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 * Copying:: GNU General Public License says
160 how you can copy and share GDB
161 * GNU Free Documentation License:: The license for this documentation
170 @unnumbered Summary of @value{GDBN}
172 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
173 going on ``inside'' another program while it executes---or what another
174 program was doing at the moment it crashed.
176 @value{GDBN} can do four main kinds of things (plus other things in support of
177 these) to help you catch bugs in the act:
181 Start your program, specifying anything that might affect its behavior.
184 Make your program stop on specified conditions.
187 Examine what has happened, when your program has stopped.
190 Change things in your program, so you can experiment with correcting the
191 effects of one bug and go on to learn about another.
194 You can use @value{GDBN} to debug programs written in C and C++.
195 For more information, see @ref{Support,,Supported languages}.
196 For more information, see @ref{C,,C and C++}.
199 Support for Modula-2 is partial. For information on Modula-2, see
200 @ref{Modula-2,,Modula-2}.
203 Debugging Pascal programs which use sets, subranges, file variables, or
204 nested functions does not currently work. @value{GDBN} does not support
205 entering expressions, printing values, or similar features using Pascal
209 @value{GDBN} can be used to debug programs written in Fortran, although
210 it may be necessary to refer to some variables with a trailing
214 * Free Software:: Freely redistributable software
215 * Contributors:: Contributors to GDB
219 @unnumberedsec Free software
221 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
222 General Public License
223 (GPL). The GPL gives you the freedom to copy or adapt a licensed
224 program---but every person getting a copy also gets with it the
225 freedom to modify that copy (which means that they must get access to
226 the source code), and the freedom to distribute further copies.
227 Typical software companies use copyrights to limit your freedoms; the
228 Free Software Foundation uses the GPL to preserve these freedoms.
230 Fundamentally, the General Public License is a license which says that
231 you have these freedoms and that you cannot take these freedoms away
234 @unnumberedsec Free Software Needs Free Documentation
236 The biggest deficiency in the free software community today is not in
237 the software---it is the lack of good free documentation that we can
238 include with the free software. Many of our most important
239 programs do not come with free reference manuals and free introductory
240 texts. Documentation is an essential part of any software package;
241 when an important free software package does not come with a free
242 manual and a free tutorial, that is a major gap. We have many such
245 Consider Perl, for instance. The tutorial manuals that people
246 normally use are non-free. How did this come about? Because the
247 authors of those manuals published them with restrictive terms---no
248 copying, no modification, source files not available---which exclude
249 them from the free software world.
251 That wasn't the first time this sort of thing happened, and it was far
252 from the last. Many times we have heard a GNU user eagerly describe a
253 manual that he is writing, his intended contribution to the community,
254 only to learn that he had ruined everything by signing a publication
255 contract to make it non-free.
257 Free documentation, like free software, is a matter of freedom, not
258 price. The problem with the non-free manual is not that publishers
259 charge a price for printed copies---that in itself is fine. (The Free
260 Software Foundation sells printed copies of manuals, too.) The
261 problem is the restrictions on the use of the manual. Free manuals
262 are available in source code form, and give you permission to copy and
263 modify. Non-free manuals do not allow this.
265 The criteria of freedom for a free manual are roughly the same as for
266 free software. Redistribution (including the normal kinds of
267 commercial redistribution) must be permitted, so that the manual can
268 accompany every copy of the program, both on-line and on paper.
270 Permission for modification of the technical content is crucial too.
271 When people modify the software, adding or changing features, if they
272 are conscientious they will change the manual too---so they can
273 provide accurate and clear documentation for the modified program. A
274 manual that leaves you no choice but to write a new manual to document
275 a changed version of the program is not really available to our
278 Some kinds of limits on the way modification is handled are
279 acceptable. For example, requirements to preserve the original
280 author's copyright notice, the distribution terms, or the list of
281 authors, are ok. It is also no problem to require modified versions
282 to include notice that they were modified. Even entire sections that
283 may not be deleted or changed are acceptable, as long as they deal
284 with nontechnical topics (like this one). These kinds of restrictions
285 are acceptable because they don't obstruct the community's normal use
288 However, it must be possible to modify all the @emph{technical}
289 content of the manual, and then distribute the result in all the usual
290 media, through all the usual channels. Otherwise, the restrictions
291 obstruct the use of the manual, it is not free, and we need another
292 manual to replace it.
294 Please spread the word about this issue. Our community continues to
295 lose manuals to proprietary publishing. If we spread the word that
296 free software needs free reference manuals and free tutorials, perhaps
297 the next person who wants to contribute by writing documentation will
298 realize, before it is too late, that only free manuals contribute to
299 the free software community.
301 If you are writing documentation, please insist on publishing it under
302 the GNU Free Documentation License or another free documentation
303 license. Remember that this decision requires your approval---you
304 don't have to let the publisher decide. Some commercial publishers
305 will use a free license if you insist, but they will not propose the
306 option; it is up to you to raise the issue and say firmly that this is
307 what you want. If the publisher you are dealing with refuses, please
308 try other publishers. If you're not sure whether a proposed license
309 is free, write to @email{licensing@@gnu.org}.
311 You can encourage commercial publishers to sell more free, copylefted
312 manuals and tutorials by buying them, and particularly by buying
313 copies from the publishers that paid for their writing or for major
314 improvements. Meanwhile, try to avoid buying non-free documentation
315 at all. Check the distribution terms of a manual before you buy it,
316 and insist that whoever seeks your business must respect your freedom.
317 Check the history of the book, and try to reward the publishers that
318 have paid or pay the authors to work on it.
320 The Free Software Foundation maintains a list of free documentation
321 published by other publishers, at
322 @url{http://www.fsf.org/doc/other-free-books.html}.
325 @unnumberedsec Contributors to @value{GDBN}
327 Richard Stallman was the original author of @value{GDBN}, and of many
328 other @sc{gnu} programs. Many others have contributed to its
329 development. This section attempts to credit major contributors. One
330 of the virtues of free software is that everyone is free to contribute
331 to it; with regret, we cannot actually acknowledge everyone here. The
332 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
333 blow-by-blow account.
335 Changes much prior to version 2.0 are lost in the mists of time.
338 @emph{Plea:} Additions to this section are particularly welcome. If you
339 or your friends (or enemies, to be evenhanded) have been unfairly
340 omitted from this list, we would like to add your names!
343 So that they may not regard their many labors as thankless, we
344 particularly thank those who shepherded @value{GDBN} through major
346 Andrew Cagney (releases 5.3, 5.2, 5.1 and 5.0);
347 Jim Blandy (release 4.18);
348 Jason Molenda (release 4.17);
349 Stan Shebs (release 4.14);
350 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
351 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
352 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
353 Jim Kingdon (releases 3.5, 3.4, and 3.3);
354 and Randy Smith (releases 3.2, 3.1, and 3.0).
356 Richard Stallman, assisted at various times by Peter TerMaat, Chris
357 Hanson, and Richard Mlynarik, handled releases through 2.8.
359 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
360 in @value{GDBN}, with significant additional contributions from Per
361 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
362 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
363 much general update work leading to release 3.0).
365 @value{GDBN} uses the BFD subroutine library to examine multiple
366 object-file formats; BFD was a joint project of David V.
367 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
369 David Johnson wrote the original COFF support; Pace Willison did
370 the original support for encapsulated COFF.
372 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
374 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
375 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
377 Jean-Daniel Fekete contributed Sun 386i support.
378 Chris Hanson improved the HP9000 support.
379 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
380 David Johnson contributed Encore Umax support.
381 Jyrki Kuoppala contributed Altos 3068 support.
382 Jeff Law contributed HP PA and SOM support.
383 Keith Packard contributed NS32K support.
384 Doug Rabson contributed Acorn Risc Machine support.
385 Bob Rusk contributed Harris Nighthawk CX-UX support.
386 Chris Smith contributed Convex support (and Fortran debugging).
387 Jonathan Stone contributed Pyramid support.
388 Michael Tiemann contributed SPARC support.
389 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
390 Pace Willison contributed Intel 386 support.
391 Jay Vosburgh contributed Symmetry support.
392 Marko Mlinar contributed OpenRISC 1000 support.
394 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
396 Rich Schaefer and Peter Schauer helped with support of SunOS shared
399 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
400 about several machine instruction sets.
402 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
403 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
404 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
405 and RDI targets, respectively.
407 Brian Fox is the author of the readline libraries providing
408 command-line editing and command history.
410 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
411 Modula-2 support, and contributed the Languages chapter of this manual.
413 Fred Fish wrote most of the support for Unix System Vr4.
414 He also enhanced the command-completion support to cover C@t{++} overloaded
417 Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and
420 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
422 Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors.
424 Toshiba sponsored the support for the TX39 Mips processor.
426 Matsushita sponsored the support for the MN10200 and MN10300 processors.
428 Fujitsu sponsored the support for SPARClite and FR30 processors.
430 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
433 Michael Snyder added support for tracepoints.
435 Stu Grossman wrote gdbserver.
437 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
438 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
440 The following people at the Hewlett-Packard Company contributed
441 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
442 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
443 compiler, and the terminal user interface: Ben Krepp, Richard Title,
444 John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
445 Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
446 information in this manual.
448 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
449 Robert Hoehne made significant contributions to the DJGPP port.
451 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
452 development since 1991. Cygnus engineers who have worked on @value{GDBN}
453 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
454 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
455 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
456 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
457 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
458 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
459 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
460 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
461 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
462 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
463 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
464 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
465 Zuhn have made contributions both large and small.
467 Jim Blandy added support for preprocessor macros, while working for Red
471 @chapter A Sample @value{GDBN} Session
473 You can use this manual at your leisure to read all about @value{GDBN}.
474 However, a handful of commands are enough to get started using the
475 debugger. This chapter illustrates those commands.
478 In this sample session, we emphasize user input like this: @b{input},
479 to make it easier to pick out from the surrounding output.
482 @c FIXME: this example may not be appropriate for some configs, where
483 @c FIXME...primary interest is in remote use.
485 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
486 processor) exhibits the following bug: sometimes, when we change its
487 quote strings from the default, the commands used to capture one macro
488 definition within another stop working. In the following short @code{m4}
489 session, we define a macro @code{foo} which expands to @code{0000}; we
490 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
491 same thing. However, when we change the open quote string to
492 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
493 procedure fails to define a new synonym @code{baz}:
502 @b{define(bar,defn(`foo'))}
506 @b{changequote(<QUOTE>,<UNQUOTE>)}
508 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
511 m4: End of input: 0: fatal error: EOF in string
515 Let us use @value{GDBN} to try to see what is going on.
518 $ @b{@value{GDBP} m4}
519 @c FIXME: this falsifies the exact text played out, to permit smallbook
520 @c FIXME... format to come out better.
521 @value{GDBN} is free software and you are welcome to distribute copies
522 of it under certain conditions; type "show copying" to see
524 There is absolutely no warranty for @value{GDBN}; type "show warranty"
527 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
532 @value{GDBN} reads only enough symbol data to know where to find the
533 rest when needed; as a result, the first prompt comes up very quickly.
534 We now tell @value{GDBN} to use a narrower display width than usual, so
535 that examples fit in this manual.
538 (@value{GDBP}) @b{set width 70}
542 We need to see how the @code{m4} built-in @code{changequote} works.
543 Having looked at the source, we know the relevant subroutine is
544 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
545 @code{break} command.
548 (@value{GDBP}) @b{break m4_changequote}
549 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
553 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
554 control; as long as control does not reach the @code{m4_changequote}
555 subroutine, the program runs as usual:
558 (@value{GDBP}) @b{run}
559 Starting program: /work/Editorial/gdb/gnu/m4/m4
567 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
568 suspends execution of @code{m4}, displaying information about the
569 context where it stops.
572 @b{changequote(<QUOTE>,<UNQUOTE>)}
574 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
576 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
580 Now we use the command @code{n} (@code{next}) to advance execution to
581 the next line of the current function.
585 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
590 @code{set_quotes} looks like a promising subroutine. We can go into it
591 by using the command @code{s} (@code{step}) instead of @code{next}.
592 @code{step} goes to the next line to be executed in @emph{any}
593 subroutine, so it steps into @code{set_quotes}.
597 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
599 530 if (lquote != def_lquote)
603 The display that shows the subroutine where @code{m4} is now
604 suspended (and its arguments) is called a stack frame display. It
605 shows a summary of the stack. We can use the @code{backtrace}
606 command (which can also be spelled @code{bt}), to see where we are
607 in the stack as a whole: the @code{backtrace} command displays a
608 stack frame for each active subroutine.
611 (@value{GDBP}) @b{bt}
612 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
614 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
616 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
617 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
619 #4 0x79dc in expand_input () at macro.c:40
620 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
624 We step through a few more lines to see what happens. The first two
625 times, we can use @samp{s}; the next two times we use @code{n} to avoid
626 falling into the @code{xstrdup} subroutine.
630 0x3b5c 532 if (rquote != def_rquote)
632 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
633 def_lquote : xstrdup(lq);
635 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
638 538 len_lquote = strlen(rquote);
642 The last line displayed looks a little odd; we can examine the variables
643 @code{lquote} and @code{rquote} to see if they are in fact the new left
644 and right quotes we specified. We use the command @code{p}
645 (@code{print}) to see their values.
648 (@value{GDBP}) @b{p lquote}
649 $1 = 0x35d40 "<QUOTE>"
650 (@value{GDBP}) @b{p rquote}
651 $2 = 0x35d50 "<UNQUOTE>"
655 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
656 To look at some context, we can display ten lines of source
657 surrounding the current line with the @code{l} (@code{list}) command.
663 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
665 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
668 538 len_lquote = strlen(rquote);
669 539 len_rquote = strlen(lquote);
676 Let us step past the two lines that set @code{len_lquote} and
677 @code{len_rquote}, and then examine the values of those variables.
681 539 len_rquote = strlen(lquote);
684 (@value{GDBP}) @b{p len_lquote}
686 (@value{GDBP}) @b{p len_rquote}
691 That certainly looks wrong, assuming @code{len_lquote} and
692 @code{len_rquote} are meant to be the lengths of @code{lquote} and
693 @code{rquote} respectively. We can set them to better values using
694 the @code{p} command, since it can print the value of
695 any expression---and that expression can include subroutine calls and
699 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
701 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
706 Is that enough to fix the problem of using the new quotes with the
707 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
708 executing with the @code{c} (@code{continue}) command, and then try the
709 example that caused trouble initially:
715 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
722 Success! The new quotes now work just as well as the default ones. The
723 problem seems to have been just the two typos defining the wrong
724 lengths. We allow @code{m4} exit by giving it an EOF as input:
728 Program exited normally.
732 The message @samp{Program exited normally.} is from @value{GDBN}; it
733 indicates @code{m4} has finished executing. We can end our @value{GDBN}
734 session with the @value{GDBN} @code{quit} command.
737 (@value{GDBP}) @b{quit}
741 @chapter Getting In and Out of @value{GDBN}
743 This chapter discusses how to start @value{GDBN}, and how to get out of it.
747 type @samp{@value{GDBP}} to start @value{GDBN}.
749 type @kbd{quit} or @kbd{C-d} to exit.
753 * Invoking GDB:: How to start @value{GDBN}
754 * Quitting GDB:: How to quit @value{GDBN}
755 * Shell Commands:: How to use shell commands inside @value{GDBN}
759 @section Invoking @value{GDBN}
761 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
762 @value{GDBN} reads commands from the terminal until you tell it to exit.
764 You can also run @code{@value{GDBP}} with a variety of arguments and options,
765 to specify more of your debugging environment at the outset.
767 The command-line options described here are designed
768 to cover a variety of situations; in some environments, some of these
769 options may effectively be unavailable.
771 The most usual way to start @value{GDBN} is with one argument,
772 specifying an executable program:
775 @value{GDBP} @var{program}
779 You can also start with both an executable program and a core file
783 @value{GDBP} @var{program} @var{core}
786 You can, instead, specify a process ID as a second argument, if you want
787 to debug a running process:
790 @value{GDBP} @var{program} 1234
794 would attach @value{GDBN} to process @code{1234} (unless you also have a file
795 named @file{1234}; @value{GDBN} does check for a core file first).
797 Taking advantage of the second command-line argument requires a fairly
798 complete operating system; when you use @value{GDBN} as a remote
799 debugger attached to a bare board, there may not be any notion of
800 ``process'', and there is often no way to get a core dump. @value{GDBN}
801 will warn you if it is unable to attach or to read core dumps.
803 You can optionally have @code{@value{GDBP}} pass any arguments after the
804 executable file to the inferior using @code{--args}. This option stops
807 gdb --args gcc -O2 -c foo.c
809 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
810 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
812 You can run @code{@value{GDBP}} without printing the front material, which describes
813 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
820 You can further control how @value{GDBN} starts up by using command-line
821 options. @value{GDBN} itself can remind you of the options available.
831 to display all available options and briefly describe their use
832 (@samp{@value{GDBP} -h} is a shorter equivalent).
834 All options and command line arguments you give are processed
835 in sequential order. The order makes a difference when the
836 @samp{-x} option is used.
840 * File Options:: Choosing files
841 * Mode Options:: Choosing modes
845 @subsection Choosing files
847 When @value{GDBN} starts, it reads any arguments other than options as
848 specifying an executable file and core file (or process ID). This is
849 the same as if the arguments were specified by the @samp{-se} and
850 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
851 first argument that does not have an associated option flag as
852 equivalent to the @samp{-se} option followed by that argument; and the
853 second argument that does not have an associated option flag, if any, as
854 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
855 If the second argument begins with a decimal digit, @value{GDBN} will
856 first attempt to attach to it as a process, and if that fails, attempt
857 to open it as a corefile. If you have a corefile whose name begins with
858 a digit, you can prevent @value{GDBN} from treating it as a pid by
859 prefixing it with @file{./}, eg. @file{./12345}.
861 If @value{GDBN} has not been configured to included core file support,
862 such as for most embedded targets, then it will complain about a second
863 argument and ignore it.
865 Many options have both long and short forms; both are shown in the
866 following list. @value{GDBN} also recognizes the long forms if you truncate
867 them, so long as enough of the option is present to be unambiguous.
868 (If you prefer, you can flag option arguments with @samp{--} rather
869 than @samp{-}, though we illustrate the more usual convention.)
871 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
872 @c way, both those who look for -foo and --foo in the index, will find
876 @item -symbols @var{file}
878 @cindex @code{--symbols}
880 Read symbol table from file @var{file}.
882 @item -exec @var{file}
884 @cindex @code{--exec}
886 Use file @var{file} as the executable file to execute when appropriate,
887 and for examining pure data in conjunction with a core dump.
891 Read symbol table from file @var{file} and use it as the executable
894 @item -core @var{file}
896 @cindex @code{--core}
898 Use file @var{file} as a core dump to examine.
900 @item -c @var{number}
901 @item -pid @var{number}
902 @itemx -p @var{number}
905 Connect to process ID @var{number}, as with the @code{attach} command.
906 If there is no such process, @value{GDBN} will attempt to open a core
907 file named @var{number}.
909 @item -command @var{file}
911 @cindex @code{--command}
913 Execute @value{GDBN} commands from file @var{file}. @xref{Command
914 Files,, Command files}.
916 @item -directory @var{directory}
917 @itemx -d @var{directory}
918 @cindex @code{--directory}
920 Add @var{directory} to the path to search for source files.
924 @cindex @code{--mapped}
926 @emph{Warning: this option depends on operating system facilities that are not
927 supported on all systems.}@*
928 If memory-mapped files are available on your system through the @code{mmap}
929 system call, you can use this option
930 to have @value{GDBN} write the symbols from your
931 program into a reusable file in the current directory. If the program you are debugging is
932 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
933 Future @value{GDBN} debugging sessions notice the presence of this file,
934 and can quickly map in symbol information from it, rather than reading
935 the symbol table from the executable program.
937 The @file{.syms} file is specific to the host machine where @value{GDBN}
938 is run. It holds an exact image of the internal @value{GDBN} symbol
939 table. It cannot be shared across multiple host platforms.
943 @cindex @code{--readnow}
945 Read each symbol file's entire symbol table immediately, rather than
946 the default, which is to read it incrementally as it is needed.
947 This makes startup slower, but makes future operations faster.
951 You typically combine the @code{-mapped} and @code{-readnow} options in
952 order to build a @file{.syms} file that contains complete symbol
953 information. (@xref{Files,,Commands to specify files}, for information
954 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
955 but build a @file{.syms} file for future use is:
958 gdb -batch -nx -mapped -readnow programname
962 @subsection Choosing modes
964 You can run @value{GDBN} in various alternative modes---for example, in
965 batch mode or quiet mode.
972 Do not execute commands found in any initialization files. Normally,
973 @value{GDBN} executes the commands in these files after all the command
974 options and arguments have been processed. @xref{Command Files,,Command
980 @cindex @code{--quiet}
981 @cindex @code{--silent}
983 ``Quiet''. Do not print the introductory and copyright messages. These
984 messages are also suppressed in batch mode.
987 @cindex @code{--batch}
988 Run in batch mode. Exit with status @code{0} after processing all the
989 command files specified with @samp{-x} (and all commands from
990 initialization files, if not inhibited with @samp{-n}). Exit with
991 nonzero status if an error occurs in executing the @value{GDBN} commands
992 in the command files.
994 Batch mode may be useful for running @value{GDBN} as a filter, for
995 example to download and run a program on another computer; in order to
996 make this more useful, the message
999 Program exited normally.
1003 (which is ordinarily issued whenever a program running under
1004 @value{GDBN} control terminates) is not issued when running in batch
1009 @cindex @code{--nowindows}
1011 ``No windows''. If @value{GDBN} comes with a graphical user interface
1012 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1013 interface. If no GUI is available, this option has no effect.
1017 @cindex @code{--windows}
1019 If @value{GDBN} includes a GUI, then this option requires it to be
1022 @item -cd @var{directory}
1024 Run @value{GDBN} using @var{directory} as its working directory,
1025 instead of the current directory.
1029 @cindex @code{--fullname}
1031 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1032 subprocess. It tells @value{GDBN} to output the full file name and line
1033 number in a standard, recognizable fashion each time a stack frame is
1034 displayed (which includes each time your program stops). This
1035 recognizable format looks like two @samp{\032} characters, followed by
1036 the file name, line number and character position separated by colons,
1037 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1038 @samp{\032} characters as a signal to display the source code for the
1042 @cindex @code{--epoch}
1043 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1044 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1045 routines so as to allow Epoch to display values of expressions in a
1048 @item -annotate @var{level}
1049 @cindex @code{--annotate}
1050 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1051 effect is identical to using @samp{set annotate @var{level}}
1052 (@pxref{Annotations}).
1053 Annotation level controls how much information does @value{GDBN} print
1054 together with its prompt, values of expressions, source lines, and other
1055 types of output. Level 0 is the normal, level 1 is for use when
1056 @value{GDBN} is run as a subprocess of @sc{gnu} Emacs, level 2 is the
1057 maximum annotation suitable for programs that control @value{GDBN}.
1060 @cindex @code{--async}
1061 Use the asynchronous event loop for the command-line interface.
1062 @value{GDBN} processes all events, such as user keyboard input, via a
1063 special event loop. This allows @value{GDBN} to accept and process user
1064 commands in parallel with the debugged process being
1065 run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1066 MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1067 suspended when the debuggee runs.}, so you don't need to wait for
1068 control to return to @value{GDBN} before you type the next command.
1069 (@emph{Note:} as of version 5.1, the target side of the asynchronous
1070 operation is not yet in place, so @samp{-async} does not work fully
1072 @c FIXME: when the target side of the event loop is done, the above NOTE
1073 @c should be removed.
1075 When the standard input is connected to a terminal device, @value{GDBN}
1076 uses the asynchronous event loop by default, unless disabled by the
1077 @samp{-noasync} option.
1080 @cindex @code{--noasync}
1081 Disable the asynchronous event loop for the command-line interface.
1084 @cindex @code{--args}
1085 Change interpretation of command line so that arguments following the
1086 executable file are passed as command line arguments to the inferior.
1087 This option stops option processing.
1089 @item -baud @var{bps}
1091 @cindex @code{--baud}
1093 Set the line speed (baud rate or bits per second) of any serial
1094 interface used by @value{GDBN} for remote debugging.
1096 @item -tty @var{device}
1097 @itemx -t @var{device}
1098 @cindex @code{--tty}
1100 Run using @var{device} for your program's standard input and output.
1101 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1103 @c resolve the situation of these eventually
1105 @cindex @code{--tui}
1106 Activate the Terminal User Interface when starting.
1107 The Terminal User Interface manages several text windows on the terminal,
1108 showing source, assembly, registers and @value{GDBN} command outputs
1109 (@pxref{TUI, ,@value{GDBN} Text User Interface}).
1110 Do not use this option if you run @value{GDBN} from Emacs
1111 (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1114 @c @cindex @code{--xdb}
1115 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1116 @c For information, see the file @file{xdb_trans.html}, which is usually
1117 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1120 @item -interpreter @var{interp}
1121 @cindex @code{--interpreter}
1122 Use the interpreter @var{interp} for interface with the controlling
1123 program or device. This option is meant to be set by programs which
1124 communicate with @value{GDBN} using it as a back end.
1125 @xref{Interpreters, , Command Interpreters}.
1127 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1128 @value{GDBN} to use the current @dfn{@sc{gdb/mi} interface}
1129 (@pxref{GDB/MI, , The @sc{gdb/mi} Interface}). The previous @sc{gdb/mi}
1130 interface, included in @value{GDBN} version 5.3, can be selected with
1131 @samp{--interpreter=mi1}. Earlier @sc{gdb/mi} interfaces
1135 @cindex @code{--write}
1136 Open the executable and core files for both reading and writing. This
1137 is equivalent to the @samp{set write on} command inside @value{GDBN}
1141 @cindex @code{--statistics}
1142 This option causes @value{GDBN} to print statistics about time and
1143 memory usage after it completes each command and returns to the prompt.
1146 @cindex @code{--version}
1147 This option causes @value{GDBN} to print its version number and
1148 no-warranty blurb, and exit.
1153 @section Quitting @value{GDBN}
1154 @cindex exiting @value{GDBN}
1155 @cindex leaving @value{GDBN}
1158 @kindex quit @r{[}@var{expression}@r{]}
1159 @kindex q @r{(@code{quit})}
1160 @item quit @r{[}@var{expression}@r{]}
1162 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1163 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1164 do not supply @var{expression}, @value{GDBN} will terminate normally;
1165 otherwise it will terminate using the result of @var{expression} as the
1170 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1171 terminates the action of any @value{GDBN} command that is in progress and
1172 returns to @value{GDBN} command level. It is safe to type the interrupt
1173 character at any time because @value{GDBN} does not allow it to take effect
1174 until a time when it is safe.
1176 If you have been using @value{GDBN} to control an attached process or
1177 device, you can release it with the @code{detach} command
1178 (@pxref{Attach, ,Debugging an already-running process}).
1180 @node Shell Commands
1181 @section Shell commands
1183 If you need to execute occasional shell commands during your
1184 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1185 just use the @code{shell} command.
1189 @cindex shell escape
1190 @item shell @var{command string}
1191 Invoke a standard shell to execute @var{command string}.
1192 If it exists, the environment variable @code{SHELL} determines which
1193 shell to run. Otherwise @value{GDBN} uses the default shell
1194 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1197 The utility @code{make} is often needed in development environments.
1198 You do not have to use the @code{shell} command for this purpose in
1203 @cindex calling make
1204 @item make @var{make-args}
1205 Execute the @code{make} program with the specified
1206 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1210 @chapter @value{GDBN} Commands
1212 You can abbreviate a @value{GDBN} command to the first few letters of the command
1213 name, if that abbreviation is unambiguous; and you can repeat certain
1214 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1215 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1216 show you the alternatives available, if there is more than one possibility).
1219 * Command Syntax:: How to give commands to @value{GDBN}
1220 * Completion:: Command completion
1221 * Help:: How to ask @value{GDBN} for help
1224 @node Command Syntax
1225 @section Command syntax
1227 A @value{GDBN} command is a single line of input. There is no limit on
1228 how long it can be. It starts with a command name, which is followed by
1229 arguments whose meaning depends on the command name. For example, the
1230 command @code{step} accepts an argument which is the number of times to
1231 step, as in @samp{step 5}. You can also use the @code{step} command
1232 with no arguments. Some commands do not allow any arguments.
1234 @cindex abbreviation
1235 @value{GDBN} command names may always be truncated if that abbreviation is
1236 unambiguous. Other possible command abbreviations are listed in the
1237 documentation for individual commands. In some cases, even ambiguous
1238 abbreviations are allowed; for example, @code{s} is specially defined as
1239 equivalent to @code{step} even though there are other commands whose
1240 names start with @code{s}. You can test abbreviations by using them as
1241 arguments to the @code{help} command.
1243 @cindex repeating commands
1244 @kindex RET @r{(repeat last command)}
1245 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1246 repeat the previous command. Certain commands (for example, @code{run})
1247 will not repeat this way; these are commands whose unintentional
1248 repetition might cause trouble and which you are unlikely to want to
1251 The @code{list} and @code{x} commands, when you repeat them with
1252 @key{RET}, construct new arguments rather than repeating
1253 exactly as typed. This permits easy scanning of source or memory.
1255 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1256 output, in a way similar to the common utility @code{more}
1257 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1258 @key{RET} too many in this situation, @value{GDBN} disables command
1259 repetition after any command that generates this sort of display.
1261 @kindex # @r{(a comment)}
1263 Any text from a @kbd{#} to the end of the line is a comment; it does
1264 nothing. This is useful mainly in command files (@pxref{Command
1265 Files,,Command files}).
1267 @cindex repeating command sequences
1268 @kindex C-o @r{(operate-and-get-next)}
1269 The @kbd{C-o} binding is useful for repeating a complex sequence of
1270 commands. This command accepts the current line, like @kbd{RET}, and
1271 then fetches the next line relative to the current line from the history
1275 @section Command completion
1278 @cindex word completion
1279 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1280 only one possibility; it can also show you what the valid possibilities
1281 are for the next word in a command, at any time. This works for @value{GDBN}
1282 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1284 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1285 of a word. If there is only one possibility, @value{GDBN} fills in the
1286 word, and waits for you to finish the command (or press @key{RET} to
1287 enter it). For example, if you type
1289 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1290 @c complete accuracy in these examples; space introduced for clarity.
1291 @c If texinfo enhancements make it unnecessary, it would be nice to
1292 @c replace " @key" by "@key" in the following...
1294 (@value{GDBP}) info bre @key{TAB}
1298 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1299 the only @code{info} subcommand beginning with @samp{bre}:
1302 (@value{GDBP}) info breakpoints
1306 You can either press @key{RET} at this point, to run the @code{info
1307 breakpoints} command, or backspace and enter something else, if
1308 @samp{breakpoints} does not look like the command you expected. (If you
1309 were sure you wanted @code{info breakpoints} in the first place, you
1310 might as well just type @key{RET} immediately after @samp{info bre},
1311 to exploit command abbreviations rather than command completion).
1313 If there is more than one possibility for the next word when you press
1314 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1315 characters and try again, or just press @key{TAB} a second time;
1316 @value{GDBN} displays all the possible completions for that word. For
1317 example, you might want to set a breakpoint on a subroutine whose name
1318 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1319 just sounds the bell. Typing @key{TAB} again displays all the
1320 function names in your program that begin with those characters, for
1324 (@value{GDBP}) b make_ @key{TAB}
1325 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1326 make_a_section_from_file make_environ
1327 make_abs_section make_function_type
1328 make_blockvector make_pointer_type
1329 make_cleanup make_reference_type
1330 make_command make_symbol_completion_list
1331 (@value{GDBP}) b make_
1335 After displaying the available possibilities, @value{GDBN} copies your
1336 partial input (@samp{b make_} in the example) so you can finish the
1339 If you just want to see the list of alternatives in the first place, you
1340 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1341 means @kbd{@key{META} ?}. You can type this either by holding down a
1342 key designated as the @key{META} shift on your keyboard (if there is
1343 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1345 @cindex quotes in commands
1346 @cindex completion of quoted strings
1347 Sometimes the string you need, while logically a ``word'', may contain
1348 parentheses or other characters that @value{GDBN} normally excludes from
1349 its notion of a word. To permit word completion to work in this
1350 situation, you may enclose words in @code{'} (single quote marks) in
1351 @value{GDBN} commands.
1353 The most likely situation where you might need this is in typing the
1354 name of a C@t{++} function. This is because C@t{++} allows function
1355 overloading (multiple definitions of the same function, distinguished
1356 by argument type). For example, when you want to set a breakpoint you
1357 may need to distinguish whether you mean the version of @code{name}
1358 that takes an @code{int} parameter, @code{name(int)}, or the version
1359 that takes a @code{float} parameter, @code{name(float)}. To use the
1360 word-completion facilities in this situation, type a single quote
1361 @code{'} at the beginning of the function name. This alerts
1362 @value{GDBN} that it may need to consider more information than usual
1363 when you press @key{TAB} or @kbd{M-?} to request word completion:
1366 (@value{GDBP}) b 'bubble( @kbd{M-?}
1367 bubble(double,double) bubble(int,int)
1368 (@value{GDBP}) b 'bubble(
1371 In some cases, @value{GDBN} can tell that completing a name requires using
1372 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1373 completing as much as it can) if you do not type the quote in the first
1377 (@value{GDBP}) b bub @key{TAB}
1378 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1379 (@value{GDBP}) b 'bubble(
1383 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1384 you have not yet started typing the argument list when you ask for
1385 completion on an overloaded symbol.
1387 For more information about overloaded functions, see @ref{C plus plus
1388 expressions, ,C@t{++} expressions}. You can use the command @code{set
1389 overload-resolution off} to disable overload resolution;
1390 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1394 @section Getting help
1395 @cindex online documentation
1398 You can always ask @value{GDBN} itself for information on its commands,
1399 using the command @code{help}.
1402 @kindex h @r{(@code{help})}
1405 You can use @code{help} (abbreviated @code{h}) with no arguments to
1406 display a short list of named classes of commands:
1410 List of classes of commands:
1412 aliases -- Aliases of other commands
1413 breakpoints -- Making program stop at certain points
1414 data -- Examining data
1415 files -- Specifying and examining files
1416 internals -- Maintenance commands
1417 obscure -- Obscure features
1418 running -- Running the program
1419 stack -- Examining the stack
1420 status -- Status inquiries
1421 support -- Support facilities
1422 tracepoints -- Tracing of program execution without@*
1423 stopping the program
1424 user-defined -- User-defined commands
1426 Type "help" followed by a class name for a list of
1427 commands in that class.
1428 Type "help" followed by command name for full
1430 Command name abbreviations are allowed if unambiguous.
1433 @c the above line break eliminates huge line overfull...
1435 @item help @var{class}
1436 Using one of the general help classes as an argument, you can get a
1437 list of the individual commands in that class. For example, here is the
1438 help display for the class @code{status}:
1441 (@value{GDBP}) help status
1446 @c Line break in "show" line falsifies real output, but needed
1447 @c to fit in smallbook page size.
1448 info -- Generic command for showing things
1449 about the program being debugged
1450 show -- Generic command for showing things
1453 Type "help" followed by command name for full
1455 Command name abbreviations are allowed if unambiguous.
1459 @item help @var{command}
1460 With a command name as @code{help} argument, @value{GDBN} displays a
1461 short paragraph on how to use that command.
1464 @item apropos @var{args}
1465 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1466 commands, and their documentation, for the regular expression specified in
1467 @var{args}. It prints out all matches found. For example:
1478 set symbol-reloading -- Set dynamic symbol table reloading
1479 multiple times in one run
1480 show symbol-reloading -- Show dynamic symbol table reloading
1481 multiple times in one run
1486 @item complete @var{args}
1487 The @code{complete @var{args}} command lists all the possible completions
1488 for the beginning of a command. Use @var{args} to specify the beginning of the
1489 command you want completed. For example:
1495 @noindent results in:
1506 @noindent This is intended for use by @sc{gnu} Emacs.
1509 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1510 and @code{show} to inquire about the state of your program, or the state
1511 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1512 manual introduces each of them in the appropriate context. The listings
1513 under @code{info} and under @code{show} in the Index point to
1514 all the sub-commands. @xref{Index}.
1519 @kindex i @r{(@code{info})}
1521 This command (abbreviated @code{i}) is for describing the state of your
1522 program. For example, you can list the arguments given to your program
1523 with @code{info args}, list the registers currently in use with @code{info
1524 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1525 You can get a complete list of the @code{info} sub-commands with
1526 @w{@code{help info}}.
1530 You can assign the result of an expression to an environment variable with
1531 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1532 @code{set prompt $}.
1536 In contrast to @code{info}, @code{show} is for describing the state of
1537 @value{GDBN} itself.
1538 You can change most of the things you can @code{show}, by using the
1539 related command @code{set}; for example, you can control what number
1540 system is used for displays with @code{set radix}, or simply inquire
1541 which is currently in use with @code{show radix}.
1544 To display all the settable parameters and their current
1545 values, you can use @code{show} with no arguments; you may also use
1546 @code{info set}. Both commands produce the same display.
1547 @c FIXME: "info set" violates the rule that "info" is for state of
1548 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1549 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1553 Here are three miscellaneous @code{show} subcommands, all of which are
1554 exceptional in lacking corresponding @code{set} commands:
1557 @kindex show version
1558 @cindex version number
1560 Show what version of @value{GDBN} is running. You should include this
1561 information in @value{GDBN} bug-reports. If multiple versions of
1562 @value{GDBN} are in use at your site, you may need to determine which
1563 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1564 commands are introduced, and old ones may wither away. Also, many
1565 system vendors ship variant versions of @value{GDBN}, and there are
1566 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1567 The version number is the same as the one announced when you start
1570 @kindex show copying
1572 Display information about permission for copying @value{GDBN}.
1574 @kindex show warranty
1576 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1577 if your version of @value{GDBN} comes with one.
1582 @chapter Running Programs Under @value{GDBN}
1584 When you run a program under @value{GDBN}, you must first generate
1585 debugging information when you compile it.
1587 You may start @value{GDBN} with its arguments, if any, in an environment
1588 of your choice. If you are doing native debugging, you may redirect
1589 your program's input and output, debug an already running process, or
1590 kill a child process.
1593 * Compilation:: Compiling for debugging
1594 * Starting:: Starting your program
1595 * Arguments:: Your program's arguments
1596 * Environment:: Your program's environment
1598 * Working Directory:: Your program's working directory
1599 * Input/Output:: Your program's input and output
1600 * Attach:: Debugging an already-running process
1601 * Kill Process:: Killing the child process
1603 * Threads:: Debugging programs with multiple threads
1604 * Processes:: Debugging programs with multiple processes
1608 @section Compiling for debugging
1610 In order to debug a program effectively, you need to generate
1611 debugging information when you compile it. This debugging information
1612 is stored in the object file; it describes the data type of each
1613 variable or function and the correspondence between source line numbers
1614 and addresses in the executable code.
1616 To request debugging information, specify the @samp{-g} option when you run
1619 Most compilers do not include information about preprocessor macros in
1620 the debugging information if you specify the @option{-g} flag alone,
1621 because this information is rather large. Version 3.1 of @value{NGCC},
1622 the @sc{gnu} C compiler, provides macro information if you specify the
1623 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1624 debugging information in the Dwarf 2 format, and the latter requests
1625 ``extra information''. In the future, we hope to find more compact ways
1626 to represent macro information, so that it can be included with
1629 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1630 options together. Using those compilers, you cannot generate optimized
1631 executables containing debugging information.
1633 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1634 without @samp{-O}, making it possible to debug optimized code. We
1635 recommend that you @emph{always} use @samp{-g} whenever you compile a
1636 program. You may think your program is correct, but there is no sense
1637 in pushing your luck.
1639 @cindex optimized code, debugging
1640 @cindex debugging optimized code
1641 When you debug a program compiled with @samp{-g -O}, remember that the
1642 optimizer is rearranging your code; the debugger shows you what is
1643 really there. Do not be too surprised when the execution path does not
1644 exactly match your source file! An extreme example: if you define a
1645 variable, but never use it, @value{GDBN} never sees that
1646 variable---because the compiler optimizes it out of existence.
1648 Some things do not work as well with @samp{-g -O} as with just
1649 @samp{-g}, particularly on machines with instruction scheduling. If in
1650 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1651 please report it to us as a bug (including a test case!).
1653 Older versions of the @sc{gnu} C compiler permitted a variant option
1654 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1655 format; if your @sc{gnu} C compiler has this option, do not use it.
1659 @section Starting your program
1665 @kindex r @r{(@code{run})}
1668 Use the @code{run} command to start your program under @value{GDBN}.
1669 You must first specify the program name (except on VxWorks) with an
1670 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1671 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1672 (@pxref{Files, ,Commands to specify files}).
1676 If you are running your program in an execution environment that
1677 supports processes, @code{run} creates an inferior process and makes
1678 that process run your program. (In environments without processes,
1679 @code{run} jumps to the start of your program.)
1681 The execution of a program is affected by certain information it
1682 receives from its superior. @value{GDBN} provides ways to specify this
1683 information, which you must do @emph{before} starting your program. (You
1684 can change it after starting your program, but such changes only affect
1685 your program the next time you start it.) This information may be
1686 divided into four categories:
1689 @item The @emph{arguments.}
1690 Specify the arguments to give your program as the arguments of the
1691 @code{run} command. If a shell is available on your target, the shell
1692 is used to pass the arguments, so that you may use normal conventions
1693 (such as wildcard expansion or variable substitution) in describing
1695 In Unix systems, you can control which shell is used with the
1696 @code{SHELL} environment variable.
1697 @xref{Arguments, ,Your program's arguments}.
1699 @item The @emph{environment.}
1700 Your program normally inherits its environment from @value{GDBN}, but you can
1701 use the @value{GDBN} commands @code{set environment} and @code{unset
1702 environment} to change parts of the environment that affect
1703 your program. @xref{Environment, ,Your program's environment}.
1705 @item The @emph{working directory.}
1706 Your program inherits its working directory from @value{GDBN}. You can set
1707 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1708 @xref{Working Directory, ,Your program's working directory}.
1710 @item The @emph{standard input and output.}
1711 Your program normally uses the same device for standard input and
1712 standard output as @value{GDBN} is using. You can redirect input and output
1713 in the @code{run} command line, or you can use the @code{tty} command to
1714 set a different device for your program.
1715 @xref{Input/Output, ,Your program's input and output}.
1718 @emph{Warning:} While input and output redirection work, you cannot use
1719 pipes to pass the output of the program you are debugging to another
1720 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1724 When you issue the @code{run} command, your program begins to execute
1725 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1726 of how to arrange for your program to stop. Once your program has
1727 stopped, you may call functions in your program, using the @code{print}
1728 or @code{call} commands. @xref{Data, ,Examining Data}.
1730 If the modification time of your symbol file has changed since the last
1731 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1732 table, and reads it again. When it does this, @value{GDBN} tries to retain
1733 your current breakpoints.
1736 @section Your program's arguments
1738 @cindex arguments (to your program)
1739 The arguments to your program can be specified by the arguments of the
1741 They are passed to a shell, which expands wildcard characters and
1742 performs redirection of I/O, and thence to your program. Your
1743 @code{SHELL} environment variable (if it exists) specifies what shell
1744 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1745 the default shell (@file{/bin/sh} on Unix).
1747 On non-Unix systems, the program is usually invoked directly by
1748 @value{GDBN}, which emulates I/O redirection via the appropriate system
1749 calls, and the wildcard characters are expanded by the startup code of
1750 the program, not by the shell.
1752 @code{run} with no arguments uses the same arguments used by the previous
1753 @code{run}, or those set by the @code{set args} command.
1758 Specify the arguments to be used the next time your program is run. If
1759 @code{set args} has no arguments, @code{run} executes your program
1760 with no arguments. Once you have run your program with arguments,
1761 using @code{set args} before the next @code{run} is the only way to run
1762 it again without arguments.
1766 Show the arguments to give your program when it is started.
1770 @section Your program's environment
1772 @cindex environment (of your program)
1773 The @dfn{environment} consists of a set of environment variables and
1774 their values. Environment variables conventionally record such things as
1775 your user name, your home directory, your terminal type, and your search
1776 path for programs to run. Usually you set up environment variables with
1777 the shell and they are inherited by all the other programs you run. When
1778 debugging, it can be useful to try running your program with a modified
1779 environment without having to start @value{GDBN} over again.
1783 @item path @var{directory}
1784 Add @var{directory} to the front of the @code{PATH} environment variable
1785 (the search path for executables) that will be passed to your program.
1786 The value of @code{PATH} used by @value{GDBN} does not change.
1787 You may specify several directory names, separated by whitespace or by a
1788 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1789 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1790 is moved to the front, so it is searched sooner.
1792 You can use the string @samp{$cwd} to refer to whatever is the current
1793 working directory at the time @value{GDBN} searches the path. If you
1794 use @samp{.} instead, it refers to the directory where you executed the
1795 @code{path} command. @value{GDBN} replaces @samp{.} in the
1796 @var{directory} argument (with the current path) before adding
1797 @var{directory} to the search path.
1798 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1799 @c document that, since repeating it would be a no-op.
1803 Display the list of search paths for executables (the @code{PATH}
1804 environment variable).
1806 @kindex show environment
1807 @item show environment @r{[}@var{varname}@r{]}
1808 Print the value of environment variable @var{varname} to be given to
1809 your program when it starts. If you do not supply @var{varname},
1810 print the names and values of all environment variables to be given to
1811 your program. You can abbreviate @code{environment} as @code{env}.
1813 @kindex set environment
1814 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1815 Set environment variable @var{varname} to @var{value}. The value
1816 changes for your program only, not for @value{GDBN} itself. @var{value} may
1817 be any string; the values of environment variables are just strings, and
1818 any interpretation is supplied by your program itself. The @var{value}
1819 parameter is optional; if it is eliminated, the variable is set to a
1821 @c "any string" here does not include leading, trailing
1822 @c blanks. Gnu asks: does anyone care?
1824 For example, this command:
1831 tells the debugged program, when subsequently run, that its user is named
1832 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1833 are not actually required.)
1835 @kindex unset environment
1836 @item unset environment @var{varname}
1837 Remove variable @var{varname} from the environment to be passed to your
1838 program. This is different from @samp{set env @var{varname} =};
1839 @code{unset environment} removes the variable from the environment,
1840 rather than assigning it an empty value.
1843 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1845 by your @code{SHELL} environment variable if it exists (or
1846 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1847 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1848 @file{.bashrc} for BASH---any variables you set in that file affect
1849 your program. You may wish to move setting of environment variables to
1850 files that are only run when you sign on, such as @file{.login} or
1853 @node Working Directory
1854 @section Your program's working directory
1856 @cindex working directory (of your program)
1857 Each time you start your program with @code{run}, it inherits its
1858 working directory from the current working directory of @value{GDBN}.
1859 The @value{GDBN} working directory is initially whatever it inherited
1860 from its parent process (typically the shell), but you can specify a new
1861 working directory in @value{GDBN} with the @code{cd} command.
1863 The @value{GDBN} working directory also serves as a default for the commands
1864 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1869 @item cd @var{directory}
1870 Set the @value{GDBN} working directory to @var{directory}.
1874 Print the @value{GDBN} working directory.
1878 @section Your program's input and output
1883 By default, the program you run under @value{GDBN} does input and output to
1884 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1885 to its own terminal modes to interact with you, but it records the terminal
1886 modes your program was using and switches back to them when you continue
1887 running your program.
1890 @kindex info terminal
1892 Displays information recorded by @value{GDBN} about the terminal modes your
1896 You can redirect your program's input and/or output using shell
1897 redirection with the @code{run} command. For example,
1904 starts your program, diverting its output to the file @file{outfile}.
1907 @cindex controlling terminal
1908 Another way to specify where your program should do input and output is
1909 with the @code{tty} command. This command accepts a file name as
1910 argument, and causes this file to be the default for future @code{run}
1911 commands. It also resets the controlling terminal for the child
1912 process, for future @code{run} commands. For example,
1919 directs that processes started with subsequent @code{run} commands
1920 default to do input and output on the terminal @file{/dev/ttyb} and have
1921 that as their controlling terminal.
1923 An explicit redirection in @code{run} overrides the @code{tty} command's
1924 effect on the input/output device, but not its effect on the controlling
1927 When you use the @code{tty} command or redirect input in the @code{run}
1928 command, only the input @emph{for your program} is affected. The input
1929 for @value{GDBN} still comes from your terminal.
1932 @section Debugging an already-running process
1937 @item attach @var{process-id}
1938 This command attaches to a running process---one that was started
1939 outside @value{GDBN}. (@code{info files} shows your active
1940 targets.) The command takes as argument a process ID. The usual way to
1941 find out the process-id of a Unix process is with the @code{ps} utility,
1942 or with the @samp{jobs -l} shell command.
1944 @code{attach} does not repeat if you press @key{RET} a second time after
1945 executing the command.
1948 To use @code{attach}, your program must be running in an environment
1949 which supports processes; for example, @code{attach} does not work for
1950 programs on bare-board targets that lack an operating system. You must
1951 also have permission to send the process a signal.
1953 When you use @code{attach}, the debugger finds the program running in
1954 the process first by looking in the current working directory, then (if
1955 the program is not found) by using the source file search path
1956 (@pxref{Source Path, ,Specifying source directories}). You can also use
1957 the @code{file} command to load the program. @xref{Files, ,Commands to
1960 The first thing @value{GDBN} does after arranging to debug the specified
1961 process is to stop it. You can examine and modify an attached process
1962 with all the @value{GDBN} commands that are ordinarily available when
1963 you start processes with @code{run}. You can insert breakpoints; you
1964 can step and continue; you can modify storage. If you would rather the
1965 process continue running, you may use the @code{continue} command after
1966 attaching @value{GDBN} to the process.
1971 When you have finished debugging the attached process, you can use the
1972 @code{detach} command to release it from @value{GDBN} control. Detaching
1973 the process continues its execution. After the @code{detach} command,
1974 that process and @value{GDBN} become completely independent once more, and you
1975 are ready to @code{attach} another process or start one with @code{run}.
1976 @code{detach} does not repeat if you press @key{RET} again after
1977 executing the command.
1980 If you exit @value{GDBN} or use the @code{run} command while you have an
1981 attached process, you kill that process. By default, @value{GDBN} asks
1982 for confirmation if you try to do either of these things; you can
1983 control whether or not you need to confirm by using the @code{set
1984 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
1988 @section Killing the child process
1993 Kill the child process in which your program is running under @value{GDBN}.
1996 This command is useful if you wish to debug a core dump instead of a
1997 running process. @value{GDBN} ignores any core dump file while your program
2000 On some operating systems, a program cannot be executed outside @value{GDBN}
2001 while you have breakpoints set on it inside @value{GDBN}. You can use the
2002 @code{kill} command in this situation to permit running your program
2003 outside the debugger.
2005 The @code{kill} command is also useful if you wish to recompile and
2006 relink your program, since on many systems it is impossible to modify an
2007 executable file while it is running in a process. In this case, when you
2008 next type @code{run}, @value{GDBN} notices that the file has changed, and
2009 reads the symbol table again (while trying to preserve your current
2010 breakpoint settings).
2013 @section Debugging programs with multiple threads
2015 @cindex threads of execution
2016 @cindex multiple threads
2017 @cindex switching threads
2018 In some operating systems, such as HP-UX and Solaris, a single program
2019 may have more than one @dfn{thread} of execution. The precise semantics
2020 of threads differ from one operating system to another, but in general
2021 the threads of a single program are akin to multiple processes---except
2022 that they share one address space (that is, they can all examine and
2023 modify the same variables). On the other hand, each thread has its own
2024 registers and execution stack, and perhaps private memory.
2026 @value{GDBN} provides these facilities for debugging multi-thread
2030 @item automatic notification of new threads
2031 @item @samp{thread @var{threadno}}, a command to switch among threads
2032 @item @samp{info threads}, a command to inquire about existing threads
2033 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2034 a command to apply a command to a list of threads
2035 @item thread-specific breakpoints
2039 @emph{Warning:} These facilities are not yet available on every
2040 @value{GDBN} configuration where the operating system supports threads.
2041 If your @value{GDBN} does not support threads, these commands have no
2042 effect. For example, a system without thread support shows no output
2043 from @samp{info threads}, and always rejects the @code{thread} command,
2047 (@value{GDBP}) info threads
2048 (@value{GDBP}) thread 1
2049 Thread ID 1 not known. Use the "info threads" command to
2050 see the IDs of currently known threads.
2052 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2053 @c doesn't support threads"?
2056 @cindex focus of debugging
2057 @cindex current thread
2058 The @value{GDBN} thread debugging facility allows you to observe all
2059 threads while your program runs---but whenever @value{GDBN} takes
2060 control, one thread in particular is always the focus of debugging.
2061 This thread is called the @dfn{current thread}. Debugging commands show
2062 program information from the perspective of the current thread.
2064 @cindex @code{New} @var{systag} message
2065 @cindex thread identifier (system)
2066 @c FIXME-implementors!! It would be more helpful if the [New...] message
2067 @c included GDB's numeric thread handle, so you could just go to that
2068 @c thread without first checking `info threads'.
2069 Whenever @value{GDBN} detects a new thread in your program, it displays
2070 the target system's identification for the thread with a message in the
2071 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2072 whose form varies depending on the particular system. For example, on
2073 LynxOS, you might see
2076 [New process 35 thread 27]
2080 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2081 the @var{systag} is simply something like @samp{process 368}, with no
2084 @c FIXME!! (1) Does the [New...] message appear even for the very first
2085 @c thread of a program, or does it only appear for the
2086 @c second---i.e.@: when it becomes obvious we have a multithread
2088 @c (2) *Is* there necessarily a first thread always? Or do some
2089 @c multithread systems permit starting a program with multiple
2090 @c threads ab initio?
2092 @cindex thread number
2093 @cindex thread identifier (GDB)
2094 For debugging purposes, @value{GDBN} associates its own thread
2095 number---always a single integer---with each thread in your program.
2098 @kindex info threads
2100 Display a summary of all threads currently in your
2101 program. @value{GDBN} displays for each thread (in this order):
2104 @item the thread number assigned by @value{GDBN}
2106 @item the target system's thread identifier (@var{systag})
2108 @item the current stack frame summary for that thread
2112 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2113 indicates the current thread.
2117 @c end table here to get a little more width for example
2120 (@value{GDBP}) info threads
2121 3 process 35 thread 27 0x34e5 in sigpause ()
2122 2 process 35 thread 23 0x34e5 in sigpause ()
2123 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2129 @cindex thread number
2130 @cindex thread identifier (GDB)
2131 For debugging purposes, @value{GDBN} associates its own thread
2132 number---a small integer assigned in thread-creation order---with each
2133 thread in your program.
2135 @cindex @code{New} @var{systag} message, on HP-UX
2136 @cindex thread identifier (system), on HP-UX
2137 @c FIXME-implementors!! It would be more helpful if the [New...] message
2138 @c included GDB's numeric thread handle, so you could just go to that
2139 @c thread without first checking `info threads'.
2140 Whenever @value{GDBN} detects a new thread in your program, it displays
2141 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2142 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2143 whose form varies depending on the particular system. For example, on
2147 [New thread 2 (system thread 26594)]
2151 when @value{GDBN} notices a new thread.
2154 @kindex info threads
2156 Display a summary of all threads currently in your
2157 program. @value{GDBN} displays for each thread (in this order):
2160 @item the thread number assigned by @value{GDBN}
2162 @item the target system's thread identifier (@var{systag})
2164 @item the current stack frame summary for that thread
2168 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2169 indicates the current thread.
2173 @c end table here to get a little more width for example
2176 (@value{GDBP}) info threads
2177 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2179 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2180 from /usr/lib/libc.2
2181 1 system thread 27905 0x7b003498 in _brk () \@*
2182 from /usr/lib/libc.2
2186 @kindex thread @var{threadno}
2187 @item thread @var{threadno}
2188 Make thread number @var{threadno} the current thread. The command
2189 argument @var{threadno} is the internal @value{GDBN} thread number, as
2190 shown in the first field of the @samp{info threads} display.
2191 @value{GDBN} responds by displaying the system identifier of the thread
2192 you selected, and its current stack frame summary:
2195 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2196 (@value{GDBP}) thread 2
2197 [Switching to process 35 thread 23]
2198 0x34e5 in sigpause ()
2202 As with the @samp{[New @dots{}]} message, the form of the text after
2203 @samp{Switching to} depends on your system's conventions for identifying
2206 @kindex thread apply
2207 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2208 The @code{thread apply} command allows you to apply a command to one or
2209 more threads. Specify the numbers of the threads that you want affected
2210 with the command argument @var{threadno}. @var{threadno} is the internal
2211 @value{GDBN} thread number, as shown in the first field of the @samp{info
2212 threads} display. To apply a command to all threads, use
2213 @code{thread apply all} @var{args}.
2216 @cindex automatic thread selection
2217 @cindex switching threads automatically
2218 @cindex threads, automatic switching
2219 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2220 signal, it automatically selects the thread where that breakpoint or
2221 signal happened. @value{GDBN} alerts you to the context switch with a
2222 message of the form @samp{[Switching to @var{systag}]} to identify the
2225 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2226 more information about how @value{GDBN} behaves when you stop and start
2227 programs with multiple threads.
2229 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2230 watchpoints in programs with multiple threads.
2233 @section Debugging programs with multiple processes
2235 @cindex fork, debugging programs which call
2236 @cindex multiple processes
2237 @cindex processes, multiple
2238 On most systems, @value{GDBN} has no special support for debugging
2239 programs which create additional processes using the @code{fork}
2240 function. When a program forks, @value{GDBN} will continue to debug the
2241 parent process and the child process will run unimpeded. If you have
2242 set a breakpoint in any code which the child then executes, the child
2243 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2244 will cause it to terminate.
2246 However, if you want to debug the child process there is a workaround
2247 which isn't too painful. Put a call to @code{sleep} in the code which
2248 the child process executes after the fork. It may be useful to sleep
2249 only if a certain environment variable is set, or a certain file exists,
2250 so that the delay need not occur when you don't want to run @value{GDBN}
2251 on the child. While the child is sleeping, use the @code{ps} program to
2252 get its process ID. Then tell @value{GDBN} (a new invocation of
2253 @value{GDBN} if you are also debugging the parent process) to attach to
2254 the child process (@pxref{Attach}). From that point on you can debug
2255 the child process just like any other process which you attached to.
2257 On HP-UX (11.x and later only?), @value{GDBN} provides support for
2258 debugging programs that create additional processes using the
2259 @code{fork} or @code{vfork} function.
2261 By default, when a program forks, @value{GDBN} will continue to debug
2262 the parent process and the child process will run unimpeded.
2264 If you want to follow the child process instead of the parent process,
2265 use the command @w{@code{set follow-fork-mode}}.
2268 @kindex set follow-fork-mode
2269 @item set follow-fork-mode @var{mode}
2270 Set the debugger response to a program call of @code{fork} or
2271 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2272 process. The @var{mode} can be:
2276 The original process is debugged after a fork. The child process runs
2277 unimpeded. This is the default.
2280 The new process is debugged after a fork. The parent process runs
2284 The debugger will ask for one of the above choices.
2287 @item show follow-fork-mode
2288 Display the current debugger response to a @code{fork} or @code{vfork} call.
2291 If you ask to debug a child process and a @code{vfork} is followed by an
2292 @code{exec}, @value{GDBN} executes the new target up to the first
2293 breakpoint in the new target. If you have a breakpoint set on
2294 @code{main} in your original program, the breakpoint will also be set on
2295 the child process's @code{main}.
2297 When a child process is spawned by @code{vfork}, you cannot debug the
2298 child or parent until an @code{exec} call completes.
2300 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2301 call executes, the new target restarts. To restart the parent process,
2302 use the @code{file} command with the parent executable name as its
2305 You can use the @code{catch} command to make @value{GDBN} stop whenever
2306 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2307 Catchpoints, ,Setting catchpoints}.
2310 @chapter Stopping and Continuing
2312 The principal purposes of using a debugger are so that you can stop your
2313 program before it terminates; or so that, if your program runs into
2314 trouble, you can investigate and find out why.
2316 Inside @value{GDBN}, your program may stop for any of several reasons,
2317 such as a signal, a breakpoint, or reaching a new line after a
2318 @value{GDBN} command such as @code{step}. You may then examine and
2319 change variables, set new breakpoints or remove old ones, and then
2320 continue execution. Usually, the messages shown by @value{GDBN} provide
2321 ample explanation of the status of your program---but you can also
2322 explicitly request this information at any time.
2325 @kindex info program
2327 Display information about the status of your program: whether it is
2328 running or not, what process it is, and why it stopped.
2332 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2333 * Continuing and Stepping:: Resuming execution
2335 * Thread Stops:: Stopping and starting multi-thread programs
2339 @section Breakpoints, watchpoints, and catchpoints
2342 A @dfn{breakpoint} makes your program stop whenever a certain point in
2343 the program is reached. For each breakpoint, you can add conditions to
2344 control in finer detail whether your program stops. You can set
2345 breakpoints with the @code{break} command and its variants (@pxref{Set
2346 Breaks, ,Setting breakpoints}), to specify the place where your program
2347 should stop by line number, function name or exact address in the
2350 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2351 breakpoints in shared libraries before the executable is run. There is
2352 a minor limitation on HP-UX systems: you must wait until the executable
2353 is run in order to set breakpoints in shared library routines that are
2354 not called directly by the program (for example, routines that are
2355 arguments in a @code{pthread_create} call).
2358 @cindex memory tracing
2359 @cindex breakpoint on memory address
2360 @cindex breakpoint on variable modification
2361 A @dfn{watchpoint} is a special breakpoint that stops your program
2362 when the value of an expression changes. You must use a different
2363 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2364 watchpoints}), but aside from that, you can manage a watchpoint like
2365 any other breakpoint: you enable, disable, and delete both breakpoints
2366 and watchpoints using the same commands.
2368 You can arrange to have values from your program displayed automatically
2369 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2373 @cindex breakpoint on events
2374 A @dfn{catchpoint} is another special breakpoint that stops your program
2375 when a certain kind of event occurs, such as the throwing of a C@t{++}
2376 exception or the loading of a library. As with watchpoints, you use a
2377 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2378 catchpoints}), but aside from that, you can manage a catchpoint like any
2379 other breakpoint. (To stop when your program receives a signal, use the
2380 @code{handle} command; see @ref{Signals, ,Signals}.)
2382 @cindex breakpoint numbers
2383 @cindex numbers for breakpoints
2384 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2385 catchpoint when you create it; these numbers are successive integers
2386 starting with one. In many of the commands for controlling various
2387 features of breakpoints you use the breakpoint number to say which
2388 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2389 @dfn{disabled}; if disabled, it has no effect on your program until you
2392 @cindex breakpoint ranges
2393 @cindex ranges of breakpoints
2394 Some @value{GDBN} commands accept a range of breakpoints on which to
2395 operate. A breakpoint range is either a single breakpoint number, like
2396 @samp{5}, or two such numbers, in increasing order, separated by a
2397 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2398 all breakpoint in that range are operated on.
2401 * Set Breaks:: Setting breakpoints
2402 * Set Watchpoints:: Setting watchpoints
2403 * Set Catchpoints:: Setting catchpoints
2404 * Delete Breaks:: Deleting breakpoints
2405 * Disabling:: Disabling breakpoints
2406 * Conditions:: Break conditions
2407 * Break Commands:: Breakpoint command lists
2408 * Breakpoint Menus:: Breakpoint menus
2409 * Error in Breakpoints:: ``Cannot insert breakpoints''
2413 @subsection Setting breakpoints
2415 @c FIXME LMB what does GDB do if no code on line of breakpt?
2416 @c consider in particular declaration with/without initialization.
2418 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2421 @kindex b @r{(@code{break})}
2422 @vindex $bpnum@r{, convenience variable}
2423 @cindex latest breakpoint
2424 Breakpoints are set with the @code{break} command (abbreviated
2425 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2426 number of the breakpoint you've set most recently; see @ref{Convenience
2427 Vars,, Convenience variables}, for a discussion of what you can do with
2428 convenience variables.
2430 You have several ways to say where the breakpoint should go.
2433 @item break @var{function}
2434 Set a breakpoint at entry to function @var{function}.
2435 When using source languages that permit overloading of symbols, such as
2436 C@t{++}, @var{function} may refer to more than one possible place to break.
2437 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2439 @item break +@var{offset}
2440 @itemx break -@var{offset}
2441 Set a breakpoint some number of lines forward or back from the position
2442 at which execution stopped in the currently selected @dfn{stack frame}.
2443 (@xref{Frames, ,Frames}, for a description of stack frames.)
2445 @item break @var{linenum}
2446 Set a breakpoint at line @var{linenum} in the current source file.
2447 The current source file is the last file whose source text was printed.
2448 The breakpoint will stop your program just before it executes any of the
2451 @item break @var{filename}:@var{linenum}
2452 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2454 @item break @var{filename}:@var{function}
2455 Set a breakpoint at entry to function @var{function} found in file
2456 @var{filename}. Specifying a file name as well as a function name is
2457 superfluous except when multiple files contain similarly named
2460 @item break *@var{address}
2461 Set a breakpoint at address @var{address}. You can use this to set
2462 breakpoints in parts of your program which do not have debugging
2463 information or source files.
2466 When called without any arguments, @code{break} sets a breakpoint at
2467 the next instruction to be executed in the selected stack frame
2468 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2469 innermost, this makes your program stop as soon as control
2470 returns to that frame. This is similar to the effect of a
2471 @code{finish} command in the frame inside the selected frame---except
2472 that @code{finish} does not leave an active breakpoint. If you use
2473 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2474 the next time it reaches the current location; this may be useful
2477 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2478 least one instruction has been executed. If it did not do this, you
2479 would be unable to proceed past a breakpoint without first disabling the
2480 breakpoint. This rule applies whether or not the breakpoint already
2481 existed when your program stopped.
2483 @item break @dots{} if @var{cond}
2484 Set a breakpoint with condition @var{cond}; evaluate the expression
2485 @var{cond} each time the breakpoint is reached, and stop only if the
2486 value is nonzero---that is, if @var{cond} evaluates as true.
2487 @samp{@dots{}} stands for one of the possible arguments described
2488 above (or no argument) specifying where to break. @xref{Conditions,
2489 ,Break conditions}, for more information on breakpoint conditions.
2492 @item tbreak @var{args}
2493 Set a breakpoint enabled only for one stop. @var{args} are the
2494 same as for the @code{break} command, and the breakpoint is set in the same
2495 way, but the breakpoint is automatically deleted after the first time your
2496 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2499 @item hbreak @var{args}
2500 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2501 @code{break} command and the breakpoint is set in the same way, but the
2502 breakpoint requires hardware support and some target hardware may not
2503 have this support. The main purpose of this is EPROM/ROM code
2504 debugging, so you can set a breakpoint at an instruction without
2505 changing the instruction. This can be used with the new trap-generation
2506 provided by SPARClite DSU and some x86-based targets. These targets
2507 will generate traps when a program accesses some data or instruction
2508 address that is assigned to the debug registers. However the hardware
2509 breakpoint registers can take a limited number of breakpoints. For
2510 example, on the DSU, only two data breakpoints can be set at a time, and
2511 @value{GDBN} will reject this command if more than two are used. Delete
2512 or disable unused hardware breakpoints before setting new ones
2513 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2514 @xref{set remote hardware-breakpoint-limit}.
2518 @item thbreak @var{args}
2519 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2520 are the same as for the @code{hbreak} command and the breakpoint is set in
2521 the same way. However, like the @code{tbreak} command,
2522 the breakpoint is automatically deleted after the
2523 first time your program stops there. Also, like the @code{hbreak}
2524 command, the breakpoint requires hardware support and some target hardware
2525 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2526 See also @ref{Conditions, ,Break conditions}.
2529 @cindex regular expression
2530 @item rbreak @var{regex}
2531 Set breakpoints on all functions matching the regular expression
2532 @var{regex}. This command sets an unconditional breakpoint on all
2533 matches, printing a list of all breakpoints it set. Once these
2534 breakpoints are set, they are treated just like the breakpoints set with
2535 the @code{break} command. You can delete them, disable them, or make
2536 them conditional the same way as any other breakpoint.
2538 The syntax of the regular expression is the standard one used with tools
2539 like @file{grep}. Note that this is different from the syntax used by
2540 shells, so for instance @code{foo*} matches all functions that include
2541 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2542 @code{.*} leading and trailing the regular expression you supply, so to
2543 match only functions that begin with @code{foo}, use @code{^foo}.
2545 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2546 breakpoints on overloaded functions that are not members of any special
2549 @kindex info breakpoints
2550 @cindex @code{$_} and @code{info breakpoints}
2551 @item info breakpoints @r{[}@var{n}@r{]}
2552 @itemx info break @r{[}@var{n}@r{]}
2553 @itemx info watchpoints @r{[}@var{n}@r{]}
2554 Print a table of all breakpoints, watchpoints, and catchpoints set and
2555 not deleted, with the following columns for each breakpoint:
2558 @item Breakpoint Numbers
2560 Breakpoint, watchpoint, or catchpoint.
2562 Whether the breakpoint is marked to be disabled or deleted when hit.
2563 @item Enabled or Disabled
2564 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2565 that are not enabled.
2567 Where the breakpoint is in your program, as a memory address.
2569 Where the breakpoint is in the source for your program, as a file and
2574 If a breakpoint is conditional, @code{info break} shows the condition on
2575 the line following the affected breakpoint; breakpoint commands, if any,
2576 are listed after that.
2579 @code{info break} with a breakpoint
2580 number @var{n} as argument lists only that breakpoint. The
2581 convenience variable @code{$_} and the default examining-address for
2582 the @code{x} command are set to the address of the last breakpoint
2583 listed (@pxref{Memory, ,Examining memory}).
2586 @code{info break} displays a count of the number of times the breakpoint
2587 has been hit. This is especially useful in conjunction with the
2588 @code{ignore} command. You can ignore a large number of breakpoint
2589 hits, look at the breakpoint info to see how many times the breakpoint
2590 was hit, and then run again, ignoring one less than that number. This
2591 will get you quickly to the last hit of that breakpoint.
