starting time, user CPU time, and system CPU time for your program and
11158 @kindex info proc id
11160 Report on the process IDs related to your program: its own process ID,
11161 the ID of its parent, the process group ID, and the session ID.
11163 @kindex info proc status
11164 @item info proc status
11165 General information on the state of the process. If the process is
11166 stopped, this report includes the reason for stopping, and any signal
11169 @item info proc all
11170 Show all the above information about the process.
11175 @subsection Features for Debugging @sc{djgpp} Programs
11176 @cindex @sc{djgpp} debugging
11177 @cindex native @sc{djgpp} debugging
11178 @cindex MS-DOS-specific commands
11180 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11181 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11182 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11183 top of real-mode DOS systems and their emulations.
11185 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11186 defines a few commands specific to the @sc{djgpp} port. This
11187 subsection describes those commands.
11192 This is a prefix of @sc{djgpp}-specific commands which print
11193 information about the target system and important OS structures.
11196 @cindex MS-DOS system info
11197 @cindex free memory information (MS-DOS)
11198 @item info dos sysinfo
11199 This command displays assorted information about the underlying
11200 platform: the CPU type and features, the OS version and flavor, the
11201 DPMI version, and the available conventional and DPMI memory.
11206 @cindex segment descriptor tables
11207 @cindex descriptor tables display
11209 @itemx info dos ldt
11210 @itemx info dos idt
11211 These 3 commands display entries from, respectively, Global, Local,
11212 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11213 tables are data structures which store a descriptor for each segment
11214 that is currently in use. The segment's selector is an index into a
11215 descriptor table; the table entry for that index holds the
11216 descriptor's base address and limit, and its attributes and access
11219 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11220 segment (used for both data and the stack), and a DOS segment (which
11221 allows access to DOS/BIOS data structures and absolute addresses in
11222 conventional memory). However, the DPMI host will usually define
11223 additional segments in order to support the DPMI environment.
11225 @cindex garbled pointers
11226 These commands allow to display entries from the descriptor tables.
11227 Without an argument, all entries from the specified table are
11228 displayed. An argument, which should be an integer expression, means
11229 display a single entry whose index is given by the argument. For
11230 example, here's a convenient way to display information about the
11231 debugged program's data segment:
11234 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11235 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11239 This comes in handy when you want to see whether a pointer is outside
11240 the data segment's limit (i.e.@: @dfn{garbled}).
11242 @cindex page tables display (MS-DOS)
11244 @itemx info dos pte
11245 These two commands display entries from, respectively, the Page
11246 Directory and the Page Tables. Page Directories and Page Tables are
11247 data structures which control how virtual memory addresses are mapped
11248 into physical addresses. A Page Table includes an entry for every
11249 page of memory that is mapped into the program's address space; there
11250 may be several Page Tables, each one holding up to 4096 entries. A
11251 Page Directory has up to 4096 entries, one each for every Page Table
11252 that is currently in use.
11254 Without an argument, @kbd{info dos pde} displays the entire Page
11255 Directory, and @kbd{info dos pte} displays all the entries in all of
11256 the Page Tables. An argument, an integer expression, given to the
11257 @kbd{info dos pde} command means display only that entry from the Page
11258 Directory table. An argument given to the @kbd{info dos pte} command
11259 means display entries from a single Page Table, the one pointed to by
11260 the specified entry in the Page Directory.
11262 @cindex direct memory access (DMA) on MS-DOS
11263 These commands are useful when your program uses @dfn{DMA} (Direct
11264 Memory Access), which needs physical addresses to program the DMA
11267 These commands are supported only with some DPMI servers.
11269 @cindex physical address from linear address
11270 @item info dos address-pte @var{addr}
11271 This command displays the Page Table entry for a specified linear
11272 address. The argument linear address @var{addr} should already have the
11273 appropriate segment's base address added to it, because this command
11274 accepts addresses which may belong to @emph{any} segment. For
11275 example, here's how to display the Page Table entry for the page where
11276 the variable @code{i} is stored:
11279 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11280 @exdent @code{Page Table entry for address 0x11a00d30:}
11281 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11285 This says that @code{i} is stored at offset @code{0xd30} from the page
11286 whose physical base address is @code{0x02698000}, and prints all the
11287 attributes of that page.
11289 Note that you must cast the addresses of variables to a @code{char *},
11290 since otherwise the value of @code{__djgpp_base_address}, the base
11291 address of all variables and functions in a @sc{djgpp} program, will
11292 be added using the rules of C pointer arithmetics: if @code{i} is
11293 declared an @code{int}, @value{GDBN} will add 4 times the value of
11294 @code{__djgpp_base_address} to the address of @code{i}.
11296 Here's another example, it displays the Page Table entry for the
11300 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11301 @exdent @code{Page Table entry for address 0x29110:}
11302 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11306 (The @code{+ 3} offset is because the transfer buffer's address is the
11307 3rd member of the @code{_go32_info_block} structure.) The output of
11308 this command clearly shows that addresses in conventional memory are
11309 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11311 This command is supported only with some DPMI servers.
11314 @node Cygwin Native
11315 @subsection Features for Debugging MS Windows PE executables
11316 @cindex MS Windows debugging
11317 @cindex native Cygwin debugging
11318 @cindex Cygwin-specific commands
11320 @value{GDBN} supports native debugging of MS Windows programs, including
11321 DLLs with and without symbolic debugging information. There are various
11322 additional Cygwin-specific commands, described in this subsection. The
11323 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11324 that have no debugging symbols.
11330 This is a prefix of MS Windows specific commands which print
11331 information about the target system and important OS structures.
11333 @item info w32 selector
11334 This command displays information returned by
11335 the Win32 API @code{GetThreadSelectorEntry} function.
11336 It takes an optional argument that is evaluated to
11337 a long value to give the information about this given selector.
11338 Without argument, this command displays information
11339 about the the six segment registers.
11343 This is a Cygwin specific alias of info shared.
11345 @kindex dll-symbols
11347 This command loads symbols from a dll similarly to
11348 add-sym command but without the need to specify a base address.
11350 @kindex set new-console
11351 @item set new-console @var{mode}
11352 If @var{mode} is @code{on} the debuggee will
11353 be started in a new console on next start.
11354 If @var{mode} is @code{off}i, the debuggee will
11355 be started in the same console as the debugger.
11357 @kindex show new-console
11358 @item show new-console
11359 Displays whether a new console is used
11360 when the debuggee is started.
11362 @kindex set new-group
11363 @item set new-group @var{mode}
11364 This boolean value controls whether the debuggee should
11365 start a new group or stay in the same group as the debugger.
11366 This affects the way the Windows OS handles
11369 @kindex show new-group
11370 @item show new-group
11371 Displays current value of new-group boolean.
11373 @kindex set debugevents
11374 @item set debugevents
11375 This boolean value adds debug output concerning events seen by the debugger.
11377 @kindex set debugexec
11378 @item set debugexec
11379 This boolean value adds debug output concerning execute events
11380 seen by the debugger.
11382 @kindex set debugexceptions
11383 @item set debugexceptions
11384 This boolean value adds debug ouptut concerning exception events
11385 seen by the debugger.
11387 @kindex set debugmemory
11388 @item set debugmemory
11389 This boolean value adds debug ouptut concerning memory events
11390 seen by the debugger.
11394 This boolean values specifies whether the debuggee is called
11395 via a shell or directly (default value is on).
11399 Displays if the debuggee will be started with a shell.
11404 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11407 @node Non-debug DLL symbols
11408 @subsubsection Support for DLLs without debugging symbols
11409 @cindex DLLs with no debugging symbols
11410 @cindex Minimal symbols and DLLs
11412 Very often on windows, some of the DLLs that your program relies on do
11413 not include symbolic debugging information (for example,
11414 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11415 symbols in a DLL, it relies on the minimal amount of symbolic
11416 information contained in the DLL's export table. This subsubsection
11417 describes working with such symbols, known internally to @value{GDBN} as
11418 ``minimal symbols''.
11420 Note that before the debugged program has started execution, no DLLs
11421 will have been loaded. The easiest way around this problem is simply to
11422 start the program --- either by setting a breakpoint or letting the
11423 program run once to completion. It is also possible to force
11424 @value{GDBN} to load a particular DLL before starting the executable ---
11425 see the shared library information in @pxref{Files} or the
11426 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11427 explicitly loading symbols from a DLL with no debugging information will
11428 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11429 which may adversely affect symbol lookup performance.
11431 @subsubsection DLL name prefixes
11433 In keeping with the naming conventions used by the Microsoft debugging
11434 tools, DLL export symbols are made available with a prefix based on the
11435 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11436 also entered into the symbol table, so @code{CreateFileA} is often
11437 sufficient. In some cases there will be name clashes within a program
11438 (particularly if the executable itself includes full debugging symbols)
11439 necessitating the use of the fully qualified name when referring to the
11440 contents of the DLL. Use single-quotes around the name to avoid the
11441 exclamation mark (``!'') being interpreted as a language operator.
11443 Note that the internal name of the DLL may be all upper-case, even
11444 though the file name of the DLL is lower-case, or vice-versa. Since
11445 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11446 some confusion. If in doubt, try the @code{info functions} and
11447 @code{info variables} commands or even @code{maint print msymbols} (see
11448 @pxref{Symbols}). Here's an example:
11451 (gdb) info function CreateFileA
11452 All functions matching regular expression "CreateFileA":
11454 Non-debugging symbols:
11455 0x77e885f4 CreateFileA
11456 0x77e885f4 KERNEL32!CreateFileA
11460 (gdb) info function !
11461 All functions matching regular expression "!":
11463 Non-debugging symbols:
11464 0x6100114c cygwin1!__assert
11465 0x61004034 cygwin1!_dll_crt0@@0
11466 0x61004240 cygwin1!dll_crt0(per_process *)
11470 @subsubsection Working with minimal symbols
11472 Symbols extracted from a DLL's export table do not contain very much
11473 type information. All that @value{GDBN} can do is guess whether a symbol
11474 refers to a function or variable depending on the linker section that
11475 contains the symbol. Also note that the actual contents of the memory
11476 contained in a DLL are not available unless the program is running. This
11477 means that you cannot examine the contents of a variable or disassemble
11478 a function within a DLL without a running program.
11480 Variables are generally treated as pointers and dereferenced
11481 automatically. For this reason, it is often necessary to prefix a
11482 variable name with the address-of operator (``&'') and provide explicit
11483 type information in the command. Here's an example of the type of
11487 (gdb) print 'cygwin1!__argv'
11492 (gdb) x 'cygwin1!__argv'
11493 0x10021610: "\230y\""
11496 And two possible solutions:
11499 (gdb) print ((char **)'cygwin1!__argv')[0]
11500 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11504 (gdb) x/2x &'cygwin1!__argv'
11505 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11506 (gdb) x/x 0x10021608
11507 0x10021608: 0x0022fd98
11508 (gdb) x/s 0x0022fd98
11509 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11512 Setting a break point within a DLL is possible even before the program
11513 starts execution. However, under these circumstances, @value{GDBN} can't
11514 examine the initial instructions of the function in order to skip the
11515 function's frame set-up code. You can work around this by using ``*&''
11516 to set the breakpoint at a raw memory address:
11519 (gdb) break *&'python22!PyOS_Readline'
11520 Breakpoint 1 at 0x1e04eff0
11523 The author of these extensions is not entirely convinced that setting a
11524 break point within a shared DLL like @file{kernel32.dll} is completely
11528 @section Embedded Operating Systems
11530 This section describes configurations involving the debugging of
11531 embedded operating systems that are available for several different
11535 * VxWorks:: Using @value{GDBN} with VxWorks
11538 @value{GDBN} includes the ability to debug programs running on
11539 various real-time operating systems.
11542 @subsection Using @value{GDBN} with VxWorks
11548 @kindex target vxworks
11549 @item target vxworks @var{machinename}
11550 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11551 is the target system's machine name or IP address.
11555 On VxWorks, @code{load} links @var{filename} dynamically on the
11556 current target system as well as adding its symbols in @value{GDBN}.
11558 @value{GDBN} enables developers to spawn and debug tasks running on networked
11559 VxWorks targets from a Unix host. Already-running tasks spawned from
11560 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11561 both the Unix host and on the VxWorks target. The program
11562 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11563 installed with the name @code{vxgdb}, to distinguish it from a
11564 @value{GDBN} for debugging programs on the host itself.)
11567 @item VxWorks-timeout @var{args}
11568 @kindex vxworks-timeout
11569 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11570 This option is set by the user, and @var{args} represents the number of
11571 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11572 your VxWorks target is a slow software simulator or is on the far side
11573 of a thin network line.
11576 The following information on connecting to VxWorks was current when
11577 this manual was produced; newer releases of VxWorks may use revised
11580 @kindex INCLUDE_RDB
11581 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11582 to include the remote debugging interface routines in the VxWorks
11583 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11584 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11585 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11586 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11587 information on configuring and remaking VxWorks, see the manufacturer's
11589 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11591 Once you have included @file{rdb.a} in your VxWorks system image and set
11592 your Unix execution search path to find @value{GDBN}, you are ready to
11593 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11594 @code{vxgdb}, depending on your installation).
11596 @value{GDBN} comes up showing the prompt:
11603 * VxWorks Connection:: Connecting to VxWorks
11604 * VxWorks Download:: VxWorks download
11605 * VxWorks Attach:: Running tasks
11608 @node VxWorks Connection
11609 @subsubsection Connecting to VxWorks
11611 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11612 network. To connect to a target whose host name is ``@code{tt}'', type:
11615 (vxgdb) target vxworks tt
11619 @value{GDBN} displays messages like these:
11622 Attaching remote machine across net...
11627 @value{GDBN} then attempts to read the symbol tables of any object modules
11628 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11629 these files by searching the directories listed in the command search
11630 path (@pxref{Environment, ,Your program's environment}); if it fails
11631 to find an object file, it displays a message such as:
11634 prog.o: No such file or directory.
11637 When this happens, add the appropriate directory to the search path with
11638 the @value{GDBN} command @code{path}, and execute the @code{target}
11641 @node VxWorks Download
11642 @subsubsection VxWorks download
11644 @cindex download to VxWorks
11645 If you have connected to the VxWorks target and you want to debug an
11646 object that has not yet been loaded, you can use the @value{GDBN}
11647 @code{load} command to download a file from Unix to VxWorks
11648 incrementally. The object file given as an argument to the @code{load}
11649 command is actually opened twice: first by the VxWorks target in order
11650 to download the code, then by @value{GDBN} in order to read the symbol
11651 table. This can lead to problems if the current working directories on
11652 the two systems differ. If both systems have NFS mounted the same
11653 filesystems, you can avoid these problems by using absolute paths.
11654 Otherwise, it is simplest to set the working directory on both systems
11655 to the directory in which the object file resides, and then to reference
11656 the file by its name, without any path. For instance, a program
11657 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11658 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11659 program, type this on VxWorks:
11662 -> cd "@var{vxpath}/vw/demo/rdb"
11666 Then, in @value{GDBN}, type:
11669 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11670 (vxgdb) load prog.o
11673 @value{GDBN} displays a response similar to this:
11676 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11679 You can also use the @code{load} command to reload an object module
11680 after editing and recompiling the corresponding source file. Note that
11681 this makes @value{GDBN} delete all currently-defined breakpoints,
11682 auto-displays, and convenience variables, and to clear the value
11683 history. (This is necessary in order to preserve the integrity of
11684 debugger's data structures that reference the target system's symbol
11687 @node VxWorks Attach
11688 @subsubsection Running tasks
11690 @cindex running VxWorks tasks
11691 You can also attach to an existing task using the @code{attach} command as
11695 (vxgdb) attach @var{task}
11699 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11700 or suspended when you attach to it. Running tasks are suspended at
11701 the time of attachment.
11703 @node Embedded Processors
11704 @section Embedded Processors
11706 This section goes into details specific to particular embedded
11712 * H8/300:: Hitachi H8/300
11713 * H8/500:: Hitachi H8/500
11714 * M32R/D:: Mitsubishi M32R/D
11715 * M68K:: Motorola M68K
11716 * MIPS Embedded:: MIPS Embedded
11717 * OpenRISC 1000:: OpenRisc 1000
11718 * PA:: HP PA Embedded
11721 * Sparclet:: Tsqware Sparclet
11722 * Sparclite:: Fujitsu Sparclite
11723 * ST2000:: Tandem ST2000
11724 * Z8000:: Zilog Z8000
11733 @item target rdi @var{dev}
11734 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11735 use this target to communicate with both boards running the Angel
11736 monitor, or with the EmbeddedICE JTAG debug device.
11739 @item target rdp @var{dev}
11745 @subsection Hitachi H8/300
11749 @kindex target hms@r{, with H8/300}
11750 @item target hms @var{dev}
11751 A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host.
11752 Use special commands @code{device} and @code{speed} to control the serial
11753 line and the communications speed used.
11755 @kindex target e7000@r{, with H8/300}
11756 @item target e7000 @var{dev}
11757 E7000 emulator for Hitachi H8 and SH.
11759 @kindex target sh3@r{, with H8/300}
11760 @kindex target sh3e@r{, with H8/300}
11761 @item target sh3 @var{dev}
11762 @itemx target sh3e @var{dev}
11763 Hitachi SH-3 and SH-3E target systems.
11767 @cindex download to H8/300 or H8/500
11768 @cindex H8/300 or H8/500 download
11769 @cindex download to Hitachi SH
11770 @cindex Hitachi SH download
11771 When you select remote debugging to a Hitachi SH, H8/300, or H8/500
11772 board, the @code{load} command downloads your program to the Hitachi
11773 board and also opens it as the current executable target for
11774 @value{GDBN} on your host (like the @code{file} command).
11776 @value{GDBN} needs to know these things to talk to your
11777 Hitachi SH, H8/300, or H8/500:
11781 that you want to use @samp{target hms}, the remote debugging interface
11782 for Hitachi microprocessors, or @samp{target e7000}, the in-circuit
11783 emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is
11784 the default when @value{GDBN} is configured specifically for the Hitachi SH,
11785 H8/300, or H8/500.)
11788 what serial device connects your host to your Hitachi board (the first
11789 serial device available on your host is the default).
11792 what speed to use over the serial device.
11796 * Hitachi Boards:: Connecting to Hitachi boards.
11797 * Hitachi ICE:: Using the E7000 In-Circuit Emulator.
11798 * Hitachi Special:: Special @value{GDBN} commands for Hitachi micros.
11801 @node Hitachi Boards
11802 @subsubsection Connecting to Hitachi boards
11804 @c only for Unix hosts
11806 @cindex serial device, Hitachi micros
11807 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11808 need to explicitly set the serial device. The default @var{port} is the
11809 first available port on your host. This is only necessary on Unix
11810 hosts, where it is typically something like @file{/dev/ttya}.
11813 @cindex serial line speed, Hitachi micros
11814 @code{@value{GDBN}} has another special command to set the communications
11815 speed: @samp{speed @var{bps}}. This command also is only used from Unix
11816 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11817 the DOS @code{mode} command (for instance,
11818 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11820 The @samp{device} and @samp{speed} commands are available only when you
11821 use a Unix host to debug your Hitachi microprocessor programs. If you
11823 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11824 called @code{asynctsr} to communicate with the development board
11825 through a PC serial port. You must also use the DOS @code{mode} command
11826 to set up the serial port on the DOS side.
11828 The following sample session illustrates the steps needed to start a
11829 program under @value{GDBN} control on an H8/300. The example uses a
11830 sample H8/300 program called @file{t.x}. The procedure is the same for
11831 the Hitachi SH and the H8/500.
11833 First hook up your development board. In this example, we use a
11834 board attached to serial port @code{COM2}; if you use a different serial
11835 port, substitute its name in the argument of the @code{mode} command.
11836 When you call @code{asynctsr}, the auxiliary comms program used by the
11837 debugger, you give it just the numeric part of the serial port's name;
11838 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
11842 C:\H8300\TEST> asynctsr 2
11843 C:\H8300\TEST> mode com2:9600,n,8,1,p
11845 Resident portion of MODE loaded
11847 COM2: 9600, n, 8, 1, p
11852 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
11853 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
11854 disable it, or even boot without it, to use @code{asynctsr} to control
11855 your development board.
11858 @kindex target hms@r{, and serial protocol}
11859 Now that serial communications are set up, and the development board is
11860 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
11861 the name of your program as the argument. @code{@value{GDBN}} prompts
11862 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
11863 commands to begin your debugging session: @samp{target hms} to specify
11864 cross-debugging to the Hitachi board, and the @code{load} command to
11865 download your program to the board. @code{load} displays the names of
11866 the program's sections, and a @samp{*} for each 2K of data downloaded.
11867 (If you want to refresh @value{GDBN} data on symbols or on the
11868 executable file without downloading, use the @value{GDBN} commands
11869 @code{file} or @code{symbol-file}. These commands, and @code{load}
11870 itself, are described in @ref{Files,,Commands to specify files}.)
11873 (eg-C:\H8300\TEST) @value{GDBP} t.x
11874 @value{GDBN} is free software and you are welcome to distribute copies
11875 of it under certain conditions; type "show copying" to see
11877 There is absolutely no warranty for @value{GDBN}; type "show warranty"
11879 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
11880 (@value{GDBP}) target hms
11881 Connected to remote H8/300 HMS system.
11882 (@value{GDBP}) load t.x
11883 .text : 0x8000 .. 0xabde ***********
11884 .data : 0xabde .. 0xad30 *
11885 .stack : 0xf000 .. 0xf014 *
11888 At this point, you're ready to run or debug your program. From here on,
11889 you can use all the usual @value{GDBN} commands. The @code{break} command
11890 sets breakpoints; the @code{run} command starts your program;
11891 @code{print} or @code{x} display data; the @code{continue} command
11892 resumes execution after stopping at a breakpoint. You can use the
11893 @code{help} command at any time to find out more about @value{GDBN} commands.
11895 Remember, however, that @emph{operating system} facilities aren't
11896 available on your development board; for example, if your program hangs,
11897 you can't send an interrupt---but you can press the @sc{reset} switch!
11899 Use the @sc{reset} button on the development board
11902 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
11903 no way to pass an interrupt signal to the development board); and
11906 to return to the @value{GDBN} command prompt after your program finishes
11907 normally. The communications protocol provides no other way for @value{GDBN}
11908 to detect program completion.
11911 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
11912 development board as a ``normal exit'' of your program.
11915 @subsubsection Using the E7000 in-circuit emulator
11917 @kindex target e7000@r{, with Hitachi ICE}
11918 You can use the E7000 in-circuit emulator to develop code for either the
11919 Hitachi SH or the H8/300H. Use one of these forms of the @samp{target
11920 e7000} command to connect @value{GDBN} to your E7000:
11923 @item target e7000 @var{port} @var{speed}
11924 Use this form if your E7000 is connected to a serial port. The
11925 @var{port} argument identifies what serial port to use (for example,
11926 @samp{com2}). The third argument is the line speed in bits per second
11927 (for example, @samp{9600}).
11929 @item target e7000 @var{hostname}
11930 If your E7000 is installed as a host on a TCP/IP network, you can just
11931 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
11934 @node Hitachi Special
11935 @subsubsection Special @value{GDBN} commands for Hitachi micros
11937 Some @value{GDBN} commands are available only for the H8/300:
11941 @kindex set machine
11942 @kindex show machine
11943 @item set machine h8300
11944 @itemx set machine h8300h
11945 Condition @value{GDBN} for one of the two variants of the H8/300
11946 architecture with @samp{set machine}. You can use @samp{show machine}
11947 to check which variant is currently in effect.
11956 @kindex set memory @var{mod}
11957 @cindex memory models, H8/500
11958 @item set memory @var{mod}
11960 Specify which H8/500 memory model (@var{mod}) you are using with
11961 @samp{set memory}; check which memory model is in effect with @samp{show
11962 memory}. The accepted values for @var{mod} are @code{small},
11963 @code{big}, @code{medium}, and @code{compact}.
11968 @subsection Mitsubishi M32R/D
11972 @kindex target m32r
11973 @item target m32r @var{dev}
11974 Mitsubishi M32R/D ROM monitor.
11981 The Motorola m68k configuration includes ColdFire support, and
11982 target command for the following ROM monitors.
11986 @kindex target abug
11987 @item target abug @var{dev}
11988 ABug ROM monitor for M68K.
11990 @kindex target cpu32bug
11991 @item target cpu32bug @var{dev}
11992 CPU32BUG monitor, running on a CPU32 (M68K) board.
11994 @kindex target dbug
11995 @item target dbug @var{dev}
11996 dBUG ROM monitor for Motorola ColdFire.
11999 @item target est @var{dev}
12000 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12002 @kindex target rom68k
12003 @item target rom68k @var{dev}
12004 ROM 68K monitor, running on an M68K IDP board.
12010 @kindex target rombug
12011 @item target rombug @var{dev}
12012 ROMBUG ROM monitor for OS/9000.
12016 @node MIPS Embedded
12017 @subsection MIPS Embedded
12019 @cindex MIPS boards
12020 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12021 MIPS board attached to a serial line. This is available when
12022 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12025 Use these @value{GDBN} commands to specify the connection to your target board:
12028 @item target mips @var{port}
12029 @kindex target mips @var{port}
12030 To run a program on the board, start up @code{@value{GDBP}} with the
12031 name of your program as the argument. To connect to the board, use the
12032 command @samp{target mips @var{port}}, where @var{port} is the name of
12033 the serial port connected to the board. If the program has not already
12034 been downloaded to the board, you may use the @code{load} command to
12035 download it. You can then use all the usual @value{GDBN} commands.
12037 For example, this sequence connects to the target board through a serial
12038 port, and loads and runs a program called @var{prog} through the
12042 host$ @value{GDBP} @var{prog}
12043 @value{GDBN} is free software and @dots{}
12044 (@value{GDBP}) target mips /dev/ttyb
12045 (@value{GDBP}) load @var{prog}
12049 @item target mips @var{hostname}:@var{portnumber}
12050 On some @value{GDBN} host configurations, you can specify a TCP
12051 connection (for instance, to a serial line managed by a terminal
12052 concentrator) instead of a serial port, using the syntax
12053 @samp{@var{hostname}:@var{portnumber}}.
12055 @item target pmon @var{port}
12056 @kindex target pmon @var{port}
12059 @item target ddb @var{port}
12060 @kindex target ddb @var{port}
12061 NEC's DDB variant of PMON for Vr4300.
12063 @item target lsi @var{port}
12064 @kindex target lsi @var{port}
12065 LSI variant of PMON.
12067 @kindex target r3900
12068 @item target r3900 @var{dev}
12069 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12071 @kindex target array
12072 @item target array @var{dev}
12073 Array Tech LSI33K RAID controller board.
12079 @value{GDBN} also supports these special commands for MIPS targets:
12082 @item set processor @var{args}
12083 @itemx show processor
12084 @kindex set processor @var{args}
12085 @kindex show processor
12086 Use the @code{set processor} command to set the type of MIPS
12087 processor when you want to access processor-type-specific registers.
12088 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12089 to use the CPU registers appropriate for the 3041 chip.
12090 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12091 is using. Use the @code{info reg} command to see what registers
12092 @value{GDBN} is using.
12094 @item set mipsfpu double
12095 @itemx set mipsfpu single
12096 @itemx set mipsfpu none
12097 @itemx show mipsfpu
12098 @kindex set mipsfpu
12099 @kindex show mipsfpu
12100 @cindex MIPS remote floating point
12101 @cindex floating point, MIPS remote
12102 If your target board does not support the MIPS floating point
12103 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12104 need this, you may wish to put the command in your @value{GDBN} init
12105 file). This tells @value{GDBN} how to find the return value of
12106 functions which return floating point values. It also allows
12107 @value{GDBN} to avoid saving the floating point registers when calling
12108 functions on the board. If you are using a floating point coprocessor
12109 with only single precision floating point support, as on the @sc{r4650}
12110 processor, use the command @samp{set mipsfpu single}. The default
12111 double precision floating point coprocessor may be selected using
12112 @samp{set mipsfpu double}.
12114 In previous versions the only choices were double precision or no
12115 floating point, so @samp{set mipsfpu on} will select double precision
12116 and @samp{set mipsfpu off} will select no floating point.
12118 As usual, you can inquire about the @code{mipsfpu} variable with
12119 @samp{show mipsfpu}.
12121 @item set remotedebug @var{n}
12122 @itemx show remotedebug
12123 @kindex set remotedebug@r{, MIPS protocol}
12124 @kindex show remotedebug@r{, MIPS protocol}
12125 @cindex @code{remotedebug}, MIPS protocol
12126 @cindex MIPS @code{remotedebug} protocol
12127 @c FIXME! For this to be useful, you must know something about the MIPS
12128 @c FIXME...protocol. Where is it described?
12129 You can see some debugging information about communications with the board
12130 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12131 @samp{set remotedebug 1}, every packet is displayed. If you set it
12132 to @code{2}, every character is displayed. You can check the current value
12133 at any time with the command @samp{show remotedebug}.
12135 @item set timeout @var{seconds}
12136 @itemx set retransmit-timeout @var{seconds}
12137 @itemx show timeout
12138 @itemx show retransmit-timeout
12139 @cindex @code{timeout}, MIPS protocol
12140 @cindex @code{retransmit-timeout}, MIPS protocol
12141 @kindex set timeout
12142 @kindex show timeout
12143 @kindex set retransmit-timeout
12144 @kindex show retransmit-timeout
12145 You can control the timeout used while waiting for a packet, in the MIPS
12146 remote protocol, with the @code{set timeout @var{seconds}} command. The
12147 default is 5 seconds. Similarly, you can control the timeout used while
12148 waiting for an acknowledgement of a packet with the @code{set
12149 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12150 You can inspect both values with @code{show timeout} and @code{show
12151 retransmit-timeout}. (These commands are @emph{only} available when
12152 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12154 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12155 is waiting for your program to stop. In that case, @value{GDBN} waits
12156 forever because it has no way of knowing how long the program is going
12157 to run before stopping.
12160 @node OpenRISC 1000
12161 @subsection OpenRISC 1000
12162 @cindex OpenRISC 1000
12164 @cindex or1k boards
12165 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12166 about platform and commands.
12170 @kindex target jtag
12171 @item target jtag jtag://@var{host}:@var{port}
12173 Connects to remote JTAG server.
12174 JTAG remote server can be either an or1ksim or JTAG server,
12175 connected via parallel port to the board.