2594 @value{GDBN} allows you to set any number of breakpoints at the same place in
2595 your program. There is nothing silly or meaningless about this. When
2596 the breakpoints are conditional, this is even useful
2597 (@pxref{Conditions, ,Break conditions}).
2599 @cindex negative breakpoint numbers
2600 @cindex internal @value{GDBN} breakpoints
2601 @value{GDBN} itself sometimes sets breakpoints in your program for
2602 special purposes, such as proper handling of @code{longjmp} (in C
2603 programs). These internal breakpoints are assigned negative numbers,
2604 starting with @code{-1}; @samp{info breakpoints} does not display them.
2605 You can see these breakpoints with the @value{GDBN} maintenance command
2606 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2609 @node Set Watchpoints
2610 @subsection Setting watchpoints
2612 @cindex setting watchpoints
2613 @cindex software watchpoints
2614 @cindex hardware watchpoints
2615 You can use a watchpoint to stop execution whenever the value of an
2616 expression changes, without having to predict a particular place where
2619 Depending on your system, watchpoints may be implemented in software or
2620 hardware. @value{GDBN} does software watchpointing by single-stepping your
2621 program and testing the variable's value each time, which is hundreds of
2622 times slower than normal execution. (But this may still be worth it, to
2623 catch errors where you have no clue what part of your program is the
2626 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2627 @value{GDBN} includes support for
2628 hardware watchpoints, which do not slow down the running of your
2633 @item watch @var{expr}
2634 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2635 is written into by the program and its value changes.
2638 @item rwatch @var{expr}
2639 Set a watchpoint that will break when watch @var{expr} is read by the program.
2642 @item awatch @var{expr}
2643 Set a watchpoint that will break when @var{expr} is either read or written into
2646 @kindex info watchpoints
2647 @item info watchpoints
2648 This command prints a list of watchpoints, breakpoints, and catchpoints;
2649 it is the same as @code{info break}.
2652 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2653 watchpoints execute very quickly, and the debugger reports a change in
2654 value at the exact instruction where the change occurs. If @value{GDBN}
2655 cannot set a hardware watchpoint, it sets a software watchpoint, which
2656 executes more slowly and reports the change in value at the next
2657 statement, not the instruction, after the change occurs.
2659 When you issue the @code{watch} command, @value{GDBN} reports
2662 Hardware watchpoint @var{num}: @var{expr}
2666 if it was able to set a hardware watchpoint.
2668 Currently, the @code{awatch} and @code{rwatch} commands can only set
2669 hardware watchpoints, because accesses to data that don't change the
2670 value of the watched expression cannot be detected without examining
2671 every instruction as it is being executed, and @value{GDBN} does not do
2672 that currently. If @value{GDBN} finds that it is unable to set a
2673 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2674 will print a message like this:
2677 Expression cannot be implemented with read/access watchpoint.
2680 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2681 data type of the watched expression is wider than what a hardware
2682 watchpoint on the target machine can handle. For example, some systems
2683 can only watch regions that are up to 4 bytes wide; on such systems you
2684 cannot set hardware watchpoints for an expression that yields a
2685 double-precision floating-point number (which is typically 8 bytes
2686 wide). As a work-around, it might be possible to break the large region
2687 into a series of smaller ones and watch them with separate watchpoints.
2689 If you set too many hardware watchpoints, @value{GDBN} might be unable
2690 to insert all of them when you resume the execution of your program.
2691 Since the precise number of active watchpoints is unknown until such
2692 time as the program is about to be resumed, @value{GDBN} might not be
2693 able to warn you about this when you set the watchpoints, and the
2694 warning will be printed only when the program is resumed:
2697 Hardware watchpoint @var{num}: Could not insert watchpoint
2701 If this happens, delete or disable some of the watchpoints.
2703 The SPARClite DSU will generate traps when a program accesses some data
2704 or instruction address that is assigned to the debug registers. For the
2705 data addresses, DSU facilitates the @code{watch} command. However the
2706 hardware breakpoint registers can only take two data watchpoints, and
2707 both watchpoints must be the same kind. For example, you can set two
2708 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2709 @strong{or} two with @code{awatch} commands, but you cannot set one
2710 watchpoint with one command and the other with a different command.
2711 @value{GDBN} will reject the command if you try to mix watchpoints.
2712 Delete or disable unused watchpoint commands before setting new ones.
2714 If you call a function interactively using @code{print} or @code{call},
2715 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2716 kind of breakpoint or the call completes.
2718 @value{GDBN} automatically deletes watchpoints that watch local
2719 (automatic) variables, or expressions that involve such variables, when
2720 they go out of scope, that is, when the execution leaves the block in
2721 which these variables were defined. In particular, when the program
2722 being debugged terminates, @emph{all} local variables go out of scope,
2723 and so only watchpoints that watch global variables remain set. If you
2724 rerun the program, you will need to set all such watchpoints again. One
2725 way of doing that would be to set a code breakpoint at the entry to the
2726 @code{main} function and when it breaks, set all the watchpoints.
2729 @cindex watchpoints and threads
2730 @cindex threads and watchpoints
2731 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2732 usefulness. With the current watchpoint implementation, @value{GDBN}
2733 can only watch the value of an expression @emph{in a single thread}. If
2734 you are confident that the expression can only change due to the current
2735 thread's activity (and if you are also confident that no other thread
2736 can become current), then you can use watchpoints as usual. However,
2737 @value{GDBN} may not notice when a non-current thread's activity changes
2740 @c FIXME: this is almost identical to the previous paragraph.
2741 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2742 have only limited usefulness. If @value{GDBN} creates a software
2743 watchpoint, it can only watch the value of an expression @emph{in a
2744 single thread}. If you are confident that the expression can only
2745 change due to the current thread's activity (and if you are also
2746 confident that no other thread can become current), then you can use
2747 software watchpoints as usual. However, @value{GDBN} may not notice
2748 when a non-current thread's activity changes the expression. (Hardware
2749 watchpoints, in contrast, watch an expression in all threads.)
2752 @xref{set remote hardware-watchpoint-limit}.
2754 @node Set Catchpoints
2755 @subsection Setting catchpoints
2756 @cindex catchpoints, setting
2757 @cindex exception handlers
2758 @cindex event handling
2760 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2761 kinds of program events, such as C@t{++} exceptions or the loading of a
2762 shared library. Use the @code{catch} command to set a catchpoint.
2766 @item catch @var{event}
2767 Stop when @var{event} occurs. @var{event} can be any of the following:
2771 The throwing of a C@t{++} exception.
2775 The catching of a C@t{++} exception.
2779 A call to @code{exec}. This is currently only available for HP-UX.
2783 A call to @code{fork}. This is currently only available for HP-UX.
2787 A call to @code{vfork}. This is currently only available for HP-UX.
2790 @itemx load @var{libname}
2792 The dynamic loading of any shared library, or the loading of the library
2793 @var{libname}. This is currently only available for HP-UX.
2796 @itemx unload @var{libname}
2797 @kindex catch unload
2798 The unloading of any dynamically loaded shared library, or the unloading
2799 of the library @var{libname}. This is currently only available for HP-UX.
2802 @item tcatch @var{event}
2803 Set a catchpoint that is enabled only for one stop. The catchpoint is
2804 automatically deleted after the first time the event is caught.
2808 Use the @code{info break} command to list the current catchpoints.
2810 There are currently some limitations to C@t{++} exception handling
2811 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2815 If you call a function interactively, @value{GDBN} normally returns
2816 control to you when the function has finished executing. If the call
2817 raises an exception, however, the call may bypass the mechanism that
2818 returns control to you and cause your program either to abort or to
2819 simply continue running until it hits a breakpoint, catches a signal
2820 that @value{GDBN} is listening for, or exits. This is the case even if
2821 you set a catchpoint for the exception; catchpoints on exceptions are
2822 disabled within interactive calls.
2825 You cannot raise an exception interactively.
2828 You cannot install an exception handler interactively.
2831 @cindex raise exceptions
2832 Sometimes @code{catch} is not the best way to debug exception handling:
2833 if you need to know exactly where an exception is raised, it is better to
2834 stop @emph{before} the exception handler is called, since that way you
2835 can see the stack before any unwinding takes place. If you set a
2836 breakpoint in an exception handler instead, it may not be easy to find
2837 out where the exception was raised.
2839 To stop just before an exception handler is called, you need some
2840 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2841 raised by calling a library function named @code{__raise_exception}
2842 which has the following ANSI C interface:
2845 /* @var{addr} is where the exception identifier is stored.
2846 @var{id} is the exception identifier. */
2847 void __raise_exception (void **addr, void *id);
2851 To make the debugger catch all exceptions before any stack
2852 unwinding takes place, set a breakpoint on @code{__raise_exception}
2853 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2855 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2856 that depends on the value of @var{id}, you can stop your program when
2857 a specific exception is raised. You can use multiple conditional
2858 breakpoints to stop your program when any of a number of exceptions are
2863 @subsection Deleting breakpoints
2865 @cindex clearing breakpoints, watchpoints, catchpoints
2866 @cindex deleting breakpoints, watchpoints, catchpoints
2867 It is often necessary to eliminate a breakpoint, watchpoint, or
2868 catchpoint once it has done its job and you no longer want your program
2869 to stop there. This is called @dfn{deleting} the breakpoint. A
2870 breakpoint that has been deleted no longer exists; it is forgotten.
2872 With the @code{clear} command you can delete breakpoints according to
2873 where they are in your program. With the @code{delete} command you can
2874 delete individual breakpoints, watchpoints, or catchpoints by specifying
2875 their breakpoint numbers.
2877 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2878 automatically ignores breakpoints on the first instruction to be executed
2879 when you continue execution without changing the execution address.
2884 Delete any breakpoints at the next instruction to be executed in the
2885 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2886 the innermost frame is selected, this is a good way to delete a
2887 breakpoint where your program just stopped.
2889 @item clear @var{function}
2890 @itemx clear @var{filename}:@var{function}
2891 Delete any breakpoints set at entry to the function @var{function}.
2893 @item clear @var{linenum}
2894 @itemx clear @var{filename}:@var{linenum}
2895 Delete any breakpoints set at or within the code of the specified line.
2897 @cindex delete breakpoints
2899 @kindex d @r{(@code{delete})}
2900 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2901 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2902 ranges specified as arguments. If no argument is specified, delete all
2903 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2904 confirm off}). You can abbreviate this command as @code{d}.
2908 @subsection Disabling breakpoints
2910 @kindex disable breakpoints
2911 @kindex enable breakpoints
2912 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2913 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2914 it had been deleted, but remembers the information on the breakpoint so
2915 that you can @dfn{enable} it again later.
2917 You disable and enable breakpoints, watchpoints, and catchpoints with
2918 the @code{enable} and @code{disable} commands, optionally specifying one
2919 or more breakpoint numbers as arguments. Use @code{info break} or
2920 @code{info watch} to print a list of breakpoints, watchpoints, and
2921 catchpoints if you do not know which numbers to use.
2923 A breakpoint, watchpoint, or catchpoint can have any of four different
2924 states of enablement:
2928 Enabled. The breakpoint stops your program. A breakpoint set
2929 with the @code{break} command starts out in this state.
2931 Disabled. The breakpoint has no effect on your program.
2933 Enabled once. The breakpoint stops your program, but then becomes
2936 Enabled for deletion. The breakpoint stops your program, but
2937 immediately after it does so it is deleted permanently. A breakpoint
2938 set with the @code{tbreak} command starts out in this state.
2941 You can use the following commands to enable or disable breakpoints,
2942 watchpoints, and catchpoints:
2945 @kindex disable breakpoints
2947 @kindex dis @r{(@code{disable})}
2948 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2949 Disable the specified breakpoints---or all breakpoints, if none are
2950 listed. A disabled breakpoint has no effect but is not forgotten. All
2951 options such as ignore-counts, conditions and commands are remembered in
2952 case the breakpoint is enabled again later. You may abbreviate
2953 @code{disable} as @code{dis}.
2955 @kindex enable breakpoints
2957 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2958 Enable the specified breakpoints (or all defined breakpoints). They
2959 become effective once again in stopping your program.
2961 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
2962 Enable the specified breakpoints temporarily. @value{GDBN} disables any
2963 of these breakpoints immediately after stopping your program.
2965 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
2966 Enable the specified breakpoints to work once, then die. @value{GDBN}
2967 deletes any of these breakpoints as soon as your program stops there.
2970 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
2971 @c confusing: tbreak is also initially enabled.
2972 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
2973 ,Setting breakpoints}), breakpoints that you set are initially enabled;
2974 subsequently, they become disabled or enabled only when you use one of
2975 the commands above. (The command @code{until} can set and delete a
2976 breakpoint of its own, but it does not change the state of your other
2977 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
2981 @subsection Break conditions
2982 @cindex conditional breakpoints
2983 @cindex breakpoint conditions
2985 @c FIXME what is scope of break condition expr? Context where wanted?
2986 @c in particular for a watchpoint?
2987 The simplest sort of breakpoint breaks every time your program reaches a
2988 specified place. You can also specify a @dfn{condition} for a
2989 breakpoint. A condition is just a Boolean expression in your
2990 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
2991 a condition evaluates the expression each time your program reaches it,
2992 and your program stops only if the condition is @emph{true}.
2994 This is the converse of using assertions for program validation; in that
2995 situation, you want to stop when the assertion is violated---that is,
2996 when the condition is false. In C, if you want to test an assertion expressed
2997 by the condition @var{assert}, you should set the condition
2998 @samp{! @var{assert}} on the appropriate breakpoint.
3000 Conditions are also accepted for watchpoints; you may not need them,
3001 since a watchpoint is inspecting the value of an expression anyhow---but
3002 it might be simpler, say, to just set a watchpoint on a variable name,
3003 and specify a condition that tests whether the new value is an interesting
3006 Break conditions can have side effects, and may even call functions in
3007 your program. This can be useful, for example, to activate functions
3008 that log program progress, or to use your own print functions to
3009 format special data structures. The effects are completely predictable
3010 unless there is another enabled breakpoint at the same address. (In
3011 that case, @value{GDBN} might see the other breakpoint first and stop your
3012 program without checking the condition of this one.) Note that
3013 breakpoint commands are usually more convenient and flexible than break
3015 purpose of performing side effects when a breakpoint is reached
3016 (@pxref{Break Commands, ,Breakpoint command lists}).
3018 Break conditions can be specified when a breakpoint is set, by using
3019 @samp{if} in the arguments to the @code{break} command. @xref{Set
3020 Breaks, ,Setting breakpoints}. They can also be changed at any time
3021 with the @code{condition} command.
3023 You can also use the @code{if} keyword with the @code{watch} command.
3024 The @code{catch} command does not recognize the @code{if} keyword;
3025 @code{condition} is the only way to impose a further condition on a
3030 @item condition @var{bnum} @var{expression}
3031 Specify @var{expression} as the break condition for breakpoint,
3032 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3033 breakpoint @var{bnum} stops your program only if the value of
3034 @var{expression} is true (nonzero, in C). When you use
3035 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3036 syntactic correctness, and to determine whether symbols in it have
3037 referents in the context of your breakpoint. If @var{expression} uses
3038 symbols not referenced in the context of the breakpoint, @value{GDBN}
3039 prints an error message:
3042 No symbol "foo" in current context.
3047 not actually evaluate @var{expression} at the time the @code{condition}
3048 command (or a command that sets a breakpoint with a condition, like
3049 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3051 @item condition @var{bnum}
3052 Remove the condition from breakpoint number @var{bnum}. It becomes
3053 an ordinary unconditional breakpoint.
3056 @cindex ignore count (of breakpoint)
3057 A special case of a breakpoint condition is to stop only when the
3058 breakpoint has been reached a certain number of times. This is so
3059 useful that there is a special way to do it, using the @dfn{ignore
3060 count} of the breakpoint. Every breakpoint has an ignore count, which
3061 is an integer. Most of the time, the ignore count is zero, and
3062 therefore has no effect. But if your program reaches a breakpoint whose
3063 ignore count is positive, then instead of stopping, it just decrements
3064 the ignore count by one and continues. As a result, if the ignore count
3065 value is @var{n}, the breakpoint does not stop the next @var{n} times
3066 your program reaches it.
3070 @item ignore @var{bnum} @var{count}
3071 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3072 The next @var{count} times the breakpoint is reached, your program's
3073 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3076 To make the breakpoint stop the next time it is reached, specify
3079 When you use @code{continue} to resume execution of your program from a
3080 breakpoint, you can specify an ignore count directly as an argument to
3081 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3082 Stepping,,Continuing and stepping}.
3084 If a breakpoint has a positive ignore count and a condition, the
3085 condition is not checked. Once the ignore count reaches zero,
3086 @value{GDBN} resumes checking the condition.
3088 You could achieve the effect of the ignore count with a condition such
3089 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3090 is decremented each time. @xref{Convenience Vars, ,Convenience
3094 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3097 @node Break Commands
3098 @subsection Breakpoint command lists
3100 @cindex breakpoint commands
3101 You can give any breakpoint (or watchpoint or catchpoint) a series of
3102 commands to execute when your program stops due to that breakpoint. For
3103 example, you might want to print the values of certain expressions, or
3104 enable other breakpoints.
3109 @item commands @r{[}@var{bnum}@r{]}
3110 @itemx @dots{} @var{command-list} @dots{}
3112 Specify a list of commands for breakpoint number @var{bnum}. The commands
3113 themselves appear on the following lines. Type a line containing just
3114 @code{end} to terminate the commands.
3116 To remove all commands from a breakpoint, type @code{commands} and
3117 follow it immediately with @code{end}; that is, give no commands.
3119 With no @var{bnum} argument, @code{commands} refers to the last
3120 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3121 recently encountered).
3124 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3125 disabled within a @var{command-list}.
3127 You can use breakpoint commands to start your program up again. Simply
3128 use the @code{continue} command, or @code{step}, or any other command
3129 that resumes execution.
3131 Any other commands in the command list, after a command that resumes
3132 execution, are ignored. This is because any time you resume execution
3133 (even with a simple @code{next} or @code{step}), you may encounter
3134 another breakpoint---which could have its own command list, leading to
3135 ambiguities about which list to execute.
3138 If the first command you specify in a command list is @code{silent}, the
3139 usual message about stopping at a breakpoint is not printed. This may
3140 be desirable for breakpoints that are to print a specific message and
3141 then continue. If none of the remaining commands print anything, you
3142 see no sign that the breakpoint was reached. @code{silent} is
3143 meaningful only at the beginning of a breakpoint command list.
3145 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3146 print precisely controlled output, and are often useful in silent
3147 breakpoints. @xref{Output, ,Commands for controlled output}.
3149 For example, here is how you could use breakpoint commands to print the
3150 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3156 printf "x is %d\n",x
3161 One application for breakpoint commands is to compensate for one bug so
3162 you can test for another. Put a breakpoint just after the erroneous line
3163 of code, give it a condition to detect the case in which something
3164 erroneous has been done, and give it commands to assign correct values
3165 to any variables that need them. End with the @code{continue} command
3166 so that your program does not stop, and start with the @code{silent}
3167 command so that no output is produced. Here is an example:
3178 @node Breakpoint Menus
3179 @subsection Breakpoint menus
3181 @cindex symbol overloading
3183 Some programming languages (notably C@t{++}) permit a single function name
3184 to be defined several times, for application in different contexts.
3185 This is called @dfn{overloading}. When a function name is overloaded,
3186 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3187 a breakpoint. If you realize this is a problem, you can use
3188 something like @samp{break @var{function}(@var{types})} to specify which
3189 particular version of the function you want. Otherwise, @value{GDBN} offers
3190 you a menu of numbered choices for different possible breakpoints, and
3191 waits for your selection with the prompt @samp{>}. The first two
3192 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3193 sets a breakpoint at each definition of @var{function}, and typing
3194 @kbd{0} aborts the @code{break} command without setting any new
3197 For example, the following session excerpt shows an attempt to set a
3198 breakpoint at the overloaded symbol @code{String::after}.
3199 We choose three particular definitions of that function name:
3201 @c FIXME! This is likely to change to show arg type lists, at least
3204 (@value{GDBP}) b String::after
3207 [2] file:String.cc; line number:867
3208 [3] file:String.cc; line number:860
3209 [4] file:String.cc; line number:875
3210 [5] file:String.cc; line number:853
3211 [6] file:String.cc; line number:846
3212 [7] file:String.cc; line number:735
3214 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3215 Breakpoint 2 at 0xb344: file String.cc, line 875.
3216 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3217 Multiple breakpoints were set.
3218 Use the "delete" command to delete unwanted
3224 @c @ifclear BARETARGET
3225 @node Error in Breakpoints
3226 @subsection ``Cannot insert breakpoints''
3228 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3230 Under some operating systems, breakpoints cannot be used in a program if
3231 any other process is running that program. In this situation,
3232 attempting to run or continue a program with a breakpoint causes
3233 @value{GDBN} to print an error message:
3236 Cannot insert breakpoints.
3237 The same program may be running in another process.
3240 When this happens, you have three ways to proceed:
3244 Remove or disable the breakpoints, then continue.
3247 Suspend @value{GDBN}, and copy the file containing your program to a new
3248 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3249 that @value{GDBN} should run your program under that name.
3250 Then start your program again.
3253 Relink your program so that the text segment is nonsharable, using the
3254 linker option @samp{-N}. The operating system limitation may not apply
3255 to nonsharable executables.
3259 A similar message can be printed if you request too many active
3260 hardware-assisted breakpoints and watchpoints:
3262 @c FIXME: the precise wording of this message may change; the relevant
3263 @c source change is not committed yet (Sep 3, 1999).
3265 Stopped; cannot insert breakpoints.
3266 You may have requested too many hardware breakpoints and watchpoints.
3270 This message is printed when you attempt to resume the program, since
3271 only then @value{GDBN} knows exactly how many hardware breakpoints and
3272 watchpoints it needs to insert.
3274 When this message is printed, you need to disable or remove some of the
3275 hardware-assisted breakpoints and watchpoints, and then continue.
3278 @node Continuing and Stepping
3279 @section Continuing and stepping
3283 @cindex resuming execution
3284 @dfn{Continuing} means resuming program execution until your program
3285 completes normally. In contrast, @dfn{stepping} means executing just
3286 one more ``step'' of your program, where ``step'' may mean either one
3287 line of source code, or one machine instruction (depending on what
3288 particular command you use). Either when continuing or when stepping,
3289 your program may stop even sooner, due to a breakpoint or a signal. (If
3290 it stops due to a signal, you may want to use @code{handle}, or use
3291 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3295 @kindex c @r{(@code{continue})}
3296 @kindex fg @r{(resume foreground execution)}
3297 @item continue @r{[}@var{ignore-count}@r{]}
3298 @itemx c @r{[}@var{ignore-count}@r{]}
3299 @itemx fg @r{[}@var{ignore-count}@r{]}
3300 Resume program execution, at the address where your program last stopped;
3301 any breakpoints set at that address are bypassed. The optional argument
3302 @var{ignore-count} allows you to specify a further number of times to
3303 ignore a breakpoint at this location; its effect is like that of
3304 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3306 The argument @var{ignore-count} is meaningful only when your program
3307 stopped due to a breakpoint. At other times, the argument to
3308 @code{continue} is ignored.
3310 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3311 debugged program is deemed to be the foreground program) are provided
3312 purely for convenience, and have exactly the same behavior as
3316 To resume execution at a different place, you can use @code{return}
3317 (@pxref{Returning, ,Returning from a function}) to go back to the
3318 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3319 different address}) to go to an arbitrary location in your program.
3321 A typical technique for using stepping is to set a breakpoint
3322 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3323 beginning of the function or the section of your program where a problem
3324 is believed to lie, run your program until it stops at that breakpoint,
3325 and then step through the suspect area, examining the variables that are
3326 interesting, until you see the problem happen.
3330 @kindex s @r{(@code{step})}
3332 Continue running your program until control reaches a different source
3333 line, then stop it and return control to @value{GDBN}. This command is
3334 abbreviated @code{s}.
3337 @c "without debugging information" is imprecise; actually "without line
3338 @c numbers in the debugging information". (gcc -g1 has debugging info but
3339 @c not line numbers). But it seems complex to try to make that
3340 @c distinction here.
3341 @emph{Warning:} If you use the @code{step} command while control is
3342 within a function that was compiled without debugging information,
3343 execution proceeds until control reaches a function that does have
3344 debugging information. Likewise, it will not step into a function which
3345 is compiled without debugging information. To step through functions
3346 without debugging information, use the @code{stepi} command, described
3350 The @code{step} command only stops at the first instruction of a source
3351 line. This prevents the multiple stops that could otherwise occur in
3352 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3353 to stop if a function that has debugging information is called within
3354 the line. In other words, @code{step} @emph{steps inside} any functions
3355 called within the line.
3357 Also, the @code{step} command only enters a function if there is line
3358 number information for the function. Otherwise it acts like the
3359 @code{next} command. This avoids problems when using @code{cc -gl}
3360 on MIPS machines. Previously, @code{step} entered subroutines if there
3361 was any debugging information about the routine.
3363 @item step @var{count}
3364 Continue running as in @code{step}, but do so @var{count} times. If a
3365 breakpoint is reached, or a signal not related to stepping occurs before
3366 @var{count} steps, stepping stops right away.
3369 @kindex n @r{(@code{next})}
3370 @item next @r{[}@var{count}@r{]}
3371 Continue to the next source line in the current (innermost) stack frame.
3372 This is similar to @code{step}, but function calls that appear within
3373 the line of code are executed without stopping. Execution stops when
3374 control reaches a different line of code at the original stack level
3375 that was executing when you gave the @code{next} command. This command
3376 is abbreviated @code{n}.
3378 An argument @var{count} is a repeat count, as for @code{step}.
3381 @c FIX ME!! Do we delete this, or is there a way it fits in with
3382 @c the following paragraph? --- Vctoria
3384 @c @code{next} within a function that lacks debugging information acts like
3385 @c @code{step}, but any function calls appearing within the code of the
3386 @c function are executed without stopping.
3388 The @code{next} command only stops at the first instruction of a
3389 source line. This prevents multiple stops that could otherwise occur in
3390 @code{switch} statements, @code{for} loops, etc.
3392 @kindex set step-mode
3394 @cindex functions without line info, and stepping
3395 @cindex stepping into functions with no line info
3396 @itemx set step-mode on
3397 The @code{set step-mode on} command causes the @code{step} command to
3398 stop at the first instruction of a function which contains no debug line
3399 information rather than stepping over it.
3401 This is useful in cases where you may be interested in inspecting the
3402 machine instructions of a function which has no symbolic info and do not
3403 want @value{GDBN} to automatically skip over this function.
3405 @item set step-mode off
3406 Causes the @code{step} command to step over any functions which contains no
3407 debug information. This is the default.
3411 Continue running until just after function in the selected stack frame
3412 returns. Print the returned value (if any).
3414 Contrast this with the @code{return} command (@pxref{Returning,
3415 ,Returning from a function}).
3418 @kindex u @r{(@code{until})}
3421 Continue running until a source line past the current line, in the
3422 current stack frame, is reached. This command is used to avoid single
3423 stepping through a loop more than once. It is like the @code{next}
3424 command, except that when @code{until} encounters a jump, it
3425 automatically continues execution until the program counter is greater
3426 than the address of the jump.
3428 This means that when you reach the end of a loop after single stepping
3429 though it, @code{until} makes your program continue execution until it
3430 exits the loop. In contrast, a @code{next} command at the end of a loop
3431 simply steps back to the beginning of the loop, which forces you to step
3432 through the next iteration.
3434 @code{until} always stops your program if it attempts to exit the current
3437 @code{until} may produce somewhat counterintuitive results if the order
3438 of machine code does not match the order of the source lines. For
3439 example, in the following excerpt from a debugging session, the @code{f}
3440 (@code{frame}) command shows that execution is stopped at line
3441 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3445 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3447 (@value{GDBP}) until
3448 195 for ( ; argc > 0; NEXTARG) @{
3451 This happened because, for execution efficiency, the compiler had
3452 generated code for the loop closure test at the end, rather than the
3453 start, of the loop---even though the test in a C @code{for}-loop is
3454 written before the body of the loop. The @code{until} command appeared
3455 to step back to the beginning of the loop when it advanced to this
3456 expression; however, it has not really gone to an earlier
3457 statement---not in terms of the actual machine code.
3459 @code{until} with no argument works by means of single
3460 instruction stepping, and hence is slower than @code{until} with an
3463 @item until @var{location}
3464 @itemx u @var{location}
3465 Continue running your program until either the specified location is
3466 reached, or the current stack frame returns. @var{location} is any of
3467 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3468 ,Setting breakpoints}). This form of the command uses breakpoints, and
3469 hence is quicker than @code{until} without an argument. The specified
3470 location is actually reached only if it is in the current frame. This
3471 implies that @code{until} can be used to skip over recursive function
3472 invocations. For instance in the code below, if the current location is
3473 line @code{96}, issuing @code{until 99} will execute the program up to
3474 line @code{99} in the same invocation of factorial, i.e. after the inner
3475 invocations have returned.
3478 94 int factorial (int value)
3480 96 if (value > 1) @{
3481 97 value *= factorial (value - 1);
3488 @kindex advance @var{location}
3489 @itemx advance @var{location}
3490 Continue running the program up to the given location. An argument is
3491 required, anything of the same form as arguments for the @code{break}
3492 command. Execution will also stop upon exit from the current stack
3493 frame. This command is similar to @code{until}, but @code{advance} will
3494 not skip over recursive function calls, and the target location doesn't
3495 have to be in the same frame as the current one.
3499 @kindex si @r{(@code{stepi})}
3501 @itemx stepi @var{arg}
3503 Execute one machine instruction, then stop and return to the debugger.
3505 It is often useful to do @samp{display/i $pc} when stepping by machine
3506 instructions. This makes @value{GDBN} automatically display the next
3507 instruction to be executed, each time your program stops. @xref{Auto
3508 Display,, Automatic display}.
3510 An argument is a repeat count, as in @code{step}.
3514 @kindex ni @r{(@code{nexti})}
3516 @itemx nexti @var{arg}
3518 Execute one machine instruction, but if it is a function call,
3519 proceed until the function returns.
3521 An argument is a repeat count, as in @code{next}.
3528 A signal is an asynchronous event that can happen in a program. The
3529 operating system defines the possible kinds of signals, and gives each
3530 kind a name and a number. For example, in Unix @code{SIGINT} is the
3531 signal a program gets when you type an interrupt character (often @kbd{C-c});
3532 @code{SIGSEGV} is the signal a program gets from referencing a place in
3533 memory far away from all the areas in use; @code{SIGALRM} occurs when
3534 the alarm clock timer goes off (which happens only if your program has
3535 requested an alarm).
3537 @cindex fatal signals
3538 Some signals, including @code{SIGALRM}, are a normal part of the
3539 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3540 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3541 program has not specified in advance some other way to handle the signal.
3542 @code{SIGINT} does not indicate an error in your program, but it is normally
3543 fatal so it can carry out the purpose of the interrupt: to kill the program.
3545 @value{GDBN} has the ability to detect any occurrence of a signal in your
3546 program. You can tell @value{GDBN} in advance what to do for each kind of
3549 @cindex handling signals
3550 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3551 @code{SIGALRM} be silently passed to your program
3552 (so as not to interfere with their role in the program's functioning)
3553 but to stop your program immediately whenever an error signal happens.
3554 You can change these settings with the @code{handle} command.
3557 @kindex info signals
3560 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3561 handle each one. You can use this to see the signal numbers of all
3562 the defined types of signals.
3564 @code{info handle} is an alias for @code{info signals}.
3567 @item handle @var{signal} @var{keywords}@dots{}
3568 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3569 can be the number of a signal or its name (with or without the
3570 @samp{SIG} at the beginning); a list of signal numbers of the form
3571 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3572 known signals. The @var{keywords} say what change to make.
3576 The keywords allowed by the @code{handle} command can be abbreviated.
3577 Their full names are:
3581 @value{GDBN} should not stop your program when this signal happens. It may
3582 still print a message telling you that the signal has come in.
3585 @value{GDBN} should stop your program when this signal happens. This implies
3586 the @code{print} keyword as well.
3589 @value{GDBN} should print a message when this signal happens.
3592 @value{GDBN} should not mention the occurrence of the signal at all. This
3593 implies the @code{nostop} keyword as well.
3597 @value{GDBN} should allow your program to see this signal; your program
3598 can handle the signal, or else it may terminate if the signal is fatal
3599 and not handled. @code{pass} and @code{noignore} are synonyms.
3603 @value{GDBN} should not allow your program to see this signal.
3604 @code{nopass} and @code{ignore} are synonyms.
3608 When a signal stops your program, the signal is not visible to the
3610 continue. Your program sees the signal then, if @code{pass} is in
3611 effect for the signal in question @emph{at that time}. In other words,
3612 after @value{GDBN} reports a signal, you can use the @code{handle}
3613 command with @code{pass} or @code{nopass} to control whether your
3614 program sees that signal when you continue.
3616 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3617 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3618 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3621 You can also use the @code{signal} command to prevent your program from
3622 seeing a signal, or cause it to see a signal it normally would not see,
3623 or to give it any signal at any time. For example, if your program stopped
3624 due to some sort of memory reference error, you might store correct
3625 values into the erroneous variables and continue, hoping to see more
3626 execution; but your program would probably terminate immediately as
3627 a result of the fatal signal once it saw the signal. To prevent this,
3628 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3632 @section Stopping and starting multi-thread programs
3634 When your program has multiple threads (@pxref{Threads,, Debugging
3635 programs with multiple threads}), you can choose whether to set
3636 breakpoints on all threads, or on a particular thread.
3639 @cindex breakpoints and threads
3640 @cindex thread breakpoints
3641 @kindex break @dots{} thread @var{threadno}
3642 @item break @var{linespec} thread @var{threadno}
3643 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3644 @var{linespec} specifies source lines; there are several ways of
3645 writing them, but the effect is always to specify some source line.
3647 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3648 to specify that you only want @value{GDBN} to stop the program when a
3649 particular thread reaches this breakpoint. @var{threadno} is one of the
3650 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3651 column of the @samp{info threads} display.
3653 If you do not specify @samp{thread @var{threadno}} when you set a
3654 breakpoint, the breakpoint applies to @emph{all} threads of your
3657 You can use the @code{thread} qualifier on conditional breakpoints as
3658 well; in this case, place @samp{thread @var{threadno}} before the
3659 breakpoint condition, like this:
3662 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3667 @cindex stopped threads
3668 @cindex threads, stopped
3669 Whenever your program stops under @value{GDBN} for any reason,
3670 @emph{all} threads of execution stop, not just the current thread. This
3671 allows you to examine the overall state of the program, including
3672 switching between threads, without worrying that things may change
3675 @cindex continuing threads
3676 @cindex threads, continuing
3677 Conversely, whenever you restart the program, @emph{all} threads start
3678 executing. @emph{This is true even when single-stepping} with commands
3679 like @code{step} or @code{next}.
3681 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3682 Since thread scheduling is up to your debugging target's operating
3683 system (not controlled by @value{GDBN}), other threads may
3684 execute more than one statement while the current thread completes a
3685 single step. Moreover, in general other threads stop in the middle of a
3686 statement, rather than at a clean statement boundary, when the program
3689 You might even find your program stopped in another thread after
3690 continuing or even single-stepping. This happens whenever some other
3691 thread runs into a breakpoint, a signal, or an exception before the
3692 first thread completes whatever you requested.
3694 On some OSes, you can lock the OS scheduler and thus allow only a single
3698 @item set scheduler-locking @var{mode}
3699 Set the scheduler locking mode. If it is @code{off}, then there is no
3700 locking and any thread may run at any time. If @code{on}, then only the
3701 current thread may run when the inferior is resumed. The @code{step}
3702 mode optimizes for single-stepping. It stops other threads from
3703 ``seizing the prompt'' by preempting the current thread while you are
3704 stepping. Other threads will only rarely (or never) get a chance to run
3705 when you step. They are more likely to run when you @samp{next} over a
3706 function call, and they are completely free to run when you use commands
3707 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3708 thread hits a breakpoint during its timeslice, they will never steal the
3709 @value{GDBN} prompt away from the thread that you are debugging.
3711 @item show scheduler-locking
3712 Display the current scheduler locking mode.
3717 @chapter Examining the Stack
3719 When your program has stopped, the first thing you need to know is where it
3720 stopped and how it got there.
3723 Each time your program performs a function call, information about the call
3725 That information includes the location of the call in your program,
3726 the arguments of the call,
3727 and the local variables of the function being called.
3728 The information is saved in a block of data called a @dfn{stack frame}.
3729 The stack frames are allocated in a region of memory called the @dfn{call
3732 When your program stops, the @value{GDBN} commands for examining the
3733 stack allow you to see all of this information.
3735 @cindex selected frame
3736 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3737 @value{GDBN} commands refer implicitly to the selected frame. In
3738 particular, whenever you ask @value{GDBN} for the value of a variable in
3739 your program, the value is found in the selected frame. There are
3740 special @value{GDBN} commands to select whichever frame you are
3741 interested in. @xref{Selection, ,Selecting a frame}.
3743 When your program stops, @value{GDBN} automatically selects the
3744 currently executing frame and describes it briefly, similar to the
3745 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3748 * Frames:: Stack frames
3749 * Backtrace:: Backtraces
3750 * Selection:: Selecting a frame
3751 * Frame Info:: Information on a frame
3756 @section Stack frames
3758 @cindex frame, definition
3760 The call stack is divided up into contiguous pieces called @dfn{stack
3761 frames}, or @dfn{frames} for short; each frame is the data associated
3762 with one call to one function. The frame contains the arguments given
3763 to the function, the function's local variables, and the address at
3764 which the function is executing.
3766 @cindex initial frame
3767 @cindex outermost frame
3768 @cindex innermost frame
3769 When your program is started, the stack has only one frame, that of the
3770 function @code{main}. This is called the @dfn{initial} frame or the
3771 @dfn{outermost} frame. Each time a function is called, a new frame is
3772 made. Each time a function returns, the frame for that function invocation
3773 is eliminated. If a function is recursive, there can be many frames for
3774 the same function. The frame for the function in which execution is
3775 actually occurring is called the @dfn{innermost} frame. This is the most
3776 recently created of all the stack frames that still exist.
3778 @cindex frame pointer
3779 Inside your program, stack frames are identified by their addresses. A
3780 stack frame consists of many bytes, each of which has its own address; each
3781 kind of computer has a convention for choosing one byte whose
3782 address serves as the address of the frame. Usually this address is kept
3783 in a register called the @dfn{frame pointer register} while execution is
3784 going on in that frame.
3786 @cindex frame number
3787 @value{GDBN} assigns numbers to all existing stack frames, starting with
3788 zero for the innermost frame, one for the frame that called it,
3789 and so on upward. These numbers do not really exist in your program;
3790 they are assigned by @value{GDBN} to give you a way of designating stack
3791 frames in @value{GDBN} commands.
3793 @c The -fomit-frame-pointer below perennially causes hbox overflow
3794 @c underflow problems.
3795 @cindex frameless execution
3796 Some compilers provide a way to compile functions so that they operate
3797 without stack frames. (For example, the @value{GCC} option
3799 @samp{-fomit-frame-pointer}
3801 generates functions without a frame.)
3802 This is occasionally done with heavily used library functions to save
3803 the frame setup time. @value{GDBN} has limited facilities for dealing
3804 with these function invocations. If the innermost function invocation
3805 has no stack frame, @value{GDBN} nevertheless regards it as though
3806 it had a separate frame, which is numbered zero as usual, allowing
3807 correct tracing of the function call chain. However, @value{GDBN} has
3808 no provision for frameless functions elsewhere in the stack.
3811 @kindex frame@r{, command}
3812 @cindex current stack frame
3813 @item frame @var{args}
3814 The @code{frame} command allows you to move from one stack frame to another,
3815 and to print the stack frame you select. @var{args} may be either the
3816 address of the frame or the stack frame number. Without an argument,
3817 @code{frame} prints the current stack frame.
3819 @kindex select-frame
3820 @cindex selecting frame silently
3822 The @code{select-frame} command allows you to move from one stack frame
3823 to another without printing the frame. This is the silent version of
3832 @cindex stack traces
3833 A backtrace is a summary of how your program got where it is. It shows one
3834 line per frame, for many frames, starting with the currently executing
3835 frame (frame zero), followed by its caller (frame one), and on up the
3840 @kindex bt @r{(@code{backtrace})}
3843 Print a backtrace of the entire stack: one line per frame for all
3844 frames in the stack.
3846 You can stop the backtrace at any time by typing the system interrupt
3847 character, normally @kbd{C-c}.
3849 @item backtrace @var{n}
3851 Similar, but print only the innermost @var{n} frames.
3853 @item backtrace -@var{n}
3855 Similar, but print only the outermost @var{n} frames.
3860 @kindex info s @r{(@code{info stack})}
3861 The names @code{where} and @code{info stack} (abbreviated @code{info s})
3862 are additional aliases for @code{backtrace}.
3864 Each line in the backtrace shows the frame number and the function name.
3865 The program counter value is also shown---unless you use @code{set
3866 print address off}. The backtrace also shows the source file name and
3867 line number, as well as the arguments to the function. The program
3868 counter value is omitted if it is at the beginning of the code for that
3871 Here is an example of a backtrace. It was made with the command
3872 @samp{bt 3}, so it shows the innermost three frames.
3876 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
3878 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
3879 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
3881 (More stack frames follow...)
3886 The display for frame zero does not begin with a program counter
3887 value, indicating that your program has stopped at the beginning of the
3888 code for line @code{993} of @code{builtin.c}.
3890 @kindex set backtrace-below-main
3891 @kindex show backtrace-below-main
3893 Most programs have a standard entry point---a place where system libraries
3894 and startup code transition into user code. For C this is @code{main}.
3895 When @value{GDBN} finds the entry function in a backtrace it will terminate
3896 the backtrace, to avoid tracing into highly system-specific (and generally
3897 uninteresting) code. If you need to examine the startup code, then you can
3898 change this behavior.
3901 @item set backtrace-below-main off
3902 Backtraces will stop when they encounter the user entry point. This is the
3905 @item set backtrace-below-main
3906 @itemx set backtrace-below-main on
3907 Backtraces will continue past the user entry point to the top of the stack.
3909 @item show backtrace-below-main
3910 Display the current backtrace policy.
3914 @section Selecting a frame
3916 Most commands for examining the stack and other data in your program work on
3917 whichever stack frame is selected at the moment. Here are the commands for
3918 selecting a stack frame; all of them finish by printing a brief description
3919 of the stack frame just selected.
3922 @kindex frame@r{, selecting}
3923 @kindex f @r{(@code{frame})}
3926 Select frame number @var{n}. Recall that frame zero is the innermost
3927 (currently executing) frame, frame one is the frame that called the
3928 innermost one, and so on. The highest-numbered frame is the one for
3931 @item frame @var{addr}
3933 Select the frame at address @var{addr}. This is useful mainly if the
3934 chaining of stack frames has been damaged by a bug, making it
3935 impossible for @value{GDBN} to assign numbers properly to all frames. In
3936 addition, this can be useful when your program has multiple stacks and
3937 switches between them.
3939 On the SPARC architecture, @code{frame} needs two addresses to
3940 select an arbitrary frame: a frame pointer and a stack pointer.
3942 On the MIPS and Alpha architecture, it needs two addresses: a stack
3943 pointer and a program counter.
3945 On the 29k architecture, it needs three addresses: a register stack
3946 pointer, a program counter, and a memory stack pointer.
3947 @c note to future updaters: this is conditioned on a flag
3948 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
3949 @c as of 27 Jan 1994.
3953 Move @var{n} frames up the stack. For positive numbers @var{n}, this
3954 advances toward the outermost frame, to higher frame numbers, to frames
3955 that have existed longer. @var{n} defaults to one.
3958 @kindex do @r{(@code{down})}
3960 Move @var{n} frames down the stack. For positive numbers @var{n}, this
3961 advances toward the innermost frame, to lower frame numbers, to frames
3962 that were created more recently. @var{n} defaults to one. You may
3963 abbreviate @code{down} as @code{do}.
3966 All of these commands end by printing two lines of output describing the
3967 frame. The first line shows the frame number, the function name, the
3968 arguments, and the source file and line number of execution in that
3969 frame. The second line shows the text of that source line.
3977 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
3979 10 read_input_file (argv[i]);
3983 After such a printout, the @code{list} command with no arguments
3984 prints ten lines centered on the point of execution in the frame.
3985 You can also edit the program at the point of execution with your favorite
3986 editing program by typing @code{edit}.
3987 @xref{List, ,Printing source lines},
3991 @kindex down-silently
3993 @item up-silently @var{n}
3994 @itemx down-silently @var{n}
3995 These two commands are variants of @code{up} and @code{down},
3996 respectively; they differ in that they do their work silently, without
3997 causing display of the new frame. They are intended primarily for use
3998 in @value{GDBN} command scripts, where the output might be unnecessary and
4003 @section Information about a frame
4005 There are several other commands to print information about the selected
4011 When used without any argument, this command does not change which
4012 frame is selected, but prints a brief description of the currently
4013 selected stack frame. It can be abbreviated @code{f}. With an
4014 argument, this command is used to select a stack frame.
4015 @xref{Selection, ,Selecting a frame}.
4018 @kindex info f @r{(@code{info frame})}
4021 This command prints a verbose description of the selected stack frame,
4026 the address of the frame
4028 the address of the next frame down (called by this frame)
4030 the address of the next frame up (caller of this frame)
4032 the language in which the source code corresponding to this frame is written
4034 the address of the frame's arguments
4036 the address of the frame's local variables
4038 the program counter saved in it (the address of execution in the caller frame)
4040 which registers were saved in the frame
4043 @noindent The verbose description is useful when
4044 something has gone wrong that has made the stack format fail to fit
4045 the usual conventions.
4047 @item info frame @var{addr}
4048 @itemx info f @var{addr}
4049 Print a verbose description of the frame at address @var{addr}, without
4050 selecting that frame. The selected frame remains unchanged by this
4051 command. This requires the same kind of address (more than one for some
4052 architectures) that you specify in the @code{frame} command.
4053 @xref{Selection, ,Selecting a frame}.
4057 Print the arguments of the selected frame, each on a separate line.
4061 Print the local variables of the selected frame, each on a separate
4062 line. These are all variables (declared either static or automatic)
4063 accessible at the point of execution of the selected frame.
4066 @cindex catch exceptions, list active handlers
4067 @cindex exception handlers, how to list
4069 Print a list of all the exception handlers that are active in the
4070 current stack frame at the current point of execution. To see other
4071 exception handlers, visit the associated frame (using the @code{up},
4072 @code{down}, or @code{frame} commands); then type @code{info catch}.
4073 @xref{Set Catchpoints, , Setting catchpoints}.
4079 @chapter Examining Source Files
4081 @value{GDBN} can print parts of your program's source, since the debugging
4082 information recorded in the program tells @value{GDBN} what source files were
4083 used to build it. When your program stops, @value{GDBN} spontaneously prints
4084 the line where it stopped. Likewise, when you select a stack frame
4085 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4086 execution in that frame has stopped. You can print other portions of
4087 source files by explicit command.
4089 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4090 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4091 @value{GDBN} under @sc{gnu} Emacs}.
4094 * List:: Printing source lines
4095 * Edit:: Editing source files
4096 * Search:: Searching source files
4097 * Source Path:: Specifying source directories
4098 * Machine Code:: Source and machine code
4102 @section Printing source lines
4105 @kindex l @r{(@code{list})}
4106 To print lines from a source file, use the @code{list} command
4107 (abbreviated @code{l}). By default, ten lines are printed.
4108 There are several ways to specify what part of the file you want to print.
4110 Here are the forms of the @code{list} command most commonly used:
4113 @item list @var{linenum}
4114 Print lines centered around line number @var{linenum} in the
4115 current source file.
4117 @item list @var{function}
4118 Print lines centered around the beginning of function
4122 Print more lines. If the last lines printed were printed with a
4123 @code{list} command, this prints lines following the last lines
4124 printed; however, if the last line printed was a solitary line printed
4125 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4126 Stack}), this prints lines centered around that line.
4129 Print lines just before the lines last printed.
4132 By default, @value{GDBN} prints ten source lines with any of these forms of
4133 the @code{list} command. You can change this using @code{set listsize}:
4136 @kindex set listsize
4137 @item set listsize @var{count}
4138 Make the @code{list} command display @var{count} source lines (unless
4139 the @code{list} argument explicitly specifies some other number).
4141 @kindex show listsize
4143 Display the number of lines that @code{list} prints.
4146 Repeating a @code{list} command with @key{RET} discards the argument,
4147 so it is equivalent to typing just @code{list}. This is more useful
4148 than listing the same lines again. An exception is made for an
4149 argument of @samp{-}; that argument is preserved in repetition so that
4150 each repetition moves up in the source file.
4153 In general, the @code{list} command expects you to supply zero, one or two
4154 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4155 of writing them, but the effect is always to specify some source line.
4156 Here is a complete description of the possible arguments for @code{list}:
4159 @item list @var{linespec}
4160 Print lines centered around the line specified by @var{linespec}.
4162 @item list @var{first},@var{last}
4163 Print lines from @var{first} to @var{last}. Both arguments are
4166 @item list ,@var{last}
4167 Print lines ending with @var{last}.
4169 @item list @var{first},
4170 Print lines starting with @var{first}.
4173 Print lines just after the lines last printed.
4176 Print lines just before the lines last printed.
4179 As described in the preceding table.
4182 Here are the ways of specifying a single source line---all the
4187 Specifies line @var{number} of the current source file.
4188 When a @code{list} command has two linespecs, this refers to
4189 the same source file as the first linespec.
4192 Specifies the line @var{offset} lines after the last line printed.
4193 When used as the second linespec in a @code{list} command that has
4194 two, this specifies the line @var{offset} lines down from the
4198 Specifies the line @var{offset} lines before the last line printed.
4200 @item @var{filename}:@var{number}
4201 Specifies line @var{number} in the source file @var{filename}.
4203 @item @var{function}
4204 Specifies the line that begins the body of the function @var{function}.
4205 For example: in C, this is the line with the open brace.
4207 @item @var{filename}:@var{function}
4208 Specifies the line of the open-brace that begins the body of the
4209 function @var{function} in the file @var{filename}. You only need the
4210 file name with a function name to avoid ambiguity when there are
4211 identically named functions in different source files.
4213 @item *@var{address}
4214 Specifies the line containing the program address @var{address}.
4215 @var{address} may be any expression.
4219 @section Editing source files
4220 @cindex editing source files
4223 @kindex e @r{(@code{edit})}
4224 To edit the lines in a source file, use the @code{edit} command.
4225 The editing program of your choice
4226 is invoked with the current line set to
4227 the active line in the program.
4228 Alternatively, there are several ways to specify what part of the file you
4229 want to print if you want to see other parts of the program.
4231 Here are the forms of the @code{edit} command most commonly used:
4235 Edit the current source file at the active line number in the program.
4237 @item edit @var{number}
4238 Edit the current source file with @var{number} as the active line number.
4240 @item edit @var{function}
4241 Edit the file containing @var{function} at the beginning of its definition.
4243 @item edit @var{filename}:@var{number}
4244 Specifies line @var{number} in the source file @var{filename}.
4246 @item edit @var{filename}:@var{function}
4247 Specifies the line that begins the body of the
4248 function @var{function} in the file @var{filename}. You only need the
4249 file name with a function name to avoid ambiguity when there are
4250 identically named functions in different source files.
4252 @item edit *@var{address}
4253 Specifies the line containing the program address @var{address}.
4254 @var{address} may be any expression.
4257 @subsection Choosing your editor
4258 You can customize @value{GDBN} to use any editor you want
4260 The only restriction is that your editor (say @code{ex}), recognizes the
4261 following command-line syntax:
4263 ex +@var{number} file
4265 The optional numeric value +@var{number} designates the active line in
4266 the file.}. By default, it is @value{EDITOR}, but you can change this
4267 by setting the environment variable @code{EDITOR} before using
4268 @value{GDBN}. For example, to configure @value{GDBN} to use the
4269 @code{vi} editor, you could use these commands with the @code{sh} shell:
4275 or in the @code{csh} shell,
4277 setenv EDITOR /usr/bin/vi
4282 @section Searching source files
4284 @kindex reverse-search
4286 There are two commands for searching through the current source file for a
4291 @kindex forward-search
4292 @item forward-search @var{regexp}
4293 @itemx search @var{regexp}
4294 The command @samp{forward-search @var{regexp}} checks each line,
4295 starting with the one following the last line listed, for a match for
4296 @var{regexp}. It lists the line that is found. You can use the
4297 synonym @samp{search @var{regexp}} or abbreviate the command name as
4300 @item reverse-search @var{regexp}
4301 The command @samp{reverse-search @var{regexp}} checks each line, starting
4302 with the one before the last line listed and going backward, for a match
4303 for @var{regexp}. It lists the line that is found. You can abbreviate
4304 this command as @code{rev}.
4308 @section Specifying source directories
4311 @cindex directories for source files
4312 Executable programs sometimes do not record the directories of the source
4313 files from which they were compiled, just the names. Even when they do,
4314 the directories could be moved between the compilation and your debugging
4315 session. @value{GDBN} has a list of directories to search for source files;
4316 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4317 it tries all the directories in the list, in the order they are present
4318 in the list, until it finds a file with the desired name. Note that
4319 the executable search path is @emph{not} used for this purpose. Neither is
4320 the current working directory, unless it happens to be in the source
4323 If @value{GDBN} cannot find a source file in the source path, and the
4324 object program records a directory, @value{GDBN} tries that directory
4325 too. If the source path is empty, and there is no record of the
4326 compilation directory, @value{GDBN} looks in the current directory as a
4329 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4330 any information it has cached about where source files are found and where
4331 each line is in the file.
4335 When you start @value{GDBN}, its source path includes only @samp{cdir}
4336 and @samp{cwd}, in that order.
4337 To add other directories, use the @code{directory} command.
4340 @item directory @var{dirname} @dots{}
4341 @item dir @var{dirname} @dots{}
4342 Add directory @var{dirname} to the front of the source path. Several
4343 directory names may be given to this command, separated by @samp{:}
4344 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4345 part of absolute file names) or
4346 whitespace. You may specify a directory that is already in the source
4347 path; this moves it forward, so @value{GDBN} searches it sooner.
4351 @vindex $cdir@r{, convenience variable}
4352 @vindex $cwdr@r{, convenience variable}
4353 @cindex compilation directory
4354 @cindex current directory
4355 @cindex working directory
4356 @cindex directory, current
4357 @cindex directory, compilation
4358 You can use the string @samp{$cdir} to refer to the compilation
4359 directory (if one is recorded), and @samp{$cwd} to refer to the current
4360 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4361 tracks the current working directory as it changes during your @value{GDBN}
4362 session, while the latter is immediately expanded to the current
4363 directory at the time you add an entry to the source path.
4366 Reset the source path to empty again. This requires confirmation.
4368 @c RET-repeat for @code{directory} is explicitly disabled, but since
4369 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4371 @item show directories
4372 @kindex show directories
4373 Print the source path: show which directories it contains.
4376 If your source path is cluttered with directories that are no longer of
4377 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4378 versions of source. You can correct the situation as follows:
4382 Use @code{directory} with no argument to reset the source path to empty.
4385 Use @code{directory} with suitable arguments to reinstall the
4386 directories you want in the source path. You can add all the
4387 directories in one command.
4391 @section Source and machine code
4393 You can use the command @code{info line} to map source lines to program
4394 addresses (and vice versa), and the command @code{disassemble} to display
4395 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4396 mode, the @code{info line} command causes the arrow to point to the
4397 line specified. Also, @code{info line} prints addresses in symbolic form as
4402 @item info line @var{linespec}
4403 Print the starting and ending addresses of the compiled code for
4404 source line @var{linespec}. You can specify source lines in any of
4405 the ways understood by the @code{list} command (@pxref{List, ,Printing
4409 For example, we can use @code{info line} to discover the location of
4410 the object code for the first line of function
4411 @code{m4_changequote}:
4413 @c FIXME: I think this example should also show the addresses in
4414 @c symbolic form, as they usually would be displayed.
4416 (@value{GDBP}) info line m4_changequote
4417 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4421 We can also inquire (using @code{*@var{addr}} as the form for
4422 @var{linespec}) what source line covers a particular address:
4424 (@value{GDBP}) info line *0x63ff
4425 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4428 @cindex @code{$_} and @code{info line}
4429 @kindex x@r{(examine), and} info line
4430 After @code{info line}, the default address for the @code{x} command
4431 is changed to the starting address of the line, so that @samp{x/i} is
4432 sufficient to begin examining the machine code (@pxref{Memory,
4433 ,Examining memory}). Also, this address is saved as the value of the
4434 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4439 @cindex assembly instructions
4440 @cindex instructions, assembly
4441 @cindex machine instructions
4442 @cindex listing machine instructions
4444 This specialized command dumps a range of memory as machine
4445 instructions. The default memory range is the function surrounding the
4446 program counter of the selected frame. A single argument to this
4447 command is a program counter value; @value{GDBN} dumps the function
4448 surrounding this value. Two arguments specify a range of addresses
4449 (first inclusive, second exclusive) to dump.
4452 The following example shows the disassembly of a range of addresses of
4453 HP PA-RISC 2.0 code:
4456 (@value{GDBP}) disas 0x32c4 0x32e4
4457 Dump of assembler code from 0x32c4 to 0x32e4:
4458 0x32c4 <main+204>: addil 0,dp
4459 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4460 0x32cc <main+212>: ldil 0x3000,r31
4461 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4462 0x32d4 <main+220>: ldo 0(r31),rp
4463 0x32d8 <main+224>: addil -0x800,dp
4464 0x32dc <main+228>: ldo 0x588(r1),r26
4465 0x32e0 <main+232>: ldil 0x3000,r31
4466 End of assembler dump.
4469 Some architectures have more than one commonly-used set of instruction
4470 mnemonics or other syntax.
4473 @kindex set disassembly-flavor
4474 @cindex assembly instructions
4475 @cindex instructions, assembly
4476 @cindex machine instructions
4477 @cindex listing machine instructions
4478 @cindex Intel disassembly flavor
4479 @cindex AT&T disassembly flavor
4480 @item set disassembly-flavor @var{instruction-set}
4481 Select the instruction set to use when disassembling the
4482 program via the @code{disassemble} or @code{x/i} commands.
4484 Currently this command is only defined for the Intel x86 family. You
4485 can set @var{instruction-set} to either @code{intel} or @code{att}.
4486 The default is @code{att}, the AT&T flavor used by default by Unix
4487 assemblers for x86-based targets.
4492 @chapter Examining Data
4494 @cindex printing data
4495 @cindex examining data
4498 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4499 @c document because it is nonstandard... Under Epoch it displays in a
4500 @c different window or something like that.
4501 The usual way to examine data in your program is with the @code{print}
4502 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4503 evaluates and prints the value of an expression of the language your
4504 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4505 Different Languages}).
4508 @item print @var{expr}
4509 @itemx print /@var{f} @var{expr}
4510 @var{expr} is an expression (in the source language). By default the
4511 value of @var{expr} is printed in a format appropriate to its data type;
4512 you can choose a different format by specifying @samp{/@var{f}}, where
4513 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4517 @itemx print /@var{f}
4518 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4519 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4520 conveniently inspect the same value in an alternative format.
4523 A more low-level way of examining data is with the @code{x} command.
4524 It examines data in memory at a specified address and prints it in a
4525 specified format. @xref{Memory, ,Examining memory}.
4527 If you are interested in information about types, or about how the
4528 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4529 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4533 * Expressions:: Expressions
4534 * Variables:: Program variables
4535 * Arrays:: Artificial arrays
4536 * Output Formats:: Output formats
4537 * Memory:: Examining memory
4538 * Auto Display:: Automatic display
4539 * Print Settings:: Print settings
4540 * Value History:: Value history
4541 * Convenience Vars:: Convenience variables
4542 * Registers:: Registers
4543 * Floating Point Hardware:: Floating point hardware
4544 * Vector Unit:: Vector Unit
4545 * Memory Region Attributes:: Memory region attributes
4546 * Dump/Restore Files:: Copy between memory and a file
4547 * Character Sets:: Debugging programs that use a different
4548 character set than GDB does
4552 @section Expressions
4555 @code{print} and many other @value{GDBN} commands accept an expression and
4556 compute its value. Any kind of constant, variable or operator defined
4557 by the programming language you are using is valid in an expression in
4558 @value{GDBN}. This includes conditional expressions, function calls,
4559 casts, and string constants. It also includes preprocessor macros, if
4560 you compiled your program to include this information; see
4563 @value{GDBN} supports array constants in expressions input by
4564 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4565 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4566 memory that is @code{malloc}ed in the target program.
4568 Because C is so widespread, most of the expressions shown in examples in
4569 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4570 Languages}, for information on how to use expressions in other
4573 In this section, we discuss operators that you can use in @value{GDBN}
4574 expressions regardless of your programming language.
4576 Casts are supported in all languages, not just in C, because it is so
4577 useful to cast a number into a pointer in order to examine a structure
4578 at that address in memory.
4579 @c FIXME: casts supported---Mod2 true?
4581 @value{GDBN} supports these operators, in addition to those common
4582 to programming languages:
4586 @samp{@@} is a binary operator for treating parts of memory as arrays.
4587 @xref{Arrays, ,Artificial arrays}, for more information.
4590 @samp{::} allows you to specify a variable in terms of the file or
4591 function where it is defined. @xref{Variables, ,Program variables}.
4593 @cindex @{@var{type}@}
4594 @cindex type casting memory
4595 @cindex memory, viewing as typed object
4596 @cindex casts, to view memory
4597 @item @{@var{type}@} @var{addr}
4598 Refers to an object of type @var{type} stored at address @var{addr} in
4599 memory. @var{addr} may be any expression whose value is an integer or
4600 pointer (but parentheses are required around binary operators, just as in
4601 a cast). This construct is allowed regardless of what kind of data is
4602 normally supposed to reside at @var{addr}.
4606 @section Program variables
4608 The most common kind of expression to use is the name of a variable
4611 Variables in expressions are understood in the selected stack frame
4612 (@pxref{Selection, ,Selecting a frame}); they must be either:
4616 global (or file-static)
4623 visible according to the scope rules of the
4624 programming language from the point of execution in that frame
4627 @noindent This means that in the function
4642 you can examine and use the variable @code{a} whenever your program is
4643 executing within the function @code{foo}, but you can only use or
4644 examine the variable @code{b} while your program is executing inside
4645 the block where @code{b} is declared.
4647 @cindex variable name conflict
4648 There is an exception: you can refer to a variable or function whose
4649 scope is a single source file even if the current execution point is not
4650 in this file. But it is possible to have more than one such variable or
4651 function with the same name (in different source files). If that
4652 happens, referring to that name has unpredictable effects. If you wish,
4653 you can specify a static variable in a particular function or file,
4654 using the colon-colon notation:
4656 @cindex colon-colon, context for variables/functions
4658 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4659 @cindex @code{::}, context for variables/functions
4662 @var{file}::@var{variable}
4663 @var{function}::@var{variable}
4667 Here @var{file} or @var{function} is the name of the context for the
4668 static @var{variable}. In the case of file names, you can use quotes to
4669 make sure @value{GDBN} parses the file name as a single word---for example,
4670 to print a global value of @code{x} defined in @file{f2.c}:
4673 (@value{GDBP}) p 'f2.c'::x
4676 @cindex C@t{++} scope resolution
4677 This use of @samp{::} is very rarely in conflict with the very similar
4678 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4679 scope resolution operator in @value{GDBN} expressions.
4680 @c FIXME: Um, so what happens in one of those rare cases where it's in
4683 @cindex wrong values
4684 @cindex variable values, wrong
4686 @emph{Warning:} Occasionally, a local variable may appear to have the
4687 wrong value at certain points in a function---just after entry to a new
4688 scope, and just before exit.
4690 You may see this problem when you are stepping by machine instructions.
4691 This is because, on most machines, it takes more than one instruction to
4692 set up a stack frame (including local variable definitions); if you are
4693 stepping by machine instructions, variables may appear to have the wrong
4694 values until the stack frame is completely built. On exit, it usually
4695 also takes more than one machine instruction to destroy a stack frame;
4696 after you begin stepping through that group of instructions, local
4697 variable definitions may be gone.
4699 This may also happen when the compiler does significant optimizations.
4700 To be sure of always seeing accurate values, turn off all optimization
4703 @cindex ``No symbol "foo" in current context''
4704 Another possible effect of compiler optimizations is to optimize
4705 unused variables out of existence, or assign variables to registers (as
4706 opposed to memory addresses). Depending on the support for such cases
4707 offered by the debug info format used by the compiler, @value{GDBN}
4708 might not be able to display values for such local variables. If that
4709 happens, @value{GDBN} will print a message like this:
4712 No symbol "foo" in current context.
4715 To solve such problems, either recompile without optimizations, or use a
4716 different debug info format, if the compiler supports several such
4717 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler
4718 usually supports the @option{-gstabs+} option. @option{-gstabs+}
4719 produces debug info in a format that is superior to formats such as
4720 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
4721 an effective form for debug info. @xref{Debugging Options,,Options
4722 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
4726 @section Artificial arrays
4728 @cindex artificial array
4729 @kindex @@@r{, referencing memory as an array}
4730 It is often useful to print out several successive objects of the
4731 same type in memory; a section of an array, or an array of
4732 dynamically determined size for which only a pointer exists in the
4735 You can do this by referring to a contiguous span of memory as an
4736 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4737 operand of @samp{@@} should be the first element of the desired array
4738 and be an individual object. The right operand should be the desired length
4739 of the array. The result is an array value whose elements are all of
4740 the type of the left argument. The first element is actually the left
4741 argument; the second element comes from bytes of memory immediately
4742 following those that hold the first element, and so on. Here is an
4743 example. If a program says
4746 int *array = (int *) malloc (len * sizeof (int));
4750 you can print the contents of @code{array} with
4756 The left operand of @samp{@@} must reside in memory. Array values made
4757 with @samp{@@} in this way behave just like other arrays in terms of
4758 subscripting, and are coerced to pointers when used in expressions.
4759 Artificial arrays most often appear in expressions via the value history
4760 (@pxref{Value History, ,Value history}), after printing one out.
4762 Another way to create an artificial array is to use a cast.
4763 This re-interprets a value as if it were an array.
4764 The value need not be in memory:
4766 (@value{GDBP}) p/x (short[2])0x12345678
4767 $1 = @{0x1234, 0x5678@}
4770 As a convenience, if you leave the array length out (as in
4771 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4772 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4774 (@value{GDBP}) p/x (short[])0x12345678
4775 $2 = @{0x1234, 0x5678@}
4778 Sometimes the artificial array mechanism is not quite enough; in
4779 moderately complex data structures, the elements of interest may not
4780 actually be adjacent---for example, if you are interested in the values
4781 of pointers in an array. One useful work-around in this situation is
4782 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4783 variables}) as a counter in an expression that prints the first
4784 interesting value, and then repeat that expression via @key{RET}. For
4785 instance, suppose you have an array @code{dtab} of pointers to
4786 structures, and you are interested in the values of a field @code{fv}
4787 in each structure. Here is an example of what you might type:
4797 @node Output Formats
4798 @section Output formats
4800 @cindex formatted output
4801 @cindex output formats
4802 By default, @value{GDBN} prints a value according to its data type. Sometimes
4803 this is not what you want. For example, you might want to print a number
4804 in hex, or a pointer in decimal. Or you might want to view data in memory
4805 at a certain address as a character string or as an instruction. To do
4806 these things, specify an @dfn{output format} when you print a value.
4808 The simplest use of output formats is to say how to print a value
4809 already computed. This is done by starting the arguments of the
4810 @code{print} command with a slash and a format letter. The format
4811 letters supported are:
4815 Regard the bits of the value as an integer, and print the integer in
4819 Print as integer in signed decimal.
4822 Print as integer in unsigned decimal.
4825 Print as integer in octal.
4828 Print as integer in binary. The letter @samp{t} stands for ``two''.
4829 @footnote{@samp{b} cannot be used because these format letters are also
4830 used with the @code{x} command, where @samp{b} stands for ``byte'';
4831 see @ref{Memory,,Examining memory}.}
4834 @cindex unknown address, locating
4835 @cindex locate address
4836 Print as an address, both absolute in hexadecimal and as an offset from
4837 the nearest preceding symbol. You can use this format used to discover
4838 where (in what function) an unknown address is located:
4841 (@value{GDBP}) p/a 0x54320
4842 $3 = 0x54320 <_initialize_vx+396>
4846 The command @code{info symbol 0x54320} yields similar results.
4847 @xref{Symbols, info symbol}.
4850 Regard as an integer and print it as a character constant.
4853 Regard the bits of the value as a floating point number and print
4854 using typical floating point syntax.
4857 For example, to print the program counter in hex (@pxref{Registers}), type
4864 Note that no space is required before the slash; this is because command
4865 names in @value{GDBN} cannot contain a slash.
4867 To reprint the last value in the value history with a different format,
4868 you can use the @code{print} command with just a format and no
4869 expression. For example, @samp{p/x} reprints the last value in hex.
4872 @section Examining memory
4874 You can use the command @code{x} (for ``examine'') to examine memory in
4875 any of several formats, independently of your program's data types.
4877 @cindex examining memory
4879 @kindex x @r{(examine memory)}
4880 @item x/@var{nfu} @var{addr}
4883 Use the @code{x} command to examine memory.
4886 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
4887 much memory to display and how to format it; @var{addr} is an
4888 expression giving the address where you want to start displaying memory.
4889 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
4890 Several commands set convenient defaults for @var{addr}.
4893 @item @var{n}, the repeat count
4894 The repeat count is a decimal integer; the default is 1. It specifies
4895 how much memory (counting by units @var{u}) to display.
4896 @c This really is **decimal**; unaffected by 'set radix' as of GDB
4899 @item @var{f}, the display format
4900 The display format is one of the formats used by @code{print},
4901 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
4902 The default is @samp{x} (hexadecimal) initially.
4903 The default changes each time you use either @code{x} or @code{print}.
4905 @item @var{u}, the unit size
4906 The unit size is any of
4912 Halfwords (two bytes).
4914 Words (four bytes). This is the initial default.
4916 Giant words (eight bytes).
4919 Each time you specify a unit size with @code{x}, that size becomes the
4920 default unit the next time you use @code{x}. (For the @samp{s} and
4921 @samp{i} formats, the unit size is ignored and is normally not written.)