12177 Example: @code{target jtag jtag://localhost:9999}
12180 @item or1ksim @var{command}
12181 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12182 Simulator, proprietary commands can be executed.
12184 @kindex info or1k spr
12185 @item info or1k spr
12186 Displays spr groups.
12188 @item info or1k spr @var{group}
12189 @itemx info or1k spr @var{groupno}
12190 Displays register names in selected group.
12192 @item info or1k spr @var{group} @var{register}
12193 @itemx info or1k spr @var{register}
12194 @itemx info or1k spr @var{groupno} @var{registerno}
12195 @itemx info or1k spr @var{registerno}
12196 Shows information about specified spr register.
12199 @item spr @var{group} @var{register} @var{value}
12200 @itemx spr @var{register @var{value}}
12201 @itemx spr @var{groupno} @var{registerno @var{value}}
12202 @itemx spr @var{registerno @var{value}}
12203 Writes @var{value} to specified spr register.
12206 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12207 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12208 program execution and is thus much faster. Hardware breakpoints/watchpoint
12209 triggers can be set using:
12212 Load effective address/data
12214 Store effective address/data
12216 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12221 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12222 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12224 @code{htrace} commands:
12225 @cindex OpenRISC 1000 htrace
12228 @item hwatch @var{conditional}
12229 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12230 or Data. For example:
12232 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12234 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12236 @kindex htrace info
12238 Display information about current HW trace configuration.
12240 @kindex htrace trigger
12241 @item htrace trigger @var{conditional}
12242 Set starting criteria for HW trace.
12244 @kindex htrace qualifier
12245 @item htrace qualifier @var{conditional}
12246 Set acquisition qualifier for HW trace.
12248 @kindex htrace stop
12249 @item htrace stop @var{conditional}
12250 Set HW trace stopping criteria.
12252 @kindex htrace record
12253 @item htrace record [@var{data}]*
12254 Selects the data to be recorded, when qualifier is met and HW trace was
12257 @kindex htrace enable
12258 @item htrace enable
12259 @kindex htrace disable
12260 @itemx htrace disable
12261 Enables/disables the HW trace.
12263 @kindex htrace rewind
12264 @item htrace rewind [@var{filename}]
12265 Clears currently recorded trace data.
12267 If filename is specified, new trace file is made and any newly collected data
12268 will be written there.
12270 @kindex htrace print
12271 @item htrace print [@var{start} [@var{len}]]
12272 Prints trace buffer, using current record configuration.
12274 @kindex htrace mode continuous
12275 @item htrace mode continuous
12276 Set continuous trace mode.
12278 @kindex htrace mode suspend
12279 @item htrace mode suspend
12280 Set suspend trace mode.
12285 @subsection PowerPC
12289 @kindex target dink32
12290 @item target dink32 @var{dev}
12291 DINK32 ROM monitor.
12293 @kindex target ppcbug
12294 @item target ppcbug @var{dev}
12295 @kindex target ppcbug1
12296 @item target ppcbug1 @var{dev}
12297 PPCBUG ROM monitor for PowerPC.
12300 @item target sds @var{dev}
12301 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12306 @subsection HP PA Embedded
12310 @kindex target op50n
12311 @item target op50n @var{dev}
12312 OP50N monitor, running on an OKI HPPA board.
12314 @kindex target w89k
12315 @item target w89k @var{dev}
12316 W89K monitor, running on a Winbond HPPA board.
12321 @subsection Hitachi SH
12325 @kindex target hms@r{, with Hitachi SH}
12326 @item target hms @var{dev}
12327 A Hitachi SH board attached via serial line to your host. Use special
12328 commands @code{device} and @code{speed} to control the serial line and
12329 the communications speed used.
12331 @kindex target e7000@r{, with Hitachi SH}
12332 @item target e7000 @var{dev}
12333 E7000 emulator for Hitachi SH.
12335 @kindex target sh3@r{, with SH}
12336 @kindex target sh3e@r{, with SH}
12337 @item target sh3 @var{dev}
12338 @item target sh3e @var{dev}
12339 Hitachi SH-3 and SH-3E target systems.
12344 @subsection Tsqware Sparclet
12348 @value{GDBN} enables developers to debug tasks running on
12349 Sparclet targets from a Unix host.
12350 @value{GDBN} uses code that runs on
12351 both the Unix host and on the Sparclet target. The program
12352 @code{@value{GDBP}} is installed and executed on the Unix host.
12355 @item remotetimeout @var{args}
12356 @kindex remotetimeout
12357 @value{GDBN} supports the option @code{remotetimeout}.
12358 This option is set by the user, and @var{args} represents the number of
12359 seconds @value{GDBN} waits for responses.
12362 @cindex compiling, on Sparclet
12363 When compiling for debugging, include the options @samp{-g} to get debug
12364 information and @samp{-Ttext} to relocate the program to where you wish to
12365 load it on the target. You may also want to add the options @samp{-n} or
12366 @samp{-N} in order to reduce the size of the sections. Example:
12369 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12372 You can use @code{objdump} to verify that the addresses are what you intended:
12375 sparclet-aout-objdump --headers --syms prog
12378 @cindex running, on Sparclet
12380 your Unix execution search path to find @value{GDBN}, you are ready to
12381 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12382 (or @code{sparclet-aout-gdb}, depending on your installation).
12384 @value{GDBN} comes up showing the prompt:
12391 * Sparclet File:: Setting the file to debug
12392 * Sparclet Connection:: Connecting to Sparclet
12393 * Sparclet Download:: Sparclet download
12394 * Sparclet Execution:: Running and debugging
12397 @node Sparclet File
12398 @subsubsection Setting file to debug
12400 The @value{GDBN} command @code{file} lets you choose with program to debug.
12403 (gdbslet) file prog
12407 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12408 @value{GDBN} locates
12409 the file by searching the directories listed in the command search
12411 If the file was compiled with debug information (option "-g"), source
12412 files will be searched as well.
12413 @value{GDBN} locates
12414 the source files by searching the directories listed in the directory search
12415 path (@pxref{Environment, ,Your program's environment}).
12417 to find a file, it displays a message such as:
12420 prog: No such file or directory.
12423 When this happens, add the appropriate directories to the search paths with
12424 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12425 @code{target} command again.
12427 @node Sparclet Connection
12428 @subsubsection Connecting to Sparclet
12430 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12431 To connect to a target on serial port ``@code{ttya}'', type:
12434 (gdbslet) target sparclet /dev/ttya
12435 Remote target sparclet connected to /dev/ttya
12436 main () at ../prog.c:3
12440 @value{GDBN} displays messages like these:
12446 @node Sparclet Download
12447 @subsubsection Sparclet download
12449 @cindex download to Sparclet
12450 Once connected to the Sparclet target,
12451 you can use the @value{GDBN}
12452 @code{load} command to download the file from the host to the target.
12453 The file name and load offset should be given as arguments to the @code{load}
12455 Since the file format is aout, the program must be loaded to the starting
12456 address. You can use @code{objdump} to find out what this value is. The load
12457 offset is an offset which is added to the VMA (virtual memory address)
12458 of each of the file's sections.
12459 For instance, if the program
12460 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12461 and bss at 0x12010170, in @value{GDBN}, type:
12464 (gdbslet) load prog 0x12010000
12465 Loading section .text, size 0xdb0 vma 0x12010000
12468 If the code is loaded at a different address then what the program was linked
12469 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12470 to tell @value{GDBN} where to map the symbol table.
12472 @node Sparclet Execution
12473 @subsubsection Running and debugging
12475 @cindex running and debugging Sparclet programs
12476 You can now begin debugging the task using @value{GDBN}'s execution control
12477 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12478 manual for the list of commands.
12482 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12484 Starting program: prog
12485 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12486 3 char *symarg = 0;
12488 4 char *execarg = "hello!";
12493 @subsection Fujitsu Sparclite
12497 @kindex target sparclite
12498 @item target sparclite @var{dev}
12499 Fujitsu sparclite boards, used only for the purpose of loading.
12500 You must use an additional command to debug the program.
12501 For example: target remote @var{dev} using @value{GDBN} standard
12507 @subsection Tandem ST2000
12509 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12512 To connect your ST2000 to the host system, see the manufacturer's
12513 manual. Once the ST2000 is physically attached, you can run:
12516 target st2000 @var{dev} @var{speed}
12520 to establish it as your debugging environment. @var{dev} is normally
12521 the name of a serial device, such as @file{/dev/ttya}, connected to the
12522 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12523 connection (for example, to a serial line attached via a terminal
12524 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12526 The @code{load} and @code{attach} commands are @emph{not} defined for
12527 this target; you must load your program into the ST2000 as you normally
12528 would for standalone operation. @value{GDBN} reads debugging information
12529 (such as symbols) from a separate, debugging version of the program
12530 available on your host computer.
12531 @c FIXME!! This is terribly vague; what little content is here is
12532 @c basically hearsay.
12534 @cindex ST2000 auxiliary commands
12535 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12539 @item st2000 @var{command}
12540 @kindex st2000 @var{cmd}
12541 @cindex STDBUG commands (ST2000)
12542 @cindex commands to STDBUG (ST2000)
12543 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12544 manual for available commands.
12547 @cindex connect (to STDBUG)
12548 Connect the controlling terminal to the STDBUG command monitor. When
12549 you are done interacting with STDBUG, typing either of two character
12550 sequences gets you back to the @value{GDBN} command prompt:
12551 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12552 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12556 @subsection Zilog Z8000
12559 @cindex simulator, Z8000
12560 @cindex Zilog Z8000 simulator
12562 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12565 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12566 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12567 segmented variant). The simulator recognizes which architecture is
12568 appropriate by inspecting the object code.
12571 @item target sim @var{args}
12573 @kindex target sim@r{, with Z8000}
12574 Debug programs on a simulated CPU. If the simulator supports setup
12575 options, specify them via @var{args}.
12579 After specifying this target, you can debug programs for the simulated
12580 CPU in the same style as programs for your host computer; use the
12581 @code{file} command to load a new program image, the @code{run} command
12582 to run your program, and so on.
12584 As well as making available all the usual machine registers
12585 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12586 additional items of information as specially named registers:
12591 Counts clock-ticks in the simulator.
12594 Counts instructions run in the simulator.
12597 Execution time in 60ths of a second.
12601 You can refer to these values in @value{GDBN} expressions with the usual
12602 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12603 conditional breakpoint that suspends only after at least 5000
12604 simulated clock ticks.
12606 @node Architectures
12607 @section Architectures
12609 This section describes characteristics of architectures that affect
12610 all uses of @value{GDBN} with the architecture, both native and cross.
12623 @kindex set rstack_high_address
12624 @cindex AMD 29K register stack
12625 @cindex register stack, AMD29K
12626 @item set rstack_high_address @var{address}
12627 On AMD 29000 family processors, registers are saved in a separate
12628 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12629 extent of this stack. Normally, @value{GDBN} just assumes that the
12630 stack is ``large enough''. This may result in @value{GDBN} referencing
12631 memory locations that do not exist. If necessary, you can get around
12632 this problem by specifying the ending address of the register stack with
12633 the @code{set rstack_high_address} command. The argument should be an
12634 address, which you probably want to precede with @samp{0x} to specify in
12637 @kindex show rstack_high_address
12638 @item show rstack_high_address
12639 Display the current limit of the register stack, on AMD 29000 family
12647 See the following section.
12652 @cindex stack on Alpha
12653 @cindex stack on MIPS
12654 @cindex Alpha stack
12656 Alpha- and MIPS-based computers use an unusual stack frame, which
12657 sometimes requires @value{GDBN} to search backward in the object code to
12658 find the beginning of a function.
12660 @cindex response time, MIPS debugging
12661 To improve response time (especially for embedded applications, where
12662 @value{GDBN} may be restricted to a slow serial line for this search)
12663 you may want to limit the size of this search, using one of these
12667 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12668 @item set heuristic-fence-post @var{limit}
12669 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12670 search for the beginning of a function. A value of @var{0} (the
12671 default) means there is no limit. However, except for @var{0}, the
12672 larger the limit the more bytes @code{heuristic-fence-post} must search
12673 and therefore the longer it takes to run.
12675 @item show heuristic-fence-post
12676 Display the current limit.
12680 These commands are available @emph{only} when @value{GDBN} is configured
12681 for debugging programs on Alpha or MIPS processors.
12684 @node Controlling GDB
12685 @chapter Controlling @value{GDBN}
12687 You can alter the way @value{GDBN} interacts with you by using the
12688 @code{set} command. For commands controlling how @value{GDBN} displays
12689 data, see @ref{Print Settings, ,Print settings}. Other settings are
12694 * Editing:: Command editing
12695 * History:: Command history
12696 * Screen Size:: Screen size
12697 * Numbers:: Numbers
12698 * ABI:: Configuring the current ABI
12699 * Messages/Warnings:: Optional warnings and messages
12700 * Debugging Output:: Optional messages about internal happenings
12708 @value{GDBN} indicates its readiness to read a command by printing a string
12709 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12710 can change the prompt string with the @code{set prompt} command. For
12711 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12712 the prompt in one of the @value{GDBN} sessions so that you can always tell
12713 which one you are talking to.
12715 @emph{Note:} @code{set prompt} does not add a space for you after the
12716 prompt you set. This allows you to set a prompt which ends in a space
12717 or a prompt that does not.
12721 @item set prompt @var{newprompt}
12722 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12724 @kindex show prompt
12726 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12730 @section Command editing
12732 @cindex command line editing
12734 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12735 @sc{gnu} library provides consistent behavior for programs which provide a
12736 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12737 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12738 substitution, and a storage and recall of command history across
12739 debugging sessions.
12741 You may control the behavior of command line editing in @value{GDBN} with the
12742 command @code{set}.
12745 @kindex set editing
12748 @itemx set editing on
12749 Enable command line editing (enabled by default).
12751 @item set editing off
12752 Disable command line editing.
12754 @kindex show editing
12756 Show whether command line editing is enabled.
12760 @section Command history
12762 @value{GDBN} can keep track of the commands you type during your
12763 debugging sessions, so that you can be certain of precisely what
12764 happened. Use these commands to manage the @value{GDBN} command
12768 @cindex history substitution
12769 @cindex history file
12770 @kindex set history filename
12771 @kindex GDBHISTFILE
12772 @item set history filename @var{fname}
12773 Set the name of the @value{GDBN} command history file to @var{fname}.
12774 This is the file where @value{GDBN} reads an initial command history
12775 list, and where it writes the command history from this session when it
12776 exits. You can access this list through history expansion or through
12777 the history command editing characters listed below. This file defaults
12778 to the value of the environment variable @code{GDBHISTFILE}, or to
12779 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12782 @cindex history save
12783 @kindex set history save
12784 @item set history save
12785 @itemx set history save on
12786 Record command history in a file, whose name may be specified with the
12787 @code{set history filename} command. By default, this option is disabled.
12789 @item set history save off
12790 Stop recording command history in a file.
12792 @cindex history size
12793 @kindex set history size
12794 @item set history size @var{size}
12795 Set the number of commands which @value{GDBN} keeps in its history list.
12796 This defaults to the value of the environment variable
12797 @code{HISTSIZE}, or to 256 if this variable is not set.
12800 @cindex history expansion
12801 History expansion assigns special meaning to the character @kbd{!}.
12802 @ifset have-readline-appendices
12803 @xref{Event Designators}.
12806 Since @kbd{!} is also the logical not operator in C, history expansion
12807 is off by default. If you decide to enable history expansion with the
12808 @code{set history expansion on} command, you may sometimes need to
12809 follow @kbd{!} (when it is used as logical not, in an expression) with
12810 a space or a tab to prevent it from being expanded. The readline
12811 history facilities do not attempt substitution on the strings
12812 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12814 The commands to control history expansion are:
12817 @kindex set history expansion
12818 @item set history expansion on
12819 @itemx set history expansion
12820 Enable history expansion. History expansion is off by default.
12822 @item set history expansion off
12823 Disable history expansion.
12825 The readline code comes with more complete documentation of
12826 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12827 or @code{vi} may wish to read it.
12828 @ifset have-readline-appendices
12829 @xref{Command Line Editing}.
12833 @kindex show history
12835 @itemx show history filename
12836 @itemx show history save
12837 @itemx show history size
12838 @itemx show history expansion
12839 These commands display the state of the @value{GDBN} history parameters.
12840 @code{show history} by itself displays all four states.
12846 @item show commands
12847 Display the last ten commands in the command history.
12849 @item show commands @var{n}
12850 Print ten commands centered on command number @var{n}.
12852 @item show commands +
12853 Print ten commands just after the commands last printed.
12857 @section Screen size
12858 @cindex size of screen
12859 @cindex pauses in output
12861 Certain commands to @value{GDBN} may produce large amounts of
12862 information output to the screen. To help you read all of it,
12863 @value{GDBN} pauses and asks you for input at the end of each page of
12864 output. Type @key{RET} when you want to continue the output, or @kbd{q}
12865 to discard the remaining output. Also, the screen width setting
12866 determines when to wrap lines of output. Depending on what is being
12867 printed, @value{GDBN} tries to break the line at a readable place,
12868 rather than simply letting it overflow onto the following line.
12870 Normally @value{GDBN} knows the size of the screen from the terminal
12871 driver software. For example, on Unix @value{GDBN} uses the termcap data base
12872 together with the value of the @code{TERM} environment variable and the
12873 @code{stty rows} and @code{stty cols} settings. If this is not correct,
12874 you can override it with the @code{set height} and @code{set
12881 @kindex show height
12882 @item set height @var{lpp}
12884 @itemx set width @var{cpl}
12886 These @code{set} commands specify a screen height of @var{lpp} lines and
12887 a screen width of @var{cpl} characters. The associated @code{show}
12888 commands display the current settings.
12890 If you specify a height of zero lines, @value{GDBN} does not pause during
12891 output no matter how long the output is. This is useful if output is to a
12892 file or to an editor buffer.
12894 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
12895 from wrapping its output.
12900 @cindex number representation
12901 @cindex entering numbers
12903 You can always enter numbers in octal, decimal, or hexadecimal in
12904 @value{GDBN} by the usual conventions: octal numbers begin with
12905 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
12906 begin with @samp{0x}. Numbers that begin with none of these are, by
12907 default, entered in base 10; likewise, the default display for
12908 numbers---when no particular format is specified---is base 10. You can
12909 change the default base for both input and output with the @code{set
12913 @kindex set input-radix
12914 @item set input-radix @var{base}
12915 Set the default base for numeric input. Supported choices
12916 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12917 specified either unambiguously or using the current default radix; for
12927 sets the base to decimal. On the other hand, @samp{set radix 10}
12928 leaves the radix unchanged no matter what it was.
12930 @kindex set output-radix
12931 @item set output-radix @var{base}
12932 Set the default base for numeric display. Supported choices
12933 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12934 specified either unambiguously or using the current default radix.
12936 @kindex show input-radix
12937 @item show input-radix
12938 Display the current default base for numeric input.
12940 @kindex show output-radix
12941 @item show output-radix
12942 Display the current default base for numeric display.
12946 @section Configuring the current ABI
12948 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
12949 application automatically. However, sometimes you need to override its
12950 conclusions. Use these commands to manage @value{GDBN}'s view of the
12957 One @value{GDBN} configuration can debug binaries for multiple operating
12958 system targets, either via remote debugging or native emulation.
12959 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
12960 but you can override its conclusion using the @code{set osabi} command.
12961 One example where this is useful is in debugging of binaries which use
12962 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
12963 not have the same identifying marks that the standard C library for your
12968 Show the OS ABI currently in use.
12971 With no argument, show the list of registered available OS ABI's.
12973 @item set osabi @var{abi}
12974 Set the current OS ABI to @var{abi}.
12977 @cindex float promotion
12978 @kindex set coerce-float-to-double
12980 Generally, the way that an argument of type @code{float} is passed to a
12981 function depends on whether the function is prototyped. For a prototyped
12982 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
12983 according to the architecture's convention for @code{float}. For unprototyped
12984 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
12985 @code{double} and then passed.
12987 Unfortunately, some forms of debug information do not reliably indicate whether
12988 a function is prototyped. If @value{GDBN} calls a function that is not marked
12989 as prototyped, it consults @kbd{set coerce-float-to-double}.
12992 @item set coerce-float-to-double
12993 @itemx set coerce-float-to-double on
12994 Arguments of type @code{float} will be promoted to @code{double} when passed
12995 to an unprototyped function. This is the default setting.
12997 @item set coerce-float-to-double off
12998 Arguments of type @code{float} will be passed directly to unprototyped
13003 @kindex show cp-abi
13004 @value{GDBN} needs to know the ABI used for your program's C@t{++}
13005 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
13006 used to build your application. @value{GDBN} only fully supports
13007 programs with a single C@t{++} ABI; if your program contains code using
13008 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
13009 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
13010 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
13011 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
13012 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
13013 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
13018 Show the C@t{++} ABI currently in use.
13021 With no argument, show the list of supported C@t{++} ABI's.
13023 @item set cp-abi @var{abi}
13024 @itemx set cp-abi auto
13025 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
13028 @node Messages/Warnings
13029 @section Optional warnings and messages
13031 By default, @value{GDBN} is silent about its inner workings. If you are
13032 running on a slow machine, you may want to use the @code{set verbose}
13033 command. This makes @value{GDBN} tell you when it does a lengthy
13034 internal operation, so you will not think it has crashed.
13036 Currently, the messages controlled by @code{set verbose} are those
13037 which announce that the symbol table for a source file is being read;
13038 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
13041 @kindex set verbose
13042 @item set verbose on
13043 Enables @value{GDBN} output of certain informational messages.
13045 @item set verbose off
13046 Disables @value{GDBN} output of certain informational messages.
13048 @kindex show verbose
13050 Displays whether @code{set verbose} is on or off.
13053 By default, if @value{GDBN} encounters bugs in the symbol table of an
13054 object file, it is silent; but if you are debugging a compiler, you may
13055 find this information useful (@pxref{Symbol Errors, ,Errors reading
13060 @kindex set complaints
13061 @item set complaints @var{limit}
13062 Permits @value{GDBN} to output @var{limit} complaints about each type of
13063 unusual symbols before becoming silent about the problem. Set
13064 @var{limit} to zero to suppress all complaints; set it to a large number
13065 to prevent complaints from being suppressed.
13067 @kindex show complaints
13068 @item show complaints
13069 Displays how many symbol complaints @value{GDBN} is permitted to produce.
13073 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
13074 lot of stupid questions to confirm certain commands. For example, if
13075 you try to run a program which is already running:
13079 The program being debugged has been started already.
13080 Start it from the beginning? (y or n)
13083 If you are willing to unflinchingly face the consequences of your own
13084 commands, you can disable this ``feature'':
13088 @kindex set confirm
13090 @cindex confirmation
13091 @cindex stupid questions
13092 @item set confirm off
13093 Disables confirmation requests.
13095 @item set confirm on
13096 Enables confirmation requests (the default).
13098 @kindex show confirm
13100 Displays state of confirmation requests.
13104 @node Debugging Output
13105 @section Optional messages about internal happenings
13107 @kindex set debug arch
13108 @item set debug arch
13109 Turns on or off display of gdbarch debugging info. The default is off
13110 @kindex show debug arch
13111 @item show debug arch
13112 Displays the current state of displaying gdbarch debugging info.
13113 @kindex set debug event
13114 @item set debug event
13115 Turns on or off display of @value{GDBN} event debugging info. The
13117 @kindex show debug event
13118 @item show debug event
13119 Displays the current state of displaying @value{GDBN} event debugging
13121 @kindex set debug expression
13122 @item set debug expression
13123 Turns on or off display of @value{GDBN} expression debugging info. The
13125 @kindex show debug expression
13126 @item show debug expression
13127 Displays the current state of displaying @value{GDBN} expression
13129 @kindex set debug frame
13130 @item set debug frame
13131 Turns on or off display of @value{GDBN} frame debugging info. The
13133 @kindex show debug frame
13134 @item show debug frame
13135 Displays the current state of displaying @value{GDBN} frame debugging
13137 @kindex set debug overload
13138 @item set debug overload
13139 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13140 info. This includes info such as ranking of functions, etc. The default
13142 @kindex show debug overload
13143 @item show debug overload
13144 Displays the current state of displaying @value{GDBN} C@t{++} overload
13146 @kindex set debug remote
13147 @cindex packets, reporting on stdout
13148 @cindex serial connections, debugging
13149 @item set debug remote
13150 Turns on or off display of reports on all packets sent back and forth across
13151 the serial line to the remote machine. The info is printed on the
13152 @value{GDBN} standard output stream. The default is off.
13153 @kindex show debug remote
13154 @item show debug remote
13155 Displays the state of display of remote packets.
13156 @kindex set debug serial
13157 @item set debug serial
13158 Turns on or off display of @value{GDBN} serial debugging info. The
13160 @kindex show debug serial
13161 @item show debug serial
13162 Displays the current state of displaying @value{GDBN} serial debugging
13164 @kindex set debug target
13165 @item set debug target
13166 Turns on or off display of @value{GDBN} target debugging info. This info
13167 includes what is going on at the target level of GDB, as it happens. The
13169 @kindex show debug target
13170 @item show debug target
13171 Displays the current state of displaying @value{GDBN} target debugging
13173 @kindex set debug varobj
13174 @item set debug varobj
13175 Turns on or off display of @value{GDBN} variable object debugging
13176 info. The default is off.
13177 @kindex show debug varobj
13178 @item show debug varobj
13179 Displays the current state of displaying @value{GDBN} variable object
13184 @chapter Canned Sequences of Commands
13186 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13187 command lists}), @value{GDBN} provides two ways to store sequences of
13188 commands for execution as a unit: user-defined commands and command
13192 * Define:: User-defined commands
13193 * Hooks:: User-defined command hooks
13194 * Command Files:: Command files
13195 * Output:: Commands for controlled output
13199 @section User-defined commands
13201 @cindex user-defined command
13202 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13203 which you assign a new name as a command. This is done with the
13204 @code{define} command. User commands may accept up to 10 arguments
13205 separated by whitespace. Arguments are accessed within the user command
13206 via @var{$arg0@dots{}$arg9}. A trivial example:
13210 print $arg0 + $arg1 + $arg2
13214 To execute the command use:
13221 This defines the command @code{adder}, which prints the sum of
13222 its three arguments. Note the arguments are text substitutions, so they may
13223 reference variables, use complex expressions, or even perform inferior
13229 @item define @var{commandname}
13230 Define a command named @var{commandname}. If there is already a command
13231 by that name, you are asked to confirm that you want to redefine it.
13233 The definition of the command is made up of other @value{GDBN} command lines,
13234 which are given following the @code{define} command. The end of these
13235 commands is marked by a line containing @code{end}.
13240 Takes a single argument, which is an expression to evaluate.
13241 It is followed by a series of commands that are executed
13242 only if the expression is true (nonzero).
13243 There can then optionally be a line @code{else}, followed
13244 by a series of commands that are only executed if the expression
13245 was false. The end of the list is marked by a line containing @code{end}.
13249 The syntax is similar to @code{if}: the command takes a single argument,
13250 which is an expression to evaluate, and must be followed by the commands to
13251 execute, one per line, terminated by an @code{end}.
13252 The commands are executed repeatedly as long as the expression
13256 @item document @var{commandname}
13257 Document the user-defined command @var{commandname}, so that it can be
13258 accessed by @code{help}. The command @var{commandname} must already be
13259 defined. This command reads lines of documentation just as @code{define}
13260 reads the lines of the command definition, ending with @code{end}.
13261 After the @code{document} command is finished, @code{help} on command
13262 @var{commandname} displays the documentation you have written.
13264 You may use the @code{document} command again to change the
13265 documentation of a command. Redefining the command with @code{define}
13266 does not change the documentation.
13268 @kindex help user-defined
13269 @item help user-defined
13270 List all user-defined commands, with the first line of the documentation
13275 @itemx show user @var{commandname}
13276 Display the @value{GDBN} commands used to define @var{commandname} (but
13277 not its documentation). If no @var{commandname} is given, display the
13278 definitions for all user-defined commands.
13280 @kindex show max-user-call-depth
13281 @kindex set max-user-call-depth
13282 @item show max-user-call-depth
13283 @itemx set max-user-call-depth
13284 The value of @code{max-user-call-depth} controls how many recursion
13285 levels are allowed in user-defined commands before GDB suspects an
13286 infinite recursion and aborts the command.
13290 When user-defined commands are executed, the
13291 commands of the definition are not printed. An error in any command
13292 stops execution of the user-defined command.
13294 If used interactively, commands that would ask for confirmation proceed
13295 without asking when used inside a user-defined command. Many @value{GDBN}
13296 commands that normally print messages to say what they are doing omit the
13297 messages when used in a user-defined command.
13300 @section User-defined command hooks
13301 @cindex command hooks
13302 @cindex hooks, for commands
13303 @cindex hooks, pre-command
13307 You may define @dfn{hooks}, which are a special kind of user-defined
13308 command. Whenever you run the command @samp{foo}, if the user-defined
13309 command @samp{hook-foo} exists, it is executed (with no arguments)
13310 before that command.
13312 @cindex hooks, post-command
13315 A hook may also be defined which is run after the command you executed.
13316 Whenever you run the command @samp{foo}, if the user-defined command
13317 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13318 that command. Post-execution hooks may exist simultaneously with
13319 pre-execution hooks, for the same command.
13321 It is valid for a hook to call the command which it hooks. If this
13322 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13324 @c It would be nice if hookpost could be passed a parameter indicating
13325 @c if the command it hooks executed properly or not. FIXME!
13327 @kindex stop@r{, a pseudo-command}
13328 In addition, a pseudo-command, @samp{stop} exists. Defining
13329 (@samp{hook-stop}) makes the associated commands execute every time
13330 execution stops in your program: before breakpoint commands are run,
13331 displays are printed, or the stack frame is printed.
13333 For example, to ignore @code{SIGALRM} signals while
13334 single-stepping, but treat them normally during normal execution,
13339 handle SIGALRM nopass
13343 handle SIGALRM pass
13346 define hook-continue
13347 handle SIGLARM pass
13351 As a further example, to hook at the begining and end of the @code{echo}
13352 command, and to add extra text to the beginning and end of the message,
13360 define hookpost-echo
13364 (@value{GDBP}) echo Hello World
13365 <<<---Hello World--->>>
13370 You can define a hook for any single-word command in @value{GDBN}, but
13371 not for command aliases; you should define a hook for the basic command
13372 name, e.g. @code{backtrace} rather than @code{bt}.