4923 @item @var{addr}, starting display address
4924 @var{addr} is the address where you want @value{GDBN} to begin displaying
4925 memory. The expression need not have a pointer value (though it may);
4926 it is always interpreted as an integer address of a byte of memory.
4927 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
4928 @var{addr} is usually just after the last address examined---but several
4929 other commands also set the default address: @code{info breakpoints} (to
4930 the address of the last breakpoint listed), @code{info line} (to the
4931 starting address of a line), and @code{print} (if you use it to display
4932 a value from memory).
4935 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
4936 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
4937 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
4938 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
4939 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
4941 Since the letters indicating unit sizes are all distinct from the
4942 letters specifying output formats, you do not have to remember whether
4943 unit size or format comes first; either order works. The output
4944 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
4945 (However, the count @var{n} must come first; @samp{wx4} does not work.)
4947 Even though the unit size @var{u} is ignored for the formats @samp{s}
4948 and @samp{i}, you might still want to use a count @var{n}; for example,
4949 @samp{3i} specifies that you want to see three machine instructions,
4950 including any operands. The command @code{disassemble} gives an
4951 alternative way of inspecting machine instructions; see @ref{Machine
4952 Code,,Source and machine code}.
4954 All the defaults for the arguments to @code{x} are designed to make it
4955 easy to continue scanning memory with minimal specifications each time
4956 you use @code{x}. For example, after you have inspected three machine
4957 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
4958 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
4959 the repeat count @var{n} is used again; the other arguments default as
4960 for successive uses of @code{x}.
4962 @cindex @code{$_}, @code{$__}, and value history
4963 The addresses and contents printed by the @code{x} command are not saved
4964 in the value history because there is often too much of them and they
4965 would get in the way. Instead, @value{GDBN} makes these values available for
4966 subsequent use in expressions as values of the convenience variables
4967 @code{$_} and @code{$__}. After an @code{x} command, the last address
4968 examined is available for use in expressions in the convenience variable
4969 @code{$_}. The contents of that address, as examined, are available in
4970 the convenience variable @code{$__}.
4972 If the @code{x} command has a repeat count, the address and contents saved
4973 are from the last memory unit printed; this is not the same as the last
4974 address printed if several units were printed on the last line of output.
4977 @section Automatic display
4978 @cindex automatic display
4979 @cindex display of expressions
4981 If you find that you want to print the value of an expression frequently
4982 (to see how it changes), you might want to add it to the @dfn{automatic
4983 display list} so that @value{GDBN} prints its value each time your program stops.
4984 Each expression added to the list is given a number to identify it;
4985 to remove an expression from the list, you specify that number.
4986 The automatic display looks like this:
4990 3: bar[5] = (struct hack *) 0x3804
4994 This display shows item numbers, expressions and their current values. As with
4995 displays you request manually using @code{x} or @code{print}, you can
4996 specify the output format you prefer; in fact, @code{display} decides
4997 whether to use @code{print} or @code{x} depending on how elaborate your
4998 format specification is---it uses @code{x} if you specify a unit size,
4999 or one of the two formats (@samp{i} and @samp{s}) that are only
5000 supported by @code{x}; otherwise it uses @code{print}.
5004 @item display @var{expr}
5005 Add the expression @var{expr} to the list of expressions to display
5006 each time your program stops. @xref{Expressions, ,Expressions}.
5008 @code{display} does not repeat if you press @key{RET} again after using it.
5010 @item display/@var{fmt} @var{expr}
5011 For @var{fmt} specifying only a display format and not a size or
5012 count, add the expression @var{expr} to the auto-display list but
5013 arrange to display it each time in the specified format @var{fmt}.
5014 @xref{Output Formats,,Output formats}.
5016 @item display/@var{fmt} @var{addr}
5017 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5018 number of units, add the expression @var{addr} as a memory address to
5019 be examined each time your program stops. Examining means in effect
5020 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5023 For example, @samp{display/i $pc} can be helpful, to see the machine
5024 instruction about to be executed each time execution stops (@samp{$pc}
5025 is a common name for the program counter; @pxref{Registers, ,Registers}).
5028 @kindex delete display
5030 @item undisplay @var{dnums}@dots{}
5031 @itemx delete display @var{dnums}@dots{}
5032 Remove item numbers @var{dnums} from the list of expressions to display.
5034 @code{undisplay} does not repeat if you press @key{RET} after using it.
5035 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5037 @kindex disable display
5038 @item disable display @var{dnums}@dots{}
5039 Disable the display of item numbers @var{dnums}. A disabled display
5040 item is not printed automatically, but is not forgotten. It may be
5041 enabled again later.
5043 @kindex enable display
5044 @item enable display @var{dnums}@dots{}
5045 Enable display of item numbers @var{dnums}. It becomes effective once
5046 again in auto display of its expression, until you specify otherwise.
5049 Display the current values of the expressions on the list, just as is
5050 done when your program stops.
5052 @kindex info display
5054 Print the list of expressions previously set up to display
5055 automatically, each one with its item number, but without showing the
5056 values. This includes disabled expressions, which are marked as such.
5057 It also includes expressions which would not be displayed right now
5058 because they refer to automatic variables not currently available.
5061 If a display expression refers to local variables, then it does not make
5062 sense outside the lexical context for which it was set up. Such an
5063 expression is disabled when execution enters a context where one of its
5064 variables is not defined. For example, if you give the command
5065 @code{display last_char} while inside a function with an argument
5066 @code{last_char}, @value{GDBN} displays this argument while your program
5067 continues to stop inside that function. When it stops elsewhere---where
5068 there is no variable @code{last_char}---the display is disabled
5069 automatically. The next time your program stops where @code{last_char}
5070 is meaningful, you can enable the display expression once again.
5072 @node Print Settings
5073 @section Print settings
5075 @cindex format options
5076 @cindex print settings
5077 @value{GDBN} provides the following ways to control how arrays, structures,
5078 and symbols are printed.
5081 These settings are useful for debugging programs in any language:
5084 @kindex set print address
5085 @item set print address
5086 @itemx set print address on
5087 @value{GDBN} prints memory addresses showing the location of stack
5088 traces, structure values, pointer values, breakpoints, and so forth,
5089 even when it also displays the contents of those addresses. The default
5090 is @code{on}. For example, this is what a stack frame display looks like with
5091 @code{set print address on}:
5096 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5098 530 if (lquote != def_lquote)
5102 @item set print address off
5103 Do not print addresses when displaying their contents. For example,
5104 this is the same stack frame displayed with @code{set print address off}:
5108 (@value{GDBP}) set print addr off
5110 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5111 530 if (lquote != def_lquote)
5115 You can use @samp{set print address off} to eliminate all machine
5116 dependent displays from the @value{GDBN} interface. For example, with
5117 @code{print address off}, you should get the same text for backtraces on
5118 all machines---whether or not they involve pointer arguments.
5120 @kindex show print address
5121 @item show print address
5122 Show whether or not addresses are to be printed.
5125 When @value{GDBN} prints a symbolic address, it normally prints the
5126 closest earlier symbol plus an offset. If that symbol does not uniquely
5127 identify the address (for example, it is a name whose scope is a single
5128 source file), you may need to clarify. One way to do this is with
5129 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5130 you can set @value{GDBN} to print the source file and line number when
5131 it prints a symbolic address:
5134 @kindex set print symbol-filename
5135 @item set print symbol-filename on
5136 Tell @value{GDBN} to print the source file name and line number of a
5137 symbol in the symbolic form of an address.
5139 @item set print symbol-filename off
5140 Do not print source file name and line number of a symbol. This is the
5143 @kindex show print symbol-filename
5144 @item show print symbol-filename
5145 Show whether or not @value{GDBN} will print the source file name and
5146 line number of a symbol in the symbolic form of an address.
5149 Another situation where it is helpful to show symbol filenames and line
5150 numbers is when disassembling code; @value{GDBN} shows you the line
5151 number and source file that corresponds to each instruction.
5153 Also, you may wish to see the symbolic form only if the address being
5154 printed is reasonably close to the closest earlier symbol:
5157 @kindex set print max-symbolic-offset
5158 @item set print max-symbolic-offset @var{max-offset}
5159 Tell @value{GDBN} to only display the symbolic form of an address if the
5160 offset between the closest earlier symbol and the address is less than
5161 @var{max-offset}. The default is 0, which tells @value{GDBN}
5162 to always print the symbolic form of an address if any symbol precedes it.
5164 @kindex show print max-symbolic-offset
5165 @item show print max-symbolic-offset
5166 Ask how large the maximum offset is that @value{GDBN} prints in a
5170 @cindex wild pointer, interpreting
5171 @cindex pointer, finding referent
5172 If you have a pointer and you are not sure where it points, try
5173 @samp{set print symbol-filename on}. Then you can determine the name
5174 and source file location of the variable where it points, using
5175 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5176 For example, here @value{GDBN} shows that a variable @code{ptt} points
5177 at another variable @code{t}, defined in @file{hi2.c}:
5180 (@value{GDBP}) set print symbol-filename on
5181 (@value{GDBP}) p/a ptt
5182 $4 = 0xe008 <t in hi2.c>
5186 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5187 does not show the symbol name and filename of the referent, even with
5188 the appropriate @code{set print} options turned on.
5191 Other settings control how different kinds of objects are printed:
5194 @kindex set print array
5195 @item set print array
5196 @itemx set print array on
5197 Pretty print arrays. This format is more convenient to read,
5198 but uses more space. The default is off.
5200 @item set print array off
5201 Return to compressed format for arrays.
5203 @kindex show print array
5204 @item show print array
5205 Show whether compressed or pretty format is selected for displaying
5208 @kindex set print elements
5209 @item set print elements @var{number-of-elements}
5210 Set a limit on how many elements of an array @value{GDBN} will print.
5211 If @value{GDBN} is printing a large array, it stops printing after it has
5212 printed the number of elements set by the @code{set print elements} command.
5213 This limit also applies to the display of strings.
5214 When @value{GDBN} starts, this limit is set to 200.
5215 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5217 @kindex show print elements
5218 @item show print elements
5219 Display the number of elements of a large array that @value{GDBN} will print.
5220 If the number is 0, then the printing is unlimited.
5222 @kindex set print null-stop
5223 @item set print null-stop
5224 Cause @value{GDBN} to stop printing the characters of an array when the first
5225 @sc{null} is encountered. This is useful when large arrays actually
5226 contain only short strings.
5229 @kindex set print pretty
5230 @item set print pretty on
5231 Cause @value{GDBN} to print structures in an indented format with one member
5232 per line, like this:
5247 @item set print pretty off
5248 Cause @value{GDBN} to print structures in a compact format, like this:
5252 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5253 meat = 0x54 "Pork"@}
5258 This is the default format.
5260 @kindex show print pretty
5261 @item show print pretty
5262 Show which format @value{GDBN} is using to print structures.
5264 @kindex set print sevenbit-strings
5265 @item set print sevenbit-strings on
5266 Print using only seven-bit characters; if this option is set,
5267 @value{GDBN} displays any eight-bit characters (in strings or
5268 character values) using the notation @code{\}@var{nnn}. This setting is
5269 best if you are working in English (@sc{ascii}) and you use the
5270 high-order bit of characters as a marker or ``meta'' bit.
5272 @item set print sevenbit-strings off
5273 Print full eight-bit characters. This allows the use of more
5274 international character sets, and is the default.
5276 @kindex show print sevenbit-strings
5277 @item show print sevenbit-strings
5278 Show whether or not @value{GDBN} is printing only seven-bit characters.
5280 @kindex set print union
5281 @item set print union on
5282 Tell @value{GDBN} to print unions which are contained in structures. This
5283 is the default setting.
5285 @item set print union off
5286 Tell @value{GDBN} not to print unions which are contained in structures.
5288 @kindex show print union
5289 @item show print union
5290 Ask @value{GDBN} whether or not it will print unions which are contained in
5293 For example, given the declarations
5296 typedef enum @{Tree, Bug@} Species;
5297 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5298 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5309 struct thing foo = @{Tree, @{Acorn@}@};
5313 with @code{set print union on} in effect @samp{p foo} would print
5316 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5320 and with @code{set print union off} in effect it would print
5323 $1 = @{it = Tree, form = @{...@}@}
5329 These settings are of interest when debugging C@t{++} programs:
5333 @kindex set print demangle
5334 @item set print demangle
5335 @itemx set print demangle on
5336 Print C@t{++} names in their source form rather than in the encoded
5337 (``mangled'') form passed to the assembler and linker for type-safe
5338 linkage. The default is on.
5340 @kindex show print demangle
5341 @item show print demangle
5342 Show whether C@t{++} names are printed in mangled or demangled form.
5344 @kindex set print asm-demangle
5345 @item set print asm-demangle
5346 @itemx set print asm-demangle on
5347 Print C@t{++} names in their source form rather than their mangled form, even
5348 in assembler code printouts such as instruction disassemblies.
5351 @kindex show print asm-demangle
5352 @item show print asm-demangle
5353 Show whether C@t{++} names in assembly listings are printed in mangled
5356 @kindex set demangle-style
5357 @cindex C@t{++} symbol decoding style
5358 @cindex symbol decoding style, C@t{++}
5359 @item set demangle-style @var{style}
5360 Choose among several encoding schemes used by different compilers to
5361 represent C@t{++} names. The choices for @var{style} are currently:
5365 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5368 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5369 This is the default.
5372 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5375 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5378 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5379 @strong{Warning:} this setting alone is not sufficient to allow
5380 debugging @code{cfront}-generated executables. @value{GDBN} would
5381 require further enhancement to permit that.
5384 If you omit @var{style}, you will see a list of possible formats.
5386 @kindex show demangle-style
5387 @item show demangle-style
5388 Display the encoding style currently in use for decoding C@t{++} symbols.
5390 @kindex set print object
5391 @item set print object
5392 @itemx set print object on
5393 When displaying a pointer to an object, identify the @emph{actual}
5394 (derived) type of the object rather than the @emph{declared} type, using
5395 the virtual function table.
5397 @item set print object off
5398 Display only the declared type of objects, without reference to the
5399 virtual function table. This is the default setting.
5401 @kindex show print object
5402 @item show print object
5403 Show whether actual, or declared, object types are displayed.
5405 @kindex set print static-members
5406 @item set print static-members
5407 @itemx set print static-members on
5408 Print static members when displaying a C@t{++} object. The default is on.
5410 @item set print static-members off
5411 Do not print static members when displaying a C@t{++} object.
5413 @kindex show print static-members
5414 @item show print static-members
5415 Show whether C@t{++} static members are printed, or not.
5417 @c These don't work with HP ANSI C++ yet.
5418 @kindex set print vtbl
5419 @item set print vtbl
5420 @itemx set print vtbl on
5421 Pretty print C@t{++} virtual function tables. The default is off.
5422 (The @code{vtbl} commands do not work on programs compiled with the HP
5423 ANSI C@t{++} compiler (@code{aCC}).)
5425 @item set print vtbl off
5426 Do not pretty print C@t{++} virtual function tables.
5428 @kindex show print vtbl
5429 @item show print vtbl
5430 Show whether C@t{++} virtual function tables are pretty printed, or not.
5434 @section Value history
5436 @cindex value history
5437 Values printed by the @code{print} command are saved in the @value{GDBN}
5438 @dfn{value history}. This allows you to refer to them in other expressions.
5439 Values are kept until the symbol table is re-read or discarded
5440 (for example with the @code{file} or @code{symbol-file} commands).
5441 When the symbol table changes, the value history is discarded,
5442 since the values may contain pointers back to the types defined in the
5447 @cindex history number
5448 The values printed are given @dfn{history numbers} by which you can
5449 refer to them. These are successive integers starting with one.
5450 @code{print} shows you the history number assigned to a value by
5451 printing @samp{$@var{num} = } before the value; here @var{num} is the
5454 To refer to any previous value, use @samp{$} followed by the value's
5455 history number. The way @code{print} labels its output is designed to
5456 remind you of this. Just @code{$} refers to the most recent value in
5457 the history, and @code{$$} refers to the value before that.
5458 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5459 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5460 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5462 For example, suppose you have just printed a pointer to a structure and
5463 want to see the contents of the structure. It suffices to type
5469 If you have a chain of structures where the component @code{next} points
5470 to the next one, you can print the contents of the next one with this:
5477 You can print successive links in the chain by repeating this
5478 command---which you can do by just typing @key{RET}.
5480 Note that the history records values, not expressions. If the value of
5481 @code{x} is 4 and you type these commands:
5489 then the value recorded in the value history by the @code{print} command
5490 remains 4 even though the value of @code{x} has changed.
5495 Print the last ten values in the value history, with their item numbers.
5496 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5497 values} does not change the history.
5499 @item show values @var{n}
5500 Print ten history values centered on history item number @var{n}.
5503 Print ten history values just after the values last printed. If no more
5504 values are available, @code{show values +} produces no display.
5507 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5508 same effect as @samp{show values +}.
5510 @node Convenience Vars
5511 @section Convenience variables
5513 @cindex convenience variables
5514 @value{GDBN} provides @dfn{convenience variables} that you can use within
5515 @value{GDBN} to hold on to a value and refer to it later. These variables
5516 exist entirely within @value{GDBN}; they are not part of your program, and
5517 setting a convenience variable has no direct effect on further execution
5518 of your program. That is why you can use them freely.
5520 Convenience variables are prefixed with @samp{$}. Any name preceded by
5521 @samp{$} can be used for a convenience variable, unless it is one of
5522 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5523 (Value history references, in contrast, are @emph{numbers} preceded
5524 by @samp{$}. @xref{Value History, ,Value history}.)
5526 You can save a value in a convenience variable with an assignment
5527 expression, just as you would set a variable in your program.
5531 set $foo = *object_ptr
5535 would save in @code{$foo} the value contained in the object pointed to by
5538 Using a convenience variable for the first time creates it, but its
5539 value is @code{void} until you assign a new value. You can alter the
5540 value with another assignment at any time.
5542 Convenience variables have no fixed types. You can assign a convenience
5543 variable any type of value, including structures and arrays, even if
5544 that variable already has a value of a different type. The convenience
5545 variable, when used as an expression, has the type of its current value.
5548 @kindex show convenience
5549 @item show convenience
5550 Print a list of convenience variables used so far, and their values.
5551 Abbreviated @code{show conv}.
5554 One of the ways to use a convenience variable is as a counter to be
5555 incremented or a pointer to be advanced. For example, to print
5556 a field from successive elements of an array of structures:
5560 print bar[$i++]->contents
5564 Repeat that command by typing @key{RET}.
5566 Some convenience variables are created automatically by @value{GDBN} and given
5567 values likely to be useful.
5570 @vindex $_@r{, convenience variable}
5572 The variable @code{$_} is automatically set by the @code{x} command to
5573 the last address examined (@pxref{Memory, ,Examining memory}). Other
5574 commands which provide a default address for @code{x} to examine also
5575 set @code{$_} to that address; these commands include @code{info line}
5576 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5577 except when set by the @code{x} command, in which case it is a pointer
5578 to the type of @code{$__}.
5580 @vindex $__@r{, convenience variable}
5582 The variable @code{$__} is automatically set by the @code{x} command
5583 to the value found in the last address examined. Its type is chosen
5584 to match the format in which the data was printed.
5587 @vindex $_exitcode@r{, convenience variable}
5588 The variable @code{$_exitcode} is automatically set to the exit code when
5589 the program being debugged terminates.
5592 On HP-UX systems, if you refer to a function or variable name that
5593 begins with a dollar sign, @value{GDBN} searches for a user or system
5594 name first, before it searches for a convenience variable.
5600 You can refer to machine register contents, in expressions, as variables
5601 with names starting with @samp{$}. The names of registers are different
5602 for each machine; use @code{info registers} to see the names used on
5606 @kindex info registers
5607 @item info registers
5608 Print the names and values of all registers except floating-point
5609 and vector registers (in the selected stack frame).
5611 @kindex info all-registers
5612 @cindex floating point registers
5613 @item info all-registers
5614 Print the names and values of all registers, including floating-point
5615 and vector registers (in the selected stack frame).
5617 @item info registers @var{regname} @dots{}
5618 Print the @dfn{relativized} value of each specified register @var{regname}.
5619 As discussed in detail below, register values are normally relative to
5620 the selected stack frame. @var{regname} may be any register name valid on
5621 the machine you are using, with or without the initial @samp{$}.
5624 @value{GDBN} has four ``standard'' register names that are available (in
5625 expressions) on most machines---whenever they do not conflict with an
5626 architecture's canonical mnemonics for registers. The register names
5627 @code{$pc} and @code{$sp} are used for the program counter register and
5628 the stack pointer. @code{$fp} is used for a register that contains a
5629 pointer to the current stack frame, and @code{$ps} is used for a
5630 register that contains the processor status. For example,
5631 you could print the program counter in hex with
5638 or print the instruction to be executed next with
5645 or add four to the stack pointer@footnote{This is a way of removing
5646 one word from the stack, on machines where stacks grow downward in
5647 memory (most machines, nowadays). This assumes that the innermost
5648 stack frame is selected; setting @code{$sp} is not allowed when other
5649 stack frames are selected. To pop entire frames off the stack,
5650 regardless of machine architecture, use @code{return};
5651 see @ref{Returning, ,Returning from a function}.} with
5657 Whenever possible, these four standard register names are available on
5658 your machine even though the machine has different canonical mnemonics,
5659 so long as there is no conflict. The @code{info registers} command
5660 shows the canonical names. For example, on the SPARC, @code{info
5661 registers} displays the processor status register as @code{$psr} but you
5662 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5663 is an alias for the @sc{eflags} register.
5665 @value{GDBN} always considers the contents of an ordinary register as an
5666 integer when the register is examined in this way. Some machines have
5667 special registers which can hold nothing but floating point; these
5668 registers are considered to have floating point values. There is no way
5669 to refer to the contents of an ordinary register as floating point value
5670 (although you can @emph{print} it as a floating point value with
5671 @samp{print/f $@var{regname}}).
5673 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5674 means that the data format in which the register contents are saved by
5675 the operating system is not the same one that your program normally
5676 sees. For example, the registers of the 68881 floating point
5677 coprocessor are always saved in ``extended'' (raw) format, but all C
5678 programs expect to work with ``double'' (virtual) format. In such
5679 cases, @value{GDBN} normally works with the virtual format only (the format
5680 that makes sense for your program), but the @code{info registers} command
5681 prints the data in both formats.
5683 Normally, register values are relative to the selected stack frame
5684 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5685 value that the register would contain if all stack frames farther in
5686 were exited and their saved registers restored. In order to see the
5687 true contents of hardware registers, you must select the innermost
5688 frame (with @samp{frame 0}).
5690 However, @value{GDBN} must deduce where registers are saved, from the machine
5691 code generated by your compiler. If some registers are not saved, or if
5692 @value{GDBN} is unable to locate the saved registers, the selected stack
5693 frame makes no difference.
5695 @node Floating Point Hardware
5696 @section Floating point hardware
5697 @cindex floating point
5699 Depending on the configuration, @value{GDBN} may be able to give
5700 you more information about the status of the floating point hardware.
5705 Display hardware-dependent information about the floating
5706 point unit. The exact contents and layout vary depending on the
5707 floating point chip. Currently, @samp{info float} is supported on
5708 the ARM and x86 machines.
5712 @section Vector Unit
5715 Depending on the configuration, @value{GDBN} may be able to give you
5716 more information about the status of the vector unit.
5721 Display information about the vector unit. The exact contents and
5722 layout vary depending on the hardware.
5725 @node Memory Region Attributes
5726 @section Memory region attributes
5727 @cindex memory region attributes
5729 @dfn{Memory region attributes} allow you to describe special handling
5730 required by regions of your target's memory. @value{GDBN} uses attributes
5731 to determine whether to allow certain types of memory accesses; whether to
5732 use specific width accesses; and whether to cache target memory.
5734 Defined memory regions can be individually enabled and disabled. When a
5735 memory region is disabled, @value{GDBN} uses the default attributes when
5736 accessing memory in that region. Similarly, if no memory regions have
5737 been defined, @value{GDBN} uses the default attributes when accessing
5740 When a memory region is defined, it is given a number to identify it;
5741 to enable, disable, or remove a memory region, you specify that number.
5745 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5746 Define memory region bounded by @var{lower} and @var{upper} with
5747 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5748 special case: it is treated as the the target's maximum memory address.
5749 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5752 @item delete mem @var{nums}@dots{}
5753 Remove memory regions @var{nums}@dots{}.
5756 @item disable mem @var{nums}@dots{}
5757 Disable memory regions @var{nums}@dots{}.
5758 A disabled memory region is not forgotten.
5759 It may be enabled again later.
5762 @item enable mem @var{nums}@dots{}
5763 Enable memory regions @var{nums}@dots{}.
5767 Print a table of all defined memory regions, with the following columns
5771 @item Memory Region Number
5772 @item Enabled or Disabled.
5773 Enabled memory regions are marked with @samp{y}.
5774 Disabled memory regions are marked with @samp{n}.
5777 The address defining the inclusive lower bound of the memory region.
5780 The address defining the exclusive upper bound of the memory region.
5783 The list of attributes set for this memory region.
5788 @subsection Attributes
5790 @subsubsection Memory Access Mode
5791 The access mode attributes set whether @value{GDBN} may make read or
5792 write accesses to a memory region.
5794 While these attributes prevent @value{GDBN} from performing invalid
5795 memory accesses, they do nothing to prevent the target system, I/O DMA,
5796 etc. from accessing memory.
5800 Memory is read only.
5802 Memory is write only.
5804 Memory is read/write. This is the default.
5807 @subsubsection Memory Access Size
5808 The acccess size attributes tells @value{GDBN} to use specific sized
5809 accesses in the memory region. Often memory mapped device registers
5810 require specific sized accesses. If no access size attribute is
5811 specified, @value{GDBN} may use accesses of any size.
5815 Use 8 bit memory accesses.
5817 Use 16 bit memory accesses.
5819 Use 32 bit memory accesses.
5821 Use 64 bit memory accesses.
5824 @c @subsubsection Hardware/Software Breakpoints
5825 @c The hardware/software breakpoint attributes set whether @value{GDBN}
5826 @c will use hardware or software breakpoints for the internal breakpoints
5827 @c used by the step, next, finish, until, etc. commands.
5831 @c Always use hardware breakpoints
5832 @c @item swbreak (default)
5835 @subsubsection Data Cache
5836 The data cache attributes set whether @value{GDBN} will cache target
5837 memory. While this generally improves performance by reducing debug
5838 protocol overhead, it can lead to incorrect results because @value{GDBN}
5839 does not know about volatile variables or memory mapped device
5844 Enable @value{GDBN} to cache target memory.
5846 Disable @value{GDBN} from caching target memory. This is the default.
5849 @c @subsubsection Memory Write Verification
5850 @c The memory write verification attributes set whether @value{GDBN}
5851 @c will re-reads data after each write to verify the write was successful.
5855 @c @item noverify (default)
5858 @node Dump/Restore Files
5859 @section Copy between memory and a file
5860 @cindex dump/restore files
5861 @cindex append data to a file
5862 @cindex dump data to a file
5863 @cindex restore data from a file
5865 You can use the commands @code{dump}, @code{append}, and
5866 @code{restore} to copy data between target memory and a file. The
5867 @code{dump} and @code{append} commands write data to a file, and the
5868 @code{restore} command reads data from a file back into the inferior's
5869 memory. Files may be in binary, Motorola S-record, Intel hex, or
5870 Tektronix Hex format; however, @value{GDBN} can only append to binary
5876 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
5877 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
5878 Dump the contents of memory from @var{start_addr} to @var{end_addr},
5879 or the value of @var{expr}, to @var{filename} in the given format.
5881 The @var{format} parameter may be any one of:
5888 Motorola S-record format.
5890 Tektronix Hex format.
5893 @value{GDBN} uses the same definitions of these formats as the
5894 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
5895 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
5899 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
5900 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
5901 Append the contents of memory from @var{start_addr} to @var{end_addr},
5902 or the value of @var{expr}, to @var{filename}, in raw binary form.
5903 (@value{GDBN} can only append data to files in raw binary form.)
5906 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
5907 Restore the contents of file @var{filename} into memory. The
5908 @code{restore} command can automatically recognize any known @sc{bfd}
5909 file format, except for raw binary. To restore a raw binary file you
5910 must specify the optional keyword @code{binary} after the filename.
5912 If @var{bias} is non-zero, its value will be added to the addresses
5913 contained in the file. Binary files always start at address zero, so
5914 they will be restored at address @var{bias}. Other bfd files have
5915 a built-in location; they will be restored at offset @var{bias}
5918 If @var{start} and/or @var{end} are non-zero, then only data between
5919 file offset @var{start} and file offset @var{end} will be restored.
5920 These offsets are relative to the addresses in the file, before
5921 the @var{bias} argument is applied.
5925 @node Character Sets
5926 @section Character Sets
5927 @cindex character sets
5929 @cindex translating between character sets
5930 @cindex host character set
5931 @cindex target character set
5933 If the program you are debugging uses a different character set to
5934 represent characters and strings than the one @value{GDBN} uses itself,
5935 @value{GDBN} can automatically translate between the character sets for
5936 you. The character set @value{GDBN} uses we call the @dfn{host
5937 character set}; the one the inferior program uses we call the
5938 @dfn{target character set}.
5940 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
5941 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
5942 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
5943 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
5944 then the host character set is Latin-1, and the target character set is
5945 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
5946 target-charset EBCDIC-US}, then @value{GDBN} translates between
5947 @sc{ebcdic} and Latin 1 as you print character or string values, or use
5948 character and string literals in expressions.
5950 @value{GDBN} has no way to automatically recognize which character set
5951 the inferior program uses; you must tell it, using the @code{set
5952 target-charset} command, described below.
5954 Here are the commands for controlling @value{GDBN}'s character set
5958 @item set target-charset @var{charset}
5959 @kindex set target-charset
5960 Set the current target character set to @var{charset}. We list the
5961 character set names @value{GDBN} recognizes below, but if you type
5962 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
5963 list the target character sets it supports.
5967 @item set host-charset @var{charset}
5968 @kindex set host-charset
5969 Set the current host character set to @var{charset}.
5971 By default, @value{GDBN} uses a host character set appropriate to the
5972 system it is running on; you can override that default using the
5973 @code{set host-charset} command.
5975 @value{GDBN} can only use certain character sets as its host character
5976 set. We list the character set names @value{GDBN} recognizes below, and
5977 indicate which can be host character sets, but if you type
5978 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
5979 list the host character sets it supports.
5981 @item set charset @var{charset}
5983 Set the current host and target character sets to @var{charset}. As
5984 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
5985 @value{GDBN} will list the name of the character sets that can be used
5986 for both host and target.
5990 @kindex show charset
5991 Show the names of the current host and target charsets.
5993 @itemx show host-charset
5994 @kindex show host-charset
5995 Show the name of the current host charset.
5997 @itemx show target-charset
5998 @kindex show target-charset
5999 Show the name of the current target charset.
6003 @value{GDBN} currently includes support for the following character
6009 @cindex ASCII character set
6010 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6014 @cindex ISO 8859-1 character set
6015 @cindex ISO Latin 1 character set
6016 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6017 characters needed for French, German, and Spanish. @value{GDBN} can use
6018 this as its host character set.
6022 @cindex EBCDIC character set
6023 @cindex IBM1047 character set
6024 Variants of the @sc{ebcdic} character set, used on some of IBM's
6025 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6026 @value{GDBN} cannot use these as its host character set.
6030 Note that these are all single-byte character sets. More work inside
6031 GDB is needed to support multi-byte or variable-width character
6032 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6034 Here is an example of @value{GDBN}'s character set support in action.
6035 Assume that the following source code has been placed in the file
6036 @file{charset-test.c}:
6042 = @{72, 101, 108, 108, 111, 44, 32, 119,
6043 111, 114, 108, 100, 33, 10, 0@};
6044 char ibm1047_hello[]
6045 = @{200, 133, 147, 147, 150, 107, 64, 166,
6046 150, 153, 147, 132, 90, 37, 0@};
6050 printf ("Hello, world!\n");
6054 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6055 containing the string @samp{Hello, world!} followed by a newline,
6056 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6058 We compile the program, and invoke the debugger on it:
6061 $ gcc -g charset-test.c -o charset-test
6062 $ gdb -nw charset-test
6063 GNU gdb 2001-12-19-cvs
6064 Copyright 2001 Free Software Foundation, Inc.
6069 We can use the @code{show charset} command to see what character sets
6070 @value{GDBN} is currently using to interpret and display characters and
6075 The current host and target character set is `ISO-8859-1'.
6079 For the sake of printing this manual, let's use @sc{ascii} as our
6080 initial character set:
6082 (gdb) set charset ASCII
6084 The current host and target character set is `ASCII'.
6088 Let's assume that @sc{ascii} is indeed the correct character set for our
6089 host system --- in other words, let's assume that if @value{GDBN} prints
6090 characters using the @sc{ascii} character set, our terminal will display
6091 them properly. Since our current target character set is also
6092 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6095 (gdb) print ascii_hello
6096 $1 = 0x401698 "Hello, world!\n"
6097 (gdb) print ascii_hello[0]
6102 @value{GDBN} uses the target character set for character and string
6103 literals you use in expressions:
6111 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6114 @value{GDBN} relies on the user to tell it which character set the
6115 target program uses. If we print @code{ibm1047_hello} while our target
6116 character set is still @sc{ascii}, we get jibberish:
6119 (gdb) print ibm1047_hello
6120 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6121 (gdb) print ibm1047_hello[0]
6126 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6127 @value{GDBN} tells us the character sets it supports:
6130 (gdb) set target-charset
6131 ASCII EBCDIC-US IBM1047 ISO-8859-1
6132 (gdb) set target-charset
6135 We can select @sc{ibm1047} as our target character set, and examine the
6136 program's strings again. Now the @sc{ascii} string is wrong, but
6137 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6138 target character set, @sc{ibm1047}, to the host character set,
6139 @sc{ascii}, and they display correctly:
6142 (gdb) set target-charset IBM1047
6144 The current host character set is `ASCII'.
6145 The current target character set is `IBM1047'.
6146 (gdb) print ascii_hello
6147 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6148 (gdb) print ascii_hello[0]
6150 (gdb) print ibm1047_hello
6151 $8 = 0x4016a8 "Hello, world!\n"
6152 (gdb) print ibm1047_hello[0]
6157 As above, @value{GDBN} uses the target character set for character and
6158 string literals you use in expressions:
6166 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6171 @chapter C Preprocessor Macros
6173 Some languages, such as C and C++, provide a way to define and invoke
6174 ``preprocessor macros'' which expand into strings of tokens.
6175 @value{GDBN} can evaluate expressions containing macro invocations, show
6176 the result of macro expansion, and show a macro's definition, including
6177 where it was defined.
6179 You may need to compile your program specially to provide @value{GDBN}
6180 with information about preprocessor macros. Most compilers do not
6181 include macros in their debugging information, even when you compile
6182 with the @option{-g} flag. @xref{Compilation}.
6184 A program may define a macro at one point, remove that definition later,
6185 and then provide a different definition after that. Thus, at different
6186 points in the program, a macro may have different definitions, or have
6187 no definition at all. If there is a current stack frame, @value{GDBN}
6188 uses the macros in scope at that frame's source code line. Otherwise,
6189 @value{GDBN} uses the macros in scope at the current listing location;
6192 At the moment, @value{GDBN} does not support the @code{##}
6193 token-splicing operator, the @code{#} stringification operator, or
6194 variable-arity macros.
6196 Whenever @value{GDBN} evaluates an expression, it always expands any
6197 macro invocations present in the expression. @value{GDBN} also provides
6198 the following commands for working with macros explicitly.
6202 @kindex macro expand
6203 @cindex macro expansion, showing the results of preprocessor
6204 @cindex preprocessor macro expansion, showing the results of
6205 @cindex expanding preprocessor macros
6206 @item macro expand @var{expression}
6207 @itemx macro exp @var{expression}
6208 Show the results of expanding all preprocessor macro invocations in
6209 @var{expression}. Since @value{GDBN} simply expands macros, but does
6210 not parse the result, @var{expression} need not be a valid expression;
6211 it can be any string of tokens.
6213 @kindex macro expand-once
6214 @item macro expand-once @var{expression}
6215 @itemx macro exp1 @var{expression}
6216 @i{(This command is not yet implemented.)} Show the results of
6217 expanding those preprocessor macro invocations that appear explicitly in
6218 @var{expression}. Macro invocations appearing in that expansion are
6219 left unchanged. This command allows you to see the effect of a
6220 particular macro more clearly, without being confused by further
6221 expansions. Since @value{GDBN} simply expands macros, but does not
6222 parse the result, @var{expression} need not be a valid expression; it
6223 can be any string of tokens.
6226 @cindex macro definition, showing
6227 @cindex definition, showing a macro's
6228 @item info macro @var{macro}
6229 Show the definition of the macro named @var{macro}, and describe the
6230 source location where that definition was established.
6232 @kindex macro define
6233 @cindex user-defined macros
6234 @cindex defining macros interactively
6235 @cindex macros, user-defined
6236 @item macro define @var{macro} @var{replacement-list}
6237 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6238 @i{(This command is not yet implemented.)} Introduce a definition for a
6239 preprocessor macro named @var{macro}, invocations of which are replaced
6240 by the tokens given in @var{replacement-list}. The first form of this
6241 command defines an ``object-like'' macro, which takes no arguments; the
6242 second form defines a ``function-like'' macro, which takes the arguments
6243 given in @var{arglist}.
6245 A definition introduced by this command is in scope in every expression
6246 evaluated in @value{GDBN}, until it is removed with the @command{macro
6247 undef} command, described below. The definition overrides all
6248 definitions for @var{macro} present in the program being debugged, as
6249 well as any previous user-supplied definition.
6252 @item macro undef @var{macro}
6253 @i{(This command is not yet implemented.)} Remove any user-supplied
6254 definition for the macro named @var{macro}. This command only affects
6255 definitions provided with the @command{macro define} command, described
6256 above; it cannot remove definitions present in the program being
6261 @cindex macros, example of debugging with
6262 Here is a transcript showing the above commands in action. First, we
6263 show our source files:
6271 #define ADD(x) (M + x)
6276 printf ("Hello, world!\n");
6278 printf ("We're so creative.\n");
6280 printf ("Goodbye, world!\n");
6287 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6288 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6289 compiler includes information about preprocessor macros in the debugging
6293 $ gcc -gdwarf-2 -g3 sample.c -o sample
6297 Now, we start @value{GDBN} on our sample program:
6301 GNU gdb 2002-05-06-cvs
6302 Copyright 2002 Free Software Foundation, Inc.
6303 GDB is free software, @dots{}
6307 We can expand macros and examine their definitions, even when the
6308 program is not running. @value{GDBN} uses the current listing position
6309 to decide which macro definitions are in scope:
6315 5 #define ADD(x) (M + x)
6320 10 printf ("Hello, world!\n");
6322 12 printf ("We're so creative.\n");
6323 (gdb) info macro ADD
6324 Defined at /home/jimb/gdb/macros/play/sample.c:5
6325 #define ADD(x) (M + x)
6327 Defined at /home/jimb/gdb/macros/play/sample.h:1
6328 included at /home/jimb/gdb/macros/play/sample.c:2
6330 (gdb) macro expand ADD(1)
6331 expands to: (42 + 1)
6332 (gdb) macro expand-once ADD(1)
6333 expands to: once (M + 1)
6337 In the example above, note that @command{macro expand-once} expands only
6338 the macro invocation explicit in the original text --- the invocation of
6339 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6340 which was introduced by @code{ADD}.
6342 Once the program is running, GDB uses the macro definitions in force at
6343 the source line of the current stack frame:
6347 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6349 Starting program: /home/jimb/gdb/macros/play/sample
6351 Breakpoint 1, main () at sample.c:10
6352 10 printf ("Hello, world!\n");
6356 At line 10, the definition of the macro @code{N} at line 9 is in force:
6360 Defined at /home/jimb/gdb/macros/play/sample.c:9
6362 (gdb) macro expand N Q M
6369 As we step over directives that remove @code{N}'s definition, and then
6370 give it a new definition, @value{GDBN} finds the definition (or lack
6371 thereof) in force at each point:
6376 12 printf ("We're so creative.\n");
6378 The symbol `N' has no definition as a C/C++ preprocessor macro
6379 at /home/jimb/gdb/macros/play/sample.c:12
6382 14 printf ("Goodbye, world!\n");
6384 Defined at /home/jimb/gdb/macros/play/sample.c:13
6386 (gdb) macro expand N Q M
6387 expands to: 1729 < 42
6395 @chapter Tracepoints
6396 @c This chapter is based on the documentation written by Michael
6397 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6400 In some applications, it is not feasible for the debugger to interrupt
6401 the program's execution long enough for the developer to learn
6402 anything helpful about its behavior. If the program's correctness
6403 depends on its real-time behavior, delays introduced by a debugger
6404 might cause the program to change its behavior drastically, or perhaps
6405 fail, even when the code itself is correct. It is useful to be able
6406 to observe the program's behavior without interrupting it.
6408 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6409 specify locations in the program, called @dfn{tracepoints}, and
6410 arbitrary expressions to evaluate when those tracepoints are reached.
6411 Later, using the @code{tfind} command, you can examine the values
6412 those expressions had when the program hit the tracepoints. The
6413 expressions may also denote objects in memory---structures or arrays,
6414 for example---whose values @value{GDBN} should record; while visiting
6415 a particular tracepoint, you may inspect those objects as if they were
6416 in memory at that moment. However, because @value{GDBN} records these
6417 values without interacting with you, it can do so quickly and
6418 unobtrusively, hopefully not disturbing the program's behavior.
6420 The tracepoint facility is currently available only for remote
6421 targets. @xref{Targets}. In addition, your remote target must know how
6422 to collect trace data. This functionality is implemented in the remote
6423 stub; however, none of the stubs distributed with @value{GDBN} support
6424 tracepoints as of this writing.
6426 This chapter describes the tracepoint commands and features.
6430 * Analyze Collected Data::
6431 * Tracepoint Variables::
6434 @node Set Tracepoints
6435 @section Commands to Set Tracepoints
6437 Before running such a @dfn{trace experiment}, an arbitrary number of
6438 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6439 tracepoint has a number assigned to it by @value{GDBN}. Like with
6440 breakpoints, tracepoint numbers are successive integers starting from
6441 one. Many of the commands associated with tracepoints take the
6442 tracepoint number as their argument, to identify which tracepoint to
6445 For each tracepoint, you can specify, in advance, some arbitrary set
6446 of data that you want the target to collect in the trace buffer when
6447 it hits that tracepoint. The collected data can include registers,
6448 local variables, or global data. Later, you can use @value{GDBN}
6449 commands to examine the values these data had at the time the
6452 This section describes commands to set tracepoints and associated
6453 conditions and actions.
6456 * Create and Delete Tracepoints::
6457 * Enable and Disable Tracepoints::
6458 * Tracepoint Passcounts::
6459 * Tracepoint Actions::
6460 * Listing Tracepoints::
6461 * Starting and Stopping Trace Experiment::
6464 @node Create and Delete Tracepoints
6465 @subsection Create and Delete Tracepoints
6468 @cindex set tracepoint
6471 The @code{trace} command is very similar to the @code{break} command.
6472 Its argument can be a source line, a function name, or an address in
6473 the target program. @xref{Set Breaks}. The @code{trace} command
6474 defines a tracepoint, which is a point in the target program where the
6475 debugger will briefly stop, collect some data, and then allow the
6476 program to continue. Setting a tracepoint or changing its commands
6477 doesn't take effect until the next @code{tstart} command; thus, you
6478 cannot change the tracepoint attributes once a trace experiment is
6481 Here are some examples of using the @code{trace} command:
6484 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6486 (@value{GDBP}) @b{trace +2} // 2 lines forward
6488 (@value{GDBP}) @b{trace my_function} // first source line of function
6490 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6492 (@value{GDBP}) @b{trace *0x2117c4} // an address
6496 You can abbreviate @code{trace} as @code{tr}.
6499 @cindex last tracepoint number
6500 @cindex recent tracepoint number
6501 @cindex tracepoint number
6502 The convenience variable @code{$tpnum} records the tracepoint number
6503 of the most recently set tracepoint.
6505 @kindex delete tracepoint
6506 @cindex tracepoint deletion
6507 @item delete tracepoint @r{[}@var{num}@r{]}
6508 Permanently delete one or more tracepoints. With no argument, the
6509 default is to delete all tracepoints.
6514 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6516 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6520 You can abbreviate this command as @code{del tr}.
6523 @node Enable and Disable Tracepoints
6524 @subsection Enable and Disable Tracepoints
6527 @kindex disable tracepoint
6528 @item disable tracepoint @r{[}@var{num}@r{]}
6529 Disable tracepoint @var{num}, or all tracepoints if no argument
6530 @var{num} is given. A disabled tracepoint will have no effect during
6531 the next trace experiment, but it is not forgotten. You can re-enable
6532 a disabled tracepoint using the @code{enable tracepoint} command.
6534 @kindex enable tracepoint
6535 @item enable tracepoint @r{[}@var{num}@r{]}
6536 Enable tracepoint @var{num}, or all tracepoints. The enabled
6537 tracepoints will become effective the next time a trace experiment is
6541 @node Tracepoint Passcounts
6542 @subsection Tracepoint Passcounts
6546 @cindex tracepoint pass count
6547 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6548 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6549 automatically stop a trace experiment. If a tracepoint's passcount is
6550 @var{n}, then the trace experiment will be automatically stopped on
6551 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6552 @var{num} is not specified, the @code{passcount} command sets the
6553 passcount of the most recently defined tracepoint. If no passcount is
6554 given, the trace experiment will run until stopped explicitly by the
6560 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6561 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6563 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6564 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6565 (@value{GDBP}) @b{trace foo}
6566 (@value{GDBP}) @b{pass 3}
6567 (@value{GDBP}) @b{trace bar}
6568 (@value{GDBP}) @b{pass 2}
6569 (@value{GDBP}) @b{trace baz}
6570 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6571 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6572 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6573 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6577 @node Tracepoint Actions
6578 @subsection Tracepoint Action Lists
6582 @cindex tracepoint actions
6583 @item actions @r{[}@var{num}@r{]}
6584 This command will prompt for a list of actions to be taken when the
6585 tracepoint is hit. If the tracepoint number @var{num} is not
6586 specified, this command sets the actions for the one that was most
6587 recently defined (so that you can define a tracepoint and then say
6588 @code{actions} without bothering about its number). You specify the
6589 actions themselves on the following lines, one action at a time, and
6590 terminate the actions list with a line containing just @code{end}. So
6591 far, the only defined actions are @code{collect} and
6592 @code{while-stepping}.
6594 @cindex remove actions from a tracepoint
6595 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6596 and follow it immediately with @samp{end}.
6599 (@value{GDBP}) @b{collect @var{data}} // collect some data
6601 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6603 (@value{GDBP}) @b{end} // signals the end of actions.
6606 In the following example, the action list begins with @code{collect}
6607 commands indicating the things to be collected when the tracepoint is
6608 hit. Then, in order to single-step and collect additional data
6609 following the tracepoint, a @code{while-stepping} command is used,
6610 followed by the list of things to be collected while stepping. The
6611 @code{while-stepping} command is terminated by its own separate
6612 @code{end} command. Lastly, the action list is terminated by an
6616 (@value{GDBP}) @b{trace foo}
6617 (@value{GDBP}) @b{actions}
6618 Enter actions for tracepoint 1, one per line:
6627 @kindex collect @r{(tracepoints)}
6628 @item collect @var{expr1}, @var{expr2}, @dots{}
6629 Collect values of the given expressions when the tracepoint is hit.
6630 This command accepts a comma-separated list of any valid expressions.
6631 In addition to global, static, or local variables, the following
6632 special arguments are supported:
6636 collect all registers
6639 collect all function arguments
6642 collect all local variables.
6645 You can give several consecutive @code{collect} commands, each one
6646 with a single argument, or one @code{collect} command with several
6647 arguments separated by commas: the effect is the same.
6649 The command @code{info scope} (@pxref{Symbols, info scope}) is
6650 particularly useful for figuring out what data to collect.
6652 @kindex while-stepping @r{(tracepoints)}
6653 @item while-stepping @var{n}
6654 Perform @var{n} single-step traces after the tracepoint, collecting
6655 new data at each step. The @code{while-stepping} command is
6656 followed by the list of what to collect while stepping (followed by
6657 its own @code{end} command):
6661 > collect $regs, myglobal
6667 You may abbreviate @code{while-stepping} as @code{ws} or
6671 @node Listing Tracepoints
6672 @subsection Listing Tracepoints
6675 @kindex info tracepoints
6676 @cindex information about tracepoints
6677 @item info tracepoints @r{[}@var{num}@r{]}
6678 Display information about the tracepoint @var{num}. If you don't specify
6679 a tracepoint number, displays information about all the tracepoints
6680 defined so far. For each tracepoint, the following information is
6687 whether it is enabled or disabled
6691 its passcount as given by the @code{passcount @var{n}} command
6693 its step count as given by the @code{while-stepping @var{n}} command
6695 where in the source files is the tracepoint set
6697 its action list as given by the @code{actions} command
6701 (@value{GDBP}) @b{info trace}
6702 Num Enb Address PassC StepC What
6703 1 y 0x002117c4 0 0 <gdb_asm>
6704 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6705 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6710 This command can be abbreviated @code{info tp}.
6713 @node Starting and Stopping Trace Experiment
6714 @subsection Starting and Stopping Trace Experiment
6718 @cindex start a new trace experiment
6719 @cindex collected data discarded
6721 This command takes no arguments. It starts the trace experiment, and
6722 begins collecting data. This has the side effect of discarding all
6723 the data collected in the trace buffer during the previous trace
6727 @cindex stop a running trace experiment
6729 This command takes no arguments. It ends the trace experiment, and
6730 stops collecting data.
6732 @strong{Note:} a trace experiment and data collection may stop
6733 automatically if any tracepoint's passcount is reached
6734 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6737 @cindex status of trace data collection
6738 @cindex trace experiment, status of
6740 This command displays the status of the current trace data
6744 Here is an example of the commands we described so far:
6747 (@value{GDBP}) @b{trace gdb_c_test}
6748 (@value{GDBP}) @b{actions}
6749 Enter actions for tracepoint #1, one per line.
6750 > collect $regs,$locals,$args
6755 (@value{GDBP}) @b{tstart}
6756 [time passes @dots{}]
6757 (@value{GDBP}) @b{tstop}
6761 @node Analyze Collected Data
6762 @section Using the collected data
6764 After the tracepoint experiment ends, you use @value{GDBN} commands
6765 for examining the trace data. The basic idea is that each tracepoint
6766 collects a trace @dfn{snapshot} every time it is hit and another
6767 snapshot every time it single-steps. All these snapshots are
6768 consecutively numbered from zero and go into a buffer, and you can
6769 examine them later. The way you examine them is to @dfn{focus} on a
6770 specific trace snapshot. When the remote stub is focused on a trace
6771 snapshot, it will respond to all @value{GDBN} requests for memory and
6772 registers by reading from the buffer which belongs to that snapshot,
6773 rather than from @emph{real} memory or registers of the program being
6774 debugged. This means that @strong{all} @value{GDBN} commands
6775 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6776 behave as if we were currently debugging the program state as it was
6777 when the tracepoint occurred. Any requests for data that are not in
6778 the buffer will fail.
6781 * tfind:: How to select a trace snapshot
6782 * tdump:: How to display all data for a snapshot
6783 * save-tracepoints:: How to save tracepoints for a future run
6787 @subsection @code{tfind @var{n}}
6790 @cindex select trace snapshot
6791 @cindex find trace snapshot
6792 The basic command for selecting a trace snapshot from the buffer is
6793 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6794 counting from zero. If no argument @var{n} is given, the next
6795 snapshot is selected.
6797 Here are the various forms of using the @code{tfind} command.
6801 Find the first snapshot in the buffer. This is a synonym for
6802 @code{tfind 0} (since 0 is the number of the first snapshot).
6805 Stop debugging trace snapshots, resume @emph{live} debugging.
6808 Same as @samp{tfind none}.
6811 No argument means find the next trace snapshot.
6814 Find the previous trace snapshot before the current one. This permits
6815 retracing earlier steps.
6817 @item tfind tracepoint @var{num}
6818 Find the next snapshot associated with tracepoint @var{num}. Search
6819 proceeds forward from the last examined trace snapshot. If no
6820 argument @var{num} is given, it means find the next snapshot collected
6821 for the same tracepoint as the current snapshot.
6823 @item tfind pc @var{addr}
6824 Find the next snapshot associated with the value @var{addr} of the
6825 program counter. Search proceeds forward from the last examined trace
6826 snapshot. If no argument @var{addr} is given, it means find the next
6827 snapshot with the same value of PC as the current snapshot.
6829 @item tfind outside @var{addr1}, @var{addr2}
6830 Find the next snapshot whose PC is outside the given range of
6833 @item tfind range @var{addr1}, @var{addr2}
6834 Find the next snapshot whose PC is between @var{addr1} and
6835 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6837 @item tfind line @r{[}@var{file}:@r{]}@var{n}
6838 Find the next snapshot associated with the source line @var{n}. If
6839 the optional argument @var{file} is given, refer to line @var{n} in
6840 that source file. Search proceeds forward from the last examined
6841 trace snapshot. If no argument @var{n} is given, it means find the
6842 next line other than the one currently being examined; thus saying
6843 @code{tfind line} repeatedly can appear to have the same effect as
6844 stepping from line to line in a @emph{live} debugging session.
6847 The default arguments for the @code{tfind} commands are specifically
6848 designed to make it easy to scan through the trace buffer. For
6849 instance, @code{tfind} with no argument selects the next trace
6850 snapshot, and @code{tfind -} with no argument selects the previous
6851 trace snapshot. So, by giving one @code{tfind} command, and then
6852 simply hitting @key{RET} repeatedly you can examine all the trace
6853 snapshots in order. Or, by saying @code{tfind -} and then hitting
6854 @key{RET} repeatedly you can examine the snapshots in reverse order.
6855 The @code{tfind line} command with no argument selects the snapshot
6856 for the next source line executed. The @code{tfind pc} command with
6857 no argument selects the next snapshot with the same program counter
6858 (PC) as the current frame. The @code{tfind tracepoint} command with
6859 no argument selects the next trace snapshot collected by the same
6860 tracepoint as the current one.
6862 In addition to letting you scan through the trace buffer manually,
6863 these commands make it easy to construct @value{GDBN} scripts that
6864 scan through the trace buffer and print out whatever collected data
6865 you are interested in. Thus, if we want to examine the PC, FP, and SP
6866 registers from each trace frame in the buffer, we can say this:
6869 (@value{GDBP}) @b{tfind start}
6870 (@value{GDBP}) @b{while ($trace_frame != -1)}
6871 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
6872 $trace_frame, $pc, $sp, $fp
6876 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
6877 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
6878 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
6879 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
6880 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
6881 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
6882 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
6883 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
6884 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
6885 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
6886 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
6889 Or, if we want to examine the variable @code{X} at each source line in
6893 (@value{GDBP}) @b{tfind start}
6894 (@value{GDBP}) @b{while ($trace_frame != -1)}
6895 > printf "Frame %d, X == %d\n", $trace_frame, X
6905 @subsection @code{tdump}
6907 @cindex dump all data collected at tracepoint
6908 @cindex tracepoint data, display
6910 This command takes no arguments. It prints all the data collected at
6911 the current trace snapshot.
6914 (@value{GDBP}) @b{trace 444}
6915 (@value{GDBP}) @b{actions}
6916 Enter actions for tracepoint #2, one per line:
6917 > collect $regs, $locals, $args, gdb_long_test
6920 (@value{GDBP}) @b{tstart}
6922 (@value{GDBP}) @b{tfind line 444}
6923 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
6925 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
6927 (@value{GDBP}) @b{tdump}
6928 Data collected at tracepoint 2, trace frame 1:
6929 d0 0xc4aa0085 -995491707
6933 d4 0x71aea3d 119204413
6938 a1 0x3000668 50333288
6941 a4 0x3000698 50333336
6943 fp 0x30bf3c 0x30bf3c
6944 sp 0x30bf34 0x30bf34
6946 pc 0x20b2c8 0x20b2c8
6950 p = 0x20e5b4 "gdb-test"
6957 gdb_long_test = 17 '\021'
6962 @node save-tracepoints
6963 @subsection @code{save-tracepoints @var{filename}}
6964 @kindex save-tracepoints
6965 @cindex save tracepoints for future sessions
6967 This command saves all current tracepoint definitions together with
6968 their actions and passcounts, into a file @file{@var{filename}}
6969 suitable for use in a later debugging session. To read the saved
6970 tracepoint definitions, use the @code{source} command (@pxref{Command
6973 @node Tracepoint Variables
6974 @section Convenience Variables for Tracepoints
6975 @cindex tracepoint variables
6976 @cindex convenience variables for tracepoints
6979 @vindex $trace_frame
6980 @item (int) $trace_frame
6981 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
6982 snapshot is selected.
6985 @item (int) $tracepoint
6986 The tracepoint for the current trace snapshot.
6989 @item (int) $trace_line
6990 The line number for the current trace snapshot.
6993 @item (char []) $trace_file
6994 The source file for the current trace snapshot.
6997 @item (char []) $trace_func
6998 The name of the function containing @code{$tracepoint}.
7001 Note: @code{$trace_file} is not suitable for use in @code{printf},
7002 use @code{output} instead.
7004 Here's a simple example of using these convenience variables for
7005 stepping through all the trace snapshots and printing some of their
7009 (@value{GDBP}) @b{tfind start}
7011 (@value{GDBP}) @b{while $trace_frame != -1}
7012 > output $trace_file
7013 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7019 @chapter Debugging Programs That Use Overlays
7022 If your program is too large to fit completely in your target system's
7023 memory, you can sometimes use @dfn{overlays} to work around this
7024 problem. @value{GDBN} provides some support for debugging programs that
7028 * How Overlays Work:: A general explanation of overlays.
7029 * Overlay Commands:: Managing overlays in @value{GDBN}.
7030 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7031 mapped by asking the inferior.
7032 * Overlay Sample Program:: A sample program using overlays.
7035 @node How Overlays Work
7036 @section How Overlays Work
7037 @cindex mapped overlays
7038 @cindex unmapped overlays
7039 @cindex load address, overlay's
7040 @cindex mapped address
7041 @cindex overlay area
7043 Suppose you have a computer whose instruction address space is only 64
7044 kilobytes long, but which has much more memory which can be accessed by
7045 other means: special instructions, segment registers, or memory
7046 management hardware, for example. Suppose further that you want to
7047 adapt a program which is larger than 64 kilobytes to run on this system.
7049 One solution is to identify modules of your program which are relatively
7050 independent, and need not call each other directly; call these modules
7051 @dfn{overlays}. Separate the overlays from the main program, and place
7052 their machine code in the larger memory. Place your main program in
7053 instruction memory, but leave at least enough space there to hold the
7054 largest overlay as well.
7056 Now, to call a function located in an overlay, you must first copy that
7057 overlay's machine code from the large memory into the space set aside
7058 for it in the instruction memory, and then jump to its entry point
7061 @c NB: In the below the mapped area's size is greater or equal to the
7062 @c size of all overlays. This is intentional to remind the developer
7063 @c that overlays don't necessarily need to be the same size.
7067 Data Instruction Larger
7068 Address Space Address Space Address Space
7069 +-----------+ +-----------+ +-----------+
7071 +-----------+ +-----------+ +-----------+<-- overlay 1
7072 | program | | main | .----| overlay 1 | load address
7073 | variables | | program | | +-----------+
7074 | and heap | | | | | |
7075 +-----------+ | | | +-----------+<-- overlay 2
7076 | | +-----------+ | | | load address
7077 +-----------+ | | | .-| overlay 2 |
7079 mapped --->+-----------+ | | +-----------+
7081 | overlay | <-' | | |
7082 | area | <---' +-----------+<-- overlay 3
7083 | | <---. | | load address
7084 +-----------+ `--| overlay 3 |
7091 @anchor{A code overlay}A code overlay
7095 The diagram (@pxref{A code overlay}) shows a system with separate data
7096 and instruction address spaces. To map an overlay, the program copies
7097 its code from the larger address space to the instruction address space.
7098 Since the overlays shown here all use the same mapped address, only one
7099 may be mapped at a time. For a system with a single address space for
7100 data and instructions, the diagram would be similar, except that the
7101 program variables and heap would share an address space with the main
7102 program and the overlay area.
7104 An overlay loaded into instruction memory and ready for use is called a
7105 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7106 instruction memory. An overlay not present (or only partially present)
7107 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7108 is its address in the larger memory. The mapped address is also called
7109 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7110 called the @dfn{load memory address}, or @dfn{LMA}.
7112 Unfortunately, overlays are not a completely transparent way to adapt a
7113 program to limited instruction memory. They introduce a new set of
7114 global constraints you must keep in mind as you design your program:
7119 Before calling or returning to a function in an overlay, your program
7120 must make sure that overlay is actually mapped. Otherwise, the call or
7121 return will transfer control to the right address, but in the wrong
7122 overlay, and your program will probably crash.
7125 If the process of mapping an overlay is expensive on your system, you
7126 will need to choose your overlays carefully to minimize their effect on
7127 your program's performance.
7130 The executable file you load onto your system must contain each
7131 overlay's instructions, appearing at the overlay's load address, not its
7132 mapped address. However, each overlay's instructions must be relocated
7133 and its symbols defined as if the overlay were at its mapped address.
7134 You can use GNU linker scripts to specify different load and relocation
7135 addresses for pieces of your program; see @ref{Overlay Description,,,
7136 ld.info, Using ld: the GNU linker}.
7139 The procedure for loading executable files onto your system must be able
7140 to load their contents into the larger address space as well as the
7141 instruction and data spaces.
7145 The overlay system described above is rather simple, and could be
7146 improved in many ways:
7151 If your system has suitable bank switch registers or memory management
7152 hardware, you could use those facilities to make an overlay's load area
7153 contents simply appear at their mapped address in instruction space.
7154 This would probably be faster than copying the overlay to its mapped
7155 area in the usual way.
7158 If your overlays are small enough, you could set aside more than one
7159 overlay area, and have more than one overlay mapped at a time.
7162 You can use overlays to manage data, as well as instructions. In
7163 general, data overlays are even less transparent to your design than
7164 code overlays: whereas code overlays only require care when you call or
7165 return to functions, data overlays require care every time you access
7166 the data. Also, if you change the contents of a data overlay, you
7167 must copy its contents back out to its load address before you can copy a
7168 different data overlay into the same mapped area.
7173 @node Overlay Commands
7174 @section Overlay Commands
7176 To use @value{GDBN}'s overlay support, each overlay in your program must
7177 correspond to a separate section of the executable file. The section's
7178 virtual memory address and load memory address must be the overlay's
7179 mapped and load addresses. Identifying overlays with sections allows
7180 @value{GDBN} to determine the appropriate address of a function or
7181 variable, depending on whether the overlay is mapped or not.
7183 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7184 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7189 Disable @value{GDBN}'s overlay support. When overlay support is
7190 disabled, @value{GDBN} assumes that all functions and variables are
7191 always present at their mapped addresses. By default, @value{GDBN}'s
7192 overlay support is disabled.
7194 @item overlay manual
7195 @kindex overlay manual
7196 @cindex manual overlay debugging
7197 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7198 relies on you to tell it which overlays are mapped, and which are not,
7199 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7200 commands described below.
7202 @item overlay map-overlay @var{overlay}
7203 @itemx overlay map @var{overlay}
7204 @kindex overlay map-overlay
7205 @cindex map an overlay
7206 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7207 be the name of the object file section containing the overlay. When an
7208 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7209 functions and variables at their mapped addresses. @value{GDBN} assumes
7210 that any other overlays whose mapped ranges overlap that of
7211 @var{overlay} are now unmapped.
7213 @item overlay unmap-overlay @var{overlay}
7214 @itemx overlay unmap @var{overlay}
7215 @kindex overlay unmap-overlay
7216 @cindex unmap an overlay
7217 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7218 must be the name of the object file section containing the overlay.
7219 When an overlay is unmapped, @value{GDBN} assumes it can find the
7220 overlay's functions and variables at their load addresses.
7223 @kindex overlay auto
7224 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7225 consults a data structure the overlay manager maintains in the inferior
7226 to see which overlays are mapped. For details, see @ref{Automatic
7229 @item overlay load-target
7231 @kindex overlay load-target
7232 @cindex reloading the overlay table
7233 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7234 re-reads the table @value{GDBN} automatically each time the inferior
7235 stops, so this command should only be necessary if you have changed the
7236 overlay mapping yourself using @value{GDBN}. This command is only
7237 useful when using automatic overlay debugging.
7239 @item overlay list-overlays
7241 @cindex listing mapped overlays
7242 Display a list of the overlays currently mapped, along with their mapped
7243 addresses, load addresses, and sizes.
7247 Normally, when @value{GDBN} prints a code address, it includes the name
7248 of the function the address falls in:
7252 $3 = @{int ()@} 0x11a0 <main>
7255 When overlay debugging is enabled, @value{GDBN} recognizes code in
7256 unmapped overlays, and prints the names of unmapped functions with
7257 asterisks around them. For example, if @code{foo} is a function in an
7258 unmapped overlay, @value{GDBN} prints it this way:
7262 No sections are mapped.
7264 $5 = @{int (int)@} 0x100000 <*foo*>
7267 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7272 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7273 mapped at 0x1016 - 0x104a
7275 $6 = @{int (int)@} 0x1016 <foo>
7278 When overlay debugging is enabled, @value{GDBN} can find the correct
7279 address for functions and variables in an overlay, whether or not the
7280 overlay is mapped. This allows most @value{GDBN} commands, like
7281 @code{break} and @code{disassemble}, to work normally, even on unmapped
7282 code. However, @value{GDBN}'s breakpoint support has some limitations:
7286 @cindex breakpoints in overlays
7287 @cindex overlays, setting breakpoints in
7288 You can set breakpoints in functions in unmapped overlays, as long as
7289 @value{GDBN} can write to the overlay at its load address.
7291 @value{GDBN} can not set hardware or simulator-based breakpoints in
7292 unmapped overlays. However, if you set a breakpoint at the end of your
7293 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7294 you are using manual overlay management), @value{GDBN} will re-set its
7295 breakpoints properly.
7299 @node Automatic Overlay Debugging
7300 @section Automatic Overlay Debugging
7301 @cindex automatic overlay debugging
7303 @value{GDBN} can automatically track which overlays are mapped and which
7304 are not, given some simple co-operation from the overlay manager in the
7305 inferior. If you enable automatic overlay debugging with the
7306 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7307 looks in the inferior's memory for certain variables describing the
7308 current state of the overlays.
7310 Here are the variables your overlay manager must define to support
7311 @value{GDBN}'s automatic overlay debugging:
7315 @item @code{_ovly_table}:
7316 This variable must be an array of the following structures:
7321 /* The overlay's mapped address. */
7324 /* The size of the overlay, in bytes. */
7327 /* The overlay's load address. */
7330 /* Non-zero if the overlay is currently mapped;
7332 unsigned long mapped;
7336 @item @code{_novlys}:
7337 This variable must be a four-byte signed integer, holding the total
7338 number of elements in @code{_ovly_table}.
7342 To decide whether a particular overlay is mapped or not, @value{GDBN}
7343 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7344 @code{lma} members equal the VMA and LMA of the overlay's section in the
7345 executable file. When @value{GDBN} finds a matching entry, it consults
7346 the entry's @code{mapped} member to determine whether the overlay is
7349 In addition, your overlay manager may define a function called
7350 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7351 will silently set a breakpoint there. If the overlay manager then
7352 calls this function whenever it has changed the overlay table, this
7353 will enable @value{GDBN} to accurately keep track of which overlays
7354 are in program memory, and update any breakpoints that may be set
7355 in overlays. This will allow breakpoints to work even if the
7356 overlays are kept in ROM or other non-writable memory while they
7357 are not being executed.
7359 @node Overlay Sample Program
7360 @section Overlay Sample Program
7361 @cindex overlay example program
7363 When linking a program which uses overlays, you must place the overlays
7364 at their load addresses, while relocating them to run at their mapped
7365 addresses. To do this, you must write a linker script (@pxref{Overlay
7366 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7367 since linker scripts are specific to a particular host system, target
7368 architecture, and target memory layout, this manual cannot provide
7369 portable sample code demonstrating @value{GDBN}'s overlay support.
7371 However, the @value{GDBN} source distribution does contain an overlaid
7372 program, with linker scripts for a few systems, as part of its test
7373 suite. The program consists of the following files from
7374 @file{gdb/testsuite/gdb.base}:
7378 The main program file.
7380 A simple overlay manager, used by @file{overlays.c}.
7385 Overlay modules, loaded and used by @file{overlays.c}.
7388 Linker scripts for linking the test program on the @code{d10v-elf}
7389 and @code{m32r-elf} targets.
7392 You can build the test program using the @code{d10v-elf} GCC
7393 cross-compiler like this:
7396 $ d10v-elf-gcc -g -c overlays.c
7397 $ d10v-elf-gcc -g -c ovlymgr.c
7398 $ d10v-elf-gcc -g -c foo.c
7399 $ d10v-elf-gcc -g -c bar.c
7400 $ d10v-elf-gcc -g -c baz.c
7401 $ d10v-elf-gcc -g -c grbx.c
7402 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7403 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7406 The build process is identical for any other architecture, except that
7407 you must substitute the appropriate compiler and linker script for the
7408 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7412 @chapter Using @value{GDBN} with Different Languages
7415 Although programming languages generally have common aspects, they are
7416 rarely expressed in the same manner. For instance, in ANSI C,
7417 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7418 Modula-2, it is accomplished by @code{p^}. Values can also be
7419 represented (and displayed) differently. Hex numbers in C appear as
7420 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7422 @cindex working language
7423 Language-specific information is built into @value{GDBN} for some languages,
7424 allowing you to express operations like the above in your program's
7425 native language, and allowing @value{GDBN} to output values in a manner
7426 consistent with the syntax of your program's native language. The
7427 language you use to build expressions is called the @dfn{working
7431 * Setting:: Switching between source languages
7432 * Show:: Displaying the language
7433 * Checks:: Type and range checks
7434 * Support:: Supported languages
7438 @section Switching between source languages
7440 There are two ways to control the working language---either have @value{GDBN}
7441 set it automatically, or select it manually yourself. You can use the
7442 @code{set language} command for either purpose. On startup, @value{GDBN}
7443 defaults to setting the language automatically. The working language is
7444 used to determine how expressions you type are interpreted, how values
7447 In addition to the working language, every source file that
7448 @value{GDBN} knows about has its own working language. For some object
7449 file formats, the compiler might indicate which language a particular
7450 source file is in. However, most of the time @value{GDBN} infers the
7451 language from the name of the file. The language of a source file
7452 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7453 show each frame appropriately for its own language. There is no way to
7454 set the language of a source file from within @value{GDBN}, but you can
7455 set the language associated with a filename extension. @xref{Show, ,
7456 Displaying the language}.
7458 This is most commonly a problem when you use a program, such
7459 as @code{cfront} or @code{f2c}, that generates C but is written in
7460 another language. In that case, make the
7461 program use @code{#line} directives in its C output; that way
7462 @value{GDBN} will know the correct language of the source code of the original
7463 program, and will display that source code, not the generated C code.
7466 * Filenames:: Filename extensions and languages.
7467 * Manually:: Setting the working language manually
7468 * Automatically:: Having @value{GDBN} infer the source language
7472 @subsection List of filename extensions and languages
7474 If a source file name ends in one of the following extensions, then
7475 @value{GDBN} infers that its language is the one indicated.
7495 Modula-2 source file
7499 Assembler source file. This actually behaves almost like C, but
7500 @value{GDBN} does not skip over function prologues when stepping.
7503 In addition, you may set the language associated with a filename
7504 extension. @xref{Show, , Displaying the language}.
7507 @subsection Setting the working language
7509 If you allow @value{GDBN} to set the language automatically,
7510 expressions are interpreted the same way in your debugging session and
7513 @kindex set language
7514 If you wish, you may set the language manually. To do this, issue the
7515 command @samp{set language @var{lang}}, where @var{lang} is the name of
7517 @code{c} or @code{modula-2}.
7518 For a list of the supported languages, type @samp{set language}.
7520 Setting the language manually prevents @value{GDBN} from updating the working
7521 language automatically. This can lead to confusion if you try
7522 to debug a program when the working language is not the same as the
7523 source language, when an expression is acceptable to both
7524 languages---but means different things. For instance, if the current
7525 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7533 might not have the effect you intended. In C, this means to add
7534 @code{b} and @code{c} and place the result in @code{a}. The result
7535 printed would be the value of @code{a}. In Modula-2, this means to compare
7536 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7539 @subsection Having @value{GDBN} infer the source language
7541 To have @value{GDBN} set the working language automatically, use
7542 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7543 then infers the working language. That is, when your program stops in a
7544 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7545 working language to the language recorded for the function in that
7546 frame. If the language for a frame is unknown (that is, if the function
7547 or block corresponding to the frame was defined in a source file that
7548 does not have a recognized extension), the current working language is
7549 not changed, and @value{GDBN} issues a warning.
7551 This may not seem necessary for most programs, which are written
7552 entirely in one source language. However, program modules and libraries
7553 written in one source language can be used by a main program written in
7554 a different source language. Using @samp{set language auto} in this
7555 case frees you from having to set the working language manually.
7558 @section Displaying the language
7560 The following commands help you find out which language is the
7561 working language, and also what language source files were written in.
7563 @kindex show language
7564 @kindex info frame@r{, show the source language}
7565 @kindex info source@r{, show the source language}
7568 Display the current working language. This is the
7569 language you can use with commands such as @code{print} to
7570 build and compute expressions that may involve variables in your program.
7573 Display the source language for this frame. This language becomes the
7574 working language if you use an identifier from this frame.
7575 @xref{Frame Info, ,Information about a frame}, to identify the other
7576 information listed here.
7579 Display the source language of this source file.
7580 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7581 information listed here.
7584 In unusual circumstances, you may have source files with extensions
7585 not in the standard list. You can then set the extension associated
7586 with a language explicitly:
7588 @kindex set extension-language
7589 @kindex info extensions
7591 @item set extension-language @var{.ext} @var{language}
7592 Set source files with extension @var{.ext} to be assumed to be in
7593 the source language @var{language}.
7595 @item info extensions
7596 List all the filename extensions and the associated languages.
7600 @section Type and range checking
7603 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7604 checking are included, but they do not yet have any effect. This
7605 section documents the intended facilities.
7607 @c FIXME remove warning when type/range code added
7609 Some languages are designed to guard you against making seemingly common
7610 errors through a series of compile- and run-time checks. These include
7611 checking the type of arguments to functions and operators, and making
7612 sure mathematical overflows are caught at run time. Checks such as
7613 these help to ensure a program's correctness once it has been compiled
7614 by eliminating type mismatches, and providing active checks for range
7615 errors when your program is running.
7617 @value{GDBN} can check for conditions like the above if you wish.
7618 Although @value{GDBN} does not check the statements in your program, it
7619 can check expressions entered directly into @value{GDBN} for evaluation via
7620 the @code{print} command, for example. As with the working language,
7621 @value{GDBN} can also decide whether or not to check automatically based on
7622 your program's source language. @xref{Support, ,Supported languages},
7623 for the default settings of supported languages.
7626 * Type Checking:: An overview of type checking
7627 * Range Checking:: An overview of range checking
7630 @cindex type checking
7631 @cindex checks, type
7633 @subsection An overview of type checking
7635 Some languages, such as Modula-2, are strongly typed, meaning that the
7636 arguments to operators and functions have to be of the correct type,
7637 otherwise an error occurs. These checks prevent type mismatch
7638 errors from ever causing any run-time problems. For example,
7646 The second example fails because the @code{CARDINAL} 1 is not
7647 type-compatible with the @code{REAL} 2.3.
7649 For the expressions you use in @value{GDBN} commands, you can tell the
7650 @value{GDBN} type checker to skip checking;
7651 to treat any mismatches as errors and abandon the expression;
7652 or to only issue warnings when type mismatches occur,
7653 but evaluate the expression anyway. When you choose the last of
7654 these, @value{GDBN} evaluates expressions like the second example above, but
7655 also issues a warning.
7657 Even if you turn type checking off, there may be other reasons
7658 related to type that prevent @value{GDBN} from evaluating an expression.
7659 For instance, @value{GDBN} does not know how to add an @code{int} and
7660 a @code{struct foo}. These particular type errors have nothing to do
7661 with the language in use, and usually arise from expressions, such as
7662 the one described above, which make little sense to evaluate anyway.
7664 Each language defines to what degree it is strict about type. For
7665 instance, both Modula-2 and C require the arguments to arithmetical
7666 operators to be numbers. In C, enumerated types and pointers can be
7667 represented as numbers, so that they are valid arguments to mathematical
7668 operators. @xref{Support, ,Supported languages}, for further
7669 details on specific languages.
7671 @value{GDBN} provides some additional commands for controlling the type checker:
7673 @kindex set check@r{, type}
7674 @kindex set check type
7675 @kindex show check type
7677 @item set check type auto
7678 Set type checking on or off based on the current working language.
7679 @xref{Support, ,Supported languages}, for the default settings for
7682 @item set check type on
7683 @itemx set check type off
7684 Set type checking on or off, overriding the default setting for the
7685 current working language. Issue a warning if the setting does not
7686 match the language default. If any type mismatches occur in
7687 evaluating an expression while type checking is on, @value{GDBN} prints a
7688 message and aborts evaluation of the expression.
7690 @item set check type warn
7691 Cause the type checker to issue warnings, but to always attempt to
7692 evaluate the expression. Evaluating the expression may still
7693 be impossible for other reasons. For example, @value{GDBN} cannot add
7694 numbers and structures.
7697 Show the current setting of the type checker, and whether or not @value{GDBN}
7698 is setting it automatically.
7701 @cindex range checking
7702 @cindex checks, range
7703 @node Range Checking
7704 @subsection An overview of range checking
7706 In some languages (such as Modula-2), it is an error to exceed the
7707 bounds of a type; this is enforced with run-time checks. Such range
7708 checking is meant to ensure program correctness by making sure
7709 computations do not overflow, or indices on an array element access do
7710 not exceed the bounds of the array.
7712 For expressions you use in @value{GDBN} commands, you can tell
7713 @value{GDBN} to treat range errors in one of three ways: ignore them,
7714 always treat them as errors and abandon the expression, or issue
7715 warnings but evaluate the expression anyway.
7717 A range error can result from numerical overflow, from exceeding an
7718 array index bound, or when you type a constant that is not a member
7719 of any type. Some languages, however, do not treat overflows as an
7720 error. In many implementations of C, mathematical overflow causes the
7721 result to ``wrap around'' to lower values---for example, if @var{m} is
7722 the largest integer value, and @var{s} is the smallest, then
7725 @var{m} + 1 @result{} @var{s}
7728 This, too, is specific to individual languages, and in some cases
7729 specific to individual compilers or machines. @xref{Support, ,
7730 Supported languages}, for further details on specific languages.
7732 @value{GDBN} provides some additional commands for controlling the range checker:
7734 @kindex set check@r{, range}
7735 @kindex set check range
7736 @kindex show check range
7738 @item set check range auto
7739 Set range checking on or off based on the current working language.
7740 @xref{Support, ,Supported languages}, for the default settings for
7743 @item set check range on
7744 @itemx set check range off
7745 Set range checking on or off, overriding the default setting for the
7746 current working language. A warning is issued if the setting does not
7747 match the language default. If a range error occurs and range checking is on,
7748 then a message is printed and evaluation of the expression is aborted.
7750 @item set check range warn
7751 Output messages when the @value{GDBN} range checker detects a range error,
7752 but attempt to evaluate the expression anyway. Evaluating the
7753 expression may still be impossible for other reasons, such as accessing
7754 memory that the process does not own (a typical example from many Unix
7758 Show the current setting of the range checker, and whether or not it is
7759 being set automatically by @value{GDBN}.
7763 @section Supported languages
7765 @value{GDBN} supports C, C@t{++}, Fortran, Java, assembly, and Modula-2.
7766 @c This is false ...
7767 Some @value{GDBN} features may be used in expressions regardless of the
7768 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7769 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7770 ,Expressions}) can be used with the constructs of any supported
7773 The following sections detail to what degree each source language is
7774 supported by @value{GDBN}. These sections are not meant to be language
7775 tutorials or references, but serve only as a reference guide to what the
7776 @value{GDBN} expression parser accepts, and what input and output
7777 formats should look like for different languages. There are many good
7778 books written on each of these languages; please look to these for a
7779 language reference or tutorial.
7783 * Modula-2:: Modula-2
7787 @subsection C and C@t{++}
7789 @cindex C and C@t{++}
7790 @cindex expressions in C or C@t{++}
7792 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7793 to both languages. Whenever this is the case, we discuss those languages
7797 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
7798 @cindex @sc{gnu} C@t{++}
7799 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7800 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7801 effectively, you must compile your C@t{++} programs with a supported
7802 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
7803 compiler (@code{aCC}).
7805 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
7806 format; if it doesn't work on your system, try the stabs+ debugging
7807 format. You can select those formats explicitly with the @code{g++}
7808 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
7809 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7810 CC, gcc.info, Using @sc{gnu} CC}.
7813 * C Operators:: C and C@t{++} operators
7814 * C Constants:: C and C@t{++} constants
7815 * C plus plus expressions:: C@t{++} expressions
7816 * C Defaults:: Default settings for C and C@t{++}
7817 * C Checks:: C and C@t{++} type and range checks
7818 * Debugging C:: @value{GDBN} and C
7819 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
7823 @subsubsection C and C@t{++} operators
7825 @cindex C and C@t{++} operators
7827 Operators must be defined on values of specific types. For instance,
7828 @code{+} is defined on numbers, but not on structures. Operators are
7829 often defined on groups of types.
7831 For the purposes of C and C@t{++}, the following definitions hold:
7836 @emph{Integral types} include @code{int} with any of its storage-class
7837 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
7840 @emph{Floating-point types} include @code{float}, @code{double}, and
7841 @code{long double} (if supported by the target platform).
7844 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
7847 @emph{Scalar types} include all of the above.
7852 The following operators are supported. They are listed here
7853 in order of increasing precedence:
7857 The comma or sequencing operator. Expressions in a comma-separated list
7858 are evaluated from left to right, with the result of the entire
7859 expression being the last expression evaluated.
7862 Assignment. The value of an assignment expression is the value
7863 assigned. Defined on scalar types.
7866 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
7867 and translated to @w{@code{@var{a} = @var{a op b}}}.
7868 @w{@code{@var{op}=}} and @code{=} have the same precedence.
7869 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
7870 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
7873 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
7874 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
7878 Logical @sc{or}. Defined on integral types.
7881 Logical @sc{and}. Defined on integral types.
7884 Bitwise @sc{or}. Defined on integral types.
7887 Bitwise exclusive-@sc{or}. Defined on integral types.
7890 Bitwise @sc{and}. Defined on integral types.
7893 Equality and inequality. Defined on scalar types. The value of these
7894 expressions is 0 for false and non-zero for true.
7896 @item <@r{, }>@r{, }<=@r{, }>=
7897 Less than, greater than, less than or equal, greater than or equal.
7898 Defined on scalar types. The value of these expressions is 0 for false
7899 and non-zero for true.
7902 left shift, and right shift. Defined on integral types.
7905 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
7908 Addition and subtraction. Defined on integral types, floating-point types and
7911 @item *@r{, }/@r{, }%
7912 Multiplication, division, and modulus. Multiplication and division are
7913 defined on integral and floating-point types. Modulus is defined on
7917 Increment and decrement. When appearing before a variable, the
7918 operation is performed before the variable is used in an expression;
7919 when appearing after it, the variable's value is used before the
7920 operation takes place.
7923 Pointer dereferencing. Defined on pointer types. Same precedence as
7927 Address operator. Defined on variables. Same precedence as @code{++}.
7929 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
7930 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
7931 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
7932 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
7936 Negative. Defined on integral and floating-point types. Same
7937 precedence as @code{++}.
7940 Logical negation. Defined on integral types. Same precedence as
7944 Bitwise complement operator. Defined on integral types. Same precedence as
7949 Structure member, and pointer-to-structure member. For convenience,
7950 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
7951 pointer based on the stored type information.
7952 Defined on @code{struct} and @code{union} data.
7955 Dereferences of pointers to members.
7958 Array indexing. @code{@var{a}[@var{i}]} is defined as
7959 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
7962 Function parameter list. Same precedence as @code{->}.
7965 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
7966 and @code{class} types.
7969 Doubled colons also represent the @value{GDBN} scope operator
7970 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
7974 If an operator is redefined in the user code, @value{GDBN} usually
7975 attempts to invoke the redefined version instead of using the operator's
7983 @subsubsection C and C@t{++} constants
7985 @cindex C and C@t{++} constants
7987 @value{GDBN} allows you to express the constants of C and C@t{++} in the
7992 Integer constants are a sequence of digits. Octal constants are
7993 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
7994 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
7995 @samp{l}, specifying that the constant should be treated as a
7999 Floating point constants are a sequence of digits, followed by a decimal
8000 point, followed by a sequence of digits, and optionally followed by an
8001 exponent. An exponent is of the form:
8002 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8003 sequence of digits. The @samp{+} is optional for positive exponents.
8004 A floating-point constant may also end with a letter @samp{f} or
8005 @samp{F}, specifying that the constant should be treated as being of
8006 the @code{float} (as opposed to the default @code{double}) type; or with
8007 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8011 Enumerated constants consist of enumerated identifiers, or their
8012 integral equivalents.
8015 Character constants are a single character surrounded by single quotes
8016 (@code{'}), or a number---the ordinal value of the corresponding character
8017 (usually its @sc{ascii} value). Within quotes, the single character may
8018 be represented by a letter or by @dfn{escape sequences}, which are of
8019 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8020 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8021 @samp{@var{x}} is a predefined special character---for example,
8022 @samp{\n} for newline.
8025 String constants are a sequence of character constants surrounded by
8026 double quotes (@code{"}). Any valid character constant (as described
8027 above) may appear. Double quotes within the string must be preceded by
8028 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8032 Pointer constants are an integral value. You can also write pointers
8033 to constants using the C operator @samp{&}.
8036 Array constants are comma-separated lists surrounded by braces @samp{@{}
8037 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8038 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8039 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8043 * C plus plus expressions::
8050 @node C plus plus expressions
8051 @subsubsection C@t{++} expressions
8053 @cindex expressions in C@t{++}
8054 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8056 @cindex debugging C@t{++} programs
8057 @cindex C@t{++} compilers
8058 @cindex debug formats and C@t{++}
8059 @cindex @value{NGCC} and C@t{++}
8061 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8062 proper compiler and the proper debug format. Currently, @value{GDBN}
8063 works best when debugging C@t{++} code that is compiled with
8064 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8065 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8066 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8067 stabs+ as their default debug format, so you usually don't need to
8068 specify a debug format explicitly. Other compilers and/or debug formats
8069 are likely to work badly or not at all when using @value{GDBN} to debug
8075 @cindex member functions
8077 Member function calls are allowed; you can use expressions like
8080 count = aml->GetOriginal(x, y)
8083 @vindex this@r{, inside C@t{++} member functions}
8084 @cindex namespace in C@t{++}
8086 While a member function is active (in the selected stack frame), your
8087 expressions have the same namespace available as the member function;
8088 that is, @value{GDBN} allows implicit references to the class instance
8089 pointer @code{this} following the same rules as C@t{++}.
8091 @cindex call overloaded functions
8092 @cindex overloaded functions, calling
8093 @cindex type conversions in C@t{++}
8095 You can call overloaded functions; @value{GDBN} resolves the function
8096 call to the right definition, with some restrictions. @value{GDBN} does not
8097 perform overload resolution involving user-defined type conversions,
8098 calls to constructors, or instantiations of templates that do not exist
8099 in the program. It also cannot handle ellipsis argument lists or
8102 It does perform integral conversions and promotions, floating-point
8103 promotions, arithmetic conversions, pointer conversions, conversions of
8104 class objects to base classes, and standard conversions such as those of
8105 functions or arrays to pointers; it requires an exact match on the
8106 number of function arguments.
8108 Overload resolution is always performed, unless you have specified
8109 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8110 ,@value{GDBN} features for C@t{++}}.
8112 You must specify @code{set overload-resolution off} in order to use an
8113 explicit function signature to call an overloaded function, as in
8115 p 'foo(char,int)'('x', 13)
8118 The @value{GDBN} command-completion facility can simplify this;
8119 see @ref{Completion, ,Command completion}.
8121 @cindex reference declarations
8123 @value{GDBN} understands variables declared as C@t{++} references; you can use
8124 them in expressions just as you do in C@t{++} source---they are automatically
8127 In the parameter list shown when @value{GDBN} displays a frame, the values of
8128 reference variables are not displayed (unlike other variables); this
8129 avoids clutter, since references are often used for large structures.
8130 The @emph{address} of a reference variable is always shown, unless
8131 you have specified @samp{set print address off}.
8134 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8135 expressions can use it just as expressions in your program do. Since
8136 one scope may be defined in another, you can use @code{::} repeatedly if
8137 necessary, for example in an expression like
8138 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8139 resolving name scope by reference to source files, in both C and C@t{++}
8140 debugging (@pxref{Variables, ,Program variables}).
8143 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8144 calling virtual functions correctly, printing out virtual bases of
8145 objects, calling functions in a base subobject, casting objects, and
8146 invoking user-defined operators.
8149 @subsubsection C and C@t{++} defaults
8151 @cindex C and C@t{++} defaults
8153 If you allow @value{GDBN} to set type and range checking automatically, they
8154 both default to @code{off} whenever the working language changes to
8155 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8156 selects the working language.
8158 If you allow @value{GDBN} to set the language automatically, it
8159 recognizes source files whose names end with @file{.c}, @file{.C}, or
8160 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8161 these files, it sets the working language to C or C@t{++}.
8162 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8163 for further details.
8165 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8166 @c unimplemented. If (b) changes, it might make sense to let this node
8167 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8170 @subsubsection C and C@t{++} type and range checks
8172 @cindex C and C@t{++} checks
8174 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8175 is not used. However, if you turn type checking on, @value{GDBN}
8176 considers two variables type equivalent if:
8180 The two variables are structured and have the same structure, union, or
8184 The two variables have the same type name, or types that have been
8185 declared equivalent through @code{typedef}.
8188 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8191 The two @code{struct}, @code{union}, or @code{enum} variables are
8192 declared in the same declaration. (Note: this may not be true for all C
8197 Range checking, if turned on, is done on mathematical operations. Array
8198 indices are not checked, since they are often used to index a pointer
8199 that is not itself an array.
8202 @subsubsection @value{GDBN} and C
8204 The @code{set print union} and @code{show print union} commands apply to
8205 the @code{union} type. When set to @samp{on}, any @code{union} that is
8206 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8207 appears as @samp{@{...@}}.
8209 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8210 with pointers and a memory allocation function. @xref{Expressions,
8214 * Debugging C plus plus::
8217 @node Debugging C plus plus
8218 @subsubsection @value{GDBN} features for C@t{++}
8220 @cindex commands for C@t{++}
8222 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8223 designed specifically for use with C@t{++}. Here is a summary:
8226 @cindex break in overloaded functions
8227 @item @r{breakpoint menus}
8228 When you want a breakpoint in a function whose name is overloaded,
8229 @value{GDBN} breakpoint menus help you specify which function definition
8230 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8232 @cindex overloading in C@t{++}
8233 @item rbreak @var{regex}
8234 Setting breakpoints using regular expressions is helpful for setting
8235 breakpoints on overloaded functions that are not members of any special
8237 @xref{Set Breaks, ,Setting breakpoints}.
8239 @cindex C@t{++} exception handling
8242 Debug C@t{++} exception handling using these commands. @xref{Set
8243 Catchpoints, , Setting catchpoints}.
8246 @item ptype @var{typename}
8247 Print inheritance relationships as well as other information for type
8249 @xref{Symbols, ,Examining the Symbol Table}.
8251 @cindex C@t{++} symbol display
8252 @item set print demangle
8253 @itemx show print demangle
8254 @itemx set print asm-demangle
8255 @itemx show print asm-demangle
8256 Control whether C@t{++} symbols display in their source form, both when
8257 displaying code as C@t{++} source and when displaying disassemblies.
8258 @xref{Print Settings, ,Print settings}.
8260 @item set print object
8261 @itemx show print object
8262 Choose whether to print derived (actual) or declared types of objects.
8263 @xref{Print Settings, ,Print settings}.
8265 @item set print vtbl
8266 @itemx show print vtbl
8267 Control the format for printing virtual function tables.
8268 @xref{Print Settings, ,Print settings}.
8269 (The @code{vtbl} commands do not work on programs compiled with the HP
8270 ANSI C@t{++} compiler (@code{aCC}).)
8272 @kindex set overload-resolution
8273 @cindex overloaded functions, overload resolution
8274 @item set overload-resolution on
8275 Enable overload resolution for C@t{++} expression evaluation. The default
8276 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8277 and searches for a function whose signature matches the argument types,
8278 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8279 expressions}, for details). If it cannot find a match, it emits a
8282 @item set overload-resolution off
8283 Disable overload resolution for C@t{++} expression evaluation. For
8284 overloaded functions that are not class member functions, @value{GDBN}
8285 chooses the first function of the specified name that it finds in the
8286 symbol table, whether or not its arguments are of the correct type. For
8287 overloaded functions that are class member functions, @value{GDBN}
8288 searches for a function whose signature @emph{exactly} matches the
8291 @item @r{Overloaded symbol names}
8292 You can specify a particular definition of an overloaded symbol, using
8293 the same notation that is used to declare such symbols in C@t{++}: type
8294 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8295 also use the @value{GDBN} command-line word completion facilities to list the
8296 available choices, or to finish the type list for you.
8297 @xref{Completion,, Command completion}, for details on how to do this.
8301 @subsection Modula-2
8303 @cindex Modula-2, @value{GDBN} support
8305 The extensions made to @value{GDBN} to support Modula-2 only support
8306 output from the @sc{gnu} Modula-2 compiler (which is currently being
8307 developed). Other Modula-2 compilers are not currently supported, and
8308 attempting to debug executables produced by them is most likely
8309 to give an error as @value{GDBN} reads in the executable's symbol
8312 @cindex expressions in Modula-2
8314 * M2 Operators:: Built-in operators
8315 * Built-In Func/Proc:: Built-in functions and procedures
8316 * M2 Constants:: Modula-2 constants
8317 * M2 Defaults:: Default settings for Modula-2
8318 * Deviations:: Deviations from standard Modula-2
8319 * M2 Checks:: Modula-2 type and range checks
8320 * M2 Scope:: The scope operators @code{::} and @code{.}
8321 * GDB/M2:: @value{GDBN} and Modula-2
8325 @subsubsection Operators
8326 @cindex Modula-2 operators
8328 Operators must be defined on values of specific types. For instance,
8329 @code{+} is defined on numbers, but not on structures. Operators are
8330 often defined on groups of types. For the purposes of Modula-2, the
8331 following definitions hold:
8336 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8340 @emph{Character types} consist of @code{CHAR} and its subranges.
8343 @emph{Floating-point types} consist of @code{REAL}.
8346 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8350 @emph{Scalar types} consist of all of the above.
8353 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8356 @emph{Boolean types} consist of @code{BOOLEAN}.
8360 The following operators are supported, and appear in order of
8361 increasing precedence:
8365 Function argument or array index separator.
8368 Assignment. The value of @var{var} @code{:=} @var{value} is
8372 Less than, greater than on integral, floating-point, or enumerated
8376 Less than or equal to, greater than or equal to
8377 on integral, floating-point and enumerated types, or set inclusion on
8378 set types. Same precedence as @code{<}.
8380 @item =@r{, }<>@r{, }#
8381 Equality and two ways of expressing inequality, valid on scalar types.
8382 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8383 available for inequality, since @code{#} conflicts with the script
8387 Set membership. Defined on set types and the types of their members.
8388 Same precedence as @code{<}.
8391 Boolean disjunction. Defined on boolean types.
8394 Boolean conjunction. Defined on boolean types.
8397 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8400 Addition and subtraction on integral and floating-point types, or union
8401 and difference on set types.
8404 Multiplication on integral and floating-point types, or set intersection
8408 Division on floating-point types, or symmetric set difference on set
8409 types. Same precedence as @code{*}.
8412 Integer division and remainder. Defined on integral types. Same
8413 precedence as @code{*}.
8416 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8419 Pointer dereferencing. Defined on pointer types.
8422 Boolean negation. Defined on boolean types. Same precedence as
8426 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8427 precedence as @code{^}.
8430 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8433 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8437 @value{GDBN} and Modula-2 scope operators.
8441 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8442 treats the use of the operator @code{IN}, or the use of operators
8443 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8444 @code{<=}, and @code{>=} on sets as an error.
8448 @node Built-In Func/Proc
8449 @subsubsection Built-in functions and procedures
8450 @cindex Modula-2 built-ins
8452 Modula-2 also makes available several built-in procedures and functions.
8453 In describing these, the following metavariables are used:
8458 represents an @code{ARRAY} variable.
8461 represents a @code{CHAR} constant or variable.
8464 represents a variable or constant of integral type.
8467 represents an identifier that belongs to a set. Generally used in the
8468 same function with the metavariable @var{s}. The type of @var{s} should
8469 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8472 represents a variable or constant of integral or floating-point type.
8475 represents a variable or constant of floating-point type.
8481 represents a variable.
8484 represents a variable or constant of one of many types. See the
8485 explanation of the function for details.
8488 All Modula-2 built-in procedures also return a result, described below.
8492 Returns the absolute value of @var{n}.
8495 If @var{c} is a lower case letter, it returns its upper case
8496 equivalent, otherwise it returns its argument.
8499 Returns the character whose ordinal value is @var{i}.
8502 Decrements the value in the variable @var{v} by one. Returns the new value.
8504 @item DEC(@var{v},@var{i})
8505 Decrements the value in the variable @var{v} by @var{i}. Returns the
8508 @item EXCL(@var{m},@var{s})
8509 Removes the element @var{m} from the set @var{s}. Returns the new
8512 @item FLOAT(@var{i})
8513 Returns the floating point equivalent of the integer @var{i}.
8516 Returns the index of the last member of @var{a}.
8519 Increments the value in the variable @var{v} by one. Returns the new value.
8521 @item INC(@var{v},@var{i})
8522 Increments the value in the variable @var{v} by @var{i}. Returns the
8525 @item INCL(@var{m},@var{s})
8526 Adds the element @var{m} to the set @var{s} if it is not already
8527 there. Returns the new set.
8530 Returns the maximum value of the type @var{t}.
8533 Returns the minimum value of the type @var{t}.
8536 Returns boolean TRUE if @var{i} is an odd number.
8539 Returns the ordinal value of its argument. For example, the ordinal
8540 value of a character is its @sc{ascii} value (on machines supporting the
8541 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8542 integral, character and enumerated types.
8545 Returns the size of its argument. @var{x} can be a variable or a type.
8547 @item TRUNC(@var{r})
8548 Returns the integral part of @var{r}.
8550 @item VAL(@var{t},@var{i})
8551 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8555 @emph{Warning:} Sets and their operations are not yet supported, so
8556 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8560 @cindex Modula-2 constants
8562 @subsubsection Constants
8564 @value{GDBN} allows you to express the constants of Modula-2 in the following
8570 Integer constants are simply a sequence of digits. When used in an
8571 expression, a constant is interpreted to be type-compatible with the
8572 rest of the expression. Hexadecimal integers are specified by a
8573 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8576 Floating point constants appear as a sequence of digits, followed by a
8577 decimal point and another sequence of digits. An optional exponent can
8578 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8579 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8580 digits of the floating point constant must be valid decimal (base 10)
8584 Character constants consist of a single character enclosed by a pair of
8585 like quotes, either single (@code{'}) or double (@code{"}). They may
8586 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8587 followed by a @samp{C}.
8590 String constants consist of a sequence of characters enclosed by a
8591 pair of like quotes, either single (@code{'}) or double (@code{"}).
8592 Escape sequences in the style of C are also allowed. @xref{C
8593 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8597 Enumerated constants consist of an enumerated identifier.
8600 Boolean constants consist of the identifiers @code{TRUE} and
8604 Pointer constants consist of integral values only.
8607 Set constants are not yet supported.
8611 @subsubsection Modula-2 defaults
8612 @cindex Modula-2 defaults
8614 If type and range checking are set automatically by @value{GDBN}, they
8615 both default to @code{on} whenever the working language changes to
8616 Modula-2. This happens regardless of whether you or @value{GDBN}
8617 selected the working language.
8619 If you allow @value{GDBN} to set the language automatically, then entering
8620 code compiled from a file whose name ends with @file{.mod} sets the
8621 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8622 the language automatically}, for further details.
8625 @subsubsection Deviations from standard Modula-2
8626 @cindex Modula-2, deviations from
8628 A few changes have been made to make Modula-2 programs easier to debug.
8629 This is done primarily via loosening its type strictness:
8633 Unlike in standard Modula-2, pointer constants can be formed by
8634 integers. This allows you to modify pointer variables during
8635 debugging. (In standard Modula-2, the actual address contained in a
8636 pointer variable is hidden from you; it can only be modified
8637 through direct assignment to another pointer variable or expression that
8638 returned a pointer.)
8641 C escape sequences can be used in strings and characters to represent
8642 non-printable characters. @value{GDBN} prints out strings with these
8643 escape sequences embedded. Single non-printable characters are
8644 printed using the @samp{CHR(@var{nnn})} format.
8647 The assignment operator (@code{:=}) returns the value of its right-hand
8651 All built-in procedures both modify @emph{and} return their argument.
8655 @subsubsection Modula-2 type and range checks
8656 @cindex Modula-2 checks
8659 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8662 @c FIXME remove warning when type/range checks added
8664 @value{GDBN} considers two Modula-2 variables type equivalent if:
8668 They are of types that have been declared equivalent via a @code{TYPE
8669 @var{t1} = @var{t2}} statement
8672 They have been declared on the same line. (Note: This is true of the
8673 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8676 As long as type checking is enabled, any attempt to combine variables
8677 whose types are not equivalent is an error.
8679 Range checking is done on all mathematical operations, assignment, array
8680 index bounds, and all built-in functions and procedures.
8683 @subsubsection The scope operators @code{::} and @code{.}
8685 @cindex @code{.}, Modula-2 scope operator
8686 @cindex colon, doubled as scope operator
8688 @vindex colon-colon@r{, in Modula-2}
8689 @c Info cannot handle :: but TeX can.
8692 @vindex ::@r{, in Modula-2}
8695 There are a few subtle differences between the Modula-2 scope operator
8696 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8701 @var{module} . @var{id}
8702 @var{scope} :: @var{id}
8706 where @var{scope} is the name of a module or a procedure,
8707 @var{module} the name of a module, and @var{id} is any declared
8708 identifier within your program, except another module.
8710 Using the @code{::} operator makes @value{GDBN} search the scope
8711 specified by @var{scope} for the identifier @var{id}. If it is not
8712 found in the specified scope, then @value{GDBN} searches all scopes
8713 enclosing the one specified by @var{scope}.
8715 Using the @code{.} operator makes @value{GDBN} search the current scope for
8716 the identifier specified by @var{id} that was imported from the
8717 definition module specified by @var{module}. With this operator, it is
8718 an error if the identifier @var{id} was not imported from definition
8719 module @var{module}, or if @var{id} is not an identifier in
8723 @subsubsection @value{GDBN} and Modula-2
8725 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
8726 Five subcommands of @code{set print} and @code{show print} apply
8727 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
8728 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
8729 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
8730 analogue in Modula-2.
8732 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
8733 with any language, is not useful with Modula-2. Its
8734 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
8735 created in Modula-2 as they can in C or C@t{++}. However, because an
8736 address can be specified by an integral constant, the construct
8737 @samp{@{@var{type}@}@var{adrexp}} is still useful.
8739 @cindex @code{#} in Modula-2
8740 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
8741 interpreted as the beginning of a comment. Use @code{<>} instead.
8744 @chapter Examining the Symbol Table
8746 The commands described in this chapter allow you to inquire about the
8747 symbols (names of variables, functions and types) defined in your
8748 program. This information is inherent in the text of your program and
8749 does not change as your program executes. @value{GDBN} finds it in your
8750 program's symbol table, in the file indicated when you started @value{GDBN}
8751 (@pxref{File Options, ,Choosing files}), or by one of the
8752 file-management commands (@pxref{Files, ,Commands to specify files}).
8754 @cindex symbol names
8755 @cindex names of symbols
8756 @cindex quoting names
8757 Occasionally, you may need to refer to symbols that contain unusual
8758 characters, which @value{GDBN} ordinarily treats as word delimiters. The
8759 most frequent case is in referring to static variables in other
8760 source files (@pxref{Variables,,Program variables}). File names
8761 are recorded in object files as debugging symbols, but @value{GDBN} would
8762 ordinarily parse a typical file name, like @file{foo.c}, as the three words
8763 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
8764 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
8771 looks up the value of @code{x} in the scope of the file @file{foo.c}.
8774 @kindex info address
8775 @cindex address of a symbol
8776 @item info address @var{symbol}
8777 Describe where the data for @var{symbol} is stored. For a register
8778 variable, this says which register it is kept in. For a non-register
8779 local variable, this prints the stack-frame offset at which the variable
8782 Note the contrast with @samp{print &@var{symbol}}, which does not work
8783 at all for a register variable, and for a stack local variable prints
8784 the exact address of the current instantiation of the variable.
8787 @cindex symbol from address
8788 @item info symbol @var{addr}
8789 Print the name of a symbol which is stored at the address @var{addr}.
8790 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
8791 nearest symbol and an offset from it:
8794 (@value{GDBP}) info symbol 0x54320
8795 _initialize_vx + 396 in section .text
8799 This is the opposite of the @code{info address} command. You can use
8800 it to find out the name of a variable or a function given its address.
8803 @item whatis @var{expr}
8804 Print the data type of expression @var{expr}. @var{expr} is not
8805 actually evaluated, and any side-effecting operations (such as
8806 assignments or function calls) inside it do not take place.
8807 @xref{Expressions, ,Expressions}.
8810 Print the data type of @code{$}, the last value in the value history.
8813 @item ptype @var{typename}
8814 Print a description of data type @var{typename}. @var{typename} may be
8815 the name of a type, or for C code it may have the form @samp{class
8816 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
8817 @var{union-tag}} or @samp{enum @var{enum-tag}}.
8819 @item ptype @var{expr}
8821 Print a description of the type of expression @var{expr}. @code{ptype}
8822 differs from @code{whatis} by printing a detailed description, instead
8823 of just the name of the type.
8825 For example, for this variable declaration:
8828 struct complex @{double real; double imag;@} v;
8832 the two commands give this output:
8836 (@value{GDBP}) whatis v
8837 type = struct complex
8838 (@value{GDBP}) ptype v
8839 type = struct complex @{
8847 As with @code{whatis}, using @code{ptype} without an argument refers to
8848 the type of @code{$}, the last value in the value history.
8851 @item info types @var{regexp}
8853 Print a brief description of all types whose names match @var{regexp}
8854 (or all types in your program, if you supply no argument). Each
8855 complete typename is matched as though it were a complete line; thus,
8856 @samp{i type value} gives information on all types in your program whose
8857 names include the string @code{value}, but @samp{i type ^value$} gives
8858 information only on types whose complete name is @code{value}.
8860 This command differs from @code{ptype} in two ways: first, like
8861 @code{whatis}, it does not print a detailed description; second, it
8862 lists all source files where a type is defined.
8865 @cindex local variables
8866 @item info scope @var{addr}
8867 List all the variables local to a particular scope. This command
8868 accepts a location---a function name, a source line, or an address
8869 preceded by a @samp{*}, and prints all the variables local to the
8870 scope defined by that location. For example:
8873 (@value{GDBP}) @b{info scope command_line_handler}
8874 Scope for command_line_handler:
8875 Symbol rl is an argument at stack/frame offset 8, length 4.
8876 Symbol linebuffer is in static storage at address 0x150a18, length 4.
8877 Symbol linelength is in static storage at address 0x150a1c, length 4.
8878 Symbol p is a local variable in register $esi, length 4.
8879 Symbol p1 is a local variable in register $ebx, length 4.
8880 Symbol nline is a local variable in register $edx, length 4.
8881 Symbol repeat is a local variable at frame offset -8, length 4.
8885 This command is especially useful for determining what data to collect
8886 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
8891 Show information about the current source file---that is, the source file for
8892 the function containing the current point of execution:
8895 the name of the source file, and the directory containing it,
8897 the directory it was compiled in,
8899 its length, in lines,
8901 which programming language it is written in,
8903 whether the executable includes debugging information for that file, and
8904 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
8906 whether the debugging information includes information about
8907 preprocessor macros.
8911 @kindex info sources
8913 Print the names of all source files in your program for which there is
8914 debugging information, organized into two lists: files whose symbols
8915 have already been read, and files whose symbols will be read when needed.
8917 @kindex info functions
8918 @item info functions
8919 Print the names and data types of all defined functions.
8921 @item info functions @var{regexp}
8922 Print the names and data types of all defined functions
8923 whose names contain a match for regular expression @var{regexp}.
8924 Thus, @samp{info fun step} finds all functions whose names
8925 include @code{step}; @samp{info fun ^step} finds those whose names
8926 start with @code{step}. If a function name contains characters
8927 that conflict with the regular expression language (eg.
8928 @samp{operator*()}), they may be quoted with a backslash.
8930 @kindex info variables
8931 @item info variables
8932 Print the names and data types of all variables that are declared
8933 outside of functions (i.e.@: excluding local variables).
8935 @item info variables @var{regexp}
8936 Print the names and data types of all variables (except for local
8937 variables) whose names contain a match for regular expression
8941 This was never implemented.
8942 @kindex info methods
8944 @itemx info methods @var{regexp}
8945 The @code{info methods} command permits the user to examine all defined
8946 methods within C@t{++} program, or (with the @var{regexp} argument) a
8947 specific set of methods found in the various C@t{++} classes. Many
8948 C@t{++} classes provide a large number of methods. Thus, the output
8949 from the @code{ptype} command can be overwhelming and hard to use. The
8950 @code{info-methods} command filters the methods, printing only those
8951 which match the regular-expression @var{regexp}.
8954 @cindex reloading symbols
8955 Some systems allow individual object files that make up your program to
8956 be replaced without stopping and restarting your program. For example,
8957 in VxWorks you can simply recompile a defective object file and keep on
8958 running. If you are running on one of these systems, you can allow
8959 @value{GDBN} to reload the symbols for automatically relinked modules:
8962 @kindex set symbol-reloading
8963 @item set symbol-reloading on
8964 Replace symbol definitions for the corresponding source file when an
8965 object file with a particular name is seen again.
8967 @item set symbol-reloading off
8968 Do not replace symbol definitions when encountering object files of the
8969 same name more than once. This is the default state; if you are not
8970 running on a system that permits automatic relinking of modules, you
8971 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
8972 may discard symbols when linking large programs, that may contain
8973 several modules (from different directories or libraries) with the same
8976 @kindex show symbol-reloading
8977 @item show symbol-reloading
8978 Show the current @code{on} or @code{off} setting.
8981 @kindex set opaque-type-resolution
8982 @item set opaque-type-resolution on
8983 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
8984 declared as a pointer to a @code{struct}, @code{class}, or
8985 @code{union}---for example, @code{struct MyType *}---that is used in one
8986 source file although the full declaration of @code{struct MyType} is in
8987 another source file. The default is on.
8989 A change in the setting of this subcommand will not take effect until
8990 the next time symbols for a file are loaded.
8992 @item set opaque-type-resolution off
8993 Tell @value{GDBN} not to resolve opaque types. In this case, the type
8994 is printed as follows:
8996 @{<no data fields>@}
8999 @kindex show opaque-type-resolution
9000 @item show opaque-type-resolution
9001 Show whether opaque types are resolved or not.
9003 @kindex maint print symbols
9005 @kindex maint print psymbols
9006 @cindex partial symbol dump
9007 @item maint print symbols @var{filename}
9008 @itemx maint print psymbols @var{filename}
9009 @itemx maint print msymbols @var{filename}
9010 Write a dump of debugging symbol data into the file @var{filename}.
9011 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9012 symbols with debugging data are included. If you use @samp{maint print
9013 symbols}, @value{GDBN} includes all the symbols for which it has already
9014 collected full details: that is, @var{filename} reflects symbols for
9015 only those files whose symbols @value{GDBN} has read. You can use the
9016 command @code{info sources} to find out which files these are. If you
9017 use @samp{maint print psymbols} instead, the dump shows information about
9018 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9019 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9020 @samp{maint print msymbols} dumps just the minimal symbol information
9021 required for each object file from which @value{GDBN} has read some symbols.
9022 @xref{Files, ,Commands to specify files}, for a discussion of how
9023 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9025 @kindex maint info symtabs
9026 @kindex maint info psymtabs
9027 @cindex listing @value{GDBN}'s internal symbol tables
9028 @cindex symbol tables, listing @value{GDBN}'s internal
9029 @cindex full symbol tables, listing @value{GDBN}'s internal
9030 @cindex partial symbol tables, listing @value{GDBN}'s internal
9031 @item maint info symtabs @r{[} @var{regexp} @r{]}
9032 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
9034 List the @code{struct symtab} or @code{struct partial_symtab}
9035 structures whose names match @var{regexp}. If @var{regexp} is not
9036 given, list them all. The output includes expressions which you can
9037 copy into a @value{GDBN} debugging this one to examine a particular
9038 structure in more detail. For example:
9041 (@value{GDBP}) maint info psymtabs dwarf2read
9042 @{ objfile /home/gnu/build/gdb/gdb
9043 ((struct objfile *) 0x82e69d0)
9044 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
9045 ((struct partial_symtab *) 0x8474b10)
9048 text addresses 0x814d3c8 -- 0x8158074
9049 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
9050 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
9054 (@value{GDBP}) maint info symtabs
9058 We see that there is one partial symbol table whose filename contains
9059 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
9060 and we see that @value{GDBN} has not read in any symtabs yet at all.
9061 If we set a breakpoint on a function, that will cause @value{GDBN} to
9062 read the symtab for the compilation unit containing that function:
9065 (@value{GDBP}) break dwarf2_psymtab_to_symtab
9066 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
9068 (@value{GDBP}) maint info symtabs
9069 @{ objfile /home/gnu/build/gdb/gdb
9070 ((struct objfile *) 0x82e69d0)
9071 @{ symtab /home/gnu/src/gdb/dwarf2read.c
9072 ((struct symtab *) 0x86c1f38)
9075 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
9085 @chapter Altering Execution
9087 Once you think you have found an error in your program, you might want to
9088 find out for certain whether correcting the apparent error would lead to
9089 correct results in the rest of the run. You can find the answer by
9090 experiment, using the @value{GDBN} features for altering execution of the
9093 For example, you can store new values into variables or memory
9094 locations, give your program a signal, restart it at a different
9095 address, or even return prematurely from a function.
9098 * Assignment:: Assignment to variables
9099 * Jumping:: Continuing at a different address
9100 * Signaling:: Giving your program a signal
9101 * Returning:: Returning from a function
9102 * Calling:: Calling your program's functions
9103 * Patching:: Patching your program
9107 @section Assignment to variables
9110 @cindex setting variables
9111 To alter the value of a variable, evaluate an assignment expression.
9112 @xref{Expressions, ,Expressions}. For example,
9119 stores the value 4 into the variable @code{x}, and then prints the
9120 value of the assignment expression (which is 4).
9121 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9122 information on operators in supported languages.
9124 @kindex set variable
9125 @cindex variables, setting
9126 If you are not interested in seeing the value of the assignment, use the
9127 @code{set} command instead of the @code{print} command. @code{set} is
9128 really the same as @code{print} except that the expression's value is
9129 not printed and is not put in the value history (@pxref{Value History,
9130 ,Value history}). The expression is evaluated only for its effects.
9132 If the beginning of the argument string of the @code{set} command
9133 appears identical to a @code{set} subcommand, use the @code{set
9134 variable} command instead of just @code{set}. This command is identical
9135 to @code{set} except for its lack of subcommands. For example, if your
9136 program has a variable @code{width}, you get an error if you try to set
9137 a new value with just @samp{set width=13}, because @value{GDBN} has the
9138 command @code{set width}:
9141 (@value{GDBP}) whatis width
9143 (@value{GDBP}) p width
9145 (@value{GDBP}) set width=47
9146 Invalid syntax in expression.
9150 The invalid expression, of course, is @samp{=47}. In
9151 order to actually set the program's variable @code{width}, use
9154 (@value{GDBP}) set var width=47
9157 Because the @code{set} command has many subcommands that can conflict
9158 with the names of program variables, it is a good idea to use the
9159 @code{set variable} command instead of just @code{set}. For example, if
9160 your program has a variable @code{g}, you run into problems if you try
9161 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9162 the command @code{set gnutarget}, abbreviated @code{set g}:
9166 (@value{GDBP}) whatis g
9170 (@value{GDBP}) set g=4
9174 The program being debugged has been started already.
9175 Start it from the beginning? (y or n) y
9176 Starting program: /home/smith/cc_progs/a.out
9177 "/home/smith/cc_progs/a.out": can't open to read symbols:
9179 (@value{GDBP}) show g
9180 The current BFD target is "=4".
9185 The program variable @code{g} did not change, and you silently set the
9186 @code{gnutarget} to an invalid value. In order to set the variable
9190 (@value{GDBP}) set var g=4
9193 @value{GDBN} allows more implicit conversions in assignments than C; you can
9194 freely store an integer value into a pointer variable or vice versa,
9195 and you can convert any structure to any other structure that is the
9196 same length or shorter.
9197 @comment FIXME: how do structs align/pad in these conversions?
9198 @comment /doc@cygnus.com 18dec1990
9200 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9201 construct to generate a value of specified type at a specified address
9202 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9203 to memory location @code{0x83040} as an integer (which implies a certain size
9204 and representation in memory), and
9207 set @{int@}0x83040 = 4
9211 stores the value 4 into that memory location.
9214 @section Continuing at a different address
9216 Ordinarily, when you continue your program, you do so at the place where
9217 it stopped, with the @code{continue} command. You can instead continue at
9218 an address of your own choosing, with the following commands:
9222 @item jump @var{linespec}
9223 Resume execution at line @var{linespec}. Execution stops again
9224 immediately if there is a breakpoint there. @xref{List, ,Printing
9225 source lines}, for a description of the different forms of
9226 @var{linespec}. It is common practice to use the @code{tbreak} command
9227 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9230 The @code{jump} command does not change the current stack frame, or
9231 the stack pointer, or the contents of any memory location or any
9232 register other than the program counter. If line @var{linespec} is in
9233 a different function from the one currently executing, the results may
9234 be bizarre if the two functions expect different patterns of arguments or
9235 of local variables. For this reason, the @code{jump} command requests
9236 confirmation if the specified line is not in the function currently
9237 executing. However, even bizarre results are predictable if you are
9238 well acquainted with the machine-language code of your program.
9240 @item jump *@var{address}
9241 Resume execution at the instruction at address @var{address}.
9244 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9245 On many systems, you can get much the same effect as the @code{jump}
9246 command by storing a new value into the register @code{$pc}. The
9247 difference is that this does not start your program running; it only
9248 changes the address of where it @emph{will} run when you continue. For
9256 makes the next @code{continue} command or stepping command execute at
9257 address @code{0x485}, rather than at the address where your program stopped.
9258 @xref{Continuing and Stepping, ,Continuing and stepping}.
9260 The most common occasion to use the @code{jump} command is to back
9261 up---perhaps with more breakpoints set---over a portion of a program
9262 that has already executed, in order to examine its execution in more
9267 @section Giving your program a signal
9271 @item signal @var{signal}
9272 Resume execution where your program stopped, but immediately give it the
9273 signal @var{signal}. @var{signal} can be the name or the number of a
9274 signal. For example, on many systems @code{signal 2} and @code{signal
9275 SIGINT} are both ways of sending an interrupt signal.
9277 Alternatively, if @var{signal} is zero, continue execution without
9278 giving a signal. This is useful when your program stopped on account of
9279 a signal and would ordinary see the signal when resumed with the
9280 @code{continue} command; @samp{signal 0} causes it to resume without a
9283 @code{signal} does not repeat when you press @key{RET} a second time
9284 after executing the command.
9288 Invoking the @code{signal} command is not the same as invoking the
9289 @code{kill} utility from the shell. Sending a signal with @code{kill}
9290 causes @value{GDBN} to decide what to do with the signal depending on
9291 the signal handling tables (@pxref{Signals}). The @code{signal} command
9292 passes the signal directly to your program.
9296 @section Returning from a function
9299 @cindex returning from a function
9302 @itemx return @var{expression}
9303 You can cancel execution of a function call with the @code{return}
9304 command. If you give an
9305 @var{expression} argument, its value is used as the function's return
9309 When you use @code{return}, @value{GDBN} discards the selected stack frame
9310 (and all frames within it). You can think of this as making the
9311 discarded frame return prematurely. If you wish to specify a value to
9312 be returned, give that value as the argument to @code{return}.
9314 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9315 frame}), and any other frames inside of it, leaving its caller as the
9316 innermost remaining frame. That frame becomes selected. The
9317 specified value is stored in the registers used for returning values
9320 The @code{return} command does not resume execution; it leaves the
9321 program stopped in the state that would exist if the function had just
9322 returned. In contrast, the @code{finish} command (@pxref{Continuing
9323 and Stepping, ,Continuing and stepping}) resumes execution until the
9324 selected stack frame returns naturally.
9327 @section Calling program functions
9329 @cindex calling functions
9332 @item call @var{expr}
9333 Evaluate the expression @var{expr} without displaying @code{void}
9337 You can use this variant of the @code{print} command if you want to
9338 execute a function from your program, but without cluttering the output
9339 with @code{void} returned values. If the result is not void, it
9340 is printed and saved in the value history.
9343 @section Patching programs
9345 @cindex patching binaries
9346 @cindex writing into executables
9347 @cindex writing into corefiles
9349 By default, @value{GDBN} opens the file containing your program's
9350 executable code (or the corefile) read-only. This prevents accidental
9351 alterations to machine code; but it also prevents you from intentionally
9352 patching your program's binary.
9354 If you'd like to be able to patch the binary, you can specify that
9355 explicitly with the @code{set write} command. For example, you might
9356 want to turn on internal debugging flags, or even to make emergency
9362 @itemx set write off
9363 If you specify @samp{set write on}, @value{GDBN} opens executable and
9364 core files for both reading and writing; if you specify @samp{set write
9365 off} (the default), @value{GDBN} opens them read-only.
9367 If you have already loaded a file, you must load it again (using the
9368 @code{exec-file} or @code{core-file} command) after changing @code{set
9369 write}, for your new setting to take effect.
9373 Display whether executable files and core files are opened for writing
9378 @chapter @value{GDBN} Files
9380 @value{GDBN} needs to know the file name of the program to be debugged,
9381 both in order to read its symbol table and in order to start your
9382 program. To debug a core dump of a previous run, you must also tell
9383 @value{GDBN} the name of the core dump file.
9386 * Files:: Commands to specify files
9387 * Separate Debug Files:: Debugging information in separate files
9388 * Symbol Errors:: Errors reading symbol files
9392 @section Commands to specify files
9394 @cindex symbol table
9395 @cindex core dump file
9397 You may want to specify executable and core dump file names. The usual
9398 way to do this is at start-up time, using the arguments to
9399 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9400 Out of @value{GDBN}}).
9402 Occasionally it is necessary to change to a different file during a
9403 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9404 a file you want to use. In these situations the @value{GDBN} commands
9405 to specify new files are useful.
9408 @cindex executable file
9410 @item file @var{filename}
9411 Use @var{filename} as the program to be debugged. It is read for its
9412 symbols and for the contents of pure memory. It is also the program
9413 executed when you use the @code{run} command. If you do not specify a
9414 directory and the file is not found in the @value{GDBN} working directory,
9415 @value{GDBN} uses the environment variable @code{PATH} as a list of
9416 directories to search, just as the shell does when looking for a program
9417 to run. You can change the value of this variable, for both @value{GDBN}
9418 and your program, using the @code{path} command.
9420 On systems with memory-mapped files, an auxiliary file named
9421 @file{@var{filename}.syms} may hold symbol table information for
9422 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9423 @file{@var{filename}.syms}, starting up more quickly. See the
9424 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9425 (available on the command line, and with the commands @code{file},
9426 @code{symbol-file}, or @code{add-symbol-file}, described below),
9427 for more information.
9430 @code{file} with no argument makes @value{GDBN} discard any information it
9431 has on both executable file and the symbol table.
9434 @item exec-file @r{[} @var{filename} @r{]}
9435 Specify that the program to be run (but not the symbol table) is found
9436 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9437 if necessary to locate your program. Omitting @var{filename} means to
9438 discard information on the executable file.
9441 @item symbol-file @r{[} @var{filename} @r{]}
9442 Read symbol table information from file @var{filename}. @code{PATH} is
9443 searched when necessary. Use the @code{file} command to get both symbol
9444 table and program to run from the same file.
9446 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9447 program's symbol table.
9449 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9450 of its convenience variables, the value history, and all breakpoints and
9451 auto-display expressions. This is because they may contain pointers to
9452 the internal data recording symbols and data types, which are part of
9453 the old symbol table data being discarded inside @value{GDBN}.
9455 @code{symbol-file} does not repeat if you press @key{RET} again after
9458 When @value{GDBN} is configured for a particular environment, it
9459 understands debugging information in whatever format is the standard
9460 generated for that environment; you may use either a @sc{gnu} compiler, or
9461 other compilers that adhere to the local conventions.
9462 Best results are usually obtained from @sc{gnu} compilers; for example,
9463 using @code{@value{GCC}} you can generate debugging information for
9466 For most kinds of object files, with the exception of old SVR3 systems
9467 using COFF, the @code{symbol-file} command does not normally read the
9468 symbol table in full right away. Instead, it scans the symbol table
9469 quickly to find which source files and which symbols are present. The
9470 details are read later, one source file at a time, as they are needed.
9472 The purpose of this two-stage reading strategy is to make @value{GDBN}
9473 start up faster. For the most part, it is invisible except for
9474 occasional pauses while the symbol table details for a particular source
9475 file are being read. (The @code{set verbose} command can turn these
9476 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9477 warnings and messages}.)
9479 We have not implemented the two-stage strategy for COFF yet. When the
9480 symbol table is stored in COFF format, @code{symbol-file} reads the
9481 symbol table data in full right away. Note that ``stabs-in-COFF''
9482 still does the two-stage strategy, since the debug info is actually
9486 @cindex reading symbols immediately
9487 @cindex symbols, reading immediately
9489 @cindex memory-mapped symbol file
9490 @cindex saving symbol table
9491 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9492 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9493 You can override the @value{GDBN} two-stage strategy for reading symbol
9494 tables by using the @samp{-readnow} option with any of the commands that
9495 load symbol table information, if you want to be sure @value{GDBN} has the
9496 entire symbol table available.
9498 If memory-mapped files are available on your system through the
9499 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9500 cause @value{GDBN} to write the symbols for your program into a reusable
9501 file. Future @value{GDBN} debugging sessions map in symbol information
9502 from this auxiliary symbol file (if the program has not changed), rather
9503 than spending time reading the symbol table from the executable
9504 program. Using the @samp{-mapped} option has the same effect as
9505 starting @value{GDBN} with the @samp{-mapped} command-line option.
9507 You can use both options together, to make sure the auxiliary symbol
9508 file has all the symbol information for your program.
9510 The auxiliary symbol file for a program called @var{myprog} is called
9511 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9512 than the corresponding executable), @value{GDBN} always attempts to use
9513 it when you debug @var{myprog}; no special options or commands are
9516 The @file{.syms} file is specific to the host machine where you run
9517 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9518 symbol table. It cannot be shared across multiple host platforms.
9520 @c FIXME: for now no mention of directories, since this seems to be in
9521 @c flux. 13mar1992 status is that in theory GDB would look either in
9522 @c current dir or in same dir as myprog; but issues like competing
9523 @c GDB's, or clutter in system dirs, mean that in practice right now
9524 @c only current dir is used. FFish says maybe a special GDB hierarchy
9525 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9530 @item core-file @r{[} @var{filename} @r{]}
9531 Specify the whereabouts of a core dump file to be used as the ``contents
9532 of memory''. Traditionally, core files contain only some parts of the
9533 address space of the process that generated them; @value{GDBN} can access the
9534 executable file itself for other parts.
9536 @code{core-file} with no argument specifies that no core file is
9539 Note that the core file is ignored when your program is actually running
9540 under @value{GDBN}. So, if you have been running your program and you
9541 wish to debug a core file instead, you must kill the subprocess in which
9542 the program is running. To do this, use the @code{kill} command
9543 (@pxref{Kill Process, ,Killing the child process}).
9545 @kindex add-symbol-file
9546 @cindex dynamic linking
9547 @item add-symbol-file @var{filename} @var{address}
9548 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9549 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9550 The @code{add-symbol-file} command reads additional symbol table
9551 information from the file @var{filename}. You would use this command
9552 when @var{filename} has been dynamically loaded (by some other means)
9553 into the program that is running. @var{address} should be the memory
9554 address at which the file has been loaded; @value{GDBN} cannot figure
9555 this out for itself. You can additionally specify an arbitrary number
9556 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9557 section name and base address for that section. You can specify any
9558 @var{address} as an expression.
9560 The symbol table of the file @var{filename} is added to the symbol table
9561 originally read with the @code{symbol-file} command. You can use the
9562 @code{add-symbol-file} command any number of times; the new symbol data
9563 thus read keeps adding to the old. To discard all old symbol data
9564 instead, use the @code{symbol-file} command without any arguments.
9566 @cindex relocatable object files, reading symbols from
9567 @cindex object files, relocatable, reading symbols from
9568 @cindex reading symbols from relocatable object files
9569 @cindex symbols, reading from relocatable object files
9570 @cindex @file{.o} files, reading symbols from
9571 Although @var{filename} is typically a shared library file, an
9572 executable file, or some other object file which has been fully
9573 relocated for loading into a process, you can also load symbolic
9574 information from relocatable @file{.o} files, as long as:
9578 the file's symbolic information refers only to linker symbols defined in
9579 that file, not to symbols defined by other object files,
9581 every section the file's symbolic information refers to has actually
9582 been loaded into the inferior, as it appears in the file, and
9584 you can determine the address at which every section was loaded, and
9585 provide these to the @code{add-symbol-file} command.
9589 Some embedded operating systems, like Sun Chorus and VxWorks, can load
9590 relocatable files into an already running program; such systems
9591 typically make the requirements above easy to meet. However, it's
9592 important to recognize that many native systems use complex link
9593 procedures (@code{.linkonce} section factoring and C++ constructor table
9594 assembly, for example) that make the requirements difficult to meet. In
9595 general, one cannot assume that using @code{add-symbol-file} to read a
9596 relocatable object file's symbolic information will have the same effect
9597 as linking the relocatable object file into the program in the normal
9600 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
9602 You can use the @samp{-mapped} and @samp{-readnow} options just as with
9603 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
9604 table information for @var{filename}.
9606 @kindex add-shared-symbol-file
9607 @item add-shared-symbol-file
9608 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
9609 operating system for the Motorola 88k. @value{GDBN} automatically looks for
9610 shared libraries, however if @value{GDBN} does not find yours, you can run
9611 @code{add-shared-symbol-file}. It takes no arguments.
9615 The @code{section} command changes the base address of section SECTION of
9616 the exec file to ADDR. This can be used if the exec file does not contain
9617 section addresses, (such as in the a.out format), or when the addresses
9618 specified in the file itself are wrong. Each section must be changed
9619 separately. The @code{info files} command, described below, lists all
9620 the sections and their addresses.
9626 @code{info files} and @code{info target} are synonymous; both print the
9627 current target (@pxref{Targets, ,Specifying a Debugging Target}),
9628 including the names of the executable and core dump files currently in
9629 use by @value{GDBN}, and the files from which symbols were loaded. The
9630 command @code{help target} lists all possible targets rather than
9633 @kindex maint info sections
9634 @item maint info sections
9635 Another command that can give you extra information about program sections
9636 is @code{maint info sections}. In addition to the section information
9637 displayed by @code{info files}, this command displays the flags and file
9638 offset of each section in the executable and core dump files. In addition,
9639 @code{maint info sections} provides the following command options (which
9640 may be arbitrarily combined):
9644 Display sections for all loaded object files, including shared libraries.
9645 @item @var{sections}
9646 Display info only for named @var{sections}.
9647 @item @var{section-flags}
9648 Display info only for sections for which @var{section-flags} are true.
9649 The section flags that @value{GDBN} currently knows about are:
9652 Section will have space allocated in the process when loaded.
9653 Set for all sections except those containing debug information.
9655 Section will be loaded from the file into the child process memory.
9656 Set for pre-initialized code and data, clear for @code{.bss} sections.
9658 Section needs to be relocated before loading.
9660 Section cannot be modified by the child process.
9662 Section contains executable code only.
9664 Section contains data only (no executable code).
9666 Section will reside in ROM.
9668 Section contains data for constructor/destructor lists.
9670 Section is not empty.
9672 An instruction to the linker to not output the section.
9673 @item COFF_SHARED_LIBRARY
9674 A notification to the linker that the section contains
9675 COFF shared library information.
9677 Section contains common symbols.
9680 @kindex set trust-readonly-sections
9681 @item set trust-readonly-sections on
9682 Tell @value{GDBN} that readonly sections in your object file
9683 really are read-only (i.e.@: that their contents will not change).
9684 In that case, @value{GDBN} can fetch values from these sections
9685 out of the object file, rather than from the target program.
9686 For some targets (notably embedded ones), this can be a significant
9687 enhancement to debugging performance.
9691 @item set trust-readonly-sections off
9692 Tell @value{GDBN} not to trust readonly sections. This means that
9693 the contents of the section might change while the program is running,
9694 and must therefore be fetched from the target when needed.
9697 All file-specifying commands allow both absolute and relative file names
9698 as arguments. @value{GDBN} always converts the file name to an absolute file
9699 name and remembers it that way.
9701 @cindex shared libraries
9702 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
9705 @value{GDBN} automatically loads symbol definitions from shared libraries
9706 when you use the @code{run} command, or when you examine a core file.
9707 (Before you issue the @code{run} command, @value{GDBN} does not understand
9708 references to a function in a shared library, however---unless you are
9709 debugging a core file).
9711 On HP-UX, if the program loads a library explicitly, @value{GDBN}
9712 automatically loads the symbols at the time of the @code{shl_load} call.
9714 @c FIXME: some @value{GDBN} release may permit some refs to undef
9715 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
9716 @c FIXME...lib; check this from time to time when updating manual
9718 There are times, however, when you may wish to not automatically load
9719 symbol definitions from shared libraries, such as when they are
9720 particularly large or there are many of them.
9722 To control the automatic loading of shared library symbols, use the
9726 @kindex set auto-solib-add
9727 @item set auto-solib-add @var{mode}
9728 If @var{mode} is @code{on}, symbols from all shared object libraries
9729 will be loaded automatically when the inferior begins execution, you
9730 attach to an independently started inferior, or when the dynamic linker
9731 informs @value{GDBN} that a new library has been loaded. If @var{mode}
9732 is @code{off}, symbols must be loaded manually, using the
9733 @code{sharedlibrary} command. The default value is @code{on}.
9735 @kindex show auto-solib-add
9736 @item show auto-solib-add
9737 Display the current autoloading mode.
9740 To explicitly load shared library symbols, use the @code{sharedlibrary}
9744 @kindex info sharedlibrary
9747 @itemx info sharedlibrary
9748 Print the names of the shared libraries which are currently loaded.
9750 @kindex sharedlibrary
9752 @item sharedlibrary @var{regex}
9753 @itemx share @var{regex}
9754 Load shared object library symbols for files matching a
9755 Unix regular expression.
9756 As with files loaded automatically, it only loads shared libraries
9757 required by your program for a core file or after typing @code{run}. If
9758 @var{regex} is omitted all shared libraries required by your program are
9762 On some systems, such as HP-UX systems, @value{GDBN} supports
9763 autoloading shared library symbols until a limiting threshold size is
9764 reached. This provides the benefit of allowing autoloading to remain on
9765 by default, but avoids autoloading excessively large shared libraries,
9766 up to a threshold that is initially set, but which you can modify if you
9769 Beyond that threshold, symbols from shared libraries must be explicitly
9770 loaded. To load these symbols, use the command @code{sharedlibrary
9771 @var{filename}}. The base address of the shared library is determined
9772 automatically by @value{GDBN} and need not be specified.
9774 To display or set the threshold, use the commands:
9777 @kindex set auto-solib-limit
9778 @item set auto-solib-limit @var{threshold}
9779 Set the autoloading size threshold, in an integral number of megabytes.
9780 If @var{threshold} is nonzero and shared library autoloading is enabled,
9781 symbols from all shared object libraries will be loaded until the total
9782 size of the loaded shared library symbols exceeds this threshold.
9783 Otherwise, symbols must be loaded manually, using the
9784 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
9787 @kindex show auto-solib-limit
9788 @item show auto-solib-limit
9789 Display the current autoloading size threshold, in megabytes.
9792 Shared libraries are also supported in many cross or remote debugging
9793 configurations. A copy of the target's libraries need to be present on the
9794 host system; they need to be the same as the target libraries, although the
9795 copies on the target can be stripped as long as the copies on the host are
9798 You need to tell @value{GDBN} where the target libraries are, so that it can
9799 load the correct copies---otherwise, it may try to load the host's libraries.
9800 @value{GDBN} has two variables to specify the search directories for target
9804 @kindex set solib-absolute-prefix
9805 @item set solib-absolute-prefix @var{path}
9806 If this variable is set, @var{path} will be used as a prefix for any
9807 absolute shared library paths; many runtime loaders store the absolute
9808 paths to the shared library in the target program's memory. If you use
9809 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
9810 out in the same way that they are on the target, with e.g.@: a
9811 @file{/usr/lib} hierarchy under @var{path}.
9813 You can set the default value of @samp{solib-absolute-prefix} by using the
9814 configure-time @samp{--with-sysroot} option.
9816 @kindex show solib-absolute-prefix
9817 @item show solib-absolute-prefix
9818 Display the current shared library prefix.
9820 @kindex set solib-search-path
9821 @item set solib-search-path @var{path}
9822 If this variable is set, @var{path} is a colon-separated list of directories
9823 to search for shared libraries. @samp{solib-search-path} is used after
9824 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
9825 the library is relative instead of absolute. If you want to use
9826 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
9827 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
9828 @value{GDBN} from finding your host's libraries.
9830 @kindex show solib-search-path
9831 @item show solib-search-path
9832 Display the current shared library search path.
9836 @node Separate Debug Files
9837 @section Debugging Information in Separate Files
9838 @cindex separate debugging information files
9839 @cindex debugging information in separate files
9840 @cindex @file{.debug} subdirectories
9841 @cindex debugging information directory, global
9842 @cindex global debugging information directory
9844 @value{GDBN} allows you to put a program's debugging information in a
9845 file separate from the executable itself, in a way that allows
9846 @value{GDBN} to find and load the debugging information automatically.
9847 Since debugging information can be very large --- sometimes larger
9848 than the executable code itself --- some systems distribute debugging
9849 information for their executables in separate files, which users can
9850 install only when they need to debug a problem.