13373 @c FIXME! So how does Joe User discover whether a command is an alias
13375 If an error occurs during the execution of your hook, execution of
13376 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13377 (before the command that you actually typed had a chance to run).
13379 If you try to define a hook which does not match any known command, you
13380 get a warning from the @code{define} command.
13382 @node Command Files
13383 @section Command files
13385 @cindex command files
13386 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13387 commands. Comments (lines starting with @kbd{#}) may also be included.
13388 An empty line in a command file does nothing; it does not mean to repeat
13389 the last command, as it would from the terminal.
13392 @cindex @file{.gdbinit}
13393 @cindex @file{gdb.ini}
13394 When you start @value{GDBN}, it automatically executes commands from its
13395 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13396 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13397 limitations of file names imposed by DOS filesystems.}.
13398 During startup, @value{GDBN} does the following:
13402 Reads the init file (if any) in your home directory@footnote{On
13403 DOS/Windows systems, the home directory is the one pointed to by the
13404 @code{HOME} environment variable.}.
13407 Processes command line options and operands.
13410 Reads the init file (if any) in the current working directory.
13413 Reads command files specified by the @samp{-x} option.
13416 The init file in your home directory can set options (such as @samp{set
13417 complaints}) that affect subsequent processing of command line options
13418 and operands. Init files are not executed if you use the @samp{-nx}
13419 option (@pxref{Mode Options, ,Choosing modes}).
13421 @cindex init file name
13422 On some configurations of @value{GDBN}, the init file is known by a
13423 different name (these are typically environments where a specialized
13424 form of @value{GDBN} may need to coexist with other forms, hence a
13425 different name for the specialized version's init file). These are the
13426 environments with special init file names:
13428 @cindex @file{.vxgdbinit}
13431 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13433 @cindex @file{.os68gdbinit}
13435 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13437 @cindex @file{.esgdbinit}
13439 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13442 You can also request the execution of a command file with the
13443 @code{source} command:
13447 @item source @var{filename}
13448 Execute the command file @var{filename}.
13451 The lines in a command file are executed sequentially. They are not
13452 printed as they are executed. An error in any command terminates
13453 execution of the command file and control is returned to the console.
13455 Commands that would ask for confirmation if used interactively proceed
13456 without asking when used in a command file. Many @value{GDBN} commands that
13457 normally print messages to say what they are doing omit the messages
13458 when called from command files.
13460 @value{GDBN} also accepts command input from standard input. In this
13461 mode, normal output goes to standard output and error output goes to
13462 standard error. Errors in a command file supplied on standard input do
13463 not terminate execution of the command file --- execution continues with
13467 gdb < cmds > log 2>&1
13470 (The syntax above will vary depending on the shell used.) This example
13471 will execute commands from the file @file{cmds}. All output and errors
13472 would be directed to @file{log}.
13475 @section Commands for controlled output
13477 During the execution of a command file or a user-defined command, normal
13478 @value{GDBN} output is suppressed; the only output that appears is what is
13479 explicitly printed by the commands in the definition. This section
13480 describes three commands useful for generating exactly the output you
13485 @item echo @var{text}
13486 @c I do not consider backslash-space a standard C escape sequence
13487 @c because it is not in ANSI.
13488 Print @var{text}. Nonprinting characters can be included in
13489 @var{text} using C escape sequences, such as @samp{\n} to print a
13490 newline. @strong{No newline is printed unless you specify one.}
13491 In addition to the standard C escape sequences, a backslash followed
13492 by a space stands for a space. This is useful for displaying a
13493 string with spaces at the beginning or the end, since leading and
13494 trailing spaces are otherwise trimmed from all arguments.
13495 To print @samp{@w{ }and foo =@w{ }}, use the command
13496 @samp{echo \@w{ }and foo = \@w{ }}.
13498 A backslash at the end of @var{text} can be used, as in C, to continue
13499 the command onto subsequent lines. For example,
13502 echo This is some text\n\
13503 which is continued\n\
13504 onto several lines.\n
13507 produces the same output as
13510 echo This is some text\n
13511 echo which is continued\n
13512 echo onto several lines.\n
13516 @item output @var{expression}
13517 Print the value of @var{expression} and nothing but that value: no
13518 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13519 value history either. @xref{Expressions, ,Expressions}, for more information
13522 @item output/@var{fmt} @var{expression}
13523 Print the value of @var{expression} in format @var{fmt}. You can use
13524 the same formats as for @code{print}. @xref{Output Formats,,Output
13525 formats}, for more information.
13528 @item printf @var{string}, @var{expressions}@dots{}
13529 Print the values of the @var{expressions} under the control of
13530 @var{string}. The @var{expressions} are separated by commas and may be
13531 either numbers or pointers. Their values are printed as specified by
13532 @var{string}, exactly as if your program were to execute the C
13534 @c FIXME: the above implies that at least all ANSI C formats are
13535 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13536 @c Either this is a bug, or the manual should document what formats are
13540 printf (@var{string}, @var{expressions}@dots{});
13543 For example, you can print two values in hex like this:
13546 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13549 The only backslash-escape sequences that you can use in the format
13550 string are the simple ones that consist of backslash followed by a
13555 @chapter Command Interpreters
13556 @cindex command interpreters
13558 @value{GDBN} supports multiple command interpreters, and some command
13559 infrastructure to allow users or user interface writers to switch
13560 between interpreters or run commands in other interpreters.
13562 @value{GDBN} currently supports two command interpreters, the console
13563 interpreter (sometimes called the command-line interpreter or @sc{cli})
13564 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13565 describes both of these interfaces in great detail.
13567 By default, @value{GDBN} will start with the console interpreter.
13568 However, the user may choose to start @value{GDBN} with another
13569 interpreter by specifying the @option{-i} or @option{--interpreter}
13570 startup options. Defined interpreters include:
13574 @cindex console interpreter
13575 The traditional console or command-line interpreter. This is the most often
13576 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13577 @value{GDBN} will use this interpreter.
13580 @cindex mi interpreter
13581 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13582 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13583 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13587 @cindex mi2 interpreter
13588 The current @sc{gdb/mi} interface.
13591 @cindex mi1 interpreter
13592 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13596 @cindex invoke another interpreter
13597 The interpreter being used by @value{GDBN} may not be dynamically
13598 switched at runtime. Although possible, this could lead to a very
13599 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13600 enters the command "interpreter-set console" in a console view,
13601 @value{GDBN} would switch to using the console interpreter, rendering
13602 the IDE inoperable!
13604 @kindex interpreter-exec
13605 Although you may only choose a single interpreter at startup, you may execute
13606 commands in any interpreter from the current interpreter using the appropriate
13607 command. If you are running the console interpreter, simply use the
13608 @code{interpreter-exec} command:
13611 interpreter-exec mi "-data-list-register-names"
13614 @sc{gdb/mi} has a similar command, although it is only available in versions of
13615 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13618 @chapter @value{GDBN} Text User Interface
13622 * TUI Overview:: TUI overview
13623 * TUI Keys:: TUI key bindings
13624 * TUI Single Key Mode:: TUI single key mode
13625 * TUI Commands:: TUI specific commands
13626 * TUI Configuration:: TUI configuration variables
13629 The @value{GDBN} Text User Interface, TUI in short,
13630 is a terminal interface which uses the @code{curses} library
13631 to show the source file, the assembly output, the program registers
13632 and @value{GDBN} commands in separate text windows.
13633 The TUI is available only when @value{GDBN} is configured
13634 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13637 @section TUI overview
13639 The TUI has two display modes that can be switched while
13644 A curses (or TUI) mode in which it displays several text
13645 windows on the terminal.
13648 A standard mode which corresponds to the @value{GDBN} configured without
13652 In the TUI mode, @value{GDBN} can display several text window
13657 This window is the @value{GDBN} command window with the @value{GDBN}
13658 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13659 managed using readline but through the TUI. The @emph{command}
13660 window is always visible.
13663 The source window shows the source file of the program. The current
13664 line as well as active breakpoints are displayed in this window.
13667 The assembly window shows the disassembly output of the program.
13670 This window shows the processor registers. It detects when
13671 a register is changed and when this is the case, registers that have
13672 changed are highlighted.
13676 The source and assembly windows show the current program position
13677 by highlighting the current line and marking them with the @samp{>} marker.
13678 Breakpoints are also indicated with two markers. A first one
13679 indicates the breakpoint type:
13683 Breakpoint which was hit at least once.
13686 Breakpoint which was never hit.
13689 Hardware breakpoint which was hit at least once.
13692 Hardware breakpoint which was never hit.
13696 The second marker indicates whether the breakpoint is enabled or not:
13700 Breakpoint is enabled.
13703 Breakpoint is disabled.
13707 The source, assembly and register windows are attached to the thread
13708 and the frame position. They are updated when the current thread
13709 changes, when the frame changes or when the program counter changes.
13710 These three windows are arranged by the TUI according to several
13711 layouts. The layout defines which of these three windows are visible.
13712 The following layouts are available:
13722 source and assembly
13725 source and registers
13728 assembly and registers
13732 On top of the command window a status line gives various information
13733 concerning the current process begin debugged. The status line is
13734 updated when the information it shows changes. The following fields
13739 Indicates the current gdb target
13740 (@pxref{Targets, ,Specifying a Debugging Target}).
13743 Gives information about the current process or thread number.
13744 When no process is being debugged, this field is set to @code{No process}.
13747 Gives the current function name for the selected frame.
13748 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13749 When there is no symbol corresponding to the current program counter
13750 the string @code{??} is displayed.
13753 Indicates the current line number for the selected frame.
13754 When the current line number is not known the string @code{??} is displayed.
13757 Indicates the current program counter address.
13762 @section TUI Key Bindings
13763 @cindex TUI key bindings
13765 The TUI installs several key bindings in the readline keymaps
13766 (@pxref{Command Line Editing}).
13767 They allow to leave or enter in the TUI mode or they operate
13768 directly on the TUI layout and windows. The TUI also provides
13769 a @emph{SingleKey} keymap which binds several keys directly to
13770 @value{GDBN} commands. The following key bindings
13771 are installed for both TUI mode and the @value{GDBN} standard mode.
13780 Enter or leave the TUI mode. When the TUI mode is left,
13781 the curses window management is left and @value{GDBN} operates using
13782 its standard mode writing on the terminal directly. When the TUI
13783 mode is entered, the control is given back to the curses windows.
13784 The screen is then refreshed.
13788 Use a TUI layout with only one window. The layout will
13789 either be @samp{source} or @samp{assembly}. When the TUI mode
13790 is not active, it will switch to the TUI mode.
13792 Think of this key binding as the Emacs @kbd{C-x 1} binding.
13796 Use a TUI layout with at least two windows. When the current
13797 layout shows already two windows, a next layout with two windows is used.
13798 When a new layout is chosen, one window will always be common to the
13799 previous layout and the new one.
13801 Think of it as the Emacs @kbd{C-x 2} binding.
13805 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
13806 (@pxref{TUI Single Key Mode}).
13810 The following key bindings are handled only by the TUI mode:
13815 Scroll the active window one page up.
13819 Scroll the active window one page down.
13823 Scroll the active window one line up.
13827 Scroll the active window one line down.
13831 Scroll the active window one column left.
13835 Scroll the active window one column right.
13839 Refresh the screen.
13843 In the TUI mode, the arrow keys are used by the active window
13844 for scrolling. This means they are not available for readline. It is
13845 necessary to use other readline key bindings such as @key{C-p}, @key{C-n},
13846 @key{C-b} and @key{C-f}.
13848 @node TUI Single Key Mode
13849 @section TUI Single Key Mode
13850 @cindex TUI single key mode
13852 The TUI provides a @emph{SingleKey} mode in which it installs a particular
13853 key binding in the readline keymaps to connect single keys to
13857 @kindex c @r{(SingleKey TUI key)}
13861 @kindex d @r{(SingleKey TUI key)}
13865 @kindex f @r{(SingleKey TUI key)}
13869 @kindex n @r{(SingleKey TUI key)}
13873 @kindex q @r{(SingleKey TUI key)}
13875 exit the @emph{SingleKey} mode.
13877 @kindex r @r{(SingleKey TUI key)}
13881 @kindex s @r{(SingleKey TUI key)}
13885 @kindex u @r{(SingleKey TUI key)}
13889 @kindex v @r{(SingleKey TUI key)}
13893 @kindex w @r{(SingleKey TUI key)}
13899 Other keys temporarily switch to the @value{GDBN} command prompt.
13900 The key that was pressed is inserted in the editing buffer so that
13901 it is possible to type most @value{GDBN} commands without interaction
13902 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
13903 @emph{SingleKey} mode is restored. The only way to permanently leave
13904 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
13908 @section TUI specific commands
13909 @cindex TUI commands
13911 The TUI has specific commands to control the text windows.
13912 These commands are always available, that is they do not depend on
13913 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
13914 is in the standard mode, using these commands will automatically switch
13920 List and give the size of all displayed windows.
13923 @kindex layout next
13924 Display the next layout.
13927 @kindex layout prev
13928 Display the previous layout.
13932 Display the source window only.
13936 Display the assembly window only.
13939 @kindex layout split
13940 Display the source and assembly window.
13943 @kindex layout regs
13944 Display the register window together with the source or assembly window.
13946 @item focus next | prev | src | asm | regs | split
13948 Set the focus to the named window.
13949 This command allows to change the active window so that scrolling keys
13950 can be affected to another window.
13954 Refresh the screen. This is similar to using @key{C-L} key.
13958 Update the source window and the current execution point.
13960 @item winheight @var{name} +@var{count}
13961 @itemx winheight @var{name} -@var{count}
13963 Change the height of the window @var{name} by @var{count}
13964 lines. Positive counts increase the height, while negative counts
13969 @node TUI Configuration
13970 @section TUI configuration variables
13971 @cindex TUI configuration variables
13973 The TUI has several configuration variables that control the
13974 appearance of windows on the terminal.
13977 @item set tui border-kind @var{kind}
13978 @kindex set tui border-kind
13979 Select the border appearance for the source, assembly and register windows.
13980 The possible values are the following:
13983 Use a space character to draw the border.
13986 Use ascii characters + - and | to draw the border.
13989 Use the Alternate Character Set to draw the border. The border is
13990 drawn using character line graphics if the terminal supports them.
13994 @item set tui active-border-mode @var{mode}
13995 @kindex set tui active-border-mode
13996 Select the attributes to display the border of the active window.
13997 The possible values are @code{normal}, @code{standout}, @code{reverse},
13998 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
14000 @item set tui border-mode @var{mode}
14001 @kindex set tui border-mode
14002 Select the attributes to display the border of other windows.
14003 The @var{mode} can be one of the following:
14006 Use normal attributes to display the border.
14012 Use reverse video mode.
14015 Use half bright mode.
14017 @item half-standout
14018 Use half bright and standout mode.
14021 Use extra bright or bold mode.
14023 @item bold-standout
14024 Use extra bright or bold and standout mode.
14031 @chapter Using @value{GDBN} under @sc{gnu} Emacs
14034 @cindex @sc{gnu} Emacs
14035 A special interface allows you to use @sc{gnu} Emacs to view (and
14036 edit) the source files for the program you are debugging with
14039 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
14040 executable file you want to debug as an argument. This command starts
14041 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
14042 created Emacs buffer.
14043 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
14045 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
14050 All ``terminal'' input and output goes through the Emacs buffer.
14053 This applies both to @value{GDBN} commands and their output, and to the input
14054 and output done by the program you are debugging.
14056 This is useful because it means that you can copy the text of previous
14057 commands and input them again; you can even use parts of the output
14060 All the facilities of Emacs' Shell mode are available for interacting
14061 with your program. In particular, you can send signals the usual
14062 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
14067 @value{GDBN} displays source code through Emacs.
14070 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
14071 source file for that frame and puts an arrow (@samp{=>}) at the
14072 left margin of the current line. Emacs uses a separate buffer for
14073 source display, and splits the screen to show both your @value{GDBN} session
14076 Explicit @value{GDBN} @code{list} or search commands still produce output as
14077 usual, but you probably have no reason to use them from Emacs.
14080 @emph{Warning:} If the directory where your program resides is not your
14081 current directory, it can be easy to confuse Emacs about the location of
14082 the source files, in which case the auxiliary display buffer does not
14083 appear to show your source. @value{GDBN} can find programs by searching your
14084 environment's @code{PATH} variable, so the @value{GDBN} input and output
14085 session proceeds normally; but Emacs does not get enough information
14086 back from @value{GDBN} to locate the source files in this situation. To
14087 avoid this problem, either start @value{GDBN} mode from the directory where
14088 your program resides, or specify an absolute file name when prompted for the
14089 @kbd{M-x gdb} argument.
14091 A similar confusion can result if you use the @value{GDBN} @code{file} command to
14092 switch to debugging a program in some other location, from an existing
14093 @value{GDBN} buffer in Emacs.
14096 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
14097 you need to call @value{GDBN} by a different name (for example, if you keep
14098 several configurations around, with different names) you can set the
14099 Emacs variable @code{gdb-command-name}; for example,
14102 (setq gdb-command-name "mygdb")
14106 (preceded by @kbd{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or
14107 in your @file{.emacs} file) makes Emacs call the program named
14108 ``@code{mygdb}'' instead.
14110 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14111 addition to the standard Shell mode commands:
14115 Describe the features of Emacs' @value{GDBN} Mode.
14118 Execute to another source line, like the @value{GDBN} @code{step} command; also
14119 update the display window to show the current file and location.
14122 Execute to next source line in this function, skipping all function
14123 calls, like the @value{GDBN} @code{next} command. Then update the display window
14124 to show the current file and location.
14127 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14128 display window accordingly.
14130 @item M-x gdb-nexti
14131 Execute to next instruction, using the @value{GDBN} @code{nexti} command; update
14132 display window accordingly.
14135 Execute until exit from the selected stack frame, like the @value{GDBN}
14136 @code{finish} command.
14139 Continue execution of your program, like the @value{GDBN} @code{continue}
14142 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
14145 Go up the number of frames indicated by the numeric argument
14146 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14147 like the @value{GDBN} @code{up} command.
14149 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
14152 Go down the number of frames indicated by the numeric argument, like the
14153 @value{GDBN} @code{down} command.
14155 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
14158 Read the number where the cursor is positioned, and insert it at the end
14159 of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code
14160 around an address that was displayed earlier, type @kbd{disassemble};
14161 then move the cursor to the address display, and pick up the
14162 argument for @code{disassemble} by typing @kbd{C-x &}.
14164 You can customize this further by defining elements of the list
14165 @code{gdb-print-command}; once it is defined, you can format or
14166 otherwise process numbers picked up by @kbd{C-x &} before they are
14167 inserted. A numeric argument to @kbd{C-x &} indicates that you
14168 wish special formatting, and also acts as an index to pick an element of the
14169 list. If the list element is a string, the number to be inserted is
14170 formatted using the Emacs function @code{format}; otherwise the number
14171 is passed as an argument to the corresponding list element.
14174 In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
14175 tells @value{GDBN} to set a breakpoint on the source line point is on.
14177 If you accidentally delete the source-display buffer, an easy way to get
14178 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14179 request a frame display; when you run under Emacs, this recreates
14180 the source buffer if necessary to show you the context of the current
14183 The source files displayed in Emacs are in ordinary Emacs buffers
14184 which are visiting the source files in the usual way. You can edit
14185 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14186 communicates with Emacs in terms of line numbers. If you add or
14187 delete lines from the text, the line numbers that @value{GDBN} knows cease
14188 to correspond properly with the code.
14190 @c The following dropped because Epoch is nonstandard. Reactivate
14191 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14193 @kindex Emacs Epoch environment
14197 Version 18 of @sc{gnu} Emacs has a built-in window system
14198 called the @code{epoch}
14199 environment. Users of this environment can use a new command,
14200 @code{inspect} which performs identically to @code{print} except that
14201 each value is printed in its own window.
14206 @chapter The @sc{gdb/mi} Interface
14208 @unnumberedsec Function and Purpose
14210 @cindex @sc{gdb/mi}, its purpose
14211 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14212 specifically intended to support the development of systems which use
14213 the debugger as just one small component of a larger system.
14215 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14216 in the form of a reference manual.
14218 Note that @sc{gdb/mi} is still under construction, so some of the
14219 features described below are incomplete and subject to change.
14221 @unnumberedsec Notation and Terminology
14223 @cindex notational conventions, for @sc{gdb/mi}
14224 This chapter uses the following notation:
14228 @code{|} separates two alternatives.
14231 @code{[ @var{something} ]} indicates that @var{something} is optional:
14232 it may or may not be given.
14235 @code{( @var{group} )*} means that @var{group} inside the parentheses
14236 may repeat zero or more times.
14239 @code{( @var{group} )+} means that @var{group} inside the parentheses
14240 may repeat one or more times.
14243 @code{"@var{string}"} means a literal @var{string}.
14247 @heading Dependencies
14250 @heading Acknowledgments
14252 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14256 * GDB/MI Command Syntax::
14257 * GDB/MI Compatibility with CLI::
14258 * GDB/MI Output Records::
14259 * GDB/MI Command Description Format::
14260 * GDB/MI Breakpoint Table Commands::
14261 * GDB/MI Data Manipulation::
14262 * GDB/MI Program Control::
14263 * GDB/MI Miscellaneous Commands::
14265 * GDB/MI Kod Commands::
14266 * GDB/MI Memory Overlay Commands::
14267 * GDB/MI Signal Handling Commands::
14269 * GDB/MI Stack Manipulation::
14270 * GDB/MI Symbol Query::
14271 * GDB/MI Target Manipulation::
14272 * GDB/MI Thread Commands::
14273 * GDB/MI Tracepoint Commands::
14274 * GDB/MI Variable Objects::
14277 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14278 @node GDB/MI Command Syntax
14279 @section @sc{gdb/mi} Command Syntax
14282 * GDB/MI Input Syntax::
14283 * GDB/MI Output Syntax::
14284 * GDB/MI Simple Examples::
14287 @node GDB/MI Input Syntax
14288 @subsection @sc{gdb/mi} Input Syntax
14290 @cindex input syntax for @sc{gdb/mi}
14291 @cindex @sc{gdb/mi}, input syntax
14293 @item @var{command} @expansion{}
14294 @code{@var{cli-command} | @var{mi-command}}
14296 @item @var{cli-command} @expansion{}
14297 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14298 @var{cli-command} is any existing @value{GDBN} CLI command.
14300 @item @var{mi-command} @expansion{}
14301 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14302 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14304 @item @var{token} @expansion{}
14305 "any sequence of digits"
14307 @item @var{option} @expansion{}
14308 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14310 @item @var{parameter} @expansion{}
14311 @code{@var{non-blank-sequence} | @var{c-string}}
14313 @item @var{operation} @expansion{}
14314 @emph{any of the operations described in this chapter}
14316 @item @var{non-blank-sequence} @expansion{}
14317 @emph{anything, provided it doesn't contain special characters such as
14318 "-", @var{nl}, """ and of course " "}
14320 @item @var{c-string} @expansion{}
14321 @code{""" @var{seven-bit-iso-c-string-content} """}
14323 @item @var{nl} @expansion{}
14332 The CLI commands are still handled by the @sc{mi} interpreter; their
14333 output is described below.
14336 The @code{@var{token}}, when present, is passed back when the command
14340 Some @sc{mi} commands accept optional arguments as part of the parameter
14341 list. Each option is identified by a leading @samp{-} (dash) and may be
14342 followed by an optional argument parameter. Options occur first in the
14343 parameter list and can be delimited from normal parameters using
14344 @samp{--} (this is useful when some parameters begin with a dash).
14351 We want easy access to the existing CLI syntax (for debugging).
14354 We want it to be easy to spot a @sc{mi} operation.
14357 @node GDB/MI Output Syntax
14358 @subsection @sc{gdb/mi} Output Syntax
14360 @cindex output syntax of @sc{gdb/mi}
14361 @cindex @sc{gdb/mi}, output syntax
14362 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14363 followed, optionally, by a single result record. This result record
14364 is for the most recent command. The sequence of output records is
14365 terminated by @samp{(@value{GDBP})}.
14367 If an input command was prefixed with a @code{@var{token}} then the
14368 corresponding output for that command will also be prefixed by that same
14372 @item @var{output} @expansion{}
14373 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14375 @item @var{result-record} @expansion{}
14376 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14378 @item @var{out-of-band-record} @expansion{}
14379 @code{@var{async-record} | @var{stream-record}}
14381 @item @var{async-record} @expansion{}
14382 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14384 @item @var{exec-async-output} @expansion{}
14385 @code{[ @var{token} ] "*" @var{async-output}}
14387 @item @var{status-async-output} @expansion{}
14388 @code{[ @var{token} ] "+" @var{async-output}}
14390 @item @var{notify-async-output} @expansion{}
14391 @code{[ @var{token} ] "=" @var{async-output}}
14393 @item @var{async-output} @expansion{}
14394 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14396 @item @var{result-class} @expansion{}
14397 @code{"done" | "running" | "connected" | "error" | "exit"}
14399 @item @var{async-class} @expansion{}
14400 @code{"stopped" | @var{others}} (where @var{others} will be added
14401 depending on the needs---this is still in development).
14403 @item @var{result} @expansion{}
14404 @code{ @var{variable} "=" @var{value}}
14406 @item @var{variable} @expansion{}
14407 @code{ @var{string} }
14409 @item @var{value} @expansion{}
14410 @code{ @var{const} | @var{tuple} | @var{list} }
14412 @item @var{const} @expansion{}
14413 @code{@var{c-string}}
14415 @item @var{tuple} @expansion{}
14416 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14418 @item @var{list} @expansion{}
14419 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14420 @var{result} ( "," @var{result} )* "]" }
14422 @item @var{stream-record} @expansion{}
14423 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14425 @item @var{console-stream-output} @expansion{}
14426 @code{"~" @var{c-string}}
14428 @item @var{target-stream-output} @expansion{}
14429 @code{"@@" @var{c-string}}
14431 @item @var{log-stream-output} @expansion{}
14432 @code{"&" @var{c-string}}
14434 @item @var{nl} @expansion{}
14437 @item @var{token} @expansion{}
14438 @emph{any sequence of digits}.
14446 All output sequences end in a single line containing a period.
14449 The @code{@var{token}} is from the corresponding request. If an execution
14450 command is interrupted by the @samp{-exec-interrupt} command, the
14451 @var{token} associated with the @samp{*stopped} message is the one of the
14452 original execution command, not the one of the interrupt command.
14455 @cindex status output in @sc{gdb/mi}
14456 @var{status-async-output} contains on-going status information about the
14457 progress of a slow operation. It can be discarded. All status output is
14458 prefixed by @samp{+}.
14461 @cindex async output in @sc{gdb/mi}
14462 @var{exec-async-output} contains asynchronous state change on the target
14463 (stopped, started, disappeared). All async output is prefixed by
14467 @cindex notify output in @sc{gdb/mi}
14468 @var{notify-async-output} contains supplementary information that the
14469 client should handle (e.g., a new breakpoint information). All notify
14470 output is prefixed by @samp{=}.
14473 @cindex console output in @sc{gdb/mi}
14474 @var{console-stream-output} is output that should be displayed as is in the
14475 console. It is the textual response to a CLI command. All the console
14476 output is prefixed by @samp{~}.
14479 @cindex target output in @sc{gdb/mi}
14480 @var{target-stream-output} is the output produced by the target program.
14481 All the target output is prefixed by @samp{@@}.
14484 @cindex log output in @sc{gdb/mi}
14485 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14486 instance messages that should be displayed as part of an error log. All
14487 the log output is prefixed by @samp{&}.
14490 @cindex list output in @sc{gdb/mi}
14491 New @sc{gdb/mi} commands should only output @var{lists} containing
14497 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14498 details about the various output records.
14500 @node GDB/MI Simple Examples
14501 @subsection Simple Examples of @sc{gdb/mi} Interaction
14502 @cindex @sc{gdb/mi}, simple examples
14504 This subsection presents several simple examples of interaction using
14505 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14506 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14507 the output received from @sc{gdb/mi}.
14509 @subsubheading Target Stop
14510 @c Ummm... There is no "-stop" command. This assumes async, no?
14511 Here's an example of stopping the inferior process:
14522 <- *stop,reason="stop",address="0x123",source="a.c:123"
14526 @subsubheading Simple CLI Command
14528 Here's an example of a simple CLI command being passed through
14529 @sc{gdb/mi} and on to the CLI.
14539 @subsubheading Command With Side Effects
14542 -> -symbol-file xyz.exe
14543 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14547 @subsubheading A Bad Command
14549 Here's what happens if you pass a non-existent command:
14553 <- ^error,msg="Undefined MI command: rubbish"
14557 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14558 @node GDB/MI Compatibility with CLI
14559 @section @sc{gdb/mi} Compatibility with CLI
14561 @cindex compatibility, @sc{gdb/mi} and CLI
14562 @cindex @sc{gdb/mi}, compatibility with CLI
14563 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14564 accepts existing CLI commands. As specified by the syntax, such
14565 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14568 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14569 clients and not as a reliable interface into the CLI. Since the command
14570 is being interpreteted in an environment that assumes @sc{gdb/mi}
14571 behaviour, the exact output of such commands is likely to end up being
14572 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14574 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14575 @node GDB/MI Output Records
14576 @section @sc{gdb/mi} Output Records
14579 * GDB/MI Result Records::
14580 * GDB/MI Stream Records::
14581 * GDB/MI Out-of-band Records::
14584 @node GDB/MI Result Records
14585 @subsection @sc{gdb/mi} Result Records
14587 @cindex result records in @sc{gdb/mi}
14588 @cindex @sc{gdb/mi}, result records
14589 In addition to a number of out-of-band notifications, the response to a
14590 @sc{gdb/mi} command includes one of the following result indications:
14594 @item "^done" [ "," @var{results} ]
14595 The synchronous operation was successful, @code{@var{results}} are the return
14600 @c Is this one correct? Should it be an out-of-band notification?
14601 The asynchronous operation was successfully started. The target is
14604 @item "^error" "," @var{c-string}
14606 The operation failed. The @code{@var{c-string}} contains the corresponding
14610 @node GDB/MI Stream Records
14611 @subsection @sc{gdb/mi} Stream Records
14613 @cindex @sc{gdb/mi}, stream records
14614 @cindex stream records in @sc{gdb/mi}
14615 @value{GDBN} internally maintains a number of output streams: the console, the
14616 target, and the log. The output intended for each of these streams is
14617 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14619 Each stream record begins with a unique @dfn{prefix character} which
14620 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14621 Syntax}). In addition to the prefix, each stream record contains a
14622 @code{@var{string-output}}. This is either raw text (with an implicit new
14623 line) or a quoted C string (which does not contain an implicit newline).