9852 If an executable's debugging information has been extracted to a
9853 separate file, the executable should contain a @dfn{debug link} giving
9854 the name of the debugging information file (with no directory
9855 components), and a checksum of its contents. (The exact form of a
9856 debug link is described below.) If the full name of the directory
9857 containing the executable is @var{execdir}, and the executable has a
9858 debug link that specifies the name @var{debugfile}, then @value{GDBN}
9859 will automatically search for the debugging information file in three
9864 the directory containing the executable file (that is, it will look
9865 for a file named @file{@var{execdir}/@var{debugfile}},
9867 a subdirectory of that directory named @file{.debug} (that is, the
9868 file @file{@var{execdir}/.debug/@var{debugfile}}, and
9870 a subdirectory of the global debug file directory that includes the
9871 executable's full path, and the name from the link (that is, the file
9872 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
9873 @var{globaldebugdir} is the global debug file directory, and
9874 @var{execdir} has been turned into a relative path).
9877 @value{GDBN} checks under each of these names for a debugging
9878 information file whose checksum matches that given in the link, and
9879 reads the debugging information from the first one it finds.
9881 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
9882 which has a link containing the name @file{ls.debug}, and the global
9883 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
9884 for debug information in @file{/usr/bin/ls.debug},
9885 @file{/usr/bin/.debug/ls.debug}, and
9886 @file{/usr/lib/debug/usr/bin/ls.debug}.
9888 You can set the global debugging info directory's name, and view the
9889 name @value{GDBN} is currently using.
9893 @kindex set debug-file-directory
9894 @item set debug-file-directory @var{directory}
9895 Set the directory which @value{GDBN} searches for separate debugging
9896 information files to @var{directory}.
9898 @kindex show debug-file-directory
9899 @item show debug-file-directory
9900 Show the directory @value{GDBN} searches for separate debugging
9905 @cindex @code{.gnu_debuglink} sections
9907 A debug link is a special section of the executable file named
9908 @code{.gnu_debuglink}. The section must contain:
9912 A filename, with any leading directory components removed, followed by
9915 zero to three bytes of padding, as needed to reach the next four-byte
9916 boundary within the section, and
9918 a four-byte CRC checksum, stored in the same endianness used for the
9919 executable file itself. The checksum is computed on the debugging
9920 information file's full contents by the function given below, passing
9921 zero as the @var{crc} argument.
9924 Any executable file format can carry a debug link, as long as it can
9925 contain a section named @code{.gnu_debuglink} with the contents
9928 The debugging information file itself should be an ordinary
9929 executable, containing a full set of linker symbols, sections, and
9930 debugging information. The sections of the debugging information file
9931 should have the same names, addresses and sizes as the original file,
9932 but they need not contain any data --- much like a @code{.bss} section
9933 in an ordinary executable.
9935 As of December 2002, there is no standard GNU utility to produce
9936 separated executable / debugging information file pairs. Ulrich
9937 Drepper's @file{elfutils} package, starting with version 0.53,
9938 contains a version of the @code{strip} command such that the command
9939 @kbd{strip foo -f foo.debug} removes the debugging information from
9940 the executable file @file{foo}, places it in the file
9941 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
9943 Since there are many different ways to compute CRC's (different
9944 polynomials, reversals, byte ordering, etc.), the simplest way to
9945 describe the CRC used in @code{.gnu_debuglink} sections is to give the
9946 complete code for a function that computes it:
9948 @kindex @code{gnu_debuglink_crc32}
9951 gnu_debuglink_crc32 (unsigned long crc,
9952 unsigned char *buf, size_t len)
9954 static const unsigned long crc32_table[256] =
9956 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
9957 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
9958 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
9959 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
9960 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
9961 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
9962 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
9963 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
9964 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
9965 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
9966 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
9967 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
9968 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
9969 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
9970 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
9971 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
9972 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
9973 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
9974 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
9975 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
9976 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
9977 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
9978 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
9979 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
9980 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
9981 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
9982 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
9983 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
9984 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
9985 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
9986 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
9987 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
9988 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
9989 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
9990 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
9991 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
9992 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
9993 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
9994 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
9995 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
9996 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
9997 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
9998 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
9999 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
10000 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
10001 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
10002 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
10003 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
10004 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
10005 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
10006 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
10009 unsigned char *end;
10011 crc = ~crc & 0xffffffff;
10012 for (end = buf + len; buf < end; ++buf)
10013 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
10014 return ~crc & 0xffffffff;;
10019 @node Symbol Errors
10020 @section Errors reading symbol files
10022 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10023 such as symbol types it does not recognize, or known bugs in compiler
10024 output. By default, @value{GDBN} does not notify you of such problems, since
10025 they are relatively common and primarily of interest to people
10026 debugging compilers. If you are interested in seeing information
10027 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10028 only one message about each such type of problem, no matter how many
10029 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10030 to see how many times the problems occur, with the @code{set
10031 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10034 The messages currently printed, and their meanings, include:
10037 @item inner block not inside outer block in @var{symbol}
10039 The symbol information shows where symbol scopes begin and end
10040 (such as at the start of a function or a block of statements). This
10041 error indicates that an inner scope block is not fully contained
10042 in its outer scope blocks.
10044 @value{GDBN} circumvents the problem by treating the inner block as if it had
10045 the same scope as the outer block. In the error message, @var{symbol}
10046 may be shown as ``@code{(don't know)}'' if the outer block is not a
10049 @item block at @var{address} out of order
10051 The symbol information for symbol scope blocks should occur in
10052 order of increasing addresses. This error indicates that it does not
10055 @value{GDBN} does not circumvent this problem, and has trouble
10056 locating symbols in the source file whose symbols it is reading. (You
10057 can often determine what source file is affected by specifying
10058 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10061 @item bad block start address patched
10063 The symbol information for a symbol scope block has a start address
10064 smaller than the address of the preceding source line. This is known
10065 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10067 @value{GDBN} circumvents the problem by treating the symbol scope block as
10068 starting on the previous source line.
10070 @item bad string table offset in symbol @var{n}
10073 Symbol number @var{n} contains a pointer into the string table which is
10074 larger than the size of the string table.
10076 @value{GDBN} circumvents the problem by considering the symbol to have the
10077 name @code{foo}, which may cause other problems if many symbols end up
10080 @item unknown symbol type @code{0x@var{nn}}
10082 The symbol information contains new data types that @value{GDBN} does
10083 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10084 uncomprehended information, in hexadecimal.
10086 @value{GDBN} circumvents the error by ignoring this symbol information.
10087 This usually allows you to debug your program, though certain symbols
10088 are not accessible. If you encounter such a problem and feel like
10089 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10090 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10091 and examine @code{*bufp} to see the symbol.
10093 @item stub type has NULL name
10095 @value{GDBN} could not find the full definition for a struct or class.
10097 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10098 The symbol information for a C@t{++} member function is missing some
10099 information that recent versions of the compiler should have output for
10102 @item info mismatch between compiler and debugger
10104 @value{GDBN} could not parse a type specification output by the compiler.
10109 @chapter Specifying a Debugging Target
10111 @cindex debugging target
10114 A @dfn{target} is the execution environment occupied by your program.
10116 Often, @value{GDBN} runs in the same host environment as your program;
10117 in that case, the debugging target is specified as a side effect when
10118 you use the @code{file} or @code{core} commands. When you need more
10119 flexibility---for example, running @value{GDBN} on a physically separate
10120 host, or controlling a standalone system over a serial port or a
10121 realtime system over a TCP/IP connection---you can use the @code{target}
10122 command to specify one of the target types configured for @value{GDBN}
10123 (@pxref{Target Commands, ,Commands for managing targets}).
10126 * Active Targets:: Active targets
10127 * Target Commands:: Commands for managing targets
10128 * Byte Order:: Choosing target byte order
10129 * Remote:: Remote debugging
10130 * KOD:: Kernel Object Display
10134 @node Active Targets
10135 @section Active targets
10137 @cindex stacking targets
10138 @cindex active targets
10139 @cindex multiple targets
10141 There are three classes of targets: processes, core files, and
10142 executable files. @value{GDBN} can work concurrently on up to three
10143 active targets, one in each class. This allows you to (for example)
10144 start a process and inspect its activity without abandoning your work on
10147 For example, if you execute @samp{gdb a.out}, then the executable file
10148 @code{a.out} is the only active target. If you designate a core file as
10149 well---presumably from a prior run that crashed and coredumped---then
10150 @value{GDBN} has two active targets and uses them in tandem, looking
10151 first in the corefile target, then in the executable file, to satisfy
10152 requests for memory addresses. (Typically, these two classes of target
10153 are complementary, since core files contain only a program's
10154 read-write memory---variables and so on---plus machine status, while
10155 executable files contain only the program text and initialized data.)
10157 When you type @code{run}, your executable file becomes an active process
10158 target as well. When a process target is active, all @value{GDBN}
10159 commands requesting memory addresses refer to that target; addresses in
10160 an active core file or executable file target are obscured while the
10161 process target is active.
10163 Use the @code{core-file} and @code{exec-file} commands to select a new
10164 core file or executable target (@pxref{Files, ,Commands to specify
10165 files}). To specify as a target a process that is already running, use
10166 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10169 @node Target Commands
10170 @section Commands for managing targets
10173 @item target @var{type} @var{parameters}
10174 Connects the @value{GDBN} host environment to a target machine or
10175 process. A target is typically a protocol for talking to debugging
10176 facilities. You use the argument @var{type} to specify the type or
10177 protocol of the target machine.
10179 Further @var{parameters} are interpreted by the target protocol, but
10180 typically include things like device names or host names to connect
10181 with, process numbers, and baud rates.
10183 The @code{target} command does not repeat if you press @key{RET} again
10184 after executing the command.
10186 @kindex help target
10188 Displays the names of all targets available. To display targets
10189 currently selected, use either @code{info target} or @code{info files}
10190 (@pxref{Files, ,Commands to specify files}).
10192 @item help target @var{name}
10193 Describe a particular target, including any parameters necessary to
10196 @kindex set gnutarget
10197 @item set gnutarget @var{args}
10198 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10199 knows whether it is reading an @dfn{executable},
10200 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10201 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10202 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10205 @emph{Warning:} To specify a file format with @code{set gnutarget},
10206 you must know the actual BFD name.
10210 @xref{Files, , Commands to specify files}.
10212 @kindex show gnutarget
10213 @item show gnutarget
10214 Use the @code{show gnutarget} command to display what file format
10215 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10216 @value{GDBN} will determine the file format for each file automatically,
10217 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10220 Here are some common targets (available, or not, depending on the GDB
10224 @kindex target exec
10225 @item target exec @var{program}
10226 An executable file. @samp{target exec @var{program}} is the same as
10227 @samp{exec-file @var{program}}.
10229 @kindex target core
10230 @item target core @var{filename}
10231 A core dump file. @samp{target core @var{filename}} is the same as
10232 @samp{core-file @var{filename}}.
10234 @kindex target remote
10235 @item target remote @var{dev}
10236 Remote serial target in GDB-specific protocol. The argument @var{dev}
10237 specifies what serial device to use for the connection (e.g.
10238 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10239 supports the @code{load} command. This is only useful if you have
10240 some other way of getting the stub to the target system, and you can put
10241 it somewhere in memory where it won't get clobbered by the download.
10245 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10253 works; however, you cannot assume that a specific memory map, device
10254 drivers, or even basic I/O is available, although some simulators do
10255 provide these. For info about any processor-specific simulator details,
10256 see the appropriate section in @ref{Embedded Processors, ,Embedded
10261 Some configurations may include these targets as well:
10265 @kindex target nrom
10266 @item target nrom @var{dev}
10267 NetROM ROM emulator. This target only supports downloading.
10271 Different targets are available on different configurations of @value{GDBN};
10272 your configuration may have more or fewer targets.
10274 Many remote targets require you to download the executable's code
10275 once you've successfully established a connection.
10279 @kindex load @var{filename}
10280 @item load @var{filename}
10281 Depending on what remote debugging facilities are configured into
10282 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10283 is meant to make @var{filename} (an executable) available for debugging
10284 on the remote system---by downloading, or dynamic linking, for example.
10285 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10286 the @code{add-symbol-file} command.
10288 If your @value{GDBN} does not have a @code{load} command, attempting to
10289 execute it gets the error message ``@code{You can't do that when your
10290 target is @dots{}}''
10292 The file is loaded at whatever address is specified in the executable.
10293 For some object file formats, you can specify the load address when you
10294 link the program; for other formats, like a.out, the object file format
10295 specifies a fixed address.
10296 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10298 @code{load} does not repeat if you press @key{RET} again after using it.
10302 @section Choosing target byte order
10304 @cindex choosing target byte order
10305 @cindex target byte order
10307 Some types of processors, such as the MIPS, PowerPC, and Hitachi SH,
10308 offer the ability to run either big-endian or little-endian byte
10309 orders. Usually the executable or symbol will include a bit to
10310 designate the endian-ness, and you will not need to worry about
10311 which to use. However, you may still find it useful to adjust
10312 @value{GDBN}'s idea of processor endian-ness manually.
10315 @kindex set endian big
10316 @item set endian big
10317 Instruct @value{GDBN} to assume the target is big-endian.
10319 @kindex set endian little
10320 @item set endian little
10321 Instruct @value{GDBN} to assume the target is little-endian.
10323 @kindex set endian auto
10324 @item set endian auto
10325 Instruct @value{GDBN} to use the byte order associated with the
10329 Display @value{GDBN}'s current idea of the target byte order.
10333 Note that these commands merely adjust interpretation of symbolic
10334 data on the host, and that they have absolutely no effect on the
10338 @section Remote debugging
10339 @cindex remote debugging
10341 If you are trying to debug a program running on a machine that cannot run
10342 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10343 For example, you might use remote debugging on an operating system kernel,
10344 or on a small system which does not have a general purpose operating system
10345 powerful enough to run a full-featured debugger.
10347 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10348 to make this work with particular debugging targets. In addition,
10349 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10350 but not specific to any particular target system) which you can use if you
10351 write the remote stubs---the code that runs on the remote system to
10352 communicate with @value{GDBN}.
10354 Other remote targets may be available in your
10355 configuration of @value{GDBN}; use @code{help target} to list them.
10358 @section Kernel Object Display
10360 @cindex kernel object display
10361 @cindex kernel object
10364 Some targets support kernel object display. Using this facility,
10365 @value{GDBN} communicates specially with the underlying operating system
10366 and can display information about operating system-level objects such as
10367 mutexes and other synchronization objects. Exactly which objects can be
10368 displayed is determined on a per-OS basis.
10370 Use the @code{set os} command to set the operating system. This tells
10371 @value{GDBN} which kernel object display module to initialize:
10374 (@value{GDBP}) set os cisco
10377 If @code{set os} succeeds, @value{GDBN} will display some information
10378 about the operating system, and will create a new @code{info} command
10379 which can be used to query the target. The @code{info} command is named
10380 after the operating system:
10383 (@value{GDBP}) info cisco
10384 List of Cisco Kernel Objects
10386 any Any and all objects
10389 Further subcommands can be used to query about particular objects known
10392 There is currently no way to determine whether a given operating system
10393 is supported other than to try it.
10396 @node Remote Debugging
10397 @chapter Debugging remote programs
10400 * Server:: Using the gdbserver program
10401 * NetWare:: Using the gdbserve.nlm program
10402 * Remote configuration:: Remote configuration
10403 * remote stub:: Implementing a remote stub
10407 @section Using the @code{gdbserver} program
10410 @cindex remote connection without stubs
10411 @code{gdbserver} is a control program for Unix-like systems, which
10412 allows you to connect your program with a remote @value{GDBN} via
10413 @code{target remote}---but without linking in the usual debugging stub.
10415 @code{gdbserver} is not a complete replacement for the debugging stubs,
10416 because it requires essentially the same operating-system facilities
10417 that @value{GDBN} itself does. In fact, a system that can run
10418 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10419 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10420 because it is a much smaller program than @value{GDBN} itself. It is
10421 also easier to port than all of @value{GDBN}, so you may be able to get
10422 started more quickly on a new system by using @code{gdbserver}.
10423 Finally, if you develop code for real-time systems, you may find that
10424 the tradeoffs involved in real-time operation make it more convenient to
10425 do as much development work as possible on another system, for example
10426 by cross-compiling. You can use @code{gdbserver} to make a similar
10427 choice for debugging.
10429 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10430 or a TCP connection, using the standard @value{GDBN} remote serial
10434 @item On the target machine,
10435 you need to have a copy of the program you want to debug.
10436 @code{gdbserver} does not need your program's symbol table, so you can
10437 strip the program if necessary to save space. @value{GDBN} on the host
10438 system does all the symbol handling.
10440 To use the server, you must tell it how to communicate with @value{GDBN};
10441 the name of your program; and the arguments for your program. The usual
10445 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10448 @var{comm} is either a device name (to use a serial line) or a TCP
10449 hostname and portnumber. For example, to debug Emacs with the argument
10450 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10454 target> gdbserver /dev/com1 emacs foo.txt
10457 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10460 To use a TCP connection instead of a serial line:
10463 target> gdbserver host:2345 emacs foo.txt
10466 The only difference from the previous example is the first argument,
10467 specifying that you are communicating with the host @value{GDBN} via
10468 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10469 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10470 (Currently, the @samp{host} part is ignored.) You can choose any number
10471 you want for the port number as long as it does not conflict with any
10472 TCP ports already in use on the target system (for example, @code{23} is
10473 reserved for @code{telnet}).@footnote{If you choose a port number that
10474 conflicts with another service, @code{gdbserver} prints an error message
10475 and exits.} You must use the same port number with the host @value{GDBN}
10476 @code{target remote} command.
10478 On some targets, @code{gdbserver} can also attach to running programs.
10479 This is accomplished via the @code{--attach} argument. The syntax is:
10482 target> gdbserver @var{comm} --attach @var{pid}
10485 @var{pid} is the process ID of a currently running process. It isn't necessary
10486 to point @code{gdbserver} at a binary for the running process.
10488 @item On the @value{GDBN} host machine,
10489 you need an unstripped copy of your program, since @value{GDBN} needs
10490 symbols and debugging information. Start up @value{GDBN} as usual,
10491 using the name of the local copy of your program as the first argument.
10492 (You may also need the @w{@samp{--baud}} option if the serial line is
10493 running at anything other than 9600@dmn{bps}.) After that, use @code{target
10494 remote} to establish communications with @code{gdbserver}. Its argument
10495 is either a device name (usually a serial device, like
10496 @file{/dev/ttyb}), or a TCP port descriptor in the form
10497 @code{@var{host}:@var{PORT}}. For example:
10500 (@value{GDBP}) target remote /dev/ttyb
10504 communicates with the server via serial line @file{/dev/ttyb}, and
10507 (@value{GDBP}) target remote the-target:2345
10511 communicates via a TCP connection to port 2345 on host @w{@file{the-target}}.
10512 For TCP connections, you must start up @code{gdbserver} prior to using
10513 the @code{target remote} command. Otherwise you may get an error whose
10514 text depends on the host system, but which usually looks something like
10515 @samp{Connection refused}.
10519 @section Using the @code{gdbserve.nlm} program
10521 @kindex gdbserve.nlm
10522 @code{gdbserve.nlm} is a control program for NetWare systems, which
10523 allows you to connect your program with a remote @value{GDBN} via
10524 @code{target remote}.
10526 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10527 using the standard @value{GDBN} remote serial protocol.
10530 @item On the target machine,
10531 you need to have a copy of the program you want to debug.
10532 @code{gdbserve.nlm} does not need your program's symbol table, so you
10533 can strip the program if necessary to save space. @value{GDBN} on the
10534 host system does all the symbol handling.
10536 To use the server, you must tell it how to communicate with
10537 @value{GDBN}; the name of your program; and the arguments for your
10538 program. The syntax is:
10541 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10542 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10545 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10546 the baud rate used by the connection. @var{port} and @var{node} default
10547 to 0, @var{baud} defaults to 9600@dmn{bps}.
10549 For example, to debug Emacs with the argument @samp{foo.txt}and
10550 communicate with @value{GDBN} over serial port number 2 or board 1
10551 using a 19200@dmn{bps} connection:
10554 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10557 @item On the @value{GDBN} host machine,
10558 you need an unstripped copy of your program, since @value{GDBN} needs
10559 symbols and debugging information. Start up @value{GDBN} as usual,
10560 using the name of the local copy of your program as the first argument.
10561 (You may also need the @w{@samp{--baud}} option if the serial line is
10562 running at anything other than 9600@dmn{bps}. After that, use @code{target
10563 remote} to establish communications with @code{gdbserve.nlm}. Its
10564 argument is a device name (usually a serial device, like
10565 @file{/dev/ttyb}). For example:
10568 (@value{GDBP}) target remote /dev/ttyb
10572 communications with the server via serial line @file{/dev/ttyb}.
10575 @node Remote configuration
10576 @section Remote configuration
10578 The following configuration options are available when debugging remote
10582 @kindex set remote hardware-watchpoint-limit
10583 @kindex set remote hardware-breakpoint-limit
10584 @anchor{set remote hardware-watchpoint-limit}
10585 @anchor{set remote hardware-breakpoint-limit}
10586 @item set remote hardware-watchpoint-limit @var{limit}
10587 @itemx set remote hardware-breakpoint-limit @var{limit}
10588 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
10589 watchpoints. A limit of -1, the default, is treated as unlimited.
10593 @section Implementing a remote stub
10595 @cindex debugging stub, example
10596 @cindex remote stub, example
10597 @cindex stub example, remote debugging
10598 The stub files provided with @value{GDBN} implement the target side of the
10599 communication protocol, and the @value{GDBN} side is implemented in the
10600 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10601 these subroutines to communicate, and ignore the details. (If you're
10602 implementing your own stub file, you can still ignore the details: start
10603 with one of the existing stub files. @file{sparc-stub.c} is the best
10604 organized, and therefore the easiest to read.)
10606 @cindex remote serial debugging, overview
10607 To debug a program running on another machine (the debugging
10608 @dfn{target} machine), you must first arrange for all the usual
10609 prerequisites for the program to run by itself. For example, for a C
10614 A startup routine to set up the C runtime environment; these usually
10615 have a name like @file{crt0}. The startup routine may be supplied by
10616 your hardware supplier, or you may have to write your own.
10619 A C subroutine library to support your program's
10620 subroutine calls, notably managing input and output.
10623 A way of getting your program to the other machine---for example, a
10624 download program. These are often supplied by the hardware
10625 manufacturer, but you may have to write your own from hardware
10629 The next step is to arrange for your program to use a serial port to
10630 communicate with the machine where @value{GDBN} is running (the @dfn{host}
10631 machine). In general terms, the scheme looks like this:
10635 @value{GDBN} already understands how to use this protocol; when everything
10636 else is set up, you can simply use the @samp{target remote} command
10637 (@pxref{Targets,,Specifying a Debugging Target}).
10639 @item On the target,
10640 you must link with your program a few special-purpose subroutines that
10641 implement the @value{GDBN} remote serial protocol. The file containing these
10642 subroutines is called a @dfn{debugging stub}.
10644 On certain remote targets, you can use an auxiliary program
10645 @code{gdbserver} instead of linking a stub into your program.
10646 @xref{Server,,Using the @code{gdbserver} program}, for details.
10649 The debugging stub is specific to the architecture of the remote
10650 machine; for example, use @file{sparc-stub.c} to debug programs on
10653 @cindex remote serial stub list
10654 These working remote stubs are distributed with @value{GDBN}:
10659 @cindex @file{i386-stub.c}
10662 For Intel 386 and compatible architectures.
10665 @cindex @file{m68k-stub.c}
10666 @cindex Motorola 680x0
10668 For Motorola 680x0 architectures.
10671 @cindex @file{sh-stub.c}
10674 For Hitachi SH architectures.
10677 @cindex @file{sparc-stub.c}
10679 For @sc{sparc} architectures.
10681 @item sparcl-stub.c
10682 @cindex @file{sparcl-stub.c}
10685 For Fujitsu @sc{sparclite} architectures.
10689 The @file{README} file in the @value{GDBN} distribution may list other
10690 recently added stubs.
10693 * Stub Contents:: What the stub can do for you
10694 * Bootstrapping:: What you must do for the stub
10695 * Debug Session:: Putting it all together
10698 @node Stub Contents
10699 @subsection What the stub can do for you
10701 @cindex remote serial stub
10702 The debugging stub for your architecture supplies these three
10706 @item set_debug_traps
10707 @kindex set_debug_traps
10708 @cindex remote serial stub, initialization
10709 This routine arranges for @code{handle_exception} to run when your
10710 program stops. You must call this subroutine explicitly near the
10711 beginning of your program.
10713 @item handle_exception
10714 @kindex handle_exception
10715 @cindex remote serial stub, main routine
10716 This is the central workhorse, but your program never calls it
10717 explicitly---the setup code arranges for @code{handle_exception} to
10718 run when a trap is triggered.
10720 @code{handle_exception} takes control when your program stops during
10721 execution (for example, on a breakpoint), and mediates communications
10722 with @value{GDBN} on the host machine. This is where the communications
10723 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
10724 representative on the target machine. It begins by sending summary
10725 information on the state of your program, then continues to execute,
10726 retrieving and transmitting any information @value{GDBN} needs, until you
10727 execute a @value{GDBN} command that makes your program resume; at that point,
10728 @code{handle_exception} returns control to your own code on the target
10732 @cindex @code{breakpoint} subroutine, remote
10733 Use this auxiliary subroutine to make your program contain a
10734 breakpoint. Depending on the particular situation, this may be the only
10735 way for @value{GDBN} to get control. For instance, if your target
10736 machine has some sort of interrupt button, you won't need to call this;
10737 pressing the interrupt button transfers control to
10738 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
10739 simply receiving characters on the serial port may also trigger a trap;
10740 again, in that situation, you don't need to call @code{breakpoint} from
10741 your own program---simply running @samp{target remote} from the host
10742 @value{GDBN} session gets control.
10744 Call @code{breakpoint} if none of these is true, or if you simply want
10745 to make certain your program stops at a predetermined point for the
10746 start of your debugging session.
10749 @node Bootstrapping
10750 @subsection What you must do for the stub
10752 @cindex remote stub, support routines
10753 The debugging stubs that come with @value{GDBN} are set up for a particular
10754 chip architecture, but they have no information about the rest of your
10755 debugging target machine.
10757 First of all you need to tell the stub how to communicate with the
10761 @item int getDebugChar()
10762 @kindex getDebugChar
10763 Write this subroutine to read a single character from the serial port.
10764 It may be identical to @code{getchar} for your target system; a
10765 different name is used to allow you to distinguish the two if you wish.
10767 @item void putDebugChar(int)
10768 @kindex putDebugChar
10769 Write this subroutine to write a single character to the serial port.
10770 It may be identical to @code{putchar} for your target system; a
10771 different name is used to allow you to distinguish the two if you wish.
10774 @cindex control C, and remote debugging
10775 @cindex interrupting remote targets
10776 If you want @value{GDBN} to be able to stop your program while it is
10777 running, you need to use an interrupt-driven serial driver, and arrange
10778 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
10779 character). That is the character which @value{GDBN} uses to tell the
10780 remote system to stop.
10782 Getting the debugging target to return the proper status to @value{GDBN}
10783 probably requires changes to the standard stub; one quick and dirty way
10784 is to just execute a breakpoint instruction (the ``dirty'' part is that
10785 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
10787 Other routines you need to supply are:
10790 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
10791 @kindex exceptionHandler
10792 Write this function to install @var{exception_address} in the exception
10793 handling tables. You need to do this because the stub does not have any
10794 way of knowing what the exception handling tables on your target system
10795 are like (for example, the processor's table might be in @sc{rom},
10796 containing entries which point to a table in @sc{ram}).
10797 @var{exception_number} is the exception number which should be changed;
10798 its meaning is architecture-dependent (for example, different numbers
10799 might represent divide by zero, misaligned access, etc). When this
10800 exception occurs, control should be transferred directly to
10801 @var{exception_address}, and the processor state (stack, registers,
10802 and so on) should be just as it is when a processor exception occurs. So if
10803 you want to use a jump instruction to reach @var{exception_address}, it
10804 should be a simple jump, not a jump to subroutine.
10806 For the 386, @var{exception_address} should be installed as an interrupt
10807 gate so that interrupts are masked while the handler runs. The gate
10808 should be at privilege level 0 (the most privileged level). The
10809 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
10810 help from @code{exceptionHandler}.
10812 @item void flush_i_cache()
10813 @kindex flush_i_cache
10814 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
10815 instruction cache, if any, on your target machine. If there is no
10816 instruction cache, this subroutine may be a no-op.
10818 On target machines that have instruction caches, @value{GDBN} requires this
10819 function to make certain that the state of your program is stable.
10823 You must also make sure this library routine is available:
10826 @item void *memset(void *, int, int)
10828 This is the standard library function @code{memset} that sets an area of
10829 memory to a known value. If you have one of the free versions of
10830 @code{libc.a}, @code{memset} can be found there; otherwise, you must
10831 either obtain it from your hardware manufacturer, or write your own.
10834 If you do not use the GNU C compiler, you may need other standard
10835 library subroutines as well; this varies from one stub to another,
10836 but in general the stubs are likely to use any of the common library
10837 subroutines which @code{@value{GCC}} generates as inline code.
10840 @node Debug Session
10841 @subsection Putting it all together
10843 @cindex remote serial debugging summary
10844 In summary, when your program is ready to debug, you must follow these
10849 Make sure you have defined the supporting low-level routines
10850 (@pxref{Bootstrapping,,What you must do for the stub}):
10852 @code{getDebugChar}, @code{putDebugChar},
10853 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
10857 Insert these lines near the top of your program:
10865 For the 680x0 stub only, you need to provide a variable called
10866 @code{exceptionHook}. Normally you just use:
10869 void (*exceptionHook)() = 0;
10873 but if before calling @code{set_debug_traps}, you set it to point to a
10874 function in your program, that function is called when
10875 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
10876 error). The function indicated by @code{exceptionHook} is called with
10877 one parameter: an @code{int} which is the exception number.
10880 Compile and link together: your program, the @value{GDBN} debugging stub for
10881 your target architecture, and the supporting subroutines.
10884 Make sure you have a serial connection between your target machine and
10885 the @value{GDBN} host, and identify the serial port on the host.
10888 @c The "remote" target now provides a `load' command, so we should
10889 @c document that. FIXME.
10890 Download your program to your target machine (or get it there by
10891 whatever means the manufacturer provides), and start it.
10894 To start remote debugging, run @value{GDBN} on the host machine, and specify
10895 as an executable file the program that is running in the remote machine.
10896 This tells @value{GDBN} how to find your program's symbols and the contents
10900 @cindex serial line, @code{target remote}
10901 Establish communication using the @code{target remote} command.
10902 Its argument specifies how to communicate with the target
10903 machine---either via a devicename attached to a direct serial line, or a
10904 TCP or UDP port (usually to a terminal server which in turn has a serial line
10905 to the target). For example, to use a serial line connected to the
10906 device named @file{/dev/ttyb}:
10909 target remote /dev/ttyb
10912 @cindex TCP port, @code{target remote}
10913 To use a TCP connection, use an argument of the form
10914 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
10915 For example, to connect to port 2828 on a
10916 terminal server named @code{manyfarms}:
10919 target remote manyfarms:2828
10922 If your remote target is actually running on the same machine as
10923 your debugger session (e.g.@: a simulator of your target running on
10924 the same host), you can omit the hostname. For example, to connect
10925 to port 1234 on your local machine:
10928 target remote :1234
10932 Note that the colon is still required here.
10934 @cindex UDP port, @code{target remote}
10935 To use a UDP connection, use an argument of the form
10936 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
10937 on a terminal server named @code{manyfarms}:
10940 target remote udp:manyfarms:2828
10943 When using a UDP connection for remote debugging, you should keep in mind
10944 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
10945 busy or unreliable networks, which will cause havoc with your debugging
10950 Now you can use all the usual commands to examine and change data and to
10951 step and continue the remote program.
10953 To resume the remote program and stop debugging it, use the @code{detach}
10956 @cindex interrupting remote programs
10957 @cindex remote programs, interrupting
10958 Whenever @value{GDBN} is waiting for the remote program, if you type the
10959 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
10960 program. This may or may not succeed, depending in part on the hardware
10961 and the serial drivers the remote system uses. If you type the
10962 interrupt character once again, @value{GDBN} displays this prompt:
10965 Interrupted while waiting for the program.
10966 Give up (and stop debugging it)? (y or n)
10969 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
10970 (If you decide you want to try again later, you can use @samp{target
10971 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
10972 goes back to waiting.
10975 @node Configurations
10976 @chapter Configuration-Specific Information
10978 While nearly all @value{GDBN} commands are available for all native and
10979 cross versions of the debugger, there are some exceptions. This chapter
10980 describes things that are only available in certain configurations.
10982 There are three major categories of configurations: native
10983 configurations, where the host and target are the same, embedded
10984 operating system configurations, which are usually the same for several
10985 different processor architectures, and bare embedded processors, which
10986 are quite different from each other.
10991 * Embedded Processors::
10998 This section describes details specific to particular native
11003 * SVR4 Process Information:: SVR4 process information
11004 * DJGPP Native:: Features specific to the DJGPP port
11005 * Cygwin Native:: Features specific to the Cygwin port
11011 On HP-UX systems, if you refer to a function or variable name that
11012 begins with a dollar sign, @value{GDBN} searches for a user or system
11013 name first, before it searches for a convenience variable.
11015 @node SVR4 Process Information
11016 @subsection SVR4 process information
11019 @cindex process image
11021 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11022 used to examine the image of a running process using file-system
11023 subroutines. If @value{GDBN} is configured for an operating system with
11024 this facility, the command @code{info proc} is available to report on
11025 several kinds of information about the process running your program.
11026 @code{info proc} works only on SVR4 systems that include the
11027 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11028 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11033 Summarize available information about the process.
11035 @kindex info proc mappings
11036 @item info proc mappings
11037 Report on the address ranges accessible in the program, with information
11038 on whether your program may read, write, or execute each range.
11040 @comment These sub-options of 'info proc' were not included when
11041 @comment procfs.c was re-written. Keep their descriptions around
11042 @comment against the day when someone finds the time to put them back in.
11043 @kindex info proc times
11044 @item info proc times
11045 Starting time, user CPU time, and system CPU time for your program and
11048 @kindex info proc id
11050 Report on the process IDs related to your program: its own process ID,
11051 the ID of its parent, the process group ID, and the session ID.
11053 @kindex info proc status
11054 @item info proc status
11055 General information on the state of the process. If the process is
11056 stopped, this report includes the reason for stopping, and any signal
11059 @item info proc all
11060 Show all the above information about the process.
11065 @subsection Features for Debugging @sc{djgpp} Programs
11066 @cindex @sc{djgpp} debugging
11067 @cindex native @sc{djgpp} debugging
11068 @cindex MS-DOS-specific commands
11070 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11071 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11072 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11073 top of real-mode DOS systems and their emulations.
11075 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11076 defines a few commands specific to the @sc{djgpp} port. This
11077 subsection describes those commands.
11082 This is a prefix of @sc{djgpp}-specific commands which print
11083 information about the target system and important OS structures.
11086 @cindex MS-DOS system info
11087 @cindex free memory information (MS-DOS)
11088 @item info dos sysinfo
11089 This command displays assorted information about the underlying
11090 platform: the CPU type and features, the OS version and flavor, the
11091 DPMI version, and the available conventional and DPMI memory.
11096 @cindex segment descriptor tables
11097 @cindex descriptor tables display
11099 @itemx info dos ldt
11100 @itemx info dos idt
11101 These 3 commands display entries from, respectively, Global, Local,
11102 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11103 tables are data structures which store a descriptor for each segment
11104 that is currently in use. The segment's selector is an index into a
11105 descriptor table; the table entry for that index holds the
11106 descriptor's base address and limit, and its attributes and access
11109 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11110 segment (used for both data and the stack), and a DOS segment (which
11111 allows access to DOS/BIOS data structures and absolute addresses in
11112 conventional memory). However, the DPMI host will usually define
11113 additional segments in order to support the DPMI environment.
11115 @cindex garbled pointers
11116 These commands allow to display entries from the descriptor tables.
11117 Without an argument, all entries from the specified table are
11118 displayed. An argument, which should be an integer expression, means
11119 display a single entry whose index is given by the argument. For
11120 example, here's a convenient way to display information about the
11121 debugged program's data segment:
11124 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11125 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11129 This comes in handy when you want to see whether a pointer is outside
11130 the data segment's limit (i.e.@: @dfn{garbled}).
11132 @cindex page tables display (MS-DOS)
11134 @itemx info dos pte
11135 These two commands display entries from, respectively, the Page
11136 Directory and the Page Tables. Page Directories and Page Tables are
11137 data structures which control how virtual memory addresses are mapped
11138 into physical addresses. A Page Table includes an entry for every
11139 page of memory that is mapped into the program's address space; there
11140 may be several Page Tables, each one holding up to 4096 entries. A
11141 Page Directory has up to 4096 entries, one each for every Page Table
11142 that is currently in use.
11144 Without an argument, @kbd{info dos pde} displays the entire Page
11145 Directory, and @kbd{info dos pte} displays all the entries in all of
11146 the Page Tables. An argument, an integer expression, given to the
11147 @kbd{info dos pde} command means display only that entry from the Page
11148 Directory table. An argument given to the @kbd{info dos pte} command
11149 means display entries from a single Page Table, the one pointed to by
11150 the specified entry in the Page Directory.
11152 @cindex direct memory access (DMA) on MS-DOS
11153 These commands are useful when your program uses @dfn{DMA} (Direct
11154 Memory Access), which needs physical addresses to program the DMA
11157 These commands are supported only with some DPMI servers.
11159 @cindex physical address from linear address
11160 @item info dos address-pte @var{addr}
11161 This command displays the Page Table entry for a specified linear
11162 address. The argument linear address @var{addr} should already have the
11163 appropriate segment's base address added to it, because this command
11164 accepts addresses which may belong to @emph{any} segment. For
11165 example, here's how to display the Page Table entry for the page where
11166 the variable @code{i} is stored:
11169 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11170 @exdent @code{Page Table entry for address 0x11a00d30:}
11171 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11175 This says that @code{i} is stored at offset @code{0xd30} from the page
11176 whose physical base address is @code{0x02698000}, and prints all the
11177 attributes of that page.
11179 Note that you must cast the addresses of variables to a @code{char *},
11180 since otherwise the value of @code{__djgpp_base_address}, the base
11181 address of all variables and functions in a @sc{djgpp} program, will
11182 be added using the rules of C pointer arithmetics: if @code{i} is
11183 declared an @code{int}, @value{GDBN} will add 4 times the value of
11184 @code{__djgpp_base_address} to the address of @code{i}.
11186 Here's another example, it displays the Page Table entry for the
11190 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11191 @exdent @code{Page Table entry for address 0x29110:}
11192 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11196 (The @code{+ 3} offset is because the transfer buffer's address is the
11197 3rd member of the @code{_go32_info_block} structure.) The output of
11198 this command clearly shows that addresses in conventional memory are
11199 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11201 This command is supported only with some DPMI servers.
11204 @node Cygwin Native
11205 @subsection Features for Debugging MS Windows PE executables
11206 @cindex MS Windows debugging
11207 @cindex native Cygwin debugging
11208 @cindex Cygwin-specific commands
11210 @value{GDBN} supports native debugging of MS Windows programs, including
11211 DLLs with and without symbolic debugging information. There are various
11212 additional Cygwin-specific commands, described in this subsection. The
11213 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
11214 that have no debugging symbols.
11220 This is a prefix of MS Windows specific commands which print
11221 information about the target system and important OS structures.
11223 @item info w32 selector
11224 This command displays information returned by
11225 the Win32 API @code{GetThreadSelectorEntry} function.
11226 It takes an optional argument that is evaluated to
11227 a long value to give the information about this given selector.
11228 Without argument, this command displays information
11229 about the the six segment registers.
11233 This is a Cygwin specific alias of info shared.
11235 @kindex dll-symbols
11237 This command loads symbols from a dll similarly to
11238 add-sym command but without the need to specify a base address.
11240 @kindex set new-console
11241 @item set new-console @var{mode}
11242 If @var{mode} is @code{on} the debuggee will
11243 be started in a new console on next start.
11244 If @var{mode} is @code{off}i, the debuggee will
11245 be started in the same console as the debugger.
11247 @kindex show new-console
11248 @item show new-console
11249 Displays whether a new console is used
11250 when the debuggee is started.
11252 @kindex set new-group
11253 @item set new-group @var{mode}
11254 This boolean value controls whether the debuggee should
11255 start a new group or stay in the same group as the debugger.
11256 This affects the way the Windows OS handles
11259 @kindex show new-group
11260 @item show new-group
11261 Displays current value of new-group boolean.
11263 @kindex set debugevents
11264 @item set debugevents
11265 This boolean value adds debug output concerning events seen by the debugger.
11267 @kindex set debugexec
11268 @item set debugexec
11269 This boolean value adds debug output concerning execute events
11270 seen by the debugger.
11272 @kindex set debugexceptions
11273 @item set debugexceptions
11274 This boolean value adds debug ouptut concerning exception events
11275 seen by the debugger.
11277 @kindex set debugmemory
11278 @item set debugmemory
11279 This boolean value adds debug ouptut concerning memory events
11280 seen by the debugger.
11284 This boolean values specifies whether the debuggee is called
11285 via a shell or directly (default value is on).
11289 Displays if the debuggee will be started with a shell.
11294 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
11297 @node Non-debug DLL symbols
11298 @subsubsection Support for DLLs without debugging symbols
11299 @cindex DLLs with no debugging symbols
11300 @cindex Minimal symbols and DLLs
11302 Very often on windows, some of the DLLs that your program relies on do
11303 not include symbolic debugging information (for example,
11304 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
11305 symbols in a DLL, it relies on the minimal amount of symbolic
11306 information contained in the DLL's export table. This subsubsection
11307 describes working with such symbols, known internally to @value{GDBN} as
11308 ``minimal symbols''.
11310 Note that before the debugged program has started execution, no DLLs
11311 will have been loaded. The easiest way around this problem is simply to
11312 start the program --- either by setting a breakpoint or letting the
11313 program run once to completion. It is also possible to force
11314 @value{GDBN} to load a particular DLL before starting the executable ---
11315 see the shared library information in @pxref{Files} or the
11316 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
11317 explicitly loading symbols from a DLL with no debugging information will
11318 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
11319 which may adversely affect symbol lookup performance.
11321 @subsubsection DLL name prefixes
11323 In keeping with the naming conventions used by the Microsoft debugging
11324 tools, DLL export symbols are made available with a prefix based on the
11325 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
11326 also entered into the symbol table, so @code{CreateFileA} is often
11327 sufficient. In some cases there will be name clashes within a program
11328 (particularly if the executable itself includes full debugging symbols)
11329 necessitating the use of the fully qualified name when referring to the
11330 contents of the DLL. Use single-quotes around the name to avoid the
11331 exclamation mark (``!'') being interpreted as a language operator.
11333 Note that the internal name of the DLL may be all upper-case, even
11334 though the file name of the DLL is lower-case, or vice-versa. Since
11335 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
11336 some confusion. If in doubt, try the @code{info functions} and
11337 @code{info variables} commands or even @code{maint print msymbols} (see
11338 @pxref{Symbols}). Here's an example:
11341 (gdb) info function CreateFileA
11342 All functions matching regular expression "CreateFileA":
11344 Non-debugging symbols:
11345 0x77e885f4 CreateFileA
11346 0x77e885f4 KERNEL32!CreateFileA
11350 (gdb) info function !
11351 All functions matching regular expression "!":
11353 Non-debugging symbols:
11354 0x6100114c cygwin1!__assert
11355 0x61004034 cygwin1!_dll_crt0@@0
11356 0x61004240 cygwin1!dll_crt0(per_process *)
11360 @subsubsection Working with minimal symbols
11362 Symbols extracted from a DLL's export table do not contain very much
11363 type information. All that @value{GDBN} can do is guess whether a symbol
11364 refers to a function or variable depending on the linker section that
11365 contains the symbol. Also note that the actual contents of the memory
11366 contained in a DLL are not available unless the program is running. This
11367 means that you cannot examine the contents of a variable or disassemble
11368 a function within a DLL without a running program.
11370 Variables are generally treated as pointers and dereferenced
11371 automatically. For this reason, it is often necessary to prefix a
11372 variable name with the address-of operator (``&'') and provide explicit
11373 type information in the command. Here's an example of the type of
11377 (gdb) print 'cygwin1!__argv'
11382 (gdb) x 'cygwin1!__argv'
11383 0x10021610: "\230y\""
11386 And two possible solutions:
11389 (gdb) print ((char **)'cygwin1!__argv')[0]
11390 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
11394 (gdb) x/2x &'cygwin1!__argv'
11395 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
11396 (gdb) x/x 0x10021608
11397 0x10021608: 0x0022fd98
11398 (gdb) x/s 0x0022fd98
11399 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
11402 Setting a break point within a DLL is possible even before the program
11403 starts execution. However, under these circumstances, @value{GDBN} can't
11404 examine the initial instructions of the function in order to skip the
11405 function's frame set-up code. You can work around this by using ``*&''
11406 to set the breakpoint at a raw memory address:
11409 (gdb) break *&'python22!PyOS_Readline'
11410 Breakpoint 1 at 0x1e04eff0
11413 The author of these extensions is not entirely convinced that setting a
11414 break point within a shared DLL like @file{kernel32.dll} is completely
11418 @section Embedded Operating Systems
11420 This section describes configurations involving the debugging of
11421 embedded operating systems that are available for several different
11425 * VxWorks:: Using @value{GDBN} with VxWorks
11428 @value{GDBN} includes the ability to debug programs running on
11429 various real-time operating systems.
11432 @subsection Using @value{GDBN} with VxWorks
11438 @kindex target vxworks
11439 @item target vxworks @var{machinename}
11440 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11441 is the target system's machine name or IP address.
11445 On VxWorks, @code{load} links @var{filename} dynamically on the
11446 current target system as well as adding its symbols in @value{GDBN}.
11448 @value{GDBN} enables developers to spawn and debug tasks running on networked
11449 VxWorks targets from a Unix host. Already-running tasks spawned from
11450 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11451 both the Unix host and on the VxWorks target. The program
11452 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11453 installed with the name @code{vxgdb}, to distinguish it from a
11454 @value{GDBN} for debugging programs on the host itself.)
11457 @item VxWorks-timeout @var{args}
11458 @kindex vxworks-timeout
11459 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11460 This option is set by the user, and @var{args} represents the number of
11461 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11462 your VxWorks target is a slow software simulator or is on the far side
11463 of a thin network line.
11466 The following information on connecting to VxWorks was current when
11467 this manual was produced; newer releases of VxWorks may use revised
11470 @kindex INCLUDE_RDB
11471 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11472 to include the remote debugging interface routines in the VxWorks
11473 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11474 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11475 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11476 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11477 information on configuring and remaking VxWorks, see the manufacturer's
11479 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11481 Once you have included @file{rdb.a} in your VxWorks system image and set
11482 your Unix execution search path to find @value{GDBN}, you are ready to
11483 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11484 @code{vxgdb}, depending on your installation).
11486 @value{GDBN} comes up showing the prompt:
11493 * VxWorks Connection:: Connecting to VxWorks
11494 * VxWorks Download:: VxWorks download
11495 * VxWorks Attach:: Running tasks
11498 @node VxWorks Connection
11499 @subsubsection Connecting to VxWorks
11501 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11502 network. To connect to a target whose host name is ``@code{tt}'', type:
11505 (vxgdb) target vxworks tt
11509 @value{GDBN} displays messages like these:
11512 Attaching remote machine across net...
11517 @value{GDBN} then attempts to read the symbol tables of any object modules
11518 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11519 these files by searching the directories listed in the command search
11520 path (@pxref{Environment, ,Your program's environment}); if it fails
11521 to find an object file, it displays a message such as:
11524 prog.o: No such file or directory.
11527 When this happens, add the appropriate directory to the search path with
11528 the @value{GDBN} command @code{path}, and execute the @code{target}
11531 @node VxWorks Download
11532 @subsubsection VxWorks download
11534 @cindex download to VxWorks
11535 If you have connected to the VxWorks target and you want to debug an
11536 object that has not yet been loaded, you can use the @value{GDBN}
11537 @code{load} command to download a file from Unix to VxWorks
11538 incrementally. The object file given as an argument to the @code{load}
11539 command is actually opened twice: first by the VxWorks target in order
11540 to download the code, then by @value{GDBN} in order to read the symbol
11541 table. This can lead to problems if the current working directories on
11542 the two systems differ. If both systems have NFS mounted the same
11543 filesystems, you can avoid these problems by using absolute paths.
11544 Otherwise, it is simplest to set the working directory on both systems
11545 to the directory in which the object file resides, and then to reference
11546 the file by its name, without any path. For instance, a program
11547 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11548 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11549 program, type this on VxWorks:
11552 -> cd "@var{vxpath}/vw/demo/rdb"
11556 Then, in @value{GDBN}, type:
11559 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11560 (vxgdb) load prog.o
11563 @value{GDBN} displays a response similar to this:
11566 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11569 You can also use the @code{load} command to reload an object module
11570 after editing and recompiling the corresponding source file. Note that
11571 this makes @value{GDBN} delete all currently-defined breakpoints,
11572 auto-displays, and convenience variables, and to clear the value
11573 history. (This is necessary in order to preserve the integrity of
11574 debugger's data structures that reference the target system's symbol
11577 @node VxWorks Attach
11578 @subsubsection Running tasks
11580 @cindex running VxWorks tasks
11581 You can also attach to an existing task using the @code{attach} command as
11585 (vxgdb) attach @var{task}
11589 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11590 or suspended when you attach to it. Running tasks are suspended at
11591 the time of attachment.
11593 @node Embedded Processors
11594 @section Embedded Processors
11596 This section goes into details specific to particular embedded
11602 * H8/300:: Hitachi H8/300
11603 * H8/500:: Hitachi H8/500
11604 * M32R/D:: Mitsubishi M32R/D
11605 * M68K:: Motorola M68K
11606 * MIPS Embedded:: MIPS Embedded
11607 * OpenRISC 1000:: OpenRisc 1000
11608 * PA:: HP PA Embedded
11611 * Sparclet:: Tsqware Sparclet
11612 * Sparclite:: Fujitsu Sparclite
11613 * ST2000:: Tandem ST2000
11614 * Z8000:: Zilog Z8000
11623 @item target rdi @var{dev}
11624 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11625 use this target to communicate with both boards running the Angel
11626 monitor, or with the EmbeddedICE JTAG debug device.
11629 @item target rdp @var{dev}
11635 @subsection Hitachi H8/300
11639 @kindex target hms@r{, with H8/300}
11640 @item target hms @var{dev}
11641 A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host.
11642 Use special commands @code{device} and @code{speed} to control the serial
11643 line and the communications speed used.
11645 @kindex target e7000@r{, with H8/300}
11646 @item target e7000 @var{dev}
11647 E7000 emulator for Hitachi H8 and SH.
11649 @kindex target sh3@r{, with H8/300}
11650 @kindex target sh3e@r{, with H8/300}
11651 @item target sh3 @var{dev}
11652 @itemx target sh3e @var{dev}
11653 Hitachi SH-3 and SH-3E target systems.
11657 @cindex download to H8/300 or H8/500
11658 @cindex H8/300 or H8/500 download
11659 @cindex download to Hitachi SH
11660 @cindex Hitachi SH download
11661 When you select remote debugging to a Hitachi SH, H8/300, or H8/500
11662 board, the @code{load} command downloads your program to the Hitachi
11663 board and also opens it as the current executable target for
11664 @value{GDBN} on your host (like the @code{file} command).
11666 @value{GDBN} needs to know these things to talk to your
11667 Hitachi SH, H8/300, or H8/500:
11671 that you want to use @samp{target hms}, the remote debugging interface
11672 for Hitachi microprocessors, or @samp{target e7000}, the in-circuit
11673 emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is
11674 the default when @value{GDBN} is configured specifically for the Hitachi SH,
11675 H8/300, or H8/500.)
11678 what serial device connects your host to your Hitachi board (the first
11679 serial device available on your host is the default).
11682 what speed to use over the serial device.
11686 * Hitachi Boards:: Connecting to Hitachi boards.
11687 * Hitachi ICE:: Using the E7000 In-Circuit Emulator.
11688 * Hitachi Special:: Special @value{GDBN} commands for Hitachi micros.
11691 @node Hitachi Boards
11692 @subsubsection Connecting to Hitachi boards
11694 @c only for Unix hosts
11696 @cindex serial device, Hitachi micros
11697 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11698 need to explicitly set the serial device. The default @var{port} is the
11699 first available port on your host. This is only necessary on Unix
11700 hosts, where it is typically something like @file{/dev/ttya}.
11703 @cindex serial line speed, Hitachi micros
11704 @code{@value{GDBN}} has another special command to set the communications
11705 speed: @samp{speed @var{bps}}. This command also is only used from Unix
11706 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11707 the DOS @code{mode} command (for instance,
11708 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11710 The @samp{device} and @samp{speed} commands are available only when you
11711 use a Unix host to debug your Hitachi microprocessor programs. If you
11713 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11714 called @code{asynctsr} to communicate with the development board
11715 through a PC serial port. You must also use the DOS @code{mode} command
11716 to set up the serial port on the DOS side.
11718 The following sample session illustrates the steps needed to start a
11719 program under @value{GDBN} control on an H8/300. The example uses a
11720 sample H8/300 program called @file{t.x}. The procedure is the same for
11721 the Hitachi SH and the H8/500.
11723 First hook up your development board. In this example, we use a
11724 board attached to serial port @code{COM2}; if you use a different serial
11725 port, substitute its name in the argument of the @code{mode} command.
11726 When you call @code{asynctsr}, the auxiliary comms program used by the
11727 debugger, you give it just the numeric part of the serial port's name;
11728 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
11732 C:\H8300\TEST> asynctsr 2
11733 C:\H8300\TEST> mode com2:9600,n,8,1,p
11735 Resident portion of MODE loaded
11737 COM2: 9600, n, 8, 1, p
11742 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
11743 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
11744 disable it, or even boot without it, to use @code{asynctsr} to control
11745 your development board.
11748 @kindex target hms@r{, and serial protocol}
11749 Now that serial communications are set up, and the development board is
11750 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
11751 the name of your program as the argument. @code{@value{GDBN}} prompts
11752 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
11753 commands to begin your debugging session: @samp{target hms} to specify
11754 cross-debugging to the Hitachi board, and the @code{load} command to
11755 download your program to the board. @code{load} displays the names of
11756 the program's sections, and a @samp{*} for each 2K of data downloaded.
11757 (If you want to refresh @value{GDBN} data on symbols or on the
11758 executable file without downloading, use the @value{GDBN} commands
11759 @code{file} or @code{symbol-file}. These commands, and @code{load}
11760 itself, are described in @ref{Files,,Commands to specify files}.)
11763 (eg-C:\H8300\TEST) @value{GDBP} t.x
11764 @value{GDBN} is free software and you are welcome to distribute copies
11765 of it under certain conditions; type "show copying" to see
11767 There is absolutely no warranty for @value{GDBN}; type "show warranty"
11769 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
11770 (@value{GDBP}) target hms
11771 Connected to remote H8/300 HMS system.
11772 (@value{GDBP}) load t.x
11773 .text : 0x8000 .. 0xabde ***********
11774 .data : 0xabde .. 0xad30 *
11775 .stack : 0xf000 .. 0xf014 *
11778 At this point, you're ready to run or debug your program. From here on,
11779 you can use all the usual @value{GDBN} commands. The @code{break} command
11780 sets breakpoints; the @code{run} command starts your program;
11781 @code{print} or @code{x} display data; the @code{continue} command
11782 resumes execution after stopping at a breakpoint. You can use the
11783 @code{help} command at any time to find out more about @value{GDBN} commands.
11785 Remember, however, that @emph{operating system} facilities aren't
11786 available on your development board; for example, if your program hangs,
11787 you can't send an interrupt---but you can press the @sc{reset} switch!
11789 Use the @sc{reset} button on the development board
11792 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
11793 no way to pass an interrupt signal to the development board); and
11796 to return to the @value{GDBN} command prompt after your program finishes
11797 normally. The communications protocol provides no other way for @value{GDBN}
11798 to detect program completion.
11801 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
11802 development board as a ``normal exit'' of your program.
11805 @subsubsection Using the E7000 in-circuit emulator
11807 @kindex target e7000@r{, with Hitachi ICE}
11808 You can use the E7000 in-circuit emulator to develop code for either the
11809 Hitachi SH or the H8/300H. Use one of these forms of the @samp{target
11810 e7000} command to connect @value{GDBN} to your E7000:
11813 @item target e7000 @var{port} @var{speed}
11814 Use this form if your E7000 is connected to a serial port. The
11815 @var{port} argument identifies what serial port to use (for example,
11816 @samp{com2}). The third argument is the line speed in bits per second
11817 (for example, @samp{9600}).
11819 @item target e7000 @var{hostname}
11820 If your E7000 is installed as a host on a TCP/IP network, you can just
11821 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
11824 @node Hitachi Special
11825 @subsubsection Special @value{GDBN} commands for Hitachi micros
11827 Some @value{GDBN} commands are available only for the H8/300:
11831 @kindex set machine
11832 @kindex show machine
11833 @item set machine h8300
11834 @itemx set machine h8300h
11835 Condition @value{GDBN} for one of the two variants of the H8/300
11836 architecture with @samp{set machine}. You can use @samp{show machine}
11837 to check which variant is currently in effect.
11846 @kindex set memory @var{mod}
11847 @cindex memory models, H8/500
11848 @item set memory @var{mod}
11850 Specify which H8/500 memory model (@var{mod}) you are using with
11851 @samp{set memory}; check which memory model is in effect with @samp{show
11852 memory}. The accepted values for @var{mod} are @code{small},
11853 @code{big}, @code{medium}, and @code{compact}.
11858 @subsection Mitsubishi M32R/D
11862 @kindex target m32r
11863 @item target m32r @var{dev}
11864 Mitsubishi M32R/D ROM monitor.
11871 The Motorola m68k configuration includes ColdFire support, and
11872 target command for the following ROM monitors.
11876 @kindex target abug
11877 @item target abug @var{dev}
11878 ABug ROM monitor for M68K.
11880 @kindex target cpu32bug
11881 @item target cpu32bug @var{dev}
11882 CPU32BUG monitor, running on a CPU32 (M68K) board.
11884 @kindex target dbug
11885 @item target dbug @var{dev}
11886 dBUG ROM monitor for Motorola ColdFire.
11889 @item target est @var{dev}
11890 EST-300 ICE monitor, running on a CPU32 (M68K) board.
11892 @kindex target rom68k
11893 @item target rom68k @var{dev}
11894 ROM 68K monitor, running on an M68K IDP board.
11900 @kindex target rombug
11901 @item target rombug @var{dev}
11902 ROMBUG ROM monitor for OS/9000.
11906 @node MIPS Embedded
11907 @subsection MIPS Embedded
11909 @cindex MIPS boards
11910 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
11911 MIPS board attached to a serial line. This is available when
11912 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
11915 Use these @value{GDBN} commands to specify the connection to your target board:
11918 @item target mips @var{port}
11919 @kindex target mips @var{port}
11920 To run a program on the board, start up @code{@value{GDBP}} with the
11921 name of your program as the argument. To connect to the board, use the
11922 command @samp{target mips @var{port}}, where @var{port} is the name of
11923 the serial port connected to the board. If the program has not already
11924 been downloaded to the board, you may use the @code{load} command to
11925 download it. You can then use all the usual @value{GDBN} commands.
11927 For example, this sequence connects to the target board through a serial
11928 port, and loads and runs a program called @var{prog} through the
11932 host$ @value{GDBP} @var{prog}
11933 @value{GDBN} is free software and @dots{}
11934 (@value{GDBP}) target mips /dev/ttyb
11935 (@value{GDBP}) load @var{prog}
11939 @item target mips @var{hostname}:@var{portnumber}
11940 On some @value{GDBN} host configurations, you can specify a TCP
11941 connection (for instance, to a serial line managed by a terminal
11942 concentrator) instead of a serial port, using the syntax
11943 @samp{@var{hostname}:@var{portnumber}}.
11945 @item target pmon @var{port}
11946 @kindex target pmon @var{port}
11949 @item target ddb @var{port}
11950 @kindex target ddb @var{port}
11951 NEC's DDB variant of PMON for Vr4300.
11953 @item target lsi @var{port}
11954 @kindex target lsi @var{port}
11955 LSI variant of PMON.
11957 @kindex target r3900
11958 @item target r3900 @var{dev}
11959 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
11961 @kindex target array
11962 @item target array @var{dev}
11963 Array Tech LSI33K RAID controller board.
11969 @value{GDBN} also supports these special commands for MIPS targets:
11972 @item set processor @var{args}
11973 @itemx show processor
11974 @kindex set processor @var{args}
11975 @kindex show processor
11976 Use the @code{set processor} command to set the type of MIPS
11977 processor when you want to access processor-type-specific registers.
11978 For example, @code{set processor @var{r3041}} tells @value{GDBN}
11979 to use the CPU registers appropriate for the 3041 chip.
11980 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
11981 is using. Use the @code{info reg} command to see what registers
11982 @value{GDBN} is using.
11984 @item set mipsfpu double
11985 @itemx set mipsfpu single
11986 @itemx set mipsfpu none
11987 @itemx show mipsfpu
11988 @kindex set mipsfpu
11989 @kindex show mipsfpu
11990 @cindex MIPS remote floating point
11991 @cindex floating point, MIPS remote
11992 If your target board does not support the MIPS floating point
11993 coprocessor, you should use the command @samp{set mipsfpu none} (if you
11994 need this, you may wish to put the command in your @value{GDBN} init
11995 file). This tells @value{GDBN} how to find the return value of
11996 functions which return floating point values. It also allows
11997 @value{GDBN} to avoid saving the floating point registers when calling
11998 functions on the board. If you are using a floating point coprocessor
11999 with only single precision floating point support, as on the @sc{r4650}
12000 processor, use the command @samp{set mipsfpu single}. The default
12001 double precision floating point coprocessor may be selected using
12002 @samp{set mipsfpu double}.
12004 In previous versions the only choices were double precision or no
12005 floating point, so @samp{set mipsfpu on} will select double precision
12006 and @samp{set mipsfpu off} will select no floating point.
12008 As usual, you can inquire about the @code{mipsfpu} variable with
12009 @samp{show mipsfpu}.
12011 @item set remotedebug @var{n}
12012 @itemx show remotedebug
12013 @kindex set remotedebug@r{, MIPS protocol}
12014 @kindex show remotedebug@r{, MIPS protocol}
12015 @cindex @code{remotedebug}, MIPS protocol
12016 @cindex MIPS @code{remotedebug} protocol
12017 @c FIXME! For this to be useful, you must know something about the MIPS
12018 @c FIXME...protocol. Where is it described?
12019 You can see some debugging information about communications with the board
12020 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12021 @samp{set remotedebug 1}, every packet is displayed. If you set it
12022 to @code{2}, every character is displayed. You can check the current value
12023 at any time with the command @samp{show remotedebug}.
12025 @item set timeout @var{seconds}
12026 @itemx set retransmit-timeout @var{seconds}
12027 @itemx show timeout
12028 @itemx show retransmit-timeout
12029 @cindex @code{timeout}, MIPS protocol
12030 @cindex @code{retransmit-timeout}, MIPS protocol
12031 @kindex set timeout
12032 @kindex show timeout
12033 @kindex set retransmit-timeout
12034 @kindex show retransmit-timeout
12035 You can control the timeout used while waiting for a packet, in the MIPS
12036 remote protocol, with the @code{set timeout @var{seconds}} command. The
12037 default is 5 seconds. Similarly, you can control the timeout used while
12038 waiting for an acknowledgement of a packet with the @code{set
12039 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12040 You can inspect both values with @code{show timeout} and @code{show
12041 retransmit-timeout}. (These commands are @emph{only} available when
12042 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12044 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12045 is waiting for your program to stop. In that case, @value{GDBN} waits
12046 forever because it has no way of knowing how long the program is going
12047 to run before stopping.
12050 @node OpenRISC 1000
12051 @subsection OpenRISC 1000
12052 @cindex OpenRISC 1000
12054 @cindex or1k boards
12055 See OR1k Architecture document (@uref{www.opencores.org}) for more information
12056 about platform and commands.
12060 @kindex target jtag
12061 @item target jtag jtag://@var{host}:@var{port}
12063 Connects to remote JTAG server.
12064 JTAG remote server can be either an or1ksim or JTAG server,
12065 connected via parallel port to the board.
12067 Example: @code{target jtag jtag://localhost:9999}
12070 @item or1ksim @var{command}
12071 If connected to @code{or1ksim} OpenRISC 1000 Architectural
12072 Simulator, proprietary commands can be executed.
12074 @kindex info or1k spr
12075 @item info or1k spr
12076 Displays spr groups.
12078 @item info or1k spr @var{group}
12079 @itemx info or1k spr @var{groupno}
12080 Displays register names in selected group.
12082 @item info or1k spr @var{group} @var{register}
12083 @itemx info or1k spr @var{register}
12084 @itemx info or1k spr @var{groupno} @var{registerno}
12085 @itemx info or1k spr @var{registerno}
12086 Shows information about specified spr register.
12089 @item spr @var{group} @var{register} @var{value}
12090 @itemx spr @var{register @var{value}}
12091 @itemx spr @var{groupno} @var{registerno @var{value}}
12092 @itemx spr @var{registerno @var{value}}
12093 Writes @var{value} to specified spr register.
12096 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
12097 It is very similar to @value{GDBN} trace, except it does not interfere with normal
12098 program execution and is thus much faster. Hardware breakpoints/watchpoint
12099 triggers can be set using:
12102 Load effective address/data
12104 Store effective address/data
12106 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
12111 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
12112 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
12114 @code{htrace} commands:
12115 @cindex OpenRISC 1000 htrace
12118 @item hwatch @var{conditional}
12119 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
12120 or Data. For example:
12122 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12124 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
12126 @kindex htrace info
12128 Display information about current HW trace configuration.
12130 @kindex htrace trigger
12131 @item htrace trigger @var{conditional}
12132 Set starting criteria for HW trace.
12134 @kindex htrace qualifier
12135 @item htrace qualifier @var{conditional}
12136 Set acquisition qualifier for HW trace.
12138 @kindex htrace stop
12139 @item htrace stop @var{conditional}
12140 Set HW trace stopping criteria.
12142 @kindex htrace record
12143 @item htrace record [@var{data}]*
12144 Selects the data to be recorded, when qualifier is met and HW trace was
12147 @kindex htrace enable
12148 @item htrace enable
12149 @kindex htrace disable
12150 @itemx htrace disable
12151 Enables/disables the HW trace.
12153 @kindex htrace rewind
12154 @item htrace rewind [@var{filename}]
12155 Clears currently recorded trace data.
12157 If filename is specified, new trace file is made and any newly collected data
12158 will be written there.
12160 @kindex htrace print
12161 @item htrace print [@var{start} [@var{len}]]
12162 Prints trace buffer, using current record configuration.
12164 @kindex htrace mode continuous
12165 @item htrace mode continuous
12166 Set continuous trace mode.
12168 @kindex htrace mode suspend
12169 @item htrace mode suspend
12170 Set suspend trace mode.
12175 @subsection PowerPC
12179 @kindex target dink32
12180 @item target dink32 @var{dev}
12181 DINK32 ROM monitor.
12183 @kindex target ppcbug
12184 @item target ppcbug @var{dev}
12185 @kindex target ppcbug1
12186 @item target ppcbug1 @var{dev}
12187 PPCBUG ROM monitor for PowerPC.
12190 @item target sds @var{dev}
12191 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12196 @subsection HP PA Embedded
12200 @kindex target op50n
12201 @item target op50n @var{dev}
12202 OP50N monitor, running on an OKI HPPA board.
12204 @kindex target w89k
12205 @item target w89k @var{dev}
12206 W89K monitor, running on a Winbond HPPA board.
12211 @subsection Hitachi SH
12215 @kindex target hms@r{, with Hitachi SH}
12216 @item target hms @var{dev}
12217 A Hitachi SH board attached via serial line to your host. Use special
12218 commands @code{device} and @code{speed} to control the serial line and
12219 the communications speed used.
12221 @kindex target e7000@r{, with Hitachi SH}
12222 @item target e7000 @var{dev}
12223 E7000 emulator for Hitachi SH.
12225 @kindex target sh3@r{, with SH}
12226 @kindex target sh3e@r{, with SH}
12227 @item target sh3 @var{dev}
12228 @item target sh3e @var{dev}
12229 Hitachi SH-3 and SH-3E target systems.
12234 @subsection Tsqware Sparclet
12238 @value{GDBN} enables developers to debug tasks running on
12239 Sparclet targets from a Unix host.
12240 @value{GDBN} uses code that runs on
12241 both the Unix host and on the Sparclet target. The program
12242 @code{@value{GDBP}} is installed and executed on the Unix host.
12245 @item remotetimeout @var{args}
12246 @kindex remotetimeout
12247 @value{GDBN} supports the option @code{remotetimeout}.
12248 This option is set by the user, and @var{args} represents the number of
12249 seconds @value{GDBN} waits for responses.
12252 @cindex compiling, on Sparclet
12253 When compiling for debugging, include the options @samp{-g} to get debug
12254 information and @samp{-Ttext} to relocate the program to where you wish to
12255 load it on the target. You may also want to add the options @samp{-n} or
12256 @samp{-N} in order to reduce the size of the sections. Example:
12259 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12262 You can use @code{objdump} to verify that the addresses are what you intended:
12265 sparclet-aout-objdump --headers --syms prog
12268 @cindex running, on Sparclet
12270 your Unix execution search path to find @value{GDBN}, you are ready to
12271 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12272 (or @code{sparclet-aout-gdb}, depending on your installation).
12274 @value{GDBN} comes up showing the prompt:
12281 * Sparclet File:: Setting the file to debug
12282 * Sparclet Connection:: Connecting to Sparclet
12283 * Sparclet Download:: Sparclet download
12284 * Sparclet Execution:: Running and debugging
12287 @node Sparclet File
12288 @subsubsection Setting file to debug
12290 The @value{GDBN} command @code{file} lets you choose with program to debug.
12293 (gdbslet) file prog
12297 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12298 @value{GDBN} locates
12299 the file by searching the directories listed in the command search
12301 If the file was compiled with debug information (option "-g"), source
12302 files will be searched as well.
12303 @value{GDBN} locates
12304 the source files by searching the directories listed in the directory search
12305 path (@pxref{Environment, ,Your program's environment}).
12307 to find a file, it displays a message such as:
12310 prog: No such file or directory.
12313 When this happens, add the appropriate directories to the search paths with
12314 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12315 @code{target} command again.
12317 @node Sparclet Connection
12318 @subsubsection Connecting to Sparclet
12320 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12321 To connect to a target on serial port ``@code{ttya}'', type:
12324 (gdbslet) target sparclet /dev/ttya
12325 Remote target sparclet connected to /dev/ttya
12326 main () at ../prog.c:3
12330 @value{GDBN} displays messages like these:
12336 @node Sparclet Download
12337 @subsubsection Sparclet download
12339 @cindex download to Sparclet
12340 Once connected to the Sparclet target,
12341 you can use the @value{GDBN}
12342 @code{load} command to download the file from the host to the target.
12343 The file name and load offset should be given as arguments to the @code{load}
12345 Since the file format is aout, the program must be loaded to the starting
12346 address. You can use @code{objdump} to find out what this value is. The load
12347 offset is an offset which is added to the VMA (virtual memory address)
12348 of each of the file's sections.
12349 For instance, if the program
12350 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12351 and bss at 0x12010170, in @value{GDBN}, type:
12354 (gdbslet) load prog 0x12010000
12355 Loading section .text, size 0xdb0 vma 0x12010000
12358 If the code is loaded at a different address then what the program was linked
12359 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12360 to tell @value{GDBN} where to map the symbol table.
12362 @node Sparclet Execution
12363 @subsubsection Running and debugging
12365 @cindex running and debugging Sparclet programs
12366 You can now begin debugging the task using @value{GDBN}'s execution control
12367 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12368 manual for the list of commands.
12372 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12374 Starting program: prog
12375 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12376 3 char *symarg = 0;
12378 4 char *execarg = "hello!";
12383 @subsection Fujitsu Sparclite
12387 @kindex target sparclite
12388 @item target sparclite @var{dev}
12389 Fujitsu sparclite boards, used only for the purpose of loading.
12390 You must use an additional command to debug the program.
12391 For example: target remote @var{dev} using @value{GDBN} standard
12397 @subsection Tandem ST2000
12399 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12402 To connect your ST2000 to the host system, see the manufacturer's
12403 manual. Once the ST2000 is physically attached, you can run:
12406 target st2000 @var{dev} @var{speed}
12410 to establish it as your debugging environment. @var{dev} is normally
12411 the name of a serial device, such as @file{/dev/ttya}, connected to the
12412 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12413 connection (for example, to a serial line attached via a terminal
12414 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12416 The @code{load} and @code{attach} commands are @emph{not} defined for
12417 this target; you must load your program into the ST2000 as you normally
12418 would for standalone operation. @value{GDBN} reads debugging information
12419 (such as symbols) from a separate, debugging version of the program
12420 available on your host computer.
12421 @c FIXME!! This is terribly vague; what little content is here is
12422 @c basically hearsay.
12424 @cindex ST2000 auxiliary commands
12425 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12429 @item st2000 @var{command}
12430 @kindex st2000 @var{cmd}
12431 @cindex STDBUG commands (ST2000)
12432 @cindex commands to STDBUG (ST2000)
12433 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12434 manual for available commands.
12437 @cindex connect (to STDBUG)
12438 Connect the controlling terminal to the STDBUG command monitor. When
12439 you are done interacting with STDBUG, typing either of two character
12440 sequences gets you back to the @value{GDBN} command prompt:
12441 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12442 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12446 @subsection Zilog Z8000
12449 @cindex simulator, Z8000
12450 @cindex Zilog Z8000 simulator
12452 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12455 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12456 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12457 segmented variant). The simulator recognizes which architecture is
12458 appropriate by inspecting the object code.
12461 @item target sim @var{args}
12463 @kindex target sim@r{, with Z8000}
12464 Debug programs on a simulated CPU. If the simulator supports setup
12465 options, specify them via @var{args}.
12469 After specifying this target, you can debug programs for the simulated
12470 CPU in the same style as programs for your host computer; use the
12471 @code{file} command to load a new program image, the @code{run} command
12472 to run your program, and so on.
12474 As well as making available all the usual machine registers
12475 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12476 additional items of information as specially named registers:
12481 Counts clock-ticks in the simulator.
12484 Counts instructions run in the simulator.
12487 Execution time in 60ths of a second.
12491 You can refer to these values in @value{GDBN} expressions with the usual
12492 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12493 conditional breakpoint that suspends only after at least 5000
12494 simulated clock ticks.
12496 @node Architectures
12497 @section Architectures
12499 This section describes characteristics of architectures that affect
12500 all uses of @value{GDBN} with the architecture, both native and cross.
12513 @kindex set rstack_high_address
12514 @cindex AMD 29K register stack
12515 @cindex register stack, AMD29K
12516 @item set rstack_high_address @var{address}
12517 On AMD 29000 family processors, registers are saved in a separate
12518 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12519 extent of this stack. Normally, @value{GDBN} just assumes that the
12520 stack is ``large enough''. This may result in @value{GDBN} referencing
12521 memory locations that do not exist. If necessary, you can get around
12522 this problem by specifying the ending address of the register stack with
12523 the @code{set rstack_high_address} command. The argument should be an
12524 address, which you probably want to precede with @samp{0x} to specify in
12527 @kindex show rstack_high_address
12528 @item show rstack_high_address
12529 Display the current limit of the register stack, on AMD 29000 family
12537 See the following section.
12542 @cindex stack on Alpha
12543 @cindex stack on MIPS
12544 @cindex Alpha stack
12546 Alpha- and MIPS-based computers use an unusual stack frame, which
12547 sometimes requires @value{GDBN} to search backward in the object code to
12548 find the beginning of a function.
12550 @cindex response time, MIPS debugging
12551 To improve response time (especially for embedded applications, where
12552 @value{GDBN} may be restricted to a slow serial line for this search)
12553 you may want to limit the size of this search, using one of these
12557 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12558 @item set heuristic-fence-post @var{limit}
12559 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12560 search for the beginning of a function. A value of @var{0} (the
12561 default) means there is no limit. However, except for @var{0}, the
12562 larger the limit the more bytes @code{heuristic-fence-post} must search
12563 and therefore the longer it takes to run.
12565 @item show heuristic-fence-post
12566 Display the current limit.
12570 These commands are available @emph{only} when @value{GDBN} is configured
12571 for debugging programs on Alpha or MIPS processors.
12574 @node Controlling GDB
12575 @chapter Controlling @value{GDBN}
12577 You can alter the way @value{GDBN} interacts with you by using the
12578 @code{set} command. For commands controlling how @value{GDBN} displays
12579 data, see @ref{Print Settings, ,Print settings}. Other settings are
12584 * Editing:: Command editing
12585 * History:: Command history
12586 * Screen Size:: Screen size
12587 * Numbers:: Numbers
12588 * ABI:: Configuring the current ABI
12589 * Messages/Warnings:: Optional warnings and messages
12590 * Debugging Output:: Optional messages about internal happenings
12598 @value{GDBN} indicates its readiness to read a command by printing a string
12599 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12600 can change the prompt string with the @code{set prompt} command. For
12601 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12602 the prompt in one of the @value{GDBN} sessions so that you can always tell
12603 which one you are talking to.
12605 @emph{Note:} @code{set prompt} does not add a space for you after the
12606 prompt you set. This allows you to set a prompt which ends in a space
12607 or a prompt that does not.
12611 @item set prompt @var{newprompt}
12612 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12614 @kindex show prompt
12616 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12620 @section Command editing
12622 @cindex command line editing
12624 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12625 @sc{gnu} library provides consistent behavior for programs which provide a
12626 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12627 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12628 substitution, and a storage and recall of command history across
12629 debugging sessions.
12631 You may control the behavior of command line editing in @value{GDBN} with the
12632 command @code{set}.
12635 @kindex set editing
12638 @itemx set editing on
12639 Enable command line editing (enabled by default).
12641 @item set editing off
12642 Disable command line editing.
12644 @kindex show editing
12646 Show whether command line editing is enabled.
12650 @section Command history
12652 @value{GDBN} can keep track of the commands you type during your
12653 debugging sessions, so that you can be certain of precisely what
12654 happened. Use these commands to manage the @value{GDBN} command
12658 @cindex history substitution
12659 @cindex history file
12660 @kindex set history filename
12661 @kindex GDBHISTFILE
12662 @item set history filename @var{fname}
12663 Set the name of the @value{GDBN} command history file to @var{fname}.
12664 This is the file where @value{GDBN} reads an initial command history
12665 list, and where it writes the command history from this session when it
12666 exits. You can access this list through history expansion or through
12667 the history command editing characters listed below. This file defaults
12668 to the value of the environment variable @code{GDBHISTFILE}, or to
12669 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12672 @cindex history save
12673 @kindex set history save
12674 @item set history save
12675 @itemx set history save on
12676 Record command history in a file, whose name may be specified with the
12677 @code{set history filename} command. By default, this option is disabled.
12679 @item set history save off
12680 Stop recording command history in a file.
12682 @cindex history size
12683 @kindex set history size
12684 @item set history size @var{size}
12685 Set the number of commands which @value{GDBN} keeps in its history list.
12686 This defaults to the value of the environment variable
12687 @code{HISTSIZE}, or to 256 if this variable is not set.
12690 @cindex history expansion
12691 History expansion assigns special meaning to the character @kbd{!}.
12692 @ifset have-readline-appendices
12693 @xref{Event Designators}.
12696 Since @kbd{!} is also the logical not operator in C, history expansion
12697 is off by default. If you decide to enable history expansion with the
12698 @code{set history expansion on} command, you may sometimes need to
12699 follow @kbd{!} (when it is used as logical not, in an expression) with
12700 a space or a tab to prevent it from being expanded. The readline
12701 history facilities do not attempt substitution on the strings
12702 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12704 The commands to control history expansion are:
12707 @kindex set history expansion
12708 @item set history expansion on
12709 @itemx set history expansion
12710 Enable history expansion. History expansion is off by default.
12712 @item set history expansion off
12713 Disable history expansion.
12715 The readline code comes with more complete documentation of
12716 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12717 or @code{vi} may wish to read it.
12718 @ifset have-readline-appendices
12719 @xref{Command Line Editing}.
12723 @kindex show history
12725 @itemx show history filename
12726 @itemx show history save
12727 @itemx show history size
12728 @itemx show history expansion
12729 These commands display the state of the @value{GDBN} history parameters.
12730 @code{show history} by itself displays all four states.
12736 @item show commands
12737 Display the last ten commands in the command history.
12739 @item show commands @var{n}
12740 Print ten commands centered on command number @var{n}.
12742 @item show commands +
12743 Print ten commands just after the commands last printed.
12747 @section Screen size
12748 @cindex size of screen
12749 @cindex pauses in output
12751 Certain commands to @value{GDBN} may produce large amounts of
12752 information output to the screen. To help you read all of it,
12753 @value{GDBN} pauses and asks you for input at the end of each page of
12754 output. Type @key{RET} when you want to continue the output, or @kbd{q}
12755 to discard the remaining output. Also, the screen width setting
12756 determines when to wrap lines of output. Depending on what is being
12757 printed, @value{GDBN} tries to break the line at a readable place,
12758 rather than simply letting it overflow onto the following line.
12760 Normally @value{GDBN} knows the size of the screen from the terminal
12761 driver software. For example, on Unix @value{GDBN} uses the termcap data base
12762 together with the value of the @code{TERM} environment variable and the
12763 @code{stty rows} and @code{stty cols} settings. If this is not correct,
12764 you can override it with the @code{set height} and @code{set
12771 @kindex show height
12772 @item set height @var{lpp}
12774 @itemx set width @var{cpl}
12776 These @code{set} commands specify a screen height of @var{lpp} lines and
12777 a screen width of @var{cpl} characters. The associated @code{show}
12778 commands display the current settings.
12780 If you specify a height of zero lines, @value{GDBN} does not pause during
12781 output no matter how long the output is. This is useful if output is to a
12782 file or to an editor buffer.
12784 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
12785 from wrapping its output.
12790 @cindex number representation
12791 @cindex entering numbers
12793 You can always enter numbers in octal, decimal, or hexadecimal in
12794 @value{GDBN} by the usual conventions: octal numbers begin with
12795 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
12796 begin with @samp{0x}. Numbers that begin with none of these are, by
12797 default, entered in base 10; likewise, the default display for
12798 numbers---when no particular format is specified---is base 10. You can
12799 change the default base for both input and output with the @code{set
12803 @kindex set input-radix
12804 @item set input-radix @var{base}
12805 Set the default base for numeric input. Supported choices
12806 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12807 specified either unambiguously or using the current default radix; for
12817 sets the base to decimal. On the other hand, @samp{set radix 10}
12818 leaves the radix unchanged no matter what it was.
12820 @kindex set output-radix
12821 @item set output-radix @var{base}
12822 Set the default base for numeric display. Supported choices
12823 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12824 specified either unambiguously or using the current default radix.
12826 @kindex show input-radix
12827 @item show input-radix
12828 Display the current default base for numeric input.
12830 @kindex show output-radix
12831 @item show output-radix
12832 Display the current default base for numeric display.
12836 @section Configuring the current ABI
12838 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
12839 application automatically. However, sometimes you need to override its
12840 conclusions. Use these commands to manage @value{GDBN}'s view of the
12847 One @value{GDBN} configuration can debug binaries for multiple operating
12848 system targets, either via remote debugging or native emulation.
12849 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
12850 but you can override its conclusion using the @code{set osabi} command.
12851 One example where this is useful is in debugging of binaries which use
12852 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
12853 not have the same identifying marks that the standard C library for your
12858 Show the OS ABI currently in use.
12861 With no argument, show the list of registered available OS ABI's.
12863 @item set osabi @var{abi}
12864 Set the current OS ABI to @var{abi}.
12867 @cindex float promotion
12868 @kindex set coerce-float-to-double
12870 Generally, the way that an argument of type @code{float} is passed to a
12871 function depends on whether the function is prototyped. For a prototyped
12872 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
12873 according to the architecture's convention for @code{float}. For unprototyped
12874 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
12875 @code{double} and then passed.
12877 Unfortunately, some forms of debug information do not reliably indicate whether
12878 a function is prototyped. If @value{GDBN} calls a function that is not marked
12879 as prototyped, it consults @kbd{set coerce-float-to-double}.
12882 @item set coerce-float-to-double
12883 @itemx set coerce-float-to-double on
12884 Arguments of type @code{float} will be promoted to @code{double} when passed
12885 to an unprototyped function. This is the default setting.
12887 @item set coerce-float-to-double off
12888 Arguments of type @code{float} will be passed directly to unprototyped
12893 @kindex show cp-abi
12894 @value{GDBN} needs to know the ABI used for your program's C@t{++}
12895 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
12896 used to build your application. @value{GDBN} only fully supports
12897 programs with a single C@t{++} ABI; if your program contains code using
12898 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
12899 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
12900 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
12901 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
12902 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
12903 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
12908 Show the C@t{++} ABI currently in use.
12911 With no argument, show the list of supported C@t{++} ABI's.
12913 @item set cp-abi @var{abi}
12914 @itemx set cp-abi auto
12915 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
12918 @node Messages/Warnings
12919 @section Optional warnings and messages
12921 By default, @value{GDBN} is silent about its inner workings. If you are
12922 running on a slow machine, you may want to use the @code{set verbose}
12923 command. This makes @value{GDBN} tell you when it does a lengthy
12924 internal operation, so you will not think it has crashed.
12926 Currently, the messages controlled by @code{set verbose} are those
12927 which announce that the symbol table for a source file is being read;
12928 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
12931 @kindex set verbose
12932 @item set verbose on
12933 Enables @value{GDBN} output of certain informational messages.
12935 @item set verbose off
12936 Disables @value{GDBN} output of certain informational messages.
12938 @kindex show verbose
12940 Displays whether @code{set verbose} is on or off.
12943 By default, if @value{GDBN} encounters bugs in the symbol table of an
12944 object file, it is silent; but if you are debugging a compiler, you may
12945 find this information useful (@pxref{Symbol Errors, ,Errors reading
12950 @kindex set complaints
12951 @item set complaints @var{limit}
12952 Permits @value{GDBN} to output @var{limit} complaints about each type of
12953 unusual symbols before becoming silent about the problem. Set
12954 @var{limit} to zero to suppress all complaints; set it to a large number
12955 to prevent complaints from being suppressed.
12957 @kindex show complaints
12958 @item show complaints
12959 Displays how many symbol complaints @value{GDBN} is permitted to produce.
12963 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
12964 lot of stupid questions to confirm certain commands. For example, if
12965 you try to run a program which is already running:
12969 The program being debugged has been started already.
12970 Start it from the beginning? (y or n)
12973 If you are willing to unflinchingly face the consequences of your own
12974 commands, you can disable this ``feature'':
12978 @kindex set confirm
12980 @cindex confirmation
12981 @cindex stupid questions
12982 @item set confirm off
12983 Disables confirmation requests.
12985 @item set confirm on
12986 Enables confirmation requests (the default).
12988 @kindex show confirm
12990 Displays state of confirmation requests.
12994 @node Debugging Output
12995 @section Optional messages about internal happenings
12997 @kindex set debug arch
12998 @item set debug arch
12999 Turns on or off display of gdbarch debugging info. The default is off
13000 @kindex show debug arch
13001 @item show debug arch
13002 Displays the current state of displaying gdbarch debugging info.
13003 @kindex set debug event
13004 @item set debug event
13005 Turns on or off display of @value{GDBN} event debugging info. The
13007 @kindex show debug event
13008 @item show debug event
13009 Displays the current state of displaying @value{GDBN} event debugging
13011 @kindex set debug expression
13012 @item set debug expression
13013 Turns on or off display of @value{GDBN} expression debugging info. The
13015 @kindex show debug expression
13016 @item show debug expression
13017 Displays the current state of displaying @value{GDBN} expression
13019 @kindex set debug frame
13020 @item set debug frame
13021 Turns on or off display of @value{GDBN} frame debugging info. The
13023 @kindex show debug frame
13024 @item show debug frame
13025 Displays the current state of displaying @value{GDBN} frame debugging
13027 @kindex set debug overload
13028 @item set debug overload
13029 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13030 info. This includes info such as ranking of functions, etc. The default
13032 @kindex show debug overload
13033 @item show debug overload
13034 Displays the current state of displaying @value{GDBN} C@t{++} overload
13036 @kindex set debug remote
13037 @cindex packets, reporting on stdout
13038 @cindex serial connections, debugging
13039 @item set debug remote
13040 Turns on or off display of reports on all packets sent back and forth across
13041 the serial line to the remote machine. The info is printed on the
13042 @value{GDBN} standard output stream. The default is off.
13043 @kindex show debug remote
13044 @item show debug remote
13045 Displays the state of display of remote packets.
13046 @kindex set debug serial
13047 @item set debug serial
13048 Turns on or off display of @value{GDBN} serial debugging info. The
13050 @kindex show debug serial
13051 @item show debug serial
13052 Displays the current state of displaying @value{GDBN} serial debugging
13054 @kindex set debug target
13055 @item set debug target
13056 Turns on or off display of @value{GDBN} target debugging info. This info
13057 includes what is going on at the target level of GDB, as it happens. The
13059 @kindex show debug target
13060 @item show debug target
13061 Displays the current state of displaying @value{GDBN} target debugging
13063 @kindex set debug varobj
13064 @item set debug varobj
13065 Turns on or off display of @value{GDBN} variable object debugging
13066 info. The default is off.
13067 @kindex show debug varobj
13068 @item show debug varobj
13069 Displays the current state of displaying @value{GDBN} variable object
13074 @chapter Canned Sequences of Commands
13076 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13077 command lists}), @value{GDBN} provides two ways to store sequences of
13078 commands for execution as a unit: user-defined commands and command
13082 * Define:: User-defined commands
13083 * Hooks:: User-defined command hooks
13084 * Command Files:: Command files
13085 * Output:: Commands for controlled output
13089 @section User-defined commands
13091 @cindex user-defined command
13092 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13093 which you assign a new name as a command. This is done with the
13094 @code{define} command. User commands may accept up to 10 arguments
13095 separated by whitespace. Arguments are accessed within the user command
13096 via @var{$arg0@dots{}$arg9}. A trivial example:
13100 print $arg0 + $arg1 + $arg2
13104 To execute the command use:
13111 This defines the command @code{adder}, which prints the sum of
13112 its three arguments. Note the arguments are text substitutions, so they may
13113 reference variables, use complex expressions, or even perform inferior
13119 @item define @var{commandname}
13120 Define a command named @var{commandname}. If there is already a command
13121 by that name, you are asked to confirm that you want to redefine it.
13123 The definition of the command is made up of other @value{GDBN} command lines,
13124 which are given following the @code{define} command. The end of these
13125 commands is marked by a line containing @code{end}.
13130 Takes a single argument, which is an expression to evaluate.
13131 It is followed by a series of commands that are executed
13132 only if the expression is true (nonzero).
13133 There can then optionally be a line @code{else}, followed
13134 by a series of commands that are only executed if the expression
13135 was false. The end of the list is marked by a line containing @code{end}.
13139 The syntax is similar to @code{if}: the command takes a single argument,
13140 which is an expression to evaluate, and must be followed by the commands to
13141 execute, one per line, terminated by an @code{end}.
13142 The commands are executed repeatedly as long as the expression
13146 @item document @var{commandname}
13147 Document the user-defined command @var{commandname}, so that it can be
13148 accessed by @code{help}. The command @var{commandname} must already be
13149 defined. This command reads lines of documentation just as @code{define}
13150 reads the lines of the command definition, ending with @code{end}.
13151 After the @code{document} command is finished, @code{help} on command
13152 @var{commandname} displays the documentation you have written.
13154 You may use the @code{document} command again to change the
13155 documentation of a command. Redefining the command with @code{define}
13156 does not change the documentation.
13158 @kindex help user-defined
13159 @item help user-defined
13160 List all user-defined commands, with the first line of the documentation
13165 @itemx show user @var{commandname}
13166 Display the @value{GDBN} commands used to define @var{commandname} (but
13167 not its documentation). If no @var{commandname} is given, display the
13168 definitions for all user-defined commands.
13170 @kindex show max-user-call-depth
13171 @kindex set max-user-call-depth
13172 @item show max-user-call-depth
13173 @itemx set max-user-call-depth
13174 The value of @code{max-user-call-depth} controls how many recursion
13175 levels are allowed in user-defined commands before GDB suspects an
13176 infinite recursion and aborts the command.
13180 When user-defined commands are executed, the
13181 commands of the definition are not printed. An error in any command
13182 stops execution of the user-defined command.
13184 If used interactively, commands that would ask for confirmation proceed
13185 without asking when used inside a user-defined command. Many @value{GDBN}
13186 commands that normally print messages to say what they are doing omit the
13187 messages when used in a user-defined command.
13190 @section User-defined command hooks
13191 @cindex command hooks
13192 @cindex hooks, for commands
13193 @cindex hooks, pre-command
13197 You may define @dfn{hooks}, which are a special kind of user-defined
13198 command. Whenever you run the command @samp{foo}, if the user-defined
13199 command @samp{hook-foo} exists, it is executed (with no arguments)
13200 before that command.
13202 @cindex hooks, post-command
13205 A hook may also be defined which is run after the command you executed.
13206 Whenever you run the command @samp{foo}, if the user-defined command
13207 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13208 that command. Post-execution hooks may exist simultaneously with
13209 pre-execution hooks, for the same command.
13211 It is valid for a hook to call the command which it hooks. If this
13212 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13214 @c It would be nice if hookpost could be passed a parameter indicating
13215 @c if the command it hooks executed properly or not. FIXME!
13217 @kindex stop@r{, a pseudo-command}
13218 In addition, a pseudo-command, @samp{stop} exists. Defining
13219 (@samp{hook-stop}) makes the associated commands execute every time
13220 execution stops in your program: before breakpoint commands are run,
13221 displays are printed, or the stack frame is printed.
13223 For example, to ignore @code{SIGALRM} signals while
13224 single-stepping, but treat them normally during normal execution,
13229 handle SIGALRM nopass
13233 handle SIGALRM pass
13236 define hook-continue
13237 handle SIGLARM pass
13241 As a further example, to hook at the begining and end of the @code{echo}
13242 command, and to add extra text to the beginning and end of the message,
13250 define hookpost-echo
13254 (@value{GDBP}) echo Hello World
13255 <<<---Hello World--->>>
13260 You can define a hook for any single-word command in @value{GDBN}, but
13261 not for command aliases; you should define a hook for the basic command
13262 name, e.g. @code{backtrace} rather than @code{bt}.
13263 @c FIXME! So how does Joe User discover whether a command is an alias
13265 If an error occurs during the execution of your hook, execution of
13266 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13267 (before the command that you actually typed had a chance to run).
13269 If you try to define a hook which does not match any known command, you
13270 get a warning from the @code{define} command.
13272 @node Command Files
13273 @section Command files
13275 @cindex command files
13276 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13277 commands. Comments (lines starting with @kbd{#}) may also be included.
13278 An empty line in a command file does nothing; it does not mean to repeat
13279 the last command, as it would from the terminal.
13282 @cindex @file{.gdbinit}
13283 @cindex @file{gdb.ini}
13284 When you start @value{GDBN}, it automatically executes commands from its
13285 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13286 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13287 limitations of file names imposed by DOS filesystems.}.
13288 During startup, @value{GDBN} does the following:
13292 Reads the init file (if any) in your home directory@footnote{On
13293 DOS/Windows systems, the home directory is the one pointed to by the
13294 @code{HOME} environment variable.}.
13297 Processes command line options and operands.
13300 Reads the init file (if any) in the current working directory.
13303 Reads command files specified by the @samp{-x} option.
13306 The init file in your home directory can set options (such as @samp{set
13307 complaints}) that affect subsequent processing of command line options
13308 and operands. Init files are not executed if you use the @samp{-nx}
13309 option (@pxref{Mode Options, ,Choosing modes}).
13311 @cindex init file name
13312 On some configurations of @value{GDBN}, the init file is known by a
13313 different name (these are typically environments where a specialized
13314 form of @value{GDBN} may need to coexist with other forms, hence a
13315 different name for the specialized version's init file). These are the
13316 environments with special init file names:
13318 @cindex @file{.vxgdbinit}
13321 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13323 @cindex @file{.os68gdbinit}
13325 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13327 @cindex @file{.esgdbinit}
13329 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13332 You can also request the execution of a command file with the
13333 @code{source} command:
13337 @item source @var{filename}
13338 Execute the command file @var{filename}.
13341 The lines in a command file are executed sequentially. They are not
13342 printed as they are executed. An error in any command terminates
13343 execution of the command file and control is returned to the console.
13345 Commands that would ask for confirmation if used interactively proceed
13346 without asking when used in a command file. Many @value{GDBN} commands that
13347 normally print messages to say what they are doing omit the messages
13348 when called from command files.
13350 @value{GDBN} also accepts command input from standard input. In this
13351 mode, normal output goes to standard output and error output goes to
13352 standard error. Errors in a command file supplied on standard input do
13353 not terminate execution of the command file --- execution continues with
13357 gdb < cmds > log 2>&1
13360 (The syntax above will vary depending on the shell used.) This example
13361 will execute commands from the file @file{cmds}. All output and errors
13362 would be directed to @file{log}.
13365 @section Commands for controlled output
13367 During the execution of a command file or a user-defined command, normal
13368 @value{GDBN} output is suppressed; the only output that appears is what is
13369 explicitly printed by the commands in the definition. This section
13370 describes three commands useful for generating exactly the output you
13375 @item echo @var{text}
13376 @c I do not consider backslash-space a standard C escape sequence
13377 @c because it is not in ANSI.
13378 Print @var{text}. Nonprinting characters can be included in
13379 @var{text} using C escape sequences, such as @samp{\n} to print a
13380 newline. @strong{No newline is printed unless you specify one.}
13381 In addition to the standard C escape sequences, a backslash followed
13382 by a space stands for a space. This is useful for displaying a
13383 string with spaces at the beginning or the end, since leading and
13384 trailing spaces are otherwise trimmed from all arguments.
13385 To print @samp{@w{ }and foo =@w{ }}, use the command
13386 @samp{echo \@w{ }and foo = \@w{ }}.
13388 A backslash at the end of @var{text} can be used, as in C, to continue
13389 the command onto subsequent lines. For example,
13392 echo This is some text\n\
13393 which is continued\n\
13394 onto several lines.\n
13397 produces the same output as
13400 echo This is some text\n
13401 echo which is continued\n
13402 echo onto several lines.\n
13406 @item output @var{expression}
13407 Print the value of @var{expression} and nothing but that value: no
13408 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13409 value history either. @xref{Expressions, ,Expressions}, for more information
13412 @item output/@var{fmt} @var{expression}
13413 Print the value of @var{expression} in format @var{fmt}. You can use
13414 the same formats as for @code{print}. @xref{Output Formats,,Output
13415 formats}, for more information.
13418 @item printf @var{string}, @var{expressions}@dots{}
13419 Print the values of the @var{expressions} under the control of
13420 @var{string}. The @var{expressions} are separated by commas and may be
13421 either numbers or pointers. Their values are printed as specified by
13422 @var{string}, exactly as if your program were to execute the C
13424 @c FIXME: the above implies that at least all ANSI C formats are
13425 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13426 @c Either this is a bug, or the manual should document what formats are
13430 printf (@var{string}, @var{expressions}@dots{});
13433 For example, you can print two values in hex like this:
13436 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13439 The only backslash-escape sequences that you can use in the format
13440 string are the simple ones that consist of backslash followed by a
13445 @chapter Command Interpreters
13446 @cindex command interpreters
13448 @value{GDBN} supports multiple command interpreters, and some command
13449 infrastructure to allow users or user interface writers to switch
13450 between interpreters or run commands in other interpreters.
13452 @value{GDBN} currently supports two command interpreters, the console
13453 interpreter (sometimes called the command-line interpreter or @sc{cli})
13454 and the machine interface interpreter (or @sc{gdb/mi}). This manual
13455 describes both of these interfaces in great detail.
13457 By default, @value{GDBN} will start with the console interpreter.
13458 However, the user may choose to start @value{GDBN} with another
13459 interpreter by specifying the @option{-i} or @option{--interpreter}
13460 startup options. Defined interpreters include:
13464 @cindex console interpreter
13465 The traditional console or command-line interpreter. This is the most often
13466 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
13467 @value{GDBN} will use this interpreter.
13470 @cindex mi interpreter
13471 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
13472 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
13473 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
13477 @cindex mi2 interpreter
13478 The current @sc{gdb/mi} interface.
13481 @cindex mi1 interpreter
13482 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
13486 @cindex invoke another interpreter
13487 The interpreter being used by @value{GDBN} may not be dynamically
13488 switched at runtime. Although possible, this could lead to a very
13489 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
13490 enters the command "interpreter-set console" in a console view,
13491 @value{GDBN} would switch to using the console interpreter, rendering
13492 the IDE inoperable!
13494 @kindex interpreter-exec
13495 Although you may only choose a single interpreter at startup, you may execute
13496 commands in any interpreter from the current interpreter using the appropriate
13497 command. If you are running the console interpreter, simply use the
13498 @code{interpreter-exec} command:
13501 interpreter-exec mi "-data-list-register-names"
13504 @sc{gdb/mi} has a similar command, although it is only available in versions of
13505 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
13508 @chapter @value{GDBN} Text User Interface
13512 * TUI Overview:: TUI overview
13513 * TUI Keys:: TUI key bindings
13514 * TUI Single Key Mode:: TUI single key mode
13515 * TUI Commands:: TUI specific commands
13516 * TUI Configuration:: TUI configuration variables
13519 The @value{GDBN} Text User Interface, TUI in short,
13520 is a terminal interface which uses the @code{curses} library
13521 to show the source file, the assembly output, the program registers
13522 and @value{GDBN} commands in separate text windows.
13523 The TUI is available only when @value{GDBN} is configured
13524 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13527 @section TUI overview
13529 The TUI has two display modes that can be switched while
13534 A curses (or TUI) mode in which it displays several text
13535 windows on the terminal.
13538 A standard mode which corresponds to the @value{GDBN} configured without
13542 In the TUI mode, @value{GDBN} can display several text window
13547 This window is the @value{GDBN} command window with the @value{GDBN}
13548 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13549 managed using readline but through the TUI. The @emph{command}
13550 window is always visible.
13553 The source window shows the source file of the program. The current
13554 line as well as active breakpoints are displayed in this window.
13557 The assembly window shows the disassembly output of the program.
13560 This window shows the processor registers. It detects when
13561 a register is changed and when this is the case, registers that have
13562 changed are highlighted.
13566 The source and assembly windows show the current program position
13567 by highlighting the current line and marking them with the @samp{>} marker.
13568 Breakpoints are also indicated with two markers. A first one
13569 indicates the breakpoint type:
13573 Breakpoint which was hit at least once.
13576 Breakpoint which was never hit.
13579 Hardware breakpoint which was hit at least once.
13582 Hardware breakpoint which was never hit.
13586 The second marker indicates whether the breakpoint is enabled or not:
13590 Breakpoint is enabled.
13593 Breakpoint is disabled.
13597 The source, assembly and register windows are attached to the thread
13598 and the frame position. They are updated when the current thread
13599 changes, when the frame changes or when the program counter changes.
13600 These three windows are arranged by the TUI according to several
13601 layouts. The layout defines which of these three windows are visible.
13602 The following layouts are available:
13612 source and assembly
13615 source and registers
13618 assembly and registers
13622 On top of the command window a status line gives various information
13623 concerning the current process begin debugged. The status line is
13624 updated when the information it shows changes. The following fields
13629 Indicates the current gdb target
13630 (@pxref{Targets, ,Specifying a Debugging Target}).
13633 Gives information about the current process or thread number.
13634 When no process is being debugged, this field is set to @code{No process}.
13637 Gives the current function name for the selected frame.
13638 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13639 When there is no symbol corresponding to the current program counter
13640 the string @code{??} is displayed.
13643 Indicates the current line number for the selected frame.
13644 When the current line number is not known the string @code{??} is displayed.
13647 Indicates the current program counter address.
13652 @section TUI Key Bindings
13653 @cindex TUI key bindings
13655 The TUI installs several key bindings in the readline keymaps
13656 (@pxref{Command Line Editing}).
13657 They allow to leave or enter in the TUI mode or they operate
13658 directly on the TUI layout and windows. The TUI also provides
13659 a @emph{SingleKey} keymap which binds several keys directly to
13660 @value{GDBN} commands. The following key bindings
13661 are installed for both TUI mode and the @value{GDBN} standard mode.
13670 Enter or leave the TUI mode. When the TUI mode is left,
13671 the curses window management is left and @value{GDBN} operates using
13672 its standard mode writing on the terminal directly. When the TUI
13673 mode is entered, the control is given back to the curses windows.
13674 The screen is then refreshed.
13678 Use a TUI layout with only one window. The layout will
13679 either be @samp{source} or @samp{assembly}. When the TUI mode
13680 is not active, it will switch to the TUI mode.
13682 Think of this key binding as the Emacs @kbd{C-x 1} binding.
13686 Use a TUI layout with at least two windows. When the current
13687 layout shows already two windows, a next layout with two windows is used.
13688 When a new layout is chosen, one window will always be common to the
13689 previous layout and the new one.
13691 Think of it as the Emacs @kbd{C-x 2} binding.
13695 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
13696 (@pxref{TUI Single Key Mode}).
13700 The following key bindings are handled only by the TUI mode:
13705 Scroll the active window one page up.
13709 Scroll the active window one page down.
13713 Scroll the active window one line up.
13717 Scroll the active window one line down.
13721 Scroll the active window one column left.
13725 Scroll the active window one column right.
13729 Refresh the screen.
13733 In the TUI mode, the arrow keys are used by the active window
13734 for scrolling. This means they are not available for readline. It is
13735 necessary to use other readline key bindings such as @key{C-p}, @key{C-n},
13736 @key{C-b} and @key{C-f}.
13738 @node TUI Single Key Mode
13739 @section TUI Single Key Mode
13740 @cindex TUI single key mode
13742 The TUI provides a @emph{SingleKey} mode in which it installs a particular
13743 key binding in the readline keymaps to connect single keys to
13747 @kindex c @r{(SingleKey TUI key)}
13751 @kindex d @r{(SingleKey TUI key)}
13755 @kindex f @r{(SingleKey TUI key)}
13759 @kindex n @r{(SingleKey TUI key)}
13763 @kindex q @r{(SingleKey TUI key)}
13765 exit the @emph{SingleKey} mode.
13767 @kindex r @r{(SingleKey TUI key)}
13771 @kindex s @r{(SingleKey TUI key)}
13775 @kindex u @r{(SingleKey TUI key)}
13779 @kindex v @r{(SingleKey TUI key)}
13783 @kindex w @r{(SingleKey TUI key)}
13789 Other keys temporarily switch to the @value{GDBN} command prompt.
13790 The key that was pressed is inserted in the editing buffer so that
13791 it is possible to type most @value{GDBN} commands without interaction
13792 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
13793 @emph{SingleKey} mode is restored. The only way to permanently leave
13794 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
13798 @section TUI specific commands
13799 @cindex TUI commands
13801 The TUI has specific commands to control the text windows.
13802 These commands are always available, that is they do not depend on
13803 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
13804 is in the standard mode, using these commands will automatically switch
13810 List and give the size of all displayed windows.
13813 @kindex layout next
13814 Display the next layout.
13817 @kindex layout prev
13818 Display the previous layout.
13822 Display the source window only.
13826 Display the assembly window only.
13829 @kindex layout split
13830 Display the source and assembly window.
13833 @kindex layout regs
13834 Display the register window together with the source or assembly window.
13836 @item focus next | prev | src | asm | regs | split
13838 Set the focus to the named window.
13839 This command allows to change the active window so that scrolling keys
13840 can be affected to another window.
13844 Refresh the screen. This is similar to using @key{C-L} key.
13848 Update the source window and the current execution point.
13850 @item winheight @var{name} +@var{count}
13851 @itemx winheight @var{name} -@var{count}
13853 Change the height of the window @var{name} by @var{count}
13854 lines. Positive counts increase the height, while negative counts
13859 @node TUI Configuration
13860 @section TUI configuration variables
13861 @cindex TUI configuration variables
13863 The TUI has several configuration variables that control the
13864 appearance of windows on the terminal.
13867 @item set tui border-kind @var{kind}
13868 @kindex set tui border-kind
13869 Select the border appearance for the source, assembly and register windows.
13870 The possible values are the following:
13873 Use a space character to draw the border.
13876 Use ascii characters + - and | to draw the border.
13879 Use the Alternate Character Set to draw the border. The border is
13880 drawn using character line graphics if the terminal supports them.
13884 @item set tui active-border-mode @var{mode}
13885 @kindex set tui active-border-mode
13886 Select the attributes to display the border of the active window.
13887 The possible values are @code{normal}, @code{standout}, @code{reverse},
13888 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
13890 @item set tui border-mode @var{mode}
13891 @kindex set tui border-mode
13892 Select the attributes to display the border of other windows.
13893 The @var{mode} can be one of the following:
13896 Use normal attributes to display the border.
13902 Use reverse video mode.
13905 Use half bright mode.
13907 @item half-standout
13908 Use half bright and standout mode.
13911 Use extra bright or bold mode.
13913 @item bold-standout
13914 Use extra bright or bold and standout mode.
13921 @chapter Using @value{GDBN} under @sc{gnu} Emacs
13924 @cindex @sc{gnu} Emacs
13925 A special interface allows you to use @sc{gnu} Emacs to view (and
13926 edit) the source files for the program you are debugging with
13929 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
13930 executable file you want to debug as an argument. This command starts
13931 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
13932 created Emacs buffer.
13933 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
13935 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
13940 All ``terminal'' input and output goes through the Emacs buffer.
13943 This applies both to @value{GDBN} commands and their output, and to the input
13944 and output done by the program you are debugging.
13946 This is useful because it means that you can copy the text of previous
13947 commands and input them again; you can even use parts of the output
13950 All the facilities of Emacs' Shell mode are available for interacting
13951 with your program. In particular, you can send signals the usual
13952 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
13957 @value{GDBN} displays source code through Emacs.
13960 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
13961 source file for that frame and puts an arrow (@samp{=>}) at the
13962 left margin of the current line. Emacs uses a separate buffer for
13963 source display, and splits the screen to show both your @value{GDBN} session
13966 Explicit @value{GDBN} @code{list} or search commands still produce output as
13967 usual, but you probably have no reason to use them from Emacs.
13970 @emph{Warning:} If the directory where your program resides is not your
13971 current directory, it can be easy to confuse Emacs about the location of
13972 the source files, in which case the auxiliary display buffer does not
13973 appear to show your source. @value{GDBN} can find programs by searching your
13974 environment's @code{PATH} variable, so the @value{GDBN} input and output
13975 session proceeds normally; but Emacs does not get enough information
13976 back from @value{GDBN} to locate the source files in this situation. To
13977 avoid this problem, either start @value{GDBN} mode from the directory where
13978 your program resides, or specify an absolute file name when prompted for the
13979 @kbd{M-x gdb} argument.
13981 A similar confusion can result if you use the @value{GDBN} @code{file} command to
13982 switch to debugging a program in some other location, from an existing
13983 @value{GDBN} buffer in Emacs.
13986 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
13987 you need to call @value{GDBN} by a different name (for example, if you keep
13988 several configurations around, with different names) you can set the
13989 Emacs variable @code{gdb-command-name}; for example,
13992 (setq gdb-command-name "mygdb")
13996 (preceded by @kbd{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or
13997 in your @file{.emacs} file) makes Emacs call the program named
13998 ``@code{mygdb}'' instead.
14000 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
14001 addition to the standard Shell mode commands:
14005 Describe the features of Emacs' @value{GDBN} Mode.
14008 Execute to another source line, like the @value{GDBN} @code{step} command; also
14009 update the display window to show the current file and location.
14012 Execute to next source line in this function, skipping all function
14013 calls, like the @value{GDBN} @code{next} command. Then update the display window
14014 to show the current file and location.
14017 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
14018 display window accordingly.
14020 @item M-x gdb-nexti
14021 Execute to next instruction, using the @value{GDBN} @code{nexti} command; update
14022 display window accordingly.
14025 Execute until exit from the selected stack frame, like the @value{GDBN}
14026 @code{finish} command.
14029 Continue execution of your program, like the @value{GDBN} @code{continue}
14032 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
14035 Go up the number of frames indicated by the numeric argument
14036 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
14037 like the @value{GDBN} @code{up} command.
14039 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
14042 Go down the number of frames indicated by the numeric argument, like the
14043 @value{GDBN} @code{down} command.
14045 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
14048 Read the number where the cursor is positioned, and insert it at the end
14049 of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code
14050 around an address that was displayed earlier, type @kbd{disassemble};
14051 then move the cursor to the address display, and pick up the
14052 argument for @code{disassemble} by typing @kbd{C-x &}.
14054 You can customize this further by defining elements of the list
14055 @code{gdb-print-command}; once it is defined, you can format or
14056 otherwise process numbers picked up by @kbd{C-x &} before they are
14057 inserted. A numeric argument to @kbd{C-x &} indicates that you
14058 wish special formatting, and also acts as an index to pick an element of the
14059 list. If the list element is a string, the number to be inserted is
14060 formatted using the Emacs function @code{format}; otherwise the number
14061 is passed as an argument to the corresponding list element.
14064 In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
14065 tells @value{GDBN} to set a breakpoint on the source line point is on.
14067 If you accidentally delete the source-display buffer, an easy way to get
14068 it back is to type the command @code{f} in the @value{GDBN} buffer, to
14069 request a frame display; when you run under Emacs, this recreates
14070 the source buffer if necessary to show you the context of the current
14073 The source files displayed in Emacs are in ordinary Emacs buffers
14074 which are visiting the source files in the usual way. You can edit
14075 the files with these buffers if you wish; but keep in mind that @value{GDBN}
14076 communicates with Emacs in terms of line numbers. If you add or
14077 delete lines from the text, the line numbers that @value{GDBN} knows cease
14078 to correspond properly with the code.
14080 @c The following dropped because Epoch is nonstandard. Reactivate
14081 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
14083 @kindex Emacs Epoch environment
14087 Version 18 of @sc{gnu} Emacs has a built-in window system
14088 called the @code{epoch}
14089 environment. Users of this environment can use a new command,
14090 @code{inspect} which performs identically to @code{print} except that
14091 each value is printed in its own window.
14096 @chapter The @sc{gdb/mi} Interface
14098 @unnumberedsec Function and Purpose
14100 @cindex @sc{gdb/mi}, its purpose
14101 @sc{gdb/mi} is a line based machine oriented text interface to @value{GDBN}. It is
14102 specifically intended to support the development of systems which use
14103 the debugger as just one small component of a larger system.
14105 This chapter is a specification of the @sc{gdb/mi} interface. It is written
14106 in the form of a reference manual.
14108 Note that @sc{gdb/mi} is still under construction, so some of the
14109 features described below are incomplete and subject to change.
14111 @unnumberedsec Notation and Terminology
14113 @cindex notational conventions, for @sc{gdb/mi}
14114 This chapter uses the following notation:
14118 @code{|} separates two alternatives.
14121 @code{[ @var{something} ]} indicates that @var{something} is optional:
14122 it may or may not be given.
14125 @code{( @var{group} )*} means that @var{group} inside the parentheses
14126 may repeat zero or more times.
14129 @code{( @var{group} )+} means that @var{group} inside the parentheses
14130 may repeat one or more times.
14133 @code{"@var{string}"} means a literal @var{string}.
14137 @heading Dependencies
14140 @heading Acknowledgments
14142 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
14146 * GDB/MI Command Syntax::
14147 * GDB/MI Compatibility with CLI::
14148 * GDB/MI Output Records::
14149 * GDB/MI Command Description Format::
14150 * GDB/MI Breakpoint Table Commands::
14151 * GDB/MI Data Manipulation::
14152 * GDB/MI Program Control::
14153 * GDB/MI Miscellaneous Commands::
14155 * GDB/MI Kod Commands::
14156 * GDB/MI Memory Overlay Commands::
14157 * GDB/MI Signal Handling Commands::
14159 * GDB/MI Stack Manipulation::
14160 * GDB/MI Symbol Query::
14161 * GDB/MI Target Manipulation::
14162 * GDB/MI Thread Commands::
14163 * GDB/MI Tracepoint Commands::
14164 * GDB/MI Variable Objects::
14167 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14168 @node GDB/MI Command Syntax
14169 @section @sc{gdb/mi} Command Syntax
14172 * GDB/MI Input Syntax::
14173 * GDB/MI Output Syntax::
14174 * GDB/MI Simple Examples::
14177 @node GDB/MI Input Syntax
14178 @subsection @sc{gdb/mi} Input Syntax
14180 @cindex input syntax for @sc{gdb/mi}
14181 @cindex @sc{gdb/mi}, input syntax
14183 @item @var{command} @expansion{}
14184 @code{@var{cli-command} | @var{mi-command}}
14186 @item @var{cli-command} @expansion{}
14187 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
14188 @var{cli-command} is any existing @value{GDBN} CLI command.
14190 @item @var{mi-command} @expansion{}
14191 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
14192 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
14194 @item @var{token} @expansion{}
14195 "any sequence of digits"
14197 @item @var{option} @expansion{}
14198 @code{"-" @var{parameter} [ " " @var{parameter} ]}
14200 @item @var{parameter} @expansion{}
14201 @code{@var{non-blank-sequence} | @var{c-string}}
14203 @item @var{operation} @expansion{}
14204 @emph{any of the operations described in this chapter}
14206 @item @var{non-blank-sequence} @expansion{}
14207 @emph{anything, provided it doesn't contain special characters such as
14208 "-", @var{nl}, """ and of course " "}
14210 @item @var{c-string} @expansion{}
14211 @code{""" @var{seven-bit-iso-c-string-content} """}
14213 @item @var{nl} @expansion{}
14222 The CLI commands are still handled by the @sc{mi} interpreter; their
14223 output is described below.
14226 The @code{@var{token}}, when present, is passed back when the command
14230 Some @sc{mi} commands accept optional arguments as part of the parameter
14231 list. Each option is identified by a leading @samp{-} (dash) and may be
14232 followed by an optional argument parameter. Options occur first in the
14233 parameter list and can be delimited from normal parameters using
14234 @samp{--} (this is useful when some parameters begin with a dash).
14241 We want easy access to the existing CLI syntax (for debugging).
14244 We want it to be easy to spot a @sc{mi} operation.
14247 @node GDB/MI Output Syntax
14248 @subsection @sc{gdb/mi} Output Syntax
14250 @cindex output syntax of @sc{gdb/mi}
14251 @cindex @sc{gdb/mi}, output syntax
14252 The output from @sc{gdb/mi} consists of zero or more out-of-band records
14253 followed, optionally, by a single result record. This result record
14254 is for the most recent command. The sequence of output records is
14255 terminated by @samp{(@value{GDBP})}.
14257 If an input command was prefixed with a @code{@var{token}} then the
14258 corresponding output for that command will also be prefixed by that same
14262 @item @var{output} @expansion{}
14263 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
14265 @item @var{result-record} @expansion{}
14266 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
14268 @item @var{out-of-band-record} @expansion{}
14269 @code{@var{async-record} | @var{stream-record}}
14271 @item @var{async-record} @expansion{}
14272 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
14274 @item @var{exec-async-output} @expansion{}
14275 @code{[ @var{token} ] "*" @var{async-output}}
14277 @item @var{status-async-output} @expansion{}
14278 @code{[ @var{token} ] "+" @var{async-output}}
14280 @item @var{notify-async-output} @expansion{}
14281 @code{[ @var{token} ] "=" @var{async-output}}
14283 @item @var{async-output} @expansion{}
14284 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
14286 @item @var{result-class} @expansion{}
14287 @code{"done" | "running" | "connected" | "error" | "exit"}
14289 @item @var{async-class} @expansion{}
14290 @code{"stopped" | @var{others}} (where @var{others} will be added
14291 depending on the needs---this is still in development).
14293 @item @var{result} @expansion{}
14294 @code{ @var{variable} "=" @var{value}}
14296 @item @var{variable} @expansion{}
14297 @code{ @var{string} }
14299 @item @var{value} @expansion{}
14300 @code{ @var{const} | @var{tuple} | @var{list} }
14302 @item @var{const} @expansion{}
14303 @code{@var{c-string}}
14305 @item @var{tuple} @expansion{}
14306 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
14308 @item @var{list} @expansion{}
14309 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
14310 @var{result} ( "," @var{result} )* "]" }
14312 @item @var{stream-record} @expansion{}
14313 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
14315 @item @var{console-stream-output} @expansion{}
14316 @code{"~" @var{c-string}}
14318 @item @var{target-stream-output} @expansion{}
14319 @code{"@@" @var{c-string}}
14321 @item @var{log-stream-output} @expansion{}
14322 @code{"&" @var{c-string}}
14324 @item @var{nl} @expansion{}
14327 @item @var{token} @expansion{}
14328 @emph{any sequence of digits}.
14336 All output sequences end in a single line containing a period.
14339 The @code{@var{token}} is from the corresponding request. If an execution
14340 command is interrupted by the @samp{-exec-interrupt} command, the
14341 @var{token} associated with the @samp{*stopped} message is the one of the
14342 original execution command, not the one of the interrupt command.
14345 @cindex status output in @sc{gdb/mi}
14346 @var{status-async-output} contains on-going status information about the
14347 progress of a slow operation. It can be discarded. All status output is
14348 prefixed by @samp{+}.
14351 @cindex async output in @sc{gdb/mi}
14352 @var{exec-async-output} contains asynchronous state change on the target
14353 (stopped, started, disappeared). All async output is prefixed by
14357 @cindex notify output in @sc{gdb/mi}
14358 @var{notify-async-output} contains supplementary information that the
14359 client should handle (e.g., a new breakpoint information). All notify
14360 output is prefixed by @samp{=}.
14363 @cindex console output in @sc{gdb/mi}
14364 @var{console-stream-output} is output that should be displayed as is in the
14365 console. It is the textual response to a CLI command. All the console
14366 output is prefixed by @samp{~}.
14369 @cindex target output in @sc{gdb/mi}
14370 @var{target-stream-output} is the output produced by the target program.
14371 All the target output is prefixed by @samp{@@}.
14374 @cindex log output in @sc{gdb/mi}
14375 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
14376 instance messages that should be displayed as part of an error log. All
14377 the log output is prefixed by @samp{&}.
14380 @cindex list output in @sc{gdb/mi}
14381 New @sc{gdb/mi} commands should only output @var{lists} containing
14387 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
14388 details about the various output records.
14390 @node GDB/MI Simple Examples
14391 @subsection Simple Examples of @sc{gdb/mi} Interaction
14392 @cindex @sc{gdb/mi}, simple examples
14394 This subsection presents several simple examples of interaction using
14395 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
14396 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
14397 the output received from @sc{gdb/mi}.
14399 @subsubheading Target Stop
14400 @c Ummm... There is no "-stop" command. This assumes async, no?
14401 Here's an example of stopping the inferior process:
14412 <- *stop,reason="stop",address="0x123",source="a.c:123"
14416 @subsubheading Simple CLI Command
14418 Here's an example of a simple CLI command being passed through
14419 @sc{gdb/mi} and on to the CLI.
14429 @subsubheading Command With Side Effects
14432 -> -symbol-file xyz.exe
14433 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
14437 @subsubheading A Bad Command
14439 Here's what happens if you pass a non-existent command:
14443 <- ^error,msg="Undefined MI command: rubbish"
14447 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14448 @node GDB/MI Compatibility with CLI
14449 @section @sc{gdb/mi} Compatibility with CLI
14451 @cindex compatibility, @sc{gdb/mi} and CLI
14452 @cindex @sc{gdb/mi}, compatibility with CLI
14453 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
14454 accepts existing CLI commands. As specified by the syntax, such
14455 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
14458 This mechanism is provided as an aid to developers of @sc{gdb/mi}
14459 clients and not as a reliable interface into the CLI. Since the command
14460 is being interpreteted in an environment that assumes @sc{gdb/mi}
14461 behaviour, the exact output of such commands is likely to end up being
14462 an un-supported hybrid of @sc{gdb/mi} and CLI output.
14464 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14465 @node GDB/MI Output Records
14466 @section @sc{gdb/mi} Output Records
14469 * GDB/MI Result Records::
14470 * GDB/MI Stream Records::
14471 * GDB/MI Out-of-band Records::
14474 @node GDB/MI Result Records
14475 @subsection @sc{gdb/mi} Result Records
14477 @cindex result records in @sc{gdb/mi}
14478 @cindex @sc{gdb/mi}, result records
14479 In addition to a number of out-of-band notifications, the response to a
14480 @sc{gdb/mi} command includes one of the following result indications:
14484 @item "^done" [ "," @var{results} ]
14485 The synchronous operation was successful, @code{@var{results}} are the return
14490 @c Is this one correct? Should it be an out-of-band notification?
14491 The asynchronous operation was successfully started. The target is
14494 @item "^error" "," @var{c-string}
14496 The operation failed. The @code{@var{c-string}} contains the corresponding
14500 @node GDB/MI Stream Records
14501 @subsection @sc{gdb/mi} Stream Records
14503 @cindex @sc{gdb/mi}, stream records
14504 @cindex stream records in @sc{gdb/mi}
14505 @value{GDBN} internally maintains a number of output streams: the console, the
14506 target, and the log. The output intended for each of these streams is
14507 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
14509 Each stream record begins with a unique @dfn{prefix character} which
14510 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
14511 Syntax}). In addition to the prefix, each stream record contains a
14512 @code{@var{string-output}}. This is either raw text (with an implicit new
14513 line) or a quoted C string (which does not contain an implicit newline).
14516 @item "~" @var{string-output}
14517 The console output stream contains text that should be displayed in the
14518 CLI console window. It contains the textual responses to CLI commands.
14520 @item "@@" @var{string-output}
14521 The target output stream contains any textual output from the running
14524 @item "&" @var{string-output}
14525 The log stream contains debugging messages being produced by @value{GDBN}'s
14529 @node GDB/MI Out-of-band Records
14530 @subsection @sc{gdb/mi} Out-of-band Records
14532 @cindex out-of-band records in @sc{gdb/mi}
14533 @cindex @sc{gdb/mi}, out-of-band records
14534 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
14535 additional changes that have occurred. Those changes can either be a
14536 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
14537 target activity (e.g., target stopped).
14539 The following is a preliminary list of possible out-of-band records.
14546 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14547 @node GDB/MI Command Description Format
14548 @section @sc{gdb/mi} Command Description Format
14550 The remaining sections describe blocks of commands. Each block of
14551 commands is laid out in a fashion similar to this section.
14553 Note the the line breaks shown in the examples are here only for
14554 readability. They don't appear in the real output.
14555 Also note that the commands with a non-available example (N.A.@:) are
14556 not yet implemented.
14558 @subheading Motivation
14560 The motivation for this collection of commands.
14562 @subheading Introduction
14564 A brief introduction to this collection of commands as a whole.
14566 @subheading Commands
14568 For each command in the block, the following is described:
14570 @subsubheading Synopsis
14573 -command @var{args}@dots{}
14576 @subsubheading @value{GDBN} Command
14578 The corresponding @value{GDBN} CLI command.
14580 @subsubheading Result
14582 @subsubheading Out-of-band
14584 @subsubheading Notes
14586 @subsubheading Example
14589 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
14590 @node GDB/MI Breakpoint Table Commands
14591 @section @sc{gdb/mi} Breakpoint table commands
14593 @cindex breakpoint commands for @sc{gdb/mi}
14594 @cindex @sc{gdb/mi}, breakpoint commands
14595 This section documents @sc{gdb/mi} commands for manipulating
14598 @subheading The @code{-break-after} Command
14599 @findex -break-after
14601 @subsubheading Synopsis
14604 -break-after @var{number} @var{count}
14607 The breakpoint number @var{number} is not in effect until it has been
14608 hit @var{count} times. To see how this is reflected in the output of
14609 the @samp{-break-list} command, see the description of the
14610 @samp{-break-list} command below.
14612 @subsubheading @value{GDBN} Command
14614 The corresponding @value{GDBN} command is @samp{ignore}.
14616 @subsubheading Example
14621 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
14628 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14629 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14630 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14631 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14632 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14633 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14634 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14635 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14636 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
14642 @subheading The @code{-break-catch} Command
14643 @findex -break-catch
14645 @subheading The @code{-break-commands} Command
14646 @findex -break-commands
14650 @subheading The @code{-break-condition} Command
14651 @findex -break-condition
14653 @subsubheading Synopsis
14656 -break-condition @var{number} @var{expr}
14659 Breakpoint @var{number} will stop the program only if the condition in
14660 @var{expr} is true. The condition becomes part of the
14661 @samp{-break-list} output (see the description of the @samp{-break-list}
14664 @subsubheading @value{GDBN} Command
14666 The corresponding @value{GDBN} command is @samp{condition}.
14668 @subsubheading Example
14672 -break-condition 1 1
14676 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14677 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14678 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14679 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14680 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14681 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14682 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14683 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14684 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
14685 times="0",ignore="3"@}]@}
14689 @subheading The @code{-break-delete} Command
14690 @findex -break-delete
14692 @subsubheading Synopsis
14695 -break-delete ( @var{breakpoint} )+
14698 Delete the breakpoint(s) whose number(s) are specified in the argument
14699 list. This is obviously reflected in the breakpoint list.
14701 @subsubheading @value{GDBN} command
14703 The corresponding @value{GDBN} command is @samp{delete}.
14705 @subsubheading Example
14713 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
14714 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14715 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14716 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14717 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14718 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14719 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14724 @subheading The @code{-break-disable} Command
14725 @findex -break-disable
14727 @subsubheading Synopsis
14730 -break-disable ( @var{breakpoint} )+
14733 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
14734 break list is now set to @samp{n} for the named @var{breakpoint}(s).
14736 @subsubheading @value{GDBN} Command
14738 The corresponding @value{GDBN} command is @samp{disable}.
14740 @subsubheading Example
14748 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14749 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14750 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14751 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14752 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14753 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14754 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14755 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
14756 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14760 @subheading The @code{-break-enable} Command
14761 @findex -break-enable
14763 @subsubheading Synopsis
14766 -break-enable ( @var{breakpoint} )+
14769 Enable (previously disabled) @var{breakpoint}(s).
14771 @subsubheading @value{GDBN} Command
14773 The corresponding @value{GDBN} command is @samp{enable}.
14775 @subsubheading Example
14783 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
14784 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14785 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14786 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14787 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14788 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14789 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14790 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
14791 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
14795 @subheading The @code{-break-info} Command
14796 @findex -break-info
14798 @subsubheading Synopsis
14801 -break-info @var{breakpoint}
14805 Get information about a single breakpoint.
14807 @subsubheading @value{GDBN} command
14809 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
14811 @subsubheading Example
14814 @subheading The @code{-break-insert} Command
14815 @findex -break-insert
14817 @subsubheading Synopsis
14820 -break-insert [ -t ] [ -h ] [ -r ]
14821 [ -c @var{condition} ] [ -i @var{ignore-count} ]
14822 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
14826 If specified, @var{line}, can be one of:
14833 @item filename:linenum
14834 @item filename:function
14838 The possible optional parameters of this command are:
14842 Insert a tempoary breakpoint.
14844 Insert a hardware breakpoint.
14845 @item -c @var{condition}
14846 Make the breakpoint conditional on @var{condition}.
14847 @item -i @var{ignore-count}
14848 Initialize the @var{ignore-count}.
14850 Insert a regular breakpoint in all the functions whose names match the
14851 given regular expression. Other flags are not applicable to regular
14855 @subsubheading Result
14857 The result is in the form:
14860 ^done,bkptno="@var{number}",func="@var{funcname}",
14861 file="@var{filename}",line="@var{lineno}"
14865 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
14866 is the name of the function where the breakpoint was inserted,
14867 @var{filename} is the name of the source file which contains this
14868 function, and @var{lineno} is the source line number within that file.
14870 Note: this format is open to change.
14871 @c An out-of-band breakpoint instead of part of the result?
14873 @subsubheading @value{GDBN} Command
14875 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
14876 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
14878 @subsubheading Example
14883 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
14885 -break-insert -t foo
14886 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
14889 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
14890 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14891 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14892 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14893 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14894 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14895 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14896 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14897 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
14898 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
14899 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
14901 -break-insert -r foo.*
14902 ~int foo(int, int);
14903 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
14907 @subheading The @code{-break-list} Command
14908 @findex -break-list
14910 @subsubheading Synopsis
14916 Displays the list of inserted breakpoints, showing the following fields:
14920 number of the breakpoint
14922 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
14924 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
14927 is the breakpoint enabled or no: @samp{y} or @samp{n}
14929 memory location at which the breakpoint is set
14931 logical location of the breakpoint, expressed by function name, file
14934 number of times the breakpoint has been hit
14937 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
14938 @code{body} field is an empty list.
14940 @subsubheading @value{GDBN} Command
14942 The corresponding @value{GDBN} command is @samp{info break}.
14944 @subsubheading Example
14949 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
14950 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14951 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14952 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14953 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14954 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14955 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14956 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
14957 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
14958 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
14959 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
14963 Here's an example of the result when there are no breakpoints:
14968 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
14969 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
14970 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
14971 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
14972 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
14973 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
14974 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
14979 @subheading The @code{-break-watch} Command
14980 @findex -break-watch
14982 @subsubheading Synopsis
14985 -break-watch [ -a | -r ]
14988 Create a watchpoint. With the @samp{-a} option it will create an
14989 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
14990 read from or on a write to the memory location. With the @samp{-r}
14991 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
14992 trigger only when the memory location is accessed for reading. Without
14993 either of the options, the watchpoint created is a regular watchpoint,
14994 i.e. it will trigger when the memory location is accessed for writing.
14995 @xref{Set Watchpoints, , Setting watchpoints}.
14997 Note that @samp{-break-list} will report a single list of watchpoints and
14998 breakpoints inserted.
15000 @subsubheading @value{GDBN} Command
15002 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
15005 @subsubheading Example
15007 Setting a watchpoint on a variable in the @code{main} function:
15012 ^done,wpt=@{number="2",exp="x"@}
15016 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
15017 value=@{old="-268439212",new="55"@},
15018 frame=@{func="main",args=[],file="recursive2.c",line="5"@}
15022 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
15023 the program execution twice: first for the variable changing value, then
15024 for the watchpoint going out of scope.
15029 ^done,wpt=@{number="5",exp="C"@}
15033 ^done,reason="watchpoint-trigger",
15034 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
15035 frame=@{func="callee4",args=[],
15036 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15040 ^done,reason="watchpoint-scope",wpnum="5",
15041 frame=@{func="callee3",args=[@{name="strarg",
15042 value="0x11940 \"A string argument.\""@}],
15043 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15047 Listing breakpoints and watchpoints, at different points in the program
15048 execution. Note that once the watchpoint goes out of scope, it is
15054 ^done,wpt=@{number="2",exp="C"@}
15057 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
15058 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15059 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15060 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15061 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15062 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15063 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15064 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15065 addr="0x00010734",func="callee4",
15066 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15067 bkpt=@{number="2",type="watchpoint",disp="keep",
15068 enabled="y",addr="",what="C",times="0"@}]@}
15072 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
15073 value=@{old="-276895068",new="3"@},
15074 frame=@{func="callee4",args=[],
15075 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
15078 ^done,BreakpointTable=@{nr_rows="2",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"@}],
15085 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15086 addr="0x00010734",func="callee4",
15087 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
15088 bkpt=@{number="2",type="watchpoint",disp="keep",
15089 enabled="y",addr="",what="C",times="-5"@}]@}
15093 ^done,reason="watchpoint-scope",wpnum="2",
15094 frame=@{func="callee3",args=[@{name="strarg",
15095 value="0x11940 \"A string argument.\""@}],
15096 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
15099 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
15100 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
15101 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
15102 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
15103 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
15104 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
15105 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
15106 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
15107 addr="0x00010734",func="callee4",
15108 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
15112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15113 @node GDB/MI Data Manipulation
15114 @section @sc{gdb/mi} Data Manipulation
15116 @cindex data manipulation, in @sc{gdb/mi}
15117 @cindex @sc{gdb/mi}, data manipulation
15118 This section describes the @sc{gdb/mi} commands that manipulate data:
15119 examine memory and registers, evaluate expressions, etc.
15121 @c REMOVED FROM THE INTERFACE.
15122 @c @subheading -data-assign
15123 @c Change the value of a program variable. Plenty of side effects.
15124 @c @subsubheading GDB command
15126 @c @subsubheading Example
15129 @subheading The @code{-data-disassemble} Command
15130 @findex -data-disassemble
15132 @subsubheading Synopsis
15136 [ -s @var{start-addr} -e @var{end-addr} ]
15137 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
15145 @item @var{start-addr}
15146 is the beginning address (or @code{$pc})
15147 @item @var{end-addr}
15149 @item @var{filename}
15150 is the name of the file to disassemble
15151 @item @var{linenum}
15152 is the line number to disassemble around
15154 is the the number of disassembly lines to be produced. If it is -1,
15155 the whole function will be disassembled, in case no @var{end-addr} is
15156 specified. If @var{end-addr} is specified as a non-zero value, and
15157 @var{lines} is lower than the number of disassembly lines between
15158 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
15159 displayed; if @var{lines} is higher than the number of lines between
15160 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
15163 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
15167 @subsubheading Result
15169 The output for each instruction is composed of four fields:
15178 Note that whatever included in the instruction field, is not manipulated
15179 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
15181 @subsubheading @value{GDBN} Command
15183 There's no direct mapping from this command to the CLI.
15185 @subsubheading Example
15187 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
15191 -data-disassemble -s $pc -e "$pc + 20" -- 0
15194 @{address="0x000107c0",func-name="main",offset="4",
15195 inst="mov 2, %o0"@},
15196 @{address="0x000107c4",func-name="main",offset="8",
15197 inst="sethi %hi(0x11800), %o2"@},
15198 @{address="0x000107c8",func-name="main",offset="12",
15199 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
15200 @{address="0x000107cc",func-name="main",offset="16",
15201 inst="sethi %hi(0x11800), %o2"@},
15202 @{address="0x000107d0",func-name="main",offset="20",
15203 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
15207 Disassemble the whole @code{main} function. Line 32 is part of
15211 -data-disassemble -f basics.c -l 32 -- 0
15213 @{address="0x000107bc",func-name="main",offset="0",
15214 inst="save %sp, -112, %sp"@},
15215 @{address="0x000107c0",func-name="main",offset="4",
15216 inst="mov 2, %o0"@},
15217 @{address="0x000107c4",func-name="main",offset="8",
15218 inst="sethi %hi(0x11800), %o2"@},
15220 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
15221 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
15225 Disassemble 3 instructions from the start of @code{main}:
15229 -data-disassemble -f basics.c -l 32 -n 3 -- 0
15231 @{address="0x000107bc",func-name="main",offset="0",
15232 inst="save %sp, -112, %sp"@},
15233 @{address="0x000107c0",func-name="main",offset="4",
15234 inst="mov 2, %o0"@},
15235 @{address="0x000107c4",func-name="main",offset="8",
15236 inst="sethi %hi(0x11800), %o2"@}]
15240 Disassemble 3 instructions from the start of @code{main} in mixed mode:
15244 -data-disassemble -f basics.c -l 32 -n 3 -- 1
15246 src_and_asm_line=@{line="31",
15247 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15248 testsuite/gdb.mi/basics.c",line_asm_insn=[
15249 @{address="0x000107bc",func-name="main",offset="0",
15250 inst="save %sp, -112, %sp"@}]@},
15251 src_and_asm_line=@{line="32",
15252 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
15253 testsuite/gdb.mi/basics.c",line_asm_insn=[
15254 @{address="0x000107c0",func-name="main",offset="4",
15255 inst="mov 2, %o0"@},
15256 @{address="0x000107c4",func-name="main",offset="8",
15257 inst="sethi %hi(0x11800), %o2"@}]@}]
15262 @subheading The @code{-data-evaluate-expression} Command
15263 @findex -data-evaluate-expression
15265 @subsubheading Synopsis
15268 -data-evaluate-expression @var{expr}
15271 Evaluate @var{expr} as an expression. The expression could contain an
15272 inferior function call. The function call will execute synchronously.