14626 @item "~" @var{string-output}
14627 The console output stream contains text that should be displayed in the
14628 CLI console window. It contains the textual responses to CLI commands.
14630 @item "@@" @var{string-output}
14631 The target output stream contains any textual output from the running
14634 @item "&" @var{string-output}
14635 The log stream contains debugging messages being produced by @value{GDBN}'s
14639 @node GDB/MI Out-of-band Records
14640 @subsection @sc{gdb/mi} Out-of-band Records
14642 @cindex out-of-band records in @sc{gdb/mi}
14643 @cindex @sc{gdb/mi}, out-of-band records
14644 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14645 additional changes that have occurred. Those changes can either be a
14646 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14647 target activity (e.g., target stopped).
14649 The following is a preliminary list of possible out-of-band records.
14656 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14657 @node GDB/MI Command Description Format
14658 @section @sc{gdb/mi} Command Description Format
14660 The remaining sections describe blocks of commands. Each block of
14661 commands is laid out in a fashion similar to this section.
14663 Note the the line breaks shown in the examples are here only for
14664 readability. They don't appear in the real output.
14665 Also note that the commands with a non-available example (N.A.@:) are
14666 not yet implemented.
14668 @subheading Motivation
14670 The motivation for this collection of commands.
14672 @subheading Introduction
14674 A brief introduction to this collection of commands as a whole.
14676 @subheading Commands
14678 For each command in the block, the following is described:
14680 @subsubheading Synopsis
14683 -command @var{args}@dots{}
14686 @subsubheading @value{GDBN} Command
14688 The corresponding @value{GDBN} CLI command.
14690 @subsubheading Result
14692 @subsubheading Out-of-band
14694 @subsubheading Notes
14696 @subsubheading Example
14699 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14700 @node GDB/MI Breakpoint Table Commands
14701 @section @sc{gdb/mi} Breakpoint table commands
14703 @cindex breakpoint commands for @sc{gdb/mi}
14704 @cindex @sc{gdb/mi}, breakpoint commands
14705 This section documents @sc{gdb/mi} commands for manipulating
14708 @subheading The @code{-break-after} Command
14709 @findex -break-after
14711 @subsubheading Synopsis
14714 -break-after @var{number} @var{count}
14717 The breakpoint number @var{number} is not in effect until it has been
14718 hit @var{count} times. To see how this is reflected in the output of
14719 the @samp{-break-list} command, see the description of the
14720 @samp{-break-list} command below.
14722 @subsubheading @value{GDBN} Command
14724 The corresponding @value{GDBN} command is @samp{ignore}.
14726 @subsubheading Example
14731 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
14738 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14739 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14740 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14741 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14742 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14743 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14744 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14745 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14746 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
14752 @subheading The @code{-break-catch} Command
14753 @findex -break-catch
14755 @subheading The @code{-break-commands} Command
14756 @findex -break-commands
14760 @subheading The @code{-break-condition} Command
14761 @findex -break-condition
14763 @subsubheading Synopsis
14766 -break-condition @var{number} @var{expr}
14769 Breakpoint @var{number} will stop the program only if the condition in
14770 @var{expr} is true. The condition becomes part of the
14771 @samp{-break-list} output (see the description of the @samp{-break-list}
14774 @subsubheading @value{GDBN} Command
14776 The corresponding @value{GDBN} command is @samp{condition}.
14778 @subsubheading Example
14782 -break-condition 1 1
14786 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14787 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14788 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14789 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14790 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14791 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14792 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14793 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14794 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
14795 times="0",ignore="3"@}]@}
14799 @subheading The @code{-break-delete} Command
14800 @findex -break-delete
14802 @subsubheading Synopsis
14805 -break-delete ( @var{breakpoint} )+
14808 Delete the breakpoint(s) whose number(s) are specified in the argument
14809 list. This is obviously reflected in the breakpoint list.
14811 @subsubheading @value{GDBN} command
14813 The corresponding @value{GDBN} command is @samp{delete}.
14815 @subsubheading Example
14823 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
14824 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14825 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14826 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14827 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14828 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14829 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14834 @subheading The @code{-break-disable} Command
14835 @findex -break-disable
14837 @subsubheading Synopsis
14840 -break-disable ( @var{breakpoint} )+
14843 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
14844 break list is now set to @samp{n} for the named @var{breakpoint}(s).
14846 @subsubheading @value{GDBN} Command
14848 The corresponding @value{GDBN} command is @samp{disable}.
14850 @subsubheading Example
14858 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14859 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14860 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14861 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14862 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14863 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14864 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14865 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
14866 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14870 @subheading The @code{-break-enable} Command
14871 @findex -break-enable
14873 @subsubheading Synopsis
14876 -break-enable ( @var{breakpoint} )+
14879 Enable (previously disabled) @var{breakpoint}(s).
14881 @subsubheading @value{GDBN} Command
14883 The corresponding @value{GDBN} command is @samp{enable}.
14885 @subsubheading Example
14893 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14894 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14895 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14896 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14897 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14898 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14899 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14900 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
14901 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14905 @subheading The @code{-break-info} Command
14906 @findex -break-info
14908 @subsubheading Synopsis
14911 -break-info @var{breakpoint}
14915 Get information about a single breakpoint.
14917 @subsubheading @value{GDBN} command
14919 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
14921 @subsubheading Example
14924 @subheading The @code{-break-insert} Command
14925 @findex -break-insert
14927 @subsubheading Synopsis
14930 -break-insert [ -t ] [ -h ] [ -r ]
14931 [ -c @var{condition} ] [ -i @var{ignore-count} ]
14932 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
14936 If specified, @var{line}, can be one of:
14943 @item filename:linenum
14944 @item filename:function
14948 The possible optional parameters of this command are:
14952 Insert a tempoary breakpoint.
14954 Insert a hardware breakpoint.
14955 @item -c @var{condition}
14956 Make the breakpoint conditional on @var{condition}.
14957 @item -i @var{ignore-count}
14958 Initialize the @var{ignore-count}.
14960 Insert a regular breakpoint in all the functions whose names match the
14961 given regular expression. Other flags are not applicable to regular
14965 @subsubheading Result
14967 The result is in the form:
14970 ^done,bkptno="@var{number}",func="@var{funcname}",
14971 file="@var{filename}",line="@var{lineno}"
14975 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
14976 is the name of the function where the breakpoint was inserted,
14977 @var{filename} is the name of the source file which contains this
14978 function, and @var{lineno} is the source line number within that file.
14980 Note: this format is open to change.
14981 @c An out-of-band breakpoint instead of part of the result?
14983 @subsubheading @value{GDBN} Command
14985 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
14986 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
14988 @subsubheading Example
14993 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
14995 -break-insert -t foo
14996 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
14999 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15000 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15001 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15002 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15003 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15004 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15005 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15006 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15007 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
15008 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
15009 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
15011 -break-insert -r foo.*
15012 ~int foo(int, int);
15013 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
15017 @subheading The @code{-break-list} Command
15018 @findex -break-list
15020 @subsubheading Synopsis
15026 Displays the list of inserted breakpoints, showing the following fields:
15030 number of the breakpoint
15032 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
15034 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
15037 is the breakpoint enabled or no: @samp{y} or @samp{n}
15039 memory location at which the breakpoint is set
15041 logical location of the breakpoint, expressed by function name, file
15044 number of times the breakpoint has been hit
15047 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
15048 @code{body} field is an empty list.
15050 @subsubheading @value{GDBN} Command
15052 The corresponding @value{GDBN} command is @samp{info break}.
15054 @subsubheading Example
15059 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15060 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15061 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15062 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15063 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15064 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15065 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15066 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15067 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
15068 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
15069 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
15073 Here's an example of the result when there are no breakpoints:
15078 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
15079 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15080 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15081 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15082 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15083 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15084 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15089 @subheading The @code{-break-watch} Command
15090 @findex -break-watch
15092 @subsubheading Synopsis
15095 -break-watch [ -a | -r ]
15098 Create a watchpoint. With the @samp{-a} option it will create an
15099 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
15100 read from or on a write to the memory location. With the @samp{-r}
15101 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
15102 trigger only when the memory location is accessed for reading. Without
15103 either of the options, the watchpoint created is a regular watchpoint,
15104 i.e. it will trigger when the memory location is accessed for writing.
15105 @xref{Set Watchpoints, , Setting watchpoints}.
15107 Note that @samp{-break-list} will report a single list of watchpoints and
15108 breakpoints inserted.
15110 @subsubheading @value{GDBN} Command
15112 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15115 @subsubheading Example
15117 Setting a watchpoint on a variable in the @code{main} function:
15122 ^done,wpt=@{number="2",exp="x"@}
15126 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15127 value=@{old="-268439212",new="55"@},
15128 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15132 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15133 the program execution twice: first for the variable changing value, then
15134 for the watchpoint going out of scope.
15139 ^done,wpt=@{number="5",exp="C"@}
15143 ^done,reason="watchpoint-trigger",
15144 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15145 frame=@{func="callee4",args=[],
15146 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15150 ^done,reason="watchpoint-scope",wpnum="5",
15151 frame=@{func="callee3",args=[@{name="strarg",
15152 value="0x11940 \"A string argument.\""@}],
15153 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15157 Listing breakpoints and watchpoints, at different points in the program
15158 execution. Note that once the watchpoint goes out of scope, it is
15164 ^done,wpt=@{number="2",exp="C"@}
15167 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15168 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15169 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15170 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15171 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15172 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15173 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15174 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15175 addr="0x00010734",func="callee4",
15176 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15177 bkpt=@{number="2",type="watchpoint",disp="keep",
15178 enabled="y",addr="",what="C",times="0"@}]@}
15182 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15183 value=@{old="-276895068",new="3"@},
15184 frame=@{func="callee4",args=[],
15185 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15188 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15189 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15190 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15191 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15192 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15193 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15194 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15195 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15196 addr="0x00010734",func="callee4",
15197 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15198 bkpt=@{number="2",type="watchpoint",disp="keep",
15199 enabled="y",addr="",what="C",times="-5"@}]@}
15203 ^done,reason="watchpoint-scope",wpnum="2",
15204 frame=@{func="callee3",args=[@{name="strarg",
15205 value="0x11940 \"A string argument.\""@}],
15206 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15209 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15210 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15211 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15212 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15213 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15214 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15215 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15216 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15217 addr="0x00010734",func="callee4",
15218 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15222 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15223 @node GDB/MI Data Manipulation
15224 @section @sc{gdb/mi} Data Manipulation
15226 @cindex data manipulation, in @sc{gdb/mi}
15227 @cindex @sc{gdb/mi}, data manipulation
15228 This section describes the @sc{gdb/mi} commands that manipulate data:
15229 examine memory and registers, evaluate expressions, etc.
15231 @c REMOVED FROM THE INTERFACE.
15232 @c @subheading -data-assign
15233 @c Change the value of a program variable. Plenty of side effects.
15234 @c @subsubheading GDB command
15236 @c @subsubheading Example
15239 @subheading The @code{-data-disassemble} Command
15240 @findex -data-disassemble
15242 @subsubheading Synopsis
15246 [ -s @var{start-addr} -e @var{end-addr} ]
15247 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15255 @item @var{start-addr}
15256 is the beginning address (or @code{$pc})
15257 @item @var{end-addr}
15259 @item @var{filename}
15260 is the name of the file to disassemble
15261 @item @var{linenum}
15262 is the line number to disassemble around
15264 is the the number of disassembly lines to be produced. If it is -1,
15265 the whole function will be disassembled, in case no @var{end-addr} is
15266 specified. If @var{end-addr} is specified as a non-zero value, and
15267 @var{lines} is lower than the number of disassembly lines between
15268 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15269 displayed; if @var{lines} is higher than the number of lines between
15270 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15273 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15277 @subsubheading Result
15279 The output for each instruction is composed of four fields:
15288 Note that whatever included in the instruction field, is not manipulated
15289 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15291 @subsubheading @value{GDBN} Command
15293 There's no direct mapping from this command to the CLI.
15295 @subsubheading Example
15297 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15301 -data-disassemble -s $pc -e "$pc + 20" -- 0
15304 @{address="0x000107c0",func-name="main",offset="4",
15305 inst="mov 2, %o0"@},
15306 @{address="0x000107c4",func-name="main",offset="8",
15307 inst="sethi %hi(0x11800), %o2"@},
15308 @{address="0x000107c8",func-name="main",offset="12",
15309 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15310 @{address="0x000107cc",func-name="main",offset="16",
15311 inst="sethi %hi(0x11800), %o2"@},
15312 @{address="0x000107d0",func-name="main",offset="20",
15313 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15317 Disassemble the whole @code{main} function. Line 32 is part of
15321 -data-disassemble -f basics.c -l 32 -- 0
15323 @{address="0x000107bc",func-name="main",offset="0",
15324 inst="save %sp, -112, %sp"@},
15325 @{address="0x000107c0",func-name="main",offset="4",
15326 inst="mov 2, %o0"@},
15327 @{address="0x000107c4",func-name="main",offset="8",
15328 inst="sethi %hi(0x11800), %o2"@},
15330 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15331 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15335 Disassemble 3 instructions from the start of @code{main}:
15339 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15341 @{address="0x000107bc",func-name="main",offset="0",
15342 inst="save %sp, -112, %sp"@},
15343 @{address="0x000107c0",func-name="main",offset="4",
15344 inst="mov 2, %o0"@},
15345 @{address="0x000107c4",func-name="main",offset="8",
15346 inst="sethi %hi(0x11800), %o2"@}]
15350 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15354 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15356 src_and_asm_line=@{line="31",
15357 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15358 testsuite/gdb.mi/basics.c",line_asm_insn=[
15359 @{address="0x000107bc",func-name="main",offset="0",
15360 inst="save %sp, -112, %sp"@}]@},
15361 src_and_asm_line=@{line="32",
15362 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15363 testsuite/gdb.mi/basics.c",line_asm_insn=[
15364 @{address="0x000107c0",func-name="main",offset="4",
15365 inst="mov 2, %o0"@},
15366 @{address="0x000107c4",func-name="main",offset="8",
15367 inst="sethi %hi(0x11800), %o2"@}]@}]
15372 @subheading The @code{-data-evaluate-expression} Command
15373 @findex -data-evaluate-expression
15375 @subsubheading Synopsis
15378 -data-evaluate-expression @var{expr}
15381 Evaluate @var{expr} as an expression. The expression could contain an
15382 inferior function call. The function call will execute synchronously.
15383 If the expression contains spaces, it must be enclosed in double quotes.
15385 @subsubheading @value{GDBN} Command
15387 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15388 @samp{call}. In @code{gdbtk} only, there's a corresponding
15389 @samp{gdb_eval} command.
15391 @subsubheading Example
15393 In the following example, the numbers that precede the commands are the
15394 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15395 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15399 211-data-evaluate-expression A
15402 311-data-evaluate-expression &A
15403 311^done,value="0xefffeb7c"
15405 411-data-evaluate-expression A+3
15408 511-data-evaluate-expression "A + 3"
15414 @subheading The @code{-data-list-changed-registers} Command
15415 @findex -data-list-changed-registers
15417 @subsubheading Synopsis
15420 -data-list-changed-registers
15423 Display a list of the registers that have changed.
15425 @subsubheading @value{GDBN} Command
15427 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15428 has the corresponding command @samp{gdb_changed_register_list}.
15430 @subsubheading Example
15432 On a PPC MBX board:
15440 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15441 args=[],file="try.c",line="5"@}
15443 -data-list-changed-registers
15444 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15445 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15446 "24","25","26","27","28","30","31","64","65","66","67","69"]
15451 @subheading The @code{-data-list-register-names} Command
15452 @findex -data-list-register-names
15454 @subsubheading Synopsis
15457 -data-list-register-names [ ( @var{regno} )+ ]
15460 Show a list of register names for the current target. If no arguments
15461 are given, it shows a list of the names of all the registers. If
15462 integer numbers are given as arguments, it will print a list of the
15463 names of the registers corresponding to the arguments. To ensure
15464 consistency between a register name and its number, the output list may
15465 include empty register names.
15467 @subsubheading @value{GDBN} Command
15469 @value{GDBN} does not have a command which corresponds to
15470 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15471 corresponding command @samp{gdb_regnames}.
15473 @subsubheading Example
15475 For the PPC MBX board:
15478 -data-list-register-names
15479 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15480 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15481 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15482 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15483 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15484 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15485 "", "pc","ps","cr","lr","ctr","xer"]
15487 -data-list-register-names 1 2 3
15488 ^done,register-names=["r1","r2","r3"]
15492 @subheading The @code{-data-list-register-values} Command
15493 @findex -data-list-register-values
15495 @subsubheading Synopsis
15498 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15501 Display the registers' contents. @var{fmt} is the format according to
15502 which the registers' contents are to be returned, followed by an optional
15503 list of numbers specifying the registers to display. A missing list of
15504 numbers indicates that the contents of all the registers must be returned.
15506 Allowed formats for @var{fmt} are:
15523 @subsubheading @value{GDBN} Command
15525 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15526 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15528 @subsubheading Example
15530 For a PPC MBX board (note: line breaks are for readability only, they
15531 don't appear in the actual output):
15535 -data-list-register-values r 64 65
15536 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15537 @{number="65",value="0x00029002"@}]
15539 -data-list-register-values x
15540 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15541 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15542 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15543 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15544 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15545 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15546 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15547 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15548 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15549 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15550 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15551 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15552 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15553 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15554 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15555 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15556 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15557 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15558 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15559 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15560 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15561 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15562 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15563 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15564 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15565 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15566 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15567 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15568 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15569 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15570 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15571 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15572 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15573 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15574 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15575 @{number="69",value="0x20002b03"@}]
15580 @subheading The @code{-data-read-memory} Command
15581 @findex -data-read-memory
15583 @subsubheading Synopsis
15586 -data-read-memory [ -o @var{byte-offset} ]
15587 @var{address} @var{word-format} @var{word-size}
15588 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15595 @item @var{address}
15596 An expression specifying the address of the first memory word to be
15597 read. Complex expressions containing embedded white space should be
15598 quoted using the C convention.
15600 @item @var{word-format}
15601 The format to be used to print the memory words. The notation is the
15602 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15605 @item @var{word-size}
15606 The size of each memory word in bytes.
15608 @item @var{nr-rows}
15609 The number of rows in the output table.
15611 @item @var{nr-cols}
15612 The number of columns in the output table.
15615 If present, indicates that each row should include an @sc{ascii} dump. The
15616 value of @var{aschar} is used as a padding character when a byte is not a
15617 member of the printable @sc{ascii} character set (printable @sc{ascii}
15618 characters are those whose code is between 32 and 126, inclusively).
15620 @item @var{byte-offset}
15621 An offset to add to the @var{address} before fetching memory.
15624 This command displays memory contents as a table of @var{nr-rows} by
15625 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15626 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15627 (returned as @samp{total-bytes}). Should less than the requested number
15628 of bytes be returned by the target, the missing words are identified
15629 using @samp{N/A}. The number of bytes read from the target is returned
15630 in @samp{nr-bytes} and the starting address used to read memory in
15633 The address of the next/previous row or page is available in
15634 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15637 @subsubheading @value{GDBN} Command
15639 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15640 @samp{gdb_get_mem} memory read command.
15642 @subsubheading Example
15644 Read six bytes of memory starting at @code{bytes+6} but then offset by
15645 @code{-6} bytes. Format as three rows of two columns. One byte per
15646 word. Display each word in hex.
15650 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15651 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15652 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15653 prev-page="0x0000138a",memory=[
15654 @{addr="0x00001390",data=["0x00","0x01"]@},
15655 @{addr="0x00001392",data=["0x02","0x03"]@},
15656 @{addr="0x00001394",data=["0x04","0x05"]@}]
15660 Read two bytes of memory starting at address @code{shorts + 64} and
15661 display as a single word formatted in decimal.
15665 5-data-read-memory shorts+64 d 2 1 1
15666 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15667 next-row="0x00001512",prev-row="0x0000150e",
15668 next-page="0x00001512",prev-page="0x0000150e",memory=[
15669 @{addr="0x00001510",data=["128"]@}]
15673 Read thirty two bytes of memory starting at @code{bytes+16} and format
15674 as eight rows of four columns. Include a string encoding with @samp{x}
15675 used as the non-printable character.
15679 4-data-read-memory bytes+16 x 1 8 4 x
15680 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15681 next-row="0x000013c0",prev-row="0x0000139c",
15682 next-page="0x000013c0",prev-page="0x00001380",memory=[
15683 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15684 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15685 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15686 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15687 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15688 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15689 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15690 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15694 @subheading The @code{-display-delete} Command
15695 @findex -display-delete
15697 @subsubheading Synopsis
15700 -display-delete @var{number}
15703 Delete the display @var{number}.
15705 @subsubheading @value{GDBN} Command
15707 The corresponding @value{GDBN} command is @samp{delete display}.
15709 @subsubheading Example
15713 @subheading The @code{-display-disable} Command
15714 @findex -display-disable
15716 @subsubheading Synopsis
15719 -display-disable @var{number}
15722 Disable display @var{number}.
15724 @subsubheading @value{GDBN} Command
15726 The corresponding @value{GDBN} command is @samp{disable display}.
15728 @subsubheading Example
15732 @subheading The @code{-display-enable} Command
15733 @findex -display-enable
15735 @subsubheading Synopsis
15738 -display-enable @var{number}
15741 Enable display @var{number}.
15743 @subsubheading @value{GDBN} Command
15745 The corresponding @value{GDBN} command is @samp{enable display}.
15747 @subsubheading Example
15751 @subheading The @code{-display-insert} Command
15752 @findex -display-insert
15754 @subsubheading Synopsis
15757 -display-insert @var{expression}
15760 Display @var{expression} every time the program stops.
15762 @subsubheading @value{GDBN} Command
15764 The corresponding @value{GDBN} command is @samp{display}.
15766 @subsubheading Example
15770 @subheading The @code{-display-list} Command
15771 @findex -display-list
15773 @subsubheading Synopsis
15779 List the displays. Do not show the current values.
15781 @subsubheading @value{GDBN} Command
15783 The corresponding @value{GDBN} command is @samp{info display}.
15785 @subsubheading Example
15789 @subheading The @code{-environment-cd} Command
15790 @findex -environment-cd
15792 @subsubheading Synopsis
15795 -environment-cd @var{pathdir}
15798 Set @value{GDBN}'s working directory.
15800 @subsubheading @value{GDBN} Command
15802 The corresponding @value{GDBN} command is @samp{cd}.
15804 @subsubheading Example
15808 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15814 @subheading The @code{-environment-directory} Command
15815 @findex -environment-directory
15817 @subsubheading Synopsis
15820 -environment-directory [ -r ] [ @var{pathdir} ]+
15823 Add directories @var{pathdir} to beginning of search path for source files.
15824 If the @samp{-r} option is used, the search path is reset to the default
15825 search path. If directories @var{pathdir} are supplied in addition to the
15826 @samp{-r} option, the search path is first reset and then addition
15828 Multiple directories may be specified, separated by blanks. Specifying
15829 multiple directories in a single command
15830 results in the directories added to the beginning of the
15831 search path in the same order they were presented in the command.
15832 If blanks are needed as
15833 part of a directory name, double-quotes should be used around
15834 the name. In the command output, the path will show up separated
15835 by the system directory-separator character. The directory-seperator
15836 character must not be used
15837 in any directory name.
15838 If no directories are specified, the current search path is displayed.
15840 @subsubheading @value{GDBN} Command
15842 The corresponding @value{GDBN} command is @samp{dir}.
15844 @subsubheading Example
15848 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15849 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15851 -environment-directory ""
15852 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15854 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
15855 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
15857 -environment-directory -r
15858 ^done,source-path="$cdir:$cwd"
15863 @subheading The @code{-environment-path} Command
15864 @findex -environment-path
15866 @subsubheading Synopsis
15869 -environment-path [ -r ] [ @var{pathdir} ]+
15872 Add directories @var{pathdir} to beginning of search path for object files.
15873 If the @samp{-r} option is used, the search path is reset to the original
15874 search path that existed at gdb start-up. If directories @var{pathdir} are
15875 supplied in addition to the
15876 @samp{-r} option, the search path is first reset and then addition
15878 Multiple directories may be specified, separated by blanks. Specifying
15879 multiple directories in a single command
15880 results in the directories added to the beginning of the
15881 search path in the same order they were presented in the command.
15882 If blanks are needed as
15883 part of a directory name, double-quotes should be used around
15884 the name. In the command output, the path will show up separated
15885 by the system directory-separator character. The directory-seperator
15886 character must not be used
15887 in any directory name.
15888 If no directories are specified, the current path is displayed.
15891 @subsubheading @value{GDBN} Command
15893 The corresponding @value{GDBN} command is @samp{path}.
15895 @subsubheading Example
15900 ^done,path="/usr/bin"
15902 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
15903 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
15905 -environment-path -r /usr/local/bin
15906 ^done,path="/usr/local/bin:/usr/bin"
15911 @subheading The @code{-environment-pwd} Command
15912 @findex -environment-pwd
15914 @subsubheading Synopsis
15920 Show the current working directory.
15922 @subsubheading @value{GDBN} command
15924 The corresponding @value{GDBN} command is @samp{pwd}.
15926 @subsubheading Example
15931 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
15935 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15936 @node GDB/MI Program Control
15937 @section @sc{gdb/mi} Program control
15939 @subsubheading Program termination
15941 As a result of execution, the inferior program can run to completion, if
15942 it doesn't encounter any breakpoints. In this case the output will
15943 include an exit code, if the program has exited exceptionally.
15945 @subsubheading Examples
15948 Program exited normally:
15956 *stopped,reason="exited-normally"
15961 Program exited exceptionally:
15969 *stopped,reason="exited",exit-code="01"
15973 Another way the program can terminate is if it receives a signal such as
15974 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
15978 *stopped,reason="exited-signalled",signal-name="SIGINT",
15979 signal-meaning="Interrupt"
15983 @subheading The @code{-exec-abort} Command
15984 @findex -exec-abort
15986 @subsubheading Synopsis
15992 Kill the inferior running program.
15994 @subsubheading @value{GDBN} Command
15996 The corresponding @value{GDBN} command is @samp{kill}.
15998 @subsubheading Example
16002 @subheading The @code{-exec-arguments} Command
16003 @findex -exec-arguments
16005 @subsubheading Synopsis
16008 -exec-arguments @var{args}
16011 Set the inferior program arguments, to be used in the next
16014 @subsubheading @value{GDBN} Command
16016 The corresponding @value{GDBN} command is @samp{set args}.
16018 @subsubheading Example
16021 Don't have one around.
16024 @subheading The @code{-exec-continue} Command
16025 @findex -exec-continue
16027 @subsubheading Synopsis
16033 Asynchronous command. Resumes the execution of the inferior program
16034 until a breakpoint is encountered, or until the inferior exits.
16036 @subsubheading @value{GDBN} Command
16038 The corresponding @value{GDBN} corresponding is @samp{continue}.
16040 @subsubheading Example
16047 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
16048 file="hello.c",line="13"@}
16053 @subheading The @code{-exec-finish} Command
16054 @findex -exec-finish
16056 @subsubheading Synopsis
16062 Asynchronous command. Resumes the execution of the inferior program
16063 until the current function is exited. Displays the results returned by
16066 @subsubheading @value{GDBN} Command
16068 The corresponding @value{GDBN} command is @samp{finish}.
16070 @subsubheading Example
16072 Function returning @code{void}.
16079 *stopped,reason="function-finished",frame=@{func="main",args=[],
16080 file="hello.c",line="7"@}
16084 Function returning other than @code{void}. The name of the internal
16085 @value{GDBN} variable storing the result is printed, together with the
16092 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
16093 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
16094 file="recursive2.c",line="14"@},
16095 gdb-result-var="$1",return-value="0"
16100 @subheading The @code{-exec-interrupt} Command
16101 @findex -exec-interrupt
16103 @subsubheading Synopsis
16109 Asynchronous command. Interrupts the background execution of the target.
16110 Note how the token associated with the stop message is the one for the
16111 execution command that has been interrupted. The token for the interrupt
16112 itself only appears in the @samp{^done} output. If the user is trying to
16113 interrupt a non-running program, an error message will be printed.
16115 @subsubheading @value{GDBN} Command
16117 The corresponding @value{GDBN} command is @samp{interrupt}.
16119 @subsubheading Example
16130 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16131 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16136 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16141 @subheading The @code{-exec-next} Command
16144 @subsubheading Synopsis
16150 Asynchronous command. Resumes execution of the inferior program, stopping
16151 when the beginning of the next source line is reached.
16153 @subsubheading @value{GDBN} Command
16155 The corresponding @value{GDBN} command is @samp{next}.
16157 @subsubheading Example
16163 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16168 @subheading The @code{-exec-next-instruction} Command
16169 @findex -exec-next-instruction
16171 @subsubheading Synopsis
16174 -exec-next-instruction
16177 Asynchronous command. Executes one machine instruction. If the
16178 instruction is a function call continues until the function returns. If
16179 the program stops at an instruction in the middle of a source line, the
16180 address will be printed as well.
16182 @subsubheading @value{GDBN} Command
16184 The corresponding @value{GDBN} command is @samp{nexti}.
16186 @subsubheading Example
16190 -exec-next-instruction
16194 *stopped,reason="end-stepping-range",
16195 addr="0x000100d4",line="5",file="hello.c"
16200 @subheading The @code{-exec-return} Command
16201 @findex -exec-return
16203 @subsubheading Synopsis
16209 Makes current function return immediately. Doesn't execute the inferior.
16210 Displays the new current frame.
16212 @subsubheading @value{GDBN} Command
16214 The corresponding @value{GDBN} command is @samp{return}.
16216 @subsubheading Example
16220 200-break-insert callee4
16221 200^done,bkpt=@{number="1",addr="0x00010734",
16222 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16227 000*stopped,reason="breakpoint-hit",bkptno="1",
16228 frame=@{func="callee4",args=[],
16229 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16235 111^done,frame=@{level="0",func="callee3",
16236 args=[@{name="strarg",
16237 value="0x11940 \"A string argument.\""@}],
16238 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16243 @subheading The @code{-exec-run} Command
16246 @subsubheading Synopsis
16252 Asynchronous command. Starts execution of the inferior from the
16253 beginning. The inferior executes until either a breakpoint is
16254 encountered or the program exits.