15273 If the expression contains spaces, it must be enclosed in double quotes.
15275 @subsubheading @value{GDBN} Command
15277 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
15278 @samp{call}. In @code{gdbtk} only, there's a corresponding
15279 @samp{gdb_eval} command.
15281 @subsubheading Example
15283 In the following example, the numbers that precede the commands are the
15284 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
15285 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
15289 211-data-evaluate-expression A
15292 311-data-evaluate-expression &A
15293 311^done,value="0xefffeb7c"
15295 411-data-evaluate-expression A+3
15298 511-data-evaluate-expression "A + 3"
15304 @subheading The @code{-data-list-changed-registers} Command
15305 @findex -data-list-changed-registers
15307 @subsubheading Synopsis
15310 -data-list-changed-registers
15313 Display a list of the registers that have changed.
15315 @subsubheading @value{GDBN} Command
15317 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
15318 has the corresponding command @samp{gdb_changed_register_list}.
15320 @subsubheading Example
15322 On a PPC MBX board:
15330 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
15331 args=[],file="try.c",line="5"@}
15333 -data-list-changed-registers
15334 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
15335 "10","11","13","14","15","16","17","18","19","20","21","22","23",
15336 "24","25","26","27","28","30","31","64","65","66","67","69"]
15341 @subheading The @code{-data-list-register-names} Command
15342 @findex -data-list-register-names
15344 @subsubheading Synopsis
15347 -data-list-register-names [ ( @var{regno} )+ ]
15350 Show a list of register names for the current target. If no arguments
15351 are given, it shows a list of the names of all the registers. If
15352 integer numbers are given as arguments, it will print a list of the
15353 names of the registers corresponding to the arguments. To ensure
15354 consistency between a register name and its number, the output list may
15355 include empty register names.
15357 @subsubheading @value{GDBN} Command
15359 @value{GDBN} does not have a command which corresponds to
15360 @samp{-data-list-register-names}. In @code{gdbtk} there is a
15361 corresponding command @samp{gdb_regnames}.
15363 @subsubheading Example
15365 For the PPC MBX board:
15368 -data-list-register-names
15369 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
15370 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
15371 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
15372 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
15373 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
15374 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
15375 "", "pc","ps","cr","lr","ctr","xer"]
15377 -data-list-register-names 1 2 3
15378 ^done,register-names=["r1","r2","r3"]
15382 @subheading The @code{-data-list-register-values} Command
15383 @findex -data-list-register-values
15385 @subsubheading Synopsis
15388 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
15391 Display the registers' contents. @var{fmt} is the format according to
15392 which the registers' contents are to be returned, followed by an optional
15393 list of numbers specifying the registers to display. A missing list of
15394 numbers indicates that the contents of all the registers must be returned.
15396 Allowed formats for @var{fmt} are:
15413 @subsubheading @value{GDBN} Command
15415 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
15416 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
15418 @subsubheading Example
15420 For a PPC MBX board (note: line breaks are for readability only, they
15421 don't appear in the actual output):
15425 -data-list-register-values r 64 65
15426 ^done,register-values=[@{number="64",value="0xfe00a300"@},
15427 @{number="65",value="0x00029002"@}]
15429 -data-list-register-values x
15430 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
15431 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
15432 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
15433 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
15434 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
15435 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
15436 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
15437 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
15438 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
15439 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
15440 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
15441 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
15442 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
15443 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
15444 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
15445 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
15446 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
15447 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
15448 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
15449 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
15450 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
15451 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
15452 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
15453 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
15454 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
15455 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
15456 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
15457 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
15458 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
15459 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
15460 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
15461 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
15462 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
15463 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
15464 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
15465 @{number="69",value="0x20002b03"@}]
15470 @subheading The @code{-data-read-memory} Command
15471 @findex -data-read-memory
15473 @subsubheading Synopsis
15476 -data-read-memory [ -o @var{byte-offset} ]
15477 @var{address} @var{word-format} @var{word-size}
15478 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
15485 @item @var{address}
15486 An expression specifying the address of the first memory word to be
15487 read. Complex expressions containing embedded white space should be
15488 quoted using the C convention.
15490 @item @var{word-format}
15491 The format to be used to print the memory words. The notation is the
15492 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
15495 @item @var{word-size}
15496 The size of each memory word in bytes.
15498 @item @var{nr-rows}
15499 The number of rows in the output table.
15501 @item @var{nr-cols}
15502 The number of columns in the output table.
15505 If present, indicates that each row should include an @sc{ascii} dump. The
15506 value of @var{aschar} is used as a padding character when a byte is not a
15507 member of the printable @sc{ascii} character set (printable @sc{ascii}
15508 characters are those whose code is between 32 and 126, inclusively).
15510 @item @var{byte-offset}
15511 An offset to add to the @var{address} before fetching memory.
15514 This command displays memory contents as a table of @var{nr-rows} by
15515 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
15516 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
15517 (returned as @samp{total-bytes}). Should less than the requested number
15518 of bytes be returned by the target, the missing words are identified
15519 using @samp{N/A}. The number of bytes read from the target is returned
15520 in @samp{nr-bytes} and the starting address used to read memory in
15523 The address of the next/previous row or page is available in
15524 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
15527 @subsubheading @value{GDBN} Command
15529 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
15530 @samp{gdb_get_mem} memory read command.
15532 @subsubheading Example
15534 Read six bytes of memory starting at @code{bytes+6} but then offset by
15535 @code{-6} bytes. Format as three rows of two columns. One byte per
15536 word. Display each word in hex.
15540 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
15541 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
15542 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
15543 prev-page="0x0000138a",memory=[
15544 @{addr="0x00001390",data=["0x00","0x01"]@},
15545 @{addr="0x00001392",data=["0x02","0x03"]@},
15546 @{addr="0x00001394",data=["0x04","0x05"]@}]
15550 Read two bytes of memory starting at address @code{shorts + 64} and
15551 display as a single word formatted in decimal.
15555 5-data-read-memory shorts+64 d 2 1 1
15556 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
15557 next-row="0x00001512",prev-row="0x0000150e",
15558 next-page="0x00001512",prev-page="0x0000150e",memory=[
15559 @{addr="0x00001510",data=["128"]@}]
15563 Read thirty two bytes of memory starting at @code{bytes+16} and format
15564 as eight rows of four columns. Include a string encoding with @samp{x}
15565 used as the non-printable character.
15569 4-data-read-memory bytes+16 x 1 8 4 x
15570 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
15571 next-row="0x000013c0",prev-row="0x0000139c",
15572 next-page="0x000013c0",prev-page="0x00001380",memory=[
15573 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
15574 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
15575 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
15576 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
15577 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
15578 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
15579 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
15580 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
15584 @subheading The @code{-display-delete} Command
15585 @findex -display-delete
15587 @subsubheading Synopsis
15590 -display-delete @var{number}
15593 Delete the display @var{number}.
15595 @subsubheading @value{GDBN} Command
15597 The corresponding @value{GDBN} command is @samp{delete display}.
15599 @subsubheading Example
15603 @subheading The @code{-display-disable} Command
15604 @findex -display-disable
15606 @subsubheading Synopsis
15609 -display-disable @var{number}
15612 Disable display @var{number}.
15614 @subsubheading @value{GDBN} Command
15616 The corresponding @value{GDBN} command is @samp{disable display}.
15618 @subsubheading Example
15622 @subheading The @code{-display-enable} Command
15623 @findex -display-enable
15625 @subsubheading Synopsis
15628 -display-enable @var{number}
15631 Enable display @var{number}.
15633 @subsubheading @value{GDBN} Command
15635 The corresponding @value{GDBN} command is @samp{enable display}.
15637 @subsubheading Example
15641 @subheading The @code{-display-insert} Command
15642 @findex -display-insert
15644 @subsubheading Synopsis
15647 -display-insert @var{expression}
15650 Display @var{expression} every time the program stops.
15652 @subsubheading @value{GDBN} Command
15654 The corresponding @value{GDBN} command is @samp{display}.
15656 @subsubheading Example
15660 @subheading The @code{-display-list} Command
15661 @findex -display-list
15663 @subsubheading Synopsis
15669 List the displays. Do not show the current values.
15671 @subsubheading @value{GDBN} Command
15673 The corresponding @value{GDBN} command is @samp{info display}.
15675 @subsubheading Example
15679 @subheading The @code{-environment-cd} Command
15680 @findex -environment-cd
15682 @subsubheading Synopsis
15685 -environment-cd @var{pathdir}
15688 Set @value{GDBN}'s working directory.
15690 @subsubheading @value{GDBN} Command
15692 The corresponding @value{GDBN} command is @samp{cd}.
15694 @subsubheading Example
15698 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15704 @subheading The @code{-environment-directory} Command
15705 @findex -environment-directory
15707 @subsubheading Synopsis
15710 -environment-directory [ -r ] [ @var{pathdir} ]+
15713 Add directories @var{pathdir} to beginning of search path for source files.
15714 If the @samp{-r} option is used, the search path is reset to the default
15715 search path. If directories @var{pathdir} are supplied in addition to the
15716 @samp{-r} option, the search path is first reset and then addition
15718 Multiple directories may be specified, separated by blanks. Specifying
15719 multiple directories in a single command
15720 results in the directories added to the beginning of the
15721 search path in the same order they were presented in the command.
15722 If blanks are needed as
15723 part of a directory name, double-quotes should be used around
15724 the name. In the command output, the path will show up separated
15725 by the system directory-separator character. The directory-seperator
15726 character must not be used
15727 in any directory name.
15728 If no directories are specified, the current search path is displayed.
15730 @subsubheading @value{GDBN} Command
15732 The corresponding @value{GDBN} command is @samp{dir}.
15734 @subsubheading Example
15738 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
15739 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15741 -environment-directory ""
15742 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
15744 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
15745 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
15747 -environment-directory -r
15748 ^done,source-path="$cdir:$cwd"
15753 @subheading The @code{-environment-path} Command
15754 @findex -environment-path
15756 @subsubheading Synopsis
15759 -environment-path [ -r ] [ @var{pathdir} ]+
15762 Add directories @var{pathdir} to beginning of search path for object files.
15763 If the @samp{-r} option is used, the search path is reset to the original
15764 search path that existed at gdb start-up. If directories @var{pathdir} are
15765 supplied in addition to the
15766 @samp{-r} option, the search path is first reset and then addition
15768 Multiple directories may be specified, separated by blanks. Specifying
15769 multiple directories in a single command
15770 results in the directories added to the beginning of the
15771 search path in the same order they were presented in the command.
15772 If blanks are needed as
15773 part of a directory name, double-quotes should be used around
15774 the name. In the command output, the path will show up separated
15775 by the system directory-separator character. The directory-seperator
15776 character must not be used
15777 in any directory name.
15778 If no directories are specified, the current path is displayed.
15781 @subsubheading @value{GDBN} Command
15783 The corresponding @value{GDBN} command is @samp{path}.
15785 @subsubheading Example
15790 ^done,path="/usr/bin"
15792 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
15793 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
15795 -environment-path -r /usr/local/bin
15796 ^done,path="/usr/local/bin:/usr/bin"
15801 @subheading The @code{-environment-pwd} Command
15802 @findex -environment-pwd
15804 @subsubheading Synopsis
15810 Show the current working directory.
15812 @subsubheading @value{GDBN} command
15814 The corresponding @value{GDBN} command is @samp{pwd}.
15816 @subsubheading Example
15821 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
15825 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
15826 @node GDB/MI Program Control
15827 @section @sc{gdb/mi} Program control
15829 @subsubheading Program termination
15831 As a result of execution, the inferior program can run to completion, if
15832 it doesn't encounter any breakpoints. In this case the output will
15833 include an exit code, if the program has exited exceptionally.
15835 @subsubheading Examples
15838 Program exited normally:
15846 *stopped,reason="exited-normally"
15851 Program exited exceptionally:
15859 *stopped,reason="exited",exit-code="01"
15863 Another way the program can terminate is if it receives a signal such as
15864 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
15868 *stopped,reason="exited-signalled",signal-name="SIGINT",
15869 signal-meaning="Interrupt"
15873 @subheading The @code{-exec-abort} Command
15874 @findex -exec-abort
15876 @subsubheading Synopsis
15882 Kill the inferior running program.
15884 @subsubheading @value{GDBN} Command
15886 The corresponding @value{GDBN} command is @samp{kill}.
15888 @subsubheading Example
15892 @subheading The @code{-exec-arguments} Command
15893 @findex -exec-arguments
15895 @subsubheading Synopsis
15898 -exec-arguments @var{args}
15901 Set the inferior program arguments, to be used in the next
15904 @subsubheading @value{GDBN} Command
15906 The corresponding @value{GDBN} command is @samp{set args}.
15908 @subsubheading Example
15911 Don't have one around.
15914 @subheading The @code{-exec-continue} Command
15915 @findex -exec-continue
15917 @subsubheading Synopsis
15923 Asynchronous command. Resumes the execution of the inferior program
15924 until a breakpoint is encountered, or until the inferior exits.
15926 @subsubheading @value{GDBN} Command
15928 The corresponding @value{GDBN} corresponding is @samp{continue}.
15930 @subsubheading Example
15937 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
15938 file="hello.c",line="13"@}
15943 @subheading The @code{-exec-finish} Command
15944 @findex -exec-finish
15946 @subsubheading Synopsis
15952 Asynchronous command. Resumes the execution of the inferior program
15953 until the current function is exited. Displays the results returned by
15956 @subsubheading @value{GDBN} Command
15958 The corresponding @value{GDBN} command is @samp{finish}.
15960 @subsubheading Example
15962 Function returning @code{void}.
15969 *stopped,reason="function-finished",frame=@{func="main",args=[],
15970 file="hello.c",line="7"@}
15974 Function returning other than @code{void}. The name of the internal
15975 @value{GDBN} variable storing the result is printed, together with the
15982 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
15983 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
15984 file="recursive2.c",line="14"@},
15985 gdb-result-var="$1",return-value="0"
15990 @subheading The @code{-exec-interrupt} Command
15991 @findex -exec-interrupt
15993 @subsubheading Synopsis
15999 Asynchronous command. Interrupts the background execution of the target.
16000 Note how the token associated with the stop message is the one for the
16001 execution command that has been interrupted. The token for the interrupt
16002 itself only appears in the @samp{^done} output. If the user is trying to
16003 interrupt a non-running program, an error message will be printed.
16005 @subsubheading @value{GDBN} Command
16007 The corresponding @value{GDBN} command is @samp{interrupt}.
16009 @subsubheading Example
16020 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
16021 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",line="13"@}
16026 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
16031 @subheading The @code{-exec-next} Command
16034 @subsubheading Synopsis
16040 Asynchronous command. Resumes execution of the inferior program, stopping
16041 when the beginning of the next source line is reached.
16043 @subsubheading @value{GDBN} Command
16045 The corresponding @value{GDBN} command is @samp{next}.
16047 @subsubheading Example
16053 *stopped,reason="end-stepping-range",line="8",file="hello.c"
16058 @subheading The @code{-exec-next-instruction} Command
16059 @findex -exec-next-instruction
16061 @subsubheading Synopsis
16064 -exec-next-instruction
16067 Asynchronous command. Executes one machine instruction. If the
16068 instruction is a function call continues until the function returns. If
16069 the program stops at an instruction in the middle of a source line, the
16070 address will be printed as well.
16072 @subsubheading @value{GDBN} Command
16074 The corresponding @value{GDBN} command is @samp{nexti}.
16076 @subsubheading Example
16080 -exec-next-instruction
16084 *stopped,reason="end-stepping-range",
16085 addr="0x000100d4",line="5",file="hello.c"
16090 @subheading The @code{-exec-return} Command
16091 @findex -exec-return
16093 @subsubheading Synopsis
16099 Makes current function return immediately. Doesn't execute the inferior.
16100 Displays the new current frame.
16102 @subsubheading @value{GDBN} Command
16104 The corresponding @value{GDBN} command is @samp{return}.
16106 @subsubheading Example
16110 200-break-insert callee4
16111 200^done,bkpt=@{number="1",addr="0x00010734",
16112 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16117 000*stopped,reason="breakpoint-hit",bkptno="1",
16118 frame=@{func="callee4",args=[],
16119 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
16125 111^done,frame=@{level="0",func="callee3",
16126 args=[@{name="strarg",
16127 value="0x11940 \"A string argument.\""@}],
16128 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
16133 @subheading The @code{-exec-run} Command
16136 @subsubheading Synopsis
16142 Asynchronous command. Starts execution of the inferior from the
16143 beginning. The inferior executes until either a breakpoint is
16144 encountered or the program exits.
16146 @subsubheading @value{GDBN} Command
16148 The corresponding @value{GDBN} command is @samp{run}.
16150 @subsubheading Example
16155 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
16160 *stopped,reason="breakpoint-hit",bkptno="1",
16161 frame=@{func="main",args=[],file="recursive2.c",line="4"@}
16166 @subheading The @code{-exec-show-arguments} Command
16167 @findex -exec-show-arguments
16169 @subsubheading Synopsis
16172 -exec-show-arguments
16175 Print the arguments of the program.
16177 @subsubheading @value{GDBN} Command
16179 The corresponding @value{GDBN} command is @samp{show args}.
16181 @subsubheading Example
16184 @c @subheading -exec-signal
16186 @subheading The @code{-exec-step} Command
16189 @subsubheading Synopsis
16195 Asynchronous command. Resumes execution of the inferior program, stopping
16196 when the beginning of the next source line is reached, if the next
16197 source line is not a function call. If it is, stop at the first
16198 instruction of the called function.
16200 @subsubheading @value{GDBN} Command
16202 The corresponding @value{GDBN} command is @samp{step}.
16204 @subsubheading Example
16206 Stepping into a function:
16212 *stopped,reason="end-stepping-range",
16213 frame=@{func="foo",args=[@{name="a",value="10"@},
16214 @{name="b",value="0"@}],file="recursive2.c",line="11"@}
16224 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
16229 @subheading The @code{-exec-step-instruction} Command
16230 @findex -exec-step-instruction
16232 @subsubheading Synopsis
16235 -exec-step-instruction
16238 Asynchronous command. Resumes the inferior which executes one machine
16239 instruction. The output, once @value{GDBN} has stopped, will vary depending on
16240 whether we have stopped in the middle of a source line or not. In the
16241 former case, the address at which the program stopped will be printed as
16244 @subsubheading @value{GDBN} Command
16246 The corresponding @value{GDBN} command is @samp{stepi}.
16248 @subsubheading Example
16252 -exec-step-instruction
16256 *stopped,reason="end-stepping-range",
16257 frame=@{func="foo",args=[],file="try.c",line="10"@}
16259 -exec-step-instruction
16263 *stopped,reason="end-stepping-range",
16264 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",line="10"@}
16269 @subheading The @code{-exec-until} Command
16270 @findex -exec-until
16272 @subsubheading Synopsis
16275 -exec-until [ @var{location} ]
16278 Asynchronous command. Executes the inferior until the @var{location}
16279 specified in the argument is reached. If there is no argument, the inferior
16280 executes until a source line greater than the current one is reached.
16281 The reason for stopping in this case will be @samp{location-reached}.
16283 @subsubheading @value{GDBN} Command
16285 The corresponding @value{GDBN} command is @samp{until}.
16287 @subsubheading Example
16291 -exec-until recursive2.c:6
16295 *stopped,reason="location-reached",frame=@{func="main",args=[],
16296 file="recursive2.c",line="6"@}
16301 @subheading -file-clear
16302 Is this going away????
16306 @subheading The @code{-file-exec-and-symbols} Command
16307 @findex -file-exec-and-symbols
16309 @subsubheading Synopsis
16312 -file-exec-and-symbols @var{file}
16315 Specify the executable file to be debugged. This file is the one from
16316 which the symbol table is also read. If no file is specified, the
16317 command clears the executable and symbol information. If breakpoints
16318 are set when using this command with no arguments, @value{GDBN} will produce
16319 error messages. Otherwise, no output is produced, except a completion
16322 @subsubheading @value{GDBN} Command
16324 The corresponding @value{GDBN} command is @samp{file}.
16326 @subsubheading Example
16330 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16336 @subheading The @code{-file-exec-file} Command
16337 @findex -file-exec-file
16339 @subsubheading Synopsis
16342 -file-exec-file @var{file}
16345 Specify the executable file to be debugged. Unlike
16346 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
16347 from this file. If used without argument, @value{GDBN} clears the information
16348 about the executable file. No output is produced, except a completion
16351 @subsubheading @value{GDBN} Command
16353 The corresponding @value{GDBN} command is @samp{exec-file}.
16355 @subsubheading Example
16359 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16365 @subheading The @code{-file-list-exec-sections} Command
16366 @findex -file-list-exec-sections
16368 @subsubheading Synopsis
16371 -file-list-exec-sections
16374 List the sections of the current executable file.
16376 @subsubheading @value{GDBN} Command
16378 The @value{GDBN} command @samp{info file} shows, among the rest, the same
16379 information as this command. @code{gdbtk} has a corresponding command
16380 @samp{gdb_load_info}.
16382 @subsubheading Example
16386 @subheading The @code{-file-list-exec-source-file} Command
16387 @findex -file-list-exec-source-file
16389 @subsubheading Synopsis
16392 -file-list-exec-source-file
16395 List the line number, the current source file, and the absolute path
16396 to the current source file for the current executable.
16398 @subsubheading @value{GDBN} Command
16400 There's no @value{GDBN} command which directly corresponds to this one.
16402 @subsubheading Example
16406 123-file-list-exec-source-file
16407 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
16412 @subheading The @code{-file-list-exec-source-files} Command
16413 @findex -file-list-exec-source-files
16415 @subsubheading Synopsis
16418 -file-list-exec-source-files
16421 List the source files for the current executable.
16423 @subsubheading @value{GDBN} Command
16425 There's no @value{GDBN} command which directly corresponds to this one.
16426 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
16428 @subsubheading Example
16432 @subheading The @code{-file-list-shared-libraries} Command
16433 @findex -file-list-shared-libraries
16435 @subsubheading Synopsis
16438 -file-list-shared-libraries
16441 List the shared libraries in the program.
16443 @subsubheading @value{GDBN} Command
16445 The corresponding @value{GDBN} command is @samp{info shared}.
16447 @subsubheading Example
16451 @subheading The @code{-file-list-symbol-files} Command
16452 @findex -file-list-symbol-files
16454 @subsubheading Synopsis
16457 -file-list-symbol-files
16462 @subsubheading @value{GDBN} Command
16464 The corresponding @value{GDBN} command is @samp{info file} (part of it).
16466 @subsubheading Example
16470 @subheading The @code{-file-symbol-file} Command
16471 @findex -file-symbol-file
16473 @subsubheading Synopsis
16476 -file-symbol-file @var{file}
16479 Read symbol table info from the specified @var{file} argument. When
16480 used without arguments, clears @value{GDBN}'s symbol table info. No output is
16481 produced, except for a completion notification.
16483 @subsubheading @value{GDBN} Command
16485 The corresponding @value{GDBN} command is @samp{symbol-file}.
16487 @subsubheading Example
16491 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
16496 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16497 @node GDB/MI Miscellaneous Commands
16498 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
16500 @c @subheading -gdb-complete
16502 @subheading The @code{-gdb-exit} Command
16505 @subsubheading Synopsis
16511 Exit @value{GDBN} immediately.
16513 @subsubheading @value{GDBN} Command
16515 Approximately corresponds to @samp{quit}.
16517 @subsubheading Example
16524 @subheading The @code{-gdb-set} Command
16527 @subsubheading Synopsis
16533 Set an internal @value{GDBN} variable.
16534 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
16536 @subsubheading @value{GDBN} Command
16538 The corresponding @value{GDBN} command is @samp{set}.
16540 @subsubheading Example
16550 @subheading The @code{-gdb-show} Command
16553 @subsubheading Synopsis
16559 Show the current value of a @value{GDBN} variable.
16561 @subsubheading @value{GDBN} command
16563 The corresponding @value{GDBN} command is @samp{show}.
16565 @subsubheading Example
16574 @c @subheading -gdb-source
16577 @subheading The @code{-gdb-version} Command
16578 @findex -gdb-version
16580 @subsubheading Synopsis
16586 Show version information for @value{GDBN}. Used mostly in testing.
16588 @subsubheading @value{GDBN} Command
16590 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
16591 information when you start an interactive session.
16593 @subsubheading Example
16595 @c This example modifies the actual output from GDB to avoid overfull
16601 ~Copyright 2000 Free Software Foundation, Inc.
16602 ~GDB is free software, covered by the GNU General Public License, and
16603 ~you are welcome to change it and/or distribute copies of it under
16604 ~ certain conditions.
16605 ~Type "show copying" to see the conditions.
16606 ~There is absolutely no warranty for GDB. Type "show warranty" for
16608 ~This GDB was configured as
16609 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
16614 @subheading The @code{-interpreter-exec} Command
16615 @findex -interpreter-exec
16617 @subheading Synopsis
16620 -interpreter-exec @var{interpreter} @var{command}
16623 Execute the specified @var{command} in the given @var{interpreter}.
16625 @subheading @value{GDBN} Command
16627 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
16629 @subheading Example
16633 -interpreter-exec console "break main"
16634 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
16635 &"During symbol reading, bad structure-type format.\n"
16636 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
16642 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16643 @node GDB/MI Kod Commands
16644 @section @sc{gdb/mi} Kod Commands
16646 The Kod commands are not implemented.
16648 @c @subheading -kod-info
16650 @c @subheading -kod-list
16652 @c @subheading -kod-list-object-types
16654 @c @subheading -kod-show
16656 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16657 @node GDB/MI Memory Overlay Commands
16658 @section @sc{gdb/mi} Memory Overlay Commands
16660 The memory overlay commands are not implemented.
16662 @c @subheading -overlay-auto
16664 @c @subheading -overlay-list-mapping-state
16666 @c @subheading -overlay-list-overlays
16668 @c @subheading -overlay-map
16670 @c @subheading -overlay-off
16672 @c @subheading -overlay-on
16674 @c @subheading -overlay-unmap
16676 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16677 @node GDB/MI Signal Handling Commands
16678 @section @sc{gdb/mi} Signal Handling Commands
16680 Signal handling commands are not implemented.
16682 @c @subheading -signal-handle
16684 @c @subheading -signal-list-handle-actions
16686 @c @subheading -signal-list-signal-types
16690 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16691 @node GDB/MI Stack Manipulation
16692 @section @sc{gdb/mi} Stack Manipulation Commands
16695 @subheading The @code{-stack-info-frame} Command
16696 @findex -stack-info-frame
16698 @subsubheading Synopsis
16704 Get info on the current frame.
16706 @subsubheading @value{GDBN} Command
16708 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
16709 (without arguments).
16711 @subsubheading Example
16714 @subheading The @code{-stack-info-depth} Command
16715 @findex -stack-info-depth
16717 @subsubheading Synopsis
16720 -stack-info-depth [ @var{max-depth} ]
16723 Return the depth of the stack. If the integer argument @var{max-depth}
16724 is specified, do not count beyond @var{max-depth} frames.
16726 @subsubheading @value{GDBN} Command
16728 There's no equivalent @value{GDBN} command.
16730 @subsubheading Example
16732 For a stack with frame levels 0 through 11:
16739 -stack-info-depth 4
16742 -stack-info-depth 12
16745 -stack-info-depth 11
16748 -stack-info-depth 13
16753 @subheading The @code{-stack-list-arguments} Command
16754 @findex -stack-list-arguments
16756 @subsubheading Synopsis
16759 -stack-list-arguments @var{show-values}
16760 [ @var{low-frame} @var{high-frame} ]
16763 Display a list of the arguments for the frames between @var{low-frame}
16764 and @var{high-frame} (inclusive). If @var{low-frame} and
16765 @var{high-frame} are not provided, list the arguments for the whole call
16768 The @var{show-values} argument must have a value of 0 or 1. A value of
16769 0 means that only the names of the arguments are listed, a value of 1
16770 means that both names and values of the arguments are printed.
16772 @subsubheading @value{GDBN} Command
16774 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
16775 @samp{gdb_get_args} command which partially overlaps with the
16776 functionality of @samp{-stack-list-arguments}.
16778 @subsubheading Example
16785 frame=@{level="0",addr="0x00010734",func="callee4",
16786 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
16787 frame=@{level="1",addr="0x0001076c",func="callee3",
16788 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
16789 frame=@{level="2",addr="0x0001078c",func="callee2",
16790 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
16791 frame=@{level="3",addr="0x000107b4",func="callee1",
16792 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
16793 frame=@{level="4",addr="0x000107e0",func="main",
16794 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
16796 -stack-list-arguments 0
16799 frame=@{level="0",args=[]@},
16800 frame=@{level="1",args=[name="strarg"]@},
16801 frame=@{level="2",args=[name="intarg",name="strarg"]@},
16802 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
16803 frame=@{level="4",args=[]@}]
16805 -stack-list-arguments 1
16808 frame=@{level="0",args=[]@},
16810 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16811 frame=@{level="2",args=[
16812 @{name="intarg",value="2"@},
16813 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
16814 @{frame=@{level="3",args=[
16815 @{name="intarg",value="2"@},
16816 @{name="strarg",value="0x11940 \"A string argument.\""@},
16817 @{name="fltarg",value="3.5"@}]@},
16818 frame=@{level="4",args=[]@}]
16820 -stack-list-arguments 0 2 2
16821 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
16823 -stack-list-arguments 1 2 2
16824 ^done,stack-args=[frame=@{level="2",
16825 args=[@{name="intarg",value="2"@},
16826 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
16830 @c @subheading -stack-list-exception-handlers
16833 @subheading The @code{-stack-list-frames} Command
16834 @findex -stack-list-frames
16836 @subsubheading Synopsis
16839 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
16842 List the frames currently on the stack. For each frame it displays the
16847 The frame number, 0 being the topmost frame, i.e. the innermost function.
16849 The @code{$pc} value for that frame.
16853 File name of the source file where the function lives.
16855 Line number corresponding to the @code{$pc}.
16858 If invoked without arguments, this command prints a backtrace for the
16859 whole stack. If given two integer arguments, it shows the frames whose
16860 levels are between the two arguments (inclusive). If the two arguments
16861 are equal, it shows the single frame at the corresponding level.
16863 @subsubheading @value{GDBN} Command
16865 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
16867 @subsubheading Example
16869 Full stack backtrace:
16875 [frame=@{level="0",addr="0x0001076c",func="foo",
16876 file="recursive2.c",line="11"@},
16877 frame=@{level="1",addr="0x000107a4",func="foo",
16878 file="recursive2.c",line="14"@},
16879 frame=@{level="2",addr="0x000107a4",func="foo",
16880 file="recursive2.c",line="14"@},
16881 frame=@{level="3",addr="0x000107a4",func="foo",
16882 file="recursive2.c",line="14"@},
16883 frame=@{level="4",addr="0x000107a4",func="foo",
16884 file="recursive2.c",line="14"@},
16885 frame=@{level="5",addr="0x000107a4",func="foo",
16886 file="recursive2.c",line="14"@},
16887 frame=@{level="6",addr="0x000107a4",func="foo",
16888 file="recursive2.c",line="14"@},
16889 frame=@{level="7",addr="0x000107a4",func="foo",
16890 file="recursive2.c",line="14"@},
16891 frame=@{level="8",addr="0x000107a4",func="foo",
16892 file="recursive2.c",line="14"@},
16893 frame=@{level="9",addr="0x000107a4",func="foo",
16894 file="recursive2.c",line="14"@},
16895 frame=@{level="10",addr="0x000107a4",func="foo",
16896 file="recursive2.c",line="14"@},
16897 frame=@{level="11",addr="0x00010738",func="main",
16898 file="recursive2.c",line="4"@}]
16902 Show frames between @var{low_frame} and @var{high_frame}:
16906 -stack-list-frames 3 5
16908 [frame=@{level="3",addr="0x000107a4",func="foo",
16909 file="recursive2.c",line="14"@},
16910 frame=@{level="4",addr="0x000107a4",func="foo",
16911 file="recursive2.c",line="14"@},
16912 frame=@{level="5",addr="0x000107a4",func="foo",
16913 file="recursive2.c",line="14"@}]
16917 Show a single frame:
16921 -stack-list-frames 3 3
16923 [frame=@{level="3",addr="0x000107a4",func="foo",
16924 file="recursive2.c",line="14"@}]
16929 @subheading The @code{-stack-list-locals} Command
16930 @findex -stack-list-locals
16932 @subsubheading Synopsis
16935 -stack-list-locals @var{print-values}
16938 Display the local variable names for the current frame. With an
16939 argument of 0 prints only the names of the variables, with argument of 1
16940 prints also their values.
16942 @subsubheading @value{GDBN} Command
16944 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
16946 @subsubheading Example
16950 -stack-list-locals 0
16951 ^done,locals=[name="A",name="B",name="C"]
16953 -stack-list-locals 1
16954 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
16955 @{name="C",value="3"@}]
16960 @subheading The @code{-stack-select-frame} Command
16961 @findex -stack-select-frame
16963 @subsubheading Synopsis
16966 -stack-select-frame @var{framenum}
16969 Change the current frame. Select a different frame @var{framenum} on
16972 @subsubheading @value{GDBN} Command
16974 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
16975 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
16977 @subsubheading Example
16981 -stack-select-frame 2
16986 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16987 @node GDB/MI Symbol Query
16988 @section @sc{gdb/mi} Symbol Query Commands
16991 @subheading The @code{-symbol-info-address} Command
16992 @findex -symbol-info-address
16994 @subsubheading Synopsis
16997 -symbol-info-address @var{symbol}
17000 Describe where @var{symbol} is stored.
17002 @subsubheading @value{GDBN} Command
17004 The corresponding @value{GDBN} command is @samp{info address}.
17006 @subsubheading Example
17010 @subheading The @code{-symbol-info-file} Command
17011 @findex -symbol-info-file
17013 @subsubheading Synopsis
17019 Show the file for the symbol.
17021 @subsubheading @value{GDBN} Command
17023 There's no equivalent @value{GDBN} command. @code{gdbtk} has
17024 @samp{gdb_find_file}.
17026 @subsubheading Example
17030 @subheading The @code{-symbol-info-function} Command
17031 @findex -symbol-info-function
17033 @subsubheading Synopsis
17036 -symbol-info-function
17039 Show which function the symbol lives in.
17041 @subsubheading @value{GDBN} Command
17043 @samp{gdb_get_function} in @code{gdbtk}.
17045 @subsubheading Example
17049 @subheading The @code{-symbol-info-line} Command
17050 @findex -symbol-info-line
17052 @subsubheading Synopsis
17058 Show the core addresses of the code for a source line.
17060 @subsubheading @value{GDBN} Command
17062 The corresponding @value{GDBN} comamnd is @samp{info line}.
17063 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
17065 @subsubheading Example
17069 @subheading The @code{-symbol-info-symbol} Command
17070 @findex -symbol-info-symbol
17072 @subsubheading Synopsis
17075 -symbol-info-symbol @var{addr}
17078 Describe what symbol is at location @var{addr}.
17080 @subsubheading @value{GDBN} Command
17082 The corresponding @value{GDBN} command is @samp{info symbol}.
17084 @subsubheading Example
17088 @subheading The @code{-symbol-list-functions} Command
17089 @findex -symbol-list-functions
17091 @subsubheading Synopsis
17094 -symbol-list-functions
17097 List the functions in the executable.
17099 @subsubheading @value{GDBN} Command
17101 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
17102 @samp{gdb_search} in @code{gdbtk}.
17104 @subsubheading Example
17108 @subheading The @code{-symbol-list-lines} Command
17109 @findex -symbol-list-lines
17111 @subsubheading Synopsis
17114 -symbol-list-lines @var{filename}
17117 Print the list of lines that contain code and their associated program
17118 addresses for the given source filename. The entries are sorted in
17119 ascending PC order.
17121 @subsubheading @value{GDBN} Command
17123 There is no corresponding @value{GDBN} command.
17125 @subsubheading Example
17128 -symbol-list-lines basics.c
17129 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
17134 @subheading The @code{-symbol-list-types} Command
17135 @findex -symbol-list-types
17137 @subsubheading Synopsis
17143 List all the type names.
17145 @subsubheading @value{GDBN} Command
17147 The corresponding commands are @samp{info types} in @value{GDBN},
17148 @samp{gdb_search} in @code{gdbtk}.
17150 @subsubheading Example
17154 @subheading The @code{-symbol-list-variables} Command
17155 @findex -symbol-list-variables
17157 @subsubheading Synopsis
17160 -symbol-list-variables
17163 List all the global and static variable names.
17165 @subsubheading @value{GDBN} Command
17167 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
17169 @subsubheading Example
17173 @subheading The @code{-symbol-locate} Command
17174 @findex -symbol-locate
17176 @subsubheading Synopsis
17182 @subsubheading @value{GDBN} Command
17184 @samp{gdb_loc} in @code{gdbtk}.
17186 @subsubheading Example
17190 @subheading The @code{-symbol-type} Command
17191 @findex -symbol-type
17193 @subsubheading Synopsis
17196 -symbol-type @var{variable}
17199 Show type of @var{variable}.
17201 @subsubheading @value{GDBN} Command
17203 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
17204 @samp{gdb_obj_variable}.
17206 @subsubheading Example
17210 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17211 @node GDB/MI Target Manipulation
17212 @section @sc{gdb/mi} Target Manipulation Commands
17215 @subheading The @code{-target-attach} Command
17216 @findex -target-attach
17218 @subsubheading Synopsis
17221 -target-attach @var{pid} | @var{file}
17224 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
17226 @subsubheading @value{GDBN} command
17228 The corresponding @value{GDBN} command is @samp{attach}.
17230 @subsubheading Example
17234 @subheading The @code{-target-compare-sections} Command
17235 @findex -target-compare-sections
17237 @subsubheading Synopsis
17240 -target-compare-sections [ @var{section} ]
17243 Compare data of section @var{section} on target to the exec file.
17244 Without the argument, all sections are compared.
17246 @subsubheading @value{GDBN} Command
17248 The @value{GDBN} equivalent is @samp{compare-sections}.
17250 @subsubheading Example
17254 @subheading The @code{-target-detach} Command
17255 @findex -target-detach
17257 @subsubheading Synopsis
17263 Disconnect from the remote target. There's no output.
17265 @subsubheading @value{GDBN} command
17267 The corresponding @value{GDBN} command is @samp{detach}.
17269 @subsubheading Example
17279 @subheading The @code{-target-download} Command
17280 @findex -target-download
17282 @subsubheading Synopsis
17288 Loads the executable onto the remote target.
17289 It prints out an update message every half second, which includes the fields:
17293 The name of the section.
17295 The size of what has been sent so far for that section.
17297 The size of the section.
17299 The total size of what was sent so far (the current and the previous sections).
17301 The size of the overall executable to download.
17305 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
17306 @sc{gdb/mi} Output Syntax}).
17308 In addition, it prints the name and size of the sections, as they are
17309 downloaded. These messages include the following fields:
17313 The name of the section.
17315 The size of the section.
17317 The size of the overall executable to download.
17321 At the end, a summary is printed.
17323 @subsubheading @value{GDBN} Command
17325 The corresponding @value{GDBN} command is @samp{load}.
17327 @subsubheading Example
17329 Note: each status message appears on a single line. Here the messages
17330 have been broken down so that they can fit onto a page.
17335 +download,@{section=".text",section-size="6668",total-size="9880"@}
17336 +download,@{section=".text",section-sent="512",section-size="6668",
17337 total-sent="512",total-size="9880"@}
17338 +download,@{section=".text",section-sent="1024",section-size="6668",
17339 total-sent="1024",total-size="9880"@}
17340 +download,@{section=".text",section-sent="1536",section-size="6668",
17341 total-sent="1536",total-size="9880"@}
17342 +download,@{section=".text",section-sent="2048",section-size="6668",
17343 total-sent="2048",total-size="9880"@}
17344 +download,@{section=".text",section-sent="2560",section-size="6668",
17345 total-sent="2560",total-size="9880"@}
17346 +download,@{section=".text",section-sent="3072",section-size="6668",
17347 total-sent="3072",total-size="9880"@}
17348 +download,@{section=".text",section-sent="3584",section-size="6668",
17349 total-sent="3584",total-size="9880"@}
17350 +download,@{section=".text",section-sent="4096",section-size="6668",
17351 total-sent="4096",total-size="9880"@}
17352 +download,@{section=".text",section-sent="4608",section-size="6668",
17353 total-sent="4608",total-size="9880"@}
17354 +download,@{section=".text",section-sent="5120",section-size="6668",
17355 total-sent="5120",total-size="9880"@}
17356 +download,@{section=".text",section-sent="5632",section-size="6668",
17357 total-sent="5632",total-size="9880"@}
17358 +download,@{section=".text",section-sent="6144",section-size="6668",
17359 total-sent="6144",total-size="9880"@}
17360 +download,@{section=".text",section-sent="6656",section-size="6668",
17361 total-sent="6656",total-size="9880"@}
17362 +download,@{section=".init",section-size="28",total-size="9880"@}
17363 +download,@{section=".fini",section-size="28",total-size="9880"@}
17364 +download,@{section=".data",section-size="3156",total-size="9880"@}
17365 +download,@{section=".data",section-sent="512",section-size="3156",
17366 total-sent="7236",total-size="9880"@}
17367 +download,@{section=".data",section-sent="1024",section-size="3156",
17368 total-sent="7748",total-size="9880"@}
17369 +download,@{section=".data",section-sent="1536",section-size="3156",
17370 total-sent="8260",total-size="9880"@}
17371 +download,@{section=".data",section-sent="2048",section-size="3156",
17372 total-sent="8772",total-size="9880"@}
17373 +download,@{section=".data",section-sent="2560",section-size="3156",
17374 total-sent="9284",total-size="9880"@}
17375 +download,@{section=".data",section-sent="3072",section-size="3156",
17376 total-sent="9796",total-size="9880"@}
17377 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
17383 @subheading The @code{-target-exec-status} Command
17384 @findex -target-exec-status
17386 @subsubheading Synopsis
17389 -target-exec-status
17392 Provide information on the state of the target (whether it is running or
17393 not, for instance).
17395 @subsubheading @value{GDBN} Command
17397 There's no equivalent @value{GDBN} command.
17399 @subsubheading Example
17403 @subheading The @code{-target-list-available-targets} Command
17404 @findex -target-list-available-targets
17406 @subsubheading Synopsis
17409 -target-list-available-targets
17412 List the possible targets to connect to.
17414 @subsubheading @value{GDBN} Command
17416 The corresponding @value{GDBN} command is @samp{help target}.
17418 @subsubheading Example
17422 @subheading The @code{-target-list-current-targets} Command
17423 @findex -target-list-current-targets
17425 @subsubheading Synopsis
17428 -target-list-current-targets
17431 Describe the current target.
17433 @subsubheading @value{GDBN} Command
17435 The corresponding information is printed by @samp{info file} (among
17438 @subsubheading Example
17442 @subheading The @code{-target-list-parameters} Command
17443 @findex -target-list-parameters
17445 @subsubheading Synopsis
17448 -target-list-parameters
17453 @subsubheading @value{GDBN} Command
17457 @subsubheading Example
17461 @subheading The @code{-target-select} Command
17462 @findex -target-select
17464 @subsubheading Synopsis
17467 -target-select @var{type} @var{parameters @dots{}}
17470 Connect @value{GDBN} to the remote target. This command takes two args:
17474 The type of target, for instance @samp{async}, @samp{remote}, etc.
17475 @item @var{parameters}
17476 Device names, host names and the like. @xref{Target Commands, ,
17477 Commands for managing targets}, for more details.
17480 The output is a connection notification, followed by the address at
17481 which the target program is, in the following form:
17484 ^connected,addr="@var{address}",func="@var{function name}",
17485 args=[@var{arg list}]
17488 @subsubheading @value{GDBN} Command
17490 The corresponding @value{GDBN} command is @samp{target}.
17492 @subsubheading Example
17496 -target-select async /dev/ttya
17497 ^connected,addr="0xfe00a300",func="??",args=[]
17501 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17502 @node GDB/MI Thread Commands
17503 @section @sc{gdb/mi} Thread Commands
17506 @subheading The @code{-thread-info} Command
17507 @findex -thread-info
17509 @subsubheading Synopsis
17515 @subsubheading @value{GDBN} command
17519 @subsubheading Example
17523 @subheading The @code{-thread-list-all-threads} Command
17524 @findex -thread-list-all-threads
17526 @subsubheading Synopsis
17529 -thread-list-all-threads
17532 @subsubheading @value{GDBN} Command
17534 The equivalent @value{GDBN} command is @samp{info threads}.
17536 @subsubheading Example
17540 @subheading The @code{-thread-list-ids} Command
17541 @findex -thread-list-ids
17543 @subsubheading Synopsis
17549 Produces a list of the currently known @value{GDBN} thread ids. At the
17550 end of the list it also prints the total number of such threads.
17552 @subsubheading @value{GDBN} Command
17554 Part of @samp{info threads} supplies the same information.
17556 @subsubheading Example
17558 No threads present, besides the main process:
17563 ^done,thread-ids=@{@},number-of-threads="0"
17573 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17574 number-of-threads="3"
17579 @subheading The @code{-thread-select} Command
17580 @findex -thread-select
17582 @subsubheading Synopsis
17585 -thread-select @var{threadnum}
17588 Make @var{threadnum} the current thread. It prints the number of the new
17589 current thread, and the topmost frame for that thread.
17591 @subsubheading @value{GDBN} Command
17593 The corresponding @value{GDBN} command is @samp{thread}.
17595 @subsubheading Example
17602 *stopped,reason="end-stepping-range",thread-id="2",line="187",
17603 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
17607 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
17608 number-of-threads="3"
17611 ^done,new-thread-id="3",
17612 frame=@{level="0",func="vprintf",
17613 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
17614 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
17618 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17619 @node GDB/MI Tracepoint Commands
17620 @section @sc{gdb/mi} Tracepoint Commands
17622 The tracepoint commands are not yet implemented.
17624 @c @subheading -trace-actions
17626 @c @subheading -trace-delete
17628 @c @subheading -trace-disable
17630 @c @subheading -trace-dump
17632 @c @subheading -trace-enable
17634 @c @subheading -trace-exists
17636 @c @subheading -trace-find
17638 @c @subheading -trace-frame-number
17640 @c @subheading -trace-info
17642 @c @subheading -trace-insert
17644 @c @subheading -trace-list
17646 @c @subheading -trace-pass-count
17648 @c @subheading -trace-save
17650 @c @subheading -trace-start
17652 @c @subheading -trace-stop
17655 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17656 @node GDB/MI Variable Objects
17657 @section @sc{gdb/mi} Variable Objects
17660 @subheading Motivation for Variable Objects in @sc{gdb/mi}
17662 For the implementation of a variable debugger window (locals, watched
17663 expressions, etc.), we are proposing the adaptation of the existing code
17664 used by @code{Insight}.
17666 The two main reasons for that are:
17670 It has been proven in practice (it is already on its second generation).
17673 It will shorten development time (needless to say how important it is
17677 The original interface was designed to be used by Tcl code, so it was
17678 slightly changed so it could be used through @sc{gdb/mi}. This section
17679 describes the @sc{gdb/mi} operations that will be available and gives some
17680 hints about their use.
17682 @emph{Note}: In addition to the set of operations described here, we
17683 expect the @sc{gui} implementation of a variable window to require, at
17684 least, the following operations:
17687 @item @code{-gdb-show} @code{output-radix}
17688 @item @code{-stack-list-arguments}
17689 @item @code{-stack-list-locals}
17690 @item @code{-stack-select-frame}
17693 @subheading Introduction to Variable Objects in @sc{gdb/mi}
17695 @cindex variable objects in @sc{gdb/mi}
17696 The basic idea behind variable objects is the creation of a named object
17697 to represent a variable, an expression, a memory location or even a CPU
17698 register. For each object created, a set of operations is available for
17699 examining or changing its properties.
17701 Furthermore, complex data types, such as C structures, are represented
17702 in a tree format. For instance, the @code{struct} type variable is the
17703 root and the children will represent the struct members. If a child
17704 is itself of a complex type, it will also have children of its own.
17705 Appropriate language differences are handled for C, C@t{++} and Java.
17707 When returning the actual values of the objects, this facility allows
17708 for the individual selection of the display format used in the result
17709 creation. It can be chosen among: binary, decimal, hexadecimal, octal
17710 and natural. Natural refers to a default format automatically
17711 chosen based on the variable type (like decimal for an @code{int}, hex
17712 for pointers, etc.).
17714 The following is the complete set of @sc{gdb/mi} operations defined to
17715 access this functionality:
17717 @multitable @columnfractions .4 .6
17718 @item @strong{Operation}
17719 @tab @strong{Description}
17721 @item @code{-var-create}
17722 @tab create a variable object
17723 @item @code{-var-delete}
17724 @tab delete the variable object and its children
17725 @item @code{-var-set-format}
17726 @tab set the display format of this variable
17727 @item @code{-var-show-format}
17728 @tab show the display format of this variable
17729 @item @code{-var-info-num-children}
17730 @tab tells how many children this object has
17731 @item @code{-var-list-children}
17732 @tab return a list of the object's children
17733 @item @code{-var-info-type}
17734 @tab show the type of this variable object
17735 @item @code{-var-info-expression}
17736 @tab print what this variable object represents
17737 @item @code{-var-show-attributes}
17738 @tab is this variable editable? does it exist here?
17739 @item @code{-var-evaluate-expression}
17740 @tab get the value of this variable
17741 @item @code{-var-assign}
17742 @tab set the value of this variable
17743 @item @code{-var-update}
17744 @tab update the variable and its children
17747 In the next subsection we describe each operation in detail and suggest
17748 how it can be used.
17750 @subheading Description And Use of Operations on Variable Objects
17752 @subheading The @code{-var-create} Command
17753 @findex -var-create
17755 @subsubheading Synopsis
17758 -var-create @{@var{name} | "-"@}
17759 @{@var{frame-addr} | "*"@} @var{expression}
17762 This operation creates a variable object, which allows the monitoring of
17763 a variable, the result of an expression, a memory cell or a CPU
17766 The @var{name} parameter is the string by which the object can be
17767 referenced. It must be unique. If @samp{-} is specified, the varobj
17768 system will generate a string ``varNNNNNN'' automatically. It will be
17769 unique provided that one does not specify @var{name} on that format.
17770 The command fails if a duplicate name is found.
17772 The frame under which the expression should be evaluated can be
17773 specified by @var{frame-addr}. A @samp{*} indicates that the current
17774 frame should be used.
17776 @var{expression} is any expression valid on the current language set (must not
17777 begin with a @samp{*}), or one of the following:
17781 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
17784 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
17787 @samp{$@var{regname}} --- a CPU register name
17790 @subsubheading Result
17792 This operation returns the name, number of children and the type of the
17793 object created. Type is returned as a string as the ones generated by
17794 the @value{GDBN} CLI:
17797 name="@var{name}",numchild="N",type="@var{type}"
17801 @subheading The @code{-var-delete} Command
17802 @findex -var-delete
17804 @subsubheading Synopsis
17807 -var-delete @var{name}
17810 Deletes a previously created variable object and all of its children.
17812 Returns an error if the object @var{name} is not found.
17815 @subheading The @code{-var-set-format} Command
17816 @findex -var-set-format
17818 @subsubheading Synopsis
17821 -var-set-format @var{name} @var{format-spec}
17824 Sets the output format for the value of the object @var{name} to be
17827 The syntax for the @var{format-spec} is as follows:
17830 @var{format-spec} @expansion{}
17831 @{binary | decimal | hexadecimal | octal | natural@}
17835 @subheading The @code{-var-show-format} Command
17836 @findex -var-show-format
17838 @subsubheading Synopsis
17841 -var-show-format @var{name}
17844 Returns the format used to display the value of the object @var{name}.
17847 @var{format} @expansion{}
17852 @subheading The @code{-var-info-num-children} Command
17853 @findex -var-info-num-children
17855 @subsubheading Synopsis
17858 -var-info-num-children @var{name}
17861 Returns the number of children of a variable object @var{name}:
17868 @subheading The @code{-var-list-children} Command
17869 @findex -var-list-children
17871 @subsubheading Synopsis
17874 -var-list-children @var{name}
17877 Returns a list of the children of the specified variable object:
17880 numchild=@var{n},children=[@{name=@var{name},
17881 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
17885 @subheading The @code{-var-info-type} Command
17886 @findex -var-info-type
17888 @subsubheading Synopsis
17891 -var-info-type @var{name}
17894 Returns the type of the specified variable @var{name}. The type is
17895 returned as a string in the same format as it is output by the
17899 type=@var{typename}
17903 @subheading The @code{-var-info-expression} Command
17904 @findex -var-info-expression
17906 @subsubheading Synopsis
17909 -var-info-expression @var{name}
17912 Returns what is represented by the variable object @var{name}:
17915 lang=@var{lang-spec},exp=@var{expression}
17919 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
17921 @subheading The @code{-var-show-attributes} Command
17922 @findex -var-show-attributes
17924 @subsubheading Synopsis
17927 -var-show-attributes @var{name}
17930 List attributes of the specified variable object @var{name}:
17933 status=@var{attr} [ ( ,@var{attr} )* ]
17937 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
17939 @subheading The @code{-var-evaluate-expression} Command
17940 @findex -var-evaluate-expression
17942 @subsubheading Synopsis
17945 -var-evaluate-expression @var{name}
17948 Evaluates the expression that is represented by the specified variable
17949 object and returns its value as a string in the current format specified
17956 Note that one must invoke @code{-var-list-children} for a variable
17957 before the value of a child variable can be evaluated.
17959 @subheading The @code{-var-assign} Command
17960 @findex -var-assign
17962 @subsubheading Synopsis
17965 -var-assign @var{name} @var{expression}
17968 Assigns the value of @var{expression} to the variable object specified
17969 by @var{name}. The object must be @samp{editable}. If the variable's
17970 value is altered by the assign, the variable will show up in any
17971 subsequent @code{-var-update} list.
17973 @subsubheading Example
17981 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
17985 @subheading The @code{-var-update} Command
17986 @findex -var-update
17988 @subsubheading Synopsis
17991 -var-update @{@var{name} | "*"@}
17994 Update the value of the variable object @var{name} by evaluating its
17995 expression after fetching all the new values from memory or registers.
17996 A @samp{*} causes all existing variable objects to be updated.
18000 @chapter @value{GDBN} Annotations
18002 This chapter describes annotations in @value{GDBN}. Annotations are
18003 designed to interface @value{GDBN} to graphical user interfaces or
18004 other similar programs which want to interact with @value{GDBN} at a
18005 relatively high level.
18008 This is Edition @value{EDITION}, @value{DATE}.
18012 * Annotations Overview:: What annotations are; the general syntax.
18013 * Server Prefix:: Issuing a command without affecting user state.
18014 * Value Annotations:: Values are marked as such.
18015 * Frame Annotations:: Stack frames are annotated.
18016 * Displays:: @value{GDBN} can be told to display something periodically.
18017 * Prompting:: Annotations marking @value{GDBN}'s need for input.
18018 * Errors:: Annotations for error messages.
18019 * Breakpoint Info:: Information on breakpoints.
18020 * Invalidation:: Some annotations describe things now invalid.
18021 * Annotations for Running::
18022 Whether the program is running, how it stopped, etc.
18023 * Source Annotations:: Annotations describing source code.
18024 * TODO:: Annotations which might be added in the future.
18027 @node Annotations Overview
18028 @section What is an Annotation?
18029 @cindex annotations
18031 To produce annotations, start @value{GDBN} with the @code{--annotate=2} option.
18033 Annotations start with a newline character, two @samp{control-z}
18034 characters, and the name of the annotation. If there is no additional
18035 information associated with this annotation, the name of the annotation
18036 is followed immediately by a newline. If there is additional
18037 information, the name of the annotation is followed by a space, the
18038 additional information, and a newline. The additional information
18039 cannot contain newline characters.
18041 Any output not beginning with a newline and two @samp{control-z}
18042 characters denotes literal output from @value{GDBN}. Currently there is
18043 no need for @value{GDBN} to output a newline followed by two
18044 @samp{control-z} characters, but if there was such a need, the
18045 annotations could be extended with an @samp{escape} annotation which
18046 means those three characters as output.
18048 A simple example of starting up @value{GDBN} with annotations is:
18053 Copyright 2000 Free Software Foundation, Inc.
18054 GDB is free software, covered by the GNU General Public License,
18055 and you are welcome to change it and/or distribute copies of it
18056 under certain conditions.
18057 Type "show copying" to see the conditions.
18058 There is absolutely no warranty for GDB. Type "show warranty"
18060 This GDB was configured as "sparc-sun-sunos4.1.3"
18071 Here @samp{quit} is input to @value{GDBN}; the rest is output from
18072 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
18073 denotes a @samp{control-z} character) are annotations; the rest is
18074 output from @value{GDBN}.
18076 @node Server Prefix
18077 @section The Server Prefix
18078 @cindex server prefix for annotations
18080 To issue a command to @value{GDBN} without affecting certain aspects of
18081 the state which is seen by users, prefix it with @samp{server }. This
18082 means that this command will not affect the command history, nor will it
18083 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18084 pressed on a line by itself.
18086 The server prefix does not affect the recording of values into the value
18087 history; to print a value without recording it into the value history,
18088 use the @code{output} command instead of the @code{print} command.
18090 @node Value Annotations
18093 @cindex annotations for values
18094 When a value is printed in various contexts, @value{GDBN} uses
18095 annotations to delimit the value from the surrounding text.
18097 @findex value-history-begin
18098 @findex value-history-value
18099 @findex value-history-end
18100 If a value is printed using @code{print} and added to the value history,
18101 the annotation looks like
18104 ^Z^Zvalue-history-begin @var{history-number} @var{value-flags}
18105 @var{history-string}
18106 ^Z^Zvalue-history-value
18108 ^Z^Zvalue-history-end
18112 where @var{history-number} is the number it is getting in the value
18113 history, @var{history-string} is a string, such as @samp{$5 = }, which
18114 introduces the value to the user, @var{the-value} is the output
18115 corresponding to the value itself, and @var{value-flags} is @samp{*} for
18116 a value which can be dereferenced and @samp{-} for a value which cannot.
18118 @findex value-begin
18120 If the value is not added to the value history (it is an invalid float
18121 or it is printed with the @code{output} command), the annotation is similar:
18124 ^Z^Zvalue-begin @var{value-flags}
18130 @findex arg-name-end
18133 When @value{GDBN} prints an argument to a function (for example, in the output
18134 from the @code{backtrace} command), it annotates it as follows:
18138 @var{argument-name}
18140 @var{separator-string}
18141 ^Z^Zarg-value @var{value-flags}
18147 where @var{argument-name} is the name of the argument,
18148 @var{separator-string} is text which separates the name from the value
18149 for the user's benefit (such as @samp{=}), and @var{value-flags} and
18150 @var{the-value} have the same meanings as in a
18151 @code{value-history-begin} annotation.
18153 @findex field-begin
18154 @findex field-name-end
18155 @findex field-value
18157 When printing a structure, @value{GDBN} annotates it as follows:
18160 ^Z^Zfield-begin @var{value-flags}
18163 @var{separator-string}
18170 where @var{field-name} is the name of the field, @var{separator-string}
18171 is text which separates the name from the value for the user's benefit
18172 (such as @samp{=}), and @var{value-flags} and @var{the-value} have the
18173 same meanings as in a @code{value-history-begin} annotation.
18175 When printing an array, @value{GDBN} annotates it as follows:
18178 ^Z^Zarray-section-begin @var{array-index} @var{value-flags}
18182 where @var{array-index} is the index of the first element being
18183 annotated and @var{value-flags} has the same meaning as in a
18184 @code{value-history-begin} annotation. This is followed by any number
18185 of elements, where is element can be either a single element:
18189 @samp{,} @var{whitespace} ; @r{omitted for the first element}
18194 or a repeated element
18197 @findex elt-rep-end
18199 @samp{,} @var{whitespace} ; @r{omitted for the first element}
18201 ^Z^Zelt-rep @var{number-of-repetitions}
18202 @var{repetition-string}
18206 In both cases, @var{the-value} is the output for the value of the
18207 element and @var{whitespace} can contain spaces, tabs, and newlines. In
18208 the repeated case, @var{number-of-repetitions} is the number of
18209 consecutive array elements which contain that value, and
18210 @var{repetition-string} is a string which is designed to convey to the
18211 user that repetition is being depicted.
18213 @findex array-section-end
18214 Once all the array elements have been output, the array annotation is
18218 ^Z^Zarray-section-end
18221 @node Frame Annotations
18224 @cindex annotations for frames
18225 Whenever @value{GDBN} prints a frame, it annotates it. For example, this applies
18226 to frames printed when @value{GDBN} stops, output from commands such as
18227 @code{backtrace} or @code{up}, etc.
18229 @findex frame-begin
18230 The frame annotation begins with
18233 ^Z^Zframe-begin @var{level} @var{address}
18238 where @var{level} is the number of the frame (0 is the innermost frame,
18239 and other frames have positive numbers), @var{address} is the address of
18240 the code executing in that frame, and @var{level-string} is a string
18241 designed to convey the level to the user. @var{address} is in the form
18242 @samp{0x} followed by one or more lowercase hex digits (note that this
18243 does not depend on the language). The frame ends with
18250 Between these annotations is the main body of the frame, which can
18255 @findex function-call
18258 @var{function-call-string}
18261 where @var{function-call-string} is text designed to convey to the user
18262 that this frame is associated with a function call made by @value{GDBN} to a
18263 function in the program being debugged.
18266 @findex signal-handler-caller
18268 ^Z^Zsignal-handler-caller
18269 @var{signal-handler-caller-string}
18272 where @var{signal-handler-caller-string} is text designed to convey to
18273 the user that this frame is associated with whatever mechanism is used
18274 by this operating system to call a signal handler (it is the frame which
18275 calls the signal handler, not the frame for the signal handler itself).
18280 @findex frame-address
18281 @findex frame-address-end
18282 This can optionally (depending on whether this is thought of as
18283 interesting information for the user to see) begin with
18288 ^Z^Zframe-address-end
18289 @var{separator-string}
18292 where @var{address} is the address executing in the frame (the same
18293 address as in the @code{frame-begin} annotation, but printed in a form
18294 which is intended for user consumption---in particular, the syntax varies
18295 depending on the language), and @var{separator-string} is a string
18296 intended to separate this address from what follows for the user's
18299 @findex frame-function-name
18304 ^Z^Zframe-function-name
18305 @var{function-name}
18310 where @var{function-name} is the name of the function executing in the
18311 frame, or @samp{??} if not known, and @var{arguments} are the arguments
18312 to the frame, with parentheses around them (each argument is annotated
18313 individually as well, @pxref{Value Annotations}).
18315 @findex frame-source-begin
18316 @findex frame-source-file
18317 @findex frame-source-file-end
18318 @findex frame-source-line
18319 @findex frame-source-end
18320 If source information is available, a reference to it is then printed:
18323 ^Z^Zframe-source-begin
18324 @var{source-intro-string}
18325 ^Z^Zframe-source-file
18327 ^Z^Zframe-source-file-end
18329 ^Z^Zframe-source-line
18331 ^Z^Zframe-source-end
18334 where @var{source-intro-string} separates for the user's benefit the
18335 reference from the text which precedes it, @var{filename} is the name of
18336 the source file, and @var{line-number} is the line number within that
18337 file (the first line is line 1).
18339 @findex frame-where
18340 If @value{GDBN} prints some information about where the frame is from (which
18341 library, which load segment, etc.; currently only done on the RS/6000),
18342 it is annotated with
18349 Then, if source is to actually be displayed for this frame (for example,
18350 this is not true for output from the @code{backtrace} command), then a
18351 @code{source} annotation (@pxref{Source Annotations}) is displayed. Unlike
18352 most annotations, this is output instead of the normal text which would be
18353 output, not in addition.
18359 @findex display-begin
18360 @findex display-number-end
18361 @findex display-format
18362 @findex display-expression
18363 @findex display-expression-end
18364 @findex display-value
18365 @findex display-end
18366 @cindex annotations for display
18367 When @value{GDBN} is told to display something using the @code{display} command,
18368 the results of the display are annotated:
18373 ^Z^Zdisplay-number-end
18374 @var{number-separator}
18377 ^Z^Zdisplay-expression
18379 ^Z^Zdisplay-expression-end
18380 @var{expression-separator}
18387 where @var{number} is the number of the display, @var{number-separator}
18388 is intended to separate the number from what follows for the user,
18389 @var{format} includes information such as the size, format, or other
18390 information about how the value is being displayed, @var{expression} is
18391 the expression being displayed, @var{expression-separator} is intended
18392 to separate the expression from the text that follows for the user,
18393 and @var{value} is the actual value being displayed.
18396 @section Annotation for @value{GDBN} Input
18398 @cindex annotations for prompts
18399 When @value{GDBN} prompts for input, it annotates this fact so it is possible
18400 to know when to send output, when the output from a given command is
18403 Different kinds of input each have a different @dfn{input type}. Each
18404 input type has three annotations: a @code{pre-} annotation, which
18405 denotes the beginning of any prompt which is being output, a plain
18406 annotation, which denotes the end of the prompt, and then a @code{post-}
18407 annotation which denotes the end of any echo which may (or may not) be
18408 associated with the input. For example, the @code{prompt} input type
18409 features the following annotations:
18417 The input types are
18422 @findex post-prompt
18424 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
18426 @findex pre-commands
18428 @findex post-commands
18430 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
18431 command. The annotations are repeated for each command which is input.
18433 @findex pre-overload-choice
18434 @findex overload-choice
18435 @findex post-overload-choice
18436 @item overload-choice
18437 When @value{GDBN} wants the user to select between various overloaded functions.
18443 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
18445 @findex pre-prompt-for-continue
18446 @findex prompt-for-continue
18447 @findex post-prompt-for-continue
18448 @item prompt-for-continue
18449 When @value{GDBN} is asking the user to press return to continue. Note: Don't
18450 expect this to work well; instead use @code{set height 0} to disable
18451 prompting. This is because the counting of lines is buggy in the
18452 presence of annotations.
18457 @cindex annotations for errors, warnings and interrupts
18464 This annotation occurs right before @value{GDBN} responds to an interrupt.
18471 This annotation occurs right before @value{GDBN} responds to an error.
18473 Quit and error annotations indicate that any annotations which @value{GDBN} was
18474 in the middle of may end abruptly. For example, if a
18475 @code{value-history-begin} annotation is followed by a @code{error}, one
18476 cannot expect to receive the matching @code{value-history-end}. One
18477 cannot expect not to receive it either, however; an error annotation
18478 does not necessarily mean that @value{GDBN} is immediately returning all the way
18481 @findex error-begin
18482 A quit or error annotation may be preceded by
18488 Any output between that and the quit or error annotation is the error
18491 Warning messages are not yet annotated.
18492 @c If we want to change that, need to fix warning(), type_error(),
18493 @c range_error(), and possibly other places.
18495 @node Breakpoint Info
18496 @section Information on Breakpoints
18498 @cindex annotations for breakpoints
18499 The output from the @code{info breakpoints} command is annotated as follows:
18501 @findex breakpoints-headers
18502 @findex breakpoints-table
18504 ^Z^Zbreakpoints-headers
18506 ^Z^Zbreakpoints-table
18510 where @var{header-entry} has the same syntax as an entry (see below) but
18511 instead of containing data, it contains strings which are intended to
18512 convey the meaning of each field to the user. This is followed by any
18513 number of entries. If a field does not apply for this entry, it is
18514 omitted. Fields may contain trailing whitespace. Each entry consists
18543 Note that @var{address} is intended for user consumption---the syntax
18544 varies depending on the language.
18546 The output ends with
18548 @findex breakpoints-table-end
18550 ^Z^Zbreakpoints-table-end
18554 @section Invalidation Notices
18556 @cindex annotations for invalidation messages
18557 The following annotations say that certain pieces of state may have
18561 @findex frames-invalid
18562 @item ^Z^Zframes-invalid
18564 The frames (for example, output from the @code{backtrace} command) may
18567 @findex breakpoints-invalid
18568 @item ^Z^Zbreakpoints-invalid
18570 The breakpoints may have changed. For example, the user just added or
18571 deleted a breakpoint.
18574 @node Annotations for Running
18575 @section Running the Program
18576 @cindex annotations for running programs
18580 When the program starts executing due to a @value{GDBN} command such as
18581 @code{step} or @code{continue},
18587 is output. When the program stops,
18593 is output. Before the @code{stopped} annotation, a variety of
18594 annotations describe how the program stopped.
18598 @item ^Z^Zexited @var{exit-status}
18599 The program exited, and @var{exit-status} is the exit status (zero for
18600 successful exit, otherwise nonzero).
18603 @findex signal-name
18604 @findex signal-name-end
18605 @findex signal-string
18606 @findex signal-string-end
18607 @item ^Z^Zsignalled
18608 The program exited with a signal. After the @code{^Z^Zsignalled}, the
18609 annotation continues:
18615 ^Z^Zsignal-name-end
18619 ^Z^Zsignal-string-end
18624 where @var{name} is the name of the signal, such as @code{SIGILL} or
18625 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
18626 as @code{Illegal Instruction} or @code{Segmentation fault}.
18627 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
18628 user's benefit and have no particular format.
18632 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
18633 just saying that the program received the signal, not that it was
18634 terminated with it.
18637 @item ^Z^Zbreakpoint @var{number}
18638 The program hit breakpoint number @var{number}.
18641 @item ^Z^Zwatchpoint @var{number}
18642 The program hit watchpoint number @var{number}.
18645 @node Source Annotations
18646 @section Displaying Source
18647 @cindex annotations for source display
18650 The following annotation is used instead of displaying source code:
18653 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
18656 where @var{filename} is an absolute file name indicating which source
18657 file, @var{line} is the line number within that file (where 1 is the
18658 first line in the file), @var{character} is the character position
18659 within the file (where 0 is the first character in the file) (for most
18660 debug formats this will necessarily point to the beginning of a line),
18661 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
18662 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
18663 @var{addr} is the address in the target program associated with the
18664 source which is being displayed. @var{addr} is in the form @samp{0x}
18665 followed by one or more lowercase hex digits (note that this does not
18666 depend on the language).
18669 @section Annotations We Might Want in the Future
18673 the target might have changed (registers, heap contents, or
18674 execution status). For performance, we might eventually want
18675 to hit `registers-invalid' and `all-registers-invalid' with
18678 - systematic annotation for set/show parameters (including
18679 invalidation notices).
18681 - similarly, `info' returns a list of candidates for invalidation
18686 @chapter Reporting Bugs in @value{GDBN}
18687 @cindex bugs in @value{GDBN}
18688 @cindex reporting bugs in @value{GDBN}
18690 Your bug reports play an essential role in making @value{GDBN} reliable.
18692 Reporting a bug may help you by bringing a solution to your problem, or it
18693 may not. But in any case the principal function of a bug report is to help
18694 the entire community by making the next version of @value{GDBN} work better. Bug
18695 reports are your contribution to the maintenance of @value{GDBN}.
18697 In order for a bug report to serve its purpose, you must include the
18698 information that enables us to fix the bug.
18701 * Bug Criteria:: Have you found a bug?
18702 * Bug Reporting:: How to report bugs
18706 @section Have you found a bug?
18707 @cindex bug criteria
18709 If you are not sure whether you have found a bug, here are some guidelines:
18712 @cindex fatal signal
18713 @cindex debugger crash
18714 @cindex crash of debugger
18716 If the debugger gets a fatal signal, for any input whatever, that is a
18717 @value{GDBN} bug. Reliable debuggers never crash.
18719 @cindex error on valid input
18721 If @value{GDBN} produces an error message for valid input, that is a
18722 bug. (Note that if you're cross debugging, the problem may also be
18723 somewhere in the connection to the target.)
18725 @cindex invalid input
18727 If @value{GDBN} does not produce an error message for invalid input,
18728 that is a bug. However, you should note that your idea of
18729 ``invalid input'' might be our idea of ``an extension'' or ``support
18730 for traditional practice''.
18733 If you are an experienced user of debugging tools, your suggestions
18734 for improvement of @value{GDBN} are welcome in any case.
18737 @node Bug Reporting
18738 @section How to report bugs
18739 @cindex bug reports
18740 @cindex @value{GDBN} bugs, reporting
18742 A number of companies and individuals offer support for @sc{gnu} products.
18743 If you obtained @value{GDBN} from a support organization, we recommend you
18744 contact that organization first.
18746 You can find contact information for many support companies and
18747 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
18749 @c should add a web page ref...
18751 In any event, we also recommend that you submit bug reports for
18752 @value{GDBN}. The prefered method is to submit them directly using
18753 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
18754 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
18757 @strong{Do not send bug reports to @samp{info-gdb}, or to
18758 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
18759 not want to receive bug reports. Those that do have arranged to receive
18762 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
18763 serves as a repeater. The mailing list and the newsgroup carry exactly
18764 the same messages. Often people think of posting bug reports to the
18765 newsgroup instead of mailing them. This appears to work, but it has one
18766 problem which can be crucial: a newsgroup posting often lacks a mail
18767 path back to the sender. Thus, if we need to ask for more information,
18768 we may be unable to reach you. For this reason, it is better to send
18769 bug reports to the mailing list.
18771 The fundamental principle of reporting bugs usefully is this:
18772 @strong{report all the facts}. If you are not sure whether to state a
18773 fact or leave it out, state it!
18775 Often people omit facts because they think they know what causes the
18776 problem and assume that some details do not matter. Thus, you might
18777 assume that the name of the variable you use in an example does not matter.
18778 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
18779 stray memory reference which happens to fetch from the location where that
18780 name is stored in memory; perhaps, if the name were different, the contents
18781 of that location would fool the debugger into doing the right thing despite
18782 the bug. Play it safe and give a specific, complete example. That is the
18783 easiest thing for you to do, and the most helpful.
18785 Keep in mind that the purpose of a bug report is to enable us to fix the
18786 bug. It may be that the bug has been reported previously, but neither
18787 you nor we can know that unless your bug report is complete and
18790 Sometimes people give a few sketchy facts and ask, ``Does this ring a
18791 bell?'' Those bug reports are useless, and we urge everyone to
18792 @emph{refuse to respond to them} except to chide the sender to report
18795 To enable us to fix the bug, you should include all these things:
18799 The version of @value{GDBN}. @value{GDBN} announces it if you start
18800 with no arguments; you can also print it at any time using @code{show
18803 Without this, we will not know whether there is any point in looking for
18804 the bug in the current version of @value{GDBN}.
18807 The type of machine you are using, and the operating system name and
18811 What compiler (and its version) was used to compile @value{GDBN}---e.g.
18812 ``@value{GCC}--2.8.1''.
18815 What compiler (and its version) was used to compile the program you are
18816 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
18817 C Compiler''. For GCC, you can say @code{gcc --version} to get this
18818 information; for other compilers, see the documentation for those
18822 The command arguments you gave the compiler to compile your example and
18823 observe the bug. For example, did you use @samp{-O}? To guarantee
18824 you will not omit something important, list them all. A copy of the
18825 Makefile (or the output from make) is sufficient.
18827 If we were to try to guess the arguments, we would probably guess wrong
18828 and then we might not encounter the bug.
18831 A complete input script, and all necessary source files, that will
18835 A description of what behavior you observe that you believe is
18836 incorrect. For example, ``It gets a fatal signal.''
18838 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
18839 will certainly notice it. But if the bug is incorrect output, we might
18840 not notice unless it is glaringly wrong. You might as well not give us
18841 a chance to make a mistake.
18843 Even if the problem you experience is a fatal signal, you should still
18844 say so explicitly. Suppose something strange is going on, such as, your
18845 copy of @value{GDBN} is out of synch, or you have encountered a bug in
18846 the C library on your system. (This has happened!) Your copy might
18847 crash and ours would not. If you told us to expect a crash, then when
18848 ours fails to crash, we would know that the bug was not happening for
18849 us. If you had not told us to expect a crash, then we would not be able
18850 to draw any conclusion from our observations.
18853 If you wish to suggest changes to the @value{GDBN} source, send us context
18854 diffs. If you even discuss something in the @value{GDBN} source, refer to
18855 it by context, not by line number.
18857 The line numbers in our development sources will not match those in your
18858 sources. Your line numbers would convey no useful information to us.
18862 Here are some things that are not necessary:
18866 A description of the envelope of the bug.
18868 Often people who encounter a bug spend a lot of time investigating
18869 which changes to the input file will make the bug go away and which
18870 changes will not affect it.
18872 This is often time consuming and not very useful, because the way we
18873 will find the bug is by running a single example under the debugger
18874 with breakpoints, not by pure deduction from a series of examples.
18875 We recommend that you save your time for something else.
18877 Of course, if you can find a simpler example to report @emph{instead}
18878 of the original one, that is a convenience for us. Errors in the
18879 output will be easier to spot, running under the debugger will take
18880 less time, and so on.
18882 However, simplification is not vital; if you do not want to do this,
18883 report the bug anyway and send us the entire test case you used.
18886 A patch for the bug.
18888 A patch for the bug does help us if it is a good one. But do not omit
18889 the necessary information, such as the test case, on the assumption that
18890 a patch is all we need. We might see problems with your patch and decide
18891 to fix the problem another way, or we might not understand it at all.
18893 Sometimes with a program as complicated as @value{GDBN} it is very hard to
18894 construct an example that will make the program follow a certain path
18895 through the code. If you do not send us the example, we will not be able
18896 to construct one, so we will not be able to verify that the bug is fixed.
18898 And if we cannot understand what bug you are trying to fix, or why your
18899 patch should be an improvement, we will not install it. A test case will
18900 help us to understand.
18903 A guess about what the bug is or what it depends on.
18905 Such guesses are usually wrong. Even we cannot guess right about such
18906 things without first using the debugger to find the facts.
18909 @c The readline documentation is distributed with the readline code
18910 @c and consists of the two following files:
18912 @c inc-hist.texinfo
18913 @c Use -I with makeinfo to point to the appropriate directory,
18914 @c environment var TEXINPUTS with TeX.
18915 @include rluser.texinfo
18916 @include inc-hist.texinfo
18919 @node Formatting Documentation
18920 @appendix Formatting Documentation
18922 @cindex @value{GDBN} reference card
18923 @cindex reference card
18924 The @value{GDBN} 4 release includes an already-formatted reference card, ready
18925 for printing with PostScript or Ghostscript, in the @file{gdb}
18926 subdirectory of the main source directory@footnote{In
18927 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
18928 release.}. If you can use PostScript or Ghostscript with your printer,
18929 you can print the reference card immediately with @file{refcard.ps}.
18931 The release also includes the source for the reference card. You
18932 can format it, using @TeX{}, by typing:
18938 The @value{GDBN} reference card is designed to print in @dfn{landscape}
18939 mode on US ``letter'' size paper;
18940 that is, on a sheet 11 inches wide by 8.5 inches
18941 high. You will need to specify this form of printing as an option to
18942 your @sc{dvi} output program.
18944 @cindex documentation
18946 All the documentation for @value{GDBN} comes as part of the machine-readable
18947 distribution. The documentation is written in Texinfo format, which is
18948 a documentation system that uses a single source file to produce both
18949 on-line information and a printed manual. You can use one of the Info
18950 formatting commands to create the on-line version of the documentation
18951 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
18953 @value{GDBN} includes an already formatted copy of the on-line Info
18954 version of this manual in the @file{gdb} subdirectory. The main Info
18955 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
18956 subordinate files matching @samp{gdb.info*} in the same directory. If
18957 necessary, you can print out these files, or read them with any editor;
18958 but they are easier to read using the @code{info} subsystem in @sc{gnu}
18959 Emacs or the standalone @code{info} program, available as part of the
18960 @sc{gnu} Texinfo distribution.
18962 If you want to format these Info files yourself, you need one of the
18963 Info formatting programs, such as @code{texinfo-format-buffer} or
18966 If you have @code{makeinfo} installed, and are in the top level
18967 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
18968 version @value{GDBVN}), you can make the Info file by typing:
18975 If you want to typeset and print copies of this manual, you need @TeX{},
18976 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
18977 Texinfo definitions file.
18979 @TeX{} is a typesetting program; it does not print files directly, but
18980 produces output files called @sc{dvi} files. To print a typeset
18981 document, you need a program to print @sc{dvi} files. If your system
18982 has @TeX{} installed, chances are it has such a program. The precise
18983 command to use depends on your system; @kbd{lpr -d} is common; another
18984 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
18985 require a file name without any extension or a @samp{.dvi} extension.
18987 @TeX{} also requires a macro definitions file called
18988 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
18989 written in Texinfo format. On its own, @TeX{} cannot either read or
18990 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
18991 and is located in the @file{gdb-@var{version-number}/texinfo}
18994 If you have @TeX{} and a @sc{dvi} printer program installed, you can
18995 typeset and print this manual. First switch to the the @file{gdb}
18996 subdirectory of the main source directory (for example, to
18997 @file{gdb-@value{GDBVN}/gdb}) and type:
19003 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
19005 @node Installing GDB
19006 @appendix Installing @value{GDBN}
19007 @cindex configuring @value{GDBN}
19008 @cindex installation
19009 @cindex configuring @value{GDBN}, and source tree subdirectories
19011 @value{GDBN} comes with a @code{configure} script that automates the process
19012 of preparing @value{GDBN} for installation; you can then use @code{make} to
19013 build the @code{gdb} program.
19015 @c irrelevant in info file; it's as current as the code it lives with.
19016 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
19017 look at the @file{README} file in the sources; we may have improved the
19018 installation procedures since publishing this manual.}
19021 The @value{GDBN} distribution includes all the source code you need for
19022 @value{GDBN} in a single directory, whose name is usually composed by
19023 appending the version number to @samp{gdb}.
19025 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
19026 @file{gdb-@value{GDBVN}} directory. That directory contains:
19029 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
19030 script for configuring @value{GDBN} and all its supporting libraries
19032 @item gdb-@value{GDBVN}/gdb
19033 the source specific to @value{GDBN} itself
19035 @item gdb-@value{GDBVN}/bfd
19036 source for the Binary File Descriptor library
19038 @item gdb-@value{GDBVN}/include
19039 @sc{gnu} include files
19041 @item gdb-@value{GDBVN}/libiberty
19042 source for the @samp{-liberty} free software library
19044 @item gdb-@value{GDBVN}/opcodes
19045 source for the library of opcode tables and disassemblers
19047 @item gdb-@value{GDBVN}/readline
19048 source for the @sc{gnu} command-line interface
19050 @item gdb-@value{GDBVN}/glob
19051 source for the @sc{gnu} filename pattern-matching subroutine
19053 @item gdb-@value{GDBVN}/mmalloc
19054 source for the @sc{gnu} memory-mapped malloc package
19057 The simplest way to configure and build @value{GDBN} is to run @code{configure}
19058 from the @file{gdb-@var{version-number}} source directory, which in
19059 this example is the @file{gdb-@value{GDBVN}} directory.
19061 First switch to the @file{gdb-@var{version-number}} source directory
19062 if you are not already in it; then run @code{configure}. Pass the
19063 identifier for the platform on which @value{GDBN} will run as an
19069 cd gdb-@value{GDBVN}
19070 ./configure @var{host}
19075 where @var{host} is an identifier such as @samp{sun4} or
19076 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
19077 (You can often leave off @var{host}; @code{configure} tries to guess the
19078 correct value by examining your system.)
19080 Running @samp{configure @var{host}} and then running @code{make} builds the
19081 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
19082 libraries, then @code{gdb} itself. The configured source files, and the
19083 binaries, are left in the corresponding source directories.
19086 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
19087 system does not recognize this automatically when you run a different
19088 shell, you may need to run @code{sh} on it explicitly:
19091 sh configure @var{host}
19094 If you run @code{configure} from a directory that contains source
19095 directories for multiple libraries or programs, such as the
19096 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
19097 creates configuration files for every directory level underneath (unless
19098 you tell it not to, with the @samp{--norecursion} option).
19100 You should run the @code{configure} script from the top directory in the
19101 source tree, the @file{gdb-@var{version-number}} directory. If you run
19102 @code{configure} from one of the subdirectories, you will configure only
19103 that subdirectory. That is usually not what you want. In particular,
19104 if you run the first @code{configure} from the @file{gdb} subdirectory
19105 of the @file{gdb-@var{version-number}} directory, you will omit the
19106 configuration of @file{bfd}, @file{readline}, and other sibling
19107 directories of the @file{gdb} subdirectory. This leads to build errors
19108 about missing include files such as @file{bfd/bfd.h}.
19110 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
19111 However, you should make sure that the shell on your path (named by
19112 the @samp{SHELL} environment variable) is publicly readable. Remember
19113 that @value{GDBN} uses the shell to start your program---some systems refuse to
19114 let @value{GDBN} debug child processes whose programs are not readable.
19117 * Separate Objdir:: Compiling @value{GDBN} in another directory
19118 * Config Names:: Specifying names for hosts and targets
19119 * Configure Options:: Summary of options for configure
19122 @node Separate Objdir
19123 @section Compiling @value{GDBN} in another directory
19125 If you want to run @value{GDBN} versions for several host or target machines,
19126 you need a different @code{gdb} compiled for each combination of
19127 host and target. @code{configure} is designed to make this easy by
19128 allowing you to generate each configuration in a separate subdirectory,
19129 rather than in the source directory. If your @code{make} program
19130 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
19131 @code{make} in each of these directories builds the @code{gdb}
19132 program specified there.
19134 To build @code{gdb} in a separate directory, run @code{configure}
19135 with the @samp{--srcdir} option to specify where to find the source.
19136 (You also need to specify a path to find @code{configure}
19137 itself from your working directory. If the path to @code{configure}
19138 would be the same as the argument to @samp{--srcdir}, you can leave out
19139 the @samp{--srcdir} option; it is assumed.)
19141 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
19142 separate directory for a Sun 4 like this:
19146 cd gdb-@value{GDBVN}
19149 ../gdb-@value{GDBVN}/configure sun4
19154 When @code{configure} builds a configuration using a remote source
19155 directory, it creates a tree for the binaries with the same structure
19156 (and using the same names) as the tree under the source directory. In
19157 the example, you'd find the Sun 4 library @file{libiberty.a} in the
19158 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
19159 @file{gdb-sun4/gdb}.
19161 Make sure that your path to the @file{configure} script has just one
19162 instance of @file{gdb} in it. If your path to @file{configure} looks
19163 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
19164 one subdirectory of @value{GDBN}, not the whole package. This leads to
19165 build errors about missing include files such as @file{bfd/bfd.h}.
19167 One popular reason to build several @value{GDBN} configurations in separate
19168 directories is to configure @value{GDBN} for cross-compiling (where
19169 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
19170 programs that run on another machine---the @dfn{target}).
19171 You specify a cross-debugging target by
19172 giving the @samp{--target=@var{target}} option to @code{configure}.
19174 When you run @code{make} to build a program or library, you must run
19175 it in a configured directory---whatever directory you were in when you
19176 called @code{configure} (or one of its subdirectories).
19178 The @code{Makefile} that @code{configure} generates in each source
19179 directory also runs recursively. If you type @code{make} in a source
19180 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
19181 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
19182 will build all the required libraries, and then build GDB.
19184 When you have multiple hosts or targets configured in separate
19185 directories, you can run @code{make} on them in parallel (for example,
19186 if they are NFS-mounted on each of the hosts); they will not interfere
19190 @section Specifying names for hosts and targets
19192 The specifications used for hosts and targets in the @code{configure}
19193 script are based on a three-part naming scheme, but some short predefined
19194 aliases are also supported. The full naming scheme encodes three pieces
19195 of information in the following pattern:
19198 @var{architecture}-@var{vendor}-@var{os}
19201 For example, you can use the alias @code{sun4} as a @var{host} argument,
19202 or as the value for @var{target} in a @code{--target=@var{target}}
19203 option. The equivalent full name is @samp{sparc-sun-sunos4}.
19205 The @code{configure} script accompanying @value{GDBN} does not provide
19206 any query facility to list all supported host and target names or
19207 aliases. @code{configure} calls the Bourne shell script
19208 @code{config.sub} to map abbreviations to full names; you can read the
19209 script, if you wish, or you can use it to test your guesses on
19210 abbreviations---for example:
19213 % sh config.sub i386-linux
19215 % sh config.sub alpha-linux
19216 alpha-unknown-linux-gnu
19217 % sh config.sub hp9k700
19219 % sh config.sub sun4
19220 sparc-sun-sunos4.1.1
19221 % sh config.sub sun3
19222 m68k-sun-sunos4.1.1
19223 % sh config.sub i986v
19224 Invalid configuration `i986v': machine `i986v' not recognized
19228 @code{config.sub} is also distributed in the @value{GDBN} source
19229 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
19231 @node Configure Options
19232 @section @code{configure} options
19234 Here is a summary of the @code{configure} options and arguments that
19235 are most often useful for building @value{GDBN}. @code{configure} also has
19236 several other options not listed here. @inforef{What Configure
19237 Does,,configure.info}, for a full explanation of @code{configure}.
19240 configure @r{[}--help@r{]}
19241 @r{[}--prefix=@var{dir}@r{]}
19242 @r{[}--exec-prefix=@var{dir}@r{]}
19243 @r{[}--srcdir=@var{dirname}@r{]}
19244 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
19245 @r{[}--target=@var{target}@r{]}
19250 You may introduce options with a single @samp{-} rather than
19251 @samp{--} if you prefer; but you may abbreviate option names if you use
19256 Display a quick summary of how to invoke @code{configure}.
19258 @item --prefix=@var{dir}
19259 Configure the source to install programs and files under directory
19262 @item --exec-prefix=@var{dir}
19263 Configure the source to install programs under directory
19266 @c avoid splitting the warning from the explanation:
19268 @item --srcdir=@var{dirname}
19269 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
19270 @code{make} that implements the @code{VPATH} feature.}@*
19271 Use this option to make configurations in directories separate from the
19272 @value{GDBN} source directories. Among other things, you can use this to
19273 build (or maintain) several configurations simultaneously, in separate
19274 directories. @code{configure} writes configuration specific files in
19275 the current directory, but arranges for them to use the source in the
19276 directory @var{dirname}. @code{configure} creates directories under
19277 the working directory in parallel to the source directories below
19280 @item --norecursion
19281 Configure only the directory level where @code{configure} is executed; do not
19282 propagate configuration to subdirectories.
19284 @item --target=@var{target}
19285 Configure @value{GDBN} for cross-debugging programs running on the specified
19286 @var{target}. Without this option, @value{GDBN} is configured to debug
19287 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
19289 There is no convenient way to generate a list of all available targets.
19291 @item @var{host} @dots{}
19292 Configure @value{GDBN} to run on the specified @var{host}.
19294 There is no convenient way to generate a list of all available hosts.
19297 There are many other options available as well, but they are generally
19298 needed for special purposes only.
19300 @node Maintenance Commands
19301 @appendix Maintenance Commands
19302 @cindex maintenance commands
19303 @cindex internal commands
19305 In addition to commands intended for @value{GDBN} users, @value{GDBN}
19306 includes a number of commands intended for @value{GDBN} developers.
19307 These commands are provided here for reference.
19310 @kindex maint info breakpoints
19311 @item @anchor{maint info breakpoints}maint info breakpoints
19312 Using the same format as @samp{info breakpoints}, display both the
19313 breakpoints you've set explicitly, and those @value{GDBN} is using for
19314 internal purposes. Internal breakpoints are shown with negative
19315 breakpoint numbers. The type column identifies what kind of breakpoint
19320 Normal, explicitly set breakpoint.
19323 Normal, explicitly set watchpoint.
19326 Internal breakpoint, used to handle correctly stepping through
19327 @code{longjmp} calls.
19329 @item longjmp resume
19330 Internal breakpoint at the target of a @code{longjmp}.
19333 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
19336 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
19339 Shared library events.
19343 @kindex maint internal-error
19344 @kindex maint internal-warning
19345 @item maint internal-error
19346 @itemx maint internal-warning
19347 Cause @value{GDBN} to call the internal function @code{internal_error}
19348 or @code{internal_warning} and hence behave as though an internal error
19349 or internal warning has been detected. In addition to reporting the
19350 internal problem, these functions give the user the opportunity to
19351 either quit @value{GDBN} or create a core file of the current
19352 @value{GDBN} session.
19355 (gdb) @kbd{maint internal-error testing, 1, 2}
19356 @dots{}/maint.c:121: internal-error: testing, 1, 2
19357 A problem internal to GDB has been detected. Further
19358 debugging may prove unreliable.
19359 Quit this debugging session? (y or n) @kbd{n}
19360 Create a core file? (y or n) @kbd{n}
19364 Takes an optional parameter that is used as the text of the error or
19367 @kindex maint print dummy-frames
19368 @item maint print dummy-frames
19370 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
19375 (gdb) @kbd{print add(2,3)}
19376 Breakpoint 2, add (a=2, b=3) at @dots{}
19378 The program being debugged stopped while in a function called from GDB.
19380 (gdb) @kbd{maint print dummy-frames}
19381 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
19382 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
19383 call_lo=0x01014000 call_hi=0x01014001
19387 Takes an optional file parameter.
19389 @kindex maint print registers
19390 @kindex maint print raw-registers
19391 @kindex maint print cooked-registers
19392 @kindex maint print register-groups
19393 @item maint print registers
19394 @itemx maint print raw-registers
19395 @itemx maint print cooked-registers
19396 @itemx maint print register-groups
19397 Print @value{GDBN}'s internal register data structures.
19399 The command @code{maint print raw-registers} includes the contents of
19400 the raw register cache; the command @code{maint print cooked-registers}
19401 includes the (cooked) value of all registers; and the command
19402 @code{maint print register-groups} includes the groups that each
19403 register is a member of. @xref{Registers,, Registers, gdbint,
19404 @value{GDBN} Internals}.
19406 Takes an optional file parameter.
19408 @kindex maint print reggroups
19409 @item maint print reggroups
19410 Print @value{GDBN}'s internal register group data structures.
19412 Takes an optional file parameter.
19415 (gdb) @kbd{maint print reggroups}
19426 @kindex maint set profile
19427 @kindex maint show profile
19428 @cindex profiling GDB
19429 @item maint set profile
19430 @itemx maint show profile
19431 Control profiling of @value{GDBN}.
19433 Profiling will be disabled until you use the @samp{maint set profile}
19434 command to enable it. When you enable profiling, the system will begin
19435 collecting timing and execution count data; when you disable profiling or
19436 exit @value{GDBN}, the results will be written to a log file. Remember that
19437 if you use profiling, @value{GDBN} will overwrite the profiling log file
19438 (often called @file{gmon.out}). If you have a record of important profiling
19439 data in a @file{gmon.out} file, be sure to move it to a safe location.
19441 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
19442 compiled with the @samp{-pg} compiler option.
19447 @node Remote Protocol
19448 @appendix @value{GDBN} Remote Serial Protocol
19453 * Stop Reply Packets::
19454 * General Query Packets::
19455 * Register Packet Format::
19457 * File-I/O remote protocol extension::
19463 There may be occasions when you need to know something about the
19464 protocol---for example, if there is only one serial port to your target
19465 machine, you might want your program to do something special if it
19466 recognizes a packet meant for @value{GDBN}.
19468 In the examples below, @samp{->} and @samp{<-} are used to indicate
19469 transmitted and received data respectfully.
19471 @cindex protocol, @value{GDBN} remote serial
19472 @cindex serial protocol, @value{GDBN} remote
19473 @cindex remote serial protocol
19474 All @value{GDBN} commands and responses (other than acknowledgments) are
19475 sent as a @var{packet}. A @var{packet} is introduced with the character
19476 @samp{$}, the actual @var{packet-data}, and the terminating character
19477 @samp{#} followed by a two-digit @var{checksum}:
19480 @code{$}@var{packet-data}@code{#}@var{checksum}
19484 @cindex checksum, for @value{GDBN} remote
19486 The two-digit @var{checksum} is computed as the modulo 256 sum of all
19487 characters between the leading @samp{$} and the trailing @samp{#} (an
19488 eight bit unsigned checksum).
19490 Implementors should note that prior to @value{GDBN} 5.0 the protocol
19491 specification also included an optional two-digit @var{sequence-id}:
19494 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
19497 @cindex sequence-id, for @value{GDBN} remote
19499 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
19500 has never output @var{sequence-id}s. Stubs that handle packets added
19501 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
19503 @cindex acknowledgment, for @value{GDBN} remote
19504 When either the host or the target machine receives a packet, the first
19505 response expected is an acknowledgment: either @samp{+} (to indicate
19506 the package was received correctly) or @samp{-} (to request
19510 -> @code{$}@var{packet-data}@code{#}@var{checksum}
19515 The host (@value{GDBN}) sends @var{command}s, and the target (the
19516 debugging stub incorporated in your program) sends a @var{response}. In
19517 the case of step and continue @var{command}s, the response is only sent
19518 when the operation has completed (the target has again stopped).
19520 @var{packet-data} consists of a sequence of characters with the
19521 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
19524 Fields within the packet should be separated using @samp{,} @samp{;} or
19525 @cindex remote protocol, field separator
19526 @samp{:}. Except where otherwise noted all numbers are represented in
19527 @sc{hex} with leading zeros suppressed.
19529 Implementors should note that prior to @value{GDBN} 5.0, the character
19530 @samp{:} could not appear as the third character in a packet (as it
19531 would potentially conflict with the @var{sequence-id}).
19533 Response @var{data} can be run-length encoded to save space. A @samp{*}
19534 means that the next character is an @sc{ascii} encoding giving a repeat count
19535 which stands for that many repetitions of the character preceding the
19536 @samp{*}. The encoding is @code{n+29}, yielding a printable character
19537 where @code{n >=3} (which is where rle starts to win). The printable
19538 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
19539 value greater than 126 should not be used.
19541 Some remote systems have used a different run-length encoding mechanism
19542 loosely refered to as the cisco encoding. Following the @samp{*}
19543 character are two hex digits that indicate the size of the packet.
19550 means the same as "0000".
19552 The error response returned for some packets includes a two character
19553 error number. That number is not well defined.
19555 For any @var{command} not supported by the stub, an empty response
19556 (@samp{$#00}) should be returned. That way it is possible to extend the
19557 protocol. A newer @value{GDBN} can tell if a packet is supported based
19560 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
19561 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
19567 The following table provides a complete list of all currently defined
19568 @var{command}s and their corresponding response @var{data}.
19572 @item @code{!} --- extended mode
19573 @cindex @code{!} packet
19575 Enable extended mode. In extended mode, the remote server is made
19576 persistent. The @samp{R} packet is used to restart the program being
19582 The remote target both supports and has enabled extended mode.
19585 @item @code{?} --- last signal
19586 @cindex @code{?} packet
19588 Indicate the reason the target halted. The reply is the same as for
19592 @xref{Stop Reply Packets}, for the reply specifications.
19594 @item @code{a} --- reserved
19596 Reserved for future use.
19598 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
19599 @cindex @code{A} packet
19601 Initialized @samp{argv[]} array passed into program. @var{arglen}
19602 specifies the number of bytes in the hex encoded byte stream @var{arg}.
19603 See @code{gdbserver} for more details.
19611 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
19612 @cindex @code{b} packet
19614 Change the serial line speed to @var{baud}.
19616 JTC: @emph{When does the transport layer state change? When it's
19617 received, or after the ACK is transmitted. In either case, there are
19618 problems if the command or the acknowledgment packet is dropped.}
19620 Stan: @emph{If people really wanted to add something like this, and get
19621 it working for the first time, they ought to modify ser-unix.c to send
19622 some kind of out-of-band message to a specially-setup stub and have the
19623 switch happen "in between" packets, so that from remote protocol's point
19624 of view, nothing actually happened.}
19626 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
19627 @cindex @code{B} packet
19629 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
19630 breakpoint at @var{addr}.
19632 This packet has been replaced by the @samp{Z} and @samp{z} packets
19633 (@pxref{insert breakpoint or watchpoint packet}).
19635 @item @code{c}@var{addr} --- continue
19636 @cindex @code{c} packet
19638 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19642 @xref{Stop Reply Packets}, for the reply specifications.
19644 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
19645 @cindex @code{C} packet
19647 Continue with signal @var{sig} (hex signal number). If
19648 @code{;}@var{addr} is omitted, resume at same address.
19651 @xref{Stop Reply Packets}, for the reply specifications.
19653 @item @code{d} --- toggle debug @strong{(deprecated)}
19654 @cindex @code{d} packet
19658 @item @code{D} --- detach
19659 @cindex @code{D} packet
19661 Detach @value{GDBN} from the remote system. Sent to the remote target
19662 before @value{GDBN} disconnects.
19666 @item @emph{no response}
19667 @value{GDBN} does not check for any response after sending this packet.
19670 @item @code{e} --- reserved
19672 Reserved for future use.
19674 @item @code{E} --- reserved
19676 Reserved for future use.
19678 @item @code{f} --- reserved
19680 Reserved for future use.
19682 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
19683 @cindex @code{F} packet
19685 This packet is send by @value{GDBN} as reply to a @code{F} request packet
19686 sent by the target. This is part of the File-I/O protocol extension.
19687 @xref{File-I/O remote protocol extension}, for the specification.
19689 @item @code{g} --- read registers
19690 @anchor{read registers packet}
19691 @cindex @code{g} packet
19693 Read general registers.
19697 @item @var{XX@dots{}}
19698 Each byte of register data is described by two hex digits. The bytes
19699 with the register are transmitted in target byte order. The size of
19700 each register and their position within the @samp{g} @var{packet} are
19701 determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE}
19702 and @var{REGISTER_NAME} macros. The specification of several standard
19703 @code{g} packets is specified below.
19708 @item @code{G}@var{XX@dots{}} --- write regs
19709 @cindex @code{G} packet
19711 @xref{read registers packet}, for a description of the @var{XX@dots{}}
19722 @item @code{h} --- reserved
19724 Reserved for future use.
19726 @item @code{H}@var{c}@var{t@dots{}} --- set thread
19727 @cindex @code{H} packet
19729 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
19730 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
19731 should be @samp{c} for step and continue operations, @samp{g} for other
19732 operations. The thread designator @var{t@dots{}} may be -1, meaning all
19733 the threads, a thread number, or zero which means pick any thread.
19744 @c 'H': How restrictive (or permissive) is the thread model. If a
19745 @c thread is selected and stopped, are other threads allowed
19746 @c to continue to execute? As I mentioned above, I think the
19747 @c semantics of each command when a thread is selected must be
19748 @c described. For example:
19750 @c 'g': If the stub supports threads and a specific thread is
19751 @c selected, returns the register block from that thread;
19752 @c otherwise returns current registers.
19754 @c 'G' If the stub supports threads and a specific thread is
19755 @c selected, sets the registers of the register block of
19756 @c that thread; otherwise sets current registers.
19758 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
19759 @anchor{cycle step packet}
19760 @cindex @code{i} packet
19762 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
19763 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
19764 step starting at that address.
19766 @item @code{I} --- signal then cycle step @strong{(reserved)}
19767 @cindex @code{I} packet
19769 @xref{step with signal packet}. @xref{cycle step packet}.
19771 @item @code{j} --- reserved
19773 Reserved for future use.
19775 @item @code{J} --- reserved
19777 Reserved for future use.
19779 @item @code{k} --- kill request
19780 @cindex @code{k} packet
19782 FIXME: @emph{There is no description of how to operate when a specific
19783 thread context has been selected (i.e.@: does 'k' kill only that
19786 @item @code{K} --- reserved
19788 Reserved for future use.
19790 @item @code{l} --- reserved
19792 Reserved for future use.
19794 @item @code{L} --- reserved
19796 Reserved for future use.
19798 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
19799 @cindex @code{m} packet
19801 Read @var{length} bytes of memory starting at address @var{addr}.
19802 Neither @value{GDBN} nor the stub assume that sized memory transfers are
19803 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
19804 transfer mechanism is needed.}
19808 @item @var{XX@dots{}}
19809 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
19810 to read only part of the data. Neither @value{GDBN} nor the stub assume
19811 that sized memory transfers are assumed using word aligned
19812 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
19818 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
19819 @cindex @code{M} packet
19821 Write @var{length} bytes of memory starting at address @var{addr}.
19822 @var{XX@dots{}} is the data.
19829 for an error (this includes the case where only part of the data was
19833 @item @code{n} --- reserved
19835 Reserved for future use.
19837 @item @code{N} --- reserved
19839 Reserved for future use.
19841 @item @code{o} --- reserved
19843 Reserved for future use.
19845 @item @code{O} --- reserved
19847 Reserved for future use.
19849 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
19850 @cindex @code{p} packet
19852 @xref{write register packet}.
19856 @item @var{r@dots{}.}
19857 The hex encoded value of the register in target byte order.
19860 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
19861 @anchor{write register packet}
19862 @cindex @code{P} packet
19864 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
19865 digits for each byte in the register (target byte order).
19875 @item @code{q}@var{query} --- general query
19876 @anchor{general query packet}
19877 @cindex @code{q} packet
19879 Request info about @var{query}. In general @value{GDBN} queries have a
19880 leading upper case letter. Custom vendor queries should use a company
19881 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
19882 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
19883 that they match the full @var{query} name.
19887 @item @var{XX@dots{}}
19888 Hex encoded data from query. The reply can not be empty.
19892 Indicating an unrecognized @var{query}.
19895 @item @code{Q}@var{var}@code{=}@var{val} --- general set
19896 @cindex @code{Q} packet
19898 Set value of @var{var} to @var{val}.
19900 @xref{general query packet}, for a discussion of naming conventions.
19902 @item @code{r} --- reset @strong{(deprecated)}
19903 @cindex @code{r} packet
19905 Reset the entire system.
19907 @item @code{R}@var{XX} --- remote restart
19908 @cindex @code{R} packet
19910 Restart the program being debugged. @var{XX}, while needed, is ignored.
19911 This packet is only available in extended mode.
19915 @item @emph{no reply}
19916 The @samp{R} packet has no reply.
19919 @item @code{s}@var{addr} --- step
19920 @cindex @code{s} packet
19922 @var{addr} is address to resume. If @var{addr} is omitted, resume at
19926 @xref{Stop Reply Packets}, for the reply specifications.
19928 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
19929 @anchor{step with signal packet}
19930 @cindex @code{S} packet
19932 Like @samp{C} but step not continue.
19935 @xref{Stop Reply Packets}, for the reply specifications.
19937 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
19938 @cindex @code{t} packet
19940 Search backwards starting at address @var{addr} for a match with pattern
19941 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
19942 @var{addr} must be at least 3 digits.
19944 @item @code{T}@var{XX} --- thread alive
19945 @cindex @code{T} packet
19947 Find out if the thread XX is alive.
19952 thread is still alive
19957 @item @code{u} --- reserved
19959 Reserved for future use.
19961 @item @code{U} --- reserved
19963 Reserved for future use.
19965 @item @code{v} --- reserved
19967 Reserved for future use.
19969 @item @code{V} --- reserved
19971 Reserved for future use.
19973 @item @code{w} --- reserved
19975 Reserved for future use.
19977 @item @code{W} --- reserved
19979 Reserved for future use.
19981 @item @code{x} --- reserved
19983 Reserved for future use.
19985 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
19986 @cindex @code{X} packet
19988 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
19989 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
19990 escaped using @code{0x7d}.
20000 @item @code{y} --- reserved
20002 Reserved for future use.
20004 @item @code{Y} reserved
20006 Reserved for future use.
20008 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
20009 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
20010 @anchor{insert breakpoint or watchpoint packet}
20011 @cindex @code{z} packet
20012 @cindex @code{Z} packets
20014 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
20015 watchpoint starting at address @var{address} and covering the next
20016 @var{length} bytes.
20018 Each breakpoint and watchpoint packet @var{type} is documented
20021 @emph{Implementation notes: A remote target shall return an empty string
20022 for an unrecognized breakpoint or watchpoint packet @var{type}. A
20023 remote target shall support either both or neither of a given
20024 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
20025 avoid potential problems with duplicate packets, the operations should
20026 be implemented in an idempotent way.}
20028 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
20029 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
20030 @cindex @code{z0} packet
20031 @cindex @code{Z0} packet
20033 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
20034 @code{addr} of size @code{length}.
20036 A memory breakpoint is implemented by replacing the instruction at
20037 @var{addr} with a software breakpoint or trap instruction. The
20038 @code{length} is used by targets that indicates the size of the
20039 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
20040 @sc{mips} can insert either a 2 or 4 byte breakpoint).
20042 @emph{Implementation note: It is possible for a target to copy or move
20043 code that contains memory breakpoints (e.g., when implementing
20044 overlays). The behavior of this packet, in the presence of such a
20045 target, is not defined.}
20057 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
20058 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
20059 @cindex @code{z1} packet
20060 @cindex @code{Z1} packet
20062 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
20063 address @code{addr} of size @code{length}.
20065 A hardware breakpoint is implemented using a mechanism that is not
20066 dependant on being able to modify the target's memory.
20068 @emph{Implementation note: A hardware breakpoint is not affected by code
20081 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
20082 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
20083 @cindex @code{z2} packet
20084 @cindex @code{Z2} packet
20086 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
20098 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
20099 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
20100 @cindex @code{z3} packet
20101 @cindex @code{Z3} packet
20103 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
20115 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
20116 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
20117 @cindex @code{z4} packet
20118 @cindex @code{Z4} packet
20120 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
20134 @node Stop Reply Packets
20135 @section Stop Reply Packets
20136 @cindex stop reply packets
20138 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
20139 receive any of the below as a reply. In the case of the @samp{C},
20140 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
20141 when the target halts. In the below the exact meaning of @samp{signal
20142 number} is poorly defined. In general one of the UNIX signal numbering
20143 conventions is used.
20148 @var{AA} is the signal number
20150 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
20151 @cindex @code{T} packet reply
20153 @var{AA} = two hex digit signal number; @var{n...} = register number
20154 (hex), @var{r...} = target byte ordered register contents, size defined
20155 by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} =
20156 thread process ID, this is a hex integer; @var{n...} = (@samp{watch} |
20157 @samp{rwatch} | @samp{awatch}, @var{r...} = data address, this is a hex
20158 integer; @var{n...} = other string not starting with valid hex digit.
20159 @value{GDBN} should ignore this @var{n...}, @var{r...} pair and go on
20160 to the next. This way we can extend the protocol.
20164 The process exited, and @var{AA} is the exit status. This is only
20165 applicable to certain targets.
20169 The process terminated with signal @var{AA}.
20171 @item N@var{AA};@var{t@dots{}};@var{d@dots{}};@var{b@dots{}} @strong{(obsolete)}
20173 @var{AA} = signal number; @var{t@dots{}} = address of symbol
20174 @code{_start}; @var{d@dots{}} = base of data section; @var{b@dots{}} =
20175 base of bss section. @emph{Note: only used by Cisco Systems targets.
20176 The difference between this reply and the @samp{qOffsets} query is that
20177 the @samp{N} packet may arrive spontaneously whereas the @samp{qOffsets}
20178 is a query initiated by the host debugger.}
20180 @item O@var{XX@dots{}}
20182 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
20183 any time while the program is running and the debugger should continue
20184 to wait for @samp{W}, @samp{T}, etc.
20186 @item F@var{call-id}@code{,}@var{parameter@dots{}}
20188 @var{call-id} is the identifier which says which host system call should
20189 be called. This is just the name of the function. Translation into the
20190 correct system call is only applicable as it's defined in @value{GDBN}.
20191 @xref{File-I/O remote protocol extension}, for a list of implemented
20194 @var{parameter@dots{}} is a list of parameters as defined for this very
20197 The target replies with this packet when it expects @value{GDBN} to call
20198 a host system call on behalf of the target. @value{GDBN} replies with
20199 an appropriate @code{F} packet and keeps up waiting for the next reply
20200 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
20201 @samp{s} action is expected to be continued.
20202 @xref{File-I/O remote protocol extension}, for more details.
20206 @node General Query Packets
20207 @section General Query Packets
20209 The following set and query packets have already been defined.
20213 @item @code{q}@code{C} --- current thread
20215 Return the current thread id.
20219 @item @code{QC}@var{pid}
20220 Where @var{pid} is a HEX encoded 16 bit process id.
20222 Any other reply implies the old pid.
20225 @item @code{q}@code{fThreadInfo} -- all thread ids
20227 @code{q}@code{sThreadInfo}
20229 Obtain a list of active thread ids from the target (OS). Since there
20230 may be too many active threads to fit into one reply packet, this query
20231 works iteratively: it may require more than one query/reply sequence to
20232 obtain the entire list of threads. The first query of the sequence will
20233 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
20234 sequence will be the @code{qs}@code{ThreadInfo} query.
20236 NOTE: replaces the @code{qL} query (see below).
20240 @item @code{m}@var{id}
20242 @item @code{m}@var{id},@var{id}@dots{}
20243 a comma-separated list of thread ids
20245 (lower case 'el') denotes end of list.
20248 In response to each query, the target will reply with a list of one or
20249 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
20250 will respond to each reply with a request for more thread ids (using the
20251 @code{qs} form of the query), until the target responds with @code{l}
20252 (lower-case el, for @code{'last'}).
20254 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
20256 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
20257 string description of a thread's attributes from the target OS. This
20258 string may contain anything that the target OS thinks is interesting for
20259 @value{GDBN} to tell the user about the thread. The string is displayed
20260 in @value{GDBN}'s @samp{info threads} display. Some examples of
20261 possible thread extra info strings are ``Runnable'', or ``Blocked on
20266 @item @var{XX@dots{}}
20267 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
20268 the printable string containing the extra information about the thread's
20272 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
20274 Obtain thread information from RTOS. Where: @var{startflag} (one hex
20275 digit) is one to indicate the first query and zero to indicate a
20276 subsequent query; @var{threadcount} (two hex digits) is the maximum
20277 number of threads the response packet can contain; and @var{nextthread}
20278 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
20279 returned in the response as @var{argthread}.
20281 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
20286 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
20287 Where: @var{count} (two hex digits) is the number of threads being
20288 returned; @var{done} (one hex digit) is zero to indicate more threads
20289 and one indicates no further threads; @var{argthreadid} (eight hex
20290 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
20291 is a sequence of thread IDs from the target. @var{threadid} (eight hex
20292 digits). See @code{remote.c:parse_threadlist_response()}.
20295 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
20299 @item @code{E}@var{NN}
20300 An error (such as memory fault)
20301 @item @code{C}@var{CRC32}
20302 A 32 bit cyclic redundancy check of the specified memory region.
20305 @item @code{q}@code{Offsets} --- query sect offs
20307 Get section offsets that the target used when re-locating the downloaded
20308 image. @emph{Note: while a @code{Bss} offset is included in the
20309 response, @value{GDBN} ignores this and instead applies the @code{Data}
20310 offset to the @code{Bss} section.}
20314 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
20317 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
20319 Returns information on @var{threadid}. Where: @var{mode} is a hex
20320 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
20327 See @code{remote.c:remote_unpack_thread_info_response()}.
20329 @item @code{q}@code{Rcmd,}@var{command} --- remote command
20331 @var{command} (hex encoded) is passed to the local interpreter for
20332 execution. Invalid commands should be reported using the output string.
20333 Before the final result packet, the target may also respond with a
20334 number of intermediate @code{O}@var{output} console output packets.
20335 @emph{Implementors should note that providing access to a stubs's
20336 interpreter may have security implications}.
20341 A command response with no output.
20343 A command response with the hex encoded output string @var{OUTPUT}.
20344 @item @code{E}@var{NN}
20345 Indicate a badly formed request.
20347 When @samp{q}@samp{Rcmd} is not recognized.
20350 @item @code{qSymbol::} --- symbol lookup
20352 Notify the target that @value{GDBN} is prepared to serve symbol lookup
20353 requests. Accept requests from the target for the values of symbols.
20358 The target does not need to look up any (more) symbols.
20359 @item @code{qSymbol:}@var{sym_name}
20360 The target requests the value of symbol @var{sym_name} (hex encoded).
20361 @value{GDBN} may provide the value by using the
20362 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
20365 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
20367 Set the value of @var{sym_name} to @var{sym_value}.
20369 @var{sym_name} (hex encoded) is the name of a symbol whose value the
20370 target has previously requested.
20372 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
20373 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
20379 The target does not need to look up any (more) symbols.
20380 @item @code{qSymbol:}@var{sym_name}
20381 The target requests the value of a new symbol @var{sym_name} (hex
20382 encoded). @value{GDBN} will continue to supply the values of symbols
20383 (if available), until the target ceases to request them.
20388 @node Register Packet Format
20389 @section Register Packet Format
20391 The following @samp{g}/@samp{G} packets have previously been defined.
20392 In the below, some thirty-two bit registers are transferred as
20393 sixty-four bits. Those registers should be zero/sign extended (which?)
20394 to fill the space allocated. Register bytes are transfered in target
20395 byte order. The two nibbles within a register byte are transfered
20396 most-significant - least-significant.
20402 All registers are transfered as thirty-two bit quantities in the order:
20403 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
20404 registers; fsr; fir; fp.
20408 All registers are transfered as sixty-four bit quantities (including
20409 thirty-two bit registers such as @code{sr}). The ordering is the same
20417 Example sequence of a target being re-started. Notice how the restart
20418 does not get any direct output:
20423 @emph{target restarts}
20426 <- @code{T001:1234123412341234}
20430 Example sequence of a target being stepped by a single instruction:
20433 -> @code{G1445@dots{}}
20438 <- @code{T001:1234123412341234}
20442 <- @code{1455@dots{}}
20446 @node File-I/O remote protocol extension
20447 @section File-I/O remote protocol extension
20448 @cindex File-I/O remote protocol extension
20451 * File-I/O Overview::
20452 * Protocol basics::
20453 * The `F' request packet::
20454 * The `F' reply packet::
20455 * Memory transfer::
20456 * The Ctrl-C message::
20458 * The isatty call::
20459 * The system call::
20460 * List of supported calls::
20461 * Protocol specific representation of datatypes::
20463 * File-I/O Examples::
20466 @node File-I/O Overview
20467 @subsection File-I/O Overview
20468 @cindex file-i/o overview
20470 The File I/O remote protocol extension (short: File-I/O) allows the
20471 target to use the hosts file system and console I/O when calling various
20472 system calls. System calls on the target system are translated into a
20473 remote protocol packet to the host system which then performs the needed
20474 actions and returns with an adequate response packet to the target system.
20475 This simulates file system operations even on targets that lack file systems.
20477 The protocol is defined host- and target-system independent. It uses
20478 it's own independent representation of datatypes and values. Both,
20479 @value{GDBN} and the target's @value{GDBN} stub are responsible for
20480 translating the system dependent values into the unified protocol values
20481 when data is transmitted.
20483 The communication is synchronous. A system call is possible only
20484 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
20485 packets. While @value{GDBN} handles the request for a system call,
20486 the target is stopped to allow deterministic access to the target's
20487 memory. Therefore File-I/O is not interuptible by target signals. It
20488 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
20490 The target's request to perform a host system call does not finish
20491 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
20492 after finishing the system call, the target returns to continuing the
20493 previous activity (continue, step). No additional continue or step
20494 request from @value{GDBN} is required.
20498 <- target requests 'system call X'
20499 target is stopped, @value{GDBN} executes system call
20500 -> GDB returns result
20501 ... target continues, GDB returns to wait for the target
20502 <- target hits breakpoint and sends a Txx packet
20505 The protocol is only used for files on the host file system and
20506 for I/O on the console. Character or block special devices, pipes,
20507 named pipes or sockets or any other communication method on the host
20508 system are not supported by this protocol.
20510 @node Protocol basics
20511 @subsection Protocol basics
20512 @cindex protocol basics, file-i/o
20514 The File-I/O protocol uses the @code{F} packet, as request as well
20515 as as reply packet. Since a File-I/O system call can only occur when
20516 @value{GDBN} is waiting for the continuing or stepping target, the
20517 File-I/O request is a reply that @value{GDBN} has to expect as a result
20518 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
20519 This @code{F} packet contains all information needed to allow @value{GDBN}
20520 to call the appropriate host system call:
20524 A unique identifier for the requested system call.
20527 All parameters to the system call. Pointers are given as addresses
20528 in the target memory address space. Pointers to strings are given as
20529 pointer/length pair. Numerical values are given as they are.
20530 Numerical control values are given in a protocol specific representation.
20534 At that point @value{GDBN} has to perform the following actions.
20538 If parameter pointer values are given, which point to data needed as input
20539 to a system call, @value{GDBN} requests this data from the target with a
20540 standard @code{m} packet request. This additional communication has to be
20541 expected by the target implementation and is handled as any other @code{m}
20545 @value{GDBN} translates all value from protocol representation to host
20546 representation as needed. Datatypes are coerced into the host types.
20549 @value{GDBN} calls the system call
20552 It then coerces datatypes back to protocol representation.
20555 If pointer parameters in the request packet point to buffer space in which
20556 a system call is expected to copy data to, the data is transmitted to the
20557 target using a @code{M} or @code{X} packet. This packet has to be expected
20558 by the target implementation and is handled as any other @code{M} or @code{X}
20563 Eventually @value{GDBN} replies with another @code{F} packet which contains all
20564 necessary information for the target to continue. This at least contains
20571 @code{errno}, if has been changed by the system call.
20578 After having done the needed type and value coercion, the target continues
20579 the latest continue or step action.
20581 @node The `F' request packet
20582 @subsection The @code{F} request packet
20583 @cindex file-i/o request packet
20584 @cindex @code{F} request packet
20586 The @code{F} request packet has the following format:
20591 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
20594 @var{call-id} is the identifier to indicate the host system call to be called.
20595 This is just the name of the function.
20597 @var{parameter@dots{}} are the parameters to the system call.
20601 Parameters are hexadecimal integer values, either the real values in case
20602 of scalar datatypes, as pointers to target buffer space in case of compound
20603 datatypes and unspecified memory areas or as pointer/length pairs in case
20604 of string parameters. These are appended to the call-id, each separated
20605 from its predecessor by a comma. All values are transmitted in ASCII
20606 string representation, pointer/length pairs separated by a slash.
20608 @node The `F' reply packet
20609 @subsection The @code{F} reply packet
20610 @cindex file-i/o reply packet
20611 @cindex @code{F} reply packet
20613 The @code{F} reply packet has the following format:
20618 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
20621 @var{retcode} is the return code of the system call as hexadecimal value.
20623 @var{errno} is the errno set by the call, in protocol specific representation.
20624 This parameter can be omitted if the call was successful.
20626 @var{Ctrl-C flag} is only send if the user requested a break. In this
20627 case, @var{errno} must be send as well, even if the call was successful.
20628 The @var{Ctrl-C flag} itself consists of the character 'C':
20635 or, if the call was interupted before the host call has been performed:
20642 assuming 4 is the protocol specific representation of @code{EINTR}.
20646 @node Memory transfer
20647 @subsection Memory transfer
20648 @cindex memory transfer, in file-i/o protocol
20650 Structured data which is transferred using a memory read or write as e.g.@:
20651 a @code{struct stat} is expected to be in a protocol specific format with
20652 all scalar multibyte datatypes being big endian. This should be done by
20653 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
20654 it transfers memory to the target. Transferred pointers to structured
20655 data should point to the already coerced data at any time.
20657 @node The Ctrl-C message
20658 @subsection The Ctrl-C message
20659 @cindex ctrl-c message, in file-i/o protocol
20661 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
20662 reply packet. In this case the target should behave, as if it had
20663 gotten a break message. The meaning for the target is ``system call
20664 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
20665 (as with a break message) and return to @value{GDBN} with a @code{T02}
20666 packet. In this case, it's important for the target to know, in which
20667 state the system call was interrupted. Since this action is by design
20668 not an atomic operation, we have to differ between two cases:
20672 The system call hasn't been performed on the host yet.
20675 The system call on the host has been finished.
20679 These two states can be distinguished by the target by the value of the
20680 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
20681 call hasn't been performed. This is equivalent to the @code{EINTR} handling
20682 on POSIX systems. In any other case, the target may presume that the
20683 system call has been finished --- successful or not --- and should behave
20684 as if the break message arrived right after the system call.
20686 @value{GDBN} must behave reliable. If the system call has not been called
20687 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
20688 @code{errno} in the packet. If the system call on the host has been finished
20689 before the user requests a break, the full action must be finshed by
20690 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
20691 The @code{F} packet may only be send when either nothing has happened
20692 or the full action has been completed.
20695 @subsection Console I/O
20696 @cindex console i/o as part of file-i/o
20698 By default and if not explicitely closed by the target system, the file
20699 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
20700 on the @value{GDBN} console is handled as any other file output operation
20701 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
20702 by @value{GDBN} so that after the target read request from file descriptor
20703 0 all following typing is buffered until either one of the following
20708 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
20710 system call is treated as finished.
20713 The user presses @kbd{Enter}. This is treated as end of input with a trailing
20717 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
20718 character, especially no Ctrl-D is appended to the input.
20722 If the user has typed more characters as fit in the buffer given to
20723 the read call, the trailing characters are buffered in @value{GDBN} until
20724 either another @code{read(0, @dots{})} is requested by the target or debugging
20725 is stopped on users request.
20727 @node The isatty call
20728 @subsection The isatty(3) call
20729 @cindex isatty call, file-i/o protocol
20731 A special case in this protocol is the library call @code{isatty} which
20732 is implemented as it's own call inside of this protocol. It returns
20733 1 to the target if the file descriptor given as parameter is attached
20734 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
20735 would require implementing @code{ioctl} and would be more complex than
20738 @node The system call
20739 @subsection The system(3) call
20740 @cindex system call, file-i/o protocol
20742 The other special case in this protocol is the @code{system} call which
20743 is implemented as it's own call, too. @value{GDBN} is taking over the full
20744 task of calling the necessary host calls to perform the @code{system}
20745 call. The return value of @code{system} is simplified before it's returned
20746 to the target. Basically, the only signal transmitted back is @code{EINTR}
20747 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
20748 entirely of the exit status of the called command.
20750 Due to security concerns, the @code{system} call is refused to be called
20751 by @value{GDBN} by default. The user has to allow this call explicitly by
20755 @kindex set remote system-call-allowed 1
20756 @item @code{set remote system-call-allowed 1}
20759 Disabling the @code{system} call is done by
20762 @kindex set remote system-call-allowed 0
20763 @item @code{set remote system-call-allowed 0}
20766 The current setting is shown by typing
20769 @kindex show remote system-call-allowed
20770 @item @code{show remote system-call-allowed}
20773 @node List of supported calls
20774 @subsection List of supported calls
20775 @cindex list of supported file-i/o calls
20792 @unnumberedsubsubsec open
20793 @cindex open, file-i/o system call
20797 int open(const char *pathname, int flags);
20798 int open(const char *pathname, int flags, mode_t mode);
20801 Fopen,pathptr/len,flags,mode
20805 @code{flags} is the bitwise or of the following values:
20809 If the file does not exist it will be created. The host
20810 rules apply as far as file ownership and time stamps
20814 When used with O_CREAT, if the file already exists it is
20815 an error and open() fails.
20818 If the file already exists and the open mode allows
20819 writing (O_RDWR or O_WRONLY is given) it will be
20820 truncated to length 0.
20823 The file is opened in append mode.
20826 The file is opened for reading only.
20829 The file is opened for writing only.
20832 The file is opened for reading and writing.
20835 Each other bit is silently ignored.
20840 @code{mode} is the bitwise or of the following values:
20844 User has read permission.
20847 User has write permission.
20850 Group has read permission.
20853 Group has write permission.
20856 Others have read permission.
20859 Others have write permission.
20862 Each other bit is silently ignored.
20867 @exdent Return value:
20868 open returns the new file descriptor or -1 if an error
20876 pathname already exists and O_CREAT and O_EXCL were used.
20879 pathname refers to a directory.
20882 The requested access is not allowed.
20885 pathname was too long.
20888 A directory component in pathname does not exist.
20891 pathname refers to a device, pipe, named pipe or socket.
20894 pathname refers to a file on a read-only filesystem and
20895 write access was requested.
20898 pathname is an invalid pointer value.
20901 No space on device to create the file.
20904 The process already has the maximum number of files open.
20907 The limit on the total number of files open on the system
20911 The call was interrupted by the user.
20915 @unnumberedsubsubsec close
20916 @cindex close, file-i/o system call
20925 @exdent Return value:
20926 close returns zero on success, or -1 if an error occurred.
20933 fd isn't a valid open file descriptor.
20936 The call was interrupted by the user.
20940 @unnumberedsubsubsec read
20941 @cindex read, file-i/o system call
20945 int read(int fd, void *buf, unsigned int count);
20948 Fread,fd,bufptr,count
20950 @exdent Return value:
20951 On success, the number of bytes read is returned.
20952 Zero indicates end of file. If count is zero, read
20953 returns zero as well. On error, -1 is returned.
20960 fd is not a valid file descriptor or is not open for
20964 buf is an invalid pointer value.
20967 The call was interrupted by the user.
20971 @unnumberedsubsubsec write
20972 @cindex write, file-i/o system call
20976 int write(int fd, const void *buf, unsigned int count);
20979 Fwrite,fd,bufptr,count
20981 @exdent Return value:
20982 On success, the number of bytes written are returned.
20983 Zero indicates nothing was written. On error, -1
20991 fd is not a valid file descriptor or is not open for
20995 buf is an invalid pointer value.
20998 An attempt was made to write a file that exceeds the
20999 host specific maximum file size allowed.
21002 No space on device to write the data.
21005 The call was interrupted by the user.
21009 @unnumberedsubsubsec lseek
21010 @cindex lseek, file-i/o system call
21014 long lseek (int fd, long offset, int flag);
21017 Flseek,fd,offset,flag
21020 @code{flag} is one of:
21024 The offset is set to offset bytes.
21027 The offset is set to its current location plus offset
21031 The offset is set to the size of the file plus offset
21036 @exdent Return value:
21037 On success, the resulting unsigned offset in bytes from
21038 the beginning of the file is returned. Otherwise, a
21039 value of -1 is returned.
21046 fd is not a valid open file descriptor.
21049 fd is associated with the @value{GDBN} console.
21052 flag is not a proper value.
21055 The call was interrupted by the user.
21059 @unnumberedsubsubsec rename
21060 @cindex rename, file-i/o system call
21064 int rename(const char *oldpath, const char *newpath);
21067 Frename,oldpathptr/len,newpathptr/len
21069 @exdent Return value:
21070 On success, zero is returned. On error, -1 is returned.
21077 newpath is an existing directory, but oldpath is not a
21081 newpath is a non-empty directory.
21084 oldpath or newpath is a directory that is in use by some
21088 An attempt was made to make a directory a subdirectory
21092 A component used as a directory in oldpath or new
21093 path is not a directory. Or oldpath is a directory
21094 and newpath exists but is not a directory.
21097 oldpathptr or newpathptr are invalid pointer values.
21100 No access to the file or the path of the file.
21104 oldpath or newpath was too long.
21107 A directory component in oldpath or newpath does not exist.
21110 The file is on a read-only filesystem.
21113 The device containing the file has no room for the new
21117 The call was interrupted by the user.
21121 @unnumberedsubsubsec unlink
21122 @cindex unlink, file-i/o system call
21126 int unlink(const char *pathname);
21129 Funlink,pathnameptr/len
21131 @exdent Return value:
21132 On success, zero is returned. On error, -1 is returned.
21139 No access to the file or the path of the file.
21142 The system does not allow unlinking of directories.
21145 The file pathname cannot be unlinked because it's
21146 being used by another process.
21149 pathnameptr is an invalid pointer value.
21152 pathname was too long.
21155 A directory component in pathname does not exist.
21158 A component of the path is not a directory.
21161 The file is on a read-only filesystem.
21164 The call was interrupted by the user.
21168 @unnumberedsubsubsec stat/fstat
21169 @cindex fstat, file-i/o system call
21170 @cindex stat, file-i/o system call
21174 int stat(const char *pathname, struct stat *buf);
21175 int fstat(int fd, struct stat *buf);
21178 Fstat,pathnameptr/len,bufptr
21181 @exdent Return value:
21182 On success, zero is returned. On error, -1 is returned.
21189 fd is not a valid open file.
21192 A directory component in pathname does not exist or the
21193 path is an empty string.
21196 A component of the path is not a directory.
21199 pathnameptr is an invalid pointer value.
21202 No access to the file or the path of the file.
21205 pathname was too long.
21208 The call was interrupted by the user.
21212 @unnumberedsubsubsec gettimeofday
21213 @cindex gettimeofday, file-i/o system call
21217 int gettimeofday(struct timeval *tv, void *tz);
21220 Fgettimeofday,tvptr,tzptr
21222 @exdent Return value:
21223 On success, 0 is returned, -1 otherwise.
21230 tz is a non-NULL pointer.
21233 tvptr and/or tzptr is an invalid pointer value.
21237 @unnumberedsubsubsec isatty
21238 @cindex isatty, file-i/o system call
21242 int isatty(int fd);
21247 @exdent Return value:
21248 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
21255 The call was interrupted by the user.
21259 @unnumberedsubsubsec system
21260 @cindex system, file-i/o system call
21264 int system(const char *command);
21267 Fsystem,commandptr/len
21269 @exdent Return value:
21270 The value returned is -1 on error and the return status
21271 of the command otherwise. Only the exit status of the
21272 command is returned, which is extracted from the hosts
21273 system return value by calling WEXITSTATUS(retval).
21274 In case /bin/sh could not be executed, 127 is returned.
21281 The call was interrupted by the user.
21284 @node Protocol specific representation of datatypes
21285 @subsection Protocol specific representation of datatypes
21286 @cindex protocol specific representation of datatypes, in file-i/o protocol
21289 * Integral datatypes::
21295 @node Integral datatypes
21296 @unnumberedsubsubsec Integral datatypes
21297 @cindex integral datatypes, in file-i/o protocol
21299 The integral datatypes used in the system calls are
21302 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
21305 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
21306 implemented as 32 bit values in this protocol.
21308 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
21310 @xref{Limits}, for corresponding MIN and MAX values (similar to those
21311 in @file{limits.h}) to allow range checking on host and target.
21313 @code{time_t} datatypes are defined as seconds since the Epoch.
21315 All integral datatypes transferred as part of a memory read or write of a
21316 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
21319 @node Pointer values
21320 @unnumberedsubsubsec Pointer values
21321 @cindex pointer values, in file-i/o protocol
21323 Pointers to target data are transmitted as they are. An exception
21324 is made for pointers to buffers for which the length isn't
21325 transmitted as part of the function call, namely strings. Strings
21326 are transmitted as a pointer/length pair, both as hex values, e.g.@:
21333 which is a pointer to data of length 18 bytes at position 0x1aaf.
21334 The length is defined as the full string length in bytes, including
21335 the trailing null byte. Example:
21338 ``hello, world'' at address 0x123456
21349 @unnumberedsubsubsec struct stat
21350 @cindex struct stat, in file-i/o protocol
21352 The buffer of type struct stat used by the target and @value{GDBN} is defined
21357 unsigned int st_dev; /* device */
21358 unsigned int st_ino; /* inode */
21359 mode_t st_mode; /* protection */
21360 unsigned int st_nlink; /* number of hard links */
21361 unsigned int st_uid; /* user ID of owner */
21362 unsigned int st_gid; /* group ID of owner */
21363 unsigned int st_rdev; /* device type (if inode device) */
21364 unsigned long st_size; /* total size, in bytes */
21365 unsigned long st_blksize; /* blocksize for filesystem I/O */
21366 unsigned long st_blocks; /* number of blocks allocated */
21367 time_t st_atime; /* time of last access */
21368 time_t st_mtime; /* time of last modification */
21369 time_t st_ctime; /* time of last change */
21373 The integral datatypes are conforming to the definitions given in the
21374 approriate section (see @ref{Integral datatypes}, for details) so this
21375 structure is of size 64 bytes.
21377 The values of several fields have a restricted meaning and/or
21384 st_ino: No valid meaning for the target. Transmitted unchanged.
21386 st_mode: Valid mode bits are described in Appendix C. Any other
21387 bits have currently no meaning for the target.
21389 st_uid: No valid meaning for the target. Transmitted unchanged.
21391 st_gid: No valid meaning for the target. Transmitted unchanged.
21393 st_rdev: No valid meaning for the target. Transmitted unchanged.
21395 st_atime, st_mtime, st_ctime:
21396 These values have a host and file system dependent
21397 accuracy. Especially on Windows hosts the file systems
21398 don't support exact timing values.
21401 The target gets a struct stat of the above representation and is
21402 responsible to coerce it to the target representation before
21405 Note that due to size differences between the host and target
21406 representation of stat members, these members could eventually
21407 get truncated on the target.
21409 @node struct timeval
21410 @unnumberedsubsubsec struct timeval
21411 @cindex struct timeval, in file-i/o protocol
21413 The buffer of type struct timeval used by the target and @value{GDBN}
21414 is defined as follows:
21418 time_t tv_sec; /* second */
21419 long tv_usec; /* microsecond */
21423 The integral datatypes are conforming to the definitions given in the
21424 approriate section (see @ref{Integral datatypes}, for details) so this
21425 structure is of size 8 bytes.
21428 @subsection Constants
21429 @cindex constants, in file-i/o protocol
21431 The following values are used for the constants inside of the
21432 protocol. @value{GDBN} and target are resposible to translate these
21433 values before and after the call as needed.
21444 @unnumberedsubsubsec Open flags
21445 @cindex open flags, in file-i/o protocol
21447 All values are given in hexadecimal representation.
21459 @node mode_t values
21460 @unnumberedsubsubsec mode_t values
21461 @cindex mode_t values, in file-i/o protocol
21463 All values are given in octal representation.
21480 @unnumberedsubsubsec Errno values
21481 @cindex errno values, in file-i/o protocol
21483 All values are given in decimal representation.
21508 EUNKNOWN is used as a fallback error value if a host system returns
21509 any error value not in the list of supported error numbers.
21512 @unnumberedsubsubsec Lseek flags
21513 @cindex lseek flags, in file-i/o protocol
21522 @unnumberedsubsubsec Limits
21523 @cindex limits, in file-i/o protocol
21525 All values are given in decimal representation.
21528 INT_MIN -2147483648
21530 UINT_MAX 4294967295
21531 LONG_MIN -9223372036854775808
21532 LONG_MAX 9223372036854775807
21533 ULONG_MAX 18446744073709551615
21536 @node File-I/O Examples
21537 @subsection File-I/O Examples
21538 @cindex file-i/o examples
21540 Example sequence of a write call, file descriptor 3, buffer is at target
21541 address 0x1234, 6 bytes should be written:
21544 <- @code{Fwrite,3,1234,6}
21545 @emph{request memory read from target}
21548 @emph{return "6 bytes written"}
21552 Example sequence of a read call, file descriptor 3, buffer is at target
21553 address 0x1234, 6 bytes should be read:
21556 <- @code{Fread,3,1234,6}
21557 @emph{request memory write to target}
21558 -> @code{X1234,6:XXXXXX}
21559 @emph{return "6 bytes read"}
21563 Example sequence of a read call, call fails on the host due to invalid
21564 file descriptor (EBADF):
21567 <- @code{Fread,3,1234,6}
21571 Example sequence of a read call, user presses Ctrl-C before syscall on
21575 <- @code{Fread,3,1234,6}
21580 Example sequence of a read call, user presses Ctrl-C after syscall on
21584 <- @code{Fread,3,1234,6}
21585 -> @code{X1234,6:XXXXXX}
21599 % I think something like @colophon should be in texinfo. In the
21601 \long\def\colophon{\hbox to0pt{}\vfill
21602 \centerline{The body of this manual is set in}
21603 \centerline{\fontname\tenrm,}
21604 \centerline{with headings in {\bf\fontname\tenbf}}
21605 \centerline{and examples in {\tt\fontname\tentt}.}
21606 \centerline{{\it\fontname\tenit\/},}
21607 \centerline{{\bf\fontname\tenbf}, and}
21608 \centerline{{\sl\fontname\tensl\/}}
21609 \centerline{are used for emphasis.}\vfill}
21611 % Blame: doc@cygnus.com, 1991.