16256 @subsubheading @value{GDBN} Command
16258 The corresponding @value{GDBN} command is @samp{run}.
16260 @subsubheading Example
16265 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16270 *stopped,reason="breakpoint-hit",bkptno="1",
16271 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16276 @subheading The @code{-exec-show-arguments} Command
16277 @findex -exec-show-arguments
16279 @subsubheading Synopsis
16282 -exec-show-arguments
16285 Print the arguments of the program.
16287 @subsubheading @value{GDBN} Command
16289 The corresponding @value{GDBN} command is @samp{show args}.
16291 @subsubheading Example
16294 @c @subheading -exec-signal
16296 @subheading The @code{-exec-step} Command
16299 @subsubheading Synopsis
16305 Asynchronous command. Resumes execution of the inferior program, stopping
16306 when the beginning of the next source line is reached, if the next
16307 source line is not a function call. If it is, stop at the first
16308 instruction of the called function.
16310 @subsubheading @value{GDBN} Command
16312 The corresponding @value{GDBN} command is @samp{step}.
16314 @subsubheading Example
16316 Stepping into a function:
16322 *stopped,reason="end-stepping-range",
16323 frame=@{func="foo",args=[@{name="a",value="10"@},
16324 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16334 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16339 @subheading The @code{-exec-step-instruction} Command
16340 @findex -exec-step-instruction
16342 @subsubheading Synopsis
16345 -exec-step-instruction
16348 Asynchronous command. Resumes the inferior which executes one machine
16349 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16350 whether we have stopped in the middle of a source line or not. In the
16351 former case, the address at which the program stopped will be printed as
16354 @subsubheading @value{GDBN} Command
16356 The corresponding @value{GDBN} command is @samp{stepi}.
16358 @subsubheading Example
16362 -exec-step-instruction
16366 *stopped,reason="end-stepping-range",
16367 frame=@{func="foo",args=[],file="try.c",line="10"@}
16369 -exec-step-instruction
16373 *stopped,reason="end-stepping-range",
16374 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16379 @subheading The @code{-exec-until} Command
16380 @findex -exec-until
16382 @subsubheading Synopsis
16385 -exec-until [ @var{location} ]
16388 Asynchronous command. Executes the inferior until the @var{location}
16389 specified in the argument is reached. If there is no argument, the inferior
16390 executes until a source line greater than the current one is reached.
16391 The reason for stopping in this case will be @samp{location-reached}.
16393 @subsubheading @value{GDBN} Command
16395 The corresponding @value{GDBN} command is @samp{until}.
16397 @subsubheading Example
16401 -exec-until recursive2.c:6
16405 *stopped,reason="location-reached",frame=@{func="main",args=[],
16406 file="recursive2.c",line="6"@}
16411 @subheading -file-clear
16412 Is this going away????
16416 @subheading The @code{-file-exec-and-symbols} Command
16417 @findex -file-exec-and-symbols
16419 @subsubheading Synopsis
16422 -file-exec-and-symbols @var{file}
16425 Specify the executable file to be debugged. This file is the one from
16426 which the symbol table is also read. If no file is specified, the
16427 command clears the executable and symbol information. If breakpoints
16428 are set when using this command with no arguments, @value{GDBN} will produce
16429 error messages. Otherwise, no output is produced, except a completion
16432 @subsubheading @value{GDBN} Command
16434 The corresponding @value{GDBN} command is @samp{file}.
16436 @subsubheading Example
16440 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16446 @subheading The @code{-file-exec-file} Command
16447 @findex -file-exec-file
16449 @subsubheading Synopsis
16452 -file-exec-file @var{file}
16455 Specify the executable file to be debugged. Unlike
16456 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16457 from this file. If used without argument, @value{GDBN} clears the information
16458 about the executable file. No output is produced, except a completion
16461 @subsubheading @value{GDBN} Command
16463 The corresponding @value{GDBN} command is @samp{exec-file}.
16465 @subsubheading Example
16469 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16475 @subheading The @code{-file-list-exec-sections} Command
16476 @findex -file-list-exec-sections
16478 @subsubheading Synopsis
16481 -file-list-exec-sections
16484 List the sections of the current executable file.
16486 @subsubheading @value{GDBN} Command
16488 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16489 information as this command. @code{gdbtk} has a corresponding command
16490 @samp{gdb_load_info}.
16492 @subsubheading Example
16496 @subheading The @code{-file-list-exec-source-file} Command
16497 @findex -file-list-exec-source-file
16499 @subsubheading Synopsis
16502 -file-list-exec-source-file
16505 List the line number, the current source file, and the absolute path
16506 to the current source file for the current executable.
16508 @subsubheading @value{GDBN} Command
16510 There's no @value{GDBN} command which directly corresponds to this one.
16512 @subsubheading Example
16516 123-file-list-exec-source-file
16517 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
16522 @subheading The @code{-file-list-exec-source-files} Command
16523 @findex -file-list-exec-source-files
16525 @subsubheading Synopsis
16528 -file-list-exec-source-files
16531 List the source files for the current executable.
16533 @subsubheading @value{GDBN} Command
16535 There's no @value{GDBN} command which directly corresponds to this one.
16536 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16538 @subsubheading Example
16542 @subheading The @code{-file-list-shared-libraries} Command
16543 @findex -file-list-shared-libraries
16545 @subsubheading Synopsis
16548 -file-list-shared-libraries
16551 List the shared libraries in the program.
16553 @subsubheading @value{GDBN} Command
16555 The corresponding @value{GDBN} command is @samp{info shared}.
16557 @subsubheading Example
16561 @subheading The @code{-file-list-symbol-files} Command
16562 @findex -file-list-symbol-files
16564 @subsubheading Synopsis
16567 -file-list-symbol-files
16572 @subsubheading @value{GDBN} Command
16574 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16576 @subsubheading Example
16580 @subheading The @code{-file-symbol-file} Command
16581 @findex -file-symbol-file
16583 @subsubheading Synopsis
16586 -file-symbol-file @var{file}
16589 Read symbol table info from the specified @var{file} argument. When
16590 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16591 produced, except for a completion notification.
16593 @subsubheading @value{GDBN} Command
16595 The corresponding @value{GDBN} command is @samp{symbol-file}.
16597 @subsubheading Example
16601 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16606 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16607 @node GDB/MI Miscellaneous Commands
16608 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16610 @c @subheading -gdb-complete
16612 @subheading The @code{-gdb-exit} Command
16615 @subsubheading Synopsis
16621 Exit @value{GDBN} immediately.
16623 @subsubheading @value{GDBN} Command
16625 Approximately corresponds to @samp{quit}.
16627 @subsubheading Example
16634 @subheading The @code{-gdb-set} Command
16637 @subsubheading Synopsis
16643 Set an internal @value{GDBN} variable.
16644 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16646 @subsubheading @value{GDBN} Command
16648 The corresponding @value{GDBN} command is @samp{set}.
16650 @subsubheading Example
16660 @subheading The @code{-gdb-show} Command
16663 @subsubheading Synopsis
16669 Show the current value of a @value{GDBN} variable.
16671 @subsubheading @value{GDBN} command
16673 The corresponding @value{GDBN} command is @samp{show}.
16675 @subsubheading Example
16684 @c @subheading -gdb-source
16687 @subheading The @code{-gdb-version} Command
16688 @findex -gdb-version
16690 @subsubheading Synopsis
16696 Show version information for @value{GDBN}. Used mostly in testing.
16698 @subsubheading @value{GDBN} Command
16700 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16701 information when you start an interactive session.
16703 @subsubheading Example
16705 @c This example modifies the actual output from GDB to avoid overfull
16711 ~Copyright 2000 Free Software Foundation, Inc.
16712 ~GDB is free software, covered by the GNU General Public License, and
16713 ~you are welcome to change it and/or distribute copies of it under
16714 ~ certain conditions.
16715 ~Type "show copying" to see the conditions.
16716 ~There is absolutely no warranty for GDB. Type "show warranty" for
16718 ~This GDB was configured as
16719 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
16724 @subheading The @code{-interpreter-exec} Command
16725 @findex -interpreter-exec
16727 @subheading Synopsis
16730 -interpreter-exec @var{interpreter} @var{command}
16733 Execute the specified @var{command} in the given @var{interpreter}.
16735 @subheading @value{GDBN} Command
16737 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
16739 @subheading Example
16743 -interpreter-exec console "break main"
16744 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
16745 &"During symbol reading, bad structure-type format.\n"
16746 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
16752 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16753 @node GDB/MI Kod Commands
16754 @section @sc{gdb/mi} Kod Commands
16756 The Kod commands are not implemented.
16758 @c @subheading -kod-info
16760 @c @subheading -kod-list
16762 @c @subheading -kod-list-object-types
16764 @c @subheading -kod-show
16766 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16767 @node GDB/MI Memory Overlay Commands
16768 @section @sc{gdb/mi} Memory Overlay Commands
16770 The memory overlay commands are not implemented.
16772 @c @subheading -overlay-auto
16774 @c @subheading -overlay-list-mapping-state
16776 @c @subheading -overlay-list-overlays
16778 @c @subheading -overlay-map
16780 @c @subheading -overlay-off
16782 @c @subheading -overlay-on
16784 @c @subheading -overlay-unmap
16786 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16787 @node GDB/MI Signal Handling Commands
16788 @section @sc{gdb/mi} Signal Handling Commands
16790 Signal handling commands are not implemented.
16792 @c @subheading -signal-handle
16794 @c @subheading -signal-list-handle-actions
16796 @c @subheading -signal-list-signal-types
16800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16801 @node GDB/MI Stack Manipulation
16802 @section @sc{gdb/mi} Stack Manipulation Commands
16805 @subheading The @code{-stack-info-frame} Command
16806 @findex -stack-info-frame
16808 @subsubheading Synopsis
16814 Get info on the current frame.
16816 @subsubheading @value{GDBN} Command
16818 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
16819 (without arguments).
16821 @subsubheading Example
16824 @subheading The @code{-stack-info-depth} Command
16825 @findex -stack-info-depth
16827 @subsubheading Synopsis
16830 -stack-info-depth [ @var{max-depth} ]
16833 Return the depth of the stack. If the integer argument @var{max-depth}
16834 is specified, do not count beyond @var{max-depth} frames.
16836 @subsubheading @value{GDBN} Command
16838 There's no equivalent @value{GDBN} command.
16840 @subsubheading Example
16842 For a stack with frame levels 0 through 11:
16849 -stack-info-depth 4
16852 -stack-info-depth 12
16855 -stack-info-depth 11
16858 -stack-info-depth 13
16863 @subheading The @code{-stack-list-arguments} Command
16864 @findex -stack-list-arguments
16866 @subsubheading Synopsis
16869 -stack-list-arguments @var{show-values}
16870 [ @var{low-frame} @var{high-frame} ]
16873 Display a list of the arguments for the frames between @var{low-frame}
16874 and @var{high-frame} (inclusive). If @var{low-frame} and
16875 @var{high-frame} are not provided, list the arguments for the whole call
16878 The @var{show-values} argument must have a value of 0 or 1. A value of
16879 0 means that only the names of the arguments are listed, a value of 1
16880 means that both names and values of the arguments are printed.
16882 @subsubheading @value{GDBN} Command
16884 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
16885 @samp{gdb_get_args} command which partially overlaps with the
16886 functionality of @samp{-stack-list-arguments}.
16888 @subsubheading Example
16895 frame=@{level="0",addr="0x00010734",func="callee4",
16896 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
16897 frame=@{level="1",addr="0x0001076c",func="callee3",
16898 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
16899 frame=@{level="2",addr="0x0001078c",func="callee2",
16900 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
16901 frame=@{level="3",addr="0x000107b4",func="callee1",
16902 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
16903 frame=@{level="4",addr="0x000107e0",func="main",
16904 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
16906 -stack-list-arguments 0
16909 frame=@{level="0",args=[]@},
16910 frame=@{level="1",args=[name="strarg"]@},
16911 frame=@{level="2",args=[name="intarg",name="strarg"]@},
16912 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
16913 frame=@{level="4",args=[]@}]
16915 -stack-list-arguments 1
16918 frame=@{level="0",args=[]@},
16920 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16921 frame=@{level="2",args=[
16922 @{name="intarg",value="2"@},
16923 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16924 @{frame=@{level="3",args=[
16925 @{name="intarg",value="2"@},
16926 @{name="strarg",value="0x11940 \"A string argument.\""@},
16927 @{name="fltarg",value="3.5"@}]@},
16928 frame=@{level="4",args=[]@}]
16930 -stack-list-arguments 0 2 2
16931 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
16933 -stack-list-arguments 1 2 2
16934 ^done,stack-args=[frame=@{level="2",
16935 args=[@{name="intarg",value="2"@},
16936 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
16940 @c @subheading -stack-list-exception-handlers
16943 @subheading The @code{-stack-list-frames} Command
16944 @findex -stack-list-frames
16946 @subsubheading Synopsis
16949 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
16952 List the frames currently on the stack. For each frame it displays the
16957 The frame number, 0 being the topmost frame, i.e. the innermost function.
16959 The @code{$pc} value for that frame.
16963 File name of the source file where the function lives.
16965 Line number corresponding to the @code{$pc}.
16968 If invoked without arguments, this command prints a backtrace for the
16969 whole stack. If given two integer arguments, it shows the frames whose
16970 levels are between the two arguments (inclusive). If the two arguments
16971 are equal, it shows the single frame at the corresponding level.
16973 @subsubheading @value{GDBN} Command
16975 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
16977 @subsubheading Example
16979 Full stack backtrace:
16985 [frame=@{level="0",addr="0x0001076c",func="foo",
16986 file="recursive2.c",line="11"@},
16987 frame=@{level="1",addr="0x000107a4",func="foo",
16988 file="recursive2.c",line="14"@},
16989 frame=@{level="2",addr="0x000107a4",func="foo",
16990 file="recursive2.c",line="14"@},
16991 frame=@{level="3",addr="0x000107a4",func="foo",
16992 file="recursive2.c",line="14"@},
16993 frame=@{level="4",addr="0x000107a4",func="foo",
16994 file="recursive2.c",line="14"@},
16995 frame=@{level="5",addr="0x000107a4",func="foo",
16996 file="recursive2.c",line="14"@},
16997 frame=@{level="6",addr="0x000107a4",func="foo",
16998 file="recursive2.c",line="14"@},
16999 frame=@{level="7",addr="0x000107a4",func="foo",
17000 file="recursive2.c",line="14"@},
17001 frame=@{level="8",addr="0x000107a4",func="foo",
17002 file="recursive2.c",line="14"@},
17003 frame=@{level="9",addr="0x000107a4",func="foo",
17004 file="recursive2.c",line="14"@},
17005 frame=@{level="10",addr="0x000107a4",func="foo",
17006 file="recursive2.c",line="14"@},
17007 frame=@{level="11",addr="0x00010738",func="main",
17008 file="recursive2.c",line="4"@}]
17012 Show frames between @var{low_frame} and @var{high_frame}:
17016 -stack-list-frames 3 5
17018 [frame=@{level="3",addr="0x000107a4",func="foo",
17019 file="recursive2.c",line="14"@},
17020 frame=@{level="4",addr="0x000107a4",func="foo",
17021 file="recursive2.c",line="14"@},
17022 frame=@{level="5",addr="0x000107a4",func="foo",
17023 file="recursive2.c",line="14"@}]
17027 Show a single frame:
17031 -stack-list-frames 3 3
17033 [frame=@{level="3",addr="0x000107a4",func="foo",
17034 file="recursive2.c",line="14"@}]
17039 @subheading The @code{-stack-list-locals} Command
17040 @findex -stack-list-locals
17042 @subsubheading Synopsis
17045 -stack-list-locals @var{print-values}
17048 Display the local variable names for the current frame. With an
17049 argument of 0 prints only the names of the variables, with argument of 1
17050 prints also their values.
17052 @subsubheading @value{GDBN} Command
17054 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
17056 @subsubheading Example
17060 -stack-list-locals 0
17061 ^done,locals=[name="A",name="B",name="C"]
17063 -stack-list-locals 1
17064 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
17065 @{name="C",value="3"@}]
17070 @subheading The @code{-stack-select-frame} Command
17071 @findex -stack-select-frame
17073 @subsubheading Synopsis
17076 -stack-select-frame @var{framenum}
17079 Change the current frame. Select a different frame @var{framenum} on
17082 @subsubheading @value{GDBN} Command
17084 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
17085 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
17087 @subsubheading Example
17091 -stack-select-frame 2
17096 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17097 @node GDB/MI Symbol Query
17098 @section @sc{gdb/mi} Symbol Query Commands
17101 @subheading The @code{-symbol-info-address} Command
17102 @findex -symbol-info-address
17104 @subsubheading Synopsis
17107 -symbol-info-address @var{symbol}
17110 Describe where @var{symbol} is stored.
17112 @subsubheading @value{GDBN} Command
17114 The corresponding @value{GDBN} command is @samp{info address}.
17116 @subsubheading Example
17120 @subheading The @code{-symbol-info-file} Command
17121 @findex -symbol-info-file
17123 @subsubheading Synopsis
17129 Show the file for the symbol.
17131 @subsubheading @value{GDBN} Command
17133 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17134 @samp{gdb_find_file}.
17136 @subsubheading Example
17140 @subheading The @code{-symbol-info-function} Command
17141 @findex -symbol-info-function
17143 @subsubheading Synopsis
17146 -symbol-info-function
17149 Show which function the symbol lives in.
17151 @subsubheading @value{GDBN} Command
17153 @samp{gdb_get_function} in @code{gdbtk}.
17155 @subsubheading Example
17159 @subheading The @code{-symbol-info-line} Command
17160 @findex -symbol-info-line
17162 @subsubheading Synopsis
17168 Show the core addresses of the code for a source line.
17170 @subsubheading @value{GDBN} Command
17172 The corresponding @value{GDBN} comamnd is @samp{info line}.
17173 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17175 @subsubheading Example
17179 @subheading The @code{-symbol-info-symbol} Command
17180 @findex -symbol-info-symbol
17182 @subsubheading Synopsis
17185 -symbol-info-symbol @var{addr}
17188 Describe what symbol is at location @var{addr}.
17190 @subsubheading @value{GDBN} Command
17192 The corresponding @value{GDBN} command is @samp{info symbol}.
17194 @subsubheading Example
17198 @subheading The @code{-symbol-list-functions} Command
17199 @findex -symbol-list-functions
17201 @subsubheading Synopsis
17204 -symbol-list-functions
17207 List the functions in the executable.
17209 @subsubheading @value{GDBN} Command
17211 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17212 @samp{gdb_search} in @code{gdbtk}.
17214 @subsubheading Example
17218 @subheading The @code{-symbol-list-lines} Command
17219 @findex -symbol-list-lines
17221 @subsubheading Synopsis
17224 -symbol-list-lines @var{filename}
17227 Print the list of lines that contain code and their associated program
17228 addresses for the given source filename. The entries are sorted in
17229 ascending PC order.
17231 @subsubheading @value{GDBN} Command
17233 There is no corresponding @value{GDBN} command.
17235 @subsubheading Example
17238 -symbol-list-lines basics.c
17239 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17244 @subheading The @code{-symbol-list-types} Command
17245 @findex -symbol-list-types
17247 @subsubheading Synopsis
17253 List all the type names.
17255 @subsubheading @value{GDBN} Command
17257 The corresponding commands are @samp{info types} in @value{GDBN},
17258 @samp{gdb_search} in @code{gdbtk}.
17260 @subsubheading Example
17264 @subheading The @code{-symbol-list-variables} Command
17265 @findex -symbol-list-variables
17267 @subsubheading Synopsis
17270 -symbol-list-variables
17273 List all the global and static variable names.
17275 @subsubheading @value{GDBN} Command
17277 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17279 @subsubheading Example
17283 @subheading The @code{-symbol-locate} Command
17284 @findex -symbol-locate
17286 @subsubheading Synopsis
17292 @subsubheading @value{GDBN} Command
17294 @samp{gdb_loc} in @code{gdbtk}.
17296 @subsubheading Example
17300 @subheading The @code{-symbol-type} Command
17301 @findex -symbol-type
17303 @subsubheading Synopsis
17306 -symbol-type @var{variable}
17309 Show type of @var{variable}.
17311 @subsubheading @value{GDBN} Command
17313 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17314 @samp{gdb_obj_variable}.
17316 @subsubheading Example
17320 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17321 @node GDB/MI Target Manipulation
17322 @section @sc{gdb/mi} Target Manipulation Commands
17325 @subheading The @code{-target-attach} Command
17326 @findex -target-attach
17328 @subsubheading Synopsis
17331 -target-attach @var{pid} | @var{file}
17334 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17336 @subsubheading @value{GDBN} command
17338 The corresponding @value{GDBN} command is @samp{attach}.
17340 @subsubheading Example
17344 @subheading The @code{-target-compare-sections} Command
17345 @findex -target-compare-sections
17347 @subsubheading Synopsis
17350 -target-compare-sections [ @var{section} ]
17353 Compare data of section @var{section} on target to the exec file.
17354 Without the argument, all sections are compared.
17356 @subsubheading @value{GDBN} Command
17358 The @value{GDBN} equivalent is @samp{compare-sections}.
17360 @subsubheading Example
17364 @subheading The @code{-target-detach} Command
17365 @findex -target-detach
17367 @subsubheading Synopsis
17373 Disconnect from the remote target. There's no output.
17375 @subsubheading @value{GDBN} command
17377 The corresponding @value{GDBN} command is @samp{detach}.
17379 @subsubheading Example
17389 @subheading The @code{-target-disconnect} Command
17390 @findex -target-disconnect
17392 @subsubheading Synopsis
17398 Disconnect from the remote target. There's no output.
17400 @subsubheading @value{GDBN} command
17402 The corresponding @value{GDBN} command is @samp{disconnect}.
17404 @subsubheading Example
17414 @subheading The @code{-target-download} Command
17415 @findex -target-download
17417 @subsubheading Synopsis
17423 Loads the executable onto the remote target.
17424 It prints out an update message every half second, which includes the fields:
17428 The name of the section.
17430 The size of what has been sent so far for that section.
17432 The size of the section.
17434 The total size of what was sent so far (the current and the previous sections).
17436 The size of the overall executable to download.
17440 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17441 @sc{gdb/mi} Output Syntax}).
17443 In addition, it prints the name and size of the sections, as they are
17444 downloaded. These messages include the following fields:
17448 The name of the section.
17450 The size of the section.
17452 The size of the overall executable to download.
17456 At the end, a summary is printed.
17458 @subsubheading @value{GDBN} Command
17460 The corresponding @value{GDBN} command is @samp{load}.
17462 @subsubheading Example
17464 Note: each status message appears on a single line. Here the messages
17465 have been broken down so that they can fit onto a page.
17470 +download,@{section=".text",section-size="6668",total-size="9880"@}
17471 +download,@{section=".text",section-sent="512",section-size="6668",
17472 total-sent="512",total-size="9880"@}
17473 +download,@{section=".text",section-sent="1024",section-size="6668",
17474 total-sent="1024",total-size="9880"@}
17475 +download,@{section=".text",section-sent="1536",section-size="6668",
17476 total-sent="1536",total-size="9880"@}
17477 +download,@{section=".text",section-sent="2048",section-size="6668",
17478 total-sent="2048",total-size="9880"@}
17479 +download,@{section=".text",section-sent="2560",section-size="6668",
17480 total-sent="2560",total-size="9880"@}
17481 +download,@{section=".text",section-sent="3072",section-size="6668",
17482 total-sent="3072",total-size="9880"@}
17483 +download,@{section=".text",section-sent="3584",section-size="6668",
17484 total-sent="3584",total-size="9880"@}
17485 +download,@{section=".text",section-sent="4096",section-size="6668",
17486 total-sent="4096",total-size="9880"@}
17487 +download,@{section=".text",section-sent="4608",section-size="6668",
17488 total-sent="4608",total-size="9880"@}
17489 +download,@{section=".text",section-sent="5120",section-size="6668",
17490 total-sent="5120",total-size="9880"@}
17491 +download,@{section=".text",section-sent="5632",section-size="6668",
17492 total-sent="5632",total-size="9880"@}
17493 +download,@{section=".text",section-sent="6144",section-size="6668",
17494 total-sent="6144",total-size="9880"@}
17495 +download,@{section=".text",section-sent="6656",section-size="6668",
17496 total-sent="6656",total-size="9880"@}
17497 +download,@{section=".init",section-size="28",total-size="9880"@}
17498 +download,@{section=".fini",section-size="28",total-size="9880"@}
17499 +download,@{section=".data",section-size="3156",total-size="9880"@}
17500 +download,@{section=".data",section-sent="512",section-size="3156",
17501 total-sent="7236",total-size="9880"@}
17502 +download,@{section=".data",section-sent="1024",section-size="3156",
17503 total-sent="7748",total-size="9880"@}
17504 +download,@{section=".data",section-sent="1536",section-size="3156",
17505 total-sent="8260",total-size="9880"@}
17506 +download,@{section=".data",section-sent="2048",section-size="3156",
17507 total-sent="8772",total-size="9880"@}
17508 +download,@{section=".data",section-sent="2560",section-size="3156",
17509 total-sent="9284",total-size="9880"@}
17510 +download,@{section=".data",section-sent="3072",section-size="3156",
17511 total-sent="9796",total-size="9880"@}
17512 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17518 @subheading The @code{-target-exec-status} Command
17519 @findex -target-exec-status
17521 @subsubheading Synopsis
17524 -target-exec-status
17527 Provide information on the state of the target (whether it is running or
17528 not, for instance).
17530 @subsubheading @value{GDBN} Command
17532 There's no equivalent @value{GDBN} command.
17534 @subsubheading Example
17538 @subheading The @code{-target-list-available-targets} Command
17539 @findex -target-list-available-targets
17541 @subsubheading Synopsis
17544 -target-list-available-targets
17547 List the possible targets to connect to.
17549 @subsubheading @value{GDBN} Command
17551 The corresponding @value{GDBN} command is @samp{help target}.
17553 @subsubheading Example
17557 @subheading The @code{-target-list-current-targets} Command
17558 @findex -target-list-current-targets
17560 @subsubheading Synopsis
17563 -target-list-current-targets
17566 Describe the current target.
17568 @subsubheading @value{GDBN} Command
17570 The corresponding information is printed by @samp{info file} (among
17573 @subsubheading Example
17577 @subheading The @code{-target-list-parameters} Command
17578 @findex -target-list-parameters
17580 @subsubheading Synopsis
17583 -target-list-parameters
17588 @subsubheading @value{GDBN} Command
17592 @subsubheading Example
17596 @subheading The @code{-target-select} Command
17597 @findex -target-select
17599 @subsubheading Synopsis
17602 -target-select @var{type} @var{parameters @dots{}}
17605 Connect @value{GDBN} to the remote target. This command takes two args:
17609 The type of target, for instance @samp{async}, @samp{remote}, etc.
17610 @item @var{parameters}
17611 Device names, host names and the like. @xref{Target Commands, ,
17612 Commands for managing targets}, for more details.
17615 The output is a connection notification, followed by the address at
17616 which the target program is, in the following form:
17619 ^connected,addr="@var{address}",func="@var{function name}",
17620 args=[@var{arg list}]
17623 @subsubheading @value{GDBN} Command
17625 The corresponding @value{GDBN} command is @samp{target}.
17627 @subsubheading Example
17631 -target-select async /dev/ttya
17632 ^connected,addr="0xfe00a300",func="??",args=[]
17636 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17637 @node GDB/MI Thread Commands
17638 @section @sc{gdb/mi} Thread Commands
17641 @subheading The @code{-thread-info} Command
17642 @findex -thread-info
17644 @subsubheading Synopsis
17650 @subsubheading @value{GDBN} command
17654 @subsubheading Example
17658 @subheading The @code{-thread-list-all-threads} Command
17659 @findex -thread-list-all-threads
17661 @subsubheading Synopsis
17664 -thread-list-all-threads
17667 @subsubheading @value{GDBN} Command
17669 The equivalent @value{GDBN} command is @samp{info threads}.
17671 @subsubheading Example
17675 @subheading The @code{-thread-list-ids} Command
17676 @findex -thread-list-ids
17678 @subsubheading Synopsis
17684 Produces a list of the currently known @value{GDBN} thread ids. At the
17685 end of the list it also prints the total number of such threads.
17687 @subsubheading @value{GDBN} Command
17689 Part of @samp{info threads} supplies the same information.
17691 @subsubheading Example
17693 No threads present, besides the main process:
17698 ^done,thread-ids=@{@},number-of-threads="0"
17708 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17709 number-of-threads="3"
17714 @subheading The @code{-thread-select} Command
17715 @findex -thread-select
17717 @subsubheading Synopsis
17720 -thread-select @var{threadnum}
17723 Make @var{threadnum} the current thread. It prints the number of the new
17724 current thread, and the topmost frame for that thread.
17726 @subsubheading @value{GDBN} Command
17728 The corresponding @value{GDBN} command is @samp{thread}.
17730 @subsubheading Example
17737 *stopped,reason="end-stepping-range",thread-id="2",line="187",
17738 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
17742 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17743 number-of-threads="3"
17746 ^done,new-thread-id="3",
17747 frame=@{level="0",func="vprintf",
17748 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
17749 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
17753 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17754 @node GDB/MI Tracepoint Commands
17755 @section @sc{gdb/mi} Tracepoint Commands
17757 The tracepoint commands are not yet implemented.
17759 @c @subheading -trace-actions
17761 @c @subheading -trace-delete
17763 @c @subheading -trace-disable
17765 @c @subheading -trace-dump
17767 @c @subheading -trace-enable
17769 @c @subheading -trace-exists
17771 @c @subheading -trace-find
17773 @c @subheading -trace-frame-number
17775 @c @subheading -trace-info
17777 @c @subheading -trace-insert
17779 @c @subheading -trace-list
17781 @c @subheading -trace-pass-count
17783 @c @subheading -trace-save
17785 @c @subheading -trace-start
17787 @c @subheading -trace-stop
17790 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17791 @node GDB/MI Variable Objects
17792 @section @sc{gdb/mi} Variable Objects
17795 @subheading Motivation for Variable Objects in @sc{gdb/mi}
17797 For the implementation of a variable debugger window (locals, watched
17798 expressions, etc.), we are proposing the adaptation of the existing code
17799 used by @code{Insight}.
17801 The two main reasons for that are:
17805 It has been proven in practice (it is already on its second generation).
17808 It will shorten development time (needless to say how important it is
17812 The original interface was designed to be used by Tcl code, so it was
17813 slightly changed so it could be used through @sc{gdb/mi}. This section
17814 describes the @sc{gdb/mi} operations that will be available and gives some
17815 hints about their use.
17817 @emph{Note}: In addition to the set of operations described here, we
17818 expect the @sc{gui} implementation of a variable window to require, at
17819 least, the following operations:
17822 @item @code{-gdb-show} @code{output-radix}
17823 @item @code{-stack-list-arguments}
17824 @item @code{-stack-list-locals}
17825 @item @code{-stack-select-frame}
17828 @subheading Introduction to Variable Objects in @sc{gdb/mi}
17830 @cindex variable objects in @sc{gdb/mi}
17831 The basic idea behind variable objects is the creation of a named object
17832 to represent a variable, an expression, a memory location or even a CPU
17833 register. For each object created, a set of operations is available for
17834 examining or changing its properties.
17836 Furthermore, complex data types, such as C structures, are represented
17837 in a tree format. For instance, the @code{struct} type variable is the
17838 root and the children will represent the struct members. If a child
17839 is itself of a complex type, it will also have children of its own.
17840 Appropriate language differences are handled for C, C@t{++} and Java.
17842 When returning the actual values of the objects, this facility allows
17843 for the individual selection of the display format used in the result
17844 creation. It can be chosen among: binary, decimal, hexadecimal, octal
17845 and natural. Natural refers to a default format automatically
17846 chosen based on the variable type (like decimal for an @code{int}, hex
17847 for pointers, etc.).
17849 The following is the complete set of @sc{gdb/mi} operations defined to
17850 access this functionality:
17852 @multitable @columnfractions .4 .6
17853 @item @strong{Operation}
17854 @tab @strong{Description}
17856 @item @code{-var-create}
17857 @tab create a variable object
17858 @item @code{-var-delete}
17859 @tab delete the variable object and its children
17860 @item @code{-var-set-format}
17861 @tab set the display format of this variable
17862 @item @code{-var-show-format}
17863 @tab show the display format of this variable
17864 @item @code{-var-info-num-children}
17865 @tab tells how many children this object has
17866 @item @code{-var-list-children}
17867 @tab return a list of the object's children
17868 @item @code{-var-info-type}
17869 @tab show the type of this variable object
17870 @item @code{-var-info-expression}
17871 @tab print what this variable object represents
17872 @item @code{-var-show-attributes}
17873 @tab is this variable editable? does it exist here?
17874 @item @code{-var-evaluate-expression}
17875 @tab get the value of this variable
17876 @item @code{-var-assign}
17877 @tab set the value of this variable
17878 @item @code{-var-update}
17879 @tab update the variable and its children
17882 In the next subsection we describe each operation in detail and suggest
17883 how it can be used.
17885 @subheading Description And Use of Operations on Variable Objects
17887 @subheading The @code{-var-create} Command
17888 @findex -var-create
17890 @subsubheading Synopsis
17893 -var-create @{@var{name} | "-"@}
17894 @{@var{frame-addr} | "*"@} @var{expression}
17897 This operation creates a variable object, which allows the monitoring of
17898 a variable, the result of an expression, a memory cell or a CPU
17901 The @var{name} parameter is the string by which the object can be
17902 referenced. It must be unique. If @samp{-} is specified, the varobj
17903 system will generate a string ``varNNNNNN'' automatically. It will be
17904 unique provided that one does not specify @var{name} on that format.
17905 The command fails if a duplicate name is found.
17907 The frame under which the expression should be evaluated can be
17908 specified by @var{frame-addr}. A @samp{*} indicates that the current
17909 frame should be used.
17911 @var{expression} is any expression valid on the current language set (must not
17912 begin with a @samp{*}), or one of the following:
17916 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
17919 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
17922 @samp{$@var{regname}} --- a CPU register name
17925 @subsubheading Result
17927 This operation returns the name, number of children and the type of the
17928 object created. Type is returned as a string as the ones generated by
17929 the @value{GDBN} CLI:
17932 name="@var{name}",numchild="N",type="@var{type}"
17936 @subheading The @code{-var-delete} Command
17937 @findex -var-delete
17939 @subsubheading Synopsis
17942 -var-delete @var{name}
17945 Deletes a previously created variable object and all of its children.
17947 Returns an error if the object @var{name} is not found.
17950 @subheading The @code{-var-set-format} Command
17951 @findex -var-set-format
17953 @subsubheading Synopsis
17956 -var-set-format @var{name} @var{format-spec}
17959 Sets the output format for the value of the object @var{name} to be
17962 The syntax for the @var{format-spec} is as follows:
17965 @var{format-spec} @expansion{}
17966 @{binary | decimal | hexadecimal | octal | natural@}
17970 @subheading The @code{-var-show-format} Command
17971 @findex -var-show-format
17973 @subsubheading Synopsis
17976 -var-show-format @var{name}
17979 Returns the format used to display the value of the object @var{name}.
17982 @var{format} @expansion{}
17987 @subheading The @code{-var-info-num-children} Command
17988 @findex -var-info-num-children
17990 @subsubheading Synopsis
17993 -var-info-num-children @var{name}
17996 Returns the number of children of a variable object @var{name}:
18003 @subheading The @code{-var-list-children} Command
18004 @findex -var-list-children
18006 @subsubheading Synopsis
18009 -var-list-children @var{name}
18012 Returns a list of the children of the specified variable object:
18015 numchild=@var{n},children=[@{name=@var{name},
18016 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
18020 @subheading The @code{-var-info-type} Command
18021 @findex -var-info-type
18023 @subsubheading Synopsis
18026 -var-info-type @var{name}
18029 Returns the type of the specified variable @var{name}. The type is
18030 returned as a string in the same format as it is output by the
18034 type=@var{typename}
18038 @subheading The @code{-var-info-expression} Command
18039 @findex -var-info-expression
18041 @subsubheading Synopsis
18044 -var-info-expression @var{name}
18047 Returns what is represented by the variable object @var{name}:
18050 lang=@var{lang-spec},exp=@var{expression}
18054 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
18056 @subheading The @code{-var-show-attributes} Command
18057 @findex -var-show-attributes
18059 @subsubheading Synopsis
18062 -var-show-attributes @var{name}
18065 List attributes of the specified variable object @var{name}:
18068 status=@var{attr} [ ( ,@var{attr} )* ]
18072 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
18074 @subheading The @code{-var-evaluate-expression} Command
18075 @findex -var-evaluate-expression
18077 @subsubheading Synopsis
18080 -var-evaluate-expression @var{name}
18083 Evaluates the expression that is represented by the specified variable
18084 object and returns its value as a string in the current format specified
18091 Note that one must invoke @code{-var-list-children} for a variable
18092 before the value of a child variable can be evaluated.
18094 @subheading The @code{-var-assign} Command
18095 @findex -var-assign
18097 @subsubheading Synopsis
18100 -var-assign @var{name} @var{expression}
18103 Assigns the value of @var{expression} to the variable object specified
18104 by @var{name}. The object must be @samp{editable}. If the variable's
18105 value is altered by the assign, the variable will show up in any
18106 subsequent @code{-var-update} list.
18108 @subsubheading Example
18116 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
18120 @subheading The @code{-var-update} Command
18121 @findex -var-update
18123 @subsubheading Synopsis
18126 -var-update @{@var{name} | "*"@}
18129 Update the value of the variable object @var{name} by evaluating its
18130 expression after fetching all the new values from memory or registers.
18131 A @samp{*} causes all existing variable objects to be updated.
18135 @chapter @value{GDBN} Annotations
18137 This chapter describes annotations in @value{GDBN}. Annotations are
18138 designed to interface @value{GDBN} to graphical user interfaces or
18139 other similar programs which want to interact with @value{GDBN} at a
18140 relatively high level.
18143 This is Edition @value{EDITION}, @value{DATE}.
18147 * Annotations Overview:: What annotations are; the general syntax.
18148 * Server Prefix:: Issuing a command without affecting user state.
18149 * Value Annotations:: Values are marked as such.
18150 * Frame Annotations:: Stack frames are annotated.
18151 * Displays:: @value{GDBN} can be told to display something periodically.
18152 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18153 * Errors:: Annotations for error messages.
18154 * Breakpoint Info:: Information on breakpoints.
18155 * Invalidation:: Some annotations describe things now invalid.
18156 * Annotations for Running::
18157 Whether the program is running, how it stopped, etc.
18158 * Source Annotations:: Annotations describing source code.
18159 * TODO:: Annotations which might be added in the future.
18162 @node Annotations Overview
18163 @section What is an Annotation?
18164 @cindex annotations
18166 To produce annotations, start @value{GDBN} with the @code{--annotate=2} option.
18168 Annotations start with a newline character, two @samp{control-z}
18169 characters, and the name of the annotation. If there is no additional
18170 information associated with this annotation, the name of the annotation
18171 is followed immediately by a newline. If there is additional
18172 information, the name of the annotation is followed by a space, the
18173 additional information, and a newline. The additional information
18174 cannot contain newline characters.
18176 Any output not beginning with a newline and two @samp{control-z}
18177 characters denotes literal output from @value{GDBN}. Currently there is
18178 no need for @value{GDBN} to output a newline followed by two
18179 @samp{control-z} characters, but if there was such a need, the
18180 annotations could be extended with an @samp{escape} annotation which
18181 means those three characters as output.
18183 A simple example of starting up @value{GDBN} with annotations is:
18188 Copyright 2000 Free Software Foundation, Inc.
18189 GDB is free software, covered by the GNU General Public License,
18190 and you are welcome to change it and/or distribute copies of it
18191 under certain conditions.
18192 Type "show copying" to see the conditions.
18193 There is absolutely no warranty for GDB. Type "show warranty"
18195 This GDB was configured as "sparc-sun-sunos4.1.3"
18206 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18207 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18208 denotes a @samp{control-z} character) are annotations; the rest is
18209 output from @value{GDBN}.
18211 @node Server Prefix
18212 @section The Server Prefix
18213 @cindex server prefix for annotations
18215 To issue a command to @value{GDBN} without affecting certain aspects of
18216 the state which is seen by users, prefix it with @samp{server }. This
18217 means that this command will not affect the command history, nor will it
18218 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18219 pressed on a line by itself.
18221 The server prefix does not affect the recording of values into the value
18222 history; to print a value without recording it into the value history,
18223 use the @code{output} command instead of the @code{print} command.
18225 @node Value Annotations
18228 @cindex annotations for values
18229 When a value is printed in various contexts, @value{GDBN} uses
18230 annotations to delimit the value from the surrounding text.
18232 @findex value-history-begin
18233 @findex value-history-value
18234 @findex value-history-end
18235 If a value is printed using @code{print} and added to the value history,
18236 the annotation looks like
18239 ^Z^Zvalue-history-begin @var{history-number} @var{value-flags}
18240 @var{history-string}
18241 ^Z^Zvalue-history-value
18243 ^Z^Zvalue-history-end
18247 where @var{history-number} is the number it is getting in the value
18248 history, @var{history-string} is a string, such as @samp{$5 = }, which
18249 introduces the value to the user, @var{the-value} is the output
18250 corresponding to the value itself, and @var{value-flags} is @samp{*} for
18251 a value which can be dereferenced and @samp{-} for a value which cannot.
18253 @findex value-begin
18255 If the value is not added to the value history (it is an invalid float
18256 or it is printed with the @code{output} command), the annotation is similar:
18259 ^Z^Zvalue-begin @var{value-flags}
18265 @findex arg-name-end
18268 When @value{GDBN} prints an argument to a function (for example, in the output
18269 from the @code{backtrace} command), it annotates it as follows:
18273 @var{argument-name}
18275 @var{separator-string}
18276 ^Z^Zarg-value @var{value-flags}
18282 where @var{argument-name} is the name of the argument,
18283 @var{separator-string} is text which separates the name from the value
18284 for the user's benefit (such as @samp{=}), and @var{value-flags} and
18285 @var{the-value} have the same meanings as in a
18286 @code{value-history-begin} annotation.
18288 @findex field-begin
18289 @findex field-name-end
18290 @findex field-value
18292 When printing a structure, @value{GDBN} annotates it as follows:
18295 ^Z^Zfield-begin @var{value-flags}
18298 @var{separator-string}
18305 where @var{field-name} is the name of the field, @var{separator-string}
18306 is text which separates the name from the value for the user's benefit
18307 (such as @samp{=}), and @var{value-flags} and @var{the-value} have the
18308 same meanings as in a @code{value-history-begin} annotation.
18310 When printing an array, @value{GDBN} annotates it as follows:
18313 ^Z^Zarray-section-begin @var{array-index} @var{value-flags}
18317 where @var{array-index} is the index of the first element being
18318 annotated and @var{value-flags} has the same meaning as in a
18319 @code{value-history-begin} annotation. This is followed by any number
18320 of elements, where is element can be either a single element:
18324 @samp{,} @var{whitespace} ; @r{omitted for the first element}
18329 or a repeated element
18332 @findex elt-rep-end
18334 @samp{,} @var{whitespace} ; @r{omitted for the first element}
18336 ^Z^Zelt-rep @var{number-of-repetitions}
18337 @var{repetition-string}
18341 In both cases, @var{the-value} is the output for the value of the
18342 element and @var{whitespace} can contain spaces, tabs, and newlines. In
18343 the repeated case, @var{number-of-repetitions} is the number of
18344 consecutive array elements which contain that value, and
18345 @var{repetition-string} is a string which is designed to convey to the
18346 user that repetition is being depicted.
18348 @findex array-section-end
18349 Once all the array elements have been output, the array annotation is
18353 ^Z^Zarray-section-end
18356 @node Frame Annotations
18359 @cindex annotations for frames
18360 Whenever @value{GDBN} prints a frame, it annotates it. For example, this applies
18361 to frames printed when @value{GDBN} stops, output from commands such as
18362 @code{backtrace} or @code{up}, etc.
18364 @findex frame-begin
18365 The frame annotation begins with
18368 ^Z^Zframe-begin @var{level} @var{address}
18373 where @var{level} is the number of the frame (0 is the innermost frame,
18374 and other frames have positive numbers), @var{address} is the address of
18375 the code executing in that frame, and @var{level-string} is a string
18376 designed to convey the level to the user. @var{address} is in the form
18377 @samp{0x} followed by one or more lowercase hex digits (note that this
18378 does not depend on the language). The frame ends with
18385 Between these annotations is the main body of the frame, which can
18390 @findex function-call
18393 @var{function-call-string}
18396 where @var{function-call-string} is text designed to convey to the user
18397 that this frame is associated with a function call made by @value{GDBN} to a
18398 function in the program being debugged.
18401 @findex signal-handler-caller
18403 ^Z^Zsignal-handler-caller
18404 @var{signal-handler-caller-string}
18407 where @var{signal-handler-caller-string} is text designed to convey to
18408 the user that this frame is associated with whatever mechanism is used
18409 by this operating system to call a signal handler (it is the frame which
18410 calls the signal handler, not the frame for the signal handler itself).
18415 @findex frame-address
18416 @findex frame-address-end
18417 This can optionally (depending on whether this is thought of as
18418 interesting information for the user to see) begin with
18423 ^Z^Zframe-address-end
18424 @var{separator-string}
18427 where @var{address} is the address executing in the frame (the same
18428 address as in the @code{frame-begin} annotation, but printed in a form
18429 which is intended for user consumption---in particular, the syntax varies
18430 depending on the language), and @var{separator-string} is a string
18431 intended to separate this address from what follows for the user's
18434 @findex frame-function-name
18439 ^Z^Zframe-function-name
18440 @var{function-name}
18445 where @var{function-name} is the name of the function executing in the
18446 frame, or @samp{??} if not known, and @var{arguments} are the arguments
18447 to the frame, with parentheses around them (each argument is annotated
18448 individually as well, @pxref{Value Annotations}).
18450 @findex frame-source-begin
18451 @findex frame-source-file
18452 @findex frame-source-file-end
18453 @findex frame-source-line
18454 @findex frame-source-end
18455 If source information is available, a reference to it is then printed:
18458 ^Z^Zframe-source-begin
18459 @var{source-intro-string}
18460 ^Z^Zframe-source-file
18462 ^Z^Zframe-source-file-end
18464 ^Z^Zframe-source-line
18466 ^Z^Zframe-source-end
18469 where @var{source-intro-string} separates for the user's benefit the
18470 reference from the text which precedes it, @var{filename} is the name of
18471 the source file, and @var{line-number} is the line number within that
18472 file (the first line is line 1).
18474 @findex frame-where
18475 If @value{GDBN} prints some information about where the frame is from (which
18476 library, which load segment, etc.; currently only done on the RS/6000),
18477 it is annotated with
18484 Then, if source is to actually be displayed for this frame (for example,
18485 this is not true for output from the @code{backtrace} command), then a
18486 @code{source} annotation (@pxref{Source Annotations}) is displayed. Unlike
18487 most annotations, this is output instead of the normal text which would be
18488 output, not in addition.
18494 @findex display-begin
18495 @findex display-number-end
18496 @findex display-format
18497 @findex display-expression
18498 @findex display-expression-end
18499 @findex display-value
18500 @findex display-end
18501 @cindex annotations for display
18502 When @value{GDBN} is told to display something using the @code{display} command,
18503 the results of the display are annotated:
18508 ^Z^Zdisplay-number-end
18509 @var{number-separator}
18512 ^Z^Zdisplay-expression
18514 ^Z^Zdisplay-expression-end
18515 @var{expression-separator}
18522 where @var{number} is the number of the display, @var{number-separator}
18523 is intended to separate the number from what follows for the user,
18524 @var{format} includes information such as the size, format, or other
18525 information about how the value is being displayed, @var{expression} is
18526 the expression being displayed, @var{expression-separator} is intended
18527 to separate the expression from the text that follows for the user,
18528 and @var{value} is the actual value being displayed.
18531 @section Annotation for @value{GDBN} Input
18533 @cindex annotations for prompts
18534 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18535 to know when to send output, when the output from a given command is
18538 Different kinds of input each have a different @dfn{input type}. Each
18539 input type has three annotations: a @code{pre-} annotation, which
18540 denotes the beginning of any prompt which is being output, a plain
18541 annotation, which denotes the end of the prompt, and then a @code{post-}
18542 annotation which denotes the end of any echo which may (or may not) be
18543 associated with the input. For example, the @code{prompt} input type
18544 features the following annotations:
18552 The input types are
18557 @findex post-prompt
18559 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18561 @findex pre-commands
18563 @findex post-commands
18565 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18566 command. The annotations are repeated for each command which is input.
18568 @findex pre-overload-choice
18569 @findex overload-choice
18570 @findex post-overload-choice
18571 @item overload-choice
18572 When @value{GDBN} wants the user to select between various overloaded functions.
18578 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18580 @findex pre-prompt-for-continue
18581 @findex prompt-for-continue
18582 @findex post-prompt-for-continue
18583 @item prompt-for-continue
18584 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18585 expect this to work well; instead use @code{set height 0} to disable
18586 prompting. This is because the counting of lines is buggy in the
18587 presence of annotations.
18592 @cindex annotations for errors, warnings and interrupts
18599 This annotation occurs right before @value{GDBN} responds to an interrupt.
18606 This annotation occurs right before @value{GDBN} responds to an error.
18608 Quit and error annotations indicate that any annotations which @value{GDBN} was
18609 in the middle of may end abruptly. For example, if a
18610 @code{value-history-begin} annotation is followed by a @code{error}, one
18611 cannot expect to receive the matching @code{value-history-end}. One
18612 cannot expect not to receive it either, however; an error annotation
18613 does not necessarily mean that @value{GDBN} is immediately returning all the way
18616 @findex error-begin
18617 A quit or error annotation may be preceded by
18623 Any output between that and the quit or error annotation is the error
18626 Warning messages are not yet annotated.
18627 @c If we want to change that, need to fix warning(), type_error(),
18628 @c range_error(), and possibly other places.
18630 @node Breakpoint Info
18631 @section Information on Breakpoints
18633 @cindex annotations for breakpoints
18634 The output from the @code{info breakpoints} command is annotated as follows:
18636 @findex breakpoints-headers
18637 @findex breakpoints-table
18639 ^Z^Zbreakpoints-headers
18641 ^Z^Zbreakpoints-table
18645 where @var{header-entry} has the same syntax as an entry (see below) but
18646 instead of containing data, it contains strings which are intended to
18647 convey the meaning of each field to the user. This is followed by any
18648 number of entries. If a field does not apply for this entry, it is
18649 omitted. Fields may contain trailing whitespace. Each entry consists
18678 Note that @var{address} is intended for user consumption---the syntax
18679 varies depending on the language.
18681 The output ends with
18683 @findex breakpoints-table-end
18685 ^Z^Zbreakpoints-table-end
18689 @section Invalidation Notices
18691 @cindex annotations for invalidation messages
18692 The following annotations say that certain pieces of state may have
18696 @findex frames-invalid
18697 @item ^Z^Zframes-invalid
18699 The frames (for example, output from the @code{backtrace} command) may
18702 @findex breakpoints-invalid
18703 @item ^Z^Zbreakpoints-invalid
18705 The breakpoints may have changed. For example, the user just added or
18706 deleted a breakpoint.
18709 @node Annotations for Running
18710 @section Running the Program
18711 @cindex annotations for running programs
18715 When the program starts executing due to a @value{GDBN} command such as
18716 @code{step} or @code{continue},
18722 is output. When the program stops,
18728 is output. Before the @code{stopped} annotation, a variety of
18729 annotations describe how the program stopped.
18733 @item ^Z^Zexited @var{exit-status}
18734 The program exited, and @var{exit-status} is the exit status (zero for
18735 successful exit, otherwise nonzero).
18738 @findex signal-name
18739 @findex signal-name-end
18740 @findex signal-string
18741 @findex signal-string-end
18742 @item ^Z^Zsignalled
18743 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18744 annotation continues:
18750 ^Z^Zsignal-name-end
18754 ^Z^Zsignal-string-end
18759 where @var{name} is the name of the signal, such as @code{SIGILL} or
18760 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18761 as @code{Illegal Instruction} or @code{Segmentation fault}.
18762 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18763 user's benefit and have no particular format.
18767 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18768 just saying that the program received the signal, not that it was
18769 terminated with it.
18772 @item ^Z^Zbreakpoint @var{number}
18773 The program hit breakpoint number @var{number}.
18776 @item ^Z^Zwatchpoint @var{number}
18777 The program hit watchpoint number @var{number}.
18780 @node Source Annotations
18781 @section Displaying Source
18782 @cindex annotations for source display
18785 The following annotation is used instead of displaying source code:
18788 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18791 where @var{filename} is an absolute file name indicating which source
18792 file, @var{line} is the line number within that file (where 1 is the
18793 first line in the file), @var{character} is the character position
18794 within the file (where 0 is the first character in the file) (for most
18795 debug formats this will necessarily point to the beginning of a line),
18796 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18797 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18798 @var{addr} is the address in the target program associated with the
18799 source which is being displayed. @var{addr} is in the form @samp{0x}
18800 followed by one or more lowercase hex digits (note that this does not
18801 depend on the language).
18804 @section Annotations We Might Want in the Future
18808 the target might have changed (registers, heap contents, or
18809 execution status). For performance, we might eventually want
18810 to hit `registers-invalid' and `all-registers-invalid' with
18813 - systematic annotation for set/show parameters (including
18814 invalidation notices).
18816 - similarly, `info' returns a list of candidates for invalidation
18821 @chapter Reporting Bugs in @value{GDBN}
18822 @cindex bugs in @value{GDBN}
18823 @cindex reporting bugs in @value{GDBN}
18825 Your bug reports play an essential role in making @value{GDBN} reliable.
18827 Reporting a bug may help you by bringing a solution to your problem, or it
18828 may not. But in any case the principal function of a bug report is to help
18829 the entire community by making the next version of @value{GDBN} work better. Bug
18830 reports are your contribution to the maintenance of @value{GDBN}.
18832 In order for a bug report to serve its purpose, you must include the
18833 information that enables us to fix the bug.
18836 * Bug Criteria:: Have you found a bug?
18837 * Bug Reporting:: How to report bugs
18841 @section Have you found a bug?
18842 @cindex bug criteria
18844 If you are not sure whether you have found a bug, here are some guidelines:
18847 @cindex fatal signal
18848 @cindex debugger crash
18849 @cindex crash of debugger
18851 If the debugger gets a fatal signal, for any input whatever, that is a
18852 @value{GDBN} bug. Reliable debuggers never crash.
18854 @cindex error on valid input
18856 If @value{GDBN} produces an error message for valid input, that is a
18857 bug. (Note that if you're cross debugging, the problem may also be
18858 somewhere in the connection to the target.)
18860 @cindex invalid input
18862 If @value{GDBN} does not produce an error message for invalid input,
18863 that is a bug. However, you should note that your idea of
18864 ``invalid input'' might be our idea of ``an extension'' or ``support
18865 for traditional practice''.
18868 If you are an experienced user of debugging tools, your suggestions
18869 for improvement of @value{GDBN} are welcome in any case.
18872 @node Bug Reporting
18873 @section How to report bugs
18874 @cindex bug reports
18875 @cindex @value{GDBN} bugs, reporting
18877 A number of companies and individuals offer support for @sc{gnu} products.
18878 If you obtained @value{GDBN} from a support organization, we recommend you
18879 contact that organization first.
18881 You can find contact information for many support companies and
18882 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18884 @c should add a web page ref...
18886 In any event, we also recommend that you submit bug reports for
18887 @value{GDBN}. The prefered method is to submit them directly using
18888 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18889 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18892 @strong{Do not send bug reports to @samp{info-gdb}, or to
18893 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18894 not want to receive bug reports. Those that do have arranged to receive
18897 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18898 serves as a repeater. The mailing list and the newsgroup carry exactly
18899 the same messages. Often people think of posting bug reports to the
18900 newsgroup instead of mailing them. This appears to work, but it has one
18901 problem which can be crucial: a newsgroup posting often lacks a mail
18902 path back to the sender. Thus, if we need to ask for more information,
18903 we may be unable to reach you. For this reason, it is better to send
18904 bug reports to the mailing list.
18906 The fundamental principle of reporting bugs usefully is this:
18907 @strong{report all the facts}. If you are not sure whether to state a
18908 fact or leave it out, state it!
18910 Often people omit facts because they think they know what causes the
18911 problem and assume that some details do not matter. Thus, you might
18912 assume that the name of the variable you use in an example does not matter.
18913 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18914 stray memory reference which happens to fetch from the location where that
18915 name is stored in memory; perhaps, if the name were different, the contents
18916 of that location would fool the debugger into doing the right thing despite
18917 the bug. Play it safe and give a specific, complete example. That is the
18918 easiest thing for you to do, and the most helpful.
18920 Keep in mind that the purpose of a bug report is to enable us to fix the
18921 bug. It may be that the bug has been reported previously, but neither
18922 you nor we can know that unless your bug report is complete and
18925 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18926 bell?'' Those bug reports are useless, and we urge everyone to
18927 @emph{refuse to respond to them} except to chide the sender to report
18930 To enable us to fix the bug, you should include all these things:
18934 The version of @value{GDBN}. @value{GDBN} announces it if you start
18935 with no arguments; you can also print it at any time using @code{show
18938 Without this, we will not know whether there is any point in looking for
18939 the bug in the current version of @value{GDBN}.
18942 The type of machine you are using, and the operating system name and
18946 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18947 ``@value{GCC}--2.8.1''.
18950 What compiler (and its version) was used to compile the program you are
18951 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18952 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18953 information; for other compilers, see the documentation for those
18957 The command arguments you gave the compiler to compile your example and
18958 observe the bug. For example, did you use @samp{-O}? To guarantee
18959 you will not omit something important, list them all. A copy of the
18960 Makefile (or the output from make) is sufficient.
18962 If we were to try to guess the arguments, we would probably guess wrong
18963 and then we might not encounter the bug.
18966 A complete input script, and all necessary source files, that will
18970 A description of what behavior you observe that you believe is
18971 incorrect. For example, ``It gets a fatal signal.''
18973 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18974 will certainly notice it. But if the bug is incorrect output, we might
18975 not notice unless it is glaringly wrong. You might as well not give us
18976 a chance to make a mistake.
18978 Even if the problem you experience is a fatal signal, you should still
18979 say so explicitly. Suppose something strange is going on, such as, your
18980 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18981 the C library on your system. (This has happened!) Your copy might
18982 crash and ours would not. If you told us to expect a crash, then when
18983 ours fails to crash, we would know that the bug was not happening for
18984 us. If you had not told us to expect a crash, then we would not be able
18985 to draw any conclusion from our observations.
18988 If you wish to suggest changes to the @value{GDBN} source, send us context
18989 diffs. If you even discuss something in the @value{GDBN} source, refer to
18990 it by context, not by line number.
18992 The line numbers in our development sources will not match those in your
18993 sources. Your line numbers would convey no useful information to us.
18997 Here are some things that are not necessary:
19001 A description of the envelope of the bug.
19003 Often people who encounter a bug spend a lot of time investigating
19004 which changes to the input file will make the bug go away and which
19005 changes will not affect it.
19007 This is often time consuming and not very useful, because the way we
19008 will find the bug is by running a single example under the debugger
19009 with breakpoints, not by pure deduction from a series of examples.
19010 We recommend that you save your time for something else.
19012 Of course, if you can find a simpler example to report @emph{instead}
19013 of the original one, that is a convenience for us. Errors in the
19014 output will be easier to spot, running under the debugger will take
19015 less time, and so on.
19017 However, simplification is not vital; if you do not want to do this,
19018 report the bug anyway and send us the entire test case you used.
19021 A patch for the bug.
19023 A patch for the bug does help us if it is a good one. But do not omit
19024 the necessary information, such as the test case, on the assumption that
19025 a patch is all we need. We might see problems with your patch and decide
19026 to fix the problem another way, or we might not understand it at all.
19028 Sometimes with a program as complicated as @value{GDBN} it is very hard to
19029 construct an example that will make the program follow a certain path
19030 through the code. If you do not send us the example, we will not be able
19031 to construct one, so we will not be able to verify that the bug is fixed.
19033 And if we cannot understand what bug you are trying to fix, or why your
19034 patch should be an improvement, we will not install it. A test case will
19035 help us to understand.
19038 A guess about what the bug is or what it depends on.
19040 Such guesses are usually wrong. Even we cannot guess right about such
19041 things without first using the debugger to find the facts.
19044 @c The readline documentation is distributed with the readline code
19045 @c and consists of the two following files:
19047 @c inc-hist.texinfo
19048 @c Use -I with makeinfo to point to the appropriate directory,
19049 @c environment var TEXINPUTS with TeX.
19050 @include rluser.texinfo
19051 @include inc-hist.texinfo
19054 @node Formatting Documentation
19055 @appendix Formatting Documentation
19057 @cindex @value{GDBN} reference card
19058 @cindex reference card
19059 The @value{GDBN} 4 release includes an already-formatted reference card, ready
19060 for printing with PostScript or Ghostscript, in the @file{gdb}
19061 subdirectory of the main source directory@footnote{In
19062 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
19063 release.}. If you can use PostScript or Ghostscript with your printer,
19064 you can print the reference card immediately with @file{refcard.ps}.
19066 The release also includes the source for the reference card. You
19067 can format it, using @TeX{}, by typing:
19073 The @value{GDBN} reference card is designed to print in @dfn{landscape}
19074 mode on US ``letter'' size paper;
19075 that is, on a sheet 11 inches wide by 8.5 inches
19076 high. You will need to specify this form of printing as an option to
19077 your @sc{dvi} output program.
19079 @cindex documentation
19081 All the documentation for @value{GDBN} comes as part of the machine-readable
19082 distribution. The documentation is written in Texinfo format, which is
19083 a documentation system that uses a single source file to produce both
19084 on-line information and a printed manual. You can use one of the Info
19085 formatting commands to create the on-line version of the documentation
19086 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
19088 @value{GDBN} includes an already formatted copy of the on-line Info
19089 version of this manual in the @file{gdb} subdirectory. The main Info
19090 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
19091 subordinate files matching @samp{gdb.info*} in the same directory. If
19092 necessary, you can print out these files, or read them with any editor;
19093 but they are easier to read using the @code{info} subsystem in @sc{gnu}
19094 Emacs or the standalone @code{info} program, available as part of the
19095 @sc{gnu} Texinfo distribution.
19097 If you want to format these Info files yourself, you need one of the
19098 Info formatting programs, such as @code{texinfo-format-buffer} or
19101 If you have @code{makeinfo} installed, and are in the top level
19102 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
19103 version @value{GDBVN}), you can make the Info file by typing:
19110 If you want to typeset and print copies of this manual, you need @TeX{},
19111 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
19112 Texinfo definitions file.
19114 @TeX{} is a typesetting program; it does not print files directly, but
19115 produces output files called @sc{dvi} files. To print a typeset
19116 document, you need a program to print @sc{dvi} files. If your system
19117 has @TeX{} installed, chances are it has such a program. The precise
19118 command to use depends on your system; @kbd{lpr -d} is common; another
19119 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
19120 require a file name without any extension or a @samp{.dvi} extension.
19122 @TeX{} also requires a macro definitions file called
19123 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
19124 written in Texinfo format. On its own, @TeX{} cannot either read or
19125 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
19126 and is located in the @file{gdb-@var{version-number}/texinfo}
19129 If you have @TeX{} and a @sc{dvi} printer program installed, you can
19130 typeset and print this manual. First switch to the the @file{gdb}
19131 subdirectory of the main source directory (for example, to
19132 @file{gdb-@value{GDBVN}/gdb}) and type:
19138 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19140 @node Installing GDB
19141 @appendix Installing @value{GDBN}
19142 @cindex configuring @value{GDBN}
19143 @cindex installation
19144 @cindex configuring @value{GDBN}, and source tree subdirectories
19146 @value{GDBN} comes with a @code{configure} script that automates the process
19147 of preparing @value{GDBN} for installation; you can then use @code{make} to
19148 build the @code{gdb} program.
19150 @c irrelevant in info file; it's as current as the code it lives with.
19151 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19152 look at the @file{README} file in the sources; we may have improved the
19153 installation procedures since publishing this manual.}
19156 The @value{GDBN} distribution includes all the source code you need for
19157 @value{GDBN} in a single directory, whose name is usually composed by
19158 appending the version number to @samp{gdb}.
19160 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19161 @file{gdb-@value{GDBVN}} directory. That directory contains:
19164 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19165 script for configuring @value{GDBN} and all its supporting libraries
19167 @item gdb-@value{GDBVN}/gdb
19168 the source specific to @value{GDBN} itself
19170 @item gdb-@value{GDBVN}/bfd
19171 source for the Binary File Descriptor library
19173 @item gdb-@value{GDBVN}/include
19174 @sc{gnu} include files
19176 @item gdb-@value{GDBVN}/libiberty
19177 source for the @samp{-liberty} free software library
19179 @item gdb-@value{GDBVN}/opcodes
19180 source for the library of opcode tables and disassemblers
19182 @item gdb-@value{GDBVN}/readline
19183 source for the @sc{gnu} command-line interface
19185 @item gdb-@value{GDBVN}/glob
19186 source for the @sc{gnu} filename pattern-matching subroutine
19188 @item gdb-@value{GDBVN}/mmalloc
19189 source for the @sc{gnu} memory-mapped malloc package
19192 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19193 from the @file{gdb-@var{version-number}} source directory, which in
19194 this example is the @file{gdb-@value{GDBVN}} directory.
19196 First switch to the @file{gdb-@var{version-number}} source directory
19197 if you are not already in it; then run @code{configure}. Pass the
19198 identifier for the platform on which @value{GDBN} will run as an
19204 cd gdb-@value{GDBVN}
19205 ./configure @var{host}
19210 where @var{host} is an identifier such as @samp{sun4} or
19211 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19212 (You can often leave off @var{host}; @code{configure} tries to guess the
19213 correct value by examining your system.)
19215 Running @samp{configure @var{host}} and then running @code{make} builds the
19216 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19217 libraries, then @code{gdb} itself. The configured source files, and the
19218 binaries, are left in the corresponding source directories.
19221 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19222 system does not recognize this automatically when you run a different
19223 shell, you may need to run @code{sh} on it explicitly:
19226 sh configure @var{host}
19229 If you run @code{configure} from a directory that contains source
19230 directories for multiple libraries or programs, such as the
19231 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19232 creates configuration files for every directory level underneath (unless
19233 you tell it not to, with the @samp{--norecursion} option).
19235 You should run the @code{configure} script from the top directory in the
19236 source tree, the @file{gdb-@var{version-number}} directory. If you run
19237 @code{configure} from one of the subdirectories, you will configure only
19238 that subdirectory. That is usually not what you want. In particular,
19239 if you run the first @code{configure} from the @file{gdb} subdirectory
19240 of the @file{gdb-@var{version-number}} directory, you will omit the
19241 configuration of @file{bfd}, @file{readline}, and other sibling
19242 directories of the @file{gdb} subdirectory. This leads to build errors
19243 about missing include files such as @file{bfd/bfd.h}.
19245 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19246 However, you should make sure that the shell on your path (named by
19247 the @samp{SHELL} environment variable) is publicly readable. Remember
19248 that @value{GDBN} uses the shell to start your program---some systems refuse to
19249 let @value{GDBN} debug child processes whose programs are not readable.
19252 * Separate Objdir:: Compiling @value{GDBN} in another directory
19253 * Config Names:: Specifying names for hosts and targets
19254 * Configure Options:: Summary of options for configure
19257 @node Separate Objdir
19258 @section Compiling @value{GDBN} in another directory
19260 If you want to run @value{GDBN} versions for several host or target machines,
19261 you need a different @code{gdb} compiled for each combination of
19262 host and target. @code{configure} is designed to make this easy by
19263 allowing you to generate each configuration in a separate subdirectory,
19264 rather than in the source directory. If your @code{make} program
19265 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19266 @code{make} in each of these directories builds the @code{gdb}
19267 program specified there.
19269 To build @code{gdb} in a separate directory, run @code{configure}
19270 with the @samp{--srcdir} option to specify where to find the source.
19271 (You also need to specify a path to find @code{configure}
19272 itself from your working directory. If the path to @code{configure}
19273 would be the same as the argument to @samp{--srcdir}, you can leave out
19274 the @samp{--srcdir} option; it is assumed.)
19276 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19277 separate directory for a Sun 4 like this:
19281 cd gdb-@value{GDBVN}
19284 ../gdb-@value{GDBVN}/configure sun4
19289 When @code{configure} builds a configuration using a remote source
19290 directory, it creates a tree for the binaries with the same structure
19291 (and using the same names) as the tree under the source directory. In
19292 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19293 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19294 @file{gdb-sun4/gdb}.
19296 Make sure that your path to the @file{configure} script has just one
19297 instance of @file{gdb} in it. If your path to @file{configure} looks
19298 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19299 one subdirectory of @value{GDBN}, not the whole package. This leads to
19300 build errors about missing include files such as @file{bfd/bfd.h}.
19302 One popular reason to build several @value{GDBN} configurations in separate
19303 directories is to configure @value{GDBN} for cross-compiling (where
19304 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19305 programs that run on another machine---the @dfn{target}).
19306 You specify a cross-debugging target by
19307 giving the @samp{--target=@var{target}} option to @code{configure}.
19309 When you run @code{make} to build a program or library, you must run
19310 it in a configured directory---whatever directory you were in when you
19311 called @code{configure} (or one of its subdirectories).
19313 The @code{Makefile} that @code{configure} generates in each source
19314 directory also runs recursively. If you type @code{make} in a source
19315 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19316 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19317 will build all the required libraries, and then build GDB.
19319 When you have multiple hosts or targets configured in separate
19320 directories, you can run @code{make} on them in parallel (for example,
19321 if they are NFS-mounted on each of the hosts); they will not interfere
19325 @section Specifying names for hosts and targets
19327 The specifications used for hosts and targets in the @code{configure}
19328 script are based on a three-part naming scheme, but some short predefined
19329 aliases are also supported. The full naming scheme encodes three pieces
19330 of information in the following pattern:
19333 @var{architecture}-@var{vendor}-@var{os}
19336 For example, you can use the alias @code{sun4} as a @var{host} argument,
19337 or as the value for @var{target} in a @code{--target=@var{target}}
19338 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19340 The @code{configure} script accompanying @value{GDBN} does not provide
19341 any query facility to list all supported host and target names or
19342 aliases. @code{configure} calls the Bourne shell script
19343 @code{config.sub} to map abbreviations to full names; you can read the
19344 script, if you wish, or you can use it to test your guesses on
19345 abbreviations---for example:
19348 % sh config.sub i386-linux
19350 % sh config.sub alpha-linux
19351 alpha-unknown-linux-gnu
19352 % sh config.sub hp9k700
19354 % sh config.sub sun4
19355 sparc-sun-sunos4.1.1
19356 % sh config.sub sun3
19357 m68k-sun-sunos4.1.1
19358 % sh config.sub i986v
19359 Invalid configuration `i986v': machine `i986v' not recognized
19363 @code{config.sub} is also distributed in the @value{GDBN} source
19364 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19366 @node Configure Options
19367 @section @code{configure} options
19369 Here is a summary of the @code{configure} options and arguments that
19370 are most often useful for building @value{GDBN}. @code{configure} also has
19371 several other options not listed here. @inforef{What Configure
19372 Does,,configure.info}, for a full explanation of @code{configure}.
19375 configure @r{[}--help@r{]}
19376 @r{[}--prefix=@var{dir}@r{]}
19377 @r{[}--exec-prefix=@var{dir}@r{]}
19378 @r{[}--srcdir=@var{dirname}@r{]}
19379 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19380 @r{[}--target=@var{target}@r{]}
19385 You may introduce options with a single @samp{-} rather than
19386 @samp{--} if you prefer; but you may abbreviate option names if you use
19391 Display a quick summary of how to invoke @code{configure}.
19393 @item --prefix=@var{dir}
19394 Configure the source to install programs and files under directory
19397 @item --exec-prefix=@var{dir}
19398 Configure the source to install programs under directory
19401 @c avoid splitting the warning from the explanation:
19403 @item --srcdir=@var{dirname}
19404 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19405 @code{make} that implements the @code{VPATH} feature.}@*
19406 Use this option to make configurations in directories separate from the
19407 @value{GDBN} source directories. Among other things, you can use this to
19408 build (or maintain) several configurations simultaneously, in separate
19409 directories. @code{configure} writes configuration specific files in
19410 the current directory, but arranges for them to use the source in the
19411 directory @var{dirname}. @code{configure} creates directories under
19412 the working directory in parallel to the source directories below
19415 @item --norecursion
19416 Configure only the directory level where @code{configure} is executed; do not
19417 propagate configuration to subdirectories.
19419 @item --target=@var{target}
19420 Configure @value{GDBN} for cross-debugging programs running on the specified
19421 @var{target}. Without this option, @value{GDBN} is configured to debug
19422 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19424 There is no convenient way to generate a list of all available targets.
19426 @item @var{host} @dots{}
19427 Configure @value{GDBN} to run on the specified @var{host}.
19429 There is no convenient way to generate a list of all available hosts.
19432 There are many other options available as well, but they are generally
19433 needed for special purposes only.
19435 @node Maintenance Commands
19436 @appendix Maintenance Commands
19437 @cindex maintenance commands
19438 @cindex internal commands
19440 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19441 includes a number of commands intended for @value{GDBN} developers.
19442 These commands are provided here for reference.
19445 @kindex maint info breakpoints
19446 @item @anchor{maint info breakpoints}maint info breakpoints
19447 Using the same format as @samp{info breakpoints}, display both the
19448 breakpoints you've set explicitly, and those @value{GDBN} is using for
19449 internal purposes. Internal breakpoints are shown with negative
19450 breakpoint numbers. The type column identifies what kind of breakpoint
19455 Normal, explicitly set breakpoint.
19458 Normal, explicitly set watchpoint.
19461 Internal breakpoint, used to handle correctly stepping through
19462 @code{longjmp} calls.
19464 @item longjmp resume
19465 Internal breakpoint at the target of a @code{longjmp}.
19468 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19471 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19474 Shared library events.
19478 @kindex maint internal-error
19479 @kindex maint internal-warning
19480 @item maint internal-error
19481 @itemx maint internal-warning
19482 Cause @value{GDBN} to call the internal function @code{internal_error}
19483 or @code{internal_warning} and hence behave as though an internal error
19484 or internal warning has been detected. In addition to reporting the
19485 internal problem, these functions give the user the opportunity to
19486 either quit @value{GDBN} or create a core file of the current
19487 @value{GDBN} session.
19490 (gdb) @kbd{maint internal-error testing, 1, 2}
19491 @dots{}/maint.c:121: internal-error: testing, 1, 2
19492 A problem internal to GDB has been detected. Further
19493 debugging may prove unreliable.
19494 Quit this debugging session? (y or n) @kbd{n}
19495 Create a core file? (y or n) @kbd{n}
19499 Takes an optional parameter that is used as the text of the error or
19502 @kindex maint print dummy-frames
19503 @item maint print dummy-frames
19505 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19510 (gdb) @kbd{print add(2,3)}
19511 Breakpoint 2, add (a=2, b=3) at @dots{}
19513 The program being debugged stopped while in a function called from GDB.
19515 (gdb) @kbd{maint print dummy-frames}
19516 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19517 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19518 call_lo=0x01014000 call_hi=0x01014001
19522 Takes an optional file parameter.
19524 @kindex maint print registers
19525 @kindex maint print raw-registers
19526 @kindex maint print cooked-registers
19527 @kindex maint print register-groups
19528 @item maint print registers
19529 @itemx maint print raw-registers
19530 @itemx maint print cooked-registers
19531 @itemx maint print register-groups
19532 Print @value{GDBN}'s internal register data structures.
19534 The command @code{maint print raw-registers} includes the contents of
19535 the raw register cache; the command @code{maint print cooked-registers}
19536 includes the (cooked) value of all registers; and the command
19537 @code{maint print register-groups} includes the groups that each
19538 register is a member of. @xref{Registers,, Registers, gdbint,
19539 @value{GDBN} Internals}.
19541 Takes an optional file parameter.
19543 @kindex maint print reggroups
19544 @item maint print reggroups
19545 Print @value{GDBN}'s internal register group data structures.
19547 Takes an optional file parameter.
19550 (gdb) @kbd{maint print reggroups}
19561 @kindex maint set profile
19562 @kindex maint show profile
19563 @cindex profiling GDB
19564 @item maint set profile
19565 @itemx maint show profile
19566 Control profiling of @value{GDBN}.
19568 Profiling will be disabled until you use the @samp{maint set profile}
19569 command to enable it. When you enable profiling, the system will begin
19570 collecting timing and execution count data; when you disable profiling or
19571 exit @value{GDBN}, the results will be written to a log file. Remember that
19572 if you use profiling, @value{GDBN} will overwrite the profiling log file
19573 (often called @file{gmon.out}). If you have a record of important profiling
19574 data in a @file{gmon.out} file, be sure to move it to a safe location.
19576 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19577 compiled with the @samp{-pg} compiler option.
19582 @node Remote Protocol
19583 @appendix @value{GDBN} Remote Serial Protocol
19588 * Stop Reply Packets::
19589 * General Query Packets::
19590 * Register Packet Format::
19592 * File-I/O remote protocol extension::
19598 There may be occasions when you need to know something about the
19599 protocol---for example, if there is only one serial port to your target
19600 machine, you might want your program to do something special if it
19601 recognizes a packet meant for @value{GDBN}.
19603 In the examples below, @samp{->} and @samp{<-} are used to indicate
19604 transmitted and received data respectfully.
19606 @cindex protocol, @value{GDBN} remote serial
19607 @cindex serial protocol, @value{GDBN} remote
19608 @cindex remote serial protocol
19609 All @value{GDBN} commands and responses (other than acknowledgments) are
19610 sent as a @var{packet}. A @var{packet} is introduced with the character
19611 @samp{$}, the actual @var{packet-data}, and the terminating character
19612 @samp{#} followed by a two-digit @var{checksum}:
19615 @code{$}@var{packet-data}@code{#}@var{checksum}
19619 @cindex checksum, for @value{GDBN} remote
19621 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19622 characters between the leading @samp{$} and the trailing @samp{#} (an
19623 eight bit unsigned checksum).
19625 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19626 specification also included an optional two-digit @var{sequence-id}:
19629 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19632 @cindex sequence-id, for @value{GDBN} remote
19634 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19635 has never output @var{sequence-id}s. Stubs that handle packets added
19636 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19638 @cindex acknowledgment, for @value{GDBN} remote
19639 When either the host or the target machine receives a packet, the first
19640 response expected is an acknowledgment: either @samp{+} (to indicate
19641 the package was received correctly) or @samp{-} (to request
19645 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19650 The host (@value{GDBN}) sends @var{command}s, and the target (the
19651 debugging stub incorporated in your program) sends a @var{response}. In
19652 the case of step and continue @var{command}s, the response is only sent
19653 when the operation has completed (the target has again stopped).
19655 @var{packet-data} consists of a sequence of characters with the
19656 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19659 Fields within the packet should be separated using @samp{,} @samp{;} or
19660 @cindex remote protocol, field separator
19661 @samp{:}. Except where otherwise noted all numbers are represented in
19662 @sc{hex} with leading zeros suppressed.
19664 Implementors should note that prior to @value{GDBN} 5.0, the character
19665 @samp{:} could not appear as the third character in a packet (as it
19666 would potentially conflict with the @var{sequence-id}).
19668 Response @var{data} can be run-length encoded to save space. A @samp{*}
19669 means that the next character is an @sc{ascii} encoding giving a repeat count
19670 which stands for that many repetitions of the character preceding the
19671 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19672 where @code{n >=3} (which is where rle starts to win). The printable
19673 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19674 value greater than 126 should not be used.
19676 Some remote systems have used a different run-length encoding mechanism
19677 loosely refered to as the cisco encoding. Following the @samp{*}
19678 character are two hex digits that indicate the size of the packet.
19685 means the same as "0000".
19687 The error response returned for some packets includes a two character
19688 error number. That number is not well defined.
19690 For any @var{command} not supported by the stub, an empty response
19691 (@samp{$#00}) should be returned. That way it is possible to extend the
19692 protocol. A newer @value{GDBN} can tell if a packet is supported based
19695 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19696 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19702 The following table provides a complete list of all currently defined
19703 @var{command}s and their corresponding response @var{data}.
19707 @item @code{!} --- extended mode
19708 @cindex @code{!} packet
19710 Enable extended mode. In extended mode, the remote server is made
19711 persistent. The @samp{R} packet is used to restart the program being
19717 The remote target both supports and has enabled extended mode.
19720 @item @code{?} --- last signal
19721 @cindex @code{?} packet
19723 Indicate the reason the target halted. The reply is the same as for
19727 @xref{Stop Reply Packets}, for the reply specifications.
19729 @item @code{a} --- reserved
19731 Reserved for future use.
19733 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19734 @cindex @code{A} packet
19736 Initialized @samp{argv[]} array passed into program. @var{arglen}
19737 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19738 See @code{gdbserver} for more details.
19746 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19747 @cindex @code{b} packet
19749 Change the serial line speed to @var{baud}.
19751 JTC: @emph{When does the transport layer state change? When it's
19752 received, or after the ACK is transmitted. In either case, there are
19753 problems if the command or the acknowledgment packet is dropped.}
19755 Stan: @emph{If people really wanted to add something like this, and get
19756 it working for the first time, they ought to modify ser-unix.c to send
19757 some kind of out-of-band message to a specially-setup stub and have the
19758 switch happen "in between" packets, so that from remote protocol's point
19759 of view, nothing actually happened.}
19761 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19762 @cindex @code{B} packet
19764 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19765 breakpoint at @var{addr}.
19767 This packet has been replaced by the @samp{Z} and @samp{z} packets
19768 (@pxref{insert breakpoint or watchpoint packet}).
19770 @item @code{c}@var{addr} --- continue
19771 @cindex @code{c} packet
19773 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19777 @xref{Stop Reply Packets}, for the reply specifications.
19779 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19780 @cindex @code{C} packet
19782 Continue with signal @var{sig} (hex signal number). If
19783 @code{;}@var{addr} is omitted, resume at same address.
19786 @xref{Stop Reply Packets}, for the reply specifications.
19788 @item @code{d} --- toggle debug @strong{(deprecated)}
19789 @cindex @code{d} packet
19793 @item @code{D} --- detach
19794 @cindex @code{D} packet
19796 Detach @value{GDBN} from the remote system. Sent to the remote target
19797 before @value{GDBN} disconnects via the @code{detach} command.
19801 @item @emph{no response}
19802 @value{GDBN} does not check for any response after sending this packet.
19805 @item @code{e} --- reserved
19807 Reserved for future use.
19809 @item @code{E} --- reserved
19811 Reserved for future use.
19813 @item @code{f} --- reserved
19815 Reserved for future use.
19817 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19818 @cindex @code{F} packet
19820 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19821 sent by the target. This is part of the File-I/O protocol extension.
19822 @xref{File-I/O remote protocol extension}, for the specification.
19824 @item @code{g} --- read registers
19825 @anchor{read registers packet}
19826 @cindex @code{g} packet
19828 Read general registers.
19832 @item @var{XX@dots{}}
19833 Each byte of register data is described by two hex digits. The bytes
19834 with the register are transmitted in target byte order. The size of
19835 each register and their position within the @samp{g} @var{packet} are
19836 determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE}
19837 and @var{REGISTER_NAME} macros. The specification of several standard
19838 @code{g} packets is specified below.
19843 @item @code{G}@var{XX@dots{}} --- write regs
19844 @cindex @code{G} packet
19846 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19857 @item @code{h} --- reserved
19859 Reserved for future use.
19861 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19862 @cindex @code{H} packet
19864 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19865 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19866 should be @samp{c} for step and continue operations, @samp{g} for other
19867 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19868 the threads, a thread number, or zero which means pick any thread.
19879 @c 'H': How restrictive (or permissive) is the thread model. If a
19880 @c thread is selected and stopped, are other threads allowed
19881 @c to continue to execute? As I mentioned above, I think the
19882 @c semantics of each command when a thread is selected must be
19883 @c described. For example:
19885 @c 'g': If the stub supports threads and a specific thread is
19886 @c selected, returns the register block from that thread;
19887 @c otherwise returns current registers.
19889 @c 'G' If the stub supports threads and a specific thread is
19890 @c selected, sets the registers of the register block of
19891 @c that thread; otherwise sets current registers.
19893 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19894 @anchor{cycle step packet}
19895 @cindex @code{i} packet
19897 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19898 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19899 step starting at that address.
19901 @item @code{I} --- signal then cycle step @strong{(reserved)}
19902 @cindex @code{I} packet
19904 @xref{step with signal packet}. @xref{cycle step packet}.
19906 @item @code{j} --- reserved
19908 Reserved for future use.
19910 @item @code{J} --- reserved
19912 Reserved for future use.
19914 @item @code{k} --- kill request
19915 @cindex @code{k} packet
19917 FIXME: @emph{There is no description of how to operate when a specific
19918 thread context has been selected (i.e.@: does 'k' kill only that
19921 @item @code{K} --- reserved
19923 Reserved for future use.
19925 @item @code{l} --- reserved
19927 Reserved for future use.
19929 @item @code{L} --- reserved
19931 Reserved for future use.
19933 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19934 @cindex @code{m} packet
19936 Read @var{length} bytes of memory starting at address @var{addr}.
19937 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19938 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19939 transfer mechanism is needed.}
19943 @item @var{XX@dots{}}
19944 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19945 to read only part of the data. Neither @value{GDBN} nor the stub assume
19946 that sized memory transfers are assumed using word aligned
19947 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19953 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19954 @cindex @code{M} packet
19956 Write @var{length} bytes of memory starting at address @var{addr}.
19957 @var{XX@dots{}} is the data.
19964 for an error (this includes the case where only part of the data was
19968 @item @code{n} --- reserved
19970 Reserved for future use.
19972 @item @code{N} --- reserved
19974 Reserved for future use.
19976 @item @code{o} --- reserved
19978 Reserved for future use.
19980 @item @code{O} --- reserved
19982 Reserved for future use.
19984 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19985 @cindex @code{p} packet
19987 @xref{write register packet}.
19991 @item @var{r@dots{}.}
19992 The hex encoded value of the register in target byte order.
19995 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19996 @anchor{write register packet}
19997 @cindex @code{P} packet
19999 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
20000 digits for each byte in the register (target byte order).
20010 @item @code{q}@var{query} --- general query
20011 @anchor{general query packet}
20012 @cindex @code{q} packet
20014 Request info about @var{query}. In general @value{GDBN} queries have a
20015 leading upper case letter. Custom vendor queries should use a company
20016 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
20017 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
20018 that they match the full @var{query} name.
20022 @item @var{XX@dots{}}
20023 Hex encoded data from query. The reply can not be empty.
20027 Indicating an unrecognized @var{query}.
20030 @item @code{Q}@var{var}@code{=}@var{val} --- general set
20031 @cindex @code{Q} packet
20033 Set value of @var{var} to @var{val}.
20035 @xref{general query packet}, for a discussion of naming conventions.
20037 @item @code{r} --- reset @strong{(deprecated)}
20038 @cindex @code{r} packet
20040 Reset the entire system.
20042 @item @code{R}@var{XX} --- remote restart
20043 @cindex @code{R} packet
20045 Restart the program being debugged. @var{XX}, while needed, is ignored.
20046 This packet is only available in extended mode.
20050 @item @emph{no reply}
20051 The @samp{R} packet has no reply.
20054 @item @code{s}@var{addr} --- step
20055 @cindex @code{s} packet
20057 @var{addr} is address to resume. If @var{addr} is omitted, resume at
20061 @xref{Stop Reply Packets}, for the reply specifications.
20063 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
20064 @anchor{step with signal packet}
20065 @cindex @code{S} packet
20067 Like @samp{C} but step not continue.
20070 @xref{Stop Reply Packets}, for the reply specifications.
20072 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
20073 @cindex @code{t} packet
20075 Search backwards starting at address @var{addr} for a match with pattern
20076 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
20077 @var{addr} must be at least 3 digits.
20079 @item @code{T}@var{XX} --- thread alive
20080 @cindex @code{T} packet
20082 Find out if the thread XX is alive.
20087 thread is still alive
20092 @item @code{u} --- reserved
20094 Reserved for future use.
20096 @item @code{U} --- reserved
20098 Reserved for future use.
20100 @item @code{v} --- reserved
20102 Reserved for future use.
20104 @item @code{V} --- reserved
20106 Reserved for future use.
20108 @item @code{w} --- reserved
20110 Reserved for future use.
20112 @item @code{W} --- reserved
20114 Reserved for future use.
20116 @item @code{x} --- reserved
20118 Reserved for future use.
20120 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
20121 @cindex @code{X} packet
20123 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
20124 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
20125 escaped using @code{0x7d}.
20135 @item @code{y} --- reserved
20137 Reserved for future use.
20139 @item @code{Y} reserved
20141 Reserved for future use.
20143 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20144 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20145 @anchor{insert breakpoint or watchpoint packet}
20146 @cindex @code{z} packet
20147 @cindex @code{Z} packets
20149 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20150 watchpoint starting at address @var{address} and covering the next
20151 @var{length} bytes.
20153 Each breakpoint and watchpoint packet @var{type} is documented
20156 @emph{Implementation notes: A remote target shall return an empty string
20157 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20158 remote target shall support either both or neither of a given
20159 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20160 avoid potential problems with duplicate packets, the operations should
20161 be implemented in an idempotent way.}
20163 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20164 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20165 @cindex @code{z0} packet
20166 @cindex @code{Z0} packet
20168 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20169 @code{addr} of size @code{length}.
20171 A memory breakpoint is implemented by replacing the instruction at
20172 @var{addr} with a software breakpoint or trap instruction. The
20173 @code{length} is used by targets that indicates the size of the
20174 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20175 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20177 @emph{Implementation note: It is possible for a target to copy or move
20178 code that contains memory breakpoints (e.g., when implementing
20179 overlays). The behavior of this packet, in the presence of such a
20180 target, is not defined.}
20192 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20193 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20194 @cindex @code{z1} packet
20195 @cindex @code{Z1} packet
20197 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20198 address @code{addr} of size @code{length}.
20200 A hardware breakpoint is implemented using a mechanism that is not
20201 dependant on being able to modify the target's memory.
20203 @emph{Implementation note: A hardware breakpoint is not affected by code
20216 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20217 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20218 @cindex @code{z2} packet
20219 @cindex @code{Z2} packet
20221 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20233 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20234 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20235 @cindex @code{z3} packet
20236 @cindex @code{Z3} packet
20238 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20250 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20251 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20252 @cindex @code{z4} packet
20253 @cindex @code{Z4} packet
20255 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20269 @node Stop Reply Packets
20270 @section Stop Reply Packets
20271 @cindex stop reply packets
20273 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20274 receive any of the below as a reply. In the case of the @samp{C},
20275 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20276 when the target halts. In the below the exact meaning of @samp{signal
20277 number} is poorly defined. In general one of the UNIX signal numbering
20278 conventions is used.
20283 @var{AA} is the signal number
20285 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20286 @cindex @code{T} packet reply
20288 @var{AA} = two hex digit signal number; @var{n...} = register number
20289 (hex), @var{r...} = target byte ordered register contents, size defined
20290 by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} =
20291 thread process ID, this is a hex integer; @var{n...} = (@samp{watch} |
20292 @samp{rwatch} | @samp{awatch}, @var{r...} = data address, this is a hex
20293 integer; @var{n...} = other string not starting with valid hex digit.
20294 @value{GDBN} should ignore this @var{n...}, @var{r...} pair and go on
20295 to the next. This way we can extend the protocol.
20299 The process exited, and @var{AA} is the exit status. This is only
20300 applicable to certain targets.
20304 The process terminated with signal @var{AA}.
20306 @item N@var{AA};@var{t@dots{}};@var{d@dots{}};@var{b@dots{}} @strong{(obsolete)}
20308 @var{AA} = signal number; @var{t@dots{}} = address of symbol
20309 @code{_start}; @var{d@dots{}} = base of data section; @var{b@dots{}} =
20310 base of bss section. @emph{Note: only used by Cisco Systems targets.
20311 The difference between this reply and the @samp{qOffsets} query is that
20312 the @samp{N} packet may arrive spontaneously whereas the @samp{qOffsets}
20313 is a query initiated by the host debugger.}
20315 @item O@var{XX@dots{}}
20317 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20318 any time while the program is running and the debugger should continue
20319 to wait for @samp{W}, @samp{T}, etc.
20321 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20323 @var{call-id} is the identifier which says which host system call should
20324 be called. This is just the name of the function. Translation into the
20325 correct system call is only applicable as it's defined in @value{GDBN}.
20326 @xref{File-I/O remote protocol extension}, for a list of implemented
20329 @var{parameter@dots{}} is a list of parameters as defined for this very
20332 The target replies with this packet when it expects @value{GDBN} to call
20333 a host system call on behalf of the target. @value{GDBN} replies with
20334 an appropriate @code{F} packet and keeps up waiting for the next reply
20335 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20336 @samp{s} action is expected to be continued.
20337 @xref{File-I/O remote protocol extension}, for more details.
20341 @node General Query Packets
20342 @section General Query Packets
20344 The following set and query packets have already been defined.
20348 @item @code{q}@code{C} --- current thread
20350 Return the current thread id.
20354 @item @code{QC}@var{pid}
20355 Where @var{pid} is a HEX encoded 16 bit process id.
20357 Any other reply implies the old pid.
20360 @item @code{q}@code{fThreadInfo} -- all thread ids
20362 @code{q}@code{sThreadInfo}
20364 Obtain a list of active thread ids from the target (OS). Since there
20365 may be too many active threads to fit into one reply packet, this query
20366 works iteratively: it may require more than one query/reply sequence to
20367 obtain the entire list of threads. The first query of the sequence will
20368 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20369 sequence will be the @code{qs}@code{ThreadInfo} query.
20371 NOTE: replaces the @code{qL} query (see below).
20375 @item @code{m}@var{id}
20377 @item @code{m}@var{id},@var{id}@dots{}
20378 a comma-separated list of thread ids
20380 (lower case 'el') denotes end of list.
20383 In response to each query, the target will reply with a list of one or
20384 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20385 will respond to each reply with a request for more thread ids (using the
20386 @code{qs} form of the query), until the target responds with @code{l}
20387 (lower-case el, for @code{'last'}).
20389 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20391 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20392 string description of a thread's attributes from the target OS. This
20393 string may contain anything that the target OS thinks is interesting for
20394 @value{GDBN} to tell the user about the thread. The string is displayed
20395 in @value{GDBN}'s @samp{info threads} display. Some examples of
20396 possible thread extra info strings are ``Runnable'', or ``Blocked on
20401 @item @var{XX@dots{}}
20402 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20403 the printable string containing the extra information about the thread's
20407 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20409 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20410 digit) is one to indicate the first query and zero to indicate a
20411 subsequent query; @var{threadcount} (two hex digits) is the maximum
20412 number of threads the response packet can contain; and @var{nextthread}
20413 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20414 returned in the response as @var{argthread}.
20416 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20421 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20422 Where: @var{count} (two hex digits) is the number of threads being
20423 returned; @var{done} (one hex digit) is zero to indicate more threads
20424 and one indicates no further threads; @var{argthreadid} (eight hex
20425 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20426 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20427 digits). See @code{remote.c:parse_threadlist_response()}.
20430 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20434 @item @code{E}@var{NN}
20435 An error (such as memory fault)
20436 @item @code{C}@var{CRC32}
20437 A 32 bit cyclic redundancy check of the specified memory region.
20440 @item @code{q}@code{Offsets} --- query sect offs
20442 Get section offsets that the target used when re-locating the downloaded
20443 image. @emph{Note: while a @code{Bss} offset is included in the
20444 response, @value{GDBN} ignores this and instead applies the @code{Data}
20445 offset to the @code{Bss} section.}
20449 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20452 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20454 Returns information on @var{threadid}. Where: @var{mode} is a hex
20455 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20462 See @code{remote.c:remote_unpack_thread_info_response()}.
20464 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20466 @var{command} (hex encoded) is passed to the local interpreter for
20467 execution. Invalid commands should be reported using the output string.
20468 Before the final result packet, the target may also respond with a
20469 number of intermediate @code{O}@var{output} console output packets.
20470 @emph{Implementors should note that providing access to a stubs's
20471 interpreter may have security implications}.
20476 A command response with no output.
20478 A command response with the hex encoded output string @var{OUTPUT}.
20479 @item @code{E}@var{NN}
20480 Indicate a badly formed request.
20482 When @samp{q}@samp{Rcmd} is not recognized.
20485 @item @code{qSymbol::} --- symbol lookup
20487 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20488 requests. Accept requests from the target for the values of symbols.
20493 The target does not need to look up any (more) symbols.
20494 @item @code{qSymbol:}@var{sym_name}
20495 The target requests the value of symbol @var{sym_name} (hex encoded).
20496 @value{GDBN} may provide the value by using the
20497 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20500 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20502 Set the value of @var{sym_name} to @var{sym_value}.
20504 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20505 target has previously requested.
20507 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20508 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20514 The target does not need to look up any (more) symbols.
20515 @item @code{qSymbol:}@var{sym_name}
20516 The target requests the value of a new symbol @var{sym_name} (hex
20517 encoded). @value{GDBN} will continue to supply the values of symbols
20518 (if available), until the target ceases to request them.
20523 @node Register Packet Format
20524 @section Register Packet Format
20526 The following @samp{g}/@samp{G} packets have previously been defined.
20527 In the below, some thirty-two bit registers are transferred as
20528 sixty-four bits. Those registers should be zero/sign extended (which?)
20529 to fill the space allocated. Register bytes are transfered in target
20530 byte order. The two nibbles within a register byte are transfered
20531 most-significant - least-significant.
20537 All registers are transfered as thirty-two bit quantities in the order:
20538 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20539 registers; fsr; fir; fp.
20543 All registers are transfered as sixty-four bit quantities (including
20544 thirty-two bit registers such as @code{sr}). The ordering is the same
20552 Example sequence of a target being re-started. Notice how the restart
20553 does not get any direct output:
20558 @emph{target restarts}
20561 <- @code{T001:1234123412341234}
20565 Example sequence of a target being stepped by a single instruction:
20568 -> @code{G1445@dots{}}
20573 <- @code{T001:1234123412341234}
20577 <- @code{1455@dots{}}
20581 @node File-I/O remote protocol extension
20582 @section File-I/O remote protocol extension
20583 @cindex File-I/O remote protocol extension
20586 * File-I/O Overview::
20587 * Protocol basics::
20588 * The `F' request packet::
20589 * The `F' reply packet::
20590 * Memory transfer::
20591 * The Ctrl-C message::
20593 * The isatty call::
20594 * The system call::
20595 * List of supported calls::
20596 * Protocol specific representation of datatypes::
20598 * File-I/O Examples::
20601 @node File-I/O Overview
20602 @subsection File-I/O Overview
20603 @cindex file-i/o overview
20605 The File I/O remote protocol extension (short: File-I/O) allows the
20606 target to use the hosts file system and console I/O when calling various
20607 system calls. System calls on the target system are translated into a
20608 remote protocol packet to the host system which then performs the needed
20609 actions and returns with an adequate response packet to the target system.
20610 This simulates file system operations even on targets that lack file systems.
20612 The protocol is defined host- and target-system independent. It uses
20613 it's own independent representation of datatypes and values. Both,
20614 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20615 translating the system dependent values into the unified protocol values
20616 when data is transmitted.
20618 The communication is synchronous. A system call is possible only
20619 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20620 packets. While @value{GDBN} handles the request for a system call,
20621 the target is stopped to allow deterministic access to the target's
20622 memory. Therefore File-I/O is not interuptible by target signals. It
20623 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20625 The target's request to perform a host system call does not finish
20626 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20627 after finishing the system call, the target returns to continuing the
20628 previous activity (continue, step). No additional continue or step
20629 request from @value{GDBN} is required.
20633 <- target requests 'system call X'
20634 target is stopped, @value{GDBN} executes system call
20635 -> GDB returns result
20636 ... target continues, GDB returns to wait for the target
20637 <- target hits breakpoint and sends a Txx packet
20640 The protocol is only used for files on the host file system and
20641 for I/O on the console. Character or block special devices, pipes,
20642 named pipes or sockets or any other communication method on the host
20643 system are not supported by this protocol.
20645 @node Protocol basics
20646 @subsection Protocol basics
20647 @cindex protocol basics, file-i/o
20649 The File-I/O protocol uses the @code{F} packet, as request as well
20650 as as reply packet. Since a File-I/O system call can only occur when
20651 @value{GDBN} is waiting for the continuing or stepping target, the
20652 File-I/O request is a reply that @value{GDBN} has to expect as a result
20653 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20654 This @code{F} packet contains all information needed to allow @value{GDBN}
20655 to call the appropriate host system call:
20659 A unique identifier for the requested system call.
20662 All parameters to the system call. Pointers are given as addresses
20663 in the target memory address space. Pointers to strings are given as
20664 pointer/length pair. Numerical values are given as they are.
20665 Numerical control values are given in a protocol specific representation.
20669 At that point @value{GDBN} has to perform the following actions.
20673 If parameter pointer values are given, which point to data needed as input
20674 to a system call, @value{GDBN} requests this data from the target with a
20675 standard @code{m} packet request. This additional communication has to be
20676 expected by the target implementation and is handled as any other @code{m}
20680 @value{GDBN} translates all value from protocol representation to host
20681 representation as needed. Datatypes are coerced into the host types.
20684 @value{GDBN} calls the system call
20687 It then coerces datatypes back to protocol representation.
20690 If pointer parameters in the request packet point to buffer space in which
20691 a system call is expected to copy data to, the data is transmitted to the
20692 target using a @code{M} or @code{X} packet. This packet has to be expected
20693 by the target implementation and is handled as any other @code{M} or @code{X}
20698 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20699 necessary information for the target to continue. This at least contains
20706 @code{errno}, if has been changed by the system call.
20713 After having done the needed type and value coercion, the target continues
20714 the latest continue or step action.
20716 @node The `F' request packet
20717 @subsection The @code{F} request packet
20718 @cindex file-i/o request packet
20719 @cindex @code{F} request packet
20721 The @code{F} request packet has the following format:
20726 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20729 @var{call-id} is the identifier to indicate the host system call to be called.
20730 This is just the name of the function.
20732 @var{parameter@dots{}} are the parameters to the system call.
20736 Parameters are hexadecimal integer values, either the real values in case
20737 of scalar datatypes, as pointers to target buffer space in case of compound
20738 datatypes and unspecified memory areas or as pointer/length pairs in case
20739 of string parameters. These are appended to the call-id, each separated
20740 from its predecessor by a comma. All values are transmitted in ASCII
20741 string representation, pointer/length pairs separated by a slash.
20743 @node The `F' reply packet
20744 @subsection The @code{F} reply packet
20745 @cindex file-i/o reply packet
20746 @cindex @code{F} reply packet
20748 The @code{F} reply packet has the following format:
20753 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20756 @var{retcode} is the return code of the system call as hexadecimal value.
20758 @var{errno} is the errno set by the call, in protocol specific representation.
20759 This parameter can be omitted if the call was successful.
20761 @var{Ctrl-C flag} is only send if the user requested a break. In this
20762 case, @var{errno} must be send as well, even if the call was successful.
20763 The @var{Ctrl-C flag} itself consists of the character 'C':
20770 or, if the call was interupted before the host call has been performed:
20777 assuming 4 is the protocol specific representation of @code{EINTR}.
20781 @node Memory transfer
20782 @subsection Memory transfer
20783 @cindex memory transfer, in file-i/o protocol
20785 Structured data which is transferred using a memory read or write as e.g.@:
20786 a @code{struct stat} is expected to be in a protocol specific format with
20787 all scalar multibyte datatypes being big endian. This should be done by
20788 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20789 it transfers memory to the target. Transferred pointers to structured
20790 data should point to the already coerced data at any time.
20792 @node The Ctrl-C message
20793 @subsection The Ctrl-C message
20794 @cindex ctrl-c message, in file-i/o protocol
20796 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20797 reply packet. In this case the target should behave, as if it had
20798 gotten a break message. The meaning for the target is ``system call
20799 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20800 (as with a break message) and return to @value{GDBN} with a @code{T02}
20801 packet. In this case, it's important for the target to know, in which
20802 state the system call was interrupted. Since this action is by design
20803 not an atomic operation, we have to differ between two cases:
20807 The system call hasn't been performed on the host yet.
20810 The system call on the host has been finished.
20814 These two states can be distinguished by the target by the value of the
20815 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20816 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20817 on POSIX systems. In any other case, the target may presume that the
20818 system call has been finished --- successful or not --- and should behave
20819 as if the break message arrived right after the system call.
20821 @value{GDBN} must behave reliable. If the system call has not been called
20822 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20823 @code{errno} in the packet. If the system call on the host has been finished
20824 before the user requests a break, the full action must be finshed by
20825 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20826 The @code{F} packet may only be send when either nothing has happened
20827 or the full action has been completed.
20830 @subsection Console I/O
20831 @cindex console i/o as part of file-i/o
20833 By default and if not explicitely closed by the target system, the file
20834 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20835 on the @value{GDBN} console is handled as any other file output operation
20836 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20837 by @value{GDBN} so that after the target read request from file descriptor
20838 0 all following typing is buffered until either one of the following
20843 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20845 system call is treated as finished.
20848 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20852 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20853 character, especially no Ctrl-D is appended to the input.
20857 If the user has typed more characters as fit in the buffer given to
20858 the read call, the trailing characters are buffered in @value{GDBN} until
20859 either another @code{read(0, @dots{})} is requested by the target or debugging
20860 is stopped on users request.
20862 @node The isatty call
20863 @subsection The isatty(3) call
20864 @cindex isatty call, file-i/o protocol
20866 A special case in this protocol is the library call @code{isatty} which
20867 is implemented as it's own call inside of this protocol. It returns
20868 1 to the target if the file descriptor given as parameter is attached
20869 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20870 would require implementing @code{ioctl} and would be more complex than
20873 @node The system call
20874 @subsection The system(3) call
20875 @cindex system call, file-i/o protocol
20877 The other special case in this protocol is the @code{system} call which
20878 is implemented as it's own call, too. @value{GDBN} is taking over the full
20879 task of calling the necessary host calls to perform the @code{system}
20880 call. The return value of @code{system} is simplified before it's returned
20881 to the target. Basically, the only signal transmitted back is @code{EINTR}
20882 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20883 entirely of the exit status of the called command.
20885 Due to security concerns, the @code{system} call is refused to be called
20886 by @value{GDBN} by default. The user has to allow this call explicitly by
20890 @kindex set remote system-call-allowed 1
20891 @item @code{set remote system-call-allowed 1}
20894 Disabling the @code{system} call is done by
20897 @kindex set remote system-call-allowed 0
20898 @item @code{set remote system-call-allowed 0}
20901 The current setting is shown by typing
20904 @kindex show remote system-call-allowed
20905 @item @code{show remote system-call-allowed}
20908 @node List of supported calls
20909 @subsection List of supported calls
20910 @cindex list of supported file-i/o calls
20927 @unnumberedsubsubsec open
20928 @cindex open, file-i/o system call
20932 int open(const char *pathname, int flags);
20933 int open(const char *pathname, int flags, mode_t mode);
20936 Fopen,pathptr/len,flags,mode
20940 @code{flags} is the bitwise or of the following values:
20944 If the file does not exist it will be created. The host
20945 rules apply as far as file ownership and time stamps
20949 When used with O_CREAT, if the file already exists it is
20950 an error and open() fails.
20953 If the file already exists and the open mode allows
20954 writing (O_RDWR or O_WRONLY is given) it will be
20955 truncated to length 0.
20958 The file is opened in append mode.
20961 The file is opened for reading only.
20964 The file is opened for writing only.
20967 The file is opened for reading and writing.
20970 Each other bit is silently ignored.
20975 @code{mode} is the bitwise or of the following values:
20979 User has read permission.
20982 User has write permission.
20985 Group has read permission.
20988 Group has write permission.
20991 Others have read permission.
20994 Others have write permission.
20997 Each other bit is silently ignored.
21002 @exdent Return value:
21003 open returns the new file descriptor or -1 if an error
21011 pathname already exists and O_CREAT and O_EXCL were used.
21014 pathname refers to a directory.
21017 The requested access is not allowed.
21020 pathname was too long.
21023 A directory component in pathname does not exist.
21026 pathname refers to a device, pipe, named pipe or socket.
21029 pathname refers to a file on a read-only filesystem and
21030 write access was requested.
21033 pathname is an invalid pointer value.
21036 No space on device to create the file.
21039 The process already has the maximum number of files open.
21042 The limit on the total number of files open on the system
21046 The call was interrupted by the user.
21050 @unnumberedsubsubsec close
21051 @cindex close, file-i/o system call
21060 @exdent Return value:
21061 close returns zero on success, or -1 if an error occurred.
21068 fd isn't a valid open file descriptor.
21071 The call was interrupted by the user.
21075 @unnumberedsubsubsec read
21076 @cindex read, file-i/o system call
21080 int read(int fd, void *buf, unsigned int count);
21083 Fread,fd,bufptr,count
21085 @exdent Return value:
21086 On success, the number of bytes read is returned.
21087 Zero indicates end of file. If count is zero, read
21088 returns zero as well. On error, -1 is returned.
21095 fd is not a valid file descriptor or is not open for
21099 buf is an invalid pointer value.
21102 The call was interrupted by the user.
21106 @unnumberedsubsubsec write
21107 @cindex write, file-i/o system call
21111 int write(int fd, const void *buf, unsigned int count);
21114 Fwrite,fd,bufptr,count
21116 @exdent Return value:
21117 On success, the number of bytes written are returned.
21118 Zero indicates nothing was written. On error, -1
21126 fd is not a valid file descriptor or is not open for
21130 buf is an invalid pointer value.
21133 An attempt was made to write a file that exceeds the
21134 host specific maximum file size allowed.
21137 No space on device to write the data.
21140 The call was interrupted by the user.
21144 @unnumberedsubsubsec lseek
21145 @cindex lseek, file-i/o system call
21149 long lseek (int fd, long offset, int flag);
21152 Flseek,fd,offset,flag
21155 @code{flag} is one of:
21159 The offset is set to offset bytes.
21162 The offset is set to its current location plus offset
21166 The offset is set to the size of the file plus offset
21171 @exdent Return value:
21172 On success, the resulting unsigned offset in bytes from
21173 the beginning of the file is returned. Otherwise, a
21174 value of -1 is returned.
21181 fd is not a valid open file descriptor.
21184 fd is associated with the @value{GDBN} console.
21187 flag is not a proper value.
21190 The call was interrupted by the user.
21194 @unnumberedsubsubsec rename
21195 @cindex rename, file-i/o system call
21199 int rename(const char *oldpath, const char *newpath);
21202 Frename,oldpathptr/len,newpathptr/len
21204 @exdent Return value:
21205 On success, zero is returned. On error, -1 is returned.
21212 newpath is an existing directory, but oldpath is not a
21216 newpath is a non-empty directory.
21219 oldpath or newpath is a directory that is in use by some
21223 An attempt was made to make a directory a subdirectory
21227 A component used as a directory in oldpath or new
21228 path is not a directory. Or oldpath is a directory
21229 and newpath exists but is not a directory.
21232 oldpathptr or newpathptr are invalid pointer values.
21235 No access to the file or the path of the file.
21239 oldpath or newpath was too long.
21242 A directory component in oldpath or newpath does not exist.
21245 The file is on a read-only filesystem.
21248 The device containing the file has no room for the new
21252 The call was interrupted by the user.
21256 @unnumberedsubsubsec unlink
21257 @cindex unlink, file-i/o system call
21261 int unlink(const char *pathname);
21264 Funlink,pathnameptr/len
21266 @exdent Return value:
21267 On success, zero is returned. On error, -1 is returned.
21274 No access to the file or the path of the file.
21277 The system does not allow unlinking of directories.
21280 The file pathname cannot be unlinked because it's
21281 being used by another process.
21284 pathnameptr is an invalid pointer value.
21287 pathname was too long.
21290 A directory component in pathname does not exist.
21293 A component of the path is not a directory.
21296 The file is on a read-only filesystem.
21299 The call was interrupted by the user.
21303 @unnumberedsubsubsec stat/fstat
21304 @cindex fstat, file-i/o system call
21305 @cindex stat, file-i/o system call
21309 int stat(const char *pathname, struct stat *buf);
21310 int fstat(int fd, struct stat *buf);
21313 Fstat,pathnameptr/len,bufptr
21316 @exdent Return value:
21317 On success, zero is returned. On error, -1 is returned.
21324 fd is not a valid open file.
21327 A directory component in pathname does not exist or the
21328 path is an empty string.
21331 A component of the path is not a directory.
21334 pathnameptr is an invalid pointer value.
21337 No access to the file or the path of the file.
21340 pathname was too long.
21343 The call was interrupted by the user.
21347 @unnumberedsubsubsec gettimeofday
21348 @cindex gettimeofday, file-i/o system call
21352 int gettimeofday(struct timeval *tv, void *tz);
21355 Fgettimeofday,tvptr,tzptr
21357 @exdent Return value:
21358 On success, 0 is returned, -1 otherwise.
21365 tz is a non-NULL pointer.
21368 tvptr and/or tzptr is an invalid pointer value.
21372 @unnumberedsubsubsec isatty
21373 @cindex isatty, file-i/o system call
21377 int isatty(int fd);
21382 @exdent Return value:
21383 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21390 The call was interrupted by the user.
21394 @unnumberedsubsubsec system
21395 @cindex system, file-i/o system call
21399 int system(const char *command);
21402 Fsystem,commandptr/len
21404 @exdent Return value:
21405 The value returned is -1 on error and the return status
21406 of the command otherwise. Only the exit status of the
21407 command is returned, which is extracted from the hosts
21408 system return value by calling WEXITSTATUS(retval).
21409 In case /bin/sh could not be executed, 127 is returned.
21416 The call was interrupted by the user.
21419 @node Protocol specific representation of datatypes
21420 @subsection Protocol specific representation of datatypes
21421 @cindex protocol specific representation of datatypes, in file-i/o protocol
21424 * Integral datatypes::
21430 @node Integral datatypes
21431 @unnumberedsubsubsec Integral datatypes
21432 @cindex integral datatypes, in file-i/o protocol
21434 The integral datatypes used in the system calls are
21437 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21440 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21441 implemented as 32 bit values in this protocol.
21443 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21445 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21446 in @file{limits.h}) to allow range checking on host and target.
21448 @code{time_t} datatypes are defined as seconds since the Epoch.
21450 All integral datatypes transferred as part of a memory read or write of a
21451 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21454 @node Pointer values
21455 @unnumberedsubsubsec Pointer values
21456 @cindex pointer values, in file-i/o protocol
21458 Pointers to target data are transmitted as they are. An exception
21459 is made for pointers to buffers for which the length isn't
21460 transmitted as part of the function call, namely strings. Strings
21461 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21468 which is a pointer to data of length 18 bytes at position 0x1aaf.
21469 The length is defined as the full string length in bytes, including
21470 the trailing null byte. Example:
21473 ``hello, world'' at address 0x123456
21484 @unnumberedsubsubsec struct stat
21485 @cindex struct stat, in file-i/o protocol
21487 The buffer of type struct stat used by the target and @value{GDBN} is defined
21492 unsigned int st_dev; /* device */
21493 unsigned int st_ino; /* inode */
21494 mode_t st_mode; /* protection */
21495 unsigned int st_nlink; /* number of hard links */
21496 unsigned int st_uid; /* user ID of owner */
21497 unsigned int st_gid; /* group ID of owner */
21498 unsigned int st_rdev; /* device type (if inode device) */
21499 unsigned long st_size; /* total size, in bytes */
21500 unsigned long st_blksize; /* blocksize for filesystem I/O */
21501 unsigned long st_blocks; /* number of blocks allocated */
21502 time_t st_atime; /* time of last access */
21503 time_t st_mtime; /* time of last modification */
21504 time_t st_ctime; /* time of last change */
21508 The integral datatypes are conforming to the definitions given in the
21509 approriate section (see @ref{Integral datatypes}, for details) so this
21510 structure is of size 64 bytes.
21512 The values of several fields have a restricted meaning and/or
21519 st_ino: No valid meaning for the target. Transmitted unchanged.
21521 st_mode: Valid mode bits are described in Appendix C. Any other
21522 bits have currently no meaning for the target.
21524 st_uid: No valid meaning for the target. Transmitted unchanged.
21526 st_gid: No valid meaning for the target. Transmitted unchanged.
21528 st_rdev: No valid meaning for the target. Transmitted unchanged.
21530 st_atime, st_mtime, st_ctime:
21531 These values have a host and file system dependent
21532 accuracy. Especially on Windows hosts the file systems
21533 don't support exact timing values.
21536 The target gets a struct stat of the above representation and is
21537 responsible to coerce it to the target representation before
21540 Note that due to size differences between the host and target
21541 representation of stat members, these members could eventually
21542 get truncated on the target.
21544 @node struct timeval
21545 @unnumberedsubsubsec struct timeval
21546 @cindex struct timeval, in file-i/o protocol
21548 The buffer of type struct timeval used by the target and @value{GDBN}
21549 is defined as follows:
21553 time_t tv_sec; /* second */
21554 long tv_usec; /* microsecond */
21558 The integral datatypes are conforming to the definitions given in the
21559 approriate section (see @ref{Integral datatypes}, for details) so this
21560 structure is of size 8 bytes.
21563 @subsection Constants
21564 @cindex constants, in file-i/o protocol
21566 The following values are used for the constants inside of the
21567 protocol. @value{GDBN} and target are resposible to translate these
21568 values before and after the call as needed.
21579 @unnumberedsubsubsec Open flags
21580 @cindex open flags, in file-i/o protocol
21582 All values are given in hexadecimal representation.
21594 @node mode_t values
21595 @unnumberedsubsubsec mode_t values
21596 @cindex mode_t values, in file-i/o protocol
21598 All values are given in octal representation.
21615 @unnumberedsubsubsec Errno values
21616 @cindex errno values, in file-i/o protocol
21618 All values are given in decimal representation.
21643 EUNKNOWN is used as a fallback error value if a host system returns
21644 any error value not in the list of supported error numbers.
21647 @unnumberedsubsubsec Lseek flags
21648 @cindex lseek flags, in file-i/o protocol
21657 @unnumberedsubsubsec Limits
21658 @cindex limits, in file-i/o protocol
21660 All values are given in decimal representation.
21663 INT_MIN -2147483648
21665 UINT_MAX 4294967295
21666 LONG_MIN -9223372036854775808
21667 LONG_MAX 9223372036854775807
21668 ULONG_MAX 18446744073709551615
21671 @node File-I/O Examples
21672 @subsection File-I/O Examples
21673 @cindex file-i/o examples
21675 Example sequence of a write call, file descriptor 3, buffer is at target
21676 address 0x1234, 6 bytes should be written:
21679 <- @code{Fwrite,3,1234,6}
21680 @emph{request memory read from target}
21683 @emph{return "6 bytes written"}
21687 Example sequence of a read call, file descriptor 3, buffer is at target
21688 address 0x1234, 6 bytes should be read:
21691 <- @code{Fread,3,1234,6}
21692 @emph{request memory write to target}
21693 -> @code{X1234,6:XXXXXX}
21694 @emph{return "6 bytes read"}
21698 Example sequence of a read call, call fails on the host due to invalid
21699 file descriptor (EBADF):
21702 <- @code{Fread,3,1234,6}
21706 Example sequence of a read call, user presses Ctrl-C before syscall on
21710 <- @code{Fread,3,1234,6}
21715 Example sequence of a read call, user presses Ctrl-C after syscall on
21719 <- @code{Fread,3,1234,6}
21720 -> @code{X1234,6:XXXXXX}
21724 @include agentexpr.texi
21736 % I think something like @colophon should be in texinfo. In the
21738 \long\def\colophon{\hbox to0pt{}\vfill
21739 \centerline{The body of this manual is set in}
21740 \centerline{\fontname\tenrm,}
21741 \centerline{with headings in {\bf\fontname\tenbf}}
21742 \centerline{and examples in {\tt\fontname\tentt}.}
21743 \centerline{{\it\fontname\tenit\/},}
21744 \centerline{{\bf\fontname\tenbf}, and}
21745 \centerline{{\sl\fontname\tensl\/}}
21746 \centerline{are used for emphasis.}\vfill}
21748 % Blame: doc@cygnus.com, 1991.